| Summary: | 碩士 === 高雄醫學大學 === 職業安全衛生研究所碩士班 === 95 === Paraquat (PQ) not only is commonly used as a method of committing suicide, but also is excessively used as herbicides. Acute exposures of Paraquat will result in liver and kidney failure while chronic exposures may cause lung caner, nephritic disease and Parkinson disease. Epidemiology and animal experimentation is more widely examined than experimentation on normal liver cells for researching on how Paraquat causes harm to the liver. Therefore, we test Paraquat on normal WB-F344 cell, Gap junctional intercellular communication, Apoptosis and Cell cycle to analyze the effect of Paraquat on liver cells and the mechanism of the toxicity.
During the MTT & Colony Forming Efficiency experimentation, Paraquat interferes with cell breeding, and also kills the normal function of cells with toxic. The exposure of Paraquat between 24 to 48 hours at 40µg/mL reached to IC50 and also had Dose & Time dependent. During the GJIC experiment, because of Paraquat exposures at 25µg/mL, the cell’s Connexon communication therefore is destroyed. Thus, based on previous studies, lost of communication may be the cause of cancer. When Paraquat enters cells, the toxic mechanism can be examined by Immunoblot analysis & Western Blot experimentation. The influence of these proteins: Caspase 3, Caspase 8, Caspase 9, MDM2, Bax, Cyto-C and P53 will cause Apoptosis. Cell cycle will be analyzed by Flow Cytometry, and the influence of P21, P27 and P53 will cause the division of cell to not function properly.
Experimental results confirmed that, after the exposure of WB-F344 cells to Paraquat, affected plasma memberane cytosol releases FADD, which in turn stimulates the increase of caspase 8. Caspase 3 is activated by the elevated level of caspase 8, thereby cause DNA fragmentation and cell death. The exposure of Paraquat causes P53 to become unstable, the unstable P53 in turn binds to MDM2, and loses the ability to control cancerous genes. Accompanied by the weakening of Bcl-2, Bax moves from cytosol to mitochondrion; mitochondrion partially binds to BAX and become permeable. Simultaneously, cytochrome-C is released from the permeable spot and activates caspase 9 and stimulates caspase 3, thereby causes DNA fragmentation and apoptosis. The increasing, stimulated P53 will affect P21 and P27 and result in the Cell Cycle to stagnate.
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