Synaptic dysfunction, memory deficits and hippocampal atrophy due to ablation of mitochondrial fission in adult forebrain neurons.

Well-balanced mitochondrial fission and fusion processes are essential for nervous system development. Loss of function of the main mitochondrial fission mediator, dynamin-related protein 1 (Drp1), is lethal early during embryonic development or around birth, but the role of mitochondrial fission in adult neurons remains unclear. Here we show that inducible Drp1 ablation in neurons of the adult mouse forebrain results in progressive, neuronal subtype-specific alterations of mitochondrial morphology in the hippocampus that are marginally responsive to antioxidant treatment. Furthermore, DRP1 loss affects synaptic transmission and memory function. Although these changes culminate in hippocampal atrophy, they are not sufficient to cause neuronal cell death within 10 weeks of genetic Drp1 ablation. Collectively, our in vivo observations clarify the role of mitochondrial fission in neurons, demonstrating that Drp1 ablation in adult forebrain neurons compromises critical neuronal functions without causing overt neurodegeneration.

Immunomodulating treatment with low dose interleukin-4, interleukin-10 and interleukin-11 in psoriasis vulgaris.

Psoriasis is a chronic inflammatory skin disease affecting approximately 2-3 percent of the world population; it is characterised by hyperproliferation and hyperplasia of the superficial layers of the epidermis. Inappropriate signals released by the immune system determine an altered keratinocyte differentiation, resulting in the formation of desquamating, thickened, inflamed and erythematous plaques. The aim of this investigation was to study the pharmacological activity and safety of three low dose cytokines, Guna-Interleukin 4, Guna-Interleukin 10 and Guna-Interleukin 11 at the concentration of 10 fg/ml in patients affected by moderate to slight psoriasis vulgaris. The multicenter, double-blind, randomized, placebo-controlled clinical trial involved 48 patients who were enrolled and followed up according to a 8-month experimental project. All patients received, according to a cross-over model, either the experimental treatment or placebo, alternatively. Globally, in the 41 evaluated patients it was observed a PASI significant reduction (Friedman test: p=0.00960). The DLQI too decreased significantly in all subjects compared to baseline (Friedman test: p=0.00007). The safety of the treatment with three low dose cytokines administered simultaneously was proved; no adverse event was reported during the whole trial.

Endoplasmic reticulum refilling and mitochondrial calcium extrusion promoted in neurons by NCX1 and NCX3 in ischemic preconditioning are determinant for neuroprotection.

Ischemic preconditioning (IPC), an important endogenous adaptive mechanism of the CNS, renders the brain more tolerant to lethal cerebral ischemia. The molecular mechanisms responsible for the induction and maintenance of ischemic tolerance in the brain are complex and still remain undefined. Considering the increased expression of the two sodium calcium exchanger (NCX) isoforms, NCX1 and NCX3, during cerebral ischemia and the relevance of nitric oxide (NO) in IPC modulation, we investigated whether the activation of the NO/PI3K/Akt pathway induced by IPC could regulate calcium homeostasis through changes in NCX1 and NCX3 expression and activity, thus contributing to ischemic tolerance. To this aim, we set up an in vitro model of IPC by exposing cortical neurons to a 30-min oxygen and glucose deprivation (OGD) followed by 3-h OGD plus reoxygenation. IPC was able to stimulate NCX activity, as revealed by Fura-2AM single-cell microfluorimetry. This effect was mediated by the NO/PI3K/Akt pathway since it was blocked by the following: (a) the NOS inhibitors L-NAME and 7-Nitroindazole, (b) the IP3K/Akt inhibitors LY294002, wortmannin and the Akt-negative dominant, (c) the NCX1 and NCX3 siRNA. Intriguingly, this IPC-mediated upregulation of NCX1 and NCX3 activity may control calcium level within endoplasimc reticulum (ER) and mitochondria, respectively. In fact, IPC-induced NCX1 upregulation produced an increase in ER calcium refilling since this increase was prevented by siNCX1. Moreover, by increasing NCX3 activity, IPC reduced mitochondrial calcium concentration. Accordingly, the inhibition of NCX by CGP37157 reverted this effect, thus suggesting that IPC-induced NCX3-increased activity may improve mitochondrial function during OGD/reoxygenation. Collectively, these results indicate that IPC-induced neuroprotection may occur through the modulation of calcium homeostasis in ER and mitochondria through NO/PI3K/Akt-mediated NCX1 and NCX3 upregulation.

