Protection of human nasal respiratory epithelium from complement-mediated lysis by cell-membrane regulators of complement activation

Exogenous and Endogenous Triggers Differentially Stimulate Pigr Expression and Antibacterial Secretory Immunity in the Murine Respiratory Tract

PURPOSE

Transport of secretory immunoglobulin A (SIgA) through the airway epithelial cell barrier into the mucosal lumen by the polymeric immunoglobulin receptor (pIgR) is an important mechanism of respiratory mucosal host defense. Identification of immunomodulating substances that regulate secretory immunity might have therapeutic implications with regard to an improved immune exclusion. Thus, we sought to analyze secretory immunity under homeostatic and immunomodulating conditions in different compartments of the murine upper and lower respiratory tract (URT&LRT).

METHODS

Pigr gene expression in lung, trachea, and nasal-associated lymphoid tissue (NALT) of germ-free mice, specific pathogen-free mice, mice with an undefined microbiome, as well as LPS- and IFN-γ-treated mice was determined by quantitative real-time PCR. IgA levels in bronchoalveolar lavage (BAL), nasal lavage (NAL), and serum were determined by ELISA. LPS- and IFN-γ-treated mice were colonized with Streptococcus pneumoniae and bacterial CFUs were determined in URT and LRT.

RESULTS

Respiratory Pigr expression and IgA levels were dependent on the degree of exposure to environmental microbial stimuli. While immunostimulation with LPS and IFN-γ differentially impacts respiratory Pigr expression and IgA in URT vs. LRT, only prophylactic IFN-γ treatment reduces nasal colonization with S. pneumoniae.

CONCLUSION

Airway-associated secretory immunity can be partly modulated by exposure to microbial ligands and proinflammatory stimuli. Prophylactic IFN-γ-treatment modestly improves antibacterial immunity in the URT, but this does not appear to be mediated by SIgA or pIgR.

Modulation of host CD59 expression by varicella-zoster virus in human xenografts in vivo

Varicella-zoster virus (VZV) is the causative agent of both chickenpox (varicella) and shingles (zoster). VZV survives host defenses, even with an intact immune system, and disseminates in the host before causing disease. To date, several diverse immunomodulatory strategies used by VZV to undermine host immunity have been identified; however, few studies have addressed the complement evasion strategies used by this virus. Here, we show that expression of CD59, which is a key member of host regulators of complement activation (RCA), is significantly upregulated in response to VZV infection in human T cells and dorsal root ganglia (DRG) but not in human skin xenografts in SCID-hu mice in vivo. This is the first report demonstrating that VZV infection upregulates host CD59 expression in a tissue-specific manner in vivo, which may aid VZV in complement evasion and pathogenesis.

A panel of glycoproteins as candidate biomarkers for early diagnosis and treatment evaluation of B-cell acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia is the most common malignant cancer in childhood. The signs and symptoms of childhood cancer are difficult to recognize, as it is not the first diagnosis to be considered for nonspecific complaints, leading to potential uncertainty in diagnosis. The aim of this study was to perform proteomic analysis of serum from pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL) to identify candidate biomarker proteins, for use in early diagnosis and evaluation of treatment.

METHODS

Serum samples were obtained from ten patients at the time of diagnosis (B-ALL group) and after induction therapy (AIT group). Sera from healthy children were used as controls (Control group). The samples were subjected to immunodepletion, affinity chromatography with α-d-galactose-binding lectin (from Artocarpus incisa seeds) immobilized on a Sepharose(TM) 4B gel, concentration, and digestion for subsequent analysis with nano-UPLC tandem nano-ESI-MS(E). The program Expression (E) was used to quantify differences in protein expression between groups.

RESULTS

A total of 96 proteins were identified. Leucine-rich alpha-2-glycoprotein 1 (LRG1), Clusterin (CLU), thrombin (F2), heparin cofactor II (SERPIND1), alpha-2-macroglobulin (A2M), alpha-2-antiplasmin (SERPINF2), Alpha-1 antitrypsin (SERPINA1), Complement factor B (CFB) and Complement C3 (C3) were identified as candidate biomarkers for early diagnosis of B-ALL, as they were upregulated in the B-ALL group relative to the control and AIT groups. Expression levels of the candidate biomarkers did not differ significantly between the AIT and control groups, providing further evidence that the candidate biomarkers are present only in the disease state, as all patients achieved complete remission after treatment.

CONCLUSION

A panel of protein biomarker candidates has been developed for pre-diagnosis of B-ALL and also provided information that would indicate a favorable response to treatment after induction therapy.

