Diabetes undermines estrogen control of inducible nitric oxide synthase function in rat aortic smooth muscle cells through overexpression of estrogen receptor-beta.
BACKGROUND
Previous reports from our group have shown that 17beta-estradiol reduces the synthesis and activity of inducible nitric oxide synthase (iNOS) in rat aortic smooth muscle cells (SMC) in response to inflammatory mediators. In this study, we investigated the effect of 17beta-estradiol on iNOS function in aortic SMC from streptozotocin-diabetic rats.


RESULTS
Comparative analysis of NO release and of iNOS mRNA and protein content after 24-hour stimulation with a cytokine mixture revealed milder iNOS activation in diabetic than in control SMC. Furthermore, 17beta-estradiol dose-dependently blocked iNOS synthesis and activity in control but not in diabetic SMC. The defective estrogen response in diabetic SMC at 24 hours could not be attributed to reduced expression of estrogen receptors (ER). In fact, mRNA and protein levels of ERalpha and, to a greater extent, of ERbeta, were increased in diabetic compared with nondiabetic SMC. Cytokines decreased ERalpha and ERbeta expression in both groups. However, 17beta-estradiol dose-dependently restored the expression of ERalpha but further downregulated that of ERbeta, indicating a differential regulation of ER isoforms.


CONCLUSIONS
Estrogenic control of iNOS was impaired in diabetic SMC. This was associated with a larger increase of ERbeta than of ERalpha protein, whereas 17beta-estradiol regulated the two isoforms in an opposite fashion. Thus, modifications in the estrogen modulation of iNOS and in the expression pattern of ER may be involved in diabetic vascular dysfunction.
Maggi
Adriana
A
Department of Pharmacological Sciences and Center of Excellence on Neurodegenerative Disease, University of Milan, Italy. adriana.maggi@unimi.it
Cignarella
Andrea
A
Brusadelli
Alessia
A
Bolego
Chiara
C
Pinna
Christian
C
Puglisi
Lina
L
D000818:Animals; D001011:Aorta / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000503:physiopathology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D004351:Drug Resistance; D004790:Enzyme Induction / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D013311:Streptozocin
D016207:Cytokines; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D009573:Nitrites; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D009569:Nitric Oxide; D004958:Estradiol; D013311:Streptozocin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat