Mechanisms of sterile inflammation

CAR, mGPS and hs-mGPS: What is among them the best gero-biomarker for age-related diseases? And for what clinical application?

The identification of biomarkers linked to the onset, progression, and prevention of age-related diseases (ARD), in the era of personalized medicine, represents the best goal of geroscience. Geroscience has the fundamental role of exploring and identifying the biological mechanisms of aging to suggest interventions capable of stopping/delaying the many pathological conditions and disabilities related to age. Therefore, it has become its key priority, as well as that of clinical practice and research, based on identifying and validating a range of biomarkers, geromarkers, which can be used to diagnostic, prognostic, or predictive clinical purposes. Indeed, geromarkers have, the potential to predict ARD trajectories and facilitate targeted interventions to slow down the related disabilities. Here our attention is paid to the inflammatory indexes (CAR, mGPS, hs-mGPS) linked to the relationship between the plasma levels of two inflammatory analytes, the typical positive protein of the acute phase, and the negative one, i.e. c-reactive protein (CRP) and albumin, respectively. These indexes allow us to understand the magnitude of the two main mechanisms predicted to influence the aging process, including inflammation and immunosenescence, as well as the degree of ARD severity. Evidence on their relationship with ARD is widely reported and discussed, to understand which can represent the best ARD geromarker, and its clinical application.

CXCR4/CXCL12 axis: "old" pathway as "novel" target for anti-inflammatory drug discovery

Inflammation is the body's defense response to exogenous or endogenous stimuli, involving complex regulatory mechanisms. Discovering anti-inflammatory drugs with both effectiveness and long-term use safety is still the direction of researchers' efforts. The inflammatory pathway was initially identified to be involved in tumor metastasis and HIV infection. However, research in recent years has proved that the CXC chemokine receptor type 4 (CXCR4)/CXC motif chemokine ligand 12 (CXCL12) axis plays a critical role in the upstream of the inflammatory pathway due to its chemotaxis to inflammatory cells. Blocking the chemotaxis of inflammatory cells by CXCL12 at the inflammatory site may block and alleviate the inflammatory response. Therefore, developing CXCR4 antagonists has become a novel strategy for anti-inflammatory therapy. This review aimed to systematically summarize and analyze the mechanisms of action of the CXCR4/CXCL12 axis in more than 20 inflammatory diseases, highlighting its crucial role in inflammation. Additionally, the anti-inflammatory activities of CXCR4 antagonists were discussed. The findings might help generate new perspectives for developing anti-inflammatory drugs targeting the CXCR4/CXCL12 axis.

hCeO2@ Cu5.4O nanoparticle alleviates inflammatory responses by regulating the CTSB-NLRP3 signaling pathway

Inflammatory responses, especially chronic inflammation, are closely associated with many systemic diseases. There are many ways to treat and alleviate inflammation, but how to solve this problem at the molecular level has always been a hot topic in research. The use of nanoparticles (NPs) as anti-inflammatory agents is a potential treatment method. We synthesized new hollow cerium oxide nanomaterials (hCeO2 NPs) doped with different concentrations of Cu5.4O NPs [the molar ratio of Cu/(Ce + Cu) was 50%, 67%, and 83%, respectively], characterized their surface morphology and physicochemical properties, and screened the safe concentration of hCeO2@Cu5.4O using the CCK8 method. Macrophages were cultured, and P.g-lipopolysaccharide-stimulated was used as a model of inflammation and co-cultured with hCeO2@Cu5.4O NPs. We then observe the effect of the transcription levels of CTSB, NLRP3, caspase-1, ASC, IL-18, and IL-1β by PCR and detect its effect on the expression level of CTSB protein by Western blot. The levels of IL-18 and IL-1β in the cell supernatant were measured by enzyme-linked immunosorbent assay. Our results indicated that hCeO2@Cu5.4O NPs could reduce the production of reactive oxygen species and inhibit CTSB and NLRP3 to alleviate the damage caused by the inflammatory response to cells. More importantly, hCeO2@Cu5.4O NPs showed stronger anti-inflammatory effects as Cu5.4O NP doping increased. Therefore, the development of the novel nanomaterial hCeO2@Cu5.4O NPs provides a possible new approach for the treatment of inflammatory diseases.

Terpenoids from the endophytic fungus Microdiplodia sp. and their anti-inflammatory activities

Motivated by the potential anti-inflammatory effect of the crude extract of endophytic fungus Microdiplodia sp. CJ01 derived from Camellia sinensis, chemical investigation of the extract of Microdiplodia sp. CJ01 led to the isolation and identification of sixteen terpenoids, including five undescribed eremophilane sesquiterpenoids named microdiplodins A-E (1-5), one undescribed meroterpenoid 13-carboxymacrophorin A (13), seven known eremophilane sesquiterpenoids (6-12), and three known meroterpenoids (14-16). The structures of these compounds were elucidated based on extensive spectroscopic analysis, including nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) data. Their absolute configurations were determined by calculational and experimental electronic circular dichroism (ECD) data. Anti-inflammatory activity assays revealed that compounds 3, 4, 14-16 exhibited moderate inhibitory effects on the production of nitric oxide (NO) in the lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells.

