Angiotensin-(1-7) prevents T3-induced cardiomyocyte hypertrophy by upregulating FOXO3/SOD1/catalase and downregulating NF-ĸB.

Clinical studies have shown a correlation between thyroid disorders and cardiac diseases. High levels of triiodothyronine (T3) induce cardiac hypertrophy, a risk factor for cardiac complications and heart failure. Previous results have demonstrated that angiotensin-(1-7) is able to block T3-induced cardiac hypertrophy; however, the molecular mechanisms involved in this event have not been fully elucidated. Here, we evidenced the contribution of FOXO3 signaling to angiotensin-(1-7) effects. Angiotensin-(1-7) treatment increased nuclear FOXO3 levels and reduced p-FOXO3 levels (inactive form) in isolated cardiomyocytes. Knockdown of FOXO3 by RNA silencing abrogated the antihypertrophic effect of angiotensin-(1-7). Increased expression of antioxidant enzymes superoxide dismutase 1 (SOD1 and catalase) and lower levels of reactive oxygen species and nuclear factor-κB (NF-κB) were observed after angiotensin-(1-7) treatment in vitro. Consistent with these results, transgenic rats overexpressing angiotensin-(1-7) displayed increased nuclear FOXO3 and SOD1 levels and reduced NF-κB levels in the heart. These results provide a new molecular mechanism responsible for the antihypertrophic effect of angiotensin-(1-7), which may contribute to future therapeutic targets.

Association of testosterone with estrogen abolishes the beneficial effects of estrogen treatment by increasing ROS generation in aorta endothelial cells.

Testosterone has been added to hormone replacement therapy to treat sexual dysfunction in postmenopausal women. Whereas estrogen has been associated with vascular protection, the vascular effects of testosterone are contradictory and the effects of its association with estrogen are largely unknown. In this study we determined the effects of testosterone associated with conjugated equine estrogen (CEE) on vascular function using a model of hypertensive postmenopausal female: ovariectomized spontaneously hypertensive rats. Female spontaneously hypertensive rats were divided into sham-operated, ovariectomized (OVX), and OVX treated for 15 days with either CEE alone (OVX+CEE) or associated with testosterone (OVX+CEE+T). Angiotensin II (ANG II)-induced contraction was markedly increased in aortic rings from OVX compared with sham-operated rats. CEE treatment restored ANG-II responses, a beneficial effect abrogated with CEE+T. CEE treatment also increased endothelium-dependent relaxation, which was impaired in OVX rats. This effect was lost by CEE+T. Treatment of aortas with losartan (ANG-II type-1 receptor antagonist) or apocynin (NADPH-oxidase inhibitor) restored the endothelium-dependent relaxation in OVX and CEE+T, establishing an interplay between ANG-II and endothelial dysfunction in OVX and CEE+T. The benefits by CEE were associated with downregulation of NADPH-oxidase subunits mRNA expression and decreased reactive oxygen species generation. The association of testosterone with CEE impairs the benefits of estrogen on OVX-associated endothelial dysfunction and reactive oxygen species generation in rat aorta by a mechanism that involves phosphorylation of the cytosolic NADPH-oxidase subunit p47(phox).

Metformin reduces the Walker-256 tumor development in obese-MSG rats via AMPK and FOXO3a.

AIMS: Studies have associated obesity with a wide variety of cancers. Metformin, an anti-diabetic drug, has recently received attention as a potentially useful therapeutic agent for treating cancer. Therefore, the objective of this study was to analyze the mechanisms involved in the increase in tumor development and the reduction of it by metformin in obesity using an experimental breast tumor model. MATERIAL AND METHODS: Newborn male Wistar rats were subcutaneously injected with 400mg/kg monosodium glutamate (MSG) (obese) or saline (control) at 2, 3, 4, 5 and 6 days of age. After 16 weeks, 1 × 10(7) Walker-256 tumor cells were subcutaneously injected in the right flank of the rats and concomitantly the treatment with metformin 300 mg/kg/15 days, via gavage, started. The rats were divided into 4 groups: control tumor (CT), control tumor metformin (CTM), obese-MSG tumor (OT) and obese-MSG tumor metformin (OTM). On the 18th week the tumor development and metformin effect were analyzed. KEY FINDINGS: Tumor development was higher in OT rats compared with CT rats. Activation of insulin-IR-ERK1/2 pathway and an anti-apoptotic effect might be the mechanisms involved in the higher development of tumor in obesity. The effect of metformin reducing the tumor development in obese rats might involve increased mRNA expression of pRb and p27, increased activity of AMPK and FOXO3a and decreased expression of p-ERK1/2 (Thr202/Tyr204) in Walker-256 tumor. SIGNIFICANCE: Our data allow us to suggest that metformin, reducing the stimulatory effect of obesity on tumor development, has a potential role in the management of cancers.

