Cytochemistry of type II pneumocytes in Chediak-Higashi syndrome of mice

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.

Lung pathology of pale ear mouse (model of Hermansky-Pudlak syndrome 1) and beige mouse (model of Chediak-Higashi syndrome): severity of giant lamellar body degeneration of type II pneumocytes correlates with interstitial inflammation

The authors have recently reported the presence of characteristic foamy swelling/degeneration (giant lamellar body degeneration, GLBD) of type II pneumocytes in the lungs affected by Hermansky-Pudlak syndrome (HPS)-associated interstitial pneumonia (HPSIP), and proposed the hypothesis that GLBD may be the triggering factor in the development of HPSIP (Virchows Arch 2000; 437: 304-13). The purpose of the present paper was to investigate the lung pathology of pale ear (ep) mouse, a mouse model of HPS1, and of beige (bg) mouse, a mouse model of Chediak-Higashi syndrome (CHS) with a reference to GLBD and associated pathologic changes. GLBD was found in both ep and bg mice soon after birth, and increased in severity as the mice grew older. Younger mice had only GLBD with no evidence of interstitial change. Aged bg mice showed the most prominent GLBD and patchy areas of alveolar collapse accompanied by lymphocytic infiltration and slight fibrosis. Aged ep mice with less severe GLBD than bg mice of comparable ages also had a slight tendency to develop interstitial inflammation but no fibrosis. The pneumocytes with GLBD were immunoreactive for surfactant protein B and composed of giant lamellar bodies ultrastructurally, findings which were almost identical to those of human GLBD. The results of the present study support the hypothesis that GLBD may play an important role in the development of HPSIP. Ep and bg mice, especially the latter, may be useful mouse models of HPSIP.

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.