Toll-like receptor 7 stimulates production of specialized pro-resolving lipid mediators and promotes resolution of airway inflammation

Lipid mediators obtained from docosahexaenoic acid by soybean lipoxygenase alleviate ovalbumin‑induced allergic asthma in mice by reducing airway inflammation and oxidative stress

Asthma is a chronic allergic respiratory disease lacking effective therapies. The present study investigated the anti‑asthmatic properties of lipid mediators using an ovalbumin (OVA)‑induced allergic asthma model. Lipid mediators (LM; 17S‑monohydroxy docosahexaenoic acid, resolvin D5 and protectin DX at a ratio of 3:47:50) were derived from docosahexaenoic acid through soybean lipoxygenase. LM treatment significantly alleviated major features of allergic asthma, including inflammatory cell infiltration, with a particular reduction in eosinophils in bronchoalveolar lavage fluid, downregulation of Th2 cytokine expression, attenuation of airway remodeling, and oxidative stress, thereby closely resembling the normal condition. Additionally, a significant increase in the serum levels of interleukin‑6 [167.12±6.25 pg/ml; P<0.0001 vs. negative control (NC) group], tumor necrosis factor‑α (109.17±7.17 pg/ml; P<0.0001 vs. NC group) and IgE (90.24±5.98 ng/ml; P<0.0001 vs. NC group) was observed following OVA challenge; however, oral administration of LM resulted in a notable reduction in these levels to 99.45±6.12 pg/ml (P<0.001 vs. OVA group), 62.51±4.03 pg/ml (P<0.001 vs. OVA group) and 56.50±2.70 ng/ml (P<0.001 vs. OVA group), respectively. Furthermore, the heightened expression of Th2‑related cytokines induced by OVA was observed to be restored closely to normal conditions following LM treatment, as demonstrated for both gene and protein expression levels. Histological analysis demonstrated that LM mitigated inflammatory cell infiltration while reducing mucus secretion. Additionally, LM effectively ameliorated oxidative stress in OVA‑induced asthma, with a significant increase in the activity of superoxide dismutase (~185% vs. OVA group; P<0.001), elevated levels of glutathione (~74% higher than the OVA group; P<0.001) and reduced content of malondialdehyde (~40% lower than the OVA group; P<0.001) in lung tissues. Collectively, these findings suggested that LM effectively protected lung tissues from inflammation and oxidative stress, thereby representing a promising therapeutic option for the treatment of allergic asthma.

Proresolving Lipid Mediators in the Respiratory System

Lung inflammation, infection, and injury can lead to critical illness and death. The current means to pharmacologically treat excessive uncontrolled lung inflammation needs improvement because many treatments are or will become immunosuppressive. The inflammatory response evolved to protect the host from microbes, injury, and environmental insults. This response brings phagocytes from the bloodstream to the tissue site to phagocytize and neutralize bacterial invaders and enables airway antimicrobial functions. This physiologic response is ideally self-limited with initiation and resolution phases. Polyunsaturated essential fatty acids are precursors to potent molecules that govern both phases. In the initiation phase, arachidonic acid is converted to prostaglandins and leukotrienes that activate leukocytes to transmigrate from postcapillary venules. The omega-3 fatty acids (e.g., DHA and EPA) are precursors to resolvins, protectins, and maresins, which are families of chemically distinct mediators with potent functions in resolution of acute and chronic inflammation in the respiratory system.

Clinical assessment and transcriptome analysis of host immune responses in a vaccination-challenge study using a glycoprotein G deletion mutant vaccine strain of infectious laryngotracheitis virus

A glycoprotein-G-deleted live-attenuated vaccine strain of the infectious laryngotracheitis virus (ILTV), ΔgG-ILTV, is safe and efficacious against ILTV challenge. In the current study, the transcriptome of peripheral blood mononuclear cells (PBMCs) of the ΔgG-ILTV-vaccinated group of specific-pathogen-free chickens were compared to those of the nonvaccinated group at 7 days post-vaccination. Tracheal transcriptomes after challenge with virulent ILTV were compared between groups of the non-vaccinated-challenged and the vaccinated-challenged as well as the non-vaccinated-challenged and the uninfected chickens at 4 to 5 days post-challenge. The clinical outcomes after challenge between these groups were also evaluated. Significant differences were observed in the tracheal transcriptome of the non-vaccinated-challenged birds compared to the other two groups. Enriched gene ontologies and pathways that indicated heightened immune responses and impairments to ciliary and neuronal functions, cell junction components, and potential damages to cartilaginous and extracellular components in the trachea of the non-vaccinated-challenged birds were consistent with their severe tracheal pathology compared to the other two groups. On the contrary, the absence of any difference in the tracheal transcriptome between the vaccinated-challenged and the uninfected birds were reflected by the preservation of tracheal mucosal integrity in both groups and mild infiltration of leukocytes in the vaccinated-challenged birds. The results from this study demonstrated that vaccination with ΔgG-ILTV prevented the changes in tracheal transcriptome induced during ILTV challenge, resulting in clinical protection. Additionally, these results also provide insights into the molecular mechanisms underlying the tracheal pathology induced by ILTV infection.

Disrupted balance between pro-inflammatory lipid mediators and anti-inflammatory specialized pro-resolving mediators is linked to hyperinflammation in patients with alcoholic hepatitis

Background

Alcoholic hepatitis (AH) is characterized by intense systemic and liver inflammation, posing significant risks of health complications and mortality. While inflammation is a crucial defense mechanism against injury and infection, its timely resolution is essential to prevent tissue damage and restore tissue homeostasis. The resolution of inflammation is primarily governed by specialized pro-resolving mediators (SPMs), lipid metabolites derived from w-6 and w-3 poly-unsaturated fatty acids (PUFAs). Currently, the balance between pro-inflammatory lipid mediators (PLMs) and SPMs in the w-6 and w-3 PUFA metabolic pathways and the impact of alcohol abstinence on profiles of PLMs and SPMs in AH patients are not well studied.

Methods

In this study, we used LC-MS/MS and ELISA to quantify levels of lipid mediators (LMs) and their precursors in the plasma samples from 58 AH patients, 29 heavy drinkers without overt liver diseases (HDCs), and 35 healthy controls (HCs). Subsequently, we assessed correlations of altered LMs with clinical parameters and inflammatory mediators. Furthermore, we conducted a longitudinal study to analyze the effects of alcohol abstinence on LMs over 6- and 12-month follow-ups.

Results

AH patients exhibited significantly higher plasma levels of w-6 PLMs (PGD2 and LTB4) and SPM RvE1 compared to HDCs or HCs. Conversely, the SPM LXA4 was significantly downregulated in AH patients. Some of these altered LMs were found to correlate with AH disease severity and various inflammatory cytokines. Particularly, the LTB4/LXA4 ratio was substantially elevated in AH patients relative to HDCs and HCs. This altered ratio displayed a positive correlation with the MELD score. Importantly, the majority of dysregulated LMs, particularly PLMs, were normalized following alcohol abstinence.

Alveolar hypoxia induces organ-specific inflammasome-related inflammation in male mouse lungs

Inflammation through activation of caspase-1, seems to play a role in pulmonary hypertension induced by alveolar hypoxia. Whether alveolar hypoxia induces caspase-1-mediated inflammation and influx of leukocytes in other organs than the lungs, is not known. Our aim was to explore sites of caspase-1-related inflammation in alveolar hypoxia. Wild type (WT) mice were exposed to environmental hypoxia or room-air, and organs were analyzed. Right heart catheterization was performed after 14 days of alveolar hypoxia in WT mice and mice transplanted with WT or caspase-1-/- bone marrow. Hypoxia induced leukocyte accumulation and increased caspase-1 protein in the lungs, not in other organs. WT mice transplanted with WT or caspase-1-/- bone marrow showed no difference in pulmonary leukocyte accumulation or development of pulmonary hypertension after alveolar hypoxia. Caspase-1 and IL-18 were detected in bronchial epithelium in WT mice, and hypoxia induced IL-18 secretion from bronchial epithelial cells. IL-18 stimulation generated IL-6 mRNA in monocytes. Phosphorylated STAT3 was increased in hypoxic lungs, not in other organs. Alveolar hypoxia induces caspase-1 activation and leukocyte accumulation specific to the lungs, not in other organs. Caspase-1 activation and IL-18 secretion from bronchial epithelial cells might initiate hypoxia-induced inflammation, leading to pulmonary hypertension.

