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A patient's demographics often guide healthcare providers toward clues to a diagnosis. A recent travel history becomes an essential piece of the puzzle when there is a high suspicion of an infectious cause. When a patient walks into the hospital after having traveled to or from a resource-poor country with systemic afflictions, a physician's mind quickly jumps to infectious causes, and in most circumstances, it proves to be correct. We report an interesting case of a 28-year-old male from Guatemala who experienced acute gastrointestinal (GI) symptoms. Previous research in this field has shown that patients with inflammatory bowel disease (IBD) are prone to a slew of GI infections. Interestingly, our patient's presenting symptoms were initially attributed to "infections," but a thorough investigation revealed an unexpected twist of events. Our patient presented with multiple GI infections after the usual triggers, which masqueraded the coexistence of underlying primary sclerosing cholangitis and ulcerative colitis for a short course but were diagnosed promptly after a thorough workup.

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Chronic cholestasis due to heritable causes is usually diagnosed in childhood. However, many cases can present and survive into adulthood. The time course varies considerably depending on the underlying etiology. Laboratory data usually reveal elevated conjugated hyperbilirubinemia, alkaline phosphatase, and gamma-glutamyl transpeptidase. Patients may be asymptomatic; however, when present, the typical symptoms are pruritus, jaundice, fatigue, and alcoholic stools. The diagnostic methods and management required depend on the underlying etiology. The development of genome-wide associated studies has allowed the identification of specific genetic mutations related to the pathophysiology of cholestatic liver diseases. The aim of this review was to highlight the genetics, clinical pathophysiology, presentation, diagnosis, and treatment of heritable etiologies of chronic cholestatic liver disease.

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Cholestatic liver diseases (CLD) are characterized by impaired normal bile flow, culminating in excessive accumulation of toxic bile acids. The majority of patients with CLD ultimately progress to liver cirrhosis and hepatic failure, necessitating liver transplantation due to the lack of effective treatment. Recent investigations have underscored the pivotal role of the gut microbiota-bile acid axis in the progression of hepatic fibrosis via various pathways. The obstruction of bile drainage can induce gut microbiota dysbiosis and disrupt the intestinal mucosal barrier, leading to bacteria translocation. The microbial translocation activates the immune response and promotes liver fibrosis progression. The identification of therapeutic targets for modulating the gut microbiota-bile acid axis represents a promising strategy to ameliorate or perhaps reverse liver fibrosis in CLD. This review focuses on the mechanisms in the gut microbiota-bile acids axis in CLD and highlights potential therapeutic targets, aiming to lay a foundation for innovative treatment approaches.

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Cholestatic liver disease is a group of diseases in which bile acid accumulates in the liver for various reasons, resulting in abnormal liver biochemical indicators and histological damage. Cholestasis can be divided into intrahepatic cholestasis and extrahepatic cholestasis, which will contribute to liver damage and progress to liver fibrosis and cirrhosis. Primary biliary cholangitis (PBC) and primary sclerosing cholangitis are the two most typical cholestatic liver diseases. Ursodeoxycholic acid is currently the first-line treatment for PBC, while obeticholic acid, budesonide and fibrates have also shown good potential in the treatment of PBC. There are currently no official drugs approved to treat primary sclerosing cholangitis, and the use of ursodeoxycholic acid may have certain clinical benefits. At present, progress has been made in new treatment directions for cholestatic liver disease, including fibroblast growth factor 19, cholestyramine, S-adenosyl-L-methionine, steroid drugs, farnesoid X receptor agonists, and more. Considerable progress has been made in the management of cholestatic liver disease but there are still many opportunities and challenges. In this review, we summarized the recommended guidelines for the management of cholestatic disease and the progress of new drug research and development, in order to provide an important reference for the clinical practice of cholestatic liver disease.

