Neutrophil recruitment to the lung in both C5a- and CXCL1-induced alveolitis is impaired in vitamin D-binding protein-deficient mice

Vitamin D Binding Protein and Postsurgical Outcomes and Tissue Injury Markers After Hip Fracture: A Prospective Study

CONTEXT

Hip fracture is a serious injury that can lead to increased morbidity and mortality. Vitamin D binding protein (DBP) is a potential prognostic indicator of outcomes since it is important for actin scavenging and inflammation after tissue injury.

OBJECTIVE

To determine whether circulating DBP is associated with mobility or mortality after hip fracture and its association with acute tissue injury markers.

METHODS

Post hoc analysis of a multisite North American prospective study of 260 patients with hip fracture; mobility assessed at 30 and 60 days and mortality at 60 days after repair surgery. Biochemical markers were measured before, and 2 to 4 days after surgery. Tissue injury markers were measured in 100 randomly selected patients and controls. The primary outcome was mobility and mortality by DBP tertiles. Secondary outcomes were assessment of pre- and postoperative biomarkers.

RESULTS

Among all patients (81 ± 9 years, BMI 25 ± 4 kg/m2; 72% female), the highest DBP tertile had greater mobility at 30 (OR: 2.66; 95% CI: 1.43, 4.92; P = .002) and 60 days (OR: 2.31; 95% CI: 1.17, 4.54; P = .014) and reduced mortality (OR: 0.18; 95% CI: 0.04, 0.86; P = .032) compared with the lowest DBP tertile (<28.0 mg/dL). Total 25-hydroxyvitamin-D did not differ between tertiles (22.0 ± 9.5 ng/mL). Circulating DBP and gelsolin were lower and interleukin-6, C-reactive protein, and F-actin were higher (P < .01) in patients vs controls, and worsened (P < .01) after surgery.

CONCLUSION

High circulating DBP concentrations are associated with better mobility and reduced mortality after hip fracture surgery. The role of DBP as an acute phase reactant to tissue injury and clinical outcomes should be addressed in future study.

A review of the critical role of vitamin D axis on the immune system

In recent years, the physiological and molecular functions of vitamin D (Vit-D) have been deeply investigated. At first, Vit-D was considered a regulator of mineral and skeletal homeostasis. However, due to the extensive-expression pattern of Vit-D receptor (VDR) in almost every non-skeletal cell, Vit-D is considered mainly a multifunctional agent with broad effects on various tissues, notably the immune system. The expression of VDR in immune cells such as dendritic cells, monocyte/macrophage, neutrophils, B cells and T cells has been well demonstrated. Besides, such immune cells are capable of metabolizing the active form of Vit-D which means that it can module the immune system in both paracrine and autocrine manners. Vit-D binding protein (DBP), that regulates the levels and homeostasis of Vit-D, is another key molecule capable of modulating the immune system. Recent studies indicate that dysregulation of Vit-D axis, variations in the DBP and VDR genes, and Vit-D levels might be risk factors for the development of autoimmune disease. Here, the current evidence regarding the role of Vit-D axis on the immune system, as well as its role in the development of autoimmune disease will be clarified. Further insight will be given to those studies that investigated the association between single nucleotide polymorphisms of DBP and VDR genes with autoimmune disease susceptibility.

Transcriptomic analysis reveal the responses of dendritic cells to VDBP

BACKGROUND

Vitamin D binding protein (VDBP) is an essential plasma carrier protein, which plays possible roles in reproductive health, disease and so on. However, the effects of VDBP on immunity have not been fully studied and the pertinent literatures remain very limited.

OBJECTIVE

In this study, we introduced the exogenous VDBP into DC2.4 and established a stable DC2.4/VDBP cell line to explore the role of this gene in immunity.

METHODS

Dendritic cells (DCs), as the most effective antigen presenting cells (APC) found so far, are directly involved in regulating some innate immunity. In order to evaluate the biological role of VDBP in DCs, we stably overexpressed VDBP in DCs, and conducted Cell Counting Kit‑8 (CCK-8 kit) and flow cytometry to detect changes in cell function. CCK-8 kit was used to monitor the viability of DCs after gene overexpression, and flow cytometry was used to detect changes in cell cycle distribution and apoptosis. Subsequently, in order to reveal the mechanism of VDBP regulating DCs, we adopted RNA sequencing (RNA-seq).

RESULTS

CCK-8 results revealed VDBP successfully inhibited viability of DCs. Besides, we found that overexpression of this gene greatly promoted apoptosis and obviously altered the cell cycle distribution of DCs in G1 and G2 phases. Moreover, RNA-seq was carried out and 151 differently expression genes (DEGs) were obtained. In addition, gene differential expression analysis showed that most of them were uniformly enriched in immunity-related pathways.

CONCLUSION

These results indicated that VDBP greatly repressed proliferation, facilitated apoptosis and changed cell cycle in DCs via altering the expression levels of gene associated with their cellular immunity.

Free Vitamin D3 Index and Vitamin D-binding protein in multiple sclerosis - a presymptomatic case-control study

Background and purpose

High levels of 25‐hydroxyvitamin D₃ (25[OH]D₃) are associated with a lower risk for multiple sclerosis (MS). The bioavailability of 25(OH)D₃ is regulated by its main plasma carrier, vitamin D‐binding protein (DBP). Free 25(OH)D₃ can be estimated by also measuring DBP concentration. In addition, DBP has immunomodulatory functions that may independently affect MS pathogenesis. No previous studies have assessed free 25(OH)D₃ or DBP in presymptomatically collected samples. This study was undertaken to assess free 25(OH)D₃ and DBP as risk factors for MS.

Methods

A nested case–control study was performed with presymptomatic serum samples identified through cross‐linkage of MS registries and Swedish biobanks. Concentration of 25(OH)D₃ was measured with liquid chromatography and DBP levels with sandwich immunoassay. Free 25(OH)D₃ was approximated as free vitamin D₃ index: (25[OH]D₃/DBP) × 10³. MS risk was analyzed by conditional logistic regression, calculating odds ratios (ORs) with 95% confidence intervals (CIs).

