Sex steroid hormones regulate constitutive expression ofCyp2e1in female mouse liver

Abstract

Konstandi M, Cheng J, Gonzalez FJ. Sex steroid hormones regulate constitutive expression of Cyp2e1 in female mouse liver. Am J Physiol Endocrinol Metab 304: E1118 -E1128, 2013. First published April 2, 2013; doi:10.1152/ajpendo.00585.2012.-CYP2E1 is of paramount toxicological significance because it metabolically activates a large number of low-molecular-weight toxicants and carcinogens. In this context, factors that interfere with Cyp2e1 regulation may critically affect xenobiotic toxicity and carcinogenicity. The aim of this study was to investigate the role of female steroid hormones in the regulation of CYP2E1, as estrogens and progesterone are the bases of contraceptives and hormonal replacement therapy in menopausal women. Interestingly, a fluctuation in the hepatic expression pattern of Cyp2e1 was revealed in the different phases of the estrous cycle of female mice, with higher Cyp2e1 expression at estrus (E) and lower at methestrus (ME), highly correlated with that in plasma gonadal hormone levels. Depletion of sex steroids by ovariectomy repressed Cyp2e1 expression to levels similar to those detected in males and cyclic females at ME. Hormonal supplementation brought Cyp2e1 expression back to levels detected at E. The role of progesterone appeared to be more prominent than that of 17␤-estradiol. Progesterone-induced Cyp2e1 upregulation could be attributed to inactivation of the insulin/PI3K/Akt/FOXO1 signaling pathway. Tamoxifen, an anti-estrogen, repressed Cyp2e1 expression potentially via activation of the PI3K/Akt/FOXO1 and GH/STAT5b-linked pathways. The sex steroid hormone-related changes in hepatic Cyp2e1 expression were highly correlated with those observed in Hnf-1␣, ␤-catenin, and Srebp-1c. In conclusion, female steroid hormones are clearly involved in the regulation of CYP2E1, thus affecting the metabolism of a plethora of toxicants and carcinogenic agents, conditions that may trigger several pathologies or exacerbate the outcomes of various pathophysiological states.Cyp2e1; 17␤-estradiol; progesterone; estrous cycle; mice PITUITARY HORMONES, in particular, growth hormone (GH), are considered critical in Cyp2e1 regulation. Previous studies revealed that pituitary hormone depletion by hypophysectomy resulted in Cyp2e1 upregulation in the liver of rats and GH supplementation normalized Cyp2e1 expression to constitutive levels by suppressing Cyp2e1 transcription (11,28,70,71,80). It is of interest to note that sex steroid hormones target complex regulatory dynamics including GH secretion. On the one hand, they augment GH-secretory burst by amplifying feedforward [via both GH-releasing hormone, GH-releasing peptide(s)] and on the other hand they attenuate feedback (imposed by somatostatin and GH). The role of testosterone is less clear (49,67). Previous studies in humans and experimental animals presented contradictory findings regarding sex differentiation in CYP2E1 constitutive expression and the role of sex steroid hormones in this regulation (5,11,29,33,34,59). This contradiction is probably du...

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