Effects Of Simvastatin Pretreatment On Spinal Cord Ischemia-Reperfusion Injury In Rats

Objective To investigate the effects of simvastatin pretreatment on spinal cord ischemia-reperfusion (I/R) injury in rats and the mechanism involved.Methods Ninety-six male SD rats weighing 220~280g were randomly divided into 3 groups (n=32): sham operation (group S), ischemia-reperfusion injury (group I/R) and simvastatin pretreatment (group Si). Group Si and group I/R were to prepare for spinal cord ischemia-reperfusion, the model was induced by 45 min occlusion via a 10g artery clip and then opened the abdominal aorta. Group Si was given simvastatin 20 mg.kg-1.d-1 for 3 days via an orogastric tube before the preparation. Every group was divided into four subgroup (n=8): reperfusion 2 h (T1), 6 h (T2),12 h (T3), 24 h (T4). Taken eight rats from each group at T2~4 for measuring the neurological function scores, then theses rats were used to collect blood samples for determining the CK-BB content. All the animals were killed at each time point and their spinal cord were removed for HE staining, and determination of expression of toll-like receptors (TLR4) mRNA, nuclear factor-kappa B (NF-κB) p65 protein at T1~4, tumor necrosis factor-α(TNF-α), intercellular adhesion molecule-1 (ICAM-1), Interleukin-10 (IL-10) content, immunohistochemical staining of S-100 protein, colorimetric detection of the activity of subtypes of nitricoxide synthase (NOS) in spinal cord at T2~4. The trial data were analyzed with ANOVA by SPSS 13.0 statistical software.Results Compared to group S, the neurological function scores of group I/R and Si at T2~4 were decreased, the expression of TLR4 mRNA of group I/R and Si at T1~4 were increased, the content of CK-BB, TNF-αand ICAM-1, S-100 proteins and the activity of cNOS at T2~4 were higher, the content of IL-10 at T3~4 were higher, the NF-κB p65 protein in I/R group at T1 ~ 4, Si group at T2 ~ T4 were increased, the iNOS activity in I/R group at T2 ~ 4, Si group at T3 ~ T4 were higher (P <0.05 or 0.01), The histologic damage was significantly more serious in group I/R and Si.Compared to group I/R, the neurological function scores of group Si at T3~4 were higher, the expression of TLR4 mRNA, and the NF-κB p65 protein in group Si were more decreased, the content of CK-BB, TNF-αat T2~4 were decreased, the content of ICAM-1, S-100 proteins and iNOS activity were lower, cNOS activity at T2~3 was increased, IL-10 levels in group Si at T4 was less increased than I/R (P <0.05或0.01), The histologic damage of group Si was slighter than group I/R.Conclusion Simvastatin pretreatment can reduce spinal cord I/R injury through down-regulation of TLR4 expression, inhibition of NF-κB activation, thereby attenuating the inflammatory response (including inflammatory mediators and inflammatory enzymes).