Chronic p38 mitogen-activated protein kinase inhibition improves vascular function and remodeling in angiotensin II-dependent hypertension.

INTRODUCTION: An excess of angiotensin II (Ang II) causes hypertension and vascular injury. Activation of mitogen-activated protein kinase p38 (p38-MAPK) plays a substantial role in Ang II-dependent organ damage. Recently, we showed that p38-MAPK activation regulates the pressor response to Ang II. This study evaluates the effect of chronic p38-MAPK inhibition in Ang II-dependent hypertension. MATERIALS AND METHODS: C57Bl/6J mice were infused with Ang II for 14 days and either treated with the p38-MAPK inhibitor BIRB796 (50 mg/kg/day) or the vehicle as the control. We assessed vascular function in the aorta and isolated perfused kidneys. RESULTS: Chronic p38-MAPK inhibition did not alter blood pressure at the baseline, but attenuated Ang II-induced hypertension significantly (baseline: 122 ± 2 versus 119 ± 4 mmHg; Ang II: 173 ± 3 versus 155 ± 3 mmHg; p < 0.001). In addition, BIRB796 treatment improved vascular remodeling by reducing the aortic media-to-lumen ratio and decreasing the expression of the membrane metalloproteinases (MMP) MMP-1 and MMP-9. Moreover, renal vascular dysfunction induced by chronic Ang II infusion was significantly ameliorated in the BIRP796-treated mice. Acute p38-MAPK inhibition also improved vascular function in the aorta and kidneys of Ang II-treated mice, highlighting the important role of p38-MAPK activation in the pathogenesis of vascular dysfunction. CONCLUSIONS: Our findings indicated there is an important role for p38-MAPK in regulating blood pressure and vascular injury, and highlighted its potential as a pharmaceutical target.

Chronic treatment with angiotensin-(1-7) improves renal endothelial dysfunction in apolipoproteinE-deficient mice.

BACKGROUND AND PURPOSE: ApolipoproteinE-deficient [apoE (-/-)] mice, a model of human atherosclerosis, develop endothelial dysfunction caused by decreased levels of nitric oxide (NO). The endogenous peptide, angiotensin-(1-7) [Ang-(1-7)], acting through its specific GPCR, the Mas receptor, has endothelium-dependent vasodilator properties. Here we have investigated if chronic treatment with Ang-(1-7) improved endothelial dysfunction in apoE (-/-) mice. EXPERIMENTAL APPROACH: ApoE (-/-) mice fed on a lipid-rich Western diet were divided into three groups and treated via osmotic minipumps with either saline, Ang-(1-7) (82 µg·kg(-1) ·h(-1) ) or the same dose of Ang-(1-7) together with D-Ala-Ang-(1-7) (125 µg·kg(-1) ·h(-1) ) for 6 weeks. Renal vascular function was assessed in isolated perfused kidneys. KEY RESULTS: Ang-(1-7)-treated apoE (-/-) mice showed improved renal endothelium-dependent vasorelaxation induced by carbachol and increased renal basal cGMP production, compared with untreated apoE (-/-) mice. Tempol, a reactive oxygen species (ROS) scavenger, improved endothelium-dependent vasorelaxation in kidneys of saline-treated apoE (-/-) mice whereas no effect was observed in Ang-(1-7)-treated mice. Chronic treatment with D-Ala-Ang-(1-7), a specific Mas receptor antagonist, abolished the beneficial effects of Ang-(1-7) on endothelium-dependent vasorelaxation. Renal endothelium-independent vasorelaxation showed no differences between treated and untreated mice. ROS production and expression levels of the NAD(P)H oxidase subunits gp91phox and p47phox were reduced in isolated preglomerular arterioles of Ang-(1-7)-treated mice, compared with untreated mice, whereas eNOS expression was increased. CONCLUSION AND IMPLICATIONS: Chronic infusion of Ang-(1-7) improved renal endothelial function via Mas receptors, in an experimental model of human cardiovascular disease, by increasing levels of endogenous NO.

