Vascular dysfunction programmed in male rats by topiramate during peripubertal period.

AIM: The present study evaluated whether topiramate (TPM) treatment during the peripubertal period affects vascular parameters of male rats and whether oxidative stress plays a role in these changes. MAIN METHODS: Rats were treated with TPM (41 mg/kg/day, gavage) or vehicle (CTR group) from the postnatal day (PND) 28 to 50. At PND 51 and 120 the rats were evaluated for: thoracic aorta reactivity to phenylephrine, in the presence (Endo+) or absence of endothelium (Endo-), to acetylcholine and to sodium nitroprusside (SNP), aortic thickness and endothelial nitric oxide synthase (eNOS) expression. In serum were analyzed: the antioxidant capacity by ferric reducing antioxidant power assay; endogenous antioxidant reduced glutathione, and superoxide anion. Results were expressed as mean ± s.e.m., differences when p < 0.05. STATISTICS: Two-way ANOVA (and Tukey's) or Student t-test. KEY FINDINGS: At PND 51, the contraction induced by phenylephrine in Endo+ ring was higher in TPM when compared to CTR. At PND 120, the aortic sensitivity to acetylcholine in TPM rats was reduced in comparison with CTR. The aortic eNOs expression and the aortic thickness were similar between the groups. At PND 51 and 120, TPM group presented a decrease in antioxidants when compared to CTR groups and at PND 120, in TPM group the superoxide anion was increased. SIGNIFICANCE: Taken together, the treatment of rats with TPM during peripubertal period promoted permanent impairment of endothelial function probably mediated by oxidative stress.

Autoregulation of blood flow drives early hypotension in a rat model of systemic inflammation induced by bacterial lipopolysaccharide.

Uncontrolled vasodilation is known to account for hypotension in the advanced stages of sepsis and other systemic inflammatory conditions, but the mechanisms of hypotension in earlier stages of such conditions are not clear. By monitoring hemodynamics with the highest temporal resolution in unanesthetized rats, in combination with ex-vivo assessment of vascular function, we found that early development of hypotension following injection of bacterial lipopolysaccharide is brought about by a fall in vascular resistance when arterioles are still fully responsive to vasoactive agents. This approach further uncovered that the early development of hypotension stabilized blood flow. We thus hypothesized that prioritization of the local mechanisms of blood flow regulation (tissue autoregulation) over the brain-driven mechanisms of pressure regulation (baroreflex) underscored the early development of hypotension in this model. Consistent with this hypothesis, an assessment of squared coherence and partial-directed coherence revealed that, at the onset of hypotension, the flow-pressure relationship was strengthened at frequencies (<0.2 Hz) known to be associated with autoregulation. The autoregulatory escape to phenylephrine-induced vasoconstriction, another proxy of autoregulation, was also strengthened in this phase. The competitive demand that drives prioritization of flow over pressure regulation could be edema-associated hypovolemia, as this became detectable at the onset of hypotension. Accordingly, blood transfusion aimed at preventing hypovolemia brought the autoregulation proxies back to normal and prevented the fall in vascular resistance. This novel hypothesis opens a new avenue of investigation into the mechanisms that can drive hypotension in systemic inflammation.

Carotid dysfunction in senescent female mice is mediated by increased α1A-adrenoceptor activity and COX-derived vasoconstrictor prostanoids.

