Department of Cardiovascular Medicine, Kyoto Prefectural University School of Medicine, 465 Kajii, Kawaramachi-Hirokoji, Kamigyo, Kyoto 602-8566, Japan.
Biochem Biophys Res Commun. 2012 Aug 17;425(1):39-44. doi: 10.1016/j.bbrc.2012.07.045. Epub 2012 Jul 17.
Vascular calcification is a major risk factor for the cardiovascular disease, yet its underlying molecular mechanisms remain to be elucidated. Recently, we identified that osteogenic signals via bone morphogenetic protein (BMP)-2 exerted by vascular smooth muscle cells (VSMCs) play a crucial role in the formation of atherosclerotic plaque calcification. Here we report a synergistic interaction between macrophages and VSMCs with respect to plaque calcification. Treatment with conditioned medium (CM) of macrophages dramatically enhanced BMP-2 expression in VSMCs, while it substantially reduced the expression of matrix Gla-protein (MGP) that inhibits the BMP-2 osteogenic signaling. As a result, macrophages significantly accelerated the osteoblastic differentiation of C2C12 cells induced by VSMC-CM. In contrast, macrophage-CM did not enhance the osteoblastic gene expressions in VSMCs, indicating that macrophages unlikely induced the osteoblastic trans-differentiation of VSMCs. We then examined the effect of recombinant TNF-α and IL-1β on the VSMC-derived osteogenic signals. Similar to the macrophage-CM, both cytokines enhanced BMP-2 expression and reduced MGP expression in VSMCs. Nevertheless, only the neutralization of TNF-α but not IL-1β attenuated the effect of macrophage-CM on the expression of these genes in VSMCs, due to the very low concentration of IL-1β in the macrophage-CM. On the other hand, VSMCs significantly enhanced IL-1β expression in macrophages, which might in turn accelerate the VSMC-mediated osteogenic signals. Together, we identified a unique role of macrophages in the formation of plaque calcification in coordination with VSMCs. This interaction between macrophages and VSMCs is a potential therapeutic target to treat and prevent the atherosclerotic plaque calcification.
血管钙化是心血管疾病的一个主要危险因素，但它的潜在分子机制仍有待阐明。最近，我们发现血管平滑肌细胞（VSMCs）通过骨形态发生蛋白（BMP）-2产生的成骨信号在动脉粥样硬化斑块钙化的形成中起着关键作用。在这里，我们报告了巨噬细胞和 VSMCs 之间在斑块钙化方面的协同相互作用。巨噬细胞条件培养基（CM）处理显著增强了 VSMCs 中的 BMP-2 表达，同时显著降低了抑制 BMP-2 成骨信号的基质 Gla 蛋白（MGP）的表达。结果，巨噬细胞显著加速了 VSMC-CM 诱导的 C2C12 细胞的成骨分化。相比之下，巨噬细胞 CM 并没有增强 VSMCs 中的成骨基因表达，表明巨噬细胞不太可能诱导 VSMCs 的成骨转分化。然后，我们检查了重组 TNF-α 和 IL-1β 对 VSMC 衍生的成骨信号的影响。与巨噬细胞 CM 相似，两种细胞因子均增强了 VSMCs 中的 BMP-2 表达并降低了 MGP 表达。然而，只有 TNF-α 的中和而非 IL-1β 减弱了巨噬细胞 CM 对 VSMCs 中这些基因表达的影响，这是由于巨噬细胞 CM 中 IL-1β 的浓度非常低。另一方面，VSMCs 显著增强了巨噬细胞中的 IL-1β 表达，这可能反过来又加速了 VSMC 介导的成骨信号。总之，我们确定了巨噬细胞在与 VSMCs 协调形成斑块钙化中的独特作用。巨噬细胞和 VSMCs 之间的这种相互作用是治疗和预防动脉粥样硬化斑块钙化的潜在治疗靶点。