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The erythropoietic protoporphyrias consist of three ultra-rare genetic disorders of the erythroid heme biosynthesis, including erythropoietic protoporphyria (EPP1), X-linked protoporphyria (XLEPP) and CLPX-protoporphyria (EPP2), which all lead to the accumulation of protoporphyrin IX (PPIX) in erythrocytes. Affected patients usually present from early childhood with episodes of severe phototoxic pain in the skin exposed to visible light. The quantification of PPIX in erythrocytes with a metal-free PPIX ≥3 times the upper limit of normal confirms the diagnosis. Protoporphyria-related complications include liver failure, gallstones, mild anaemia and vitamin D deficiency with reduced bone mineral density. The management is focused on preventing phototoxic reactions and treating the complications. Vitamin D should be supplemented, and DEXA scans in adults should be considered. In EPP1, even in cases of biochemically determined iron deficiency, supplementation of iron may stimulate PPIX production, resulting in an increase in photosensitivity and the risk of cholestatic liver disease. However, for patients with XLEPP, iron supplementation can reduce PPIX levels, phototoxicity and liver damage. Because of its rarity, there is little data on the management of EPP-related liver disease. As a first measure, any hepatotoxins should be eliminated. Depending on the severity of the liver disease, phlebotomies, exchange transfusions and ultimately liver transplantation with subsequent haematopoietic stem cell transplantation (HSCT) are therapeutic options, whereby multidisciplinary management including porphyria experts is mandatory. Afamelanotide, an alpha-melanocyte-stimulating hormone analogue, is currently the only approved specific treatment that increases pain-free sunlight exposure and quality of life.

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OBJECTIVES: The gut-liver axis disruption is a unified pathogenetic principle of cholestatic liver disease (CSLD). Increased gut permeability is the leading cause of gut-liver axis disruption. HO-1 is capable of protecting against gut-liver axis injury. However, it has rarely been reported whether autophagy is involved in HO-1 protecting gut-liver barrier integrity and the underlying mechanism. MATERIALS AND METHODS: Mice underwent bile duct ligation (BDL) was established as CSLD model in vivo. Caco-2 cells with LPS treatment was established as in vitro cell model. Immunofluorescence, western blot and transepithelial electrical resistance (TER) assay were used to observe epithelial tight junction (TJ) and autophagy. Liver injury and fibrosis were evaluated as well through H&E staining, masson staining, sirius red staining and ELISA. RESULTS AND CONCLUSIONS: Our study demonstrated that the epithelial TJ and TER were notably reduced both in BDL mice and in LPS treated intestinal epithelial cells. Increased HO-1 expression could significantly induce intestinal epithelial cell autophagy. Additionally, this increased autophagy level reversed the reduction effects of BDL or LPS on epithelial TJ and TER in vivo and in vitro, therefore decreased transaminase level in serum and relieved liver fibrosis in BDL mice. Besides, increased autophagy level in turn upregulated the expression of HO-1 by p62 degradation of Keap1 and subsequent activation of Nrf2 pathway. Collectively, these results indicate that HO-1 reduces gut permeability by enhancing autophagy level in CSLD, the increased autophagy establishes a HO-1-p62-Nrf2 positive feedback loop to further improve gut-liver axis disruption. Therefore, our study confirms the critical role of autophagy in HO-1 ameliorating gut-liver axis injury during CSLD, highlighting HO-1 as a promising therapeutic target.

