Effects of erythropoietin on the expression of tumor necrosis factor-alpha and Bax after facial nerve axotomy in rats

This study sought to evaluate the effect of high-dose erythropoietin (EPO; 5 000 IU/kg) on the expression of tumor necrosis factor-alpha (TNF-alpha) and Bax in the facial nucleus after facial nerve transection in rats. A total of 42 Wistar rats of both genders were used in this study, and 40 rats were randomly divided into 2 groups: EPO group and model group. The EPO group was treated with EPO once a day for 5 days at a dose of 5 000 IU/kg body weight. The model group was treated with saline of the same amount. At day 3 after EPO (or saline) treatment, the right facial nerves of the 40 rats were transected at the level of the stylomastoid foramen, with the left sides untreated. The remaining 2 rats that did not undergo axotomy served as the control group. The surviving motor neurons in operated rats were counted in coronal paraffin sections of the facial nucleus. The expression of TNF-alpha and Bax in the facial nucleus was detected by immunohistochemical staining at days 3, 7, 14, 21, and 28 after axotomy. At days 14, 21, and 28 after facial nerve axotomy, a, significantly greater proportion of facial motor neurons survived in the EPO group than in the model group. After axotomy, the expression of TNF-alpha and Bax increased in motor neurons in both the EPO and the model groups. TNF-alpha expression reached its peak level at day 14 after axotomy, while Bax expression reached its peak level at day 21. TNF-alpha expression was much lower in the EPO group than in the model group at all time points. No significant difference in Bax expression was found between the EPO and the model groups. These results indicate that high-dose EPO treatment attenuates the increase in TNF-alpha expression in the facial nucleus and reduces the loss of motor neurons after facial nerve transection in rats. However, high-dose EPO treatment has little effect on Bax expression.