Preservation of Autophagy May Be a Mechanism Behind Healthy Aging.

Autophagy is intricately linked with protective cellular processes, including mitochondrial function, proteostasis, and cellular senescence. Animal studies have indicated that autophagy becomes dysfunctional with aging and may contribute to T cell immunosenescence. In humans, it remains unclear whether autophagy is impaired in CD4(+) T cells as people age. To answer this question, we examined basal and inducible autophagic activity in a series of experiments comparing CD4(+) T cells from younger (23-35 years old) and older (67-93 years old) healthy donors. We used immunofluorescence to detect LC3 (a marker of autophagosomes and autolysosomes) and LAMP2 (a marker of endolysosomes) in conjunction with bafilomycin A(1) (which inhibits the acidification of lysosomes) and CCCP (a mitochondrial uncoupler) to manipulate autophagic flux. We found a significantly higher autophagy flux in CD4(+) T cells from older compared to younger donors and a higher number of LC3(+) compartments among older donors. Since the overall amount of autophagosomes degraded was comparable between the two groups, we concluded that autophagosome biogenesis was reduced in the older group. Rather than a decline, our findings in healthy older donors point toward a compensatory enhancement of human CD4(+) T cell autophagy with age, which may be a mechanism behind healthy aging.