Influence of estrogen on pulmonary arterial hypertension: role of oxidative stress

Hydrogen Sulfide Attenuated Angiotensin II-Induced Sympathetic Excitation in Offspring of Renovascular Hypertensive Rats

Objective

Numerous findings have demonstrated a strong association between parental health during pregnancy and cardiovascular disease in adult offspring. This study investigated whether sensitivity to angiotensin II (Ang II) is enhanced in offspring of renovascular hypertensive animals and whether hydrogen sulfide (H₂S) can attenuate the increased response to Ang II in offspring.

Method

The systolic blood pressure (SBP) was measured by non-invasive tail-cuff plethysmograpy every two weeks in all offspring from 8 to 16 weeks. After intracerebroventricular microinjection of Ang II in the offspring, blood pressure, heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded to test the response to Ang II in the offspring. Western blot analysis was used to examine the protein expression of AT1R, AT1R-associated protein (ATRAP), Nox2, p67^phox, and nitrotyrosine in the nucleus tractus solitarii (NTS).

Results

The SBP in the offspring of hypertensive rats were significantly higher than that in control group, and the above effects were significantly improved by prenatal or postnatal administration of H₂S. Intralateroventricular microinjection of Ang II induced greater sympathetic responses in offspring of hypertensive rats than control group. The expression of AT1R and oxidative stress-related protein was increased, whereas that of ATRAP was decreased in the NTS in offspring of hypertensive rats. Exogenous administration of H₂S prenatally or postnatally improved the above effects.

Conclusion

Prenatal or postnatal administration of H₂S attenuated AngII-induced sympathetic excitation in offspring of hypertensive rats, which may occur by modulating the balance between AT1R and ATRAP and downregulating oxidative stress-related protein expression in the NTS.

Effect of Free and Nanoencapsulated Copaiba Oil on Monocrotaline-induced Pulmonary Arterial Hypertension

Copaiba oil comes from an Amazonian tree and has been used as an alternative medicine in Brazil. However, it has not been investigated yet in the treatment of cardiovascular diseases. This study was designed to test whether copaiba oil or nanocapsules containing this oil could modulate monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). Male Wistar rats (170 ± 20 g) received oil or nanocapsules containing this oil (400 mg/kg) by gavage daily for 1 week. At the end of this period, a single injection of MCT (60 mg/kg i.p.) was administered and measurements were performed after 3 weeks. The animals were divided into 6 groups: control, copaiba oil, nanocapsules with copaiba oil, MCT, oil + MCT, and nanocapsules + MCT. Afterward, echocardiographic assessments were performed, and rats were killed to collect hearts for morphometry and oxidative stress. MCT promoted a significant increase in pulmonary vascular resistance, right ventricle (RV) hypertrophy, and RV oxidative stress. Both oil and copaiba nanocapsules significantly reduced RV hypertrophy and oxidative stress. Pulmonary vascular resistance was reduced by copaiba oil in natura but not by nanocapsules. In conclusion, copaiba oil seems to offer protection against MCT-induced PAH. Our preliminary results suggest that copaiba oil may be an important adjuvant treatment for PAH.

Effects of ovariectomy on antioxidant defence systems in the right ventricle of female rats with pulmonary arterial hypertension induced by monocrotaline

The aim of this study was to evaluate the impact of ovariectomy on oxidative stress in the right ventricle (RV) of female rats with pulmonary arterial hypertension (PAH) induced by monocrotaline (MCT). Rats were divided into 4 groups (n = 6 per group): sham (S), sham + MCT (SM), ovariectomized (O), and ovariectomized + MCT (OM). MCT (60 mg·kg^-1 i.p.) was injected 1 week after ovariectomy or sham surgery. Three weeks later, echocardiographic analysis and RV catheterisation were performed. RV morphometric, biochemical, and protein expression analysis through Western blotting were done. MCT promoted a slight increase in pulmonary artery pressure, without differences between the SM and OM groups, but did not induce RV hypertrophy. RV hydrogen peroxide increased in the MCT groups, but SOD, CAT, and GPx activities were also enhanced. Non-classical antioxidant defenses diminished in ovariectomized groups, probably due to a decrease in the nuclear factor Nrf2. Hemoxygenase-1 and thioredoxin-1 protein expression was increased in the OM group compared with SM, being accompanied by an elevation in the estrogen receptor β (ER-β). Hemoxygenase-1 and thioredoxin-1 may be involved in the modulation of oxidative stress in the OM group, and this could be responsible for attenuation of PAH and RV remodeling.

