Biomedical subjects

Ferran Padilla

Publications and source records attributed to Ferran Padilla.

7 recordsLinked to original sources

PubMed2005

Antagonism of selectin function attenuates microvascular platelet deposition and platelet-mediated myocardial injury after transient ischemia.

OBJECTIVES: The goal of this study was to assess whether selectin blockade reduces myocardial platelet deposition and platelet-mediated injury after transient ischemia. BACKGROUND: Selectins participate in platelet adhesion to reperfused endothelium. METHODS: Thiopental-anesthetized, open-chest pigs were subjected to mechanical injury of the left anterior descending coronary artery followed by a 48-min occlusion and 2 (n = 20) or 4 (n = 16) h of reperfusion. Fifteen minutes before occlusion, animals were blindly allocated to receive a continuous intravenous infusion of the selectin blocker fucoidan (30 microg/kg/min, plus a 1-mg/kg bolus in the latter group) or saline. In isolated rat hearts infused with thrombin-activated platelets, the effects of fucoidan (30 microg/ml) administered during reperfusion after 40 min of global ischemia were also analyzed. RESULTS: Fucoidan did not prevent the development of cyclic reductions in coronary flow, but reduced the content of (99m)Tc-labeled platelets in reperfused myocardium after 2 h of reperfusion (23.4 +/- 3.3 vs. 42.1 +/- 8.3 x 10(6) platelets/g in treated and untreated animals, p = 0.03) and attenuated the impairment in the coronary flow reserve and reduced infarct size after 4 h (53 +/- 2% vs. 73 +/- 5% of the ischemic region, respectively, p = 0.003). Treated animals showed a trend toward less neutrophil infiltration early after reperfusion, but not after 4 h. In isolated hearts, fucoidan improved functional recovery and reduced coronary resistance and lactate dehydrogenase release, lacking any beneficial effects if given in the absence of platelets. CONCLUSIONS: The results suggest that selectin-dependent adhesion is a prominent mechanism of platelet deposition in reperfused cardiac microvessels and highlight its potential as a therapeutic target in patients with acute myocardial infarction.

Animals↗

PubMed2003

Protection afforded by ischemic preconditioning is not mediated by effects on cell-to-cell electrical coupling during myocardial ischemia-reperfusion.

The end-effectors of ischemic preconditioning (IPC) are not well known. It has been recently shown that transgenic mice underexpressing the gap junction protein connexin43 (Cx43) cannot be preconditioned. Because gap junctions allow spreading of cell death during ischemia-reperfusion in different tissues, including myocardium, we hypothesized that the protection afforded by IPC is mediated by effects on gap junction-mediated intercellular communication. To test this hypothesis, we analyzed the effect of IPC (5 min ischemia-5 min reperfusion x 2) on the changes in electrical impedance (four electrode probe) and impulse propagation velocity (transmembrane action potential) induced by ischemia (60 min) and reperfusion (60 min) in isolated rat hearts. IPC (n = 8) reduced reperfusion-induced lactate dehydrogenase release by 65.8% with respect to control hearts (n = 9) (P = 0.04) but had no effect on the time of onset of rigor contracture (increase in diastolic tension), electrical uncoupling (sharp changes in tissue resistivity and phase angle in impedance recordings), or block of impulse propagation during ischemia. Normalization of electrical impedance during reperfusion was also unaffected by IPC. The lack of effect of IPC on ischemic rigor contracture and on changes in tissue impedance during ischemia-reperfusion were validated under in vivo conditions in pigs submitted to 48 min of coronary occlusion and 120 min of reperfusion. IPC (n = 12) reduced infarct size (triphenyltetrazolium) by 64.9% (P = 0.01) with respect to controls (n = 17). We conclude that the protection afforded by IPC is not mediated by effects on electrical coupling. This result is consistent with recent findings suggesting that Cx43 could have effects on cell survival independent on changes in cell-to-cell communication.

Action Potentials↗

PubMed2003

Pre-treatment with the Na+/H+ exchange inhibitor cariporide delays cell-to-cell electrical uncoupling during myocardial ischemia.

