High-fat diet promotes lung fibrosis and attenuates airway eosinophilia after exposure to cockroach allergen in mice

Obesity Enhances Non-Th2 Airway Inflammation in a Murine Model of Allergic Asthma

Obese patients with asthma present with aggravated symptoms that are also harder to treat. Here, we used a mouse model of allergic asthma sensitised and challenged to house dust mite (HDM) extracts to determine whether high-fat-diet consumption would exacerbate the key features of allergic airway inflammation. C57BL/6 mice were intranasally sensitised and challenged with HDM extracts over a duration of 3 weeks. The impact of high-fat-diet (HFD) vs. normal diet (ND) chow was studied on HDM-induced lung inflammation and inflammatory cell infiltration as well as cytokine production. HFD-fed mice had greater inflammatory cell infiltration around airways and blood vessels, and an overall more severe degree of inflammation than in the ND-fed mice (semiquantitative blinded evaluation). Quantitative assessment of HDM-associated Th2 responses (numbers of lung CD4+ T cells, eosinophils, serum levels of allergen-specific IgE as well as the expression of Th2 cytokines (Il5 and Il13)) did not show significant changes between the HFD and ND groups. Interestingly, the HFD group exhibited a more pronounced neutrophilic infiltration within their lung tissues and an increase in non-Th2 cytokines (Il17, Tnfa, Tgf-b, Il-1b). These findings provide additional evidence that obesity triggered by a high-fat-diet regimen may exacerbate asthma by involving non-Th2 and neutrophilic pathways.

Effect of Semaglutide and Empagliflozin on Pulmonary Structure and Proteomics in Obese Mice

Objective

This study utilized proteomics to investigate changes in protein expression associated with lung health in obese mice exposed to semaglutide and empagliflozin through a high-fat diet.

Methods

Twenty-eight male C57BL/6JC mice were randomly assigned to two groups: a control diet group (n = 7) and a high-fat diet group (n = 21). The HFD group was further divided into three groups: HFD group (n = 7), Sema group (n = 7), and Empa group (n = 7). Post-treatment, mice underwent assessments including glucose tolerance, lipids, oxidative stress markers, body weight, lung weight, and structure. Proteomics identified differentially expressed proteins (DEPs) in lung tissue, and bioinformatics analyzed the biological processes and functions of these proteins.

Results

Semaglutide and empagliflozin significantly attenuated obesity-induced hyperglycemia, abnormal lipid metabolism, oxidative stress response, and can decrease alveolar wall thickness, enlarge alveolar lumen, and reduce collagen content in lung tissue. Both medications also attenuated lung elastic fibre cracking and disintegration. In the HFD/NCD group, there were 66 DEPs, comprising 30 proteins that were increased and 36 that were decreased. Twenty-three DEPs overlapped between Sema/HFD and Empa/HFD, with 11 up-regulated and 12 down-regulated simultaneously. After analysing DEPs in different groups, four proteins - LYVE1, BRAF, RGCC, and CHMP5 - were all downregulated in the HFD group and upregulated by semaglutide and empagliflozin treatment.

Conclusion

This study demonstrates that obesity induced by a high-fat diet causes a reduction in the expression of LYVE1, BRAF, RGCC, and CHMP5 proteins, potentially affecting lung function and structure in mice. Significantly, the administration of semaglutide and empagliflozin elevates the levels of these proteins, potentially offering therapeutic benefits against lung injury caused by obesity. Merging semaglutide with empagliflozin may exert a more pronounced impact.

Ectopic and visceral fat deposition in aging, obesity, and idiopathic pulmonary fibrosis: an interconnected role

Idiopathic pulmonary fibrosis (IPF) is considered an age-related disease. Age-related changes, along with other factors such as obesity, hormonal imbalances, and various metabolic disorders, lead to ectopic fat deposition (EFD). This accumulation of fat outside of its normal storage sites is associated with detrimental effects such as lipotoxicity, oxidative stress, inflammation, and insulin resistance. This narrative review provides an overview of the connection between ectopic and visceral fat deposition in aging, obesity, and IPF. It also elucidates the mechanism by which ectopic fat deposition in the airways and lungs, pericardium, skeletal muscles, and pancreas contributes to lung injury and fibrosis in patients with IPF, directly or indirectly. Moreover, the review discusses the impact of EFD on the severity of the disease, quality of life, presence of comorbidities, and overall prognosis in IPF patients. The review provides detailed information on recent research regarding representative lipid-lowering drugs, hypoglycemic drugs, and lipid-targeting drugs in animal experiments and clinical studies. This may offer new therapeutic directions for patients with IPF.

High-Fat Diet Related Lung Fibrosis-Epigenetic Regulation Matters

Pulmonary fibrosis (PF) is an interstitial lung disease characterized by the destruction of the pulmonary parenchyma caused by excessive extracellular matrix deposition. Despite the well-known etiological factors such as senescence, aberrant epithelial cell and fibroblast activation, and chronic inflammation, PF has recently been recognized as a metabolic disease and abnormal lipid signature was observed both in serum and bronchoalveolar lavage fluid (BALF) of PF patients and mice PF model. Clinically, observational studies suggest a significant link between high-fat diet (HFD) and PF as manifested by high intake of saturated fatty acids (SFAs) and meat increases the risk of PF and mice lung fibrosis. However, the possible mechanisms between HFD and PF remain unclear. In the current review we emphasize the diversity effects of the epigenetic dysregulation induced by HFD on the fibrotic factors such as epithelial cell injury, abnormal fibroblast activation and chronic inflammation. Finally, we discuss the potential ways for patients to improve their conditions and emphasize the prospect of targeted therapy based on epigenetic regulation for scientific researchers or drug developers.

