Distinct alleles of mannose-binding lectin (MBL) and surfactant proteins A (SP-A) in patients with chronic cavitary pulmonary aspergillosis and allergic bronchopulmonary aspergillosis

BACKGROUND

Distinct host immune status predisposes to different forms of pulmonary aspergillosis.

METHODS

Patients with chronic cavitary pulmonary aspergillosis (CCPA; n=15) or allergic bronchopulmonary aspergillosis (ABPA; n=7) of Caucasian origin were screened for single nucleotide polymorphisms (SNPs) in the collagen region of surfactant proteins A1 (SP-A1) and A2 (SP-A2) and mannose binding lectin (MBL).

RESULTS

The T allele at T1492C and G allele at G1649C of SP-A2 were observed at slightly higher frequencies in ABPA patients (86% and 93%) than in controls (63% and 83%), and the C alleles at position 1492 and 1649 were found in higher frequencies in CCPA patients (33% and 25%) than in ABPA patients (14% and 7%) (all p>0.05). However, the CC genotype at position 1649 of SP-A2 was significantly associated with CCPA (chi(2)=7.94; p(corr)< or =0.05). Similarly, ABPA patients showed a higher frequency of the TT genotype (71%) at 1492 of SP-A2 than controls (43%) and CCPA patients (41%) (p>0.05). In the case of MBL, the T allele (OR=3.1, range 1.2-8.9; p< or =0.02) and CT genotype (chi(2)=6.54; p(corr)< or =0.05) at position 868 (codon 52) were significantly associated with CCPA, but not with ABPA. Further analysis of genotype combinations at position 1649 of SP-A2 and at 868 of MBL between patient groups showed that both CC/CC and CC/CT SP-A2/MBL were found only in CCPA patients, while GG/CT SP-A2/MBL was significantly higher in CCPA patients in comparison to ABPA patients (p< or =0.05). SNPs analysed in SP-A1 did not differ between cases and controls.

CONCLUSIONS

Distinct alleles, genotypes and genotype combinations of SP-A2 and MBL may contribute to differential susceptibility of the host to CCPA or ABPA.

Respiratory symptoms among infants at risk for asthma: association with surfactant protein A haplotypes

Background

We examined the association between single nucleotide polymorphisms (SNPs) in loci encoding surfactant protein A (SFTPA) and risk of wheeze and persistent cough during the first year of life among a cohort of infants at risk for developing asthma.

Methods

Between September 1996 and December 1998, mothers of newborn infants were invited to participate if they had an older child with clinician-diagnosed asthma. Each mother was given a standardized questionnaire within 4 months of her infant's birth. Infant respiratory symptoms were collected during quarterly telephone interviews at 6, 9 and 12 months of age. Due to the association of SFTPA polymorphisms and race/ethnicity, analyses were restricted to 221 white infants for whom whole blood and respiratory data were available. Ordered logistic regression models were used to examine the association between respiratory symptom frequency and SFTPA haplotypes.

Results

The 6A allele haplotype of SFTPA1, with an estimated frequency of 6% among our study infants, was associated with an increased risk of persistent cough (OR 3.69, 95% CI 1.71, 7.98) and wheeze (OR 4.72, 95% CI 2.20, 10.11). The 6A/1A haplotype of SFTPA, found among approximately 5% of the infants, was associated with an increased risk of persistent cough (OR 3.20, 95% CI 1.39, 7.36) and wheeze (OR 3.25, 95% CI 1.43, 7.37).

Conclusion

Polymorphisms within SFTPA loci may be associated with wheeze and persistent cough in white infants at risk for asthma. These associations require replication and exploration in other ethnic/racial groups.

Pulmonary adenocarcinoma-targeted gene therapy by a cancer- and tissue-specific promoter system

Gene therapy is one of the approaches used to treat lung cancer. The benefit of cancer gene therapy is that different types of tumors can be selectively targeted by tumor-specific expression of therapeutic genes that include an apoptosis gene to destroy the tumor. Previously, we described a promoter (TTS promoter) that we designed that is specifically targeted to lung cancer cells but not to other types of cancer or normal cells including stem cells. In this pursuit, we further characterize the specificity of the TTS promoter in four types of lung cancer cells (squamous cell lung carcinoma, pulmonary adenocarcinoma, small-cell lung carcinoma, large-cell lung carcinoma). The TTS promoter is highly active only in pulmonary adenocarcinoma cells but not in the other three types of lung cancer cells. The specificity seems to be derived from transcription factor thyroid transcription factor 1-associating cofactors that affect human surfactant protein A1 promoter activity in pulmonary adenocarcinoma. We inserted the proapoptotic gene Bcl-2-associated X protein (Bax) into the TTS promoter (TTS/Bax). The TTS/Bax selectively causes BAX expression and cell death in pulmonary adenocarcinoma but not in other cells. Cell death caused by the BAX expression was also observed in pulmonary adenocarcinoma that is resistant to the anticancer drug gefitinib (epidermal growth factor receptor tyrosine kinase inhibitor). BAX expression and cell death can be suppressed by dexamethasone (a glucocorticoid) treatment through negative glucocorticoid elements in the TTS promoter. Here we report a drug-controllable TTS/Bax system targeting pulmonary adenocarcinoma.

