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Objective To investigate the effect and mechanism of CXC chemokine ligand 12 (CXCL12) on oxidized low density lipoprotein (ox-LDL)-induced foaming and apoptosis of macrophages. Methods RAW264.7 was incubated with 60 mg/L of ox-LDL to induce foaming of macrophages, which was recorded as ox-LDL group, and to compare with the control without ox-LDL; si-con and si-CXCL12 were transfected to RAW264.7 cells and thenincubated with ox-LDL at 60 mg/L as ox-LDL+si-con group and ox-LDL+si-CXCL12 group, respectively. Oil Red O staining was used to detect cellular foaming; Western blot was used to detect ABCA-1, SRB-1, cleaved caspase-3, cleaved caspase-9, CXCL12, p38 mitogen-activated protein kinase (p38MAPK), and phosphorylated p38MAPK (p-p38MAPK) protein expression; flow cytometry is used to detect apoptosis; CXCL12 mRNA expression was measured by real-time fluorescence quantitative PCR(RT-qPCR). Results The size of ox-LDL-treated macrophages increased, the shape became round, and a large number of red lipid droplets were found in the cytoplasm; the expression of ABCA-1 and SRB-1 and cleaved caspase-3 as well as cleaved caspase-9 were all significantly increased; the apoptosis rate and the expression of CXCL12 and p-p38MAPK were significantly increased(P＜0.05). Silencing CXCL12, no red-stained lipid droplets were found in most cells, only a few cells had partial lipid droplets, the expressions of ABCA-1 and SRB-1 were significantly reduced, and the expression of cleaved caspase-3 and cleaved caspase-9, apoptosis rate and the expression of p-p38MAPK significantly reduced(P＜0.05). Conclusions Silencing CXCL12 inhibits ox-LDL-induced foaming and apoptosis of mouse macrophage cell line RAW264.7, which may be related to the p38MAPK signaling pathway.

ABSTRACT: In this paper, the mechanical properties of gas hydrate-bearing sediments (GHBS) were summarized and the instability mechanism of submarine hydrate-bearing slope (SHBS) was analyzed under the background of the test production of gas hydrate in the northern part of the South China Sea. The strength reduction finite element method (SRFEM) was introduced to the stability analysis of submarine slopes for the safety of the test production. Two schemes were designed to determine the physical and mechanical parameters of four target wells. Through the division of the hydrate dissociation region and the design of four working conditions, the range and degree of hydrate dissociation at different stages during the test production were simulated. Based on the software ABAQUS, 37 FEM models of SHBS were set up to analyze and assess the stability of the submarine slopes in the area of the test production. Necessary information such as safety factors, deformation, and displacement were obtained at different stages and under different working conditions. According to the calculation results, the submarine slope area is stable before the test production, and the safety factors almost remains the same during and after the test production. All these indicate that the test production has no obvious influence on the area of the test production and the submarine slopes in the area are stable during and after the test production.