Extending neutrophil survival in neutropenia-related pneumonia

Neutropenia-related pneumonias account for 40% of infections at sites other than the bloodstream and are typically treated with broad-spectrum antibiotics and G-CSF therapy. However, not all patients respond to these treatments. The long-term goal of this project is to explore an alternative strategy for treating and preventing neutropenia-related pneumonia by increasing the lifespan of neutrophils in the lungs of neutropenic patients. Since neutropenia-related pneumonia primarily results from an insufficient number of neutrophils in the infected lungs to eliminate invading pathogens, prolonging neutrophil survival will increase the neutrophil count in the infected lungs, thereby enhancing host defense against invading pathogens. Here, it is proposed that prolonged neutrophil survival can be achieved by targeting Gasdermin D (GSDMD), a pore-forming cell death executor. The premise of this study is supported by preliminary data on the role of GSDMD in mediating bacteria-induced neutrophil death. The hypothesis is that inhibiting GSDMD will prevent bacteria-induced neutrophil death and elevate neutrophil-mediated host defense, thus representing a viable therapeutic strategy for the treatment of neutropenia-related bacterial pneumonia. To further advance the understanding of the role and regulation of GSDMD in neutropenia-related bacterial pneumonia and explore its therapeutic potential, three specific aims will be investigated. (1) GSDMD activation depends on the cleavage of the full-length protein and the generation of the GSDMD N-terminal fragment (GSDMD-NT). Aim 1 will uncover the underlying mechanism responsible for GSDMD cleavage and activation in neutropenia-related bacterial pneumonia. (2) Preliminary data show that GSDMD mediates bacteria-induced neutrophil death in vitro, but it has never been investigated whether Gsdmd-deficiency in neutrophils can intrinsically lead to their prolonged survival in vivo in neutropenia-related bacterial pneumonia. Aim 2 will elucidate the role of GSDMD in regulating neutrophil lifespan in the lungs of bacteria-infected neutropenic mice. (3) Aim 3 will explore GSDMD inhibition as a therapeutic strategy for treating neutropenia-related bacterial pneumonia. It will determine whether neutrophil specific Gsdmd disruption or pharmacological inhibition of GSDMD can enhance host defense and mitigate lung damage. Additionally, the effect of GSDMD inhibition on bacteria-induced death of human neutrophils will be investigated both in vitro and in vivo using NSG mice. Together, results from this study will confirm GSDMD-mediated neutrophil death in the lungs as a key regulatory mechanism in host defense and as a novel therapeutic target for the treatment of neutropenia-related bacterial pneumonia. Furthermore, a better understanding of the underlying mechanisms responsible for the cleavage and subsequent activation of GSDMD in bacteria-infected lungs will aid in designing strategies to achieve specific inhibition of GSDMD activation and GSDMD-elicited cell death in neutrophils. Project Number: 1R01HL178823-01 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Hongbo Luo | Institution: BRIGHAM AND WOMEN'S HOSPITAL, BOSTON, MA | Award Amount: $676,748 | Activity Code: R01 | Study Section: Lung Immunology and Infection Study Section[LII] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01HL17882301