الفهرس 
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Abstract
This study was carried out to assess the genotoxic effect of small and large doses of MSG and its clastogenic effects as a food additive on mice. Besides, to study the possible protective effect of ginger to MSG genotoxicity.
The study was done on 120 mice weighing approximately 20-25 gm and ageing 8 weeks age. The mice were divided into six groups, and each group contained 20 mice. Frist group (G1) act as control without any treatment, the second group (G2) received 160 mg /kg b.wt ginger powder in diet, the third group (G3) received 100 mg/kg b.wt Monosodium glutamate (MSG) as crystal salt in the diet. The fourth group (G4) received large dose from MSG (240 mg/kg b.wt) in diet, the fifth group (G5) received the same average daily dose from MSG 100 mg/kg b.wt and 160 mg/kg b.wt from ginger powder in diet, the sixth group (G6) received large dose from MSG (240 mg/kg b.wt) and 160 mg/kg b.wt of ginger in the diet.
The samples were collected from the experimental groups twice; after 6 weeks (short term) and 12 weeks |(long term) from the onset of the treatment (four mice were used from each group at each collection time). The peripheral blood samples were collected from vein of tail for micronucleus assay. Also, liver samples were collected for selected gene expression analysis. The qRT-PCR was used for assessed of the expression of antioxidant genes Glutathione S-Transferase (GST), Metallothionein-1 (MT1) and Catalase (CAT), Single strand DNA repair gene X-ray repair cross-complementing 1 (XRCC1) and double strand DNA repair gene Flap
Endonuclease 1 (FEN1).
The results of the present study could be summarized in the following:
1- No significant differences were observed in GST gene expression after short exposure to large dose of MSG. However, a significant increase in its expression was observed after long term exposure with a large dose. A significant reduction in its expression was observed at the groups received MSG with ginger.
2- MT1 gene expression was significantly up-regulated at the groups received ginger alone (G2) and different doses of MSG (G3 and G4) after short and long term of exposure. Otherwise, the groups received ginger with MSG (G5 and G6) showed a significant down-regulation of MT1 gene in both short and long term exposure than G3 and G4 received MSG only.
3- Significant up-regulation of CAT gene expression was observed by ginger (G2) as well as by the small and large doses MSG (G3 and G4) in short term exposure. A significant down-regulation in its expression was observed when the mice received ginger with MSG (G5 and G6) in short term exposure and long one than G3 and G4 received MSG only.
4- XRCC1 gene expression significantly increased by ginger alone (G2), also by the small and large doses of MSG (G3 and G4), meanwhile, its expression was significantly decreased when the ginger was administered with MSG in long term exposure (G5 and G6). No significant difference was observed among the treated groups in short term MSG exposure.
5- FEN1 gene expression showed no significant differences among the different groups in short term MSG exposure although, elevation was noticed with different doses of MSG (G3 and G4) and decline when adding ginger with MSG (G5 and G6) than G3 and G4 received MSG only. A significant up-regulation was observed in the long term of exposure when the small and large doses of MSG (G3 and G4) were added; meanwhile, its expression was down-regulated when the mice were treated with ginger and MSG together (G5 and G6).
6- Micronucleus number was significantly increased in mice received a small and large dose of MSG and decreased when the mice received ginger with MSG compering with mice received only MSG in both short and long term exposure. Moreover, a significant increase in MN in the long term compering with the short term of study.
In conclusion, the results were revealed:
1- Monosodium glutamate induced an oxidative stress in the liver leading to up regulation of the antioxidant genes GST, MT1 and CAT and this increment is related positively with dose and duration.
2- MSG caused DNA damage as an increment in DNA repair genes expression
XRCC1 and FEN1 and it is positively related to dose and duration.
3- Ginger has an ameliorating effect on genotoxicity caused by MSG on mice.
4- Long term administration to MSG (12 weeks) is associated with increased micronucleus frequency in long term exposure, which is dose-dependent, and the combined treatment with ginger positively reduce the micronucleus frequency.