Regulation of inflammatory monocyte/macrophage recruitment from the bone marrow during murine cytomegalovirus infection: role for type I interferons in localized induction of CCR2 ligands

Shufeng Jiedu capsule alleviates influenza A (H1N1) virus induced acute lung injury by regulating the lung inflammatory microenvironment

Background

Death caused by respiratory tract infection is one of the leading causes of death in the world today. Shufeng Jiedu Capsule (SFJDC) is a traditional Chinese medicine that has been widely used clinically for coronavirus disease 2019 (COVID-19), H1N1 influenza virus pneumonia and other diseases. Its pharmacological effect is to inhibit inflammation and improve the body's ability to clear viruses. However, the mechanism of SFJDC in the treatment of viral pneumonia, especially its effect on the inflammatory-immune microenvironment of lung tissue remains unclear.

Methods

Mice with H1N1 influenza virus pneumonia were used as a model to verify the efficacy of SFJDC through death protection, lung index, viral load, and HE staining of lung tissue. The levels of inflammatory cytokines and chemokines in lung tissue were investigated by multi-analyte immunoassay. The number and proportion of cells in peripheral blood were detected by blood routine. The percentage of infiltrating immune cells in lung tissue was detected by flow cytometry and immunofluorescence.

Results

SFJDC (2.2 g/kg·d-1 and 1.1 g/kg·d-1) increased survival rate (P＜0.01, P＜0.05), prolonged the survival period of mice, and alleviated the histopathological damage in lung (P＜0.01). SFJDC (2.2 g/kg·d-1, 1.1 g/kg·d-1 and 0.055 g/kg·d-1) increased body weight(P＜0.01, P＜0.05), improved activity status, reduced the lung index (P＜0.01, P＜0.05) and viral load (P＜0.01). SFJDC (2.2 g/kg·d-1 and 1.1 g/kg·d-1) reduced interleukin-1β (IL-1β), interleukin-18(IL-18), tumour necrosis factor α (TNF-α), monocyte chemoattractant protein (MCP), chemokine (C-X-C motif) ligand 1 (CXCL1) (P＜0.01, P＜0.05), and SFJDC (2.2 g/kg·d-1) increased IL-10 levels (P＜0.05) to regulate inflammation. SFJDC (2.2 g/kg·d-1) increased the percentages of CD4+ T cells (P＜0.01), CD8+ T cells (P＜0.05), and B cells(P＜0.05), and decreased F4/80+ macrophages (P＜0.05).

Conclusion

Our findings indicated that SFJDC could inhibit inflammation and lung injury while maintaining the function of the adaptive immune response mediated by T and B cells, and promote the clearance of the virus, thereby treating influenza A (H1N1) virus-induced pneumonia.

Comprehensive Analysis of Soluble Mediator Profiles in Congenital CMV Infection Using an MCMV Model

Congenital human cytomegalovirus (HCMV) infection may cause life-threatening disease and permanent damage to the central nervous system. The mouse model of CMV infection is most commonly used to study mechanisms of infection and pathogenesis. While essential to limit mouse CMV (MCMV) replication, the inflammatory responses, particularly IFNγ and TNFα, cause neurodevelopmental abnormalities. Other soluble mediators of the immune response in most tissues remain largely unexplored. To address this gap, we quantified 48 soluble mediators of the immune response, including 32 cytokines, 10 chemokines, 3 growth factors/regulators, and 3 soluble receptors in the spleen, liver, lungs, and brain at 9 and 14 days postinfection (dpi). Our analysis found 25 induced molecules in the brain at 9 dpi, with an additional 8 showing statistically elevated responses at 14 dpi. Specifically, all analyzed CCL group cytokines (CCL2, CCL3, CCL4, CCL5, CCL7, and CCL11) were upregulated at 14 dpi in the brain. Furthermore, data revealed differentially regulated analytes across tissues, such as CCL11, CXCL5, and IL-10 in the brain, IL-33/IL-33R in the liver, and VEGF-a and IL-5 in the lungs. Overall, this study provides an overview of the immune dynamics of soluble mediators in congenital CMV.

M-CSF directs myeloid and NK cell differentiation to protect from CMV after hematopoietic cell transplantation

Therapies reconstituting autologous antiviral immunocompetence may represent an important prophylaxis and treatment for immunosuppressed individuals. Following hematopoietic cell transplantation (HCT), patients are susceptible to Herpesviridae including cytomegalovirus (CMV). We show in a murine model of HCT that macrophage colony-stimulating factor (M-CSF) promoted rapid antiviral activity and protection from viremia caused by murine CMV. M-CSF given at transplantation stimulated sequential myeloid and natural killer (NK) cell differentiation culminating in increased NK cell numbers, production of granzyme B and interferon-γ. This depended upon M-CSF-induced myelopoiesis leading to IL15Rα-mediated presentation of IL-15 on monocytes, augmented by type I interferons from plasmacytoid dendritic cells. Demonstrating relevance to human HCT, M-CSF induced myelomonocytic IL15Rα expression and numbers of functional NK cells in G-CSF-mobilized hematopoietic stem and progenitor cells. Together, M-CSF-induced myelopoiesis triggered an integrated differentiation of myeloid and NK cells to protect HCT recipients from CMV. Thus, our results identify a rationale for the therapeutic use of M-CSF to rapidly reconstitute antiviral activity in immunocompromised individuals, which may provide a general paradigm to boost innate antiviral immunocompetence using host-directed therapies.

Lessons on Drug Development: A Literature Review of Challenges Faced in Nonalcoholic Fatty Liver Disease (NAFLD) Clinical Trials

NAFLD is the most common chronic liver disease worldwide, occurring in both obese and lean patients. It can lead to life-threatening liver diseases and nonhepatic complications, such as cirrhosis and cardiovascular diseases, that burden public health and the health care system. Current care is weight loss through diet and exercise, which is a challenging goal to achieve. However, there are no FDA-approved pharmacotherapies for NAFLD. This review thoroughly examines the clinical trial findings from 22 drugs (Phase 2 and above) and evaluates the future direction that trials should take for further drug development. These trialed drugs can broadly be categorized into five groups-hypoglycemic, lipid-lowering, bile-pathway, anti-inflammatory, and others, which include nutraceuticals. The multitude of challenges faced in these yet-to-be-approved NAFLD drug trials provided insight into a few areas of improvement worth considering. These include drug repurposing, combinations, noninvasive outcomes, standardization, adverse event alleviation, and the need for precision medicine with more extensive consideration of NAFLD heterogenicity in drug trials. Understandably, every evolution of the drug development landscape lies with its own set of challenges. However, this paper believes in the importance of always learning from lessons of the past, with each potential improvement pushing clinical trials an additional step forward toward discovering appropriate drugs for effective NAFLD management.

Cutting edges and therapeutic opportunities on tumor-associated macrophages in lung cancer

Lung cancer is a disease with remarkable heterogeneity. A deep understanding of the tumor microenvironment (TME) offers potential therapeutic strategies against this malignant disease. More and more attention has been paid to the roles of macrophages in the TME. This article briefly summarizes the origin of macrophages, the mutual regulation between anti-tumoral immunity and pro-tumoral statuses derived from macrophage polarization, and the therapeutic opportunities targeting alternately activated macrophages (AAM)-type macrophage polarization. Among them, cellular components including T cells, as well as acellular components represented by IL-4 and IL-13 are key regulators driving the polarization of AAM macrophages. Novel treatments targeting macrophage-associated mechanisms are mainly divided into small molecule inhibitors, monoclonal antibodies, and other therapies to re-acclimate AMM macrophages. Finally, we paid special attention to an immunosuppressive subgroup of macrophages with T cell immunoglobulin and mucin domain-3 (TIM-3) expression. Based on cellular interactions with cancer cells, TIM3+ macrophages facilitate the proliferation and progression of cancer cells, yet this process exposes targets blocking the ligand-receptor recognition. To sum up, this is a systematic review on the mechanism of tumor-associated macrophages (TAM) polarization, therapeutic strategies and the biological functions of Tim-3 positive macrophages that aims to provide new insights into the pathogenesis and treatment of lung cancer.

Host Immune Response and Associated Clinical Features in a Primary Cytomegalovirus Eye Infection Model Using Anterior Chamber Inoculation

Purpose

To investigate the pathogenesis of cytomegalovirus (CMV)-associated anterior segment infection in immunocompetent hosts and evaluate the effects of ganciclovir and glucocorticoid treatment in management of the disease.

Methods

We used an inoculation model to reproduce CMV anterior segment infection in immunocompetent rats. Flow cytometry, cytokine analysis, histopathological sections, and quantitative polymerase chain reaction were performed to investigate the immune response after CMV infection. The effects of ganciclovir and glucocorticoid treatment were also assessed.