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BACKGROUND: Farnesoid X receptor (FXR) is a vital receptor for bile acids and plays an important role in the treatment of cholestatic liver disease. In addition to traditional bile acid-based steroidal agonists, synthetic alkaloids are the most commonly reported non-steroidal FXR agonists. Sarmentol H is a nor-sesquiterpenoid obtained from Sedum sarmentosum Bunge, and in vitro screening experiments have shown that it might be related to the regulation of the FXR pathway in a previous study. PURPOSE: To investigate the therapeutic effects of sarmentol H on cholestasis and to determine whether sarmentol H directly targets FXR to mitigate cholestasis. Furthermore, this study aimed to explore the key amino acid residues involved in the binding of sarmentol H to FXR through site-directed mutagenesis. METHODS: An intrahepatic cholestasis mouse model was established to investigate the therapeutic effects of sarmentol H on cholestasis. In vitro experiments, including Co-Ip and FXR-EcRE-Luc assays, were performed to assess whether sarmentol H activates FXR by recruiting the receptor coactivator SRC1. CETSA, SIP, DARTS, and ITC were used to determine the binding of sarmentol H to FXR protein. The key amino acid residues for sarmentol H binding to FXR were analyzed by molecular docking and site-directed mutagenesis. Finally, we conducted in vivo experiments on wild-type and Fxr-/- mice to further validate the anticholestatic target of sarmentol H. RESULTS: Sarmentol H had significant ameliorative effects on the pathological conditions of cholestatic mice induced with ANIT. In vitro experiments suggested that it is capable of activating FXR and regulating downstream signaling pathways by recruiting SRC1. The target validation experiments showed that sarmentol H had the ability to bind to FXR as a ligand (KD = 2.55 µmol/L) and enhance the stability of its spatial structure. Moreover, site-directed mutagenesis revealed that THR292 and TYR365 were key binding sites for sarmentol H and FXR. Furthermore, knockout of the Fxr gene resulted in a significantly higher degree of ANIT-induced cholestatic liver injury than that in wild-type cholestatic mice, and the amelioration of cholestasis or regulatory effects on FXR downstream genes by sarmentol H also disappeared in Fxr-/- cholestatic mice. CONCLUSION: Sarmentol H is an FXR agonist. This is the first study to show that it exerts a significant therapeutic effect on cholestatic mice, and can directly bind to FXR and activate it by recruiting the coactivator SRC1.

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Impaired formation of the biliary network can lead to congenital cholestatic liver diseases; however, the genes responsible for proper biliary system formation and maintenance have not been fully identified. Combining computational network structure analysis algorithms with a zebrafish forward genetic screen, we identified 24 new zebrafish mutants that display impaired intrahepatic biliary network formation. Complementation tests suggested these 24 mutations affect 24 different genes. We applied unsupervised clustering algorithms to unbiasedly classify the recovered mutants into three classes. Further computational analysis revealed that each of the recovered mutations in these three classes has a unique phenotype on node-subtype composition and distribution within the intrahepatic biliary network. In addition, we found most of the recovered mutations are viable. In those mutant fish, which are already good animal models to study chronic cholestatic liver diseases, the biliary network phenotypes persist into adulthood. Altogether, this study provides unique genetic and computational toolsets that advance our understanding of the molecular pathways leading to biliary system malformation and cholestatic liver diseases.

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BACKGROUND AND OBJECTIVES: The impact of dominant stricture (DS) on the outcomes of paediatric-onset primary sclerosing cholangitis (PSC) is unknown. This study was aimed at investigating the impact of DS on the clinical course and prognosis of patients with paediatric-onset PSC. METHODS: Patients with paediatric-onset PSC diagnosed between January 1993 and May 2017 were identified from hospital records or our PSC registry. Data including clinical, laboratory, cholangiography, and cytology at diagnosis and during follow-up (until July 2023) were reviewed. We graphed the Kaplan-Meier failure function and fitted crude and multivariable Cox model to calculate hazard ratios (HR) and 95% confidence intervals (CI) for selected variables. In these analyses, DS was treated as a time-varying variable. RESULTS: We identified 68 patients (42 males) with paediatric-onset PSC (median age at diagnosis 15 years). The median follow-up was 13 years and the median age at the last follow-up was 27 years. In total, 35 (51%) had concomitant autoimmune hepatitis. DS was diagnosed in 33 patients (48%): in eight at the time of PSC diagnosis (12%) and in 25 (37%) by the end of follow-up. In patients with DS, two developed cirrhosis, seven were transplanted and one patient was operated for a biliary mass with low-grade dysplasia. In patients without a DS, two developed cirrhosis, and four were transplanted; one female was excluded from survival analysis because she already had cirrhosis at the time of PSC diagnosis. Cirrhosis or biliary dysplasia or needing liver transplantation for these indications were more frequent after the development of DS (10/33, adjusted HR 4.26, 95%CI: 1.26-14.4). No cholangiocarcinomas or deaths occurred during the follow-up. CONCLUSIONS: DS was present at diagnosis or developed during follow-up in about half of the patients with paediatric-onset PSC and was associated with impaired outcome.

