2-Aminomethyl phenothiazine, its alkyl and triphenylphosphonium derivatives suppress erastin-induced ferroptosis in BT-474 cells but exhibit distinct cytotoxic activities.

This work demonstrates the antiferroptotic and cytotoxic effects of 2-aminomethyl phenothiazine (PTZ-NH₂), and its alkyl derivative (PTZ-capryl) and mitochondria-targeted triphenylphosphonium conjugate (PTZ-TPP) on BT-474 cells, as well as their effects on isolated rat liver mitochondria. It was found that all studied compounds at 0.5 and 1 μM concentrations have a protective effect in the erastin-induced ferroptosis model. This effect of the tested compounds may be associated with the elimination of ROS overproduction in erastin-treated cells. The antioxidant effect of the compounds was also demonstrated on isolated rat liver mitochondria. At the same time, high concentrations of PTZ-NH₂ had a cytotoxic effect on BT-474 cells (IC₅₀=55 μM), and it was significantly enhanced in the case of PTZ-TPP (IC₅₀=15 μM), which is possibly due to the mitochondrial targeting of PTZ-TPP. In contrast, the alkyl derivative did not exhibit cytotoxic action up to a maximum concentration of 100 μM, which allows it to be recommended as a promising antiferroptotic agent with a wide therapeutic window. The current findings discuss the possible mechanisms of inhibitory action of the tested compounds on ferroptotic cell death.