Home
JournalsCollections
For Authors For Reviewers For Editorial Board Members
Article Processing Charges Open Access
Ethics Advertising Policy
Editorial Policy Resource Center
Company Information Contact Us
OPEN ACCESS

Mitochondria at the Crossroads of Cholestatic Liver Injury: Targeting Novel Therapeutic Avenues

  • Xutao Li1,#,
  • Tianyin Ruan1,#,
  • Siyuan Wang1,
  • Xin Sun1,2,
  • Chenghai Liu1,2,3,
  • Yuan Peng1,*  and
  • Yanyan Tao1,2,3,* 
Journal of Clinical and Translational Hepatology   2024;12(9):792-801

doi: 10.14218/JCTH.2024.00087

Received:

Revised:

Accepted:

Published online:

 Author information

Citation: Li X, Ruan T, Wang S, Sun X, Liu C, Peng Y, et al. Mitochondria at the Crossroads of Cholestatic Liver Injury: Targeting Novel Therapeutic Avenues. J Clin Transl Hepatol. 2024;12(9):792-801. doi: 10.14218/JCTH.2024.00087.

Abstract

Bile acids are byproducts of cholesterol metabolism in the liver and constitute the primary components of bile. Disruption of bile flow leads to cholestasis, characterized by the accumulation of hydrophobic bile acids in the liver and bloodstream. Such accumulation can exacerbate liver impairment. This review discussed recent developments in understanding how bile acids contribute to liver damage, including disturbances in mitochondrial function, endoplasmic reticulum stress, inflammation, and autophagy dysfunction. Mitochondria play a pivotal role in cholestatic liver injury by influencing hepatocyte apoptosis and inflammation. Recent findings linking bile acids to liver damage highlight new potential treatment targets for cholestatic liver injury.

Graphical Abstract

Keywords

Bile acids, Mitochondria, Endoplasmic reticulum, Inflammatory, Cholestatic liver injury, Review

Introduction

Bile acids (BAs) are signaling molecules generated from cholesterol in the liver and subsequently modified by the gut microbiome in the intestines.1,2 Synthesis of BAs in the human body involves both classical and nonclassical pathways.3 In the classical pathway, primarily involving the liver, cholesterol 7-hydroxylase acts as the key rate-limiting enzyme, facilitating the production of two hydrophobic primary BAs: cholic acid and chenodeoxycholic acid (CDCA). The nonclassical pathway, which involves various tissues and macrophages, is initiated by sterol 27A-hydroxylase in mitochondria and steroid 7-hydroxylase in the endoplasmic reticulum (ER).4,5 This pathway, as described by Axelson et al,6 primarily becomes prominent in certain pathological conditions. When cholesterol 7-hydroxylase activity in the liver decreases, the nonclassical pathway plays a regulatory role in vivo, influencing metabolic equilibrium through the production of CDCA.

Cholestasis is a multifactorial condition characterized by stagnation of bile flow and accumulation of potentially harmful BAs in the liver and bloodstream.7 The etiological factors of cholestasis include viral infections, inflammation, and autoimmune diseases.8–10 Although researchers have extensively investigated the causes of cholestasis, the specific molecular pathways through which accumulated toxic BAs induce liver damage remain incompletely understood.11,12 Earlier theories indicated that elevated hepatic levels of BAs led to hepatocyte death through direct cytolytic effects.13,14 However, these studies exposed cultured human hepatocytes to submillimolar levels of toxic secondary BAs, concentrations rarely observed in patient serum.12 The studies reported that BAs contribute to cholestatic liver injury through alternative mechanisms. Subsequent experiments implicated mitochondrial oxidative stress and ER stress as pivotal contributors to cholestatic liver injury,15,16 although the specific molecular details remained elusive. As research advanced, novel mechanisms were identified, including the generation of inflammatory signals, infiltration of immune cells, and dysfunction of autophagy. Notably, mitochondria play a critical role in these processes, influencing the release of apoptotic signals and contributing to the production of inflammatory signals.

Mitochondria are complex organelles enclosed in a dual-layer membrane structure comprising the mitochondrial outer membrane (MOM) and mitochondrial inner membrane (MIM). The MOM is fairly permeable because it contains porins such as the voltage-dependent anion channel (VDAC) that enable the passage of small, uncharged molecules and ionic species up to approximately 5 kDa.17 In contrast, the MIM acts as the primary barrier between the cytosol and the mitochondrial matrix, and it is predominantly impermeable. The MIM curves inward to shape the mitochondrial matrix, a highly intricate environment housing the electron transport chain (ETC), ATP synthase, and human mitochondrial DNA (mtDNA), which comprises 13 structural genes encoding partial proteins of respiratory chain complexes I, II, III, and IV.18 Additionally, studies have highlighted the importance of the mitochondrial permeability transition pore (mPTP) located on the mitochondrial membrane, comprising adenine nucleotide translocase and F1F0 ATPase, and regulated by VDAC and cyclophilin D receptors.19–21 The mPTP periodically opens under physiological conditions to maintain electrochemical balance within mitochondria. Mitochondria also play a central role in regulating cell death and inflammatory signaling processes.22,23

Pathways of hepatocyte apoptosis mediated by BAs

Death receptor-independent pathways

Mitochondria, the primary loci for oxidative phosphorylation within cells, play a pivotal role in the complex landscape of energy metabolism. In this process, NADH and FADH2 act as electron carriers, facilitating the transfer of electrons obtained from the tricarboxylic acid cycle to the ETC. The majority of these electrons traverse the ETC, ultimately combining with oxygen molecules at cytochrome oxidase to form water. However, approximately 2% of electrons from complexes I and III deviate from the ETC.24 These electrons directly interact with oxygen molecules, generating a superoxide anion, which is then converted to H2O2 by manganese MnSOD/SOD-2.25 Hydrophobic BAs can directly impair ETC complex III, thereby reducing the respiratory control ratio of respiratory state 3. Within the iron-sulfur centers of proteins, superoxide anions can reduce Fe3+ to Fe2+, leading to subsequent interaction of H2O2 with Fe2+, which can yield ·OH.26 Furthermore, the superoxide anion can react with N2O, resulting in the formation of ONOO−. Both ·OH and ONOO− have high reactivity and can therefore exert detrimental effects on mitochondrial membranes, proteins, and mtDNA.

