Rôle physico-pathologique de voies d'entrée des ions calcium (courant Isoc) et sodium (courant Inal) (étude dans un modèle de cellules endothéliales humaines et dans des myocytes atriaux de cobaye)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Remote Ischemic Conditioning in a Model of Severe Renal Ischemia-Reperfusion Injury

International audienceIschemia-reperfusion (I/R) injury is a leading cause of acute renal dysfunction. Remote ischemic conditioning (rIC) is known to protect organs exposed to I/R. We sought to investigate whether rIC would influence renal function recovery in a severe renal I/R injury rat model. Rats were randomly assigned to four experimental groups following median laparotomy and right nephrectomy: Sham (n = 6); 30-min left renal ischemia (RI) only (n = 20); RI+rIC (n = 20) (four 5-min cycles of limb ischemia interspersed with 5-min limb reperfusion during RI); RI+erythropoietin pre-treatment (EPO) (n = 20). Renal function was evaluated by assessing blood urea nitrogen (BUN) and serum creatinine (Cr) levels before surgery and after 1 day of reperfusion. All animals were monitored for 7 days for survival analysis. BUN and Cr baseline levels did not significantly differ between groups. At Day 1, BUN and Cr were significantly higher than baseline values in all groups. BUN and Cr levels did not significantly differ at Day 1 between RI and RI+rIC (p = 0.68). Conversely, EPO pre-treatment injected 60 minutes before RI was associated with lower BUN and Cr levels compared to RI (p &lt; 0.001 and p = 0.003, respectively) and RI+rIC (p &lt; 0.001 and p = 0.001, respectively). In addition, 7-day survival rates were significantly higher in the Sham group (100%) compared to RI (50%; p = 0.039 vs Sham) and RI+rIC (45%; p = 0.026 vs Sham). Conversely, survival rate did not significantly differ between the Sham and RI+EPO groups (70%, p = 0.15). In conclusion, rIC affected neither acute renal dysfunction nor early mortality in a severe I/R renal injury rat model, contrary to EPO pre-treatment.</p

Cardioprotective Role of Colchicine Against Inflammatory Injury in a Rat Model of Acute Myocardial Infarction

International audienceBACKGROUND: Inflammation plays a crucial role in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury. A clinical trial has recently reported a smaller infarct size in a cohort of patients with ST-segment elevation myocardial infarction (MI) treated with a short colchicine course. The mechanism underlying colchicine-induced cardioprotection in the early MI phase remains unclear. We hypothesized that a short pretreatment with colchicine could induce acute beneficial effects by protecting the heart against inflammation in myocardial I/R injury.METHODS AND RESULTS: Rats were subjected to 40-minute left anterior descending coronary occlusion, followed by 120-minute reperfusion. Colchicine (0.3 mg/kg) or a vehicle was administered per os 24 hours and immediately before surgery. Infarct size was significantly reduced in the colchicine group (35.6% ± 3.0% vs 46.6% ± 3.3%, P &lt; .05). The beneficial effects of colchicine were associated with an increased systemic interleukin-10 (IL-10) level and decreased cardiac transforming growth factor-β level. Interleukin-1β was found to increase in a "time of reperfusion"-dependent manner. Colchicine inhibited messenger RNA expression of caspase-1 and pro-IL-18. Interleukin-1β injected 10 minutes prior to myocardial ischemia induced greater infarct size (58.0% ± 2.0%, P &lt; .05) as compared to the vehicle. Colchicine combined to IL-1β injection significantly decreased infarct size (47.1% ± 2.2%, P &lt; .05) as compared to IL-1β alone, while colchicine alone exhibited a significantly more marked cardioprotective effect than the colchicine-IL-1β association.CONCLUSION: The cardioprotection induced by a short colchicine pretreatment was associated with an anti-inflammatory effect in the early reperfusion phase in our rat MI model.</p

Different pathways for sodium entry in cardiac cells during ischemia and early reperfusion.

