The multiple roles of monocyte subsets in steady state and inflammation

Polypyrrole/iron-glycol chitosan nanozymes mediate M1 macrophages to enhance the X-ray-triggered photodynamic therapy for bladder cancer by promoting antitumor immunity

X-ray Photodynamic Therapy (XPDT) is an emerging, deeply penetrating, and non-invasive tumor treatment that stimulates robust antitumor immune responses. However, its efficacy is often limited by low therapeutic delivery and immunosuppressant within the tumor microenvironment. This challenge can potentially be addressed by utilizing X-ray responsive iron-glycol chitosan-polypyrrole nanozymes (GCS-I-PPy NZs), which activate M1 macrophages. These nanozymes increase tumor infiltration and enhance the macrophages' intrinsic immune response and their ability to stimulate adaptive immunity. Authors have designed biocompatible, photosensitizer-containing GCS-I-PPy NZs using oxidation/reduction reactions. These nanozymes were internalized by M1 macrophages to form RAW-GCS-I-PPy NZs. Authors' results demonstrated that these engineered macrophages effectively delivered the nanozymes with potentially high tumor accumulation. Within the tumor microenvironment, the accumulated GCS-I-PPy NZs underwent X-ray irradiation, generating reactive oxygen species (ROS). This ROS augmentation significantly enhanced the therapeutic effect of XPDT and synergistically promoted T cell infiltration into the tumor. These findings suggest that nano-engineered M1 macrophages can effectively boost the immune effects of XPDT, providing a promising strategy for enhancing cancer immunotherapy. The ability of GCS-I-PPy NZs to mediate M1 macrophage activation and increase tumor infiltration highlights their potential in overcoming the limitations of current XPDT approaches and improving therapeutic outcomes in melanoma and other cancers.

High-density lipoprotein mimetic nano-therapeutics targeting monocytes and macrophages for improved cardiovascular care: a comprehensive review

The prevalence of cardiovascular diseases continues to be a challenge for global health, necessitating innovative solutions. The potential of high-density lipoprotein (HDL) mimetic nanotherapeutics in the context of cardiovascular disease and the intricate mechanisms underlying the interactions between monocyte-derived cells and HDL mimetic showing their impact on inflammation, cellular lipid metabolism, and the progression of atherosclerotic plaque. Preclinical studies have demonstrated that HDL mimetic nanotherapeutics can regulate monocyte recruitment and macrophage polarization towards an anti-inflammatory phenotype, suggesting their potential to impede the progression of atherosclerosis. The challenges and opportunities associated with the clinical application of HDL mimetic nanotherapeutics, emphasize the need for additional research to gain a better understanding of the precise molecular pathways and long-term effects of these nanotherapeutics on monocytes and macrophages to maximize their therapeutic efficacy. Furthermore, the use of nanotechnology in the treatment of cardiovascular diseases highlights the potential of nanoparticles for targeted treatments. Moreover, the concept of theranostics combines therapy and diagnosis to create a selective platform for the conversion of traditional therapeutic medications into specialized and customized treatments. The multifaceted contributions of HDL to cardiovascular and metabolic health via highlight its potential to improve plaque stability and avert atherosclerosis-related problems. There is a need for further research to maximize the therapeutic efficacy of HDL mimetic nanotherapeutics and to develop targeted treatment approaches to prevent atherosclerosis. This review provides a comprehensive overview of the potential of nanotherapeutics in the treatment of cardiovascular diseases, emphasizing the need for innovative solutions to address the challenges posed by cardiovascular diseases.

Distinct transcriptomic profiles in children prior to the appearance of type 1 diabetes-linked islet autoantibodies and following enterovirus infection

Although the genetic basis and pathogenesis of type 1 diabetes have been studied extensively, how host responses to environmental factors might contribute to autoantibody development remains largely unknown. Here, we use longitudinal blood transcriptome sequencing data to characterize host responses in children within 12 months prior to the appearance of type 1 diabetes-linked islet autoantibodies, as well as matched control children. We report that children who present with insulin-specific autoantibodies first have distinct transcriptional profiles from those who develop GADA autoantibodies first. In particular, gene dosage-driven expression of GSTM1 is associated with GADA autoantibody positivity. Moreover, compared with controls, we observe increased monocyte and decreased B cell proportions 9-12 months prior to autoantibody positivity, especially in children who developed antibodies against insulin first. Lastly, we show that control children present transcriptional signatures consistent with robust immune responses to enterovirus infection, whereas children who later developed islet autoimmunity do not. These findings highlight distinct immune-related transcriptomic differences between case and control children prior to case progression to islet autoimmunity and uncover deficient antiviral response in children who later develop islet autoimmunity.

Decoding the immune landscape following hip fracture in elderly patients: unveiling temporal dynamics through single-cell RNA sequencing

BACKGROUND

Hip fractures in the elderly have significant consequences, stemming from the initial trauma and subsequent surgeries. Hidden blood loss and stress due to concealed injury sites could impact the whole osteoimmune microenvironment. This study employs scRNA-seq technique to map immune profiles in elderly hip fracture patients from post-trauma to the recovery period, investigating the dynamic changes of immune inflammation regulation subgroups.

METHODS

We collected peripheral blood samples from four elderly hip fracture patients (two males and two females, all > 75 years of age) at three different time points (24 h post-trauma, 24 h post-operation, and day 7 post-operation) and applied scRNA-seq technique to analyze the cellular heterogeneity and identify differentially expressed genes in peripheral blood individual immune cells from elderly hip fracture patients.

RESULTS

In this study, we analyzed the composition and gene expression profiles of peripheral blood mononuclear cells (PBMCs) from elderly hip fracture patients by scRNA-seq and further identified new CD14 monocyte subpopulations based on marker genes and transcriptional profiles. Distinct gene expression changes were observed in various cell subpopulations at different time points. C-Mono2 monocyte mitochondria-related genes were up-regulated and interferon-related and chemokine-related genes were down-regulated within 24 h post-operation. Further analysis of gene expression profiles at day 7 post-operation showed that C-Mono2 monocytes showed downregulation of inflammation-related genes and osteoblast differentiation-related genes. However, the expression of these genes in cytotoxic T cells, Treg cells, and B cell subsets exhibited a contrasting trend. GZMK+CD8+ cytotoxic T cells showed downregulation of chemokine-related genes, and Treg cells showed upregulation of genes related to the JAK/STAT signaling pathway. Furthermore, we examined interactions among diverse immune cell subsets, pinpointing specific ligand-receptor pairs. These findings imply cross-talk and communication between various cell types in the post-traumatic immune response.

CONCLUSIONS

Our study elucidates the notable alterations in immune cell subpopulations during different stages of hip fracture in elderly patients, both in terms of proportions and differential gene expressions. These changes provide significant clinical implications for tissue repair, infection prevention, and fracture healing in clinic.

New investigation of anti-inflammatory activity of Polycladia crinita and biosynthesized selenium nanoparticles: isolation and characterization

BACKGROUND

Marine macroalgae have gained interest recently, mostly due to their bioactive components. Polycladia crinita is an example of marine macroalgae from the Phaeophyceae class, also known as brown algae. They are characterized by a variety of bioactive compounds with valuable medical applications. The prevalence of such naturally active marine resources has made macroalgae-mediated manufacturing of nanoparticles an appealing strategy. In the present study, we aimed to evaluate the antioxidant and anti-inflammatory features of an aqueous extract of Polycladia crinita and biosynthesized P. crinita selenium nanoparticles (PCSeNPs) via a carrageenan-induced rat paw edema model. The synthesized PCSeNPs were fully characterized by UV-visible spectroscopy, FTIR, XRD, and EDX analyses.

