Estrogen-induced superoxide production in coronary artery endothelial cells via uncoupled Nitric Oxide Synthase (NOS) in Diabetes
Location
Georgia
Start Date
12-5-2015 1:00 PM
Description
Premenopausal women are at substantially lower risk for cardiovascular disease (CVD) than men of similar age; however, diabetes eliminates this sex-related protection such that diabetic women have nearly double the risk of CVD as diabetic men. In fact, diabetes increases a woman’s risk for coronary heart disease (CHD) by approximately 10-fold. Although estrogens protect cardiovascular function in women, the effect of diabetes on how coronary arteries respond to estrogen is largely unknown. To address this important gap in our knowledge, the present study has investigated the effects of estrogen on human coronary artery endothelial cells obtained from female donors with either type 1 (HCAEC-D1) or type 2 (HCAEC-D2) diabetes. Human umbilical vein endothelial cells (HUVECS) were employed as non-diabetic controls. Production of nitric oxide was detected via fluorescence microscopy using 4-Amino-5-methylamino-2’,7’-difluorescein (DAF-FM; 2 μM), whereas superoxide production was detected with dihydroethidium (DHE; 20mM). We found that treating HUVECS with 100nM 17b-estradiol (17b-E; 20-30 min) markedly increased NO production, but this response was blunted in both HCAEC-D1 and HCAEC-D2. In the presence of 100 mM L-NAME, an inhibitor of nitric oxide synthase (NOS), 17b-E had little effect on NO production. In contrast, 17b-E increased production of superoxide in both HCAEC-D1 and HCAEC-D2, but had only minimal effects on DHE fluorescence in control HUVECS. Interestingly, L-NAME inhibited the effect of 17b-E on superoxide production in diabetic cells. Taken together, these findings suggest that estrogens stimulate the release of NO from normal vascular endothelial cells, but that in diabetes estrogens stimulate the production of superoxide. Further, the fact that L-NAME inhibits both NO and superoxide production strongly suggests that NOS is the primary target of estrogen in these cells. Thus, we conclude that diabetes uncouples NOS activity in coronary arteries. Instead of producing NO, which has many beneficial cardiovascular effects, estrogen stimulates NOS to produce predominately superoxide in diabetes to increase oxidative stress and CVD. It is likely that this mechanism contributes to the greater risk for CVD experienced by female diabetics, and suggests a novel therapeutic target to alleviate cardiovascular dysfunction in women afflicted by this disease.
Estrogen-induced superoxide production in coronary artery endothelial cells via uncoupled Nitric Oxide Synthase (NOS) in Diabetes
Georgia
Premenopausal women are at substantially lower risk for cardiovascular disease (CVD) than men of similar age; however, diabetes eliminates this sex-related protection such that diabetic women have nearly double the risk of CVD as diabetic men. In fact, diabetes increases a woman’s risk for coronary heart disease (CHD) by approximately 10-fold. Although estrogens protect cardiovascular function in women, the effect of diabetes on how coronary arteries respond to estrogen is largely unknown. To address this important gap in our knowledge, the present study has investigated the effects of estrogen on human coronary artery endothelial cells obtained from female donors with either type 1 (HCAEC-D1) or type 2 (HCAEC-D2) diabetes. Human umbilical vein endothelial cells (HUVECS) were employed as non-diabetic controls. Production of nitric oxide was detected via fluorescence microscopy using 4-Amino-5-methylamino-2’,7’-difluorescein (DAF-FM; 2 μM), whereas superoxide production was detected with dihydroethidium (DHE; 20mM). We found that treating HUVECS with 100nM 17b-estradiol (17b-E; 20-30 min) markedly increased NO production, but this response was blunted in both HCAEC-D1 and HCAEC-D2. In the presence of 100 mM L-NAME, an inhibitor of nitric oxide synthase (NOS), 17b-E had little effect on NO production. In contrast, 17b-E increased production of superoxide in both HCAEC-D1 and HCAEC-D2, but had only minimal effects on DHE fluorescence in control HUVECS. Interestingly, L-NAME inhibited the effect of 17b-E on superoxide production in diabetic cells. Taken together, these findings suggest that estrogens stimulate the release of NO from normal vascular endothelial cells, but that in diabetes estrogens stimulate the production of superoxide. Further, the fact that L-NAME inhibits both NO and superoxide production strongly suggests that NOS is the primary target of estrogen in these cells. Thus, we conclude that diabetes uncouples NOS activity in coronary arteries. Instead of producing NO, which has many beneficial cardiovascular effects, estrogen stimulates NOS to produce predominately superoxide in diabetes to increase oxidative stress and CVD. It is likely that this mechanism contributes to the greater risk for CVD experienced by female diabetics, and suggests a novel therapeutic target to alleviate cardiovascular dysfunction in women afflicted by this disease.