Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Denver at Anschutz Medical Center, Denver, CO 80045, USA.
J Immunol. 2010 Apr 1;184(7):3830-40. doi: 10.4049/jimmunol.0901913. Epub 2010 Feb 26.
Macrophages provide a first line of defense against Mycobacterium tuberculosis. However, in instances where macrophage activation for killing is suboptimal, M. tuberculosis is capable of surviving intracellularly. IL-32 is a recently described cytokine induced by M. tuberculosis in a variety of cell types including human monocytes and macrophages. In this study, we investigated the biological significance of IL-32 in an in vitro model of M. tuberculosis infection in differentiated THP-1 human macrophages in which IL-32 expression was silenced using stable expression of short hairpin RNA (shRNA). Inhibition of endogenous IL-32 production in THP-1 cells that express one of three distinct shRNA-IL-32 constructs significantly decreased M. tuberculosis induction of TNF-alpha by approximately 60%, IL-1beta by 30-60%, and IL-8 by 40-50% and concomitantly increased the number of cell-associated M. tuberculosis bacteria compared with THP-1 cells stably expressing a scrambled shRNA. In THP-1 cells infected with M. tuberculosis and stimulated with rIL-32, a greater level of apoptosis was observed compared with that with M. tuberculosis infection alone. Obversely, there was significant abrogation of apoptosis induced by M. tuberculosis and a concomitant decrease in caspase-3 activation in cells depleted of endogenous IL-32. rIL-32gamma significantly reduced the number of viable intracellular M. tuberculosis bacteria, which was modestly but significantly abrogated with a caspase-3 inhibitor. We conclude that IL-32 plays a host defense role against M. tuberculosis in differentiated THP-1 human macrophages.
巨噬细胞提供了针对结核分枝杆菌的第一道防线。然而，在巨噬细胞杀伤作用不足的情况下，结核分枝杆菌能够在细胞内存活。IL-32 是一种最近描述的细胞因子，可被结核分枝杆菌在多种细胞类型中诱导产生，包括人单核细胞和巨噬细胞。在这项研究中，我们使用短发夹 RNA（shRNA）的稳定表达沉默了分化的 THP-1 人巨噬细胞中结核分枝杆菌感染的体外模型中的 IL-32 表达，从而研究了 IL-32 在其中的生物学意义。抑制表达三种不同 shRNA-IL-32 构建体之一的 THP-1 细胞中内源性 IL-32 的产生，可使 TNF-α的诱导减少约 60%，IL-1β减少 30-60%，IL-8 减少 40-50%，同时与稳定表达乱序 shRNA 的 THP-1 细胞相比，细胞结合的结核分枝杆菌数量增加。与仅感染结核分枝杆菌相比，在感染结核分枝杆菌并刺激 rIL-32 的 THP-1 细胞中观察到更高水平的细胞凋亡。相反，在耗尽内源性 IL-32 的细胞中，结核分枝杆菌诱导的细胞凋亡显著减少，同时 caspase-3 的激活也减少。rIL-32gamma 可显著减少细胞内存活的结核分枝杆菌数量，而 caspase-3 抑制剂则可适度但显著地阻断该作用。我们得出结论，IL-32 在分化的 THP-1 人巨噬细胞中发挥针对结核分枝杆菌的宿主防御作用。
