A macrophage protein, Ym1, transiently expressed during inflammation is a novel mammalian lectin

Evolutionary insights into sequence modifications governing chitin recognition and chitinase inactivity in YKL-40 (HC-gp39, CHI3L1)

YKL-40, also known as human cartilage glycoprotein-39 (HC-gp39) or CHI3L1, shares structural similarities with chitotriosidase (CHIT1), an active chitinase, but lacks chitinase activity. Despite being a biomarker for inflammatory disorders and cancer, the reasons for YKL-40's inert chitinase function have remained elusive. This study reveals that the loss of chitinase activity in YKL-40 has risen from multiple sequence modifications influencing its chitin affinity. Contrary to the common belief associating the lack of chitinase activity with amino acid substitutions in the catalytic motif, attempts to activate YKL-40 by creating two amino acid mutations in the catalytic motif (MT-YKL-40) proved ineffective. Subsequent exploration that included creating chimeras of MT-YKL-40 and CHIT1 catalytic domains (CatDs) identified key exons responsible for YKL-40 inactivation. Introducing YKL-40 exons 3, 6, or 8 into CHIT1 CatD resulted in chitinase inactivation. Conversely, incorporating CHIT1 exons 3, 6, and 8 into MT-YKL-40 led to its activation. Our recombinant proteins exhibited properly formed disulfide bonds, affirming a defined structure in active molecules. Biochemical and evolutionary analysis indicated that the reduced chitinase activity of MT-YKL-40 correlates with specific amino acids in exon 3. M61I and T69W substitutions in CHIT1 CatD diminished chitinase activity and increased chitin binding. Conversely, substituting I61 with M and W69 with T in MT-YKL-40 triggered chitinase activity while reducing the chitin-binding activity. Thus, W69 plays a crucial role in a unique subsite within YKL-40. These findings emphasize that YKL-40, though retaining the structural framework of a mammalian chitinase, has evolved to recognize chitin while surrendering chitinase activity.

Lethal eosinophilic crystalline pneumonia in mice expressing a stabilized Csf2 mRNA

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine that stimulates the proliferation and differentiation of granulocyte and macrophage precursors. The mouse gene-encoding GM-CSF, Csf2, is regulated at both transcriptional and post-transcriptional levels. An adenine-uridine-rich element (ARE) within the 3'-untranslated region of Csf2 mRNA was shown in cell transfection studies to confer instability on this transcript. To explore the physiological importance of this element in an intact animal, we generated mice with a knock-in deletion of the 75-nucleotide ARE. Mice heterozygous for this ARE deletion developed severe respiratory distress and death within about 12 weeks of age. There was dense infiltration of lung alveolar spaces by crystal-containing macrophages. Increased stability of Csf2 mRNA was confirmed in bone marrow-derived macrophages, and elevated GM-CSF levels were observed in serum and lung. These mice did not exhibit notable abnormalities in blood or bone marrow, and transplantation of bone marrow from mutant mice into lethally irradiated WT mice did not confer the pulmonary phenotype. Mice with a conditional deletion of the ARE restricted to lung type II alveolar cells exhibited an essentially identical lethal lung phenotype at the same ages as the mice with the whole-body deletion. In contrast, mice with the same conditional ARE deletion in myeloid cells, including macrophages, exhibited lesser degrees of macrophage infiltration into alveolar spaces much later in life, at approximately 9 months of age. Post-transcriptional Csf2 mRNA stability regulation in pulmonary alveolar epithelial cells appears to be essential for normal physiological GM-CSF secretion and pulmonary macrophage homeostasis.

Chitinases and chitinase-like proteins in asthma

Despite the lack of endogenous chitin synthesis, mammalian genomes encode two enzymatically active true chitinases (chitotriosidase and acidic mammalian chitinase) and a variable number of chitinase-like proteins (CLPs) that have no enzyme activity but bind chitin. Chitinases and CLPs are prominent components of type-2 immune response-mediated respiratory diseases. However, despite extensive research into their role in allergic airway disease, there is still no agreement on whether they are mere biomarkers of disease or actual disease drivers. Functions ascribed to chitinases and CLPs include, but are not limited to host defense against chitin-containing pathogens, directly promoting inflammation, and modulating tissue remodeling and fibrosis. Here, we discuss in detail the chitin-dependent and -independent roles of chitinases and CLPs in the context of allergic airway disease, and recent advances and emerging concepts in the field that might identify opportunities for new therapies.

Irreversible evolutionary loss of chitin-degrading ability in the chitinase-like protein Ym1 under positive selection in rodents

Ym1 (chitinase-like 3, Chil3) expressed in mice is a nonenzymatic chitinase-like protein, which shows 67% identity with mouse acidic chitinase (Chia). Similar to Chia, Ym1 is overexpressed in asthma and parasitic infections in mouse lungs. Due to the lack of chitin-degrading activity, the biomedical role of Ym1 under these pathophysiological conditions remains to be determined. In this study, we investigated what region and amino acid changes in Ym1 resulted in the loss of enzymatic activity. Replacing two amino acids at the catalytic motif to obtain a Chia-like sequence (N136D and Q140E; MT-Ym1) did not activate the protein. We conducted a comparative study of Ym1 and Chia. We found that three protein segments-(i) the catalytic motif residues, (ii) exons 6 and 7, and (iii) exon 10-are responsible for chitinase activity loss in Ym1. We show that replacing each of these three segments in Chia that are also involved in substrate recognition and binding by the Ym1 sequence can fully abolish the enzymatic activity. In addition, we show that there have been extensive gene duplication events at the Ym1 locus specific to the rodent lineages. Consistent with this result, Ym1 orthologs from the rodent genome were under positive selection when analyzed through the CODEML program. These data suggest that numerous amino acid substitutions in the regions involved in the chitin recognition, binding, and degradation ability of the ancestor Ym1 molecule lead to the irreversible inactivation of the protein.

Back2Basics: animal lectins: an insight into a highly versatile recognition protein

The rapid advancement of molecular research has contributed to the discovery of 'Lectin', a carbohydrate-binding protein which specifically interacts with receptors on surface glycan moieties that regulate various critical cellular activities. The first animal lectin reported was 'the asialoglycoprotein receptor' in mammalian cells which helped analyze how animal lectins differ in glycoconjugate binding. Animal lectins are classified into several families, depending on their diverse cellular localization, and the binding specificities of their Carbohydrate-Recognition Domain (CRD) modules. Earlier characterization of animal lectins classified them into two structural families, the C-type (Ca²⁺-dependent binding) and S-type galectins (sulfhydryl-dependent binding) lectins. The C-type lectin includes the most significant animal lectins, such as endocytic receptors, mannose receptors, selectins, and collectins. The recent developments in research based on the complexity of the carbohydrate ligands, the metabolic processes they perform, their expression levels, and their reliance on divalent cations have identified more than 100 animal lectins and classified them into around 13 different families, such as Calnexin, F-lectin, Intelectin, Chitinase-like lectin, F-box lectin, etc. Understanding their structure and expression patterns have aided in defining their significant functions including cell adhesion, antimicrobial activity, innate immunity, disease diagnostic biomarkers, and drug delivery through specific carbohydrate-protein interactions. Such extensive potential roles of animal lectins made it equally important to plant lectins among researchers. Hence, the review focuses on providing an overview of animal lectins, their taxonomy, structural characteristics, and functions in diverse aspects interconnected to their specific carbohydrate and glycoconjugate binding.

Graphical abstract

Chitinase-like protein 3: A novel niche factor for mouse neural stem cells

The concept of a perivascular niche has been proposed for neural stem cells (NSCs). This study examined endothelial colony-forming cell (ECFC)-secreted proteins as potential niche factors for NSCs. Intraventricle infusion with ECFC-secreted proteins increased the number of NSCs. ECFC-secreted proteins were more effective in promoting NSC self-renewal than marrow stromal cell (MSC)-secreted proteins. Differential proteomics analysis of MSC-secreted and ECFC-secreted proteins was performed, which revealed chitinase-like protein 3 (CHIL3; also called ECF-L or Ym1) as a candidate niche factor for NSCs. Experiments with recombinant CHIL3, small interfering RNA, and neutralizing antibodies demonstrated that CHIL3 stimulated NSC self-renewal with neurogenic propensity. CHIL3 was endogenously expressed in the neurogenic niche of the brain and retina as well as in the injured brain and retina. Transcriptome and phosphoproteome analyses revealed that CHIL3 activated various genes and proteins associated with NSC maintenance or neurogenesis. Thus, CHIL3 is a novel niche factor for NSCs.

