Acute hypothalamo-pituitary-adrenal axis response to LPS-induced endotoxemia: expression pattern of kinin type B1 and B2 receptors.

Bradykinin (BK) and des-Arg9-BK are pro-inflammatory mediators acting via B2 (B2R) and B1 (B1R) receptors, respectively. We investigated the role of B2R and B1R in lipopolysaccharide (LPS)-induced hypothalamo-pituitary-adrenal (HPA) axis activation in SD rats. LPS given intraperitoneally (ip) up-regulated B1R mRNA in the hypothalamus, both B1R and B2R were up-regulated in pituitary and adrenal glands. Receptor localization was performed using immunofluorescence staining. B1R was localized in the endothelial cells, nucleus supraopticus (SON), adenohypophysis and adrenal cortex. B2R was localized nucleus paraventricularis (PVN) and SON, pituitary and adrenal medulla. Blockade of B1R prior to LPS further increased ACTH release and blockade of B1R 1 h after LPS decreased its release. In addition, we evaluated if blockade of central kinin receptors influence the LPS-induced stimulation of hypothalamic neurons. Blockade of both B1R and B2R reduced the LPS-induced c-Fos immunoreactivity in the hypothalamus. Our data demonstrate that a single injection of LPS induced a differential expression pattern of kinin B1R and B2R in the HPA axis. The tissue specific cellular localization of these receptors indicates that they may play a crucial role in the maintenance of body homeostasis during endotoxemia.

Overfeeding-induced obesity in spontaneously hypertensive rats: an animal model of the human metabolic syndrome.

BACKGROUND/AIMS: The metabolic syndrome (MS) has become an epidemiological problem in Western countries. We developed a diet-induced obese rat model that mimics all the symptoms of MS in humans, but whose insulin resistance, hyperphagia and hyperleptinemia are caused by nutrition rather than genetic modifications. METHODS: Spontaneously hypertensive rats (SHR) were allowed for 12 weeks to choose between a cafeteria diet (CD, 20.3 kJ/g) and standard rat chow (11.7 kJ/g). Controls received rat chow. RESULTS: Body weight (BW) exceeded control levels when SHR were fed with CD. The increase in BW was attributed to enhanced energy intake. The abundance of abdominal fat as well as the plasma levels of leptin and triglycerides increased concomitant with glucose, insulin and C-peptide. This prediabetic condition was further confirmed by a markedly increased insulin response following glucose challenge and by impaired glucose utilization after insulin tolerance tests. CONCLUSION: Increases in food intake and BW despite hyperleptinemia indicate leptin resistance following CD feeding. CD-fed SHR feature leptin and insulin resistance, hypertension and obesity, thus mimicking the situation of MS patients. As such, our model is more suitable than the genetically modified rat models used to study human MS.

Stress sensitivity is increased in transgenic rats with low brain angiotensinogen.

AT(1) blockers attenuate hypothalamo-pituitary-adrenal (HPA) axis reactivity in hypertension independently of their potency to lower blood pressure. A reduced pituitary sensitivity to CRH and a downregulation of hypothalamic CRH expression have been suggested to influence HPA axis activity during chronic AT(1) blockade. This study was aimed at confirming the role of central angiotensin II in regulating HPA reactivity by using the transgenic rat TGR(ASrAOGEN), a model featuring low levels of brain angiotensinogen. Different stress tests were performed to determine HPA reactivity in TGR(ASrAOGEN) and appropriate controls. In TGR(ASrAOGEN), blood pressure was diminished compared to controls. The corticosterone response to a CRH or ACTH challenge and a forced swim test was more distinct in TGR(ASrAOGEN) than it was in controls and occurred independently of a concurrent enhancement in ACTH. Using quantitative real-time PCR, we found increased mRNA levels of melanocortin 2 (Mc2r) and AT(2) receptors (Agtr2) in the adrenals of TGR(ASrAOGEN), whereas mRNA levels of Crh, Pomc, and AT(1) receptors (Agtr1) remained unchanged in hypothalami and pituitary glands. Since stress responses were increased rather than attenuated in TGR(ASrAOGEN), we conclude that the reduced HPA reactivity during AT(1) blockade could not be mimicked in a specific transgenic rat model featuring a centrally inactivated renin-angiotensin-aldosterone system. The ACTH independency of the enhanced corticosterone release during CRH test and the enhanced corticosterone response to ACTH rather indicates an adrenal mechanism. The upregulation of adrenal MC2 and AT(2) receptors seems to be involved in the stimulated facilitation of adrenal corticosterone release for effectuating the stimulated stress responses.

