Previous studies have shown that hypoxia inducible factor-1α (HIF-1α could regulate the expression of tight junction-related genes, including claudin-5, in cerebral ischemia using iPS cell-derived brain microvascular endothelial cells [18], and heat stress is known to induce the expression of HIF-1α via heat shock proteins [19]. Here, HIF1A is linked to brain ischemia.