Pro-Inflammatory Responses in Human Bronchial Epithelial Cells Induced by Spores and Hyphal Fragments of Common Damp Indoor Molds

[Medical clinical diagnostics for indoor mould exposure - Update 2023 (AWMF Register No. 161/001)]

This article is an abridged version of the updated AWMF mould guideline "Medical clinical diagnostics in case of indoor mould exposure - Update 2023", presented in July 2023 by the German Society of Hygiene, Environmental Medicine and Preventive Medicine (Gesellschaft für Hygiene, Umweltmedizin und Präventivmedizin, GHUP), in collaboration with German and Austrian scientific medical societies, and experts. Indoor mould growth is a potential health risk, even if a quantitative and/or causal relationship between the occurrence of individual mould species and health problems has yet to be established. There is no evidence for a causal relationship between moisture/mould damage and human diseases, mainly because of the ubiquitous presence of fungi and hitherto inadequate diagnostic methods. Sufficient evidence for an association between moisture/mould damage and the following health effects has been established for: allergic respiratory diseases, allergic rhinitis, allergic rhino-conjunctivitis, allergic bronchopulmonary aspergillosis (ABPA), other allergic bronchopulmonary mycosis (ABPM), aspergilloma, Aspergillus bronchitis, asthma (manifestation, progression, exacerbation), bronchitis (acute, chronic), community-acquired Aspergillus pneumonia, hypersensitivity pneumonitis (HP; extrinsic allergic alveolitis (EEA)), invasive Aspergillosis, mycoses, organic dust toxic syndrome (ODTS) [workplace exposure], promotion of respiratory infections, pulmonary aspergillosis (subacute, chronic), and rhinosinusitis (acute, chronically invasive, or granulomatous, allergic). In this context the sensitizing potential of moulds is obviously low compared to other environmental allergens. Recent studies show a comparatively low sensitization prevalence of 3-22,5 % in the general population across Europe. Limited or suspected evidence for an association exist with respect to atopic eczema (atopic dermatitis, neurodermatitis; manifestation), chronic obstructive pulmonary disease (COPD), mood disorders, mucous membrane irritation (MMI), odor effects, and sarcoidosis. (iv) Inadequate or insufficient evidence for an association exist for acute idiopathic pulmonary hemorrhage in infants, airborne transmitted mycotoxicosis, arthritis, autoimmune diseases, cancer, chronic fatigue syndrome (CFS), endocrinopathies, gastrointestinal effects, multiple chemical sensitivity (MCS), multiple sclerosis, neuropsychological effects, neurotoxic effects, renal effects, reproductive disorders, rheumatism, sick building syndrome (SBS), sudden infant death syndrome, teratogenicity, thyroid diseases, and urticaria.The risk of infection posed by moulds regularly occurring indoors is low for healthy persons; most species are in risk group 1 and a few in risk group 2 (Aspergillus fumigatus, A. flavus) of the German Biological Agents Act (Biostoffverordnung). Only moulds that are potentially able to form toxins can be triggers of toxic reactions. Whether or not toxin formation occurs in individual cases is determined by environmental and growth conditions, water activity, temperature and above all the growth substrates.In case of indoor moisture/mould damage, everyone can be affected by odor effects and/or mood disorders.However, this is not an acute health hazard. Predisposing factors for odor effects can include genetic and hormonal influences, imprinting, context and adaptation effects. Predisposing factors for mood disorders may include environmental concerns, anxiety, condition, and attribution, as well as various diseases. Risk groups to be protected particularly regarding infection risk are immunocompromised persons according to the classification of the German Commission for Hospital Hygiene and Infection Prevention (Kommission für Krankenhaushygiene und Infektionsprävention, KRINKO) at the Robert Koch-Institute (RKI), persons suffering from severe influenza, persons suffering from severe COVID-19, and persons with cystic fibrosis (mucoviscidosis); with regard to allergic risk, persons with cystic fibrosis (mucoviscidosis) and patients with bronchial asthma must be protected. The rational diagnostics include the medical history, physical examination, and conventional allergy diagnostics including provocation tests if necessary; sometimes cellular test systems are indicated. In the case of mould infections, the reader is referred to the specific guidelines. Regarding mycotoxins, there are currently no useful and validated test procedures for clinical diagnostics. From a preventive medical point of view, it is important that indoor mould infestation in relevant magnitudes cannot be tolerated for precautionary reasons.For evaluation of mould damage in the indoor environment and appropriate remedial procedures, the reader is referred to the mould guideline issued by the German Federal Environment Agency (Umweltbundesamt, UBA).

