ObjectiveTo explore the potential mechanism underlying electroacupuncture therapy with the midnight-noon ebb-low method with hour-prescription for chronic obstructive pulmonary disease （COPD） with lung-qi deficiency syndrome from the perspective of brain and muscle basic helix-loop-helix ARNT-like 1 （BMAL1） as well as neutrophil extracellular traps （NETs）. MethodsThe experiment was conducted in two phases. For the therapeutic effectiveness observation， 24 rats were randomly allocated into control group 1， model group 1， midnight-noon electro-acupuncture group 1 and conventional electro-acupuncture group， with 6 rats per group. Rat models of COPD with lung-qi deficiency syndrome were established via cigarette smoke exposure combined with intratracheal instillation of lipopolysaccharide （LPS）. After successful modelling， rats in midnight-noon electro-acupuncture group 1 received electro-acupuncture at acupoints "Taiyuan （LU 9）"， "Feishu （BL 13）" and "Zusanli （ST 36）" during 05：00—07：00， 30 minutes per treatment once every other day for 14 consecutive days （7 sessions in total）. Rats in the conventional electro-acupuncture group received identical electroacupuncture manipulation at random daytime hours （08：00—18：00）. Pulmonary function parameters including forced expiratory volume in 0.3 second （FEV_0.3）， forced vital capacity （FVC） and FEV_0.3/FVC ratio were detected. Pulmonary histopathological changes were observed via hematoxylin-eosin （HE） staining. Plasma levels of pro-inflammatory factors interleukin-1β （IL-1β） and tumor necrosis factor-α （TNF-α）， as well as pulmonary reactive oxygen species （ROS） content， BMAL1 protein expression and the levels of neutrophil extracellular traps （NETs） biomarkers such as myeloperoxidase （MPO）， neutrophil elastase （NE）， and citrullinated histone H3 （CitH3） in lung tissue were determined. For the mechanistic verification phase， 36 rats were divided into control group 2， model group 2， midnight-noon electro-acupuncture group 2， overexpression empty group， overexpression BMAL1 group and overexpression with midnight-noon electro-acupuncture group， with 6 rats in each group. At the 5th week of model construction， rats in the overexpression BMAL1 group and overexpression with midnight-noon electro-acupuncture group received intratracheal instillation of 100 μl adenoviral suspension carrying overexpressed Bmal1 gene. Rats in the overexpression empty group were injected with an equal titer and equal volume of blank adenovirus without the Bmal1 coding sequence into the lung at the identical time point. Midnight-noon electro-acupuncture group 2 and overexpression with midnight-noon electro-acupuncture group were consistent with the aforementioned protocol. Finally， pulmonary levels of MPO， NE and CitH3 were measured in all groups. ResultsCompared with the control group 1， the model group 1 exhibited decreased FEV_0.3， FVC and FEV_0.3/FVC ratio， elevated plasma IL-1β， TNF-α and pulmonary ROS levels， downregulated lung BMAL1 protein expression， and increased contents of MPO， NE and CitH3 （all P＜0.05）； typical NETs-like structures with sparse granular substances attached to fibrous networks were observed under scanning electron microscopy； HE staining revealed damaged alveolar architecture accompanied by inflammatory cell infiltration. Compared with model group 1， both the midnight-noon electro-acupuncture group 1 and conventional electro-acupuncture group achieved obvious improvements in all above indicators， with superior therapeutic effects in midnight-noon electro-acupuncture group 1 （P＜0.05）. Consistently， midnight-noon electro-acupuncture group 1 showed more prominent alleviation of NETs-like structure formation and lung pathological injury compared to the conventional electro-acupuncture group. Mechanistic validation results demonstrated that compared with model group 2， the average optical density of MPO as well as the protein levels of MPO， NE and CitH3 were markedly reduced in midnight-noon electro-acupuncture group 2， overexpression BMAL1 group and overexpression with midnight-noon electro-acupuncture group （P＜0.05）； furthermore， these parameters were significantly lower in the overexpression with midnight-noon electro-acupuncture group than in midnight-noon electro-acupuncture group 2 （P＜0.05）. ConclusionElectro-acupuncture based on the midnight-noon ebb-low method with hour-prescription may alleviate pulmonary inflammation in COPD by upregulating the expression of clock protein BMAL1 and inhibiting excessive accumulation of NETs in lung tissue.