Moxibustion influences hippocampal microglia polarization via IL-33/ST2 pathway in Alzheimer's disease mice.

Objectives: To observe the effect of moxibustion on the polarization of microglia towards M2 direction in Alzheimer's disease (AD) mice through the interleukin-33 (IL-33)/growth stimulating gene 2 protein (ST2) signaling pathway.

Methods: Five-month-old APP/PS1 male mice were randomly divided into model and moxibustion (Moxi) groups, and C57BL/6J mice of the same age were as the control group, with 9 mice in each group. In the Moxi group, moxibustion was applied at "Baihui" (GV20) and "Yongquan" (KI1) for 30 min, once a day, 5 days a week for 4 weeks. The spatial learning memory ability was observed by the Morris water maze test. The relative expressions of IL-33 and ST2 in hippocampus were detected by Western blot. The positive expression of amyloid-β (Aβ), phosphorylated Tau (p-Tau), IL-33/ionized calcium binding adapter molecule 1(Iba-1), ST2/Iba-1, arginase 1 (Arg1)/Iba-1 and indu-cible nitric oxide synthase (iNOS)/Iba-1 in hippocampal CA1 region were detected by immunofluorescence.

Results: Compared with the control group, the escape latency of the mice in the model group was prolonged (P<0.001, P<0.01), the number of times to enter the effective area and the percentage of target quadrant swimming time were reduced (P<0.001), the positive expression of both Aβ and p-Tau, the positive expression of iNOS/Iba-1 in the hippocampal CA1 region was increased (P<0.001), while the expression of IL-33 and ST2 protein in hippocampal tissue, the positive expression levels of IL-33/Iba-1, ST2/Iba-1 and Arg1/Iba-1 in hippocampal CA1 region were all decreased (P<0.05, P<0.001). After treatment, compared with the model group, the escape latency of the mice in the moxibustion group was shortened (P<0.001, P<0.01), the number of entries into the effective area and the percentage of target quadrant swimming time were increased (P<0.001), the positive expression of Aβ and p-Tau in the hippocampal CA1 region, and the positive expression of iNOS/Iba-1 were decreased (P<0.001), while the expression of IL-33 and ST2 protein in the hippocampal tissue, the positive expression of IL-33/Iba-1, ST2/Iba-1 and Arg1/Iba-1 in hippocampal CA1 region were all increased (P<0.05, P<0.01, P<0.001).

Conclusions: Moxibustion can improve the spatial learning and memory abilities, reduce the pathological deposition of Aβ and p-Tau in APP/PS1 mice, which may be related to its function in up-regulating the IL-33/ST2 signaling pathway to regulate the polarization of microglia towards M2 direction.