α-Adrenergic receptors are crucial regulators of vascular hemodynamics and essential pharmacological targets for cardiovascular diseases. With aging, there is an increase in sympathetic activation, which could contribute to the progression of aging-associated cardiovascular dysfunction, including stroke. Nevertheless, there is little information directly associating adrenergic receptor dysfunction in the blood vessels of aged females. This study determined the role of a-adrenergic receptors in carotid dysfunction of senescent female mice (accelerated-senescence prone, SAMP8), compared with a nonsenescent (accelerated-senescence prone, SAMR1). Vasoconstriction to phenylephrine (Phe) was markedly increased in common carotid artery of SAMP8 [area under the curve (AUC), 527 ± 53] compared with SAMR1 (AUC, 334 ± 30, P = 0.006). There were no changes in vascular responses to the vasoconstrictor agent U46619 or the vasodilators acetylcholine (ACh) and sodium nitroprusside (NPS). Hyperactivity to Phe in female SAMP8 was reduced by cyclooxygenase-1 and cyclooxygenase-2 inhibition and associated with augmented ratio of TXA2/PGI2 release (SAMR1, 1.1 ± 0.1 vs. SAMP8, 2.1 ± 0.3, P = 0.007). However, no changes in cyclooxygenase expression were seen in SAMP8 carotids. Selective α1A-receptor antagonism markedly reduced maximal contraction, whereas α1D antagonism induced a minor shift in Phe contraction in SAMP8 carotids. Ligand binding analysis revealed a threefold increase of α-adrenergic receptor density in smooth muscle cells (VSMCs) of SAMP8 vs. SAMR1. Phe rapidly increased intracellular calcium (Cai2+) in VSMCs via the α1A-receptor, with a higher peak in VSMCs from SAMP8. In conclusion, senescence intensifies vasoconstriction mediated by α1A-adrenergic signaling in the carotid of female mice by mechanisms involving increased Cai2+ and release of cyclooxygenase-derived prostanoids.NEW & NOTEWORTHY The present study provides evidence that senescence induces hyperreactivity of α1-adrenoceptor-mediated contraction of the common carotid. Impairment of α1-adrenoceptor responses is linked to increased Ca2+ influx and release of COX-derived vasoconstrictor prostanoids, contributing to carotid dysfunction in the murine model of female senescence (SAMP8). Increased reactivity of the common carotid artery during senescence may lead to morphological and functional changes in arteries of the cerebral microcirculation and contribute to cognitive decline in females. Because the elderly population is growing, elucidating the mechanisms of aging- and sex-associated vascular dysfunction is critical to better direct pharmacological and lifestyle interventions to prevent cardiovascular risk in both sexes.

Intrauterine growth restriction leads to a high-corticosterone producing offspring: An implication for pulmonary infection susceptibility.

AIMS: Although intrauterine growth restriction (IUGR) impairs immune system homeostasis and lung development, its relationship with the susceptibility to pulmonary infections remains unclear. Thus, this study aimed to investigate the impact of IUGR on acute lung inflammatory response induced by bacterial stimulus. MATERIALS AND METHODS: Pregnant female Wistar rats were subjected to 50% caloric-protein food restriction during gestation. To mimic bacterial lung infection, adult male offspring (12 weeks old) were challenged with a single lipopolysaccharide (LPS) intranasal instillation, and 6 h later, we assessed the acute inflammatory response. Normal birth weight (NBW) animals represent the control group. KEY FINDINGS: LPS instillation increased the protein levels in the airways of both the NBW and low birth weight (LBW) groups, indicating vascular leakage. LBW animals exhibited a lower number of neutrophils, reduced production of interleukin-6 and macrophage-inflammatory protein-2 and decreased upregulation of intercellular adhesion molecule-1 gene expression in lung tissues. Further analysis revealed that the LBW group produced lower levels of prostaglandin-E2 and failed to secrete leukotriene-B4 upon LPS stimulation, which correlated with impaired cyclooxygenase-2 and 5-lipoxygenase expression. These results were probably associated with their inability to upregulate the expression of Toll-like receptor-4 and downstream signaling proteins, such as nuclear factor kappa-B, in the lungs. The LBW group also exhibited abnormal airway thickening and high corticosterone levels under basal conditions. SIGNIFICANCE: This study suggests that IUGR-induced foetal programming in LBW offspring threatens HPA axis physiology and corticosterone biodisponibility, and impairs the innate response to bacterial antigens, increasing future susceptibility to pulmonary infection.

Gold nanoparticles reduce inflammation in cerebral microvessels of mice with sepsis.

