Transgenic Overexpression Of IL-37 Protects Against Atherosclerosis And Strengthens Plaque Stability

Background/Aims: Inflammation processes promote atheroscleosis characterized by the generation and release of various inflammatory cytokines.Recently,studies have shown that interleukin-37(IL-37)is involved in many inflammatory and atherosclerosis-related diseases.However,the regulatory mechanisms of IL-37 in atherosclerosis remain unknown.This study aims to determine the role of IL-37 in atherosclerosis and to investigate the underlying mechanisms involved.Methods: This study will be verified by the following studies: 1.Examine the expression of IL-37 in human atherosclerotic plaque;2.Study the effect of IL-37 overexpression in mice in atherosclerosis;3.Assess the signaling pathway of IL-37 in mouse atherosclerosis and study the underlying mechanisms involved.IL-37 expression in human atherosclerotic plaques was detected by immunohistochemical staining and real-time reverse transcription polymerase chain reaction(RT-PCR).The role of IL-37 in atherosclerosis was determined by transgenic overexpression of IL-37 in mice.Oil Red O staining was used to measure the size of plaques.Protein expression levels of IL-37,IL-18R? and p-Smad3 were measured by Western blot.Genetic deficiency of smad3 or neutralization of IL-18R? was used to study the mechanisms.Cell apoptosis in vitro and in vivo was measured by flow cytometric analysis and terminal deoxynucleotidyl-transferase mediated d UTP nick-end labeling(TUNEL)staining,respectively.Flow cytometry was used to test the immune cells in spleen and the plaque of vessel.ELISA was used to test the expression of IL-37 mouse circulation and cytokines in culture supernatant.Results: Immunohistochemical staining revealed that IL-37 was highly expressed in human atherosclerotic plaques.Intracellular cytokine staining revealed that infiltrated CD4+ T lymphocytes and vascular smooth muscle cells(VSMCs),but not macrophages,were the major sources of IL-37.Mice that overexpressed IL-37 exhibited significant improvements in their atherosclerotic burden,as demonstrated by reduced plaque size,increased collagen levels,and reduced numbers of apoptotic cells in vivo.Subsequently,mechanistic studies showed that IL-37 played an anti-atherosclerotic role,at least partially,by reducing inflammation through promoting the differentiation of the T helper cell anti-inflammatory phenotype.Also,IL-37 increased plaque stability by decreasing matrix metalloproteinase(MMP)-2/13-mediated degradation of collagen and inhibiting VSMCs apoptosis.Conclusion: Transgenic overexpression of IL-37 protects against atherosclerosis and strengthens plaque stability by promoting the Th2 differentiation,decreasing MMP-2/13-mediated degradation of collagen,and inhibiting VSMCs apoptosis.