NADPH oxidase 2 limits amplification of IL-1β-G-CSF axis and an immature neutrophil subset in murine lung inflammation.

The leukocyte NADPH oxidase 2 (NOX2) regulates inflammation independent of its anti-microbial activity. Inherited defects in NOX2 lead to chronic granulomatous disease (CGD), associated with recurrent bacterial and fungal infections, often with excessive neutrophilic inflammation that results in significant inflammatory burden and tissue damage. We previously showed that excessive leukotriene B4 production by NOX2-deficient mouse neutrophils was a key driver of elevated lung neutrophil infiltration in the initial response to pulmonary challenge with the model fungal particle zymosan. We now identify IL-1β and downstream G-CSF as critical amplifying signals that augment and sustain neutrophil accrual in CGD mice. Neutrophils, delivered into the lung via LTB4, were the primary source of IL-1β within the airways, and their increased numbers in CGD lungs led to significantly elevated local and plasma G-CSF. Elevated G-CSF simultaneously promoted increased granulopoiesis and mobilized the release of higher numbers of an immature CD101neg neutrophil subset from the marrow, which trafficked to the lung and acquired a significantly more pro-inflammatory transcriptome in CGD mice compared to WT mice. Thus, neutrophil-produced IL-1β and downstream G-CSF act sequentially but non-redundantly with LTB4 to deploy neutrophils and amplify inflammation in CGD mice following inhalation of zymosan. NOX2 plays a critical role in dampening multiple components of a feed-forward pipeline for neutrophil recruitment, and these findings highlight NOX2 as a key regulator of neutrophil number, subsets and function at inflamed sites.