Generation of an immortal differentiated lung type-II epithelial cell line from the adult H-2K(b)tsA58 transgenic mouse

Lipopolysaccharide and lipoteichoic acid enhance serum amyloid A3 mRNA expression in murine alveolar epithelial cells

Serum amyloid A (SAA) is an acute-phase protein indicative of inflammation. In murine colonic epithelial cells, lipopolysaccharide (LPS), a gram-negative bacterial antigen, strongly enhanced mRNA expression of SAA3, but not SAA1 or SAA2, suggesting that SAA3 might respond to bacterial infection in other epithelia. We examined SAA1/2 and SAA3 mRNA expression in murine alveolar epithelial cells exposed to LPS or the gram-positive bacterial antigen, lipoteichoic acid (LTA), using real-time PCR. LPS enhanced SAA3 mRNA expression at lower concentrations than did LTA, whereas SAA1/2 mRNA expression was not enhanced by either LPS or LTA. These results suggest that SAA3 expression is enhanced in lung epithelium upon bacterial infection as part of innate immunity, with higher sensitivity to LPS than to LTA.

Allergen induced pulmonary inflammation enhances mammary tumor growth and metastasis: Role of CHI3L1

Metastasis is the primary cause of mortality in women with breast cancer. Metastasis to the lungs is greater in patients with pulmonary inflammatory illnesses. It is unknown how pre-existing pulmonary inflammation affects mammary tumor progression. We developed a novel breast cancer model in which pulmonary inflammation is induced in mice prior to tumor cell implantation. In the present study, we determined how pre-existing allergen-induced inflammation changes the pulmonary microenvironment to exacerbate tumor metastasis. We showed that pre-existing pulmonary inflammation in mammary tumor bearers is associated with: 1) an increase in growth of the primary tumor and metastasis; 2) an increase in the expression of a glycoprotein known as CHI3L1; and 3) increase in the levels of myeloid populations in their lungs. We also showed that myeloid derived cells from the lungs of allergic tumor bearers produce higher amounts of CHI3L1 than the saline controls. We previously showed that CHI3L1 induces the expression of proinflammatory and protumorigenic molecules. In this study, we show that CHI3L1 knockout tumor bearers with pre-existing allergic pulmonary inflammation had decreased levels of myeloid-derived cells, decreased levels of proinflammatory mediators, and a significant reduction in tumor volume and metastasis compared with the wild-type controls. Pre-existing inflammation and CHI3L1 might be driving the establishment of a premetastatic milieu in the lungs and aiding in the support of metastatic foci. Understanding the role of allergen-induced CHI3L1 and inflammation in tumor bearers and its effects on the pulmonary microenvironment could result in targeted therapies for breast cancer.

Cholera toxin induces a shift from inactive to active cyclooxygenase 2 in alveolar macrophages activated by Mycobacterium bovis BCG

Intranasal vaccination stimulates formation of cyclooxygenases (COX) and release of prostaglandin E(2) (PGE(2)) by lung cells, including alveolar macrophages. PGE(2) plays complex pro- or anti-inflammatory roles in facilitating mucosal immune responses, but the relative contributions of COX-1 and COX-2 remain unclear. Previously, we found that Mycobacterium bovis BCG, a human tuberculosis vaccine, stimulated increased release of PGE(2) by macrophages activated in vitro; in contrast, intranasal BCG activated no PGE(2) release in the lungs, because COX-1 and COX-2 in alveolar macrophages were subcellularly dissociated from the nuclear envelope (NE) and catalytically inactive. This study tested the hypothesis that intranasal administration of BCG with cholera toxin (CT), a mucosal vaccine component, would shift the inactive, NE-dissociated COX-1/COX-2 to active, NE-associated forms. The results showed increased PGE(2) release in the lungs and NE-associated COX-2 in the majority of COX-2(+) macrophages. These COX-2(+) macrophages were the primary source of PGE(2) release in the lungs, since there was only slight enhancement of NE-associated COX-1 and there was no change in COX-1/COX-2 levels in alveolar epithelial cells following treatment with CT and/or BCG. To further understand the effect of CT, we investigated the timing of BCG versus CT administration for in vivo and in vitro macrophage activations. When CT followed BCG treatment, macrophages in vitro had elevated COX-2-mediated PGE(2) release, but macrophages in vivo exhibited less activation of NE-associated COX-2. Our results indicate that inclusion of CT in the intranasal BCG vaccination enhances COX-2-mediated PGE(2) release by alveolar macrophages and further suggest that the effect of CT in vivo is mediated by other lung cells.

