Neutrophils from F508del cystic fibrosis patients produce IL-17A and express IL-23 - dependent IL-17RC

Pseudomonas aeruginosa in chronic lung disease: untangling the dysregulated host immune response

Pseudomonas aeruginosa is a highly adaptable opportunistic pathogen capable of exploiting barriers and immune defects to cause chronic lung infections in conditions such as cystic fibrosis. In these contexts, host immune responses are ineffective at clearing persistent bacterial infection, instead driving a cycle of inflammatory lung damage. This review outlines key components of the host immune response to chronic P. aeruginosa infection within the lung, beginning with initial pathogen recognition, followed by a robust yet maladaptive innate immune response, and an ineffective adaptive immune response that propagates lung damage while permitting bacterial persistence. Untangling the interplay between host immunity and chronic P. aeruginosa infection will allow for the development and refinement of strategies to modulate immune-associated lung damage and potentiate the immune system to combat chronic infection more effectively.

Nasal airway inflammatory responses and pathogen detection in infants with cystic fibrosis

BACKGROUND

Detecting airway inflammation non-invasively in infants with cystic fibrosis (CF) is difficult. We hypothesized that markers of inflammation in CF [IL-1β, IL-6, IL-8, IL-10, IL-17A, neutrophil elastase (NE) and tumor necrosis factor (TNF-α)] could be measured in infants with CF from nasal fluid and would be elevated during viral infections or clinician-defined pulmonary exacerbations (PEx).

METHODS

We collected nasal fluid, nasal swabs, and hair samples from 34 infants with CF during monthly clinic visits, sick visits, and hospitalizations. Nasal fluid was isolated and analyzed for cytokines. Respiratory viral detection on nasal swabs was performed using the Luminex NxTAG® Respiratory Pathogen Panel. Hair samples were analyzed for nicotine concentration by reverse-phase high-performance liquid chromatography. We compared nasal cytokine concentrations between the presence and absence of detected respiratory viruses, PEx, and smoke exposure.

RESULTS

A total of 246 samples were analyzed. Compared to measurements in the absence of respiratory viruses, mean concentrations of IL-6, IL-8, TNF-α, and NE were significantly increased while IL-17A was significantly decreased in infants positive for respiratory viruses. IL-17A was significantly decreased and NE increased in those with a PEx. IL-8 and NE were significantly increased in infants with enteric pathogen positivity on airway cultures, but not P. aeruginosa or S. aureus. Compared to those with no smoke exposure, there were significantly higher levels of IL-6, IL-10, and NE in infants with detectable levels of nicotine.

CONCLUSIONS

Noninvasive collection of nasal fluid may identify inflammation in infants with CF during changing clinical or environmental exposures.

The Airway Microbiome-IL-17 Axis: a Critical Regulator of Chronic Inflammatory Disease

The respiratory tract is home to a diverse microbial community whose influence on local and systemic immune responses is only beginning to be appreciated. Increasing reports have linked changes in this microbiome to a range of pulmonary and extrapulmonary disorders, including asthma, chronic obstructive pulmonary disease and rheumatoid arthritis. Central to many of these findings is the role of IL-17-type immunity as an important driver of inflammation. Despite the crucial role played by IL-17-mediated immune responses in protection against infection, overt Th17 cell responses have been implicated in the pathogenesis of several chronic inflammatory diseases. However, our knowledge of the influence of bacteria that commonly colonise the respiratory tract on IL-17-driven inflammatory responses remains sparse. In this article, we review the current knowledge on the role of specific members of the airway microbiota in the modulation of IL-17-type immunity and discuss how this line of research may support the testing of susceptible individuals and targeting of inflammation at its earliest stages in the hope of preventing the development of chronic disease.

