Effect of a chemical chaperone, tauroursodeoxycholic acid, on HDM-induced allergic airway disease

Effects of glial-derived neurotrophic factor on remodeling and mitochondrial function in human airway smooth muscle cells

Airway smooth muscle (ASM) cells play important roles in airway remodeling of asthma. Our previous studies show that in vivo administration of glial-derived neurotrophic factor (GDNF) in mice induces thickening and collagen deposition in bronchial airways, whereas chelation of GDNF by GFRα1-Fc attenuates airway remodeling in the context of allergen exposure. To determine whether GDNF has direct effects on ASM, in this study, we examined GDNF in ASM cells from normal versus asthmatic humans. We found that GDNF treatment of human ASM cells had only minor effects on cell proliferation and migration, intracellular expression or extracellular deposition of collagen I (COL1), collagen III (COL3), and fibronectin. Endoplasmic reticulum (ER) stress response and mitochondrial function have been implicated in asthma. We investigated whether GDNF regulates these aspects in human ASM. We found that GDNF treatment did not affect ER stress protein expression in normal or asthmatic cells. However, GDNF treatment impaired mitochondrial morphology in ASM but without significant effects on mitochondrial respiration. Thus, it is likely that in vivo effects of GDNF on airway remodeling per se involve cell types other than those on ASM, and thus ASM may serve more as a source of GDNF rather than a target.NEW & NOTEWORTHY Our previous study suggests that glial-derived neurotrophic factor (GDNF) is involved in allergen-induced airway hyperreactivity and remodeling in vivo. Here, we show that GDNF has no direct effects in remodeling of human airway smooth muscle (ASM) but GDNF dysregulates mitochondrial morphology in human ASM in the context of asthma.

Untargeted metabolomic analysis reveals different metabolites associated with response to mepolizumab and omalizumab in asthma

Background

There is limited evidence on biomarkers associated with response to the monoclonal antibodies currently approved for asthma treatment. We sought to identify circulatory metabolites associated with response to treatment with mepolizumab or omalizumab.

Methods

We conducted global metabolomic profiling of pre-treatment plasma samples from 100 patients with moderate-to-severe asthma who initiated mepolizumab (n=31) or omalizumab (n=69). The primary outcome was the change in exacerbations within 12 months of therapy. Negative binomial models were used to assess the association between each metabolite and exacerbations, adjusting for age, sex, body mass index, baseline exacerbations and inhaled corticosteroid use. Chemical similarity enrichment analysis (ChemRICH) was conducted to identify chemical subclasses associated with treatment response.

Results

The mean age of the mepolizumab group was 58.7 years with on average 2.9 exacerbations over the year prior to initiation of biologic therapy. The mean age in the omalizumab group was 48.8 years with 1.5 exacerbations in the preceding year. Patients with higher levels of two tocopherol metabolites were associated with more exacerbations on mepolizumab (δ-carboxyethyl hydroxychroman (CEHC) (p=2.65E-05, false discovery rate (FDR=0.01) and δ-CEHC glucuronide (p=2.47E-06, FDR=0.003)). Higher levels of six androgenic steroids, three carnitine metabolites and two bile acid metabolites were associated with decreased exacerbations in the omalizumab group. In enrichment analyses, xanthine metabolites (cluster FDR=0.0006) and tocopherol metabolites (cluster FDR=0.02) were associated with worse mepolizumab response, while androgenic steroids (cluster FDR=1.9E-18), pregnenolone steroids (cluster p=3.2E-07, FDR=1.4E-05) and secondary bile acid metabolites (cluster p=0.0003, FDR=0.006) were the top subclasses associated with better omalizumab response.

Conclusion

This study identifies distinct metabolites associated with response to mepolizumab and omalizumab, with androgenic steroids associated with response to both mepolizumab and omalizumab.

Chemical chaperone TUDCA selectively inhibits production of allergen-specific IgE in a low-dose model of allergy

The cellular response to endoplasmic reticulum (ER) stress accompanies plasma cell maturation and is one of triggers and cofactors of the local inflammatory response. Chemical chaperones, low-molecular substances that eliminate pathological ER stress, are proposed as means of treating pathologies associated with ER stress. The aim of this study was to evaluate the effect and mechanisms of influence of chemical chaperones on the humoral response in a low-dose model of allergy. The allergic immune response was induced in BALB/c mice by repeated administration of ovalbumin at a dose of 100 ng for 6 weeks. Some animals were injected with both the antigen and the chemical chaperones, TUDCA (tauroursodeoxycholic acid) or 4-PBA (4-phenylbutyrate). Administration of TUDCA, but not 4-PBA, suppressed production of allergen-specific IgE (a 2.5-fold decrease in titer). None of the chemical chaperones affected the production of specific IgG1. The effect of TUDCA was associated with suppression of the switch to IgE synthesis in regional lymph nodes. This phenomenon was associated with suppressed expression of genes encoding cytokines involved in type 2 immune response, especially Il4 and Il9, which in turn could be caused by suppression of IL-33 release. In addition, TUDCA significantly suppressed expression of the cytokine APRIL, and to a lesser extent, BAFF. Thus, TUDCA inhibition of the allergy-specific IgE production is due to suppression of the release of IL-33 and a decrease in the production of type 2 immune response cytokines, as well as suppression of the expression of the cytokines APRIL and BAFF.

