SP-D and regulation of the pulmonary innate immune system in allergic airway changes

Primary immunodeficiency-related genes and varicella-zoster virus reactivation syndrome: a Mendelian randomization study

Background

Currently, evidence regarding the causal relationship between primary immunodeficiency-related genes and varicella-zoster virus reactivation syndrome is limited and inconsistent. Therefore, this study employs Mendelian randomization (MR) methodology to investigate the causal relationship between the two.

Methods

This study selected 110 single-nucleotide polymorphisms (SNPs) of primary immunodeficiency-related genes as instrumental variables (IVs). Genetic associations of primary immunodeficiency-related genes were derived from recent genome-wide association studies (GWAS) data on human plasma protein levels and circulating immune cells. Data on genes associated with varicella-zoster virus reactivation syndrome were obtained from the GWAS Catalog and FINNGEN database, primarily analyzed using inverse variance weighting (IVW) and sensitivity analysis.

Results

Through MR analysis, we identified 9 primary immunodeficiency-related genes causally associated with herpes zoster and its subsequent neuralgia; determined causal associations of 20 primary immunodeficiency-related genes with three vascular lesions (stroke, cerebral aneurysm, giant cell arteritis); revealed causal associations of 10 primary immunodeficiency-related genes with two ocular diseases (retinopathy, keratitis); additionally, three primary immunodeficiency-related genes each were associated with encephalitis, cranial nerve palsy, and gastrointestinal infections.

Conclusions

This study discovers a certain association between primary immunodeficiency-related genes and varicella-zoster virus reactivation syndrome, yet further investigations are warranted to explore the specific mechanisms underlying these connections.

COPD with elevated sputum group 2 innate lymphoid cells is characterized by severe disease

Rationale

Pulmonary innate immune cells play a central role in the initiation and perpetuation of chronic obstructive pulmonary disease (COPD), however the precise mechanisms that orchestrate the development and severity of COPD are poorly understood.

Objectives

We hypothesized that the recently described family of innate lymphoid cells (ILCs) play an important role in COPD.

Methods

Subjects with COPD and healthy controls were clinically evaluated, and their sputum samples were assessed by flow cytometry. A mouse model of spontaneous COPD [genetically deficient in surfactant protein-D (SP-D -/- )] and ozone (O 3 ) exposure were used to examine the mechanism by which lack of functional SP-D may skew ILC2s to produce IL-17A in combination with IL-5 and IL-13, leading to a mixed inflammatory profile and more severe disease.

Measurements and Main Results

COPD was characterized by poor spirometry, sputum inflammation, and the emergence of sputum GATA3 + ILCs (ILC2s), but not T-bet + ILCs (ILC1s) nor RORγt + ILCs (ILC3s). COPD subjects with elevated sputum ILC2s (the ILC2 high group) had worse spirometry and sputum neutrophilia and eosinophilia than healthy and ILC2 low subjects. This was associated with the presence of dual-positive IL-5 + IL-17A + and IL-13 + IL-17A + ILCs and nonfunctional SP-D in the sputum in ILC2 high subjects. SP-D -/- mice showed spontaneous airway neutrophilia. Lack of SP-D in the mouse lung licensed ILC2s to produce IL-17A, which was dose-dependently inhibited by recombinant SP-D. SP-D -/- mice showed enhanced susceptibility to O 3 -induced airway neutrophilia, which was associated with the emergence of inflammatory IL-13 + IL-17A + ILCs.

Conclusions

We report that the presence of sputum ILC2s predicts the severity of COPD, and unravel a novel pathway of IL-17A plasticity in lung ILC2s, prevented by the immunomodulatory protein SP-D.

[Lung-protective effect of esketamine combined with distal limb ischemic preconditioning in elderly patients undergoing thoracoscopic radical surgery for lung cancer: a randomized controlled trial in 160 cases]

OBJECTIVE

To evaluate the effect of esketamine combined with distal limb ischemic preconditioning (LIP) for lung protection in elderly patients undergoing thoracoscopic radical surgery for lung cancer.

METHODS

This randomized trial was conducted in 160 patients undergoing elective thoracoscopic surgery for lung cancer, who were randomized into control group (with saline injection and sham LIP), esketamine group, LIP group, and esketamine + LIP group (n=40). Before anesthesia induction, according to the grouping, the patients received an intravenous injection with 0.5 mg/kg esketamine or 10 ml saline (in control group). LIP was induced by applying a tourniquet 1-2 cm above the popliteal fossa in the left lower limb to block the blood flow for 5 min for 3 times at the interval of 5 min, and sham LIP was performed by applying the tourniquet without pressurization for 30 min. Oxygenation index (OI) and alveolar-arterial PO2 difference (A-aDO2) were calculated before induction (T0), at 30 min (T0.5) and 1 h (T1) of one-lung ventilation (OLV), and at 1 h after two-lung ventilation (T3). Serum levels of SP-D, CC-16 and TNF-α were measured by ELISA at T0, T1, T2 (2 h of OLV), T3, and 24 h after the operation (T4). The length of hospital stay and postoperative pulmonary complications of the patients were recorded.

