RESUMEN
Intestinal ischemia and reperfusion injury is dependent on the recruitment and activation of neutrophils. Glibenclamide, an ATP-sensitive potassium channel (K(ATP)) blocker, has been shown to suppress neutrophil migration and chemotaxis during acute inflammatory responses by a mechanism dependent on its K(ATP) channel blocking activity. In the present study, we evaluated whether the treatment with glibenclamide prevented local, remote and systemic injury following reperfusion of the ischemic superior mesenteric artery in rats. The artery was made ischemic for a period of 30 or 120 min followed by 30 (mild I/R) or 120 (severe I/R) min of reperfusion, respectively. Glibenclamide (0.8 to 20 mg/kg) or vehicle was administered subcutaneously 40 min prior to the reperfusion. Glibenclamide dose-dependently inhibited the reperfusion-associated increase in vascular permeability and neutrophil accumulation in mild I/R. In the severe injury model, glibenclamide inhibited inflammatory parameters, as assessed by Evans blue extravasation, neutrophil influx and haemoglobin content, and the increase in TNF-alpha (tumor necrose factor-alpha) and IL (interleukin)-6 levels in the intestine and lung. The drug did not affect the increase in IL-1beta and IL-10 levels. TEA, a nonselective potassium channel blocker, also inhibited reperfusion injury in both intestine and lungs of animals submitted to mild and severe I/R. Our experiments suggest a role for K(ATP) channels in mediating neutrophil influx and consequent reperfusion-associated injury in rats. The lack of effect of these drugs on the reperfusion-associated hypotension and lethality may limit their usefulness after severe reperfusion injury.
Asunto(s)
Adenosina Trifosfato/fisiología , Gliburida/uso terapéutico , Intestinos/irrigación sanguínea , Isquemia/prevención & control , Bloqueadores de los Canales de Potasio/uso terapéutico , Daño por Reperfusión/prevención & control , Animales , Permeabilidad Capilar/efectos de los fármacos , Quimiotaxis de Leucocito/efectos de los fármacos , Citocinas/biosíntesis , Gliburida/administración & dosificación , Intestinos/patología , Activación del Canal Iónico , Isquemia/patología , Isquemia/fisiopatología , Masculino , Arteria Mesentérica Superior/fisiopatología , Minoxidil/uso terapéutico , Neutrófilos/efectos de los fármacos , Neutrófilos/fisiología , Bloqueadores de los Canales de Potasio/administración & dosificación , Ratas , Ratas Wistar , Daño por Reperfusión/mortalidad , Daño por Reperfusión/patología , Tetraetilamonio/uso terapéuticoRESUMEN
BACKGROUND: Renal ischemia/reperfusion (I/R) is a complex neutrophil-mediated syndrome. Adenosine-triphosphate (ATP)-sensitive potassium (K(ATP)) channels are involved in neutrophil migration in vivo. In the present study, we have investigated the effects of glibenclamide, a K(ATP) channel blocker, in renal I/R injury in rats. METHODS: The left kidney of the rats was excised through a flank incision and ischemia was performed in the contralateral kidney by total interruption of renal artery flow for 45 minutes. Renal perfusion was reestablished, and the kidney and lungs were removed for analysis of vascular permeability, neutrophil accumulation, and content of cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-10] 4 and 24 hours later. Renal function was assessed by measuring creatinine, Na(+), and K(+) levels in the plasma and by determination of creatinine clearance. Drugs were administered subcutaneously after the onset of ischemia. RESULTS: Reperfusion of the ischemic kidney induced local (kidney) and remote (lung) inflammatory injury and marked renal dysfunction. Glibenclamide (20 mg/kg) significantly inhibited the reperfusion-associated increase in vascular permeability, neutrophil accumulation, increase in TNF-alpha levels and nuclear factor-kappaB (NF-kappaB) translocation. These inhibitory effects were noticed in the kidney and lungs. Moreover, glibenclamide markedly ameliorated the renal dysfunction at 4 and 24 hours. CONCLUSION: Treatment with glibenclamide is associated with inhibition of neutrophil recruitment and amelioration of renal dysfunction following renal I/R. Glibenclamide may have a therapeutic role in the treatment of renal I/R injury, such as after renal transplantation.
Asunto(s)
Gliburida/farmacología , Riñón/efectos de los fármacos , Riñón/lesiones , Bloqueadores de los Canales de Potasio/farmacología , Canales de Potasio/metabolismo , Daño por Reperfusión/prevención & control , Adenosina Trifosfato/metabolismo , Animales , Citocinas/metabolismo , Diazóxido/farmacología , Modelos Animales de Enfermedad , Interleucina-10/metabolismo , Riñón/irrigación sanguínea , Riñón/metabolismo , Masculino , FN-kappa B/metabolismo , Neutrófilos/efectos de los fármacos , Neutrófilos/metabolismo , Ratas , Ratas Wistar , Daño por Reperfusión/metabolismo , Daño por Reperfusión/patología , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
The role of nitric oxide (NO), K(+) channels, and arachidonic acid metabolism, via cytochrome P450 and cyclooxygenase pathways, in the renal vasodilatory effect of bradykinin was examined in the isolated rat kidney perfused ex situ with a blood-free solution. Bradykinin (BK, 0.25-1.0 microM) induced a dose-dependent reduction of 10-35% in the relative renal vascular resistance (rRVR) of isolated kidneys preconstricted with phenylephrine (PHE, 0.17-0.35 microM). The vasodilating effect of 0.5 microM bradykinin was significantly inhibited by the nitric oxide synthase inhibitors, N(G)-nitro-L-arginine (95% inhibition) and N(G)-nitro-L-arginine methyl ester (45-75% inhibition). Clotrimazole, an inhibitor of cytochrome P450 pathway but not indomethacin, a cyclooxygenase inhibitor, reduced the renal vasodilator response to bradykinin by 84%. The nonspecific K(+) channel inhibitor, tetraethylammonium ion (TEA) and the selective inhibitor of Ca(2+)-activated K(+) channels, charybdotoxin (ChTX) greatly attenuated the vasodilator response to bradykinin by approximately 84% and 79%, respectively. These two K(+) channel inhibitors showed similar effects on vasodilatation induced by S-nitroso-acetyl-D,L-penicillamine (1 microM), a nitric oxide donor. The results suggest that bradykinin releases nitric oxide which, by opening potassium channels specifically the Ca(+)-dependent type, mediates the renal vasodilator response to bradykinin in the isolated kidney perfused ex situ.