Since the discovery of the neuron-specific protein by Moore and McGregor in 1965, tens of thousands of studies have investigated the basic and applied significance of neuron-specific enolase (NSE). This promising biomarker, according to many researchers, has not found widespread use in clinical practice, particularly in acute cerebrovascular accidents. Moreover, the several studies refuting the usefulness of serum NSE measurement in critically ill patients leads us to consider the reasons for such contradictory conclusions. In this article, we have analyzed the main directions in the study of NSE and expressed our perspective on the reasons for the contradictory results and the difficulties in implementing the results of these studies in clinical practice. In our opinion, the method of the enzyme-linked immunosorbent assay (ELISA) used in the majority of the studies is inappropriate for the evaluation of NSE as a marker of central nervous system damage, because it does not allow for the differentiation of heterodimers of enolases and the assessment of the enzymatic activity of this group of enzymatic proteins. Therefore, the methodological approach for the evaluation of NSE (γγ-enolase) as a biomarker needs to be elaborated and improved. Furthermore, the specificity of the applied research methods and the appropriateness of the continued use of the term “neuron-specific enolase” must be addressed.

This is the first in vivo study to investigate the neuroprotective effects of krypton on focal cerebral ischemia. The aim of the study was to analyze the effect of 2 h of inhalation of a krypton–oxygen mixture (Kr 70%/O₂ 30%) on the recovery of neurological functions and the degree of brain damage in rats after photoinduced ischemic stroke (PIS) and to investigate the possible mechanisms responsible for this neuroprotection. Experiments were performed on male Wistar rats weighing 250–300 g (n = 32). Animals were randomized into four groups. Two groups (n = 20) underwent photoinduced ischemic stroke, followed by 2 h of inhalation of krypton–oxygen mixture consisting of Kr 70%/O₂ 30% or a nitrogen–oxygen breathing mixture consisting of N₂ 70%/O₂ 30%, followed by neurological examinations on days 3 and 7. The other two groups (n = 12) received only gas mixtures of the same concentration and exposure duration as in those in the PIS groups, then Western blot analysis of the potential molecular mechanisms was performed. The results of the study show that treatment with the krypton–oxygen mixture consisting of Kr 70%/O₂ 30% improves the neurological status on day 7 of observation, reduces the lesion volume according to the MRI examination and the number of Iba-1- and caspase-3-positive cells in the damaged area, promotes the activation of neoangiogenesis (an increase in the von Willebrand factor), and reduces the penumbra area and the number of NeuN-positive cells in it on day 14 of observation. Inhalation of the krypton–oxygen mixture also significantly increases the levels of phosphorylated AKT kinase (protein kinase B) and glycogen synthase kinase 3b (pGSK3b) and promotes the expression of transcription factor Nrf2, which was accompanied by the lowered expression of transcription factor NFkB (p50). Thus, we showed pronounced neuroprotection induced by krypton inhalation after stroke and identified the signaling pathways that may be responsible for restoring neurological functions and reducing damage.

Despite the enormous interest in COVID-19, there is no clear understanding of the mechanisms underlying the neurological symptoms in COVID-19. Microglia have been hypothesized to be a potential mediator of the neurological manifestations associated with COVID-19. In most existing studies to date, morphological changes in internal organs, including the brain, are considered in isolation from clinical data and defined as a consequence of COVID-19. We performed histological immunohistochemical (IHC) studies of brain autopsy materials of 18 patients who had died from COVID-19. We evaluated the relationship of microglial changes with the clinical and demographic characteristics of the patients. The results revealed neuronal alterations and circulatory disturbances. We found an inverse correlation between the integral density Iba-1 (microglia/macrophage-specific marker) IHC staining and the duration of the disease (R = −0.81, p = 0.001), which may indicate a reduced activity of microglia and do not exclude their damage in the long-term course of COVID-19. The integral density of Iba-1 IHC staining was not associated with other clinical and demographic factors. We observed a significantly higher number of microglial cells in close contact with neurons in female patients, which confirms gender differences in the course of the disease, indicating the need to study the disease from the standpoint of personalized medicine.