Fine particulate matter promotes airway inflammation and mucin production by activating endoplasmic reticulum stress and the IRE1α/NOD1/NF‑κB pathway

Fine particulate matter (PM2.5) is a type of small particle that is <2.5 µm in diameter that may cause airway inflammation. Thus, the present study aimed to explore the effects of PM2.5 on endoplasmic reticulum (ER) stress and airway inflammation in human airway epithelial cells. For this purpose, HBE135‑E6E7 airway epithelial cells were cultured and exposed to specific concentrations of PM2.5 for various periods of time, and cell viability was determined using a Cell Counting Kit‑8 assay. The results of the present study demonstrated that exposure to PM2.5 increased the mRNA and protein expression levels of interleukin (IL)‑6, tumor necrosis factor (TNF)‑α and mucin 5AC (MUC5AC). Moreover, the expression levels of ER stress‑related proteins, such as glucose‑regulated protein 78, CCAAT‑enhancer binding protein homologous protein, activating transcription factor 6, protein kinase R‑like ER kinase (PERK), phosphorylated (p‑)PERK, inositol‑requiring enzyme 1α (IRE1α) and p‑IRE1α, and nucleotide‑binding oligomerization domain 1 (NOD1) expression levels were increased following exposure to PM2.5. Transfection with IRE1α small interfering RNA (siRNA) led to the increased production of IL‑6, TNF‑α and MUC5AC. Moreover, the expression of NOD1 and the translocation of NF‑κB p65 were inhibited following transfection with IRE1α siRNA. In addition, the results of the present study demonstrated that transfection with NOD1 siRNA decreased the production of IL‑6, TNF‑α and MUC5AC, and decreased the translocation of NF‑κB p65. The expression levels of IL‑6, TNF‑α and MUC5AC were increased in the HBE135‑E6E7 cells following treatment with C12‑iE‑DAP, a NOD1 agonist. Moreover, treatment with C12‑iE‑DAP led to the activation of NF‑κB p65. Collectively, the results of the present study suggest that PM2.5 promotes airway inflammation and mucin production by activating ER stress in HBE135‑E6E7 airway epithelial cells, and that the IRE1α/NOD1/NF‑κB pathway may be involved in this process.

Deletion of Miro1 in airway club cells potentiates allergic asthma phenotypes

Mitochondria are multifaceted organelles necessary for numerous cellular signaling and regulatory processes. Mitochondria are dynamic organelles, trafficked and anchored to subcellular sites depending upon the cellular and tissue requirements. Precise localization of mitochondria to apical and basolateral membranes in lung epithelial cells is important for key mitochondrial processes. Miro1 is an outer mitochondrial membrane GTPase that associates with adapter proteins and microtubule motors to promote intracellular movement of mitochondria. We show that deletion of Miro1 in lung epithelial cells leads to perinuclear clustering of mitochondria. However, the role of Miro1 in epithelial cell response to allergic insults remains unknown. We generated a conditional mouse model to delete Miro1 in Club Cell Secretory Protein (CCSP) positive lung epithelial cells to examine the potential roles of Miro1 and mitochondrial trafficking in the lung epithelial response to the allergen, house dust mite (HDM). Our data show that Miro1 suppresses epithelial induction and maintenance of the inflammatory response to allergen, as Miro1 deletion modestly induces increases in pro-inflammatory signaling, specifically IL-6, IL-33, CCL20 and eotaxin levels, tissue reorganization, and airway hyperresponsiveness. Furthermore, loss of Miro1 in CCSP+ lung epithelial cells blocks resolution of the asthmatic insult. This study further demonstrates the important contribution of mitochondrial dynamic processes to the airway epithelial allergen response and the pathophysiology of allergic asthma.

25 Years of translational research in the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC)

The Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) mother-child cohorts have provided a foundation of 25 years of research on the origins, prevention, and natural history of childhood asthma and related disorders. COPSAC's approach is characterized by clinical translational research with longitudinal deep phenotyping and exposure assessments from pregnancy, in combination with multi-omic data layers and embedded randomized controlled trials. One trial showed that fish oil supplementation during pregnancy prevented childhood asthma and identified pregnant women with the highest benefits from supplementation, thereby creating the potential for personalized prevention. COPSAC revealed that airway colonization with pathogenic bacteria in early life is associated with an increased risk of asthma. Further, airway bacteria were shown to be a trigger of acute asthma-like symptoms, with benefit from antibiotic treatment. COPSAC identified an immature gut microbiome in early life as a risk factor for asthma and allergy and further demonstrated that asthma can be predicted by infant lung function. At a molecular level, COPSAC has identified novel susceptibility genes, early immune deviations, and metabolomic alterations associated with childhood asthma. Thus, the COPSAC research program has enhanced our understanding of the processes causing childhood asthma and has suggested means of personalized prevention and treatment.

Asthmatic lung fibroblasts promote type 2 immune responses via endoplasmic reticulum stress response dependent thymic stromal lymphopoietin secretion

Lung fibroblasts contribute to asthma pathology partly through modulation of the immune environment in the airway. Tumor necrosis factor-α (TNFα) expression is upregulated in asthmatic lungs. How asthmatic lung fibroblasts respond to TNFα stimulation and subsequently regulate immune responses is not well understood. Endoplasmic reticulum (ER) stress and unfolded protein responses (UPR) play important roles in asthma, but their functional roles are still under investigation. In this study, we investigated TNFα-induced cytokine production in primary lung fibroblasts from asthmatic vs. non-asthmatic human subjects, and downstream effects on type 2 immune responses. TNFα significantly upregulated IL-6, IL-8, C-C motif chemokine ligand 5 (CCL5), and thymic stromal lymphopoietin (TSLP) mRNA expression and protein secretion by lung fibroblasts. Asthmatic lung fibroblasts secreted higher levels of TSLP which promoted IL-33-induced IL-5 and IL-13 production by peripheral blood mononuclear cells. TNFα exposure enhanced expression of ER stress/UPR pathways in both asthmatic and non-asthmatic lung fibroblasts, especially inositol-requiring protein 1α in asthmatics. ER stress/UPR inhibitors decreased IL-6, CCL5, and TSLP protein secretion by asthmatic lung fibroblasts. Our data suggest that TNFα and lung fibroblasts form an important axis in asthmatic lungs to promote asthmatic inflammation that can be attenuated by inhibiting ER stress/UPR pathway.

