Analysis of inflammatory processes in diffuse thickening of human aorta intima

It is generally recognized that accumulation of lipids and immune inflammatory cells is an early sign of atherosclerosis. In the present study, we investigated the relationship between the deposition of lipids, immune inflammatory cell content and expression of HLA-DR molecules, and class II major histocompatibility complex (MHC) (a marker of immune activation) in diffuse intima thickening (DIT). Lipids, including triglycerides, cholesterol esters, free cholesterol, and phospholipids were studied by chromatography and Oil Red O histochemistry, as well as by electron microscopy. Immune inflammatory cells and the expression of HLA-DR were investigated by immunohistochemistry in serial sections of the same tissue samples. It has been shown that the lipids were unevenly distributed in DIT. In the juxtaluminal sublayer, lipids were detected in the cytoplasm of intima cells and the extracellular area. In the juxtamedial musculoelastic sublayer of the intima, lipids were present predominantly along elastic fibers. The positive correlation between the presence of lipids and the expression of HLA-DR was revealed (r = 0.79; p < 0.001). A positive correlation was also found between the deposition of lipids and the number of immune inflammatory cells, although correlation was different for different sublayers of the intima. In particular, the correlation between the deposition of lipids and immune inflammatory cells in the juxtaluminal sublayer of the intima was higher (r = 0.69; p < 0.001) than in the juxtamedial musculoelastic layer (r = 0.28; p < 0.001). These data support the hypothesis that the accumulation of lipids in the intima is a key factor in the initiation of inflammatory reactions. At the preatherosclerotic stage of development of this disease, earlier pathological processes associated with lipid-dependent activation of immune cells occur mainly in the juxtaluminal portion of the intima.     

Dendritic cells and their role in immune reactions of atherosclerosis

Dendritic cells were discovered and recognized as antigen-presenting cells in 1973. Since then, a large volume of information has been accumulated showing the role of dendritic cells as a key element connecting the innate and adaptive immunity. Today, dendritic cells are considered to be dedicated sensors of the immune system that are capable of recognizing both antigen amounts and antigen persistence via complex mechanisms that involve decoding and integration of various signals received in a receptor-dependant manner. The tissue microenvironment plays an important role in the modulation of effector functions of dendritic cells, inducing either activation or suppression of immune reactions. Dendritic cells maintain homeostasis and are involved in a number of diseases, including infectious diseases and cancer. The presence of dendritic cells in arteries was reported in 1995, and, since then, the involvement of dendritic cells in atherogenesis has been evaluated. This review briefly describes the current knowledge of dendritic cells and their role in atherosclerosis.     

Astrocyte death in organotypic cultures of fetal spinal cord from rats with unilateral micromelia

Growth and differentiation of neurons and glia in spinal cord explants of 16 days old rat fetuses with teratogen-induced left-sided micromelia were studied. Progressive destruction of astrocytes that differentiate in interstitial zone of cultures was observed in 37% of explants of the left side, while the development was normal in cultures of the right side. Possible mechanisms leading to destruction of astrocytes in cultures of spinal cord regions that innervate anomalous limbs are discussed.     

The effects of desensitization of capsaicin-sensitive neurons on the blood flow in microvessels of the rat gastric serous muscular membrane with normal and insufficient contents of glucocorticoids

The effects of desensitization of capsaicin-sensitive neurons on the blood flow velocity in microvessels of the gastric muscular membrane were investigated before and after indomethacin (35 mg/kg) administration in adrenalectomized rats with or without corticosterone replacement (4 mg/kg sc) and in sham-operated animals. Desensitization of capsaicin-sensitive neurons was performed with neurotoxic dose of capsaicin (20 + 30 + 50 mg/kg sc) two weeks before the experiment. Adrenalectomy was created one week before the experiment. The in vivo microscopy technique for direct visualization of gastric microcirculation and analysis of red blood cell (RBC) velocity was employed. Indomethacin decreased the RBC velocity. Adrenalectomy by itself profoundly decreased the RBC velocity, whereas corticosterone replacement prevented this effect. Desensitization of capsaicin-sensitive neurons did not influence the RBC velocity in sham-adrenalectomized rats; however, it induced further fall of both basal and indomethacin-induced RBC velocity in adrenalectomized rats that was prevented by corticosterone. We conclude that glucocorticoid hormones have a beneficial effect on the blood flow velocity in microvessels of the gastric muscular membrane in rats with desensitization of capsaicin-sensitive neurons.     

