Subacute cadmium exposure changes different metabolic functions, leading to type 1 and 2 diabetes mellitus features in female rats.

Cadmium (Cd) is a heavy metal that acts as endocrine disrupting chemical (EDC). Few studies have investigated the effects of Cd exposure on metabolic dysfunctions, such as type 1 and 2 diabetes mellitus (T1DM and T2DM). Thus, we assessed whether subacute Cd exposure at occupational levels causes abnormalities in white adipose tissue (WAT), liver, pancreas, and skeletal muscle. We administered cadmium chloride (CdCl2) (100 ppm in drinking water for 30 days) to female rats and evaluated Cd levels in serum and metabolic organs, morphophysiology, inflammation, oxidative stress, fibrosis, and gene expression. High Cd levels were found in serum, WAT, liver, pancreas, and skeletal muscle. Cd-exposed rats showed low adiposity, dyslipidemia, insulin resistance, systemic inflammation, and oxidative stress compared to controls. Cd exposure reduced adipocyte size, hyperleptinemia, increased cholesterol levels, inflammation, apoptosis and fibrosis in WAT. Cd-exposed rats had increased liver cholesterol levels, insulin receptor beta (IRß) and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC1α) expression, karyomegaly, inflammation, and fibrosis. Cd exposure reduced insulin levels and pancreatic islet size and increased inflammation and fibrosis. Cd exposure reduced skeletal muscle fiber diameter and increased IR expression and inflammation. Finally, strong positive correlations were observed between serum, tissue Cd levels, abnormal morphology, tissue inflammation and fibrosis. Thus, these data suggest that subacute Cd exposure impairs WAT, liver, pancreas and skeletal muscle function, leading to T1DM and T2DM features and other complications in female rats.

Short-term Effects of Cadmium Exposure on Blood Pressure and Vascular Function in Wistar Rats.

Chronic cadmium exposure is known to be associated with vascular changes and increased blood pressure, but its short-term effects on the cardiovascular system remain poorly understood. This study aimed to investigate the pressoric and vascular effects of a 7-day exposure to CdCl2 in Wistar rats. The rats were divided in control group (Ct), which received tap water, and the Cd group, which received a 100 mg/L CdCl2 solution via drinking water for 7 days. We analyzed body weight, plasma Cadmium concentration, systolic blood pressure (SBP), and vascular responses. Despite relatively low plasma Cadmium concentration, the Cd group exhibited elevated SBP and increased contractile response to phenylephrine. Endothelium removal and NOS inhibition increased contractions in both groups. In the Cd group's aorta, we observed enhanced levels of phospho-eNOS (Ser1177) and basal NO release. Cd group showed reduced Catalase expression and increased basal release of H2O2, with catalase reducing the contractile response. In arteries pre-contracted with phenylephrine, Cd group showed impaired endothelium-dependent (Acetylcholine) and independent (sodium nitroprussiate-SNP) relaxation responses. However, responses to SNP were similar after pre-contraction with KCl in both groups. These data suggest early effects of Cadmium on blood pressure and aortic function, indicating impaired H2O2-scavenging by catalase. Increased H2O2 due to Cadmium exposure might explain heightened responses to phenylephrine and weakened relaxation responses mediated by the NO-K+-channels pathway. Our findings shed light on Cadmium's short-term impact on the cardiovascular system, providing insights into potential mechanisms underlying its effects on blood pressure regulation and vascular function.

In vitro cadmium exposure induces structural damage and endothelial dysfunction in female rat aorta.