RESULTS

FTIR analysis of Polycladia crinita extract showed several sharp absorption peaks at 3435.2, 1423.5, and 876.4 cm-1 which represent O-H, C=O and C=C groups. Moreover, the most frequent functional groups identified in P. crinita aqueous extract that are responsible for producing SeNPs are the -NH2-, -C=O-, and -SH- groups. The EDX spectrum analysis revealed that the high percentages of Se and O, 1.09 ± 0.13 and 36.62 ± 0.60%, respectively, confirmed the formation of SeNPs. The percentages of inhibition of the edema in pretreated groups with doses of 25 and 50 mg/kg, i.p., of PCSeNPs were 62.78% and 77.24%, respectively. Furthermore, the pretreated groups with 25, 50 mg/kg of P. crinita extract displayed a substantial decrease in the MDA levels (P < 0.00, 26.9%, and 51.68% decrease, respectively), indicating potent antioxidant effect. Additionally, the pretreated groups with PCSeNPs significantly suppressed the MDA levels (P < 0.00, 54.77%, and 65.08% decreases, respectively). The results of immune-histochemical staining revealed moderate COX-2 and Il-1β expressions with scores 2 and 1 in rats pre-treated with 25 and 50 mg/kg of free extract, respectively. Additionally, the rats pre-treated with different doses of PCSeNPs demonstrated weak COX-2 and Il-1β expressions with score 1 (25 mg/kg) and negative expression with score 0 (50 mg/kg). Both antioxidant and anti-inflammatory effects were dose-dependent.

CONCLUSIONS

These distinguishing features imply that this unique alga is a promising anti-inflammatory agent. Further studies are required to investigate its main active ingredients and possible side effects.

Transcriptomic profile comparison of monocytes from rheumatoid arthritis patients in treatment with methotrexate, anti-TNFa, abatacept or tocilizumab

It is well documented that patients affected by rheumatoid arthritis (RA) have distinct susceptibility to the different biologic DMARDs available on the market, probably because of the many facets of the disease. Monocytes are deeply involved in the pathogenesis of RA and we therefore evaluated and compared the transcriptomic profile of monocytes isolated from patients on treatment with methotrexate alone or in combination with tocilizumab, anti-TNFα or abatacept and from healthy donors. Whole-genome transcriptomics yielded a list of regulated genes by Rank Product statistics and DAVID was then used for functional annotation enrichment analysis. Last, data were validated by qRT-PCR. Abatacept, tocilizumab and anti-TNFa cohorts were separately compared with methotrexate, leading to the identification of 78, 6, and 436 differentially expressed genes, respectively. The upper-most ranked genes were related to inflammatory processes and immune responses. Such an approach draws the genomic profile of monocytes in treated RA patients and lays the basis for finding gene signature for tailored therapeutic choices.

Hyperglycemia remission after Roux-en-Y gastric bypass: Implicated to altered monocyte inflammatory response in type 2 diabetes rats

Hyperglycemia remission by metabolic surgery is implicated in the resolution of low-grade inflammation in type 2 diabetes mellitus (T2DM). However, whether this beneficial effect of metabolic surgery is related to improving monocyte inflammatory response remains undefined. This investigation is addressed to evaluate this relationship. For this purpose, T2DM rats were subjected to Roux-en-Y gastric bypass (RYGB) and/or monocyte depletion or splenic sympathetic denervation. Fasting blood glucose (FBG), plasma tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) were measured, and monocyte inflammatory response was assessed in vitro. The data showed that RYGB significantly reduced lipopolysaccharide (LPS)-induced release of TNF-α and IL-1β from peripheral monocytes while alleviating hyperglycemia and reducing plasma TNF-α and IL-1β levels. Hyperglycemia resulting from monocyte depletion by injection of clodronate liposomes resolved one week earlier than vehicle control after RYGB. Splenic denervation abrogated the glucose-lowering effect and decreased LPS-stimulated TNF-α and IL-1β release from monocytes following RYGB. Overall, our results reveal that a marked reduction of monocyte inflammatory response after RYGB contributes to hyperglycemia remission in T2DM rats. The beneficial effect of RYGB is mediated through vagal-spleen axis anti-inflammatory activity.

HMGB1-Mediated Activation of the Inflammatory-Reparative Response Following Myocardial Infarction

Different cell types belonging to the innate and adaptive immune system play mutually non-exclusive roles during the different phases of the inflammatory-reparative response that occurs following myocardial infarction. A timely and finely regulation of their action is fundamental for the process to properly proceed. The high-mobility group box 1 (HMGB1), a highly conserved nuclear protein that in the extracellular space can act as a damage-associated molecular pattern (DAMP) involved in a large variety of different processes, such as inflammation, migration, invasion, proliferation, differentiation, and tissue regeneration, has recently emerged as a possible regulator of the activity of different immune cell types in the distinct phases of the inflammatory reparative process. Moreover, by activating endogenous stem cells, inducing endothelial cells, and by modulating cardiac fibroblast activity, HMGB1 could represent a master regulator of the inflammatory and reparative responses following MI. In this review, we will provide an overview of cellular effectors involved in these processes and how HMGB1 intervenes in regulating each of them. Moreover, we will summarize HMGB1 roles in regulating other cell types that are involved in the different phases of the inflammatory-reparative response, discussing how its redox status could affect its activity.

Pre-vaccination frequency of circulatory Tfh is associated with robust immune response to TV003 dengue vaccine

It has been estimated that more than 390 million people are infected with Dengue virus every year; around 96 millions of these infections result in clinical pathologies. To date, there is only one licensed viral vector-based Dengue virus vaccine CYD-TDV approved for use in dengue endemic areas. While initially approved for administration independent of serostatus, the current guidance only recommends the use of this vaccine for seropositive individuals. Therefore, there is a critical need for investigating the influence of Dengue virus serostatus and immunological mechanisms that influence vaccine outcome. Here, we provide comprehensive evaluation of sero-status and host immune factors that correlate with robust immune responses to a Dengue virus vector based tetravalent vaccine (TV003) in a Phase II clinical cohort of human participants. We observed that sero-positive individuals demonstrate a much stronger immune response to the TV003 vaccine. Our multi-layered immune profiling revealed that sero-positive subjects have increased baseline/pre-vaccination frequencies of circulating T follicular helper (cTfh) cells and the Tfh related chemokine CXCL13/BLC. Importantly, this baseline/pre-vaccination cTfh profile correlated with the vaccinees' ability to launch neutralizing antibody response against all four sero-types of Dengue virus, an important endpoint for Dengue vaccine clinical trials. Overall, we provide novel insights into the favorable cTfh related immune status that persists in Dengue virus sero-positive individuals that correlate with their ability to mount robust vaccine specific immune responses. Such detailed interrogation of cTfh cell biology in the context of clinical vaccinology will help uncover mechanisms and targets for favorable immuno-modulatory agents.

Neutrophil Homeostasis and Emergency Granulopoiesis: The Example of Systemic Juvenile Idiopathic Arthritis

Neutrophils are key pathogen exterminators of the innate immune system endowed with oxidative and non-oxidative defense mechanisms. More recently, a more complex role for neutrophils as decision shaping cells that instruct other leukocytes to fine-tune innate and adaptive immune responses has come into view. Under homeostatic conditions, neutrophils are short-lived cells that are continuously released from the bone marrow. Their development starts with undifferentiated hematopoietic stem cells that pass through different immature subtypes to eventually become fully equipped, mature neutrophils capable of launching fast and robust immune responses. During severe (systemic) inflammation, there is an increased need for neutrophils. The hematopoietic system rapidly adapts to this increased demand by switching from steady-state blood cell production to emergency granulopoiesis. During emergency granulopoiesis, the de novo production of neutrophils by the bone marrow and at extramedullary sites is augmented, while additional mature neutrophils are rapidly released from the marginated pools. Although neutrophils are indispensable for host protection against microorganisms, excessive activation causes tissue damage in neutrophil-rich diseases. Therefore, tight regulation of neutrophil homeostasis is imperative. In this review, we discuss the kinetics of neutrophil ontogenesis in homeostatic conditions and during emergency myelopoiesis and provide an overview of the different molecular players involved in this regulation. We substantiate this review with the example of an autoinflammatory disease, i.e. systemic juvenile idiopathic arthritis.

