Hypothesis

Chronic type I interferon (IFN-I) signaling in aging is driven by the release of mitochondrial DNA (mtDNA) into the cytosol, where it activates the cGAS‑STING pathway. We hypothesize that stabilizing the inner mitochondrial membrane phospholipid cardiolipin prevents mtDNA efflux, thereby dampening tonic IFN‑I activation and ameliorating inflammaging.

Mechanistic Rationale

• Cardiolipin is essential for cristae architecture and limits permeability transition pore (mPTP) opening; its peroxidation increases membrane fragility and promotes mtDNA release [1 [2].
• Restoring cardiolipin content via overexpression of the remodeling enzyme TAZ (tafazzin) or supplementation with linoleic acid‑derived phospholipids reduces mitochondrial outer membrane permeabilization and limits mtDNA escape [3] [4].
• Lower cytosolic mtDNA diminishes cGAS‑STING activation, decreasing IFN‑β production, restoring NRF2 activity, and reversing myeloid skewing and T‑cell exhaustion [5] [6].

Experimental Plan

1. In vitro: Treat aged human fibroblasts with a cardiolipin‑stabilizing peptide (e.g., SS‑31) or overexpress TAZ; measure cytosolic mtDNA by qPCR, IFN‑β ELISA, and cGAS‑STING phosphorylation.
2. In vivo: Generate knock‑in mice with cardiomyocyte‑specific TAZ overexpression; assess mtDNA release in serum, IFN‑signature in splenocytes, frailty index, and lifespan.
3. Intervention: Administer SS‑31 to wild‑type aged mice; compare outcomes to mtDNA mutator (PolG) controls.

Testable Predictions

• Prediction 1: Cardiolipin stabilization will reduce cytosolic mtDNA levels by ≥50 % relative to untreated aged cells.
• Prediction 2: Correspondingly, IFN‑β secretion will drop to youthful levels (<2‑fold over baseline).
• Prediction 3: Treated aged mice will exhibit improved grip strength, reduced inflammatory cytokines (IL‑6, TNF‑α), and a ≥15 % increase in median lifespan versus controls.

Falsifiability

If cardiolipin stabilization fails to lower cytosolic mtDNA or IFN‑I signaling despite verified target engagement, or if lifespan and healthspan metrics do not improve, the hypothesis would be refuted, indicating that mtDNA release is not the primary driver of chronic IFN‑I in aging.

Broader Implications

This work shifts focus from editing mtDNA sequences to preserving mitochondrial membrane integrity as a proximate lever to silence the innate immune alarm that fuels aging.