Peroxisomes in airway epithelia and future prospects of these organelles for pulmonary cell biology

Peroxisomes are intimately involved in the metabolism of reactive oxygen species, in the synthesis of ether lipids and of polyunsaturated fatty acids as well as in the beta-oxidation of bioactive and toxic lipid derivatives. Therefore, the metabolic pathways of this organelle might play an important role in pulmonary biology by protection of inner pulmonary surface epithelia against oxidative stress, induced by the high oxygen levels in the air and/or by regulation of the lipid homeostasis in pulmonary epithelia and the pulmonary surfactant film. In this article, original results on the distribution of peroxisomal marker proteins, involved in the biogenesis, ROS- and lipid-metabolism of this organelle in the bronchiolar epithelium and the alveolar region of the adult human lung in comparison to newborn and adult murine lungs are presented. In addition, we investigated the expression of the PEX11 beta-mRNA, encoding a protein involved in peroxisomal division. Our study revealed significant differences in the abundance and distribution of peroxisomal proteins in distinct cell types of the lung and different developmental stages and led to the discovery of species-specific differences in the peroxisomal compartment in pulmonary epithelia between mouse and man. Finally, the structure and general biology of pulmonary airways-with special emphasis on Clara cells-are reviewed and discussed in relation to peroxisomal metabolism and proliferation. Future prospects of peroxisomes and Pex11 proteins for pulmonary cell biology are highlighted.