Dose-dependent acute and sustained renal effects of the endothelin receptor antagonist avosentan in healthy subjects.

The endothelin receptor antagonist avosentan may cause fluid overload at doses of 25 and 50 mg, but the actual mechanisms of this effect are unclear. We conducted a placebo-controlled study in 23 healthy subjects to assess the renal effects of avosentan and the dose dependency of these effects. Oral avosentan was administered once daily for 8 days at doses of 0.5, 1.5, 5, and 50 mg. The drug induced a dose-dependent median increase in body weight, most pronounced at 50 mg (0.8 kg on day 8). Avosentan did not affect renal hemodynamics or plasma electrolytes. A dose-dependent median reduction in the fractional renal excretion of sodium was found (up to 8.7% at avosentan 50 mg); this reduction was paralleled by a dose-related increase in proximal sodium reabsorption. It is suggested that avosentan dose-dependently induces sodium retention by the kidney, mainly through proximal tubular effects. The potential clinical benefits of avosentan should therefore be investigated at doses of <or= 5 mg.

Control of the adaptive response of the heart to stress via the Notch1 receptor pathway.

In the damaged heart, cardiac adaptation relies primarily on cardiomyocyte hypertrophy. The recent discovery of cardiac stem cells in the postnatal heart, however, suggests that these cells could participate in the response to stress via their capacity to regenerate cardiac tissues. Using models of cardiac hypertrophy and failure, we demonstrate that components of the Notch pathway are up-regulated in the hypertrophic heart. The Notch pathway is an evolutionarily conserved cell-to-cell communication system, which is crucial in many developmental processes. Notch also plays key roles in the regenerative capacity of self-renewing organs. In the heart, Notch1 signaling takes place in cardiomyocytes and in mesenchymal cardiac precursors and is activated secondary to stimulated Jagged1 expression on the surface of cardiomyocytes. Using mice lacking Notch1 expression specifically in the heart, we show that the Notch1 pathway controls pathophysiological cardiac remodeling. In the absence of Notch1, cardiac hypertrophy is exacerbated, fibrosis develops, function is altered, and the mortality rate increases. Therefore, in cardiomyocytes, Notch controls maturation, limits the extent of the hypertrophic response, and may thereby contribute to cell survival. In cardiac precursors, Notch prevents cardiogenic differentiation, favors proliferation, and may facilitate the expansion of a transient amplifying cell compartment.

Actualités en hépatologie [Highlights in hepatology]

This review highlights recent advances in hepatology, including new insights into the clinical penetrance of hereditary hemochromatosis, the development of non-immunosuppressive cyclosporin A analogs for the treatment of chronic hepatitis C, thrombopoietin receptor agonists for thrombocytopenia in cirrhosis, the development of vasopressin V2 receptor antagonists (vaptans) for the management of ascites and hyponatremia in portal hypertension, the description of chronic hepatitis E in immunosuppressed patients, and the development of sorafenib as the first molecularly targeted therapy with a demonstrated benefit in the treatment of advanced hepatocellular carcinoma. These new developments will be summarized and discussed critically, with a particular emphasis on their potential implications for current and future clinical practice.

Variation d'expression des récepteurs hormonaux et d'HER-2 dans l'évolution du cancer du sein : quelles implications en pratique clinique [Hormone receptors and HER-2 changes during breast cancer progression: clinical implications].

Breast cancer remains a major public health problem. Even if there is an increase in this cancer curability, metastatic breast cancer remains a lethal disease in the vast majority of cases. Therapeutic advances in the chemotherapeutic and targeted therapies fields induced an increase in survival, however the proportion of long survivors remains low. Phenotypic instability, an early process initiated during tumour progression, and continued on the metastatic stage of the disease, can be one of the putative hypotheses explaining these results. An increasing amount of scientific data are pledging for a reanalysis of the phenotypic profile regarding hormone receptors and HER-2 status of metastatic lesions in order to identify drugable targets and allow individualisation of the treatment of these metastatic breast cancer patients. Phenotypic changes between the primary tumour and the paired metastatic lymph nodes are a challenging pitfall, raising the question of which site has to be assessed in the adjuvant treatment decision process. This article presents a comprehensive analysis of the frequency of theses phenotypic changes altogether with new modalities to evaluate this phenotypic status.

