Effect of Neuregulin on the expression of MMP-9 and TIMP-1 in spinal cord ischemia reperfusion injury of rats

English Keywords:Spinal cord injury  Neuregulin  Ischemia reperfusion  Matrix metalloproteinases-9  Tissue inhibitor of metalloproteinase-1  Rat

English Abstract:

  【Abstract】 Objectives: Objectives: To observe the effect of Neuregulin-1β(NRG-1β) on the expression of matrix metalloproteinase-9(MMP-9) and tissue inhibitor of metalloproteinase-1(TIMP-1) in rats with spinal cord ischemia reperfusion injury, and to investigate its function and mechanism. Methods: 48 SD rats were randomly divided into control group(n=16), ischemia reperfusion model group(n=16), NRG-1β treatment group(n=16). Abdominal aorta was only exposed in control group. Spinal cord ischemia reperfusion injury was in?鄄duced by occluding the abdominal aorta in the other two groups. The NRG-1β(10μg/kg) was injected through tail vein immediately after opening the artery clamp in the treatment group, and the ischemia reperfusion model group was injected with an equal amount of 0.1mol/L PBS buffer solution after opening the artery clamp. Neurological function was assessed by using the modified Tarlov standard. Sampling test was performed at 3h, 6h, 12h, 24h respectively after injury(4 rats at each time point). The pathological changes were observed by HE staining. Protein and mRNA expressions of MMP-9 and TIMP-1 were assessed by immunohistochemistry and real-time PCR. Results: The Tarlov scorein model group decreased significantly at each time point compared with that in control group(P<0.05). Neuregulin treatment group induced a markedly improved Tarlov score at 6h, 12h, 24h compared with model group(P<0.05). Spinal cord injury was identified by HE staining in both model and treatment group. However, the injury in treatment group was alleviated compared with that in model group. Immunohistochemistry result showed that there was no positive expression of MMP-9 or TIMP-1 in control group. The number of MMP-9 positive cells in 3h, 6h, 12h, 24h model group was 9.00±1.63, 23.80±1.71, 28.30±1.50, 34.80±2.63 respectively, which was 8.50±0.58, 17.80±0.96, 20.80±3.50, 30.00±2.16 respectively in treatment group. The number of positive cells significantly decreased in 6h, 12h, 24h treatment group compared with that in model group(P<0.05). The number of TIMP-1 positive cells in 3h, 6h, 12h, 24h model groups was 11.80±0.96, 12.30±1.50, 7.80±0.96, 7.80±1.50　respectively,　which was 12.30±0.96, 13.80±0.96, 10.50±1.73, 10.30±0.96 respectively in treatment group. The number of positive cells significantly increased in 12h, 24h treatment group compared with that in model group(P<0.05). Real-time PCR result showed that the mRNA expression of MMP-9 in 3h, 6h, 12h, 24h control group was 4.93±0.21, 4.95±0.24, 4.96±0.25, 4.98±0.23 respectively, 5.38±0.25, 6.53±0.31, 6.87±0.29, 7.53±0.33 respectively in model group, and 5.35±0.26, 5.56±0.22, 5.74±0.27, 5.90±0.31 respectively in treatment group, the mRNA expression of MMP-9 in 6h, 12h, 24h model group significantly increased compared with that in control group(P<0.05). and the mRNA expression of MMP-9 in 6h, 12h, 24h treatment group significantly decreased compared with that in model group(P<0.05). The mRNA expression of TIMP-1 in 3h, 6h, 12h, 24h control group was 4.74±0.23, 4.76±0.21, 4.73±0.25, 4.76±0.24 respectively, was 4.53±0.32, 4.62±0.21, 3.83±0.20, 3.65±0.32 respectively in model group, and 4.55±0.26, 4.65±0.27, 4.28±0.22, 4.25±0.24 respectively in treatment group, the mRNA expressions of TIMP-1 in 12h, 24h model groups decreased significantly compared with that in control groups, and the mRNA expression of TIMP-1 in 12h, 24h treatment group significantly increased compared with that in model group(P<0.05). Conclusions: Neuregulin plays a role in neural protection in spinal cord ischemia reperfusion injury, and the activation mechanism may be caused by the down-regulated expression of MMP-9 and the up-regulated expression of TIMP-1.