Obstructive nephropathy and molecular pathophysiology of renal interstitial fibrosis

The kidneys play a key role in maintaining total body homeostasis. The complexity of this task is reflected in the unique architecture of the organ. Ureteral obstruction greatly affects renal physiology by altering hemodynamics, changing glomerular filtration and renal metabolism, and inducing architectural malformations of the kidney parenchyma, most importantly renal fibrosis. Persisting pathological changes lead to chronic kidney disease, which currently affects ∼10% of the global population and is one of the major causes of death worldwide. Studies on the consequences of ureteral obstruction date back to the 1800s. Even today, experimental unilateral ureteral obstruction (UUO) remains the standard model for tubulointerstitial fibrosis. However, the model has certain limitations when it comes to studying tubular injury and repair, as well as a limited potential for human translation. Nevertheless, ureteral obstruction has provided the scientific community with a wealth of knowledge on renal (patho)physiology. With the introduction of advanced omics techniques, the classical UUO model has remained relevant to this day and has been instrumental in understanding renal fibrosis at the molecular, genomic, and cellular levels. This review details key concepts and recent advances in the understanding of obstructive nephropathy, highlighting the pathophysiological hallmarks responsible for the functional and architectural changes induced by ureteral obstruction, with a special emphasis on renal fibrosis.

P2Y11/IL-1 receptor crosstalk controls macrophage inflammation: a novel target for anti-inflammatory strategies?

Although first cloning of the human ATP receptor P2Y11 was successful 25 years ago, the exact downstream signaling pathways of P2Y11 receptor, which can couple to Gq and Gs proteins, have remained unclear. Especially the lack of rodent models as well as the limited availability of antibodies and pharmacological tools have hampered examination of P2Y11 expression and function. Many meaningful observations related to P2Y11 have been made in primary immune cells, indicating that P2Y11 receptors are important regulators of inflammation and cell migration, also by controlling mitochondrial activity. Our recent studies have shown that P2Y11 is upregulated during macrophage development and activates signaling through IL-1 receptor, which is well known for its ability to direct inflammatory and migratory processes. This review summarizes the results of the first transcriptomic and secretomic analyses of both, ectopic and native P2Y11 receptors, and discusses how P2Y11 crosstalk with the IL-1 receptor may govern anti-inflammatory and pro-angiogenic processes in human M2 macrophages.

Non-Neuronal Acetylcholinesterase Activity Shows Limited Utility for Early Detection of Sepsis

(1) Background: Sepsis is a severe systemic inflammatory condition characterized by rapid clinical deterioration and organ dysfunction. The cholinergic system has been implicated in modulating the inflammatory response. Acetylcholinesterase (AChE), an enzyme primarily responsible for the hydrolysis of acetylcholine, has been proposed as a potential early indicator of sepsis onset. However, the exact role of non-neuronal AChE activity in sepsis and its correlation with disease severity and patient outcomes remain unclear. This study aimed to investigate the involvement of AChE activity in sepsis and evaluate its association with disease severity and clinical outcomes. (2) Methods: A prospective study included 43 septic patients. AChE activity was measured at sepsis detection, as well as 7 and 28 days later. Inflammatory biomarkers, disease severity scores, and patient outcomes were evaluated. (3) Results: AChE activity remained stable for 7 days and decreased at 28 days. However, there was no correlation between initial AChE activity and inflammatory biomarkers, disease severity scores, ICU stay, or hospital stay. (4) Conclusions: Non-neuronal AChE activity may not reliably indicate early sepsis or predict disease severity.

The Molecular Basis and Clinical Consequences of Chronic Inflammation in Prostatic Diseases: Prostatitis, Benign Prostatic Hyperplasia, and Prostate Cancer

Chronic inflammation is now recognized as one of the major risk factors and molecular hallmarks of chronic prostatitis, benign prostatic hyperplasia (BPH), and prostate tumorigenesis. However, the molecular mechanisms by which chronic inflammation signaling contributes to the pathogenesis of these prostate diseases are poorly understood. Previous efforts to therapeutically target the upstream (e.g., TLRs and IL1-Rs) and downstream (e.g., NF-κB subunits and cytokines) inflammatory signaling molecules in people with these conditions have been clinically ambiguous and unsatisfactory, hence fostering the recent paradigm shift towards unraveling and understanding the functional roles and clinical significance of the novel and relatively underexplored inflammatory molecules and pathways that could become potential therapeutic targets in managing prostatic diseases. In this review article, we exclusively discuss the causal and molecular drivers of prostatitis, BPH, and prostate tumorigenesis, as well as the potential impacts of microbiome dysbiosis and chronic inflammation in promoting prostate pathologies. We specifically focus on the importance of some of the underexplored druggable inflammatory molecules, by discussing how their aberrant signaling could promote prostate cancer (PCa) stemness, neuroendocrine differentiation, castration resistance, metabolic reprogramming, and immunosuppression. The potential contribution of the IL1R-TLR-IRAK-NF-κBs signaling molecules and NLR/inflammasomes in prostate pathologies, as well as the prospective benefits of selectively targeting the midstream molecules in the various inflammatory cascades, are also discussed. Though this review concentrates more on PCa, we envision that the information could be applied to other prostate diseases. In conclusion, we have underlined the molecular mechanisms and signaling pathways that may need to be targeted and/or further investigated to better understand the association between chronic inflammation and prostate diseases.

Putative Role of Neutrophil Extracellular Trap Formation in Chronic Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are hematologic malignancies characterized by gene mutations that promote myeloproliferation and resistance to apoptosis via constitutively active signaling pathways, with Janus kinase 2-signal transducers and the activators of transcription (JAK-STAT) axis as a core part. Chronic inflammation has been described as a pivot for the development and advancement of MPNs from early stage cancer to pronounced bone marrow fibrosis, but there are still unresolved questions regarding this issue. The MPN neutrophils are characterized by upregulation of JAK target genes, they are in a state of activation and with deregulated apoptotic machinery. Deregulated neutrophil apoptotic cell death supports inflammation and steers them towards secondary necrosis or neutrophil extracellular trap (NET) formation, a trigger of inflammation both ways. NETs in proinflammatory bone marrow microenvironment induce hematopoietic precursor proliferation, which has an impact on hematopoietic disorders. In MPNs, neutrophils are primed for NET formation, and even though it seems obvious for NETs to intervene in the disease progression by supporting inflammation, no reliable data are available. We discuss in this review the potential pathophysiological relevance of NET formation in MPNs, with the intention of contributing to a better understanding of how neutrophils and neutrophil clonality can orchestrate the evolution of a pathological microenvironment in MPNs.