[The low molecular weight heparin on rat pulmonary surfactant associated protein A of acute pulmonary embolism]

OBJECTIVE

To explore the effect of low molecular weight heparin (LMWH) on the changes of pulmonary surfactant associated protein A (SPA) of rats in acute pulmonary embolism.

METHODS

Male SD rats were injected with medical gelfoam microspheres via jugular vein to induce PE model. Rats were randomized into three groups: control group (n = 8), embolism for 2 weeks group (n = 8) and LMWH therapy group (n = 8); The LMWH therapy group were injected Nadroparin subcutaneously immediately after operation, 0.1 ml/10 kg, once every 12 h. Saline were injected into the control group instead of gelfoam granule solution without further procedure. All the rats were sacrificed at the time of 2 weeks. Pulmonary artery pressure were detected by right heart catheterization and artery blood gas were analyzed at the time of sacrifice. Lung tissue were sliced and dyed with HE to observe the embolism of pulmonary artery. Methods of RT-PCR and western blot were used to study the changes of SPA mRNA and SPA protein in lung tissue.

RESULTS

In control group, embolism group and LMWH group, the pulmonary pressure were (14.2 +/- 4.1) mm Hg, (29.0 +/- 8.2) mm Hg, (25.50 +/- 2.74) mm Hg respectively (F3.01, P < 0.05); the artery oxygen blood pressure (PaO2) were (94.1 +/- 8.8) mm Hg, (73.4 +/- 14.3) mm Hg, (82.86 +/- 3.73) mm Hg respectively (F 1.31, P < 0.05); SPA mRNA in three groups were 1.43 +/- 0.51, 0.87 +/- 0.35, 1.07 +/- 0.20 respectively (F 2.87, P < 0.05); and SPA protein were 1.00 +/- 0.00, 0.52 +/- 0.32, 0.90 +/- 0.22 respectively (F 2.96, P < 0.05); Under microscope, lung tissue were seen congestion, edema, infiltration of inflammatory cells in embolism group, which were lessened in LMWH group.

CONCLUSIONS

The lung SPA decrease significantly in acute pulmonary embolism, and LMWH can increase the SPA, which may be one of mechanisms of LMWH in treatment of pulmonary embolism.

[Single nucleotide polymorphisms study of surfactant protein A gene between Tibet Sherpas and Guangdong Chinese Hans]

AIM

To investigate the relationship between single nucleotide polymorphisms(SNPs) of surfactant protein A(SP-A) gene of Chinese Han and Sherpas and their adaptation to high altitude hypoxia.

METHODS

The genotypes of 90 Chinese Han in Guangdong and 104 Sherpas in Tibet were analyzed by sequence special primer polymerase chain reaction(SSP-PCR) sequencing the surfactant protein A gene.

RESULTS

The frequencies of genotypes and alleles at SP-A1 1544 locus showed no difference between the Sherpas and the Chinese Han (P>0.05). However, the frequencies of genotypes C/C, C/T and T/T at SP-A1 3241 locus were 75.0%, 22.1% and 2.9%, respectively in Sherpas, difference to Han population, they were 50.0%, 35.6% and 14.4%, respectirely(P<0.05). Whilst in Sherpas allele frequencies of C and T were 86.1% and 13.9% respectively but they were 67.8% and 32.2% respectively in the Chinese Han(P<0.05); The frequencies of C/C, A/C and A/A at SP-A2 3265 locus were 37.5%, 53.8%, and 8.7%, respectively in the Sherpas were also difference to Chinese Han, they were 63.3%, 30.0%, and 6.7%, respectively. Whilst allele frequencies of C and A were 64.4% and 35.6% in Sherpas but 78.3% and 21.7% in Chinese Han, which showed statistically difference between two groups(P<0.05).

CONCLUSION

There were statistically differences of genotypes and alleles at SP-A2 3265 locus in Hans and Sherpas. SNP in SP-A2 at 3265 may be related to the adaptation of Sherpas to high altitude hypoxia.