Cellular and Molecular Control of Lipid Metabolism in Idiopathic Pulmonary Fibrosis: Clinical Application of the Lysophosphatidic Acid Pathway

Idiopathic pulmonary fibrosis (IPF) is a representative disease that causes fibrosis of the lungs. Its pathogenesis is thought to be characterized by sustained injury to alveolar epithelial cells and the resultant abnormal tissue repair, but it has not been fully elucidated. IPF is currently difficult to cure and is known to follow a chronic progressive course, with the patient's survival period estimated at about three years. The disease occasionally exacerbates acutely, leading to a fatal outcome. In recent years, it has become evident that lipid metabolism is involved in the fibrosis of lungs, and various reports have been made at the cellular level as well as at the organic level. The balance among eicosanoids, sphingolipids, and lipid composition has been reported to be involved in fibrosis, with particularly close attention being paid to a bioactive lipid "lysophosphatidic acid (LPA)" and its pathway. LPA signals are found in a wide variety of cells, including alveolar epithelial cells, vascular endothelial cells, and fibroblasts, and have been reported to intensify pulmonary fibrosis via LPA receptors. For instance, in alveolar epithelial cells, LPA signals reportedly induce mitochondrial dysfunction, leading to epithelial damage, or induce the transcription of profibrotic cytokines. Based on these mechanisms, LPA receptor inhibitors and the metabolic enzymes involved in LPA formation are now considered targets for developing novel means of IPF treatment. Advances in basic research on the relationships between fibrosis and lipid metabolism are opening the path to new therapies targeting lipid metabolism in the treatment of IPF.

Exogenous leptin enhances markers of airway fibrosis in a mouse model of chronic allergic airways disease

BACKGROUND

Asthma patients with comorbid obesity exhibit increased disease severity, in part, due to airway remodeling, which is also observed in mouse models of asthma and obesity. A mediator of remodeling that is increased in obesity is leptin. We hypothesized that in a mouse model of allergic airways disease, mice receiving exogenous leptin would display increased airway inflammation and fibrosis.

METHODS

Five-week-old male and female C57BL/6J mice were challenged with intranasal house dust mite (HDM) allergen or saline 5 days per week for 6 weeks (n = 6-9 per sex, per group). Following each HDM exposure, mice received subcutaneous recombinant human leptin or saline. At 48 h after the final HDM challenge, lung mechanics were evaluated and the mice were sacrificed. Bronchoalveolar lavage was performed and differential cell counts were determined. Lung tissue was stained with Masson's trichrome, periodic acid-Schiff, and hematoxylin and eosin stains. Mouse lung fibroblasts were cultured, and whole lung mRNA was isolated.

RESULTS

Leptin did not affect mouse body weight, but HDM+leptin increased baseline blood glucose. In mixed-sex groups, leptin increased mouse lung fibroblast invasiveness and increased lung Col1a1 mRNA expression. Total lung resistance and tissue damping were increased with HDM+leptin treatment, but not leptin or HDM alone. Female mice exhibited enhanced airway responsiveness to methacholine with HDM+leptin treatment, while leptin alone decreased total respiratory system resistance in male mice.

CONCLUSIONS

In HDM-induced allergic airways disease, administration of exogenous leptin to mice enhanced lung resistance and increased markers of fibrosis, with differing effects between males and females.

Clinical Characteristics and Management Strategies for Adult Obese Asthma Patients

The rates of asthma and obesity are increasing concurrently in the United States. Epidemiologic studies demonstrate that the incidence of asthma increases with obesity. Furthermore, obese individuals have asthma that is more severe, harder to control, and resistant to standard medications. In fact, specific asthma-obesity phenotypes have been identified. Various pathophysiologic mechanisms, including mechanical, inflammatory, metabolic and microbiome-associated, are at play in promulgating the obese-asthma phenotypes. While standard asthma medications, such as inhaled corticosteroids and biologics, are currently used to treat obese asthmatics, they may have limited effectiveness. Targeting the underlying aberrant processes, such as addressing steroid resistance, microbiome, metabolic and weight loss approaches, may be helpful.

Obesity and the Development of Lung Fibrosis

Obesity is an epidemic worldwide and the obese people suffer from a range of respiratory complications including fibrotic changes in the lung. The influence of obesity on the lung is multi-factorial, which is related to both mechanical injury and various inflammatory mediators produced by excessive adipose tissues, and infiltrated immune cells. Adiposity causes increased production of inflammatory mediators, for example, cytokines, chemokines, and adipokines, both locally and in the systemic circulation, thereby rendering susceptibility to respiratory diseases, and altered responses. Lung fibrosis is closely related to chronic inflammation in the lung. Current data suggest a link between lung fibrosis and diet-induced obesity, although the mechanism remains incomplete understood. This review summarizes findings on the association of lung fibrosis with obesity, highlights the role of several critical inflammatory mediators (e.g., TNF-α, TGF-β, and MCP-1) in obesity related lung fibrosis and the implication of obesity in the outcomes of idiopathic pulmonary fibrosis patients.

