Hypothesis

Chronic suppression of prostaglandin‑E2 (PGE2) signaling by NSAIDs or COX‑2 inhibitors diminishes a neuronal AMPK‑activating hormetic pathway, leading to reduced systemic autophagy, heightened mTORC1 activity, and accelerated inflammaging.

Mechanistic Basis

Low‑grade pain triggers COX‑2‑dependent PGE2 synthesis in peripheral neurons and glia. PGE2 binds EP2/EP4 receptors, raising intracellular cAMP and activating PKA, which phosphorylates and activates the upstream AMPK kinase LKB1. Activated AMPK then phosphorylates ULK1, initiating autophagy, and inhibits mTORC1 via TSC2 and Raptor phosphorylation. Simultaneously, PGE2‑EP4 signaling stimulates PI3K‑Akt pathways that paradoxically keep basal mTOR activity in check through feedback inhibition. When NSAIDs block COX‑2, neuronal PGE2 falls, PKA/LKB1‑AMPK signaling wanes, autophagy declines, and mTORC1 disinhibition promotes protein synthesis, senescence‑associated secretory phenotype (SASP) secretion, and systemic low‑grade inflammation. This creates a feed‑forward loop where diminished neuronal AMPK reduces circulating mitokines (e.g., FGF21, GDF15) that normally sustain peripheral AMPK activity, further eroding tissue‑specific homeostatic circuits.[1][2][3][4][5]

Testable Predictions

1. In humans, habitual NSAID users (>3 days/week for >6 months) will show lower phosphorylated AMPK (p‑AMPKThr172) in peripheral blood mononuclear cells and higher p‑S6K (mTORC1 read‑out) compared with age‑matched non‑users, after adjusting for comorbidities.
2. These users will exhibit reduced autophagy flux markers (elevated p62/SQSTM1, decreased LC3‑II/I ratio) in isolated monocytes.
3. Serum levels of neuron‑derived mitokines (FGF21, GDF15) will be negatively correlated with NSAID dosage.
4. In a mouse model, neuron‑specific COX‑2 knockout (Syn‑Cre; Cox2^fl/fl) will recapitulate the pharmacological phenotype: decreased hippocampal p‑AMPK, increased colonic mTORC1 activity, impaired gut‑barrier autophagy, and elevated circulating IL‑6 and TNF‑α, leading to shortened median lifespan versus wild‑type controls.
5. Acute, low‑dose PGE2 supplementation (via EP4‑selective agonist) in NSAID‑treated mice will restore neuronal p‑AMPK, normalize autophagy markers, and mitigate inflammaging readouts.

Potential Confounders and Controls

Indication bias (painful conditions themselves drive inflammation) must be addressed by stratifying users by underlying pain severity and using new‑user designs. Off‑target effects of NSAIDs on mitochondrial uncoupling should be measured (e.g., OCR in PBMCs) to distinguish COX‑specific actions. Use of celecoxib (COX‑2 selective) versus ibuprofen (non‑selective) will help isolate the prostaglandin axis.

Conclusion

Reframing transient pain as a prostaglandin‑driven AMPK activator positions analgesic overuse as a modifiable risk factor for premature inflammaging. Targeting the neuronal PGE2‑EP4‑PKA‑LKB1‑AMPK axis—either by sparing low‑dose COX‑2 activity or by downstream AMPK agonists—could preserve the hormetic benefits of pain while alleviating its nociceptive burden.