In mitochondria isolated from rat livers,27 CDCA was found to directly trigger sudden opening of the mPTP. This opening allows unrestricted passage of molecules with a relative molecular mass exceeding 1.5 × 103, disrupting the mitochondrial membrane potential and hindering ATP production, ultimately causing mitochondrial swelling and rupture.28,29 Due to the substantially larger surface area of the MIM compared to the MOM, swelling of the mitochondrial matrix induced by mPTP opening triggers rupture of the MOM, resulting in the release of cytochrome C (Cyto C) into the cytoplasm. Cyto C initiates the intrinsic pathway of apoptosis.30 Activation of the cysteine aspartate protease family is a pivotal step in apoptosis induction. This family includes multiple members primarily categorized into two groups: executors, such as caspase-3, which directly degrade intracellular structural and functional proteins to induce apoptosis without undergoing autocatalysis or self-splicing, and promoters, such as caspase-9, which undergo self-splicing activation and subsequently initiate a cascade reaction of caspases without specific intracellular protein degradation.31 Scientific investigations have confirmed that activation of caspase-9 depends on Cyto C and apoptosis-inducing factors within mitochondria, with the mPTP governing their release.30 Cyclosporine A (CsA) was identified as the most potent inhibitor regulating mPTP opening.27 CsA directly binds to cyclophilin D, hindering mPTP opening; this prevents MIM depolarization and caspase-3 activation, exerting a strong inhibitory effect on programmed cell death.32 Experimental evidence has indicated that pretreatment of mitochondria with CsA significantly inhibits mitochondrial permeability transition.33 Additionally, BAs have been observed to reduce mitochondrial biogenesis, as evidenced by a notable reduction in the levels and activities of mitochondrial transcription factors in bile duct-ligated (BDL) mice.34,35

Death receptor-dependent pathways

Studies have indicated that BAs can trigger apoptosis through death receptors. This process is typically initiated by BAs interacting with death receptors such as tumor necrosis factor receptor superfamily, member 6 (FAS) and TNF ligand superfamily, member 10 (TRAIL). Research has demonstrated that in BDL mice, deficiency in FAS reduces liver fibrosis and apoptosis.36,37 Hydrophobic BAs facilitate FAS receptor phosphorylation, leading to its translocation to the cell membrane and subsequent activation.38 Increased density of FAS receptors on the cell membrane renders hepatocytes more susceptible to the FAS receptor-induced cell death pathway.

Additionally, exposure of hepatocytes to glycochenodeoxycholate can induce transcriptional upregulation of TRAILR2 and inactivation of FAS-associated via death domain-like apoptosis regulator through phosphorylation.39–41 Death receptors oligomerize, leading to the formation of a death-initiating signaling complex comprising FAS-associated via death domain and pro-caspase 8/10.42 Upon activation of caspase 8, downstream caspases can be directly activated, initiating apoptosis. Simultaneously, BH3 interacting domain death agonist is activated by caspase 8, which then activates B-cell lymphoma-2 (Bcl-2)-associated X protein (BAX) and Bcl-2-antagonist/killer 1 (BAK).43,44

The Bcl-2 family proteins BAX and BAK play pivotal roles in the formation of the apoptotic pore, which facilitates mitochondrial permeabilization during apoptosis.45,46 BAX and BAK are typically inactive, but when activated, conformational rearrangements occur in the MOM, leading to the opening of mitochondrial membrane pores of varying sizes.47 Evidence indicates that Cyto C can be released when the membrane pore radius is as small as 2 nm.48 Following such a release, Cyto C triggers the binding of apoptotic protease activator to the precursor caspase-9, activating it. This cascade of events within the caspase system ultimately leads to irreversible death of liver cells (Fig. 1).49

BAs induce hepatocyte apoptosis by mediating mitochondrial dysfunction through death receptors via independent & dependent pathways.
Fig. 1  BAs induce hepatocyte apoptosis by mediating mitochondrial dysfunction through death receptors via independent & dependent pathways.

BAs, Bile acid; NTCP, sodium-taurocholate co-transporting polypeptide; FADD, FAS-associated via death domain; BID, BH3 interacting domain death agonist; BAX, Bcl-2-associated X protein; BAK, Bcl-2-antagonist/killer 1; ETC, electron transport chain; mtDNA, mitochondrial DNA; TCA, tricarboxylic acid; mPTP, mitochondrial permeability transition pore; ROS, reactive oxygen species; Cyto C, cytochrome C.

ER stress-dependent pathways

The ER is present in all eukaryotic cells and plays various roles, including protein synthesis, secretion, and storage and release of calcium ions (Ca2+). It is essential for the synthesis, processing, folding, assembly, and transportation of new synthetic peptide chains, as well as for the modification of existing proteins.50 Proteins designated for modification are initially synthesized on the ribosome and then transported to the ER for further processing. When proteins undergo appropriate modification and folding, mature proteins are produced, whereas those unable to fold correctly are identified and degraded. Unfolded proteins accumulate in the ER due to imbalances in protein folding and degradation processes; this phenomenon is referred to as ER stress.51

Research has indicated that cholestasis can trigger ER stress.52–54 In cases of mild to moderate ER stress, liver cells can eliminate unfolded and misfolded proteins and restore ER homeostasis through three pathways mediated by inositol-requiring enzyme 1a (IRE1a), PKR-like ER kinase, and activating transcription factor 6a. However, prolonged cholestasis can result in severe ER stress, overwhelming hyperactivation of the unfolded protein response, and subsequent activation of the intrinsic apoptotic machinery.55 Although the precise mechanisms governing apoptosis induced by ER stress remain incompletely understood, they may involve sustained release of ER calcium, activation of mitogen-activated protein kinase c-jun N-terminal kinase (JNK), upregulation of proapoptotic Bcl-2 family members, generation of reactive oxygen species (ROS), and induction of the proapoptotic transcription factor C/EBP homologous protein (CHOP).

Studies have suggested that IRE1a plays a role in modulating ER stress-induced apoptosis. Upon activation of IRE1a, apoptosis signal-regulating kinase 1 and JNK are activated, which recruits adaptor protein tumor necrosis factor receptor-associated factor 2. This activation triggers proapoptotic effects from JNK, including inactivation of antiapoptotic Bcl-2 proteins and phosphorylation-induced activation of BAX and BAK.56,57 Activation of BAK and BAX leads to mitochondrial permeabilization, resulting in the opening of the mitochondrial membrane and the release of Cyto C and other small apoptotic precursors. The transcription factor CHOP, a well-studied proapoptotic pathway arising from ER stress, is primarily activated by recombinant activating transcription factor 4 and activating transcription factor 6a.58,59 A study discovered reduced apoptosis in CHOP knockout mouse hepatocytes treated with toxic BAs, indicating that CHOP plays a pivotal role in apoptosis.60 CHOP is implicated in apoptosis through various mechanisms, including controlling growth arrest and DNA damage-inducible 34 (hereinafter referred to as GADD34) expression. GADD34, upon binding to protein phosphatase 1, induces dephosphorylation of eukaryotic initiation factor 2A, thereby restoring protein translation when ER stress persists and consequently exacerbating ER stress.61 Another study indicated that CHOP is essential for the apoptotic response to ER stress, as cells isolated from mice deficient in CHOP were found to be resistant to ER stress-induced cell death.62 CHOP may transcriptionally upregulate expression of the death receptor TRAIL receptor 2,63 a key receptor for death receptor-mediated mitochondrial dysfunction. Moreover, CHOP could upregulate proapoptotic Bcl-2-interacting mediator of cell death and BID proteins while suppressing the expression of antiapoptotic Bcl-2.64

