Compound 21 (C21), a Selective Angiotensin Type 2 (AT2) Receptor Agonist Attenuates Bleomycin induced Alveolar Epithelial Cell Death

Abstract

BackgroundIdiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by excessive deposition of collagen‐rich matrix, which progressively leads to respiratory failure and death. Patients with IPF have a reduced survival rate and the disease remains refractory to current therapies. Hence, identifying novel targets and developing effective drugs are of paramount importance. Accumulating evidence indicate that death of alveolar epithelial cells (AEC) is a key event for the initiation of IPF. Bleomycin, a well‐known fibrotic agent is a potent inducer of apoptotic cell death in AEC through synthesis of Angiotensin II (Ang II). While the apoptotic actions of Ang II on AEC are mediated via the angiotensin type 1 (AT1) receptor, the functional role of angiotensin type 2 (AT2) receptor in AEC has not yet been characterized. We hypothesized that stimulation of the angiotensin type 2 (AT2) receptor by a non‐peptide agonist, Compound 21 (C21) protects against bleomycin‐induced alveolar epithelial cell death.MethodsIn this study, we investigated the effects of C21, the selective AT2 receptor agonist against bleomycin‐induced death of human pulmonary alveolar epithelial cells (A549). The MTT (3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide) assay was performed to determine cell viability of A549.ResultsWe first determined the concentration of bleomycin required for the induction of cell death in cultured A549 cells. A dose‐dependent induction of cell death was obtained with different concentration of bleomycin (μg/mL: % cell death; 1: 30%; 10:42% and 20:61%). Since we observed optimal cell death with 10 μg/mL concentration of bleomycin, we selected this dose for subsequent experiments. Next, we evaluated the cell‐protective effects of C21 at different drug doses (0.001, 0.005, 0.01, 0.05 and 0.1 μM). C21 treatment of bleomycin‐challenged A549 cells (10 μg/mL) produced a dose‐dependent decrease in cell death (μM: % cell death; 0.001:31%; 0.005:29%; 0.01:16%; 0.05:14% and 0.1:9%) as analyzed by the MTT assay. We also observed that treatment of control A549 cells with the above mentioned doses of C21 had little effect on cell proliferation or cell death.ConclusionOur results suggest that C21, the selective AT2 receptor agonist protects against bleomycin‐induced alveolar epithelial cell death. Further studies are warranted to elucidate the mechanisms underlying the cytoprotective effects of C21.Support or Funding InformationAmerican Heart Association Grant (SDG12080302) awarded to Vinayak ShenoyStart‐up Grant from California Health Sciences UniversityThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.