Results

Anterior chamber inoculation of CMV in rats provoked characteristic pathological features of human CMV anterior segment infection. The innate and adaptive immunity sequentially developed in an anterior segment after inoculation, and the elevation of intraocular pressure (IOP) was highly associated with ocular infiltration and inflammation. Early ocular immune response reduced virus DNA in the anterior segment and alleviated viral lymphadenopathy. Early intervention with ganciclovir enhanced the release of cytokines associated with T response and facilitated recruitment of NKT and T cells in drainage lymph nodes. Glucocorticoid treatment, alone or combined with ganciclovir, decreased elevation of IOP but also impeded DNA clearance.

Conclusions

The inoculation model reproduced characteristic pathological features of human CMV anterior segment infection. The use of glucocorticoid in current practice may hinder viral clearance, and ganciclovir therapy can assist cytokine expression to combat the virus.

Role of Histone Deacetylases in Monocyte Function in Health and Chronic Inflammatory Diseases

Histone deacetylases (HDACs) are a family of 18 members that participate in the epigenetic regulation of gene expression. In addition to histones, some HDACs also deacetylate transcription factors and specific cytoplasmic proteins.Monocytes, as part of the innate immune system, maintain tissue homeostasis and help fight infections and cancer. In these cells, HDACs are involved in multiple processes including proliferation, migration, differentiation, inflammatory response, infections, and tumorigenesis. Here, a systematic description of the role that most HDACs play in these functions is reviewed. Specifically, some HDACs induce a pro-inflammatory response and play major roles in host defense. Conversely, other HDACs reprogram monocytes and macrophages towards an immunosuppressive phenotype. The right balance between both types helps monocytes to respond correctly to the different physiological/pathological stimuli. However, aberrant expressions or activities of specific HDACs are associated with autoimmune diseases along with other chronic inflammatory diseases, infections, or cancer.This paper critically reviews the interesting and extensive knowledge regarding the role of some HDACs in these pathologies. It also shows that as yet, very little progress has been made toward the goal of finding effective HDAC-targeted therapies. However, given their obvious potential, we conclude that it is worth the effort to develop monocyte-specific drugs that selectively target HDAC subtypes with the aim of finding effective treatments for diseases in which our innate immune system is involved.

The Mechanism behind Influenza Virus Cytokine Storm

Influenza viruses are still a serious threat to human health. Cytokines are essential for cell-to-cell communication and viral clearance in the immune system, but excessive cytokines can cause serious immune pathology. Deaths caused by severe influenza are usually related to cytokine storms. The recent literature has described the mechanism behind the cytokine–storm network and how it can exacerbate host pathological damage. Biological factors such as sex, age, and obesity may cause biological differences between different individuals, which affects cytokine storms induced by the influenza virus. In this review, we summarize the mechanism behind influenza virus cytokine storms and the differences in cytokine storms of different ages and sexes, and in obesity.

Aging and Interferons: Impacts on Inflammation and Viral Disease Outcomes

As highlighted by the COVID-19 global pandemic, elderly individuals comprise the majority of cases of severe viral infection outcomes and death. A combined inability to control viral replication and exacerbated inflammatory immune activation in elderly patients causes irreparable immune-mediated tissue pathology in response to infection. Key to these responses are type I, II, and III interferons (IFNs), which are involved in inducing an antiviral response, as well as controlling and suppressing inflammation and immunopathology. IFNs support monocyte/macrophage-stimulated immune responses that clear infection and promote their immunosuppressive functions that prevent excess inflammation and immune-mediated pathology. The timing and magnitude of IFN responses to infection are critical towards their immunoregulatory functions and ability to prevent immunopathology. Aging is associated with multiple defects in the ability of macrophages and dendritic cells to produce IFNs in response to viral infection, leading to a dysregulation of inflammatory immune responses. Understanding the implications of aging on IFN-regulated inflammation will give critical insights on how to treat and prevent severe infection in vulnerable individuals. In this review, we describe the causes of impaired IFN production in aging, and the evidence to suggest that these impairments impact the regulation of the innate and adaptive immune response to infection, thereby causing disease pathology.

Dysregulation of Leukocyte Trafficking in Type 2 Diabetes: Mechanisms and Potential Therapeutic Avenues

Type 2 Diabetes Mellitus (T2DM) is a chronic inflammatory disorder that is characterized by chronic hyperglycemia and impaired insulin signaling which in addition to be caused by common metabolic dysregulations, have also been associated to changes in various immune cell number, function and activation phenotype. Obesity plays a central role in the development of T2DM. The inflammation originating from obese adipose tissue develops systemically and contributes to insulin resistance, beta cell dysfunction and hyperglycemia. Hyperglycemia can also contribute to chronic, low-grade inflammation resulting in compromised immune function. In this review, we explore how the trafficking of innate and adaptive immune cells under inflammatory condition is dysregulated in T2DM. We particularly highlight the obesity-related accumulation of leukocytes in the adipose tissue leading to insulin resistance and beta-cell dysfunction and resulting in hyperglycemia and consequent changes of adhesion and migratory behavior of leukocytes in different vascular beds. Thus, here we discuss how potential therapeutic targeting of leukocyte trafficking could be an efficient way to control inflammation as well as diabetes and its vascular complications.

Cytomegaloviruses and Macrophages-Friends and Foes From Early on?

Starting at birth, newborn infants are exposed to numerous microorganisms. Adaptation of the innate immune system to them is a delicate process, with potentially advantageous and harmful implications for health development. Cytomegaloviruses (CMVs) are highly adapted to their specific mammalian hosts, with which they share millions of years of co-evolution. Throughout the history of mankind, human CMV has infected most infants in the first months of life without overt implications for health. Thus, CMV infections are intertwined with normal immune development. Nonetheless, CMV has retained substantial pathogenicity following infection in utero or in situations of immunosuppression, leading to pathology in virtually any organ and particularly the central nervous system (CNS). CMVs enter the host through mucosal interfaces of the gastrointestinal and respiratory tract, where macrophages (MACs) are the most abundant immune cell type. Tissue MACs and their potential progenitors, monocytes, are established target cells of CMVs. Recently, several discoveries have revolutionized our understanding on the pre- and postnatal development and site-specific adaptation of tissue MACs. In this review, we explore experimental evidences and concepts on how CMV infections may impact on MAC development and activation as part of host-virus co-adaptation.

The Suppressive Attitude of Inflammatory Monocytes in Antiviral Antibody Responses

Inflammatory monocytes play important functions in antiviral immune responses, including release of inflammatory cytokines and antigen presentation to T lymphocytes. Depending on the pathological context, these functions might translate into beneficial or detrimental effects in the resolution of the disease. Recent literature has highlighted a role for inflammatory monocytes also in direct suppression of B cell responses. In this review, we will briefly discuss research showing the relationship between inflammatory monocytes and B lymphocytes, its functional consequences on antiviral antibody responses, and possible implications in the design of future vaccination strategies.

The Role of Chemokines and Chemokine Receptors in Diabetic Nephropathy

Kidney function decline is one of the complications of diabetes mellitus and may be indicated as diabetic nephropathy (DN). DN is a chronic inflammatory disease featuring proteinuria and a decreasing glomerular filtration rate. Despite several therapeutic options being currently available, DN is still the major cause of end-stage renal disease. Accordingly, widespread innovation is needed to improve outcomes in patients with DN. Chemokines and their receptors are critically involved in the inflammatory progression in the development of DN. Although recent studies have shown multiple pathways related to the chemokine system, the specific and direct effects of chemokines and their receptors remain unclear. In this review, we provide an overview of the potential role and mechanism of chemokine systems in DN proposed in recent years. Chemokine system-related mechanisms may provide potential therapeutic targets in DN.

Myeloid Cells Restrict MCMV and Drive Stress-Induced Extramedullary Hematopoiesis through STAT1

Cytomegalovirus (CMV) has a high prevalence worldwide, is often fatal for immunocompromised patients, and causes bone marrow suppression. Deficiency of signal transducer and activator of transcription 1 (STAT1) results in severely impaired antiviral immunity. We have used cell-type restricted deletion of Stat1 to determine the importance of myeloid cell activity for the defense against murine CMV (MCMV). We show that myeloid STAT1 limits MCMV burden and infection-associated pathology in the spleen but does not affect ultimate clearance of infection. Unexpectedly, we found an essential role of myeloid STAT1 in the induction of extramedullary hematopoiesis (EMH). The EMH-promoting function of STAT1 was not restricted to MCMV infection but was also observed during CpG oligodeoxynucleotide-induced sterile inflammation. Collectively, we provide genetic evidence that signaling through STAT1 in myeloid cells is required to restrict MCMV at early time points post-infection and to induce compensatory hematopoiesis in the spleen.