Endothelial dysfunction and stroke.

Endothelial dysfunction, intended as the complex multifaced pathological product of different vasculotoxic agents or injuries, is viewed today as an attractant intermediate phenotype of cardiovascular diseases with usually long and unpredictable natural history. Furthermore, endothelial dysfunction may not only represent a vascular disease marker, but may actually play an important pathogenetic role, leading to progression of the disease and unfavourable outcomes. Among these vascular diseases, cerebrovascular accidents, namely stroke, clearly represent a paradigmatic example of the potential role of dysfunctional endothelium. In fact, in the world's growing elderly population few diseases are more dreaded than stroke. With an increasing incidence and mortality of 30%, stroke carries the threat of death or long-term disability and suffering. Endothelium produces nitric oxide (NO) under basal conditions and in response to a variety of vasoactive stimuli in large cerebral arteries and in the cerebral microcirculation. In addition to exerting a tonic dilator effect on the cerebral circulation, basal release of NO may protect cerebral endothelium by inhibiting aggregation of platelets and leukocytes. In this paper, we analyse current evidence suggesting that endothelial dysfunction can play a role in the pathogenesis of ischaemic stroke.

Therapeutic applications of angiotensin II receptor antagonists.

The renin-angiotensin system (RAS) represents today one of the most strategic targets of the therapy of cardiovascular diseases. During the last 30 years a number of more or less successful approaches to inhibit the activity of the RAS have been attempted. In particular, the use of ACE-inhibitiors has led to significant improvments in the outcom/treatment of hypertension, congestive heart failure, ischemic heart disease and nephropathies. On the other hand, Ace-inhibitors are not specifically targeted to RAS since they interfere with an enzyme with multiple different substrates. Furthermore, the inhibition of ACE does not prevent the formation of angiotensin II through alternative pathways, and thus the inhibition of RAS is often incomplete, especially under pathologic conditions stimulating RAS. For these reasons, the recent discovery of angiotensin II receptors antagonists, which selectively inhibit the action of angiotensin II at the level of the AT1 subtype receptor, is particularly attracting. This article reviews the background, the rationale and some of the clinical findings and potential applications with this new class of compounds.

Defective suppression of the aldosterone biosynthesis during stroke permissive diet in the stroke-prone phenotype of the spontaneously hypertensive rat.

Previous studies have shown that short-term high salt intake unmasks blunted plasma aldosterone suppression in stroke-prone spontaneously hypertensive rats (SHRsp). The aim of this study was to evaluate the response of aldosterone biosynthesis and production to a sustained exposure to the stroke-permissive Japanese-style diet (JD) in young stroke-prone and stroke-resistant SHRs. For this purpose, 6-week old male rats from both strains were divided into 2 dietary groups and received regular diet (SHR = 37, SHRsp = 32) or the JD and 1% saline to drink (SHR = 34, SHRsp = 30) for 4 weeks. All measurements were carried out at the end of the dietary periods. After JD, plasma aldosterone levels were significantly decreased in SHR (from 357.8 +/- 57 to 163.3 +/- 31.5 pg/ml, p < 0.05) but markedly increased in SHRsp (from 442 +/- 56.5 to 739 +/- 125.7 pg/ml, p < 0.05). Consistently, the adrenal aldosterone synthase expression was reduced by JD in SHR (p < 0.05), whereas it was even slightly raised by JD in SHRsp so that, at the end of JD, aldosterone synthase mRNA was 5-fold higher in SHRsp than in SHR. Urinary sodium excretion (mEq/24h) achieved lower levels in SHRsp, so that fractional excretion of sodium was 80.2 +/- 9% in SHR and 40.3 +/- 8% in SHRsp (p < 0.05) in balance studies performed at the end of JD. These different responses of mineralocorticoid biosynthesis and urinary sodium excretion to JD were not accounted for by different adaptations of the renin-angiotensin and atrial natriuretic peptide systems, of serum potassium levels, or of adrenal 11beta-hydroxylase expression in the two strains. Systolic blood pressure was comparable in both strains throughout the experiment. These results demonstrate enhanced aldosterone biosynthesis, associated with reduced urinary excretion of sodium in response to JD in SHRsp before the onset of stroke. This abnormality may play a role in the higher susceptibility to stroke of this model.

