Novel aryl hydrocarbon receptor modulator promotes immunosupressive immune response by stimulating T regulatory cells in the gut

Introduction: The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor which is highly expressed in mucosal tissues - by epithelial cells and immune cells such as Th17 CD4+ and T reg- ulatory cells (Treg). Besides its function of clearing environmental pollutants from the body, it was also revealed that AhR has immunoregulatory effects, thus becoming a potential therapeutic target for mod- ulating the immune response. For that purpose we tested a novel synthetic AhR modulator under the code name C43. Methods: CYP1A1 (downstream effector of AhR) activation was tested by the EROD assay. Sort-purified CD4+ cells from mesenteric lymph nodes (MLN) were treated with C43 for 24 h. Zebrafish embryos were used to test the toxicity of C43. Male C57BL/6 mice orally received C43 (10 mg/kg) for 5 consecutive days, after which MLN were harvested. Phenotype and function of the cells were analyzed by flow cytometry. Results: C43 showed mild AhR agonistic activity. After treating the sort-purified CD4+ cells with C43, there was a shift in the Th17/Treg ratio in favour of the latter. C43 showed no signs of toxicity when tested on zebrafish embryos. MLN cells from mice that received C43 revealed a shift in the Th1/Treg ratio in favour of Tregs, with a documented rise of the portion of Tregs that expressed CYP1A1 in comparison with the control group of mice. Conclusion: C43 can modulate the immune response through the intestine by promoting the im- munosuppressive Treg population

Development of Type 1 Diabetes in Mice Is Associated with a Decrease in IL-2-Producing ILC3 and FoxP3⁺ Treg in the Small Intestine

Recent data indicate the link between the number and function of T regulatory cells (Treg) in the gut immune tissue and initiation and development of autoimmunity associated with type 1 diabetes (T1D). Since type 3 innate lymphoid cells (ILC3) in the small intestine are essential for maintaining FoxP3+ Treg and there are no data about the possible role of ILC3 in T1D pathogenesis, the aim of this study was to explore ILC3-Treg link during the development of T1D. Mature diabetic NOD mice had lower frequencies of IL-2-producing ILC3 and Treg in small intestine lamina propria (SILP) compared to prediabetic NOD mice. Similarly, in multiple low doses of streptozotocin (MLDS)-induced T1D in C57BL/6 mice, hyperglycemic mice exhibited lower numbers of ILC3, IL-2+ ILC3 and Treg in SILP compared to healthy controls. To boost T1D severity, mice were treated with broad-spectrum antibiotics (ABX) for 14 days prior to T1D induction by MLDS. The higher incidence of T1D in ABX-treated mice was associated with significantly lower frequencies of IL-2+ ILC3 and FoxP3+ Treg in SILP compared with mice without ABX treatment. The obtained findings show that the lower proportions of IL-2-expressing ILC3 and FoxP3+ Treg in SILP coincided with diabetes progression and severity

Mesenchymal Stem Cells from Mouse Hair Follicles Inhibit the Development of Type 1 Diabetes

Mesenchymal stem cells (MSCs) are known for their immunosuppressive properties. Based on the demonstrated anti-inflammatory effect of mouse MSCs from hair follicles (moMSCORS) in a murine wound closure model, this study evaluates their potential for preventing type 1 diabetes (T1D) in C57BL/6 mice. T1D was induced in C57BL/6 mice by repeated low doses of streptozotocin. moMSCORS were injected intravenously on weekly basis. moMSCORS reduced T1D incidence, the insulitis stage, and preserved insulin production in treated animals. moMSCORS primarily exerted immunomodulatory effects by inhibiting CD4+ T cell proliferation and activation. Ex vivo analysis indicated that moMSCORS modified the cellular immune profile within pancreatic lymph nodes and pancreatic infiltrates by reducing the numbers of M1 pro-inflammatory macrophages and T helper 17 cells and upscaling the immunosuppressive T regulatory cells. The proportion of pathogenic insulin-specific CD4+ T cells was down-scaled in the lymph nodes, likely via soluble factors. The moMSCORS detected in the pancreatic infiltrates of treated mice presumably exerted the observed suppressive effect on CD4+ through direct contact. moMSCORS alleviated T1D symptoms in the mouse, qualifying as a candidate for therapeutic products by multiple advantages: non-invasive sampling by epilation, easy access, permanent availability, scalability, and benefits of auto-transplantation