PPARgamma activation primes human monocytes into alternative M2 macrophages with anti-inflammatory properties

Diet-Microbiota Interplay: An Emerging Player in Macrophage Plasticity and Intestinal Health

Inflammatory bowel diseases (IBD) are chronic disorders of the gastrointestinal tract with an increasing prevalence worldwide. Targeted therapies for IBD are limited by several factors, including the therapeutic ceiling and the high incidence of non-responders or loss-of-response. In order to improve therapeutic efficacy, there is critical need to decipher disease pathogenesis, currently not well understood. Macrophages, innate immune cells that exhibit high plasticity, perpetuate inflammatory signalling in IBD through excessive release of inflammatory mediators. In recent years, pioneering research has revealed the importance of the interplay between macrophages and gut microbiota in maintaining intestinal homeostasis. Particular attention is focusing on microbiota-derived metabolites, believed to possess immunomodulatory properties capable of manipulating macrophage plasticity. Microbiota-derived short-chain fatty acids (SCFAs) and indole compounds, along with dietary sourced omega-3 (ω-3) polyunsaturated fatty acids (PUFA), exert anti-inflammatory effects, attributable to interactions with macrophages. Before we can effectively incorporate these metabolites into IBD therapies, a deeper understanding of microbiota-macrophage interactions at a molecular level is necessary. Therefore, the aim of this review is firstly to detail current knowledge regarding how diet and microbiota-derived metabolites modify macrophage plasticity. Later, we discuss the concept of therapeutic strategies directed at microbiota-macrophage interactions, which could be highly valuable for IBD therapies in the future.

Pharmacologic Recruitment of Endogenous Neural Stem/Progenitor Cells for the Treatment of Spinal Cord Injury

STUDY DESIGN

Laboratory study using a rat T9 contusion model of spinal cord injury.

OBJECTIVE

This study aims to examine whether a combinatory treatment of Pioglitazone (PGZ) and granulocyte colony-stimulating factor (GCSF) can support neural stem/progenitor cells (NSPCs) directly and provide a sustainable microenvironment through immunomodulatory mechanisms.

SUMMARY OF BACKGROUND DATA

Neuroinflammation plays a crucial role in the progression of spinal cord injury (SCI) and hinders NSPC-mediated repair and regeneration. Broad acting drugs that mitigate inflammation and support NSPC proliferation have not been tested together in SCI research models.

METHODS

Isolated NSPCs were treated with vehicle control, PGZ, GCSF, or both PGZ and GSCF for 24 hours and stained with proliferation marker Ki67. Adult female Sprague-Dawley rats sustained moderate-to-severe contusion-based SCI at T9 and were administered either vehicle control, PGZ, GCSF, or both PGZ and GCSF treatments.

RESULTS

Immunocytochemistry revealed that cultured NSPCs treated with both drugs produced higher numbers of actively proliferating cells and total cell numbers. ELISA on spinal cord tissue lysates at 1, 3, and 7 days post-injury (DPI) demonstrated that animals treated with PGZ, GCSF, or combination therapy showed significantly higher doublecortin levels at 7 DPI compared to control animals (P < 0.05). Immunohistochemistry of injured tissue at 3, 7, and 14 DPI revealed no difference of ependymal NSPC proliferation between groups, but showed a significant decrease in lesion size with combination therapy compared to controls. Functional recovery was assessed by the Basso, Beattie, Bresnahan locomotor rating scale. Animals treated with both drugs had significantly higher levels of function at 1 (P < 0.001), 3 (P < 0.001), 7 (P < 0.05), and 14 (P < 0.05) DPI compared to controls.

CONCLUSION

These results indicate that PGZ and GCSF treatment synergistically enhance NSPCs numbers and improve functional recovery after SCI. Our findings support an immunomodulatory strategy to recruit native NSPCs as a potential acute care intervention for SCI.Level of Evidence: N/A.

The Role of Peroxisome Proliferator-Activated Receptor Gamma and Atherosclerosis: Post-translational Modification and Selective Modulators

Atherosclerosis is the hallmark of cardiovascular disease (CVD) which is a leading cause of death in type 2 diabetes patients, and glycemic control is not beneficial in reducing the potential risk of CVD. Clinically, it was shown that Thiazolidinediones (TZDs), a class of peroxisome proliferator-activated receptor gamma (PPARγ) agonists, are insulin sensitizers with reducing risk of CVD, while the potential adverse effects, such as weight gain, fluid retention, bone loss, and cardiovascular risk, restricts its use in diabetic treatment. PPARγ, a ligand-activated nuclear receptor, has shown to play a crucial role in anti-atherosclerosis by promoting cholesterol efflux, repressing monocytes infiltrating into the vascular intima under endothelial layer, their transformation into macrophages, and inhibiting vascular smooth muscle cells proliferation as well as migration. The selective activation of subsets of PPARγ targets, such as through PPARγ post-translational modification, is thought to improve the safety profile of PPARγ agonists. Here, this review focuses on the significance of PPARγ activity regulation (selective activation and post-translational modification) in the occurrence, development and treatment of atherosclerosis, and further clarifies the value of PPARγ as a safe therapeutic target for anti-atherosclerosis especially in diabetic treatment.

Diet, lipids, and antitumor immunity

Tumour growth and dissemination is largely dependent on nutrient availability. It has recently emerged that the tumour microenvironment is rich in a diverse array of lipids that increase in abundance with tumour progression and play a role in promoting tumour growth and metastasis. Here, we describe the pro-tumorigenic roles of lipid uptake, metabolism and synthesis and detail the therapeutic potential of targeting lipid metabolism in cancer. Additionally, we highlight new insights into the distinct immunosuppressive effects of lipids in the tumour microenvironment. Lipids threaten an anti-tumour environment whereby metabolic adaptation to lipid metabolism is linked to immune dysfunction. Finally, we describe the differential effects of commondietary lipids on cancer growth which may uncover a role for specific dietary regimens in association with traditional cancer therapies. Understanding the relationship between dietary lipids, tumour, and immune cells is important in the context of obesity which may reveal a possibility to harness the diet in the treatment of cancers.

Immunomodulatory activity of β-glucan polysaccharides isolated from different species of mushroom - A potential treatment for inflammatory lung conditions

Acute respiratory distress syndrome (ARDS) is the most common form of acute severe hypoxemic respiratory failure in the critically ill with a hospital mortality of 40%. Alveolar inflammation is one of the hallmarks for this disease. β-Glucans are polysaccharides isolated from a variety of natural sources including mushrooms, with documented immune modulating properties. To investigate the immunomodulatory activity of β-glucans and their potential as a treatment for ARDS, we isolated and measured glucan-rich polysaccharides from seven species of mushrooms. We used three models of in-vitro injury in THP-1 macrophages, Peripheral blood mononuclear cells (CD14+) (PMBCs) isolated from healthy volunteers and lung epithelial cell lines. We observed variance between β-glucan content in extracts isolated from seven mushroom species. The extracts with the highest β-glucan content found was Lentinus edodes which contained 70% w/w and Hypsizygus tessellatus which contained 80% w/w with low levels of α-glucan. The extracts had the ability to induce secretion of up to 4000 pg/mL of the inflammatory cytokine IL-6, and up to 5000 pg/mL and 500 pg/mL of the anti-inflammatory cytokines IL-22 and IL-10, respectively, at a concentration of 1 mg/mL in THP-1 macrophages. In the presence of cytokine injury, IL-8 was reduced from 15,000 pg/mL to as low as 10,000 pg/mL in THP-1 macrophages. After insult with LPS, phagocytosis dropped from 70-90% to as low 10% in CD14+ PBMCs. After LPS insult CCL8 relative gene expression was reduced, and IL-10 relative gene expression increased from 50 to 250-fold in THP-1 macrophages. In lung epithelial cells, both A549 and BEAS-2B after IL-1β insult, IL-8 levels dropped from 10,000 pg/mL to as low as 6000 pg/mL. TNF-α levels dropped 10-fold from 100 pg/mL to just below 10 pg/mL. These results demonstrate the therapeutic potential of β-glucans in inflammatory lung conditions. Findings also advance bio-based research that connects green innovation with One Health applications for the betterment of society.

