Sepsis-induced inhibition of neutrophil chemotaxis is mediated by activation of peroxisome proliferator-activated receptor-{gamma}

Carbohydrate metabolism in supporting and regulating neutrophil effector functions

Neutrophils, the first responders of the innate immune system, can turn on a range of effector functions upon activation. Emerging research shows activated neutrophils undergo highly dynamic metabolic rewiring. This metabolic rewiring provides energy and reducing power to fuel effector functions and modulate signaling molecules to regulate neutrophil functions. Here, we review the current understanding of the specific metabolic requirements and regulators of neutrophil migration, neutrophil extracellular traps release, and pathogen killing. Particularly, we discuss how major carbohydrate metabolic pathways, including glycolysis, glycogen cycling, pentose phosphate pathway, and TCA cycle, are rewired upon neutrophil activation to support these functions. Continued investigation into the metabolic regulators of neutrophil functions can lead to therapeutic opportunities in various diseases.

Metabolic regulation of neutrophil functions in homeostasis and diseases

Neutrophils are the most abundant leukocytes in humans and play a role in the innate immune response by being the first cells attracted to the site of infection. While early studies presented neutrophils as almost exclusively glycolytic cells, recent advances show that these cells use several metabolic pathways other than glycolysis, such as the pentose phosphate pathway, oxidative phosphorylation, fatty acid oxidation, and glutaminolysis, which they modulate to perform their functions. Metabolism shifts from fatty acid oxidation-mediated mitochondrial respiration in immature neutrophils to glycolysis in mature neutrophils. Tissue environments largely influence neutrophil metabolism according to nutrient sources, inflammatory mediators, and oxygen availability. Inhibition of metabolic pathways in neutrophils results in impairment of certain effector functions, such as NETosis, chemotaxis, degranulation, and reactive oxygen species generation. Alteration of these neutrophil functions is implicated in certain human diseases, such as antiphospholipid syndrome, coronavirus disease 2019, and bronchiectasis. Metabolic regulators such as AMPK, HIF-1α, mTOR, and Arf6 are linked to neutrophil metabolism and function and could potentially be targeted for the treatment of diseases associated with neutrophil dysfunction. This review details the effects of alterations in neutrophil metabolism on the effector functions of these cells.

Sided Stimulation of Endothelial Cells Modulates Neutrophil Trafficking in an In Vitro Sepsis Model

While the role of dysregulated polymorphonuclear leukocyte (PMN) transmigration in septic mediated tissue damage is well documented, strategies to mitigate aberrant transmigration across endothelium have yet to yield viable therapeutics. Recently, microphysiological systems (MPS) have emerged as novel in vitro mimetics that facilitate the development of human models of disease. With this advancement, aspects of endothelial physiology that are difficult to assess with other models can be directly probed. In this study, the role of endothelial cell (EC) apicobasal polarity on leukocyte trafficking response is evaluated with the µSiM-MVM (microphysiological system enabled by a silicon membrane - microvascular mimetic). Here, ECs are stimulated either apically or basally with a cytokine cocktail to model a septic-like challenge before introducing healthy donor PMNs into the device. Basally oriented stimulation generated a stronger PMN transmigratory response versus apical stimulation. Importantly, healthy PMNs are unable to migrate towards a bacterial peptide chemoattractant when ECs are apically stimulated, which mimics the attenuated PMN chemotaxis seen in sepsis. Escalating the apical inflammatory stimulus by a factor of five is necessary to elicit high PMN transmigration levels across endothelium. These results demonstrate that EC apicobasal polarity modulates PMN transmigratory behavior and provides insight into the mechanisms underlying sepsis.

Prenatal exposures to per- and polyfluoroalkyl substances and epigenetic aging in umbilical cord blood: The Healthy Start study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous, environmentally persistent chemicals, and prenatal exposures have been associated with adverse child health outcomes. Prenatal PFAS exposure may lead to epigenetic age acceleration (EAA), defined as the discrepancy between an individual's chronologic and epigenetic or biological age.

OBJECTIVES

We estimated associations of maternal serum PFAS concentrations with EAA in umbilical cord blood DNA methylation using linear regression, and a multivariable exposure-response function of the PFAS mixture using Bayesian kernel machine regression.

METHODS

Five PFAS were quantified in maternal serum (median: 27 weeks of gestation) among 577 mother-infant dyads from a prospective cohort. Cord blood DNA methylation data were assessed with the Illumina HumanMethylation450 array. EAA was calculated as the residuals from regressing gestational age on epigenetic age, calculated using a cord-blood specific epigenetic clock. Linear regression tested for associations between each maternal PFAS concentration with EAA. Bayesian kernel machine regression with hierarchical selection estimated an exposure-response function for the PFAS mixture.

RESULTS

In single pollutant models we observed an inverse relationship between perfluorodecanoate (PFDA) and EAA (-0.148 weeks per log-unit increase, 95% CI: -0.283, -0.013). Mixture analysis with hierarchical selection between perfluoroalkyl carboxylates and sulfonates indicated the carboxylates had the highest group posterior inclusion probability (PIP), or relative importance. Within this group, PFDA had the highest conditional PIP. Univariate predictor-response functions indicated PFDA and perfluorononanoate were inversely associated with EAA, while perfluorohexane sulfonate had a positive association with EAA.

CONCLUSIONS

Maternal mid-pregnancy serum concentrations of PFDA were negatively associated with EAA in cord blood, suggesting a pathway by which prenatal PFAS exposures may affect infant development. No significant associations were observed with other PFAS. Mixture models suggested opposite directions of association between perfluoroalkyl sulfonates and carboxylates. Future studies are needed to determine the importance of neonatal EAA for later child health outcomes.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Long Noncoding RNA U90926 Is Induced in Activated Macrophages, Is Protective in Endotoxic Shock, and Encodes a Novel Secreted Protein

Thousands of long noncoding RNAs are encoded in mammalian genomes, yet most remain uncharacterized. In this study, we functionally characterized a mouse long noncoding RNA named U90926. Analysis of U90926 RNA levels revealed minimal expression across multiple tissues at steady state. However, the expression of this gene was highly induced in macrophages and dendritic cells by TLR activation, in a p38 MAPK- and MyD88-dependent manner. To study the function of U90926, we generated U90926-deficient (U9-KO) mice. Surprisingly, we found minimal effects of U90926 deficiency in cultured macrophages. Given the lack of macrophage-intrinsic effect, we investigated the subcellular localization of U90926 transcript and its protein-coding potential. We found that U90926 RNA localizes to the cytosol, associates with ribosomes, and contains an open reading frame that encodes a novel glycosylated protein (termed U9-ORF), which is secreted from the cell. An in vivo model of endotoxic shock revealed that, in comparison with wild type mice, U9-KO mice exhibited increased sickness responses and mortality. Mechanistically, serum levels of IL-6 were elevated in U9-KO mice, and IL-6 neutralization improved endotoxemia outcomes in U9-KO mice. Taken together, these results suggest that U90926 expression is protective during endotoxic shock, potentially mediated by the paracrine and/or endocrine actions of the novel U9-ORF protein secreted by activated myeloid cells.

The emerging role for metabolism in fueling neutrophilic inflammation

Neutrophils are a critical element of host defense and are rapidly recruited to inflammatory sites. Such sites are frequently limited in oxygen and/or nutrient availability, presenting a metabolic challenge for infiltrating cells. Long believed to be uniquely dependent on glycolysis, it is now clear that neutrophils possess far greater metabolic plasticity than previously thought, with the capacity to generate energy stores and utilize extracellular proteins to fuel central carbon metabolism and biosynthetic activity. Out-with cellular energetics, metabolic programs have also been implicated in the production of neutrophils and their progenitors in the bone marrow compartment, activation of neutrophil antimicrobial responses, inflammatory and cell survival signaling cascades, and training of the innate immune response. Thus, understanding the mechanisms by which metabolic processes sustain changes in neutrophil effector functions and how these are subverted in disease states provides exciting new avenues for the treatment of dysfunctional neutrophilic inflammation which are lacking in clinical practice to date.

