Hypothesis

Intermittent dosing of dasatinib plus quercetin (D+Q) guided by dynamic SASP biomarker levels will achieve sustained senescent cell clearance without triggering compensatory epigenetic aging, whereas fixed‑interval regimens either under‑dose (allowing SASP rebound) or over‑dose (inducing off‑target epigenetic stress).

Mechanistic Rationale

• D+Q clears senescent cells and transiently suppresses SASP IL‑6, CXCL1, MCP‑1 2.
• SASP suppression lifts inhibitory feedback on NF‑κB and JAK/STAT pathways in neighboring cells, promoting a rebound surge of SASP factors within 48–72 h post‑withdrawal (observed as mRNA‑level persistence but protein‑level rise) 2.
• Repeated SASP spikes drive chronic low‑grade inflammation that activates DNMT3A and TET2 in immune cells, accelerating epigenetic age as seen in first‑generation clocks after prolonged D+Q exposure 9.
• Adaptive dosing that re‑administers D+Q at the onset of SASP protein rise (≥25 % increase from nadir) would maintain suppression before the inflammatory feedback loop engages, limiting epigenetic drift.

Testable Predictions

1. In aged mice, serum MCP‑1, IL‑6, and CXCL1 will show a predictable nadir 24 h post‑D+Q followed by a reproducible rebound peak at 60 h.
2. Mice receiving D+Q only when SASP biomarkers cross a predefined upward threshold will exhibit (a) lower cumulative senescent cell burden (p16^INK4a^+ cells by flow cytometry) after 6 months than biweekly fixed‑dose groups, and (b) no significant increase in epigenetic age acceleration (Horvath clock) compared with untreated controls.
3. Continuous low‑dose D+Q will suppress SASP but elevate markers of DNA damage response (γH2AX) in non‑senescent tissues, indicating off‑target stress.

Experimental Design

• Animals: 20‑month‑old C57BL/6J mice (n=10 per group).
• Groups: (A) Vehicle, (B) Fixed biweekly D+Q (5 mg/kg dasatinib + 50 mg/kg quercetin), (C) Adaptive D+Q (dose administered when plasma MCP‑1 rises ≥25 % above individual baseline), (D) Continuous low‑dose D+Q (half the biweekly dose given 3×/week).
• Measurements: Twice‑weekly blood draws for SASP proteins (IL‑6, CXCL1, MCP‑1) via ELISA; weekly flow cytometry for p16^INK4a^+ cells in liver, adipose, and brain; monthly epigenetic DNA methylation arrays (Horvath & Hannum clocks);终点 assessment of frailty index and cognitive performance.
• Analysis: Compare area under the curve (AUC) for SASP levels, senescent cell frequency, and epigenetic age delta across groups using mixed‑effects models; adaptive arm predicted to have lowest AUC for SASP rebound and senescent cells while showing neutral epigenetic age change.

Implications

If validated, this approach transforms senolytic therapy from a static supplement‑like schedule to a precision medicine strategy, aligning drug exposure with the biology of SASP kinetics and mitigating unintended epigenetic consequences.