Demonstration of calcitonin and calmodulin by immunoperoxidase in the cystic fibrosis lung

Neuropeptides in asthma, chronic obstructive pulmonary disease and cystic fibrosis

The nervous system mediates key airway protective behaviors, including cough, mucus secretion, and airway smooth muscle contraction. Thus, its involvement and potential involvement in several airway diseases has become increasingly recognized. In the current review, we focus on the contribution of select neuropeptides in three distinct airway diseases: asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. We present data on some well-studied neuropeptides, as well as call attention to a few that have not received much consideration. Because mucus hypersecretion and mucus obstruction are common features of many airway diseases, we place special emphasis on the contribution of neuropeptides to mucus secretion. Finally, we highlight evidence implicating involvement of neuropeptides in mucus phenotypes in asthma, COPD and cystic fibrosis, as well as bring to light knowledge that is still lacking in the field.

Cystic fibrosis transmembrane conductance regulator modulates neurosecretory function in pulmonary neuroendocrine cell-related tumor cell line models

The pulmonary neuroendocrine cell (PNEC) system consists of solitary cells and distinctive cell clusters termed neuroepithelial bodies (NEB) localized in the airway epithelium. PNEC/NEB express a variety of bioactive substances, including amine (serotonin, 5HT) and neuropeptides. We have previously shown that NEB cells are O(2) sensors expressing nicotinamide adenine diphosphate oxidase complex and O(2) sensitive K(+) channel. Recently, we demonstrated expression of functional cystic fibrosis transmembrane conductance regulator (CFTR) and Cl(-) conductances in NEB cells of rabbit neonatal lung. Because PNEC/NEB are sparsely distributed and difficult to study in native lung, we investigated small-cell lung carcinoma (SCLC) and carcinoid tumor cell lines (tumor counterparts of normal PNEC/NEB) as models for PNEC/NEB. SCLC (H146, H345) and carcinoid (H727) cell lines express neuroendocrine cell markers, including chromogranin A, neural cell adhesion molecule (N-CAM), 5HT, and tryptophan hydroxylase. We report that H146, H345, and H727 express CFTR messenger RNA (reverse transcription polymerase chain reaction) and protein (immunoblotting) and possess functional CFTR Cl(-) conductance, demonstrated by an iodide efflux assay inhibitable by transfection with antisense CFTR. Using an immunoassay to quantitate 5HT secretion, we also show that downregulation of CFTR abolishes hypoxia-induced 5HT release, and reduces secretory response to high potassium. Our findings suggest that CFTR may modulate neurosecretory activity of PNEC/NEB possessing O(2) sensor function. We propose that these tumor cell lines may be useful models for investigating the role of CFTR in PNEC/NEB functions in health and disease.

Expression of CFTR and Cl(-) conductances in cells of pulmonary neuroepithelial bodies

The pulmonary neuroendocrine cell system comprises solitary neuroendocrine cells and clusters of innervated cells or neuroepithelial bodies (NEBs). NEBs figure prominently during the perinatal period when they are postulated to be involved in physiological adaptation to air breathing. Previous studies have documented hyperplasia of NEBs in cystic fibrosis (CF) lungs and increased neuropeptide (bombesin) content produced by these cells, possibly secondary to chronic hypoxia related to CF lung disease. However, little is known about the role of NEBs in the pathogenesis of CF lung disease. In the present study, using a panel of cystic fibrosis transmembrane conductance regulator (CFTR)-specific antibodies and confocal microscopy in combination with RT-PCR, we demonstrate expression of CFTR message and protein in NEB cells of rabbit neonatal lungs. NEB cells expressed CFTR along with neuroendocrine markers. Confocal microscopy established apical membrane localization of the CFTR protein in NEB cells. Cl(-) conductances corresponding to functional CFTR were demonstrated in NEB cells in a fresh lung slice preparation. Our findings suggest that NEBs, and related neuroendocrine mechanisms, likely play a role in the pathogenesis of CF lung disease, including the early stages before establishment of chronic infection and chronic lung disease.

The relationship of eosinophil granule proteins to ions in the sputum of patients with cystic fibrosis

Increased sputum levels of eosinophil granule proteins have been reported despite normal eosinophil numbers in peripheral blood and in the lung in cystic fibrosis (CF). Mechanisms of eosinophil priming and activation are still unclear in CF. In the present study we investigated whether ion concentrations in the sputa of CF patients are related to eosinophil activity. We assessed concentrations of eosinophil cationic protein (ECP), eosinophil protein X (EPX), major basic protein (MBP) and ions (Na+, Cl-, Ca2+, Mg2+) in sputum samples of 29 children with CF as well as in 10 controls with bronchial asthma. Patients with CF demonstrated significantly higher levels of ECP, Na+, Cl- and Ca2+ levels than asthmatics (P < 0.04, P < 0.0001, P < 0.0001, P < 0.02). No differences were seen between concentrations of EPX and Mg2+ in the two groups. In CF, eosinophil granule proteins correlated significantly with Ca2+ and Mg2+ concentrations (ECP, P < 0.0001, r = 0.65, P < 0.0001, r = 0.66; MBP, P < 0.03, r = 0.41, P < 0.03, r = 0.42), furthermore inversely with Cl- concentrations (ECP, P < 0. 0003, r = - 0.63; EPX, P < 0.02, r = - 0.45; MBP, P < 0.03, r = - 0. 41) but not with Na+ levels. ECP, Na+ and Cl- were also correlated with lung function variables (FVC, P < 0.04, r = - 0.38, P < 0.02, r = 0.44, P < 0.03, r = 0.41; FEV1, P < 0.007, r = - 0.49, P < 0.006, r = 0.5, P < 0.008, r = 0.48; MEF50, P < 0.003, r = - 0.54, NS, P < 0.03, r = 0.42; MEF25, P < 0.039, r = - 0.4, P < 0.005, r = 0.51, P < 0.05, r = 0.37). Our results demonstrated a significant relationship of eosinophil degranulation and ions in CF, indicating that ion composition in CF sputa may be at least partly be responsible for high levels of eosinophil products despite low eosinophil numbers.

