Losartan attenuates the antimigratory effect of diclofenac in spontaneously hypertensive rats.

Many patients with hypertension, particularly elderly patients, take nonsteroidal antiinflammatory drugs (NSAIDs) and antihypertensive agents. However, few studies describe the effect of the association of antihypertensive agents with NSAIDs on inflammatory response in hypertension. To investigate this, spontaneously hypertensive rats (SHRs) were treated with either diclofenac alone or diclofenac combined with losartan (an AT1 angiotensin II antagonist). The leukocyte-endothelial interaction was then observed using intravital microscopy. Blood pressure of SHR (169.6+/-3.6) was increased by diclofenac (186.4+/-2.9), reduced by losartan (152.6+/-3.5), and reduced by the combination of the 2 (158.9+/-3.7). All the treatments tested reduced the number of rollers, adherent and migrated leukocytes, and the expression of endothelial intercellular adhesion molecule-1 and P-selectin. The association of losartan reduced the effect of diclofenac on leukocyte migration. Neither treatment tested increased the venular shear rate or modified the venular diameters, number of circulating leukocytes, and L-selectin expression on granulocytes. The reduction of CD11/CD18 expression induced by diclofenac alone was hindered by losartan. A pharmacokinetic interference between losartan and diclofenac was ruled out since no significant differences were observed in the plasma concentrations of each drug when they were associated. In conclusion, although diclofenac does not interfere with the losartan antihypertensive effect, losartan attenuates the effect of diclofenac has on leukocyte behavior and expression of adhesion molecules. Losartan has an antimigratory effect, reducing leukocyte migration by reducing ICAM-1 and P-selectin expression. Losartan may hinder the full expression of the antimigratory effect of diclofenac.

Receptores nucleares, receptores de membrana e mensageiros secundários / Nuclear receptors, membrane receptors and second messengers

Os efeitos produzidos por fármacos ou medicamentos utilizados no tratamento da hipertensão arterial são decorrentes de sua interação com componentes macromoleculares das células, como receptores, enzimas, proteínas transportadoras, canais iônicos. A ativação de um receptor modifica a função de componentes interligados ao mesmo, iniciando uma série de alterações intracelulares, como ativação de proteínas efetoras e geração de mensageiros secundários, que irão determinar mudanças na função celular. Existem quatro famílias de receptores: (1) acoplados a proteínas G; (2) nucleares; (3) com atividade enzimática intrínseca e (4) tipo canais iônicos. Os mensageiros secundários mais conhecidos são AMPc, GMPc, IP 3' DAG, íons Ca2+ e óxido nítrico. Os alvos celulares para os medicamentos utilizados no tratamento da hipertensão arterial são apresentados no texto

A lower ratio of AT1/AT2 receptors of angiotensin II is found in female than in male spontaneously hypertensive rats.

OBJECTIVE: Sexual dimorphism has been observed in arterial hypertension. Blood pressure levels are lower in female than in male spontaneously hypertensive rats (SHR). Angiotensin II (Ang II) plays a major role in the regulation of blood pressure. The aim of this study was to compare Ang II vascular reactivity and AT(1) and AT(2) receptor gene expression in female and male SHR. METHODS: SHR animals were divided into four groups: (I) male, (II) female in physiological estrus, (III) ovariectomized and (IV) ovariectomized treated with estrogen. Arterial blood pressure, AT(1) and AT(2) mRNA expression were determined. Ang II responses in aorta and mesenteric vessels were also evaluated. RESULTS: In female SHR, aorta and mesenteric microvessels were hyporeactive to Ang II in comparison to male SHR. In ovariectomized females, Ang II vasoconstriction was similar to that of males. Estrogen treatment abolished this difference. The mRNA expression for AT(1) was higher in aorta and mesenteric vessels from males than in females. In ovariectomized SHR, mRNA expression for AT(1) was comparable to that of males. Treatment with estrogen reversed the over expression observed. Whereas AT(2) gene expression did not differ, a lower ratio AT(1)/AT(2) was found in female than in male vessels. A higher mRNA expression for AT(1) was observed in kidney from male than in female. Ovariectomy resulted in up-regulation of this subtype receptor. Treatment with estrogen reversed the overexpression. AT(2) gene expression was higher in kidney from female than male SHR. Ovariectomy reduced AT(2) gene expression and estrogen treatment reversed the alteration observed in kidney. CONCLUSION: There is sexual dimorphism in vascular reactivity and in receptor gene expression to Ang II in SHR. We conclude that estrogen modulates AT(1) and AT(2) receptor gene expression and that this might explain at least partially the lower blood pressure observed in female SHR.

