When two is better than one: macrophages and neutrophils work in concert in innate immunity as complementary and cooperative partners of a myeloid phagocyte system

Effects of Preexisting Diabetes Mellitus on the Severity of Traumatic Brain Injury

Falls and traffic accidents can cause traumatic brain injury (TBI). Assessment of the injury severity is essential to determine the prognosis or the cause of death. Diabetes mellitus (DM) is a common preexisting disease in elderly adults. We hypothesized that preexisting DM exacerbates TBI secondary to prolonged inflammation. In this study, we investigated TBI-induced changes in nerve function and inflammatory cell migration to the injury site, and the extent of brain contusion in KK-Ay (DM) and C57BL/6J (non-DM) mice. A controlled cortical impact device was used to induce TBI in each mouse. The brain contusion volume was measured using magnetic resonance imaging. Nerve function changes were assessed using the following animal behavior tasks: neurological severity score (NSS), Morris water maze, forced swim test, and beam walking. Immunohistochemical examinations of brain sections were performed to assess the infiltration of neutrophils, astrocytes, microglia, and macrophages, and to detect apoptosis. These experiments were performed on post-injury days 1-90 (over five experiments/time-points in each group). Compared with non-DM mice, DM mice showed significantly greater brain contusion volume, greater deterioration in the NSS, and a higher number of neutrophils, macrophages, and apoptotic cells in the brain tissue specimens. This study indicates that the prognosis of normal mice and DM mice differs, even if they acquire a TBI of the same severity. Therefore, it is important to evaluate patients with TBI for DM and other preexisting diseases in order to provide adequate treatment or to determine the correct cause of death.

Structure of fish Toll-like receptors (TLR) and NOD-like receptors (NLR)

Innate immunity driven by pattern recognition receptor (PRR) protects the host from invading pathogens. Aquatic animals like fish where the adaptive immunity is poorly developed majorly rely on their innate immunity modulated by PRRs like toll-like receptors (TLR) and NOD-like receptors (NLR). However, current development to improve the fish immunity via TLR/NLR signaling is affected by a poor understanding of its mechanistic and structural features. This review discusses the structure of fish TLRs/NLRs and its interaction with pathogen associated molecular patterns (PAMPs) and downstream signaling molecules. Over the past one decade, significant progress has been done in studying the structure of TLRs/NLRs in higher eukaryotes; however, structural studies on fish innate immune receptors are undermined. Several novel TLR genes are identified in fish that are absent in higher eukaryotes, but the function is still poorly understood. Unlike the fundamental progress achieved in developing antagonist/agonist to modulate human innate immunity, analogous studies in fish are nearly lacking due to structural inadequacy. This underlies the importance of exploring the structural and mechanistic details of fish TLRs/NLRs at an atomic and molecular level. This review outlined the mechanistic and structural basis of fish TLR and NLR activation.

Toll-like receptors in sepsis-associated cytokine storm and their endogenous negative regulators as future immunomodulatory targets

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Sepsis infects more than 48.9 million people world-wide, with 19.7 million deaths.

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Cytokine storm plays a significant role in sepsis, along with severe COVID-19.

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TLR signaling pathways plays a crucial role in generating the cytokine storm.

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Endogenous negative regulators of TLR signaling are crucial to regulate cytokine storm.

Cytokine storm generates during various systemic acute infections, including sepsis and current pandemic called COVID-19 (severe) causing devastating inflammatory conditions, which include multi-organ failure or multi-organ dysfunction syndrome (MODS) and death of the patient. Toll-like receptors (TLRs) are one of the major pattern recognition receptors (PRRs) expressed by immune cells as well as non-immune cells, including neurons, which play a crucial role in generating cytokine storm. They recognize microbial-associated molecular patterns (MAMPs, expressed by pathogens) and damage or death-associate molecular patterns (DAMPs; released and/expressed by damaged/killed host cells). Upon recognition of MAMPs and DAMPs, TLRs activate downstream signaling pathways releasing several pro-inflammatory mediators [cytokines, chemokines, interferons, and reactive oxygen and nitrogen species (ROS or RNS)], which cause acute inflammation meant to control the pathogen and repair the damage. Induction of an exaggerated response due to genetic makeup of the host and/or persistence of the pathogen due to its evasion mechanisms may lead to severe systemic inflammatory condition called sepsis in response to the generation of cytokine storm and organ dysfunction. The activation of TLR-induced inflammatory response is hardwired to the induction of several negative feedback mechanisms that come into play to conclude the response and maintain immune homeostasis. This state-of-the-art review describes the importance of TLR signaling in the onset of the sepsis-associated cytokine storm and discusses various host-derived endogenous negative regulators of TLR signaling pathways. The subject is very important as there is a vast array of genes and processes implicated in these negative feedback mechanisms. These molecules and mechanisms can be targeted for developing novel therapeutic drugs for cytokine storm-associated diseases, including sepsis, severe COVID-19, and other inflammatory diseases, where TLR-signaling plays a significant role.

Brucella abortus-infected platelets modulate the activation of neutrophils

Brucellosis is a contagious disease caused by bacteria of the genus Brucella. Platelets (PLTs) have been widely involved in the modulation of the immune response. We have previously reported the modulation of Brucella abortus-mediated infection of monocytes. As a result, PLTs cooperate with monocytes and increase their inflammatory capacity, promoting the resolution of the infection. Extending these results, in this study we demonstrate that patients with brucellosis present slightly elevated levels of complexes between PLTs and both monocytes and neutrophils. We then assessed whether PLTs were capable of modulating functional aspects of neutrophils. The presence of PLTs throughout neutrophil infection increased the production of interleukin-8, CD11b surface expression and reactive oxygen species formation, whereas it decreased the expression of CD62L, indicating an activated status of these cells. We next analyzed whether this modulation was mediated by released factors. To discriminate between these options, neutrophils were treated with supernatants collected from B. abortus-infected PLTs. Our results show that CD11b expression was induced by soluble factors of PLTs but direct contact between cell populations was needed to enhance the respiratory burst. Additionally, B. abortus-infected PLTs recruit polymorphonuclear (PMN) cells to the site of infection. Finally, the presence of PLTs did not modify the initial invasion of PMN cells by B. abortus but improved the control of the infection at extended times. Altogether, our results demonstrate that PLTs interact with neutrophils and promote a proinflammatory phenotype which could also contribute to the resolution of the infection.

Tumor-associated neutrophils suppress antitumor immunity of NK cells through the PD-L1/PD-1 axis

Studies have begun to emerge showing the protumor effects of tumor-associated neutrophils (TANs) in tumorigenesis, which may involve dysfunction of NK cells. However, the mechanism through which these rebellious neutrophils modulate NK cell immunity in tumor-bearing state remains unclear. In the present study, we demonstrate that neutrophils can impair the cytotoxicity and infiltration capability of NK cells, and downregulate CCR1 resulting in the weakened infiltration capability of NK cells. Moreover, neutrophils can decrease the responsiveness of NK-activating receptors, NKp46 and NKG2D. Mechanistically, enhanced PD-L1 on neutrophils and PD-1 on NK cells, and subsequent PD-L1/PD-1 interactions were the main mechanisms determining the suppression of neutrophils in NK cell immunity. G-CSF/STAT3 pathway was responsible for PD-L1 upregulation on neutrophils, while IL-18 was essential for PD-1 enhancement on NK cells. The crosstalk between neutrophils and NK cells was cell-cell interaction-dependent. These findings suggest that neutrophils can suppress the antitumor immunity of NK cells in tumor-bearing status through the PD-L1/PD-1 axis, highlighting the importance of PD-L1/PD-1 in the inhibitory effect of neutrophils on NK cells. Targeting G-CSF/STAT3 and IL-18 signaling pathway may be potential strategies to inhibit residual tumor in tumor therapy.

