Human Cystic Fibrosis Macrophages Have Defective Calcium-Dependent Protein Kinase C Activation of the NADPH Oxidase, an Effect Augmented by Burkholderia cenocepacia

Abstract

Macrophage intracellular pathogen killing is defective in cystic fibrosis (CF), despite abundant production of reactive oxygen species (ROS) in lung tissue. Burkholderia species can cause serious infection in CF and themselves affect key oxidase components in murine non-CF cells. However, it is unknown whether human CF macrophages have an independent defect in the oxidative burst and whether Burkholderia contributes to this defect in terms of assembly of the NADPH oxidase complex and subsequent ROS production. In this article, we analyze CF and non-CF human monocyte-derived macrophages (MDMs) for ROS production, NADPH assembly capacity, protein kinase C expression, and calcium release in response to PMA and CF pathogens. CF MDMs demonstrate a nearly 60% reduction in superoxide production after PMA stimulation compared with non-CF MDMs. Although CF MDMs generally have increased total NADPH component protein expression, they demonstrate decreased expression of the calcium-dependent protein kinase C conventional subclass α/β leading to reduced phosphorylation of NADPH oxidase components p47 ^phox and p40 ^phox in comparison with non-CF MDMs. Ingestion of B. cenocepacia independently contributes to and worsens the overall oxidative burst deficits in CF MDMs compared with non-CF MDMs. Together, these results provide evidence for inherent deficits in the CF macrophage oxidative burst caused by decreased phosphorylation of NADPH oxidase cytosolic components that are augmented by Burkholderia These findings implicate a critical role for defective macrophage oxidative responses in persistent bacterial infections in CF and create new opportunities for boosting the macrophage immune response to limit infection.