Cadmium is a heavy metal that is widespread in the environment and has been described as a metalloestrogen and a cardiovascular risk factor. Experimental studies conducted in male animals have shown that cadmium exposure induces vascular dysfunction, which could lead to vasculopathies caused by this metal. However, it is necessary to investigate the vascular effects of cadmium in female rats to understand its potential sex-dependent impact on the cardiovascular system. While its effects on male rats have been studied, cadmium may act differently in females due to its potential as a metalloestrogen. In vitro studies conducted in a controlled environment allow for a direct assessment of cadmium's impact on vascular function, and the use of female rats ensures that sex-dependent effects are evaluated. Therefore, the aim of this study was to investigate the in vitro effects of Cadmium Chloride (CdCl2, 5 µM) exposure on vascular reactivity in the isolated aorta of female Wistar rats. Exposure to CdCl2 damaged the architecture of the vascular endothelium. CdCl2 incubation increased the production and release of O2•-, reduced the participation of potassium (K+) channels, and increased the participation of the angiotensin II pathway in response to phenylephrine. Moreover, estrogen receptors alpha (Erα) modulated vascular reactivity to phenylephrine in the presence of cadmium, supporting the hypothesis that cadmium could act as a metalloestrogen. Our results demonstrated that in vitro cadmium exposure induces damage to endothelial architecture and an increase in oxidative stress in the isolated aorta of female rats, which could precipitate vasculopathies. Graphical Abstract. Own source from Canva and Servier Medical Art servers.

Cessation Restores Blood Pressure Levels and Endothelial Function Affected by Cadmium Exposure on Rats.

Chronic cadmium exposure produces high blood pressure and endothelial damage; however, it is not known whether these effects could be reversed by interrupting the exposure to the metal. Therefore, we evaluate the systolic blood pressure (SBP) and vascular reactivity during and following chronic cadmium-exposure discontinuance. Rats received 100 mg.L-1 cadmium chloride (CdCl2) in the drinking water or tap water (Ct) for 30 days and/or tap water for 30 days more. The cadmium plasma content, blood pressure and vascular reactivity of isolated aorta were evaluated. Cadmium exposure increased cadmium plasma content, SBP and aorta contractile responses to phenylephrine, all reversed after suspending exposure. Endothelial removal and nitric oxide synthase (NOS) inhibition increased phenylephrine response both on control and Cd-discontinuation models. Cd-discontinuation group presented increased CAMKII and PKA protein expression, as peNOSSer1177. Superoxide dismutase (SOD) incubation reduced contractile response on control group, and catalase incubation enhanced the response to phenylephrine in this group. Meanwhile, both SOD2 and catalase protein expression were increased in Cd-cessation rats. Our findings provide evidence that increased SBP and endothelial dysfunction induced by Cd chronic exposure are reversed by suspending the metal exposure probably due to an improvement of antioxidant enzymes and eNOS function.

Sex-dependent vascular effects of cadmium sub-chronic exposure on rats.

Cadmium exposure is related to several cardiovascular diseases, such as hypertension, atherosclerosis and endothelial dysfunction. However, the toxic effect of cadmium can be dependent on the sex when examined sex in experimental models. The aim of this study was to analyze the effects of cadmium exposure on the cardiovascular system of male and female rodents. The experiments were carried out on both-sexes Wistar at 4 months of age, where from 3 months onwards, cadmium (CdCl2 100 mg/l in placed the drinking water for 30 days) or vehicle delivered (distilled water) was ingested. Before and after 30 days of exposure to cadmium, systolic blood pressure was regularly measured. After exposure, blood was collected to measure dosage of cadmium, in male and female, and estrogen in females. Vascular reactivity to phenylephrine (Phe), acetylcholine (ACh), and sodium nitroprusside (SNP) was studied at respective isolated aortic segments. After the period to Cd-exposure, systolic blood pressure was increased only in the male rats. Males also had higher levels of plasma cadmium than those of female rats, and exposure to the metal did not affect the amount of estrogen produced in the female rats. Increased myeloperoxidase (MPO) activity was also observed in both the males and females that had been exposed to the metal. Moreover, exposure to the cadmium reduced the ACh relaxation and increased vascular reactivity to Phe, resulting in an imbalance between nitric oxide superoxide anion in the isolated aorta of male rats. In female rats, sub-chronic cadmium exposure did not modify the vascular reactivity to Phe and neither to the ACh. The present study revealed that the Cd exposure for 30 days induced sex-dependent cardiovascular abnormalities.

Oxidative Stress Induced by 30 Days of Mercury Exposure Accelerates Hypertension Development in Prehypertensive Young SHRs.

