Abstract
Purpose:
Flavonoids may have a potential as neuroprotective drugs for neurodegenerative diseases such as glaucomatous optic neuropathy. The purpose of this study is to investigate whether flavonoid components derived from three kinds of Japanese violas indicate neuroprotective effect on primary culture of rat retinal ganglion cells (RGCs) death induced by oxidative stress, and to clarify the active site of chemical structure of flavonoids.
Methods:
RGCs were purified using a two-step immunopanning procedure from postnatal days 5-6 newborn Wistar rats. After 72 hours’ cultivation under normal condition, RGCs were pretreated with three kinds of flavonoid components from Viola japonica (JA), Viola eizanensis (EZ) and Viola chaerophylloides (CH) for 1 hour, and subsequently exposed to oxidative stress by B27 medium without anti-oxidant (AO-) during 6 hours. Each assay was repeated 8 times with or without each flavonoid 1, 10, 100 and 1000nM. After oxidative stress, a number of RGCs was counted by cell viability assay. RGC viability in each condition was evaluated in comparison with that under the normal condition. Cell death types, i.e. necrosis or apopotosis, by oxidative stress with or without flavonoids were assessed using annexinV/PI and calpain immunoreactivity assays.
Results:
Under oxidative stress, RGCs viability reduced to 54%. Pretreatment with 1, 10,100 and 1000nM of JA, EZ and CH increased cell viability to 69, 75, 90 and 77% by JA, 67, 83, 93 and 71% by EZ, 71, 80, 91 and 72% by CH, respectively. RGCs viability was significantly increased by all of flavonoid treatment. (Dunnett test p<0.05) Oxidative stress affected only necrotic activity and the proportion of necrotic cells significantly increased to 32% by flavonoids treatment compared to 19% in normal cultivation. (p<0.05) In contrast, 100nM of JA, EZ and CH reduced the proportions of necrotic cells to 19, 23 and 20%, respectively. (p<0.05)
Conclusions:
Our results suggest that different types of flavonoid components from three kinds of Japanese viola equally had strong neuroprotective effects on RGCs death induced by oxidative stress.
Keywords: 615 neuroprotection •
531 ganglion cells •
424 antioxidants