Disturbances in ER calcium levels have been reported to be linked to apoptosis mechanisms. Hydrophobic BAs can trigger sustained release of Ca2+ from the ER. This process involves a protein complex consisting of VDAC, 75 kDa glucose regulatory protein, and inositol 1,4,5-trisphosphate receptor, which facilitates the transfer of Ca2+ between the ER and mitochondria at the mitochondria-associated ER membrane.65–67 Increased uptake of Ca2+ by mitochondria reduces the activities of MnSOD, catalase, and peroxidase in the mitochondria, leading to accumulation of oxygen radicals. Excessive oxygen radicals can damage the mitochondrial membrane, denature membrane proteins, increase membrane permeability, and disrupt mitochondrial structure. Moreover, research has demonstrated that mitochondrial Ca2+ overload is a crucial factor in the pathological opening of the mPTP (Fig. 2).68

Pathways leading to apoptosis induced by ER stress are depicted, including ER calcium release, activation of JNK, upregulation of pro-apoptotic BCL-2 family members, ROS production, and the proapoptotic transcription factor CHOP.
Fig. 2  Pathways leading to apoptosis induced by ER stress are depicted, including ER calcium release, activation of JNK, upregulation of pro-apoptotic BCL-2 family members, ROS production, and the proapoptotic transcription factor CHOP.

BAs, Bile acid; ER, endoplasmic reticulum; NTCP, sodium-taurocholate co-transporting polypeptide; ROS, reactive oxygen species; IRE1a, inositol-requiring enzyme 1a; PERK, PKR-like ER kinase; eIF-2a, eukaryotic initiation factor 2A; BAX, Bcl-2-associated X protein; BAK, Bcl-2-antagonist/killer 1; Bcl-2, B-cell lymphoma-2; Cyto C, cytochrome C; CHOP, C/EBP homologous protein; ASK1, apoptosis signal-regulating kinase 1; TRAF2, tumor necrosis factor receptor-associated factor 2; ATF4, activating transcription factor 4; GADD34, growth arrest and DNA damage-inducible 34; GRP75, 75 kDa glucose-regulated protein; IP3R, inositol 1,4,5-trisphosphate receptor; VDAC, voltage-dependent anion channel; JNK, c-Jun N-terminal kinase; Ca2+, calcium ions.

Inflammatory response mediated by BAs

Apoptosis is an immune-silent form of cell death that typically does not elicit an inflammatory response. However, investigations observing neutrophil infiltration in cholestatic rodent models have suggested that BAs might induce liver injury through inflammation.69,70 Additionally, elevated levels of cytokines have been detected in the liver and serum of patients with cholestasis as well as in BDL mice.71–73 Research has also demonstrated that reducing inflammatory cytokines can alleviate liver damage in BDL mice,74–76 further indicating the involvement of the inflammatory response in cholestatic liver injury. These findings imply that BAs can harm hepatocytes through nonapoptotic means, specifically by triggering inflammatory responses.

Research indicates that caspase-independent cell death, induced by BAX and BAK even in the absence of caspase activity, is strongly associated with changes in mitochondrial membrane permeability.77 Typically, mtDNA is confined to the mitochondrial matrix and isolated from cytoplasmic components. However, when BAs activate BAX and BAK, these proteins gradually form larger supramolecular structures, facilitating the release of mtDNA. Simultaneously, mitochondrial calcium overload induced by BAs alters the permeability of the MIM, leading to the release of mtDNA from the mPTP. According to the endosymbiosis theory, mitochondria are considered to be damage-associated molecular patterns because they originated from aerobic bacteria phagocytosed by primordial eukaryotic cells, and mtDNA retains features of their bacterial ancestry. Toll-like receptors (TLRs) play a crucial role in initiating inflammatory responses to tissue damage caused by both endogenous sterile insults and pathogen recognition. BAs induce mitochondrial damage through various mechanisms, thereby exposing mtDNA to TLR9, an intracellular DNA receptor.78 TLR9, located on the endosomal reticulum, has a high affinity for unmethylated CpG dinucleotides.79 Since mitochondrial DNA contains unmethylated CpG DNA repeats, it serves as a ligand for TLR9.80,81 Upon activation, TLR9 stimulates the production of inflammatory cytokines, which in turn promote chemotaxis of neutrophils as part of the innate immune response to damage-associated molecular patterns.82 Stimulation by TLR9 and inflammatory cytokines activates the transcription factor nuclear factor kappa-B (NF-κB), triggering a cascade of intracellular signaling molecules that ultimately activate the NF-κB pathway, a key regulator of TLR-induced signaling pathways.81 TLR9 binding to CpG DNA repeats activates the NF-κB signaling pathway, leading to transcription of a range of inflammatory factors.80–84

Neutrophils play a critical role in sterile inflammation. Under normal conditions, circulating neutrophils act as first responders to inflammatory signals, migrating to the site of inflammation due to their abundance, mobility, and potent cytotoxicity. Elevated levels of neutrophils have been observed around the hepatic sinusoids of BDL mice, detectable as early as 8 h after biliary ligation.70,84,85 However, excessive tissue damage caused by neutrophil infiltration results in persistent inflammation, hindering the progression of injury to healing. Additionally, studies have revealed that ROS activated the NOD-like receptor thermal protein domain associated protein 3 (hereinafter referred to as NLRP3) inflammasome, composed of caspase-1 and NLRP3, thereby enhancing production of proinflammatory cytokines (Fig. 3).86–88

Continuous accumulation of BAs in liver cells leads to an inflammatory response.
Fig. 3  Continuous accumulation of BAs in liver cells leads to an inflammatory response.

BAs, Bile acid; NF-κB, nuclear factor kappa-B; ROS, reactive oxygen species; NLRP3, NOD-like receptor thermal protein domain associated protein 3; BAX, Bcl-2-associated X protein; BAK, Bcl-2-antagonist/killer 1; mtDNA, mitochondrial DNA.

Mediation of autophagy dysfunction by BAs

Mitochondrial autophagy, as proposed by Lemasters et al,89 becomes relevant following severe mitochondrial injury or fusion defects because it maintains intracellular stability. Studies indicate that autophagy serves as a survival mechanism in the liver, protecting against cholestasis-induced hepatocyte injury. Inhibiting autophagy with chloroquine exacerbates cholestasis-induced liver damage and hepatocyte death, while promoting autophagy with rapamycin partially mitigates cholestasis-related hepatotoxicity. Transcription factor EB (TFEB) regulates genes essential for lysosomal biogenesis and function.90 Proteomic analysis has shown that glycochenodeoxycholic acid impairs the expression of transcription factor E3, a member of the TFEB family, synergistically influencing TFEB signaling and decreasing lysosomal production.91 Research indicates compromised autophagy in human cholestatic conditions. In vitro experiments demonstrate that BAs accumulated during cholestasis induce the expression of the RUN domain and Beclin1-interacting protein in a farnesoid X receptor (FXR)-dependent manner. Furthermore, rubicon significantly impedes the fusion of autophagosomes and lysosomes, impairing the normal degradation process of autophagosomes.

