Lipoxin A4 prevents tight junction disruption and delays the colonization of cystic fibrosis bronchial epithelial cells by Pseudomonas aeruginosa

Resolution pharmacology and the treatment of infectious diseases

Inflammation is elicited by the host in response to microbes, and is believed to be essential for protection against infection. However, we have previously hypothesized that excessive or misplaced inflammation may be a major contributor to tissue dysfunction and death associated with viral and bacterial infections. The resolutive phase of inflammation is a necessary condition to achieve homeostasis after acute inflammation. It is possible that targeting inflammation resolution may be beneficial for the host during infection. In this review, we summarize the evidence demonstrating the expression, roles and effects of the best described pro-resolving molecules in the context of bacterial and viral infections. Pro-resolving molecules play a pivotal role in modulating a spectrum of pathways associated with tissue inflammation and damage during both viral and bacterial infections. These molecules offer a blend of anti-inflammatory, pro-resolving and sometimes anti-infective benefits, all the while circumventing the undesired and immune-suppressive unwanted effects associated with glucocorticoids. Whether these beneficial effects will translate into benefits to patients clearly deserve further investigation.

In vitro modelling of bacterial pneumonia: a comparative analysis of widely applied complex cell culture models

Bacterial pneumonia greatly contributes to the disease burden and mortality of lower respiratory tract infections among all age groups and risk profiles. Therefore, laboratory modelling of bacterial pneumonia remains important for elucidating the complex host-pathogen interactions and to determine drug efficacy and toxicity. In vitro cell culture enables for the creation of high-throughput, specific disease models in a tightly controlled environment. Advanced human cell culture models specifically, can bridge the research gap between the classical two-dimensional cell models and animal models. This review provides an overview of the current status of the development of complex cellular in vitro models to study bacterial pneumonia infections, with a focus on air-liquid interface models, spheroid, organoid, and lung-on-a-chip models. For the wide scale, comparative literature search, we selected six clinically highly relevant bacteria (Pseudomonas aeruginosa, Mycoplasma pneumoniae, Haemophilus influenzae, Mycobacterium tuberculosis, Streptococcus pneumoniae, and Staphylococcus aureus). We reviewed the cell lines that are commonly used, as well as trends and discrepancies in the methodology, ranging from cell infection parameters to assay read-outs. We also highlighted the importance of model validation and data transparency in guiding the research field towards more complex infection models.

Bacterial extracellular vesicles: Emerging nanoplatforms for biomedical applications

Bacterial extracellular vesicles (BEVs) are nanosized lipid bilayers generated from membranes that are filled with components derived from bacteria. BEVs are important for the physiology, pathogenicity, and interactions between bacteria and their hosts as well. BEVs represent an important mechanism of transport and interaction between cells. Recent advances in biomolecular nanotechnology have enabled the desired properties to be engineered on the surface of BEVs and decoration with desired and diverse biomolecules and nanoparticles, which have potential biomedical applications. BEVs have been the focus of various fields, including nanovaccines, therapeutic agents, and drug delivery vehicles. In this review, we delineate the fundamental aspects of BEVs, including their biogenesis, cargo composition, function, and interactions with host cells. We comprehensively summarize the factors influencing the biogenesis of BEVs. We further highlight the importance of the isolation, purification, and characterization of BEVs because they are essential processes for potential benefits related to host-microbe interactions. In addition, we address recent advancements in BEVs in biomedical applications. Finally, we provide conclusions and future perspectives as well as highlight the remaining challenges of BEVs for different biomedical applications.

Lipoxin receptor agonist and inhibition of LTA4 hydrolase prevent tight junction disruption caused by P. aeruginosa filtrate in airway epithelial cells

Airway diseases can disrupt tight junction proteins, compromising the epithelial barrier and making it more permeable to pathogens. In people with pulmonary disease who are prone to infection with Pseudomonas aeruginosa, pro-inflammatory leukotrienes are increased and anti-inflammatory lipoxins are decreased. Upregulation of lipoxins is effective in counteracting inflammation and infection. However, whether combining a lipoxin receptor agonist with a specific leukotriene A4 hydrolase (LTA4H) inhibitor could enhance these protective effects has not to our knowledge been investigated. Therefore, we explored the effect of lipoxin receptor agonist BML-111 and JNJ26993135 a specific LTA4H inhibitor that prevents the production of pro-inflammatory LTB4 on tight junction proteins disrupted by P. aeruginosa filtrate (PAF) in human airway epithelial cell lines H441 and 16HBE-14o. Pre-treatment with BML-111 prevented an increase in epithelial permeability induced by PAF and conserved ZO-1 and claudin-1 at the cell junctions. JNJ26993135 similarly prevented the increased permeability induced by PAF, restored ZO-1 and E-cadherin and reduced IL-8 but not IL-6. Cells pre-treated with BML-111 plus JNJ26993135 restored TEER and permeability, ZO-1 and claudin-1 to the cell junctions. Taken together, these data indicate that the combination of a lipoxin receptor agonist with a LTA4H inhibitor could provide a more potent therapy.

Is there a role for specialized pro-resolving mediators in pulmonary fibrosis?

Pulmonary fibrotic diseases are characterized by proliferation of lung fibroblasts and myofibroblasts and excessive deposition of extracellular matrix proteins. Depending on the specific form of lung fibrosis, there can be progressive scarring of the lung, leading in some cases to respiratory failure and/or death. Recent and ongoing research has demonstrated that resolution of inflammation is an active process regulated by families of small bioactive lipid mediators termed "specialized pro-resolving mediators." While there are many reports of beneficial effects of SPMs in animal and cell culture models of acute and chronic inflammatory and immune diseases, there have been fewer reports investigating SPMs and fibrosis, especially pulmonary fibrosis. Here, we will review evidence that resolution pathways are impaired in interstitial lung disease, and that SPMs and other similar bioactive lipid mediators can inhibit fibroblast proliferation, myofibroblast differentiation, and accumulation of excess extracellular matrix in cell culture and animal models of pulmonary fibrosis, and we will consider future therapeutic implications of SPMs in fibrosis.

