Peroxisome proliferator-activated receptors alpha and gamma down-regulate allergic inflammation and eosinophil activation

Lipid metabolism-related genes are involved in the occurrence of asthma and regulate the immune microenvironment

BACKGROUND

Lipid metabolism plays a pivotal role in asthma pathogenesis. However, a comprehensive analysis of the importance of lipid metabolism-related genes (LMRGs) in regulating the immune microenvironment in asthma remains lacking. The transcriptome matrix was downloaded from the Gene Expression Omnibus (GEO) dataset. Differentially expressed analysis and weighted gene coexpression network analysis (WGCNA) were conducted on the GSE74986 dataset to select hub LMRGs, and gene set enrichment analysis (GSEA) was conducted to explore their biological functions. The CIBERSORT algorithm was used to determine immune infiltration in the asthma and control groups, and the correlation of diagnostic biomarkers and immune cells was performed via Spearman correlation analysis. Subsequently, a competitive endogenous RNA (ceRNA) network was constructed to investigate the hidden molecular mechanism of asthma. The expression levels of the hub genes were further validated in the GSE143192 dataset, and RT‒qPCR and immunofluorescence were performed to verify the reliability of the results in the OVA asthma model. Lastly, the ceRNA network was confirmed by qRT-PCR and RNAi experiments in the characteristic cytokine (IL-13)-induced asthma cellular model.

RESULTS

ASAH1, ACER3 and SGPP1 were identified as hub LMRGs and were mainly involved in protein secretion, mTORC1 signaling, and fatty acid metabolism. We found more infiltration of CD8+ T cells, activated NK cells, and monocytes and less M0 macrophage infiltration in the asthma group than in the healthy control group. In addition, ASAH1, ACER3, and SGPP1 were negatively correlated with CD8+ T cells and activated NK cells, but positively correlated with M0 macrophages. Within the ceRNA network, SNHG9-hsa-miR-615-3p-ACER3, hsa-miR-212-5p and hsa-miR-5682 may play crucial roles in asthma pathogenesis. The low expression of ASAH1 and SGPP1 in asthma was also validated in the GSE74075 dataset. After SNHG9 knockdown, miR-615-3p expression was significantly upregulated, while that of ACER3 was significantly downregulated.

CONCLUSION

ASAH1, ACER3 and SGPP1 might be diagnostic biomarkers for asthma, and are associated with increased immune system activation. In addition, SNHG9-hsa-miR-615-3p-ACER3 may be viewed as effective therapeutic targets for asthma. Our findings might provide a novel perspective for future research on asthma.

Role of PPARα in inflammatory response of C2C12 myotubes

Recent studies have shown a role of inflammation in muscle atrophy and sarcopenia. However, no anti-inflammatory pharmacotherapy has been established for the treatment of sarcopenia. Here, we investigate the potential role of PPARα and its ligands on inflammatory response and PGC-1α gene expression in LPS-treated C2C12 myotubes. Knockdown of PPARα, whose expression was upregulated upon differentiation, augmented IL-6 or TNFα gene expression. Conversely, PPARα overexpression or its activation by ligands suppressed 2-h LPS-induced cytokine expression, with pemafibrate attenuating NF-κB or STAT3 phosphorylation. Of note, reduction of PGC-1α gene expression by LPS treatment for 24 hours was partially reversed by fenofibrate. Our data demonstrate a critical inhibitory role of PPARα in inflammatory response of C2C12 myotubes and suggest a future possibility of PPARα ligands as a candidate for anti-inflammatory therapy against sarcopenia.

Mirabegron, dependent on β3-adrenergic receptor, alleviates mercuric chloride-induced kidney injury by reversing the impact on the inflammatory network, M1/M2 macrophages, and claudin-2

The β3-adrenergic receptor (β3-AR) agonism mirabegron is used to treat overactive urinary bladder syndrome; however, its role against acute kidney injury (AKI) is not unveiled, hence, we aim to repurpose mirabegron in the treatment of mercuric chloride (HgCl2)-induced AKI. Rats were allocated into normal, normal + mirabegron, HgCl2 untreated, HgCl2 + mirabegron, and HgCl2 + the β3-AR blocker SR59230A + mirabegron. The latter increased the mRNA of β3-AR and miR-127 besides downregulating NF-κB p65 protein expression and the contents of its downstream targets iNOS, IL-4, -13, and -17 but increased that of IL-10 to attest its anti-inflammatory capacity. Besides, mirabegron downregulated the protein expression of STAT-6, PI3K, and ERK1/2, the downstream targets of the above cytokines. Additionally, it enhanced the transcription factor PPAR-α but turned off the harmful hub HNF-4α/HNF-1α and the lipid peroxide marker MDA. Mirabegron also downregulated the CD-163 protein expression, which besides the inhibited correlated cytokines of M1 (NF-κB p65, iNOS, IL-17) and M2 (IL-4, IL-13, CD163, STAT6, ERK1/2), inactivated the macrophage phenotypes. The crosstalk between these parameters was echoed in the maintenance of claudin-2, kidney function-related early (cystatin-C, KIM-1, NGAL), and late (creatinine, BUN) injury markers, besides recovering the microscopic structures. Nonetheless, the pre-administration of SR59230A has nullified the beneficial effects of mirabegron on the aforementioned parameters. Here we verified that mirabegron can berepurposedto treat HgCl2-induced AKI by activating the β3-AR. Mirabegron signified its effect by inhibiting inflammation, oxidative stress, and the activated M1/M2 macrophages, events that preserved the proximal tubular tight junction claudin-2 via the intersection of several trajectories.

LC-MS-based metabolomics reveals the in vivo effect of Shegan Mahuang Decoction in an OVA-induced rat model of airway hyperresponsiveness

The traditional Chinese medicine (TCM) formula Shegan Mahuang Decoction (SMD) has been used for treating asthma with significant clinical efficacy, but its mechanism of action has not been well investigated. This study aimed to investigate the anti-asthma effects of SMD on ovalbumin (OVA)-induced airway hyperresponsiveness (AHR) in rats and its potential mechanisms using liquid chromatography-mass spectrometry (LC-MS)-based metabolomics combined with Gene Expression Omnibus (GEO) data mining. The results showed that the administration of SMD significantly attenuated OVA-induced lung histopathological changes. OVA-induced elevation of the immunoglobulin (IgE) and interleukin-4 (IL-4) levels was also inhibited by SMD. A total of 28 significantly changed metabolites in plasma were selected from metabolomics analysis. After treatment with SMD, 24 of them were negatively regulated and the related metabolisms were involved in multiple metabolic pathways such as sphingolipid metabolism and arachidonic acid metabolism. The differentially expressed genes (DEGs) were obtained by GEO data mining. The integrated pathway analysis highlighted 11 signaling pathways that were associated with the anti-asthma effect of SMD. Among them, the metabolite-gene-pathway network showed that the peroxisome proliferator-activated receptors (PPAR) signaling pathway might be the most significant one. This study revealed that SMD exerted an anti-asthma effect against OVA-induced AHR via comprehensively modulating the sphingolipid metabolism, arachidonic acid metabolism, and PPAR signaling, which indicated the synergistic effect of multi-component, multi-target, and multi-pathway of TCM in the treatment of the disease. This study expands our understanding of SMD in the treatment of asthma from a metabolomics perspective.

PPAR Alpha as a Metabolic Modulator of the Liver: Role in the Pathogenesis of Nonalcoholic Steatohepatitis (NASH)

Simple Summary

In the context of liver disease, one of the more growing public health problems is the transition from simple steatosis to non-alcoholic steatohepatitis. Profound metabolic dysregulations linked to inflammation and hepatic injury are features of non-alcoholic steatohepatitis. Since the peroxisomal-proliferator-activated receptor alpha has long been considered one of the key transcriptional factors in hepatic metabolism, its role in the pathogenesis of non-alcoholic steatohepatitis is discussed in this review.

Abstract

The strong relationship between metabolic alterations and non-alcoholic steatohepatitis (NASH) suggests a pathogenic interplay. However, many aspects have not yet been fully clarified. Nowadays, NASH is becoming the main cause of liver-associated morbidity and mortality. Therefore, an effort to understand the mechanisms underlying the pathogenesis of NASH is critical. Among the nuclear receptor transcription factors, peroxisome-proliferator-activated receptor alpha (PPARα) is highly expressed in the liver, where it works as a pivotal transcriptional regulator of the intermediary metabolism. In this context, PPARα’s function in regulating the lipid metabolism is essential for proper liver functioning. Here, we review metabolic liver genes under the control of PPARα and discuss how this aspect can impact the inflammatory condition and pathogenesis of NASH.

