Fig 1: Conserved dopamine neurotrophic factor (CDNF) concentration (pg/mL) after 24 h exposure to MnCl2, ZnCl2, and CuCl2 and 100 µM 6-ODHA. As a positive control, 50 µM menadione was used, and 1% PBS was used as a negative control. After 24 h exposure, ZnCl2 at lethal and sublethal concentrations had the highest effect, then CuCl2 and MnCl2. Statistical significance codes: treatment vs. untreated control (UT, *) and positive control (6-ODHA, +). Asterisks or plus signs indicate p-value ranges: *,+ 0.01–0.05, ++ 0.001–0.01, *** 0.0001 to 0.001, ****,++++ <0.0001.