Specialized Proresolving Mediators in Innate and Adaptive Immune Responses in Airway Diseases

TRPV1: Receptor structure, activation, modulation and role in neuro-immune interactions and pain

In the 1990s, the identification of a non-selective ion channel, especially responsive to capsaicin, revolutionized the studies of somatosensation and pain that were to follow. The TRPV1 channel is expressed mainly in neuronal cells, more specifically, in sensory neurons responsible for the perception of noxious stimuli. However, its presence has also been detected in other non-neuronal cells, such as immune cells, β- pancreatic cells, muscle cells and adipocytes. Activation of the channel occurs in response to a wide range of stimuli, such as noxious heat, low pH, gasses, toxins, endocannabinoids, lipid-derived endovanilloid, and chemical agents, such as capsaicin and resiniferatoxin. This activation results in an influx of cations through the channel pore, especially calcium. Intracellular calcium triggers different responses in sensory neurons. Dephosphorylation of the TRPV1 channel leads to its desensitization, which disrupts its function, while its phosphorylation increases the channel's sensitization and contributes to the channel's rehabilitation after desensitization. Kinases, phosphoinositides, and calmodulin are the main signaling pathways responsible for the channel's regulation. Thus, in this review we provide an overview of TRPV1 discovery, its tissue expression as well as on the mechanisms by which TRPV1 activation (directly or indirectly) induces pain in different disease models.

The role of fatty acid metabolism in acute lung injury: a special focus on immunometabolism

Reputable evidence from multiple studies suggests that excessive and uncontrolled inflammation plays an indispensable role in mediating, amplifying, and protracting acute lung injury (ALI). Traditionally, immunity and energy metabolism are regarded as separate functions regulated by distinct mechanisms, but recently, more and more evidence show that immunity and energy metabolism exhibit a strong interaction which has given rise to an emerging field of immunometabolism. Mammalian lungs are organs with active fatty acid metabolism, however, during ALI, inflammation and oxidative stress lead to a series metabolic reprogramming such as impaired fatty acid oxidation, increased expression of proteins involved in fatty acid uptake and transport, enhanced synthesis of fatty acids, and accumulation of lipid droplets. In addition, obesity represents a significant risk factor for ALI/ARDS. Thus, we have further elucidated the mechanisms of obesity exacerbating ALI from the perspective of fatty acid metabolism. To sum up, this paper presents a systematical review of the relationship between extensive fatty acid metabolic pathways and acute lung injury and summarizes recent advances in understanding the involvement of fatty acid metabolism-related pathways in ALI. We hold an optimistic believe that targeting fatty acid metabolism pathway is a promising lung protection strategy, but the specific regulatory mechanisms are way too complex, necessitating further extensive and in-depth investigations in future studies.

RvD1 improves resident alveolar macrophage self-renewal via the ALX/MAPK14/S100A8/A9 pathway in acute respiratory distress syndrome

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is a pulmonary inflammatory process primarily caused by sepsis. The resolution of inflammation is an active process involving the endogenous biosynthesis of specialized pro-resolving mediators, including resolvin D1 (RvD1). Resident alveolar macrophages (RAMs) maintain pulmonary homeostasis and play a key role in the resolution phase. However, the role of RAMs in promoting the resolution of inflammation by RvD1 is unclear.

OBJECTIVES

Here, we investigated the mechanisms of RvD1 on regulating RAMs to promote the resolution of ARDS.

METHODS

Mice were administered lipopolysaccharide and/or Escherichia coli via aerosol inhalation to establish a self-limited ARDS model. Then, RvD1 was administered at the peak inflammatory response. RAMs self-renewal was measured by flow cytometry, RAM phagocytosis was measured by two-photon fluorescence imaging. In addition, plasma was collected from intensive care unit patients on days 0-2, 3-5, and 6-9 to measure RvD1 and S100A8/A9 levels using triple quadrupole/linear ion trap mass spectrometry.

RESULTS

RAMs were found to play a pivotal role in resolving inflammation during ARDS, and RvD1 enhanced RAM proliferation and phagocytosis, which was abrogated by a lipoxin A4 receptor (ALX, RvD1 receptor) inhibitor. Both primary RAMs transfected with rS100A8/A9 and/or S100A8/A9 siRNA and S100A9-/- mice (also deficient in S100A8 function) showed higher turnover and phagocytic function, indicating that RvD1 exerted its effects on RAMs by inhibiting S100A8/A9 production in the resolution phase. RvD1 reduced S100A8/A9 and its upstream MAPK14 levels in vivo and in vitro. Finally, in the patients, RvD1 levels were lower, but S100A8/A9 levels were higher.

CONCLUSIONS

We propose that RvD1 improved RAM self-renewal and phagocytosis via the ALX/MAPK14/S100A8/A9 signaling pathway. Plasma RvD1 and S100A8/A9 levels were negatively correlated, and associated with the outcome of sepsis-induced ARDS.

Efficient pulmonary lymphatic drainage is necessary for inflammation resolution in ARDS

The lymphatic vasculature is the natural pathway for the resolution of inflammation, yet the role of pulmonary lymphatic drainage function in sepsis-induced acute respiratory distress syndrome (ARDS) remains poorly characterized. In this study, indocyanine green-near infrared lymphatic living imaging was performed to examine pulmonary lymphatic drainage function in septic mouse models. We found that the pulmonary lymphatic drainage was impaired owing to the damaged lymphatic structure in sepsis-induced ARDS. Moreover, prior lymphatic defects by blocking vascular endothelial growth factor receptor-3 (VEGFR-3) worsened sepsis-induced lymphatic dysfunction and inflammation. Posttreatment with vascular endothelial growth factor-C (Cys156Ser) (VEGF-C156S), a ligand of VEGFR-3, ameliorated lymphatic drainage by rejuvenating lymphatics to reduce the pulmonary edema and promote draining of pulmonary macrophages and neutrophils to pretracheal lymph nodes. Meanwhile, VEGF-C156S posttreatment reversed sepsis-inhibited CC chemokine ligand 21 (CCL21), which colocalizes with pulmonary lymphatic vessels. Furthermore, the advantages of VEGF-C156S on the drainage of inflammatory cells and edema fluid were abolished by blocking VEGFR-3 or CCL21. These results suggest that efficient pulmonary lymphatic drainage is necessary for inflammation resolution in ARDS. Our findings offer a therapeutic approach to sepsis-induced ARDS by promoting lymphatic drainage function.

Biomimetic Nanocarriers of Pro-Resolving Lipid Mediators for Resolution of Inflammation in Atherosclerosis

Atherosclerosis (ATH) is a systemic disease characterized by a chronic inflammatory process and lipid deposition in the arterial walls. The chronic inflammation within ATH lesions results, at least in part, from the failed resolution of inflammation. This process is controlled actively by specialized pro-resolving lipid mediators (SPMs), namely lipoxins, resolvins, protectins, and maresins. Herein, biomimetic nanocarriers are produced comprising a cocktail of SPMs-loaded lipid nanoemulsions (LN) covered with macrophage membranes (Bio-LN/SPMs). Bio-LN/SPMs retain on their surface the macrophage receptors involved in cellular interactions and the "marker of self" CD47, which impede their recognition and uptake by other macrophages. The binding of Bio-LN/SPMs to the surface of endothelial cells (EC) and smooth muscle cells (SMC) is facilitated by the receptors on the macrophage membranes and partly by SPMs receptors. In addition, Bio-LN/SPMs prove functional by reducing monocyte adhesion and transmigration to/through activated EC and by stimulating macrophage phagocytic activity. After intravenous administration, Bio-LN/SPMs accumulate in the aorta of ApoE-deficient mice at the level of atherosclerotic lesions. Also, the safety assessment testing reveals no side effects or immunotoxicity of Bio-LN/SPMs. Thus, the newly developed Bio-LN/SPMs represent a reliable targeted nanomedicine for the resolution of inflammation in atherosclerosis.