Hypocretin/orexin increases the expression of steroidogenic enzymes in human adrenocortical NCI H295R cells.

Hypocretins/orexins act through two receptor subtypes: OX(1) and OX(2). Outside the brain, orexin receptors are expressed in adrenal glands, where orexins stimulate the release of glucocorticoids. To further address the regulation of steroidogenesis, we analyzed the effect of orexins on the expression of steroidogenic enzymes in human adrenocortical National Cancer Institute (NCI) H295R cells by qPCR. In NCI H295R cells, OX(2) receptors were highly expressed, as they were in human adrenal glands. After treatment of NCI H295R cells with orexin A for 12-24 h, the cortisol synthesis rate was significantly increased, whereas 30 min of treatment showed no effect. While CYP11B1 and CYP11B2 mRNA levels were increased already at earlier time points, the expression of HSD3B2 and CYP21 mRNA was significantly up-regulated after treatment with orexin A for 12 h. Likewise, orexin B increased CYP21 and HSD3B2 mRNA levels showing, however, a lower potency compared with orexin A. The mRNA levels of CYP11A and CYP17 were unaffected by orexin A. OX(2) receptor mRNA levels were down-regulated after 12 and 24 h of orexin A treatment. Orexin A increased intracellular Ca(2+) but not cAMP concentrations in NCI H295R cells. Furthermore, inhibition of PKC and MAPK kinase/ERK kinase (MEK1/2) prevented the increase of HSD3B2 expression by orexin A. Accordingly, orexin A treatment of NCI H295R cells markedly enhanced ERK1/2 phosphorylation that was prevented by PKC and, in part, PKA inhibition. In conclusion, orexins may influence adrenal steroidogenesis by differential regulation of the expression of steroidogenic enzymes involving Ca(2+), as well as PKC-ERK1/2 signaling.

The PHARAO study: prevention of hypertension with the angiotensin-converting enzyme inhibitor ramipril in patients with high-normal blood pressure: a prospective, randomized, controlled prevention trial of the German Hypertension League.

BACKGROUND: The prevention of hypertension with the angiotensin-converting enzyme inhibitor ramipril in patients with high-normal blood pressure study addresses the issue of whether progression to manifest hypertension in patients with high-normal blood pressure can be prevented with treatment. METHODS: A total of 1008 participants with high-normal office blood pressure were randomized to ramipril treatment group (n = 505) and a control group (n = 503). The patients were followed up for 3 years. Primary endpoint was to prevent or delay the progression to manifest hypertension. Secondary endpoints were reduction in the incidence of cerebrovascular and cardiovascular events, as well as the development of hypertension as defined by ambulatory blood pressure monitoring. FINDINGS: One hundred and fifty-five patients (30.7%) in the ramipril group, and 216 (42.9%) in the control group reached the primary endpoint (relative risk reduction 34.4%, P = 0.0001). Ramipril also proved to be more effective in reducing the incidence of manifest office hypertension in patients with baseline ambulatory blood pressure monitoring high-normal blood pressure. The incidence of cerebrovascular and cardiovascular events showed no statistically significant differences between the two groups. Cough was more frequent in the ramipril group (4.8 vs. 0.4%). INTERPRETATION: There is now good clinical evidence that patients with high-normal blood pressure (prehypertension) are more likely to progress to manifest hypertension than patients with optimal or normal blood pressure. Additional ambulatory blood pressure monitoring seems to be essential to achieve correct diagnosis. Treatment of patients with high-normal office blood pressure with the angiotensin-converting enzyme inhibitor was well tolerated, and significantly reduced the risk of progression to manifest hypertension.

Remote vs. ischaemic preconditioning: the differential role of mitogen-activated protein kinase pathways.