BACKGROUND: Sepsis is an emergency medical condition that can lead to death and it is defined as a life-threatening organ dysfunction caused by immune dysregulation in response to an infection. It is considered the main killer in intensive care units. Sepsis associated-encephalopathy (SAE) is mostly caused by a sepsis-induced systemic inflammatory response. Studies report SAE in 14-63% of septic patients. Main SAE symptoms are not specific and usually include acute impairment of consciousness, delirium and/or coma, along with electroencephalogram (EEG) changes. For those who recover from sepsis and SAE, impaired cognitive function, mobility and quality of life are often observed months to years after hospital discharge, and there is no treatment available today to prevent that. Inflammation and oxidative stress are key players for the SAE pathophysiology. Gold nanoparticles have been demonstrated to own important anti-inflammatory properties. It was also reported 20 nm citrate-covered gold nanoparticles (cit-AuNP) reduce oxidative stress. In this context, we tested whether 20 nm cit-AuNP could alleviate the acute changes caused by sepsis in brain of mice, with focus on inflammation. Sepsis was induced in female C57BL/6 mice by cecal ligation and puncture (CLP), 20 nm cit-AuNP or saline were intravenously (IV) injected 2 h after induction of sepsis and experiments performed 6 h after induction. Intravital microscopy was used for leukocyte and platelet adhesion study in brain, blood brain barrier (BBB) permeability carried out by Evans blue assay, cytokines measured by ELISA and real time PCR, cell adhesion molecules (CAMs) by flow cytometry and immunohistochemistry, and transcription factors, by western blotting. RESULTS: 20 nm cit-AuNP treatment reduced leukocyte and platelet adhesion to cerebral blood vessels, prevented BBB failure, reduced TNF- concentration in brain, and ICAM-1 expression both in circulating polymorphonuclear (PMN) leukocytes and cerebral blood vessels of mice with sepsis. Furthermore, 20 nm cit-AuNP did not interfere with the antibiotic effect on the survival rate of mice with sepsis. CONCLUSIONS: Cit-AuNP showed important anti-inflammatory properties in the brain of mice with sepsis, being a potential candidate to be used as adjuvant drug along with antibiotics in the treatment of sepsis to avoid SAE.

Vascular Aging in Rodent Models: Contrasting Mechanisms Driving the Female and Male Vascular Senescence.

Increasing scientific interest has been directed to sex as a biological and decisive factor on several diseases. Several different mechanisms orchestrate vascular function, as well as vascular dysfunction in cardiovascular and metabolic diseases in males and females. Certain vascular sex differences are present throughout life, while others are more evident before the menopause, suggesting two important and correlated drivers: genetic and hormonal factors. With the increasing life expectancy and aging population, studies on aging-related diseases and aging-related physiological changes have steeply grown and, with them, the use of aging animal models. Mouse and rat models of aging, the most studied laboratory animals in aging research, exhibit sex differences in many systems and physiological functions, as well as sex differences in the aging process and aging-associated cardiovascular changes. In the present review, we introduce the most common aging and senescence-accelerated animal models and emphasize that sex is a biological variable that should be considered in aging studies. Sex differences in the cardiovascular system, with a focus on sex differences in aging-associated vascular alterations (endothelial dysfunction, remodeling and oxidative and inflammatory processes) in these animal models are reviewed and discussed.

Toll-Like Receptors Represent an Important Link for Sex Differences in Cardiovascular Aging and Diseases.

Human life span expectancy has increased, and aging affects the organism in several ways, leading, for example, to an increased risk of cardiovascular diseases. Age-adjusted prevalence of the cardiovascular diseases is higher in males than females. Aging also affects the gonadal sex hormones and the sex differences observed in cardiovascular diseases may be therefore impacted. Hormonal changes associated with aging may also affect the immune system and the immune response is sexually different. The immune system plays a role in the pathogenesis of cardiovascular diseases. In this context, toll-like receptors (TLRs) are a family of pattern recognition receptors of the immune system whose activation induces the synthesis of pro-inflammatory molecules. They are expressed throughout the cardiovascular system and their activation has been widely described in cardiovascular diseases. Some recent evidence demonstrates that there are sex differences associated with TLR responses and that these receptors may be affected by sex hormones and their receptors, suggesting that TLRs may contribute to the sex differences observed in cardiovascular diseases. Recent evidence also shows that sex differences of TLRs in cardiovascular system persists with aging, which may represent a new paradigm about the mechanisms that contribute to the sex differences in cardiovascular aging. Therefore, in this mini review we describe the latest findings regarding the sex differences of TLRs and associated signaling in cardiovascular diseases during aging.