An update on Ym1 and its immunoregulatory role in diseases

Ym1 is a rodent-specific chitinase-like protein (CLP) lacking catalytic activity, whose cellular origins are mainly macrophages, neutrophils and other cells. Although the detailed function of Ym1 remains poorly understood, Ym1 has been generally recognized as a fundamental feature of alternative activation of macrophages in mice and hence one of the prevalent detecting targets in macrophage phenotype distinguishment. Studies have pointed out that Ym1 may have regulatory effects, which are multifaceted and even contradictory, far more than just a mere marker. Allergic lung inflammation, parasite infection, autoimmune diseases, and central nervous system diseases have been found associations with Ym1 to varying degrees. Thus, insights into Ym1’s role in diseases would help us understand the pathogenesis of different diseases and clarify the genuine roles of CLPs in mammals. This review summarizes the information on Ym1 from the gene to its expression and regulation and focuses on the association between Ym1 and diseases.

Occupational exposure to gasoline in gasoline station male attendants promotes M1 polarization in macrophages

Several studies have reported the toxicological implications of exposure to petroleum hydrocarbon fumes in animal models. There is little documentation on the effect of such exposure on oxidative stress levels and immune response. To our knowledge, no documentation of M1 polarization in macrophages in gasoline station male attendants. Therefore, this study aimed to evaluate the harmful effects of gasoline vapors in 62 male attendants (16-70 years) compared to 29 age- and sex-matched-unexposed controls. The attendants were recruited from Damietta governorate gasoline stations. Gasoline exposure induced a significant increase in tumor necrosis factor-α (TNF-α) level (p < 0.05) as well as a slight but non-significant increase in the activity of acidic mammalian chitinase (AMCase) (p > 0.05). Further TNF-α/AMCase ratio was significantly increased (p < 0.01) in sera of the attendants when compared to those of the healthy controls. Also, the total leucocytic and lymphocytic counts were significantly increased (p < 0.01 and p < 0.001, respectively). On contrary, neutrophils to lymphocytes ratio (NLR) and platelets to lymphocytes ratio (PLR) were significantly decreased (p < 0.05 and p < 0.001, respectively). In addition, significant reduction in hemoglobin (Hb) concentration, plasma glutathione reduced form (GSH), and catalase, as well as superoxide dismutase (SOD) activities in red blood cells were observed in the exposed attendants. As a result, malondialdehyde (MDA), nitric oxide (NO) levels, and NO/AMCase ratio were significantly increased (p < 0.05). In conclusion, this study inferred that prolonged gasoline exposure can mediate immune activation, especially M1 macrophages polarization, possibly via oxidative stress-mediated mechanism.

Acute and chronic immunomodulatory response mechanisms against Toxocara canis larvae infection in mice

Abstract The objective of this work was to evaluate the early and late immunological modulation of an experimental infection of T. canis larvae in mice. Mice were infected with 100 infective larvae and euthanized at different period: 24, 48 hours post infection (HPI), 15- and 30 days post infection (DPI). The humoral response was evaluated by indirect ELISA. Quantitative RT–PCR (qPCR) was used to quantify the mRNA transcription of cytokines IL4, IL10, IL12 and Ym1 in the early and late infection periods. Infection with T. canis was able to generate specific total IgG at 15- and 30- DPI. Analyzing the IgG isotype revealed a significant differentiation for IgG1 compared with IgG2a, IgG2b and IgG3, characterizing a Th-2 response. Evaluating the gene transcription at the early phase of infection, higher transcription levels of IL10, IL4 and Ym1 and a downregulation of IL12 were observed. By the late phase, increased transcription levels of IL4, Ym1 and IL12 were observed, and downregulation of IL-10 transcription was observed. The data obtained suggest that during experimental infection with T. canis, the participation of the IL4, IL10, IL12 cytokines and Ym1 can play an important role in T. canis immunomodulation.

Renal fibrosis due to multiple cisplatin treatment is exacerbated by kinin B1 receptor antagonism

Cisplatin is a widely used chemotherapeutic drug, but its side effects are a major limiting factor. Nephrotoxicity occurs in one third of patients undergoing cisplatin treatment. The acute tubular injury caused by cisplatin often leads to a defective repair process, which translates into chronic renal disorders. In this way, cisplatin affects tubular cells, and maladaptive tubules regeneration will ultimately result in tubulointerstitial fibrosis. Kinins are well known for being important peptides in the regulation of inflammatory stimuli, and kinin B1 receptor deficiency and antagonism have been shown to be beneficial against acute cisplatin nephrotoxicity. This study aimed to analyze the effects of kinin B1 receptor deletion and antagonism against repeated cisplatin-induced chronic renal dysfunction and fibrosis. Both the deletion and the antagonism of B1 receptor exacerbated cisplatin-induced chronic renal dysfunction. Moreover, the inhibition of B1 receptor increased tubular injury and tubulointerstitial fibrosis after repeated treatment with cisplatin. The balance between M1/M2 macrophage polarization plays an important role in renal fibrosis. Kinin B1 receptor antagonism had no impact on M1 markers when compared to cisplatin. However, YM1, an M2 marker and an important molecule for the wound healing process, was decreased in mice treated with kinin B1 receptor antagonist, compared to cisplatin alone. Endothelin-1 levels were also increased in mice with B1 receptor inhibition. This study showed that kinin B1 receptor inhibition exacerbated cisplatin-induced chronic renal dysfunction and fibrosis, associated with reduced YM1 M2 marker expression, thus possibly affecting the wound healing process.

The Ectodomains of rBAT and 4F2hc Are Fake or Orphan α-Glucosidases

It is known that 4F2hc and rBAT are the heavy subunits of the heteromeric amino acid transporters (HATs). These heavy subunits are N-glycosylated proteins, with an N-terminal domain, one transmembrane domain and a bulky extracellular domain (ectodomain) that belongs to the α-amylase family. The heavy subunits are covalently linked to a light subunit from the SLC7 family, which is responsible for the amino acid transport activity, forming a heterodimer. The functions of 4F2hc and rBAT are related mainly to the stability and trafficking of the HATs in the plasma membrane of vertebrates, where they exert the transport activity. Moreover, 4F2hc is a modulator of integrin signaling, has a role in cell fusion and it is overexpressed in some types of cancers. On the other hand, some mutations in rBAT are found to cause the malfunctioning of the b0,+ transport system, leading to cystinuria. The ectodomains of 4F2hc and rBAT share both sequence and structure homology with α-amylase family members. Very recently, cryo-EM has revealed the structure of several HATs, including the ectodomains of rBAT and 4F2hc. Here, we analyze available data on the ectodomains of rBAT and 4Fhc and their relationship with the α-amylase family. The physiological relevance of this relationship remains largely unknown.

Sevoflurane preconditioning protects experimental ischemic stroke by enhancing anti-inflammatory microglia/macrophages phenotype polarization through GSK-3β/Nrf2 pathway

Aims

Sevoflurane preconditioning (SPC) results in cerebral ischemic tolerance; however, the mechanism remains unclear. Promoting microglia/macrophages polarization from pro‐inflammatory state to anti‐inflammatory phenotype has been indicated as a potential treatment target against ischemic stroke. In this study, we aimed to assess the effect of SPC on microglia polarization after stroke and which signaling pathway was involved in this transition.

Methods

Mouse primary microglia with SPC were challenged by oxygen‐glucose deprivation (OGD) or lipopolysaccharide (LPS), and mice with SPC were subjected to middle cerebral artery occlusion (MCAO). Then, the mRNA and protein levels of pro‐inflammatory/anti‐inflammatory factors were analyzed. GSK‐3β phosphorylation and Nrf2 nuclear translocation were measured. The mRNA and protein expression of pro‐inflammatory/anti‐inflammatory factors, neurological scores, infarct volume, cellular apoptosis, the proportion of pro‐inflammatory/anti‐inflammatory microglia/macrophages, and the generation of super‐oxidants were examined after SPC or GSK‐3β inhibitor TDZD treatment with or without Nrf2 deficiency.

Results

Sevoflurane preconditioning promoted anti‐inflammatory and inhibited pro‐inflammatory microglia/macrophages phenotype both in vitro and in vivo. GSK‐3β phosphorylation at Ser9 was increased after SPC. Both SPC and TDZD administration enhanced Nrf2 nuclear translocation, reduced pro‐inflammatory microglia/macrophages markers expression, promoted anti‐inflammatory markers level, and elicited a neuroprotective effect. Nrf2 deficiency abolished the promoted anti‐inflammatory microglia/macrophages polarization and ischemic tolerance induced by TDZD treatment. The reduced percentage of pro‐inflammatory positive cells and super‐oxidants generation induced by SFC or TDZD was also reversed by Nrf2 knockdown.

