Roberto Stella

Cellular Prion Protein Promotes Regeneration of Adult Muscle Tissue

ABSTRACT It is now well established that the conversion of the cellular prion protein, PrPC, into its anomalous conformer, PrPSc, is central to the onset of prion disease. However, both the mechanism of prion-related neurodegeneration and the physiologic role of PrPC are still unknown. The use of animal and cell models has suggested a number of putative functions for the protein, including cell signaling, adhesion, proliferation, and differentiation. Given that skeletal muscles express significant amounts of PrPC and have been related to PrPC pathophysiology, in the present study, we used skeletal muscles to analyze whether the protein plays a role in adult morphogenesis. We employed an in vivo paradigm that allowed us to compare the regeneration of acutely damaged hind-limb tibialis anterior muscles of mice expressing, or not expressing, PrPC. Using morphometric and biochemical parameters, we provide compelling evidence that the absence of PrPC significantly slows the regeneration process compared to wild-type muscles by attenuating the stress-activated p38 pathway, and the consequent exit from the cell cycle, of myogenic precursor cells. Demonstrating the specificity of this finding, restoring PrPC expression completely rescued the muscle phenotype evidenced in the absence of PrPC.

Cellular prion protein is implicated in the regulation of local Ca2+ movements in cerebellar granule neurons

J. Neurochem. (2011) 116, 881–890.

Protein Expression Changes in Skeletal Muscle in Response to Growth Promoter Abuse in Beef Cattle

The fraudulent treatment of cattle with growth promoting agents (GPAs) is a matter of great concern for the European Union (EU) authorities and consumers. It has been estimated that 10% of animals are being illegally treated in the EU. In contrast, only a much lower percentage of animals (<0.5%) are actually found as being noncompliant by conventional analytical methods. Thus, it has been proposed that methods should be developed that can detect the use of the substances via the biological effects of these substances on target organs, such as the alteration of protein expression profiles. Here we present a study aimed at evaluating if a correlation exists between the treatment with GPAs and alterations in the two-dimensional electrophoresis (2DE) protein pattern obtained from the biceps brachii skeletal muscle from mixed-bred cattle. After image analysis and statistical evaluation, protein spots that differentiate between treated and control groups were selected for analysis by mass spectrometry. A set of proteins could be defined that accurately detect the use of glucocorticoids and β(2)-agonists as growth promoters through the changes caused in muscle differentiation. As a further validation, we repeated the analysis using an independent set of samples from a strain of pure-bred cattle and verified these proteins by Western blot analysis.

Evaluation of thymus morphology and serum cortisol concentration as indirect biomarkers to detect low-dose dexamethasone illegal treatment in beef cattle

BackgroundCorticosteroids are illegally used in several countries as growth promoters in veal calves and beef cattle, either alone or in association with sex steroids and β-agonists, especially at low dosages and primarily through oral administration, in order to enhance carcasses and meat quality traits. The aim of the present study is to evaluate the reliability of the histological evaluation of the thymus, as well as the serum cortisol determination, in identifying beef cattle, treated with two different dexamethasone-based growth-promoting protocols and the application of different withdrawal times before slaughter.ResultsOur findings demonstrate that low dosages of dexamethasone (DXM), administered alone or in association with clenbuterol as growth promoter in beef cattle, induce morphologic changes in the thymus, resulting in increase fat infiltration with concurrent cortical atrophy and reduction of the cortex/medulla ratio (C/M). In fact, the C/M value was significantly lower in treated animals than in control ones, with both the protocols applied. The cut off value of 0.93 for the cortex/medulla ratio resulted to be highly effective to distinguish control and treated animals. The animals treated with DXM showed inhibition of cortisol secretion during the treatment period, as well as at the slaughterhouse, 3 days after treatment suspension. The animals treated with lower doses of DXM in association with clenbuterol, showed inhibition of cortisol secretion during the treatment period, but serum cortisol concentration was restored to physiological levels at slaughterhouse, 8 days after treatment suspension.ConclusionsThe histological evaluation of thymus morphology, and particularly of the C/M may represent a valuable and reproducible method applicable to large-scale screening programs, due to the easy sampling procedures at slaughterhouse, as well as time and cost-saving of the analysis. Serum cortisol determination could be considered as an useful in vivo biomarker of dexamethasone illegal treatment in beef cattle during the fattening period, whilst it does not appear to be a good biomarker at the slaughterhouse, since the protocol of DXM administration, as well as the withdrawal period could affect the reliability of the method.

Relative quantification of membrane proteins in wild-type and prion protein (PrP)-knockout cerebellar granule neurons.

Approximately 25% of eukaryotic proteins possessing homology to at least two transmembrane domains are predicted to be embedded in biological membranes. Nevertheless, this group of proteins is not usually well represented in proteome-wide experiments due to their refractory nature. Here we present a quantitative mass spectrometry-based comparison of membrane protein expression in cerebellar granule neurons grown in primary culture that were isolated from wild-type mice and mice lacking the cellular prion protein. This protein is a cell-surface glycoprotein that is mainly expressed in the central nervous system and is involved in several neurodegenerative disorders, though its physiological role is unclear. We used a low specificity enzyme α-chymotrypsin to digest membrane proteins preparations that had been separated by SDS-PAGE. The resulting peptides were labeled with tandem mass tags and analyzed by MS. The differentially expressed proteins identified using this approach were further analyzed by multiple reaction monitoring to confirm the expression level changes.