Effects of desensitization of capsaicin-sensitive afferent neurons on gastric microcirculation in rats depend on the blood glucocorticoid hormone level

The effects of desensitization of capsaicin-sensitive afferent neurons on gastric microcirculation were investigated before and after administration of indomethacin at ulcerogenic dose in adrenalectomized rats with or without corticosterone replacement and in sham-operated animals. We estimated the blood flow velocity in submucosal microvessels; the diameters and permeability of mucosal venous microvessels as parameters of gastric microcirculation. Desensitization of capsaicin-sensitive neurons was performed with capsaicin at the dose 100 mg/kg two weeks before the experiment. Adrenalectomy was created one week before experiment. In vivo microscopy technique for the direct visualization of gastric microcirculation and the analysis of the blood flow was employed. Indomethacin at ulcerogenic dose decreased the blood flow velocity in submucosal microvessels, caused dilatation of superficial mucosal microvessels and increased their permeability. Desensitization of capsaicin-sensitive afferent neurons potentiated indomethacin-induced microvascular disturbances in gastric submucosa-mucosa. These potentiated effects of the desensitization are obviously promoted by concomitant glucocorticoid deficiency. Thus, glucocorticoid hormones have a beneficial effect on gastric microcirculation in rats with desensitization of capsaicin-sensitive afferent neurons.     

Numbers of cells and cell proliferation in intima of different human arteries

Increased cell proliferation in early atherosclerotic lesions is recognized as an essential event of atherogenesis but the levels of cell proliferation in different stages of atherosclerotic plague formation in different types of human large arteries are still insufficiently studied. In the present work, we studied intima thickness and proliferation of newly "infiltrates" hematogenous and resident cells in atherosclerotic lesions of the carotid and coronary arteries and compared these parameters with those in the aorta, reported by us in earlier publication. Analysis of intima thickness and proliferation in grossly unaffected intima and in different types pf atherosclerotic lesions (initial lesions, fatty streaks, lipofibrous, plaques, and fibrous plaque) revealed that although there were similar tendencies in the change of the infiltration levels of hematogenous cells and proliferation in different types of arteries, there were significant quantitative differences between different types of arteries. Hematogenous cells in lipofibrous plaques of the coronary and carotid arteries were found to account for a third and almost for a half of the total cell population, respectively, while atherosclerotic lesions in the aorta, as it has been shown by us earlier, to contain no more than 15% ofhematogenous cells. This suggests that the contribution of hematogenous cells to the development of atherosclerosis in the carotid and the coronary artery appears to be more significant than that in the aorta. Despite the differences in numbers of accumulating hematogenous cells in the intima, a similar "bell-shaped" dependence of cell numbers on the lesion type, involved in the following sequence: unaffected intima-initial lesions-fatty streaks-lipofibrous plaques-fibrous plaques, was detected in the coronary and carotid arteries. The visualization of proliferating cells (PCNA-positive) in atherosclerotic and unaffected zones of the coronary and carotid arteries revealed similar patterns. The maximum numbers of PCNA-positive resident cells were identified in lipofibrous plaques. The changes in the total cell numbers were accompanied by the changes in the numbers of both proliferating resident cells and proliferating hematogenous cells.     

S100A8 and S100A9 in human arterial wall. Implications for atherogenesis

Atherogenesis is a complex process involving inflammation. S100A8 and S100A9, the Ca2+-binding neutrophil cytosolic proteins, are associated with innate immunity and regulate processes leading to leukocyte adhesion and transmigration. In neutrophils and monocytes the S100A8-S100A9 complex regulates phosphorylation, NADPH-oxidase activity, and fatty acid transport. The proteins have anti-microbial properties, and S100A8 may play a role in oxidant defense in inflammation. Murine S100A8 is regulated by inflammatory mediators and recruits macrophages with a proatherogenic phenotype. S100A9 but not S100A8 was found in macrophages in ApoE-/- murine atherosclerotic lesions, whereas both proteins are expressed in human giant cell arteritis. Here we demonstrate S100A8 and S100A9 protein and mRNA in macrophages, foam cells, and neovessels in human atheroma. Monomeric and complexed forms were detected in plaque extracts. S100A9 was strongly expressed in calcifying areas and the surrounding extracellular matrix. Vascular matrix vesicles contain high levels of Ca2+-binding proteins and phospholipids that regulate calcification. Matrix vesicles characterized by electron microscopy, x-ray microanalysis, nucleoside triphosphate pyrophosphohydrolase assay and cholesterol/phospholipid analysis contained predominantly S100A9. We propose that S100A9 associated with lipid structures in matrix vesicles may influence phospholipid-Ca2+ binding properties to promote dystrophic calcification. S100A8 and S100A9 were more sensitive to hypochlorite oxidation than albumin or low density lipoprotein and immunoaffinity confirmed S100A8-S100A9 complexes; some were resistant to reduction, suggesting that hypochlorite may contribute to protein cross-linking. S100A8 and S100A9 in atherosclerotic plaque and calcifying matrix vesicles may significantly influence redox- and Ca2+-dependent processes during atherogenesis and its chronic complications, particularly dystrophic calcification.     

55-kD actin-bundling protein (p55) is a specific marker for identifying vascular dendritic cells.

Compared with other members of the dendritic cell family, the antigen profile of the recently recognized vascular dendritic cells has received limited attention. This study demonstrates that vascular dendritic cells in the human aorta and carotid arteries express 55-kD actin-bundling protein (p55), a specific marker for blood dendritic cells and Langerhans cells. This finding will facilitate screening of dendritic cells during their isolation from the arterial wall, as well as other investigations.(J Histochem Cytochem 47:1481-1486, 1999)     

Changes of lysosomes in the earliest stages of the development of atherosclerosis

One of hypotheses of atherosclerosis is based on a presumption that the zones prone to the development of atherosclerosis contain lysosomes which are characterized by enzyme deficiency and thus, are unable to dispose of lipoproteins. The present study was undertaken to investigate the characteristics and changes of lysosomes in the earliest stages of the development of atherosclerosis. Electron microscopic immunocytochemistry revealed that there were certain changes in the distribution of CD68 antigen in lysosomes along the ‘normal intima‐initial lesion‐fatty streak’ sequence. There were no significant changes found in the key mRNAs encoding for the components of endosome/lysosome compartment in initial atherosclerotic lesions, but in fatty streaks, the contents of EEA1 and Rab5a mRNAs were found to be diminished while the contents of CD68 and p62 mRNAs were increased, compared with the intact tissue. The study reinforces a view that changes occurring in lysosomes play a role in atherogenesis from the very earlier stages of the disease.     

Morphologic characteristics of intercellular junctions in early embryogenesis of mice

Dynamics concerning certain intercellular junctions have been followed during the preimplantation period of development in mouse embryos. The morphological analysis of the preimplantational embryos has demonstrated, that at the initial stages of cleavage (2-4 blastomeres) the cells make contacts by means of nonspecific junctions. Specialized intercellular junctions appear at the stage of 8 blastomeres and are presented as dotted tight and gap junctions. When the embryo is developing from the stage of 8 up to the stage of 16 blastomeres, certain connective complexes appear, consisting of dotted or cord-like tight and gap junctions. At the late morula stage, the external blastomeres in the apical part have contacts with each other by means of cingular tight junctions. In this place a connective complex might emerge; it is displayed as a tight junction and one or two gap junctions. At the blastocyst stage desmosomes and adhision zones appear. Between trophectodermal cells a connective complex arises; it is presented in the slice as a tight cingular junction, desmosomes (as a rule two) and an adhision zone. Between cells of the internal cellular mass the intercellular junctions are presented as dotted tight and gap junctions. Cells of the polar trophoectoderm and cells of the internal cellular mass could have contacts by means of gap and dotted tight junctions.