Age-associated changes in the subcellular localization of phosphorylated p38 MAPK in human granulosa cells
p38 MAPK (p38) plays pivotal roles in aging and reproductive physiology. Nevertheless, involvement of p38 in female reproductive aging is uncertain. To improve knowledge of the role of p38 in age-associated reproductive failure, the expression and subcellular localization of phosphorylated p38 was investigated in human granulosa cells. p38 was 7-fold more activated in cells from older subjects than in those from younger subjects. Similar results were obtained in human granulosa-like KGN cells treated with hydrogen peroxide (H2O2). Interestingly, phosphorylated p38 was detected in the nucleus less frequently in older cells than in younger cells (Younger: 58.6%; Older: 29.8%, P< 0.01). Similarly cytoplasmic localization of phosphorylated p38 in KGN cells was observed after treatment with H2O2. The activation and cytoplasmic localization of p38 in H2O2-treated KGN cells were blocked by N-acetylcysteine and SB203580. Although the p38 activators, FSH and tumor necrosis factor-, induced a similar localization of phosphorylated p38 in KGN cells, the expression and localization patterns of p38 were distinct from those in older granulosa cells and H2O2-treated KGN cells. These results indicate that the characteristic localization of p38 in older granulosa cells is induced by oxidative stress.