Relationship between type 2 cytokine and inflammasome responses in obesity-associated asthma

BACKGROUND

Obesity is a risk factor for asthma, and obese asthmatic individuals are more likely to have severe, steroid-insensitive disease. How obesity affects the pathogenesis and severity of asthma is poorly understood. Roles for increased inflammasome-mediated neutrophilic responses, type 2 immunity, and eosinophilic inflammation have been described.

OBJECTIVE

We investigated how obesity affects the pathogenesis and severity of asthma and identified effective therapies for obesity-associated disease.

METHODS

We assessed associations between body mass index and inflammasome responses with type 2 (T2) immune responses in the sputum of 25 subjects with asthma. Functional roles for NLR family, pyrin domain-containing (NLRP) 3 inflammasome and T2 cytokine responses in driving key features of disease were examined in experimental high-fat diet-induced obesity and asthma.

RESULTS

Body mass index and inflammasome responses positively correlated with increased IL-5 and IL-13 expression as well as C-C chemokine receptor type 3 expression in the sputum of subjects with asthma. High-fat diet-induced obesity resulted in steroid-insensitive airway hyperresponsiveness in both the presence and absence of experimental asthma. High-fat diet-induced obesity was also associated with increased NLRP3 inflammasome responses and eosinophilic inflammation in airway tissue, but not lumen, in experimental asthma. Inhibition of NLRP3 inflammasome responses reduced steroid-insensitive airway hyperresponsiveness but had no effect on IL-5 or IL-13 responses in experimental asthma. Depletion of IL-5 and IL-13 reduced obesity-induced NLRP3 inflammasome responses and steroid-insensitive airway hyperresponsiveness in experimental asthma.

CONCLUSION

We found a relationship between T2 cytokine and NLRP3 inflammasome responses in obesity-associated asthma, highlighting the potential utility of T2 cytokine-targeted biologics and inflammasome inhibitors.

Effect of High Fat Diet on the Severity and Repair of Lung Fibrosis in Mice

Lung fibrosis is a progressive fatal disease, and the underlying mechanisms remain unclear. These involve a combination of altered fibroblasts, excessive accumulation of extracellular matrix, inflammation, and aberrant activation of epithelial cells. Previously, we showed that high-fat diet (HFD) induces lung inflammation, aberrant activation of stem cells, and lung mitochondria impairment. Therefore, we hypothesized that HFD-induced changes would influence lung fibrosis. Mice were fed standard diet (SD) or HFD, administered bleomycin, then examined for fibrosis severity and the start of repair 3 weeks after injury, and for fibrosis repair/resolution 6-9 weeks after injury. At 3 weeks, no significant differences in inflammation and fibrosis severity were observed between SD- and HFD-fed mice. However, infiltration of alveolar type (AT)-2 cells and bronchioalveolar stem cells (BASCs) into the fibrotic areas (the start of repair) was impaired in HFD-fed mice. At 6 weeks, SD-fed mice showed near-complete resolution/repair of fibrosis and inflammation, while HFD-fed mice still showed residual fibrosis and inflammation. Infiltration of the fibrotic areas with AT2 cells was observed, but very few BASCs were detectable. At 9 weeks, mice from both groups showed complete resolution/repair of fibrosis and inflammation, indicating that HFD induced delayed, rather than failed, resolution of fibrosis and alveolar repair. To further confirm the direct role of enhanced fatty-acid oxidation (FAO) in delayed resolution/repair, we administered etomoxir, a FAO inhibitor, to HFD-fed mice for 3-6 weeks after bleomycin injury. Inhibition of FAO abolished the HFD-induced delay in alveolar repair and fibrosis resolution at both time points. In conclusion, after a fibrosis-inducing injury, HFD slows resolution of fibrosis/inflammation and delays alveolar repair by slowing the contribution of AT2 stem cells and abolishing the contribution of BASCs in the repair process. FAO activation appears to be involved in this delay mechanism; thus, inhibiting FAO may be useful in the treatment of lung injury and fibrosis.

Impact of controlled high-sucrose and high-fat diets on eosinophil recruitment and cytokine content in allergen-challenged mice

Despite an ongoing focus on the role of diet in health and disease, we have only a limited understanding of these concepts at the cellular and molecular levels. While obesity has been clearly recognized as contributing to metabolic syndrome and the pathogenesis of adult asthma, recent evidence has linked high sugar intake alone to an increased risk of developing asthma in childhood. In this study, we examined the impact of diet in a mouse model of allergic airways inflammation with a specific focus on eosinophils. As anticipated, male C57BL/6 mice gained weight on a high-calorie, high-fat diet. However, mice also gained weight on an isocaloric high-sucrose diet. Elevated levels of leptin were detected in the serum and airways of mice maintained on the high-fat, but not the high-sucrose diets. We found that diet alone had no impact on eosinophil numbers in the airways at baseline or their recruitment in response to allergen (Alternaria alternata) challenge in either wild-type or leptin-deficient ob/ob mice. However, both bronchoalveolar lavage fluid and eosinophils isolated from lung tissue of allergen-challenged mice exhibited profound diet-dependent differences in cytokine content. Similarly, while all wild-type mice responded to allergen challenge with significant increases in methacholine-dependent total airway resistance (R_rs), airway resistance in mice maintained on the isocaloric high-sucrose (but not the high-calorie/high-fat) diet significantly exceeded that of mice maintained on the basic diet. In summary, our findings revealed that mice maintained on an isocaloric high-sucrose diet responded to allergen challenge with significant changes in both BAL and eosinophil cytokine content together with significant increases in R_rs. These results provide a model for further exploration of the unique risks associated with a high-sugar diet and its impact on allergen-associated respiratory dysfunction.