Several studies have reported reduced expression of the Rab7 protein in a murine model of cholestasis.92,93 Rab7 is involved in the fusion of autophagosomes with lysosomes through interactions with a new FYVE and coiled-coil domain-containing protein and is crucial for microtubule plus-end-directed transport.94 Decreased Rab7 expression leads to impaired fusion between autophagosomes and lysosomes, resulting in p62 accumulation. This accumulation promotes the formation of intrahyaline bodies, contributing to cholestatic liver damage. Moreover, the accumulation of p62-containing intrahyaline bodies inhibits the FXR nuclear receptor and activates the NF-E2-related factor 2 (hereinafter referred to as NRF2) pathway.95 Despite ongoing investigations, the precise mechanism by which impaired autophagy flux contributes to cholestatic liver injury remains unclear. Nonetheless, these findings underscore the pathological significance of the autophagy-p62-NRF2-FXR pathway (Fig. 4).96

Accumulation of BAs in cholestatic conditions impairs the fusion of autophagosomes and lysosomes.
Fig. 4  Accumulation of BAs in cholestatic conditions impairs the fusion of autophagosomes and lysosomes.

↑, expression increased; ↓, expression decreased; BAs, Bile acid; FXR, farnesoid X receptor; NRF2, NF-E2-related factor 2; NTCP, sodium-taurocholate co-transporting polypeptide; Rubicon, RUN domain and Beclin1-interacting protein; TFE3, transcription factor E3.

Advances in clinical research of cholestatic diseases

Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are the two most common chronic cholestatic liver diseases. Ursodeoxycholic acid (UDCA) has long been considered the first-line drug for treating PBC, as it can accelerate BAs excretion and alter BAs composition. However, approximately 40% of patients do not respond to UDCA and are therefore at risk of disease progression.42,97 Furthermore, there is currently no available medical therapy for PSC. Recent advances in molecular biochemistry, specifically in BAs regulation and understanding of immunologic pathways, have led to the emergence of novel pharmacologic treatments.

Advances in clinical research of drugs targeting BAs metabolism

Most clinical trials focus on therapeutic interventions targeting the effector phase of BAs synthesis, metabolism, and inflammation. Obeticholic acid (OCA) exhibits a strong affinity for the farnesoid X receptor. In a clinical study, approximately 50% of patients who did not adequately respond to UDCA showed improvement with OCA, expediting its approval process by the Food and Drug Administration.98 However, findings of a significantly increased incidence of itching in the POISE treatment group may pose a notable barrier to its clinical application.98 Moreover, treatment with OCA led to decreased high-density lipoprotein cholesterol and triglyceride levels, along with an initial mild increase in low-density lipoprotein cholesterol levels; the long-term consequences of these changes in the lipid profile induced by OCA are yet to be determined. New molecules with alterations to fibroblast growth factor 19’s amino acid sequence have been developed to limit its procarcinogenic properties and enhance its anticholestatic effect.99 NGM282 is one such nontumorigenic derivative of fibroblast growth factor 19. In a phase II multicenter, randomized, double-blinded, placebo-controlled trial involving 45 PBC patients who were inadequate responders to UDCA, NGM282 was administered as a daily subcutaneous injection of 0.3 mg or 3 mg versus placebo for 28 days.100 Treated patients showed statistically significant reductions in ALP levels and other liver biochemistries, but some adverse events were reported, including diarrhea, nausea, and headache. It remains unclear whether NGM282 will undergo further examination in PSC.

In recent years, researchers have shifted their focus toward interventions targeting inflammatory effects, such as cytokine neutralizers and their signal transducers.101,102 Rituximab, a monoclonal antibody targeting the CD20 antigen on B cells, has been investigated for potential benefits in PBC. In one study, six PBC patients with inadequate response to UDCA showed improvement in ALP levels following rituximab infusions.100 However, another study involving 14 PBC patients reported less pronounced reductions in liver biochemistries despite improvements in pruritus.103,104 Abatacept, a monoclonal antibody targeting CD80 and CD86 on antigen-presenting cells and interfering with T-cell activation, failed to meet the primary endpoint in a small study for PBC.105 New therapeutic targets are urgently needed.

Advances in clinical research of mitochondria-targeted drugs

The regulation of mitochondrial membrane barrier function is of medical interest, as it can modulate access to mitochondrial contents, including DAMPs, into the cytosol, thereby influencing downstream cell death and inflammatory signaling pathways. Drugs that effectively modulate mitochondrial pore formation and DAMPs release could potentially be used in therapeutics. Research on potential treatments for cholestasis targeting mitochondria is rare, reflecting the novelty of this research area and the scarcity of pharmacological interventions specifically targeting mitochondrial function, especially mitochondrial outer membrane permeabilization (MOMP) and mPTP. CsA, a commonly used inhibitor of MOMP and mPTP, has been approved for clinical trials due to its inhibitory effect on mPTP when used in conjunction with mitochondrial recombinant cyclophilin D. CsA has demonstrated protective effects against ischemia/reperfusion injury in the heart. Although the therapeutic efficacy of CsA in cholestasis remains unclear and requires further investigation, findings regarding this drug provide valuable insights into the study of drugs targeting MOMP and mPTP.106

Discussion and future prospects

The etiology of cholestatic liver injury is multifaceted, and its pathogenesis is complex. A key pathological feature of cholestatic liver injury is elevated levels of BAs in the blood and liver. BAs, especially hydrophobic ones, act as pathological factors that can exacerbate liver cell damage. Mitochondria are key regulatory targets in apoptosis and inflammation induced by cholestasis. A growing body of evidence from various experimental environments suggests a close relationship between the structural and functional integrity of mitochondria and cholestatic liver injury.

However, several questions and obstacles remain to be addressed for the development of clinically viable mitochondria-targeting agents for the treatment of cholestatic liver injury. First, although abundant correlational evidence linking mitochondrial dysfunction to the pathogenesis of cholestatic liver injury exists, well-established mechanistic links are often missing and urgently need to be established. Second, additional work is needed to understand the crosstalk between autophagy and apoptotic caspases in regulating mitochondrial DAMP-driven inflammation. Third, although recent discoveries have allowed important progress in our understanding of the mPTP, we still lack a comprehensive view of the pore architecture and the molecular connections between MOM and MIM, which calls for the development of more refined experimental tools. Finally, studies on potential treatments of cholestasis with drugs targeting mitochondria are rare, which not only reflects the novelty of research targeting mitochondrial function but also indicates that the clinical trial basis for targeted mitochondrial drugs is insufficient. This hypothesis has only been confirmed in the laboratory and lacks clinical evidence. Therefore, further elucidation of the molecular mechanisms underlying mitochondrial dysfunction and cholestatic liver injury is crucial, as it will pave the way for the development of mitochondria-targeting drugs aimed at effectively managing cholestatic liver injury.

