Elevated soluble ADAM8 in bronchoalveolar lavage fluid in patients with eosinophilic pneumonia

A Disintegrin and Metalloproteinase Protein 8 (ADAM 8) in Autism Spectrum Disorder: Links to Neuroinflammation

Background

Converging lines of evidence confirmed neuroinflammation's role in autism spectrum disorder (ASD) etiological pathway. A disintegrin and metalloproteinase 8 (ADAM8) play major roles in inflammatory and allergic processes in various diseases.

Aim

This study aimed to investigate ADAM8 plasma levels in autistic children compared to healthy controls. Also, to discover the association between ADAM8, disease severity, and neuroinflammation in ASD.

Methodology

This case-control study included children with ASD (n=40) and aged-matched healthy controls (n=40). The plasma levels of the ADAM 8 were determined using enzyme-linked immunosorbent assay (ELISA). The assessment of ASD severity and social and sensory behaviors were categorized as mild, moderate and severe. Correlations among ADAM8 plasma levels and ASD severity scores [Childhood Autism Rating Scale (CARS), Social Responsiveness Scale (SRS) and Short Sensory Profile (SSP)] were obtained by Spearman correlation coefficient (r).

Results

ASD children (n=40), including severe autism (n=21) and mild-to-moderate autism (n=19), showed significantly (p ≤ 0.05) lower plasma levels of ADAM8 [4683 (2885-5229); 4663 (4060-5000); 4632 (2885-5229)], respectively, than those of healthy controls [5000 (4047-5000)] [median (IQR) pg/mL]. However, there was no significant difference between the ADAM8 levels of children with severe and mild-to-moderate autism (p = 0.71). Moreover, ADAM8 plasma levels were not significantly correlated with the severity of ASD measured by behavioral scales [CARS (r= -0.11, p=0.55), SRS (r=0.11, p= 0.95), SSP (r=-0.23, p=0.23)].

Conclusion

The low ADAM8 plasma levels in children with ASD possibly indicated that ADAM8 might be implicated in the pathogenesis of ASD but not in the severity of the disease. These results should be interpreted with caution until additional studies are carried out with larger populations to decide whether the reduction in plasma ADAM8 levels is a mere consequence of ASD or if it plays a pathogenic role in the disease.

Ectopic Tumor VCAM-1 Expression in Cancer Metastasis and Therapy Resistance

Vascular Cell Adhesion Molecule-1 (VCAM-1; CD106) is a membrane protein that contributes critical physiologic functional roles in cellular immune response, including leukocyte extravasation in inflamed and infected tissues. Expressed as a cell membrane protein, VCAM-1 can also be cleaved from the cell surface into a soluble form (sVCAM-1). The integrin α4β1 (VLA-4) was identified as the first major ligand for VCAM-1. Ongoing studies suggest that, in addition to mediating physiologic immune functions, VCAM-1/VLA-4 signaling plays an increasingly vital role in the metastatic progression of various tumors. Additionally, elevated concentrations of sVCAM-1 have been found in the peripheral blood of patients with cancer, suggesting the tumor microenvironment (TME) as the source of sVCAM-1. Furthermore, over-expression of VLA-4 was linked to tumor progression in various malignancies when VCAM-1 was also up-regulated. This review explores the functional role of VCAM-1 expression in cancer metastasis and therapy resistance, and the potential for the disruption of VCAM-1/VLA-4 signaling as a novel immunotherapeutic approach in cancer, including osteosarcoma, which disproportionately affects the pediatric, adolescent and young adult population, as an unmet medical need.

VCAM-1 as a predictor biomarker in cardiovascular disease

The vascular cellular adhesion molecule-1 (VCAM-1) is a protein that canonically participates in the adhesion and transmigration of leukocytes to the interstitium during inflammation. VCAM-1 expression, together with soluble VCAM-1 (sVCAM-1) induced by the shedding of VCAM-1 by metalloproteinases, have been proposed as biomarkers in immunological diseases, cancer, autoimmune myocarditis, and as predictors of mortality and morbidity in patients with chronic heart failure (HF), endothelial injury in patients with coronary artery disease, and arrhythmias. This revision aims to discuss the role of sVCAM-1 as a biomarker to predict the occurrence, development, and preservation of cardiovascular disease.

