Macrophage polarization in metabolic disorders: functions and regulation

Immunological dynamics in MASH: from landscape analysis to therapeutic intervention

Metabolic dysfunction-associated steatohepatitis (MASH), previously known as nonalcoholic steatohepatitis (NASH), is a multifaceted liver disease characterized by inflammation and fibrosis that develops from simple steatosis. Immune and inflammatory pathways have a central role in the pathogenesis of MASH, yet, how to target immune pathways to treat MASH remains perplexed. This review emphasizes the intricate role that immune cells play in the etiology and pathophysiology of MASH and highlights their significance as targets for therapeutic approaches. It discusses both current strategies and novel therapies aimed at modulating the immune response in MASH. It also highlights challenges in liver-specific drug delivery, potential off-target effects, and difficulties in targeting diverse immune cell populations within the liver. This review is a comprehensive resource that integrates current knowledge with future perspectives in the evolving field of MASH, with the goal of driving forward progress in medical therapies designed to treat this complex liver disease.

Reversal of atherosclerosis by restoration of vascular copper homeostasis

Atherosclerosis has traditionally been considered as a disorder characterized by the accumulation of cholesterol and thrombotic materials within the arterial wall. However, it is now understood to be a complex inflammatory disease involving multiple factors. Central to the pathogenesis of atherosclerosis are the interactions among monocytes, macrophages, and neutrophils, which play pivotal roles in the initiation, progression, and destabilization of atherosclerotic lesions. Recent advances in our understanding of atherosclerosis pathogenesis, coupled with results obtained from experimental interventions, lead us to propose the hypothesis that atherosclerosis may be reversible. This paper outlines the evolution of this hypothesis and presents corroborating evidence that supports the potential for atherosclerosis regression through the restoration of vascular copper homeostasis. We posit that these insights may pave the way for innovative therapeutic approaches aimed at the reversal of atherosclerosis.

IL-31-dependent neurogenic inflammation restrains cutaneous type 2 immune response in allergic dermatitis

Despite robust literature associating IL-31 with pruritic inflammatory skin diseases, its influence on cutaneous inflammation and the interplay between inflammatory and neurosensory pathways remain unmapped. Here, we examined the consequences of disrupting Il31 and its receptor Il31ra in a mouse model of house dust mite (HDM)-induced allergic dermatitis. Il31-deficient mice displayed a deficit in HDM dermatitis-associated scratching, consistent with its well-established role as a pruritogen. In contrast, Il31 deficiency increased the number and proportion of cutaneous type 2 cytokine-producing CD4+ T cells and serum IgE in response to HDM. Furthermore, Il4ra+ monocytes and macrophages capable of fueling a feedforward type 2 inflammatory loop were selectively enriched in Il31ra-deficient HDM dermatitis skin. Thus, IL-31 is not strictly a proinflammatory cytokine but rather an immunoregulatory factor that limits the magnitude of type 2 inflammatory responses in skin. Our data support a model wherein IL-31 activation of IL31RA+ pruritoceptors triggers release of calcitonin gene-related protein (CGRP), which can mediate neurogenic inflammation, inhibit CD4+ T cell proliferation, and reduce T cell production of the type 2 cytokine IL-13. Together, these results illustrate a previously unrecognized neuroimmune pathway that constrains type 2 tissue inflammation in the setting of chronic cutaneous allergen exposure and may explain paradoxical dermatitis flares in atopic patients treated with anti-IL31RA therapy.

The role of fibromodulin in inflammatory responses and diseases associated with inflammation

Inflammation is an immune response that the host organism eliminates threats from foreign objects or endogenous signals. It plays a key role in the progression, prognosis as well as therapy of diseases. Chronic inflammatory diseases have been regarded as the main cause of death worldwide at present, which greatly affect a vast number of individuals, producing economic and social burdens. Thus, developing drugs targeting inflammation has become necessary and attractive in the world. Currently, accumulating evidence suggests that small leucine-rich proteoglycans (SLRPs) exhibit essential roles in various inflammatory responses by acting as an anti-inflammatory or pro-inflammatory role in different scenarios of diseases. Of particular interest was a well-studied member, termed fibromodulin (FMOD), which has been largely explored in the role of inflammatory responses in inflammatory-related diseases. In this review, particular focus is given to the role of FMOD in inflammatory response including the relationship of FMOD with the complement system and immune cells, as well as the role of FMOD in the diseases associated with inflammation, such as skin wounding healing, osteoarthritis (OA), tendinopathy, atherosclerosis, and heart failure (HF). By conducting this review, we intend to gain insight into the role of FMOD in inflammation, which may open the way for the development of new anti-inflammation drugs in the scenarios of different inflammatory-related diseases.

MicroRNAs and Periodontal Disease: Helpful Therapeutic Targets?

Periodontal disease is the most common oral disease. This disease can be considered as an inflammatory disease. The immune response to bacteria accumulated in the gum line plays a key role in the pathogenesis of periodontal disease. In addition to immune cells, periodontal ligament cells and gingival epithelial cells are also involved in the pathogenesis of this disease. miRNAs which are small RNA molecules with around 22 nucleotides have a considerable relationship with the immune system affecting a wide range of immunological events. These small molecules are also in relation with periodontium tissues especially periodontal ligament cells. Extensive studies have been performed in recent years on the role of miRNAs in the pathogenesis of periodontal disease. In this review paper, we have reviewed the results of these studies and discussed the role of miRNAs in the immunopathogenesis of periodontal disease comprehensively. miRNAs play an important role in the pathogenesis of periodontal disease and maybe helpful therapeutic targets for the treatment of periodontal disease.

Innate Immune System in the Pathogenesis of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a prevalent condition characterized by lipid accumulation in hepatocytes with low alcohol consumption. The development of sterile inflammation, which occurs in response to a range of cellular stressors or injuries, has been identified as a major contributor to the pathogenesis of NAFLD. Recent studies of the pathogenesis of NAFLD reported the newly developed roles of damage-associated molecular patterns (DAMPs). These molecules activate pattern recognition receptors (PRRs), which are placed in the infiltrated neutrophils, dendritic cells, monocytes, or Kupffer cells. DAMPs cause the activation of PRRs, which triggers a number of immunological responses, including the generation of cytokines that promote inflammation and the localization of immune cells to the site of the damage. This review provides a comprehensive overview of the impact of DAMPs and PRRs on the development of NAFLD.

Single-cell RNA-Seq reveals CVI-mAb-induced Lyve1+ M2-like macrophages reduce atherosclerotic plaque area in Apoe-/- mice

BACKGROUND

Atherosclerosis is a lipid imbalance-induced autoimmune disease. Macrophages participate in the development and progression of atherosclerosis. Although numerous studies have utilized single-cell RNA sequencing to identify the role of various macrophage phenotypes in atherosclerosis, the macrophage subpopulations that have therapeutic benefits against atherosclerosis are not fully understood.

METHODS

In this study, a single-cell RNA sequencing analysis was performed on the F4/80⁺ macrophages of apolipoprotein E-deficient (Apoe^-/-) mice on a normal diet (ND), a high-fat diet (HFD), and a high-fat diet (HFD) with collagen VI monoclonal antibodies (CVI-mAb) treatment. A population of M2-like macrophages expressing the hyaluronan receptor Lyve1 was almost exclusively detectable in Apoe^-/- mice on an HFD with CVI-mAb treatment, compared with other groups. Differential gene expression and gene ontology enrichment analyses revealed specific gene expression patterns that distinguished this macrophage subset and uncovered its functions.

RESULTS

Lyve1⁺ M2 macrophages appear to have specialized functions in lipid metabolism. Lyve1⁺ M2-like macrophages were sorted via fluorescence- activated cell sorting (FACS) and adoptively transferred to Apoe^-/- mice fed an HFD.

CONCLUSION

Our result showed that Lyve1⁺ M2 macrophages could reduce the plaque areas in Apoe^-/- mice.

