Decreased translation of Dio3 mRNA is associated with drug-induced hepatotoxicity

Selenoprotein Gene mRNA Expression Evaluation During Renal Ischemia-Reperfusion Injury in Rats and Ebselen Intervention Effects

Effects of selenoproteins on many renal diseases have been reported. However, their role in renal ischemia-reperfusion (I/R) injury is unclear. The present study was performed to investigate the impact of ebselen and renal I/R injury on the expression of selenoproteins. Sprague-Dawley rats were pretreated with or without ebselen (10 mg/kg) through a daily single oral administration from 3 days before renal I/R surgery. RT-qPCR (real-time quantitative PCR) was performed to determine the mRNA expression of 25 selenoprotein genes in the renal tissues. The expression levels of two selenoproteins, including GPX3 (glutathione peroxidase 3) and DIO1 (iodothyronine deiodinase 1), were evaluated by Western blot or/and IHF (immunohistofluorescence) assays. Furthermore, renal function, renal damage, oxidative stress, and apoptosis were assessed. The results showed that in renal I/R injury, the mRNA levels of 15 selenoprotein genes (GPX1, GPX3, GPX4, DIO1, DIO2, TXNRD2, TXNRD3, SEPHS2, MSRB1, SELENOF, SELENOK, SELENOO, SELENOP, SELENOS, and SELENOT) were decreased, whereas those of eight selenoprotein genes (GPX2, GPX6, DIO3, TXNRD1, SELENOH, SELENOM, SELENOV, and SELENOW) were increased. I/R also induced a reduction in the expression levels of GPX3 and DIO1 proteins. In addition, our results indicated that ebselen reversed the changes in those selenoprotein genes, excluding SELENOH, SELENOM, SELENOP, and SELENOT, in renal I/R injury and alleviated I/R-induced renal dysfunction, tissue damage, oxidative stress, and apoptosis. To our knowledge, this is the first study to investigate the changes of 25 mammalian selenoprotein genes in renal I/R injury kidneys. The present study also provided more evidence for the roles of ebselen against renal I/R injury.

Deiodinases control local cellular and systemic thyroid hormone availability

Iodothyronine deiodinases (DIO) are a family of selenoproteins controlling systemic and local availability of the major thyroid hormone l-thyroxine (T4), a prohormone secreted by the thyroid gland. T4 is activated to the active 3,3'-5-triiodothyronine (T3) by two 5'-deiodinases, DIO1 and DIO2. DIO3, a 5-deiodinase selenoenzyme inactivates both the prohormone T4 and its active form T3. DIOs show species-specific different patterns of temporo-spatial expression, regulation and function and exhibit different mechanisms of reaction and inhibitor sensitivities. The main regulators of DIO expression and function are the thyroid hormone status, several growth factors, cytokines and altered pathophysiological conditions. Selenium (Se) status has a modest impact on DIO expression and translation. DIOs rank high in the priority of selenium supply to various selenoproteins; thus, their function is impaired only during severe selenium deficiency. DIO variants, polymorphisms, SNPs and rare mutations have been identified. Development of DIO isozyme selective drugs is ongoing. A first X-ray structure has been reported for DIO3. This review focusses on the biochemical characteristics and reaction mechanisms, the relationships between DIO selenoproteins and their importance for local and systemic provision of the active hormone T3. Nutritional, pharmacological, and environmental factors and inhibitors, such as endocrine disruptors, impact DIO functions.

Integration of Epigenetic Mechanisms into Non-Genotoxic Carcinogenicity Hazard Assessment: Focus on DNA Methylation and Histone Modifications

