Blunted JNK/AP-1 Response to Acute Stress Predicts Accelerated Epigenetic Aging and Reduced Pain Tolerance
Hypothesis
Individuals who exhibit a deficient JNK/AP-1 activation transiently after a standardized acute stressor will show (1) lower experimental pain thresholds at baseline, (2) a faster increase in epigenetic age over 12 months, and (3) a greater burden of senescent markers in circulating DRG‑derived extracellular vesicles. Restoring JNK/AP-1 signaling pharmacologically or via senolysis will normalize pain sensitivity and attenuate epigenetic aging.
Rationale
- Chronic pain sensitivity correlates with epigenetic age acceleration (1, 2).
- Senescent dorsal root ganglion (DRG) neurons secrete IL‑6 and other SASP factors that heighten excitability of neighboring nociceptors (3).
- Aging selectively impairs stress‑induced JNK phosphorylation and downstream AP‑1 transcriptional activity (4), a pathway known to drive both inflammatory responses and cellular senescence (5).
- Acute stress normally triggers a hormetic JNK/AP-1 pulse that upregulates antioxidant and DNA‑repair genes; a blunted pulse fails to engage these protective programs, favoring senescence accumulation in pain‑processing neurons.
Predictions
- Baseline correlation – Lower heat and pressure pain thresholds will associate with reduced phospho‑JNK levels in peripheral blood mononuclear cells (PBMCs) after a cold pressor test (CPT).
- Prospective link – Participants in the lowest quartile of CPT‑induced JNK activation will exhibit a ≥0.5‑year increase in DNAmPhenoAge per year, whereas the top quartile will show ≤0.1‑year change.
- Mediator – Elevated IL‑6‑positive extracellular vesicles isolated from blood will mediate the relationship between blunted JNK response and pain threshold decline.
- Intervention – A four‑week regimen of the JNK activator anisomycin (low dose, peripherally restricted) or the senolytic navitoclax (ABT263) will increase CPT‑induced phospho‑JNK by ≥30 %, raise pain thresholds by ≥15 %, and slow epigenetic age accrual relative to placebo.
Experimental Design
- Cohort: 120 adults aged 45‑70, stratified by sex and baseline pain sensitivity.
- Baseline: Measure heat/pressure pain thresholds, PBMC phospho‑JNK before and immediately after a 2‑minute CPT (4 °C water hand immersion), plasma IL‑6, and DNAmPhenoAge/GrimAge.
- Follow‑up: Repeat pain testing, JNK response, and epigenetic clocks at 6 and 12 months.
- Intervention sub‑study: Randomized double‑blind placebo‑controlled trial (n=40) receiving anisomycin (0.5 mg/kg) or navitoclax (50 mg weekly) for 4 weeks, with pre/post CPT JNK and pain assessments.
- Analysis: Mixed‑effects models to test interaction between JNK response quartile and time on epigenetic age; mediation analysis for vesicle IL‑6; ANOVA for intervention effects.
Falsifiability
If (a) CPT‑induced JNK activation does not predict baseline pain thresholds, (b) the lowest JNK responders show no accelerated epigenetic aging over 12 months, or (c) pharmacologic JNK activation or senolysis fails to improve pain sensitivity or slow epigenetic change, the hypothesis is falsified.
Significance
Linking an acute, measurable stress‑response pathway to both subjective pain and biological age offers a rapid, non‑invasive prognostic tool. It also suggests that enhancing hormetic JNK/AP-1 signaling could decouple pain perception from aging, opening preventive strategies for age‑related pain comorbidities.