Peroxisome proliferator-activated receptors mediate host cell proinflammatory responses to Pseudomonas aeruginosa autoinducer.

The pathogenic bacterium Pseudomonas aeruginosa utilizes the 3-oxododecanoyl homoserine lactone (3OC(12)-HSL) autoinducer as a signaling molecule to coordinate the expression of virulence genes through quorum sensing. 3OC(12)-HSL also affects responses in host cells, including the upregulation of genes encoding inflammatory cytokines. This proinflammatory response may exacerbate underlying disease during P. aeruginosa infections. The specific mechanism(s) through which 3OC(12)-HSL influences host responses is unclear, and no mammalian receptors for 3OC(12)-HSL have been identified to date. Here, we report that 3OC(12)-HSL increases mRNA levels for a common panel of proinflammatory genes in murine fibroblasts and human lung epithelial cells. To identify putative 3OC(12)-HSL receptors, we examined the expression patterns of a panel of nuclear hormone receptors in these two cell lines and determined that both peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) and PPARgamma were expressed. 3OC(12)-HSL functioned as an agonist of PPARbeta/delta transcriptional activity and an antagonist of PPARgamma transcriptional activity and inhibited the DNA binding ability of PPARgamma. The proinflammatory effect of 3OC(12)-HSL in lung epithelial cells was blocked by the PPARgamma agonist rosiglitazone, suggesting that 3OC(12)-HSL and rosiglitazone are mutually antagonistic negative and positive regulators of PPARgamma activity, respectively. These data identify PPARbeta/delta and PPARgamma as putative mammalian 3OC(12)-HSL receptors and suggest that PPARgamma agonists may be employed as anti-inflammatory therapeutics for P. aeruginosa infections.

Inhibition of the renin-angiotensin-aldosterone system: is there room for dual blockade in the cardiorenal continuum?

Antagonism of renin-angiotensin-aldosterone system is exerted through angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, renin inhibitors and mineralocorticoid receptor antagonists. These drugs have been successfully tested in numerous trials and in different clinical settings. The original indications of renin-angiotensin-aldosterone system blockers have progressively expanded from the advanced stages to the earlier stages of cardiorenal continuum. To optimize the degree of blockade of renin-angiotensin-aldosterone system, dose uptitrations of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists or the use of a dual blockade, initially identified with the combination of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists, have been proposed. The data from the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) study do not support this specific dual blockade approach. However, the dual blockade of angiotensin-converting enzyme inhibitors/angiotensin receptor antagonists with direct renin inhibitors is currently under investigation while that based on an aldosterone blocker with any of the previous three drugs requires more evidence beyond heart failure. In this review, we revisited potential advantages of dual blockade of renin-angiotensin-aldosterone system in arterial hypertension and diabetes.

TRAIL receptors 1 (DR4) and 2 (DR5) signal FADD-dependent apoptosis and activate NF-kappaB.

TRAIL induces apoptosis through two closely related receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5). Here we show that TRAIL-R1 can associate with TRAIL-R2, suggesting that TRAIL may signal through heteroreceptor signaling complexes. Both TRAIL receptors bind the adaptor molecules FADD and TRADD, and both death signals are interrupted by a dominant negative form of FADD and by the FLICE-inhibitory protein FLIP. The recruitment of TRADD may explain the potent activation of NF-kappaB observed by TRAIL receptors. Thus, TRAIL receptors can signal both death and gene transcription, functions reminiscent of those of TNFR1 and TRAMP, two other members of the death receptor family.

The expression of nuclear 3,5,3' triiodothyronine receptors is induced in Schwann cells by nerve transection.

