Akt and Notch pathways mediate polyhexamethylene guanidine phosphate-induced epithelial-mesenchymal transition via ZEB2

Next generation risk assessment of biocides (PHMG-p and CMIT/MIT)-induced pulmonary fibrosis using adverse outcome pathway-based transcriptome analysis

Next-generation risk assessment (NGRA) has emerged as a promising alternative to non-animal studies owing to the increasing demand for the risk assessment of inhaled toxicants. In this study, NGRA was used to assess the inhalation risks of two biocides commonly used as humidifier disinfectants: polyhexamethylene guanidine phosphate (PHMG-p) and chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT). Human bronchial epithelial cell transcriptomic data were processed based on adverse outcome pathways and used to establish transcriptome-based points of departure (tPODs) for each biocide. tPOD values were 0.00500-0.0510 μg/cm2 and 0.0342-0.0544 μg/cm2 for PHMG-p and CMIT/MIT, respectively. tPODs may provide predictive power comparable to that of traditional animal-based PODs (aPODs). The tPOD-based NGRA determined that both PHMG-p and CMIT/MIT present a high inhalation risk. Moreover, the identified PHMG-p posed a higher risk than CMIT/MIT, and children were identified as more susceptible population compared to adults. This finding is consistent with observations from actual exposure events. Our findings suggest that NGRA with transcriptomics offers a reliable approach for risk assessment of specific humidifier disinfectant biocides, while acknowledging the limitations of current models and in vitro systems, particularly regarding uncertainties in pharmacokinetics (PK) and pharmacodynamics (PD).

Synergistic interaction of co-exposure to humidifier disinfectant chemicals CMIT/MIT and PHMG in lung injury

A number of biocidal disinfectant chemicals are used as household products to prevent spread of pathogens. People are commonly exposed to multiple chemicals through those disinfectants. However, effects of interactions (e.g., synergism) between disinfectants on human health outcomes have been rarely studied. In this study, we aimed to investigate associations of a mixture of chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) and polyhexamethylene guanidine (PHMG), which had been used as humidifier disinfectants (HDs) in South Korea, with HD-associated lung injury (HDLI) in a Korean population (n = 4058) with HD exposure through use of HD products. Exposure to HD was retrospectively assessed by an interview-based standardized survey, and HDLI was determined by clinical assessment. After adjusting for covariates, PHMG-specific exposure indices (e.g., amount of use, indoor air concentration, and weekly exposure level) were dose-dependently associated with HDLI (their odds ratios for the comparison of third tertile versus first tertile were 1.95, 1.77, and 2.16, respectively). CMIT/MIT exposure was not observed to have a significant association with HDLI in a single chemical exposure model; however, associations between PHMG exposure and HDLI were strengthened by co-exposure to CMIT/MIT in combined chemical exposure models, where synergistic interactions between CMIT/MIT use and PHMG indices (amount of use and weekly exposure level) were observed (p-interaction in additive scale: 0.02 and 0.03, respectively). Our findings imply that adverse effects of PHMG exposure on lung injury among HD users might be worsened by co-exposure to CMIT/MIT. Given that plenty of household products contain disinfectants on global markets, epidemiological and toxicological investigations are warranted on interaction effects of co-exposure to disinfectants.

Polyhexamethylene guanidine accelerates the macrophage foamy formation mediated pulmonary fibrosis

Polyhexamethylene guanidine (PHMG) is manufactured and applied extensively due to its superior disinfectant capabilities. However, the inhalatory exposure to PHMG aerosols is increasingly recognized as a potential instigator of pulmonary fibrosis, prompting an urgent call for elucidation of the underlying pathophysiological mechanisms. Within this context, alveolar macrophages play a pivotal role in the primary immune defense in the respiratory tract. Dysregulated lipid metabolism within alveolar macrophages leads to the accumulation of foam cells, a process that is intimately linked with the pathogenesis of pulmonary fibrosis. Therefore, this study examines PHMG's effects on alveolar macrophage foaminess and its underlying mechanisms. We conducted a 3-week inhalation exposure followed by a 3-week recovery period in C57BL/6 J mice using a whole-body exposure system equipped with a disinfection aerosol generator (WESDAG). The presence of lipid-laden alveolar macrophages and downregulation of pulmonary tissue lipid transport proteins ABCA1 and ABCG1 were observed in mice. In cell culture models involving lipid-loaded macrophages, we demonstrated that PHMG promotes foam cell formation by inhibiting lipid efflux in mouse alveolar macrophages. Furthermore, PHMG-induced foam cells were found to promote an increase in the release of TGF-β1, fibronectin deposition, and collagen remodeling. In vivo interventions were subsequently implemented on mice exposed to PHMG aerosols, aiming to restore macrophage lipid efflux function. Remarkably, this intervention demonstrated the potential to retard the progression of pulmonary fibrosis. In conclusion, this study underscores the pivotal role of macrophage foaming in the pathogenesis of PHMG disinfectants-induced pulmonary fibrosis. Moreover, it provides compelling evidence to suggest that the regulation of macrophage efflux function holds promise for mitigating the progression of pulmonary fibrosis, thereby offering novel insights into the mechanisms underlying inhaled PHMG disinfectants-induced pulmonary fibrosis.

