ATF4 is a novel regulator of MCP-1 in microvascular endothelial cells

Background: monocyte chemoattractant protein-1 (mcp-1) is a major chemokine that recruits monocyte/macrophage to the site of tissue injury and plays a critical role in microvascular complications of diabetes. however,the mechanisms underlying the regulation of mcp-1 are not fully understood. the present study aims to explore the role of activating transcription factor 4 (atf4),an er stress-inducible transcription factor,in regulation of mcp-1 expression and production in brain and retinal microvascular endothelial cells. methods: for in vitro study,primary brain microvascular endothelial cells isolated from atf4 knockout mice or mouse retinal endothelial cells were treated with lipopolysaccharide (lps) to induce mcp-1 expression. atf4 expression/function was manipulated by adenoviruses expressing wild type atf4 (ad-atf4) or a dominant negative mutant of the protein (ad-atf4dn). for in vivo study,mcp-1 expression was induced by intravitreal injection of lps or ad-atf4 in heterozygous atf4 knockout or wild type mice. results: lps treatment induced a dose- and time-dependent increase in atf4 expression,er stress and mcp-1 production in brain and retinal microvascular endothelial cells. overexpression of atf4 in endothelial cells significantly increased the secretion of mcp-1 and promoted thp-1 monocyte-endothelial cell adhesion. conditioned medium from atf4-overexpressiing endothelial cells significantly enhanced thp-1 cell migration. consistently,intravitreal injection of ad-atf4 remarkably enhanced retinal levels of mcp-1 and promoted inflammatory cell infiltration into the vitreous and retina. in contrast,lps-induced mcp-1 upregulation was markedly attenuated in atf4-deficient endothelial cells and in retinas of atf4 knockout mice,suggesting that atf4 is essential for lps-induced mcp-1 production in endothelial cells and in the retina. mechanistically,overexpression of atf4 enhanced,while inhibition of atf4,attenuated the basal and lps-stimulated phosphorylation of nf-κb,p38,and jnk. furthermore,pharmacological inhibition of nf-κb,p38,or jnk significantly reduced atf4-stimulated mcp-1 secretion from endothelial cells. conclusions: taken together,our results suggest a critical role of atf4 in the regulation of mcp-1 production in retinal and brain microvascular endothelial cells,which may contribute to inflammation-related endothelial injury in diseases such as diabetic retinopathy. © 2015 huang et al.; licensee biomed central.