Declarations

Funding

This work was supported by grants from the National Natural Science Foundation of China (No. 82174057 and 82004146) and the Shuguang Siming Scholar Plan (No. SGXZ-201910).

Conflict of interest

The authors have no conflict of interests related to this publication.

Authors’ contributions

Manuscript writing and reference collection (XL, TR), manuscript review and editing (SW, XS), and final critical revision for the manuscript (CL, YP, YT). All authors have read and agreed to the published version of the manuscript.

References

  1. de Aguiar Vallim TQ, Tarling EJ, Edwards PA. Pleiotropic roles of bile acids in metabolism. Cell Metab 2013;17(5):657-669 View Article PubMed/NCBI
  2. Chiang JYL, Ferrell JM. Bile Acids as Metabolic Regulators and Nutrient Sensors. Annu Rev Nutr 2019;39:175-200 View Article PubMed/NCBI
  3. Vlahcevic ZR, Heuman DM, Hylemon PB. Regulation of bile acid synthesis. Hepatology 1991;13(3):590-600 View Article PubMed/NCBI
  4. Chiang JY. Bile acid metabolism and signaling. Compr Physiol 2013;3(3):1191-1212 View Article PubMed/NCBI
  5. Chiang JY. Recent advances in understanding bile acid homeostasis. F1000Res 2017;6:2029 View Article PubMed/NCBI
  6. Axelson M, Sjövall J. Potential bile acid precursors in plasma—possible indicators of biosynthetic pathways to cholic and chenodeoxycholic acids in man. J Steroid Biochem 1990;36(6):631-640 View Article PubMed/NCBI
  7. Trauner M, Meier PJ, Boyer JL. Molecular pathogenesis of cholestasis. N Engl J Med 1998;339(17):1217-1227 View Article PubMed/NCBI
  8. Fuchs G, Ahmed T, Araya M, Baker S, Croft N, Weaver L, et al. Malnutrition: Working Group report of the second World Congress of Pediatric Gastroenterology, Hepatology, and Nutrition. J Pediatr Gastroenterol Nutr 2004;39(Suppl 2):S670-S677 View Article PubMed/NCBI
  9. Bezerra JA. The next challenge in pediatric cholestasis: deciphering the pathogenesis of biliary atresia. J Pediatr Gastroenterol Nutr 2006;43(Suppl 1):S23-S29 View Article PubMed/NCBI
  10. Reyes H. Review: intrahepatic cholestasis. A puzzling disorder of pregnancy. J Gastroenterol Hepatol 1997;12(3):211-216 View Article PubMed/NCBI
  11. Fickert P, Wagner M. Biliary bile acids in hepatobiliary injury - What is the link?. J Hepatol 2017;67(3):619-631 View Article PubMed/NCBI
  12. Woolbright BL, Jaeschke H. Novel insight into mechanisms of cholestatic liver injury. World J Gastroenterol 2012;18(36):4985-4993 View Article PubMed/NCBI
  13. Spivey JR, Bronk SF, Gores GJ. Glycochenodeoxycholate-induced lethal hepatocellular injury in rat hepatocytes. Role of ATP depletion and cytosolic free calcium. J Clin Invest 1993;92(1):17-24 View Article PubMed/NCBI
  14. Galle PR, Theilmann L, Raedsch R, Otto G, Stiehl A. Ursodeoxycholate reduces hepatotoxicity of bile salts in primary human hepatocytes. Hepatology 1990;12(3 Pt 1):486-491 View Article PubMed/NCBI
  15. Arduini A, Serviddio G, Tormos AM, Monsalve M, Sastre J. Mitochondrial dysfunction in cholestatic liver diseases. Front Biosci (Elite Ed) 2012;4(6):2233-2252 View Article PubMed/NCBI
  16. Malhi H, Kaufman RJ. Endoplasmic reticulum stress in liver disease. J Hepatol 2011;54(4):795-809 View Article PubMed/NCBI
  17. Bayrhuber M, Meins T, Habeck M, Becker S, Giller K, Villinger S, et al. Structure of the human voltage-dependent anion channel. Proc Natl Acad Sci U S A 2008;105(40):15370-15375 View Article PubMed/NCBI
  18. Calvo SE, Mootha VK. The mitochondrial proteome and human disease. Annu Rev Genomics Hum Genet 2010;11:25-44 View Article PubMed/NCBI
  19. Fayaz SM, Raj YV, Krishnamurthy RG. CypD: The Key to the Death Door. CNS Neurol Disord Drug Targets 2015;14(5):654-663 View Article PubMed/NCBI
  20. Mnatsakanyan N, Llaguno MC, Yang Y, Yan Y, Weber J, Sigworth FJ, et al. A mitochondrial megachannel resides in monomeric F(1)F(O) ATP synthase. Nat Commun 2019;10(1):5823 View Article PubMed/NCBI
  21. Bernardi P, Carraro M, Lippe G. The mitochondrial permeability transition: Recent progress and open questions. FEBS J 2022;289(22):7051-7074 View Article PubMed/NCBI
  22. Du C, Fang M, Li Y, Li L, Wang X. Smac, a mitochondrial protein that promotes cytochrome c-dependent caspase activation by eliminating IAP inhibition. Cell 2000;102(1):33-42 View Article PubMed/NCBI
  23. Liu X, Kim CN, Yang J, Jemmerson R, Wang X. Induction of apoptotic program in cell-free extracts: requirement for dATP and cytochrome c. Cell 1996;86(1):147-157 View Article PubMed/NCBI
  24. Zhang Y, Wong HS. Are mitochondria the main contributor of reactive oxygen species in cells?. J Exp Biol 2021;224(Pt 5):jeb221606 View Article PubMed/NCBI
  25. Kitada M, Xu J, Ogura Y, Monno I, Koya D. Manganese Superoxide Dismutase Dysfunction and the Pathogenesis of Kidney Disease. Front Physiol 2020;11:755 View Article PubMed/NCBI
  26. Liu Y, Zhao Y, Wang J. Fenton/Fenton-like processes with in-situ production of hydrogen peroxide/hydroxyl radical for degradation of emerging contaminants: Advances and prospects. J Hazard Mater 2021;404(Pt B):124191 View Article PubMed/NCBI
  27. Rolo AP, Oliveira PJ, Moreno AJ, Palmeira CM. Chenodeoxycholate is a potent inducer of the permeability transition pore in rat liver mitochondria. Biosci Rep 2001;21(1):73-80 View Article PubMed/NCBI
  28. Hausenloy DJ, Yellon DM. The mitochondrial permeability transition pore: its fundamental role in mediating cell death during ischaemia and reperfusion. J Mol Cell Cardiol 2003;35(4):339-341 View Article PubMed/NCBI