Conclusions

Our results indicated that SPC exerts brain ischemic tolerance and promotes anti‐inflammatory microglia/macrophages polarization by GSK‐3β‐dependent Nrf2 activation, which provides a novel mechanism for SPC‐induced neuroprotection.

Evolution of proteomics technologies for understanding respiratory syncytial virus pathogenesis

Introduction: Respiratory syncytial virus (RSV) is a major human pathogen associated with long term morbidity. RSV replication occurs primarily in the epithelium, producing a complex cellular response associated with acute inflammation and long-lived changes in pulmonary function and allergic disease. Proteomics approaches provide important insights into post-transcriptional regulatory processes including alterations in cellular complexes regulating the coordinated innate response and epigenome.Areas covered: Peer-reviewed proteomics studies of host responses to RSV infections and proteomics techniques were analyzed. Methodologies identified include 1)." bottom-up" discovery proteomics, 2). Organellar proteomics by LC-gel fractionation; 3). Dynamic changes in protein interaction networks by LC-MS; and 4). selective reaction monitoring MS. We introduce recent developments in single-cell proteomics, top-down mass spectrometry, and photo-cleavable surfactant chemistries that will have impact on understanding how RSV induces extracellular matrix (ECM) composition and airway remodeling.Expert opinion: RSV replication induces global changes in the cellular proteome, dynamic shifts in nuclear proteins, and remodeling of epigenetic regulatory complexes linked to the innate response. Pathways discovered by proteomics technologies have led to deeper mechanistic understanding of the roles of heat shock proteins, redox response, transcriptional elongation complex remodeling and ECM secretion remodeling in host responses to RSV infections and pathological sequelae.

Charcot-Leyden crystals and other protein crystals driving type 2 immunity and allergy

Protein crystals derived from innate immune cells have been synonymous with a Type-2 immune response in both mouse and man for over 150 years. Eosinophilic Galectin-10 (Charcot-Leyden) crystals in humans, and Ym1/Ym2 crystals in mice are frequently found in the context of parasitic infections, but also in diseases such as asthma and chronic rhinosinusitis. Despite their notable presence, these crystals are often overlooked as trivial markers of Type-2 inflammation. Here, we discuss the source, context, and role of protein crystallization. We focus on similarities observed between Galectin-10 and Ym1/2 crystals in driving immune responses; the subsequent benefit to the host during worm infection, and conversely the detrimental exacerbation of inflammation and mucus production during asthma.

Crystal structure of breast regression protein 39 (BRP39), a signaling glycoprotein expressed during mammary gland apoptosis, at 2.6 Å resolution

Breast regression protein 39 (BRP39) is a 39 kDa protein that is a member of chitolectin class of glycosyl hydrolase family 18 (GH18). High expression levels of BRP39 have been detected in breast carcinoma. It helps in proliferation of cells during the progression of this disease and may act as a signaling factor. BRP39 may act as a potential candidate for rational structure-based drug design against breast carcinoma. In this study, we report the crystal structure of mouse recombinant BRP39 expressed in E. coli. The structure was solved by molecular replacement and refined to 2.6 Å resolution. The overall structure of BRP39 consisted of two globular domains: a large (β/α)₈ triosephosphate isomerase (TIM) barrel domain and a small (α + β) domain. Three non-proline cis-peptides were detected in the sugar-binding cleft of BRP39, including Ser57-Phe58, Leu141-Tyr142, and Trp353-Ala354. The latter residues were conserved in other GH18 family members. It was notable that the conformation of critical Trp100 residue within the sugar-binding cleft was oriented away from the barrel. The side-chain conformation was found to be similar to that observed in chitinases, however, it was oriented into the barrel in other chitinase-like proteins (CLPs). The conformation of this critical residue may have significant implications in sugar binding. Further, two amino acid substitutions were observed in the sugar-binding groove of BRP39. The conserved Asn100 and Arg263 in Hcgp39 and other CLPs proteins (SPX-40 structures) were substituted by Lys101 and Lys264 in BRP39 which may have a significant impact on the sugar-binding properties.

Dimethyl Itaconate-Loaded Nanofibers Rewrite Macrophage Polarization, Reduce Inflammation, and Enhance Repair of Myocardic Infarction

Cellular metabolism plays a major role in the regulation of inflammation. The inflammatory macrophages undergo a wide-range of metabolic rewriting due to the production of significant amount of itaconate metabolite from cis-aconitate in the tricarboxylic acid cycle. This itaconate molecule has been recently described as a promising immunoregulator. However, its function and mode of action on macrophages and tissue repair and regeneration are yet unclear. Herein, the itaconate-derivative dimethyl itaconate (DMI) suppresses the IL-23/IL-17 inflammatory axis-associated genes and promotes antioxidant nuclear factor erythroid 2-related factor 2 target genes. The poly-ε-caprolactone (PCL)/DMI nanofibers implanted in mice initially maintain inflammation by suppressing anti-inflammatory activity and particular inflammation, while at later stage promotes anti-inflammatory activity for an appropriate tissue repair. Furthermore, the PCL/DMI nanofiber patches show an excellent myocardial protection by reducing infarct area and improving ventricular function via time-dependent regulation of myocardium-associated genes. This study unveils potential DMI macrophage modulatory functions in tissue microenvironment and macrophages rewriting for proper tissue repair.

Intact Glucocorticoid Receptor Dimerization Is Deleterious in Trauma-Induced Impaired Fracture Healing

Following severe trauma, fracture healing is impaired because of overwhelming systemic and local inflammation. Glucocorticoids (GCs), acting via the glucocorticoid receptor (GR), influence fracture healing by modulating the trauma-induced immune response. GR dimerization-dependent gene regulation is essential for the anti-inflammatory effects of GCs. Therefore, we investigated in a murine trauma model of combined femur fracture and thoracic trauma, whether effective GR dimerization influences the pathomechanisms of trauma-induced compromised fracture healing. To this end, we used mice with decreased GR dimerization ability (GR^dim). The healing process was analyzed by cytokine/chemokine multiplex analysis, flow cytometry, gene-expression analysis, histomorphometry, micro-computed tomography, and biomechanical testing. GR^dim mice did not display a systemic or local hyper-inflammation upon combined fracture and thorax trauma. Strikingly, we discovered that GR^dim mice were protected from fracture healing impairment induced by the additional thorax trauma. Collectively and in contrast to previous studies describing the beneficial effects of intact GR dimerization in inflammatory models, we report here an adverse role of intact GR dimerization in trauma-induced compromised fracture healing.

Effects of acute and chronic arecoline in adult zebrafish: Anxiolytic-like activity, elevated brain monoamines and the potential role of microglia

Arecoline is a naturally occurring psychoactive alkaloid with partial agonism at nicotinic and muscarinic acetylcholine receptors. Arecoline consumption is widespread, making it the fourth (after alcohol, nicotine and caffeine) most used substance by humans. However, the mechanisms of acute and chronic action of arecoline in-vivo remain poorly understood. Animal models are a valuable tool for CNS disease modeling and drug screening. Complementing rodent studies, the zebrafish (Danio rerio) emerges as a promising novel model organism for neuroscience research. Here, we assessed the effects of acute and chronic arecoline on adult zebrafish behavior and physiology. Overall, acute and chronic arecoline treatments produced overt anxiolytic-like behavior (without affecting general locomotor activity and whole-body cortisol levels), with similar effects also caused by areca nut water extracts. Acute arecoline at 10 mg/L disrupted shoaling, increased social preference, elevated brain norepinephrine and serotonin levels and reduced serotonin turnover. Acute arecoline also upregulated early protooncogenes c-fos and c-jun in the brain, whereas chronic treatment with 1 mg/L elevated brain expression of microglia-specific biomarker genes egr2 and ym1 (thus, implicating microglial mechanisms in potential effects of long-term arecoline use). Finally, acute 2-h discontinuation of chronic arecoline treatment evoked withdrawal-like anxiogenic behavior in zebrafish. In general, these findings support high sensitivity of zebrafish screens to arecoline and related compounds, and reinforce the growing utility of zebrafish for probing molecular mechanisms of CNS drugs. Our study also suggests that novel anxiolytic drugs can eventually be developed based on arecoline-like molecules, whose integrative mechanisms of CNS action may involve monoaminergic and neuro-immune modulation.