Bivalent Inhibitor with Selectivity for Trimeric MMP-9 Amplifies Neutrophil Chemotaxis and Enables Functional Studies on MMP-9 Proteoforms

A fundamental part of the immune response to infection or injury is leukocyte migration. Matrix metalloproteinases (MMPs) are a class of secreted or cell-bound endopeptidases, implicated in every step of the process of inflammatory cell migration. Hence, specific inhibition of MMPs is an interesting approach to control inflammation. We evaluated the potential of a bivalent carboxylate inhibitor to selectively inhibit the trimeric proteoform of MMP-9 and compared this with a corresponding monovalent inhibitor. The bivalent inhibitor efficiently inhibited trimeric MMP-9 (IC₅₀ = 0.1 nM), with at least 500-fold selectivity for MMP-9 trimers over monomers. Surprisingly, in a mouse model for chemotaxis, the bivalent inhibitor amplified leukocyte influxes towards lipopolysaccharide-induced inflammation. We verified by microscopic and flow cytometry analysis increased amounts of neutrophils. In a mouse model for endotoxin shock, mice treated with the bivalent inhibitor had significantly increased levels of MMP-9 in plasma and lungs, indicative for increased inflammation. In conclusion, we propose a new role for MMP-9 trimers in tempering excessive neutrophil migration. In addition, we have identified a small molecule inhibitor with a high selectivity for the trimeric proteoform of MMP-9, which will allow further research on the functions of MMP-9 proteoforms.

Neutrophils acquire antigen-presenting cell features after phagocytosis of IgG-opsonized erythrocytes

Neutrophils are particularly well known for their antimicrobial function. Although historically they are regarded as strictly a phagocyte of the innate immune system, over time it has become clear that neutrophils are versatile cells with numerous functions including innate and adaptive immune regulation. We have previously described a role for human neutrophils in antibody-mediated red blood cell (RBC) clearance. Under homeostatic conditions, neutrophils do not take up RBCs. Yet, when RBCs are immunoglobulin G (IgG) opsonized, which can occur in alloimmunization or autoimmunization reactions, neutrophils can effectively phagocytose RBCs. In the present study, we show that human neutrophils acquire an antigen-presenting cell (APC) phenotype following RBC phagocytosis. Subsequent to RBC phagocytosis, neutrophils expressed major histocompatibility complex class II (MHC-II) and costimulatory molecules such as CD40 and CD80. Moreover, in classical APCs, the respiratory burst is known to regulate antigen presentation. We found that the respiratory burst in neutrophils is reduced after IgG-mediated RBC phagocytosis. Additionally, following RBC phagocytosis, neutrophils were demonstrated to elicit an antigen-specific T-cell response, using tetanus toxoid (TT) as an antigen to elicit an autologous TT-specific CD4⁺ T-cell response. Lastly, although the "don't eat me" signal CD47 is known to have a powerful restrictive role in the activation of immunity against RBCs in dendritic cells, CD47 does not seem to have a significant effect on the antigen-presenting function of neutrophils in this context. Overall, these findings reveal that besides their classical antimicrobial role, neutrophils show plasticity in their phenotype.

Macrophage Dysregulation and Impaired Skin Wound Healing in Diabetes

Monocytes (Mo) and macrophages (Mϕ) play important roles in normal skin wound healing, and dysregulation of wound Mo/Mϕ leads to impaired wound healing in diabetes. Although skin wound Mϕ originate both from tissue resident Mϕ and infiltrating bone marrow-derived Mo, the latter play dominant roles during the inflammatory phase of wound repair. Increased production of bone marrow Mo caused by alterations of hematopoietic stem and progenitor cell (HSPC) niche and epigenetic modifications of HSPCs likely contributes to the enhanced number of wound Mϕ in diabetes. In addition, an impaired transition of diabetic wound Mϕ from “pro-inflammatory” to “pro-healing” phenotypes driven by the local wound environment as well as intrinsic changes in bone marrow Mo is also thought to be partly responsible for impaired diabetic wound healing. The current brief review describes the origin, heterogeneity and function of wound Mϕ during normal skin wound healing followed by discussion of how dysregulated wound Mϕ numbers and phenotype are associated with impaired diabetic wound healing. The review also highlights the possible links between altered bone marrow myelopoiesis and increased Mo production as well as extrinsic and intrinsic factors that drive wound macrophage dysregulation leading to impaired wound healing in diabetes.

Illuminating Macrophage Contributions to Host-Pathogen Interactions In Vivo: the Power of Zebrafish

Macrophages are a key cell type in innate immunity. Years of in vitro cell culture studies have unraveled myriad macrophage pathways that combat pathogens and demonstrated how pathogen effectors subvert these mechanisms. However, in vitro cell culture studies may not accurately reflect how macrophages fit into the context of an innate immune response in whole animals with multiple cell types and tissues. Larval zebrafish have emerged as an intermediate model of innate immunity and host-pathogen interactions to bridge the gap between cell culture studies and mammalian models. These organisms possess an innate immune system largely conserved with that of humans and allow state-of-the-art genetic and imaging techniques, all in the context of an intact organism. Using larval zebrafish, researchers are elucidating the function of macrophages in response to many different infections, including both bacterial and fungal pathogens. The goal of this review is to highlight studies in zebrafish that utilized live-imaging techniques to analyze macrophage activities in response to pathogens. Recent studies have explored the roles of specific pathways and mechanisms in macrophage killing ability, explored how pathogens subvert these responses, identified subsets of macrophages with differential microbicidal activities, and implicated macrophages as an intracellular niche for pathogen survival and trafficking. Research using this model continues to advance our understanding of how macrophages, and specific pathways inside these cells, fit into complex multicellular innate immune responses in vivo, providing important information on how pathogens evade these pathways and how we can exploit them for development of treatments against microbial infections.

Mechanisms Regulating Muscle Regeneration: Insights into the Interrelated and Time-Dependent Phases of Tissue Healing

Despite a massive body of knowledge which has been produced related to the mechanisms guiding muscle regeneration, great interest still moves the scientific community toward the study of different aspects of skeletal muscle homeostasis, plasticity, and regeneration. Indeed, the lack of effective therapies for several physiopathologic conditions suggests that a comprehensive knowledge of the different aspects of cellular behavior and molecular pathways, regulating each regenerative stage, has to be still devised. Hence, it is important to perform even more focused studies, taking the advantage of robust markers, reliable techniques, and reproducible protocols. Here, we provide an overview about the general aspects of muscle regeneration and discuss the different approaches to study the interrelated and time-dependent phases of muscle healing.

Hydrogen peroxide in neutrophil inflammation: Lesson from the zebrafish

The zebrafish has become an excellent model for the study of inflammation and immunity. Its unique advantages for in vivo imaging and gene and drug screening have allowed the visualization of dual oxidase 1 (Duox1)-derived hydrogen peroxide (H₂O₂) tissue gradients and its crosstalk with neutrophil infiltration to inflamed tissue. Thus, it has been shown that H₂O₂ directly recruits neutrophils via the Src-family tyrosine kinase Lyn and indirectly by the activation of several signaling pathways involved in inflammation, such as nuclear factor κB (NF-κB), mitogen activated kinases and the transcription factor AP1. In addition, this model has also unmasked the unexpected ability of H₂O₂ to induce the expression of the gene encoding the key neutrophil chemoattractant CXC chemokine ligand 8 by facilitating the accessibility of transcription factors to its promoter through histone covalent modifications. Finally, zebrafish models of psoriasis have shown that a H₂O₂/NF-κB/Duox1 positive feedback inflammatory loop operates in this chronic inflammatory disorder and that pharmacological inhibition of Duox1, but not of downstream mediators, inhibits inflammation and restores epithelial homeostasis. Therefore, these results have pointed out DUOX1 and H₂O₂ as therapeutic targets for the treatment of skin inflammatory disorders, such as psoriasis.

