The pathogenesis, models and therapeutic advances of primary biliary cholangitis

Innate lymphoid cell subsets in the pathogenesis of primary biliary cholangitis

BACKGROUND AND AIM

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by destructive lymphocytic cholangitis and specific anti-mitochondrial antibodies. Innate lymphoid cells (ILCs) have been reported to play a role in liver homeostasis and autoimmunity.

METHODS

We evaluated the features of peripheral ILC1s and ILC3 in patients with PBC and hepatic ILC1 and ILC3 in two different PBC mouse models (dominant-negative transforming growth factor-beta receptor II [dnTGFβRII] and 2-octynoic acid-bovine serum albumin [2OA-BSA]).

RESULTS

A total of 115 patients and 18 healthy controls were enrolled in the study. Decreased circulating ILC1/3s were observed in early-stage PBC patients, and the numbers of ILC1/3s were negatively correlated with specific parameters and the proportion of T-helper (Th) 1 and Th17 cells. Reduced numbers of ILC1s were observed in PBC mouse models with different etiologies. ILC1-deficient mice had more severe hepatic inflammation after inducing the 2OA-BSA model. Continuous low-dose injections of lipopolysaccharide (LPS) reduced ILC1 levels in mice, consistent with the lower level of ILC1s in PBC patients with high LPS (> 50 ng/mL), and aggravated hepatic lymphocyte infiltration.

CONCLUSION

Patients with PBC had decreased ILC1s, which were negatively correlated with CD4+ T cells. Deficient ILC1 populations led to disease exacerbations in mice. Our results indicated that ILC1s may participate in the pathogenesis of PBC.

ELMO1 regulates macrophage directed migration and attenuates inflammation via NF-κB signaling pathway in primary biliary cholangitis

BACKGROUND & AIMS

Primary biliary cholangitis (PBC), a typical autoimmune liver disease, is characterized by an increased infiltration of immune cells. However, the specific molecular mechanisms regulating immune cell migration in PBC are unknown. Engulfment and cell motility 1 (ELMO1) plays an important function in cellular dynamics. In view of this, the aim of this study was to explore the expression of ELMO1 in PBC, its effects on the proliferation, migration, and secretion of inflammatory factors by the mainly regulated immune cells and the specific molecular mechanisms behind it.

METHODS

To determine the expression of ELMO1 in PBC and its major regulatory immune cells in PBC. The migratory and proliferative capacities of ELMO1-deficient macrophages were measured, and their pro-inflammatory cytokine secretion was also detected and explored mechanistically.

RESULTS

ELMO1 expression was up-regulated in the PBC patients and positively correlated with alkaline phosphatase (ALP). ELMO1 mainly regulated macrophages in the liver of PBC patients. Knockdown of ELMO1 did not affect macrophage proliferation, however,knockdown of ELMO1 significantly inhibited macrophage migration,downstream RAC1 activity was diminished, and reduced F-actin synthesis. Knockdown of ELMO1 reduced macrophage inflammatory factor secretion and NF-κB signaling pathway activity was decreased.

CONCLUSIONS

ELMO1 regulates macrophage directed migration and attenuates inflammation via NF-κB signaling pathway in primary biliary cholangitis.

Causal relationship between primary biliary cholangitis and inflammatory bowel disease: a Mendelian randomization study

Background

Several studies indicated that inflammatory bowel disease (IBD) may contribute to increased susceptibility to primary biliary cholangitis (PBC). However, the causal relationship between IBD and PBC remains unclear.

Methods

The genetic variant data of patients with IBD and PBC were obtained from published genome-wide association studies (GWASs). The IBD data were further divided into a discovery dataset and a validation dataset depending on the data source. We conducted a two-sample Mendelian randomization (MR) analysis using the inverse variance weighting (IVW), MR-Egger, weighted median (WM), MR robust adjusted profile score (MR-RAPS), and maximum likelihood (ML) methods, with IVW being the main focus, to verify the causal relationship between IBD and PBC. Additionally, a series of sensitivity analyses were performed to ensure the reliability of the results.

