Wnt5a-Induced Wnt1-Inducible Secreted Protein-1 Suppresses Vascular Smooth Muscle Cell Apoptosis Induced by Oxidative Stress

Abstract

Objective-Apoptosis of vascular smooth muscle cells (VSMCs) contributes to thinning and rupture of the atherosclerotic plaque fibrous cap and is thereby associated with myocardial infarction. Wnt protein activation of β-catenin regulates numerous genes that are associated with cell survival. We therefore investigated Wnt/β-catenin survival signaling in VSMCs and assessed the presence of this pathway in human atherosclerotic plaques at various stages of the disease process. Approach and Results-Wnt5a induced β-catenin/T-cell factor signaling and retarded oxidative stress (H 2 O 2 )-induced apoptosis in mouse aortic VSMCs. Quantification of mRNA levels revealed a >4-fold (P<0.05; n=9) increase in the expression of the Wnt/β-catenin responsive gene, Wnt1-inducible secreted protein-1 (WISP-1), which was dependent on cAMP response element-binding protein and sustained in the presence of H 2 O 2 . Exogenous WISP-1 significantly reduced H 2 O 2 -induced apoptosis by 43% (P<0.05; n=3) and was shown using silencing small interfering RNA, to be important for Wnt5a-dependent survival responses to H 2 O 2 (P<0.05; n=3). WISP-1 protein levels were significantly lower (≈50%) in unstable atherosclerosis compared with stable plaques (n=11 and n=14). Conclusions-These results indicate for the first time that Wnt5a induces β-catenin survival signaling in VSMCs viaWISP-1. The deficiency of the novel survival factor, WISP-1 in intimal VSMCs of unstable coronary plaques, suggests that there is altered Wnt/β-catenin/ T-cell factor signaling with progressive atherosclerosis, and restoration of WISP-1 protein might be an effective stabilization factor for vulnerable atherosclerotic plaques. Deregulated Wnt signaling is associated with many diseases including cancer 22 ; however, its involvement in atherosclerosis remains to be fully elucidated.It has been shown previously that Wnt5a is expressed in atherosclerotic plaques, predominantly in macrophages. 25,26 The effect of Wnt5a in atherosclerotic plaques, and its role as a survival factor for VSMCs, is however still to be determined. In this study, we investigated the effect of exogenous Wnt5a on canonical Wnt pathway activation in VSMCs and directly assessed the effect that Wnt5a had on VSMC survival under conditions of oxidative stress. We highlighted an association of Wnt1-inducible secreted protein-1 (WISP-1) expression with atherosclerotic plaque stability and propose that it is a distinct survival factor, which has potential as a plaque stabilizing protein. Materials and MethodsMaterials and Methods are available in the online-only Supplement. Results Activation of Wnt/β-Catenin Signaling in VSMCs by Wnt5aWnt5a protein was not detectable in mouse or human VSMC lysates or conditioned media but was readily detectable in macrophage lysates ( Figure IA and IB in the online-only Data Supplement). This was confirmed by quantitative polymerase chain reaction ( Figure IC in the online-only Data Supplement). Moreover, treatment with Wnt5a or H 2 O 2 did not induce expression of Wnt5a prot...

Reactive Oxygen Species Generation and Atherosclerosis

“…Interestingly, SMC in stable plaques in human coronary arteries showed higher staining for WISP-1 than those in unstable plaques. 79 Wnt2 also induced WISP-1 expression in SMC in β-catenin-dependent manner. 80 Levels of Wnt2 and WISP-1 were elevated in ligated carotid arteries.…”

“…78 Wnt/β-catenin/WISP-1 (WNT1-induciblesignaling pathway protein 1) represents example of the pathway that can protect SMCs from apoptosis 79 and oxidative stress but, on the other hand, enhance SMC migration and contribute to intimal thickening. 80 Mill et al 79 showed recently that macrophage-derived Wnt5a could protect SMC from H 2 O 2 -induced apoptosis. Exogenous Wnt5a increased amounts of active and nuclear β-catenin in SMC and induced TCF (transcription factor) signaling.…”

Atherosclerosis

“…Wnt/β-catenin responsive gene, Wnt1-inducible secreted protein-1 (WISP-1), was associated with suppression of mouse aortic SMC apoptosis induced by oxidative stress, and WISP-1 was lower in unstable, compared to stable, human atherosclerotic lesions. 90 Inhibition of Akt1 (the serine-threonine kinase) interaction with forkhead class O transcription factor 3a (FoxO3a) contributed to survival of vascular SMCs in vitro. 91 Transgenic mice with SMC-specific overexpression of Akt1 inhibited SMC apoptosis in atherosclerotic lesions without changing lesion size.…”

MicroRNA-129-5p inhibits vascular smooth muscle cell proliferation by targeting Wnt5a

“…Previous studies have indicated that several miRNAs play a role in vascular physiology, including miRNA-145, miRNA-21 and miRNA-221 (15,16). However, the mechanism of regulation of SMC function by miRNAs in AAA remains unknown.…”

“…The results of the present study identified that Wnt5a was a direct target gene of miR-129-5p. Previous reports demonstrated that Wnt5a-induced Wnt1-inducible secreted protein-1 suppresses vascular smooth muscle cell apoptosis induced by oxidative stress (16). Wnt5a is induced by TGF-β/Smad3 in rat aortic SMC and promotes its proliferation (17).…”