| Objective:Coal worker's pneumoconiosis (CWP) is the disease that is caused by the long-term inhalation of the production of dust pneumoconiosis of coal mine workers.Because long-term inhalation of the production of dust pneumoconiosis, so that impaired lung function and causes a chronic continuous oxygen deficit.With the gradually deeper awareness about coal worker's pneumoconiosis,it has been found that in the progress of coal worker's pneumoconiosis process,it is prone to appear a variety of complications and secondary diseases resulting in the death. Chronic continuous oxygen deficit can cause multiple organ damage, especially the central nervous system. The relationship between hypoxia and apoptosis studies, found that the induction of hypoxia play the role of apoptosis. Neuronal apoptosis can cause brain dysfunction. It is now generally agreed that mitochondria is the executor of apoptosis. Mitochondria in apoptosis regulation is also important, the vast majority of protein molecules in regulating apoptosis through the mitochondria.Cognitive impairment caused by chronic continuous oxygen deficit of CWP happens after a long term, so it is difficult to conduct prospective study about the pathogenesis of coal worker's pneumoconiosis with cognitive impairment on human. Moreover, many intervening factors exist in clinical research, so experiments carried out on humans beings are limited. Therefore researches on CWP animals model would be useful to clarify the influence of CWP on cognitive and its payhogenesis. We look forward to establishing an suitable coal worker's pneumoconiosis model in rat, so that we can do some further researches on the influence of chronic continuous oxygen deficit on cognitive and the number of apoptosis neuron in hippocampus the possible pathogenesis. It will supply laboratory evidences for prevention and the clinical therapy coal worker's pneumoconiosis in patients with cognitive impairment.Methods:1.Establishment of Chronic continuous oxygen deficit model of coal worker's pneumoconiosis in rat:60 healthy 3-month-old Wistar rats were chosen. All the rats were fed one week to adapt to the new environment before the experiement. rats were randomly divided into 2 groups, namely control group, coal worker's pneumoconiosis (CWP) group, every group 30.They were 10%chloral hydrate (300mg/kg) intraperitoneal anesthetized, then were tracheal intubated. CWP group rats were filled with lml coal dust suspension (the particle diameter <5μm of coal dust was made 50g/L of normal saline suspension) the control group rats were filled with 1 ml normal saline. All rats were fed with the normal feed, and their water and activities are not limited. Experimental time was16weeks.2. The determination of the ability of lerning and memory (1) Morris water maze test learning scores (place navigation):evaluated the ability of lerning. (2) Morris water maze test memory scores(spatial probe)evaluated the ability of memory.3. Blood gas analysis the two groups were respectively chosen 10 rats weeks intraperiton-eal anesthetized in4,8,16, were abdominal dissected, took 0.5ml of blood from the abdominal aorta with blood gas Lancets for the detection of blood oxygen partial pressure.4.The determination of morphology:At the end of the experiment, rats were killed, took lung tissue and brain tissue to do HE staining to observe pathological changes of lung tissue and the structure of brain tissue. Observe the number of apoptosis neuron in hippocampus-(TUNEL) and the expression of BCL-2/BAX Protein of hippocampus.Results(1)The determination of the ability of lerning and memory①Morris water maze test learning scores:the escape latency in CWP rats was significantly longer than that in UC rats (P<0.05);②Morris water maze test memory scores. The number of times of crossing the platform in CWP group was significantly reduced than that in UC group (P<0.01). The percentage of time spent on crossing the target quadrant to the total swimming time in CWP group was also significantly decreased compared with that in UC group (P<0.01)(2)The results of blood gas analysis and lung biopsyof chronic continuous oxygen defict model of CWP in rats:In the pre-experiment, the arterial partial pressure of oxygen in rats after experiment was 85.8-90.2mmHg, which comparing with the previous blood pressure was decreasing significantly, although did not meet the standard of hypoxemia,but was a state of chronic oxygen defict. After 4 weeks, inflammatory cells, alveolar macrophages with dust, coal-dust accumulation plaques or nodules, and emphysema increases.After 8and16 weeks, small areas of pulmonary fibrosis was formed which is consistent with the pathological characteristics of coal worker's pneumoconiosis. Therefore, from the pathological changes of the lung tissue and the state of chronic continuous oxygen deficit, this model was consistent with the diagnostic criteria of CWP in human.(3)The results of the determination of morphology:from light microscope, in the control group and after two weeks, neurons and glial cells were normal. After 4 weeks, endothelial cell gap of small vessel wall increased and microglial cells aggregated.After 8,16 weeks, glial cells phagocytized neurons,neurons necrosis,reducedgrit-like mollification.Changes in the ultrastructure of hippocampus neurons and synapsis were obvious in CWP group as compared with the unhandled control group(2)the number of TUNEL positive nerve in hippocampus increased, CWP obviously higher than UC, the difference between the two groups is statistically significant(P<0.05)(4)The expression of BCL-2/BAX of hippocampus:CWP was obviously decreased compared with that in UC group (p<0.05), spearman correlation analysis showed that bone cell apoptosis rate was negatively correlated withBCL-2/BAXratio (p<0.01).Conclusion(1) CWP can lead to cognitive impairment of the rats(2) Chronic continuous oxygen deficit could lead the neuron poptosis in hippocampus maybe one of mechanism that chronic oxygen deficit hypoxia lead to cognitive impairment. |
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