The role of G protein-coupled receptor in neutrophil dysfunction during sepsis-induced acute respiratory distress syndrome

Sepsis is defined as a life-threatening dysfunction due to a dysregulated host response to infection. It is a common and complex syndrome and is the leading cause of death in intensive care units. The lungs are most vulnerable to the challenge of sepsis, and the incidence of respiratory dysfunction has been reported to be up to 70%, in which neutrophils play a major role. Neutrophils are the first line of defense against infection, and they are regarded as the most responsive cells in sepsis. Normally, neutrophils recognize chemokines including the bacterial product N-formyl-methionyl-leucyl-phenylalanine (fMLP), complement 5a (C5a), and lipid molecules Leukotriene B4 (LTB4) and C-X-C motif chemokine ligand 8 (CXCL8), and enter the site of infection through mobilization, rolling, adhesion, migration, and chemotaxis. However, numerous studies have confirmed that despite the high levels of chemokines in septic patients and mice at the site of infection, the neutrophils cannot migrate to the proper target location, but instead they accumulate in the lungs, releasing histones, DNA, and proteases that mediate tissue damage and induce acute respiratory distress syndrome (ARDS). This is closely related to impaired neutrophil migration in sepsis, but the mechanism involved is still unclear. Many studies have shown that chemokine receptor dysregulation is an important cause of impaired neutrophil migration, and the vast majority of these chemokine receptors belong to the G protein-coupled receptors (GPCRs). In this review, we summarize the signaling pathways by which neutrophil GPCR regulates chemotaxis and the mechanisms by which abnormal GPCR function in sepsis leads to impaired neutrophil chemotaxis, which can further cause ARDS. Several potential targets for intervention are proposed to improve neutrophil chemotaxis, and we hope that this review may provide insights for clinical practitioners.

Recent advances in neutrophil chemotaxis abnormalities during sepsis

Sepsis remains one of the leading causes of death globally, in spite of advanced developments in intensive care and better understandings of pathophysiology related to sepsis. There is no special treatment or drug available for sepsis, currently. Under normal circumstances, neutrophil is a major player in acute infection control. However, during sepsis, the migration abilities and antimicrobial functions of neutrophils are impaired, resulting in a dysregulated immune response. Recent studies have indeed demonstrated that blocking or reversing neutrophil migration and impaired antibacterial function can improve the outcomes in septic animal models. This article systemically synthesized information regarding related factors and signaling involved in the functions of neutrophils in sepsis. This review also discussed the possibility that neutrophils be used as a marker for specific diagnosis and/or prediction of the outcomes of sepsis.

The Role of Transcription Factor PPAR-γ in the Pathogenesis of Psoriasis, Skin Cells, and Immune Cells

The peroxisome proliferator-activated receptor PPAR-γ is one of three PPAR nuclear receptors that act as ligand-activated transcription factors. In immune cells, the skin, and other organs, PPAR-γ regulates lipid, glucose, and amino acid metabolism. The receptor translates nutritional, pharmacological, and metabolic stimuli into the changes in gene expression. The activation of PPAR-γ promotes cell differentiation, reduces the proliferation rate, and modulates the immune response. In the skin, PPARs also contribute to the functioning of the skin barrier. Since we know that the route from identification to the registration of drugs is long and expensive, PPAR-γ agonists already approved for other diseases may also represent a high interest for psoriasis. In this review, we discuss the role of PPAR-γ in the activation, differentiation, and proliferation of skin and immune cells affected by psoriasis and in contributing to the pathogenesis of the disease. We also evaluate whether the agonists of PPAR-γ may become one of the therapeutic options to suppress the inflammatory response in lesional psoriatic skin and decrease the influence of comorbidities associated with psoriasis.

m6A demethylase ALKBH5 is required for antibacterial innate defense by intrinsic motivation of neutrophil migration

Neutrophil migration into the site of infection is necessary for antibacterial innate defense, whereas impaired neutrophil migration may result in excessive inflammation and even sepsis. The neutrophil migration directed by extracellular signals such as chemokines has been extensively studied, yet the intrinsic mechanism for determining neutrophil ability to migrate needs further investigation. N⁶-methyladenosine (m⁶A) RNA modification is important in immunity and inflammation, and our preliminary data indicate downregulation of RNA m⁶A demethylase alkB homolog 5 (ALKBH5) in neutrophils during bacterial infection. Whether m⁶A modification and ALKBH5 might intrinsically modulate neutrophil innate response remain unknown. Here we report that ALKBH5 is required for antibacterial innate defense by enhancing intrinsic ability of neutrophil migration. We found that deficiency of ALKBH5 increased mortality of mice with polymicrobial sepsis induced by cecal ligation and puncture (CLP), and Alkbh5-deficient CLP mice exhibited higher bacterial burden and massive proinflammatory cytokine production in the peritoneal cavity and blood because of less neutrophil migration. Alkbh5-deficient neutrophils had lower CXCR2 expression, thus exhibiting impaired migration toward chemokine CXCL2. Mechanistically, ALKBH5-mediated m⁶A demethylation empowered neutrophils with high migration capability through altering the RNA decay, consequently regulating protein expression of its targets, neutrophil migration-related molecules, including increased expression of neutrophil migration-promoting CXCR2 and NLRP12, but decreased expression of neutrophil migration-suppressive PTGER4, TNC, and WNK1. Our findings reveal a previously unknown role of ALKBH5 in imprinting migration-promoting transcriptome signatures in neutrophils and intrinsically promoting neutrophil migration for antibacterial defense, highlighting the potential application of targeting neutrophil m⁶A modification in controlling bacterial infections.

Parsing the Role of PPARs in Macrophage Processes

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

Exposure, health effects, sensing, and remediation of the emerging PFAS contaminants - Scientific challenges and potential research directions

Per- and polyfluoroalkyl substances (PFAS) make up a large group of persistent anthropogenic chemicals which are difficult to degrade and/or destroy. PFAS are an emerging class of contaminants, but little is known about the long-term health effects related to exposure. In addition, technologies to identify levels of contamination in the environment and to remediate contaminated sites are currently inadequate. In this opinion-type discussion paper, a team of researchers from the University of Connecticut and the University at Albany discuss the scientific challenges in their specific but intertwined PFAS research areas, including rapid and low-cost detection, energy-saving remediation, the role of T helper cells in immunotoxicity, and the biochemical and molecular effects of PFAS among community residents with measurable PFAS concentrations. Potential research directions that may be employed to address those challenges and improve the understanding of sensing, remediation, exposure to, and health effects of PFAS are then presented. We hope our account of emerging problems related to PFAS contamination will encourage a broad range of scientific experts to bring these research initiatives addressing PFAS into play on a national scale.

Mobilization efficiency is critically regulated by fat via marrow PPARδ

The mobilization efficiency of hematopoietic stem/progenitor cells from bone marrow (BM) to circulation by granulocyte colony-stimulating factor (G-CSF) is dramatically dispersed in humans and mice with no mechanistic lead for poor mobilizers. The regulatory mechanism for mobilization efficiency by dietary fat was assessed in mice. Fat-free diet (FFD) for 2 weeks greatly increased mobilization compared to normal diet (ND). The BM mRNA level of peroxisome proliferator-activated receptor δ (PPARδ), a receptor for lipid mediators, was markedly up-regulated by G-CSF in mice fed with ND and displayed strong positive correlation with widely scattered mobilization efficiency. It was hypothesized that BM fat ligand for PPARδ might inhibit mobilization. The PPARδ agonist inhibited mobilization in mice fed with ND and enhanced mobilization by FFD. Treatment with the PPARδ antagonist and chimeric mice with PPARδ+/- BM showed enhanced mobilization. Immunohistochemical staining and flow cytometry revealed that BM PPARδ expression was enhanced by G-CSF mainly in mature/immature neutrophils. BM lipid mediator analysis revealed that G-CSF treatment and FFD resulted in the exhaustion of ω3-polyunsaturated fatty acids such as eicosapentaenoic acid (EPA). EPA induced the up-regulation of genes downstream of PPARδ, such as carnitine palmitoyltransferase-1α and angiopoietin-like protein 4 (Angptl4), in mature/immature neutrophils in vitro and inhibited enhanced mobilization in mice fed with FFD in vivo. Treatment of wild-type mice with the anti-Angptl4 antibody enhanced mobilization together with BM vascular permeability. Collectively, PPARδ signaling in BM mature/immature neutrophils induced by dietary fatty acids negatively regulates mobilization, at least partially, via Angptl4 production.