The Effects of Rosiglitazone on Task Specific Anxiety-Like Behavior and Novelty Seeking in a Model of Chronic Adolescent Unpredictable Stress

Adolescence is characterized as a period of increased social behavior, risk taking, and novelty seeking, partly due to ongoing maturation in critical brain areas and the hypothalamic-pituitary-adrenal (HPA) negative-feedback system. During this period there is heightened vulnerability to stress that can drive neuro-immune-endocrine remodeling, resulting in the emergence of maladaptive behaviors that increase susceptibility to alcohol and substance abuse. Here we used a rat model to investigate the impact of chronic adolescent unpredictable stress on a battery of behavioral measures to assess anxiety, novelty seeking, risk taking, depression, and voluntary ethanol consumption while determining whether the PPARγ agonist rosiglitazone can attenuate these effects. Adolescent female rats that experienced stress showed increased risk taking behavior and novelty seeking behavior with no change in ethanol consumption. The administration of rosiglitazone during stress induction attenuated stress-induced cortisol elevation, normalized risk taking behavior in a model anxiety, and attenuated novelty seeking in a task-specific manner. Depressive-like behavior was not impacted by adolescent unpredictable stress or the administration of rosiglitazone. The results from this study demonstrate that exposure to unpredictable stress during adolescence increases the prevalence of maladaptive behaviors that are known to increase susceptibility to alcohol and substance abuse, and that rosiglitazone may be an effective therapeutic to attenuate the emergence of select risk taking and novelty seeking behaviors in females.

Early differential responses elicited by BRAFV600E in adult mouse models

The BRAF gene is frequently mutated in cancer. The most common genetic mutation is a single nucleotide transition which gives rise to a constitutively active BRAF kinase (BRAF^V600E) which in turn sustains continuous cell proliferation. The study of BRAF^V600E murine models has been mainly focused on the role of BRAF^V600E in tumor development but little is known on the early molecular impact of BRAF^V600E expression in vivo. Here, we study the immediate effects of acute ubiquitous BRAF^V600E activation in vivo. We find that BRAF^V600E elicits a rapid DNA damage response in the liver, spleen, lungs but not in thyroids. This DNA damage response does not occur at telomeres and is accompanied by activation of the senescence marker p21^CIP1 only in lungs but not in liver or spleen. Moreover, in lungs, BRAF^V600E provokes an acute inflammatory state with a tissue-specific recruitment of neutrophils in the alveolar parenchyma and macrophages in bronchi/bronchioles, as well as bronchial/bronchiolar epithelium transdifferentiation and development of adenomas. Furthermore, whereas in non-tumor alveolar type II (ATIIs) pneumocytes, acute BRAF^V600E induction elicits rapid p53-independent p21^CIP1 activation, adenoma ATIIs express p53 without resulting in p21^CIP1 gene activation. Conversely, albeit in Club cells BRAF^V600E-mediated proliferative cue is more exacerbated compared to that occurring in ATIIs, such oncogenic stimulus culminates with p21^CIP1-mediated cell cycle arrest and apoptosis. Our findings indicate that acute BRAF^V600E expression drives an immediate induction of DNA damage response in vivo. More importantly, it also results in rapid differential responses of cell cycle and senescence-associated proteins in lung epithelia, thus revealing the early molecular changes emerging in BRAF^V600E-challenged cells during tumorigenesis in vivo.

Role of Pyroptosis and Ferroptosis in the Progression of Atherosclerotic Plaques

Pyroptosis is a special way of programmed cell death which is dependent on the activation of cysteinyl aspartate specific proteinase 1 (Caspase-1) and Caspase-4/5/11. Ferroptosis is an iron-dependent cell death that characterized by the intra-cellular lipid peroxidation-mediated membrane damage. Pyroptosis or ferroptosis in macrophages, smooth muscle cells, and vascular endothelial cells are believed to be closely related to the progression of atherosclerotic plaques. Therefore, we discuss the role of pyroptosis and ferroptosis in the development of atherosclerotic plaques and may provide new strategies for the treatment of atherosclerosis.

Long-Chain Polyunsaturated Fatty Acids and Their Metabolites Regulate Inflammation in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a blinding eye disease, whose incidence strongly increases with ages. The etiology of AMD is complex, including aging, abnormal lipid metabolism, chronic inflammation and oxidative stress. Long-chain polyunsaturated fatty acids (LCPUFA) are essential for ocular structures and functions. This review summarizes the regulatory effects of LCPUFA on inflammation in AMD. LCPUFA are related to aging, autophagy and chronic inflammation. They are metabolized to pro- and anti-inflammatory metabolites by various enzymes. These metabolites stimulate inflammation in response to oxidative stress, causing innate and acquired immune responses. This review also discusses the possible clinical applications, which provided novel targets for the prevention and treatment of AMD and other age-related diseases.

Therapeutic strategies targeting inflammation and immunity in atherosclerosis: how to proceed?

Atherosclerosis is a chronic inflammatory disease of the arterial wall, characterized by the formation of plaques containing lipid, connective tissue and immune cells in the intima of large and medium-sized arteries. Over the past three decades, a substantial reduction in cardiovascular mortality has been achieved largely through LDL-cholesterol-lowering regimes and therapies targeting other traditional risk factors for cardiovascular disease, such as hypertension, smoking, diabetes mellitus and obesity. However, the overall benefits of targeting these risk factors have stagnated, and a huge global burden of cardiovascular disease remains. The indispensable role of immunological components in the establishment and chronicity of atherosclerosis has come to the forefront as a clinical target, with proof-of-principle studies demonstrating the benefit and challenges of targeting inflammation and the immune system in cardiovascular disease. In this Review, we provide an overview of the role of the immune system in atherosclerosis by discussing findings from preclinical research and clinical trials. We also identify important challenges that need to be addressed to advance the field and for successful clinical translation, including patient selection, identification of responders and non-responders to immunotherapies, implementation of patient immunophenotyping and potential surrogate end points for vascular inflammation. Finally, we provide strategic guidance for the translation of novel targets of immunotherapy into improvements in patient outcomes.

In this Review, the authors provide an overview of the immune cells involved in atherosclerosis, discuss preclinical research and published and ongoing clinical trials assessing the therapeutic potential of targeting the immune system in atherosclerosis, highlight emerging therapeutic targets from preclinical studies and identify challenges for successful clinical translation.

Inflammation is an important component of the pathophysiology of cardiovascular disease; an imbalance between pro-inflammatory and anti-inflammatory processes drives chronic inflammation and the formation of atherosclerotic plaques in the vessel wall.

Clinical trials assessing canakinumab and colchicine therapies in atherosclerotic cardiovascular disease have provided proof-of-principle of the benefits associated with therapeutic targeting of the immune system in atherosclerosis.