Results

Serum samples from 660 pairs of matched cases and controls were included.

At <20 years of age, high levels of free vitamin D₃ index were associated with a lower risk of MS (highest vs. lowest quintile: OR = 0.37, 95% CI = 0.15–0.91, p for trend across quintiles = 0.04). At age 30–39 years, high levels of DBP were associated with a lower MS risk (highest vs. lowest quintile: OR = 0.36, 95% CI = 0.15–0.85, p for trend = 0.02).

Conclusions

These findings support the hypothesis that high levels of free 25(OH)D₃ at a young age reduce the risk of MS later in life. They also implicate a role for DBP in MS etiology.

The association of free vitamin D₃ index, vitamin D‐binding protein, and the risk of developing multiple sclerosis was assessed in a case–control study of presymptomatically collected samples. High free vitamin D₃ index before the age of 20 years was associated with a lower risk of developing multiple sclerosis later in life. High levels of vitamin D binding protein after the age of 30 years were associated with a lower risk of developing multiple sclerosis.

Shedding light on vitamin D: the shared mechanistic and pathophysiological role between hypovitaminosis D and COVID-19 risk factors and complications

Severe acute respiratory syndrome coronavirus (SARS-COV-2) is the culprit of the Coronavirus Disease (COVID-19), which has infected approximately 173 million people and killed more than 3.73 million. At risk groups including diabetic and obese patients are more vulnerable to COVID-19-related complications and poor outcomes. Substantial evidence points to hypovitaminosis D as a risk factor for severe disease, the need for ICU, and mortality. 1,25(OH)D, a key regulator of calcium homeostasis, is believed to have various immune-regulatory roles including; promoting anti-inflammatory cytokines, down regulating pro-inflammatory cytokines, dampening entry and replication of SARS-COV-2, and the production of antimicrobial peptides. In addition, there are strong connections which suggest that dysregulated 1,25(OH)D levels play a mechanistic and pathophysiologic role in several disease processes that are shared with COVID-19 including: diabetes, obesity, acute respiratory distress syndrome (ARDS), cytokine storm, and even hypercoagulable states. With evidence continuing to grow for the case that low vitamin D status is a risk factor for COVID-19 disease and poor outcomes, there is a need now to address the public health efforts set in place to minimize infection, such as lock down orders, which may have inadvertently increased hypovitaminosis D in the general population and those already at risk (elderly, obese, and disabled). Moreover, there is a need to address the implications of this evidence and how we may apply the use of cheaply available supplementation, which has yet to overcome the near global concern of hypovitaminosis D. In our review, we exhaustively scope these shared pathophysiologic connections between COVID-19 and hypovitaminosis D.

Vitamin D binding protein genotype frequency in familial Mediterranean fever patients

Objective: Familial Mediterranean fever (FMF) is an autosomal recessive disorder characterized by recurrent short episodes (1-3 days) of inflammation and fever. FMF is associated with MEFV gene mutations but some patients with FMF symptoms do not have a mutation in the coding region of the MEFV gene. Vitamin D binding protein (VDBP) has important functions, including transporting vitamin D and its metabolites to target cells. Circulating levels of vitamin D are decreased in several inflammatory conditions, including FMF. Thus, we hypothesize that VDBP may play a crucial role in FMF pathogenesis, in addition to the MEFV gene. Method: VDBP genotyping was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism in 107 FMF patients and 25 healthy individuals without FMF or family history. For this, after amplification of genomic DNA, PCR products were digested with restriction enzymes HaeIII and StyI and evaluated electrophoretically. Results: We observed a statistically significant difference in the frequency of the 1F-2 genotype. The frequency of allele 2 was significantly higher and allele 1S was significantly lower compared to the [MEFV(-)] group and healthy controls (p = 0.034, 0.001, and 0.012, respectively). We observed a significant association between the presence of allele 2 and amyloidosis (p = 0.026) and arthritis (p = 0.044) in the [MEFV(-)] group. Conclusion: Our results suggest that FMF symptoms in the absence of MEFV gene mutations may be due to the presence of VDBP allele 2. Therefore, VDBP genotype may explain the symptoms in FMF [MEFV(-)] patients.

Vitamin D-binding protein as a biomarker to confirm specific clinical diagnoses

Introduction: Vitamin D-binding protein (DBP) performs a variety of functions as a transporter for various ligands and takes part in a number of systemic and local physiological and pathological processes. The knowledge about the pathomechanisms of this protein involvement justifies its use as a biomarker to confirm specific clinical diagnoses suggested by nonspecific signs and symptoms.Areas covered: DBP has properties of both systemic laboratory parameters measured in the blood plasma and specific parameters measured in variety of physiological fluids to assess local changes in specific body organs. Articles published in English between 1993 and 2019 were searched for in PubMed using terms DBP, vitamin D, and metabolites, inflammation. DBP is a transport protein and a regulator of immune and inflammatory processes.Expert opinion: DBP capacity for transporting numerous ligands and co-involvement of DBP in immune and inflammatory processes suggest that DBP may be used in laboratory diagnostics as a specific parameter to confirm pathomechanisms of several systemic diseases and local conditions. Changes in the concentration of DBP present in a variety of clinical material may provide valuable information for use in assessing the severity and treatment of pathological processes.

Modifiers of Plasma 25-Hydroxyvitamin D and Chronic Kidney Disease Outcomes in Black Americans: The Jackson Heart Study

BACKGROUND

25-hydroxyvitamin D [25(OH)D] is lower in black compared with white Americans but is not consistently associated with outcomes in this group, possibly due to genetic and other biological differences. We examined the association of plasma 25(OH)D and renal outcomes in black Americans with a focus on effect modifiers.

METHODS

We studied associations between baseline 25(OH)D with (i) annual rate of estimated glomerular filtration rate (eGFR) decline and (ii) incident chronic kidney disease (CKD) in the Jackson Heart Study, a prospective cohort of black Americans. Plasma 25(OH)D levels were corrected for monthly variation in sunlight exposure using the residual method. We used adjusted generalized linear models to evaluate outcomes and assessed potential effect modification by diabetes mellitus, vitamin D binding protein (DBP) genotype, obesity, dietary sodium intake, and use of renin-angiotensin-aldosterone system inhibitors.