Restoring airway epithelial homeostasis in Cystic Fibrosis

Cystic fibrosis (CF), the most common life-threatening genetic disorder in Caucasians, is caused by recessive mutations in the Cystic Fibrosis Transmembrane Regulator (CFTR) gene encoding a chloride ion channel. Aberrant function of CFTR involves mucus- and sweat-producing epithelia affecting multiple organs, including airways and lungs. This condition facilitates the colonization of fungi, bacteria, or viruses. Recurrent antibiotic administration is commonly used to treat pathogen infections leading to the insurgence of resistant bacteria and to a chronic inflammatory state that jeopardizes airway epithelium repair. The phenotype of patients carrying CFTR mutations does not always present a strict correlation with their genotype, suggesting that the disease may occur because of multiple additive effects. Among them, the frequent microbiota dysbiosis observed in patients affected by CF, might be one cause of the discrepancy observed in their genotype-phenotype correlation. Interestingly, the abnormal polarity of the CF airway epithelium has been observed also under non-infectious and non-inflammatory conditions, suggesting that CFTR dysfunction "per se" perturbs epithelial homeostasis. New pathogen- or host-directed strategies are thus needed to counteract bacterial infections and restore epithelial homeostasis in individuals with CF. In this review, we summarized alternative cutting-edge approaches to high-efficiency modulator therapy that might be promising for these patients.

Diabetes downregulates the antimicrobial peptide psoriasin and increases E. coli burden in the urinary bladder

Diabetes is known to increase susceptibility to infections, partly due to impaired granulocyte function and changes in the innate immunity. Here, we investigate the effect of diabetes, and high glucose on the expression of the antimicrobial peptide, psoriasin and the putative consequences for E. coli urinary tract infection. Blood, urine, and urine exfoliated cells from patients are studied. The influence of glucose and insulin is examined during hyperglycemic clamps in individuals with prediabetes and in euglycemic hyperinsulinemic clamped patients with type 1 diabetes. Important findings are confirmed in vivo in type 2 diabetic mice and verified in human uroepithelial cell lines. High glucose concentrations induce lower psoriasin levels and impair epithelial barrier function together with altering cell membrane proteins and cytoskeletal elements, resulting in increasing bacterial burden. Estradiol treatment restores the cellular function with increasing psoriasin and bacterial killing in uroepithelial cells, confirming its importance during urinary tract infection in hyperglycemia. In conclusion, our findings present the effects and underlying mechanisms of high glucose compromising innate immunity.

CF Patients’ Airway Epithelium and Sex Contribute to Biosynthesis Defects of Pro-Resolving Lipids

Specialized pro-resolving lipid mediators (SPMs) as lipoxins (LX), resolvins (Rv), protectins (PD) and maresins (MaR) promote the resolution of inflammation. We and others previously reported reduced levels of LXA4 in bronchoalveolar lavages from cystic fibrosis (CF) patients. Here, we investigated the role of CF airway epithelium in SPMs biosynthesis, and we evaluated its sex specificity. Human nasal epithelial cells (hNEC) were obtained from women and men with or without CF. Lipids were quantified by mass spectrometry in the culture medium of hNEC grown at air-liquid interface and the expression level and localization of the main enzymes of SPMs biosynthesis were assessed. The 5-HETE, LXA4, LXB4, RvD2, RvD5, PD1 and RvE3 levels were significantly lower in samples derived from CF patients compared with non-CF subjects. Within CF samples, the 12-HETE, 15-HETE, RvD3, RvD4, 17-HODHE and PD1 were significantly lower in samples derived from females. While the mean expression levels of 15-LO, 5-LO and 12-LO do not significantly differ either between CF and non-CF or between female and male samples, the SPMs content correlates with the level of expression of several enzymes involved in SPMs metabolism. In addition, the 5-LO localization significantly differed from cytoplasmic in non-CF to nucleic (or nuclear envelope) in CF hNEC. Our studies provided evidence for lower abilities of airway epithelial cells derived from CF patients and more markedly, females to produce SPMs. These data are consistent with a contribution of CF airway epithelium in the abnormal resolution of inflammation and with worse pulmonary outcomes in women.

Surface Hydration Protects Cystic Fibrosis Airways from Infection by Restoring Junctional Networks

Defective hydration of airway surface mucosa is associated with recurrent lung infection in cystic fibrosis (CF), a disease caused by CF transmembrane conductance regulator (CFTR) gene mutations. Whether the composition and/or presence of an airway surface liquid (ASL) is sufficient to prevent infection remains unclear. The susceptibility to infection of polarized wild type and CFTR knockdown (CFTR-KD) airway epithelial cells was determined in the presence or absence of a healthy ASL or physiological saline. CFTR-KD epithelia exhibited strong ASL volume reduction, enhanced susceptibility to infection, and reduced junctional integrity. Interestingly, the presence of an apical physiological saline alleviated disruption of the airway epithelial barrier by stimulating essential junctional protein expression. Thus, rehydrated CFTR-KD cells were protected from infection despite normally intense bacterial growth. This study indicates that an epithelial integrity gatekeeper is modulated by the presence of an apical liquid volume, irrespective of the liquid's composition and of expression of a functional CFTR.

GM-CSF: Orchestrating the Pulmonary Response to Infection

This review summarizes the structure and function of the alveolar unit, comprised of alveolar macrophage and epithelial cell types that work in tandem to respond to infection. Granulocyte-macrophage colony-stimulating factor (GM-CSF) helps to maintain the alveolar epithelium and pulmonary immune system under physiological conditions and plays a critical role in restoring homeostasis under pathologic conditions, including infection. Given the emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and global spread of coronavirus disease 2019 (COVID-19), with subsequent acute respiratory distress syndrome, understanding basic lung physiology in infectious diseases is especially warranted. This review summarizes clinical and preclinical data for GM-CSF in respiratory infections, and the rationale for sargramostim (yeast-derived recombinant human [rhu] GM-CSF) as adjunctive treatment for COVID-19 and other pulmonary infectious diseases.

