IL-37 reduces calcification by inhibiting the oxidized low-density lipoprotein(ox-LDL)-induced toll-like receptor(TLR)/nuclear factor kappa-B(NF-κB) signaling pathway and suppressing cellular osteogenic transformation in smooth muscle cells

[Objective] Cardiovascular disease (CVD) is one of the leading causes of high mortality worldwide, and vascular calcification (VC) increases the incidence of adverse prognostic events and mortality in CVD. Osteogenic transformation of vascular smooth muscle cells (VSMCs) and induction of inflammation could be among the mechanisms of VC. Interleukin 37 (IL-37) is an anti-inflammatory factor that protects against atherosclerosis (AS) and VC by unknown mechanisms. Thus, the present study aimed to investigate the effect and mechanism of IL-37 on calcification in human aortic smooth muscle cells (HASMCs). [Methods] The human aortic smooth muscle cells (HA-SMC) were purchased from CTCC (Meisen, China), Alizarin red S staining was used to measure the degree of cell calcification, flow cytometry measured the level of apoptosis, cell counting kit-8 (CCK-8) measured the cell proliferation activity, and qPCR was used to measure the expression of toll-like receptor(TLR4),nuclear factor kappa-B( NF-κB), Runt-related Transcription Factor 2(RUNX2), Smooth muscle actin(SMA), smooth muscle 22 alpha (SM22α), Msh homeobox 2(MSX2)、Osteocalcin(OC) and alkaline phosphatase (ALP). Western blot measured the level of TLR4, NF-κB, RUNX2, and phosphorylated NF-κB(PP65), and immunofluorescence was used to detect the expression and location of SM22α.Differences were analyzed via Student’s t test or one-way analysis of variance [Results] Ox-LDL induction caused HA-SMC calcification and promoted HA-SMC apoptosis and value addition. After IL-37 intervention, calcification was significantly reduced, TLR4/NF-κB/RUNX2 expression activated by ox-LDL was decreased, and cell proliferation activity was inhibited, apoptosis rate was decreased, and PP65 expression was downregulated. IL-37 inhibited P65phosphorylation by inhibiting TLR. Down-regulation of osteogenesis-related factor expression plays a protective role against cellular calcification. [Conclusion] The current data demonstrated that IL-37 inhibits NF-κB phosphorylation by downregulating the ox-LDL-activated TLR4-NF-κ Bsignaling pathway, reduces the expression of the osteogenic transcription factor RUNX2/ALP, and inhibits VSMC osteogenic transformation, thereby reducing the level of cellular calcification. These findings provided a basis for the use of IL-37 as a novel therapeutic target.