Mercury is considered a risk factor for the development of hypertension and other cardiovascular diseases. We investigated whether the effects of mercury exposure on haemodynamic parameters of young Wistar rats and prehypertensive SHRs might alter the time course of hypertension development. Young (4 weeks) male Wistar rats and SHRs were randomly assigned to four groups: untreated Wistar rats (Wistar Ct), Wistar rats exposed to mercury chloride for 30 days (Wistar Hg), untreated SHRs (SHR Ct) and SHRs exposed to mercury chloride (SHR Hg) for 30 days. Non-invasive and invasive arterial pressures were measured to investigate pressure reactivity; nitrite/nitrate levels, ACE activity, and lipid peroxidation were measured in plasma. The systolic blood pressure (SBP) of the Wistar rat groups did not change but increased in the SHRs from the second week to the last week. Hg exposure accelerated the increase in the SBP of SHRs. L-NAME administration increased SBP and diastolic blood pressure (DBP) in all groups, but this increase was smaller in SHRs exposed to Hg. A decrease in plasma nitrite and nitrate levels in the SHR Hg group suggested that mercury reduced NO bioavailability. Tempol-reduced blood pressure suggesting that the superoxide anion played a role in the marked increase in this parameter. These findings provide evidence that Hg exposure might activate mechanisms to accelerate hypertension development, including a reduction in NO bioavailability. Therefore, predisposed individuals under mercury exposure are at greater risk from an enhanced development of hypertension.

Endothelial alpha globin is a nitrite reductase.

Resistance artery vasodilation in response to hypoxia is essential for matching tissue oxygen and demand. In hypoxia, erythrocytic hemoglobin tetramers produce nitric oxide through nitrite reduction. We hypothesized that the alpha subunit of hemoglobin expressed in endothelium also facilitates nitrite reduction proximal to smooth muscle. Here, we create two mouse strains to test this: an endothelial-specific alpha globin knockout (EC Hba1Δ/Δ) and another with an alpha globin allele mutated to prevent alpha globin's inhibitory interaction with endothelial nitric oxide synthase (Hba1WT/Δ36-39). The EC Hba1Δ/Δ mice had significantly decreased exercise capacity and intracellular nitrite consumption in hypoxic conditions, an effect absent in Hba1WT/Δ36-39 mice. Hypoxia-induced vasodilation is significantly decreased in arteries from EC Hba1Δ/Δ, but not Hba1WT/Δ36-39 mice. Hypoxia also does not lower blood pressure in EC Hba1Δ/Δ mice. We conclude the presence of alpha globin in resistance artery endothelium acts as a nitrite reductase providing local nitric oxide in response to hypoxia.

Post-weaning protein malnutrition induces myocardial dysfunction associated with oxidative stress and altered calcium handling proteins in adult rats.

Hypercaloric low-protein diet may lead to a state of malnutrition found in the low-income population of Northeastern Brazil. Although malnutrition during critical periods in the early life is associated with cardiovascular diseases in adulthood, the mechanisms of cardiac dysfunction are still unclear. Here we studied the effects of post-weaning malnutrition due to low protein intake induced by a regional basic diet on the cardiac contractility of young adult rats. In vivo arterial hemodynamic and in vitro myocardial contractility were evaluated in 3-month-old rats. Additionally, protein content of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), total phospholamban (PLB) and phosphorylated at serine 16 (p-Ser(16)-PLB), α2-subunit of the Na(+)/K(+)-ATPase (α2-NKA), and Na(+)/Ca(2+) exchanger (NXC) and in situ production of superoxide anion (O2(-)) were measured in the heart. Blood pressure and heart rate increased in the post-weaning malnourished (PWM) rats. Moreover, malnutrition decreased twitch force and inotropic responses of the isolated cardiac muscle. Protein expression of SERCA, PLB/SERCA, and p-Ser(16)-PLB/PLB ratios and α2-NKA were decreased without changing NCX. The contraction dependent on transsarcolemmal calcium influx was unchanged but responsiveness to Ca(2+) and tetanic peak contractions were impaired in the PWM group. Myocardial O2(-) production was significantly increased by PWM. Our data demonstrated that this hypercaloric low-protein diet in rats is associated with myocardial dysfunction, altered expression of major calcium handling proteins, and increased local oxidative stress. These findings reinforce the attention needed for pediatric care, since chronic malnutrition in early life is related to increased cardiovascular risk in adulthood. Graphical Abstract.