Changes in the vascular beta-adrenoceptor-activated signalling pathway in 2Kidney-1Clip hypertensive rats.

1. beta-Adrenoceptor (beta-AR)-mediated vasodilation, which plays an important physiological role in the regulation of vascular tone, is decreased in two-kidney, one clip (2K-1C) renal hypertension. In this study, downstream pathways related to vascular beta-AR activation were evaluated in 2K-1C rats. 2. Relaxation responses to isoprenaline, forskolin and 8-Br-cAMP were diminished in aortas without endothelium from 2K-1C when compared to those in normotensive two kidney (2K). Basal adenosine-3',5'-monophosphate (cAMP), as well as isoprenaline-induced increase in cAMP levels, was not different between 2K and 2K-1C aortas. 3. Contractile responses to caffeine, after depletion and reloading of intracellular Ca(2+) stores, were greater in 2K-1C than in 2K. The presence of isoprenaline during the Ca(2+)-reloading period abolished the differences between groups by increasing caffeine contraction in 2K without changing this response in 2K-1C aortas. Inhibition of the sarcolemmal Ca(2+)ATPase with thapsigargin markedly attenuated isoprenaline vasodilation in both 2K and 2K-1C and abolished the differences between groups. 4. Blockade of ATP-sensitive K(+) channels (K(ATP)) channels with glibenclamide significantly decreased isoprenaline vasodilation in 2K-1C without affecting this response in 2K. Both vascular gene and protein expression of protein kinase A (PKA), as well as phosphoserine-containing proteins, were increased in 2K-1C vs 2K rats. 5. In conclusion, decreased isoprenaline vasodilation in 2K-1C hypertensive rats is related to impaired modulation of the sarcolemmal Ca(2+)ATPase activity. Moreover, K(ATP) channels may play a compensatory role on isoprenaline-induced relaxation in renal hypertension. Both Ca(2+)ATPase and K(ATP) channel functional alterations, associated with decreased beta-AR vasodilation, are paralleled by an upregulation of protein kinase A (PKA) and phosphoserine proteins expression.

Relative contribution of estrogen withdrawal and gonadotropins increase secondary to ovariectomy on prostaglandin generation in mesenteric microvessels.

Recent studies have established that ovariectomy impairs endothelial function, partially by increasing vasoconstrictor prostaglandins generation. Because ovariectomy causes concomitant lack of estrogen and increase of gonadotropins (ie, LH and FSH), in this study we explored the relative role of estrogen and LH/FSH in modulating vasoconstrictor prostaglandins generation in mesenteric arteriolar bed of SHR. Endothelium-dependent relaxation to acetylcholine (ACh) and bradykinin (Bk) was markedly reduced in ovariectomized (OVX) compared with SHR in physiological estrus (OE). Estrogen replacement (OVX + E), but not the decrease in LH/FSH levels with leuprolide (OVX + Leu), corrected the altered vasorelaxation response in OVX. Treatment of mesenteries with diclofenac, prostaglandin-H synthase (PGHS) inhibitor, significantly enhanced the relaxing response in arteries from OVX and OVX + Leu, but not those from OE, indicating that a PGHS-derived vasoconstrictor has modified the endothelium-dependent response during estrogen but not LH/FSH deprivation. Confirming these data, in response to exogenous arachidonic acid, whereas arteries from OVX and OVX + Leu exhibited a marked and similar vasoconstrictor response, the arteries from OE and OVX + E rats exhibited a slight vasodilation. We also demonstrated by RT-PCR that ovariectomy significantly increased PGHS-2 but not PGHS-1 mRNA expression in comparison to OE. The PGHS-2 overexpression in OVX was corrected by estrogen replacement, but not by the reduction of LH/FSH levels. Altogether these data strongly support a role for hypoestrogenism rather than LH/FSH enhancement, associated with the removal of ovaries, in the increase of vasoconstrictor prostaglandins, possibly by a mechanism involving PGHS-2 overexpression.

