Ursodeoxycholic acid mitigates cerebral ischemia/reperfusion injury by inhibiting thrombin-induced lipid peroxidation through activation of ALDH3A1.

Thrombin accumulation following ischemic stroke (IS) promotes lipid peroxidation and ferroptosis to exacerbate tissue injury; however, effective interventions targeting this pathological process remain limited. Although bile acids (BAs) have demonstrated potential benefits against IS, their alterations and specific roles in IS pathogenesis are still poorly understood. This study was designed to further validate the detrimental effects of thrombin in neuronal injury, investigate BA profile changes in an IS model, and elucidate the underlying mechanisms. Serum and cerebral bile acid profiles in a mouse middle cerebral artery occlusion (MCAO) model were analyzed. Infarct volume, neurological deficits, lipid peroxidation, and ferroptosis were assessed. RNA sequencing was employed to explore potential mechanisms, followed by verification using pharmacological inhibitors. Results showed that MCAO induced upregulation of thrombin and its receptor PAR1 in neurons, leading to lipid peroxidation, ferroptosis, and subsequent neuronal injury. Bile acid profiles in brain tissues were significantly altered, and ursodeoxycholic acid (UDCA) levels were negatively correlated with infarct size. Furthermore, UDCA supplementation alleviated thrombin-induced neuronal lipid peroxidation, restored mitochondrial function, suppressed ferroptosis, and improved neurological outcomes. Mechanistically, transcriptomic analysis revealed significant changes in arachidonic acid metabolism and aldehyde dehydrogenase 3A1 (ALDH3A1) expression. UDCA was found to upregulate ALDH3A1, thereby mitigating oxidative stress and lipid peroxidation-an effect that was reversed by ALDH3A1 inhibition. We further demonstrated that UDCA upregulated ALDH3A1 through the TGR5-PKA signaling pathway, which mediated Nrf2 nuclear translocation and its subsequent binding to the Aldh3a1 promoter. In summary, UDCA confered neuroprotection against thrombin-induced lipid peroxidation in IS through the TGR5/PKA/ALDH3A1 axis. These findings identified UDCA as a promising therapeutic candidate for IS and reveal a novel signaling mechanism underlying its neuroprotective effects.