Background: Androgen deficiency produces heart failure, which can be ameliorated by testosterone supplementation. Cardiac fibrosis plays a critical role in the pathophysiology of heart failure. This study aimed to evaluate whether testosterone can attenuate cardiac fibroblast activity through modulating transforming growth factor (TGF)-β and angiotensin (Ang) II signaling. Methods:Migration, proliferation, myofibroblast differentiation, collagen production, and transcription signaling were evaluated in adult male rat (weighing 300-350 g) cardiac fibroblasts with and without incubation with testosterone (10 nM) and co-administration of TGF-β1 (10 ng/ml) or Ang II (100 nM) by cell migration analysis, proliferation assay, soluble collagenmeasurement, zymographic analysis, immunofluorescence microscopy, realtime PCR and Western blot. Results: Compared to thosewithout testosterone, testosterone-treated fibroblasts exhibited less collagen production. Testosterone-treated fibroblasts also had less migration, proliferation, myofibroblast differentiation, and collagen production in the presence of TGF-β1, or had less collagen production with Ang II. Testosteronetreated fibroblasts had decreased phosphorylated Akt, mammalian target of rapamycin, and 4E binding protein-1 irrespective of TGF-β1 treatment and had increased matrix metalloproteinase (MMP)-2 in the presence of TGF-β1 treatment, and had decreased phosphorylated P38 and Smad 2/3 levels in the presence of Ang II. Cardiac fibroblasts with and without testosterone had similar mRNA and protein expressions of total Akt and total Smad 2/3 irrespective of TGF-β1 or Ang II treatment. Conclusion: Physiological level of testosterone attenuated Akt and Smad 2/3 phosphorylation mediated by TGF- β1 and angiotensin II respectively, which can result in decreased cardiac fibroblast activation and potentially contribute to beneficial effects in heart failure.
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