Surfactant protein A--from genes to human lung diseases

Surfactant associated protein-A (SP-A) is the most abundant pulmonary surfactant protein and belongs to the family of innate host defense proteins termed collectins. Besides pulmonary host defense, SP-A is also involved in the formation of pulmonary surfactant, as it is essential for the structure of tubular myelin. The human SP-A gene locus includes two functional genes, SFTPA1 and SFTPA2 which are expressed independently, and a pseudo gene. The largest amount of SP-A1 proteins assemble to larger molecular complexes, whereas SP-A2 forms mainly dimers and trimers. SP-A polymorphisms play a role in respiratory distress syndrome, allergic bronchopulmonary aspergillosis and idiopathic pulmonary fibrosis. The levels of SP-A are decreased in the lungs of patients with cystic fibrosis, respiratory distress syndrome and further chronic lung diseases. Future areas for clinical research include disease specific SP-A expression pattern and their functional consequences, the differential roles of SP-A1 and SP-A2 in human lung diseases, and therapeutical approaches to correct altered SP-A levels.

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.

Surfactant protein A without the interruption of Gly-X-Y repeats loses a kink of oligomeric structure and exhibits impaired phospholipid liposome aggregation ability

Pulmonary surfactant protein A (SP-A) belongs to the collectin subgroup of the C-type lectin superfamily. SP-A oligomerizes as an octadecamer, which forms a flower bouquet-like structure. A collagen-like domain of human SP-A consists of 23 Gly-X-Y repeats with an interruption near the midpoint of this domain. This interruption causes a kink, but its role remains unknown. To define the importance of the kink region of SP-A, two mutated proteins were constructed to disrupt the interruption of Gly-X-Y repeats: SP-ADEL, which lacks the Pro47-Cys48-Pro49-Pro50 sequence at the interruption, and SP-AINS, in which two glycines were introduced to insert Gly-X-Y repeats (Gly-Pro47-Cys48-Gly-Pro49-Pro50). Electron microscopy using rotary shadowing revealed that both mutants form octadecamers that lack a bend in the collagenous domain. Electrophoretic analysis under nondenaturing conditions and gel filtration chromatography demonstrated that SP-AINS consisted of a large assembly of oligomers whereas SP-ADEL formed mainly octadecamers. Both SP-ADEL and SP-AINS mutants as well as wild-type SP-A bound to liposomes containing dipalmitoylphosphatidylcholine and galactosylceramide at equivalent levels, but the abilities of the mutants to induce phospholipid liposome aggregation were significantly less developed than that of the wild type. The mutants SP-ADEL and SP-AINS augmented liposome uptake by alveolar type II cells and inhibited secretion of phospholipids from type II cells at a level comparable to that of wild-type SP-A. These results indicate that the interruption of Gly-X-Y repeats in the SP-A molecule is critical for the formation of a flower bouquet-like octadecamer and contributes to SP-A's capacity to aggregate phospholipid liposomes.

Surfactant protein A2 (SP-A2) variants expressed in CHO cells stimulate phagocytosis of Pseudomonas aeruginosa more than do SP-A1 variants

Surfactant protein A (SP-A) enhances phagocytosis of Pseudomonas aeruginosa. Two functional genes, SP-A1 and SP-A2, encode human SP-A. As we showed before, baculovirus-mediated insect cell-expressed SP-A2 enhances the association of P. aeruginosa with rat alveolar macrophages (rAMs) more than does SP-A1. However, true phagocytosis (internalization) was not shown, and insect cell derived proteins lack or are defective in certain mammalian posttranslational modifications that may be important for SP-A1 and SP-A2 activity and specificity. Here we used SP-A1 (6A(2), 6A(4)) and SP-A2 (1A(0), 1A(1)) allele variants expressed by CHO (Chinese hamster ovary) mammalian cells to study their effect on association and/or internalization of P. aeruginosa by rAMs and/or human AMs (hAMs) and to study if phagocytosis can be modulated differentially and/or more effectively by CHO cell-expressed SP-A variants than by insect-cell expressed SP-A variants. For cell association and internalization assessments, light microscopy and fluorescence-activated cell sorter analyses were used, respectively. We found the following for the first time. (i) SP-A2 variants enhanced phagocytosis (cell association and/or internalization) of P. aeruginosa more than SP-A1 variants did, and the cell association correlated with internalization. (ii) Differences in the activities of SP-A variants were observed in the following order: 1A(1)>1A(0)>6A(2)>6A(4). (iii) rAMs, although more active than hAMs, are an appropriate model, as SP-A2 variants exhibited activity higher than that seen for SP-A1 variants with either rAMs or hAMs. (iv) CHO cell-expressed SP-A was considerably more active than insect cell-expressed variants. We conclude that SP-A2 variants stimulate phagocytosis of P. aeruginosa more effectively than SP-A1 variants and that posttranslational modifications positively influence the phagocytic activity of SP-A.