Toll-like receptor 4 contributes to blood pressure regulation and vascular contraction in spontaneously hypertensive rats.

Activation of TLRs (Toll-like receptors) induces gene expression of proteins involved in the immune system response. TLR4 has been implicated in the development and progression of CVDs (cardio-vascular diseases). Innate and adaptive immunity contribute to hypertension-associated end-organ damage, although the mechanism by which this occurs remains unclear. In the present study, we hypothesize that inhibition of TLR4 decreases BP (blood pressure) and improves vascular contractility in resistance arteries from SHR (spontaneously hypertensive rats). TLR4 protein expression in mesenteric resistance arteries was higher in 15-week-old SHR than in age-matched Wistar controls or in 5-week-old SHR. To decrease the activation of TLR4, 15-week-old SHR and Wistar rats were treated with anti-TLR4 (anti-TLR4 antibody) or non-specific IgG control antibody for 15 days (1 µg per day, intraperitoneal). Treatment with anti-TLR4 decreased MAP (mean arterial pressure) as well as TLR4 protein expression in mesenteric resistance arteries and IL-6 (interleukin 6) serum levels from SHR when compared with SHR treated with IgG. No changes in these parameters were found in treated Wistar control rats. Mesenteric resistance arteries from anti-TLR4-treated SHR exhibited decreased maximal contractile response to NA (noradrenaline) compared with IgG-treated SHR. Inhibition of COX (cyclo-oxygenase)-1 and COX-2, enzymes related to inflammatory pathways, decreased NA responses only in mesenteric resistance arteries of SHR treated with IgG. COX-2 expression and TXA2 (thromboxane A2) release were decreased in SHR treated with anti-TLR4 compared with IgG-treated SHR. Our results suggest that TLR4 activation contributes to increased BP, low-grade inflammation and plays a role in the augmented vascular contractility displayed by SHR.

Oxidative stress and inflammatory mediators contribute to endothelial dysfunction in high-fat diet-induced obesity in mice.

OBJECTIVE: We investigated the effects of high-fat diet-induced obesity on vascular proinflammatory factors and oxidative stress on endothelium-dependent relaxation of the aorta. METHODS: Female Swiss mice were submitted to a high-fat diet for 16 weeks. At the end of the experimental period, we evaluated blood pressure, relaxation in response to acetylcholine in aortic rings in the absence and the presence of the superoxide anion scavenger, superoxide dismutase (SOD, 150 U/ml), and the nuclear factor (NF)-κB inhibitor, sodium salicylate (5 mmol/l). Aortic protein expression of endothelial nitric oxide synthase, Cu/Zn-SOD, NF-κB, IκB-α, and proinflammatory cytokines were also evaluated. RESULTS: Obese mice presented higher systolic and diastolic blood pressure than control mice (P < 0.05). The relaxation of aortas to acetylcholine, but not to sodium nitroprusside, was significantly decreased in obese mice and was corrected by both SOD and sodium salicylate (P < 0.05). The protein expression of endothelial nitric oxide synthase and Cu/Zn-SOD was significantly decreased in aorta from obese mice (P < 0.05). Total p65 NF-κB subunit protein expression was not affected by obesity, but the protein expression of NF-κB inhibitor IκB-α was lower in aorta from obese mice (P < 0.05). There were no significant differences in the interleukin (IL)-1ß and IL-6 protein expression between groups. In contrast, the expression of TNF-α was significantly increased in aortas from obese mice. CONCLUSION: Our results suggest that the reduced antioxidant defense and the local NF-κB pathway play an important role in the impairment of endothelium-dependent relaxation in aorta from obese mice.

Obesity induced by high-fat diet promotes insulin resistance in the ovary.

Besides the effects on peripheral energy homeostasis, insulin also has an important role in ovarian function. Obesity has a negative effect on fertility, and may play a role in the development of the polycystic ovary syndrome in susceptible women. Since insulin resistance in the ovary could contribute to the impairment of reproductive function in obese women, we evaluated insulin signaling in the ovary of high-fat diet-induced obese rats. Female Wistar rats were submitted to a high-fat diet for 120 or 180 days, and the insulin signaling pathway in the ovary was evaluated by immunoprecipitation and immunoblotting. At the end of the diet period, we observed insulin resistance, hyperinsulinemia, an increase in progesterone serum levels, an extended estrus cycle, and altered ovarian morphology in obese female rats. Moreover, in female obese rats treated for 120 days with the high-fat diet, the increase in progesterone levels occurred together with enhancement of LH levels. The ovary from high-fat-fed female rats showed a reduction in the insulin receptor substrate/phosphatidylinositol 3-kinase/AKT intracellular pathway, associated with an increase in FOXO3a, IL1B, and TNFalpha protein expression. These changes in the insulin signaling pathway may have a role in the infertile state associated with obesity.