Human nasal epithelium adsorbs complement C3-related fragments and expresses cell membrane complement regulatory proteins

Analytical constraints for the analysis of human cell line secretomes by shotgun proteomics

Human cell line secretome represents a valuable source of therapeutic targets and candidate biomarkers. Secreted proteins found in biological fluids or culture media are by essence highly diluted. Secretome investigation with proteomic approaches is hardly compatible with the high content of proteins found in complete cell culture media. Therefore, many studies are currently done with media containing few or no protein. Such conditions may perturb cell metabolism and proliferation. Here, we compared seventeen different compositions of culture media for the human bronchial epithelial BEAS-2B cell line. Cell viability, proliferation rate and initial protein charge were systematically compared. We have shown that an important difficulty for the proteomic analysis is due to the presence of detergents such as Pluronic F-68 which hinders peptide mass spectrometry. The high glucose containing DMEM medium which is free of proteins was shown to preserve a good viability and proliferation of cells. With this conditioning medium, we identified 81 extracellular proteins in the secretome of BEAS-2B cells. Moreover, to illustrate this approach, we exposed BEAS-2B cells to a low toxic dose of CoCl(2,) and found 24 extracellular proteins modulated by cobalt. This study highlights the possible contribution of such proteomic approach in the field of toxicology.

The role of complement in the diagnosis and management of allergic rhinitis and allergic asthma

Allergic rhinitis and asthma are common chronic inflammatory diseases of the nasal mucus membranes and the upper airways with a high prevalence in Western countries. In addition to maladaptive T-helper type 2 (Th2) immunity, Th17 cells can drive the inflammatory responses in both diseases. Several reports have shown that the complement system is activated locally and systemically in allergic rhinitis and/or allergic asthma patients. Importantly, recent findings in experimental models of allergic rhinitis and allergic asthma suggest that the complement cleavage products complement 3a and complement 5a and the activation of their corresponding receptors in antigen-presenting cells regulate the development of maladaptive Th2 and Th17 immunity. These findings in experimental asthma are corroborated by genome-wide searches and candidate gene studies in humans. We discuss recent findings in experimental and human allergic airway diseases suggesting that complement may serve as a new diagnostic and therapeutic target for both disorders.

Allergic rhinitis: past, present and the future

Allergic rhinitis represents a global health issue affecting between 10% to 25% of the world population, with increasing prevalence over the last decade. Although often trivialized by patients and doctors, allergic rhinitis is a significant cause of morbidity, in addition to its substantial economic impact. While allergic rhinitis is an inflammatory disorder of the upper airways, inflammation alone is insufficient to explain the chronic nature of the disease. An exciting concept which has recently emerged in asthma concerns the role of the bronchial epithelium as a key regulator of airway inflammatory and remodelling responses in asthma. It has been shown by our group that the disruption and alteration in the function of the lower airway epithelium in asthma leads to the generation of a variety of stimuli that lead to the restructuring of the airway wall. This raises interesting questions regarding a similar role for the upper airway epithelium in allergic rhinitis. This review aims to interpret past and current research into allergic rhinitis, and to address specific areas where future research is warranted, particularly in relation to the possibility of an altered upper airway epithelial phenotype in allergic rhinitis.

Generation of complement C3 and expression of cell membrane complement inhibitory proteins by human bronchial epithelium cell line

BACKGROUND

The interrelationship between human airway epithelium and complement proteins may affect airway defence, airway function, and airway epithelial integrity. A study was undertaken to determine (1) whether unstimulated human bronchial epithelium generates complement proteins and expresses cell membrane complement inhibitory proteins (CIP) and (2) whether stimulation by proinflammatory cytokines affects the generation of complement and expression of cell membrane CIP by these cells.

METHODS

Human bronchial epithelium cell line BEAS-2B was cultured in a serum-free medium. Cells were incubated with and without proinflammatory cytokines to assess unstimulated and stimulated generation of complement C3, C1q and C5 (by ELISA), and to examine the expression of cell membrane CIP decay accelerating factor (DAF; CD55), membrane cofactor protein (MCP; CD46), and CD59 (protectin) by flow cytometry analysis.