C-offset and crop energy efficiency increase due industrial poultry waste use in long-term no-till soil minimizing environmental pollution.

Brazil is one of the major global poultry producers, and the organic waste generated by the chicken slaughterhouses can potentially be used as a biofertilizer in agriculture. This study was designed to test the hypothesis that continuous use of biofertilizer to the crops, substituting the use of mineral fertilizer promote C-offset for the soil and generate crop energy efficiency for the production system. Thus, the objectives of this study were to evaluate the effects of biofertilizer use alone or in combination with mineral fertilizer on soil organic carbon (SOC) stock, carbon dioxide (CO2) mitigation, C-offset, crop energy efficiency and productivity, and alleviation of environmental pollution. The experiment was established in southern Brazil on a soil under 15 years of continuous no-till (NT). Experimental treatments were as follows: i) Control with no fertilizer application, ii) 100% use of industrial mineral fertilizer (Min-F); iii) 100% use of organic waste originated from poultry slaughterhouses and hereinafter designated biofertilizer (Bio-F), and iv) Mixed fertilizer equivalent to the use of 50% mineral fertilizer + 50% of biofertilizer (Mix-F). Effects of experimental treatments were assessed for the crop sequence based on bean (Phaseolus vulgaris), soybean (Glycine max) and corn (Zea mays) in the summer and wheat (Triticum aestivum) and black oat (Avena strigosaSchreb) in the winter composing two crops per year, as follow: bean/wheat-soybean/black oat-corn/wheat-soybean/black oat-corn/wheat-bean. The continuous use of Bio-F treatment significantly increased the index of crop energy efficiency. It was higher than that of control, and increased it by 25.4 Mg CO2eq ha-1 over that of Min-F treatment because of higher inputs of crop biomass-C into the system. Further, continuous use of Bio-F resulted in a significantly higher CO2eq stock and offset than those for Min-F treatment. A positive relationship between the C-offset and the crop energy efficiency (R2 = 0.71, p < 0.001) indicated that the increase of C-offset was associated with the increase of energy balance and the amount of SOC sequestered. The higher energy efficiency and C-offset by application of Bio-F indicated that the practice of crop bio fertilization with poultry slaughterhouse waste is a viable alternative for recycling and minimizing the environmental impacts.

Subacute cadmium exposure disrupts the hypothalamic-pituitary-gonadal axis, leading to polycystic ovarian syndrome and premature ovarian failure features in female rats.

Cadmium (Cd), a toxic heavy metal, is a known endocrine disruptor that is associated with reproductive complications. However, few studies have explored the effects of Cd exposure on features of polycystic ovary syndrome (PCOS) and premature ovary failure (POF). In this study, we assessed whether doses found in workers occupationally exposed to Cd and subacute exposure result in hypothalamic-pituitary-gonadal (HPG) axis and other irregularities. We administered CdCl2 to female rats (100 ppm in drinking water for 30 days) and then assessed Cd levels in the blood, HPG axis and uterus. Metabolic features, HPG axis function, reproductive tract (RT) morphophysiology, inflammation, oxidative stress (OS), and fibrosis were evaluated. Cd exposure increased Cd levels in the serum, HPG axis, and uterus. Cd rats displayed metabolic impairments, such as a reduction in adiposity, dyslipidemia, and insulin resistance (IR). Cd exposure also caused improper functioning in the HPG. Specifically, Cd exposure caused irregular estrous cyclicity, abnormal hypothalamic gene expression (upregulated - Kiss1, AR and mTOR; downregulated - Kiss1R, LepR and TNF-α), high LH levels, low AMH levels and abnormal ovarian follicular development, coupled with a reduction in ovarian reserve and antral follicle number was observed, suggesting ovarian depletion. Further, Cd exposure caused a reduction in corpora lutea (CL) and granulosa layer thickness together with an increase in cystic/atretic follicles. In addition, Cd exposure caused RT inflammation, OS and fibrosis. Finally, strong positive correlations were observed between serum, RT Cd levels, IR, dyslipidemia and estrous cycle length, cystic, atretic follicles, LH levels, and RT inflammation. Thus, these data suggest that subacute Cd exposure using doses found in workers occupationally exposed to Cd disrupt the HPG axis function, leading to PCOS and POF features and other abnormalities in female rats.