RESULTS

Compared with those in the control group, the patients in the other 3 groups had significantly lower CC-16, SP-D and TNF-α levels, shorter hospital stay, and lower incidences of lung infection and lung atelectasis (all P < 0.05). Serum CC-16, SP-D and TNF-α levels, hospital stay, incidences of complications were significantly lower or shorter in the combined treatment group than in esketamine group and LIP group (all P < 0.05).

CONCLUSION

In elderly patients undergoing thoracoscopic radical surgery for lung cancer, treatment with esketamine combined with LIP can alleviate acute lung injury by enhancing anti-inflammatory response to shorten postoperative hospital stay, reduce lung complications and promote the patients' recovery.

Pulmonary Surfactant: A Mighty Thin Film

Pulmonary surfactant is a critical component of lung function in healthy individuals. It functions in part by lowering surface tension in the alveoli, thereby allowing for breathing with minimal effort. The prevailing thinking is that low surface tension is attained by a compression-driven squeeze-out of unsaturated phospholipids during exhalation, forming a film enriched in saturated phospholipids that achieves surface tensions close to zero. A thorough review of past and recent literature suggests that the compression-driven squeeze-out mechanism may be erroneous. Here, we posit that a surfactant film enriched in saturated lipids is formed shortly after birth by an adsorption-driven sorting process and that its composition does not change during normal breathing. We provide biophysical evidence for the rapid formation of an enriched film at high surfactant concentrations, facilitated by adsorption structures containing hydrophobic surfactant proteins. We examine biophysical evidence for and against the compression-driven squeeze-out mechanism and propose a new model for surfactant function. The proposed model is tested against existing physiological and pathophysiological evidence in neonatal and adult lungs, leading to ideas for biophysical research, that should be addressed to establish the physiological relevance of this new perspective on the function of the mighty thin film that surfactant provides.

Mechanisms of ag85a/b DNA vaccine conferred immunotherapy and recovery from Mycobacterium tuberculosis-induced injury

Our previous research developed a novel tuberculosis (TB) DNA vaccine ag85a/b that showed a significant therapeutic effect on the mouse tuberculosis model by intramuscular injection (IM) and electroporation (EP). However, the action mechanisms between these two vaccine immunization methods remain unclear. In a previous study, 96 Mycobacterium tuberculosis (MTB) H37 Rv-infected BALB/c mice were treated with phosphate-buffered saline, 10, 50, 100, and 200 μg ag85a/b DNA vaccine delivered by IM and EP three times at 2-week intervals, respectively. In this study, peripheral blood mononuclear cells (PBMCs) from three mice in each group were isolated to extract total RNA. The gene expression profiles were analyzed using gene microarray technology to obtain differentially expressed (DE) genes. Finally, DE genes were validated by real-time reverse transcription-quantitive polymerase chain reaction and the GEO database. After MTB infection, most of the upregulated DE genes were related to the digestion and absorption of nutrients or neuroendocrine (such as Iapp, Scg2, Chga, Amy2a5), and most of the downregulated DE genes were related to cellular structural and functional proteins, especially the structure and function proteins of the alveolar epithelial cell (such as Sftpc, Sftpd, Pdpn). Most of the abnormally upregulated or downregulated DE genes in the TB model group were recovered in the 100 and 200 μg ag85a/b DNA IM groups and four DNA EP groups. The pancreatic secretion pathway downregulated and the Rap1 signal pathway upregulated had particularly significant changes during the immunotherapy of the ag85a/b DNA vaccine on the mouse TB model. The action targets and mechanisms of IM and EP are highly consistent. Tuberculosis infection causes rapid catabolism and slow anabolism in mice. For the first time, we found that the effective dose of the ag85a/b DNA vaccine immunized whether by IM or EP could significantly up-regulate immune-related pathways and recover the metabolic disorder and the injury caused by MTB.

SP-A binding to the SARS-CoV-2 spike protein using hybrid quantum and classical in silico modeling and molecular pruning by Quantum Approximate Optimization Algorithm (QAOA) Based MaxCut with ZDOCK

The pulmonary surfactant protein A (SP-A) is a constitutively expressed immune-protective collagenous lectin (collectin) in the lung. It binds to the cell membrane of immune cells and opsonizes infectious agents such as bacteria, fungi, and viruses through glycoprotein binding. SARS-CoV-2 enters airway epithelial cells by ligating the Angiotensin Converting Enzyme 2 (ACE2) receptor on the cell surface using its Spike glycoprotein (S protein). We hypothesized that SP-A binds to the SARS-CoV-2 S protein and this binding interferes with ACE2 ligation. To study this hypothesis, we used a hybrid quantum and classical in silico modeling technique that utilized protein graph pruning. This graph pruning technique determines the best binding sites between amino acid chains by utilizing the Quantum Approximate Optimization Algorithm (QAOA)-based MaxCut (QAOA-MaxCut) program on a Near Intermediate Scale Quantum (NISQ) device. In this, the angles between every neighboring three atoms were Fourier-transformed into microwave frequencies and sent to a quantum chip that identified the chemically irrelevant atoms to eliminate based on their chemical topology. We confirmed that the remaining residues contained all the potential binding sites in the molecules by the Universal Protein Resource (UniProt) database. QAOA-MaxCut was compared with GROMACS with T-REMD using AMBER, OPLS, and CHARMM force fields to determine the differences in preparing a protein structure docking, as well as with Goemans-Williamson, the best classical algorithm for MaxCut. The relative binding affinity of potential interactions between the pruned protein chain residues of SP-A and SARS-CoV-2 S proteins was assessed by the ZDOCK program. Our data indicate that SP-A could ligate the S protein with a similar affinity to the ACE2-Spike binding. Interestingly, however, the results suggest that the most tightly-bound SP-A binding site is localized to the S2 chain, in the fusion region of the SARS-CoV-2 S protein, that is responsible for cell entry Based on these findings we speculate that SP-A may not directly compete with ACE2 for the binding site on the S protein, but interferes with viral entry to the cell by hindering necessary conformational changes or the fusion process.