Elevated Levels of Intelectin-1, a Pathogen-binding Lectin, in the BAL Fluid of Patients with Chronic Eosinophilic Pneumonia and Hypersensitivity Pneumonitis

Objective Human intelectin-1 (hITLN-1) binds to galactofuranosyl residues, which are present in the microbial cell wall, but which are absent in mammalian tissues, and has been suggested to play an immunological role against microorganisms. However, the involvement of hITLN-1 in the pathogenesis of diffuse pulmonary diseases remains unknown. The aim of this study was to compare the hITLN-1 concentrations in the bronchoalveolar lavage (BAL) fluid of patients with diffuse pulmonary diseases. Methods The cell components and concentrations of hITLN-1 were analyzed in the BAL fluid of 8 patients with idiopathic chronic eosinophilic pneumonia (ICEP), 3 patients with drug-induced eosinophilic pneumonia, 4 patients with hypersensitivity pneumonitis (HP), 11 patients with sarcoidosis, 9 patients with cryptogenic organizing pneumonia, and 5 patients with idiopathic fibrosing interstitial pneumonia (fibrosing nonspecific interstitial pneumonia or usual interstitial pneumonia). Results The hITLN-1 concentrations in the BAL fluid of patients with ICEP and HP were higher than in those with other diseases. In the ICEP group, no significant difference was observed in the hITLN-1 concentrations of patients with or without a history of bronchial asthma. Conclusion The results of the present study suggest that hITLN-1 may be involved in the pathogenesis of ICEP and HP, and that an increase in the hITLN-1 concentration in the BAL fluid may represent a new biomarker for these diseases.

Deregulated PSGL-1 Expression in B Cells and Dendritic Cells May Be Implicated in Human Systemic Sclerosis Development

Systemic sclerosis (SSc) is an autoimmune disorder with high morbidity and mortality, is difficult to diagnose early, and has no curative treatment. PSGL-1 is a leukocyte receptor whose deficiency in mice promotes an SSc-like disease. ADAM8, a metalloprotease that cleaves PSGL-1, is implicated in inflammatory processes. Our goal was to evaluate whether PSGL-1 and ADAM8 contribute to the pathogenesis of human SSc. We found that patients with SSc presented increased PSGL-1 expression on monocytes, dendritic cells, and T cells and decreased expression of PSGL-1 on B cells. PSGL-1 on monocytes from SSc patients failed to induce Syk phosphorylation or IL-10 production after interaction with P-selectin. Up to 60% of the IL-10-producing B cells expressed PSGL-1, pointing to a regulatory role for PSGL-1 in B cells, and PSGL-1⁺ B cells from SSc patients had decreased IL-10 production. ADAM8 expression was increased on antigen-presenting cells and T lymphocytes of SSc patients. Patients treated with calcium antagonists had lower levels of ADAM8 on APCs and T lymphocytes. Multivariate analysis indicated that the high percentage of ADAM8-expressing plasmacytoid dendritic cells discriminated patients from healthy donors. High PSGL-1 expression on dendritic cells was associated with the presence of interstitial lung disease.

An improved fluorescent substrate for assaying soluble and membrane-associated ADAM family member activities

A fluorescent resonance energy transfer substrate with improved sensitivity for ADAM17, -10, and -9 (where ADAM represents a disintegrin and metalloproteinase) has been designed. The new substrate, Dabcyl-Pro-Arg-Ala-Ala-Ala-Homophe-Thr-Ser-Pro-Lys(FAM)-NH2, has specificity constants of 6.3 (±0.3) × 10(4) M(-1) s(-1) and 2.4 (±0.3) × 10(3) M(-1) s(-1) for ADAM17 and ADAM10, respectively. The substrate is more sensitive than widely used peptides based on the precursor tumor necrosis factor-alpha (TNF-alpha) cleavage site, PEPDAB010 or Dabcyl-Ser-Pro-Leu-Ala-Gln-Ala-Val-Arg-Ser-Ser-Lys(FAM)-NH2 and Mca-Pro-Leu-Ala-Gln-Ala-Val-Dpa-Arg-Ser-Ser-Arg-NH2. ADAM9 also processes the new peptide more than 18-fold better than the TNF-alpha-based substrates. The new substrate has a unique selectivity profile because it is processed less efficiently by ADAM8 and MMP1, -2, -3, -8, -9, -12, and -14. This substrate provides a unique tool in which to assess ADAM17, -10, and -9 activities.