Better understanding of ischemic brain injury mechanisms is important for the development and improvement of diagnostic and therapeutic modalities for management of ischemic stroke. As experimental studies are on demand, there’s a need for relevant models of focal brain lesions. Photochemically induced thrombosis remains one of the most popular models of ischemic stroke.The purpose of the reviewis to consider the pathogenesis and applicational relevance of the photochemical thrombosis in ischemic stroke modeling.Material and methods.The information was searched using PubMed and Google Scholar databases and keywords «photothrombotic stroke» without language restrictions. 74 papers out of more than 600 sources were found the most relevant for the purpose of this review and selected for the analysis. Of these, more than 50% have been published in the last five years. The criterion for excluding a source was an inconsistency with the objectives of the review and low information content.Results.We outlined a variety of features in modeling photothrombotic stroke, analyzed the advantages and disadvantages of the model, presented data on current method’s modifications, as well as approaches to evaluation of brain lesions in ischemic stroke induced by photothrombosis, and summarized information about the mechanisms of brain damage induced in this model.Conclusion.Several advantages of the photothrombotic stroke model, such as low invasiveness, high reproducibility, inherent control of brain infarction volume and low mortality, determine its active use in experimental studies of ischemic stroke. Pathological processes in the brain modeled by photochemical thrombosis are similar to the processes occurring in acute ischemic cerebral circulation events. Therefore, this model provides insights into cellular and molecular mechanisms of ischemic brain damage, and can be used for developing novel therapeutic approaches for management of ischemic stroke.

Hemorrhagic stroke is the deadliest type of stroke. Cellular and molecular biomarkers are important for understanding the pathophysiology of stroke. Microglia are among the most promising biological markers. However, the morphological and physiological characteristics of microglia, as well as the structural and functional aspects of their interactions with neurons and other cells, are largely unknown. Due to the large number of different morphological phenotypes and very limited information on microglial changes in subarachnoid hemorrhage (SAH), we performed this study aimed at identifying the features of the distribution of various microglial phenotypes in the layers of the cerebral cortex in the hyperacute phase of non-traumatic SAH. We studied the distribution of various microglial phenotypes in the layers of the cerebral cortex of SAH non-survivors with a control group (coronary heart disease and sudden cardiac death were the underlying causes of death). An immunohistochemical study using antibodies to iba-1 (a marker of microglia) revealed changes in the morphological phenotypes of microglia in the cerebral cortex after subarachnoid hemorrhage. Significant differences between the groups indicate a rapid microglial response to injury. The findings indicate that there are quantitative and phenotypic changes in microglia in the cerebral cortex during early SAH in the human cortex.

BACKGROUND: Stroke is a global health problem and the second leading cause of death worldwide, with ischemic stroke accounting for the majority of acute cerebrovascular accidents. Predicting outcomes in patients with ischemic stroke is challenging due to the limited prognostic performance of existing models. The lack of reliable and predictive biomarkers of ischemic stroke used in clinical practice provides a rationale for studies to address this issue. AIM: The aim of this study was to identify clinical, demographic, neuroimaging and molecular biomarkers of ischemic stroke associated with the fatal outcome of the disease. MATERIALS AND METHODS: We retrospectively analyzed cases of ischemic stroke confirmed by computed tomography of the brain with a duration of 3 months or less. As factors potentially related to the outcome of ischemic stroke, we considered (1) clinical and demographic characteristics, including sex, age, history of acute cerebrovascular accident, time from stroke to hospitalization, phase and type of stroke, neurological status on admission (level of consciousness, FOUR coma scale), comorbidities (diabetes mellitus, infectious complications, oncological diseases); (2) molecular biomarkers including blood glucose and neuron-specific enolase (NSE) levels at different phases of stroke; (3) neuroimaging biomarkers such as number and location of stroke lesion, total infarct volume, signs of edema, hemorrhagic component according to computed tomography. RESULTS: 38 patients with ischemic stroke were included in the study. Lesion volume was larger in non-survivors: 123 [44.6–206.2] versus 42.7 [8.2–88.7] ml3 (p=0.032), and cerebral edema was detected significantly more often on admission CT scan than in survivors: 7 (77.8%) versus 10 (34.5%), p=0.022. Stroke lesion volume was a predictor of mortality (AUC 0.739; 95% CI 0.542–0.937; p=0.032). The optimal cut-off for stroke lesion volume was found to be 90 ml3. CONCLUSION: Signs of edema/brain stem dislocation and cerebral lesion volume 90 ml3 documented at hospital admission are predictors of fatal outcome. Therefore, neuroimaging biomarkers can be used for risk stratification of fatal outcome in ischemic stroke patients.