Proteasome dysfunction inhibits surfactant protein gene expression in lung epithelial cells: mechanism of inhibition of SP-B gene expression

Surfactant proteins maintain lung function through their actions to reduce alveolar surface tension and control of innate immune responses in the lung. The ubiquitin proteasome pathway is responsible for the degradation of majority of intracellular proteins in eukaryotic cells, and proteasome dysfunction has been linked to the development of neurodegenerative, cardiac, and other diseases. Proteasome function is impaired in interstitial lung diseases associated with surfactant protein C (SP-C) mutation mapping to the BRICHOS domain located in the proSP-C protein. In this study we determined the effects of proteasome inhibition on surfactant protein expression in H441 and MLE-12 lung epithelial cells to understand the relationship between proteasome dysfunction and surfactant protein gene expression. Proteasome inhibitors lactacystin and MG132 reduced the levels of SP-A, SP-B, and SP-C mRNAs in a concentration-dependent manner in H441 and MLE-12 cells. In H441 cells, lactacystin and MG132 inhibition of SP-B mRNA was associated with similar decreases in SP-B protein, and the inhibition was due to inhibition of gene transcription. Proteasome inhibitors decreased thyroid transcription factor-1 (TTF-1)/Nkx2.1 DNA binding activity, and the reduced TTF-1 DNA binding activity was due to reduced expression levels of TTF-1 protein. These data indicated that the ubiquitin proteasome pathway is essential for the maintenance of surfactant protein gene expression and that disruption of this pathway inhibits surfactant protein gene expression via reduced expression of TTF-1 protein.

Surfactant dysfunction in SP-A-/- and iNOS-/- mice with mycoplasma infection

Surfactant dysfunction was studied in C57BL/6 (B6), B6.SP-A(-/-), and B6.iNOS(-/-) mice with pulmonary mycoplasma infection (10(7) colony-forming units). Cell-free bronchoalveolar lavage (BAL) from uninfected B6.SP-A(-/-) versus B6 mice had a reduced content of very large aggregates (VLA) and an increase in intermediate large aggregates (ILA), with no difference in total large aggregates (LA = VLA + ILA). However, LA from uninfected B6.SP-A(-/-) versus B6 mice contained less protein and were more sensitive to inhibition by serum albumin and lysophosphatidylcholine in pulsating bubble studies in vitro. Infection with Mycoplasma pulmonis caused significant lung injury and surfactant abnormalities in B6.SP-A(-/-), B6.iNOS(-/-), and B6 mice at 24, 48, 72 h after infection compared with uninfected mice of the same strain. Analyses of time-pooled data indicated that mycoplasma-infected B6.SP-A(-/-) and B6.iNOS(-/-) mice had significantly lower levels of LA and higher protein/phospholipid ratios in BAL compared with infected B6 mice. Infected B6.iNOS(-/-) versus B6 mice also had increased minimum surface tensions on the pulsating bubble and decreased levels of surfactant protein (SP)-B in BAL. These results indicate that pulmonary mycoplasma infection in vivo causes lung injury and surfactant abnormalities that are dependent in part on iNOS and SP-A. In addition, SP-A deficiency modifies surfactant aggregate content and lowers the inhibition resistance of LA surfactant in vitro compared with congenic normal mice.

Characterization of a human surfactant protein A1 (SP-A1) gene-specific antibody; SP-A1 content variation among individuals of varying age and pulmonary health

The human surfactant protein A (SP-A) locus consists of two functional genes (SP-A1, SP-A2) with gene-specific products exhibiting qualitative and quantitative differences. The aim here was twofold: 1) generate SP-A1 gene-specific antibody, and 2) use this to assess gene-specific SP-A content in the bronchoalveolar lavage fluid (BALF). An SP-A1-specific polyclonal antibody (hSP-A1_Ab(68-88)_Col) was raised in chicken, and its specificity was determined by immunoblot and ELISA using mammalian Chinese hamster ovary (CHO) cell-expressed SP-A1 and SP-A2 variants and by immunofluorescence with stably transfected CHO cell lines expressing SP-A1 or SP-A2 variants. SP-A1 content was evaluated according to age and lung status. A gradual decrease (P < 0.05) in SP-A1/SP-A ratio was observed in healthy subjects (HS) with increased age, although no significant change was observed in total SP-A content among age groups. Total SP-A and SP-A1 content differed significantly between alveolar proteinosis (AP) patients and HS, with no significant difference observed in SP-A1/SP-A ratio between AP and HS. The cystic fibrosis (CF) ratio was significantly higher compared with AP, HS, and noncystic fibrosis (NCF), even though SP-A1 and total SP-A were decreased in CF compared with most of the other groups. The ratio was higher in culture-positive vs. culture-negative samples from CF and NCF (P = 0.031). A trend of an increased ratio was observed in culture-positive CF (0.590 +/- 0.10) compared with culture-positive NCF (0.368 +/- 0.085). In summary, we developed and characterized an SP-A1 gene-specific antibody and used it to identify gene-specific SP-A content in BALFs as a function of age and lung health.

