Effects of pre-moxibustion on expression of phosphorylated Tau protein and related protein kinases in hippocampal CA3 region of AD rats

Abstract

To observe the effect of pre-moxibustion at "Baihui"(GV20), "Shenshu"(BL23) and "Zusanli"(ST36) on expression of Tau protein and related protein kinases as glycogen synthase kinase-3β (GSK-3β), etc. in the hippocampal CA3 region of Alzheimer's disease (AD) rats, so as to explore its mechanism underlying prevention and treatment of AD cognitive impairment. Male SD rats were randomly divided into 4 groups: normal control, sham operation， model and pre-moxibustion，with 9 rats in each group. Rats of the pre-moxibustion group received moxibustion of GV20, BL23 and ST36 for 15 min, once a day, 6 days a week for 3 weeks. After completion of moxibustion, the AD model was reproduced by injection of amyloid beta-peptide 25-35(Aβ 25-35) aggregation solution 1 μL (5 μg/μL) into the bilateral hippocampus, rats of the sham operation group received injection of the same dose of normal saline into the hippocampus. The spatial learning-memory ability was detected using Morris water maze test, and changes of the ultrastructure of hippocampal neurons were observed using electron microscope, and those of histopathological changes of hippocampus tissue observed using hematoxylin eosin (H.E.) staining. The expression levels of hippocampal GSK-3β, p-Tau, CDK5 and Synapsin I proteins were detected by Western blot and immunohistochemistry, respectively. No significances were found between the normal control and sham groups in all the indexes (P>0.05). Compared with the control group, the escape latency of place navigation test of Morris water maze test, expression of GSK-3β and CDK5 and the immunoactivity of GSK-3β, CDK5 and p-Tau were significantly increased (P<0.01), and the residence time in the platform quadrant and the number of platform crossing of spatial prob test and the expression of Synapsin Ⅰ significantly reduced in the model group (P<0.01). Following the intervention, the increase of escape latency, expression of GSK-3β and CDK5 and the immunoactivity of GSK-3β, CDK5 and p-Tau, and the decrease of residence time in the platform quadrant, number of platform crossing and the expression of Synapsin Ⅰ were reversed in the pre-moxibustion group (P<0.05, P<0.01). Outcomes of ultrastructure and histopathological observations respectively showed edema of hippocampal nerve cells at varying degrees, moderate edema of the cytoplasma, chromatin condensation at the edge of the nucleus, partial mitochondrial vacuole-like degeneration, fracture of tubular crest, edema and expansion of Golgi body, disappearance of polarity, fracture of the rough endoplasmic reticulum, degeneration of ribosome and partial myelin axon and reduced synaptic vesicles in the presynaptic capsule; and reduced number of neurons with shrank body, disappearance of nucleolus and blurred nuclear boundary and vacuole-like degeneration in some of them in the model group, which were relatively milder in the pre-moxibustion group. Pre-moxibustion at GV20, BL23 and ST36 plays a role in slowing down the occurrence and development of cognitive impairment in AD rats, which may be related to its functions in inhibiting tau protein hyperphosphorylation and reducing the expression of some related protein kinases in the hippocampus.