Endoplasmic reticulum stress in airway hyperresponsiveness

Airway hyperresponsiveness(AHR) is a major clinical phenomenon in lung diseases (asthma, COPD and pulmonary fibrosis) and not only a high-risk factor for perioperative airway spasm leading to hypoxaemia, haemodynamic instability and even "silent lung", but also a potential risk for increased mortality from underlying diseases (e.g. asthma, COPD). Airway reactivity is closely linked to airway inflammation, remodelling and increased mucus secretion, and endoplasmic reticulum stress is an important mechanism for the development of these pathologies. This review, therefore, focuses on the effects of endoplasmic reticulum stress on the immune cells involved in airway hyperreactivity (epithelial cells, dendritic cells, eosinophils and neutrophils) in inflammation and mucus & sputum secretion; and on the differentiation and remodelling of airway smooth muscle cells and epithelial cells. The aim is to clarify the mechanisms associated with endoplasmic reticulum stress in airway hyperresponsiveness and to find new ideas and methods for the prevention of airway hyperresponsiveness in the perioperative period.

Resveratrol attenuates inflammation and apoptosis through alleviating endoplasmic reticulum stress via Akt/mTOR pathway in fungus-induced allergic airways inflammation

BACKGROUND

Resveratrol has shown pleiotropic effects against inflammation and oxidative response. The present study aimed to investigate the effects and mechanisms of resveratrol on fungus-induced allergic airway inflammation.

METHODS

Female BALB/c mice were injected intraperitoneally with Aspergillus fumigatus (Af) extract emulsified with aluminum on day 0 and 7 and intranasally challenged with Af extracts on day 14 and 15. Resveratrol or dexamethasone or a vehicle was injected intraperitoneally 1 h before each challenge. Mice were sacrificed for serum, bronchoalveolar lavage fluid (BALF), and lungs 24 h after the last challenge. The control group was administered with saline. BEAS-2B was used for the experiments in vitro that Af-exposed airway epithelial cells.

RESULTS

Resveratrol and dexamethasone attenuated the airway inflammation and eosinophilia, and reduced not only the production of IL-4, IL-5, and IL-13 in the BALF and lung tissues but also the mRNA levels of lung IL-6, TNF-α, and TGF-β induced by Af challenge (P < 0.05). Furthermore, Af-induced lung endoplasmic reticulum (ER) stress-related proteins PERK, CHOP, and GRP78 and the apoptosis markers including cleaved caspase-3 and cleaved caspase-7 were both suppressed significantly by resveratrol (P < 0.05). In vitro, activation of ER stress and the Akt/mTOR pathway in Af-exposed BEAS-2B cells were effectively ameliorated by resveratrol. Inhibition of the Akt/mTOR pathway using LY294002 suppressed the ER stress while ER stress inhibitor 4-PBA decreased the apoptosis in Af-exposed BEAS-2B cells.

CONCLUSIONS

Our findings collectively revealed that resveratrol alleviated the Af-exposed allergic inflammation and apoptosis through inhibiting ER stress via Akt/mTOR pathway, exerting therapeutic effects on the fungus-induced allergic lung disorder.

The Impact of Endoplasmic Reticulum-Associated Protein Modifications, Folding and Degradation on Lung Structure and Function

The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and induces the unfolded protein response (UPR) and other mechanisms to restore ER homeostasis, including translational shutdown, increased targeting of mRNAs for degradation by the IRE1-dependent decay pathway, selective translation of proteins that contribute to the protein folding capacity of the ER, and activation of the ER-associated degradation machinery. When ER stress is excessive or prolonged and these mechanisms fail to restore proteostasis, the UPR triggers the cell to undergo apoptosis. This review also examines the overlooked role of post-translational modifications and their roles in protein processing and effects on ER stress and the UPR. Finally, these effects are examined in the context of lung structure, function, and disease.

Effects of Cell Proteostasis Network on the Survival of SARS-CoV-2

The proteostasis network includes all the factors that control the function of proteins in their native state and minimize their non-functional or harmful reactions. The molecular chaperones, the important mediator in the proteostasis network can be considered as any protein that contributes to proper folding and assembly of other macromolecules, through maturating of unfolded or partially folded macromolecules, refolding of stress-denatured proteins, and modifying oligomeric assembly, otherwise it leads to their proteolytic degradation. Viruses that use the hosts' gene expression tools and protein synthesis apparatus to survive and replicate, are obviously protected by such a host chaperone system. This means that many viruses use members of the hosts' chaperoning system to infect the target cells, replicate, and spread. During viral infection, increase in endoplasmic reticulum (ER) stress due to high expression of viral proteins enhances the level of heat shock proteins (HSPs) and induces cell apoptosis or necrosis. Indeed, evidence suggests that ER stress and the induction of unfolded protein response (UPR) may be a major aspect of the corona-host virus interaction. In addition, several clinical reports have confirmed the autoimmune phenomena in COVID-19-patients, and a strong association between this autoimmunity and severe SARS-CoV-2 infection. Part of such autoimmunity is due to shared epitopes among the virus and host. This article reviews the proteostasis network and its relationship to the immune system in SARS-CoV-2 infection.

