Oxidative stress-induced cellular damage caused by UV and methyl viologen in Euglena gracilis and its suppression with rutin

The effects of ultraviolet radiation (UV-A: 320–400 nm and UV-B: 280–320 nm) and methyl viologen (MV) single or combined exposure, on the cell growth, viability and morphology of two strains of the unicellular flagellate Euglena gracilis, using the Z strain as a plant model and the achlorophyllous mutant SMZ strain as an animal model were investigated. Cell growth was not affected by MV only, whereas UV-A or UV-B single and combined exposure with MV inhibited the cell growth or decreased the viability. The SMZ strain had a higher number of abnormal cells than the Z strain after the third dose of UV-B was delivered simultaneously with MV. The abnormal cell number decreased when E. gracilis SMZ cells were preincubated with 100 μM rutin prior to the UV-B and MV exposure. There were higher abnormal cell numbers with groups exposed to UV rather than MV single exposure. Combined exposure to UV-B and 200 μM MV induced the highest levels of TBARS in both strains, and with the supplementation of rutin these high levels were suppressed. These results suggest that UV-A or UV-B irradiation alone or combined with MV cause considerable oxidative damage in E. gracilis cells, and rutin supplementation may suppress their adverse effects.