动物模型,阿尔茨海默病 z-bo 2020-08-11 467

　　1. Aging animal model

　　AD mostly occurs in the elderly. Aging is a certain risk factor for AD. With the aging of the world population, the prevalence of AD has increased significantly, and it has become the fourth cause of death in adults. Therefore, animal models based on aging as the basis for the onset of AD have emerged.

　　(1) Natural aging cognitive impairment animal model

　　AD animal models obtained through the natural aging of animals, including aged rats, mice and monkeys. The neurological changes such as cognitive impairment in this type of model are naturally occurring and are closer to the true pathophysiological changes of AD. Cummings et al. reported that there are Aβ precipitation plaques in the brain of old dogs, and there is corresponding selective behavioral impairment; Higgins et al. reported that Aβ deposits in the basal area of the forebrain in old mice and memory deficits. However, these models generally do not have the characteristics of AD, such as SP and NFT, and are prone to death.

　　(2) Rapid aging mouse model and neurofibrillary tangles

　　A kind of senescence accelerated mouse (SAM) was obtained by inbred and extended AKR/J natural mutation mice. The SAM P/8 and SAM P/10 of many strains in this family showed obvious The learning and memory function is reduced, and he is in a state of dementia with low tension and low horror.

　　(3) D-galactose-induced subacute aging model in rats and mice

　　After administration, the central nervous system of the animals showed a series of degenerative changes, such as a decrease in the number of hippocampal pyramidal cells, a decrease in protein synthesis in cortical neurons, a decrease in superoxide dismutase activity in brain tissue, and an increase in malondialdehyde content. Shows signs of aging such as decline in learning and memory, cognitive impairment, slow movement, and thinning of hair. But such models also did not show NTF and senile plaque-like changes.

　　Two, cholinergic injury animal model

　　The cholinergic neurons in the forebrain basal area of the mammalian brain, the hippocampus and the cortex and the pathways between them are important structural foundations for learning and memory functions. A large number of cholinergic neurons in the basal area of the forebrain of AD patients are damaged or died, the synthesis of presynaptic acetylcholine, the activity of ChAT (choline acetyltransferase) and the ability to uptake choline are significantly reduced. The extent of these changes is consistent with the patient The degree of cognitive impairment is positively correlated, so people use various methods to destroy the cholinergic system of animal brains. Promote the occurrence of learning and memory disorders to achieve the purpose of making AD animal models.

　　(1) Electrical damage, surgical damage model

　　With reference to the stereotactic map of the animal brain, the Meynert basal nucleus was damaged by the method of electric burns, and the hippocampus-fornix was surgically cut off. Destroy cholinergic and non-cholinergic fiber afferents, resulting in experimental animal behavior and neurochemical defects, resulting in animal spatial orientation and memory impairment and the loss of cholinergic neurons. However, senile plaques and NFT did not appear pathologically. In 1994, the experimental results of Jeltsch et al. showed that the AD model caused by cutting the bilateral hippocampal fimbriae pathway cannot recover its behavioral and neurochemical deficits after several months. Using this method to establish an AD model has a short period, but the surgical positioning is difficult to control, and it is difficult to avoid damage to the adjacent tissues of the surgical area.

　　(2) Chemical damage model

　　An AD model can be established by injecting ibotenic acid, quinolinic acid, and kainic acid into the Meynert basal nucleus of rats. This method can reduce cholinergic neurons and decrease cortical ChAT activity, but does not damage the nerve fibers passing through this area. . After the operation, hippocampal nerve cells decreased significantly, and the ability of learning and memory decreased. However, AD neurotransmitter deficiency is widespread. This type of model only simulates the characteristics of cholinergic dysfunction, and does not replicate the characteristics of other transmitter dysfunction, and the model also does not show the typical pathological changes of AD—— Senile plaques and NFT, therefore, it is still necessary to further observe the types of drugs, dosage, site of action, and time when making models.

