| BackgroundAlzheimer’s disease is a form of onset hidden and chronic progressive neurodegenerative disease,which is mainly characterised by memory deficit and cognitive impairment in clinical practice. With the gradually intensified aging degree and increased incidence,AD has became the most common reason of dementia and the fourth killer threatening the health of elderly people followed by angiocardiopathy, tumor and stroke.So far, AD has made a heavy social and family burden. Hence, how to curb the development of AD has been a urgent problem. It is well-known that the main pathology of AD is the accumulation of extracellular senile plaques filaments, the intraneuronal neurofibrillary tangles as well as chronic inflammation in brian.The (3amyloid (Betamylaoid protein, AP) is a kind of nonspecific binding protein from amyloid precursor protein (amyloid precusor protein, APP) hydrolyze by β secretase (β secretion enzyme, BACE1). Recent studies have confirmed that Aβ can not only accumulate to participate in the pathological characteristic of AD,namely formation of senile plaque, but it is also the common pathway of many factors inducing AD [3]. The main mechanism is that AP can bind different substances such as the receptor for advanced glycation end products (RAGE) at the early stage to activate the corresponding cell signaling pathway and then induce the neuron toxity, oxidative stress and inflammation cascade reaction. Aβ involves nerve injury at different stages and contributes to the cognitive decline such as amnesia.Therefore Aβ is the key factor in the formation and development of AD and reducing the generation of AP may become an effective method to control AD. Advanced glycation end products(AGEs) is an insoluble polymeric compound generated by Amino from protein and carbonyl groups from reducing sugars in no enzyme and irreversible conditions. A mount of studies indicated that AGEs involves in organs injuries affected by diabetes. Studies also indicated that AD may be a endocrine disease as diabetes.The animal studies of AD have found that the primitive plaques, coronas of classic plaques and some glial cells in affected regions of the AD brain were positive for AGEs.Furthermore, nucleation-dependent polymerization of Aβ peptide is significantly accelerated by crosslinking through AGEs with the progression of AD, which suggest that AGEs is the main factor involving in AD and acting in the whole progression. Receptor for advanced glycation endproducts (RAGE) is the common receptor on membrane in the central nervous system for AGEs and Aβ, especially highly expressed in AD brains. RAGE can help Aβ pass through the blood brain barrier(BBB),intense the accumulation of Aβ as well as entanglement of nerve fibers. It can also activate the microglia by combing AGEs and Aβ to cause the inflammation.Furthermore,the downstream factor in inflammation can upregulate the expression of RAGE. This result is a vicious circle that expands the injury further. Moreover,the nowadays researches havc shown that the common pathways of diabetic encephalopathy, vasculopathy in AD and cognitive impairment were a series of reactions induced by the combination of RAGE and its ligands AGEs as well as Aβ.Meanwhile, AGEs is a significant factor in aging.To sum up,blocking the combination of RAGE and its ligands may curb the diseases mentioned above especially AD. Although the preclinical studies comfirm that RAGE is an effective target of AD, but because the RAGE antibody can not pass through BBB to influence the metabolism of AGEs and Aβ in brain,there has not been anti-RAGE that can be successfully used in clinic. Un addition, the exsisting treatments of AD can act evidently only on one link in the pathogenesis, but the practice shows that these cures can not block the progression of AD, which also explains the phenomenon that why the patients using the exsisting treatments usually receive enhancement at the early stage but little progressment at the late stage. Moreover, some medicine can actually change the symptoms in preclinical studies, but were stopped using because of the serious side effects.So it is significant to find a safe medicine that can curb more links in the course of AD and have higher BBB passing rate. FPS-ZM1is a non-toxic specific inhibitor synthesized by Deane, the research conducting on APP transgenic mice found that FPS-ZM1can not only alleviate Aβ-induced various reaction including inflammation by accross the BBB to inhibit the combination of RAGE and Aβ in brain,but also curb the peripheral Aβ inflowing into the BBB by blocking RAGE on the BBB, therefore it may become a new cure for AD [15]Now we all know that both AGEs and Aβ are the critical factors in the beginning and development of AD, but the present studies only concentrate on the effects of FPS-ZM1on AD models generagted by Aβ, while except for the involvement of Ap, the direct effects of FPS-ZM1on Aβ metabolism and inflammation induced by AGEs has not been researched so far. In this study, we will further explore the relationship of AP metabolism and inflammation induced by AGEs and discuss the effects of FPS-ZM1on AP metabolism and inflammation induced by AGEs.Objectives(1)To explicit the relationships between highly expressed β secretase and the inflammation centered on pNF-κB.