Anti-fibrotic mechanisms of angiotensin AT2 -receptor stimulation.

The angiotensin AT2 -receptor is a main receptor of the protective arm of the renin-angiotensin system. Understanding of this unconventional G-protein coupled receptor has significantly advanced during the past decade, largely because of the availability of a selective non-peptide AT2 -receptor agonist, which allowed the conduct of a multitude of studies in animal disease models. This article reviews such preclinical studies that in their entirety provide strong evidence for an anti-fibrotic effect mediated by activation of the AT2 -receptor. Prevention of the development of fibrosis by AT2 -receptor stimulation has been demonstrated in lungs, heart, blood vessels, kidney, pancreas and skin. In lungs, AT2 -receptor stimulation was even able to reverse existing fibrosis. The article further discusses intracellular signalling mechanisms mediating the AT2 -receptor-coupled anti-fibrotic effect, including activation of phosphatases and subsequent interference with pro-fibrotic signalling pathways, induction of matrix-metalloproteinases and hetero-dimerization with the AT1 -receptor, the TGF-βRII-receptor or the RXFP1-receptor for relaxin. Knowledge of the anti-fibrotic effects of the AT2 -receptor is of particular relevance because drugs targeting this receptor have entered clinical development for indications involving fibrotic diseases.