Control of macrophage metabolism and activation by mTOR and Akt signaling

Cell polarization in ischemic stroke: molecular mechanisms and advances

Ischemic stroke is a cerebrovascular disease associated with high mortality and disability rates. Since the inflammation and immune response play a central role in driving ischemic damage, it becomes essential to modulate excessive inflammatory reactions to promote cell survival and facilitate tissue repair around the injury site. Various cell types are involved in the inflammatory response, including microglia, astrocytes, and neutrophils, each exhibiting distinct phenotypic profiles upon stimulation. They display either proinflammatory or anti-inflammatory states, a phenomenon known as 'cell polarization.' There are two cell polarization therapy strategies. The first involves inducing cells into a neuroprotective phenotype in vitro, then reintroducing them autologously. The second approach utilizes small molecular substances to directly affect cells in vivo. In this review, we elucidate the polarization dynamics of the three reactive cell populations (microglia, astrocytes, and neutrophils) in the context of ischemic stroke, and provide a comprehensive summary of the molecular mechanisms involved in their phenotypic switching. By unraveling the complexity of cell polarization, we hope to offer insights for future research on neuroinflammation and novel therapeutic strategies for ischemic stroke.

Redistribution of SOD3 expression due to R213G polymorphism affects pulmonary interstitial macrophage reprogramming in response to hypoxia

The extracellular isoform of superoxide dismutase (SOD3) is decreased in patients and animals with pulmonary hypertension (PH). The human R213G single-nucleotide polymorphism (SNP) in SOD3 causes its release from tissue extracellular matrix (ECM) into extracellular fluids, without modulating enzyme activity, increasing cardiovascular disease risk in humans and exacerbating chronic hypoxic PH in mice. Given the importance of interstitial macrophages (IMs) to PH pathogenesis, this study aimed to determine whether R213G SOD3 increases IM accumulation and alters IM reprogramming in response to hypoxia. R213G mice and wild-type (WT) controls were exposed to hypobaric hypoxia for 4 or 14 days compared with normoxia. Flow cytometry demonstrated a transient increase in IMs at day 4 in both strains. Contrary to our hypothesis, the R213G SNP did not augment IM accumulation. To determine strain differences in the IM reprogramming response to hypoxia, we performed RNAsequencing on IMs isolated at each timepoint. We found that IMs from R213G mice exposed to hypoxia activated ECM-related pathways and a combination of alternative macrophage and proinflammatory signaling. Furthermore, when compared with WT responses, IMs from R213G mice lacked metabolic remodeling and demonstrated a blunted anti-inflammatory response between the early (day 4) and later (day 14) timepoints. We confirmed metabolic responses using Agilent Seahorse assays, whereby WT, but not R213G, IMs upregulated glycolysis at day 4 that returned to baseline at day 14. Finally, we identify differential regulation of several redox-sensitive upstream regulators that could be investigated in future studies.NEW & NOTEWORTHY Redistributed expression of SOD3 out of tissue ECM due to the human R213G SNP exacerbates chronic hypoxic PH. Highlighting the importance of macrophage phenotype, our findings reveal that the R213G SNP does not exacerbate pulmonary macrophage accumulation in response to hypoxia but influences their metabolic and phenotypic reprogramming. We demonstrate a deficiency in the metabolic response to hypoxic stress in R213G macrophages, associated with weakened inflammatory resolution and activation of profibrotic pathways implicated in PH.

Sulfated polysaccharide from Antrodia cinnamomea mycelium cultured with zinc sulfate stimulates M1 polarization of macrophages through AKT/mTOR pathways