Novel population of human monocyte and osteoclast progenitors from pluripotent stem cells and peripheral blood

Osteoclasts are multinuclear cells of monocytic lineage, with the ability to resorb bone. Studies in mouse have identified bone marrow clonal progenitors able to generate mature osteoclast cells (OCs) in vitro and in vivo. These osteoclast progenitors (OCPs) can also generate macrophages and dendritic cells. Interestingly, cells with equivalent potential can be detected in periphery. In humans, cells with OCP activity have been identified in bone marrow and periphery; however, their characterization has not been as extensive. We have developed reproducible methods to derive, from human pluripotent stem cells, a population containing monocyte progenitors able to generate functional OCs. Within this population, we have identified cells with monocyte and osteoclast progenitor activity based on CD11b and CD14 expression. A population double positive for CD11b and CD14 contains cells with expected osteoclastic potential. However, the double negative (DN) population, containing most of the hematopoietic progenitor activity, also presents a very high osteoclastic potential. These progenitor cells can also be differentiated to macrophage and dendritic cells. Further dissection within the DN population identified cells bearing the phenotype CD15-CD115+ as the population with highest monocytic progenitor and osteoclastic potential. When similar methodology was used to identify OCPs from human peripheral blood, we confirmed a published OCP population with the phenotype CD11b+CD14+. In addition, we identified a second population (CD14-CD11bloCD115+) with high monocytic progenitor activity that was also able to form osteoclast like cells, similar to the 2 populations identified from pluripotent stem cells.

Soluble and Microparticle-Based Delivery of TLR4 and TLR9 Agonists Differentially Modulate 3D Chemotaxis of Bone Marrow-Derived Dendritic Cells

Vaccines are commonly administered subcutaneously or intramuscularly, and local immune cells, notably dendritic cells (DCs), play a significant role in transporting vaccine antigens and adjuvants to draining lymph nodes. Here, it is compared how soluble and biomaterial-mediated delivery of Toll-like receptor (TLR)-targeted adjuvants, monophosphoryl lipid A (MPLA, TLR4 ligand) and 5'-C-phosphate-G-3' DNA (CpG DNA, TLR9 ligand), modulate 3D chemotaxis of bone marrow-derived dendritic cells (BMDCs) toward lymphatic chemokine gradients. Within microfluidic devices containing 3D collagen-based matrices to mimic tissue conditions, soluble MPLA increases BMDC chemotaxis toward gradients of CCL19 and CCL21, while soluble CpG has no effect. Delivering CpG on poly(lactic-co-glycolic) acid microparticles (MPs) enhances BMDC chemotaxis compared to MPLA-encapsulated MPs, and when co-delivered, MPLA and CpG do not synergistically enhance BMDC migration. It is concluded that supplementing granulocyte-macrophage colony stimulating factor-derived BMDC culture with interleukin-4 is necessary to induce CCR7 expression and chemotaxis of BMDCs. Different cell subsets in BMDC culture upregulate CCR7 in response to soluble versus biomaterial-loaded MPLA and CpG, and CCR7 expression does not consistently correlate with functional migration. The results show both adjuvant type and delivery method influence chemotaxis of DCs, and these findings uncover new directions for the rational design of vaccine formulations.

Monocyte phenotype as a predictive marker for wound healing in diabetes-related foot ulcers

AIMS

Delayed healing of diabetes-related foot ulcers (DRFUs) is associated with increased macrophage and matrix metalloproteinases (MMPs) at the wound site. Whether circulating monocyte phenotype and/or MMPs are altered in association with wound healing outcome is unknown, and was investigated in this study.

METHODS

Blood was obtained from 21 participants with DRFU, at initial visit (V1), week-4 (V2), and week-8 (V3) for measurement of monocyte number (CD14⁺), phenotype (CD16, CD163) and chemokine receptors (CCRs) by flow cytometry, and circulating MMPs and TIMP-1 by ELISA.

RESULTS

Six wounds healed during the study. At V1, non-classical CD16⁺⁺ monocytes and MMP-3 were higher in healed vs unhealed (both p < 0.05). At V3, the increased %CD16⁺⁺ persisted and %CCR2⁺ was decreased in healed, but no other monocyte markers nor MMP/TIMP differed between groups. Increased wound closure rate (WCR) at V3 correlated with increased %CD16⁺⁺ monocytes and decreased MMP-2 at V1 or V1 + V2. Receiver operating characteristic (ROC) curves yielded an area-under-the-curve of %CD16⁺⁺ at V1 of 0.78 to predict ulcer healing at V3.

CONCLUSIONS

These results indicate that circulating monocyte phenotype and MMPs alter as DRFUs heal. The relationship of %CD16⁺⁺ monocytes with WCR and ROC curve suggest a predictive role of %CD16⁺⁺ monocytes for ulcer healing.

Macrophage 3D migration: A potential therapeutic target for inflammation and deleterious progression in diseases

Macrophages are heterogeneous cells that have different physiological functions, such as chemotaxis, phagocytosis, endocytosis, and secretion of various factors. All physiological functions of macrophages are integral to homeostasis, immune defense and tissue repair. However, in several diseases, macrophages are recruited from the blood towards inflammatory sites. This process is called macrophage migration, which promotes deleterious disease progression. Macrophage migration is a key player in many inflammatory diseases, autoimmune diseases and cancers because it contributes to the accumulation of proinflammatory factors, the destruction of tissues and the development of tumors. Therefore, macrophage migration is proposed to be a potential therapeutic target. Macrophages migrate between two-dimensional (2D) and three-dimensional (3D) environments, implying that distinct migratory features and mechanisms are involved. Compared with the 2D migration of macrophages, 3D migration involves more complex variations in cellular morphology and dynamics. The structure of the extracellular matrix, a key factor, is modified in diseases that influence macrophage 3D migration. Macrophage 3D migration relates to disease pathology. Research that focuses on macrophage 3D migration is an emerging field and was reviewed in this article to indicate the molecular and cellular mechanisms of macrophage migration in 3D environments and to provide potential targets for controlling disease progression associated with this migration.

ERK1/2 Has Divergent Roles in LPS-Induced Microvascular Endothelial Cell Cytokine Production and Permeability

ABSTRACT

Endothelial cells play a major role in inflammatory responses to infection and sterile injury. Endothelial cells express Toll-like receptor 4 (TLR4) and are activated by LPS to express inflammatory cytokines/chemokines, and to undergo functional changes, including increased permeability. The extracellular signal-regulated kinase 1/2 (ERK1/2) mediates pro-inflammatory signaling in monocytes and macrophages, but the role of ERK1/2 in LPS-induced activation of microvascular endothelial cells has not been defined. We therefore studied the role of ERK1/2 in LPS-induced inflammatory activation and permeability of primary human lung microvascular endothelial cells (HMVEC). Inhibition of ERK1/2 augmented LPS-induced IL-6 and vascular cell adhesion protein (VCAM-1) production by HMVEC. ERK1/2 siRNA knockdown also augmented IL-6 production by LPS-treated HMVEC. Conversely, ERK1/2 inhibition abrogated permeability and restored cell-cell junctions of LPS-treated HMVEC. Consistent with the previously described pro-inflammatory role for ERK1/2 in leukocytes, inhibition of ERK1/2 reduced LPS-induced cytokine/chemokine production by primary human monocytes. Our study identifies a complex role for ERK1/2 in TLR4-activation of HMVEC, independent of myeloid differentiation primary response gene (MyD88) and TIR domain-containing adaptor inducing IFN-β (TRIF) signaling pathways. The activation of ERK1/2 limits LPS-induced IL-6 production by HMVEC, while at the same time promoting HMVEC permeability. Conversely, ERK1/2 activation promotes IL-6 production by human monocytes. Our results suggest that ERK1/2 may play an important role in the nuanced regulation of endothelial cell inflammation and vascular permeability in sepsis and injury.