Macrophages: From Simple Phagocyte to an Integrative Regulatory Cell for Inflammation and Tissue Regeneration-A Review of the Literature

The understanding of macrophages and their pathophysiological role has dramatically changed within the last decades. Macrophages represent a very interesting cell type with regard to biomaterial-based tissue engineering and regeneration. In this context, macrophages play a crucial role in the biocompatibility and degradation of implanted biomaterials. Furthermore, a better understanding of the functionality of macrophages opens perspectives for potential guidance and modulation to turn inflammation into regeneration. Such knowledge may help to improve not only the biocompatibility of scaffold materials but also the integration, maturation, and preservation of scaffold-cell constructs or induce regeneration. Nowadays, macrophages are classified into two subpopulations, the classically activated macrophages (M1 macrophages) with pro-inflammatory properties and the alternatively activated macrophages (M2 macrophages) with anti-inflammatory properties. The present narrative review gives an overview of the different functions of macrophages and summarizes the recent state of knowledge regarding different types of macrophages and their functions, with special emphasis on tissue engineering and tissue regeneration.

Auriculotherapy Modulates Macrophage Polarization to Reduce Inflammatory Response in a Rat Model of Acne

Background

The inflammatory response is an important part of the pathogenesis of acne vulgaris. Auriculotherapy has been shown to have a good therapeutic effect on this disease. The aim of this study was to explore the mechanism underlying the anti-inflammatory effect of auriculotherapy in the treatment of acne vulgaris.

Methods

Propionibacterium acnes was injected subcutaneously into the ears of rats to establish an animal model of acne. The auriculotherapy intervention in rats consisted of auricular bloodletting therapy (ABT), auricular point sticking (APS), or a combination of both (ABPS). The anti-inflammatory effects of auriculotherapy were evaluated by measuring changes in ear thickness, local body surface microcirculation in the ear, and serum inflammatory factors in rats. The polarization of macrophages was analyzed by flow cytometry, and the expression of TLR2/NF-κB signaling pathway in the target tissues was analyzed using western blot.

Results

ABT, APS, and ABPS all reduced the erythema of ear acne, decreased microcirculation in localized ear acne, and decreased serum levels of TNF-α and IL-1β in rats. Meanwhile, the three interventions reduced M1-type macrophages and increased M2-type macrophages; only APS could reduce the expression of TLR2/NF-κB signaling pathway.

Conclusion

ABT, APS, and ABPS can improve the inflammatory symptoms of acne and reduce inflammatory cytokines. APS may exert anti-inflammatory effects by altering macrophage polarization and decreasing TLR2/NF-κB expression.

Palmitoleic Acid Acts on Adipose-Derived Stromal Cells and Promotes Anti-Hypertrophic and Anti-Inflammatory Effects in Obese Mice

Adipose tissue (AT) secretes adipokines, modulators of low-grade chronic inflammation in obesity. Molecules that induce the emergence of new and functional adipocytes in AT can alleviate or prevent inflammatory and metabolic disorders. The objective of this study was to investigate the role of palmitoleic acid (n7) in 3T3-L1 and primary pre-adipocyte differentiation and AT inflammation. C57BL/6j mice were submitted to a control or high-fat diet (HFD) for 8 weeks, and treated with n7 for 4 weeks. Mice consuming a HFD presented an increase in body weight, epididymal (Epi) fat mass, and Epi adipocytes size. N7 treatment attenuated the body weight gain and completely prevented the hypertrophy of Epi adipocytes, but not the increment in Epi mass induced by the HFD, suggesting a greater adipocytes hyperplasia in animals treated with n7. It was agreed that n7 increased 3T3-L1 proliferation and differentiation, as well as the expression of genes involved in adipogenesis, such as Cebpa, Pparg, aP2, Perilipin, and Scl2a4. Furthermore, n7 decreased the inflammatory cytokines Mcp1, Tnfa, Il6, Cxcl10, and Nos2 genes in Epi vascular stromal cells, but not in the whole AT. These findings show that n7 exerts anti-hypertrophic effects in adipocytes which influence the surrounding cells by attenuating the overexpression of pro-inflammatory cytokines triggered by a HFD.

Multi-OMICs analysis reveals metabolic and epigenetic changes associated with macrophage polarization

Macrophages (MФ) are an essential immune cell for defense and repair that travel to different tissues and adapt based on local stimuli. A critical factor that may govern their polarization is the crosstalk between metabolism and epigenetics. However, simultaneous measurements of metabolites, epigenetics, and proteins (phenotype) have been a major technical challenge. To address this, we have developed a novel triomics approach using mass spectrometry to comprehensively analyze metabolites, proteins, and histone modifications in a single sample. To demonstrate this technique, we investigated the metabolic-epigenetic-phenotype axis following polarization of human blood–derived monocytes into either ‘proinflammatory M1-’ or ‘anti-inflammatory M2-’ MФs. We report here a complex relationship between arginine, tryptophan, glucose, and the citric acid cycle metabolism, protein and histone post-translational modifications, and human macrophage polarization that was previously not described. Surprisingly, M1-MФs had globally reduced histone acetylation levels but high levels of acetylated amino acids. This suggests acetyl-CoA was diverted, in part, toward acetylated amino acids. Consistent with this, stable isotope tracing of glucose revealed reduced usage of acetyl-CoA for histone acetylation in M1-MФs. Furthermore, isotope tracing also revealed MФs uncoupled glycolysis from the tricarboxylic acid cycle, as evidenced by poor isotope enrichment of succinate. M2-MФs had high levels of kynurenine and serotonin, which are reported to have immune-suppressive effects. Kynurenine is upstream of de novo NAD⁺ metabolism that is a necessary cofactor for Sirtuin-type histone deacetylases. Taken together, we demonstrate a complex interplay between metabolism and epigenetics that may ultimately influence cell phenotype.

Biology of macrophage fate decision: Implication in inflammatory disorders

The activation of immune cells in response to stimuli present in their microenvironment is regulated by their metabolic profile. Unlike the signal transduction events, which overlap to a huge degree in diverse cellular processes, the metabolome of a cell reflects a more precise picture of cell physiology and function. Different factors governing the cellular metabolome include receptor signaling, macro and micronutrients, normoxic and hypoxic conditions, energy needs, and biomass demand. Macrophages have enormous plasticity and can perform diverse functions depending upon their phenotypic state. This review presents recent updates on the cellular metabolome and molecular patterns associated with M1 and M2 macrophages, also termed "classically activated macrophages" and "alternatively activated macrophages," respectively. M1 macrophages are proinflammatory in nature and predominantly Th1-specific immune responses induce their polarization. On the contrary, M2 macrophages are anti-inflammatory in nature and primarily participate in Th2-specific responses. Interestingly, the same macrophage cell can adapt to the M1 or M2 phenotype depending upon the clues from its microenvironment. We elaborate on the various tissue niche-specific factors, which govern macrophage metabolism and heterogeneity. Furthermore, the current review provides an in-depth account of deregulated macrophage metabolism associated with pathological disorders such as cancer, obesity, and atherosclerosis. We further highlight significant differences in various metabolic pathways governing the cellular bioenergetics and their impact on macrophage effector functions and associated disorders.

A Bibliometric and Knowledge-Map Analysis of Macrophage Polarization in Atherosclerosis From 2001 to 2021

In recent years, studies of macrophage polarization in atherosclerosis have become an intense area of research. However, there are few bibliometric analyses regarding this area. In this review, we used CiteSpace 5.8.R3 and VOSviewer 1.6.16 software to perform text mining and knowledge-map analysis. We explored the development process, knowledge structure, research hotspots, and potential trends using a bibliometric and knowledge-map analysis to provide researchers with a macroscopic view of this field. The studies concerning macrophage polarization in atherosclerosis were downloaded from the Web of Science Core Collection. A total of 781 studies were identified and published by 954 institutions from 51 countries/regions. The number of studies of macrophage polarization in atherosclerosis increased over time. Arteriosclerosis Thrombosis and Vascular Biology published the highest number of articles and was the top co-cited journal. De Winther was the most prolific researcher, and Moore had the most co-citations. The author co-occurrence map illustrated that there was active cooperation among researchers. The most productive countries were the United States and China. Amsterdam University, Harvard University, and Maastricht University were the top three productive institutions in the research field. Keyword Co-occurrence, Clusters, and Burst analysis showed that “inflammation,” “monocyte,” “NF kappa B,” “mechanism,” and “foam cell” appeared with the highest frequency in studies. “Oxidative stress,” “coronary heart disease,” and “prevention” were the strongest citation burst keywords from 2019 to 2021.

