The interplay among gut microbiota, hypertension and kidney diseases: The role of short-chain fatty acids.

The bacteria community living in the gut maintains a symbiotic relationship with the host and its unbalance has been associated with progression of a wide range of intestinal and extra intestinal conditions. Hypertension and chronic kidney disease (CKD) are closely associated diseases with high incidence rates all over the world. Increasing data have supported the involvement of gut microbiome in the blood pressure regulation and the impairment of CKD prognosis. In hypertension, the reduced number of short-chain fatty acids (SCFAs) producing bacteria is associated with modifications in gut environment, involving reduction of the hypoxic gut profile and worsening of the microbial balance, leading to a loss of epithelial barrier integrity, development of gut inflammation and the reduction of SCFAs plasma levels. These modifications compromise the blood pressure regulation and, as a consequence, favor the end organ damage, also affecting the kidneys. In CKD, impaired renal function leads to accumulation of high levels of uremic toxins that reach the intestine and cause alterations in bacteria composition and fecal metabolite profile, inducing a positive feedback that allows translocation of endotoxins into the bloodstream, which enhances local kidney inflammation and exacerbate kidney injury, compromising even more CKD prognosis. In line with these data, the use of prebiotics, probiotics and fecal microbiota transplantation are becoming efficient therapies to improve the gut dysbiosis aiming hypertension and CKD treatment. This review describes how changes in gut microbiota composition can affect the development of hypertension and the progression of kidney diseases, highlighting the importance of the gut microbial composition uncovering to improve human health maintenance and, especially, for the development of new alternative therapies.

Influence of N-methyl-D-aspartate receptors on ouabain activation of nuclear factor-κB in the rat hippocampus.

It has been shown that ouabain (OUA) can activate the Na,K-ATPase complex and mediate intracellular signaling in the central nervous system (CNS). Inflammatory stimulus increases glutamatergic transmission, especially at N-methyl-D-aspartate (NMDA) receptors, which are usually coupled to the activation of nitric oxide synthase (NOS). Nuclear factor-κB (NF-κB) activation modulates the expression of genes involved in development, plasticity, and inflammation. The present work investigated the effects of OUA on NF-κB binding activity in rat hippocampus and the influence of this OUA-Na,K-ATPase signaling cascade in NMDA-mediated NF-κB activation. The findings presented here are the first report indicating that intrahippocampal administration of OUA, in a concentration that did not alter Na,K-ATPase or NOS activity, induced an activation of NF-κB, leading to increases in brain-derived neurotrophic factor (Bdnf), inducible NOS (iNos), tumor necrosis factor-α (Tnf-α), and B-cell leukemia/lymphoma 2 (Bcl2) mRNA levels. This response was not linked to any significant signs of neurodegeneration as showed via Fluoro-Jade B and Nissl stain. Intrahippocampal administration of NMDA induced NF-κB activation and increased NOS and α(2/3) -Na,K-ATPase activities. NMDA treatment further increased OUA-induced NF-κB activation, which was partially blocked by MK-801, an antagonist of NMDA receptor. These results suggest that OUA-induced NF-κB activation is at least in part dependent on Na,K-ATPase modulatory action of NMDA receptor in hippocampus. The interaction of these signaling pathways could be associated with biological mechanisms that may underlie the basal homeostatic state linked to the inflammatory signaling cascade in the brain.

Increased vascular contractility and oxidative stress in ß2-adrenoceptor knockout mice: the role of NADPH oxidase.