Eosinophil Phenotypes Are Functionally Regulated by Resolvin D2 during Allergic Lung Inflammation

Eosinophils (Eos) reside in multiple organs during homeostasis and respond rapidly to an inflammatory challenge. Although Eos share chemical staining properties, they also demonstrate phenotypic and functional plasticity that is not fully understood. Here, we used a murine model of allergic lung inflammation to characterize Eos subsets and determine their spatiotemporal and functional regulation during inflammation and its resolution in response to resolvin D2 (RvD2), a potent specialized proresolving mediator. Two Eos subsets were identified by CD101 expression with distinct anatomic localization and transcriptional signatures at baseline and during inflammation. CD101low Eos were predominantly located in a lung vascular niche and responded to allergen challenge by moving into the lung interstitium. CD101high Eos were predominantly located in bronchoalveolar lavage (BAL) and extravascular lung, only present during inflammation, and had transcriptional evidence for cell activation. RvD2 reduced total Eos numbers and changed their phenotype and activation by at least two distinct mechanisms: decreasing interleukin 5-dependent recruitment of CD101low Eos and decreasing conversion of CD101low Eos to CD101high Eos. Collectively, these findings indicate that Eos are a heterogeneous pool of cells with distinct activation states and spatiotemporal regulation during resolution of inflammation and that RvD2 is a potent proresolving mediator for Eos recruitment and activation.

Imbalanced serum levels of resolvin E1 (RvE1) and leukotriene B4 (LTB4) may contribute to the pathogenesis of atherosclerosis

Persistent and chronic unresolved inflammation exerts a critical role in developing atherosclerosis; however, mechanisms that prevent the resolution of inflammation in atherosclerosis are poorly delineated. This study aims to evaluate the serum levels of inflammatory high-sensitivity C-reactive protein (hsCRP), pro-inflammatory leukotriene B4 (LTB4), besides anti-inflammatory compounds, including eicosapentaenoic acid (EPA) and its derivative resolvin E1 (RvE1) in patients with atherosclerosis. Thirty-four atherosclerosis patients and thirty-two age- and sex-matched healthy individuals were included in this study. The serum levels of hsCRP, LTB4, EPA, and RvE1 were measured using the enzyme-linked immunosorbent assay (ELISA) technique. Our results showed that the hsCRP serum levels in the three-vessel disease (3VD) subgroup of patients are significantly lower than those in the mild and single-vessel disease (SVD) subgroups (P < 0.05). Besides, the serum levels of LTB4 were meaningfully greater in patients with atherosclerosis compared to healthy controls (P < 0.05). Also, the serum EPA and RvE1 levels were significantly higher in patients than in controls (P < 0.01 and P < 0.05, respectively). However, the ratio of RvE1 to LTB4 (RvE1:LTB4) in patients was significantly reduced to that in controls (P < 0.0001). These findings illustrate that imbalanced pro-resolving RvE1 and pro-inflammatory LTB4 might contribute to failing vascular inflammation resolution and subsequent progression toward chronic inflammation in atherosclerosis.

Prolonged experimental sleep disturbance affects the inflammatory resolution pathways in healthy humans

BACKGROUND

Sleep disturbances, as manifested in insomnia symptoms of difficulties falling asleep or frequent nighttime awakenings, are a strong risk factor for a diverse range of diseases involving immunopathology. Low-grade systemic inflammation has been frequently found associated with sleep disturbances and may mechanistically contribute to increased disease risk. Effects of sleep disturbances on inflammation have been observed to be long lasting and remain after recovery sleep has been obtained, suggesting that sleep disturbances may not only affect inflammatory mediators, but also the so-called specialized pro-resolving mediators (SPMs) that actively resolve inflammation. The goal of this investigation was to test for the first time whether the omega-3 fatty acid-derived D- (RvD) and E-series (RvE) resolvins are impacted by prolonged experimental sleep disturbance (ESD).

METHODS

Twenty-four healthy participants (12 F, age 20-42 years) underwent two 19-day in-hospital protocols (ESD/control), separated by > 2 months. The ESD protocol consisted of repeated nights of short and disrupted sleep with intermittent nights of undisturbed sleep, followed by three nights of recovery sleep at the end of the protocol. Under the control sleep condition, participants had an undisturbed sleep opportunity of 8 h/night throughout the protocol. The D- and E-series resolvins were measured in plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

The precursor of the D-series resolvins, 17-HDHA, was downregulated in the ESD compared to the control sleep condition (p <.001 for condition), and this effect remained after the third night of recovery sleep has been obtained. This effect was also observed for the resolvins RvD3, RvD4, and RvD5 (p <.001 for condition), while RvD1 was higher in the ESD compared to the control sleep condition (p <.01 for condition) and RvD2 showed a mixed effect of a decrease during disturbed sleep followed by an increase during recovery sleep in the ESD condition (p <.001 for condition*day interaction). The precursor of E-series resolvins, 18-HEPE, was downregulated in the ESD compared to the control sleep condition (p <.01 for condition) and remained low after recovery sleep has been obtained. This effect of downregulation was also observed for RvE2 (p <.01 for condition), while there was no effect for RvE1 (p >.05 for condition or condition*day interaction). Sex-differential effects were found for two of the D-series resolvins, i.e., RvD2 and RvD4.

CONCLUSION

This first investigation on the effects of experimental sleep disturbance on inflammatory resolution processes shows that SPMs, particularly resolvins of the D-series, are profoundly downregulated by sleep disturbances and remain downregulated after recovery sleep has been obtained, suggesting a longer lasting impact of sleep disturbances on these mediators. These findings also suggest that sleep disturbances contribute to the development and progression of a wide range of diseases characterized by immunopathology by interfering with processes that actively resolve inflammation. Pharmacological interventions aimed at promoting inflammatory resolution physiology may help to prevent future disease risk as a common consequence of sleep disturbances.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02484742.

Respiratory viral infection and resolution of inflammation: Roles for specialized pro-resolving mediators

Respiratory viral infections with influenza A virus (IAV) or respiratory syncytial virus (RSV) pose a significant threat to public health due to excess morbidity and mortality. Dysregulated and excessive inflammatory responses are major underlying causes of viral pneumonia severity and morbidity, including aberrant host immune responses and increased risk for secondary bacterial infections. Currently available antiviral therapies have not substantially reduced the risk of severe viral pneumonia for these pathogens. Thus, new therapeutic approaches that can promote resolution of the pathogen-initiated inflammation without impairing host defense would represent a significant advance. Recent research has uncovered the potential for specialized pro-resolving mediators (SPMs) to transduce multipronged actions for the resolution of serious respiratory viral infection without increased risk for subsequent host susceptibility to bacterial infection. Here, we review recent advances in our understanding of SPM production and SPM receptor signaling in respiratory virus infections and the intriguing potential of harnessing SPM pathways to control excess morbidity and mortality from IAV and RSV pneumonia.

Air Pollution and Diet: Potential Interacting Exposures in Asthma

PURPOSE OF REVIEW

To provide a review of emerging literature describing the impact of diet on the respiratory response to air pollution in asthma.

RECENT FINDINGS

Asthma phenotyping (observable characteristics) and endotyping (mechanistic pathways) have increased the specificity of diagnostic and treatment pathways and opened the doors to the identification of subphenotypes with enhanced susceptibility to exposures and interventions. Mechanisms underlying the airway immune response to air pollution are still being defined but include oxidative stress, inflammation, and activation of adaptive and innate immune responses, with genetic susceptibility highlighted. Of these, neutrophil recruitment and activation appear prominent; however, understanding neutrophil function in response to pollutant exposures is a research gap. Diet may play a role in asthma pathogenesis and morbidity; therefore, diet modification is a potential target opportunity to protect against pollutant-induced lung injury. In particular, in vivo and in vitro data suggest the potential for diet to modify the inflammatory response in the airways, including impacts on neutrophil recruitment and function. Murine models provide compelling results in regard to the potential for dietary components (including fiber, antioxidants, and omega-3 fatty acids) to buffer against the inflammatory response to air pollution in the lung. Precision lifestyle approaches to asthma management and respiratory protection in the context of air pollution exposures may evolve to include diet, pending the results of further epidemiologic and causal investigation and with neutrophil recruitment and activation as a candidate mechanism.

The Emerging Role of Ferroptosis in Sepsis, Opportunity or Challenge?