AIMS: Since mitogen-activated protein kinases (MAPKs) were found to be implicated in the signalling of ischaemic preconditioning (IPC), we tested the hypothesis of a contribution of these protein kinases to remote preconditioning (RPC). METHODS AND RESULTS: To determine the role of p38, ERK1/2, and JNK1/2 MAPKs in mediating cardiac protection, an in vivo model of myocardial infarction was applied in male Wistar rats. RPC or IPC was induced by occlusion of the superior mesenteric artery or the left coronary artery, respectively. Infarct size (IS) was determined based on 2,3,5-triphenyltetrazolium chloride staining. Phosphorylation of the various MAPKs was analysed by immunoblotting in samples of the small intestine and myocardium obtained after IPC or RPC procedures. The MAPK inhibitors SB203580 (p38), PD98059 (ERK1/2), and SP600125 (JNK1/2) were administered to assess the potential significance of MAPK signalling in RPC. Both preconditioning stimuli decreased myocardial IS significantly after a lethal period of ischaemia. Each of the applied MAPK inhibitors was capable of abrogating the RPC-induced cardioprotection. Western blot analysis of myocardial samples revealed an increase in phosphorylated amounts of ERK1/2 and JNK1 after IPC, whereas phosphorylation of p38 protein was decreased significantly. Likewise, RPC resulted in a considerable increase in phosphorylation of ERK1/2 and JNK1/2 proteins in the small intestine, whereas it did not alter the MAPK phosphorylation state in the myocardium. CONCLUSION: All investigated MAPK pathways appear to be involved in RPC-induced cardioprotection; however, they do not contribute to the alterations that define the preconditioned state of the myocardium prior to the infarction.

Gene expression of mineralocorticoid and glucocorticoid receptors in the limbic system is related to type-2 like diabetes in leptin-resistant rats.

Diabetes is often accompanied by a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis which is regulated centrally via glucocorticoid (GR) and mineralocorticoid receptors (MR). Here, we compared the expression of both receptor subtypes in the brain of Zucker fatty and Zucker diabetic fatty (ZDF) rats together with their respective control rats. Both strains are primarily leptin resistant due to a mutated leptin receptor; ZDF rats, however, develop type-2 like diabetes. Using quantitative real-time PCR (qPCR) we found increased hypothalamic corticotrophin releasing hormone (CRH) levels in rats with the genetic ZDF background independently from leptin resistance. This was accompanied by elevated plasma corticosterone levels and by a higher reactivity of the HPA axis in response to CRH. Rats with the genetic ZDF background showed increased mRNA levels of GR in the amygdala and hypothalamus and increased mRNA levels of MR in the hippocampus and hypothalamus compared to rats with the Zucker fatty background. In leptin resistant ZDF rats but not in Zucker fatty rats, the mRNA levels of MR were selectively increased in the amygdala compared to nondiabetic control rats. No differences in the GR mRNA levels were found between leptin resistant Zucker fatty rats and lean control rats. Thus, an increased drive of the HPA axis in rats with ZDF background is associated with a differential expression of GR and MR in the limbic system. This dysregulation of the HPA axis may eventually lead, in combination with leptin resistance, to the development of diabetes in ZDF rats.

Angiotensin II stimulates the reactivity of the pituitary-adrenal axis in leptin-resistant Zucker rats, thereby influencing the glucose utilization.

The HPA axis is hyperactive under conditions of leptin and insulin resistance as well as after ANG II administration. We hypothesized that a hyperreactivity of the HPA axis to ANG contributes to an impaired glucose utilization in obesity, since leptin resistance and an overactive renin-angiotensin-aldosterone system are features of obesity. Zucker rats were treated with ANG via subcutaneous minipumps (0, 0.9, and 9.0 mug/h; 4 wk). PA axis reactivity and glucose homeostasis were characterized after CRH treatment and during an oral glucose tolerance test (OGTT). The elevated plasma profile of corticosterone after CRH stimulation in saline-treated OZR compared with LZR confirmed that the sensitization of the PA axis depended on leptin resistance. Irrespective of the rat strain, circulating ANG levels and blood pressure were selectively increased after administration of 9 mug/h ANG (high ANG). Only high ANG induced an elevation of the corticosterone and glucose response after CRH stimulation in OZR but did not affect the ACTH secretion. During OGTT, corticosterone and consequently glucose increased in OZR after high ANG, whereas the insulin secretion was decreased. In the adrenal glands of OZR, AT(1A) receptor mRNA levels increased after high ANG. We conclude that the impairment of glucose utilization after ANG stimulation is potentiated in leptin-resistant rats as a result of a hyperreactive PA axis, thereby confirming the functional importance of a dysregulation within the HPA axis in metabolic syndrome or obesity. The ACTH-independent stimulation of corticosterone release and the selective increase of AT(1A) receptor mRNA in the adrenals of OZR indicated a sensitization of adrenals toward ANG, causing a stimulation of the PA axis.