Estrogenic Impact on Cardiac Ischemic/Reperfusion Injury

The increase in cardiovascular disease and metabolic syndrome incidence following the onset of menopause has highlighted the role of estrogen as a cardiometabolic protective agent. Specifically regarding the heart, estrogen induced an improvement in cardiac function, preserved calcium homeostasis, and inhibited the mitochondrial apoptotic pathway. The beneficial effects of estrogen in relation to cardiac ischemia/reperfusion (I/R) injury, such as reduced infarction and ameliorated post-ischemic recovery, have also been shown. Nevertheless, controversial findings exist and estrogen therapy is reported to be related to a higher rate of thromboembolic events and atrial fibrillation in post-menopausal women. Therefore, greater clarification is needed to evaluate the exact potential of estrogen use in cases of cardiac I/R injury. This article reviews the effects of estrogen, in both acute and chronic treatment, and collates the studies with regard to their in vivo, in vitro, or clinical trial settings in cases of cardiac I/R injury and myocardial infarction.

Exposure to 2,5-hexanedione is accompanied by ovarian and uterine oxidative stress and disruption of endocrine balance in rats

2,5-Hexanedione (2,5-HD) is an aliphatic diketone identified as the main neurotoxic metabolite of the industrial chemicals n-hexane and methyl-n-butyl ketone. Considering the dearth of information on the female reproductive toxicity effects of 2,5-HD in the literature, we assessed the potential oxidative stress mechanisms of 2,5-HD in the ovary and uterus of Wistar rats. A total of 32 female rats were randomly allotted to four groups, in which rats were exposed to 2,5-HD at doses of 0% (control), 0.25%, 0.5% and 1.0% respectively in their drinking water for 21 days. The results showed that 2,5-HD significantly increased ovarian and uterine malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels (p < 0.05). Additionally, while significant decreases in ovarian catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) activities occurred in all the 2,5-HD-treated groups, uterine catalase, GST, and GPx activities increased. Further, 2,5-HD increased follicle stimulating hormone, but decreased estrogen levels in all the 2,5-HD-treated groups, while prolactin increased in the 0.5, and 1.0% 2,5-HD-treated rats compared with the control (p < 0.05). Thus, these data imply that 2,5-HD exposure disrupts hormonal homeostasis and induces oxidative stress in the ovary and uterus of rats. These findings may therefore have toxicological implications in women occupationally exposed to n-hexane and methyl-n-butyl ketone.

Low-dose estrogen is as effective as high-dose treatment in rats with postmenopausal hypertension

: This study was conducted to test the hypothesis that 17β-estradiol therapy improves redox balance by decreasing reactive oxygen species production and increasing nitric oxide (NO) bioavailability, favoring Akt pathway activation and resulting in a better autonomic vascular control. Ovariectomized female Wistar rats were divided into 4 groups: (1) vehicle (VL) and animals treated with a pellet of 17β-estradiol for 21 days; (2) low dose (LE; 0.05 mg); (3) medium dose (ME; 0.2 mg); and (4) high dose (HE; 0.5 mg). Arterial pressure and its sympathetic nervous system modulation were evaluated by spectral analysis. Nitric oxide synthase and NADPH oxidase (Nox) activities, H2O2 concentration, redox status (GSH/GSSG), protein expression of Trx-1 and p-Akt/Akt were evaluated in the aorta, whereas NO metabolites were measured in the serum. Estrogen-treated groups showed a significant decrease in arterial pressure and sympathetic vascular drive. Redox status was significantly improved and NADPH oxidase and H2O2 were decreased in all estrogen-treated groups. Estrogen also induced an enhancement in NO metabolites, nitric oxide synthase activity, and Akt phosphorylation. This study demonstrated that estrogen treatment to ovariectomized rats induced cardioprotection, which was evidenced by reduced blood pressure variability and vascular sympathetic drive. These effects were associated with an improved redox balance and Akt activation, resulting in an enhanced NO bioavailability.

