Electro‐nape‐acupuncture regulates the differentiation of microglia through PD‐1/PD‐L1 reducing secondary brain injury in acute phase intracerebral hemorrhage rats

INTRODUCTION: This study aimed to investigate the effect of electro‐nape‐acupuncture (ENA) on the differentiation of microglia and the secondary brain injury in rats with acute‐phase intracerebral hemorrhage (ICH) through the programmed cell death protein‐1/ligand‐1 (PD‐1/PD‐L1) pathway. METHODS: A total of 27 male Sprague‐Dawley rats were randomly divided into three groups: sham group, ICH group, and ENA group. The autologous blood infusion intracerebral hemorrhage model was used to study the effects of ENA by administering electroacupuncture at GB20 (Fengchi) and Jiaji (EX‐B2) acupoints on 24 h after the modeling, once per day for 3 days. The neurological function damage, hematoma lesion, and inflammatory cell infiltration were measured by the beam walking test and hematoxylin‐eosin staining. The expression of PD‐1, PD‐L1, CD86, CD206, and related cytokines around the hematoma was measured by western blot, quantitative reverse transcription polymerase chain reaction, and immunofluorescence. RESULTS: The ICH group had significant neurological deficits (p < .001), hematoma lesions, and inflammatory cell infiltration. The levels of CD86 protein, inflammatory factors tumor necrosis factors (TNF)‐α, interleukin (IL)‐1β, and IL‐6 were increased (p < .001), while CD206 protein was reduced (p < .01), and the number of CD86(+)/CD11b(+) cells was also increased (p < .001) compared to the sham group. However, after ENA intervention, there was a significant reduction in neurological function damage (p < .05), infiltration of inflammatory cells, and the expression levels of CD86(+)/CD11b(+) cells (p < .05), resulting in the increased expression of PD‐1 protein and differentiation of M2 phenotype significantly (p < .001). CONCLUSION: The study concludes that ENA could reduce neurological function damage, inhibit the expression of pro‐inflammatory cytokines, and improve the infiltration of inflammatory cells to improve secondary brain injury in acute‐phase intracerebral hemorrhage rats. These effects could be related to the increased expression of PD‐1 around the lesion, promoting the differentiation of microglia from M1 to M2 phenotype.