The role of macrophage subtypes and exosomes in immunomodulation

Macrophages are influential members of the innate immune system that can be reversibly polarized by different microenvironment signals. Cell polarization leads to a wide range of features, involving the migration, development, and organization of the cells. There is mounting evidence that macrophage polarization plays a key role in the initiation and development of a wide range of diseases. This study aims to give an overview of macrophage polarization, their different subtypes, and the importance of alternatively activated M2 macrophage and classically activated M1 macrophage in immune responses and pathological conditions. This review provides insight on the role of exosomes in M1/M2-like macrophage polarization and their potential as a promising therapeutic candidate.

The P2Y11 receptor of human M2 macrophages activates canonical and IL-1 receptor signaling to translate the extracellular danger signal ATP into anti-inflammatory and pro-angiogenic responses

The cytoprotective ATP receptor P2Y₁₁ is upregulated during M2 macrophage differentiation and contributes to the anti-inflammatory properties of this macrophage subset. Here, we studied P2Y₁₁-induced reprogramming of human M2 macrophages at the level of mRNA and protein expression. Upregulation of IL-1 receptor (IL-1R) and its known downstream effectors VEGF, CCL20 and SOCS3 as well as downregulation of the ATP-degrading ecto-ATPase CD39 emerged as hallmarks of P2Y₁₁ activation. The anti-inflammatory signature of the P2Y₁₁ transcriptome was further characterized by the downregulation of P2RX7, toll-like receptors and inflammasome components. P2Y₁₁-induced IL-1R upregulation formed the basis for reinforced IL-1 responsiveness of activated M2 macrophages, as IL-1α and IL-1ß each enhanced P2Y₁₁-induced secretion of VEGF and CCL20 as well as the previously reported shedding of soluble tumor necrosis factor receptor 2 (sTNFR2). Raising intracellular cyclic AMP (cAMP) in M2 macrophages through phosphodiesterase 4 inhibition enhanced P2Y₁₁-driven responses. The cAMP-binding effector, exchange protein activated by cAMP 1 (Epac1), which is known to induce SOCS3, differentially regulated the P2Y₁₁/IL-1R response because pharmacological Epac1 inhibition enhanced sTNFR2 and CCL20 release, but had no effect on VEGF secretion. In addition to cAMP, calcium and protein kinase C participated in P2Y₁₁ signaling. Our study reveals how P2Y₁₁ harnesses canonical and IL-1R signaling to promote an anti-inflammatory and pro-angiogenic switch of human M2 macrophages, which may be controlled in part by an Epac1-SOCS3 axis.

Biodistribution of intravenous [99mTc]Tc-phytate in mouse models of chemically and foreign-body induced sterile inflammation

When injected intravenously, [^99mTc]Tc-phytate forms particles in the nanometer range. This size can favor its extravasation into tumor and inflammation through pores of the vasculature. The aim of this work is the evaluation of the use of [^99mTc]Tc-phytate to assess sterile inflammation in mouse models. Biodistribution studies of [^99mTc]Tc-phytate were performed in two groups of male Swiss Albino mice. Sterile inflammation was induced after intramuscular injection of turpentine in the first group (chemically induced sterile inflammation model) and after implantation of sterile metal bolts in the second group (foreign-body induced sterile inflammation model). [^99mTc]Tc-phytate was intravenously injected after the development of inflammation in both groups and ex vivo biodistribution of the radiolabelled complex followed at different time-points. Biodistribution was expressed as percent injected dose per gram (%ID/g). Target-to-background ratios were also recorded. For the chemically induced sterile inflammation model, ex vivo biodistribution evaluation measurements revealed a pronounced uptake in the inflamed muscle when compared to uptake in the control/non-inflamed muscle. Moreover, as expected, there is a high uptake in the liver and spleen. For the foreign-body induced sterile inflammation model, a significantly higher uptake was observed in the inflamed muscle post [^99mTc]Tc-phytate injection, both for the 24 hours post-bolt implantation and for the 7 days post-bolt implantation groups. The nanoparticle properties of [^99mTc]Tc-phytate are potentially useful in the imaging of different types of sterile inflammation with translational potential clinical SPECT (single photon emission computed tomography) imaging applications in humans.

Role of Bioactive Compounds in Obesity: Metabolic Mechanism Focused on Inflammation

Obesity is a disease characterized by an inflammatory process in the adipose tissue due to diverse infiltrated immune cells, an increased secretion of proinflammatory molecules, and a decreased secretion of anti-inflammatory molecules. On the other hand, obesity increases the risk of several diseases, such as cardiovascular diseases, diabetes, and cancer. Their treatment is based on nutritional and pharmacological strategies. However, natural products are currently implemented as complementary and alternative medicine (CAM). Polyphenols and fiber are naturally compounds with potential action to reduce inflammation through several pathways and play an important role in the prevention and treatment of obesity, as well as in other non-communicable diseases. Hence, this review focuses on the recent evidence of the molecular mechanisms of polyphenols and dietary fiber, from Scopus, Science Direct, and PubMed, among others, by using key words and based on recent in vitro and in vivo studies.

