Poly(ADP-ribose) polymerase 1 induces cardiac fibrosis by mediating mammalian target of rapamycin activity.

Cardiac fibrosis is involved in nearly all forms of heart diseases and is characterized by excessive deposition of extracellular matrix proteins by cardiac fibroblasts (CFs). We and others have reported the possibility of poly(ADP-ribose) polymerase 1 the founding subtype of the enzyme family, as a novel therapeutic target of heart diseases. The cardiac fibrotic induction of mammalian target of rapamycin (mTOR) is mainly due to collagen expression, Smad3- and p53/JNK-mediated apoptosis. However, the possible link between and mTOR in the progression of cardiac fibrosis remains unclear. In this study, Pduanyu371 protein expression, and the activity of mTOR and its three target substrates (p70 ribosomal S6 Kinase 1, eukaryotic initiation factor 4E--binding protein 1, and UNC-51-like kinase 1) were augmented; meanwhile, the nicotinamide adenine dinucleotide (NAD) content was significantly reduced in the process of cardiac fibrosis in vivo and in vitro. Sprague-Dawley rats were intraperitoneally injected with 3-aminobenzamide (3AB) (20 mg/kg/d; a well-established Pduanyu371 inhibitor) or rapamycin (Rapa; 1 mg/kg/d; used for mTOR inhibition) 7 days after abdominal aortic constriction (AAC) surgery for 6 weeks. Pretreatment of 3AB or Rapa both relieved AAC-caused cardiac fibrosis and heart dysfunction. Overexpression of Pduanyu371 with adenovirus carrying Pduanyu371 gene specifically transduced into the hearts via intramyocardial multipoint injection caused similar myocardial damage. In CFs, preincubation with Pduanyu371 or mTOR inhibitors all blocked TGF-β1 induced cardiac fibrosis. Pduanyu371 overexpression evoked cardiac fibrosis, which could be antagonized by mTOR inhibitors or NAD supplementation in CFs. These results provide novel and compelling evidence that Pduanyu371 exacerbated cardiac fibrosis, which was partially attributed to NAD-dependent activation of mTOR.

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