Effects of high dose olmesartan medoxomil plus hydrochlorothiazide on blood pressure control in patients with grade 2 and grade 3 hypertension.

High dose (40 mg) olmesartan medoxomil (OM) blocks the angiotensin II receptor, significantly reducing blood pressure (BP). Adding hydrochlorothiazide (HCTZ) to OM increases efficacy, but has not been evaluated in patients inadequately controlled by OM 40 mg. Patients with grade 2 and grade 3 hypertension with inadequately controlled BP (seated diastolic blood pressure [SeDBP] 90-115 mm Hg and seated systolic blood pressure [SeSBP] 140-180 mm Hg, plus ambulatory BP criteria) after 8 weeks of OM 40 mg open-label treatment were randomized to 8 weeks of double-blind treatment with OM/HCTZ 40/25 (n=140), 40/12.5 (n=278), 20/12.5 mg (n=280) or OM 40 mg (n=274). Treatment with OM/HCTZ 40/25 mg and 40/12.5 mg significantly reduced SeDBP (-5.3 and -3.4 mm Hg, respectively), and SeSBP (-7.4 and -5.2 mm Hg, respectively), vs OM 40 mg monotherapy (P<0.0001 for each) in patients inadequately controlled on OM 40 mg alone. OM/HCTZ 40/12.5 mg reduced SeSBP significantly more than OM/HCTZ 20/12.5 mg (-2.6 mm Hg, P=0.0255), and also produced a further reduction in SeDBP vs the lower dose. All treatments were well tolerated, with similar low proportions of patients reporting treatment-emergent adverse events in all treatment groups. In conclusion, adding HCTZ to OM 40 mg significantly improves BP reductions and target BP rates in harder-to-treat patients and a clear dose-response was observed for efficacy.

Small but powerful: short peptide hormones and their role in autoimmune inflammation.

In the recent years, it has become increasingly clear that the immune response is also influenced by mediators which were first discovered as regulators in the nervous or also cardiovascular system. Here, small peptide hormones may play an important role. Kinins like bradykinins act on the endothelium and play a role for trafficking of lymphocytes over the blood-brain barrier. Neuropeptides like vasoactive intestinal peptide or neuropeptide Y also directly act on T cells and favour the differentiation of Th2 cells or regulatory T cell populations. Recently, the renin-angiotensin system (RAS) came into the focus of interest. Inhibition of the RAS at different levels may influence autoimmune responses and involve T cells as well as antigen-presenting cells, probably via different signalling pathways. Inhibitors of angiotensin converting enzyme and antagonists of the angiotensin 1 receptors are used in the treatment of hypertension, kidney disease or stroke by millions of people worldwide. These inexpensive and safe pharmaceuticals may also represent an interesting and innovative approach for the (combination) treatment of autoimmune diseases like multiple sclerosis.

Oncogenic osteomalacia, a rare paraneoplastic syndrome due to phosphate wasting--a case report and review of the literature.

An appropriate phosphate homeostasis is absolutely required for correct bone mineralization and remodeling, for diverse signaling pathways as well as cell membrane formation. Its disequilibrium results in serious complications like hypophosphatemia and excessively reduced fractional tubule phosphate reabsorption (TRP). A rare cause of such a disturbed phosphate balance is tumor-induced osteomalacia (TIO)--a phosphate wasting disorder sometimes associated with certain mesenchymal tumors. These primitive tumors secrete so-called phosphatonins--recently identified factors involved in the regulation of phosphate homeostasis such as the secreted frizzled related protein 4 (sFRP-4), the fibroblast growth factors 7 and 23 (FGF-7/-23), or the matrix extracellular phosphoglycoprotein (MEPE). Progressive muscular weakness and spontaneous bone fractures caused by inadequate osteoid mineralization are the characteristic clinical symptoms, which completely resolve after tumor resection. Here we report a new case of TIO caused by tumor secreted FGF-23 and review the literature to facilitate the correct diagnosis of this rare disorder.

