ABSTRACT
ObjectiveTo investigate the effect of icariin （ICA）-mediated vitamin D system on peripheral blood dendritic cells （DCs） and helper T cells 17 （Th17）/regulatory T cells （Treg） balance in myocardial remodeling model of Dahl salt-sensitive rats. MethodFifty SPF Dahl salt-sensitive rats were divided into model group， vitamin D group （3×10-5 mg·kg-1·d-1）， and high-， medium-， and low-dose ICA groups （120， 60， 30 mg·kg-1·d-1）， and 10 Dahl salt-resistant rats were used as normal group. The myocardial remodeling model was established by feeding rats with a high-salt diet containing 8% NaCl. After six weeks of modeling， the normal group and the model group were given an equal volume of ultrapure water by gavage， and other groups were continuously administrated for six weeks. Cardiac echocardiography， hematoxylin-eosin （HE） staining， and Masson staining were used to observe the pathological changes in cardiac structure and fibrosis. The levels of serum 25（OH）D3， B-type N-terminal pro-brain natriuretic peptide （NT-ProBNP）， interleukin （IL）-17， transforming growth factor （TGF）-β1， IL-12， and IL-10 were detected by enzyme-linked immunosorbent assay （ELISA）. The phenotype of peripheral blood DCs and the ratio of Th17/Treg cells of rats were detected by flow cytometry. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot were used to detect the mRNA and protein expressions of vitamin D receptor （VDR），1α-hydroxylase （CYP27B1）， and 24-hydroxylase （CYP24A1） in peripheral blood DCs of rats. ResultCompared with the control group， the rats in the model group had pathological changes such as disordered arrangement of myocardial cells and cytoplasmic hypertrophy and swelling. Myocardial collagen fibers proliferated significantly， and the arrangement of myocardial fibers was disordered. The levels of serum 25（OH）D3 and IL-10 were significantly decreased， and the levels of serum IL-17， TGF-β1， IL-6， IL-12， and NT-ProBNP were significantly increased （P<0.05）. The costimulatory molecules CD40， CD80， CD86， and MHC-Ⅱ were highly expressed in the peripheral blood DCs， and the expression of CD11 and CD11b was lower （P<0.05）. The proportion of Th17 cells in the peripheral blood was significantly increased， and the proportion of Treg cells was decreased. The ratio of Th17/Treg was increased （P<0.05）. The mRNA and protein expressions of CYP24A1 in peripheral blood DCs increased， and the mRNA and protein expressions of CYP27B1 and VDR decreased （P<0.05）. Compared with the model group， the arrangement of myocardial fibers in each drug administration group was relatively regular， and the swelling of myocardial cells was significantly reduced. The pathological morphology of myocardial tissue was improved to varying degrees. The pathological changes in myocardial tissue were improved and alleviated to varying degrees. The drug could reduce the serum levels of NT-ProBNP， IL-17， TGF-β1， IL-6， and IL-12 and increase the level of serum 25（OH）D3 and IL-10 （P<0.05）. The expression of costimulatory molecules CD40， CD80， CD86， and MHC-Ⅱ in the peripheral blood DCs of rats was decreased， and the expression of CD11 and CD11b molecules was increased （P<0.05）. The drug could reduce the proportion of Th17 cells in peripheral blood and the ratio of Th17/Treg cells and increase the proportion of Treg cells （P<0.05）. It could decrease the mRNA and protein expressions of CYP24A1 in peripheral blood DCs of rats and elevate the mRNA and protein expression of VDR and CYP27B1 （P<0.05）. ConclusionICA can regulate the phenotype of peripheral blood DCs and the ratio of Th17/Treg cells by regulating the vitamin D system and play a role in improving myocardial remodeling from the perspective of immune balance.