A homozygous R148W mutation in Semaphorin 7A causes progressive familial intrahepatic cholestasis

Sarmentol H derived from Sedum sarmentosum Bunge directly targets FXR to mitigate cholestasis by recruiting SRC-1

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.

SLC10A5 deficiency causes hypercholanemia

BACKGROUND AND AIMS

Solute Carrier Family 10 Member 5 (SLC10A5) is a member of SLC10, comprising transporters of bile acids, steroidal hormones, and other substrates, but its function remains unclear. The aim of the current investigation was to clarify its function in the metabolism of bile acid and hypercholanemia.

APPROACH AND RESULTS

Whole-exome sequencing and Sanger sequencing were used to identify and confirm the variant in the subjects of hypercholanemia. CRISPR/Cas9-mediated genome engineering was used to establish the knockout and point mutation mice. Primary mouse hepatocytes were isolated, and cell lines were cultured. SLC10A5 was silenced by siRNA and overexpressed by wild-type and mutant plasmids. The fluorescent bile acid derivative was used for the bile acid uptake assay. Bile acids were assessed with ultra-performance liquid chromatography tandem mass spectrometry. A heterozygous variant SLC10A5 : c.994_995del (p.D332X) was identified in subjects with elevated total bile acid or altered bile acid profiles. Bile acids were increased in the serum and liver of knockout and point mutation mice. The expressions of FXR and SHP, regulators involved in the negative feedback of bile acid synthesis, were downregulated, while the bile acid synthesis genes CYP7A1 and CYP8B1 were upregulated in both gene-edited mice. Both the wild and mutant SLC10A5 proteins were localized on the plasma membrane. Knockdown, knockout, or targeted mutation of SLC10A5 led to the inhibition of bile acid uptake by cell lines and primary mouse hepatocytes.

CONCLUSION

SLC10A5 is involved in the uptake of bile acid, and its deficiency causes hypercholanemia.

Diagnostic yield and novel candidate genes by next generation sequencing in 166 children with intrahepatic cholestasis

BACKGROUND AND AIMS

Cholestatic liver disease is a leading referral to pediatric liver transplant centers. Inherited disorders are the second most frequent cause of cholestasis in the first month of life.

METHODS

We retrospectively characterized the genotype and phenotype of 166 participants with intrahepatic cholestasis, and re-analyzed phenotype and whole-exome sequencing (WES) data from patients with previously undetermined genetic etiology for newly published genes and novel candidates. Functional validations of selected variants were conducted in cultured cells.

RESULTS

Overall, we identified disease-causing variants in 31% (52/166) of our study participants. Of the 52 individuals, 18 (35%) had metabolic liver diseases, 9 (17%) had syndromic cholestasis, 9 (17%) had progressive familial intrahepatic cholestasis, 3 (6%) had bile acid synthesis defects, 3(6%) had infantile liver failure and 10 (19%) had a phenocopy of intrahepatic cholestasis. By reverse phenotyping, we identified a de novo variant c.1883G > A in FAM111B of a case with high glutamyl transpeptidase (GGT) cholestasis. By re-analyzing WES data, two patients were newly solved, who had compound heterozygous variants in recently published genes KIF12 and USP53, respectively. Our additional search for novel candidates in unsolved WES families revealed four potential novel candidate genes (NCOA6, CCDC88B, USP24 and ATP11C), among which the patients with variants in NCOA6 and ATP11C recapitulate the cholestasis phenotype in mice models.

CONCLUSIONS

In a single-center pediatric cohort, we identified monogenic variants in 22 known human intrahepatic cholestasis or phenocopy genes, explaining up to 31% of the intrahepatic cholestasis patients. Our findings suggest that re-evaluating existing WES data from well-phenotyped patients on a regular basis can increase the diagnostic yield for cholestatic liver disease in children.

Paediatric research sets new standards for therapy in paediatric and adult cholestasis

Children with Alagille syndrome and progressive familial intrahepatic cholestasis (PFIC) experience debilitating pruritus, for which there have been few effective treatment options. In the past 2 years, the ileal bile acid transporter (IBAT) inhibitors maralixibat and odevixibat have been approved for the management of cholestatic pruritus in these individuals, representing an important step forward in improving their quality of life. Emerging data suggest these drugs might also improve event-free survival, therefore potentially altering the typical disease course currently seen in these disorders. This Review will discuss how genetic advances have clarified the molecular basis of cholestatic disorders, facilitating the development of new therapeutic options that have only been evaluated in children. We focus specifically on the newly licensed IBAT inhibitors for patients with Alagille syndrome and PFIC and explore the next steps for these drugs in relation to other paediatric and adult cholestatic disorders, recognising that they have the potential to benefit a wider group of patients with gastrointestinal and liver disease.

