Baicalin From Scutellaria baicalensis Impairs Th1 Polarization Through Inhibition of Dendritic Cell Maturation

Background: Baicalin from Scutellaria baicalensisis a major flavonoid constituent found in the traditional Chinese medicinal herb Baikal skull cap and has been widely used for the treatment of various diseases such as pneumonia, diarrhea, and hepatitis. Recent studies have demonstrated that baicalin possesses a wide range of pharmacological and biological activities, including anti-inflammatory, anti-microbial, anti-oxidant, and anti-tumor properties; however, its effects on dendritic cells (DCs) maturation and immuno-stimulatory activities are still unknown.

Methods: To investigate the effect of Baicalin on DCs, we isolated DCs from bone marrow of B57BL/6. And we attempted to determine expression of surface molecules, antigen uptake capacity, cytokine production, and capacity to induce T-cell differentiation. DC surface molecules and antigen uptake were measured by flow cytometry using specific antibodies and dextran-FITC, respectively. In cytokine assay, intracellular cytokine was determined by flow cytometry and also cytokine production was measured by ELISA. To verify the T cell polarization, we isolated T cells from spleen of BALB/C mice and performed the mixed lymphocyte reaction, and the T cells were co-cultured with DCs.

Results: Baicalin was shown to significantly suppress the expression of surface molecules CD80, CD86, major histocompatibility complex (MHC) class I, and MHC class II as well as the levels of interleukin-12 production in lipopolysaccharide stimulated DCs. Moreover, baicalin-treated DCs showed an impaired induction of the T helper type 1 immune response and a normal cell-mediated immune response.

Conclusions: These findings provide important understanding of the immunopharmacological functions of baicalin and have ramifications for the development of therapeutic adjuvants for the treatment of DCs-related acute and chronic diseases.