Long-term stability and circadian variation in circulating levels of surfactant protein D

Particles in Exhaled Air (PExA): Clinical Uses and Future Implications

Access to distal airway samples to assess respiratory diseases is not straightforward and requires invasive procedures such as bronchoscopy and bronchoalveolar lavage. The particles in exhaled air (PExA) device provides a non-invasive means of assessing small airways; it captures distal airway particles (PEx) sized around 0.5-7 μm and contains particles of respiratory tract lining fluid (RTLF) that originate during airway closure and opening. The PExA device can count particles and measure particle mass according to their size. The PEx particles can be analysed for metabolites on various analytical platforms to quantitatively measure targeted and untargeted lung specific markers of inflammation. As such, the measurement of distal airway components may help to evaluate acute and chronic inflammatory conditions such as asthma, chronic obstructive pulmonary disease, acute respiratory distress syndrome, and more recently, acute viral infections such as COVID-19. PExA may provide an alternative to traditional methods of airway sampling, such as induced sputum, tracheal aspirate, or bronchoalveolar lavage. The measurement of specific biomarkers of airway inflammation obtained directly from the RTLF by PExA enables a more accurate and comprehensive understanding of pathophysiological changes at the molecular level in patients with acute and chronic lung diseases.

Bioaerosol-induced in vitro activation of toll-like receptors and inflammatory biomarker expression in waste workers

PURPOSE

Occupational exposure to bioaerosols during waste handling remains a health concern for exposed workers. However, exposure-related health effects and underlying immunological mechanisms are still poorly described.

METHODS

The present study assessed the inflammatory potential of work-air samples (n = 56) in vitro and investigated biomarker expression in exposed workers (n = 69) compared to unexposed controls (n = 25). These quantitative results were compared to self-reported health conditions.

RESULTS

Personal air samples provoked an activation of TLR2 and TLR4 HEK reporter cells in one-third of all samples, indicating that the work environment contained ligands capable of inducing an immune response in vitro. Monocyte levels, as well as plasma biomarker levels, such as IL-1Ra, IL-18 and TNFα were significantly higher in exposed workers, compared to the control group when confounding factors such as BMI, sex, age and smoking habits were accounted for. Furthermore, a significant exposure-related increase in midweek IL-8 levels was measured among exposed workers. Tendencies of increased prevalence of health effects of the respiratory tract were identified in exposed workers.

CONCLUSION

Inhalable dust provoked TLR activation in vitro, indicating that an exposure-related immune response may be expected in susceptible workers. However, despite significant differences in inflammatory plasma biomarker levels between exposed and unexposed workers, prevalence of self-reported health effects did not differ between the groups. This may be due to the healthy worker effect, or other factors such as adequate use of personal protective respiratory devices or adaptation to the work environment with reduced activation of the immune system.

Circadian, Week-to-Week, and Physical Exercise-Induced Variation of Serum Microfibrillar-Associated Protein 4

Serum microfibrillar-associated protein 4 (sMFAP4) has been investigated as a biomarker for various diseases and is demonstrated to show significant gradual increase with severity of liver fibrosis. Ideal biomarkers used for disease diagnosis or prognosis should display deviating levels in affected individuals only and be robust to factors unrelated to the disease. Here we show the impact of normal physiological variation of sMFAP4 by characterizing the circadian variation, week-to-week variation, and physical exercise-induced levels. Serum samples from 3 groups of healthy volunteers were drawn: 7 times during a 24-hour period, 5 times during a 3-week period, and before and after a standardized physical exercise challenge. sMFAP4 was determined by AlphaLISA. Statistical analysis was performed using mixed effects modeling of repeated measurements. Circadian variation of sMFAP4 was demonstrated, with time of peak and nadir values depending on age and gender. For males, the peak values were observed during nighttime whereas for females, peak values were observed in the morning. Individual sMFAP4 levels remained stable over a period of 3 weeks and physical exercise inferred a mild negative influence. In conclusion, the circadian sMFAP4 variation was significant, and the levels could be influenced by physical activity. However, these variations were of limited magnitude relative to previously observed disease-induced levels in support of the biomarker potential of sMFAP4.