A literature review of bioactive substances for the treatment of periodontitis: In vitro, in vivo and clinical studies

Periodontitis is a common chronic inflammatory disease of the supporting tissues of the tooth that involves a complex interaction of microorganisms and various cell lines around the infected site. To prevent and treat this disease, several options are available, such as scaling, root planning, antibiotic treatment, and dental surgeries, depending on the stage of the disease. However, these treatments can have various side effects, including additional inflammatory responses, chronic wounds, and the need for secondary surgery. Consequently, numerous studies have focused on developing new therapeutic agents for more effective periodontitis treatment. This review explores the latest trends in bioactive substances with therapeutic effects for periodontitis using various search engines. Therefore, this study aimed to suggest effective directions for therapeutic approaches. Additionally, we provide a summary of the current applications and underlying mechanisms of bioactive substances, which can serve as a reference for the development of periodontitis treatments.

Involvement of Epithelial-Mesenchymal Transition (EMT) in Autoimmune Diseases

Epithelial-mesenchymal transition (EMT) is a complex reversible biological process characterized by the loss of epithelial features and the acquisition of mesenchymal features. EMT was initially described in developmental processes and was further associated with pathological conditions including metastatic cascade arising in neoplastic progression and organ fibrosis. Fibrosis is delineated by an excessive number of myofibroblasts, resulting in exuberant production of extracellular matrix (ECM) proteins, thereby compromising organ function and ultimately leading to its failure. It is now well acknowledged that a significant number of myofibroblasts result from the conversion of epithelial cells via EMT. Over the past two decades, evidence has accrued linking fibrosis to many chronic autoimmune and inflammatory diseases, including systemic sclerosis (SSc), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), and inflammatory bowel diseases (IBD). In addition, chronic inflammatory states observed in most autoimmune and inflammatory diseases can act as a potent trigger of EMT, leading to the development of a pathological fibrotic state. In the present review, we aim to describe the current state of knowledge regarding the contribution of EMT to the pathophysiological processes of various rheumatic conditions.

Emodin inhibiting epithelial-mesenchymal transition in pulmonary fibrosis through the c-MYC/miR-182-5p/ZEB2 axis

Emodin is a natural anthraquinone compound, which is the main component found in the traditional Chinese herb Polygonum cuspidatum. The anti-fibrosis effects of Emodin have been reported. This study aimed to explore the specific mechanism of Emodin in the epithelial-mesenchymal transition (EMT) of pulmonary fibrosis. The pulmonary fibrosis mice models were constructed with bleomycin, the EMT models of alveolar epithelial cells were stimulated by TGF-β1, and Emodin was used for intervention. c-MYC and miR-182-5p were overexpressed or silenced by cell transfection. Our results demonstrated that Emodin attenuated pulmonary fibrosis induced by bleomycin in mice, and inhibited EMT, meanwhile downregulated c-MYC, upregulated miR-182-5p, and downregulated ZEB2 in vitro and vivo. Next, overexpression of c-MYC promoted EMT, while silencing c-MYC and overexpressing miR-182-5p inhibited EMT. Then, c-MYC negatively regulated the expression of miR-182-5p with a direct binding relationship. And miR-182-5p inhibited ZEB2 expression in a targeted manner. Finally, Emodin inhibited EMT that had been promoted by overexpression of c-MYC. In conclusion, Emodin could attenuate pulmonary fibrosis and EMT by regulating the c-MYC/miR-182-5p/ZEB2 axis, which might provide evidence for the application of Emodin in the treatment of pulmonary fibrosis.