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Background: Previous studies have suggested that the gut microbiota (GM) is closely associated with the development of autoimmune cholestatic liver disease (ACLD), but limitations, such as the presence of confounding factors, have resulted in a causal relationship between the gut microbiota and autoimmune cholestatic liver disease that remains uncertain. Thus, we used two-sample Mendelian randomization as a research method to explore the causal relationship between the two. Methods: Pooled statistics of gut microbiota from a meta-analysis of genome-wide association studies conducted by the MiBioGen consortium were used as an instrumental variable for exposure factors. The Pooled statistics for primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) were obtained from the R9 version of the FinnGen database (https://r9.finngen.fi/). Inverse-variance Weighted (IVW), cML-MA, MR-Egger regression, Weighted median (WME), Weighted mode (WM), and Simple mode (SM) were used to detect the association between intestinal flora and the causal relationship between intestinal flora and ACLD, in which IVW method was dominant, was assessed based on the effect indicator dominance ratio (odds ratio, OR) and 95% confidence interval (CI). Sensitivity analysis, heterogeneity test, gene pleiotropy test, MR pleiotropy residual sum and outlier test (MR-PRESSO) were combined to verify the stability and reliability of the results. Reverse Mendelian randomization analysis was performed on gut microbiota and found to be causally associated with ACLD. Results: The IVW results showed that the relative abundance of the genus Clostridium innocuum group, genus Butyricicoccus, and genus Erysipelatoclostridium was negatively correlated with the risk of PBC, that is, increased abundance reduced the risk of PBC and was a protective, and the relative abundance of the genus Eubacterium hallii was positively correlated with the risk of PSC, which is a risk factor for PSC. Family Clostridiaceae1 and family Lachnospiraceae were negatively correlated with the risk of PSC, which is a protective factor for PSC. Conclusion: This study found a causal relationship between gut microbiota and ACLD. This may provide valuable insights into gut microbiota-mediated pathogenesis of ACLD. It is necessary to conduct a large-sample randomized controlled trial (RCT) at a later stage to validate the associated role of the relevant gut microbiota in the risk of ACLD development and to explore the associated mechanisms.

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BACKGROUND: ABCB4 gene-related cholestatic liver diseases have a wide spectrum of clinical and genetic variations. The correlation between genotype and clinical phenotype still unclear. This study retrospectively analyzed the clinical and pathological characteristics of 23 patients with ABCB4 gene-related cholestatic liver diseases. Next-generation sequencing was used to identify the genetic causes. RESULTS: The 23 included patients (15 children and 8 adults) were diagnosed as progressive familial intrahepatic cholestasis type 3 (PFIC3), drug-induced liver injury (DILI), cirrhosis cholestasis, cirrhosis, and mild liver fibrosis. Nineteen patients underwent liver pathological examination of the liver, exhibiting fibrosis, small bile duct hyperplasia, CK7(+), Cu(+), bile duct deletion, and cirrhosis. Thirty ABCB4 variants were identified, including 18 novel variants. CONCLUSION: ABCB4 gene-related cholestatic liver diseases have a wide spectrum of clinical and genetic variations. Biallelic ABCB4 mutation carriers tended to severe PFIC3, which mostly occurs in children; while ABCB4 non-biallelic variants can lead to milder ICP, LACP, DILI or overlapping, mostly in adults. Thus, the ABCB4 genotype has a specific correlation with the phenotype, but there are exceptions. Non-biallelic null mutations can cause severe diseases. The mechanisms underlying this genetic phenotype require further investigation.

