p38 mitogen-activated protein kinase drives senescence in CD4 T lymphocytes and increases their pathological potential.

BACKGROUND

In several diseases, senescent T lymphocytes increase in number and release a senescence-associated secretory phenotype (SASP) with inflammatory and osteoclastogenic potential, favoring inflammation and bone loss. It is well known that the activation of p38 mitogen-activated protein kinase (p38 MAPK) orchestrates senescence in CD8 T lymphocytes. However, p38 MAPK contribution to CD4 T lymphocyte senescence remains less comprehensively characterized and warrants further investigation. This study investigates the contribution of p38 MAPK to senescence in CD4 T lymphocytes, focusing on mitochondrial dysfunction and SASP production to elucidate their pathological potential.

RESULTS

Splenic CD4 T lymphocytes isolated from wild-type C57BL/6 mice were subjected to subcytotoxic oxidative stress by HO exposure to generate stress-induced premature senescence. HO-exposed CD4 T lymphocytes exhibited hallmark features of senescence, including increased cell size, reduced cell proliferation, and upregulation of the cell cycle regulators p16 and p21. Additionally, these cells displayed defective mitophagy, accumulation of dysfunctional mitochondria, and a SASP enriched in Th17-associated cytokines. In senescence-induced CD4 T lymphocytes, an increase in the expression of phospho-p38 MAPK was also detected. The senescence changes were reversed when p38 MAPK was blocked using the specific inhibitor BIRB-796. In particular, neutralizing p38 MAPK reduced mitochondrial dysfunction and Th17-type SASP production, demonstrating its critical role in driving these senescent traits in CD4 T lymphocytes. These findings ratify the involvement of p38 MAPK as a central regulator of CD4 T lymphocyte senescence, particularly concerning the accumulation of dysfunctional mitochondria and pro-inflammatory SASP production.

CONCLUSIONS

This study provides critical insights into immune aging mechanisms in CD4 T lymphocytes and underscores the therapeutic potential of targeting p38 MAPK to mitigate senescence-driven inflammatory diseases.