Quantification of Membrane Proteins Using Nonspecific Protease Digestions

We present a mass spectrometry-based method for the identification and quantification of membrane proteins using the low-specificity protease Proteinase K, at very high pH, to digest proteins isolated by a modified SDS-PAGE protocol. The resulting peptides are modified with a fragmentation-directing isotope labeled tag. We apply the method to quantify differences in membrane protein expression of Bacillus subtilis grown in the presence or absence of glucose.

Proteomics for the detection of indirect markers of steroids treatment in bovine muscle.

Despite the ban by the European Union, anabolic steroids might still be illicitly employed in bovine meat production. The surveillance of misuse of such potentially harmful molecules is necessary to guarantee consumers’ health. Analytical methods for drug residue control are based on LC‐MS/MS, but their efficacy can be hindered due to undetectable residual concentrations as a result of low‐dosage treatments. Screening methods based on the recognition of indirect biological effects of growth promoters’ administration, such as the alteration of protein expression, can improve the efficacy of surveillance. The present study was aimed at identifying modifications in the muscle protein expression pattern between bulls treated with an ear implant (Revalor‐XS®) containing trenbolone acetate (200 mg) and estradiol (40 mg), and untreated animals. The analysis of skeletal muscle was carried out using a tandem mass tags shotgun proteomics approach. We defined 28 candidate protein markers with a significantly altered expression induced by steroids administration. A subset of 18 candidate markers was validated by SRM and allowed to build a predictive model based on partial least square discriminant analysis. Our findings confirm the effectiveness of the proteomics approach as potential tool to overcome analytical limitations of drug residue monitoring.

Development and validation of a QuEChERS method coupled to liquid chromatography and high resolution mass spectrometry to determine pyrrolizidine and tropane alkaloids in honey

Awareness about pyrrolizidine alkaloids (PAs) and tropane alkaloids (TAs) in food was recently raised by the European Food Safety Authority stressing the lack of data and gaps of knowledge required to improve the risk assessment strategy. The present study aimed at the elaboration and validation of a method to determine PAs and TAs in honey. QuEChERS sample treatment and liquid chromatography coupled to hybrid high resolution mass spectrometry, were used. The method resulted in good linearity (R2>0.99) and low limits of detection and quantification, ranging from 0.04 to 0.2µgkg-1 and from 0.1 to 0.7µgkg-1 respectively. Recoveries ranged from 92.3 to 114.8% with repeatability lying between 0.9 and 15.1% and reproducibility between 1.1 and 15.6%. These performances demonstrate the selectivity and sensitivity of the method for simultaneous trace detection and quantification of PAs and TAs in honey, verified through the analysis of forty commercial samples.

Confirmation of Protein Biomarkers of Corticosteroids Treatment in Veal Calves Sampled under Field Conditions

In veal calf production, growth promoters are still illicitly used. Surveillance of misuse of such molecules is necessary to preserve human health. Methods currently adopted for their analysis are based on liquid chromatography-tandem mass spectrometry, but their efficacy can be affected by undetectable residual concentrations in biological matrices due to treatments at low-dosage or based on unknown anabolic compounds. The development of screening methods to identify the indirect biological effects of administration of growth promoters can improve the efficiency of drug residue monitoring. To this purpose, an integrated approach has been used to further validate the set of protein biomarkers defined in a previous controlled study to detect the use of corticosteroids through the changes caused in muscle protein expression. The thymus morphology of 48 samples collected under field conditions was evaluated to assess the presence of potential corticosteroids treatment. Animals were divided on the basis of their thymus characteristics in negative or suspected for illegal corticosteroids treatment. Drug residue analyses were performed on the liver, giving a satisfactory correlation with the histological examination (∼85%). Finally, the proteomics analysis of muscle protein extracts was carried out by 2D differential in gel electrophoresis, and proteins that were differentially expressed between the two animal groups (p value <0.01) were selected for MALDI-MS/MS analysis. This approach allowed us to identify 29 different proteins, and our findings indicate that the altered protein expression pattern can be used as an indirect method for the detection of illicit corticosteroids administration. A subset of the identified proteins was already reported in a previous controlled study, proving that these biomarkers can be used to develop a screening assay to improve the tools currently available for the detection of corticosteroids abuse in bovine meat production.

Age-dependent neuromuscular impairment in prion protein knockout mice.

Introduction: The cellular prion protein (PrPC) is commonly recognized as the precursor of prions, the infectious agents of the fatal transmissible spongiform encephalopathies, or prion diseases. Despite extensive effort, the physiological role of PrPC is still ambiguous. Evidence has suggested that PrPC is involved in different cellular functions, including peripheral nerve integrity and skeletal muscle physiology. Methods: We analyzed the age‐dependent influence of PrPC on treadmill test–based aerobic exercise capacity and on a series of morphological and metabolic parameters using wild‐type and genetically modified mice of different ages expressing, or knockout (KO) for, PrPC. Results: We found that aged PrP‐KO mice displayed a reduction in treadmill performance compared with PrP‐expressing animals, which was associated with peripheral nerve demyelination and alterations of skeletal muscle fiber type. Conclusion: PrP‐KO mice have an age‐dependent impairment of aerobic performance as a consequence of specific peripheral nerve and muscle alterations. Muscle Nerve 53: 269–279, 2016