Cathepsin H and napsin A are active in the alveoli and increased in alveolar proteinosis

Cathepsins and cancer risk: a Mendelian randomization study

Background

Previous observational epidemiological studies reported an association between cathepsins and cancer, however, a causal relationship is uncertain. This study evaluated the causal relationship between cathepsins and cancer using Mendelian randomization (MR) analysis.

Methods

We used publicly available genome-wide association study (GWAS) data for bidirectional MR analysis. Inverse variance weighting (IVW) was used as the primary MR method of MR analysis.

Results

After correction for the False Discovery Rate (FDR), two cathepsins were found to be significantly associated with cancer risk: cathepsin H (CTSH) levels increased the risk of lung cancer (OR = 1.070, 95% CI = 1.027-1.114, P = 0.001, PFDR = 0.009), and CTSH levels decreased the risk of basal cell carcinoma (OR = 0.947, 95% CI = 0.919-0.975, P = 0.0002, P FDR = 0.002). In addition, there was no statistically significant effect of the 20 cancers on the nine cathepsins. Some unadjusted low P-value phenotypes are worth mentioning, including a positive correlation between cathepsin O (CTSO) and breast cancer (OR = 1.012, 95% CI = 1.001-1.025, P = 0.041), cathepsin S (CTSS) and pharyngeal cancer (OR = 1.017, 95% CI = 1.001-1.034, P = 0.043), and CTSS and endometrial cancer (OR = 1.055, 95% CI = 1.012-1.101, P = 0.012); and there was a negative correlation between cathepsin Z and ovarian cancer (CTSZ) (OR = 0.970, 95% CI = 0.949-0.991, P = 0.006), CTSS and prostate cancer (OR = 0.947, 95% CI = 0.902-0.944, P = 0.028), and cathepsin E (CTSE) and pancreatic cancer (OR = 0.963, 95% CI = 0.938-0.990, P = 0.006).

Conclusion

Our MR analyses showed a causal relationship between cathepsins and cancers and may help provide new insights for further mechanistic and clinical studies of cathepsin-mediated cancer.

Mendelian randomization analyses explore the relationship between cathepsins and lung cancer

Lung cancer, a major contributor to cancer-related fatalities worldwide, involves a complex pathogenesis. Cathepsins, lysosomal cysteine proteases, play roles in various physiological and pathological processes, including tumorigenesis. Observational studies have suggested an association between cathepsins and lung cancer. However, the causal link between the cathepsin family and lung cancer remains undetermined. This study employed Mendelian randomization analyses to investigate this causal association. The univariable Mendelian randomization analysis results indicate that elevated cathepsin H levels increase the overall risk of lung cancer, adenocarcinoma, and lung cancer among smokers. Conversely, reverse Mendelian randomization analyses suggest that squamous carcinoma may lead to increased cathepsin B levels. A multivariable analysis using nine cathepsins as covariates reveals that elevated cathepsin H levels lead to an increased overall risk of lung cancer, adenocarcinoma, and lung cancer in smokers. In conclusion, cathepsin H may serve as a marker for lung cancer, potentially inspiring directions in lung cancer diagnosis and treatment.

Cathepsin H: molecular characteristics and clues to function and mechanism

Cathepsin H (CatH) is a lysosomal cysteine protease with a unique aminopeptidase activity that is extensively expressed in the lung, pancreas, thymus, kidney, liver, skin, and brain. Owing to its specific enzymatic activity, CatH has critical effects on the regulation of biological behaviours of cancer cells and pathological processes in brain diseases. Moreover, a neutral pH level is optimal for CatH activity, so it is expected to be active in the extra-lysosomal and extracellular space. In the present review, we describe the expression, maturation, and enzymatic properties of CatH, and summarize the available experimental evidence that mechanistically links CatH to various physiological and pathological processes. Finally, we discuss the challenges and potentials of CatH inhibitors in CatH-induced disease therapy.

Cathepsins in Bacteria-Macrophage Interaction: Defenders or Victims of Circumstance?

