TLR4 knockout ameliorates acute LPS-sensitized tolvaptan-induced idiosyncratic liver injury by disrupting drug metabolism, inflammation, and bile acid homeostasis.

Tolvaptan (TVP), a vasopressin V2 receptor antagonist for hyponatremia and autosomal dominant polycystic kidney disease, is associated with infrequent yet severe idiosyncratic drug-induced liver injury (IDILI), posing critical challenges to clinical medication safety. Toll-like receptor 4 knockout (TLR4-KO) confers protection against drug-induced liver injury, yet its precise role and underlying mechanisms in TVP-induced hepatotoxicity remain unclear. This study investigated the hepatoprotective potential of TLR4-KO against TVP-induced liver injury using acute lipopolysaccharide (LPS)-sensitized mouse and primary hepatocyte models, characterized by 3-day TVP administration and intraperitoneal LPS injection 2 h before the final TVP dose in vivo, and 100 ng/mL LPS and 0-25 μM TVP for 24 h in vitro. Inflammatory stress suppressed TVP metabolism (37 metabolites detected under LPS vs. 47 under normal conditions) via downregulating CYP3A11. TLR4-KO showed a significant protective effect against LPS/TVP-induced hepatotoxicity, evidenced by reduced liver enzymes, attenuated histopathological damage in mice, and decreased aminotransferase activities in primary hepatocytes. Mechanistically, TLR4 knockout reversed abnormal TVP pharmacokinetics and alleviated hepatic accumulation by restoring CYP3A11 and inhibiting inflammatory signaling pathway activation. Additionally, TLR4-KO reversed LPS/TVP-induced hepatic bile acid (BA) accumulation and reduced BA levels in bile/plasma, which correlated with the amelioration of CYP7A1 upregulation and the reversal of farnesoid X receptor and efflux transporter downregulation. The study underscores TLR4 as a pivotal mediator linking TVP metabolism, inflammation, and BA homeostasis disruption in IDILI pathogenesis, providing novel mechanistic insights for mitigating TVP-associated IDILI.