Division of Endocrinology, Diabetes and Medical Genetics, Department of Medicine, College of Medicine, Medical University of South Carolina, Charleston, SC, USA.
Immunology. 2013 Nov;140(3):301-13. doi: 10.1111/imm.12138.
We reported recently that treatment of diabetic apolipoprotein E-deficient mice with the Toll-like receptor 4 (TLR4) antagonist Rs-LPS, a lipopolysaccharide isolated from Rhodobacter sphaeroides, inhibited atherosclerosis. Since it is known that Rs-LPS antagonizes TLR4 by targeting TLR4 co-receptor MD-2, this finding indicates that MD-2 is a potential target for the treatment of atherosclerosis. In this study, we determined if MD-2 is involved in the gene expression regulated by signalling pathways independent of TLR4. Given that interferon-γ (IFNγ) and hyperglycaemia play key roles in atherosclerosis, we determined if MD-2 is involved in IFN-γ and high-glucose-regulated gene expression in mononuclear cells. Results showed that IFN-γ and high glucose synergistically stimulated matrix metalloproteinase 1 (MMP-1), a proteinase essential for vascular tissue remodelling and atherosclerosis, in U937 mononuclear cells, but Rs-LPS inhibited the MMP-1 stimulation. To provide more evidence for a role of MD-2 in IFN-γ-stimulated MMP-1, studies using antibodies and small interfering RNA demonstrated that MD-2 blockade or knockdown attenuated the effect of IFN-γ on MMP-1. Furthermore, studies using PCR arrays showed that MD-2 blockade had a similar effect as IFN-γ receptor blockade on the inhibition of IFN-γ-stimulated pro-inflammatory molecules. Although these findings indicate the involvement of MD-2 in IFN-γ signalling, we also observed that MD-2 was up-regulated by IFN-γ and high glucose. We found that MD-2 up-regulation by IFN-γ played an essential role in the synergistic effect of IFN-γ and LPS on MMP-1 expression. Taken together, these findings indicate that MD-2 is involved in IFN-γ signalling and IFN-γ-augmented MMP-1 up-regulation by LPS.
我们最近报道称，用 Rhodobacter sphaeroides 分离得到的脂多糖 Toll 样受体 4（TLR4）拮抗剂 Rs-LPS 治疗糖尿病载脂蛋白 E 缺陷型小鼠可抑制动脉粥样硬化。由于已知 Rs-LPS 通过靶向 TLR4 共受体 MD-2 拮抗 TLR4，这一发现表明 MD-2 是治疗动脉粥样硬化的潜在靶点。在这项研究中，我们确定 MD-2 是否参与了信号通路调控的基因表达，而这些信号通路与 TLR4 无关。鉴于干扰素-γ（IFNγ）和高血糖在动脉粥样硬化中起关键作用，我们确定 MD-2 是否参与单核细胞中 IFNγ 和高糖调节的基因表达。结果表明，IFNγ 和高糖协同刺激单核细胞 U937 中基质金属蛋白酶 1（MMP-1）的表达，MMP-1 是血管组织重塑和动脉粥样硬化所必需的蛋白水解酶，但 Rs-LPS 抑制了 MMP-1 的刺激。为了提供更多证据证明 MD-2 在 IFNγ 刺激的 MMP-1 中的作用，使用抗体和小干扰 RNA 的研究表明，MD-2 阻断或敲低减弱了 IFNγ 对 MMP-1 的作用。此外，使用 PCR 阵列的研究表明，MD-2 阻断与 IFNγ 受体阻断对 IFNγ 刺激的促炎分子的抑制作用相似。尽管这些发现表明 MD-2 参与了 IFNγ 信号通路，但我们也观察到 IFNγ 和高血糖会上调 MD-2。我们发现，IFNγ 上调 MD-2 在 IFNγ 和 LPS 对 MMP-1 表达的协同作用中起着至关重要的作用。综上所述，这些发现表明 MD-2 参与了 IFNγ 信号通路以及 LPS 增强的 IFNγ 诱导的 MMP-1 上调。