Epigenetics involves a series of mechanisms that entail histone and DNA covalent modifications and non-coding RNAs, and that collectively contribute to programing cell functions and differentiation. Epigenetic anomalies and DNA mutations are co-drivers of cellular dysfunctions, including carcinogenesis. Alterations of the epigenetic system occur in cancers whether the initial carcinogenic events are from genotoxic (GTxC) or non-genotoxic (NGTxC) carcinogens. NGTxC are not inherently DNA reactive, they do not have a unifying mode of action and as yet there are no regulatory test guidelines addressing mechanisms of NGTxC. To fil this gap, the Test Guideline Programme of the Organisation for Economic Cooperation and Development is developing a framework for an integrated approach for the testing and assessment (IATA) of NGTxC and is considering assays that address key events of cancer hallmarks. Here, with the intent of better understanding the applicability of epigenetic assays in chemical carcinogenicity assessment, we focus on DNA methylation and histone modifications and review: (1) epigenetic mechanisms contributing to carcinogenesis, (2) epigenetic mechanisms altered following exposure to arsenic, nickel, or phenobarbital in order to identify common carcinogen-specific mechanisms, (3) characteristics of a series of epigenetic assay types, and (4) epigenetic assay validation needs in the context of chemical hazard assessment. As a key component of numerous NGTxC mechanisms of action, epigenetic assays included in IATA assay combinations can contribute to improved chemical carcinogen identification for the better protection of public health.

Loss of Selenoprotein Iodothyronine Deiodinase 3 Expression Correlates with Progression of Complete Hydatidiform Mole to Gestational Trophoblastic Neoplasia

To investigate if differences in imprinting at tropho-microRNA (miRNA) genomic clusters can distinguish between pre-gestational trophoblastic neoplasia cases (pre-GTN) and benign complete hydatidiform mole (CHM) cases at the time of initial uterine evacuation. miRNA sequencing was performed on frozen tissue from 39 CHM cases including 9 GTN cases. DIO3, DLK1, RTL1, and MEG 3 mRNA levels were assessed by qRT-PCR. Protein abundance was assessed by Western blot for DIO3, DLK1, and RTL1. qRT-PCR and Western blot were performed for selenoproteins and markers of oxidative stress. Immunohistochemistry (IHC) was performed for DIO3 on an independent validation set of clinical samples (n = 42) and compared to normal placenta controls across gestational ages. Relative expression of the 14q32 miRNA cluster was lower in pre-GTN cases. There were no differences in protein abundance of DLK1 or RTL1. Notably, there was lower protein expression of DIO3 in pre-GTN cases (5-fold, p < 0.03). There were no differences in mRNA levels of DIO3, DLK1, RTL1 or MEG 3. mRNA levels were higher in all CHM cases compared to normal placenta. IHC showed syncytiotrophoblast-specific DIO3 immunostaining in benign CHM cases and normal placenta, while pre-GTN cases of CHM lacked DIO3 expression. We describe two new biomarkers of pre-GTN CHM cases: decreased 14q32 miRNA expression and loss of DIO3 expression by IHC. Differences in imprinting between benign CHM and pre-GTN cases may provide insight into the fundamental development of CHM.

Current concepts and challenges to unravel the role of iodothyronine deiodinases in human neoplasias

Thyroid hormones (THs) are essential for the regulation of several metabolic processes and the energy consumption of the organism. Their action is exerted primarily through interaction with nuclear receptors controlling the transcription of thyroid hormone-responsive genes. Proper regulation of TH levels in different tissues is extremely important for the equilibrium between normal cellular proliferation and differentiation. The iodothyronine deiodinases types 1, 2 and 3 are key enzymes that perform activation and inactivation of THs, thus controlling TH homeostasis in a cell-specific manner. As THs seem to exert their effects in all hallmarks of the neoplastic process, dysregulation of deiodinases in the tumoral context can be critical to the neoplastic development. Here, we aim at reviewing the deiodinases expression in different neoplasias and exploit the mechanisms by which they play an essential role in human carcinogenesis. TH modulation by deiodinases and other classical pathways may represent important targets with the potential to oppose the neoplastic process.

