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Summary and conclusion
Summary and conclusion
Various mechanisms of Al toxicity have been presented till now but the results are still below satisfaction. Recently, it is widely accepted as a neurotoxicant and may induce its toxic manifestations by exacerbating oxidative stress in brain. Additionally, Al and other free-radical generating metals show neurotoxic activity in vivo and in vitro, thus indicating that above normal intake of Al is an environmental factor which may promote cognitive impairment in rodents and humans, irrespective of whether they are at risk for developing AD.
In addition, it is evident that the use of various antioxidants and derived plant products either alone or in combination have produced beneficial effects in Al induced oxidative stress but the ameliorating effect of these antioxidants in Al neurotoxicity remain to be further clarified and whether these can be proved with similar effectiveness in human.
Since the mechanism of AlCl3 neurotoxicity was not clearly understood, it is aimed by the present study to investigate the toxic effects of AlCl3 on the cerebral cortex, hippocampus and hind brain regions, as well as plasma of male rats. Also, the present study aimed to evaluate the protective effects of Spirulina and/or vitamin C against AlCl3 toxicity. To achieve this aim, 48 adult male Sprague Dawely rats weighing 160-l80g were used as experimental animals. Rats were divided equally into eight groups identified as follows:
Group I: Negative control group. Rats were received 2 ml distilled water as vehicle orally by gavages, daily for 50 days.
Group II: Spirulina-treated group (SP). Rats were received 1ml Spirulina alone orally at a dose of 1500 mg/kg body weight, daily for 50 days.
Group III: Vitamin C-treated group (Vit.C). Rats were received 0.5 ml ascorbic acid (Vit.C) alone orally at a dose of 40 mg/100g body weight, daily for 50 days.
Group IV: Vitamin C and Spirulina-treated group (Vit.C + SP). Rats were received 0.5 ml of oral Vit.C at a dose 40 mg/100g BW/day for 8 weeks in combination with 0.5 ml of oral SP at a dose 1500 mg/kg BW (Vit.C was given to rats 30 minutes before Spirulina).
Group V: Aluminum-treated group (AlCl3). Rats in this group were received 0.5 ml of oral aluminum chloride at a dose 34 mg/ kg BW (1/25 LD50)/day for 8 weeks.
Group VI: Spirulina and AlCl3-treated group. Rats were pre-treated with Spirulina at a dose 1500 mg/kg BW for 10 consecutive days and in-combination with aluminum chloride at a dose 34 mg/kg BW/day (Spirulina was given 30 minutes before aluminum chloride administration).
Group VII: Vit.C+AlCl3-treated group. Rats were treated with ascorbic acid at a dose 40 mg/ 100g BW for 10 consecutive days and in-combination with aluminum chloride at a dose 34 mg/kg BW daily for 8 weeks (ascorbic acid was given 30 minutes before aluminum chloride administration).
Group VIII: Vit.C+SP+AlCl3-treated group. Rats were pre-treated with ascorbic acid plus Spirulina for 10 consecutive days and in-combination with aluminum chloride at a dose 40 mg/ 100g, 1500 mg/kg and 34 mg/kg BW/day, respectively for 8 weeks.
At the end of the experimental period, the final body weight of rats were recorded after fast 24 hours from the last treatment then rats were anesthetized with ether and sacrificed. The blood samples were collected in tubes containing anticoagulant EDTA and placed immediately on ice for haematological profile. Plasma was obtained by centrifugation of blood samples at 860xg for 20 minutes. However, brain tissues (cerebral cortex, hippocampus and hind brain regions) were immediately isolated from the rats at the end of the experiment, weighed, washed in ice-cold saline solution 0.9% and kept frozen at -80°C until assayed. As well as, a part of cerebral cortex and hippocampus were putted in 10% buffered formalin for histopathological examinations. Therefore, it was planned to estimate the effect of AlCl3 alone and during pre-treatment and in combination with Spirulina and/or vitamin C to assess whether these effects can be ameliorated by co-treatment with Spirulina and/or vitamin C on the following analysis:
- Hematological indices.
Oxidative stress markers:
- Plasma and brain regions TBARS levels.
