| Objective:NPC is one of common malignancies in the south of China, The incidence rate of nasopharyngeal cancer is the highest in the province of GuangXi than any other provinces in the country except the province of GuangDong, It accounts for the top of the incidence of the head and neck tumors, At present radiation therapy is one of the main treatment of the head and neck of the malignant tumors, such as nasopharyngeal carcinoma. Sensorineural hearing loss is a common complication of nasopharyngeal carcinoma after radiotherapy, but its pathogenesis is not yet clear at present, most scholars believe that the sensorineural hearing loss has relations with the ray-induced injury of cochlear after radiotherapy. Because of in the radiotherapy of nasopharyngeal carcinoma, the patient’s auditory organs such as inner ear, acoustic nerve, brainstem, are inevitably affected by irradiation, and sensorineural hearing loss has not been reported whether the cochlear nucleus are damaged, besides the damage of cochlea after radiotherapy. In this study, the guinea pigs were used as animal models,60Coyray was made use for irradiation of the guinea pigs of temporal section. By observing the auditory brainstem response and the morphology changes of the cochlear nucleus as well as proteins that had closely relations with apoptosis were expressed in the cochlear nucleus after radiotherapy, We discussed preliminarily which60Coyradiation caused the damage of the cochlear nucleus and the morphological changes of the cochlear nucleus, we provide experimental basis for the sensorineural hearing loss of the pathological changes of the central nervous system after radiotherapy.Methods:Forty eight guinea pigs which had white hair and a pair of red eyes were randomly divided into normal control group (erght guinea pigs) and the experimental group (forty guinea pigs), The control group is the healthy guinea pigs which were not carried out the irradiation, The experimental group were measured with the auditory brainstem response in1,4,7,14and30days after irradiation of40Gy, Then the guinea pigs were sacrificed,4%formaldehyde solution was made use of the cardiac perfusion of all the guinea pigs, Then we removed the cochlear nucleus from the guinea pigs, All cochlear nucleuses were made into paraffin sections.Sections were stained with heamatoxylin and eosin and Caspase3 Bax, Bcl-2,immunohistochemistry for light microscopic examination. We had eight guinea pigs at each time point.Results:1. Gross specimen observation:The auditory sac had no hydrops and purulent discharge in1,4,7,14,30days after60Co y-ray irradiation of40Gy.2. ABR wave latency and response threshold value: It was found that ABR threshold (31.88±2.59dB SPL) is slightly higher than that of the control group (29.17±1.95dB dB SPL) in1day after irradiation, But the difference was not statistically significant(p>0.05). It was found that ABR threshold of the control group was29.17±1.95dB SPL, ABR reflecting threshold were respectively31.88±2.59dB SPL,35.00±3.17dB SPL,35.83±2.04dB SPL,39.17±2.05dB SPL,41.67±2.58dB SPL after60Co irradiation in1,4,7d14,30days groups, The difference of ABR threshold was statistically significant (P<0.05) in4,7,14,30days groups After irradiation, compared with the control group. It was found that the I wave latency of ABR of the control group was1.21±0.04ms, The I wave latency of ABR were respectively1.27±0.09ms,1.29±0.02ms,1.32±0.16ms,1.38±0.05ms,1.44±0.06ms after60Co irradiation in1,4,7d14,30days groups, The difference of the I wave latency of ABR was statistically significant (P<0.05) in1,4,714,30days groups After irradiation, compared with the control group.It was found that the Ⅱ wave latency of ABR of the control group was1.96±0.07ms, The Ⅱ wave latency of ABR were respectively2.07±0.15ms, 2.10±0.05ms,2.14±0.03ms,2.21±0.07ms,2.33±0.09ms after60Co irradiation in1,4,7d14,30days groups, The difference of the Ⅱ wave latency of ABR was statistically significant (P<0.05) in1,4,7,14,30days groups After irradiation, compared with the control group. It was found that the Ⅲ wave latency of ABR of the control group was2.67±0.06ms, The Ⅲ wave latency of ABR were respectively2.87±0.21ms,2.90±0.05ms,2.92±0.06ms,3.02±0.11ms,3.17±0.19ms after60Co irradiation in1,4,7d14,30days groups, The difference of the Ⅲ wave latency of ABR was statistically significant (P<0.05) in1,4,7,14,30days groups After irradiation, compared with the control group. It was found that the interval period of the Ⅰ～Ⅱ peak of the control group was0.74±0.04ms, The interval period of the Ⅰ～Ⅱ peak were