Pinellic Acid Isolated from Quercetin-rich Onions has a Peroxisome Proliferator-Activated Receptor-Alpha/Gamma (PPAR-α/γ) Transactivation Activity

Quercetin, a flavonol, is a functional compound that is abundant in onions and is known to have antioxidant and anti-inflammatory effects. Quercetin and its glucoside are known to function as peroxisome proliferator-activated receptor (PPAR) ligands and showed high PPAR-α transactivation activity but little PPAR-γ transactivation activity in some reports. In this study, we demonstrated that an aqueous extract of a quercetin-rich onion cultivar increased transactivation activities not only of PPAR-α but also of PPAR-γ. We isolated (9S,12S,13S)-(10E)-9,12,13-trihydroxyoctadec-10-enoic acid (pinellic acid) obtained from the aqueous extract using PPAR-γ transactivation as an index. Furthermore, it was revealed that pinellic acid could transactivate PPAR-α. Our findings are the first report mentioned showing that trihydroxyoctadec-10-enoic acids showed PPAR-α/γ transactivation activities.

Obesity alters pathology and treatment response in inflammatory disease

Decades of work have elucidated cytokine signalling and transcriptional pathways that control T cell differentiation and have led the way to targeted biologic therapies that are effective in a range of autoimmune, allergic and inflammatory diseases. Recent evidence indicates that obesity and metabolic disease can also influence the immune system1-7, although the mechanisms and effects on immunotherapy outcomes remain largely unknown. Here, using two models of atopic dermatitis, we show that lean and obese mice mount markedly different immune responses. Obesity converted the classical type 2 T helper (TH2)-predominant disease associated with atopic dermatitis to a more severe disease with prominent TH17 inflammation. We also observed divergent responses to biologic therapies targeting TH2 cytokines, which robustly protected lean mice but exacerbated disease in obese mice. Single-cell RNA sequencing coupled with genome-wide binding analyses revealed decreased activity of nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) in TH2 cells from obese mice relative to lean mice. Conditional ablation of PPARγ in T cells revealed that PPARγ is required to focus the in vivo TH response towards a TH2-predominant state and prevent aberrant non-TH2 inflammation. Treatment of obese mice with a small-molecule PPARγ agonist limited development of TH17 pathology and unlocked therapeutic responsiveness to targeted anti-TH2 biologic therapies. These studies reveal the effects of obesity on immunological disease and suggest a precision medicine approach to target the immune dysregulation caused by obesity.

Parsing the Role of PPARs in Macrophage Processes

Cells are richly equipped with nuclear receptors, which act as ligand-regulated transcription factors. Peroxisome proliferator activated receptors (PPARs), members of the nuclear receptor family, have been extensively studied for their roles in development, differentiation, and homeostatic processes. In the recent past, there has been substantial interest in understanding and defining the functions of PPARs and their agonists in regulating innate and adaptive immune responses as well as their pharmacologic potential in combating acute and chronic inflammatory disease. In this review, we focus on emerging evidence of the potential roles of the PPAR subtypes in macrophage biology. We also discuss the roles of dual and pan PPAR agonists as modulators of immune cell function, microbial infection, and inflammatory diseases.

The Role of PPAR-γ in Allergic Disease

Purpose of Review

The incidence of allergic diseases such as asthma, rhinitis and atopic dermatitis has risen at an alarming rate over the last century. Thus, there is a clear need to understand the critical factors that drive such pathologic immune responses. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear receptor that has emerged as an important regulator of multiple cell types involved in the inflammatory response to allergens; from airway epithelial cells to T Helper (TH) cells.

Recent Findings

Initial studies suggested that agonists of PPAR-γ could be employed to temper allergic inflammation, suppressing pro-inflammatory gene expression programs in epithelial cells. Several lines of work now suggest that PPAR-γ plays an essential in promoting ‘type 2’ immune responses that are typically associated with allergic disease. PPAR-γ has been found to promote the functions of TH2 cells, type 2 innate lymphoid cells, M2 macrophages and dendritic cells, regulating lipid metabolism and directly inducing effector gene expression. Moreover, preclinical models of allergy in gene-targeted mice have increasingly implicated PPAR-γ in driving allergic inflammation.

Summary

Herein, we highlight the contrasting roles of PPAR-γ in allergic inflammation and hypothesize that the availability of environmental ligands for PPAR-γ may be at the heart of the rise in allergic diseases worldwide.

PPARγ ligands modulate the immune response mediators in the pig myometrium - An in vitro study

The current study was conducted with the aim to investigate effects of PPARγ ligands on synthesis of nuclear receptor κB (NF-κB) and selected cytokines (IL-1β, IFNγ, TNFα, IL-4, IL-10, LIF) in the pig myometrium on days 14-15 of the estrous cycle (late-luteal phase) and days 14-15 of the gestational period (beginning of embryonic implantation). The myometrial slices were incubated in vitro for 6 h in medium containing PPARγ ligands, agonists: 15d-prostaglandin J₂ or pioglitazone, and antagonist - T0070907. The mRNA transcript and protein abundances were evaluated in tissues and culture medium. During the estrous cycle, PPARγ ligands did not have an effect on the mRNA transcript abundance of the immune response mediators used for treatments. The IL-10 protein abundance in the tissue was less when there was inclusions of pioglitazone in the medium, while the treatment with T0070907 resulted in a larger abundance of NF-κB, IL-1β (in the tissue) and IL-4 (in tissue and culture media). During the gestational period, pioglitazone or PGJ₂ suppressed mRNA IFNγ and IL-10 transcript and protein abundances (in the tissue and culture media), whereas there was an enhanced NF-κB protein abundance (in the tissue). Treatment with T0070907 had diverse effects (e.g., for NFκB inhibited mRNA transcript abundance or enhanced protein abundance). The observed changes are related mainly in tissues from pregnant animals. Responses to PPARγ antagonist are indicative of the possible involvement of PPARγ-independent factors as well as ligand-independent activation of the receptor, ligand selectivity/functionality or tissue receptivity to the factors evaluated.

What's the deal with efferocytosis and asthma?

Mucosal sites, such as the lung, serve as crucial, yet vulnerable barriers to environmental insults such as pathogens, allergens, and toxins. Often, these exposures induce massive infiltration and death of short-lived immune cells in the lung, and efficient clearance of these cells is important for preventing hyperinflammation and resolving immunopathology. Herein, we review recent advances in our understanding of efferocytosis, a process whereby phagocytes clear dead cells in a noninflammatory manner. We further discuss how efferocytosis impacts the onset and severity of asthma in humans and mammalian animal models of disease. Finally, we explore how recently identified genetic perturbations or biological pathway modulations affect pathogenesis and shed light on novel therapies aimed at treating or preventing asthma.

The Role of PPAR Alpha in the Modulation of Innate Immunity

Peroxisome proliferator-activated receptor α is a potent regulator of systemic and cellular metabolism and energy homeostasis, but it also suppresses various inflammatory reactions. In this review, we focus on its role in the regulation of innate immunity; in particular, we discuss the PPARα interplay with inflammatory transcription factor signaling, pattern-recognition receptor signaling, and the endocannabinoid system. We also present examples of the PPARα-specific immunomodulatory functions during parasitic, bacterial, and viral infections, as well as approach several issues associated with innate immunity processes, such as the production of reactive nitrogen and oxygen species, phagocytosis, and the effector functions of macrophages, innate lymphoid cells, and mast cells. The described phenomena encourage the application of endogenous and pharmacological PPARα agonists to alleviate the disorders of immunological background and the development of new solutions that engage PPARα activation or suppression.

Antifibrotic Effects of the Thiazolidinediones in Eosinophilic Esophagitis Pathologic Remodeling: A Preclinical Evaluation

Eosinophilic esophagitis (EoE) is a T-helper 2 (Th2), eosinophilic disease associated with pathologic tissue remodeling that leads to end-organ dysfunction. During early-stage disease, inflammation and subepithelial fibrosis are coupled and reversible, but in late-stage or therapy-resistant disease, there can be uncoupling of these features with progressive esophageal rigidity and strictures contributing to clinical dysphagia and food impactions. No current pharmacotherapeutic interventions directly target esophageal fibrosis. Based on the ability of the thiazolidinediones (TZD) to regulate intestinal and hepatic fibrosis, we tested the antifibrotic effects of the TZDs, rosiglitazone and pioglitazone, in preclinical studies using primary human esophageal fibroblasts.