TLR2-ERK signaling pathway regulates expression of galectin-3 in a murine model of OVA-induced allergic airway inflammation

Toll-like receptor 2 (TLR2) and galectin-3 (Gal-3) are involved in the pathological process of asthma, but the underlying mechanism is not fully understood. We hypothesized that TLR2 pathway may regulate expression of Gal-3 in allergic airway inflammation. Wild-type (WT) and TLR2-/- mice were sensitized on day 0 and challenged with ovalbumin (OVA) on days 14-21 to establish a model of allergic airway inflammation, and were treated with a specific ERK inhibitor U0126. Histological changes in the lungs were analyzed by hematoxylin-eosin (HE) and Periodic Acid-Schiff (PAS) staining; cytokines and anti-OVA immunoglobulin E (IgE) were tested by ELISA; and related protein expression in lung tissues was measured by western blot. We found that the expression levels of TLR2 and Gal-3 markedly increased concomitantly with airway inflammation after OVA induction, while TLR2 deficiency significantly alleviated airway inflammation and reduced Gal-3 expression. Moreover, the expression levels of phosphorylated mitogen-activated protein kinases (p-MAPKs) were significantly elevated in OVA-challenged WT mice, while TLR2 deficiency only significantly decreased phosphorylated extracellular signal-regulated kinase (p-ERK) levels. Furthermore, we found that U0126 treatment significantly alleviated allergic airway inflammation and decreased Gal-3 levels in OVA-challenged WT mice, but had no further effect in OVA-challenged TLR2-/- mice. These above results suggested that TLR2 is an upstream signal molecule of ERK. We further demonstrated that TLR2 regulates Gal-3 expression through the ERK pathway in LTA-stimulated macrophages in vitro. Our findings showed that the TLR2-ERK signaling pathway regulates Gal-3 expression in a murine model of allergic airway inflammation.

Disrupted balance between pro-inflammatory lipid mediators and anti-inflammatory specialized pro-resolving mediators is linked to hyperinflammation in patients with alcoholic hepatitis

Background

Chronic excessive alcohol consumption leads to a spectrum of alcohol-associated liver diseases (ALD), including alcoholic hepatitis (AH). AH is characterized by intense systemic and liver inflammation, posing significant risks of health complications and mortality. While inflammation is a crucial defense mechanism against injury and infection, its timely resolution is essential to prevent tissue damage and restore tissue homeostasis. The resolution of inflammation is an actively regulated process, primarily governed by specialized pro-resolving mediators (SPMs), lipid metabolites derived from ω-6 and ω-3 poly-unsaturated fatty acids (PUFAs). We investigated the balance between pro-inflammatory lipid mediators (PLMs) and SPMs in the ω-6 and ω-3 PUFA metabolic pathways and examined the impact of alcohol abstinence on rectifying the dysregulated biosynthesis of PLMs and SPMs in AH patients.

Methods

LC-MS/MS and ELISA were used to quantify levels of bioactive lipid mediators (LMs) and their precursors in the plasma samples from 58 AH patients, 29 heavy drinkers without overt liver diseases (HDCs), and 35 healthy controls (HCs). Subsequently, we assessed correlations of altered LMs with clinical parameters and various markers of inflammatory cascade andmicrobial translocation. Furthermore, we conducted a longitudinal study to track changes in levels of LMs over 6- and 12-month follow-ups in AH patients who underwent alcohol abstinence.

Results

AH patients exhibited significantly higher plasma levels of ω-6 PLMs (PGD 2 and LTB 4 ) and SPM RvE1 compared to HDCs and/or HCs. Conversely, key SPMs such as LXA4, RvD1, and several precursors in the ω-3 pathway were significantly downregulated in AH patients. Some of these altered LMs were found to correlate with AH disease severity, clinical parameters, and various inflammatory cytokines. In particular, the LTB4/LXA4 ratio was substantially elevated in AH patients relative to HDCs and HCs. This altered ratio displayed a positive correlation with the MELD score, suggesting its potential utility as an indicator of disease severity in AH patients. Importantly, the majority of dysregulated LMs, particularly PLMs, were normalized following alcohol abstinence.

Conclusion

Our study reveals significant dysregulation in the levels of PLM metabolites and anti-inflammatory SPMs in both ω-6 and ω-3 PUFA pathways in AH patients. This disrupted biosynthesis, characterized by an overabundance of PLMs and a deficiency in SPMs, is linked to the heightened inflammation observed in AH patients. Importantly, our findings suggest an important role of alcohol abstinence in restoring the balance of these LMs and the potential therapeutic benefits of SPM supplements in alleviating the inflammatory cascade in AH patients.

Inflammation resolution and specialized pro-resolving lipid mediators in chronic rhinosinusitis

INTRODUCTION

In chronic rhinosinusitis (CRS), a complex pathophysiology results from varied pro-inflammatory stimuli but is consistently characterized by classic cellular, molecular, and microbial alterations. Normally, endogenous specialized pro-resolving mediators (SPM) actively promote resolution of inflammation through numerous pathways, including those involved in host antimicrobial defense. However, these pathways appear to be disrupted in CRS.

AREAS COVERED

This paper describes features of CRS in the context of chronic tissue inflammation, and potential mechanisms by which specialized pro-resolving mediators promote active resolution of tissue inflammation.

EXPERT OPINION

Temporal phases of resolution must be tightly regulated to successfully resolve inflammation in CRS while preserving tissue functions such as barrier maintenance and special sensory function. Dysregulation of SPM enzymatic pathways has been recently shown in CRS and is associated with disease phenotypes and microbial colonization patterns. Current research in animal models and in vitro human cell culture, as well as human dietary studies, demonstrate relevant changes in cell signaling with lipid mediator bioavailability. Further clinical research may provide insight into the therapeutic value of this approach in CRS.

Epithelial barrier hypothesis: Effect of the external exposome on the microbiome and epithelial barriers in allergic disease

Environmental exposure plays a major role in the development of allergic diseases. The exposome can be classified into internal (e.g., aging, hormones, and metabolic processes), specific external (e.g., chemical pollutants or lifestyle factors), and general external (e.g., broader socioeconomic and psychological contexts) domains, all of which are interrelated. All the factors we are exposed to, from the moment of conception to death, are part of the external exposome. Several hundreds of thousands of new chemicals have been introduced in modern life without our having a full understanding of their toxic health effects and ways to mitigate these effects. Climate change, air pollution, microplastics, tobacco smoke, changes and loss of biodiversity, alterations in dietary habits, and the microbiome due to modernization, urbanization, and globalization constitute our surrounding environment and external exposome. Some of these factors disrupt the epithelial barriers of the skin and mucosal surfaces, and these disruptions have been linked in the last few decades to the increasing prevalence and severity of allergic and inflammatory diseases such as atopic dermatitis, food allergy, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, and asthma. The epithelial barrier hypothesis provides a mechanistic explanation of how these factors can explain the rapid increase in allergic and autoimmune diseases. In this review, we discuss factors affecting the planet's health in the context of the 'epithelial barrier hypothesis,' including climate change, pollution, changes and loss of biodiversity, and emphasize the changes in the external exposome in the last few decades and their effects on allergic diseases. In addition, the roles of increased dietary fatty acid consumption and environmental substances (detergents, airborne pollen, ozone, microplastics, nanoparticles, and tobacco) affecting epithelial barriers are discussed. Considering the emerging data from recent studies, we suggest stringent governmental regulations, global policy adjustments, patient education, and the establishment of individualized control measures to mitigate environmental threats and decrease allergic disease.

CD103 integrin identifies a high IL-10-producing FoxP3+ regulatory T-cell population suppressing allergic airway inflammation

BACKGROUND

Although FoxP3⁺ regulatory T (Treg) cells constitute a highly heterogeneous population, with different regulatory potential depending on the disease context, distinct subsets or phenotypes remain poorly defined. This hampers the development of immunotherapy for allergic and autoimmune disorders. The present study aimed at characterizing distinct FoxP3⁺ Treg subpopulations involved in the suppression of Th2-mediated allergic inflammation in the lung.

METHODS

We used an established mouse model of allergic airway disease based on ovalbumin sensitization and challenge to analyze FoxP3⁺ Tregs during the induction and resolution of inflammation, and identify markers that distinguish their most suppressive phenotypes. We also developed a new knock-in mouse model (Foxp3^cre Cd103^dtr ) enabling the specific ablation of CD103⁺ FoxP3⁺ Tregs for functional studies.

RESULTS

We found that during resolution of allergic airway inflammation in mice >50% of FoxP3⁺ Treg cells expressed the integrin CD103 which marks FoxP3⁺ Treg cells of high IL-10 production, increased expression of immunoregulatory molecules such as KLRG1, ICOS and CD127, and enhanced suppressive capacity for Th2-mediated inflammatory responses. CD103⁺ FoxP3⁺ Tregs were essential for keeping allergic inflammation under control as their specific depletion in Foxp3^cre Cd103^dtr mice lead to severe alveocapillary damage, eosinophilic pneumonia, and markedly reduced lifespan of the animals. Conversely, adoptive transfer of CD103⁺ FoxP3⁺ Tregs effectively treated disease, attenuating Th2 responses and allergic inflammation in an IL-10-dependent manner.