Macrophages are the first encounters of invading bacteria and are responsible for engulfing and digesting pathogens through phagocytosis leading to initiation of the innate inflammatory response. Intracellular digestion occurs through a close relationship between phagocytic/endocytic and lysosomal pathways, in which proteolytic enzymes, such as cathepsins, are involved. The presence of cathepsins in the endo-lysosomal compartment permits direct interaction with and killing of bacteria, and may contribute to processing of bacterial antigens for presentation, an event necessary for the induction of antibacterial adaptive immune response. Therefore, it is not surprising that bacteria can control the expression and proteolytic activity of cathepsins, including their inhibitors – cystatins, to favor their own intracellular survival in macrophages. In this review, we summarize recent developments in defining the role of cathepsins in bacteria-macrophage interaction and describe important strategies engaged by bacteria to manipulate cathepsin expression and activity in macrophages. Particularly, we focus on specific bacterial species due to their clinical relevance to humans and animal health, i.e., Mycobacterium, Mycoplasma, Staphylococcus, Streptococcus, Salmonella, Shigella, Francisella, Chlamydia, Listeria, Brucella, Helicobacter, Neisseria, and other genera.

Pepstatin pull-down at high pH is a powerful tool for detection and analysis of napsin A

Napsin A is an intracellular aspartic protease and biomarker of various malignancies like lung adenocarcinoma and ovarian clear cell carcinoma, but its detection is usually limited to immunohistochemical techniques gaining excellent information on its distribution but missing information about posttranslational modifications (e.g. maturation state) of the protein. We present a protocol for specific enrichment of napsin A from clinical or biological specimens, that facilitates detailed analysis of the protein. By using the exceptionally broad pH range under which napsin A binds to its inhibitor pepstatin A we achieve highly selective binding of napsin A while other aspartic proteases have negligible affinity. Using this method we demonstrate that lung napsin A in many mammals is a heterogeneous enzyme with a characteristic ladder-like appearance in SDS-PAGE that might be caused by proteolytically processed N- and/or C-termini, in contrast to the more homogeneous form found in kidneys and primary lung adenocarcinoma.

Napsin A levels in epithelial lining fluid as a diagnostic biomarker of primary lung adenocarcinoma

BACKGROUND

It is crucial to develop novel diagnostic approaches for determining if peripheral lung nodules are malignant, as such nodules are frequently detected due to the increased use of chest computed tomography scans. To this end, we evaluated levels of napsin A in epithelial lining fluid (ELF), since napsin A has been reported to be an immunohistochemical biomarker for histological diagnosis of primary lung adenocarcinoma.

METHODS

In consecutive patients with indeterminate peripheral lung nodules, ELF samples were obtained using a bronchoscopic microsampling (BMS) technique. The levels of napsin A and carcinoembryonic antigen (CEA) in ELF at the nodule site were compared with those at the contralateral site. A final diagnosis of primary lung adenocarcinoma was established by surgical resection.

RESULTS

We performed BMS in 43 consecutive patients. Among patients with primary lung adenocarcinoma, the napsin A levels in ELF at the nodule site were markedly higher than those at the contralateral site, while there were no significant differences in CEA levels. Furthermore, in 18 patients who were undiagnosed by bronchoscopy and finally diagnosed by surgery, the napsin A levels in ELF at the nodule site were identically significantly higher than those at the contralateral site. In patients with non-adenocarcinoma, there were no differences in napsin A levels in ELF. The area under the receiver operator characteristic curve for identifying primary lung adenocarcinoma was 0.840 for napsin A and 0.542 for CEA.

CONCLUSION

Evaluation of napsin A levels in ELF may be useful for distinguishing primary lung adenocarcinoma.