Inflammatory factors driving atherosclerotic plaque progression new insights

Coronary atherosclerosis is a chronic inflammatory disease that can lead to varying degrees of blood flow obstruction and a common pathophysiological basis of cardiovascular disease. Inflammatory factors run through the whole process of atherosclerotic lesions. Macrophages, T cells, and neutrophils play important roles in the process of atherosclerotic inflammation. Considering the evolutionary characteristics, atherosclerosis can be divided into different stages as early atherosclerotic plaque, plaque formation stage, and plaque rupture stage. In this paper, the changes in inflammatory cells at different stages of lesions and their related mechanisms are discussed, which can provide new insights from a clinical to bench perspective for atherosclerosis me chanism.

Pathogenic TNF-α drives peripheral nerve inflammation in an Aire-deficient model of autoimmunity

Immune cells infiltrate the peripheral nervous system (PNS) after injury and with autoimmunity, but their net effect is divergent. After injury, immune cells are reparative, while in inflammatory neuropathies (e.g., Guillain Barré Syndrome and chronic inflammatory demyelinating polyneuropathy), immune cells are proinflammatory and promote autoimmune demyelination. An understanding of immune cell phenotypes that distinguish these conditions may, therefore, reveal new therapeutic targets for switching immune cells from an inflammatory role to a reparative state. In an autoimmune regulator (Aire)-deficient mouse model of inflammatory neuropathy, we used single-cell RNA sequencing of sciatic nerves to discover a transcriptionally heterogeneous cellular landscape, including multiple myeloid, innate lymphoid, and lymphoid cell types. Analysis of cell-cell ligand-receptor interactions uncovered a macrophage-mediated tumor necrosis factor-α (TNF-α) signaling axis that is induced by interferon-γ and required for initiation of autoimmune demyelination. Developmental trajectory visualization suggested that TNF-α signaling is associated with metabolic reprogramming of macrophages and polarization of macrophages from a reparative state in injury to a pathogenic, inflammatory state in autoimmunity. Autocrine TNF-α signaling induced macrophage expression of multiple genes (Clec4e, Marcksl1, Cxcl1, and Cxcl10) important in immune cell activation and recruitment. Genetic and antibody-based blockade of TNF-α/TNF-α signaling ameliorated clinical neuropathy, peripheral nerve infiltration, and demyelination, which provides preclinical evidence that the TNF-α axis may be effectively targeted to resolve inflammatory neuropathies.

Single-Cell RNA-Seq Reveals a Crosstalk between Hyaluronan Receptor LYVE-1-Expressing Macrophages and Vascular Smooth Muscle Cells

Background: Atherosclerosis is a chronic inflammatory disease where macrophages participate in the progression of the disease. However, the role of resident-like macrophages (res-like) in the atherosclerotic aorta is not completely understood. Methods: A single-cell RNA sequencing analysis of CD45⁺ leukocytes in the atherosclerotic aorta of apolipoprotein E–deficient (Apoe^−/−) mice on a normal cholesterol diet (NCD) or a high cholesterol diet (HCD), respecting the side-to-specific predisposition to atherosclerosis, was performed. A population of res-like macrophages expressing hyaluronan receptor LYVE-1 was investigated via flow cytometry, co-culture experiments, and immunofluorescence in human atherosclerotic plaques from carotid artery disease patients (CAD). Results: We identified 12 principal leukocyte clusters with distinct atherosclerosis disease-relevant gene expression signatures. LYVE-1⁺ res-like macrophages, expressing a high level of CC motif chemokine ligand 24 (CCL24, eotaxin-2), expanded under hypercholesteremia in Apoe^−/− mice and promoted VSMC phenotypic modulation to osteoblast/chondrocyte-like cells, ex vivo, in a CCL24-dependent manner. Moreover, the abundance of LYVE-1⁺CCL24⁺ macrophages and elevated systemic levels of CCL24 were associated with vascular calcification and CAD events. Conclusions: LYVE-1 res-like macrophages, via the secretion of CCL24, promote the transdifferentiation of VSMC to osteogenic-like cells with a possible role in vascular calcification and likely a detrimental role in atherosclerotic plaque destabilization.

Flavonoids, alkaloids and terpenoids: a new hope for the treatment of diabetes mellitus

Diabetes mellitus is a metabolic syndrome characterized by a hyperglycemic state and multi-organ failure. Millions of people worldwide are suffering from this deadly disease taking a hit on their pocket and mental health in the name of its treatment. Modern medical practices with new technological advancements and discoveries have made revolutionary changes in the treatment. But, unfortunately, Glucose-lowering drugs used have many accompanying effects such as chronic vascular disease, renal malfunction, liver disease and, many skin problems. These complications have made us think about alternative treatments for diabetes with minimum or no side effects. Nowadays, in addition to modern medicine, herbal treatment has been suggested to treat diabetes mellitus. These herbal medicines contain biological macromolecules such as flavonoids, Terpenoids, glycosides, and alkaloids, which show versatile anti-diabetic effects. These phytochemicals are generally considered safe, and naturally occurring compounds have a potential role in preventing or controlling diabetes mellitus. The underlying mechanism of their anti-diabetic effects includes improvement in insulin secretion, decrease in insulin resistance, enhanced liver glycogen synthesis, antioxidant and anti-inflammatory activities. In this review, we have focused on the mechanism of various phytochemicals targeting hyperglycemia and its underlying pathogenesis.

Effect of Acinetobacter lwoffii on the modulation of macrophage activation and asthmatic inflammation

BACKGROUND

Although lung macrophages are directly exposed to external stimuli, their exact immunologic roles in asthma are still largely unknown. The aim of this study was to investigate the anti-asthmatic effect of Acinetobacter lwoffii in terms of lung macrophage modulation.

METHODS

Six-week-old female BALB/c mice were sensitized and challenged with ovalbumin (OVA) with or without intranasal administration of A. lwoffii during the sensitization period. Airway hyperresponsiveness and inflammation were evaluated. Using flow cytometry, macrophages were subclassified according to their activation status. In the in vitro study, a murine alveolar macrophage cell line (MH-S) treated with or without A. lwoffii before IL-13 stimulation were analysed by quantitative RT-PCR.

RESULTS

In a murine asthma model, the number of inflammatory cells, including macrophages and eosinophils, decreased in mice treated with A. lwoffii (A. lwoffii/OVA group) compared with untreated mice (OVA group). The enhanced expression of MHCII in macrophages in the OVA group was decreased by A. lwoffii treatment. M2 macrophage subtypes were significantly altered. A. lwoffii treatment decreased CD11b⁺ M2a and CD11b⁺ M2c macrophages, which showed strong positive correlations with Th2 cells, ILC2 and eosinophils. In contrast, CD11b⁺ M2b macrophages were significantly increased by A. lwoffii treatment and showed strong positive correlations with ILC1 and ILC3. In vitro, A. lwoffii down-regulated the expression of M2 markers related but up-regulated those related to M2b macrophages.

CONCLUSIONS AND CLINICAL RELEVANCE

Intranasal A. lwoffii exposure suppresses asthma development by suppressing the type 2 response via modulating lung macrophage activation, shifting M2a and M2c macrophages to M2b macrophages.

Current Status and Future Perspectives on Therapeutic Potential of Apigenin: Focus on Metabolic-Syndrome-Dependent Organ Dysfunction

Metabolic syndrome and its associated disorders such as obesity, insulin resistance, atherosclerosis and type 2 diabetes mellitus are globally prevalent. Different molecules showing therapeutic potential are currently available for the management of metabolic syndrome, although their efficacy has often been compromised by their poor bioavailability and side effects. Studies have been carried out on medicinal plant extracts for the treatment and prevention of metabolic syndrome. In this regard, isolated pure compounds have shown promising efficacy for the management of metabolic syndrome, both in preclinical and clinical settings. Apigenin, a natural bioactive flavonoid widely present in medicinal plants, functional foods, vegetables and fruits, exerts protective effects in models of neurological disorders and cardiovascular diseases and most of these effects are attributed to its antioxidant action. Various preclinical and clinical studies carried out so far show a protective effect of apigenin against metabolic syndrome. Herein, we provide a comprehensive review on both in vitro and in vivo evidence related to the promising antioxidant role of apigenin in cardioprotection, neuroprotection and renoprotection, and to its beneficial action in metabolic-syndrome-dependent organ dysfunction. We also provide evidence on the potential of apigenin in the prevention and/or treatment of metabolic syndrome, analysing the potential and limitation of its therapeutic use.

