Constant activity of glutamine synthetase after morphine administration versus proteomic results

Assessing effects of tamoxifen on tolerance, dependence, and glutamate and glutamine levels in frontal cortex and hippocampus in chronic morphine treatment

Tamoxifen has been shown to reduce glutamate release from presynaptic glutamatergic nerves and reverse tolerance to morphine-induced respiratory depression. Changes in glutamatergic neurotransmission in the central nervous system contribute to morphine tolerance, dependence, and withdrawal. This study, therefore, evaluated effects of tamoxifen on development of analgesic tolerance and dependence, and brain glutamate and glutamine levels in chronic morphine administration. Mice implanted with placebo or morphine pellets were injected with tamoxifen (0.6-2 mg/kg) or vehicle twice daily for 3 days. Nociceptive response was evaluated in the hot plate and tail immersion tests, 4, 48 and 72 h post-implant, and following a challenge dose of morphine (10 mg/kg). Withdrawal signs were determined after naloxone (1 mg/kg) administration. Morphine increased nociceptive threshold which declined over time. At 72 h, acute morphine elicited tolerance to the analgesic effect in the hot plate test in vehicle or tamoxifen administered animals. In the tail immersion test, however, tolerance to morphine analgesia was observed in tamoxifen, but not vehicle, co-administration. Tamoxifen did not reduce withdrawal signs. In contrast to previous reports, glutamate and glutamine levels in the hippocampus and frontal cortex did not change in the morphine-vehicle group. Confirming previous findings, tamoxifen (2 mg/kg) decreased glutamate and glutamine concentrations in the hippocampus in animals with placebo pellets. Both doses of tamoxifen significantly changed glutamate and/or glutamine concentrations in both regions in morphine pellet implanted animals. These results suggest that tamoxifen has no effect on dependence but may facilitate tolerance development to the antinociception, possibly mediated at the spinal level, in chronic morphine administration.

Impact of Opioids on Cellular Metabolism: Implications for Metabolic Pathways Involved in Cancer

Opioid utilization for pain management is prevalent among cancer patients. There is significant evidence describing the many effects of opioids on cancer development. Despite the pivotal role of metabolic reprogramming in facilitating cancer growth and metastasis, the specific impact of opioids on crucial oncogenic metabolic pathways remains inadequately investigated. This review provides an understanding of the current research on opioid-mediated changes to cellular metabolic pathways crucial for oncogenesis, including glycolysis, the tricarboxylic acid cycle, glutaminolysis, and oxidative phosphorylation (OXPHOS). The existing literature suggests that opioids affect energy production pathways via increasing intracellular glucose levels, increasing the production of lactic acid, and reducing ATP levels through impediment of OXPHOS. Opioids modulate pathways involved in redox balance which may allow cancer cells to overcome ROS-mediated apoptotic signaling. The majority of studies have been conducted in healthy tissue with a predominant focus on neuronal cells. To comprehensively understand the impact of opioids on metabolic pathways critical to cancer progression, research must extend beyond healthy tissue and encompass patient-derived cancer tissue, allowing for a better understanding in the context of the metabolic reprogramming already undergone by cancer cells. The current literature is limited by a lack of direct experimentation exploring opioid-induced changes to cancer metabolism as they relate to tumor growth and patient outcome.

Alterations in the Proteome and Phosphoproteome Profiles of Rat Hippocampus after Six Months of Morphine Withdrawal: Comparison with the Forebrain Cortex

The knowledge about proteome changes proceeding during protracted opioid withdrawal is lacking. Therefore, the aim of this work was to analyze the spectrum of altered proteins in the rat hippocampus in comparison with the forebrain cortex after 6-month morphine withdrawal. We utilized 2D electrophoretic workflow (Pro-Q® Diamond staining and Colloidal Coomassie Blue staining) which was preceded by label-free quantification (MaxLFQ). The phosphoproteomic analysis revealed six significantly altered hippocampal (Calm1, Ywhaz, Tuba1b, Stip1, Pgk1, and Aldoa) and three cortical proteins (Tubb2a, Tuba1a, and Actb). The impact of 6-month morphine withdrawal on the changes in the proteomic profiles was higher in the hippocampus—14 proteins, only three proteins were detected in the forebrain cortex. Gene Ontology (GO) enrichment analysis of differentially expressed hippocampal proteins revealed the most enriched terms related to metabolic changes, cytoskeleton organization and response to oxidative stress. There is increasing evidence that energy metabolism plays an important role in opioid addiction. However, the way how morphine treatment and withdrawal alter energy metabolism is not fully understood. Our results indicate that the rat hippocampus is more susceptible to changes in proteome and phosphoproteome profiles induced by 6-month morphine withdrawal than is the forebrain cortex.