The effects of thyroid hormones on the nervous system are mediated by the presence of nuclear T3 receptors (NT3R). In this study, the expression of NT3R was investigated in spinal cord, dorsal root ganglia (DRG), or sciatic nerve of adult rats after immunostaining with a 2B3-NT3R monoclonal antibody which recognizes both alpha and beta types of NT3R. The specificity of this monoclonal antibody was confirmed by Western blots. The 2B3-NT3R monoclonal antibody recognized one band corresponding to a molecular weight of 57 kDa in extract of spinal cord or DRG. No staining was observed on immunoblot of intact sciatic nerve. In the spinal cord, the nuclei of the neurons and glial cells including both astrocytes and oligodendrocytes exhibited 2B3-NT3R immunoreactivity. While all the nuclei of the DRG sensory neurons expressed the NT3R, all the nuclei of the satellite and Schwann cells were devoid of any immunoreaction. In the sciatic nerve, the nuclei of the Schwann cells also lacked 2B3-NT3R-immunoreactivity. After sciatic nerve transection in vivo, Schwann cell nuclei, which never expressed NT3R in intact nerves of adult rats, displayed a clear 2B3-NT3R immunoreaction in proximal and distal stumps adjacent to the section. Double immunostaining with antibodies raised to 3-sulfogalactosylceramide or S100 confirmed that most of the NT3R containing nuclei belong to Schwann cells. In dissociated cell cultures grown in vitro from sciatic nerves, Schwann cells exhibited 2B3-NT3R immunoreactivity. These data suggest that the inhibition of NT3R expression in Schwann cells ensheathing axons in intact nerve is reversed when the axons are degenerating or lacking.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute antihypertensive effect of angiotensin converting enzyme inhibition and calcium entry blockade.

The acute blood pressure response to an angiotensin converting enzyme inhibitor (enalaprilat) was compared in patients with uncomplicated essential hypertension with that obtained under similar conditions with a calcium entry blocker (nifedipine). The patients were studied after a 3 week washout period. At a 48 h interval, each patient received in randomized order either enalaprilat (5 mg i.v.) or nifedipine (10 mg p.o.). Enalaprilat and nifedipine were equally effective in acutely lowering blood pressure. However, good responders to one agent were not necessarily good responders to the other.

Effects of a dual inhibitor of angiotensin converting enzyme and neutral endopeptidase, MDL 100,240, on endocrine and renal functions in healthy volunteers.

OBJECTIVE: To investigate the endocrine and renal effects of the dual inhibitor of angiotensin converting enzyme and neutral endopeptidase, MDL 100,240. DESIGN: A randomized, placebo-controlled, crossover study was performed in 12 healthy volunteers. METHODS: MDL 100,240 was administered intravenously over 20 min at single doses of 6.25 and 25 mg in subjects with a sodium intake of 280 (n = 6) or 80 (n = 6) mmol/day. Measurements were taken of supine and standing blood pressure, plasma angiotensin converting enzyme activity, angiotensin II, atrial natriuretic peptide, urinary atrial natriuretic peptide and cyclic GMP excretion, effective renal plasma flow and the glomerular filtration rate as p-aminohippurate and inulin clearances, electrolytes and segmental tubular function by endogenous lithium clearance. RESULTS: Supine systolic blood pressure was consistently decreased by MDL 100,240, particularly after the high dose and during the low-salt intake. Diastolic blood pressure and heart rate did not change. Plasma angiotensin converting enzyme activity decreased rapidly and dose-dependently. In both the high- and the low-salt treatment groups, plasma angiotensin II levels fell and renin activity rose accordingly, while plasma atrial natriuretic peptide levels remained unchanged. In contrast, urinary atrial natriuretic peptide excretion increased dose-dependently under both diets, as did urinary cyclic GMP excretion. Effective renal plasma flow and the glomerular filtration rate did not change. The urinary flow rate increased markedly during the first 2 h following administration of either dose of MDL 100,240 (P < 0.001) and, similarly, sodium excretion tended to increase from 0 to 4 h after the dose (P = 0.07). Potassium excretion remained stable. Proximal and distal fractional sodium reabsorption were not significantly altered by the treatment. Uric acid excretion was increased. The safety and clinical tolerance of MDL 100,240 were good. CONCLUSIONS: The increased fall in blood pressure in normal volunteers together with the preservation of renal hemodynamics and the increased urinary volume, atrial natriuretic peptide and cyclic GMP excretion distinguish MDL 100,240 as a double-enzyme inhibitor from inhibitors of the angiotensin converting enzyme alone. The differences appear to be due, at least in part, to increased renal exposure to atrial natriuretic peptide following neutral endopeptidase blockade.

Les récepteurs nucléaires PPARs (Peroxisome Proliferator Activated Receptors) : Trois isotypes pour de multiples fonctions.