[Comparison of adrenal imaging and selective adrenal vein sampling in primary hyperaldosteronism]. / Vergleich von Bildgebung und seitengetrennter Nebennierenvenen-Blutentnahme zur Differentialdiagnose bei primärem Hyperaldosteronismus.

BACKGROUND AND OBJECTIVES: There is a high prevalence for primary hyperaldosteronism (PHA) in hypertensive patients. This retrospective study was performed to determine the role of adrenal scanning and adrenal vein sampling (AVS) in distinguishing unilateral autonomous adenoma from idiopathic bilateral hyperplasia (IHA). METHODS: 93 patients, admitted to the radiology department for AVS between 1996 and 2004, were enrolled. 44 had a diagnosis of PHA, 22 or whom had an adenoma and 22 had IHA. RESULTS: 17 of the 22 patients with adenoma and 15 with IHA had an aldosterone-renin ratio > 50. Adrenal CT or MR scanning was performed in 73 patients. Sensitivity and specificity were 56 % and 60 %, respectively, for CT and 57% and 67% for MR. In 87 patients AVS provided values for aldosterone (A) and cortisol (C) from the adrenal veins and vena cava inferior (VCI). Successful sampling (C-adrenal vein/C-VCI > 1.1) was achieved from 55 % of the right and from 92 % of the left adrenal veins. When AVS was successful on both sides, localizing adenoma was possible using A/C (site of adenoma) vs. A/C (contralateral) at a cut-off point > 3 (sensitivity 85 %, specifity 88 %). In patients with adenoma, aldosterone release was suppressed on the contralateral site (A/C-adrenal vein/A/C-VCI ratio = 0.8). CONCLUSION: AVS is a useful tool for localizing unilateral autonomous adenoma. However, selective sampling often fails on the right adrenal vein, which limits its significance. In this case the A/C-adrenal vein/A/C-VCI in combination with the posture test should be utilized. CT or MRI are of limited value.

[Renal resistance index in patients with obstructive sleep apnea]. / Renaler Widerstandsindex bei obstruktiver Schlafapnoe.

BACKGROUND AND OBJECTIVE: Previous studies have demonstrated renal dysfunction in patients with obstructive sleep apnea (OSA). The renal resistance index (RI) measured by renal duplexsonography (RI = 1-[enddiastolic velocity/peak systolic velocity]) is at the same time a marker of parenchymal renal damage and predictor of the progression of renal dysfunction. It was the aim of this study to test the influence of OSA on RI. PATIENTS AND METHODS: RI was compared between patients with (n = 97) and those without OSA (n = 61). The impact of OSA on the RI was analysed by adjusting for age. Thus, the difference between the measured RI and the age-based RI was expressed as a percentage of the normal age-adjusted value (RI (%)). RESULTS: OSA patients showed a trend towards an increase in RI (69.1+/-8.8 vs. 66.5+/-8.3 %, p = 0.068) and RI (%) (10.2+/-12.9 vs. 6.4+/-11.4 %, p = 0.060), respectively. In patients with mild or moderate OSA (apnea-hypopnea-index [AHI] 5 - 30/h) this difference was significant (RI: 70.5+/-9.1 vs. 66.5+/-8.2, p = 0.012; RI (%): 12.1+/-13,4 vs. 6.5+/-11.4 %, p = 0.012). RI of patients with severe OSA did not significantly differ from those without OSA. In patients with mild and moderate OSA there was a significant linear association between AHI and RI or RI (%). This association was independent of hypertension or diabetes. CONCLUSION: An impairment of renal perfusion and renal parenchymal damage due to increased sympathetic activity may promote renal dysfunction in patients with obstructive sleep apnea.

Alpha(2A)-adrenoceptors regulate sympathetic transmitter release in mice kidneys.