The role of alveolar epithelial cells in initiating and shaping pulmonary immune responses: communication between innate and adaptive immune systems

Macrophages and dendritic cells have been recognized as key players in the defense against mycobacterial infection. However, more recently, other cells in the lungs such as alveolar epithelial cells (AEC) have been found to play important roles in the defense and pathogenesis of infection. In the present study we first compared AEC with pulmonary macrophages (PuM) isolated from mice in their ability to internalize and control Bacillus Calmette-Guérin (BCG) growth and their capacity as APCs. AEC were able to internalize and control bacterial growth as well as present antigen to primed T cells. Secondly, we compared both cell types in their capacity to secrete cytokines and chemokines upon stimulation with various molecules including mycobacterial products. Activated PuM and AEC displayed different patterns of secretion. Finally, we analyzed the profile of response of AEC to diverse stimuli. AEC responded to both microbial and internal stimuli exemplified by TLR ligands and IFNs, respectively. The response included synthesis by AEC of several factors, known to have various effects in other cells. Interestingly, TNF could stimulate the production of CCL2/MCP-1. Since MCP-1 plays a role in the recruitment of monocytes and macrophages to sites of infection and macrophages are the main producers of TNF, we speculate that both cell types can stimulate each other. Also, another cell-cell interaction was suggested when IFNs (produced mainly by lymphocytes) were able to induce expression of chemokines (IP-10 and RANTES) by AEC involved in the recruitment of circulating lymphocytes to areas of injury, inflammation, or viral infection. In the current paper we confirm previous data on the capacity of AEC regarding internalization of mycobacteria and their role as APC, and extend the knowledge of AEC as a multifunctional cell type by assessing the secretion of a broad array of factors in response to several different types of stimuli.

Lipocalin 2-dependent inhibition of mycobacterial growth in alveolar epithelium

Mycobacterium tuberculosis invades alveolar epithelial cells as well as macrophages. However, the role of alveolar epithelial cells in the host defense against M. tuberculosis remains unknown. In this study, we report that lipocalin 2 (Lcn2)-dependent inhibition of mycobacterial growth within epithelial cells is required for anti-mycobacterial innate immune responses. Lcn2 is secreted into the alveolar space by alveolar macrophages and epithelial cells during the early phase of respiratory mycobacterial infection. Lcn2 inhibits the in vitro growth of mycobacteria through sequestration of iron uptake. Lcn2-deficient mice are highly susceptible to intratracheal infection with M. tuberculosis. Histological analyses at the early phase of mycobacterial infection in Lcn2-deficient mice reveal increased numbers of mycobacteria in epithelial cell layers, but not in macrophages, in the lungs. Increased intracellular mycobacterial growth is observed in alveolar epithelial cells, but not in alveolar macrophages, from Lcn2-deficient mice. The inhibitory action of Lcn2 is blocked by the addition of endocytosis inhibitors, suggesting that internalization of Lcn2 into the epithelial cells is a prerequisite for the inhibition of intracellular mycobacterial growth. Taken together, these findings highlight a pivotal role for alveolar epithelial cells during mycobacterial infection, in which Lcn2 mediates anti-mycobacterial innate immune responses within the epithelial cells.