Biochanin A Ameliorates Ovalbumin-induced Airway Inflammation through Peroxisome Proliferator-Activated Receptor-Gamma in a Mouse Model

OBJECTIVE

Asthma is an inflammatory airway disease affecting most of the population in the world. The current medication for asthma relieves airway inflammation but it has serious adverse effects. Biochanin A (BCA), a phytoestrogen, is an active component present in red clover, alfalfa, soy having anti-oxidant and anti-inflammatory properties. BCA was identified as a natural activator of peroxisome proliferator-activated receptor-gamma (PPARγ).

METHODS

The study aims to evaluate the effects of BCA in ovalbumin (OVA)-induced murine model of asthma and to study the role of PPARγ.

RESULTS

We found that BCA administration reduced the severity of murine allergic asthma as evidenced histologically, and measurement of allergen-specific IgE levels in serum as well as in BAL fluid. BCA also reversed the elevated levels of inflammatory cytokines, cell infiltration, protein leakage into the airways and expression of hemoxygenase-1 in OVA-induced lungs. Further, we confirmed that BCA mediated inhibitory effects are mediated through PPARγ as assessed by treatment with PPARγ antagonist GW9662.

CONCLUSION

Our results suggest that BCA is efficacious in a preclinical model of asthma and may have the potential for the treatment of asthma in humans.

Nuclear Receptors in Asthma: Empowering Classical Molecules Against a Contemporary Ailment

The escalation in living standards and adoption of 'Western lifestyle' has an allied effect on the increased allergy and asthma burden in both developed and developing countries. Current scientific reports bespeak an association between allergic diseases and metabolic dysfunction; hinting toward the critical requirement of organized lifestyle and dietary habits. The ubiquitous nuclear receptors (NRs) translate metabolic stimuli into gene regulatory signals, integrating diet inflences to overall developmental and physiological processes. As a consequence of such promising attributes, nuclear receptors have historically been at the cutting edge of pharmacy world. This review discusses the recent findings that feature the cardinal importance of nuclear receptors and how they can be instrumental in modulating current asthma pharmacology. Further, it highlights a possible future employment of therapy involving dietary supplements and synthetic ligands that would engage NRs and aid in eliminating both asthma and linked comorbidities. Therefore, uncovering new and evolving roles through analysis of genomic changes would represent a feasible approach in both prevention and alleviation of asthma.

Could Arachidonic Acid-Derived Pro-Resolving Mediators Be a New Therapeutic Strategy for Asthma Therapy?

Asthma represents one of the leading chronic diseases worldwide and causes a high global burden of death and disability. In asthmatic patients, the exacerbation and chronification of the inflammatory response are often related to a failure in the resolution phase of inflammation. We reviewed the role of the main arachidonic acid (AA) specialized pro-resolving mediators (SPMs) in the resolution of chronic lung inflammation of asthmatics. AA is metabolized by two classes of enzymes, cyclooxygenases (COX), which produce prostaglandins (PGs) and thromboxanes, and lypoxygenases (LOX), which form leukotrienes and lipoxins (LXs). In asthma, two primary pro-resolving derived mediators from COXs are PGE₂ and the cyclopentenone prostaglandin15-Deoxy-Delta-12,14-PGJ₂ (15d-PGJ₂) while from LOXs are the LXA₄ and LXB₄. In different models of asthma, PGE₂, 15d-PGJ₂, and LXs reduced lung inflammation and remodeling. Furthermore, these SPMs inhibited chemotaxis and function of several inflammatory cells involved in asthma pathogenesis, such as eosinophils, and presented an antiremodeling effect in airway epithelial, smooth muscle cells and fibroblasts in vitro. In addition, PGE₂, 15d-PGJ₂, and LXs are all able to induce macrophage reprogramming to an alternative M2 pro-resolving phenotype in vitro and in vivo. Although PGE₂ and LXA₄ showed some beneficial effects in asthmatic patients, there are limitations to their clinical use, since PGE₂ caused side effects, while LXA₄ presented low stability. Therefore, despite the strong evidence that these AA-derived SPMs induce resolution of both inflammatory response and tissue remodeling in asthma, safer and more stable analogs must be developed for further clinical investigation of their application in asthma treatment.

Imbalanced serum levels of resolvin E1 (RvE1) and leukotriene B4 (LTB4) in patients with allergic rhinitis

Timely and successful resolution of acute inflammation plays a crucial role in preventing the development of chronic airway inflammation in allergic rhinitis (AR). This study intends to assess the serum levels of pro-inflammatory leukotriene B4 (LTB4), anti-inflammatory mediators, including resolvin E1 (RvE1), RvD1, IL-10, and TGF-β, besides mRNA expression level of G-protein coupled receptor 120 (GPR120) and peroxisome proliferator-activated receptor-γ (PPAR-γ) receptors in peripheral blood leukocytes of AR patients. Thirty-seven AR patients and thirty age- and gender-matched healthy subjects were enrolled in this study. The serum levels of LTB4, RvE1, RvD1, IL-10, and TGF-β were measured using enzyme-linked immunosorbent assay (ELISA) technique, and the mRNA expression level of GPR120 and PPAR-γ was assessed by the real-time PCR method. The serum levels of RvE1 and LTB4 were significantly higher in patients with AR than in healthy subjects (P < 0.01 and P < 0.0001, respectively). However, a significantly lower ratio of RvE1 and RvD1 to LTB4 was found in patients with AR relative to healthy subjects (P < 0.05 and P < 0.0001, respectively). Likewise, the serum levels of both IL-10 and TGF-β cytokines were significantly reduced in patients with AR compared to healthy subjects (P < 0.01 and P < 0.0001, respectively). Furthermore, the mRNA expression of PPAR-γ was significantly lower in patients with AR than in healthy subjects (P < 0.05). Our findings indicate that imbalanced pro-resolving lipid mediator RvE1 and pro-inflammatory LTB4 might contribute to the defective airway inflammation-resolution and subsequent progression toward chronic inflammation in AR patients.

What Makes the Lung Unique – Tissue-Specific Immunity in the Respiratory Tract

The immune system constitutes a critical mechanism of the human body to preserve health and mitigate disease. In the lung, immunity is seen as a critical driver in many respiratory diseases, in particular in those characterised by aberrant inflammation, such as chronic obstructive pulmonary disease, fibrosis, and asthma. In this review, the specialised set of immune cells and lung tissue-specific regulators, including key cytokines such as granulocyte-macrophage colony-stimulating factor and transforming growth factor β, that control immune responses in the respiratory tract will be discussed. Furthermore, the current understanding of the impact of key environmental components such as the role of oxygen and lung microbiota on lung immunity will be highlighted. The goal is to identify the unique aspects of lung immune biology to facilitate insights into the aetiology of common lung inflammatory diseases and to provide the basis for a deeper mechanistic understanding of the underlying immune processes. Finally, key future avenues of research such as using more comprehensive quantitative approaches for elucidating molecular disease mechanisms as well as the potential to exploit tissue-specific regulators of immunity for therapy of lung inflammatory disorders will be discussed.

In vitro and in vivo Antiallergic Effects of Taurine on Allergic Rhinitis

BACKGROUND

The current treatment for allergic rhinitis (AR) is inadequate.

OBJECTIVE

The present study aimed to investigate the therapeutic effect of taurine on AR and to identify the underlying molecular mechanisms.

METHODS

The serum level of the antioxidant enzyme extracellular superoxide dismutase (SOD3) was determined in AR patients and in healthy controls. The antiallergic inflammatory effects of taurine were evaluated in a dinitrophenyl-human serum albumin (DNP-HSA)-stimulated human mast cell line (HMC-1) and in an ovalbumin (OVA)-induced AR mouse model.

RESULTS

Clinically, a reduction in serum level of SOD3 was observed in AR patients. Taurine treatment led to dose-dependent increases in SOD3 at both protein and mRNA levels in HMC-1 cells. SOD3 production was regulated by peroxisome proliferator-activated receptor-γ (PPAR-γ) in response to taurine. SOD3 overexpression inhibited the release of proinflammatory cytokines including tumor necrosis factor-α (, interleukin (IL)-4, and IL-6. Its overexpression also ameliorated the loss of interferon-γ. SOD3 and PPAR-γ influenced inflammatory cytokine production via regulation of the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). An OVA-induced AR animal model study showed that taurine was efficacious in alleviating allergic inflammatory reactions by relieving behavior symptoms of AR mice and reducing eosinophilic and mast cell infiltration into the nasal cavity. In addition, taurine treatment increased the production of SOD3 and PPAR-γ, which, in turn, suppressed expression of proinflammatory cytokines through phosphorylation of ERK1/2.

