High glucose inhibits expression of inducible and constitutive nitric oxide synthase in bovine aortic endothelial cells

AIM: To investigate the effects of high glucose on the expression of nitric-oxide synthase (NOS) in cultured bovine aortic endothelial cells (BAEC). METHODS: BAEC were cultured and passaged in normal glucose (NG) 5.5 mmol.L-1, high glucose (HG) 25 mmol.L-1, or high osmolarity (glucose 5.5 mmol.L-1 + mannitol 19.5 mmol.L-1, Mann-BAEC), lipopolysaccharides (LPS)-induced nitric oxide (NO) production was assessed by Griess reaction. The expression of inducible NOS (iNOS) and constitutive NOS (ecNOS) was determined by Western blot. RESULTS: At a concentration range from 0.5 to 2 mg.L-1, LPS stimulated NO production in NG-BAEC in a concentration-dependent manner. NO production reached the peak level at LPS 1 mg.L-1. HG inhibited NO production, when compared with NG- and Mann-BAEC (nitrite mu mol.L-1: HG-BAEC 43 +/- 8, vs NG-BAEC 71 +/- 11, Mann-BAEC 70 +/- 9, n = 4 experiments, P < 0.01). iNOS expression was decreased by 39.9 % and 39.3 %, and ecNOS by 28 % and 24 % respectively in HG-BAEC, when compared with NG- or Mann-BAEC. However, no marked difference was observed in the LPS-induced NO production and the expression of iNOS and ecNOS between NG- and Mann-BAEC. CONCLUSIONS: Inhibition of BAEC NO production by HG was mainly due to a decreased expression of NOS protein.