Inflammation triggers immediate rather than progressive changes in monocyte differentiation in the small intestine

Bone marrow-derived circulating monocytes contribute to the replenishment and maintenance of the intestinal macrophage population. Intestinal monocytes undergo context-dependent phenotypic and functional adaptations to either maintain local immune balance or support intestinal inflammation. Here we use monocyte adoptive transfer to dissect the dynamics of monocyte-to-macrophage differentiation in normal and inflamed small intestine. We find that during homeostasis CCR2 and β7-integrin mediate constitutive homing of monocytes to the gut. By contrast, intestinal inflammation increases monocyte recruitment via CCR2, but not β7-integrin. In the non-inflamed intestine, monocytes gradually differentiate to express genes typically associated with tolerogenic macrophage functions. Conversely, immediately upon entry into the inflamed intestine, monocytes adapt a different expression pattern in a partly Trem-1-dependent manner. Our observations suggest that inflammation fundamentally changes the kinetics and modalities of monocyte differentiation in tissues.

Bone marrow-derived monocytes are recruited to the gut to replenish the local macrophage pool. Here the authors show that, while such replenishment constitutively occur under homeostasis, gut inflammation induces an immediate, Trem1-related transcription change to recruited monocyte to enable a context-dependent modulation of macrophage functions.

Cytomegalovirus Infection May Trigger Adult-Onset Still's Disease Onset or Relapses

Previous studies have revealed that several micro-organisms, especially DNA viruses, have been associated with adult-onset Still's disease (AOSD). However, there are no studies on the relationship between the presence of viral infections in AOSD patients with disease occurrence and reactivation. In the present study, we aimed to investigate the presence of antibodies against virus, virus DNA load and nucleic acid sensors in AOSD patients. Anti-viral antibodies were measured by enzyme-linked immunosorbent assay (ELISA) in plasma samples from 100 AOSD patients and 70 healthy controls (HCs). The copy number of cytomegalovirus (CMV) DNA in 100 AOSD patients was detected by PCR. The expression levels of nucleic acid sensors interferon gamma-inducible protein 16 (IFI16) and absent in melanoma 2 (AIM2) in peripheral blood mononuclear cell (PBMC) and skin from AOSD patients and HCs were analyzed by PCR and immunohistochemistry. The levels of antibodies against CMV were significantly higher in AOSD patients compared to HCs. Moreover, the level of anti-CMV IgM antibody was significantly increased in patients with fever, sore throat, arthralgia and rash. CMV DNA was found in plasma of AOSD patients with disease new-onset and relapse. Furthermore, the copy number of CMV DNA significantly increased in patients with fever, sore throat, arthralgia and rash. And the significant associations of the CMV DNA level with the levels of leukocytes, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and tumor necrosis factor-α (TNF-α) were observed. Moreover, we found an upregulation of cytoplasmic DNA-sensing receptor IFI16 and AIM2 in PBMC and skin from AOSD patients. In conclusion, our results showed that CMV infection may play a role in the initiation or amplification of inflammatory responses in AOSD.

Variety matters: Diverse functions of monocyte subtypes in vascular inflammation and atherogenesis

Monocytes are important mediators of the innate immunity by recognizing and attacking especially bacterial pathogens but also play crucial roles in various inflammatory diseases, including vascular inflammation and atherosclerosis. Maturation, differentiation and function of monocytes have been intensively explored for a long time in innumerable experimental and clinical studies. Monocytes do not represent a uniform cell type but could be further subdivided into subpopulations with distinct features and functions. Those subpopulations have been identified in experimental mouse models as well as in humans, albeit distinguished by different cell surface markers. While Ly6C is used for subpopulation differentiation in mice, corresponding human subsets are differentiated by CD14 and CD16. In this review, we specifically focused on new experimental insights from recent years mainly in regard to murine monocyte subpopulations and their roles in vascular inflammation und atherogenesis.

Microglia Are Derived from Peripheral Blood Mononuclear Cells After Pseudorabies Infection in Mice

Pseudorabies virus (PRV) can spread along the peripheral nerves near the site of infection in the animals, and gradually migrates into the central nervous system, where it leads to the development of brain lesions. The aim of this study was to investigate the dynamics of microglia after PRV inoculation. A mouse model inoculated with PRV was established to study the interactions between PRV and microglia, microglial recruitment, and polarization effects. The mice were subcutaneously inoculated with different doses of PRV-Bartha K61 vaccine strain. The obtained results showed that mouse mortality rates increased with the applied doses of virus, and brain lesions, located in the brain tail and brain stem, were observed in each investigated group. Inflammatory cells were shown to infiltrate through the vasculature into perivascular cuff, and the number of microglia was increased as well. Mouse group treated with a medium infection dose demonstrated a high survival rate while developing serious brain lesions, and therefore, this dose was selected for further experiments. Immunohistochemistry, flow cytometry, and confocal laser scanning microscopy were used to analyze PRV-microglia interactions. After PRV inoculation, proliferating cell nuclear antigen (Pcna) and Iba1 double-positive cells were observed in the brain lesions, together with the activated microglia, suggesting that PRV can induce microglial proliferation and activation. Furthermore, 5-bromo-deoxy-uridine (BrdU) labeling demonstrated that microglial cells did not proliferate in situ and the proliferating cells originated from peripheral blood monocytes, mainly from the inflammatory monocytes (Ly6C^high). In addition, microglia polarized into both M1 and M2 phenotypes by PRV infection. The results obtained in this study may help understand the development of pseudorabies infection and help improve the treatment, by recruiting and enhancing immune response.

Interleukin-17D and Nrf2 mediate initial innate immune cell recruitment and restrict MCMV infection

Innate immune cells quickly infiltrate the site of pathogen entry and not only stave off infection but also initiate antigen presentation and promote adaptive immunity. The recruitment of innate leukocytes has been well studied in the context of extracellular bacterial and fungal infection but less during viral infections. We have recently shown that the understudied cytokine Interleukin (IL)-17D can mediate neutrophil, natural killer (NK) cell and monocyte infiltration in sterile inflammation and cancer. Herein, we show that early immune cell accumulation at the peritoneal site of infection by mouse cytomegalovirus (MCMV) is mediated by IL-17D. Mice deficient in IL-17D or the transcription factor Nuclear factor (erythroid-derived 2)-like 2 (Nrf2), an inducer of IL-17D, featured an early decreased number of innate immune cells at the point of viral entry and were more susceptible to MCMV infection. Interestingly, we were able to artificially induce innate leukocyte infiltration by applying the Nrf2 activator tert-butylhydroquinone (tBHQ), which rendered mice less susceptible to MCMV infection. Our results implicate the Nrf2/IL-17D axis as a sensor of viral infection and suggest therapeutic benefit in boosting this pathway to promote innate antiviral responses.

Effect of PF-04634817, an Oral CCR2/5 Chemokine Receptor Antagonist, on Albuminuria in Adults with Overt Diabetic Nephropathy

Introduction

Inflammatory cell recruitment, which is potentially mediated by the monocyte chemoattractant protein 1/C-C chemokine receptor type 2 (CCR2) system and by C-C chemokine receptor type 5 (CCR5) activity, may play a role in the development and progression of diabetic nephropathy. PF-04634817 is a dual chemokine CCR2/5 receptor antagonist that is being developed for the treatment of diabetic nephropathy.

Methods

We evaluated the efficacy of PF-04634817 compared with matching placebo for reduction of albuminuria after 12 weeks of treatment in subjects with type 2 diabetes who received standard of care (SOC; angiotensin-converting enzyme inhibitor or angiotensin receptor blocker therapy), in a randomized, double-blind, placebo-controlled, parallel-group phase 2 study.

Results

A total of 226 subjects who received SOC with baseline estimated glomerular filtration rates between 20 and 75 ml/min per 1.73 m² and a baseline urinary albumin-to-creatinine ratio (UACR) of ≥300 mg/g were randomly assigned 3:1 to receive PF-04634817 (150 or 200 mg orally, once daily) or placebo. The primary analysis was Bayesian, with an informative prior for placebo response (equivalent to including an additional 80 subjects in the placebo arm). We observed a placebo-adjusted reduction in UACR of 8.2% (ratio 0.918; 95% credible interval: 0.75–1.09) at week 12 in the PF-04634817 arm. PF-04634817 appeared to be safe and well-tolerated.

Conclusion

Despite the good safety profile shown by PF-04634817, clinical development for this indication was discontinued in light of the modest efficacy observed.