Phagocytosis: Phenotypically Simple Yet a Mechanistically Complex Process

Phagocytosis is a pivotal immunological process, and its discovery by Elia Metchnikoff in 1882 was a step toward the establishment of the innate immune system as a separate branch of immunology. Elia Metchnikoff received the Nobel Prize in physiology and medicine for this discovery in 1908. Since its discovery almost 140 years before, phagocytosis remains the hot topic of research in immunology. The phagocytosis research has seen a great advancement since its first discovery. Functionally, phagocytosis is a simple immunological process required to engulf and remove pathogens, dead cells and tumor cells to maintain the immune homeostasis. However, mechanistically, it is a very complex process involving different mechanisms, induced and regulated by several pattern recognition receptors, soluble pattern recognition molecules, scavenger receptors (SRs) and opsonins. These mechanisms involve the formation of phagosomes, their maturation into phagolysosomes causing pathogen destruction or antigen synthesis to present them to major histocompatibility complex molecules for activating an adaptive immune response. Any defect in this mechanism may predispose the host to certain infections and inflammatory diseases (autoinflammatory and autoimmune diseases) along with immunodeficiency. The article is designed to discuss its mechanistic complexity at each level, varying from phagocytosis induction to phagolysosome resolution.

Therapeutic effect and mechanism study of L-cysteine derivative 5P39 on LPS-induced acute lung injury in mice

Organosulfur compounds, such as L-cysteine, allicin and other sulfur-containing organic compounds in Allium species, have been proposed to possess many important physiological and pharmacological functions. A novel L-cysteine derivative, t-Butyl S-allylthio-L-cysteinate (5P39), was designed and synthesized by combining L-cysteine derivative and allicin pharmacophore through a disulfide bond. This study aimed to explore the effects and mechanisms of 5P39 on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. At the experimental concentration (5, 10 and 20 μM), 5P39 suppressed the excessive secretion of nitric oxide (NO) and interleukin-6 (IL-6) in mice peritoneal macrophages stimulated by LPS. A mouse model of ALI was established by tracheal instillation of LPS for 2 h before 5P39 (30 and 60 mg/kg) administration. The results showed that 5P39 treatment down-regulated the wet/dry weight ratio (W/D ratio) of lungs and reduced the protein concentration, the number of total cells as well as the myeloperoxidase (MPO) activity in bronchoalveolar lavage fluid (BALF). 5P39 administration improved the histopathological changes of lungs in ALI mice with the decreased levels of pro-inflammatory cytokines in BALF. The inhibitory effects of 5P39 on the toll-like receptor 4 (TLR4) expression and macrophages accumulation in lung tissues were observed by immunohistochemistry. Additionally, 5P39 significantly attenuated the LPS-activated high expression of key proteins in TLR4/MyD88 signaling pathway. Taken together, the present study showed that 5P39 effectively alleviate the severity of ALI, and its mechanism might relate to the inhibition of LPS-activated TLR4/MyD88 signaling pathway, demonstrating a promising potential for further development into an anti-inflammatory drug candidate.

A comprehensive mechanistic review insight into the effects of micronutrients on toll-like receptors functions

Toll-like receptors (TLRs) are the special proteins receptors for recognition of molecules related to the pathogens. In this way, TLRs and secreted cytokines as a result of TLRs activation are involved in the inflammation pathways. So far, in vivo and in vitro studies have demonstrated that micronutrients (vitamins & minerals) with a broad range of effects on body health, can regulate TLRs signaling pathways. Current review aimed at determining the possible mechanisms of micronutrient effects on TLRs functions. In the aspect of gene expression, micronutrients have inconsistent effects on mRNA level of TLRs which are dependent on time, dose and type of studied TLR. Also, some micronutrients affect gene expression of TLRs signaling mediators namely TLRs adaptors like Myeloid differentiation primary response 88 (MyD88). In the aspect of TLRs signaling pathways, nuclear factor-κB (NF-κB) is an important mediator which is regulated by micronutrients. Also, the regulatory effects of micronutrients on phosphorylation reactions may be effective in the activation/inactivation of TLRs signaling mediators. In addition, zinc can regulate TLRs signaling indirectly via the zinc finger proteins which have contradictory effects on TLRs cascade. In conclusion, the relationship between micronutrients and TLRs signaling is complicated and depends on some known internal, external and genetic factors like form of studied micronutrient, cell type, TLR agonist, dose and time of exposure, inflammation, apoptosis, cell cycle, and environmental factors. Some unknown factors may be effective in TLRs response and as a result additional mechanistic studies are needed to elucidate exact effect of micronutrients on TLRs signaling.

Human Enteric Defensin 5 Promotes Shigella Infection of Macrophages

Human α-defensins are 3- to 5-kDa disulfide-bridged peptides with a multitude of antimicrobial activities and immunomodulatory functions. Recent studies show that human enteric α-defensin 5 (HD5), a host defense peptide important for intestinal homeostasis and innate immunity, aids the highly infectious enteropathogen Shigella in breaching the intestinal epithelium in vitro and in vivo Whether and how HD5 influences Shigella infection of resident macrophages following its invasion of the intestinal epithelium remain poorly understood. Here, we report that HD5 greatly promoted phagocytosis of Shigella by macrophages by targeting the bacteria to enhance bacterium-to-cell contacts in a structure- and sequence-dependent fashion. Subsequent intracellular multiplication of phagocytosed Shigella led to massive necrotic cell death and release of the bacteria. HD5-promoted phagocytosis of Shigella was independent of the status of the type 3 secretion system. Furthermore, HD5 neither inhibited nor enhanced phagosomal escape of Shigella Collectively, these findings confirm a potential pathogenic role of HD5 in Shigella infection of not only epithelial cells but also macrophages, illuminating how an enteropathogen exploits a host protective factor for virulence and infection.

Immune effector monocyte-neutrophil cooperation induced by the primary tumor prevents metastatic progression of breast cancer

Metastatic behavior varies significantly among breast cancers. Mechanisms explaining why the majority of breast cancer patients never develop metastatic outgrowth are largely lacking but could underlie the development of novel immunotherapeutic target molecules. Here we show interplay between nonmetastatic primary breast cancer and innate immune response, acting together to control metastatic progression. The primary tumor systemically recruits IFNγ-producing immune effector monocytes to the lung. IFNγ up-regulates Tmem173/STING in neutrophils and enhances their killing capacity. The immune effector monocytes and tumoricidal neutrophils target disseminated tumor cells in the lungs, preventing metastatic outgrowth. Importantly, our findings could underlie the development of immunotherapeutic target molecules that augment the function of immune effector monocytes and neutrophils.

Metal Nanoparticles Released from Dental Implant Surfaces: Potential Contribution to Chronic Inflammation and Peri-Implant Bone Loss

Peri-implantitis is an inflammatory disease affecting tissues surrounding dental implants. Although it represents a common complication of dental implant treatments, the underlying mechanisms have not yet been fully described. The aim of this study is to identify the role of titanium nanoparticles released form the implants on the chronic inflammation and bone lysis in the surrounding tissue. We analyzed the in vitro effect of titanium (Ti) particle exposure on mesenchymal stem cells (MSCs) and fibroblasts (FU), evaluating cell proliferation by MTT test and the generation of reactive oxygen species (ROS). Subsequently, in vivo analysis of peri-implant Ti particle distribution, histological, and molecular analyses were performed. Ti particles led to a time-dependent decrease in cell viability and increase in ROS production in both MSCs and FU. Tissue analyses revealed presence of oxidative stress, high extracellular and intracellular Ti levels and imbalanced bone turnover. High expression of ZFP467 and the presence of adipose-like tissue suggested dysregulation of the MSC population; alterations in vessel morphology were identified. The results suggest that Ti particles may induce the production of high ROS levels, recruiting abnormal quantity of neutrophils able to produce high level of metalloproteinase. This induces the degradation of collagen fibers. These events may influence MSC commitment, with an imbalance of bone regeneration.

