| Summary: | 碩士 === 長庚大學 === 生物醫學研究所 === 99 === Lifespan extension by reducing ambient temperature, which is also called “temperature reduction” (TR), has been observed in many organisms such as Caenorhabditis elegans, Drosophila melanogaster, and zebrafish. However, the precise regulatory mechanism of this phenomenon has not been elucidated. In this study, I used a single-celled eukaryote Trichomonas vaginalis to investigate the influence of temperature on the lifespan of this protozoan. The relative short lifespan of T. vaginalis compared with the multi-cellular organisms provided a platform to unravel the mechanism of TR at cellular level. This study showed that T. vaginalis grown at 22℃, 27℃, and 32℃ have a longer life span than cells grown at 37℃. In addition, cells cultivated at 27℃ not only extended their lifespan, but also increased their doubling time. Since TR cells can regain their mitotic ability when transfer to 37℃, implying that the life span extension at 27℃is totally temperature dependent. Based on the recovery rate index, the 36th hour post-TR was an important time point for T. vaginalis to recover from TR. Also, TR cells were more resistant to oxidative stress than cells grown at 37℃. Furthermore, the expression of antioxidative genes, such as superoxide dismutase (sod-1, sod-2), thioredoxin peroxidase (tpx-1, tpx-2, tpx-3), thioredoxin reductase (trxr), and thiol peroxidase (thiolpx), were increased at 24 hours or 36 hours at 27℃. Interestingly, the longevity marker genes, sir2 and lag, were differentially expressed under TR. In conclusion, T vaginalis can serve as a model organism to study TR-induced longevity, and this model will exploit a new research field on aging and longevity in protist.
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