Angiotensin II-mediated collagen production is inhibited by a transforming growth factor-beta receptor kinase inhibitor

Introduction. The purpose of this experiment is to determine if the pro-fibrotic effect of angiotensin II (AII) is mediated through a transforming growth factor-beta (TGF-beta) receptor kinase. Methods. Neonatal rat heart fibroblast were cultured and incubated with SB 431542 (an inhibitor of TGF-beta receptor kinase activity) or vehicle. Recombinant human TGF-beta or AII was then added to the cardiac fibroblasts, and cells were incubated for 48 h under the experimental conditions. The cells were then fixed and stained with Sirius red collagen stain. Sirius red was extracted and quantified by absorbance at 540 nm. Five replicates were performed in each group and compared using the unpaired Student’s t-test. Results. Addition of SB 431542 to cells treated with TGF-beta showed an absorbance of 0.14 ± 0.01 (mean ± SE) compared to treatment with TGF-beta alone which showed an absorbance of 0.19 ± 0.01 representing a 26% reduction in total collagen (P = 0.03). Cells treated with SB 431542 and AII showed an absorbance of 0.105 ± 0.004, while cells treated with AII alone showed an absorbance of 0.147 ± 0.008 representing a 28% reduction in total collagen (P < 0.01). Conclusion. Angiotensin II induced collagen production is mediated through a TGF-beta receptor kinase in neonatal rat heart fibroblasts. The TGF-beta receptor kinase-mediated effect of AII may be responsible for the increased fibrosis seen in the myocardium of patients with congestive heart failure and may provide a target for therapeutic intervention.