RESULTS

Among 5164 participants with 25(OH)D available, plasma 25(OH)D was 14.5 ± 6.5 ng/mL (mean ± SD), and eGFR was 94.1 ± 22.0 mL/min/1.73 m2. Over a median of 8 years, eGFR decline was 1.3 ± 2.0 mL/min/1.73 m2 per year in 3228 participants with complete data, and 220 out of 1803 eligible participants developed incident CKD. Overall, 25(OH)D was not associated with eGFR decline in fully adjusted models. However, higher 25(OH)D was associated with slower eGFR decline among those with diabetes: each 5 ng/mL higher 25(OH)D was associated with a 0.27 mL/min/1.73 m2/y slower eGFR decline (95% CI, 0.13 to 0.41; P < 0.001). Higher 25(OH)D was not associated with incident CKD overall, but it was associated with lower odds of incident CKD among participants with the GG or GT genotype at rs7041 in the gene encoding DBP [OR, 0.69 per 5 ng/mL higher 25(OH)D; 95% CI, 0.51 to 0.93; P-interaction = 0.005]. Other interactions were not significant.

CONCLUSION

These findings support a potential benefit of higher 25(OH)D for kidney health in black Americans with diabetes or specific variants in DBP.

Comparison of three congruent patient-specific cell types for the modelling of a human genetic Schwann-cell disorder

Patient-specific human induced pluripotent stem cells (hiPSCs) hold great promise for the modelling of genetic disorders. However, these cells display wide intra-individual and inter-individual variations in gene expression, making it challenging to distinguish true-positive and false-positive phenotypes. Also, data from hiPSC phenotypes and from human embryonic stem cells (hESCs) harbouring the same disease mutation are lacking. Here, we report a comparison of molecular, cellular and functional characteristics of three congruent patient-specific cell types ― hiPSCs, hESCs, and direct lineage-converted cells ― derived from currently available differentiation and direct-reprogramming technologies, for the modelling of Charcot Marie Tooth 1A, a human genetic Schwann-cell disorder featuring a 1.4 megabase chromosomal duplication. In particular, we find that the chemokines CXCL1 and MCP1 are commonly upregulated in all three congruent models and in clinical patient samples. The development of congruent models of a single genetic disease by using somatic cells from a common patient will facilitate the search for convergent phenotypes.

Vitamin D-Binding Protein Deficiency and Homozygous Deletion of the GC Gene

A 58-year-old woman with debilitating ankylosing spondylitis who was born to consanguineous parents was found to have an apparent severe vitamin D deficiency that did not respond to supplementation. Liquid chromatography-tandem mass spectrometry showed the absence of circulating vitamin D-binding protein, and chromosomal microarray confirmed a homozygous deletion of the group-specific component (GC) gene that encodes the protein. Congenital absence of vitamin D-binding protein resulted in normocalcemia and a relatively mild disruption of bone metabolism, in this case complicated by severe autoimmune disease. (Funded by the National Institutes of Health and the University of Washington.).

Vitamin D-binding protein deficiency in mice decreases systemic and select tissue levels of inflammatory cytokines in a murine model of acute muscle injury

BACKGROUND

Severe acute muscle injury results in massive cell damage, causing the release of actin into extracellular fluids where it complexes with the vitamin D-binding protein (DBP). We hypothesized that a systemic DBP deficiency would result in a less proinflammatory phenotype.

METHODS

C57BL/6 wild-type (WT) and DBP-deficient (DBP-/-) mice received intramuscular injections of either 50% glycerol or phosphate-buffered saline into thigh muscles. Muscle injury was assessed by histology. Cytokine levels were measured in plasma, muscle, kidney, and lung.

RESULTS

All animals survived the procedure, but glycerol injection in both strains of mice showed lysis of skeletal myocytes and inflammatory cell infiltrate. The muscle inflammatory cell infiltrate in DBP-deficient mice had remarkably few neutrophils as compared with WT mice. The neutrophil chemoattractant CXCL1 was significantly reduced in muscle tissue from DBP-/- mice. However, there were no other significant differences in muscle cytokine levels. In contrast, plasma obtained 48 hours after glycerol injection revealed that DBP-deficient mice had significantly lower levels of systemic cytokines interleukin 6, CCL2, CXCL1, and granulocyte colony-stimulating factor. Lung tissue from DBP-/- mice showed significantly decreased amounts of CCL2 and CXCL1 as compared with glycerol-treated WT mice. Several chemokines in kidney homogenates following glycerol-induced injury were significantly reduced in DBP-/- mice: CCL2, CCL5, CXCL1, and CXCL2.

CONCLUSIONS

Acute muscle injury triggered a systemic proinflammatory response as noted by elevated plasma cytokine levels. However, mice with a systemic DBP deficiency demonstrated a change in their cytokine profile 48 hours after muscle injury to a less proinflammatory phenotype.

Vitamin D Binding Protein, Total and Free Vitamin D Levels in Different Physiological and Pathophysiological Conditions

