The morphology of the ependymal rosettes.

<p>Microscopic view of the ependymal rosettes formed at the ventral part of right lateral ventricle. Sections of the rat brains at 8 weeks after the administration of the studied substances are shown: A—DMSO, B—MG-132, and C—epoxomicin. Staining—Nissl method; scale bar = 100 μm.</p

The ubiquitin-positive aggregates within the cells of subventricular area.

<p>The localization of the ubiquitin-positive aggregates in the cells of striatum after the administration of A—DMSO and B, C—epoxomicin is shown. The arrow points to the clusters of ubiquitin-positive aggregates in astrocytes, while the arrowheads indicate small ubiquitin inclusions in cells that are not astrocytes. Scale bars: A, B—50 μm; C—25 μm.</p

Glial scar formation in the lateral ventricle.

<p>Glial activation in the striatum (Str) and glial scar formation 2 weeks after the administration of DMSO (A) and epoxomicin (B) into the right lateral ventricle (LV). An anti-GFAP antibody was used as a marker of astroglia, an anti-NogoA antibody was used as a marker of oligodendroglia, and Neuro Trace Red stained the neuronal bodies and nuclei of both the vascular endothelial cells and glial cells. Scale bar—50 μm.</p

Evolution of the morphological changes within the rat lateral ventricle at 2 and 8 weeks after the administration of the studied substances.

<p>Microscopic view of the morphological changes (glial scar, mononuclear cells infiltration) associated with the adhesion area within lateral ventricle; a comparison of the view from coronal sections of the brains from the representative rats at 2 and 8 weeks after the administration of the studied substances– DMSO, MG-132, lactacystin and epoxomicin. Staining—Nissl method; scale bar = 100 μm.</p

The characteristics of the mononuclear cell infiltrations after intraventricular proteasome inhibitor administration.

<p>Microscopic view of the mononuclear inflammatory cells observed at the lateral ventricular surface (A) and the different degrees of inflammatory cell infiltration: B—mild, C—moderate, and D—high. Sections of the rat brains at 2 weeks after the administration of the studied substances, A –DMSO, B, C—MG-132 and D—epoxomicin, are shown. Staining—Nissl method; scale bar = 50 μm.</p

Morphological Changes within the Rat Lateral Ventricle after the Administration of Proteasome Inhibitors

<div><p>The broad variety of substances that inhibit the action of the ubiquitin-proteasome system (UPS)—known as proteasome inhibitors—have been used extensively in previous studies, and they are currently frequently proposed as a novel form of cancer treatment and as a protective factor in intracerebral hemorrhage treatment. The experimental data on the safest route of proteasome inhibitor administration, their associated side effects, and the possible ways of minimizing these effects have recently become a very important topic. The aim of our present study was to determine the effects of administering of MG-132, lactacystin and epoxomicin, compounds belonging to three different classes of proteasome inhibitors, on the ependymal walls of the lateral ventricle. Observations were made 2 and 8 weeks after the intraventricular administration of the studied substances dissolved in dimethyl sulfoxide (DMSO) into the lateral ventricle of adult Wistar rats. Qualitative and quantitative analysis of brain sections stained with histochemical and inmmunofluorescence techniques showed that the administration of proteasome inhibitors caused a partial occlusion of the injected ventricle in all of the studied animals. The occlusion was due to ependymal cells damage and subsequent ependymal discontinuity, which caused direct contact between the striatum and the lateral nuclei of the septum, mononuclear cell infiltration and the formation of a glial scar between these structures (with the activation of astroglia, microglia and oligodendroglia). Morphologically, the ubiquitin-positive aggregates corresponded to aggresomes, indicating impaired activity of the UPS and the accumulation and aggregation of ubiquitinated proteins that coincided with the occurrence of glial scars. The most significant changes were observed in the wall covering the striatum in animals that were administered epoxomicin, and milder changes were observed in animals administered lactacystin and MG-132. Interestingly, DMSO administration also caused damage to some of the ependymal cells, but the aggresome-like structures were not formed. Our results indicate that all of the studied classes of proteasome inhibitors are detrimental to ependymal cells to some extent, and may cause severe changes in the ventricular system. The safety implications of their usage in therapeutic strategies to attenuate intracerebral hemorrhagic injury and in brain cancer treatment will require further studies.</p></div

Morphological hallmarks of apoptosis and subependymal gliosis after intraventricular proteasome inhibitor administration.

<p>Apoptotic bodies (encircled) and glial tubercles (arrow) were present in the ependymal lining of the striatum (Str) 2 weeks after MG-132 (A) and epoxomicin (B, C) administration into the right lateral ventricle (LV). Staining—Nissl method; scale bars: A, B—25 μm; C—50 μm.</p

Microglia infiltrations within the walls of the lateral ventricle.

<p>The OX-42-positive cells (microglia) present within inflammatory cell infiltrations are shown in sections of the rat brains at 2 weeks after the administration of the studied substances: A—DMSO, B—MG-132, C—lactacystin and D—epoxomicin. Immunohistochemistry, scale bar = 50 μm.</p

The morphology of the ubiquitin-positive aggregates in the lateral ventricular walls and subventricular area after the proteasome inhibitor treatment.

<p>The morphology of the ubiquitin-positive aggregates in the cells of the striatum at 2 weeks after the administration of the proteasome inhibitors into lateral ventricle is shown: <b>A</b>—single, small juxtanuclear aggregates (arrowhead), <b>B</b>—numerous larger cytoplasmic aggregates (arrowheads), and <b>C</b>—numerous cytoplasmic aggregates (arrowheads) and large clusters of ubiquitin-positive aggregates with a foamy morphology (arrows), which may provide the content of the phagocytic cells. Immunohistochemistry, scale bar = 50 μm.</p

The characteristics of the ependymal discontinuity after epoxomicin administration.

<p>Microscopic view of the ependymal atrophy on the surface of the corpus callosum (A). (B) Normal control with an unchanged ventricular ependymal lining from the same section as (A), but from opposite side. The arrows indicate the borders between area of the ependymal atrophy and the existing normal ependymal lining. Sections of the rat brains at 8 weeks after epoxomicin administration are shown. Staining—Nissl method; scale bar = 50 μm.</p