[Effect of inhaled nitric oxide on surfactant protein A and mannose binding ability in the lung of neonatal rats with hyperoxia-induced lung injury]

OBJECTIVE

To investigate the effect of inhaled nitric oxide (NO) on surfactant protein A (SP-A) and mannose binding ability (MBA) in neonatal rats with hyperoxia-induced lung injury.

METHODS

Sixty-four neonatal rats were randomly exposed to room air (Control group), >95% oxygen for 6 days (Hyperoxia group), 10 ppm NO for 24 hrs (NO group), and >95% oxygen for 6 days along with 10 ppm NO for 24 hrs (Hyperoxia + NO group). After 2 and 6 days of exposure, the lung pathologic changes, gene and protein expressions of SP-A and MBA were measured.

RESULTS

The rats from the Hyperoxia group presented with obvious lung injuries. The SP-A expressions of mRNA (0.81 +/- 0.04 vs 1.53 +/- 0.25) and protein (59.45 +/- 18.37 vs 89.77 +/- 16.41) in the Hyperoxia group decreased significantly 2 days after exposure but increased significantly 6 days after exposure (SP-A mRNA 0.81 +/- 0.02 vs 0.63 +/- 0.03; SP-A protein 93.57 +/- 13.71 vs 47.73 +/- 21.69) compared with those of the Control group (P < 0.05). NO treatment alleviated the hyperoxia-induced pathologic injuries 2 days after exposure. The SP-A mRNA expression (0.55 +/- 0.91) in the Hyperoxia + NO group was significantly reduced as compared to both the Control and Hyperoxia groups (P < 0.05), and the SP-A protein expression (55.12 +/- 17.53) in the Hyperoxia + NO group was noticeably lower than that of the Control group (P < 0.01) 2 days after exposure. The SP-A protein expression in the Hyperoxia + NO group (67.33 +/- 18.59) was significantly lower than that of the Hyperoxia group 6 days after exposure (P < 0.05). Two days after exposure, the NO group had significantly higher MBA than the Control group (0.821 +/- 0.133 vs 0.58 +/- 0.158); the Hyperoxia + NO group had significantly higher MBA than the Hyperoxia group (0.43 +/- 0.175 vs 0.738 +/- 0.141) (P < 0.05).

CONCLUSIONS

Inhaled low dose NO may decrease SP-A protein expression and increase MBA of the lung tissue. This lessens the pathologic lung injury in neonatal rats with hyperoxia.

Regulation of surfactant protein and defensin mRNA expression in cultured ovine type II pneumocytes by all-trans retinoic acid and VEGF

Beta-defensins and surfactant proteins are components of the pulmonary innate immune system. Their gene expression is regulated by development, hormones, growth and immunoregulatory factors. It was our hypothesis that growth and differentiation factors such as all-trans retinoic acid (RA) and vascular endothelial growth factor (VEGF) may affect expression of selected innate immune genes by respiratory epithelial cells. Ovine JS7 cells (alveolar type II pneumocytes) were incubated in serum-free Dulbecco's modified Eagle's medium (DMEM) complete media that contained: no treatment (negative control), RA (500 nM), or VEGF (100 ng/ml) for 6, 12 or 24 h incubation. Total RNA was isolated, cDNA synthesized, and relative mRNA levels of surfactant protein A (SP-A) and SP-D, and sheep beta-defensin-1 (SBD-1) were determined by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Cells had significantly increased expression of SP-D mRNA at 6 h and 24 h, decreased expression of SP-A mRNA at 12 h, and unchanged levels of SBD-1 mRNA after the treatment with RA compared with their respective negative controls. VEGF did not alter the expression of the three innate immune genes. These findings suggest that SP-A and SP-D have different transcription regulation pathways, and that expression of SBD-1 is not inducible by RA similar to its human homolog HBD-1. The lack of changes induced by VEGF treatment suggests that VEGF does not have a direct effect on epithelial cells, but may affect gene expression indirectly.

Surfactant protein A and D in human sinus mucosa: a preliminary report

INTRODUCTION

Surfactant-associated proteins (SPs) play a crucial role in the innate defense system and serve as the initial step in the immune response to inhaled pathogens. SP-A and SP-D expression and function are altered in a variety of inflammatory and infectious diseases of the lungs, such as asthma, allergies, and cystic fibrosis, but their presence and function in the sinonasal cavity has not been investigated. The objective of this study was to test our hypothesis that SP-A and SP-D are present in the human sinus.