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Current therapy for hepatic injury induced by the accumulation of bile acids is limited. Leucine-rich repeat G protein-coupled receptor 4 (LGR4), also known as GPR48, is critical for cytoprotection and cell proliferation. Here, we reported a novel function for the LGR4 in cholestatic liver injury. In the bile duct ligation (BDL)-induced liver injury model, hepatic LGR4 expression was significantly downregulated. Deficiency of LGR4 in hepatocytes (Lgr4LKO) notably decreased BDL-induced liver injury measured by hepatic necrosis, fibrosis, and circulating liver enzymes and total bilirubin. Levels of total bile acids in plasma and liver were markedly reduced in these mice. However, deficiency of LGR4 in macrophages (Lyz2-Lgr4MKO) demonstrated no significant effect on liver injury induced by BDL. Deficiency of LGR4 in hepatocytes significantly attenuated S1PR2 and the phosphorylation of protein kinase B (AKT) induced by BDL. Recombinant Rspo1 and Rspo3 potentiated the taurocholic acid (TCA)-induced upregulation in S1PR2 and phosphorylation of AKT in hepatocytes. Inhibition of S1PR2-AKT signaling by specific AKT or S1PR2 inhibitors blocked the increase of bile acid secretion induced by Rspo1/3 in hepatocytes. Our studies indicate that the R-spondins (Rspos)-LGR4 signaling in hepatocytes aggravates the cholestatic liver injury by potentiating the production of bile acids in a S1PR2-AKT-dependent manner.NEW & NOTEWORTHY Deficiency of LGR4 in hepatocytes alleviates BDL-induced liver injury. LGR4 in macrophages demonstrates no effect on BDL-induced liver injury. Rspos-LGR4 increases bile acid synthesis and transport via potentiating S1PR2-AKT signaling in hepatocytes.

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Cholestatic liver diseases in children often have an underlying genetic defect. Genetic testing by next-generation sequencing has become a crucial part of the diagnostic armamentarium in such clinical scenarios. Here, we report three children who presented with early-onset cholestatic jaundice and pruritus. All of them had low gamma-glutamyl transferase and high serum bile acid levels. Symptoms were alleviated with ursodeoxycholic acid and cholestyramine in all 3 children with normal LFT at follow-up. They were detected to have novel pathogenic USP53 mutations (2 homozygous, 1 compound heterozygous) on next-generation sequencing which have previously not been reported.

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BACKGROUND: Aetiological therapy improves liver function and may enable hepatic recompensation in decompensated cirrhosis. AIMS: We explored the potential for recompensation in patients with decompensated primary biliary cholangitis (PBC) - considering a biochemical response to ursodeoxycholic acid (UDCA) according to Paris-II criteria as a surrogate for successful aetiological treatment. METHODS: Patients with PBC were retrospectively included at the time of first decompensation. Recompensation was defined as (i) resolution of ascites and hepatic encephalopathy (HE) despite discontinuation of diuretic/HE therapy, (ii) absence of variceal bleeding and (iii) sustained liver function improvement. RESULTS: In total, 42 patients with PBC with decompensated cirrhosis (age: 63.5 [IQR: 51.9-69.2] years; 88.1% female; MELD-Na: 13.5 [IQR: 11.0-15.0]) were included and followed for 41.9 (IQR: 11.0-70.9) months after decompensation. Seven patients (16.7%) achieved recompensation. Lower MELD-Na (subdistribution hazard ratio [SHR]: 0.90; p = 0.047), bilirubin (SHR per mg/dL: 0.44; p = 0.005) and alkaline phosphatase (SHR per 10 U/L: 0.67; p = 0.001) at decompensation, as well as variceal bleeding as decompensating event (SHR: 4.37; p = 0.069), were linked to a higher probability of recompensation. Overall, 33 patients were treated with UDCA for ≥1 year and 12 (36%) achieved Paris-II response criteria. Recompensation occurred in 5/12 (41.7%) and in 2/21 (9.5%) patients with vs. without UDCA response at 1 year, respectively. Recompensation was linked to a numerically improved transplant-free survival (HR: 0.46; p = 0.335). Nonetheless, 4/7 recompensated patients presented with liver-related complications after developing hepatic malignancy and/or portal vein thrombosis and 2 eventually died. CONCLUSIONS: Patients with PBC and decompensated cirrhosis may achieve hepatic recompensation under UDCA therapy. However, since liver-related complications still occur after recompensation, patients should remain under close follow-up.

