Gut-brain axis modulation by fecal microbiota transplantation improves dual-organ injury after cerebral ischemia-reperfusion via Caspase-8 dependent inhibition of necroptosis

The pathological features of cerebral ischemia-reperfusion (CIR) include necroptosis activation. This study investigated how healthy fecal microbiota transplantation (H-FMT) improves CIR and intestinal barrier damage. Rats subjected to middle cerebral artery occlusion and reperfusion (MCAO/R) were treated with H-FMT and/or a Cysteine-aspartic acid protease-8 (Caspase-8) inhibitor. Survival and body weight were monitored throughout the experiment. Neurological function, tissue damage, inflammatory cytokines, and Caspase-8/Receptor-interacting protein kinase 1 (RIPK1)-Receptor-interacting protein kinase 3 (RIPK3)-Mixed lineage kinase domain-like protein (MLKL) expression were assessed. Ultrastructural changes were examined by transmission electron microscopy (TEM), p-RIPK1/p-RIPK3 expression by immunohistochemistry (IHC), and gut microbiota by 16 S sequencing. H-FMT significantly ameliorated neurological deficits and intestinal barrier disruption, reduced infarct volume and neuronal loss, and attenuated mitochondrial damage. These effects were accompanied by reduced apoptosis and inflammation, increased Caspase-8 activation, and suppressed RIPK1-RIPK3-MLKL phosphorylation. IHC confirmed reduced p-RIPK1/p-RIPK3 signals after H-FMT. 16 S sequencing revealed that H-FMT restored microbial diversity, reduced pathogenic Proteobacteria, and enriched beneficial Lactobacillus, which positively correlated with Caspase-8 activation. Our findings suggest that H-FMT alleviates CIR injury by activating Caspase-8 and suppressing necroptosis. However, due to the small sample size, these results should be considered preliminary.