　　(3) Aβ-based animal model

　　Aβ in the brain is degraded by a series of enzymes from the amyloid precursor protein (APP). APP is a type of transmembrane protein widely present in the body. APP has two metabolic pathways in the body: ① It is catalyzed by p-secretase and γ-secretase, and it breaks near residue 712 to produce Aβ which is toxic to cells; ②APP Soluble APPa (sAPPa) is catalyzed by α-secretase and γ-secretase. It is worth noting that α-secretase breaks down from within the Aβ molecule. The production of the complete Aβ sequence is avoided, and sAPPa can produce nutrition and protective effects on nerve cells. The excessive production of Aβ is deposited in the brain, causing the imbalance of calcium homeostasis, activating glial cells to release a large number of inflammatory mediators and oxygen free radicals, and ultimately leading to extensive neuronal degeneration, apoptosis, and loss of synapses. Therefore, it is believed that Aβ deposition is the central link in the pathogenesis of AD. Therefore, a variety of Aβ-based models have emerged, and they have also brought new drug targets. Injection of synthetic Aβ into the brain of animals can produce Aβ aggregation and neurotoxic effects. Usually a small amount of soluble Aβ is injected, and there is no obvious short-term neurotoxic effect. However, if the injected amount is large, Aβ will be promoted to aggregate. When Aβ aggregates, Aβ deposition or amyloidosis can be easily observed. Cholinergic neuron apoptosis and decreased synaptic structure. Microglia and local astrocytes are activated. After Nitta et al. injected 100Pg of Aβ into the brain ventricle of rats, they found that the rats had behavioral disorders, such as passive avoidance reflex and water maze learning disorder. If 2 μg of Aβ is injected into the hippocampus through the catheter every day, the rats will also experience behavioral disorders after 15 days. These models indicate that deposition is related to behavior (learning, memory) impairment. However, there are three shortcomings in the animal model of injection of Aβ: firstly, it will cause a penetrating brain injury; secondly, it is impossible to study the pathological process formed by Aβ itself; finally, the injection of a large amount of Aβ has certain operating difficulties, because Aβ is easy to accumulate before the injection, and controlling the aggregation will make it difficult to get a large amount of Aβ scattered in the brain outside the injury site.

　　(4) Aluminum poisoning induced dementia model

　　People found that external environmental risk factors also play an important role in the onset of AD, so an AD animal model of chronic aluminum poisoning was established. As early as 1937, Scherp and Church proposed that aluminum can cause neuron degeneration. In 1965, Klatzo et al. proposed that aluminum poisoning may be related to the onset of AD. They found that NFT can be seen in the brains of AD patients and aluminum poisoning patients. Later, in 1937, Graper et al. proposed that aluminum may be a neurotoxin, and they injected aluminum salts directly into the cat's brain. It has been found that aluminum has neurotoxin-like effects, leading to nerve fiber degeneration. Some domestic scholars established models by intraperitoneal injection and oral administration of aluminum salts in rats or mice. As a result, the model mice showed decreased brain mass and decreased learning and memory capabilities. Clinical data show that the brain aluminum content of AD patients is significantly higher than the normal value; the serum aluminum level is also significantly higher than the control group. Looking at the experimental research on the relationship between aluminum and AD, it is basically certain that the content of aluminum in the brain of AD patients is significantly higher than the normal value: aluminum is toxic to the central nervous system, causing neuronal degeneration or death, resulting in NFT pathological changes, and then It is manifested by atrophy of the cerebral cortex, reduced brain mass, and memory and cognitive dysfunction. In short, the method of establishing an AD model with aluminum induction is better, but the disadvantage is that the NFT of this AD model is slightly different from that of AD patients, and the cycle of modeling with aluminum is long.

　　(5) Animal model caused by hypoxia

　　Research found that AD patients are actually chronically hypoxic for a long time. By depriving rodents of oxygen, it can induce energy metabolism disorders similar to aging brain functions. Since both aging and hypoxia can damage oxidative metabolism and can lead to similar behavioral disorders, hypoxia and aging may have certain similarities. The model is to first train the animal to passively avoid sexual behavior once, and then immediately put it into a hypoxic environment, the animal may have retrograde memory retention disorder. The experimental hypoxic animal model is similar to the elderly rodents in terms of neurochemistry and behavior, so it can be used to evaluate experimental research and drugs for the treatment of senile memory disorders. This animal model is simple and economical, and can be used to develop preclinical screening of drugs for memory disorders. The main shortcoming of this model is that the hypoxic animal model is widely related to the neuropathological changes of different neurotransmitters (including the cholinergic system), and cannot show the brain area-specific cholinergic nerve damage of AD; another shortcoming is This model lacks histopathological features similar to those in the AD brain.