Role of the Notch ligands Jagged1 and Delta4 in Th17/Treg immune imbalance in a mouse model of chronic asthma

PURPOSE

Asthma is associated with a T helper (Th)17/regulatory T (Treg) cells immune imbalance where the Notch signaling pathway contributes vitally. This study aimed to explore the role of Notch ligands Jagged1 and Delta4 in the Th17/Treg immune imbalance of chronic asthmatic mice.

METHODS

The experimental animals were randomly assigned to the Saline, ovalbumin (OVA), and OVA + γ-secretase inhibitor (GSI) groups. A mouse model of chronic asthma was induced by OVA sensitization and challenge. GSI was injected intraperitoneally before the OVA challenge in the OVA + GSI group. Lung function, lung histopathology and immunohistochemistry to assess airway inflammation, enzyme-linked immunosorbent assay to measure cytokines levels, flow cytometry to measure the proportions of Th17 (Th17%) and Treg% in CD4+T cells, quantitative real-time polymerase chain reaction and western blot to measure mRNA and protein levels of Jagged1 and Delta4 in lung tissue, and correlation analysis were performed.

RESULTS

Lung function and histopathology and IL-4, IL-13, and IFN-γ levels in the bronchoalveolar lavage fluid (BALF) of chronic asthmatic mice showed characteristic changes of asthma. The Th17%, Th17/Treg ratio, BALF and serum IL-17 levels, and IL-17/IL-10 ratio increased significantly in the OVA group, while the Treg% and IL-10 level significantly decreased. mRNA and protein expression levels of Jagged1 and Delta4 increased significantly. GSI could reduce the Th17%, Th17/Treg ratio, IL-17, IL-17/IL-10 ratio, and Jagged1 expression in chronic asthmatic mice. The mRNA and protein levels of Jagged1 and Delta4 were positively correlated with the Th17/Treg ratio in the OVA group, while only those of Jagged1 were positively correlated with the Th17/Treg ratio in the OVA + GSI group.

CONCLUSIONS

In chronic asthmatic mice, the Th17/Treg ratio increased, and the Notch ligands Jagged1 and Delta4 were overactive and positively regulated the Th17/Treg imbalance. GSI partially inhibited Jagged1 and relieved the Th17/Treg imbalance.

The impact of obesity on immune function in pediatric asthma

PURPOSE OF REVIEW

Pediatric obese asthma is a complex disease that remains poorly understood. The increasing worldwide incidence of both asthma and obesity over the last few decades, their current high prevalence and the challenges in treating obese asthmatic patients all highlight the importance of a better understanding of the pathophysiological mechanisms in obese asthma. While it is well established that patients with obesity are at an increased risk of developing asthma, the mechanisms by which obesity drives the onset of asthma, and modifies existing asthma, remain unclear. Here, we will focus on mechanisms by which obesity alters immune function in asthma.

RECENT FINDINGS

Lung parenchyma has an altered structure in some pediatric obese asthmatics, known as dysanapsis. Central adiposity is linked to reduced pulmonary function and a better predictor of asthma risk in children than BMI. Obesity in young children is associated with an increased risk of developing asthma, as well as early puberty, and hormonal alterations are implicated in obese asthma. Obesity and asthma each yield immunometabolic dysregulation separately and we are learning more about alterations in these pathways in pediatric obese asthma and the potential impact of bariatric surgery on those processes.

SUMMARY

The recent progress in clarifying the connections between childhood obesity and asthma and their combined impacts on immune function moves us closer to the goals of improved understanding of the pathophysiological mechanisms underpinning obese asthma and improved therapeutic target selection. However, this common inflammatory disease remains understudied, especially in children, and much remains to be learned.

Procedures to Evaluate Inflammatory and Pathological Changes During Allergic Airway Inflammation

Cellular inflammation, with elevated levels of Th1/Th2 cytokines, airway mucus hypersecretion, and thickening of the airway smooth muscle, are characteristic features of the allergic lung. Assessment of pathophysiological changes in allergic lungs serves as an important tool to determine disease progression and understand the underlying mechanisms of pathogenesis. This can be achieved by evaluating the lung tissue for inflammation and airway structural changes along with the measurement of important pro-inflammatory mediators such as Th1/Th2 cytokines and eotaxins. This chapter describes procedures to histologically evaluate inflammatory and pathological changes observed during allergic airway inflammation using lung tissue from mice.

TGF-β: The missing link in obesity-associated airway diseases?

