Paraquat Induces Apoptosis of Cultured Rat Cortical Cells

摘要

Paraquat (PQ; 1,1'-dimethyl-4,4'-bipyridinium dichloride) is widely used as a universal herbicide. Although systemic treatment with PQ gives rise to the highest level of the herbicide in the cerebral cortex, our knowledge of its effects in this brain region is very limited. We took advantage of rat cortical cell cultures to analyze how PQ affects cortical neurons. Lactate dehydrogenase (LDH) assay and propidium iodide (PI) staining showed that PQ was cytotoxic to cortical neurons with an IC_(50) on the third day after treatment of ～10 μM. PQ-treated cells had shrunken soma with condensed nuclei and disintegrated dendrites, typical signs of apoptosis. Immunocytochemistry of 8-day in vitro (DIV) cells one day after PQ treatment with anti-phospho-H2AX antibody showed that the average number of punctae per nucleus had increased several-fold, indicating substantial DNA fragmentation. Furthermore, double-staining of 7.5 DIV cultures (50 mM PQ) with PI and an antibody against annexin V (AN), an impermeable plasma protein which specifically binds to phosphatidylserine (PS), showed that the percentages of AN(+)/PI(-) cells had also increased several-fold, pointing to considerable movement of PS from the inner to the outer leaflet of the plasma membrane. Taken together, our data indicate that PQ induces apoptosis in cortical cell cultures.