Sepsis is a syndrome in multi-organ dysfunction triggered by a deleterious immunological reaction of the body to a condition caused by infection, surgery, or trauma. Currently, sepsis is thought to be primarily associated with abnormal immune responses resulting in organ microcirculatory disturbances, cellular mitochondrial dysfunction, and induced cell death, although the exact pathogenesis of sepsis is still inconclusive. In recent years, the role of abnormal metabolism of trace nutrients in the pathogenesis of sepsis has been investigated. Ferroptosis is a type of cell death that relies on iron and is characterized by unique morphological, biochemical, and genetic features. Unlike other forms of cell death, such as autophagy, apoptosis, necrosis, and pyroptosis, ferroptosis is primarily driven by lipid peroxidation. Ferroptosis cells may be immunogenic, amplify inflammatory responses, cause more cell death, and ultimately induce multi-organ failure. An increasing number of studies have indicated the significance of ferroptosis in sepsis and its role in reducing inflammation. The effectiveness of sepsis treatment has been demonstrated by the use of drugs that specifically target molecules associated with the ferroptosis pathway, including ferroptosis inhibitors. Nevertheless, there is a scarcity of studies investigating the multi-organ dysfunction caused by ferroptosis in sepsis. This article presents a summary and evaluation of recent progress in the role of ferroptosis through molecularly regulated mechanisms and its potential mechanisms of action in the multi-organ dysfunction associated with sepsis. It also discusses the current challenges and prospects in understanding the connection between sepsis and ferroptosis, and proposes innovative ideas and strategies for the treatment of sepsis.

The Role of Specialized Pro-Resolving Lipid Mediators in Inflammation-Induced Carcinogenesis

Cancer is a process involving cell mutation, increased proliferation, invasion, and metastasis. Over the years, this condition has represented one of the most concerning health problems worldwide due to its significant morbidity and mortality. At present, the incidence of cancer continues to grow exponentially. Thus, it is imperative to open new avenues in cancer research to understand the molecular changes driving DNA transformation, cell-to-cell interaction derangements, and immune system surveillance decay. In this regard, evidence supports the relationship between chronic inflammation and cancer. In light of this, a group of bioactive lipids derived from polyunsaturated fatty acids (PUFAs) may have a position as novel anti-inflammatory molecules known as the specialized pro-resolving mediators (SPMs), a group of pro-resolutive inflammation agents that could improve the anti-tumor immunity. These molecules have the potential role of chemopreventive and therapeutic agents for various cancer types, and their effects have been documented in the scientific literature. Thus, this review objective centers around understanding the effect of SPMs on carcinogenesis and their potential therapeutic effect.

Specialized Pro-Resolving Lipid Mediators: Endogenous Roles and Pharmacological Activities in Infections

During an infection, inflammation mobilizes immune cells to eliminate the pathogen and protect the host. However, inflammation can be detrimental when exacerbated and/or chronic. The resolution phase of the inflammatory process is actively orchestrated by the specialized pro-resolving lipid mediators (SPMs), generated from omega-3 and -6 polyunsaturated fatty acids (PUFAs) that bind to different G-protein coupled receptors to exert their activity. As immunoresolvents, SPMs regulate the influx of leukocytes to the inflammatory site, reduce cytokine and chemokine levels, promote bacterial clearance, inhibit the export of viral transcripts, enhance efferocytosis, stimulate tissue healing, and lower antibiotic requirements. Metabolomic studies have evaluated SPM levels in patients and animals during infection, and temporal regulation of SPMs seems to be essential to properly coordinate a response against the microorganism. In this review, we summarize the current knowledge on SPM biosynthesis and classifications, endogenous production profiles and their effects in animal models of bacterial, viral and parasitic infections.

Plasma metabolic profiling implicates dysregulated lipid metabolism and glycolytic shift in hyperinflammatory ARDS

Using latent class analysis (LCA) of clinical and protein biomarkers, researchers have identified two phenotypes of the acute respiratory distress syndrome (ARDS) with divergent clinical trajectories and treatment responses. We investigated whether plasma metabolites differed among patients with LCA-derived hyperinflammatory and hypoinflammatory ARDS, and we tested the prognostic utility of adding metabolic clusters to LCA phenotypes. We analyzed data from 93 patients with ARDS and sepsis enrolled in a multicenter prospective cohort of critically ill patients, comparing 970 metabolites between the two LCA-derived phenotypes. In all, 188 metabolites were differentially abundant between the two LCA-derived phenotypes. After adjusting for age, sex, confounding medications, and comorbid liver and kidney disease, 82 metabolites remained significantly different. Patients with hyperinflammatory ARDS had reduced circulating lipids but high levels of pyruvate, lactate, and malate. Metabolic cluster and LCA-derived phenotypes were each significantly and independently associated with survival. Patients with hyperinflammatory ARDS may be experiencing a glycolytic shift leading to dysregulated lipid metabolism. Metabolic profiling offers prognostic information beyond what is captured by LCA phenotypes alone. Deeper biological profiling may identify key differences in pathogenesis among patients with ARDS and may lead to novel targeted therapies.

Possibility of averting cytokine storm in SARS-COV 2 patients using specialized pro-resolving lipid mediators

Fatal "cytokine storms (CS)" observed in critically ill COVID-19 patients are consequences of dysregulated host immune system and over-exuberant inflammatory response. Acute respiratory distress syndrome (ARDS), multi-system organ failure, and eventual death are distinctive symptoms, attributed to higher morbidity and mortality rates among these patients. Consequent efforts to save critical COVID-19 patients via the usage of several novel therapeutic options are put in force. Strategically, drugs being used in such patients are dexamethasone, remdesivir, hydroxychloroquine, etc. along with the approved vaccines. Moreover, it is certain that activation of the resolution process is important for the prevention of chronic diseases. Until recently Inflammation resolution was considered a passive process, rather it's an active biochemical process that can be achieved by the use of specialized pro-resolving mediators (SPMs). These endogenous mediators are an array of atypical lipid metabolites that include Resolvins, lipoxins, maresins, protectins, considered as immunoresolvents, but their role in COVID-19 is ambiguous. Recent evidence from studies such as the randomized clinical trial, in which omega 3 fatty acid was used as supplement to resolve inflammation in COVID-19, suggests that direct supplementation of SPMs or the use of synthetic SPM mimetics (which are still being explored) could enhance the process of resolution by regulating the aberrant inflammatory process and can be useful in pain relief and tissue remodeling. Here we discussed the biosynthesis of SPMs, & their mechanistic pathways contributing to inflammation resolution along with sequence of events leading to CS in COVID-19, with a focus on therapeutic potential of SPMs.

The Maresin 1-LGR6 axis decreases respiratory syncytial virus-induced lung inflammation

The resolution of infection is an active process with specific molecular and cellular mechanisms that temper inflammation and enhance pathogen clearance. Here, the specialized pro-resolving mediator (SPM) Maresin 1 (MaR1) inhibited respiratory syncytial virus (RSV)-induced inflammation. inlerleukin-13 production from type 2 innate lymphoid cells (ILC) and CD4 T helper type 2 cells was decreased by exogenous MaR1. In addition, MaR1 increased amphiregulin production and decreased RSV viral transcripts to promote resolution. MaR1 also promoted interferon-β production in mouse lung tissues and also in pediatric lung slices. MaR1 significantly inhibited the RSV-triggered aberrant inflammatory phenotype in FoxP3-expressing Tregs. The receptor for MaR1, leucine-rich repeat-containing G protein-coupled receptor 6 (LGR6), was constitutively expressed on Tregs. Following RSV infection, mice lacking Lgr6 had exacerbated type 2 immune responses with an increased viral burden and blunted responses to MaR1. Together, these findings have uncovered a multi-pronged protective signaling axis for MaR1-Lgr6, improving Tregs's suppressive function and upregulating host antiviral genes resulting in decreased viral burden and pathogen-mediated inflammation, ultimately promoting restoration of airway mucosal homeostasis.

Resolution Potential of Necrotic Cell Death Pathways

During tissue damage caused by infection or sterile inflammation, not only damage-associated molecular patterns (DAMPs), but also resolution-associated molecular patterns (RAMPs) can be activated. These dying cell-associated factors stimulate immune cells localized in the tissue environment and induce the production of inflammatory mediators or specialized proresolving mediators (SPMs). Within the current prospect of science, apoptotic cell death is considered the main initiator of resolution. However, more RAMPs are likely to be released during necrotic cell death than during apoptosis, similar to what has been observed for DAMPs. The inflammatory potential of many regulated forms of necrotic cell death modalities, such as pyroptosis, necroptosis, ferroptosis, netosis, and parthanatos, have been widely studied in necroinflammation, but their possible role in resolution is less considered. In this review, we aim to summarize the relationship between necrotic cell death and resolution, as well as present the current available data regarding the involvement of certain forms of regulated necrotic cell death in necroresolution.

