Expression of hepatic and ovarian cytochrome P450 during estrous cycle in rats

Human CYP2D6 varies across the estrous cycle in brains of transgenic mice altering drug response

Cytochrome P450 (CYP) 2Ds are drug metabolizing enzymes found in brain and liver which metabolize numerous centrally acting drugs. Inhibition and induction of CYP2D-mediated metabolism in rodent brain alters brain drug and metabolite concentrations and resulting drug response. In female rats, brain CYP2D metabolism varies across the estrous cycle and with exogenous estrogen, changing brain drug concentrations and response. In this study harmine-induced hypothermia was lower in humanized CYP2D6 transgenic female mice during estrus compared to diestrus. Pretreatment into the cerebral ventricles with propranolol, a selective irreversible inhibitor of human CYP2D6 in brain, increased hypothermia in estrus but not in diestrus. In vivo enzyme activity was higher in brains of transgenic mice in estrus compared to diestrus and was lower after pretreatment with inhibitor in estrus, but not in diestrus. Hepatic activity and plasma harmine concentrations were unaffected by either estrous phase or inhibition of brain CYP2D6. In wild-type female mice, harmine-induced hypothermia was unaffected by either estrous phase or inhibitor pretreatment. Male mice were used as positive controls, where pretreatment with inhibitor increased harmine-induced hypothermia in transgenic but not wild-type, mice. This study provides evidence for female hormone cycle-based regulation of drug metabolism by human CYP2D6 in brain and resulting drug response. This suggests that brain CYP2D6 metabolism may vary, for example, during the menstrual cycle, pregnancy, or menopause, or while taking oral contraceptives or hormone therapy. This variation could contribute to individual differences in response to centrally acting CYP2D6-substrate drugs by altering local brain drug and/or metabolite concentrations.

Liver and ovarian toxicities boosted by bisphenol and gamma radiation in female albino rats

Bisphenol A (BPA), a carbon-based synthetic polymer compound, was newly classified as an environmental toxicant and an endocrine-disrupting chemical leading to abnormalities in cell proliferation, apoptosis, or migration that contributes to cancer development and progression. This study aims to evaluate the effect of the elevation of γ- radiation dose and BPA on the liver and ovaries of female rats. In this study, eighty female albino rats (130-150 g) were used in this work. Rats in this experiment received BPA in ethanol (50 mg/kg b. wt.) for 30 days, day after day, and in the irradiated groups, animals were administered BPA and then exposed to γ- radiation in doses (2, 4, and 6 Gy) one shot dose. Several members of the cytochrome family were examined. Exposure to γ-radiation and BPA showed an increase in cytochrome P450 and b5 fold change. Further, BPA and γ-radiation activate α and β estrogen receptors and also downregulate aromatase (CYT19) fold change. The current results also revealed that BPA and/or γ-radiation regulate the protein expression of the PI3K/Akt signaling pathway. The steroidogenic acute regulatory protein (StAR) appeared to be targeted by BPA and γ-radiation and its relative expression was elevated significantly by raising the γ-radiation dose. In conclusion, exposure to BPA, an endocrine-disrupting chemical, leads to marked toxicity. Additionally, toxicity is heightened by increasing the γ-radiation dose, either alone or in combination with BPA.

Safety and Efficacy Assessment of Isoflavones from Pueraria (Kudzu) Flower Extract in Ovariectomised Mice: A Comparison with Soy Isoflavones

Numerous Foods with Function Claims that contain the extract of Pueraria flower (kudzu) isoflavones (PFI) are available in the Japanese market. These are labelled with function claims of reducing visceral fat. However, these foods have not undergone proper safety assessment such as the evaluation of their oestrogenic activity and effects on drug-metabolising enzymes (cytochrome P-450: CYP) in the liver. This study evaluated the estrogenic effect and the hepatic CYP activity and mRNA expression in normal female mice as a safety assessment of PFI (Experiment 1). In addition, the bone mineral density and visceral fat weight in ovariectomised mice (OVX) compared to soy isoflavones (SI) was evaluated to assess the efficacy of PFI (Experiment 2). OVX control fed a control diet, OVX fed a PFI diet (the recommended human intake of PFI), OVX fed a PFI20 diet (20- times the recommended PFI), OVX fed an SI diet (the recommended human intake of SI), and OVX fed an SI20 diet (20 -times the recommended intake of SI) for 28 days in Experiment 2. Body, liver, and visceral fat weights were not affected by the PFI, PFI20, SI, or SI20 diets. The hepatic CYP1A and CYP3A activities were elevated by the SI20 treatment. Ovariectomy-induced bone loss was inhibited by the SI20 treatment, but not by the PFI20 treatment. These results suggest that (1) PFI intake in human doses had no oestrogenic properties and did not affect CYP activity in the liver; (2) there was no evidence that PFI affects the amount of visceral fat in OVX mice.