Antrodia cinnamomea-derived sulfated polysaccharides (Ac-SPSs) have health benefits, but their yield is low. This study explores a strategy to increase Ac-SPS yield and elucidates the biofunctions of Ac-SPS. For this, A. cinnamomea mycelia were treated with zinc sulfate (ZnSO4) administered at 1, 10, and 100 μM. Firstly, functional assay indicated that ZnSO4 increases the Ac-SPS yield by 20 %-30 % compared with the control treatment. ZnSO4 engenders a population of middle-molecular-weight (~200 kDa) Ac-SPSs. Ac-SPS (ASZ-10) from A. cinnamomea treated with 10 μM ZnSO4 exhibits the best anti-proliferation ability against lung cancer A549 cells. Co-treatment of ASZ-10 does not inhibit lipopolysaccharide-induced inflammation but does induce M1-related markers of macrophage RAW264.7 cells. Secondly, immunomodulatory properties showed that ASZ-10 increases the expression of CD80+ and CD86+ in M-CSF-stimulated bone-marrow-derived macrophages. ASZ-10 induces M1 polarization through up-regulation of the AKT/mTOR pathway as confirmed by AKT and mTOR inhibitors eliminating ASZ-10-induced M1-like markers of macrophages. Through systemic chemical and functional analysis, this study shows that trace amounts (10 μM) of ZnSO4 increase Ac-SPS yield and it reveals that ASZ-10 exhibits anti-cancer activity and acts as a stimulator for M1 macrophages by stimulation of AKT and mTOR.

Macrophage NRF1 promotes mitochondrial protein turnover via the ubiquitin proteasome system to limit mitochondrial stress and inflammation

Macrophage elaboration of inflammatory responses is dynamically regulated, shifting from acute induction to delayed suppression during the course of infection. Here, we show that such regulation of inflammation is modulated by dynamic shifts in metabolism. In macrophages exposed to the bacterial product lipopolysaccharide (LPS), an initial induction of protein biosynthesis is followed by compensatory induction of the transcription factor nuclear factor erythroid 2-like 1 (NRF1), leading to increased flux through the ubiquitin proteasome system (UPS). A major target of NRF1-mediated UPS flux is the mitochondrial proteome, and in the absence of NRF1, ubiquitinated mitochondrial proteins accumulate to trigger severe mitochondrial stress. Such mitochondrial stress engages the integrated stress response-ATF4 axis, which limits mitochondrial translation to attenuate mitochondrial stress but amplifies inflammatory responses to augment susceptibility to septic shock. Therefore, NRF1 mediates a dynamic regulation of mitochondrial proteostasis in inflammatory macrophages that contributes to curbing inflammatory responses.

Triptolide alleviates acute gouty arthritis caused by monosodium urate crystals by modulating macrophage polarization and neutrophil activity

The present study focused on the efficacy and role of triptolide (TPL) in relieving symptoms of acute gouty arthritis (AGA) in vivo and in vitro. The effects of TPL in AGA were investigated in monosodium urate (MSU)-treated rat ankles, RAW264.7 macrophages, and neutrophils isolated from mouse peritoneal cavity. Observation of pathological changes in the ankle joint of rats. Enzyme-linked immunosorbent assay and real-time quantitative polymerase chain reaction (RT-qPCR) were performed to detect the expression levels of inflammatory factors and chemokines. The levels of the indicators of macrophage M1/M2 polarization, and the mechanistic targets of Akt and rapamycin complex 2, were determined via western blotting and RT-qPCR. The expression levels of CD86 and CD206 were detected using immunohistochemistry. Neutrophil migration was observed via air pouch experiments in vivo and Transwell cell migration assay in vitro. Myeloperoxidase (MPO) and Neutrophil elastase (NE) release was analyzed by via immunohistochemistry and immunofluorescence. The expression levels of beclin-1, LC3B, Bax, Bcl-2, and cleaved caspase-3 in neutrophils were determined via western blotting and immunofluorescence. Neutrophil apoptosis was detected using the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Our results suggest that TPL inhibited inflammatory cell infiltration in rat ankle joints and inflammatory factor and chemokine secretion in rat serum, regulated macrophage polarization through the PI3K/AKT signaling pathway, suppressed inflammatory factor and chemokine expression in neutrophils, and inhibited neutrophil migration, neutrophil extracellular trap formation, transitional autophagy, and apoptosis. This suggests that TPL can prevent and treat MSU-induced AGA by regulating macrophage polarization through the PI3K/Akt pathway and modulating neutrophil activity.

Targeting Macrophage Phenotypes and Metabolism as Novel Therapeutic Approaches in Atherosclerosis and Related Cardiovascular Diseases

PURPOSE OF THE REVIEW

Macrophage accumulation and activation function as hallmarks of atherosclerosis and have complex and intricate dynamics throughout all components and stages of atherosclerotic plaques. In this review, we focus on the regulatory roles and underlying mechanisms of macrophage phenotypes and metabolism in atherosclerosis. We highlight the diverse range of macrophage phenotypes present in atherosclerosis and their potential roles in progression and regression of atherosclerotic plaque. Furthermore, we discuss the challenges and opportunities in developing therapeutic strategies for preventing and treating atherosclerotic cardiovascular disease.