Interferon-β regulates proresolving lipids to promote the resolution of acute airway inflammation

Acute respiratory distress syndrome is characterized by aberrant inflammatory responses, including polymorphonuclear neutrophil granulocyte dysfunction and hyperactive Toll-like receptor signaling. Timely resolution of bacterial infections depends on efficient removal of neutrophils from the inflamed tissue. Here we show that the antiviral cytokine interferon-β is essential for the resolution of neutrophil-driven airway inflammation by countering Toll-like receptor 9–mediated suppression of phagocytosis, neutrophil apoptosis, and uptake by macrophages. We also report that the beneficial effects of interferon-β are, in part, mediated by production of proresolving lipid mediators, such as 15-epi-lipoxin A₄ and resolvin D1, which act through the lipoxin receptor ALX/FPR2. These findings uncover an interferon-β–initiated ALX/FPR2-centered resolution program as a potential target for facilitating the resolution of airway inflammation.

Aberrant immune responses, including hyperresponsiveness to Toll-like receptor (TLR) ligands, underlie acute respiratory distress syndrome (ARDS). Type I interferons confer antiviral activities and could also regulate the inflammatory response, whereas little is known about their actions to resolve aberrant inflammation. Here we report that interferon-β (IFN-β) exerts partially overlapping, but also cooperative actions with aspirin-triggered 15-epi-lipoxin A₄ (15-epi-LXA₄) and 17-epi-resolvin D1 to counter TLR9-generated cues to regulate neutrophil apoptosis and phagocytosis in human neutrophils. In mice, TLR9 activation impairs bacterial clearance, prolongs Escherichia coli–evoked lung injury, and suppresses production of IFN-β and the proresolving lipid mediators 15-epi-LXA₄ and resolvin D1 (RvD1) in the lung. Neutralization of endogenous IFN-β delays pulmonary clearance of E. coli and aggravates mucosal injury. Conversely, treatment of mice with IFN-β accelerates clearance of bacteria, restores neutrophil phagocytosis, promotes neutrophil apoptosis and efferocytosis, and accelerates resolution of airway inflammation with concomitant increases in 15-epi-LXA₄ and RvD1 production in the lungs. Pharmacological blockade of the lipoxin receptor ALX/FPR2 partially prevents IFN-β–mediated resolution. These findings point to a pivotal role of IFN-β in orchestrating timely resolution of neutrophil and TLR9 activation–driven airway inflammation and uncover an IFN-β–initiated resolution program, activation of an ALX/FPR2-centered, proresolving lipids-mediated circuit, for ARDS.

Effects of statins on specialized pro-resolving mediators: An additional pathway leading to resolution of inflammation

Statins are a class of cholesterol-lowering drugs that inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Anti-inflammatory and antioxidant properties, as well as improvement of endothelial function and plaque stabilization have also been proposed as parts of the pleiotropic effects of statins. Specialized pro-resolving mediators (SPMs) are endogenous lipid-derived molecules originating from ω-6 and ω-3 polyunsaturated fatty acids, such as arachidonic, docosahexaenoic and eicosapentaenoic acid that trigger and modulate the resolution of inflammation. Impaired SPM biosynthesis can lead to excessive or chronic inflammation and is implicated in the pathogenesis of several diseases. Exogenous administration of SPMs, including lipoxin, maresin, protectin, have been shown to improve both bacterial and viral infections, mainly in preclinical models, thus minimizing inflammation. Statin-triggered-SPM production in several in vitro and in vivo models may represent another anti-inflammatory pathway involving these drugs. This commentary discusses scientific publications on the effects of statins on SPMs and the resolution of inflammation process.

Inverse Association between Omega-3 Index and Severity of COVID-19: A Case-Control Study

Background: Omega-3 fatty acids enhance immune response and modulate inflammation. This study aimed to determine the relationship between omega-3 fatty acid status and the severity of SARS-CoV-2 infection. Methods: Using a case−control design, we compared hospitalized patients with severe SARS-CoV-2 infection (cases, n = 73) with a group of ambulatory patients with mild SARS-CoV-2 infection (controls, n = 71). No patients were vaccinated against SARS-CoV-2. Results: The cases were older (p = 0.003), less educated (p = 0.001), had larger neck and smaller waist circumferences (p = 0.035 and p = 0.003, respectively), more frequently had diabetes (p < 0.001), consumed less fish (p < 0.001), consumed higher proportions of fried fish (p = 0.001), and had lower Omega-3 Index (O3I) values (p = 0.001) than controls. Cases had significantly lower rates of upper airway symptoms than controls. Lower O3I was associated with an increased likelihood of developing severe COVID-19 after adjusting for potential confounders (OR: 0.52; CI 0.32−0.86). Diabetes (OR: 4.41; CI 1.60−12.12), neck circumference (OR: 1.12; CI 1.03−1.21), and older age (OR: 1.03; CI 1.002−1.062) were also linked to COVID-19 severity. Fried fish consumption and low educational level were independent risk factors for severe COVID-19. Conclusions: This study suggests incorporating nutritional interventions to improve omega-3 status within nonpharmacological measures may help to reduce the severity of COVID-19.

The Role of Defective Epithelial Barriers in Allergic Lung Disease and Asthma Development

The respiratory epithelium constitutes the physical barrier between the human body and the environment, thus providing functional and immunological protection. It is often exposed to allergens, microbial substances, pathogens, pollutants, and environmental toxins, which lead to dysregulation of the epithelial barrier and result in the chronic inflammation seen in allergic diseases and asthma. This epithelial barrier dysfunction results from the disturbed tight junction formation, which are multi-protein subunits that promote cell-cell adhesion and barrier integrity. The increasing interest and evidence of the role of impaired epithelial barrier function in allergy and asthma highlight the need for innovative approaches that can provide new knowledge in this area. Here, we review and discuss the current role and mechanism of epithelial barrier dysfunction in developing allergic diseases and the effect of current allergy therapies on epithelial barrier restoration.

Potential of Omega 3 Supplementation for Coronavirus Disease 2019 (COVID-19): A Scoping Review

COVID-19 can cause fever, cough, headache, and shortness of breath but patients with comorbidities can experience worsening and death. An action is needed to treat this condition in COVID-19 patients. Omega 3 fatty acids may be one possibility associated with COVID-19 prevention, management, and treatment. Therefore, this review aimed to identify the existing studies on potency of omega 3 fatty acid supplementation on COVID-19. We searched studies from PubMed, Google Scholar, Springer Link, and Emerald Insight databases published on January 31, 2020, to September 1, 2021. The studies selected were the full-text, non-review ones which focused on the omega 3 fatty acid intervention in COVID-19 with COVID-19 patients and people affected by COVID-19 as their subjects and clinical manifestations or the results of supporting examinations as their outcomes. No quality assessment was performed in this review. Of the 211, there were 4 studies selected for this review. They showed that severe COVID-19 patients have low levels of omega 3 in their blood. Omega 3 was considered to reduce the risk of positive for SARS-CoV-infection and the duration of symptoms, overcome the renal and respiratory dysfunction, and increase survival rate in COVID-19 patients. Omega 3 fatty acid supplementations were thought to have a potential effect in preventing and treating COVID-19. This can be a reference for further research about omega 3 fatty acid supplementation and COVID-19.