The immunosuppressive adverse effects associated with the systemic use of anti-inflammatory drugs can be minimized through targeted delivery of anti-inflammatory drugs to the atherosclerotic plaque, defining the window of opportunity for treatment and identifying more specific targets for cardiovascular inflammation.

Implementing immunophenotyping in clinical trials in patients with atherosclerotic cardiovascular disease will allow the identification of immune signatures and the selection of patients with the highest probability of deriving benefit from a specific therapy.

Clinical stratification via novel risk factors and discovery of new surrogate markers of vascular inflammation are crucial for identifying new immunotherapeutic targets and their successful translation into the clinic.

Therapeutic Application of Extracellular Vesicles-Capsulated Adeno-Associated Virus Vector via nSMase2/Smpd3, Satellite, and Immune Cells in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is caused by loss-of-function mutations in the dystrophin gene on chromosome Xp21. Disruption of the dystrophin–glycoprotein complex (DGC) on the cell membrane causes cytosolic Ca²⁺ influx, resulting in protease activation, mitochondrial dysfunction, and progressive myofiber degeneration, leading to muscle wasting and fragility. In addition to the function of dystrophin in the structural integrity of myofibers, a novel function of asymmetric cell division in muscular stem cells (satellite cells) has been reported. Therefore, it has been suggested that myofiber instability may not be the only cause of dystrophic degeneration, but rather that the phenotype might be caused by multiple factors, including stem cell and myofiber functions. Furthermore, it has been focused functional regulation of satellite cells by intracellular communication of extracellular vesicles (EVs) in DMD pathology. Recently, a novel molecular mechanism of DMD pathogenesis—circulating RNA molecules—has been revealed through the study of target pathways modulated by the Neutral sphingomyelinase2/Neutral sphingomyelinase3 (nSMase2/Smpd3) protein. In addition, adeno-associated virus (AAV) has been clinically applied for DMD therapy owing to the safety and long-term expression of transduction genes. Furthermore, the EV-capsulated AAV vector (EV-AAV) has been shown to be a useful tool for the intervention of DMD, because of the high efficacy of the transgene and avoidance of neutralizing antibodies. Thus, we review application of AAV and EV-AAV vectors for DMD as novel therapeutic strategy.

Decreased Iron Ion Concentrations in the Peripheral Blood Correlate with Coronary Atherosclerosis

(1) Background: Obesity and diabetes continue to reach epidemic levels in the population with major health impacts that include a significantly increased risk of coronary atherosclerosis. The imbalance of trace elements in the body caused by nutritional factors can lead to the progression of coronary atherosclerosis. (2) Methods: We measured the concentrations of sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), Zinc (Zn), and iron (Fe) in peripheral blood samples from 4243 patients and performed baseline analysis and propensity matching of the patient datasets. The patients were grouped into acute myocardial infarction (AMI, 702 patients) and stable coronary heart disease (SCAD1, 253 patients) groups. Both of these groups were included in the AS that had a total of 1955 patients. The control group consisted of 2288 patients. The plasma concentrations of calcium, magnesium, and iron were measured using a colorimetric method. For comparison, 15 external quality assessment (EQA) samples were selected from the Clinical Laboratory Center of the Ministry of Health of China. SPSS software was used for statistical analysis. The average values and deviations of all of the indicators in each group were calculated, and a p-value threshold of <0.05 was used to indicate statistical significance. (3) Results: The iron ion concentrations of the acute myocardial infarction (AMI) group were significantly lower than the control group (p < 0.05, AUC = 0.724, AUC = 0.702), irrespective of tendency matching. Compared to the data from the stable coronary artery disease (SCAD) group, the concentration of iron ions in the acute myocardial infarction group was significantly lower (p < 0.05, AUC = 0.710, AUC = 0.682). Furthermore, the iron ion concentrations in the (AMI + SCAD) group were significantly lower (p < 0.05) than in the control group. (4) Conclusions: The data presented in this study strongly indicate that the concentration of iron ions in the peripheral blood is related to coronary atherosclerosis. Decreases in the levels of iron ions in the peripheral blood can be used as a predictive biomarker of coronary atherosclerosis.

Chronic exposure to biomass ambient particulate matter triggers alveolar macrophage polarization and activation in the rat lung

The role of alveolar macrophages (AMs) in chronic obstructive pulmonary disease is unclear. We characterized the function of AMs in rats chronically exposed to biomass fuel smoke (BMF) and studied the signal pathways that regulate AMs polarization. One hundred and eighty male Sprague‐Dawley rats were divided into BMF group and clean air control (CON) group. After BMF smoke exposure for 4 days, 1 month and 6 months, the cytokine secretion and function of AMs were determined by flow cytometry, quantitative polymerase chain reaction, Western blotting and immunofluorescence. Bone marrow‐derived macrophages were cultured and exposed to particulate matter (PM) from the smoke. Exposure initially promoted pro‐inflammatory factors, but pro‐inflammatory macrophages shared features of anti‐inflammatory macrophages. Consistent with IL‐4 upregulated in bronchoalveolar lavage fluid, p‐Stat6 and peroxisome proliferator‐activated receptor γ (PPARγ) in AMs elevated at 4 days of exposure. After 6 months of exposure, CD206, TGF‐β1 and p‐Smad3 were significantly higher than the control groups. PPARγ reversed the M1 phenotype induced by PM in vitro and drove the macrophages into the M2 phenotype. Altogether, the study demonstrates the dynamic phenotype and functional changes in AMs during exposure to BMF smoke.

Antioxidants as Therapeutic Agents in Acute Respiratory Distress Syndrome (ARDS) Treatment-From Mice to Men

Acute respiratory distress syndrome (ARDS) is a major cause of patient mortality in intensive care units (ICUs) worldwide. Considering that no causative treatment but only symptomatic care is available, it is obvious that there is a high unmet medical need for a new therapeutic concept. One reason for a missing etiologic therapy strategy is the multifactorial origin of ARDS, which leads to a large heterogeneity of patients. This review summarizes the various kinds of ARDS onset with a special focus on the role of reactive oxygen species (ROS), which are generally linked to ARDS development and progression. Taking a closer look at the data which already have been established in mouse models, this review finally proposes the translation of these results on successful antioxidant use in a personalized approach to the ICU patient as a potential adjuvant to standard ARDS treatment.

Changes in immune profile affect disease progression in hepatocellular carcinoma

Objective: Hepatocellular carcinoma (HCC) as a chronic liver condition is largely associated with immune responses. Previous studies have revealed that different subsets of lymphocytes play fundamental roles in controlling or improving the development and outcome of solid tumors like HCC. Hence, this study aimed to investigate whether immune system changes were related to disease development in HCC patients. Methods: Peripheral blood mononuclear cells were isolated from 30 HCC patients and 30 healthy volunteers using Ficoll density centrifugation. The isolated cells were stained with different primary antibodies and percentages of different immune cells were determined by flow cytometry. Results: HCC patients indicated significant reductions in the numbers of CD4⁺ cells, Tbet+IFNγ+cells, and GATA+IL-4+cells in peripheral blood in comparison with healthy individuals (p < 0.05). There was no significant change in IL-17+RORγt+cells between patient and healthy groups. In contrast, Foxp3+CD127^lowcell frequency was significantly higher in patients than healthy subjects (p < 0.0001). The numbers of Th1, Th2, and Th17 cells were significantly lower in HCC patients than healthy control (p < 0.0001), although the reduction in Th2 cell numbers was not statistically significant. On the contrary, Treg percentage showed a significant increase in patients compared to healthy subjects (p < 0.0001). Other data revealed that Th1, Th2, and Th17 cell frequencies were significantly higher in healthy individuals than patients with different TNM stages of HCC, with the exception of Th2 in patients with stage II HCC (p < 0.01-0.05). Treg percentage was significantly increased in patients with different TNM stages (p < 0.0001). Among all CD4⁺ T cells, the frequency of Th2 cell was significantly associated with TNM stages of HCC (p < 0.05). Conclusion: Our data provide further evidence to show that immune changes may participate in determining HCC progression and disease outcome. However, it should be mentioned that more investigations are needed to clarify our results and explain possible impacts of other immune cells on the pathogenesis of HCC.

