Functional characterization of Acanthamoeba castellanii ribonucleotide reductase

Autor: Jia-YenWoo, 武珈言
Rok vydání: 2017
Druh dokumentu: 學位論文 ; thesis
Popis: 105
Acanthamoeba species are free-living eukaryotic protozoa which are ubiquitous in nature. These free-living protozoa can exist as motile trophozoites and dormant cysts in many environments. Acanthamoeba species are also opportunistic human parasites which are rare and typically occur in persons with a compromised immune system, but Acanthamoeba keratitis (AK) is the exception. Although the number of AK reported cases worldwide is increasing year after year, mostly in contact lens wearers, the adequately effective diagnosis and treatments against AK are still lacking. Hydrogen peroxide (H2O2) and polyhexamethylene biguanide (PHMB) are two key disinfectants of contact lens solution for AK prevention. Previous study showed that superoxide dismutases (SODs), which are the enzymes that play a pivotal role in metabolizing oxidative stresses, were not induced after the treatment of H2O2 in Acanthamoeba castellanii. We discovered that A. castellanii ribonucleotide reductases (AcRNRs) chelated ferrous (Fe2+) iron compounds and blocked fenton reaction to decrease the formation of hydroxyl radicals and retard DNA damage. In this study, AcRNRs were induced by UV-C exposure and different dosages of H2O2. AcRNRs also showed the high sensitivity to reactive oxygen species (ROS) when we exposed A. castellanii under different dosages of H2O2 after N-Acetyl L-Cysteine (NAC) pretreatment. The tolerance of H2O2 in A. castellanii was down-regulated after we knocked down RNA expression of the AcRNRs isoform ACA1_119180. In addition, we found gene deficiency for two of AcRNRs isoforms (ACA1_066200 and ACA1_066210) from the PHMB-resistant clinical strains (NCKH_B and NCKH_D). Overall, this study is the first report to confirm the existence and expression level of AcRNRs in A. castellanii and to validate AcRNRs antioxidant activity. We hope this study can help people to clarify the mechanism of antioxidation in A. castellanii and improve the prevention and treatment of AK.
Databáze: Networked Digital Library of Theses & Dissertations
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