Glycosylated human oxyhaemoglobin activates nuclear factor-jB and activator protein-1 in cultured human aortic smooth muscle

Abstract

1 Diabetic vessels undergo structural changes that are linked to a high incidence of cardiovascular diseases. Reactive oxygen species (ROS) mediate cell signalling in the vasculature, where they can promote cell growth and activate redox-regulated transcription factors, like activator protein-1 (AP-1) or nuclear factor-kB (NF-kB), which are involved in remodelling and inflammation processes. Amadori adducts, formed through nonenzymatic glycosylation, can contribute to ROS formation in diabetes.

2 In this study, we analysed whether Amadori-modified human oxyhaemoglobin, glycosylated at either normal (N-Hb) or elevated (E-Hb) levels, can induce cell growth and activate AP-1 and NF-kB in cultured human aortic smooth muscle cells (HASMC).

3 E-Hb (1 nM–1 mM), but not N-Hb, promoted a concentration-dependent increase in cell size from nanomolar concentrations, although it failed to stimulate HASMC proliferation. At 10 nM, E-Hb stimulated both AP-1 and NF-kB activity, as assessed by transient transfection, electromobility shift assays or immunofluorescence staining. The effects of E-Hb resembled those of the proinflammatory cytokine tumour necrosis factor-a (TNF-a). E-Hb enhanced intracellular superoxide anions content and its effects on HASMC were abolished by different ROS scavengers.

4 In conclusion, E-Hb stimulates growth and activates AP-1 and NF-kB in human vascular smooth muscle by redox-sensitive pathways, thus suggesting a possible direct role for Amadori adducts in diabetic vasculopathy.