Epsilon toxin induces cytotoxicity by mediating autophagy and apoptosis via the PI3K/AKT/mTOR signaling pathway in A549 cells.

backgroundEpsilon toxin, which is synthesized by Clostridium perfringens, is a type of pore-forming protein that is associated with the development of enterotoxemia in ruminants. As toxins are agents of bioterrorism, exposure to toxin aerosols causes endothelial cell damage and cytotoxicity in human lung cells. However, little information is available regarding the cytotoxicity and mechanisms associated with lung cancer cell lines. The aim of the present study was to explore the cytotoxic effects of epsilon toxin on the human lung cell line A549 and its involvement in the PI3K/AKT/mTOR signaling pathway to clarify the underlying molecular mechanism involved. METHODS AND

resultsA549 cells were treated with epsilon toxin, and cytotoxicity was assessed via MTT and LDH assays. Flow cytometry evaluated ROS levels, cell cycle arrest, and apoptosis, while Hoechst 33,258 staining confirmed apoptotic morphology. qRT‒PCR and Western blotting measured apoptosis-, autophagy-, and PI3K/AKT/mTOR-related markers. Epsilon toxin reduced cell viability and increased membrane leakage in a concentration-dependent manner, accompanied by ROS overproduction. It upregulated autophagy markers (beclin-1, LC3 II/I, p62) and suppressed PI3K/AKT/mTOR signaling. Cell cycle arrest at the sub-G1 phase and apoptosis were induced via p53 activation, Bax/Bcl-2 imbalance, and caspase-3 cleavage, as confirmed by annexin V/PI and Hoechst 33,258 staining.

conclusionsEpsilon toxin triggers cytotoxicity in A549 cells by activating apoptosis and autophagy through PI3K/AKT/mTOR pathway inhibition. These findings elucidate molecular mechanisms underlying epsilon toxin's action in lung cancer cells, highlighting its dual role in programmed cell death and potential therapeutic relevance.