The Orphan GPR50 Receptor Regulates the Aggressiveness of Breast Cancer Stem-like Cells via Targeting the NF-kB Signaling Pathway

The expression of GPR50 in CSLC and several breast cancer cell lines was assessed by RT-PCR and online platform (UALCAN, GEPIA, and R2 gene analysis). The role of GPR50 in driving CSLC, sphere formation, cell proliferation, and migration was performed using shGPR50 gene knockdown, and the role of GPR50-regulated signaling pathways was examined by Western blotting and Luciferase Assay. Herein, we confirmed that the expression of G protein-coupled receptor 50 (GPR50) in cancer stem-like cells (CSLC) is higher than that in other cancer cells. We examined that the knockdown of GPR50 in CSLC led to decreased cancer properties, such as sphere formation, cell proliferation, migration, and stemness. GPR50 silencing downregulates NF-kB signaling, which is involved in sphere formation and aggressiveness of CSLC. In addition, we demonstrated that GPR50 also regulates ADAM-17 activity by activating NOTCH signaling pathways through the AKT/SP1 axis in CSLC. Overall, we demonstrated a novel GPR50-mediated regulation of the NF-κB-Notch signaling pathway, which can provide insights into CSLC progression and prognosis, and NF-κB-NOTCH-based CSLC treatment strategies.

A multiplex inhalation platform to model in situ like aerosol delivery in a breathing lung-on-chip

Prolonged exposure to environmental respirable toxicants can lead to the development and worsening of severe respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD) and fibrosis. The limited number of FDA-approved inhaled drugs for these serious lung conditions has led to a shift from in vivo towards the use of alternative in vitro human-relevant models to better predict the toxicity of inhaled particles in preclinical research. While there are several inhalation exposure models for the upper airways, the fragile and dynamic nature of the alveolar microenvironment has limited the development of reproducible exposure models for the distal lung. Here, we present a mechanistic approach using a new generation of exposure systems, the Cloud α AX12. This novel in vitro inhalation tool consists of a cloud-based exposure chamber (VITROCELL) that integrates the breathing ^AXLung-on-chip system (AlveoliX). The ultrathin and porous membrane of the AX12 plate was used to create a complex multicellular model that enables key physiological culture conditions: the air-liquid interface (ALI) and the three-dimensional cyclic stretch (CS). Human-relevant cellular models were established for a) the distal alveolar-capillary interface using primary cell-derived immortalized alveolar epithelial cells (^AXiAECs), macrophages (THP-1) and endothelial (HLMVEC) cells, and b) the upper-airways using Calu3 cells. Primary human alveolar epithelial cells (^AXhAEpCs) were used to validate the toxicity results obtained from the immortalized cell lines. To mimic in vivo relevant aerosol exposures with the Cloud α AX12, three different models were established using: a) titanium dioxide (TiO2) and zinc oxide nanoparticles b) polyhexamethylene guanidine a toxic chemical and c) an anti-inflammatory inhaled corticosteroid, fluticasone propionate (FL). Our results suggest an important synergistic effect on the air-blood barrier sensitivity, cytotoxicity and inflammation, when air-liquid interface and cyclic stretch culture conditions are combined. To the best of our knowledge, this is the first time that an in vitro inhalation exposure system for the distal lung has been described with a breathing lung-on-chip technology. The Cloud α AX12 model thus represents a state-of-the-art pre-clinical tool to study inhalation toxicity risks, drug safety and efficacy.

Health Effects Associated With Humidifier Disinfectant Use: A Systematic Review for Exploration

BACKGROUND

It has been 10 years since the outbreak of lung disease caused by humidifier disinfectants in Korea, but the health effects have not yet been summarized. Therefore, this study aims to systematically examine the health effects of humidifier disinfectants that have been discovered so far.

METHODS

All literature with humidifier disinfectants and their representative components as the main words were collected based on the web, including PubMed, Research Information Sharing Service, and government publication reports. A total of 902 studies were searched, of which 196 were selected. They were divided into four groups: published human studies (group 1), published animal and cytotoxicology studies (group 2), technical reports (group 3), and gray literature (group 4).

RESULTS

Out of the 196 studies, 97 (49.5%) were published in peer-reviewed journals as original research. Group 1 consisted of 49 articles (50.5%), while group 2 consisted of 48 articles (49.5%). Overall, respiratory diseases such as humidifier disinfectant associated lung injury, interstitial lung disease, and asthma have a clear correlation, but other effects such as liver, heart, thymus, thyroid, fetal growth, metabolic abnormalities, and eyes are observed in toxicological experimental studies, but have not yet been identified in epidemiologic studies.

