Inhibition of ERK phosphorylation contributed to DHA-induced apoptosis. A.

<p>PD98059, an inhibitor of ERK phosphorylation, enhanced DHA-induced decrease of cell viability. Cells were pretreated with 10 μM PD98059 for 2 h, and then incubated with 10 μM DHA for another 24 h. The residual cell viability was determined by MTT assay. Data are mean ± SD of three independent experiments, *<i>P</i><0.05. <b>B.</b> PD98059 treatment increased the production of apoptotic body. Cells pretreated with 10 μM PD98059 for 2 h, and then incubated with 10 μM DHA for another 24 h were stained with Hoechst 33342 dye. DNA fragmentation (indicated by asterisks) and nuclear condensation (denoted by arrows) were observed under a fluorescence microscope. <b>C.</b> PD98059 treatment enhanced DHA-induced apoptosis. TUNEL assay was performed to determine apoptosis. The number of apoptotic cells was determined and the percentage was indicated by histogram. *<i>P</i><0.05. <b>D.</b> PD98059 plus DHA treatment led to cleavages of PARP and caspase 3. Proteins collected from cells treated with PD98059 and DHA for 24 h were subjected to western blot to detect the cleavages of PARP and caspase 3. Actin was used as a loading control.