| Alzheimer disease (AD) is a progressive cerebral neurodegenerative process with cognition impairment. Its pathogenesis is not so clear and there are not effective therapies for it now. The pathological hallmarks of AD are extracellelar AP containing senile plaques, intracellular neurofibrillary tangles, loss of neurons and synapses, and cerebrovascular amyloidosis. AP hypothesis is the most popular pathogenesis for AD, claiming the AP accumulation and its neurotoxicity result in the pathological changes and clinical symptoms. Cerebral AP level is associated with the Aβproduction and elimination in the brain; imbalance between AP production and elimination will lead to cerebral AP elevation. AP elimination across blood-brain barrier had been a hot topic in the study of AD pathogenesis and therapeutic targets.In the theory of Chinese medicine, brain and kidney are the most important organs to senile dementia; AD was caused by kidney essence deficiency, which failed to supply the brain, and cerebral collateral blockage due to blood stasis, phlegm and endogenetic toxin. Acupuncture has a good effect on disorders of central nervous system; DU 20 is the point connecting brain directly, and KI 1 is the source point of Kidney meridian; so acupuncture on DU 20 and KI 1 can dredge meridians and collaterals, promote qi and blood circulation, remove blood stasis, tonify kidney and brain, and recover cognitive impairment. Its effect regulating the function and structure of cerebrovasculature (cerebral collaterals) may promote cerebral Aβelimination across BBB, resulting in reduction of cerebral AP level and its neurotoxicity. So, we discuss the mechanism of acupuncture on AD by affecting cerebral Aβlevel, by promoting Aβelimination across BBB.OBJECTIVE:To study the mechanism of high cerebral Aβlevel in APP tg mice by investigating the positive site of Aβin cortex and hippocampus, by investigating the positive site of LRP1, the main Aβtransport receptor on BBB. At the same time, investigate the effect of EA on cerebral Aβlevel, on LRP1, on cerebrovascular amyloidosis to discuss the mechanism of reduction of cerebral Aβlevel by EA on APP tg mice, which may support the theory that AD was caused by cerebral collateral blockage, and acupuncture may dredge cerebral collateral, remove endogenetic toxin.METHOD:The present experiment assigned randomly APPV695717I transgenic mice (tg mice) aged 13 months to AD model group (M) and Electroacupuncture group (EA), and compared with same aged C57BL/6 mice. EA group were treated with EA on DU20 and KI1 for 3 months. Techniques and methods of immunohistochemistry (IH), ELISA, Western blot, and transmission electron microscopy were applied to study the effect of EA on cerebral Aβlevel, on LRP1, the main Aβtransport receptor on BBB, on ultrastructure of microvessels.RESULTS:1. Showed by Lashley III water maze test, APP tg mice experienced longer swimming time and much error times than control group did (P＜0.05); Showed by Y-electric maze test, APP tg mice need much acquiring times than control group did (P<0.05); And EA can ameliorate cognitive impairment of APP tg mice tested by LashleyⅢwater maze (P<0.05) and by Y-electric maze (P<0.05).2. EA can ameliorate ultrastructure pathologic changes of APP tg mice, such as neuronal degeneration with abundant multivascula and lysosome, endothelium thinning, basement membrane thickening in cerebral microvasculature, and astroglial endfoot swelling.3. By immunohistochemistry imaging, Aβ1-40/Aβ1-42 immune positive were shown in neuron bodies and synapses, and walls of microvasculature were positive to Aβ1-42 antibody, which confirmed by Thioflavin S staining as microvascular amloidgenesis. Integrated optical densities (IOD) of Aβ1-40/Aβ1-42 in cortex of model group were higher than that in control group (P<0.05, P＜0.01). And IOD of AP 1-42 in hippocampus of model group were also higher than that in control group (P＜0.05). And EA could reduce immune positive expression of Aβ1-40/Aβ1-42 in cortex of APP tg mice (P＜0.05, P＜0.01); EA could reduce immune positive expression of Aβ1-42 in hippocampus microvasculae of APP tg mice (P＜0.05). LRP1 immune positive expressions in cortex and hippocampus microvessels of model group were lower than that in control group (P＜0.01, P＜0.01); And EA could improve LRP1 immune positive expressions in cortex and hippocampus microvessels of APP tg mice (P＜0.05, P＜0.05).4. ELISA showed that cerebral Aβ1-42 levels of model group were higher than that in control group (P＜0.01), and EA could reduce cerebral Aβ1-42 levels of APP tg mice (P＜0.01). At the same time, EA could reduce AP 1-42 levels in cerebrospinal fluid and plasma of APP tg mice.5. Western Blot showed that cerebral LRP1 levels of model group were lower than that in control group, and EA could improve cerebral LRP1 levels of APP tg mice tested by WB.CONCLUSION:1. High cerebral Aβlevel, result from increased intracellular Aβproduction and decreased AP elimination by microvessels, is the right curse of AD manifesting cognitive impairment.2. EA could ameliorate cognitive impairment of APP tg mice by its function reducing cerebral Aβlevel.3. Cerebral Aβproduction may be reduced by EA effect on lysosome autophagy mechanism; cerebral Aβelimination may be improved by EA effect on LRP1 BBB transport mechanism.4. Acupuncture may affect the structure and function of microvessels, improving AP elimination by microvessels, reducing Aβaccumulation around microvessels, which support the theory that AD was caused by cerebral collateral blockage, and acupuncture may dredge cerebral collateral, remove endogenetic toxin.It was the first time for APP tg mouse be applied to EA study on AD. And we found that cerebral microvascular amyloidosis existed in APP695V717I tg mice, and it appeared early than typical amyloid plaques did. Main constitute of cerebral microvascular amyloidosis in APP695V717I tg mice was Aβ1-42.
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