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.

The Relevance of Thimet Oligopeptidase in the Regulation of Energy Metabolism and Diet-Induced Obesity.

Thimet oligopeptidase (EC 3.4.24.15; EP24.15; THOP1) is a potential therapeutic target, as it plays key biological functions in processing biologically functional peptides. The structural conformation of THOP1 provides a unique restriction regarding substrate size, in that it only hydrolyzes peptides (optimally, those ranging from eight to 12 amino acids) and not proteins. The proteasome activity of hydrolyzing proteins releases a large number of intracellular peptides, providing THOP1 substrates within cells. The present study aimed to investigate the possible function of THOP1 in the development of diet-induced obesity (DIO) and insulin resistance by utilizing a murine model of hyperlipidic DIO with both C57BL6 wild-type (WT) and THOP1 null (THOP1-/-) mice. After 24 weeks of being fed a hyperlipidic diet (HD), THOP1-/- and WT mice ingested similar chow and calories; however, the THOP1-/- mice gained 75% less body weight and showed neither insulin resistance nor non-alcoholic fatty liver steatosis when compared to WT mice. THOP1-/- mice had increased adrenergic-stimulated adipose tissue lipolysis as well as a balanced level of expression of genes and microRNAs associated with energy metabolism, adipogenesis, or inflammation. Altogether, these differences converge to a healthy phenotype of THOP1-/- fed a HD. The molecular mechanism that links THOP1 to energy metabolism is suggested herein to involve intracellular peptides, of which the relative levels were identified to change in the adipose tissue of WT and THOP1-/- mice. Intracellular peptides were observed by molecular modeling to interact with both pre-miR-143 and pre-miR-222, suggesting a possible novel regulatory mechanism for gene expression. Therefore, we successfully demonstrated the previously unanticipated relevance of THOP1 in energy metabolism regulation. It was suggested that intracellular peptides were responsible for mediating the phenotypic differences that are described herein by a yet unknown mechanism of action.

Detrimental Effects of Testosterone Addition to Estrogen Therapy Involve Cytochrome P-450-Induced 20-HETE Synthesis in Aorta of Ovariectomized Spontaneously Hypertensive Rat (SHR), a Model of Postmenopausal Hypertension.

Postmenopausal period has been associated to different symptoms such as hot flashes, vulvovaginal atrophy, hypoactive sexual desire disorder (HSDD) and others. Clinical studies have described postmenopausal women presenting HSDD can benefit from the association of testosterone to conventional hormonal therapy. Testosterone has been linked to development of cardiovascular diseases including hypertension and it also increases cytochrome P-450-induced 20-HETE synthesis which in turn results in vascular dysfunction. However, the effect of testosterone plus estrogen in the cardiovascular system is still very poorly studied. The aim of the present study is to evaluate the role of cytochrome P-450 pathway in a postmenopausal hypertensive female treated with testosterone plus estrogen. For that, hypertensive ovariectomized rats (OVX-SHR) were used as a model of postmenopausal hypertension and four groups were created: SHAM-operated (SHAM), ovariectomized SHR (OVX), OVX treated for 15 days with conjugated equine estrogens [(CEE) 9.6 µg/Kg/day/po] or CEE associated to testosterone [(CEE+T) 2.85 mg/kg/weekly/im]. Phenylephrine-induced contraction and generation of reactive oxygen species (ROS) were markedly increased in aortic rings from OVX-SHR compared to SHAM rats which were restored by CEE treatment. On the other hand, CEE+T abolished vascular effects by CEE and augmented both systolic and diastolic blood pressure of SHR. Treatment of aortic rings with the CYP/20-HETE synthesis inhibitor HET0016 (1 µM) reduced phenylephrine hyperreactivity and the augmented ROS generation in the CEE+T group. These results are paralleled by the increased CYP4F3 protein expression and activity in aortas of CEE+T. In conclusion, we showed that association of testosterone to estrogen therapy produces detrimental effects in cardiovascular system of ovariectomized hypertensive females via CYP4F3/20-HETE pathway. Therefore, our findings support the standpoint that the CYP/20-HETE pathway is an important therapeutic target for the prevention of cardiovascular disease in menopausal women in the presence of high levels of testosterone.