Prolactin Upregulates Female-Predominant P450 Gene Expressions and Downregulates Male-Predominant Gene Expressions in Mouse Liver

Prolactin is a polypeptide hormone with over 300 separate biologic activities. Its serum level is increased during pregnancy and lactation, and it has been reported that pregnancy and lactation affect drug and steroid metabolism in mice and humans. Several studies reported that pregnancy or lactation influences liver cytochrome P450 (P450) expression and its activity, affecting the biosynthesis of steroids and xenobiotics through growth hormone or sex hormones; however, the role of prolactin as the regulator of liver P450 expression has not been elucidated so far. In the present study, we focused on prolactin as the regulator of expression of liver sex-predominant genes, including P450s. To investigate the role of prolactin in the hepatic gene expressions, pCAGGS expression vector containing mouse prolactin cDNA was transfected by hydrodynamic injection into both male and female mice. Hyperprolactinemia phosphorylated signal transducer and activator of transcription 5 in the liver and augmented female mouse liver mRNA expression of Cyp3a16, Cyp3a41, Cyp3a44, Cyp2b9, and prolactin receptor genes, whose expressions were female-predominant in hepatocytes. Moreover, liver expression of male-predominant genes such as Cyp2d9, Cyp7b1, Mup1, and Alas2 were reduced in male mice with hyperprolactinemia. The serum levels of conventional regulators of hepatic gene expressions, growth hormone, and testosterone were not affected by hyperprolactinemia. We demonstrated that prolactin upregulated female-predominant genes in female mice and downregulated male-predominant genes in male mice. We conjecture that higher concentration of prolactin would alter steroid and xenobiotic metabolisms by modulating hepatic P450 gene expressions during pregnancy and lactation.

Progesterone production is affected by unfolded protein response (UPR) signaling during the luteal phase in mice

AIMS

We examined whether the three unfolded protein response (UPR) signaling pathways, which are activated in response to endoplasmic reticulum (ER)-stress, are involved in progesterone production in the luteal cells of the corpus luteum (CL) during the mouse estrous cycle.

MAIN METHODS

The luteal phase of C57BL/6 female mice (8 weeks old) was divided into two stages: the functional stage (16, 24, and 48 h) and the regression stage (72 and 96 h). Western blotting and reverse transcription (RT)-PCR were performed to analyze UPR protein/gene expression levels in each stage. We investigated whether ER stress affects the progesterone production by using Tm (0.5 μg/g BW) or TUDCA (0.5 μg/g BW) through intra-peritoneal injection.

KEY FINDINGS

Our results indicate that expressions of Grp78/Bip, p-eIF2α/ATF4, p50ATF6, and p-IRE1/sXBP1 induced by UPR activation were predominantly maintained in functional and early regression stages of the CL. Furthermore, the expression of p-JNK, CHOP, and cleaved caspase3 as ER-stress mediated apoptotic factors increased during the regression stage. Cleaved caspase3 levels increased in the late-regression stage after p-JNK and CHOP expression in the early-regression stage. Additionally, although progesterone secretion and levels of steroidogenic enzymes decreased following intra-peritoneal injection of Tunicamycin, an ER stress inducer, the expression of Grp78/Bip, p50ATF6, and CHOP dramatically increased.

SIGNIFICANCE

These results suggest that the UPR signaling pathways activated in response to ER stress may play important roles in the regulation of the CL function. Furthermore, our findings enhance the understanding of the basic mechanisms affecting the CL life span.

Estradiol activates epithelial sodium channels in rat alveolar cells through the G protein-coupled estrogen receptor