Targeting Neutrophils in Sepsis: From Mechanism to Translation

Sepsis is a life-threatening condition caused by a dysregulated host response to infection. Although our understanding in the pathophysiological features of sepsis has increased significantly during the past decades, there is still lack of specific treatment for sepsis. Neutrophils are important regulators against invading pathogens, and their role during sepsis has been studied extensively. It has been suggested that the migration, the antimicrobial activity, and the function of neutrophil extracellular traps (NETs) have all been impaired during sepsis, which results in an inappropriate response to primary infection and potentially increase the susceptibility to secondary infection. On the other hand, accumulating evidence has shown that the reversal or restoration of neutrophil function can promote bacterial clearance and improve sepsis outcome, supporting the idea that targeting neutrophils may be a promising strategy for sepsis treatment. In this review, we will give an overview of the role of neutrophils during sepsis and discuss the potential therapeutic strategy targeting neutrophils.

Chinese Herbs and Repurposing Old Drugs as Therapeutic Agents in the Regulation of Oxidative Stress and Inflammation in Pulmonary Diseases

Several pro-inflammatory factors and proteins have been characterized that are involved in the pathogenesis of inflammatory diseases, including acute respiratory distress syndrome, chronic obstructive pulmonary disease, and asthma, induced by oxidative stress, cytokines, bacterial toxins, and viruses. Reactive oxygen species (ROS) act as secondary messengers and are products of normal cellular metabolism. Under physiological conditions, ROS protect cells against oxidative stress through the maintenance of cellular redox homeostasis, which is important for proliferation, viability, cell activation, and organ function. However, overproduction of ROS is most frequently due to excessive stimulation of either the mitochondrial electron transport chain and xanthine oxidase or reduced nicotinamide adenine dinucleotide phosphate (NADPH) by pro-inflammatory cytokines, such as interleukin-1β and tumor necrosis factor α. NADPH oxidase activation and ROS overproduction could further induce numerous inflammatory target proteins that are potentially mediated via Nox/ROS-related transcription factors triggered by various intracellular signaling pathways. Thus, oxidative stress is considered important in pulmonary inflammatory processes. Previous studies have demonstrated that redox signals can induce pulmonary inflammatory diseases. Thus, therapeutic strategies directly targeting oxidative stress may be effective for pulmonary inflammatory diseases. Therefore, drugs with anti-inflammatory and anti-oxidative properties may be beneficial to these diseases. Recent studies have suggested that traditional Chinese medicines, statins, and peroxisome proliferation-activated receptor agonists could modulate inflammation-related signaling processes and may be beneficial for pulmonary inflammatory diseases. In particular, several herbal medicines have attracted attention for the management of pulmonary inflammatory diseases. Therefore, we reviewed the pharmacological effects of these drugs to dissect how they induce host defense mechanisms against oxidative injury to combat pulmonary inflammation. Moreover, the cytotoxicity of oxidative stress and apoptotic cell death can be protected via the induction of HO-1 by these drugs. The main objective of this review is to focus on Chinese herbs and old drugs to develop anti-inflammatory drugs able to induce HO-1 expression for the management of pulmonary inflammatory diseases.

Electrophilic nitrated fatty acids are potential therapeutic candidates for inflammatory and fibrotic lung diseases

Several types of exposures can cause acute or chronic inflammatory reactions in the lungs often leading to asthma, pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), acute lung injury, lung cancer, and other deleterious health outcomes. Current therapy, with inhaled or oral glucocorticoids, successfully targets inflammation but also produces adverse effects that limit their enthusiastic use. Accordingly, the need remains for interventions that are safer and more effective. Nitrated fatty acids (NFAs) are highly electrophilic and are produced endogenously by non-enzymatic reactions of nitric oxide with conjugated unsaturated fatty acids. The literature indicates that NFAs are detected in humans at the nanomolar range and are produced more robustly under inflammatory conditions. Recent studies on novel NFAs report antiinflammatory, antioxidant, and antifibrotic effects, while also acting as partial agonists of peroxisome proliferator-activated receptor-gamma (PPAR-γ). Furthermore, these functions of NFAs occur via reversible electrophilic alkylation of cysteine residues and regulation of antiinflammatory, antioxidant signaling through modulation of transcription factors, including nuclear factor E2-related factor 2 (Nrf2), PPAR-γ, and NF-κB. Here, we review and update the role of NFA signaling mechanisms and their therapeutic potential in various lung diseases. As NFAs display strong electrophilic interaction with multimechanistic pathways, they can be considered promising drug candidates for challenging lung diseases.

Phytochemical drug candidates for the modulation of peroxisome proliferator-activated receptor γ in inflammatory bowel diseases

Plant-based compounds or phytochemicals such as alkaloids, glycosides, flavonoids, volatile oils, tannins, resins, and polyphenols have been used extensively in traditional medicine for centuries and more recently in Western alternative medicine. Extensive evidence suggests that consumption of dietary polyphenolic compounds lowers the risk of inflammatory diseases. The anti-inflammatory properties of several phytochemicals are mediated through ligand-inducible peroxisome proliferator-activated receptors (PPARs), particularly the PPARγ transcription factor. Inflammatory bowel disease (IBD) is represented by ulcerative colitis, which occurs in the mucosa of the colon and rectum, and Crohn's disease (CD) that can involve any segment of gastrointestinal tract. Because of the lack of cost-effective pharmaceutical treatment options, many IBD patients seek and use alternative and unconventional therapies to alleviate their symptoms. PPARγ plays a role in the inhibition of inflammatory cytokine expression and activation of anti-inflammatory immune cells. The phytochemicals reported here are ligands that activate PPARγ, which in turn modulates inflammatory responses. PPARγ is highly expressed in the gut making it a potential therapeutic target for IBDs. This review summarizes the effects of the currently published phytochemicals that modulate the PPARγ pathway and reduce or eliminate colonic inflammation.

IL4Rα Signaling Abrogates Hypoxic Neutrophil Survival and Limits Acute Lung Injury Responses In Vivo

Rationale: Acute respiratory distress syndrome is defined by the presence of systemic hypoxia and consequent on disordered neutrophilic inflammation. Local mechanisms limiting the duration and magnitude of this neutrophilic response remain poorly understood. Objectives: To test the hypothesis that during acute lung inflammation tissue production of proresolution type 2 cytokines (IL-4 and IL-13) dampens the proinflammatory effects of hypoxia through suppression of HIF-1α (hypoxia-inducible factor-1α)-mediated neutrophil adaptation, resulting in resolution of lung injury. Methods: Neutrophil activation of IL4Ra (IL-4 receptor α) signaling pathways was explored ex vivo in human acute respiratory distress syndrome patient samples, in vitro after the culture of human peripheral blood neutrophils with recombinant IL-4 under conditions of hypoxia, and in vivo through the study of IL4Ra-deficient neutrophils in competitive chimera models and wild-type mice treated with IL-4. Measurements and Main Results: IL-4 was elevated in human BAL from patients with acute respiratory distress syndrome, and its receptor was identified on patient blood neutrophils. Treatment of human neutrophils with IL-4 suppressed HIF-1α-dependent hypoxic survival and limited proinflammatory transcriptional responses. Increased neutrophil apoptosis in hypoxia, also observed with IL-13, required active STAT signaling, and was dependent on expression of the oxygen-sensing prolyl hydroxylase PHD2. In vivo, IL-4Ra-deficient neutrophils had a survival advantage within a hypoxic inflamed niche; in contrast, inflamed lung treatment with IL-4 accelerated resolution through increased neutrophil apoptosis. Conclusions: We describe an important interaction whereby IL4Rα-dependent type 2 cytokine signaling can directly inhibit hypoxic neutrophil survival in tissues and promote resolution of neutrophil-mediated acute lung injury.

