Global gene expression changes underlying Stachybotrys chartarum toxin-induced apoptosis in murine alveolar macrophages: Evidence of multiple signal transduction pathways

Lung inflammation caused by inhaled toxicants: a review

Exposure of the lungs to airborne toxicants from different sources in the environment may lead to acute and chronic pulmonary or even systemic inflammation. Cigarette smoke is the leading cause of chronic obstructive pulmonary disease, although wood smoke in urban areas of underdeveloped countries is now recognized as a leading cause of respiratory disease. Mycotoxins from fungal spores pose an occupational risk for respiratory illness and also present a health hazard to those living in damp buildings. Microscopic airborne particulates of asbestos and silica (from building materials) and those of heavy metals (from paint) are additional sources of indoor air pollution that contributes to respiratory illness and is known to cause respiratory illness in experimental animals. Ricin in aerosolized form is a potential bioweapon that is extremely toxic yet relatively easy to produce. Although the aforementioned agents belong to different classes of toxic chemicals, their pathogenicity is similar. They induce the recruitment and activation of macrophages, activation of mitogen-activated protein kinases, inhibition of protein synthesis, and production of interleukin-1 beta. Targeting either macrophages (using nanoparticles) or the production of interleukin-1 beta (using inhibitors against protein kinases, NOD-like receptor protein-3, or P2X7) may potentially be employed to treat these types of lung inflammation without affecting the natural immune response to bacterial infections.

Early transcriptional responses of internalization defective Brucella abortus mutants in professional phagocytes, RAW 264.7

Background

Brucella abortus is an intracellular zoonotic pathogen which causes undulant fever, endocarditis, arthritis and osteomyelitis in human and abortion and infertility in cattle. This bacterium is able to invade and replicate in host macrophage instead of getting removed by this defense mechanism. Therefore, understanding the interaction between virulence of the bacteria and the host cell is important to control brucellosis. Previously, we generated internalization defective mutants and analyzed the envelope proteins. The present study was undertaken to evaluate the changes in early transcriptional responses between wild type and internalization defective mutants infected mouse macrophage, RAW 264.7.

Results

Both of the wild type and mutant infected macrophages showed increased expression levels in proinflammatory cytokines, chemokines, apoptosis and G-protein coupled receptors (Gpr84, Gpr109a and Adora2b) while the genes related with small GTPase which mediate intracellular trafficking was decreased. Moreover, cytohesin 1 interacting protein (Cytip) and genes related to ubiquitination (Arrdc3 and Fbxo21) were down-regulated, suggesting the survival strategy of this bacterium. However, we could not detect any significant changes in the mutant infected groups compared to the wild type infected group.

Conclusions

In summary, it was very difficult to clarify the alterations in host cellular transcription in response to infection with internalization defective mutants. However, we found several novel gene changes related to the GPCR system, ubiquitin-proteosome system, and growth arrest and DNA damages in response to B. abortus infection. These findings may contribute to a better understanding of the molecular mechanisms underlying host-pathogen interactions and need to be studied further.

Prenatal and postnatal risk factors for infantile pneumonia in a representative birth cohort

Pneumonia is an important cause of mortality and morbidity in infants. However, information of risk factors for pneumonia in children aged <6 months is limited. This study aimed to evaluate the risk factors and their contribution to infantile pneumonia in a large population-based survey. Of 24,200 randomly sampled main caregivers invited, 21,248 (87.8%) participated in this study. A structured questionnaire was used to interview the main caregivers. Information regarding whether hospitalization was required, family environment, and medical history were obtained. The prevalence of pneumonia was 0.62% in our study cohort. Multivariate logistic regression analysis showed that preterm birth, congenital cardiopulmonary disease, antibiotic use during pregnancy, maternal overweight, daily prenatal exposure to environmental tobacco smoke, maternal smoking during pregnancy, and visible mould on walls at home are risk factors associated with infantile pneumonia. Further study is warranted to investigate the causality and mechanisms of these novel factors.