Anti-inflammatory consequences of bile acid accumulation in virus-infected bile duct ligated mice

Cholestatic patients exhibiting high bile acid serum levels were reported to be more susceptible to bacterial and viral infections. Animal studies in bile duct ligated (BDL) mice suggest that cholestasis leads to an aggravation of hepatic bacterial infections. We have investigated the impact of cholestasis on mouse cytomegalovirus (MCMV)-induced immune responses and viral replication. While MCMV did not aggravate BDL-induced liver damage, BDL markedly reduced MCMV-triggered chemokine expression and immune cell recruitment to the liver. MCMV-infected BDL mice showed diminished trafficking of Ly6C+/F4/80+ myeloid cells and NK1.1+ NK cells to the liver compared to MCMV infected control mice. Moreover, virus-driven expression of CCL7, CCL12, CXCL9 and CXCL10 was clearly impaired in BDL- compared to sham-operated mice. Furthermore, production of the anti-inflammatory cytokine IL-10 was massively augmented in infected BDL mice. In contrast, intra- and extrahepatic virus replication was unaltered in BDL-MCMV mice when compared to sham-MCMV mice. Cholestasis in the BDL model severely impaired pathogen-induced chemokine expression in the liver affecting CCR2- and CXCR3-dependent cell trafficking. Cholestasis resulted in reduced recruitment of inflammatory monocytes and NK cells to the liver.

Nasal priming by a murine coronavirus provides protective immunity against lethal heterologous virus pneumonia

The nasal mucosa is an important component of mucosal immunity. Immunogenic particles in inspired air are known to activate the local nasal mucosal immune system and can lead to sinonasal inflammation; however, little is known about the effect of this activation on the lung immune environment. Here, we showed that nasal inoculation of murine coronavirus (CoV) in the absence of direct lung infection primes the lung immune environment by recruiting activated monocytes (Ly6C+ inflammatory monocytes) and NK cells into the lungs. Unlike infiltration of these cells into directly infected lungs, a process that requires type I IFN signaling, nasally induced infiltration of Ly6C+ inflammatory monocytes into the lungs is IFN-I independent. These activated macrophages ingested antigen and migrated to pulmonary lymph nodes, and enhanced both innate and adaptive immunity after heterologous virus infection. Clinically, such nasal-only inoculation of MHV-1 failed to cause pneumonia but significantly reduced mortality and morbidity of lethal pneumonia caused by severe acute respiratory syndrome CoV (SARS-CoV) or influenza A virus. Together, the data indicate that the nose and upper airway remotely prime the lung immunity to protect the lungs from direct viral infections.

Towards the Application of Human Defensins as Antivirals

Defensins are antimicrobial peptides that participate in the innate immunity of hosts. Humans constitutively and/or inducibly express α- and β-defensins, which are known for their antiviral and antibacterial activities. This review describes the application of human defensins. We discuss the extant experimental results, limited though they are, to consider the potential applicability of human defensins as antiviral agents. Given their antiviral effects, we propose that basic research be conducted on human defensins that focuses on RNA viruses, such as human immunodeficiency virus (HIV), influenza A virus (IAV), respiratory syncytial virus (RSV), and dengue virus (DENV), which are considered serious human pathogens but have posed huge challenges for vaccine development for different reasons. Concerning the prophylactic and therapeutic applications of defensins, we then discuss the applicability of human defensins as antivirals that has been demonstrated in reports using animal models. Finally, we discuss the potential adjuvant-like activity of human defensins and propose an exploration of the ‘defensin vaccine’ concept to prime the body with a controlled supply of human defensins. In sum, we suggest a conceptual framework to achieve the practical application of human defensins to combat viral infections.

Histone deacetylase 6 modulates macrophage infiltration during inflammation

Mice with histone deacetylase 6 (HDAC6) deficiency grow and develop normally but exhibit impaired immune response. The molecular mechanisms for this phenotype remain largely elusive.

Methods: A mouse acute peritonitis model was used to study the infiltration of neutrophils and monocyte-derived macrophages. In vitro cell motility assays were performed to analyze monocyte/macrophage recruitment. Fluorescence microscopy and flow cytometry were performed to examine the phagocytic ability of macrophages. Immunofluorescence microscopy was used to investigate protein localization, protrusion formation, and microtubule acetylation.

Results: HDAC6 deficiency does not affect neutrophil infiltration, but instead attenuates the infiltration of monocyte-derived macrophages into the peritoneal cavity. HDAC6 plays a specific role in monocyte/macrophage recruitment. Loss of HDAC6 suppresses the phagocytic capacity of macrophages challenged with E. coli. Lipopolysaccharide stimulation results in the translocation of HDAC6 and cortactin from the cytosol to the cell periphery, promotes the formation of filopodial protrusions, and enhances microtubule acetylation around the microtubule-organizing center, all of which are abrogated by HDAC6 deficiency.

Conclusion: These findings implicate HDAC6 in the innate immune response and suggest that it may serve as a promising target for the treatment of macrophage-associated immune diseases.

Inflammatory Monocytes Drive Influenza A Virus-Mediated Lung Injury in Juvenile Mice

Healthy children are more likely to die of influenza A virus (IAV) infection than healthy adults. However, little is known about the mechanisms underlying the impact of young age on the development of life-threatening IAV infection. We report increased mortality in juvenile mice compared with adult mice at each infectious dose of IAV. Juvenile mice had sustained elevation of type I IFNs and persistent NLRP3 inflammasome activation in the lungs, both of which were independent of viral titer. Juvenile mice, but not adult mice, had increased MCP-1 levels that remained high even after viral clearance. Importantly, continued production of MCP-1 was associated with persistent recruitment of monocytes to the lungs and prolonged elevation of inflammatory cytokines. Transcriptional signatures of recruited monocytes to the juvenile and adult IAV-infected lungs were assessed by RNA-seq. Genes associated with a proinflammatory signature were upregulated in the juvenile monocytes compared with adult monocytes. Depletion of monocytes with anti-CCR2 Ab decreased type I IFN secretion, NLRP3 inflammasome activation, and lung injury in juvenile mice. This suggests an exaggerated inflammatory response mediated by increased recruitment of monocytes to the lung, and not an inability to control viral replication, is responsible for severe IAV infection in juvenile mice. This study provides insight into severe IAV infection in juveniles and identifies key inflammatory monocytes that may be central to pediatric acute lung injury secondary to IAV.

The PSMP-CCR2 interactions trigger monocyte/macrophage-dependent colitis

Monocytes/macrophages have been found to be an important component of colitis. However, the key chemokine that initiates the CCR2⁺ monocytes migration from circulation to colitis tissue remains to be undiscovered. PC3-secreted microprotein (PSMP) is a novel chemokine whose receptor is CCR2. The physiological and pathological functions of PSMP have not yet been reported. In this study, PSMP was found to be expressed in colitis and colonic tumor tissues from patients and significantly up-regulated in mouse DSS-induced colitis tissues. PSMP overexpression in the colon aggravated the DSS-induced colitis and the anti-PSMP neutralizing antibody mollified the colitis by reducing macrophage infiltration and inhibiting the expression of IL-6, TNF-α and CCL2. Furthermore, we demonstrated that lipopolysaccharide and muramyl dipeptide induced PSMP expression in the colonic epithelial cells. PSMP was up-regulated in the initial stage prior to IL-6, TNF-α and CCL2 up-regulated expression in DSS colitis and promoted the M1 macrophages to produce CCL2. PSMP chemo-attracted Ly6C^hi monocytes in a CCR2 dependent manner via in situ chemotaxis and adoptive transfer assays. Our data identify PSMP as a key molecule in ulcerative colitis, which provides a novel mechanism of monocyte/macrophage migration that affects gut innate immunity and makes PSMP a potential target for controlling colitis.

Aging and cancer: The role of macrophages and neutrophils

Impaired immune function has been implicated in the declining health and higher incidence of cancer in the elderly. However, age-related changes to immunity are not completely understood. Neutrophils and macrophages represent the first line of defence yet their ability to phagocytose pathogens decrease with aging. Cytotoxic T lymphocytes are critical in eliminating tumors, but T cell function is also compromised with aging. T cell responses can be regulated by macrophages and may depend on the functional phenotype macrophages adopt in response to microenvironmental signals. This can range from pro-inflammatory, anti-tumorigenic M1 to anti-inflammatory, pro-tumorigenic M2 macrophages. Macrophages in healthy elderly adipose and hepatic tissue exhibit a more pro-inflammatory M1 phenotype compared to young hosts whilst immunosuppressive M2 macrophages increase in elderly lymphoid tissues, lung and muscle. These M2-like macrophages demonstrate altered responses to stimuli. Recent studies suggest that neutrophils also regulate T cell function and, like macrophages, neutrophil function is modulated with aging. It is possible that age-modified tissue-specific macrophages and neutrophils contribute to chronic low-grade inflammation that is associated with dysregulated macrophage-mediated immunosuppression, which together are responsible for development of multiple pathologies, including cancer. This review discusses recent advances in macrophage and neutrophil biology in healthy aging and cancer.

