Modulation of the pentose phosphate pathway alters phase I metabolism of testosterone and dextromethorphan in HepG2 cells

Exposure to haloacetic acid disinfection by-products and male steroid hormones: An epidemiological and in vitro study

Haloacetic acids (HAAs) are ubiquitous in drinking water and have been associated with impaired male reproductive health. However, epidemiological evidence exploring the associations between HAA exposure and reproductive hormones among males is scarce. In the current study, the urinary concentrations of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the internal exposure markers of HAAs, as well as sex hormones (testosterone [T], progesterone [P], and estradiol [E2]) were measured among 449 Chinese men. Moreover, in vitro experiments, designed to simulate the real-world scenarios of human exposure, were conducted to assess testosterone synthesis in the Leydig cell line MLTC-1 and testosterone metabolism in the hepatic cell line HepG2 in response to low-dose HAA exposure. The DCAA and TCAA urinary concentrations were found to be positively associated with urinary T, P, and E2 levels (all p < 0.001), but negatively associated with the ratio of urinary T to E2 (p < 0.05). Combined with in vitro experiments, the results suggest that environmentally-relevant doses of HAA stimulate sex hormone synthesis and steroidogenesis pathway gene expression in MLTC-1 cells. In addition, the inhibition of the key gene CYP3A4 involved in the testosterone phase Ⅰ catabolism, and induction of the gene UGT2B15 involved in testosterone phase Ⅱ glucuronide conjugation metabolism along with the ATP-binding cassette (ABC) transport genes (ABCC4 and ABCG2) in HepG2 cells could play a role in elevation of urinary hormone excretion upon low-dose exposure to HAAs. Our novel findings highlight that exposure to HAAs at environmentally-relevant concentrations is associated with increased synthesis and excretion of sex hormones in males, which potentially provides an alternative approach involving urinary hormones for the noninvasive evaluation of male reproductive health following exposure to DBPs.

Mechanistic study of cytochrome P450 enzyme-mediated cytotoxicity of psoralen and isopsoralen

Psoralen and isopsoralen are the major components responsible for Psoraleae Fructus-induced hepatotoxicity. This study explored the role of metabolic activation by cytochrome P450 (CYP) enzymes in psoralen- and isopsoralen-induced cytotoxicity and its potential mechanisms. Inhibitors of CYP1A2, 2C9, 2C19, 2D6, 2E1, and 3A4 were used to screen specific CYP enzymes responsible for the metabolic activation of psoralen and isopsoralen in mouse primary hepatocytes, which was verified using the corresponding transfected cell lines. Network toxicology and transcriptome analyses were performed to explore the mechanisms underlying toxicity. Psoralen and isopsoralen decreased the viability of mouse primary hepatocytes, whereas the inhibition of CYP2C9, 2C19, 2D6, and 2E1 significantly increased their viability. Psoralen-induced cytotoxicity was significantly enhanced by the overexpression of CYP2C19 in Chinese hamster ovary cells, whereas the overexpression of the above CYP enzymes did not affect the cytotoxicity of isopsoralen. Psoralen- and isopsoralen-induced cytotoxic effects were associated with putative core targets (i.e., Fn1, Thbs1, and Tlr2) and multiple signaling pathways (e.g., PI3K-Akt, MAPK, and TNF pathways). Our results demonstrate that the metabolic activation of psoralen and isopsoralen is mediated by CYP enzymes, thereby regulating multiple core targets and signaling pathways and resulting in cytotoxicity.

Exploring Dynamic Metabolome of the HepG2 Cell Line: Rise and Fall

Both biological and technical variations can discredit the reliability of obtained data in omics studies. In this technical note, we investigated the effect of prolonged cultivation of the HepG2 hepatoma cell line on its metabolomic profile. Using the GC × GC-MS approach, we determined the degree of metabolic variability across HepG2 cells cultured in uniform conditions for 0, 5, 10, 15, and 20 days. Post-processing of obtained data revealed substantial changes in relative abundances of 110 metabolites among HepG2 samples under investigation. Our findings have implications for interpreting metabolomic results obtained from immortal cells, especially in longitudinal studies. There are still plenty of unanswered questions regarding metabolomics variability and many potential areas for future targeted and panoramic research. However, we suggest that the metabolome of cell lines is unstable and may undergo significant transformation over time, even if the culture conditions remain the same. Considering metabolomics variability on a relatively long-term basis, careful experimentation with particular attention to control samples is required to ensure reproducibility and relevance of the research results when testing both fundamentally and practically significant hypotheses.

