Gender dictates the nuclear receptor-mediated regulation of CYP3A44

Hepatotropic activity of a betulonic acid based compound

Using the model of cyclophosphamide (CP)-induced immunosuppression in C57BL/6 mice, the hepatotropic effects of a conjugate of betulonic acid with 9-(4-methylpiperazin-1-ylmethyl)-2-(1,2,3-triazolyl) oreozelone (BABC) have been studied. In the liver of treated animals the expression of genes for cytochromes (CYP 1A1, CYP 1A2, CYP 3A44, CYP 2B10, CYP 2C29, CYP 17A1), PPARA, and cytokines (TNF-α, IL-1β, IL-12α, IL-10) and the relative levels of NF-κB p65, GST-π, and NAT-1 proteins were determined. On day six after administration of the compound and CP to animals a significant (3.2-fold) increase in the expression of the CYP 2B10 as compared to the control group was observed. Treatment of mice with the compound and CP also caused a 2.4-fold increase in the mRNA level of the pro-inflammatory TNF-α gene as compared to the group of animals receiving CP. Administration of the studied compound to intact animals was accompanied by a 2.5-fold increase in the IL-1β expression and a 1.8-fold decrease in the IL-10 expression as compared to the control group. An increase in the expression of pro-inflammatory cytokine genes in the liver of animals treated with the compound was accompanied by an increase in the content of NF-κB p65 (by 1.6 times), as well as an increase in the relative amount of NAT-1 protein (by 2.7 times) as compared to control animals.

Toxicological and physiological effects of successive exposure to ochratoxin A at food regulatory limits

Ochratoxin A (OTA), a potent mycotoxin, is a common contaminant of agro-products, which seriously threatens food safety. The OTA regulatory limits vary from different countries/regions. However, little is known about the toxicological effects of successive exposure to regulatory levels of OTA. In this study, feedstuffs contaminated with 0.5-20 μg kg^-1 OTA were evaluated in Sprague-Dawley (SD) rats. During the study, poisoning-associated behaviors, and significant differences of body weight and food intake, were not observed between OTA-treated rats and control group. However, the renal function indexes of blood urea nitrogen (BUN) and creatinine (CR) increased, and architecture destruction of glomeruli and tubuli was observed from the OTA-treated groups. The apoptosis study indicated that at a concentration of 20 μg kg^-1, OTA modulated apoptosis in renal tissues via the Bcl-2/Bax pathway. The results of this study suggest that exposure to low doses of OTA successively at levels lower than the regulatory limits of certain countries could induce nephrotoxicity, and modulate apoptosis. Therefore, agencies pertaining to food safety should establish strict OTA regulatory limits for food and feedstuff.

Synergistic Antitumorigenic Activity of Calcitriol with Curcumin or Resveratrol is Mediated by Angiogenesis Inhibition in Triple Negative Breast Cancer Xenografts

Calcitriol is a multitarget anticancer hormone; however, its effects on angiogenesis remain contradictory. Herein, we tested whether the antiangiogenic phytochemicals curcumin or resveratrol improved calcitriol antitumorigenic effects in vivo. Triple-negative breast cancer tumoral cells (MBCDF-T) were xenografted in nude mice, maintaining treatments for 3 weeks. Tumor onset, volume and microvessel density were significantly reduced in mice coadministered with calcitriol and curcumin (Cal+Cur). Vessel count was also reduced in mice simultaneously treated with calcitriol and resveratrol (Cal+Rsv). Cal+Cur and Cal+Rsv treatments resulted in less tumor activated endothelium, as demonstrated by decreased tumor uptake of integrin-targeted biosensors in vivo. The renal gene expression of Cyp24a1 and Cyp27b1 suggested increased calcitriol bioactivity in the combined regimens. In vitro, the phytochemicals inhibited both MBCDF-T and endothelial cells proliferation, while potentiated calcitriol’s ability to reduce MBCDF-T cell-growth and endothelial cells migration. Resveratrol induced endothelial cell death, as deduced by increased sub-G1 cells accumulation, explaining the reduced tumor vessel number in resveratrol-treated mice, which further diminished when combined with calcitriol. In conclusion, the concomitant administration of calcitriol with curcumin or resveratrol synergistically promoted anticancer effects in vitro and in vivo in human mammary tumor cells. Whereas the results suggest different mechanisms of action of the phytochemicals when coadministered with calcitriol, the converging biological effect was inhibition of tumor neoangiogenesis.