CONCLUSION

The current level of evidence does not completely rule out the effects of humidifier disinfectants on extrapulmonary disease. Based on the toxicological evidence so far, it is required to monitor the population of humidifier disinfectant exposure continuously to see if similar damage occurs.

Epithelial-mesenchymal transition in organ fibrosis development: current understanding and treatment strategies

Organ fibrosis is a process in which cellular homeostasis is disrupted and extracellular matrix is excessively deposited. Fibrosis can lead to vital organ failure and there are no effective treatments yet. Although epithelial–mesenchymal transition (EMT) may be one of the key cellular mechanisms, the underlying mechanisms of fibrosis remain largely unknown. EMT is a cell phenotypic process in which epithelial cells lose their cell-to-cell adhesion and polarization, after which they acquire mesenchymal features such as infiltration and migration ability. Upon injurious stimulation in different organs, EMT can be triggered by multiple signaling pathways and is also regulated by epigenetic mechanisms. This narrative review summarizes the current understanding of the underlying mechanisms of EMT in fibrogenesis and discusses potential strategies for attenuating EMT to prevent and/or inhibit fibrosis. Despite better understanding the role of EMT in fibrosis development, targeting EMT and beyond in developing therapeutics to tackle fibrosis is challenging but likely feasible.

Analysis of lung cancer-related genetic changes in long-term and low-dose polyhexamethylene guanidine phosphate (PHMG-p) treated human pulmonary alveolar epithelial cells

BACKGROUND

Lung injury elicited by respiratory exposure to humidifier disinfectants (HDs) is known as HD-associated lung injury (HDLI). Current elucidation of the molecular mechanisms related to HDLI is mostly restricted to fibrotic and inflammatory lung diseases. In our previous report, we found that lung tumors were caused by intratracheal instillation of polyhexamethylene guanidine phosphate (PHMG-p) in a rat model. However, the lung cancer-related genetic changes concomitant with the development of these lung tumors have not yet been fully defined. We aimed to discover the effect of long-term exposure of PHMG-p on normal human lung alveolar cells.

METHODS

We investigated whether PHMG-p could increase distorted homeostasis of oncogenes and tumor-suppressor genes, with long-term and low-dose treatment, in human pulmonary alveolar epithelial cells (HPAEpiCs). Total RNA sequencing was performed with cells continuously treated with PHMG-p and harvested after 35 days.

RESULTS

After PHMG-p treatment, genes with transcriptional expression changes of more than 2.0-fold or less than 0.5-fold were identified. Within 10 days of exposure, 2 protein-coding and 5 non-coding genes were selected, whereas in the group treated for 27-35 days, 24 protein-coding and 5 non-coding genes were identified. Furthermore, in the long-term treatment group, 11 of the 15 upregulated genes and 9 of the 14 downregulated genes were reported as oncogenes and tumor suppressor genes in lung cancer, respectively. We also found that 10 genes of the selected 24 protein-coding genes were clinically significant in lung adenocarcinoma patients.

CONCLUSIONS

Our findings demonstrate that long-term exposure of human pulmonary normal alveolar cells to low-dose PHMG-p caused genetic changes, mainly in lung cancer-associated genes, in a time-dependent manner.

Polyhexamethylene guanidine phosphate increases stress granule formation in human 3D lung organoids under respiratory syncytial virus infection

Polyhexamethylene guanidine phosphate (PHMG-p), a humidifier disinfectant, is known to cause lung toxicity, including inflammation and pulmonary fibrosis. In this study, we aimed to investigate the effect of PHMG-p on human lung tissue models (2D epithelial cells and 3D organoids) under conditions of oxidative stress and viral infection. The effect of PHMG-p was studied by evaluating the formation of stress granules (SGs), which play a pivotal role in cellular adaptation to various stress conditions. Under oxidative stress and respiratory syncytial virus (RSV) infection, exposure to PHMG-p remarkably increased eIF2α phosphorylation, which is essential for SG-related signalling, and significantly increased SG formation. Furthermore, PHMG-p induced fibrotic gene expression and caused cell death due to severe DNA damage, which was further increased under oxidative stress and RSV infection, indicating that PHMG-p induces severe lung toxicity under stress conditions. Taken together, toxicity evaluation under various stressful conditions is necessary to accurately predict potential lung toxicity of chemicals affecting the respiratory tract.