Effects of dietary exposure to chlorpyrifos on immune cell populations and inflammatory responses in mice with dextran sulfate sodium-induced colitis

This study investigated the effects of chlorpyrifos (CPF) on immune-cell populations and intestinal inflammation using a mouse model of inflammatory bowel disease induced by dextran sulfate sodium (DSS). C57BL/6 mice were randomly assigned to five groups with one normal control (NC) and four DSS-treated groups. Mice in the NC group were given distilled water, whereas the DSS-treated groups received distilled water containing 3% DSS for 6 days to induce colitis. The NC and disease control (DC) groups were fed a control semipurified diet, while the remaining groups were exposed to CPF in the AIN-93 diet at doses of 1, 2.5, or 5 mg/kg/day throughout the study. Results showed that dietary exposure to CPF in colitic mice significantly increased circulating classical monocytes and upregulated gene expressions of chemokines in the colon compared to the NC group. Meanwhile, CPF exposure groups had lower plasma cholinesterase activities and higher percentages of circulating neutrophils than those of the DC group. A shorten length, tissue edema, and lipid peroxidation of the colon were also observed in all CPF-exposed mice. These findings suggest that dietary exposure to CPF affected immune-cell populations and inflammatory responses, which led to more severe tissue injury in mice with DSS-induced colitis.

Skin Acute Wound Healing: A Comprehensive Review

Experimental work of the last two decades has revealed the general steps of the wound healing process. This complex network has been organized in three sequential and overlapping steps. The first step of the inflammatory phase is an immediate response to injury; primary sensory neurons sense injury and send danger signals to the brain, to stop bleeding and start inflammation. The following target of the inflammatory phase, led by the peripheral blood mononuclear cells, is to eliminate the pathogens and clean the wound. Once this is completed, the inflammatory phase is resolved and homeostasis is restored. The aim of the proliferative phase, the second phase, is to repair wound damage and begin tissue remodeling. Fibroplasia, reepithelialization, angiogenesis, and peripheral nerve repair are the central actions of this phase. Lastly, the objective of the final phase is to complete tissue remodeling and restore skin integrity. This review provides present day information regarding the status of the participant cells, extracellular matrix, cytokines, chemokines, and growth factors, as well as their interactions with the microenvironment during the wound healing process.

The Role of Macrophage in the Pathogenesis of Osteoporosis

Osteoporosis is a systemic disease with progressive bone loss. The bone loss is associated with an imbalance between bone resorption via osteoclasts and bone formation via osteoblasts. Other cells including T cells, B cells, macrophages, and osteocytes are also involved in the pathogenesis of osteoporosis. Different cytokines from activated macrophages can regulate or stimulate the development of osteoclastogenesis-associated bone loss. The fusion of macrophages can form multinucleated osteoclasts and, thus, cause bone resorption via the expression of IL-4 and IL-13. Different cytokines, endocrines, and chemokines are also expressed that may affect the presentation of macrophages in osteoporosis. Macrophages have an effect on bone formation during fracture-associated bone repair. However, activated macrophages may secrete proinflammatory cytokines that induce bone loss by osteoclastogenesis, and are associated with the activation of bone resorption. Targeting activated macrophages at an appropriate stage may help inhibit or slow the progression of bone loss in patients with osteoporosis.

Advanced antibacterial activity of biocompatible tantalum nanofilm via enhanced local innate immunity

Tantalum (Ta) has been shown to enhance osseointegration in clinical practice, yet little is known about whether Ta nanofilms can be used as antimicrobial coatings in vivo. A highly biocompatible Ta nanofilm was developed using magnetron sputtering technology to further study the mechanism of its antibacterial effects in vivo and elucidate its potential for clinical translation. The Ta nanofilms exhibited effective antimicrobial activity against soft tissue infections but did not show an intrinsic antimicrobial effect in vitro. This inconsistency between the in vivo and in vitro antimicrobial effects was further investigated using ex vivo models. The Ta nanofilms could enhance the phagocytosis of bacteria by polymorphonuclear neutrophils (PMNs, neutrophils), reduce the lysis of neutrophils and enhance the proinflammatory cytokine release of macrophages. This accumulative enhancement of the local host defenses contributed to the favorable antibacterial effect in vivo. The alleviated osteolysis observed in the presence of the Ta nanofilms in the osteomyelitis model further proved the practicality of this antibacterial strategy in the orthopedic field. In summary, Ta nanofilms show excellent biocompatibility and in vivo antimicrobial activity mediated by the enhancement of local innate immunity and are promising for clinical application. STATEMENT OF SIGNIFICANCE: In this study, Ta nanofilms were deposited on titanium substrate by magnetron sputtering. Ta nanofilms exhibited excellent in vivo and in vitro biocompatibility. In vivo antimicrobial effects of Ta nanofilms were revealed by soft tissue infection and osteomyelitis models, while no direct antibacterial activity was observed in vitro. Comprehensive ex vivo models revealed that Ta nanofilms could enhance the phagocytosis of bacteria by neutrophils, reduce the lysis of neutrophils and promote the release of proinflammatory cytokines from macrophages. This immunomodulatory effect helps host to eliminate bacteria. In contrast to traditional antimicrobial nanocoatings which apply toxic materials to kill bacteria, this work proposes a safe, practical and effective Ta nanofilm immunomodulatory antimicrobial strategy with clinical translational prospect.

Molecular and transcriptional insights into viperin protein from Big-belly seahorse (Hippocampus abdominalis), and its potential antiviral role

Viperin is recognized as an antiviral protein that is stimulated by interferon, viral exposures, and other pathogenic molecules in vertebrate. In this study, a viperin homolog in the Big-belly seahorse (Hippocampus abdominalis; HaVip) was functionally characterized to determine its subcellular localization, expression pattern, and antiviral activity in vitro. The HaVip coding sequence encodes a 348 amino acid polypeptide with predicted molecular weight of 38.48 kDa. Sequence analysis revealed that HaVip comprises three main domains: the N-terminal amphipathic α-helix, a radical S-adenosyl-l-methionine (SAM) domain, and a conserved C-terminal domain. Transfected GFP-tagged HaVip protein was found to localize to the endoplasmic reticulum (ER). Overexpressed-HaVip in FHM cells was found to significantly reduce viral capsid gene expression in VHSV infection in vitro. Under normal physiological conditions, HaVip expression was ubiquitously detected in all 14 examined tissues of the seahorse, with the highest expression observed in the heart, followed by skin and blood. In vivo studies showed that HaVip was rapidly and predominantly upregulated in blood, kidney, and intestinal tissue upon poly (I:C) stimulus. LPS and Streptococus iniae challenges caused a significant increase in expression of HaVip in all the analyzed tissues. The obtained results suggest that HaVip is involved in the immune system of the seahorse, triggering antiviral and antibacterial responses, upon viral and bacterial pathogenic infections.

Reactive species and pathogen antioxidant networks during phagocytosis

This review discusses the generation of phagosomal cytotoxic reactive species by activated macrophages and neutrophils for the control of intracellular pathogens, and the mechanisms by which microbes combat host-derived oxidants via antioxidant networks that mitigate the redox-dependent control of infection.