An Update on the Pathogenic Role of Neutrophils in Systemic Juvenile Idiopathic Arthritis and Adult-Onset Still's Disease

Neutrophils are innate immune phagocytes that play a key role in immune defense against invading pathogens. The main offensive mechanisms of neutrophils are the phagocytosis of pathogens, release of granules, and production of cytokines. The formation of neutrophil extracellular traps (NETs) has been described as a novel defense mechanism in the literature. NETs are a network of fibers assembled from chromatin deoxyribonucleic acid, histones, and neutrophil granule proteins that have the ability to kill pathogens, while they can also cause toxic effects in hosts. Activated neutrophils with NET formation stimulate autoimmune responses related to a wide range of inflammatory autoimmune diseases by exposing autoantigens in susceptible individuals. The association between increased NET formation and autoimmunity was first reported in antineutrophil cytoplasmic antibody-related vasculitis, and the role of NETs in various diseases, including systemic lupus erythematosus, rheumatoid arthritis, and psoriasis, has since been elucidated in research. Herein, we discuss the mechanistic role of neutrophils, including NETs, in the pathogenesis of systemic juvenile idiopathic arthritis (SJIA) and adult-onset Still’s disease (AOSD), and provide their clinical values as biomarkers for monitoring and prognosis.

Actions of the NLRP3 and NLRC4 inflammasomes overlap in bone resorption

Overwhelming evidence indicates that excessive stimulation of innate immune receptors of the NOD-like receptor (NLR) family causes significant damage to multiple tissues, yet the role of these proteins in bone metabolism is not well known. Here, we studied the interaction between the NLRP3 and NLRC4 inflammasomes in bone homeostasis and disease. We found that loss of NLRP3 or NLRC4 inflammasome attenuated osteoclast differentiation in vitro. At the tissue level, lack of NLRP3, or NLRC4 to a lesser extent, resulted in higher baseline bone mass compared to wild-type (WT) mice, and conferred protection against LPS-induced inflammatory osteolysis. Bone mass accrual in mutant mice correlated with lower serum IL-1β levels in vivo. Unexpectedly, the phenotype of Nlrp3-deficient mice was reversed upon loss of NLRC4 as bone mass was comparable between WT mice and Nlrp3;Nlrc4 knockout mice. Thus, although bone homeostasis is perturbed to various degrees by the lack of NLRP3 or NLRC4, this tissue appears to function normally upon compound loss of the inflammasomes assembled by these receptors.

Probiotics and gut health: linking gut homeostasis and poultry productivity

The use of probiotics in poultry production has increased rapidly, and this movement has been promoted by global events, such as the prohibition or decline in the use of antibiotic growth promotants in poultry feeds. There has been a persistent search for alternative feed additives, and probiotics have shown that they can restore the composition of the gut microbiota, and produce health benefits to the host, including improvements in performance. Probiotics have shown potential to increase productivity in poultry, especially in flocks challenged by stressors. However, the outcomes of probiotic use have not always been consistent. There is an increasing demand for well defined products that can be applied strategically, and currently, probiotic research is focusing on delineating their mechanisms of action in the gut that contribute to an improved efficacy. In particular, mechanisms involved in the maintenance and protection of intestinal barrier integrity and the role of the gut microbiota are being extensively investigated. It has been shown that probiotics modulate intestinal immune pathways both directly and through interactions with the gut microbiota. These interactions are key to maintaining gut homeostasis and function, and improving feed efficiency. Research has demonstrated that probiotics execute their effects through multiple mechanisms. The present review describes recent advances in probiotic use in poultry. It focuses on the current understanding of gut homeostasis and gut health in chickens, and how it can be assessed and improved through supplementation of poultry diets with probiotics in poultry diets. In particular, cellular and molecular mechanisms involved in the maintenance and protection of gut barrier structure and function are described. It also highlights important factors that influence probiotic efficacy and bird performance.

Extracellular Vesicles: Potential Mediators of Psychosocial Stress Contribution to Osteoporosis?

Osteoporosis is characterized by low bone mass and damage to the bone tissue’s microarchitecture, leading to increased fracture risk. Several studies have provided evidence for associations between psychosocial stress and osteoporosis through various pathways, including the hypothalamic-pituitary-adrenocortical axis, the sympathetic nervous system, and other endocrine factors. As psychosocial stress provokes oxidative cellular stress with consequences for mitochondrial function and cell signaling (e.g., gene expression, inflammation), it is of interest whether extracellular vesicles (EVs) may be a relevant biomarker in this context or act by transporting substances. EVs are intercellular communicators, transfer substances encapsulated in them, modify the phenotype and function of target cells, mediate cell-cell communication, and, therefore, have critical applications in disease progression and clinical diagnosis and therapy. This review summarizes the characteristics of EVs, their role in stress and osteoporosis, and their benefit as biological markers. We demonstrate that EVs are potential mediators of psychosocial stress and osteoporosis and may be beneficial in innovative research settings.

Mechanistic Insight into Orthodontic Tooth Movement Based on Animal Studies: A Critical Review

Alveolar bone remodeling in orthodontic tooth movement (OTM) is a highly regulated process that coordinates bone resorption by osteoclasts and new bone formation by osteoblasts. Mechanisms involved in OTM include mechano-sensing, sterile inflammation-mediated osteoclastogenesis on the compression side and tensile force-induced osteogenesis on the tension side. Several intracellular signaling pathways and mechanosensors including the cilia and ion channels transduce mechanical force into biochemical signals that stimulate formation of osteoclasts or osteoblasts. To date, many studies were performed in vitro or using human gingival crevicular fluid samples. Thus, the use of transgenic animals is very helpful in examining a cause and effect relationship. Key cell types that participate in mediating the response to OTM include periodontal ligament fibroblasts, mesenchymal stem cells, osteoblasts, osteocytes, and osteoclasts. Intercellular signals that stimulate cellular processes needed for orthodontic tooth movement include receptor activator of nuclear factor-κB ligand (RANKL), tumor necrosis factor-α (TNF-α), dickkopf Wnt signaling pathway inhibitor 1 (DKK1), sclerostin, transforming growth factor beta (TGF-β), and bone morphogenetic proteins (BMPs). In this review, we critically summarize the current OTM studies using transgenic animal models in order to provide mechanistic insight into the cellular events and the molecular regulation of OTM.