Selective suppression of M1 macrophages is involved in zinc inhibition of liver fibrosis in mice

Zinc deficiency is common in the liver of patients with chronic liver disease. Zinc supplementation suppresses the progression of liver fibrosis induced by bile duct ligation (BDL) in mice. The present study was undertaken to specifically investigate a possible mechanism by which zinc plays this role in the liver. Kunming mice were subjected to BDL for 4 weeks to induce liver fibrosis, and concomitantly treated with zinc sulfite or saline as control by gavage once a day. The results showed that zinc supplementation significantly suppressed liver fibrosis and inflammation along with inhibition of hepatic stellate cells activation induced by BDL. These inhibitory effects were accompanied by the reduction of collagen deposition and a significant reduction of macrophage infiltration affected livers. Importantly, zinc selectively inhibited M1 macrophage polarization and M1-related inflammatory cytokines. This inhibitory effect was further confirmed by the reduction of relevant biomarkers of M1 macrophages including inducible NO synthase (iNOS), monocyte chemotactic protein-1 (MCP-1/CCL2), and tumor necrosis factor-α in the zinc supplemented BDL livers. In addition, zinc inhibition of M1 macrophages was associated with a decrease of Notch1 expression. Taken together, these data indicated that zinc supplementation inhibited liver inflammation and fibrosis in BDL mice through selective suppression of M1 macrophages, which is associated with inhibition of Notch1 pathway in M1 macrophage polarization.

miR-138 inhibits epithelial-mesenchymal transition in silica-induced pulmonary fibrosis by regulating ZEB2

Silica dust is a common pollutant in the occupational environment, such as coal mines. Inhalation of silica dust can cause progressive pulmonary fibrosis and then silicosis. Silicosis is still one of the most harmful occupational diseases in the world, so the study of its pathogenesis is necessary for the treatment of silicosis. In this study, we constructed a mouse model of pulmonary fibrosis via intratracheal instillation of silica particles and identified the decreased expression of miR-138 in fibrotic lung tissues of mice. Moreover, the overexpression of miR-138 retarded the process of epithelial-mesenchymal transition (EMT) in a mouse model of silica particles exposure and epithelial cells stimulated by silica particles. Further studies showed that ZEB2 was one of the potential targets of miR-138, and the up-regulation of miR-138 reduced ZEB2 levels in mouse lung tissues and in epithelial cells. We next found that the expression levels of ɑ-SMA and Vimentin were significantly increased and E-cadherin levels were decreased after transfection with miR-138 inhibitor in epithelial cells. However, these effects were abated by the knockdown of ZEB2. Consistently, the increased migration ability of epithelial cells by miR-138 inhibitor transfection was also reversed by the knockdown of ZEB2. Collectively, we revealed that miR-138 significantly targeted ZEB2, thus inhibited the EMT process and mitigated the development of pulmonary fibrosis. miR-138 may be a potential target for the treatment of pulmonary fibrosis.

Reprogrammed lung epithelial cells by decrease of miR-451a in extracellular vesicles contribute to aggravation of pulmonary fibrosis

Extracellular vesicles (EVs) play novel roles in homeostasis through cell-to-cell communication in human airways via transferring miRNAs. However, the contribution of EV miRNAs to pulmonary phenotypic homeostasis is not clearly understood. Hence, the aim of this study was to elucidate the functional role of miRNAs obtained from epithelium-derived EVs in lung fibrogenesis. Pulmonary fibrosis was induced by exposure of polyhexamethylene guanidine phosphate (PHMG-p)-instilled mice. In histopathological changes, a clear phenotypic change was observed in bronchial epithelium. For figuring out the role of EVs derived from conditioned media of untreated cells (EV-Con) and PHMG-p-treated BEAS-2B (EV-PHMG), significant increase in EVs released from PHMG-p-treated BEAS-2B was detected. Functional analysis with targets of differentially expressed miRNAs in EVs was annotated to epithelial-mesenchymal transition (EMT). Especially, the most abundant miRNA, miR-451a, was downregulated in EV of PHMG-p-treated BEAS-2B cells. We found that odd-skipped related 1 (OSR1) was a putative target for miR-451a, which had been known as a transcription factor of several fibrosis-associated genes. Transfer of decreased miR-451a via EV-PHMG upregulated OSR1 and induced EMT compared to Con-EV-treated cells. In pulmonary fibrosis mice, miR-451a levels were significantly reduced in EV derived from bronchoalveolar lavage fluid and OSR1 expression was increased in lung tissues of mice with PHMG-p exposure. MiR-451a-transfected EVs markedly alleviated fibrogenesis in the PHMG-p-exposed lungs. Low level of miR-451a in EVs modulated EMT and fibrogenesis in recipient cells by increasing OSR1 levels in vitro and in vivo. Our results suggest that transferring EV miR-451a induces anti-fibrotic autocrine effect by downregulating its target, OSR1 maintaining pulmonary homeostasis disrupted by PHMG-p exposure, which can be a potential therapeutic target.

