Introduction:
Ischemic heart disease is the leading cause of morbidity and mortality worldwide. Ischemic preconditioning (IPC) is the most powerful intrinsic protection against cardiac ischemia/reperfusion (I/R) injury. Previous studies have shown that a multifunctional TRIM family protein, MG53 (or TRIM72), not only plays an essential role in IPC-mediated cardioprotection, but also as a myokine/cardiokine, can be secreted from the heart and skeletal muscle in response to metabolic stress in addition to its intracellular actions.
Hypothesis:
We hypothesized that IPC-mediated cardioprotection is causally related to MG53 secretion and figured out the underlying mechanism.
Methods and Results:
Using proteomic analysis in conjunction with genetic and pharmacological approaches, we examined MG53 secretion in response to IPC and explored the underlying mechanism using rodents in
in vivo
, isolated perfused hearts, and cultured neonatal rat ventricular cardiomyocytes. IPC profoundly increased perfusate MG53 levels in mouse hearts by 5.50 ± 0.32 and 4.26 ± 0.40 folds from baseline over 0-60 and 60-120 min of reperfusion, respectively. Mechanistically, IPC-induced MG53 secretion is dependent on H
2
O
2
-evoked, Src-mediated phosphorylation of PKC-δ-Y311. Functionally, systemic delivery of recombinant human MG53 proteins (rhMG53) to mimic elevated circulating MG53 not only restored IPC function in MG53-deficient mice, but also protected rodent hearts from I/R injury even in the absence of IPC. Treatment of rhMG53 overtly decreased the infarct size (IF/AAR) induced by I/R compared to the BSA-treated control group (11.9 ± 1.8% vs 27.3 ± 2.0%, P <0.01), and reduced the mortality from 44.7% to 5.3% in rats. Moreover, H
2
O
2
augmented MG53 secretion, and MG53 knockdown exacerbated H
2
O
2
-induced cell injury in human embryonic stem cell-derived cardiomyocytes.
Conclusions:
In conclusion, IPC and oxidative stress can trigger MG53 secretion from the heart via an H
2
O
2
-PKC-δ-dependent mechanism, and secreted MG53 acts as an essential factor conveying IPC-induced cardioprotection against ischemia/reperfusion injury. Recombinant MG53 proteins can be developed into a novel treatment for various diseases of human heart in which the endogenous MG53 is low.
CREB activation in the rapid, intermediate, and delayed ischemic preconditioning against hypoxic-ischemia in neonatal rat