Suppression of macrophage migration by down-regulating Src/FAK/P130Cas activation contributed to the anti-inflammatory activity of sinomenine

A large number of macrophages in inflamed sites not only amplify the severity of inflammatory responses but also contribute to the deleterious progression of many chronic inflammatory diseases, autoimmune diseases and cancers. Macrophage migration is a prerequisite for their entry into inflammatory sites and their participation of macrophages in the pathologic processes. Inhibition of macrophage migration is therefore a potential anti-inflammatory mechanism. Moreover, alleviation of inflammation also prevents the macrophages infiltration. Sinomenine (SIN) is an alkaloid derived from the Chinese medicinal plant Sinomenium acutum. It has multiple pharmacological effects, including anti-inflammation, immunosuppression, and anti-arthritis. However, its anti-inflammatory molecular mechanisms and effect on macrophage migration are not fully understood. The purpose of this research was to investigate the pharmacological effects and the molecular mechanism of SIN on macrophage migration in vivo and in vitro as well as to elucidate its anti-inflammatory mechanisms associated with macrophage migration. Our results showed that SIN reduced the number of RAW264.7 cells migrating into inflammatory paws and blocked lipopolysaccharide (LPS)-induced RAW264.7 cells and bone marrow-derived macrophages (BMDMs) migration in vitro. Furthermore, SIN attenuated the 3D mesenchymal migration of BMDMs. The absence of macrophage migration after circulatory and periphery macrophages depletion led to a reduction in the severity of inflammatory response. In macrophages depleted (macrophages^-/-) mice, as inflammatory severity decreased, RAW264.7 cells migration was suppressed. A non-obvious effect of SIN on the inflammatory response was found in macrophages^-/- mice, while the inhibitory effect of SIN on RAW264.7 cells migration was still observed. Furthermore, the migration of RAW264.7 cells pre-treated with SIN was suppressed in normal mice. Finally, Src/focal adhesion kinase (FAK)/P130Cas axis activation, which supports macrophages mesenchymal migration, and iNOS expression, NO production, integrin αV and in integrin β3 expressions, which promote Src/FAK/P130Cas activation, were down-regulated by SIN. However, SIN had no obvious effect on the expression of the monocyte chemoattractant protein-1 (MCP-1), which is an important chemokine for macrophage migration. These results indicated that SIN significantly inhibited macrophage mesenchymal migration by down-regulating on Src/FAK/P130Cas axis activation. There was a mutual regulatory correlation between the inflammatory response and macrophage migration, and the effects of SIN on macrophage migration were involved in its anti-inflammatory activity.

Granulopoiesis and Neutrophil Homeostasis: A Metabolic, Daily Balancing Act

Granulopoiesis is part of the hematopoietic hierarchic architecture, where hematopoietic stem cells give rise to highly proliferative multipotent and lineage-committed granulocytic progenitor cells that differentiate into unipotent neutrophil progenitors. Given their short lifespan, neutrophils are rapidly cleared from circulation through specialized efferocytic macrophages. Together with an intrinsic clock, these processes contribute to circadian fluctuations, preserving self-tolerance and protection against invading pathogens. However, metabolic perturbation of granulopoiesis and neutrophil homeostasis can result in low-grade chronic inflammation, as observed with aging. During acute pathogenic infections, hematopoiesis can also be switched into emergency mode, which has been recently associated with significant neutrophil functional heterogeneity. This review focuses on a new reassessment of regulatory mechanisms governing neutrophil production, life-cycle, and diversity in health and disease.

Community violence and cellular and cytokine indicators of inflammation in adolescents

Neighborhood violence is associated with a range of health consequences but little is known about the biological processes involved. Research in disease pathogenesis has identified low-grade inflammation as a process that, beginning in the first decades of life, is both induced by chronic stress and a contributor to multiple cardiometabolic diseases that present throughout the lifecourse. Previous research has examined whether neighborhood violence is associated with inflammatory biomarkers, but has been limited to cytokine indicators of inflammation. In a sample of adolescents (n = 203) residing in Chicago, we tested cross-sectional associations between neighborhood violence and cellular and cytokine indicators of inflammation. Neighborhood-level violence was measured in multiple ways (as murder rates of Census block groups and as the sum of homicides within 1 and ½ mile zones) in the areas surrounding where youth lived and attended school. At the individual level, violence exposure was measured by self-report (direct victimization, witnessing violence, and/or victimization of family or friends in the past year). Adolescents residing in high-violence neighborhoods evidenced higher numbers of pro-inflammatory classical (CD14++CD16-) monocytes relative to those in less violent neighborhoods. In contrast, neighborhood-level violence was not consistently associated with cytokine levels across different model specifications. Self-reported violence exposure was also not consistently associated with inflammatory biomarkers. Neighborhood-level violence and self-reported violence exposure interacted, such that the positive association between neighborhood-level violence and classical monocytes was observed only among adolescents who reported being exposed to violence. Associations were largely specific to the neighborhoods in which youth lived as opposed to those in which they attended school. Findings provide the first evidence that youth residing in high-violence neighborhoods show mobilization of classical monocytes, suggesting a pro-inflammatory mechanism through which contextual stressors such as neighborhood violence may compromise health.

Qishen Granule Improved Cardiac Remodeling via Balancing M1 and M2 Macrophages

Macrophages play a pivotal role in myocardial remodeling (MR) process which could eventually lead to heart failure. Splenic monocytes could be mobilized and recruited under inflammatory conditions and differentiated into different types of macrophages in heart tissues. Inflammatory M1 macrophages could aggravate tissue damage whereas M2 macrophages could promote angiogenesis and tissue repair process. Unbalanced ratio of M1/M2 macrophages may eventually lead to adverse remodeling. Therefore, regulating differentiation and activities of macrophages are potential strategies for the management of myocardial remodeling. Qishen Granule (QSG) is an effective Chinese medicine for treating heart failure. Our previous studies demonstrated that QSG could inhibit myocardial fibrosis through regulating secretion of cytokines and activation of macrophages. However, the detailed effects of QSG on had not been elucidated yet. In this study, we aimed to explore the effect of QSG on the release of splenic monocytes, the recruitment of monocytes into heart tissues and the differentiation of macrophages under ischemic conditions. Our results showed that QSG could suppress the release of monocytes from the spleen and recruitment of monocytes to heart tissues via inhibiting splenic angiotensin (Ang) II/AT1-cardiac monocyte chemotactic protein (MCP)-1/CC chemokine receptor 2 (CCR2) pathway. The anti-fibrotic effect of QSG was exerted by inhibiting M1 macrophage-activated transforming growth factor (TGF)-β1/Smad3 pathway. Meanwhile, QSG could promote angiogenesis by promoting differentiation of M1 macrophages into M2 macrophages. Our results suggest that compounds of Chinese medicine have synergistic effects on cardiac and splenic organs through regulating differentiation of monocytes/macrophages in inhibiting myocardial remodeling.

Association between CD16++ monocytes in peripheral blood and clinical features and short-term therapeutic effects of polycystic ovary syndrome

OBJECTIVE

To evaluate the association between CD16⁺⁺ monocytes in peripheral blood and the clinical features and short-term therapeutic effects of polycystic ovary syndrome (PCOS).

METHODS

This prospective cross-sectional study included women diagnosed with PCOS at a University Hospital in Shanghai, China, between June 4 and November 28, 2016. Patients received Diane-35, metformin, or both combined for 3 months. We collected anthropometric measures and used flow cytometry to detect CD16⁺⁺ monocytes.

RESULTS

The final analysis included 70 patients: 18 in the Diane-35 group, 30 in the metformin group, and 22 in the Diane-35 plus metformin group. The control group comprised 60 women without PCOS. The proportion of CD16⁺⁺ monocytes was significantly higher in patients with PCOS than in those with no PCOS (16.05% vs 10.73%; P=0.001). The proportion differed significantly between patients with and those without hyperandrogenism (13.12% vs 17.30%; P=0.002) and showed moderate accuracy in diagnosing hyperandrogenism before treatment. We noted a decrease in monocytes post-treatment in patients given metformin and Diane-35 plus metformin.

CONCLUSIONS

The proportion of CD16⁺⁺ monocytes was most significantly associated with hyperandrogenism before treatment. Our findings suggest that the proportion of CD16⁺⁺ monocytes in peripheral blood might be related to the inflammatory condition of PCOS.

