Sophoridine alleviates sepsis-associated encephalopathy by inhibiting MARK4 and NLRP3 signaling

Sepsis is a life-threatening systemic inflammatory response syndrome with high morbidity and mortality. A frequent complication is sepsis-associated encephalopathy (SAE), characterized by neurological impairments. Microglia pyrin domain-containing receptor 3 (NLRP3) inflammasome activation is a pivotal pathogenic mechanism in SAE. Microtubule-affinity regulating kinase 4 (MARK4) has been implicated in neuroinflammatory diseases, but its role in SAE and microglial NLRP3 inflammasome activation is unclear. Sophoridine (SRI), a MARK4 antagonist with anti-inflammatory and neuroprotective properties, has not yet been thoroughly investigated in SAE. Here, we used a cecum ligation puncture (CLP)-induced SAE mouse model and LPS + ATP or LPS + nigericin (Nig)-treated microglia, to assess the role of MARK4 in SAE. Molecular docking, Nissl staining, the enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and behavioral tests were applied to assess SRI's effects on SAE. Our findings demonstrate that MARK4 is significantly upregulated in SAE. Knockdown of MARK4 effectively suppressed microglial pyroptosis and pro-inflammatory cytokine release by inhibiting NLRP3 inflammasome activation. SRI binds to MARK4 and enhances its stability. By suppressing MARK4 protein expression, SRI reduces NLRP3 inflammasome-mediated microglia inflammation. In vivo, SRI treatment increased survival, improved neurological behavioral deficits, attenuated blood-brain barrier disruption, and provided neuroprotective effects against brain injury. In summary, MARK4 contributes to microglial pyroptosis and neuroinflammation through NLRP3 pathway in SAE, resulting in neuronal injury and cognitive impairment. SRI alleviates SAE by targeting MARK4. These results suggest MARK4 as a potential therapeutic target and SRI as a promising candidate for treating SAE.