Core Cross-Linked Polymeric Micelles for Specific Iron Delivery: Inducing Sterile Inflammation in Macrophages

Iron is an essential co-factor for cellular processes. In the immune system, it can activate macrophages and represents a potential therapeutic for various diseases. To specifically deliver iron to macrophages, iron oxide nanoparticles are embedded in polymeric micelles of reactive polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine). Upon surface functionalization via dihydrolipoic acid, iron oxide cores act as crosslinker themselves and undergo chemoselective disulfide bond formation with the surrounding poly(S-ethylsulfonyl-l-cysteine) block, yielding glutathione-responsive core cross-linked polymeric micelles (CCPMs). When applied to primary murine and human macrophages, these nanoparticles display preferential uptake, sustained intracellular iron release, and induce a strong inflammatory response. This response is also demonstrated in vivo when nanoparticles are intratracheally administered to wild-type C57Bl/6N mice. Most importantly, the controlled release concept to deliver iron oxide in redox-responsive CCPMs induces significantly stronger macrophage activation than any other iron source at identical iron levels (e.g., Feraheme), directing to a new class of immune therapeutics.

Effects of Live and Pasteurized Forms of Akkermansia from the Human Gut on Obesity and Metabolic Dysregulation

Akkermansia muciniphila (A. muciniphila) is a promising probiotic candidate owing to its health-promoting properties. A previous study reported that the pasteurized form of A. muciniphila strains isolated from human stool samples had a beneficial impact on high-fat diet-induced obese mice. On the other hand, the differences in the probiotic effects between live and pasteurized A. muciniphila on the metabolism and immune system of the host are still inconclusive. This study examines the differences between the live and pasteurized forms of A. muciniphila strains on the lipid and glucose metabolism and on regulating the inflammatory immune responses using a HFD-fed obese mouse model. The animals were administered the live and pasteurized forms of two A. muciniphila strains five times per week for the entire study period of 12 weeks. Both forms of the bacterial strains improved the HFD-induced obesity and metabolic dysregulation in the mice by preventing body-weight gains after one week. In addition, they cause a decrease in the weights of the major adipose tissues, adipogenesis/lipogenesis and serum TC levels, improvement in glucose homeostasis and suppression of inflammatory insults. Furthermore, these treatments restored the damaged gut architecture and integrity and improved the hepatic structure and function in HFD-induced animals. On the other hand, for both bacterial strains, the pasteurized form was more potent in improving glucose tolerance than the live form. Moreover, specific A. muciniphila preparations with either live or pasteurized bacteria decreased the number and population (%) of splenic Treg cells (CD4+ Foxp3+) significantly in the HFD-fed animals, further supporting the anti-inflammatory properties of these bacteria.

Metabolic Hormones Modulate Macrophage Inflammatory Responses

Simple Summary

Macrophages are a type of immune cell which play an important role in the development of cancer. Obesity increases the risk of cancer and obesity also causes disruption to the normal levels of hormones that are produced to coordinate metabolism. Recent research now shows that these metabolic hormones also play important roles in macrophage immune responses and so through macrophages, disrupted metabolic hormone levels may promote cancer. This review article aims to highlight and summarise these recent findings so that the scientific community may better understand how important this new area of research is, and how these findings can be capitalised on for future scientific studies.

Abstract

Macrophages are phagocytotic leukocytes that play an important role in the innate immune response and have established roles in metabolic diseases and cancer progression. Increased adiposity in obese individuals leads to dysregulation of many hormones including those whose functions are to coordinate metabolism. Recent evidence suggests additional roles of these metabolic hormones in modulating macrophage inflammatory responses. In this review, we highlight key metabolic hormones and summarise their influence on the inflammatory response of macrophages and consider how, in turn, these hormones may influence the development of different cancer types through the modulation of macrophage functions.

Does iron overload in metabolic syndrome affect macrophage profile? A case control study

AIMS

Dysmetabolic iron overload syndrome (DIOS) is common but the clinical relevance of iron overload is not understood. Macrophages are central cells in iron homeostasis and inflammation. We hypothesized that iron overload in DIOS could affect the phenotype of monocytes and impair macrophage gene expression.

METHODS

This study compared 20 subjects with DIOS to 20 subjects with metabolic syndrome (MetS) without iron overload, and 20 healthy controls. Monocytes were phenotyped by Fluorescence-Activated Cell Sorting (FACS) and differentiated into anti-inflammatory M2 macrophages in the presence of IL-4. The expression of 38 genes related to inflammation, iron metabolism and M2 phenotype was assessed by real-time PCR.

RESULTS

FACS showed no difference between monocytes across the three groups. The macrophagic response to IL-4-driven differentiation was altered in four of the five genes of M2 phenotype (MRC1, F13A1, ABCA1, TGM2 but not FABP4), in DIOS vs Mets and controls demonstrating an impaired M2 polarization. The expression profile of inflammatory genes was not different in DIOS vs MetS. Several genes of iron metabolism presented a higher expression in DIOS vs MetS: SCL11A2 (a free iron transporter, +76 %, p = 0.04), SOD1 (an antioxidant enzyme, +27 %, p = 0.02), and TFRC (the receptor 1 of transferrin, +59 %, p = 0.003).

CONCLUSIONS

In DIOS, macrophage polarization toward the M2 alternative phenotype is impaired but not associated with a pro-inflammatory profile. The up regulation of transferrin receptor 1 (TFRC) in DIOS macrophages suggests an adaptive role that may limit iron toxicity in DIOS.

The G2A Receptor Deficiency Aggravates Atherosclerosis in Rats by Regulating Macrophages and Lipid Metabolism

The orphan G protein-coupled receptor G2A has been linked to atherosclerosis development. However, available data from mouse models are controversial. Rat G2A receptor bears more similarities with its human homolog. We proposed that the atherosclerosis model established from Ldlr^–/– rat, which has been reported to share more similar phenotypes with the human disease, may help to further understand this lipid receptor. G2A deletion was found markedly aggravated in the lipid disorder in the rat model, which has not been reported in mouse studies. Examination of aortas revealed exacerbated atherosclerotic plaques in G2A deficient rats, together with increased oxidative stress and macrophage accumulation. In addition, consistently promoted migration and apoptosis were noticed in G2A deficient macrophages, even in macrophages from G2A single knockout rats. Further analysis found significantly declined phosphorylation of PI3 kinase (PI3K) and AKT, together with reduced downstream genes Bcl2 and Bcl-xl, suggesting possible involvement of PI3K/AKT pathway in G2A regulation to macrophage apoptosis. These data indicate that G2A modulates atherosclerosis by regulating lipid metabolism and macrophage migration and apoptosis. Our study provides a new understanding of the role of G2A in atherosclerosis, supporting it as a potential therapeutic target.

Promotion Effect of EGCG on the Raised Expression of IL-23 through the Signaling of STAT3-BATF2-c-JUN/ATF2

Tea polyphenol of epigallocatechin-3-gallate (EGCG) has been verified to possess multiple biological activities. Interleukin-23 (IL-23) is a heterodimeric cytokine consisting of two subunits of IL-23p19 and IL-12p40, with the functionality in regulating the production of cytokines under physiological or pathological conditions. By serendipity, the raised expression of IL-23 was observed after treating cells with EGCG, whereas the detailed mechanism remains poorly understood. This study was proposed to investigate the signaling related to EGCG-induced IL-23. The raised expression of IL-23 was confirmed primarily by intraperitoneally injecting with different concentrations of EGCG (0, 20, 50, 80 mg/kg) into BALB/c mice, and the raised expression was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. Results from enzyme-linked immunosorbent assay (ELISA) revealed the increase of IL-23 in serum from 116.09 to 153.90 pg/mL after treating with EGCG. The same results were also observed in RAW264.7 and peritoneal macrophages after treating with EGCG (0, 1, 5, 10, 25 μM) with the increased tendency of IL-23 in cultural medium (7.98 to 25.38 pg/mL for RAW264.7; 3.64 to 260.93 pg/mL for peritoneal macrophages). After preliminary exploration of the signaling related to the increased IL-23, the classical signaling pathways and key transcription factors, such as nuclear factor kappa-B (NF-κB), mitogen-activated protein kinase (MAPK) signaling pathways, and interferon regulatory factor 5 (IRF5), were demonstrated with no relevant contribution. A further study revealed the involvement of the key transcription factor of BATF2, which could antagonistically modulate the transcription and translation of IL-23. The signaling of STAT3-BATF2-c-JUN/ATF2-IL-23 has been further verified in RAW264.7 macrophages using the STAT3 inhibitor of AG490 and the activator of Colivelin TFA. The results indicated that EGCG inhibits the phosphorylation of STAT3 to facilitate the decreased level of BATF2, which contributed to the increased level of IL-23 by the enhancing heterodimerization of c-JUN and ATF2.