MATERIALS AND METHODS

Sinus mucosal biopsies were performed in 8 patients undergoing endoscopic sinus surgery for chronic rhinosinusitis with nasal polyposis, pituitary tumors, and cerebrospinal fluid leak repairs. Expression of SP mRNA and protein by the sinus mucosa was detected by RT-PCR and immunoblot analysis, respectively.

RESULTS

Analyses of mucosal biopsies from these patients revealed the presence of SP-A and SP-D mRNA and protein in all specimens.

CONCLUSION

SP-A and SP-D are expressed in both normal and diseased human sinus tissue. Understanding the role of SPs in diseased and healthy states may elucidate their possible roles in innate immunity in the upper airway and allow us to develop novel treatments for sinonasal pathologies.

Estrogen related receptor-alpha enhances surfactant protein-A gene expression in fetal lung type II cells

Surfactant protein-A (SP-A) gene expression is developmentally regulated in fetal lung type II cells in concert with surfactant glycerophospholipid synthesis. In studies using transfected type II cells, we characterized a nuclear receptor element (NRE(SP-A), 5'-TGACCTTA-3') at -242 bp in the 5'-flanking sequence of human SP-A2 (hSP-A) gene that is essential for basal and cAMP-induced expression. NRE(SP-A) has high sequence similarity to the consensus binding site for estrogen-related receptor (ERR). In the present study, we observed that ERRalpha and ERRgamma, but not ERRbeta, were expressed in human fetal lung type II cells. In vitro transcribed/translated ERRalpha and ERRgamma bound to the NRE(SP-A); DNase I footprinting using bacterially expressed ERRalpha revealed a single DNase I protected region that included NRE(SP-A). In transient transfection assays of COS-7 and primary cultures of lung type II cells, ERRalpha acting through NRE(SP-A) increased hSP-A promoter activity, whereas ERRgamma had no effect. ERRalpha overexpression in lung type II cells enhanced cAMP induction of endogenous hSP-A expression, whereas cotransfection of protein kinase A catalytic subunit enhanced ERRalpha stimulation of hSP-A promoter activity in lung adenocarcinoma cells. Mice homozygous null for the ERRalpha gene manifested decreased SP-A expression relative to wild-type and heterozygous littermates. The ERRalpha-specific inverse agonist XCT790 inhibited cAMP induced hSP-A expression in human fetal lung type II cells in a concentration-dependent manner, suggesting a role of peroxisome proliferator-activated receptor-gamma coactivator 1alpha. These findings suggest that ERRalpha acting through NRE(SP-A) is an important mediator of hSP-A gene expression and its induction by cAMP.

Genetic polymorphism of the binding domain of surfactant protein-A2 increases susceptibility to meningococcal disease

BACKGROUND

Meningococcal disease occurs after colonization of the nasopharynx with Neisseria meningitidis. Surfactant protein (SP)-A and SP-D are pattern-recognition molecules of the respiratory tract that activate inflammatory and phagocytic defences after binding to microbial sugars. Variation in the genes of the surfactant proteins affects the expression and function of these molecules.

METHODS

Allele frequencies of SP-A1, SP-A2, and SP-D were determined by polymerase chain reaction in 303 patients with microbiologically proven meningococcal disease, including 18 patients who died, and 222 healthy control subjects.

RESULTS

Homozygosity of allele 1A1 of SP-A2 increased the risk of meningococcal disease (odds ratio [OR], 7.4; 95% confidence interval [CI], 1.3-42.4); carriage of 1A5 reduced the risk (OR, 0.3; 95% CI, 0.1-0.97). An analysis of the multiple single-nucleotide polymorphisms in SP-A demonstrated that homozygosity for alleles encoding lysine (in 1A1) rather than glutamine (in 1A5) at amino acid 223 in the carbohydrate recognition domain was associated with an increased risk of meningococcal disease (OR, 6.7; 95% CI, 1.4-31.5). Carriage of alleles encoding lysine at residue 223 was found in 61% of patients who died, compared with 35% of those who survived (OR adjusted for age, 2.9; 95% CI, 1.1-7.7). Genetic variation of SP-A1 and SP-D was not associated with meningococcal disease.

CONCLUSIONS

Gene polymorphism resulting in the substitution of glutamine with lysine at residue 223 in the carbohydrate recognition domain of SP-A2 increases susceptibility to meningococcal disease, as well as the risk of death.

Surfactant protein A promoter directs the expression of Cre recombinase in brain microvascular endothelial cells of transgenic mice

Brain microvascular endothelial cells (ECs) have unique characteristics distinguished from peripheral ECs and play important roles in blood-brain barrier (BBB). To investigate the physiological control of the brain ECs, we generated a transgenic mouse line in which the expression of Cre recombinase was driven by the promoter of the mouse surfactant protein A (SP-A) gene. The Cre activity was detected in blood vessels of brain, alveolar type II cells of lung and epithelium of gland stomach. In brain ECs, the Cre activity started at embryonic day 11.5, indicating that the subpopulation of ECs in brain could be molecularly defined at early embryonic stages. The use of SP-A-Cre mice should facilitate analysis of gene function in the brain ECs.