BACKGROUND/AIMS: ß(2)-adrenoceptor (ß(2)-AR) activation induces smooth muscle relaxation and endothelium-derived nitric oxide (NO) release. However, whether endogenous basal ß(2)-AR activity controls vascular redox status and NO bioavailability is unclear. Thus, we aimed to evaluate vascular reactivity in mice lacking functional ß(2)-AR (ß(2)KO), focusing on the role of NO and superoxide anion. METHODS AND RESULTS: Isolated thoracic aortas from ß(2)KO and wild-type mice (WT) were studied. ß(2)KO aortas exhibited an enhanced contractile response to phenylephrine compared to WT. Endothelial removal and L-NAME incubation increased phenylephrine-induced contraction, abolishing the differences between ß(2)KO and WT mice. Basal NO availability was reduced in aortas from ß(2)KO mice. Incubation of ß(2)KO aortas with superoxide dismutase or NADPH inhibitor apocynin restored the enhanced contractile response to phenylephrine to WT levels. ß(2)KO aortas exhibited oxidative stress detected by enhanced dihydroethidium fluorescence, which was normalized by apocynin. Protein expression of eNOS was reduced, while p47(phox) expression was enhanced in ß(2)KO aortas. CONCLUSIONS: The present results demonstrate for the first time that enhanced NADPH-derived superoxide anion production is associated with reduced NO bioavailability in aortas of ß(2)KO mice. This study extends the knowledge of the relevance of the endogenous activity of ß(2)-AR to the maintenance of the vascular physiology.

Obesity induced by neonatal treatment with monosodium glutamate impairs microvascular reactivity in adult rats: role of NO and prostanoids.

BACKGROUND AND AIM: given that obesity is an independent risk factor for the development of cardiovascular diseases we decided to investigate the mechanisms involved in microvascular dysfunction using a monosodium glutamate (MSG)-induced model of obesity, which allows us to work on both normotensive and normoglycemic conditions. METHODS AND RESULTS: Male offspring of Wistar rats received MSG from the second to the sixth day after birth. Sixteen-week-old MSG rats displayed higher Lee index, fat accumulation, dyslipidemia and insulin resistance, with no alteration in glycemia and blood pressure. The effect of norepinephrine (NE), which was increased in MSG rats, was potentiated by L-nitro arginine methyl ester (L-NAME) or tetraethylammonium (TEA) and was reversed by indomethacin and NS-398. Sensitivity to acetylcholine (ACh), which was reduced in MSG rats, was further impaired by L-NAME or TEA, and was corrected by indomethacin, NS-398 and tetrahydrobiopterin (BH4). MSG rats displayed increased endothelium-independent relaxation to sodium nitroprusside. A reduced prostacyclin/tromboxane ratio was found in the mesenteric beds of MSG rats. Mesenteric arterioles of MSG rats also displayed reduced nitric oxide (NO) production along with increased reactive oxygen species (ROS) generation; these were corrected by BH4 and either L-NAME or superoxide dismutase, respectively. The protein expression of eNOS and cyclooxygenase (COX)-2 was increased in mesenteric arterioles from MSG rats. CONCLUSION: Obesity/insulin resistance has a detrimental impact on vascular function. Reduced NO bioavailability and increased ROS generation from uncoupled eNOS and imbalanced release of COX products from COX-2 play a critical role in the development of these vascular alterations.

Aldosterone induces endothelial dysfunction in resistance arteries from normotensive and hypertensive rats by increasing thromboxane A2 and prostacyclin.

BACKGROUND AND PURPOSE: The present study was designed to assess whether cyclooxygenase-2 (COX-2) activation is involved in the effects of chronic aldosterone treatment on endothelial function of mesenteric resistance arteries (MRA) from Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). EXPERIMENTAL APPROACH: Relaxation to acetylcholine was measured in MRA from both untreated and aldosterone-treated strains. Vasomotor responses to prostacyclin and U46619 were also analysed. Release of 6-oxo-prostaglandin (PG)F1alpha and thromboxane B2 (TxB2) was determined by enzyme immunoassay. COX-2 protein expression was measured by western blot. KEY RESULTS: Aldosterone reduced acetylcholine relaxation in MRA from both strains. In MRA from both aldosterone-treated strains the COX-1/2 or COX-2 inhibitor (indomethacin and NS-398, respectively), TxA2 synthesis inhibitor (furegrelate), prostacyclin synthesis inhibitor (tranylcypromine) or TxA2/ PGH2 receptor antagonist (SQ 29 548), but not COX-1 inhibitor SC-560, increased acetylcholine relaxation. In untreated rats this response was increased only in SHR. Prostacyclin elicited a biphasic vasomotor response: lower concentrations elicited relaxation, whereas higher concentrations elicited contraction that was reduced by SQ 29 548. Aldosterone increased the acetylcholine-stimulated production of 6-oxo-PGF(1alpha) and TxB2 in MRA from both strains. COX-2 expression was higher in both strains of rats treated with aldosterone. CONCLUSIONS AND IMPLICATIONS: Chronic treatment with aldosterone impaired endothelial function in MRA under normotensive and hypertensive conditions by increasing COX-2-derived prostacyclin and thromboxane A2. As endothelial dysfunction participates in the pathogenesis of many cardiovascular disorders we hypothesize that anti-inflammatory drugs, specifically COX-2 inhibitors, could ameliorate vascular damage in patients with elevated aldosterone production.