RECENT FINDINGS

Dysregulation of macrophage polarization between the proinflammatory M1 and anti-inflammatory M2 phenotypealters the immuno-inflammatory response during atherosclerosis progression, leading to plaque initiation, growth, and ultimately rupture. Altered metabolism of macrophage is a key feature for their function and the subsequent progression of atherosclerotic cardiovascular disease. The immunometabolism of macrophage has been implicated to macrophage activation and metabolic rewiring of macrophages within atherosclerotic lesions, thereby shifting altered macrophage immune-effector and tissue-reparative function. Targeting macrophage phenotypes and metabolism are potential therapeutic strategies in the prevention and treatment of atherosclerosis and atherosclerotic cardiovascular diseases. Understanding the precise function and metabolism of specific macrophage subsets and their contributions to the composition and growth of atherosclerotic plaques could reveal novel strategies to delay or halt development of atherosclerotic cardiovascular diseases and their associated pathophysiological consequences. Identifying biological stimuli capable of modulating macrophage phenotypes and metabolism may lead to the development of innovative therapeutic approaches for treating patients with atherosclerosis and coronary artery diseases.

Crosstalk between macrophages and immunometabolism and their potential roles in tissue repair and regeneration

Immune metabolism is a result of many specific metabolic reactions, such as glycolysis, the tricarboxylic acid (TCA) pathway, the pentose phosphate pathway (PPP), mitochondrial oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO), fatty acid biosynthesis (FAs) and amino acid pathways, which promote cell proliferation and maintenance with structural and pathological energy to regulate cellular signaling. The metabolism of macrophages produces many metabolic intermediates that play important regulatory roles in tissue repair and regeneration. The metabolic activity of proinflammatory macrophages (M1) mainly depends on glycolysis and the TCA cycle system, but anti-inflammatory macrophages (M2) have intact functions of the TCA cycle, which enhances FAO and is dependent on OXPHOS. However, the metabolic mechanisms of macrophages in tissue repair and regeneration have not been well investigated. Thus, we review how three main metabolic mechanisms of macrophages, glucose metabolism, lipid metabolism, and amino acid metabolism, regulate tissue repair and regeneration.

CXCR4 regulates macrophage M1 polarization by altering glycolysis to promote prostate fibrosis

BACKGROUND

C-X-C receptor 4(CXCR4) is widely considered to be a highly conserved G protein-coupled receptor, widely involved in the pathophysiological processes in the human body, including fibrosis. However, its role in regulating macrophage-related inflammation in the fibrotic process of prostatitis has not been confirmed. Here, we aim to describe the role of CXCR4 in modulating macrophage M1 polarization through glycolysis in the development of prostatitis fibrosis.

METHODS

Use inducible experimental chronic prostatitis as a model of prostatic fibrosis. Reduce CXCR4 expression in immortalized bone marrow-derived macrophages using lentivirus. In the fibrotic mouse model, use adenovirus carrying CXCR4 agonists to detect the silencing of CXCR4 and assess the in vivo effects.

RESULTS

In this study, we demonstrated that reducing CXCR4 expression during LPS treatment of macrophages can alleviate M1 polarization. Silencing CXCR4 can inhibit glycolytic metabolism, enhance mitochondrial function, and promote macrophage transition from M1 to M2. Additionally, in vivo functional experiments using AAV carrying CXCR4 showed that blocking CXCR4 in experimental autoimmune prostatitis (EAP) can alleviate inflammation and experimental prostate fibrosis development. Mechanistically, CXCR4, a chemokine receptor, when silenced, weakens the PI3K/AKT/mTOR pathway as its downstream signal, reducing c-MYC expression. PFKFB3, a key enzyme involved in glucose metabolism, is a target gene of c-MYC, thus impacting macrophage polarization and glycolytic metabolism processes.