Non-hypoxic induction of HIF-3alpha by 2-deoxy-D-glucose and insulin.

Hypoxia-inducible factors (HIFs) are key mediators of cellular adaptation to hypoxia, but also respond to non-hypoxic stimuli. To clarify involvement in metabolic disturbances, HIFs were characterised in rats subjected to insulin-induced hypoglycaemia or cellular glucoprivation provoked by 2-deoxy-D-glucose (2-DG). Using real-time qPCR, organ-specific expression of HIF-1alpha, -2alpha, -3alpha, -1beta, and of the target gene GLUT-1 was determined. Distribution of HIF-3alpha proteins was examined by immunohistochemistry. Both, insulin and 2-DG resulted in a widespread increase in HIF-3alpha mRNA. HIF-2alpha mRNA increased in lung and heart after 2-DG only, whereas other HIFs remained unaffected. A pronounced increase of protein levels in cerebral cortex was observed for HIF-3alpha. Functional significance of HIF induction was reflected in enhancement of GLUT-1 mRNA. Transcriptional up-regulation of HIF-3alpha represents a typical response to in vivo hypoglycaemia and glucoprivation. These data suggest an involvement of the HIF system in metabolic derangements as for instance caused by diabetes.

Adrenal expression of orexin receptor subtypes is differentially regulated in experimental streptozotocin induced type-1 diabetes.

Orexins (hypocretins) are involved in the regulation of energy homeostasis and sleeping behavior. Orexins were also implicated in the regulation of neuroendocrine and autonomic functions. Recent data show the expression of orexin receptors within the hypothalamic-pituitary-adrenal (HPA) axis and suggest specific actions of orexins at the pituitary and adrenal glands. To further evaluate the role of orexin in the HPA axis, we investigated the mRNA expression of prepro-orexin (PPO) and orexin receptors within the HPA axis of streptozotocin-injected (STZ) rats showing type-1 like diabetes. PPO, as well as OX(1) and OX(2) receptor levels were analyzed by quantitative real-time PCR (qPCR). STZ rats were characterized by decreased body weight, plasma insulin, and leptin levels and by increased plasma glucose. Hypothalamic PPO mRNA levels were significantly reduced in STZ compared to non-diabetic control rats. No differences were found in the mRNA levels of hypothalamic or pituitary OX(1) and OX(2) receptors between control and STZ rats. In adrenals, OX(1) receptor mRNA levels were significantly elevated in STZ rats while OX(2) receptors were significantly reduced. Our results imply distinct functions of adrenal orexin receptor subtypes during type-1 like diabetes.

Angiotensin II inhibition reduces stress sensitivity of hypothalamo-pituitary-adrenal axis in spontaneously hypertensive rats.

