Hypothesis

Chronic inflammaging drives persistent suppression of TET-mediated DNA demethylation at autophagy gene promoters, locking these loci in a methylated, transcriptionally silent state and thereby enforcing autophagy stall in old age.

Mechanistic Rationale

Aged tissues exhibit elevated levels of pro‑inflammatory cytokines such as IL-6 and TNFalpha, which activate JAK/STAT and NF-kB signaling pathways. These pathways up‑regulate DNA methyltransferases (DNMT1, DNMT3A) while simultaneously reducing intracellular alpha‑ketoglutarate (alpha‑KG) concentrations through increased succinate production and ROS‑mediated inhibition of TET enzyme activity. Reduced alpha‑KG and elevated succinate act as competitive inhibitors of TET dioxygenases, impairing 5‑mC oxidation to 5‑hmC and downstream demethylation. Consequently, promoters of key autophagy genes (Atg5, LC3B, Ulk1) acquire and retain CpG methylation, diminishing transcription factor binding and autophagic flux. This model integrates three observations from the seed research: (1) epigenetic silencing of autophagy genes is causal and reversible by DNMT inhibition; (2) immune cell activation drives epigenetic aging; (3) mTORC1 hyperactivation sustains the suppressed state by blocking TFEB nuclear entry. In this view, inflammaging‑induced metabolic stress creates a self‑reinforcing loop where cytokine signaling sustains both DNA methylation and mTORC1 activity, preventing autophagy restoration even when nutrient stress would normally induce it.

Testable Predictions

1. Blocking IL-6 signaling with an IL-6R antibody in aged macrophages will increase nuclear TET2 levels, raise 5‑hmC at autophagy gene promoters, and rescue autophagic flux without altering mTORC1 activity.
2. Supplementing aged cells with cell‑permeable alpha‑KG will restore TET activity, reduce promoter methylation of Atg5 and LC3B, and enhance autophagy independent of rapamycin treatment.
3. Simultaneous inhibition of DNMT activity (e.g., with 5-aza-2'-deoxycytidine) and mTORC1 (rapamycin) will produce a synergistic increase in autophagic flux greater than either intervention alone, reflecting additive effects of epigenetic and signaling brakes.
4. In vivo, aged mice treated with IL-6R blockade will show decreased epigenetic age signatures in blood neutrophils, concomitant with increased LC3‑II conversion in tissue macrophages.

Experimental Approach

• Isolate bone‑marrow derived macrophages from young (3 mo) and aged (24 mo) mice. Treat aged macrophages with anti‑IL‑6R antibody, alpha‑KG (5 mM), DNMT inhibitor (5‑aza, 1 µM), rapamycin (20 nM), or combinations for 24 h.
• Measure TET2 nuclear localization by immunofluorescence, global 5‑hmC by dot blot, and locus‑specific 5‑hmC at Atg5 and LC3B promoters using hMeDIP‑qPCR.
• Quantify autophagic flux via LC3‑II turnover in the presence of bafilomycin A1 and p62 degradation by Western blot.
• Assess mTORC1 activity (p‑S6K) to confirm that IL‑6R or alpha‑KG treatments do not alter this pathway, isolating the epigenetic effect.
• In a parallel in vivo cohort, administer anti‑IL‑6R antibody weekly for 4 weeks to aged mice, then isolate peritoneal macrophages and splenic neutrophils for epigenetic clock analysis (e.g., Horvath mouse clock) and autophagy markers.
• Statistical analysis using ANOVA with post‑hoc Tukey; n≥5 per group to ensure power.

If IL‑6R blockade or alpha‑KG supplementation restores TET‑dependent demethylation and autophagy without affecting mTORC1, the hypothesis that inflammaging‑driven metabolic inhibition of TET enzymes enforces autophagy stall will be supported. Conversely, lack of effect would falsify the proposed epigenetic mechanism and point to alternative suppression routes.