Inhibition of the cardiac p38-MAPK pathway by SB203580 delays ischemic cell death

We report that SB203580 (SB), a specific inhibitor of p38-MAPK, protects pi g myocardium against ischemic injury in an in vivo model. SE was applied by local infusion into the subsequently ischemic myocardium for 60 min before a 60-min period of coronary occlusion followed by 60-min reperfusion (inde x ischemia). Infarct size was reduced from a control value of 69.3 +/- 2.7% to 36.8 +/- 3.7%. When SE was infused systemically for 10 min before index ischemia, infarct size was reduced to 36.1 +/- 5.6%. We measured the conte nt of phosphorylated p38-MAPK after systemic infusion of SE and Krebs-Hense leit buffer (KHB; negative control) and during the subsequent ischemic peri od using an antibody that reacts specifically with dual-phosphorylated p38- MAPK (Thr180/ Tyr182). Ischemia with and without SE significantly increased phospho-p38-MAPK, with a maximum reached at 20 min but was less at 30 and 45 min under the influence of the inhibitor. The systemic infusion of SE fo r 10 min before index ischemia did nor significantly change the p38-MAPK ac tivities (compared with vehicle, studied by in-gel phosphorylation) less th an or equal to 20 min of ischemia, but activities were reduced at 30 and 45 min. Measurements of p38-MAPK activities in situations in which SE was pre sent during in-gel phosphorylation showed significant inhibition of p38-MAP K activities. The systemic infusion of SE significantly inhibited the ische mia-induced phosphorylation of nuclear activating transcription factor 2 (A TF-2). Using a specific ATF-2 antibody, we did not observe significant chan ges in ATF-2 abundance when nuclear fractions from untreated, KHB-, and SB- treated tissues were compared. We investigated also the effect of local and systemic infusion of SE on the cardioprotection induced by ischemic precon ditioning (IP). The infusions (local or systemic) of SE before and during t he IP protocol dill not influence the infarct size reduction mediated by IF . The observed protection of the myocardium against ischemic damage by SE p oints to the negative role of the p38-MAPK pathway during ischemia.