High-glucose-induced nuclear factor κB activation in vascular smooth muscle cells

Objective: Vascular smooth muscle cell (VSMC) dysfunction plays a role in diabetic macrovasculopathy. This dysfunction may be caused or exacerbated by expression of many of genes potently activated by the transcriptional factor nuclear factor kappa B (NF-kappa B). We have examined whether culture of VSMCs under high glucose conditions to stimulate the diabetic state can lead to the activation of NF-kappa B. Methods: NF-kappa B activation was assessed in VSMCs stably transfected with a cis-reporter plasmid containing the NF-kappa B binding sites. Results: Within 3-h incubation, high glucose (27.5 or 55 mmol/l) alone induced an increase in NF-kappa B activity in VSMCs; this increase was mimicked by mannitol given to deliver the same osmolar stress to the cells. High glucose or mannitol also enhanced TNF alpha-stimulated NF-kappa B activity. Incubation with high glucose for 48 h followed by stimulation with TNF alpha led to a marked potentiation of NF-kappa B activation compared with normoglycemic (5.5 mmol/l) VSMCs exposed to TNF alpha. while mannitol attenuated this effect. A 48-h incubation with high glucose substantially reduced glutathione (GSH) levels compared with normoglycemic VSMCs, whereas mannitol significantly increased GSH levels. An antioxidant N-acetyl-L-cysteine and a selective protein kinase C (PKC) inhibitor GF109203X significantly suppressed the TNF alpha-induced NF-kappa B activation, and abrogated potentiation of TNF alpha-induced NF-kappa B activity caused by high glucose (27.5 mmol/l). Conclusion: These results suggest that acutely high glucose causes alterations in osmolarity leading to activation of NF-kappa B, but that exposure to high glucose for more prolonged times causes changes in antioxidant defences and activation of PKC, which potentiates cytokine activation of NF-kappa B. Further definition of these pathways will help to delineate important signals mediating the aberrant behavior of VSMCs under hyperglycemic/diabetic conditions. (C) 2000 Elsevier Science B.V. All rights reserved.