Role of dietary fatty acids in shaping lung macrophage homeostasis and inflammatory function - PROJECT SUMMARY Obesity is a major modulator of lung immunity and is associated with poor outcomes in multiple inflammatory lung diseases including asthma. Notably, the pathological features of obesity-associated asthma (OAA) are distinct from non-obesity-related or “atopic” asthma: While atopic asthma is typified by type 2 inflammation and eosinophilia, OAA is characterized by type 1 inflammation and neutrophilia, indicating a change in innate immune activation with obesity. Yet, the underlying mechanisms by which diet-induced obesity alters innate immune cell activation in the lung are unclear. Previous research demonstrated that diets high in saturated fat have considerable effects on tissue-resident myeloid populations, including transcriptional and functional shifts toward a metabolically activated state in adipose tissue. As saturated long chain fatty acids become more prevalent in modern diets in the form of animal fats and preservatives, it is critical to determine their health consequences in other tissues. The broad objective of this proposal is to decipher the effects of a saturated fat-enriched diet on the lung in the steady-state and with an allergic stimulus. The central hypothesis is that the saturated 18-carbon fatty acid stearate promotes cellular membrane rigidity and induces pro-inflammatory cytokine secretion in a subset of lung-resident macrophages, which aggravates innate responses to an allergic airway challenge, including exacerbated neutrophilia and worse pulmonary function. Aim 1 investigates the steady-state profile of lung myeloid populations in mice fed normal chow or stearate-rich diets with or without myeloid-specific deletion of the enzyme required for stearate incorporation into the membrane. The experimental approaches are 1) single lung cell transcriptomic analysis for differentially expressed genes and gene sets and 2) flow cytometric cellular phenotyping for inflammatory activation, myeloid infiltration, and cytokine production in the lung. Aim 2 determines the consequences of diet-induced inflammation in the lung in the context of an innate immune challenge by leveraging a HDM/LPS model of OAA, assessing 1) protective effects of myeloid-specific deletion of the stearate-processing enzyme, and 2) in vivo tests of pulmonary function in mice. Together, these studies will provide insights into the impact of dietary saturated fatty acids on lung myeloid function and the development of OAA, elucidating the role of metabolic activation and transcriptional shifts in innate immune responses, thus paving the way for therapeutic interventions and a deeper understanding of the pathogenesis of obesity-related lung inflammatory diseases. Conducted within the resource-rich, multidisciplinary environment of the Children’s Hospital of Philadelphia, which is committed to training the next generation of scientific leaders, support of this proposal positions the fellow to gain comprehensive skills in immunology, metabolism, and advanced research methodologies. The proposed research strategy and training plan will foster critical thinking, leadership abilities, and scientific innovation, paving the way for the fellow's transition to an independent research career dedicated to addressing complex health challenges.
