Agomelatine Alleviates Methotrexate‐Induced Lung Injury by Concurrently Inhibiting CD45/CD68‐Positive Immune Cell Infiltration and Modulating the BAX/BCL2 Apoptosis Pathway

Methotrexate (MTX)-induced pulmonary toxicity severely limits its clinical use and effective preventive strategies are lacking. This study evaluated the protective effects of agomelatine (AGO), a melatonergic antidepressant, against MTX-induced lung injury, focusing on its dual-pathway action targeting both immune cell infiltration and apoptotic signaling. Thirty-two female Wistar rats were assigned to: Control, AGO (20 mg/kg/day, p.o., 7 days), MTX (single i.p. dose, 20 mg/kg), and MTX + AGO groups. Lung tissues were examined by histopathology, immunohistochemistry (CD45⁺, CD68⁺), and RT-qPCR (BAX, BCL2). MTX administration caused marked pulmonary damage (histopathological score: 2.75 ± 0.25, p < 0.001), significant infiltration of CD45⁺ leukocytes and CD68⁺ macrophages and an elevated BAX/BCL2 ratio (3.5 ± 0.4 vs. 1.0 ± 0.2 in Control, p < 0.001). AGO cotreatment significantly ameliorated these alterations via its dual activity, lowering the histopathological score (1.25 ± 0.25, p < 0.01), reducing CD45⁺/CD68 immunopositivity, and restoring the BAX/BCL2 ratio toward cell survival (1.4 ± 0.3, p < 0.01 vs. MTX). These findings provide integrated immunohistochemical and molecular evidence supporting the concurrent modulation of immune cell infiltration and apoptotic signaling by AGO in MTX-induced lung injury. Given its established clinical use and favorable safety profile, AGO may represent a potential adjunctive candidate to reduce the risk of MTX-related pulmonary complications, through concurrent targeting of immune and apoptotic pathways.