The blood–brain barrier (BBB) is an interface primarily comprised of brain endothelial cells (BECs), separating the central nervous system (CNS) from the systemic circulation while carefully regulating the transport of molecules and inflammatory cells, and maintaining the required steady-state environment. Inflammation modulates many BBB functions, but the ultrastructural cytoarchitectural changes of the BBB with inflammation are understudied. Inflammation was induced in male 8–10-week-old CD-1 mice with intraperitoneal lipopolysaccharide (LPS), using a regimen (3 mg/kg at 0, 6, and 24 h) that caused robust BBB disruption but had minimal lethality at the study timepoint of 28 h. Perfusion-fixed brains were collected and the frontal cortical layer III regions were analyzed using a transmission electron microscopy (TEM). The LPS-treated mice had pronounced ultrastructural remodeling changes in BECs that included plasma membrane ruffling, increased numbers of extracellular microvesicles, small exosome formation, aberrant BEC mitochondria, increased BEC transcytosis, while tight junctions appeared to be unaltered. Aberrant pericytes were contracted with rounded nuclei and a loss of their elongated cytoplasmic processes. Surveilling microglial cells were attracted to the neurovascular unit (NVU) of BECs, and astrocyte detachment and separation were associated with the formation of a perivascular space and pericapillary edema. The LPS treatment resulted in numerous ultrastructural aberrant remodeling changes to the neurovascular unit’s BECs, microglia, pericytes, and astrocytes. In summary, a disturbance of the NVU morphology is a consequence of LPS treatment.

Perivascular spaces (PVS) and their enlargement (EPVS) have been gaining interest as EPVS can be visualized non-invasively by magnetic resonance imaging (MRI) when viewing T-2-weighted images. EPVS are most commonly observed in the regions of the basal ganglia and the centrum semiovale; however, they have also been identified in the frontal cortex and hippocampal regions. EPVS are known to be increased in aging and hypertension, and are considered to be a biomarker of cerebral small vessel disease (SVD). Interest in EPVS has been significantly increased because these PVS are now considered to be an essential conduit necessary for the glymphatic pathway to provide the necessary efflux of metabolic waste. Metabolic waste includes misfolded proteins of amyloid beta and tau that are known to accumulate in late-onset Alzheimer’s disease (LOAD) within the interstitial fluid that is delivered to the subarachnoid space and eventually the cerebral spinal fluid (CSF). The CSF acts as a sink for accumulating neurotoxicities and allows clinical screening to potentially detect if LOAD may be developing early on in its clinical progression via spinal fluid examination. EPVS are thought to occur by obstruction of the PVS that associates with excessive neuroinflammation, oxidative stress, and vascular stiffening that impairs flow due to a dampening of the arterial and arteriolar pulsatility that aids in the convective flow of the metabolic debris within the glymphatic effluxing system. Additionally, increased EPVS has also been associated with Parkinson’s disease and non-age-related multiple sclerosis (MS).

Sepsis and acute liver failure are associated with severe endogenous intoxication. Microglia, which are the resident immune brain cells, play diverse roles in central nervous system development, surveillance, and defense, as well as contributing to neuroinflammatory reactions. In particular, microglia are fundamental to the pathophysiology of reactive toxic encephalopathies. We analyzed microglial ultrastructure, morphotypes, and phagocytosis in the sensorimotor cortex of cecal ligation and puncture (CLP) and acetaminophen-induced liver failure (AILF) Wistar rats. A CLP model induced a gradual shift of ~50% of surveillant microglia to amoeboid hypertrophic-like and gitter cell-like reactive phenotypes with active phagocytosis and frequent contacts with damaged neurons. In contrast, AILF microglia exhibited amoeboid, rod-like, and hypertrophic-like reactive morphotypes with minimal indications for efficient phagocytosis, and were mostly in contact with edematous astrocytes. Close interactions of reactive microglia with neurons, astrocytes, and blood–brain barrier components reflect an active contribution of these cells to the tissue adaptation and cellular remodeling to toxic brain damage. Partial disability of reactive microglia may affect the integrity and metabolism in all tissue compartments, leading to failure of the compensatory mechanisms in acute endogenous toxic encephalopathies.

