Optical control of adenosine A3 receptor function in psoriasis.

Psoriasis is a chronic and relapsing inflammatory skin disease lacking a cure that affects approximately 2% of the population. Defective keratinocyte proliferation and differentiation, and aberrant immune responses are major factors in its pathogenesis. Available treatments for moderate to severe psoriasis are directed to immune system causing systemic immunosuppression over time, and thus concomitant serious side effects (i.e. infections and cancer) may appear. In recent years, the Gi protein-coupled A3 receptor (A3R) for adenosine has been suggested as a novel and very promising therapeutic target for psoriasis. Accordingly, selective, and high affinity A3R agonists are known to induce robust anti-inflammatory effects in animal models of autoimmune inflammatory diseases. Here, we demonstrated the efficacy of a selective A3R agonist, namely MRS5698, in preventing the psoriatic-like phenotype in the IL-23 mouse model of psoriasis. Subsequently, we photocaged this molecule with a coumarin moiety to yield the first photosensitive A3R agonist, MRS7344, which in photopharmacological experiments prevented the psoriatic-like phenotype in the IL-23 animal model. Thus, we have demonstrated the feasibility of using a non-invasive, site-specific, light-directed approach to psoriasis treatment.