The function of specialized pro-resolving endogenous lipid mediators, vitamins, and other micronutrients in the control of the inflammatory processes: Possible role in patients with SARS-CoV-2 related infection

Inflammation is an essential protective response against harmful stimuli, such as invading pathogens, damaged cells, or irritants. Physiological inflammation eliminates pathogens and promotes tissue repair and healing. Effective immune response in humans depends on a tightly regulated balance among inflammatory and anti-inflammatory mechanisms involving both innate and adaptive arms of the immune system. Excessive inflammation can become pathological and induce detrimental effects. If this process is not self-limited, an inappropriate remodeling of the tissues and organs can occur and lead to the onset of chronic degenerative diseases. A wide spectrum of infectious and non-infectious agents may activate the inflammation, via the release of mediators and cytokines by distinct subtypes of lymphocytes and macrophages. Several molecular mechanisms regulate the onset, progression, and resolution of inflammation. All these steps, even the termination of this process, are active and not passive events. In particular, a complex interplay exists between mediators (belonging to the group of Eicosanoids), which induce the beginning of inflammation, such as Prostaglandins (PGE2), Leukotrienes (LT), and thromboxane A2 (TXA2), and molecules which display a key role in counteracting this process and in promoting its proper resolution. The latter group of mediators includes: ω-6 arachidonic acid (AA)-derived metabolites, such as Lipoxins (LXs), ω -3 eicosapentaenoic acid (EPA)-derived mediators, such as E-series Resolvins (RvEs), and ω -3 docosahexaenoic (DHA)-derived mediators, such as D-series Resolvins (RvDs), Protectins (PDs) and Maresins (MaRs). Overall, these mediators are defined as specialized pro-resolving mediators (SPMs). Reduced synthesis of these molecules may lead to uncontrolled inflammation with possible harmful effects. ω-3 fatty acids are widely used in clinical practice as rather inexpensive, safe, readily available supplemental therapy. Taking advantage of this evidence, several researchers are suggesting that SPMs may have beneficial effects in the complementary treatment of patients with severe forms of SARS-CoV-2 related infection, to counteract the "cytokine storm" observed in these individuals. Well-designed and sized trials in patients suffering from COVID-19 with different degrees of severity are needed to investigate the real impact in the clinical practice of this promising therapeutic approach.

Interconnections between Inflammageing and Immunosenescence during Ageing

Acute inflammation is a physiological response to injury or infection, with a cascade of steps that ultimately lead to the recruitment of immune cells to clear invading pathogens and heal wounds. However, chronic inflammation arising from the continued presence of the initial trigger, or the dysfunction of signalling and/or effector pathways, is harmful to health. While successful ageing in older adults, including centenarians, is associated with low levels of inflammation, elevated inflammation increases the risk of poor health and death. Hence inflammation has been described as one of seven pillars of ageing. Age-associated sterile, chronic, and low-grade inflammation is commonly termed inflammageing-it is not simply a consequence of increasing chronological age, but is also a marker of biological ageing, multimorbidity, and mortality risk. While inflammageing was initially thought to be caused by "continuous antigenic load and stress", reports from the last two decades describe a much more complex phenomenon also involving cellular senescence and the ageing of the immune system. In this review, we explore some of the main sources and consequences of inflammageing in the context of immunosenescence and highlight potential interventions. In particular, we assess the contribution of cellular senescence to age-associated inflammation, identify patterns of pro- and anti-inflammatory markers characteristic of inflammageing, describe alterations in the ageing immune system that lead to elevated inflammation, and finally assess the ways that diet, exercise, and pharmacological interventions can reduce inflammageing and thus, improve later life health.

Non-Specific Targets for Correction of Pneumonia Caused by Aerosols Containing Damaging Factors of Various Nature

This review article provides data on the current state of the pathogenesis peculiarities of body and lung inflammation (pneumonia) under the influence of damaging factors of various nature: infectious agents, chemical toxicants, as well as incorporated radionuclides, etc. The peculiarities of inflammation itself, as a typical pathological process, are considered. Information on mediators that induce the so-called pro-resolving phase of inflammation manifestations is given. Approaches to the neuroimmune correction of non-specific inflammation are substantiated. Data on the following alternative approaches to the correction of nonspecific inflammation are summarized: factors of the coagulation system, modulators of the integrated stress response, and modulators of sigma-1 receptors. Based on the data presented, general directions for the treatment of nonspecific pneumonia are formulated, including reflexogenic and anti-inflammatory therapy in combination with multimodal drugs, as well as pro-resolving therapy in combination with drugs that prevent fibrosis.

Nature of the Interplay Between Periodontal Diseases and COVID-19

The coronavirus disease 2019 (COVID-19) is mostly a mild condition, however, in some patients, it could progress into a severe and even fatal disease. Recent studies have shown that COVID-19 infection and severity could be associated with the presence of periodontitis, one of the most prevalent chronic diseases. This association could be explained by the fact that periodontitis and COVID-19 share some common risk factors that included chronic diseases, such as diabetes and hypertension as well as conditions such as age, sex, and genetic variants. Another possible explanation could be the systemic inflammation and the aspiration of periodontopathogens seen in patients with periodontitis, which could have a synergism with the virus or compromise the reaction of the body against COVID-19. This narrative review explores the nature of these associations, the evidence behind them, and their implications.

Resolvin Conjugates in Tissue Regeneration 1 Promote Alveolar Fluid Clearance by Activating Alveolar Epithelial Sodium Channels and Na, K-ATPase in Lipopolysaccharide-Induced Acute Lung Injury

Acute respiratory distress syndrome (ARDS), a common and fatal clinical condition, is characterized by the destruction of epithelium and augmented permeability of the alveolar-capillary barrier. Resolvin conjugates in tissue regeneration 1 (RCTR1) is an endogenous lipid mediator derived from docosahexaenoic acid , exerting proresolution effects in the process of inflammation. In our research, we evaluated the role of RCTR1 in alveolar fluid clearance (AFC) in lipopolysaccharide-induced ARDS/acute lung injury (ALI) rat model. Rats were injected with RCTR1 (5 μg/kg) via caudal veins 8 hours after lipopolysaccharide (LPS) (14 mg/kg) treatment, and then AFC was estimated after 1 hour of ventilation. Primary type II alveolar epithelial cells were incubated with LPS (1 ug/ml) with or without RCTR1 (10 nM) for 8 hours. Our results showed that RCTR1 significantly enhanced the survival rate, promoted the AFC, and alleviated LPS-induced ARDS/ALI in vivo. Furthermore, RCTR1 remarkably elevated the protein expression of sodium channels and Na, K-ATPase and the activity of Na, K-ATPase in vivo and in vitro. Additionally, RCTR1 also decreased neural precursor cell expressed developmentally downregulated 4-2 (Nedd4-2) level via upregulating Ser⁴⁷³-phosphorylated-Akt expression. Besides this, inhibitors of receptor for lipoxin A4 (ALX), cAMP, and phosphatidylinositol 3-kinase (PI3K) (BOC-2, KH-7, and LY294002) notably inhibited the effects of RCTR1 on AFC. In summary, RCTR1 enhances the protein levels of sodium channels and Na, K-ATPase and the Na, K-ATPase activity to improve AFC in ALI through ALX/cAMP/PI3K/Nedd4-2 pathway, suggesting that RCTR1 may become a therapeutic drug for ARDS/ALI. SIGNIFICANCE STATEMENT: RCTR1, an endogenous lipid mediator, enhanced the rate of AFC to accelerate the resolution of inflammation in the LPS-induced murine lung injury model. RCTR1 upregulates the expression of epithelial sodium channels (ENaCs) and Na, K-ATPase in vivo and in vitro to accelerate the AFC. The efficacy of RCTR1 on the ENaC and Na, K-ATPase level was in an ALX/cAMP/PI3K/Nedd4-2-dependent manner.

Regulation of Neutrophil Function by Marine n-3 Fatty Acids-A Mini Review

While normal functioning neutrophils contribute in various, critical ways to the maintenance of a stable immune system, their hypo- or hyper-activation has been implicated in the onset or exacerbation of multiple inflammatory conditions often affecting the vulnerable, aging population. As such, many would benefit from interventions capable of targeting neutrophils in disease-specific ways without disrupting their primary role in maintaining immune function. After consumption, marine omega-3 fatty acids are rapidly incorporated into the phospholipid bilayer of neutrophils, changing the fatty acid composition and consequently modifying neutrophil function. In addition to eicosanoid synthesis, the mechanisms by which marine n-3 fatty acids and their metabolites alter neutrophil function involve blockage of transcription factors that subsequently reduce pro-inflammatory gene expression by neutrophils and through the disruption of lipid rafts. In the current mini-review, a brief explanation of marine n-3 fatty acid metabolism is provided and the subsequent impact on neutrophil function is discussed. In addition, current evidence of the effects of marine n-3 fatty acid supplementation on neutrophil function from clinical trials conducted in the past 15 years is summarized.