Lipid Receptor G2A-Mediated Signal Pathway Plays a Critical Role in Inflammatory Response by Promoting Classical Macrophage Activation

Macrophage polarization is a dynamic and integral process in tissue inflammation and remodeling. In this study, we describe that lipoprotein-associated phospholipase A₂ (Lp-PLA₂) plays an important role in controlling inflammatory macrophage (M1) polarization in rodent experimental autoimmune encephalomyelitis (EAE) and in monocytes from multiple sclerosis (MS) patients. Specific inhibition of Lp-PLA₂ led to an ameliorated EAE via markedly decreased inflammatory and demyelinating property of M1. The effects of Lp-PLA₂ on M1 function were mediated by lysophosphatidylcholine, a bioactive product of oxidized lipids hydrolyzed by Lp-PLA₂ through JAK2-independent activation of STAT5 and upregulation of IRF5. This process was directed by the G2A receptor, which was only found in differentiated M1 or monocytes from MS patients. M1 polarization could be inhibited by a G2A neutralizing Ab, which led to an inhibited disease in rat EAE. In addition, G2A-deficient rats showed an ameliorated EAE and an inhibited autoimmune response. This study has revealed a mechanism by which lipid metabolites control macrophage activation and function, modification of which could lead to a new therapeutic approach for MS and other inflammatory disorders.

Protein Adsorption on Surfaces Functionalized with COOH Groups Promotes Anti-inflammatory Macrophage Responses

Implants can induce a foreign body reaction that leads to chronic inflammation and fibrosis in the surrounding tissue. Macrophages help detect the foreign material, play a role in the inflammatory response, and may promote fibrosis instead of the desired tissue regeneration around implants. Implant surface properties impact macrophage responses by changing the nature of the adsorbed protein layer, but conflicting studies highlight the complexity of this relationship. In this study, the effect of surface chemistry on macrophage behavior was investigated with poly(styrene) surfaces containing common functional groups at similar surface densities. The protein layer was characterized to identify the proteins that adsorbed on the surfaces from the medium and the proteins secreted onto the surfaces by adherent macrophages. Of the surface chemistries studied, carboxylic acid (COOH) groups promoted anti-inflammatory responses from unstimulated macrophages and did not exacerbate inflammation upon stimulation. These surfaces also enhanced the adsorption of proteins involved in integrin signaling and promoted the secretion of proteins related to angiogenesis, integrin signaling, and cytokine signaling, which have been previously associated with improved biomaterial integration. Therefore, this study suggests that surface modification with COOH groups may help improve the integration of implants in the body by enhancing anti-inflammatory macrophage responses through altered protein adsorption.

Monounsaturated Fatty Acids in Obesity-Related Inflammation

Obesity is an important aspect of the metabolic syndrome and is often associated with chronic inflammation. In this context, inflammation of organs participating in energy homeostasis (such as liver, adipose tissue, muscle and pancreas) leads to the recruitment and activation of macrophages, which secrete pro-inflammatory cytokines. Interleukin-1β secretion, sustained C-reactive protein plasma levels and activation of the NLRP3 inflammasome characterize this inflammation. The Stearoyl-CoA desaturase-1 (SCD1) enzyme is a central regulator of lipid metabolism and fat storage. This enzyme catalyzes the generation of monounsaturated fatty acids (MUFAs)-major components of triglycerides stored in lipid droplets-from saturated fatty acid (SFA) substrates. In this review, we describe the molecular effects of specific classes of fatty acids (saturated and unsaturated) to better understand the impact of different diets (Western versus Mediterranean) on inflammation in a metabolic context. Given the beneficial effects of a MUFA-rich Mediterranean diet, we also present the most recent data on the role of SCD1 activity in the modulation of SFA-induced chronic inflammation.

Functioning of Long Noncoding RNAs Expressed in Macrophage in the Development of Atherosclerosis

Chronic inflammation is part of the pathological process during atherosclerosis (AS). Due to the abundance of monocytes/macrophages within the arterial plaque, monocytes/macrophages have become a critical cellular target in AS studies. In recent decades, a number of long noncoding RNAs (lncRNAs) have been found to exert regulatory roles on the macrophage metabolism and macrophage plasticity, consequently promoting or suppressing atherosclerotic inflammation. In this review, we provide a comprehensive overview of lncRNAs in macrophage biology, highlighting the potential role of lncRNAs in AS based on recent findings, with the aim to identify disease biomarkers and future therapeutic interventions for AS.

Non-hematopoietic erythropoietin-derived peptides for atheroprotection and treatment of cardiovascular diseases

Relevance: Cardiovascular diseases continue to be the leading cause of premature adult death.

Lipid profile and atherogenesis: Dislipidaemia leads to subsequent lipid accumulation and migration of immunocompetent cells into the vessel intima. Macrophages accumulate cholesterol forming foam cells – the morphological substrate of atherosclerosis in its initial stage.

Inflammation and atherogenesis: Pro-inflammatory factors provoke oxidative stress, vascular wall damage and foam cells formation.

Endothelial and mitochondrial dysfunction in the development of atherosclerosis: Endothelial mitochondria are some of the organelles most sensitive to oxidative stress. Damaged mitochondria produce excess superoxide and H2O2, which are the main factors of intracellular damage, further increasing endothelial dysfunction.

Short non-hematopoietic erythropoietin-based peptides as innovative atheroprotectors: Research in recent decades has shown that erythropoietin has a high cytoprotective activity, which is mainly associated with exposure to the mitochondrial link and has been confirmed in various experimental models. There is also a short-chain derivative, the 11-amino acid pyroglutamate helix B surface peptide (PHBSP), which selectively binds to the erythropoietin heterodymic receptor and reproduces its cytoprotective properties. This indicates the promising use of short-chain derivatives of erythropoietin for the treatment and prevention of atherosclerotic vascular injury. In the future, it is planned to study the PHBSP derivatives, the modification of which consists in adding RGD and PGP tripeptides with antiaggregant properties to the original 11-member peptide.

The influenza virus NS1A binding protein gene modulates macrophages response to cytokines and phagocytic potential in inflammation

Macrophages show remarkable phenotypic plasticity in response to environmental signals. Although it is generally less considered, cytoskeletal changes in macrophages influence their phenotype, including phagocytosis and secretion of soluble cytokines. Influenza virus NS1A-binding protein (Ivns1abp) belongs to the Kelch family of proteins that play a central role in actin cytoskeleton dynamics by directly associating with F-actin and by protecting against actin derangement. Due to its role in cytoskeleton preservation, the Ivns1abp gene might be a critical regulator of the macrophage phenotype and function under inflammatory conditions. In this study, we determine that the modulation of the Ivns1abp gene in macrophages could modify resistance to macrophages against inflammation and maintain functional phagocytosis. Our results indicate that inflammatory insults inhibit the Ivns1abp gene, whereby phagocytosis is inhibited and the ability of macrophages to induce proliferation and repair of damaged cells is compromised. Furthermore, our results show that inflammatory insults alter the activity of the transcription factor c-myc, a factor which directly modulates the expression of the Ivns1abp gene. In conclusion, this study demonstrates a central role of lvns1abp in promoting and preserving a reparative macrophage phenotype and resistance to this inflammatory environment.