AWMF mold guideline "Medical clinical diagnostics for indoor mold exposure" - Update 2023 AWMF Register No. 161/001

None.

Indoor microbial exposure increases complement component C3a and C-reactive protein concentrations in serum

Indoor exposure to microbial growth, caused by moisture damage, has been an established health risk for several decades. It is likely that a damp indoor environment contains biological pollutants that trigger both the innate and adaptive branches of the immune system. In this study, we investigated the association between moisture damage related microbial exposure and serum C3a, C5a and CRP concentrations in Finnish adults. Serum C3a and CRP concentrations were elevated in individuals exposed to moisture damage and microbial growth in an indoor air environment. The elevated concentrations may be due to environmental factors present in moisture-damaged buildings. Complement activation and the resulting proinflammatory cleavage products may be a driving factor in inflammatory responses following exposure to indoor moisture damage and related microbial growth.

Pneumocystis carinii infection drives upregulation of Fn1 expression that causes pulmonary fibrosis with an inflammatory response

BACKGROUND

Pneumocystis carinii is an opportunistic fungal pathogen that may cause pneumonia and lead to pulmonary fibrosis.

AIMS

This study attempted to investigate the role of P. carinii infection-related genes in regulating lung fibrosis in mice.

METHODS

A screening of P. carinii infection-related differential mRNAs was performed using the GEO database, followed by protein-protein interaction (PPI) network construction using the STRING website in order to obtain P. carinii infection-related key genes. The development of a mouse model with gene aberrant expression was achieved by utilizing mice carrying the Cre-LoxP recombinase system. Dexamethasone was employed to induce tracheal infection in order to develop a model of pulmonary fibrosis, and the magnitude of lung injury was assessed by performing hematoxylin-eosin (H&E) staining and Masson staining. Lung coefficient and hydroxyproline level were assessed on sections of lung tissue as well. Finally, the magnitude of lung fibrosis and inflammation in mice was determined based on immunofluorescence and on the expression of genes associated with lung fibrosis and inflammation.

RESULTS

Fn1 was found by PPI with the highest connectivity in the PPI network associated with immunity and inflammation. Besides, Fn1 was significantly highly expressed in P. carinii-infected mice samples. The P carinii pneumonia (PCP)+Fn1fl/fl group had significantly higher lung coefficients, hydroxyproline levels and TNF-α, IL-6, IL-1β, IL-8 and NLRP3 expression levels, and significantly lower IL-10 expression levels. The results found in PCP+SPC-Cre:Fn1fl/fl group were the opposite. The results of the pulmonary fibrosis level study showed that the PCP+Fn1fl/fl group had the most intense H&E and Masson staining, and significantly higher expression levels of Col1A2, Col3A1 and α-SMA, which were lower in the PCP+SPC-Cre:Fn1fl/fl group.

CONCLUSIONS

P. carinii infection may promote the upregulation of Fn1, which causes pulmonary fibrosis with an inflammatory response.

Pathogenicity and virulence of Aspergillus fumigatus

Pulmonary infections caused by the mould pathogen Aspergillus fumigatus are a major cause of morbidity and mortality globally. Compromised lung defences arising from immunosuppression, chronic respiratory conditions or more recently, concomitant viral or bacterial pulmonary infections are recognised risks factors for the development of pulmonary aspergillosis. In this review, we will summarise our current knowledge of the mechanistic basis of pulmonary aspergillosis with a focus on emerging at-risk populations.

Potential Proallergenic Activity of Phytopathogenic Erysiphe palczewskii and Erysiphe convolvuli in in vitro Studies

Purpose

Allergic diseases have reached epidemic proportions globally, affecting nearly 30% of the world's population. One of the most prominent sources of allergens is fungi, causing up to 6% of respiratory diseases in the general population. However, the cause of respiratory allergies is not always identifiable. Therefore, we studied the ability of two representatives of common powdery mildew (Erysiphales), Erysiphe palczewskii and Erysiphe convolvuli, to induce a proinflammatory response in in vitro models of the upper and lower respiratory tract.