CONCLUSIONS

Our study identifies a novel regulatory T-cell population, defined by CD103 expression, programmed to prevent exuberant type 2 inflammation and keep homeostasis in the respiratory tract under control. This has important therapeutic implications.

Gestational exposure to titanium dioxide, diesel exhaust, and concentrated urban air particles affects levels of specialized pro-resolving mediators in response to allergen in asthma-susceptible neonate lungs

Maternal gestational exposures to traffic and urban air pollutant particulates have been linked to increased risk and/or worsening asthma in children; however, mechanisms underlying this vertical transmission are not entirely understood. It was postulated that gestational particle exposure might affect the ability to elicit specialized proresolving mediator (SPM) responses upon allergen encounter in neonates. Lipidomic profiling of 50 SPMs was performed in lungs of neonates born to mice exposed to concentrated urban air particles (CAP), diesel exhaust particles (DEP), or less immunotoxic titanium dioxide particles (TiO2). While asthma-like phenotypes were induced with identical eosinophilia intensity across neonates of all particle-exposed mothers, levels of LXA4, HEPE and HETE isoforms, and HDoHe were only decreased by CAP and DEP only but not by TiO2. However, RvE2 and RvD1 were inhibited by all particles. In contrast, isomers of Maresin1 and Protectin D1 were variably elevated by CAP and DEP, whereas Protectin DX, PGE2, and TxB2 were increased in all groups. Only Protectin D1/DX, MaR1(n-3,DPA), 5(S),15(S)-DiHETE, PGE2, and RvE3 correlated with eosinophilia but the majority of other analytes, elevated or inhibited, showed no marked correlation with inflammation intensity. Evidence indicates that gestational particle exposure leads to both particle-specific and nonspecific effects on the SPM network.

E-series resolvin metabolome, biosynthesis and critical role of stereochemistry of specialized pro-resolving mediators (SPMs) in inflammation-resolution: Preparing SPMs for long COVID-19, human clinical trials, and targeted precision nutrition

The COVID-19 pandemic has raised international awareness of the importance of rigorous scientific evidence and the havoc caused by uncontrolled excessive inflammation. Here we consider the evidence on whether the specialized pro-resolving mediators (SPMs) are ready to meet this challenge as well as targeted metabololipidomics of the resolution-inflammation metabolomes. Specific stereochemical mechanisms in the biosynthesis of SPMs from omega-3 essential fatty acids give rise to unique local-acting lipid mediators. SPMs possess stereochemically defined potent bioactive structures that are high-affinity ligands for cognate G protein-coupled surface receptors that evoke the cellular responses required for efficient resolution of acute inflammation. The SPMs biosynthesized from the major omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are coined Resolvins (resolution phase interaction products; E series and D-series), Protectins and Maresins (macrophage mediators in resolving inflammation). Their biosynthesis and stereochemical assignments are established and confirmed (>1,441 resolvin publications in PubMed.gov) as well as their functional roles on innate immune cells and adaptive immune cells (both lymphocyte T-cell subsets and B-cells). The resolution of a protective acute inflammatory response is governed mainly by phagocytes that actively clear apoptotic cells, debris, blood clots and pathogens. These resolution phase functions of the acute inflammatory response are enhanced by SPMs, which together prepare the inflammatory loci for homeostasis and stimulate tissue regeneration via activating stem cells and the biosynthesis of novel cys-SPMs (e.g. MCTRs, PCTRs and RCTRs). These cys-SPMs also activate regeneration, are organ protective and stimulate resolution of local inflammation. Herein, we review the biosynthesis and functions of the E-series resolvins, namely resolvin E1 (the first n-3 resolvin identified), resolvin E2, resolvin E3 and resolvin E4 biosynthesized from their precursor eicosapentaenoic acid (EPA), and the critical role of total organic synthesis in confirming SPM complete stereochemistry, establishing their potent functions in resolution of inflammation, and novel structures. The physical properties of each biologically derived SPM, i.e., ultra-violet (UV) absorbance, chromatographic behavior, and tandem mass spectrometry (MS2) fragmentation, were matched to SPMs biosynthesized and prepared by stereospecific total organic synthesis. We briefly review this approach, also used with the endogenous D-series resolvins, protectins and maresins confirming their potent functions in resolution of inflammation, that paves the way for their rigorous evaluation in human tissues and clinical trials. The assignment of complete stereochemistry for each of the E and D series Resolvins, Protectins and Maresins was a critical and required step that enabled human clinical studies as in SPM profiling in COVID-19 infections and experimental animal disease models that also opened the promise of resolution physiology, resolution pharmacology and targeted precision nutrition as new areas for monitoring health and disease mechanisms.

Solid lipid nanoparticle delivery of rhynchophylline enhanced the efficiency of allergic asthma treatment via the upregulation of suppressor of cytokine signaling 1 by repressing the p38 signaling pathway

Allergic asthma is one of the most common chronic airway diseases, and there is still a lack of effective drugs for the treatment of allergic asthma. The purpose of this work is to formulate rhynchophylline (Rhy)-solid lipid nanoparticles (SLNs) to improve their therapeutic efficacy in a mice allergic model of asthma. A solvent injection method was employed to prepare the Rhy-SLNs. Physicochemical characterization of Rhy-SLNs was measured, and the release assessment was investigated, followed by the release kinetics. Next, a model of murine experimental asthma was established. Mice were subcutaneously injected with 20 μg ovalbumin mixed with 1 mg aluminum hydroxide on days 0, 14, 28, and 42 and administrated aerosolized 1% ovalbumin (w/v) by inhalation from day 21 to day 42. Mice were intraperitoneally injected with 20 mg/kg Rhy-SLNs or Rhy at one hour before the airway challenge with ovalbumin. The results showed that Rhy-SLNs revealed a mean particle size of 62.06 ± 1.62 nm with a zeta potential value of −6.53 ± 0.04 mV and 82.6 ± 1.8% drug entrapment efficiency. The release curve of Rhy-SLNs was much higher than the drug released in phosphate buffer saline at 0, 1, 1.5, 2, 4, or 6 h. Moreover, Rhy-SLNs exerted better effects on inhibiting ovalbumin-induced airway inflammation, oxidative stress, airway remodeling (including collagen deposition and mucus gland hyperplasia) than Rhy in murine experimental asthma. Subsequently, we found that Rhy-SLNs relieved allergic asthma via the upregulation of the suppressor of cytokine signaling 1 by repressing the p38 signaling pathway.

Specialized Pro-resolving Mediators Reduce Pro-nociceptive Inflammatory Mediator Production in Models of Localized Provoked Vulvodynia

Localized provoked vulvodynia (LPV) is the most common cause of chronic dyspareunia in premenopausal women, characterized by pain with light touch to the vulvar vestibule surrounding the vaginal opening. The devastating impact of LPV includes sexual dysfunction, infertility, depression, and even suicide. Yet, its etiology is unclear. No effective medical therapy exists; surgical removal of the painful vestibule is the last resort. In LPV, the vestibule expresses a unique inflammatory profile with elevated levels of pro-nociceptive proinflammatory mediators prostaglandin E2 (PGE2) and interleukin-6 (IL-6), which are linked to lower mechanical sensitivity thresholds. Specialized pro-resolving mediators (SPMs), lipids produced endogenously within the body, hold promise as an LPV treatment by resolving inflammation without impairing host defense. Ten of 13 commercially available SPMs reduced IL-6 and PGE2 production by vulvar fibroblasts, administered either before or after inflammatory stimulation. Using a murine vulvar pain model, coupling proinflammatory mediator quantification with mechanical sensitivity threshold determination, topical treatment with the SPM, maresin 1, decreased sensitivity and suppressed PGE2 levels. Docosahexaenoic acid, a precursor of maresin 1, was also effective in reducing PGE2 in vulvar fibroblasts and rapidly restored mouse sensitivity thresholds. Overall, SPMs and their precursors may be a safe and efficacious for LPV. Perspective: Vulvodynia, like many pain conditions, is difficult to treat because disease origins are incompletely understood. Here, we applied our knowledge of more recently discovered vulvodynia disease mechanisms to screen novel therapeutics. We identified several specialized pro-resolving mediators as likely potent and safe for treating LPV with potential for broader application.

Specialized Pro-Resolving Mediators as Potential Regulators of Inflammatory Macrophage Responses in COVID-19

The recent outbreak of SARS-CoV2 has emerged as one of the biggest pandemics of our century, with outrageous health, social and economic consequences globally. Macrophages may lay in the center of COVID-19 pathogenesis and lethality and treatment of the macrophage-induced cytokine storm has emerged as essential. Specialized pro-resolving mediators (SPMs) hold strong therapeutic potentials in the management of COVID-19 as they can regulate macrophage infiltration and cytokine production but also promote a pro-resolving macrophage phenotype. In this review, we discuss the homeostatic functions of SPMs acting directly on macrophages on various levels, towards the resolution of inflammation. Moreover, we address the molecular events that link the lipid mediators with COVID-19 severity and discuss the clinical potentials of SPMs in COVID-19 immunotherapeutics.