Results

In the discovery cohort, the IVW analysis results (OR = 1.114, P = 0.011) indicated a significant association between IBD and PBC. The MR-RAPS (OR = 1.130, P = 0.007) and ML (OR = 1.115, P = 0.011) analyses yielded results consistent with those of IVW in confirming IBD as a risk factor for PBC. In the validation cohort, consistent findings were observed regarding the causal relationship between IBD and PBC using IVW, MR-RAPS, and ML analyses; all three methods identified IBD as a risk factor for developing PBC. By the IVW analysis, Crohn's disease (CD) emerged as the most prominent subtype of IBD associated with an increased risk of developing PBC in both the discovery cohort (OR = 1.068, P = 0.049) and the validation cohort (OR = 1.082, P = 0.019).

Conclusion

The results of the MR analysis suggest a causal relationship between IBD and PBC, highlighting the necessity for proactive PBC prevention in patients with IBD, particularly those with CD.

Peripheral helper T cells in human diseases

Peripheral helper T cells (Tph) are a specialized subset of CD4+ T cells with the ability to help B cells and induce antibody production. Although usually located in ectopic lymphoid-like structures (ELS), inside the peripheral blood, Tph cells can also be identified. The aberrant proliferation and functions of Tph cells are commonly found in the patients with disease. In this review, first we will summarize the biological characteristics of Tph cells, such as the expression of surface molecules, transcription factors and cytokines, and discuss its B cell help functions. Tph cells also have roles in a wide range of human diseases, including autoimmune diseases, infectious diseases, malignancies etc. Therefore, there is a strong interest in targeting Tph cells to improve treat strategies of human diseases.

Exploring Advanced Therapies for Primary Biliary Cholangitis: Insights from the Gut Microbiota-Bile Acid-Immunity Network

Primary biliary cholangitis (PBC) is a cholestatic liver disease characterized by immune-mediated injury to small bile ducts. Although PBC is an autoimmune disease, the effectiveness of conventional immunosuppressive therapy is disappointing. Nearly 40% of PBC patients do not respond to the first-line drug UDCA. Without appropriate intervention, PBC patients eventually progress to liver cirrhosis and even death. There is an urgent need to develop new therapies. The gut-liver axis emphasizes the interconnection between the gut and the liver, and evidence is increasing that gut microbiota and bile acids play an important role in the pathogenesis of cholestatic diseases. Dysbiosis of gut microbiota, imbalance of bile acids, and immune-mediated bile duct injury constitute the triad of pathophysiology in PBC. Autoimmune cholangitis has the potential to be improved through immune system modulation. Considering the failure of conventional immunotherapies and the involvement of gut microbiota and bile acids in the pathogenesis, targeting immune factors associated with them, such as bile acid receptors, microbial-derived molecules, and related specific immune cells, may offer breakthroughs. Understanding the gut microbiota-bile acid network and related immune dysfunctions in PBC provides a new perspective on therapeutic strategies. Therefore, we summarize the latest advances in research of gut microbiota and bile acids in PBC and, for the first time, explore the possibility of related immune factors as novel immunotherapy targets. This article discusses potential therapeutic approaches focusing on regulating gut microbiota, maintaining bile acid homeostasis, their interactions, and related immune factors.

Elucidation of pericholangitis and periductal fibrosis in cholestatic liver diseases via extracellular vesicles released by polarized biliary epithelial cells

