Intermittent TRPV1‑driven calcium signaling promotes longevity through CaMKK2‑AMPK‑SIRT1 axis

Hypothesis

Repeated, low‑intensity activation of the nociceptor ion channel TRPV1 triggers a hormetic cascade that enhances cellular stress resistance and extends lifespan. This effect depends on calcium‑mediated activation of the CaMKK2‑AMPK‑SIRT1 signaling axis, leading to increased NAD+ levels, FOXO3 deacetylation, and upregulation of antioxidant and autophagy genes. Chronic analgesic use that suppresses TRPV1 activity abolishes this benefit, thereby accelerating age‑related decline.

Mechanistic Rationale

1. TRPV1‑mediated Ca²⁺ influx – Brief capsaicin or heat exposure raises intracellular calcium in peripheral nociceptors without inducing lasting injury.
2. CaMKK2 activation – Elevated Ca²⁺ binds calmodulin, activating CaMKK2, which phosphorylates and activates AMPK.
3. AMPK‑SIRT1 coupling – AMPK raises NAD+ via increased NAMPT expression and inhibits mTORC1, creating a permissive environment for SIRT1 deacetylase activity.
4. FOXO3 and NRF2 activation – SIRT1 deacetylates FOXO3, promoting its nuclear translocation and transcription of SOD2, CAT, and autophagy genes (e.g., LC3B). Concurrently, AMPK phosphorylates NRF2, enhancing its stability and antioxidant response element (ARE) driven gene expression.
5. Outcome – Improved mitochondrial biogenesis, reduced ROS accumulation, enhanced proteostasis, and lower senescent cell burden.

Testable Predictions

• In vivo – Mice receiving intermittent, low‑dose capsaicin (0.1 mg/kg, i.p., twice weekly) will show increased median lifespan (~10‑15 %) and reduced senescence‑associated β‑galactosidase activity in liver and skin compared with vehicle‑treated controls. The same regimen will elevate p‑AMPK, SIRT1 activity, and FOXO3 target expression in nociceptor‑rich tissues.
• Pharmacological blockade – Co‑administration of the TRPV1 antagonist capsazepine or the CaMKK2 inhibitor STO‑609 with intermittent capsaicin will abolish the lifespan extension and molecular markers of hormesis.
• Analgesic interference – Chronic morphine (10 mg/kg, s.c., daily) or high‑dose ibuprofen (50 mg/kg, oral, daily) administered alongside intermittent capsaicin will blunt the longevity benefit, confirming that analgesic suppression of TRPV1 signaling interferes with the hormetic pathway.
• Genetic validation – Nociceptor‑specific Trpv1 knockout mice will fail to exhibit lifespan extension under intermittent capsaicin dosing, whereas overexpression of a constitutively active CaMKK2 in sensory neurons will mimic the effect even without capsaicin.

Falsifiability

If intermittent TRPV1 activation does not increase lifespan, or if blocking CaMKK2‑AMPK‑SIRT1 signaling fails to reduce the benefit, the hypothesis is refuted. Likewise, if chronic analgesic use shows no impact on longevity phenotypes in this paradigm, the proposed link between pain signaling suppression and accelerated aging would be unsupported.

Relation to Existing Work

The hypothesis diverges from prior models that equate pain signaling solely with maladaptive plasticity [3][4] or attribute neuronal stress longevity to hypoxic HIF‑1 pathways in C. elegans [2]. It positions acute, intermittent nociceptor calcium flux as a conserved upstream trigger of evolutionarily conserved nutrient‑sensing and stress‑response networks, distinct from the serotonin/GABA/tyramine‑driven HIF‑1 route.

By framing pain as a potential regulatory signal rather than a purely pathological noise, this work invites a reevaluation of analgesic strategies and suggests that calibrated, intermittent nociceptor stimulation could be harnessed as a geroprotective intervention.