Surfactant protein D regulates NF-kappa B and matrix metalloproteinase production in alveolar macrophages via oxidant-sensitive pathways

Foam cell formation of alveolar macrophages in Clara cell ablated mice inhaling crystalline silica

We investigated the function of Clara cells in vivo during exposure to inhaled crystalline silica by morphological and immunohistochemical examination of intra-alveolar cells and alveolar macrophages in Clara cell-ablated mice. The Clara cells of male FVB/n mice (8-12 weeks old) were ablated by intraperitoneal administration of naphthalene (300 mg/kg). The mice were then exposed to crystalline silica (Min-U-Sil-5, 97.1 ± 9.5 mg/m³, 6 hours/day, 5 days/week) for up to two weeks. The lungs were assessed by morphometry, as well as by immunohistochemistry of CD36, lectin-like oxygenated low-density lipoprotein receptor (LOX)-1, and matrix metalloproteinases (MMPs) -2, -9 and -12. There was a significantly greater number of intra-alveolar cells in Clara cell-ablated mouse groups than in wild-type mouse groups that were exposed to crystalline silica. A marked number of foamy alveolar macrophages were only detected in the Clara cell-ablated group exposed to crystalline silica, indicating that Clara cells inhibit infiltration and foam cell formation of alveolar macrophages. Immunohistochemical analysis indicated that foamy alveolar macrophages in the Clara cell-ablated group that inhaled crystalline silica overexpress CD36 and LOX-1, indicating upregulation of scavenger receptors of alveolar macrophages. These cells also express MMP-2, -9 and -12, suggesting increased gelatinolytic and elastolytic activities. Our findings suggest that Clara cells not only inhibit infiltration of alveolar macrophages but also their phagocytotic and gelatinolytic functions in silica-induced pulmonary injury.

Redox signaling at invasive microdomains in cancer cells

Redox signaling contributes to the regulation of cancer cell proliferation, survival, and invasion and participates in the adaptation of cancer cells to their microenvironment. NADPH oxidases are important mediators of redox signaling in normal and cancer cells. Redox signal specificity in normal cells is in part achieved by targeting enzymes that generate reactive oxygen species to specific subcellular microdomains such as focal adhesions, dorsal ruffles, lipid rafts, or caveolae. In a similar fashion, redox signal specificity during cancer cell invasion can be regulated by targeting reactive oxygen generation to invasive microdomains such as invadopodia. Here we summarize recent advances in the understanding of the redox signaling processes that control the cancer cell proinvasive program by modulating cell adhesion, migration, and proteolysis as well as the interaction of cancer cells with the tumor microenvironment. We focus on redox signaling events mediated by invadopodia NADPH oxidase complexes and their contribution to cancer cell invasion.

Pulmonary Collectins in Diagnosis and Prevention of Lung Diseases

Pulmonary surfactant is a complex mixture of lipids and proteins, and is synthesized and secreted by alveolar type II epithelial cells and bronchiolar Clara cells. It acts to keep alveoli from collapsing during the expiratory phase of the respiratory cycle. After its secretion, lung surfactant forms a lattice structure on the alveolar surface, known as tubular myelin. Surfactant proteins (SP)-A, B, C and D make up to 10% of the total surfactant. SP-B and SPC are relatively small hydrophobic proteins, and are involved in the reduction of surface-tension at the air-liquid interface. SP-A and SP-D, on the other hand, are large oligomeric, hydrophilic proteins that belong to the collagenous Ca²⁺-dependent C-type lectin family (known as “Collectins”), and play an important role in host defense and in the recycling and transport of lung surfactant (Awasthi 2010) (Fig. 43.1). In particular, there is increasing evidence that surfactant-associated proteins A and -D (SP-A and SP-D, respectively) contribute to the host defense against inhaled microorganisms (see 10.1007/978-3-7091-1065_24 and 10.1007/978-3-7091-1065_25). Based on their ability to recognize pathogens and to regulate the host defense, SP-A and SP-D have been recently categorized as “Secretory Pathogen Recognition Receptors”. While SP-A and SP-D were first identified in the lung; the expression of these proteins has also been observed at other mucosal surfaces, such as lacrimal glands, gastrointestinal mucosa, genitourinary epithelium and periodontal surfaces. SP-A is the most prominent among four proteins in the pulmonary surfactant-system. The expression of SP-A is complexly regulated on the transcriptional and the chromosomal level. SP-A is a major player in the pulmonary cytokine-network and moreover has been described to act in the pulmonary host defense. This chapter gives an overview on the understanding of role of SP-A and SP-D in for human pulmonary disorders and points out the importance for pathology-orientated research to further elucidate the role of these molecules in adult lung diseases. As an outlook, it will become an issue of pulmonary pathology which might provide promising perspectives for applications in research, diagnosis and therapy (Awasthi 2010).

Genetically manipulated mouse models of lung disease: potential and pitfalls

Gene targeting in mice (transgenic and knockout) has provided investigators with an unparalleled armamentarium in recent decades to dissect the cellular and molecular basis of critical pathophysiological states. Fruitful information has been derived from studies using these genetically engineered mice with significant impact on our understanding, not only of specific biological processes spanning cell proliferation to cell death, but also of critical molecular events involved in the pathogenesis of human disease. This review will focus on the use of gene-targeted mice to study various models of lung disease including airways diseases such as asthma and chronic obstructive pulmonary disease, and parenchymal lung diseases including idiopathic pulmonary fibrosis, pulmonary hypertension, pneumonia, and acute lung injury. We will attempt to review the current technological approaches of generating gene-targeted mice and the enormous dataset derived from these studies, providing a template for lung investigators.

Plaque oxysterols induce unbalanced up-regulation of matrix metalloproteinase-9 in macrophagic cells through redox-sensitive signaling pathways: Implications regarding the vulnerability of atherosclerotic lesions

An imbalance in the matrix metalloproteinases/tissue inhibitors of metalloproteinases (MMPs/TIMPs) contributes to atherosclerotic plaque destabilization and rupture. Here we determined whether oxysterols accumulating in advanced atherosclerotic lesions play a role in plaque destabilization. In human promonocytic U937 cells, we investigated the effects of an oxysterol mixture of composition similar to that in advanced human carotid plaques on the expression and synthesis of MMP-9 and its endogenous inhibitors TIMP-1 and TIMP-2. A marked increment of MMP-9 gene expression, but not of its inhibitors, was observed by real-time RT-PCR; MMP-9 gelatinolytic activity was also found increased by gel zymography. Consistently, a net increment of MMP-9 protein level was also observed by immunoblotting. Using antioxidants or specific inhibitors or siRNAs, we demonstrated that the oxysterol mixture induces MMP-9 expression through: (i) overproduction of reactive oxygen species, probably by NADPH-oxidase and mitochondria; (ii) up-regulation of mitogen-activated protein kinase signaling pathways via protein kinase C; and (iii) up-regulation of activator protein-1- and nuclear factor-κB-DNA binding. These results suggest, for the first time, that oxysterols accumulating in advanced atherosclerotic lesions significantly contribute to plaque vulnerability by promoting MMP-9/TIMP-1/2 imbalance in phagocytic cells.

Surfactant protein D deficiency increases lung injury during endotoxemia

Acute lung injury (ALI) and its severe form, acute respiratory distress syndrome (ARDS), are major causes of acute respiratory failure with high rates of morbidity and mortality. Although surfactant protein (SP)-D plays a critical role in pulmonary innate immunity and several clinical studies suggest that this protein may be implicated in the pathophysiology of ARDS, little is known regarding the function of SP-D in ARDS. In the present study, we induced indirect lung injury by intraperitoneal injection of LPS and direct lung injury by intratracheal injection of LPS in wild-type and Sftpd(-/-) mice to elucidate the role of SP-D during ALI/ARDS. Results indicate that pulmonary levels of IL-6 and TNF-α were higher in Sftpd(-/-) mice when compared with wild-type mice. However, the magnitude of this difference was 10-fold greater after indirect lung injury compared with direct lung injury. After indirect lung injury, there was a 2-fold increase in the number of pulmonary monocyte/macrophages in the Sftpd(-/-) mice when compared with wild-type mice, whereas pulmonary neutrophils were not increased. After indirect injury, the concentration of granulocyte-macrophage colony stimulating factor (GM-CSF) was approximately 5-fold greater in Sftpd(-/-) mice than wild-type mice. In contrast, after direct injury, the concentration of GM-CSF was 20-fold less in Sftpd(-/-) mice than wild-type mice. Despite increased inflammatory cells and markers of inflammation, survival in Sftpd(-/-) mice after indirect lung injury was paradoxically increased. In conclusion, these results suggest that SP-D inhibits pulmonary inflammation and migration of peripheral monocyte/macrophages into the lung through GM-CSF-dependent pathways during indirect lung injury.