Role of Hepatocyte- and Macrophage-Specific PPARγ in Hepatotoxicity Induced by Diethylhexyl Phthalate in Mice

BACKGROUND

Phthalates may disturb metabolic homeostasis in the liver by interfering with the peroxisome proliferator-activated receptors (PPARs). However, the role of hepatic macrophages in the lipid metabolic dysregulation induced by diethylhexyl phthalate (DEHP) remains unclear.

OBJECTIVES

We aimed to evaluate the respective role of hepatocyte- and macrophage-specific PPARγ in the hepatotoxicity induced by DEHP.

METHODS

Wild-type (WT), hepatocyte-specific PPARγ knockout (Hep-KO), and macrophage-specific PPAR knockout (Mac-KO) mice were administered DEHP (625mg/kg body weight) by daily gavage for 28 d, followed by hepatotoxicity examination and macrophage analysis. RNA sequencing and lipid metabolomic analysis were used to characterize the molecular changes in mouse liver. Mouse bone marrow-derived macrophages (BMDMs) and human monocytic THP-1 cell-derived macrophages were used to investigate the mechanistic regulation of macrophages' polarization by DEHP and mono(2-ethylhexyl) phthalate (MEHP).

RESULTS

The levels of hepatic steatosis and triglyceride were significantly higher in the mice treated with DEHP compared with the control mice in the WT and Hep-KO model. Lipid accumulation induced by DEHP was notably attenuated in the Mac-KO mice, but M2-polarization of hepatic macrophages in the Mac-KO mice was significantly higher compared with the WT mice under DEHP treatment. The M2-polarization of BMDMs and human macrophages was suppressed by DEHP and MEHP. Transcriptomic and lipidomic data suggested lower levels of lipid biosynthesis, fatty acid oxidation, and oxidative phosphorylation in the Mac-KO mice compared with the WT and Hep-KO mice under DEHP treatment.

CONCLUSIONS

Our data suggested that the orchestrated activation of PPARα and PPARγ by MEHP may reprogram hepatic macrophages' polarization, thereby affecting lipid homeostasis in the mouse liver. Although this conclusion was based on studies conducted in mice and in vitro, these findings may aid in elucidating the health effect of environmental phthalate exposure. https://doi.org/10.1289/EHP9373.

Parsing the Role of PPARs in Macrophage Processes

Cells are richly equipped with nuclear receptors, which act as ligand-regulated transcription factors. Peroxisome proliferator activated receptors (PPARs), members of the nuclear receptor family, have been extensively studied for their roles in development, differentiation, and homeostatic processes. In the recent past, there has been substantial interest in understanding and defining the functions of PPARs and their agonists in regulating innate and adaptive immune responses as well as their pharmacologic potential in combating acute and chronic inflammatory disease. In this review, we focus on emerging evidence of the potential roles of the PPAR subtypes in macrophage biology. We also discuss the roles of dual and pan PPAR agonists as modulators of immune cell function, microbial infection, and inflammatory diseases.

Macrophage-Osteoclast Associations: Origin, Polarization, and Subgroups

Cellular associations in the bone microenvironment are involved in modulating the balance between bone remodeling and resorption, which is necessary for maintaining a normal bone morphology. Macrophages and osteoclasts are both vital components of the bone marrow. Macrophages can interact with osteoclasts and regulate bone metabolism by secreting a variety of cytokines, which make a significant contribution to the associations. Although, recent studies have fully explored either macrophages or osteoclasts, indicating the significance of these two types of cells. However, it is of high importance to report the latest discoveries on the relationships between these two myeloid-derived cells in the field of osteoimmunology. Therefore, this paper reviews this topic from three novel aspects of the origin, polarization, and subgroups based on the previous work, to provide a reference for future research and treatment of bone-related diseases.

Extracellular CIRP-Impaired Rab26 Restrains EPOR-Mediated Macrophage Polarization in Acute Lung Injury

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a condition with an imbalanced inflammatory response and delayed resolution of inflammation. Macrophage polarization plays an important role in inflammation and resolution. However, the mechanism of macrophage polarization in ALI/ARDS is not fully understood. We found that mice with lipopolysaccharide administration developed lung injury with the accumulation of extracellular cold-inducible RNA-binding protein (eCIRP) in the lungs. eCIRP, as a damage-associated molecular pattern (DAMP), inhibited M2 macrophage polarization, thereby tipping the balance toward inflammation rather than resolution. Anti-CIRP antibodies reversed such phenotypes. The levels of macrophage erythropoietin (EPO) receptor (EPOR) were reduced after eCIRP treatment. Myeloid-specific EPOR-deficient mice displayed restrained M2 macrophage polarization and impaired inflammation resolution. Mechanistically, eCIRP impaired Rab26, a member of Ras superfamilies of small G proteins, and reduced the transportation of surface EPOR, which resulted in macrophage polarization toward the M1 phenotype. Moreover, EPO treatment hardly promotes M2 polarization in Rab26 knockout (KO) macrophages through EPOR. Collectively, macrophage EPOR signaling is impaired by eCIRP through Rab26 during ALI/ARDS, leading to the restrained M2 macrophage polarization and delayed inflammation resolution. These findings identify a mechanism of persistent inflammation and a potential therapy during ALI/ARDS.

A nonhuman primate model of vertical sleeve gastrectomy facilitates mechanistic and translational research in human obesity

The obesity epidemic significantly contributes to overall morbidity and mortality. Bariatric surgery is the gold standard treatment for obesity and metabolic dysfunction, yet the mechanisms by which it exerts metabolic benefit remain unclear. Here, we demonstrate a model of vertical sleeve gastrectomy (VSG) in nonhuman primates (NHP) that mimics the complexity and outcomes in humans. We also show that VSG confers weight loss and durable metabolic benefit, where equivalent caloric intake in shams resulted in significant weight gain following surgery. Furthermore, we show that VSG is associated with early, weight-independent increases in bile acids, short-chain fatty acids, and reduced visceral adipose tissue (VAT) inflammation with a polarization of VAT-resident immunocytes toward highly regulatory myeloid cells and Tregs. These data demonstrate that this strongly translational NHP model can be used to interrogate factors driving successful intervention to unravel the interplay between physiologic systems and improve therapies for obesity and metabolic syndrome.