Morphologic changes in alveolar macrophages in response to UVEC-activated pulmonary Type II epithelial cells

We hypothesize that Type II epithelial cells, which line the distal airspaces of the lung, are early responders to invading pathogens and release a signal, which activates and alters the phenotype and phagocytosis properties of alveolar macrophages even at a distance. The T(7) cell line is a conditionally immortalized murine Type II epithelial cell line developed in our laboratory. Using an in vitro transwell model we have previously shown that UV-irradiated Escherichia coli (UVEC)-stimulated T(7) cells cultured in the lower transwell chamber, release a diffusible signal which activates MH-S cells (immortalized murine alveolar macrophages) cultured in the upper transwell chamber, to produce nitric oxide. Using scanning electron microscopy, we show that MH-S cells activated in this manner exhibit increased cell surface ruffling, numerous long filopodia, increased lamellipodia and cell flattening. DynaBead uptake studies show that these morphologic changes are accompanied by increased phagocytosis. These findings indicate that a diffusible signal released at a distance by UVEC-stimulated Type II epithelial cells initiates changes in morphology and phagocytosis reflective of macrophage activation concomitant with the functional activation we previously reported.

Development of vaccines and passive immunotherapy against SARS coronavirus using mouse and SCID-PBL/hu mouse models

We have investigated novel vaccines strategies against severe acute respiratory syndrome (SARS) CoV infection using cDNA constructs encoding the structural antigens; spike (S), membrane (M), envelope (E), or nucleocapsid (N) protein, derived from SARS CoV (strain HKU39849, TW1, or FFM-1). As SARS-CoV is thought to infect the alveolar epithelial cell of the lung,in the present study, a type II alveolar epithelial cell clone, T7, was used to analyze the mechanism of CTL against SARS CoV membrane antigens. Mice vaccinated with SARS CoV (N) DNA or (M) DNA using pcDNA 3.1 (+) plasmid vector showed T-cell immune responses (CTL induction and proliferation) against type II alveolar epithelial cells (T7) transfected with SARS (N) or (M) DNA, respectively. To determine whether these DNA vaccines could induce T-cell immune responses in humans as well as in mice, SCID-PBL/hu mice were immunized with these DNA vaccines. PBL from healthy human volunteers were administered i.p. into IL-2 receptor gamma-chain-disrupted NOD-SCID mice [IL-2R(-/-) NOD-SCID]. SCID-PBL/hu mice thus constructed can be used to analyze the human immune response in vivo. The SCID-PBL/hu mice were immunized with SARS (N) DNA or (M) DNA and analyzed for a human T-cell immune response. The M DNA vaccine enhanced CTL activity and proliferation in the presence of M peptide in SCID-PBL/hu mice. Furthermore, the SARS N DNA vaccine induced CTL activity (IFN-gamma production by recombinant N protein or N protein-pulsed autologous B blast cells) and proliferation of spleen cells in SCID-PBL/hu mice. These results, demonstrate that SARS M and N DNA vaccines induced human CTL and human T-cell proliferative responses. On the other hand, we have developed SARS DNA vaccines that induce human neutralizing antibodies and human monoclonal antibodies against SARS CoV. Transgenic mice expressing SARS-CoV receptor (angiotensin converting enzyme 2) are also under development. These vaccines are expected to induce immune responses specific for SARS CoV in human and should provide useful tool for development of protective vaccines.

A novel inflammation-induced ubiquitin E3 ligase in alveolar type II cells

LINCR was identified as a glucocorticoid-attenuated response gene induced in the lung during endotoxemia. The LINCR protein has structural similarities to Drosophila Neuralized, which regulates the developmentally important Notch signaling pathway. Endotoxemia-induced LINCR expression in vivo was localized by in situ hybridization to alveolar epithelial type II cells, and shown to be induced by LPS and inflammatory cytokines in the T7 alveolar epithelial type II cell line. RING domain-dependent ubiquitin E3 ligase activity of LINCR was demonstrated using full-length FLAG-LINCR or a deletion mutant lacking the RING domain expressed in 293T cells, and using a GST-LINCR RING fusion protein expressed in Escherichia coli. LINCR preferentially interacted with the ubiquitin-conjugating enzyme UbcH6 and preferentially generated polyubiquitin chains linked via non-canonical lysine residues. We conclude that LINCR is a novel inflammation-induced ubiquitin E3 ligase expressed in alveolar epithelial type II cells, and discuss its potential role in the lung response to inflammation.