Mass Spectrometry versus Conventional Techniques of Protein Detection: Zika Virus NS3 Protease Activity towards Cellular Proteins

Mass spectrometry (MS) used in proteomic approaches is able to detect hundreds of proteins in a single assay. Although undeniable high analytical power of MS, data acquired sometimes lead to confusing results, especially during a search of very selective, unique interactions in complex biological matrices. Here, we would like to show an example of such confusing data, providing an extensive discussion on the observed phenomenon. Our investigations focus on the interaction between the Zika virus NS3 protease, which is essential for virus replication. This enzyme is known for helping to remodel the microenvironment of the infected cells. Several reports show that this protease can process cellular substrates and thereby modify cellular pathways that are important for the virus. Herein, we explored some of the targets of NS3, clearly shown by proteomic techniques, as processed during infection. Unfortunately, we could not confirm the biological relevance of protein targets for viral infections detected by MS. Thus, although mass spectrometry is highly sensitive and useful in many instances, also being able to show directions where cell/virus interaction occurs, we believe that deep recognition of their biological role is essential to receive complete insight into the investigated process.

Proteome profiling of different rat brain regions reveals the modulatory effect of prolonged maternal separation on proteins involved in cell death-related processes

Background

Early-life stress in the form of maternal separation can be associated with alterations in offspring neurodevelopment and brain functioning. Here, we aimed to investigate the potential impact of prolonged maternal separation on proteomic profiling of prefrontal cortex, hippocampus and cerebellum of juvenile and young adult rats. A special attention was devoted to proteins involved in the process of cell death and redox state maintenance.

Methods

Long-Evans pups were separated from their mothers for 3 h daily over the first 3 weeks of life (during days 2–21 of age). Brain tissue samples collected from juvenile (22-day-old) and young adult (90-day-old) rats were used for label-free quantitative (LFQ) proteomic analysis. In parallel, selected oxidative stress markers and apoptosis-related proteins were assessed biochemically and by Western blot, respectively.

Results

In total, 5526 proteins were detected in our proteomic analysis of rat brain tissue. Approximately one tenth of them (586 proteins) represented those involved in cell death processes or regulation of oxidative stress balance. Prolonged maternal separation caused changes in less than half of these proteins (271). The observed alterations in protein expression levels were age-, sex- and brain region-dependent. Interestingly, the proteins detected by mass spectrometry that are known to be involved in the maintenance of redox state were not markedly altered. Accordingly, we did not observe any significant differences between selected oxidative stress markers, such as the levels of hydrogen peroxide, reduced glutathione, protein carbonylation and lipid peroxidation in brain samples from rats that underwent maternal separation and from the corresponding controls. On the other hand, a number of changes were found in cell death-associated proteins, mainly in those involved in the apoptotic and autophagic pathways. However, there were no detectable alterations in the levels of cleaved products of caspases or Bcl-2 family members. Taken together, these data indicate that the apoptotic and autophagic cell death pathways were not activated by maternal separation either in adolescent or young adult rats.

Conclusion

Prolonged maternal separation can distinctly modulate expression profiles of proteins associated with cell death pathways in prefrontal cortex, hippocampus and cerebellum of juvenile rats and the consequences of early-life stress may last into adulthood and likely participate in variations in stress reactivity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00327-5.