Chronic ouabain treatment increases the contribution of nitric oxide to endothelium-dependent relaxation.

The aim of this study was to analyze the contribution of nitric oxide, prostacyclin and endothelium-dependent hyperpolarizing factor to endothelium-dependent vasodilation induced by acetylcholine in rat aorta from control and ouabain-induced hypertensive rats. Preincubation with the nitric oxide synthase inhibitor N-omega-nitro-L-arginine methyl esther (L-NAME) inhibited the vasodilator response to acetylcholine in segments from both groups but to a greater extent in segments from ouabain-treated rats. Basal and acetylcholine-induced nitric oxide release were higher in segments from ouabain-treated rats. Preincubation with the prostacyclin synthesis inhibitor tranylcypromine or with the cyclooxygenase inhibitor indomethacin inhibited the vasodilator response to acetylcholine in aortic segments from both groups. The Ca2+-dependent potassium channel blocker charybdotoxin inhibited the vasodilator response to acetylcholine only in segments from control rats. These results indicate that hypertension induced by chronic ouabain treatment is accompanied by increased endothelial nitric oxide participation and impaired endothelium-dependent hyperpolarizing factor contribution in acetylcholine-induced relaxation. These effects might explain the lack of effect of ouabain treatment on acetylcholine responses in rat aorta.

Effects of ouabain on the pressor response to phenylephrine and on the sodium pump activity in diabetic rats.

The diabetes mellitus insulin-dependent is usually associated with cardiovascular disorders and with changes in the activity of the Na(+),K(+)-ATPase. The effects of ouabain, a Na(+),K(+)-ATPase inhibitor, on the pressor response of 7-day streptozotocin-induced diabetes were investigated in anesthetized rats and on the vascular reactivity of the perfused rat tail vascular bed. Diabetes was characterized by hyperglycemia (86+/-7.8 vs. 471+/-18.5 mg/dl) without changes in arterial blood pressure. Blood pressure increased after the treatment with 18 microg/kg ouabain in controls but not in diabetic rats; acute hyperglycemia, in non-treated rats, did not change these effects. Control tail vascular beds showed increased maximal response to phenylephrine after treatment with 10 nM ouabain for 1 h; this response was abolished in streptozotocin-treated rats. These rats showed an increased sensitivity to phenylephrine without changing the maximal vasoconstrictor response when compared to control rats. The relaxation induced by acetylcholine was reduced in diabetic rats. The functional activity of the Na(+),K(+)-ATPase was inhibited in vascular beds from diabetic rats, when compared to control rats, and the inhibition of the Na(+),K(+)-ATPase with 10 nM ouabain was not effective in these rats. Results suggested that in 7-day diabetic rats, the increase of arterial blood pressure or the sensitization of the vascular bed produced by ouabain is lost as a consequence of the reduction of the functional activity of the Na(+), K(+)-ATPase probably as a result of insulin lack and a deficient endothelial nitric oxide activity.

Effects of small doses of ouabain on the arterial blood pressure of anesthetized hypertensive and normotensive rats.