The complex interplay between endoplasmic reticulum stress and the NLRP3 inflammasome: a potential therapeutic target for inflammatory disorders

Inflammation is the result of a complex network of cellular and molecular interactions and mechanisms that facilitate immune protection against intrinsic and extrinsic stimuli, particularly pathogens, to maintain homeostasis and promote tissue healing. However, dysregulation in the immune system elicits excess/abnormal inflammation resulting in unintended tissue damage and causes major inflammatory diseases including asthma, chronic obstructive pulmonary disease, atherosclerosis, inflammatory bowel diseases, sarcoidosis and rheumatoid arthritis. It is now widely accepted that both endoplasmic reticulum (ER) stress and inflammasomes play critical roles in activating inflammatory signalling cascades. Notably, evidence is mounting for the involvement of ER stress in exacerbating inflammasome-induced inflammatory cascades, which may provide a new axis for therapeutic targeting in a range of inflammatory disorders. Here, we comprehensively review the roles, mechanisms and interactions of both ER stress and inflammasomes, as well as their interconnected relationships in inflammatory signalling cascades. We also discuss novel therapeutic strategies that are being developed to treat ER stress- and inflammasome-related inflammatory disorders.

Role of unfolded proteins in lung disease

The lungs are exposed to a range of environmental toxins (including cigarette smoke, air pollution, asbestos) and pathogens (bacterial, viral and fungal), and most respiratory diseases are associated with local or systemic hypoxia. All of these adverse factors can trigger endoplasmic reticulum (ER) stress. The ER is a key intracellular site for synthesis of secretory and membrane proteins, regulating their folding, assembly into complexes, transport and degradation. Accumulation of misfolded proteins within the lumen results in ER stress, which activates the unfolded protein response (UPR). Effectors of the UPR temporarily reduce protein synthesis, while enhancing degradation of misfolded proteins and increasing the folding capacity of the ER. If successful, homeostasis is restored and protein synthesis resumes, but if ER stress persists, cell death pathways are activated. ER stress and the resulting UPR occur in a range of pulmonary insults and the outcome plays an important role in many respiratory diseases. The UPR is triggered in the airway of patients with several respiratory diseases and in corresponding experimental models. ER stress has been implicated in the initiation and progression of pulmonary fibrosis, and evidence is accumulating suggesting that ER stress occurs in obstructive lung diseases (particularly in asthma), in pulmonary infections (some viral infections and in the setting of the cystic fibrosis airway) and in lung cancer. While a number of small molecule inhibitors have been used to interrogate the role of the UPR in disease models, many of these tools have complex and off-target effects, hence additional evidence (eg, from genetic manipulation) may be required to support conclusions based on the impact of such pharmacological agents. Aberrant activation of the UPR may be linked to disease pathogenesis and progression, but at present, our understanding of the context-specific and disease-specific mechanisms linking these processes is incomplete. Despite this, the ability of the UPR to defend against ER stress and influence a range of respiratory diseases is becoming increasingly evident, and the UPR is therefore attracting attention as a prospective target for therapeutic intervention strategies.

Mechanisms Targeting the Unfolded Protein Response in Asthma

Lung cells are constantly exposed to various internal and external stressors that disrupt protein homeostasis. To cope with these stimuli, cells evoke a highly conserved adaptive mechanism called the unfolded protein response (UPR). UPR stressors can impose greater protein secretory demands on the endoplasmic reticulum (ER), resulting in the development, differentiation, and survival of these cell types to meet these increasing functional needs. Dysregulation of the UPR leads to the development of the disease. The UPR and ER stress are involved in several human conditions, such as chronic inflammation, neurodegeneration, metabolic syndrome, and cancer. Furthermore, potent and specific compounds that target the UPR pathway are under development as future therapies. The focus of this review is to thoroughly describe the effects of both internal and external stressors on the ER in asthma. Furthermore, we discuss how the UPR signaling pathway is activated in the lungs to overcome cellular damage. We also present an overview of the pathogenic mechanisms, with a brief focus on potential strategies for pharmacological interventions.

Inflammation-Induced Protein Unfolding in Airway Smooth Muscle Triggers a Homeostatic Response in Mitochondria

The effects of airway inflammation on airway smooth muscle (ASM) are mediated by pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα). In this review article, we will provide a unifying hypothesis for a homeostatic response to airway inflammation that mitigates oxidative stress and thereby provides resilience to ASM. Previous studies have shown that acute exposure to TNFα increases ASM force generation in response to muscarinic stimulation (hyper-reactivity) resulting in increased ATP consumption and increased tension cost. To meet this increased energetic demand, mitochondrial O₂ consumption and oxidative phosphorylation increases but at the cost of increased reactive oxygen species (ROS) production (oxidative stress). TNFα-induced oxidative stress results in the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and mitochondria of ASM. In the ER, TNFα selectively phosphorylates inositol-requiring enzyme 1 alpha (pIRE1α) triggering downstream splicing of the transcription factor X-box binding protein 1 (XBP1s); thus, activating the pIRE1α/XBP1s ER stress pathway. Protein unfolding in mitochondria also triggers an unfolded protein response (^mtUPR). In our conceptual framework, we hypothesize that activation of these pathways is homeostatically directed towards mitochondrial remodeling via an increase in peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α) expression, which in turn triggers: (1) mitochondrial fragmentation (increased dynamin-related protein-1 (Drp1) and reduced mitofusin-2 (Mfn2) expression) and mitophagy (activation of the Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)/Parkin mitophagy pathway) to improve mitochondrial quality; (2) reduced Mfn2 also results in a disruption of mitochondrial tethering to the ER and reduced mitochondrial Ca²⁺ influx; and (3) mitochondrial biogenesis and increased mitochondrial volume density. The homeostatic remodeling of mitochondria results in more efficient O₂ consumption and oxidative phosphorylation and reduced ROS formation by individual mitochondrion, while still meeting the increased ATP demand. Thus, the energetic load of hyper-reactivity is shared across the mitochondrial pool within ASM cells.