Cholestatic liver diseases causes inflammation and fibrosis around bile ducts. However, the pathological mechanism has not been elucidated. Extracellular vesicles (EVs) are released from both the basolateral and apical sides of polarized biliary epithelial cells. We aimed to investigate the possibility that EVs released from the basolateral sides of biliary epithelial cells by bile acid stimulation induce inflammatory cells and fibrosis around bile ducts, and they may be involved in the pathogenesis of cholestatic liver disease. Human biliary epithelial cells (H69) were grown on cell culture inserts and stimulated with chenodeoxycholic acid + IFN-γ. Human THP-1-derived M1-macrophages, LX-2 cells, and KMST-6 cells were treated with the extracted basolateral EVs, and inflammatory cytokines and fibrosis markers were detected by RT-PCR. Highly expressed proteins from stimulated EVs were identified, and M1-macrophages, LX-2, KMST-6 were treated with these recombinant proteins. Stimulated EVs increased the expression of TNF, IL-1β, and IL-6 in M1-macrophages, TGF-β in LX-2 and KMST-6 compared with the corresponding expression levels in unstimulated EVs. Nucleophosmin, nucleolin, and midkine levels were increased in EVs from stimulated cells compared with protein expression in EVs from unstimulated cells. Leukocyte cell-derived chemotaxin-2 (LECT2) is highly expressed only in EVs from stimulated cells. Stimulation of M1-macrophages with recombinant nucleophosmin, nucleolin, and midkine significantly increased the expression of inflammatory cytokines. Stimulation of LX-2 and KMST-6 with recombinant LECT2 significantly increased the expression of fibrotic markers. These results suggest that basolateral EVs are related to the development of pericholangitis and periductal fibrosis in cholestatic liver diseases.NEW & NOTEWORTHY Our research elucidated that the composition of basolateral EVs from the biliary epithelial cells changed under bile acid exposure and the basolateral EVs contained the novel inflammation-inducing proteins NPM, NCL, and MK and the fibrosis-inducing protein LECT2. We report that these new results are possible to lead to the potential therapeutic target of cholestatic liver diseases in the future.

Efficacy and Safety of Elafibranor in Primary Biliary Cholangitis

BACKGROUND

Primary biliary cholangitis is a rare, chronic cholestatic liver disease characterized by the destruction of interlobular bile ducts, leading to cholestasis and liver fibrosis. Whether elafibranor, an oral, dual peroxisome proliferator-activated receptor (PPAR) α and δ agonist, may have benefit as a treatment for primary biliary cholangitis is unknown.

METHODS

In this multinational, phase 3, double-blind, placebo-controlled trial, we randomly assigned (in a 2:1 ratio) patients with primary biliary cholangitis who had had an inadequate response to or unacceptable side effects with ursodeoxycholic acid to receive once-daily elafibranor, at a dose of 80 mg, or placebo. The primary end point was a biochemical response (defined as an alkaline phosphatase level of <1.67 times the upper limit of the normal range, with a reduction of ≥15% from baseline, and normal total bilirubin levels) at week 52. Key secondary end points were normalization of the alkaline phosphatase level at week 52 and a change in pruritus intensity from baseline through week 52 and through week 24, as measured on the Worst Itch Numeric Rating Scale (WI-NRS; scores range from 0 [no itch] to 10 [worst itch imaginable]).

RESULTS

A total of 161 patients underwent randomization. A biochemical response (the primary end point) was observed in 51% of the patients (55 of 108) who received elafibranor and in 4% (2 of 53) who received placebo, for a difference of 47 percentage points (95% confidence interval [CI], 32 to 57; P<0.001). The alkaline phosphatase level normalized in 15% of the patients in the elafibranor group and in none of the patients in the placebo group at week 52 (difference, 15 percentage points; 95% CI, 6 to 23; P = 0.002). Among patients who had moderate-to-severe pruritus (44 patients in the elafibranor group and 22 in the placebo group), the least-squares mean change from baseline through week 52 on the WI-NRS did not differ significantly between the groups (-1.93 vs. -1.15; difference, -0.78; 95% CI, -1.99 to 0.42; P = 0.20). Adverse events that occurred more frequently with elafibranor than with placebo included abdominal pain, diarrhea, nausea, and vomiting.

CONCLUSIONS

Treatment with elafibranor resulted in significantly greater improvements in relevant biochemical indicators of cholestasis than placebo. (Funded by GENFIT and Ipsen; ELATIVE ClinicalTrials.gov number, NCT04526665.).