Angiotensin II type 1 (AT(1)) receptors are expressed within organs of the hypothalamo-pituitary-adrenal (HPA) axis and seem to be important for its stress responsiveness. Secretion of CRH, ACTH, and corticosterone (CORT) is increased by stimulation of AT(1) receptors. In the present study, we tested whether a blockade of the angiotensin II system attenuates the HPA axis reactivity in spontaneously hypertensive rats. Spontaneously hypertensive rats were treated with candesartan (2 mg/kg), ramipril (1 mg/kg), or mibefradil (12 mg/kg) for 5 wk. In addition to baseline levels, CORT and ACTH responses to injection of CRH (100 microg/kg) were monitored over 4 h. mRNA of CRH, proopiomelanocortin, AT(1A), AT(1B), and AT(2) receptors was quantified by real-time PCR. All treatments induced equivalent reductions of blood pressure and had no effect on baseline levels of CORT and ACTH. However, both candesartan and ramipril significantly reduced CRH-stimulated plasma levels of ACTH (-26 and -15%) and CORT (-36 and -18%) and lowered hypothalamic CRH mRNA (-25 and -29%). Mibefradil did not affect any of these parameters. Gene expression of AT(1A), AT(1B), and AT(2) receptors within the HPA axis was not altered by any drug. We show for the first time that antihypertensive treatment by inhibition of AT(1) receptors or angiotensin-converting enzyme attenuates HPA axis reactivity independently of blood pressure reduction. This action is solely evident after CRH stimulation but not under baseline conditions. Both a reduced pituitary sensitivity to CRH and a down-regulation of hypothalamic CRH expression have the potential to reduce HPA axis activity during chronic AT(1) blockade or angiotensin-converting enzyme inhibition.

Microalbuminuria and tubular proteinuria as risk predictors of cardiovascular morbidity and mortality in essential hypertension: final results of a prospective long-term study (MARPLE Study)*.

OBJECTIVE: To evaluate the impact of microalbuminuria (MAU) or tubular proteinuria (TPU) on cardiovascular and cerebrovascular events and all-cause mortality, and to assess whether a normalization of MAU and/or TPU induced by angiotensin-converting enzyme-inhibitor-based antihypertensive treatment with ramipril improves cerebrovascular prognosis in essential hypertensive patients without diabetes mellitus. METHOD: A prospective, controlled, multicenter study was performed involving 3529 hypertensive participants (average follow-up 42.5 months). Ramipril was the basic antihypertensive medication. Proteinuria analysis (albumin, alpha 1-microglobulin, SDS electrophoresis) was performed by quantitative measurement every year. Ambulatory blood pressure monitoring was performed once yearly. The main outcome determined was cardiovascular and cerebrovascular events and all-cause mortality. RESULTS: In patients with TPU and/or MAU, the risk for endpoints increased significantly compared with normal (TPU, 30.0%; MAU, 54.7%; MAU + TPU, 64.0%; macroproteinuria, 74.4%). A change of protein excretion either from pathologic to normal or from normal to pathologic showed a clear trend to correlate with cerebrovascular endpoints (P = 0.056 and P = 0.055). Normal protein excretion at baseline and during follow-up indicated a significantly better prognosis than pathologic proteinuria at baseline and during follow-up. (P < 0.0001). TPU normalized in 31.9%, MAU in 30.6%, MAU + TPU in 29.3%, and macroproteinuria in 10.2% of patients. A total of 445 (25.4%) patients with normal protein excretion developed pathologic proteinuria during follow-up. CONCLUSIONS: In non-diabetic hypertensive patients, MAU as well as TPU increases the incidence of cardiovascular events. Normalization of MAU, TPU or macroproteinuria during angiotensin-converting enzyme-inhibitor-based treatment correlates with a reduction of cardiovascular events. Beyond blood pressure control, normalization of MAU and TPU should be considered as a further therapeutic goal. There is a need for further studies to optimize treatment if proteinuria is unresponsive to angiotensin-converting enzyme inhibitors.

Inhibition of nonexocytotic norepinephrine release by desipramine reduces myocardial infarction size.

During myocardial ischemia, a substantial accumulation of norepinephrine occurs in the ischemic zone due to a local nonexocytotic release of norepinephrine. Norepinephrine release is driven by the neuronal monoamine transporter (NET), which reverses its usual transmembrane transport direction. We investigated whether this local accumulation of norepinephrine contributes to irreversible myocardial injury in an in vivo model of myocardial infarction. Male, anaesthetized Wistar rats were subjected to 30 min coronary occlusion and subsequent 120 min reperfusion. Five minutes prior to coronary occlusion, the NET inhibitor desipramine was administered intravenously. Infarct size (IS) was determined by TTC-staining and was related to the area at risk (AAR). The influence of desipramine on cardiac norepinephrine release was investigated in isolated perfused hearts with 30 min of regional ischemia. Norepinephrine was measured in the effluent from the hearts by HPLC and electrochemical detection. Desipramine (0.1-0.8 mg/kg) dose-dependently reduced infarct size (IS/AAR) from 0.54 to 0.21 and suppressed postischemic norepinephrine release from 245 to 108 pg/mL. In summary, the data indicate that nonexocytotic release of norepinephrine in myocardial ischemia exaggerates acute ischemic damage, because suppression of ischemia-induced release of norepinephrine by the tricyclic antidepressant desipramine effectively reduces infarct size in an in vivo model of myocardial ischemia.