Role of Non-Coding RNAs in Lung Circadian Clock Related Diseases

Circadian oscillations are regulated at both central and peripheral levels to maintain physiological homeostasis. The central circadian clock consists of a central pacemaker in the suprachiasmatic nucleus that is entrained by light dark cycles and this, in turn, synchronizes the peripheral clock inherent in other organs. Circadian dysregulation has been attributed to dysregulation of peripheral clock and also associated with several diseases. Components of the molecular clock are disrupted in lung diseases like chronic obstructive pulmonary disease (COPD), asthma and IPF. Airway epithelial cells play an important role in temporally organizing magnitude of immune response, DNA damage response and acute airway inflammation. Non-coding RNAs play an important role in regulation of molecular clock and in turn are also regulated by clock components. Dysregulation of these non-coding RNAs have been shown to impact the expression of core clock genes as well as clock output genes in many organs. However, no studies have currently looked at the potential impact of these non-coding RNAs on lung molecular clock. This review focuses on the ways how these non-coding RNAs regulate and in turn are regulated by the lung molecular clock and its potential impact on lung diseases.

Intra-individual variation of particles in exhaled air and of the contents of Surfactant protein A and albumin

INTRODUCTION

Particles in exhaled air (PEx) provide samples of respiratory tract lining fluid from small airways containing, for example, Surfactant protein A (SP-A) and albumin, potential biomarkers of small airway disease. We hypothesized that there are differences between morning, noon, and afternoon measurements and that the variability of repeated measurements is larger between days than within days.

METHODS

PEx was obtained in sixteen healthy non-smoking adults on 11 occasions, within one day and between days. SP-A and albumin were quantified by ELISA. The coefficient of repeatability (CR), intraclass correlation coefficient (ICC), and coefficient of variation (CV) were used to assess the variation of repeated measurements.

RESULTS

SP-A and albumin increased significantly from morning towards the noon and afternoon by 13% and 25% on average, respectively, whereas PEx number concentration and particle mean mass did not differ significantly between the morning, noon and afternoon. Between-day CRs were not larger than within-day CRs.

CONCLUSIONS

Time of the day influences the contents of SP-A and albumin in exhaled particles. The variation of repeated measurements was rather high but was not influenced by the time intervals between measurements.

Systematic Review and Meta-Analysis Confirms Significant Contribution of Surfactant Protein D in Chronic Obstructive Pulmonary Disease

Background: Surfactant protein D (SFTPD) is a lung specific protein which performs several key regulatory processes to maintain overall lung function. Several infectious and immune mediated diseases have been shown to be associated with SFTPD. Recent findings have suggested the serum concentration of SFTPD can be used as a diagnostic or prognostic marker for chronic obstructive pulmonary disease (COPD) and acute exacerbation COPD (AECOPD). But these findings lack replication studies from different ethnic populations and meta-analysis, to establish SFTPD as reliable diagnostic or prognostic biomarker for COPD and associated conditions.

Methods: We performed systematic literature search based on stringent inclusion and exclusion criteria to identify eligible studies to perform a meta-analysis. Our objective was to assess the predictability of serum SFTPD concentration and SFTPD allelic conformation at rs721917 (C > T) with COPD and AECOPD outcome. These variables were compared between COPD and healthy controls, where mean difference (MD), and odds ratio (OR) were calculated to predict the overall effect size. Review manager (RevMan-v5.3) software was used to analyse the data.

Results: A total of eight published reports were included in this study. Comparative serum SFTPD concentration data were extracted from six studies and three studies were evaluated for assessment of genetic marker from SFTPD. Our study identified strong association of elevated serum SFTPD with COPD and AECOPD. Significant association of risk was also observed for “T” allele or “TT” genotype of rs721917 from SFTPD with COPD and AECOPD.

Conclusion: Serum concentration and alleleic conformation of SFTPD has a significantly high predictive value for COPD and AECOPD. Thus, these can be tested further and could be applied as a predictive or prognostic marker.

