Expression of AhR-regulated miRNAs in non-small cell lung cancer in smokers and never smokers.

Smoking is a risk factor for non-small cell lung cancer (NSCLC). The most common subtypes of NSCLC are lung adenocarcinoma (LAC) and squamous cell carcinoma (SCC). The cigarette smoke contains aryl hydrocarbon receptor (AhR) ligands, such as benzo(a)pyrene (BaP). By activating the AhR, BaP can change the expression of many genes, including miRNA-encoding genes. In this study, we have evaluated the expression of few miRNAs potentially regulated by AhR (miR-21, -342, -93, -181a, -146a), as well as CYP1A1, a known AhR target gene, in lung tumor samples from smoking (n=40) and non-smoking (n=30) patients with LAC and from smoking patients with SCC (n=40). We have also collected macroscopically normal lung tissue >5 cm from the tumor margin. We compared the obtained data on the miRNA expression in tumors with data from The Cancer Genome Atlas (TCGA). We found that in 76.7% of non-smoking LAC patients, CYP1A1 mRNA was not detected in tumor and normal lung tissues, while in smoking patients, CYP1A1 expression was detected in tumors in almost half of the cases (47.5% for SCC and 42.5% for LAC). The expression profile of AhR-regulated miRNAs differed between LAC and SCC and depended on the smoking status. In LAC patients, the expression of oncogenic miRNA-21 and miRNA-93 in tumors was higher than in normal lung tissue from the same patients. However, in SCC patients from our sample, the levels of these miRNAs in tumor and non-transformed lung tissue did not differ significantly. The results of our studies and TCGA data indicate that the expression levels of miRNA-181a and miRNA-146a in LAC are associated with smoking: expression of these miRNAs was significantly lower in tumors of smokers. It is possible that their expression is regulated by AhR and AhRR (AhR repressor), and inhibition of AhR by AhRR leads to a decrease in miRNA expression in tumors of smoking patients. Overall, these results confirm that smoking has an effect on the miRNA expression profile. This should be taken into account when searching for new diagnostic and therapeutic targets for NSCLC.

Role of Nuclear Constitutive Androstane Receptor in Regulation of Hepatocyte Proliferation and Hepatocarcinogenesis.

Activation of the constitutive androstane receptor (CAR) in hepatocytes occurs as a body adaptation in response to a number of external influences, and its functional activity is primarily related to induction of enzymes detoxifying xenobiotics. However, special attention was recently given to CAR due to the fact that its key role becomes unveiled in various physiological and pathophysiological processes occurring in the liver: gluconeogenesis, metabolism of fatty acids and bilirubin, hormonal regulation, proliferation of hepatocytes, and hepatocarcinogenesis. Here we review the main pathways and mechanisms that elevate hepatocyte proliferative activity related to CAR and whose disturbance may be a pivotal factor in hepatocarcinogenesis.

Sirt1 Regulates p53 Stability and Expression of Its Target S100B during Long-Term Potentiation in Rat Hippocampus.

Induction of long-term potentiation in rat hippocampus was followed by short-term activation of transcription factor p53 and its subsequent degradation. We studied the effects of EX-527 (inhibitor of deacetylase Sirt1, a negative regulator of p53) and pifi thrin-ß (inhibitor of p53-dependent transcription) on the levels of p53 protein and mRNA of its target gene S100B during long-term potentiation. Pifi thrin-ß limited the increase in S100B mRNA content after tetanization, which confi rmed signifi cant contribution of p53 in the regulation of S100B during long-term potentiation. EX-527 completely prevented p53 degradation and increased S100B expression induced by tetanization. Thus, Str1 regulates stability of p53 and expression of its target gene S100B in rat hippocampus during long-term potentiation.

Mdm2-dependent regulation of p53 expression during long-term potentiation.

Induction of long-term posttetanic potentiation in rat hippocampal CA1 filed was followed by a decrease in the content of transcription factor p53 against the background of unchanged level of p53 mRNA, which implies activation of negative regulators of p53. Mdm2 is an important regulator of p53. We studied the effects of Mdm2 inhibitor nutlin-3 on p53 expression during generation of long-term posttetanic potentiation. Mdm2 inhibition completely prevented tetanization-induced decrease in the content of p53 protein; the level of p53 mRNA tended to increase in 30 min after tetanization. Thus, Mdm2 contributes to the maintenance of constant level of mRNA and plays a pivotal role in the decrease in the level of p53 protein during induction of long-term potentiation.

Gene expression of androgen metabolising enzymes in benign and malignant prostatic tissues.

Benign prostatic hyperplasia (BPH) as well as prostate cancer (CaP) are prevalent in the aging male population, and both the diseases display androgen-dependence when the circulating testosterone from the gonads decreases. This suggests that the local or intracrine production of androgens may drive these diseases. Both diseases are dependent on the conversion of androgen by the epithelial compartment to the ligand with higher affinity and can be treated by blocking synthesis of this androgen metabolite. For this approach to be effective, a detailed knowledge of androgen biosynthesis in both disease states is required. The aim of the present study was to investigate the gene expression levels of androgen metabolising enzymes in BPH compared to normal adjacent prostate tissues and CaP. Expression of the genes HSD3B1, HSD17B3, and SRD5A2 was significantly increased in BPH tissues compared to normal adjacent prostate tissues. In contrast to BPH, CaP demonstrated significant decrease in the expression of HSD17B3, AKR1C2, and SRD5A2 compared to normal adjacent prostate tissues. HSD17B2 expression was significantly decreased in all samples. Moreover, HSD3B1 and SRD5A2 mRNA levels were upregulated in BPH compared with CaP. These results suggest that a change in androgen metabolism may be an important step in the pathogenesis of BPH, leading to increased cell proliferation due to in situ androgen synthesis. These features can be used to develop differential treatment strategies for BPH. HSD3B1 and SRD5A2 could be used as therapeutic target for BPH.