Materials and Methods

Two cell lines, BEAS-2B and A549, were used to mimic upper and lower respiratory epithelial cells. The toxicity of fungal extracts was assessed with MTT and flow cytometry assay. The production of reactive oxygen species in the cells was measured with flow cytometry. ELISA tests were used to determine the production of proinflammatory cytokines. The presence of the cell integrity marker was assessed with the immunofluorescence method.

Results

In both cell lines, the extract of E. palczewskii and E. convolvuli microfungi induced marked production of proinflammatory IL-1β, TNF-α, and GM-CSF cytokines involved in developing allergic reactions. The higher levels of these cytokines with higher reactive oxygen species synthesis positively correlated with the disruption of epithelial cell junctions.

Conclusion

We conclude that E. palczewskii and E. convolvuli microfungi have strong proinflammatory and proallergenic potential, but this finding needs in vivo confirmation.

Inhibition of the NF-κB Signaling Pathway Alleviates Pyroptosis in Bladder Epithelial Cells and Neurogenic Bladder Fibrosis

Most children with a neurogenic bladder (NB) have bladder fibrosis, which causes irreversible bladder dysfunction and damage to the upper urinary tract. However, the mechanism of bladder fibrosis remains unclear. This study aimed to investigate the underlying causes of bladder fibrosis. Here, the lumbar 6 (L6) and sacral 1 (S1) spinal nerves of Sprague Dawley rats were severed bilaterally to establish NB models. Using RNA-seq, we discovered that the NF-κB signaling pathway and inflammation were upregulated in spinal cord injury (SCI)-induced bladder fibrosis. Subsequent Western blotting, enzyme-linked immunosorbent assays, immunohistochemical staining, and immunofluorescence staining verified the RNA-seq findings. To further clarify whether the NF-κB signaling pathway and pyroptosis were involved in bladder fibrosis, a TGF-β1-treated urinary epithelial cell line (SV-HUC-1 cells) was used as an in vitro model. Based on the results of RNA-seq, we consistently found that the NF-κB signaling pathway and pyroptosis might play important roles in TGF-β1-treated cells. Further experiments also confirmed the RNA-seq findings in vitro. Moreover, using the NLRP3 inhibitor MCC950 rescued TGF-β1-induced fibrosis, and the NF-κB signaling pathway inhibitor BAY 11-7082 effectively rescued TGF-β1-induced pyroptosis and the deposition of extracellular matrix by SV-HUC-1 cells. In summary, our research demonstrated for the first time that the NF-κB signaling pathway inhibition rescued bladder epithelial cells pyroptosis and fibrosis in neurogenic bladders.

Qing Fei Hua Xian Decoction ameliorates bleomycin-induced pulmonary fibrosis by suppressing oxidative stress through balancing ACE-AngII-AT1R/ACE2-Ang-(1-7)-Mas axis

Objectives

We aimed to investigate the preventative effect of Qing Fei Hua Xian Decoction (QFHXD) against pulmonary fibrosis (PF) and its potential mechanisms.

Materials and Methods

Bleomycin (BLM)-induced rats were respectively treated with 413.3, 826.6, and 1239.9 mg/kg of QFHXD and prednisone for 28 days. The lung tissues of rats were collected on day 28 for histological and western blotting analysis.

Results

QFHXD significantly reduced alveolus inflammation, collagen accumulation, and fibrosis deposition in BLM-induced PF rats (P<0.05). Collagen I and III, vimentin, and α-smooth muscle actin(α-SMA) expression levels were likewise decreased in PF rats treated with QFHXD (P<0.05). Additionally, QFHXD increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) while decreasing NADPH oxidase 4 (NOX4) expression (P<0.05). Furthermore, QFHXD suppressed the PF progression by down-regulating Angiotensin-Converting Enzyme (ACE) -Angiotensin II (AngII) -Angiotensin II Type 1 Receptor (AT1R) axis (P<0.01) and up-regulating Angiotensin-Converting Enzyme 2 (ACE2) -Angiotensin-(1-7) (Ang-(1-7)) -Mas axis (P<0.05).

