A possible signal transduction pathway for cyclin D2 expression by a pectic polysaccharide from the roots of Bupleurum falcatum L. in murine B cell

Extraction, purification, structure characteristics, biological activities and pharmaceutical application of Bupleuri Radix Polysaccharide: A review

Bupleuri Radix (BR), as a well-known plant medicine of relieving exterior syndrome, has a long history of usage in China. Bupleuri Radix Polysaccharide (BRP), as the main component and an important bioactive substance of BR, has a variety of pharmacological activities, including immunoregulation, antioxidant, antitumor, anti-diabetic and anti-aging, etc. In this review, the advancements on extraction, purification, structure characteristics, biological activities and pharmaceutical application of BRP from different sources (Bupleurum chinense DC., Bupleurum scorzonerifolium Willd., Bupleurum falcatum L. and Bupleurum smithii Woiff. var. Parvifolium Shan et Y. Li.) are summarized. Meanwhile, this review makes an in-depth discussion on the shortcomings of the research on BRP, and new valuable insights for the future researches of BRP are proposed.

A pectic polysaccharide isolated from the roots of Bupleurum falcatum L. stimulates the tyrosine phosphorylation of lipid rafts of murine B cells

Bupleuran 2IIc, a pectic polysaccharide isolated from the roots of Bupleurum falcatum L., was previously characterized as a T cell-independent B cell mitogen. The endo-(1-->4)-alpha-D-polygalacturonase-resistant moiety of bupleuran 2IIc (bupleuran 2IIc/PG-1) was the active site for expression of the activity, and expression of the cyclin D2 gene by bupleuran 2IIc/PG-1 may be mediated via activation of Src family tyrosine kinase, phosphatidylinositol 3-kinase (PI 3-K) and phospholipase C (PLC)-gamma followed by activation of protein kinase C (PKC) and calcium mobilization (Matsumoto et al., Int. Immunopharmacol., 5, 1373-1386 (2005)). Plasma membrane microdomains (lipid rafts) are enriched in signaling molecules and suggested to be involved in numerous cell functions, including membrane traffic and signaling. When B cells were stimulated with bupleuran 2IIc/PG-1, clustering of membrane lipid rafts was observed. To consider whether lipid rafts are implicated in bupleuran 2IIc/PG-1-mediated B cell proliferation, we analyzed the phosphorylation of tyrosine residues of proteins in lipid rafts. When murine B cells were stimulated with bupleuran 2IIc/PG-1, tyrosine phosphorylation of proteins in lipid rafts fraction was observed within 5 min. Tyrosine phosphorylation in lipid rafts fraction by bupleuran 2IIc/PG-1 was inhibited by the Src-family tyrosine kinase inhibitor, PP2. Together with previously published data, the results presented in this study suggest that activation of signaling molecules in lipid rafts by stimulation of bupleuran 2IIc/PG-1 contributes to B cell proliferation as the membrane-proximal signaling event.