A look through the new therapeutic window: irbesartan

Although an impressive array of efficacious antihypertensive agents are available to treat hypertension, the optimal use of these agents is limited by dose-related side-effect profiles. This is particularly the case for widely used first-line antihypertensive agents such as diuretics, beta-blockers, calcium antagonists, and alpha1-blockers; this represents a major therapeutic dilemma in treating hypertension. With the development of the angiotensin II receptor antagonists (AIIRAs), this dilemma might have been solved. Irbesartan is a long-acting AIIRA that provides dose-related efficacy with placebo-like tolerability at all clinical doses. The results of placebo and active-control trials of irbesartan have demonstrated that the agent is as effective as the leading members of major antihypertensive classes with respect to blood pressure control, while having superior tolerability. Pooled data from nine multicenter, randomized, placebo-controlled trials with irbesartan have documented no adverse events caused by dose-response. This feature could widen the traditionally narrow therapeutic window in the treatment of hypertension and point to the use of AIIRAs such as irbesartan as first-line therapy in the management of hypertension.

IL-13 induces expression of CD36 in human monocytes through PPARgamma activation.

The class B scavenger receptor CD36 is a component of the pattern recognition receptors on monocytes that recognizes a variety of molecules. CD36 expression in monocytes depends on exposure to soluble mediators. We demonstrate here that CD36 expression is induced in human monocytes following exposure to IL-13, a Th2 cytokine, via the peroxisome proliferator-activated receptor (PPAR)gamma pathway. Induction of CD36 protein was paralleled by an increase in CD36 mRNA. The PPARgamma pathway was demonstrated using transfection of a PPARgamma expression plasmid into the murine macrophage cell line RAW264.7, expressing very low levels of PPARgamma, and in peritoneal macrophages from PPARgamma-conditional null mice. We also show that CD36 induction by IL-13 via PPARgamma is dependent on phospholipase A2 activation and that IL-13 induces the production of endogenous 15-deoxy-Delta12,14-prostaglandin J2, an endogenous PPARgamma ligand, and its nuclear localization in human monocytes. Finally, we demonstrate that CD36 and PPARgamma are involved in IL-13-mediated phagocytosis of Plasmodium falciparum-parasitized erythrocytes. These results reveal a novel role for PPARgamma in the alternative activation of monocytes by IL-13, suggesting that endogenous PPARgamma ligands, produced by phospholipase A2 activation, could contribute to the biochemical and cellular functions of CD36.

Evaluation of oral versus intravenous dose of vinorelbine to achieve equivalent blood exposures in patients with solid tumours.

Patient's preference is for oral chemotherapy when both oral and i.v. are available, provided that efficacy is equivalent. Reliable switch from oral to i.v. is possible if correspondence between respective doses has been established. Vinorelbine oral was developed as a line extension of VRL i.v. on the basis that similar AUCs result in similar activities. From a first crossover study on 24 patients receiving VRL 25 mg/m2 i.v. and 80 mg/m2 oral data extrapolation concluded on AUCs bioequivalence between Vinorelbine 30 mg/m2 i.v. and 80 mg/m2 oral. A new trial was performed to support this calculation. In a crossover design study on patients (PS 0-1) with advanced solid tumours (44% breast carcinoma), VRL was administered (30 mg/m2 i.v., 80 mg/m2 oral) with a standard meal and 5-HT3 antagonists, at 2 weeks interval. Pharmacokinetics was performed over 168 h and VRL was measured by LC-MS/MS. Statistics included bioequivalence tests. Forty-eight patients were evaluable for PK: median age 58 years (25-71), PS0/PS1: 20/28, M/F: 11/37. Mean AUCs were 1,230 +/- 290 and 1,216 +/- 521 ng/ml for i.v. and oral, respectively. The confidence interval of the AUC ratio (0.83-1.03) was within the required regulatory range (0.8-1.25) and proved the bioequivalence between the two doses. The absolute bioavailability was 37.8 +/- 16.0%, and close to the value from the first study (40%). Patient tolerability was globally comparable between both forms with no significant difference on either haematological or non-haematological toxicities (grade 3-4). This new study, conducted on a larger population, confirmed the reliable dose correspondence previously established between vinorelbine 80 mg/m2 oral and 30 mg/m2 i.v.

Nitrosative stress and corneal transplant endothelial cell death during acute graft rejection.