  29. Halestrap AP, Richardson AP. The mitochondrial permeability transition: a current perspective on its identity and role in ischaemia/reperfusion injury. J Mol Cell Cardiol 2015;78:129-141 View Article PubMed/NCBI
  30. Ong SB, Samangouei P, Kalkhoran SB, Hausenloy DJ. The mitochondrial permeability transition pore and its role in myocardial ischemia reperfusion injury. J Mol Cell Cardiol 2015;78:23-34 View Article PubMed/NCBI
  31. Zamaraev AV, Kopeina GS, Prokhorova EA, Zhivotovsky B, Lavrik IN. Post-translational Modification of Caspases: The Other Side of Apoptosis Regulation. Trends Cell Biol 2017;27(5):322-339 View Article PubMed/NCBI
  32. Baines CP, Kaiser RA, Purcell NH, Blair NS, Osinska H, Hambleton MA, et al. Loss of cyclophilin D reveals a critical role for mitochondrial permeability transition in cell death. Nature 2005;434(7033):658-662 View Article PubMed/NCBI
  33. Liu J, Wei Y, Shen P. Effect of membrane permeability transition on hepatocyte apoptosis of the microcystin-LR-induced mice. Wei Sheng Yan Jiu 2011;40(1):53-56 View Article PubMed/NCBI
  34. Litonin D, Sologub M, Shi Y, Savkina M, Anikin M, Falkenberg M, et al. Human mitochondrial transcription revisited: only TFAM and TFB2M are required for transcription of the mitochondrial genes in vitro. J Biol Chem 2010;285(24):18129-18133 View Article PubMed/NCBI
  35. Tiao MM, Lin TK, Liou CW, Wang PW, Chen JB, Kuo FY, et al. Early transcriptional deregulation of hepatic mitochondrial biogenesis and its consequent effects on murine cholestatic liver injury. Apoptosis 2009;14(7):890-899 View Article PubMed/NCBI
  36. Miyoshi H, Rust C, Roberts PJ, Burgart LJ, Gores GJ. Hepatocyte apoptosis after bile duct ligation in the mouse involves Fas. Gastroenterology 1999;117(3):669-677 View Article PubMed/NCBI
  37. Gujral JS, Liu J, Farhood A, Jaeschke H. Reduced oncotic necrosis in Fas receptor-deficient C57BL/6J-lpr mice after bile duct ligation. Hepatology 2004;40(4):998-1007 View Article PubMed/NCBI
  38. Reinehr R, Becker S, Eberle A, Grether-Beck S, Häussinger D. Involvement of NADPH oxidase isoforms and Src family kinases in CD95-dependent hepatocyte apoptosis. J Biol Chem 2005;280(29):27179-27194 View Article PubMed/NCBI
  39. Higuchi H, Miyoshi H, Bronk SF, Zhang H, Dean N, Gores GJ. Bid antisense attenuates bile acid-induced apoptosis and cholestatic liver injury. J Pharmacol Exp Ther 2001;299(3):866-873 View Article PubMed/NCBI
  40. Higuchi H, Yoon JH, Grambihler A, Werneburg N, Bronk SF, Gores GJ. Bile acids stimulate cFLIP phosphorylation enhancing TRAIL-mediated apoptosis. J Biol Chem 2003;278(1):454-461 View Article PubMed/NCBI
  41. Higuchi H, Grambihler A, Canbay A, Bronk SF, Gores GJ. Bile acids up-regulate death receptor 5/TRAIL-receptor 2 expression via a c-Jun N-terminal kinase-dependent pathway involving Sp1. J Biol Chem 2004;279(1):51-60 View Article PubMed/NCBI
  42. Corpechot C, Abenavoli L, Rabahi N, Chrétien Y, Andréani T, Johanet C, et al. Biochemical response to ursodeoxycholic acid and long-term prognosis in primary biliary cirrhosis. Hepatology 2008;48(3):871-877 View Article PubMed/NCBI
  43. Yin XM, Wang K, Gross A, Zhao Y, Zinkel S, Klocke B, et al. Bid-deficient mice are resistant to Fas-induced hepatocellular apoptosis. Nature 1999;400(6747):886-891 View Article PubMed/NCBI
  44. Zhao Y, Li S, Childs EE, Kuharsky DK, Yin XM. Activation of pro-death Bcl-2 family proteins and mitochondria apoptosis pathway in tumor necrosis factor-alpha-induced liver injury. J Biol Chem 2001;276(29):27432-27440 View Article PubMed/NCBI
  45. Flores-Romero H, Hohorst L, John M, Albert MC, King LE, Beckmann L, et al. BCL-2-family protein tBID can act as a BAX-like effector of apoptosis. EMBO J 2022;41(2):e108690 View Article PubMed/NCBI
  46. Ke FS, Holloway S, Uren RT, Wong AW, Little MH, Kluck RM, et al. The BCL-2 family member BID plays a role during embryonic development in addition to its BH3-only protein function by acting in parallel to BAX, BAK and BOK. EMBO J 2022;41(15):e110300 View Article PubMed/NCBI
  47. Riley JS, Quarato G, Cloix C, Lopez J, O’Prey J, Pearson M, et al. Mitochondrial inner membrane permeabilisation enables mtDNA release during apoptosis. EMBO J 2018;37(17):e99238 View Article PubMed/NCBI
  48. McArthur K, Whitehead LW, Heddleston JM, Li L, Padman BS, Oorschot V, et al. BAK/BAX macropores facilitate mitochondrial herniation and mtDNA efflux during apoptosis. Science 2018;359(6378):eaao6047 View Article PubMed/NCBI
  49. Yin XM, Ding WX. Death receptor activation-induced hepatocyte apoptosis and liver injury. Curr Mol Med 2003;3(6):491-508 View Article PubMed/NCBI
  50. Bravo R, Gutierrez T, Paredes F, Gatica D, Rodriguez AE, Pedrozo Z, et al. Endoplasmic reticulum: ER stress regulates mitochondrial bioenergetics. Int J Biochem Cell Biol 2012;44(1):16-20 View Article PubMed/NCBI
  51. Oakes SA, Papa FR. The role of endoplasmic reticulum stress in human pathology. Annu Rev Pathol 2015;10:173-194 View Article PubMed/NCBI
  52. Krajarng A, Imoto M, Tashiro E, Fujimaki T, Shinjo S, Watanapokasin R. Apoptosis induction associated with the ER stress response through up-regulation of JNK in HeLa cells by gambogic acid. BMC Complement Altern Med 2015;15:26 View Article PubMed/NCBI
  53. Dong Z, Su L, Esmaili S, Iseli TJ, Ramezani-Moghadam M, Hu L, et al. Adiponectin attenuates liver fibrosis by inducing nitric oxide production of hepatic stellate cells. J Mol Med (Berl) 2015;93(12):1327-1339 View Article PubMed/NCBI