- Plasma and brain regions GSH levels.
- Brain regions total thiol content.
- Brain regions total antioxidant capacity (TAC).
- Plasma and brain regions antioxidant enzymes activities such as SOD, CAT, GPX and GST.
- Brain function enzymes:
- Plasma and brain regions AChE activity.
- Plasma and brain regions MAO activity.
- Brain regions Na-K ATPase and total ATPase activities.
- Lipid profile tests:
- Plasma triglyceride level.
- Plasma total cholesterol level.
- Plasma HDL-cholesterol level.
- Plasma LDL-cholesterol level.
- Plasma VLDL-cholesterol level.
- Plasma Chol/HDL ratio.
- Plasma Apo B level.
- Plasma total protein level and brain regions total protein contents.
- Brain concentrations of Al, Fe, Ca and Mg.
- Intensity of brain TNF-α expression.
- Histopathological alterations in cerebral cortex and hippocampus.
The results obtained were statistically analyzed and summarized as follows:
- There was a reduction in daily body weight gain of male rats treated with AlCl3 compared to control and all treated groups may indicate that Al-treatment influence the bioavailability of some nutrients and general effects of aluminium on metabolic processes depression or reduce nutritional efficiency. On the other hand, rats treated with Spirulina+AlCl3, Vit.C+AlCl3 and Vit.C+Spirulina+AlCl3 showed significant increase in their gain body weight compared to AlCl3-treated group.
- Brain relative weights showed a significant decrease in AlCl3-treated rats may be attributed to retarded development of the animal. In contrast, the pretreatment with Spirulina, Vit.C and their combination with AlCl3 showed significant increase compared to AlCl3-treated group.
- There were marked decrease in RBCs, Hb, Ht, MCV, MCH, MCHC, lymphocyte, monocyte and eosinophil values and there were marked increase in WBCs, neutrophil, platelet counts and RDW after administration of AlCl3 as compared to control due to degradation of RBCs or disturbances in heme biosynthesis and indicating the activation of the immune system. On the other hand, pretreatment of rats with Spirulina or Vit.C and Spirulina plus Vit.C in combination with AlCl3 showed greatly significant improvements on the rates of RBCs, Hb, Ht, MCV, MCH, MCHC, lymphocyte, monocyte and eosinophil, whereas highly significant decrease in WBCs, neutrophil, platelet counts and RDW as compared to AlCl3-treated group.
- The level of plasma and brain regions TBARS were significantly increased in AlCl3-treated rats compared to the control group, which suggest participation of free radical-induced oxidative cell injury in mediating the toxicity of Al. On the other hand, pretreatment with Spirulina and/or Vit.C+AlCl3-treated groups showed significantly decreased in the levels of TBARS in plasma and different brain regions compared to AlCl3-treated group.
- GSH level of plasma and brain regions in AlCl3-treated group were significantly decreased than that of control and all other treated groups due to excessive accumulation of reactive oxygen species. In contrast, pretreatment of Spirulina or Vit.C and Vit.C plus Spirulina in combination with AlCl3-intoxicated rats restored the levels of GSH toward the normal values of the control.
- Total thiol content was significantly decreased in AlCl3 compared to the control group due to reduced GSH content as greater production of H2O2 induced by treatment with AlCl3. Unlike, co-administration of Vit.C and/or Spirulina in combination with AlCl3 resulted in highly significant elevation in the thiol content when compared to AlCl3-intoxicated rats.
- Total antioxidant capacity showed significant reduction in AlCl3-treated group. However, the TAC levels in the pretreatment of Spirulina, Vit.C and Vit.C+ Spirulina in combination with AlCl3-treated group revealed significant increase in brain regions compared to AlCl3-treated group.
- The activity of antioxidant enzymes such as SOD, GPX and GST were significantly inhibited in AlCl3-treated rats compared to control group, which may attributed to oxidative stress are accompanied by depletion of endogenous antioxidants levels and implicated in the etiology of AD. Likewise, administration of Spirulina and/or Vit.C prior to AlCl3 enhanced the enzymatic antioxidative status as demonstrated by the significant increase in the activities of SOD, GPX and GST in plasma, cerebral cortex, hippocampus and hind brain regions.
