Catalase positive particles from pig lung. Biochemical preparations and morphological studies

Be different--the diversity of peroxisomes in the animal kingdom

Peroxisomes represent so-called "multipurpose organelles" as they contribute to various anabolic as well as catabolic pathways. Thus, with respect to the physiological specialization of an individual organ or animal species, peroxisomes exhibit a functional diversity, which is documented by significant variations in their proteome. These differences are usually regarded as an adaptational response to the nutritional and environmental life conditions of a specific organism. Thus, human peroxisomes can be regarded as an in part physiologically unique organellar entity fulfilling metabolic functions that differ from our animal model systems. In line with this, a profound understanding on how peroxisomes acquired functional heterogeneity in terms of an evolutionary and mechanistic background is required. This review summarizes our current knowledge on the heterogeneity of peroxisomal physiology, providing insights into the genetic and cell biological mechanisms, which lead to the differential localization or expression of peroxisomal proteins and further gives an overview on peroxisomal biochemical pathways, which are specialized in different animal species and organs. Moreover, it addresses the impact of proteome studies on our understanding of differential peroxisome function describing the utility of mass spectrometry and computer-assisted algorithms to identify peroxisomal target sequences for the detection of new organ- or species-specific peroxisomal proteins.

Peroxisomes in mouse and human lung: their involvement in pulmonary lipid metabolism

Only sparse information is available from the literature on the peroxisomal compartment and its enzyme composition in mouse and human lungs. Therefore, in the present investigation we have characterized peroxisomes in different cell types of adult mouse (C57BL/6J) and human lungs in a comprehensive study using a variety of light-, fluorescence- and electron microscopic as well as biochemical techniques and by the use of various peroxisomal marker proteins (Pex13p, Pex14p, ABCD3, beta-oxidation enzymes and catalase). In contrast to previous reports, we have found that peroxisomes are present in all cell types in human and mouse lungs. However, they differ significantly and in a cell-type-specific manner in their structure, numerical abundance and enzyme composition. Whereas catalase showed significant differences between distinct cell types, Pex14p proved to be the marker of choice for labeling all lung peroxisomes. In alveolar type II cells and alveolar macrophages peroxisomes contained significant amounts of the lipid transporter ABCD3 and beta-oxidation enzymes, suggesting their involvement in the modification and recycling of surfactant lipids and in the control of lipid mediators and ligands for nuclear receptors of the PPAR family. Possible connections between ROS and lipid metabolism of lung peroxisomes are discussed.

Cell biology of peroxisomes and their characteristics in aquatic organisms

The general characteristics of peroxisomes in different organisms, including aquatic organisms such as fish, crustaceans, and mollusks, are reviewed, with special emphasis on different aspects of the organelle biogenesis and mechanistic aspects of peroxisome proliferation. Peroxisome proliferation and peroxisomal enzyme inductions elicited by xenobiotics or physiological conditions have become useful tools to study the mechanisms of peroxisome biogenesis. During peroxisome proliferation, the induction of peroxisomal proteins is heterogeneous, enzymes that show increased activity being involved in different aspects of lipid homeostasis. The process of peroxisome biogenesis is coordinately triggered by a whole array of structurally dissimilar compounds known as peroxisome proliferators, and investigating the effect of some of these compounds that commonly appear as pollutants in the environment on the peroxisomes of aquatic animals inhabiting marine and estuarine habitats seems interesting. It is also important to determine whether peroxisome proliferation in these animals is a phenomenon that might occur under normal physiological or season-related conditions and plays a metabolic or functional role. This would help set the basis for understanding the process of peroxisome biogenesis in aquatic animals.

Rat lung alveolar type I epithelial cell injury and response to hyperoxia

Hyperoxia has been shown to cause extensive lung injury, which involves all components of the alveolar septum, although the type I epithelium has generally been reported to be resistant to significant injury. Electron microscopic morphometry was performed to define changes in volumes of subcellular components of alveolar epithelial cells in rats exposed to 85% O2 for 0, 7, and 14 d. Because of their large size, type I cells in control animals actually contain a greater volume of most of the organelles involved in cell metabolism than do type II cells. Hyperoxic exposure causes a dramatic change in the subcellular composition of the average type I cell, suggesting significant injury and/or response. Injury was suggested by the finding that lysosomes plus peroxisomes increased 1,250% after 7 d in hyperoxia and remained elevated by 200% after 14 d of exposure. Volumes of mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, and Golgi apparatus increased by 100%, 51%, 91%, and 500%, respectively, after hyperoxia. Qualitative analysis showed an altered, ruffled air border with focal areas of cytoplasmic translucency (suggesting injury) and focal areas of subcellular hypertrophy. Exposure to hyperoxia was associated with more organelles being found in peripheral or attenuated portions of type I alveolar cells. Since the increase in type I organelles exceeds the volume of these organelles in its progenitor, the type II cell, it is likely that hyperoxia causes hypertrophy of the type I alveolar epithelium itself, independent of simple type II cell differentiation. Because of the large size and wide distribution of the type I cell, dramatic shifts in cell substructure caused by hyperoxia are more difficult to detect and require quantitative analysis to fully ascertain the extent of cell alterations.

