The Delayed Phase of Protection in Heat-Induced Preconditioning: Role of the Heat Shock Protein associated with cytoskeleton

ABSTRACT

BACKGROUND AND OBJECTIVES: We investigated the ability of a brief heat shock on day one to provide delayed protection against lethal heat stress on day two in a rat-derived H9c2 cardiomyoblast cell line with reference to the role of heat shock protein 25/27, 70i and the p38MAPK signalling pathway. MATERIALS, METHODS AND RESULTS: Heat preconditioning(Heat P; 20min at 42+/-0.1degrees C) and adenosine(ADO) administered on day 1 protected against cell death under lethal heat challenge (75min at 42+/-0.1degrees C) on day 2 as measured by MTT test ( % cell viability Heat P 79.9+/-3.23%, ADO 71.9+/-4.10% vs. control 52.7+/-1.65% respectively ). This protection was abolished by treatment with SB203580 or cytochalasine D prior to the protective stimulus on day 1( SB203580 64.1+/-4.37%, cytochalasine D 73.1+/-4.33% vs. Heat P ). Western blotting analysis indicated a significant accumulation of hsp70i in Heat P and SB203580-treated Heat P cells compared to control and adenosine-, SB203580-treated cells. Phosphorylation of hsp25 was significantly increased in Heat P cells compared to control cells. We also observed fragmentation of F-actin and formation of F-actin aggregates in cells exposed to lethal heat challenge. In contrast, the delayed cytoprotection preserved the F-actin bundles under lethal heat challenge. Hsp27-overexpressed, stable clones were more resistant to lethal heat shock when compared to control cells transfected with the vector alone. CONCLUSION: These data suggest an important role for p38MAPK/hsp25/27 pathway as a potential distal effector of heat-induced delayed protection.