Understanding the role of S-nitrosylation/nitrosative stress in inflammation and the role of cellular denitrosylases in inflammation modulation: Implications in health and diseases

S-nitrosylation is a very fundamental post-translational modification of protein and non-protein thiols due the involvement of it in a variety of cellular processes including activation/inhibition of several ion channels such as ryanodine receptor in the cardiovascular system; blood vessel dilation; cGMP signaling and neurotransmission. S-nitrosothiol homeostasis in the cell is tightly regulated and perturbations in homeostasis result in an altered redox state leading to a plethora of disease conditions. However, the exact role of S-nitrosylated proteins and nitrosative stress metabolites in inflammation and in inflammation modulation is not well-reviewed. The cell utilizes its intricate defense mechanisms i.e. cellular denitrosylases such as Thioredoxin (Trx) and S-nitrosoglutathione reductase (GSNOR) systems to combat nitric oxide (NO) pathology which has also gained current attraction as novel anti-inflammatory molecules. This review attempts to provide state-of-the-art knowledge from past and present research on the mechanistic role of nitrosative stress intermediates (RNS, OONO^-, PSNO) in pulmonary and autoimmune diseases and how cellular denitrosylases particularly GSNOR and Trx via imparting opposing effects can modulate and reduce inflammation in several health and disease conditions. This review would also bring into notice the existing gaps in current research where denitrosylases can be utilized for ameliorating inflammation that would leave avenues for future therapeutic interventions.

Research article expression of surfactant protein-A and D, and CD9 in lungs of 1 and 30 day old foals

Background

Respiratory diseases are a major cause of morbidity and mortality in the horses of all ages including foals. There is limited understanding of the expression of immune molecules such as tetraspanins and surfactant proteins (SP) and the regulation of the immune responses in the lungs of the foals. Therefore, the expression of CD9, SP-A and SP-D in foal lungs was examined.

Results

Lungs from one day old (n = 6) and 30 days old (n = 5) foals were examined for the expression of CD9, SP-A, and SP-D with immunohistology and Western blots. Western blot data showed significant increase in the amount of CD9 protein (p = 0.0397) but not of SP-A and SP-D at 30 days of age compared to one day. Immunohistology detected CD9 in the alveolar septa and vascular endothelium but not the bronchiolar epithelium in the lungs of the foals in both age groups. SP-A and SP-D expression was localized throughout the alveolar septa including type II alveolar epithelial cells and the vascular endothelium of the lungs in all the foals. Compared to one day old foals, the expression of SP-A and SP-D appeared to be increased in the bronchiolar epithelium of 30 day old foals. Pulmonary intravascular macrophages were also positive for SP-A and SP-D in 30 days old foals and these cells are not developed in the day old foals.

Conclusions

This is the first data on the expression of CD9, SP-A and SP-D in the lungs of foals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02943-5.

A community study of the risk for obstructive sleep apnea and respiratory inflammation in an adult Chinese population

Objectives: We aimed to investigate the relationship between obstructive sleep apnea (OSA) risk and respiratory inflammation evaluated by the exhaled breath condensate (EBC) interleukin-6 (IL-6) and plasma surfactant protein-D (SP-D), based on the Berlin questionnaire (BQ) screening values in an adult, urban community in Beijing, China.Methods: Volunteers aged >40 years were recruited from the Shichahai community of central Beijing (Registration number: NCT04832711). Their general information and disease history were recorded. OSA risk was assessed using the BQ. IL-6 in EBC and plasma SP-D were d etected by enzyme-linked immunoassay through specimens collected while fasting. The differences in IL-6 and SP-D values between high-risk and low-risk groups for OSA were compared, and the factors affecting their values were analyzed.Results: Among 1,239 participants, 18.8% of participants were in the high-risk group. There were more participants with higher body mass index, chronic hypertension, coronary heart disease, and diabetes in the high-risk group than in the low-risk group (P < 0.05). There were no significant differences in EBC IL-6 and plasma SP-D between the high- and low-OSA risk groups (p > 0.05). After adjustment for age, sex and chronic comorbidities, multivariate logistic regression showed that there was no correlation between risk of OSA and IL-6 in EBC. However, the risk of OSA (odds ratio [OR] [95% CI]: 1.69 [1.15,2.48]; β = 0.522) and BMI (OR [95%CI]: 0.94 [0.91,0.98]; β = -0.061) were independently associated with plasma SP-D level (p < 0.05 for both). Stratification analysis showed that OSA risk were independently associated with plasma SP-D levels in participants <65 years, or men, or participants with BMI<25.Conclusion: This study showed that plasma SP-D, an inflammation biomarker, was associated with risk of OSA and BMI in a Chinese central urban community.The relationship between the risk of OSA and respiratory inflammation in community populations needs to be further evaluated.

