—NF-κB is a family of nuclear transcription factors that play a leading role in the pathogenesis of many chronic inflammatory processes and in immune response regulation. At the end of the last century, NF-κB was mainly considered as a mediator of apoptosis in immune cells. Subsequent studies demonstrated its involvement in the development of the central nervous system, plasticity, neuronal differentiation, neurodegeneration, and brain injury. However, its role in the regulation of survival of mature CNS neurons in neuroinflammation proved controversial. This review summarizes the data on the involvement of NF-κB in the response of different brain cell types to the action of pro-inflammatory factors. Different subunits of the NF-κB family form dimers whose involvement in the regulation of gene expression depends on stimulus type. Interestingly, NF-κB is involved in the pro-inflammatory activation of microglia and astrocytes, whereas in neurons its protective or degenerative effects depend on the type of stimulus and on the time of the delayed cell response. The stimulus-dependent nature of NF-κB activation is determined by a wide range of receptors triggering a number of cell signaling cascades that terminate in the activation of the transcription factor. Tumor necrosis factor receptors (TNFR) or death receptors, Toll-like receptors (TLR), and protease-activated receptors (PAR) are among the membrane receptors capable of initiating intracellular cascades leading to the activation of NF-κB. Importantly, NF-κB activity and its effects can be modulated by other transcription factors. STAT1, STAT3, and Sirt1 are the molecules that, according to recent studies, are able to change the character of the NF-κB-mediated cellular responses. Thus, NF-κB is a transcription factor playing one of the key roles in determining the outcome of negative stimuli on the nervous system, which is why it may be considered as a pharmacological target for treating neurodegenerative processes associated with inflammation.

Insulin receptors are widely distributed in the brain, where they play roles in synaptic function, memory formation, and neuroprotection. Autophosphorylation of the receptor in response to insulin stimulation is a critical step in receptor activation. In neurons, insulin stimulation leads to a rise in mitochondrial H2O2 production, which plays a role in receptor autophosphorylation. However, the kinetic characteristics of the H2O2 signal and its functional relationships with the insulin receptor during the autophosphorylation process in neurons remain unexplored to date.

Mechanical properties of neuronal cells have a key role for growth, generation of traction forces, adhesion, migration, etc. Mechanical properties are regulated by chemical signaling, neurotransmitters, and neuronal ion exchange. Disturbance of chemical signaling is accompanied by several diseases such as ischemia, trauma, and neurodegenerative diseases. It is known that the disturbance of chemical signaling, like that caused by glutamate excitotoxicity, leads to the structural reorganization of the cytoskeleton of neuronal cells and the deviation of native mechanical properties. Thus, to investigate the mechanical properties of living neuronal cells in the presence of glutamate, it is crucial to use noncontact and low-stress methods, which are the advantages of scanning ion-conductance microscopy (SICM). Moreover, a nanopipette may be used for the local delivery of small molecules as well as for a probe. In this work, SICM was used as an advanced technique for the simultaneous local delivery of glutamate and investigation of living neuronal cell morphology and mechanical behavior caused by an excitotoxic effect of glutamate.

Diabetes mellitus is associated with various complications, mainly caused by the chronic exposure of the cells to high glucose (HG) concentrations. The effects of long-term HG exposure in vitro accompanied by lipopolysaccharide (LPS) application on astrocytes are relatively unknown. We used cell medium with normal (NG, 5.5 mM) or high glucose (HG, 25 mM) for rat astrocyte cultures and measured the release of NO, IL-6, β-hexosaminidase and cell survival in response to LPS. We first demonstrated that HG long-term incubation of astrocytes increased the release of β-hexosaminidase without decreasing MTT-detected cell survival, suggesting that there is no cell membrane damage or astrocyte death but could be lysosome exocytosis. Different from what was observed for NG, all LPS concentrations tested at HG resulted in an increase in IL-6, and this was detected for both 6 h and 48 h treatments. Interestingly, β-hexosaminidase level increased after 48 h of LPS and only at HG. The NO release from astrocytes also increased with LPS application at HG but was less significant. These data endorsed the original hypothesis that long-term hyperglycemia increases proinflammatory activation of astrocytes, and β-hexosaminidase could be a specific marker of excessive activation of astrocytes associated with exocytosis.

Serine proteases regulate cell functions through G protein-coupled protease-activated receptors (PARs). Cleavage of one peptide bond of the receptor amino terminus results in the formation of a new N-terminus (“tethered ligand”) that can specifically interact with the second extracellular loop of the PAR receptor and activate it. Activation of PAR1 by thrombin (canonical agonist) and activated protein C (APC, noncanonical agonist) was described as a biased agonism. Here, we have supposed that synthetic peptide analogs to the PAR1 tethered ligand liberated by APC could have neuroprotective effects like APC. To verify this hypothesis, a model of the ischemic brain impairment based on glutamate (Glu) excitotoxicity in primary neuronal cultures of neonatal rats has been used. It was shown that the nanopeptide NPNDKYEPF-NH2 (AP9) effectively reduced the neuronal death induced by Glu. The influence of AP9 on cell survival was comparable to that of APC. Both APC and AP9 reduced the dysregulation of intracellular calcium homeostasis in cultured neurons induced by excitotoxic Glu (100 µM) or NMDA (200 µM) concentrations. PAR1 agonist synthetic peptides might be noncanonical PAR1 agonists and a basis for novel neuroprotective drugs for disorders related to Glu excitotoxicity such as brain ischemia, trauma and some neurodegenerative diseases.

The present study focuses on possible ways to protect brain neurons during neuroinflammation. For the first time it is shown that peptide NPNDKYEPF amide, similar to activated protein C (APC),...