Ouabain increases vascular resistance and may induce hypertension by inhibiting the Na+ pump. The effects of 0.18 and 18 microg/kg, and 1.8 mg/kg ouabain pretreatment on the phenylephrine (PHE; 0.1, 0.25 and 0.5 microg, in bolus)-evoked pressor responses were investigated using anesthetized normotensive (control and uninephrectomized) and hypertensive (1K1C and DOCA-salt treated) rats. Treatment with 18 microg/kg ouabain increased systolic and diastolic blood pressure in all groups studied. However, the magnitude of this increase was larger for the hypertensive 1K1C and DOCA-salt rats than for normotensive animals, while the pressor effect of 0.18 microg/kg ouabain was greater only in DOCA-salt rats. A very large dose (1.8 mg/kg) produced toxic effects on the normotensive control but not on uninephrectomized or 1K1C rats. Rat tail vascular beds were perfused to analyze the effects of 10 nM ouabain on the pressor response to PHE. In all animals, 10 nM ouabain increased the PHE pressor response, but this increase was larger in hypertensive DOCA-salt rats than in normotensive and 1K1C rats. Results suggested that a) increases in diastolic blood pressure induced by 18 microg/kg ouabain were larger in hypertensive than normotensive rats; b) in DOCA-salt rats, smaller ouabain doses had a stronger effect than in other groups; c) hypertensive and uninephrectomized rats were less sensitive to toxic doses of ouabain, and d) after treatment with 10 nM ouabain isolated tail vascular beds from DOCA-salt rats were more sensitive to the pressor effect of PHE than those from normotensive and 1K1C hypertensive rats. These data suggest that very small doses of ouabain, which might produce nanomolar plasma concentrations, enhance pressor reactivity in DOCA-salt hypertensive rats, supporting the idea that endogenous ouabain may contribute to the increase and maintenance of vascular tone in hypertension.

Effects of ouabain on vascular reactivity.

Ouabain is an endogenous substance occurring in the plasma in the nanomolar range, that has been proposed to increase vascular resistance and induce hypertension. This substance acts on the alpha-subunit of Na+,K(+)-ATPase inhibiting the Na(+)-pump activity. In the vascular smooth muscle this effect leads to intracellular Na+ accumulation that reduces the activity of the Na+/Ca2+ exchanger and to an increased vascular tone. It was also suggested that circulating ouabain, even in the nanomolar range, sensitizes the vascular smooth muscle to vasopressor substances. We tested the latter hypothesis by studying the effects of ouabain in the micromolar and nanomolar range on phenylephrine (PE)-evoked pressor responses. The experiments were performed in normotensive and hypertensive rats in vivo, under anesthesia, and in perfused rat tail vascular beds. The results showed that ouabain pretreatment increased the vasopressor responses to PE in vitro and in vivo. This sensitization after ouabain treatment was also observed in hypertensive animals which presented an enhanced vasopressor response to PE in comparison to normotensive animals. It is suggested that ouabain at nanomolar concentrations can sensitize vascular smooth muscle to vasopressor stimuli possibly contributing to increased tone in hypertension.

Reactivity of the isolated perfused rat tail vascular bed.

Isolated segments of the perfused rat tail artery display a high basal tone when compared to other isolated arteries such as the mesenteric and are suitable for the assay of vasopressor agents. However, the perfusion of this artery in the entire tail has not yet been used for functional studies. The main purpose of the present study was to identify some aspects of the vascular reactivity of the rat tail vascular bed and validate this method to measure vascular reactivity. The tail severed from the body was perfused with Krebs solution containing different Ca2+ concentrations at different flow rates. Rats were anesthetized with sodium pentobarbital (65 mg/kg) and heparinized (500 U). The tail artery was dissected near the tail insertion, cannulated and perfused with Krebs solution plus 30 microM EDTA at 36 degrees C and 2.5 ml/min and the procedures were started after equilibration of the perfusion pressure. In the first group a dose-response curve to phenylephrine (PE) (0.5, 1, 2 and 5 micrograms, bolus injection) was obtained at different flow rates (1.5, 2.5 and 3.5 ml/min). The mean perfusion pressure increased with flow as well as PE vasopressor responses. In a second group the flow was changed (1.5, 2, 2.5, 3 and 3.5 ml/min) at different Ca2+ concentrations (0.62, 1.25, 2.5 and 3.75 mM) in the Krebs solution. Increasing Ca2+ concentrations did not alter the flow-pressure relationship. In the third group a similar protocol was performed but the rat tail vascular bed was perfused with Krebs solution containing PE (0.1 microgram/ml). There was an enhancement of the effect of PE with increasing external Ca2+ and flow. PE vasopressor responses increased after endothelial damage with air and CHAPS, suggesting an endothelial modulation of the tone of the rat tail vascular bed. These experiments validate the perfusion of the rat tail vascular bed as a method to investigate vascular reactivity.