INFLUENCE OF CONCOMITANT ARTERIAL HYPERTENSION ON ACTIVITY OF INFLAMMATORY PROCESS IN PATIENTS WITH COMMUNITY-ACQUIRED PNEUMONIA

The aim of the work was to determine the diagnostic value of the markers of surfactant protein D (SP-D) and C-reactive protein (C-RP) in patients with community-acquired pneumonia (CAP) with concomitant arterial hypertension (AH) and its effects on the activity of the inflammatory process. The study included 79 people. Among them, 63 patients with CAP and 16 healthy individuals who were a control group. Depending on the presence of hypertension, the patients were divided into two groups. The first group included 26 patients with CAP with AH, the second – 37 patients with CAP without AH. All patients were given general-clinical methods of examination, radiography of the chest organs in two projections. Plasma levels of SP-D and C-RP were determined. Reliable connection (p<0.05) was determined between the presence of AH and the probability of occurrence of CAP (OR - odds ratio 2.27 [95 % CI 1.05–4.94]). The level of SP-D and C-RP in patients with AH on the first day was significantly higher than in healthy subjects (p<0.05). In patients in the first group, SP-D levels were significantly higher (p<0.05) for the first, third and ninth day relative to the second group. The existence of a direct tie of average strength between the presence of AH and SP-D (R=0.41, p<0.05) has been determined. The presence of a direct correlation link of mean strength (R=0.38; p<0.05) between the AH and the level of C-RP indicates that arterial hypertension in patients with CAP increases the activity of the systemic inflammatory response.

Surfactant Protein D in Respiratory and Non-Respiratory Diseases

Surfactant protein D (SP-D) is a multimeric collectin that is involved in innate immune defense and expressed in pulmonary, as well as non-pulmonary, epithelia. SP-D exerts antimicrobial effects and dampens inflammation through direct microbial interactions and modulation of host cell responses via a series of cellular receptors. However, low protein concentrations, genetic variation, biochemical modification, and proteolytic breakdown can induce decomposition of multimeric SP-D into low-molecular weight forms, which may induce pro-inflammatory SP-D signaling. Multimeric SP-D can decompose into trimeric SP-D, and this process, and total SP-D levels, are partly determined by variation within the SP-D gene, SFTPD. SP-D has been implicated in the development of respiratory diseases including respiratory distress syndrome, bronchopulmonary dysplasia, allergic asthma, and chronic obstructive pulmonary disease. Disease-induced breakdown or modifications of SP-D facilitate its systemic leakage from the lung, and circulatory SP-D is a promising biomarker for lung injury. Moreover, studies in preclinical animal models have demonstrated that local pulmonary treatment with recombinant SP-D is beneficial in these diseases. In recent years, SP-D has been shown to exert antimicrobial and anti-inflammatory effects in various non-pulmonary organs and to have effects on lipid metabolism and pro-inflammatory effects in vessel walls, which enhance the risk of atherosclerosis. A common SFTPD polymorphism is associated with atherosclerosis and diabetes, and SP-D has been associated with metabolic disorders because of its effects in the endothelium and adipocytes and its obesity-dampening properties. This review summarizes and discusses the reported genetic associations of SP-D with disease and the clinical utility of circulating SP-D for respiratory disease prognosis. Moreover, basic research on the mechanistic links between SP-D and respiratory, cardiovascular, and metabolic diseases is summarized. Perspectives on the development of SP-D therapy are addressed.

Surfactant protein D multimerization and gene polymorphism in COPD and asthma

BACKGROUND AND OBJECTIVE

A structural single nucleotide polymorphism rs721917 in the surfactant protein D (SP-D) gene, known as Met11Thr, was reported to influence the circulating levels and degree of multimerization of SP-D and was associated with both COPD and atopy in asthma. Moreover, disease-related processes are known to degrade multimerized SP-D, however, the degree of the protein degradation in these diseases is not clarified. We aimed to determine the distribution of multimerized (high molecular weight (HMW)) and non-multimerized (low molecular weight (LMW)) species of serum SP-D and their correlation with genetic polymorphisms and presence of disease in Lebanese COPD and asthmatic patients.

METHODS

Serum SP-D levels were measured by ELISA in 88 COPD, 121 asthmatic patients and 223 controls. Randomly selected subjects were chosen for genotyping of rs721917 and multimerization studies. HMW and LMW SP-D were separated by gel permeation chromatography.

