Electroacupuncture Attenuates Surgical Stress-Induced Reduction of T Lymphocytes through Modulation of Peripheral Opioid System

Objective: To investigate the action mechanisms of electroacupuncture (EA) on postoperative immunosuppression.

Methods: Male C57BL/6 mice (5`-7 weeks old) were randomly divided into: the sham injury group, the surgical trauma stressed group, the EA group [surgery + 2/100 Hz EA at Neiguan (PC 6)], and the EA+ Nal (surgery + EA + intraperitoneal injection of naloxone). Abdominal surgical trauma stress mice model was established. EA was performed on bilateral PC 6 acupoints by an EA apparatus (2/100 Hz) for 20 min once a day for 3 days. The mRNA expressions of MOR, DOR, and KOR in thymus and L3`-L5 dorsal root ganglions (DRG) were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and the protein expressions of MOR, DOR, and KOR in thymus were measured by Western blot. Flow cytometry assay was used to detect the levels of T lymphocyte subtypes in the peripheral blood.

Results: Surgical trauma induced decreased the mRNA expression level of MOR in both thymus (P<0.01) and L3`-L5 DRGs (P<0.05). Moreover, EA treatment not only significantly attenuated the MOR protein and mRNA expression in the thymus (both P<0.05), but also markedly increased expression of DOR and KOR opioid receptor in thymus (P<0.01). However, the mRNA expressions of opioid receptors were not regulated by EA in the DRG (all P>0.05). Furthermore, T lymphocyte population of CD3⁺ and CD4⁺ was decreased in the peripheral blood after surgical trauma (both P<0.01). EA treatment can significantly elevate the population of CD₃⁺ (P<0.01), CD₄⁺ (P<0.05) and CD₈⁺ T cells (P<0.01). Intraperitoneal injection of the non-selective opioid receptor antagonist naloxone blocked the up-regulation of T lymphocytes by EA.

Conclusion: EA may improve postoperative immunosuppression through the peripheral opioid system.