The left ventricular contractility of the rat heart is modulated by changes in flow and alpha 1-adrenoceptor stimulation.

Myocardial contractility depends on several mechanisms such as coronary perfusion pressure (CPP) and flow as well as on alpha 1-adrenoceptor stimulation. Both effects occur during the sympathetic stimulation mediated by norepinephrine. Norepinephrine increases force development in the heart and produces vasoconstriction increasing arterial pressure and, in turn, CPP. The contribution of each of these factors to the increase in myocardial performance needs to be clarified. Thus, in the present study we used two protocols: in the first we measured mean arterial pressure, left ventricular pressure and rate of rise of left ventricular pressure development in anesthetized rats (N = 10) submitted to phenylephrine (PE) stimulation before and after propranolol plus atropine treatment. These observations showed that in vivo alpha 1-adrenergic stimulation increases left ventricular developed pressure (P < 0.05) together with arterial blood pressure (P < 0.05). In the second protocol, we measured left ventricular isovolumic systolic pressure (ISP) and CPP in Langendorff constant flow-perfused hearts. The hearts (N = 7) were perfused with increasing flow rates under control conditions and PE or PE + nitroprusside (NP). Both CPP and ISP increased (P < 0.01) as a function of flow. CPP changes were not affected by drug treatment but ISP increased (P < 0.01). The largest ISP increase was obtained with PE + NP treatment (P < 0.01). The results suggest that both mechanisms, i.e., direct stimulation of myocardial alpha 1-adrenoceptors and increased flow, increased cardiac performance acting simultaneously and synergistically.

Effects of mercury on the arterial blood pressure of anesthetized rats.

The available data suggests that hypotension caused by Hg2+ administration may be produced by a reduction of cardiac contractility or by cholinergic mechanisms. The hemodynamic effects of an intravenous injection of HgCl2 (5 mg/kg) were studied in anesthetized rats (N = 12) by monitoring left and right ventricular (LV and RV) systolic and diastolic pressures for 120 min. After HgCl2 administration the LV systolic pressure decreased only after 40 min (99 +/- 3.3 to 85 +/- 8.8 mmHg at 80 min). However, RV systolic pressure increased, initially slowly but faster after 30 min (25 +/- 1.8 to 42 +/- 1.6 mmHg at 80 min). Both right and left diastolic pressures increased after HgCl2 treatment, suggesting the development of diastolic ventricular dysfunction. Since HgCl2 could be increasing pulmonary vascular resistance, isolated lungs (N = 10) were perfused for 80 min with Krebs solution (continuous flow of 10 ml/min) containing or not 5 microM HgCl2. A continuous increase in pulmonary vascular resistance was observed, suggesting the direct effect of Hg2+ on the pulmonary vessels (12 +/- 0.4 to 29 +/- 3.2 mmHg at 30 min). To examine the interactions of Hg2+ and changes in cholinergic activity we analyzed the effects of acetylcholine (Ach) on mean arterial blood pressure (ABP) in anesthetized rats (N = 9) before and after Hg2+ treatment (5 mg/kg). Using the same amount and route used to study the hemodynamic effects we also examined the effects of Hg2+ administration on heart and plasma cholinesterase activity (N = 10). The in vivo hypotensive response to Ach (0.035 to 10.5 microg) was reduced after Hg2+ treatment. Cholinesterase activity (microM h-1 mg protein-1) increased in heart and plasma (32 and 65%, respectively) after Hg2+ treatment. In conclusion, the reduction in ABP produced by Hg2+ is not dependent on a putative increase in cholinergic activity. HgCl2 mainly affects cardiac function. The increased pulmonary vascular resistance and cardiac failure due to diastolic dysfunction of both ventricles are factors that might contribute to the reduction of cardiac output and the fall in arterial pressure.

Resistance exercise acutely enhances mesenteric artery insulin-induced relaxation in healthy rats.