Distinct macrophage populations and phenotypes associated with IL-4 mediated immunomodulation at the host implant interface

The host macrophage response to implants has shown to be affected by tissue location and physio-pathological conditions of the patient. Success in immunomodulatory strategies is thus predicated on the proper understanding of the macrophage populations participating on each one of these contexts. The present study uses an in vivo implantation model to analyze how immunomodulation via an IL-4 eluting implant affects distinct macrophage populations at the tissue-implant interface and how this may affect downstream regenerative processes. Populations identified as F4/80+, CD68+ and CD11b+ macrophages at the peri-implant space showed distinct susceptibility to polarize towards an M2-like phenotype under the effects of delivered IL-4. Also, the presence of the coating resulted in a significant reduction in F4/80+ macrophages, while other populations remained unchanged. These results suggests that the F4/80+ macrophage population may be predominant in the early stages of the host response at the surface of these implants, in contrast to CD11b+ macrophage populations which were either fewer in number or located more distant from the implant surface. Gene expression assays showed increased proteolytic activity and diminished matrix deposition as possible mechanisms explaining the decreased fibrotic capsule deposition and improved peri-implant tissue quality shown in previous studies using IL-4 eluting coatings. The pattern of M2-like gene expression promoted by IL-4 was correlated with glycosaminoglycan production within the site of implantation at early stages of the host response, suggesting a significant role in this response. These findings demonstrate that immunomodulatory strategies can be utilized to design and implement targeted delivery for improving biomaterial performance.

Chitinases and Chitinase-Like Proteins in Obstructive Lung Diseases - Current Concepts and Potential Applications

Chitinases, enzymes that cleave chitin’s chain to low molecular weight chitooligomers, are widely distributed in nature. Mammalian chitinases belong to the 18-glycosyl-hydrolase family and can be divided into two groups: true chitinases with enzymatic activity (AMCase and chitotriosidase) and chitinase-like proteins (CLPs) molecules which can bind to chitin or chitooligosaccharides but lack enzymatic activity (eg, YKL-40). Chitinases are thought to be part of an innate immunity against chitin-containing parasites and fungal infections. Both groups of these hydrolases are lately evaluated also as chemical mediators or biomarkers involved in airway inflammation and fibrosis. The aim of this article is to present the current knowledge on the potential role of human chitinases and CLPs in the pathogenesis, diagnosis, and course of obstructive lung diseases. We also assessed the potential role of chitinase and CLPs inhibitors as therapeutic targets in chronic obstructive pulmonary disease and asthma.

Finding intestinal fortitude: Integrating the microbiome into a holistic view of depression mechanisms, treatment, and resilience

Depression affects at least 322 million people globally, or approximately 4.4% of the world's population. While the earnestness of researchers and clinicians to understand and treat depression is not waning, the number of individuals suffering from depression continues to increase over and above the rate of global population growth. There is a sincere need for a paradigm shift. Research in the past decade is beginning to take a more holistic approach to understanding depression etiology and treatment, integrating multiple body systems into whole-body conceptualizations of this mental health affliction. Evidence supports the hypothesis that the gut microbiome, or the collective trillions of microbes inhabiting the gastrointestinal tract, is an important factor determining both the risk of development of depression and persistence of depressive symptoms. This review discusses recent advances in both rodent and human research that explore bidirectional communication between the gut microbiome and the immune, endocrine, and central nervous systems implicated in the etiology and pathophysiology of depression. Through interactions with circulating inflammatory markers and hormones, afferent and efferent neural systems, and other, more niche, pathways, the gut microbiome can affect behavior to facilitate the development of depression, exacerbate current symptoms, or contribute to treatment and resilience. While the challenge of depression may be the direst mental health crisis of our age, new discoveries in the gut microbiome, when integrated into a holistic perspective, hold great promise for the future of positive mental health.

YKL-39 as a Potential New Target for Anti-Angiogenic Therapy in Cancer

YKL-39 belongs to the evolutionarily conserved family of Glyco_18-containing proteins composed of chitinases and chitinase-like proteins. Chitinase-like proteins (CLPs) are secreted lectins that lack hydrolytic activity due to the amino acid substitutions in their catalytic domain and combine the functions of cytokines and growth factors. One of the major cellular sources that produce CLPs in various pathologies, including cancer, are macrophages. Monocytes recruited to the tumor site and programmed by tumor cells differentiate into tumor-associated macrophages (TAMs), which are the primary source of pro-angiogenic factors. Tumor angiogenesis is a crucial process for supplying rapidly growing tumors with essential nutrients and oxygen. We recently determined that YKL-39 is produced by tumor-associated macrophages in breast cancer. YKL-39 acts as a strong chemotactic factor for monocytes and stimulates angiogenesis. Chemotherapy is a common strategy to reduce tumor size and aggressiveness before surgical intervention, but chemoresistance, resulting in the relapse of tumors, is a common clinical problem that is critical for survival in cancer patients. Accumulating evidence indicates that TAMs are essential regulators of chemoresistance. We have recently found that elevated levels of YKL-39 expression are indicative of the efficiency of the metastatic process in patients who undergo neoadjuvant chemotherapy. We suggest YKL-39 as a new target for anti-angiogenic therapy that can be combined with neoadjuvant chemotherapy to reduce chemoresistance and inhibit metastasis in breast cancer patients.

Targeted delivery of Chil3/Chil4 siRNA to alveolar macrophages using ternary complexes composed of HMG and oligoarginine micelles

Cell-type-specific genes involved in disease can be effective therapeutic targets; therefore, the development of a cell-type-specific gene delivery system is essential. In this study, targeted delivery of Chil3 and Chil4 siRNA to activated macrophages was developed using a ligand called high mobility group (HMG) and oligoarginine (OR) micelles. HMG binds to TLR4 and RAGE located on the surface of activated macrophages. Since HMG is positively charged, it binds to the negatively charged siRNA by charge interaction. However, the stable formation of the siRNA/HMG complex requires an additional molecule to act as a carrier. In this study, OR micelles were used as the carrier. Gel retardation assays showed that siRNA, HMG, and OR micelles formed stable siRNA/HMG/OR micelle ternary complexes. In vitro transfection showed that the ternary complexes selectively delivered siRNA to TLR4 expressing macrophages. In addition, intratracheal administration of siRNA/HMG/OR ternary complexes delivered Chil3 and Chil4 siRNA specifically to alveolar macrophages. Furthermore, the siRNA that was delivered using ternary complexes reduced Chil3 and Chil4 expression and suppressed the symptoms of asthma, such as airway inflammation and mucin secretion.

Eosinophils and Macrophages within the Th2-Induced Granuloma: Balancing Killing and Healing in a Tight Space

Granuloma formation is a key host immune response generated to confine invading pathogens and limit extensive host damage. It consists of an accumulation of host immune cells around a pathogen. This host response has been extensively studied in the context of inflammatory diseases. However, there is much less known about Th2-type granulomas generated in response to parasitic worms. Based on in vitro data, innate immune cells within the granuloma are thought to immobilize and kill parasites but also act to repair damaged tissue. Understanding this dual function is key. The two billion people and many livestock/wild animals infected with helminths demonstrate that granulomas are not effective at clearing infection. However, the lack of high mortality highlights their importance in ensuring that parasite migration/tissue damage is restricted and wound healing is effective. In this review, we define two key cellular players (macrophages and eosinophils) and their associated molecular players involved in Th2 granuloma function. To date, the underlying mechanisms remain poorly understood, which is in part due to a lack of conclusive studies. Most have been performed in vitro rather than in vivo, using cells that have not been obtained from granulomas. Experiments using genetically modified mouse strains and/or antibody/chemical-mediated cell depletion have also generated conflicting results depending on the model. We discuss the caveats of previous studies and the new tools available that will help fill the gaps in our knowledge and allow a better understanding of the balance between immune killing and healing.