Therapeutic potential of ALKB homologs for cardiovascular disease

Cardiovascular diseases (CVDs) are the leading causes of human death. Recently, ALKB homologs, including ALKBH1-8 and FTO, have been found to have a variety of biological functions, such as histone demethylation, RNA demethylation, and DNA demethylation. These functions may regulate the physiological and pathological processes of CVDs, including inflammation, oxidative stress, cell apoptosis, and mitochondrial, endothelial, and fat metabolism dysfunction. In the present review, we summarize the biological functions of ALKB homologs and the relationship between the ALKB homologs and CVDs. Importantly, we discuss the roles of ALKB homologs in the regulation of oxidative stress, inflammation, autophagy, and DNA damage in CVDs, as well as the practical applications of ALKB homologs inhibitors or agonists in treating CVDs. In conclusion, the ALKBH family might be a promising target for CVDs therapy.

A novel chrysin thiazole derivative polarizes macrophages to an M1 phenotype via targeting TLR4

Tumor-associated macrophages (TAMs) are an important cause of tumorigenesis and tumor development. M2 macrophages can promote tumor growth while M1 macrophages kill tumor cells, therefore, polarizing macrophages to achieve a functional M1 phenotype could effectively play its anti-tumor role. In the current study, we synthesized a novel chrysin derivative which is termed as ChR-TD. And we found ChR-TD might be a ligand of TLR4 that polarized the TAMs towards M1 phenotype and played its anti-tumor role. Further study indicated that ChR-TD reprogrammed the macrophages into an M1 phenotype via TLR4 activation. Moreover, ChR-TD activated TLR4/NF-κB signaling pathway and promoted the NF-κB/p65 translocated into the nuclear, leading to the activation of NF-κB and proinflammatory cytokines release. In addition, type I interferon signaling was also activated by ChR-TD, leading to the expressions of IFN-α and IFN-β and its targeted genes NOS2, MCP-1 and IP-10 were significantly increased in macrophages. Importantly, these effects were disturbed in TLR4^-/- macrophages, which are constructed by using CRISPR/Cas9 system. And the molecule docking simulation further indicated that ChR-TD could bind to TLR4 and might be a ligand of TLR4. Hence, these findings suggested that ChR-TD might be a ligand of TLR4 and can be used as a potential lead compound for tumors treatment.

Metabolic Profiling Reveals Aggravated Non-Alcoholic Steatohepatitis in High-Fat High-Cholesterol Diet-Fed Apolipoprotein E-Deficient Mice Lacking Ron Receptor Signaling

Non-alcoholic steatohepatitis (NASH) represents the progressive sub-disease of non-alcoholic fatty liver disease that causes chronic liver injury initiated and sustained by steatosis and necroinflammation. The Ron receptor is a tyrosine kinase of the Met proto-oncogene family that potentially has a beneficial role in adipose and liver-specific inflammatory responses, as well as glucose and lipid metabolism. Since its discovery two decades ago, the Ron receptor has been extensively investigated for its differential roles on inflammation and cancer. Previously, we showed that Ron expression on tissue-resident macrophages limits inflammatory macrophage activation and promotes a repair phenotype, which can retard the progression of NASH in a diet-induced mouse model. However, the metabolic consequences of Ron activation have not previously been investigated. Here, we explored the effects of Ron receptor activation on major metabolic pathways that underlie the development and progression of NASH. Mice lacking apolipoprotein E (ApoE KO) and double knockout (DKO) mice that lack ApoE and Ron were maintained on a high-fat high-cholesterol diet for 18 weeks. We observed that, in DKO mice, the loss of ligand-dependent Ron signaling aggravated key pathological features in steatohepatitis, including steatosis, inflammation, oxidation stress, and hepatocyte damage. Transcriptional programs positively regulating fatty acid (FA) synthesis and uptake were upregulated in the absence of Ron receptor signaling, whereas lipid disposal pathways were downregulated. Consistent with the deregulation of lipid metabolism pathways, the DKO animals exhibited increased accumulation of FAs in the liver and decreased level of bile acids. Altogether, ligand-dependent Ron receptor activation provides protection from the deregulation of major metabolic pathways that initiate and aggravate non-alcoholic steatohepatitis.

Pancreatic Macrophages: Critical Players in Obesity-Promoted Pancreatic Cancer

Obesity is a known risk factor for the development of pancreatic cancer, one of the deadliest types of malignancies. In recent years it has become clear that the pancreatic microenvironment is critically involved and a contributing factor in accelerating pancreatic neoplasia. In this context obesity-associated chronic inflammation plays an important role. Among several immune cells, macrophages have been shown to contribute to obesity-induced tissue inflammation. This review article summarizes the current knowledge about the role of pancreatic macrophages in early pancreatic cancer development. It describes the heterogenous origin and mixture of pancreatic macrophages, their role in pancreatic endocrine and exocrine pathology, and the impact of obesity on islet and stromal macrophages. A model is postulated, by which during obesity monocytes are recruited into the pancreas, where they are polarized into pro-inflammatory macrophages that drive early pancreatic neoplasia. This occurs in the presence of local inflammatory, metabolic, and endocrine signals. A stronger appreciation and more detailed knowledge about the role of macrophages in early pancreatic cancer development will lead to innovative preventive or interceptive strategies.

Surgical Injury and Ischemia Prime the Adipose Stromal Vascular Fraction and Increase Angiogenic Capacity in a Mouse Limb Ischemia Model

The adipose-derived stromal vascular fraction (SVF) is an effective source for autologous cell transplantation. However, the quality and quantity of SVFs vary depending on the patient's age, complications, and other factors. In this study, we developed a method to reproducibly increase the cell number and improve the quality of adipose-derived SVFs by surgical procedures, which we term “wound repair priming.” Subcutaneous fat from the inguinal region of BALB/c mice was surgically processed (primed) by mincing adipose parenchyma (injury) and ligating the subcutaneous fat-feeding artery (ischemia). SVFs were isolated on day 0, 1, 3, 5, or 7 after the priming procedures. Gene expression levels of the primed SVFs were measured via microarray and pathway analyses which were performed for differentially expressed genes. Changes in cellular compositions of primed SVFs were analyzed by flow cytometry. SVFs were transplanted into syngeneic ischemic hindlimbs to measure their angiogenic and regeneration potential. Hindlimb blood flow was measured using a laser Doppler blood perfusion imager, and capillary density was quantified by CD31 staining of ischemic tissues. Stabilization of HIF-1 alpha and VEGF-A synthesis in the SVFs were measured by fluorescent immunostaining and Western blotting, respectively. As a result, the number of SVFs per fat weight was increased significantly on day 7 after priming. Among the differentially expressed genes were innate immunity-related signals on both days 1 and 3 after priming. In primed SVFs, the CD45-positive blood mononuclear cell fraction decreased, and the CD31-CD45-double negative mesenchymal cell fraction increased on day 7. The F4/80-positive macrophage fraction was increased on days 1 and 7 after priming. There was a serial decrease in the mesenchymal-gated CD34-positive adipose progenitor fraction and mesenchymal-gated CD140A-positive/CD9-positive preadipocyte fraction on days 1 and 3. Transplantation of primed SVFs resulted in increased capillary density and augmented blood flow, improving regeneration of the ischemic limbs. HIF-1 alpha was stabilized in the primed cutaneous fat in situ, and VEGF-A synthesis of the primed SVFs was on a peak on 5 days after priming. Wound repair priming thus resulted in SVFs with increased number and augmented angiogenic potential.

Adipose stromal/stem cells in regenerative medicine: Potentials and limitations

This article presents the stem and progenitor cells from subcutaneous adipose tissue, briefly comparing them with their bone marrow counterparts, and discussing their potential for use in regenerative medicine. Subcutaneous adipose tissue differs from other mesenchymal stromal/stem cells (MSCs) sources in that it contains a pre-adipocyte population that dwells in the adventitia of robust blood vessels. Pre-adipocytes are present both in the stromal-vascular fraction (SVF; freshly isolated cells) and in the adherent fraction of adipose stromal/stem cells (ASCs; in vitro expanded cells), and have an active role on the chronic inflammation environment established in obesity, likely due their monocytic-macrophage lineage identity. The SVF and ASCs have been explored in cell therapy protocols with relative success, given their paracrine and immunomodulatory effects. Importantly, the widely explored multipotentiality of ASCs has direct application in bone, cartilage and adipose tissue engineering. The aim of this editorial is to reinforce the peculiarities of the stem and progenitor cells from subcutaneous adipose tissue, revealing the spheroids as a recently described biotechnological tool for cell therapy and tissue engineering. Innovative cell culture techniques, in particular 3D scaffold-free cultures such as spheroids, are now available to increase the potential for regeneration and differentiation of mesenchymal lineages. Spheroids are being explored not only as a model for cell differentiation, but also as powerful 3D cell culture tools to maintain the stemness and expand the regenerative and differentiation capacities of mesenchymal cell lineages.