Spatially-Resolved Proteomics: Rapid Quantitative Analysis of Laser Capture Microdissected Alveolar Tissue Samples

Laser capture microdissection (LCM)-enabled region-specific tissue analyses are critical to better understand complex multicellular processes. However, current proteomics workflows entail several manual sample preparation steps and are challenged by the microscopic mass-limited samples generated by LCM, impacting measurement robustness, quantification and throughput. Here, we coupled LCM with a proteomics workflow that provides fully automated analysis of proteomes from microdissected tissues. Benchmarking against the current state-of-the-art in ultrasensitive global proteomics (FASP workflow), our approach demonstrated significant improvements in quantification (~2-fold lower variance) and throughput (>5 times faster). Using our approach we for the first time characterized, to a depth of >3,400 proteins, the ontogeny of protein changes during normal lung development in microdissected alveolar tissue containing only 4,000 cells. Our analysis revealed seven defined modules of coordinated transcription factor-signaling molecule expression patterns, suggesting a complex network of temporal regulatory control directs normal lung development with epigenetic regulation fine-tuning pre-natal developmental processes.

Immunohistochemical Comparison of Ovarian and Uterine Endometrioid Carcinoma, Endometrioid Carcinoma With Clear Cell Change, and Clear Cell Carcinoma

Accurate distinction of clear cell carcinoma (CCC) from endometrioid carcinoma (EC) has important clinical implications, but, not infrequently, EC demonstrates clear cell change (EC-CC), mimicking CCC. We examined whether a panel of immunomarkers can help distinguish between these tumors. Sixty-four CCCs (40 ovarian and 24 uterine), 34 ECs (21 ovarian and 13 uterine), and 34 EC-CCs (6 ovarian and 28 uterine) were stained for HNF1β, BAF250a, Napsin A, ER, and PR. Intensity and extent of immunoreactivity was assessed. Fifty-seven of 64 (89%) CCCs, 14/34 (41%) EC-CCs, and 16/34 (47%) ECs expressed HNF1β, and 56/64 (88%) CCCs, 4/34 (12%) EC-CCs, and 1/34 (3%) ECs stained for Napsin A. Most CCCs demonstrated at least moderate and diffuse staining for both markers, whereas only focal and weak expression was identified in most EC-CC/EC. Compared to HNF1β, Napsin A showed increased specificity (93.0% vs. 55.9%, P<0.0001) and similar sensitivity (87.5% vs. 89.1%) in distinguishing CCC from EC-CC/EC. Thirteen of 64 (20%) CCCs, 6/34 (18%) EC-CCs, and 2/34 (6%) ECs showed loss of BAF250a. ER was expressed by 10/64 (16%) CCCs, 30/34 (88%) EC-CCs, and 33/34 (97%) ECs, whereas PR positivity was identified in 9/64 (14%) CCCs, 26/34 (77%) EC-CCs, and 33/34 (97%) ECs. The majority of EC and EC-CC demonstrated diffuse staining for ER/PR, whereas most CCCs showed very focal positivity. There is a statistically significant difference in HNF1β, Napsin A, ER, and PR immunoexpression between CCC and EC/EC-CC, with Napsin A being a more specific marker for CCC than HNF1β. Overall, the immunoprofile of EC-CC is more comparable to that of EC than CCC. The use of a panel of immunostains can help distinguish EC-CC from CCC.

Cysteine cathepsins and cystatins: from ancillary tasks to prominent status in lung diseases

Human cysteine cathepsins (family C1, clan CA) have long been regarded as ubiquitous household enzymes, primarily involved in the recycling and degradation of proteins in lysosomes. This opinion has changed considerably during recent decades, however, with the demonstration of their involvement in various physiological processes. A growing body of evidence supports the theory that cathepsins play specific functions in lung homeostasis and pathophysiological events such as asthma, lung fibrosis (including idiopathic pulmonary fibrosis), chronic obstructive pulmonary disease (embracing emphysema and chronic bronchitis), silicosis, bronchopulmonary dysplasia or tumor invasion. The objective of this review is to provide an update on the current knowledge of the role of these enzymes in the lung. Particular attention has been paid to the understanding of the role of these proteases and their natural inhibitors, cystatins (family I25, clan IH), in TGF-β1-driven fibrotic processes with an emphasis on lung fibrosis.