Toll-Like Receptor 7 Mediates Inflammation Resolution and Inhibition of Angiogenesis in Non-Small Cell Lung Cancer

Simple Summary

The progression of cancer is strictly linked to the formation of new blood vessels responsible for nutrition supply of the tumor. We identified TLR7 as an inhibitor of lung cancer vascularization. TLR7 is part of a large family of immune receptors that function as “sensors” of pathogen- and damage-derived signals. We found that TLR7 exerts antitumor functions in non-small cell lung cancer by inducing the production of specific molecules with inhibitory properties against new blood vessel formation. These molecules are known as specialized pro-resolving mediators (SPMs) and are derived from ω-3 and ω-6 fatty acids. We believe that the results obtained suggest novel potential targets and strategies to treat lung cancer.

Abstract

Pattern recognition receptors (PRR) promote inflammation but also its resolution. We demonstrated that a specific PRR—formyl peptide receptor 1 (FPR1)—sustains an inflammation resolution response with anti-angiogenic and antitumor potential in gastric cancer. Since toll-like receptor 7 (TLR7) is crucial in the physiologic resolution of airway inflammation, we asked whether it could be responsible for pro-resolving and anti-angiogenic responses in non-small cell lung cancer (NSCLC). TLR7 correlated directly with pro-resolving and inversely with angiogenic mediators in NSCLC patients, as revealed by a publicly available RNAseq analysis. In NSCLC cells, depletion of TLR7 caused an upregulation of angiogenic mediators and a stronger vasculogenic response of endothelial cells compared to controls, assessed by qPCR, ELISA, protein array, and endothelial cell responses. TLR7 activation induced the opposite effects. TLR7 silencing reduced, while its activation increased, the pro-resolving potential of NSCLC cells, evaluated by qPCR, flow cytometry, and EIA. The increased angiogenic potential of TLR7-silenced NSCLC cells is due to the lack of pro-resolving mediators. MAPK and STAT3 signaling are responsible for these activities, as demonstrated through Western blotting and inhibitors. Our data indicate that TLR7 sustains a pro-resolving signaling in lung cancer that inhibits angiogenesis. This opens new possibilities to be exploited for cancer treatment.

Suppression of autophagy through JAK2/STAT3 contributes to the therapeutic action of rhynchophylline on asthma

Background

Asthma is a chronic inflammatory disease characterized by airway remodeling and inflammation. Rhynchophylline is a kind of indole alkaloid isolated from Uncaria rhynchophylla. Here we investigated the effect of rhynchophylline on autophagy in asthma.

Methods

A mice model of asthma was established by ovalbumin challenge. Histopathological changes were assessed by hematoxylin-eosin staining, periodic acid-schiff staining and Masson staining. The levels of IgE in serum, interleukin-6 and interleukin-13 in bronchoalveolar lavage fluid, as well as the activities of superoxide dismutase and catalase in lung tissues were detected. The expression of autophagy-related genes and Janus kinase (JAK) 2/ signal transducer and activator of transcription (STAT) 3 signal was detected by western blot and immunofluorescence. Airway smooth muscle cells (ASMCs) were isolated, and the effect rhynchophylline on autophagy in ASMCs was explored.

Results

Our data showed that rhynchophylline treatment alleviated inflammation, airway remodeling, and oxidative stress in asthma. In addition, autophagy, which was implicated in asthma, was suppressed by rhynchophylline with decreased level of autophagy-related proteins. Furthermore, rhynchophylline suppressed the JAK2/STAT3 signaling pathway, which was activated in asthma. In vitro study showed that rhynchophylline suppressed ASMC autophagy through suppressing the activation of JAK2/STAT3 signal.

Conclusions

Our study demonstrated that rhynchophylline can alleviate asthma through suppressing autophagy in asthma, and that JAK2/STAT3 signal was involved in this effect of rhynchophylline. This study indicates that rhynchophylline may become a promising drug for the treatment of asthma.

Effect of RvD1/FPR2 on inflammatory response in chorioamnionitis

Chorioamnionitis (CAM), as a common intrauterine infectious disease, is the leading cause of premature birth, stillbirth, neonatal infection and sepsis. The formyl peptide receptor 2 (FPR2) is a member of GPCRs widely distributed in a variety of tissues and is associated with many inflammatory diseases. With the discovery of FPR2 in human placenta, the possibility of exploring the function of FPR2 in obstetrics is evolving. The Resolvin D1 (RvD1) plays an important role in the resolution of inflammation by combining with FPR2. In this study, we evaluated the role of FPR2 and RvD1 in CAM, not only in the human placenta but also in mouse models. The expression of FPR2 increased in the placenta of CAM patients and the downstream PPARγ/NF-κB signalling changed accordingly. Moreover, Fpr2^-/- mice were highly susceptible to LPS, displaying a worse CAM symptom, compared with WT mice. By establishing a model of trophoblast inflammation in vitro, it was confirmed that RvD1 rescued the effect of LPS on inflammation by combining with FPR2 and its downstream PPARγ/NF-κB pathway. Otherwise, RvD1 improved the preterm labour in a mouse model of CAM induced by LPS. Altogether, these findings show that RvD1 alleviated the inflammation of trophoblast in vivo and in vitro through FPR2/PPARγ/NF-κB pathway, suggesting RvD1/FPR2 might be a novel therapeutic strategy to alleviate CAM.

Treatment with a Toll-like Receptor 7 ligand evokes protective immunity against atherosclerosis in hypercholesterolaemic mice

BACKGROUND

The interplay between innate and adaptive immunity is central in life-threatening clinical complications of atherosclerosis such as myocardial infarction and stroke. The specific mechanisms involved and their protective versus detrimental effects in the disease process remain poorly understood. We have previously shown that higher levels of Toll-like receptor 7 (TLR7) expression in human atherosclerotic lesions are correlated with better patient outcome.

OBJECTIVE

In this study, we explored whether TLR7 activation can ameliorate disease in experimental atherosclerosis in mice.

METHODS

Apolipoprotein E deficient mice (Apoe^-/- ) with established disease were injected for five weeks intraperitoneally with the TLR7 ligand R848. Local effects were evaluated by characterization of the lesion. Systemic effects of the treatment were investigated by immune composition analysis in the spleen and plasma measurements.

RESULTS

The in vivo treatment arrested lesion progression in the aorta. We also detected expansion of marginal zone B cells and T_reg in the spleen together with increased plasma IgM antibodies against oxidized low-density lipoprotein (oxLDL) and reduced plasma cholesterol levels. These changes were accompanied by increased accumulation of IgM antibodies, decreased necrosis and fewer apoptotic cells in atherosclerotic lesions.

CONCLUSIONS

Our findings show that TLR7 stimulation could ameliorate atherosclerotic lesion burden and reduce plasma cholesterol in Apoe^-/- mice. TLR7 stimulation was associated with an atheroprotective B-cell and T_reg response, which may have systemic and local effects within lesions that could prevent arterial lipid accumulation and inflammation.

15-Lipoxygenase-1 biosynthesis of 7S,14S-diHDHA implicates 15-lipoxygenase-2 in biosynthesis of resolvin D5

The two oxylipins 7S,14S-dihydroxydocosahexaenoic acid (diHDHA) and 7S,17S-diHDHA [resolvin D5 (RvD5)] have been found in macrophages and infectious inflammatory exudates and are believed to function as specialized pro-resolving mediators (SPMs). Their biosynthesis is thought to proceed through sequential oxidations of DHA by lipoxygenase (LOX) enzymes, specifically, by human 5-LOX (h5-LOX) first to 7(S)-hydroxy-4Z,8E,10Z,13Z,16Z,19Z-DHA (7S-HDHA), followed by human platelet 12-LOX (h12-LOX) to form 7(S),14(S)-dihydroxy-4Z,8E,10Z,12E,16Z,19Z-DHA (7S,14S-diHDHA) or human reticulocyte 15-LOX-1 (h15-LOX-1) to form RvD5. In this work, we determined that oxidation of 7(S)-hydroperoxy-4Z,8E,10Z,13Z,16Z,19Z-DHA to 7S,14S-diHDHA is performed with similar kinetics by either h12-LOX or h15-LOX-1. The oxidation at C14 of DHA by h12-LOX was expected, but the noncanonical reaction of h15-LOX-1 to make over 80% 7S,14S-diHDHA was larger than expected. Results of computer modeling suggested that the alcohol on C7 of 7S-HDHA hydrogen bonds with the backbone carbonyl of Ile399, forcing the hydrogen abstraction from C12 to oxygenate on C14 but not C17. This result raised questions regarding the synthesis of RvD5. Strikingly, we found that h15-LOX-2 oxygenates 7S-HDHA almost exclusively at C17, forming RvD5 with faster kinetics than does h15-LOX-1. The presence of h15-LOX-2 in neutrophils and macrophages suggests that it may have a greater role in biosynthesizing SPMs than previously thought. We also determined that the reactions of h5-LOX with 14(S)-hydroperoxy-4Z,7Z,10Z,12E,16Z,19Z-DHA and 17(S)-hydroperoxy-4Z,7Z,10Z,13Z,15E,19Z-DHA are kinetically slow compared with DHA, suggesting that these reactions may be minor biosynthetic routes in vivo. Additionally, we show that 7S,14S-diHDHA and RvD5 have anti-aggregation properties with platelets at low micromolar potencies, which could directly regulate clot resolution.

