ステロイド薬による副腎萎縮の仕組みを解明 ACTH分泌低下が副腎皮質のミトコンドリア障害と細胞死を引き起こす ―副腎不全の新たな予防・治療法の開発に期待―

Exogenous glucocorticoids are widely used to treat inflammatory and autoimmune diseases, yet the prolonged administration often leads to adrenocortical atrophy and subsequent adrenal insufficiency. However, the molecular mechanisms underlying glucocorticoid-induced adrenocortical atrophy remain incompletely understood. Here, we show that adrenocortical alterations in dexamethasone (DEX)-treated mice are similar to those in human adrenocortical tissues adjacent to cortisol-producing adenoma. During DEX treatment, marked cell death occurs, being restricted to the adrenocortical zona fasciculata (ZF), as a result of reactive oxygen species (ROS)-mediated mitochondrial dysfunction; the pathological changes are all attenuated by co-administration of adrenocorticotropic hormone (ACTH). In DEX-treated mice, ACTH deficiency impairs nuclear factor E2-related factor 2 (NRF2)-dependent redox homeostasis in ZF cells. Activation of the cAMP-PKA signaling pathway, a downstream signaling of ACTH stimulation, increases gene expression of steroidogenic factor 1 (SF1; NR5A1) in cultured adrenocortical cells in vitro, where it binds directly to the Nrf2 promoter and enhances its transcription, thereby promoting antioxidant gene expression to maintain redox homeostasis. This study highlights the role of the ACTH-SF1-NRF2 axis in glucocorticoid-induced adrenocortical cell death through mitochondrial ROS accumulation, thereby providing a clue to a new therapeutic strategy to prevent or treat secondary adrenal insufficiency during glucocorticoid excess.