Polymorphisms in surfactant protein-D are associated with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by alveolar destruction and abnormal inflammatory responses to noxious stimuli. Surfactant protein-D (SFTPD) is immunomodulatory and essential to host defense. We hypothesized that polymorphisms in SFTPD could influence the susceptibility to COPD. We genotyped six single-nucleotide polymorphisms (SNPs) in surfactant protein D in 389 patients with COPD in the National Emphysema Treatment Trial (NETT) and 472 smoking control subjects from the Normative Aging Study (NAS). Case-control association analysis was performed using Cochran-Armitage trend tests and multivariate logistic regression. The replication of significant associations was attempted in the Boston Early-Onset COPD Study, the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) Study, and the Bergen Cohort. We also correlated SFTPD genotypes with serum concentrations of surfactant protein-D (SP-D) in the ECLIPSE Study. In the NETT-NAS case-control analysis, four SFTPD SNPs were associated with susceptibility to COPD: rs2245121 (P = 0.01), rs911887 (P = 0.006), rs6413520 (P = 0.004), and rs721917 (P = 0.006). In the family-based analysis of the Boston Early-Onset COPD Study, rs911887 was associated with prebronchodilator and postbronchodilator FEV(1) (P = 0.003 and P = 0.02, respectively). An intronic SNP in SFTPD, rs7078012, was associated with COPD in the ECLIPSE Study and the Bergen Cohort. Multiple SFTPD SNPs were associated with serum SP-D concentrations in the ECLIPSE Study. We demonstrated an association of polymorphisms in SFTPD with COPD in multiple populations. We demonstrated a correlation between SFTPD SNPs and SP-D protein concentrations. The SNPs associated with COPD and SP-D concentrations differed, suggesting distinct genetic influences on susceptibility to COPD and SP-D concentrations.

Surfactant protein D-mediated decrease of allergen-induced inflammation is dependent upon CTLA4

Pulmonary surfactant protein D (SP-D), a member of the collectin family, is an innate immune molecule critical for defense that can also modulate adaptive immune responses. We previously showed that SP-D-deficient mice exhibit enhanced allergic responses and that SP-D induction requires lymphocytes. Thus, we postulated that SP-D may decrease adaptive allergic responses through interaction with T cells. In this study, we used two forms of SP-D, a dodecamer and a shorter fragment containing the trimeric neck and carbohydrate recognition domains (SP-D NCRD). Both forms decreased immune responses in vitro and in a murine model of pulmonary inflammation. SP-D NCRD increased transcription of CTLA4, a negative regulator of T cell activation, in T cells. SP-D NCRD no longer decreased lymphoproliferation and IL-2 cytokine production when CTLA4 signals were abrogated. Administration of SP-D NCRD in vivo no longer decreased allergen induced responses when CTLA4 was inhibited. Our results indicate that SP-D decreases allergen responses, an effect that may be mediated by increase of CTLA4 in T cells.

Azithromycin suppresses interleukin-12p40 expression in lipopolysaccharide and interferon-gamma stimulated macrophages

Azithromycin (AZM), a 15-member macrolide antibiotic, possesses anti-inflammatory activity. Macrophages are important in innate and acquired immunity, and produce pro-inflammatory cytokines such as interleukin (IL)-12, which are composed of subunit p40 and p35. The key function of IL-12 is the induction and maintenance of T-helper-1 responses, which is associated with the pathogenesis of chronic inflammatory diseases. We investigated the effect of azithromycin on IL-12p40 production in macrophages after lipopolysaccharide (LPS)/interferon (IFN)-γ stimulation. RAW264.7 macrophage cell line was pre-treated with vehicle or AZM, followed by the stimulation with LPS/IFN-γ. We measured IL-12 production by RT-PCR and ELISA. IL-12 transcriptional regulation was assessed by electrophoretic mobility shift assay and reporter assay. Phosphorylation of activator protein (AP)-1 and interferon consensus sequence binding protein (ICSBP) was assessed by immunoprecipitation using phosphotyrosine antibody, and immunoblotting using specific antibodies against JunB and ICSBP. AZM reduced the induction of IL-12p40 by LPS/IFN-γ in a dose dependent manner. AZM inhibited the binding of AP-1, nuclear factor of activated T cells (NFAT), and ICSBP, to the DNA binding site in the IL-12p40 promoter. AZM also reduced LPS/IFN-γ-induced IL-12p40 promoter activity. Phosphorylation of JunB and ICSBP was inhibited by azithromycin-treatment in stimulated cells. In conclusion, AZM reduced IL-12p40 transcriptional activity by inhibiting the binding of AP-1, NFAT, and ICSBP to the promoter site. This may represent an important mechanism for regulating the anti-inflammatory effects of AZM in macrophages.

SP-D-dependent regulation of NO metabolism in lipopolysaccharide-stimulated peritoneal macrophages

This work was designed to study the role of surfactant protein D in the regulation of NO synthesis by "non-alveolar" microphages. We evaluated whether the effects of surfactant protein D depend on the phenotype of macrophages. In the absence of surfactant protein D, the LPS-induced iNOS response was shown to decrease in macrophages of native and proinflammatory phenotypes by 30%, and in macrophages of the antiinflammatory phenotype (by 63%). Under the influence of lipopolysaccharide in high doses (500 ng/ml), NO(2)*- production by mouse macrophages without surfactant protein D was reduced in native cells (by 25%), but increased in proinflammatory (by 40%) and antiinflammatory phenotypes (by 12% compared to mouse macrophages with surfactant protein D). Our results suggest that surfactant protein D is involved in the immune response in the whole organism, but not only in the lungs. The effect of surfactant protein D depends on the phenotype of macrophages.

Simultaneous absence of surfactant proteins A and D increases lung inflammation and injury after allogeneic HSCT in mice

The relative contributions of the hydrophilic surfactant proteins (SP)-A and -D to early inflammatory responses associated with lung dysfunction after experimental allogeneic hematopoietic stem cell transplantation (HSCT) were investigated. We hypothesized that the absence of SP-A and SP-D would exaggerate allogeneic T cell-dependent inflammation and exacerbate lung injury. Wild-type, SP-D-deficient (SP-D(-/-)), and SP-A and -D double knockout (SP-A/D(-/-)) C57BL/6 mice were lethally conditioned with cyclophosphamide and total body irradiation and given allogeneic bone marrow plus donor spleen T cells, simulating clinical HSCT regimens. On day 7, after HSCT, permeability edema progressively increased in SP-D(-/-) and SP-A/D(-/-) mice. Allogeneic T cell-dependent inflammatory responses were also increased in SP-D(-/-) and SP-A/D(-/-) mice, but the altered mediators of inflammation were not identical. Compared with wild-type, bronchoalveolar lavage fluid (BALF) levels of nitrite plus nitrate, GM-CSF, and MCP-1, but not TNF-alpha and IFN-gamma, were higher in SP-D-deficient mice before and after HSCT. In SP-A/D(-/-) mice, day 7 post-HSCT BALF levels of TNF-alpha and IFN-gamma, in addition to nitrite plus nitrate and MCP-1, were higher compared with mice lacking SP-D alone. After HSCT, both SP-A and SP-D exhibited anti-inflammatory lung-protective functions that were not completely redundant in vivo.

Effects of melatonin in an experimental model of ventilator-induced lung injury

Melatonin is a free radical scavenger and a broad-spectrum antioxidant and has well-documented immunomodulatory effects. We studied the effects of this hormone on lung damage, oxidative stress, and inflammation in a model of ventilator-induced lung injury (VILI), using 8- to 12-wk-old Swiss mice ( n = 48). Animals were randomized into three experimental groups: control (not ventilated); low-pressure ventilation [peak inspiratory pressure 15 cmH2O, positive end-expiratory pressure (PEEP) 2 cmH2O], and high-pressure ventilation (peak inspiratory pressure 25 cmH2O, PEEP 0 cmH2O). Each group was divided into two subgroups: eight animals were treated with melatonin (10 mg/kg ip, 30 min before the onset of ventilation) and the remaining eight with vehicle. After 2 h of ventilation, lung injury was evaluated by gas exchange, wet-to-dry weight ratio, and histological analysis. Levels of malondialdehyde, glutathione peroxidase, interleukins IL-1β, IL-6, TNF-α, and IL-10, and matrix metalloproteinases 2 and 9 in lung tissue were measured as indicators of oxidation status, pro-/anti-inflammatory cytokines, and matrix turnover, respectively. Ventilation with high pressures induced severe lung damage and release of TNF-α, IL-6, and matrix metalloproteinase-9. Treatment with melatonin improved oxygenation and decreased histological lung injury but significantly increased oxidative stress quantified by malondialdehyde levels. There were no differences in TNF-α, IL-1β, IL-6, or matrix metalloproteinases caused by melatonin treatment, but IL-10 levels were significantly higher in treated animals. These results suggest that melatonin decreases VILI by increasing the anti-inflammatory response despite an unexpected increase in oxidative stress.