TLR2-Melatonin Feedback Loop Regulates the Activation of NLRP3 Inflammasome in Murine Allergic Airway Inflammation

Toll-like receptor 2 (TLR2) is suggested to initiate the activation of NLRP3 inflammasome, and considered to be involved in asthma. The findings that melatonin modulates TLRs-mediated immune responses, together with the suppressing effect of TLRs on endogenous melatonin synthesis, support the possibility that a feedback loop exists between TLRs system and endogenous melatonin synthesis. To determine whether TLR2-melatonin feedback loop exists in allergic airway disease and regulates NLRP3 inflammasome activity, wild-type (WT) and TLR2^−/− mice were challenged with OVA to establish allergic airway disease model. Following OVA challenge, WT mice exhibited increased-expression of TLR2, activation of NLRP3 inflammasome and marked airway inflammation, which were all effectively inhibited in the TLR2^−/− mice, indicating that TLR2-NLRP3 mediated airway inflammation. Meanwhile, melatonin biosynthesis was reduced in OVA-challenged WT mice, while such reduction was notably rescued by TLR2 deficiency, suggesting that TLR2-NLRP3-mediated allergic airway inflammation was associated with decreased endogenous melatonin biosynthesis. Furthermore, addition of melatonin to OVA-challenged WT mice pronouncedly ameliorated airway inflammation, decreased TLR2 expression and NLRP3 inflammasome activation, further implying that melatonin in turn inhibited airway inflammation via suppressing TLR2-NLRP3 signal. Most interestingly, although melatonin receptor antagonist luzindole significantly reduced the protein expressions of ASMT, AANAT and subsequent level of melatonin in OVA-challenged TLR2^−/− mice, it exhibited null effect on leukocytes infiltration, Th2-cytokines production and NLRP3 activity. These results indicate that a TLR2-melatonin feedback loop regulates NLRP3 inflammasome activity in allergic airway inflammation, and melatonin may be a promising therapeutic medicine for airway inflammatory diseases such as asthma.

Particulate matters induce acute exacerbation of allergic airway inflammation via the TLR2/NF-κB/NLRP3 signaling pathway

BACKGROUND

Exposure to particulate matters (PMs) can lead to an acute exacerbation of allergic airway diseases, increasing the severity of symptoms and mortality. However, little is known about the underlying molecular mechanism. This study aimed to investigate the effects of PMs on acute exacerbation of allergic airway inflammation and seek potential therapeutic targets.

METHODS

Non-allergic control and ovalbumin (OVA)-allergic wide-type (WT) and Toll-like receptor 2 knockout (Tlr2-/-) mice were exposed to 100 μg of PM (diameter 5.85 μm) or saline by the oropharyngeal instillation. The responses were examined three days after exposure. In the RAW264.7 macrophage cell line, Tlr2 was knocked down by small-interfering RNA or the NF-κB inhibitor JSH-23 was used, and then the cells were stimulated with PMs for 12 h before comparison of the inflammatory responses.

RESULTS

PM exposure led to increased inflammatory cell recruitment and airway intensity of PAS + staining in OVA-allergic WT mice, accompanied with an accumulation of inflammatory cells and elevated inflammatory cytokines, such as IL-6 and IL-18, in the bronchoalveolar lavage fluid (BALF). Furthermore, the protein levels of TLR2 and the NLRP3 inflammasome were elevated concomitantly with the airway inflammation post-OVA/PMs challenge. Tlr2 deficiency effectively inhibited the airway inflammation, including pulmonary inflammatory cell recruitment, mucus secretion, serum OVA-specific immunoglobulin E (IgE), and BALF inflammatory cytokine production. Additionally, the P-induced NLRP3 activation in the RAW 264.7 cell line was diminished by the knockdown of Tlr2 or JSH-23 treatment in vitro.

CONCLUSION

Our results indicated that PMs exacerbate the allergic airway inflammation mediated by the TLR2/ NF-κB/NLRP3 signaling pathway. Inhibition of NF-κB seems to be a possible treatment.

Specialized pro-resolving lipid mediators are differentially altered in peripheral blood of patients with multiple sclerosis and attenuate monocyte and blood-brain barrier dysfunction

Chronic inflammation is a key pathological hallmark of multiple sclerosis (MS) and suggests that resolution of inflammation, orchestrated by specialized pro-resolving lipid mediators (LM), is impaired. Here, through targeted-metabololipidomics in peripheral blood of patients with MS, we revealed that each disease form was associated with distinct LM profiles that significantly correlated with disease severity. In particular, relapsing and progressive MS patients were associated with high eicosanoids levels, whereas the majority of pro-resolving LM were significantly reduced or below limits of detection and correlated with disease progression. Furthermore, we found impaired expression of several pro-resolving LM biosynthetic enzymes and receptors in blood-derived leukocytes of MS patients. Mechanistically, differentially expressed mediators like LXA4, LXB4, RvD1 and PD1 reduced MS-derived monocyte activation and cytokine production, and inhibited inflammation-induced blood-brain barrier dysfunction and monocyte transendothelial migration. Altogether, these findings reveal peripheral defects in the resolution pathway in MS, suggesting pro-resolving LM as novel diagnostic biomarkers and potentially safe therapeutics.

Melatonin biosynthesis restored by CpG oligodeoxynucleotides attenuates allergic airway inflammation via regulating NLRP3 inflammasome

AIMS

Both CpG oligodeoxynucleotide (CpG-ODN) and melatonin have been reported to induce Th1 response and contribute to allergic asthma resistance. Here, we aimed to reveal how they confer such effect as well as whether they crosstalk with each other.

MAIN METHODS

Six-week-old Female C57BL/6 mice were challenged by OVA to induce allergic airway inflammation, and were treated with CpG-ODN, CpG-ODN plus Luzindole or melatonin respectively. Bronchoalveolar lavage fluid (BALF) cellularity was classified and counted by Wright's-Giemsa staining. HE and PAS staining were used to analyze airway inflammation. The levels of IL-4, IL-5, IL-13,GM-CSF and IFN-γ, as well as IL-1β and IL-18 were analyzed by ELISA. Protein expressions of ASMT, AANAT, NLRP3, IL-1β and caspase-1 in lung tissue were detected by Western blotting, expression of ASMT and AANAT were further observed by immunohistochemistry.

KEY FINDINGS

We found that CpG-ODN considerably suppressed OVA-induced airway leukocytes infiltration, goblet cell hyperplasia and Th2 cytokines production. Furthermore, the resolution effect of CpG-ODN on OVA-induced allergic airway inflammation occurred in parallel with decreased-activation of NLRP3 inflammasome and increased biosynthesis of melatonin. Blocking the effect of endogenous melatonin by Luzindole abolished the suppressive effect of CpG-ODN on OVA-induced airway inflammation and activation of NLRP3 inflammasome, suggesting such effect was mediated by endogenous melatonin. Moreover, exogenous melatonin pronouncedly ameliorated airway inflammation and decreased the activation of NLRP3 inflammasome.

SIGNIFICANCE

These results proven that CpG-ODN protects against allergic airway inflammation via suppressing the activation of NLRP3 inflammasome, and such effect may be resulted from the restored-production of melatonin.