RESULTS

Unstimulated human bronchial epithelial cell line BEAS-2B in serum-free medium generates complement C3 (mean 32 ng/10(6) cells/72 h, range 18-52) but not C1q and C5, and expresses cell membrane DAF, MCP, and CD59. Interleukin (IL)-1alpha (100 U/ml/72 h) and tumour necrosis factor (TNF-alpha; 1000 U/ml/72 h) increased generation of C3 up to a mean of 78% and 138%, respectively, above C3 generation by unstimulated cells. DAF was the only cell membrane CIP affected by cytokine stimulation. Interferon (IFN)-gamma (10 U/ml/72 h) and TNF-alpha (1000 U/ml/72 h) increased DAF expression up to a mean of 116% and 45%, respectively, above that in unstimulated cells. MCP and CD59 expression was not consistently affected by IL-1alpha, TNF-alpha, or IFN-gamma.

CONCLUSIONS

Local generation of complement C3 and expression of cell membrane CIP by human bronchial epithelium and its modulation by proinflammatory cytokines might be an additional regulatory mechanism of local airway defence and may affect airway function and epithelial integrity in health and disease.

Human lung cancer cell lines express cell membrane complement inhibitory proteins and are extremely resistant to complement-mediated lysis; a comparison with normal human respiratory epithelium in vitro, and an insight into mechanism(s) of resistance

Human lung cancer expresses cell membrane complement inhibitory proteins (CIP). We investigated whether human lung cancer cell lines also express cell-membrane CIP molecules and whether the biology of CIP molecules in these cell lines differs from that of CIP in normal human respiratory epithelium in culture. The cell lines ChaGo K-1 and NCI-H596 were compared with normal human nasal epithelium in primary cultures in respect to the level of cell membrane CIP expression of membrane cofactor protein (MCP; CD46), decay-accelerating factor (DAF; CD55) and CD59, in respect to the level of cell resistance to complement-mediated lysis, and in respect to the contribution of cell membrane CIP to cell resistance against complement-mediated lysis. We found, using flow cytometry, that both human lung cancer cell lines expressed MCP, DAF and CD59, as did normal nasal epithelial cells. However, normal cells showed a large subpopulation of low DAF-expressing cells (60% of all cells) and a smaller subpopulation of high DAF-expressing cells (40%), while the lung cancer cell lines showed only one cell population, of high DAF expression. In addition, both lung cancer cell lines expressed higher MCP levels, and NCI-H596 cells showed higher levels of CD59. Cell resistance to complement-mediated lysis of both lung cancer cell lines was much higher than that of normal cells. Fifty percent normal human serum, under the same concentrations of complement activators, induced lysis of less than a mean of 10% of lung cancer cells, while lysing up to a mean of 50% of nasal epithelial cells. Lung cancer cell resistance to complement was due to its ability to prevent significant activation of complement upon its cell membrane, as manifested by a failure of complement activators to increase cell membrane deposition of C3-related fragments. The exact mechanism for this resistance remains obscure. Unexpectedly, neutralizing antibodies, anti-MCP and anti-DAF were entirely ineffective and anti-CD59 was only slightly effective (18% mean cell lysis) in increasing the susceptibility of the lung cancer cell lines to complement, while the same antibodies were very effective in facilitating complement-mediated lysis of the normal nasal epithelial cells (50% mean cell lysis with CD59 MoAb). On the other hand, detachment of DAF and CD59 by phosphatidylinositol-specific phospholipase C (PIPLC) from the lung cancer cell lines abrogated their resistance to lysis. We suggest that the biology of cell membrane CIP molecules in human lung cancer cell lines is different from that of CIP in normal respiratory epithelial cells. Human lung cancer cell lines are able to prevent significant complement activation upon its cell membrane and are therefore especially resistant to complement-mediated lysis. Complement resistance may serve this common and highly lethal human cancer as an escape mechanism from the body's immunosurveillance and prevent effective immunotherapy with tumour-specific MoAbs.