BACKGROUND: Nitrosative stress takes place in endothelial cells (EC) during corneal acute graft rejection. The purpose of this study was to evaluate the potential role of peroxynitrite on corneal EC death. METHODS: The effect of peroxynitrite was evaluated in vivo. Fifty, 250, and 500 microM in 1.5 microL of the natural or denatured peroxynitrite in 50 microM NaOH, 50 microM NaOH alone, or balanced salt solution were injected into the anterior chamber of rat eyes (n=3/group). Corneal toxic signs after injection were assessed by slit-lamp, in vivo confocal imaging, pachymetry, and EC count. The effect of peroxynitrite was also evaluated on nitrotyrosine and leucocyte elastase inhibitor/LDNase II immunohistochemistry. Human corneas were incubated with peroxynitrite and the effect on EC viability was evaluated. A specific inducible nitric oxide synthase inhibitor (iNOS) was administered systemically in rats undergoing allogeneic corneal graft rejection and the effect on EC was evaluated by EC count. RESULTS: Rat eyes receiving as little as 50 microM peroxynitrite showed a specific dose-dependent toxicity on EC. We observed an intense nitrotyrosine staining of human and rat EC exposed to peroxynitrite associated with leucocyte elastase inhibitor nuclear translocation, a noncaspase dependent apoptosis reaction. Specific inhibition of iNOS generation prevented EC death and enhanced EC survival of the grafted corneas. However, inhibition of iNOS did not have a significant influence on the incidence of graft rejection. CONCLUSION: Nitrosative stress during acute corneal graft rejection in rat eyes induces a noncaspase dependent apoptotic death in EC. Inhibition of nitric oxide production during the corneal graft rejection has protective effects on the corneal EC survival.

Molecular aspects of Schistosoma mansoni female maturation

Incubation of total protein extracts of Schistosoma mansoni with 3H 17-beta-estradiol and 20-hydroxyecdysone, revealed steroid binding proteins in both, male and female worms. The interaction of nuclear proteins with restriction fragments of the gender and stage-specific gene F-10 was investigated using the "Band-Shift" technique. Distinct male and female nuclear proteins bound to the fragments of this gene. Among the nuclear proteins, only those rich in cysteine residues bound to DNA. In vitro incubation of live worms with the estrogen antagonist Tamoxifen, altered the pattern of the DNA binding proteins, producing in females, a band profile similar to that obtained with male worm protein extracts. When Tamoxifen was injected into schistosome infected mice, the eggs produced by females presented an abnormal morphology, compatible with non-viable eggs. These results suggest that the regulation of transcription of the F-10 gene might involve steroid receptors.

A role for the src family kinase Fyn in NK cell activation and the formation of the repertoire of Ly49 receptors.

NK cell function is regulated by a dual receptor system, which integrates signals from triggering receptors and MHC class I-specific inhibitory receptors. We show here that the src family kinase Fyn is required for efficient, NK cell-mediated lysis of target cells, which lack both self-MHC class I molecules and ligands for NKG2D, an activating NK cell receptor. In contrast, NK cell inhibition by the MHC class I-specific receptor Ly49A was independent of Fyn, suggesting that Fyn is specifically required for NK cell activation via non-MHC receptor(s). Compared to wild type, significantly fewer Fyn-deficient NK cells expressed the inhibitory Ly49A receptor. The presence of a transgenic Ly49A receptor together with its H-2(d) ligand strongly reduced the usage of endogenous Ly49 receptors in Fyn-deficient mice. These data suggest a model in which the repertoire of inhibitory Ly49 receptors is formed under the influenced of Fyn-dependent NK cell activation as well as the respective MHC class I environment. NK cells may acquire Ly49 receptors until they generate sufficient inhibitory signals to balance their activation levels. Such a process would ensure the induction of NK cell self-tolerance.

Normal glucagon signaling and β-cell function after near-total α-cell ablation in adult mice.

OBJECTIVEEvaluate whether healthy or diabetic adult mice can tolerate an extreme loss of pancreatic α-cells and how this sudden massive depletion affects β-cell function and blood glucose homeostasis.RESEARCH DESIGN AND METHODSWe generated a new transgenic model allowing near-total α-cell removal specifically in adult mice. Massive α-cell ablation was triggered in normally grown and healthy adult animals upon diphtheria toxin (DT) administration. The metabolic status of these mice was assessed in 1) physiologic conditions, 2) a situation requiring glucagon action, and 3) after β-cell loss.RESULTSAdult transgenic mice enduring extreme (98%) α-cell removal remained healthy and did not display major defects in insulin counter-regulatory response. We observed that 2% of the normal α-cell mass produced enough glucagon to ensure near-normal glucagonemia. β-Cell function and blood glucose homeostasis remained unaltered after α-cell loss, indicating that direct local intraislet signaling between α- and β-cells is dispensable. Escaping α-cells increased their glucagon content during subsequent months, but there was no significant α-cell regeneration. Near-total α-cell ablation did not prevent hyperglycemia in mice having also undergone massive β-cell loss, indicating that a minimal amount of α-cells can still guarantee normal glucagon signaling in diabetic conditions.CONCLUSIONSAn extremely low amount of α-cells is sufficient to prevent a major counter-regulatory deregulation, both under physiologic and diabetic conditions. We previously reported that α-cells reprogram to insulin production after extreme β-cell loss and now conjecture that the low α-cell requirement could be exploited in future diabetic therapies aimed at regenerating β-cells by reprogramming adult α-cells.