Mechanisms of mycotoxin-induced neurotoxicity through oxidative stress-associated pathways

Among many mycotoxins, T-2 toxin, macrocyclic trichothecenes, fumonisin B(1) (FB(1)) and ochratochin A (OTA) are known to have the potential to induce neurotoxicity in rodent models. T-2 toxin induces neuronal cell apoptosis in the fetal and adult brain. Macrocyclic trichothecenes bring about neuronal cell apoptosis and inflammation in the olfactory epithelium and olfactory bulb. FB(1) induces neuronal degeneration in the cerebral cortex, concurrent with disruption of de novo ceramide synthesis. OTA causes acute depletion of striatal dopamine and its metabolites, accompanying evidence of neuronal cell apoptosis in the substantia nigra, striatum and hippocampus. This paper reviews the mechanisms of neurotoxicity induced by these mycotoxins especially from the viewpoint of oxidative stress-associated pathways.

Pulmonary responses to Stachybotrys chartarum and its toxins: mouse strain affects clearance and macrophage cytotoxicity

We investigated differences in the pulmonary and systemic clearance of Stachybotrys chartarum spores in two strains of mice, BALB/c and C57BL/6J. To evaluate clearance, mice were intratracheally instilled with a suspension of radiolabeled S. chartarum spores or with unlabeled spores. The lungs of C57BL/6J mice showed more rapid spore clearance than the lungs of BALB/c mice, which correlated with increased levels of spore-associated radioactivity in the GI tracts of C57BL/6J as compared with BALB/c mice. To identify mechanisms responsible for mouse strain differences in spore clearance and previously described lung inflammatory responses, we exposed alveolar macrophages (AMs) lavaged from BALB/c and C57BL/6J mice to S. chartarum spores, S. chartarum spore toxin (SST), and satratoxin G (SG) in vitro. The S. chartarum spores were found to be highly toxic with most cells from either mouse strain being killed within 24 h when exposed to a spore:cell ratio of 1:75. The spores were more lethal to AMs from C57BL/6J than those from BALB/c mice. In mice, the SST elicited many of the same inflammatory responses as the spores in vivo, including AM recruitment, pulmonary hemorrhage, and cytokine production. Our data suggest that differences in pulmonary spore clearance may contribute to the differences in pulmonary responses to S. chartarum between BALB/c and C57BL/6J mice. Enhanced AM survival and subsequent macrophage-mediated inflammation may also contribute to the higher susceptibility of BALB/c mice to S. chartarum pulmonary effects. Analogous genetic differences among humans may contribute to reported variable sensitivity to S. chartarum.

Bax is upregulated by p53 signal pathway in the SPE B-induced apoptosis

We identify integrin α(v)β(3) and Fas as receptors for the streptococcal pyrogenic exotoxin B (SPE B), and G308S (SPE B mutant, glycine at residue 308 is changed to serine), which interacts with Fas only, in our previous study. Here, we explore the signal pathways that regulate proapoptotic protein expression after SPE B stimulation. We find that both SPE B and G308S can stimulate the serine phosphorylation of p53, and p53 phosphorylation is inhibited by the anti-Fas antibody but not by anti-α(V)β(3) antibody. p38 inhibitor and siRNA decrease the activation and translocation of p53 into the nucleus, which executes its transcription activity. These results indicate that after SPE B treatment, p53 is activated and p38 is the upstream of p53. p38 siRNA also decreases the binding of p53 to the bax promoter and interferes with the association of p53 and STAT1. p53, p38, and STAT1 siRNAs downregulate SPE B-induced Bax expression. This shows that SPE B activates the bax promoter via p38/p53 signal pathways through the Fas receptor, and that STAT1 acts as a coactivator of p53. In addition, p38 and p53 siRNAs inhibit SPE B-induced apoptosis. This is consistent with the findings that SPE B upregulates Bax expression through p38/p53 signal pathways that enhance cell apoptosis.

[Non allergic disorders associated with domestic moulds]

INTRODUCTION

Mouldy surfaces are encountered in up to 20 % of dwellings. Because this indoor air contamination is so widespread, respiratory physicians should be aware of its effects on health and especially of its impact on respiratory diseases.