Nephropathy in Hypertensive Animals Is Linked to M2 Macrophages and Increased Expression of the YM1/Chi3l3 Protein

Macrophages contribute to a continuous increase in blood pressure and kidney damage in hypertension, but their polarization status and the underlying mechanisms have not been clarified. This study revealed an important role for M2 macrophages and the YM1/Chi3l3 protein in hypertensive nephropathy in a mouse model of hypertension. Bone marrow cells were isolated from the femurs and tibia of male FVB/N (control) and transgenic hypertensive animals that overexpressed the rat form of angiotensinogen (TGM(rAOGEN)123, TGM123-FVB/N). The cells were treated with murine M-CSF and subsequently with LPS+IFN-γ to promote their polarization into M1 macrophages and IL-4+IL-13 to trigger the M2 phenotype. We examined the kidneys of TGM123-FVB/N animals to assess macrophage polarization and end-organ damage. mRNA expression was evaluated using real-time PCR, and protein levels were assessed through ELISA, CBA, Western blot, and immunofluorescence. Histology confirmed high levels of renal collagen. Cells stimulated with LPS+IFN-γ in vitro showed no significant difference in the expression of CD86, an M1 marker, compared to cells from the controls or the hypertensive mice. When stimulated with IL-4+IL-13, however, macrophages of the hypertensive group showed a significant increase in CD206 expression, an M2 marker. The M2/M1 ratio reached 288%. Our results indicate that when stimulated in vitro, macrophages from hypertensive mice are predisposed toward polarization to an M2 phenotype. These data support results from the kidneys where we found an increased infiltration of macrophages predominantly polarized to M2 associated with high levels of YM1/Chi3l3 (91,89%), suggesting that YM1/Chi3l3 may be a biomarker of hypertensive nephropathy.

Angiotensin II Receptor 1 Blockage Limits Brain Damage and Improves Functional Outcome After Brain Injury in Aged Animals Despite Age-Dependent Reduction in AT1 Expression

Traumatic brain injury (TBI) is a frequent pathology associated with poor neurological outcome in the aged population. We recently observed accelerated cerebral inflammation in aged mice in response to TBI. Candesartan is a potent specific inhibitor of angiotensin II receptor type 1 (AT1) which limits cerebral inflammation and brain damage in juvenile animals after experimental TBI. In the present study, we show significantly lower posttraumatic AT1 mRNA levels in aged (21 months) compared to young (2 months) mice. Despite low cerebral At1 expression, pharmacologic blockade by treatment with candesartan [daily, beginning 30 min after experimental TBI by controlled cortical impact (CCI)] was highly effective in both young and aged animals and reduced histological brain damage by -20% after 5 days. In young mice, neurological improvement was enhanced by AT1 inhibition 5 days after CCI. In older animals, candesartan treatment reduced functional impairment already on day 3 after TBI and post-traumatic body weight (BW) loss was attenuated. Candesartan reduced microglia activation (-40%) in young and aged animals, and neutrophil infiltration (-40% to 50%) in aged mice, whereas T-cell infiltration was not changed in either age group. In young animals, markers of anti-inflammatory microglia M2a polarization [arginase 1 (Arg1), chitinase3-like 3 (Ym1)] were increased by candesartan at days 1 and 5 after insult. In older mice 5 days after insult, expression of Arg1 was significantly higher independently of the treatment, whereas Ym1 gene expression was further enhanced by AT1 inhibition. Despite age-dependent posttraumatic differences in At1 expression levels, inhibition of AT1 was highly effective in a posttreatment paradigm. Targeting inflammation with candesartan is, therefore, a promising therapeutic strategy to limit secondary brain damage independent of the age.

Adoptive transfer of Trichinella spiralis-activated macrophages can ameliorate both Th1- and Th2-activated inflammation in murine models

Trichinella spiralis is a zoonotic nematode and food borne parasite and infection with T. spiralis leads to suppression of the host immune response and other immunopathologies. Alternative activated macrophages (M2) as well as T_reg cells, a target for immunomodulation by the helminth parasite, play a critical role in initiating and modulating the host immune response to parasite. The precise mechanism by which helminths modulate host immune response is not fully understood. To determine the functions of parasite-induced M2 macrophages, we compared the effects of M1 and M2 macrophages obtained from Trichinella spiralis-infected mice with those of T. spiralis excretory/secretory (ES) protein-treated macrophages on experimental intestinal inflammation and allergic airway inflammation. T. spiralis infection induced M2 macrophage polarization by increasing the expression of CD206, ARG1, and Fizz2. In a single application, we introduced macrophages obtained from T. spiralis-infected mice and T. spiralis ES protein-treated macrophages into mice tail veins before the induction of dextran sulfate sodium (DSS)-induced colitis, ovalbumin (OVA)-alum sensitization, and OVA challenge. Colitis severity was assessed by determining the severity of colitis symptoms, colon length, histopathologic parameters, and Th1-related inflammatory cytokine levels. Compared with the DSS-colitis group, T. spiralis-infected mice and T. spiralis ES protein-treated macrophages showed significantly lower disease activity index (DAI) at sacrifice and smaller reductions of body weight and proinflammatory cytokine level. The severity of allergic airway inflammation was assessed by determining the severity of symptoms of inflammation, airway hyperresponsiveness (AHR), differential cell counts, histopathologic parameters, and levels of Th2-related inflammatory cytokines. Severe allergic airway inflammation was induced after OVA-alum sensitization and OVA challenge, which significantly increased Th2-related cytokine levels, eosinophil infiltration, and goblet cell hyperplasia in the lung. However, these severe allergic symptoms were significantly decreased in T. spiralis-infected mice and T. spiralis ES protein-treated macrophages. Helminth infection and helminth ES proteins induce M2 macrophages. Adoptive transfer of macrophages obtained from helminth-infected mice and helminth ES protein-activated macrophages is an effective treatment for preventing and treating airway allergy in mice and is promising as a therapeutic for treating inflammatory diseases.

Chi3l3 induces oligodendrogenesis in an experimental model of autoimmune neuroinflammation

In demyelinating diseases including multiple sclerosis (MS), neural stem cells (NSCs) can replace damaged oligodendrocytes if the local microenvironment supports the required differentiation process. Although chitinase-like proteins (CLPs) form part of this microenvironment, their function in this differentiation process is unknown. Here, we demonstrate that murine Chitinase 3-like-3 (Chi3l3/Ym1), human Chi3L1 and Chit1 induce oligodendrogenesis. In mice, Chi3l3 is highly expressed in the subventricular zone, a stem cell niche of the adult brain, and in inflammatory brain lesions during experimental autoimmune encephalomyelitis (EAE). We find that silencing Chi3l3 increases severity of EAE. We present evidence that in NSCs Chi3l3 activates the epidermal growth factor receptor (EGFR), thereby inducing Pyk2-and Erk1/2- dependent expression of a pro-oligodendrogenic transcription factor signature. Our results implicate CLP-EGFR-Pyk2-MEK-ERK as a key intrinsic pathway controlling oligodendrogenesis.

Developmental differences in microglia morphology and gene expression during normal brain development and in response to hypoxia-ischemia

BACKGROUND

Neuroinflammation plays an important role in ischemic brain injury and recovery, however the interplay between brain development and the neuroinflammatory response is poorly understood. We previously described age-dependent differences in the microglial response and the effect of microglial inhibition. Here we investigate whether age-dependent microglial responses may be related to pre-injury developmental differences in microglial phenotype.

METHODS

Measures of microglia morphology were quantified using semi-automated software analysis of immunostained sections from postnatal day 2 (P2), P9, P30 and P60 mice using IMARIS. Microglia were isolated from P2, P9, P30 and P60 mice, and expression of markers of classical and alternative microglial activation was assessed, as well as transforming growth factor beta (TGF-β) receptor, Serpine1, Mer Tyrosine Kinase (MerTK), and the suppressor of cytokine signaling (SOCS3). Hypoxia-ischemia (HI) was induced in P9 and P30 mice using unilateral carotid artery ligation and exposure to 10% oxygen for 50 min. Microglia morphology and microglial expression of genes in the TGF-β and MerTK pathways were determined in ipsilateral and contralateral hippocampus.

RESULTS

A progressive and significant increase in microglia branching morphology was seen in all brain regions from P2 to P30. No consistent classical or alternative activation profile was seen in isolated microglia. A clear transition to increased expression of TGF-β and its downstream effector serpine1 was seen between P9 and P30. A similar increase in expression was seen in MerTK and its downstream effector SOCS3. HI resulted in a significant decrease in branching morphology only in the P9 mice, and expression of TGF-β receptor, Serpine1, MerTK, and SOCS3 were elevated in P30 mice compared to P9 post-HI.

CONCLUSION

Microglia maturation is associated with changes in morphology and gene expression, and microglial responses to ischemia in the developing brain differ based on the age at which injury occurs.