Mineralocorticoid receptor is involved in rat and human ocular chorioretinopathy.

Central serous chorioretinopathy (CSCR) is a vision-threatening eye disease with no validated treatment and unknown pathogeny. In CSCR, dilation and leakage of choroid vessels underneath the retina cause subretinal fluid accumulation and retinal detachment. Because glucocorticoids induce and aggravate CSCR and are known to bind to the mineralocorticoid receptor (MR), CSCR may be related to inappropriate MR activation. Our aim was to assess the effect of MR activation on rat choroidal vasculature and translate the results to CSCR patients. Intravitreous injection of the glucocorticoid corticosterone in rat eyes induced choroidal enlargement. Aldosterone, a specific MR activator, elicited the same effect, producing choroid vessel dilation -and leakage. We identified an underlying mechanism of this effect: aldosterone upregulated the endothelial vasodilatory K channel KCa2.3. Its blockade prevented aldosterone-induced thickening. To translate these findings, we treated 2 patients with chronic nonresolved CSCR with oral eplerenone, a specific MR antagonist, for 5 weeks, and observed impressive and rapid resolution of retinal detachment and choroidal vasodilation as well as improved visual acuity. The benefit was maintained 5 months after eplerenone withdrawal. Our results identify MR signaling as a pathway controlling choroidal vascular bed relaxation and provide a pathogenic link with human CSCR, which suggests that blockade of MR could be used therapeutically to reverse choroid vasculopathy.

The distribution of congenital anomalies within the VACTERL association among tumor necrosis factor antagonist-exposed pregnancies is similar to the general population.

OBJECTIVE: To compare the distribution of congenital anomalies within the VACTERL association (vertebral defects, anal atresia, cardiac, tracheoesophageal, renal, and limb abnormalities) between patients exposed to tumor necrosis factor-α (TNF-α) antagonist and the general population. METHODS: Analysis for comparison of proportional differences to a previous publication between anomaly subgroups, according to subgroup definitions of the European Surveillance of Congenital Anomalies (EUROCAT), a population-based database. RESULTS: Most EUROCAT subgroups belonging to the VACTERL association contained only one or 2 records of TNF-α antagonist exposure, so comparison of proportions was imprecise. Only the category "limb abnormalities" showed a significantly higher proportion in the general population. CONCLUSION: The high number of congenital anomalies belonging to the VACTERL association from a report of pregnancies exposed to TNF-α antagonists could not be confirmed using a population-based congenital anomaly database.

TWEAK-FN14 signaling induces lysosomal degradation of a cIAP1-TRAF2 complex to sensitize tumor cells to TNFalpha.

Synthetic inhibitor of apoptosis (IAP) antagonists induce degradation of IAP proteins such as cellular IAP1 (cIAP1), activate nuclear factor kappaB (NF-kappaB) signaling, and sensitize cells to tumor necrosis factor alpha (TNFalpha). The physiological relevance of these discoveries to cIAP1 function remains undetermined. We show that upon ligand binding, the TNF superfamily receptor FN14 recruits a cIAP1-Tnf receptor-associated factor 2 (TRAF2) complex. Unlike IAP antagonists that cause rapid proteasomal degradation of cIAP1, signaling by FN14 promotes the lysosomal degradation of cIAP1-TRAF2 in a cIAP1-dependent manner. TNF-like weak inducer of apoptosis (TWEAK)/FN14 signaling nevertheless promotes the same noncanonical NF-kappaB signaling elicited by IAP antagonists and, in sensitive cells, the same autocrine TNFalpha-induced death occurs. TWEAK-induced loss of the cIAP1-TRAF2 complex sensitizes immortalized and minimally passaged tumor cells to TNFalpha-induced death, whereas primary cells remain resistant. Conversely, cIAP1-TRAF2 complex overexpression limits FN14 signaling and protects tumor cells from TWEAK-induced TNFalpha sensitization. Lysosomal degradation of cIAP1-TRAF2 by TWEAK/FN14 therefore critically alters the balance of life/death signals emanating from TNF-R1 in immortalized cells.