The Stimulated Innate Resistance Event in Bordetella pertussis Infection Is Dependent on Reactive Oxygen Species Production

Abstract

The exacerbated induction of innate immune responses in airways can abrogate diverse lung infections by a phenomenon known as stimulated innate resistance (StIR). We recently demonstrated that the enhancement of innate response activation can efficiently impair Bordetella pertussis colonization in a Toll-like receptor 4 (TLR4)-dependent manner. The aim of this work was to further characterize the effect of lipopolysaccharide (LPS) on StIR and to identify the mechanisms that mediate this process. Our results showed that bacterial infection was completely abrogated in treated mice when the LPS of B. pertussis (1 g) was added before (48 h or 24 h), after (24 h), or simultaneously with the B. pertussis challenge (10 7 CFU). Moreover, we detected that LPS completely cleared bacterial infection as soon as 2 h posttreatment. This timing suggests that the observed StIR phenomenon should be mediated by fast-acting antimicrobial mechanisms. Although neutrophil recruitment was already evident at this time point, depletion assays using an anti-GR1 antibody showed that B. pertussis clearance was achieved even in the absence of neutrophils. To evaluate the possible role of free radicals in StIR, we performed animal assays using the antioxidant N-acetyl cysteine (NAC), which is known to inactivate oxidant species. NAC administration blocked the B. pertussis clearance induced by LPS. Nitrite concentrations were also increased in the LPS-treated mice; however, the inhibition of nitric oxide synthetases did not suppress the LPS-induced bacterial clearance. Taken together, our results show that reactive oxygen species (ROS) play an essential role in the TLR4-dependent innate clearance of B. pertussis.

Early Innate Immunity to Bacterial Infection in the Lung Is Regulated Systemically by the Commensal Microbiota via Nod-Like Receptor Ligands

“…To do this, the indicated groups of mice were intranasally administered Nacetyl-L-cysteine (NAC) 2 h prior to intranasal inoculation with K. pneumoniae. NAC is an oxidant scavenger, and its intranasal administration is an established method to reduce reactive oxygen species levels in the lung (36). Importantly, at the concentrations used in this study, NAC has no direct effect on K. pneumoniae growth (55).…”

“…To determine bacterial CFU, mice were sacrificed and lungs removed, homogenized in PBS, and plated on LB agar. To inhibit ROS production in the lung, mice were intranasally administered with 50 ml 0.5 mM N-acetyl-L-cysteine (NAC) (Sigma) 2 h prior to bacterial inoculation (36). Animal work was conducted in accordance with the Animal Scientific Procedures outlined by the UK Home Office regulations.…”

A Toll-Like Receptor 5 Agonist Improves the Efficacy of Antibiotics in Treatment of Primary and Influenza Virus-Associated Pneumococcal Mouse Infections

“…Several studies have highlighted the ability of TLR2/6, TLR4, TLR5, and TLR9 agonists and microbial extracts (delivered by the respiratory route) to prevent bacterial pneumonia (18,19,(33)(34)(35)(36). However, the effective use of this type of treatment is restricted to prophylactic regimens or is limited by a narrow therapeutic window.…”

Estudio de la enteropatía inducida por péptidos de gliadinas y ligandos de la inmunidad innata en modelos experimentales

“…2,0mg/ml), o un control de isotipo (HB152) según un protocolo previamente establecido para la depleción de la población de neutrófilos principalmente (Zurita et al 2013). El esquema consistió en la administración de 400 μg de anticuerpo 24hs antes de la cirugía.…”