title: Helenalin, an anti-inflammatory sesquiterpene lactone from Arnica, selectively inhibits transcription factor NF-kappaB.
abstract: Alcoholic extracts prepared form Arnicae flos, the collective name for flowerheads from Arnica montana and A. chamissonis ssp. foliosa, are used therapeutically as anti-inflammatory remedies. The active ingredients mediating the pharmacological effect are mainly sesquiterpene lactones, such as helenalin, 11alpha,13-dihydrohelenalin, chamissonolid and their ester derivatives. While these compounds affect various cellular processes, current data do not fully explain how sesquiterpene lactones exert their anti-inflammatory effect. We show here that helenalin, and, to a much lesser degree, 11alpha,13-dihydrohelenalin and chamissonolid, inhibit activation of transcription factor NF-kappaB. This difference in efficacy, which correlates with the compounds' anti-inflammatory potency in vivo, may be explained by differences in structure and conformation. NF-kappaB, which resides in an inactive, cytoplasmic complex in unstimulated cells, is activated by phosphorylation and degradation of its inhibitory subunit, IkappaB. Helenalin inhibits NF-kappaB activation in response to four different stimuli in T-cells, B-cells and epithelial cells and abrogates kappaB-driven gene expression. This inhibition is selective, as the activity of four other transcription factors, Oct-1, TBP, Sp1 and STAT 5 was not affected. We show that inhibition is not due to a direct modification of the active NF-kappaB heterodimer. Rather, helenalin modifies the NF-kappaB/IkappaB complex, preventing the release of IkappaB. These data suggest a molecular mechanism for the anti-inflammatory effect of sesquiterpene lactones, which differs from that of other nonsteroidal anti-inflammatory drugs (NSAIDs), indomethacin and acetyl salicylic acid.
authors.affiliation: Institut für Pharmazeutische Biologie, Universität Freiburg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Lyss
authors.forename: T J
authors.initials: TJ
authors.lastname: Schmidt
authors.forename: I
authors.initials: I
authors.lastname: Merfort
authors.forename: H L
authors.initials: HL
authors.lastname: Pahl
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D018650:Arnica; D001402:B-Lymphocytes / Q000187:drug effects; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D019169:Jurkat Cells / Q000187:drug effects; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D010766:Phosphorylation; D010936:Plant Extracts / Q000494:pharmacology; D010946:Plants, Medicinal; D012717:Sesquiterpenes / Q000494:pharmacology*; D045789:Sesquiterpenes, Guaiane; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000187:drug effects; D014162:Transfection
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000972:Antineoplastic Agents, Phytogenic; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D010936:Plant Extracts; D012717:Sesquiterpenes; D045789:Sesquiterpenes, Guaiane; C107401:chamissonolide; D000072000:NF-KappaB Inhibitor alpha; C026745:plenolin; C001329:helenalin