Surfactant protein D is expressed and modulates inflammatory responses in human coronary artery smooth muscle cells

Surfactant protein D (SP-D) is a constituent of the innate immune system that plays a role in the host defense against lung pathogens and in modulating inflammatory responses. While SP-D has been detected in extrapulmonary tissues, little is known about its expression and function in the vasculature. Immunostaining of human coronary artery tissue sections demonstrated immunoreactive SP-D protein in smooth muscle cells (SMCs) and endothelial cells. SP-D was also detected in isolated human coronary artery SMCs (HCASMCs) by PCR and immunoblot analysis. Treatment of HCASMCs with endotoxin (LPS) stimulated the release of IL-8, a proinflammatory cytokine. This release was inhibited >70% by recombinant SP-D. Overexpression of SP-D by adenoviral-mediated gene transfer in HCASMCs inhibited both LPS- and TNF-alpha-induced IL-8 release. Overexpression of SP-D also enhanced uptake of Chlamydia pneumoniae elementary bodies into HCASMCs while attenuating IL-8 production induced by bacterial exposure. Both LPS and TNF-alpha increased SP-D mRNA levels by five- to eightfold in HCASMCs, suggesting that inflammatory mediators upregulate the expression of SP-D. In conclusion, SP-D is expressed in human coronary arteries and functions as an anti-inflammatory protein in HCASMCs. SP-D may also participate in the host defense against pathogens that invade the vascular wall.

Selective inhibition of inducible NO synthase activity in vivo reverses inflammatory abnormalities in surfactant protein D-deficient mice

Surfactant protein D (SP-D)-deficient (SP-D-/-) mice exhibit early development of emphysema. Previously we have shown that SP-D deficiency results in increased production and activity of inducible NO synthase (iNOS). In this study, we examined whether treatment with the iNOS inhibitor 1400W could inhibit the inflammatory phenotype. Mice were treated with 1400W systemically for 7 wk from 3 wk of age. Treatment reduced total lung NO synthase activity to 14.7+/-6.1% of saline-treated 10-wk-old SP-D-/- littermates. Long-term administration of 1400W reduced lung inflammation and cellular infiltration; and significantly attenuated the increased levels of matrix metalloproteinases 2 and 9, chemokines (KC, TARC), and cytokines (IFN-gamma) seen in bronchoalveolar lavage (BAL) of SP-D-/- mice. Abrogation of these levels was associated with decreasing BAL chemotactic activity for RAW cells. Two weeks of treatment with 1400W reduced total lung NO synthase (NOS) activity to 12.7+/-6.3% of saline-treated SP-D-/- mice. Short-term iNOS inhibition resulted in attenuation of pulmonary inflammation within SP-D-/- mice as shown by decreases in total BAL cell count (63+/-6% of SP-D-/- control), macrophage size (>25 microm) within the BAL (62+/-10% of SP-D-/- control), and a percentage of BAL macrophages producing oxidants (76+/-9% of SP-D-/- control). These studies showed that s.c. delivery of 1400W can be achieved in vivo and can attenuate the inflammatory processes within SP-D deficiency. Our results represent the first report linking defects in the innate immune system in the lung with alterations in NO homeostasis.

Inhibition of NF-kappaB activation reduces the tissue effects of transgenic IL-13

IL-13 is a major Th2 cytokine that is capable of inducing inflammation, excessive mucus production, airway hyperresponsiveness, alveolar remodeling, and fibrosis in the murine lung. Although IL-13 through its binding to IL-4Ralpha/IL-13Ralpha1 uses the canonical STAT6-signaling pathway to mediate these tissue responses, recent studies have demonstrated that other signaling pathways may also be involved. Previous studies from our laboratory demonstrated that IL-13 mediates its tissue effects by inducing a wide variety of downstream genes many of which are known to be regulated by NF-kappaB. As a result, we hypothesized that NF-kappaB activation plays a critical role in the pathogenesis of IL-13-induced tissue alterations. To test this hypothesis, we compared the effects of transgenic IL-13 in mice with normal and diminished levels of NF-kappaB activity. Three pharmacologic approaches were used to inhibit NF-kappaB including 1) PS1145, a small molecule inhibitor of IkappaBalpha kinase (IKK2), 2) antennapedia-linked NF-kappaB essential modulator-binding domain (NBD) peptide (wild-type NBD), and 3) an adenoviral construct expressing a dominant-negative version of IKK2. We also crossed IL-13-transgenic mice with mice with null mutations of p50 to generate mice that overproduced IL-13 in the presence and absence of this NF-kappaB component. These studies demonstrate that all these interventions reduced IL-13-induced tissue inflammation, fibrosis and alveolar remodeling. In addition, we show that both PS1145 and wild-type NBD inhibit lung inflammatory and structural cell apoptosis. PS1145 inhibits caspase activation and up-regulates inhibitor of apoptosis protein cellular-inhibitor of apoptosis protein 1 (c-IAP-1). Therefore, NF-kappaB is an attractive target for immunotherapy of IL-13-mediated diseases.

Diesel exhaust enhanced susceptibility to influenza infection is associated with decreased surfactant protein expression

We have previously shown that exposure of respiratory epithelial cells to diesel exhaust (DE) enhances susceptibility to influenza infection and increases the production of interleukin (IL)-6 and interferon (IFN)-beta. The purpose of this study was to confirm and expand upon these in vitro results by assessing the effects of DE exposure on the progression of influenza infection and on development of associated pulmonary immune and inflammatory responses in vivo. BALB/c mice were exposed to air or to DE containing particulate matter at concentrations of 0.5 or 2 mg/m(3) for 4 h/day for 5 days and subsequently instilled with influenza A/Bangkok/1/79 virus. Exposure to 0.5 mg/m(3) (but not the higher 2-mg/m(3) dose) of DE increased susceptibility to influenza infection as demonstrated by a significant increase in hemagglutinin (HA) mRNA levels, a marker of influenza copies, and greater immunohistochemical staining for influenza virus protein in the lung. The enhanced susceptibility to infection observed in mice exposed to 0.5 mg/m(3) of DE was associated with a significant increase in the expression of IL-6, while antiviral lung IFN levels were unaffected. Analysis of the expression and production of surfactant proteins A and D, which are components of the interferon-independent antiviral defenses, showed that these factors were decreased following exposure to 0.5 mg/m(3) of DE but not to the higher 2-mg/m(3) concentration. Taken together, the results demonstrate that exposure to DE enhances the susceptibility to respiratory viral infections by reducing the expression and production of antimicrobial surfactant proteins.

Truncated recombinant human SP-D attenuates emphysema and type II cell changes in SP-D deficient mice

BACKGROUND

Surfactant protein D (SP-D) deficient mice develop emphysema-like pathology associated with focal accumulations of foamy alveolar macrophages, an excess of surfactant phospholipids in the alveolar space and both hypertrophy and hyperplasia of alveolar type II cells. These findings are associated with a chronic inflammatory state. Treatment of SP-D deficient mice with a truncated recombinant fragment of human SP-D (rfhSP-D) has been shown to decrease the lipidosis and alveolar macrophage accumulation as well as production of proinflammatory chemokines. The aim of this study was to investigate if rfhSP-D treatment reduces the structural abnormalities in parenchymal architecture and type II cells characteristic of SP-D deficiency.

METHODS

SP-D knock-out mice, aged 3 weeks, 6 weeks and 9 weeks were treated with rfhSP-D for 9, 6 and 3 weeks, respectively. All mice were sacrificed at age 12 weeks and compared to both PBS treated SP-D deficient and wild-type groups. Lung structure was quantified by design-based stereology at the light and electron microscopic level. Emphasis was put on quantification of emphysema, type II cell changes and intracellular surfactant. Data were analysed with two sided non-parametric Mann-Whitney U-test.

