Transcriptome of monocytes from liver, brain and bone marrow reveals organ-specific features in aging and alcohol...

Aging and alcohol misuse independently alter monocyte (MO) and macrophage (MØ) function, leading to impaired antimicrobial responses. However, how alcohol misuse contributes to impaired MO/MØ function during aging remains unclear.

We compared the transcriptomes of MOs and MØs from alcohol-modulated niches (liver, brain, and bone marrow [BM]) in young (3-month-old) and old (20-24-month-old) female C57BL/6N mice (n = 4-6 per group). Statistical significance was determined using two-way ANOVA.

MO/MØ transcriptomes showed unique organ-specific responses to aging and alcohol. Aging elicited a common deregulation of pathogen-responsive pathways, while alcohol misuse commonly inhibited IFN signaling in the aged populations. Our studies on intercellular communication using ligand-receptor interactions revealed that BM MOs were the least communicative and liver MØs were the most communicative. Alcohol misuse specifically increased MO/MØ communication in aging. We also identified and validated specific pathways driving inter-organ MO/MØ crosstalk in alcohol misuse during aging, including APOE-TREM2 signaling from the liver to microglia and the NRXN2 and SPP1 pathways.

Our results provide a unique insight into the heterogeneity of the MO/MØ transcriptome and define the inter-organ crosstalk between BM, liver, and brain during aging and alcohol misuse.

Aging and alcohol misuse are linked to immune dysfunction, systemic inflammation, and altered innate immune responses. Here, we examined monocyte/macrophage responses in the liver, brain, and bone marrow of young and aged mice under alcohol exposure at the transcriptomic level. We observed that aging and alcohol predominantly elicited organ-specific changes in gene expression, with minimal overlap between the monocyte/macrophage populations across different tissues. However, aging commonly upregulated pathogen response pathways while alcohol misuse inhibited interferon signaling. We also assessed cell-cell communication by analyzing ligand-receptor expression in the different monocyte/macrophage populations and identified candidate molecules (APOE, TREM2, NRXN2, SPP1) from the top pathways guiding inter-organ signaling specifically in aging and alcohol misuse. Our findings have generated a unique repository and provide novel insights on how aging and alcohol impact tissue-specific monocytes/macrophages and their crosstalk.