Increased endothelial nitric oxide production after low level lead exposure in rats involves activation of angiotensin II receptors and PI3K/Akt pathway.

BACKGROUND: Lead induces endothelial dysfunction and hypertension in humans and animals. Seven-day exposure to a low dose in rats reduces vasocontractile responses and increases nitric oxide (NO) bioavailability. We hypothesized that this occurs by angiotensin II receptors (AT1/AT2) activation. MATERIALS AND RESULTS: Wistar rats were exposed to lead acetate (1 st dose 4 µg/100 g, subsequent dose 0.05 µg/100 g/day i.m., 7 days) or saline (control group). Lead acetate exposure reduced the phenylephrine vascular response. Pre-incubations with NO synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) or phosphatidylinositol 3-kinase (PI3K) inhibitor (wortmannin) increased the contractile response in aortas from lead-treated rats. Pre-incubation with AT2 antagonist (PD123319) restored normal vascular contraction, and both PD123319 or AT1 antagonist (losartan) impeded the potentiated effects of L-NAME and wortmannin. Reinforcing those findings, increased NO bioavailability was blunted by AT1 and AT2 antagonists without summative effect when co-incubated. Finally, to test whether activation of AT1 could upregulate AT2 to increase NO bioavailability rats were simultaneously exposed to lead acetate and treated with losartan (15 mg/kg/day, orally given). Losartan prevented changes on vascular reactivity and endothelial modulation in lead-exposed group. Moreover, incubation with PD123319 had no more effects in aortic from losartan-treated rats. CONCLUSION: Our results suggest that low-dose lead acetate exposure induces an increase of NO involving mainly AT2 receptor activation and the PI3K/Protein Kinase B (PI3K/Akt) pathway. Additionally, we suggest that AT1 activation plays a role in AT2 upregulation, probably as a protective mechanism. Altogether, these effects might contribute to preserving endothelial function against the harmful effects by lead in the vascular system.

The Role of Antioxidants in the Prevention of Cadmium-Induced Endothelial Dysfunction.

BACKGROUND: Cadmium is a worldwide spread toxicant that accumulates in tissues and affects many organs, mainly through oxidative damage. Oxidative stress is often associated with cardiovascular diseases and, when it affects vessels, it induces endothelial dysfunction, which, in turn, could precipitate atherosclerosis and hypertension. Therefore, it is reasonable to suggest antioxidant supplementation as a therapy against cadmiuminduced endothelial dysfunction. OBJECTIVE: This literature review aims to present the mechanisms involving oxidative stress in which cadmium induces endothelial dysfunction and the benefits of antioxidant supplementation as a therapeutic strategy against its harmful effects. METHODS: On PubMed Central, articles that contemplated studies on cadmium intoxication and associated oxidative stress with endothelial dysfunction as well as articles that reported the use of antioxidant supplementation in an attempt to prevent or avoid endothelial dysfunction induced by cadmium exposure were selected. RESULTS: Most of the studies that associated cadmium intoxication with endothelial dysfunction suggested oxidative stress as the major mechanism for this damage. Furthermore, experimental studies also revealed that the administration of substances with antioxidant properties, such as ascorbic acid and curcumin, has beneficial effects on the prevention of such dysfunction, reducing reactive oxygen species within the vessels, preventing a reduction in the amount of glutathione and the increase in blood pressure observed in animals exposed to cadmium. CONCLUSION: Antioxidant therapy demonstrated to be a potential treatment to reduce cardiovascular injuries provoked by cadmium, but more studies are needed to determine the best antioxidant substance and dose to treat or avoid this complication.

Endothelium: A Target for Harmful Actions of Metals.