[Effects of isoflurane on lung surfactant protein A in rats]

OBJECTIVE

To examine the effects of different concentrations of Isoflurane on the level of surfactant protein A(SP-A) and the expression of SP-A mRNA in the lung of rats.

METHODS

Thirty-two male Wistar rats were randomly divided into 4 groups: control group received 40% (volume fraction) O2 inhalation (40% O2, n=8); 0.7% isoflurane group (n=8), 1.5% isoflurane group (n=8), and 2.0% isoflurane group (n=8). They were treated with 40% O2 with 0.7%, 1.5% and 2.0% isoflurane respectively. In each group, the rats inhaled experimental gas for 8 hours, and then were put to death immediately. Morphological changes of type II pneumocytes were observed by transmission electron microscopy. Surfactant protein content in broncho-alveolar lavage fluid (BALF) was measured with Western Blotting. The level of intracellular SP-A was examined with immunohistochemistry (IHC). To assess the relative levels of SP-A mRNA in lung tissue, reverse transcriptase-polymerase chain reaction (RT-PCR) was used with the co-amplification of the "housekeeping" gene GAPDH as internal control.

RESULTS

Morphological changes of type II pneumocytes were distinct in 1.5% isoflurane and 2.0% isoflurane groups. Isoflurane, after three doses, significantly reduced the SP-A content in BALF. Control group, 437,112+/-25,654; 0.7% isoflurane group, 355,789+/-28,116; 1.5% isoflurane group, 238,554+/-31,531; 2.0% isoflurane group, 223,632+/-25,710 (P<0.01); Intracellular SP-A content of 1.5% and 2.0% isoflurane groups was less than that of the control, whereas 0.7% isoflurane groups did not show any significant difference from the control. RT-PCR indicated a reduced expression of SP-A mRNA in the lung after 1.5% and 2.0% isoflurane exposure. Control group, 1.47+/-0.18; 1.5% isoflurane group, 1.19+/-0.13; 2.0% isoflurane group, 1.13+/-0.12 (P<0.01).

CONCLUSION

These findings indicate that 1.5% or more than 1.5% isoflurane exposure for eight hours could decrease the expression of the SP-A mRNA and synthesis of SP-A in rats, and maybe it could also affect the secretion and reuse.

Association of surfactant protein A polymorphisms with otitis media in infants at risk for asthma

Background

Otitis media is one of the most common infections of early childhood. Surfactant protein A functions as part of the innate immune response, which plays an important role in preventing infections early in life. This prospective study utilized a candidate gene approach to evaluate the association between polymorphisms in loci encoding SP-A and risk of otitis media during the first year of life among a cohort of infants at risk for developing asthma.

Methods

Between September 1996 and December 1998, women were invited to participate if they had at least one other child with physician-diagnosed asthma. Each mother was given a standardized questionnaire within 4 months of her infant's birth. Infant respiratory symptoms were collected during quarterly telephone interviews at 6, 9 and 12 months of age. Genotyping was done on 355 infants for whom whole blood and complete otitis media data were available.

Results

Polymorphisms at codons 19, 62, and 133 in SP-A1, and 223 in SP-A2 were associated with race/ethnicity. In logistic regression models incorporating estimates of uncertainty in haplotype assignment, the 6A⁴/1A⁵haplotype was protective for otitis media among white infants in our study population (OR 0.23; 95% CI 0.07,0.73).

Conclusion

These results indicate that polymorphisms within SP-A loci may be associated with otitis media in white infants. Larger confirmatory studies in all ethnic groups are warranted.

Neither SP-A nor NH2-terminal domains of SP-A can substitute for SP-D in regulation of alveolar homeostasis

