RUNX3-dependent oxidative epithelial-to-mesenchymal transition in methamphetamine-induced chronic lung injury

Lung toxicity is the main cause of the death from methamphetamine (MA) abuse, but its mechanism has remained unclear. The purpose of our study was to investigate if MA can induce epithelial-to-mesenchymal transition (EMT) and if RUNX3 is involved in oxidative EMT in MA-induced chronic lung injury. The rats were divided into the control group and MA group. Extracted lungs were used for morphological measurements and Western blot. The alveolar epithelial cells were cultured or transfected and then treated with MA or/and N-acetyl cysteine (NAC) followed by flow cytometry, Western blot, and immunohistochemistry. Chronic exposure to MA resulted in the lower growth ratio of weight, increased right ventricular index, thickened alveolar walls, and reduced number of alveolar sacs. Long-term administration with MA caused oxidative stress and pulmonary EMT. NAC increased RUNX3 and alleviated EMT. However, after knockdown of RUNX3, reactive oxygen species (ROS) levels were significantly upregulated, indicating that RUNX3 was closely related to oxidative stress. Knockdown of RUNX3 aggravated MA-induced EMT by activating RUNX3-dependent TGF-β signaling. Therefore, RUNX3 may be the key to oxidative EMT in methamphetamine-induced chronic lung injury.