Blockade of Phosphatidylinositol 3-Kinase (PI3K)δ or PI3Kγ Reduces IL-17 and Ameliorates Imiquimod-Induced Psoriasis-like Dermatitis

Psoriasis is a chronic inflammatory skin disease triggered by interplay between immune mediators from both innate and adaptive immune systems and skin tissue, in which the IL-23/IL-17 axis is critical. PI3Kδ and PI3Kγ play important roles in various immune cell functions. We found that mice lacking functional PI3Kδ or PI3Kγ are largely protected from imiquimod (IMQ)-induced psoriasis-like dermatitis, correlating with reduced IL-17 levels in the lesions, serum, and the draining lymph nodes. TCRγδ T cells were the major IL-17–producing population in the draining lymph nodes and were significantly diminished in IMQ-treated PI3Kδ knockin and PI3Kγ knockout mice. We also show that PI3Kδ and PI3Kγ inhibitors reduced IFN-γ production by human TCRγδ T cells and IL-17 and IFN-γ production by PBMCs from psoriatic or healthy donors. In addition, inhibition of PI3Kγ, but not PI3Kδ, blocked chemotaxis of CCR6 + IL-17–producing cells from IMQ-treated mice or healthy human donors. Taken together, these data indicate that PI3Kδ and/or PI3Kγ inhibitors should be considered for treating IL-17–driven diseases, such as psoriasis.