Granulocytic Myeloid-Derived Suppressor Cells in Cystic Fibrosis

Cystic Fibrosis (CF) is a genetic disease that causes chronic and severe lung inflammation and infection associated with high rates of mortality. In CF, disrupted ion exchange in the epithelium results in excessive mucus production and reduced mucociliary clearance, leading to immune system exacerbation and chronic infections with pathogens such as P. aeruginosa and S. aureus. Constant immune stimulation leads to altered immune responses including T cell impairment and neutrophil dysfunction. Specifically, CF is considered a Th17-mediated disease, and it has been proposed that both P. aeruginosa and a subset of neutrophils known as granulocytic myeloid suppressor cells (gMDSCs) play a role in T cell suppression. The exact mechanisms behind these interactions are yet to be determined, but recent works demonstrate a role for arginase-1. It is also believed that P. aeruginosa drives gMDSC function as a means of immune evasion, leading to chronic infection. Herein, we review the current literature regarding immune suppression in CF by gMDSCs with an emphasis on T cell impairment and the role of P. aeruginosa in this dynamic interaction.

Th17 associated cytokines in sputum samples from patients with cystic fibrosis

Cystic fibrosis (CF) is a genetic disease leading to chronic bacterial airway infection and inflammation. T helper 17 (Th17) cells are identified by their production of interleukin (IL)-17A, which recruit neutrophils to the site of airway infection. IL-23 is an important inducer of IL-17 and IL-22 production. The aim of this study was to study the role of Th17 cells in CF airway infection by measuring the levels of Th17 associated cytokines in sputum from CF patients with or without airway infection and by comparison with non-CF-controls. In a cross-sectional screening study, cytokine levels were measured with a Th17 multiplex cytokine ELISA. Significantly lower levels of IL-17A and IL-23 were found in sputa from infected CF patients. The lowest levels of IL-17A were found in patients chronically infected with P. aeruginosa, which also had the lowest IL-17/IL-22 ratio, while children had a higher ratio. Children also had higher IL-23 levels than adults. IL-1ß and IL-10 were significantly lower in CF sputum compared to controls. Thus, in our study CF patients with chronic infections had a lower production of Th17 associated cytokines in sputum compared with non-infected CF patients and infected patient without CF.

Airway Inflammation and Host Responses in the Era of CFTR Modulators

The arrival of cystic fibrosis transmembrane conductance regulator (CFTR) modulators as a new class of treatment for cystic fibrosis (CF) in 2012 represented a pivotal advance in disease management, as these small molecules directly target the upstream underlying protein defect. Further advancements in the development and scope of these genotype-specific therapies have been transformative for an increasing number of people with CF (PWCF). Despite clear improvements in CFTR function and clinical endpoints such as lung function, body mass index (BMI), and frequency of pulmonary exacerbations, current evidence suggests that CFTR modulators do not prevent continued decline in lung function, halt disease progression, or ameliorate pathogenic organisms in those with established lung disease. Furthermore, it remains unknown whether their restorative effects extend to dysfunctional CFTR expressed in phagocytes and other immune cells, which could modulate airway inflammation. In this review, we explore the effects of CFTR modulators on airway inflammation, infection, and their influence on the impaired pulmonary host defences associated with CF lung disease. We also consider the role of inflammation-directed therapies in light of the widespread clinical use of CFTR modulators and identify key areas for future research.

Scnn1b-Transgenic BALB/c Mice as a Model of Pseudomonas aeruginosa Infections of the Cystic Fibrosis Lung

The opportunistic pathogen Pseudomonas aeruginosa is responsible for much of the morbidity and mortality associated with cystic fibrosis (CF), a condition that predisposes patients to chronic lung infections. P. aeruginosa lung infections are difficult to treat because P. aeruginosa adapts to the CF lung, can develop multidrug resistance, and can form biofilms. Despite the clinical significance of P. aeruginosa, modeling P. aeruginosa infections in CF has been challenging. Here, we characterize Scnn1b-transgenic (Tg) BALB/c mice as P. aeruginosa lung infection models. Scnn1b-Tg mice overexpress the epithelial Na+ channel (ENaC) in their lungs, driving increased sodium absorption that causes lung pathology similar to CF. We intranasally infected Scnn1b-Tg mice and wild-type littermates with the laboratory P. aeruginosa strain PAO1 and CF clinical isolates and then assessed differences in bacterial clearance, cytokine responses, and histological features up to 12 days postinfection. Scnn1b-Tg mice carried higher bacterial burdens when infected with biofilm-grown rather than planktonic PAO1; Scnn1b-Tg mice also cleared infections more slowly than their wild-type littermates. Infection with PAO1 elicited significant increases in proinflammatory and Th17-linked cytokines on day 3. Scnn1b-Tg mice infected with nonmucoid early CF isolates maintained bacterial burdens and mounted immune responses similar to those of PAO1-infected Scnn1b-Tg mice. In contrast, Scnn1b-Tg mice infected with a mucoid CF isolate carried high bacterial burdens, produced significantly more interleukin 1β (IL-1β), IL-13, IL-17, IL-22, and KC, and showed severe immune cell infiltration into the bronchioles. Taken together, these results show the promise of Scnn1b-Tg mice as models of early P. aeruginosa colonization in the CF lung.