MOF-mediated PRDX1 acetylation regulates inflammatory macrophage activation

Signaling-dependent changes in protein phosphorylation are critical to enable coordination of transcription and metabolism during macrophage activation. However, the role of acetylation in signal transduction during macrophage activation remains obscure. Here, we identify the redox signaling regulator peroxiredoxin 1 (PRDX1) as a substrate of the lysine acetyltransferase MOF. MOF acetylates PRDX1 at lysine 197, preventing hyperoxidation and thus maintaining its activity under stress. PRDX1 K197ac responds to inflammatory signals, decreasing rapidly in mouse macrophages stimulated with bacterial lipopolysaccharides (LPSs) but not with interleukin (IL)-4 or IL-10. The LPS-induced decrease of PRDX1 K197ac elevates cellular hydrogen peroxide accumulation and augments ERK1/2, but not p38 or AKT, phosphorylation. Concomitantly, diminished PRDX1 K197ac stimulates glycolysis, potentiates H3 serine 28 phosphorylation, and ultimately enhances the production of pro-inflammatory mediators such as IL-6. Our work reveals a regulatory role for redox protein acetylation in signal transduction and coordinating metabolic and transcriptional programs during inflammatory macrophage activation.

Depletion of essential mycobacterial gene glmM reduces pathogen survival and induces host-protective immune responses against tuberculosis

The limitations of TB treatment are the long duration and immune-dampening effects of anti-tuberculosis therapy. The Cell wall plays a crucial role in survival and virulence; hence, enzymes involved in its biosynthesis are good therapeutic targets. Here, we identify Mycobacterium tuberculosis (Mtb) GlmM, (GlmMMtb) engaged in the UDP-GlcNAc synthesis pathway as an essential enzyme. We generated a conditional knockdown strain, Rv-glmMkD using the CRISPR interference-mediated gene silencing approach. Depletion of GlmMMtb affects the morphology and thickness of the cell wall. The Rv-glmMkD strain attenuated Mtb survival in vitro, in the host macrophages (ex vivo), and in a murine mice infection model (in vivo). Results suggest that the depletion of GlmMMtb induces M1 macrophage polarization, prompting a pro-inflammatory cytokine response, apparent from the upregulation of activation markers, including IFNɣ and IL-17 that resists the growth of Mtb. These observations provide a rationale for exploring GlmMMtb as a potential therapeutic target.

Macrophage plasticity: signaling pathways, tissue repair, and regeneration

Macrophages are versatile immune cells with remarkable plasticity, enabling them to adapt to diverse tissue microenvironments and perform various functions. Traditionally categorized into classically activated (M1) and alternatively activated (M2) phenotypes, recent advances have revealed a spectrum of macrophage activation states that extend beyond this dichotomy. The complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications orchestrates macrophage polarization, allowing them to respond to various stimuli dynamically. Here, we provide a comprehensive overview of the signaling cascades governing macrophage plasticity, focusing on the roles of Toll-like receptors, signal transducer and activator of transcription proteins, nuclear receptors, and microRNAs. We also discuss the emerging concepts of macrophage metabolic reprogramming and trained immunity, contributing to their functional adaptability. Macrophage plasticity plays a pivotal role in tissue repair and regeneration, with macrophages coordinating inflammation, angiogenesis, and matrix remodeling to restore tissue homeostasis. By harnessing the potential of macrophage plasticity, novel therapeutic strategies targeting macrophage polarization could be developed for various diseases, including chronic wounds, fibrotic disorders, and inflammatory conditions. Ultimately, a deeper understanding of the molecular mechanisms underpinning macrophage plasticity will pave the way for innovative regenerative medicine and tissue engineering approaches.

Inhibition of mevalonate pathway by macrophage-specific delivery of atorvastatin prevents their pro-inflammatory polarisation

Adjustment of the cellular metabolism of pro-inflammatory macrophages is essential for their bactericidal function; however, it underlies the development of many human diseases if induced chronically. Therefore, intervention of macrophage metabolic polarisation has been recognised as a potent strategy for their treatment. Although many small-molecule inhibitors affecting macrophage metabolism have been identified, their in vivo administration requires a tool for macrophage-specific delivery to limit their potential side effects. Here, we establish Drosophila melanogaster as a simple experimental model for in vivo testing of macrophage-specific delivery tools. We found that yeast-derived glucan particles (GPs) are suitable for macrophage-specific delivery of small-molecule inhibitors. Systemic administration of GPs loaded with atorvastatin, the inhibitor of hydroxy-methyl-glutaryl-CoA reductase (Hmgcr), leads to intervention of mevalonate pathway specifically in macrophages, without affecting HMGCR activity in other tissues. Using this tool, we demonstrate that mevalonate pathway is essential for macrophage pro-inflammatory polarisation and individual's survival of infection.