  54. Yao X, Li Y, Cheng X, Li H. ER stress contributes to alpha-naphthyl isothiocyanate-induced liver injury with cholestasis in mice. Pathol Res Pract 2016;212(6):560-567 View Article PubMed/NCBI
  55. Szegezdi E, Logue SE, Gorman AM, Samali A. Mediators of endoplasmic reticulum stress-induced apoptosis. EMBO Rep 2006;7(9):880-885 View Article PubMed/NCBI
  56. Lei K, Davis RJ. JNK phosphorylation of Bim-related members of the Bcl2 family induces Bax-dependent apoptosis. Proc Natl Acad Sci U S A 2003;100(5):2432-2437 View Article PubMed/NCBI
  57. Yamamoto K, Ichijo H, Korsmeyer SJ. BCL-2 is phosphorylated and inactivated by an ASK1/Jun N-terminal protein kinase pathway normally activated at G(2)/M. Mol Cell Biol 1999;19(12):8469-8478 View Article PubMed/NCBI
  58. Fawcett TW, Martindale JL, Guyton KZ, Hai T, Holbrook NJ. Complexes containing activating transcription factor (ATF)/cAMP-responsive-element-binding protein (CREB) interact with the CCAAT/enhancer-binding protein (C/EBP)-ATF composite site to regulate Gadd153 expression during the stress response. Biochem J 1999;339(Pt 1):135-141 View Article PubMed/NCBI
  59. Ma Y, Brewer JW, Diehl JA, Hendershot LM. Two distinct stress signaling pathways converge upon the CHOP promoter during the mammalian unfolded protein response. J Mol Biol 2002;318(5):1351-1365 View Article PubMed/NCBI
  60. Tamaki N, Hatano E, Taura K, Tada M, Kodama Y, Nitta T, et al. CHOP deficiency attenuates cholestasis-induced liver fibrosis by reduction of hepatocyte injury. Am J Physiol Gastrointest Liver Physiol 2008;294(2):G498-G505 View Article PubMed/NCBI
  61. Novoa I, Zeng H, Harding HP, Ron D. Feedback inhibition of the unfolded protein response by GADD34-mediated dephosphorylation of eIF2alpha. J Cell Biol 2001;153(5):1011-1022 View Article PubMed/NCBI
  62. Zinszner H, Kuroda M, Wang X, Batchvarova N, Lightfoot RT, Remotti H, et al. CHOP is implicated in programmed cell death in response to impaired function of the endoplasmic reticulum. Genes Dev 1998;12(7):982-995 View Article PubMed/NCBI
  63. Yamaguchi H, Wang HG. CHOP is involved in endoplasmic reticulum stress-induced apoptosis by enhancing DR5 expression in human carcinoma cells. J Biol Chem 2004;279(44):45495-45502 View Article PubMed/NCBI
  64. Puthalakath H, O’Reilly LA, Gunn P, Lee L, Kelly PN, Huntington ND, et al. ER stress triggers apoptosis by activating BH3-only protein Bim. Cell 2007;129(7):1337-1349 View Article PubMed/NCBI
  65. Muñoz JP, Zorzano A. FUNDC1: A Novel Protein in Cardiac Health. Circulation 2017;136(23):2267-2270 View Article PubMed/NCBI
  66. Peng TI, Jou MJ. Oxidative stress caused by mitochondrial calcium overload. Ann N Y Acad Sci 2010;1201:183-188 View Article PubMed/NCBI
  67. Deniaud A, Sharaf el dein O, Maillier E, Poncet D, Kroemer G, Lemaire C, et al. Endoplasmic reticulum stress induces calcium-dependent permeability transition, mitochondrial outer membrane permeabilization and apoptosis. Oncogene 2008;27(3):285-299 View Article PubMed/NCBI
  68. Bonora M, Pinton P. The mitochondrial permeability transition pore and cancer: molecular mechanisms involved in cell death. Front Oncol 2014;4:302 View Article PubMed/NCBI
  69. Saito JM, Maher JJ. Bile duct ligation in rats induces biliary expression of cytokine-induced neutrophil chemoattractant. Gastroenterology 2000;118(6):1157-1168 View Article PubMed/NCBI
  70. Gujral JS, Farhood A, Bajt ML, Jaeschke H. Neutrophils aggravate acute liver injury during obstructive cholestasis in bile duct-ligated mice. Hepatology 2003;38(2):355-363 View Article PubMed/NCBI
  71. Allen K, Jaeschke H, Copple BL. Bile acids induce inflammatory genes in hepatocytes: a novel mechanism of inflammation during obstructive cholestasis. Am J Pathol 2011;178(1):175-186 View Article PubMed/NCBI
  72. Sasaki M, Miyakoshi M, Sato Y, Nakanuma Y. Chemokine-chemokine receptor CCL2-CCR2 and CX3CL1-CX3CR1 axis may play a role in the aggravated inflammation in primary biliary cirrhosis. Dig Dis Sci 2014;59(2):358-364 View Article PubMed/NCBI
  73. El-Faramawy AA, El-Shazly LB, Abbass AA, Ismail HA. Serum IL-6 and IL-8 in infants with biliary atresia in comparison to intrahepatic cholestasis. Trop Gastroenterol 2011;32(1):50-55 View Article PubMed/NCBI
  74. Bohan A, Chen WS, Denson LA, Held MA, Boyer JL. Tumor necrosis factor alpha-dependent up-regulation of Lrh-1 and Mrp3(Abcc3) reduces liver injury in obstructive cholestasis. J Biol Chem 2003;278(38):36688-36698 View Article PubMed/NCBI
  75. Seki E, de Minicis S, Inokuchi S, Taura K, Miyai K, van Rooijen N, et al. CCR2 promotes hepatic fibrosis in mice. Hepatology 2009;50(1):185-197 View Article PubMed/NCBI
  76. O’Brien KM, Allen KM, Rockwell CE, Towery K, Luyendyk JP, Copple BL. IL-17A synergistically enhances bile acid-induced inflammation during obstructive cholestasis. Am J Pathol 2013;183(5):1498-1507 View Article PubMed/NCBI
  77. Tait SW, Green DR. Caspase-independent cell death: leaving the set without the final cut. Oncogene 2008;27(50):6452-6461 View Article PubMed/NCBI
  78. Zhang Q, Raoof M, Chen Y, Sumi Y, Sursal T, Junger W, et al. Circulating mitochondrial DAMPs cause inflammatory responses to injury. Nature 2010;464(7285):104-107 View Article PubMed/NCBI
  79. Latz E, Schoenemeyer A, Visintin A, Fitzgerald KA, Monks BG, Knetter CF, et al. TLR9 signals after translocating from the ER to CpG DNA in the lysosome. Nat Immunol 2004;5(2):190-198 View Article PubMed/NCBI