Human Chitinases: Structure, Function, and Inhibitor Discovery

Chitinases are glycosyl hydrolases that hydrolyze the β-(1-4)-linkage of N-acetyl-D-glucosamine units present in chitin polymers. Chitinases are widely distributed enzymes and are present in a wide range of organisms including insects, plants, bacteria, fungi, and mammals. These enzymes play key roles in immunity, nutrition, pathogenicity, and arthropod molting. Humans express two chitinases, chitotriosidase 1 (CHIT1) and acid mammalian chitinase (AMCase) along with several chitinase-like proteins (CLPs). Human chitinases are reported to play a protective role against chitin-containing pathogens through their capability to degrade chitin present in the cell wall of pathogens. Now, human chitinases are gaining attention as the key players in innate immune response. Although the exact mechanism of their role in immune response is not known, studies in recent years begin to relate chitin recognition and degradation with the activation of signaling pathways involved in inflammation. The roles of both CHIT1 and AMCase in the development of various diseases have been revealed and several classes of inhibitors have been developed. However, a clear understanding could not be established due to complexities in the design of the right experiment for studying the role of human chitinase in various diseases. In this chapter, we will first outline the structural features of CHIT1 and AMcase. We will then review the progress in understanding the role of human chitinases in the development of various diseases. Finally, we will summarize the inhibitor discovery efforts targeting both CHIT1 and AMCase.

A chitinase-like protein from Sarcoptes scabiei as a candidate anti-mite vaccine that contributes to immune protection in rabbits

BACKGROUND

Scabies is caused by Sarcoptes scabiei burrowing into the stratum corneum of the host's skin and is detrimental to the health of humans and animals. Vaccines are an attractive alternative to replace the acaricides currently used in their control.

METHODS

In the present study, the S. scabiei chitinase-like protein 5 (SsCLP5) was characterized and recombinant SsCLP5 (rSsCLP5) was evaluated as a candidate vaccine protein for anti-mite protection in rabbits. The expression, characterization and immunolocalization of SsCLP5 were examined. Vaccination experiments were performed on three test groups (n = 12 per group) immunized with purified rSsCLP5. Control groups (n = 12 per group) were immunized with PBS, QuilA saponin or empty vector protein. After challenge, the inflammatory reaction and skin lesions were graded and rSsCLP5 indirect ELISA was used to detect antibody IgG levels in serum samples at the time of vaccination and post-challenge.

RESULTS

The results showed that rSsCLP5 had high immunoreactivity and immunogenicity. In S. scabiei, SsCLP5 had a wide distribution in the chewing mouthpart, legs and exoskeleton, especially the outer layer of the exoskeleton. Vaccination with rSsCLP5 resulted in 74.3% (26/35) of rabbits showing no detectable lesions after challenge with S. scabiei.

CONCLUSIONS

Our data demonstrate that rSsCLP5 is a promising candidate for a recombinant protein-based vaccine against S. scabiei. This study also provides a method for studying scabies vaccine using rabbit as an animal model and a basis for screening more effective candidate proteins.

Ym1 induces RELMα and rescues IL-4Rα deficiency in lung repair during nematode infection

Ym1 and RELMα are established effector molecules closely synonymous with Th2-type inflammation and associated pathology. Here, we show that whilst largely dependent on IL-4Rα signaling during a type 2 response, Ym1 and RELMα also have IL-4Rα-independent expression patterns in the lung. Notably, we found that Ym1 has opposing effects on type 2 immunity during nematode infection depending on whether it is expressed at the time of innate or adaptive responses. During the lung migratory stage of Nippostrongylus brasiliensis, Ym1 promoted the subsequent reparative type 2 response but once that response was established, IL-4Rα-dependent Ym1 was important for limiting the magnitude of type 2 cytokine production from both CD4+ T cells and innate lymphoid cells in the lung. Importantly, our study demonstrates that delivery of Ym1 to IL-4Rα deficient animals drives RELMα production and overcomes lung repair deficits in mice deficient in type 2 immunity. Together, Ym1 and RELMα, exhibit time and dose-dependent interactions that determines the outcome of lung repair during nematode infection.

Impaired wound healing in type 1 diabetes is dependent on 5-lipoxygenase products

Type 1 diabetes is associated with systemic low grade inflammation (LGI). We have previously shown that LGI in diabetic mice depends on systemic circulation of leukotriene (LTB₄) which potentiates the toll-like/IL1β receptors response in macrophages. Impaired wound healing is an important co-morbidity in diabetes, and macrophages play a key role in this process. Here, we investigated the role of leukotrienes on monocytes and macrophages phenotype and in the impaired wound healing in diabetic mice. Type 1 diabetes was induced with streptozotocin in 129SvE wild-type (WT) and leukotrienes-deficient 5LO^−/− (5-lipoxygenase knockout) mice. In diabetics, the systemic levels of LTB4, TNF-α, IL-6, IL-10, IL-12 and IFNγ were increased as well as the frequency of pro-inflammatory monocytes (CD11b⁺Ly6C^highLy6G⁻) compared to healthy mice. In diabetic 5LO^−/− mice, these parameters were similar to those in healthy mice. Resident peritoneal macrophages from diabetic WT mice showed a classically activated M1-like phenotype (high Nos2, Stat and Il12 expression, and nitrite levels). Macrophages from diabetic 5LO^−/− mice presented alternatively activated M2-macrophages markers (high Arg1 and Chi3l3 expression and arginase activity) and when stimulated with IL4, enhanced phosphorylated-STAT6. Cutaneous wound healing in diabetic WT mice was impaired, which correlated with the decreased frequency of M2-macrophages (CD45⁺F4/80⁺CD206⁺) in the lesions. In diabetic 5LO^−/− mice, the frequency of M2-macrophages in the wound was similar to that in healthy mice, suggesting that the impaired healing of diabetic mice depends on 5LO products. The inhibition of leukotrienes or antagonism of its receptors could be a therapeutic alternative for diabetic patients with impaired healing.

Vascular Permeability and Remodelling Coincide with Inflammatory and Reparative Processes after Joint Bleeding in Factor VIII-Deficient Mice

Vascular remodelling is a prominent feature of haemophilic arthropathy (HA) that may underlie re-bleeding, yet the nature of vascular changes and underlying mechanisms remain largely unknown. Here, we aimed to characterize synovial vascular remodelling and vessel integrity after haemarthrosis, as well as temporal changes in inflammatory and tissue-reparative pathways. Thirty acutely painful joints in patients with haemophilia (PWH) were imaged by musculoskeletal ultrasound with Power Doppler (MSKUS/PD) to detect vascular abnormalities and bloody effusions. Nineteen out of 30 painful joint episodes in PWH were associated with haemarthrosis, and abnormal vascular perfusion was unique to bleeding joints. A model of induced haemarthrosis in factor VIII (FVIII)-deficient mice was used for histological assessment of vascular remodelling (α-smooth muscle actin [αSMA] expression), and monitoring of in vivo vascular perfusion and permeability by MSKUS/PD and albumin extravasation, respectively. Inflammatory (M1) and reparative (M2) macrophage markers were quantified in murine synovium over a 10-week time course by real-time polymerase chain reaction. The abnormal vascular perfusion observed in PWH was recapitulated in FVIII-deficient mice after induced haemarthrosis. Neovascularization and increased vessel permeability were apparent 2 weeks post-bleed in FVIII-deficient mice, after a transient elevation of inflammatory macrophage M1 markers. These vascular changes subsided by week 4, while vascular remodelling, evidenced by architectural changes and pronounced αSMA expression, persisted alongside a reparative macrophage M2 response. In conclusion, haemarthrosis leads to transient inflammation coupled with neovascularization and associated vascular permeability, while subsequent tissue repair mechanisms coincide with vascular remodelling. Together, these vascular changes may promote re-bleeding and HA progression.

Imaging Reporter Strategy to Monitor Gene Activation of Microglia Polarisation States under Stimulation

Microglial cells as innate immune key players have a critical and unique role in neurodegenerative disorders. They strongly interact with their microenvironment in a complex manner and react to changes by switching their phenotype and functional activation states. In order to understand the development of brain diseases, it is imperative to elucidate up- or down-regulation of genes involved in microglia polarisation in time-profile by a simple-to-use strategy. Here, we present a new imaging strategy to follow promoter activity of genes involved in microglia polarisation. We lentivirally transduced BV-2 microglia cells in culture with constructs consisting of the induced nitric oxide synthase (iNOS), Fc gamma receptor III (Fcgr3) (both resembling the pro-inflammatory M1-like phenotype) or Chitinase-like 3 (Chil3/Ym1) (resembling the anti-inflammatory M2-like phenotype) promoters and stimulated transgenic cells with potent activators for pro- or anti-inflammatory response, such as lipopolysaccharide (LPS) + interferon gamma (IFN-γ) or interleukin (IL)-4, respectively. Promoter activities upon polarisation phases were quantitatively assessed by the two imaging reporters Luc2 for bioluminescence and eGFP for fluorescence.