The generation of phagosomal cytotoxic reactive species (i.e., free radicals and oxidants) by activated macrophages and neutrophils is a crucial process for the control of intracellular pathogens. The chemical nature of these species, the reactions they are involved in, and the subsequent effects are multifaceted and depend on several host- and pathogen-derived factors that influence their production rates and catabolism inside the phagosome. Pathogens rely on an intricate and synergistic antioxidant armamentarium that ensures their own survival by detoxifying reactive species. In this review, we discuss the generation, kinetics, and toxicity of reactive species generated in phagocytes, with a focus on the response of macrophages to internalized pathogens and concentrating on Mycobacterium tuberculosis and Trypanosoma cruzi as examples of bacterial and parasitic infection, respectively. The ability of pathogens to deal with host-derived reactive species largely depends on the competence of their antioxidant networks at the onset of invasion, which in turn can tilt the balance toward pathogen survival, proliferation, and virulence over redox-dependent control of infection.

CXCR4 signaling regulates metastatic onset by controlling neutrophil motility and response to malignant cells

Developing tumors interact with the surrounding microenvironment. Myeloid cells exert both anti- and pro-tumor functions and chemokines are known to drive immune cell migration towards cancer cells. It is documented that CXCR4 signaling supports tumor metastasis formation in tissues where CXCL12, its cognate ligand, is abundant. On the other hand, the role of the neutrophilic CXCR4 signaling in driving cancer invasion and metastasis formation is poorly understood. Here, we use the zebrafish xenotransplantation model to study the role of CXCR4 signaling in driving the interaction between invasive human tumor cells and host neutrophils, supporting early metastasis formation. We found that zebrafish cxcr4 (cxcr4b) is highly expressed in neutrophils and experimental micrometastases fail to form in mutant larvae lacking a functional Cxcr4b. We demonstrated that Cxcr4b controls neutrophil number and motility and showed that Cxcr4b transcriptomic signature relates to motility and adhesion regulation in neutrophils in tumor-naïve larvae. Finally, Cxcr4b deficient neutrophils failed to interact with cancer cells initiating early metastatic events. In conclusion, we propose that CXCR4 signaling supports the interaction between tumor cells and host neutrophils in developing tumor metastases. Therefore, targeting CXCR4 on tumor cells and neutrophils could serve as a double bladed razor to limit cancer progression.

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

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

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

Inflammasomes, Autophagy, and Cell Death: The Trinity of Innate Host Defense against Intracellular Bacteria

Inflammasome activation is an innate host defense mechanism initiated upon sensing pathogens or danger in the cytosol. Both autophagy and cell death are cell autonomous processes important in development, as well as in host defense against intracellular bacteria. Inflammasome, autophagy, and cell death pathways can be activated by pathogens, pathogen-associated molecular patterns (PAMPs), cell stress, and host-derived damage-associated molecular patterns (DAMPs). Phagocytosis and toll-like receptor (TLR) signaling induce reactive oxygen species (ROS), type I IFN, NFκB activation of proinflammatory cytokines, and the mitogen-activated protein kinase cascade. ROS and IFNγ are also prominent inducers of autophagy. Pathogens, PAMPs, and DAMPs activate TLRs and intracellular inflammasomes, inducing apoptotic and inflammatory caspases in a context-dependent manner to promote various forms of cell death to eliminate pathogens. Common downstream signaling molecules of inflammasomes, autophagy, and cell death pathways interact to initiate appropriate measures against pathogens and determine host survival as well as pathological consequences of infection. The integration of inflammasome activation, autophagy, and cell death is central to pathogen clearance. Various pathogens produce virulence factors to control inflammasomes, subvert autophagy, and modulate host cell death in order to evade host defense. This review highlights the interaction of inflammasomes, autophagy, and host cell death pathways in counteracting Burkholderia pseudomallei, the causative agent of melioidosis. Contrasting evasion strategies used by B. pseudomallei, Mycobacterium tuberculosis, and Legionella pneumophila to avoid and dampen these innate immune responses will be discussed.

Probiotic Exopolysaccharide Protects against Systemic Staphylococcus aureus Infection, Inducing Dual-Functioning Macrophages That Restrict Bacterial Growth and Limit Inflammation

Staphylococcus aureus causes severe systemic infection with high mortality rates. We previously identified exopolysaccharide (EPS) from a probiotic, Bacillus subtilis, that induces anti-inflammatory macrophages with an M2 phenotype and protects mice from Citrobacter rodentium-induced colitis. We tested if EPS could protect from systemic infection induced by S. aureus and found that EPS-treated mice had enhanced survival as well as reduced weight loss, systemic inflammation, and bacterial burden. While macrophages from EPS-treated mice display an M2 phenotype, they also restrict growth of internalized S. aureus through reactive oxygen species (ROS), reminiscent of proinflammatory phagocytes. These EPS-induced macrophages also limit T cell activation by S. aureus superantigens, and EPS abrogates systemic induction of gamma interferon after infection. We conclude that B. subtilis EPS is an immunomodulatory agent that induces hybrid macrophages that bolster antibacterial immunity and simultaneously limit inflammation, reducing disease burden and promoting host survival.

SAG/RBX2 E3 Ubiquitin Ligase Differentially Regulates Inflammatory Responses of Myeloid Cell Subsets

Macrophages form an important component of the innate immune system and serve as first responders against invading pathogens. While pathways critical for initiation of inflammatory responses between macrophages and other LysM⁺ myeloid cells are largely similar, it remains unknown whether a specific pathway has differential effects on inflammatory responses mediated between these cells. Recent studies demonstrated that depletion of SAG (Sensitive to Apoptosis Gene), an E3 ubiquitin ligase, blocked inflammatory responses generated by macrophages and dendritic cells in response to LPS in cell culture settings. However, the in vivo role of Sag on modulation of macrophages and neutrophil is not known. Here we generated LysM-Cre/Sag ^fl/fl mice with selective Sag deletion in myeloid lineage, and found that in contrast to in vitro observations, LysM-Cre/Sag ^fl/fl mice showed increased serum levels of proinflammatory cytokines and enhanced mortality in response to LPS. Interestingly, while Sag ^-/- macrophages released less proinflammatory cytokines, Sag ^-/- neutrophils released more. Mechanistically, expression of a list of genes response to LPS was significantly altered in bone marrow cells from LysM-Cre ⁺/Sag ^fl/fl mice after LPS challenge. Specifically, induction by LPS of myeloperoxidase (Mpo), a key neutrophil enzyme, and Elane, neutrophil expressed elastase, was significantly decreased upon Sag depletion. Collectively, our study revealed that Sag plays a differential role in the activation of macrophages and neutrophils.

Antiemetic doses of dexamethasone and their effects on immune cell populations and plasma mediators of inflammation resolution in healthy volunteers

INTRODUCTION

The synthetic glucocorticoid dexamethasone is a commonly administered antiemetic. It has immunosuppressive effects and may alter postoperative blood glucose concentrations. Dexamethasone can effect key enzymes involved in inflammation resolution that is an active process driven by specialised lipid mediators of inflammation resolution (SPM). The purpose of this study in healthy volunteers was to examine whether dexamethasone effects cell populations and synthesis of SPM that are critical for the resolution of inflammation.

METHODS

Thirty-two healthy volunteers were randomly allocated to receive saline (Control) or dexamethasone 2 mg, 4 mg or 8 mg intravenously. Venous blood samples were collected at baseline before administration of treatment, and at 4 h, 24 h and one-week post-treatment. At each time point, measurements included blood glucose and macrophage migration inhibition factor (MMIF), full blood count including lymphocyte subsets, monocytes, neutrophils, eosinophils and basophils by flow cytometry, and plasma SPM using liquid chromatography tandem mass spectrometry. The effect of dexamethasone dose and time on all measures was analysed using linear mixed models.

