Abstract 3618: A Cross Talk Between Stat3 and HSF1 Plays a Critical Role in G-CSF-induced Cardiac Protection Against Ischemia/Reperfusion Injury
Background-Granulocyte colony-stimulating factor (G-CSF) has been reported to protect cardiomyocytes (CM) from ischemic injury through Jak2/Stat3 pathway. Heat shock transcription factor 1 (HSF1), a definite protective factor in the heart, may interact with Stat family under stress conditions. However, whether the interaction between HSF1 and Stat3 is involved in G-CSF-induced cardiac protection after ischemia/reperfusion (I/R) injury is unclear.
Methods and Results-In the present study, HSF1 knockout (KO) and their littermate wild type mice (WT) were administered with G-CSF (100 μg/kg/day) or vehicle subcutaneously. Three days later, the mice were subjected to ischemia for 30 min and then reperfusion for 24 h. Comparing with vehicle treatment, G-CSF not only had a beneficial effect on cardiac functions characterized by a higher EF%, a lower LVEDP and a larger dP/dt value but also decreased infarction area in WT group. In HSF1 KO mice, however, these protective effects on cardiac dysfunction and infarction by G-CSF were declined, suggesting that HSF1 is involved in protective effects of G-CSF on myocardial infarction. Moreover, phosphorylation levels of Stat3 in I/R myocardium of KO mice were lower than those in WT mice heart after treatment with G-CSF. In vitro experiments using cultured CM of neonatal rats showed that treatment with G-CSF for 24 h didn’t affect the expression levels of HSF1 mRNA but increased the protein expression of heat shock proteins (HSP), such as HSP 90, HSP70 and HSP27, suggesting that although G-CSF could not upregulate the expression of HSF1, it increased transcriptional activities of HSF1. G-CSF also elevated the levels of phosphor-Stat3 in CM. Furthermore, G-CSF-induced increases in HSP were inhibited by a Stat3 inhibitor, S3I-201, and a siRNA of HSF1 suppressed phosphorylation of Stat3 by G-CSF. Finally, Co-immunoprecipitation experiment revealed that association of phosphor-Stat3 with HSF1 was increased after adding G-CSF to CM, and the association could be abolished by S3I-201 and the siRNA of HSF1.
Conclusion-G-CSF can induce an interaction between HSF1 and phosphor-Stat3, which increases the transcriptional activities of HSF1 and therefore protects the heart against ischemia/reperfusion injury.