Sterile inflammation in the pathogenesis of maturation failure of arteriovenous fistula

Chronic kidney disease is a widespread terminal illness that afflicts millions of people across the world. Hemodialysis is the predominant therapeutic management strategy for kidney failure and involves the external filtration of metabolic waste within the circulation. This process requires an arteriovenous fistula (AVF) for vascular access. However, AVF maturation failures are significant obstacles in establishing long-term vascular access for hemodialysis. Appropriate stimulation, activation, and proliferation of smooth muscle cells, proper endothelial cell orientation, adequate structural changes in the ECM, and the release of anti-inflammatory markers are associated with maturation. AVFs often fail to mature due to inadequate tissue repair and remodeling, leading to neointimal hyperplasia lesions. The transdifferentiation of myofibroblasts and sterile inflammation are possibly involved in AVF maturation failures; however, limited data is available in this regard. The present article critically reviews the interplay of various damage-associated molecular patterns (DAMPs) and the downstream sterile inflammatory signaling with a focus on the NLRP3 inflammasome. Improved knowledge concerning AVF maturation pathways can be unveiled by investigating the novel DAMPs and the mediators of sterile inflammation in vascular remodeling that would open improved therapeutic opportunities in the management of AVF maturation failures and its associated complications.

Brain Disorders and Chemical Pollutants: A Gap Junction Link?

The incidence of brain pathologies has increased during last decades. Better diagnosis (autism spectrum disorders) and longer life expectancy (Parkinson's disease, Alzheimer's disease) partly explain this increase, while emerging data suggest pollutant exposures as a possible but still underestimated cause of major brain disorders. Taking into account that the brain parenchyma is rich in gap junctions and that most pollutants inhibit their function; brain disorders might be the consequence of gap-junctional alterations due to long-term exposures to pollutants. In this article, this hypothesis is addressed through three complementary aspects: (1) the gap-junctional organization and connexin expression in brain parenchyma and their function; (2) the effect of major pollutants (pesticides, bisphenol A, phthalates, heavy metals, airborne particles, etc.) on gap-junctional and connexin functions; (3) a description of the major brain disorders categorized as neurodevelopmental (autism spectrum disorders, attention deficit hyperactivity disorders, epilepsy), neurobehavioral (migraines, major depressive disorders), neurodegenerative (Parkinson's and Alzheimer's diseases) and cancers (glioma), in which both connexin dysfunction and pollutant involvement have been described. Based on these different aspects, the possible involvement of pollutant-inhibited gap junctions in brain disorders is discussed for prenatal and postnatal exposures.

Mechanisms of Macrophage Polarization in Insulin Signaling and Sensitivity

Type-2 diabetes (T2D) is a disease of two etiologies: metabolic and inflammatory. At the cross-section of these etiologies lays the phenomenon of metabolic inflammation. Whilst metabolic inflammation is characterized as systemic, a common starting point is the tissue-resident macrophage, who's successful physiological or aberrant pathological adaptation to its microenvironment determines disease course and severity. This review will highlight the key mechanisms in macrophage polarization, inflammatory and non-inflammatory signaling that dictates the development and progression of insulin resistance and T2D. We first describe the known homeostatic functions of tissue macrophages in insulin secreting and major insulin sensitive tissues. Importantly we highlight the known mechanisms of aberrant macrophage activation in these tissues and the ways in which this leads to impairment of insulin sensitivity/secretion and the development of T2D. We next describe the cellular mechanisms that are known to dictate macrophage polarization. We review recent progress in macrophage bio-energetics, an emerging field of research that places cellular metabolism at the center of immune-effector function. Importantly, following the advent of the metabolically-activated macrophage, we cover the known transcriptional and epigenetic factors that canonically and non-canonically dictate macrophage differentiation and inflammatory polarization. In closing perspectives, we discuss emerging research themes and highlight novel non-inflammatory or non-immune roles that tissue macrophages have in maintaining microenvironmental and systemic homeostasis.

Basal and Infectious Enteritis in Broilers Under the I See Inside Methodology: A Chronological Evaluation

Recently, the inflammation of the intestinal mucosa has been related to many diseases in humans and animals. The concept of Microscopic Enteritis (ME) used in human pathology through the Marsh classification system has no counter-part in veterinary medicine. In poultry science, the I See Inside (ISI) methodology, unlike the current linear measures of villi and crypts, generates possibilities to describe and understand the avian ME. Through specific parameters, graded from 0 to 3, the model links proliferative and/or inflammatory reactions in the intestinal layers to some loss in performance. Herein, two trials were conducted in order to describe the development of ME through the ISI methodology in chickens challenged or not with Eimeria spp. and Clostridium perfringens. In each trial, a total of 64 birds were divided in 2 treatments with 4 replicates containing 8 birds each: non-challenged (NCH) and challenged (CH) through gavage with an Eimeria spp. vaccine at 1 day of age and 10⁸ CFU/mL of Clostridium perfringens administered at 10, 11, and 12 days of age. At 7, 14, 21, and 28 days of age birds were euthanized and samples of ileum and liver were collected for ISI evaluation, cytokines and presence of macrophages, CD4+ and CD8+ cell. The results allowed the description of the avian Microscopic Enteritis and of its two basic components: a basal enteritis (BE) in NCH broilers, over which the infectious enteritis is developed in CH birds. In addition, the chronology of ME translated by the ISI methodology parameters were associated to losses in zootechnical performance.