Female sex predisposes individuals to poorer outcomes during respiratory disorders like cystic fibrosis and influenza-associated pneumonia. A common link between these disorders is dysregulation of alveolar fluid clearance via disruption of epithelial sodium channel (ENaC) activity. Recent evidence suggests that female sex hormones directly regulate expression and activity of alveolar ENaC. In our study, we identified the mechanism by which estradiol (E2) or progesterone (P4) independently regulates alveolar ENaC. Using cell-attached patch clamp, we measured ENaC single-channel activity in a rat alveolar cell line (L2) in response to overnight exposure to either E2 or P4. In contrast to P4, E2 increased ENaC channel activity (NPo) through an increase in channel open probability (Po) and an increased number of patches with observable channel activity. Apical plasma membrane abundance of the ENaC α-subunit (αENaC) more than doubled in response to E2 as determined by cell surface biotinylation. αENaC membrane abundance was approximately threefold greater in lungs from female rats in proestrus, when serum E2 is greatest, compared with diestrus, when it is lowest. Our results also revealed a significant role for the G protein-coupled estrogen receptor (Gper) to mediate E2's effects on ENaC. Overall, our results demonstrate that E2 signaling through Gper selectively activates alveolar ENaC through an effect on channel gating and channel density, the latter via greater trafficking of channels to the plasma membrane. The results presented herein implicate E2-mediated regulation of alveolar sodium channels in the sex differences observed in the pathogenesis of several pulmonary diseases.

Sex and gender differences in cardiovascular drug therapy

This chapter outlines sex differences in pharmacokinetics and pharmacodynamics of the most frequently used drugs in cardiovascular diseases, e.g., coronary artery disease, hypertension, heart failure. Retrospective analysis of previously published drug trials revealed marked sex differences in efficacy and adverse effects in a number of cardiovascular drugs. This includes a higher mortality among women taking digoxin for heart failure, more torsade de pointes arrhythmia in QT prolonging drugs and more cough with ACE inhibitors. Trends towards a greater benefit for women and/or female animals have been observed in some studies for endothelin receptor antagonists, the calcium channel blocker amlodipine, the ACE-inhibitor ramipril and the aldosterone antagonist eplerenone. However, reproduction of these results in independent studies and solid statistical evidence is still lacking. Some drugs require a particularly careful dose adaptation in women: the beta-blocker metoprolol, the calcium channel blocker verapamil, loop-, and thiazide diuretics. In conclusion, sex differences in pharmacokinetics and pharmacodynamics have to be taken into account for cardiovascular drug therapy in women.

Cytochrome P450-mediated herb-drug interaction potential of Galgeun-tang

We evaluated the herb-drug interaction potential of Galgeun-tang (GGT) extracts, mediated by cytochrome P450 (CYP) inhibition/induction. Further, the effects of fermentation on the CYP-mediated herb-drug interaction potential of GGT extracts were determined. As measured by LC-ESI/MS/MS, GGT extracts (0-300μg/mL) showed no inhibitory activity toward eight CYP isoforms (1A2, 2A6, 2B6, 2C9, 2C19, 2D6, 2E1, and 3A4) in pooled human liver microsomes, suggesting that GGT may have low potential for herb-drug interactions mediated by CYP inhibition. Hepatic CYP expression and activity in rats treated with GGT extracts twice per day for 1week was examined. Among the tested CYP isoforms (1A1, 1A2, 1B1, 2B1, 2C11, 2E1, 3A1, 3A2, and 4A1), CYP1B1 and 4A1 were increased by GGT extracts. Hepatic activities of 7-ethoxyresorufin-O-deethylase, 7-pentoxyresorufin-O-depentylase, and chlorzoxazone 6-hydroxylase, but not midazolam hydroxylase were also elevated. These results raise the possibility that GGT extracts may increase the toxicity of environmental toxicants through the elevating CYP-dependent metabolic activation. Interestingly, the increases in CYP1B1 and CYP4A1 levels, and 7-ethoxyresorufin-O-deethylase, 7-pentoxyresorufin-O-depentylase, and chlorzoxazone 6-hydroxylase activities were attenuated by fermentation of GGT extract using Lactobacillus plantarum KFRI 402, but not 144. Further studies are needed to identify the CYP regulatory component(s) from GGT and determination its metabolism.

Bayesian Analysis of a Lipid-Based Physiologically Based Toxicokinetic Model for a Mixture of PCBs in Rats

A lipid-based physiologically based toxicokinetic (PBTK) model has been developed for a mixture of six polychlorinated biphenyls (PCBs) in rats. The aim of this study was to apply population Bayesian analysis to a lipid PBTK model, while incorporating an internal exposure-response model linking enzyme induction and metabolic rate. Lipid-based physiologically based toxicokinetic models are a subset of PBTK models that can simulate concentrations of highly lipophilic compounds in tissue lipids, without the need for partition coefficients. A hierarchical treatment of population metabolic parameters and a CYP450 induction model were incorporated into the lipid-based PBTK framework, and Markov-Chain Monte Carlo was applied to in vivo data. A mass balance of CYP1A and CYP2B in the liver was necessary to model PCB metabolism at high doses. The linked PBTK/induction model remained on a lipid basis and was capable of modeling PCB concentrations in multiple tissues for all dose levels and dose profiles.