Lung Dysfunction and Systemic Inflammation: A Role for HO-1 and NLRP3 in a COVID-19 Murine Model.

RATIONALE: The COVID-19 (C19) pandemic caused significant mortality often due to lung injury and systemic inflammation, but there is significant heterogeneity in severity and the pathobiology is not well understood. We examined COVID-19-induced pulmonary and inflammatory sequelae using a murine noninfectious model to further define the models utility and to also understand the role of mediators such as heme oxgenase-1. METHODS: k18-hACE2 male mice oropharyngeally aspirated C19-spike or equal volume control. After 72 hours, we collected: pulmonary mechanics, bronchoalveolar lavage(BAL) and plasma, snap-froze right lung, and fixed/stained left lung for histologic injury assessment(Qupath). Cytokine elaboration in BAL and plasma was quantified(Luminex), and lung homogenates were probed for HO-1 and NLRP3 (Western). Statistical (SPSS and R) and pathways comparisons(Ingenuity Pathway Analysis) were made between control and C19. RESULTS: Lung Mechanics. C19 exposure significantly reduced inspiratory capacity and static lung compliance;tissue elastance and airway hyperreactivity were increased. Histology: C19 exposure caused significant inflammation and thickened alveolar septae. Cytokines: C19 exposure led to inflammatory response in BAL and plasma with simultaneous activation of Type 1 and Type 2 pathways. Pathways. NLRP3 and HO-1 protein expression is significantly induced by C19. Regulator networks show involvement of multiple cell lines and lung damage. CONCLUSION: A noninfectious C19 murine model showed worsened lung parameters and increased inflammation. HO-1 and NLRP3 may be key mediators in the inflammatory process and induce both inflammatory and counter-regulatory effects. Further studies will focus on targeted therapeutic pathways that probe into the mechanistic relationship of HO-1 and NLRP3 in C19-related disease.