Anti-inflammatory mechanisms of isoflavone metabolites in lipopolysaccharide-stimulated microglial cells.
The microglial activation plays an important role in neurodegenerative diseases by producing several proinflammatory cytokines and nitric oxide (NO). We found that three types of isoflavones and their metabolites that are transformed by the human intestinal microflora suppress lipopolysaccharide (LPS)-induced release of NO and tumor necrosis factor (TNF)-alpha in primary cultured microglia and BV2 microglial cell lines. The inhibitory effect of the isoflavone metabolites (aglycon form) was more potent than that of isoflavones (glycoside form). The RNase protection assay showed that the isoflavone metabolites regulated inducible nitric oxide synthase (iNOS) and the cytokines at either the transcriptional or post-transcriptional level. A further molecular mechanism study was performed for irisolidone, a metabolite of kakkalide, which had the most potent anti-inflammatory effect among the six isoflavones tested. Irisolidone significantly inhibited the DNA binding and transcriptional activity of nuclear factor (NF)-kappaB and activator protein-1. Moreover, it repressed the LPS-induced extracellular signal-regulated kinase (ERK) phosphorylation without affecting the activity of c-Jun N-terminal kinase or p38 mitogen-activated protein kinase. The level of NF-kappaB inhibition by irisolidone correlated with the level of iNOS, TNF-alpha, and interleukin (IL)-1beta suppression in LPS-stimulated microglia, whereas the level of ERK inhibition correlated with the level of TNF-alpha and IL-1beta repression. Overall, the repression of proinflammatory cytokines and iNOS gene expression in activated microglia by isoflavones such as irisolidone might have therapeutic potential for various neurodegenerative diseases including ischemic cerebral disease.
Park
Jin-Sun
JS
Department of Neuroscience, College of Medicine, Ewha Womans University, Mok-6-dong 911-1, Yangchun-Ku, Seoul 158-710, South Korea.
Woo
Moon-Sook
MS
Kim
Dong-Hyun
DH
Hyun
Jin-Won
JW
Kim
Won-Ki
WK
Lee
Jae-Chul
JC
Kim
Hee-Sun
HS
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D007529:Isoflavones / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D015394:Molecular Structure; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D029908:Pueraria / Q000737:chemistry; D012260:Ribonucleases / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D016207:Cytokines; D004268:DNA-Binding Proteins; D007529:Isoflavones; D008070:Lipopolysaccharides; D052247:Nitric Oxide Synthase Type II; D012260:Ribonucleases