Monocyte chemoattractant protein-1 is not required for liver regeneration after partial hepatectomy

Background

Liver regeneration following 70 % partial hepatectomy (PH) requires the coordinated expression of soluble mediators produced by macrophages. Monocyte chemoattractant protein-1 (MCP-1) is a potent stimulus of monocyte recruitment and macrophage activation. The goal of this study was to determine how MCP-1 contributes to liver regeneration.

Methods

PH was performed on anesthetized C57Bl/6 (wild type) and MCP-1 knockout mice, and macrophage-produced cytokines and hepatocyte proliferation were measured.

Results

In wild type mice, hepatic MCP-1 protein levels increased 4–6 h after PH, and elevated plasma MCP-1 levels were detected 12 h after PH. Hepatocyte proliferation was comparable in MCP-1 knockout and wild type mice, as was the expression of macrophage-derived cytokines, TNFα and IL-6, and levels of phosphorylated STAT3. The number of CCR2⁺ cells in the liver was similar in MCP-1 knockout and wild type mice, which suggests that other chemokines may recruit CCR2⁺ cells in the absence of MCP-1. Studies with CCR2 knockout mice revealed that hepatocyte proliferation was suppressed ~40 % compared to wild type mice 36 h after PH, but proliferation and liver-body-weight ratios were similar at 48 h.

Conclusion

These findings suggest that MCP-1 is not required for PH-induced liver regeneration, yet the role of CCR2 warrants further study.

Inflammatory monocytes and NK cells play a crucial role in DNAM-1-dependent control of cytomegalovirus infection

Jonjic et al. show that inflammatory macrophages play an essential role in the control of murine CMV (MCMV) infection through a DNAM-1–PVR pathway.

The poliovirus receptor (PVR) is a ubiquitously expressed glycoprotein involved in cellular adhesion and immune response. It engages the activating receptor DNAX accessory molecule (DNAM)-1, the inhibitory receptor TIGIT, and the CD96 receptor with both activating and inhibitory functions. Human cytomegalovirus (HCMV) down-regulates PVR expression, but the significance of this viral function in vivo remains unknown. Here, we demonstrate that mouse CMV (MCMV) also down-regulates the surface PVR. The m20.1 protein of MCMV retains PVR in the endoplasmic reticulum and promotes its degradation. A MCMV mutant lacking the PVR inhibitor was attenuated in normal mice but not in mice lacking DNAM-1. This attenuation was partially reversed by NK cell depletion, whereas the simultaneous depletion of mononuclear phagocytes abolished the virus control. This effect was associated with the increased expression of DNAM-1, whereas TIGIT and CD96 were absent on these cells. An increased level of proinflammatory cytokines in sera of mice infected with the virus lacking the m20.1 and an increased production of iNOS by inflammatory monocytes was observed. Blocking of CCL2 or the inhibition of iNOS significantly increased titer of the virus lacking m20.1. In this study, we have demonstrated that inflammatory monocytes, together with NK cells, are essential in the early control of CMV through the DNAM-1–PVR pathway.

Distinct Upstream Role of Type I IFN Signaling in Hematopoietic Stem Cell-Derived and Epithelial Resident Cells for Concerted Recruitment of Ly-6Chi Monocytes and NK Cells via CCL2-CCL3 Cascade

Type I interferon (IFN-I)-dependent orchestrated mobilization of innate cells in inflamed tissues is believed to play a critical role in controlling replication and CNS-invasion of herpes simplex virus (HSV). However, the crucial regulators and cell populations that are affected by IFN-I to establish the early environment of innate cells in HSV-infected mucosal tissues are largely unknown. Here, we found that IFN-I signaling promoted the differentiation of CCL2-producing Ly-6C^hi monocytes and IFN-γ/granzyme B-producing NK cells, whereas deficiency of IFN-I signaling induced Ly-6C^lo monocytes producing CXCL1 and CXCL2. More interestingly, recruitment of Ly-6C^hi monocytes preceded that of NK cells with the levels peaked at 24 h post-infection in IFN-I–dependent manner, which was kinetically associated with the CCL2-CCL3 cascade response. Early Ly-6C^hi monocyte recruitment was governed by CCL2 produced from hematopoietic stem cell (HSC)-derived leukocytes, whereas NK cell recruitment predominantly depended on CC chemokines produced by resident epithelial cells. Also, IFN-I signaling in HSC-derived leukocytes appeared to suppress Ly-6G^hi neutrophil recruitment to ameliorate immunopathology. Finally, tissue resident CD11b^hiF4/80^hi macrophages and CD11c^hiEpCAM⁺ dendritic cells appeared to produce initial CCL2 for migration-based self-amplification of early infiltrated Ly-6C^hi monocytes upon stimulation by IFN-I produced from infected epithelial cells. Ultimately, these results decipher a detailed IFN-I–dependent pathway that establishes orchestrated mobilization of Ly-6C^hi monocytes and NK cells through CCL2-CCL3 cascade response of HSC-derived leukocytes and epithelium-resident cells. Therefore, this cascade response of resident–to-hematopoietic–to-resident cells that drives cytokine–to-chemokine–to-cytokine production to recruit orchestrated innate cells is critical for attenuation of HSV replication in inflamed tissues.

Herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) are the most common cause of genital ulceration in humans worldwide with lifelong latent infection after peripheral replication in mucosal tissues. Furthermore, acquisition of human immunodeficiency virus (HIV) is increased in HSV-infected individuals, underscoring the contribution of this virus in facilitating increased susceptibility to other microbial pathogens. Therefore, it is imperative to characterize the host defense to HSV infection and identify key components that regulate virus resistance, in order to devise therapeutic strategy. Although type I interferon (IFN-I)-dependent orchestrated mobilization of innate cells in inflamed tissues is considered a key player to control replication and CNS-invasion of HSV, the regulators and cell population that are affected by IFN-I to establish the orchestrated environment of innate cells in HSV-infected tissues are largely unknown. In the present study, we demonstrate that IFN-I signal governs the sequential recruitment of Ly-6C^hi monocytes and then NK cells into mucosal tissues, depending on CCL2-CCL3 cascade mediated by HSC-derived leukocytes and epithelial resident cells, respectively. Also, tissue resident CD11b^hiF4/80^hi macrophages and CD11c^hiEpCAM⁺ dendritic cells were involved in producing the initial CCL2 for migration-based self-amplification of rapidly infiltrated Ly-6C^hi monocytes through stimulation by IFN-I produced from infected epithelial cells. This study deciphers detailed IFN-I-dependent pathway that establishes orchestrated mobilization of Ly-6C^hi monocytes and NK cells through CCL2-CCL3 cascade.

Differential Roles of Chemokines CCL2 and CCL7 in Monocytosis and Leukocyte Migration during West Nile Virus Infection

West Nile virus (WNV) is a re-emerging pathogen and the leading cause of epidemic encephalitis in the United States. Inflammatory monocytes are a critical component of the cellular infiltrate found in the CNS during WNV encephalitis, although the molecular cues involved in their migration are not fully understood. In mice, we previously showed that WNV infection induces a CCR2-dependent monocytosis that precedes monocyte migration into the CNS. Currently, the relative contribution of the CCR2 ligands, chemokines CCL2 and CCL7, in directing monocyte mobilization and leukocyte migration into the CNS is unclear. In this study, we demonstrate that, although both CCL2 and CCL7 are required for efficient monocytosis and monocyte accumulation in the CNS, only CCL7 deficiency resulted in increased viral burden in the brain and enhanced mortality. The enhanced susceptibility in the absence of CCL7 was associated with the delayed migration of neutrophils and CD8(+) T cells into the CNS compared with WT or Ccl2(-/-) mice. To determine whether CCL7 reconstitution could therapeutically alter the survival outcome of WNV infection, we administered exogenous CCL7 i.v. to WNV-infected Ccl7(-/-) mice and observed a significant increase in monocytes and neutrophils, but not CD8(+) T cells, within the CNS, as well as an enhancement in survival compared with Ccl7(-/-) mice treated with a linear CCL7 control peptide. Our experiments suggest that CCL7 is an important protective signal involved in leukocyte trafficking during WNV infection, and it may have therapeutic potential for the treatment of acute viral infections of the CNS.