RESULTS

There was a dose-dependent increase in neutrophil count after dexamethasone that persisted for 24 h. In contrast, there was a dose-dependent reduction in counts of monocytes, lymphocytes, basophils and eosinophils 4 h after dexamethasone, followed by a rebound increase in cell counts at 24 h. Seven days after administration of dexamethasone, all cell counts were similar to baseline levels. MMIF concentration, glucose and natural killer cell counts were not significantly affected by dexamethasone. There was a significant gender effect on plasma SPM such that levels of 17-HDHA, RvD1, 17R-RvD1 and RvE2 in females were on average 14%-50% lower than males. In a linear mixed model that adjusted for neutrophil count, there was a significant interaction between the dose of dexamethasone and time, on plasma 17R-RvD1 such that plasma 17R-RvD1 fell in a dose-dependent manner until 4 h after administration of dexamethasone. There were no significant effects of dexamethasone on the other plasma SPM (18-HEPE, RvE2, 17-HDHA, RvD1, RvD2 and 14-HDHA) measured.

DISCUSSION

This is the first study in healthy volunteers to demonstrate that commonly employed antiemetic doses of dexamethasone affect immune cell populations and plasma levels of 17R-RvD1 an SPM with anti-nociceptive properties. If similar changes occur in surgical patients, then this may have implications for acute infection risk in the post-operative period.

Living dangerously: Burkholderia pseudomallei modulates phagocyte cell death to survive

Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is a major cause of sepsis and mortality in endemic regions of Southeast Asia and Northern Australia. As a facultative intracellular pathogen, B. pseudomallei produces virulence factors to evade innate host response and survive within host cells. Neutrophils and macrophages are phagocytes that play critical roles in host defense against pathogens by their ability to detect and eliminate microbes. Host defense processes against B. pseudomallei including phagocytosis, oxidative burst, autophagy, apoptosis, and proinflammatory cytokine release are all initiated by these two phagocytes in the fight against this bacterium. In vitro studies with mouse macrophage cell lines revealed multiple evasion strategies used by B. pseudomallei to counteract these innate processes. B. pseudomallei invades and replicates in neutrophils but little is known regarding its evasion mechanisms. The bidirectional interaction of neutrophils and macrophages in controlling B. pseudomallei infection has also been overlooked. Here the hypothesis that B. pseudomallei hijacks neutrophils and uses them to transport and infect new phagocytes is proposed as an evasion strategy to survive and persist in host phagocytes. This two-pronged approach by B. pseudomallei to replicate in two different types of phagocytes and to modulate their cell death modes is effective in promoting persistence and survival of the bacterium.

The proteome of pus from human brain abscesses: host-derived neurotoxic proteins and the cell-type diversity of CNS pus

OBJECTIVE

What determines the extent of tissue destruction during brain abscess formation is not known. Pyogenic brain infections cause destruction of brain tissue that greatly exceeds the area occupied by microbes, as seen in experimental studies, pointing to cytotoxic factors other than microbes in pus. This study examined whether brain abscess pus contains cytotoxic proteins that might explain the extent of tissue destruction.

METHODS

Pus proteins from 20 human brain abscesses and, for comparison, 7 subdural empyemas were analyzed by proteomics mass spectrometry. Tissue destruction was determined from brain abscess volumes as measured by MRI.

RESULTS

Brain abscess volume correlated with extracellular pus levels of antibacterial proteins from neutrophils and macrophages: myeloperoxidase (r = 0.64), azurocidin (r = 0.61), lactotransferrin (r = 0.57), and cathelicidin (r = 0.52) (p values 0.002–0.018), suggesting an association between leukocytic activity and tissue damage. In contrast, perfringolysin O, a cytotoxic protein from Streptococcus intermedius that was detected in 16 patients, did not correlate with abscess volume (r = 0.12, p = 0.66). The median number of proteins identified in each pus sample was 870 (range 643–1094). Antibiotic or steroid treatment prior to pus evacuation did not reduce the number or levels of pus proteins. Some of the identified proteins have well-known neurotoxic effects, e.g., eosinophil cationic protein and nonsecretory ribonuclease (also known as eosinophil-derived neurotoxin). The cellular response to brain infection was highly complex, as reflected by the presence of proteins that were specific for neutrophils, eosinophils, macrophages, platelets, fibroblasts, or mast cells in addition to plasma and erythrocytic proteins. Other proteins (neurofilaments, myelin basic protein, and glial fibrillary acidic protein) were specific for brain cells and reflected damage to neurons, oligodendrocytes, and astrocytes, respectively. Pus from subdural empyemas had significantly higher levels of plasma proteins and lower levels of leukocytic proteins than pus from intracerebral abscesses, suggesting greater turnover of the extracellular fluid of empyemas and washout of pus constituents.

CONCLUSIONS

Brain abscess pus contains leukocytic proteins that are neurotoxic and likely participate actively in the excessive tissue destruction inherent in brain abscess formation. These findings underscore the importance of rapid evacuation of brain abscess pus.

IFN-γ protects from apoptotic neutrophil-mediated tissue injury during acute Listeria monocytogenes infection

Listeria monocytogenes (LM) is a foodborne Gram-positive intracellular pathogen that can cause listeriosis in humans and animals. Although phagocytes are known to be involved in the response to this infection, the role of neutrophils is not entirely clear. Here, we have demonstrated that soon after LM infection, a large number of IFN-γ-producing neutrophils quickly accumulated in the spleen, blood, and peritoneal cavity. Both in vivo and in vitro experiments demonstrated that neutrophils were an important source of IFN-γ. IFN-γ played a critical protective role against acute LM infection, as demonstrated by the poor survival of Ifng^-/- mice. Moreover, IFN-γ promoted bacterial clearance by the neutrophils, thereby inhibiting LM-induced neutrophil apoptosis and spleen damage. In addition to this, IFN-γ could effectively drive macrophage-mediated phagocytosis of apoptotic neutrophils, which was accompanied with TGF-β secretion and was involved in protection against tissue injury. Importantly, by phagocytizing apoptotic neutrophils, macrophages obtained myeloperoxidase, an important bactericidal molecule only produced by neutrophils, which further promoted the antibacterial activity of macrophages. These findings demonstrate that neutrophils are an important source of IFN-γ at the early stage of LM infection, which is characterized by both LM elimination and tissue-protective effects.

Therapeutic Effect of a Novel Nano-Drug Delivery System on Membranous Glomerulonephritis Rat Model Induced by Cationic Bovine Serum

In order to explore a novel high efficacy drug delivery system for membranous glomerulonephritis (MGN), a complex chronic inflammation, methylprednisolone bovine serum albumin nanoparticles (ME BSA NPs) were designed. The nanoparticles were prepared by desolvation-chemical crosslinking method and its physicochemical characterizations were conducted. The experimental MGN rat models induced by cationic bovine serum albumin were established by a modified Border's method and applied in the pharmacodynamics study of ME BSA NPs. The results showed that the particle size, particle dispersion index, and entrapment efficiency of ME BSA NPs were 131.1 ± 3.4 nm, 0.159 ± 0.036, and 71.51 ± 1.74%, respectively. In addition, the image of transmission electron microscopy showed that the ME BSA NPs were the relatively uniform spherical particles. In the in vivo pharmacodynamics study, compared with saline group and SOLU-MEDROL® group, that the ME BSA NPs group was significantly reduced the levels of 24 h urinary protein (P < 0.01) and serum creatinine (P < 0.05). Consequently, these outcomes indicated that the nanoparticles we studied were a promising drug delivery system for the MGN disease, and it may be also useful for other complex chronic inflammations.