The use of heavy metals is closely linked to the history of mankind. They have been used as important materials in a wide variety of human activities such as manufacturing utensils and tools. Such extended use has significantly increased professional and environmental exposure to mercury, lead and cadmium. These metals are known to produce hypertension in humans and animals and, among other effects, they can also affect endothelial function. Results described here suggest that mercury, lead and cadmium affect vascular reactivity, even at low doses or concentrations. Several vascular actions are mediated by the endothelium via increasing the production of free radicals and angiotensin II by local ACE stimulation. These results provide further evidence that these toxic metals, even at low doses, are an environmental risk factor to the exposed population. These results also suggest that continuous exposure to these metals, followed by their absorption and progressive accumulation in the body, may be hazardous to cardiovascular function. Therefore, the current reference values, which are considered safe, need to be reduced.

Long-term Mercury Exposure Accelerates the Development of Hypertension in Prehypertensive Spontaneously Hypertensive Rats Inducing Endothelial Dysfunction: the Role of Oxidative Stress and Cyclooxygenase-2.

Mercury is a metal widely dispersed in nature that when in contact with human organism, it damages the cardiovascular system. Long-term mercury exposure for 30 days induces endothelial dysfunction without blood pressure changes in normotensive adult rats. However, it is not known whether exposure to mercury can exacerbate endothelial dysfunction and hypertension development in predisposed animals. Thus, we aimed to investigate the effects of long-term mercury exposure on the blood pressure (BP) and in the isolated aortas of young normotensive and prehypertensive spontaneously hypertensive rats (SHRs). Four-week-old male Wistar rats and SHRs were treated daily with mercury chloride (HgCl2) (1st dose, 4.6 µg/kg; subsequent dose, 0.07 µg/kg/day, im, 30 days) or vehicle. BP was assessed weekly and the vascular reactivity to phenylephrine was evaluated in isolated aorta from rats exposed or not to mercury. Mercury exposure did not affect BP in young Wistar rats but accelerated the development of hypertension in young SHRs. Vascular reactivity to phenylephrine increased only in the aorta from mercury-exposed SHRs. While HgCl2 exposure in SHRs did not alter nitric oxide production, we observed increased superoxide anion production and decreased superoxide dismutase-1 protein expression, and enhanced cyclooxygenase-2 (COX-2) participation with increased prostaglandin (PGE2) production and decreased prostacyclin. In the Wistar group, mercury exposure did not alter superoxide anion production or the COX-2 pathway. Mercury exposure accelerated the natural course of hypertension in young SHRs and increased oxidative stress associated with reduced participation of antioxidant enzymes, an activated COX-2 pathway, thereby producing endothelial dysfunction, which is a risk factor in prehypertensive individuals.

Chronic Cadmium Exposure Accelerates the Development of Atherosclerosis and Induces Vascular Dysfunction in the Aorta of ApoE-/- Mice.

Cadmium exposure is related to cardiovascular diseases, including hypertension, atherosclerosis, increased oxidative stress, endothelial dysfunction, and specific biochemical changes induced by this metal. Thus, we aimed to investigate whether cadmium exposure induces endothelial dysfunction, accelerates atherosclerotic plaque formation in the aorta, and enhances oxidative stress in apolipoprotein E knockout (ApoE-/-) mice. Experiments were performed in 14-week-old male wild-type and ApoE-/- mice. ApoE-/- mice received cadmium (CdCl2 100 mg/L in drinking water for 28 days) or vehicle (distilled water). After treatment, vascular reactivity to phenylephrine, acetylcholine, and sodium nitroprusside was analyzed using isolated aorta. Bone marrow cells were isolated to assess the production of nitric oxide and reactive oxygen and nitrogen species. ApoE-/- cadmium-treated mice had higher cholesterol levels than non-exposed mice. Cadmium exposure decreased the vasodilatation response to acetylcholine in aortic ring of ApoE-/- mice, though no changes in phenylephrine or sodium nitroprusside responses were observed. L-NAME reduced vasodilator responses to acetylcholine; this effect was lower in ApoE-/- cadmium-treated mice, suggesting reduction in nitric oxide (NO) bioavailability. Moreover, in bone marrow cells, cadmium decreased cytoplasmic levels of NO and increased superoxide anions, hydrogen peroxide, and peroxynitrite in ApoE-/- mice. Morphological analysis showed that cadmium exposure increased plaque deposition in the aorta by approximately 3-fold. Our results suggest that cadmium exposure induces endothelial dysfunction in ApoE-/- mice. Moreover, cadmium increased total cholesterol levels, which may promote the early development of atherosclerosis in the aorta of ApoE-/- mice. Our findings support the hypothesis that cadmium exposure might increase the risk of atherosclerosis.