Peripheral sympatholytic actions of four AT1 antagonists: are they relevant for long-term antihypertensive efficacy?

BACKGROUND: Angiotensin II causes hypertension not only by direct constriction of vascular smooth muscle, but also by facilitating the release of noradrenaline from sympathetic terminals and by enhancing vascular noradrenaline sensitivity. AT1 receptor antagonists attenuate all these actions, but display some evidence of substance-related selectivities. OBJECTIVE: The contribution of pre- or postsynaptic impairment of sympathetic transmission to long-term antihypertensive efficacy should be determined for four structurally different, clinically approved AT1 antagonists. DESIGN: Spontaneously hypertensive rats were treated with candesartan, eprosartan, irbesartan, or losartan via osmotic minipumps for 4 weeks at doses yielding identical reductions of blood pressure. Maximum efficacy was obtained with a tripled dose of candesartan. METHODS: In the pithed rat model, stimulus/response dependencies were determined for vasopressor effectivity of preganglionic electrical stimulation, and of intravenous bolus applications of noradrenaline and angiotensin II. RESULTS: Losartan, irbesartan, eprosartan, and candesartan at doses of 5, 40, 20, and 0.05 mg/kg per day, were equally effective in reducing basal systolic blood pressure (-42 mmHg), and the vasopressor potency of angiotensin II (approximately 10-fold). The efficacies of preganglionic stimulation and exogenous noradrenaline were unaltered, with the exception of irbesartan, which reduced vascular noradrenaline sensitivity. The tripled dose of candesartan further reduced basal and angiotensin II-stimulated blood pressures, and significantly attenuated vascular noradrenaline sensitivity. CONCLUSION: AT1 antagonists at doses that effectively reduce blood pressure in chronic therapy do not generally suppress peripheral sympathetic function. A potential interaction consists in a reduction of vascular noradrenaline sensitivity, which can be considered as a class effect of AT1 antagonists at high dosage.

Angiotensin I-converting enzyme-dependent and neutral endopeptidase-dependent generation and degradation of angiotensin II contrarily modulate noradrenaline release: implications for vasopeptidase-inhibitor therapy?

OBJECTIVES: Vasopeptidase inhibitors inhibit neutral endopeptidase (NEP) and angiotensin I-converting enzyme (ACE). Since angiotensin (ANG) II availability is decreased by ACE inhibition but is increased by NEP inhibition, we evaluated the influence of the vasopeptidase inhibitor omapatrilat on ANG II-dependent noradrenaline (NA) release. DESIGN: The functional relevance of ACE-dependent and NEP-dependent generation and degradation of ANG II on NA overflow was determined in pithed rats by applications of ANG I (0.1-100 microg/kg) or ANG II (0.01-10 microg/kg) after single injections of ramipril (1 mg/kg), the NEP inhibitor candoxatril (100 mg/kg), or the vasopeptidase inhibitor omapatrilat (30 mg/kg). RESULTS: Blood pressure was equipotently decreased by ramipril and omapatrilat, but not by candoxatril. NA overflow was increased after ANG I infusions in controls (EC50 = 9.0 microg/kgANG I, Emax = 5680 pg/ml), but almost completely suppressed by ramipril and omapatrilat. Candoxatril decreased EC50 (4.1 microg/kg) and increased Emax (7259 pg/ml). NA overflow after ANG II infusions was enhanced by candoxatril or omapatrilat. Ex vivo ACE activity was extensively inhibited by ramipril or omapatrilat, whereas ex vivo NEP activity was reduced by omapatrilat and candoxatril only. In vitro, omapatrilat inhibited NEP and ACE with similar potencies (IC50 NEP/IC50 ACE = 0.4). CONCLUSIONS: Vasopeptidase inhibitors influence ANG II-related NA release depending on their ability to modulate the availability of ANG II via ACE or NEP. After acute application, the vasopeptidase inhibitor suppresses NA release in response to ANG I due to a predominant reduction of ANG II formation. These results indicate that the ratio of ACE-inhibitory and NEP-inhibitory potencies of vasopeptidase inhibitors may be relevant for sympathetic activation in chronic therapy.