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BACKGROUND AND AIMS: The risk of intrahepatic cholestasis of pregnancy [ICP] is increased in thiopurine-exposed pregnancies. Thiopurine 'shunting', with a 6-methylmercaptopurine [MMP] to 6-thioguanine [TGN] ratio of >11, progresses over pregnancy, and may promote ICP development. We aimed to explore the association between thiopurine exposure and ICP, including the hypothesised impact of thiopurine shunting, and identify risk minimisation strategies. METHODS: This prospective multicentre cohort study compared thiopurine and biologic monotherapy-exposed pregnant participants. Disease activity and obstetric outcome data, thiopurine metabolites, bile acids, and transaminases were obtained before conception, in each trimester, at delivery, and postpartum. Thiopurine dose management was at the discretion of the treating physician. RESULTS: Included were 131 thiopurine and 147 biologic monotherapy-exposed pregnancies. MMP/TGN ratio increased from preconception to third trimester [p <0.01], with approximately 25% of participants shunting in pregnancy. Second trimester split dosing led to a decrease in the median MMP/TGN ratio from 18 (interquartile range [IQR] 6-57) to 3 [IQR 2-3.5] at delivery [p = 0.04]. The risk of ICP was increased in thiopurine-exposed pregnancies (6.7% [7/105] vs 0% [0/112], p <0.001), with all ICP cases occurring in the setting of antenatal thiopurine shunting. Thiopurine dose increases (risk ratio [RR] 8.10, 95% confidence interval [CI] 1.88-34.85, p = 0.005) and shunting in third trimester [6.20, 1.21-30.73, p = 0.028] and at delivery [14.18, 1.62-123.9, p = 0.016] were associated with an increased risk of ICP. CONCLUSIONS: Thiopurine exposure is associated with an increased risk of ICP, particularly following dose increases antenatally and with shunting in late pregnancy. The latter may be effectively managed with split dosing, although further studies are warranted.

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Aims: The objective of this study is to examine the impact of inhibiting Sphingosine 1-phosphate receptor 2 (S1PR2) on liver inflammation, fibrogenesis, and changes of gut microbiome in the context of cholestasis-induced conditions. Methods: The cholestatic liver injury model was developed by common bile duct ligation (CBDL). Sprague-Dawley rats were randomly allocated to three groups, sham operation, CBDL group and JTE-013 treated CBDL group. Biochemical and histological assessments were conducted to investigate the influence of S1PR2 on the modulation of fibrogenic factors and inflammatory infiltration. We conducted an analysis of the fecal microbiome by using 16S rRNA sequencing. Serum bile acid composition was evaluated through the utilization of liquid chromatography-mass spectrometry techniques. Results: In the BDL rat model, the study findings revealed a significant increase in serum levels of conjugated bile acids, accompanied by an overexpression of S1PR2. Treatment with the specific inhibitor of S1PR2, known as JTE-013, resulted in a range of specific effects on the BDL rats. These effects included the improvement of liver function, reduction of liver inflammation, inhibition of hepatocyte apoptosis, and suppression of NETosis. These effects are likely mediated through the TCA/S1PR2/NOX2/NLRP3 pathway. Furthermore, the administration of JTE-013 resulted in an augmentation of the diversity of the bacterial community's diversity, facilitating the proliferation of advantageous species while concurrently inhibiting the prevalence of detrimental bacteria. Conclusions: The results of our study suggest that the administration of JTE-013 may have a beneficial effect in alleviating cholestatic liver disease and restoring the balance of intestinal flora.

