الفهرس 
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Abstract
Monosodium glutamate (MSG) is a flavor enhancing food additive and found in unlimited amounts in a varied of packaged foods, fast foods and restaurant foods. Propolis is a natural substance produced by honeybees and used by bees to protect its hive. Also, it is antioxidant. The point of present study is the genotoxic effects of monosodium glutamate and protective role of propolis on bone marrow chromosomes, DNA and histological structure of liver of male albino mice.
Sixty male albino mice (16-18 weeks old) were used in this study and divided into six groups. The first and sixth groups contain 6 mice and other groups contain 12 mice. First group served as control while the sixth group treated with 100 mg/kg b.wt. of propolis. The second and third groups treated with 0.5g/kg b.wt. and 1g/kg b.wt. of MSG respectively. The fourth and fifth groups treated with 0.5g/kg b.wt. and 1g/kg b.wt. of MSG in addition to propolis (100 mg/kg b.wt.) respectively. All animals killed after 2 and 4 weeks of treatment. Each MSG and propolis treated animals were orally injected daily for 2 and 4 weeks with the selected doses.
Treatment with MSG to male albino mice induced bone marrow chromosomal aberrations whether structural and numerical aberrations. The Structural aberrations such as centromeric attenuation, deletion, ring chromosome, fragment, centric fusion, beaded chromosome, sticky chromosome, end to end associations and chromatid gap while the numerical aberrations like as polyploidy. chromosomal aberrations amplified high significantly (p < 0.001) by time and dose especially after 4 weeks of treatment with 1 g/kg b.wt. of MSG compared with control group. While the treatment with MSG in addition to propolis reduced the mean of structural and numerical chromosomal aberrations.
Micronucleus assay results showed that monosodium glutamate treatment induced genotoxicity in bone marrow cells and the number of micronucleated polychromatic erythrocytes (MNPCEs) was gradually increased significantly (p < 0.001) by the increase of dose and time in treated groups with MSG when compared to the control one. Also, cytotoxicity test showed that the ratio of polychromatic erythrocytes/normochromatic erythrocytes was gradually decreased significantly (p < 0.001) by the increase of dose and time in treated groups with MSG when compared to the control one. While the treatment with MSG in addition to propolis statistical decreased (p < 0.05) the number of micronucleated polychromatic erythrocytes (MNPCEs) and improved the ratio of polychromatic erythrocytes/normochromatic erythrocytes in bone marrow compared to control one.
The current results of comet assay indicated that treatment with monosodium glutamate significantly (p < 0.001) increased DNA damage in the liver cells in dose and time dependent manner especially after 4 weeks of treatment with 1 g/kg b.wt. of MSG while the treatment with MSG in addition to propolis statistical decreased (p < 0.05) the DNA damage compared to control one.
Results of quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR) analysis showed the treatment with MSG decreased the gene expression of liver genes such as FAS, SREBP-1c and HSL while the treatment with MSG in addition to propolis (fourth and fifth groups) improved the gene expression of liver genes in comparison with control one.
MSG treatment displayed variable changes in liver tissue and the histological changes including vacuolar degeneration of hepatocytes, multiple pyknotic nuclei, hemolyzed blood in portal vessels and mononuclear cell infiltration. Triglyceride (TG) quantification were also significantly (p < 0.01) increased by time and dose compared to control one.
The present study showed that no changes on the normal structure of chromosomes, DNA and histological structure of liver in groups treatment with propolis only compared to the control one.
Results of the present study indicated that MSG treatment induced genotoxic effect on bone marrow chromosomes, DNA content and histological structure of liver of male albino mice and propolis treatment improved these changes. Therefore, the using of MSG should be restricted to a very narrow range border.
Key words: MSG, Propolis, chromosomes, Micronucleus, Comet assay, qRT-PCR, Histopathology, Liver, TG quantification and Mice.