Dietary Factors as Triggers of Low-Grade Chronic Intestinal Inflammation in Poultry

Inflammation is the reaction of the immune system to an injury; it is aimed at the recovery and repair of damaged tissue. The inflammatory response can be beneficial to the animal since it will reestablish tissue homeostasis if well regulated. However, if it is not controlled, inflammation might lead to a chronic response with a subsequent loss of tissue function. The intestine is constantly exposed to a number of environmental triggers that stimulate inflammation and lead to a reduction in performance. The diet and dietary components constitute consistent inflammatory triggers in poultry. Dietary components, such as anti-nutritional compounds, oxidized lipids, mycotoxins, and excess of soluble fiber or protein, are all capable of inducing a low-grade inflammatory response in the intestine of broilers throughout a 5-week grow-out period. We hypothesized that dietary factor-induced chronic intestinal inflammation is a key driver of the lower performance and higher incidence of intestinal problems observed in poultry production. Therefore, this review was aimed at exploring feed-induced chronic inflammation in poultry, the constituents of the diet that might act as inflammatory triggers and the possible effects of chronic intestinal inflammation on the poultry industry.

Ultrastructural Characteristics of DHA-Induced Pyroptosis

Microglial cells are resident macrophages of the central nervous system (CNS) that respond to bioactive lipids such as docosahexaenoic acid (DHA). Low micromolar concentrations of DHA typically promote anti-inflammatory functions of microglia, but higher concentrations result in a form of pro-inflammatory programmed cell death known as pyroptosis. This study used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to investigate the morphological characteristics of pyroptosis in BV-2 microglial cells following exposure to 200 µM DHA. Vehicle-treated cells are characterized by extended processes, spine-like projections or 0.4 to 5.2 µm in length, and numerous extracellular vesicles (EVs) tethered to the surface of the plasma membrane. In contrast to vehicle-treated cells, gross abnormalities are observed after treating cells with 200 µM DHA for 4 h. These include the appearance of numerous pits or pores of varying sizes across the cell surface, structural collapse and flattening of the cell shape. Moreover, EVs and spines were lost following DHA treatment, possibly due to release from the cell surface. The membrane pores appear after DHA treatment initially measured ~ 30 nm, consistent with the previously reported gasdermin D (GSDMD) pore complexes. Complete collapse of cytoplasmic organization and loss of nuclear envelope integrity were also observed in DHA-treated cells. These processes are morphologically distinct from the changes that occur during cisplatin-induced apoptosis, such as the appearance of apoptotic bodies and tightly packed organelles, and the maintenance of EVs and nuclear envelope integrity. Cumulatively, this study provides a systematic description of the ultrastructural characteristics of DHA-induced pyroptosis, including distinguishing features that differentiate this process from apoptosis.

MCC950 closes the active conformation of NLRP3 to an inactive state

NLRP3 (NOD-like receptor pyrin domain-containing protein 3) is an innate immune sensor that contributes to the development of different diseases, including monogenic autoinflammatory syndromes, gout, atherosclerosis, and Alzheimer's disease. The molecule sulfonylurea MCC950 is a NLRP3 inflammasome inhibitor with potential clinical utility. However, the mechanism of action of MCC950 remains unknown. Here, we characterize the mechanism of action of MCC950 in both wild-type and autoinflammatory-related NLRP3 mutants, and demonstrate that MCC950 closes the 'open' conformation of active NLRP3.

Transcriptional control of macrophage polarisation in type 2 diabetes

Type-2 diabetes (T2D) is considered today as an inflammatory disease. Inflammatory processes in T2D are orchestrated by macrophage activation in different organs. Macrophages undergo classical M1 pro-inflammatory or alternative M2 anti-inflammatory activation in response to tissue microenvironmental signals. These subsets of macrophages are characterised by their expression of cell surface markers, secreted cytokines and chemokines. Transcriptional regulation is central to the polarisation of macrophages, and several major pathways have been described as essential to promote the expression of specific genes, which dictate the functional polarisation of macrophages. In this review, we summarise the current knowledge of transcriptional control of macrophage polarisation and the role this plays in development of insulin resistance.

Inflammation and Hypoxia: HIF and PHD Isoform Selectivity

Cells sense and respond to hypoxia through the activity of the transcription factor HIF (hypoxia-inducible factor) and its regulatory hydroxylases, the prolyl hydroxylase domain enzymes (PHDs). Multiple isoforms of HIFs and PHDs exist, and isoform-selective roles have been identified in the context of the inflammatory environment, which is itself frequently hypoxic. Recent advances in the field have highlighted the complexity of this system, particularly with regards to the cell and context-specific activity of HIFs and PHDs. Because novel therapeutic agents which regulate this pathway are nearing the clinic, understanding the role of HIFs and PHDs in inflammation outcomes is an essential step in avoiding off-target effects and, crucially, in developing new anti-inflammatory strategies.

