Hypothesis

Chronic pharmacological suppression of COX‑derived prostacyclin (PGI2) silences a hormetic prostaglandin signal that normally activates endothelial EP2/EP4‑cAMP‑PKA‑FOXO3a pathways, thereby reducing stress‑responsive autophagy and DNA repair. This loss of adaptive signaling accelerates endothelial senescence, manifested as increased arterial stiffness and higher cardiovascular event risk.

Mechanistic Rationale

1. PGI2 binds endothelial IP receptors, raising cAMP and activating PKA, which phosphorylates FOXO3a, promoting transcription of genes involved in oxidative‑stress resistance (SOD2, CAT) and autophagic flux (LC3B, BNIP3).
2. Low‑level COX activity also generates PGI2‑dependent microvascular vasodilation that creates intermittent shear stress, a known trigger for endothelial nitric oxide synthase (eNOS) uncoupling/re‑coupling cycles that maintain redox balance.
3. NSAIDs shunt arachidonic acid toward 5‑LOX leukotrienes, increasing proinflammatory signaling that further inhibits FOXO3a via Akt activation, creating a double hit: loss of protective PGI2 signaling and gain of inflammatory inhibition of longevity pathways.
4. Consequently, endothelial cells accumulate senescent markers (p16^INK4a, SASP cytokines) and exhibit reduced proliferative capacity, accelerating arterial wall remodeling and stiffening.

Testable Predictions

• In humans, long‑term NSAID users will show a steeper increase in carotid‑femoral pulse wave velocity (cfPWV) over 3 years compared with matched non‑users, independent of blood pressure and lipid levels.
• Peripheral endothelial progenitors from NSAID users will exhibit lower basal cAMP, reduced FOXO3a nuclear localization, and higher p16^INK4a expression ex vivo.
• Pharmacologic rescue with an IP receptor agonist (e.g., selexipag) in NSAID‑treated mice will restore autophagic flux (LC3‑II/I ratio) and blunt age‑related cfPWV rise, without affecting analgesic efficacy.
• Genetic endothelial‑specific deletion of COX‑2 will recapitulate the senescent phenotype, while endothelial overexpression of PGI2 synthase will protect against NSAID‑induced arterial stiffness.

Experimental Approach

• Cohort study: enroll 500 adults aged 45‑65, stratify by NSAID exposure (>3 days/week for >1 year). Measure cfPWV, plasma 6‑keto‑PGF1α (stable PGI2 metabolite), serum SASP (IL‑6, IL‑8), and leukocyte telomere length annually for 3 years. Use mixed‑effects models to test interaction between NSAID use and time on cfPWV.
• Mechanistic sub‑study: isolate circulating endothelial progenitors from 30 participants per group; assess cAMP levels (ELISA), FOXO3a localization (immunofluorescence), autophagy markers (Western blot for LC3‑II, p62), and senescence (β‑galactosidase, p16^INK4a qPCR).
• Animal validation: treat aged mice with chronic celecoxib vs vehicle; assign sub‑groups to receive selexipag or control. Monitor cfPWV (doppler), aortic histology (elastic fiber fragmentation, collagen), and endothelial senescence markers. Include COX‑2 endothelial knockout and PGI2 synthase overexpression cohorts.

Falsifiability

If longitudinal data show no difference in cfPWV trajectories between NSAID users and non‑users, or if IP agonist fails to improve autophagy and arterial stiffness despite restored cAMP‑FOXO3a signaling, the hypothesis would be refuted. Conversely, confirmation would support the notion that prostaglandin‑mediated hormetic signaling constitutes a latent longevity pathway whose pharmacological silencing accelerates vascular aging.

Key references: 1, 2, 3, 4, 5