SP-R210 (Myo18A) Isoforms as Intrinsic Modulators of Macrophage Priming and Activation

The surfactant protein (SP-A) receptor SP-R210 has been shown to increase phagocytosis of SP-A-bound pathogens and to modulate cytokine secretion by immune cells. SP-A plays an important role in pulmonary immunity by enhancing opsonization and clearance of pathogens and by modulating macrophage inflammatory responses. Alternative splicing of the Myo18A gene results in two isoforms: SP-R210S and SP-R210L, with the latter predominantly expressed in alveolar macrophages. In this study we show that SP-A is required for optimal expression of SP-R210L on alveolar macrophages. Interestingly, pre-treatment with SP-A prepared by different methods either enhances or suppresses responsiveness to LPS, possibly due to differential co-isolation of SP-B or other proteins. We also report that dominant negative disruption of SP-R210L augments expression of receptors including SR-A, CD14, and CD36, and enhances macrophages' inflammatory response to TLR stimulation. Finally, because SP-A is known to modulate CD14, we used a variety of techniques to investigate how SP-R210 mediates the effect of SP-A on CD14. These studies revealed a novel physical association between SP-R210S, CD14, and SR-A leading to an enhanced response to LPS, and found that SP-R210L and SP-R210S regulate internalization of CD14 via distinct macropinocytosis-like mechanisms. Together, our findings support a model in which SP-R210 isoforms differentially regulate trafficking, expression, and activation of innate immune receptors on macrophages.

Translational research in pediatrics III: bronchoalveolar lavage

The role of flexible bronchoscopy and bronchoalveolar lavage (BAL) for the care of children with airway and pulmonary diseases is well established, with collected BAL fluid most often used clinically for microbiologic pathogen identification and cellular analyses. More recently, powerful analytic research methods have been used to investigate BAL samples to better understand the pathophysiological basis of pediatric respiratory disease. Investigations have focused on the cellular components contained in BAL fluid, such as macrophages, lymphocytes, neutrophils, eosinophils, and mast cells, as well as the noncellular components such as serum molecules, inflammatory proteins, and surfactant. Molecular techniques are frequently used to investigate BAL fluid for the presence of infectious pathologies and for cellular gene expression. Recent advances in proteomics allow identification of multiple protein expression patterns linked to specific respiratory diseases, whereas newer analytic techniques allow for investigations on surfactant quantification and function. These translational research studies on BAL fluid have aided our understanding of pulmonary inflammation and the injury/repair responses in children. We review the ethics and practices for the execution of BAL in children for translational research purposes, with an emphasis on the optimal handling and processing of BAL samples.

The expression and activity of cathepsins D, H and K in asthmatic airways

Tumstatin is an anti-angiogenic collagen IV α3 fragment, levels of which are reduced in the airways of asthmatics. Its reduction may be due to the degradation by extracellular matrix (ECM) proteases. Cathepsins play a role in ECM remodelling, with cathepsin D, H and K (CTSD, CTSH and CTSK) being associated with lung diseases. CTSD modulates the NC1 domains of collagen molecules including tumstatin, while CTSH and CTSK are involved in ECM degradation. The role of these cathepsins in the regulation of tumstatin in the lung has not previously been examined. We demonstrated that CTSB, D, F, H, K, L and S mRNA was expressed in the airways. Quantification of immunohistochemistry showed that there is no difference in the global expression of CTSD, CTSH and CTSK between asthmatics and non-asthmatics. CTSD and CTSK, but not CTSH had the capacity to degrade tumstatin. No difference was observed in the activity of CTSD and H in bronchoalveolar lavage fluid of asthmatic and non-asthmatics, while CTSK was undetectable. This indicates that while CTSD possesses the potential to directly regulate tumstatin, and thus angiogenesis through this mechanism however, it is not likely to be involved in the dysregulation of tumstatin found in asthmatic airways.