Specialized pro-resolving mediators: biosynthesis and biological role in bacterial infections

Acute inflammation caused by bacterial infections is an essential biological defence mechanism of the host in order to neutralize and clear the invaders and to return to homeostasis. Despite its protective function, inflammation may become persistent and uncontrolled, resulting in chronic diseases and tissue destruction as consequence of the unresolved inflammatory process. Therefore, spatiotemporal induction of endogenous inflammation resolution programs that govern bacterial clearance as well as tissue repair and regeneration, are of major importance in order to enable tissues to restore functions. Lipid mediators that are de-novo biosynthesized from polyunsaturated fatty acids (PUFAs) mainly by lipoxygenases and cyclooxygenases, critically regulate the initiation, the maintenance but also the resolution of infectious inflammation and tissue regeneration. The discovery of specialized pro-resolving mediators (SPMs) generated from omega-3 PUFAs stimulated intensive research in inflammation resolution, especially in infectious inflammation elicited by bacteria. SPMs are immunoresolvents that actively terminate inflammation by limiting neutrophil influx, stimulating phagocytosis, bacterial killing and clearance as well as efferocytosis of apoptotic neutrophils and cellular debris by macrophages. Moreover, SPMs prevent collateral tissue damage, promote tissue repair and regeneration and lower antibiotic requirement. Here, we review the biosynthesis of SPMs in bacterial infections and cover specific mechanisms of SPMs that govern the resolution of bacteria-initiated inflammation.

Role of specialized pro-resolving lipid mediators in pulmonary inflammation diseases: mechanisms and development

Inflammation is an essential mechanism of various diseases. The development and resolution of inflammation are complex immune-modulation processes which induce the involvement of various types of immune cells. Specialized pro-resolving lipid mediators (SPMs) have been demonstrated to be signaling molecules in inflammation. SPMs are involved in the pathophysiology of different diseases, especially respiratory diseases, including asthma, pneumonia, and chronic obstructive pulmonary disease. All of these diseases are related to the inflammatory response and its persistence. Therefore, a deeper understanding of the mechanisms and development of inflammation in respiratory disease, and the roles of the SPM family in the resolution process, might be useful in the quest for novel therapies and preventive measures for pulmonary diseases.

Hyperinflammation and airway surface liquid dehydration in cystic fibrosis: purinergic system as therapeutic target

OBJECTIVE AND DESIGN

The exacerbate inflammatory response contributes to the progressive loss of lung function in cystic fibrosis (CF), a genetic disease that affects the osmotic balance of mucus and mucociliary clearance, resulting in a microenvironment that favors infection and inflammation. The purinergic system, an extracellular signaling pathway characterized by nucleotides, enzymes and receptors, may have a protective role in the disease, through its action in airway surface liquid (ASL) and anti-inflammatory response.

MATERIALS AND METHODS

To make up this review, studies covering topics of CF, inflammation, ASL and purinergic system were selected from the main medical databases, such as Pubmed and ScienceDirect.

CONCLUSION

We propose several ways to modulate the purinergic system as a potential therapy for CF, like inhibition of P2X7, activation of P2Y2, A2A and A2B receptors and blocking of adenosine deaminase. Among them, we postulate that the most suitable strategy is to block the action of adenosine deaminase, which culminates in the increase of Ado levels that presents anti-inflammatory actions and improves mucociliary clearance. Furthermore, it is possible to maintain the physiological levels of ATP to control the hydration of ASL. These therapies could correct the main mechanisms that contribute to the progression of CF.

Current and novel therapeutic strategies for the management of cystic fibrosis

Introduction: Cystic fibrosis (CF), is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and affects thousands of people throughout the world. Lung disease is the leading cause of death in CF patients. Despite the advances in treatments, the management of CF mainly targets symptoms. Recent CFTR modulators however target common mutations in patients, alleviating symptoms of CF. Unfortunately, there is still no approved treatments for patients with rare mutations to date.Areas covered: This paper reviews current treatments of CF that mitigate symptoms and target genetic defects. The use of gene and drug delivery systems such as viral or non-viral vectors and nano-compounds to enhance CFTR expression and the activity of antimicrobials against chronic pulmonary infections respectively, will also be discussed.Expert opinion: Nano-compounds tackle biological barriers to drug delivery and revitalize antimicrobials, anti-inflammatory drugs and even genes delivery to CF patients. Gene therapy and gene editing are of particular interest because they have the potential to directly target genetic defects. Nanoparticles should be formulated to more specifically target epithelial cells, and biofilms. Finally, the development of more potent gene vectors to increase the duration of gene expression and reduce inflammation is a promising strategy to eventually cure CF.

Resolution-Based Therapies: The Potential of Lipoxins to Treat Human Diseases

Inflammation is an a physiological response instead an essential response of the organism to injury and its adequate resolution is essential to restore homeostasis. However, defective resolution can be the precursor of severe forms of chronic inflammation and fibrosis. Nowadays, it is known that an excessive inflammatory response underlies the most prevalent human pathologies worldwide. Therefore, great biomedical research efforts have been driven toward discovering new strategies to promote the resolution of inflammation with fewer side-effects and more specificity than the available anti-inflammatory treatments. In this line, the use of endogenous specialized pro-resolving mediators (SPMs) has gained a prominent interest. Among the different SPMs described, lipoxins stand out as one of the most studied and their deficiency has been widely associated with a wide range of pathologies. In this review, we examined the current knowledge on the therapeutic potential of lipoxins to treat diseases characterized by a severe inflammatory background affecting main physiological systems, paying special attention to the signaling pathways involved. Altogether, we provide an updated overview of the evidence suggesting that increasing endogenously generated lipoxins may emerge as a new therapeutic approach to prevent and treat many of the most prevalent diseases underpinned by an increased inflammatory response.