Crosstalk between TGF-β1 and complement activation augments epithelial injury in pulmonary fibrosis

The epithelial complement inhibitory proteins (CIPs) cluster of differentiation 46 and 55 (CD46 and CD55) regulate circulating immune complex-mediated complement activation in idiopathic pulmonary fibrosis (IPF). Our previous studies demonstrated that IL-17A mediates epithelial injury via transforming growth factor β1 (TGF-β1) and down-regulates CIPs. In the current study, we examined the mechanistic role of TGF-β1 in complement activation-mediated airway epithelial injury in IPF pathogenesis. We observed lower epithelial CIP expression in IPF lungs compared to normal lungs, associated with elevated levels of complement component 3a and 5a (C3a and C5a), locally and systemically. In normal primary human small airway epithelial cells (SAECs) treated with TGF-β1 (10 ng/ml), C3a, or C5a (100 nM), we observed loss of CIPs and increased poly(ADP-ribose) polymerase (PARP) activation [also observed with RNA interference (RNAi) of CD46/CD55]. TGF-β1-mediated loss of CIPs and Snail induction [SNAI1; a transcriptional repressor of E-cadherin (E-CAD)] was blocked by inhibiting mitogen-activated protein kinase (p38MAPK; SB203580) and RNAi silencing of SNAI1. C3a- and C5a-mediated loss of CIPs was also blocked by p38MAPK inhibition. While C3a upregulated TGFb transcripts, both C3a and C5a down-regulated SMAD7 (negative regulator of TGF-β), and whereas TGF-β1 induced C3a/C5a receptor (C3aR/C5aR) expression, pharmacologic C3aR/C5aR inhibition protected against C3a-/C5a-mediated loss of CIPs. Taken together, our results suggest that epithelial injury in IPF can be collectively amplified as a result of TGF-β1-induced loss of CIPs leading to complement activation that down-regulates CIPs and induces TGF-β1 expression

The role of complement in tumor growth

Complement is a central part of the immune system that has developed as a first defense against non-self cells. Neoplastic transformation is accompanied by an increased capacity of the malignant cells to activate complement. In fact, clinical data demonstrate complement activation in cancer patients. On the basis of the use of protective mechanisms by malignant cells, complement activation has traditionally been considered part of the body's immunosurveillance against cancer. Inhibitory mechanisms of complement activation allow cancer cells to escape from complement-mediated elimination and hamper the clinical efficacy of monoclonal antibody-based cancer immunotherapies. To overcome this limitation, many strategies have been developed with the goal of improving complement-mediated effector mechanisms. However, significant work in recent years has identified new and surprising roles for complement activation within the tumor microenvironment. Recent reports suggest that complement elements can promote tumor growth in the context of chronic inflammation. This chapter reviews the data describing the role of complement activation in cancer immunity, which offers insights that may aid the development of more effective therapeutic approaches to control cancer.

Caveolin-1 and dynamin-2 are essential for removal of the complement C5b-9 complex via endocytosis

The complement system, an important element of both innate and adaptive immunity, is executing complement-dependent cytotoxicity (CDC) with its C5b-9 protein complex that is assembled on cell surfaces and transmits to the cell death signals. In turn, cells, and in particular cancer cells, protect themselves from CDC in various ways. Thus, cells actively remove the C5b-9 complexes from their plasma membrane by endocytosis. Inhibition of clathrin by transfection with shRNA or of EPS-15 with a dominant negative plasmid had no effect on C5b-9 endocytosis and on cell death. In contrast, inhibition of caveolin-1 (Cav-1) by transfection with an shRNA or a dominant negative plasmid sensitized cells to CDC and inhibited C5b-9 endocytosis. Similarly, both inhibition of dynamin-2 by transfection with a dominant negative plasmid or by treatment with Dynasore reduced C5b-9 endocytosis and enhanced CDC. C5b-9 endocytosis was also disrupted by pretreatment of the cells with methyl-β-cyclodextrin or Filipin III, hence implicating membrane cholesterol in the process. Analyses by confocal microscopy demonstrated co-localization of Cav-1-EGFP with C5b-9 at the plasma membrane, in early endosomes, at the endocytic recycling compartment and in secreted vesicles. Further investigation of the process of C5b-9 removal by exo-vesiculation demonstrated that inhibition of Cav-1 and cholesterol depletion abrogated C5b-9 exo-vesiculation, whereas, over-expression of Cav-1 increased C5b-9 exo-vesiculation. Our results show that Cav-1 and dynamin-2 (but not clathrin) support cell resistance to CDC, probably by facilitating purging of the C5b-9 complexes by endocytosis and exo-vesiculation.

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.

Yeast whole glucan particle (WGP) beta-glucan in conjunction with antitumour monoclonal antibodies to treat cancer

Beta-glucans, biological response modifiers (BRMs) derived from the cell walls of yeast and other sources, have been demonstrated to prime leukocyte complement receptor 3 (CR3), thus enabling these cells to kill tumours opsonised with complement fragment iC3b. Many tumours activate complement via the classical pathway mediated by antitumour monoclonal antibodies (mAbs) or natural antibodies. Studies into the cellular and molecular mechanisms of action have demonstrated that orally administrated yeast beta-glucans are ingested and processed by macrophages. These macrophages secrete the active moiety that primes neutrophil CR3 to kill iC3b-opsonised tumour cells. Extensive studies in preclinical animal tumour models have demonstrated the efficacy of combined oral particulate yeast beta-glucan with antitumour mAb therapy in terms of tumour regression and long-term survival. It is proposed that the addition of beta-glucan will further improve the clinical therapeutic efficacy of antitumour mAbs in cancer patients.