Helminth Infections: Recognition and Modulation of the Immune Response by Innate Immune Cells

The survival of helminths in the host over long periods of time is the result of a process of adaptation or dynamic co-evolution between the host and the parasite. However, infection with helminth parasites causes damage to the host tissues producing the release of danger signals that induce the recruitment of various cells, including innate immune cells such as macrophages (Mo), dendritic cells (DCs), eosinophils, basophils, and mast cells. In this scenario, these cells are able to secrete soluble factors, which orchestrate immune effector mechanisms that depend on the different niches these parasites inhabit. Here, we focus on recent advances in the knowledge of excretory-secretory products (ESP), resulting from helminth recognition by DCs and Mo. Phagocytes and other cells types such as innate lymphocyte T cells 2 (ILC2), when activated by ESP, participate in an intricate cytokine network to generate innate and adaptive Th2 responses. In this review, we also discuss the mechanisms of innate immune cell-induced parasite killing and the tissue repair necessary to assure helminth survival over long periods of time.

Chi3l3: a potential key orchestrator of eosinophil recruitment in meningitis induced by Angiostrongylus cantonensis

BACKGROUND

Angiostrongylus cantonensis, an important foodborne parasite, can induce serious eosinophilic meningitis in non-permissive hosts, such as mouse and human. However, the characteristics and mechanisms of the infection are still poorly understood. This study sought to determine the key molecules and its underlying mechanism in inducing brain eosinophilic infiltration caused by Angiostrongylus cantonensis.

METHODS

Mathematical models were established for prediction of significantly changing genes and the functional associated protein with RNA-seq data in Angiostrongylus cantonensis infection. The expression level of Chi3l3, the predicted key molecule, was verified using Western blotting and real-time quantitative PCR. Critical cell source of Chi3l3 and its relationship with eosinophils were identified with flow cytometry, immunohistochemistry, and further verified by macrophage depletion using liposomal clodronate. The role of soluble antigens of Angiostrongylus cantonensis in eosinophilic response was identified with mice airway allergy model by intranasal administration of Alternaria alternate. The relationship between Chi3l3 and IL-13 was identified with flow cytometry, Western blotting, and Seahorse Bioscience extracellular flux analyzer.

RESULTS

We analyzed the skewed cytokine pattern in brains of Angiostrongylus cantonensis-infected mice and found Chi3l3 to be an important molecule, which increased sharply during the infection. The percentage of inflammatory macrophages, the main source of Chi3l3, also increased, in line with eosinophils percentage in the brain. Network analysis and mathematical modeling predirect a functional association between Chi3l3 and IL-13. Further experiments verified that the soluble antigen of Angiostrongylus cantonensis induce brain eosinophilic meningitis via aggravating a positive feedback loop between IL-13 and Chi3l3.

CONCLUSIONS

We present evidences in favor of a key role for macrophave-derived Chi3l3 molecule in the infection of Angiostrongylus cantonensis, which aggravates eosinophilic meningitis induced by Angiostrongylus cantonensis via a IL-13-mediated positive feedback loop. These reported results constitute a starting point for future research of angiostrongyliasis pathogenesis and imply that targeting chitinases and chitinase-like-proteins may be clinically beneficial in Angiostrongylus cantonensis-induced eosinophilic meningitis.

Chitinase-like proteins as regulators of innate immunity and tissue repair: helpful lessons for asthma?

Chitinases and chitinase-like proteins (CLPs) belong to the glycoside hydrolase family 18 of proteins. Chitinases are expressed in mammals and lower organisms, facilitate chitin degradation, and hence act as host-defence enzymes. Gene duplication and loss-of-function mutations of enzymatically active chitinases have resulted in the expression of a diverse range of CLPs across different species. CLPs are genes that are increasingly associated with inflammation and tissue remodelling not only in mammals but also across distant species. While the focus has remained on understanding the functions and expression patterns of CLPs during disease in humans, studies in mouse and lower organisms have revealed important and overlapping roles of the CLP family during physiology, host defence and pathology. This review will summarise recent insights into the regulatory functions of CLPs on innate immune pathways and discuss how these effects are not only important for host defence and tissue injury/repair after pathogen invasion, but also how they have extensive implications for pathological processes involved in diseases such as asthma.

Human Chitinases and Chitinase-Like Proteins as Indicators for Inflammation and Cancer

Human Glyco_18 domain-containing proteins constitute a family of chitinases and chitinase-like proteins. Chitotriosidase and AMCase are true enzymes which hydrolyse chitin and have a C-terminal chitin-binding domain. YKL-40, YKL-39, SI-CLP and murine YM1/2 proteins possess solely Glyco_18 domain and do not have the hydrolytic activity. The major sources of Glyco_18 containing proteins are macrophages, neutrophils, epithelial cells, chondrocytes, synovial cells, and cancer cells. Both macrophages and neutrophils use the regulated secretory mechanism for the release of Glyco_18 containing proteins. Glyco_18 containing proteins are established biomarkers for human diseases. Chitotriosidase is overproduced by lipid-laden macrophages and is a major marker for the inherited lysosomal storage Gaucher disease. AMCase and murine lectin YM1 are upregulated in Th2-environment, and enzymatic activity of AMCase contributes to asthma pathogenesis. YKL proteins act as soluble mediators for the cell proliferation and migration, and are also involved in rheumatoid arthritis, inflammatory bowel disease, hepatic fibrosis and cirrhosis. Chitotriosidase and YKL-40 reflect the macrophage activation in atherosclerotic plaques. Serum level of YKL-40 is a diagnostic and prognostic marker for numerous types of solid tumors. YKL-39 is a marker for the activation of chondrocytes and the progression of the osteoarthritis in human. Recently identified SI-CLP is upregulated by Th2 cytokine IL-4 as well as by glucocorticoids. This unique feature of SI-CLP makes it an attractive candidate for the examination of individual sensitivity of patients to glucocorticoid treatment and prediction of side effects of glucocorticoid therapy. Human chitinases and chitinase-like proteins are found in tissues and circulation, and can be detected by non-invasive technologies.

Extra-Large Pore Mesoporous Silica Nanoparticles for Directing in Vivo M2 Macrophage Polarization by Delivering IL-4

Over the past decade, mesoporous silica nanoparticles (MSNs) smaller than 200 nm with a high colloidal stability have been extensively studied for systemic drug delivery. Although small molecule delivery via MSNs has been successful, the encapsulation of large therapeutic biomolecules, such as proteins or DNA, is limited due to small pore size of the conventional MSNs obtained by soft-templating. Here, we report the synthesis of mesoporous silica nanoparticles with extra-large pores (XL-MSNs) and their application to in vivo cytokine delivery for macrophage polarization. Uniform, size-controllable XL-MSNs with 30 nm extra-large pores were synthesized using organic additives and inorganic seed nanoparticles. XL-MSNs showed significantly higher loadings for the model proteins with different molecular weights compared to conventional small pore MSNs. XL-MSNs were used to deliver IL-4, which is an M2-polarizing cytokine and very quickly degraded in vivo, to macrophages and polarize them to anti-inflammatory M2 macrophages in vivo. XL-MSNs induced a low level of reactive oxygen species (ROS) production and no pro-inflammatory cytokines in bone marrow-derived macrophages (BMDMs) and in mice injected intravenously with XL-MSNs. We found that the injected XL-MSNs were targeted to phagocytic myeloid cells, such as neutrophils, monocytes, macrophages, and dendritic cells. Finally, we demonstrated that the injection of IL-4-loaded XL-MSNs successfully triggered M2 macrophage polarization in vivo, suggesting the clinical potential of XL-MSNs for modulating immune systems via targeted delivery of various cytokines.

Heparin and Heparin-Derivatives in Post-Subarachnoid Hemorrhage Brain Injury: A Multimodal Therapy for a Multimodal Disease

Pharmacologic efforts to improve outcomes following aneurysmal subarachnoid hemorrhage (aSAH) remain disappointing, likely owing to the complex nature of post-hemorrhage brain injury. Previous work suggests that heparin, due to the multimodal nature of its actions, reduces the incidence of clinical vasospasm and delayed cerebral ischemia that accompany the disease. This narrative review examines how heparin may mitigate the non-vasospastic pathological aspects of aSAH, particularly those related to neuroinflammation. Following a brief review of early brain injury in aSAH and heparin’s general pharmacology, we discuss potential mechanistic roles of heparin therapy in treating post-aSAH inflammatory injury. These roles include reducing ischemia-reperfusion injury, preventing leukocyte extravasation, modulating phagocyte activation, countering oxidative stress, and correcting blood-brain barrier dysfunction. Following a discussion of evidence to support these mechanistic roles, we provide a brief discussion of potential complications of heparin usage in aSAH. Our review suggests that heparin’s use in aSAH is not only safe, but effectively addresses a number of pathologies initiated by aSAH.