Therapeutic Effects of Specialized Pro-Resolving Lipids Mediators on Cardiac Fibrosis via NRF2 Activation

Heart disease is the number one mortality disease in the world. In particular, cardiac fibrosis is considered as a major factor causing myocardial infarction and heart failure. In particular, oxidative stress is a major cause of heart fibrosis. In order to control such oxidative stress, the importance of nuclear factor erythropoietin 2 related factor 2 (NRF2) has recently been highlighted. In this review, we will discuss the activation of NRF2 by docosahexanoic acid (DHA), eicosapentaenoic acid (EPA), and the specialized pro-resolving lipid mediators (SPMs) derived from polyunsaturated lipids, including DHA and EPA. Additionally, we will discuss their effects on cardiac fibrosis via NRF2 activation.

Lipoxin A4 promotes reduction and antibiotic efficacy against Pseudomonas aeruginosa biofilm

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic bacterium commonly found in wound infections and airways of cystic fibrosis patients. P. aeruginosa readily forms biofilms which can reduce the efficacy of antibiotics used to eradicate the pathogen. We have previously shown that a Specialized Pro-resolving Mediator (SPM), Lipoxin A4 (LxA₄) is a quorum sensing inhibitor which can reduce P. aeruginosa virulence. In this study, we examined the direct actions of LxA₄ and RvD₂ on P. aeruginosa biofilm formation and virulence gene expression. The influence of LxA₄ on antibiotic efficacy and the combined effects on biofilm formation were also investigated. LxA₄ and RvD₂ reduced P. aeruginosa biofilm formation and virulence gene expression. LxA₄ increased ciprofloxacin inhibition on biofilm formation but did not affect ciprofloxacin's action on non-adherent bacteria. On the other hand, LxA₄ increased bacterial killing action of imipenem but did not affect imipenem's action on biofilm. We also found that LxA₄ can increase ciprofloxacin's bacterial killing ability in established biofilm. Together these results suggest that LxA₄ has direct effects on P. aeruginosa biofilm formation and can increase antibiotic efficacy directly.

An in vitro model for assessing drug transport in cystic fibrosis treatment: Characterisation of the CuFi-1 cell line

Cystic fibrosis (CF) is a disease that most commonly affects the lungs and is characterized by mucus retention and a continuous cycle of bacterial infection and inflammation. Current CF treatment strategies are focused on targeted drug delivery to the lungs. Novel inhalable drug therapies require an in vitro CF model that appropriately mimics the in vivo CF lung environment to better understand drug delivery and transport across the CF epithelium, and predict drug therapeutic efficacy. Therefore, the aim of this research was to determine the appropriate air-liquid interface (ALI) culture method of the CuFi-1 (CF cell line) compared to the NuLi-1 (healthy cell line) cells to be used as in vitro models of CF airway epithelia. Furthermore, drug transport on both CuFi-1 and NuLi-1 was investigated to determine whether these cell lines could be used to study transport of drugs used in CF treatment using Ibuprofen (the only anti-inflammatory drug currently approved for CF) as a model drug. Differentiating characteristics specific to airway epithelia such as mucus production, inflammatory response and tight junction formation at two seeding densities (Low and High) were assessed throughout an 8-week ALI culture period. This study demonstrated that both the NuLi-1 and CuFi-1 cell lines fully differentiate in ALI culture with significant mucus secretion, IL-6 and IL-8 production, and functional tight junctions at week 8. Additionally, the High seeding density was found to alter the phenotype of the NuLi-1 cell line. For the first time, this study identifies that ibuprofen is transported via the paracellular pathway in ALI models of NuLi-1 and CuFi-1 cell lines. Overall, these findings highlight that NuLi-1 and CuFi-1 as promising in vitro ALI models to investigate the transport properties of novel inhalable drug therapies for CF treatment.

The Role of Specialized Pro-Resolving Mediators in Cystic Fibrosis Airways Disease

Cystic Fibrosis (CF) is a recessive genetic disease due to mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene encoding the CFTR chloride channel. The ion transport abnormalities related to CFTR mutation generate a dehydrated airway surface liquid (ASL) layer, which is responsible for an altered mucociliary clearance, favors infections and persistent inflammation that lead to progressive lung destruction and respiratory failure. The inflammatory response is normally followed by an active resolution phase to return to tissue homeostasis, which involves specialized pro-resolving mediators (SPMs). SPMs promote resolution of inflammation, clearance of microbes, tissue regeneration and reduce pain, but do not evoke unwanted immunosuppression. The airways of CF patients showed a decreased production of SPMs even in the absence of pathogens. SPMs levels in the airway correlated with CF patients' lung function. The prognosis for CF has greatly improved but there remains a critical need for more effective treatments that prevent excessive inflammation, lung damage, and declining pulmonary function for all CF patients. This review aims to highlight the recent understanding of CF airway inflammation and the possible impact of SPMs on functions that are altered in CF airways.

The Resolution Approach to Cystic Fibrosis Inflammation

Despite the high expectations associated with the recent introduction of CFTR modulators, airway inflammation still remains a relevant clinical issue in cystic fibrosis (CF). The classical anti-inflammatory drugs have shown very limited efficacy, when not being harmful, raising the question of whether alternative approaches should be undertaken. Thus, a better knowledge of the mechanisms underlying the aberrant inflammation observed in CF is pivotal to develop more efficacious pharmacology. In this respect, the observation that endogenous proresolving pathways are defective in CF and that proresolving mediators, physiologically generated during an acute inflammatory reaction, do not completely suppress inflammation, but promote resolution, tissue healing and microbial clearance, without compromising immune host defense mechanisms, opens interesting therapeutic scenarios for CF. In this mini-review, we present the current knowledge and perspectives of proresolving pharmacology in CF, focusing on the specialized proresolving lipid mediators and selected peptides.

