Biol. Pharm. Bull. 30(1) 139—144 (2007)

lation of a series of enzymes and signaling proteins in affected tissues and cells. These pro-inflammatory enzymes include the inducible forms of nitric oxide synthase (NOS) and cyclooxygenase (COX), which are responsible for increasing the levels of NO and prostaglandins (PGs), respectively. Moreover, they are known to be involved in the pathogenesis of many chronic diseases including multiple sclerosis, Parkinson’s and Alzheimer’s diseases, and colon cancer. Nitric oxide (NO), which is synthesized from L-arginine by nitric oxide synthase (NOS), is a short-lived free radical and an intercellular messenger that mediates a variety of biological functions, including vascular homeostasis, neurotransmission, antimicrobial defense, and antitumor activities. To date, three isoforms of NOS have been identified: endothelial NOS (eNOS), neuronal NOS (nNOS), and inducible NOS (iNOS). Of these three isoforms, iNOS (the high-output isoform) is most widely expressed in various cell after its transcriptional activation. Importantly, iNOS is highly expressed in lipopolysaccharide (LPS)-activated macrophages, and this contributes to the pathogenesis of septic shock. In some cases, the induction of iNOS by other stimuli leads to organ destruction in some inflammatory and autoimmune diseases. Thus, the inhibition of NO production by blocking iNOS expression may result in a useful strategy for the treatment of various inflammatory diseases. COX is the enzyme that converts arachidonic acid to PGs, and exists as two isoforms (COX-1 and -2). COX-2, the inducible form, is responsible for the production of large amounts of pro-inflammatory PGs at sites of inflammation. LPS is a major inflammatory molecule that triggers the production of pro-inflammatory toxins, cytokines such as TNF-a and IL-1b in various cell types. TNF-a plays a key role in the induction and perpetuation of inflammation in autoimmune reactions, and it also activates T cells and macrophages and up-regulates other pro-inflammatory cytokines and endothelial adhesion molecules, such as intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), which enhance the recruitment of leukocytes to sites of inflammation. On the other hand, IL-1b is one of the most important inflammatory cytokines secreted by macrophages. During inflammation, increased IL-1b release leads to cell or tissue damage, alternatively, a reduction in IL-1b release from macrophages may slow down inflammatory responses to LPS stimulation. Nuclear transcription factor kappa-B (NF-kB) is one of the most ubiquitous transcription factors, and regulates the expressions of genes involved in cellular proliferation, inflammatory responses and cell adhesion. The activation of NF-kB induces the transcription of multiple pro-inflammatory mediators including iNOS, COX-2, TNF-a , IL-1b , and others. Active NF-kB exists mainly as a heterodimer that consists of subunits of the Rel family p50 and p65, which is normally sequestered in the cytosol as an inactive complex by binding to inhibitors of kB (IkBs) in unstimulated cells. The mechanism of NF-kB activation involves the phosphorylation of IkBs at two critical serine residues (Ser and Ser) via the IkB kinase (IKK) signalosome complex. Once IkBs are phosphorylated, they are ubiquitinated and degraded by 26S proteosome. The resulting free NF-kB is then translocated into the nucleus, where it binds to kB binding sites in the promoter region of target genes, and induces the transcription of pro-inflammatory mediators. Thus, as a part of our on-going screening program to evaluate the anti-inflammatory potentials of natural compounds, we investigated the in vitro anti-inflammatory activities of constituents isolated from the stem barks of S. japonica. The pericarps of S. japonica are used in soap and cough mediJanuary 2007 139