Endothelial PPARγ Is Crucial for Averting Age-Related Vascular Dysfunction by Stalling Oxidative Stress and ROCK

Aging plays a significant role in the progression of vascular diseases and vascular dysfunction. Activation of the ADP-ribosylation factor 6 and small GTPases by inflammatory signals may cause vascular permeability and endothelial leakage. Pro-inflammatory molecules have a significant effect on smooth muscle cells (SMC). The migration and proliferation of SMC can be promoted by tumor necrosis factor alpha (TNF-α). TNF-α can also increase oxidative stress in SMCs, which has been identified to persuade DNA damage resulting in apoptosis and cellular senescence. Peroxisome proliferator-activated receptor (PPAR) acts as a ligand-dependent transcription factor and a member of the nuclear receptor superfamily. They play key roles in a wide range of biological processes, including cell differentiation and proliferation, bone formation, cell metabolism, tissue remodeling, insulin sensitivity, and eicosanoid signaling. The PPARγ activation regulates inflammatory responses, which can exert protective effects in the vasculature. In addition, loss of function of PPARγ enhances cardiovascular events and atherosclerosis in the vascular endothelium. This appraisal, therefore, discusses the critical linkage of PPARγ in the inflammatory process and highlights a crucial defensive role for endothelial PPARγ in vascular dysfunction and disease, as well as therapy for vascular aging.

A Novel Standardized Cannabis sativa L. Extract and Its Constituent Cannabidiol Inhibit Human Polymorphonuclear Leukocyte Functions

Cannabis and cannabinoids offer significant therapeutic benefits for a wide scope of pathological conditions. Among them, the clinical issues rooted in inflammation stand out, nonetheless, the underlying mechanisms are not yet plainly understood. Circumstantial evidence points to polymorphonuclear leukocytes (PMN) as targets for the anti-inflammatory effects of cannabis. Therefore, we conducted this study to assess the effects of CM5, a novel Cannabis sativa L. extract standardized in 5% cannabidiol (CBD), on human PMN functions, including cell migration, oxidative metabolism and production of tumour necrosis factor (TNF)-α. We then sought to investigate whether such effects could be ascribed to its content in CBD. Cell migration was assessed by the Boyden chamber assay, oxidative metabolism by means of spectrofluorimetric measurement of reactive oxygen species (ROS) production, and TNF-α was measured by real time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Results show that both CM5 and CBD inhibit PMN migration, ROS and TNF-α production, indicating that CBD may be the main item responsible for the effects of CM5. CM5 is however more potent than CBD on cell migration and TNF-α production, and less effective on ROS production, suggesting that beyond CBD, other components of the cannabis plant may contribute to the biological effects of the extract. As a whole, such results support the use of cannabis standardized extract and CBD to stem inflammation; however, they also warrant in-depth investigation of the underlying cellular and molecular mechanisms to better exploit their therapeutic potential.

The Neutrophil’s Role During Health and Disease

Neutrophils have always been considered as uncomplicated front-line troopers of the innate immune system equipped with limited proinflammatory duties. Yet recently, the role of the neutrophil has been undergoing a rejuvenation of sorts. Neutrophils are now considered complex cells capable of a significant array of specialized functions, and as an effector of the innate immune response, they are able to regulate many processes such as acute injury and repair, cancer, autoimmunity, and chronic inflammatory processes. Furthermore, evidence exists to indicate that neutrophils also contribute to adaptive immunity by aiding the development of specific adaptive immune responses or guiding the subsequent adaptive immune response. With this revived interest in neutrophils and their many novel functions, it is prudent to review what is currently known about neutrophils and, even more importantly, understand what information is lacking. We discuss the essential features of the neutrophil, from its origins, lifespan, subsets, margination and sequestration of the neutrophil to the death of the neutrophil. We highlight neutrophil recruitment to both infected and injured tissues and outline differences in recruitment of neutrophils between different tissues. Finally, we examine how neutrophils use different mechanisms to either bolster protective immune responses or negatively cause pathological outcomes at different locations.

Treatment of Borrelia burgdorferi-Infected Mice with Apoptotic Cells Attenuates Lyme Arthritis via PPAR-γ

Infection of mice with Borrelia burgdorferi causes an inflammatory arthritis that peaks 3-4 wk postinfection and then spontaneously resolves. Although the recruitment of neutrophils is known to drive the development of arthritis, mechanisms of disease resolution remain unclear. Efficient clearance of apoptotic cells (AC) is likely an important component of arthritis resolution. In this article, we show the number of AC increases in the joints of B. burgdorferi-infected mice around day 21 postinfection and peaks around day 28. Injection of AC directly into the ankles of B. burgdorferi-infected mice limited ankle swelling but had no effect on spirochete clearance or arthritis severity scores. In vitro, addition of AC to bone marrow macrophage cultures decreased B. burgdorferi-induced TNF-α and KC and increased IL-10. In addition, phagocytosis of B. burgdorferi and neutrophil migration to LTB₄ were inhibited by AC. Exogenous AC caused an increase in peroxisome proliferator-activated receptor-γ (PPAR-γ) expression both in vitro and in vivo during B. burgdorferi infection. The PPAR-γ agonist rosiglitazone elicited similar changes in macrophage cytokine production and neutrophil migration as exogenous AC. Addition of the PPAR-γ antagonist GW 9662 abrogated the effects of AC in vitro. Injection of rosiglitazone directly into the tibiotarsal joints of B. burgdorferi-infected mice decreased ankle swelling and immune cell recruitment, similar to the injection of AC. These results suggest that clearance of AC plays a role in the resolution of inflammation during experimental Lyme arthritis through the activation of PPAR-γ. PPAR-γ agonists, such as rosiglitazone, may therefore be effective treatments for inducing arthritis resolution.

Role of an indole-thiazolidiene PPAR pan ligand on actions elicited by G-protein coupled receptor activated neutrophils

Neutrophils are the first line of defence during inflammatory processes; nevertheless, exacerbated influx and actions of neutrophils in terms of uncontrolled inflammation are harmful to the host. Hence, neutrophil activity is the target of drugs seeking to address undesired inflammation. Here, we investigated the mechanisms of action of a ligand of the three isoforms of peroxisome proliferator-activated receptors (PPAR; (5Z)-5-[(5-bromo-1H-indole-3-yl)methylene]-3-(4-chlorobenzyl)-thiazolidine-2,4-dione), dubbed LYSO-7, on neutrophils activated by N-formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLP), an agonist of G-protein coupled receptors (GPCRs) that binds to membrane-formylated peptide and activates intracellular inflammation pathways. Neutrophils were collected from the peritoneal cavity of male Wistar rats four hours after oyster glycogen injection. Afterwards, the neutrophils were incubated with saline or LYSO-7 (1 or 10 μM, 30 min), washed and stimulated with fMLP (10^-7 μM, 1 h). LYSO-7 treatment inhibited gene and protein expression of adhesion molecules, CD62 L and CD18, abolished adhesion of neutrophils to endothelial cells, impaired chemotaxis, blocked the enhancement of intracellular calcium levels, induced the expression of PPARγ as well as PPARβδ and reduced nuclear translocation of nuclear factor κB (NF-κB). Moreover, topical application of LYSO-7 (10 mM) prior to local application of fMLP (10^-7 μM) diminished the in vivo leukocyte-endothelial interactions in the mesentery microcirculation of rats. Together, our data highlight the effectiveness of anti-inflammatory actions of LYSO-7 on neutrophils activated by GPCRs, depending, at least in part, on impaired of NF-κB activation and induction of PPAR expression.