Ozone-Induced Oxidative Stress, Neutrophilic Airway Inflammation, and Glucocorticoid Resistance in Asthma

Despite recent advances in using biologicals that target Th2 pathways, glucocorticoids form the mainstay of asthma treatment. Asthma morbidity and mortality remain high due to the wide variability of treatment responsiveness and complex clinical phenotypes driven by distinct underlying mechanisms. Emerging evidence suggests that inhalation of the toxic air pollutant, ozone, worsens asthma by impairing glucocorticoid responsiveness. This review discusses the role of oxidative stress in glucocorticoid resistance in asthma. The underlying mechanisms point to a central role of oxidative stress pathways. The primary data source for this review consisted of peer-reviewed publications on the impact of ozone on airway inflammation and glucocorticoid responsiveness indexed in PubMed. Our main search strategy focused on cross-referencing "asthma and glucocorticoid resistance" against "ozone, oxidative stress, alarmins, innate lymphoid, NK and γδ T cells, dendritic cells and alveolar type II epithelial cells, glucocorticoid receptor and transcription factors". Recent work was placed in the context from articles in the last 10 years and older seminal research papers and comprehensive reviews. We excluded papers that did not focus on respiratory injury in the setting of oxidative stress. The pathways discussed here have however wide clinical implications to pathologies associated with inflammation and oxidative stress and in which glucocorticoid treatment is essential.

The collagen receptor uPARAP/Endo180 regulates collectins through unique structural elements in its FNII domain

C-type lectins that contain collagen-like domains are known as collectins. These proteins are present both in the circulation and in extravascular compartments and are central players of the innate immune system, contributing to first-line defenses against viral, bacterial, and fungal pathogens. The collectins mannose-binding lectin (MBL) and surfactant protein D (SP-D) are regulated by tissue fibroblasts at extravascular sites via an endocytic mechanism governed by urokinase plasminogen activator receptor-associated protein (uPARAP or Endo180), which is also a collagen receptor. Here, we investigated the molecular mechanisms that drive the uPARAP-mediated cellular uptake of MBL and SP-D. We found that the uptake depends on residues within a protruding loop in the fibronectin type-II (FNII) domain of uPARAP that are also critical for collagen uptake. Importantly, however, we also identified FNII domain residues having an exclusive role in collectin uptake. We noted that these residues are absent in the related collagen receptor, the mannose receptor (MR or CD206), which consistently does not interact with collectins. We also show that the second C-type lectin-like domain (CTLD2) is critical for the uptake of SP-D, but not MBL, indicating an additional level of complexity in the interactions between collectins and uPARAP. Finally, we demonstrate that the same molecular mechanisms enable uPARAP to engage MBL immobilized on the surface of pathogens, thereby expanding the potential biological implications of this interaction. Our study reveals molecular details of the receptor-mediated cellular regulation of collectins and offers critical clues for future investigations into collectin biology and pathology.

Ozone Inhalation Attenuated the Effects of Budesonide on Aspergillus fumigatus-Induced Airway Inflammation and Hyperreactivity in Mice

Inhaled glucocorticoids form the mainstay of asthma treatment because of their anti-inflammatory effects in the lung. Exposure to the air pollutant ozone (O₃) exacerbates chronic airways disease. We and others showed that presence of the epithelial-derived surfactant protein-D (SP-D) is important in immunoprotection against inflammatory changes including those induced by O₃ inhalation in the airways. SP-D synthesis requires glucocorticoids. We hypothesized here that O₃ exposure impairs glucocorticoid responsiveness (including SP-D production) in allergic airway inflammation. The effects of O₃ inhalation and glucocorticoid treatment were studied in a mouse model of allergic asthma induced by sensitization and challenge with Aspergillus fumigatus (Af) in vivo. The role of O₃ and glucocorticoids in regulation of SP-D expression was investigated in A549 and primary human type II alveolar epithelial cells in vitro. Budesonide inhibited airway hyperreactivity, eosinophil counts in the lung and bronchoalveolar lavage (BAL) and CCL11, IL-13, and IL-23p19 release in the BAL of mice sensitized and challenged with Af (p < 0.05). The inhibitory effects of budesonide were attenuated on inflammatory changes and were completely abolished on airway hyperreactivity after O₃ exposure of mice sensitized and challenged with Af. O₃ stimulated release of pro-neutrophilic mediators including CCL20 and IL-6 into the airways and impaired the inhibitory effects of budesonide on CCL11, IL-13 and IL-23. O₃ also prevented budesonide-induced release of the immunoprotective lung collectin SP-D into the airways of allergen-challenged mice. O₃ had a bi-phasic direct effect with early (<12 h) inhibition and late (>48 h) activation of SP-D mRNA (sftpd) in vitro. Dexamethasone and budesonide induced sftpd transcription and translation in human type II alveolar epithelial cells in a glucocorticoid receptor and STAT3 (an IL-6 responsive transcription factor) dependent manner. Our study indicates that O₃ exposure counteracts the effects of budesonide on airway inflammation, airway hyperreactivity, and SP-D production. We speculate that impairment of SP-D expression may contribute to the acute O₃-induced airway inflammation. Asthmatics exposed to high ambient O₃ levels may become less responsive to glucocorticoid treatment during acute exacerbations.

