| Objective: Recent years, with deepening the study on secondary spinal cord injury (SCI),the role of oxidative stress gradually attracted people's attention. Studies had shown that lipid peroxidation product acrolein generated by oxidative stress is a potential regulator in spinal cord second injury~[1], it can promote the production of oxygen free radicals in the body and increase lipid peroxidation which free radical induced and oxidative stress persist through positive feedback~[2]. Therefore, reducing or inhibiting the yields of acrolein will be an effective method for treating secondary SCI. Lipoic acid (alpha lipoic acid, LA) is a potent antioxidant, study found that not only remove production of various free radicals by the physiological and pathological processes and reduce oxidative stress~[3,4], but also is efficiently scavenger of acrolein and other peroxide aldehyde~[5]. At present there is not literature about LA on the role of oxidative stress in secondary SCI.In this study we established the model of secondary SCI and applicated LA in early, then observed the functional recovery after spinal cord injury with motor scores, detected content of malondialdehyde (MDA) by thiobarbituric acid test, peroxidase oxidase (SOD) activity by xanthine oxidase method, and semi-quantitatively determined expression of acrolein (ACR) by immunohistochemistry combined with computer image analysis ,to further exploring the protective role of LA on secondary SCI and finding effectively measures of clinical treatment,Methods: Select 66 healthy, adult Sprague-Dawley (SD) rats; weight 240-280g, age 3-4 months, male or female. Using modified Allen's-WD model of spinal cord injury ,66 SD rats were randomly divided into 6 of normal group, 30 of drug intervention group( spinal cord injury + lipoic acid intraven-ously), 30 of injury control group(spinal cord injury +normal saline intrave- nously). 24 hours(h), 3 day(d), 7d after spinal cord injury were drawn,8 of every group, 4 of which HE staining and immunohistochemical measured expression of acrolein, the others directly detected SOD activity and MDA content by using the spectrophotometer. 6 of injury control group and 6 of drug intervention group were observed behavior changes with BBB score in the 3,7,14,21 d after SCI. SPSS13.0 statistical software was used .The measured value of SOD and MDA, the average optical density value of ACR and the value of BBB motor score among the three groups were compared using single factor analysis of variance ,LSD Test were used to compare between two groups.Results:1 At light microscope normal neurons have good shape, useful quantity, intact structure of membrane. Focal hemorrhage, neuronal cell swelling and round, reducing of the number, fragmentation and shrinkage of the nucleus,lightly stained or disappear of Nissl bodies can be seen at 24h after the secondary SCI. Lipoic acid reduced swelling of nerve cells, increased the number of nerve cells at 24h after treatment. At 7d after injury showed neuronal loss and formation of cavity. The shape of neurons in theatment group close to normal neuronal morphology.Swelling, necrosis, cavitation and other changes more lightly than the control group. At 24h and 7d pathological changes of spinal cord slices in treatment group more lightly than control group.2 Results of Basso-Beattie-Bresnahan (BBB) behavioral score:Among three groups before surgery there was no significant difference in BBB scores (P> 0.05), At 3d, 7d, 14d, 21d after surgery compared with lipoic acid treatment group were highly significant difference (p <0.01), The scores of treatment group were significantly higher than the injury group; At each time point of 3d, 7d, 14d, 21d after surgery,the scores between treatment group andnormal group were not significantly different (p> 0.05) treatment. Reviews score at each time close to the normal group, but did not reach normal values3 Results of SOD determination:In lipoic acid treatment group, SOD activity values were 173.7±6.9,221.1±16.7,225.3±13.8 at 24h, 3d, 7d, significantly increased with time changes.In injury group, SOD activity values were 124.7±8.8,137.67±4.8,145.9±5.7 at 24h, 3d, 7d.There was no obvious increasing with time.At three time points SOD activity values between two groups were significantly differences (p <0.01 .)The treatment group and normal group (234.6±11.9) showed no significant difference at 3d, 7d (p> 0.05), SOD activity in the treatment group is similar to normal group.4 Results of MDA determination, In lipoic acid treatment group MDA contents were 7.43±1.1,6.20±0.71,5.85±0.70 at 24h, 3d, 7d ,and reduced with time. In injury group MDA contents were 12.3±1.2,11.9±1.14,11.011±1.09 at 24h, 3d, 7d ,.The was no obvious decreasing with time.MDA content of the three time points between two groups were significantly differences (p <0.01).The MDA contents of treatment group at three time points were significantly lower than the injury group. At 3d, 7d treatment group and normal group (5.5±0.54) was no significant difference (p> 0.05), MDA content of treatment group was similar to normal group.5 Results of acrolein immunohistochemistry, In lipoic acid treatment group, the average optical density values were 0.2252±0.0402,0.1965±0.0435,0.1847±0.0401 at 24h, 3d, 7d, decreased with time. In injury group, the average optical density values were 0.3636±0.0100,0.3462±0.0157,0.3052±0.0162,There was also downward trend with time.At three time points, the average optical density values of the treatment group were significantly lower than the injury group, At the three time points the average optical density of the two groups were significantly differences (p <0.01). At 3d, 7d there was no significant difference between treatment group and normal group (5.5±0.54) (p> 0.05).The average optical density value of the treatment group was close to normal group.Conclution: This study further confirmed expression changes of lipid peroxidation products acrolein with time after the secondary spinal cord injury, and also verified both the acrolein and free radical participate in process of neuronal cell damaged during the secondary SCI. Powerful antioxidants lipoic acid can inhibit the expression of acrolein, and eliminate product of free radic- al, protect and promote the regeneration of endogenous antioxidant enzymes, for the spinal cord neuron cells have better protective effection and more significant role in promoting. recovery of motor function.
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