MAIN RESULTS

After 3 weeks of treatment, alveolar number was higher and mean alveolar size was smaller compared to saline-treated SP-D knock-out controls. There was no significant difference concerning these indices of pulmonary emphysema within rfhSP-D treated groups. Type II cell number and size were smaller as a consequence of treatment. The total volume of lamellar bodies per type II cell and per lung was smaller after 6 weeks of treatment.

CONCLUSION

Treatment of SP-D deficient mice with rfhSP-D leads to a reduction in the degree of emphysema and a correction of type II cell hyperplasia and hypertrophy. This supports the concept that rfhSP-D might become a therapeutic option in diseases that are characterized by decreased SP-D levels in the lung.

Regulation of surfactant secretion in alveolar type II cells

Molecular mechanisms of surfactant delivery to the air/liquid interface in the lung, which is crucial to lower the surface tension, have been studied for more than two decades. Lung surfactant is synthesized in the alveolar type II cells. Its delivery to the cell surface is preceded by surfactant component synthesis, packaging into specialized organelles termed lamellar bodies, delivery to the apical plasma membrane and fusion. Secreted surfactant undergoes reuptake, intracellular processing, and finally resecretion of recycled material. This review focuses on the mechanisms of delivery of surfactant components to and their secretion from lamellar bodies. Lamellar bodies-independent secretion is also considered. Signal transduction pathways involved in regulation of these processes are discussed as well as disorders associated with their malfunction.

Pulmonary collectins in innate immunity of the lung

Pulmonary collectins, hydrophilic surfactant proteins A and D (SP-A and SP-D), have been implicated in the regulation of pulmonary host defence and inflammation. SP-A and SP-D directly interact with a variety of microorganisms including bacteria and viruses, and attenuate the growth of Gram-negative bacteria, Histoplasma capsulatum and Mycoplasma pneumoniae. The collectins are thought to contribute to bacterial clearance. These lectins augment the phagocytosis of the bacteria by macrophages. SP-A serves as an opsonin and stimulates the uptake of bacteria and bacillus Calmette-Guérin through a C1q receptor- and an SP-R210-mediated processes. The collectin also stimulates FcR- and CR1-mediated phagocytosis by activating the macrophages. In addition, SP-A and SP-D directly interact with macrophages and enhance the phagocytosis of Streptococcus pneumoniae and Mycobacterium by increasing cell surface localization of the phagocytic receptors, scavenger receptor A and mannose receptor. The collectins also modulate pulmonary inflammation. SP-A and SP-D bind to cell surface receptors including Toll-like receptors, SIRPalpha and calreticulin/CD91, and attenuate or enhance inflammation in a microbial ligand-specific manner. In this article we review the immunomodulatory functions of SP-A and SP-D and their possible mechanisms in direct actions on microbes, macrophage phagocytosis and modulation of inflammation.

Differential regulation of the superoxide dismutase family in experimental aortic aneurysms and rat aortic explants

OBJECTIVE

Oxidative stress has been implicated in abdominal aortic aneurysm pathogenesis. This study sought to characterize the relevance of superoxide dismutases (SOD), a family of reactive oxygen catalyzing metalloenzymes, including manganese SOD (MnSOD), copper-zinc SOD (CuZnSOD), and extracellular SOD (EcSOD), in a rodent aortic aneurysm model.

METHODS

Male rat infrarenal abdominal aortas were perfused with either saline (control) or porcine pancreatic elastase (6 U/mL). Aortic diameter was measured and aortas harvested on post-operation days 1, 2, and 7 (N=5-6 per treatment group per day). MnSOD, CuZnSOD, EcSOD, catalase, MMP-2, MMP-9, and beta-actin expression in aortic tissue was determined by quantitative real-time PCR. MnSOD protein levels were measured using western immunoblotting and immunohistochemistry. In subsequent experiments, aimed at understanding the mechanism by which SOD is involved in AAA pathogenesis, rat aortic explants (RAEs) were incubated in media for 24 h in the presence of interleukin-1beta (IL-1beta, 2 ng/mL) and TEMPOL (SOD mimetic), catalase, or a combined SOD and catalase mimetic. Media MMP-2 and MMP-9 activity was determined by zymography. Data were analyzed by Student's t-tests and ANOVA.

RESULTS

Elastase-perfused aortic diameters were significantly increased compared to control aortas by post-perfusion day 7 (P=0.016). MnSOD mRNA levels in elastase perfused aortas were 6.0 (P=0.05) and 7.5 times (P<0.01) greater than control aortas at post-perfusion days 1 and 2, respectively. EcSOD, CuZnSOD, catalase, and MMP-2 mRNA expression did not statistically vary between the two groups. MMP-9 expression was 3.5-fold higher in the elastase group on post-perfusion day 2 (P=0.04). Western immunoblotting confirmed MnSOD protein was up-regulated on day 4 in the elastase-perfused group compared to controls (P=0.02). Immunohistrochemistry demonstrated increased MnSOD staining in the elastase group on day 4. In RAE experiments, TEMPOL increased both MMP-9 and MMP-2 activity 2 (P=0.09) and 3-fold (P=0.05), respectively, whereas catalase and the combined SOD/catalase mimetic failed to increase MMP-2 or MMP-9 activity.

CONCLUSION

Experimental abdominal aortic aneurysm formation is associated with early increases in MnSOD expression and an increase in MMP-9 activity. Strategies aimed at inhibiting oxidative stress during AAA formation should focus on MnSOD.

Enhanced Expression of MafB Inhibits Macrophage Apoptosis Induced by Cigarette Smoke Exposure

In the lungs of smokers, oxidative stress rises due to increase of free radicals and oxidants, including lipid peroxide (LPO). The functions of alveolar macrophages (AMs) are altered in such an environment, and their survival is prolonged against toxicities of cigarette smoke (CS) by an unknown mechanism. Whereas functions of AMs are potentially regulated by various transcriptional factors, their expressions and roles in smoking individuals have not been elucidated. Therefore, we investigated their expressions using murine model of CS exposure. Eight-week-old male B6C3F1 mice were whole-bodily exposed to CS (2 cigarettes/mouse/day, 5 d/wk) for 6 mo. Development of pulmonary emphysema in 6-mo CS-exposed mice was confirmed by a morphometric analysis. Among the transcriptional factors investigated, only MafB was upregulated in AMs from CS-exposed mice. DNA binding capacity of MafB for Maf recognition element was also increased in AMs from those mice. LPO was increased significantly in the lungs of CS-exposed mice. Because the end product of LPO, 4-hydroxy-2-nonenal, enhanced MafB expression and its transcriptional activity in a cultured macrophage cell line, LPO-related oxidative stress was suggested to be involved in the mechanism of MafB expression in CS-exposed lung. Furthermore, we established a macrophage cell line that can overexpress MafB and thereby clarify the role of MafB. Forced expression of MafB heightened cell viability and attenuated the occurrence of apoptosis in cells treated with CS-extract. These results suggest that enhanced MafB expression by oxidative stress inhibits AM cell death and prolongs their survival in the CS-exposed lung.

Enhanced inflammatory responses of chronic granulomatous disease leukocytes involve ROS-independent activation of NF-κB

Reactive oxygen species (ROS) generated by the cellular NADPH-oxidase are crucial for phagocytic killing of ingested microbes and have been implicated as signaling molecules in various processes. For example, ROS are thought to be involved in activation of the transcription factor NF-kappaB, central for mediating production of proinflammatory cytokines in response to inflammatory stimuli. Several studies have demonstrated that inhibitors of the NADPH-oxidase interfere with NF-kappaB activation and production of proinflammatory cytokines. Curiously, patients with chronic granulomatous disease (CGD), an immunodeficiency characterized by an inability to produce ROS, are not only predisposed to severe infections, but also frequently develop various inflammatory complications indicative of exaggerated inflammatory responses. Here, we show that human CGD leukocytes display a hyperinflammatory phenotype with increased production of proinflammatory cytokines in response to stimulation with Toll-like receptor agonists. The hyperinflammatory phenotype was also evident in mononuclear cells from CGD mice (gp91(phox) -/-), but not in control cells in the presence of NADPH-oxidase inhibitor diphenyleneiodonium, probably reflecting NADPH-oxidase-independent effects of the inhibitor. Furthermore, we show that the major steps involved in NF-kappaB activation were intact in human CGD cells. These data indicate that ROS were nonessential for activation of NF-kappaB and their production may even attenuate inflammation.

