Inhibition of the NLRP3 inflammasome by progesterone is attenuated by abnormal autophagy induction in endometriotic cyst stromal cells: implications for endometriosis

The NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome is a cytosolic multi-protein complex that induces inflammation and is known to be regulated negatively by autophagy. Previous studies reported an abnormal induction of autophagy linked to progesterone resistance in human endometriotic cells. Therefore, an aberrant autophagy induction response to progesterone might contribute to the altered inflammatory response observed in endometriotic tissues. To evaluate this hypothesis, we elucidate whether regulation of the NLRP3 inflammasome by ovarian steroids is mediated by autophagy in human endometrial stromal cells (normal endometrial stromal cells (NESCs)) from patients with uterine leiomyoma (presumed normal) and whether abnormal autophagy induction in endometriotic cyst stromal cells (ECSCs) affects NLRP3 inflammasome-induced interleukin-1β (IL-1β) production. Our results show that estrogen enhanced NLRP3 inflammasome activation in NESCs, resulting in increased IL-1β production. Progesterone decreased NLRP3 inflammasome activity with an increase in autophagy induction in estrogen-treated NESCs. Inhibition of NLRP3 inflammasome activity by progesterone was blocked by autophagy inhibition. However, progesterone failed to change NLRP3 inflammasome activity and autophagy induction in estrogen-treated ECSCs. In contrast, dienogest, a specific progesterone receptor agonist, reduced NLRP3 inflammasome-mediated IL-1β production through autophagy induction in ECSCs. Furthermore, autophagy induction was decreased and NLRP3 inflammasome activity was increased in endometriotic tissues, which was reversed by preoperative administration of dienogest. In conclusion, our results suggest that progesterone inhibits NLRP3 inflammasome activation through autophagy in endometrial stromal cells. However, this inhibitory effect is attenuated in endometriotic stromal cells due to an aberrant autophagic response to progesterone, which could lead to an altered inflammatory response in endometriosis.