The Mouse Microbiome Is Required for Sex-Specific Diurnal Rhythms of Gene Expression and Metabolism

The circadian clock and associated feeding rhythms have a profound impact on metabolism and the gut microbiome. To what extent microbiota reciprocally affect daily rhythms of physiology in the host remains elusive. Here, we analyzed transcriptome and metabolome profiles of male and female germ-free mice. While mRNA expression of circadian clock genes revealed subtle changes in liver, intestine, and white adipose tissue, germ-free mice showed considerably altered expression of genes associated with rhythmic physiology. Strikingly, the absence of the microbiome attenuated liver sexual dimorphism and sex-specific rhythmicity. The resulting feminization of male and masculinization of female germ-free animals is likely caused by altered sexual development and growth hormone secretion, associated with differential activation of xenobiotic receptors. This defines a novel mechanism by which the microbiome regulates host metabolism.

High fat diet induced obesity is mitigated in Cyp3a-null female mice

Recent studies indicate a role for the constitutive androstane receptor (CAR), pregnane X-receptor (PXR), and hepatic xenobiotic detoxifying CYPs in fatty liver disease or obesity. Therefore, we examined whether Cyp3a-null mice show increased obesity and fatty liver disease following 8-weeks of exposure to a 60% high-fat diet (HFD). Surprisingly, HFD-fed Cyp3a-null females fed a HFD gained 50% less weight than wild-type (WT; B6) females fed a HFD. In contrast, Cyp3a-null males gained more weight than WT males, primarily during the first few weeks of HFD-treatment. Cyp3a-null females also recovered faster than WT females from a glucose tolerance test; males showed no difference in glucose tolerance between the groups. Serum concentrations of the anti-obesity hormone, adiponectin are 60% higher and β-hydroxybutyrate levels are nearly 50% lower in Cyp3a-null females than WT females, in agreement with reduced weight gain, faster glucose response, and reduced ketogenesis. In contrast, Cyp3a-null males have higher liver triglyceride concentrations and lipidomic analysis indicates an increase in phosphatidylinositol, phosphatidylserine and sphingomyelin. None of these changes were observed in females. Last, Pxr, Cyp2b, and IL-6 expression increased in Cyp3a-null females following HFD-treatment. Cyp2b and Fatp1 increased, while Pxr, Cpt1a, Srebp1 and Fasn decreased in Cyp3a-null males following a HFD, indicating compensatory biochemical responses in male (and to a lesser extent) female mice fed a HFD. In conclusion, lack of Cyp3a has a positive effect on acclimation to a HFD in females as it improves weight gain, glucose response and ketosis.

A high-fat high-energy diet influences hepatic CYP3A expression and activity in low-birth-weight developing female rats

BACKGROUND

The objective of this study was to investigate the effects of a high-fat, high-energy (HFHE) diet on the hepatic expression of CYP3A in low-birthweight developing female rats.

METHODS

Pregnant rats were divided into nourished and undernourished groups. The offspring of the nourished rats were defined as the normal-birth-weight (NBW) group, and those of undernourished rats were defined as the low-birth-weight (LBW) group. According to their birth weights and diets, the rats were subdivided into the following four groups: NBW-normal diet (NN) group; NBW-HFHE (NH) group; LBW-normal diet (LN) group; and LBW-HFHE (LH) group. Liver samples were isolated on days 3, 7, 14, 21, 28, 56 and 84 after birth.

RESULTS

The CYP3A1 mRNA levels in the LH group on days 3, 56 and 84 were significantly higher than those of the NN group (P<0.05). CYP3A1 expression was significantly higher in the LH group than that in the NH group on days 21, 28 and 84 (P<0.05). CYP3A1 mRNA expression was higher in the LH group than that in the LN group on days 3 and 21 (P<0.05). No zonal CYP3A1 expression pattern was observed in the LH developmental group. The LH group had significantly higher mean activity than the LN group on days 7, 14, 28 and 56.

CONCLUSION

Our results indicated that an HFHE diet can result in alterations of CYP3A expression in a developmental LBW rat model.

Hepatic CYP3A expression and activity in low birth weight developing female rats

BACKGROUND

We aimed to investigate the effects of low birth weight (LBW) on the hepatic expression of cytochrome P-450 3A (CYP3A) in developing female rats.

