TLR4 and brain ischemia: Rat neuronal cells in a model of cerebral ischemia and reperfusion (I/R) exhibit significant upregulation of C5aR1 gene expression, and inflammatory cascade signals, including TLR4, TNF-α, IL-1β, and IL-6, are regulated in parallel with the regulation of C5AR1 expression levels, demonstrating the pathogenic role of C5AR1 in the progression of brain injury and inflammatory response after I/R injury (42).