P38 MAPK Signaling Pathway Mediates Angiotensin II-Induced miR143/145 Gene Cluster Downregulation during Aortic Dissection Formation

Background: We endeavored to prove that angiotensin II (Ang II) regulates both the expression of micro-RNA143/145 (miR143/145) and differentiation of vascular smooth muscle cells (VSMCs) during the formation of aortic dissection (AD). We also studied the contribution of p38 mitogen-activated protein kinase (MAPK) signaling pathway toward this process. Methods: Ascending aortic tissues were harvested from the patients with AD and organ donors. Tissues were immunostained with labeled antibodies targeting p38 MAPK, phospho-p38 MAPK, alpha-smooth muscle actin (alpha-SMA), and osteopontin (OPN). Next, we treated mouse aortic VSMCs with different regimens of Ang II (duration and dosages) in vitro and determined expression levels of miR143/145 and VSMC phenotype marker proteins (alpha-SMA and OPN) by quantitative polymerase chain reaction and/or western blotting. SB203580 was used to inhibit the p38 MAPK signaling pathway. Finally, the VSMC phenotype was validated by immunofluorescence microscopy. Results: Expression of phospho-p38 MAPK was significantly greater in the AD tissue. Ang II induced the phenotypic switching of VSMCs along with the downregulation of an miR143/145 gene cluster. Expression of OPN and phospho-p38 was significantly increased in VSMCs treated with 0.1 1.1.M Ang II for 12 hr. Furthermore, the expression of miR143 and miR145 was downregulated by Ang II treatment. When the p38 MAPK signaling pathway was blocked by pretreatment with an SB203580 inhibitor, the expression of miR143, miR145, and VSMC phenotypic markers was not affected by Ang II. Immunohistochemical staining of aortic tissues donated by AD patients and healthy donors showed that the expression of alpha-SMA decreased in pathological tissue, while the OPN increased and the arrangement of the smooth muscle cells of the media was dysregulated, which we verified in vitro. Conclusions: Ang II could regulate the expression of miR143/145 gene cluster and the phenotypic switching of VSMCs via the p38 MAPK signaling pathway. This may play an important role in the pathogenesis of AD.