International audienceA number of data are consistent with the hypothesis that increases in intracellular Na+ concentration (Na+i) during ischemia and early reperfusion lead to calcium overload and exacerbation of myocardial injury. However, the mechanisms underlying the increased Na+i remain unclear. 23Na nuclear magnetic resonance spectroscopy was used to monitor Na+i in isolated rat hearts perfused with a high concentration of fatty acid as can occur under some pathological conditions. Whole-cell patch-clamp experiments were also performed on isolated cardiomyocytes in order to investigate the role of voltage-gated sodium channels. Na+i increased to substantially above control levels during no-flow ischemia. The results show that a pharmacological reduction of Na+i increase by cariporide (1 micromol/L, a Na+/H+ exchange blocker) is not the only protection against ischemia-reperfusion damage, but that such protection may also be brought about by metabolic action aimed at reducing fatty acid utilization by myocardial cells. This action was obtained in the presence of etomoxir (0.1 micromol/L), an inhibitor of carnitine palmitoyltransferase-1 (the key enzyme involved in fatty acid uptake by the mitochondria) which also decreases long-chain acyl carnitine accumulation. The possibility of Na+ channels participating in Na+i increase as a consequence of alterations in cardiac metabolism was studied in isolated cells. Sustained I(Na) was stimulated by the presence of lysophosphatidylcholine (LPC, 10 micromol/L) whose accumulation during ischemia is, at least partly, dependent on increased long-chain acyl carnitine. Current activation was particularly significant in the range of potentials between -60 and -20 mV. This may have particular relevance in ischemia. The quantity of charge carried by sustained I(Na) was reduced by 24% in the presence of 1 micromol/L cariporide. Therefore, limitation of long-chain fatty acid metabolism, and consequent limitation of ischemia-induced long-chain acyl carnitine accumulation, may contribute to reducing intracellular Na+ increase during ischemia-reperfusion

Modifications in Rat Plasma Proteome after Remote Ischemic Preconditioning (RIPC) Stimulus: Identification by a SELDI-TOF-MS Approach

<div><p>Remote ischemic preconditioning’s (RIPC) ability to render the myocardium resistant to subsequent prolonged ischemia is now clearly established in different species, including humans. Strong evidence suggests that circulating humoral mediators play a key role in signal transduction, but their identities still need to be established. Our study sought to identify potential circulating RIPC mediators using a proteomic approach. Rats were exposed to 10-min limb ischemia followed by 5- (RIPC 5′) or 10-min (RIPC 10′) reperfusion prior to blood sampling. The control group only underwent blood sampling. Plasma samples were isolated for proteomic analysis using surface-enhanced laser desorption and ionization - time of flight - mass spectrometry (SELDI-TOF-MS). A total of seven proteins, including haptoglobin and transthyretin, were detected as up- or down-regulated in response to RIPC. These proteins had previously been identified as associated with organ protection, anti-inflammation, and various cellular and molecular responses to ischemia. In conclusion, this study indicates that RIPC results in significant modulations of plasma proteome.</p></div

Apolipoprotein a-I is a potential mediator of remote ischemic preconditioning.

BACKGROUND: Remote ischemic preconditioning (RIPC) has emerged as an attractive strategy in clinical settings. Despite convincing evidence of the critical role played by circulating humoral mediators, their actual identities remain unknown. In this study, we aimed to identify RIPC-induced humoral mediators using a proteomic approach. METHODS: and Results Rats were exposed to 10-min limb ischemia followed by 5- (RIPC 5') or 10-min (RIPC 10') reperfusion prior to blood sampling. The control group only underwent blood sampling. Plasma samples were analyzed using surface-enhanced laser desorption and ionization - time of flight - mass spectrometry (SELDI-TOF-MS). Three protein peaks were selected for their significant increase in RIPC 10'. They were identified and confirmed as apolipoprotein A-I (ApoA-I). Additional rats were exposed to myocardial ischemia-reperfusion (I/R) and assigned to one of the following groups RIPC+myocardial infarction (MI) (10-min limb ischemia followed by 10-min reperfusion initiated 20 minutes prior to myocardial I/R), ApoA-I+MI (10 mg/kg ApoA-I injection 10 minutes before myocardial I/R), and MI (no further intervention). In comparison with untreated MI rats, RIPC reduced infarct size (52.2±3.7% in RIPC+MI vs. 64.9±2.6% in MI; p<0.05). Similarly, ApoA-I injection decreased infarct size (50.9±3.8%; p<0.05 vs. MI). CONCLUSIONS: RIPC was associated with a plasmatic increase in ApoA-I. Furthermore, ApoA-I injection before myocardial I/R recapitulated the cardioprotection offered by RIPC in rats. This data suggests that ApoA-I may be a protective blood-borne factor involved in the RIPC mechanism

SELDI peaks selected to be differentially expressed.

<p>Only peaks with statistical difference expression (p<0.05) between two groups are indicated and expressed in m/z.</p><p>Peaks outlined are common between two groups.</p><p>Peaks underlined are impossible to purify for protein identification.</p