YKL-40 Aggravates Early-Stage Atherosclerosis by Inhibiting Macrophage Apoptosis in an Aven-dependent Way
Huan Wei, Yandong Liu, Chao Wang, Zou Sili, Bai Jun, Liao MingFang, Yu Chen, Lefeng Qu
Abstract
Objective: programmed cell removal in atherosclerotic plaques plays a crucial role in retarding lesion progression. Macrophage apoptosis has a critical role in PrCR, especially in early-stage lesions. YKL-40 has been shown to be elevated as lesions develop and is closely related to macrophages. This study aimed to determine the effect of YKL-40 on regulating macrophage apoptosis and early-stage atherosclerosis progression. Research design and Methods: The correlations among the expression level of YKL-40, the area of early-stage plaque, and the macrophage apoptosis rate in plaques have been shown in human carotid atherosclerotic plaques through pathological and molecular biological detection. These results were successively confirmed in vivo ( Ldlr −/- mice treated by YKL-40 recombinant protein/neutralizing antibody) and in vitro (macrophages that Ykl40 up-/down-expressed) experiments. The downstream targets were predicted by iTRAQ analysis. Results: In early-stage human carotid plaques and murine plaques, the YKL-40 expression level had a significant positive correlation with the area of the lesion and a significant negative correlation with the macrophage apoptosis rate. In vivo , the plaque area of aortic roots was significantly larger in the recomb-YKL-40 group than that in IgG group ( p = 0.0247) and was significantly smaller in the anti-YKL-40 group than in the IgG group ( p = 0.0067); the macrophage apoptosis rate of the plaque in aortic roots was significantly lower in the recomb-YKL-40 group than that in IgG group ( p = 0.0018) and was higher in anti-YKL-40 group than that in VC group. In vitro , the activation level of caspase-9 was significantly lower in RAW264.7 with Ykl40 overexpressed than that in controls ( p = 0.0054), while the expression level of Aven was significantly higher than that in controls ( p = 0.0031). The apoptosis rate of RAW264.7 treated by recomb-YKL40 was significantly higher in the Aven down-regulated group than that in the control group ( p < 0.001). The apoptosis inhibitor Aven was confirmed as the target molecule of YKL-40. Mechanistically, YKL-40 could inhibit macrophage apoptosis by upregulating Aven to suppress the activation of caspase-9. Conclusion: YKL-40 inhibits macrophage apoptosis by upregulating the apoptosis inhibitor Aven to suppress the activation of caspase-9, which may impede normal PrCR and promote substantial accumulation in early-stage plaques, thereby leading to the progression of atherosclerosis.