Tissue-preserving antibody cocktails to differentiate primary squamous cell carcinoma, adenocarcinoma, and small cell carcinoma of lung

CONTEXT

With the availability of cell type-specific therapies, differentiating primary lung squamous cell carcinomas (SCCs) and adenocarcinomas (ACAs) has become important. The limitations of small sample size and the need to conserve tissue for additional molecular studies necessitate the use of sensitive and specific marker panels on a single slide.

OBJECTIVE

To distinguish SCC from ACA and small cell carcinoma (SmCC) of lung using 2 novel tissue-conserving cocktails.

DESIGN

We compared two antibody cocktails, desmoglein 3 + cytokeratin 5/napsin A and p40/thyroid transcription factor 1 (Biocare Medical, Concord, California) in diagnosing SCC and ACA of the lung on tissue microarray, cytology, and surgical specimens. Both lung and nonlung tissue were evaluated on an 1150-core tissue microarray that contained 200 lung cancers. A microarray of 35 SmCCs and 5 small cell SCCs was also evaluated.

RESULTS

A cocktail of desmoglein 3 + cytokeratin 5/napsin A provided diagnostic accuracy in lung cancers with a sensitivity and specificity of 100% in SCCs and a sensitivity of 86% and a specificity of 100% in ACAs. A p40/thyroid transcription factor 1 cocktail showed p40 to have a specificity of 92% and a sensitivity of 93% in SCCs, whereas thyroid transcription factor 1 had a specificity of 100% and a sensitivity of 77% in ACAs. Cell blocks of fine-needle aspiration cytology compared with corresponding surgical (n = 20) specimens displayed similar findings. The p40 was useful in differentiating bladder from prostate carcinoma with 88% sensitivity. Isolated carcinomas from nonlung tissues were desmoglein 3 + cytokeratin 5 positive. Napsin A was positive in 22% of renal tumors as previously observed. Both cocktails were excellent in differentiating SmCCs and small cell SCCs because none of the SmCCs stained with p40.

CONCLUSIONS

Both antibody cocktails are excellent in differentiating primary lung ACA from SCC, as well as excluding SmCC and ACAs from all other sites on small specimens. A cocktail of desmoglein 3 + cytokeratin 5/napsin A is slightly superior compared with p40/thyroid transcription factor 1 cocktail.

Serum cystatin C and emphysema: results from the National Health and Nutrition Examination Survey (NHANES)

BACKGROUND

Cystatin C (CysC) is a potent nonorgan-specific cysteine protease inhibitor and may contribute to elastolysis and tissue destruction by a mechanism of protease–antiprotease imbalance. Given the prevalence of CysC in the serum of smokers and its role in tissue destruction, we aimed to evaluate the association between CysC and emphysema.

METHODS

Pooled cross-sectional data from the National Health and Nutrition Examination Survey 1999–2002 were used. Emphysema and chronic bronchitis were defined by a self-reported history ascertained using standardized questionnaires. Active smokers were defined as self-reported current smokers or measured serum cotinine ≥10 ng/mL. Nonactive smokers with a serum cotinine level >0.05 ng/mL were defined as environmental tobacco smoke (ETS)-exposed.

RESULTS

The prevalence (95% CI) of emphysema was 1.3% (range = 0.9–1.8%). The mean (SE) CysC level in the emphysema group was significantly higher than in normal controls [1,139 (22) vs. 883 (8) μg/L; p = 0.001]. Upon stratification of the study population by C-reactive protein (CRP) concentrations, we demonstrated a progressive increase in the mean serum CysC level with serially increasing CRP concentrations. Active smokers with emphysema had 115.4 (46.5) μg/L higher mean (SE) CysC levels than the normal controls (p < 0.001). Upon adjusted analysis, we observed that nonactive smokers with significant ETS exposure had 31.2 (15.2) μg/L higher mean (SE) serum CysC levels as compared to ETS unexposed nonactive smokers (p = 0.04).

CONCLUSION

In a large representative noninstitutionalized US population, we demonstrated an association between emphysema and serum CysC. Active smokers with emphysema had significantly higher CysC levels. These findings suggest that CysC may play a role in the pathogenesis of smoking-related emphysema.

