TGF-ß1-PML SUMOylation-peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1) form a positive feedback loop to regulate cardiac fibrosis.

Transforming growth factor-ß (TGF-ß) signaling pathway is involved in fibrosis in most, if not all forms of cardiac diseases. Here, we evaluate a positive feedback signaling the loop of TGF-ß1/promyelocytic leukemia (PML) SUMOylation/Pin1 promoting the cardiac fibrosis. To test this hypothesis, the mice underwent transverse aortic constriction (3 weeks) were developed and the morphological evidence showed obvious interstitial fibrosis with TGF-ß1, Pin1 upregulation, and increase in PML SUMOylation. In neonatal mouse cardiac fibroblasts (NMCFs), we found that exogenous TGF-ß1 induced the upregulation of TGF-ß1 itself in a time- and dose-dependent manner, and also triggered the PML SUMOylation and the formation of PML nuclear bodies (PML-NBs), and consequently recruited Pin1 into nuclear to colocalize with PML. Pharmacological inhibition of TGF-ß signal or Pin1 with LY364947 (3 µM) or Juglone (3 µM), the TGF-ß1-induced PML SUMOylation was reduced significantly with downregulation of the messenger RNA and protein for TGF-ß1 and Pin1. To verify the cellular function of PML by means of gain- or loss-of-function, the positive feedback signaling loop was enhanced or declined, meanwhile, TGF-ß-Smad signaling pathway was activated or weakened, respectively. In summary, we uncovered a novel reciprocal loop of TGF-ß1/PML SUMOylation/Pin1 leading to myocardial fibrosis.

Transforming Growth Factor-ß Receptor III is a Potential Regulator of Ischemia-Induced Cardiomyocyte Apoptosis.

BACKGROUND: Myocardial infarction (MI) is often accompanied by cardiomyocyte apoptosis, which decreases heart function and leads to an increased risk of heart failure. The aim of this study was to examine the effects of transforming growth factor-ß receptor III (TGFßR3) on cardiomyocyte apoptosis during MI. METHODS AND RESULTS: An MI mouse model was established by left anterior descending coronary artery ligation. Cell viability, apoptosis, TGFßR3, and mitogen-activated protein kinase signaling were assessed by methylthiazolyldiphenyl-tetrazolium bromide assay, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, immunofluorescence, electron microscopy, and Western blotting. Our results demonstrated that TGFßR3 expression in the border region of the heart was dynamically changed during MI. After stimulation with H2O2, TGFßR3 overexpression in cardiomyocytes led to increased cell apoptosis and activation of p38 signaling, whereas TGFßR3 knockdown had the opposite effect. ERK1/2 and JNK1/2 signaling was not altered by TGFßR3 modulation, and p38 inhibitor (SB203580) reduced the effect of TGFßR3 on apoptosis, suggesting that p38 has a nonredundant function in activating apoptosis. Consistent with the in vitro observations, cardiac TGFßR3 transgenic mice showed augmented cardiomyocyte apoptosis, enlarged infarct size, increased injury, and enhanced p38 signaling upon MI. Conversely, cardiac loss of function of TGFßR3 by adeno-associated viral vector serotype 9-TGFßR3 short hairpin RNA attenuated the effects of MI in mice. CONCLUSIONS: TGFßR3 promotes apoptosis of cardiomyocytes via a p38 pathway-associated mechanism, and loss of TGFßR3 reduces MI injury, which suggests that TGFßR3 may serve as a novel therapeutic target for MI.