Conclusion

QFHXD suppressed inflammatory infiltration and PF brought on by BLM in lung tissues through reducing oxidative stress by maintaining the equilibrium of ACE-AngII-AT1R and ACE2-Ang-(1-7) -Mas axes. This study may provide a novel clinical therapy option for PF.

Respiratory Epithelial Cells: More Than Just a Physical Barrier to Fungal Infections

The respiratory epithelium is highly complex, and its composition varies along the conducting airways and alveoli. In addition to their primary function in maintaining the respiratory barrier and lung homeostasis for gas exchange, epithelial cells interact with inhaled pathogens, which can manipulate cell signaling pathways, promoting adhesion to these cells or hosting tissue invasion. Moreover, pathogens (or their products) can induce the secretion of chemokines and cytokines by epithelial cells, and in this way, these host cells communicate with the immune system, modulating host defenses and inflammatory outcomes. This review will focus on the response of respiratory epithelial cells to two human fungal pathogens that cause systemic mycoses: Aspergillus and Paracoccidioides. Some of the host epithelial cell receptors and signaling pathways, in addition to fungal adhesins or other molecules that are responsible for fungal adhesion, invasion, or induction of cytokine secretion will be addressed in this review.

What should be tested in patients with suspected mold exposure? Usefulness of serological markers for the diagnosis

The associations of mold exposure, IgE-mediated sensitization, inflammatory markers, and respiratory symptoms were analyzed in 46 exposed and 23 non-exposed individuals. Both exposure and clinical symptoms were assessed by questionnaire. Specific (s)IgE to mold mixture (mx1) was significantly higher and found more frequently in exposed (41%) than non-exposed individuals (17%), which was not observed for sIgG to mold mix (Gmx6). Notably, exposed asthmatics were more frequently sensitized to molds (55%) compared to exposed non-asthmatics (18%). In addition, the serum concentrations of club cell protein (CC16) were significantly lower in exposed subjects, especially in asthmatics. Positive associations were observed among mold sensitization, asthma, and mold exposure, but not in subjects with predominantly environmental sensitizations without mold sensitization. Thus, sIgE to mx1 but not sIgG to Gmx6 is a useful diagnostic marker to verify mold-associated respiratory symptoms.

Efficacy of Ebselen Against Invasive Aspergillosis in a Murine Model

Invasive aspergillosis is one of the major causes of morbidity and mortality among invasive fungal infections. The search for new antifungal drugs becomes imperative when existing drugs are not able to efficiently treat these infections. Ebselen, is an organoselenium compound, already successfully approved in clinical trials as a repositioned drug for the treatment of bipolar disorder and prevention of noise-induced hearing loss. In this study, we aimed to reposition ebselen for the treatment of invasive aspergillosis by showing ebselen effectiveness in a murine model. For this, BALB/c mice were immunosuppressed and infected systemically with Aspergillus fumigatus. Animals were divided and treated with ebselen, voriconazole, or drug-free control, for four days. The kidneys were used for CFU count and, histopathological and cytokine analysis. Ebselen was able to significantly reduce the fungal burden in the kidneys of infected mice with efficacy comparable with voriconazole treatment as both had reductions to the same extent. The absence of hyphae and intact kidney tissue structure observed in the histopathological sections analyzed from treated groups corroborate with the downregulation of IL-6 and TNF. In summary, this study brings for the first time in vivo evidence of ebselen efficacy against invasive aspergillosis. Despite these promising results, more animal studies are warranted to evaluate the potential role of ebselen as an alternative option for the management of invasive aspergillosis in humans.