CircMMP11 regulates proliferation, migration, invasion, and apoptosis of breast cancer cells through miR-625-5p/ZEB2 axis

Background

Circular RNAs (circRNAs) have been demonstrated to play significant roles in regulating gene expression in tumorigenesis, including breast cancer (BC). This study was designed to explore the role and underlying molecular mechanisms of circMMP11 in BC.

Methods

The real-time quantitative polymerase chain reaction (RT-qPCR) assay was used for examining expression of circMMP11, microRNA-625-5p (miR-625-5p), and Zinc finger E-box binding homeobox-2 (ZEB2). The protein expression of ZEB2, Vimentin, and E-cadherin was assessed by western blot assay. The proliferation ability of BC cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazol-3-ium bromide (MTT) and colony-forming assays. The transwell assay was used to measure migration and invasion of BC cells. The apoptotic cells were examined by flow cytometry assay. The interaction association among circMMP11, miR-625-5p, and ZEB2 was confirmed by RNA pull-down and dual-luciferase report assays. A xenograft experiment was established to clarify the role of circMMP11 silencing in vivo.

Results

We found that circMMP11 and ZEB2 were overexpressed in BC tissues and cells compared with controls. The suppression of circMMP11 or ZEB2 repressed proliferation, migration, and invasion while induced apoptosis of BC cells. Additionally, miR-625-5p, interacted with ZEB2, was a target of circMMP11 in BC cells. CircMMP11 regulated the expression of ZEB2 by targeting miR-625-5p. Knockdown of circMMP11-mediated effects on BC cells could be abolished by overexpression of ZEB2. Consistently, silencing of circMMP11 impeded the tumor growth in vivo.

Conclusions

CircMMP11/miR-625-5p/ZEB2 axis affected proliferation, migration, invasion, and apoptosis of BC cells through the mechanism of competing endogenous RNAs (ceRNA), indicating that circMMP11 was an oncogenic circRNA in BC.

Polyhexamethylene Guanidine Phosphate Induces Apoptosis through Endoplasmic Reticulum Stress in Lung Epithelial Cells

Airway epithelial cell death contributes to the pathogenesis of lung fibrosis. Polyhexamethylene guanidine phosphate (PHMG-p), commonly used as a disinfectant, has been shown to be strongly associated with lung fibrosis in epidemiological and toxicological studies. However, the molecular mechanism underlying PHMG-p-induced epithelial cell death is currently unclear. We synthesized a PHMG-p–fluorescein isothiocyanate (FITC) conjugate and assessed its uptake into lung epithelial A549 cells. To examine intracellular localization, the cells were treated with PHMG-p–FITC; then, the cytoplasmic organelles were counterstained and observed with confocal microscopy. Additionally, the organelle-specific cell death pathway was investigated in cells treated with PHMG-p. PHMG-p–FITC co-localized with the endoplasmic reticulum (ER), and PHMG-p induced ER stress in A549 cells and mice. The ER stress inhibitor tauroursodeoxycholic acid (TUDCA) was used as a pre-treatment to verify the role of ER stress in PHMG-p-induced cytotoxicity. The cells treated with PHMG-p showed apoptosis, which was inhibited by TUDCA. Our results indicate that PHMG-p is rapidly located in the ER and causes ER-stress-mediated apoptosis, which is an initial step in PHMG-p-induced lung fibrosis.

