Pathological Changes In Nervous System And The Correlation With Activation Of Rho/ROCK Pathway In Rats With Methylmercury Induced Toxication

Objective To explore the pathologica l changes and the mecha n-ism of nervous systeminjuries induced by methylmercury chloride(MMC)toxication in rats.The correla tion ofactivation of R-ho/ROCK pathway and MMC toxica tion was studied.Method Thirty ma le Wista r rats,weight 300-350g,were divided into one control group(6rats) and four experimental groups(6 in every group).We established a toxic modelsuccessfully by given rats intragastric administration everyday with MMC(dosa-ge: 4.0mg/kg weight).The rats were sacrificed on days 7,11,15,and 19.We chronologica l observed thepathologica l changes of cerebellum,spinal cord,dorsal root ganglion(DRG) and sciaticnerve .We also studied the expression of Rho/ROCK pathway to a-pproach the significa nce ofRho/ROCK pathway and gitter cell reaction in nevous system injuries induced bymethylmercury chloride toxica tion.Results 1. Ethological changes: The MMC treated rats showed a loss of locomotorycapacity at first,and a granully aggra vation.Atactic gait,paralysis,bod y weight loss andincreasing neuro impairment index were also observed.Neither bodyweight loss nor abnorma lactivity was observed in the contro1 anima ls．2.Pathologica l changes:(1) Periphera l nerve :Onday 11,a mild axona l degeneration could be found and it was getting worse following theintoxca tion time. On day 15, Bodian staining and NF200/68 immunosta ining demonstratedaxona l fragmentation,darken stain and myelin bodies. A mild amyelination was observed inKB and MBP immunosta ining. (2) Cerebellum:There were no obvious changes in cerebellumof 7-d and 11-d after MMC intoxication. On day 15, HE immunosta ining finded a cell lossand destroied granular cells in the granular cell la yer. TUNEL staining recognized somesparse positive granule cells, which indica ted that an early apoptotic .On day 19,a severe cellloss was observed in the cerebellar granules on HE staining．TUNEL disclosed numerousapoptotic cells．GFAP and ED-1 immunosta inig also demonstrated astrocytosis and a stronghyperplasia of gitter cells. (3)Spia nl cord: Vacuolar degeneration were observed in dorsal rootand posterior cord on day 11 and it was getting worse after 15 days. Numerous vacuole swhich induced by disa -ggregation of axons and myelin sheathes emerged as well as a sparsegitter cell reaction could be found in gelatinous substa nce of spinal cord in ED-1staining.3.The expression of Rho/ROCK pathway:Neurons and gliocyte s displa yed theexpression of ROCK in cerebellum,spinal cord and periphera l nerve on day 7.But the phagocyte and neurite expressed ROCK 2 strongly according the prolongation of toxica l timeand it parallelled with the neurite reaction.4.Western blot analysis verified the expression ofROCK2 in cerebellum and periphera l nerve on 7-d.The higher expression than in normalnervous system mea ns the activation of Rho pathwa y accompanied the toxic timeprolongation.ConclusiConclusion 1.A subacute rat toxic model can be established successfully by given ratsintragastric administration with 4.0mg/kg weight /day MMC.2.The target organs of MMC in this rat toxic model are cerebellum, nervussensorialis ,dorsal root and posterior cord.3.Rho/ROCK pathway is activated in nervous system after MMC toxica tion. The earlyexpression of Rho/ROCK can be observed in neurons and gliocyte s and it parallelled with theneurite reaction in the later time,which implied the intimate correlation between the activationof the pathway and the nervous system injuries induced by methylmercurychloride(MMC)toxication.But the precise mecha nism needs to be considered for futureresearch.