α-lipoic acid-based PPARγ agonists for treating inflammatory skin diseases

Abstract

Novel thiazolidinedione derivatives of the potent antioxidant, α-lipoic (thioctic, 1,2-dithiolane) acid, were prepared. The prototype N-(2-{4-[2,4-dioxo(1,3-thiazolidin-5-yl)methyl]phenoxy}ethyl)-5-(1, 2-dithiolan-3-yl)-N-methylpentanamide (designated BP-1003), and dithioester derivatives thereof were shown to be potent activators of peroxisome proliferator-activated receptor gamma (PPARγ) (EC50 range 15 nM) and modest activators of PPARα (EC50 5 μM). Both the relatively hydrophobic dithiolane prototype, BP-1003, and its water-soluble dithioglycinate derivative, BP-1017, were shown to inhibit the proliferation of human keratinocytes and suppress the production of interleukin-2 by human peripheral lymphocytes to a greater extent than the antidiabetic thiazolidinedione, rosiglitazone. Both oral and topical administration of BP-1017 showed significant antiinflammatory effects in the oxazolone-sensitized mouse model of allergic contact dermatitis (ACD). These findings suggest that water-soluble lipoic acid-based thiazolidinediones may be efficacious as oral and topical agents for treating inflammatory skin conditions such as contact dermatitis, atopic dermatitis, and psoriasis.