Update on the role of endoplasmic reticulum stress in asthma

Asthma has long attracted extensive attention because of its recurring symptoms of reversible airflow obstruction, airway hyperresponsiveness (AHR) and airway inflammation. Although accumulating evidence has enabled gradual increases in understanding of the pathogenesis of asthma, many questions regarding the mechanisms underlying asthma onset and progression remain unanswered. Recent advances delineating the potential functions of endoplasmic reticulum (ER) stress in meeting the need for an airway hypersensitivity response have revealed critical roles of unfolded protein response (UPR) pathways in asthma. In this review, we highlight the roles of ER stress and UPR activation in the etiology, pathogenesis and treatment of asthma and discuss whether the related mechanisms could be targets for therapeutic strategies.

Endoplasmic Reticulum Stress and Mitochondrial Function in Airway Smooth Muscle

Inflammatory airway diseases such as asthma affect more than 300 million people world-wide. Inflammation triggers pathophysiology via such as tumor necrosis factor α (TNFα) and interleukins (e.g., IL-13). Hypercontraction of airway smooth muscle (ASM) and ASM cell proliferation are major contributors to the exaggerated airway narrowing that occurs during agonist stimulation. An emergent theme in this context is the role of inflammation-induced endoplasmic reticulum (ER) stress and altered mitochondrial function including an increase in the formation of reactive oxygen species (ROS). This may establish a vicious cycle as excess ROS generation leads to further ER stress. Yet, it is unclear whether inflammation-induced ROS is the major mechanism leading to ER stress or the consequence of ER stress. In various diseases, inflammation leads to an increase in mitochondrial fission (fragmentation), associated with reduced levels of mitochondrial fusion proteins, such as mitofusin 2 (Mfn2). Mitochondrial fragmentation may be a homeostatic response since it is generally coupled with mitochondrial biogenesis and mitochondrial volume density thereby reducing demand on individual mitochondrion. ER stress is triggered by the accumulation of unfolded proteins, which induces a homeostatic response to alter protein balance via effects on protein synthesis and degradation. In addition, the ER stress response promotes protein folding via increased expression of molecular chaperone proteins. Reduced Mfn2 and altered mitochondrial dynamics may not only be downstream to ER stress but also upstream such that a reduction in Mfn2 triggers further ER stress. In this review, we summarize the current understanding of the link between inflammation-induced ER stress and mitochondrial function and the role played in the pathophysiology of inflammatory airway diseases.

Altered Mitochondrial Functions and Morphologies in Epithelial Cells Are Associated With Pathogenesis of Chronic Rhinosinusitis With Nasal Polyps

Purpose

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex inflammatory disease of the nasal and paranasal sinus mucosa. The disease is associated with mitochondrial dysfunction, structural changes in the mitochondria, and reactive oxygen species (ROS) generation. This study investigated whether there are functional and morphological changes in the mitochondria in the epithelial cells of nasal polyps (NPs) and Staphylococcus aureus enterotoxin B (SEB)-stimulated nasal epithelial cells.

Methods

In all, 30 patients with CRSwNP and 15 healthy subjects were enrolled. Mitochondrial ROS (mtROS) and changes in mitochondrial functions and structures were investigated in the uncinate tissue (UT) of healthy controls, the UT or NPs of CRSwNP patients, and human nasal epithelial cells with or without SEB stimulation.

Results

Oxidative phosphorylation complexes showed various responses following SEB stimulation in the nasal epithelial cells, and their expressions were significantly higher in the NPs of patients with CRSwNP than in the UT of controls. Generation of mtROS was increased following SEB exposure in nasal epithelial cells and was reduced by pretreatment with MitoTEMPO, which is used as an mtROS scavenger. In the tissues, mtROS was significantly increased in the NPs of CRSwNP patients compared to the UT of controls or CRSwNP patients. The expressions of fusion- and fission-related molecules were also significantly higher in SEB-exposed nasal epithelial cells than in non-exposed cells. In tissues, the expression of fission (fission mediator protein 1)- and fusion (membrane and mitofusin-1, and optic atrophy protein 1)-related molecules was significantly higher in the NPs of CRSwNP patients than in UT of controls or CRSwNP patients. Transmission electron microscopy revealed elongated mitochondria in SEB-exposed nasal epithelial cells and epithelial cells of NPs.

Conclusions

Production of mtROS, disrupted mitochondrial function, and structural changes in nasal epithelial cells might be involved in the pathogenesis of CRSwNP.

Protein Misfolding and Endoplasmic Reticulum Stress in Chronic Lung Disease: Will Cell-Specific Targeting Be the Key to the Cure?

