McPhillips Kathleen, Janssen William J, Ghosh Moumita, Byrne Aideen, Gardai Shyra, Remigio Linda, Bratton Donna L, Kang Jihee L, Henson Peter
Department of Pathology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
J Immunol. 2007 Jun 15;178(12):8117-26. doi: 10.4049/jimmunol.178.12.8117.
Removal of apoptotic cells from inflammatory sites is an important step in the resolution of inflammation. Both murine and human macrophages stimulated with TNF-alpha or directly administered arachidonic acid showed an impaired ability to ingest apoptotic cells (efferocytosis). The inhibition was shown to be due to generation of reactive oxygen species, was blocked with a superoxide dismutase mimetic, MnTBAP, and was mimicked by direct addition of H2O2. To determine the mechanism of TNF-alpha-stimulated oxidant production, bone marrow-derived macrophages from gp91(phox)-deficient mice were examined but shown to still produce oxidants and exhibit defective apoptotic cell uptake. In contrast, a specific cytosolic phospholipase A2 inhibitor blocked the oxidant production and reversed the inhibited uptake. The suppressive effect of endogenous or exogenous oxidants on efferocytosis was mediated through activation of the GTPase, Rho. It was reversed in macrophages pretreated with C3 transferase to inactivate Rho or with an inhibitor of Rho kinase. During maturation of human monocyte-derived macrophages, only mature cells exhibited TNF-alpha-induced suppression of apoptotic cell clearance. The resistance of immature macrophages to such inhibition was shown to result not from defective generation of oxidants, but rather, from lack of response of these cells to the oxidants. Overall, the data suggest that macrophages in a TNF-alpha- and oxidant-rich inflammatory environment are less able to remove apoptotic cells and, thereby, may contribute to the local intensity of the inflammatory response.
从炎症部位清除凋亡细胞是炎症消退的重要步骤。用肿瘤坏死因子-α（TNF-α）刺激或直接给予花生四烯酸的小鼠和人类巨噬细胞摄取凋亡细胞（噬菌作用）的能力均受损。这种抑制作用被证明是由于活性氧的产生，用超氧化物歧化酶模拟物MnTBAP可阻断，直接添加过氧化氢可模拟。为了确定TNF-α刺激产生氧化剂的机制，对gp91（phox）缺陷小鼠的骨髓来源巨噬细胞进行了检测，但结果显示其仍能产生氧化剂并表现出凋亡细胞摄取缺陷。相反，一种特异性胞质磷脂酶A2抑制剂可阻断氧化剂的产生并逆转摄取抑制。内源性或外源性氧化剂对噬菌作用的抑制作用是通过GTP酶Rho的激活介导的。在用C3转移酶预处理使Rho失活或用Rho激酶抑制剂处理的巨噬细胞中，这种抑制作用被逆转。在人类单核细胞来源巨噬细胞的成熟过程中，只有成熟细胞表现出TNF-α诱导的凋亡细胞清除抑制。未成熟巨噬细胞对这种抑制的抗性被证明不是由于氧化剂产生缺陷，而是由于这些细胞对氧化剂缺乏反应。总体而言，数据表明，处于富含TNF-α和氧化剂的炎症环境中的巨噬细胞清除凋亡细胞的能力较弱，从而可能导致炎症反应的局部强度增加。
