Mechanisms of xenon‐ and isoflurane‐induced preconditioning – a potential link to the cytoskeleton via the MAPKAPK‐2/HSP27 pathway

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Abstract
We previously demonstrated that the anesthetic gas xenon exerts cardioprotection by preconditioning in vivo via activation of protein kinase C (PKC)-epsilon and p38 mitogen-activated protein kinase (MAPK). P38 MAPK interacts with the actin cytoskeleton via the MAPK-activated protein kinase-2 (MAPKAPK-2) and heat-shock protein 27 (HSP27). The present study further elucidated the underlying molecular mechanism of xenon-induced preconditioning (Xe-PC) by focusing on a potential link of xenon to the cytoskeleton. Anesthetized rats received either xenon (Xe-PC, n = 6) or the volatile anesthetic isoflurane (Iso-PC, n = 6) during three 5-min periods interspersed with two 5-min and one final 10-min washout period. Control rats (n = 6) remained untreated for 45 min. Additional rats were either pretreated with the PKC inhibitor Calphostin C (0.1 mg kg(-1)) or with the p38 MAPK inhibitor SB203580 (1 mg kg(-1)) with and without anesthetic preconditioning (each, n = 6). Hearts were excised for immunohistochemistry of F-actin fibers and phosphorylated HSP27. Phosphorylation of MAPKAPK-2 and HSP27 were assessed by Western blot. HSP27 and actin colocalization were investigated by co-immunoprecipitation. Xe-PC induced phosphorylation of MAPKAPK-2 (control 1.0 +/- 0.2 vs Xe-PC 1.6 +/- 0.1, P < 0.05) and HSP27 (control 5.0 +/- 0.5 vs Xe-PC 9.8 +/- 1.0, P < 0.001). Both effects were blocked by Calphostin C and SB203580. Xe-PC enhanced translocation of HSP27 to the particulate fraction and increased F-actin polymerization. F-actin and pHSP27 were colocalized after Xe-PC. Xe-PC activates MAPKAPK-2 and HSP27 downstream of PKC and p38 MAPK. These data link Xe-PC to the cytoskeleton, revealing new insights into the mechanisms of Xe-PC in vivo.