COX-2: an in vivo evidence of its participation in heat stress-induced myocardial preconditioning.

International audienceOBJECTIVE: Heat stress (HS) is known to induce delayed protection against myocardial infarction. We have previously shown that inducible nitric oxide synthase (iNOS), was involved in mediating this form of preconditioning. Since iNOS and cyclooxygenase-2 (COX-2) are co-induced in various cell types, the goal of this study was to investigate whether COX-2 could also participate to the HS-induced cardioprotection. METHODS AND RESULTS: A total of 78 male Wistar rats, subjected to either heat stress (42 degrees C for 15 min) or sham anaesthesia were used for this study. Twenty-four hours later, they were treated or not with a selective COX-2 inhibitor, either celecoxib (3 mg kg(-1), i.p.) or NS-398 (5 mg kg(-1), i.p.), 30 min before being subjected to a 30-min occlusion of the left coronary artery followed by a 120-min reperfusion, in vivo. HS resulted in a marked increase in myocardial COX-2 protein expression at 24 h, associated with a significant protection against infarction (46.0+/-1.4% in sham vs. 26.8+/-3.8% in HS group) (

Intermittent hypoxia-induced delayed cardioprotection is mediated by PKC and triggered by p38 MAP kinase and Erk1/2.

We previously reported that acute intermittent hypoxia (IH) confers delayed cardioprotection against a prolonged ischemic insult in the rat, via the involvement of nitric oxide synthase and K(ATP) channels. In the present study, we investigated the role of protein kinase C (PKC), phosphatidylinositol-3-kinase (PI3K), stress activated p38 MAP kinase (MAPK) and extracellular signal-regulated kinase (ERK1/2) using selective inhibitors of these pathways. Adult male rats were exposed to 1-min cycles of IH (10% O(2), 40 s)/normoxia (21% O(2), 20 s) during 4 h or to normoxic cycles. 24 h later, isolated hearts were perfused in Langendorff mode and subjected to a 30-min global ischemia followed by 120 min of reperfusion. Compared to normoxic conditions, IH significantly reduced infarct size (22.2+/-2.4% vs. 33.8+/-2.6%, p<0.05), improved coronary flow and decreased the contracture at reperfusion. When administered before sustained ischemia, chelerythrine (a PKC inhibitor) abolished both the IH-induced reduction in infarct size (36.1+/-4.9%) and improvement in hemodynamic parameters. In contrast, chelerythrine administration 10 min before IH, did not modify the delayed cardioprotective response. Similarly, wortmannin (a PI3K inhibitor) administration 10 min before IH was unable to block the cardioprotective effects. However, administration of SB203580 (a p38 MAPK inhibitor) and PD98059 (an Erk1/2 inhibitor), 30 min before IH abolished its delayed infarct-sparing effect (32.2+/-3.4% and 33.9+/-2.9%, respectively). In addition, 24 h after IH, a significant increase in p38 MAPK and Erk1/2 phosphorylation was observed by Western blot. These results suggest that the delayed preconditioning induced by intermittent hypoxia does not involve the PI3K signalling pathway and that is mediated by PKC and triggered by p38 MAPK and Erk1/2

New insight into the signalling pathways of heat stress-induced myocardial preconditioning: protein kinase Cepsilon translocation and heat shock protein 27 phosphorylation.

International audience1. Heat stress (HS) is known to induce delayed preconditioning against myocardial infarction 24 h later, but the exact signalling pathway of this response remains to be elucidated. In previous studies, we have shown evidence for the implication of protein kinase C (PKC) and p38 mitogen-activated protein kinase (MAPK) in the HS-induced reduction in infarct size. Furthermore, in their phosphorylated state, small heat shock proteins (Hsp27) seem to confer cytoskeletal protection. In the present study, we sought to determine the effect of HS on the subcellular distribution of PKC isoforms and on Hsp27 phosphorylation. 2. Rats were subjected to either HS (42 degrees C for 15 min; HS group) or sham anaesthesia (sham group) before their hearts were excised. Myocardial tissue extracts obtained 20 min or 24 h after HS were processed for western blot analysis. 3. In the HS group, PKCepsilon translocated from the cytosolic to the particulate fraction (4426 +/- 128 vs 6258 +/- 316 arbitrary units; P = 0.002). Chelerythrine (5 mg/kg, i.p.), a PKC inhibitor, abolished this translocation. Western blot analysis of Hsp27 24 h after HS showed a marked increase in protein expression and phosphorylation in the particulate fraction. 4. In the present study, we have shown that HS induces the translocation of PKCepsilon from the cytosolic to the particulate fraction. Along with our previous observation that PKC is a trigger of HS-induced myocardial preconditioning, the results of the present study suggest an important role of the epsilon isoform of PKC in this cardioprotective mechanism. Furthermore, we have also demonstrated that the cytoprotective protein Hsp27 is phosphorylated following HS. Therefore, we can conclude that PKC and MAPK/Hsp27 are involved in the signalling pathway of HS-induced cardioprotection

