Long noncoding RNA Sngh20 promotes vascular smooth muscle cell senescence and abdominal aortic aneurysm growth by interacting with dead-box helicase 5

Abstract Background Development of non-surgical treatment of human abdominal aortic aneurysm (AAA) has clinical significance. Long noncoding RNAs (lncRNAs) are emerging as powerful mediators participated in cellular senescence process that a critical pathological alteration prompting AAA development. Purpose To investigate the role and underlying mechanism of lncRNA Small nucleolar RNA host gene-20 (Snhg20) in AAA formation. Methods Experimental AAA mice models were produced by peri-aortic CaPO4 injury in C57bl/6J mice or Subcutaneousangiotensin-II (Ang-II) infusion in Apoe–/– mice and gapmeR was used to knockdown Snhg20 expression. Adeno-associated virus and anti-IL-6 monoclonal antibody was used to knockdown dead-box helicase 5 (DDX5) and neutralize IL-6, respectively.Immunohistochemical and immunofluorescent staining, ELISA and real-time PCR were performed to determine the vascular structure and inflammation, cellular senescence and senescence-associated secretory phenotype (SASP) content in human and mouse AAA lesions. Human aortic SMC cell line was used to investigate the effect of Snhg20 knockdown on senescence and SASP in vitro. LncRNA pulldown and mass spectrometry were used to identify potential targets that interact with Snhg20. p53 DNA binding affinity was examined by EMSA. Results The expression of Snhg20 was downregulated in both human and mice AAA lesion. Snhg20 knockdown promoted SMC senescence and loss, vascular inflammation and AAA growth in both experimental AAA mice models. Mechanistically, Snhg20 interacted with DDX5, an important transcriptional coactivator of p53. The absence of snhg20 increased DDX5 and p53 interaction and thereby promoted p53 DNA binding affinity to transcriptionally initiate p21expression, resulting in increased cellular senescence and senescence-associated secretory phenotype (SASP) secretion, including IL-6. Moreover, DDX5 silencing or anti-IL-6 therapy rescued the SMC senescence and loss, vascular inflammation and AAA growth mediated by Snhg20 knockdown. Furthermore, human AAA lesions showed increased DDX5 co-localization with p53 and abundant senescent vascular SMC. Conclusion These findings identify an important role of Snhg20 in controlling vascular SMC senescence and SPAP expression and suggest that Snhg20 is a potential target for AAA treatment aimed at reducing VSMCs senescence.Schematic summary