TLR4 and necrotizing enterocolitis: In addition to a significant decrease in the expression of the tight junction protein genes zonula occludens-1 protein (ZO-1), occludin, cingulin, and claudin-4 in NEC, the expression of genes encoding TLR4, Bcl-2-associated X protein (BAX) and sirtuin 1 (SIRT1), and HIF-1α was upregulated in NEC patients [69].