Redox-dependent suppression of ATF3 impairs steroid sensitivity in asthma through MKP-1/p38 MAPK signaling

Chronic oxidative stress (OS) is a critical contributor to steroid insensitivity (SI) in asthma, in which p38 mitogen-activated protein kinase (p38 MAPK) overactivation playing a central role. Although mitogen-activated protein kinase phosphatase-1 (MKP-1) downregulation has been implicated in this process, the redox-sensitive upstream regulators remain poorly understood. This study aimed to elucidate the role of activating transcription factor 3 (ATF3) in chronic OS-induced SI using an ovalbumin-ozone (OVA-ozone) murine asthma model. Chronic (8-week) ozone exposure led to sustained ROS accumulation and significantly reduced ATF3 and MKP-1 expression in lung tissue, contrasting with the upregulation observed under acute conditions. A steroid-insensitive asthma model was successfully established through chronic ozone exposure combined with repeated OVA stimulations, in which the inhibitory effects of Dexamethasone (DEX) on the pulmonary inflammation and lung function were substantially blunted. Treatment with antioxidant or gene augmentation of ATF3 can both restored the steroids insensitivity of this chronic OVA-ozone asthma model, accompanied by elevated ATF3 and MKP-1 expression and suppressed p38 MAPK phosphorylation. Furthermore, steroid sensitivity of allergic asthma model established with ATF3 knockout mice was blunted, while genetic supplementation of ATF3 gene can partly restore the inhibitory effects of DEX. Particularly, in vitro, ATF3 gene was shown to transactivate the MKP-1 promoter, upregulate MKP-1 expression and suppress p38 MAPK phosphorylation. Collectively, our findings identify ATF3 as a redox-sensitive transcriptional regulator that critically controls steroid responsiveness in asthma through the MKP-1/p38 MAPK axis. Under chronic OS, ATF3 downregulation drives SI, while its restoration-pharmacologically via NAC or genetically via overexpression-reinstates steroid sensitivity by modulating this pathway. These results reveal a novel redox-dependent mechanism underlying SI and highlight ATF3 as a promising therapeutic target for restoring steroid efficacy in refractory asthma.