Obesity is emerging as a global public health epidemic. The co-morbidities associated with obesity significantly contribute to reduced quality of life, mortality, and global healthcare burden. Compared to other asthma comorbidities, obesity prominently engenders susceptibility to inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), contributes to greater disease severity and evokes insensitivity to current therapies. Unlike in other metabolic diseases associated with obesity, the mechanistic link between obesity and airway diseases is only poorly defined. Transforming growth factor-β (TGF-β) is a pleiotropic inflammatory cytokine belonging to a family of growth factors with pivotal roles in asthma. In this review, we summarize the role of TGF-β in major obesity-associated co-morbidities to shed light on mechanisms of the diseases. Literature evidence shows that TGF-β mechanistically links many co-morbidities with obesity through its profibrotic, remodeling, and proinflammatory functions. We posit that TGF-β plays a similar mechanistic role in obesity-associated inflammatory airway diseases such as asthma and COPD. Concerning the role of TGF-β on metabolic effects of obesity, we posit that TGF-β has a similar mechanistic role in obesity-associated inflammatory airway diseases in interplay with different comorbidities such as hypertension, metabolic diseases like type 2 diabetes, and cardiomyopathies. Future studies in TGF-β-dependent mechanisms in obesity-associated inflammatory airway diseases will advance our understanding of obesity-induced asthma and help find novel therapeutic targets for prevention and treatment.

Insights into the Role of Bioactive Food Ingredients and the Microbiome in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic disease mainly associated with aging and, to date, its causes are still largely unknown. It has been shown that dietary habits can accelerate or delay the occurrence of aging-related diseases; however, their potential role in IPF development has been underestimated so far. The present review summarizes the evidence regarding the relationship between diet and IPF in humans, and in animal models of pulmonary fibrosis, in which we discuss the bioactivity of specific dietary food ingredients, including fatty acids, peptides, amino acids, carbohydrates, vitamins, minerals and phytochemicals. Interestingly, many animal studies reveal preventive and therapeutic effects of particular compounds. Furthermore, it has been recently suggested that the lung and gut microbiota could be involved in IPF, a relationship which may be linked to changes in immunological and inflammatory factors. Thus, all the evidence so far puts forward the idea that the gut-lung axis could be modulated by dietary factors, which in turn have an influence on IPF development. Overall, the data reviewed here support the notion of identifying food ingredients with potential benefits in IPF, with the ultimate aim of designing nutritional approaches as an adjuvant therapeutic strategy.

Pulmonary delivery of ORMDL3 short hairpin RNA - a potential tool to regulate allergen-induced airway inflammation

Aim/Purpose: Exposure to various allergens has been shown to increase expression of ORMDL3 in the lung in models of allergic asthma. Studies using genetically modified (transgenic or knock out) mice have revealed some of the functions of ORMDL3 in asthma pathogenesis, although amid debate. The goal of this study was to use targeted post-transcriptional downregulation of ORMDL3 in allergen-challenged wild-type (WT) mice by RNA interference to further elucidate the functional role of ORMDL3 in asthma pathogenesis and evaluate a potential therapeutic option.Methods: Allergen (ovalbumin [OVA])-challenged WT mice were administered intranasally (i.n) with a single dose of five short hairpin RNA (shRNA) constructs with different target sequence for murine ORMDL3 cloned in a lentiviral vector or with the empty vector (control). Mice were evaluated for allergen-induced airway hyperresponsiveness (AHR) and various features of airway inflammation after 72 hours.Results: I.n administration of a single dose of ORMDL3 shRNAs to OVA-challenged mice resulted in reduction of ORMDL3 gene expression in the lungs associated with a significant reduction in AHR to inhaled methacholine and in the number of inflammatory cells recruited in the airways, specifically eosinophils, as well as in airway mucus secretion compared to OVA-challenged mice that received the empty vector. Administration of ORMDL3 shRNAs also significantly inhibited levels of IL-13, eotaxin-2 and sphingosine in the lungs. Additionally, ORMDL3 shRNAs significantly inhibited the allergen-mediated increase in monohexyl ceramides C22:0 and C24:0.Conclusions: Post-transcriptional down regulation of ORMDL3 in allergic lungs using i.n-delivered ORMDL3 shRNA (akin to inhaled therapy) attenuates development of key features of airway allergic disease, confirming the involvement of ORMDL3 in allergic asthma pathogenesis and serving as a model for a potential therapeutic strategy.

Palmitic Acid-Rich High-Fat Diet Exacerbates Experimental Pulmonary Fibrosis by Modulating Endoplasmic Reticulum Stress

The impact of lipotoxicity on the development of lung fibrosis is unclear. Saturated fatty acids, such as palmitic acid (PA), activate endoplasmic reticulum (ER) stress, a cellular stress response associated with the development of idiopathic pulmonary fibrosis (IPF). We tested the hypothesis that PA increases susceptibility to lung epithelial cell death and experimental fibrosis by modulating ER stress. Total liquid chromatography and mass spectrometry were used to measure fatty acid content in IPF lungs. Wild-type mice were fed a high-fat diet (HFD) rich in PA or a standard diet and subjected to bleomycin-induced lung injury. Lung fibrosis was determined by hydroxyproline content. Mouse lung epithelial cells were treated with PA. ER stress and cell death were assessed by Western blotting, TUNEL staining, and cell viability assays. IPF lungs had a higher level of PA compared with controls. Bleomycin-exposed mice fed an HFD had significantly increased pulmonary fibrosis associated with increased cell death and ER stress compared with those fed a standard diet. PA increased apoptosis and activation of the unfolded protein response in lung epithelial cells. This was attenuated by genetic deletion and chemical inhibition of CD36, a fatty acid transporter. In conclusion, consumption of an HFD rich in saturated fat increases susceptibility to lung fibrosis and ER stress, and PA mediates lung epithelial cell death and ER stress via CD36. These findings demonstrate that lipotoxicity may have a significant impact on the development of lung injury and fibrosis by enhancing pro-death ER stress pathways.