OBJECTIVE: Inhibition of Na(+)-H(+) exchange (NHE) delays the onset of myocardial rigor contracture during ischemia. The aim of this study was to analyse the effects of NHE inhibition on cell-to-cell electrical uncoupling during myocardial ischemia/reperfusion. METHODS: Twenty-six isolated rat hearts and 23 in situ porcine hearts were submitted to no-flow ischemia followed by reperfusion, with or without pre-treatment with cariporide (7 microM in rats and 3 mg/kg in pigs). Ischemic rigor and hypercontracture, conduction velocity and myocardial electrical impedance were monitored. RESULTS: Pre-treatment with cariporide delayed ATP depletion (luminescence assay in rat myocardium) and onset of rigor contracture (tension recordings or ultrasonic crystals) during ischemia both in rat and pig hearts (P<0.05). In addition, cariporide delayed the onset of sharp changes in tissue resistivity and phase angle in impedance recordings (four-electrode probes) from 10+/-1 to 13+/-1 min (P<0.001) in rat hearts, and from 22+/-1 to 38+/-2 min (P<0.001) in pigs. Blockade of impulse propagation (transmembrane action potentials in rat hearts) was also markedly delayed by cariporide (from 14+/-1 to 20+/-1 min, P<0.001). Reperfusion-induced LDH release in rat hearts and infarct size in pigs were markedly reduced by pre-treatment with cariporide. CONCLUSIONS: Inhibition of NHE with cariporide slows the progression of ischemic injury during myocardial ischemia, and delays the onset of cell-to-cell electrical uncoupling.

Action Potentials↗

PubMed2002

Gap junction-mediated intercellular communication in ischemic preconditioning.

Gap junction-mediated communication can modulate cell death in different tissues. In myocardium, gap junction communication is altered during ischemia, which contributes to the development of arrhythmias, but still allows synchronization of the onset of rigor contracture in the progression of injury. During reperfusion, gap junction communication allows cell-to-cell spread of hypercontracture and cell death. Since the intracellular signal transduction systems involved in modulation of gap junction-mediated communication are activated during ischemic preconditioning, the hypothesis can be raised that gap junctions are end-effectors of preconditioning contributing to its protective effect on cell death. This paper reviews the available information supporting this hypothesis. It has been shown that ischemic preconditioning may influence gap junction-mediated intercellular communication by activation of different kinases, including PKC and MAPK cascades, and by preservation of cGMP among other mechanisms. Connexin phosphorylation by PKC, p38/MAPK, and PKG, tends to reduce intercellular communication. This effect of ischemic preconditioning seems to have no relevant consequences during prolonged ischemia, and does not significantly modify the time course of either electrical uncoupling or the frequency or temporal distribution of ventricular arrhythmias during this period. However, any modification of gap junction communication during initial reperfusion could contribute to the reduced extent of hypercontracture and cell death observed in preconditioned hearts. The potential role of gap junctions as effectors of ischemic preconditioning against lethal injury secondary to ischemia-reperfusion deserves to be investigated in depth.

Animals↗

PubMed2002

Ventricular fibrillation during acute coronary occlusion is related to the dilation of the ischemic region.

Myocardial stretch induces several electrophysiological changes and arrhythmias, but little is known on its possible role in triggering ventricular fibrillation (VF) during acute coronary occlusion. In thiopental-anesthetized, open-chest pigs submitted to a 40-min ligation of the left anterior descending coronary artery, the association between the early increase in end-diastolic length (measured by means of ultrasonic crystals) in the ischemic region and subsequent VF was analyzed. Animals received no treatment (n = 35) or intravenous nitroglycerin (2.5 microg/kg/min for 20 min, starting 10 min after coronary occlusion, n = 8) or Gd(3+) (80 microM/kg for 35 min, starting 5 min before occlusion, n = 15). Twenty-four animals (41 %) had VF, 16 to 39 min after coronary occlusion. The magnitude of ischemic dilation and the incidence of VF were similar among groups. End-diastolic length in the ischemic region 15 min after coronary occlusion was 115.7 +/- 1.2 % of baseline in animals with VF and 111.4 +/- 0.9 % in those without (P = 0.007), and was the strongest predictor of this arrhythmia (P = 0.003) after adjusting for treatment and other possible confounding variables. Thus, the dilation of the ischemic region is closely and independently associated with VF following coronary occlusion. Although the interventions tested in the present study failed to protect against this arrhythmia, the results strongly suggest an influence of ischemic dilation on VF.