Surfactant proteins (SP)-A and -D are members of the collectin family of host defense proteins that share four distinct structural domains: NH2-terminal oligomerization, collagenous, neck, and carbohydrate recognition (CRD). To determine the specificity of the functions of these domains, the SFTPC promoter was used to express 1) full-length rat (r) Sftpa; 2) NH2- rSftpa/d, consisting of NH2-terminal and collagenous domains of SP-A with neck domain and CRD of SP-D; and 3) rSftpd/a, consisting of NH2-terminal and collagenous domains of SP-D with neck domain and CRD of SP-A, in Sftpd−/−mice. Increased expression of SP-A in Sftpd−/−mice did not correct the increased pulmonary saturated phosphatidylcholine levels, emphysema, or foamy alveolar macrophage and lymphocyte infiltrations characteristic of Sftpd−/−mice, indicating that the decreased SP-A level noted in Sftpd−/−mice does not account for the observed pulmonary abnormalities. The chimeric protein NH2-rSftpa/d was expressed and detected in the airways of transgenic mice, migrating as an SP-A-like oligomer that associated with large aggregate surfactant in a manner similar to that of SP-A rather than SP-D. NH2-rSftpa/d did not correct emphysema, foamy macrophage and lymphocyte infiltration, or the increased lipid accumulations characteristic of Sftpd−/−mice. Thus oligomerization and surfactant lipid association of SP-D requires its NH2-terminal and collagenous domains, which are needed for SP-D-dependent regulation of surfactant homeostasis in vivo. Attempts to express rSftpd/a fusion protein in vivo were unsuccessful. Mmp9−/−/Sftpd−/−and Mmp12−/−/Sftpd−/−mice developed air space enlargement similar to Sftpd−/−mice, supporting the concept that the increased expression of each metalloproteinase seen in Sftpd−/−lungs is not the major cause of emphysema.

Spatial and temporal expression of surfactant proteins in hyperoxia-induced neonatal rat lung injury

Background

Bronchopulmonary dysplasia, a complex chronic lung disease in premature children in which oxidative stress and surfactant deficiency play a crucial role, is characterized by arrested alveolar and vascular development of the immature lung. The spatial and temporal patterns of expression of surfactant proteins are not yet fully established in newborn infants and animal models suffering from BPD.

Methods

We studied the mRNA expression of surfactant proteins (SP) A, -B, -C and -D and Clara cell secretory protein (CC10) with RT-PCR and in situ hybridization and protein expression of CC10, SP-A and -D with immunohistochemistry in the lungs of a preterm rat model, in which experimental BPD was induced by prolonged oxidative stress.

Results

Gene expression of all surfactant proteins (SP-A, -B, -C and -D) was high at birth and initially declined during neonatal development, but SP-A, -B, and -D mRNA levels increased during exposure to hyperoxia compared to room-air controls. Peak levels were observed in adult lungs for SP-A, SP-C and CC10. Except for SP-A, the cellular distribution of SP-B, -C, -D and CC10, studied with in situ hybridization and/or immunohistochemistry, did not change in room air nor in hyperoxia. Exposure to normoxia was associated with high levels of SP-A mRNA and protein in alveolar type 2 cells and low levels in bronchial Clara cells, whereas hyperoxia induced high levels of SP-A expression in bronchial Clara cells.

Conclusion

The increased expression of SP-A mRNA under hyperoxia can be attributed, at least in part, to an induction of mRNA and protein expression in bronchial Clara cells. The expanded role of Clara cells in the defence against hyperoxic injury suggests that they support alveolar type 2 cell function and may play an important role in the supply of surfactant proteins to the lower airways.

Permissive effects of oxygen on cyclic AMP and interleukin-1 stimulation of surfactant protein A gene expression are mediated by epigenetic mechanisms

Surfactant protein A (SP-A) is important for immune defense within the alveolus. Cyclic AMP (cAMP) stimulation of SP-A expression in lung type II cells is O(2) dependent and mediated by increased phosphorylation and binding of thyroid transcription factor 1 (TTF-1) to an upstream response element (TTF-1-binding element [TBE]). Interleukin-1 (IL-1) stimulation of SP-A expression is mediated by NF-kappaB (p65/p50) activation and increased binding to the TBE. In this study, we found that O(2) also was permissive for IL-1 induction of SP-A expression and for cAMP and IL-1 stimulation of type II cell nuclear protein binding to the TBE. Using chromatin immunoprecipitation, we observed that when type II cells were cultured in 20% O(2), cAMP and IL-1 stimulated the recruitment of TTF-1, p65, CBP, and steroid receptor coactivator 1 to the TBE region of the SP-A promoter and increased local acetylation of histone H3; these effects were prevented by hypoxia. Hypoxia markedly reduced global levels of CBP and acetylated histone H3 and increased the expression of histone deacetylases. Furthermore, hypoxia caused a global increase in histone H3 dimethylated on Lys9 and increased the association of dimethyl histone H3 with the SP-A promoter. These results, together with findings that the histone deacetylase inhibitor trichostatin A and the methyltransferase inhibitor 5'-deoxy(5'-methylthio)adenosine markedly enhanced SP-A expression in lung type II cells, suggest that increased O(2) availability to type II cells late in gestation causes epigenetic changes that permit access of TTF-1 and NF-kappaB to the SP-A promoter. The binding of these transcription factors facilitates the recruitment of coactivators, resulting in the further opening of the chromatin structure and activation of SP-A transcription.