Unit for Laboratory Animal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Infect Immun. 2011 Jun;79(6):2460-9. doi: 10.1128/IAI.00050-11. Epub 2011 Apr 4.
Brucella spp. are intracellular bacteria that cause an infectious disease called brucellosis in humans and many domestic and wildlife animals. B. suis primarily infects pigs and is pathogenic to humans. The macrophage-Brucella interaction is critical for the establishment of a chronic Brucella infection. Our studies showed that smooth virulent B. suis strain 1330 (S1330) prevented programmed cell death of infected macrophages and rough attenuated B. suis strain VTRS1 (a vaccine candidate) induced strong macrophage cell death. To further investigate the mechanism of VTRS1-induced macrophage cell death, microarrays were used to analyze temporal transcriptional responses of murine macrophage-like J774.A1 cells infected with S1330 or VTRS1. In total 17,685 probe sets were significantly regulated based on the effects of strain, time and their interactions. A miniTUBA dynamic Bayesian network analysis predicted that VTRS1-induced macrophage cell death was mediated by a proinflammatory gene (the tumor necrosis factor alpha [TNF-α] gene), an NF-κB pathway gene (the IκB-α gene), the caspase-2 gene, and several other genes. VTRS1 induced significantly higher levels of transcription of 40 proinflammatory genes than S1330. A Mann-Whitney U test confirmed the proinflammatory response in VTRS1-infected macrophages. Increased production of TNF-α and interleukin 1β (IL-1β) were also detected in the supernatants in VTRS1-infected macrophage cell culture. Hyperphosphorylation of IκB-α was observed in macrophages infected with VTRS1 but not S1330. The important roles of TNF-α and IκB-α in VTRS1-induced macrophage cell death were further confirmed by individual inhibition studies. VTRS1-induced macrophage cell death was significantly inhibited by a caspase-2 inhibitor but not a caspase-1 inhibitor. The role of caspase-2 in regulating the programmed cell death of VTRS1-infected macrophages was confirmed in another study using caspase-2-knockout mice. In summary, VTRS1 induces a proinflammatory, caspase-2- and NF-κB-mediated macrophage cell death. This unique cell death differs from apoptosis, which is not proinflammatory. It is also different from classical pyroptosis, which is caspase-1 mediated.
布鲁氏菌属是一种细胞内细菌，可引起人类和许多家养和野生动物的传染病，称为布鲁氏菌病。猪主要感染猪种布鲁氏菌，对人类具有致病性。巨噬细胞与布鲁氏菌的相互作用对于慢性布鲁氏菌感染的建立至关重要。我们的研究表明，光滑毒力布鲁氏菌 1330 株（S1330）可防止受感染的巨噬细胞程序性细胞死亡，而粗糙减毒布鲁氏菌 VTRS1 株（候选疫苗）则诱导强烈的巨噬细胞死亡。为了进一步研究 VTRS1 诱导的巨噬细胞死亡的机制，我们使用微阵列分析了受 S1330 或 VTRS1 感染的鼠源巨噬细胞样 J774.A1 细胞的时间转录反应。根据菌株、时间及其相互作用的影响，共有 17685 个探针集被显著调控。一个 miniTUBA 动态贝叶斯网络分析预测，VTRS1 诱导的巨噬细胞死亡是由一个促炎基因（肿瘤坏死因子α[TNF-α]基因）、一个 NF-κB 途径基因（IκB-α 基因）、半胱天冬酶-2 基因和其他几个基因介导的。VTRS1 诱导的 40 个促炎基因转录水平明显高于 S1330。Mann-Whitney U 检验证实了 VTRS1 感染巨噬细胞中的促炎反应。还在 VTRS1 感染的巨噬细胞培养物上清液中检测到 TNF-α和白细胞介素 1β（IL-1β）的产量增加。在感染 VTRS1 的巨噬细胞中观察到 IκB-α的过度磷酸化，但在感染 S1330 的巨噬细胞中没有观察到。单独抑制研究进一步证实了 TNF-α和 IκB-α在 VTRS1 诱导的巨噬细胞死亡中的重要作用。半胱天冬酶-2 抑制剂而非半胱天冬酶-1 抑制剂显著抑制 VTRS1 诱导的巨噬细胞死亡。在另一项使用半胱天冬酶-2 敲除小鼠的研究中，证实了半胱天冬酶-2 在调节 VTRS1 感染的巨噬细胞程序性细胞死亡中的作用。总之，VTRS1 诱导了一种促炎、半胱天冬酶-2 和 NF-κB 介导的巨噬细胞死亡。这种独特的细胞死亡与不促炎的细胞凋亡不同，也与经典的细胞焦亡不同，后者是半胱天冬酶-1 介导的。