Role of macrophage polarization in heart failure and traditional Chinese medicine treatment

Heart failure (HF) has a severe impact on public health development due to high morbidity and mortality and is associated with imbalances in cardiac immunoregulation. Macrophages, a major cell population involved in cardiac immune response and inflammation, are highly heterogeneous and polarized into M1 and M2 types depending on the microenvironment. M1 macrophage releases inflammatory factors and chemokines to activate the immune response and remove harmful substances, while M2 macrophage releases anti-inflammatory factors to inhibit the overactive immune response and promote tissue repair. M1 and M2 restrict each other to maintain cardiac homeostasis. The dynamic balance of M1 and M2 is closely related to the Traditional Chinese Medicine (TCM) yin-yang theory, and the imbalance of yin and yang will result in a pathological state of the organism. Studies have confirmed that TCM produces positive effects on HF by regulating macrophage polarization. This review describes the critical role of macrophage polarization in inflammation, fibrosis, angiogenesis and electrophysiology in the course of HF, as well as the potential mechanism of TCM regulation of macrophage polarization in preventing and treating HF, thereby providing new ideas for clinical treatment and scientific research design of HF.

Focal Adhesion Kinase and Colony Stimulating Factors: Intestinal Homeostasis and Innate Immunity Crosstalk

Thousands struggle with acute and chronic intestinal injury due to various causes. Epithelial intestinal healing is dependent on phenotypic transitions to a mobile phenotype. Focal adhesion kinase (FAK) is a ubiquitous protein that is essential for cell mobility. This phenotype change is mediated by FAK activation and proves to be a promising target for pharmaceutical intervention. While FAK is crucial for intestinal healing, new evidence connects FAK with innate immunity and the importance it plays in macrophage/monocyte chemotaxis, as well as other intracellular signaling cascades. These cascades play a part in macrophage/monocyte polarization, maturation, and inflammation that is associated with intestinal injury. Colony stimulating factors (CSFs) such as macrophage colony stimulating factor (M-CSF/CSF-1) and granulocyte macrophage colony stimulating factor (GM-CSF/CSF-2) play a critical role in maintaining homeostasis within intestinal mucosa by crosstalk capabilities between macrophages and epithelial cells. The communication between these cells is imperative in orchestrating healing upon injury. Diving deeper into these connections may allow us a greater insight into the role that our immune system plays in healing, as well as a better comprehension of inflammatory diseases of the gut.

Comparison of genetic and epigenetic profiles of periodontitis according to the presence of type 2 diabetes

Type 2 diabetes mellitus (T2DM) and periodontitis (PD) have intricated connections as chronic inflammatory diseases. While the immune response is a key factor that accounts for their association, the underlying mechanisms remain unclear. To gain a deeper understanding of the connection, we conducted research using a multiomics approach. We generated whole genome and methylation profiling array data from the periodontium of PD patients with DM (PDDM) and without DM to confirm genetic and epigenetic changes. Independent bulk and single-cell RNA sequencing data were employed to verify the expression levels of hypo-methylated genes. We observed a gradual rise in C>T base substitutions and hypomethylation in PD and PDDM patients compared with healthy participants. Furthermore, specific genetic and epigenetic alterations were prominently associated with the Fc-gamma receptor-mediated phagocytosis pathway. The upregulation of these genes was confirmed in both the periodontal tissues of PD patients and the pancreatic tissues of T2DM patients. Through single-cell RNA analysis of peripheral blood mononuclear cells, substantial upregulation of Fc-gamma receptors and related genes was particularly identified in monocytes. Our findings suggest that targeting the Fc-gamma signaling pathway in monocytes holds promise as a potential treatment strategy for managing systemic complications associated with diabetes.

