Immunology and Microbial Pathogenesis Program, Weill Graduate School of Medical Sciences of Cornell University, New York City, NY, USA.
Department of Microbiology & Immunology, Weill Cornell Medicine, New York City, NY, USA.
Eur J Immunol. 2018 Apr;48(4):612-620. doi: 10.1002/eji.201747180. Epub 2018 Feb 28.
Genetic deficiency of protein kinase R (PKR) in mice was reported to enhance macrophage activation in vitro in response to interferon-γ (IFNγ) and to reduce the burden of Mycobacterium tuberculosis (Mtb) in vivo (Wu et al. PloS One. 2012 7:e30512). Consistent with this, treatment of wild-type (WT) macrophages in vitro with a novel PKR inhibitor (Bryk et al., Bioorg. Med. Chem. Lett. 2011 21:4108-4114) also enhanced IFN-γ-dependent macrophage activation (Wu et al. PloS One. 2012 7:e30512). Here we show that co-treatment with IFN-γ and a new PKR inhibitor identified herein to be highly but not completely selective likewise induced macrophages to produce more reactive nitrogen intermediates (RNI) and tumor necrosis factor alpha (TNF-α) and less interleukin 10 (IL-10) than seen with IFN-γ alone. Unexpectedly, however, this new PKR inhibitor had a comparable effect on PKR-deficient macrophages. Retrospective investigation revealed that the PKR-deficient mice in (Wu et al. PloS One. 2012 7:e30512) had not been backcrossed. On comparing genetically matched PKR-deficient and WT mice, we saw no impact of PKR deficiency on macrophage activation in vitro or during the course of Mtb infection in vivo. In addition, although 129S1/SvImJ macrophage responses to IFN-γ were greater than those of C57BL/6J macrophages, PKR was not required to mediate the IFN-γ-dependent production of IL-10, RNI or TNF-α in either strain. Together the data cast doubt on PKR as a potential therapeutic target for tuberculosis.
在小鼠中，蛋白激酶 R（PKR）的遗传缺陷被报道会增强干扰素-γ（IFNγ）刺激下的巨噬细胞体外激活，并降低体内结核分枝杆菌（Mtb）的负担（Wu 等人，《公共科学图书馆·综合》，2012 年 7 月，e30512）。与此一致的是，新型 PKR 抑制剂（Bryk 等人，《生物有机与医药化学快报》，2011 年 21 卷，4108-4114）体外处理野生型（WT）巨噬细胞也增强了 IFNγ 依赖性的巨噬细胞激活（Wu 等人，《公共科学图书馆·综合》，2012 年 7 月，e30512）。在这里，我们发现与 IFNγ 联合治疗新型高选择性但非完全选择性的 PKR 抑制剂同样会诱导巨噬细胞产生更多的活性氮中间产物（RNI）和肿瘤坏死因子-α（TNF-α），而产生更少的白细胞介素 10（IL-10），比单独使用 IFNγ 时观察到的效果更明显。然而，出乎意料的是，这种新型 PKR 抑制剂对 PKR 缺陷型巨噬细胞有类似的作用。回顾性调查显示，（Wu 等人，《公共科学图书馆·综合》，2012 年 7 月，e30512）中报道的 PKR 缺陷型小鼠并未进行回交。在比较基因匹配的 PKR 缺陷型和 WT 小鼠时，我们没有发现 PKR 缺陷对体内 Mtb 感染过程中巨噬细胞的体外激活有影响。此外，尽管 129S1/SvImJ 巨噬细胞对 IFNγ 的反应大于 C57BL/6J 巨噬细胞，但在这两种品系中，PKR 都不是介导 IFNγ 依赖性产生 IL-10、RNI 或 TNF-α所必需的。综合这些数据，PKR 作为结核病的潜在治疗靶点存在疑问。
