Kaurane Diterpenes from Isodon japonicus Inhibit Nitric Oxide and Prostaglandin E2 Production and NF-κB Activation in LPS-Stimulated Macrophage RAW264.7 Cells

Abstract

A methanolic extract of the whole plant of Isodon japonicus (Labiatae) showed potent inhibition on the LPS-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production in RAW264.7 cells. Four known kaurane diterpenes were isolated by activity-guided fractionation and their structures were identified as kamebanin (1), kamebacetal A (2), kamebakaurin (3), excisanin A (4). All compounds also inhibited the LPS-induced NF-kappaB activation as assessed by NF-kappaB reporter assay and electrophoretic mobility shift assay (EMSA). Compounds 2-4 showed comparable inhibitory effects on the LPS-induced production of NO and PGE2, and activation of NF-kappaB without affecting cell viability. These results suggest that kaurane diterpenes could exert their inhibitory effects on the production of NO and PGE2 through the suppression of NF-kappaB activation, and be partially responsible for the anti-inflammatory activities of the genus Isodon.

Medicinal chemistry and pharmacology of genus Tripterygium (Celastraceae)

“…4.1.3. Transcription factors and molecular mode of action-Transcription of the genes for iNOS and COX-2 is activated by the transcription factor nuclear factor-kappa B (NF-κB) (Hwang et al, 2001). NF-κB is a protein normally located in the cytoplasm in an inactive form bound to another protein, IκB.…”

“…Over 200 genes are induced by NF-κB (Aggarwal and Shishodia, 2004), including some that suppress apoptosis and many that encode components of the immune and inflammation responses (Schorr et al, 2002;Hwang et al, 2003). While the promoter regions of the iNOS and COX-2 genes have NF-κB binding sites, the promoter region of the COX-1 gene does not (Maekawa et al, 1999;Hwang et al, 2001). Thus, inhibitors of NF-κB are of interest as potential antiinflammatory drugs.…”

Inflexinol inhibits colon cancer cell growth through inhibition of nuclear factor-κB activity via direct interaction with p50

“…It was previously found that kaurane diterpenoid compounds have a number of biological properties such as the induction of apoptosis (19,31) and cytotoxicity against cancer cells, as well as anti-inflammatory effects through inactivation of NF-κB (20,21). Kamebakaurin, isolated from Isodon japonicus, suppressed the TNF-α-induced expression of antiapoptotic proteins via inactivation of NF-κB DNAbinding activity in human breast cancer cells (MCF-7; ref.…”

“…Inflexinol was isolated from I. excisus (Labiatae) and characterized as described elsewhere (21). The structure of inflexinol was shown in Supplementary Fig.…”

“…Several diterpenoids with C-20 nonoxygenated or oxygenated ent-kaurane, 7,6-seco-ent-kaurane, 8,9-seco-entkaurane, and ent-kaurane dimer have been isolated and characterized from the genus Isodon (18), and some kaurane compounds exhibit not only cytotoxic activity against various cancer cell lines but also inhibitory activity against NF-κB (19,20). We recently isolated and characterized several kaurane diterpenoids from I. excisus (21), and found that this compound (named inflexinol) has strong NF-κB inhibitory effects on lipopolysaccharide (LPS)-treated macrophage RAW 264.7 cells and astrocytes (22). To investigate the antitumor activity of inflexinol in vitro and in vivo, as well as its interaction with target molecules, we studied the effect of inflexinol on NF-κB activity and its binding to NF-κB subunit, as well as its effect on NF-κB target gene expression, in colon cancer cells in vitro and in vivo in parallel with the effects of this compound on colon cancer cell growth and the induction of apoptosis.…”