RESULTS

Serum SP-D levels were significantly increased in patients with COPD, but not in asthmatic patients, when compared to controls. Met11Thr variation strongly affected serum SP-D levels and the degree of multimerization, but was not associated with COPD and asthma in the study. Remarkably, HMW/LMW serum SP-D ratio was significantly lower in Met11/Met11 COPD and asthmatic patients compared to controls.

CONCLUSION

Collectively, non-multimerized species of serum SP-D were dominant in COPD and asthmatic patients suggesting that degradation of SP-D takes place to a significant degree in pulmonary disease. Assays that can separate SP-D proteolytic breakdown products or modified forms from naturally occurring SP-D trimers may result in optimal disease markers for pulmonary inflammatory diseases.

Disruption of Sirtuin 1-Mediated Control of Circadian Molecular Clock and Inflammation in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is the fourth most common cause of death, and it is characterized by abnormal inflammation and lung function decline. Although the circadian molecular clock regulates inflammatory responses, there is no information available regarding the impact of COPD on lung molecular clock function and its regulation by sirtuin 1 (SIRT1). We hypothesize that the molecular clock in the lungs is disrupted, leading to increased inflammatory responses in smokers and patients with COPD and its regulation by SIRT1. Lung tissues, peripheral blood mononuclear cells (PBMCs), and sputum cells were obtained from nonsmokers, smokers, and patients with COPD for measurement of core molecular clock proteins (BMAL1, CLOCK, PER1, PER2, and CRY1), clock-associated nuclear receptors (REV-ERBα, REV-ERBβ, and RORα), and SIRT1 by immunohistochemistry, immunofluorescence, and immunoblot. PBMCs were treated with the SIRT1 activator SRT1720 followed by LPS treatment, and supernatant was collected at 6-hour intervals. Levels of IL-8, IL-6, and TNF-α released from PBMCs were determined by ELISA. Expression of BMAL1, PER2, CRY1, and REV-ERBα was reduced in PBMCs, sputum cells, and lung tissues from smokers and patients with COPD when compared with nonsmokers. SRT1720 treatment attenuated LPS-mediated reduction of BMAL1 and REV-ERBα in PBMCs from nonsmokers. Additionally, LPS differentially affected the timing and amplitude of cytokine (IL-8, IL-6, and TNF-α) release from PBMCs in nonsmokers, smokers, and patients with COPD. Moreover, SRT1720 was able to inhibit LPS-induced cytokine release from cultured PBMCs. In conclusion, disruption of the molecular clock due to SIRT1 reduction contributes to abnormal inflammatory response in smokers and patients with COPD.

Surfactant protein D, a clinical biomarker for chronic obstructive pulmonary disease with excellent discriminant values

Biological markers can help to better identify a disease or refine its diagnosis. In the present study, the association between surfactant protein D (SP-D) and chronic obstructive pulmonary disease (COPD) was studied among subjects consulting for respiratory diseases or symptoms and was compared with C-reactive protein (CRP) and fibrinogen. A further aim of this study was to identify the optimal cut-off point of SP-D able to discriminate COPD patients. A case-control study including 90 COPD patients, 124 asthma patients and 180 controls was conducted. Standardized questionnaires were administered and lung function tests were performed. Biological markers were measured in blood samples according to standardized procedures. The association between SP-D and COPD was investigated using logistic regression models. Receiver-operating characteristic curves were used for threshold identification. SP-D levels above the median value were positively associated with COPD [adjusted odds ratio (OR)=3.86, 95% confidence interval (CI): 1.51-9.85, P=0.005). No associations with COPD or asthma were found for CRP or fibrinogen levels. Scores for COPD diagnosis in all COPD patients or ever-smoker COPD patients were identified (sensitivity, 76.4 and 77.8%; specificity, 89.3 and 88.5%, respectively). The results indicate that SP-D can differentiate COPD from other respiratory symptoms or diseases. Used with socio-demographic characteristics and respiratory symptoms, SP-D is able to discriminate COPD patients from controls, particularly among smokers.

Factors influencing the measurement of plasma/serum surfactant protein D levels by ELISA

Background

Extensive variations in human surfactant protein D (SP-D) levels in circulation as measured by ELISA exist in the published literature. In order to determine the source of these variations, factors influencing the measurement by ELISA were explored.

