The impact of graphene oxide on androgen receptor signalling in prostate cancer cells.

Androgen receptor (AR) signalling is triggered by androgens that have lipophilic nature. Since it was indicated that graphene oxide (GO) might facilitate passive diffusion of lipophilic compounds probably via Trojan horse-like mechanism, we tested the hypothesis if this suggestion would apply for androgens as well. Thus, we investigated if GO affects dihydrotestosterone (DHT)-triggered signalling of AR in two prostate cancer-derived cell lines, 22Rv1 and LNCaP. These cell lines differ in number of AR variants, i.e. there are two variants in 22Rv1 cells (full length and truncated) but only one in LNCaP cells (full length). Graphene oxide had no effect on basal luciferase activity but significantly decreased DHT-inducible AR-dependent luciferase activity in stably transfected cells. In 22Rv1 cells, it induced concentration-dependent decrease of DHT-inducible KLK3 mRNA and PSA protein after 24 h. While there was no effect on UBE2C mRNA (regulated by truncated variant), there was synergistic effect of DHT and GO on UBE2C protein level. Translocation of full-length AR (AR-FL) was potentiated by GO in the presence of DHT in 22Rv1 cells but it was suppressed in LNCaP cells. DHT-stimulated enrichment of AR-FL on KLK3 promoter was not significantly affected by GO in any tested cell line neither was KLK3 mRNA at 4 h of incubation. In conclusion, GO affects DHT-triggered signalling in both types of cells in similar manner, but ligand-triggered redistribution of AR-FL is affected differently. One of the reasons may be the presence of truncated variant of androgen receptor.

Interleukin-23 Represses the Level of Cell Senescence Induced by the Androgen Receptor Antagonists Enzalutamide and Darolutamide in Castration-Resistant Prostate Cancer Cells.

Prostate cancer (PCa) is the most common cancer and the second leading cause of cancer-related deaths of men in Western countries. Androgen deprivation therapy is initially successful, however eventually fails, and tumors progress to the more aggressive castration-resistant PCa (CRPC). Yet, androgen receptor (AR) usually remains as a major regulator of tumor cell proliferation in CRPC. Interleukin-23 (IL-23) was recently shown to promote the development of CRPC by driving AR transcription. Here we used the androgen-sensitive LNCaP, castration-resistant C4-2, and 22Rv1 cells. Interestingly, cellular senescence is induced in these human cell lines by treatment with the AR antagonists enzalutamide (ENZ) or darolutamide (ODM), which might be one underlying mechanism for inhibition of PCa cell proliferation. Treatment with IL-23 alone did not change cellular senescence levels in these cell lines, whereas IL-23 inhibited significantly cellular senescence levels induced by ENZ or ODM in both CRPC cell lines C4-2 and 22Rv1 but not in LNCaP cells. This indicates a response of IL-23 specific in CRPC cells. Generating LNCaP and C4-2 three-dimensional (3D) spheroids and treatment with AR antagonists resulted in the reduced spheroid volume and thus growth inhibition. However, the combination of AR antagonists with IL-23 did not affect the antagonist-mediated reduction of spheroid volumes. This observation was confirmed with proliferation assays using adherent monolayer cell cultures. Taken together, the data indicate that IL-23 treatment reduces the AR antagonists-induced level of cellular senescence of CRPC cells, which could be one possible mechanism for promoting castration resistance.

The effect of graphene oxide on signalling of xenobiotic receptors involved in biotransformation.

Graphene oxide (GO) is an engineered nanomaterial which was demonstrated to have outstanding capacity for adsorption of organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), the ligands and activators of the aryl hydrocarbon receptor (AhR). Due to the partially overlapping ligand capacity of AhR and pregnane X receptor (PXR), we tested the impact of GO particles on their signalling. While reporter gene assay revealed potentiating effect of GO on ligand-activated AhR-dependent luciferase activity, there was no effect for PXR. However, inducible target genes for AhR (CYP1A1) or PXR (ABCB1) were decreased at mRNA as well as protein levels by the presence of GO in HepG2 (for AhR), LS180 (for PXR) or primary human hepatocytes (both receptors). Moreover, the presence of GO diminished PXR and AhR protein levels in primary cultures of human hepatocytes. This was partially reversed by proteasome inhibitor MG132 for AhR but not for PXR. In conclusion, GO decreases ligand-stimulated activities of AhR and PXR in human cells.