Intrauterine undernutrition--renal and vascular origin of hypertension.

OBJECTIVE: A large number of clinical and experimental studies supports the hypothesis that intrauterine undernutrition is an important determinant of hypertension, coronary heart disease and non-insulin-dependent diabetes in the adult offspring. In this review, the renal and vascular repercussions of maternal undernutrition are emphasized, and the physiopatologic mechanisms discussed. The origin of hypertension is detailed based upon the findings of kidney functional parameters and endothelium function studies. A working model linking hypertension to intrauterine undernutrition is proposed.

Intrauterine undernutrition: expression and activity of the endothelial nitric oxide synthase in male and female adult offspring.

OBJECTIVE: Epidemiological studies suggest that intrauterine undernutrition plays an important role in the development of arterial hypertension in adulthood. In an attempt to define the mechanisms whereby blood pressure may be raised, we have hypothesized that arteries from offspring of nutritionally restricted dams exhibit abnormalities in the endothelial function and in nitric oxide synthesis. In order to investigate the existence of potential gender differences on the effects of intrauterine undernutrition, both male and female offspring of pregnant Wistar rats on normal and restricted diets were studied in adulthood. METHODS: Female pregnant Wistar rats were fed either normal or 50% of the normal intake diets, during the whole gestational period. At 14 weeks of age, the rats were used for the study of vascular reactivity, eNOS and iNOS gene expression, eNOS activity and, in the case of females, estrogen levels. RESULTS: Intrauterine undernutrition induced hypertension in both male and female offspring, but hypertension was more severe in male rats. Endothelium-intact aortic rings from male and female rats in the restricted diet group exhibited increased responses to norepinephrine, decreased vasodilation to acetylcholine and unaltered responses to sodium nitroprusside in comparison to aortic rings from control rats. No gender-related differences were observed in the vascular reactivity studies. Intrauterine undernutrition promoted decreased gene expression for eNOS in aorta isolated from male, but not female, offspring, reduction in eNOS activity in both male and female offspring and impairment in synthesis of estrogen in female offspring. CONCLUSION: Our data show that intrauterine undernutrition: (1) induces hypertension both in the male and female offspring, hypertension being more severe in male than in female rats; (2) alters endothelium-dependent responses in aortas from the resulting offspring. The endothelial dysfunction is associated with a decrease in activity/expression of eNOS in aortas from male offspring. The mechanism involved in altered response to ACh in female offspring might be a consequence of reduction in estrogen levels leading to reduced eNOS activity.

Contribution of endothelin-1 to renal activator protein-1 activation and macrophage infiltration in aldosterone-induced hypertension.