TNF-α Inhibitors Decrease Classical CD14hiCD16- Monocyte Subsets in Highly Active, Conventional Treatment Refractory Rheumatoid Arthritis and Ankylosing Spondylitis

Monocytes are pivotal cells in inflammatory joint diseases. We aimed to determine the effect of TNF-α inhibitors (TNFi) on peripheral blood monocyte subpopulations and their activation in ankylosing spondylitis (AS) and rheumatoid arthritis (RA) patients with high disease activity. To address this, we studied 50 (32 AS, 18 RA) patients with highly active disease with no prior history of TNFi use who were recruited and assigned to TNFi or placebo treatment for 12 weeks. Cytometric and clinical assessment was determined at baseline, four, and 12 weeks after initiation of TNFi treatment. We observed that treatment with TNFi led to a significant decrease in CD14^hiCD16- monocytes in comparison to placebo, while circulating CD14^dimCD16+ monocytes significantly increased. The TNFi-induced monocyte subset shifts were similar in RA and AS patients. While the percentage of CD14^dimCD16+ monocytes increased, expression of CD11b and CD11c integrins on their surface was significantly reduced by TNFi. Additionally, CD45RA+ cells were more frequent. The shift towards nonclassical CD14^dimCD16+ monocytes in peripheral blood due to TNFi treatment was seen in both AS and RA. This may reflect reduced recruitment of these cells to sites of inflammation due to lower inflammatory burden, which is associated with decreased disease activity.

The Role of Norepinephrine and α-Adrenergic Receptors in Acute Stress-Induced Changes in Granulocytes and Monocytes

OBJECTIVE

Acute stress induces redistribution of circulating leucocytes in humans. Although effects on lymphocytes as adaptive immune cells are well understood, the mechanisms underlying stress effects on granulocytes and monocytes as innate immune blood cells are still elusive. We investigated whether the stress hormone norepinephrine (NE) and α-adrenergic receptors (α-ADRs) may play a mediating role.

METHODS

In a stress study, we cross-sectionally tested 44 healthy men for associations between stress-induced NE increases and simultaneous granulocyte and monocyte cell count increases, as measured immediately before and several times after the Trier Social Stress Test. In a subsequent infusion study, 21 healthy men participated in three different experimental trials with sequential infusions of 1- and 15-minute duration with varying substances (saline as placebo, the nonspecific α-ADR blocker phentolamine [2.5 mg/min], and NE [5 μg/min]): trial 1 = saline+saline, trial 2 = saline+NE, trial 3 = phentolamine+NE. Granulocyte and monocyte cell numbers were assessed before, immediately after, 10 minutes, and 30 minutes after infusion procedures.

RESULTS

In the stress study, higher NE related to higher neutrophil stress changes (β = .31, p = .045, R change = .09), but not epinephrine stress changes. In the infusion study, saline+NE induced significant increases in neutrophil (F(3/60) = 43.50, p < .001, η = .69) and monocyte (F(3/60) = 18.56, p < .001, η = .48) numbers compared with saline+saline. With phentolamine+NE, neutrophil (F(3/60) = 14.41, p < .001, η = .42) and monocyte counts (F(2.23/44.6) = 4.32, p = .016, η = .18) remained increased compared with saline+saline but were lower compared with saline+NE (neutrophils: F(3/60) = 19.55, p < .001, η = .494, monocytes: F(3/60) = 2.54, p = .065, η = .11) indicating partial mediation by α-ADRs. Trials did not differ in eosinophil and basophil count reactivity.

CONCLUSIONS

Our findings suggest that NE-induced immediate increases in neutrophil and monocyte numbers resemble psychosocial stress effects and can be reduced by blockade of α-ADRs.

Monocyte Subsets: Phenotypes and Function in Tuberculosis Infection

Monocytes are critical defense components that play an important role in the primary innate immune response. The heterogeneous nature of monocytes and their ability to differentiate into either monocyte-derived macrophages or monocyte-derived dendritic cells allows them to serve as a bridge between the innate and adaptive immune responses. Current studies of monocytes based on immunofluorescence, single-cell RNA sequencing and whole mass spectrometry finger printing reveals different classification systems for monocyte subsets. In humans, three circulating monocyte subsets are classified based on relative expression levels of CD14 and CD16 surface proteins, namely classical, intermediate and non-classical subsets. Transcriptomic analyses of these subsets help to define their distinct functional properties. Tuberculosis (TB) is a disease instigated by the deadly pathogen Mycobacterium tuberculosis. Current research on monocytes in TB has indicated that there are alterations in the frequency of intermediate and non-classical subsets suggesting their impact in bacterial persistence. In this review, we will focus on these monocyte subsets, including their classification, frequency distribution, cytokine profiles, role as a biomarker and will comment on future directions for understanding the salient phenotypic and functional properties relevant to TB pathogenesis.

Dextran‑coated superparamagnetic iron oxide nanoparticles activate the MAPK pathway in human primary monocyte cells

With the increase in applications of superparamagnetic iron oxide nanoparticles (SPIONs) in biomedicine, it is essential to investigate the bio‑security of these nanoparticles, especially with respect to the human immune system. In the present study, the biological effects of dextran‑coated superparamagnetic iron oxide nanoparticles (Dex‑SPIONs) on human primary monocyte cells were evaluated. The results of the present study demonstrated that Dex‑SPIONs can be identified in phagosomes or freed in the cytoplasm and did not affect cell viability or induce apoptosis. Notably, there were certain bulky vacuoles and a number of pseudopodia from the cell membrane, suggesting potential activation of human monocyte cells. In addition, the expression levels of pro‑inflammatory cytokines interleukin (IL)‑1β and tumor necrosis factor (TNF)‑α were also increased following treatment with Dex‑SPIONs. Simultaneously, the phosphorylation levels of mitogen‑activated protein kinase (MAPK) p38, c‑Jun N‑terminal kinase 1 and extracellular signal regulated kinase were markedly enhanced following nanoparticle exposure and MAPK inhibitors could abate the production of IL‑1β and TNF‑α. The results of the present study demonstrated that Dex‑SPIONs could activate human monocyte cells and that activation of MAPK pathway may be involved in these effects.

Stability of Cellular Immune Parameters over 12 Weeks in Patients with Major Depression or Somatoform Disorder and in Healthy Controls

OBJECTIVE

Cellular immune status in major depression (MD) patients differs from that in somatoform disorder (SFD) patients and healthy controls (HC). It is still questionable whether the patterns of immune parameters remain stable over time. Therefore, we studied lymphocyte and monocyte cell counts and neopterin levels in peripheral blood of MD and SFD patients and HC over 12 weeks and tested for correlations between biochemical and psychometric parameters.

METHODS

Thirty-nine patients with MD, 27 with SFD, and 51 HC were recruited. Peripheral blood was drawn at four visits, at 4-week intervals. We assessed the total cell count of B lymphocytes, natural killer (NK) cells, T lymphocyte subpopu-lations, and monocytes by flow cytometry, and neopterin serum levels by ELISA. Psychometric parameters were measured with questionnaires.

RESULTS

Counts of lymphocytes, monocytes, and neopterin were stable in the SFD and HC groups. In the MD group, total CD3+, CD3+CD8+, NK cells, and CD3+CD25+ T cells showed inhomogeneous variances in Friedman tests, particularly in females. Neopterin correlated with depressed mood in MD patients, and with body mass index in HC.

CONCLUSIONS

Cellular immune parameters are stable in HC and SFD. Our results may indicate influences of MD and gender on some cellular immune parameters. This may need to be considered in future immunological studies.