Primary type II alveolar epithelial cells present microbial antigens to antigen-specific CD4+T cells

Type II alveolar epithelial cells (AEC) can produce various antimicrobial and proinflammatory effector molecules. This, together with their abundance and strategic location, suggests a role in host defense against pulmonary pathogens. We report that murine type II AEC, like their human counterparts, express class II major histocompatibility complex (MHC). Using a murine model of pulmonary tuberculosis, we find that type II AEC become activated and have increased cell surface expression of class II MHC, CD54, and CD95 following infection. Type II AEC use the class II MHC pathway to process and present mycobacterial antigens to immune CD4+T cells isolated from mice infected with Mycobacterium tuberculosis. Therefore, not only can type II AEC contribute to the pulmonary immunity by secreting chemokines that recruit inflammatory cells to the lung, but they can also serve as antigen-presenting cells. Although type II AEC are unlikely to prime naïve T cells, their ability to present antigens to T cells demonstrates that they can participate in the effector phase of the immune response. This represents a novel role for type II AEC in the immunological response to pulmonary pathogens.

The development of vaccines against SARS corona virus in mice and SCID-PBL/hu mice

We have investigated to develop novel vaccines against SARS CoV using cDNA constructs encoding the structural antigen; spike protein (S), membrane protein (M), envelope protein (E), or nucleocapsid (N) protein, derived from SARS CoV. Mice vaccinated with SARS-N or -M DNA using pcDNA 3.1(+) plasmid vector showed T cell immune responses (CTL induction and proliferation) against N or M protein, respectively. CTL responses were also detected to SARS DNA-transfected type II alveolar epithelial cells (T7 cell clone), which are thought to be initial target cells for SARS virus infection in human. To determine whether these DNA vaccines could induce T cell immune responses in humans as well as in mice, SCID-PBL/hu mice was immunized with these DNA vaccines. As expected, virus-specific CTL responses and T cell proliferation were induced from human T cells. SARS-N and SARS-M DNA vaccines and SCID-PBL/hu mouse model will be important in the development of protective vaccines.

Pulmonary phosphatidic acid phosphatase and lipid phosphate phosphohydrolase

The lung contains two distinct forms of phosphatidic acid phosphatase (PAP). PAP1 is a cytosolic enzyme that is activated through fatty acid-induced translocation to the endoplasmic reticulum, where it converts phosphatidic acid (PA) to diacylglycerol (DAG) for the biosynthesis of phospholipids and neutral lipids. PAP1 is Mg(2+) dependent and sulfhydryl reagent sensitive. PAP2 is a six-transmembrane-domain integral protein localized to the plasma membrane. Because PAP2 degrades sphingosine-1-phosphate (S1P) and ceramide-1-phosphate in addition to PA and lyso-PA, it has been renamed lipid phosphate phosphohydrolase (LPP). LPP is Mg(2+) independent and sulfhydryl reagent insensitive. This review describes LPP isoforms found in the lung and their location in signaling platforms (rafts/caveolae). Pulmonary LPPs likely function in the phospholipase D pathway, thereby controlling surfactant secretion. Through lowering the levels of lyso-PA and S1P, which serve as agonists for endothelial differentiation gene receptors, LPPs regulate cell division, differentiation, apoptosis, and mobility. LPP activity could also influence transdifferentiation of alveolar type II to type I cells. It is considered likely that these lipid phosphohydrolases have critical roles in lung morphogenesis and in acute lung injury and repair.