Mild chronic exposure to pesticides alters physiological markers of honey bee health without perturbing the core gut microbiota

Recent studies highlighted that exposure to glyphosate can affect specific members of the core gut microbiota of honey bee workers. However, in this study, bees were exposed to relatively high glyphosate concentrations. Here, we chronically exposed newly emerged honey bees to imidacloprid, glyphosate and difenoconazole, individually and in a ternary mixture, at an environmental concentration of 0.1 µg/L. We studied the effects of these exposures on the establishment of the gut microbiota, the physiological status, the longevity, and food consumption of the host. The core bacterial species were not affected by the exposure to the three pesticides. Negative effects were observed but they were restricted to few transient non-core bacterial species. However, in the absence of the core microbiota, the pesticides induced physiological disruption by directly altering the detoxification system, the antioxidant defenses, and the metabolism of the host. Our study indicates that even mild exposure to pesticides can directly alter the physiological homeostasis of newly emerged honey bees and particularly if the individuals exhibit a dysbiosis (i.e. mostly lack the core microbiota). This highlights the importance of an early establishment of a healthy gut bacterial community to strengthen the natural defenses of the honey bee against xenobiotic stressors.

Spectrophotometric and chromatographic strategies for exploring of the nanostructure pharmaceutical formulations which contains testosterone undecanoate

The nanostructure pharmaceutical formulations (NPF) which contains testosterone undecanoate (TU) been used in life science as parent compound delivery systems for therapeutic, but and been used to enhance the performance in sport, so it is a significant substance for public health and nutritional supplements. In most Pharmacopoeias testosterone is described as an ester of some lower acids (often propionate). The aim of this study is to determine purity of the parent compound by chromatography and absorption spectrum in the frame of middle infrared. Chemical structure of undecanoate was prepared and used in order to achieve a better absorption. This is explained by increased lipophilicity of undecanoate. Due to its lipophilic character, TU is soluble in non–polar solvents but shows a satisfactory solubility in absolute ethanol. Based on the molecular structure, a moderate absorption in the frame of UV with a maximum absorption at a not too high wave-length can be predicted. Maximum absorption occurs in a spectral region in which usual ingredients do not present significant interference.

Disrupted hepatic pentose phosphate pathway directly participates in and indirectly promotes CYP3A reduction: A new strategy for CYP3A-mediated drug hepatotoxicity

BACKGROUND AND PURPOSE

Hepatic CYP450s play an important role in drug-induced hepatotoxicity. They are altered in liver diseases and in many non-liver diseases, such as extra-hepatic tumours. Consequently, CYP450-mediated abnormal drug exposure increases the incidence and extent of hepatotoxicity. This risk is often underestimated because the mechanisms underlying decreases in hepatic CYP450s in extra-hepatic tumours remain unclear.

EXPERIMENTAL APPROACH

We used Balb/c nude mice with s.c. transplanted 4T1, LoVo and HepG2 tumours to model extra-hepatic tumours. Decreased levels of CYP3A were evaluated by qPCR, western blotting, and metabolic activity. LC-Q/TOF-MS and GC-MS were used in combination for analysing liver metabolomics. The contribution of the pentose phosphate pathway (PPP) to decreased CYP3A was assessed using menadione and silencing of glucose-6-phosphate dehydrogenase.

KEY RESULTS

CYP3A activity was inhibited at early stages of tumour growth when no significant inflammatory response was observed. The PPP was predominately disrupted at this non-inflammatory stage. Disruption of the PPP directly inhibited CYP3A through the chk2/p53/p65 pathway at the non-inflammatory stage, but at the later inflammatory stage, it indirectly potentiated the subsequent IL-6-mediated CYP3A decrease. Recovery of the PPP with menadione at the non-inflammatory stage, reversed the decreased CYP3A. Similar reversal was obtained with the IL-6 inhibitor, tocilizumab. Such modulation of the PPP to alleviate CYP3A-mediated drug hepatotoxicity was validated with dasatinib in vivo.

CONCLUSIONS AND IMPLICATIONS

PPP modulation at early, non-inflammatory stages might provide a novel and distinctive approach to manage drug hepatotoxicity mediated by decreased CYP3A.

Niacin analogue, 6-Aminonicotinamide, a novel inhibitor of hepatitis B virus replication and HBsAg production

Background: Hepatitis B surface antigen (HBsAg) is one of the important clinical indexes for hepatitis B virus (HBV) infection diagnosis and sustained seroconversion of HBsAg is an indicator for functional cure. However, the level of HBsAg could not be reduced by interferons and nucleoside analogs effectively. Therefore, identification of a new drug targeting HBsAg is urgently needed.

Methods: In this study, 6-AN was screened out from 1500 compounds due to its low cytotoxicity and high antiviral activity. The effect of 6-AN on HBV was examined in HepAD38, HepG2-NTCP and PHHs cells. In addition, the antivirus effect of 6-AN was also identified in mouse model.

Findings: 6-AN treatment resulted in a significant decrease of HBsAg and other viral markers both in vitro and in vivo. Furthermore, we found that 6-AN inhibited the activities of HBV SpI, SpII and core promoter by decreasing transcription factor PPARα, subsequently reduced HBV RNAs transcription and HBsAg production.

Interpretation: We have identified a novel small molecule to inhibit HBV core DNA, HBV RNAs, HBsAg production, as well as cccDNA to a minor degree both in vitro and in vivo. This study may shed light on the development of a novel class of anti-HBV agent.