This review focuses on the biologic importance of the vitamin D binding protein (DBP) with emphasis on its regulation of total and free vitamin D metabolite levels in various clinical conditions. Nearly all DBP is produced in the liver, where its regulation is influenced by estrogen, glucocorticoids and inflammatory cytokines but not by vitamin D itself. DBP is the most polymorphic protein known, and different DBP alleles can have substantial impact on its biologic functions. The three most common alleles-Gc1f, Gc1s, Gc2-differ in their affinity with the vitamin D metabolites and have been variably associated with a number of clinical conditions. Although DBP has a number of biologic functions independent of vitamin D, its major biologic function is that of regulating circulating free and total levels of vitamin D metabolites. 25 hydroxyvitamin D (25(OH)D) is the best studied form of vitamin D as it provides the best measure of vitamin D status. In a normal non-pregnant individual, approximately 0.03% of 25(OH)D is free; 85% is bound to DBP, 15% is bound to albumin. The free hormone hypothesis postulates that only free 25(OH)D can enter cells. This hypothesis is supported by the observation that mice lacking DBP, and therefore with essentially undetectable 25(OH)D levels, do not show signs of vitamin D deficiency unless put on a vitamin D deficient diet. Similar observations have recently been described in a family with a DBP mutation. This hypothesis also applies to other protein bound lipophilic hormones including glucocorticoids, sex steroids, and thyroid hormone. However, tissues expressing the megalin/cubilin complex, such as the kidney, have the capability of taking up 25(OH)D still bound to DBP, but most tissues rely on the free level. Attempts to calculate the free level using affinity constants generated in a normal individual along with measurement of DBP and total 25(OH)D have not accurately reflected directly measured free levels in a number of clinical conditions. In this review, we examine the impact of different clinical conditions as well as different DBP alleles on the relationship between total and free 25(OH)D, using only data in which the free 25(OH)D level was directly measured. The major conclusion is that a number of clinical conditions alter this relationship, raising the question whether measuring just total 25(OH)D might be misleading regarding the assessment of vitamin D status, and such assessment might be improved by measuring free 25(OH)D instead of or in addition to total 25(OH)D.

The Vitamin D Binding Protein and Inflammatory Injury: A Mediator or Sentinel of Tissue Damage?

Neutrophils are the most abundant type of white blood cell in most mammals including humans. The primary role of these cells is host defense against microbes and clearance of tissue debris in order to facilitate wound healing and tissue regeneration. The recruitment of neutrophils from blood into tissues is a key step in this process and is mediated by numerous different chemoattractants. The neutrophil migratory response is essential for host defense and survival, but excessive tissue accumulation of neutrophils is observed in many inflammatory disorders and strongly correlates with disease pathology. The vitamin D binding protein (DBP) is a circulating multifunctional plasma protein that can significantly enhance the chemotactic activity of neutrophil chemoattractants both in vitro and in vivo. Recent in vivo studies using DBP deficient mice showed that DBP plays a larger and more central role during inflammation since it induces selective recruitment of neutrophils, and this cofactor function is not restricted to C5a, as prior in vitro studies indicated, but can enhance chemotaxis to many chemoattractants. DBP also is an extracellular scavenger for actin released from damaged/dead cells and formation of DBP-actin complexes is an immediate host response to tissue injury. Recent in vitro evidence indicates that DBP bound to G-actin, and not free DBP, functions as an indirect but essential cofactor for neutrophil migration. DBP-actin complexes always will be formed regardless of what initiated an inflammation, since release of actin from damaged cells is a common feature in all types of injury and DBP is abundant and ubiquitous in all extracellular fluids. Indeed, these complexes have been detected in blood and tissue fluids from both humans and experimental animals following various forms of injury. The published data strongly supports the premise that DBP-actin complexes are the functional neutrophil chemotactic cofactor that enhances neutrophil chemotaxis in vitro and augments neutrophilic inflammation in vivo. This review will assess the fundamental role of DBP in neutrophilic inflammation and injury.

Vitamin D-binding protein is inversely associated with the incidence of gastrointestinal and ear infections in school-age children

Circulating 25-hydroxy vitamin D (25(OH)D) is related to decreased rates of gastrointestinal and ear infections in school-age children. Vitamin D-binding protein (DBP) transports 25(OH)D and exerts immunological functions; however, it is unknown whether DBP is associated with infectious morbidity in children. We quantified plasma DBP concentrations in 540 school-age children at the time of recruitment into a cohort study in Bogotá, Colombia and obtained daily information on infectious morbidity symptoms and doctor visits during the school year. We compared the incidence rates of gastrointestinal and respiratory symptoms across quartiles of DBP concentration by estimating adjusted incidence rate ratios (IRRs) with 95% confidence interval (CI). We also estimated the per cent of the associations between DBP and morbidity that were mediated through 25(OH)D using a counterfactual frame. Mean ± s.d. DBP concentration was 2650 ± 1145 nmol/l. DBP was inversely associated with the rates of diarrhoea with vomiting (IRR for quartiles 2-4 vs. 1 = 0.48; 95% CI 0.25-0.92; P = 0.03) and earache/ear discharge with fever (IRR for quartiles 2-4 vs. 1 = 0.29; 95% CI 0.12-0.71; P = 0.006). The DBP-morbidity associations were not mediated through 25(OH)D. We conclude that plasma DBP predicts lower incidence of gastrointestinal and ear infections in school-age children independent of 25(OH)D.

Attenuation of pulmonary ACE2 activity impairs inactivation of des-Arg9 bradykinin/BKB1R axis and facilitates LPS-induced neutrophil infiltration

Angiotensin-converting enzyme 2 (ACE2) is a terminal carboxypeptidase with important functions in the renin-angiotensin system and plays a critical role in inflammatory lung diseases. ACE2 cleaves single-terminal residues from several bioactive peptides such as angiotensin II. However, few of its substrates in the respiratory tract have been identified, and the mechanism underlying the role of ACE2 in inflammatory lung disease has not been fully characterized. In an effort to identify biological targets of ACE2 in the lung, we tested its effects on des-Arg⁹ bradykinin (DABK) in airway epithelial cells on the basis of the hypothesis that DABK is a biological substrate of ACE2 in the lung and ACE2 plays an important role in the pathogenesis of acute lung inflammation partly through modulating DABK/bradykinin receptor B1 (BKB1R) axis signaling. We found that loss of ACE2 function in mouse lung in the setting of endotoxin inhalation led to activation of the DABK/BKB1R axis, release of proinflammatory chemokines such as C-X-C motif chemokine 5 (CXCL5), macrophage inflammatory protein-2 (MIP2), C-X-C motif chemokine 1 (KC), and TNF-α from airway epithelia, increased neutrophil infiltration, and exaggerated lung inflammation and injury. These results indicate that a reduction in pulmonary ACE2 activity contributes to the pathogenesis of lung inflammation, in part because of an impaired ability to inhibit DABK/BKB1R axis-mediated signaling, resulting in more prompt onset of neutrophil infiltration and more severe inflammation in the lung. Our study identifies a biological substrate of ACE2 within the airways, as well as a potential new therapeutic target for inflammatory diseases.