A dual role of 12/15-lipoxygenase in LPS-induced acute renal inflammation and injury

Recent studies suggest a potential role of bioactive lipids in acute kidney injury induced by lipopolysaccharide (LPS). The current study was designed to determine the profiling activities of various polyunsaturated fatty acid (PUFA) metabolizing enzymes, including lipoxygenases (LO), cyclooxygenase, and cytochrome P450 in the plasma of LPS-injected mice using LC-MS. Heat map analysis revealed that out of 126 bioactive lipids screened, only the 12/15-LO metabolite, 12-HETE, had a significant (2.24 ± 0.4) fold increase relative to control (P = 0.0001) after Bonferroni Correction (BCF α = 0.003). We then determined the role of the 12/15-LO in LPS-induced acute kidney injury using genetic and pharmacological approaches. Treatment of LPS injected mice with the 12/15-LO inhibitor, baicalein, significantly reduced levels of renal injury and inflammation markers including urinary thiobarbituric acid reactive substance (TBARs), urinary monocyte chemoattractant protein-1 (MCP-1), renal interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Similarly, knocking-out of 12/15-LO reduced levels of renal inflammation and injury markers elicited by LPS injection. Next, we tested whether exogenous supplementation with docosahexaenoic acid (DHA) as a substrate would divert the role of 12/15-LO from being pro-inflammatory to anti-inflammatory via increased production of the anti-inflammatory metabolite. DHA treatment restored the decreased in plasma level of resolvin D2 (RvD2) and reduced renal injury in LPS-injected mice whereas DHA treatment failed to provide any synergistic effects in reducing renal injury in LPS injected 12/15-LO knock-out mice. The ability of RvD2 to protect kidney against LPS-induced renal injury was further confirmed by exogenous RvD2 which significantly reduced the elevation in renal injury in LPS injected mice. These data suggest a double-edged sword role of 12/15-LO in LPS-induced acute renal inflammation and injury, depending on the type of substrate available for its activity.

Estrogen ameliorates allergic airway inflammation by regulating activation of NLRP3 in mice

Background: Estrogen has been suggested to play a protective role against airway inflammations, such as asthma. In these processes, the inflammasome nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3 (NLRP3) partly accounts for the activation of pro-inflammatory factors. The aim of the present study was to investigate whether NLRP3 was involved in the protective effect of estrogen against allergic airway inflammation. Methods: An ovariectomy was performed on female C57BL/6 mice; some were sham-operated (sham). We then sensitized and challenged them with ovalbumin (OVA) to establish an airway inflammation model. Meanwhile, some mice were treated with 17β-estradiol (E2) for 28 days. Results: The expression of NLRP3 inflammasome and its downstream products, caspase-1 and the pro-inflammatory cytokine interleukin (IL)-1β (IL-1β), increased concomitantly with OVA-challenged airway inflammation and decreased with the expression of estrogen receptor β (ERβ). In addition, treating ovariectomized (OVX) mice with E2 dramatically ameliorated airway inflammation via such mechanisms as leukocyte recruitment, mucus production, and secretion of pro-inflammatory cytokines other than IL-18 in bronchoalveolar lavage (BAL) fluid (BALF). Furthermore, E2 suppressed both the mRNA expression and protein expression of NLRP3, caspase-1, and IL-1β. In summary, our study showed that NLRP3 inflammasome activation and pro-inflammatory cytokine production markedly increased in OVA-induced airway inflammation, and E2 effectively abrogated such inflammation by regulating the activation of NLRP3.

New pro-resolving n-3 mediators bridge resolution of infectious inflammation to tissue regeneration

While protective, the acute inflammatory response when uncontrolled can lead to further tissue damage and chronic inflammation that is now widely recognized to play important roles in many commonly occurring diseases, such as cardiovascular disease, neurodegenerative diseases, metabolic syndrome, and many other diseases of significant public health concern. The ideal response to initial challenges of the host is complete resolution of the acute inflammatory response, which is now recognized to be a biosynthetically active process governed by specialized pro-resolving mediators (SPM). These chemically distinct families include lipoxins, resolvins, protectins and maresins that are biosynthesized from essential fatty acids. The biosynthesis and complete stereochemical assignments of the major SPM are established, and new profiling procedures have recently been introduced to document the activation of these pathways in vivo with isolated cells and in human tissues. The active resolution phase leads to tissue regeneration, where we've recently identified new molecules that communicate during resolution of inflammation to activate tissue regeneration in model organisms. This review presents an update on the documentation of the roles of SPMs and the biosynthesis and structural elucidation of novel mediators that stimulate tissue regeneration, coined conjugates in tissue regeneration. The identification and actions of the three families, maresin conjugates in tissue regeneration (MCTR), protectin conjugates in tissue regeneration (PCTR), and resolvin conjugates in tissue regeneration (RCTR), are reviewed here. The identification, structural elucidation and the pathways and biosynthesis of these new mediators in tissue regeneration demonstrate the host capacity to protect from collateral tissue damage, stimulate clearance of bacteria and debris, and promote tissue regeneration via endogenous pathways and molecules in the resolution metabolome.

Sevoflurane Inhibits the Th2 Response and NLRP3 Expression in Murine Allergic Airway Inflammation

Background

Our colleagues have demonstrated an impressive therapeutic role of sevoflurane in a murine allergic airway inflammation model, but the mechanisms underlying this effect remain undefined. In this study, we tried to investigate the effect of sevoflurane on the resolution of allergic airway inflammation and to assess whether NLRP3 or the NLRP3 inflammasome is involved in this process.

Methods

Female (C57BL/6) mice were sensitized and challenged with ovalbumin (OVA). Then, some of the mice received MCC950 (10 mg/kg; i.p.) or 3% sevoflurane. Total and differential inflammatory cell numbers, proinflammatory cytokines in bronchoalveolar lavage fluid (BALF), the peribronchial inflammation density, and mucus production were evaluated. In addition, we analysed the protein levels of NLRP3, the apoptosis-associated speck-like protein containing the caspase activation and recruitment domain (ASC), pro-caspase-1, and caspase-1 in the lung tissue.

Results

We found that OVA-induced inflammatory cell recruitment to peribronchial regions, goblet cell hyperplasia, the serum levels of IgE, inflammatory cells, and the Th2 cytokine secretion in BALF was potently suppressed by sevoflurane with an efficacy comparable with that suppressed by MCC950 treatment. Furthermore, sevoflurane, similar to MCC950, clearly inhibited the OVA-induced activity of NLRP3 in the lungs. In addition, we found that OVA challenge failed to increase the expression of ASC, pro-caspase-1, and caspase-1 in the lungs and the levels of IL-18 and IL-1β in BALF.

Conclusion

Taken together, our data showed that sevoflurane ameliorated allergic airway inflammation by inhibiting Th2 responses and NLRP3 expression. The NLRP3 independent of inflammasomes participated in the pathogenesis of allergic asthma in this model.

Eicosapentaenoic Acid Enhances the Effects of Mesenchymal Stromal Cell Therapy in Experimental Allergic Asthma

Asthma is characterized by chronic lung inflammation and airway hyperresponsiveness. Despite recent advances in the understanding of its pathophysiology, asthma remains a major public health problem and, at present, there are no effective interventions capable of reversing airway remodeling. Mesenchymal stromal cell (MSC)-based therapy mitigates lung inflammation in experimental allergic asthma; however, its ability to reduce airway remodeling is limited. We aimed to investigate whether pre-treatment with eicosapentaenoic acid (EPA) potentiates the therapeutic properties of MSCs in experimental allergic asthma. Seventy-two C57BL/6 mice were used. House dust mite (HDM) extract was intranasally administered to induce severe allergic asthma in mice. Unstimulated or EPA-stimulated MSCs were administered intratracheally 24 h after final HDM challenge. Lung mechanics, histology, protein levels of biomarkers, and cellularity in bronchoalveolar lavage fluid (BALF), thymus, lymph nodes, and bone marrow were analyzed. Furthermore, the effects of EPA on lipid body formation and secretion of resolvin-D₁ (RvD₁), prostaglandin E₂ (PGE₂), interleukin (IL)-10, and transforming growth factor (TGF)-β1 by MSCs were evaluated in vitro. EPA-stimulated MSCs, compared to unstimulated MSCs, yielded greater therapeutic effects by further reducing bronchoconstriction, alveolar collapse, total cell counts (in BALF, bone marrow, and lymph nodes), and collagen fiber content in airways, while increasing IL-10 levels in BALF and M2 macrophage counts in lungs. In conclusion, EPA potentiated MSC-based therapy in experimental allergic asthma, leading to increased secretion of pro-resolution and anti-inflammatory mediators (RvD₁, PGE₂, IL-10, and TGF-β), modulation of macrophages toward an anti-inflammatory phenotype, and reduction in the remodeling process. Taken together, these modifications may explain the greater improvement in lung mechanics obtained. This may be a promising novel strategy to potentiate MSCs effects.

Prominent release of lipoxygenase generated mediators in a murine house dust mite-induced asthma model

The profile of activation of lipid mediator (LM) pathways in asthmatic airway inflammation remains unclear. This experimental study quantified metabolite levels of ω3-, ω6- and ω9-derived polyunsaturated fatty acids in bronchoalveolar lavage fluid (BALF) after 4-weeks of repeated house dust mite (HDM) exposure in a murine (C57BL/6) asthma model. The challenge induced airway hyperresponsiveness, pulmonary eosinophil infiltration, but with low and unchanged mast cell numbers. Of the 112 screened LMs, 26 were increased between 2 to >25-fold in BALF with HDM treatment (p < 0.05, false discovery rate = 5%). While cysteinyl-leukotrienes were the most abundant metabolites at baseline, their levels did not increase after HDM treatment, whereas elevation of PGD₂, LTB₄ and multiple 12/15-lipoxygenase products, such as 5,15-DiHETE, 15-HEDE and 15-HEPE were observed. We conclude that this model has identified a global lipoxygenase activation signature, not linked to mast cells, but with aspects that mimic chronic allergic airway inflammation in asthma.

