OBJECTIVETo investigate the cytotoxicity of bromoxynil on SH-SY5Y cells and its effect on the expression of nuclear factor-kappa B (NF-κB) and I kappa B alpha (IκBα) in SH-SY5Y cells.

METHODSSH-SY5Y cells were exposed to bromoxynil (10, 50, or 100 µmol/L) for 24 and 48 h, and other SH-SY5Y cells, which were used as a control, were exposed only to dimethyl sulfoxide. After 24 and 48 h of exposure, the morphological changes of these cells were observed under an inverted microscope, and the cytotoxicity of bromoxynil was measured by MTT assay. The cellular proliferation was examined by cell counting after 12, 24, 48, 72, and 96 h of exposure. After 24 h of exposure, the expression of NF-κB was evaluated by Western blot and immunocytochemistry, and the expression of IκBα was evaluated by Western blot.

RESULTSThe cellular proliferation inhibition rates (CPIRs) of 50 and 100 µmol/L groups were significantly higher than that of the control group after 24 and 48 h of exposure (P < 0.05); the CPIR was significantly higher after 48 h than after 24 h in the two groups (P < 0.05). The growth curve revealed that these groups began to show differences in cell count at the 24th of exposure and that the differences were even more marked as the exposure went on (F = 17.15, P < 0.05). The control group had a significantly increased cell count at the 48th, 72nd, and 96th h of exposure (P < 0.05); the 10 and 50 µmol/L groups had a significantly increased cell count at the 72nd and 96th h of exposure (P < 0.05); the 100 µmol/L group showed no significant change in cell count during 96h of exposure. The 50 and 100 µmol/L groups hada significantly longer cell doubling time than the control group (P < 0.05). The immunocytochemistry showed that as the dose of bromoxynil increased, the brownish yellow particles in the cytoplasm and nuclei became darker, the expression of NF-κB was upregulated, and the nuclear translocation of NF-κB was increased. The Western blot showed that the 100 µmol/L group had significantly higher expression of NF-κB in the nuclei than the control group (P < 0.05) and that the 50 and 100 µmol/L groups had significantly lower expression of IκBα in total proteins than the control group (P < 0.05).

CONCLUSIONBromoxynil can inhibit the proliferation of SH-SY5Y cells under this experimental condition, which may be related to activation of NF-κB.