Runt-related transcription factor-1 ameliorates bile acid-induced hepatic inflammation in cholestasis through JAK/STAT3 signaling

BACKGROUND AND AIMS

Bile acids trigger a hepatic inflammatory response, causing cholestatic liver injury. Runt-related transcription factor-1 (RUNX1), primarily known as a master modulator in hematopoiesis, plays a pivotal role in mediating inflammatory responses. However, RUNX1 in hepatocytes is poorly characterized, and its role in cholestasis is unclear. Herein, we aimed to investigate the role of hepatic RUNX1 and its underlying mechanisms in cholestasis.

APPROACH AND RESULTS

Hepatic expression of RUNX1 was examined in cholestatic patients and mouse models. Mice with liver-specific ablation of Runx1 were generated. Bile duct ligation and 1% cholic acid diet were used to induce cholestasis in mice. Primary mouse hepatocytes and the human hepatoma PLC/RPF/5- ASBT cell line were used for mechanistic studies. Hepatic RUNX1 mRNA and protein levels were markedly increased in cholestatic patients and mice. Liver-specific deletion of Runx1 aggravated inflammation and liver injury in cholestatic mice induced by bile duct ligation or 1% cholic acid feeding. Mechanistic studies indicated that elevated bile acids stimulated RUNX1 expression by activating the RUNX1 -P2 promoter through JAK/STAT3 signaling. Increased RUNX1 is directly bound to the promotor region of inflammatory chemokines, including CCL2 and CXCL2 , and transcriptionally repressed their expression in hepatocytes, leading to attenuation of liver inflammatory response. Blocking the JAK signaling or STAT3 phosphorylation completely abolished RUNX1 repression of bile acid-induced CCL2 and CXCL2 in hepatocytes.

CONCLUSIONS

This study has gained initial evidence establishing the functional role of hepatocyte RUNX1 in alleviating liver inflammation during cholestasis through JAK/STAT3 signaling. Modulating hepatic RUNX1 activity could be a new therapeutic target for cholestasis.

Genetic alterations and molecular mechanisms underlying hereditary intrahepatic cholestasis

Hereditary cholestatic liver disease caused by a class of autosomal gene mutations results in jaundice, which involves the abnormality of the synthesis, secretion, and other disorders of bile acids metabolism. Due to the existence of a variety of gene mutations, the clinical manifestations of children are also diverse. There is no unified standard for diagnosis and single detection method, which seriously hinders the development of clinical treatment. Therefore, the mutated genes of hereditary intrahepatic cholestasis were systematically described in this review.

Guidelines for the Management of Cholestatic Liver Diseases (2021)

In 2015, the Chinese Society of Hepatology and the Chinese Society of Gastroenterology issued a consensus statement on the diagnosis and management of cholestatic liver diseases. More clinical data on this topic have appeared during recent years. The Autoimmune Liver Disease Group of the Chinese Society of Hepatology organized an expert group to review recent evidence and provide an update to these previous guidelines. Herein, we provide 22 recommendations as a working reference for the management of cholestatic liver diseases by clinical practitioners.

Biochemical and Bioinformatic Characterization of Patients with a Sodium Taurocholate Cotransporting Polypeptide Mutation

Background: SLC10A1 codes for the sodium taurocholate cotransporting polypeptide (NTCP). The SLC10A1S267F mutation is associated with loss of function of bile acid (BA) uptake and defined as a new type of hypercholanemia. This kind of hypercholanemia is characterized by high levels of serum BA. However, limited studies have been conducted on this topic. Objectives: This study aimed to describe the biochemical and bioinformatic characterization of patients with an SLC10A1S267F mutation, as well as to dissect pathogenesis in hypercholanemia. Methods: In this study, a total of 12 individuals (including 5 homozygous, 3 heterozygous, and 4 wild-type individuals) were recruited. Whole-genome sequencing (WGS) and Sanger sequencing were used to confirm the genotype. Tests of liver function, renal function, and serum lipid level, in addition to routine blood tests, were performed to evaluate the clinical consequences of patients with an SLC10A1S267F mutation. The ClinVar website and protein prediction tools were used to analyze other cholesterol and BAs related gene mutations in SLC10A1S267F patients, as well as to evaluate their possible effects on serum BA levels of patients. Results: All SLC10A1S267F homozygous patients displayed high levels of BAs. Liver and renal functions were generally normal. According to previous reports, homozygous patients are prone to vitamin D deficiency and deviated blood lipids. However, all homozygous individuals had normal levels of blood lipids, thyroid hormones, and vitamin D (25(OH)D). Moreover, except for the SLC10A1S267F mutation, according to the WGS results, multiple gene mutations were found in 5 homozygous and might affect the level of BAs, but the SLC10A1S267F mutation still is the most important reason resulting in a high level of BAs. Conclusions: This study provided a more detailed description of the SLC10A1S267F mutation-induced hypercholanemia, delivering a new idea that there might be some mutations in SLC10A1S267F homozygotes, probably influencing BA metabolism.