Interleukin-1beta increases expression of tryptophan 2,3-dioxygenase and stimulates tryptophan metabolism in ectopic endometrial stromal cells

Abstract

ObjectiveTryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) are enzymes that catalyze the first and rate-limiting step of tryptophan degradation (i.e. from tryptophan to kynurenine) and thereby regulate tryptophan levels. Decrease in tryptophan levels inhibits T cell function and contributes to immune tolerance. While IFNγ increases IDO expression, a molecule that regulates TDO expression remains to be elucidated. We evaluated the effect of interleukin (IL)-1β, a typical endometriosis-associated cytokine, on TDO expression in ectopic endometrial stromal cells (ESCs).DesignExperimental study.Materials and MethodsUnder the approval of Institutional Review Board, ovarian endometriomas were obtained from women who had regular menstrual cycles and underwent laparoscopic surgery. ESCs were isolated from ovarian endometriomas. ESCs were treated with IL-1β for 5 hours to examine gene expression, for 24 hours to examine protein expression, and for 48 hours to examine the enzyme activity. Expression levels of TDO mRNA and IDO mRNA in ESCs were determined by quantitative real-time polymerase chain reaction. TDO protein was detected using western blotting. To study the enzyme activity of TDO and IDO, kynurenine concentration in the conditioned medium was measured.ResultsIL-1β (1 ng/ml) increased TDO mRNA expression to 6.3-fold of control but had no effect on IDO mRNA expression in ESCs. IL-1β (1 ng/ml) increased TDO protein to 1.3-fold in ESCs and also increased kynurenine production to 1.9-fold in the conditioned medium. TDO siRNA suppressed the increase in IL-1β-induced kynurenine production.ConclusionIL-1β increased TDO expression and stimulated tryptophan metabolism in ESCs. The IL-1β-induced increase in TDO expression may enhance immune tolerance to promote endometriosis. ObjectiveTryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) are enzymes that catalyze the first and rate-limiting step of tryptophan degradation (i.e. from tryptophan to kynurenine) and thereby regulate tryptophan levels. Decrease in tryptophan levels inhibits T cell function and contributes to immune tolerance. While IFNγ increases IDO expression, a molecule that regulates TDO expression remains to be elucidated. We evaluated the effect of interleukin (IL)-1β, a typical endometriosis-associated cytokine, on TDO expression in ectopic endometrial stromal cells (ESCs). Tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) are enzymes that catalyze the first and rate-limiting step of tryptophan degradation (i.e. from tryptophan to kynurenine) and thereby regulate tryptophan levels. Decrease in tryptophan levels inhibits T cell function and contributes to immune tolerance. While IFNγ increases IDO expression, a molecule that regulates TDO expression remains to be elucidated. We evaluated the effect of interleukin (IL)-1β, a typical endometriosis-associated cytokine, on TDO expression in ectopic endometrial stromal cells (ESCs). DesignExperimental study. Experimental study. Materials and MethodsUnder the approval of Institutional Review Board, ovarian endometriomas were obtained from women who had regular menstrual cycles and underwent laparoscopic surgery. ESCs were isolated from ovarian endometriomas. ESCs were treated with IL-1β for 5 hours to examine gene expression, for 24 hours to examine protein expression, and for 48 hours to examine the enzyme activity. Expression levels of TDO mRNA and IDO mRNA in ESCs were determined by quantitative real-time polymerase chain reaction. TDO protein was detected using western blotting. To study the enzyme activity of TDO and IDO, kynurenine concentration in the conditioned medium was measured. Under the approval of Institutional Review Board, ovarian endometriomas were obtained from women who had regular menstrual cycles and underwent laparoscopic surgery. ESCs were isolated from ovarian endometriomas. ESCs were treated with IL-1β for 5 hours to examine gene expression, for 24 hours to examine protein expression, and for 48 hours to examine the enzyme activity. Expression levels of TDO mRNA and IDO mRNA in ESCs were determined by quantitative real-time polymerase chain reaction. TDO protein was detected using western blotting. To study the enzyme activity of TDO and IDO, kynurenine concentration in the conditioned medium was measured. ResultsIL-1β (1 ng/ml) increased TDO mRNA expression to 6.3-fold of control but had no effect on IDO mRNA expression in ESCs. IL-1β (1 ng/ml) increased TDO protein to 1.3-fold in ESCs and also increased kynurenine production to 1.9-fold in the conditioned medium. TDO siRNA suppressed the increase in IL-1β-induced kynurenine production. IL-1β (1 ng/ml) increased TDO mRNA expression to 6.3-fold of control but had no effect on IDO mRNA expression in ESCs. IL-1β (1 ng/ml) increased TDO protein to 1.3-fold in ESCs and also increased kynurenine production to 1.9-fold in the conditioned medium. TDO siRNA suppressed the increase in IL-1β-induced kynurenine production. ConclusionIL-1β increased TDO expression and stimulated tryptophan metabolism in ESCs. The IL-1β-induced increase in TDO expression may enhance immune tolerance to promote endometriosis. IL-1β increased TDO expression and stimulated tryptophan metabolism in ESCs. The IL-1β-induced increase in TDO expression may enhance immune tolerance to promote endometriosis.