CONCLUSION

Taurine could potentially serve as a therapeutic treatment for allergic disorders.

Inhibition of NADPH Oxidase-Derived Reactive Oxygen Species Decreases Expression of Inflammatory Cytokines in A549 Cells

Various experimental models strongly support the hypothesis that airway inflammation can be caused by oxidative stress. Inflammatory airway diseases like asthma and COPD are characterized by higher levels of ROS and inflammatory cytokines. One of the sources of ROS is NADPH oxidase. Therefore, the aim of the study was to investigate influence of NADPH oxidase inhibition on the expression of IL-6, IL-8, TNF, TSLP, CD59, and PPAR-γ in vitro. A549 cells were incubated with apocynin in three concentrations (0.5 mg/ml, 1 mg/ml, and 3 mg/ml). Cells were trypsinized and RNA isolated after 1 h, 2 h, and 4 h of apocynin incubation at each concentration. Afterwards, reverse transcription was performed to evaluate mRNA expression using real-time PCR. The time-response and dose-response study showed that apocynin significantly influenced the relative expression of chosen genes (IL-6, IL-8, TNF, PPAR-γ, TSLP, and CD59). Apocynin decreased the mRNA expression of TNF-α at all concentrations used, and of IL-6 at concentrations of 1 and 3 mg/ml (p < 0.05). TSLP mRNA expression was also reduced by apocynin after 1 h and 2 h, and CD59 mRNA after 1 h, but only at the highest concentration. The expression of PPAR-γ was reduced after apocynin in the highest concentrations only (p < 0.05). The results might suggest that proinflammatory agents’ expression levels are strongly connected to the presence of oxidative stress generated by NADPH oxidase and this might be at least partially eliminated by anti-oxidative action. Apocynin, as an effective inhibitor of NADPH oxidase, seems to be useful in potential anti-oxidative and anti-inflammatory therapy.

Erythromycin Releasing PVA/sucrose and PVA/honey Hydrogels as Wound Dressings with Antibacterial Activity and Enhanced Bio-adhesion

The present study deals with preparation and characterization of thermally crosslinked PVA-based hydrogels containing honey and sucrose for the purpose of erythromycin delivery. The hydrogels have been characterized and compared by scanning electron microscopy, Fourier transform infrared spectroscopy, and bio-adhesion tests. Swelling measurements showed that addition of sucrose and honey decreased the equilibrium swelling of the hydrogels. Results of release studies showed that the amount of erythromycin, released at the early hours was higher for PVA/sucrose and PVA/honey hydrogels compared to PVA hydrogel while the drug released at later times was highly reduced for PVA/honey hydrogel. Both Peppas-Sahlin and Korsmeyer-Peppas models fitted well to the release data. Fitting Peppas-Sahlin model to the release data showed that at the initial times, release of drug from the hydrogel network was mainly governed by Fickian mechanism; however, at later times the drug is dominantly released by relaxational mechanism due to swelling of the network,. Addition of honey improved the bio-adhesion of PVA/honey hydrogel as compared to PVA/sucrose and pure PVA hydrogel. Results of antibacterial tests showed growth inhibitory action of erythromycin-loaded PVA hydrogels against Pseudomonas aeruginosa and Staphylococcus aureus bacteria. This study indicates that these hybrid hydrogels are capable of being used as functional wound dressings aiming to control the rate of antibiotic delivery to the wound site and prevent the wounds from infection.

CB2 Agonist (AM1241) Improving Effect on Ovalbumin-Induced Asthma in Rats

Asthma is a disease characterized by spontaneous contraction of the airways in response to a wide variety of endogenous and exogenous stimuli. Many asthma models are used to mimic the human asthma model in the literature. In order to better understand the role of the cannabinoid (CB) 2 receptor in the ovalbumin (OVA)-induced asthma model, a combination of both selective CB2 agonist (AM1241) and antagonist (AM630) was used to improve inflammatory hypersensitivity and edema in rats. In the present study, it was found that OVA decreased body weight (p < 0.05), increased lung weights (p < 0.05), increased diastolic and systolic blood pressure (p < 0.001), and caused irregularity in pulmonary functions (p < 0.001). Moreover, CB2 agonist was found not to reduce body weight, cause blood pressure and respiratory irregularities (p < 0.05). OVA led to increase in IgE, TNF-α, IL-4, MDA level (p < 0.001), and total WBC count (p < .05). CB2 treatment caused to reduce the number of total WBC and the level of total protein in BALF, to hinder to increase level of MDA, IgE, TNF-α, and IL-4 (p < 0.05) in BALF or serum or lung tissue. But CB2-antagonist treatment prevented the protective effect of CB2 agonist. The aim of this study was to study the role of the CB2 receptor in the OVA induced asthma model, to improve inflammatory hypersensitivity, and edema in the rats. The results suggested that CB2 agonist administration to OVA induced asthmatic rats via anti-asthmatic potential through inhibition of parameters such as IgE, IL-4, TNF-α, microvascular escape, and oxidative stress.

The Metabolic Requirements of Th2 Cell Differentiation

Upon activation, naïve CD4⁺ T cells differentiate into a number of specialized T helper (Th) cell subsets. Th2 cells are central players in immunity to helminths and are implicated in mediating the inflammatory pathology associated with allergies. The differentiation of Th2 cells is dependent on transcription factors such as GATA3 and STAT6, which prime Th2 cells for the secretion of interleukin- (IL-) 4, IL-5, and IL-13. Several lines of work now suggest that differentiating Th2 cells in the lymph node are potent IL-4 cytokine producers, but do not become competent IL-5- and IL-13-producing cells until after receiving cues from non-lymphoid tissue. It is evident that Th2 cells that enter tissues undergo considerable changes in chromatin architecture and gene expression, and that over this time, the metabolic requirements of these cells change considerably. Herein, we discuss the metabolic requirements of Th2 cells during their early and late differentiation, focusing on the impact of glucose and lipid metabolism, mTOR activation, the nuclear receptor PPAR-γ and several metabolites.

NeTFactor, a framework for identifying transcriptional regulators of gene expression-based biomarkers

Biological and regulatory mechanisms underlying many multi-gene expression-based disease biomarkers are often not readily evident. We describe an innovative framework, NeTFactor, that combines network analyses with gene expression data to identify transcription factors (TFs) that significantly and maximally regulate such a biomarker. NeTFactor uses a computationally-inferred context-specific gene regulatory network and applies topological, statistical, and optimization methods to identify regulator TFs. Application of NeTFactor to a multi-gene expression-based asthma biomarker identified ETS translocation variant 4 (ETV4) and peroxisome proliferator-activated receptor gamma (PPARG) as the biomarker's most significant TF regulators. siRNA-based knock down of these TFs in an airway epithelial cell line model demonstrated significant reduction of cytokine expression relevant to asthma, validating NeTFactor's top-scoring findings. While PPARG has been associated with airway inflammation, ETV4 has not yet been implicated in asthma, thus indicating the possibility of novel, disease-relevant discovery by NeTFactor. We also show that NeTFactor's results are robust when the gene regulatory network and biomarker are derived from independent data. Additionally, our application of NeTFactor to a different disease biomarker identified TF regulators of interest. These results illustrate that the application of NeTFactor to multi-gene expression-based biomarkers could yield valuable insights into regulatory mechanisms and biological processes underlying disease.

Elevated faecal 12,13-diHOME concentration in neonates at high risk for asthma is produced by gut bacteria and impedes immune tolerance

Neonates at risk of childhood atopy and asthma exhibit perturbation of the gut microbiome, metabolic dysfunction and increased concentrations of 12,13-diHOME in their faeces. However, the mechanism, source and contribution of this lipid to allergic inflammation remain unknown. Here, we show that intra-abdominal treatment of mice with 12,13-diHOME increased pulmonary inflammation and decreased the number of regulatory T (T_reg) cells in the lungs. Treatment of human dendritic cells with 12,13-diHOME altered expression of PPARγ-regulated genes and reduced anti-inflammatory cytokine secretion and the number of T_reg cells in vitro. Shotgun metagenomic sequencing of neonatal faeces indicated that bacterial epoxide hydrolase (EH) genes are more abundant in the gut microbiome of neonates who develop atopy and/or asthma during childhood. Three of these bacterial EH genes (3EH) specifically produce 12,13-diHOME, and treatment of mice with bacterial strains expressing 3EH caused a decrease in the number of lung T_reg cells in an allergen challenge model. In two small birth cohorts, an increase in the copy number of 3EH or the concentration of 12,13-diHOME in the faeces of neonates was found to be associated with an increased probability of developing atopy, eczema or asthma during childhood. Our data indicate that elevated 12,13-diHOME concentrations impede immune tolerance and may be produced by bacterial EHs in the neonatal gut, offering a mechanistic link between perturbation of the gut microbiome during early life and atopy and asthma during childhood.

