G-protein coupled receptor (GPR)55 Deficiency on Neutrophil Function: Attenuation of Inflammation in an Acute Lung Injury Mouse Model of Infection

Inflammatory lung diseases from respiratory infections affect over 5 million people worldwide, ranking 3rd cause of mortality. Severe infections progress to acute respiratory distress syndrome (ARDS), marked by substantial tissue damage and inflammation, with neutrophils as key immune cells involved in the lung's initial response. This study explores the role of G-protein coupled receptor 55 (GPR55) in neutrophil function and ARDS. Using intratracheal instillation of lipopolysaccharide (LPS;2mg/mL in 75µl) or Poly(I:C) (10mg/ml in 75µl) to induce acute lung injury (ALI) in wildtype (WT) and GPR55-knockout (KO) mice; neutrophil numbers and functionality in bronchoalveolar lavage (BAL), blood, and bone marrow (BM) were examined after 6 hours. GPR55-KO mice exhibited reduced neutrophil infiltration in BAL post-LPS stimulation, yet these neutrophils showed heightened activation with more reactive oxygen species expression. Healthy GPR55-KO mice showed higher circulating neutrophil counts and less mobilization post-LPS or Poly(I:C). Deficient GPR55 mice have disrupted neutrophil production & maturation in BM during ALI, indicating GPR55's impact on hematopoiesis. Lung inflammation (IL1β,IL6,TNFα) was reduced in GPR55-KO versus WT mice post-infection. RNA-sequencing of blood neutrophils revealed GPR55 deficiency associated with increased IFNα/γ and TNFα pathways and enhanced responsiveness to viruses and cytokine production, supported by qPCR analysis of proinflammatory cytokines in blood & BM neutrophils. Functional in vitro studies further confirmed weakened stimulation in GPR55-KO isolated neutrophils compared to WT neutrophils following LPS or Poly(I:C) exposure. Our results highlight the significant role of GPR55 receptor in modulating neutrophil function and response to infections.