Glucocorticoids Orchestrate Adult Hippocampal Plasticity: Growth Points and Translational Aspects

The review analyzes modern concepts about the control of various mechanisms of the hippocampal neuroplasticity in adult mammals and humans by glucocorticoids. Glucocorticoid hormones ensure the coordinated functioning of key components and mechanisms of hippocampal plasticity: neurogenesis, glutamatergic neurotransmission, microglia and astrocytes, systems of neurotrophic factors, neuroinflammation, proteases, metabolic hormones, neurosteroids. Regulatory mechanisms are diverse; along with the direct action of glucocorticoids through their receptors, there are conciliated glucocorticoid-dependent effects, as well as numerous interactions between various systems and components. Despite the fact that many connections in this complex regulatory scheme have not yet been established, the study of the factors and mechanisms considered in the work forms growth points in the field of glucocorticoid-regulated processes in the brain and primarily in the hippocampus. These studies are fundamentally important for the translation into the clinic and the potential treatment/prevention of common diseases of the emotional and cognitive spheres and respective comorbid conditions.

[Molecular mechanisms of brain peptide-containing drugs: cortexin]

The goal of treatment of brain pathologies may be regarded as re-establishment of optimal brain plasticity. Disturbances in neuroplasticity are associated with the appearance of multiple targets that should be subjects for pharmacological correction. Peptide hydrolysates derived from animal brain became a basis for multi-component organ-specific drugs which are widely used for treatment of cerebral pathologies. Potentially, the presence of many components in such drugs may be beneficial for simultaneous effects on different targets. In this article, new data are analyzed related to relevant molecular mechanisms underlying neuroprotective properties of cortexin. On a model of accelerated aging in rats, cortexin restored the ratio of pro- and antioxidative systems and demonstrated a significant anti-inflammatory effect both in the brain and at the systemic level. In in vitro experiments cortexin effectively and tissue-specifically inhibited brain caspase-8. Neuron-specific proteins β5-tubulin, creatine kinase B and protein 14-3-3 α/β were shown to be molecular partners of cortexin peptides in the brain. Thus, potential molecular mechanisms of cortexin neuroprotective effects are various and associated with key processes underlying neuroplasticity: signal transduction, energy metabolism, proteolytic protein modification, cell structure, as well as neuroinflammation. The pleiotropicity of mechanisms of cortexin action is based on the composition of the drug containing a variety of neuropeptides. The tissue specificity of these mechanisms determines to a significant degree the efficacy of the drug in treatment of cerebral pathologies.

High levels of glucose induces a dose-dependent apoptosis in human periodontal ligament fibroblasts by activating caspase-3 signaling pathway

Periodontitis is one of the main complications of diabetes mellitus and many researches have been done on the relationship between periodontitis and diabetes mellitus, but too much are still unclear, especially the mechanisms by which high glucose induces damage of periodontal ligament fibroblasts. So in this study, we investigated the effects of different concentration of high glucose on apoptosis in human periodontal ligament fibroblasts and the possible mechanisms involved. Human periodontal ligament fibroblasts were cultured and subjected to glucose of different concentration (5.5, 15, 25, and 35 mM) for 24 h. Apoptosis was studied by flow cytometry, caspase assays, fluorescent real-time PCR and Western blot. We also determined Fas/FasL expression was by Western blot. The application of different concentration of high glucose induced a concentration-dependent increase of apoptosis and the activity of caspase-3 in cultured human periodontal ligament fibroblasts. Furthermore, inhibitor of caspase-3 could prevent the high-glucose-induced apoptosis in human periodontal ligament fibroblasts. Protein levels of Fas and FasL remained unchanged. These data indicate that high glucose induces a concentration- and caspase-3-dependent increase of apoptosis in cultured human periodontal ligament fibroblasts in vitro. Activation of caspase-3 caused by high glucose is independent of Fas/FasL signaling pathways system. These results suggest a novel mechanism for the regulation of human periodontal ligament fibroblasts apoptosis by high glucose.

Region-specific changes in activities of cell death-related proteases and nitric oxide metabolism in rat brain in a chronic unpredictable stress model

Effects of a chronic combined unpredictable stress on activities of two cell death-related proteases, calpain and cathepsin B, were studied along with indices of nitrergic system in rat brain structures. Male Wistar rats were subjected to a 2-week-long combined stress (combination of unpaired flash light and moderate footshock associated with a white noise session). Stress resulted in a significant loss in the body and thymus weight and increased defecation in the open field test, though neither motor and exploratory activity, nor plasma corticosterone differed from the respective control levels. Decreased calpain activity and increased cathepsin B activity were demonstrated in the hippocampus of stressed rats (previously we have shown that caspase-3 activity was significantly suppressed in the brain of rats subjected to same type of stress). A significant reduction in the number of NOS-containing neurons was accompanied by a chronic stressinduced decline in NOS activity in the neocortex. Similar changes were observed in the hippocampus. However, levels of NO metabolites were elevated in both structures. Thus, stress-induced structural modifications in the brain may be mediated by disturbances in the nitrergic system and increased lysosomal proteolysis.