Materials and Methods

Peripheral blood from healthy individuals was collected into various vacutainers during the same blood draw. Recombinant SP-D was diluted into different matrices and used for a standard curve. Samples were analyzed by capture ELISA using one of two distinct detection antibodies.

Results

The type of matrix had some effects on detection of recombinant SP-D. The type of anticoagulant used and dilution factor had very little effect, except for in plasma collected in EDTA vacutainers. The extent of variation in published values seemed to be due to the ELISA configuration employed, and, in agreement with this, we found that by switching the detection antibody, there was a 50% decrease in the extrapolated SP-D value of serum and plasma samples. Storage of samples resulted in slight changes in measured SP-D levels.

Conclusions

The ELISA configuration employed to measure circulating levels of SP-D has a significant effect on the extrapolated values. In both configurations tested, the use of EDTA as a coagulant resulted in inconsistent values, and we, therefore, suggest the avoidance of this anticoagulant when assaying for SP-D by ELISA. While the demonstrated effects of several factors on measurement of SP-D may not account for all the disparities amongst the previous studies, they stress that variations in methodologies for measuring the same protein can result in very inconsistent results.

Role of serum and induced sputum surfactant protein D in predicting the response to treatment in chronic obstructive pulmonary disease

This study was designed to determine the expression of serum and sputum surfactant protein D (SP-D) in chronic obstructive pulmonary disease (COPD) and its association with treatment response. Sixty-five treatment-naive patients with COPD and 26 normal control subjects were recruited in the study. The concentrations of serum and sputum SP-D were measured, and the associations of SP-D with pulmonary function and the modified Medical Research Council dyspnea scale (mMRC) and the St. George's Respiratory Questionnaire (SGRQ) scores before and after three months of treatment with an inhaled corticosteroid and a long-acting β2-agonist were analyzed. The concentrations of serum and sputum SP-D in the COPD group (45.46±37.78 and 173.23±186.93 ng/ml, respectively) were significantly higher than those of the normal control group (31.68±12.04 and 89.59±70.29 ng/ml, respectively). After three months of treatment, serum SP-D levels were reduced to 30.7±13.9 ng/ml and were significantly lower than the baseline levels (t=2.217, P=0.031). However, no significant reduction in sputum SP-D levels was observed following the treatment (P>0.05). A significant association between baseline sputum SP-D and change in SGRQ activity scores (r=-0.652, P=0.012) was observed; however no association was established with the changes in other clinical profiles following the treatment (P>0.05). This result suggested that an increased baseline sputum SP-D may be a weak predictive indicator of response to treatment with inhaled corticosteroids and long-acting β2-agonists in patients with COPD.

Circadian clock function is disrupted by environmental tobacco/cigarette smoke, leading to lung inflammation and injury via a SIRT1-BMAL1 pathway

Patients with obstructive lung diseases display abnormal circadian rhythms in lung function. We determined the mechanism whereby environmental tobacco/cigarette smoke (CS) modulates expression of the core clock gene BMAL1, through Sirtuin1 (SIRT1) deacetylase during lung inflammatory and injurious responses. Adult C57BL6/J and various mice mutant for SIRT1 and BMAL1 were exposed to both chronic (6 mo) and acute (3 and 10 d) CS, and we measured the rhythmic expression of clock genes, circadian rhythms of locomotor activity, lung function, and inflammatory and emphysematous responses in the lungs. CS exposure (100-300 mg/m(3) particulates) altered clock gene expression and reduced locomotor activity by disrupting the central and peripheral clocks and increased lung inflammation, causing emphysema in mice. BMAL1 was acetylated and degraded in the lungs of mice exposed to CS and in patients with chronic obstructive pulmonary disease (COPD), compared with lungs of the nonsmoking controls, linking it mechanistically to CS-induced reduction of SIRT1. Targeted deletion of Bmal1 in lung epithelium augmented inflammation in response to CS, which was not attenuated by the selective SIRT1 activator SRT1720 (EC50=0.16 μM) in these mice. Thus, the circadian clock, specifically the enhancer BMAL1 in epithelium, plays a pivotal role, mediated by SIRT1-dependent BMAL1, in the regulation of CS-induced lung inflammatory and injurious responses.