The role of inflammation in cystic fibrosis pulmonary exacerbations

INTRODUCTION

Cystic Fibrosis pulmonary exacerbations are critical events in the lives of people with CF that have deleterious effects on lung function, quality of life, and life expectancy. There are significant unmet needs in the management of exacerbations. We review here the associated inflammatory changes that underlie these events and are of interest for the development of biomarkers of exacerbation.

AREAS COVERED

Inflammatory responses in CF are abnormal and contribute to a sustained proinflammatory lung microenvironment, abundant in proinflammatory mediators and deficient in counter-regulatory mediators that terminate and resolve inflammation. There is increasing interest in these inflammatory pathways to discover novel biomarkers for pulmonary exacerbation management. In this review, we explore the inflammatory changes occurring during intravenous antibiotic therapy for exacerbation and how they may be applied as biomarkers to guide exacerbation therapy. A literature search was conducted using the PubMed database in February 2020.

EXPERT OPINION

Heterogeneity in inflammatory responses to treatment of a pulmonary exacerbation, a disease process with complex pathophysiology, limits the clinical utility of individual biomarkers. Biomarker panels may be a more successful strategy to capture informative changes within the CF population to improve pulmonary exacerbation management and outcomes.

Mycobacterium tuberculosis-Induced Bronchoalveolar Lavage Gene Expression Signature in Latent Tuberculosis Infection Is Dominated by Pleiotropic Effects of CD4+ T Cell-Dependent IFN-γ Production despite the Presence of Polyfunctional T Cells within the Airways

Tuberculosis (TB) remains a worldwide public health threat. Development of a more effective vaccination strategy to prevent pulmonary TB, the most common and contagious form of the disease, is a research priority for international TB control. A key to reaching this goal is improved understanding of the mechanisms of local immunity to Mycobacterium tuberculosis, the causative organism of TB. In this study, we evaluated global M. tuberculosis-induced gene expression in airway immune cells obtained by bronchoalveolar lavage (BAL) of individuals with latent TB infection (LTBI) and M. tuberculosis-naive controls. In prior studies, we demonstrated that BAL cells from LTBI individuals display substantial enrichment for M. tuberculosis-responsive CD4⁺ T cells compared with matched peripheral blood samples. We therefore specifically assessed the impact of the depletion of CD4⁺ and CD8⁺ T cells on M. tuberculosis-induced BAL cell gene expression in LTBI. Our studies identified 12 canonical pathways and a 47-gene signature that was both sensitive and specific for the contribution of CD4⁺ T cells to local recall responses to M. tuberculosis In contrast, depletion of CD8⁺ cells did not identify any genes that fit our strict criteria for inclusion in this signature. Although BAL CD4⁺ T cells in LTBI displayed polyfunctionality, the observed gene signature predominantly reflected the impact of IFN-γ production on a wide range of host immune responses. These findings provide a standard for comparison of the efficacy of standard bacillus Calmette-Guérin vaccination as well as novel TB vaccines now in development at impacting the initial response to re-exposure to M. tuberculosis in the human lung.

Vitamin D inhibits pro-inflammatory cytokines in the airways of cystic fibrosis patients infected by Pseudomonas aeruginosa- pilot study

Background

Vitamin D plays an important role in inflammatory responses after antigen exposure. Interleukin-23 (Il-23) promotes Il-17-dependent inflammation during Pseudomonas aeruginosa (P. aeruginosa) pulmonary infection. We aimed to compare the ability of calcitriol and cholecalciferol to modulate the inflammatory response of the CF airways infected with P. aeruginosa.

