Inhibition of Pro-Inflammatory Cytokine Secretion by Select Antioxidants in Human Coronary Artery Endothelial Cells

Inflammatory and oxidative stress in endothelial cells are implicated in the pathogenesis of premature atherosclerosis in diabetes. To determine whether high-dextrose concentrations induce the expression of pro-inflammatory cytokines, human coronary artery endothelial cells (HCAEC) were exposed to either 5.5 or 27.5 mM dextrose for 24-hours and interteukin-1 beta (IL-1 beta), interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor alpha (TNF alpha) levels were measured by enzyme immunoassays. To determine the effect of antioxidants on inflammatory cytokine secretion, cells were also treated with alpha-tocopherot, ascorbic acid, and the gtutathione peroxidase mimetic ebselen. Only the concentration of IL-1 beta in culture media from cells exposed to 27.5 mM dextrose increased relative to cells maintained in 5.5 mM dextrose. Treatment with alpha-tocopherol (10, 100, and 1,000 mu M) and ascorbic acid (15, 150, and 1,500 mu M) at the same time that the dextrose was added reduced IL-1 beta, IL-6, and IL-8 levels in culture media from cells maintained at 5.5 mM dextrose but had no effect on IL-1 beta, IL-6, and IL-8 levels in cells exposed to 27.5 mM dextrose. However, ebselen treatment reduced IL-1 beta, IL-6, and IL-8 levels in cells maintained in either 5.5 or 27.5 mM dextrose. IL-2 and TNF alpha concentrations in culture media were below the limit of detection under all experimental conditions studied suggesting that these cells may not synthesize detectable quantities of these cytokines. These results suggest that dextrose at certain concentrations may increase IL-1 beta levels and that antioxidants have differential effects on suppressing the secretion of pro-inflammatory cytokines in HCAEC.