In addition to the classical mode of phagocytosis and intracellular oxidative killing of pathogens, a recently discovered antimicrobial function of neutrophils is the formation of extracellular traps (Neutrophil Extracellular Traps, NETs), which can trap and kill pathogens extracellularly. As NET formation (NETosis) generally requires reactive oxygen species (ROS) generation, we and others have found that neutrophils from Chronic Granulomatous Diseases (CGD) patients and Gp91phox-/- CGD mice with mutations in NADPH oxidase complex exhibit impaired NET generation in-vitro and in-vivo in response to various stimuli and pulmonary bacterial infection. We recently reported that Tamoxifen (TMX), an FDA approved selective estrogen receptor (ER) modifier for treatment of breast cancer, induces antimicrobial NETs in CGD neutrophils in a ROS independent manner. We further showed that activation of autophagy is necessary and sufficient to induce TMX-mediated NETs. In addition to this seminal report, the premise of the proposed research is derived from our preliminary data indicating a novel pathway of ROS-and ER-independent NETosis by TMX via a non-canonical autophagy activation. The two proposed specific aims will establish TMX as NET-inducing agent with antimicrobial and anti- inflammatory effect in preclinical murine CGD and human CGD neutrophils (Aim 1); and elucidate TMX-mediated non-canonical autophagy signaling pathway in neutrophils that culminates in disintegration of nuclear lamina to facilitate the release of NETs (Aim 2). Our studies provide important mechanistic insights into a novel autophagy pathway activated by TMX which will have implications not only for NET research but also for exploiting autophagy and NETs to treat infectious and autoimmune diseases. By leveraging neutrophils from a well- characterized cohort of CGD patients at NIH Clinical Center, these studies also present an exciting opportunity for preclinical testing of TMX in CGD to restore antimicrobial function of neutrophils to combat pneumonic bacterial infections, frequently observed in these patients.
Significance of modulating neutrophil extracellular trap (NET) formation, a relative newly discovered aspect of neutrophil activation in respiratory and inflammatory disease conditions is now well recognized. Our proposed studies elucidate a novel autophagy-mediated, ROS independent NET formation pathway activated by Tamoxifen, a breast cancer drug, in ROS-deficient neutrophils and its implications in pulmonary infections in Chronic Granulomatous Disease (CGD). Validation of this drug and its target pathway will have significant impact on therapeutic measures to correct the neutrophil dysfunction in airway diseases.