Methods

This was a randomized, placebo-controlled, double-blind, cross-over trial. Twenty-three patients with CF (aged 6–19), chronically infected by P. aeruginosa were randomly assigned to: calcitriol group receiving 1,25(OH)₂D 0,5 mcg daily or cholecalciferol group receiving cholecalciferol 1000 IU daily for three months. The levels of Il-23 and Il-17A in the exhaled breath concentrate (EBC) were measured. Calcium-phosphorus balance was also evaluated (serum concentration of calcium, phosphorus, 25OHD, parathormone (PTH) and calcium/creatinine ratio in urine). Data were analyzed using means of Stata/Special Edition, release 14.2. A level of P < 0.05 was considered statistically significant.

Results

The level of Il-17A in EBC significantly decreased in calcitriol group from 0,475 pg/mL (± SD 0,515 pg/mL) to 0,384 pg/mL (± SD 0,429 pg/mL) (p = 0,008); there was no change in cholecalciferol group (p = 0,074). The level of Il-23 in EBC did not significantly change in calcitriol group (p = 0,086); there was significant decrease in cholecalciferol group from 8,90 pg/mL (± SD 4,07 pg/mL) to 7,33 pg/mL (± SD 3,88 pg/mL) (p = 0,001). In calcitriol group serum phosphorus and PTH significantly decreased (p = 0,021 and p = 0,019 respectively), the concentration of calcium significantly increased (p = 0,001); there were no changes in cholecalciferol group.

Conclusions

Both analogs of vitamin D revealed their anti-inflammatory effect and reduced the level of Il-17A and Il-23 in the airway of CF patients with chronic P. aeruginosa infection. We observed improvement in calcium-phosphorus metabolism after supplementation with calcitriol, without adverse effects. It is recommended to use vitamin D in CF patients.

Progression of Cystic Fibrosis Lung Disease from Childhood to Adulthood: Neutrophils, Neutrophil Extracellular Trap (NET) Formation, and NET Degradation

Genetic defects in cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene cause CF. Infants with CFTR mutations show a peribronchial neutrophil infiltration prior to the establishment of infection in their lung. The inflammatory response progressively increases in children that include both upper and lower airways. Infectious and inflammatory response leads to an increase in mucus viscosity and mucus plugging of small and medium-size bronchioles. Eventually, neutrophils chronically infiltrate the airways with biofilm or chronic bacterial infection. Perpetual infection and airway inflammation destroy the lungs, which leads to increased morbidity and eventual mortality in most of the patients with CF. Studies have now established that neutrophil cytotoxins, extracellular DNA, and neutrophil extracellular traps (NETs) are associated with increased mucus clogging and lung injury in CF. In addition to opportunistic pathogens, various aspects of the CF airway milieux (e.g., airway pH, salt concentration, and neutrophil phenotypes) influence the NETotic capacity of neutrophils. CF airway milieu may promote the survival of neutrophils and eventual pro-inflammatory aberrant NETosis, rather than the anti-inflammatory apoptotic death in these cells. Degrading NETs helps to manage CF airway disease; since DNAse treatment release cytotoxins from the NETs, further improvements are needed to degrade NETs with maximal positive effects. Neutrophil-T cell interactions may be important in regulating viral infection-mediated pulmonary exacerbations in patients with bacterial infections. Therefore, clarifying the role of neutrophils and NETs in CF lung disease and identifying therapies that preserve the positive effects of neutrophils, while reducing the detrimental effects of NETs and cytotoxic components, are essential in achieving innovative therapeutic advances.

Gamma Interferon and Interleukin-17A Differentially Influence the Response of Human Macrophages and Neutrophils to Pseudomonas aeruginosa Infection

Macrophages are important orchestrators of inflammation during bacterial infection, acting as both effector cells and regulators of neutrophil recruitment and life span. Differently activated macrophage populations with distinct inflammatory and microbicidal potentials have been described.