A novel peptide ADAM8 inhibitor attenuates bronchial hyperresponsiveness and Th2 cytokine mediated inflammation of murine asthmatic models

A disintegrin and metalloproteinase 8 (ADAM8) has been identified as a signature gene associated with moderate and severe asthma. Studies in mice have demonstrated that the severity of asthma can be reduced by either transgenic knock-out or by antibodies blocking ADAM8 function, highlighting ADAM8 as potential drug target for asthma therapy. Here, we examined the therapeutic effect of an ADAM8 inhibitor peptide (BK-1361) that specifically blocks cellular ADAM8 activity in ovalbumin-sensitized and challenged Balb/c mice. We found that BK-1361 (25 μg/g body weight) attenuated airway responsiveness to methacholine stimulation by up to 42%, concomitantly reduced tissue remodeling by 50%, and decreased inflammatory cells (e.g. eosinophils down by 54%)/inflammatory factors (e.g. sCD23 down by 50%)/TH2 cytokines (e.g. IL-5 down by 70%)/ADAM8-positive eosinophils (down by 60%) in the lung. We further verified that BK-1361 specifically targets ADAM8 in vivo as the peptide caused significantly reduced levels of soluble CD23 in wild-type but not in ADAM8-deficient mice. These findings suggest that BK-1361 blocks ADAM8-dependent asthma effects in vivo by inhibiting infiltration of eosinophils and TH2 lymphocytes, thus leading to reduction of TH2-mediated inflammation, tissue remodeling and bronchial hyperresponsiveness. Taken together, pharmacological ADAM8 inhibition appears as promising novel therapeutic strategy for the treatment of asthma.

ADAM-family metalloproteinases in lung inflammation: potential therapeutic targets

Acute and chronic lung inflammation is driven and controlled by several endogenous mediators that undergo proteolytic conversion from surface-expressed proteins to soluble variants by a disintegrin and metalloproteinase (ADAM)-family members. TNF and epidermal growth factor receptor ligands are just some of the many substrates by which these proteases regulate inflammatory or regenerative processes in the lung. ADAM10 and ADAM17 are the most prominent members of this protease family. They are constitutively expressed in most lung cells and, as recent research has shown, are the pivotal shedding enzymes mediating acute lung inflammation in a cell-specific manner. ADAM17 promotes endothelial and epithelial permeability, transendothelial leukocyte migration, and inflammatory mediator production by smooth muscle and epithelial cells. ADAM10 is critical for leukocyte migration and alveolar leukocyte recruitment. ADAM10 also promotes allergic asthma by driving B cell responses. Additionally, ADAM10 acts as a receptor for Staphylococcus aureus (S. aureus) α-toxin and is crucial for bacterial virulence. ADAM8, ADAM9, ADAM15, and ADAM33 are upregulated during acute or chronic lung inflammation, and recent functional or genetic analyses have linked them to disease development. Pharmacological inhibitors that allow us to locally or systemically target and differentiate ADAM-family members in the lung suppress acute and asthmatic inflammatory responses and S. aureus virulence. These promising results encourage further research to develop therapeutic strategies based on selected ADAMs. These studies need also to address the role of the ADAMs in repair and regeneration in the lung to identify further therapeutic opportunities and possible side effects.

Sputum ADAM8 expression is increased in severe asthma and COPD

BACKGROUND

Severe asthma and chronic obstructive pulmonary disease (COPD) are chronic inflammatory airway diseases in which the mechanisms are not fully understood. A disintegrin and metalloproteinase domain 8 (ADAM8) is an enzyme expressed on most leucocytes and may be important for facilitating leucocyte migration in respiratory disease.

OBJECTIVE

To investigate ADAM8 mRNA and protein expression in asthma and COPD and its relationship between asthma severity and inflammatory phenotypes.

METHODS

Induced sputum was collected from 113 subjects with asthma (severe n = 31, uncontrolled n = 39 and controlled n = 35), 20 subjects with COPD and 21 healthy controls. Sputum ADAM8 mRNA expression was measured by qPCR, and soluble ADAM8 (sADAM8) protein was measured in the sputum supernatant by validated ELISA.

