Abstract
As the global population ages, understanding the mechanisms underlying age-related diseases becomes increasingly important. Inflammaging, a state of chronic inflammation and immune dysregulation, is a key feature of aging. Macrophages, as master regulators of inflammation, are critical to this process. However, the effects of natural aging on alveolar macrophages (AMs) in the lungs remain poorly understood. In this study, we evaluated AM biology in older compared with young rhesus macaques. We compared cytokine profiles in plasma and bronchoalveolar lavage (BAL) fluid between young and aged macaques and performed single-cell RNA sequencing (scRNA-seq) to characterize age-related transcriptional and functional changes in AMs. Compared to young animals, AMs from aged animals exhibited similar cytokine inflammaging profile observed in the plasma of elderly humans. However, the general decrease of chemokine levels in BAL fluid relative to plasma suggest BAL may not reflect AM status in the lung tissues of rhesus macaques. scRNA-seq data corroborated plasma inflammaging findings, revealing increased inflammatory cytokine responses in AMs from older macaques. The consistent elevation of macrophage migration inhibitory factor (MIF) across plasma, AMs, and BAL fluid marks it as a promising biomarker and potential therapeutic target for age-associated inflammation. scRNA-seq further identified genes and pathways linked to macrophage senescence and turnover, suggesting potential targets for therapeutic intervention. Overall, our findings highlight the essential role of tissue-resident macrophages in pulmonary aging and underscores the need to further investigate their role in age-associated lung disease.