Chronic lung disease accounts for a significant global burden with respect to death, disability, and health-care costs. Due to the heterogeneous nature and limited treatment options for these diseases, it is imperative that the cellular and molecular mechanisms underlying the disease pathophysiology are further understood. The lung is a complex organ with a diverse cell population, and each cell type will likely have different roles in disease initiation, progression, and resolution. The effectiveness of a given therapeutic agent may depend on the net effect on each of these cell types. Over the past decade, it has been established that endoplasmic reticulum stress and the unfolded protein response are involved in the development of several chronic lung diseases. These conserved cellular pathways are important for maintaining cellular proteostasis, but their aberrant activation can result in pathology. This review discusses the current understanding of endoplasmic reticulum stress and the unfolded protein response at the cellular level in the development and progression of various chronic lung diseases. We highlight the need for increased understanding of the specific cellular contributions of unfolded protein response activation to these pathologies and suggest that the development of cell-specific targeted therapies is likely required to further decrease disease progression and to promote resolution of chronic lung disease.

Tauroursodeoxycholate-Bile Acid with Chaperoning Activity: Molecular and Cellular Effects and Therapeutic Perspectives

Tauroursodeoxycholic acid (TUDCA) is a naturally occurring hydrophilic bile acid that has been used for centuries in Chinese medicine. Chemically, TUDCA is a taurine conjugate of ursodeoxycholic acid (UDCA), which in contemporary pharmacology is approved by Food and Drug Administration (FDA) for treatment of primary biliary cholangitis. Interestingly, numerous recent studies demonstrate that mechanisms of TUDCA functioning extend beyond hepatobiliary disorders. Thus, TUDCA has been demonstrated to display potential therapeutic benefits in various models of many diseases such as diabetes, obesity, and neurodegenerative diseases, mostly due to its cytoprotective effect. The mechanisms underlying this cytoprotective activity have been mainly attributed to alleviation of endoplasmic reticulum (ER) stress and stabilization of the unfolded protein response (UPR), which contributed to naming TUDCA as a chemical chaperone. Apart from that, TUDCA has also been found to reduce oxidative stress, suppress apoptosis, and decrease inflammation in many in-vitro and in-vivo models of various diseases. The latest research suggests that TUDCA can also play a role as an epigenetic modulator and act as therapeutic agent in certain types of cancer. Nevertheless, despite the massive amount of evidence demonstrating positive effects of TUDCA in pre-clinical studies, there are certain limitations restraining its wide use in patients. Here, molecular and cellular modes of action of TUDCA are described and therapeutic opportunities and limitations of this bile acid are discussed.

Neonatal Urine Metabolic Profiling and Development of Childhood Asthma

Urine metabolomics case-control studies of childhood asthma have demonstrated a discriminative ability. Here, we investigated whether urine metabolic profiles from healthy neonates were associated with the development of asthma in childhood. Untargeted metabolomics by liquid chromatography-mass spectrometry was applied to urine samples collected at age 4 weeks in 171 and 161 healthy neonates born from mothers with asthma from the COPSAC2000 and COPSAC2010 cohorts, respectively, where persistent wheeze/asthma was prospectively diagnosed using a symptom-based algorithm. Univariate and multivariate analyses were applied to investigate differences in metabolic profiles between children who developed asthma and healthy children. Univariate analysis showed 63 and 87 metabolites (q-value < 0.15) in COPSAC2000 and COPSAC2010, respectively, which is promising for discriminating between asthmatic and healthy children. Of those, 14 metabolites were common among the two cohorts. Multivariate random forest and projection to latent structures discriminant analyses confirmed the discriminatory capacity of the metabolic profiles in both cohorts with estimated errors in prediction equal to 35% and AUCpred > 0.60. Database search enabled annotation of three discriminative features: a glucoronidated compound (steroid), 3-hydroxytetradecanedioic acid (fatty acid), and taurochenodeoxycholate-3-sulfate (bile acid). The urine metabolomics profiles from healthy neonates were associated with the development of childhood asthma, but further research is needed to understand underlying metabolic pathways.

Aberrant MUC1 accumulation in salivary glands of Sjögren’s syndrome patients is reversed by TUDCA in vitro

Objectives

Xerostomia in SS patients has been associated with low quality and quantity of salivary mucins, which are fundamental for the hydration and protection of the oral mucosa. The aim of this study was to evaluate if cytokines induce aberrant mucin expression and whether tauroursodeoxycholic acid (TUDCA) is able to counteract such an anomaly.

Methods

Labial salivary glands from 16 SS patients and 15 control subjects, as well as 3D acini or human submandibular gland cells stimulated with TNF-α or IFN-γ and co-incubated with TUDCA, were analysed. mRNA and protein levels of Mucin 1 (MUC1) and MUC7 were determined by RT-qPCR and western blot, respectively. Co-immunoprecipitation and immunofluorescence assays for mucins and GRP78 [an endoplasmic reticulum (ER)-resident protein] were also performed. mRNA levels of RelA/p65 (nuclear factor-κB subunit), TNF-α, IL-1β, IL-6, SEL1L and EDEM1 were determined by RT-qPCR, and RelA/p65 localization was evaluated by immunofluorescence.

Results

MUC1 is overexpressed and accumulated in the ER of labial salivary gland from SS patients, while MUC7 accumulates throughout the cytoplasm of acinar cells; however, MUC1, but not MUC7, co-precipitated with GRP78. TUDCA diminished the overexpression and aberrant accumulation of MUC1 induced by TNF-α and IFN-γ, as well as the nuclear translocation of RelA/p65, together with the expression of inflammatory and ER stress markers in 3D acini.