SIRT3 promotes antimycobacterial defenses by coordinating mitochondrial and autophagic functions

SIRT3 (sirtuin 3), a mitochondrial protein deacetylase, maintains respiratory function, but its role in the regulation of innate immune defense is largely unknown. Herein, we show that SIRT3 coordinates mitochondrial function and macroautophagy/autophagy activation to promote anti-mycobacterial responses through PPARA (peroxisome proliferator activated receptor alpha). SIRT3 deficiency enhanced inflammatory responses and mitochondrial dysfunction, leading to defective host defense and pathological inflammation during mycobacterial infection. Antibody-mediated depletion of polymorphonuclear neutrophils significantly increased protection against mycobacterial infection in sirt3^-/- mice. In addition, mitochondrial oxidative stress promoted excessive inflammation induced by Mycobacterium tuberculosis infection in sirt3^-/- macrophages. Notably, SIRT3 was essential for the enhancement of PPARA, a key regulator of mitochondrial homeostasis and autophagy activation in the context of infection. Importantly, overexpression of either PPARA or TFEB (transcription factor EB) in sirt3^-/- macrophages recovered antimicrobial activity through autophagy activation. Furthermore, pharmacological activation of SIRT3 enhanced antibacterial autophagy and functional mitochondrial pools during mycobacterial infection. Finally, the levels of SIRT3 and PPARA were downregulated and inversely correlated with TNF (tumor necrosis factor) levels in peripheral blood mononuclear cells from tuberculosis patients. Collectively, these data demonstrate a previously unappreciated function of SIRT3 in orchestrating mitochondrial and autophagic functions to promote antimycobacterial responses. Abbreviations: Ab: antibody; BCG: M. bovis Bacillus Calmette-Guérin; Baf-A₁: bafilomycin A₁; BMDMs: bone marrow-derived macrophages; CFU: colony forming unit; CXCL5: C-X-C motif chemokine ligand 5; EGFP: enhanced green fluorescent protein; ERFP: enhanced red fluorescent protein; FOXO3: forkhead box O3; HC: healthy controls; H&E: haematoxylin and eosin; HKL: honokiol; IHC: immunohistochemistry; IL1B: interleukin 1 beta; IL6: interleukin 6; IL12B: interleukin 12B; MDMs: monocyte-derived macrophages; MMP: mitochondrial membrane potential; Mtb: Mycobacterium tuberculosis; PBMC: peripheral blood mononuclear cells; PBS: phosphate buffered saline; PMN: polymorphonuclear neutrophil; PPARA: peroxisome proliferator activated receptor alpha; ROS: reactive oxygen species; SIRT3: sirtuin 3; TB: tuberculosis; TEM: transmission electron microscopy; TFEB: transcription factor EB; TNF: tumor necrosis factor.

The Ethanol Extract of Holotrichia diomphalia Larvae, Containing Fatty acids and Amino acids, Exerts Anti-Asthmatic Effects through Inhibition of the GATA-3/Th2 Signaling Pathway in Asthmatic Mice

Holotrichia diomphalia larvae (HD), a natural product from an insect resource, possesses many pharmacological properties, including anticoagulant, antitumor, anti-inflammatory, and analgesic activity. The major bioactive ingredients include oleic acid, palmitic acid, palmitoleic acid, linoleic acid, proline, and glutamic acid. Although HD is associated with immunoregulatory activities in allergic diseases, the therapeutic mechanisms of the action of HD in allergic diseases have not been investigated. The aim of this study was to evaluate the anti-asthmatic potential of HD in an ovalbumin (OVA)-induced mouse model of allergic asthma. Moreover, the anti-inflammatory potential of HD was examined to identify a plausible mechanism of action of HD in vitro. HD strongly reduced goblet cell hyperplasia, eosinophil infiltration, and reactive oxygen species (ROS), which reduced airway hyperresponsiveness (AHR), inflammation, and the expression of Th2 cytokines (IL-5 and IL-13) in bronchoalveolar lavage fluid (BALF). The expression of IL-5, IL-4, eotaxin-2, lysyl oxidase-like 2 (loxl2), and GATA-binding protein 3 (GATA-3) was attenuated in the lungs. In an in vitro assay, HD exerted immunomodulatory effects through the suppression of Th2 cytokines (IL-5, IL-13), IL-17, and tumor necrosis factor (TNF)-α production through downregulation of GATA-3 expression in EL-4 T cells. These findings suggest that the anti-asthmatic activity of HD may occur through the suppression of Th2 cytokines and total Immunoglobulin E (IgE) production by inhibition of the GATA-3 transcription pathway. Our results suggest that HD may be a potential alternative therapy, or a novel therapeutic traditional medicine, for the treatment of allergic asthma.

Immunoresolvents in asthma and allergic diseases: Review and update

Asthma and allergic diseases are inflammatory conditions developed by excessive reaction of the immune system against normally harmless environmental substances. Although acute inflammation is necessary to eradicate the damaging agents, shifting to chronic inflammation can be potentially detrimental. Essential fatty-acids-derived immunoresolvents, namely, lipoxins, resolvins, protectins, and maresins, are anti-inflammatory compounds that are believed to have protective and beneficial effects in inflammatory disorders, including asthma and allergies. Accordingly, impaired biosynthesis and defective production of immunoresolvents could be involved in the development of chronic inflammation. In this review, recent evidence on the anti-inflam]matory effects of immunoresolvents, their enzymatic biosynthesis routes, as well as their receptors are discussed.

Peroxisome proliferator-activated receptor gamma ligands affect NF-kB and cytokine synthesis in the porcine endometrium-An in vitro study

PROBLEM

Cytokines, mediators of the immune response, are involved in the regulation of female reproductive processes during the estrous cycle and pregnancy. The present study aimed to investigate the effect of selected peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the expression of nuclear factor kappa B (NF-κB) and selected cytokines, such as interleukin (IL)-1β, -4, -6, -8, -10, and the leukemia inhibitory factor, in the porcine endometrium on days 10-12 and 14-16 of the estrous cycle (mid- and late luteal phase, respectively) or pregnancy (maternal recognition of pregnancy and beginning of implantation, respectively).

METHOD OF STUDY

Endometrial slices were incubated in vitro in the presence of PPARγ agonists, 15-deoxy-Δ12, 14-prostaglandin J₂ or rosiglitazone, and PPARγ antagonist T0070907. mRNA and protein levels in tissues were determined by real-time PCR and Western blot.

RESULTS

On days 10-12 of the estrous cycle and days 14-16 of pregnancy, PPARγ ligands enhanced the expression of NF-κB, mRNA cytokines, and/or proteins. During the late luteal phase of the estrous cycle (days 14-16) and maternal recognition of pregnancy (days 10-12), PPARγ ligands inhibited the expression of NF-κB, and they differentially affected the expression of mRNA and proteins of cytokines.

CONCLUSION

Our results indicate that PPARγ is engaged in the endometrial synthesis of NF-κB and selected cytokines in pigs. The influence of PPARγ ligands on the tested components of the immune system varied subject to the physiological status of females, and it could be associated with differences in endometrial receptivity.

Fluoxetine protects against OVA induced bronchial asthma and depression in rats

Depression is very common in asthmatic patients and may increases risk for morbidity and mortality. The present work aimed to investigate the protective effect of fluoxetine, on behavioral and biochemical changes, associated with ovalbumin (OVA) - induced bronchial asthma and depression in rats. Rats were sensitized with intraperitoneal administration of OVA plus aluminum hydroxide for 3 consecutive days then at day 11 followed by OVA intranasal challenge at days 19, 20, 21. Rats were either pretreated with dexamethasone, fluoxetine10mg/kg or fluoxetine 20 mg/kg. At the end of the experiment, various tests were performed, including open field, forced swimming and respiratory function tests. Blood was drawn for serum IgE detection. Finally, rats were euthanized, brain-derived neurotrophic factor (BDNF) was estimated in bronchoalveolar lavage (BAL) fluid and lung content of reduced glutathione (GSH), superoxide dismutase (SOD), tumor necrosis factor-alpha (TNF-α) and interleukin 4 (IL-4) were determined. Histopathological study was also performed. The results showed that fluoxetine significantly ameliorated OVA- induced biochemical and behavioral changes. Fluoxetine may protect against OVA-induced asthma and depression in rats. This effect may be mediated at least in part by its antioxidant, anti-inflammatory and immunosuppressant effect.

