Heme Oxygenase-1 Modulates Inflammatory Response Associated With Human Endothelial Cell Activation In Uremic Milieu

BackgroudHeme oxygenase-1 (HO-1) has recently been shown to be cytoprotective and is known to be induced by hemin. We investigated the effects of hemin on HO-1 induction and the regulation of inflammatory response and growth inhibition of HUVECs in uremic milieu.METHODSHUVECs were grown to confluence and then preincubated with hemin and/or protoporphyrin zinc IX(ZnPP)for 6 hours. The cultures were subsequently incubated with M199 cell medium containing 10% serum of health people (control) or with medium containing 10% serum of patients accepting MHD treatment (experimental). HO-1 protein and gene expression was detected by immunohistochemistry and semi-quantitative reverse transcription- polymerase chain raction (RT-PCR). Intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), and vascular endothelial growth factor (VEGF) gene expression was measured by semi-quantitative RT-PCR, and MCP-1 protein was further quantified by ELISA. Growth activity was evaluated using 3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay.RESULTSOverexpression of ICAM-1,MCP-1,IL-8 and VEGF gene and growth inhibition were detected in HUVECs incubated with medium containing 10%-20% serum of patients accepting MHD treatment. Hemin induced expression of HO-1 gene and protein, and concurrently inhibited uremic milieu induced ICAM-1 and MCP-1 overexpression, but in contract, further enhanced VEGF gene overexpression. Hemin also protected HUVECs against growth inhibition of uremia serum.CONCLUSIONSIn conclusion, we have shown that uremia milieu stimulates expression of ICAM-1, MCP-1, IL-8 and VEGF gene and inhibits growth activity of HUVECs. Hemin is capable of inducing endothelial HO-1 expression , resulting in inhibition of ICAM-1 and MCP-1 gene overexpression, enhancement of VEGF gene expression, and protection against growth inhibition of uremic serum. These effects may offer a novel mechanism by which HO-1 may be exploited therapeutically in protection against endothelial cell damage and atherosclerosis in ESRD, since atherosclerosis is characteristic as chronic vascular inflammation and endothelial dysfuction.