Tetrahydrobiopterin levels regulate endothelial cell proliferation

1 Cardiovascular Research Institute and Department of Medical Physiology, Texas A&M University System Health Science Center, and 2 Department of Animal Science, Texas A&M University, College Station, Texas 77843-1114 Vascular abnormalities, including altered angiogenesis, are major factors contributing to the morbidity and mortality of diabetes. We hypothesized that impaired angiogenesis in diabetes results from decreased tetrahydrobiopterin (BH 4 )-dependent synthesis of nitric oxide (NO) by endothelial cells (EC). To test this hypothesis, we utilized EC from spontaneously diabetic BB (BBd) and nondiabetes-prone BB (BBn) rats to investigate the link between BH 4 and EC proliferation. There were significant decreases in the proliferation rate and expression of proliferating cell nuclear antigen in BBd versus BBn EC, with no evidence of apoptosis in either group. Sepiapterin (a precursor of BH 4 via the salvage pathway) increased BH 4 synthesis and enhanced proliferation of BBd EC. The stimulating effect of sepiapterin on EC proliferation was attenuated by N G -monomethyl- L -arginine, a NO synthase inhibitor. Reducing BH 4 concentrations in BBn EC caused a decrease in proliferation, which was attenuated by a long-acting NO donor. Our results suggest that BH 4 levels regulate proliferation of normal EC and that a BH 4 deficiency impairs NO-dependent proliferation of BBd EC. angiogenesis; nitric oxide; biopterin; diabetes mellitus; wound healing