Synedrella nodiflora (Linn.) Gaertn. inhibits inflammatory responses through the regulation of Syk in RAW 264.7 macrophages

Synedrella nodiflora (Linn.) Gaertn. (S. nodiflora) has long been used for the treatment of inflammatory diseases, including liver disease, asthma, rheumatism and earache, in tropical countries throughout America, Asia and Africa. However, the biological effects of S. nodiflora have not been extensively studied at the molecular level. Notably, it remains unclear how S. nodiflora exerts anti-inflammatory activity. In the present study, the anti-inflammatory mechanism of a methanol extract of S. nodiflora (MSN) in RAW 264.7 macrophages activated by lipopolysaccharide (LPS) was investigated. Non-cytotoxic concentrations of MSN (≤400 µg/ml) decreased the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), which resulted in a decrease in nitric oxide and prostaglandin E₂ (PGE₂) production. The mRNA expression of pro-inflammatory cytokines such as interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α was reduced upon MSN treatment. In addition, the activation of spleen tyrosine kinase (Syk) and Akt was suppressed by MSN. Taken together, these findings recommend the traditional medicinal application of S. nodiflora in the treatment of several inflammation-associated diseases and indicate the possibility of MSN as a novel therapeutic reagent of inflammation-related diseases.

Keywords: inflammatory mediators; lipopolysaccharide; macrophages; nuclear factor-κB; spleen associated tyrosine kinase; synedrella nodiflora.