Role of angiotensin II AT1 and AT2 subtype receptors in the regulation of atrial natriuretic peptide expression in salt-restricted rats.

Previous studies have suggested that angiotensin II modulates ANP secretion and this action appears to be largely independent from its hemodynamic effects. In order to explore the contribution of angiotensin II AT1 (AT1r) and AT2 (AT2r) receptor subtypes in the regulation of cardiac ANP, we studied the effects of selective antagonists of these receptors on ANP mRNA levels in the cardiac chambers of salt-restricted rats. Thirty-one Sprague-Dawley rats (12 weeks-old) weighing 250-350 g were studied during a low salt regimen and randomly assigned to the following treatment groups: AT1r-blockade (losartan) (10 mg/kg/day) (n = 18), AT2r-blockade (PD123319) (50 microg/kg/min) (n = 6), Control (salt-restriction) (n = 7). Treatments were maintained for 7 days; subsequently, 12 rats from the AT1r-blockade group were subdivided in to two groups: AT1r/AT2r-blockade (losartan +PD123319) (n = 6) and AT1r-blockade/vehicle (losartan+vehible) (n = 6), and treated for 7 additional days. Systolic blood pressure was significantly reduced by AT1r-blockade (p < 0.001), while it was not affected by AT2r-blockade. Concomitant treatment with both antagonists (AT1r/AT2r-blockade) restored blood pressure values to baseline (p < 0.001 vs. AT1r-blockade, p = n.s. vs Control). Atrial ANP mRNA was reduced by AT1r-blockade (-42%, p < 0.05) and did not change during AT1r-blockade alone. On the contrary, concomitant treatment with both antagonists resulted in a further significant inhibition of ANP expression (-65% and -36% vs Control and AT1r-blockade, respectively, both p < 0.05). ANP expression in ventricles was not affected by any of these treatments. Our results demonstrate that angiotensin II tonically modulates cardiac ANP expression in our experimental model. In particular, angiotensin II receptor subtypes AT1r and AT2r regulate atrial ANP mRNA levels through a synergic action and independently from blood pressure changes.

Modulation of the AT2 subtype receptor gene activation and expression by the AT1 receptor in endothelial cells.

OBJECTIVE: To investigate whether angiotensin II type 2 (AT2) receptor (AT2-r) promoter activity and expression are modulated by angiotensin II (Ang II), and whether the AT1 receptor (AT1-r) is involved in this effect. DESIGN AND METHODS: Primary endothelial cells obtained from NEONATAL rat aorta, expressing both receptors, were transfected with the rat AT2-r promoter region cloned into a pCAT-reporter vector. The reporter-expression study was performed in a transient transfection assay system. Transfected cells were studied following angiotensin-converting enzyme inhibition to prevent endogenous formation of Ang II. Cells were subsequently stimulated for 6 h with Ang II, either alone or in combination with the AT1-r antagonist DuP753. AT2-r mRNA was assessed by RNase protection assay during the same pharmacological stimuli. RESULTS: Stimulation with Ang II caused an increase in promoter activity (+50%, P < 0.05 versus baseline), whereas mRNA expression was reduced by 50% (P < 0.05 versus baseline). Concomitant treatment with DuP753 and Ang II was associated with a 98% increase in promoter activity (P < 0.05 versus baseline). DuP753 also prevented the reduction in mRNA; it actually produced a 100% increase in AT2-r mRNA accumulation (P < 0.01 versus baseline). Studies with the AT2-r antagonist PD123319 indicate that the AT2-r is also involved in the regulation of AT2-r gene promoter activity. CONCLUSIONS: These data indicate that Ang II increases AT2-r promoter activity and decreases AT2-r mRNA accumulation in endothelial cells. The AT1 subtype receptor is involved in the modulation of both effects of Ang II. These findings suggest that changes in the expression of AT2 receptors may occur during treatment with AT1-r antagonists, and they indicate the existence of a cross-talk between AT1 and AT2 receptors.