Aerosol inhalation of a hydrogen-rich solution restored septic renal function

Sepsis-related acute kidney injury (AKI) is known to be caused by inflammation. We explored the renal protective effects of aerosol inhalation of a hydrogen-rich solution (HRS; hydrogen gas dissolved to saturation in saline) in a mouse model of septic AKI. Septic AKI was induced through 18 hours of cecal ligation and puncture. AKI occurred during the early stage of sepsis, as evidenced by increased blood urea nitrogen and serum creatinine levels, pathological changes, renal fibrosis and renal tubular epithelial cell apoptosis, accompanied by macrophage infiltration and M1 macrophage-associated pro-inflammatory cytokine (Il-6 and Tnf-α) generation in renal tissues. Aerosol inhalation of the HRS increased anti-inflammatory cytokine (Il-4 and Il-13) mRNA levels in renal tissues and promoted macrophage polarization to the M2 type, which generated additional anti-inflammatory cytokines (Il-10 and Tgf-β). Ultimately, aerosol inhalation of HRS protected the kidneys and increased survival among septic mice. HRS was confirmed to promote M2 macrophage polarization in lipopolysaccharide-stimulated RAW 264.7 cells. The TGF-β1 receptor inhibitor SB-431542 partly reversed the effects of HRS on renal function, fibrosis, tubular epithelial cell apoptosis and senescence in mice. Thus, HRS aerosol inhalation appears highly useful for renal protection and inflammation reduction in septic AKI.

Transcriptome landscape of myeloid cells in human skin reveals diversity, rare populations and putative DC progenitors

BACKGROUND

The heterogeneous functions of dermal myeloid cells in antigen presentation, and scavenging pathogens and cell debris places them centrally in cutaneous inflammation. Single cell transcriptomics can provide new understanding of the heterogeneity and function of yet incompletely understood human dermal myeloid cell subsets.

OBJECTIVE

Investigate the transcriptome landscape of myeloid cells in healthy human skin.

METHODS

Single cell RNA-sequencing was performed on skin biopsies from ten healthy donors and analyzed to identify myeloid cell populations.

RESULTS

One LIN^- HLA-DR⁺ cluster with expression of myeloid-specific genes was identified as a cluster of myeloid cells. Upon reanalysis of this cluster, we identified three macrophage subsets, marked by high expression of CCR1, MARCO or TREM2; and six dendritic cell subsets, marked by high expression of CLEC9A, CXorf21, MCOLN2, LAMP3, KIAA0101 and Langerin, representing respectively cDC1, two subsets of cDC2, a novel DC type, a cluster of proliferating DC, and a Langerhans cell subset. GO term analysis indicated specialized functions for the discrete rare populations of myeloid cells: TREM2 Mφ in lipid metabolism and LAMP3 DC as a mature cDC. Proliferating DCs appeared to represent cDC2 progenitors.

CONCLUSION

The transcriptional landscape of myeloid cell populations in human skin indicates several, novel populations with specialized functions, as well as a rare proliferating DC population that likely accounts for local regeneration or expansion of dermal DCs. We provide robust gene expression markers for each of these populations that should permit better understandings of their roles in various homeostatic and pathologic immune processes in the skin.

Low-Frequency Intermittent Hypoxia Suppresses Subcutaneous Adipogenesis and Induces Macrophage Polarization in Lean Mice

BACKGROUND

The relationship between obstructive sleep apnoea (OSA) and metabolic disorders is complex and highly associated. The impairment of adipogenic capacity in pre-adipocytes may promote adipocyte hypertrophy and increase the risk of further metabolic dysfunction. We hypothesize that intermittent hypoxia (IH), as a pathophysiologic feature of OSA, may regulate adipogenesis by promoting macrophage polarization.

METHODS

Male C57BL/6N mice were exposed to either IH (240 seconds of 10% O₂ followed by 120 seconds of 21% O₂, i.e., 10 cycles/hour) or intermittent normoxia (IN) for 6 weeks. Stromal-vascular fractions derived from subcutaneous (SUB-SVF) and visceral (VIS-SVF) adipose tissues were cultured and differentiated. Conditioned media from cultured RAW 264.7 macrophages after air (Raw) or IH exposure (Raw-IH) were incubated with SUB-SVF during adipogenic differentiation.

RESULTS

Adipogenic differentiation of SUB-SVF but not VIS-SVF from IH-exposed mice was significantly downregulated in comparison with that derived from IN-exposed mice. IH-exposed mice compared to IN-exposed mice showed induction of hypertrophic adipocytes and increased preferential infiltration of M1 macrophages in subcutaneous adipose tissue (SAT) compared to visceral adipose tissue. Complementary in vitro analysis demonstrated that Raw-IH media significantly enhanced inhibition of adipogenesis of SUB-SVF compared to Raw media, in agreement with corresponding gene expression levels of differentiation-associated markers and adipogenic transcription factors.

CONCLUSION

Low frequency IH exposure impaired adipogenesis of SAT in lean mice, and macrophage polarization may be a potential mechanism for the impaired adipogenesis.

Dexamethasone exhibits its anti-inflammatory effects in S. aureus induced microglial inflammation via modulating TLR-2 and glucocorticoid receptor expression

Microglial inflammation plays crucial role in the pathogenesis of CNS infections including brain abscesses. Staphylococcus aureus (S. aureus) is considered as one of the major causative agents of brain abscesses. Due to the emergence of multidrug resistant bacteria the available treatment options including conventional antibiotics and steroid therapy become ineffective in terms of inflammation regulation which warrants further investigation to resolve this health issue. Microglial TLR-2 plays important roles in the bacterial recognition as well as induction of inflammation whereas glucocorticoid receptor (GR) triggers anti-inflammatory pathways in presence of glucocorticoids (GCs). The main objective of this study was to figure out the interdependency between TLR-2 and GR in presence of exogenous dexamethasone during microglial inflammation as an alternative therapeutic approach. Experiments were done either in TLR-2 neutralized condition or GR blocked condition in presence of dexamethasone. Free radicals production, arginase, superoxide dismutase (SOD), catalase enzyme activities and corticosterone concentration were measured along with Western blot analysis of TLR-2, GR and other inflammatory molecules. The results suggested that dexamethasone pre-treatment in TLR-2 neutralized condition efficiently reduces the inflammatory consequences of S. aureus induced microglial inflammation through up regulating GR expression. During TLR-2 blocking dexamethasone exerted its potent anti-inflammatory activities via suppressing reactive oxygen species (ROS), NO production and up regulating arginase, SOD and catalase activities at the time point of 90 min. Further in-vivo experiments are needed to conclude that dexamethasone could resolve brain inflammation possibly through microglial phenotypic switching from pro-inflammatory M1 to anti-inflammatory M2.

Ghrelin Signaling in Immunometabolism and Inflamm-Aging

Intracellular changes in immune cells lead to metabolic dysfunction, which is termed immunometabolism. Chronic inflammation is a hallmark of aging; this phenomenon is described as inflamm-aging. Immunometabolism and inflamm-aging are closely linked to obesity, insulin resistance, type 2 diabetes (T2D), cardiovascular diseases, and cancers, which consequently reduce life span and health span of the elderly. Ghrelin is an orexigenic hormone that regulates appetite and food intake. Ghrelin's functions are mediated through its receptor, growth hormone secretagogue receptor (GHS-R). Ghrelin and GHS-R have important roles in age-associated obesity, insulin resistance, and T2D. In this chapter, we have discussed the roles of ghrelin signaling in diet-induced obesity and normal aging as it relates to energy metabolism and inflammation in key metabolic tissues and organs. The new findings reveal that ghrelin signaling is an important regulatory mechanism for immunometabolism and inflamm-aging. Ghrelin signaling offers an exciting novel therapeutic strategy for treatment of obesity and insulin resistance of the elderly.