Senescent tumor cells: an overlooked adversary in the battle against cancer

Senescent cells in cancer tissue, including senescent fibroblasts and macrophages, have been reported to increase the malignant potency of cancer cells by secreting senescence-associated secretory phenotype (SASP). Otherwise, Senescence of tumor cells has been believed to inhibit tumor growth by halting the massive proliferation and increasing the chances of immune clearance. In particular, senescent tumor cells (STCs) have been thought that they rarely exist in carcinomas because oncogene-induced senescence needs to be overcome for protumorigenic cells to become malignant. However, recent studies have revealed that a considerable number of STCs are present in cancer tissue, even in metastatic sites. In fact, STCs are widely involved in cancer progression by leading to collective invasion and building a cytokine barrier to protect nonsenescent tumor cells from immune attack. Furthermore, therapy-induced STCs can induce tumor progression and recurrence by increasing stemness. However, obscure causative factors and their heterogeneity in various cancers make it difficult to establish the physiological role of STCs. Here, we summarize and review the current knowledge of the pathophysiology and role of STCs. We also outline the current status of therapeutic strategies for directly removing STCs or modulating the SASPs to maximize the positive functions of STCs while suppressing the negative functions.

Single cell atlas for 11 non-model mammals, reptiles and birds

The availability of viral entry factors is a prerequisite for the cross-species transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Large-scale single-cell screening of animal cells could reveal the expression patterns of viral entry genes in different hosts. However, such exploration for SARS-CoV-2 remains limited. Here, we perform single-nucleus RNA sequencing for 11 non-model species, including pets (cat, dog, hamster, and lizard), livestock (goat and rabbit), poultry (duck and pigeon), and wildlife (pangolin, tiger, and deer), and investigated the co-expression of ACE2 and TMPRSS2. Furthermore, cross-species analysis of the lung cell atlas of the studied mammals, reptiles, and birds reveals core developmental programs, critical connectomes, and conserved regulatory circuits among these evolutionarily distant species. Overall, our work provides a compendium of gene expression profiles for non-model animals, which could be employed to identify potential SARS-CoV-2 target cells and putative zoonotic reservoirs.

Ubiquitinated ligation protein NEDD4L participates in MiR-30a-5p attenuated atherosclerosis by regulating macrophage polarization and lipid metabolism

MiR-30a-5p plays an important role in various cardiovascular diseases, but its effect in atherosclerosis has not been reported. Apolipoprotein E-deficient (Apo E^−/−) mice were used to investigate the role of miR-30a-5p in atherosclerosis, and the underlying mechanism was investigated in vivo and in vitro. The fluorescence in situ hybridization test revealed that miR-30a-5p was expressed in Apo E^−/− mice lesions. Nevertheless, in RAW264.7 macrophages, the expression of miR-30a-5p was reduced by lipopolysaccharide (LPS) or oxidized low-density lipoprotein. MiR-30a-5p-ago-treated Apo E^−/− mice significantly reduced lesion areas in the aorta and aortic root, reduced levels of lipoprotein and pro-inflammatory cytokines, and increased levels of anti-inflammatory cytokines. The ratio of M1/M2 macrophages was decreased in miR-30a-5p-ago-treated Apo E^−/− mice and LPS-treated RAW264.7 macrophages by the regulation of Smad-1/2 phosphorylation. MiR-30a-5p reduced lipid uptake in oxidized low-density lipoprotein-treated macrophages by regulating the expression of PPAR-γ, ABCA1, ABCG1, LDLR, and PCSK9. Ubiquitinated ligase NEDD4L was identified as a target of miR-30a-5p. Interestingly, knockdown of NEDD4L decreased the M1/M2 ratio and oxidized low-density lipoprotein uptake in macrophages by inhibiting the ubiquitination of PPAR-γ and phosphorylation of Smad-1/2 and regulating ABCA1, ABCG1, LDLR, and PCSK9. We demonstrated a novel effect and mechanism of miR-30a-5p in atherosclerosis.

PPAR control of metabolism and cardiovascular functions

Peroxisome proliferator-activated receptor-α (PPARα), PPARδ and PPARγ are transcription factors that regulate gene expression following ligand activation. PPARα increases cellular fatty acid uptake, esterification and trafficking, and regulates lipoprotein metabolism genes. PPARδ stimulates lipid and glucose utilization by increasing mitochondrial function and fatty acid desaturation pathways. By contrast, PPARγ promotes fatty acid uptake, triglyceride formation and storage in lipid droplets, thereby increasing insulin sensitivity and glucose metabolism. PPARs also exert antiatherogenic and anti-inflammatory effects on the vascular wall and immune cells. Clinically, PPARγ activation by glitazones and PPARα activation by fibrates reduce insulin resistance and dyslipidaemia, respectively. PPARs are also physiological master switches in the heart, steering cardiac energy metabolism in cardiomyocytes, thereby affecting pathological heart failure and diabetic cardiomyopathy. Novel PPAR agonists in clinical development are providing new opportunities in the management of metabolic and cardiovascular diseases.

The pleiotropic peroxisome proliferator activated receptors: Regulation and therapeutics

The Peroxisome proliferator-activated receptors (PPARs) are key regulators of metabolic events in our body. Owing to their implication in maintenance of homeostasis, both PPAR agonists and antagonists assume therapeutic significance. Understanding the molecular mechanisms of each of the PPAR isotypes in the healthy body and during disease is crucial to exploiting their full therapeutic potential. This article is an attempt to present a rational analysis of the multifaceted therapeutic effects and underlying mechanisms of isotype-specific PPAR agonists, dual PPAR agonists, pan PPAR agonists as well as PPAR antagonists. A holistic understanding of the mechanistic dimensions of these key metabolic regulators will guide future efforts to identify novel molecules in the realm of metabolic, inflammatory and immunotherapeutic diseases.

Resolving macrophage polarization through distinct Ca2+ entry channel that maintains intracellular signaling and mitochondrial bioenergetics

Transformation of naive macrophages into classically (M1) or alternatively (M2) activated macrophages regulates the inflammatory response. Here, we identified that distinct Ca2+ entry channels determine the IFNγ-induced M1 or IL-4-induced M2 transition. Naive or M2 macrophages exhibit a robust Ca2+ entry that was dependent on Orai1 channels, whereas the M1 phenotype showed a non-selective TRPC1 current. Blockade of Ca2+ entry suppresses pNF-κB/pJNK/STAT1 or STAT6 signaling events and consequently lowers cytokine production that is essential for M1 or M2 functions. Of importance, LPS stimulation shifted M2 cells from Orai1 toward TRPC1-mediated Ca2+ entry and TRPC1-/- mice exhibited transcriptional changes that suppress pro-inflammatory cytokines. In contrast, Orai1-/- macrophages showed a decrease in anti-inflammatory cytokines and exhibited a suppression of mitochondrial oxygen consumption rate and inhibited mitochondrial shape transition specifically in the M2 cells. Finally, alterations in TRPC1 or Orai1 expression determine macrophage polarization suggesting a distinct role of Ca2+ channels in modulating macrophage transformation.

Acsbg1-dependent mitochondrial fitness is a metabolic checkpoint for tissue Treg cell homeostasis

Regulatory T (Treg) cells are critical for immunological tolerance and immune homeostasis. Treg cells strongly rely on mitochondrial metabolism and show a lower level of glycolysis. However, little is known about the role of lipid metabolism in the regulation of Treg cell homeostasis. Some members of the ACSL family of acyl-coenzyme A (CoA) synthases are expressed in T cells, but their function remains unclear. A combination of RNA-sequencing and proteome analyses shows that Acsbg1, a member of ACSL, is selectively expressed in Treg cells. We show that the genetic deletion of Acsbg1 not only causes mitochondrial dysfunction, but it also dampens other metabolic pathways. The extrinsic supplementation of Acsbg1-deficient Treg cells with oleoyl-CoA restores the phenotype of the Treg metabolic signature. Furthermore, this pathway in ST2+ effector Treg cells enhances immunosuppressive capacity in airway inflammation. Thus, Acsbg1 serves as a metabolic checkpoint governing Treg cell homeostasis and the resolution of lung inflammation.

