Nadra Imad, Boccaccini Aldo R, Philippidis Pandelis, Whelan Linda C, McCarthy Geraldine M, Haskard Dorian O, Landis R Clive
British Heart Foundation Cardiovascular Medicine Unit, Eric Bywaters Centre for Vascular Inflammation, Faculty of Medicine, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 ONN, UK.
Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP, UK.
Atherosclerosis. 2008 Jan;196(1):98-105. doi: 10.1016/j.atherosclerosis.2007.02.005. Epub 2007 Mar 9.
Macrophages may promote a vicious cycle of inflammation and calcification in the vessel wall by ingesting neointimal calcific deposits (predominantly hydroxyapatite) and secreting tumor necrosis factor (TNF)alpha, itself a vascular calcifying agent. Here we have investigated whether particle size affects the proinflammatory potential of hydroxyapatite crystals in vitro and whether the nuclear factor (NF)-kappaB pathway plays a role in the macrophage TNFalpha response. The particle size and nano-topography of nine different crystal preparations was analyzed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and gas sorbtion analysis. Macrophage TNFalpha secretion was inversely related to hydroxyapatite particle size (P=0.011, Spearman rank correlation test) and surface pore size (P=0.014). A necessary role for the NF-kappaB pathway was demonstrated by time-dependent I kappaB alpha degradation and sensitivity to inhibitors of I kappaB alpha degradation. To test whether smaller particles were intrinsically more bioactive, their mitogenic activity on fibroblast proliferation was examined. This showed close correlation between TNFalpha secretion and crystal-induced fibroblast proliferation (P=0.007). In conclusion, the ability of hydroxyapatite crystals to stimulate macrophage TNFalpha secretion depends on NF-kappaB activation and is inversely related to particle and pore size, with crystals of 1-2 microm diameter and pore size of 10-50 A the most bioactive. Microscopic calcific deposits in early stages of atherosclerosis may therefore pose a greater inflammatory risk to the plaque than macroscopically or radiologically visible deposits in more advanced lesions.
巨噬细胞可能通过摄取新生内膜钙化沉积物（主要是羟基磷灰石）并分泌肿瘤坏死因子（TNF）α（其本身就是一种血管钙化剂）来促进血管壁炎症和钙化的恶性循环。在此，我们研究了颗粒大小是否会影响体外羟基磷灰石晶体的促炎潜能，以及核因子（NF）-κB途径是否在巨噬细胞TNFα反应中发挥作用。通过X射线衍射、拉曼光谱、扫描电子显微镜和气吸附分析对九种不同晶体制剂的颗粒大小和纳米形貌进行了分析。巨噬细胞TNFα分泌与羟基磷灰石颗粒大小（P = 0.011，Spearman等级相关检验）和表面孔径（P = 0.014）呈负相关。通过IκBα的时间依赖性降解以及对IκBα降解抑制剂的敏感性证明了NF-κB途径的必要作用。为了测试较小颗粒是否本质上具有更高的生物活性，检测了它们对成纤维细胞增殖的促有丝分裂活性。结果显示TNFα分泌与晶体诱导的成纤维细胞增殖密切相关（P = 0.007）。总之，羟基磷灰石晶体刺激巨噬细胞TNFα分泌的能力取决于NF-κB激活，并且与颗粒和孔径呈负相关，直径为1-2微米且孔径为10-50埃的晶体生物活性最高。因此，动脉粥样硬化早期的微观钙化沉积物可能比更晚期病变中肉眼或放射学可见的沉积物对斑块构成更大的炎症风险。