RESULTS

ADAM8 mRNA correlated with ADAM8 protein levels (r = 0.27, P < 0.01). ADAM8 mRNA (P = 0.004) and sADAM8 protein (P = 0.014) levels were significantly higher in both asthma and COPD compared with healthy controls. ADAM8 mRNA (P = 0.035) and sADAM8 protein (P = 0.002) levels were significantly higher in severe asthma compared with controlled asthma. Total inflammatory cell count (P < 0.01) and neutrophils (P < 0.01) were also elevated in severe asthmatic sputum. Although ADAM8 mRNA was significantly higher in eosinophilic and neutrophilic asthma (P < 0.001), sADAM8 did not differ between asthma inflammatory phenotypes. ADAM8 expression positively correlated with sputum total cell count and sputum neutrophils.

CONCLUSIONS AND CLINICAL RELEVANCE

ADAM8 expression is increased in both severe asthma and COPD and associated with sputum total cell count and neutrophils. ADAM8 may facilitate neutrophil migration to the airways in severe asthma and COPD.

Vascular cell adhesion molecule-1 (VCAM-1)--an increasing insight into its role in tumorigenicity and metastasis

Vascular cell adhesion molecule-1 (VCAM-1) first attracted attention more than two decades ago as endothelial adhesion receptor with key function for leukocyte recruitment in term of cellular immune response. The early finding of VCAM-1 binding to melanoma cells, and thus a suggested mechanistic contribution to metastatic spread, was the first and for a long time the only link of VCAM-1 to cancer sciences. In the last few years, hallmarked by a growing insight into the molecular understanding of tumorigenicity and metastasis, an impressive variety of VCAM-1 functionalities in cancer have been elucidated. The present review aims to provide a current overview of VCAM-1 relevance for tumor growth, metastasis, angiogenesis, and related processes. By illustrating the intriguing role of VCAM-1 in cancer disease, VCAM-1 is suggested as a new and up to now underestimated target in cancer treatment and in clinical diagnosis of malignancies.

ADAM8 in asthma. Friend or foe to airway inflammation?

Airway inflammation has been suggested as the pathological basis in asthma pathogenesis. Recruitment of leukocytes from the vasculature into airway sites is essential for induction of airway inflammation, a process thought to be mediated by a disintegrin and metalloprotease 8 (ADAM8). However, there is an apparent controversy about whether ADAM8 helps or hampers transmigration of leukocytes through endothelium in airway inflammation of asthma. This review outlines the current contradictory concepts concerning the role of ADAM8 in airway inflammation, particularly focusing on the recruitment of leukocytes during asthma, and attempts to bridge the existing experimental data on the basis of the functional analysis of different domains of ADAM8 and their endogenous processing in vivo. We suggest a possible hypothesis for the specific mechanism by which ADAM8 regulates the transmigration of leukocytes to explain the disparity existing in current studies, and we also raise some questions that require future investigations.

New insights of P2X7 receptor signaling pathway in alveolar functions

Purinergic P2X7 receptor (P2X7R), an ATP-gated cation channel, is unique among all other family members because of its ability to respond to various stimuli and to modulate pro-inflammatory signaling. The activation of P2X7R in immune cells is absolutely required for mature interleukin -1beta (IL-1beta) and IL-18 production and release. Lung alveoli are lined by the structural alveolar epithelial type I (AEC I) and alveolar epithelial type II cells (AEC II). AEC I plays important roles in alveolar barrier protection and fluid homeostasis whereas AEC II synthesizes and secrete surfactant and prevents alveoli from collapse. Earlier studies indicated that purinergic P2X7 receptors were specifically expressed in AEC I. However, their implication in alveolar functions has not been explored. This paper reviews two important signaling pathways of P2X7 receptors in surfactant homeostatsis and Acute Lung Injury (ALI). Thus, P2X7R resides at the critical nexus of alveolar pathophysiology.

Eosinophilic pneumonias

This review starts with discussions of several infectious causes of eosinophilic pneumonia, which are almost exclusively parasitic in nature. Pulmonary infections due specifically to Ascaris, hookworms, Strongyloides, Paragonimus, filariasis, and Toxocara are considered in detail. The discussion then moves to noninfectious causes of eosinophilic pulmonary infiltration, including allergic sensitization to Aspergillus, acute and chronic eosinophilic pneumonias, Churg-Strauss syndrome, hypereosinophilic syndromes, and pulmonary eosinophilia due to exposure to specific medications or toxins.

Elevated levels of a disintegrin and metalloproteinase 8 in gingival crevicular fluid of patients with periodontal diseases

BACKGROUND

A disintegrin and metalloproteinase 8 (ADAM8) is involved in inflammation and is essential for osteoclastogenesis. Elevated ADAM8 levels are detected in human serum and other body fluids in several inflammatory conditions. Therefore, we hypothesized that ADAM8 levels are also raised in gingival crevicular fluid (GCF) of patients with periodontal diseases.