METHODS

Pregnant rats were divided into two groups, a nourished group and an under-nourished group. The offspring of the nourished rats were defined as a normal weight, normal diet group (NN group). The offspring of the under-nourished rats were designated as a LBW, normal diet group (LN group). CYP3A mRNA expression, protein expression, protein localization and activity were determined.

RESULTS

The CYP3A1 mRNA expression levels of the LN group on days 3, 21, and 56 were significantly higher than those of the same age in the NN group (P≤0.01). The mRNA expression of CYP3A2 in the LN group on day 21 was higher than in rats of the same age in the NN group (P<0.01). The staining intensity and frequency of CYP3A1-positive hepatocytes were significantly lower on days 7 and 21 in the LN group than those of rats of the same age in the NN group (P<0.05). The staining intensity and frequency of CYP3A2-positive hepatocytes on days 14 and 21 were higher in the LN group than those on the same days in the NN group (P<0.05). The mean CYP3A activity of the LN group on day 3 was significantly higher than that of the NN group (P<0.001).

CONCLUSIONS

We found the effect of LBW on CYP3A activity was most prominent during the early days of life in rats. Investigators and clinicians should consider the effect of LBW on CYP3A in both pharmacokinetic study design and data interpretation, when prescribing drugs to LBW infants.

Nuclear receptor CAR specifically activates the two-pore K+ channel Kcnk1 gene in male mouse livers, which attenuates phenobarbital-induced hepatic hyperplasia

KCNK1, a member of the family of two-pore K(+) ion channels, is specifically induced in the livers of male mice after phenobarbital treatment. Here, we have determined the molecular mechanism of this male-specific activation of the Kcnk1 gene and characterized KCNK1 as a phenobarbital-inducible antihyperplasia factor. Upon activation by phenobarbital, nuclear receptor CAR binds the 97-bp response element (-2441/-2345) within the Kcnk1 promoter. This binding is observed in the livers of male mice, but not in the livers of female mice and requires the pituitary gland, because hypophysectomy abrogates it. Hyperplasia further progressed in the livers of Kcnk1 ( -/- ) male mice compared with those of Kcnk1 ( +/+ ) males after phenobarbital treatment. Thus, KCNK1 suppresses phenobarbital-induced hyperplasia. These results indicate that phenobarbital treatment induces KCNK1 to elicit a male-specific and growth-suppressing signal. Thus, KCNK1 and Kcnk1 ( -/- ) mice provide an experimental tool for further investigation into the molecular mechanism of CAR-mediated promotion of the development of hepatocellular carcinoma in mice.

The effects of a high-fat and high-energy diet on the hepatic expression of CYP3A in developing female rats

We aimed to investigate the effects of high-fat and high-energy (HFHE) diets on the hepatic expression of cytochrome P-450 3A (CYP3A) in developing female rats. The pups of the dams fed with the standard diet were defined as the NN group and those fed the HFHE diet were defined as the NH group. The mRNA and protein expression, the protein localization and activity was determined. The mRNA expression of CYP3A1 on day 3 in the NH group were higher versus NN groups (p < 0.05) and the expression of the NH group on days 28 and 56 were lower versus the NN group (p < 0.01). CYP3A1 immunolabeling had a zonal-restricted expressions pattern on day 28 and after in the NN groups, while the obvious zonal expression pattern was observed in the NH group on day 84. The mean activity for the NH groups on days 3, 7, 14 and 28 was higher versus the NN groups (p < 0.05). On day 84, the activity was lower for the NH group versus the NN group (p < 0.05). Our findings provide a basis for further studies on appropriate medication regimen in obese children.