Lipid-Derived Mediators are Pivotal to Leukocyte and Lung Cell Responses in Sepsis and ARDS

Acute inflammation in the lung is essential for host defense against pathogens and other injuries but chronic or excessive inflammation can contribute to several common respiratory diseases. In health, the inflammatory response is controlled by several cellular and molecular mechanisms. In addition to anti-inflammatory processes, there are non-phlogistic pro-resolving mechanisms that are engaged to promote the resolution of inflammation and a return to homeostasis. Defects in the production or actions of specialized pro-resolving mediators are associated with diseases characterized by excess or chronic inflammation. In this article, we review cellular and biochemical mechanisms for specialized pro-resolving mediators in health and in sepsis and the acute respiratory distress syndrome as examples of unrestrained inflammatory responses that result in life-threatening pathology. We are honored to contribute to this special edition of the Journal to help celebrate Professor Viswanathan Natarajan's contributions to our understanding of lipid-derived mediators and metabolism in lung cell responses to inflammatory, infectious, or mechanical insults; his foundational discoveries in cell biochemistry and biophysics are continuing to catalyze further advances by the field to uncover the mechanistic underpinnings of important human diseases.

Protectins PCTR1 and PD1 Reduce Viral Load and Lung Inflammation During Respiratory Syncytial Virus Infection in Mice

Viral pneumonias are a major cause of morbidity and mortality, owing in part to dysregulated excessive lung inflammation, and therapies to modulate host responses to viral lung injury are urgently needed. Protectin conjugates in tissue regeneration 1 (PCTR1) and protectin D1 (PD1) are specialized pro-resolving mediators (SPMs) whose roles in viral pneumonia are of interest. In a mouse model of Respiratory Syncytial Virus (RSV) pneumonia, intranasal PCTR1 and PD1 each decreased RSV genomic viral load in lung tissue when given after RSV infection. Concurrent with enhanced viral clearance, PCTR1 administration post-infection, decreased eosinophils, neutrophils, and NK cells, including NKG2D+ activated NK cells, in the lung. Intranasal PD1 administration post-infection decreased lung eosinophils and Il-13 expression. PCTR1 increased lung expression of cathelicidin anti-microbial peptide and decreased interferon-gamma production by lung CD4+ T cells. PCTR1 and PD1 each increased interferon-lambda expression in human bronchial epithelial cells in vitro and attenuated RSV-induced suppression of interferon-lambda in mouse lung in vivo. Liquid chromatography coupled with tandem mass spectrometry of RSV-infected and untreated mouse lungs demonstrated endogenous PCTR1 and PD1 that decreased early in the time course while cysteinyl-leukotrienes (cys-LTs) increased during early infection. As RSV infection resolved, PCTR1 and PD1 increased and cys-LTs decreased to pre-infection levels. Together, these results indicate that PCTR1 and PD1 are each regulated during RSV pneumonia, with overlapping and distinct mechanisms for PCTR1 and PD1 during the resolution of viral infection and its associated inflammation.

Omega-3 Index and Clinical Outcomes of Severe COVID-19: Preliminary Results of a Cross-Sectional Study

The potentially detrimental effects of the worldwide deficiency of Omega-3 fatty acids on the COVID-19 pandemic have been underestimated. The Omega-3 Index (O3I), clinical variables, biometric indices, and nutritional information were directly determined for 74 patients with severe COVID-19 and 10 healthy quality-control subjects. The relationships between the OI3 and mechanical ventilation (MV) and death were analyzed. Results: Patients with COVID-19 exhibited low O3I (mean: 4.15%; range: 3.06-6.14%)-consistent with insufficient fish and Omega-3 supplement consumption, and markedly lower than the healthy control subjects (mean: 7.84%; range: 4.65-10.71%). Inverse associations were observed between O3I and MV (OR = 0.459; C.I.: 0.211-0.997) and death (OR = 0.28; C.I.: 0.08-0.985) in severe COVID-19, even after adjusting for sex, age, and well-known risk factors. Conclusion: We present preliminary evidence to support the hypothesis that the risk of severe COVID-19 can be stratified by the O3I quartile. Further investigations are needed to assess the value of the O3I as a blood marker for COVID-19.

Hypoxia-inducible factor-dependent induction of myeloid-derived netrin-1 attenuates natural killer cell infiltration during endotoxin-induced lung injury

Sepsis and sepsis‐associated lung inflammation significantly contribute to the morbidity and mortality of critical illness. Here, we examined the hypothesis that neuronal guidance proteins could orchestrate inflammatory events during endotoxin‐induced lung injury. Through a targeted array, we identified netrin‐1 as the top upregulated neuronal guidance protein in macrophages treated with lipopolysaccharide (LPS). Furthermore, we found that netrin‐1 is highly enriched in infiltrating myeloid cells, particularly in macrophages during LPS‐induced lung injury. Transcriptional studies implicate hypoxia‐inducible factor HIF‐1α in the transcriptional induction of netrin‐1 during LPS treatment. Subsequently, the deletion of netrin‐1 in the myeloid compartment (Ntn1^loxp/loxp LysM Cre) resulted in exaggerated mortality and lung inflammation. Surprisingly, further studies revealed enhanced natural killer cells (NK cells) infiltration in Ntn1^loxp/loxp LysM Cre mice, and neutralization of NK cell chemoattractant chemokine (C‐C motif) ligand 2 (CCL2) reversed the exaggerated lung inflammation. Together, these studies provide functional insight into myeloid cell‐derived netrin‐1 in controlling lung inflammation through the modulation of CCL2‐dependent infiltration of NK cells.

Molecular Mechanisms of Lipid Metabolism Disorders in Infectious Exacerbations of Chronic Obstructive Pulmonary Disease

Exacerbations largely determine the character of the progression and prognosis of chronic obstructive pulmonary disease (COPD). Exacerbations are connected with changes in the microbiological landscape in the bronchi due to a violation of their immune homeostasis. Many metabolic and immune processes involved in COPD progression are associated with bacterial colonization of the bronchi. The objective of this review is the analysis of the molecular mechanisms of lipid metabolism and immune response disorders in the lungs in COPD exacerbations. The complex role of lipid metabolism disorders in the pathogenesis of some infections is only beginning to be understood, however, there are already fewer and fewer doubts even now about its significance both in the pathogenesis of infectious exacerbations of COPD and in general in the progression of the disease. It is shown that the lipid rafts of the plasma membranes of cells are involved in many processes related to the detection of pathogens, signal transduction, the penetration of pathogens into the cell. Smoking disrupts the normally proceeded processes of lipid metabolism in the lungs, which is a part of the COPD pathogenesis.

Leukocytes in Inflammation, Resolution of Inflammation, Autoimmune Diseases and Cancer

Inflammation is a double-edged sword [...].

The N-Formyl Peptide Receptor 2 (FPR2) Agonist MR-39 Exhibits Anti-Inflammatory Activity in LPS-Stimulated Organotypic Hippocampal Cultures

Accumulating evidence indicates a pivotal role for chronic inflammatory processes in the pathogenesis of neurodegenerative and psychiatric disorders. G protein-coupled formyl peptide receptor 2 (FPR2) mediates pro-inflammatory or anti-/pro-resolving effects upon stimulation with biased agonists. We aimed to evaluate the effects of a new FPR2 ureidopropanamide agonist, compound MR-39, on neuroinflammatory processes in organotypic hippocampal cultures (OHCs) derived from control (WT) and knockout FPR2−/− mice (KO) exposed to bacterial endotoxin (lipopolysaccharide; LPS). Higher LPS-induced cytokine expression and basal release were observed in KO FPR2 cultures than in WT cultures, suggesting that a lack of FPR2 enhances the OHCs response to inflammatory stimuli. Pretreatment with MR-39 abolished some of the LPS-induced changes in the expression of genes related to the M1/M2 phenotypes (including Il-1β, Il-6, Arg1, Il-4, Cd74, Fizz and Cx3cr1) and TNF-α, IL-1β and IL-4 release in tissue derived from WT but not KO mice. Receptor specificity was confirmed by adding the FPR2 antagonist WRW4, which abolished the abovementioned effects of MR-39. Further biochemical data showed an increase in the phospho-p65/total p65 ratio after LPS stimulation in hippocampal tissues from both WT and KO mice, and MR-39 only reversed this effect on WT OHCs. LPS also increased TRAF6 levels, which are critical for the TLR4-mediated NF-κB pro-inflammatory responses. MR-39 attenuated the LPS-evoked increase in the levels of the NLRP3 and caspase-1 proteins in WT but not KO hippocampal cultures. Since NLRP3 may be involved in the pyroptosis, a lytic type of programmed cell death in which the main role is played by Gasdermin D (GSDMD), we examined the effects of LPS and/or MR-39 on the GSDMD protein level. LPS only increased GSDMD production in the WT tissues, and this effect was ameliorated by MR-39. Collectively, this study indicates that the new FPR2 agonist efficiently abrogates LPS-induced neuroinflammation in an ex vivo model, as evidenced by a decrease in pro-inflammatory cytokine expression and release as well as the downregulation of NLRP3 inflammasome-related pathways.