Macrophages are important orchestrators of inflammation during bacterial infection, acting as both effector cells and regulators of neutrophil recruitment and life span. Differently activated macrophage populations with distinct inflammatory and microbicidal potentials have been described. Our previous work unveiled a positive and a negative correlation between levels of gamma interferon (IFN-γ) and interleukin-17A (IL-17A), respectively, and lung function in cystic fibrosis, particularly in patients chronically infected with Pseudomonas aeruginosa. This study sought to define key parameters in human antibacterial immunity under Th1- and Th17-dominated inflammatory conditions; the final aim was to identify unique characteristics that could be fine-tuned therapeutically to minimize tissue damage while maximizing bacterial clearance. Toward this aim, neutrophils were incorporated into cultures of macrophages treated with IFN-γ or IL-17A and infected with P. aeruginosa. The intent of this design was to model (i) initiation of inflammation by infected macrophages and (ii) delayed arrival of neutrophils and their exposure to macrophage-derived cytokines. Under these conditions, IFN-γ decreased bacterial killing and promoted the production of monocyte chemoattractant protein 1 (MCP-1). In contrast, IL-17A promoted bacterial killing but did not affect MCP-1 production. The level of secretion of the pyrogen IL-1β was significantly lower in the presence of IFN-γ than in the presence of IL-17A and correlated with levels of the IL1B transcript in infected macrophages. These findings support the validity of this model to investigate human antibacterial immunity. Based on these observations, the protective and damaging roles of IFN-γ and IL-17A, respectively, during P. aeruginosa infection could be caused by their contrasting effects on IL-1β and MCP-1 production.

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.

Cytokine production by human neutrophils: Revisiting the "dark side of the moon"

Polymorphonuclear neutrophils are the most numerous leucocytes present in human blood, and function as crucial players in innate immune responses. Neutrophils are indispensable for the defence towards microbes, as they effectively counter them by releasing toxic enzymes, by synthetizing reactive oxygen species and by producing inflammatory mediators. Interestingly, recent findings have highlighted an important role of neutrophils also as promoters of the resolution of inflammation process, indicating that their biological functions go well beyond simple pathogen killing. Consistently, data from the last decades have highlighted that neutrophils may even contribute to the development of adaptive immunity by performing previously unanticipated functions, including the capacity to extend their survival, directly interact with other leucocytes or cell types, and produce and release a variety of cytokines. In this article, we will summarize the main features of, as well as emphasize some important concepts on, the production of cytokines by human neutrophils.

A Reappraisal on the Potential Ability of Human Neutrophils to Express and Produce IL-17 Family Members In Vitro: Failure to Reproducibly Detect It

Neutrophils are known to perform a series of effector functions that are crucial for the innate and adaptive responses, including the synthesis and secretion of a variety of cytokines. In light of the controversial data in the literature, the main objective of this study was to more in-depth reevaluate the capacity of human neutrophils to express and produce cytokines of the IL-17 family in vitro. By reverse transcription quantitative real-time PCR, protein measurement via commercial ELISA, immunohistochemistry (IHC) and immunofluorescence (IF), flow cytometry, immunoblotting, chromatin immunoprecipitation (ChIP), and ChIP-seq experiments, we found that highly pure (>99.7%) populations of human neutrophils do not express/produce IL-17A, IL-17F, IL-17AF, or IL-17B mRNA/protein upon incubation with a variety of agonists. Similar findings were observed by analyzing neutrophils isolated from active psoriatic patients. In contrast with published studies, IL-17A and IL-17F mRNA expression/production was not even found when neutrophils were incubated with extremely high concentrations of IL-6 plus IL-23, regardless of their combination with inactivated hyphae or conidia from Aspergillus fumigatus. Consistently, no deposition of histone marks for active (H3K27Ac) and poised (H3K4me1) genomic regulatory elements was detected at the IL-17A and IL-17F locus of resting and IL-6 plus IL-23-stimulated neutrophils, indicating a closed chromatin conformation. Concurrent experiments revealed that some commercial anti-IL-17A and anti-IL-17B antibodies (Abs), although staining neutrophils either spotted on cytospin slides or present in inflamed tissue samples by IHC/IF, do not recognize intracellular protein having the molecular weight corresponding to IL-17A or IL-17B, respectively, in immunoblotting experiments of whole neutrophil lysates. By contrast, the same Abs were found to more specifically recognize other intracellular proteins of neutrophils, suggesting that their ability to positively stain neutrophils in cytospin preparations and, eventually, tissue samples derives from IL-17A- or IL-17B-independent detections. In sum, our data confirm and extend, also at epigenetic level, previous findings on the inability of highly purified populations of human neutrophils to express/produce IL-17A, IL-17B, and IL-17F mRNAs/proteins in vitro, at least under the experimental conditions herein tested. Data also provide a number of justifications explaining, in part, why it is possible to false positively detect IL-17A⁺-neutrophils.