Intrauterine exposure to metformin: Evaluation of endothelial and perivascular adipose tissue function in abdominal aorta of adult offspring.

The biguanide metformin (MET) has been used during pregnancy for treatment of polycystic ovary syndrome and gestational diabetes. MET crosses the placenta and maternal treatment can expose the progeny to this drug during important phases of body development. Direct vascular protective effects have been described with the treatment of metformin. Nevertheless, it is unclear whether intrauterine exposure to metformin is safe for the vascular system of offspring. Thus, the present study aimed to investigate the intrinsic effects of metformin exposure in utero in the offspring abdominal aorta reactivity, in the presence and absence of perivascular adipose tissue (PVAT) and endothelium. For this, Wistar rats were treated with metformin 293 mg/kg/day (MET) or water (CTR) by gavage during the gestational period. The abdominal aorta reactivity to phenylephrine, acetylcholine, and sodium nitroprusside was evaluated in male adult offspring. It was observed that abdominal aorta relaxation was similar between MET and CTR groups in the presence or absence of PVAT. In addition, the contraction to phenylephrine was similar between MET and CTR groups in the presence and absence of PVAT and endothelium. Therefore, metformin exposure during pregnancy had no intrinsic effect on the offspring abdominal aorta PVAT and endothelial function, demonstrating it to be safe to the vascular system of the offspring.

Intrauterine and lactational exposure to fluoxetine enhances endothelial modulation of aortic contractile response in adult female rats.

The study aimed to evaluate if maternal exposure to fluoxetine (FLX) during pregnancy and lactation would result in altered aortic reactivity in adult offspring. We also sought to understand the role of endothelium derived relaxing factors in aortic response. Wistar rats (75­80 days old), whose progenitors had received FLX (5 mg/kg, FLX offspring) or tap water (control offspring) during pregnancy and lactation were anesthetized, after which the aorta was removed and cut into two rings, one with (Endo+) and the other without (Endo-) endothelium. Concentration-effect curves for acetylcholine (ACh), sodium nitroprusside (SNP), and phenylephrine (Phe) were performed. The vasodilation to ACh and SNP was similar between control and FLX groups in both male and female offspring. In male rats, the response to Phe was similar between the FLX and control groups on Endo+ and Endo- rings. The response to Phe was reduced on Endo+ rings from female FLX when compared with the control group. The endothelium removal, as well as L-NAME, indomethacin, and tranylcypromine incubation corrected the reduced Phe-induced contraction in the aorta from the female FLX group. On the other hand, catalase, NS-398, and L-NIL did not interfere with the vasoconstriction. The aortic level of nitric oxide (NO) was higher in the female FLX than the control group. Although endothelial NO synthase isoform and cyclooxygenase (COX)-1 expressions were similar between the groups, there was a notable increment in neuronal NO synthase expression in the aorta of FLX-exposed female rats, suggesting an important role of this enzyme in the higher levels of NO. Our results show that developmental exposure to FLX causes sex-specific alteration in aortic function through a mechanism involving endothelial factors, probably NO and COX-1 products.

H2O2 generated from mitochondrial electron transport chain in thoracic perivascular adipose tissue is crucial for modulation of vascular smooth muscle contraction.

