The Effects of Retinoic Acid and MAPK Inhibitors on Phosphorylation of Smad2/3 Induced by Transforming Growth Factor β1

• Main Authors: Sang Hoon Lee, M.D., Ju Hye Shin, M.S., Mi Hwa Shin, B.S., Young Sam Kim, M.D., Ph.D., Kyung Soo Chung, M.D., Joo Han Song, M.D., Song Yee Kim, M.D., Ph.D., Eun Young Kim, M.D., Ph.D., Ji Ye Jung, M.D., Ph.D., Young Ae Kang, M.D., Ph.D., Joon Chang, M.D., Ph.D., Moo Suk Park, M.D., Ph.D.
• Format: Article
• Language: English
• Published: The Korean Academy of Tuberculosis and Respiratory Diseases 2019-01-01
• Series: Tuberculosis and Respiratory Diseases
• Subjects: transforming growth factor beta; retinoic acid; mitogen-activated protein kinases; meks; smad proteins
• Online Access: https://www.e-trd.org/search.php?where=aview&id=10.4046/trd.2017.0111&code=0003TRD&vmode=FULL
• ISSN: 1738-3536; 2005-6184

Background Transforming growth factor β (TGF-β), retinoic acid (RA), p38 mitogen-activated protein kinase (MAPK), and MEK signaling play critical roles in cell differentiation, proliferation, and apoptosis. We investigated the effect of RA and the role of these signaling molecules on the phosphorylation of Smad2/3 (p-Smad2/3) induced by TGF-β1. Methods A549 epithelial cells and CCD-11Lu fibroblasts were incubated and stimulated with or without all-trans RA (ATRA) and TGF-β1 and with MAPK or MEK inhibitors. The levels of p-Smad2/3 were analyzed by western blotting. For animal models, we studied three experimental mouse groups: control, bleomycin, and bleomycin+ATRA group. Changes in histopathology, lung injury score, and levels of TGF-β1 and Smad3 were evaluated at 1 and 3 weeks. Results When A549 cells were pre-stimulated with TGF-β1 prior to RA treatment, RA completely inhibited the p-Smad2/3. However, when A549 cells were pre-treated with RA prior to TGF-β1 stimulation, RA did not completely suppress the p-Smad2/3. When A549 cells were pre-treated with MAPK inhibitor, TGF-β1 failed to phosphorylate Smad2/3. In fibroblasts, p38 MAPK inhibitor suppressed TGF-β1-induced p-Smad2. In a bleomycin-induced lung injury mouse model, RA decreased the expression of TGF-β1 and Smad3 at 1 and 3 weeks. Conclusion RA had inhibitory effects on the phosphorylation of Smad induced by TGF-β1 in vitro, and RA also decreased the expression of TGF-β1 at 1 and 3 weeks in vivo. Furthermore, pre-treatment with a MAPK inhibitor showed a preventative effect on TGF-β1/Smad phosphorylation in epithelial cells. As a result, a combination of RA and MAPK inhibitors may suppress the TGF-β1-induced lung injury and fibrosis.