Heat stress-induced B(1) receptor synthesis in the rat: an ex vivo study

1. This ex vivo study was performed to characterize B(1) receptor induction in rats submitted to heat stress. Changes in aortic isometric tension were recorded after a 90 min in vitro incubation with [des-Arg(9)]-bradykinin. B(1) receptor mRNA were detected in aorta and heart using RT–PCR technique. 2. Aortic rings from sham rats did not respond to [des-Arg(9)]-bradykinin. In contrast, this agonist induced a concentration-dependent relaxation of aortic rings from rats submitted to lipopolysaccharide (LPS) treatment or to heat stress 24 h earlier. 3. The concentration-dependent relaxation induced by [des-Arg(9)]-bradykinin on aortic rings from heat-stressed rats was abolished by [des-Arg(10)]-HOE 140, a selective B(1) receptor antagonist. 4. In endothelium denuded aortic rings from heat-stress rats, [des-Arg(9)]-bradykinin induced a concentration-dependent constriction. 5. Pretreatment of intact aortic rings from heat-stress rats with the cyclo-oxygenase inhibitor, diclofenac (1 μM) did not prevent the concentration-dependent relaxation in response to [des-Arg(9)]-bradykinin. In contrast, NO synthase inhibition with N(ω)-nitro-L-arginine methyl ester (30 μM) totally prevented the vasorelaxant response. 6. B(1) receptor mRNA were not detected in aorta and heart from sham animals but were present in tissue from heat-stressed and LPS-treated rats. 7. In conclusion, our results suggest that heat stress induces a transcriptional activation of the B(1) receptor gene. The induction of B(1) receptors leads to an endothelium- and NO-dependent vasorelaxant response to [des-Arg(9)]-bradykinin

Targeting intermittent hypoxia downstream pathways for biomarker discovery and new treatment perspectives in cutaneous melanoma

International audienceNo abstract availabl

Chronic intermittent hypoxia promotes myocardial ischemia-related ventricular arrhythmias and sudden cardiac death

Abstract We investigated the effects of intermittent hypoxia (IH), such as that encountered in severe obstructive sleep apnea (OSA) patients, on the development and severity of myocardial ischemia-related ventricular arrhythmias. Rats were exposed to 14 days of IH (30 s at 5%O2 and 30 s at 21%O2, 8 h·day−1) or normoxia (N, similar air-air cycles) and submitted to a 30-min coronary ligature. Arterial blood pressure (BP) and ECG were recorded for power spectral analysis, ECG interval measurement and arrhythmia quantification. Left ventricular monophasic action potential duration (APD) and expression of L-type calcium (LTCC) and transient receptor potential (TRPC) channels were assessed in adjacent epicardial and endocardial sites. Chronic IH enhanced the incidence of ischemic arrhythmias, in particular ventricular fibrillation (66.7% vs. 33.3% in N rats, p < 0.05). IH also increased BP and plasma norepinephine levels along with increased low-frequency (LF), decreased high-frequency (HF) and increased LF/HF ratio of heart rate and BP variability. IH prolonged QTc and Tpeak-to-Tend intervals, increased the ventricular APD gradient and upregulated endocardial but not epicardial LTCC, TRPC1 and TRPC6 (p < 0.05). Chronic IH, is a major risk factor for sudden cardiac death upon myocardial ischemia through sympathoactivation and alterations in ventricular repolarization, transmural APD gradient and endocardial calcium channel expression

iNOS is a mediator of the heat stress-induced preconditioning against myocardial infarction in vivo in the rat.