Hematopoietic and nonhematopoietic cells promote Type I interferon- and TLR7-dependent monocytosis during low-dose LCMV infection

Release of inflammatory monocytes from the bone marrow (BM) into the blood is an important physiological response to infection, but the mechanisms regulating this phenomenon during viral infection are not completely defined. Here, we show that low-dose infection with lymphocytic choriomeningitis virus (LCMV) caused rapid, transient inflammatory monocytosis that required type I interferon (IFN) and Toll-like receptor (TLR) 7 signaling. Type I IFN and TLR7 signals were critical for induction of IFN-stimulated gene expression and CCR2 ligand upregulation in the BM microenvironment in response to LCMV infection. Experiments utilizing BM chimeric mice demonstrated that type I IFN and TLR7 signaling on either hematopoietic or nonhematopoietic cells was sufficient to initiate monocytosis in response to LCMV infection. BM plasmacytoid dendritic cells (pDCs) generated type I IFN directly ex vivo, suggesting that pDCs are a hematopoietic contributor of type I IFN in the BM early during LCMV infection. Overall, we describe novel roles for type I IFN and TLR7 signaling in nonhematopoietic cells and BM pDCs in directing IFN-stimulated gene and CCR2 ligand expression in the BM to initiate an increase in blood inflammatory monocytes during viral infection.

Alveolar macrophage-derived type I interferons orchestrate innate immunity to RSV through recruitment of antiviral monocytes

Goritzka et al. describe a role for recruited inflammatory monocytes in antiviral immunity and protection from RSV infection in mice. The authors demonstrate that this is critically dependent on the production of type I IFNs by alveolar macrophages triggered via RIG-I–like receptors, thus highlighting an important cell-extrinsic mechanism of type I IFN–mediated antiviral activity.

Type I interferons (IFNs) are important for host defense from viral infections, acting to restrict viral production in infected cells and to promote antiviral immune responses. However, the type I IFN system has also been associated with severe lung inflammatory disease in response to respiratory syncytial virus (RSV). Which cells produce type I IFNs upon RSV infection and how this directs immune responses to the virus, and potentially results in pathological inflammation, is unclear. Here, we show that alveolar macrophages (AMs) are the major source of type I IFNs upon RSV infection in mice. AMs detect RSV via mitochondrial antiviral signaling protein (MAVS)–coupled retinoic acid–inducible gene 1 (RIG-I)–like receptors (RLRs), and loss of MAVS greatly compromises innate immune restriction of RSV. This is largely attributable to loss of type I IFN–dependent induction of monocyte chemoattractants and subsequent reduced recruitment of inflammatory monocytes (infMo) to the lungs. Notably, the latter have potent antiviral activity and are essential to control infection and lessen disease severity. Thus, infMo recruitment constitutes an important and hitherto underappreciated, cell-extrinsic mechanism of type I IFN–mediated antiviral activity. Dysregulation of this system of host antiviral defense may underlie the development of RSV-induced severe lung inflammation.

Up-regulation of the monocyte chemotactic protein-3 in sera from bone marrow transplanted children with torquetenovirus infection

BACKGROUND

Torquetenovirus (TTV) represents a commensal human virus producing life-long viremia in approximately 80% of healthy individuals of all ages. A potential pathogenic role for TTV has been suggested in immunocompromised patients with hepatitis of unknown etiology sustained by strong proinflammatory cytokines.

OBJECTIVES

The aim of this study was to investigate the sera immunological profile linked to TTV infection in bone marrow transplant (BMT) children with liver injury.

STUDY DESIGN

TTV infection was assessed in sera from 27 BMT patients with altered hepatic parameters and histological features, by the use of quantitative real-time PCR, along with TTV genogroups and coinfection with HEV. The qualitative and quantitative nature of soluble inflammatory factors was evaluated studying a large set of cytokines using the Bioplex platform. As controls, sera from 22 healthy children negative for serological and molecular hepatitis markers including TTV and HEV, and for autoimmune diseases, were selected.

RESULTS AND CONCLUSIONS

TTV was detected in 81.4% of BMT patients with a viral load ranging from 10(5) to 10(9) copies/mL. All samples were HEV-RNA negative. A pattern of cytokines, IFN-γ, TNF-α, FGF-basic (p<0.01) and MCP-3 (p<0.001) was found significantly highly expressed in TTV-positive patients compared to TTV-negative and controls. Of note, MCP-3 chemokine showed the highest sera concentration independently of the amount of TTV load and the status of immune system deregulation (p<0.001). In this pilot study for the first time, a positive association was found between TTV and increased level of MCP-3 suggesting a indirect role of TTV in liver injury.

Organization and functions of glycolipid-enriched microdomains in phagocytes

Populations of glycolipids change markedly during leukocyte differentiation, suggesting that these molecules are involved in biological functions. About 70% of the glycosphingolipids in human neutrophils are lactosylceramide, a molecule also expressed on monocytes and dendritic cells, but not on lymphocytes. In contrast, phosphatidylglucoside is mainly expressed on neutrophils. STED microscopic analysis showed that phosphatidylglucoside and lactosylceramide form different domains on plasma membranes of neutrophils, with phosphatidylglucoside preferentially expressed along the neutrophil differentiation pathway. Phosphatidylglucoside was found to mediate the differentiation of HL-60 cells into the neutrophilic lineage, and to be involved in FAS-dependent neutrophil apoptosis. In contrast, lactosylceramide was only expressed on mature neutrophils. Complexes of lactosylceramide and the Src family kinase Lyn form membrane microdomains. LacCer-enriched membrane microdomains mediate neutrophil innate immune responses; e.g. chemotaxis, phagocytosis, and superoxide generation. C24 fatty acid chains of LacCer are indispensable for the formation of LacCer-Lyn complexes and for LacCer-dependent functions. Moreover, Lyn-coupled LacCer-enriched microdomains serve as signal transduction platforms for αMβ2 integrin-mediated phagocytosis. This review describes the organization and potential functions of glycolipids in phagocytes, as well as the roles of both phosphatidylglucoside and lactosylceramide in neutrophils. This article is part of a Special Issue entitled Linking transcription to physiology in lipidomics.

CXCR3 modulates obesity-induced visceral adipose inflammation and systemic insulin resistance

OBJECTIVE

Chemokine (C-X-C motif) receptor 3 (CXCR3) is a chemokine receptor involved in the regulation of immune cell trafficking and activation. Increased CXCR3 expression in the visceral adipose of obese humans and mice was observed. A pathophysiologic role for CXCR3 in diet-induced obesity (DIO) was hypothesized.

METHODS

Wild-type (WT) C57B/L6J and chemokine receptor 3 knockout (CXCR3(-/-) ) mice were fed a high-fat diet (HFD) for 20 weeks followed by assessment of glucose metabolism and visceral adipose tissue (VAT) inflammation.

RESULTS

CXCR3(-/-) mice exhibited lower fasting glucose and improved glucose tolerance compared with WT-HFD mice, despite similar body mass. HFD-induced VAT innate and adaptive immune cell infiltration, including immature myeloid cells (CD11b(+) F4/80(lo) Ly6C(+) ), were markedly ameliorated in CXCR3(-/-) mice. In vitro IBIDI and in vivo migration assays demonstrated no CXCR3-mediated effect on macrophage or monocyte migration, respectively. CXCR3(-/-) macrophages, however, had a blunted response to interferon-γ, a TH 1 cytokine that induces macrophage activation.

CONCLUSIONS

A previously unreported role for CXCR3 in the development of HFD-induced insulin resistance (IR) and VAT macrophage infiltration in mice was demonstrated. Our results support pharmaceutical targeting of the CXCR3 receptor as a potential treatment for obesity/IR.

Proteinase-activated receptor-1, CCL2, and CCL7 regulate acute neutrophilic lung inflammation

PAR1 plays a central role in mediating the interplay between coagulation and inflammation, but its role in regulating acute neutrophilic inflammation is unknown. We report that antagonism of PAR1 was highly effective at reducing acute neutrophil accumulation in a mouse model of LPS-induced lung inflammation. PAR1 antagonism also reduced alveolar-capillary barrier disruption in these mice. This protection was associated with a reduction in the expression of the chemokines, CCL2 and CCL7, but not the proinflammatory cytokines, TNF and IL-6, or the classic neutrophil chemoattractants, CXCL1 and CXCL2. Antibody neutralization of CCL2 and CCL7 significantly reduced LPS-induced total leukocyte and neutrophil accumulation, recovered from the bronchoalveolar lavage fluid of challenged mice. Immunohistochemical analysis revealed that CCL2 predominantly localized to alveolar macrophages and pulmonary epithelial cells, whereas CCL7 was restricted to the pulmonary epithelium. In keeping with these observations, the intranasal administration of recombinant CCL2 (rCCL2) and rCCL7 led to the accumulation of neutrophils within the lung airspaces of naive mice in the absence of any underlying inflammation. Flow cytometry analysis further demonstrated an increase in Ly6G(hi) neutrophils expressing the chemokine receptors, CCR1 and CCR2, isolated from mouse lungs compared with circulating neutrophils. Conversely, the expression of CXCR2 decreased on neutrophils isolated from the lung compared with circulating neutrophils. Furthermore, this switch in chemokine receptor expression was accentuated after acute LPS-induced lung inflammation. Collectively, these findings reveal a novel role for PAR1 and the chemokines, CCL2 and CCL7, during the early events of acute neutrophilic inflammation.

