Effect of hypoxia and hypoxia/reoxygenation on proteoglycan metabolism by vascular smooth muscle cells

Hypoxia and hypoxia/reoxygenation are known to affect vascular smooth muscl e cell physiology. In this study, we first investigated proteoglycan synthe sis by human aortic smooth muscle cells exposed to normoxia, hypoxia, or hy poxia/reoxygenation. We then compared the newly synthesized proteoglycans f rom normoxic and hypoxic-reoxygenation cultures for their ability to bind l ow density lipoprotein (LDL). Confluent smooth muscle cells under normoxia, hypoxia, or hypoxia/reoxygenation were pulsed with [S-35]sulfate, and secr eted and cell-associated proteoglycans were analyzed. Secreted proteoglycan s in cultures exposed to hypoxia (4 h)/reoxygenation (19 h) increased 28% o ver those of cells continuously exposed to normoxia. Cell-associated proteo glycans did not differ significantly between the two groups. In contrast, h ypoxia (4 h) followed by a 30-min reoxygenation produced a 37% decrease in newly synthesized proteoglycans. Hypoxia alone also resulted in a 24% decre ase in secreted proteoglycans and a 20% decrease in cell-associated proteog lycans. Proteoglycans newly synthesized by smooth muscle cells exposed to n ormoxia and hypoxia/reoxygenation did not differ in their charge densities and molecular size but did differ in glycosaminoglycan composition. Exposur e of smooth muscle cells to hypoxia/reoxygenation produced a 60% increase i n a proteoglycan subfraction that bound LDL with very high affinity. The in corporation of [H-3]leucine into total cellular protein decreased significa ntly following exposure of smooth muscle cells to hypoxia as well as hypoxi a/reoxygenation. These results indicate that hypoxia and hypoxia/reoxygenat ion cause major alterations in proteoglycan metabolism by vascular smooth m uscle cells. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.