Increased surfactant protein-D and foamy macrophages in smoking-induced mouse emphysema

BACKGROUND AND OBJECTIVE

The molecular mechanisms underlying COPD remain undetermined. The lungs of surfactant protein-D (SP-D) deficient mice show emphysema and an excessive number of foamy macrophages. This study aims to elucidate roles of SP-D and foamy macrophages in smoking-induced mouse emphysema.

METHODS

Twenty B6C3F1 mice were exposed to cigarette smoke (2 cigarettes/day/mouse for 6 months). The mice were killed, and formalin-fixed, paraffin-embedded lung sections were carried out on seven mice, BAL was carried out on six mice, and seven mice were used to make lung homogenates. In in vitro studies, A549 cells were transduced with the SP-D expression plasmid and treated with cigarette smoke extract to evaluate cell viability.

RESULTS

Emphysema was induced in the mice by chronic cigarette smoke exposure. Increased expression of matrix metalloproteinase-9 and -12 was observed, and foamy alveolar macrophages accumulated in the smoke-exposed lungs. Immunostaining of BAL cells revealed the major source of matrix metalloproteinase-12 to be foamy alveolar macrophages. Furthermore, SP-D was elevated in emphysema lungs. Expression of transcription factors, Fra-1, junB and C/EBPbeta (which induce SP-D) were significantly elevated in emphysema lungs. The in vitro expression of SP-D gene in A549 cells prolonged cell survival following exposure to cigarette smoke condensate.

CONCLUSIONS

The accumulation of foamy alveolar macrophages may play a key role in the development of smoking-induced emphysema. Increased SP-D may play a protective role in the development of smoking-induced emphysema, in part by preventing alveolar cell death.

Surfactant protein A and surfactant protein D variation in pulmonary disease

Surfactant proteins A (SP-A) and D (SP-D) have been implicated in pulmonary innate immunity. The proteins are host defense lectins, belonging to the collectin family which also includes mannan-binding lectin (MBL). SP-A and SP-D are pattern-recognition molecules with the lectin domains binding preferentially to sugars on a broad spectrum of pathogen surfaces and thereby facilitating immune functions including viral neutralization, clearance of bacteria, fungi and apoptotic and necrotic cells, modulation of allergic reactions, and resolution of inflammation. SP-A and SP-D can interact with receptor molecules present on immune cells leading to enhanced microbial clearance and modulation of inflammation. SP-A and SP-D also modulate the functions of cells of the adaptive immune system including dendritic cells and T cells. Studies on SP-A and SP-D polymorphisms and protein levels in bronchoalveolar lavage and blood have indicated associations with a multitude of pulmonary inflammatory diseases. In addition, accumulating evidence in mouse models of infection and inflammation indicates that recombinant forms of the surfactant proteins are biologically active in vivo and may have therapeutic potential in controlling pulmonary inflammatory disease. The presence of the surfactant collectins, especially SP-D, in non-pulmonary tissues, such as the gastrointestinal tract and genital organs, suggest additional actions located to other mucosal surfaces. The aim of this review is to summarize studies on genetic polymorphisms, structural variants, and serum levels of human SP-A and SP-D and their associations with human pulmonary disease.

The NOX family of ROS-generating NADPH oxidases: physiology and pathophysiology

For a long time, superoxide generation by an NADPH oxidase was considered as an oddity only found in professional phagocytes. Over the last years, six homologs of the cytochrome subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the phagocyte NADPH oxidase itself (NOX2/gp91(phox)), the homologs are now referred to as the NOX family of NADPH oxidases. These enzymes share the capacity to transport electrons across the plasma membrane and to generate superoxide and other downstream reactive oxygen species (ROS). Activation mechanisms and tissue distribution of the different members of the family are markedly different. The physiological functions of NOX family enzymes include host defense, posttranlational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. NOX enzymes also contribute to a wide range of pathological processes. NOX deficiency may lead to immunosuppresion, lack of otoconogenesis, or hypothyroidism. Increased NOX activity also contributes to a large number or pathologies, in particular cardiovascular diseases and neurodegeneration. This review summarizes the current state of knowledge of the functions of NOX enzymes in physiology and pathology.

Matrix metalloproteinases in lung: multiple, multifarious, and multifaceted

The matrix metalloproteinases (MMPs), a family of 25 secreted and cell surface-bound neutral proteinases, process a large array of extracellular and cell surface proteins under normal and pathological conditions. MMPs play critical roles in lung organogenesis, but their expression, for the most part, is downregulated after generation of the alveoli. Our knowledge about the resurgence of the MMPs that occurs in most inflammatory diseases of the lung is rapidly expanding. Although not all members of the MMP family are found within the lung tissue, many are upregulated during the acute and chronic phases of these diseases. Furthermore, potential MMP targets in the lung include all structural proteins in the extracellular matrix (ECM), cell adhesion molecules, growth factors, cytokines, and chemokines. However, what is less known is the role of MMP proteolysis in modulating the function of these substrates in vivo. Because of their multiplicity and substantial substrate overlap, MMPs are thought to have redundant functions. However, as we explore in this review, such redundancy most likely evolved as a necessary compensatory mechanism given the critical regulatory importance of MMPs. While inhibition of MMPs has been proposed as a therapeutic option in a variety of inflammatory lung conditions, a complete understanding of the biology of these complex enzymes is needed before we can reasonably consider them as therapeutic targets.

Phagocytic NADPH oxidase-dependent superoxide production stimulates matrix metalloproteinase-9: implications for human atherosclerosis

OBJECTIVE

Data suggest that matrix metalloproteinase-9 (MMP-9) has a role in atherosclerosis. The phagocytic NADPH oxidase has been also associated with atherosclerosis. This study aimed to investigate the association between phagocytic NADPH oxidase and MMP-9 in human atherosclerosis.

METHODS AND RESULTS

In vitro experiments performed in human monocytes showed that NADPH oxidase activation enhanced MMP-9 secretion and activity, determined by enzyme-linked immunosorbent assay and zymography, respectively. Immunohistochemical study showed that phagocytic NADPH oxidase localized with MMP-9 in endarterectomies from patients with carotid stenosis. In addition, a positive relationship (P<0.001) was found between phagocytic NADPH oxidase-dependent superoxide production determined with lucigenin and plasma MMP-9 levels in 188 asymptomatic subjects free of overt clinical atherosclerosis. In multivariate analysis, this association remained significant after adjustment for cardiovascular risk factors. Interestingly, subjects in the upper quartile of superoxide production exhibited the highest values of MMP-9, oxidized low-density lipoprotein, nitrotyrosine, carotid intima media thickness, and an increased presence of carotid plaques.

CONCLUSIONS

Enhanced NADPH oxidase-dependent *O2(-) production stimulates MMP-9 in monocytes and this relationship may be relevant in the atherosclerotic process. Moreover, MMP-9 emerges as an important mediator of the phagocytic NADPH oxidase-dependent oxidative stress in atherosclerosis.

SP-D-deficient mice are resistant to hyperoxia

Surfactant protein D (SP-D), a member of the collectin superfamily, modulates pulmonary inflammatory responses and innate immunity. Disruption of the SP-D gene in mice induces peribronchiolar inflammation, accumulation of large, foamy macrophages, increased bronchoalveolar lavage (BAL) phospholipid, and pulmonary emphysema. We hypothesized that absence of SP-D aggravates hyperoxia-induced injury. To test this, SP-D-deficient (SP-D-/-) and wild-type (SP-D+/+) mice were exposed to 80% or 21% oxygen. Paradoxically, during 14 days of hyperoxia, SP-D-/- mice had 100% survival vs. 30% in SP-D+/+. The survival advantage in SP-D-/- mice was accompanied by lower histopathological injury scores at days 5 and 14, although total BAL cells (8.2 +/- 1.4 x 10(5) in SP-D-/- vs. 4.04 +/- 0.25 x 10(5) in SP-D+/+ mice) and neutrophils (1.2 +/- 0.4 x 10(5) vs. 0.03 +/- 0.02 x 10(5) in SP-D-/- and SP-D+/+, respectively) were increased. In addition, BAL protein and lung-to-body weight ratios were similarly elevated in both groups after 3, 5, and 14 days of continuous exposure. Biochemically, in contrast to SP-D+/+, SP-D-/- mice had higher levels of surfactant phospholipid and SP-B at baseline and 5 days after hyperoxia accompanied by a preservation of surfactant biophysical activity. From a multiplex assay of nine cytokines, we found elevated levels of IL-13 in BAL fluid of normoxic SP-D-/- mice compared with SP-D+/+. We conclude that the resistance of SP-D-deficient mice to hyperoxia reflects homeostatic changes in the SP-D-/- phenotype involving both phospholipid and SP-B-mediated induced resistance of surfactant to inactivation as well as changes in the immunomodulatory BAL cytokine profile.