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Farnesoid X receptor (FXR) was considered as a promising drug target in the treatment of cholestasis, drug-induced liver injury, and non-alcoholic steatohepatitis (NASH). However, the existing FXR agonists have shown different degrees of side effects in clinical trials without clear interpretation. MET-409 in clinical phase Ⅲ, has been proven significantly fewer side effects than that of other FXR agonists. This may be due to the completely different structure of FEX and other non-steroidal FXR agonists. Herein, the structure-based drug design was carried out based on FEX, and the more active FXR agonist LH10 (FEX EC50 = 0,3 µM; LH10 EC50 = 0.14 µM)) was screened out by the comprehensive SAR studies. Furthermore, LH10 exhibited robust hepatoprotective activity on the ANIT-induced cholestatic model and APAP-induced acute liver injury model, which was even better than positive control OCA. In the nonalcoholic steatohepatitis (NASH) model, LH10 significantly improved the pathological characteristics of NASH by regulating several major pathways including lipid metabolism, inflammation, oxidative stress, and fibrosis. With the above attractive results, LH10 is worthy of further evaluation as a novel agent for the treatment of liver disorders.

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BACKGROUND AND AIMS: There is a lack of biliary epithelial molecular markers for primary sclerosing cholangitis (PSC). We analyzed candidates from disease susceptibility genes identified in recent genome-wide association studies (GWAS). METHODS: Expression levels of GWAS genes were analyzed in archival liver tissues of patients with PSC and controls. Immunohistochemical analysis was performed to evaluate expression levels in the biliary epithelia of PSC (N = 45) and controls (N = 12). Samples from patients with primary biliary cholangitis (PBC) were used as disease controls (N = 20). RESULTS: Hepatic expression levels of ATXN2, HHEX, PRDX5, MST1, and TNFRSF14 were significantly altered in the PSC group. We focused on the immune-related receptor, TNFRSF14. Immunohistochemistry revealed that high expression of TNFRSF14 in biliary epithelial cells was observed only in the PSC group. In addition, the expression of LIGHT, which encodes a TNFRSF14-activating ligand, was increased in PSC liver. Immunohistochemistry showed that high expression of LIGHT was more common in PSC biliary epithelia (53%) than in the PBC (15%) or control (0%) groups; moreover, it was positively associated with fibrotic progression, although it was not an independent prognostic factor. CONCLUSIONS: TNFRSF14 and LIGHT are promising candidate markers for PSC.

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Ursodeoxycholic acid (UDCA) is a natural substance physiologically produced in the liver. Initially used to dissolve gallstones, it is now successfully used in treating primary biliary cirrhosis and as adjuvant therapy for various hepatobiliary cholestatic diseases. However, the mechanisms underlying its beneficial effects still need to be clarified. Evidence suggests three mechanisms of action for UDCA that could benefit humans with cholestatic liver disease (CLD): protection of cholangiocytes against hydrophobic bile acid (BA) cytotoxicity, stimulation of hepatobiliary excretion, and protection of hepatocytes against BA-induced apoptosis. These mechanisms may act individually or together to potentiate them. At the molecular level, it has been observed that UDCA can generate modifications in the transcription and translation of proteins essential in the transport of BA, correcting the deficit in BA secretion in CLD, in addition to activating signaling pathways to translocate these transporters to the sites where they should fulfill their function. Inhibition of BA-induced hepatocyte apoptosis may play a role in CLD, characterized by BA retention in the hepatocyte. Thus, different mechanisms of action contribute to the improvement after UDCA administration in CLD. On the other hand, the effects of UDCA on tissues that possess receptors that may interact with BAs in pathological contexts, such as skeletal muscle, are still unclear. This work aims to describe the main molecular mechanisms by which UDCA acts in the human body, emphasizing the interaction in tissues other than the liver.

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