Serum surfactant protein D is associated with the prognosis in patients with chronic kidney disease

BACKGROUND

Circulating surfactant protein D (SP-D) has been proved to be associated with cardiovascular disease and total mortality in European patients with coronary artery disease (CAD). This study was to determine whether serum SP-D levels are associated with 1-year prognosis in patients with chronic kidney disease (CKD) in a Chinese population.

METHODS

Serum SP-D levels were examined by ELISA kit in 264 patients undergoing coronary angiography. An estimated glomerular filtration rate (eGFR) was used to determine the presence of CKD. Gensini scores were calculated to reflect the severity of coronary lesions. The correlations between SP-D, Gensini scores, white blood cells, high-sensitivity C-reactive protein (hs-CRP) and eGFR were calculated. Patients with eGFR less than 60 ml/min per 1.73 m2 were followed up for an average of 14 months, and major adverse cardiac events (MACEs) were recorded and analyzed.

RESULTS

Patients with CKD compared with patients without CKD were more often men, with a higher prevalence of hypertension, CAD, average age, levels of fasting glucose, hs-CRP and SP-D (179.73 ± 72.80 versus 131.65 ± 94.29 ng/ml; all P < 0.05). Serum SP-D levels were positively correlated with Gensini scores and eGFR, but not with white blood cells or hs-CRP. CKD patients suffering from MACEs had higher levels of serum SP-D (217.02 ± 102.34 versus 172.26 ± 70.27 ng/ml) and patients with SP-D at least 200 ng/ml had higher risk of MACEs (all P < 0.05). Multivariable analysis showed that smoking, multivessel disease, CKD and SP-D (OR: 1.396, 95% CI: 1.058-2.718, P = 0.028) were associated with 1-year MACEs (all P < 0.05).

CONCLUSION

SP-D levels are associated with 1-year prognosis in patients with CKD.

Effects on airways of short-term exposure to two kinds of wood smoke in a chamber study of healthy humans

INTRODUCTION

Air pollution causes respiratory symptoms and pulmonary disease. Airway inflammation may be involved in the mechanism also for cardiovascular disease. Wood smoke is a significant contributor to air pollution, with complex and varying composition. We examined airway effects of two kinds of wood smoke in a chamber study.

MATERIALS AND METHODS

Thirteen subjects were exposed to filtered air and to wood smoke from the start-up phase and the burn-out phase of the wood-burning cycle. Levels of PM(2.5) were 295 µg/m(3) and 146 µg/m(3), number concentrations 140 000/cm(3) and 100 000/cm(3). Biomarkers in blood, breath and urine were measured before and on several occasions after exposure. Effects of wood smoke exposure were assessed adjusting for results with filtered air.

RESULTS

After exposure to wood smoke from the start-up, but not the burn-out session, Clara cell protein 16 (CC16) increased in serum after 4 hours, and in urine the next morning. CC16 showed a clear diurnal variation. Fraction of exhaled nitric oxide (FENO) increased after wood smoke exposure from the burn-out phase, but partly due to a decrease after exposure to filtered air. No other airway markers increased.

CONCLUSIONS

The results indicate that relatively low levels of wood smoke exposure induce effects on airways. Effects on airway epithelial permeability was shown for the start-up phase of wood burning, while FENO increased after the burn-out session. CC16 seems to be a sensitive marker of effects of air pollution both in serum and urine, but its function and the significance need to be clarified.

Circadian rhythms: from basic mechanisms to the intensive care unit

OBJECTIVE

: Circadian rhythms are intrinsic timekeeping mechanisms that allow for adaptation to cyclic environmental changes. Increasing evidence suggests that circadian rhythms may influence progression of a variety of diseases as well as effectiveness and toxicity of drugs commonly used in the intensive care unit. In this perspective, we provide a brief review of the molecular mechanisms of circadian rhythms and its relevance to critical care. DATA SOURCES, STUDY SELECTION, DATA EXTRACTION, AND DATA SYNTHESIS:: Articles related to circadian rhythms and organ systems in normal and disease conditions were searched through the PubMed library with the goal of providing a concise review.