International audienceOBJECTIVE: The inducible isoform of nitric oxide synthase (iNOS) is known to be a trigger of the heat stress (HS)-induced cardioprotection. Since iNOS also appears to mediate various forms of myocardial preconditioning, the goal of this study was to investigate its role as a mediator of the HS response. METHODS AND RESULTS: Male Wistar rats were divided in six groups, subjected or not to HS (42 degrees C internal temperature, for 15 min). Twenty-four hours later, they were treated or not with either L-NAME, a non-selective inhibitor of NO synthase isoforms, or 1400W, a selective iNOS inhibitor, 10 min before being subjected to a 30-min left coronary artery occlusion followed by a 120-min reperfusion, in vivo. The infarct size (tetrazolium staining) reducing effect conferred by heat stress (from 46.0+/-1.4% in sham to 26.8+/-3.8% in HS groups) was completely abolished by both L-NAME (53.9+/-3.1%) and 1400W (51.8+/-3.3%). Additional studies using Western blot analysis demonstrated a 3.8-fold increase in myocardial iNOS protein expression 24 h after HS. CONCLUSION: These results suggest an involvement of iNOS as a mediator of the protection conferred by heat stress against myocardial ischaemia

Targeting the ROS-HIF-1-endothelin axis as a therapeutic approach for the treatment of obstructive sleep apnea-related cardiovascular complications

International audienceObstructive sleep apnea (OSA) is now recognized as an independent and important risk factor for cardiovascular diseases such as hypertension, coronary heart disease, heart failure and stroke. Clinical and experimental data have confirmed that intermittent hypoxia is a major contributor to these deleterious consequences. The repetitive occurrence of hypoxia-reoxygenation sequences generates significant amounts of free radicals, particularly in moderate to severe OSA patients. Moreover, in addition to hypoxia, reactive oxygen species (ROS) are potential inducers of the hypoxia inducible transcription factor-1 (HIF-1) that promotes the transcription of numerous adaptive genes some of which being deleterious for the cardiovascular system, such as the endothelin-1 gene. This review will focus on the involvement of the ROS-HIF-1-endothelin signaling pathway in OSA and intermittent hypoxia and discuss current and potential therapeutic approaches targeting this pathway to treat or prevent cardiovascular disease in moderate to severe OSA patients

15-F-isoprostane and 5-F-isoprostane are not triggers of myocardial preconditioning.

International audience1. Myocardial ischaemia-reperfusion in humans is associated with increased formation of 15-F(2t)-isoprostane and 5-F(2t)-isoprostane (15-F(2t)-IsoP and 5-F(2t)-IsoP, respectively). Whether this formation is relevant clinically remains controversial. The present study was performed in order to evaluate the ability of the isoprostanes 15-F(2t)-IsoP and 5-F(2t)-IsoP to reduce myocardial ischaemic injury in rat isolated heart. 2. Rats were divided into six groups. Hearts were excised, perfused retrogradely and pretreated with vehicle (ethanol 5.10(-7) and 2.10(-9) mol/L; n = 6), subjected to ischaemic preconditioning (n = 8) or pretreated with the isoprostanes 15-F(2t)-IsoP (3.10(-10) and 3.10(-7) mol/L; n = 8) or 5-F(2t)-IsoP (10(-9) mol/L; n = 8). After a 5 min treatment-5 min washout period, hearts were submitted to 30 min global ischaemia, followed by a 120 min reperfusion period. 3. The infarct-to-ventricle zone ratio was significantly reduced in ischaemic preconditioned (20.6 +/- 2.6%) compared with vehicle groups (44.5 +/- 4.3 and 51.3 +/- 2.5% in groups pretreated with 5.10(-7) or 2.10(-9) mol/L ethanol, respectively). Pretreatment with either isoprostane had no cardioprotective effect; the infarct-to-ventricle ratios were 43.1 +/- 2.2, 49.4 +/- 5.9 and 44.5 +/- 5.0% for groups treated with 3.10(-10) mol/L 15-F(2t)-IsoP, 3.10(-7) mol/L 15-F(2t)-IsoP or 10(-9) mol/L 5-F(2t)-IsoP, respectively. 4. These data provide evidence that the isoprostanes 15-F(2t)-IsoP and 5-F(2t)-IsoP are not implicated in early myocardial preconditioning at concentrations similar to those found in the human coronary sinus following coronary angioplasty