The human aldose reductase AKR1B1 qualifies as the primary prostaglandin F synthase in the endometrium

Context: Prostaglandins (PGs) E2 and PGF2α are produced in the endometrium and are important for menstruation and fertility. Dysmenorrhea is associated with increased production of PGF2α relative to PGE2, and the opposite is true for menorrhagia. The pathways leading to PGE2 biosynthesis are well described, but little is known for PGF2α. Aldoketoreductase (AKR)-1C3, the only PGF synthase identified in the human, cannot explain the production of PGF2α by endometrial cells. AKR1B1 appears to be an alternate candidate with promising therapeutic value.

Objective: The objective of the study was to address whether AKR1B1 (gene ID 231) is a functional PGF2α synthase in the human endometrium and a valid therapeutic target for menstrual pain.

Design: The design of the study was basic laboratory analyses to identify gene expression and protein levels associated with PGF2α production in endometrial tissues and endometrial cells from cycling women aged between 23 and 52 yr undergoing biopsies or hysterectomy for diverse gynecological disorders.

Results: AKR1B1 is expressed at a high level during the menstrual cycle during the secretory phase and in both epithelial and stromal cells, whereas AKR1C3 was found only in epithelial cells. Purified recombinant AKR1B1 protein, gene silencing, and transient transfection experiments all concur to demonstrate that this Enzyme is a functional PGF synthase. Ponalrestat, a specific inhibitor developed to block AKR1B1 activity, reduced PGF2α production in response to IL-1β in both cultured endometrial cells and endometrial explants.

Conclusions: The human Aldose Reductase AKR1B1 currently associated with diabetes complications is also a highly functional PGF synthase responsible for PGF2α production in the human endometrium and a potential target for treatment of menstrual disorders.