Hypothesis

Telomere length in myenteric neurons functions as a read‑out of cumulative oxidative informational entropy rather than a simple mitotic clock. When entropy exceeds a threshold, telomeres trigger a senescence program that selectively eliminates cholinergic enteric neurons, leading to the acetylcholine deficit and colonic hypomotility observed with aging.

Mechanistic Basis

Oxidative stress generates both DNA lesions and misfolded proteins, increasing the informational burden on chromatin. Each oxidative event perturbs the epigenetic state and raises the effective entropy of the genome. Telomeres, with their repetitive G‑rich sequences, are especially sensitive to oxidative damage; they lose repeats not only through replication‑dependent shortening but also via direct oxidation‑induced strand breaks. In post‑mitotic enteric neurons, this oxidative telomere attrition serves as a sensor of accumulated informational damage. When telomere signal falls below a critical length, ATM/ATR pathways activate p53‑dependent senescence, which is exacerbated in cholinergic neurons because they have higher basal mitochondrial activity and thus greater ROS production [2][3]. Nitrerergic neurons, with lower oxidative metabolism, show hypertrophy instead of loss, matching the selective vulnerability reported in aging colon [2].

Accompanying glial loss reflects paracrine senescence signals (SASP) that spread oxidative entropy to neighboring cells, producing the proportional neuron‑glia decline seen in aged myenteric plexus [5]. The accumulation of wild‑type and nitrated α‑synuclein further amplifies entropy by impairing proteostasis, creating a feed‑forward loop that drives telomere‑dependent senescence [6].

Predictions and Experimental Tests

1. Telomere length correlates with cholinergic neuron density – Quantitative FISH for telomeres combined with choline acetyltransferase immunostaining in young, middle‑aged, and old mouse colons will show a linear reduction of telomere signal that predicts neuron loss (r > 0.8).
2. Inducing oxidative telomere damage accelerates motility decline – Targeted expression of a mitochondria‑targeted endonuclease (mito‑TALEN) in enteric neurons will increase oxidative telomere breaks, precipitate cholinergic neuron loss, and slow colonic transit measured by bead expulsion assay.
3. Telomerase activation rescues motility without affecting proliferation – Transient delivery of TERT mRNA via AAV9 to the myenteric plexus of aged mice will lengthen telomeres, reduce p21^CIP1^ senescence markers, restore acetylcholine release (HPLC), and normalize colonic transit to youthful levels, while Ki‑67 staining remains negligible, confirming a post‑mitotic effect.
4. Senolytic clearance of SASP‑positive glia mitigates secondary neuron loss – Combining telomerase activation with a senolytic (navitocxyt) will further improve glial survival and motility outcomes beyond either treatment alone.

Potential Interventions

If telomeric entropy drives enteric neurodegeneration, therapies that lower oxidative informational load (e.g., chronic Nrf2 activators, caloric restriction) or directly reset telomere state (TERT transfection, telomere‑protective small molecules) should preserve cholinergic tone and prevent age‑related constipation. These approaches are falsifiable: a failure to observe telomere lengthening, senescence marker reduction, or functional improvement would refute the hypothesis.

References

[1] https://journals.physiology.org/doi/full/10.1152/ajpgi.00091.2002 [2] https://pubmed.ncbi.nlm.nih.gov/12878075/ [3] https://pmc.ncbi.nlm.nih.gov/articles/PMC3469348/ [4] https://pmc.ncbi.nlm.nih.gov/articles/PMC10726411/ [5] https://pubmed.ncbi.nlm.nih.gov/15480773/ [6] https://doi.org/10.3892/mmr.2016.5166