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Standard hormone therapy for menopausal women [conjugated equine estrogen (CEE) 0.625 mg] has been associated with increased risk of venous thrombosis. Regimens containing a lower CEE dose (0.30 mg) have been used clinically to decrease side effects of supraphysiologic doses of estrogen. In this study, we determined the effects of standard (SD) and low dose (LD) of CEE on venular function in ovariectomized (OVX) spontaneously hypertensive rats (SHR). Contractions by angiotensin-II (Ang-II 10 μ M) in perfused mesenteric venular bed were markedly increased in OVX (21.5 ± 1.3 mmHg) compared with Sham (14.7 ± 1.1 mm Hg, P < 0.05). CEE-SD did not modify Ang-II responses in OVX, whereas CEE-LD restored Ang-II contraction to Sham levels. Endothelial nitric oxide synthase (eNOS) inhibition by L-NAME increased Ang-II contractions in Sham and CEE-LD and was without effect in venules of OVX SHR and CEE-SD. In OVX there was decreased NO generation in association with diminished eNOS phosphorylation and increased O 2 - generation in the venular wall. CEE-LD reverted the deleterious effects of ovariectomy. Although CEE-SD augmented eNOS phosphorylation in OVX, it was unable to increase NO levels, probably owing to its inability to reduce O 2 - Distinct effects by CEE-SD and CEE-LD parallel the differential modulation of Ang-II and estrogen receptors. Compared with Sham, CEE-LD increases Ang II receptor type 2, whereas CEE-SD modified ER β expression in the venous bed. Interestingly, both CEE doses increased G protein-coupled estrogen receptor in OVX. Our data suggest that estrogen dose is an important factor for venous function. Although CEE-LD reversed deleterious effects of OVX, CEE-SD showed null effects despite its ability to increase eNOS activity., (Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.)

Cerebral ischemia followed by reperfusion alters vessel properties of brain arteries in rats, inducing an inflammatory response and excessive generation of reactive oxygen species. This study investigated the participation of oxidative stress on vessel properties after ischemia/reperfusion and the beneficial effects of 3,4-dihydro-6-hydroxy-7-methoxy-2,2-dimethyl-1(2H)-benzopyran (CR-6). The right middle cerebral artery was occluded (90 min) and reperfused (24 h). Sham-operated animals were used as controls. Ischemic rats were treated either with CR-6 (100 mg/kg in 1 ml olive oil) or vehicle (1 ml olive oil) administered orally at 2 and 8 h after the onset of ischemia. The structural, mechanical, and myogenic properties of the middle cerebral artery (MCA) were assessed by pressure myography. Superoxide anion ( ) production was evaluated by ethidium fluorescence, and protein tyrosine nitrosylation was determined by immunofluorescence. Infarct volume was smaller in rats treated with CR-6. In MCA, ischemia/reperfusion increased wall thickness, cross-sectional area, wall/lumen, and decreased wall stress. CR-6 treatment prevented all of these changes induced by ischemia/reperfusion. However, impaired myogenic response and larger lumen diameter in active conditions observed after ischemia/reperfusion were not modified by CR-6. Treatment with CR-6 prevented the increase in production and partially prevented the enhanced protein tyrosine nitrosylation that occurred in response to ischemia/reperfusion. Our findings suggest that oxidative stress is involved in the alterations of MCA properties observed after ischemia/reperfusion and that CR-6 induces protection.

Stroke triggers a local and systemic inflammatory response leading to the production of cytokines that can influence blood vessel reactivity. In this study, we aimed to assess whether cerebral ischemia/reperfusion could affect vasoconstriction and vasodilatation on mesenteric resistance arteries (MRA) from Wistar Kyoto rats. The right middle cerebral artery was occluded (90 min) and reperfused (24 h). Sham-operated animals were used as controls. Plasma levels of interleukin (IL)-6 and IL-1beta were measured at 24 h. Vasoconstrictor and vasodilator responses were recorded in a wire myograph. Protein expression was determined by Western blot and immunofluorescence, and superoxide anion (O(2)(.)) production was evaluated by ethidium fluorescence. In MRA, ischemia/reperfusion increased plasma levels of IL-6, O2. production, protein expression of cyclooxygenase-2, and protein tyrosine nitrosylation, but it impaired acetylcholine (ACh) vasodilatation without modifying the vasodilatations to sodium nitroprusside or the contractions to phenylephrine and KCl. Superoxide dismutase (SOD) and indomethacin reversed the impairment of ACh relaxation induced by ischemia/reperfusion. However, N(omega)-nitro-l-arginine methyl ester affected similarly ACh-induced vasodilatations in MRA of ischemic and sham-operated rats. Protein expression of endothelial and inducible nitric-oxide synthase, copper/zinc SOD, manganese SOD, and extracellular SOD was similar in both groups of rats. Our results show MRA endothelial dysfunction 24 h after brain ischemia/reperfusion. Excessive production of O2. in MRA mediates endothelial dysfunction, and the increase in plasma cytokine levels after brain ischemia/reperfusion might be involved in this effect.

The present study was designed to analyze the effect of long-term incubation with interleukin-1beta (IL-1beta) on endothelium-dependent relaxation in rat mesenteric resistance arteries. Vessels were incubated in culture medium with or without IL-1beta (10 ng/ml, 14 h). Changes in lumen diameter were recorded in a pressure myograph. Protein expression, nitrite, and superoxide anion (O(2)(.)) production were evaluated by either Western blot or immunofluorescence, Griess reaction, and ethidium fluorescence, respectively. IL-1beta impaired acetylcholine (ACh) and sodium nitroprusside (SNP) vasodilation and increased nitrite and O(2)(.) production and inducible nitric-oxide synthase (iNOS), xanthine oxidase, and p22(phox) expression. However, neither endothelial nitric-oxide synthase (NOS) nor soluble guanylate cyclase protein expression were affected by IL-1beta treatment. Polyethylene glycol superoxide dismutase partially reversed the impairment of ACh relaxation and abolished the O(2)(.) production observed in IL-1beta-treated arteries. The impairment of ACh relaxation induced by IL-1beta was also partially reversed by the xanthine oxidase inhibitor allopurinol (1 mM) but not by either the NADPH oxidase inhibitor apocynin (0.3 mM) or the inducible NOS inhibitor N-3-aminomethylbenzylacetamidine (1 microM). However, all these inhibitors improved the impaired SNP response. The results of the present study demonstrate that long-term incubation with IL-1beta induces an impairment of the nitric oxide-mediated relaxation in mesenteric resistance arteries through the production of O(2)(.), mainly from xanthine oxidase.