Hydrogen peroxide-mediated downregulation of matrix metalloprotease-2 in indomethacin-induced acute gastric ulceration is blocked by melatonin and other antioxidants

Gastric mucosal damage is directly associated with extracellular matrix degradation in which matrix metalloproteinases (MMPs) play a crucial role. Remodeling of connective tissues and loss of tissue integrity due to the action of MMPs are reported in several inflammatory diseases, including gastric ulcer. Indomethacin-induced gastric ulceration involves the generation of reactive oxygen species (ROS) and a reduction in MMP-2 transcription and translation. Our aim was to identify the mechanism for suppression of MMP-2 activity by ROS during acute ulceration and further to examine the possible actions of antioxidants, especially melatonin, during healing. Melatonin (N-acetyl-5-methoxytryptamine) blocked hydroxyl radical and nitrite anion generation, protein oxidation, mucosal cell disruption, and MMP-2 downregulation. In addition, suppression of MMP-2 activity by H2O2 in a dose- and time-dependent manner in vitro is blocked by melatonin, omeprazole, and curcumin. We observed that melatonin and other antioxidants (e.g., curcumin and omeprazole) offered gastroprotection in vivo by upregulation of suppressed MMP-2 expression and activity at the level of secretion and synthesis. Moreover, antioxidants reversed the suppression of MMP-2 expression by upregulation of MT1-MMP and downregulation of TIMP-2. Hence, we hypothesize that antioxidants exerted protection against H2O2-mediated inactivation and downregulation of MMP-2 expression during onset of indomethacin-induced ulceration.

Surfactant protein D augments bacterial association but attenuates major histocompatibility complex class II presentation of bacterial antigens

Surfactant protein D (SP-D) is a secreted pattern recognition molecule associated with lung surfactant and mediates the clearance of pathogens in multiple ways. SP-D is an established part of the innate immune system, but it also modulates the adaptive immune response by interacting with both antigen-presenting cells and T cells. In a previous study, antigen presentation by bone marrow-derived dendritic cells was enhanced by SP-D. As dendritic cell function varies depending on the tissue of origin, we extended these studies to antigen-presenting cells isolated from mouse lung. Flow cytometric studies showed that SP-D binds calcium dependently and specifically to lung CD11c-positive cells. Opsonization of fluorescently labeled Escherichia coli by SP-D enhanced uptake by lung dendritic cells. SP-D facilitated the association of E. coli and antigen-presenting cells by increasing the frequency of CD11+ cells associated with E. coli by up to 10-fold. In contrast to the effect on bone marrow-derived dendritic cells, SP-D decreased the antigen presentation of ovalbumin, expressed in E. coli, to ovalbumin-specific major histocompatibility complex class II-specific T-cell hybridomas by 30-50%. The reduction of antigen presentation did not depend on whether the dendritic cells were isolated from the lungs of nonstimulated mice or mice that had been exposed to LPS aerosols. Our results show that SP-D increases the opsonization of pathogens, but decreases the antigen presentation by lung dendritic cells, and thereby, potentially dampens the activation of T cells and an adaptive immune response against bacterial antigens--during both steady-state conditions and inflammation.

Surfactant catabolism

Alveolar pulmonary surfactant is a complex of macromolecular aggregates composed of phospholipids and surfactant proteins (SP) that is essential for maintenance of normal lung function. The importance of surfactant homeostasis is recognized in the patients and the animal models with pulmonary disease, although the mechanisms of surfactant homeostasis are not fully understood. In this review the author will discuss: (i) the mechanisms of the surfactant catabolism by macrophage and type II cells; and (ii) the important role of SP-D on ultrastructure of surfactant that affects uptake by type II cells.

Murine models of COPD

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation, that is not fully reversible, and that is associated with an abnormal inflammatory response of the airways and lungs to noxious particles and gases. The airflow limitation is caused by increased resistance of the small conducting airways and by decreased elastic recoil forces of the lung due to emphysematous destruction of the lung parenchyma. In vivo animal models can help to unravel the molecular and cellular mechanisms underlying the pathogenesis of COPD. Mice represent the most favored animal species with regard to the study of (both innate and adaptive) immune mechanisms, since they offer the opportunity to manipulate gene expression. Several experimental approaches are applied in order to mimic the different traits of COPD in these murine models. Firstly, the tracheal instillation of tissue-degrading enzymes induces emphysema-like lesions in the lung parenchyma, adding further proof to the protease-antiprotease imbalance hypothesis. Secondly, the inhalation of noxious stimuli, including tobacco smoke, sulfur dioxide, nitrogen dioxide, or oxidants such as ozone, may also lead to COPD-like lesions in mice, depending on concentration, duration of exposure and strainspecific genetic susceptibility. Thirdly, in transgenic mice, a specific gene is either overexpressed (non-specific or organ-specific) or selectively depleted (constitutively or conditionally). The study of these transgenic mice, either per se or in combination with the above mentioned experimental approaches (e.g. the inhalation of tobacco smoke), can offer valuable information on both the physiological function of the gene of interest as well as the pathophysiological mechanisms of diseases with complex traits such as COPD.

Surfactant protein D is proatherogenic in mice

Surfactant protein D (SP-D) is an important innate immune defense molecule that mediates clearance of pathogens and modulates the inflammatory response. Moreover, SP-D is involved in lipid homeostasis, and pulmonary accumulation of phospholipids has previously been observed in SP-D-deficient ( Spd−/−) mice. Atherogenesis involves both inflammation and lipid deposition, and we investigated the role of SP-D in the development of atherosclerosis. SP-D synthesis was localized to vascular endothelial cells. Atherosclerotic lesion areas were 5.6-fold smaller in the aortic roots in Spd−/− mice compared with wild-type C57BL/6N mice on an atherogenic diet. HDL cholesterol (HDL-C) was significantly elevated in Spd−/− mice. Treatment of Spd−/− mice with a recombinant fragment of human SP-D resulted in decreases of HDL-C (21%) as well as total cholesterol (26%), and LDL cholesterol (28%). Plasma TNF-α was reduced in Spd−/− mice (45% difference). SP-D was proatherogenic in the mouse model used. The effect is likely to be due to the observed disturbances of plasma lipid metabolism and alteration of the inflammatory process, which underlie the reduced susceptibility to atherosclerosis in Spd−/− mice.

Gene therapy for chronic obstructive pulmonary disease: twilight or triumph?

Chronic obstructive pulmonary disease (COPD) is a clinical syndrome presenting as progressive airflow limitation that is poorly reversible as a result of bronchitis and emphysema. The prevalence of COPD is alarming and even more so its current and projected impact on morbidity and mortality. To date, there are no effective treatments for emphysema, nor are there efficient clinical management strategies. Existing and prospective therapies, although promising, have yet to demonstrate their efficacy to slow, halt or reverse the disease. Novel approaches using gene therapy and stem cell technologies may offer new opportunities. However, this will remain almost entirely dependent on a more thorough understanding of the pathogenesis of COPD. This review is not aimed at highlighting the vast effort of studying COPD, but rather describing the state of the field in an abstract fashion to expose the focus of research efforts to date, which has primarily been limited to predisposing factors and inflammation. We would like to draw attention to other elements of the disease, such as the alveolar remodelling that characterises emphysema. Although the main cause may prove to be elusive, carefully designed clinical treatment and management may deliver the required therapeutic outcome.

Alveolar macrophages and emphysema in surfactant protein-D-deficient mice

Surfactant protein-D (SP-D) is a member of the collectin family of collagenous proteins with lectin activity. SP-D is expressed in numerous tissues, primarily in type II alveolar cells in the periphery of the lung. SP-D plays an important role in host defense of the lung. To evaluate the importance of SP-D in vivo, transgenic mice lacking SP-D (SP-D-/- mice) have been generated. Lipid accumulation and airspace enlargement were observed in the lungs of SP-D-/- mice within 3 weeks after birth, and progressed with advancing age. Airspace enlargement and abnormalities in elastin fibers supported the concept that SP-D was required to inhibit destruction of the alveoli. Alveolar macrophages from SP-D-/- mice produced more H2O2 and matrix metalloproteinases (MMP)-2, -9, and -12 compared with wild-type mice. In vitro studies demonstrated that oxidants derived in part from NADPH oxidase enhanced NF-kappaB activation and MMP production in alveolar macrophages from SP-D-/- mice. A specific inhibitor of NF-kappaB reduced MMP production by alveolar macrophages from SP-D-/- mice. Taken together, these data demonstrated oxidant-dependent activation of NF-kappaB and enhanced MMP expression by alveolar macrophages from SP-D-/- mice, a process likely to mediate airspace remodeling caused by SP-D deficiency. SP-D plays a critical role in regulating alveolar macrophage activation, oxidant production, and MMP activity that may influence the pathogenesis of various pulmonary disorders.

