DHT and Insulin Upregulate Secretion of the Soluble Decoy Receptor of IL-33 From Decidualized Endometrial Stromal Cells

Abstract

Interleukin 33 (IL-33) signaling regulates most of the key processes of pregnancy, including decidualization, trophoblast proliferation and invasion, vascular remodeling, and placental growth. Accordingly, dysregulation of IL-33, its membrane-bound receptor (ST2L, transducer of IL-33 signaling), and its soluble decoy receptor (sST2, inhibitor of IL-33 signaling) has been linked to a wide range of adverse pregnancy outcomes that are common in women with obesity and polycystic ovary syndrome, that is, conditions associated with hyperandrogenism, insulin resistance, and compensatory hyperinsulinemia. To reveal if androgens and insulin might modulate uteroplacental IL-33 signaling, we investigated the effect of dihydrotestosterone (DHT) and/or insulin on the expression of ST2L and sST2 (along with the activity of their promoter regions), IL-33 and sIL1RAP (heterodimerization partner of sST2), during in vitro decidualization of endometrial stromal cells from 9 healthy women. DHT and insulin markedly upregulated sST2 secretion, in addition to the upregulation of its messenger RNA (mRNA) expression, while the proximal ST2 promoter, from which the sST2 transcript originates, was upregulated by insulin, and in a synergistic manner by DHT and insulin combination treatment. On the other hand, sIL1RAP was slightly downregulated by insulin and IL-33 mRNA expression was not affected by any of the hormones, while ST2L mRNA expression and transcription from its promoter region (distal ST2 promoter) could not be detected or showed a negligibly low level. We hypothesize that high levels of androgens and insulin might lead to subfertility and pregnancy complications, at least partially, through the sST2-dependent downregulation of uteroplacental IL-33 signaling.

Keywords: DHT; IL-33; decidualization; endometrium; insulin; sST2.

Figure 1.

Effects of dihydrotestosterone (DHT) and insulin on short, soluble IL-33 receptor (sST2) messenger RNA (mRNA) expression, sST2 protein secretion, and proximal ST2 promoter activity in in vitro decidualized human endometrial stromal cells (ESCs). A and B, Relative levels of sST2 mRNA expression after 6 days in response to DHT and/or insulin in decidualized in vitro (treated with medroxyprogesterone-17-acetate [MPA] and dibutyryl–cyclic adenosine monophosphate [db-cAMP]) ESCs of 9 healthy volunteers. Main effect of DHT: P less than .05; main effect of insulin: P less than .001. C and D, sST2 protein expression in the conditioned media of in vitro decidualized (treated with MPA and db-cAMP) ESCs of 9 healthy volunteers after 6 days in response to DHT and/or insulin. Main effect of DHT: P less than .05; main effect of insulin: P less than .0001. E and F, Relative levels of ST2 mRNA originating from the proximal ST2 promoter after 6 days in response to DHT and/or insulin in decidualized in vitro (treated with MPA and db-cAMP) ESCs of 9 healthy volunteers. Interaction effect between insulin and DHT: P = .068. Data are shown as individual values (A, C, E) and as a box plot, representing median, interquartile ranges, and ranges (B, D, and F).

Figure 1.

Effects of dihydrotestosterone (DHT) and insulin on short, soluble IL-33 receptor (sST2) messenger RNA (mRNA) expression, sST2 protein secretion, and proximal ST2 promoter activity in in vitro decidualized human endometrial stromal cells (ESCs). A and B, Relative levels of sST2 mRNA expression after 6 days in response to DHT and/or insulin in decidualized in vitro (treated with medroxyprogesterone-17-acetate [MPA] and dibutyryl–cyclic adenosine monophosphate [db-cAMP]) ESCs of 9 healthy volunteers. Main effect of DHT: P less than .05; main effect of insulin: P less than .001. C and D, sST2 protein expression in the conditioned media of in vitro decidualized (treated with MPA and db-cAMP) ESCs of 9 healthy volunteers after 6 days in response to DHT and/or insulin. Main effect of DHT: P less than .05; main effect of insulin: P less than .0001. E and F, Relative levels of ST2 mRNA originating from the proximal ST2 promoter after 6 days in response to DHT and/or insulin in decidualized in vitro (treated with MPA and db-cAMP) ESCs of 9 healthy volunteers. Interaction effect between insulin and DHT: P = .068. Data are shown as individual values (A, C, E) and as a box plot, representing median, interquartile ranges, and ranges (B, D, and F).