Reactive indoor air chemistry and health-A workshop summary.

The chemical composition of indoor air changes due to the reactive nature of the indoor environment. Historically, only the stable parent compounds were investigated due to their ease of measurement by conventional methods. Today, however, scientists can better characterize oxidation products (gas and particulate-phase) formed by indoor chemistry. An understanding of occupant exposure can be developed through the investigation of indoor oxidants, the use of derivatization techniques, atmospheric pressure detection, the development of real-time technologies, and improved complex modeling techniques. Moreover, the connection between exposure and health effects is now receiving more attention from the research community. Nevertheless, a need still exists for improved understanding of the possible link between indoor air chemistry and observed acute or chronic health effects and long-term effects such as work-related asthma.

Cell types involved in allergic asthma and their use in in vitro models to assess respiratory sensitization.

This review first describes the mechanism and cell types involved in allergic asthma, which is a complex clinical disease characterized by airway obstruction, airway inflammation and airway hyperresponsiveness to a variety of stimuli. The development of allergic asthma exists of three phases, namely the induction phase, the early-phase asthmatic reaction (EAR) and the late-phase asthmatic reaction (LAR). In the induction phase, antigen-presenting cells play a major role. Most important cells in the EAR are mast cells, and during the LAR, various cell types, such as eosinophils, neutrophils, T cells, macrophages, dendritic cells (DCs), and cells that endow structure are involved. In occupational asthma, this immunological mechanism is involved in 90% of the cases. The second part of this review gives an overview of in vitro models to assess the hazardous potential of high- and low-molecular weight chemicals on the respiratory system. In order to develop a good in vitro model for respiratory allergy, the choice of appropriate cell types is important. Epithelial cells, macrophages and DCs are currently the most used models in this field of research.

Gene expression profiling of in vitro cultured macrophages after exposure to the respiratory sensitizer hexamethylene diisocyanate.

Occupational exposure to chemicals is one of the main causes of respiratory allergy and asthma. Identification of chemicals that trigger allergic asthma is difficult as underlying processes and specific markers have not yet been clearly defined. Moreover, adequate classification of the respiratory toxicity of chemicals is hampered due to the lack of validated in vivo and in vitro test methods. The study of differential gene expression profiles in appropriate human in vitro cell systems is a promising approach to identify selective markers for respiratory allergy. As alveolar macrophages display important immunological and inflammatory properties in response to foreign substances in the lung, we aimed at gaining more insight in changes of human macrophages transcriptome and to identify selective genetic markers for respiratory sensitization in response to hexamethylene diisocyanate (HDI). In vitro cultures of human THP-1 cells were differentiated into macrophages and exposed to 55 microg/ml HDI for 6 and 10h. Using human oligonucleotide microarrays, changes were observed in the expression of genes that are involved in diverse biological and molecular processes, including detoxification, oxidative stress, cytokine signaling, and apoptosis, which can lead to the development of asthma. These genes are possible markers for respiratory sensitization caused by isocyanates.

PECAM-1 and gelatinase B coexist in vascular cuffs of multiple sclerosis lesions.

In multiple sclerosis (MS), the matrix metalloprotease (MMP) gelatinase B/MMP-9 and platelet endothelial cell adhesion molecule (PECAM)-1 have both been implicated in trans-endothelial infiltration of leucocytes into the brain, but their functional connection has not yet been investigated. We investigated the expression of gelatinase B and PECAM-1 in post mortem brains of MS patients by immunohistochemistry. Because increased soluble PECAM-1 serum levels have been observed in MS patients, we also tested in vitro whether this could be due to cleavage of PECAM-1 by gelatinase B or matrilysin-1/MMP-7. Constitutive expression of PECAM-1 was found on brain endothelial cells, whilst in active MS lesions cell-bound PECAM-1 was highly up-regulated on foamy macrophages in perivascular infiltrates and co-localized with gelatinase B. However, human THP-1 monocyte-bound or soluble recombinant PECAM-1 were both resistant to proteolytic cleavage by gelatinase B or matrilysin-1 in vitro, as demonstrated by Western blot analysis and flow cytometry. These results suggest that PECAM-1 and gelatinase B may complement each other during the transmigration of the blood-brain barrier by mononuclear cells.

Flow cytometric characterisation of antigen presenting dendritic cells after in vitro exposure to diesel exhaust particles.

The aim of this study was to obtain more insight into the effect of diesel exhaust particles (DEP) on the maturation of primary human dendritic cells. Monocyte-derived dendritic cells (Mo-DC) derived from seven different donors were exposed to different DEP concentrations (0.2,2,20,200 and 2,000 ng/ml) in the presence or absence of lipopolysaccharide (LPS), and changes in the surface expression of HLA-DR, CD86 and CD83 were examined. Exposure of Mo-DC to DEP alone did not alter expression levels of any of the markers. Treatment with LPS alone increased the expression levels of all three surface markers, although the levels were not significantly different compared to untreated DCs. The LPS-induced marker expression could be further enhanced by co-stimulation of the cells with DEP. Statistical significantly increased levels of CD83 expression were observed after exposure to 0.2 (p=0.018), 20 (p=0.010) and 200 ng/ml (p=0.047) DEP combined with LPS in the group of responders. We conclude that DEP has an adjuvant effect on LPS-induced maturation of Mo-DC.