CONCLUSIONS

: Critically ill patients may be highly vulnerable to disruption of circadian rhythms as a result of the severity of their underlying diseases as well as the intensive care unit environment where noise and frequent therapeutic/diagnostic interventions take place. Further basic and clinical research addressing the importance of circadian rhythms in the context of critical care is warranted to develop a better understanding of the complex pathophysiology of critically ill patients as well as to identify novel therapeutic approaches for these patients.

Lung function in volunteers before and after exposure to trichloramine in indoor pool environments and asthma in a cohort of pool workers

OBJECTIVES

Exposure to trichloramine (NCl(3)) in indoor swimming-pool environments is known to cause mucous membrane irritation, but if it gives rise to changes in lung function or asthma in adults is not known. (1) We determined lung function in volunteers before and after exposure to indoor pool environments. (2) We studied the occurrence of respiratory symptoms and asthma in a cohort of pool workers. DESIGN/METHODS/PARTICIPANTS: (1) We studied two groups of volunteers, 37 previously non-exposed healthy persons and 14 pool workers, who performed exercise for 2 h in an indoor pool environment. NCl(3) in air was measured during pool exposures and in 10 other pool environments. Filtered air exposures were used as controls. Lung function and biomarkers of pulmonary epithelial integrity were measured before and after exposure. (2) We mailed a questionnaire to 1741 persons who indicated in the Swedish census 1990 that they worked at indoor swimming-pools.

RESULTS

(1) In previously non-exposed volunteers, statistically significant decreases in FEV(1) (forced expiratory volume) and FEV(%) (p=0.01 and 0.05, respectively) were found after exposure to pool air (0.23 mg/m(3) of NCl(3)). In pool workers, a statistically significant decrease in FEV(%) (p=0.003) was seen (but no significant change of FEV(1))(.) In the 10 other pool environments the median NCl(3) concentration was 0.18 mg/m(3). (2) Our nested case/control study in pool workers found an OR for asthma of 2.31 (95% CI 0.79 to 6.74) among those with the highest exposure. Exposure-related acute mucous membrane and respiratory symptoms were also found.

CONCLUSIONS

This is the first study in adults showing statistically significant decreases in lung function after exposure to NCl(3). An increased OR for asthma among highly exposed pool workers did not reach statistical significance, but the combined evidence supports the notion that current workroom exposures may contribute to asthma development. Further research on sensitive groups is warranted.

Genetic variant associations of human SP-A and SP-D with acute and chronic lung injury

Pulmonary surfactant, a lipoprotein complex, maintains alveolar integrity and plays an important role in lung host defense, and control of inflammation. Altered inflammatory processes and surfactant dysfunction are well described events that occur in patients with acute or chronic lung disease that can develop secondary to a variety of insults. Genetic variants of surfactant proteins, including single nucleotide polymorphisms, haplotypes, and other genetic variations have been associated with acute and chronic lung disease throughout life in several populations and study groups. The hydrophilic surfactant proteins SP-A and SP-D, also known as collectins, in addition to their surfactant-related functions, are important innate immunity molecules as these, among others, exhibit the ability to bind and enhance clearance of a wide range of pathogens and allergens. This review focuses on published association studies of human surfactant proteins A and D genetic polymorphisms with respiratory, and non-respiratory diseases in adults, children, and newborns. The potential role of genetic variations in pulmonary disease or pathogenesis is discussed following an evaluation, and comparison of the available literature.

Circulating levels of Clara cell protein 16 but not surfactant protein D identify and quantify lung damage in patients with multiple injuries

BACKGROUND

Almost 60% of all patients with severe multiple injuries sustain severe chest trauma with aggravating effect on morbidity and mortality. Diagnosis of lung contusion is performed by early posttraumatic multislice computed tomography. Because this diagnostic procedure requires time, resources, and exposure to radiation, a noninvasive approach with easy follow-up measurements is warranted.

METHODS

Serum levels of Clara cell protein 16 (CC16) and surfactant protein D as lung-specific biomarkers were obtained on admission from 104 patients with multiple injuries using enzyme-linked immunosorbent assay technique. Patients were divided into those with severe lung injury ([LI]; n = 68) and without LI (NLI; n = 36). Nonsmoking healthy volunteers served as controls. In addition, volume of lung contusions were calculated planimetrically on serial multislice computed tomography scans obtained after admission. Factors influencing CC16 serum levels were determined in uni- and multivariate analyses, and Spearman rank coefficients were calculated for correlations.

