Blocking CXCL1-dependent neutrophil recruitment prevents immune damage and reduces pulmonary bacterial infection after inhalation injury

Abstract

Smoke inhalation associated with structural fires, wildfires, or explosions leads to lung injury, for which innovative and clinically relevant animal models are needed to develop effective therapeutics. We have previously reported that damage-associated molecular patterns (DAMPs) and anti-inflammatory cytokines correlate with infectious complications in patients diagnosed with inhalational injury. In this study, we describe a novel and translational murine model of acute inhalational injury characterized by an accumulation of protein and neutrophils in the bronchoalveolar space, as well as histological evidence of tissue damage. Mice were anesthetized, and a cannula was placed in the trachea and exposed to smoldering plywood smoke three times for 2-min intervals in a smoke chamber. Here we demonstrate that this model recapitulates clinically relevant phenotypes, including early release of double-stranded DNA (dsDNA), IL-10, monocyte chemoattractant protein (MCP)-1, and CXCL1 along with neutrophilia early after injury, accompanied by subsequent susceptibility to opportunistic infection with Pseudomonas aeruginosa. Further investigation of the model, and in turn a reanalysis of patient samples, revealed a late release of the DAMP hyaluronic acid (HA) from the lung. Using nitric oxide synthase-deficient mice, we found that Nos2 was required for increases in IL-10, MCP-1, and HA following injury but not release of dsDNA, CXCL1 expression, early neutrophilia, or susceptibility to opportunistic infection. Depletion of CXCL1 attenuated early neutrophil recruitment, leading to decreased histopathology scores and improved bacterial clearance in this model of smoke inhalation. Together, these data highlight the potential therapeutic benefit of attenuating neutrophil recruitment in the first 24 h after injury in patients.

Increased Lung Catalase Activity Confers Protection Against Experimental RSV Infection

“…www.nature.com/scientificreports www.nature.com/scientificreports/ Neutrophils recruitment to the airways has also been associated with enhanced pathology in the course of RSV infection [38][39][40] . Neutrophil products, i.e., elastase and CXCL1, are strongly linked to enhanced disease severity in numerous models of lung inflammation including acute edematous injury, bleomycin-induced acute lung injury, smoke inhalation and pneumonia [41][42][43][44] . High levels of TNF-α and CXCL1 are associated with enhanced elastase release from neutrophils 45 , both of which were reduced by PG-CAT treatment.…”

Emerging therapies for smoke inhalation injury: a review

“…In particular, this project focused on the elevation of a neutrophil chemotactant CXCL1. The authors identified an attenuated response to pulmonary neutrophil infiltration after smoke inhalation injury by administering a neutralizing Mercel et al J Transl Med (2020) 18:141 antibody to CXCL1, and also found a significantly decreased amount of inflammatory cytokines (IL-6, IL-1 beta, IL-16) in the treatment group compared to untreated controls [30]. It was also noted that lung histopathology and overall bacterial clearance improved in the group receiving the CXCL1 neutralizing antibody [30].…”

“…The authors identified an attenuated response to pulmonary neutrophil infiltration after smoke inhalation injury by administering a neutralizing Mercel et al J Transl Med (2020) 18:141 antibody to CXCL1, and also found a significantly decreased amount of inflammatory cytokines (IL-6, IL-1 beta, IL-16) in the treatment group compared to untreated controls [30]. It was also noted that lung histopathology and overall bacterial clearance improved in the group receiving the CXCL1 neutralizing antibody [30]. They hypothesized that blocking this early chemotactant attenuated early neutrophil recruitment, which ultimately prevented early lung damage and provided improved bacterial clearance after smoke inhalation injury [30].…”

“…The pathological response to inhalation injury involves many aspects of the inflammatory cascade. In previous work from one of our labs, Dunn et al developed a mouse model of inhalation injury that successfully recapitulated human injury, and in doing so noted an elevation in specific cytokines and damage associated molecular patterns (DAMPs) [30]. In particular, this project focused on the elevation of a neutrophil chemotactant CXCL1.…”

“…It was also noted that lung histopathology and overall bacterial clearance improved in the group receiving the CXCL1 neutralizing antibody [30]. They hypothesized that blocking this early chemotactant attenuated early neutrophil recruitment, which ultimately prevented early lung damage and provided improved bacterial clearance after smoke inhalation injury [30].…”