Antipsoriatic effects of avarol-3′-thiosalicylate are mediated by inhibition of TNF-α generation and NF-κB activation in mouse skin

Background and purpose: Avarol is a marine sesquiterpenoid hydroquinone with anti-inflammatory and antipsoriatic properties. The aim of this study was to evaluate the in vitro and in vivo pharmacological behaviour of the derivative avarol-3'-thiosalicylate (TA) on some inflammatory parameters related to the pathogenesis of psoriasis. Experimental approach: Human neutrophils and monocytes as well as the human keratinocyte cell line HaCaT were used to study the effect of TA on oxidative stress, the arachidonic acid pathway, tumour necrosis factor-alpha (TNF-alpha) release and nuclear factor-kappa B (NF-kappa B) activation. All these parameters were also determined in vivo using the zymosan induced mouse air pouch model and the 12-O-tetradecanoylphorbol-13-acetate (TPA) induced mouse epidermal hyperplasia model. Key results: TA showed antioxidant properties in human neutrophils and in the hypoxanthine/xanthine oxidase assay. This compound reduced, in a concentration-dependent manner, leukotriene B-4, prostaglandin E-2 and TNF-alpha production in activated leukocytes. Oral and intrapouch administration of TA in the mouse air pouch model produced a dose-dependent reduction of all these inflammatory mediators. TA also inhibited secretory phospholipase A(2) activity and NF-kappa B DNA-binding in HaCaT keratinocytes. In TPA-induced mouse epidermal hyperplasia, topical administration of TA reduced oedema, leukocyte infiltration, eicosanoid levels and TNF-alpha in skin. In addition, interleukin (IL)-1 beta and IL-2 production were also inhibited. Finally, TA was also capable of suppressing NF-kappa B nuclear translocation in vivo. Conclusions and implications: TA inhibited several key biomarkers up-regulated in the inflammatory response of psoriatic skin and this compound could be a promising antipsoriatic agent.