Metabolism of Docosahexaenoic Acid (DHA) Induces Pyroptosis in BV-2 Microglial Cells

DHA is one of the most abundant fatty acids in the brain, largely present in stores of membrane phospholipids. It is readily released by the action of phospholipase A2 and is known to induce anti-inflammatory and neurotrophic effects. It is not thought to contribute to proinflammatory processes in the brain. In this study, an immortalized murine microglia cell line (BV-2) was used to evaluate the effect of DHA on neuroinflammatory cells. Pretreatment of BV-2 cells with low concentrations of DHA (30 µM) attenuates lipopolysaccharide-mediated inflammatory cytokine gene expression, consistent with known anti-inflammatory effects. However, higher (but still physiologically relevant) concentrations of DHA (200 µM) induce profound cell swelling and a reduction of viability. This is accompanied by increases in the expressions of inflammatory cytokine and lipoxygenase genes, activation of caspase-1 activity, and release of IL1β, indicating that cells were undergoing a proinflammatory cell death program known as pyroptosis. This process could be attenuated by pharmacological inhibition of 12-lipoxygenase (12-LOX, Alox12e), but not by inhibition of 5-LOX or 15-LOX. Cumulatively, these data demonstrate that DHA has an anti-inflammatory effect on microglial cells, but its metabolism by 12-LOX generates one or more products that activate a proinflammatory cell death program.

Alarmins: Feel the Stress

Over the last decade, danger-associated molecular pattern molecules, or alarmins, have been recognized as signaling mediators of sterile inflammatory responses after trauma and injury. In contrast with the accepted passive release models suggested by the "danger hypothesis," it was recently shown that alarmins can also directly sense and report damage by signaling to the environment when released from live cells undergoing physiological stress, even without loss of subcellular compartmentalization. In this article, we review the involvement of alarmins such as IL-1α, IL-33, IL-16, and high-mobility group box 1 in cellular and physiological stress, and suggest a novel activity of these molecules as central initiators of sterile inflammation in response to nonlethal stress, a function we denote "stressorins." We highlight the role of posttranslational modifications of stressorins as key regulators of their activity and propose that targeted inhibition of stressorins or their modifiers could serve as attractive new anti-inflammatory treatments for a broad range of diseases.

Multiple functions of USP18

Since the discovery of the ubiquitin system and the description of its important role in the degradation of proteins, many studies have shown the importance of ubiquitin-specific peptidases (USPs). One special member of this family is the USP18 protein (formerly UBP43). In the past two decades, several functions of USP18 have been discovered: this protein is not only an isopeptidase but also a potent inhibitor of interferon signaling. Therefore, USP18 functions as 'a' maestro of many biological pathways in various cell types. This review outlines multiple functions of USP18 in the regulation of various immunological processes, including pathogen control, cancer development, and autoimmune diseases.

Systemic HMGB1 Neutralization Prevents Postoperative Neurocognitive Dysfunction in Aged Rats

Postoperative neurocognitive disorders are common complications in elderly patients following surgery or critical illness. High mobility group box 1 protein (HMGB1) is rapidly released after tissue trauma and critically involved in response to sterile injury. Herein, we assessed the role of HMGB1 after liver surgery in aged rats and explored the therapeutic potential of a neutralizing anti-HMGB1 monoclonal antibody in a clinically relevant model of postoperative neurocognitive disorders. Nineteen to twenty-two months Sprague-Dawley rats were randomly assigned as: (1) control with saline; (2) surgery, a partial hepatolobectomy under sevoflurane anesthesia and analgesia, + immunoglobulin G as control antibody; (3) surgery + anti-HMGB1. A separate cohort of animals was used to detect His-tagged HMGB1 in the brain. Systemic anti-HMGB1 antibody treatment exerted neuroprotective effects preventing postoperative memory deficits and anxiety in aged rats by preventing surgery-induced reduction of phosphorylated cyclic AMP response element-binding protein in the hippocampus. Although no evident changes in the intracellular distribution of HMGB1 in hippocampal cells were noted after surgery, HMGB1 levels were elevated on day 3 in rat plasma samples. Experiments with tagged HMGB1 further revealed a critical role of systemic HMGB1 to enable an access to the brain and causing microglial activation. Overall, these data demonstrate a pivotal role for systemic HMGB1 in mediating postoperative neuroinflammation. This may have direct implications for common postoperative complications like delirium and postoperative cognitive dysfunction.

Mechanistic Differences Leading to Infectious and Sterile Inflammation

Inflammation is a physiologic component of pregnancy and parturition. Overwhelming intrauterine inflammatory load promotes quiescent feto-maternal tissues into a contractile phenotype. Like inflammation, oxidative stress is an inevitable component of both pregnancy and parturition. Pathologic activation of host innate immune response to adverse pregnancy conditions can lead to premature activation of inflammatory and oxidative stress. Inflammation and oxidative stress markers seen with both sterile and infectious inflammation are often similar; therefore, it is difficult to understand causality of conditions like spontaneous preterm birth. This review demonstrates potential mechanistic pathways of activation of sterile and infectious inflammation. We demonstrate the activation of two unique pathways of inflammation by factors that are well-documented proxies for oxidative stress (cigarette smoke extract) and infection (lipopolysaccharide). Sterile inflammation seen after exposure to an oxidative stress inducer is due to cellular elemental damage resulting in p38 mitogen-activated protein kinase (MAPK) induced cellular senescence. Infectious inflammation is through activation of transcription factor NF-κB and independent of oxidative stress-associated damages and p38 MAPK-induced senescence. Understanding the differences in the inflammatory pathway activation by various risk factors is important to design better screening, diagnostic and intervention strategies to reduce the risks of adverse pregnancy outcomes.

Rapid Detection of Neutrophil Oxidative Burst Capacity is Predictive of Whole Blood Cytokine Responses

BACKGROUND

Maladaptive immune responses, particularly cytokine and chemokine-driven, are a significant contributor to the deleterious inflammation present in many types of injury and infection. Widely available applications to rapidly assess individual inflammatory capacity could permit identification of patients at risk for exacerbated immune responses and guide therapy. Here we evaluate neutrophil oxidative burst (NOX) capacity measured by plate reader to immuno-type Rhesus Macaques as an acute strategy to rapidly detect inflammatory capacity and predict maladaptive immune responses as assayed by cytokine array.

