We investigated the effect of SIL-BS treatment against SM toxicity in HaCaT cells with regard to potential reduction of necrosis, apoptosis and inflammation including dose-dependency of any protective effects. We also demonstrated the biotransformation of the prodrug into free silibinin.
HaCaT cells were exposed to SM (30, 100, and 300 渭M) for 30 min and treated thereafter with SIL-BS (10, 50, and 100 渭M) for 24 h. Necrosis and apoptosis were quantified using the ToxiLight BioAssay and the nucleosome ELISA (CDDE). Pro-inflammatory interleukins-6 and -8 were determined by ELISA. HaCaT cells, incubated with silibinin-BS were lysed and investigated by LC-ESI MS/MS.
LC-ESI MS/MS results suggest that SIL-BS is absorbed by HaCaT cells and biotransformed into free silibinin. SIL-BS dose-dependently reduced SM cytotoxicity, even after 300 渭M exposure. Doses of 50-100 渭M silibinin-BS were required for significant protection. Apoptosis and interleukin production remained largely unchanged by 10-50 渭M silibinin-BS but increased after 100 渭M treatment.
Observed reductions of SM cytotoxicity by post-exposure treatment with SIL-BS suggest this as a promising approach for treatment of SM injuries. While 100 渭M SIL-BS is most effective to reduce necrosis, 50 渭M may be safer to avoid pro-inflammatory effects. Pro-apoptotic effects after high doses of SIL-BS are in agreement with findings in literature and might even be useful to eliminate cells irreversibly damaged by SM. Further investigations will focus on the protective mechanism of silibinin and its prodrug and should establish an optimum concentration for treatment.