Surfactant proteins in innate host defense of the lung

Surfactant proteins A and D (SP-A and SP-D) are members of the collectin family of host defense proteins that are expressed in epithelial cells lining the lung. SP-A and SP-D interact with surfactant lipids in complex ways to determine the structure of tubular myelin, and the ratio of surfactant subfractions that, in turn, influences surfactant uptake and metabolism, respectively. SP-A and SP-D play critical roles in host defense of the lung against diverse viral, fungal, and bacterial pathogens. The collectins bind to the surfaces of microbes via carbohydrate-dependent interaction, aggregating, opsonizing, and enhancing clearance of the organisms by alveolar macrophages in the lung. Pulmonary surfactant proteins A and D play dual roles in pulmonary homeostasis, determining the structure of alveolar lipids and mediating the innate host defense system of the lung.

The role of nuclear factor kappa B in human labour

Preterm birth remains the leading cause of perinatal mortality and morbidity, largely as a result of a poor understanding of the precise mechanisms controlling labour onset in humans. Inflammation has long been recognised as a key feature of both preterm and term labour, with an influx of inflammatory cells into the uterus and elevated levels of pro-inflammatory cytokines observed during parturition. Nuclear factor kappa B (NF-κB) is a transcription factor family classically associated with inflammation. Accumulating evidence points to a role for NF-κB in the physiology and pathophysiology of labour. NF-κB activity increases with labour onset and is central to multiple prolabour pathways. Premature or aberrant activation of NF-κB may thus contribute to preterm labour. The current understanding of NF-κB in the context of human labour is discussed here.

Role and regulation of lung collectins in allergic airway sensitization

Inhalation of allergens in atopic patients results in a characteristic inflammatory response while in normal, healthy individuals it elicits no symptoms. The mechanisms by which the pulmonary immune system accomplishes elimination of inhaled particles and suppression of the ensuing inflammatory response are poorly understood. Based on their structural uniqueness, specific localization and functional versatility the hydrophilic surfactant proteins [surfactant protein (SP)-A and SP-D] are important candidate regulators of these processes. Recent studies in our laboratory and others indicated significant changes in levels of these molecules during the asthmatic response in animal models as well as in asthmatic patients. Because of their capability to directly inhibit T-cell activation and T-cell-dependent allergic inflammatory events, SP-A and SP-D may be significant contributors to the local control of T-helper (Th)2-type inflammation in the airways. This review will discuss their relevant structural-functional features and recent evidence supporting the hypothesis that SP-A and SP-D have a role in regulation of allergic airway sensitization.

Alveolar surfactant protein D content modulates bleomycin-induced lung injury

RATIONALE

Surfactant protein D (SP-D) is a collectin family member with demonstrated immunomodulatory properties in vitro. We hypothesized that SP-D modulates inflammation during noninfectious lung injury in vivo.

OBJECTIVES

To investigate the association of alveolar SP-D and injury, we studied the responses of transgenic mice expressing varying levels of SP-D to intratracheal bleomycin (ITB).

METHODS

Eight-week old C57/BL6 SP-D-deficient (-/-) mice and syngeneic wild-type (WT) controls or Swiss Black SP-D-overexpressing (SP-D OE) mice and littermate controls received either ITB or saline and were followed for up to 21 d.

MEASUREMENTS AND RESULTS

Kaplan-Meier analysis demonstrated a dose-dependent decrease in survival in ITB SP-D (-/-) mice receiving 2 U/kg bleomycin, with a 14-d mortality of 100% versus 0% mortality for WT receiving 2 U/kg ITB or SP-D (-/-) mice given saline (p < 0.05). At 8 d, ITB SP-D (-/-) mice had greater respiratory distress (frequency/tidal volume) and weight loss than ITB WT mice. Furthermore, bronchoalveolar lavage cellularity, pulmonary parenchymal inflammation, and tissue 3-nitrotyrosine (NO2 Y) were increased to a greater extent in ITB SP-D (-/-) mice. By 21 d, compared with all groups, ITB SP-D (-/-) survivors had increased Trichrome staining and tissue hydroxyproline levels. As proof of principle, SP-D OE mice were highly resistant to bleomycin-induced morbidity and mortality at doses up to 3 U/kg.

CONCLUSIONS

These data provide new in vivo evidence for an antiinflammatory role for SP-D in response to noninfectious, subacute lung injury via modulation of oxidative-nitrative stress.

Effect of melatonin on secreted and induced matrix metalloproteinase-9 and -2 activity during prevention of indomethacin-induced gastric ulcer

Matrix metalloproteinases (MMPs) maintain the crucial role in physiological turnover of extracellular matrix (ECM) proteins in gastric tissues. However, a little is known about the relationship of MMPs with ECM degradation during gastric ulceration and ECM remodeling during healing. Our objective was to investigate the effect of melatonin (N-acetyl-5 methoxytryptamine) on the regulation of MMP-9 and MMP-2 activity during prevention of gastric ulcer. In the present study, biochemical and zymographic methods were used to analyze the mechanism of melatonin in indomethacin-induced gastric ulcer in a rat model. Our studies reveal that melatonin dose-dependently downregulates the expression and secretion of pro-MMP-9 which is induced (approximately 10-fold) during indomethacin-induced gastric ulceration. Furthermore, melatonin prevents gastric ulceration in a dose-dependent manner through upregulation (approximately two- to threefold) of both pro-MMP-2 and active MMP-2 at the level of induction as well as secretion. It also prevents gastric ulcers by blocking glutathione depletion and lipid peroxidation in cytosolic and microsomal fractions. The novel findings of this study are attributed to the attenuation of the pro-MMP-9 and increase of MMP-2 activity by pretreatment with melatonin. The finding defines one of the MMP-mediated pathways for melatonin's action in gastric ulcer.

Susceptibility of mice genetically deficient in the surfactant protein (SP)-A or SP-D gene to pulmonary hypersensitivity induced by antigens and allergens of Aspergillus fumigatus

Lung surfactant protein A (SP-A) and D (SP-D) are innate immune molecules which are known to interact with allergens and immune cells and modulate cytokine and chemokine profiles during host hypersensitivity response. We have previously shown therapeutic effects of SP-A and SP-D using a murine model of lung hypersensitivity to Aspergillus fumigatus (Afu) allergens. In this study, we have examined the susceptibility of SP-A (AKO) or SP-D gene-deficient (DKO) mice to the Afu allergen challenge, as compared with the wild-type mice. Both AKO and DKO mice exhibited intrinsic hypereosinophilia and several-fold increase in levels of IL-5 and IL-13, and lowering of IFN-gamma to IL-4 ratio in the lungs, suggesting a Th2 bias of immune response. This Th2 bias was reversible by treating AKO or DKO mice with SP-A or SP-D, respectively. The AKO and DKO mice showed distinct immune responses to Afu sensitization. DKO mice were found more susceptible than wild-type mice to pulmonary hypersensitivity induced by Afu allergens. AKO mice were found to be nearly resistant to Afu sensitization. Intranasal treatment with SP-D or rhSP-D (a recombinant fragment of human SP-D containing trimeric C-type lectin domains) was effective in rescuing the Afu-sensitized DKO mice, while SP-A-treated Afu-sensitized AKO mice showed several-fold elevated levels of IL-13 and IL-5, resulting in increased pulmonary eosinophilia and damaged lung tissue. These data reaffirm an important role for SP-A and SP-D in offering resistance to pulmonary allergenic challenge.

