Abstract: Objective To investigate the effect of minocycline (MINO) on expressions of apoptotic proteins Bcl-2, Bax, Caspase-3 and expression of Ngb in rats with spinal cord transection injury. Methods A total of 36 healthy adult male Wistar rats were randomly divided into Sham group, spinal cord injury (SCI) group and MINO group, with 12 rats in each group. Rats in Sham group were only exposed spinal cord without transecting. SCI group and MINO group were established the T3-4 spinal cord segment transection injury model. MINO group was given intraperitoneal injection of minocycline (90 mg/kg) once a day for 5 consecutive days before operation. While SCI group and Sham group were given equal volume of normal saline once a day for 5 consecutive days. After 22 days of operation, all the rats were killed. Immunohistochemical stainning and Western blot assay were used to determine the expressions of Bcl-2, Bax and Caspase-3 proteins. Hoechst staining was used to analyze the positive cells of apoptosis. Ngb protein expression was detected by immunofluorescence method. Results Compared to Sham group, the expressions of Bcl-2, Bax, Caspase-3 and apoptotic cells were increased in SCI group, and the fluorescence intensity of Ngb increased significantly (P＜0.05). Compared to SCI group, the expression of Bcl-2 was obvious increased in MINO group (P＜0.05) while the expressions of Bax and Caspase-3 were decreased and the number of apoptotic cells decreased significantly (P＜0.05). The mean fluorescence intensity of Ngb was significantly higher in MINO group than that of SCI group. Conclusion Minocycline can inhibit apoptosis and increase neuroglobin expression by downregulating the expressions of Bax and Caspase-3, upregulating the expression of Bcl-2 in SCI rats.

Key words: spinal cord injuries, minocycline, apoptosis, Bcl-2, Bax, Caspase-3, neuroglobin