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Loss of FoxO3a prevents aortic aneurysm formation through maintenance of VSMC homeostasis.

ABSTRACT: Vascular smooth muscle cell (VSMC) phenotypic switching plays a critical role in the formation of abdominal aortic aneurysms (AAAs). FoxO3a is a key suppressor of VSMC homeostasis. We found that in human and animal AAA tissues, FoxO3a was upregulated, SM22α and α-smooth muscle actin (α-SMA) proteins were downregulated and synthetic phenotypic markers were upregulated, indicating that VSMC phenotypic switching occurred in these diseased tissues. In addition, in cultured VSMCs, significant enhancement of FoxO3a expression was found during angiotensin II (Ang II)-induced VSMC phenotypic switching. In vivo, FoxO3a overexpression in C57BL/6J mice treated with Ang II increased the formation of AAAs, whereas FoxO3a knockdown exerted an inhibitory effect on AAA formation in ApoE^-/- mice infused with Ang II. Mechanistically, FoxO3a overexpression significantly inhibited the expression of differentiated smooth muscle cell (SMC) markers, activated autophagy, the essential repressor of VSMC homeostasis, and promoted AAA formation. Our study revealed that FoxO3a promotes VSMC phenotypic switching to accelerate AAA formation through the P62/LC3BII autophagy signaling pathway and that therapeutic approaches that decrease FoxO3a expression may prevent AAA formation.

SUBMITTER: Lu W

PROVIDER: S-EPMC8027644 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Abdominal aortic aneurysm (AAA) is a dangerous vascular disease without any effective drug therapies so far. Emerging evidence suggests the phenotypic differences in perivascular adipose tissue (PVAT) between regions of the aorta are implicated in the development of atherosclerosis evidenced by the abdominal aorta more vulnerable to atherosclerosis than the thoracic aorta in large animals and humans. The prevalence of thoracic aortic aneurysms (TAA) is much less than that of abdominal aortic aneurysms (AAA). In this study we investigated the effect of thoracic PVAT (T-PVAT) transplantation on aortic aneurysm formation and the impact of T-PVAT on vascular smooth muscle cells. Calcium phosphate-induced mouse AAA model was established. T-PVAT (20 mg) was implanted around the abdominal aorta of recipient mice after removal of endogenous abdominal PVAT (A-PVAT) and calcium phosphate treatment. Mice were sacrificed two weeks after the surgery and the maximum external diameter of infrarenal aorta was measured. We found that T-PVAT displayed a more BAT-like phenotype than A-PVAT; transplantation of T-PVAT significantly attenuated calcium phosphate-induced abdominal aortic dilation and elastic degradation as compared to sham control or A-PVAT transplantation. In addition, T-PVAT transplantation largely preserved smooth muscle cell content in the abdominal aortic wall. Co-culture of T-PVAT with vascular smooth muscle cells (VSMCs) significantly inhibited H2O2- or TNFα plus cycloheximide-induced VSMC apoptosis. RNA sequencing analysis showed that T-PVAT was enriched by browning adipocytes and anti-apoptotic secretory proteins. We further verified that the secretome of mature adipocytes isolated from T-PVAT significantly inhibited H2O2- or TNFα plus cycloheximide-induced VSMC apoptosis. Using proteomic and bioinformatic analyses we identified cartilage oligomeric matrix protein (COMP) as a secreted protein significantly increased in T-PVAT. Recombinant COMP protein significantly inhibited VSMC apoptosis. We conclude that T-PVAT exerts anti-apoptosis effect on VSMCs and attenuates AAA formation, which is possibly attributed to the secretome of browning adipocytes.

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Loss of FoxO3a prevents aortic aneurysm formation through maintenance of VSMC homeostasis.

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