respectively0.79±0.05ms,0.81±0.04ms,0.82±0.02ms,0.83±0.03ms,0.88±0.04ms after60Co irradiation in1,4,7d14,30days groups. The difference of the interval period of the Ⅰ～Ⅱ peak of ABR was statistically significant (P<0.05) in1,4,7,14,30days groups After irradiation, compared with the control group. It was found that the interval period of the Ⅱ～Ⅲ peak of the control group was0.70±0.07ms, The interval period of the Ⅱ～Ⅲ peak were respectively0.80±0.07ms,0.80±0.02ms,0.80±0.04ms,0.81±0.04ms0.84±0.02ms after60Co irradiation in1,4,7d14,30days groups, The difference of the interval period of the Ⅱ～Ⅲ peak of ABR was statistically significant (P<0.05) in1,4,7,14,30days groups After irradiation, compared with the control group. It was found that the interval period of the Ⅰ-Ⅲ peak of the control group was1.45±0.05ms, The interval period of the Ⅱ-Ⅲ peak were respectively1.60±0.12ms,1.61±0.04ms,1.61±0.05ms,1.64±0.07ms,1.72±0.16ms after60Co irradiation in1,4,7d14,30days groups, The difference of the interval period of the Ⅰ-Ⅲ peak of ABR was statistically significant (P<0.05) in1,4,7,14,30days groups After irradiation, compared with the control group.3. The results of HE staining and Nissl staining showed that we can see the cells of the normal control group of guinea pig cochlear nucleus whose number is large, which were stained more uniformly, whose cytoplasm were abundant, whose Nissl bodies also were normal, whose nucleus and cytoplasm did not have the apparent shrinkage and vacuolar changes, glial cells were normal. The number and dyeing change of neurons is not obvious in the Cochlear nucleus of the experimental group of guinea pigs after60Co irradiation in1,4,7days under the light microscope, but after60Co irradiation in14days the nerve cells were swelled, Their cytoplasm reduced and coloration was pale, Their nucleus were shrinked, Nissl bodies also reduced and glial cells increased, because of the proliferation, The changes is more obvious after60Coyrays irradiation in more than30days.4. The results of immunohistochemistry showed that we can see the positive results of the caspase-3immunohistochemistry is that the cytoplasm of neurons of cochlear nucleus were stained brown-yellow. The cochlear nucleus of the control group did not have significant positive expression, Caspase3immunohistochemical gray value of the nerve cells of the cochlear nucleus was172.33±17.81in the control group, The groups of the Caspase3immunohistochemical gray values were respectively136.37±24.42,94.67±15.33,91.40±11.71,110.80±4.23,123.56±32.56in the experimental groups after60Co irradiation in1,4,7,14,30days.Compared with the control group, the difference was statistically significant (P<0.05). We can see the positive results of the Bax immunohistochemistry is that the cytoplasm of neurons of cochlear nucleus were stained brown-yellow. The cochlear nucleus of the control group did not have significant positive expression, Bax immunohistochemical gray value of the nerve cells of the cochlear nucleus was164.18±1.52in the control group, The groups of the Bax immunohistochemical gray values were respectively128.10±4.89,77.85±6.08,104.48±11.12,109.65±7.55,123.56±32.56in the experimental groups after60Co irradiation in1,4,7,14,30days.Compared with the control group, the difference was statistically significant (P<0.05). We can see the positive results of the Bcl-2immunohistochemistry is that the cytoplasm of neurons of cochlear nucleus were stained brown-yellow. The cochlear nucleus of the control group had the strongest positive expression, Bcl-2immunohistochemical gray value of the nerve cells of the cochlear nucleus was74.73±7.64in the control group, The groups of the Bax immunohistochemical gray values were respectively117.77±4.62,157.30±9.50,95.64±5.54,102.97±3.57,104.99±3.33in the experimental groups after60Co irradiation in1,4,7,14,30days.Compared with the control group, the difference was statistically significant (P<0.05).Conclusions:1.40Gy60Coy-ray which irradiated the temporal section of the guinea pigs could lead to the damage of hearing function and cochlear nucleus organizational structure. The damage became more obvious with the observation time prolonged.2.60Coy-ray could resulted in the cell apoptotic proteins of Caspase-3and Bax regulated the upward extension, Bcl-2regulated the downward extension, which may be involved in the damage process of the cochlear nucleus.3.60Coy-ray could resulted in the morphological changes of the cochlear nucleus, which may be later than the changes of ABR and molecular biology. |
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