The elevation of serum napsin A in idiopathic pulmonary fibrosis, compared with KL-6, surfactant protein-A and surfactant protein-D

Background

Napsin A, an aspartic protease, is mainly expressed in alveolar type-II cells and renal proximal tubules and is a putative immunohistochemical marker for pulmonary adenocarcinomas. This study sought to determine whether napsin A could be measured in the serum to evaluate its relationship to idiopathic pulmonary fibrosis (IPF) and determine whether renal dysfunction might affect serum napsin A levels.

Methods

Serum levels of napsin A were measured in 20 patients with IPF, 34 patients with lung primary adenocarcinoma, 12 patients with kidney diseases, and 20 healthy volunteers. Surfactant protein (SP)-A, SP-D, and Krebs von den Lungen-6 (KL-6) levels in serum and pulmonary function tests were also evaluated in IPF patients.

Results

Circulating levels of napsin A were increased in patients with IPF, as compared with healthy controls, and they correlated with the severity of disease. Moreover, the serum napsin A levels were not elevated in patients with pulmonary adenocarcinoma or renal dysfunction. The distinguishing point between IPF and the controls was that the area under the receiver operating characteristic curve (ROC) of napsin A was larger than that of KL-6, SP-A, or SP-D.

Conclusion

These findings suggest that serum napsin A may be a candidate biomarker for IPF.

Napsin A, a new marker for lung adenocarcinoma, is complementary and more sensitive and specific than thyroid transcription factor 1 in the differential diagnosis of primary pulmonary carcinoma: evaluation of 1674 cases by tissue microarray

CONTEXT

Differentiation of non-small cell carcinoma into histologic types is important because of new, successful therapies that target lung adenocarcinoma (ACA). TTF-1 is a favored marker for lung ACA but has limited sensitivity and specificity. Napsin A (Nap-A) is a functional aspartic proteinase that may be an alternative marker for primary lung ACA.

OBJECTIVES

To compare Nap-A versus TTF-1 in the typing of primary lung carcinoma and the differentiation of primary lung ACA from carcinomas of other sites.

DESIGN

Immunohistochemistry for Nap-A and TTF-1 was performed on tissue microarrays of 1674 cases of carcinoma: 303 primary lung ACAs (18.1%), 200 primary squamous cell lung carcinomas (11.9%), 52 primary small cell carcinomas of the lung (3.1%), and carcinomas of the kidney (n  =  320; 19.1%), thyroid (n  =  96; 5.7%), biliary (n  =  89; 5.3%), bladder (n  =  47; 2.8%), breast (n  =  93; 5.6%), colon (n  =  95; 5.7%), liver (n  =  96; 5.7%), ovaries (n  =  45; 2.7%), pancreas (n  =  48; 2.9%), prostate (n  =  49; 2.9%), stomach (n  =  93; 5.6%), and uterus (n  =  48; 2.9%). Cases were evaluated against a negative control as negative, weak positive, and strong positive.

RESULTS

Nap-A was more sensitive than TTF-1 for primary lung ACA (87% versus 64%; P < .001). Nap-A was more specific than TTF-1 for primary lung ACA versus all tumors, excluding kidney, independent of tumor type (P < .001).

CONCLUSIONS

Nap-A is superior to TTF-1 in distinguishing primary lung ACA from other carcinomas (except kidney), particularly primary lung small cell carcinoma, and primary thyroid carcinoma. A combination of Nap-A and TTF-1 is useful in the distinction of primary lung ACA (Nap-A(+), TTF-1(+)) from primary lung squamous cell carcinoma (Nap-A(-), TTF-1(-)) and primary lung small cell carcinoma (Nap-A(-), TTF-1(+)).

Evaluation of Napsin A, Cytokeratin 5/6, p63, and Thyroid Transcription Factor 1 in Adenocarcinoma Versus Squamous Cell Carcinoma of the Lung

Context.—The distinction of lung adenocarcinoma from other types of primary lung malignancies is important clinically. Accurate morphologic classification is often hindered because 70% of lung cancers are diagnosed on limited fine-needle aspiration or transbronchial biopsy specimens. Although thyroid transcription factor 1 (TTF-1) has historically been the most specific marker for lung adenocarcinoma, a relatively new marker, napsin A, has recently been shown to be more sensitive and specific than TTF-1.