Sr-Incorporated Bioactive Glass Remodels the Immunological Microenvironment by Enhancing the Mitochondrial Function of Macrophage via the PI3K/AKT/mTOR Signaling Pathway

The repair of critical-sized bone defects continues to pose a challenge in clinics. Strontium (Sr), recognized for its function in bone metabolism regulation, has shown potential in bone repair. However, the underlying mechanism through which Sr2+ guided favorable osteogenesis by modulating macrophages remains unclear, limiting their application in the design of bone biomaterials. Herein, Sr-incorporated bioactive glass (SrBG) was synthesized for further investigation. The release of Sr ions enhanced the immunomodulatory properties and osteogenic potential by modulating the polarization of macrophages toward the M2 phenotype. In vivo, a 3D-printed SrBG scaffold was fabricated and showed consistently improved bone regeneration by creating a prohealing immunological microenvironment. RNA sequencing was performed to explore the underlying mechanisms. It was found that Sr ions might enhance the mitochondrial function of macrophage by activating PI3K/AKT/mTOR signaling, thereby favoring osteogenesis. Our findings demonstrate the relationship between the immunomodulatory role of Sr ions and the mitochondrial function of macrophages. By focusing on the mitochondrial function of macrophages, Sr2+-mediated immunomodulation sheds light on the future design of biomaterials for tissue regenerative engineering.

Opsonization Inveigles Macrophages Engulfing Carrier-Free Bilirubin/JPH203 Nanoparticles to Suppress Inflammation for Osteoarthritis Therapy

Osteoarthritis (OA) is a chronic inflammatory disease characterized by cartilage destruction, synovitis, and osteophyte formation. Disease-modifying treatments for OA are currently lacking. Because inflammation mediated by an imbalance of M1/M2 macrophages in the synovial cavities contributes to OA progression, regulating the M1 to M2 polarization of macrophages can be a potential therapeutic strategy. Basing on the inherent immune mechanism and pathological environment of OA, an immunoglobulin G-conjugated bilirubin/JPH203 self-assembled nanoparticle (IgG/BRJ) is developed, and its therapeutic potential for OA is evaluated. After intra-articular administration, IgG conjugation facilitates the recognition and engulfment of nanoparticles by the M1 macrophages. The internalized nanoparticles disassemble in response to the increased oxidative stress, and the released bilirubin (BR) and JPH203 scavenge reactive oxygen species (ROS), inhibit the nuclear factor kappa-B pathway, and suppress the activated mammalian target of rapamycin pathway, result in the repolarization of macrophages and enhance M2/M1 ratios. Suppression of the inflammatory environment by IgG/BRJ promotes cartilage protection and repair in an OA rat model, thereby improving therapeutic outcomes. This strategy of opsonization involving M1 macrophages to engulf carrier-free BR/JPH203 nanoparticles to suppress inflammation for OA therapy holds great potential for OA intervention and treatment.

Immunometabolism in cancer: basic mechanisms and new targeting strategy

Maturing immunometabolic research empowers immune regulation novel approaches. Progressive metabolic adaptation of tumor cells permits a thriving tumor microenvironment (TME) in which immune cells always lose the initial killing capacity, which remains an unsolved dilemma even with the development of immune checkpoint therapies. In recent years, many studies on tumor immunometabolism have been reported. The development of immunometabolism may facilitate anti-tumor immunotherapy from the recurrent crosstalk between metabolism and immunity. Here, we discuss clinical studies of the core signaling pathways of immunometabolism and their inhibitors or agonists, as well as the specific functions of these pathways in regulating immunity and metabolism, and discuss some of the identified immunometabolic checkpoints. Understanding the comprehensive advances in immunometabolism helps to revise the status quo of cancer treatment. An overview of the new landscape of immunometabolism. The PI3K pathway promotes anabolism and inhibits catabolism. The LKB1 pathway inhibits anabolism and promotes catabolism. Overactivation of PI3K/AKT/mTOR pathway and IDO, IL4I1, ACAT, Sirt2, and MTHFD2 promote immunosuppression of TME formation, as evidenced by increased Treg and decreased T-cell proliferation. The LKBI-AMPK pathway promotes the differentiation of naive T cells to effector T cells and memory T cells and promotes anti-tumor immunity in DCs.

