FOXO3 Regulatory Plasticity Links Microbiome-ECS Signaling to Immune Aging Resilience

FOXO3 Regulatory Plasticity — Research Brief

• HYPOTHESIS: Immune aging resilience is determined by the dynamic capacity to modulate FOXO3 under stress (regulatory plasticity) — not by high baseline FOXO3 levels. This plasticity is regulated upstream by gut microbiome composition through endocannabinoid system (ECS) signaling.

• MECHANISM: Gut microbiome → 2-AG (endocannabinoid) → PI3K/Akt → FOXO3 nuclear translocation → immune stress-response capacity. SIRT1 deacetylation is the dominant localization signal in hematopoietic cells.

• KEY FINDING: Analysis of 136,673 human PBMCs found FOXO3 regulon activity increases with age (ρ = 0.416) — contradicting the published consensus. Interpreted as a compensatory stress-response: aging immune cells run near-maximum FOXO3 engagement but lose dynamic range. No prior human study has reported this direction of effect.

• KNOWN LIMITATIONS: n = 17 donors (underpowered); regulon activity is inferred, not protein-level; no CD14+ monocyte protocol for SIRT1 inhibition exists in the literature; microbiome causality not yet directly demonstrated in this dataset.

• BROADER IMPLICATIONS: Reframes biological age measurement; repositions microbiome profiling as an immune resilience instrument; provides the significance framework for an NIA R21 grant application; redirects longevity therapeutics toward plasticity restoration rather than FOXO3 expression boosting.