Effects of C-reactive protein on the neutrophil respiratory burst in vitro

Abstract

This study determined the influence of physiologically relevant concentrations of C-reactive protein (CRP) on reactive oxygen species (ROS) production by neutrophils. Neutrophils from healthy individuals were incubated with soluble pentameric CRP prior to TLR stimulation with Fusobacterium nucleatum, or FcγR stimulation with IgG-opsonised Staphylococcus aureus or heat-Aggregated IgG. ROS generation by unstimulated cells and those after stimulation were determined using luminol, isoluminol and lucigenin chemiluminescence, detecting predominantly intracellular hypochlorous acid (HOCl), extracellular hydrogen peroxide (detected as HOCl) and extracellular superoxide respectively. Baseline (unstimulated) neutrophil ROS generation and release was reduced compared with vehicle control by 10 μg/ml CRP. There was no consistent effect of CRP on FcÎ 3;R-stimulated HOCl production, but the extracellular superoxide response was reduced by 10 μg/ml CRP. By contrast, CRP reduced intracellular (10 μg/ml) and extracellular (3 and 10 μg/ml) HOCl generation, but increased superoxide release (1-10 μg/ml) in response to TLR stimulation. Physiologically relevant concentrations of CRP inhibited baseline ROS generation and reduced FcÎ 3;R-stimulated extracellular superoxide and TLR-stimulated HOCl release, suggesting that CRP may offer some degree of host protection from neutrophil-Associated, low-level oxidative stress. However, CRP enhanced TLR-mediated superoxide release from neutrophils, potentially increasing oxidative stress but aiding host protection from infection. © 2013 The Author(s).