Monocyte subsets exhibit transcriptional plasticity and a shared response to interferon in SIV-infected rhesus macaques

The progression to AIDS is influenced by changes in the biology of heterogeneous monocyte subsets. Classical (CD14++CD16-), intermediate (CD14++CD16+), and nonclassical (CD14+CD16++) monocytes may represent progressive stages of monocyte maturation or disparate myeloid lineages with different turnover rates and function. To investigate the relationship between monocyte subsets and the response to SIV infection, we performed microarray analysis of monocyte subsets in rhesus macaques at three time points: prior to SIV infection, 26 days postinfection, and necropsy with AIDS. Genes with a 2-fold change between monocyte subsets (2023 genes) or infection time points (424 genes) were selected. We identify 172 genes differentially expressed among monocyte subsets in both uninfected and SIV-infected animals. Classical monocytes express genes associated with inflammatory responses and cell proliferation. Nonclassical monocytes express genes associated with activation, immune effector functions, and cell cycle inhibition. The classical and intermediate subsets are most similar at all time points, and transcriptional similarity between intermediate and nonclassical monocytes increases with AIDS. Cytosolic sensors of nucleic acids, restriction factors, and IFN-stimulated genes are induced in all three subsets with AIDS. We conclude that SIV infection alters the transcriptional relationship between monocyte subsets and that the innate immune response to SIV infection is conserved across monocyte subsets.

Iron oxide nanoparticles and induced autophagy in human monocytes

Superparamagnetic iron oxide nanoparticles have been widely used in biomedical applications, but understanding of their interactions with the biological immune system is relatively limited. This work is focused on dextran-coated iron oxide nanoparticles and their induced autophagy in human monocytes. We found that these nanoparticles can be taken up by human monocytes, followed by localization within vesicles or free in cytoplasm. Autophagosome formation was observed with increased expression of LC3II protein, the specific marker of autophagy. The autophagy substrate p62 was degraded in a dose-dependent manner, and autophagy was blocked by autophagy (or lysosome) inhibitors alone or along with iron oxide nanoparticles, indicating that autophagosome accumulation was mainly due to autophagy induction, rather than blockade of autophagy flux. Interestingly, iron oxide nanoparticles increased the viability of human monocytes, but the mechanism was not clear. We further found that inhibition of autophagy mostly attenuated the survival of cells, with acceleration of the inflammation induced by these nanoparticles. Taken together, autophagic activation in human monocytes may play a protective role against the cytotoxicity of iron oxide nanoparticles.

Social regulation of the lymph node transcriptome in rhesus macaques (Macaca mulatta)

Previous research has shown that adverse social conditions may promote a conserved transcriptional response to adversity (CTRA) involving up-regulation of proinflammatory gene expression and down-regulation of Type I interferon anti-viral genes in circulating blood cells. However, the impact of social conditions on lymphoid tissue gene regulation remains largely unexplored. This project assessed how social instability in adult male rhesus macaques (N=10, 5 in unstable, and 5 in stable social conditions) might regulate gene expression within secondary lymphoid tissue (lymph nodes; LN). Unstable social conditions down-regulated axillary LN expression of genes involved in Type I interferon anti-viral responses. Transcript origin analyses implicated monocytes and B cells as cellular mediators of these effects, and promoter-based bioinformatics analyses indicated reduced activity of AP-1, NF-κB, IRF, and CREB transcription factors within the axillary LN microenvironment. Although the current study is limited in sample size, these results suggest that social influences on immune cell gene regulation extend beyond the circulating leukocyte pool to alter generalized transcriptome profiles in secondary lymphoid tissue, and they do so in a regulatory program that resembles the pattern of antiviral inhibition previously observed in circulating leukocytes.

Resting and injury-induced inflamed periosteum contain multiple macrophage subsets that are located at sites of bone growth and regeneration

Better understanding of bone growth and regeneration mechanisms within periosteal tissues will improve understanding of bone physiology and pathology. Macrophage contributions to bone biology and repair have been established but specific investigation of periosteal macrophages has not been undertaken. We used an immunohistochemistry approach to characterize macrophages in growing murine bone and within activated periosteum induced in a mouse model of bone injury. Osteal tissue macrophages (osteomacs) and resident macrophages were distributed throughout resting periosteum. In tissues collected from 4-week-old mice, osteomacs were observed intimately associated with sites of periosteal diaphyseal and metaphyseal bone dynamics associated with normal growth. This included F4/80⁺Mac-2^-/low osteomac association with extended tracks of bone formation (modeling) on diphyseal periosteal surfaces. Although this recapitulated endosteal osteomac characteristics, there was subtle variance in the morphology and spatial organization of periosteal modeling-associated osteomacs, which likely reflects the greater structural complexity of periosteum. Osteomacs, resident macrophages and inflammatory macrophages (F4/80⁺Mac-2^hi) were associated with the complex bone dynamics occurring within the periosteum at the metaphyseal corticalization zone. These three macrophage subsets were also present within activated native periosteum after bone injury across a 9-day time course that spanned the inflammatory through remodeling bone healing phases. This included osteomac association with foci of endochondral ossification within the activated native periosteum. These observations confirm that osteomacs are key components of both osteal tissues, in spite of salient differences between endosteal and periosteal structure and that multiple macrophage subsets are involved in periosteal bone dynamics.

The spleen as an extramedullary source of inflammatory cells responding to acetaminophen-induced liver injury

Macrophages have been shown to play a role in acetaminophen (APAP)-induced hepatotoxicity, contributing to both pro- and anti-inflammatory processes. In these studies, we analyzed the role of the spleen as an extramedullary source of hepatic macrophages. APAP administration (300mg/kg, i.p.) to control mice resulted in an increase in CD11b(+) infiltrating Ly6G(+) granulocytic and Ly6G(-) monocytic cells in the spleen and the liver. The majority of the Ly6G(+) cells were also positive for the monocyte/macrophage activation marker, Ly6C, suggesting a myeloid derived suppressor cell (MDSC) phenotype. By comparison, Ly6G(-) cells consisted of 3 subpopulations expressing high, intermediate, and low levels of Ly6C. Splenectomy was associated with increases in mature (F4/80(+)) and immature (F4/80(-)) pro-inflammatory Ly6C(hi) macrophages and mature anti-inflammatory (Ly6C(lo)) macrophages in the liver after APAP; increases in MDSCs were also noted in the livers of splenectomized (SPX) mice after APAP. This was associated with increases in APAP-induced expression of chemokine receptors regulating pro-inflammatory (CCR2) and anti-inflammatory (CX3CR1) macrophage trafficking. In contrast, APAP-induced increases in pro-inflammatory galectin-3(+) macrophages were blunted in livers of SPX mice relative to control mice, along with hepatic expression of TNF-α, as well as the anti-inflammatory macrophage markers, FIZZ-1 and YM-1. These data demonstrate that multiple subpopulations of pro- and anti-inflammatory cells respond to APAP-induced injury, and that these cells originate from distinct hematopoietic reservoirs.

Glucocorticoids enhance the in vivo migratory response of human monocytes

Glucocorticoids (GCs) are best known for their potent anti-inflammatory effects. However, an emerging model for glucocorticoid (GC) regulation of in vivo inflammation also includes a delayed, preparatory effect that manifests as enhanced inflammation following exposure to an inflammatory stimulus. When GCs are transiently elevated in vivo following exposure to a stressful event, this model proposes that a subsequent period of increased inflammatory responsiveness is adaptive because it enhances resistance to a subsequent stressor. In the present study, we examined the migratory response of human monocytes/macrophages following transient in vivo exposure to stress-associated concentrations of cortisol. Participants were administered cortisol for 6h to elevate in vivo cortisol levels to approximate those observed during major systemic stress. Monocytes in peripheral blood and macrophages in sterile inflammatory tissue (skin blisters) were studied before and after exposure to cortisol or placebo. We found that exposure to cortisol induced transient upregulation of monocyte mRNA for CCR2, the receptor for monocyte chemotactic protein-1 (MCP-1/CCL2) as well as for the chemokine receptor CX3CR1. At the same time, mRNA for the transcription factor IκBα was decreased. Monocyte surface expression of CCR2 but not CX3CR1 increased in the first 24h after cortisol exposure. Transient exposure to cortisol also led to an increased number of macrophages and neutrophils in fluid derived from a sterile inflammatory site in vivo. These findings suggest that the delayed, pro-inflammatory effects of cortisol on the human inflammatory responses may include enhanced localization of effector cells at sites of in vivo inflammation.

