Hypothesis

Periodic, sub‑nociceptive stimulation of TRPV1 triggers calcium‑dependent autophagy that clears senescent dorsal root ganglion (DRG) neurons, thereby reducing inflammaging and extending healthspan. Chronic use of analgesics that blunt TRPV1 signaling prevents this clearance, allowing senescent neurons to accumulate despite pain relief.

Mechanistic Rationale

• TRPV1 activation elevates intracellular Ca²⁺, activating CaMKK‑AMPK‑ULK1 pathways that initiate autophagy [1]. Autophagy selectively targets damaged mitochondria and senescent cells via p62/SQSTM1‑mediated cargo recognition.
• In DRG neurons, low‑level Ca²⁺ flux promotes FOXO3 nuclear translocation, upregulating lysosomal genes and enhancing senolysis [2].
• Conversely, sustained NSAID or opioid exposure inhibits TRPV1‑mediated Ca²⁺ influx (via downstream cAMP reduction or μ‑opioid receptor coupling) and blunts autophagic flux, permitting SASP‑positive senescent neurons to persist [3].
• This creates a dichotomy: acute pain signals a need for repair, while chronic analgesic masking removes the repair trigger without addressing the underlying senescent load.

Testable Predictions

1. Aged mice receiving intermittent low‑dose capsaicin (0.01 % w/w in diet, 3 days on/4 days off) will show decreased p16^Ink4a⁺ and SA‑β‑gal⁺ DRG neurons compared with vehicle controls.
2. The same regimen will lower circulating IL‑6, TNF‑α, and CGRP levels, reflecting reduced SASP.
3. Pain thresholds (von Frey filament) will improve proportionally to senescent cell clearance, without inducing hyperalgesia.
4. Lifespan analysis will reveal a significant increase in median survival for capsaicin‑treated mice relative to controls.
5. Parallel groups treated with chronic ibuprofen or morphine will exhibit unchanged or increased senescent DRG burden despite comparable analgesia, confirming that symptom suppression alone does not drive senolysis.

Experimental Design

• Animals: 20‑month‑old C57BL/6J mice, both sexes, n=15 per group.
• Groups: (1) Vehicle control, (2) Low‑dose capsaicin intermittent, (3) Chronic ibuprofen (30 mg/kg/day), (4) Chronic morphine (5 mg/kg twice daily), (5) Positive control: weekly ABT263 (50 mg/kg) senolytic.
• Duration: 6 months of treatment, with behavioral pain testing every 2 weeks.
• Outcomes: DRG immunohistochemistry for p16^Ink4a and SA‑β‑gal, ELISA of plasma SASP factors, autophagy markers (LC3‑II/I, p62) in sorted DRG neurons, and survival monitoring.
• Statistical: ANOVA with post‑hoc Tukey for endpoint comparisons; Kaplan‑Meier with log‑rank test for lifespan.

If intermittent TRPV1 activation reduces senescent neuron load and extends lifespan while chronic analgesia fails to do so, the hypothesis will be supported, reframing analgesics as potential accelerators of inflammaging when used without senolytic strategies.