The neutrophil: one cell on many missions or many cells with different agendas?

The unique role of neutrophils in host defense is not only based on their abilities to kill bacteria but is also due to their abundance in circulation and their ability to quickly migrate and accumulate in great numbers at afflicted sites. The high number of circulating neutrophils is the result of regulated release of new neutrophils from bone marrow as well as from marginated pools to balance their recruitment to tissue. Marginated pools, such as the spleen and lung, have previously been attributed to passively delay neutrophil transit time due to their large capillary network, but recent reports demonstrate that they are comprised of neutrophils with specific functions. The spleen, for instance, holds neutrophil subpopulations at different anatomical locations with distinct functions important for, e.g., bacterial eradication, and the lung was recently shown to re-educate neutrophils that had trafficked from a site of sterile injury to home back to bone marrow for elimination. Further, recent reports demonstrate subpopulations of neutrophils with different actions during homeostasis, infection, tissue restitution and cancer. It is becoming increasingly clear that this cannot be due to different stages of neutrophil activation during their life span but instead points towards distinct subpopulations of neutrophils with different effector functions. Whether these cellular distinctions are due to different education or origin is, however, not yet known. Together, the accumulating information about the heterogeneous neutrophils presents important insights into their role in development of pathologies, as well as revealing novel targets in the form of certain subpopulations to treat disease.

Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection

Interleukin-17 (IL-17) is a pro-inflammatory cytokine involved in the control of many different disorders, including autoimmune, oncogenic, and diverse infectious diseases. In the context of infectious diseases, IL-17 protects the host against various classes of microorganisms but, intriguingly, can also exacerbate the severity of some infections. The regulation of IL-17 expression stems, in part, from the activity of Interleukin-23 (IL-23), which drives the maturation of different classes of IL-17-producing cells that can alter the course of infection. In this review, we analyze IL-17/IL-23 signalling in bacterial infection, and examine the interconnecting mechanisms that link immune regulation, host genetics, and microbial virulence in the context of bacterial pathogenesis. We consider the roles of IL-17 in both acute and chronic bacterial infections, with a focus on mouse models of human bacterial disease that involve infection of mucosal surfaces in the lungs, urogenital, and gastrointestinal tracts. Polymorphisms in IL-17-encoding genes in humans, which have been associated with heightened host susceptibility to some bacterial pathogens, are discussed. Finally, we examine the implications of IL-17 biology in infectious diseases for the development of novel therapeutic strategies targeted at preventing bacterial infection.

Immunity and Fibrogenesis: The Role of Th17/IL-17 Axis in HBV and HCV-induced Chronic Hepatitis and Progression to Cirrhosis

Cirrhosis is a common final pathway for most chronic liver diseases; representing an increasing burden worldwide and is associated with increased morbidity and mortality. Current evidence has shown that, after an initial injury, the immune response has a significant participation in the ongoing damage, and progression from chronic viral hepatitis (CVH) to cirrhosis, driving the activation and maintenance of main fibrogenic pathways. Among immune deregulations, those related to the subtype 17 of T helper lymphocytes (Th17)/interleukin-17 (IL-17) axis have been recognized as key immunopathological and prognostic elements in patients with CVH. The Th17/IL-17 axis has been found involved in several points of fibrogenesis chain from the activation of stellate cells, increased expression of profibrotic factors as TGF-β, promotion of the myofibroblastic or epithelial–mesenchymal transition, stimulation of the synthesis of collagen, and induction of imbalance between matrix metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs). It also promotes the recruitment of inflammatory cells and increases the expression of proinflammatory cytokines such as IL-6 and IL-23. So, the Th17/IL-17 axis is simultaneously the fuel and the flame of a sustained proinflammatory and profibrotic environment. This work aims to present the immunopathologic and prognostic role of the Th17/IL-17 axis and related pathways in fibrogenesis and progression to cirrhosis in patients with liver disease due to hepatitis B virus (HBV) and hepatitis C virus (HCV).