　　(6) tau protein hyperphosphorylation model

　　Studies have shown that Aβ deposited in the brains of AD patients can cause nerve cell degeneration by inhibiting the uptake and utilization of glucose by cells, leading to impaired memory ability in patients. And in the high-risk population of AD with diabetes and Apo E4 carriers. There will also be a decrease in nerve cell glucose intake, and combined treatment with glucose and insulin can significantly improve the memory ability of AD patients. Based on this, the AD-like phosphorylation model of tau protein has appeared in recent years. A one-time high-dose streptozotocin (STZ) intraperitoneal injection or STZ combined with a high-fat diet induces diabetes in mice or fasts the mice to reduce the intake and utilization of glucose by nerve cells, so that the tau protein in nerve cells is reduced. The level of N-acetylglucosamine glycosylation is reduced and potential phosphorylation sites are freed. Tau protein is more easily phosphorylated. Hyperphosphorylation changes the structure and conformation of the tau protein, and finally causes the disintegration of the microtubule structure to form a large number of NFT structures.

　　(7) Experimental autoimmune dementia model

　　Subcutaneous injection of high-molecular-weight neurofilament protein (NF-H) in purified Torpedo cholinergic neurons can induce sustained immunity in rats, causing IgE precipitation in the septal and hippocampal neurons, reducing the density of neurons, The cognitive impairment of mice is manifested as short-term working memory, space and location discrimination. This animal model is called experimental autoimmune dementia (EAD). This animal model can replicate certain pathological processes of AD. It has also been proved that the anticholinergic NF-H antibody plays a certain role in the degeneration of AD neurons.

　　(8) Transgenic animal model

　　AD is a polygenic disease. There are 4 main pathogenic genes known: APP gene, PS-1 gene, PS-2 gene and ApoE4 gene. In recent years, genetically modified animals have achieved great success. APP gene is the earliest discovered disease-causing gene for AD. APP is degraded by β-secretase, p-secretase and nuclear lysosomal system to produce amyloid in vivo. Hsiao used the prion protein (pHon) promoter to transfer the KM670/671NL mutant gene of Swedish familial AD and obtained the overexpression of APP. Obvious age-related amyloid deposits and increased Aβ in the brain with memory deficits were observed. Hsiao also mentioned in the report that the hybridization of APP FVB mice and SOD transgenic mice can significantly extend the life span, allowing sufficient time to form Aβ deposits. Sommer et al. used Thyl to transfer the APP751 variant carrying the Swedish familial AD mutation gene. One year later, these mice also developed deposited amyloid plaques. Chen et al. further confirmed that mice overexpressing the APP717 codon mutation of FAD can form most of the pathological changes of AD except for NFT: amyloid plaque deposition, neuroinflammatory plaques, loss of synapses and dendritic proteins, cytoskeleton Abnormal phosphorylation of components, lysosomal stasis, acute phase proteins, reactive astrocytes, etc., and also showed significant learning and memory disorders. The Ps protein family is closely related to some early-onset familial AD. Crossing PS-1 transgenic mice with Hsiao's T92576APPsw transgenic mice can increase the level of Aft42, but the pathological changes of this model are still under further study. Chui studied PS-1 transgenic mice. It was found that after 13 months (old mice), neuronal degeneration was significantly accelerated. Although there was no amyloid plaque formation, a large number of neurons showed intracellular Aft42 deposition.

　　Increased TGF-β was found in the brains of AD patients. Wyss Coray established transgenic mice that overexpress TGF-8. TGF-β induces A3 deposition on the cerebrovascular and meninges; in the double transgenic mice of APP and TGF-β, Aβ deposition has also been accelerated. Beeri transferred the human cholinesterase (AChE) gene into mice and overexpressed them in brain neurons, obtaining AChE activity that was two times higher than that of the control group. This mouse exhibits progressive development of learning and memory impairment.