Linoleic acid reduces vascular reactivity and improves the vascular dysfunction of the small mesentery in hypertension.

We aimed to investigate the effect of linoleic acid (LA) treatment on the blood pressure and function of mesenteric resistance arteries (MRA) in spontaneous hypertensive rats (SHR). Male SHR were treated daily with LA (15 mg/kg) or vehicle (control) for 15 days. Compared with controls, LA treatment decreased blood pressure and showed the following in MRA: (1) increased lumen and external diameter, (2) decreased wall:lumen ratio and wall thickness, (3) decreased stiffness and (4) less collagen deposition. LA treatment reduced the contractile response to phenylephrine, although there were no changes observed in MRA in regard to the acetylcholine or sodium nitroprusside responses. Incubation with L-NAME left-shifted the reactivity to phenylephrine only in the MRA treated group, suggesting that LA treatment can improve NO bioavailability. This result was accompanied by an increase "in situ" NO production. Incubation with tiron decreased vascular reactivity to phenylephrine in MRA in LA rats, which was accompanied by decreased superoxide anion production. Moreover, incubation with indomethacin (non-selective COX inhibitor, 10 µM), NS 398 (COX-2 specific inhibitor, 1 µM), furegrelate (TXA2 synthase inhibitor, 1 µM), SQ 29.548 (TP receptor antagonist, 1 µM) and SC 19220 (EP1 receptor antagonist, 10 µM) reduced the vasoconstrictor responses to phenylephrine in MRA in the treated group. These results were accompanied by a reduction in COX-2 protein expression. In conclusion, these findings show that LA treatment decreases blood pressure. In addition, the improvement of endothelial dysfunction and structural changes in this hypertension model may be responsible for the reduction in blood pressure.

Preliminary Studies of Acute Cadmium Administration Effects on the Calcium-Activated Potassium (SKCa and BKCa) Channels and Na+/K+-ATPase Activity in Isolated Aortic Rings of Rats.

Cadmium is an environmental pollutant closely linked with cardiovascular diseases that seems to involve endothelium dysfunction and reduced nitric oxide (NO) bioavailability. Knowing that NO causes dilatation through the activation of potassium channels and Na+/K+-ATPase, we aimed to determine whether acute cadmium administration (10 µM) alters the participation of K+ channels, voltage-activated calcium channel, and Na+/K+-ATPase activity in vascular function of isolated aortic rings of rats. Cadmium did not modify the acetylcholine-induced relaxation. After L-NAME addition, the relaxation induced by acetylcholine was abolished in presence or absence of cadmium, suggesting that acutely, this metal did not change NO release. However, tetraethylammonium (a nonselective K+ channels blocker) reduced acetylcholine-induced relaxation but this effect was lower in the preparations with cadmium, suggesting a decrease of K+ channels function in acetylcholine response after cadmium incubation. Apamin (a selective blocker of small Ca2+-activated K+ channels-SKCa), iberiotoxin (a selective blocker of large-conductance Ca2+-activated K+ channels-BKCa), and verapamil (a blocker of calcium channel) reduced the endothelium-dependent relaxation only in the absence of cadmium. Finally, cadmium decreases Na+/K+-ATPase activity. Our results provide evidence that the cadmium acute incubation unaffected the calcium-activated potassium channels (SKCa and BKCa) and voltage-calcium channels on the acetylcholine vasodilatation. In addition, acute cadmium incubation seems to reduce the Na+/K+-ATPase activity.

Modulating Vascular Hemodynamics With an Alpha Globin Mimetic Peptide (HbαX).