Age-Related Vitamin D Deficiency Is Associated with the Immune Response in Children with Community-Acquired Pneumonia

To investigate vitamin D status in children with community-acquired pneumonia (CAP) and explore the association between vitamin D deficiency and the immune response in CAP children, 77 children with CAP were retrospectively analyzed. The baseline characteristics of patients were obtained from medical records. Based on the blood samples collected during diagnosis of CAP, the routine blood examination results and proportions of lymphocyte subsets were assessed. There were 71.4% (55/77) of patients with vitamin D deficiency among CAP children. The serum 25(OH)D level significantly decreased with age. Patients with vitamin D deficiency had a significantly higher neutrophil percentage, but significantly lower lymphocyte percentage and count as well as proportion of CD19 positive lymphocytes (CD19+). Spearman's rho test further confirmed these positive correlations and negative correlations. Moreover, significant associations of vitamin D deficiency with age and the above immune markers were also confirmed by univariate logistic regression analysis. However, only age entered the backward stepwise regression model in multivariate analysis. Vitamin D status in CAP children was negatively associated with age. Age-related vitamin D deficiency may affect the immune response in children with CAP.

Clinical Association of Chemokine (C-X-C motif) Ligand 1 (CXCL1) with Interstitial Pneumonia with Autoimmune Features (IPAF)

The term “interstitial pneumonia with autoimmune features” (IPAF) has been recently proposed. We here investigate the clinical characteristics of IPAF and evaluate the clinical implications of CXCL1-CXCR2 axis in IPAF. An increased plasma level of CXCL1 was exhibited in IPAF compared to idiopathic interstitial pneumonia (IIP), chronic obstructive pulmonary disease (COPD), and healthy controls. Additionally, plasma CXCL1 levels were clinically associated with diffusing capacity of the lungs for carbon monoxide (DLCO), erythrocyte sedimentation rate (ESR), and involved parenchyma extension in IPAF. Furthermore, circulating CXCL1 levels were highest in IPAF patients with acute exacerbations. CXCR2, the chemokine receptor for CXCL1, was readily observed in inflammatory aggregates and endothelial cells in IPAF lungs, but was lower in IIP lungs and healthy lungs. Interestingly, increased CXCL1 concentrations in BALF paralleled neutrophil counts in IPAF. Overall, the plasma concentrations of CXCL1 indicated the disease activity and prognosis in IPAF. Thus, the CXCL1/CXCR2 axis appears to be involved in the progression of IPAF.

The association between vitamin D and COPD risk, severity, and exacerbation: an updated systematic review and meta-analysis

Background

In recent years, the pleiotropic roles of vitamin D have been highlighted in various diseases. However, the association between serum vitamin D and COPD is not well studied. This updated systematic review and meta-analysis aimed to assess the relationship between vitamin D and the risk, severity, and exacerbation of COPD.

Methods

A systematic literature search was conducted in PubMed, Medline, EMBASE, Chinese National Knowledge Infrastructure, Wanfang, and Weipu databases. The pooled risk estimates were standardized mean difference (SMD) with 95% confidence interval (CI) for vitamin D levels and odds ratio (OR) with 95% CI for vitamin D deficiency. Meta-regression and subgroup analyses were performed on latitude, body mass index, and assay method.

Results

A total of 21 studies, including 4,818 COPD patients and 7,175 controls, were included. Meta-analysis showed that lower serum vitamin D levels were found in COPD patients than in controls (SMD: −0.69, 95% CI: −1.00, −0.38, P<0.001), especially in severe COPD (SMD: −0.87, 95% CI: −1.51, −0.22, P=0.001) and COPD exacerbation (SMD: −0.43, 95% CI: −0.70, −0.15, P=0.002). Vitamin D deficiency was associated with increased risk of COPD (OR: 1.77, 95% CI: 1.18, 2.64, P=0.006) and with COPD severity (OR: 2.83, 95% CI: 2.00, 4.00, P<0.001) but not with COPD exacerbation (OR: 1.17, 95% CI: 0.86, 1.59, P=0.326). Assay methods had significant influence on the heterogeneity of vitamin D deficiency and COPD risk.

Conclusion

Serum vitamin D levels were inversely associated with COPD risk, severity, and exacerbation. Vitamin D deficiency is associated with increased risk of COPD and severe COPD but not with COPD exacerbation. It is worth considering assay methods in the heterogeneity sources analysis of association between vitamin D deficiency and COPD.

Salivary Cytoprotective Proteins in Inflammation and Resolution during Experimental Gingivitis--A Pilot Study

Objective: The protective mechanisms that maintain periodontal homeostasis in gingivitis and prevent periodontal tissue destruction are poorly understood. The aim of this study was to identify changes in the salivary proteome during experimental gingivitis.

Study design: We used oral neutrophil quantification and whole saliva (WS) proteomics to assess changes that occur in the inflammatory and resolution phases of gingivitis in healthy individuals. Oral neutrophils and WS samples were collected and clinical parameters measured on days 0, 7, 14, 21, 28, and 35.

Results: Increased oral neutrophil recruitment and salivary cytoprotective proteins increased progressively during inflammation and decreased in resolution. Oral neutrophil numbers in gingival inflammation and resolution correlated moderately with salivary β-globin, thioredoxin, and albumin and strongly with collagen alpha-1 and G-protein coupled receptor 98.

Conclusions: Our results indicate that changes in salivary cytoprotective proteins in gingivitis are associated with a similar trend in oral neutrophil recruitment and clinical parameters.

Clinical relevance: We found moderate to strong correlations between oral neutrophil numbers and levels of several salivary cytoprotective proteins both in the development of the inflammation and in the resolution of gingivitis. Our proteomics approach identified and relatively quantified specific cytoprotective proteins in this pilot study of experimental gingivitis; however, future and more comprehensive studies are needed to clearly identify and validate those protein biomarkers when gingivitis is active.

