Hypothesis

Senescent CD8+ T cells accumulate with age and release mitochondrial damage‑associated molecular patterns (mtDNA, formyl peptides) that act as endogenous DAMPs, sustaining NLRP3 inflammasome activation in stromal fibroblasts and endothelial cells. This DAMP‑driven inflammasome signaling promotes a fibrotic SASP (e.g., TGF‑β, collagen deposition) that drives tissue stiffening and organ aging, independent of upstream oxidative stress. Consequently, removing senescent CD8+ T cells should diminish circulating mtDNA, lower NLRP3 activity in non‑immune tissues, and reverse age‑related fibrosis even when NLRP3 or IL‑6 pathways are pharmacologically blocked.

Mechanistic rationale

1. Senescent T cells exhibit mitochondrial dysfunction and increased extracellular mtDNA release [5].
2. Extracellular mtDNA binds TLR9 and NLRP3, triggering caspase‑1 activation and IL‑1β secretion in fibroblasts [2,4].
3. NLRP3 activation in stromal cells induces a profibrotic phenotype via caspase‑1‑mediated processing of IL‑1α and TGF‑β signaling [1,6].
4. Senolytic clearance of CD8+ T cells (e.g., using anti‑CD8‑conjugated navitoclax) reduces mtDNA burden without altering NLRP3 expression, thereby breaking the DAMP‑inflammasome loop.

Testable predictions

• Prediction 1: In 24‑month‑old mice, adoptive transfer of 1×10^6 senescent CD8+ T cells will double serum mtDNA levels and increase collagen I deposition in kidney and lung within 2 weeks, whereas transfer of naïve CD8+ T cells will not.
• Prediction 2: Treating aged mice with a senolytic that selectively removes CD8+ T cells (anti‑CD8‑ABT‑263) will reduce serum mtDNA by ~50% and decrease tissue hydroxyproline content, despite continued NLRP3 inhibition with MCC950.
• Prediction 3: NLRP3‑knockout mice that retain senescent CD8+ T cells will still develop fibrosis comparable to wild‑type controls, demonstrating that inflammasome activation downstream of mtDNA DAMPs is sufficient for fibrotic outcomes.
• Prediction 4: Blocking mtDNA release (using mitochondria‑targeted antioxidant MitoQ) will phenocopy senolytic effects, lowering fibrosis without altering senescent cell numbers.

Experimental approach

• Isolate senescent CD8+ T cells from old mice via p16^INK4a^‑GFP sorting; confirm SASP and mtDNA release.
• Transfer cells into young recipients; measure serum mtDNA (qPCR for mt‑ND1), NLRP3 activation (ASC speck formation) in isolated fibroblasts, and histology (Masson’s trichrome).
• Apply senolytic or MitoQ; assess same endpoints.
• Include controls: NLRP3‑KO, IL‑6R antibody, and vehicle.

Implications

If validated, this hypothesis repositions senescent immune cells as upstream DAMP factories that drive inflammasome‑mediated tissue aging, suggesting that combinatorial senolytics plus mitochondrial protection—not just inflammasome inhibition—are required for true rejuvenation.