Sexual dimorphism in the microbiology of the CF 'Gender Gap': Estrogen modulation of Pseudomonas aeruginosa virulence

There is increasing evidence for sexual dimorphism of estrogen (E2) actions in the exacerbation of lung function, infection and inflammation in females with cystic fibrosis - the so-called "CF gender gap". The effects of estrogen on virulence factors that enhance P. aeruginosa persistence in CF lung epithelium were investigated by phenotypic and chemical assays in various PsA clinical isolates and laboratory strains in isolation or in co-culture with normal (Nuli-1) and CF dPhe508-CFTR (CuFi-1) human bronchial epithelial cell lines. Estrogen (E2, 10 nM) significantly increased secretion of the virulence factor pyocyanin by 80% in PsA early infection isolates from female CF patients and by 280% in late infection PsA isolates. Estrogen also increased the swarming motility by up to 50% in all PsA isolates and strains tested in 0.5% agar. A significant increase of 110% in the twitching motility of all PsA isolates and strains tested was also observed with estrogen treatment. Treatment with E2 increased biofilm formation of P. aeruginosa PsAO1 which became more adherent to, and invasive into, normal and CF bronchial epithelial cells. The selective estrogen receptor modulators (SERMs), Tamoxifen and ICI 182780 inhibited P. aeruginosa motility. The potency of various steroid hormones to stimulate motility of P. aeruginosa was in the order; estradiol ≫ estrone > E3 estriol ≥ testosterone ≥ progesterone ≫ aldosterone, cortisol. Estrogen was also shown to reduce ciliary beat intensity in CF bronchial epithelium which would further exacerbate PsA trapping and virulence in the CF airways. In conclusion, we have demonstrated for the first time that estrogen exacerbates P. aeruginosa virulence factors and enhances bacterial interactions with CF bronchial epithelium which can be inhibited by tamoxifen. Our work suggests that SERMs could be used as an adjuvant treatment to reduce estrogen-induced P. aeruginosa infections and associated lung exacerbations in females with CF.

Resolvin D1 ameliorates cognitive impairment following traumatic brain injury via protecting astrocytic mitochondria

Cognitive impairment is one of the most common and devastating neuropsychiatric sequelae after traumatic brain injury (TBI), and hippocampal neuronal survival plays a causal role in this pathological process. Resolvin D1 (RvD1), an important endogenous specialized pro-resolving mediator, has recently been reported to exert a potent protective effect on mitochondria. This suggests that RvD1 may suppress neuroinflammation and protect astrocytic mitochondria at the same time to play further neuroprotective roles. C57BL/6 mice subjected to TBI using a controlled cortical impact device were used for in vivo experiments. Cultured primary mouse astrocytes and an N2a mouse neuroblastoma cell line were used for in vitro experiments. In TBI mice, RvD1 significantly ameliorated cognitive impairment, suppressed gliosis and alleviated neuronal loss in the hippocampus. To explore the mechanism underlying this activity, we verified that RvD1 can induce a higher level of mitophagy to remove damaged mitochondria and eliminate extra mitochondria-derived reactive oxygen species (mitoROS) by activating ALX4/FPR2 receptors in astrocytes. In an in vitro model, we further confirmed that RvD1 can protect mitochondrial morphology and membrane potential in astrocytes and thereby enhance the survival of neurons. Meanwhile, RvD1 was also shown to increase the expression of brain-derived neurotrophic factor and glutamate aspartate transporter in the hippocampus following TBI, which indicates a possible way by which RvD1 increases the supportive function of astrocytes. These findings suggest that RvD1 may be a potent therapeutic option for ameliorating cognitive impairment following TBI by controlling neuroinflammation and protecting astrocytic mitochondria.

Lights and Shadows in the Use of Mesenchymal Stem Cells in Lung Inflammation, a Poorly Investigated Topic in Cystic Fibrosis

Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic stem cells residing in many tissues, including the lung. MSCs have long been regarded as a promising tool for cell-based therapy because of their ability to replace damaged tissue by differentiating into the resident cell and repopulating the injured area. Their ability to release soluble factors and extracellular vesicles has emerged as crucial in the resolution of inflammation and injury. There is a growing literature on the use of MSCs and MSC secretome to hamper inflammation in different lung pathologies, including: asthma, pneumonia, acute lung injury (ALI), pulmonary hypertension, and chronic obstructive pulmonary disease (COPD). However, their potential therapeutic role in the context of Cystic Fibrosis (CF) lung inflammation is still not fully characterized. CF morbidity and mortality are mainly due to progressive lung dysfunction. Lung inflammation is a chronic and unresolved condition that triggers progressive tissue damage. Thus, it becomes even more important to develop innovative immunomodulatory therapies aside from classic anti-inflammatory agents. Here, we address the main features of CF and the implications in lung inflammation. We then review how MSCs and MSC secretome participate in attenuating inflammation in pulmonary pathologies, emphasizing the significant potential of MSCs as new therapeutic approach in CF.

Repair Process Impairment by Pseudomonas aeruginosa in Epithelial Tissues: Major Features and Potential Therapeutic Avenues

Epithelial tissues protecting organs from the environment are the first-line of defense against pathogens. Therefore, efficient repair mechanisms after injury are crucial to maintain epithelial integrity. However, these healing processes can be insufficient to restore epithelial integrity, notably in infectious conditions. Pseudomonas aeruginosa infections in cutaneous, corneal, and respiratory tract epithelia are of particular concern because they are the leading causes of hospitalizations, disabilities, and deaths worldwide. Pseudomonas aeruginosa has been shown to alter repair processes, leading to chronic wounds and infections. Because of the current increase in the incidence of multi-drug resistant isolates of P. aeruginosa, complementary approaches to decrease the negative impact of these bacteria on epithelia are urgently needed. Here, we review the recent advances in the understanding of the impact of P. aeruginosa infections on the integrity and repair mechanisms of alveolar, airway, cutaneous and corneal epithelia. Potential therapeutic avenues aimed at counteracting this deleterious impact of infection are also discussed.