Treatment of obesity-related inflammation with a novel synthetic pentacyclic oleanane triterpenoids via modulation of macrophage polarization

Background

Obesity leads to the chronic inflammation in the whole body and triggers the macrophage polarization to the pro-inflammatory phenotype. Targeting macrophage polarization provides a promising therapeutic strategy for obesity-related metabolic disorders and inflammation. Here, we show that SO1989, a derivative of natural occurring compound oleanolic acid, restores the balance between M1-polarized and M2-polarized macrophages in high fat diets (HFD)-induced obese mice resulting in the improvement of adipose inflammation and the metabolic dysfunctions.

Methods

Histological analysis, magnetic cell sorting and FACS, in vitro cell model of adipose inflammation, Western blotting, HFD mice model.

Findings

SO1989 exhibits similar or even stronger activity in inhibiting inflammation and M1 polarization of macrophages both in vitro and in vivo compared to its analogue CDDO-Me, previously known as a powerful anti-inflammation chemical small molecule. In addition, SO1989 can significantly increase the level of fatty acid oxidation in macrophages which can efficiently facilitate M2 polarization of macrophages. Unlike CDDO-Me, SO1989 shows less adverse effects on obese mice.

Interpretation

Taken all together, our findings identify SO1989 as a modulator in macrophage polarization and a safer potential leading compound for pro-resolution of inflammation treatment in metabolic disorders.

Fund

Supported by grants from the National Key Research and Development Plan (2017YFA0506000, 2017YFA0205400) and National Natural Science Foundation of China (81673439) and Natural Science Fund project in Jiangsu Province (BK20161408).

Transcriptomics Analysis Reveals New Insights into the Roles of Notch1 Signaling on Macrophage Polarization

Naïve macrophages (Mφ) polarize in response to various environmental cues to a spectrum of cells that have distinct biological functions. The extreme ends of the spectrum are classified as M1 and M2 macrophages. Previously, we demonstrated that Notch1 deficiency promotes Tgf-β2 dependent M2-polarization in a mouse model of abdominal aortic aneurysm. The present studies aimed to characterize the unique set of genes regulated by Notch1 signaling in macrophage polarization. Bone marrow derived macrophages isolated from WT or Notch1+/- mice (n = 12) were differentiated to Mφ, M1 or M2-phenotypes by 24 h exposure to vehicle, LPS/IFN-γ or IL4/IL13 respectively and total RNA was subjected to RNA-Sequencing (n = 3). Bioinformatics analyses demonstrated that Notch1 haploinsufficiency downregulated the expression of 262 genes at baseline level, 307 genes with LPS/IFN-γ and 254 genes with IL4/IL13 treatment. Among these, the most unique genes downregulated by Notch1 haploinsufficiency included fibromodulin (Fmod), caspase-4, Has1, Col1a1, Alpl and Igf. Pathway analysis demonstrated that extracellular matrix, macrophage polarization and osteogenesis were the major pathways affected by Notch1 haploinsufficiency. Gain and loss-of-function studies established a strong correlation between Notch1 haploinsufficiency and Fmod in regulating Tgf-β signaling. Collectively, our studies suggest that Notch1 haploinsufficiency increases M2 polarization through these newly identified genes.

Association between Adipose Tissue Interleukin-33 and Immunometabolic Markers in Individuals with Varying Degrees of Glycemia

Introduction

Interleukin-33 (IL-33), the ligand for the receptor ST2, is abundant in adipose tissue, including preadipocytes, adipocytes, and endothelial cells. The IL-33/ST2 axis is protective against obesity, insulin resistance, and type 2 diabetes (T2D) in animal models. We determined whether adipose tissue IL-33 was associated with glycated hemoglobin (HbA1c), as well as mediators of inflammation and immune regulation and beiging of adipose tissue, among individuals with varying degrees of glycemia.

Materials and Methods

A total of 91 adults with normoglycemia, prediabetes, and T2D were included. After measuring their anthropometric and biochemical parameters, subcutaneous adipose tissue samples were isolated and mRNA expression of cytokines, chemokines, chemokine receptors, pattern recognition receptors, and mediators involved in beiging of adipose tissue were measured.

Results

Adipose tissue IL-33 was inversely associated with HbA1c in individuals with normoglycemia and T2D but not in those with prediabetes and was inversely correlated with fasting plasma glucose in individuals with T2D and with a better glycemic control. IL-33-to-ST2 ratio was inversely correlated with HbA1c in individuals with normoglycemia but not in those with prediabetes or T2D. IL-33 was directly associated with ST2, CD302, fibrinogen-like protein 2 (FGL2), and PR domain containing 16 (PRDM16) but inversely correlated with chemokine (C-C motif) ligand (CCL) 7 and CCL8 in individuals with normoglycemia. Similarly, IL-33 was directly associated with ST2, CD302, FGL2, PRDM16, and, additionally, toll-like receptor (TLR) 3 and IL-12A in individuals with T2D. However, IL-33 was not associated with any of these mediators but was directly and strongly associated with TLR9 in individuals with prediabetes.

Conclusions

IL-33 and/or IL-33/ST2 dynamics and biological functions may play a role in overall glycemia among humans and may represent a novel target by which glucose-lowering managements confer their beneficial effects.

Amygdalar Metabolic Activity Independently Associates With Progression of Visceral Adiposity

CONTEXT

Epidemiologic data link psychological stress to adiposity. The underlying mechanisms remain uncertain.

OBJECTIVES

To test whether (i) higher activity of the amygdala, a neural center involved in the response to stress, associates with greater visceral adipose tissue (VAT) volumes and (ii) this association is mediated by increased bone marrow activity.

SETTING

Massachusetts General Hospital, Boston, Massachusetts.

PATIENTS

Two hundred forty-six patients without active oncologic, cardiovascular, or inflammatory disease who underwent clinical 18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging were studied. VAT imaging was repeated ∼1 year later in 68 subjects.

DESIGN

Metabolic activity of the amygdala (AmygA), hematopoietic tissue activity, and adiposity volumes were measured with validated methods.

MAIN OUTCOME MEASURE

The relationship between AmygA and baseline and follow-up VAT.

RESULTS

AmygA associated with baseline body mass index (standardized β = 0.15; P = 0.01), VAT (0.19; P = 0.002), and VAT/subcutaneous adipose tissue ratio (0.20; P = 0.002), all remaining significant after adjustment for age and sex. AmygA also associated with bone marrow activity (0.15; P = 0.01), which in turn associated with VAT (0.34; P < 0.001). Furthermore, path analysis showed that 48% of the relationship between AmygA and baseline VAT was mediated by increased bone marrow activity (P = 0.007). Moreover, AmygA associated with achieved VAT after 1 year (P = 0.02) after adjusting for age, sex, and baseline VAT.

CONCLUSIONS

These results suggest a neurobiological pathway involving the amygdala and bone marrow linking psychosocial stress to adiposity in humans. Future studies should test whether targeting this mechanism attenuates adiposity and its complications.

Attenuation of Atherosclerosis by Protocatechuic Acid via Inhibition of M1 and Promotion of M2 Macrophage Polarization

Macrophage polarization has a vital impact on the progression of atherosclerosis (AS). Protocatechuic acid (PCA), a flavonol, displays notable atheroprotective effects, but its mechanisms have not been clearly defined. We investigated whether PCA attenuated AS by regulating macrophage polarization. PCA consumption inhibited HCD-induced plaque formation (17.84 and 8.21% in the HCD and HCD with PCA groups, respectively, p < 0.05) and inflammatory responses in apolipoprotein E deficient (ApoE^-/-) mice. Moreover, PCA suppressed classically activated macrophage (M1) polarization, which decreased the secretion of nitric oxide synthase (54.63 and 32.86% in the HCD and HCD with PCA groups, respectively, p < 0.05) and proinflammatory factors. PCA promoted alternatively activated macrophage (M2) activation, which increased the expression of arginine I (6.97 and 26.19% in the HCD and HCD with PCA groups, respectively, p < 0.001) and anti-inflammatory factors. PCA also regulated M1-M2 polarization in J774 cells and mouse-bone-marrow-derived macrophages. Finally, PCA reduced PI3K-Akt-mediated nuclear-factor-κB activation, thereby suppressing M1 polarization, and provoked signal-transducers-and-activators-of-transcription-6 phosphorylation and peroxisome-proliferator-activated-receptor-γ activation, leading to enhanced M2 activation. Our data revealed that PCA alleviated AS by regulating M1-M2 conversion.