Tuberculosis is associated with expansion of a motile, permissive and immunomodulatory CD16(+) monocyte population via the IL-10/STAT3 axis

The human CD14(+) monocyte compartment is composed by two subsets based on CD16 expression. We previously reported that this compartment is perturbed in tuberculosis (TB) patients, as reflected by the expansion of CD16(+) monocytes along with disease severity. Whether this unbalance is beneficial or detrimental to host defense remains to be elucidated. Here in the context of active TB, we demonstrate that human monocytes are predisposed to differentiate towards an anti-inflammatory (M2-like) macrophage activation program characterized by the CD16(+)CD163(+)MerTK(+)pSTAT3(+) phenotype and functional properties such as enhanced protease-dependent motility, pathogen permissivity and immunomodulation. This process is dependent on STAT3 activation, and loss-of-function experiments point towards a detrimental role in host defense against TB. Importantly, we provide a critical correlation between the abundance of the CD16(+)CD163(+)MerTK(+)pSTAT3(+) cells and the progression of the disease either at the local level in a non-human primate tuberculous granuloma context, or at the systemic level through the detection of the soluble form of CD163 in human sera. Collectively, this study argues for the pathogenic role of the CD16(+)CD163(+)MerTK(+)pSTAT3(+) monocyte-to-macrophage differentiation program and its potential as a target for TB therapy, and promotes the detection of circulating CD163 as a potential biomarker for disease progression and monitoring of treatment efficacy.

Vascular endothelial cell Toll-like receptor pathways in sepsis

The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.

Pathophysiology of Myocardial Infarction

Myocardial infarction is defined as sudden ischemic death of myocardial tissue. In the clinical context, myocardial infarction is usually due to thrombotic occlusion of a coronary vessel caused by rupture of a vulnerable plaque. Ischemia induces profound metabolic and ionic perturbations in the affected myocardium and causes rapid depression of systolic function. Prolonged myocardial ischemia activates a "wavefront" of cardiomyocyte death that extends from the subendocardium to the subepicardium. Mitochondrial alterations are prominently involved in apoptosis and necrosis of cardiomyocytes in the infarcted heart. The adult mammalian heart has negligible regenerative capacity, thus the infarcted myocardium heals through formation of a scar. Infarct healing is dependent on an inflammatory cascade, triggered by alarmins released by dying cells. Clearance of dead cells and matrix debris by infiltrating phagocytes activates anti-inflammatory pathways leading to suppression of cytokine and chemokine signaling. Activation of the renin-angiotensin-aldosterone system and release of transforming growth factor-β induce conversion of fibroblasts into myofibroblasts, promoting deposition of extracellular matrix proteins. Infarct healing is intertwined with geometric remodeling of the chamber, characterized by dilation, hypertrophy of viable segments, and progressive dysfunction. This review manuscript describes the molecular signals and cellular effectors implicated in injury, repair, and remodeling of the infarcted heart, the mechanistic basis of the most common complications associated with myocardial infarction, and the pathophysiologic effects of established treatment strategies. Moreover, we discuss the implications of pathophysiological insights in design and implementation of new promising therapeutic approaches for patients with myocardial infarction.

Low Counts of B Cells, Natural Killer Cells, Monocytes, Dendritic Cells, Basophils, and Eosinophils are Associated with Postengraftment Infections after Allogeneic Hematopoietic Cell Transplantation

Hematopoietic cell transplant (HCT) recipients are immunocompromised and thus predisposed to infections. We set out to determine the deficiency of which immune cell subset(s) may predispose to postengraftment infections. We determined day 28, 56, 84, and 180 blood counts of multiple immune cell subsets in 219 allogeneic transplant recipients conditioned with busulfan, fludarabine, and Thymoglobulin. Deficiency of a subset was considered to be associated with infections if the low subset count was significantly associated with subsequent high infection rate per multivariate analysis in both discovery and validation cohorts. Low counts of monocytes (total and inflammatory) and basophils, and low IgA levels were associated with viral infections. Low plasmacytoid dendritic cell (PDC) counts were associated with bacterial infections. Low inflammatory monocyte counts were associated with fungal infections. Low counts of total and naive B cells, total and CD56(high) natural killer (NK) cells, total and inflammatory monocytes, myeloid dendritic cells (MDCs), PDCs, basophils and eosinophils, and low levels of IgA were associated with any infections (due to any pathogen or presumed). In conclusion, deficiencies of B cells, NK cells, monocytes, MDCs, PDCs, basophils, eosinophils, and/or IgA plasma cells appear to predispose to postengraftment infections.

Hck/Fgr Kinase Deficiency Reduces Plaque Growth and Stability by Blunting Monocyte Recruitment and Intraplaque Motility

BACKGROUND

Leukocyte migration is critical for the infiltration of monocytes and accumulation of monocyte-derived macrophages in inflammation. Considering that Hck and Fgr are instrumental in this process, their impact on atherosclerosis and on lesion inflammation and stability was evaluated.

METHODS AND RESULTS

Hematopoietic Hck/Fgr-deficient, LDLr(-/-) chimeras, obtained by bone marrow transplantation, had smaller but, paradoxically, less stable lesions with reduced macrophage content, overt cap thinning, and necrotic core expansion as the most prominent features. Despite a Ly6C(high)-skewed proinflammatory monocyte phenotype, Hck/Fgr deficiency led to disrupted adhesion of myeloid cells to and transmigration across endothelial monolayers in vitro and atherosclerotic plaques in vivo, as assessed by intravital microscopy, flow cytometry, and histological examination of atherosclerotic arteries. Moreover, Hck/Fgr-deficient macrophages showed blunted podosome formation and mesenchymal migration capacity. In consequence, transmigrated double-knockout macrophages were seen to accumulate in the fibrous cap, potentially promoting its focal erosion, as observed for double-knockout chimeras.

CONCLUSIONS

The hematopoietic deficiency of Hck and Fgr led to attenuated atherosclerotic plaque formation by abrogating endothelial adhesion and transmigration; paradoxically, it also promoted plaque instability by causing monocyte subset imbalance and subendothelial accumulation, raising a note of caution regarding src kinase-targeted intervention in plaque inflammation.

Cytomegalovirus immune evasion of myeloid lineage cells

Cytomegalovirus (CMV) evades the immune system in many different ways, allowing the virus to grow and its progeny to spread in the face of an adverse environment. Mounting evidence about the antiviral role of myeloid immune cells has prompted the research of CMV immune evasion mechanisms targeting these cells. Several cells of the myeloid lineage, such as monocytes, dendritic cells and macrophages, play a role in viral control, but are also permissive for CMV and are naturally infected by it. Therefore, CMV evasion of myeloid cells involves mechanisms that qualitatively differ from the evasion of non-CMV-permissive immune cells of the lymphoid lineage. The evasion of myeloid cells includes effects in cis, where the virus modulates the immune signaling pathways within the infected myeloid cell, and those in trans, where the virus affects somatic cells targeted by cytokines released from myeloid cells. This review presents an overview of CMV strategies to modulate and evade the antiviral activity of myeloid cells in cis and in trans.

Tracking mouse bone marrow monocytes in vivo

Real time multiphoton imaging provides a great opportunity to study cell trafficking and cell-to-cell interactions in their physiological 3-dimensionnal environment. Biological activities of immune cells mainly rely on their motility capacities. Blood monocytes have short half-life in the bloodstream; they originate in the bone marrow and are constitutively released from it. In inflammatory condition, this process is enhanced, leading to blood monocytosis and subsequent infiltration of the peripheral inflammatory tissues. Identifying the biomechanical events controlling monocyte trafficking from the bone marrow towards the vascular network is an important step to understand monocyte physiopathological relevance. We performed in vivo time-lapse imaging by two-photon microscopy of the skull bone marrow of the Csf1r-Gal4VP16/UAS-ECFP (MacBlue) mouse. The MacBlue mouse expresses the fluorescent reporters enhanced cyan fluorescent protein (ECFP) under the control of a myeloid specific promoter, in combination with vascular network labelling. We describe how this approach enables the tracking of individual medullar monocytes in real time to further quantify the migratory behaviour within the bone marrow parenchyma and the vasculature, as well as cell-to-cell interactions. This approach provides novel insights into the biology of the bone marrow monocyte subsets and allows to further address how these cells can be influenced in specific pathological conditions.

