Roshick Christine, Wood Heidi, Caldwell Harlan D, McClarty Grant
National Microbiology Laboratory, Public Health Agency of Canada, 1015 Arlington Street, Winnipeg, Manitoba, Canada R3E 3R2.
Infect Immun. 2006 Jan;74(1):225-38. doi: 10.1128/IAI.74.1.225-238.2006.
Gamma interferon (IFN-gamma)-induced effector mechanisms have potent antichlamydial activities that are critical to host defense. The most prominent and well-studied effectors are indoleamine dioxygenase (IDO) and nitric oxide (NO) synthase. The relative contributions of these mechanisms as inhibitors of chlamydial in vitro growth have been extensively studied using different host cells, induction mechanisms, and chlamydial strains with conflicting results. Here, we have undertaken a comparative analysis of cytokine- and lipopolysaccharide (LPS)-induced IDO and NO using an extensive assortment of human and murine host cells infected with human and murine chlamydial strains. Following cytokine (IFN-gamma or tumor necrosis factor alpha) and/or LPS treatment, the majority of human cell lines induced IDO but failed to produce NO. Conversely, the majority of mouse cell lines studied produced NO, not IDO. Induction of IDO in human cell lines inhibited growth of L2 and mouse pneumonitis agent, now referred to as Chlamydia muridarum MoPn equally in all but two lines, and inhibition was completely reversible by the addition of tryptophan. IFN-gamma treatment of mouse cell lines resulted in substantially greater reduction of L2 than MoPn growth. However, despite elevated NO production by murine cells, blockage of NO synthesis with the l-arginine analogue N-monomethyl-l-arginine only partially rescued chlamydial growth, suggesting the presence of another IFN-gamma-inducible antichlamydial mechanism unique to murine cells. Moreover, NO generated from the chemical nitric oxide donor sodium nitroprusside showed little direct effect on chlamydial infectivity or growth, indicating a natural resistance to NO. Finally, IFN-gamma-inducible IDO expression in human HeLa cells was inhibited following exogenous NO treatment, resulting in a permissive environment for chlamydial growth. In summary, cytokine- and LPS-inducible effectors produced by human and mouse cells differ and, importantly, these host-specific effector responses result in chlamydial strain-specific antimicrobial activities.
γ干扰素（IFN-γ）诱导的效应机制具有强大的抗衣原体活性，对宿主防御至关重要。最突出且研究充分的效应分子是吲哚胺双加氧酶（IDO）和一氧化氮（NO）合酶。使用不同的宿主细胞、诱导机制和衣原体菌株，对这些机制作为衣原体体外生长抑制剂的相对贡献进行了广泛研究，但结果相互矛盾。在此，我们使用感染了人和鼠衣原体菌株的多种人和鼠宿主细胞，对细胞因子和脂多糖（LPS）诱导的IDO和NO进行了比较分析。在细胞因子（IFN-γ或肿瘤坏死因子α）和/或LPS处理后，大多数人细胞系诱导产生IDO，但不产生NO。相反，所研究的大多数小鼠细胞系产生NO，而非IDO。人细胞系中IDO的诱导抑制了L2和小鼠肺炎病原体（现称为鼠衣原体MoPn）的生长，除两个细胞系外，在所有细胞系中抑制作用相同，并且通过添加色氨酸可完全逆转抑制作用。IFN-γ处理小鼠细胞系导致L2的生长比MoPn的生长减少得更多。然而，尽管鼠细胞产生的NO增加，但用L-精氨酸类似物N-单甲基-L-精氨酸阻断NO合成仅部分挽救了衣原体的生长，这表明鼠细胞存在另一种IFN-γ诱导的抗衣原体机制。此外，化学一氧化氮供体硝普钠产生的NO对衣原体的感染性或生长几乎没有直接影响，表明对NO具有天然抗性。最后，外源性NO处理后，人HeLa细胞中IFN-γ诱导的IDO表达受到抑制，从而形成了衣原体生长的允许环境。总之,人和小鼠细胞产生的细胞因子和LPS诱导的效应分子不同，重要的是，这些宿主特异性效应反应导致了衣原体菌株特异性的抗菌活性。