The aim of the study – comparative analysis of the ammonia level and Alzheimer type 2 astrocytes in the brain cortex and white matter of cerebral hemispheres, hippocampus, thalamus, striatum and cerebellum in the deceased patients with liver cirrhosis of classes A, B and C according to Child–Pugh. Materials and methods. The study was performed on the brain of deceased 90 patients (65 ± 3 years) suffered from non-alcoholic liver cirrhosis (LC) of classes A (n = 30, group “A”), B (n = 30, group “B”) and C (n = 30, group “C”) according to Child–Pugh score, among which 59 (65.55 %) patients had clinical symptoms of hepatic encephalopathy of I–IV grades. The control group included postmortem brains of 30 patients (59.0 ± 2.5 years) who died from acute cardiovascular insufficiency and did not suffer from liver diseases or intoxication. A retrospective analysis of clinical and laboratory data from case histories was carried out. For histochemical (HC) determination of the ammonia in paraffin sections of the cerebral cortex and white matter, hippocampus, thalamus, striatum and cerebellum we used the protocol with Nessler’s reagent proposed by Gutierrez-de-Juan et al. (2017). In the noted brain regions, the analysis of HC ammonia optical density was performed in five standardized fields of view (×200) of the microscope scope A1 “Carl Zeiss” (Germany) with Jenoptik camera progress Gryphax 60 N-C1ꞌꞌ1.0x426114 (Germany) using ImageJ software; in each noted brain region the number of Alzheimer’s type 2 astrocytes (AA2) was counted per twenty standardized fields of view at magnification ×400. Results. HC method for ammonia detection with Nessler’s reagent according to V. Gutiérrez-de-Juan et al. (2017) reveals region-dependent fine-grained expression of ammonia in the brain neuropil of deceased patients in control and cirrhotic groups. In control patients, a very low HC ammonia expression is observed with higher values in cerebellum, thalamus, and striatum, while still ranked as negative. Increased HC ammonia expression (compared to control) is observed in deceased patients with compensated LC of “A” group in the cortex, thalamus, striatum and cerebellum; in subcompensated LC of “B” group – as well in the white matter and hippocampus. In deceased patients with decompensated LC of “C” group, in cerebellum, thalamus and striatum HC ammonia expression is maximally increased (by 6.18, 5.72, and 5.50 folds, respectively). Significant correlations are present between patients’ postmortem brain HC ammonia expression and the last intravital indicators of the blood total bilirubin, AST, ALT, albumin, leukocytic intoxication index. In compensated cirrhosis, increase in AA2 numbers compared to control is found in thalamus, striatum and cerebellum, which corresponds to AA2-astrocytosis of I degree. In subcompensated cirrhosis, AA2-astrocytosis of moderate II degree is found in the cortex, thalamus and cerebellum; AA2-astrocytosis of I degree – in striatum. In decompensated cirrhosis, pronounced AA2-astrocytosis of III degree is determined in the cortex, thalamus, striatum and cerebellum; moderate AA2-astrocytosis of II degree – in cerebral white matter, and mild AA2-astrocytosis of I degree – in the hippocampus. There is a moderate, strong, and very strong positive relationship between the levels of AA2-astrocytosis and HC ammonia expression in the thalamus, striatum, and cerebellum. Conclusions. In deceased patients with LC, the neuropil HC ammonia expression in cerebellum, thalamus, striatum, and cerebral cortex directly correlates with the severity of LC according to Child–Pugh, reaching a maximum in LC of class C, and has significant correlations with intravital blood levels of total bilirubin, AST, ALT, albumin, leukocytic intoxication index. With LC progression, AA2-astrocytosis increases significantly in thalamus, cerebellum, striatum and cerebral cortex, which positively correlates with HC ammonia expression in these brain regions.