Inhibition of PARP prevents angiotensin II-induced aortic fibrosis in rats

Background: Fibrosis is one of the major pathological features of hypertensive vascular disease. In this study, we aim to explore the possible protective effects of poly(ADP-ribose) polymerase (PARP) inhibitor on angiotensin II (AngII)-induced aortic fibrosis. Methods: Sprague-Dawley rats were infused subcutaneously with AngII. PARP inhibitor was intraperitoneally injected once a day. Collagen deposition in thoracic aorta was assayed by Masson tricrome staining. The mRNA and protein expression of TGF-β target genes involved in extracellular matrix (ECM) remodeling in aorta was measured. Plasma level and aortic expression of TGF-β1 was assayed. Correlation of systolic blood pressure (SBP) with plasma level of TGF-β1 was analyzed. In cultured rat vascular smooth muscle cells (VSMCs), effects of PARP inhibition on TGF-β1 expression, Smad3 transactivity, and TGF-β/Smad3 target gene expression were investigated. Results: Infusion of AngII promoted aortic PARP activation. Treatment with PARP inhibitor alleviated AngII-induced collagen deposition and expression of TGF-β target genes involved in ECM remodeling in aorta of rat. AngII increased plasma level and aortic expression of TGF-β1. A positive correlation between SBP and plasma level of TGF-β1 was revealed. Treatment with PARP inhibitor prevented AngII-induced elevation of SBP. Further experiments uncovered that AngII treatment increased TGF-β dependent gene expression through Smad3 pathway in cultured VSMCs. Inhibition of PARP prevented AngII-induced increases in TGF-β1 expression, Smad3 transactivity and its target gene expression. Conclusions: These data indicate that inhibition of PARP prevents aortic fibrosis in AngII-induced hypertension in rats. This beneficial effect is mediated by inhibiting TGF-β/Smad3 pathway.