Renwick L C, Donaldson K, Clouter A
School of Life Sciences, Napier University, 10 Colinton Road, Edinburgh, EH10 5DT, Scotland.
Toxicol Appl Pharmacol. 2001 Apr 15;172(2):119-27. doi: 10.1006/taap.2001.9128.
We investigated whether slowed clearance after exposure to ultrafine particles was due to a failure in alveolar macrophage phagocytosis. This was achieved by measuring the ability of a macrophage cell line (J774.2 MPhi) to phagocytose 2-microg indicator latex beads following 8-h exposures to a number of test particles. Particles utilized were fine titanium dioxide (TiO2), ultrafine titanium dioxide (UTiO2), carbon black (CB), or ultrafine carbon black (UCB). Cytotoxicity of particles was measured by means of MTT activity. In a preliminary study, we assessed the effects of conditioned medium from particle-treated macrophages on the phagocytic ability of naive macrophages. Ultrafine and fine particles had no significant cytotoxic effects on J774.2 MPhi. A significant reduction in the ability of macrophages to phagocytose the indicator beads occurred after exposure to 0.39 microg/mm(2) (p < 0.001) of UCB and 0.78 microg/mm(2) (p < 0.001) of all particle types compared to the control. Furthermore, ultrafine particles were shown to significantly (p < 0.001) impair macrophage phagocytosis at a lower dose than their fine counterparts (0.39 and 0.78 microg/mm(2), respectively). At all doses, UCB resulted in a greater number (p < 0.001) of nonphagocytic macrophages compared to the other test particles. We tested whether a diffusable mediator being released from particle-exposed cells inhibited the phagocytic activity of adjacent macrophages. The conditioned medium from particle-exposed macrophages had no significant effect on the phagocytic ability of macrophages, suggesting that cell-cell contact is responsible for the pattern of failed phagocytosis (data not shown). We have demonstrated that ultrafine particles impair macrophage phagocytosis to a greater extent than fine particles compared on a mass basis. Therefore, we conclude that slowed clearance of particles, specifically the ultrafines, can in part be attributed to a particle-mediated impairment of macrophage phagocytosis.
我们研究了暴露于超细颗粒后清除减慢是否是由于肺泡巨噬细胞吞噬功能障碍所致。这是通过测量巨噬细胞系（J774.2 MPhi）在暴露于多种测试颗粒8小时后吞噬2微克指示性乳胶珠的能力来实现的。所使用的颗粒为细二氧化钛（TiO2）、超细二氧化钛（UTiO2）、炭黑（CB）或超细炭黑（UCB）。通过MTT活性测定颗粒的细胞毒性。在一项初步研究中，我们评估了来自颗粒处理巨噬细胞的条件培养基对未处理巨噬细胞吞噬能力的影响。超细颗粒和细颗粒对J774.2 MPhi没有显著的细胞毒性作用。与对照组相比，暴露于0.39微克/平方毫米（p < 0.001）的UCB和0.78微克/平方毫米（p < 0.001）的所有颗粒类型后，巨噬细胞吞噬指示性珠子的能力显著降低。此外，与细颗粒相比，超细颗粒在较低剂量（分别为0.39和0.78微克/平方毫米）时就显著（p < 0.001）损害巨噬细胞吞噬作用。在所有剂量下，与其他测试颗粒相比，UCB导致非吞噬性巨噬细胞数量更多（p < 0.001）。我们测试了从暴露于颗粒的细胞中释放的可扩散介质是否会抑制相邻巨噬细胞的吞噬活性。来自暴露于颗粒的巨噬细胞的条件培养基对巨噬细胞的吞噬能力没有显著影响，这表明细胞间接触是吞噬作用失败模式的原因（数据未显示）。我们已经证明，在质量基础上比较，超细颗粒比细颗粒更能损害巨噬细胞吞噬作用。因此，我们得出结论，颗粒清除减慢，特别是超细颗粒，部分可归因于颗粒介导的巨噬细胞吞噬作用受损。