The effects of low-dose IL-2 on Th17/Treg cell imbalance in primary biliary cholangitis mouse models

BACKGROUND/AIMS

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease. The imbalance of Th17/Treg cells has been reported in PBC patients. Low-dose IL-2 can alleviate disease severity through modulating CD4 + T cell subsets in patients with autoimmune diseases. Hence, the present study aimed to examine the effects and mechanism of low-dose IL-2 in PBC mouse models.

METHODS

PBC models were induced in female C57BL/6 mice by two immunizations with 2OA-BSA at two-week intervals, and poly I: C every three days. PBC mouse models were divided into the IL-2 treated and untreated groups and low-dose IL-2 was injected at three different time points. Th17 and Tregs were analyzed by flow cytometry, and the related cytokines were analyzed by ELISA. Liver histopathology was examined by H&E and immunohistochemical staining.

RESULTS

Twelve weeks after modeling, the serum AMA was positive and the ALP was significantly increased in PBC mouse models (P<0.05). The pathology showed lymphocyte infiltration in the portal area, damage, and reactive proliferation of the small bile duct (P<0.05). The flow cytometric showed the imbalance of Th17/Treg cells in the liver of PBC mouse models, with decreased Treg cells, increased Th17 cells, and Th17/Treg ratio (P < 0.05). After the low-dose IL-2 intervention, biochemical index and liver pathologies showed improvement at 12 weeks. Besides, the imbalance of Th17 and Treg cells recovered. Public database mining showed that Th17 cell differentiation may contribute to poor response in PBC patients.

CONCLUSION

Low-dose IL-2 can significantly improve liver biochemistry and pathology by reversing the imbalance of Th17 and Treg cells, suggesting that it may be a potential therapeutic target for PBC.

Expression of RNautophagy/DNautophagy-related genes is regulated under control of an innate immune receptor

Double-stranded RNA (dsRNA) is a molecular pattern uniquely produced in cells infected with various viruses as a product or byproduct of replication. Cells detect such molecules, which indicate non-self invasion, and induce diverse immune responses to eliminate them. The degradation of virus-derived molecules can also play a role in the removal of pathogens and suppression of their replication. RNautophagy and DNautophagy are cellular degradative pathways in which RNA and DNA are directly imported into a hydrolytic organelle, the lysosome. Two lysosomal membrane proteins, SIDT2 and LAMP2C, mediate nucleic acid uptake via this pathway. Here, we showed that the expression of both SIDT2 and LAMP2C is selectively upregulated during the intracellular detection of poly(I:C), a synthetic analog of dsRNA that mimics viral infection. The upregulation of these two gene products upon poly(I:C) introduction was transient and synchronized. We also observed that the induction of SIDT2 and LAMP2C expression by poly(I:C) was dependent on MDA5, a cytoplasmic innate immune receptor that directly recognizes poly(I:C) and induces various antiviral responses. Finally, we showed that lysosomes can target viral RNA for degradation via RNautophagy and may suppress viral replication. Our results revealed a novel degradative pathway in cells as a downstream component of the innate immune response and provided evidence suggesting that the degradation of viral nucleic acids via RNautophagy/DNautophagy contributes to the suppression of viral replication.

Hirsutella sinensis mycelium polysaccharides attenuate the TGF-β1-induced epithelial-mesenchymal transition in human intrahepatic bile duct epithelial cells

Hirsutella sinensis is the anamorph of Ophiocordyceps sinensis, and its mycelia has been used to effectively treat a variety of hepatobiliary diseases in clinical practice. In the present study, we performed a systematic study on the composition and structure of its polysaccharides, and then employed a TGF-β1-induced human intrahepatic bile duct epithelial cell-epithelial-mesenchymal transition (HIBEC-EMT) model to investigate their effects on treating primary biliary cholangitis (PBC) based on hepatic bile duct fibrosis. Four polysaccharide fractions were obtained from H. sinensis mycelia by hot-water extraction, DEAE-cellulose column and gradient ethanol precipitation separation. HSWP-1a was an α-(1,4)-D-glucan; HSWP-1b and HSWP-1d mainly consisted of mannoglucans with a backbone composed of 1,4-linked α-D-Glcp and 1,4,6-linked α-D-Manp residues branched at O-6 of the 1,4-linked α-D-Glcp with a 1-linked α-D-Glcp as a side chain; and HSWP-1c mainly contained galactomannoglucans. These polysaccharide fractions protected HIBECs from a TGF-β1-induced EMT, according to HIBEC morphological changes, cell viability, decreased E-cadherin and ZO-1 expression, and increased vimentin and collagen I expression. Furthermore, the effects of the polysaccharides might be mediated by inhibiting the activation of the TGF-β/Smad signaling pathway, which attenuated hepatic bile duct fibrosis and potential PBC effects.

