Phytomedicines prepared from Arnica flowers inhibit the transcription factors AP-1 and NF-kappaB and modulate the activity of MMP1 and MMP13 in human and bovine chondrocytes.

Arnica preparations have long been used for the symptomatic treatment of rheumatic complaints and recent clinical trials have demonstrated the beneficial effects of Arnica preparations in the treatment of osteoarthritis (OA). The efficacy of Arnica is presumed to be mainly due to its anti-inflammatory properties and inhibition of the transcription factor NF-kappaB. Here we provide further insights into its molecular mode of action. Arnica preparations suppress MMP1 and MMP13 mRNA levels in bovine and human articular chondrocytes in a concentration-dependent manner and in a low concentration range. This suppression may be due to inhibition of DNA binding of the transcription factors AP-1 and NF-kappaB. Interestingly, sesquiterpene lactones present in the preparations were always more active than the pure compounds, demonstrating the advantage of using plant preparations. Georg Thieme Verlag KG Stuttgart, New York.