Dimethyl Fumarate Limits Neuroinflammation and Oxidative Stress and Improves Cognitive Impairment After Polymicrobial Sepsis

Sepsis is caused by a dysregulated host response to infection, often associated with acute central nervous system (CNS) dysfunction, which results in long-term cognitive impairment. Dimethyl fumarate (DMF) is an important agent against inflammatory response and reactive species in CNS disorders. Evaluate the effect of DMF on acute and long-term brain dysfunction after experimental sepsis in rats. Male Wistar rats were submitted to the cecal ligation and puncture (CLP) model. The groups were divided into sham (control) + vehicle, sham + NAC, sham + DMF, CLP + vehicle, CLP + NAC, and CLP + DMF. The animals were treated with DMF (15 mg/kg at 0 and 12 h after CLP, per gavage) and the administration of n-acetylcysteine (NAC) (20 mg/kg; 3, 6, and 12 h after CLP, subcutaneously) was used as positive control. Twenty-four hours after CLP, cytokines, myeloperoxidase (MPO), nitrite/nitrate (N/N), oxidative damage to lipids and proteins, and antioxidant enzymes were evaluated in the hippocampus, total cortex, and prefrontal cortex. At 10 days after sepsis induction, behavioral tests were performed to assess cognitive damage. We observed an increase in cytokine levels, MPO activity, N/N concentration, and oxidative damage, a reduction in SOD and GPx activity in the brain structures, and cognitive damage in CLP rats. DMF treatment was effective in reversing these parameters. DMF reduces sepsis-induced neuroinflammation, oxidative stress, and cognitive impairment in rats subjected to the CLP model.

The Physiopathological Role of the Exchangers Belonging to the SLC37 Family

The human SLC37 gene family includes four proteins SLC37A1-4, localized in the endoplasmic reticulum (ER) membrane. They have been grouped into the SLC37 family due to their sequence homology to the bacterial organophosphate/phosphate (Pi) antiporter. SLC37A1-3 are the less characterized isoforms. SLC37A1 and SLC37A2 are Pi-linked glucose-6-phosphate (G6P) antiporters, catalyzing both homologous (Pi/Pi) and heterologous (G6P/Pi) exchanges, whereas SLC37A3 transport properties remain to be clarified. Furthermore, SLC37A1 is highly homologous to the bacterial glycerol 3-phosphate permeases, so it is supposed to transport also glycerol-3-phosphate. The physiological role of SLC37A1-3 is yet to be further investigated. SLC37A1 seems to be required for lipid biosynthesis in cancer cell lines, SLC37A2 has been proposed as a vitamin D and a phospho-progesterone receptor target gene, while mutations in the SLC37A3 gene appear to be associated with congenital hyperinsulinism of infancy. SLC37A4, also known as glucose-6-phosphate translocase (G6PT), transports G6P from the cytoplasm into the ER lumen, working in complex with either glucose-6-phosphatase-α (G6Pase-α) or G6Pase-β to hydrolyze intraluminal G6P to Pi and glucose. G6PT and G6Pase-β are ubiquitously expressed, whereas G6Pase-α is specifically expressed in the liver, kidney and intestine. G6PT/G6Pase-α complex activity regulates fasting blood glucose levels, whereas G6PT/G6Pase-β is required for neutrophil functions. G6PT deficiency is responsible for glycogen storage disease type Ib (GSD-Ib), an autosomal recessive disorder associated with both defective metabolic and myeloid phenotypes. Several kinds of mutations have been identified in the SLC37A4 gene, affecting G6PT function. An increased autoimmunity risk for GSD-Ib patients has also been reported, moreover, SLC37A4 seems to be involved in autophagy.

The peroxisome proliferator-activated receptor agonist pioglitazone and 5-lipoxygenase inhibitor zileuton have no effect on lung inflammation in healthy volunteers by positron emission tomography in a single-blind placebo-controlled cohort study

Background

Anti-inflammatory drug development efforts for lung disease have been hampered in part by the lack of noninvasive inflammation biomarkers and the limited ability of animal models to predict efficacy in humans. We used ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) in a human model of lung inflammation to assess whether pioglitazone, a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, and zileuton, a 5-lipoxygenase inhibitor, reduce lung inflammation.

Methods

For this single center, single-blind, placebo-controlled cohort study, we enrolled healthy volunteers sequentially into the following treatment cohorts (N = 6 per cohort): pioglitazone plus placebo, zileuton plus placebo, or dual placebo prior to bronchoscopic endotoxin instillation. ¹⁸F-FDG uptake pre- and post-endotoxin was quantified as the Patlak graphical analysis-determined K_i (primary outcome measure). Secondary outcome measures included the mean standard uptake value (SUV_mean), post-endotoxin bronchoalveolar lavage (BAL) cell counts and differentials and blood adiponectin and urinary leukotriene E₄ (LTE₄) levels, determined by enzyme-linked immunosorbent assay, to verify treatment compliance. One- or two-way analysis of variance assessed for differences among cohorts in the outcome measures (expressed as mean ± standard deviation).

Results

Ten females and eight males (29±6 years of age) completed all study procedures except for one volunteer who did not complete the post-endotoxin BAL. K_i and SUV_mean increased in all cohorts after endotoxin instillation (K_i increased by 0.0021±0.0019, 0.0023±0.0017, and 0.0024±0.0020 and SUV_mean by 0.47±0.14, 0.55±0.15, and 0.54±0.38 in placebo, pioglitazone, and zileuton cohorts, respectively, p<0.001) with no differences among treatment cohorts (p = 0.933). Adiponectin levels increased as expected with pioglitazone treatment but not urinary LTE₄ levels as expected with zileuton treatment. BAL cell counts (p = 0.442) and neutrophil percentage (p = 0.773) were similar among the treatment cohorts.

Conclusions

Endotoxin-induced lung inflammation in humans is not responsive to pioglitazone or zileuton, highlighting the challenge in translating anti-inflammatory drug efficacy results from murine models to humans.

Trial registration

ClinicalTrials.gov NCT01174056.

Microglial phenotypes in Parkinson's disease and animal models of the disease

Over the last decade the important concept has emerged that microglia, similar to other tissue macrophages, assume different phenotypes and serve several effector functions, generating the theory that activated microglia can be organized by their pro-inflammatory or anti-inflammatory and repairing functions. Importantly, microglia exist in a heterogenous population and their phenotypes are not permanently polarized into two categories; they exist along a continuum where they acquire different profiles based on their local environment. In Parkinson's disease (PD), neuroinflammation and microglia activation are considered neuropathological hallmarks, however their precise role in relation to disease progression is not clear, yet represent a critical challenge in the search of disease-modifying strategies. This review will critically address current knowledge on the activation states of microglia as well as microglial phenotypes found in PD and in animal models of PD, focusing on the expression of surface molecules as well as pro-inflammatory and anti-inflammatory cytokine production during the disease process. While human studies have reported an elevation of both pro- or anti-inflammatory markers in the serum and CSF of PD patients, animal models have provided insights on dynamic changes of microglia phenotypes in relation to disease progression especially prior to the development of motor deficits. We also review recent evidence of malfunction at multiple steps of NFκB signaling that may have a causal interrelationship with pathological microglia activation in animal models of PD. Finally, we discuss the immune-modifying strategies that have been explored regarding mechanisms of chronic microglial activation.

A PPARγ-dependent miR-424/503-CD40 axis regulates inflammation mediated angiogenesis

Activation of the endothelium by pro-inflammatory stimuli plays a key role in the pathogenesis of a multitude of vascular diseases. Angiogenesis is a crucial component of the vascular response associated with inflammatory signaling. The CD40/CD40 ligand dyad in endothelial cells (EC) has a central role in promoting vascular inflammatory response; however, the molecular mechanism underlying this component of inflammation and angiogenesis is not fully understood. Here we report a novel microRNA mediated suppression of endothelial CD40 expression. We found that CD40 is closely regulated by miR-424 and miR-503, which directly target its 3′ untranslated region. Pro-inflammatory stimuli led to increased endothelial CD40 expression, at least in part due to decreased miR-424 and miR-503 expression. In addition, miR-424 and miR-503 reduced LPS induced EC sprouting, migration and tube formation. Moreover, we found that miR-424 and miR-503 expression is directly regulated by peroxisome proliferator-activated receptor gamma (PPARγ), whose endothelial expression and activity are decreased in response to inflammatory factors. Finally, we demonstrate that mice with endothelial-specific deletion of miR-322 (miR-424 ortholog) and miR-503 have augmented angiogenic response to LPS in a Matrigel plug assay. Overall, these studies identify a PPARγ-dependent miR-424/503-CD40 signaling axis that is critical for regulation of inflammation mediated angiogenesis.

