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Abstract Exposure to environmental pollution from ionizing radiation as well as aluminum had been connected with the manifestation of neurodegenerative changes after long-term exposure. Aloe vera (barbadensis) was shown to possess anti-tumor activity, anti-inflammatory, anti-bacterial, anti-diabetic, antimicrobial and antioxidant properties. The objective of the present study is to elucidate the neurotoxic potentials of exposure to aluminum and/or - radiation induces oxidative stress and neurotransmitter alterations in rat’s brain tissue. In addition, the role of Aloe vera in modulating the severity of biochemical and histological changes that occur in the brain of irradiated and aluminum exposed rats. Adult male albino rats Sprague Dawley (100 ± 10 g), were used as experimental animals. Aloe vera was dissolved in distilled water and administered via gavages, to rats at doses of 200 mg/Kg body weight/day. Aloe vera was freshly prepared just before its daily administration. Summary and Conclusion 152 Experimental animals (144) were divided into eight groups (18 rats each) as follows: group I (Control group): rats received distilled water via gavages daily for a period of 4 weeks. group II (Aloe vera group): rats received Aloe vera gel powder (200 mg/Kg b.w/day) via gavages for a period of 4 weeks. group III (Ir group): rats were whole body -irradiated with 8 Gy administered in four fractions of 2 Gy once a week during 4 weeks. group IV (Aloe vera+Ir group): rats received Aloe vera gel powder (200 mg/Kg b.w/day) via gavages for a period of 4 weeks. On the 7th day of every week one hour post Aloe vera treatment rats were whole body -irradiated with 2 Gy once a week during four weeks . group V (Al group): rats received Al2(SO4)3 (0.2 mg/Kg b.w/day) via gavages for a period of 4 weeks. group VI (Aloe vera+Al group): rats received Aloe vera gel powder (200 mg/Kg b.w/day) one hour before the administration of Al2(SO4)3 (0.2 mg/Kg b.w/day) for a period of 4 weeks. Summary and Conclusion 153 group VII (Al+Ir group): rats received Al2(SO4)3 (0.2 mg/Kg b.w/day) via gavages for a period of 4 weeks. On the 7th day of every week 1 hour post Al2(SO4)3 treatment rats were whole body -irradiated with 2 Gy once a week during four weeks. group VIII (Aloe vera+Al+Ir group): rats received Aloe vera gel powder (200 mg/Kg b.w/day) via gavages 1 hour before the administration of Al2(SO4)3 (0.2 mg/Kg b.w/day) for a period of 4 weeks. On the 7th day every week one hour post Al2(SO4)3 treatment rats were whole body -irradiated with 2 Gy once a week during four weeks. Animals were sacrificed one day post the last dose of - radiation. The two cerebral hemispheres were separated and rapidly excised, washed in ice cold saline, wiped dry with a filter paper and weighed for the further biochemical analysis. The results obtained could be summarized as follows: 1- Oxidative stress in brain tissues: Whole body gamma irradiation of rats with 8 Gy administered in four fractions of 2 Gy/week for a period of 4 weeks and exposure to Al2(SO4)3 at a dose of 0.2 mg/kg body weight/day, induced a significant increase in the levels of brain oxidant biomarkers: thiobarbituric acid reactive substances Summary and Conclusion 154 (TBARS), protein carbonyl group (CO) and aluminum (Al) associated with a significant decrease in the levels of brain superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities and reduced glutathione (GSH) content compared to control values. 2- Neurotransmitter alterations in brain tissues: Whole body gamma irradiation of rats with 8 Gy administered in four fractions of 2 Gy/week for a period of 4 weeks and exposure to Al2(SO4)3 at a dose of 0.2 mg/kg body weight/day, induced a significant decrease in the levels of brain catecholamines: dopamine (DA), nor epinephrine (NE), epinephrine (EPI) and serotonin (5-HT). A significant increase in 5-hydroxy indole acetic acid (5-HIAA), monoamine-oxidase (MAO) activity and serotonergic activity (5-HIAA/5-HT). A significant decrease in catecholamines / serotonin ratio while a significant increase in glutamic (Glu) and aspartic (Asp) acids levels, was recorded compared to control values. 3- Modulator effect of Aloe vera: Supplementation of rats with Aloe vera gel powder at a dose of 200 mg/Kg body weight/day, via gavages for 4 weeks during exposure to Al2(SO4)3 and whole body gamma irradiation has significantly attenuated the severity of radiationSummary and Conclusion 155 induced oxidative stress and neurotransmitter alterations in brain tissues evidenced by a significant increase in SOD, CAT, GSH-Px and GSH content, associated with a significant decrease in TBARS, CO and Al levels, compared to their respective values in aluminum and/or irradiated rats not receiving Aloe vera. Amelioration of oxidative stress in brain tissues was associated with improvement of the histopathological changes noticeable by less thrombotic vessels and slight deposition of β- amyloid protein. Furthermore, a significant amelioration in the levels of DA, NE, EPI, 5-HT, 5-HIAA, MAO activity, serotonergic activity, catecholamines / serotonin ratio, glutamic and aspartic acid levels was recorded in brain tissues. 4- Histopathological changes in brain tissues: Oxidative stress in brain tissues of rats exposed to -radiation, aluminum as well as aluminum combined with -radiation was accompanied by histopathological changes manifested by large thrombotic vessels and β-amyloid protein deposition, The damage in brain tissues was aggravated by exposure of rats to the combined effect of Al and -radiation as beside large thrombotic vessels, cytotoxic edema, eosinophilia, macrophages and intensive β-amyloid protein deposition were observed. Summary and Conclusion 156 Conclusion: Exposure to aluminum and/or -radiation induced oxidative stress and histopathological damage in brain tissues with concomitant alteration in neurotransmitters. Exposure to aluminum combined with -radiation increased the severity of these changes The oral administration of Aloe vera gel powder offer protection against aluminum and/or -radiation biochemical and histopathological disorders in brain tissues, probably by exerting its effect via its free radical scavenging and membrane stabilizing ability |