Cytomegalovirus hijacks CX3CR1(hi) patrolling monocytes as immune-privileged vehicles for dissemination in mice

Peripheral blood myelomonocytic cells are important for cytomegalovirus dissemination to distal organs such as salivary glands where persistent replication and shedding dictates transmission patterns. We find that this process is markedly enhanced by the murine cytomegalovirus (MCMV)-encoded CC chemokine, MCK2, which promotes recruitment of CX3CR1(hi) patrolling monocytes to initial infection sites in the mouse. There, these cells become infected and traffic via the bloodstream to distal sites. In contrast, inflammatory monocytes, the other major myelomonocytic subset, remain virus negative. CX3CR1 deficiency prevents patrolling monocyte migration on the vascular endothelium and interrupts MCMV dissemination to the salivary glands independent of antiviral NK and T cell immune control. In this manner, CX3CR1(hi) patrolling monocytes serve as immune-privileged vehicles to transport MCMV via the bloodstream to distal organs. MCMV commandeers patrolling monocytes to mediate systemic infection and seed a persistent reservoir essential for horizontal transmission.

The early monocytic response to cytomegalovirus infection is MyD88 dependent but occurs independently of common inflammatory cytokine signals

Cytomegalovirus latently infects myeloid cells; however, the acute effects of the virus on this cell subset are poorly characterised. We demonstrate that systemic cytomegalovirus infection induced rapid activation of monocytes in the bone marrow, characterised by upregulation of CD69, CD11c, Ly6C and M-CSF receptor. Activated bone marrow monocytes were more sensitive to M-CSF and less sensitive to granulocyte-monocyte colony stimulating factor in vitro, resulting in the generation of more macrophages and fewer dendritic cells, respectively. Monocyte activation was also observed in the periphery and resulted in significant accumulation of monocytes in the spleen. MyD88 expression was required within the haematopoietic compartment to initiate monocyte activation and recruitment. However, monocytes lacking MyD88 were activated and recruited in the presence of MyD88-sufficient cells in mixed bone marrow chimeras, indicating that once initiated, the process was MyD88 independent. Interestingly, we found that monocyte activation occurred in the absence of the common inflammatory cytokines, namely type I interferons (IFNs), IL-6, TNF-α and IL-1 as well as the NLRP3 inflammasome adaptor protein, ASC. We also excluded a role for the chemokine-like protein MCK-2 (m131/129) expressed by murine CMV. Taken together, these results challenge the notion that a single inflammatory cytokine mediates activation and recruitment of monocytes in response to infection.

VPAC1 receptor expression in peripheral blood mononuclear cells in a human endotoxemia model

Background

Vasoactive intestinal peptide (VIP) exerts immune-modulatory actions mainly via VPAC1 receptor stimulation. VPAC1 may be a treatment target of inflammatory diseases, but little is known about the receptor expression profile in immune-competent cells in vivo.

Material and methods

20 male healthy subjects received a single intravenous bolus of 2ng/kg body weight Escherichia coli endotoxin (LPS). Receptor status was evaluated in peripherial blood cells before and 3, 6 and 24 h after LPS by FACS analysis and q-PCR. VIP plasma concentrations were measured by ELISA.

Results

Granulocytes accounted for 51% of leukocytes at baseline and 58 ± 37% were positive for VPAC1. The granulocyte population increased 2.6 fold after LPS, and a transient down-regulation of VPAC1 to 28 ± 23% was noted at 3 h (p < 0.001), which returned to baseline at 24 hours. Baseline VPAC1 expression was low in lymphocytes (6.3 ± 3.2%) and monocytes (11 ± 9.6%). In these cells, LPS up-regulated VPAC1 at 6 h (13.2 ± 4.9%, p < 0.001) and 24 h (31.6 ± 20.5%, p = 0.001), respectively. Consistent changes were noted for the VIP-receptors VPAC2 and PAC1. VPAC1, VPAC2 and PAC1 mRNA levels were unchanged in peripheral blood mononuclear cells (PBMC). VIP plasma concentration increased from 0.5 ± 0.3 ng/ml to 0.7 ± 0.4 ng/ml at 6 h after LPS (p < 0.05) and returned to baseline within 24 h.

Conclusion

The time profile of VPAC receptor expression differs in granulocytes, monocytes and lymphocytes after LPS challenge in humans. Changes in circulating VIP concentrations may reflect innate immune responses.

TLR2 and Nod2 mediate resistance or susceptibility to fatal intracellular Ehrlichia infection in murine models of ehrlichiosis

Our murine models of human monocytic ehrlichiosis (HME) have shown that severe and fatal ehrlichiosis is due to generation of pathogenic T cell responses causing immunopathology and multi-organ failure. However, the early events in the liver, the main site of infection, are not well understood. In this study, we examined the liver transcriptome during the course of lethal and nonlethal infections caused by Ixodes ovatus Ehrlichia and Ehrlichia muris, respectively. On day 3 post-infection (p.i.), although most host genes were down regulated in the two groups of infected mice compared to naïve counterparts, lethal infection induced significantly higher expression of caspase 1, caspase 4, nucleotide binding oligomerization domain-containing proteins (Nod1), tumor necrosis factor-alpha, interleukin 10, and CCL7 compared to nonlethal infection. On day 7 p.i., lethal infection induced highly significant upregulation of type-1 interferon, several inflammatory cytokines and chemokines, which was associated with increased expression levels of Toll-like receptor-2 (TLR2), Nod2, MyD88, nuclear factor-kappa B (NF-kB), Caspase 4, NLRP1, NLRP12, Pycard, and IL-1β, suggesting enhanced TLR signals and inflammasomes activation. We next evaluated the participation of TLR2 and Nod2 in the host response during lethal Ehrlichia infection. Although lack of TLR2 impaired bacterial elimination and increased tissue necrosis, Nod2 deficiency attenuated pathology and enhanced bacterial clearance, which correlated with increased interferon-γ and interleukin-10 levels and a decreased frequency of pathogenic CD8(+) T cells in response to lethal infection. Thus, these data indicate that Nod2, but not TLR2, contributes to susceptibility to severe Ehrlichia-induced shock. Together, our studies provide, for the first time, insight into the diversity of host factors and novel molecular pathogenic mechanisms that may contribute to severe HME.

The regulation of inflammation by interferons and their STATs

Interferons (IFN) are subdivided into type I IFN (IFN-I, here synonymous with IFN-α/β), type II (IFN-γ) and type III IFN (IFN-III/IFN-λ) that reprogram nuclear gene expression through STATs 1 and 2 by forming STAT1 dimers (mainly IFN-γ) or the ISGF3 complex, a STAT1-STAT2-IRF9 heterotrimer (IFN-I and IFN-III). Dominant IFN activities in the immune system are to protect cells from viral replication and to activate macrophages for enhanced effector function. However, the impact of IFN and their STATs on the immune system stretches far beyond these activities and includes the control of inflammation. The goal of this review is to give an overview of the different facets of the inflammatory process that show regulatory input by IFN/STAT.

Cytomegalovirus impairs antiviral CD8+ T cell immunity by recruiting inflammatory monocytes

Inflammatory monocytes are key early responders to infection that contribute to pathogen-host interactions in diverse ways. Here, we report that the murine cytomegalovirus-encoded CC chemokine, MCK2, enhanced CCR2-dependent recruitment of these cells to modulate antiviral immunity, impairing virus-specific CD8(+) T cell expansion and differentiation into effector cytotoxic T lymphocytes, thus reducing the capacity to eliminate viral antigen-bearing cells and slowing viral clearance. Adoptive transfer of inflammatory monocytes into Ccr2(-/-)Ccl2(-/-) mice impaired virus antigen-specific clearance. Cytomegalovirus therefore enhances a natural CCR2-dependent immune regulatory network to modulate adaptive immunity via nitric oxide production, reminiscent of the monocytic subtype of myeloid-derived suppressor cells primarily implicated in cancer immunomodulation.