Repeated Administration of Clinically Relevant Doses of the Prescription Opioids Tramadol and Tapentadol Causes Lung, Cardiac, and Brain Toxicity in Wistar Rats

Tramadol and tapentadol, two structurally related synthetic opioid analgesics, are widely prescribed due to the enhanced therapeutic profiles resulting from the synergistic combination between μ-opioid receptor (MOR) activation and monoamine reuptake inhibition. However, the number of adverse reactions has been growing along with their increasing use and misuse. The potential toxicological mechanisms for these drugs are not completely understood, especially for tapentadol, owing to its shorter market history. Therefore, in the present study, we aimed to comparatively assess the putative lung, cardiac, and brain cortex toxicological damage elicited by the repeated exposure to therapeutic doses of both prescription opioids. To this purpose, male Wistar rats were intraperitoneally injected with single daily doses of 10, 25, and 50 mg/kg tramadol or tapentadol, corresponding to a standard analgesic dose, an intermediate dose, and the maximum recommended daily dose, respectively, for 14 consecutive days. Such treatment was found to lead mainly to lipid peroxidation and inflammation in lung and brain cortex tissues, as shown through augmented thiobarbituric acid reactive substances (TBARS), as well as to increased serum inflammation biomarkers, such as C reactive protein (CRP) and tumor necrosis factor-α (TNF-α). Cardiomyocyte integrity was also shown to be affected, since both opioids incremented serum lactate dehydrogenase (LDH) and α-hydroxybutyrate dehydrogenase (α-HBDH) activities, while tapentadol was associated with increased serum creatine kinase muscle brain (CK-MB) isoform activity. In turn, the analysis of metabolic parameters in brain cortex tissue revealed increased lactate concentration upon exposure to both drugs, as well as augmented LDH and creatine kinase (CK) activities following tapentadol treatment. In addition, pneumo- and cardiotoxicity biomarkers were quantified at the gene level, while neurotoxicity biomarkers were quantified both at the gene and protein levels; changes in their expression correlate with the oxidative stress, inflammatory, metabolic, and histopathological changes that were detected. Hematoxylin and eosin (H & E) staining revealed several histopathological alterations, including alveolar collapse and destruction in lung sections, inflammatory infiltrates, altered cardiomyocytes and loss of striation in heart sections, degenerated neurons, and accumulation of glial and microglial cells in brain cortex sections. In turn, Masson's trichrome staining confirmed fibrous tissue deposition in cardiac tissue. Taken as a whole, these results show that the repeated administration of both prescription opioids extends the dose range for which toxicological injury is observed to lower therapeutic doses. They also reinforce previous assumptions that tramadol and tapentadol are not devoid of toxicological risk even at clinical doses.

2D Electrophoretic pattern of bovine placental proteins during early-mid pregnancy

The Placenta, like every tissue, possesses its own characteristic protein profile, which may change within the course of pregnancy. These changes can be used for the elucidation of the mechanisms related to both physiology of pregnancy and pathological events. The aim of the study was to describe proteinergic profiles of maternal and fetal parts of bovine placenta during early-mid pregnancy by the use of 2D electrophoresis and MALDI TOF/TOF MS identification to evaluate dynamics of the possible changes necessary for placentation. Placental samples were collected from six pregnant cows (3-5 months) in the local abattoir. Placentomes were separated, and proteins were extracted and subjected to 2D electrophoresis and MALDI TOF/TOF identification. Out of 907 spots identified by the statistical analysis of gels, 54 were identified. Out of this number, 36 spots were significantly different between examined samples. Moreover, the obtained patterns differed between maternal and fetal parts of the placenta with regard to the intensity of staining, suggesting quantitative differences in protein content. These preliminary results are unique for this period of pregnancy. Such data are important for further experiments to obtain full protein profiles necessary to understand biochemical mechanisms underlying the attachment between fetal and maternal parts of the placenta during placentation. Moreover, the outcomes may help in elucidating pregnancy biomarkers in the future.

Proteomic Data in Morphine Addiction Versus Real Protein Activity: Metabolic Enzymes

Drug dependence is an escalating problem worldwide and many efforts are being made to understand the molecular basis of addiction. The morphine model is widely used in these investigations. To date, at least 29 studies exploring the influence of morphine on mammals' proteomes have been published. Among various proteins indicated as up- or down-regulated, the expression changes of enzymes engaged in energy metabolism pathways have often been confirmed. To verify whether proteomics-indicated alterations in enzyme levels reflect changes in their activity, four enzymes: PK, MDH, Complex I, and Complex V were investigated in morphine addiction and abstinence models. After analyses of the rat brain mitochondria fraction in the model of morphine dependence, we found that one of the investigated enzymes (pyruvate kinase) showed statistically significant differences observed between morphine, control, and abstinence groups. J. Cell. Biochem. 118: 4323-4330, 2017. © 2017 Wiley Periodicals, Inc.