- CAT enzyme activity in plasma and brain regions showed significant inhibition in AlCl3-treated rats and a highly significant increase in hind brain when compared to control group due to the activity of CAT was directly linked to the concentration of H2O2. In contrast, administration of Spirulina and/or Vit.C prior to AlCl3 induced a significant increase in the activity of CAT, except a significant inhibition in hind brain when compared to AlCl3-treated group.
- There was a significant increase in plasma and brain acetylcholinesterase (AChE) activity in AlCl3-treated group. This could be attributed to allosteric interaction between Al and the peripheral anionic site of enzyme molecule to modify the secondary structure and eventually its activity. In contrast, Spirulina and/or Vit.C administration before and in combination with aluminum chloride significantly reduced the activity of AChE in plasma and brain regions in comparison with AlCl3-treated group.
- The activity of MAO in plasma and different brain regions of AlCl3-treated group showed significant decrease in compared to control group due to marked neuronal loss and presence of Al ions. On the other hand, the pretreatment with Spirulina and/or Vit.C in combination with AlCl3 were significantly increased the activity of MAO in plasma, cerebral, hippocampus and hind brain regions compared to AlCl3-treated group.
- There were significant decrease in brain mitochondrial Na–K ATPase and total ATPase activities on group treated with AlCl3 in all brain regions, except insignificant decreased in hind brain total ATPase compared to control values may be attributed to this membrane bound enzymes require phospholipids for their activities which are highly vulnerable to oxidative stress. Additionally, the supplementation of rats with Spirulina and/or Vit.C in combination with AlCl3 led to significant increase in the Na-K ATPase activity in different brain regions and total ATPase of hippocampus whereas, a slight increase in the total ATPase of cerebral cortex and hind brain regions as compared to aluminum treated rats.
- Plasma triglyceride, cholesterol, LDL-C, VLDL-C, Chol/HDL ratio and Apo B were significantly increased in AlCl3-treated group. In contrast, concentration of HDL-C in the same group was significantly decreased comparing to control values, thus increased the risk factors for atherosclerosis and decreased blood flow to the brain which may be explained the mechanisms involved in Al-induced neurotoxicity. On the other hand, pretreatment with Spirulina and/or Vit.C in combination with AlCl3 restored the values of these altered parameters toward to the control group.
- Plasma total protein concentration and protein contents of cerebral, hippocampus and hind brain showed a significant decrease in AlCl3-treated group compared to control rats due to reduced protein synthesis and/or metabolism. On the other hand, the administration of Spirulina and/or Vit.C in combination with AlCl3 revealed significantly increased comparing with AlCl3-induced group.
- Al and Ca concentrations showed significantly increased in AlCl3-treated group, whereas a significant inhibition in brain Fe and Mg concentrations compared to control, thus may be attributed to initiate the peroxidation of membrane lipids, causing membrane biochemical and functional alterations and thus induced cell damage. In contrast, the pretreatment with Spirulina and/or Vit.C in combination with AlCl3-treated group indicated a high significantly attenuation in the Al, Fe, Ca and Mg concentrations of brain compared to AlCl3-treated group.
- AlCl3 increased the intensity of TNF-α in rat brain homogenates when compared to control as there is a strong association between free radicals accumulation and the evolution of inflammatory-related responses. Likewise, a high significant decrease in the brain TNF-α intensity of Spirulina and/or Vit.C in combination with AlCl3-treated group when compared to aluminum-treated group.
In conclusion, aluminium has adverse effects on human health. The present results reported that aluminium chloride (AlCl3) capable of caused marked alterations in some biochemical parameters induced oxidative damage and inhibited the activities of antioxidant enzymes, as well as possible progression of AD. In contrast, Spirulina and vitamin C showed ameliorative effects against the Al-induced neurotoxicity and AD. Furthermore, the combination treatment showed the best results and could normalize the tested parameters.
This study has given rise to the following recommendations to assist with the prevention, diagnosis and treatment of AD: