The immunocytochemical localization of superoxide dismutase in the enterocytes of the avian intestine: the effect of vitamin D3

Temporal pattern changes in duodenal protein tyrosine nitration events in response to Eimeria acervulina infection in chickens

Intracellular generation of nitric oxide (NO) and superoxide anion (SOA) can result in the formation of 3'-nitrotyrosine proteins (NTp). Nitrated proteins usually are associated with significant perturbation in protein function, apoptosis, autophagy, and cell death. We undertook the present study to establish the temporal dynamics of NTp generation in cytokeratin-18-positive epithelial cells (ETCs) of broiler chickens in response to infection with Eimeria acervulina. Duodenal tissue was harvested from noninfected (NOI) and infected (INF) broilers on days (d) 1, 3, 6, 7, and 10 postinfection (PI) and fixed, embedded, and sectioned for quantitative image analysis, immunohistochemistry with antibodies specific to NTp and the SOA-generating enzyme xanthine oxidase (XO). The pixel density characteristics for NTp and XO representative of ETCs demonstrated that NTp and XO increased in intestinal villi as early as d1 PI (P < 0.05 vs. NOI). Progressive increases in NTp were evident in ETCs through d6 PI. For XO, increases in cell content increased only through d3. On d6 and d7 PI, high levels of NTp were present in immune infiltrating cells (IIC) where no XO was detected. The increases in ETC NTp occurred in a defined pattern, significant by villus-to-crypt location for day of infection, initiating in the distal villus and progressing down into the crypts. Two NTp patterns were observed for ETCs: a high level associated with ETCs harboring parasites and a low-level increase in ETCs not containing Eimeria but in proximity to such. The data suggest that NTp and XO responses may mediate some of the processes through which ETCs respond to Eimeria to limit the extent of infection by this pathogen.

Age and disease-related structural changes in the retinal pigment epithelium

As the retinal pigment epithelium (RPE) ages, a number of structural changes occur, including loss of melanin granules, increase in the density of residual bodies, accumulation of lipofuscin, accumulation of basal deposits on or within Bruch's membrane, formation of drusen (between the basal lamina of the RPE and the inner collagenous layer of Bruch's membrane), thickening of Bruch's membrane, microvilli atrophy and disorganization of the basal infoldings. Although these changes are well known, the basic mechanisms involved in them are frequently poorly understood. These age-related changes progress slowly and vary in severity in different individuals. These changes are also found in age-related macular degeneration (AMD), a late onset disease that severely impacts the RPE, but they are much more pronounced than during normal aging. However, the changes in AMD lead to severe loss of vision. Given the many supporting functions which the RPE serves for the retina, it is important to decipher the age-related changes in this epithelium in order to understand age-related changes in vision.

Proteomic characterization of isolated retinal pigment epithelium microvilli

Polarized epithelial cells are characterized by displaying compartmentalized functions associated with differential distribution of transporters, structural proteins, and signaling molecules on their apical and basolateral surfaces. Their apical surfaces frequently elaborate microvilli, which vary in structure according to the specific type and function of each epithelium. The molecular basis of this heterogeneity is poorly understood. However, differences in function will undoubtedly be reflected in the specific molecular composition of the apical surface in each epithelial subtype. We have exploited a method for isolating microvilli from the mouse eye using wheat germ agglutinin (WGA)-agarose beads to begin to understand the specific molecular composition of apical microvilli of the retinal pigment epithelium (RPE) and expand our knowledge of the potential function of this interface. Initially, apical RPE plasma membranes bound to WGA beads were processed for morphological analysis using known apical and basolateral surface markers. The protein composition of the apical microvilli was then established using proteomic analysis. Over 200 proteins were identified, including a number of proteins previously known to be localized to RPE microvilli, as well as others not known to be present at this surface. Localization of novel proteins identified with proteomics was confirmed by immunohistochemistry in both mouse and rat eye tissue. The data generated provides new information on the protein composition of the RPE apical microvilli. The isolation technique used should be amenable for isolating microvilli in other epithelia as well, allowing new insights into additional functions of this important epithelial compartment.

Microvilli elongate in response to hydrogen peroxide and to perturbations of intracellular calcium

Using scanning electron microscopy and fluorescence microscopy, we have found that apical microvilli of diverse cell types, including nonepithelial cells, elongate in culture in response to the oxidative stress of hydrogen peroxide. The microvilli induced in culture on retinal pigment epithelial cells display a 30-nm axial periodicity similar to that described for stable microvilli of intestinal brush border. Microvilli can also be induced to elongate by chelating intracellular Ca2+ and by the Ca(2+)-uptake inhibitor thapsigargin. Thus a response of microvillar protrusion occurs widely and may be related to depletion of intracellular calcium stores.

Antioxidant enzymes in the human iris: an immunogold study

AIMS

To determine the nature and extent of the antioxidant enzyme system in the human iris.

METHODS

The fine structural distribution of five antioxidant enzymes (acidic, neutral, and basic glutathione S-transferase (GST), Cu/Zn superoxide dismutase (Cu/Zn SOD), and glutathione peroxidase) was determined by immunogold labelling of ultrathin sections of tissue from six eyes appropriately fixed for immunocytochemistry and embedded in LR white resin.

RESULTS

Both Cu/Zn SOD and acidic GST were localised to all constituent cells of the iris. Glutathione peroxidase and basic GST were localised to erythrocytes alone, and labelling for neutral GST was absent.

CONCLUSIONS

Dense labelling for acidic GST could be linked with the previously documented presence of large quantities of polyunsaturated fatty acids in the iris and/or the presence of xenobiotic substances in the aqueous humour.

Superoxide formation preceding flight muscle histolysis in Solenopsis: fine structural cytochemistry and biochemistry

In Solenopsis spp., muscle histolysis or breakdown is a normal process in females and is initiated in the flight muscles only immediately after a mating flight. Information regarding the presence of the oxyradical scavenging enzyme superoxide dismutase (SOD) and the formation of the radical oxygen intermediate superoxide (SO) during the early stages of flight muscle histolysis in this insect was investigated. In normal fibrillar flight muscles from control animals, SOD was immunolocalized to vesicular and tubular components of the sarcotubular system. Lanthanum tracer studies indicated that some of these SOD-positive structures might be tubulovesicles continuous with the extracellular space. Following the injection of virgin alates with experimental haemolymph obtained from artificially inseminated females, the membrane delimited elements of the sarcotubular system became increasingly swollen and dilated with time (from 60 to 120 minutes postinjection) with a concomitant decrease in SOD activity and an increase in oxyradical formation. Many similar vesicles were lanthanum-positive. SO was not seen in the sarcoplasmic vesicles and tubules of control insects. The biochemical quantification of SO release over a 2-hour period showed a marked increase in oxyradical formation following treatment with the experimental haemolymph in comparison to control insects. Also, the addition of superoxide dismutase depressed SO formation under these conditions. Despite the histochemical and biochemical changes seen in the muscles of experimental insects, by 2 hours post-treatment there was no evidence of muscle necrosis. From these studies on flight muscle histolysis/necrosis in Solenopsis it appears that the formation of oxyradicals might represent an early event in myopathogenesis and subsequent tissue involution. The generation of SO is more than likely to be associated with alterations in the normal structure, biochemistry and permeability of the biomembranes which delimit the sarcotubular system.

Histochemical localization of oxidized glutathione-catalysing enzymes in human term placenta

This paper reports a new cytochemical affinity technique for detecting oxidized-glutathione-binding enzymes by light microscopy and for carrying out fine structural analyses by means of oxidized glutathione labelled with colloidal gold. Albumin-colloidal gold particles were prepared. Oxidized glutathione, added to the solution, replaced albumin on the surface of the gold, thus forming a new histochemical reagent. In human placenta, oxidized-glutathione-catalysing activity was detected on the brush border of the placental villi, over the foldings of endothelial membranes, and in the ground substance of connective tissue in the villous core. Every process of the cell membrane demonstrated enhanced oxidized-glutathione-catalysing activity. This new reagent is a unique example of a low-molecular-weight compound labelled with colloidal gold, and it permits direct measurement of oxidized-glutathione-binding activity in tissue sections.

The electron microscopic immunolocalization of a copper-zinc superoxide dismutase in association with collagen fibers of periodontal soft tissues

Periodontal soft tissues were cleaved from freshly extracted human teeth. Tissues were then prepared for subsequent biochemical and morphological studies according to the following plan: 1) immediate immersion in liquid nitrogen for the biochemical assay of superoxide dismutase (SOD); 2) immediate fixation prior to routine preparation for routine transmission electron microscopy; 3) immediate fixation prior to preparation for electron microscopic immunohistochemistry. Biochemical analysis showed that the human periodontal ligament contained about twice as much SOD activity as human skin (dermis), but considerably less enzyme activity than that seen in red blood cells. Interestingly, periodontal SOD activity appeared to decrease with age. Immunohistochemistry localized enzyme activity to the periphery of matrix collagen fibrils and to the glycocalyx of tissue fibroblasts. The pathophysiology of this enzyme regarding inflammatory diseases such as periodontitis is discussed.

The immunohistochemical localization of superoxide dismutase activity in the avian epithelial growth plate

Superoxide dismutase (SOD) is a 'scavenger' enzyme which catalyses the dismutation (reduction-oxidation) of the superoxide anion (O2-.), a toxic free radical generated during normal cellular respiration. Light microscopy employing immunohistochemistry was utilized for localizing SOD activity in the chick epiphyseal cartilage. Antibodies to mammalian liver CuZn-SOD were prepared and the avidin-biotin-peroxidase technique (ABC complex) was utilized to localize activity for this enzyme in the growth plate cartilage. The localization of enzyme activity varied in accordance with the characteristic zonation pattern of the growth plate (zone of proliferation, zone of maturation, zone of cell hypertrophy and zone of matrix calcification). In the upper regions of the epiphyseal cartilage (the zones of proliferation and maturation), where the vascularity is poor and the oxygen tension low, SOD activity was localized within the chondrocytes. No extracellular activity was observed. However, in the lower regions of the growth plate (the zones of cell hypertrophy and matrix calcification), where both the vascularity and the oxygen tensions are increased, SOD activity was intense in both the chondrocytes and the surrounding extracellular matrix. Thus, the distribution of SOD enzyme activity in this tissue seems to vary in accordance with the level of oxygen present. The significance of the extracellular SOD activity, seen in the lower aspects of the growth plate cartilage, may indicate the sensitivity of matrix components, especially collagen, to toxic free radicals such as the superoxide anion.