  80. Bao W, Xia H, Liang Y, Ye Y, Lu Y, Xu X, et al. Toll-like Receptor 9 Can be Activated by Endogenous Mitochondrial DNA to Induce Podocyte Apoptosis. Sci Rep 2016;6:22579 View Article PubMed/NCBI
  81. Kawai T, Akira S. Signaling to NF-kappaB by Toll-like receptors. Trends Mol Med 2007;13(11):460-469 View Article PubMed/NCBI
  82. Barber GN. Cytoplasmic DNA innate immune pathways. Immunol Rev 2011;243(1):99-108 View Article PubMed/NCBI
  83. Tsujimura H, Tamura T, Kong HJ, Nishiyama A, Ishii KJ, Klinman DM, et al. Toll-like receptor 9 signaling activates NF-kappaB through IFN regulatory factor-8/IFN consensus sequence binding protein in dendritic cells. J Immunol 2004;172(11):6820-6827 View Article PubMed/NCBI
  84. Li M, Cai SY, Boyer JL. Mechanisms of bile acid mediated inflammation in the liver. Mol Aspects Med 2017;56:45-53 View Article PubMed/NCBI
  85. Georgiev P, Jochum W, Heinrich S, Jang JH, Nocito A, Dahm F, et al. Characterization of time-related changes after experimental bile duct ligation. Br J Surg 2008;95(5):646-656 View Article PubMed/NCBI
  86. Martinon F, Pétrilli V, Mayor A, Tardivel A, Tschopp J. Gout-associated uric acid crystals activate the NALP3 inflammasome. Nature 2006;440(7081):237-241 View Article PubMed/NCBI
  87. Ross C, Chan AH, von Pein JB, Maddugoda MP, Boucher D, Schroder K. Inflammatory Caspases: Toward a Unified Model for Caspase Activation by Inflammasomes. Annu Rev Immunol 2022;40:249-269 View Article PubMed/NCBI
  88. Chen KW, Demarco B, Broz P. Pannexin-1 promotes NLRP3 activation during apoptosis but is dispensable for canonical or noncanonical inflammasome activation. Eur J Immunol 2020;50(2):170-177 View Article PubMed/NCBI
  89. Lemasters JJ. Variants of mitochondrial autophagy: Types 1 and 2 mitophagy and micromitophagy (Type 3). Redox Biol 2014;2:749-754 View Article PubMed/NCBI
  90. Sardiello M. Transcription factor EB: from master coordinator of lysosomal pathways to candidate therapeutic target in degenerative storage diseases. Ann N Y Acad Sci 2016;1371(1):3-14 View Article PubMed/NCBI
  91. Pastore N, Vainshtein A, Herz NJ, Huynh T, Brunetti L, Klisch TJ, et al. Nutrient-sensitive transcription factors TFEB and TFE3 couple autophagy and metabolism to the peripheral clock. EMBO J 2019;38(12):e101347 View Article PubMed/NCBI
  92. Ao X, Zou L, Wu Y. Regulation of autophagy by the Rab GTPase network. Cell Death Differ 2014;21(3):348-358 View Article PubMed/NCBI
  93. Schroeder B, Schulze RJ, Weller SG, Sletten AC, Casey CA, McNiven MA. The small GTPase Rab7 as a central regulator of hepatocellular lipophagy. Hepatology 2015;61(6):1896-1907 View Article PubMed/NCBI
  94. Pankiv S, Alemu EA, Brech A, Bruun JA, Lamark T, Overvatn A, et al. FYCO1 is a Rab7 effector that binds to LC3 and PI3P to mediate microtubule plus end-directed vesicle transport. J Cell Biol 2010;188(2):253-269 View Article PubMed/NCBI
  95. Byrnes K, Bailey NT, Baral K, Mercer A, Joshi S, Wahby N, et al. Impaired hepatic autophagy exacerbates hepatotoxin induced liver injury. Cell Death Discov 2023;9(1):71 View Article PubMed/NCBI
  96. Khambu B, Li T, Yan S, Yu C, Chen X, Goheen M, et al. Hepatic Autophagy Deficiency Compromises Farnesoid X Receptor Functionality and Causes Cholestatic Injury. Hepatology 2019;69(5):2196-2213 View Article PubMed/NCBI
  97. Triantos CK, Koukias NM, Nikolopoulou VN, Burroughs AK. Meta-analysis: ursodeoxycholic acid for primary sclerosing cholangitis. Aliment Pharmacol Ther 2011;34(8):901-910 View Article PubMed/NCBI
  98. Nevens F, Andreone P, Mazzella G, Strasser SI, Bowlus C, Invernizzi P, et al. A Placebo-Controlled Trial of Obeticholic Acid in Primary Biliary Cholangitis. N Engl J Med 2016;375(7):631-643 View Article PubMed/NCBI
  99. Trauner M, Fuchs CD, Halilbasic E, Paumgartner G. New therapeutic concepts in bile acid transport and signaling for management of cholestasis. Hepatology 2017;65(4):1393-1404 View Article PubMed/NCBI
  100. Santiago P, Scheinberg AR, Levy C. Cholestatic liver diseases: new targets, new therapies. Therap Adv Gastroenterol 2018;11:1756284818787400 View Article PubMed/NCBI
  101. Schmidts A, Wehrli M, Maus MV. Toward Better Understanding and Management of CAR-T Cell-Associated Toxicity. Annu Rev Med 2021;72:365-382 View Article PubMed/NCBI
  102. Le Naour J, Zitvogel L, Galluzzi L, Vacchelli E, Kroemer G. Trial watch: STING agonists in cancer therapy. Oncoimmunology 2020;9(1):1777624 View Article PubMed/NCBI
  103. Tsuda M, Moritoki Y, Lian ZX, Zhang W, Yoshida K, Wakabayashi K, et al. Biochemical and immunologic effects of rituximab in patients with primary biliary cirrhosis and an incomplete response to ursodeoxycholic acid. Hepatology 2012;55(2):512-521 View Article PubMed/NCBI
  104. Myers RP, Swain MG, Lee SS, Shaheen AA, Burak KW. B-cell depletion with rituximab in patients with primary biliary cirrhosis refractory to ursodeoxycholic acid. Am J Gastroenterol 2013;108(6):933-941 View Article PubMed/NCBI
  105. Bowlus CL, Yang GX, Liu CH, Johnson CR, Dhaliwal SS, Frank D, et al. Therapeutic trials of biologics in primary biliary cholangitis: An open label study of abatacept and review of the literature. J Autoimmun 2019;101:26-34 View Article PubMed/NCBI
  106. Bonora M, Giorgi C, Pinton P. Molecular mechanisms and consequences of mitochondrial permeability transition. Nat Rev Mol Cell Biol 2022;23(4):266-285 View Article PubMed/NCBI