Expression of nitric oxide synthase isoforms in hypothalamo-pituitary-adrenal axis during the development of spontaneous hypertension in rats.

This study was performed to investigate the expression of the major isoforms of nitric oxide synthase mRNA and protein in the hypothalamo-pituitary-adrenal axis (HPA axis) of spontaneously hypertensive rats (SHR) at two different postnatal ages corresponding to the development of genetic hypertension. Using RT-PCR and Western blot techniques, the mRNA and protein levels of neuronal (nNOS), endothelial (eNOS) and inducible (iNOS) isoforms were measured in 3- to 4-week-old (prehypertensive phase) and 12- to 13-week-old (established hypertension phase) SHR and age-matched normotensive Wistar-Kyoto (WKY) rats. nNOS but not eNOS mRNA levels were increased at prehypertensive and hypertensive phases in SHR HPA axis. Compared to age-matched WKY rats, significantly higher levels of nNOS protein were found in the hypothalamus, lower levels in the adrenal glands and no changes were observed in the pituitary gland. At both ages tested, there was no significant change in eNOS protein expression in SHR HPA axis. The expression of iNOS mRNA and protein was under detection limit. In the HPA axis, the expression of nNOS isoform appears to be differentially controlled at the transcriptional and translational levels in SHR. Increased mRNA levels and differential nNOS protein expression from birth in SHR HPA axis may contribute in the pathogenesis of genetic hypertension.

Morbidity and Mortality After Stroke, Eprosartan Compared with Nitrendipine for Secondary Prevention: principal results of a prospective randomized controlled study (MOSES).

BACKGROUND AND PURPOSE: In hypertensive stroke patients, for the same level of blood pressure control, eprosartan will be more effective than nitrendipine in reducing cerebrovascular and cardiovascular morbidity and mortality. METHODS: A total of 1405 well-defined, high-risk hypertensives with cerebral event during the last 24 months (proven by cerebral computed tomography scan or nuclear magnetic resonance) were randomized to eprosartan or nitrendipine (mean follow-up 2.5 years). Primary end point was the composite of total mortality and all cardiovascular and cerebrovascular events, including all recurrent events. RESULTS: Randomization was successful without significant differences in the baseline characteristics. Blood pressure was reduced to a comparable extent without any significant differences between the 2 groups during the whole study period (150.7/84 mm Hg and 152.0/87.2 mm Hg with eprosartan and nitrendipine therapy to 137.5/80.8 mm Hg and 136.0/80.2 mm Hg, respectively, confirmed by ambulatory blood pressure monitoring). Moreover, already after 3 months, normotensive mean values were achieved, and 75.5% reached values <140/90 mm Hg with the eprosartan regimen and 77.7% with the nitrendipine regimen. During follow-up, in total, 461 primary events occurred: 206 eprosartan and 255 nitrendipine (incidence density ratio [IDR], 0.79; 95% CI, 0.66 to 0.96; P=0.014). Cardiovascular events were: 77 eprosartan and 101 nitrendipine (IDR, 0.75; 95% CI, 0.55 to 1.02; P=0.06); cerebrovascular events: 102 eprosartan and134 nitrendipine (IDR, 0.75; 95% CI, 0.58 to 0.97; P=0.03). CONCLUSIONS: The Morbidity and Mortality After Stroke, Eprosartan Compared With Nitrendipine for Secondary Prevention (MOSES) study was the first to compare an angiotensin II type 1 receptor antagonist with a calcium antagonist in secondary stroke prevention. In these high-risk hypertensive stroke patients, an early normotensive and comparable blood pressure was achieved. The combined primary end point was significantly lower in the eprosartan group.

Calcitonin gene related peptide mediates cardioprotection by remote preconditioning.