Macrophages protect Talaromyces marneffei conidia from myeloperoxidase-dependent neutrophil fungicidal activity during infection establishment in vivo

Neutrophils and macrophages provide the first line of cellular defence against pathogens once physical barriers are breached, but can play very different roles for each specific pathogen. This is particularly so for fungal pathogens, which can occupy several niches in the host. We developed an infection model of talaromycosis in zebrafish embryos with the thermally-dimorphic intracellular fungal pathogen Talaromyces marneffei and used it to define different roles of neutrophils and macrophages in infection establishment. This system models opportunistic human infection prevalent in HIV-infected patients, as zebrafish embryos have intact innate immunity but, like HIV-infected talaromycosis patients, lack a functional adaptive immune system. Importantly, this new talaromycosis model permits thermal shifts not possible in mammalian models, which we show does not significantly impact on leukocyte migration, phagocytosis and function in an established Aspergillus fumigatus model. Furthermore, the optical transparency of zebrafish embryos facilitates imaging of leukocyte/pathogen interactions in vivo. Following parenteral inoculation, T. marneffei conidia were phagocytosed by both neutrophils and macrophages. Within these different leukocytes, intracellular fungal form varied, indicating that triggers in the intracellular milieu can override thermal morphological determinants. As in human talaromycosis, conidia were predominantly phagocytosed by macrophages rather than neutrophils. Macrophages provided an intracellular niche that supported yeast morphology. Despite their minor role in T. marneffei conidial phagocytosis, neutrophil numbers increased during infection from a protective CSF3-dependent granulopoietic response. By perturbing the relative abundance of neutrophils and macrophages during conidial inoculation, we demonstrate that the macrophage intracellular niche favours infection establishment by protecting conidia from a myeloperoxidase-dependent neutrophil fungicidal activity. These studies provide a new in vivo model of talaromycosis with several advantages over previous models. Our findings demonstrate that limiting T. marneffei's opportunity for macrophage parasitism and thereby enhancing this pathogen's exposure to effective neutrophil fungicidal mechanisms may represent a novel host-directed therapeutic opportunity.

Scutellaria baicalensis Attenuates Airway Remodeling via PI3K/Akt/NF-κB Pathway in Cigarette Smoke Mediated-COPD Rats Model

Background. Scutellaria baicalensis (SB) is commonly used in traditional Chinese medicine for chronic inflammatory diseases. This study aims to investigate the effects of the early intervention with SB on airway remodeling in a well-established rat model of COPD induced by cigarette smoking. Methods. COPD model in Sprague Dawley (SD) rats were established by exposing them to smoke for 6 days/week, for 12 weeks, 24 weeks, or 36 weeks. Meanwhile, rats were randomly divided into normal control group, model group, Budesonide (BUD) group, and the SB (low, middle, and high) dose groups with 8 rats in each group and 3 stages (12 weeks, 24 weeks, and 36 weeks). After treatment, the pulmonary function was evaluated by BUXCO system and the morphology changes of the lungs were observed with HE and Masson staining. The serum IL-6, IL-8, and IL-10 and TNF-α, TGF-beta (TGF-β1), MMP-2, MMP-9, and TIMP-1 levels in BALF were detected by ELISA-kit assay. The protein expression levels of AKT and NF-κB (p65) were determined by western blot (WB). Results. The oral of SB significantly improved pulmonary function (PF) and ameliorated the pathological damage and attenuated inflammatory cytokines infiltration into the lungs. Meanwhile, the levels of TGF-β, MMP-2, MMP-9, and TIMP-1 were partially significantly decreased. The levels of PI3K/AKT/NF-κB pathway were also markedly suppressed by SB. Conclusions. SB could significantly improve the condition of airway remodeling by inhibiting airway inflammation and partially quenching TGF-β and MMPs via PI3K/AKT/NF-κB pathway.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

The immune system is a very diverse system of the host that evolved during evolution to cope with various pathogens present in the vicinity of environmental surroundings inhabited by multicellular organisms ranging from achordates to chordates (including humans). For example, cells of immune system express various pattern recognition receptors (PRRs) that detect danger via recognizing specific pathogen-associated molecular patterns (PAMPs) and mount a specific immune response. Toll-like receptors (TLRs) are one of these PRRs expressed by various immune cells. However, they were first discovered in the Drosophila melanogaster (common fruit fly) as genes/proteins important in embryonic development and dorso-ventral body patterning/polarity. Till date, 13 different types of TLRs (TLR1-TLR13) have been discovered and described in mammals since the first discovery of TLR4 in humans in late 1997. This discovery of TLR4 in humans revolutionized the field of innate immunity and thus the immunology and host-pathogen interaction. Since then TLRs are found to be expressed on various immune cells and have been targeted for therapeutic drug development for various infectious and inflammatory diseases including cancer. Even, Single nucleotide polymorphisms (SNPs) among various TLR genes have been identified among the different human population and their association with susceptibility/resistance to certain infections and other inflammatory diseases. Thus, in the present review the current and future importance of TLRs in immunity, their pattern of expression among various immune cells along with TLR based therapeutic approach is reviewed.

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TLRs are first described PRRs that revolutionized the biology of host-pathogen interaction and immune response

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The discovery of different TLRs in humans proved milestone in the field of innate immunity and inflammation

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The pattern of expression of all the TLRs expressed by human immune cells

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An association of various TLR SNPs with different inflammatory diseases

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Currently available drugs or vaccines based on TLRs and their future in drug targeting along with the role in reproduction, and regeneration

Partners in crime: neutrophils and monocytes/macrophages in inflammation and disease

Neutrophils are becoming recognized as highly versatile and sophisticated cells that display de novo synthetic capacity and potentially prolonged lifespan. Emerging concepts such as neutrophil heterogeneity and plasticity have revealed that, under pathological conditions, neutrophils may differentiate into discrete subsets defined by distinct phenotypic and functional characteristics. Indeed, these newly described neutrophil subsets will undoubtedly add to the already complex interactions between neutrophils and other immune cell types for an effective immune response. The interactions between neutrophils and monocytes/macrophages enable the host to efficiently defend against and eliminate foreign pathogens. However, it is also becoming increasingly clear that these interactions can be detrimental to the host if not tightly regulated. In this review, we will explore the functional cooperation of neutrophil and monocytes/macrophages in homeostasis, during acute inflammation and in various disease settings. We will discuss this in the context of cardiovascular disease in the form of atherosclerosis, an autoimmune disease mainly occurring in the kidneys, as well as the unique intestinal immune response of the gut that does not conform to the norms of the typical immune system.

Neutrophil Functional Heterogeneity: Identification of Competitive Phagocytosis

Introduction

Phagocytosis by neutrophils is a key process in the innate immune response against invading microorganisms. Despite reported heterogeneity in other neutrophils functions, little is known regarding differences in phagocytosis by individual cells. Therefore, we tested the hypothesis that heterogeneity is present in the neutrophil compartment in its potency to phagocytize bacteria.

Methods

Phagocytosis assays were performed in suspension with isolated neutrophils and Staphylococcus aureus expressing different fluorescent proteins at MOIs between 1 and 10. Repetitive addition of bacteria with different fluorescent proteins and MOIs was used to compare the phagocytic capacity of S. aureus-green fluorescent protein (GFP)-positive and negative neutrophils and exclude randomness.

Results

The percentage and mean fluorescence intensity (MFI) of S. aureus-GFP-positive neutrophils increased with higher MOIs. The increase in MFI was due to phagocytosis of multiple bacteria per neutrophil as was confirmed by confocal imaging. Sequential phagocytosis of GFP- and mCherry-expressing S. aureus showed a non-random process, as S. aureus-GFP-positive neutrophils preferentially phagocytized S. aureus-mCherry.

Conclusion

All neutrophils were able to phagocytize S. aureus, but some were much more potent than others. Therefore, at physiologically relevant MOIs these potent phagocytizing neutrophils will outcompete the uptake of bacteria by less competent cells in a process we propose to name “competitive phagocytosis.”

Inflammaging and the Lung

With the coming of the "silver tsunami," expanding the knowledge about how various intrinsic and extrinsic factors affect the immune system in the elderly is timely and of immediate clinical need. The global population is increasing in age. By the year 2030, more than 20% of the population of the United States will be older than 65 years of age. This article focuses on how advanced age alters the immune systems and how this, in turn, modulates the ability of the aging lung to deal with infectious challenges from the outside world and from within the host.