Neutrophil dysregulation during sepsis: an overview and update

Sepsis remains a leading cause of death worldwide, despite advances in critical care, and understanding of the pathophysiology and treatment strategies. No specific therapy or drugs are available for sepsis. Neutrophils play a critical role in controlling infection under normal conditions, and it is suggested that their migration and antimicrobial activity are impaired during sepsis which contribute to the dysregulation of immune responses. Recent studies further demonstrated that interruption or reversal of the impaired migration and antimicrobial function of neutrophils improves the outcome of sepsis in animal models. In this review, we provide an overview of the associated mediators and signal pathways involved which govern the survival, migration and antimicrobial function of neutrophils in sepsis, and discuss the potential of neutrophils as a target to specifically diagnose and/or predict the outcome of sepsis.

Corrosion behavior and cytocompatibility of a Co–Cr and two Ni–Cr dental alloys before and after the pretreatment with a biological saline solution

Objectives. The aim of this study was to evaluate the corrosion behavior and cytocompatibility of a Co–Cr and two Ni–Cr dental alloys before and after the pretreatment with a biological saline solution.

A PPARγ AGONIST ENHANCES BACTERIAL CLEARANCE THROUGH NEUTROPHIL EXTRACELLULAR TRAP FORMATION AND IMPROVES SURVIVAL IN SEPSIS

Dysregulation of the inflammatory response against infection contributes to mortality in sepsis. Inflammation provides critical host defense, but it can cause tissue damage, multiple organ failure, and death. Because the nuclear transcription factor peroxisome proliferator-activated receptor γ (PPARγ) exhibits therapeutic potential, we characterized the role of PPARγ in sepsis. We analyzed severity of clinical signs, survival rates, cytokine production, leukocyte influx, and bacterial clearance in a cecal ligation and puncture (CLP) model of sepsis in Swiss mice. The PPARγ agonist rosiglitazone treatment improved clinical status and mortality, while increasing IL-10 production and decreasing TNF-α and IL-6 levels, and peritoneal neutrophil accumulation 24 h after CLP. We noted increased bacterial killing in rosiglitazone treated mice, correlated with increased generation of reactive oxygen species. Polymorphonuclear leukocytes (PMN) incubated with LPS or Escherichia coli and rosiglitazone increased peritoneal neutrophil extracellular trap (NET)-mediated bacterial killing, an effect reversed by the PPARγ antagonist (GW 9662) treatment. Rosiglitazone also enhanced the release of histones by PMN, a surrogate marker of NET formation, effect abolished by GW 9662. Rosiglitazone modulated the inflammatory response and increased bacterial clearance through PPARγ activation and NET formation, combining immunomodulatory and host-dependent anti-bacterial effects and, therefore, warrants further study as a potential therapeutic agent in sepsis.

PPARγ in Bacterial Infections: A Friend or Foe?

Peroxisome proliferator-activated receptor γ (PPARγ) is now recognized as an important modulator of leukocyte inflammatory responses and function. Its immunoregulatory function has been studied in a variety of contexts, including bacterial infections of the lungs and central nervous system, sepsis, and conditions such as chronic granulomatous disease. Although it is generally believed that PPARγ activation is beneficial for the host during bacterial infections via its anti-inflammatory and antibacterial properties, PPARγ agonists have also been shown to dampen the host immune response and in some cases exacerbate infection by promoting leukocyte apoptosis and interfering with leukocyte migration and infiltration. In this review we discuss the role of PPARγ and its activation during bacterial infections, with focus on the potential of PPARγ agonists and perhaps antagonists as novel therapeutic modalities. We conclude that adjustment in the dosage and timing of PPARγ agonist administration, based on the competence of host antimicrobial defenses and the extent of inflammatory response and tissue injury, is critical for achieving the essential balance between pro- and anti-inflammatory effects on the immune system.

Subsets of Visceral Adipose Tissue Nuclei with Distinct Levels of 5-Hydroxymethylcytosine

The reprogramming of cellular memory in specific cell types, and in visceral adipocytes in particular, appears to be a fundamental aspect of obesity and its related negative health outcomes. We explored the hypothesis that adipose tissue contains epigenetically distinct subpopulations of adipocytes that are differentially potentiated to record cellular memories of their environment. Adipocytes are large, fragile, and technically difficult to efficiently isolate and fractionate. We developed fluorescence nuclear cytometry (FNC) and fluorescence activated nuclear sorting (FANS) of cellular nuclei from visceral adipose tissue (VAT) using the levels of the pan-adipocyte protein, peroxisome proliferator-activated receptor gamma-2 (PPARg2), to distinguish classes of PPARg2-Positive (PPARg2-Pos) adipocyte nuclei from PPARg2-Negative (PPARg2-Neg) leukocyte and endothelial cell nuclei. PPARg2-Pos nuclei were 10-fold enriched for most adipocyte marker transcripts relative to PPARg2-Neg nuclei. PPARg2-Pos nuclei showed 2- to 50-fold higher levels of transcripts encoding most of the chromatin-remodeling factors assayed, which regulate the methylation of histones and DNA cytosine (e.g., DNMT1, TET1, TET2, KDM4A, KMT2C, SETDB1, PAXIP1, ARID1A, JMJD6, CARM1, and PRMT5). PPARg2-Pos nuclei were large with decondensed chromatin. TAB-seq demonstrated 5-hydroxymethylcytosine (5hmC) levels were remarkably dynamic in gene bodies of various classes of VAT nuclei, dropping 3.8-fold from the highest quintile of expressed genes to the lowest. In short, VAT-derived adipocytes appear to be more actively remodeling their chromatin than non-adipocytes.

Paradoxical Roles of the Neutrophil in Sepsis: Protective and Deleterious

Sepsis, an overwhelming inflammatory response syndrome secondary to infection, is one of the costliest and deadliest medical conditions worldwide. Neutrophils are classically considered to be essential players in the host defense against invading pathogens. However, several investigations have shown that impairment of neutrophil migration to the site of infection, also referred to as neutrophil paralysis, occurs during severe sepsis, resulting in an inability of the host to contain and eliminate the infection. On the other hand, the neutrophil antibacterial arsenal contributes to tissue damage and the development of organ dysfunction during sepsis. In this review, we provide an overview of the main events in which neutrophils play a beneficial or deleterious role in the outcome of sepsis.

Simvastatin and a Plant Galactolipid Protect Animals from Septic Shock by Regulating Oxylipin Mediator Dynamics through the MAPK-cPLA2 Signaling Pathway

Sepsis remains a major medical issue despite decades of research. Identification of important inflammatory cascades and key molecular mediators are crucial for developing intervention and prevention strategies. In this study, we conducted a comparative oxylipin metabolomics study to gain a comprehensive picture of lipid mediator dynamics during the initial hyperinflammatory phase of sepsis, and demonstrated, in parallel, the efficacy of simvastatin and plant galactolipid, 1,2-di-O-α-linolenoyl-3-O-β-galactopyranosyl-sn-glycerol (dLGG) in the homeostatic regulation of the oxylipin metabolome using a lipopolysaccharide (LPS)-induced sepsis C57BL/6J mouse model. LPS increased the systemic and organ levels of proinflammatory metabolites of linoleic acid including leukotoxin diols (9-,10-DHOME, 12-,13-DHOME) and octadecadienoic acids (9-HODE and 13-HODE) and arachidonic acid-derived prostanoid, PGE2, and hydroxyeicosatetraenoic acids (8-, 12- and 15-HETE). Treatment with either compound decreased the levels of proinflammatory metabolites and elevated proresolution lipoxin A₄, 5(6)-EET, 11(12)-EET and 15-deoxy-PGJ₂. dLGG and simvastatin ameliorated the effects of LPS-induced mitogen-activated protein kinase (MAPK)-dependent activation of cPLA₂, cyclooxygenase-2, lipoxygenase, cytochrome P450 and/or epoxide hydrolase lowered systemic TNF-α and IL-6 levels and aminotransferase activities and decreased organ-specific infiltration of inflammatory leukocytes and macrophages, and septic shock-induced multiple organ damage. Furthermore, both dLGG and simvastatin increased the survival rates in the cecal ligation and puncture (CLP) sepsis model. This study provides new insights into the role of oxylipins in sepsis pathogenesis and highlights the potential of simvastatin and dLGG in sepsis therapy and prevention.