METHODS

Forty-five patients with periodontal diseases (n = 15 for each group: the group of patients with gingivitis, the group with aggressive periodontitis [AgP], and the group with chronic periodontitis [CP]) and 15 volunteers who exhibited healthy gingiva were recruited. Four periodontal parameters, gingival index, plaque index, probing depth, and clinical attachment level, were recorded before GCF collection. The presence of ADAM8 in GCF was shown by immunoblotting using anti-human ADAM8 polyclonal antibody against its prodomain, and the ADAM8 levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

Four immunoreactive bands at 120, 70, 50, and <30 kDa were detected in the groups of patients with periodontitis, whose intensities were stronger than those in the group of patients with gingivitis, consistent with significantly greater ADAM8 levels in both groups of patients, with either CP or AgP, than those in the group of patients with gingivitis and in the group that was healthy (P <0.001). Moreover, the ADAM8 levels correlated significantly with the four periodontal parameters (P <0.001), indicating that ADAM8 levels are positively associated with the degree of periodontal tissue inflammation and destruction.

CONCLUSIONS

The ADAM8 levels are elevated in the GCF of patients with periodontal diseases, including gingivitis, CP, and AgP, in comparison to control participants who are healthy, and they correlate with four clinical parameters that reflect the degree of disease severity.

Vascular cell adhesion molecule-1 expression and signaling during disease: regulation by reactive oxygen species and antioxidants

The endothelium is immunoregulatory in that inhibiting the function of vascular adhesion molecules blocks leukocyte recruitment and thus tissue inflammation. The function of endothelial cells during leukocyte recruitment is regulated by reactive oxygen species (ROS) and antioxidants. In inflammatory sites and lymph nodes, the endothelium is stimulated to express adhesion molecules that mediate leukocyte binding. Upon leukocyte binding, these adhesion molecules activate endothelial cell signal transduction that then alters endothelial cell shape for the opening of passageways through which leukocytes can migrate. If the stimulation of this opening is blocked, inflammation is blocked. In this review, we focus on the endothelial cell adhesion molecule, vascular cell adhesion molecule-1 (VCAM-1). Expression of VCAM-1 is induced on endothelial cells during inflammatory diseases by several mediators, including ROS. Then, VCAM-1 on the endothelium functions as both a scaffold for leukocyte migration and a trigger of endothelial signaling through NADPH oxidase-generated ROS. These ROS induce signals for the opening of intercellular passageways through which leukocytes migrate. In several inflammatory diseases, inflammation is blocked by inhibition of leukocyte binding to VCAM-1 or by inhibition of VCAM-1 signal transduction. VCAM-1 signal transduction and VCAM-1-dependent inflammation are blocked by antioxidants. Thus, VCAM-1 signaling is a target for intervention by pharmacological agents and by antioxidants during inflammatory diseases. This review discusses ROS and antioxidant functions during activation of VCAM-1 expression and VCAM-1 signaling in inflammatory diseases.

ADAM-8, a metalloproteinase, drives acute allergen-induced airway inflammation

Asthma is a complex disease linked to various pathophysiological events including the activity of proteinases. The multifunctional A disintegrin and metalloproteinases (ADAMs) displaying the ability to cleave membrane-bound mediators or cytokines appear to be key mediators in various inflammatory processes. In the present study, we investigated ADAM-8 expression and production in a mouse model of allergen-induced airway inflammation. In allergen-exposed animals, increased expression of ADAM-8 was found in the lung parenchyma and in DC purified from the lungs. The potential role of ADAM-8 in the development of allergen-induced airway inflammation was further investigated by the use of an anti-ADAM-8 antibody and ADAM-8 knockout animals. We observed a decrease in allergen-induced acute inflammation both in BALF and the peribronchial area in anti-ADAM-8 antibody-treated mice and in ADAM-8-deficient mice (ADAM-8(-/-) ) after allergen exposure. ADAM-8 depletion led to a significant decrease of the CD11c(+) lung DC. We also report lower levels of CCL11 and CCL22 production in antibody-treated mice and ADAM-8- deficient mice that might be explained by decreased eosinophilic inflammation and lower numbers of DC, respectively. In conclusion, ADAM-8 appears to favour allergen-induced acute airway inflammation by promoting DC recruitment and CCL11 and CCL22 production.

