Modulation of Alveolar Macrophages by Sex as a Biological Variable

<b>Background:</b> Alveolar macrophages (AMs) play a key role in the innate immune system and the pathogenesis of bronchopulmonary dysplasia (BPD), a condition with a significant sex bias. However, the influence of biological sex on AM immunometabolism remains poorly defined. <b>Objective:</b> We tested the hypothesis that female AMs would exhibit greater metabolic resilience (less impact on their mitochondrial function) compared to male AMs upon exposure to hyperoxia. <b>Methods:</b> We characterized bioenergetic profiles of male (MH-S) and female (AMJ2-C11) adult murine AM cell lines and primary neonatal AMs from C57BL/6 pups. Oxygen consumption (OCR) and extracellular acidification rates (ECAR) were quantified using Seahorse extracellular flux analysis at baseline and following 48 hours of hyperoxia (85% O₂). <b>Results:</b> Adult female AMs displayed an elevated basal and maximal respiration compared to males. Upon exposure to hyperoxia, female AMs showed decreased maximal OCR and spare respiratory capacity. Conversely, male AMs showed little change in oxidative phosphorylation. Uniquely, neonatal AMs of both sexes show a suppression in their mitochondrial function upon exposure to hyperoxia, but the decline is more significant in the male macrophages. In addition, the neonatal female macrophages also showed a higher glycolytic reserve compared to their baseline in room air, upon exposure to hyperoxia. <b>Conclusions:</b> Biological sex and developmental stage are fundamental determinants of AM bioenergetics. These intrinsic sex-specific mechanisms may underlie differential susceptibility to neonatal lung injury, underscoring the necessity of sex-specific therapeutic strategies.