Antiviral T cell response triggers cytomegalovirus hepatitis in mice

One common sign of human cytomegalovirus infection is altered liver function. Murine cytomegalovirus strain v70 induces a rapid and severe hepatitis in immunocompetent mice that requires the presence of T cells in order to develop. v70 exhibits approximately 10-fold-greater virulence than the commonly used strain K181, resulting in a more severe, sustained, and lethal hepatitis but not dramatically higher viral replication levels. Hepatitis and death are markedly delayed in immunodeficient SCID compared to immunocompetent BALB/c mice. Transfer of BALB/c splenocytes to SCID mice conferred rapid disease following infection, and depletion of either CD4 or CD8 T cells in BALB/c mice reduced virus-induced hepatitis. The frequency of CD8 T cells producing gamma interferon and tumor necrosis factor in response to viral antigen was higher in settings where more severe disease occurred. Thus, virus-specific effector CD8 T cells appear to contribute to lethal virus-induced hepatitis, contrasting their protective role during sublethal infection. This study reveals how protection and disease during cytomegalovirus infection depend on viral strain and dose, as well as the quality of the T cell response.

Source and characterization of hepatic macrophages in acetaminophen-induced acute liver failure in humans

Acetaminophen-induced acute liver failure (AALF) is associated with innate immunity activation, which contributes to the severity of hepatic injury and clinical outcome. A marked increase in hepatic macrophages (h-mφ) is observed in experimental models of AALF, but controversy exists regarding their role, implicating h-mφ in both aggravation and resolution of liver injury. The role of h-mφ in human AALF is virtually unexplored. We sought to investigate the role of chemokine (C-C motif) ligand 2 (CCL2) in the recruitment of circulating monocytes to the inflamed liver and to determine how the h-mφ infiltrate and liver microenvironment may contribute to tissue repair versus inflammation in AALF. We evaluated circulating monocytes, their chemokine (C-C motif) receptor 2 (CCR2) expression, and serum CCL2 levels in patients with AALF. Cell subsets and numbers of circulation-derived (MAC387+) or resident proliferating (CD68/Ki67+) h-mφ in hepatic immune infiltrates were determined by immunohistochemistry. Inflammatory cytokine levels were determined in whole and laser microdissected liver tissue by proteome array. In AALF, circulating monocytes were depleted, with the lowest levels observed in patients with adverse outcomes. CCL2 levels were high in AALF serum and hepatic tissue, and circulating monocyte subsets expressed CCR2, suggesting CCL2-dependent hepatic monocyte recruitment. Significant numbers of both MAC387+ and CD68+ h-mφ were found in AALF compared with control liver tissue with a high proportion expressing the proliferation marker Ki67. Levels of CCL2, CCL3, interleukin (IL)-6, IL-10, and transforming growth factor-β1 were significantly elevated in AALF liver tissue relative to chronic liver disease controls.

CONCLUSION

In AALF, the h-mφ population is expanded in areas of necrosis, both through proliferation of resident cells and CCL2-dependent recruitment of circulating monocytes. The presence of h-mφ within an anti-inflammatory/regenerative microenvironment indicates that they are implicated in resolution of inflammation/tissue repair processes during AALF.

HCMV-encoded UL128 enhances TNF-α and IL-6 expression and promotes PBMC proliferation through the MAPK/ERK pathway in vitro

Cytomegalovirus (CMV) infection enhances expression of several cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), granulocyte macrophage colony-stimulating factor (GM-CSF), and IL-8, to the benefit of virus replication and dissemination. However, the stimulus for certain cytokine production remains unclear. CMV encodes a series of proteins that alter and/or mimic functions of leukocyte migration, activation, and cytokine responses. Our study revealed that human CMV (HCMV)-encoded UL128 protein, which contains signal peptides and has similar amino acid sequences to the CC chemokine, recruits monocytes as human β chemokine (microphage inflammatory protein 1α). Using RNA interference technology, we constructed an HCMV (UL128⁺/UL128⁻)-infected tissue cell (MRC-5) and peripheral blood mononuclear cell (PBMC) co-culture system. We measured 6 cytokine levels (IL-2, IL-4, IL-6, IL-10, TNF-α, and interferon-γ [IFN-γ]) in the supernatant, and found significantly elevated IL-6 and elevated TNF-α levels in the HCMV UL128⁺-infected group. Conversely, we observed decreased levels in the UL128-knockout supernatant. PBMCs presented with UL128 (50 ng/mL) demonstrated better cell viability than the UL128-absent group. Finally, the MAPK/ERK pathway was found to be involved in UL128 induction of cell proliferation. Selective induction of cytokine expression indicates that HCMV-encoded UL128 is a potent inducer of several inflammatory mediators.

Type I interferons promote fatal immunopathology by regulating inflammatory monocytes and neutrophils during Candida infections

Invasive fungal infections by Candida albicans (Ca) are a frequent cause of lethal sepsis in intensive care unit patients. While a contribution of type I interferons (IFNs-I) in fungal sepsis remains unknown, these immunostimulatory cytokines mediate the lethal effects of endotoxemia and bacterial sepsis. Using a mouse model lacking a functional IFN-I receptor (Ifnar1^−/−), we demonstrate a remarkable protection against invasive Ca infections. We discover a mechanism whereby IFN-I signaling controls the recruitment of inflammatory myeloid cells, including Ly6C^hi monocytes and neutrophils, to infected kidneys by driving expression of the chemokines CCL2 and KC. Within kidneys, monocytes differentiate into inflammatory DCs but fail to functionally mature in Ifnar1^−/− mice, as demonstrated by the impaired upregulation of the key activation markers PDCA1 and iNOS. The increased activity of inflammatory monocytes and neutrophils results in hyper-inflammation and lethal kidney pathology. Pharmacological diminution of monocytes and neutrophils by treating mice with pioglitazone, a synthetic agonist of the nuclear receptor peroxisome proliferator-activated receptor-γ (PPAR-γ), strongly reduces renal immunopathology during Ca infection and improves mouse survival. Taken together, our data connect for the first time the sepsis-promoting functions of IFNs-I to the CCL2-mediated recruitment and the activation of inflammatory monocytes/DCs with high host-destructing potency. Moreover, our data demonstrate a therapeutic relevance of PPAR-γ agonists for microbial infectious diseases where inflammatory myeloid cells may contribute to fatal tissue damage.

Inflammation constitutes a major host response in many microbial infections. Innate immune cells orchestrate the inflammatory response to kill pathogens and clear infections. However, invasive infections by pathogenic microbes including the fungus Candida albicans, can result in an uncontrolled hyper-inflammatory response, leading to severe host damage and sepsis. Type I interferons constitute a hallmark of protective innate immunity in viral and bacterial infections, but at the same time have been notoriously known for their sepsis-promoting effects in numerous experimental inflammation models. Here, we show that type I interferon-signaling mediates the lethal hyper-inflammatory response during systemic mouse infections with C. albicans. Following fungal infections, type I interferons promote the recruitment and activation of inflammatory monocytes and neutrophils to infected organs. The high abundance and activity of inflammatory phagocytes lead to fatal tissue damage. Remarkably, we show that the pharmacological suppression of these inflammatory cells with the drug pioglitazone reduces immunopathology and sepsis-related lethality, suggesting a novel therapeutic option to combat fungal sepsis. In conclusion, our data couple the sepsis-promoting role of type I interferons to the host-destructive activity of inflammatory monocytes and neutrophils. We propose that therapeutic approaches dampening hyper-inflammation might be of general importance in microbial diseases where deleterious immunopathology occurs.

Effect of Yiguanjian decoction on cell differentiation and proliferation in CCl4-treated mice

AIM: To investigate the cellular mechanisms of action of Yiguanjian (YGJ) decoction in treatment of chronic hepatic injury.

METHODS: One group of mice was irradiated, and received enhanced green fluorescent protein (EGFP)-positive bone marrow transplants followed by 13 wk of CCl₄ injection and 6 wk of oral YGJ administration. A second group of Institute for Cancer Research mice was treated with 13 wk of CCl₄ injection and 6 wk of oral YGJ administration. Liver function, histological changes in the liver, and Hyp content were analyzed. The expression of α-smooth muscle actin (α-SMA), F4/80, albumin (Alb), EGFP, mitogen-activated protein kinase-2 (PKM2), Ki-67, α fetoprotein (AFP), monocyte chemotaxis protein-1 and CC chemokine receptor 2 were assayed.

RESULTS: As hepatic damage progressed, EGFP-positive marrow cells migrated into the liver and were mainly distributed along the fibrous septa. They showed a conspicuous coexpression of EGFP with α-SMA and F4/80 but no coexpression with Alb. Moreover, the expression of PKM2, AFP and Ki-67 was enhanced dynamically and steadily over the course of liver injury. YGJ abrogated the increases in the number of bone marrow-derived fibrogenic cells in the liver, inhibited expression of both progenitor and mature hepatocyte markers, and reduced fibrogenesis.

CONCLUSION: YGJ decoction improves liver fibrosis by inhibiting the migration of bone marrow cells into the liver as well as inhibiting their differentiation and suppressing the proliferation of both progenitors and hepatocytes in the injured liver.