Hypothesis

Long‑term use of common analgesics (e.g., NSAIDs or low‑dose opioids) suppresses prostaglandin‑E2 (PGE2) signaling through the EP4 receptor, which in turn dampens the cAMP/PKA‑AMPK axis that normally cooperates with mTOR inhibition to trigger autophagy. Consequently, when analgesic‑induced PGE2/EP4 activity is low, rapamycin‑driven lifespan extension is attenuated because a key hormetic stress signal is missing.

Mechanistic rationale

• Pain‑associated COX‑2 activity produces PGE2 that binds EP4 on many cell types, raising intracellular cAMP and activating PKA.
• PKA phosphorylates AMPKα at Ser485 (or upstream LKB1), enhancing AMPK activity independent of AMP/ATP ratios.
• AMPK activation promotes ULK1‑dependent autophagy and inhibits mTORC1, creating a feed‑forward loop that amplifies the cellular cleanup initiated by rapamycin.
• Analgesics that inhibit COX‑2 (e.g., celecoxib, ibuprofen) or reduce opioid‑mediated neuroimmune signaling lower basal PGE2, thereby weakening this AMPK‑priming step.

Testable predictions

1. In mice receiving chronic rapamycin, co‑administration of a COX‑2 inhibitor will reduce hepatic and muscular LC3‑II/I ratios and increase p62 accumulation compared with rapamycin alone.
2. The same combination will shorten median lifespan extension observed with rapamycin monotherapy by at least 15%.
3. Pharmacologic rescue with an EP4 agonist (e.g., PGE‑1‑OH) will restore AMPK phosphorylation (Thr172) and autophagic flux despite COX‑2 blockade.
4. In humans, longitudinal data showing regular NSAID use among participants on rapamycin analogs (e.g., everolimus) will correlate with blunted improvements in epigenetic clocks (DunedinPACE) relative to non‑users.

Experimental approach

• Mouse cohort: C57BL/6 males, 20 mo old, split into four groups (vehicle, rapamycin, rapamycin + celecoxib, rapamycin + celecoxib + EP4 agonist). Treat 6 months, monitor survival, collect tissues for immunoblotting (p‑AMPK, LC3‑II, p62) and flux assays (chloroquine blockade).
• Human arm: Analyze existing trial data (e.g., MRT‑AGING) for everolimus users with recorded NSAID prescriptions; compute change in DunedinPACE over 12 months, adjusting for age, BMI, comorbidities.

Potential falsifying outcomes

If COX‑2 inhibition does not alter rapamycin‑induced AMPK activation, autophagy markers, or lifespan benefit, the hypothesis is falsified. Likewise, if EP4 agonism fails to rescue autophagy despite COX‑2 blockade, the proposed PGE2‑EP4‑AMPK link is insufficient.

Broader implication

This framework reframes analgesics as modulators of a specific hormetic circuit that longevity interventions rely on. It suggests that timing, dosing, or selective sparing of EP4 signaling could preserve the repair‑promoting facets of pain while still alleviating suffering.