Targeted inhibition of MLKL-mediated necroptosis attenuates chronic arsenite exposure-induced lung injury.

Arsenic, a ubiquitous environmental toxicant, poses a global public health concern through drinking water contamination. While chronic arsenic exposure is epidemiologically associated with respiratory diseases, the molecular mechanisms driving its pulmonary toxicity remain incompletely understood. Emerging evidence implicates necroptosis-a regulated cell death pathway mediated by the RIPK1-RIPK3-MLKL axis-is implicated in diverse diseases, though its contribution to arsenic-induced pulmonary injury is uncharacterized. This study aims to elucidate the contribution of necroptosis to arsenic-induced lung injury using both in vitro and in vivo models. We treated human lung epithelial cells (BEAS-2B) with sodium arsenite (NaAsO2) and applied specific necroptosis inhibitors. Cell viability, apoptosis, and phosphorylation of RIPK3 (p-RIPK3) and MLKL (p-MLKL) were assessed via CCK-8 assay, flow cytometry, and Western blot, respectively. Additionally, chronic arsenic exposure models were generated in wild-type (WT) and MLKL knockout (Mlkl-/-) mice. Lung histopathology, fibrosis, inflammatory markers (IL-6, CC16 and TNF-α), and necroptosis markers (p-RIPK3, and p-MLKL) were analyzed using H&E staining, Masson staining, ELISA, immunohistochemistry, and Western blot. Results showed that NaAsO2 induced dose-dependent cytotoxicity and RIPK3/MLKL phosphorylation in BEAS-2B cells, effects that were reversed by necroptosis inhibition. In mice, arsenic exposure promoted interstitial thickening, collagen accumulation, elevated IL-6, decreased CC16, and enhanced p-RIPK3/p-MLKL expression. Notably, Mlkl-/- mice exhibited significantly attenuated lung injury and inflammation. These findings demonstrate that MLKL-mediated necroptosis is a key mechanism driving arsenic-induced lung inflammation and fibrosis, highlighting MLKL as a promising therapeutic target for mitigating arsenic-related respiratory disease.