Surfactant protein-D regulates soluble CD14 through matrix metalloproteinase-12

Surfactant protein D (SP-D) and CD14 are important innate immune defense molecules that mediate clearance of pathogens and apoptotic cells from the lung. To test whether CD14 expression and function were influenced by SP-D, the surface expression of CD14 was assessed on alveolar macrophages from SP-D-/- mice. CD14 was reduced on alveolar macrophages from SP-D-/- mice and was associated with reduced uptake of LPS and decreased production of TNF-alpha after LPS stimulation. CD14 is proteolytically cleaved from the cell surface to form a soluble peptide. Soluble CD14 (sCD14) was increased in the bronchoalveolar lavage fluid from SP-D-/- mice. Because matrix metalloproteinase (MMP)-9 and -12 activities were increased in the lungs of SP-D-/- mice, the role of these metalloproteases in the production of sCD14 was assessed. sCD14 was decreased in both MMP(9-/-)/SP-D-/- and MMP12(-/-)/SP-D-/- mice demonstrating MMP-9 and MMP-12 contribute to proteolytic shedding of CD14. The increased sCD14 seen in SP-D-/- mice was dependent upon the activation of MMP-12 via an MMP-9-dependent mechanism. Supporting this observation, MMP-12 caused the release of sCD14 from RAW 264.7 cells in vitro. In conclusion, SP-D influences innate host defense, in part, by regulating sCD14 in a process mediated by MMP-9 and MMP-12.

The lung collectins, SP-A and SP-D, modulate pulmonary innate immunity

Pulmonary surfactant, which covers the peripheral airway, is a mixture of lipids and proteins. The hydrophilic surfactant proteins A (SP-A) and D (SP-D) play important roles in host defense mechanisms of the lung. These proteins belong to a collectin subgroup in which lectin domains are associated with collagenous structures. Collectins involve mannose-binding lectin, and are considered to function in innate immune systems. SP-A and SP-D interact with various microorganisms and pathogen-derived components. They act as opsonins by binding and agglutinating pathogens. The lung collectins also possess direct inhibitory effects on bacterial growth. SP-A and SP-D associate with immune cells, and activate various cellular functions. The direct interactions of SP-A and SP-D with macrophages result in modulation of phagocytosis or the production of reactive oxygen species. Moreover, by associating with cell surface pattern-recognition receptors, SP-A and SP-D regulate inflammatory cellular responses such as the release of lipopolysaccharides-induced proinflammatory cytokines. Animal models of SP-A- or SP-D-deficiency reveal significant defect in host defense. Significant susceptibility to bacterial and viral infections, delayed microbial clearance, and overexpression of proinflammatory cytokines are observed in SP-A or SP-D knockout mice. A more complete understanding of the mechanisms is required, but the biological relevance of SP-A and SP-D against various respiratory infections has been increasingly recognized.

The absence of reactive oxygen species production protects mice against bleomycin-induced pulmonary fibrosis

Background

Reactive oxygen species and tissue remodeling regulators, such as metalloproteinases (MMPs) and their inhibitors (TIMPs), are thought to be involved in the development of pulmonary fibrosis. We investigated these factors in the fibrotic response to bleomycin of p47^phox -/- (KO) mice, deficient for ROS production through the NADPH-oxidase pathway.

Methods

Mice are administered by intranasal instillation of 0.1 mg bleomycin. Either 24 h or 14 days after, mice were anesthetized and underwent either bronchoalveolar lavage (BAL) or lung removal.

Results

BAL cells from bleomycin treated WT mice showed enhanced ROS production after PMA stimulation, whereas no change was observed with BAL cells from p47^phox -/- mice. At day 1, the bleomycin-induced acute inflammatory response (increased neutrophil count and MMP-9 activity in the BAL fluid) was strikingly greater in KO than wild-type (WT) mice, while IL-6 levels increased significantly more in the latter. Hydroxyproline assays in the lung tissue 14 days after bleomycin administration revealed the absence of collagen deposition in the lungs of the KO mice, which had significantly lower hydroxyproline levels than the WT mice. The MMP-9/TIMP-1 ratio did not change at day 1 after bleomycin administration in WT mice, but increased significantly in the KO mice. By day 14, the ratio fell significantly from baseline in both strains, but more in the WT than KO strains.

Conclusions

These results suggest that NADPH-oxidase-derived ROS are essential to the development of pulmonary fibrosis. The absence of collagen deposition in KO mice seems to be associated with an elevated MMP-9/TIMP-1 ratio in the lungs. This finding highlights the importance of metalloproteinases and protease/anti-protease imbalances in pulmonary fibrosis.

Surfactant protein D influences surfactant ultrastructure and uptake by alveolar type II cells

Surfactant protein D (SP-D) is a member of the collectin family of the innate host defense proteins. In the lung, SP-D is expressed primarily by type II cells. Gene-targeted SP-D-deficient [SP-D(-/-)] mice have three- to fivefold higher surfactant lipid pool sizes. However, surfactant synthesis and secretion by type II cells and catabolism by alveolar macrophages are normal in SP-D(-/-) mice. Therefore, we hypothesized that SP-D might regulate surfactant homeostasis by influencing surfactant structure, thereby altering its uptake by type II cells. Large (LA) and small aggregate (SA) surfactant were isolated from bronchoalveolar lavage fluid (BALF) from SP-D(-/-), wild-type [SP-D(+/+)], and transgenic mice in which SP-D was expressed under conditional control of doxycycline in alveolar type II cells. Uptake of both LA and SA isolated from SP-D(-/-) mice by normal type II cells was decreased. Abnormally dense lipid forms were observed by electron microscopy of LA from SP-D(-/-) mice. SA from SP-D(-/-) mice consisted of atypical multilamellated small vesicles. Abnormalities in surfactant uptake by type II cells and in surfactant ultrastructure were corrected by conditional expression of SP-D in vivo. Preincubation of BALF from SP-D(-/-) mice with SP-D changed surfactant ultrastructure to be similar to that of SP-D(+/+) mice in vitro. The rapid changes in surfactant structure, increased uptake by type II cells, and decreased pool sizes normally occurring in the postnatal period were not seen in SP-D(-/-) mice. SP-D regulates uptake and catabolism by type II cells and influences the ultrastructure of surfactant in the alveolus.

GM-CSF mediates alveolar epithelial type II cell changes, but not emphysema-like pathology, in SP-D-deficient mice

Surfactant protein D (SP-D) is a member of the collectin subfamily of C-type lectins, pattern recognition proteins participating in the innate immune response. Gene-targeted mice deficient in SP-D develop abnormalities in surfactant homeostasis, hyperplasia of alveolar epithelial type II cells, and emphysema-like pathology. Granulocyte/macrophage colony-stimulating factor (GM-CSF) is required for terminal differentiation and subsequent activation of alveolar macrophages, including the expression of matrix metalloproteinases and reactive oxygen species, factors thought to contribute to lung remodeling. Type II cells also express the GM-CSF receptor. Thus we hypothesized GM-CSF might mediate some or all of the cellular and structural abnormalities in the lungs of SP-D-deficient mice. To test this, SP-D (D−G+) and GM-CSF (D+G−) single knockout mice as well as double knockout mice deficient for both SP-D and GM-CSF (D−G−) were analyzed by design-based stereology. Compared with wild type, D−G+ as well as D+G− mice showed decreased alveolar numbers, increased alveolar sizes, and decreased alveolar epithelial surface areas. These emphysema-like changes were present to a greater extent in D−G− mice. D−G+ mice developed type II cell hyperplasia and hypertrophy with increased intracellular surfactant pools, whereas D+G− mice had smaller type II cells with decreased intracellular surfactant pools. In contrast to the emphysematous changes, the type II cell alterations were mostly corrected in D−G− mice. These results indicate that GM-CSF-dependent macrophage activity is not necessary for emphysema development in SP-D-deficient mice, but that type II cell metabolism and proliferation are, either directly or indirectly, regulated by GM-CSF in this model.

Models of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major global health problem and is predicted to become the third most common cause of death by 2020. Apart from the important preventive steps of smoking cessation, there are no other specific treatments for COPD that are as effective in reversing the condition, and therefore there is a need to understand the pathophysiological mechanisms that could lead to new therapeutic strategies. The development of experimental models will help to dissect these mechanisms at the cellular and molecular level. COPD is a disease characterized by progressive airflow obstruction of the peripheral airways, associated with lung inflammation, emphysema and mucus hypersecretion. Different approaches to mimic COPD have been developed but are limited in comparison to models of allergic asthma. COPD models usually do not mimic the major features of human COPD and are commonly based on the induction of COPD-like lesions in the lungs and airways using noxious inhalants such as tobacco smoke, nitrogen dioxide, or sulfur dioxide. Depending on the duration and intensity of exposure, these noxious stimuli induce signs of chronic inflammation and airway remodelling. Emphysema can be achieved by combining such exposure with instillation of tissue-degrading enzymes. Other approaches are based on genetically-targeted mice which develop COPD-like lesions with emphysema, and such mice provide deep insights into pathophysiological mechanisms. Future approaches should aim to mimic irreversible airflow obstruction, associated with cough and sputum production, with the possibility of inducing exacerbations.