The ability of hemoglobin to scavenge the potent vasodilator nitric oxide (NO) in the blood has been well established as a mechanism of vascular tone homeostasis. In endothelial cells, the alpha chain of hemoglobin (hereafter, alpha globin) and endothelial NO synthase form a macromolecular complex, providing a sink for NO directly adjacent to the production source. We have developed an alpha globin mimetic peptide (named HbαX) that displaces endogenous alpha globin and increases bioavailable NO for vasodilation. Here we show that, in vivo, HbαX administration increases capillary oxygenation and blood flow in arterioles acutely and produces a sustained decrease in systolic blood pressure in normal and angiotensin II-induced hypertensive states. HbαX acts with high specificity and affinity to endothelial NO synthase, without toxicity to liver and kidney and no effect on p50 of O2 binding in red blood cells. In human vasculature, HbαX blunts vasoconstrictive response to cumulative doses of phenylephrine, a potent constricting agent. By binding to endothelial NO synthase and displacing endogenous alpha globin, HbαX modulates important metrics of vascular function, increasing vasodilation and flow in the resistance vasculature.

Treatment with high dose of atorvastatin reduces vascular injury in diabetic rats.

BACKGROUND: Previous reports showed conflicting results regarding the treatment effects of statin on Diabetes mellitus (DM). We investigated how treatment with high dose of atorvastatin affects the impaired vascular function in diabetic rats. METHODS: Atorvastatin (80mg/kg/day, oral gavage, 4 weeks) or its vehicle was administered to male control or streptozotocin (STZ)-induced diabetic rats. Aortic segments were used to investigate the vascular reactivity, protein expression of cyclooxygenase-2 (COX-2) and nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) 1 (NOX1) and superoxide anions levels. RESULTS: Atorvastatin treatment did not affect glycemia levels. In diabetic rats, the vascular reactivity to phenylephrine increased compared with controls and the atorvastatin treatment reduced this response. Removal of the endothelium increased the response to phenylephrine in control rats, but not in the diabetic group. Atorvastatin increased the endothelial modulation in diabetic rats. L-NAME (100µM) increased the reactivity in all groups, but this effect was greater in atorvastatin-treated diabetic rats. Indomethacin (10µM) and NS398 (1µM) decreased the contractile response in diabetic rats and atorvastatin reversed these effects, without changing COX-2 expression. Apocynin (30µM) decreased the phenylephrine response in diabetic rats, which also showed increased NOX1 and superoxide anions; these effects were prevented by atorvastatin treatment. CONCLUSIONS: The results suggest that treatment with high dose of atorvastatin, independent of glycemia, improves endothelial function in aortas from diabetic rats by reducing the constrictor prostanoids derived from COX-2 and by reducing the oxidative stress by NADPH oxidase, as well as a possible increasing of nitric oxide participation.

Tributyltin chloride increases phenylephrine-induced contraction and vascular stiffness in mesenteric resistance arteries from female rats.

Tributyltin chloride (TBT) is an organotin compound that reduces estrogen levels in female rats. We aimed to investigate the effects of TBT exposure on vascular tonus and vascular remodelling in the resistance arteries of female rats. Rats were treated daily with TBT (500 ng/kg) for 15 days. TBT did not change arterial blood pressure but did modify some morpho-physiological parameters of third-order mesenteric resistance arteries in the following ways: (1) decreased lumen and external diameters; (2) increased wall/lm ratio and wall thickness; (3) decreased distensibility and increased stiffness; (4) increased collagen deposition; and (5) increased pulse wave velocity. TBT exposure increased the phenylephrine-induced contractile response in mesenteric resistance arteries. However, vasodilatation responses induced by acetylcholine and sodium nitroprusside were not modified by TBT. It is suggested that TBT exposure reduces vascular nitric oxide (NO) production, because:(1) L-NAME incubation did not cause a leftward shift in the concentration-response curve for phenylephrine; (2) both eNOS protein expression; (3) in situ NO production were reduced. Incubation with L-NAME; and (4) SOD shifted the phenylephrine response curve to the left in TBT rats. Tiron, catalase, ML-171 and VAS2870 decreased vascular reactivity to phenylephrine only in TBT rats. Moreover, increased superoxide anion production was observed in the mesenteric resistance arteries of TBT rats accompanied by an increase in gp91phox, catalase, AT1 receptor and total ERK1/2 protein expression. In conclusion, these findings show that TBT induced alterations are most likely due to a reduction of NO production combined with increased O2(-) production derived from NADPH oxidase and ERK1/2 activation. These findings offer further evidence that TBT is an environmental risk factor for cardiovascular disease.