Interactions between Neutrophils and Pseudomonas aeruginosa in Cystic Fibrosis

Cystic fibrosis (CF) affects 70,000 patients worldwide. Morbidity and mortality in CF is largely caused by lung complications due to the triad of impaired mucociliary clearance, microbial infections and chronic inflammation. Cystic fibrosis airway inflammation is mediated by robust infiltration of polymorphonuclear neutrophil granulocytes (PMNs, neutrophils). Neutrophils are not capable of clearing lung infections and contribute to tissue damage by releasing their dangerous cargo. Pseudomonas aeruginosa is an opportunistic pathogen causing infections in immunocompromised individuals. P. aeruginosa is a main respiratory pathogen in CF infecting most patients. Although PMNs are key to attack and clear P. aeruginosa in immunocompetent individuals, PMNs fail to do so in CF. Understanding why neutrophils cannot clear P. aeruginosa in CF is essential to design novel therapies. This review provides an overview of the antimicrobial mechanisms by which PMNs attack and eliminate P. aeruginosa. It also summarizes current advances in our understanding of why PMNs are incapable of clearing P. aeruginosa and how this bacterium adapts to and resists PMN-mediated killing in the airways of CF patients chronically infected with P. aeruginosa.

Expression and Influence of Matrix Metalloproteinase–9/Tissue Inhibitor of Metalloproteinase–1 and Vascular Endothelial Growth Factor in Diabetic Foot Ulcers

A high matrix metalloproteinase–9/tissue inhibitor of metalloproteinase–1 (MMP9/TIMP1) ratio is associated with poor ulcer healing, yet how the ratio of MMP9/TIMP1 changes in diabetic foot ulcers (DFUs) with infection and how these changes may affect wound healing remain unclear. Therefore, the objective of this investigation was to explore relationships among the MMP9/TIMP1 ratio, infection, and DFUs. After being informed of the details of this study, 32 patients signed consent forms. Skin biopsies were performed for all patients. Wound tissues were obtained from all patients with wounds, and healthy skin samples were collected from patients without wounds during orthopedic surgery. Microbial cultures were obtained using the samples from diabetic patients with wounds. All patients were divided into 4 groups according to colony-forming units (CFUs) per gram of tissue (>1 × 106 or <1 × 106): group A (diabetic wounds with high quantities of bacteria), group B (diabetic wounds with low quantities of bacteria), group C (diabetic patients without wounds), and group D (nondiabetic patients with wounds). In addition, the biopsies were evaluated by both reverse transcription–quantitative polymerase chain reaction and Western blotting to assess the levels of MMP9, TIMP1, and vascular endothelial growth factor (VEGF). The results show that for both mRNA and protein, expression of MMP9 (fold change 1.14 ± 0.12 vs 0.60 ± 0.08 vs 0.39±0.09 vs 0.13 ± 0.06, P < .01) decreased, whereas that of TIMP1 (1.01 ± 0.09 vs 2.86 ± 0.85 vs 4.88 ± 0.83 vs 7.29 ± 1.55, P < .01) and VEGF (1.01 ± 0.22 vs 3.55 ± 0.97 vs 5.72 ± 0.55 vs 6.92 ± 1.55, P < .01) increased from group A to group D. These results suggest that an increase in the MMP9/TIMP1 ratio in infected DFUs may induce a decrease in VEGF expression.