Objective.—To find the most cost-effective panel to reliably distinguish lung adenocarcinoma from squamous cell carcinoma.

Design.—A total of 291 lung cancers were evaluated morphologically (197 adenocarcinomas [75%]; 66 squamous cell carcinomas [25%]; 28 cases could not be classified into either and were dropped). Immunohistochemistry for napsin A, Cytokeratin 5/6, p63, and TTF-1 was performed on a formalin-fixed tissue microarray obtained from Toyama, Japan. Cases were scored as positive or negative against a negative control.

Results.—Napsin A had 83% sensitivity and 98% specificity and TTF-1 had 60% sensitivity and 98% specificity for adenocarcinoma. Cytokeratin 5/6 had 53% sensitivity and 96% specificity and p63 had 95% sensitivity and 86% specificity for squamous cell carcinoma. A panel of napsin A and p63 has a specificity of 94% and a sensitivity of 96% for distinguishing adenocarcinoma from squamous cell carcinoma.

Conclusions.—The source of the antibody is important in avoiding false-negative results. The most cost-effective tissue-preserving panel for small biopsy specimens in the differential diagnosis of lung adenocarcinoma versus squamous cell carcinoma is a combination of p63 and napsin A.

rhKGF stimulates lung surfactant production in neonatal rats in vivo

Surfactant deficiency and bronchopulmonary dysplasia (BPD), major obstacles in preterm infants, are addressed with pre- and postnatal glucocorticoids which also evoke harmful catabolic side-effects. Keratinocyte growth factor (KGF) accelerates surfactant production in fetal type II pneumocytes (PN-II), protects epithelia from injury and is deficient in lungs developing BPD, highlighting its potential efficacy in neonates. Neonatal rats were treated with recombinant human (rh)KGF, betamethasone, or their combination for 48 hr prior to sacrifice after which body weight, surfactant, and tissue phosphatidylcholines (PC) were investigated at postnatal d3, d7, d15, and d21. Pneumocyte proliferation, surfactant protein (SP) expression and SP-B/C in lung lavage fluid (LLF) were also determined at d7 and d21 to identify broader surfactant changes occurring at the beginning and end of the initial alveolarization phase. While all treatments increased secreted surfactant PC, BM compromised animal growth whereas rhKGF did not. At d3 rhKGF was more effective in male compared to female rats. Single treatments became less effective towards d21. Neither treatment altered PC composition in LLF. BM inhibited PN-II proliferation and increased surfactant PCs at the expense of tissue PCs. rhKGF however increased surfactant PCs without decreasing other PC species. Whereas SP-B/C gene expression was induced by all treatments, the changes in secreted SP-B/C mirrored those observed for surfactant PC. Our results encourage investigation of the mechanisms by which rhKGF improves surfactant homoeostasis, and detailed examination of its efficacy in neonatal lung injury models with a view to implementing it as a non-catabolic surfactant-increasing therapeutic in neonatal intensive care.

The effect of interleukin-13 (IL-13) and interferon-γ (IFN-γ) on expression of surfactant proteins in adult human alveolar type II cells in vitro

Background

Surfactant proteins are produced predominantly by alveolar type II (ATII) cells, and the expression of these proteins can be altered by cytokines and growth factors. Th1/Th2 cytokine imbalance is suggested to be important in the pathogenesis of several adult lung diseases. Recently, we developed a culture system for maintaining differentiated adult human ATII cells. Therefore, we sought to determine the effects of IL-13 and IFN-γ on the expression of surfactant proteins in adult human ATII cells in vitro. Additional studies were done with rat ATII cells.

Methods

Adult human ATII cells were isolated from deidentified organ donors whose lungs were not suitable for transplantation and donated for medical research. The cells were cultured on a mixture of Matrigel and rat-tail collagen for 8 d with differentiation factors and human recombinant IL-13 or IFN-γ.