The perivascular adipose tissue (PVAT) releases a variety of factors that affect vascular function. PVAT in the thoracic aorta shares characteristics with the brown adipose tissue, including a large amount of mitochondria. PVAT-derived factors influence both endothelial and smooth muscle function via several signaling mechanisms including the release/generation of reactive nitrogen and oxygen species. Considering the importance of reactive oxygen species (ROS) on vascular function and that mitochondria are an important source of ROS, we hypothesized that mitochondria-derived ROS in the PVAT modulates vascular reactivity. Vascular reactivity to norephinephrine (NE) was evaluated in thoracic aortic rings, with or without endothelium and/or PVAT, from male Wistar rats. Mitochondrial uncoupling, as well as hydrogen peroxide (H2O2) removal, increased the contraction in vessels surrounded by PVAT. PVAT stimulated with NE exhibited increased protein expression, determined by Western blot analysis, of manganese superoxide dismutase (Mn-SOD) and decreased protein expression of catalase. Ultimately, NE increased superoxide anion (O2(-)) generation in PVAT via increases in intracellular calcium. These results clearly demonstrate that mitochondrial electron transport chain (mETC) in PVAT contributes to modulation of aortic muscle contraction by generating higher amounts of O2(-) that is, in turn, dismutated to hydrogen peroxide, which then acts as a pivotal signaling molecule regulating vascular smooth muscle contraction.

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.

An interaction of renin-angiotensin and kallikrein-kinin systems contributes to vascular hypertrophy in angiotensin II-induced hypertension: in vivo and in vitro studies.

The kallikrein-kinin and renin-angiotensin systems interact at multiple levels. In the present study, we tested the hypothesis that the B1 kinin receptor (B1R) contributes to vascular hypertrophy in angiotensin II (ANG II)-induced hypertension, through a mechanism involving reactive oxygen species (ROS) generation and extracellular signal-regulated kinase (ERK1/2) activation. Male Wistar rats were infused with vehicle (control rats), 400 ng/Kg/min ANG II (ANG II rats) or 400 ng/Kg/min ANG II plus B1 receptor antagonist, 350 ng/Kg/min des-Arg(9)-Leu(8)-bradykinin (ANGII+DAL rats), via osmotic mini-pumps (14 days) or received ANG II plus losartan (10 mg/Kg, 14 days, gavage - ANG II+LOS rats). After 14 days, ANG II rats exhibited increased systolic arterial pressure [(mmHg) 184 ± 5.9 vs 115 ± 2.3], aortic hypertrophy; increased ROS generation [2-hydroxyethidium/dihydroethidium (EOH/DHE): 21.8 ± 2.7 vs 6.0 ± 1.8] and ERK1/2 phosphorylation (% of control: 218.3 ± 29.4 vs 100 ± 0.25]. B1R expression was increased in aortas from ANG II and ANG II+DAL rats than in aortas from the ANG II+LOS and control groups. B1R antagonism reduced aorta hypertrophy, prevented ROS generation (EOH/DHE: 9.17 ± 3.1) and ERK1/2 phosphorylation (137 ± 20.7%) in ANG II rats. Cultured aortic vascular smooth muscle cells (VSMC) stimulated with low concentrations (0.1 nM) of ANG II plus B1R agonist exhibited increased ROS generation, ERK1/2 phosphorylation, proliferating-cell nuclear antigen expression and [H3]leucine incorporation. At this concentration, neither ANG II nor the B1R agonist produced any effects when tested individually. The ANG II/B1R agonist synergism was inhibited by losartan (AT1 blocker, 10 µM), B1R antagonist (10 µM) and Tiron (superoxide anion scavenger, 10 mM). These data suggest that B1R activation contributes to ANG II-induced aortic hypertrophy. This is associated with activation of redox-regulated ERK1/2 pathway that controls aortic smooth muscle cells growth. Our findings highlight an important cross-talk between the DABK and ANG II in the vascular system and contribute to a better understanding of the mechanisms involved in vascular remodeling in hypertension.

