| Objectives: Alzheimer’s disease (AD) is a common neurodegenerativedisease of the central nervous system which is related to age, the majorclinical manifestations are progressive loss of memory and other cognitivefunctions, and the changes of emotion, personality and behavior. Thepathogen and mechanism of AD are not quite clear and there are still noeffective treatments to reverse Alzheimer’s disease. With the development ofsociety, the aging of population has become increasingly severe, themorbidity of AD is gradually increased which will be a huge burden to thesociety and family. It’s estimated by the world health organization that ADwill be the fouth disease which brings huge burden in our country by2020.Therefore it will be significant to improve the cognition to AD. Multipleresearches indicate that there are plentiful microglia and astrocytes aroundthe senile plaques and steroid can alleviate the activation of glias which candecrease the lesion of neuron to have the nervous protection. With thedevelopment of research, now numerous scholars consider that theinflammation induced by Aβ1-42deposit is the main mechanism of AD. It willbe an important approach for treating AD to alleviate the inflammationlesion.Toll like receptors (TLRs) are a kind of natural immune receptors whichare found recently and exist in a wide range. They recognize and combinecertain pathogen associated molecular patterns (PAMPs) to activate a seriesof signal transmit which lead to the release of inflammation mediums andactivate the achieved immune system finally. Recent studies revealed thatTLR2and TLR4are all express in the neurons and TLR4will be increasedinduced by Aβ1-42. Tumor necrosis factor receptor associated factor6(TRAF6) is an important joint molecule of Toll/IL-1receptor (TIR) super-family. After TLR4is activated, TRAF6can immediately combinewith IRAK and then activate IKKs, consequently activate NF-κB and leadto the activation of inflammation cells and the release of inflammationfactors which aggravate the inflammation reaction.Atorvastatin is the limited enzyme in the cholesterol syntheses, that isthe repressive reagent. It can lower the level of glycerol ester, the totalcholesterol and LDL meanwhile increase the level of HDL, therefore it isapplied in the clinical for lowering blood fat. Multiple researches reveal thatAtorvastatin can suppress inflammation reaction, anti-oxidant and regulatethe immune except the effect of lowering the blood fat. With the evolution ofAtorvastatin in neurodegenerative diseases, recent studies manifest thatlong-term use of Atorvastatin can reduce the level of IL-1β, IL-6and TNF-αin hippocampus of AD rats. However, whether Atorvastatin has theneuroprotection by down-regulating the TLR4, TRAF6and NF-κB is notclear. The purpose of this study was to evaluate the potential neuroprotectionof Atorvastatin and the possible mechanisms in rats thus to probe themechanism of AD. In this study, we builded the AD rats model by bilateralhippocampus injection of Aβ1-42and observe the rats behavior changes andthe express of TLR4, TRAF6and NF-κB in the rats hippocampus.Methods: Thirty-two healthy male SD rats were randomly assigned tofour groups according to the random figure chart: the AD group, the Shamoperated group, the low dose group (Atorvastatin5mg/kg，Ator-L) and thehigh dose group (Atorvastatin20mg/kg，Ator-H). Every group contained8rats. The rats were adapted for one week prior to the present experiment. Thelow dose group and the high dose group were treated Atorvastatin by gavageonce a day for3weeks, the other two groups were treated with equal saline.After3weeks, the AD group, the Ator-L and Ator-H group were injectedinto the rats’ bilateral hippocampus with5μg Aβ1-42, and the Sham groupwith equal saline. All the rats were trained on a Morris water maze test onday7after the injection of Aβ1-42, to identify learning and memory ability ofthe rats. The rats were sacrificed after the MWM test (that is on the12days after the injection of Aβ1-42) and the brain tissue was obtained forpathological observation and intracellular staining. Hematoxylin and eosin(HE) staining was adopted to observe the different macroscopic pathologicalfeatures in the hippocampus. The activation of microglia was detected byimmunostaining. Western Blot was used to detect the expression of TLR4,TRAF6and NF-κB.Results：1The result of Morris water maze test showed that each group’s latentperiod of escape was not same (F=2.183, P<0.05) and either does thefrequency of crossing platform on7days after modeling(F=12.908, P<0.05).Compared with the Sham group and Ator-H group, the latent period ofescape in AD group was significantly longer (P<0.05). The escape latency ofthe Ator-H group was significantly shorter than AD group on day3(30.98±0.50seconds versus45.77±3.14seconds, P<0.05) and day4(28.06±0.54seconds versus45.54±2.64seconds, P<0.05). In the space probe test, themean number of crossing platform of the Ator-H group showed significanthigher than did the AD group (9.0±0.22versus3.4±0.2, P <0.05). Bycontrast, there was no significant effect in Ator-L group compared with theAD and Sham groups (P>0.05).2HE staining: The pyramidal cells of the rats’ hippocampal CA1areawere in large quantity, regularly arranged, the cellular nuclei were clear andhomogeneously stained in the Sham group. Compared with the Sham group,sparsely formed cells and deeply stained nuclei were obviously demonstratedin the AD group. By contrast, in the Ator-H group, the neurons and thenuclei just looked the same as in the Sham group. The number, arrangementand morphology of the neurons were all recovered in a degree, but there wasno no significant effect in the Ator-L group compared with the AD group(P>0.05).3The activation of microglia: There were significant difference duringthe four groups (F=171.71, P<0.05). Compared with the Sham group, thenumber of Iba-1positive cells was significantly increased in the AD group (P<0.05). The Ator-H group was significantly decreased compared with theAD group. Of great importance, there was still difference between theAtor-L and Ator-H group, the Ator-H group was significantly decreased thanthe Ator-L group (P<0.05).4The expression of TLR4, TRAF6and NF-κB: Compared with theSham group, the AD group significantly increased the protein level and thenumber of positive cells of TLR4, TRAF6and NF-κB. The Ator-H groupwas significantly decreased their expression compared with the AD group(P<0.05). However, there was no significant difference in the expression ofTLR4, TFAF6and NF-κB between the Ator-L and AD group (P<0.05).Conclusion:1.The AD model was established with the injection ofAβ1-42into the rat’s bilateral hippocampus, the AD rats appeared the learningand memory ability changes which demonstrated that the AD model wassuccessful and effective.2.There were plentiful of activated microglias in thehippocampus of the AD group rats, with the increase of TLR4, TRAF6andNF-κB, which indicated there was inflammation reaction in AD and thesignal way of TLR4/TRAF6/NF-κ B involved in the generation anddevelopment of AD.3.Atorvastatin can improve the learning and memoryabilities of the AD rats and decrease the loss of neurons, which indicates theneuroprotective effect of Atorvastatin.4.Atorvastatin decreased theexpression of TLR4, TRAF6and NF-κB to a certain degree, indicating thepotent anti-inflammatory activity of Atorvastatin. The neuroprotective effectmay be through down-regulation of TLR4, TRAF6and NF-κ B.TLR4/TRAF6/NF-κB pathway may be one of the targets of Atorvastatin’sneuroprotective effect for AD. |
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