SMAD3 and atrial fibrillation: Finally, PARP-1, being involved in regulating the TGF-β signaling pathway by promoting TGF-β1-induced Smad3 transactivation and expression of Smad3 target genes, such as collagen Iα1, collagen IIIα1 [13, 25] was also significantly up-regulated females, but not males with LSP-AF.