Effect Of Dual sEH/COX-2 Inhibition on Allergen-Induced Airway Inflammation

Arachidonic acid metabolites resulting from the cyclooxygenase (COX), lipoxygenase, and cytochrome P450 oxidase enzymatic pathways play pro- and anti-inflammatory roles in allergic airway inflammation (AAI) and asthma. Expression of COX-2 and soluble epoxide hydrolase (sEH) are elevated in allergic airways and their enzymatic products (e.g., prostaglandins and diols of epoxyeicosatrienoic acids, respectively) have been shown to participate in the pathogenesis of AAI. Here, we evaluated the outcome of inhibiting the COX-2 and sEH enzymatic pathways with a novel dual inhibitor, PTUPB, in A. alternata-induced AAI. Allergen-challenged mice were administered with 10 or 30 mg/kg of PTUPB, celecoxib (selective COX-2 inhibitor), t-TUCB (selective sEH inhibitor) or vehicle daily by gavage and evaluated for various features of AAI. PTUPB and t-TUCB at 30 mg/kg, but not celecoxib, inhibited eosinophilic infiltration and significantly increased levels of anti-inflammatory EETs in the lung tissue of allergen-challenged mice. t-TUCB significantly inhibited allergen-induced IL-4 and IL-13, while a less pronounced reduction was noted with PTUPB and celecoxib. Additionally, t-TUCB markedly inhibited eotaxin-2, an eosinophil-specific chemokine, which was only marginally reduced by PTUPB and remained elevated in celecoxib-treated mice. PTUPB or t-TUCB administration reversed allergen-induced reduction in levels of various lipid mediators in the lungs, with only a minimal effect noted with celecoxib. Despite the anti-inflammatory effects, PTUPB or t-TUCB did not reduce allergen-induced airway hyperresponsiveness (AHR). However, development of structural changes in the allergic airways, such as mucus hypersecretion and smooth muscle hypertrophy, was significantly inhibited by both inhibitors. Celecoxib, on the other hand, inhibited only airway smooth muscle hypertrophy, but not mucus hypersecretion. In conclusion, dual inhibition of COX-2 and sEH offers no additional advantage relative to sEH inhibition alone in attenuating various features associated with A. alternata-induced AAI, while COX-2 inhibition exerts only moderate or no effect on several of these features. Dual sEH/COX-2 inhibition may be useful in treating conditions where eosinophilic inflammation co-exists with pain-associated inflammation.

Insulin resistance mediates high-fat diet-induced pulmonary fibrosis and airway hyperresponsiveness through the TGF-β1 pathway

Prior studies have reported the presence of lung fibrosis and enhanced airway hyperresponsiveness (AHR) in mice with high-fat-diet (HFD)-induced obesity. This study evaluated the role of TGF-β1 in HFD-induced AHR and lung fibrosis in a murine model. We generated HFD-induced obesity mice and performed glucose and insulin tolerance tests. HFD mice with or without ovalbumin sensitization and challenge were also treated with an anti-TGF-β1 neutralizing antibody. AHR to methacholine, inflammatory cells in the bronchoalveolar lavage fluid (BALF), and histological features were evaluated. Insulin was intranasally administered to normal diet (ND) mice, and in vitro insulin stimulation of BEAS-2b cells was performed. HFD-induced obesity mice had increased insulin resistance, enhanced AHR, peribronchial and perivascular fibrosis, and increased numbers of macrophages in the BALF. However, they did not have meaningful eosinophilic or neutrophilic inflammation in the lungs compared with ND mice. The HFD enhanced TGF-β1 expression in the bronchial epithelium, but we found no differences in the expression of interleukin (IL)-4 or IL-5 in lung homogenates. Administration of the anti-TGF-β1 antibody attenuated HFD-induced AHR and lung fibrosis. It also attenuated goblet cell hyperplasia, but did not affect the AHR and inflammatory cell infiltration induced by OVA challenge. The intranasal administration of insulin enhanced TGF-β1 expression in the bronchial epithelium and lung fibrosis. Stimulating BEAS-2b cells with insulin also increased TGF-β1 production by 24 h. We concluded that HFD-induced obesity-associated insulin resistance enhances TGF-β1 expression in the bronchial epithelium, which may play an important role in the development of lung fibrosis and AHR in obesity.

Knob protein enhances epithelial barrier integrity and attenuates airway inflammation

BACKGROUND

Altered epithelial physical and functional barrier properties along with TH1/TH2 immune dysregulation are features of allergic asthma. Regulation of junction proteins to improve barrier function of airway epithelial cells has the potential for alleviation of allergic airway inflammation.

OBJECTIVE

We sought to determine the immunomodulatory effect of knob protein of the adenoviral capsid on allergic asthma and to investigate its mechanism of action on airway epithelial junction proteins and barrier function.