Aldosterone-induced hypertension is associated with renal damage that may be mediated by endothelin-1 (ET-1). We evaluated whether inflammatory cell infiltration and DNA-binding activity of the transcription factors nuclear factor kappa B (NF-kappa B) and activator protein-1 (AP-1) were increased in kidneys from aldosterone-infused rats. The role of ET-1 in these processes was evaluated by treating rats with the ET(A)-receptor blocker, BMS 182874. Rats were infused with aldosterone (0.75 microg/h) via a mini-osmotic pump and were given 1% NaCl in the drinking water in the absence and presence of BMS 182874 or of the aldosterone receptor blocker, spironolactone. Renal sections were used to assess inflammatory cell infiltration, which was identified immunocytochemically using monoclonal antibodies against macrophages (ED1+). Electrophoretic mobility shift assays evaluated the DNA-binding activity of NF-kappa B and AP-1 in renal tissue. Systolic blood pressure (BP) was increased in the aldosterone-infused group compared with controls (123+/-6 versus 110+/-10 mmHg, P<0.05). BMS 182874 and spironolactone significantly decreased BP (P<0.05). Macrophage infiltration was increased in the kidneys of aldosterone-infused rats compared with controls. Renal binding activity (arbitrary units) of AP-1, in contrast with that of NF-kappa B, increased in aldosterone-infused rats compared with control rats (AP-1, 4.2+/-0.3 versus 1.0+/-0.1, P<0.05; NF-kappa B, 1.6+/-0.5 versus 1.2+/-0.5). BMS 182874 and spironolactone decreased macrophage infiltration (by 70% and 50% respectively) and AP-1 binding activity (1.0+/-0.3 and 0.8+/-0.3 respectively). In conclusion, kidneys from aldosterone-infused rats exhibited macrophage infiltration and increased AP-1 DNA-binding activity. These processes were attenuated by BMS 182874. Our findings suggest that renal damage in aldosterone-dependent hypertension is associated with inflammatory processes that are mediated in part via ET-1.

In vivo evidence for antioxidant potential of estrogen in microvessels of female spontaneously hypertensive rats.

In studies conducted in vitro, it has been demonstrated that estrogen has an antioxidant potential that may contribute to its protective effects on the cardiovascular system. However, the antioxidant effect of estrogen in vivo has not been demonstrated. To address this issue, in this study the effects of estrogen on oxidative stress were evaluated in microvessels studied in vivo. Oxidative stress was evaluated by using intravital microscopy in mesenteric arterioles from female spontaneously hypertensive rats (SHR) in physiological estrous (OE), ovariectomized (OVX), OVX treated with estradiol (E(2)), or estradiol + progesterone (E/P). The mesenteries were superfused with hydroethidine, a reduced and nonfluorescent precursor of ethidium bromide (EB). In the presence of reactive oxygen species, hydroethidine is transformed intracellularly in EB, which binds to DNA and can be detected by its red fluorescence. The percentage of EB-positive nuclei along the arteriolar wall in OVX (28.4 +/- 4.3) was significantly increased compared with OE (14.2 +/- 3.9; P<0.05). The OVX overproduction of oxyradicals was attenuated by E(2) (15.7 +/- 2.2) and E/P (14.8 +/- 0.8). Treatment with the superoxide dismutase mimetic MnTMPyP attenuated by 75% the oxidation of hydroethidine in both OE and OVX. Conversely, mannitol, that decomposes hydroxyl radical, and L-NAME, a nitric oxide synthase inhibitor, had no significant effects on hydroethidine oxidation. No differences on hydrogen peroxide plasma concentration were observed among the groups, suggesting that superoxide anion is the most likely oxyradical involved in the increased oxidative stress observed in OVX. The treatment of mesenteries with diphenyleneiodonium (DPI), an nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase inhibitor, but not with oxypurinol, a xanthine-oxidase inhibitor, produced a significant reduction of oxyradical generation in OVX microvessels and a slight decrease in those from OE. Chronic treatment of female SHR with losartan caused similar decreases in oxyradicals in both OE and OVX, whereas diclofenac and verapamil had no effects. Together these data suggest that estrogen reduces superoxide anion bioavailability in vivo. The antioxidant effect of estrogen, which can contribute to a less pronounced endothelial dysfunction in female SHR, may be dependent on a direct modulatory action of estrogen on NADPH activity.