GC Gene Polymorphisms and Vitamin D-Binding Protein Levels Are Related to the Risk of Generalized Aggressive Periodontitis

Objective. To explore whether GC (group-specific component) rs17467825, rs4588, and rs7041 polymorphisms are associated with generalized aggressive periodontitis. Methods. This case-control study recruited 372 patients with generalized aggressive periodontitis (group AgP) and 133 periodontal healthy subjects (group HP). GC rs17467825, rs4588, and rs7041 genotypes and plasmatic vitamin D-binding protein (DBP) were measured. Analysis of single SNP and multiple SNPs was performed and relevance between plasmatic DBP and haplotypes was analyzed. Results. GC rs17467825 GG genotype was statistically associated with lower risk for generalized aggressive periodontitis under the recessive model (OR = 0.52, 95% CI: 0.30-0.92, p = 0.028). GC rs17467825 and rs4588 had strong linkage disequilibrium with r² ≥ 0.8 and D' ≥ 0.8. Haplotype (GC rs17467825, rs4588) GC was associated with the less risk for generalized aggressive periodontitis (OR = 0.29, 95% CI: 0.09-0.96, p = 0.043). In group AgP, individuals with combined genotype (GC rs17467825, rs4588) AG+CA had significantly lower plasmatic DBP level than those with the other two combined genotypes (AG+CA versus AA+CC p = 0.007; AG+CA versus GG+AA p = 0.026). Conclusions. GC rs17467825 genotype GG and haplotype (GC rs17467825, rs4588) GC are associated with generalized aggressive periodontitis. The association may be acquired through regulating DBP levels. The functions of GC gene and DBP in inflammatory disease need to be further studied.

Vitamin D: Metabolism, Molecular Mechanism of Action, and Pleiotropic Effects

1,25-Dihydroxvitamin D3 [1,25(OH)2D3] is the hormonally active form of vitamin D. The genomic mechanism of 1,25(OH)2D3 action involves the direct binding of the 1,25(OH)2D3 activated vitamin D receptor/retinoic X receptor (VDR/RXR) heterodimeric complex to specific DNA sequences. Numerous VDR co-regulatory proteins have been identified, and genome-wide studies have shown that the actions of 1,25(OH)2D3 involve regulation of gene activity at a range of locations many kilobases from the transcription start site. The structure of the liganded VDR/RXR complex was recently characterized using cryoelectron microscopy, X-ray scattering, and hydrogen deuterium exchange. These recent technological advances will result in a more complete understanding of VDR coactivator interactions, thus facilitating cell and gene specific clinical applications. Although the identification of mechanisms mediating VDR-regulated transcription has been one focus of recent research in the field, other topics of fundamental importance include the identification and functional significance of proteins involved in the metabolism of vitamin D. CYP2R1 has been identified as the most important 25-hydroxylase, and a critical role for CYP24A1 in humans was noted in studies showing that inactivating mutations in CYP24A1 are a probable cause of idiopathic infantile hypercalcemia. In addition, studies using knockout and transgenic mice have provided new insight on the physiological role of vitamin D in classical target tissues as well as evidence of extraskeletal effects of 1,25(OH)2D3 including inhibition of cancer progression, effects on the cardiovascular system, and immunomodulatory effects in certain autoimmune diseases. Some of the mechanistic findings in mouse models have also been observed in humans. The identification of similar pathways in humans could lead to the development of new therapies to prevent and treat disease.

Enhanced Resolution of Hyperoxic Acute Lung Injury as a result of Aspirin Triggered Resolvin D1 Treatment

Acute lung injury (ALI), which presents as acute respiratory failure, is a major clinical problem that requires aggressive care, and patients who require prolonged oxygen exposure are at risk of developing this disease. Although molecular determinants of ALI have been reported, the molecules involved in disease catabasis associated with oxygen toxicity have not been well studied. It has been reported that lung mucosa is rich in omega-3 fatty acid dicosahexanoic acid (DHA), which has antiinflammatory properties. Aspirin-triggered resolvin D1 (AT-RvD1) is a potent proresolution metabolite of DHA that can curb the inflammatory effects in various acute injuries, yet the effect of AT-RvD1 on hyperoxic acute lung injury (HALI) or in the oxygen toxicity setting in general has not been investigated. The effects of AT-RvD1 on HALI were determined for the first time in 8- to 10-week-old C57BL/6 mice that were exposed to hyperoxia (≥95% O2) for 48 hours. Mice were given AT-RvD1 (100 ng) in saline or a saline vehicle for 24 hours in normoxic (≈21% O2) conditions after hyperoxia. Lung tissue and bronchoalveolar lavage (BAL) fluid were collected for analysis associated with proinflammatory signaling and lung inflammation. AT-RvD1 treatment resulted in reduced oxidative stress, increased glutathione production, and significantly decreased tissue inflammation. AT-RvD1 treatment also significantly reduced the lung wet/dry ratio, protein in BAL fluid, and decreased apoptotic and NF-κB signaling. These results show that AT-RvD1 curbs oxygen-induced lung edema, permeability, inflammation, and apoptosis and is thus an effective therapy for prolonged hyperoxia exposure in this murine model.

Behind the scenes of vitamin D binding protein: more than vitamin D binding

Although being discovered in 1959, the number of published papers in recent years reveals that vitamin D binding protein (DBP), a member of the albuminoid superfamily, is a hot research topic. Besides the three major phenotypes (DBP1F, DBP1S and DBP2), more than 120 unique variants have been described of this polymorphic protein. The presence of DBP has been demonstrated in different body fluids (serum, urine, breast milk, ascitic fluid, cerebrospinal fluid, saliva and seminal fluid) and organs (brain, heart, lungs, kidneys, placenta, spleen, testes and uterus). Although the major function is binding, solubilization and transport of vitamin D and its metabolites, the name of this glycoprotein hides numerous other important biological functions. In this review, we will focus on the analytical aspects of the determination of DBP and discuss in detail the multifunctional capacity [actin scavenging, binding of fatty acids, chemotaxis, binding of endotoxins, influence on T cell response and influence of vitamin D binding protein-macrophage activating factor (DBP-MAF) on bone metabolism and cancer] of this abundant plasma protein.