Pathogenic Mannheimia haemolytica Invades Differentiated Bovine Airway Epithelial Cells

The Gram-negative bacterium Mannheimia haemolytica is the primary bacterial species associated with bovine respiratory disease (BRD) and is responsible for significant economic losses to livestock industries worldwide. Healthy cattle are frequently colonized by commensal serotype A2 strains, but disease is usually caused by pathogenic strains of serotype A1. For reasons that are poorly understood, a transition occurs within the respiratory tract and a sudden explosive proliferation of serotype A1 bacteria leads to the onset of pneumonic disease. Very little is known about the interactions of M. haemolytica with airway epithelial cells of the respiratory mucosa which might explain the different abilities of serotype A1 and A2 strains to cause disease. In the present study, host-pathogen interactions in the bovine respiratory tract were mimicked using a novel differentiated bovine bronchial epithelial cell (BBEC) infection model. In this model, differentiated BBECs were inoculated with serotype A1 or A2 strains of M. haemolytica and the course of infection followed over a 5-day period by microscopic assessment and measurement of key proinflammatory mediators. We have demonstrated that serotype A1, but not A2, M. haemolytica invades differentiated BBECs by transcytosis and subsequently undergoes rapid intracellular replication before spreading to adjacent cells and causing extensive cellular damage. Our findings suggest that the explosive proliferation of serotype A1 M. haemolytica that occurs within the bovine respiratory tract prior to the onset of pneumonic disease is potentially due to bacterial invasion of, and rapid proliferation within, the mucosal epithelium. The discovery of this previously unrecognized mechanism of pathogenesis is important because it will allow the serotype A1-specific virulence determinants responsible for invasion to be identified and thereby provide opportunities for the development of new strategies for combatting BRD aimed at preventing early colonization and infection of the bovine respiratory tract.

Roles, Actions, and Therapeutic Potential of Specialized Pro-resolving Lipid Mediators for the Treatment of Inflammation in Cystic Fibrosis

Non-resolving inflammation is the main mechanism of morbidity and mortality among patients suffering from cystic fibrosis (CF), the most common life-threatening human genetic disease. Resolution of inflammation is an active process timely controlled by endogenous specialized pro-resolving lipid mediators (SPMs) produced locally in inflammatory loci to restrain this innate response, prevent further damages to the host, and permit return to homeostasis. Lipoxins, resolvins, protectins, and maresins are SPM derived from polyunsaturated fatty acids that limit excessive leukocyte infiltration and pro-inflammatory signals, stimulate innate microbial killing, and enhance resolution. Their unique chemical structures, receptors, and bioactions are being elucidated. Accruing data indicate that SPMs carry protective functions against unrelenting inflammation and infections in preclinical models and human CF systems. Here, we reviewed their roles and actions in controlling resolution of inflammation, evidence for their impairment in CF, and proofs of principle for their exploitation as innovative, non-immunosuppressive drugs to address inflammation and infections in CF.

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

Airborne pathogens and environmental stimuli evoke immune responses in the lung. It is critical to health that these responses be controlled to prevent tissue damage and the compromise of organ function. Resolution of inflammation is a dynamic process that is coordinated by biochemical and cellular mechanisms. Recently, specialized proresolving mediators (SPMs) have been identified in resolution exudates. These molecules orchestrate anti-inflammatory and proresolving actions that are cell type specific. In this review, we highlight SPM biosynthesis, the influence of SPMs on the innate and adaptive immune responses in the lung, as well as recent insights from SPMs on inflammatory disease pathophysiology. Uncovering these mediators and cellular mechanisms for resolution is providing new windows into physiology and disease pathogenesis.

Inflammation in cystic fibrosis: An update

Inflammation plays a critical role in cystic fibrosis (CF) lung pathology and disease progression making it an active area of research and important therapeutic target. In this review, we explore the most recent research on the major contributors to the exuberant inflammatory response seen in CF as well as potential therapeutics to combat this response. Absence of functional cystic fibrosis transmembrane conductance regulator (CFTR) alters anion transport across CF airway epithelial cells and ultimately results in dehydration of the airway surface liquid. The dehydrated airway surface liquid in combination with abnormal mucin secretion contributes to airway obstruction and subsequent infection that may serve as a trigger point for inflammation. There is also evidence to suggest that airway inflammation may be excessive and sustained relative to the infectious stimuli. Studies have shown dysregulation of both pro-inflammatory mediators such as IL-17 and pro-resolution mediators including metabolites of the eicosanoid pathway. Recently, CFTR potentiators and correctors have garnered much attention in the CF community. Although these modulators address the underlying defect in CF, their impact on downstream consequences such as inflammation are not known. Here, we review pre-clinical and clinical data on the impact of CFTR modulators on inflammation. In addition, we examine other cell types including neutrophils, macrophages, and T-lymphocytes that express CFTR and contribute to the CF inflammatory response. Finally, we address challenges in developing anti-inflammatory therapies and highlight some of the most promising anti-inflammatory drugs under development for CF.

Specialized Pro-Resolving Lipid Mediators in Cystic Fibrosis

In cystic fibrosis (CF), impaired airway surface hydration (ASL) and mucociliary clearance that promote chronic bacterial colonization, persistent inflammation, and progressive structural damage to the airway wall architecture are typically explained by ion transport abnormalities related to the mutation of the gene coding for the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel. However, the progressive and unrelenting inflammation of the CF airway begins early in life, becomes persistent, and is excessive relative to the bacterial burden. Intrinsic abnormalities of the inflammatory response in cystic fibrosis have been suggested but the mechanisms involved remain poorly understood. This review aims to give an overview of the recent advances in the understanding of the defective resolution of inflammation in CF including the abnormal production of specialized pro-resolving lipid mediators (lipoxin and resolvin) and their impact on the pathogenesis of the CF airway disease.