Impaired vasorelaxant responses to natriuretic peptides in the stroke-prone phenotype of spontaneously hypertensive rats.

BACKGROUND: We have previously shown that a locus on rat chromosome 5, termed STR 2, co-localizes with the genes encoding atrial natriuretic and brain natriuretic peptides, and is closely linked to the development of strokes in rats of a F2 hybrid cohort obtained by crossing stroke-prone spontaneously hypertensive rats and spontaneously hypertensive rats. We also demonstrated that there are significant differences in vascular functioning that are co-segregated with stroke latency of stroke-prone spontaneously hypertensive rats. OBJECTIVE: To investigate the vascular responses to natriuretic peptides in the stroke-prone phenotype of spontaneously hypertensive rats. DESIGN AND METHODS: In view of the important vasoactive properties of natriuretic peptides, we tested the vascular responses to 10(-11)-10(-9) mol/l atrial natriuretic peptide and to 10(-11)-10(-7) mol/l brain natriuretic peptide in isolated rings of aortas and internal carotid arteries obtained from stroke-prone and stroke-resistant spontaneously hypertensive rats. The 6-week-old rats were exposed for 4 weeks either to their regular diet (n = 15 of both strains) or to the stroke-permissive Japanese-style diet (n = 14 of both strains). A group of 14 normotensive, age-matched and sex-matched Wistar-Kyoto rats was also studied. RESULTS: Systolic blood pressures in stroke-prone and stroke-resistant spontaneously hypertensive rats were similar, and were significantly higher than those in Wistar-Kyoto rats. Vascular responses to nitroglycerin, atrial natriuretic peptide, and brain natriuretic peptide in rats of the two hypertensive strains and in Wistar-Kyoto rats fed their regular diet were comparable. In contrast, the vasorelaxant responses to atrial natriuretic peptide in stroke-prone spontaneously hypertensive rats fed Japanese diet were lower both in aortas and in internal carotid arteries than were those in spontaneously hypertensive rats (both P < 0.05 by analysis of variance) and in Wistar-Kyoto rats (both P < 0.05). Similarly, vasorelaxant responses to brain natriuretic peptide were lower both in aortas and in internal carotid arteries of stroke-prone spontaneously hypertensive rats than they were in spontaneously hypertensive rats (both P < 0.05) and in Wistar-Kyoto rats (P < 0.05). The responses to nitroglycerin in the stroke-prone spontaneously hypertensive rats and spontaneously hypertensive rats fed Japanese-style diet were also similar. CONCLUSION: The vasorelaxant effects of natriuretic peptides are impaired in stroke-prone spontaneously hypertensive rats. This abnormality could play a role in the pathogenesis of stroke incidence in this hypertensive model.

[Holter monitoring of the arterial pressure in the follow up of a group of aged patients with chronic uremia]. / Follow-up della pressione arteriosa in un gruppo di uremici anziani cronici mediante monitoraggio Holter.

The cardiovascular complication represents the principal effect of death in patients uraemics cronics. The hypertension is one of most cause; for this, the control of hypertension is one important objective in this patients. The introduction of dynamic monitoring permit to estimate the adeguatesse of hypertension control or the appearance of extradialitic hypotension. The dynamic monitoring permit to value the difference in two groups, young and elderly and to conform the hypertension therapy.