Differential Proinflammatory Responses to Aspergillus fumigatus by Airway Epithelial Cells In Vitro Are Protease Dependent

Aspergillus fumigatus is an important human respiratory mould pathogen. In addition to a barrier function, airway epithelium elicits a robust defence against inhaled A. fumigatus by initiating an immune response. The manner by which A. fumigatus initiates this response and the reasons for the immunological heterogeneity with different isolates are unclear. Both direct fungal cell wall-epithelial cell interaction and secretion of soluble proteases have been proposed as possible mechanisms. Our aim was to determine the contribution of fungal proteases to the induction of epithelial IL-6 and IL-8 in response to different A. fumigatus isolates. Airway epithelial cells were exposed to conidia from a low or high protease-producing strain of A. fumigatus, and IL-6 and IL-8 gene expression and protein production were quantified. The role of proteases in cytokine production was further determined using specific protease inhibitors. The proinflammatory cytokine response correlated with conidia germination and hyphal extension. IL-8 induction was significantly reduced in the presence of matrix metalloprotease or cysteine protease inhibitors. With a high protease-producing strain of A. fumigatus, IL-6 release was metalloprotease dependent. Dectin-1 antagonism also inhibited the production of both cytokines. In conclusion, A. fumigatus-secreted proteases mediate a proinflammatory response by airway epithelial cells in a strain-dependent manner.

Scutellarin ameliorates pulmonary fibrosis through inhibiting NF-κB/NLRP3-mediated epithelial-mesenchymal transition and inflammation

Idiopathic pulmonary fibrosis (IPF) is featured with inflammation and extensive lung remodeling caused by overloaded deposition of extracellular matrix. Scutellarin is the major effective ingredient of breviscapine and its anti-inflammation efficacy has been reported before. Nevertheless, the impact of scutellarin on IPF and the downstream molecular mechanism remain unclear. In this study, scutellarin suppressed BLM-induced inflammation via NF-κB/NLRP3 pathway both in vivo and in vitro. BLM significantly elevated p-p65/p65 ratio, IκBα degradation, and levels of NLRP3, caspase-1, caspase-11, ASC, GSDMD^Nterm, IL-1β, and IL-18, while scutellarin reversed the above alterations except for that of caspase-11. Scutellarin inhibited BLM-induced epithelial-mesenchymal transition (EMT) process in vivo and in vitro. The expression levels of EMT-related markers, including fibronectin, vimentin, N-cadherin, matrix metalloproteinase 2 (MMP-2) and MMP-9, were increased in BLM group, and suppressed by scutellarin. The expression level of E-cadherin showed the opposite changes. However, overexpression of NLRP3 eliminated the anti-inflammation and anti-EMT functions of scutellarin in vitro. In conclusion, scutellarin suppressed inflammation and EMT in BLM-induced pulmonary fibrosis through NF-κB/NLRP3 signaling.

Characterization and pro-inflammatory potential of indoor mold particles

A number of epidemiological studies find an association between indoor air dampness and respiratory health effects. This is often suggested to be linked to enhanced mold growth. However, the role of mold is obviously difficult to disentangle from other dampness-related exposure including microbes as well as non-biological particles and chemical pollutants. The association may partly be due to visible mycelial growth and a characteristic musty smell of mold. Thus, the potential role of mold exposure should be further explored by evaluating information from experimental studies elucidating possible mechanistic links. Such studies show that exposure to spores and hyphal fragments may act as allergens and pro-inflammatory mediators and that they may damage airways by the production of toxins, enzymes, and volatile organic compounds. In the present review, we hypothesize that continuous exposure to mold particles may result in chronic low-grade pro-inflammatory responses contributing to respiratory diseases. We summarize some of the main methods for detection and characterization of fungal aerosols and highlight in vitro research elucidating how molds may induce toxicity and pro-inflammatory reactions in human cell models relevant for airway exposure. Data suggest that the fraction of fungal hyphal fragments in indoor air is much higher than that of airborne spores, and the hyphal fragments often have a higher pro-inflammatory potential. Thus, hyphal fragments of prevalent mold species with strong pro-inflammatory potential may be particularly relevant candidates for respiratory diseases associated with damp/mold-contaminated indoor air. Future studies linking of indoor air dampness with health effects should assess the toxicity and pro-inflammatory potential of indoor air particulate matter and combined this information with a better characterization of biological components including hyphal fragments from both pathogenic and non-pathogenic mold species. Such studies may increase our understanding of the potential role of mold exposure.

