Aim2 suppresses cigarette smoke-induced neutrophil recruitment, neutrophil caspase-1 activation and anti-Ly6G-mediated neutrophil depletion

Increased inflammasome responses are strongly implicated in inflammatory diseases; however, their specific roles are incompletely understood. Therefore, we sought to examine the roles of nucleotide-binding oligomerization domain-like receptor (NLR) family, pyrin domain-containing 3 (NLRP3) and absent in melanoma-2 (AIM2) inflammasomes in cigarette smoke-induced inflammation in a model of experimental chronic obstructive pulmonary disease (COPD). We targeted NLRP3 with the inhibitor MCC950 given prophylactically or therapeutically and examined Aim2(-/-) mice in cigarette smoke-induced experimental COPD. MCC950 treatment had minimal effects on disease development and/or progression. Aim2(-/-) mice had increased airway neutrophils with decreased caspase-1 levels, independent of changes in lung neutrophil chemokines. Suppressing neutrophils with anti-Ly6G in experimental COPD in wild-type mice reduced neutrophils in bone marrow, blood and lung. By contrast, anti-Ly6G treatment in Aim2(-/-) mice with experimental COPD had no effect on neutrophils in bone marrow, partially reduced neutrophils in the blood and had no effect on neutrophils or neutrophil caspase-1 levels in the lungs. These findings identify that following cigarette smoke exposure, Aim2 is important for anti-Ly6G-mediated depletion of neutrophils, suppression of neutrophil recruitment and mediates activation of caspase-1 in neutrophils.