Alteration of heme-oxygenase-carbon monoxide pathway in calcified rat vascular smooth muscle cells.

Objective The aim of the present study was to investigate the changes in heme-oxygenase (HO)-carbon monoxide (CO)-cyclic guanosine monophosphate (cGMP) pathway in clarified rat vascular smooth muscle cells (VSMCs). Methods Calcification of cultured rat VSMCs was induced by incubation of VSMCs with β-glycerophosphate. Cellular calcium content, ALP activities and 4 5 Ca uptake were measured. HO activity, HbCO formation and content of cGMP in VSMCs were determined. Immunocytochemistry for HO-1 expression was observed. Results In comparison of control VSMCs, the cellular calcium content, ALP activity and 4 5 Ca uptake in calcified VSMCs were obviously increased. Immunocytochemistry showed that HO-1 expression was weak and not well distributed in calcified cells as compared to non-calcified VSMCs, but interestingly, there was stronger staining in calcified nodules than in VSMCs. Compared with VSMCs, HO-1 activity in calcified cells decreased by 42.7% [36.4′2.8 pmol (mg Prxh) - 1 vs 63.5x5.3 pmol (mg Pr×h) - 1 , p<0.01], and HbCO formation decreased by 39.2% (3.38×0.69 μmol/mg Pr vs 5.56′0.48 μmol/mg Pr, p<0.05). The cGMP content in calcified VSMCs was 78.1% lower than that of non-calcified VSMCs (4.3 ′ 0.51 vs 19.6 ′ 1.2 pmol/mg, p < 0.01). Conclusion The results showed that HO-CO-cGMP pathway in calcified vascular cells obviously changed, which might contribute to disturbance of vascular function.