Wang W, Keller K, Chadee K
Institute of Parasitology of McGill University, Québec, Canada.
Immunology. 1994 Dec;83(4):601-10.
Nitric oxide (NO) is the major cytotoxic molecule produced by activated macrophages for cytotoxicity against Entamoeba histolytica trophozoites. In the present study, we determined whether E. histolytica infection and soluble amoebic proteins affected macrophage cytotoxicity against amoebae and tumour cells by modulating the inducible NO synthase gene (iNOS) and NO (measured as nitrite, NO2-) and tumour necrosis factor-alpha (TNF-alpha) production. Amoebic liver abscess-derived macrophages [days 10, 20, 30 post-infection (p.i.)] stimulated with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) showed increased cytotoxicity against L929 cells (TNF-alpha-sensitive), but were refractory for killing amoebae and P815 cells (both NO-sensitive), concomitant with low NO2- production (< 4 microM/10(6) cells). In contrast, peritoneal and spleen macrophages at 10 and 20 days p.i. activated with IFN-gamma and LPS demonstrated increased killing of amoebae, and L929 and P815 cells concomitant with high NO2- production (> 12 microM/10(6) cells). Pretreatment of mouse bone marrow-derived macrophages with amoebic proteins suppressed IFN-gamma and LPS-induced amoebicidal (33%) and tumoricidal (44-49%) activities, with a corresponding decrease in TNF-alpha (56%) and NO (41%) production as well as TNF-alpha (41%) and iNOS (27%) mRNA by Northern blot analyses as compared to untreated activated controls. Inhibition of prostaglandin E2 (PGE2) biosynthesis in abscess and naive macrophages pretreated with amoebic proteins augmented IFN-gamma- and LPS-induced killing of L929 cells and TNF-alpha production, but failed to increase killing of P815 cells and amoebae as well as iNOS mRNA levels or NO production. These results suggest that E. histolytica selectively induces dysfunction of macrophage cytotoxicity by modulating iNOS mRNA expression and NO production independent from TNF-alpha and PGE2 allowing the parasites to survive within the host by impairing host immune responses.
一氧化氮（NO）是活化巨噬细胞产生的主要细胞毒性分子，用于对溶组织内阿米巴滋养体的细胞毒性作用。在本研究中，我们确定溶组织内阿米巴感染和可溶性阿米巴蛋白是否通过调节诱导型一氧化氮合酶基因（iNOS）以及NO（以亚硝酸盐，NO2-衡量）和肿瘤坏死因子-α（TNF-α）的产生，来影响巨噬细胞对阿米巴和肿瘤细胞的细胞毒性。用干扰素-γ（IFN-γ）和脂多糖（LPS）刺激的阿米巴肝脓肿来源的巨噬细胞[感染后（p.i.）第10、20、30天]对L929细胞（对TNF-α敏感）的细胞毒性增加，但对杀死阿米巴和P815细胞（两者均对NO敏感）无效，同时NO2-产生量低（<4 microM/10(6)细胞）。相反，感染后第10天和第20天的腹膜和脾脏巨噬细胞经IFN-γ和LPS激活后，对阿米巴、L929和P815细胞的杀伤增加，同时NO2-产生量高（>12 microM/10(6)细胞）。用阿米巴蛋白预处理小鼠骨髓来源的巨噬细胞可抑制IFN-γ和LPS诱导的杀阿米巴（33%）和杀肿瘤（44-49%）活性，与未处理的活化对照相比，通过Northern印迹分析，TNF-α（56%）和NO（41%）产生以及TNF-α（41%）和iNOS（27%）mRNA相应减少。在用阿米巴蛋白预处理的脓肿巨噬细胞和未感染巨噬细胞中抑制前列腺素E2（PGE2）生物合成，可增强IFN-γ和LPS诱导的对L929细胞的杀伤和TNF-α产生，但不能增加对P815细胞和阿米巴的杀伤以及iNOS mRNA水平或NO产生。这些结果表明，溶组织内阿米巴通过调节iNOS mRNA表达和NO产生，独立于TNF-α和PGE2，选择性地诱导巨噬细胞细胞毒性功能障碍，从而使寄生虫通过损害宿主免疫反应在宿主体内存活。