The Effect of Caffeine on Calcitriol-Inducible Vitamin D Receptor-Controlled Gene Expression in Intestinal and Osteoblastic Cells.

Some epidemiological studies suggested caffeine consumption as the cause for bone mineral density loss. Certain genes involved in this process are regulated by vitamin D receptor (VDR). Therefore, we investigated if caffeine can affect inducible expression of VDR-regulated genes, some of them being involved in bone mineralization process. By employing reporter gene assay, polymerase chain reaction, and western blotting, we monitored the VDR activity and expression in cell cultures of intestinal (LS180), osteosarcoma (HOS), and normal human osteoblasts in vitro. While caffeine stimulated calcitriol-inducible VDR-dependent nanoluciferase activity in stable reporter cell line IZ-VDRE (derived from LS180), it rather modulated mRNA levels of target genes, like CYP24A1, BGLAP, SPP1, and TNSF11 in LS180 and HOS cells. However, caffeine significantly decreased calcitriol-inducible CYP24A1, TNSF11, and SPP1 transcripts in osteoblasts. This decrease had non-linear U-shaped profile. Our in vitro data demonstrate biphasic action of caffeine on the expression of certain calcitriol-inducible VDR-regulated genes in normal human osteoblasts.

Mycophenolate Mofetil induces c-Jun-N-terminal kinase expression in 22Rv1 cells: an impact on androgen receptor signaling.

Mycophenolate Mofetil (MYC) is a transplant drug used to prevent rejection in heart and kidneys transplant patients. Inosine monophosphate dehydrogenase (IMPDH), an enzyme involved in de novo synthesis of guanosine nucleotides, was considered as a primary target for MYC. Recently, we described that MYC was activates aryl hydrocarbon receptor and it antagonizes glucocorticoid receptor. Here we describe an androgen receptor (AR) as another off-target for MYC. We found that MYC increased basal and dihydrotestosterone (DHT)-inducible AR-dependent luciferase activity in AIZ-AR cells. In the same manner it induced or augmented mRNA level of KLK3 (prostate specific antigen; PSA) in 22Rv1 cells. Herein it displayed a hormetic effect on proliferation activity, since it significantly stimulated proliferation in lower concentrations but inhibited in higher (>1 µg/ml) concentrations in the presence of DHT. In contrast, MYC suppressed DHT-inducible KLK3 mRNA expression and cell proliferation in androgen-dependent LNCaP cells. MYC augmented DHT-inducible nuclear translocation of AR and increased the expression of MAPK8/9 (JNK46/54) resulting in the drop of their phosphorylation status. Moreover, MYC sensitized DHT-treated 22Rv1 cells to JNK-IN-8 mediated growth inhibition with the drop of IC50 from 1425 nM to 84 nM within 24 hrs. In conclusion, we suggest that, castrate-resistant prostate cancers progression might be retarded with the combination of MYC and chemical JNK inhibitors, involving AR-dependent mechanism.

Profiling of bisphenol S towards nuclear receptors activities in human reporter cell lines.

Bisphenol S (BPS) is heat-stable structural analog of bisphenol A (BPA), a known endocrine disruptor. Due to the effort to replace BPA with BPS, it is essential to know if BPS is suitable non-toxic replacement without reported deleterious effects of BPA. Since most of the BPA effects are ascribed to its ability to activate nuclear receptors, we screened some prominent members of this family in order to confirm or refute some recent findings. We found that BPS insignificantly activated aryl hydrocarbon receptor (AhR) in reporter gene assay and no induction of AhR target gene CYP1A1 was observed in human hepatocytes (HH). BPS was able to act like an antagonist of pregnane X receptor (PXR) in reporter gene assay, but the expression of PXR target gene CYP3A4, was only moderately affected in HH. While BPS antagonized dexamethasone-inducible glucocorticoid receptor (GR)-dependent luciferase activity in reporter gene assay (IC50=52µM), it was not able to antagonize dexamethasone effects on GR-target genes, including GILZ, NFKBIA and IL-6. Synergistic effect of BPS (range 0.001-100µM) and DHT (100nM) was observed at androgen receptor (AR) activity level only. In conclusion, we show that BPS had only limited effect on tested nuclear receptors. Moreover, submicromolar concentrations of BPS affected activated AR. Thus, due to the low levels of exposure for humans, BPS is probably of no regulatory concern. However, further investigation should delineate possible impact on male/female development or sexual functions.