Crosstalk between glucocorticoids and IL-4 modulates Ym1 expression in alternatively activated myeloid cells

Airway epithelial cells induce a tolerogenic microenvironment by modulating immune cells in the lung. We recently showed that the supernatant of airway epithelial cells induces two marker genes of alternative activation, Ym1 and Ms4a8a, in respiratory myeloid cells. This induction was partially mediated by glucocorticoids, secreted by airway epithelial cells. In this study, we further investigated Ym1 and Ms4a8a regulation in alternatively activated myeloid cells in the presence of the T_H2 cytokines IL-4 and IL-13. We show that Ym1 expression is boosted upon co-stimulation with airway epithelial cell supernatant and IL-4/IL-13, whereas Ms4a8a expression is down-regulated. This suggests that a crosstalk between IL-4/IL-13 and glucocorticoid signaling exists. Blocking protein synthesis indicated that dexamethasone-induced de novo protein synthesis is required for the interaction between glucocorticoid and IL-4 signaling regarding Ym1 regulation. Using reporter gene constructs, we demonstrate that the important regulatory region within the Ym1 promoter is found between -602bp and -969bp upstream of the start of translation. Bioinformatic analysis identified several glucocorticoid response elements (GREs) in this region. Further analysis identified overlapping but functionally active glucocorticoid receptor and STAT-6 binding sites, supporting the cooperative effect of glucocorticoids and IL-4 in the regulation of Ym1. These findings further prove the plasticity and complexity of alternatively activated myeloid cells and the importance of the local microenvironment. We believe that this regulation is of special importance in the pulmonary system, since both factors, glucocorticoids and IL-4/13, play a role in airway diseases such as asthma.

Monocyte-Derived Macrophages Contribute to Spontaneous Long-Term Functional Recovery after Stroke in Mice

Stroke is a leading cause of disability and currently lacks effective therapy enabling long-term functional recovery. Ischemic brain injury causes local inflammation, which involves both activated resident microglia and infiltrating immune cells, including monocytes. Monocyte-derived macrophages (MDMs) exhibit a high degree of functional plasticity. Here, we determined the role of MDMs in long-term spontaneous functional recovery after middle cerebral artery occlusion in mice. Analyses by flow cytometry and immunocytochemistry revealed that monocytes home to the stroke-injured hemisphere., and that infiltration peaks 3 d after stroke. At day 7, half of the infiltrating MDMs exhibited a bias toward a proinflammatory phenotype and the other half toward an anti-inflammatory phenotype, but during the subsequent 2 weeks, MDMs with an anti-inflammatory phenotype dominated. Blocking monocyte recruitment using the anti-CCR2 antibody MC-21 during the first week after stroke abolished long-term behavioral recovery, as determined in corridor and staircase tests, and drastically decreased tissue expression of anti-inflammatory genes, including TGFβ, CD163, and Ym1. Our results show that spontaneously recruited monocytes to the injured brain early after the insult contribute to long-term functional recovery after stroke.

SIGNIFICANCE STATEMENT

For decades, any involvement of circulating immune cells in CNS repair was completely denied. Only over the past few years has involvement of monocyte-derived macrophages (MDMs) in CNS repair received appreciation. We show here, for the first time, that MDMs recruited to the injured brain early after ischemic stroke contribute to long-term spontaneous functional recovery through inflammation-resolving activity. Our data raise the possibility that inadequate recruitment of MDMs to the brain after stroke underlies the incomplete functional recovery seen in patients and that boosting homing of MDMs with an anti-inflammatory bias to the injured brain tissue may be a new therapeutic approach to promote long-term improvement after stroke.

Diverse macrophages polarization in tumor microenvironment

Macrophages are traditional innate immune cells that play critical roles in the clearance of pathogens and the maintenance of tissue homeostasis. Accumulating evidence proves that macrophages affect cancer initiation and malignancy. Macrophages can be categorized into two extreme subsets, classically activated (M1) and alternatively activated (M2) macrophages based on their distinct functional abilities in response to microenvironmental stimuli. In a tumor microenvironment, tumor associated macrophages (TAMs) are considered to be of the polarized M2 phenotype that enhances tumor progression and represent a poor prognosis. Furthermore, TAMs enhance tumor angiogenesis, growth, metastasis, and immunosuppression by secreting a series of cytokines, chemokines, and proteases. The regulation of macrophage polarization is considered to be a potential future therapy for cancer management.

Glutathione Depletion Is Linked with Th2 Polarization in Mice with a Retrovirus-Induced Immunodeficiency Syndrome, Murine AIDS: Role of Proglutathione Molecules as Immunotherapeutics

Injection of the LP-BM5 murine leukemia virus into mice causes murine AIDS, a disease characterized by many dysfunctions of immunocompetent cells. To establish whether the disease is characterized by glutathione imbalance, reduced glutathione (GSH) and cysteine were quantified in different organs. A marked redox imbalance, consisting of GSH and/or cysteine depletion, was found in the lymphoid organs, such as the spleen and lymph nodes. Moreover, a significant decrease in cysteine and GSH levels in the pancreas and brain, respectively, was measured at 5 weeks postinfection. The Th2 immune response was predominant at all times investigated, as revealed by the expression of Th1/Th2 cytokines. Furthermore, investigation of the activation status of peritoneal macrophages showed that the expression of genetic markers of alternative activation, namely, Fizz1, Ym1, and Arginase1, was induced. Conversely, expression of inducible nitric oxide synthase, a marker of classical activation of macrophages, was detected only when Th1 cytokines were expressed at high levels. In vitro studies revealed that during the very early phases of infection, GSH depletion and the downregulation of interleukin-12 (IL-12) p40 mRNA were correlated with the dose of LP-BM5 used to infect the macrophages. Treatment of LP-BM5-infected mice with N-(N-acetyl-l-cysteinyl)-S-acetylcysteamine (I-152), an N-acetyl-cysteine supplier, restored GSH/cysteine levels in the organs, reduced the expression of alternatively activated macrophage markers, and increased the level of gamma interferon production, while it decreased the levels of Th2 cytokines, such as IL-4 and IL-5. Our findings thus establish a link between GSH deficiency and Th1/Th2 disequilibrium in LP-BM5 infection and indicate that I-152 can be used to restore the GSH level and a balanced Th1/Th2 response in infected mice.

IMPORTANCE

The first report of an association between Th2 polarization and alteration of the redox state in LP-BM5 infection is presented. Moreover, it provides evidence that LP-BM5 infection causes a decrease in the thiol content of peritoneal macrophages, which can influence IL-12 production. The restoration of GSH levels by GSH-replenishing molecules can represent a new therapeutic avenue to fight this retroviral infection, as it reestablishes the Th1/Th2 balance. Immunotherapy based on the use of pro-GSH molecules would permit LP-BM5 infection and probably all those viral infections characterized by GSH deficiency and a Th1/Th2 imbalance to be more effectively combated.

The adaptor protein insulin receptor substrate 2 inhibits alternative macrophage activation and allergic lung inflammation

Insulin receptor substrate 2 (IRS2) is an adaptor protein that becomes tyrosine-phosphorylated in response to the cytokines interleukin-4 (IL-4) and IL-13, which results in activation of the phosphoinositide 3-kinase (PI3K)-Akt pathway. IL-4 and IL-13 contribute to allergic lung inflammation. To examine the role of IRS2 in allergic disease, we evaluated the responses of IRS2-deficient (IRS2(-/-)) mice. Unexpectedly, loss of IRS2 resulted in a substantial increase in the expression of a subset of genes associated with the generation of alternatively activated macrophages (AAMs) in response to IL-4 or IL-13 in vitro. AAMs secrete factors that enhance allergic responses and promote airway remodeling. Moreover, compared to IRS2(+/+) mice, IRS2(+/-) and IRS2(-/-) mice developed enhanced pulmonary inflammation, accumulated eosinophils and AAMs, and exhibited airway and vascular remodeling upon allergen stimulation, responses that partially depended on macrophage-intrinsic IRS2 signaling. Both in unstimulated and IL-4-stimulated macrophages, lack of IRS2 enhanced phosphorylation of Akt and ribosomal S6 protein. Thus, we identified a critical inhibitory loop downstream of IRS2, demonstrating an unanticipated and previously unrecognized role for IRS2 in suppressing allergic lung inflammation and remodeling.