Novel alternatively spliced ADAM8 isoforms contribute to the aggressive bone metastatic phenotype of lung cancer

ADAMs (a disintegrin and metalloprotease) are transmembrane proteins involved in a variety of physiological processes and tumorigenesis. Recently, ADAM8 has been associated with poor prognosis of lung cancer. However, its contribution to tumorigenesis in the context of lung cancer metastasis remains unknown. Native ADAM8 expression levels were lower in lung cancer cell lines. In contrast, we identified and characterized two novel spliced isoforms encoding truncated proteins, Delta18a and Delta14', which were present in several tumor cell lines and not in normal cells. Overexpression of Delta18a protein resulted in enhanced invasive activity in vitro. ADAM8 and its Delta14' isoform expression levels were markedly increased in lung cancer cells, in conditions mimicking tumor microenvironment. Moreover, addition of supernatants from Delta14'-overexpressing cells resulted in a significant increase in tartrate-resistant acid phosphatase+ cells in osteoclast cultures in vitro. These findings were associated with increased pro-osteoclastogenic cytokines interleukin (IL)-8 and IL-6 protein levels. Furthermore, lung cancer cells overexpressing Delta14' increased prometastatic activity with a high tumor burden and increased osteolysis in a murine model of bone metastasis. Thus, the expression of truncated forms of ADAM8 by the lung cancer cells may result in the specific upregulation of their invasive and osteoclastogenic activities in the bone microenvironment. These findings suggest a novel mechanism of tumor-induced osteolysis in metastatic bone colonization.

The metalloprotease-disintegrin ADAM8 is essential for the development of experimental asthma

RATIONALE

Expression of the metalloprotease ADAM8 is increased in patients with asthma, but the functional significance of elevated ADAM8 expression in the context of asthma pathogenesis remains elusive.

OBJECTIVES

To study development of asthma in ADAM8-deficient mice.

METHODS

Ovalbumin-induced asthma was studied in wild-type, ADAM8-deficient, and ADAM8-chimeric mice. Lung inflammation was assessed by histology, analysis of bronchoalveolar lavage, and airway hyperresponsiveness.

MEASUREMENTS AND MAIN RESULTS

ADAM8-deficient mice are highly resistant to the development of ovalbumin-induced airway inflammation and hyperresponsiveness. ADAM8 expression was induced in both hematopoietic cells and the nonhematopoietic microenvironment after induction of asthma, and ADAM8 expression in both cell populations was required for the full manifestation of asthma. Interestingly, loss of ADAM8 on T cells alone was sufficient to significantly decrease the asthma response. The attenuated response was not due to an intrinsic defect in antigen presentation or cytokine production but reflected an impaired migration of T cells, eosinophils, CD11b(+) CD11c(-), and CD11c(+) cells from blood vessels to the lung and alveolar space, suggesting a general hematopoietic cell deficiency in the absence of ADAM8.

CONCLUSIONS

The results show that ADAM8 plays a proinflammatory role in airway inflammation. The milder disease outcome in the absence of ADAM8 suggests that this protein might be an interesting new target in treatment of this, and potentially other, inflammatory diseases in which recruitment of inflammatory cells is an essential part of pathogenesis.

ADAM8 substrate specificity: influence of pH on pre-processing and proteoglycan degradation

A disintegrin and metalloprotease-8 (ADAM8) is thought to play a role in cancer and inflammatory diseases such as allergy, arthritis, and asthma. Despite the implication of ADAM8 in these diseases, the functional role of ADAM8 catalytic activity remains unclear. In this report, we demonstrate that an early critical autolytic event, we have termed pre-processing, is accelerated at acidic pH (pH 5.5) while autolytic activation is abrogated under the same conditions. Likewise, we found that pre-processing is hindered and autolytic activation is facilitated in neutral pH conditions, and thus demonstrates a pH-dependent shift in substrate selectivity. This finding is further supported by two peptide substrates corresponding to the pre-processing and C-terminal scissile bonds that were preferentially cleaved at acidic and neutral pH, respectively. Lastly, we found fibronectin cleavage to be attenuated at pH 5.5, while two novel substrates, brevican, and vitronectin, were readily cleaved in neutral or acidic conditions.