PPAR-γ in innate and adaptive lung immunity

The transcription factor PPAR-γ (peroxisome proliferator-activated receptor-γ) is a key regulator of lung immunity exhibiting multiple cell type specific roles in controlling development and function of the lung immune system. It is strictly required for the generation of alveolar macrophages by controlling differentiation of fetal lung monocyte precursors. Furthermore, it plays an important role in lung allergic inflammation by licensing lung dendritic cell t helper 2 (Th2) priming capacity as well as acting as a master transcription factor for pathogenic Th2 cells. Due to this plethora of functions and its involvement in multiple pulmonary diseases including asthma and pulmonary alveolar proteinosis, understanding the role of PPAR-γ in lung immunity is an important subject of ongoing research.

PPARs: Key Regulators of Airway Inflammation and Potential Therapeutic Targets in Asthma

Asthma affects approximately 300 million people worldwide, significantly impacting quality of life and healthcare costs. While current therapies are effective in controlling many patients' symptoms, a large number continue to experience exacerbations or treatment-related adverse effects. Alternative therapies are thus urgently needed. Accumulating evidence has shown that the peroxisome proliferator-activated receptor (PPAR) family of nuclear hormone receptors, comprising PPARα, PPARβ/δ, and PPARγ, is involved in asthma pathogenesis and that ligand-induced activation of these receptors suppresses asthma pathology. PPAR agonists exert their anti-inflammatory effects primarily by suppressing pro-inflammatory mediators and antagonizing the pro-inflammatory functions of various cell types relevant to asthma pathophysiology. Experimental findings strongly support the potential clinical benefits of PPAR agonists in the treatment of asthma. We review current literature, highlighting PPARs' key role in asthma pathogenesis and their agonists' therapeutic potential. With additional research and rigorous clinical studies, PPARs may become attractive therapeutic targets in this disease.

Lactobacillus gasseri attenuates allergic airway inflammation through PPARγ activation in dendritic cells

Lactobacilli prevent the early development of allergic diseases in children and experimental asthma in mice. However, the detailed mechanism underlying this action remains unknown. We aimed to explore the activation pathway in the host by Lactobacillus and identify its immunomodulation mechanism in allergic asthma. Continuous administration of 10⁷ cfu, but not 10⁹ cfu, of L. gasseri for 4 weeks prevented Dermatophagoides pteronyssinus (Der p)-induced airway hypersensitivity and inflammation in a mouse model of allergic asthma. DNA microarray analysis of the mesenteric and lung draining lymph nodes revealed a significant decrease in inflammatory chemokines and increase in gene expression in carbohydrate and lipid metabolism, particularly of PPARγ, in 10⁷ cfu L. gasseri-administered mice compared with untreated mice. Compared with WT mice, Der p-sensitized PPARγ^L/+ mice showed increased airway hyperresponsiveness to methacholine, inflammatory cell infiltration, and inflammatory cytokine secretion in bronchoalveolar fluid. Moreover, the protective effects of L. gasseri were lost in Der p-induced airway inflammation in PPARγ^L/+ mice, and L. gasseri-induced PPARγ activation in BMDCs inhibited the development of allergic airway inflammation in both PPARγ WT and PPARγ^L/+ mice. L. gasseri may act via a novel PPARγ activation pathway in DCs to alleviate allergen-induced airway inflammation in allergic asthma.

KEY MESSAGES

L. gasseri prevents mite allergen (Der p)-induced airway inflammation. Prevention of airway inflammation occurs via activation of PPARγ in dendritic cells. L. gasseri administration does not reverse Der p-induced airway inflammation in PPARγ^(+/-) mice. L. gasseri-induced PPARγ activation inhibits development of airway inflammation in WT and PPARγ^(+/-) mice.

PPARγ in dendritic cells and T cells drives pathogenic type-2 effector responses in lung inflammation

Type-2 immune responses are well-established drivers of chronic inflammatory diseases, such as asthma, and represent a large burden on public health systems. The transcription factor PPARγ is known to promote M2-macrophage and alveolar macrophage development. Here, we report that PPARγ plays a key role in both T cells and dendritic cells (DCs) for development of type-2 immune responses. It is predominantly expressed in mouse Th2 cells in vitro and in vivo as well as human Th2 cells from allergic patients. Using conditional knockouts, we show that PPARγ signaling in T cells, although largely dispensable for IL-4 induction, is critical for IL-33-driven Th2 effector function in type-2 allergic airway responses. Furthermore, we demonstrate that IL-4 and IL-33 promote up-regulation of PPARγ in lung-resident CD11b⁺ DCs, which enhances migration to draining lymph nodes and Th2 priming capacity. Thus, we uncover a surprising proinflammatory role for PPARγ and establish it as a novel, important mediator of DC-T cell interactions in type-2 immunity.

Prostaglandins and Their Receptors in Eosinophil Function and As Therapeutic Targets

Of the known prostanoid receptors, human eosinophils express the prostaglandin D₂ (PGD₂) receptors DP1 [also D-type prostanoid (DP)] and DP2 (also chemoattractant receptor homologous molecule, expressed on Th2 cells), the prostaglandin E₂ receptors EP2 and EP4, and the prostacyclin (PGI₂) receptor IP. Prostanoids can bind to either one or multiple receptors, characteristically have a short half-life in vivo, and are quickly degraded into metabolites with altered affinity and specificity for a given receptor subtype. Prostanoid receptors signal mainly through G proteins and naturally activate signal transduction pathways according to the G protein subtype that they preferentially interact with. This can lead to the activation of sometimes opposing signaling pathways. In addition, prostanoid signaling is often cell-type specific and also the combination of expressed receptors can influence the outcome of the prostanoid impulse. Accordingly, it is assumed that eosinophils and their (patho-)physiological functions are governed by a sensitive prostanoid signaling network. In this review, we specifically focus on the functions of PGD₂, PGE₂, and PGI₂ and their receptors on eosinophils. We discuss their significance in allergic and non-allergic diseases and summarize potential targets for drug intervention.

15-Deoxy-Delta-12,14-Prostaglandin J2 Inhibits Lung Inflammation and Remodeling in Distinct Murine Models of Asthma

15-deoxy-Δ-12,14-prostaglandin J₂ (15d-PGJ₂) has been described as an anti-inflammatory lipid mediator in several in vitro and in vivo studies, but its effect on allergic pulmonary inflammation remains elusive. The aim of this study was to investigate the therapeutic potential of 15d-PGJ₂ based on distinct murine models of allergic asthma triggered by either ovalbumin (OVA) or house dust mite extract (HDM). Characteristics of lung inflammation, airway hyper-reactivity (AHR), mucus exacerbation, and lung remodeling in sensitized A/J mice treated or not with 15d-PGJ₂ were assessed. 15d-PGJ₂ treatments were carried out systemically or topically given via subcutaneous injection or intranasal instillation, respectively. Analyses were carried out 24 h after the last allergen provocation. Irrespective of the route of administration, 15d-PGJ₂ significantly inhibited the peribronchial accumulation of eosinophils and neutrophils, subepithelial fibrosis and also mucus exacerbation caused by either OVA or HDM challenge. The protective effect of 15d-PGJ₂ occurred in parallel with inhibition of allergen-induced AHR and lung tissue production of pro-inflammatory cytokines, such as interleukin (IL)-5, IL-13, IL-17, and TNF-α. Finally, 15d-PGJ₂ was found effective in inhibiting NF-κB phosphorylation upon HDM challenge as measured by Western blotting. In conclusion, our findings suggest that 15d-PGJ₂ can reduce crucial features of asthma, including AHR, lung inflammation, and remodeling in distinct murine models of the disease. These effects are associated with a decrease in lung tissue generation of pro-inflammatory cytokines by a mechanism related to downregulation of NF-κB phosphorylation.

PPARs in the central nervous system: roles in neurodegeneration and neuroinflammation

Over 25 years have passed since peroxisome proliferators-activated receptors (PPARs), were first described. Like other members of the nuclear receptors superfamily, PPARs have been defined as critical sensors and master regulators of cellular metabolism. Recognized as ligand-activated transcription factors, they are involved in lipid, glucose and amino acid metabolism, taking part in different cellular processes, including cellular differentiation and apoptosis, inflammatory modulation and attenuation of acute and chronic neurological damage in vivo and in vitro. Interestingly, PPAR activation can simultaneously reprogram the immune response, stimulate metabolic and mitochondrial functions, promote axonal growth, induce progenitor cells to differentiate into myelinating oligodendrocytes, and improve brain clearance of toxic molecules such as β-amyloid peptide. Although the molecular mechanisms and cross-talk with different molecular pathways are still the focus of intense research, PPARs are considered potential therapeutic targets for several neuropathological conditions, including degenerative disorders such as Alzheimer's, Parkinson's and Huntington's disease. This review considers recent advances regarding PPARs, as well as new PPAR agonists. We focus on the mechanisms behind the neuroprotective effects exerted by PPARs and summarise the roles of PPARs in different pathologies of the central nervous system, especially those associated with degenerative and inflammatory mechanisms.

