Dual NLRP3 and LDHA inhibition reverses thymic involution and peripheral inflammaging by decoupling intrathymic IL-1β from IL-6-driven glycolysis
Hypothesis
Simultaneous inhibition of the NLRP3 inflammasome in thymic myeloid cells and lactate dehydrogenase A (LDHA) in CD4+ T cells will produce a synergistic restoration of youthful immune function in aged mice, exceeding the additive benefits of each monotherapy.
Rationale
Aged thymic myeloid cells activate NLRP3 in response to lipotoxic cues, secreting IL-1β locally to drive cortical epithelial loss, naïve T cell depletion, and TCR repertoire narrowing 1. NLRP3 deficiency preserves thymic architecture and output up to 23 months 1. Peripherally, IL-6 promotes Th17 differentiation via STAT3‑dependent upregulation of Glut1 and LDHA, shifting metabolism toward glycolysis 3. LDHA blockade with FX11 selectively suppresses this pathogenic Th17 program while sparing Tregs 3. Notably, intrathymic IL-1β operates without detectable plasma elevation, indicating spatial separation from systemic IL‑6 signaling 1.
Because NLRP3‑derived IL‑1β and IL‑6‑driven glycolysis act in distinct compartments yet converge on immunosenescence, targeting both nodes may decouple the two pathways, allowing thymic regeneration while curbing peripheral inflammation.
Experimental Design
Model – C57BL/6 mice aged 18‑20 months.
Groups (n=10 per group):
- Vehicle control
- NLRP3 inhibitor MCC950 (50 mg/kg i.p., twice weekly)
- LDHA inhibitor FX11 (10 mg/kg i.p., three times weekly)
- Combined MCC950 + FX11 (same doses)
Duration – 8 weeks.
Readouts
- Thymic cellularity and cortical thymic epithelial cell (cTEC) density (immunofluorescence for EpCAM⁺Ly51⁺).
- Naïve CD4⁺CD8⁻ T cell frequency (flow cytometry).
- TCR β‑chain repertoire diversity (Shannon entropy from bulk sequencing).
- Intrathymic IL‑1β protein (ELISA on thymic lysates) vs plasma IL‑1β and IL‑6 (Luminex).
- Peripheral Th17 (IL‑17A⁺) and Treg (FoxP3⁺) frequencies (intracellular cytokine staining).
- Glycolytic flux in sorted CD4⁺ T cells (ECAR assay) and LDHA activity (Western blot).
- Senescent T cell burden (p16^INK4a^ staining, SASP cytokines).
- Vascular function (aortic ring vasodilatory response to acetylcholine).
Expected Outcomes
If the hypothesis is correct, the combination group will show:
-
2‑fold increase in thymic cellularity and cTEC area relative to either monotherapy (p<0.01).
- Naïve T cell frequencies approaching those of 3‑month‑old mice.
- TCR repertoire Shannon entropy restored to ≥80% of young baseline.
- Intrathymic IL‑1β reduced >70% without altering plasma IL‑1β, confirming compartment‑specific effect.
- Peripheral Th17 cells decreased >60% while Tregs unchanged or slightly increased.
- Glycolytic ECAR in CD4⁺ T cells suppressed to levels seen in young mice.
- Senescent T cell frequency and SASP markers lowered >50%.
- Improved aortic vasodilation (>30% increase vs control).
Critically, the magnitude of improvement in the combined group should exceed the sum of the individual group effects (synergy index >1) for at least three primary endpoints (thymic cellularity, naïve T cells, TCR diversity).
Falsifiability
Failure to observe a statistically significant synergistic improvement—i.e., combination outcomes not surpassing the additive prediction—or detection of broad immunosuppression (marked reduction in total lymphocyte counts or increased infection susceptibility) would refute the hypothesis. Additionally, if intrathymic IL‑1β levels remain unchanged despite NLRP3 inhibition, the premise of spatially distinct IL‑1β action would be challenged.