Sex differences in nuclear receptor-regulated liver metabolic pathways

Liver metabolism is markedly sex-dimorphic; accordingly, the prevalence of liver diseases is different between sexes. The superfamily of nuclear receptors (NRs) governs the proper expression of key liver metabolism genes by sensing lipid-soluble hormones and dietary lipids. When the expression of those genes is deregulated, disease development is favored. However, we lack a comprehensive picture of the differences between NR actions in males and females. Here, we reviewed explorative studies that assessed NR functions in both sexes, and we propose a first map of sex-dimorphic NR expression in the liver. Our analysis suggested that NRs in the female liver exhibited cross-talk with more liver-protective potential than NRs in male liver. This study provides empirical support to the hypothesis that women are more resilient to some liver diseases than men, based on a more compensative NR network. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Breast cancer-resistance protein (BCRP1) in the fetal mouse brain: development and glucocorticoid regulation

Breast cancer-resistance protein (BCRP1), encoded by Abcg2 mRNA, limits the penetration of a spectrum of compounds into the brain. The fetal brain is a primary target for many BCRP1 substrates; however, the developmental expression, function, and regulation of Abcg2/BCRP1 in the mouse fetal brain are unknown. Synthetic glucocorticoids (e.g., dexamethasone [DEX]) increase Abcg2/BCRP1 expression and function in vitro in endothelial cells derived from brain microvessels. A regulatory role of glucocorticoids on Abcg2/BCRP1 in the fetal brain is of importance given that approximately 10% of pregnant women are treated with synthetic glucocorticoid for threatened preterm labor. We hypothesized the following: 1) Abcg2 mRNA and BCRP1 protein expression increases with development (from Embryonic Day [E] 15.5 to E18.5), corresponding to decreased accumulation of BCRP1 substrate in the fetal brain. 2) Maternal treatment with DEX will up-regulate Abcg2 mRNA and BCRP1 protein expression in the fetal brain, resulting in decreased BCRP1 substrate accumulation. Pregnant FVB dams were euthanized on E15.5 or E18.5, and fetal brains were collected and analyzed for [(3)H]mitoxantrone (BCRP1-specific substrate) accumulation and Abcg2/BCRP1 expression. In another six groups (n = 4-5/group), pregnant mice were treated with DEX (0.1 or 1 mg/kg) or vehicle (saline) from either E9.5 to E15.5 (midgestation) or E12.5 to E18.5 (late gestation) and then injected with [(3)H]mitoxantrone. In conclusion, Abcg2 mRNA expression significantly decreases with advancing gestation, while BCRP1-mediated neuroprotection increases. Furthermore, there is a dose-, sex-, and age-dependent effect of DEX on Abcg2 mRNA in the fetal brain in vivo, indicating a complex regulatory role of glucocorticoid during development.

Activation of CAR and PXR by Dietary, Environmental and Occupational Chemicals Alters Drug Metabolism, Intermediary Metabolism, and Cell Proliferation

The constitutive androstane receptor (CAR) and the pregnane × receptor (PXR) are activated by a variety of endogenous and exogenous ligands, such as steroid hormones, bile acids, pharmaceuticals, and environmental, dietary, and occupational chemicals. In turn, they induce phase I-III detoxification enzymes and transporters that help eliminate these chemicals. Because many of the chemicals that activate CAR and PXR are environmentally-relevant (dietary and anthropogenic), studies need to address whether these chemicals or mixtures of these chemicals may increase the susceptibility to adverse drug interactions. In addition, CAR and PXR are involved in hepatic proliferation, intermediary metabolism, and protection from cholestasis. Therefore, activation of CAR and PXR may have a wide variety of implications for personalized medicine through physiological effects on metabolism and cell proliferation; some beneficial and others adverse. Identifying the chemicals that activate these promiscuous nuclear receptors and understanding how these chemicals may act in concert will help us predict adverse drug reactions (ADRs), predict cholestasis and steatosis, and regulate intermediary metabolism. This review summarizes the available data on CAR and PXR, including the environmental chemicals that activate these receptors, the genes they control, and the physiological processes that are perturbed or depend on CAR and PXR action. This knowledge contributes to a foundation that will be necessary to discern interindividual differences in the downstream biological pathways regulated by these key nuclear receptors.

Interplay of pregnane X receptor with other nuclear receptors on gene regulation

Human body needs to protect itself from a diverse array of harmful chemicals. These chemicals are also involved in drug metabolism, enzyme induction, and can cause adverse drug-drug interactions. Being a member of nuclear receptors (NRs), pregnane X receptor (PXR) has recently emerged as transcriptional regulators of cytochrome P450 (CYP) and transporters expression so as to against xenobiotics exposure. This review describes some common nuclear receptors, i.e. farnesoid X receptor (FXR), small heterodimer partner (SHP), hepatocyte nuclear factor-4alpha (HNF-4alpha), liver X receptor (LXR), glucocorticoid receptor (GR), constitutive androstane receptor (CAR) that crosstalk with PXR and involvement of coregulators thus control target genes expression.

