Expression and regulation of Enpp2 in rat uterus during the estrous cycle

Abstract

Ectonucleotide pyrophosphatase/phosphodiestrase 2 (Enpp2) isolated from the supernatant of human melanoma cells is a lysophospholipase D that transforms lysophosphatidylcholine into lysophospatidic acid. Although multiple analyses have investigated the function of Enpp2 in the hypothalamus, its role in the uterus during the estrous cycle is not well understood. In the present study, rat uterine Enpp2 was analyzed by RT-PCR, Western blotting, and immunohistochemistry. Quantitative PCR analysis demonstrated that uterine Enpp2 mRNA was decreased during estrus compared to proestrus and diestrus. To determine whether uterine Enpp2 expression is affected by sex steroid hormones, immature rats were treated with 17β-estradiol (E2), progesterone, or both on postnatal days 14 to 16. Interestingly, the expression of Enpp2 mRNA and protein were down-regulated by E2 in the uterus during estrus but not during proestrus or diestrus, suggesting that Enpp2 may play a role in uterine function during estrus. Enpp2 is primarily localized in the stromal cells of the endometrium during proestrus and estrus. During diestrus, Enpp2 was highly expressed in the epithelial cells of the endometrium. Taken together, these results suggest that uterine Enpp2 may be regulated by E2 and plays a role in reproductive functions during female rat development.

Fig. 1

Uterine ectonucleotide pyrophosphatase/phosphodiestrase 2 (Enpp2) mRNA expression in mature female rats throughout the estrous cycle. There was a significant difference in Enpp2 expression levels during diestrus compared to the other stages (^**p < 0.01, ^***p < 0.001).

Fig. 2

Uterine Enpp2 expression in mature female rats during the estrous cycle. There was a significant difference in Enpp2 expression during diestrus compared to proestrus and estrus (^*p < 0.05, ^**p < 0.01).

Fig. 3

Effects of steroid hormones along with estrogen receptor and progesterone receptor antagonists on uterine Enpp2 mRNA expression. Expression of Enpp2 was analyzed by RT-PCR (^**p < 0.01, ^***p < 0.001). E2: 17β-estradiol, P4: progesterone, ICI: ICI 182780, RU: RU 486.

Fig. 4

Effects of steroid hormones and ER/PR antagonists on uterine Enpp2 protein expression. The expression of Enpp2 protein was analyzed by Western blotting (^**p < 0.01, ^***p < 0.001).

Fig. 5

Localization of Enpp2 expression in the rat uterus. Proestrus (A), estrus (B), and diestrus (C) by immunohistochemistry. Arrows indicate the positive cells. ×400.