Several peptides, including penetratin and Tat, are known to translocate across the plasma membrane. Dynorphin opioid peptides are similar to cell-penetrating peptides in a high content of basic and hydrophobic amino acid residues. We demonstrate that dynorphin A and big dynorphin, consisting of dynorphins A and B, can penetrate into neurons and non-neuronal cells using confocal fluorescence microscopy/immunolabeling. The peptide distribution was characterized by cytoplasmic labeling with minimal signal in the cell nucleus and on the plasma membrane. Translocated peptides were associated with the endoplasmic reticulum but not with the Golgi apparatus or clathrin-coated endocytotic vesicles. Rapid entry of dynorphin A into the cytoplasm of live cells was revealed by fluorescence correlation spectroscopy. The translocation potential of dynorphin A was comparable with that of transportan-10, a prototypical cell-penetrating peptide. A central big dynorphin fragment, which retains all basic amino acids, and dynorphin B did not enter the cells. The latter two peptides interacted with negatively charged phospholipid vesicles similarly to big dynorphin and dynorphin A, suggesting that interactions of these peptides with phospholipids in the plasma membrane are not impaired. Translocation was not mediated via opioid receptors. The potential of dynorphins to penetrate into cells correlates with their ability to induce non-opioid effects in animals. Translocation across the plasma membrane may represent a previously unknown mechanism by which dynorphins can signal information to the cell interior.

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Pregabalin and gabapentin are amino-acid derivatives of gamma-aminobutyric acid. They have a high affinity to the a2d protein in the central nervous system and both have been shown to be effective for neuropathic pain disorder. The aim of this study was to investigate the efficacy of gabapentin and pregabalin in animal models of neuropathic pain, and to correlate with clinical outcomes in patients with diabetic neuropathy. Gabapentin (60 mg/kg) and pregabalin (30 mg/kg) attenuate mechanical, tactile and heat hypersensitivity in rats with chronic constriction injury of the sciatic nerve and streptozotocin (STZ)-induced diabetes. There is no evidence that one of the drugs is superior to another at the different rat models and tests. In the incisional pain model, there was partial efficacy of gabapentin. Our clinical data suggest that relative to the baseline pain score, the treatment with pregabalin at doses of 300 mg/day or gabapentin at doses of 900 mg/day would be effective and well tolerated in patients diagnosed with moderate diabetic polyneuropathy. The study suggested that pregabalin may provide better analgesic outcomes than gabapentin on the sixth month of treatment. In conclusion, the comparative effects of gabapentinoids in animal models of neuropathic pain and neuropathic patients are suggestive of similar pathophysiological mechanisms being involved, but successful outcome is determined by a patient's individuality and the drug nature as well as the drug tolerability.

We have recently identified several aroylhydrazone-based molecular hybrids with antiseizure activity. We aimed to investigate the analgesic activity of these molecules further. Male ICR mice were injected intraperitoneally with the tested substances or with the vehicle only (controls). We performed hot plate tests, formalin test and maximal electroshock (MES) test and further studied the cytokine proteome in the brain. In silico analysis was performed for prediction of the physicochemical parameters and activity. The furan-substituted aroylhydrazone-based 2Hchromene hybrid showed a significant increase of the latent time as compared with the baseline values (p < .05). Both the chlorine-substituted and the methyl-substituted aroylhydrazone-based coumarin derivatives significantly decreased the first phase of the formalin test (p < .05). We also found suppression of all the cytokines which were overexpressed in the model of acute seizures (MES test) and in the formalin paw test. The in silico model predicted hydroxymethylglutaryl coenzyme A synthetase 2 (HMGCS2) enhancer activity. Further testing is needed to confirm the mechanism of the potentially beneficial effects of the tested substances and to evaluate the toxicity and efficacy of the proposed molecules.

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Drug resistance and toxicity are the most widespread limitations in the pursuit of sufficient antitumor effectiveness and successful control of oncological diseases, including colorectal cancer (CRC). Herein the objective was to investigate some hematological side effects of the chemotherapeutic regimen FOLFOX-4, their relation to dihydropyrimidine dehydrogenase (DPD) levels and the associated alterations in CRC patients' plasma free-radical scavenging properties and extent of oxidative molecular damage. Thirty-eight patients with histologically confirmed CRC diagnoses, assigned to chemotherapy with the FOLFOX-4 regimen, were recruited. The diagnostic methods included a complete physical examination, blood routine test and general biochemistry. The DPD levels were assayed. The patients' plasma free-radical scavenging properties and extent of molecular oxidative damage were determined by spectrophotometry and enhanced chemiluminescence. The clinico-pathological and demographics characteristics of the patients were in agreement with the reports from retrospective cohort studies. The FOLFOX-4 regimen induced a decrease in plasma free-radical scavenging properties and increased extent of lipid peroxidation. White blood cells, granulocytes and lymphocytes decreased significantly after the first cycle of the therapy. The patients' DPD level decreased statistically significantly in the case of severe reduction (more than 25%) of white blood cells and granulocyte counts. The obtained data are in agreement with already known facts concerning the side effects of the FOLFOX-4 regimen and associated changes in redox homeostasis. Genetic predisposition to effectively metabolize and tolerate the applied therapy, i.e. DPD levels, could modulate some aspects of the observed changes in the aforementioned parameters.