Differentiation and proliferation of pulmonary neuroendocrine cells

In this review article the morphological profiles of pulmonary neuroendocrine cells (PNEC) in experimental animals and humans are described. Although the mechanisms of differentiation and proliferation of neuroendocrine cells in the airway epithelium remain to be solved, several experimental studies using explant culture and cell culture systems of fetal animal lungs have been performed to clarify fundamental phenomena associated with neuroendocrine differentiation and proliferation. Experimental animal studies using chronic hypoxia, toxic substances and carcinogens have succeeded in inducing alterations in PNEC systems, and these studies have elucidated the reactions of PNEC in cell injury and inflammation, and functional aspects of PNEC in disease conditions. Human pulmonary neuroendocrine tumors include various histological subtypes, and show divergent morphological and biological varieties. Molecular abnormalities of small cell carcinoma, the most aggressive subtype of pulmonary neuroendocrine tumors, have been extensively studied, but the mechanism of neuroendocrine differentiation of this tumor is still largely unknown. PNEC share common phenotypes with neuronal cells, and developmental studies have begun contributed evidence that similar transcriptional networks, including active and repressive basic helix-loop-helix (bHLH) factors, function in the differentiation of both PNEC and neuronal cells. Such a bHLH network may also play a central role in determining cell differentiation in lung carcinomas. Further studies of the neuronal bHLH network, its regulatory system and related signal transduction pathways, will be required for understanding the mechanisms of neuroendocrine differentiation and proliferation in normal and pathological lung conditions.

Pulmonary neuroendocrine cell system in pediatric and adult lung disease

In humans lungs affected by naturally occurring pulmonary disease, the pulmonary neuroendocrine cell system, which is normally arranged in a sparse but even distribution throughout the respiratory tract, increases in size. It is likely that the stimulus for this is pulmonary injury and that its purpose is the paracrine regulation of the restoration of pulmonary tissues to their normal state, an hypothesis supported by studies of animal lungs subjected to experimental injury as well as of the development of human and animal lungs in utero. Initially, this increase involves the development of interrupted rows of neuroendocrine cells. In the later stages, however, development of more disorderly intraepithelial aggregates can occur and the small, locally invasive neuroendocrine cell lesions known as tumourlets may occasionally result. Both of these latter structures often contain secretory products not found in the neuroendocrine cells of normal human lungs, probably indicating a derangement of what appears to be a fundamentally physiological response. It is likely that, in some circumstances, this disorderly change may contribute to pulmonary disease as well as being the result of it.

Immunoreactive calmodulin in cystic fibrosis kidneys

BACKGROUND

Microscopic nephrocalcinosis has been detected at autopsy in 35 of 38 (92%) cystic fibrosis (CF) patients. A primary defect of calcium metabolism in the kidney has been postulated. Intracellular calcium and calmodulin (a calcium binding protein) have been shown to be increased in CF tissues.

AIMS

To determine whether CF kidneys obtained at autopsy contain normal amounts of calmodulin and whether the presence of immunoreactive calmodulin correlates with nephrocalcinosis.

METHODS

An immunoperoxidase method was used to stain kidneys obtained from six CF individuals aged three to 27.5 years (mean 15.75 +/- 10.2 years) and five individuals who died of chronic debilitating disease aged eight to 17 years (mean 13.6 +/- 3.9 years). Calcium staining was undertaken using the von Kossa (silver precipitation) and Alizarin red methods.

RESULTS

No quantifiable difference in immunoreactive calmodulin staining was demonstrated in autopsy renal specimens between six CF patients and five chronically diseased controls. Three of six CF patients aged 22.8 +/- four years and two of five chronically diseased controls aged eight to 16 years respectively had detectable immunoreactive calmodulin staining. Within the CF group the presence of microscopic nephrocalcinosis did not correlate with immunoreactive calmodulin staining.

CONCLUSION

This study does not support the premise that a calmodulin-dependent defect of intracellular calcium handling contributes to the microscopic nephrocalcinosis seen in CF.

Mechanism of action of calcitonin on secretion in rat submandibular gland

Calcitonin (CT) was found to reduce the initial flow of pilocarpine-stimulated saliva from the submandibular glands in the rat. Although there was a concomitant increase of the concentration of calcium and protein in the saliva, the calcium/protein ratio was not significantly affected. CT also caused a significant increase of the potassium concentration in submandibular saliva. Both in vivo and in vitro, CT inhibited the production of cyclic AMP (cAMP) both in the absence and in the presence of forskolin. This decrease in intracellular cAMP levels could result in an inhibition of mucus secretion, which would explain the previously observed calcitonin-induced intracellular accumulation of mucus in the submandibular gland acinar cells. CT did not affect the cytoplasmic free Ca2+ concentration (as measured with fura 2) in isolated submandibular acini either in the absence or in the presence of cholinergic or adrenergic agonists. These results indicate that the inhibition of fluid secretion in the submandibular gland by calcitonin must be located distal to changes in [Ca2+]i. It can be concluded that CT affects both mucus and fluid secretion in the submandibular gland, but that only the inhibition of mucus secretion can as yet be explained by an effect at the level of the second messenger.