A case report of primary biliary cholangitis combined with ankylosing spondylitis

RATIONALE

A chronic autoimmune liver disease known as primary biliary cholangitis (PBC) that selectively destructs small intrahepatic biliary epithelial cells and may result in biliary cirrhosis and eventually liver transplantation or death. PBC is associated with various other extrahepatic autoimmune diseases; however, the combination of PBC with ankylosing spondylitis has been rarely reported in the literature. Here, we reported a case of PBC with ankylosing spondylitis to improve our understanding of such coexistence and provide new ideas for the treatment of such patients.

PATIENT CONCERNS

A 54-year-old man was presented to the Department of Rheumatology because of an abnormal liver function test for 7 years, chest and back pain for 1 year, and low back pain for 2 months.

DIAGNOSES

Primary biliary cholangitis, ankylosing spondylitis, and old pulmonary tuberculosis.

INTERVENTIONS

The patient refused to use nonsteroidal anti-inflammatory drugs, conventional synthetic disease-modifying antirheumatic drugs, and biologic disease-modifying antirheumatic drugs; thus, he was treated with methylenediphosphonate (99Tc-MDP) and ursodeoxycholic acid (UDCA).

OUTCOMES

The patient achieved remission with UDCA and 99Tc-MDP therapy.

LESSONS

In the treatment of PBC combined with other disorders, the characteristics of different diseases should be considered. The patient reported herein was treated with 99Tc-MDP and UDCA, and his condition improved; thus, we consider 99Tc-MDP to be an effective treatment. Furthermore, in line with the current understanding of the pathogenesis of PBC and ankylosing spondylitis, we hypothesize that interleukin-17 inhibitor is an effective treatment for such patients.

Sequence of events leading to primary biliary cholangitis

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease that is observed more frequently in middle-aged women. This disorder is considered an autoimmune disease, since liver injury is sustained by the presence of self-directed antimitochondrial antibodies targeting the bile duct cells. The prognosis may vary depending on an early diagnosis and response to therapy. However, nearly a third of patients can progress to liver cirrhosis, thus requiring a liver transplant. Traditional immunosuppressive therapies, commonly employed for other autoimmune diseases, have limited effects on PBC. In fact, dramatic functional changes that occur in the biliary epithelium in the course of inflammation play a major role in perpetuating the injury. In this minireview, after a background on the disease and possible predisposing factors, the sequential cooperation of cellular/molecular events leading to end-stage PBC is discussed in detail. The rise and maintenance of the autoimmune process, as well as the response of the biliary epithelia during inflammatory injury, are key factors in the progression of the disease. The so-called "ductular reaction (DR)", intended as a reactive expansion of cells with biliary phenotype, is a process frequently observed in PBC and partially understood. However, recent findings suggest a strict relationship between this pathological picture and the progression to liver fibrosis, cell senescence, and loss of biliary ducts. All these issues (onset of chronic inflammation, changes in secretive and proliferative biliary functions, DR, and its relationship with other pathological events) are discussed in this manuscript in an attempt to provide a snapshot, for clinicians and researchers, of the most relevant and sequential contributors to the progression of this human cholestatic disease. We believe that interpreting this disorder as a multistep process may help identify possible therapeutic targets to prevent evolution to severe disease.