Immune regulation by fibroblasts in tissue injury depends on uPARAP-mediated uptake of collectins

Collectins such as mannose-binding lectin (MBL) and surfactant protein D (SP-D) become temporarily deposited in extravascular compartments after tissue injury and perform immune-stimulatory or inflammation-limiting functions. However, their turnover mechanisms, necessary to prevent excessive tissue damage, are virtually unknown. In this study, we show that fibroblasts in injured tissues undertake the clearance of collectins by using the endocytic collagen receptor uPARAP. In cellular assays, several types of collectins were endocytosed in a highly specific uPARAP-dependent process, not shared by the closely related receptor MR/CD206. When introduced into dermis or bleomycin-injured lungs of mice, collectins MBL and SP-D were endocytosed and routed for lysosomal degradation by uPARAP-positive fibroblasts. Fibroblast-specific expression of uPARAP governed endogenous SP-D levels and overall survival after lung injury. In lung tissue from idiopathic pulmonary fibrosis patients, a strong up-regulation of uPARAP was observed in fibroblasts adjacent to regions with SP-D secretion. This study demonstrates a novel immune-regulatory function of fibroblasts and identifies uPARAP as an endocytic receptor in immunity.

Oxidative damage of SP-D abolishes control of eosinophil extracellular DNA trap formation

The asthmatic airways are highly susceptible to inflammatory injury by air pollutants such as ozone (O₃ ), characterized by enhanced activation of eosinophilic granulocytes and a failure of immune protective mechanisms. Eosinophil activation during asthma exacerbation contributes to the proinflammatory oxidative stress by high levels of nitric oxide (NO) production and extracellular DNA release. Surfactant protein-D (SP-D), an epithelial cell product of the airways, is a critical immune regulatory molecule with a multimeric structure susceptible to oxidative modifications. Using recombinant proteins and confocal imaging, we demonstrate here that SP-D directly bound to the membrane and inhibited extracellular DNA trap formation by human and murine eosinophils in a concentration and carbohydrate-dependent manner. Combined allergic airway sensitization and O₃ exposure heightened eosinophilia and nos2 mRNA (iNOS) activation in the lung tissue and S-nitrosylation related de-oligomerisation of SP-D in the airways. In vitro reproduction of the iNOS action led to similar effects on SP-D. Importantly, S-nitrosylation abolished the ability of SP-D to block extracellular DNA trap formation. Thus, the homeostatic negative regulatory feedback between SP-D and eosinophils is destroyed by the NO-rich oxidative lung tissue environment in asthma exacerbations.

Surfactant protein D delays Fas- and TRAIL-mediated extrinsic pathway of apoptosis in T cells

Only a few extracellular soluble proteins are known to modulate apoptosis. We considered that surfactant-associated protein D (SP-D), an innate immune collectin present on many mucosal surfaces, could regulate apoptosis. Although SP-D is known to be important for immune cell homeostasis, whether SP-D affects apoptosis is unknown. In this study we aimed to determine the effects of SP-D on Jurkat T cells and human T cells dying by apoptosis. Here we show that SP-D binds to Jurkat T cells and delays the progression of Fas (CD95)-Fas ligand and TRAIL-TRAIL receptor induced, but not TNF-TNF receptor-mediated apoptosis. SP-D exerts its effects by reducing the activation of initiator caspase-8 and executioner caspase-3. SP-D also delays the surface exposure of phosphatidylserine. The effect of SP-D was ablated by the presence of caspase-8 inhibitor, but not by intrinsic pathway inhibitors. The binding ability of SP-D to dying cells decreases during the early stages of apoptosis, suggesting the release of apoptotic cell surface targets during apoptosis. SP-D also delays FasL-induced death of primary human T cells. SP-D delaying the progression of the extrinsic pathway of apoptosis could have important implications in regulating immune cell homeostasis at mucosal surfaces.

Genetic Polymorphisms of SP-A, SP-B, and SP-D and Risk of Respiratory Distress Syndrome in Preterm Neonates

Background

We examined selected polymorphisms in 3 pulmonary surfactant-associated proteins (SP) for their influence on serum SP levels and risk of respiratory distress syndrome (RDS) in preterm neonates.

Material/Methods

Premature infants from a Han population were enrolled, including 100 premature infants with RDS (case group) and 120 premature infants without RDS (control group). SNP genotyping for SP-A (+186A/G and +655C/T), SP-B (−18A/C and 1580C/T), and SP-D (Met11ThrT/C and Ala160ThrG/A) used polymerase chain reaction-restriction fragment length polymorphism. Haplotypes were calculated with Shesis software and serum SP-A/B/D levels were quantified by ELISA.

Results

Case and control groups exhibited significant differences in genotype and allele frequencies of SP-A (+186A/G, +655C/T) and SP-B (1580C/T). However, no statistically significant differences were observed in the allele and genotype frequencies of SP-B −18A/C, SP-D Met11ThrT/C, and SP-D Ala160ThrG/A. Importantly, serum SP-A and SP-B levels were reduced in RDS patients carrying SP-A (+186A/G, +655C/T) and SP-B (1580C/T) polymorphisms. AA genotype of +186A/G, SP-A level, and CC genotype of 1580C/T were independently correlated with increased RDS risk.

