To investigate the mechanism of Shanzha（Hawthorn）extract affecting T cell differentiation and regulating blood lipid level in dyslipidemic mice through neutrophil extracellular trap（NETs）.

Fifty male 6-week-old C57BL/6 J mice were acclimatized for 1 week, 10 mice were fed with normal chow and 40 mice were fed with 60% high-fat chow to establish a high-fat mouse model. 4 weeks after modeling, the high-fat mice were randomly divided into a high-fat diet（HFD）group, a HFD + Shanzha（Hawthorn）extract group, and a HFD + NETs inhibitor carrier solvent group, HFD + NETs inhibitor GSK484 group. The mice in the HFD + Hawthorn extract group were treated with Shanzha（Hawthorn）extract by gavage［5.2 g/（kg·d）］. The mice in the HFD + NETs inhibitor GSK484 group were intraperitoneally injected with GSK484［4 mg/（kg·d）］. The mice in the HFD + NETs inhibitor carrier solvent group were intraperitoneally injected with an equal amount of carrier solvent, and the mice in the control group and the HFD group were injected with an equal amount of distilled water at the same time. The equal amount of the distilled water was administered orally. After 4 weeks of drug administration, the levels of serum total cholesterol, triglyceride, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol were measured by biochemical analyzer. The levels of serum interferon-γ（IFN-γ）, interleukin-4（IL-4）, interleukin-10（IL-10）, interleukin-17A（IL-17A）and interleukin-21（IL-21）were measured by enzyme-linked immunosorbent assay（ELISA）. The immunofluorescence double staining was used for the expressions of neutrophil myeloperoxidase（MPO）and citrullinated histone（CitH3）to analyze the formation of NETs, and Western blotting was used for the protein expressions of peripheral blood mononuclear cell T-box transcription factor 21（TBx21）, Gata-binding protein 3（Gata-3）, retinoic acid-related orphan nuclear receptor γt（RORγt）, forkhead-like transcription factor 3（Foxp3）and B-cell lymphoma 6（Bcl-6）.

Compared with those in the normal control group, the high-fat diet mice showed significant increase in body weights, significant increase in the levels of TC, TG and LDL-C, significant decrease in HDL-C levels, significant increase in the levels of IFN-γ, IL-17A and IL-21, and significant decrease in the levels of IL-4 and IL-10, significant increase in the expression levels of MPO and CitH3, and significant increase in the expression levels of protein expressions of Tbx21 and RORγt in the peripheral blood, and significant decrease in the levels of Gata3, Foxp3 and Bcl-6. Compared with those in the HDF group, the mice in the HFD + Shanzha（Hawthorn）extract group and the HFD + NETs inhibitor GSK484 group had significantly lower body weights, significantly lower levels of TC, TG and LDL-C, significantly higher levels of HDL-C, significantly lower levels of IFN-γ, whereas IL-10 was significantly increased in the HFD + Shanzha（Hawthorn）extract group compared to that in the HFD group, and there was no significant difference in the HFD + NETs inhibitor GSK484 group. Compared to those in the HFD group, in the HFD + Shanzha（Hawthorn）extract and HFD + NETs inhibitor GSK484 groups, the expression levels of MPO and CitH3 dropped significantly. The protein expressions of Tbx21 and RORγt decreased notably, while the Gata3 protein expression increased. Bcl-6 and Foxp3 in the HFD + Shanzha（Hawthorn）extract group increased significantly, but in the HFD + NETs inhibitor GSK484 group, Foxp3 showed no significant change.

The mechanism of action of Shanzha（Hawthorn）extract may be related to the regulation of factors such as Tbx21, RORγt and Gata3, which affect Th1/Th2 and Th17/Treg differentiation, by decreasing the level of NETs in dyslipidemic mice and thus effectively ameliorating dyslipidemia.