Corticosteroids inhibit anti-IgE activities of specialized proresolving mediators on B cells from asthma patients

Specialized proresolving mediators (SPMs) promote the resolution of inflammation and exert beneficial effects in animal models of chronic inflammatory diseases, including asthma. Previously, we have shown that certain SPMs reduce IgE production in B cells from healthy individuals, which has a critical role in allergic asthma. Here, we investigated the effects of SPMs on B cell IgE production in asthma patients. Peripheral blood mononuclear cells from asthma patients were treated with 17-HDHA or RvD1, and IgE levels were measured. RvD1 and 17-HDHA dampened IgE production in B cells from most asthma patients, whereas B cells from a subset of patients taking oral steroids were refractory to SPM treatment. Molecular mechanisms underlying the interaction between corticosteroids and SPMs were investigated by treating B cells from nonasthmatic donors with corticosteroids in vitro. Corticosteroids blocked the inhibitory effects of 17-HDHA and RvD1 on B cell IgE production by abolishing the suppressive activity of these mediators on IgE class switching. Corticosteroids decreased the expression of transcriptional repressor Bcl-6 as well as its suppressive activity on epsilon germline transcription. We conclude that 17-HDHA and RvD1 can reduce IgE production in asthma patients not taking high doses of steroids but that corticosteroids interfere with the ability of B cells to respond to proresolving mediators.

Inundation of asthma target research: Untangling asthma riddles

Asthma is an inveterate inflammatory disorder, delineated by the airway inflammation, bronchial hyperresponsiveness (BHR) and airway wall remodeling. Although, asthma is a vague term, and is recognized as heterogenous entity encompassing different phenotypes. Targeting single mediator or receptor did not prove much clinical significant, as asthma is complex disease involving myriad inflammatory mediators. Asthma may probably involve a large number of different types of molecular and cellular components interacting through complex pathophysiological pathways. This review covers the past, present, and future therapeutic approaches and pathophysiological mechanisms of asthma. Furthermore, review describe importance of targeting several mediators/modulators and receptor antagonists involved in the physiopathology of asthma. Novel targets for asthma research include Galectins, Immunological targets, K ⁺ Channels, Kinases and Transcription Factors, Toll-like receptors, Selectins and Transient receptor potential channels. But recent developments in asthma research are very promising, these include Bitter taste receptors (TAS2R) abated airway obstruction in mouse model of asthma and Calcium-sensing receptor obliterate inflammation and in bronchial hyperresponsiveness allergic asthma. All these progresses in asthma targets, and asthma phenotypes exploration are auspicious in untangling of asthma riddles.

Evaluation of the PPAR-γ Agonist Pioglitazone in Mild Asthma: A Double-Blind Randomized Controlled Trial

Background

Peroxisome proliferator-activated receptor gamma (PPAR-γ) is a nuclear receptor that modulates inflammation in models of asthma. To determine whether pioglitazone improves measures of asthma control and airway inflammation, we performed a single-center randomized, double-blind, placebo-controlled, parallel-group trial.

Methods

Sixty-eight participants with mild asthma were randomized to 12 weeks pioglitazone (30 mg for 4 weeks, then 45 mg for 8 weeks) or placebo. The primary outcome was the adjusted mean forced expiratory volume in one second (FEV₁) at 12 weeks. The secondary outcomes were mean peak expiratory flow (PEF), scores on the Juniper Asthma Control Questionnaire (ACQ) and Asthma Quality of Life Questionnaire (AQLQ), fractional exhaled nitric oxide (FeNO), bronchial hyperresponsiveness (PD₂₀), induced sputum counts, and sputum supernatant interferon gamma-inducible protein-10 (IP-10), vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1), and eosinophil cationic protein (ECP) levels. Study recruitment was closed early after considering the European Medicines Agency’s reports of a potential increased risk of bladder cancer with pioglitazone treatment. Fifty-five cases were included in the full analysis (FA) and 52 in the per-protocol (PP) analysis.

Results

There was no difference in the adjusted FEV₁ at 12 weeks (-0.014 L, 95% confidence interval [CI] -0.15 to 0.12, p = 0.84) or in any of the secondary outcomes in the FA. The PP analysis replicated the FA, with the exception of a lower evening PEF in the pioglitazone group (-21 L/min, 95% CI -39 to -4, p = 0.02).

Conclusions

We found no evidence that treatment with 12 weeks of pioglitazone improved asthma control or airway inflammation in mild asthma.

Trial Registration

ClinicalTrials.gov NCT01134835

Sex-Based Selectivity of PPARγ Regulation in Th1, Th2, and Th17 Differentiation

Peroxisome proliferator-activated receptor gamma (PPARγ) has recently been recognized to regulate adaptive immunity through Th17 differentiation, Treg functions, and T_FH responses. However, its role in adaptive immunity and autoimmune disease is still not clear, possibly due to sexual differences. Here, we investigated in vitro treatment study with the PPARγ agonist pioglitazone to compare Th1, Th2, and Th17 differentiation in male and female mouse splenic T cells. Pioglitazone treatment significantly inhibited various effector T cell differentiations including Th1, Th2, and Th17 cells from female naïve T cells, but it selectively reduced IL-17 production in male Th17 differentiation. Interestingly, pioglitazone and estradiol (E2) co-treatment of T cells in males inhibited differentiation of Th1, Th2, and Th17 cells, suggesting a mechanism for the greater sensitivity of PPARγ to ligand treatment in the regulation of effector T cell differentiation in females. Collectively, these results demonstrate that PPARγ selectively inhibits Th17 differentiation only in male T cells and modulates Th1, Th2, and Th17 differentiation in female T cells based on different level of estrogen exposure. Accordingly, PPARγ could be an important immune regulator of sexual differences in adaptive immunity.

Functional Characterization of Exonic Variants of the PPARGC1B Gene in Coregulation of Estrogen Receptor Alpha

Peroxisome proliferator-activated receptor gamma coactivator 1 beta (PPARGC1B) is a coactivator of estrogen receptor (ER)α and ERβ. We previously demonstrated a significant association between a variant of exon 5 of the PPARGC1B gene (+102525 G>A, R265Q) and airway hyperreactivity (AHR). The aims of the study were to evaluate the genetic effects of variants of the PPARGC1B gene on the function of ERs. PPARGC1B +102525G and A gene constructs were generated using PCR and cloned into a pCMV4 promoter vector. A luciferase reporter assay was undertaken in 293T cells cotransfected with one of the PPARGC1B +102525G>A constructs, ERα, and an estrogen response element (ERE) containing a luciferase construct after treatment with 17β-estradiol. According to the luciferase reporter assay, the +102525A allele showed higher ERα activity than the +102525G allele in response to stimulation with 17β-estradiol. In addition, the interaction between ERα and PPARGC1B was evaluated by coprecipitation assay. Human influenza hemagglutinin-tagged PPARGC1B coprecipitated more intensely with ERα in the +102525A than the +102525G construct after 17β estradiol treatment. The variant +102525A allele enhances the activity of ERα to a greater degree than the +102525G allele of PPARGC1B.

RIP140 down-regulation alleviates acute lung injury via the inhibition of LPS-induced PPARγ promoter methylation

Seriously inflammatory response of the lungs can induce acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) which are serious public health threats due to their high patient morbidity and mortality. While RIP140 is known to modulate proinflammatory cytokine production during an inflammatory response, its role in ALI/ARDS is unclear. In this study, we examined RIP140 and PPARγ protein expression in RAW 264.7 cells and lung tissue following LPS-induced ALI. RIP140 shRNA adenoviral knockdown significantly elevated PPARγ expression, inhibited TNF-α, IL-1β, and IL-6 production in vivo and in vitro. Conversely, treatment with a PPARγ antagonist (GW9662) reversed these outcomes. Furthermore, co-IP showed that endogenous and exogenous RIP140 interacted with DNMT3b in RAW 264.7 cells. Bisulfite conversion, pyrosequencing and activity assays demonstrated that PPARγ promoter methylation levels were increased and that PPARγ transcriptional activity was inhibited following LPS treatment in macrophages. Nevertheless, RIP140 knockdown reduced PPARγ promoter methylation levels and restored its transcriptional activity. These results indicate that RIP140 knockdown can inhibit the production of inflammation mediators and remit ALI via the repression of DNMT3b mediated PPARγ promoter methylation.