Aesculetin Attenuates Alveolar Injury and Fibrosis Induced by Close Contact of Alveolar Epithelial Cells with Blood-Derived Macrophages via IL-8 Signaling

Pulmonary fibrosis is a disease in which lung tissues become fibrous and thereby causes severe respiratory disturbances. Various stimuli induce infiltration of macrophages to the respiratory tract, secreting inflammatory cytokines, which subsequently leads to the development of pulmonary fibrosis. Aesculetin, a major component of the sancho tree and chicory, is known to biologically have antioxidant and anti-inflammatory effects. Human alveolar epithelial A549 cells were cultured for 24 h in conditioned media of THP-1 monocyte-derived macrophages (mCM) with 1–20 μM aesculetin. Micromolar aesculetin attenuated the cytotoxicity of mCM containing inflammatory tumor necrosis factor-α (TNF)-α and interleukin (IL)-8 as major cytokines. Aesculetin inhibited alveolar epithelial induction of the mesenchymal markers in mCM-exposed/IL-8-loaded A549 cells (≈47–51% inhibition), while epithelial markers were induced in aesculetin-treated cells subject to mCM/IL-8 (≈1.5–2.3-fold induction). Aesculetin added to mCM-stimulated A549 cells abrogated the collagen production and alveolar epithelial CXC-chemokine receptor 2 (CXCR2) induction. The production of matrix metalloproteinase (MMP) proteins in mCM-loaded A549 cells was reduced by aesculetin (≈52% reduction), in parallel with its increase in tissue inhibitor of metalloproteinases (TIMP) proteins (≈1.8-fold increase). In addition, aesculetin enhanced epithelial induction of tight junction proteins in mCM-/IL-8-exposed cells (≈2.3–2.5-fold induction). The inhalation of polyhexamethylene guanidine (PHMG) in mice accompanied neutrophil predominance in bronchoalveolar lavage fluid (BALF) and macrophage infiltration in alveoli, which was inhibited by orally administrating aesculetin to mice. Treating aesculetin to mice alleviated PHMG-induced IL-8-mediated subepithelial fibrosis and airway barrier disruption. Taken together, aesculetin may antagonize pulmonary fibrosis and alveolar epithelial barrier disruption stimulated by the infiltration of monocyte-derived macrophages, which is typical of PHMG toxicity, involving interaction of IL-8 and CXCR2. Aesculetin maybe a promising agent counteracting macrophage-mediated inflammation-associated pulmonary disorders.

Mitochondria disease due to humidifier disinfectants: diagnostic criteria and its evidences

Humidifier disinfectant damages caused by the misuse of humidifier disinfects, such as polyhexamethylene guanidine (PHMG), resulted in chemical disasters in South Korea in 2011. About four million people were exposed to humidifier disinfectants (HDs) in the 17 years between 1994 and 2011. Although fatal lung damage was initially reported, investigations into the victims’ injuries revealed that the damage was not limited to the lungs, but that systemic damage was also confirmed. Considering the spread of HD from the lungs to the whole body, the toxic effects of PHMG from reactive oxygen species (ROS), NOTCH signaling pathways, and mitochondrial dysfunction resulted in endothelial damage in the lungs, blood vessels, liver, kidneys, bone marrow, nerves, and muscles. The main toxic mechanisms involved in HD damage may be the NOTCH pathway and mitochondrial damage. There are many case reports which include neurologic disorders (ADHD, depression, posttraumatic stress disorder), muscular disorder (exercise intolerance, myalgia), energy metabolism disorder (chronic fatigue syndrome), and immunologic disorder (rheumatoid arthritis) in HDs victims. These case reports involve multi-system involvement in HDs victims. Further well-designed study is needed to clarify whether mitochondrial dysfunction is associated with multi-organs involvement in HDs victims.

NOTCH1 Pathway is Involved in Polyhexamethylene Guanidine-Induced Humidifier Disinfectant Lung Injuries

An outbreak of fatal humidifier disinfectant lung injuries (HDLI) occurred in Korea. Human studies on mechanisms underlying HDLI have yet to be conducted. This study aimed to investigate methylation changes and their potential role in HDLI after exposure to HDs containing polyhexamethylene guanidine-phosphate. DNA methylation analysis was performed in blood samples from 10 children with HDLI and 10 healthy children using Infinium Human MethylationEPIC BeadChip. Transcriptome analysis was performed using lung tissues from 5 children with HDLI and 5 controls. Compared to healthy controls, 92 hypo-methylated and 79 hyper-methylated CpG sites were identified in children with HDLI at the statistical significance level of |Δβ|>0.2 and p<0.05. NOTCH1 was identified as a candidate network hub gene in cases. NOTCH1 transcripts significantly increased in lung tissues from HDLI cases compared to unexposed controls (p=0.05). NOTCH1 may play an important role in pulmonary fibrosis of HDLI.