Hypothesis

We hypothesize that low‑level activation of nociceptive TRPV1 channels generates calcium oscillations that stimulate AMPK‑ULK1 dependent autophagy and promote p53‑mediated senescence surveillance, thereby acting as a hormetic signal that preserves tissue homeostasis.

Mechanistic basis

TRPV1 opening allows Ca2+ influx that activates CaMKKβ‑AMPK signaling, a known initiator of the ULK1 complex and autophagosome formation [[https://www.frontiersin.org/journals/aging/articles/10.3389/fragi.2024.1477017/full]]. Calcium‑dependent calcineurin can also dephosphorylate NFATc1, driving transcription of autophagy genes such as LC3 and BECN1 [[https://pmc.ncbi.nlm.nih.gov/articles/PMC9975512/]]. In parallel, TRPV1‑derived neuropeptides (Substance P, CGRP) modulate immune surveillance but, at sub‑nociceptive levels, their calcium signal favors repair over inflammation [[https://pmc.ncbi.nlm.nih.gov/articles/PMC6377341/]]. Pharmacological blunt­ing of this cascade—by opioids, NSAIDs, or genetic loss—reduces autophagic flux, allowing accumulation of damaged mitochondria and senescent cells.

Predictions

1. Mice with reduced TRPV1 signaling (knockout or chronic analgesic treatment) will show decreased LC3‑II/I ratios and increased p62 accumulation in liver, skeletal muscle and hippocampus.
2. These animals will exhibit elevated senescence markers (p16^INK4a mRNA, SA‑β‑gal activity) and higher mitochondrial ROS.
3. Median lifespan will be shortened and frailty index accelerated relative to wild‑type controls.
4. Intermittent low‑dose capsaicin administration will rescue autophagic flux, lower senescence markers and extend healthspan in TRPV1‑intact mice.

Experimental design

• Groups: WT and TRPV1‑KO mice; each split into vehicle, chronic morphine (10 mg/kg day⁻¹, i.p.), chronic ibuprofen (30 mg/kg day⁻¹, p.o.), and low‑dose capsaicin (0.01 % w/w in chow) arms.
• Readouts:
  • Autophagic flux via tandem mRFP‑GFP‑LC3 reporter quantified by confocal microscopy and Western blot for LC3‑II/I and p62.
  • Senescence by flow cytometry for p16^INK4a⁺ cells and SA‑β‑gal staining.
  • Mitochondrial ROS with MitoSOX.
  • Serum inflammatory cytokines (IL‑6, TNF‑α) to control for neurogenic inflammation.
  • Survival curves and frailty index (grip strength, gait speed, coat condition) over 30 months.
• Controls: Neuron‑specific TRPV1 rescue in KO mice to distinguish neuronal versus peripheral contributions; peripheral tissue‑specific KO (e.g., Alb‑Cre TRPV1^fl/fl) to test cell‑autonomous effects.

Potential confounds and mitigation

TRPV1 activation also drives neurogenic inflammation, which could independently affect aging. To isolate the autophagy‑centric pathway, we will:

• Use TRPV1 mutants that preserve ion channel function but lack neuropeptide release (e.g., TRPV1^ΔN).
• Measure cytokine levels; groups with matched inflammation will be compared.
• Include antioxidant NAC treatment to test whether ROS changes are downstream of autophagy loss rather than direct oxidative stress.

If the hypothesis holds, dampening TRPV1‑mediated calcium signaling will accelerate biomarkers of aging, suggesting that indiscriminate analgesia may erase a vital damage‑sensing system. Conversely, enhancing low‑level TRPV1 activity could become a strategy to bolster autophagy and delay age‑related decline.