| Background:The normal intestinal microbiota, mainly colonized in the intestinal downstream with number, exists with the host and symbiosis. It can help the host to resist to the pathogen invasion, promote nutrient absorption and regulate immune system development etc. Recent studies show that intestinal microbiota affects the function of central nervous system through nervous, metabolic, immune and endocrine pathways. In the metabolic pathway:microbiota can metabolize Trp in food to 5-HT or kynurenic acid, or directly produce the neurotransmitter GABA. In the nervous pathways, the vagus nerve connects the intestinal wall and the central nervous system, therefore any changes of intestinal microbiota can be passed to the brain. In the immune pathway:the bacteria can stimulate the intestinal mucosal immune cells to produce a variety of cytokines and then secrete into the blood stream. In the endocrine pathways:the bacteria induce the gut endocrine cells to produce 5-HT. The brain can also release the neurotransmitters, such as corticosterone, epinephrine, and noradrenaline to influence the intestinal microbiota because of tension and pressure.The pathways are therefore bidirectional and exist mutual influences at different levels. The mechanism of the two-way communication makes the brain can response to gastrointestinal function and the microbial intrusion, moreover, microbiota changes in the gastrointestinal tract will affect CNS. The hippocampus play roles in cognitive function, memory and individual construction and emotion management. Brain-derived neurotropic factors is a kind of protein that acts in the neuronal development and normal physiology function, It can support the survival of neurons, regulate of cell differentiation and gene expression, and protect neurons in a variety of neurodegenerative diseases, it also promotes recovery, growth and the physiological function of axon. Therefore, gut brain axis is the communication system of nerve contact with the intestinal bacteria. In recent years, probiotics are used for the treatment of autism, depression and anxiety, and has achieved certain therapeutic effects. The mechanism is still not clear. Therefore, research on the function of intestinal microbiota on CNS has the values of theoretical significance and practical application.Objective:To investigate the changes of intestinal microbiota and hippocampal BDNF expression in rats after oral antibiotic treatment and the recovery.Methods:1.40male SD rats,180-220g, were randomly divided into four groups,10 for each group. The rats in the control group drank water, the rats in the antibiotic group drank nonabsorble antibiotics, which is a mixture of bacitracin, neomycin and natamycin (neomycin 5 mg/mL; bacitracin 5 mg/mL; natamycin 1.25 g/mL), for three weeks, rats in the recovery group drank the same antibiotics for three weeks, then changed to water for three weeks.2. DGGE was used to detect bacterial diversity changes; high-throughput sequencing was used to analysis of the composition of the intestinal microbiota.3. Real-Time PCR was used to detect the expression of BDNF and IL-1β in rat hippocampus.4. Light microscopy and electron microscopy were used to observe the morphological changes of colon tissue, and Real Time-PCR method was used to detect the expression of colon cytokine factors:IL-1β and IL-10 and neurotransmitter synthetase: Dβh.5. Step-down test was used to detect the degree of rat anxiety.Results:1. After antibiotic treatment for three weeks, the intestinal microbiota diversity decreased, (For Simpson index, the antibiotic group was 0.17±0.023, and the control group was 0.043±0.0033, p<0.05; while for the Shannon index, the antibiotics group was 2.7±0.081, and the control group was 4.5±0.039, p<0.05). The percentages of Bacteroides, an unknown genus of Rikenellaceae, Ruminococcus and Klebsiella increased significantly; while the percentages of Parabacteroides, Lactobacillus, Roseburia, Ruminococcus, Phascolarctobacterium, Sutterella, Helicobacter and Anaeroplasma significantly reduced. The diversity of intestinal bacteria in the recovery group was restored(For Simpson index, recovery group was 0.043±0.019, and control group was 0.037±0.0033, p>0.05; For the Shannon index, recovery group was 4.5±0.28, and control group was 4.5±0.10, p>0.05). At the same time, the percentages of Bacteroides, an unknown genus of Rikenellaceae, Klebsiella, Lactobacillus, Roseburia, Roseburia, Phascolarctobacterium and Sutterella had no differences as compared to the control. The percentages of Oligella and Roseburia were not restored.2. The expression of BDNF mRNA in the hippocampus after antibiotics treatment for three weeks was significantly higher than that of the control group, the relative content of BDNF mRNA was 1.6:1.0, (The control group was artificially set to 1.0); the expression of BDNF mRNA in the recovery group had no significant difference as compared with that of control (1.1:1.0).3. Antibiotic-treated rats showed colonic submucosa loose and inflammatory cell infiltrations with HE staining, the expression of pro-inflammatory factor IL-1β increased significantly (antibiotic group:2.7±0.072×10-3, control group:0.94±0.049× 10-3, p<0.01), while the expression of anti-inflammatory factor IL-10 decreased significantly,(antibiotic group:3.4±0.21×105, control group:5.8±0.26×10-5,p<0.05); After recovery the colon mucosa integrity the bowel dilation and inflammation cell infiltrations were not apparent, expressions of IL-1β and IL-10 were restored as compared with the control group.4.After antibiotic treatment for three weeks, Dβh which is an essential synthetase for neurotransmitter norepinephrine increased, (antibiotic group:14.6±1.7×10-6, control group:8.8±1.0×10-6,p<0.05), and this change was recovered to the normal level, (recovery group:13.8±0.9×10-6, control group:12.3±0.7×10-6,p>0.05)5. Antibiotic-treated rats did not changed the level of IL-1β in hippocampus and did not change the structure of colon microvilli.6. Compared with the control group, the rats in the antibiotic group showed shorter latency to step down the platform, but with no significant difference.Conclusions:The oral antibiotic treatment changed the compositions of intestinal microbiota in rats, increased the expression of BDNF in the hippocampus, and resulted in mild inflammation of colon; the compositions of intestinal microbiota and the expression of BDNF restored accompanied by the recovery of colonic inflammation in the recovery group. |
PDF Full Text Request