BACKGROUND AND PURPOSE: In the present study, a rodent model was used to investigate whether the alpha(2A)-adrenoceptor (alpha(2A)) represents the presynaptic autoinhibitory receptor regulating sympathetic transmitter release in the kidney. Moreover, the potential role of alpha(2A) as a heteroceptor regulating adenosine triphosphate (ATP) release was tested. EXPERIMENTAL APPROACH: Kidneys from wild-type (WT) and alpha(2A)-knockout (KO) mice were isolated and perfused. Renal nerves were stimulated with platinum-electrodes. Endogenously released noradrenaline (NA) was measured by HPLC. The perfusion pressure was monitored continuously. KEY RESULTS: Renal nerve stimulation (RNS) induced a frequency (1,2,5,7.5,10,15 Hz)-dependent release of NA in WT mice (994+/-373, 2355+/-541, 6375+/-950, 11626+/-1818, 19138+/-2001 pg NA g(-1) kidney (means+/-s.e.m.)). There was a 2.7-fold (5 Hz) increase of NA release in alpha(2A)-KO mice. In WT animals alpha-adrenoceptor blockade by phentolamine increased RNS-induced NA release in a concentration-dependent manner up to 350% of control. No facilitation by phentolamine was observed in alpha(2A)-KO mice. Pressor responses to 1 Hz and 2 Hz were resistant to alpha(1)-adrenoceptor blockade (0.03 microM prazosin) but abolished by P(2) receptor blockade (5 microM PPADS). Blockade of alpha(2)-adrenoceptors (1 microM rauwolscine) increased these purinergic pressor responses to 296+/-112% (1 Hz) in WT but not in alpha(2A)-KO mice. Exogenous ATP (100 microM) increased basal but not RNS-induced NA release. CONCLUSIONS AND IMPLICATIONS: alpha(2A)-Adrenoceptor-activation inhibits NA and ATP release from renal sympathetic nerves. Pressor responses to RNS at higher stimulation frequencies (>2 Hz) are mediated by NA. At lower frequencies neuronally released ATP seems to be the predominant transmitter mediating renovascular resistance.

Dihydrotachysterol therapy for hypoparathyroidism: consequences of inadequate monitoring. Five cases and a review.

BACKGROUND: The half synthetic Vitamin D analogue dihydrotachysterol (DHT) is widely used for hypocalcaemic hypoparathyroidism following surgical removal of parathyroids. Such treatment generally initiated by surgeons right after surgery has to be continued in clinical practice. Unfortunately, the required careful monitoring of calcium metabolism is often lacking and as demonstrated may lead to life-threatening conditions. PATIENTS AND METHODS: Here we report on five patients referred to our nephrology unit because of unknown impairment of renal function during therapy with DHT. All patients had clinical signs of hypercalcaemia. Since most symptoms are nonspecific they were not perceived by primary care physicians. In fact DHT treatment was continued for 4 - 50 years. In all cases calcium levels were determined after inadequate long intervals ranging from 3.08 to 4.97 mmol/l. Creatinine levels ranged from 277 to 365 micromol/l. All patients suffered from symptoms of severe hypercalcaemia, three of them needing intensive care unit treatment. RESULTS: All patients were treated effectively with a regimen consisting of intravenous saline, a loop diuretic, and application of bisphosphonates. As confirmed by renal biopsy persisting alleviation of renal function was due to calcifications. After discontinuation of DHT therapy patients were safely switched to shorter acting vitamin D derivates maintaining a normal calcium level. CONCLUSIONS: In comparison to short acting vitamin-D derivates hypercalcaemic episodes with DHT appear to last longer and may therefore occur with higher incidence. A future option could be the use of synthetic parathyroid hormone (s-PTH) recently shown to be safe and effective. Nevertheless a customized therapy and careful monitoring is indispensable in any case to prevent irreversible organ damage.