Constitutive expression of drug metabolizing enzymes and related transcription factors in cattle testis and their modulation by illicit steroids

Induction by Phenobarbital of Phase I and II Xenobiotic-Metabolizing Enzymes in Bovine Liver: An Overall Catalytic and Immunochemical Characterization

In cattle, phenobarbital (PB) upregulates target drug-metabolizing enzyme (DME) mRNA levels. However, few data about PB's post-transcriptional effects are actually available. This work provides the first, and an almost complete, characterization of PB-dependent changes in DME catalytic activities in bovine liver using common probe substrates and confirmatory immunoblotting investigations. As expected, PB increased the total cytochrome P450 (CYP) content and the extent of metyrapone binding; moreover, an augmentation of protein amounts and related enzyme activities was observed for known PB targets such as CYP2B, 2C, and 3A, but also CYP2E1. However, contradictory results were obtained for CYP1A, while a decreased catalytic activity was observed for flavin-containing monooxygenases 1 and 3. The barbiturate had no effect on the chosen hydrolytic and conjugative DMEs. For the first time, we also measured the 26S proteasome activity, and the increase observed in PB-treated cattle would suggest this post-translational event might contribute to cattle DME regulation. Overall, this study increased the knowledge of cattle hepatic drug metabolism, and further confirmed the presence of species differences in DME expression and activity between cattle, humans, and rodents. This reinforced the need for an extensive characterization and understanding of comparative molecular mechanisms involved in expression, regulation, and function of DMEs.

Development and Application of a Screening Method of Absolute Quantitative PCR To Detect the Abuse of Sex Steroid Hormone Administration in Male Bovines

A methodology for the absolute quantification of regucalcin gene through quantitative PCR was set up to confirm that the decrease of regucalcin gene expression in the testis is an effective biomarker for tracing sex steroid hormone treatment in bovine husbandry. On the basis of TaqMan technology, an external standard curve was generated. Using in vivo experiments, a ROC curve was developed to calculate the criterion value, specificity, and sensitivity for this potential biomarker. Then, regucalcin gene expression was assessed in veal calves and beef intended for human consumption. In 11 of 54 calves and in 5 of 70 beef cattle the regucalcin gene was expressed under their respective cutoff. Additionally, a mild decrease of regucalcin protein expression was revealed by immunohistochemistry in subjects tested positive via qPCR. These preliminary results suggest that this transcriptomics test may be employed as a novel diagnostic screening tool, improving significantly the overall efficacy of food control.

Morphological Examination and Transcriptomic Profiling To Identify Prednisolone Treatment in Beef Cattle

In livestock production corticosteroids are licensed only for therapy; nevertheless, they are often illegally used as growth promoters. The aim of this study was to identify morphological or biomolecular alterations induced by prednisolone (PDN) in experimentally treated beef cattle, because PDN and its metabolites are no longer detectable by LC-MS/MS methods in biological fluids. Moreover, PDN does not induce any histological alterations in the thymus, different from dexamethasone treatments. Therefore, a marker of illicit treatment for this growth promoter could be useful. Eight male Italian Friesian beef cattle were administered prednisolone acetate 30 mg day^-1 per os for 35 days, and seven beef cattle represented the control group. Six days after drug withdrawal, the animals were slaughtered. Morphological and morphometric modifications were evaluated in the epididymis and testis, whereas transcriptomic changes induced by PDN administration were investigated in peripheral blood mononuclear cells (PBMCs) at different sampling times and in skeletal muscle and testis sampled at slaughtering. In the epididymis, spermatozoa number decreased in PDN-treated animals, and in some cases they were totally absent. Correspondingly, in the testis of treated animals, down-regulation for serine/threonine kinase 11 (STK11) gene expression was detected (p < 0.01). DNA microarray analysis revealed a total of 133 differentially expressed genes in skeletal muscle and testis, and 907 and 1416 in PBMCs after 33 days of treatment and at slaughtering, respectively. Histological investigations on epididymal content could represent a promising marker for PDN treatment in beef cattle and could be used as a screening method to identify animals worthy of further investigation with official methods. Moreover, the clear transcriptomic signature of PDN treatment evidenced in PBMCs supported the possibility of using this matrix to monitor the illicit treatment in vivo during ranching.

Characterization of bovine phenol sulfotransferases: evidence of a major role for SULT1B1 in the liver

1. Cattle are an important component of the human food chain. Drugs used either legally or illegally in cattle may therefore enter the food chain and it is thus important to understand pathways of drug metabolism in this species, including sulfation catalyzed by the sulfotransferases (SULTs). 2. In this study, we have analyzed the sulfation of 4-nitrophenol and other compounds in male and female bovine liver and characterized recombinant bovine SULT isoforms 1A1 and 1B1 expressed in Escherichia coli. 3. We found that, in contrast to most other mammalian species, the major phenol sulfotransferase SULT1A1 is not expressed in bovine liver. Rather SULT1B1 seems to be a major form in both male and female bovine liver. 4. We also identified kinetic differences between bovine and human SULT1A1 and, using the human SULT1A1 crystal structure, identified two amino acid positions in the active site of bovine SULT1A1 (Ile89Val and Phe247Val) that may be responsible for these differences.

Transcriptomic markers meet the real world: finding diagnostic signatures of corticosteroid treatment in commercial beef samples

Background

The use of growth-promoters in beef cattle, despite the EU ban, remains a frequent practice. The use of transcriptomic markers has already proposed to identify indirect evidence of anabolic hormone treatment. So far, such approach has been tested in experimentally treated animals. Here, for the first time commercial samples were analyzed.