IL-17 mediates neutrophil infiltration and renal fibrosis following recovery from ischemia reperfusion: compensatory role of natural killer cells in athymic rats

T cells have been implicated in the pathogenesis of acute kidney injury (AKI) and its progression to chronic kidney disease (CKD). Previous studies suggest that Th17 cells participate during the AKI-to-CKD transition, and inhibition of T cell activity by mycophenolate mofetil (MMF) or losartan attenuates the development of fibrosis following AKI. We hypothesized that T cell-deficient rats may have reduced levels of IL-17 cytokine leading to decreased fibrosis following AKI. Renal ischemis-reperfusion (I/R) was performed on T cell-deficient athymic rats (Foxn1^rnu-/rnu-) and control euthymic rats (Foxn1^rnu-/+), and CKD progression was hastened by unilateral nephrectomy at day 33 and subsequent exposure to 4.0% sodium diet. Renal fibrosis developed in euthymic rats and was reduced by MMF treatment. Athymic rats exhibited a similar degree of fibrosis, but this was unaffected by MMF treatment. FACS analysis demonstrated that the number of IL-17⁺ cells was similar between postischemic athymic vs. euthymic rats. The source of IL-17 production in euthymic rats was predominately from conventional T cells (CD3⁺/CD161^-). In the absence of conventional T cells in athymic rats, a compensatory pathway involving natural killer cells (CD3^-/CD161⁺) was the primary source of IL-17. Blockade of IL-17 activity using IL-17Rc receptor significantly decreased fibrosis and neutrophil recruitment in both euthymic and athymic rats compared with vehicle-treated controls. Taken together, these data suggest that IL-17 secretion participates in the pathogenesis of AKI-induced fibrosis possibly via the recruitment of neutrophils and that the source of IL-17 may be from either conventional T cells or NK cells.

Immune Imbalances in Non-Alcoholic Fatty Liver Disease: From General Biomarkers and Neutrophils to Interleukin-17 Axis Activation and New Therapeutic Targets

Non-alcoholic fatty liver disease (NAFLD) is an increasing problem worldwide and is associated with negative outcomes such as cirrhosis, hepatocellular carcinoma, insulin resistance, diabetes, and cardiovascular events. Current evidence shows that the immune response has an important participation driving the initiation, maintenance, and progression of the disease. So, various immune imbalances, from cellular to cytokines levels, have been studied, either for better compression of the disease pathophysiology or as biomarkers for severity assessment and outcome prediction. In this article, we performed a thorough review of studies that evaluated the role of inflammatory/immune imbalances in the NAFLD. At the cellular level, we gave special focus on the imbalance between neutrophils and lymphocytes counts (the neutrophil-to-lymphocyte ratio), and that which occurs between T helper 17 (Th17) and regulatory T cells as emerging biomarkers. By extension, we reviewed the reflection of these imbalances at the molecular level through pro-inflammatory cytokines including those involved in Th17 differentiation (IL-6, IL-21, IL-23, and transforming growth factor-beta), and those released by Th17 cells (IL-17A, IL-17F, IL-21, and IL-22). We gave particular attention to the role of IL-17, either produced by Th17 cells or neutrophils, in fibrogenesis and steatohepatitis. Finally, we reviewed the potential of these pathways as new therapeutic targets in NAFLD.

Interleukin-17 Pathophysiology and Therapeutic Intervention in Cystic Fibrosis Lung Infection and Inflammation

Cystic fibrosis (CF) is characterized by an excessive neutrophilic inflammatory response within the airway as a result of defective cystic fibrosis transmembrane receptor (CFTR) expression and function. Interleukin-17A induces airway neutrophilia and mucin production associated with Pseudomonas aeruginosa colonization, which is associated with the pathophysiology of cystic fibrosis. The objectives of this study were to use the preclinical murine model of cystic fibrosis lung infection and inflammation to investigate the role of IL-17 in CF lung pathophysiology and explore therapeutic intervention with a focus on IL-17. Cftr-deficient mice (CF mice) and wild-type mice (WT mice) infected with P. aeruginosa had robust IL-17 production early in the infection associated with a persistent elevated inflammatory response. Intratracheal administration of IL-17 provoked a neutrophilic response in the airways of WT and CF animals which was similar to that observed with P. aeruginosa infection. The neutralization of IL-17 prior to infection significantly improved the outcomes in the CF mice, suggesting that IL-17 may be a therapeutic target. We demonstrate in this report that the pathophysiological contribution of IL-17 may be due to the induction of chemokines from the epithelium which is augmented by a deficiency of Cftr and ongoing inflammation. These studies demonstrate the in vivo contribution of IL-17 in cystic fibrosis lung disease and the therapeutic validity of attenuating IL-17 activity in cystic fibrosis.