The Effect of Homocysteine on the Secretion of Il-1β, Il-6, Il-10, Il-12 and RANTES by Peripheral Blood Mononuclear Cells-An In Vitro Study

The contemporary theory of the inflammatory-immunological pathomechanism of atherosclerosis includes the participation of interleukin-1β (Il), Il-6, Il-10, Il-12, RANTES, and homocysteine in this process. The knowledge on the direct effect of hyperhomocysteinemia on inflammatory-state-related atherosclerosis is rather scarce. Our study is the first to account for the effects of homocysteine on the secretion of Il-10 and RANTES in vitro conditions. For this purpose, human mitogen-stimulated peripheral blood mononuclear cells (PBMNCs) were cultured in vitro and exposed to homocysteine at high concentrations. Subsequently, the concentrations of cytokines were assayed in the cell culture supernatant using flow cytofluorimetry. It has been shown that, in the presence of homocysteine, the secretion of IL-1, IL-6 and RANTES by PBMNCs was increased, whereas IL-10 concentration was significantly lower than that of the supernatant derived from a mitogen-stimulated cell culture without homocysteine. The secretion of Il-12 by PBMNCs exposed exclusively to mitogen, did not differ from homologous cells also treated with homocysteine. Therefore, in our opinion, high-concentration homocysteine affects the progression of atherosclerosis by increasing the secretion of proinflammatory cytokines secreted by PBMNCs, such as Il-1β, Il-6, RANTES, and by attenuating the secretion of Il-10.

Global characterization of macrophage polarization mechanisms and identification of M2-type polarization inhibitors

Macrophages undergoing M1- versus M2-type polarization differ significantly in their cell metabolism and cellular functions. Here, global quantitative time-course proteomics and phosphoproteomics paired with transcriptomics provide a comprehensive characterization of temporal changes in cell metabolism, cellular functions, and signaling pathways that occur during the induction phase of M1- versus M2-type polarization. Significant differences in, especially, metabolic pathways are observed, including changes in glucose metabolism, glycosaminoglycan metabolism, and retinoic acid signaling. Kinase-enrichment analysis shows activation patterns of specific kinases that are distinct in M1- versus M2-type polarization. M2-type polarization inhibitor drug screens identify drugs that selectively block M2- but not M1-type polarization, including mitogen-activated protein kinase kinase (MEK) and histone deacetylase (HDAC) inhibitors. These datasets provide a comprehensive resource to identify specific signaling and metabolic pathways that are critical for macrophage polarization. In a proof-of-principle approach, we use these datasets to show that MEK signaling is required for M2-type polarization by promoting peroxisome proliferator-activated receptor-γ (PPARγ)-induced retinoic acid signaling.

Indomethacin, a non-steroidal anti-inflammatory drug, induces skin dryness via PPARγ in mice

Cyclooxygenase (COX)-1-selective inhibitors have side effects such as itching and dryness of the skin. In this study, the degree of skin dryness and the onset mechanism of this condition were investigated by comparing the effects of three non-steroidal anti-inflammatory drugs (NSAIDs) in mice. Mice were orally administered either indomethacin, loxoprofen sodium, or celecoxib (n = 5 per group) once daily for four consecutive days, and blood samples as well as skin and jejunal tissues were isolated on day 5. In the mice treated with indomethacin, transepidermal water loss was significantly increased, and dry skin was observed. In addition, the expression of matrix metalloproteinase (MMP)-I, mast cells, CD163, CD23, CD21, histamine, and peroxisome proliferation-activated receptor (PPAR)γ in the skin and jejunum was increased, and the blood levels of interleukin-10 and immunoglobulin E were also increased. In contrast, the expression of collagen type I in the skin was decreased. These results show that indomethacin activates PPARγ in the skin and jejunum, changes the polarity of macrophages, increases the secretion of MMP-1 from mast cells, and decomposes collagen type I, leading to dry skin.

Trained innate immunity, long-lasting epigenetic modulation, and skewed myelopoiesis by heme

During infection, extracellular “labile” heme, released from damaged red blood or parenchymal cells, acts as prototypical alarmin stimulating myeloid cells. A characteristic hallmark of myeloid cell activation is the development of trained immunity, specified as long-lasting adaptations based on transcriptional and epigenetic modifications. In vivo, this is maintained by the rerouting of hematopoiesis. We found that heme is a previously unrecognized trained immunity inducer promoting resistance to bacterial infection in mice. This goes along with extensive long-lasting epigenetic memory in hematopoietic stem cells provoking drastic changes in the transcription factor–binding landscape of myeloid progenitor cells. Given the critical role of heme during infections, we propose that trained immunity is a more general component of innate immunity than previously suggested.

Trained immunity defines long-lasting adaptations of innate immunity based on transcriptional and epigenetic modifications of myeloid cells and their bone marrow progenitors [M. Divangahi et al., Nat. Immunol. 22, 2–6 (2021)]. Innate immune cells, however, do not exclusively differentiate between foreign and self but also react to host-derived molecules referred to as alarmins. Extracellular “labile” heme, released during infections, is a bona fide alarmin promoting myeloid cell activation [M. P. Soares, M. T. Bozza, Curr. Opin. Immunol. 38, 94–100 (2016)]. Here, we report that labile heme is a previously unrecognized inducer of trained immunity that confers long-term regulation of lineage specification of hematopoietic stem cells and progenitor cells. In contrast to previous reports on trained immunity, essentially mediated by pathogen-associated molecular patterns, heme training depends on spleen tyrosine kinase signal transduction pathway acting upstream of c-Jun N-terminal kinases. Heme training promotes resistance to sepsis, is associated with the expansion of self-renewing hematopoetic stem cells primed toward myelopoiesis and to the occurrence of a specific myeloid cell population. This is potentially evoked by sustained activity of Nfix, Runx1, and Nfe2l2 and dissociation of the transcriptional repressor Bach2. Previously reported trained immunity inducers are, however, infrequently present in the host, whereas heme abundantly occurs during noninfectious and infectious disease. This difference might explain the vanishing protection exerted by heme training in sepsis over time with sustained long-term myeloid adaptations. Hence, we propose that trained immunity is an integral component of innate immunity with distinct functional differences on infectious disease outcome depending on its induction by pathogenic or endogenous molecules.

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.

The cyclin dependent kinase inhibitor Roscovitine prevents diet-induced metabolic disruption in obese mice

Most strategies to treat obesity-related disorders have involved prevention of diet-induced weight gain in lean mice. Treatment of obese individuals will require therapies that reverse the detrimental effects of excess body weight. Cyclin-dependent kinases have been shown to contribute to obesity and its adverse complications. Here, we show that roscovitine; a an orally available cyclin-dependent kinase inhibitor; given to male mice during the last six weeks of a 19-week high fat diet, reduced weight gain and prevented accompanying insulin resistance, hepatic steatosis, visceral adipose tissue (eWAT) inflammation/fibrosis as well as restored insulin secretion and enhanced whole body energy expenditure. Proteomics and phosphoproteomics analysis of eWAT demonstrated that roscovitine suppressed expression of peptides and phosphopeptides linked to inflammation and extracellular matrix proteins. It also identified 17 putative protein kinases perturbed by roscovitine, including CMGC kinases, AGC kinases and CAMK kinases. Pathway enrichment analysis showed that lipid metabolism, TCA cycle, fatty acid beta oxidation and creatine biosynthesis are enriched following roscovitine treatment. For brown adipose tissue (BAT), analysis of upstream kinases controlling the phosphoproteome revealed two major kinase groups, AGC and CMGC kinases. Among the top enriched pathways were insulin signaling, regulation of lipolysis in adipocytes, thyroid hormone signaling, thermogenesis and cAMP-PKG signaling. We conclude that roscovitine is effective at preventing prolonged diet-induced metabolic disruption and restoring mitochondrial activity in BAT and eWAT.