(2)To detect the possible mechanism of the metabolism of Aβ effected by the intervention of FPS-ZM1.(3)To explore the effects of RAGE inhibitor FPS-ZM1on inhibiting inflammatory reaction in the brain of rats and cognition decline induced by advanced glycation end products.Methods40Wistar rats were randomly divided into4groups(n=10):normal control group (NC group), FPS-ZM1control group, AGEs group and FPS-ZM1group. They were anchored on the stereotaxic apparatus after anaesthetization and their skin was incised on the center of crania after the routine disinfection and skin preservation. According to the Miguel-Hidalg’s method, the hippocampi of AGEs group and FPS-ZM1group were injected5μl AGEs by using micro-injection pump to produce the animal models of AGEs injury in rat brain,NC group and FPS-ZM1control group were injected equal volume of saline in the same way. Before the animal models were produced, rats in FPS-ZM1control group and FPS-ZM1group were injected FPS-ZM1(1mg/kg/d, i.p.)for1week. After the models were made, FPS-ZM1continued being given for3weeks.Rats in AGEs group and NC group were injected equal volume of saline into abdominal cavity at the same time. After constructing the animal models for3weeks:The escape latency (EL) of rats in each group was assayed with Morris water maze test; After the test, the brain sections were stained by immunohistochemistry to examine the expression of TNFa in hippocampus of the rats. Western blot was performed to detect the expression of RAGE、β secretase, APP,CD11b,pNF-κB and TNFa expression in rat hippocampus. ELISA was used to measure the level of Aβ1-40, Aβ1-42in hippocampus of all groups.Results(1) The escape latency in Morris Water Maze TestComparing with NC and FPS-ZM1control groups, the EL of AGEs group was obviously longer (P<0.01). Comparing with AGEs group, the EL of FPS-ZM1group was distinctly shorter (P<0.01),while there was no evident changes compared with NC and FPS-ZM1control groups (P>0.05).(2) Expression of TNFa in hippocampus was detected by immunohistochemical sectionComparing with other groups,AGEs group can detect the strongest chocolate brown expression of TNFa. The number of positive neurons were less and stained weaker in FPS-ZM1group than AGEs group. Meanwhile, there was few positive cells in FPS-ZM1group and the cell arranged closely with no atrophy.(3) RAGE、CDll、pNF-xB、TNFα and β secretase、APP protein expressions by Western blotting with Semiquantitative analysisThe protein expression of RAGE, CD11b、 pNF-κB、TNFa and β secretase, APP was significantly higher in AGEs group than NC and FPS-ZM1control groups (P<0.01). After the intervention of FPS-ZM1,each index was evidently lower than AGEs group.Compared with NC group and FPS-ZM1control group,the expression of RAGE in FPS-ZM1was no obvious difference(P>0.05),but the expression of other indexes were a little bit stronger.(P<0.01).(4) The expression of Aβ1-40and Aβ1-42in hippocampus detected by ELISA.The concentration of Aβ1-40, Aβ1-42in the hippocampus of AGEs group was obviously increased (P<0.01).After the intervention of FPS-ZMl,these indexes were evidently lower than AGEs group(P<0.01),but relatively stronger than NC and FPS-ZM1control groups (P<0.01). Conclusions(1)AGEs can upregulate p-NF-κB,activate β-secretase and promote the generation of Aβ1-40, Aβ1-42by inducing the high expression of RAGE in hippocampus to enhance cognition of the rats..(2)FPS-ZM1, as the specific inhibitor of RAGE,can effectively suppress the upregulation of p-NF-κB to restrain the inflammatory reaction in he brain of rats induced by advanced glycation end products.(3)FPS-ZM1can effectively suppress the upregulation of p-NF-κB in brain and reduce the generation of Aβ1-40and Aβ1-42. FPS-ZM1may become a valid measurement to control Alzheime’s disease because of the high BBB pass rate advantage.SignificanceIn this study, by applying the brain stereotactic techniques to establish animal AGEs injury model, the AGEs-RAGE pathway can increase Aβ by upregulating p-NF-κB and activating βsecretase. After using the RAGE inhibitor FPS-ZMl,all the indexes were obviously decresed. These results showed that FPS-ZM1can effectively inhibit the AGEs-RAGE-p-NF-κB pathway on cell memberance in brain by passing through BBB and entering into central nerve system. Additonally, it also influences Aβmetabolisim by evidently reducing the cascade reaction of inflammation at upstream level. All these results provided new theoretical bases for the pathogenesis and treatment of AD. |
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