Palmitate-Induced Insulin Hypersecretion and Later Secretory Decline Associated with Changes in Protein Expression Patterns in Human Pancreatic Islets

In obese children with high circulating concentrations of free fatty acid palmitate, we have observed that insulin levels at fasting and in response to a glucose challenge were several times higher than in obese children with low concentrations of the fatty acid as well as in lean controls. Declining and even insufficient insulin levels were observed in obese adolescents with high levels of the fatty acid. In isolated human islets exposed to palmitate we have observed insulin hypersecretion after 2 days exposure. In contrast, insulin secretion from the islets was reduced after 7 days culture in the presence of the fatty acid. This study aims at identifying islet-related biological events potentially linked with the observed insulin hypersecretion and later secretory decline in these obese children and adolescents using the islet model. We analyzed protein expression data obtained from human islets exposed to elevated palmitate levels for 2 and 7 days by an improved methodology for statistical analysis of differentially expressed proteins. Protein profiling of islet samples by liquid chromatography-tandem mass spectrometry identified 115 differentially expressed proteins (DEPs). Several DEPs including sorcin were associated with increased glucose-stimulated insulin secretion in islets after 2 days of exposure to palmitate. Similarly, several metabolic pathways including altered protein degradation, increased autophagy, altered redox condition, and hampered insulin processing were coupled to the functional impairment of islets after 7 days of culture in the presence of palmitate. Such biological events, once validated in the islets, may give rise to novel treatment strategies aiming at normalizing insulin levels in obese children with high palmitate levels, which may reduce or even prevent obesity-related type 2 diabetes mellitus.

17β-Estradiol inhibits testosterone-induced cell proliferation in HepG2 by modulating the relative ratios of 3 estrogen receptor isoforms to the androgen receptor

Sex hormones, especially 17β-estradiol (E2) and testosterone (TEST), play crucial roles in the oncogenesis and progression of liver cancer via hormone-related receptors. As women have a lower rate of hepatocellular carcinoma (HCC) than men, estrogens might attenuate the occurrence and development of HCC. This study aimed to investigate the inhibitory effects and mechanisms of E2 on TEST-induced HCC development; the HepG2 cell line was used as an in vitro model. Five endpoints, including cell viability, cell apoptosis, cell cycle, receptor protein expression, and messenger RNA transcription, were investigated. Different roles and the ratios of androgen receptor (AR) and 3 estrogen receptor (ER) subtypes were also estimated. Cell viability assay showed that co-treatment of E2 and TEST resulted in a significant inhibition of E2-induced or TEST-induced cell proliferation. Flow cytometry analysis revealed that combined treatment of E2 and TEST blocked the cell cycle in the G0/G1 phase as well as induced cell early apoptosis, characterized by decreased cyclin-dependent kinase transcription and the ratio of Bcl-2/Bax. Real-time quantitative polymerase chain reaction and Western blot analysis results further demonstrated that estrogen receptor estrogen receptor α66 (ERα66) and estrogen receptor β (ERβ) were upregulated, whereas AR and estrogen receptor α36 (ERα36) were downregulated, irrespective of whether E2 and TEST were considered separately or together, whereas the combined treatment of E2 and TEST resulted in a decrease in the ERα66/ERβ ratio, the ERα66/ERα36 ratio, and the ERβ/ERα36 ratio, but with an increase in the ERα66/AR ratio, the ERα36/AR ratio, and the ERβ/AR ratio. To sum up, E2 could inhibit TEST-induced cell proliferation by modulating the ratio of different hormone-related receptors.

Impact of physiological, pathological and environmental factors on the expression and activity of human cytochrome P450 2D6 and implications in precision medicine

With only 1.3-4.3% in total hepatic CYP content, human CYP2D6 can metabolize more than 160 drugs. It is a highly polymorphic enzyme and subject to marked inhibition by a number of drugs, causing a large interindividual variability in drug clearance and drug response and drug-drug interactions. The expression and activity of CYP2D6 are regulated by a number of physiological, pathological and environmental factors at transcriptional, post-transcriptional, translational and epigenetic levels. DNA hypermethylation and histone modifications can repress the expression of CYP2D6. Hepatocyte nuclear factor-4α binds to a directly repeated element in the promoter of CYP2D6 and thus regulates the expression of CYP2D6. Small heterodimer partner represses hepatocyte nuclear factor-4α-mediated transactivation of CYP2D6. GW4064, a farnesoid X receptor agonist, decreases hepatic CYP2D6 expression and activity while increasing small heterodimer partner expression and its recruitment to the CYP2D6 promoter. The genotypes are key determinants of interindividual variability in CYP2D6 expression and activity. Recent genome-wide association studies have identified a large number of genes that can regulate CYP2D6. Pregnancy induces CYP2D6 via unknown mechanisms. Renal or liver diseases, smoking and alcohol use have minor to moderate effects only on CYP2D6 activity. Unlike CYP1 and 3 and other CYP2 members, CYP2D6 is resistant to typical inducers such as rifampin, phenobarbital and dexamethasone. Post-translational modifications such as phosphorylation of CYP2D6 Ser135 have been observed, but the functional impact is unknown. Further functional and validation studies are needed to clarify the role of nuclear receptors, epigenetic factors and other factors in the regulation of CYP2D6.