METHODS

Airway inflammation, including junction protein expression, was evaluated in allergen-challenged mice with and without treatment with knob. Human bronchial epithelial cells were exposed to knob, and its effects on expression of junction proteins and barrier integrity were determined.

RESULTS

Administration of knob to allergen-challenged mice suppressed airway inflammation (eosinophilia, airway hyperresponsiveness, and IL-5 levels) and prevented allergen-induced loss of airway epithelial occludin and E-cadherin expression. Additionally, knob decreased expression of TH2-promoting inflammatory mediators, specifically IL-33, by murine lung epithelial cells. At a cellular level, treatment of human bronchial epithelial cells with knob activated c-Jun N-terminal kinase, increased expression of occludin and E-cadherin, and enhanced epithelial barrier integrity.

CONCLUSION

Increased expression of junction proteins mediated by knob leading to enhanced epithelial barrier function might mitigate the allergen-induced airway inflammatory response, including asthma.

FABP4 regulates eosinophil recruitment and activation in allergic airway inflammation

Fatty acid binding protein 4 (FABP4), a member of a family of lipid-binding proteins, is known to play a role in inflammation by virtue of its ability to regulate intracellular events such as lipid fluxes and signaling. Studies have indicated a proinflammatory role for FABP4 in allergic asthma although its expression and function in eosinophils, the predominant inflammatory cells recruited to allergic airways, were not investigated. We examined expression of FABP4 in murine eosinophils and its role in regulating cell recruitment in vitro as well as in cockroach antigen (CRA)-induced allergic airway inflammation. CRA exposure led to airway recruitment of FABP4-expressing inflammatory cells, specifically eosinophils, in wild-type (WT) mice. FABP4 expression in eosinophils was induced by TNF-α as well as IL-4 and IL-13. FABP4-deficient eosinophils exhibited markedly decreased cell spreading/formation of leading edges on vascular cell adhesion molecule-1 and significantly decreased adhesion to intercellular adhesion molecule-1 associated with reduced β2-integrin expression relative to WT cells. Furthermore, FABP4-deficient eosinophils exhibited decreased migration, F-actin polymerization, calcium flux, and ERK(1/2) phosphorylation in response to eotaxin-1. In vivo, CRA-challenged FABP4-deficient mice exhibited attenuated eosinophilia and significantly reduced airway inflammation (improved airway reactivity, lower IL-5, IL-13, TNF-α, and cysteinyl leukotriene C4 levels, decreased airway structural changes) compared with WT mice. In conclusion, expression of FABP4 in eosinophils is induced during conditions of inflammation and plays a proinflammatory role in the development of allergic asthma by promoting eosinophil adhesion and migration and contributing to the development of various aspects of airway inflammation.

Innate lymphoid cells at the interface between obesity and asthma

Obesity and asthma prevalence has dramatically and concomitantly increased over the last 25 years, and many epidemiological studies have highlighted obesity as an important risk factor for asthma. Although many studies have been performed, the underlying mechanisms remain poorly understood. Innate mechanisms have been involved in both diseases, in particular through the recently described innate lymphoid cells (ILCs). ILCs are subdivided into three groups that are defined by their cytokine production and by their master transcription factor expression, in sharp correlation with their T helper counterparts. However, unlike T helper cells, ILCs do not express antigen-specific receptors, but respond to damage-induced signals. ILCs have been found in target tissues of both diseases, and data have implicated these cells in the pathogenesis of both diseases. In particular group 2 ILCs (ILC2) are activated in both the adipose and lung tissues under the effect of interleukin-33 and interleukin-25 expression. However, counter-intuitively to the well-known association between obesity and asthma, ILC2 are beneficial for obesity but deleterious for asthma. This review will examine the roles of ILCs in each disease and recent data highlighting ILCs as a putative link between obesity and asthma.

Roflumilast Ameliorates Airway Hyperresponsiveness Caused by Diet-Induced Obesity in a Murine Model

Obese patients with asthma respond poorly to conventional asthma medications, resulting in severe symptoms and poor prognosis. Roflumilast, a phosphodiesterase-4 inhibitor that lowers the levels of various substances that are implicated in obese subjects with asthma, may be effective in the treatment of those subjects. We evaluated the potential of roflumilast as a novel therapeutic agent for obese subjects with asthma. We designed three models: diet-induced obesity (DIO); DIO with ovalbumin (OVA); and OVA. We fed C57BL/6J mice a high-fat diet for 3 months with or without OVA sensitization and challenge. Roflumilast or dexamethasone was administered orally three times at 2-day intervals in the last experimental week. Airway hyperresponsiveness resulting from DIO significantly improved in the roflumilast-treated group compared with the dexamethasone-treated groups. Although DIO did not affect the cell proliferation in bronchoalveolar lavage fluid, increased fibrosis was seen in the DIO group, which significantly improved from treatment with roflumilast. DIO-induced changes in adiponectin and leptin levels were improved by roflumilast, whereas dexamethasone aggravated them. mRNA levels and proteins of TNF-α, transforming growth factor-β, IL-1β, and IFN-γ increased in the DIO group and decreased with roflumilast. The reactive oxygen species levels were also increased in the DIO group and decreased by roflumilast. In the DIO plus OVA and OVA models, roflumilast improved Th1 and Th2 cell activation to a greater extent than dexamethasone. Roflumilast is significantly more effective than dexamethasone against airway hyperresponsiveness caused by DIO in the murine model. Roflumilast may represent a promising therapeutic agent for the treatment of obese patients with asthma.