Modulation of γδ T-cell activation by neutrophil elastase

γδ T cells are non-conventional, innate-like T cells, characterized by a restricted T-cell receptor repertoire. They participate in protective immunity responses against extracellular and intracellular pathogens, tumour surveillance, modulation of innate and adaptive immune responses, tissue healing, epithelial cell maintenance and regulation of physiological organ function. In this study, we investigated the role of neutrophils during the activation of human blood γδ T cells through CD3 molecules. We found that the up-regulation of CD69 expression, and the production of interferon-γ and tumour necrosis factor-α induced by anti-CD3 antibodies was potentiated by neutrophils. We found that inhibition of caspase-1 and neutralization of interleukin-18 did not affect neutrophil-mediated modulation. By contrast, the treatment with serine protease inhibitors prevented the potentiation of γδ T-cell activation induced by neutrophils. Moreover, the addition of elastase to γδ T-cell culture increased their stimulation, and the treatment of neutrophils with elastase inhibitor prevented the effect of neutrophils on γδ T-cell activation. Furthermore, we demonstrated that the effect of elastase on γδ T cells was mediated through the protease-activated receptor, PAR1, because the inhibition of this receptor with a specific antagonist, RWJ56110, abrogated the effect of neutrophils on γδ T-cell activation.

The role of polymorphonuclear neutrophils during HIV-1 infection

It is well-recognized that human immunodeficiency virus type-1 (HIV-1) mainly targets CD4⁺ T cells and macrophages. Nonetheless, during the past three decades, a huge number of studies have reported that HIV-1 can directly or indirectly target other cellular components of the immune system including CD8⁺ T cells, B cells, dendritic cells, natural killer cells, and polymorphonuclear neutrophils (PMNs), among others. PMNs are the most abundant leukocytes in the human circulation, and are known to play principal roles in the elimination of invading pathogens, regulating different immune responses, healing of injured tissues, and maintaining mucosal homeostasis. Until recently, little was known about the impact of HIV-1 infection on PMNs as well as the impact of PMNs on HIV-1 disease progression. This is because early studies focused on neutropenia and recurrent microbial infections, particularly, during advanced disease. However, recent studies have extended the investigation area to cover new aspects of the interactions between HIV-1 and PMNs. This review aims to summarize these advances and address the impact of HIV-1 infection on PMNs as well as the impact of PMNs on HIV-1 disease progression to better understand the pathophysiology of HIV-1 infection.

Maternal and fetal microchimerism in granulocytes

Cell trafficking during pregnancy may result in durable microchimerism, both fetal microchimerism in the mother and maternal microchimerism in her children. Whether microchimerism is continuously replenished has not been well-described. To address this question, we isolated granulocytes, cells with relatively short half-lives, from peripheral blood of healthy women. CD66b-positive cells were isolated by fluorescence activated cell sorting and a panel of polymorphism-specific quantitative pCR assays was employed to investigate fetal and maternal microchimerism. Overall 33% (10/30) of study subjects had at least one source of microchimerism in CD66b(+) cells. Interestingly, maternal microchimerism was more common than fetal microchimerism, 40% vs. 15%, respectively (p = 0.05) and was present at higher levels (p = 0.03). The identification of maternal and fetal origin CD66b(+) cells is strong evidence for an active microchimeric hematopoietic stem and progenitor cell niche. Furthermore, microchimeric CD66b(+) cells could have an impact on innate and adaptive immune responses.

More than complementing Tolls: complement-Toll-like receptor synergy and crosstalk in innate immunity and inflammation

Complement and Toll-like receptors (TLRs) play key roles in the host immune response and are swiftly activated by infection or other types of immunological stress. This review focuses on the capacity of complement and TLRs to engage in signaling crosstalk, ostensibly to coordinate immune and inflammatory responses through synergistic or antagonistic (regulatory) interactions. However, overactivation or dysregulation of either system may lead-often synergistically-to exaggerated inflammation and host tissue injury. Intriguingly, moreover, certain pathogens can manipulate complement-TLR crosstalk pathways in ways that undermine host immunity and favor their persistence. In the setting of polymicrobial inflammatory disease, subversion of complement-TLR crosstalk by keystone pathogens can promote dysbiosis. Knowledge of the molecular mechanisms underlying complement-TLR crosstalk pathways can, therefore, be used productively for tailored therapeutic approaches, such as, to enhance host immunity, mitigate destructive inflammation, or counteract microbial subversion of the host response.

Chloride flux in phagocytes

Phagocytes, such as neutrophils and macrophages, engulf microbes into phagosomes and launch chemical attacks to kill and degrade them. Such a critical innate immune function necessitates ion participation. Chloride, the most abundant anion in the human body, is an indispensable constituent of the myeloperoxidase (MPO)-H2 O2 -halide system that produces the potent microbicide hypochlorous acid (HOCl). It also serves as a balancing ion to set membrane potentials, optimize cytosolic and phagosomal pH, and regulate phagosomal enzymatic activities. Deficient supply of this anion to or defective attainment of this anion by phagocytes is linked to innate immune defects. However, how phagocytes acquire chloride from their residing environment especially when they are deployed to epithelium-lined lumens, and how chloride is intracellularly transported to phagosomes remain largely unknown. This review article will provide an overview of chloride protein carriers, potential mechanisms for phagocytic chloride preservation and acquisition, intracellular chloride supply to phagosomes for oxidant production, and methods to measure chloride levels in phagocytes and their phagosomes.

Myeloid Cells in Cutaneous Wound Repair

Cutaneous wound repair is a complex, dynamic process with the goal of rapidly sealing any breach in the skin's protective barrier. Myeloid cells compose a significant proportion of the inflammatory cells recruited to a wound site and play important roles in decontaminating the injured tissue of any invading microorganisms. Subsequently, myeloid cells are able to influence many aspects of the healing response, in part through their capacity to release a large array of signaling molecules that allow them to communicate with and regulate the behavior of other wound cells and in turn, be themselves exquisitely regulated by the wound microenvironment. Macrophages, for example, appear to play important, temporally changing roles in the initiation of scarring and subsequently in matrix remodeling to resolve fibrosis. In this way, myeloid cells seem to play both positive (e.g., pathogen killing and matrix remodeling) and negative (e.g., scarring) roles in wound repair. Further research is of course needed to elucidate the precise temporal and spatial myeloid cell phenotypes and behaviors and ultimately to design effective strategies to optimize the beneficial functions of these cells while minimizing their detrimental contributions to improve wound healing in the clinic.

Human neutrophils phagocytose and kill Acinetobacter baumannii and A. pittii

Acinetobacter baumannii is a common cause of health care associated infections worldwide. A. pittii is an opportunistic pathogen also frequently isolated from Acinetobacter infections other than those from A. baumannii. Knowledge of Acinetobacter virulence factors and their role in pathogenesis is scarce. Also, there are no detailed published reports on the interactions between A. pittii and human phagocytic cells. Using confocal laser and scanning electron microscopy, immunofluorescence, and live-cell imaging, our study shows that immediately after bacteria-cell contact, neutrophils rapidly and continuously engulf and kill bacteria during at least 4 hours of infection in vitro. After 3 h of infection, neutrophils start to release neutrophil extracellular traps (NETs) against Acinetobacter. DNA in NETs colocalizes well with human histone H3 and with the specific neutrophil elastase. We have observed that human neutrophils use large filopodia as cellular tentacles to sense local environment but also to detect and retain bacteria during phagocytosis. Furthermore, co-cultivation of neutrophils with human differentiated macrophages before infections shows that human neutrophils, but not macrophages, are key immune cells to control Acinetobacter. Although macrophages were largely activated by both bacterial species, they lack the phagocytic activity demonstrated by neutrophils.