Hypothesis

Combining brief, high‑intensity morning light exposure with a low dose of an adenosine A2A/A1 receptor antagonist (e.g., CT1500) will increase PER1 transcription in the suprachiasmatic nucleus (SCN) via Ca2+-ERK-AP-1 signaling, thereby boosting circadian amplitude and accelerating phase advance. This enhanced amplitude will blunt the melatonin‑suppressing effect of evening blue‑light exposure, leading to higher nocturnal melatonin levels, improved sleep architecture, and lower CSF amyloid‑β42/tau ratios compared with morning light alone.

Mechanistic Rationale

• Morning light activates melanopsin-expressing ipRGCs, glutamatergic signaling to the SCN, triggering Ca2+ influx and ERK phosphorylation that drives AP-1–mediated Per1 transcription. Adenosine A2A/A1 antagonists raise intracellular cAMP, synergizing with Ca2+-ERK pathways to further increase AP-1 activity and Per1 mRNA stability (see Frontiers in Physiology).
• Elevated PER1 strengthens the core negative feedback loop, increasing the amplitude of Bmal1‑Clock driven transcription of downstream clock genes (Per2, Cry1) in both central and peripheral tissues.
• Higher circadian amplitude raises the threshold for melatonin suppression by evening blue light, because the SCN’s output signal to the pineal gland becomes more robust, reducing the impact of ipRGC‑mediated inhibition of melatonin synthesis.
• Consequently, nocturnal melatonin rises, enhancing its antioxidant and anti‑inflammatory actions, which have been linked to decreased amyloid‑β aggregation and tau phosphorylation in preclinical models (see ScienceDaily 2026 and BrightFocus).

Testable Predictions

1. Participants receiving morning light (10,000 lux for 30 min) plus CT1500 will show a ≥30‑minute larger phase advance in DLMO compared with morning light alone.
2. The same group will exhibit a 20‑30 % increase in nocturnal melatonin AUC under a standardized evening blue‑light challenge (480 nm, 100 lux for 2 h) versus light‑only.
3. Actigraphy will reveal increased sleep efficiency and higher proportion of slow‑wave sleep in the combination group.
4. Exploratory CSF biomarkers will demonstrate a reduction in amyloid‑β42/tau ratio after 4 weeks of intervention relative to baseline.

Experimental Design

• Randomized, crossover, double‑blind trial in healthy adults aged 30‑50 (n=30).
• Each participant completes two 2‑week conditions separated by a 1‑week washout: (A) morning light + placebo, (B) morning light + CT1500 (oral dose achieving plasma levels used in mouse studies).
• Morning light delivered via LED box at 07:00–07:30; evening blue‑light exposure fixed at 20:00–22:00 to assess melatonin suppression.
• Primary outcome: DLMO shift measured via hourly saliva sampling under dim light.
• Secondary outcomes: evening melatonin AUC, actigraphy‑derived sleep metrics, CSF amyloid‑β42/tau (lumbar puncture at end of each condition).
• Statistical analysis: paired t‑tests for primary outcomes, mixed‑effects models for secondary, with Bonferroni correction for multiple comparisons.

Potential Implications

If confirmed, this approach would translate mechanistic mouse data into a practical, low‑risk strategy to strengthen circadian rhythms in humans, offering a non‑pharmacologic adjunct to delay or mitigate Alzheimer’s disease pathology linked to circadian disruption. It would also provide a quantitative framework for personalizing light‑based interventions based on chronotype and adenosine signaling status.