In this paper, we investigated the in vitro and in vivo anti-inflammatory effects of CJ methanol extract using the LPS-mediated model and found that the extract from this plant was able to suppress the productions of iNOS, TNF-α, IL-6, and IL-12 in activated macrophages. Also, CJ methanol extract inhibited LPS or LPS/IFN-γ-triggered intracellular signaling pathways that end in the activation of such molecules as IκBα, MAPK and STAT1.
NO is a signaling molecule; it diffuses into the cytosol of neighboring cells and binds to the iron cofactor of guanylate cyclase, triggering activation of the enzyme and elevating intracellular cGMP concentrations
. However, NO is also a free radical; it reacts with reactive oxygen species to produce peroxynitrite, a potent oxidant that inactivates target proteins by direct nitrosylation. The main control of NO production is determined by iNOS, and NF-κB, STAT1, and AP-1 are among the known transcription factors involved in the regulation of iNOS expression
. In particular, NF-κB is a target modulated by many iNOS inhibitors such as glucocorticoids and antioxidants
. IκBα degradation is critical for the regulation of NF-κB. IκBα is the prototypical protein of the IκB protein family (IκBα, IκBβ, IκBγ, IκBε, Bcl-3, p100, and p105)
. Phospho-IκBα is subject to polyubiquitination by E2 UbcH5 and E3 SCFβTrCP and is then degraded by the 20S proteasome. Our results indicate that the action of CJ methanol extract occurred in the pathways linking LPS to IKK.
TNF-α and IL-6 play major roles in vascular permeability, neutrophil recruitment, blood clotting, and acute phase protein synthesis: all of which are characteristics of acute inflammation. IL-12 activates NK cells and promotes the differentiation of T-helper cells into IFN-γ-secreting Th1 cells, which enhance macrophage activity
. The MAPK signaling pathway mediates the LPS-triggered expressions of TNF-α, IL-6, and IL-12
[4, 12]. The inhibitions of p38, JNK and ERK1/2 by CJ methanol extract may explain part of the mechanism that underlies the suppression of these pro-inflammatory cytokines.
IFN-γ upregulates the receptors for PAMP and DAMP, resulting in enhanced macrophage function. IFN-γ-dependent biological responses were impaired in STAT1-deficient mice
. STAT1 has two phosphorylation sites, one at tyrosine 701 and the other at serine 727
. Phosphorylation at tyrosine 701 is a direct result of IFN-γ exposure while phosphorylation of serine 727 requires a separate signaling pathway. LPS is able to induce phosphorylation at tyrosine 701 in a delayed manner, but uses the same IFN-γ receptor-mediated pathway. Our experimental model utilized both IFN-γ and LPS to fully activate STAT1. Inhibition of STAT1 phosphorylation at tyrosine 701 by CJ methanol extract may contribute to the downregulation of macrophage activity.
Many medicinal and food plants that belong to the Apiaceae family contain bioactive polyacetylenes
. Falcarinol type polyacetylenes have been demonstrated to inhibit the release of NO and inflammatory cytokines in LPS-activated macrophages
[16, 17]. Catechol, a polyphenol found in CJ, has been reported to be a potent inhibitor of iNOS expression and NF-κB activation
. Presumably, part of the anti-inflammatory activity of CJ may be due to the presence of polyacetylene compound and catechol.