Humanized Citrullinated Histone H3 Monoclonal Antibody Improves Respiratory Function and Attenuates Neutrophil-Mediated Inflammation in a Rodent Model of Smoke Inhalation Lung Injury

BACKGROUND: Smoke inhalation-associated acute lung injury (SI-ALI) involves neutrophil infiltration and overproduction of neutrophil extracellular traps (NETs), leading to impaired respiratory function and high mortality. Citrullinated histone H3 (CitH3), a key component of NETosis, mediates inflammatory lung damage. We hypothesize that a humanized CitH3 monoclonal antibody (hCitH3-mAb) will improve respiratory function and reduce neutrophilic inflammation in a SI-ALI animal model. STUDY DESIGN: Male Sprague-Dawley rats subjected to smoke inhalation using an established model received either hCitH3-mAb or saline. A sham group exposed to air served as a negative control. Arterial blood gas samples were collected at baseline and 2, 6, and 24 hours post–smoke exposure via the ventral tail artery. At 2 hours, hCitH3-mAb or saline was injected via the tail vein. Proinflammatory proteins were assessed from the bronchoalveolar lavage fluid and whole tissue using ELISA, Western blotting, and immunofluorescence staining. RESULTS: Smoke-exposed rats developed significant hypoxemia at 2 hours vs baseline (p < 0.0001). Six hours post–smoke exposure, hCitH3-mAb-treated rats had significantly higher partial pressure of oxygen and oxygen saturation than saline-treated rats (p < 0.0001). By 24 hours, partial pressure of oxygen in arterial blood and arterial oxygen saturation levels in the hCitH3-mAb-treated rats returned to baseline levels while the saline group remained at a lower partial pressure of oxygen (p < 0.01). hCitH3-mAb treatment improved histopathological scores compared with saline treatment (p < 0.05). Neutrophils, macrophages, NET formation, and NLRP3 expression were all significantly lower in the hCitH3-mAb-treated rats compared with saline-treated rats (p < 0.01). CONCLUSIONS: hCitH3-mAb is a promising therapeutic for SI-ALI, as evidenced by the improvement in oxygenation associated with a reduction in neutrophil infiltration and NLRP3 inflammasome levels.