Conclusions

SP-A (+186A/G) and SP-B (1580C/T) polymorphisms are strongly associated with the risk of RDS in preterm infants. Notably, reduced serum SP-A levels were correlated with a high risk of RDS and may serve as novel biomarkers for RDS detection and monitoring.

Inflammation induced by inhaled lipopolysaccharide depends on particle size in healthy volunteers

AIMS

In drug development, the anti-inflammatory properties of new molecules in the lung are currently tested using the inhaled lipopolysaccharide (LPS) model. The total and regional lung bioavailability of inhaled particles depends significantly on their size. The objective of the present study was to compare inflammatory responses in healthy volunteers after the inhalation of LPS of varying droplet size.

METHODS

Three nebulizers were characterized by different droplet size distributions [mean mass median aerodynamic diameters: Microcirrus (2.0 μm), MB2 (3.2 μm) and Pari (7.9 μm)]. Participants inhaled three boluses of a 20 μg (technetium 99 m-labelled) solution of LPS, randomly delivered by each nebulizer. We measured the lung deposition of the nebulized LPS by gamma-scintigraphy, while blood and sputum biomarkers were evaluated before and after challenges.

RESULTS

MB2 and Pari achieved greater lung deposition than Microcirrus [171.5 (±72.9) and 217.6 (±97.8) counts pixel^-1 , respectively, vs. 67.9 (±20.6) counts pixel^-1 ; P < 0.01]. MB2 and Pari caused higher levels of blood C-reactive protein and more total cells and neutrophils in sputum compared with Microcirrus (P < 0.05). C-reactive protein levels correlated positively with lung deposition (P < 0.01).

CONCLUSIONS

Inhalation of large droplets of LPS gave rise to greater lung deposition and induced a more pronounced systemic and bronchial inflammatory response than small droplets. The systemic inflammatory response correlated with lung deposition. NCT01081392.

Ipr1 modified BCG as a novel vaccine induces stronger immunity than BCG against tuberculosis infection in mice

Tuberculosis is a major challenge to global public health. However, the Bacille Calmette‑Guérin (BCG), the only vaccine available against tuberculosis, has been questioned for the low protective effect. The present study used the mouse gene intracellular pathogen resistance I (Ipr1) gene to alter the current BCG vaccine and evaluated its immunity effect against tuberculosis. This study also investigated the intrinsic relationships of Ipr1 and innate immunity. The reformed BCG (BCGi) carrying the Ipr1 gene was constructed. The mice were intranasally challenged with the M. tuberculosis H37Rv strain after vaccination with BCGi. Protection efficacy of the vaccine was assessed by the organ coefficient, bacterial load and pathological changes in the lung. The differential expression of 113 immune‑related genes between BCGi and BCG groups were detected by an oligo microarray. According to the results of organ coefficient, bacterial load and pathological changes in the organization, BCGi had been shown to have stronger protective effects against M. tuberculosis than BCG. The oligo microarray and reverse transcription‑quantitative polymerase chain reaction further revealed that the Ipr1 gene could upregulate the expression of 13 genes, including a >3‑fold increase in Toll‑like receptor (TLR)4 and 10‑fold increase in surfactant protein D (sftpd). The two genes not only participate in innate immunity against pathogens, but also are closely interrelated. Ipr1 could activate the TLR4 and sftpd signaling pathway and improve the innate immunity against tuberculosis, therefore Ipr1 modified BCG may be a candidate vaccine against M. tuberculosis.

[Levels of surfactant proteins A and D in bronchoalveolar lavage fluid of children with pneumonia and their relationships with clinical characteristics]

OBJECTIVE

To observe the levels of pulmonary surfactant proteins A and D (SP-A, SP-D) in bronchoalveolar lavage fluid (BALF) of children with pneumonia, and to explore their relationships with clinical characteristics.

METHODS

Thirty-five children with pneumonia were enrolled in this study. Differential cell counts were obtained by Countstar counting board. The levels of SP-A and SP-D in BALF were detected using ELISA.

RESULTS

In children with pneumonia, SP-D levels were significantly higher than SP-A levels (P<0.001). SP-D levels were negatively correlated with the neutrophil percentage in BALF (r(s)=-0.5255, P<0.01). SP-D levels in BALF in children with increased blood C-reactive protein levels (>8 mg/L) were significantly lower than in those with a normal level of C-reactive protein (P<0.05). Compared with those in children without wheezing, SP-D levels in children with wheezing were significantly lower (P<0.01). There was no correlation between SP-A levels and clinical characteristics.

CONCLUSIONS

SP-D levels in BALF are significantly higher than SP-A levels, and have a certain correlation with clinical characteristics in children with pneumonia. As a protective factor, SP-D plays a more important role than SP-A in regulating the immune and inflammatory responses.

Macrophages: development and tissue specialization

Macrophages are myeloid immune cells that are strategically positioned throughout the body tissues, where they ingest and degrade dead cells, debris, and foreign material and orchestrate inflammatory processes. Here we review two major recent paradigm shifts in our understanding of tissue macrophage biology. The first is the realization that most tissue-resident macrophages are established prenatally and maintained through adulthood by longevity and self-renewal. Their generation and maintenance are thus independent from ongoing hematopoiesis, although the cells can be complemented by adult monocyte-derived macrophages. Second, aside from being immune sentinels, tissue macrophages form integral components of their host tissue. This entails their specialization in response to local environmental cues to contribute to the development and specific function of their tissue of residence. Factors that govern tissue macrophage specialization are emerging. Moreover, tissue specialization is reflected in discrete gene expression profiles of macrophages, as well as epigenetic signatures reporting actual and potential enhancer usage.

