Effect of acupuncture on microglia activation in prefrontal cortex of chronic stress-induced depression rats

Abstract

To observe the effect of acupuncture on the expression of proinflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), microglia marker ion calcium adaptor protein (Iba-1) and triggering receptor expressed on myeloid cells 2 (TREM2) in the prefrontal cortex of chronic stress-induced depression rats, so as to explore its antidepressant mechanism. Thirty-two SD rats were randomly divided into normal control, model, acupuncture and fluoxetine groups, with 8 rats in each group. The depression model was established by using chronic mild unpredictable stress methods for 6 weeks. Manual acupuncture stimulation was applied to "Baihui" (GV20) and "Yintang" (GV29) for 10 min before modeling for 6 weeks. Fluoxetine (10 mg/kg, 1 mg/mL) was given to rats of the fluoxetine group by gavage before stress stimulation, once every day for 6 weeks. The open field test was used to evaluate the behavioral changes of rats. The contents of IL-1β, IL-6 in the prefrontal cortex were determined by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry was used to determine the expression of Iba-1 in the prefrontal cortex. The TREM2 gene expression in the prefrontal cortex was determined by real time fluorescent quantitative polymerase chain reaction (RT-PCR). After modeling, the crossing numbers and rearing times were significantly decreased in the model group relevant to the control group (P<0.05). After the treatment, the crossing numbers were significantly increased in the acupuncture and fluoxetine groups (P<0.05), while the rearing times in the acupuncture group were significantly increased (P<0.05). Compared with the control group, the contents of IL-1β, IL-6 and the expression of Iba-1 positive cells in the prefrontal cortex were significantly increased in the model group (P<0.05), while the expression of TREM2 gene in the prefrontal cortex was significantly decreased (P<0.05). After the treatment, the increased levels of IL-1β, IL-6 and Iba-1 positive cells and the decreased TREM2 gene expression were considerably reversed in both acupuncture and fluoxetine groups compared with the model group (P<0.05). Acupuncture intervention plays a positive role in anti-depression in rats, which may be related to its effects in inhibiting the activation of microglia, reducing the expression of proinflammatory cytokines, and increasing TREM2 expression in the prefrontal cortex.