The role of neutrophils in immune dysfunction during severe inflammation

Critically ill post-surgical, post-trauma and/or septic patients are characterised by severe inflammation. This immune response consists of both a pro- and an anti-inflammatory component. The pro-inflammatory component contributes to (multiple) organ failure whereas occurrence of immune paralysis predisposes to infections. Strikingly, infectious complications arise in these patients despite the presence of a clear neutrophilia. We propose that dysfunction of neutrophils potentially increases the susceptibility to infections or can result in the inability to clear existing infections. Under homeostatic conditions these effector cells of the innate immune system circulate in a quiescent state and serve as the first line of defence against invading pathogens. In severe inflammation, however, neutrophils are rapidly activated, which affects their functional capacities, such as chemotaxis, phagocytosis, intra-cellular killing, NETosis, and their capacity to modulate adaptive immunity. This review provides an overview of the current understanding of neutrophil dysfunction in severe inflammation. We will discuss the possible mechanisms of downregulation of anti-microbial function, suppression of adaptive immunity by neutrophils and the contribution of neutrophil subsets to immune paralysis.

Activated Neutrophils Are Associated with Pediatric Cerebral Malaria Vasculopathy in Malawian Children

Most patients with cerebral malaria (CM) sustain cerebral microvascular sequestration of Plasmodium falciparum-infected red blood cells (iRBCs). Although many young children are infected with P. falciparum, CM remains a rare outcome; thus, we hypothesized that specific host conditions facilitate iRBC cerebral sequestration. To identify these host factors, we compared the peripheral whole-blood transcriptomes of Malawian children with iRBC cerebral sequestration, identified as malarial-retinopathy-positive CM (Ret+CM), to the transcriptomes of children with CM and no cerebral iRBC sequestration, defined as malarial-retinopathy-negative CM (Ret-CM). Ret+CM was associated with upregulation of 103 gene set pathways, including cytokine, blood coagulation, and extracellular matrix (ECM) pathways (P < 0.01; false-discovery rate [FDR] of <0.05). Neutrophil transcripts were the most highly upregulated individual transcripts in Ret+CM patients. Activated neutrophils can modulate diverse host processes, including the ECM, inflammation, and platelet biology to potentially facilitate parasite sequestration. Therefore, we compared plasma neutrophil proteins and neutrophil chemotaxis between Ret+CM and Ret-CM patients. Plasma levels of human neutrophil elastase, myeloperoxidase, and proteinase 3, but not lactoferrin or lipocalin, were elevated in Ret+CM patients, and neutrophil chemotaxis was impaired, possibly related to increased plasma heme. Neutrophils were rarely seen in CM brain microvasculature autopsy samples, and no neutrophil extracellular traps were found, suggesting that a putative neutrophil effect on endothelial cell biology results from neutrophil soluble factors rather than direct neutrophil cellular tissue effects. Meanwhile, children with Ret-CM had lower levels of inflammation, higher levels of alpha interferon, and upregulation of Toll-like receptor pathways and other host transcriptional pathways, which may represent responses that do not favor cerebral iRBC sequestration.

There were approximately 198 million cases of malaria worldwide in 2013, with an estimated 584,000 deaths occurring mostly in sub-Saharan African children. CM is a severe and rare form of Plasmodium falciparum infection and is associated with high rates of mortality and neurological morbidity, despite antimalarial treatment. A greater understanding of the pathophysiology of CM would allow the development of adjunctive therapies to improve clinical outcomes. A hallmark of CM is cerebral microvasculature sequestration of P. falciparum-infected red blood cells (iRBCs), which results in vasculopathy in some patients. Our data provide a global analysis of the host pathways associated with CM and newly identify an association of activated neutrophils with brain iRBC sequestration. Products of activated neutrophils could alter endothelial cell receptors and coagulation to facilitate iRBC adherence. Future studies can now examine the role of neutrophils in CM pathogenesis to improve health outcomes.

Translational Insights Into Peroxisome Proliferator-Activated Receptors in Experimental Acute Pancreatitis

Acute pancreatitis (AP) is an inflammatory disorder of the exocrine pancreas frequently associated with metabolic causes, contributing factors, or consequences, including hypertriglyceridemia, obesity, and disorders of intermediary metabolism, respectively. To date, there is no specific therapy for this disease. Future optimal therapy should correct both inflammatory and metabolic components of the disease. Peroxisome proliferator-activated receptors (PPARs) are lipid-sensing nuclear receptors that control inflammatory and metabolic pathways via ligand-dependent and ligand-independent mechanisms. There are 3 known subtypes, PPAR-α, PPAR-β/δ, and PPAR-γ, which are differentially expressed in various tissues. The PPARs interact closely with other transcription factors such as nuclear factor κB and signal tranducers and activators of transcription that have pivotal roles in the pathobiology of AP. In this comprehensive review, we summarize the role of PPARs in AP, highlighting important in vitro and in vivo experimental findings. Finally, we propose future research directions as well as potential translational use of PPAR agonists in the treatment of AP.

Invariant NKT Cell Activation Induces Late Preterm Birth That Is Attenuated by Rosiglitazone

Preterm birth (PTB) is the leading cause of neonatal morbidity and mortality worldwide. Although intra-amniotic infection is a recognized cause of spontaneous preterm labor, the noninfection-related etiologies are poorly understood. In this article, we demonstrated that the expansion of activated CD1d-restricted invariant NKT (iNKT) cells in the third trimester by administration of α-galactosylceramide (α-GalCer) induced late PTB and neonatal mortality. In vivo imaging revealed that fetuses from mice that underwent α-GalCer-induced late PTB had bradycardia and died shortly after delivery. Yet, administration of α-GalCer in the second trimester did not cause pregnancy loss. Peroxisome proliferator-activated receptor (PPAR)γ activation, through rosiglitazone treatment, reduced the rate of α-GalCer-induced late PTB and improved neonatal survival. Administration of α-GalCer in the third trimester suppressed PPARγ activation, as shown by the downregulation of Fabp4 and Fatp4 in myometrial and decidual tissues, respectively; this suppression was rescued by rosiglitazone treatment. Administration of α-GalCer in the third trimester induced an increase in the activation of conventional CD4(+) T cells in myometrial tissues and the infiltration of activated macrophages, neutrophils, and mature dendritic cells to myometrial and/or decidual tissues. All of these effects were blunted after rosiglitazone treatment. Administration of α-GalCer also upregulated the expression of inflammatory genes at the maternal-fetal interface and systemically, and rosiglitazone treatment partially attenuated these responses. Finally, an increased infiltration of activated iNKT-like cells in human decidual tissues is associated with noninfection-related preterm labor/birth. Collectively, these results demonstrate that iNKT cell activation in vivo leads to late PTB by initiating innate and adaptive immune responses and suggest that the PPARγ pathway has potential as a target for prevention of this syndrome.

PPARγ and the Innate Immune System Mediate the Resolution of Inflammation

The resolution of inflammation is an active and dynamic process, mediated in large part by the innate immune system. Resolution represents not only an increase in anti-inflammatory actions, but also a paradigm shift in immune cell function to restore homeostasis. PPARγ, a ligand activated transcription factor, has long been studied for its anti-inflammatory actions, but an emerging body of literature is investigating the role of PPARγ and its ligands (including thiazolidinediones, prostaglandins, and oleanolic acids) in all phases of resolution. PPARγ can shift production from pro- to anti-inflammatory mediators by neutrophils, platelets, and macrophages. PPARγ and its ligands further modulate platelet and neutrophil function, decreasing trafficking, promoting neutrophil apoptosis, and preventing platelet-leukocyte interactions. PPARγ alters macrophage trafficking, increases efferocytosis and phagocytosis, and promotes alternative M2 macrophage activation. There are also roles for this receptor in the adaptive immune response, particularly regarding B cells. These effects contribute towards the attenuation of multiple disease states, including COPD, colitis, Alzheimer's disease, and obesity in animal models. Finally, novel specialized proresolving mediators-eicosanoids with critical roles in resolution-may act through PPARγ modulation to promote resolution, providing another exciting area of therapeutic potential for this receptor.

