1-Methyl-tryptophan attenuates regulatory T cells differentiation due to the inhibition of estrogen-IDO1-MRC2 axis in endometriosis

Abstract

Foxp3+ regulatory T (Treg) cells contribute to the local dysfunctional immune environment in endometriosis, an estrogen-dependent gynecological disease, which affects the function of ectopic endometrial tissue clearance by the immune system. The reason for the high percentage of peritoneal Treg in endometriosis patients is unknown. Here, we show that the proportion of peritoneal Treg cells increases as endometriosis progresses. To determine the probable mechanism, we established a naive T cell-macrophage-endometrial stromal cell (ESC) co-culture system to mimic the peritoneal cavity microenvironment. After adding 1-methyl-tryptophan (1-MT), a specific inhibitor of indoleamine 2,3-dioxygenase-1 (IDO1), to the co-culture system, we found that the differentiation of Treg cells, mainly IL-10+ Treg cells, decreased. Therefore, 1-MT-pretreated ESCs-educated Treg cells performed impaired suppressive function. Moreover, estrogen promoted the differentiation of Treg cells by elevating IDO1 expression in the ectopic lesion. Subsequently, we examined mannose receptor C, type 2 (MRC2), which is an up-stream molecule of IL-10, by bioinformatics analysis and real-time PCR validation. MRC2 expression in ectopic ESCs was notably lower than that in normal ESCs, which further negatively regulated the expression of IDO1 and Ki-67 in ESCs. Furthermore, MRC2 is required for Treg differentiation in the ectopic lesion, especially that for CD4high Treg. Therefore, MRC2-silenced ESCs-educated Treg manifested a stronger suppressive function in vitro. Consistently, the percentage of Treg increased when MRC2-shRNA was administered in the peritoneal cavity of endometriosis-disease mice model. Besides, 1-MT improved the condition of endometriosis, in terms of reducing the number and weight of total ectopic lesions in vivo. These results indicate that the estrogen-IDO1-MRC2 axis participates in the differentiation and function of Treg and is involved in the development of endometriosis. Thus, blockage of IDO1 in the ectopic lesion, which does not influence physiological functions of estrogen, may be considered a potential therapy for endometriosis.

Involvement of immune cells in the pathogenesis of endometriosis

“…Many studies have shown that Treg are increased in the peritoneal cavity of endometriosis patients; however, two studies did not find a significant difference . In a mouse study, the inhibition of Treg induction (differentiation) reduced the number and weight of endometriotic lesions . These findings indicate that Treg play a role in endometriosis progress, although further studies are required to discover the mechanism and therapeutic targets.…”

“…73,88 In a mouse study, the inhibition of Treg induction (differentiation) reduced the number and weight of endometriotic lesions. 87 These findings indicate that Treg play a role in endometriosis progress, although further studies are required to discover the mechanism and therapeutic targets.…”

“…Treg is another subset of helper T cells and they are known to maintain immunological tolerance. 66 Many studies have shown that Treg are increased in the peritoneal cavity of endometriosis patients [84][85][86][87] ; however, two studies did not find a significant difference. 73,88 In a mouse study, the inhibition of Treg induction (differentiation) reduced the number and weight of endometriotic lesions.…”

γ‐Secretase inhibition affects viability, apoptosis, and the stem cell phenotype of endometriotic cells

“…Moreover, PODXL expression was significantly upregulated in these cells, whereas a downregulation was observed in 12Z cells (Figure A,B). As GSI affected the cell viability of our cell models, we evaluated a potential GSI‐induced dysregulation of IDO1 , which has been linked to proliferation, invasive growth, and immunomodulatory potential of endometriotic stroma cells . Although GSI treatment did not significantly affect IDO1 mRNA expression in 12Z cells, a trend for an upregulation ( P = 0.077) was observed in the case of patient‐derived endometriotic stroma cells (Figure A,B).…”

“…As GSI affected the cell viability of our cell models, we evaluated a potential GSI-induced dysregulation of IDO1, which has been linked to proliferation, invasive growth, and immunomodulatory potential of endometriotic stroma cells. 18,19 Although GSI treatment did not significantly affect IDO1 mRNA expression in 12Z cells, a trend for an upregulation (P = 0.077) was observed in the case of patient-derived endometriotic stroma cells (Figure 2A,B). In contrast to LIFR, SOX2, and IFITM1, we could not independently confirm a significant regulation of TERT, MNX1, IFITM2, DDX4, FOXA2, Nestin, nanog, WNT1, DES, Lefty, nodal, SOX17, MYOD1, IL6ST, and CGB in 12Z cells (Figure 3).…”