Abstract 16639: Acetylation and Stabilization of STAT3 Mediates Cardioprotection by p300 and HDAC Inhibitor Trichostatin A
Background: The nuclear acetyltransferase p300 is rapidly induced in the heart during various types of stress, and mice with 2.5x myocyte overexpression of p300 are protected against ischemia/reperfusion (I/R) injury. Transcription factor STAT3 is strongly cardioprotective, and is acetylated and coactivated by p300.
Hypothesis: p300 mediates cardioprotection against oxidative stress via activation of STAT3.
Methods: Oxidative stress was induced in neonatal rat cardiac myocytes with doxorubicin (DOX, 1µM). Protein synthesis inhibitor cycloheximide (CY) was used to assess p300 and STAT3 stability. p300 knockdown (p300KD) was achieved with p300-targeting siRNA and compared to non-targeting control (NS). STAT3 fl/fl, α-MHC-Cre+ (KO) and STAT3 wt/wt, α-MHC-Cre+ (WT) littermates were subjected to I/R injury, 1 h after injection of a singe dose of the class I/II HDAC inhibitor TSA or its vehicle.
Results: p300 protein rapidly increased to high levels after DOX treatment, and remained elevated for ≥ 16 h (3.7±1.9x of control at 8h; p<0.05), entirely through increased p300 stability (5.53±1.87x after 6h CY; p<0.05). Acetyl-STAT3 and STAT3 half-life increased in parallel (1.89±0.45 fold; p<0.05), as did activating phosphorylation of STAT3 at Tyr 705 and Ser 727. Conversely, p300 loss abrogated the effect of DOX on STAT3 content, phosphorylation, acetylation, and half-life (0.68±0.07 fold; p<0.05), accompanied by reduced cell survival and blunted DNA damage response. p300 loss led to downregulation of multiple STAT3-regulated genes (e.g. MMP9, IL1RN, SERPINA3) vs. NS cardiomyocytes. During I/R in vivo, treatment with TSA increased p300-specific HAT activity and p300 protein levels (p<0.001), associated with 32.72±15.73% reduction in infarct volume (P<0.001, n = 4) in mice, however TSA provided no cardioprotection in KO mice (3.25%, p=0.09, n =4).
Conclusion: Oxidative stress acutely stabilizes p300 in cardiac myocytes, which is required for acetylation, activation and stabilization of STAT3 and expression of STAT3-dependent genes. TSA activates p300 during ischemia-reperfusion and requires STAT3 for its cardioprotective effects. STAT3 is a critical downstream effector for both TSA- and p300-mediated protection against acute oxidative stress.
- © 2011 by American Heart Association, Inc.