Sinomenine, an alkaloid isolated from the root of Sinomenium acutum, has been used to alleviate the symptoms of rheumatic diseases. Liang Miao San (LMS), composed of the herbs Rhizoma Atractylodis (Cangzhu) and Cotex Phellodendri (Huangbai), is another traditional Chinese medicine formula for rheumatoid arthritis (RA) treatment. Although numerous studies have demonstrated the potential anti-inflammatory activities of sinomenine and LMS, the underlying intracellular mechanisms regulating the anti-inflammatory activities of sinomenine and LMS on human primary fibroblast-like synoviocytes (FLS) from RA patients and normal control subjects have not been elucidated.
We investigated the in vitro anti-inflammatory activity of sinomenine and LMS on inflammatory cytokine tumor necrosis factor (TNF)-α-mediated activation of human normal and RA-FLS. The underlying intracellular signaling molecules were analyzed quantitatively using flow cytometry.
Sinomenine was found to significantly inhibit TNF-α induced cell surface expression of vascular cell adhesion molecule (VCAM)-1 and release of inflammatory cytokine and chemokine IL-6, CCL2 and CXCL8 from both normal and RA-FLS (all p<0.05). Moreover, the suppression of sinomenine on TNF-α induced VCAM-1 expression and IL-6 release of RA-FLS was significantly higher than that of normal FLS (p<0.05). LMS significantly inhibited TNF-α-induced inflammatory chemokines CXCL10 and CCL5 release from both normal and RA-FLS, with significantly higher suppression on CXCL10 secretion in RA-FLS than that of normal FLS (all p<0.05). Further investigations showed that sinomenine and LMS could significantly suppress TNF-α-induced phosphorylation of inhibitor κBα and extracellular signal-regulated protein kinase, the central signaling molecules mediating TNF-α-induced VCAM-1 expression and chemokine production.
Our results therefore provide a new insight into the differential anti-inflammatory activities of sinomenine and LMS through the suppression of TNF-α-activated FLS by modulating distinct intracellular signaling pathways in RA.