BACKGROUND

The air contaminants within mouldy dwellings are very diverse. Therefore, a given heath effect cannot be attributed specifically to an individual contaminant. In the field of respiratory diseases, excluding asthma and allergy, long-term exposure to indoor moulds has been recognized as a risk factor for both ENT and bronchial symptoms. Hydrophilic moulds seem to have a larger health impact than other mould species. Among respiratory diseases, inhalation fever and, to a lesser extent, childhood respiratory infections are linked to exposure to moulds. In contrast, the relationship between exposure to indoor moulds and diseases such as sinusitis, mucous irritation syndrome, recurrent respiratory infections in adults, COPD and pulmonary haemorrhage has not been clearly established.

VIEWPOINT

There are still many scientific uncertainties in this field. However, the authorities are becoming more active in dealing with unhealthy buildings and encouraging research.

CONCLUSION

The health impact of mouldy dwellings represents a major public health issue. It needs incentives from institutions and financial support as well as the involvement of many specialists.

Procaspase 8 and Bax are up-regulated by distinct pathways in Streptococcal pyrogenic exotoxin B-induced apoptosis

We have previously identified integrin alpha(v)beta(3) and Fas as receptors for the streptococcal pyrogenic exotoxin B (SPE B), and G308S, a mutant of SPE B that binds to Fas only. In the current study we found that after binding to alpha(v)beta(3), SPE B stimulated the tyrosine phosphorylation of JAK2 and STAT1. STAT1 tyrosine phosphorylation was inhibited by a JAK2 inhibitor, AG490, short interfering RNA (siRNA) silencing of JAK2, and anti-alpha(V)beta(3) antibody. AG490 also decreased the binding of tyrosine-phosphorylated STAT1 to the procaspase 8 promoter, decreasing procaspase 8 expression, suggesting that SPE B up-regulates procaspase 8 expression via the JAK2/STAT1 pathway. Alternatively, both SPE B and G308S increased STAT1 phosphorylation at serine 727, which was inhibited by anti-Fas antibody, a p38 inhibitor, SB203580, and siRNA silencing of p38. In addition, SPE B and G308S increased binding of serine-phosphorylated STAT1 to the Bax promoter and Bax expression, which was decreased by SB203580. SPE B and G308S-stimulated Bax expression was also inhibited by anti-Fas antibody. These findings suggest that Fas mediate SPE B-induced Bax expression through p38. Silencing of JAK2 or p38 by siRNA blocked procaspase 8 expression, whereas only p38 siRNA decreased Bax expression. Furthermore, JAK2 inhibition and p38 inhibition reduced SPE B-induced apoptosis, but only p38 inhibition blocked G308S-induced apoptosis.

Stachybotrys chartarum, trichothecene mycotoxins, and damp building-related illness: new insights into a public health enigma

Damp building-related illnesses (DBRI) include a myriad of respiratory, immunologic, and neurologic symptoms that are sometimes etiologically linked to aberrant indoor growth of the toxic black mold, Stachybotrys chartarum. Although supportive evidence for such linkages is limited, there are exciting new findings about this enigmatic organism relative to its environmental dissemination, novel bioactive components, unique cellular targets, and molecular mechanisms of action which provide insight into the S. chartarum's potential to evoke allergic sensitization, inflammation, and cytotoxicity in the upper and lower respiratory tracts. Macrocyclic trichothecene mycotoxins, produced by one chemotype of this fungus, are potent translational inhibitors and stress kinase activators that appear to be a critical underlying cause for a number of adverse effects. Notably, these toxins form covalent protein adducts in vitro and in vivo and, furthermore, cause neurotoxicity and inflammation in the nose and brain of the mouse. A second S. chartarum chemotype has recently been shown to produce atranones-mycotoxins that can induce pulmonary inflammation. Other biologically active products of this fungus that might contribute to pathophysiologic effects include proteinases, hemolysins, beta-glucan, and spirocyclic drimanes. Solving the enigma of whether Stachybotrys inhalation indeed contributes to DBRI will require studies of the pathophysiologic effects of low dose chronic exposure to well-characterized, standardized preparations of S. chartarum spores and mycelial fragments, and, coexposures with other environmental cofactors. Such studies must be linked to improved assessments of human exposure to this fungus and its bioactive constituents in indoor air using both state-of-the-art sampling/analytical methods and relevant biomarkers.