Role of tissue renin in the regulation of aldosterone biosynthesis in the adrenal cortex of nephrectomized rats.

The aim of the study was to investigate whether the adrenal renin-angiotensin system plays an independent role in the regulation of mineralocorticoid biosynthesis in the adrenal gland and to explore the mechanisms of this action. Twelve-week-old male Sprague-Dawley rats were studied: 22 rats were maintained on a regular diet; 27 and 22 rats received a low salt diet with and without treatment, respectively, with the angiotensin II (Ang II) AT1-subtype receptor antagonist losartan (10 mg/kg per day). A fraction of each group of rats underwent bilateral nephrectomy (n = 12, 15, and 10, respectively) and was killed 48 hours later. In an additional group of 24 (12 intact and 12 nephrectomized) rats, the effects of the Ang II AT2-subtype receptor antagonist PD123319 were investigated. In intact rats, plasma renin activity (PRA) and adrenal renin activity and expression were progressively raised by salt restriction and losartan, whereas aldosterone synthase mRNA and plasma aldosterone (PA) levels were increased by salt restriction and reduced by losartan. Forty-eight hours after nephrectomy, PRA fell to undetectable levels; in contrast, adrenal renin expression, assessed by semiquantitative reverse-transcriptase polymerase chain reaction (using GAPDH as a standard for gene expression), showed an 18-fold increase and was further increased after salt restriction and losartan (all P < .05). Also, adrenal renin activity was raised after nephrectomy and further increased after salt restriction (P < .05) and losartan. Cytochrome P450 aldosterone synthase expression in the adrenal cortex was stimulated by nephrectomy alone and by nephrectomy combined with low salt intake (P < .05), with consequent increases in PA concentrations. In losartan-treated salt-restricted nephrectomized rats, cytochrome P450 aldosterone synthase expression (P < .05 versus nephrectomy alone and nephrectomy plus salt restriction) and PA concentrations were diminished (P < .05) in spite of the observed increases of adrenal renin expression. The AT2-receptor antagonism did not significantly affect PRA, adrenal renin, and aldosterone biosynthesis and production in either intact or nephrectomized salt-restricted rats. These results demonstrate that the adrenal renin-angiotensin system plays an independent role in the regulation of mineralocorticoid biosynthesis in vivo. This action is mediated primarily via the Ang II AT1-subtype receptors.

Opposite feedback control of renin and aldosterone biosynthesis in the adrenal cortex by angiotensin II AT1-subtype receptors.

The aims of this study were to identify whether tissue renin is regulated by a negative-feedback mechanism produced by locally generated angiotensin (Ang II) in the adrenal cortex and to detect the pathway of Ang II modulation. For this purpose, in 36 12-week old, salt-restricted, nephrectomized Sprague-Dawley rats, we studied the effects of the Ang II AT1-subtype receptor antagonist losartan and of the Ang II AT2-subtype receptor antagonist PD123319 on renin mRNA and activity, aldosterone synthase mRNA, and AT1a-, AT1b-, and AT2-subtype receptor expression in the adrenal cortex. Ten additional rats, kept on a regular diet and then nephrectomized, were also studied. In salt-restricted, nephrectomized rats, losartan administration caused increases of adrenal renin mRNA (P<.05) and activity (P<.05) and a concomitant reduction of aldosterone synthase mRNA (P<.05). In addition, after losartan AT1b, receptor mRNA was reduced (P<.05), AT1a receptor mRNA was unchanged, and AT2 mRNA was increased (P<.05). PD123319 did not significantly modify any of these parameters. In conclusion, in salt-restricted, nephrectomized rats, selective antagonism of AT1-subtype receptors stimulates the expression and the activity of renin in the adrenal cortex. This observation demonstrates that Ang II locally formed in the adrenal cortex exerts a modulatory negative-feedback action on adrenal renin biosynthesis independent of the influence of the circulating renin-Ang system; this action is largely mediated through the AT1b-subtype receptors.