Conclusion

Chronic inflammation alters the secretory process of MUC1, inducing ER stress and affecting the quality of saliva in SS patients. TUDCA showed anti-inflammatory properties decreasing aberrant MUC1 accumulation. Further studies are necessary to evaluate the potential therapeutic effect of TUDCA in restoring glandular homeostasis in SS patients.

The airway epithelium in asthma

Asthma is a genetically and phenotypically complex disease that has a major impact on global health. Signs and symptoms of asthma are caused by the obstruction of airflow through the airways. The epithelium that lines the airways plays a major role in maintaining airway patency and in host defense. The epithelium initiates responses to inhaled or aspirated substances, including allergens, viruses, and bacteria, and epithelial-derived cytokines are important in the recruitment and activation of immune cells in the airway. Changes in the structure and function of the airway epithelium are a prominent feature of asthma. Approximately half of individuals with asthma have evidence of active type 2 immune responses in the airway. In these individuals, epithelial cytokines promote type 2 responses, and responses to type 2 cytokines result in increased epithelial mucus production and other effects that cause airway obstruction. Recent work also implicates other epithelial responses, including interleukin-17, interferon and ER stress responses, that may contribute to asthma pathogenesis and provide new targets for therapy.

Conjugated bile acids attenuate allergen-induced airway inflammation and hyperresponsiveness by inhibiting UPR transducers

Conjugated bile acids (CBAs), such as tauroursodeoxycholic acid (TUDCA), are known to resolve the inflammatory and unfolded protein response (UPR) in inflammatory diseases, such as asthma. Whether CBAs exert their beneficial effects on allergic airway responses via 1 arm or several arms of the UPR, or alternatively through the signaling pathways for conserved bile acid receptor, remains largely unknown. We used a house dust mite-induced (HDM-induced) murine model of asthma to evaluate and compare the effects of 5 CBAs and 1 unconjugated bile acid in attenuating allergen-induced UPR and airway responses. Expression of UPR-associated transcripts was assessed in airway brushings from human patients with asthma and healthy subjects. Here we show that CBAs, such as alanyl β-muricholic acid (AβM) and TUDCA, significantly decreased inflammatory, immune, and cytokine responses; mucus metaplasia; and airway hyperresponsiveness, as compared with other CBAs in a model of allergic airway disease. CBAs predominantly bind to activating transcription factor 6α (ATF6α) compared with the other canonical transducers of the UPR, subsequently decreasing allergen-induced UPR activation and resolving allergic airway disease, without significant activation of the bile acid receptors. TUDCA and AβM also attenuated other HDM-induced ER stress markers in the lungs of allergic mice. Quantitative mRNA analysis of airway epithelial brushings from human subjects demonstrated that several ATF6α-related transcripts were significantly upregulated in patients with asthma compared with healthy subjects. Collectively, these results demonstrate that CBA-based therapy potently inhibits the allergen-induced UPR and allergic airway disease in mice via preferential binding of the canonical transducer of the UPR, ATF6α. These results potentially suggest a novel avenue to treat allergic asthma using select CBAs.

IFN-stimulated Gene Expression, Type 2 Inflammation, and Endoplasmic Reticulum Stress in Asthma

RATIONALE

Quantification of type 2 inflammation provided a molecular basis for heterogeneity in asthma. Non-type 2 pathways that contribute to asthma pathogenesis are not well understood.

OBJECTIVES

To identify dysregulated pathways beyond type 2 inflammation.

METHODS

We applied RNA sequencing to airway epithelial brushings obtained from subjects with stable mild asthma not on corticosteroids (n = 19) and healthy control subjects (n = 16). Sequencing reads were mapped to human and viral genomes. In the same cohort, and in a separate group with severe asthma (n = 301), we profiled blood gene expression with microarrays.

MEASUREMENTS AND MAIN RESULTS

In airway brushings from mild asthma on inhaled corticosteroids, RNA sequencing yielded 1,379 differentially expressed genes (false discovery rate < 0.01). Pathway analysis revealed increased expression of type 2 markers, IFN-stimulated genes (ISGs), and endoplasmic reticulum (ER) stress-related genes. Airway epithelial ISG expression was not associated with type 2 inflammation in asthma or with viral transcripts but was associated with reduced lung function by FEV₁ (ρ = -0.72; P = 0.0004). ER stress was confirmed by an increase in XBP1 (X-box binding protein 1) splicing in mild asthma and was associated with both type 2 inflammation and ISG expression. ISGs were also the most activated genes in blood cells in asthma and were correlated with airway ISG expression (ρ = 0.55; P = 0.030). High blood ISG expression in severe asthma was similarly unrelated to type 2 inflammation.

CONCLUSIONS

ISG activation is prominent in asthma, independent of viral transcripts, orthogonal to type 2 inflammation, and associated with distinct clinical features. ER stress is associated with both type 2 inflammation and ISG expression.