Induction of S100B gene expression in long-term potentiation in the hippocampal CA1 field depends on activity of NMDA receptors.

The effects of NMDA receptor blocker MK-801 on the increase in S100B protein mRNA content induced by long-term posttetanic potentiation in the hippocampal sections were studied. The level of S100B mRNA after 30-min tetanization in the presence of 10 µM MK-801 constituted 132% of the basal level, which was significantly (226%) lower than the control level. Hence, gene expression, induced by long-term posttetanic potentiation, in the glial cells (similarly as in the neurons) depended significantly on NMDA receptors.

The constitutive androstane receptor activator 4-[(4R,6R)-4,6-diphenyl-1,3-dioxan-2-yl]-N,N-dimethylaniline inhibits the gluconeogenic genes PEPCK and G6Pase through the suppression of HNF4α and FOXO1 transcriptional activity.

BACKGROUND AND PURPOSE: The dual role of the constitutive androstane receptor (CAR) as both a xenosensor and a regulator of endogenous energy metabolism (lipogenesis and gluconeogenesis) has recently gained acceptance. Here, we investigated the effects of 4-[(4R,6R)-4,6-diphenyl-1,3-dioxan-2-yl]-N,N-dimethylaniline (transpDMA), an effective CAR activator, on the gluconeogenic genes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) in rat livers. EXPERIMENTAL APPROACH: The effects of transpDMA were investigated in normal and high-fat diet-fed Wistar rats using real-time PCR, Western blotting, chromatin immunoprecipitation assays (ChIP), glucose tolerance test and insulin tolerance test. KEY RESULTS: The expression of the gluconeogenic enzymes PEPCK and G6Pase was repressed by transpDMA treatment under fasting conditions. Long-term CAR activation by transpDMA significantly reduced fasting blood glucose levels and improved glucose homeostasis and insulin sensitivity in high-fat diet-fed rats. The metabolic benefits of CAR activation by transpDMA may have resulted from the inhibition of hepatic gluconeogenic genes. ChIP assays demonstrated that transpDMA prevented the binding of forkhead box O1 (FOXO1) to insulin response sequences in the PEPCK and G6Pase gene promoters in rat livers. Moreover, transpDMA-activated CAR inhibited hepatocyte nuclear factor-4α (HNF4α) transactivation by competing with HNF4α for binding to the specific binding element (DR1-site) in the gluconeogenic gene promoters. CONCLUSIONS AND IMPLICATIONS: Our results provide evidence to support the conclusion that transpDMA inhibits the gluconeogenic genes PEPCK and G6Pase through suppression of HNF4α and FOXO1 transcriptional activity.

Constitutive androstane receptor (CAR) is a xenosensor and target for therapy.

Constitutive androstane receptor (CAR, NR1I3), which is under consideration in this review, is a member of the superfamily of nuclear receptors. However, certain features distinguish CAR from the variety of nuclear receptors. First, this receptor has structural features that allow it to display constitutive activity in the absence of a ligand and to interact in a species-specific manner with a huge number of ligands diverse in chemical structure and origin. Second, recently many researchers are focused on CAR because the significance is increasingly shown of its influence on a variety of physiological functions, such as gluconeogenesis, metabolism of xenobiotics, fatty acids, bilirubin, and bile acids, hormonal regulation, etc. In addition to the fundamental scientific interest, the study of CAR is of practical importance because changes in CAR activity can lead to disorders in physiological processes, which finally can result in changes in pathological states. However, despite intensive studies, many mechanisms are still unclear, which makes it difficult to understand the role of CAR in the overall picture of molecular regulation of physiological processes. This review analyzes the features and diversity of the functions of CAR.

Expression of S100B and S100A6 genes during long-term posttetanic potentiation in the hippocampus.

The expression of S100B and S100A6 mRNA in CA1 region of rat hippocampal sections was studied after tetanizing stimulation. The level of S100B expression increased 2-4-fold in comparison with the control after 30 min and gradually returned to the basal level 120 min after tetanization. The level of S100A6 mRNA was very low and did not change after tetanization.

Induction of cytochrome P4502B: role of regulatory elements and nuclear receptors.

Cytochrome P450 of the 2B subfamily is easily induced by many xenobiotics. In spite of intensive investigations, the molecular mechanisms of regulation of the CYP2B genes are not clear. The nuclear receptor CAR is shown to play a crucial role in the activation of CYP2B genes by xenobiotics, but many problems of CAR activation in different animal species and humans remain unsolved. This review focuses on signaling pathways involved in the control of CYP2B gene expression in mammals.

Dynamics of DNA-protein complex formation in rat liver during induction by phenobarbital and triphenyldioxane.

CYP2B gene expression in liver of rats treated with phenobarbital and triphenyldioxane at early stage of induction (40 min-18 h) was studied using electrophoretic mobility shift assay (EMSA) and RT-PCR. During first 6 h after induction, differences in the dynamics of formation of DNA-protein complexes were shown for each inducer. Later (18 h after induction), the intensity pattern of these complexes became the same for both phenobarbital and triphenyldioxane treated animals. This suggests the existence of specific signaling for each inducer only in early stages of CYP2B activation. Increase in nuclear protein (possible transcription factor) binding to Barbie-box regulatory sequence of CYP2B genes was accompanied by their increased expression. Thus, we have demonstrated for the first time that early stages of induction (40 min and 3 h after administration of phenobarbital and triphenyldioxane, respectively) are accompanied by activation of nuclear proteins that can bind to Barbie-box element of CYP2B. Although various chemical inducers cause distinct activation of such binding, this process involves activation of gene transcription.