The IL-2/STAT5 Axis Activates Treg Cells and Suppresses the Pregnancy-Harmful Pro-Inflammatory Response of Th17 Cells in Mice

Abstract

Background: Recurrent pregnancy loss (RPL) is characterized by multiple miscarriages before reaching 20 weeks of pregnancy, affecting women in their reproductive age. This study aimed to investigate the effect of interleukin-2 (IL-2)/signal transducer and activator of transcription 5 (STAT5) axis on the RPL and its association with regulatory T cells (Treg) and T helper cells (Th) 17. Methods: The female CBA/J mice were used to construct the RPL model by mating with male DBA/2 mice. The IL-2 administration was used to increase the IL-2 content and activate IL-2/STAT5 axis, and the IL-2 plus STAT5 inhibitor was used to increase the IL-2 content while at the same time inactivate the IL-2/STAT5 axis. Moreover, the resorption rate in mice was evaluated. In the mice uteri tissues and intracardiac blood sera, the levels of IL-2 and phosphorylated (p)-STAT5/STAT5, as well as levels of cytokines and factors related to Treg and Th17 cells were assessed using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis. The inflammation associated cytokines in intracardiac blood sera were detected. Additionally, the peripheral blood mononuclear cells (PBMCs) and the single-cell suspension of the spleen tissues were prepared and analyzed employing flow cytometry to determine the percentage of both Th17 cells and Treg cells. Results: IL-2 treatment increased the activation of the IL-2/STAT5 axis and decreased resorption in mice (p < 0.01), which was reversed following STAT5 inhibitor (p < 0.01). Moreover, the IL-2-induced IL-2/STAT5 axis activation promoted the expression of forkhead box P3 (Foxp3), IL-10, and transforming growth factor-beta (TGF-β) while decreasing the expression of retinoid-related orphan receptor gamma t (RORγt), IL-17 and IL-22 (p < 0.001), which was reversed by STAT5 inhibitor (p < 0.001). Furthermore, the activation of the IL-2/STAT5 axis decreased the levels of IL-1β, tumour necrosis factor-alpha (TNF-α), IL-6, Interferon-gamma (IFN-γ), granulocyte-macrophage colony-stimulating factor (GM-CSF), and Th17 percentage while increasing the levels of IL-4 and Treg percentage (p < 0.001), which was reversed with the disruption of the IL-2/STAT5 axis activation (p < 0.01). Conclusion: The IL-2/STAT5 axis can activate Treg cells while suppressing the Th17 cells and their associated inflammatory response, leading to effects on protecting pregnant mice from miscarriage. Thus, the IL-2/STAT5 axis could be a potential therapeutic target for treating RPL.