Tehran University of Medical Sciences Acta Biochimica Iranica 0001-5261 3 2 2025 06 19 114 119 Majid efati Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Sahar Ghoflchi Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Khatereh Kharazmi Department of Physiology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Soodeh Alidadi Department of Pathobiology, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran Daryoush Hamidi-alamdari Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Surgical Oncology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Hossein Hosseini Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. 2025 08 17 2025 08 17 Objectives: Acetaminophen overdose may lead to acute pulmonary complications like acute lung injury because of its overdose harmful effect on cellular systems due to oxidative stress. leucomethylene blue (LMB) may have beneficial effects by improving hemodynamic stability and reducing oxidative damage through its nitric oxide synthase inhibitory and antioxidant activities. This study aimed to evaluate the effect of LMB on acetaminophen-induced pulmonary injury in rats. Methods: Lung samples were collected from 30 male Wistar rats, which were randomly split into five groups, and frozen for later analysis. The groups included control, acetaminophen, N-acetylcysteine (NAC) treated, LMB treated, and NAC+LMB combination treated. We evaluated total antioxidant capacity (TAC), glutathione reductase (GR), TNF-α and IL-6 levels, histopathology, and relevant tissue remodeling changes. Results: Our results demonstrated that the administration of LMB greatly diminished the oxidative and inflammatory damage caused by APAP toxicity in the lungs. LMB restored TAC and GR activity that were significantly depressed by APAP toxicity. Additionally, LMB restricted the overproduction of pro-inflammatory cytokines that were released from lung tissue. Moreover, LMB substantially counteracted the pulmonary lesions caused by APAP, including edema, hemorrhage, and inflamed cells, corroborated by histopathological analysis. Conclusion: The results of this study showed that LMB can effectively reduce lung damage caused by acetaminophen poisoning. https://abi.tums.ac.ir/index.php/abi/article/view/152 https://abi.tums.ac.ir/index.php/abi/article/download/152/111