Expression analysis of immune-related genes in CD34(+) progenitor-derived dendritic cells after exposure to the chemical contact allergen DNCB.

We studied the changes in gene expression after exposure of human dendritic cells (DCs) to the model allergen dinitrochlorobenzene (DNCB). DCs were derived from CD34(+) progenitor cells of three different donors and exposed to 10 microM DNCB or solvent for several time intervals (3, 6 and 12h). cDNA microarrays were used to assess the transcriptional activity of 11,000 human genes. Compared to control gene expression, changes larger than +/-two-fold were observed for 241 genes after exposure to DNCB. Of these genes, 137 were up-regulated and 104 down-regulated. Twenty of these genes encode proteins that are related to the immune response (cytokines, chemokines, their receptors, cytokine/chemokines-related genes, transcription and signal transduction genes) and are discussed in more detail. Our data indicate that exposure to DNCB does not induce a typical maturation pattern in DCs.

Gelatinase B, PECAM-1 and MCP-3 gene polymorphisms in Belgian multiple sclerosis.

Polymorphic microsatellite markers in the genes for gelatinase B, PECAM-1 and MCP-3 have previously been analysed in Swedish and Sardinian individuals to test for association with multiple sclerosis (MS). Confirmation and comparison of genetic associations in various ethnic populations is mandatory and, therefore, we studied these three gene polymorphisms in 216 clinically definite MS patients and 193 normal controls, and in 148 simplex MS families, all of Belgian origin. No allelic associations were found between MS and the CA microsatellite marker in the promoter region of the gelatinase B gene, and the polymorphic CA repeat in the sixth intron of PECAM1. However, the two most abundant alleles of the CA/GA microsatellite polymorphism in the promoter-enhancer region of the MCP-3 gene, A2 (109 bp) and A3 (111 bp), were found to be significantly associated with disease in the case-control study [OR (95% CI)=0.68 (0.51-0.92), p (1 df)=0.015 and OR (95% CI)=1.62 (1.22-2.14), p (1 df)=0.0010, respectively], but not in the family study. These results are in agreement with previous findings in the Swedish and Sardinian populations and reinforce the possibility of a role for chemokines in MS pathogenesis.

Gelatinase B functions as regulator and effector in leukocyte biology.

Matrix metalloproteinases (MMPs) form a family of enzymes with major actions in the remodeling of extracellular matrix (ECM) components. Gelatinase B (MMP-9) is the most complex family member in terms of domain structure and regulation of its activity. Gelatinase B activity is under strict control at various levels: transcription of the gene by cytokines and cellular interactions; activation of the pro-enzyme by a cascade of enzymes comprising serine proteases and other MMPs; and regulation by specific tissue inhibitors of MMPs (TIMPs) or by unspecific inhibitors, such as alpha2-macroglobulin. Thus, remodeling ECM is the result of the local protease load, i.e., the net balance between enzymes and inhibitors. Glycosylation has a limited effect on the net activity of gelatinase B, and in contrast to the all-or-none effect of enzyme activation or inhibition, it results in a higher-level, fine-tuning effect on the ECM catalysis by proteases in mammalian species. Fast degranulation of considerable amounts of intracellularly stored gelatinase B from neutrophils, induced by various types of chemotactic factors, is another level of control of activity. Neutrophils are first-line defense leukocytes and do not produce gelatinase A or TIMP. Thus, neutrophils contrast sharply with mononuclear leukocytes, which produce gelatinase A constitutively, synthesize gelatinase B de novo after adequate triggering, and overproduce TIMP-1. Gelatinase B is also endowed with functions other than cleaving the ECM. It has been shown to generate autoimmune neo-epitopes and to activate pro-IL-1beta into active IL-1beta. Gelatinase B ablation in the mouse leads to altered bone remodeling and subfertility, results in resistance to several induced inflammatory or autoimmune pathologies, and indicates that the enzyme plays a crucial role in development and angiogenesis. The major human neutrophil chemoattractant, IL-8, stimulates fast degranulation of gelatinase B from neutrophils. Gelatinase B is also found to function as a regulator of neutrophil biology and to truncate IL-8 at the amino terminus into a tenfold more potent chemokine, resulting in an important positive feedback loop for neutrophil activation and chemotaxis. The CXC chemokines GRO-alpha, CTAP-III, and PF-4 are degraded by gelatinase B, whereas the CC chemokines MCP-2 and RANTES are not cleaved.

PECAM1, MPO and PRKAR1A at chromosome 17q21-q24 and susceptibility for multiple sclerosis in Sweden and Sardinia.