The causal effects of inflammatory bowel disease on primary biliary cholangitis: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Observational studies have indicated that the incidence of primary biliary cholangitis (PBC) is higher in inflammatory bowel disease (IBD) patients than that in healthy people. However, whether the correlation is causal remains unclear.

METHODS

The genetic associations with IBD were obtained from publicly available genome-wide association studies (GWAS) of European ancestry with 31 665 cases and 33 977 controls, consisting of 17 897 Crohn's disease (CD) and 13 768 ulcerative colitis (UC) cases. The genetic associations with PBC were obtained from a European GWAS with 2764 cases and 10 475 controls. A bidirectional two-sample Mendelian randomization (MR) design was implemented to determine the causal relationship between IBD and PBC. In the forward MR, the IBD was treated as the exposure while the PBC was the exposure in the reverse MR. The inverse-variance-weighted (IVW) method was utilized as the main statistic method, and a series of sensitivity analyses were performed to detect heterogeneity and horizontal pleiotropy.

RESULTS

A total of 99 valid instrumental variables (IVs) were selected for IBD and the number of IVs for PBC was 18. The forward MR analysis indicated that genetically predicted IBD (UC and CD) was significantly associated with an increased risk of PBC (IVW OR = 1.343; 95% CI: 1.220-1.466). Similar casual associations were observed in UC (IVW OR = 1.244; 95% CI: 1.057-1.430) and CD (IVW OR = 1.269; 95% CI: 1.159-1.379). Such results were still consistent in multiple MR methods. The reverse MR analysis implicated that genetic susceptibility to PBC might not alter the risk of IBD (IVW OR = 1.070; 95% CI: 0.984-1.164).

CONCLUSION

Our study found that genetically predicted IBD can increase the risk of PBC while not vice versa in the European population, which may enlighten the aetiology of PBC, together with the IBD patient management.

Primary biliary cholangitis: primary autoimmune disease or primary secretory defect

INTRODUCTION

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease characterized by the immune-mediated destruction of small and medium intrahepatic bile ducts, involving predominantly females. PBC has long been described as an autoimmune liver disease, also because it is very often associated with many autoimmune conditions. More recently, another pathogenic mechanism exploring the damage of cholangiocytes has been hypothesized, i.e. a defect in the biliary umbrella which is physiologically responsible for the exchange of the ions Cl- and HCO3- and maintains the integrity of glycocalyx. To provide a state-of-the-art analysis of this topic, a systematic review of literature in PubMed, Scopus, and Science Direct was conducted (inclusive dates: 1986-2023).

AREA COVERED

Although the etiology remains unknown, pathogenesis consists of a complex immune-mediated process resulting from a genetic susceptibility. PBC can be triggered by an immune-mediated response to an autoantigen, which leads to a progressive destruction of bile ducts and eventually to a progressive fibrosis with cirrhosis. The defect in the 'bicarbonate umbrella' acts as a protection against the toxic hydrophobic bile acids, leading to a toxic composition of bile.

EXPERT OPINION

This review offers a summary of the current knowledge about the pathogenesis of PBC, indicating that this is probably based on the mutual relationship between the immune insult and the unbalanced secretory mechanisms.

Plasma lipidomics of primary biliary cholangitis and its comparison with Sjögren's syndrome

Background

Abnormal lipid metabolism is common in patients with primary biliary cholangitis (PBC). PBC and Sjögren's syndrome (SS) frequently coexist in clinical practice; however, the lipid characteristics of both diseases are unknown. Therefore, we aimed to analyze the plasma lipid profiles of both diseases.

Methods

Plasma samples from 60 PBC patients, 30 SS patients, and 30 healthy controls (HC) were collected, and untargeted lipidomics was performed using ultrahigh-performance liquid chromatography high-resolution mass spectrometry. Potential lipid biomarkers were screened through an orthogonal projection to latent structure discriminant analysis and further evaluated using receiver operating characteristic (ROC) analysis.