Les récepteurs nucléaires font partie d'une superfamille de facteurs de transcription qui regroupe en particulier les récepteurs des hormones stéroïdes et thyroïdiennes, de la vitamine D3 et des rétinoïdes [1]. Ces facteurs de transcription sont impliqués dans de nombreuses fonctions cellulaires comme le développement embryonnaire, la différenciation cellulaire et le contrôle du métabolisme. Ce sont des protéines importantes en recherche médicale puisque un grand nombre d'entre elles sont impliquées dans des pathologies telles que le cancer, le diabète ou les syndromes de résistance aux hormones. À ce jour, cette superfamille comprend différents membres, dont l'activité est modulée par la présence de ligands spécifiques. Néanmoins, pour nombre d'entre eux, aucun ligand endogène spécifique n'a encore été identifié. Ceux-là sont appelés récepteurs orphelins. Orphelins lors de leur découverte il y a dix ans, les PPARs (Peroxisome proliferator-activated receptors) ont été particulièrement étudiés depuis, permettant de leur attribuer des ligands et des fonctions qui les placent au coeur de nombreuses régulations métaboliques.

Involvement of CD73, equilibrative nucleoside transporters and inosine in rhythm and conduction disturbances mediated by adenosine A1 and A2A receptors in the developing heart.

We previously established that exogenous adenosine (ADO) induces transient arrhythmias in the developing heart via the adenosine A1 receptor (A1AR) and downstream activation of NADPH oxidase/ERK and PLC/PKC pathways. Here, we investigated the mechanisms by which accumulation of endogenous ADO and its derived compound inosine (INO) in the interstitial compartment induce rhythm and conduction troubles. The validated model of the spontaneously beating heart obtained from 4-day-old chick embryos was used. Quantitative RT-PCR showed that enzymes involved in ADO and INO metabolism (CD39, CD73 and eADA) as well as equilibrative (ENT1, -3, -4) and concentrative (CNT3) nucleoside transporters were differentially expressed in atria, ventricle and outflow tract. Inactivation of ENTs by dipyridamole, 1) increased myocardial ADO level, 2) provoked atrial arrhythmias and atrio-ventricular blocks (AVB) in 70% of the hearts, 3) prolonged P wave and QT interval without altering contractility, and 4) increased ERK2 phosphorylation. Blockade of CD73-mediated phosphohydrolysis of AMP to ADO, MEK/ERK pathway inhibition or A1AR inhibition prevented these arrhythmias. Exposure to exogenous INO also caused atrial ectopy associated with AVB and ERK2 phosphorylation which were prevented by A1AR or A2AAR antagonists exclusively or by MEK/ERK inhibitor. Inhibition of ADA-mediated conversion of ADO to INO increased myocardial ADO and decreased INO as expected, but slightly augmented heart rate variability without provoking AVB. Thus, during cardiogenesis, disturbances of nucleosides metabolism and transport, can lead to interstitial accumulation of ADO and INO and provoke arrhythmias in an autocrine/paracrine manner through A1AR and A2AAR stimulation and ERK2 activation.

Nuclear hormone receptors and mouse skin homeostasis: implication of PPARbeta.

PPARbeta is expressed in the mouse epidermis during fetal development, and progressively disappears from the interfollicular epidermis after birth. Interestingly, its expression is strongly reactivated in the adult epidermis in conditions where keratinocyte proliferation is induced and during wound healing. Data obtained on PPARbeta heterozygous mice reveal that PPARbeta is implicated in the control of keratinocyte proliferation and is necessary for rapid healing of a skin wound.

Effect of immunisation against angiotensin II with CYT006-AngQb on ambulatory blood pressure: a double-blind, randomised, placebo-controlled phase IIa study.

