Meningitic Escherichia coli disrupts the blood-brain barrier through pyroptosis and tight junction degradation and NLRP6 deficiency aggravates infection outcomes.

Abstract

Extraintestinal pathogenic Escherichia coli (ExPEC) can cause meningitis by breaching the blood-brain barrier (BBB), but the underlying mechanisms remain unclear. In this study, we found that meningitic ExPEC disrupts the BBB through two distinct mechanisms: inducing endothelial pyroptotic cell death and disrupting tight junction (TJ) proteins. Transcriptomic analysis revealed activation of cell death pathways and suppression of tight junction signaling in ExPEC-stimulated human cerebral microvascular endothelial cells (hCMEC/D3). ExPEC infection induced pyroptotic cell death characterized by caspase-1 and GSDMD activation, along with inflammatory cytokine production. Additionally, ExPEC reduced TJ protein expression and disrupted their continuous distribution. Based on transcriptomic results showing simultaneous activation of NLR and TLR pathways, we investigated the role of NLRP6, a unique receptor with dual functions. Silencing NLRP6 in hCMECs exacerbated ExPEC-induced TJ protein disruption but reduced pyroptotic cell death. In vivo experiments indicated that NLRP6mice showed accelerated mortality, higher bacterial loads, more severe brain tissue damage, enhanced TJ protein disruption, and elevated inflammatory cytokines following ExPEC infection. Brain transcriptomic analysis revealed that NLRP6 deficiency resulted in impaired immune function, downregulation of tight junction pathways, and upregulation of neurological dysfunction-related pathways. These results demonstrate that meningitic ExPEC promotes bacterial meningitis through dual BBB disruption mechanisms, and NLRP6 plays a crucial protective role by maintaining BBB integrity during infection.