Synergism of glucocorticoid hormone with growth hormone for female-specific mouse Cyp3a44 gene expression

CYP3A44 and CYP3A41 are female-specific CYP3A in the mouse liver. In primary cultured mouse hepatocytes, dexamethasone concentration-dependently induced CYP3A44 mRNA, and the highest response was seen at 10(-5) M. In contrast, CYP3A41 mRNA expression was highest at lower concentrations (10(-7) or 10(-6) M). At submicromolar concentration (10(-7) M), the induction of CYP3A44 mRNA was very slight, but strongly enhanced induction was observed by the simultaneous addition of growth hormone (GH). Similar enhancement was also observed in CYP3A41 mRNA expression. Continuous exposure to GH, which mimics female-type secretion from the pituitary gland, was effective to enhance the expression of both mRNAs, but discontinuous exposure (male-type) was not. This synergistic induction of CYP3A44 mRNA was further enhanced by the transfection of glucocorticoid receptor (GR) expression plasmid or by the cotransfection of pregnane X receptor (PXR) and retinoid X receptor (RXR) alpha expression plasmids. Similar synergistic induction was seen in CYP3A41 mRNA by the transfection of GR expression plasmid but was not enhanced by cotransfection of PXR and RXR expression plasmids. These observations suggest that functional cross-talk between signaling pathways of female-type GH secretion and glucocorticoid hormone might be involved in the female-predominant expression of both genes. Additionally, one or more nuclear receptors mediating induction by glucocorticoid hormone are employed for collaboration with GH.

Redox features of the cell: a gender perspective

Reactive oxygen and nitrogen species have been implicated in diverse subcellular activities, including cell proliferation,differentiation and, in some instances, cell injury and death. The implications of reactive species inhuman pathology have also been studied in detail. However, although the role of free radicals in the pathogenesis of human diseases has been extensively analyzed in different systems (i.e., in vitro, ex vivo, and in vivo),it is still far from elucidated. In particular, the possible role of gender 4 differences in human pathophysiology associated with reactive species is a promising new field of investigation. Although the complex scenario this presents is still incomplete, important gender-associated "redox features" of cells have already been described in the literature. Here we summarize the different aspects of redox-associated molecules and enzymes in regard to gender differences in terms of the intracellular production and biochemical activity of reactive species. These are often associated with the pathogenetic mechanisms underlying several human morbidities(e.g., degenerative diseases) and can represent a specific target for new pharmacologic strategies. Gender differences may thus pose an important challenge for future studies aimed at the clinical management of diseases characterized by a redox imbalance.

Involvement of glucocorticoid receptor and pregnane X receptor in the regulation of mouse CYP3A44 female-predominant expression by glucocorticoid hormone

The role of the glucocorticoid receptor (GR) and pregnane X receptor (PXR) in the regulation of female-predominant expression of mouse CYP3A44 by glucocorticoid hormones was evaluated using a primary culture of female mouse hepatocytes, as the expression was suppressed in adrenalectomized female mice, restored by dexamethasone (DEX) treatment and was not detected in male mouse livers. Glucocorticoid hormones, such as DEX, hydrocortisone, and corticosterone, 11beta-[4-dimethylamino] phenyl-17beta-hydroxy-17-[1-propynyl]estra-4,9-diene-3-one (RU486), antagonists for GR and an agonist for PXR, and rifampicin, an agonist for PXR, were chosen to investigate the relationship of GR/PXR activation and Cyp3a44 gene expression. Glucocorticoid-inducible expression of CYP3A44 was not suppressed but rather was increased by RU486. Treatment of GR expression plasmid-transfected hepatocytes with DEX concentration dependently enhanced the expression of PXR as well as CYP3A44 mRNAs. A synergistic effect of DEX at submicromolar concentrations and rifampicin is observed. Furthermore, transfection of PXR and retinoid X receptor-alpha (RXRalpha) also showed prominent induction of CYP3A44 mRNA by DEX. These results suggest that DEX plays a dual role in CYP3A44 expression: first, direct activation of the Cyp3a44 gene by the PXR-RXRalpha complex, and, second, indirect activation of the Cyp3a44 gene through the induction of PXR gene expression by the GR pathway.