Excitation of sensory nerves and activation of myocardial protein kinase C (PKC) epsilon contribute to the transduction of remote preconditioning (RPC) to the heart. Since calcitonin gene related peptide (CGRP) is an important mediator of sensory neurons we tried to delineate whether CGRP a) protects the heart from ischemic injury, b) is involved in cardioprotection after RPC, and c) leads to an activation of myocardial PKCepsilon. RPC was achieved by brief mesenteric artery occlusion followed by reperfusion. Myocardial infarct size (IS) was measured by TTC staining after temporary coronary artery occlusion (CAO) in rats. CGRP plasma levels were determined by radioimmunoassay and PKCepsilon was measured by quantitative immunoblotting. CGRP infusion reduced infarct size by 57%, an action that was abolished after co-treatment with the PKC inhibitor chelerythrine. RPC significantly increased CGRP plasma levels, reduced infarct size, and activated myocardial PKCepsilon. Infarct size reduction was abolished and PKCepsilon activation was significantly attenuated by CGRP(8-37), a specific CGRP receptor antagonist. Ganglion blockade with hexamethonium did not influence CGRP release by RPC but abolished CGRP mediated myocardial PKCepsilon activation. In conclusion, CGRP protects the heart from ischemic injury and is involved in RPC, presumably by activating myocardial PKCepsilon.

Deferoxamine induces prolonged cardiac preconditioning via accumulation of oxygen radicals.

Iron chelation by deferoxamine (DFO) blocks the Fenton reaction, but also inhibits prolyl hydroxylases and thereby activates certain hypoxia-inducible transcription factors (HIFs) that trigger cellular adaptation to hypoxia. Because both mechanisms may alleviate tissue damage in ischemia and reperfusion, we tried to differentiate their contribution to DFO-induced cardioprotection. Myocardial ischemia and reperfusion were induced in anesthetized Wistar rats. Infarct size was related to the ischemic area. Myocardial mRNA expression was determined by real-time PCR. Radical reactivity was probed in myocardial tissue slices with the redox-sensitive dye CM-H(2)DCFDA. Single ip applications of DFO (200 mg/kg) administered 2 h to 3 days before infarction reduced infarct size from 55 +/- 7% to 22-26%. Protection was abolished by the radical scavenger N-(2-mercaptopropionyl)glycine and the protein kinase C inhibitor chelerythrine when either was given 30 min before DFO, whereas subsequent application was ineffective. DFO did not alter the expression of various HIF target genes, whereas mRNAs of HIF-independent genes, aldose reductase and glucose transporter-4, were increased in infarcted myocardium 2 days after DFO treatment. Enhancement of superoxide activity by DFO could be demonstrated in vitro. Acute and prolonged myocardial preconditioning is triggered by DFO in response to accumulation of oxygen radicals and activation of protein kinase C.

Simvastatin acutely reduces myocardial reperfusion injury in vivo by activating the phosphatidylinositide 3-kinase/Akt pathway.

Long-term pretreatment with statins reduces myocardial injury after acute ischemia and reperfusion by increasing the expression of endothelial nitric oxide synthase (eNOS). We hypothesized that statins may act rapidly enough to protect the myocardium from ischemia/reperfusion injury when given right at the beginning of the reperfusion period and tried to delineate the role of PI 3-kinase/Akt pathway in early eNOS activation. Activated simvastatin was given intravenously 3 minutes before starting the reperfusion after temporary coronary artery occlusion (CAO) in anaesthetized rats. Simvastatin significantly increased myocardial PI 3-kinase activity, AktSer473, and eNOSSer1177 phosphorylation and reduced infarct size by 42%. Infarct size reduction as well as activation of PI 3-kinase/Akt/eNOS pathway were not observed in rats co-treated with the PI 3-kinase inhibitor wortmannin. Contribution of eNOS was further delineated using the NOS inhibitor L-NAME, which could completely block cardioprotection by the statin. In summary, simvastatin acutely reduces the extent of myocardial necrosis in normocholesterolemic rats in an NO- dependent manner by activating the PI 3-kinase/Akt pathway. This is the first study demonstrating short-term cardioprotective effects of simvastatin in an in vivo model of ischemia/reperfusion.