| Abstract: | Dynamic changes in the reduction-oxidation (redox) stateof the tissue lead to the pathophysiological condition.Reduced homocysteine causes dysfunctions in endothelium. Theproliferation of smooth muscle cells may lead to occlusive vasculardisease, ischemia, and heart failure, but whether fibrosis andhypertension are a consequence of smooth muscle proliferationis unclear. Redox changes during hyperhomocyst(e)inemia may be one ofthe causes of premature atherosclerotic heart disease. To examine theeffect of homocystine on human vascular smooth muscle cells (HVSMC), weisolated HVSMC from idiopathic dilated cardiomyopathic hearts.Coronaries in these hearts were apparently normal. HVSMC numbers inculture were measured by hemocytometer in the presence and absence of homocystine. Results show that homocystine induced cellularproliferation. This proliferation was reversed by the addition of theantioxidant N-acetylcysteine (NAC).Homocystine induces collagen expression in a dose- and time-dependentmanner, as measured by Northern blot (mRNA) analysis. The 50%inhibitory concentration of 5 µM for collagen was estimated. Theinduction of collagen was reversed by the addition of NAC and reducedglutathione. To localize the receptor for homocystine on HVSMC, wesynthesized fluorescamine-labeled homocystine conjugate. Incubation oflabeled homocystine with HVSMC demonstrated membrane and cytosollocalization of homocystine binding. The receptor-ligand binding wasdisrupted by NAC. Based on sodium dodecyl sulfate-polyacrylamide gelelectrophoresis fluorography, we observed a 40- to 25-kDa homocystineredox receptor in HVSMC. Our results suggested that the redoxhomocysteine induces HVSMC proliferation by binding to the redoxreceptor and may exacerbate atherosclerotic lesion formation byinducing collagen expression. |