Linking surfactant protein SP-D and IL-13: implications in asthma and allergy

Surfactant protein D (SP-D) is an innate immune molecule that plays a protective role against lung infection, allergy, asthma and inflammation. In vivo experiments with murine models have shown that SP-D can protect against allergic challenge via a range of mechanisms including inhibition of allergen-IgE interaction, histamine release by sensitised mast cells, downregulation of specific IgE production, suppression of pulmonary and peripheral eosinophilia, inhibition of mechanisms that cause airway remodelling, and induction of apoptosis in sensitised eosinophils. SP-D can also shift helper T cell polarisation following in vivo allergenic challenge, from pathogenic Th2 to a protective Th1 cytokine response. Interestingly, SP-D gene deficient (-/-) mice show an IL-13 over-expressing phenotype. IL-13 has been shown to be involved in the development of asthma. Transgenic mice over-expressing IL-13 in the lung develop several characteristics of asthma such as pulmonary eosinophilia, airway epithelial hyperplasia, mucus cell metaplasia, sub-epithelial fibrosis, charcot-Leyden-Like crystals, airways obstruction, and non-specific airways hyper-responsiveness to cholinergic stimulation. Although both IL-4 and IL-13 are capable of inducing asthma like phenotype, the effector activity of IL-13 appears to be greater than that of IL-4. SP-D -/- mice seem to express considerably higher levels of IL-13, which is consistent with increased sensitivity and exaggerated immune response of the mice to allergenic challenge. Allergenic exposure also induces elevation in SP-D protein levels in an IL-4/IL-13-dependent manner, which prevents further activation of sensitised T cells. This negative feedback loop seems essential in protecting the airways from inflammatory damage after allergen inhalation. Here, we examine this link between IL-13 and SP-D, and its implications in the progression/regulation of asthma and allergy.

Maternal allergen exposure reprograms the developmental lung transcriptome in atopic and normoresponsive rat pups

The "fetal origins hypothesis" argued that physiological changes consequent to in utero exposures ultimately contribute to disease susceptibility in later life. The dramatic increase in asthma prevalence is attributed to early exposures acting on preexisting asthma-susceptible genotypes. We showed previously that distinct transcriptome signatures distinguish the developmental respiratory phenotype of atopic (Brown Norway, BN) and normoresponsive (Lewis) rats. We aimed to determine whether maternal allergen exposure would influence asthma pathogenesis by reprogramming primary patterns of developmental lung gene expression. Postnatal offspring of dams sensitized to ovalbumin before mating and challenged during pregnancy were assessed for lung function, inflammatory biomarkers, and respiratory gene expression. Although maternal ovalbumin exposure resulted in characteristic features of an allergic response (bronchoalveolar lavage neutrophils, IgE, methacholine-induced lung resistance) in offspring of both strains, substantial strain-specific differences were observed in respiratory gene expression. Of 799 probes representing the top 5% of transcriptomic variation, only 112 (14%) were affected in both strains. Strain-specific gene signatures also exhibited marked differences in enrichment for gene ontologies, with immune regulation and cell proliferation being prominent in the BN strain, cell cycle and microtubule assembly gene sets in the Lewis strain. Multiple ovalbumin-specific probes in both strains were also differentially expressed in lymphoblastoid cell lines from human asthmatic vs. nonasthmatic sibling pairs. Our data point to the existence of distinct, genetically programmed responses to maternal exposures in developing lung. These different response patterns, if recapitulated in human fetal development, can contribute to long-term pulmonary health including interindividual susceptibility to asthma.

Role of Allergen Source-Derived Proteases in Sensitization via Airway Epithelial Cells

Protease activity is a characteristic common to many allergens. Allergen source-derived proteases interact with lung epithelial cells, which are now thought to play vital roles in both innate and adaptive immune responses. Allergen source-derived proteases act on airway epithelial cells to induce disruption of the tight junctions between epithelial cells, activation of protease-activated receptor-2, and the production of thymic stromal lymphopoietin. These facilitate allergen delivery across epithelial layers and enhance allergenicity or directly activate the immune system through a nonallergic mechanism. Furthermore, they cleave regulatory cell surface molecules involved in allergic reactions. Thus, allergen source-derived proteases are a potentially critical factor in the development of allergic sensitization and appear to be strongly associated with heightened allergenicity.

