Neuroprotection Of Minocycline In Hippocampal CA1 Neuronal Apoptosis In A Rat Model Of Gulf War Syndrome

Background and Purpose:Gulf War syndrome is a serious condition that affects at least one fourth of the 697,000 U.S. veterans who served in the 1990-1991 Gulf War. This complex of multiple concurrent symptoms typically includes cognitive difficulties, persistent headaches, widespread pain, chronic diarrhea, skin rashes and other chronic abnormalities not explained by all-established diagnoses. A number of environmental factors specific to the Gulf conflict such as depleted uranium, oil well fires, nerve agents, pyridostigmine bromide, pesticides, immunisations, psychological stress and infectious diseases have been postulated as being linked to the syndrome. Epidemiologic studies that have assessed independent effects of multiple exposures during the Gulf War have consistently identified only two as significant risk factors for Gulf War syndrome:pyridostigmine bromide and pesticides. The studies show the volume of hippocampus and cingulate gyrus lost in GWS patients. The death in the hippocampal CA1 neurons was also found in animal experiments. Recently researchers discovered that minocycline has neuroprotective effects as Caspase-3 inhibitor. Thus, our purpose of this study is to observe the neuronal apoptosis change, the expression of Caspase-3 and Apaf-1 and to explore neuroprotective protection of minocycline in the hippocanpal CA1 in a rat model of Gulf War syndrome.Methods:The rat model of Gulf War syndrome were estalished with suture occlusion technique according to Abdel-Rahman method. The animals were randomly assigned to control and treatment groups. Animals in PB/DEET group (n=6) were treated daily with PB (1.3mg/kg/day, oral in water) and DEET (40 mg/kg/day,dermal in 70% ethanol) for 28 days. Animals in model group (n=6) were treated daily with all of the above chemicals and also subjected to 20 min of restraint stress every day in dark environment for the duration of the experiment. Animals in low dose minocycline group (n=6) were treated daily with minocycline(15 mg/kg/day,peritoneal injection) including all of the above chemicals, restraint stress every day. Animals in high-dose minocycline group (n=6) were treated daily with minocycline(45 mg/kg/day,peritoneal injection) including all of the above chemicals, restraint stress every day. Animals in control Group (n=6) were treated with a dermal application of 70% ethanol and oral water daily for 28 days. Animals in restraint group (n=6) were treated with 20 min of restraint stress in dark environment every day. The weight of each rat was weighed at the time point of 0,14 and 28 day. Following the exposure regimen described above, erery animals from each group were perfused through the heart with saline followed by 4% paraformaldehyde in Tris buffer. The brains was removed, postfixed, and embedded in paraffin and detected the expression of Apaf-1 and Caspase-3 with using immunohistochemical staining of neural cells in the hippocampal CA1. Neuronal apoptosis was detected by Tunel method.Results:The increase of weight of rats in each group after 4 weeks were 79% in the control group,75% in restraint group,49% in PB/DEET,47% in model group, 70% in low dose of minocycline group and 71% in high dose of minocycline group. The increase of weight of rats in PB/DEET group was slow compared with the control group(P<0.01). The increase of weight of rats in model group was slow compared with the restraint group (P<0.01). It is no obviously different in weight gain between the model group and PB/DEET group(.P>0.05). It is the same as restraint group and control group. The increase of weight was obviously observed in low and high dose of minocycline groups compared with model group(P<0.01). The number of neuronal apoptosis, Caspase-3 and Apaf-1 integrated optical density in hippocampal CA1 are no significant differences in restraint group compared with the control group and in PB/DEET group compared with model group (P>0.05). The increases of the number of neuronal apoptosis, Caspase-3 and Apaf-1 integrated optical density in hippocampal CA1 are significant differences in model group compared with the control group (P<0.01). The decreases of the number of neuronal apoptosis, Caspase-3 integrated optical density in hippocampal CA1 are significant differences in low and high dose of minocycline groups compared with the model group (P<0.01). It is no significantly different in the number of neuronal apoptosis, Caspase-3 and Apaf-1 integrated optical density in hippocampal CA1 in low dose of minocycline group compared with high dose of minocycline group(P>0.05).Conclusion:1. Restraint stress has no significant damage to hippocampal neurons in a rat model of Gulf War syndrome.2. The expression of caspase-3, apaf-1 and the number of neuronal apoptosis increase in the hippocampal CA1 in a rat model of Gulf War syndrome.3. Minocycline has neuroprotective effects by inhibiting the expression of Caspase-3 and neuronal apoptosis.4. Neurons protective effect of low dose of minocycline is similar to the high dose of minocycline in a rat model of Gulf War syndrome.