AIMS: We evaluated the mechanisms involved in insulin-induced vasodilatation after acute resistance exercise in healthy rats. MAIN METHODS: Wistar rats were divided into 3 groups: control (CT), electrically stimulated (ES) and resistance exercise (RE). Immediately after acute RE (15 sets with 10 repetitions at 70% of maximal intensity), the animals were sacrificed and rings of mesenteric artery were mounted in an isometric system. After this, concentration-response curves to insulin were performed in control condition and in the presence of LY294002 (PI3K inhibitor), L-NAME (NOS inhibitor), L-NAME+TEA (K(+) channels inhibitor), LY294002+BQ123 (ET-A antagonist) or ouabain (Na(+)/K(+) ATPase inhibitor). KEY FINDINGS: Acute RE increased insulin-induced vasorelaxation as compared to control (CT: Rmax=7.3 ± 0.4% and RE: Rmax=15.8 ± 0.8%; p<0.001). NOS inhibition reduced (p<0.001) this vasorelaxation from both groups (CT: Rmax=2.0 ± 0.3%, and RE: Rmax=-1.2 ± 0.1%), while PI3K inhibition abolished the vasorelaxation in CT (Rmax=-0.1±0.3%, p<0.001), and caused vasoconstriction in RE (Rmax=-6.5 ± 0.6%). That insulin-induced vasoconstriction on PI3K inhibition was abolished (p<0.001) by the ET-A antagonist (Rmax=2.9 ± 0.4%). Additionally, acute RE enhanced (p<0.001) the functional activity of the ouabain-sensitive Na(+)/K(+) ATPase activity (Rmax=10.7 ± 0.4%) and of the K(+) channels (Rmax=-6.1±0.5%; p<0.001) in the insulin-induced vasorelaxation as compared to CT. SIGNIFICANCE: Such results suggest that acute RE promotes enhanced insulin-induced vasodilatation, which could act as a fine tuning to vascular tone.

Ouabain activates NFκB through an NMDA signaling pathway in cultured cerebellar cells.

Na,K-ATPase, an ion pump, has been shown to interact with other proteins in signaling complexes in cardiac myocytes, renal and glial cells, and several other cell types. Our previous in vivo studies indicated that intrahippocampal administration of ouabain (OUA), an inhibitor of Na,K-ATPase, induces NFκB activation, leading to an increase in mRNA levels of target genes of this transcription factor in the rat hippocampus. The present work investigated whether OUA can regulate NF-κB in primary cultured rat cerebellar cells. Cells were treated with different concentrations of OUA (1, 10 or 100 µM) for different periods of time (1, 2 and 4 h). OUA induced a time- and concentration-dependent activation of NFκB (peak of activation: 10 µM, 2 h), involving both p50/p65 and p50/p50 NFκB dimers. OUA (10 µM, 2 h) induced upregulation of tumor necrosis factor α (Tnf-α), interleukin-1ß (Il-1ß), and brain derived neurotrophic factor (Bdnf) mRNA levels. Both NFκB activation and gene expression activation induced by OUA (10 µM) were abolished when cells were pre-treated for 20 min with MK-801 (N-Methyl-D-Aspartate (NMDA) receptor antagonist), manumycin A (farnesyltransferase inhibitor), PP-1(Src-family tyrosine kinase inhibitor) and PD98059 (mitogen-activated protein kinase (MAPK) inhibitor). OUA (10 µM) alone or in the presence of MK-801, PP-1, PD98059 did not cause cell death or DNA fragmentation. These findings suggest that OUA activates NFκB by NMDA-Src-Ras-like protein through MAPK pathways in cultured cerebellar cells. This pathway may mediate an adaptive response in the central nervous system.

Protective effect of estradiol on acute lung inflammation induced by an intestinal ischemic insult is dependent on nitric oxide.

INTRODUCTION: It has been shown that the innate immune system mediates acute lung inflammation triggered by intestinal trauma. Sexual dimorphism modulates the profile of TH1 and TH2 lymphocytes, and accordingly sex hormones may modulate acute lung inflammation by intestinal ischemia/reperfusion (I/R). Studies indicate that female rats are relatively resistant to organ injury caused by hemorrhagic shock and that the gut of female is more resistant than that of the male to deleterious effects of ischemic injury. At the present study, we investigated the effect of estradiol (E(2)) on the lung inflammation after intestinal I/R and its interaction with the nitric oxide (NO) pathway. METHODS: Anesthetized female rats submitted or not to 7 days ovariectomy (OVx) were subjected to occlusion of the superior mesenteric artery during 45 min, followed by 2 h of reperfusion. Groups of rats were treated with E(2) (17ß-estradiol, 280 µg/kg, s.c.) 24 h before ischemia and/or with the nonselective NO synthase inhibitor L-NAME (Nω-nitro-L-arginine methyl ester hydrochloride) (5 mg/kg, i.v.). In a parallel set of experiments, the selective NO synthase inhibitor, aminoguanidine (50 mg/kg i.v.), was given 1 h before ischemia. In all groups, lung vascular permeability (LVP) was assessed using the Evans blue dye extravasation method, neutrophil recruitment to the tissues by the standard myeloperoxidase (MPO) method, and endothelial NO synthase (eNOS) protein expression by Western blot. RESULTS: In OVx rats, LVP and MPO were increased after intestinal I/R as compared with intact controls. Estradiol reverted the LVP, but not MPO. Aminoguanidine reduced LVP in OVx rats. The E(2) protective effect on LVP was abolished by L-NAME; moreover, an increase in LVP even when compared with OVx rats treated only with L-NAME was observed. In addition, lung eNOS protein expression was reduced in OVx-I/R rats in comparison to intact controls and the E(2) inhibited this effect. CONCLUSIONS: Estradiol treatment is able to reduce lung inflammation due to intestinal I/R, but with the concomitant blockade of NOS activity, this effect is abolished. Nitric oxide probably reduces the vascular deleterious effects of intestinal I/R, and E(2) pretreatment reduces lung inflammation after intestinal I/R and exerts these effects by modulating eNOS protein expression in the lungs.

Drag reduction by polyethylene glycol in the tail arterial bed of normotensive and hypertensive rats.

This study was designed to evaluate the effect of drag reducer polymers (DRP) on arteries from normotensive (Wistar) and spontaneously hypertensive rats (SHR). Polyethylene glycol (PEG 4000 at 5000 ppm) was perfused in the tail arterial bed with (E+) and without endothelium (E-) from male, adult Wistar (N = 14) and SHR (N = 13) animals under basal conditions (constant flow at 2.5 mL/min). In these preparations, flow-pressure curves (1.5 to 10 mL/min) were constructed before and 1 h after PEG 4000 perfusion. Afterwards, the tail arterial bed was fixed and the internal diameters of the arteries were then measured by microscopy and drag reduction was assessed based on the values of wall shear stress (WSS) by computational simulation. In Wistar and SHR groups, perfusion of PEG 4000 significantly reduced pulsatile pressure (Wistar/E+: 17.5 ± 2.8; SHR/E+: 16.3 ± 2.7%), WSS (Wistar/E+: 36; SHR/E+: 40%) and the flow-pressure response. The E- reduced the effects of PEG 4000 on arteries from both groups, suggesting that endothelial damage decreased the effect of PEG 4000 as a DRP. Moreover, the effects of PEG 4000 were more pronounced in the tail arterial bed from SHR compared to Wistar rats. In conclusion, these data demonstrated for the first time that PEG 4000 was more effective in reducing the pressure-flow response as well as WSS in the tail arterial bed of hypertensive than of normotensive rats and these effects were amplified by, but not dependent on, endothelial integrity. Thus, these results show an additional mechanism of action of this polymer besides its mechanical effect through the release and/or bioavailability of endothelial factors.

Endothelial dysfunction in cardiovascular and endocrine-metabolic diseases: an update.

