A68-24 The Leptin Receptor Q223R Single Nucleotide Polymorphism Disrupts Innate Immune Pathways and Increases Proinflammatory Cytokines in Murine Alveolar Macrophages

Rationale The leptin receptor Q223R single-nucleotide polymorphism (SNP) (LepR Q223R, rs1137101) is associated with increased susceptibility and severity of gastrointestinal infections in both human patients and transgenic mice. Prior studies indicate that this heightened vulnerability is associated with elevated proinflammatory cytokine production and increased neutrophil recruitment in mice homozygous for the mutant (R) allele, compared to the ancestral (Q) allele. Furthermore, we have reported an increased risk of bacterial pneumonia diagnosis in carriers of this mutation within the Michigan Genomics Initiative cohort. In this study, we investigated gene set enrichment patterns and proinflammatory cytokine synthesis in alveolar macrophages (AMs) isolated from RR (mutant LepR) and QQ (wild type LepR) mice following lipopolysaccharide (LPS) stimulation. Methods AMs were collected from male and female mice via lung lavage and incubated overnight with 100 ng/ml LPS from Escherichia coli. The following day, cell culture supernatants and RNA were collected. Differential gene expression was profiled by RNA sequencing, while cytokine concentrations were quantified using Luminex bead-based ELISA. Analyses were adjusted for sex, and Gene Set Enrichment Analysis (GSEA) was performed, with a normalized enrichment score (NES) threshold of ± 2. Results GSEA revealed significant downregulation of Gene Ontology Biological Process (GOBP) pathways associated with innate immune responses, including Modulation of Processes by Other Organisms, Positive Regulation of Cytokine Production, Response to Bacteria, Biological Response Involved in Interaction with Host, Positive Regulation of Interleukin-6 Production, and Positive Regulation of the MAPK Cascade in RR versus QQ AMs. Additionally, we detected increased levels of macrophage migration inhibitory factor (MIF) and trends toward higher concentrations of CCL2, CXCL2, IL-1β, and TNF-α in culture media from RR compared to QQ AMs. Conclusion AMs from RR homozygous LepR mutant mice demonstrated reduced activation of GOBP pathways critical to host defense against bacterial infection, elevated production of MIF, and trends toward increased proinflammatory cytokines after LPS stimulation. These findings suggest that the rs1137101 SNP disrupts intracellular signaling, resulting in impaired innate immune responses and excessive proinflammatory cytokine production, which may underlie the increased susceptibility to bacterial infections associated with this LepR variant. This abstract is funded by: R21 AI180617