Studies On The Regulation Of The BDNF/TrkB Signaling Pathway In Rat With Spinal Cord Injury By Zinc Metabolism

Objective1. To study the high zinc or low zinc pretreatment, zinc (Zn) and its zinc trans-porter receptor-1(ZnT1) in the injured spinal cord of rat are closely related withthe changes of BDNF/TrkB distribution, suggesting that zinc metabolism isinvolved in BDNF/TrkB signaling pathway.2. After high zinc or low zinc pretreatment, along with the distribution changeof Zn, ZnT1, BDNF and TrkB in the spinal cord, in a secondary injury of spinalcord, recovery may change accordingly. High zinc diet promotes ZnT1expression, while up-regulating expression of BDNF and the TrkB. It indicatesthat ZnT1may be involved in the regulation of BDNF/TrkB signaling pathwayto promote recovery after spinal cord injury（SCI）.Methods1. To observe the expression of Zn, ZnT1, BDNF and TrkB in a spinal cord bylow or high zinc pretreatment of rats. By Autometallography (AMG), to detectdistribution changes of zinc in spinal dorsal horn; the use ofimmunohistochemical detection of zinc pretreatment on spinal cord ZnT1andBDNF and TrkB expression. To observe the expression of ZnT1, BDNF andTrkB after zinc pretreatment in spinal cord using immunohistochemicaltechniques.2. To observe the expression of Zn, ZnT1, BDNF and TrkB by theestablishment of the left side hemisection model of the spinal cord (T10) afterlow or high zinc pretreatment of rats. To detect the recovery of the neurologicalfunction by the use of combined behavior score (CBS) and evoked potential (EP) after SCI. To observe the morphological changes of the spinal cord HEstaining. By AMG, to detect the distribution changes of zinc in animal spinaldorsal horn; by use of immunohistochemical techniques and western blotrespectively, to detect the expression of ZnT1, BDNF and TrkB in the spinalcord of SCI rat after zinc pretreatment.Results1. The distribution of zinc ions in the spinal dorsal horn of the rat. The results ofAMG showed its positive reaction product was brown-black particles andgranular distribution; mainly the distribution of axon terminals in dorsal hornneurons of the rat.2. The distribution of ZnT1, BDNF and TrkB in the spinal dorsal horn neuronsof the rat. The immunohistochemistry results showed that the immunopositivereaction product was brown. ZnT1is mainly distributed in the cell membrane ofthe neurons of the spinal cord gray matter inthe rat; BDNF is mainly distributedin the cytoplasm of neurons; TrkB is mainly distributed in the nucleus ofneurons.3. The influence of zinc ions on spinal cord dorsal horn after SCI by low zinc orhigh zinc pretreatment in rat. AMG results showed that the zinc ion of thesuperficial layer of left spinal cord dorsal horn in sham operation group (Sham)is significantly decreased (P<0.05), compared to zinc-adequate dietary group(ZA) and marginal zinc-deficient dietary group (MZD), which in MZD groupdecreased more significantly than that in ZA group (P<0.05). Conversely, zincion of the spinal dorsal horn in high-zinc dietary pretreatment group wassignificantly increased (P <0.05).4. Low zinc or high zinc pretreatment effect on the expression of BDNF, TrkBand ZnT1in the spinal dorsal horn neurons. The immunohistochemistry resultsshowed that the positive products of BDNF and TrkB, and ZnT1are browngranular. BDNF is mainly distributed in the cytoplasm of the spinal cord dorsalhorn neurons, and TrkB is mainly distributed in the nucleus. ZnT1is mainly distributed on the cell membrane. Compared with Sham group, the positiveexpressions of BDNF, TrkB and ZnT1of the spinal dorsal horn in ZA, MZD orZH groups were significantly higher (p<0.01). These three protiens in ZH groupwere higher than those in the ZA group (p<0.05); three proteins expressions inMZD group were lower than the ZA group (p<0.05). The Western Blot testresults showed that, compared with the Sham group, in ZA, MZD and ZHgroups, BDNF and TrkB and ZnT1expressions of the spinal dorsal horn weresignificantly increased (P<0.05). Compared with ZA group, the positiveexpression of the ZH group increased (P<0.05); the positive expression ofMZD group decreased (p<0.05).Conclusion1. The normal rat spinal dorsal horn is rich in free zinc ions and zinc transporterreceptor-1.2. The low-zinc pretreatment reduces significantly the dorsal horn superficialzinc of the SCI model rat. There is no significant difference in the behaviorscores after SCI of rat by the low-zinc pretreatment. The high zincpretreatment enables spinal dorsal horn zinc ion to increase significantly in SCIrat, while promoting the expression, of ZnT1, BDNF and its receptor TrkB. Thehigh expression of ZnT1may promote up-regulation of BDNF and TrkB. Thusit may contribute to the improvement of the animal’s behavior and may beconducive to the recovery of the spinal cord function.