Sarafotoxin expression in the bronchopulmonary tract: immunohistochemical occurrence and colocalization with endothelins

Expression and processing of recombinant sarafotoxins precursor in Pichia pastoris

Sarafotoxins are peptides isolated from the Atractaspis snake venom, with strong constrictor effect on cardiac and smooth muscle. They are structurally and functionally related to endothelins. The sarafotoxins precursor cDNA predicts an unusual structure 'rosary-type', with 12 successive similar stretches of sarafotoxin (SRTX) and spacer. In the present work, the recombinant precursor of SRTXs was sub-cloned and expressed in the yeast Pichia pastoris, and secreted to the culture medium. Characterization by SDS-PAGE, immunoblot, mass spectrometry and biological activity, suggests that intact precursor was expressed but processing into mature toxins also occurred. Furthermore, our results indicate that the correct proportion of sarafotoxin types as contained in the precursor, is obtained in the yeast culture medium. Contractile effects of the expressed toxins, on rat and Bothrops jararaca isolated aorta, were equivalent to 5x10(-10)M and 5x10(-11)M of sarafotoxin b, respectively. The enzymes responsible for the complete maturation of sarafotoxins precursor are still unknown. Our results strongly suggest that the yeast Pichia pastoris is able to perform such a maturation process. Thus, the yeast Pichia pastoris may offer an alternative to snake venom gland to tentatively identify the molecular process responsible for SRTXs release.

Immunocytochemical mapping of the amidating enzyme PAM in the developing and adult mouse lung

The enzyme PAM is required for activation of many peptide hormones. In adult mouse lung, immunostaining for PAM was located in Clara cells, which constitute most of the epithelial cells of the mouse bronchial/bronchiolar tree. Immunoreactivity appeared for the first time in the epithelium on gestational Day 16, being slight and mostly restricted to the apical cytoplasm. As the lung developed, the labeling became gradually stronger and extended throughout the cell. Smooth muscle of airways and blood vessels, and some parenchymal cells, probably macrophages, also showed PAM immunoreactivity. Of the two enzymatically active domains of PAM, only PHM and not PAL immunoreactivity was found at all stages studied. The early appearance of PAM in developing mouse lung, as well as its presence in a variety of tissues, probably indicates a complex role of this enzyme in pulmonary development and function.

Comparative histology of pulmonary neuroendocrine cell system in mammalian lungs

It is increasingly recognized that neuroepithelial endocrine cells and organoid clusters of these cells termed neuroepithelial bodies are widely distributed in the respiratory tract of vertebrates. This review focuses on the neuroepithelial endocrine system in the airway epithelium of mammals according to observations made in a wide range of species, as it appears in light and electron microscopy by means of various visualization techniques under normal and experimental conditions. Because there are similarities but also marked differences between species, wherever possible studies in human airways are emphasized. Conventional histochemical and ultrastructural studies including microspectrofluorimetry have demonstrated the amine-handling properties and the presence of neurosecretory granules in neuroendocrine cells of the epithelium of all mammals studies so far. The neuroepithelial bodies are innervated by morphological afferent- and efferentlike synaptic specializations. These, together with the presence of reciprocal synapses, emphasize that these cells may be involved in dual functions of chemoreception and secretion. Light and electron microscopic immunohistochemistry has demonstrated that neuroepithelial endocrine cells may contain various biogenic agents, suggesting that the neuroendocrine system is highly heterogeneous. Neural elements may interact in a complex manner, and the activation of certain neural pathways may control the release of biogenic substances to influence physiological airway functions. They may be particularly relevant in pulmonary diseases. Consequently, the function of this system is complex and it is highly probable that many of its aspects are still not elucidated.

Localization of immunoreactive endothelin in the neuroendocrine cells of fish gill

Immunohistochemical tests have demonstrated for the first time the presence of endothelins in the neuroendocrine cells of fish gill. We have sought co-localization of endothelins with serotonin and neuropeptides which are regarded as neuroendocrine markers of pulmonary diffuse neuroendocrine systems in higher vertebrates. Regarding their endocrine and paracrine activities in mammals, endothelins are considered as peptide hormones and growth factors regulating respiratory function. The roles of endothelins in the gill await investigation based on the multifunctional organization of this organ.