The number of circulating monocytes as biomarkers of the clinical response to methotrexate in untreated patients with rheumatoid arthritis

Background

The aim of this work was to analyze the number and distribution of circulating monocytes, and of their CD14^+highCD16⁻, CD14^+highCD16⁺ and CD14^+lowCD16⁺ subset cells, in treatment-naive patients with rheumatoid arthritis (RA), and to determine their value in predicting the clinical response to methotrexate (MTX) treatment.

Methods

This prospective work investigated the number of circulating monocytes, and the numbers of CD14^+highCD16⁻, CD14^+highCD16⁺ and CD14^+lowCD16⁺ subset cells, in 52 untreated patients with RA before MTX treatment, and at 3 and 6 months into treatment, using flow cytometry.

Results

The absolute number of circulating monocytes, and the numbers of CD14^+highCD16⁻, CD14^+highCD16⁺ and CD14^+lowCD16⁺ subset cells, were significantly higher in MTX non-responders than in responders and healthy controls before starting and throughout treatment. Responders showed normal numbers of monocytes, and of their subset cells, over the study period. The pre-treatment absolute number of circulating monocytes, and the numbers of CD14^+highCD16⁻ and CD14^+highCD16⁺ subset cells, were found to be predictive of the clinical response to MTX, with a sensitivity and specificity of >70% and >88%, respectively.

Conclusions

Treatment-naive patients with RA showed an anomalous distribution of circulating monocyte subsets, and an anomalous number of cells in each subset. A higher pre-treatment number of circulating monocytes, and higher numbers of CD14^+highCD16⁻ and CD14^+highCD16⁺ subset cells, predict a reduced clinical response to MTX in untreated patients with RA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0375-y) contains supplementary material, which is available to authorized users.

Kruppel-like factor KLF4 facilitates cutaneous wound healing by promoting fibrocyte generation from myeloid-derived suppressor cells

Pressure ulcers (PUs) are serious skin injuries whereby the wound healing process is frequently stalled in the inflammatory phase. Myeloid-derived suppressor cells (MDSCs) accumulate as a result of inflammation and promote cutaneous wound healing by mechanisms not fully understood. Recently, MDSCs have been shown to differentiate into fibrocytes which serve as emerging effector cells that enhance cell proliferation in wound healing. We postulate that in wound healing, MDSCs not only execute their immunosuppressive function to regulate inflammation, but also stimulate cell proliferation once they differentiate into fibrocytes. In the current study, using full thickness and pressure ulcer mouse models, we found that KLF4 deficiency resulted in decreased accumulation of MDSCs and fibrocytes and wound healing was significantly delayed. Conversely, KLF4 activation by the plant-derived product, Mexicanin I, increased the numbers of MDSCs and fibrocytes and accelerated wound healing. Collectively, our study revealed a previously unreported function of MDSCs in cutaneous wound healing and identified Mexicanin I as a potential agent to accelerate PU wound healing.

Serial characterisation of monocyte and neutrophil function after lung resection

Objectives

The primary aim of this prospective study was to perform a comprehensive serial characterisation of monocyte and neutrophil function, circulating monocyte subsets, and bronchoalveolar lavage (BAL) fluid after lung resection. A secondary aim was to perform a pilot, hypothesis-generating evaluation of whether innate immune parameters were associated with postoperative pneumonia.

Methods

Forty patients undergoing lung resection were studied in detail. Blood monocytes and neutrophils were isolated preoperatively and at 6, 24 and 48 h postoperatively. BAL was performed preoperatively and immediately postoperatively. Monocyte subsets, monocyte responsiveness to lipopolysaccharide (LPS) and neutrophil phagocytic capacity were quantified at all time points. Differential cell count, protein and cytokine concentrations were measured in BAL. Pneumonia evaluation at 72 h was assessed using predefined criteria.

Results

After surgery, circulating subsets of classical and intermediate monocytes increased significantly. LPS-induced release of proinflammatory cytokines from monocytes increased significantly and by 48 h a more proinflammatory profile was found. Neutrophil phagocytosis demonstrated a small but significant fall. Factors associated with postoperative pneumonia were: increased release of specific proinflammatory and anti-inflammatory cytokines from monocytes; preoperative neutrophilia; and preoperative BAL cell count.

Conclusions

We conclude that postoperative lung inflammation is associated with specific changes in the cellular innate immune response, a better understanding of which may improve patient selection and prediction of complications in the future.

Shear flow affects selective monocyte recruitment into MCP-1-loaded scaffolds

Novel cardiovascular replacements are being developed by using degradable synthetic scaffolds, which function as a temporary guide to induce neotissue formation directly in situ. Priming of such scaffolds with fast-releasing monocyte chemoattractant protein-1 (MCP-1) was shown to improve the formation of functional neoarteries in rats. However, the underlying mechanism has not been clarified. Therefore, the goal of this study was to investigate the effect of a burst-release of MCP-1 from a synthetic scaffold on the local recruitment of circulating leucocytes under haemodynamic conditions. Herein, we hypothesized that MCP-1 initiates a desired healing cascade by recruiting favourable monocyte subpopulations into the implanted scaffold. Electrospun poly(ε-caprolactone) scaffolds were loaded with fibrin gel containing various doses of MCP-1 and exposed to a suspension of human peripheral blood mononuclear cells in static or dynamic conditions. In standard migration assay, a dose-dependent migration of specific CD14⁺ monocyte subsets was observed, as measured by flow cytometry. In conditions of pulsatile flow, on the other hand, a marked increase in immediate monocyte recruitment was observed, but without evident selectivity in monocyte subsets. This suggests that the selectivity was dependent on the release kinetics of the MCP-1, as it was overruled by the effect of shear stress after the initial burst-release. Furthermore, these findings demonstrate that local recruitment of specific MCP-1-responsive monocytes is not the fundamental principle behind the improved neotissue formation observed in long-term in vivo studies, and mobilization of MCP-1-responsive cells from the bone marrow into the bloodstream is suggested to play a predominant role in vivo.

MARCOing monocytes for elimination

Eliminating inflammatory monocytes using microparticles that bind to the MARCO receptor represents a promising strategy to reduce inflammation and injury (Getts et al., this issue).

Nitric oxide production by monocytes in children with OSA and endothelial dysfunction

Endothelial dysfunction in the context of paediatric sleep apnoea is associated with distinctive alterations in circulating monocyte subsets and reduced NO production by monocytes.

The dynamic lives of macrophage and dendritic cell subsets in atherosclerosis

Atherosclerosis, the major pathological process through which arterial plaques are formed, is a dynamic chronic inflammatory disease of large- and medium-sized arteries in which the vasculature, lipid metabolism, and the immune system all play integral roles. Both the innate and adaptive immune systems are involved in the development and progression of atherosclerosis but myeloid cells represent the major component of the burgeoning atherosclerotic plaque. Various myeloid cells, including monocytes, macrophages (MΦs), and dendritic cells (DCs) can be found within the healthy and atherosclerotic arterial wall, where they can contribute to or regulate inflammation. However, the precise behaviors and functions of these cells in situ are still active areas of investigation that continue to yield exciting and surprising new data. Here, we review recent progress in understanding of the complex biology of MΦs and DCs, focusing particularly on the dynamic regulation of these subsets in the arterial wall and novel, emerging functions of these cells during atherogenesis.

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.

From proliferation to proliferation: monocyte lineage comes full circle

Monocytes are mononuclear circulating phagocytes that originate in the bone marrow and give rise to macrophages in peripheral tissue. For decades, our understanding of monocyte lineage was bound to a stepwise model that favored an inverse relationship between cellular proliferation and differentiation. Sophisticated molecular and surgical cell tracking tools have transformed our thinking about monocyte topo-ontogeny and function. Here, we discuss how recent studies focusing on progenitor proliferation and differentiation, monocyte mobilization and recruitment, and macrophage differentiation and proliferation are reshaping knowledge of monocyte lineage in steady state and disease.

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.