METHODS

Whole blood was collected from anesthetized Rhesus Macaques (n = 25) and analyzed for plasma cytokine secretion (23-plex Luminex assay) and NOX capacity. For cytokine secretion, paired samples were either unstimulated or ex-vivo lipopolysaccharide (LPS)-stimulated (100μg/mL/24h). NOX capacity was measured in dihydrorhodamine-123 loaded samples following phorbol 12-myristate 13-acetate (PMA)/ionomycin treatment. Pearson's test was utilized to correlate NOX capacity with cytokine secretion, p<0.05 considered significant.

RESULTS

LPS stimulation induced secretion of the inflammatory molecules G-CSF, IL-1β, IL-1RA, IL-6, IL-10, IL-12/23(p40), IL-18, MIP-1α, MIP-1β, and TNFα. Although values were variable, several cytokines correlated with NOX capacity, p-values≤0.0001. Specifically, IL-1β (r = 0.66), IL-6 (r = 0.74), the Th1-polarizing cytokine IL-12/23(p40) (r = 0.78), and TNFα (r = 0.76) were strongly associated with NOX.

CONCLUSION

NOX capacity correlated with Th1-polarizing cytokine secretion, indicating its ability to rapidly predict inflammatory responses. These data suggest that NOX capacity may quickly identify patients at risk for maladaptive immune responses and who may benefit from immuno-modulatory therapies. Future studies will assess the in-vivo predictive value of NOX in animal models of immune-mediated pathologies.

Necrosis-Induced Sterile Inflammation Mediated by Interleukin-1α in Retinal Pigment Epithelial Cells

Endogenous danger signals released from necrotic cells contribute to retinal inflammation. We have now investigated the effects of necrotic cell extracts prepared from ARPE-19 human retinal pigment epithelial cells (ANCE) on the release of proinflammatory cytokines and chemokines by healthy ARPE-19 cells. ANCE were prepared by subjection of ARPE-19 cells to freeze-thaw cycles. The release of various cytokines and chemokines from ARPE-19 cells was measured with a multiplex assay system or enzyme-linked immunosorbent assays. The expression of interleukin (IL)–1α and the phosphorylation and degradation of the endogenous nuclear factor–κB (NF-κB) inhibitor IκB-α were examined by immunoblot analysis. Among the various cytokines and chemokines examined, we found that ANCE markedly stimulated the release of the proinflammatory cytokine IL-6 and the chemokines IL-8 and monocyte chemoattractant protein (MCP)–1 by ARPE-19 cells. ANCE-induced IL-6, IL-8, and MCP-1 release was inhibited by IL-1 receptor antagonist and by an IKK2 inhibitor (a blocker of NF-κB signaling) in a concentration-dependent manner, but was not affected by a pan-caspase inhibitor (Z-VAD-FMK). Recombinant IL-1α also induced the secretion of IL-6, IL-8, and MCP-1 from ARPE-19 cells, and IL-1α was detected in ANCE. Furthermore, ANCE induced the phosphorylation and degradation of IκB-α in ARPE-19 cells. Our findings thus suggest that IL-1α is an important danger signal that is released from necrotic retinal pigment epithelial cells and triggers proinflammatory cytokine and chemokine secretion from intact cells in a manner dependent on NF-κB signaling. IL-1α is therefore a potential therapeutic target for amelioration of sterile inflammation in the retina.

Circulating HMGB1 and RAGE as Clinical Biomarkers in Malignant and Autoimmune Diseases

High molecular group box 1 (HMGB1) is a highly conserved member of the HMG-box-family; abundantly expressed in almost all human cells and released in apoptosis; necrosis or by activated immune cells. Once in the extracellular space, HMGB1 can act as a danger associated molecular pattern (DAMP), thus stimulating or inhibiting certain functions of the immune system; depending on the “combinatorial cocktail” of the surrounding milieu. HMGB1 exerts its various functions through binding to a multitude of membrane-bound receptors such as TLR-2; -4 and -9; IL-1 and RAGE (receptor for advanced glycation end products); partly complex-bound with intracellular fragments like nucleosomes. Soluble RAGE in the extracellular space, however, acts as a decoy receptor by binding to HMGB1 and inhibiting its effects. This review aims to outline today’s knowledge of structure, intra- and extracellular functions including mechanisms of release and finally the clinical relevance of HMGB1 and RAGE as clinical biomarkers in therapy monitoring, prediction and prognosis of malignant and autoimmune disease.

Role of inflammasome activation in the pathophysiology of vascular diseases of the neurovascular unit

SIGNIFICANCE

Inflammation is the standard double-edged defense mechanism that aims at protecting the human physiological homeostasis from devastating threats. Both acute and chronic inflammation have been implicated in the occurrence and progression of vascular diseases. Interference with components of the immune system to improve patient outcome after ischemic injury has been uniformly unsuccessful. There is a need for a deeper understanding of the innate immune response to injury in order to modulate, rather than to block inflammation and improve the outcome for vascular diseases.

RECENT ADVANCES

Nucleotide-binding oligomerization domain-like receptors or NOD-like receptor proteins (NLRPs) can be activated by sterile and microbial inflammation. NLR family plays a major role in activating the inflammasome.

CRITICAL ISSUES

The aim of this work is to review recent findings that provided insights into key inflammatory mechanisms and define the place of the inflammasome, a multi-protein complex involved in instigating inflammation in neurovascular diseases, including retinopathy, neurodegenerative diseases, and stroke.

FUTURE DIRECTIONS

The significant contribution of NLRP-inflammasome activation to vascular disease of the neurovascular unit in the brain and retina suggests that therapeutic strategies focused on specific targeting of inflammasome components could significantly improve the outcomes of these diseases.