Hypothesis

Protein aggregates function as a molecular sink for mitochondrial danger signals that restrain NLRP3 inflammasome activation; enhancing aggregate tolerance—rather than clearance—will suppress inflammasome‑driven IL‑6 production and mitigate immunosenescence.

Rationale

• Stress granules and aggresomes sequester misfolded proteins in an ATP‑dependent manner, reducing soluble toxic species 1.
• Oxidative stress simultaneously triggers protective aggregation and up‑regulates IL‑6 4.
• NLRP3 inflammasome activation requires lysosomal destabilization by crystals, oxidized lipids, or mitochondrial DNA (mtDNA) released upon damage 5.
• We propose that the hydrophobic, β‑sheet‑rich surface of mature aggregates captures oxidized mitochondrial components (e.g., cardiolipin, mtDNA) before they can permeabilize lysosomes, thereby acting as a decoy that limits NLRP3 priming and activation.

Novel Mechanistic Insight

Aggregate surfaces display patches of exposed hydrophobic residues and negative charge that preferentially bind anionic mtDNA and oxidized phospholipids. This sequestration is reversible only when disaggregases (HSP110/HSP70/HSP40) or autophagy are engaged. By shifting the equilibrium toward longer‑lived, less dynamic aggregates (e.g., via small‑molecule promoters of amorphous aggregation or overexpression of the small HSP HSPB1), the capacity to bind mitochondrial DAMPs increases, reducing NLRP3‑mediated caspase‑1 cleavage and IL‑6β maturation.

Experimental Plan (testable & falsifiable)

1. Model – Aged (24‑month) C57BL/6J mice expressing an NLRP3‑GFP reporter and a cytosolic mtDNA‑sensor (cGAS‑STING‑Luc).
2. Interventions a. Tolerance enhancement – AAV‑mediated HSPB1 overexpression in hippocampus and peripheral monocytes. b. Clearance promotion – Trehalose or rapamycin to induce autophagy. c. Control – AAV‑GFP.
3. Readouts (at 4 weeks post‑treatment)
   • Soluble vs. aggregate‑associated mtDNA and oxidized cardiolipin (fractionation + dot blot).
   • NLRP3 inflammasome activation: ASC speck formation (imaging), caspase‑1 activity (FLICA), IL‑6β maturation (ELISA).
   • Immunosenescence markers: CD8⁺CD28⁻ T‑cell frequency, serum IL‑6, SASP factors.
   • Cognitive/behavioral assays (novel object recognition) to correlate peripheral immunity with brain function.
4. Predicted outcomes
   • HSPB1‑treated mice will show higher mtDNA/cardiolipin association with aggregates, lower NLRP3 activation, reduced IL‑6, and improved immune profiles compared with clearance‑enhanced or control groups.
   • If tolerance enhancement fails to reduce NLRP3 activity or worsens pathology, the hypothesis is falsified.

Potential Pitfalls & Alternatives

• Over‑aggregation could sequester essential proteins; monitor global proteostasis via ubiquitin‑positive inclusions and cell viability.
• HSPB1 may affect actin dynamics; include a mutant HSPB1 unable to bind aggregates as a specificity control.

By directly testing whether augmenting the cell’s “last attempt at order” dampens inflammasome signaling, this work bridges the adaptive view of protein aggregates with immunosenescence and offers a mechanistic alternative to blunt aggregate clearance strategies.