Antioxidant macromolecules in the epithelial lining fluid of the normal human lower respiratory tract

We hypothesized that the alveolar structures may contain extracellular macromolecules with antioxidant properties to defend against oxidants. To evaluate this 51Cr-labeled human lung fibroblasts (HFL-1) and cat lung epithelial cells (AKD) were exposed to a H2O2-generating system and alveolar epithelial lining fluid (ELF) from healthy nonsmokers was tested for its ability to protect the lung cells from H2O2-mediated injury. The ELF provided marked antioxidant protection, with most from a H2O-soluble fraction in the 100-300-kD range. Plasma proteins with anti-H2O2 properties were in insufficient concentrations to provide the antioxidant protection observed. However, catalase, a normal intracellular antioxidant, was present in sufficient concentration to account for most of the observed anti-H2O2 properties of ELF. Depletion of ELF with an anticatalase antibody abolished the anti-H2O2 macromolecular defenses of ELF. Since catalase is not normally released by cells, a likely explanation for its presence in high concentrations in normal ELF is that it is released by lung inflammatory and parenchymal cells onto the epithelial surface of the lower respiratory tract during their normal turnover and collects there due to the slow turnover of ELF. It is likely that catalase in the ELF of normal individuals plays a role in protecting lung parenchymal cells against oxidants present in the extracellular milieu.

The ultrastructure of epithelial cells of the distal lung

This review has focused on the structural and functional characteristics of those epithelial cells that line the walls of the lower respiratory bronchioles, alveolar ducts, and alveoli. In all, five cells types were considered: Clara cells, types I, II, and III pneumocytes, and alveolar macrophages. In addition, a very brief mention of the structure and influence of the basement membrane in alveolar development and repair was included, as well as a brief review of the role of epithelial cells in response to selected deleterious influences. No attempt was made to extend this review to cover the structure and functions of the epithelial lining of the conducting portions of the respiratory system, or the exciting and expanding complexities and interrelationships of the septal stroma. Since the volume of literature encircling this subject has virtually exploded during the last 15 years, it becomes almost impossible to review all reports. However, attempts were made to be selective in citations. Insofar as future developments are concerned, much remains to be understood concerning (1) the responses of all cell types to cytotoxic influences, including their respective abilities to repair induced damage, (2) cell-cell and cell-extracellular matrix relationships in response to injury, (3) the uniqueness of the basement membrane in the lung in controlling permeability and gaseous exchange, (4) the role(s) of alveolar macrophages in response to injury and their relationships to the septal macrophage population, (5) the aberrations in the respective cell types that can give rise to neoplastic growth, and (6) the role of the immune system in responding to the general defense of the lung. Indeed much has been learned in the past 2 decades, and it is expected that a review of this sort 1 or 2 decades hence will elucidate many of the functions and structural modifications of the lung.

Disintegration of lung peroxisomes during differentiation of type II cells to type I cells in butylated hydroxytoluene-administered mice

Ultrastructural and cytochemical changes in peroxisomes of Type II alveolar cells were investigated in butylated hydroxytoluene (BHT)-administered mouse lungs. Male mice were given a single injection of BHT (400 mg/kg, ip) and sacrificed 1 to 7 days later. By means of tracheal infusion, lungs were fixed with a 2% glutaraldehyde or half-strength Karnovsky solution. Type I epithelium was selectively destroyed by BHT and was replaced by cuboidal Type II cells. Type II cells proliferated and some became squamous, extended their cytoplasm, and might differentiate into Type I cells (Hirai, Witschi, and Côté (1977) Exp. Mol. Pathol. 27, 295-308). Peroxisomes, Type II cell constituents, were clustered around and continuous with endoplasmic reticulum. The shape of the peroxisomes became indistinct after Type I cell injury by BHT. Also the density of the matrix was reduced in proportion to the reduction in the peroxidatic activity of catalase. These changes were accompanied by a decrease in the number of peroxisomes. New pinocytotic vesicles, one of the Type I cell characteristics, were generated at the apical and basal cell surfaces. Therefore, these cells had characteristics intermediate between Type I and Type II cells. These findings may indicate further evidence of the origin of Type I cells from Type II cells.

Intestinal peroxisomes of goldfish (Carassius auratus)--examination for hydrolase, dehydrogenase and carnitine acetyltransferase activities

1. Rate sedimentation and isopycnic centrifugation were used to analyse the subcellular sites of enzymes in homogenates of goldfish intestinal mucosa. 2. The results allowed the following allocations to be made: carnitine acetyl transferase-mitochondrial and peroxisomal, xanthine dehydrogenase and NAD: alpha-glycerophosphate dehydrogenase soluble phase, NADP: isocitrate dehydrogenase soluble phase and mitochondrial, and 2-naphthyl laurate hydrolase microsomal and/or brush border. 3. Histochemistry confirmed the use of alkaline phosphatase and 1-naphthyl acetate esterase as brush border and microsome markers respectively. 4. Urate oxidase, allantoinase, allantoicase, xanthine oxidase and glycollate/lactate oxidase, activities were undetectable, and 1-naphthyl palmitate hydrolase was present only as a contaminant from pancreas.