RESULTS

Patients with LI showed a significant (p < 0.05) elevation of median CC16 levels (10.2 ng/mL) compared with NLI patients (5.4 ng/mL) and controls (5.2 ng/mL). Serum CC16 levels correlated with the volume of lung contusions (r = 0.78, p < 0.0001) and were not influenced by overall injury severity, age, gender, or preclinical ventilation. In contrast, circulating surfactant protein D levels were not associated with the presence of LI or the extent of lung contusions.

CONCLUSIONS

Our results advocate CC16 as a potential biomarker for LI in severely injured patients because of its high correlation with the volume of contused lung parenchyma. Therefore, this parameter may allow a specified initial treatment of patients with multiple injuries.

Serum concentration of surfactant protein D in horses with lower airway inflammation

REASONS FOR PERFORMING STUDY

Surfactant protein D (SP-D), mainly synthesised by alveolar type II cells and nonciliated bronchiolar cells, is one important component of innate pulmonary immunity. In man, circulating concentrations of SP-D are routinely used as biomarkers for pulmonary injury. To date, serum SP-D levels have only been investigated in horses in an experimental model of bacterial airway infection.

OBJECTIVES

To compare serum SP-D concentrations at rest and after exercise in horses with and without inflammatory airway disease (IAD).

METHODS

Venous blood samples were collected from 42 Standardbred racehorses at rest and 60 min after performing a standardised treadmill exercise test. Tracheal wash and bronchoalveolar lavage fluid (BALF) samples were collected after exercise. Based on BALF cytology, 22 horses were defined as IAD-affected and 20 classified as controls. Serum SP-D concentrations were assessed using a commercially available ELISA kit and statistically compared between groups of horses and sampling times.

RESULTS

Serum concentrations of SP-D in IAD-affected horses were significantly higher than those of control horses, both at rest and after exercise. Within the IAD-affected group, no significant correlation was found between serum SP-D concentrations and BALF cytology. Within each group of horses (IAD and control), no significant influence of exercise was found on serum SP-D levels.

CONCLUSIONS

This is the first study determining serum SP-D concentrations in a noninfectious, naturally occurring form of lower airway inflammation in horses. The results highlight that IAD is associated with a detectable, though moderate, increase of circulating SP-D levels.

POTENTIAL RELEVANCE

Serum concentration of surfactant protein D could represent a potentially valuable and readily accessible blood biomarker of equine lower airway inflammation.

Comprehensive characterisation of pulmonary and serum surfactant protein D in COPD

Background

Pulmonary surfactant protein D (SP-D) is considered as a candidate biomarker for the functional integrity of the lung and for disease progression, which can be detected in serum. The origin of SP-D in serum and how serum concentrations are related to pulmonary concentrations under inflammatory conditions is still unclear.

Methods

In a cross-sectional study comprising non-smokers (n = 10), young - (n = 10), elderly smokers (n = 20), and smokers with COPD (n = 20) we simultaneously analysed pulmonary and serum SP-D levels with regard to pulmonary function, exercise, repeatability and its quaternary structure by native gel electrophoresis. Statistical comparisons were conducted by ANOVA and post-hoc testing for multiple comparisons; repeatability was assessed by Bland-Altman analysis.

Results

In COPD, median (IQR) pulmonary SP-D levels were lower (129(68) ng/ml) compared to smokers (young: 299(190), elderly: 296(158) ng/ml; p < 0.01) and non-smokers (967(708) ng/ml; p < 0.001). The opposite was observed in serum, with higher concentrations in COPD (140(89) ng/ml) as compared to non-smokers (76(47) ng/ml; p < 0.01). SP-D levels were reproducible and correlated with the degree of airway obstruction in all smokers. In addition, smoking lead to disruption of the quaternary structure.

Conclusions

Pulmonary and serum SP-D levels are stable markers influenced by smoking and related to airflow obstruction and disease state. Smaller subunits of pulmonary SP-D and the rapid increase of serum SP-D levels in COPD due to exercise support the translocation hypothesis and its use as a COPD biomarker.

Trial registration

no interventional trial