The endothelium plays a vital role in maintaining circulatory homeostasis by the release of relaxing and contracting factors. Any change in this balance may result in a process known as endothelial dysfunction that leads to impaired control of vascular tone and contributes to the pathogenesis of some cardiovascular and endocrine/metabolic diseases. Reduced endothelium-derived nitric oxide (NO) bioavailability and increased production of thromboxane A2, prostaglandin H2 and superoxide anion in conductance and resistance arteries are commonly associated with endothelial dysfunction in hypertensive, diabetic and obese animals, resulting in reduced endothelium-dependent vasodilatation and in increased vasoconstrictor responses. In addition, recent studies have demonstrated the role of enhanced overactivation of ß-adrenergic receptors inducing vascular cytokine production and endothelial NO synthase (eNOS) uncoupling that seem to be the mechanisms underlying endothelial dysfunction in hypertension, heart failure and in endocrine-metabolic disorders. However, some adaptive mechanisms can occur in the initial stages of hypertension, such as increased NO production by eNOS. The present review focuses on the role of NO bioavailability, eNOS uncoupling, cyclooxygenase-derived products and pro-inflammatory factors on the endothelial dysfunction that occurs in hypertension, sympathetic hyperactivity, diabetes mellitus, and obesity. These are cardiovascular and endocrine-metabolic diseases of high incidence and mortality around the world, especially in developing countries and endothelial dysfunction contributes to triggering, maintenance and worsening of these pathological situations.

Cardioprotective effect of ornitho-kinin in an anesthetized, open-chest chicken model of acute coronary occlusion.

The generation of bradykinin (BK; Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) in blood and kallidin (Lys-BK) in tissues by the action of the kallikrein-kinin system has received little attention in non-mammalian vertebrates. In mammals, kallidin can be generated by the coronary endothelium and myocytes in response to ischemia, mediating cardioprotective events. The plasma of birds lacks two key components of the kallikrein-kinin system: the low molecular weight kininogen and a prekallikrein activator analogous to mammalian factor XII, but treatment with bovine plasma kallikrein generates ornitho-kinin [Thr6,Leu8]-BK. The possible cardioprotective effect of ornitho-kinin infusion was investigated in an anesthetized, open-chest chicken model of acute coronary occlusion. A branch of the left main coronary artery was reversibly ligated to produce ischemia followed by reperfusion, after which the degree of myocardial necrosis (infarct size as a percent of area at risk) was assessed by tetrazolium staining. The iv injection of a low dose of ornitho-kinin (4 microg/kg) reduced mean arterial pressure from 88 +/- 12 to 42 +/- 7 mmHg and increased heart rate from 335 +/- 38 to 402 +/- 45 bpm (N = 5). The size of the infarct was reduced by pretreatment with ornitho-kinin (500 microg/kg infused over a period of 5 min) from 35 +/- 3 to 10 +/- 2% of the area at risk. These results suggest that the physiological role of the kallikrein-kinin system is preserved in this animal model in spite of the absence of two key components, i.e., low molecular weight kininogen and factor XII.

Time course of training-induced microcirculatory changes and of vegf expression in skeletal muscles of spontaneously hypertensive female rats.

Exercise-induced vessel changes modulate arterial pressure (AP) in male spontaneously hypertensive rats (SHR). Vascular endothelial growth factor (VEGF) is important for angiogenesis of skeletal muscle. The present study evaluated the time course of VEGF and angiogenesis after short- and long-term exercise training of female SHR and Wistar Kyoto (WKY) rats, 8-9 weeks (200-250 g). Rats were allocated to daily training or remained sedentary for 3 days (N = 23) or 13 weeks (N = 23). After training, the carotid artery was catheterized for AP measurements. Locomotor (tibialis anterior and gracilis) and non-locomotor skeletal muscles (temporalis) were harvested and prepared for histologic and protein expression analyses. Training increased treadmill performance by all groups (SHR = 28%, WKY = 64%, 3 days) and (SHR = 141%, WKY = 122%, 13 weeks). SHR had higher values of AP than WKY (174 +/- 4 vs 111 +/- 2 mmHg) that were not altered by training. Three days of running increased VEGF expression (SHR = 28%, WKY = 36%) simultaneously with an increase in capillary-to-fiber ratio in gracilis muscle (SHR = 19%, WKY = 15%). In contrast, 13 weeks of training increased gracilis capillary-to-fiber ratio (SHR = 18%, WKY = 19%), without simultaneous changes in VEGF expression. Training did not change VEGF expression and capillarity of temporalis muscle. We conclude that training stimulates time- and tissue-dependent VEGF protein expression, independent of pressure levels. VEGF triggers angiogenesis in locomotor skeletal muscle shortly after the exercise starts, but is not involved in the maintenance of capillarity after long-term exercise in female rats.