SIRT1 activation synergizes with FXR agonism in hepatoprotection via governing nucleocytoplasmic shuttling and degradation of FXR

Bile acids induce liver fibrosis through the NLRP3 inflammasome pathway and the mechanism of FXR inhibition of NLRP3 activation

BACKGROUND

Altered patterns of bile acids (BAs) are frequently present in liver fibrosis, and BAs function as signaling molecules to initiate inflammatory responses. Therefore, this study was conducted to uncover the notably altered components of BAs and to explore the pathway of altered BA induced inflammation in the development of liver fibrosis.

METHODS

Bile acids were quantified by ultraperformance liquid chromatography coupled to mass spectrometry (UPLC‒MS/MS). Cell Counting Kit-8 assays were used to determine the proliferative capacity of HSCs. Transwell assays and wound healing assays were used to determine the migratory capacity of LX2 cells. Protein expression was evaluated by western blotting.

RESULTS

Plasma bile acid analysis showed higher levels of GCDCA, TCDCA, GCA and TCA in patients with liver fibrosis than in normal controls. The AUC of GCDCA was the highest. Western blotting showed that GCDCA treatment increased the expression of NLRP3-related proteins and collagen1 in vitro and significantly increased LX2 cells proliferation and migration. Furthermore, knockdown of NLRP3 or overexpression of FXR in LX2 cells decreased the expression of the above proteins, and FXR inhibited NLRP3 (ser 295) phosphorylation in vitro and vivo. In vivo, HE, Masson's trichrome, and Sirius Red staining showed that GCDCA increased collagen fibers in the mouse liver, and the expression of NLRP3-related proteins, collagen 1, and α-SMA in the liver increased significantly. However, the knockout of NLRP3 reversed these patterns.

CONCLUSION

(1) Primary conjugated bile acids increased in patients with liver fibrosis; (2) GCDCA induce hepatic fibrosis via the NLRP3 inflammasome pathway; (3) FXR inhibits NLRP3 activity by restraining its phosphorylation; (4) knockdown or knockout of NLRP3 may relieve the onset of hepatic fibrosis.

A Current Understanding of FXR in NAFLD: The multifaceted regulatory role of FXR and novel lead discovery for drug development

The global prevalence of nonalcoholic fatty liver disease (NAFLD) has reached 30 %, with an annual increase. The incidence of NAFLD-induced cirrhosis is rapidly rising and has become the leading indicator for liver transplantation in the US. However, there are currently no US Food and Drug Administration-approved drugs for NAFLD. Increasing evidence underscores the close association between NAFLD and bile acid metabolism disorder, highlighting the feasibility of targeting the bile acid signaling pathway for NAFLD treatment. The farnesoid X receptor (FXR) is an endogenous receptor for bile acids that exhibits favorable effects in ameliorating the metabolic imbalance of bile acids, lipid disorders, and disruption of intestinal homeostasis, all of which are key characteristics of NAFLD, making FXR a promising therapeutic target for NAFLD. The present review provides a comprehensive overview of the diverse mechanisms through which FXR improves NAFLD, with particular emphasis on its involvement in regulating bile acid homeostasis and the recent advancements in drug development targeting FXR for NAFLD treatment.

Natural Products in the Modulation of Farnesoid X Receptor Against Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a global health concern with a high prevalence and increasing economic burden, but official medicine remains unavailable. Farnesoid X receptor (FXR), a nuclear receptor member, is one of the most promising drug targets for NAFLD therapy that plays a crucial role in modulating bile acid, glucose, and lipid homeostasis, as well as inhibits hepatic inflammation and fibrosis. However, the rejection of the FXR agonist, obecholic acid, by the Food and Drug Administration for treating hepatic fibrosis raises a question about the functions of FXR in NAFLD progression and the therapeutic strategy to be used. Natural products, such as FXR modulators, have become the focus of attention for NAFLD therapy with fewer adverse reactions. The anti-NAFLD mechanisms seem to act as FXR agonists and antagonists or are involved in the FXR signaling pathway activation, indicating a promising target of FXR therapeutic prospects using natural products. This review discusses the effective mechanisms of FXR in NAFLD alleviation, and summarizes currently available natural products such as silymarin, glycyrrhizin, cycloastragenol, berberine, and gypenosides, for targeting FXR, which can facilitate development of naturally targeted drug by medicinal specialists for effective treatment of NAFLD.

