Smooth muscle-specific LKB1 deletion exaggerates angiotensin II-induced abdominal aortic aneurysm in mice

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease without an effective pharmaceutical treatment. Liver kinase B1 (LKB1), a tumor suppressor, is a central regulator of cell polarity and energy homeostasis. However, the role of LKB1 in the development of AAA has not been explored. In this study, mice with knockout of smooth muscle-specific LKB1 (LKB1^SMKO) were generated by cross-breeding LKB1^flox/flox mice with SM22-CreER^T2 transgenic mice and induced in adult mice by tamoxifen treatment. LKB1 deficiency increased the expression of matrix metalloproteinase 2 (MMP-2), which was inhibited by LKB1 overexpression. Mechanistically, LKB1 could bind to the MMP-2 transcription factor, specificity protein 1 (Sp1), thereby reducing the binding of Sp1 to the MMP-2 promoter to inhibit MMP-2 expression. LKB1 expression was significantly reduced in abdominal aortas of the mouse AAA model. Moreover, smooth muscle-specific LKB1 deletion exaggerated angiotensin II-induced AAA formation accompanied by increased AAA incidence and aortic expansion. Finally, LKB1 level was significantly lower and MMP-2 level higher in human AAA samples than adjacent nonaneurysmal aortic sections. Thus, these results suggest that LKB1 may play a protective role in AAA formation by inhibiting MMP-2 expression and could be a potential therapeutic target for AAA disease.