Cholesterol as a Mediator of Alcohol-Induced Risks for Respiratory Disease Hospitalizations among People Living With HIV

We analyzed the role of cholesterol as a potential mediator of alcohol-increased risk of respiratory infections that required hospitalization in People Living with HIV (PLWH). Using a longitudinal clinic-based design, 346 PLWH were consecutively admitted and followed at Jackson Memorial Medical Center(enrolled in the study). Following national guidelines, PLWH were stratified according to cholesterol levels: <150 mg/dl (Hypocholesterolemia= HypoCHL), 151-200, and >200 mg/dl Hypercholesterolemia =HyperCHL), and compared on the basis of clinical outcomes, lymphocyte phenotypes and behavioral risks. Analyses indicated that compared to HyperCHL participants, HypoCHL subjects were more likely to be hospitalized, particularly for lower respiratory tract infections (LRTI). Excessive admissions were associated with more deviant lymphocyte profiles, particularly limited NK cells. In logistic regression analyses, smoking (OR=1.5), HypoCHL (OR=7.7), and alcohol (OR=1.2) were predictors of LRTI. These findings warrant further investigation of the potential use of HypoCHL as a risk marker, and the cost-effectiveness of switching prevention gears towards HypoCHL, alcohol and tobacco in PLWH.

Innate immunity in allergic disease

The innate immune system consists of multiple cell types that express germline-encoded pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs). Allergens are frequently found in forms and mixtures that contain PAMPs and DAMPs. The innate immune system is interposed between the external environment and the internal acquired immune system. It is also an integral part of the airways, gut, and skin. These tissues face continuous exposure to allergens, PAMPs, and DAMPs. Interaction of allergens with the innate immune system normally results in immune tolerance but, in the case of allergic disease, this interaction induces recurring and/or chronic inflammation as well as the loss of immunologic tolerance. Upon activation by allergens, the innate immune response commits the acquired immune response to a variety of outcomes mediated by distinct T-cell subsets, such as T-helper 2, regulatory T, or T-helper 17 cells. New studies highlighted in this review underscore the close relationship between allergens, the innate immune system, and the acquired immune system that promotes homeostasis versus allergic disease.

Surfactant and its role in the pathobiology of pulmonary infection

Pulmonary surfactant is a complex surface-active substance comprised of key phospholipids and proteins that has many essential functions. Surfactant's unique composition is integrally related to its surface-active properties, its critical role in host defense, and emerging immunomodulatory activities ascribed to surfactant lipids. Together these effector functions provide for lung stability and protection from a barrage of potentially virulent infectious pathogens.

Identifying host genetic risk factors in the context of public health surveillance for invasive pneumococcal disease

Host genetic factors that modify risk of pneumococcal disease may help target future public health interventions to individuals at highest risk of disease. We linked data from population-based surveillance for invasive pneumococcal disease (IPD) with state-based newborn dried bloodspot repositories to identify biological samples from individuals who developed invasive pneumococcal disease. Genomic DNA was extracted from 366 case and 732 anonymous control samples. TagSNPs were selected in 34 candidate genes thought to be associated with host response to invasive pneumococcal disease, and a total of 326 variants were successfully genotyped. Among 543 European Americans (EA) (182 cases and 361 controls), and 166 African Americans (AA) (53 cases and 113 controls), common variants in surfactant protein D (SFTPD) are consistently underrepresented in IPD. SFTPD variants with the strongest association for IPD are intronic rs17886286 (allelic OR 0.45, 95% confidence interval (CI) [0.25, 0.82], with p = 0.007) in EA and 5' flanking rs12219080 (allelic OR 0.32, 95%CI [0.13, 0.78], with p = 0.009) in AA. Variants in CD46 and IL1R1 are also associated with IPD in both EA and AA, but with effects in different directions; FAS, IL1B, IL4, IL10, IL12B, SFTPA1, SFTPB, and PTAFR variants are associated (p≤0.05) with IPD in EA or AA. We conclude that variants in SFTPD may protect against IPD in EA and AA and genetic variation in other host response pathways may also contribute to risk of IPD. While our associations are not corrected for multiple comparisons and therefore must be replicated in additional cohorts, this pilot study underscores the feasibility of integrating public health surveillance with existing, prospectively collected, newborn dried blood spot repositories to identify host genetic factors associated with infectious diseases.

cAMP response element binding protein is required for differentiation of respiratory epithelium during murine development

The cAMP response element binding protein 1 (Creb1) transcription factor regulates cellular gene expression in response to elevated levels of intracellular cAMP. Creb1^−/− fetal mice are phenotypically smaller than wildtype littermates, predominantly die in utero and do not survive after birth due to respiratory failure. We have further investigated the respiratory defect of Creb1^−/− fetal mice during development. Lungs of Creb1^−/− fetal mice were pale in colour and smaller than wildtype controls in proportion to their reduced body size. Creb1^−/− lungs also did not mature morphologically beyond E16.5 with little or no expansion of airway luminal spaces, a phenotype also observed with the Creb1^−/− lung on a Crem^−/− genetic background. Creb1 was highly expressed throughout the lung at all stages examined, however activation of Creb1 was detected primarily in distal lung epithelium. Cell differentiation of E17.5 Creb1^−/− lung distal epithelium was analysed by electron microscopy and showed markedly reduced numbers of type-I and type-II alveolar epithelial cells. Furthermore, immunomarkers for specific lineages of proximal epithelium including ciliated, non-ciliated (Clara), and neuroendocrine cells showed delayed onset of expression in the Creb1^−/− lung. Finally, gene expression analyses of the E17.5 Creb1^−/− lung using whole genome microarray and qPCR collectively identified respiratory marker gene profiles and provide potential novel Creb1-regulated genes. Together, these results demonstrate a crucial role for Creb1 activity for the development and differentiation of the conducting and distal lung epithelium.