Pharmacological Mechanisms Underlying the Anti-asthmatic Effects of Modified Guomin Decoction Determined by Network Pharmacology and Molecular Docking

Background

Asthma is a chronic inflammatory disease characterized by Th2-predominant inflammation and airway remodeling. Modified Guo Min decoction (MGMD) has been an extensive practical strategy for allergic disorders in China. Although its potential anti-asthmatic activity has been reported, the exact mechanism of action of MGMD in asthma remains unexplored.

Methods

Network pharmacology approach was employed to predict the active components, potential targets, and molecular mechanism of MGMD for asthma treatment, including drug-likeness evaluation, oral bioavailability prediction, protein-protein interaction (PPI) network construction and analysis, Gene Ontology (GO) terms, and Reactome pathway annotation. Molecular docking was carried out to investigate interactions between active compounds and potential targets.

Results

A total of 92 active compounds and 72 anti-asthma targets of MGMD were selected for analysis. The GO enrichment analysis results indicated that the anti-asthmatic targets of MGMD mainly participate in inflammatory and in airway remolding processes. The Reactome pathway analysis showed that MGMD prevents asthma mainly through regulation of the IL-4 and IL-13 signaling and the specialized pro-resolving mediators (SPMs) biosynthesis. Molecular docking results suggest that each bioactive compounds (quercetin, wogonin, luteolin, naringenin, and kaempferol) is capable to bind with STAT3, PTGS2, JUN, VEGFA, EGFR, and ALOX5.

Conclusion

This study revealed the active ingredients and potential molecular mechanism by which MGMD treatment is effective against airway inflammation and remodeling in asthma through regulating IL-4 and IL-13 signaling and SPMs biosynthesis.

Emerging Role of Phospholipase-Derived Cleavage Products in Regulating Eosinophil Activity: Focus on Lysophospholipids, Polyunsaturated Fatty Acids and Eicosanoids

Eosinophils are important effector cells involved in allergic inflammation. When stimulated, eosinophils release a variety of mediators initiating, propagating, and maintaining local inflammation. Both, the activity and concentration of secreted and cytosolic phospholipases (PLAs) are increased in allergic inflammation, promoting the cleavage of phospholipids and thus the production of reactive lipid mediators. Eosinophils express high levels of secreted phospholipase A2 compared to other leukocytes, indicating their direct involvement in the production of lipid mediators during allergic inflammation. On the other side, eosinophils have also been recognized as crucial mediators with regulatory and homeostatic roles in local immunity and repair. Thus, targeting the complex network of lipid mediators offer a unique opportunity to target the over-activation and 'pro-inflammatory' phenotype of eosinophils without compromising the survival and functions of tissue-resident and homeostatic eosinophils. Here we provide a comprehensive overview of the critical role of phospholipase-derived lipid mediators in modulating eosinophil activity in health and disease. We focus on lysophospholipids, polyunsaturated fatty acids, and eicosanoids with exciting new perspectives for future drug development.

Therapeutic potential of the FPR2/ALX agonist AT-01-KG in the resolution of articular inflammation

The resolution of inflammation is a dynamic process, characterized by the biosynthesis of pro-resolving mediators, including the lipid Lipoxin A4 (LXA₄). LXA₄ acts on the N-formyl peptide receptor 2 (FPR2/ALX) to mediate anti-inflammatory and pro-resolving effects. In order to exploit the therapeutic potential of endogenous LXA₄ in the context of inflammation we have recently developed synthetic LXA₄ mimetics (sLXms) including a dimethyl-imidazole-containing FPR2/ALX agonist designated AT-01-KG. Here, we have investigated the effect of treatment with AT-01-KG in established models of articular inflammation. In a model of gout, mice were injected with MSU crystals and treated with AT-01-KG at the peak of inflammatory response. The treatment decreased the number of neutrophils in the knee exudate, an effect which was accompanied by low levels of myeloperoxidase, CXCL1 and IL-1β in periarticular tissue. AT-01-KG treatment led to reduced tissue damage and hypernociception. The effects of AT-01-KG on neutrophil accumulation were not observed in MSU treated FPR2/3^-/-mice. Importantly, AT-01-KG induced resolution of articular inflammation by increasing neutrophil apoptosis and subsequent efficient efferocytosis. In a model of antigen-induced arthritis, AT-01-KG treatment also attenuated inflammatory responses. These data suggest that AT-01-KG may be a potential new therapy for neutrophilic inflammation of the joints.

Treatment options in type-2 low asthma

Monoclonal antibodies targeting IgE or the type-2 cytokines interleukin (IL)-4, IL-5 and IL-13 are proving highly effective in reducing exacerbations and symptoms in people with severe allergic and eosinophilic asthma, respectively. However, these therapies are not appropriate for 30-50% of patients in severe asthma clinics who present with non-allergic, non-eosinophilic, "type-2 low" asthma. These patients constitute an important and common clinical asthma phenotype, driven by distinct, yet poorly understood pathobiological mechanisms. In this review we describe the heterogeneity and clinical characteristics of type-2 low asthma and summarise current knowledge on the underlying pathobiological mechanisms, which includes neutrophilic airway inflammation often associated with smoking, obesity and occupational exposures and may be driven by persistent bacterial infections and by activation of a recently described IL-6 pathway. We review the evidence base underlying existing treatment options for specific treatable traits that can be identified and addressed. We focus particularly on severe asthma as opposed to difficult-to-treat asthma, on emerging data on the identification of airway bacterial infection, on the increasing evidence base for the use of long-term low-dose macrolides, a critical appraisal of bronchial thermoplasty, and evidence for the use of biologics in type-2 low disease. Finally, we review ongoing research into other pathways including tumour necrosis factor, IL-17, resolvins, apolipoproteins, type I interferons, IL-6 and mast cells. We suggest that type-2 low disease frequently presents opportunities for identification and treatment of tractable clinical problems; it is currently a rapidly evolving field with potential for the development of novel targeted therapeutics.

Recent advances in the design and development of formyl peptide receptor 2 (FPR2/ALX) agonists as pro-resolving agents with diverse therapeutic potential

Under physiological conditions the initiation, duration and amplitude of inflammatory responses are tightly regulated to ensure the restoration of homeostasis. The resolution of inflammation in these circumstances is dictated by responses to endogenously generated mediators. Mimicry of such mediators underpins the principle of promoting the resolution of inflammation in treating inflammatory pathologies. The formyl peptide receptor 2 (FPR2/ALX) is a G-protein coupled receptor known to play a crucial role in maintaining host defence and orchestrating the inflammatory process. FPR2/ALX can be activated by a wide range of distinct agonists, including lipids, proteins, peptides, and an array of synthetic small molecule agonists. The focus of this review is to provide a comprehensive overview of recent progress made in the development of FPR2/ALX agonists which promote resolution and tissue regeneration.

Specialized proresolving mediators in infection and lung injury

Specialized proresolving mediators (SPMs) are endogenous lipid metabolites of long-chain polyunsaturated fatty acids that are involved in promoting the resolution of inflammation. Many disease conditions characterized by excessive inflammation have impaired or altered SPM biosynthesis, which may lead to chronic, unresolved inflammation. Exogenous administration of SPMs in infectious conditions has been shown to be effective at improving infection clearance and survival in preclinical models. SPMs have also shown tremendous promise in the context of inflammatory lung conditions, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease, mostly in preclinical settings. To date, SPMs have not been studied in the context of the novel Coronavirus, severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), however their preclinical efficacy in combatting infections and improving acute respiratory distress suggest they may be a valuable resource in the fight against Coronavirus disease-19 (COVID-19). Overall, while the research on SPMs is still evolving, they may offer a novel therapeutic option for inflammatory conditions.

