Study on the innate immune regulatory mechanism of transcutaneous electrical acupoint stimulation in sleep-deprived rats based on TLR4/MyD88/NF-κB signaling pathway

To observe the effect of transcutaneous electrical acupoint stimulation (TEAS) on the innate immune function of sleep-deprived rats, so as to explore its possible molecular mechanisms underlying improvement of sleep deprivation.

Twenty-four SD rats were randomly divided into control, sleep deprivation model, TEAS and sham TEAS groups, with 6 rats in each group. The sleep deprivation model was established by using the modified multi-platform aqueous environment sleep restriction method. TEAS (2 Hz/100 Hz, 2 mA) was applied to “Beixin Tiaoshen Wuxue” (the back-heart Shen-regulating region), bilateral “Sanyinjiao”(SP6) and bilateral “Zusanli”(ST36) for 25 min, once daily for 30 successive days. For rats of the sham TEAS group, the stimulating electrodes were fixed as those in the TEAS group but without electric current supplied. After the intervention, the rats’ sleep latency and sleep duration were measured by pentobarbital sodium righting reflex tests. The spleen and thymus indexes were calculated by organ mass coefficient analysis. Hematoxylin-eosin (H.E.) staining was used to observe the histopathological changes of the spleen and thymus tissues. The contents of interleukin (IL)-1β, IL-6, tumor necrosis factor-alpha(TNF-α) and IL-10 in the peripheral blood serum were detected by ELISA. The expression levels of TLR4, MyD88 and NF-κB p65 mRNAs and proteins in the splenic tissues were detected by qPCR and Western blot, separately.

Compared with the rats of the control group, those of the model group showed poorer mental state, fur color and other conditions, with a significant decrease in the body mass from day 7 to 28 after modeling, duration of sleep, index of spleen and thymus, and serum IL-10 content (P<0.05, P<0.01, P<0.001), and a considerable increase in the sleep latency, contents of serum TNF-α, IL-1β and IL-6, and the expression levels of TLR4, MyD88 NF-κB p65 mRNAs and proteins (P<0.01). In comparison with the model group and the sham TEAS group, rats in the TEAS group showed better mental state and fur color, with a significant increase in body weight (P<0.01). Other indicators were also improved to varying degrees (P<0.01, P<0.05). H.E. staining showed that both the spleen and thymus tissues in the model group had a typical organ damage including disappearance of the boundary between the white pulp and red pulp, decreased area of the white pulp, decreased density of the lymph follicles, irregular shape of the residual follicles, and interruption of the continuity of lymphatic sheath around the arteries which were apparently milder in the TEAS group rather than in the sham TEAS group.

TEAS can improve sleep and increase body mass in sleep deprivation rats, which may be related to its functions in increasing the index of the spleen and thymus, regulating the balance of pro- and anti-inflammatory cytokine levels and suppressing the activities of TLR4/MyD88/NF-κB signaling in the spleen tissue.