Results

A total of 115 lipids were differentially upregulated in PBC patients compared with HC. Seventeen lipids were positively associated with the disease activity of PBC, and ROC analysis showed that all of these lipids could differentiate between ursodeoxycholic acid (UDCA) responders and UDCA non-responders. The top six lipids based on the area under the curve (AUC) values were glycerophosphocholine (PC) (16:0/16:0), PC (18:1/18:1), PC (42:2), PC (16:0/18:1), PC (17:1/14:0), and PC (15:0/18:1). In comparison with SS, 44 lipids were found to be differentially upregulated in PBC. Additionally, eight lipids were found to have a good diagnostic performance of PBC because of the AUC values of more than 0.9 when identified from SS and HC groups, which were lysophosphatidylcholines (LysoPC) (16:1), PC (16:0/16:0), PC (16:0/16:1), PC (16:1/20:4), PC (18:0/20:3), PC (18:1/20:2), PC (20:0/22:5), and PC (20:1/22:5).

Conclusion

Our study revealed differentially expressed lipid signatures in PBC compared with HC and SS. PC is the main lipid species associated with disease activity and the UDCA response in patients with PBC.

Cholestasis: exploring the triangular relationship of gut microbiota-bile acid-cholestasis and the potential probiotic strategies

Cholestasis is a condition characterized by the abnormal production or excretion of bile, and it can be induced by a variety of causes, the factors of which are extremely complex. Although great progress has been made in understanding cholestasis pathogenesis, the specific mechanisms remain unclear. Therefore, it is important to understand and distinguish cholestasis from different etiologies, which will also provide indispensable theoretical support for the development of corresponding therapeutic drugs. At present, the treatment of cholestasis mainly involves several bile acids (BAs) and their derivatives, most of which are in the clinical stage of development. Multiple lines of evidence indicate that ecological disorders of the gut microbiota are strongly related to the occurrence of cholestasis, in which BAs also play a pivotal role. Recent studies indicate that probiotics seem to have certain effects on cholestasis, but further confirmation from clinical trials is required. This paper reviews the etiology of and therapeutic strategies for cholestasis; summarizes the similarities and differences in inducement, symptoms, and mechanisms of related diseases; and provides information about the latest pharmacological therapies currently available and those under research for cholestasis. We also reviewed the highly intertwined relationship between gut microbiota-BA-cholestasis, revealing the potential role and possible mechanism of probiotics in the treatment of cholestasis.

Endothelin receptor B enhances liver injury and pro-inflammatory responses by increasing G-protein-coupled receptor kinase-2 expression in primary biliary cholangitis

Severe diseases like cirrhosis and liver failure can be developed from primary biliary cholangitis (PBC). Endothelin-2 (EDN2) and endothelin receptor B (EDNRB) are related to the pathogenesis of PBC. However, the roles of EDN2 and EDNRB in PBC-related liver injury and inflammation along with molecular mechanisms are poorly defined. In this study, histopathologic alterations of liver tissues were assessed through hematoxylin-eosin staining. Alanine transaminase (ALT), alkaline phosphatase (ALP), aspartate transaminase (AST), and γ-Glutamyltranspetidase (GGT) (4 liver function indexes) serum levels were detected with corresponding activity assay kits. Also, we determined the levels of M2 subtype anti-mitochondrial antibody (AMA-M2), interferon-gamma (IFN-γ), and tumor-necrosis factor alpha (TNFα) in serum with ELISA assay. Later, RT-qPCR assay was used to measure the expression of genes at mRNA levels, while western blotting and immunohistochemical techniques were used to detect protein levels of genes. Our results showed that the liver tissues of PBC patients and mice presented with severe hepatocyte injury and inflammatory cell infiltration as well as destruction of intrahepatic small bile ducts. ALP, AST, ALT, GGT, AMA-M2, IFN-γ, and TNF-α serum levels were higher in PBC patients and mice. Besides, EDN2 and EDNRB were highly expressed in serums and livers of PBC patients and mice. EDNRB potentiated PBC-related liver injury and pro-inflammatory responses, as evidenced by observation of serious liver pathologic injury and increased serum levels of ALP, AST, ALT, AMA-M2, IFN-γ, and TNF-α in PBC mice following EDNRB overexpression. EDNRB overexpression or activation via its agonist IRL-1620 TFA triggered liver injury and pro-inflammatory responses, increased GRK2 expression and induced NF-κB expression and activation in wild-type mice. EDNRB knockdown or inhibition by Bosentan alleviated liver damage and inflammation, reduced GRK2 expression, and inhibited NF-κB in PBC mice. These findings suggested EDNRB loss or inhibition weakened liver injury and pro-inflammatory responses by down-regulating GRK2 and inhibiting the NF-κB pathway in PBC mice.