Results

Quantitative determination of Dexamethasone (DEX) residues in the urine collected at the slaughterhouse was performed by Liquid Chromatography-Mass Spectrometry (LC-MS). DNA-microarray technology was used to obtain transcriptomic profiles of skeletal muscle in commercial samples and negative controls. LC-MS confirmed the presence of low level of DEX residues in the urine of the commercial samples suspect for histological classification. Principal Component Analysis (PCA) on microarray data identified two clusters of samples. One cluster included negative controls and a subset of commercial samples, while a second cluster included part of the specimens collected at the slaughterhouse together with positives for corticosteroid treatment based on thymus histology and LC-MS. Functional analysis of the differentially expressed genes (3961) between the two groups provided further evidence that animals clustering with positive samples might have been treated with corticosteroids. These suspect samples could be reliably classified with a specific classification tool (Prediction Analysis of Microarray) using just two genes.

Conclusions

Despite broad variation observed in gene expression profiles, the present study showed that DNA-microarrays can be used to find transcriptomic signatures of putative anabolic treatments and that gene expression markers could represent a useful screening tool.

Effects of time culture and prototypical cytochrome P450 3A (CYP3A) inducers on CYP2B22, CYP2C, CYP3A and nuclear receptor (NR) mRNAs in long-term cryopreserved pig hepatocytes (CPHs)

In the present study, transcriptional and post-translational effects of culturing time and prototypical cytochrome P450 3A (CYP3A) inducers on principal nuclear receptors (NRs), CYP2B22, 2C and 3A were investigated in long-term stored (~10 years) cryopreserved pig hepatocytes (CPHs). In the time-course study, a crush and rise effect was observed for pregnane X receptor (NR1I2) and constitutive androstane receptor (NR1I3) mRNAs, while a time-dependent increase of retinoid X receptor alpha (NR2B1) was noticed. Cytochrome P450 gene expression profiles were down-regulated as a function of time. In the induction study, an increase of NR1I2, NR1I3 and NR2B1 mRNAs was observed in dexamethasone-exposed CPHs. About CYPs, an overall up-regulation was seen in CPHs exposed to phenobarbital, while dexamethasone and rifampicin up-regulated only CYP3A. In both studies, transcriptional CYP results were confirmed at the post-translational level (immunoblotting and enzyme activities), except for CYP2B immunoblotting in the induction study. The present data demonstrate that long-term stored CPHs may be used to investigate mechanisms involved in CYPs regulation, expression and function; provide further info about NR regulation of CYPs, and confirm species-differences in these mechanisms of regulation; finally, they suggest the usefulness and relevance of gene expression profiling to early detect any modulation of CYP expression and bioactivity.

Progesterone receptor up-regulation: a diagnostic tool for the illicit use of oestrogens in adult beef cattle

The monitoring of gene regulation via mRNA levels to detect anabolic sex steroid administration in cattle is a novel approach to detecting the illicit treatment of livestock in meat production. A previous study revealed that progesterone receptor (PR) gene expression levels were increased in the bulbourethral glands and prostates of 17β-oestradiol-treated prepubertal calves, suggesting that the PR can be used as a specific molecular biomarker for oestrogen treatment. The aim of this study was to verify the specificity and applicability of the PR to detect the illegal use of 17β-oestradiol in sexually mature beef cattle. Accessory sex glands were sampled from 42 male beef cattle that were divided into six experimental groups, including two control groups, K1 and K2. Group A cattle were treated with 17β-oestradiol (five weekly intramuscular doses of 20 mg), and group B cattle were treated with dexamethasone (40 daily doses of 0.7 mg per os). Group C cattle received an implant of Revalor-200 (200 mg of trenbolone acetate and 20 mg of 17β-oestradiol), and group D cattle received Revalor-200 plus dexamethasone (0.7 mg daily per os). 17β-Oestradiol, either alone or in combination with other steroids, up-regulated the PR gene and protein expression, even in the absence of detectable histological changes in the accessory sex glands, confirming the high sensitivity of PR gene expression as an indirect diagnostic screening tool to detect illicit oestrogen treatment in sexually mature male bovine.

Target gene expression signatures in neutrophils and lymphocytes from cattle administered with dexamethasone at growth promoting purposes

The glucocorticoid dexamethasone (DEX), when used as a growth promoter, cause morphological and functional alterations in cattle lymphoid organs and cells. In the present experiment, the transcriptional effects of an illicit DEX protocol upon six target genes were investigated in cattle neutrophils (NEU) and lymphocytes (LFC). Blood samples were taken before (T(0)) and 2, 3, 10, 19, 31 and 43 days from the beginning of DEX administration (T(1)-T(6)). Leukocytes were counted and cells isolated by gradient centrifugation; then, glutathione peroxidase 1 and 3 (GPX1 and GPX3), glucocorticoid receptor alpha (GRα), l-selectin, nuclear factor κB, subunit p65 (NFκB) and tumor necrosis factor alpha (TNFα) mRNA amounts were measured through a quantitative Real Time RT-PCR approach. A significant change vs controls in NEU/LFC ratio was noticed from T(3) forward. Compared to T(0), DEX significantly increased to a variable extent all candidate gene mRNAs abundances in NEU; in contrast, only l-selectin, GRα and GPX1 were significantly up-regulated in LFC. Present results suggest that illicit DEX affects transcription in cattle immune cells, that might be considered as a promising surrogate tissue for the screening of DEX abuse in cattle farming.