Cellular Senescence & Senolytics (Fisetin, Quercetin, Dasatinib)

Navigation & Context

• Parent Hub: 04 - Longevity & Environment MOC
• Literature Dossier: Cellular Senescence & Senolytics (Fisetin, Quercetin, Dasatinib) - References
• Related Nodes: NAD+ Salvage Pathway (NMN, NR, CD38 Inhibition), Autophagy & Mitophagy (Spermidine, Urolithin A), Mitochondrial Biogenesis & Uncoupling

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1. Geroscience & Biophysical Mechanism

Cellular senescence is an irreversible cell-cycle arrest triggered by telomere attrition, oncogenic stress, mitochondrial dysfunction, or persistent DNA damage response (DDR), mediated by the ${\text{p53/p21}}^{\text{CIP1}}$ and ${\text{p16}}^{\text{INK4a}}/\text{Rb}$ tumor-suppressor cascades. While acute senescence assists embryogenesis and wound repair, aged tissues accumulate apoptosis-resistant senescent cells that secrete a pro-inflammatory, tissue-degrading Senescence-Associated Secretory Phenotype (SASP):

• SASP Components: Pro-inflammatory cytokines ($\text{IL-6}$, $\text{IL-1}\beta$, $\text{TNF-}\alpha$), chemokines ($\text{MCP-1/CCL2}$, $\text{IL-8}$), matrix metalloproteinases ($\text{MMP-1, -3, -10}$), and reactive oxygen species.
• Paracrine Contagion & $\text{CD38}$ Induction: Even when senescent cells comprise only $2\text{–}5\%$ of a tissue’s cell population, SASP induces bystander senescence in neighboring progenitor cells and drives macrophage $\text{CD38}$ expression, depleting systemic NAD+ pools.

Senolytics vs. Senomorphics

• Senolytics (Selective Apoptosis): Senescent cells survive their own pro-apoptotic SASP by upregulating Senescent Cell Anti-Apoptotic Pathways (SCAPs)—including $\text{BCL-2/BCL-xL}$, $\text{PI3K}\delta /\text{AKT}$, $\text{p53/FOXO4}$, and $\text{Ephrin/Src}$ tyrosine kinases. Because senescent cells take 2–6 weeks to re-accumulate from dividing precursors, senolytics operate via a “hit-and-run” pulse ($2\text{–}3\text{ days}$) that briefly disables SCAPs, causing senescent cells to self-destruct via caspase-3/7 activation without requiring continuous receptor occupancy.
  • Fisetin: $3,3^{\prime },4^{\prime },7$-tetrahydroxyflavone that inhibits $\text{PI3K/AKT/mTOR}$ and $\text{BCL-xL}$, selectively clearing senescent endothelial, mesenchymal, and immune cells.
  • Dasatinib + Quercetin (D+Q): Dasatinib (a pan-Src family tyrosine kinase and ephrin receptor inhibitor) clears senescent preadipocytes/osteoblasts, while Quercetin (inhibiting $\text{PI3K}$, serpines, and $\text{BCL-2}$) targets senescent endothelial and bone marrow stem cells.
• Senomorphics (SASP Suppression): Low-dose chronic agents (e.g., apigenin, rapamycin, metformin, low-dose quercetin) that suppress $\text{NF-}\kappa \text{B}$, $\text{JAK/STAT}$, or $\text{mTOR}$ to blunt SASP secretion without killing the cell.

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2. Actionable Protocol & Dosing Architecture

Regimen	Compound & Formulation	Dosing Schedule (“Hit-and-Run”)	Target SCAP / Tissue
Mayo Protocol (Fisetin Pulse)	Fisetin (Micronized, Liposomal, or Fenugreek-galactomannan hydrogel)	$20\text{ mg/kg/day}$ (typically $1,200\text{–}1,600\text{ mg}$ standard or $500\text{–}800\text{ mg}$ high-bioavailability) for 2–3 consecutive days, repeated every 1–3 months	$\text{PI3K/AKT}$, $\text{BCL-xL}$; vascular endothelium, adipose, immune/T-cells
Flavonoid Dual Senolytic Pulse	Fisetin + Quercetin Phytosome + Piperine / Dietary Lipids	Fisetin $1,000\text{ mg}$ + Quercetin Phytosome $500\text{–}1,000\text{ mg}$ daily for 2–3 days/month with a high-fat meal (olive oil/avocado)	Synergistic $\text{PI3K}/\text{Serpin}/\text{BCL-2}$ blockade
Clinical Rx Benchmark (D+Q)	Dasatinib (Rx only) + Quercetin	Dasatinib $100\text{ mg/day}$ + Quercetin $1,000\text{ mg/day}$ for 3 consecutive days (clinical trial protocol)	Broad-spectrum $\text{Src}/\text{Ephrin}+\text{PI3K}$ (adipose, lung, bone, kidney)

Timing Relative to Exercise & Surgery

Transient senescent cells are required for acute tissue remodeling and satellite cell signaling. Pause senolytic pulses for 48 hours before and after maximal eccentric muscle damage and for 2–4 weeks around surgical procedures or acute cutaneous wounds.

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3. Biomarkers & Quantification

• Inflammaging / SASP Surrogates: High-sensitivity C-Reactive Protein ($\text{hs-CRP}<0.5\text{ mg/L}$), serum $\text{IL-6}$, $\text{TNF-}\alpha$, $\text{GDF-15}$, and matrix metalloproteinases ($\text{MMP-9}$).
• Direct Cellular Senescence Markers (Research / Specialized Panels): T-cell ${\text{p16}}^{\text{INK4a}}$ mRNA expression, $\text{SA-}\beta \text{-gal}$ (senescence-associated $\beta$-galactosidase) activity, and ${\text{CD8}}^{+}{\text{CD28}}^{-}{\text{CD57}}^{+}$ senescent T-cell immunophenotyping.
• Epigenetic Clocks: DunedinPACE, GrimAge v2 (heavily weighted toward SASP proteins like $\text{GDF-15}$, $\text{PAI-1}$, and $\text{TIMP-1}$).

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4. Key Scientific Evidence Summary

Detailed citations and trial metrics are cataloged in Cellular Senescence & Senolytics (Fisetin, Quercetin, Dasatinib) - References:

• Yousefzadeh et al. (2018, EBioMedicine): Screened 10 flavonoids and identified Fisetin as the most potent natural senolytic, reducing ${\text{p16}}^{\text{INK4a}+}$ and $\text{SA-}\beta {\text{-gal}}^{+}$ cells by 25–50% across tissues and extending median and maximum lifespan in aged mice even when started late in life (85 weeks / ~75 human years).
• Hickson et al. (2019, EBioMedicine): First-in-human open-label trial demonstrating that a single 3-day oral pulse of D+Q reduced human adipose tissue ${\text{p16}}^{\text{INK4a}+}$ cells by 35%, ${\text{p21}}^{\text{CIP1}+}$ cells by 17%, $\text{SA-}\beta {\text{-gal}}^{+}$ cells by 62%, and circulating SASP factors ($\text{IL-1}\alpha ,\text{IL-6},\text{MMP-9/-12}$) 11 days post-treatment.
• Justice et al. (2019, EBioMedicine): Intermittent D+Q (3 days/week for 3 weeks) in humans with idiopathic pulmonary fibrosis significantly improved 6-minute walk distance ($+21.5\text{ m}$), 4-meter gait speed, and chair-stand performance ($p<0.05$).