Immunologic Responses and the Pathophysiology of Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is an autoimmune liver disease with a female predisposition and selective destruction of intrahepatic small bile ducts leading to nonsuppurative destructive cholangitis. It is characterized by seropositivity of antimitochondrial antibodies or PBC-specific antinuclear antibodies, progressive cholestasis, and typical liver histologic manifestations. Destruction of the protective bicarbonate-rich umbrella is attributed to the decreased expression of membrane transporters in biliary epithelial cells (BECs), leading to the accumulation of hydrophobic bile acids and sensitizing BECs to apoptosis. A recent X-wide association study reveals a novel risk locus on the X chromosome, which reiterates the importance of Treg cells.

Imbalanced distribution of group 2 innate lymphoid cells (ILCs) and ILC precursors in peripheral blood of patients with primary biliary cholangitis

Innate lymphoid cells (ILCs), a novel group of innate immune cells, play a key role in the early immune response via rapidly reacting to signals expressed by tissue-resident cells. ILCs contribute to some autoimmune diseases. We aim to investigate the proportions of circulating ILC subgroups in patients with primary biliary cholangitis (PBC). Overall, 48 patients with PBC and 24 healthy controls (HCs) were enrolled. Circulating ILCs and cytokine production were detected by flow cytometry. The proportions of total ILCs, ILC precursors (ILCPs), and ILCP/ILC2 ratio increased and that of ILC2s decreased in patients with PBC. ILC2 proportion was negatively correlated with gamma-glutamyl transpeptidase (GGT), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). The proportion of ILCPs and ILCP/ILC2 ratio were positively correlated with alkaline phosphatase, GGT, ALT, and AST. ILC2 proportion was significantly decreased in the ursodeoxycholic acid (UDCA) -non-responder group compared with the UDCA-responder group, whereas the proportion of ILCPs and ILCP/ILC2 were ratio significantly increased. The proportions of CD38⁺ ILC2s, CD38⁺ ILCPs, CD45RO⁺ ILC2s, and CD45RO⁺ ILCPs were significantly higher in patients with PBC than in HCs. Levels of IL-17A producing ILCs were higher in patients with PBC than in HCs. PBC is accompanied by alterations in circulating ILCs. The proportions of ILC2s, ILCPs, and ILCP/ILC2 ratio were associated with the PBC disease activity. The proportions of ILCPs and ILCP/ILC2 ratio may reflect the UDCA treatment failure in patients with PBC. ILC2s and ILCPs from patients with PBC get activated, these cells may be involved in the pathogenesis of PBC.

Cellular senescence in the cholangiopathies: a driver of immunopathology and a novel therapeutic target

The cholangiopathies are a group of liver diseases that affect cholangiocytes, the epithelial cells that line the bile ducts. Biliary atresia (BA), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC) are three cholangiopathies with significant immune-mediated pathogenesis where chronic inflammation and fibrosis lead to obliteration of bile ducts and eventual liver cirrhosis. Cellular senescence is a state of cell cycle arrest in which cells become resistant to apoptosis and profusely secrete a bioactive secretome. Recent evidence indicates that cholangiocyte senescence contributes to the pathogenesis of BA, PBC, and PSC. This review explores the role of cholangiocyte senescence in BA, PBC, and PSC, ascertains how cholangiocyte senescence may promote a senescence-associated immunopathology in these cholangiopathies, and provides the rationale for therapeutically targeting senescence as a treatment option for BA, PBC, and PSC.