Department of Pediatric Pulmonology, Cystic Fibrosis Centre, University Medical Center Utrecht, Utrecht, The Netherlands.
Am J Respir Cell Mol Biol. 2013 Sep;49(3):463-70. doi: 10.1165/rcmb.2012-0502OC.
Cystic fibrosis (CF) is caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and is characterized by chronic pulmonary infections. The mechanisms underlying chronic infection and inflammation remain incompletely understood. Mutant CFTR in nonepithelial tissues such as immune cells has been suggested to contribute to infection, inflammation, and the resultant lung disease. However, much controversy still exists regarding the intrinsic role of CFTR in immune cells, especially phagocytes. Therefore, we investigated CFTR expression and function in neutrophils and monocytes isolated from human peripheral blood. CFTR function was assessed by comparing non-CF and CF cells, before and after the chemical inhibition of CFTR. We found CFTR protein expression in monocytes, but this expression was limited or undetectable in neutrophils. Furthermore, the phagocytosis and intracellular killing of Pseudomonas aeruginosa was reduced in CF monocytes, and impaired phagocyte effector mechanisms were phenocopied in non-CF monocytes upon the pharmacological inhibition of CFTR. Reduced phagocytosis in CF monocytes relied on the complement-dependent opsonization of Pseudomonas aeruginosa, and was also observed in the context of latex particles labeled with purified C3b. In mechanistic terms, we observed that CFTR function in monocytes is required for the optimal expression of CD11b. We observed no role for CFTR in neutrophil-mediated phagocytosis. These data support an intrinsic role for CFTR in monocytes, and suggest that CFTR-dependent alterations in complement-mediated interactions between Pseudomonas aeruginosa and monocytes may contribute to enhanced susceptibility to infection in patients with CF.
囊性纤维化（CF）是由囊性纤维化跨膜电导调节因子（CFTR）基因突变引起的，其特征是慢性肺部感染。慢性感染和炎症的机制仍不完全清楚。已经有人提出，非上皮组织（如免疫细胞）中的突变 CFTR 有助于感染、炎症和由此产生的肺部疾病。然而，关于 CFTR 在免疫细胞（尤其是吞噬细胞）中的固有作用仍存在很大争议。因此，我们研究了从人外周血中分离的中性粒细胞和单核细胞中 CFTR 的表达和功能。通过比较非 CF 和 CF 细胞在化学抑制 CFTR 前后的功能，评估 CFTR 功能。我们发现单核细胞中存在 CFTR 蛋白表达，但中性粒细胞中这种表达有限或无法检测到。此外，CF 单核细胞对铜绿假单胞菌的吞噬作用和细胞内杀伤作用降低，并且在药理学抑制 CFTR 后，非 CF 单核细胞中受损的吞噬细胞效应机制被模拟。CF 单核细胞中吞噬作用的降低依赖于铜绿假单胞菌的补体依赖性调理作用，并且在用纯化的 C3b 标记的乳胶颗粒的情况下也观察到这种作用。从机制上讲，我们观察到 CFTR 在单核细胞中的功能对于 CD11b 的最佳表达是必需的。我们观察到 CFTR 在中性粒细胞介导的吞噬作用中没有作用。这些数据支持 CFTR 在单核细胞中的固有作用，并表明 CFTR 依赖性改变铜绿假单胞菌与单核细胞之间的补体介导相互作用可能导致 CF 患者对感染的易感性增强。