A pilot randomized controlled trial of pioglitazone for the treatment of poorly controlled asthma in obesity

BACKGROUND

Obese asthmatics tend to have poorly controlled asthma, and resistance to standard asthma controller medications. The purpose of this study was to determine the efficacy of pioglitazone, an anti-diabetic medication which can alter circulating adipokines and have direct effects on asthmatic inflammation, in the treatment of asthma in obesity.

METHODS

A two-center, 12-week, randomized, placebo-controlled, double-blinded trial. Treatments were randomly assigned with concealment of allocation. The primary outcome was difference in change in airway reactivity between participants assigned to pioglitazone versus placebo at 12 weeks.

RESULTS

Twenty-three participants were randomized to treatment, 19 completed the study. Median airway reactivity, measured by PC20 to methacholine was 1.99 (IQR 3.08) and 1.60 (5.91) mg/ml in placebo and pioglitazone group at baseline, and 2.37 (15.22) and 5.08 (7.42) mg/ml after 12 weeks, p = 0.38. There was no difference in exhaled nitric oxide, asthma control or lung function between treatment groups over the 12 week trial. Participants assigned to pioglitazone gained a significant amount more weight than those assigned to placebo (pioglitazone group mean weight 113.6, CI 94.5-132.7 kg at randomization and 115.9, CI 96.9-135.1 at 12 weeks; placebo mean weight 127.5, CI 108.4 - 146.6 kg at randomization and 124.5, CI 105.4 - 143.6 kg at 12 weeks; p = 0.04).

CONCLUSIONS

This pilot study suggests limited efficacy for pioglitazone in the treatment of poorly controlled asthma in obesity, and also the potential for harm, given the weight gain in those assigned to active treatment, and the association between increased weight and worse outcomes in asthma.

TRIAL REGISTRATION

Clinicaltrials.gov (NCT00634036).

Nutritional control of immunity: Balancing the metabolic requirements with an appropriate immune function

The immune system is a highly integrated network of cells sensitive to a number of environmental factors. Interestingly, recent years have seen a dramatic increase in our understanding of how diet makes a crucial contribution to human health, affecting the immune system, secretion of adipocytokines and metabolic pathways. Recent experimental evidence indicates that diet and its components are able to profoundly influence immune responses, thus affecting the development of inflammatory and autoimmune diseases. This review aims to discuss some of the main topics concerning the impact of nutrients and their relative composition on immune cell development and function that may be particularly important for regulating the balance between inflammatory and tolerogenic processes. We also highlight the effects of diet on commensal bacteria and how changes in the composition of the microbiota alter intestinal and systemic immune homeostasis. Finally, we summarize the effects of dietary compounds on epigenetic mechanisms involved in the regulation of several immune related genes.

Association of peroxisome proliferator-activated receptor-gamma gene polymorphisms and gene-gene interaction with asthma risk in a Chinese adults population

AIMS

To investigate the association between single nucleotide polymorphism (SNP) of peroxisome proliferator-activated receptors γ (PPAR γ) and additional gene-gene interactions on asthma risk.

METHODS

A total of 882 subjects (602 males, 280 females), with a mean age of 61.3±14.8 years old, including 430 asthma patients and 452 normal subjects were selected in this study, including the genotyping of polymorphisms. Logistic regression was performed to investigate association between SNP and asthma. Generalized MDR (GMDR) was used to analysis the interaction among four SNP.

RESULTS

Asthma risk was significantly lower in carriers of Ala allele of the rs1805192 polymorphism than those with Pro/Pro (Pro/Ala+ Ala/Ala versus Pro/Pro, adjusted OR (95% CI)=0.70 (0.51-0.94). In addition, we also found a significant association between rs10865710 and asthma, asthma risk was significantly lower in carriers of G allele of the rs10865710 polymorphism than those with CC (CG+ GG versus CC, adjusted OR (95% CI)=0.68 (0.55-0.95). There was a significant three-locus model (P=0.0107) involving rs1805192, rs10865710 and rs709158, indicating a potential gene-gene interaction among rs1805192, rs10865710 and rs709158. Overall, the three-locus models had a cross-validation consistency of 10 of 10, and had the testing accuracy of 60.72% after covariates adjustment.

CONCLUSIONS

Our results support an important association of rs1805192 and rs10865710 with asthma, and additional interaction among rs1805192, rs10865710 and rs709158.

Rosiglitazone elicits in vitro relaxation in airways and precision cut lung slices from a mouse model of chronic allergic airways disease

Rosiglitazone (RGZ), a peroxisome proliferator-activated receptor-γ (PPARγ) ligand, is a novel dilator of small airways in mouse precision cut lung slices (PCLS). In this study, relaxation to RGZ and β-adrenoceptor agonists were compared in trachea from naïve mice and guinea pigs and trachea and PCLS from a mouse model of chronic allergic airways disease (AAD). Airways were precontracted with methacholine before addition of PPARγ ligands [RGZ, ciglitazone (CGZ), or 15-deoxy-(Δ12,14)-prostaglandin J2 (15-deoxy-PGJ2)] or β-adrenoceptor agonists (isoprenaline and salbutamol). The effects of T0070907 and GW9662 (PPARγ antagonists) or epithelial removal on relaxation were assessed. Changes in force of trachea and lumen area in PCLS were measured using preparations from saline-challenged mice and mice sensitized (days 0 and 14) and challenged with ovalbumin (3 times/wk, 6 wk). RGZ and CGZ elicited complete relaxation with greater efficacy than β-adrenoceptor agonists in mouse airways but not guinea pig trachea, while 15-deoxy-PGJ2 did not mediate bronchodilation. Relaxation to RGZ was not prevented by T0070907 or GW9662 or by epithelial removal. RGZ-induced relaxation was preserved in the trachea and increased in PCLS after ovalbumin-challenge. Although RGZ was less potent than β-adrenoceptor agonists, its effects were additive with salbutamol and isoprenaline and only RGZ maintained potency and full efficacy in maximally contracted airways or after allergen challenge. Acute PPARγ-independent, epithelial-independent airway relaxation to RGZ is resistant to functional antagonism and maintained in both trachea and PCLS from a model of chronic AAD. These novel efficacious actions of RGZ support its therapeutic potential in asthma when responsiveness to β-adrenoceptor agonists is limited.

Genomewide effects of peroxisome proliferator-activated receptor gamma in macrophages and dendritic cells--revealing complexity through systems biology

BACKGROUND

Systems biology approaches have become indispensable tools in biomedical and basic research. These data integrating bioinformatic methods gained prominence after high-throughput technologies became available to investigate complex cellular processes, such as transcriptional regulation and protein-protein interactions, on a scale that had not been studied before. Immunology is one of the medical fields that systems biology impacted profoundly due to the plasticity of cell types involved and the accessibility of a wide range of experimental models.

MATERIALS AND METHODS

In this review, we summarize the most important recent genomewide studies exploring the function of peroxisome proliferator-activated receptor γ in macrophages and dendritic cells. PPARγ ChIP-seq experiments were performed in adipocytes derived from embryonic stem cells to complement the existing data sets and to provide comparators to macrophage data. Finally, lists of regulated genes generated from such experiments were analysed with bioinformatics and system biology approaches.

RESULTS

We show that genomewide studies utilizing high-throughput data acquisition methods made it possible to gain deeper insights into the role of PPARγ in these immune cell types. We also demonstrate that analysis and visualization of data using network-based approaches can be used to identify novel genes and functions regulated by the receptor.

CONCLUSIONS

The example of PPARγ in macrophages and dendritic cells highlights the crucial importance of systems biology approaches in establishing novel cellular functions for long-known signaling pathways.

The impact of diet on asthma and allergic diseases

The incidence of allergic diseases is increasing, both in developed and developing countries, concomitantly with the rise in living standards and the adoption of a 'western lifestyle'. For two decades, the hygiene hypothesis - which proposes that the lack of early childhood exposure to infectious agents increases susceptibility to allergic diseases in later life - provided the conceptual framework for unravelling the mechanisms that could account for the increased incidence of allergic diseases. In this Review, we discuss recent evidence that highlights the role of diet as a key factor influencing immune homeostasis and the development of allergic diseases through a complex interplay between nutrients, their metabolites and immune cell populations. Although further investigations are still required to understand these complex relationships, recent data have established a possible connection between metabolic homeostasis and allergic diseases.