The p38 MAPK inhibitor, SB203580, abrogates ischaemic preconditioning in rat heart but timing of administration is critical.
ABSTRACT There is debate concerning the involvement of p38 mitogen activated protein kinase (MAPK) in the mediation of ischaemic preconditioning. Pharmacological inhibition of p38 MAPK with SB203580 has been reported to block preconditioning in some studies but not in others. We hypothesised that this divergence could be due to differences in the timing of inhibitor administration. Isolated rat hearts were perfused in the Langendorff mode and subjected to 35 min regional ischaemia followed by 120 min reperfusion. Hearts were then double stained with Evans' blue and triphenyltetrazolium chloride to determine risk (R) and infarct zones (I), expressed as I/R% ratios. Preconditioned hearts were subjected to 2 times 5 min global ischaemia with 10 min intervening reperfusion. SB203580 10 microM was perfused either during the preconditioning protocol (PC+/-SB-early),just prior to and during the first 15 min of the lethal ischaemia (PC+/-SB-late) or prior to regional ischaemia in the absence of preconditioning. Ischaemic preconditioning significantly limited infarct size (I/R 38.9 +/- 3.0% in control vs 13.4 +/- 2.4%, P < 0.01). In the PC+/-SB-early group, preconditioning was still fully protective (I/R% 14.6 +/- 1.0). However, in the PC+/-SB-late group, SB203580 completely blocked the protection afforded by preconditioning (I/R% 33.6 +/- 4.4%, P < 0.01 vs 13.4 +/- 2.4% in preconditioned hearts, p < 0.05). SB203580 alone did not affect infarct size when given prior to and during regional ischaemia (I/R 36.2 +/- 2.7%). These histological data are corroborated by a significant increase in p38 MAPK activation in the preconditioned hearts during sustained ischaemia in comparison with the controls. In conclusion the activation of p38 MAPK during lethal ischaemia, but not during the ischaemic preconditioning protocol, is essential for the mediation of protection and may resolve some of the earlier controversy surrounding the use of SB203580 in preconditioning studies.
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ABSTRACT: The immature heart is known to be resistant to ischemia-reperfusion (IR) injury, however key proteins engaged in phospho-dependent signaling pathways crucial to cell survival are not yet defined. Our goal was to determine the post-natal changes in myocardial tolerance to IR, including baseline expression of key proteins governing IR tolerance and their phosphorylation during IR. Hearts from male C57Bl/6 mice (neonates, 2, 4, 8, and 12 weeks of age, n=6/group) were assayed for survival signaling/effectors (Akt, p38MAPK, GSK3β, HSP27, connexin-43, HIF1α, caveolin-3), regulators of apoptosis (Bax, Bcl-2) and autophagy (LC3B, Parkin, Beclin1). The effect of IR on ventricular function was measured in isolated perfused hearts from immature (4 week) and adult (12 week) mice. Neonatal myocardium exhibits a large pool of inactive Akt; high phospho-activation of p38MAPK, HSP27 and connexin-43; phospho-inhibition of GSK3β; and high expression of caveolin-3, HIF1α, LC3B, Beclin1, Bax and Bcl-2. Immature hearts sustained less dysfunction and infarction following IR than adults. Emergence of IR intolerance in adult vs. immature hearts was associated with complex proteomic changes: decreased expression of Akt, Bax and Bcl-2; increased GSK3β, connexin-43, HIF1α, LC3B and Bax:Bcl-2; enhanced post-ischemic HIF1α, caveolin-3, Bax and Bcl-2; and greater post-ischemic GSK3β and HSP27 phosphorylation. Neonatal myocardial stress-resistance reflects high expression of pro-survival and autophagy proteins, and apoptotic regulators. Notably, there is high phosphorylation of GSK3β, p38MAPK, HSP27, and low phosphorylation of Akt (high Akt 'reserve'). Subsequent maturational reductions in IR tolerance are associated with reductions in Akt, Bcl-2, LC3B and Beclin1.AJP Regulatory Integrative and Comparative Physiology 09/2013; · 3.28 Impact Factor
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ABSTRACT: Kidney ischemia-reperfusion (I/R) injury is a common cause of acute kidney injury. We tested whether dexmedetomidine (Dex), an alpha2 adrenoceptor (α2-AR) agonist, protects against kidney I/R injury. Sprague–Dawley rats were divided into four groups: (1) Sham-operated group; (2) I/R group (40 min ischemia followed by 24 h reperfusion); (3) I/R group + Dex (1 μg/kg i.v. 60 min before the surgery), (4) I/R group + Dex (10 μg/kg). The effects of Dex postconditiong (Dex 1 or 10 μg/kg i.v. after reperfusion) as well as the effects of peripheral α2-AR agonism with fadolmidine were also examined. Hemodynamic effects were monitored, renal function measured, and acute tubular damage along with monocyte/macrophage infiltration scored. Kidney protein kinase B, toll like receptor 4, light chain 3B, p38 mitogen-activated protein kinase (p38 MAPK), sirtuin 1, adenosine monophosphate kinase (AMPK), and endothelial nitric oxide synthase (eNOS) expressions were measured, and kidney transciptome profiles analyzed. Dex preconditioning, but not postconditioning, attenuated I/R injury-induced renal dysfunction, acute tubular necrosis and inflammatory response. Neither pre- nor postconditioning with fadolmidine protected kidneys. Dex decreased blood pressure more than fadolmidine, ameliorated I/R-induced impairment of autophagy and increased renal p38 and eNOS expressions. Dex downregulated 245 and upregulated 61 genes representing 17 enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, in particular, integrin pathway and CD44. Ingenuity analysis revealed inhibition of Rac and nuclear factor (erythroid-derived 2)-like 2 pathways, whereas aryl hydrocarbon receptor (AHR) pathway was activated. Dex preconditioning ameliorates kidney I/R injury and inflammatory response, at least in part, through p38-CD44-pathway and possibly also through ischemic preconditioning.Pharmacology Research & Perspectives. 06/2014; 2(3).