Mechanisms of Asthma in Obesity. Pleiotropic Aspects of Obesity Produce Distinct Asthma Phenotypes

The majority of patients with severe or difficult-to-control asthma in the United States are obese. Epidemiological studies have clearly established that obese patients tend to have worse asthma control and increased hospitalizations and do not respond to standard controller therapy as well as lean patients with asthma. Less clear are the mechanistic underpinnings for the striking clinical differences between lean and obese patients with asthma. Because obesity is principally a disorder of metabolism and energy regulation, processes fundamental to the function of every cell and system within the body, it is not surprising that it affects the respiratory system; it is perhaps surprising that it has taken so long to appreciate how dysfunctional metabolism and energy regulation lead to severe airway disease. Although early investigations focused on identifying a common factor in obesity that could promote airway disease, an appreciation has emerged that the asthma of obesity is a manifestation of multiple anomalies related to obesity affecting all the different pathways that cause asthma, and likely also to de novo airway dysfunction. Consequently, all the phenotypes of asthma currently recognized in lean patients (which are profoundly modified by obesity), as well as those unique to one's obesity endotype, likely contribute to obese asthma in a particular individual. This perspective reviews what we have learned from clinical studies and animal models about the phenotypes of asthma in obesity, which show how specific aspects of obesity and altered metabolism might lead to de novo airway disease and profoundly modify existing airway disease.

Innate lymphoid cells contribute to allergic airway disease exacerbation by obesity

BACKGROUND

Epidemiologic and clinical observations identify obesity as an important risk factor for asthma exacerbation, but the underlying mechanisms remain poorly understood. Type 2 innate lymphoid cells (ILC2s) and type 3 innate lymphoid cells (ILC3s) have been implicated, respectively, in asthma and adipose tissue homeostasis and in obesity-associated airway hyperresponsiveness (AHR).

OBJECTIVE

We sought to determine the potential involvement of innate lymphoid cells (ILCs) in allergic airway disease exacerbation caused by high-fat diet (HFD)-induced obesity.

METHODS

Obesity was induced by means of HFD feeding, and allergic airway inflammation was subsequently induced by means of intranasal administration of house dust mite (HDM) extract. AHR, lung and visceral adipose tissue inflammation, humoral response, cytokines, and innate and adaptive lymphoid populations were analyzed in the presence or absence of ILCs.

RESULTS

HFD feeding exacerbated allergic airway disease features, including humoral response, airway and tissue eosinophilia, AHR, and T_H2 and T_H17 pulmonary profiles. Notably, nonsensitized obese mice already exhibited increased lung ILC counts and tissue eosinophil infiltration compared with values in lean mice in the absence of AHR. The numbers of total and cytokine-expressing lung ILC2s and ILC3s further increased in HDM-challenged obese mice compared with those in HDM-challenged lean mice, and this was accompanied by high IL-33 and IL-1β levels and decreased ILC markers in visceral adipose tissue. Furthermore, depletion of ILCs with an anti-CD90 antibody, followed by T-cell reconstitution, led to a profound decrease in allergic airway inflammatory features in obese mice, including T_H2 and T_H17 infiltration.

CONCLUSION

These results indicate that HFD-induced obesity might exacerbate allergic airway inflammation through mechanisms involving ILC2s and ILC3s.

Immunological characteristics and management considerations in obese patients with asthma

Obesity is associated with severe, poorly controlled asthma that does not respond as well to therapy as asthma in leaner asthmatics. Important insights gained from animal models of obesity and asthma suggests that different forms of obesity may lead to different manifestations of airway disease: obesity is associated with both innate increased airway reactivity and altered responses to aeroallergen and pollutant challenges. In humans, at least two broad groups of obese asthmatics have been recognized: one that is likely unique to obesity and another that is likely lean allergic asthma much complicated by obesity. This article will discuss what we have learned about the immunological and pathophysiological basis of asthma in obesity from animal and human studies, and how this might guide therapy.

Dietary patterns and pulmonary function in Korean women: findings from the Korea National Health and Nutrition Examination Survey 2007-2011

In the present study, we evaluated the association between dietary patterns and pulmonary functions in Korean women older than 40 years. This study analyzed the data from the Korea National Health and Nutrition Examination Survey IV and V (2007-2010). In total, 7615 women were included in the analysis. Using principal component analysis, two dietary patterns were identified, namely a balanced diet pattern (vegetables, fish, meat, seaweed, and mushrooms) and a refined diet (snacks, bread, milk, dairy products, and fast food). The refined diet pattern was positively associated with energy from fat but negatively associated with vitamin A, β-carotene, niacin, and fiber. After adjusting for potential confounders, the refined diet pattern was negatively associated with levels of predicted forced vital capacity (odds ratio (OR): 0.84, 95% confidence intervals (CIs): 0.70, 0.99) and predicted forced expiratory volume in 1 second (OR: 0.79, 95% CIs: 0.66, 0.93). In conclusion, the refined diet pattern was associated with decreased pulmonary function in Korean women. This information may be useful toward the development of nutritional guidelines for improving pulmonary function in Korean women.