Fine tuning of vitamin D receptor (VDR) activity by post-transcriptional and post-translational modifications.

Vitamin D receptor (VDR) is a member of the nuclear receptor (NR) superfamily of ligand-activated transcription factors. Activated VDR is responsible for maintaining calcium and phosphate homeostasis, and is required for proper cellular growth, cell differentiation and apoptosis. The expression of both phases I and II drug-metabolizing enzymes is also regulated by VDR, therefore it is clinically important.Post-translational modifications of NRs have been known as an important mechanism modulating the activity of NRs and their ability to drive the expression of target genes. The aim of this mini review is to summarize the current knowledge about post-transcriptional and post-translational modifications of VDR.

Environmental pollutants parathion, paraquat and bisphenol A show distinct effects towards nuclear receptors-mediated induction of xenobiotics-metabolizing cytochromes P450 in human hepatocytes.

Environmental pollutants parathion, bisphenol A and paraquat were not systematically studied towards the effects on the expression of phase I xenobiotics-metabolizing cytochromes P450 (CYPs). We monitored their effects on the expression of selected CYPs in primary cultures of human hepatocytes. Moreover, we investigated their effects on the receptors regulating these CYPs, particularly arylhydrocarbon receptor (AhR), pregnane X receptor (PXR) and glucocorticoid receptor (GR) by gene reporter assays. We found that parathion and bisphenol A are the activators of AhR. Moreover, they are the inducers of CYP1A1 mRNA in hepatoma cells HepG2 as well as in human hepatocytes by AhR-dependent mechanism via formation of AhR-DNA-binding complex, as revealed by gel shift assay. All three compounds possessed anti-glucocorticoid action as revealed by GR-dependent gene reporter assay and a decline in tyrosine aminotransferase (TAT) gene expression in human hepatocytes. Moreover, parathion and bisphenol A are the activators of PXR and inducers of CYP3A4 mRNA and protein in the primary cultures of human hepatocytes. In conclusion, the studied compounds displayed distinct activities towards nuclear receptors involved in many biological processes and these findings may help us to better understand their adverse actions in pathological states followed after their exposure.

The effects of drugs with immunosuppressive or immunomodulatory activities on xenobiotics-metabolizing enzymes expression in primary human hepatocytes.

In this paper we investigated the effects of several drugs used in transplant medicine, i.e. cyclosporine A, tacrolimus, rapamycin, everolimus, mycophenolate mofetil, fluvastatin and rosuvastatin, on the expression of major drug-metabolizing enzymes in human hepatocytes. Moreover, we tested the ability of these drugs to affect transcriptional activity of glucocorticoid (GR) and aryl hydrocarbon receptor (AhR). We found that most of tested compounds did not induce expression of CYP1A1/1A2/3A4/2A6/2B6/2C9 mRNAs in human hepatocytes. Slight induction was observed for CYP2A6/2C9 mRNAs and CYP2A6 protein in the rapamycin-treated hepatocytes. Decrease of CYP2A6 and CYP2B6 proteins was observed in rosuvastatin-treated cells. Mycophenolate mofetil antagonized the effects of dexamethasone on GR but it potentiated the action of dioxin on AhR. Induction of CYP1A1 mRNA in HepG2 cells by dioxin was modestly antagonized by mycophenolate mofetil, while the induction by benzo[a]pyren or S-omeprazole was significantly potentiated by this drug. In general, tested compounds can be considered safe in the terms of possible drug-drug interaction caused by induction of drug-metabolizing cytochromes P450. Nevertheless, mycophenolate mofetil is of possible concern and its combination with drugs, environmental pollutants or food constituents, which activate AhR, may represent a significant toxicological risk.