Results

IL-13 reduced the mRNA and protein levels of surfactant protein (SP)-C, whereas IFN-γ increased the mRNA level of SP-C and proSP-C protein but not mature SP-C. Neither cytokine changed the mRNA level of SP-B but IFN-γ slightly decreased mature SP-B. IFN-γ reduced the level of the active form of cathepsin H. IL-13 also reduced the mRNA and protein levels of SP-D, whereas IFN-γ increased both mRNA and protein levels of SP-D. IL-13 did not alter SP-A, but IFN-γ slightly increased the mRNA levels of SP-A.

Conclusions

We demonstrated that IL-13 and IFN-γ altered the expression of surfactant proteins in human adult ATII cells in vitro. IL-13 decreased SP-C and SP-D in human ATII cells, whereas IFN-γ had the opposite effect. The protein levels of mature SP-B were decreased by IFN-γ treatment, likely due to the reduction in active form cathpesin H. Similarly, the active form of cathepsin H was relatively insufficient to fully process proSP-C as IFN-γ increased the mRNA levels for SP-C and proSP-C protein, but there was no increase in mature SP-C. These observations suggest that in disease states with an overexpression of IL-13, there would be some deficiency in mature SP-C and SP-D. In disease states with an excess of IFN-γ or therapy with IFN-γ, these data suggest that there might be incomplete processing of SP-B and SP-C.

The surfactant lipid transporter ABCA3 is N-terminally cleaved inside LAMP3-positive vesicles

ABCA3 mutations cause fatal surfactant deficiency and interstitial lung disease. ABCA3 protein is a lipid transporter indispensible for surfactant biogenesis and storage in lamellar bodies (LB). The protein folds in endoplasmic reticulum and is glycosylated in Golgi en route to the membrane of mature LB and their precursor multivesicular bodies (MVB). In immunoblots, C-terminally labeled ABCA3 appears as two protein bands of 150 and 190 kDa. Using N- and C-terminal protein tags and hindering ABCA3 processing we show that the 150 kDa protein represents the mature ABCA3 whose N-terminus is cleaved by a cysteine protease inside MVB/LB.

Alveolar proteinosis syndrome: pathogenesis, diagnosis, and management

PURPOSE OF REVIEW

This review discusses the most recent clinical and basic research literature on pulmonary alveolar proteinosis (PAP) as it relates to pathogenesis, diagnosis, and management.

RECENT FINDINGS

The discovery of Granulocyte macrophage-colony stimulating factor (GM-CSF) and the alveolar macrophage as critical regulators of surfactant protein and lipid homeostasis has led to significant advances in PAP. Adults affected by PAP have circulating neutralizing anti-GM-CSF antibodies. Reduced localized GM-CSF activity in the lung (from neutralizing anti-GM-CSF antibodies), decreases alveolar macrophage surfactant degradation with surfactant excess and accumulation. Cause, source of antibodies or downstream effects of GM-CSF deficiency is speculative. GM-CSF antibodies above a threshold level have proved to be a useful diagnostic test. Research towards therapy has focused on improving the technique for therapeutic whole lung lavage as well as overcoming effects of neutralizing anti-GM-CSF, which include GM-CSF therapy (systemic and inhaled) and anecdotal reports of anti-B cell therapy. Whereas this approach has been somewhat successful for primary PAP, other causes of PAP (i.e. alveolar macrophage dysfunction, surfactant protein alterations) are still without therapy.

SUMMARY

Understanding of the pathogenesis of PAP has greatly increased in the last decade; study has brought better comprehension of lung biology and recognition of the critical role for GM-CSF and alveolar macrophage in surfactant clearance. Balance between resident immune cell population and normal lung function still needs further study. Resident alveolar macrophages have an essential role in surfactant homeostasis. With this knowledge more effective diagnostic tests (e.g. anti-GM-CSF antibody) and therapies for PAP are under investigation.