Electroacupuncture Attenuates Immune-Inflammatory Response in Hippocampus of Rats with Vascular Dementia by Inhibiting TLR4/MyD88 Signaling Pathway

Objective: To investigate whether electroacupuncture (EA) alleviates cognitive impairment by suppressing the Toll-like Receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88) signaling pathway, which triggers immune-inflammatory responses in the hippocampus of rats with vascular dementia (VaD).

Methods: The experiments were conducted in 3 parts and in total the Sprague-Dawley rats were randomly divided into 8 groups by a random number table, including sham, four-vessel occlusion (4-VO), 4-VO+EA, 4-VO+non-EA, sham+EA, 4-VO+lipopolysaccharide (LPS), 4-VO+LPS+EA, and 4-VO+TAK-242 groups. The VaD model was established by the 4-VO method. Seven days later, rats were treated with EA at 5 acupoints of Baihui (DV 20), Danzhong (RN 17), Geshu (BL 17), Qihai (RN 6) and Sanyinjiao (SP 6), once per day for 3 consecutive weeks. Lymphocyte subsets, lymphocyte transformation rates, and inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor α(TNF-α) were measured to assess immune function and inflammation in VaD rats. Transmission electron microscopy was used to observe the ultrastructure of nerve cells in the hippocampus. The levels of TLR4, MyD88, IL-6, and TNF-α were detected after EA treatment. TLR4/MyD88 signaling and cognitive function were also assessed after intracerebroventricular injection of TLR4 Antagonist TAK-242 or TLR4 Agonist LPS with or without EA.

Results: Compared with the 4-VO group, EA notably improved immune function of rats in the 4-VO+EA group, inhibited the protein and mRNA expressions of TLR4 and MyD88 in the hippocampus of rats, reduced the expressions of serum IL-6 and TNF-α (all P<0.05 or P<0.01), and led to neuronal repair in the hippocampus. There were no significant differences between the 4-VO+LPS+EA and 4-VO+EA groups, nor between the 4-VO+TAK-242 and 4-VO+EA groups (P>0.05).

Conclusions: EA attenuated cognitive impairment associated with immune inflammation by inhibition of the TLR4/MyD88 signaling pathway. Thus, EA may be a promising alternative therapy for the treatment of VaD.