Induction of interleukin-10 in the T helper type 17 effector population by the G protein coupled estrogen receptor (GPER) agonist G-1

Abstract

Interleukin-10 (IL-10) is a potent suppressor of the immune system, commonly produced by CD4⁺ T cells to limit ongoing inflammatory responses minimizing host damage. Many autoimmune diseases are marked by large populations of activated CD4⁺ T cells within the setting of chronic inflammation; therefore, drugs capable of inducing IL-10 production in CD4⁺ T cells would be of great therapeutic value. Previous reports have shown that the small molecule G-1, an agonist of the membrane-bound G-protein-coupled estrogen receptor GPER, attenuates disease in an animal model of autoimmune encephalomyelitis. However, the direct effects of G-1 on CD4⁺ T-cell populations remain unknown. Using ex vivo cultures of purified CD4⁺ T cells, we show that G-1 elicits IL-10 expression in T helper type 17 (Th17) -polarized cells, increasing the number of IL-10⁺ and IL-10⁺ IL-17A⁺ cells via de novo induction of IL-10. T-cell cultures differentiated in the presence of G-1 secreted threefold more IL-10, with no change in IL-17A, tumour necrosis factor-α, or interferon-γ. Moreover, inhibition of extracellular signal-regulated kinase (but not p38 or Jun N-terminal kinase) signalling blocked the response, while analysis of Foxp3 and RORγt expression demonstrated increased numbers of IL-10⁺ cells in both the Th17 (RORγt⁺) and Foxp3⁺ RORγt⁺ hybrid T-cell compartments. Our findings translated in vivo as systemic treatment of male mice with G-1 led to increased IL-10 secretion from splenocytes following T-cell receptor cross-linking. These results demonstrate that G-1 acts directly on CD4⁺ T cells, and to our knowledge provide the first example of a synthetic small molecule capable of eliciting IL-10 expression in Th17 or hybrid T-cell populations.