BACKGROUND: Hypertension can be controlled adequately with existing drugs such as angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Nevertheless, treatment success is often restricted by patients not adhering to treatment. Immunisation against angiotensin II could solve this problem. We investigated the safety and efficacy of CYT006-AngQb-a vaccine based on a virus-like particle-that targets angiotensin II to reduce ambulatory blood pressure. METHODS: In this multicentre, double-blind, randomised, placebo-controlled phase IIa trial, 72 patients with mild-to-moderate hypertension were randomly assigned with a computer-generated randomisation list to receive subcutaneous injections of either 100 mug CYT006-AngQb (n=24), 300 mug CYT006-AngQb (24), or placebo (24), at weeks 0, 4, and 12. 24-h ambulatory blood pressure was measured before treatment and at week 14. The primary outcomes were safety and tolerability. Analyses were done by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00500786. FINDINGS: Two patients in the 100 mug group, three in the 300 mug group, and none in the placebo group discontinued study treatment. All patients were included in safety analyses; efficacy analyses did not include the five dropouts, for whom no data were available at week 14. Five serious adverse events were reported (two in the 100 mug group, two in the 300 mug group, and one in the placebo group); none were deemed to be treatment related. Most side-effects were mild, transient reactions at the injection site. Mild, transient influenza-like symptoms were seen in three patients in the 100 mug group, seven in the 300 mug group, and none in the placebo group. In the 300 mug group, there was a reduction from baseline in mean ambulatory daytime blood pressure at week 14 by -9.0/-4.0 mm Hg compared with placebo (p=0.015 for systolic and 0.064 for diastolic). The 300 mug dose reduced the early morning blood-pressure surge compared with placebo (change at 0800 h -25/-13 mm Hg; p<0.0001 for systolic, p=0.0035 for diastolic). INTERPRETATION: Immunisation with CYT006-AngQb was associated with no serious adverse events; most observed adverse events were consistent with local or systemic responses similar to those seen with other vaccines. The 300 mug dose reduced blood pressure in patients with mild-to-moderate hypertension during the daytime, especially in the early morning. FUNDING: Cytos Biotechnology AG.

5-HT2A and alpha1b-adrenergic receptors entirely mediate dopamine release, locomotor response and behavioural sensitization to opiates and psychostimulants.

Addictive properties of drugs of misuse are generally considered to be mediated by an increased release of dopamine (DA) in the ventral striatum. However, recent experiments indicated an implication of alpha1b-adrenergic receptors in behavioural responses to psychostimulants and opiates. We show now that DA release induced in the ventral striatum by morphine (20 mg/kg) is completely blocked by prazosin (1 mg/kg), an alpha1-adrenergic antagonist. However, morphine-induced increases in DA release in the ventral striatum were found to be similar in mice deleted for the alpha1b-adrenergic receptor (alpha1b-AR KO) and in wild-type (WT) mice, suggesting the presence of a compensatory mechanism. This acute morphine-evoked DA release was completely blocked in alpha1b-AR KO mice by SR46349B (1 mg/kg), a 5-HT2A antagonist. SR46349B also completely blocked, in alpha1b-AR KO mice, the locomotor response and the development of behavioural sensitization to morphine (20 mg/kg) and D-amphetamine (2 mg/kg). Accordingly, the concomitant blockade of 5-HT2A and alpha1b-adrenergic receptors in WT mice entirely blocked acute locomotor responses but also the development of behavioural sensitization to morphine, D-amphetamine or cocaine (10 mg/kg). We observed, nevertheless, that inhibitory effects of each antagonist on locomotor responses to morphine or D-amphetamine were more than additive (160%) in naïve WT mice but not in those sensitized to either drug. Because of these latter data and the possible compensation by 5-HT2A receptors for the genetic deletion of alpha1b-adrenergic receptors, we postulate the existence of a functional link between these receptors, which vanishes during the development of behavioural sensitization.

La fonction rénale sous inhibition de l'enzyme de conversion de l'angiotensine [Renal function after administration of angiotensin-converting enzyme inhibitors]

Angiotensin converting enzyme (ACE) inhibitors are widely used today for the management of hypertension and congestive heart failure. These agents inhibit angiotensin II synthesis. In some particular circumstances they may be responsible for deterioration of renal function, e.g. in hypertensive patients with bilateral renal artery stenosis or with stenosis of the artery supplying a single kidney, or in patients with severe congestive heart failure or marked nephroangiosclerosis. In these patients renal perfusion pressure may become too low to maintain adequate glomerular filtration as there remains no angiotensin II to increase the tone of the efferent arteriole. In high risk patients it is therefore recommended that serum creatinine be checked after initiating therapy with an ACE inhibitor.