Increased serum ADAM8 concentration in patients with drug-induced eosinophilic pneumonia-ADAM8 expression depends on a the allergen route of entry

BACKGROUND

ADAM8 (a disintegrin and a metalloprotease 8) has been linked to asthma and eosinophilic pneumonia (EP). ADAM8 cleaves a variety of substrates and is a sheddase for CD23, the low affinity IgE receptor. The concentration of soluble ADAM8 (sADAM8) is increased in bronchoalveolar lavage fluid (BALF) from patients with smoking-induced acute eosinophilic pneumonia (AEP) and chronic eosinophilic pneumonia (CEP), but not drug-induced EP (Drug-EP). In AEP, the BALF sADAM8 concentration significantly correlates with the soluble CD23 concentration (sCD23).

METHODS

To evaluate the involvement of ADAM8 in the pathogenesis of eosinophilic pneumonia, we measured the concentrations of sADAM8 and its substrate, soluble CD23 (sCD23), in serum from patients with AEP, CEP, and Drug-EP. We also measured the change in the sADAM8 concentration after a provocation test.

RESULTS

In contrast to the BALF findings, serum sADAM8 concentrations were increased in Drug-EP (mean+/-SEM; 639.6+/-49.15) and serum ADAM8 levels correlated positively with the serum sCD23 levels in patients with Drug-EP (P=0.0080, R(2)=0.8465). Serum sADAM8 concentrations were also increased in AEP (409+/-76.91) and CEP (644.7+/-87.03). Serum ADAM8 concentrations were also elevated after the provocation test.

CONCLUSION

Serum ADAM8 concentrations were elevated in Drug-EP, although the sADAM8 concentrations were not increased in the BALF in Drug-EP. Thus, the pathogenesis of AEP and Drug-EP may be distinct with regard to allergen exposure; AEP may be caused by the inhalation of antigens, whereas Drug-EP may be caused by bloodstream antigens. These findings indicate that ADAM8 levels reflect the route of eosinophilic inflammation in EP.

ADAM8: a new therapeutic target for asthma

BACKGROUND

A proteinase with a disintegrin and a metalloproteinase domain-8 (ADAM8) has been linked to asthma.

OBJECTIVE

To explore whether ADAM8 is a therapeutic target for asthma.

METHODS

We reviewed literature on ADAM8's function and expression and activities in lungs of humans and mice with allergic airway inflammation (AAI). We used these data to generate hypotheses about the contributions of ADAM8 to asthma pathogenesis.

CONCLUSIONS

ADAM8 levels are increased in airway epithelium and airway inflammatory cells in mice with AAI and human asthma patients. Data from murine models of AAI indicate that ADAM8 dampens airway inflammation. It is not clear whether ADAM8 contributes directly to structural remodeling in asthmatic airways. Additional studies are required to validate ADAM8 as a therapeutic target for asthma.

[Idiopathic chronic eosinophilic pneumonia - a diagnostic challenge]

CASE REPORT

A 43-year-old woman with clinical signs of a febrile respiratory infection with cough and dyspnea despite several antecedent antibiotic treatments was admitted to hospital because of persistent bilateral pulmonary infiltrates.

DIAGNOSIS, THERAPY, AND COURSE

In the diagnostic work-up, the most striking laboratory abnormality was an eosinophilia of 31% within the differential blood count. Specimen obtained from bronchoalveolar lavage showed an abnormally high level of eosinophils as well. In the absence of other known causes of an eosinophilic pulmonary disease the diagnosis of idiopathic chronic eosinophilic pneumonia was made. After initiation of corticosteroid medication the abnormal laboratory results, the clinical signs, and the radiologic findings almost completely normalized within 1 week.

CONCLUSION

If an apparent pneumonia fails to respond to conventional antibiotic treatment, a blood eosinophil count should be obtained. If blood eosinophils are abnormally high, diagnosis of idiopathic acute or chronic eosinophilic pneumonia should be considered and confirmed by demonstrating an excess of eosinophils in bronchoalveolar lavage fluid. Due to prognostic and therapeutic consequences idiopathic acute and chronic eosinophilic pneumonia should be distinguished from one another. A rapid response to glucocorticoid therapy supports the diagnosis. In order to avoid relapses, patients with chronic eosinophilic pneumonia have to complete a 6-month treatment.