TLR2 Regulates Allergic Airway Inflammation and Autophagy Through PI3K/Akt Signaling Pathway

Toll-like receptors (TLRs) are innate pattern recognition receptors that play a critical role in allergic inflammation, yet their contribution to autophagy in asthma remains poorly defined. Here, we investigate the role of Toll-like receptor 2 (TLR2) in phosphoinositide 3-kinases/protein kinase B (PI3K/Akt) pathway-mediated autophagy in ovalbumin-induced airway inflammation in mice. Wild-type (WT) and TLR2-knockout (TLR2^-/-) C57BL/6 mice were ovalbumin-sensitized and ovalbumin-challenged. In ovalbumin-challenged WT mice, enhanced expression of TLR2 in lung tissue, remarkable inflammatory cell infiltrates, goblet cell hyperplasia, and increased mucus production were observed. The number of inflammatory cells and interleukin-13 (IL-13) levels increased, while interferon-gamma (IFN-γ) levels decreased in bronchoalveolar lavage fluid. Expression of PI3K, phospho-Akt, Beclin-1 and LC3-II was enhanced significantly. These changes were mitigated dose-dependently in 3-methyl adenine-treated mice. In contrast, similar but weaker changes were found in ovalbumin-challenged TLR2^-/- mice, and the changes were not significantly attenuated by 3-methyl adenine treatment. These results indicate that TLR2 confers a pivotal role in allergic airway inflammation via regulating the PI3K/Akt signaling pathway-related autophagy in mice.

Human macrophages differentially produce specific resolvin or leukotriene signals that depend on bacterial pathogenicity

Proinflammatory eicosanoids (prostaglandins and leukotrienes) and specialized pro-resolving mediators (SPM) are temporally regulated during infections. Here we show that human macrophage phenotypes biosynthesize unique lipid mediator signatures when exposed to pathogenic bacteria. E. coli and S. aureus each stimulate predominantly proinflammatory 5-lipoxygenase (LOX) and cyclooxygenase pathways (i.e., leukotriene B4 and prostaglandin E2) in M1 macrophages. These pathogens stimulate M2 macrophages to produce SPMs including resolvin D2 (RvD2), RvD5, and maresin-1. E. coli activates M2 macrophages to translocate 5-LOX and 15-LOX-1 to different subcellular locales in a Ca2+-dependent manner. Neither attenuated nor non-pathogenic E. coli mobilize Ca2+ or activate LOXs, rather these bacteria stimulate prostaglandin production. RvD5 is more potent than leukotriene B4 at enhancing macrophage phagocytosis. These results indicate that M1 and M2 macrophages respond to pathogenic bacteria differently, producing either leukotrienes or resolvins that further distinguish inflammatory or pro-resolving phenotypes.

Structural elucidation and physiologic functions of specialized pro-resolving mediators and their receptors

The acute inflammatory response is host-protective to contain foreign invaders. Many of today's pharmacopeia that block pro-inflammatory chemical mediators can cause serious unwanted side effects such as immune suppression. Uncontrolled inflammation is now considered a pathophysiologic basis associated with many widely occurring diseases such as cardiovascular disease, neurodegenerative diseases, diabetes, obesity and asthma, as well as the classic inflammatory diseases, e.g. arthritis, periodontal diseases. The inflammatory response is designated to be a self-limited process that produces a superfamily of chemical mediators that stimulate resolution of inflammatory responses. Specialized proresolving mediators (SPM) uncovered in recent years are endogenous mediators that include omega-3-derived families resolvins, protectins and maresins, as well as arachidonic acid-derived (n-6) lipoxins that stimulate and promote resolution of inflammation, clearance of microbes, reduce pain and promote tissue regeneration via novel mechanisms. Here, we review recent evidence from human and preclinical animal studies, together with the structural and functional elucidation of SPM indicating the SPM as physiologic mediators and pharmacologic agonists that stimulate resolution of inflammation and infection. These results suggest that it is time to develop immunoresolvents as agonists for testing resolution pharmacology in nutrition and health as well as in human diseases and during surgery.

Effects of prenatal n-3 fatty acid supplementation on offspring resolvins at birth and 12 years of age: a double-blind, randomised controlled clinical trial

Resolution of inflammation is an active process involving specialised pro-resolving mediators (SPM) generated from the n-3 fatty acids EPA and DHA. n-3 Fatty acid supplementation during pregnancy may provide an intervention strategy to modify these novel SPM. This study aimed to assess the effect of n-3 fatty acid supplementation in pregnancy on offspring SPM at birth and 12 years of age (12 years). In all, ninety-eight atopic pregnant women were randomised to 3·7 g daily n-3 fatty acids or a control (olive oil), from 20 weeks gestation until delivery. Blood was collected from the offspring at birth and at 12 years. Plasma SPM consisting of 18-hydroxyeicosapentaenoic acid (18-HEPE), E-series resolvins, 17-hydroxydocosahexaenoic acid (17-HDHA), D-series resolvins, 14-hydroxydocosahexaenoic acid (14-HDHA), 10 S,17S-dihydroxydocosahexaenoic acid, maresins and protectin 1, were measured by liquid chromatography-tandem MS. We identified the resolvins RvE1, RvE2, RvE3, RvD1, 17R-RvD1 and RvD2 for the first time in human cord blood. n-3 Fatty acids increased cord blood 18-HEPE (P<0·001) derived from EPA relative to the control group. DHA-derived 17-HDHA at birth was significantly increased in the n-3 fatty acid group relative to the controls (P=0·001), but other SPM were not different between the groups. n-3 Fatty acid supplementation during pregnancy was associated with an increase in SPM precursors in the offspring at birth but the effects were not sustained at 12 years. The presence of these SPM, particularly at birth, may have functions relevant in the newborn that remain to be established, which may be useful for future investigations.

Plasmacytoid dendritic cells drive acute asthma exacerbations

BACKGROUND

Although acute exacerbations, mostly triggered by viruses, account for the majority of hospitalizations in asthmatic patients, there is still very little known about the pathophysiologic mechanisms involved. Plasmacytoid dendritic cells (pDCs), prominent cells of antiviral immunity, exhibit proinflammatory or tolerogenic functions depending on the context, yet their involvement in asthma exacerbations remains unexplored.

OBJECTIVES

We sought to investigate the role of pDCs in allergic airway inflammation and acute asthma exacerbations.

METHODS

Animal models of allergic airway disease (AAD) and virus-induced AAD exacerbations were used to dissect pDC function in vivo and unwind the potential mechanisms involved. Sputum from asthmatic patients with stable disease or acute exacerbations was further studied to determine the presence of pDCs and correlation with inflammation.

RESULTS

pDCs were key mediators of the immunoinflammatory cascade that drives asthma exacerbations. In animal models of AAD and rhinovirus-induced AAD exacerbations, pDCs were recruited to the lung during inflammation and migrated to the draining lymph nodes to boost T_H2-mediated effector responses. Accordingly, pDC depletion after allergen challenge or during rhinovirus infection abrogated exacerbation of inflammation and disease. Central to this process was IL-25, which was induced by allergen challenge or rhinovirus infection and conditioned pDCs for proinflammatory function. Consistently, in asthmatic patients pDC numbers were markedly increased during exacerbations and correlated with the severity of inflammation and the risk for asthma attacks.

CONCLUSIONS

Our studies uncover a previously unsuspected role of pDCs in asthma exacerbations with potential diagnostic and prognostic implications. They also propose the therapeutic targeting of pDCs and IL-25 for the treatment of acute asthma.

Human Milk and Allergic Diseases: An Unsolved Puzzle

There is conflicting evidence on the protective role of breastfeeding in relation to the development of allergic sensitisation and allergic disease. Studies vary in methodology and definition of outcomes, which lead to considerable heterogeneity. Human milk composition varies both within and between individuals, which may partially explain conflicting data. It is known that human milk composition is very complex and contains variable levels of immune active molecules, oligosaccharides, metabolites, vitamins and other nutrients and microbial content. Existing evidence suggests that modulation of human breast milk composition has potential for preventing allergic diseases in early life. In this review, we discuss associations between breastfeeding/human milk composition and allergy development.