Control Interventions Can Impact Alveolarization and the Transcriptome in Developing Mouse Lungs

There is currently much interest in understanding the mechanisms of normal and aberrant lung alveolarization, particularly in the context of bronchopulmonary dysplasia, a common complication of preterm birth where alveolarization is impeded. To this end, the parenteral administration of pharmacological agents that modulate biochemical pathways, or facilitate modulation of gene expression in transgenic animals, has facilitated the discovery and validation of mechanisms that direct lung development. Such studies include control interventions, where the solvent vehicle, perhaps containing an inactive form of the agent applied, is administered; thereby providing a well-controlled point of reference for the analysis of the partner experiment. In the present study, the impact of several widely used control interventions in developing C57Bl/6J mouse pups was examined for effects on lung structure and the lung transcriptome. Parenteral administration of scrambled microRNA inhibitors (called antagomiRs) that are used to control in vivo microRNA neutralization studies, impacted lung volume, septal thickness, and the transcriptome of developing mouse lungs; with some effects dependent upon nucleotide sequence. Repeated intraperitoneal isotonic saline injections altered lung volume, with limited impact on the transcriptome. Parenteral administration of the tamoxifen solvent Miglyol accelerated mouse pup growth, and changed the abundance of 73 mRNA transcripts in the lung. Tamoxifen applied in Miglyol-in the absence of Cre recombinase-decreased pup growth, lung volume, and lung alveolarization and changed the abundance of 298 mRNA transcripts in the lung. These data demonstrate that widely used control interventions can directly impact lung alveolarization and the lung transcriptome in studies on lung development. Anat Rec, 302:346-363, 2019. © 2018 Wiley Periodicals, Inc.

Oxidative and endoplasmic reticulum stress in respiratory disease

Oxidative stress and endoplasmic reticulum (ER) stress are related states that can occur in cells as part of normal physiology but occur frequently in diseases involving inflammation. In this article, we review recent findings relating to the role of oxidative and ER stress in the pathophysiology of acute and chronic nonmalignant diseases of the lung, including infections, cystic fibrosis, idiopathic pulmonary fibrosis and asthma. We also explore the potential of drugs targeting oxidative and ER stress pathways to alleviate disease.

Understanding the Unfolded Protein Response in the Pathogenesis of Asthma

Asthma is a heterogeneous, chronic inflammatory disease of the airways. It is a complex disease with different clinical phenotypes and results in a substantial socioeconomic burden globally. Poor understanding of pathogenic mechanisms of the disease hinders the investigation into novel therapeutics. Emerging evidence of the unfolded protein response (UPR) in the endoplasmic reticulum (ER) has demonstrated previously unknown functions of this response in asthma development. A worsening of asthmatic condition can be brought on by stimuli such as oxidative stress, pathogenic infections, and allergen exposure. All of which can induce ER stress and activate UPR leading to activation of different inflammatory responses and dysregulate the innate immune functions in the airways. The UPR as a central regulator of asthma pathogenesis may explain several unknown mechanism of the disease onset, which leads us in new directions for future asthma treatments. In this review, we summarize and discuss the causes and impact of ER–UPR in driving the pathogenesis of asthma and highlight its importance in clinical implications.

Ghrelin Ameliorates Asthma by Inhibiting Endoplasmic Reticulum Stress

BACKGROUND

This study aimed to confirm the ameliorative effect of ghrelin on asthma and investigate its mechanism.

MATERIALS AND METHODS

The murine model of asthma was induced by ovalbumin (OVA) treatment and assessed by histological pathology and airway responsiveness to methacholine. The total and differential leukocytes were counted. Tumor necrosis factor α, interferon γ, interleukin-5 and interleukin-13 levels in bronchoalveolar lavage fluid were quantified by commercial kits. The protein levels in pulmonary tissues were measured by Western blot analysis.

RESULTS

Ghrelin ameliorated the histological pathology and airway hyperresponsiveness in the OVA-induced asthmatic mouse model. Consistently, OVA-increased total and differential leukocytes and levels of tumor necrosis factor α, interferon γ, interleukin-5 and interleukin-13 in bronchoalveolar lavage fluid were significantly attenuated by ghrelin. Ghrelin prevented the increased protein levels of the endoplasmic reticulum stress markers glucose regulated protein 78 and CCAAT/enhancer binding protein homologous protein and reversed the reduced levels of p-Akt in asthmatic mice.

CONCLUSIONS

Ghrelin might prevent endoplasmic reticulum stress activation by stimulating the Akt signaling pathway, which attenuated inflammation and ameliorated asthma in mice. Ghrelin might be a new target for asthma therapy.

Modulation of the Unfolded Protein Response by Tauroursodeoxycholic Acid Counteracts Apoptotic Cell Death and Fibrosis in a Mouse Model for Secondary Biliary Liver Fibrosis

The role of endoplasmic reticulum stress and the unfolded protein response (UPR) in cholestatic liver disease and fibrosis is not fully unraveled. Tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid, has been shown to reduce endoplasmic reticulum (ER) stress and counteract apoptosis in different pathologies. We aimed to investigate the therapeutic potential of TUDCA in experimental secondary biliary liver fibrosis in mice, induced by common bile duct ligation. The kinetics of the hepatic UPR and apoptosis during the development of biliary fibrosis was studied by measuring markers at six different timepoints post-surgery by qPCR and Western blot. Next, we investigated the therapeutic potential of TUDCA, 10 mg/kg/day in drinking water, on liver damage (AST/ALT levels) and fibrosis (Sirius red-staining), in both a preventive and therapeutic setting. Common bile duct ligation resulted in the increased protein expression of CCAAT/enhancer-binding protein homologous protein (CHOP) at all timepoints, along with upregulation of pro-apoptotic caspase 3 and 12, tumor necrosis factor receptor superfamily, member 1A (TNFRsf1a) and Fas-Associated protein with Death Domain (FADD) expression. Treatment with TUDCA led to a significant reduction of liver fibrosis, accompanied by a slight reduction of liver damage, decreased hepatic protein expression of CHOP and reduced gene and protein expression of pro-apoptotic markers. These data indicate that TUDCA exerts a beneficial effect on liver fibrosis in a model of cholestatic liver disease, and suggest that this effect might, at least in part, be attributed to decreased hepatic UPR signaling and apoptotic cell death.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.