Caspase-3 Deletion Promotes Necrosis in Atherosclerotic Plaques of ApoE Knockout Mice.

Mandy O J Grootaert,Guido R Y De Meyer,Wim Martinet,Marthe Hermans,Dorien M Schrijvers,Viviane O Van Hoof

doi:10.1155/2016/3087469

Abstract

Apoptosis of macrophages and vascular smooth muscle cells (VSMCs) in advanced atherosclerotic plaques contributes to plaque progression and instability. Caspase-3, a key executioner protease in the apoptotic pathway, has been identified in human and mouse atherosclerotic plaques but its role in atherogenesis is not fully explored. We therefore investigated the impact of caspase-3 deletion on atherosclerosis by crossbreeding caspase-3 knockout (Casp3−/−) mice with apolipoprotein E knockout (ApoE−/−) mice. Bone marrow-derived macrophages and VSMCs isolated from Casp3−/−ApoE−/− mice were resistant to apoptosis but showed increased susceptibility to necrosis. However, caspase-3 deficiency did not sensitize cells to undergo RIP1-dependent necroptosis. To study the effect on atherosclerotic plaque development, Casp3+/+ApoE−/− and Casp3−/−ApoE−/− mice were fed a western-type diet for 16 weeks. Though total plasma cholesterol, triglycerides, and LDL cholesterol levels were not altered, both the plaque size and percentage necrosis were significantly increased in the aortic root of Casp3−/−ApoE−/− mice as compared to Casp3+/+ApoE−/− mice. Macrophage content was significantly decreased in plaques of Casp3−/−ApoE−/− mice as compared to controls, while collagen content and VSMC content were not changed. To conclude, deletion of caspase-3 promotes plaque growth and plaque necrosis in ApoE−/− mice, indicating that this antiapoptotic strategy is unfavorable to improve atherosclerotic plaque stability.

Highlights

Apoptosis is a programmed form of cell death that occurs in all major cell types of atherosclerotic plaques where it is implicated in the development and progression of the disease [1,2,3]
Because previous studies have identified cleaved caspase-3 in both human [28] and mouse [29] atherosclerotic plaques, where it colocalizes with dead macrophages and lipid-rich plaque components [30], we aimed to investigate the impact of caspase-3 deletion on atherogenesis by crossbreeding caspase-3 knockout (Casp3−/−) mice with ApoE knockout (ApoE−/−) mice
Western blot analysis confirmed the absence of cleaved caspase-3 in Casp3−/−ApoE−/− Bone marrow-derived macrophages (BMDM) and Casp3−/−ApoE−/− vascular smooth muscle cells (VSMCs) in both untreated and treated conditions (Figure 1(a))

Summary

Introduction

Apoptosis is a programmed form of cell death that occurs in all major cell types of atherosclerotic plaques where it is implicated in the development and progression of the disease [1,2,3]. The apoptotic process is governed by cysteine aspartate specific proteases, termed caspases, that progressively disassemble the dying cell by the selective cleavage of cellular substrates involved in cytoskeleton reorganization and nuclear degradation [6]. In this way, apoptosis is characterized by cellular shrinkage, chromatin condensation, membrane blebbing, and internucleosomal DNA fragmentation [7]. Because the phagocytic clearance of apoptotic cells is impaired in advanced plaques, apoptotic bodies accumulate and undergo secondary necrosis [14, Oxidative Medicine and Cellular Longevity

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