Bronchoprotective mechanisms for specialized pro-resolving mediators in the resolution of lung inflammation

Bronchi are exposed daily to irritants, microbes and allergens as well as extremes of temperature and acid. The airway mucosal epithelium plays a pivotal role as a sentinel, releasing alarmins when danger is encountered. To maintain homeostasis, an elaborate counter-regulatory network of signals and cellular effector mechanisms are needed. Specialized pro-resolving mediators (SPMs) are chemical mediators that enact resolution programs in response to injury, infection or allergy. SPMs are enzymatically derived from essential polyunsaturated fatty acids with potent cell-type specific immunoresolvent properties. SPMs signal by engaging cell-based receptors to turn off acute inflammatory responses and restore tissue homeostasis. Several common lung diseases involving the airways, including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), are characterized by unresolved bronchial inflammation. In preclinical murine models of lung disease, SPMs carry potent bronchoprotective actions. Here, we review cellular and molecular effects for SPM-initiated catabasis in the lung and their human translation.

Addressing unmet needs in understanding asthma mechanisms: From the European Asthma Research and Innovation Partnership (EARIP) Work Package (WP)2 collaborators

Asthma is a heterogeneous, complex disease with clinical phenotypes that incorporate persistent symptoms and acute exacerbations. It affects many millions of Europeans throughout their education and working lives and puts a heavy cost on European productivity. There is a wide spectrum of disease severity and control. Therapeutic advances have been slow despite greater understanding of basic mechanisms and the lack of satisfactory preventative and disease modifying management for asthma constitutes a significant unmet clinical need. Preventing, treating and ultimately curing asthma requires co-ordinated research and innovation across Europe. The European Asthma Research and Innovation Partnership (EARIP) is an FP7-funded programme which has taken a co-ordinated and integrated approach to analysing the future of asthma research and development. This report aims to identify the mechanistic areas in which investment is required to bring about significant improvements in asthma outcomes.

Identification of Novel Chondroprotective Mediators in Resolving Inflammatory Exudates

We hypothesized that exudates collected at the beginning of the resolution phase of inflammation might be enriched for tissue protective molecules; thus an integrated cellular and molecular approach was applied to identify novel chondroprotective bioactions. Exudates were collected 6 h (inflammatory) and 24 h (resolving) following carrageenan-induced pleurisy in rats. The resolving exudate was subjected to gel filtration chromatography followed by proteomics, identifying 61 proteins. Fractions were added to C28/I2 chondrocytes, grown in micromasses, ions with or without IL-1β or osteoarthritic synovial fluids for 48 h. Three proteins were selected from the proteomic analysis, α1-antitrypsin (AAT), hemopexin (HX), and gelsolin (GSN), and tested against catabolic stimulation for their effects on glycosaminoglycan deposition as assessed by Alcian blue staining, and gene expression of key anabolic proteins by real-time PCR. In an in vivo model of inflammatory arthritis, cartilage integrity was determined histologically 48 h after intra-articular injection of AAT or GSN. The resolving exudate displayed protective activities on chondrocytes, using multiple readouts: these effects were retained in low m.w. fractions of the exudate (46.7% increase in glycosaminoglycan deposition; ∼20% upregulation of COL2A1 and aggrecan mRNA expression), which reversed the effect of IL-1β. Exogenous administration of HX, GSN, or AAT abrogated the effects of IL-1β and osteoarthritic synovial fluids on anabolic gene expression and increased glycosaminoglycan deposition. Intra-articular injection of AAT or GSN protected cartilage integrity in mice with inflammatory arthritis. In summary, the strategy for identification of novel chondroprotective activities in resolving exudates identified HX, GSN and AAT as potential leads for new drug discovery programs.

Low TLR7 gene expression in atherosclerotic plaques is associated with major adverse cardio- and cerebrovascular events

AIMS

Processes in the development of atherosclerotic lesions can lead to plaque rupture or erosion, which can in turn elicit myocardial infarction or ischaemic stroke. The aims of this study were to determine whether Toll-like receptor 7 (TLR7) gene expression levels influence patient outcome and to explore the mechanisms linked to TLR7 expression in atherosclerosis.

METHODS AND RESULTS

Atherosclerotic plaques were removed by carotid endarterectomy (CEA) and subjected to gene array expression analysis (n = 123). Increased levels of TLR7 transcript in the plaques were associated with better outcome in a follow-up study over a maximum of 8 years. Patients with higher TLR7 transcript levels had a lower risk of experiencing major cardiovascular and cerebrovascular events (MACCE) during the follow-up period after CEA (hazard ratio: 2.38, P = 0.012, 95% CI 1.21-4.67). TLR7 was expressed in all plaques by T cells, macrophages and endothelial cells in capillaries, as shown by immunohistochemistry. In short-term tissue cultures, ex vivo treatment of plaques with the TLR7 ligand imiquimod elicited dose-dependent secretion of IL-10, TNF-α, GM-CSF, and IL-12/IL-23p40. This secretion was blocked with a TLR7 inhibitor. Immunofluorescent tissue analysis after TLR7 stimulation showed IL-10 expression in T cells, macrophages and vascular smooth muscle cells. TLR7 mRNA levels in the plaques were correlated with IL-10 receptor (r = 0.4031, P < 0.0001) and GM-CSF receptor A (r = 0.4354, P < 0.0001) transcripts.

CONCLUSION

These findings demonstrate that TLR7 is abundantly expressed in human atherosclerotic plaques. TLR7 ligation elicits the secretion of pro-inflammatory and anti-inflammatory cytokines, and high TLR7 expression in plaques is associated with better patient outcome, suggesting that TLR7 is a potential therapeutic target for prevention of complications of atherosclerosis.

Resolvin D2 decreases TLR4 expression to mediate resolution in human monocytes

TLRs are critical for innate immunity, but excessive activation can lead to tissue damage and disease. Specialized proresolving mediators (SPMs), including resolvin D2 (RvD2), promote the active resolution of inflammation. How SPMs regulate early LPS signaling, including activation of TLR4, is unknown. We treated human THP-1 monocytic cells and primary human blood monocytes with RvD2 and LPS to evaluate modulation of TLRs. miRNA-146a overexpression and inhibition were used to dissect the mechanism of RvD2-mediated actions. We validated our studies using ELISAs for cytokines, PCR, Western blot analysis, and flow cytometry. Cells treated with 0.1% ethanol (control for RvD2) and/or PBS (control for LPS), and control microRNA mimics and inhibitors were used as controls. RvD2 reduced LPS-induced cytokines and TLR4 expression in human monocytes by up to 75%. In THP-1 cells, RvD2 reduced expression of TLR4, lymphocyte antigen 96 (MD-2), and downstream signals (MyD88, TRIF, and TAK1). These effects were partially mediated through RvD2 induction of microRNA-146a, and RvD2's actions were blocked by microRNA-146a inhibition. These new findings reveal the ability of RvD2 to reduce TLR4 expression and attenuate LPS-induced inflammation, providing a new area of SPM activity to investigate in this major area of therapeutic research.-Croasdell, A., Sime, P. J., Phipps, R. P. Resolvin D2 decreases TLR4 expression to mediate resolution in human monocytes.

JNK-TLR9 signal pathway mediates allergic airway inflammation through suppressing melatonin biosynthesis

Toll-like receptors (TLRs) play pivotal role in the pathogenesis of allergic airway diseases such as asthma. TLR9 is one of the most extensively studied TLRs as an approach to treat asthma. In this study, we investigated the role of TLR9 in the allergic airway inflammation and the underlying mechanism. Wild-type (WT) mice and TLR9(-/-) mice were sensitized and challenged with OVA to establish allergic airway disease model. We found that the expression of TLR9 was elevated concomitantly with airway inflammation post-OVA challenge, and TLR9 deficiency effectively inhibited airway inflammation, including serum OVA-specific immunoglobulin E (IgE), pulmonary inflammatory cell recruitment, mucus secretion, and bronchoalveolar lavage fluid (BALF) inflammatory cytokine production. Meanwhile, the protein expression of hydroxyindole-o-methyltransferase (HIOMT) in lung tissues, the level of melatonin in serum, and BALF were reduced in OVA-challenged WT mice, while these reductions were significantly restored by TLR9 deficiency. Additionally, we showed that although TLR9 deficiency had no effect on OVA-induced phosphorylation of JNK, inhibition of JNK by specific inhibitor SP600125 significantly decreased OVA-induced expression of TLR9, suggesting that JNK is the upstream signal molecular of TLR9. Furthermore, SP600125 treatment promoted resolution of allergic airway inflammation in OVA-challenged WT mice, but not further ameliorated allergic airway inflammation in OVA-challenged TLR9(-/-) mice. Similarly, SP600125 significantly restored the protein expression of HIOMT and the level of melatonin in OVA-challenged WT mice, while such effect was not further enhanced by TLR9 deficiency. Collectively, our results indicated that JNK-TLR9 signal pathway mediates allergic airway inflammation through suppressing melatonin biosynthesis.