Essential amino acid transporter Lat4 (Slc43a2) is required for mouse development

Amino acid (AA) uniporter Lat4 (Slc43a2) mediates facilitated diffusion of branched-chain AAs, methionine and phenylalanine, although its physiological role and subcellular localization are not known. We report that Slc43a2 knockout mice were born at expected Mendelian frequency but displayed an ∼10% intrauterine growth retardation and low amniotic fluid AAs, suggesting defective transplacental transport. Postnatal growth was strongly reduced, with premature death occurring within 9 days such that further investigations were made within 3 days of birth. Lat4 immunofluorescence showed a strong basolateral signal in the small intestine, kidney proximal tubule and thick ascending limb epithelial cells of wild-type but not Slc43a2 null littermates and no signal in liver and skeletal muscle. Experiments using Xenopus laevis oocytes demonstrated that Lat4 functioned as a symmetrical low affinity uniporter with a K₀.₅ of ∼5 mm for both in- and efflux. Plasma AA concentration was decreased in Slc43a2 null pups, in particular that of non-essential AAs alanine, serine, histidine and proline. Together with an increased level of plasma long chain acylcarnitines and a strong alteration of liver gene expression, this indicates malnutrition. Attempts to rescue pups by decreasing the litter size or by nutrients injected i.p. did not succeed. Radioactively labelled leucine but not lysine given per os accumulated in the small intestine of Slc43a2null pups, suggesting the defective transcellular transport of Lat4 substrates. In summary, Lat4 is a symmetrical uniporter for neutral essential AAs localizing at the basolateral side of (re)absorbing epithelia and is necessary for early nutrition and development.

Effects of glyphosate on juvenile rainbow trout (Oncorhynchus mykiss): transcriptional and enzymatic analyses of antioxidant defence system, histopathological liver damage and swimming performance

This study aims to determine the effect of glyphosate on the transcriptional and enzymatic activity of antioxidant metabolism enzymes of juvenile rainbow trout with short term (6, 12, 24, 48 and 96 h) and long term (21 days) exposures followed by a recovery treatment. This study also aims to determine the effects of glyphosate exposure on liver tissue damage and swimming performance due to short term (2.5, 5 and 10 mg/L) and long term (2.5 and 5 mg/L) exposures. Following pesticide administration, ten fish, each as a sample, were caught at 6th, 12th, 24th, 48th and 96th -h for the short term, and at 21st day for the long term exposure study. GPx activity was found to be significantly induced 12 h after the exposure to 2.5 mg/L of glyphosate as compared with the control group. A similar degree of induction was also observed for CAT activity but not for SOD. For long term exposure, except for the GPx activity after exposure to 5 mg/L of glyphosate, the activities of all other enzymes remained on a par with the control group. It was also observed that the levels of gene expression of these enzymes were not comparable with each other. It is assumed that these differences might result from the effect of glyphosate before translation and the possible reasons for this scenario are also discussed. The results of swimming performance are found to be consistent with responses of the antioxidant system, and they are attributed to the energy metabolism. The data are also supported with liver histopathology analysis.

DLK1-DIO3 imprinted cluster in induced pluripotency: landscape in the mist

DLK1-DIO3 represents an imprinted cluster which genes are involved in physiological cell biology as early as the stem cell level and in the pathogenesis of several diseases. Transcription factor-mediated induced pluripotent cells (iPSCs) are considered an unlimited source of patient-specific hematopoietic stem cells for clinical application in patient-tailored regenerative medicine. However, to date there is no marker established able to distinguish embryonic stem cell-equivalent iPSCs or safe human iPSCs. Recent findings suggest that the DLK1-DIO3 locus possesses the potential to represent such a marker but there are also contradictory data. This review aims to report the current data on the topic describing both sides of the coin.

Fingerprints of a message: integrating positional information on the transcriptome

The recent explosion of high-throughput sequencing methods applied to RNA molecules is allowing us to go beyond the description of sequence variants and their relative abundances, as measured by RNA-seq. We can now probe for RNA engagement in polysomes, for ribosomes, RNA binding proteins and microRNAs binding sites, for RNA secondary structure and for RNA methylation. These descriptors produce a steadily growing multidimensional array of positional information on RNA sequences, whose effective integration only would bring to decipher the regulatory interplay occurring between proteins, RNAs and their modifications on the transcriptome. This interplay ultimately dictates the degree of mRNA availability to translation, and thus the occurrence of cell phenotypes. However, several issues in data presentation are slowing down effective integration. A standardization effort for new dataset types produced should be urgently undertaken to solve these issues. Providing uniformed experimental details along with datasets processed to be directly usable and employing shared formats would greatly simplify integration efforts, strengthening hypotheses stemming from correlative observations and eventually bringing to mechanistic understanding.