Idiopathic Pulmonary Comorbidities and Mechanisms

Idiopathic pulmonary fibrosis (IPF) is a disease with an unknown etiology mainly characterized by a progressive decline of lung function due to the scarring of the tissue deep in the lungs. The overall survival after diagnosis remains low between 3 and 5 years. IPF is a heterogeneous disease and much progress has been made in the past decade in understanding the disease mechanisms that contributed to the development of two new drugs, pirfenidone and nintedanib, which improved the therapeutic management of the disease. The understanding of the cofactors and comorbidities of IPF also contributed to improved management of the disease outcome. In the present review, we evaluate scientific evidence which indicates IPF as a risk factor for other diseases based on the complexity of molecular and cellular mechanisms involved in the disease development and of comorbidities. We conclude from the existing literature that while much progress has been made in understating the mechanisms involved in IPF development, further studies are still necessary to fully understand IPF pathogenesis which will contribute to the identification of novel therapeutic targets for IPF management as well as other diseases for which IPF is a major risk factor.

The PPARα and PPARγ Epigenetic Landscape in Cancer and Immune and Metabolic Disorders

Peroxisome proliferator-activated receptors (PPARs) are ligand-modulated nuclear receptors that play pivotal roles in nutrient sensing, metabolism, and lipid-related processes. Correct control of their target genes requires tight regulation of the expression of different PPAR isoforms in each tissue, and the dysregulation of PPAR-dependent transcriptional programs is linked to disorders, such as metabolic and immune diseases or cancer. Several PPAR regulators and PPAR-regulated factors are epigenetic effectors, including non-coding RNAs, epigenetic enzymes, histone modifiers, and DNA methyltransferases. In this review, we examine advances in PPARα and PPARγ-related epigenetic regulation in metabolic disorders, including obesity and diabetes, immune disorders, such as sclerosis and lupus, and a variety of cancers, providing new insights into the possible therapeutic exploitation of PPAR epigenetic modulation.

MERTK+/hi M2c Macrophages Induced by Baicalin Alleviate Non-Alcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases worldwide. An accumulation of fat, followed by inflammation, is the major cause of NAFLD progression. During inflammation, macrophages are the most abundant immune cells recruited to the site of injury. Macrophages are classified into "proinflammatory" M1 macrophages, and "anti-inflammatory" M2 macrophages. In NAFLD, M1 macrophages are the most prominent macrophages that lead to an excessive inflammatory response. Previously, we found that baicalin could polarize macrophages into anti-inflammatory M2c subtype macrophages with an increased level of MERTK expression. Several studies have also shown a strong correlation between MERTK expression and cholesterol efflux, efferocytosis, as well as phagocytosis capability. Therefore, in this study, we aim to elucidate the potential and efficacy of mononuclear-cell (MNC)-derived MERTK+/hi M2c macrophages induced by baicalin as a cell-based therapy for NAFLD treatment. In our results, we have demonstrated that a MERTK+/hi M2c macrophage injection to NAFLD mice contributes to an increased level of serum HDL secretion in the liver, a decline in the circulating CD4+CD25- and CD8+CD25- T cells and lowers the total NAFLD pathological score by lessening the inflammation, necrosis, and fibrosis. In the liver, profibrotic COL1A1 and FN, proinflammation TNFα, as well as the regulator of lipid metabolism PPARɣ expression, were also downregulated after injection. In parallel, the transcriptomic profiles of the injected MERTK+/hi M2c macrophages showed that the various genes directly or indirectly involved in NAFLD progression (e.g., SERPINE1, FADS2) were also suppressed. Downregulation of cytokines and inflammation-associated genes, such as CCR5, may promote a pro-resolving milieu in the NAFLD liver. Altogether, cell-based therapy using MERTK+/hi M2c macrophages is promising, as it ameliorates NAFLD in mice.

Chronic tissue inflammation and metabolic disease

In this review, Lee and Olefsky discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes.

Obesity is the most common cause of insulin resistance, and the current obesity epidemic is driving a parallel rise in the incidence of T2DM. It is now widely recognized that chronic, subacute tissue inflammation is a major etiologic component of the pathogenesis of insulin resistance and metabolic dysfunction in obesity. Here, we summarize recent advances in our understanding of immunometabolism. We discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes. Last, we also review current and potential new therapeutic strategies based on immunomodulation.

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.

Macrophage metabolic regulation in atherosclerotic plaque

Metabolism plays a key role in controlling immune cell functions. In this review, we will discuss the diversity of plaque resident myeloid cells and will focus on their metabolic demands that could reflect on their particular intraplaque localization. Defining the metabolic configuration of plaque resident myeloid cells according to their topologic distribution could provide answers to key questions regarding their functions and contribution to disease development.

Identification of an allosteric hotspot for additive activation of PPARγ in antidiabetic effects

Thiazolidinediones (TZDs), such as rosiglitazone (RSG), which activates peroxisome proliferator activated receptor-γ (PPARγ), are a potent class of oral antidiabetic agents with good durability. However, the clinical use of TZDs is challenging because of their side effects, including weight gain and hepatotoxicity. Here, we found that bavachinin (BVC), a lead natural product, additively activates PPARγ with low-dose RSG to preserve the maximum antidiabetic effects while reducing weight gain and hepatotoxicity in db/db mice caused by RSG monotherapy. Structural and biochemical assays demonstrated that an unexplored hotspot around Met329 and Ser332 in helix 5 is triggered by BVC cobinding to RSG-bound PPARγ, thereby allosterically stabilizing the active state of the activation-function 2 motif responsible for additive activation with RSG. Based on this hotspot, we discovered a series of new classes of allosteric agonists inducing the activity of TZDs in the same manner as BVC. Together, our data illustrate that the hotspot of PPARγ is druggable for the discovery of new allosteric synergists, and the combination therapy of allosteric synergists and TZD drugs may provide a potential alternative approach to the treatment of type 2 diabetes mellitus.

Development of mode of action networks related to the potential role of PPARγ in respiratory diseases

The peroxisome proliferator-activated receptor γ (PPARγ) is a key transcription factor, operating at the intercept of metabolic control and immunomodulation. It is ubiquitously expressed in multiple tissues and organs, including lungs. There is a growing body of information supporting the role of PPARγ signalling in respiratory diseases. The aim of the present study was to develop mode of action (MoA) networks reflecting the relationships between PPARγ signalling and the progression/alleviation of a spectrum of lung pathologies. Data mining was performed using the resources of the NIH PubMed and PubChem information systems. By linking available data on pathological/therapeutic effects of PPARγ modulation, knowledge-based MoA networking at different levels of biological organization (molecular, cellular, tissue, organ, and system) was performed. Multiple MoA networks were developed to relate PPARγ modulation to the progress or the alleviation of pulmonary disorders, triggered by diverse pathogenic, genetic, chemical, or mechanical factors. Pharmacological targeting of PPARγ signalling was discussed with regard to ligand- and cell type-specific effects in the context of distinct disease inductor- and disease stage-dependent patterns. The proposed MoA networking analysis allows for a better understanding of the potential role of PPARγ modulation in lung pathologies. It presents a mechanistically justified basis for further computational, experimental, and clinical monitoring studies on the dynamic control of PPARγ signalling in respiratory diseases.

