https://onlinelibrary.wiley.com/doi/epdf/10.1111/acel.70246
Summary of Bektas et al., “Preservation of Autophagy May Be a Mechanism Behind Healthy Aging” (Aging Cell, 2025; e70246)
Authors and Context:
Arsun Bektas, Shepherd Schurman, Julián Candia, Olaya Santiago-Fernández, Susmita Kaushik, Ana Maria Cuervo, and Luigi Ferrucci (NIA NIH & Albert Einstein College of Medicine). The study extends prior NIA work on immunosenescence and mechanistic aging.
Main Findings
-
Objective: Determine whether autophagy in human CD4⁺ T cells declines with age — a process previously shown to falter in animal models.
-
Participants: Healthy donors — younger (23–35 y) vs. older (67–93 y) — free from chronic disease.
-
Methods:
Immunofluorescence microscopy to quantify LC3⁺ autophagosomes and LAMP2⁺ lysosomes under basal and stimulated conditions.
Perturbations:- Bafilomycin A1 → blocks lysosomal acidification (tests degradation).
- CCCP → mitochondrial uncoupler (induces energetic stress/mitophagy).
- Autophagic flux = LC3 puncta ratio (bafilomycin A1 / untreated).
- Statistical model: linear mixed effects, age as fixed factor.
Key Results
-
Basal autophagy preserved with age.
- LC3 puncta slightly lower in older donors (ns).
- LAMP2 compartments and LC3–LAMP2 colocalization unchanged.
→ No overall decline in lysosomal number or fusion efficiency.
-
Autophagic flux increased in older donors.
- LC3 flux significantly higher in older CD4⁺ T cells (p ≈ 0.02).
- Net autophagosome degradation amount unchanged → interpretation: reduced biogenesis but enhanced clearance efficiency.
-
CCCP stress response.
- CCCP induced more LC3 puncta in older donors, but unexpectedly reduced autophagy flux in both groups.
- Suggests human CD4⁺ T cells are more sensitive to CCCP than rodent cells.
-
Interpretation:
- Aging in healthy individuals shows adaptive remodeling — fewer autophagosomes but faster turnover.
- Possible compensatory mechanism preserving immune cell homeostasis and explaining “healthy aging” phenotype.
Novelty
- First direct comparison of autophagic flux in human CD4⁺ T cells from healthy young vs. elderly donors.
- Contradicts canonical view (from animal models) that autophagy declines with age.
- Introduces the concept of “autophagic compensation” — reduced vesicle biogenesis offset by improved clearance efficiency.
- Suggests autophagy flux could serve as a biomarker of immune fitness / healthy aging.
Critique
Strengths:
- Rigorous single-cell microscopy-based quantification of LC3/LAMP2 puncta.
- Carefully matched healthy donors reduce disease confounders.
- Use of both basal and inducible (CCCP, bafilomycin A1) paradigms provides dynamic insight rather than static LC3 levels.
- Collaboration with Cuervo lab (leaders in lysosomal biology) adds methodological robustness.
Limitations:
-
Small cohort (n = 9 paired experiments).
- Limited statistical power; wide confidence intervals in age coefficients.
- Mostly cross-sectional — cannot infer causality or longitudinal adaptation.
-
Healthy-elderly bias:
- Participants from the Baltimore Longitudinal Study of Aging are unusually healthy; results may not generalize to typical older adults.
-
Single cell type:
- CD4⁺ T cells only — no validation in CD8⁺ T cells, B cells, or non-immune tissues.
-
Indirect measures of autophagic flux:
- LC3 puncta ratios approximate flux but don’t measure degradation kinetics directly (no lysosomal proteolysis assays or cargo degradation markers like p62/SQSTM1).
-
CCCP artifact:
- CCCP dose (10 µM, 18 h) may over-stress human cells; paradoxical inhibition of flux complicates interpretation of inducible response.
-
Sex and batch variability:
- Some experiments mixed male/female donors; sensitivity analysis partially addressed but underpowered.
Conceptual Implications
- Supports a selective survival/adaptation hypothesis — individuals with preserved autophagic flux may resist immunosenescence.
- Points to therapeutic strategies enhancing lysosomal efficiency (e.g., TFEB activation, Beclin-1 modulation, CRMs like spermidine or metformin).
- Positions autophagic flux as a measurable parameter for clinical aging studies and possibly as an endpoint for autophagy-enhancing interventions.
Summary Table
| Aspect | Observation | Interpretation |
|---|---|---|
| Basal LC3 puncta | Slightly lower in older | ↓ Biogenesis |
| Autophagic flux | Higher in older (p < 0.05) | ↑ Clearance efficiency |
| LAMP2 puncta | Unchanged | Lysosomes stable |
| CCCP response | Flux decreased in both | Stress-induced inhibition |
| Overall conclusion | Autophagy preserved/enhanced in healthy elderly CD4⁺ T cells | Adaptive mechanism of healthy aging |
Overall verdict:
A technically solid, conceptually novel human study that challenges the prevailing “autophagy decline with age” paradigm by introducing a nuanced model of compensated autophagy efficiency in immune cells of healthy elders. Its small scale and narrow cell focus limit generality, but it meaningfully re-frames how autophagy dynamics—not just abundance—relate to longevity.