L-Plastin S-glutathionylation promotes reduced binding to β-actin and affects neutrophil functions

Posttranslational modifications (PTMs) of cytoskeleton proteins due to oxidative stress associated with several pathological conditions often lead to alterations in cell function. The current study evaluates the effect of nitric oxide (DETA-NO)-induced oxidative stress-related S-glutathionylation of cytoskeleton proteins in human PMNs. By using in vitro and genetic approaches, we showed that S-glutathionylation of L-plastin (LPL) and β-actin promotes reduced chemotaxis, polarization, bactericidal activity, and phagocytosis. We identified Cys-206, Cys-283, and Cys-460as S-thiolated residues in the β-actin-binding domain of LPL, where cys-460 had the maximum score. Site-directed mutagenesis of LPL Cys-460 further confirmed the role in the redox regulation of LPL. S-Thiolation diminished binding as well as the bundling activity of LPL. The presence of S-thiolated LPL was detected in neutrophils from both diabetic patients and db/db mice with impaired PMN functions. Thus, enhanced nitroxidative stress may results in LPL S-glutathionylation leading to impaired chemotaxis, polarization, and bactericidal activity of human PMNs, providing a mechanistic basis for their impaired functions in diabetes mellitus.

CD66b Overexpression and Loss of C5a Receptors as Surface Markers for Staphylococcus aureus-Induced Neutrophil Dysfunction

Neutrophil granulocytes constitute the main component of innate immunity in the clearance of bacterial infections. However, during systemic inflammation, immunoparalysis may occur resulting in neutrophil dysfunction. This study presents a new in vitro model for analyzing the dysfunction of human peripheral blood neutrophils resulting from the interaction with Staphylococcus aureus components in whole blood. After induction of a massive complement activation by S. aureus supernatant, the neutrophils exhibit a reduced phagocytic capacity resulting in a dramatic reduction of the antibacterial activity similar to that of neutrophils isolated from septic patients. The number of phagocytozing neutrophils is drastically reduced as well as the phagocytic capacity designated by a significantly lower number of ingested microbes. This dysfunction correlates with the loss of complement component 5a receptor 1 from the neutrophil cell surface and can be further characterized by a C5a-induced CD66b overexpression. The presented in vitro model offers a new platform for preclinical testing of immunosuppressive drugs and delivers new information for the understanding of neutrophil dysfunctions under the conditions described.

G Protein-coupled Receptor 40 (GPR40) and Peroxisome Proliferator-activated Receptor γ (PPARγ): AN INTEGRATED TWO-RECEPTOR SIGNALING PATHWAY

Peroxisome proliferator-activated receptor γ (PPARγ) ligands have been widely used to treat type 2 diabetes mellitus. However, knowledge of PPARγ signaling remains incomplete. In addition to PPARγ, these drugs also activate G protein-coupled receptor 40 (GPR40), a Gαq-coupled free fatty acid receptor linked to MAPK networks and glucose homeostasis. Notably, p38 MAPK activation has been implicated in PPARγ signaling. Here, rosiglitazone (RGZ) activation of GPR40 and p38 MAPK was found to boost PPARγ-induced gene transcription in human endothelium. Inhibition or knockdown of p38 MAPK or expression of a dominant negative (DN) p38 MAPK mutant blunted RGZ-induced PPARγ DNA binding and reporter activity in EA.hy926 human endothelial cells. GPR40 inhibition or knockdown, or expression of a DN-Gαq mutant likewise blocked activation of both p38 MAPK and PPARγ reporters. Importantly, RGZ induction of PPARγ target genes in primary human pulmonary artery endothelial cells (PAECs) was suppressed by knockdown of either p38 MAPK or GPR40. GPR40/PPARγ signal transduction was dependent on p38 MAPK activation and induction of PPARγ co-activator-1 (PGC1α). Silencing of p38 MAPK or GPR40 abolished the ability of RGZ to induce phosphorylation and expression of PGC1α in PAECs. Knockdown of PGC1α, its essential activator SIRT1, or its binding partner/co-activator EP300 inhibited RGZ induction of PPARγ-regulated genes in PAECs. RGZ/GPR40/p38 MAPK signaling also led to EP300 phosphorylation, an event that enhances PPARγ target gene transcription. Thus, GPR40 and PPARγ can function as an integrated two-receptor signal transduction pathway, a finding with implications for rational drug development.

Neutrophil migration under normal and sepsis conditions

Neutrophil migration is critical for pathogen clearance and host survival during severe sepsis. Interaction of neutrophil adhesion receptors with ligands on endothelial cells results in firm adhesion of the circulating neutrophils, followed by neutrophil activation and directed migration to sites of infection through the basement membrane and interstitial extracellular matrix. Proteolytic enzymes and reactive oxygen species are produced and released by neutrophils in response to a variety of inflammatory stimuli. Although these mediators are important for host defense, they also promote tissue damage. Excessive neutrophil migration during the early stages of sepsis may lead to an exaggerated inflammatory response with associated tissue damage and subsequent organ dysfunction. On the other hand, dysregulation of migration and insufficient migratory response that occurs during the latter stages of severe sepsis contributes to neutrophils' inability to contain and control infection and impaired wound healing. This review discusses the major steps and associated molecules involved in the balance of neutrophil trafficking, the precise regulation of which during sepsis spells life or death for the host.

New strategy for sepsis: Targeting a key role of platelet-neutrophil interaction

Neutrophil and platelet are essential arms of the innate immune response. In sepsis, platelet abnormal activation as well as neutrophil paralysis are well recognized. For platelet, it is characterized by the contribution to disseminated intravascular coagulation (DIC) and the enhanced inflammation response. In terms of neutrophil, its dysfunction is manifested by the impaired recruitment and migration to the infectious foci, abnormal sequestration in the remote organs, and the delayed clearance. More recently, it has been apparent that together platelet-neutrophil interaction can induce a faster and harder response during sepsis. This article focuses on the activation of platelet, dysfunction of neutrophil, and the interaction between them during sepsis and profiles some of the molecular mechanisms and outcomes in these cellular dialogues, providing a novel strategy for treatment of sepsis.

The Pro12Ala Polymorphism of PPAR-γ Gene Is Associated with Sepsis Disease Severity and Outcome in Chinese Han Population

Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a ligand-binding nuclear receptor, and its activation plays a prominent role in regulating the inflammatory response. Therefore, PPAR-γ has been suggested as a candidate gene for sepsis. In the present study, we investigated the association between the Pro12Ala polymorphism of PPAR-γ and sepsis in a Han Chinese population. A total of 308 patients with sepsis and 345 healthy controls were enrolled in this study. Genotyping was performed using the polymerase chain reaction-ligation detection reaction (PCR-LDR) method. No significant differences were detected in the allele and genotype distributions of the PPAR-γ Pro12Ala SNP between septic patients and controls (P = 0.622 for genotype; P = 0.629 for allele). However, stratification by subtypes (sepsis, septic shock, and severe sepsis) revealed a statistically significant difference in the frequency of the Ala allele and Ala-carrier genotype between the patients with the sepsis subtype and the healthy controls (P = 0.014 for allele and P = 0.012, for genotype). Moreover, significant differences were found in the frequency of the Ala allele and genotype between the sepsis survivors and nonsurvivors (all P = 0.002). In the survivors, the PPAR-γ Pro12Ala genotype was significantly associated with decreased disease severity and recovery time (all P < 0.001). Thus, genetic polymorphism is thought to play a role in the development and outcome of sepsis.