Piezo1 activation on microglial cells exacerbates demyelination in sepsis by influencing the CCL25/GRP78 pathway

BACKGROUND: In sepsis-associated encephalopathy (SAE), the activation of microglial cells and ensuing neuroinflammation are important in the underlying pathological mechanisms. Increasing evidence suggests that the protein Piezo1 functions as a significant regulator of neuroinflammation. However, the influence of Piezo1 on microglial cells in the context of SAE has not yet been determined. This study aims to investigate the role of Piezo1 in microglial cells in the context of SAE. METHODS: By inducing cecal ligation and puncture (CLP), a mouse model of SAE was established, while the control group underwent a sham surgery in which the cecum was exposed without ligation and puncture. Piezo1 knockout mice were employed in this study. Morris water maze tests were conducted between Days 14 and 18 postop to assess both the motor activity and cognitive function. A proteomic analysis was conducted to assess the SAE-related pathways, whereas a Mendelian randomization analysis was conducted to identify the pathways associated with cognitive impairment. Dual-label immunofluorescence and flow cytometry were used to assess the secretion of inflammatory factors, microglial status, and oligodendrocyte development. Electron microscopy was used to evaluate axonal myelination. A western blot analysis was conducted to evaluate the influence of Piezo1 on oligodendrocyte ferroptosis. RESULTS: The results of the bioinformatics analysis have revealed the significant involvement of CCL25 in the onset and progression of SAE-induced cognitive impairment. SAE leads to cognitive dysfunction by activating the microglial cells. The release of CCL25 by the activated microglia initiates the demyelination of oligodendrocytes in the hippocampus, resulting in ferroptosis and the disruption of hippocampal functional connectivity. Of note, the genetic knockout of the Piezo1 gene mitigates these changes. The treatment with siRNA targeting Piezo1 effectively reduces the secretion of inflammatory mediators CCL25 and IL-18 by inhibiting the p38 pathway, thus preventing the ferroptosis of oligodendrocytes through the modulation of the CCL25/GPR78 axis. CONCLUSION: Piezo1 is involved in the activation of microglia and demyelinating oligodendrocytes in the animal models of SAE, resulting in cognitive impairment. Consequently, targeting Piezo1 suppression can be a promising approach for therapeutic interventions aimed at addressing cognitive dysfunction associated with SAE.