FXR agonists for MASH therapy: Lessons and perspectives from obeticholic acid

Nonalcoholic fatty liver disease, also called metabolic dysfunction-associated steatotic liver disease, is the most common liver disease worldwide and has no approved pharmacotherapy. Due to its beneficial effects on metabolic regulation, inflammation suppression, cell death prevention, and fibrogenesis inhibition, farnesoid X receptor (FXR) is widely accepted as a promising therapeutic target for nonalcoholic steatosis (NASH) or called metabolic dysfunction-associated steatohepatitis (MASH). Many FXR agonists have been developed for NASH/MASH therapy. Obeticholic acid (OCA) is the pioneering frontrunner FXR agonist and the first demonstrating success in clinical trials. Unfortunately, OCA did not receive regulatory approval as a NASH pharmacotherapy because its moderate benefits did not outweigh its safety risks, which may cast a shadow over FXR-based drug development for NASH/MASH. This review summarizes the milestones in the development of OCA for NASH/MASH and discuss its limitations, including moderate hepatoprotection and the undesirable side effects of dyslipidemia, pruritus, cholelithiasis, and liver toxicity risk, in depth. More importantly, we provide perspectives on FXR-based therapy for NASH/MASH, hoping to support a successful bench-to-clinic transition.

SIRT1 and thrombosis

Thrombosis is a major cause of morbidity and mortality worldwide, with a complex and multifactorial pathogenesis. Recent studies have shown that SIRT1, a member of the sirtuin family of NAD + -dependent deacetylases, plays a crucial role in regulating thrombosis, modulating key pathways including endothelial activation, platelet aggregation, and coagulation. Furthermore, SIRT1 displays anti-inflammatory activity both in vitro, in vivo and in clinical studies, particularly via the reduction of oxidative stress. On these bases, several studies have investigated the therapeutic potential of targeting SIRT1 for the prevention of thrombosis. This review provides a comprehensive and critical overview of the main preclinical and clinical studies and of the current understanding of the role of SIRT1 in thrombosis.

β-lapachone protects against doxorubicin-induced hepatotoxicity through modulation of NAD+ /SIRT-1/FXR/p-AMPK/NF-kB and Nrf2 signaling axis

Doxorubicin (DOX) is a widely used antineoplastic drug, but its clinical use is limited by significant toxicities, such as hepatotoxicity. In this study, we evaluated the effects of β-lapachone (β-LAP), a natural quinone-containing compound, in a mouse model of DOX-induced hepatotoxicity. β-LAP was orally administered at 1.25, 2.5, and 5 mg/kg for 4 days, and a single dose of DOX (20 mg/kg) was injected intraperitoneally on the second day. Histopathological changes, liver function markers, antioxidant and inflammatory markers were assessed. β-LAP ameliorated liver injury and liver function markers evoked by DOX. β-LAP also downregulated the mRNA expression of nuclear factor-kB-corresponding genes including interleukin-6, interleukin-1β, and tumor necrosis factor-α. Moreover, β-LAP increased the nuclear factor erythroid 2-related factor 2 target genes heme oxygenase-1 and NAD(P)H: quinone oxidoreductase 1, along with antioxidant enzymes including reduced glutathione, catalase, and superoxide dismutase with simultaneous reduction in the lipid peroxidation product malondialdehyde. Meanwhile, it recovered NAD+ /NADH ratios and subsequently elevated the protein levels of sirtuin-1 (SIRT-1), farnesoid X receptor (FXR), and phosphorylated AMP-activated protein kinase (p-AMPK). Collectively, these findings suggest a protective role of β-LAP against DOX-induced hepatotoxicity by partly regulating the NAD+ /SIRT-1/FXR/p-AMPK axis.