Functional analysis of an arthritogenic synovial fibroblast

Increasing attention has been directed towards identifying non-T-cell mechanisms as potential therapeutic targets in rheumatoid arthritis. Synovial fibroblast (SF) activation, a hallmark of rheumatoid arthritis, results in inappropriate production of chemokines and matrix components, which in turn lead to bone and cartilage destruction. We have demonstrated that SFs have an autonomous pathogenic role in the development of the disease, by showing that they have the capacity to migrate throughout the body and cause pathology specifically to the joints. In order to decipher the pathogenic mechanisms that govern SF activation and pathogenic potential, we used the two most prominent methods of differential gene expression analysis, differential display and DNA microarrays, in a search for deregulated cellular pathways in the arthritogenic SF. Functional clustering of differentially expressed genes, validated by dedicated in vitro functional assays, implicated a number of cellular pathways in SF activation. Among them, diminished adhesion to the extracellular matrix was shown to correlate with increased proliferation and migration to this matrix. Our findings support an aggressive role for the SF in the development of the disease and reinforce the perspective of a transformed-like character of the SF.

Generation and characterization of a conditionally immortalized lung clara cell line from the H-2Kb-tsA58 transgenic mouse

The Clara cell is believed to be the progenitor of the peripheral airway epithelium, and it produces the surfactant proteins SP-A and SP-B, in addition to the 10-kDa Clara cell secretory protein (CCSP or CC10). To date, attempts to develop Clara cell lines have been unsuccessful. Most such attempts have involved the in vitro insertion of a transforming viral oncogene. We have reported previously the characterization of a differentiated conditionally immortalized murine lung Type II epithelial cell line, T7, from the H-2Kb-tsA58 transgenic mouse. We have also used this mouse model to derive Clara cell lines. In this model, the need for in vitro gene insertion is circumvented by the creation of a transgene, in which the large tumor antigen of a temperature-sensitive strain (tsA58) of the simian virus 40 (SV40) is fused with the major histocompatibility complex promoter H-2Kb. The promoter is active in a wide range of tissues and is induced by interferons (IFN). From the lungs of animals harboring the hybrid construct, we isolated and characterized Clara cells. The cells contain dense secretory granules and mitochondria typical of Clara cells, and express SP-A, SP-B, SP-D, and the Clara cell secretory protein, CC10. Withdrawal of the IFN and elevation of the incubation temperature permit normal cell differentiation similar to that of Clara cells in vivo. This cell line should be very useful for the investigation of normal Clara cell function and gene expression.

Characterization and application of a gastric surface mucous cell line GSM06 established from temperature-sensitive simian virus 40 large T-antigen transgenic mice

It has been indicated that transgenic mouse harboring a temperature-sensitive simian virus 40 large T-antigen gene is useful for establishing cell lines from tissues that have proved difficult to culture in vitro. The gastric surface mucous cell line GSM06 was established from a primary culture of gastric fundic mucosal cells of the transgenic mice. GSM06 cells showed temperature-sensitive growth in culture and expressed large T-antigen at a permissive temperature (33 degrees C) but not at a nonpermissive temperature (39 degrees C). At 39 degrees C, the cells produced periodic acid-Schiff positive glycoconjugates that formed a mucous sheet like the gastric surface mucosa in the stomach. Insulin markedly increased the production of glycoconjugates. In addition, proprotein-processing endoprotease furin suppression retarded cell growth, but accelerated cell differentiation. An air-liquid interface promoted the differentiation of GSM06 cells in a reconstruction culture with nitrocellulose membrane and collagen gel. The gastric surface mucous cell line GSM06 with unique characteristics, therefore, should be useful as an in vitro model of the gastric mucosa for physiological and pharmacological investigations. Moreover, experiments using immortalized cells established in vitro and having specific functions may offer an alternative to experiments using living animals and thereby offer a solution to this ethical issue.