Upregulation of ADAM8 in the airways of mice with allergic bronchial asthma

Recent microarray analyses revealed that a disintegrin and metalloproteinase (ADAM) 8 (ADAM8; also called CD156) is one of the asthma candidate genes. However, the function of ADAM8 and its localization in the airways are still poorly understood. In the present study, the changes in the expression and localization of ADAM8 in the airways of a mouse model of allergic bronchial asthma were investigated. Male BALB/c mice were sensitized and repeatedly challenged with ovalbumin antigen to induce asthmatic response. After the final antigen challenge, mRNA and protein expressions of ADAM8 were elucidated by quantitative RT-PCR and immunohistochemistry. The mRNA expression of ADAM8 in the airways was significantly increased in this animal model of asthma compared with naive animals. Immunohistochemical examinations revealed that ADAM8 was located in airway epithelia, airway smooth muscles, and infiltrated cells (mainly macrophages) into lung parenchyma. A distinctly stronger immunostaining of ADAM8 was observed in these airway cells of the repeatedly antigen-challenged mice compared with those of the sensitized control animals. An upregulation of ADAM8 in the airways might be involved in the pathogenesis of airway inflammation and/or hyperresponsiveness, characteristic features of allergic bronchial asthma.

Expression of ADAMs ("a disintegrin and metalloprotease") in the human lung

In view of the associations of "a disintegrin and metalloprotease" (ADAM) with respiratory diseases, we assessed the expression of various ADAMs in human lung tissue. Lung tissue was obtained from nine individuals who underwent surgery for lung cancer or underwent lung transplantation for emphysema. Also, 16HBE 14o- (human bronchial epithelial) and A549 (alveolar type II epithelium-like) cell lines were used. Immunohistochemistry was performed with antibodies recognizing different ADAM domains. The ADAMs were typically distributed over the bronchial epithelium. ADAM8 and ADAM10 were expressed diffusely in all layers of the epithelium. ADAM9, ADAM17, and ADAM19 were predominantly expressed in the apical part of the epithelium, and ADAM33 was predominantly and strongly expressed in basal epithelial cells. In smooth muscle, ADAM19 and ADAM17 were strongly expressed, as was ADAM33, though this expression was weaker. ADAM33 was strongly expressed in vascular endothelium. All ADAMs were generally expressed in inflammatory cells. The typical distribution of ADAMs in the lung, especially in the epithelium, is interesting and suggests a localized function. As most ADAMs are involved in release of (pro-) inflammatory mediators and growth factors, they may play an important role in the first line of defense and in initiation of repair events in the airways.

Alpha4 and beta2 integrins have nonredundant roles for asthma development, but for optimal allergen sensitization only alpha4 is critical

OBJECTIVE

Recruitment of effector cell subsets to inflammatory lung, together with airway resident cells responsive to secreted products, play pivotal roles in developing and maintaining asthma. Differential use of adhesion molecules dictates the recruitment patterns of specific cell subsets, yet a clear understanding of the distinctive adhesive molecular pathways guiding them to lung is lacking. To provide further insight into the role of alpha4beta1/VCAM-1 pathway and to compare this to the role of beta2 integrin in the development of acute asthma phenotype, we used genetically deficient mice, in contrast to previous studies with anti-functional antibodies yielding ambiguous results.

METHODS

Allergen-dependent airway inflammation and hyperresponsiveness was induced in conditional alpha4(Delta/Delta), VCAM-1(-/-), and beta2(-/-) mice. Cytology, immunocytochemistry, cytokine and immunoglobulin measurements, and cell type accumulation in lung, BAL fluid, plasma, and hemopoietic tissues were carried out.

RESULTS

Asthma phenotype was totally abrogated in alpha4- or beta2-deficient mice. Adoptive transfer of sensitized alpha4(Delta/Delta) CD4(+) cells into challenged normal mice failed to induce asthma, whereas alpha4(+/+) CD4(+) cells were able to induce asthma in challenged alpha4(Delta/Delta) mice. Parallel studies with beta2(-/-) or VCAM-1(-/-) mice uncovered novel mechanistic insights in primary sensitization and into redundant or unique functional roles of these adhesion pathways in allergic asthma.

CONCLUSIONS

The lack of alpha4 integrin not only impedes the migration of all white cell subsets to lung and airways, but also prevents upregulation of vascular cell adhesion molecule-1 (VCAM-1) in inflamed lung vasculature and, unlike beta2, attenuates optimal sensitization and ovalbumin-specific IgE production in vivo. As VCAM-1 deficiency did not protect mice from asthma, interactions of alpha4beta1(+) or alpha4beta7(+) cells with other ligands are suggested.