The effects of gender difference on monocrotaline-induced pulmonary hypertension in rats

The present study aimed to compare the effect of gender difference on hemodynamic consequences in the development of monocrotaline (MCT)-induced pulmonary hypertension in rat. The effect of antioxidant enzyme systems on the development of pulmonary hypertension mediated by the phytotoxin MCT and the effect of gender on these antioxidant systems were also investigated. For this purpose, the right ventricular pressures (RVPs) and right ventricular/heart weight (HW) ratios were compared between groups and the glutathione (GSH) level and superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) activities were determined in lung and liver tissue samples of rats. RVP and right ventricular/HW ratios significantly increased in the MCT group compared to the control group. In the MCT group, RVP was significantly higher in males than females. MCT-induced pulmonary hypertension resulted in decreased GSH level, decreased GST and SOD activities and increased CAT activity in lung and liver tissues of both male and female rats. In addition, the lung and liver GSH level and GST and SOD levels were higher in female control rats compared to male control rats. The results of the present study, that antioxidant enzyme activities were different between the groups, highlight the possible role of oxidative stress in the pathogenesis of MCT-induced pulmonary hypertension in rats. Moreover, the lower antioxidant defense capacity of male rats than female rats may be considered as a cause of more aggressive course of MCT-induced pulmonary hypertension in males compared to females.

Function of NADPH oxidase 1 in pulmonary arterial smooth muscle cells after monocrotaline-induced pulmonary vascular remodeling

AIMS

Chronic hypoxia induces pulmonary hypertension (PH) that is concomitant with pulmonary vascular remodeling. Reactive oxygen species (ROS) are thought to play a major role in this. Recent findings suggest that ROS production by NADPH oxidase 4 (Nox4) is important in this remodeling. We investigated whether ROS production by Nox is also important in an inflammatory model of monocrotaline (MCT)-induced PH. We examined ROS production, their possible sources, and their impact on the function of pulmonary arterial smooth muscle cells (PASMC) isolated from MCT-treated and healthy rats.

RESULTS

MCT-PASMC showed increased intracellular superoxide production, migration, and proliferation compared with healthy controls due to increased Nox1 expression. A comparison of PASMC from MCT- and nontreated rats revealed an up-regulation of Sod2, Nrf2, cyclin D1, and matrix metalloproteinase-9 (MMP-9) as well as an increased phosphorylation of cofilin and extracellular signal-regulated kinases (Erk). Expression of Sod2, Nrf2, and cyclin D1 and phosphorylation of cofilin and Erk were Nox1 dependent.

INNOVATION

The role of ROS in PH is not fully understood. Mitochondria and Nox have been suggested as sources of altered ROS generation in PH, yet it remains unclear whether increased or decreased ROS contributes to the development of PH. Our studies provide evidence that for different triggers of PH, different Nox isoforms regulate proliferation and migration of PASMC.

CONCLUSION

In contrast to hypoxia-induced PH, Nox1 but not Nox4 is responsible for pathophysiological proliferation and migration of PASMC in an inflammatory model of MCT-induced PH via increased superoxide production. Thus, different Nox isoforms may be targeted in different forms of PH.

Estrogen normalizes perinatal nicotine-induced hypertensive responses in adult female rat offspring

Perinatal nicotine exposure caused a sex-dependent heightened vascular response to angiotensin II (Ang II) and increased blood pressure in adult male but not in female rat offspring. The present study tested the hypothesis that estrogen normalizes perinatal nicotine-induced hypertensive response to Ang II in female offspring. Nicotine was administered to pregnant rats via subcutaneous osmotic minipumps from day 4 of gestation to day 10 after birth. Ovariectomy and 17β-estradiol replacement were performed on 8-week-old female offspring. At 5 months of age, Ang II-induced blood pressure responses were not changed by nicotine treatment in the sham groups. In contrast, nicotine significantly enhanced Ang II-induced blood pressure responses as compared with saline control in the ovariectomy groups, which was associated with increased Ang II-induced vascular contractions. These heightened responses were abrogated by 17β-estradiol replacement. In addition, nicotine enhanced Ang II receptor type I, NADPH (nicotinamide adenine dinucleotide phosphate) oxidase type 2 protein expressions, and reactive oxygen species production of aortas as compared with saline control in the ovariectomy groups. Antioxidative agents, both apocynin and tempol, inhibited Ang II-induced vascular contraction and eliminated the differences of contractions between nicotine-treated and control ovariectomy rats. These findings support a key role of estrogen in the sex difference of perinatal nicotine-induced programming of vascular dysfunction, and suggest that estrogen may counteract heightened reactive oxygen species production, leading to protection of females from development programming of hypertensive phenotype in adulthood.