Acute Disease↗

PubMed2002

Effect of inhibition of Na(+)/Ca(2+) exchanger at the time of myocardial reperfusion on hypercontracture and cell death.

OBJECTIVE: There is recent evidence that Ca(2+) influx via reverse mode Na(+)/Ca(2+) exchange (NCX) at the time of reperfusion can contribute to cardiomyocyte hypercontracture. However, forward NCX is essential for normalization of [Ca(2+)](i) during reperfusion, and its inhibition may be detrimental. This study investigates the effect of NCX inhibition with KB-R7943 at the time of reperfusion on cell viability. METHODS: The effect of several concentrations of KB-R7943 added at reperfusion was studied in Fura-2 loaded quiescent cardiomyocytes submitted to 40 min of simulated ischemia (NaCN 2 mM, pH 6.4), and in rat hearts submitted to 60 min of ischemia. [Ca(2+)](i) and cell length were monitored in myocytes, and functional recovery and LDH release in isolated hearts. From these experiments an optimal concentration of KB-R7943 was identified and tested in pigs submitted to 48 min of coronary occlusion and 2 h of reperfusion. RESULTS: In myocytes, KB-R7943 at concentrations up to 15 microM reduced [Ca(2+)](i) rise and the probability of hypercontracture during re-energization (P<0.01). Nevertheless, in rat hearts, the effects of KB-R7943 applied during reperfusion after 60 min of ischemia depended on concentration and timing of administration. During the first 5 min of reperfusion, KB-R7943 (0.3-30 microM) induced a dose-dependent reduction in LDH release (half-response concentration 0.29 microM). Beyond 6 min of re-flow, KB-R7943 had no effect on LDH release, except at concentrations > or = 15 microM, which increased LDH. KB-R7943 at 5 microM given during the first 10 min of reflow reduced contractile dysfunction (P=0.011), LDH release (P=0.019) and contraction band necrosis (P=0.014) during reperfusion. Intracoronary administration of this concentration during the first 10 min of reperfusion reduced infarct size by 34% (P=0.033) in pigs submitted to 48 min of coronary occlusion. CONCLUSIONS: These results are consistent with the hypothesis that during initial reperfusion NCX activity results in net reverse mode operation contributing to Ca(2+) overload, hypercontracture and cell death, and that NCX inhibition during this phase is beneficial. Beyond this phase, NCX inhibition may impair forward mode-dependent Ca(2+) extrusion and be detrimental. These findings may help in the design of therapeutic strategies against lethal reperfusion injury, with NCX as the target.

Analysis of Variance↗

PubMed2002

Platelets activated by transient coronary occlusion exacerbate ischemia-reperfusion injury in rat hearts.

Platelets (Plt) accumulate in reperfused myocardium but their effect on myocardial necrosis has not been established. We tested the hypothesis that the effect of Plt depends on their activation status. Pig Plt were obtained before 48 min of coronary occlusion (pre-CO-Plt), 10 min after reperfusion (R-Plt), or after a 60-min sham operation (sham-Plt). Plt were infused into isolated rat hearts (n = 124) and subsequently submitted to 60 min of ischemia and 60 min of reperfusion. P-selectin expression was higher (P = 0.02) in R-Plt than in pre-CO-Plt or sham-Plt. Lactate dehydrogenase (LDH) release during reperfusion was similar in hearts receiving pre-CO-Plt, sham-Plt, or no Plt, but R-Plt increased LDH release by 60% (P = 0.004). Activation of pre-CO-Plt with thrombin increased P-selectin expression and LDH release (P < 0.001), and these results were unaffected by tirofiban. There was a close correlation between P-selectin expression and LDH release (r = 0.84; P < 0.001), and myocardial Plt accumulation (r = 0.85; P < 0.001). We conclude that the deleterious effect of Plt on reperfused myocardium depends on their activation status as represented by P-selectin expression, which is enhanced by ischemia-reperfusion.

Animals↗