Antioxidants reduce the heterogeneity of the intracellular glutathione level in senescent cell population of human dermal fibroblasts

•Senescent HDFs showed reduced GSH levels, increased its heterogeneity, but exhibited a similar GSH regeneration activity compared with young HDFs.•GSH level in senescent HDF was inversely correlated with senescence-associated phenotypes.•Treatment with antioxidants showed a reduction of GSH level heterogeneity but no effect on mean GSH level.•This antioxidant effect on GSH levels explain why antioxidants exhibit a limited effect on preventing HDF senescence.