Inflammatory Basis of Atherosclerosis: Modulation by Sex Hormones

Atherosclerosis-related cardiovascular diseases (CVDs) are the leading cause of death globally. Several lines of evidence are supportive of the contributory role of vascular inflammation in atherosclerosis. Diverse immune cell types, including monocytes/macrophages, T-cells and neutrophils, as well as specialized proresolving lipid mediators, have been successfully characterized as key players in vascular inflammation. The increased prevalence of atherosclerotic CVD in men in comparison to age-matched premenopausal women and the abolition of sex differences in prevalence during menopause strongly suggest a pivotal role of sex hormones in the development of CVD. Indeed, many animal and human studies conclusively implicate sex hormones as a crucial component in driving the immune response. This is further corroborated by the effective identification of sex hormone receptors in vascular endothelial cells, vascular smooth muscle cells and immune cells. Collectively, these findings suggest a cellular communication between sex hormones and vascular or immune cells underlying the vascular inflammation in atherosclerosis. The aim of this review is to provide an overview of vascular inflammation as a causal cue underlying atherosclerotic CVDs within the context of the modulatory effects of sex hormones. Moreover, the cellular and molecular signaling pathways underlying the sex hormones- immune system interactions as potential culprits for vascular inflammation are highlighted with detailed and critical discussion. Finally, the review concludes by speculations on the potential sex-related efficacy of currently available immunotherapies in mitigating vascular inflammation. Conceivably, a deeper understanding of the immunoregulatory influence of sex hormones on vascular inflammation-mediated atherosclerosis permits sex-based management of atherosclerosis-related CVDs.

The Immunometabolic Roles of Various Fatty Acids in Macrophages and Lymphocytes

Macrophages and lymphocytes demonstrate metabolic plasticity, which is dependent partly on their state of activation and partly on the availability of various energy yielding and biosynthetic substrates (fatty acids, glucose, and amino acids). These substrates are essential to fuel-based metabolic reprogramming that supports optimal immune function, including the inflammatory response. In this review, we will focus on metabolism in macrophages and lymphocytes and discuss the role of fatty acids in governing the phenotype, activation, and functional status of these important cells. We summarize the current understanding of the pathways of fatty acid metabolism and related mechanisms of action and also explore possible new perspectives in this exciting area of research.

PPARs as Metabolic Sensors and Therapeutic Targets in Liver Diseases

Carbohydrates and lipids are two components of the diet that provide the necessary energy to carry out various physiological processes to help maintain homeostasis in the body. However, when the metabolism of both biomolecules is altered, development of various liver diseases takes place; such as metabolic-associated fatty liver diseases (MAFLD), hepatitis B and C virus infections, alcoholic liver disease (ALD), and in more severe cases, hepatocelular carcinoma (HCC). On the other hand, PPARs are a family of ligand-dependent transcription factors with an important role in the regulation of metabolic processes to hepatic level as well as in other organs. After interaction with specific ligands, PPARs are translocated to the nucleus, undergoing structural changes to regulate gene transcription involved in lipid metabolism, adipogenesis, inflammation and metabolic homeostasis. This review aims to provide updated data about PPARs’ critical role in liver metabolic regulation, and their involvement triggering the genesis of several liver diseases. Information is provided about their molecular characteristics, cell signal pathways, and the main pharmacological therapies that modulate their function, currently engaged in the clinic scenario, or in pharmacological development.

Sensory Neurons, Neuroimmunity, and Pain Modulation by Sex Hormones

The inclusion of women in preclinical pain studies has become more commonplace in the last decade as the National Institutes of Health (NIH) released its "Sex as a Biological Variable" mandate. Presumably, basic researchers have not had a comprehensive understanding about neuroimmune interactions in half of the population and how hormones play a role in this. To date, we have learned that sex hormones contribute to sexual differentiation of the nervous system and sex differences in behavior throughout the lifespan; however, the cycling of sex hormones does not always explain these differences. Here, we highlight recent advances in our understanding of sex differences and how hormones and immune interactions influence sensory neuron activity to contribute to physiology and pain. Neuroimmune mechanisms may be mediated by different cell types in each sex, as the actions of immune cells are sexually dimorphic. Unfortunately, the majority of studies assessing neuronal contributions to immune function have been limited to males, so it is unclear if the mechanisms are similar in females. Finally, pathways that control cellular metabolism, like nuclear receptors, have been shown to play a regulatory role both in pain and inflammation. Overall, communication between the neuroimmune and endocrine systems modulate pain signaling in a sex-dependent manner, but more research is needed to reveal nuances of these mechanisms.

Single-cell transcriptome of bronchoalveolar lavage fluid reveals sequential change of macrophages during SARS-CoV-2 infection in ferrets

Few studies have used a longitudinal approach to describe the immune response to SARS-CoV-2 infection. Here, we perform single-cell RNA sequencing of bronchoalveolar lavage fluid cells longitudinally obtained from SARS-CoV-2-infected ferrets. Landscape analysis of the lung immune microenvironment shows distinct changes in cell proportions and characteristics compared to uninfected control, at 2 and 5 days post-infection (dpi). Macrophages are classified into 10 distinct subpopulations with transcriptome changes among monocyte-derived infiltrating macrophages and differentiated M1/M2 macrophages, notably at 2 dpi. Moreover, trajectory analysis reveals gene expression changes from monocyte-derived infiltrating macrophages toward M1 or M2 macrophages and identifies a macrophage subpopulation that has rapidly undergone SARS-CoV-2-mediated activation of inflammatory responses. Finally, we find that M1 or M2 macrophages show distinct patterns of gene modules downregulated by immune-modulatory drugs. Overall, these results elucidate fundamental aspects of the immune response dynamics provoked by SARS-CoV-2 infection.

Latitudinal and longitudinal regulation of tissue macrophages in inflammatory diseases

Macrophages are dominant innate immune cells. They demonstrate remarkable heterogeneity and plasticity that are essential for homeostasis and host defense. The heterogeneity of tissue macrophages is shaped by the ontogeny, tissue factors, and environmental signals, a pattern in a tissue-associated latitudinal manner. At the same time, macrophages have long been considered as mainly plastic cells. These cells respond to stimulation quickly and in a stimulus-specific way by utilizing a longitudinal cascaded activation, including coordination of signal transducer, epigenetic elements, and transcription factors, conclusively determine the macrophage phenotypes and functions. With the development of cutting-edge technologies, such as fate-mapping, single-cell transcriptomics, ipsc platform, nanotherapeutic materials, etc., our understanding of macrophage biology and the roles in the pathogenesis of diseases is much advanced. This review summarizes recent progress on the latitudinal and longitudinal regulation of tissue macrophages in inflammatory diseases. The latitudinal regulation covers the tissue macrophage origins, tissue factors, and environmental signals, reflecting the macrophage heterogeneity. The longitudinal regulation focuses on how multiple factors shape the phenotypes and functions of macrophage subsets to gain plasticity in inflammatory diseases (i.e., inflammatory bowel disease). In addition, how to target macrophages as a potential therapeutic approach and cutting edge-technologies for tissue macrophage study are also discussed in this review.