Palmitic acid dysregulates the Hippo–YAP pathway and inhibits angiogenesis by inducing mitochondrial damage and activating the cytosolic DNA sensor cGAS–STING–IRF3 signaling mechanism

Yun Mao,Hao Xu,Wei Luo,Ying H. Shen,Xing Li Wang,Weiwei Wu,Liangshuai Yuan

doi:10.1074/jbc.m117.804005

Abstract

Impaired angiogenesis and wound healing carry significant morbidity and mortality in diabetic patients. Metabolic stress from hyperglycemia and elevated free fatty acids have been shown to inhibit endothelial angiogenesis. However, the underlying mechanisms remain poorly understood. In this study, we show that dysregulation of the Hippo-Yes-associated protein (YAP) pathway, an important signaling mechanism in regulating tissue repair and regeneration, underlies palmitic acid (PA)-induced inhibition of endothelial angiogenesis. PA inhibited endothelial cell proliferation, migration, and tube formation, which were associated with increased expression of mammalian Ste20-like kinases 1 (MST1), YAP phosphorylation/inactivation, and nuclear exclusion. Overexpression of YAP or knockdown of MST1 prevented PA-induced inhibition of angiogenesis. When searching upstream signaling mechanisms, we found that PA dysregulated the Hippo-YAP pathway by inducing mitochondrial damage. PA treatment induced mitochondrial DNA (mtDNA) release to cytosol, and activated cytosolic DNA sensor cGAS-STING-IRF3 signaling. Activated IRF3 bound to the MST1 gene promoter and induced MST1 expression, leading to MST1 up-regulation, YAP inactivation, and angiogenesis inhibition. Thus, mitochondrial damage and cytosolic DNA sensor cGAS-STING-IRF3 signaling are critically involved in PA-induced Hippo-YAP dysregulation and angiogenesis suppression. This mechanism may have implication in impairment of angiogenesis and wound healing in diabetes.

Highlights

Impaired angiogenesis and wound healing carry significant morbidity and mortality in diabetic patients
We show that dysregulation of the Hippo–Yes-associated protein (YAP) pathway, an important signaling mechanism in regulating tissue repair and regeneration, underlies palmitic acid (PA)induced inhibition of endothelial angiogenesis
Knocking down synthase (cGAS)–interferon genes protein (STING) and IRF3 prevented PA-induced mammalian Ste20-like kinases 1 (MST1) expression and YAP phosphorylation (Fig. 5B), and YAP cytosolic retention (Fig. 5C). These results indicate that the cyclic GMP-AMP synthase (cGAS)–STING–IRF3 pathway is critical to PA-induced MST1 up-regulation and YAP inhibition in endothelial cells

Summary

Results

To examine the effects of metabolic stress on endothelial angiogenesis, we treated human aortic endothelial cells (HAECs) with PA, the main type of free fatty acid in metabolic syndrome [24]. Silencing cGAS (supplemental Fig. S2C) with siRNA inhibited PA-induced IRF3 phosphorylation, MST1 expression, and YAP phosphorylation (Fig. 5A), suggesting the involvement of cGAS in STING–IRF3 activation and Hippo–Yap dysregulation. Knocking down STING and IRF3 (supplemental Fig. S2, E and F) prevented PA-induced MST1 expression and YAP phosphorylation (Fig. 5B), and YAP cytosolic retention (Fig. 5C) These results indicate that the cGAS–STING–IRF3 pathway is critical to PA-induced MST1 up-regulation and YAP inhibition in endothelial cells. Knocking down cGAS, STING, and IRF3 improved endothelial tube formation and reversed PAinduced impairment of endothelial angiogenesis (Fig. 7C) Together, these findings suggest a critical role of the cGAS– STING–IRF3 pathway in PA-induced inhibition of endothelial proliferation and angiogenesis

Discussion

Conclusions

Experimental procedures