Expression of complement factor H by lung cancer cells: effects on the activation of the alternative pathway of complement

The complement system is important in immunosurveillance against tumors. However, malignant cells are usually resistant to complement-mediated lysis. In this study, we examine the expression of factor H, an inhibitor of complement activation, and factor H-like protein 1 (FHL-1), its alternatively spliced form, in lung cancer. We also evaluate the potential effect of factor H/FHL-1 in the protection of lung cancer cells against the activation of the complement cascade. By Northern blot analysis we demonstrate a high expression of factor H and FHL-1 in most non-small cell lung cancer cell lines, although neuroendocrine pulmonary tumors (small cell lung carcinoma and carcinoid cell lines) had undetectable levels. Western blot analysis of conditioned medium showed the active secretion of factor H and FHL-1 by cells that were positive by Northern blot. Expression of factor H/FHL-1 mRNA was also shown in a series of non-small cell lung cancer biopsies by in situ hybridization. Interestingly, many cultured lung cancer cells were able to bind fluorescence-labeled factor H to their surfaces. Deposition of C3 fragments from normal human serum on H1264, a lung adenocarcinoma cell line, was more efficient when factor H/FHL-1 activity was blocked by specific antibodies. Blocking factor H/FHL-1 activity also enhanced the release of anaphylatoxin C5a and moderately increased the susceptibility of these cells to complement-mediated cytotoxicity. In summary, we demonstrate the expression of factor H and FHL-1 by some lung cancer cells and analyze the contribution of these proteins to the protection against complement activation.

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.

Complement activation and expression of membrane regulators in the middle ear mucosa in otitis media with effusion

The aetiopathogenesis of chronic otitis media with effusion (OME) in children is not yet fully understood. OME is characterized by metaplasia of the epithelium and accumulation of sticky, glue-like effusion in the middle ear containing different mediators of inflammation, including activation fragments of the complement system. Here we examined whether the fluid phase complement activation is reflected in the middle ear mucosa and how the mucosa is protected against the cytolytic activity of complement. Mucosal biopsies from 18 middle ears of children with a history of chronic OME were taken. The biopsies were analysed by immunofluorescence microscopy after staining for complement fragments iC3b/C3c, C3d and C9, and regulators membrane cofactor protein (MCP; CD46), decay-accelerating factor (DAF; CD55) and protectin (CD59). There was a strong staining for iC3b/C3c, and a weaker one for C3d and C9 on the surface of the middle ear epithelial cells of OME patients but not in controls without OME. MCP was expressed on the hyperplastic three to four outer cell layers of the epithelium, while CD59 was expressed throughout the middle ear mucosa. The results suggest a strong ongoing complement activation and consequent inflammation in the middle ear cavity. Unrestricted complement damage of the epithelial lining is prevented by the strong expression of MCP and CD59.

Cytokines modulate expression of cell-membrane complement inhibitory proteins in human lung cancer cell lines

Human lung cancers overexpress several cell-membrane complement inhibitory proteins (CIP). These complement inhibitory proteins are membrane cofactor protein (CD46), decay-accelerating factor (DAF; CD55), and CD59 (protectin). These cell-membrane proteins have a wide normal tissue distribution, are known to protect normal host cells from homologous complement-mediated lysis, and are thought to facilitate tumor escape from immunosurveillance. To study whether proinflammatory cytokines that are involved in cancer growth can modulate cell-membrane CIP expression in lung cancer cells, we studied the effect of interleukin (IL)-1alpha, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma on two human lung cancer cell lines. ChaGo K-1 and NCI-H596 cell lines, undifferentiated carcinoma and lung adenosquamous carcinoma, respectively, were stimulated with different cytokines, and the effects of incubation time and cytokine concentration on cell-membrane CIP expression were studied. Cell-membrane CIP expression was evaluated using flow cytometry and cytokine effect was calculated as percent change in mean fluorescence intensity of each CIP molecule from its untreated control. We found that DAF was the lung cancer cell-membrane CIP molecule that was the most responsive to cytokine stimulation. Maximal stimulatory effect was usually noted 72 h after a cytokine was introduced. In ChaGo K-1 and NCI-H596 lung cancer cell lines, IL-1alpha and TNF-alpha increased DAF expression. IL-1alpha (100 U/ml/72 h) increased DAF expression up to a maximal mean of 45 and 48%, respectively, in comparison with untreated cells. TNF-alpha (1, 000 U/ml/72 h) increased DAF expression up to a mean of 131 and 46%, respectively. IFN-gamma (1 U/ml/72 h) increased DAF expression in NCI-H596 cells up to a mean of 100%, but had a slight inhibitory effect on DAF expression in ChaGo K-1 cells, decreasing expression by a mean of 17% in comparison with untreated cells. We conclude that cell-membrane DAF expression in the studied human lung cancer cell lines is modulated by IL-1alpha, TNF-alpha, and IFN-gamma, and speculate that cytokine-mediated modulation of cell-membrane DAF in human lung cancer cells might affect lung cancer cell biology.

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.