Transient Mitochondrial Uncoupling as a Senosensitizer to Overcome Bcl‑2/MCL‑1‑Dependent Resistance to Dasatinib plus Quercetin

Hypothesis

Low‑dose mitochondrial uncoupling (e.g., 2,4‑dinitrophenol, DNP) administered shortly before dasatinib plus quercetin (D+Q) will sensitize senescent cells to apoptosis by destabilizing anti‑apoptotic Bcl‑2 family proteins, thereby increasing senolytic clearance beyond that achieved by D+Q alone.

Mechanistic Rationale

Recent work shows that mitochondrial stress markedly improves senolytic efficacy by disrupting the anti‑apoptotic shield of senescent cells12. This effect is thought to arise from oxidative activation of pro‑apoptotic BH3‑only proteins (e.g., BIM, PUMA) and concurrent degradation of MCL‑1 via GSK‑3β–dependent phosphorylation3. We propose that a brief, sub‑toxic pulse of DNP will transiently collapse the mitochondrial membrane potential, elevating matrix ROS without triggering necrosis. This ROS burst should:

• Oxidatively inhibit Bcl‑2 and Bcl‑xL cysteine residues, reducing their binding affinity for pro‑apoptotic effectors.
• Activate the AMPK‑GSK‑3β axis, accelerating MCL‑1 turnover.
• Lower the threshold for BAX/BAK oligomerization, priming cells for D+Q‑induced Src‑family kinase inhibition.

Importantly, mitochondrial ROS also modulate the SASP. Elevated ROS can suppress NF‑κB‑driven IL‑6 transcription through oxidation of IKKβ, weakening the IL‑6 autocrine loop that sustains senescence5. Thus, DNP pretreatment may not only increase apoptosis but also dampen the reinforcer cytokine that maintains the senescent state.

Testable Predictions

1. In vitro: Human senescent fibroblasts (induced by irradiation) treated with 0.05 mM DNP for 2 h followed by D+Q will show ≥2‑fold increase in Annexin V⁺/PI⁻ cells compared with D+Q alone, accompanied by reduced MCL‑1 and Bcl‑2 protein levels and heightened BIM activation.
2. In vivo: Aged (20‑month) C57BL/6 mice receiving intermittent low‑dose DNP (0.5 mg/kg i.p., 24 h before each D+Q dose) over a 4‑week regimen will exhibit a greater reduction in p16^Ink4a^‑positive cells in lung and spleen (≥50 % vs. ~30 % with D+Q alone) and a concomitant decline in plasma IL‑6 and GDF15.
3. Functional: The combined DNP + D+Q group will display improved frailty index scores and enhanced grip strength relative to D+Q monotherapy, with no increase in histologic markers of liver or kidney toxicity.

Experimental Design

• Cellular: Use primary human fibroblasts senescent via 10 Gy γ‑irradiation; confirm senescence by SA‑β‑gal and p21^Cip1^. Treat with DNP (0.01‑0.1 mM) for 2 h, wash, then add D+Q (10 nM dasatinib + 10 µM quercetin) for 48 h. Measure apoptosis (flow cytometry), Western blot for Bcl‑2 family proteins, and SASP cytokines (IL‑6, IL‑8) by ELISA.
• In vivo: Randomized cohorts of aged mice (n=10 per group): vehicle, DNP alone, D+Q alone, DNP → D+Q (DNP 24 h prior to each D+Q dose). D+Q administered orally twice weekly; DNP given intraperitoneally 24 h before each D+Q dose. Endpoints at week 4: senescent cell burden (p16^Ink4a^ immunohistochemistry), serum SASP multiplex, frailty index, grip strength, and clinical chemistry.

Potential Implications

If validated, this strategy would repurpose a mild mitochondrial uncoupler as a clinically translatable senosensitizer, broadening the therapeutic window of existing senolytics and addressing resistance driven by Bcl‑2/MCL‑1 dependence. Moreover, by attenuating IL‑6‑mediated autocrine reinforcement, the approach may dual‑target the apoptotic and SASP arms of senescence, potentially yielding superior functional recovery in age‑related diseases.