Specialized Pro-resolving Mediators Regulate Alveolar Fluid Clearance during Acute Respiratory Distress Syndrome

Objective

Acute respiratory distress syndrome (ARDS) is an acute and lethal clinical syndrome that is characterized by the injury of alveolar epithelium, which impairs active fluid transport in the lung, and impedes the reabsorption of edema fluid from the alveolar space. This review aimed to discuss the role of pro-resolving mediators on the regulation of alveolar fluid clearance (AFC) in ARDS.

Data Sources

Articles published up to September 2017 were selected from the PubMed, with the keywords of "alveolar fluid clearance" or "lung edema" or "acute lung injury" or "acute respiratory distress syndrome", and "specialized pro-resolving mediators" or "lipoxin" or "resolvin" or "protectin" or "maresin" or "alveolar epithelial cells" or "aspirin-triggered lipid mediators" or "carbon monoxide and heme oxygenase" or "annexin A1".

Study Selection

We included all relevant articles published up to September 2017, with no limitation of study design.

Results

Specialized pro-resolving mediators (SPMs), as the proinflammatory mediators, not only upregulated epithelial sodium channel, Na,K-ATPase, cystic fibrosis transmembrane conductance regulator (CFTR), and aquaporins levels, but also improved Na,K-ATPase activity to promote AFC in ARDS. In addition to the direct effects on ion channels and pumps of the alveolar epithelium, the SPMs also inhibited the inflammatory cytokine expression and improved the alveolar epithelial cell repair to enhance the AFC in ARDS.

Conclusions

The present review discusses a novel mechanism for pulmonary edema fluid reabsorption. SPMs might provide new opportunities to design "reabsorption-targeted" therapies with high degrees of precision in controlling ALI/ARDS.

Relationship between G proteins coupled receptors and tight junctions

Tight junctions (TJs) are sites of cell-cell adhesion, constituted by a cytoplasmic plaque of molecules linked to integral proteins that form a network of strands around epithelial and endothelial cells at the uppermost portion of the lateral membrane. TJs maintain plasma membrane polarity and form channels and barriers that regulate the transit of ions and molecules through the paracellular pathway. This structure that regulates traffic between the external milieu and the organism is affected in numerous pathological conditions and constitutes an important target for therapeutic intervention. Here, we describe how a wide array of G protein-coupled receptors that are activated by diverse stimuli including light, ions, hormones, peptides, lipids, nucleotides and proteases, signal through heterotrimeric G proteins, arrestins and kinases to regulate TJs present in the blood-brain barrier, the blood-retinal barrier, renal tubular cells, keratinocytes, lung and colon, and the slit diaphragm of the glomerulus.

microRNA-181b is increased in cystic fibrosis cells and impairs lipoxin A4 receptor-dependent mechanisms of inflammation resolution and antimicrobial defense

The involvement of microRNA (miR) in cystic fibrosis (CF) pathobiology is rapidly emerging. We previously documented that miR-181b controls the expression of the ALX/FPR2 receptor, which is recognized by the endogenous proresolution ligand, lipoxin (LX)A₄. Here, we examined whether the miR-181b-ALX/FPR2 circuit was altered in CF. We examined human airways epithelial cells, normal (16HBE14o-), carrying the ΔF508 mutation (CFBE41o-) or corrected for this mutation (CFBE41o-/CEP-CFTR wt 6.2 kb), as well as monocyte-derived macrophages (MΦs) from CF patients. CFBE41o- cells exhibited higher miR-181b and reduced ALX/FPR2 levels compared to 16HBE14o- and CFBE41o-/CEP-CFTR wt 6.2 kb cells. An anti-mir-181b significantly enhanced ALX/FPR2 expression (+ 60%) as well as LXA₄-induced increase in transepithelial electric resistance (+ 25%) in CFBE41o- cells. MΦs from CF patients also displayed increased miR-181b (+ 100%) and lower ALX/FPR2 levels (− 20%) compared to healthy cells. An anti-mir-181b enhanced ALX/FPR2 expression (+ 40%) and normalized receptor-dependent LXA₄-induced phagocytosis of fluorescent-labeled zymosan particles as well as of Pseudomonas aeruginosa by CF-MΦs. These results provide the first evidence that miR-181b is overexpressed in CF cells, impairing some mechanisms of the ALX/FPR2-dependent pathway of inflammation resolution. Thus, targeting miR-181b may represent a strategy to enhance anti-inflammatory and anti-microbial defense mechanisms in CF.

BML-111 equilibrated ACE-AngII-AT1R and ACE2-Ang-(1-7)-Mas axis to protect hepatic fibrosis in rats

BACKGROUND

It was recently reported Lipoxins (LXs) had protective effects on fibrous diseases, and renin-angiotensin-aldosterone system (RAAS) had played vital and bidirectional roles in hepatic fibrosis. In this paper, a hepatic fibrosis model, induced by carbon tetrachloride (CCL₄) in rats, was used to observe the relations between RAAS and LXs, as well as to further explore the alternative anti-fibrosis mechanisms of LXs.

METHODS

The model was evaluated by morphological observations and biochemical assays. The activities and contents of angiotensin converting enzyme (ACE) and angiotensin converting enzyme 2 (ACE2) were examined through assay kits and ELISA. The expression levels of angiotensinII (AngII), Angiotensin II type 1 receptor (AT1R), angiotensin-(1-7) (Ang-1-7), and Mas were all measured using real time PCR, ELISA, and Western blot.

RESULTS

The model was established successfully and BML-111 significantly ameliorated CCL₄-induced hepatic fibrosis, including reduction inflammation injury, decrease extracellular matrix deposition, and improvement hepatic functions. Furthermore, BML-111 could obviously decrease not only the activities of ACE but also the expression levels of ACE, AngII,and AT1R, which were induced by CCL₄. On the other hand, BML-111 could markedly increase the activities of ACE2, besides the expression levels of ACE2, Ang-(1-7) and Mas. More importantly, BOC-2, a lipoxin A₄ receptor blocker, could reverse all these phenomena.

