Effects of reduced β(2)-glycoprotein I on the expression of aortic matrix metalloproteinases and tissue inhibitor matrix metalloproteinases in diabetic mice

BACKGROUND: Reduced β(2)-glycoprotein I (reduced β(2)GP I), which has free sulfhydryl groups, is present in plasma and serum; it can protect vascular endothelial cells from damage due to oxidative stress in vitro. We investigated the effects of reduced β(2)GP I on the expression of various matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in the aortas of diabetic mice. METHODS: We provided 120 female 8-week-old Balb/c mice with a high sugar, high fat diet. After 8 weeks they were injected with streptozotocin to induce diabetes. We treated mice in the mono dose groups with β(2)GP I, reduced β(2)GP I, or phosphate-buffered saline (PBS) on day 1 and fed them for 3 weeks. The mice in the complex dose groups were treated with β(2)GP I, reduced β(2)GP I, or PBS on days 1 and 22 and fed for 6 weeks. Control mice were given a standard chow diet. Blood lipids were measured at the end of 3 or 6 weeks, and aortas removed to observe morphological and molecular biological changes. RESULTS: The low-density lipoprotein cholesterol levels in mice of the reduced β(2)GP I group were lower than those in the diabetic group. Aortic lipid deposition in the reduced β(2)GP I group was significantly less than in the diabetic control group. In the aortas, reduced β(2)GP I decreased MMP2/TIMP2 mRNA and protein expression levels, and MMP9/TIMP1 expression levels compared with those in diabetic controls. Reduced β(2)GP I down-regulated p38 mitogen-activated protein kinase (p38MAPK) mRNA expression and phosphorylated p38MAPK protein expression compared with those in diabetic controls of the complex dose group. CONCLUSIONS: Reduced β(2)GP I plays a role in diabetic mice related to vascular protection, inhibiting vascular lipid deposition, and plaque formation by reducing MMPs/TIMPs expression through down-regulation of the p38MAPK signaling pathway.