Assani Kaivon, Tazi Mia F, Amer Amal O, Kopp Benjamin T
Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America.
Department of Microbial Infection and Immunity and the Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America.
PLoS One. 2014 May 5;9(5):e96681. doi: 10.1371/journal.pone.0096681. eCollection 2014.
Burkholderia cenocepacia is a virulent pathogen that causes significant morbidity and mortality in patients with cystic fibrosis (CF), survives intracellularly in macrophages, and uniquely causes systemic infections in CF. Autophagy is a physiologic process that involves engulfing non-functional organelles and proteins and delivering them for lysosomal degradation, but also plays a role in eliminating intracellular pathogens, including B. cenocepacia. Autophagy is defective in CF but can be stimulated in murine CF models leading to increased clearance of B. cenocepacia, but little is known about autophagy stimulation in human CF macrophages. IFN-γ activates macrophages and increases antigen presentation while also inducing autophagy in macrophages. We therefore, hypothesized that treatment with IFN-γ would increase autophagy and macrophage activation in patients with CF. Peripheral blood monocyte derived macrophages (MDMs) were obtained from CF and non-CF donors and subsequently infected with B. cenocepacia. Basal serum levels of IFN-γ were similar between CF and non-CF patients, however after B. cenocepacia infection there is deficient IFN-γ production in CF MDMs. IFN-γ treated CF MDMs demonstrate increased co-localization with the autophagy molecule p62, increased autophagosome formation, and increased trafficking to lysosomes compared to untreated CF MDMs. Electron microscopy confirmed IFN-γ promotes double membrane vacuole formation around bacteria in CF MDMs, while only single membrane vacuoles form in untreated CF cells. Bacterial burden is significantly reduced in autophagy stimulated CF MDMs, comparable to non-CF levels. IL-1β production is decreased in CF MDMs after IFN-γ treatment. Together, these results demonstrate that IFN-γ promotes autophagy-mediated clearance of B. cenocepacia in human CF macrophages.
洋葱伯克霍尔德菌是一种致病性很强的病原体，可导致囊性纤维化（CF）患者出现严重的发病和死亡情况，它能在巨噬细胞内生存，并特别容易在CF患者中引发全身感染。自噬是一种生理过程，它涉及吞噬无功能的细胞器和蛋白质，并将它们送去进行溶酶体降解，但自噬在清除包括洋葱伯克霍尔德菌在内的细胞内病原体方面也发挥着作用。CF患者的自噬功能存在缺陷，但在小鼠CF模型中可被刺激，从而增加洋葱伯克霍尔德菌的清除率，不过对于人类CF巨噬细胞中的自噬刺激情况知之甚少。干扰素-γ可激活巨噬细胞并增加抗原呈递，同时还能在巨噬细胞中诱导自噬。因此，我们推测用干扰素-γ治疗会增加CF患者的自噬和巨噬细胞激活。从CF和非CF供体获取外周血单核细胞衍生的巨噬细胞（MDM），随后用洋葱伯克霍尔德菌进行感染。CF和非CF患者的基础血清干扰素-γ水平相似，然而在感染洋葱伯克霍尔德菌后，CF MDM中干扰素-γ的产生存在缺陷。与未处理的CF MDM相比，用干扰素-γ处理的CF MDM显示出与自噬分子p62的共定位增加、自噬体形成增加以及向溶酶体的转运增加。电子显微镜证实，干扰素-γ可促进CF MDM中细菌周围形成双膜空泡，而在未处理的CF细胞中仅形成单膜空泡。在自噬受到刺激的CF MDM中，细菌载量显著降低，与非CF水平相当。干扰素-γ处理后，CF MDM中白细胞介素-1β的产生减少。总之，这些结果表明干扰素-γ可促进人类CF巨噬细胞中自噬介导的洋葱伯克霍尔德菌清除。