CONCLUSIONS

Equilibrating ACE-AngII-AT1R axis and ACE2-Ang-(1-7)-Mas axis mediated the protective effect of BML-111 on hepatic fibrosis in rats.

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.

Peroxisome proliferator-activated receptor-γ agonists attenuate biofilm formation by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a significant contributor to recalcitrant multidrug-resistant infections, especially in immunocompromised and hospitalized patients. The pathogenic profile of P. aeruginosa is related to its ability to secrete a variety of virulence factors and to promote biofilm formation. Quorum sensing (QS) is a mechanism wherein P. aeruginosa secretes small diffusible molecules, specifically acyl homo serine lactones, such as N-(3-oxo-dodecanoyl)-l-homoserine lactone (3O-C12-HSL), that promote biofilm formation and virulence via interbacterial communication. Strategies that strengthen the host's ability to inhibit bacterial virulence would enhance host defenses and improve the treatment of resistant infections. We have recently shown that peroxisome proliferator-activated receptor γ (PPARγ) agonists are potent immunostimulators that play a pivotal role in host response to virulent P. aeruginosa Here, we show that QS genes in P. aeruginosa (strain PAO1) and 3O-C12-HSL attenuate PPARγ expression in bronchial epithelial cells. PAO1 and 3O-C12-HSL induce barrier derangements in bronchial epithelial cells by lowering the expression of junctional proteins, such as zonula occludens-1, occludin, and claudin-4. Expression of these proteins was restored in cells that were treated with pioglitazone, a PPARγ agonist, before infection with PAO1 and 3O-C12-HSL. Barrier function and bacterial permeation studies that have been performed in primary human epithelial cells showed that PPARγ agonists are able to restore barrier integrity and function that are disrupted by PAO1 and 3O-C12-HSL. Mechanistically, we show that these effects are dependent on the induction of paraoxonase-2, a QS hydrolyzing enzyme, that mitigates the effects of QS molecules. Importantly, our data show that pioglitazone, a PPARγ agonist, significantly inhibits biofilm formation on epithelial cells by a mechanism that is mediated via paraoxonase-2. These findings elucidate a novel role for PPARγ in host defense against P. aeruginosa Strategies that activate PPARγ can provide a therapeutic complement for treatment of resistant P. aeruginosa infections.-Bedi, B., Maurice, N. M., Ciavatta, V. T., Lynn, K. S., Yuan, Z., Molina, S. A., Joo, M., Tyor, W. R., Goldberg, J. B., Koval, M., Hart, C. M., Sadikot, R. T. Peroxisome proliferator-activated receptor-γ agonists attenuate biofilm formation by Pseudomonas aeruginosa.

Does promoting resolution instead of inhibiting inflammation represent the new paradigm in treating infections?

Infections arise when the host response is overwhelmed by pathogens leading to organ dysfunction. In some instances patients progress to more severe conditions, including septic shock, that are associated with increased mortality. Current strategies in treating infections aim at either blocking inflammation using inhibitors to pro-inflammatory molecules and/or inhibiting bacterial growth using antibiotics. These approaches find their origins in studies conducted by Joseph Lister who demonstrated that applying carbolic acid to wounds promoted wound healing without suppuration, reducing both the necessity of amputation and mortality. While this approach is still applicable to certain infections, inhibition of the immune response is also associated with increased mortality, especially in septic patients. In many instances sepsis survivors succumb later to persistent, recurrent, nosocomial and secondary infections. This, together with a rise in resistance to many frontline antibiotics, has prompted a search for alternative ways to treat infections. Recent studies investigating processes engaged by the host response during self-resolving infections identified a novel group of mediators, termed as specialized pro-resolving mediators (SPM). These molecules, produced via the enzymatic conversion of essential fatty acids, actively reprogram the immune response to promote clearance of invading pathogens, and counter-regulate the production of inflammation-initiating molecules. Furthermore, recent studies also demonstrate that these mediators promote tissue repair and regeneration, essential processes in the re-establishment of barrier and prevention of re-infection. The scope of the present review is to discuss the evidence underpinning the endogenous protective roles of these novel mediators, as well as the evidence demonstrating that dysregulation in their production and actions contribute to disease pathogenesis in infections. This review will also discuss the potential of resolution pharmacology-based approaches in developing new therapeutics for combatting infections that do not interfere with the immune response.

Aging exacerbates acute lung injury-induced changes of the air-blood barrier, lung function, and inflammation in the mouse

Acute lung injury (ALI) is characterized by hypoxemia, enhanced permeability of the air-blood barrier, and pulmonary edema. Particularly in the elderly, ALI is associated with increased morbidity and mortality. The reasons for this, however, are poorly understood. We hypothesized that age-related changes in pulmonary structure, function, and inflammation lead to a worse prognosis in ALI. ALI was induced in young (10 wk old) and old (18 mo old) male C57BL/6 mice by intranasal application of 2.5 mg lipopolysaccharide (LPS)/kg body wt or saline (control mice). After 24 h, lung function was assessed, and lungs were either processed for stereological or inflammatory analysis, such as bronchoalveolar lavage fluid (BALF) cytometry and qPCR. Both young and old mice developed severe signs of ALI, including alveolar and septal edema and enhanced inflammatory BALF cells. However, the pathology of ALI was more pronounced in old compared with young mice with nearly sixfold higher BALF protein concentration, twice the number of neutrophils, and significantly higher expression of neutrophil chemokine Cxcl1, adhesion molecule Icam-1, and metalloprotease-9, whereas the expression of tight junction protein occludin significantly decreased. The old LPS mice had thicker alveolar septa attributable to higher volumes of interstitial cells and extracellular matrix. Tissue resistance and elastance reflected observed changes at the ultrastructural level in the lung parenchyma in ALI of young and old mice. In summary, the pathology of ALI with advanced age in mice is characterized by a greater neutrophilic inflammation, leakier air-blood barrier, and altered lung function, which is in line with findings in elderly patients.