Current perspective on eicosanoids in asthma and allergic diseases: EAACI Task Force consensus report, part I

Eicosanoids are biologically active lipid mediators, comprising prostaglandins, leukotrienes, thromboxanes, and lipoxins, involved in several pathophysiological processes relevant to asthma, allergies, and allied diseases. Prostaglandins and leukotrienes are the most studied eicosanoids and established inducers of airway pathophysiology including bronchoconstriction and airway inflammation. Drugs inhibiting the synthesis of lipid mediators or their effects, such as leukotriene synthesis inhibitors, leukotriene receptors antagonists, and more recently prostaglandin D₂ receptor antagonists, have been shown to modulate features of asthma and allergic diseases. This review, produced by an European Academy of Allergy and Clinical Immunology (EAACI) task force, highlights our current understanding of eicosanoid biology and its role in mediating human pathology, with a focus on new findings relevant for clinical practice, development of novel therapeutics, and future research opportunities.

The potential of lipid mediator networks as ocular surface therapeutics and biomarkers

In the last twenty years an impressive body of evidence in diverse inflammatory animal disease models and human tissues, has established polyunsaturated fatty acids (PUFA) derived specialized-pro-resolving mediators (SPM), as essential mediators for controlling acute inflammation, immune responses, wound healing and for resolving acute inflammation in many non-ocular tissues. SPM pathways and receptors are highly expressed in the ocular surface where they regulate wound healing, nerve regeneration, innate immunity and sex-specific regulation of auto-immune responses. Recent evidence indicates that in the eye these resident SPM networks are important for maintaining ocular surface health and immune homeostasis. Here, we will review and discuss evidence for SPMs and other PUFA-derived mediators as important endogenous regulators, biomarkers for ocular surface health and disease and their therapeutic potential.

Receptors for pro-resolving mediators as a therapeutic tool for smooth muscle remodeling-associated disorders

Respiratory airway, blood vessel and intestinal wall remodeling, in which smooth muscle remodeling plays a major role, is a key pathological event underlying the development of several associated diseases, including asthma, cardiovascular disorders (e.g., atherosclerosis, hypertension, and aneurism formation), and inflammatory bowel disease. However, the mechanisms underlying these remodeling processes remain poorly understood. We hypothesize that the creation of chronic inflammation-mediated networks that support and exacerbate the airway, as well as vascular and intestinal wall remodeling, is a crucial pathogenic mechanism governing the development of the associated diseases. The failed inflammation resolution might be one of the causal pathogenic mechanisms. Hence, it is reasonable to assume that applying specialized, pro-resolving mediators (SPMs), acting via cognate G-protein coupled receptors (GPCRs), could potentially be an effective pathway for treating these disorders. However, several obstacles, such as poor understanding of the SPM/receptor signaling pathways, SMP rapid inactivation as well as their complex and costly synthesis, limit their translational potential. In this connection, stable, small-molecule SPM mimetics and receptor agonists have emerged as new, potentially suitable drugs. It has been recently shown in preclinical studies that they can effectively attenuate the manifestations of asthma, atherosclerosis and Crohn's disease. Remarkably, some biased SPM receptor agonists, which cause a signaling response in the desired inflammation pro-resolving direction, revealed similar beneficial effects. These encouraging observations suggest that SPM mimetics and receptor agonists can be applied as a novel approach for the treatment of various chronic inflammation conditions, including airway, vascular and intestinal wall remodeling-associated disorders.

Plasma Levels of Proresolving and Prophlogistic Lipid Mediators: Association With Severity of Respiratory Failure and Mortality in Acute Respiratory Distress Syndrome

Objectives

Acute respiratory distress syndrome is characterized by an overly exuberant inflammatory state in the lung. Specialized proresolving mediators are endogenous agonists for the resolution of lung inflammation and injury in health, yet their association with acute respiratory distress syndrome severity and outcomes remains to be defined. In the current study, we investigate associations between plasma levels of specialized proresolving mediators and acute respiratory distress syndrome severity and mortality.

Design

Translational pilot study nested within a large prospective cohort of patients with risk factors for acute respiratory distress syndrome.

Setting

ICU from a large medical center.

Patients

Twenty-six Caucasian patients with acute respiratory distress syndrome and available plasma from early in critical illness.

Interventions

None.

Measurements and Main Results

Here, in samples from 26 acute respiratory distress syndrome patients, we examined plasma levels of select specialized proresolving mediators that promote lung injury resolution in preclinical systems, namely lipoxin A₄ and maresin 1, and select prophlogistic lipid mediators linked to acute respiratory distress syndrome pathogenesis, namely cysteinyl leukotrienes and thromboxane B₂. These mediators were detected by sensitive enzyme-linked immunosorbent assay: lipoxin A₄ (assay range) (8.2-5,000 pg/mL), maresin 1 (7.8-1,000 pg/mL), cysteinyl leukotrienes (7.8-1,000 pg/mL), and thromboxane B₂ (15.6-2,000 pg/mL). Lower plasma levels of specialized proresolving mediators were associated with increased duration of ventilatory support and ICU length of stay. Even in this small sample size, trends were evident for increased cysteinyl leukotrienes to specialized proresolving mediator ratios (cysteinyl leukotrienes/maresin 1 and cysteinyl leukotrienes/lipoxin A₄) in acute respiratory distress syndrome nonsurvivors.

Conclusions

Lower specialized proresolving mediator levels in acute respiratory distress syndrome patients may disrupt timely resolution of lung inflammation and/or injury and contribute to clinical severity and mortality.

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.

Novel Therapies for Pneumonia-Associated Severe Asthma Phenotypes

Distinct asthma phenotypes are emerging from well-defined cohort studies and appear to be associated with a history of pneumonia. Asthmatics are more susceptible to infections caused by Streptococcus pneumoniae; however, the mechanisms that underlie defective immunity to this pathogen are still being elucidated. Here, we discuss how alternatively activated macrophages (AAMs) in asthmatics are defective in bacterial phagocytosis and how respiratory viruses disrupt essential host immunity to cause bacterial dispersion deeper into the lungs. We also describe how respiratory pathogens instigate neutrophilic inflammation and amplify type-2 inflammation in asthmatics. Finally, we propose novel dual-acting strategies including granulocyte-colony-stimulating factor receptor (G-CSFR) antagonism and specialised pro-resolving mediators (SPMs) to suppress type-2 and neutrophilic inflammation without compromising pathogen clearance.

Identifying Clinical Research Priorities in Adult Pulmonary and Critical Care. NHLBI Working Group Report

Preventing, treating, and promoting recovery from critical illness due to pulmonary disease are foundational goals of the critical care community and the NHLBI. Decades of clinical research in acute respiratory distress syndrome, acute respiratory failure, pneumonia, and sepsis have yielded improvements in supportive care, which have translated into improved patient outcomes. Novel therapeutics have largely failed to translate from promising preclinical findings into improved patient outcomes in late-phase clinical trials. Recent advances in personalized medicine, "big data," causal inference using observational data, novel clinical trial designs, preclinical disease modeling, and understanding of recovery from acute illness promise to transform the methods of pulmonary and critical care clinical research. To assess the current state of, research priorities for, and future directions in adult pulmonary and critical care research, the NHLBI assembled a multidisciplinary working group of investigators. This working group identified recommendations for future research, including 1) focusing on understanding the clinical, physiological, and biological underpinnings of heterogeneity in syndromes, diseases, and treatment response with the goal of developing targeted, personalized interventions; 2) optimizing preclinical models by incorporating comorbidities, cointerventions, and organ support; 3) developing and applying novel clinical trial designs; and 4) advancing mechanistic understanding of injury and recovery to develop and test interventions targeted at achieving long-term improvements in the lives of patients and families. Specific areas of research are highlighted as especially promising for making advances in pneumonia, acute hypoxemic respiratory failure, and acute respiratory distress syndrome.