Upregulation of ERK1/2-eNOS via AT2 receptors decreases the contractile response to angiotensin II in resistance mesenteric arteries from obese rats.

It has been clearly established that mitogen-activated protein kinases (MAPKS) are important mediators of angiotensin II (Ang II) signaling via AT1 receptors in the vasculature. However, evidence for a role of these kinases in changes of Ang II-induced vasoconstriction in obesity is still lacking. Here we sought to determine whether vascular MAPKs are differentially activated by Ang II in obese animals. The role of AT2 receptors was also evaluated. Male monosodium glutamate-induced obese (obese) and non-obese Wistar rats (control) were used. The circulating concentrations of Ang I and Ang II, determined by HPLC, were increased in obese rats. Ang II-induced isometric contraction was decreased in endothelium-intact resistance mesenteric arteries from obese compared with control rats and exhibited a retarded AT1 receptor antagonist response. Blocking of AT2 receptors and inhibition of either endothelial nitric oxide synthase (eNOS) or extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) restored Ang II-induced contraction in obese rats. Western blot analysis revealed increased protein expression of AT2 receptors in arteries from obese rats. Basal and Ang II-induced ERK1/2 phosphorylation was also increased in obese rats. Blockade of either AT1 or AT2 receptors corrected the increased ERK1/2 phosphorylation in arteries from obese rats to levels observed in control preparations. Phosphorylation of eNOS was increased in obese rats. Incubation with the ERK1/2 inhibitor before Ang II stimulation did not affect eNOS phosphorylation in control rats; however, it corrected the increased phosphorylation of eNOS in obese rats. These results clearly demonstrate that enhanced AT2 receptor and ERK1/2-induced, NO-mediated vasodilation reduces Ang II-induced contraction in an endothelium-dependent manner in obese rats.

Role of nitric oxide and endothelin in endothelial maintenance of vasoconstrictor responses in aortas of diabetic female rats.

BACKGROUND: Diabetes differentially affects the vascular system in males and females. Although various results have been reported, very few studies have focused on responses in females. In the present study, we investigated contractile responses to norepinephrine in aortas of alloxan-diabetic female rats and evaluated endothelial modulation of these responses. METHODS: Concentration-response curves were constructed to norepinephrine in the absence or presence of N(G) -nitro-l-arginine methyl ester (l-NAME), indomethacin, losartan, tezosentan, and calphostin C; pre-pro-endothelin mRNA expression was evaluated; and norepinephrine-stimulated expression of phosphorylated (p-) Akt Ser(473) , p-endothelial nitric oxide synthase (eNOS) Ser(1177) , and p-eNOS Ser(633) was determined in endothelial cells incubated in the presence of low (5 mmol/L) or high (25 mmol/L) glucose concentrations. RESULTS: Similar maximal responses (Rmax ) to norepinephrine were seen in control and diabetic endothelium-intact aortas; however, Rmax was reduced in diabetic endothelium-denuded aortas. Incubation of endothelium-intact aortas with 100 µmol/L l-NAME increased Rmax in the control group only. Inhibition of cyclo-oxygenase (10 µmol/L indomethacin) and blockade of angiotensin II receptors (10 µmol/L losartan) reduced Rmax in endothelium-intact aortas in both the control and diabetic groups. Blockade of endothelin receptors (0.1 µmol/L tezosentan) and inhibition of protein kinase C (PKC; 0.1 µmol/L calphostin C) reduced Rmax only in endothelium-intact aortas from diabetic rats. Pre-pro-endothelin mRNA expression was increased in aortas from diabetic female rats. Finally, p-Akt Ser(473) , p-eNOS Ser(1177) , and p-eNOS Ser(633) levels were enhanced after norepinephrine stimulation only in low glucose-treated endothelial cells. CONCLUSIONS: In aortas of diabetic female rats, reductions in smooth muscle contractile responses to norepinephrine are counterbalanced by the endothelium via reduced eNOS activation and increased endothelin release and PKC activation.

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.