Using genome screen, DNA sequence and mapping data, we scanned the human chromosomal region 17q21-q24 for polymorphic markers in single copy genes. Three such genes were identified: the gene for myeloperoxidase (MPO) at 17q21.3-q23.2, containing a CA-microsatellite in the eighth intron and a functional single base substitution (G to A) in the promoter region, the platelet endothelial cell adhesion molecule-1 gene (PECAM1) at 17q23, which has a CA-repeat sequence in the sixth intron, and the gene for the regulatory subunit RIalpha of cAMP-dependent protein kinase (PRKAR1A) at 17q23-q24, in which a GA-microsatellite was detected in the 5'-flanking region. Association of these polymorphisms with multiple sclerosis (MS) was studied in a Swedish case-control population of 199 MS patients and 145 control subjects, and in 203 simplex families from Sardinia. None of these polymorphic genes was found to be a genetic marker for disease susceptibility. These results are in contrast with previous studies on the involvement of MPO in MS and suggest that the elevated expression of PECAM-1 in MS, as earlier documented, is related to transactivation by other gene products.

Polymorphism analysis suggests that the gelatinase B gene is not a susceptibility factor for multiple sclerosis.

The human gelatinase B (MMP-9) gene promoter region contains a CA microsatellite repeat and a single nucleotide polymorphism which are known to influence transcriptional activity. These two polymorphisms were used to investigate the existence of an association between multiple sclerosis (MS) susceptibility and the MMP-9 gene. In a case-control analysis of 345 Swedish individuals and in a study of 125 Sardinian simplex families no genetic associations between the gelatinase B gene polymorphisms and MS susceptibility were found. These data reinforce the suggestion of epistasis in the regulation of the metalloproteinase-inhibitor balance in MS.

Deficiency in phytoalexin production causes enhanced susceptibility of Arabidopsis thaliana to the fungus Alternaria brassicicola.

The phytoalexin-deficient Arabidopsis mutant pad3-1, which is affected in the production of the indole-type phytoalexin camalexin, has previously been shown not to display altered susceptibility to either the bacterium Pseudomonas syringae (Glazebrook & Ausubel 1994; Proc. Natl. Acad. Sci. USA, 91: 8955-8959) or the biotrophic fungi Peronospora parasitica (Glazebrook et al. 1997; Genetics, 146: 381-392) and Erysiphe orontii (Reuber et al. 1998; Plant J. 16: 473-485). We now show that this mutant is markedly more susceptible than its wild-type parental line to infection by the necrotrophic fungus Alternaria brassicicola, but not to Botrytis cinerea. A strong camalexin response was elicited in wild-type plants inoculated with either Alternaria brassicicola or Botrytis cinerea, whereas no camalexin could be detected in pad3-1 challenged with these fungi. Hence, PAD3 appears to be a key determinant in resistance to at least A. brassicicola. The induction of salicylate-dependent and jasmonate/ethylene-dependent defense genes was not reduced in Alternaria-challenged pad3-1 plants compared to similarly treated wild-type plants. Camalexin production could not be triggered by exogenous application of either salicylate, ethylene or jasmonate and was not, or not strongly, reduced in mutants with defects in perception of these defense-related signal molecules. Camalexin-production appears to be controlled by a pathway that exhibits little cross-talk with salicylate-, ethylene- and jasmonate-dependent signalling events.

Microsatellite polymorphisms in the gene promoter of monocyte chemotactic protein-3 and analysis of the association between monocyte chemotactic protein-3 alleles and multiple sclerosis development.

Monocyte chemotactic protein 3 (MCP-3) is a chemokine that attracts mononuclear cells, including monocytes and lymphocytes, the inflammatory cell types that predominate in multiple sclerosis lesions. We studied the possible association between the presence of a CA/GA microsatellite repeat polymorphism in the promoter/enhancer region of the MCP-3 gene and the occurrence of multiple sclerosis. DNA samples from 192 Swedish multiple sclerosis (MS) patients and 129 healthy controls were analysed by an automated fluorescent technique. In the whole sample population, five MCP-3 allele variants (MCP-3*A1 to MCP-3*A5) were detected with an allele frequency ranging between 0.3% and 46%. The individual MCP-3 allele frequencies did not differ significantly between MS patients and control individuals. The relative MS risk, attributable to HLA-DRB1*15 was 3.05 (chi2 = 22.25, p < 0.0001). The phenotype frequency (PF) of none of the MCP-3 alleles was significantly altered in the population of controls versus unselected MS patients. When MS patients and control subjects were stratified according to positivity for HLA-DRB1*15, the MCP-3*A4-associated risk for developing MS decreased to 0.36 (p = 0.011). In the stratified groups of patients who were negative for both HLA-DRB1*15 and HLA-DRB1*03, and hence possessed a lower risk to develop MS, the MCP-3*A2-associated risk for MS development decreased significantly (p = 0.018). We conclude that the MCP-3*A4 allele might protect against MS development on the background of the increased risk in HLA-DRB1*15+ individuals and the MCP-3*A2 allele seems protective in low-risk individuals, who are both negative for DRB1*03 and DRB1*15.

Computerized exposure and in vivo exposure treatments of spider fear in children: two case reports.

Two spider phobic children were first given a computerized exposure treatment, and then received exposure in vivo. The cases provided no evidence for the effectiveness of the computerized exposure treatment. Exposure in vivo was found to be very successful, resulting in substantial reduction of self-reported spider fear and clear improvement on the behavioral avoidance test.