The deleterious effect of high concentrations of D-glucose requires pro-inflammatory preconditioning

Objectives The present study investigated whether high concentrations of D-glucose can trigger pro-inflammatory mechanisms in human aortic smooth muscle cells. Methods The expression and/or the activity of inducible nitric oxide synthase (NOS), the extracellular signal-regulated kinase (ERK)1/2 and nuclear factor (NF)-kappa B were studied in cultured human aortic smooth muscle cells (HASMC) in response to increasing concentrations of D-glucose and/or the inflammatory cytokine interleukin (IL)-1 beta. Results Increasing D-glucose in the medium from 5.5 to 22 mmol/l had no effect on any of these parameters. However, the high concentration of D-glucose did increase iNOS expression in response to low concentrations of IL-1 beta (2.5 and 5 ng/ml), as well as the IL-1 beta-induced activation of both ERK 1/2 and NF-kappa B. D-glucose also enhanced, concentration-dependently, the expression and activity of iNOS induced by co-incubation with IL-1 beta (10 ng/ml). Pretreatment with IL-1 beta sensitized the cells to the subsequent effects of high D-glucose. Conclusions The results indicate that high concentrations of D-glucose exacerbate the pro-inflammatory effects of IL-1 beta. We suggest that the observed association between inflammation and diabetes is the result of elevated D-glucose enhancing a pre-existing inflammatory condition, rather than a direct effect of D-glucose on the production of inflammatory mediators.