Experimental design of complement component 5a-induced acute lung injury (C5a-ALI): a role of CC-chemokine receptor type 5 during immune activation by anaphylatoxin

Excessive activation of the complement system is detrimental in acute inflammatory disorders. In this study, we analyzed the role of complement-derived anaphylatoxins in the pathogenesis of experimental acute lung injury/acute respiratory distress syndrome (ALI/ARDS) in C57BL/6J mice. Intratracheal administration of recombinant mouse complement component (C5a) caused alveolar inflammation with abundant recruitment of Ly6-G(+)CD11b(+) leukocytes to the alveolar spaces and severe alveolar-capillary barrier dysfunction (C5a-ALI; EC(50[C5a]) = 20 ng/g body weight). Equimolar concentrations of C3a or desarginated C5a (C5a(desArg)) did not induce alveolar inflammation. The severity of C5a-ALI was aggravated in C5-deficient mice. Depletion of Ly6-G(+) cells and use of C5aR1(-/-) bone marrow chimeras suggested an essential role of C5aR1(+) hematopoietic cells in C5a-ALI. Blockade of PI3K/Akt and MEK1/2 kinase pathways completely abrogated lung injury. The mechanistic description is that C5a altered the alveolar cytokine milieu and caused significant release of CC-chemokines. Mice with genetic deficiency of CC-chemokine receptor (CCR) type 5, the common receptor of chemokine (C-C motif) ligand (CCL) 3, CCL4, and CCL5, displayed reduced lung damage. Moreover, treatment with a CCR5 antagonist, maraviroc, was protective against C5a-ALI. In summary, our results suggest that the detrimental effects of C5a in this model are partly mediated through CCR5 activation downstream of C5aR1, which may be evaluated for potential therapeutic exploitation in ALI/ARDS.

Vitamin D-binding protein as a biomarker of active disease in acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disorder caused by a deficiency of hepatic porphobilinogen deaminase (PBGD). The disease is characterized by life threatening acute neurovisceral attacks. The aim of this study was to identify metabolites secreted by the hepatocytes that reflect differential metabolic status in the liver and that may predict response to the acute attack treatment. Plasma vitamin D binding protein (VDBP) from a mouse model of AIP displayed an abnormal migration in 2D-electrophoresis that is efficiently recovered upon gene therapy leading to liver specific over-expression of the PBGD protein. The change in VDBP mobility results from a differential isoelectric point suggesting a post-translational modification that takes place preferably in the liver. Liquid chromatography-mass spectrometry (LC-MS) analysis of human samples before and after glycosidase treatment revealed glycosylated plasma VDBP specifically in patients with recurrent attacks of AIP. Glycosylated VDBP recovered normal values in three severely afflicted AIP patients submitted to therapeutic liver transplantation. Our findings suggest that post-translational modification of VDBP might be considered as a promising biomarker to study and monitor the liver metabolic status in patients with AIP.

SIGNIFICANCE

We describe an increased glycosylation of VDBP in porphyric livers. Normal glycosylation was recovered upon liver gene therapy in a mouse model of porphyria or after liver transplantation in severely afflicted patients with AIP. Moreover, quantification of glycosylated VDBP by our ELISA immunoassay or LC-MS protocol in patients undergoing PBGD-gene therapy (www.aipgene.org) may be used as a marker indicating improvement or normalization of the patient's hepatic metabolism. This article is part of a Special Issue entitled: HUPO 2014.

Deficiency of the two-pore-domain potassium channel TREK-1 promotes hyperoxia-induced lung injury

OBJECTIVES

We previously reported the expression of the two-pore-domain K channel TREK-1 in lung epithelial cells and proposed a role for this channel in the regulation of alveolar epithelial cytokine secretion. In this study, we focused on investigating the role of TREK-1 in vivo in the development of hyperoxia-induced lung injury.

DESIGN

Laboratory animal experiments.

SETTING

University research laboratory.

SUBJECTS

Wild-type and TREK-1-deficient mice.

INTERVENTIONS

Mice were anesthetized and exposed to 1) room air, no mechanical ventilation, 2) 95% hyperoxia for 24 hours, and 3) 95% hyperoxia for 24 hours followed by mechanical ventilation for 4 hours.

MEASUREMENTS AND MAIN RESULTS

Hyperoxia exposure accentuated lung injury in TREK-1-deficient mice but not controls, resulting in increase in lung injury scores, bronchoalveolar lavage fluid cell numbers, and cellular apoptosis and a decrease in quasi-static lung compliance. Exposure to a combination of hyperoxia and injurious mechanical ventilation resulted in further morphological lung damage and increased lung injury scores and bronchoalveolar lavage fluid cell numbers in control but not TREK-1-deficient mice. At baseline and after hyperoxia exposure, bronchoalveolar lavage cytokine levels were unchanged in TREK-1-deficient mice compared with controls. Exposure to hyperoxia and mechanical ventilation resulted in an increase in bronchoalveolar lavage interleukin-6, monocyte chemotactic protein-1, and tumor necrosis factor-α levels in both mouse types, but the increase in interleukin-6 and monocyte chemotactic protein-1 levels was less prominent in TREK-1-deficient mice than in controls. Lung tissue macrophage inflammatory protein-2, keratinocyte-derived cytokine, and interleukin-1β gene expression was not altered by hyperoxia in TREK-1-deficient mice compared with controls. Furthermore, we show for the first time TREK-1 expression on alveolar macrophages and unimpaired tumor necrosis factor-α secretion from TREK-1-deficient macrophages.

CONCLUSIONS

TREK-1 deficiency resulted in increased sensitivity of lungs to hyperoxia, but this effect is less prominent if overwhelming injury is induced by the combination of hyperoxia and injurious mechanical ventilation. TREK-1 may constitute a new potential target for the development of novel treatment strategies against hyperoxia-induced lung injury.

