Anti-inflammatory compounds from medicinal herbs capable of modulating cytokines expression in human primary blood macrophages

Abstract

Inflammation plays a pivotal role in the pathogenesis of many diseases including rheumatoid arthritis, autoimmune diseases, atherosclerosis, stroke, and cancer. Current therapeutic agents such as steroid, methotrexate, cyclophosphamide and monoclonal anti-TNF-α are effective in treat ing these diseases. However, many of these agents are associated with severe adverse effects including gastrointestinal irritation and bleeding. An alternative approach of using medicinal herbs has gained popularity, especially in Asia, to treat inflammation related diseases. Black cohosh (BC), a well known plant that is native to North America and Canada, has been used historically to treat inflammatory diseases. Two other medicinal herbs, specifically Ligusticum chuanxiong (LCX) and Radix Paeoniae rubra (RPR), have also been used as anti-inflammatory agents in Asian countries. In this project, we selected these three historically important herbs (BC, LCX and RPR) to investigate whether they have immunomodulatory effects on human primary blood macrophages (PBMac). We hypothesize that the constituents from these herbs are capable of exhibiting suppressive effects on the over-production of cytokines. Using a bioassay guided fractionation and identification scheme, we isolated compounds from these herbs and then investigated their immunomodulatory effects i n a PBMac model using lipopolysaccharide (LPS) or Bacillus Calmette-Guérin (BCG) as cytokine inducers. Our results demonstrated that compounds isolated from these herbs could significantly down-regulate the production of cytokines such as TNF-α or IL-10 in LPS- or mycobacteria-treated PBMac, while other cytokines, e.g., IL-6, are not affected. Furthermore, we showed that the LPS-induced phosphorylation of extracellularsignal-regulated protein kinase −1 and −2 (ERK1/2) can be abrogated by these compounds. In addition, the nuclear translocation of p65 subunit of NF-kB induced by LPS could be suppressed. Taken together, compounds isolated from these medicinal herbs can modulate pathogen-induced inflammatory responses via the regulation of specific signaling pathways, which lead to reduced cytokine expression in immune cells.