KLF4 protects brain microvascular endothelial cells from ischemic stroke induced apoptosis by transcriptionally activating MALAT1

In this study, we investigated the expression profile and functional role of Kruppel-like family of transcription factor 4 (KLF4) in mouse cerebral microvascular endothelial cells (MECs) after focal cerebral ischemia and in cultured b.End3 cells after oxygen-glucose deprivation (OGD). Its downstream regulation was also studied. Our data showed that KLF4 was significantly upregulated in the cerebral MECs after transient ischemic insult and in cultured b.End3 cells after 24 h OGD exposure. In in vitro b.End3 cell model, KLF4 shRNA significantly increased OGD-induced activation of caspase-3 and also increased OGD-induced b.End3 cell death. KLF4 shRNA substantially enhanced OGD induced Bim and Bax expression at mRNA and protein levels and also aggravated OGD induced upregulation of E-selectin, MCP-1 and IL-6. Bioinformatic analysis suggested that MALAT1 promoter has a possible KLF4 binding site. In this study, we validated this possible binding site and also demonstrated that enforced KLF4 expression increased MALAT1 transcription. Functionally, knockdown of MALAT1 phenocopied the effect of KLF4 shRNA on enhancing OGD induced cell apoptosis and OGD induced upregulation of pro-apoptotic factors and pro-inflammatory cytokines. Based on these findings, we infer that MALAT1 is a transcriptional target of KLF4 in its protective role in cerebral MECs after ischemic insult.