Bronchial Epithelial Cells on the Front Line to Fight Lung Infection-Causing Aspergillus fumigatus

Aspergillus fumigatus is an environmental filamentous fungus that can be pathogenic for humans, wherein it is responsible for a large variety of clinical forms ranging from allergic diseases to life-threatening disseminated infections. The contamination occurs by inhalation of conidia present in the air, and the first encounter of this fungus in the human host is most likely with the bronchial epithelial cells. Although alveolar macrophages have been widely studied in the Aspergillus–lung interaction, increasing evidence suggests that bronchial epithelium plays a key role in responding to the fungus. This review focuses on the innate immune response of the bronchial epithelial cells against A. fumigatus, the predominant pathogenic species. We have also detailed the molecular interactants and the effects of the different modes of interaction between these cells and the fungus.

Ribonuclease T2 from Aspergillus fumigatus promotes T helper type 2 responses through M2 polarization of macrophages

Allergic bronchopulmonary aspergillosis (ABPA) is an allergic immunological response to Aspergillus fumigatus (Af) exposure, which induces a strong T helper 2 (Th2) response via mechanisms that have yet to be elucidated. The aim of the present study was to investigate the hypothesis that T2 ribonuclease from Af (Af RNASET2) induces M2‑type macrophage polarization to produce a T helper 2 (Th2) immune response. Recombinant Af RNASET2 (rAf RNASET2) was expressed and purified in a prokaryotic pET system and BALB/c mice were immunized with rAf RNASET2 for in vivo analyses. Expression levels of M2 polarization factors were evaluated in RAW264.7 macrophages treated with rAf RNASET2 in vitro using flow cytometry, reverse transcription‑quantitative PCR, and western blot analysis. The results predicted that the mature Af RNASET2 protein (382 amino acids; GenBank no. MN593022) contained two conserved amino acid sequence (CAS) domains, termed CAS‑1 and CAS‑2, which are also characteristic of the RNASET2 family proteins. The protein expression levels of the Th2‑related cytokines interleukin (IL)‑4, IL‑10, and IL‑13 were upregulated in mice immunized with rAf RNASET2. RAW264.7 macrophages treated with rAf RNASET2 showed increased mRNA expression levels of M2 factors [arginase 1, Il‑10, and Il‑13]; however, there was no difference in cells treated with rAf RNASET2 that had been inactivated with a ribonuclease inhibitor (RNasin). The protein expression levels of IL‑10 in macrophage culture supernatant were also increased following stimulation with rAf RNASET2. In addition, rAf RNASET2 upregulated the expression of phosphorylated mitogen activated protein kinases (MAPKs) in RAW264.7 cells, whereas MAPK inhibitors attenuated rAf RNASET2‑induced IL‑10 expression in RAW264.7 cells. In conclusion, the present study reveals that high rAf RNASET2 activity is required for rAf RNASET2‑induced M2 polarization of macrophages and suggests an important immune regulatory role for Af RNASET2 in ABPA pathogenesis.

New Approach Methods to Evaluate Health Risks of Air Pollutants: Critical Design Considerations for In Vitro Exposure Testing

Air pollution consists of highly variable and complex mixtures recognized as major contributors to morbidity and mortality worldwide. The vast number of chemicals, coupled with limitations surrounding epidemiological and animal studies, has necessitated the development of new approach methods (NAMs) to evaluate air pollution toxicity. These alternative approaches include in vitro (cell-based) models, wherein toxicity of test atmospheres can be evaluated with increased efficiency compared to in vivo studies. In vitro exposure systems have recently been developed with the goal of evaluating air pollutant-induced toxicity; though the specific design parameters implemented in these NAMs-based studies remain in flux. This review aims to outline important design parameters to consider when using in vitro methods to evaluate air pollutant toxicity, with the goal of providing increased accuracy, reproducibility, and effectiveness when incorporating in vitro data into human health evaluations. This review is unique in that experimental considerations and lessons learned are provided, as gathered from first-hand experience developing and testing in vitro models coupled to exposure systems. Reviewed design aspects include cell models, cell exposure conditions, exposure chambers, and toxicity endpoints. Strategies are also discussed to incorporate in vitro findings into the context of in vivo toxicity and overall risk assessment.