Enhanced recognition of plasma proteins in a non-native state by complement C3b. A possible clearance mechanism for damaged proteins in blood

Complement C3 is a key fluid-phase protein of the immune system that covalently tags pathogenic cells and molecules for subsequent clearance. Previously, we reported that complement activation results in the formation of multiple C3b:plasma protein complexes in serum. However, it is not known if C3b attaches to any plasma protein in close proximity or preferentially binds damaged proteins. The objective of this study was to determine if C3b couples to plasma proteins in a non-native state and if this could be a potential mechanism to detect and clear damaged proteins from the blood. Using a purified in vitro system with alternative pathway proteins C3, factors B and D it was observed that guanidinium-HCl denaturation of three purified plasma proteins (albumin, alpha-1 proteinase inhibitor, vitamin D binding protein) greatly increased their capacity to form covalent complexes with C3b. However, native vitamin D binding protein, covalently attached to C3b, still retained the ability to bind its natural ligand G-actin, indicating that C3b links to plasma proteins in their native configuration but denaturation substantially increases this interaction. Serum complement activation generated a large number of C3b:plasma protein complexes that bound red blood cell membranes, suggesting a CR1-mediated clearance mechanism. Thermally denatured (60°C) serum activated the alternative pathway when added to fresh serum as evidenced by factor B cleavage and iC3b generation, but this heat-treated serum could not generate the pro-inflammatory peptide C5a. These results show that C3 recognizes and tags damaged plasma proteins for subsequent removal from the blood without triggering proinflammatory functions.

Protein-based therapies for acute lung injury: targeting neutrophil extracellular traps

INTRODUCTION

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the acute onset of noncardiac respiratory insufficiency associated with bilateral lung infiltrations. During the past decade, mechanical ventilation strategies using low tidal volumes have reduced the mortality of ALI/ARDS to ∼ 20 - 40%. However, ALI/ARDS continues to be a major factor in global burden of diseases, with no pharmacological agents currently available.

AREAS COVERED

In this review, we discuss several inflammatory proteins involved in the molecular pathogenesis of ALI/ARDS. The complement cleavage product, C5a, is a peptide acting as a potent anaphylatoxin. C5a may trigger the formation of neutrophil extracellular traps (NETs) and release of histone proteins to the extracellular compartment during ALI/ARDS. NETs may activate platelets to release TGF-β, which is involved in tissue remodeling during the later phases of ALI/ARDS. Interception of C5a signaling or blockade of extracellular histones has recently shown promising beneficial effects in small animal models of ALI/ARDS.

EXPERT OPINION

Novel protein-based strategies for the treatment of ALI/ARDS may inspire the hopes of scientists, clinicians, and patients. Although neutralization of extracellular histones/NETs, C5a, and TGF-β is effective in experimental models of ALI/ARDS, controlled clinical trials will be necessary for further evaluation in future.

Generation of multiple fluid-phase C3b:plasma protein complexes during complement activation: possible implications in C3 glomerulopathies

The complement system is tightly regulated to safeguard against tissue damage that results from unwanted activation. The key step of C3 cleavage to C3b is regulated by multiple mechanisms that control the initiation and extent of activation. This study demonstrated that C3b:plasma protein complexes form in the fluid-phase during complement activation. Several different plasma proteins displayed a discrete high molecular SDS-resistant band when any of the three complement activating pathways were triggered in normal human serum or plasma. Serum depleted of individual complement proteins revealed that C3 and factors B and D were essential for complex formation. Inactivation of the thioester bond in C3 also prevented complex formation. In vitro, complexes could be generated using four purified proteins-C3, factor B, factor D, and target protein-and Mg(2+) to allow C3 convertase formation. These studies showed that the complexes consisted of a plasma protein covalently bound to C3b in a 1:1 molar ratio; the C3b portion was rapidly degraded by factors H and I. Analysis of plasma samples from patients with dense deposit disease and C3 glomerulonephritis demonstrated that C3b:protein complexes form spontaneously in the blood of patients with dense deposit disease and, to a lesser extent, in C3 glomerulonephritis patients, but not in healthy controls. This finding supports the underlying hypothesis that these C3 glomerulopathies are diseases of fluid-phase complement dysregulation. These complexes could normally function as a passive mechanism to intercept C3b from depositing on host cells. However, excessive generation and/or defective clearance of fluid-phase C3b:protein complexes may have pathological consequences.

Circulating complexes of the vitamin D binding protein with G-actin induce lung inflammation by targeting endothelial cells

This study investigated the actin scavenger function of the vitamin D binding protein (DBP) in vivo using DBP null (-/-) mice. Intravenous injection of G-actin into wild-type (DBP+/+) and DBP-/- mice showed that contrary to expectations, DBP+/+ mice developed more severe acute lung inflammation. Inflammation was restricted to the lung and pathological changes were clearly evident at 1.5 and 4h post-injection but were largely resolved by 24h. Histology of DBP+/+ lungs revealed noticeably more vascular leakage, hemorrhage and thickening of the alveolar wall. Flow cytometry analysis of whole lung homogenates showed significantly increased neutrophil infiltration into DBP+/+ mouse lungs at 1.5 and 4h. Increased amounts of protein and leukocytes were also noted in bronchoalveolar lavage fluid from DBP+/+ mice 4h after actin injection. In vitro, purified DBP-actin complexes did not activate complement or neutrophils but induced injury and death of cultured human lung microvascular endothelial cells (HLMVEC) and human umbilical vein endothelial cells (HUVEC). Cells treated with DBP-actin showed a significant reduction in viability at 4h, this effect was reversible if cells were cultured in fresh media for another 24h. However, a 24-h treatment with DBP-actin complexes showed a significant increase in cell death (95% for HLMVEC, 45% for HUVEC). The mechanism of endothelial cell death was via both caspase-3 dependent (HUVEC) and independent (HLMVEC) pathways. These results demonstrate that elevated levels and/or prolonged exposure to DBP-actin complexes may induce endothelial cell injury and death, particularly in the lung microvasculature.