Codonopsis pilosula-derived glycopeptide dCP1 promotes the polarization of tumor-associated macrophage from M2-like to M1 phenotype

The majority of the immune cell population in the tumor microenvironment (TME) consists of tumor-associated macrophages (TAM), which are the main players in coordinating tumor-associated inflammation. TAM has a high plasticity and is divided into two main phenotypes, pro-inflammatory M1 type and anti-inflammatory M2 type, with tumor-suppressive and tumor-promoting functions, respectively. Considering the beneficial effects of M1 macrophages for anti-tumor and the high plasticity of macrophages, the conversion of M2 TAM to M1 TAM is feasible and positive for tumor treatment. This study sought to evaluate whether the glycopeptide derived from simulated digested Codonopsis pilosula extracts could regulate the polarization of M2-like TAM toward the M1 phenotype and the potential regulatory mechanisms. The results showed that after glycopeptide dCP1 treatment, the mRNA relative expression levels of some M2 phenotype marker genes in M2-like TAM in simulated TME were reduced, and the relative expression levels of M1 phenotype marker genes and inflammatory factor genes were increased. Analysis of RNA-Seq of M2-like TAM after glycopeptide dCP1 intervention showed that the gene sets such as glycolysis, which is associated with macrophage polarization in the M1 phenotype, were significantly up-regulated, whereas those of gene sets such as IL-6-JAK-STAT3 pathway, which is associated with polarization in the M2 phenotype, were significantly down-regulated. Moreover, PCA analysis and Pearson's correlation also indicated that M2-like TAM polarized toward the M1 phenotype at the transcriptional level after treatment with the glycopeptide dCP1. Lipid metabolomics was used to further explore the efficacy of the glycopeptide dCP1 in regulating the polarization of M2-like TAM to the M1 phenotype. It was found that the lipid metabolite profiles in dCP1-treated M2-like TAM showed M1 phenotype macrophage lipid metabolism profiles compared with blank M2-like TAM. Analysis of the key differential lipid metabolites revealed that the interconversion between phosphatidylcholine (PC) and diacylglycerol (DG) metabolites may be the central reaction of the glycopeptide dCP1 in regulating the conversion of M2-like TAM to the M1 phenotype. The above results suggest that the glycopeptide dCP1 has the efficacy to regulate the polarization of M2-like TAM to M1 phenotype in simulated TME.

Metabolic Adaptations and Functional Activity of Macrophages in Homeostasis and Inflammation

In recent years, the role of cellular metabolism in immunity has come into the focus of many studies. These processes form a basis for the maintenance of tissue integrity and homeostasis, as well as represent an integral part of the immune response, in particular, inflammation. Metabolic adaptations not only ensure energy supply for immune response, but also affect the functions of immune cells by controlling transcriptional and post-transcriptional programs. Studying the immune cell metabolism facilitates the search for new treatment approaches, especially for metabolic disorders. Macrophages, innate immune cells, are characterized by a high functional plasticity and play a key role in homeostasis and inflammation. Depending on the phenotype and origin, they can either perform various regulatory functions or promote inflammation state, thus exacerbating the pathological condition. Furthermore, their adaptations to the tissue-specific microenvironment influence the intensity and type of immune response. The review examines the effect of metabolic reprogramming in macrophages on the functional activity of these cells and their polarization. The role of immunometabolic adaptations of myeloid cells in tissue homeostasis and in various pathological processes in the context of inflammatory and metabolic diseases is specifically discussed. Finally, modulation of the macrophage metabolism-related mechanisms reviewed as a potential therapeutic approach.

Taenia solium cysticerci's extracellular vesicles Attenuate the AKT/mTORC1 pathway for Alleviating DSS-induced colitis in a murine model

The excretory-secretory proteome plays a pivotal role in both intercellular communication during disease progression and immune escape mechanisms of various pathogens including cestode parasites like Taenia solium. The cysticerci of T. solium causes infection in the central nervous system known as neurocysticercosis (NCC), which affects a significant population in developing countries. Extracellular vesicles (EVs) are 30-150-nm-sized particles and constitute a significant part of the secretome. However, the role of EV in NCC pathogenesis remains undetermined. Here, for the first time, we report that EV from T. solium larvae is abundant in metabolites that can negatively regulate PI3K/AKT pathway, efficiently internalized by macrophages to induce AKT and mTOR degradation through auto-lysosomal route with a prominent increase in the ubiquitination of both proteins. This results in less ROS production and diminished bacterial killing capability among EV-treated macrophages. Due to this, both macro-autophagy and caspase-linked apoptosis are upregulated, with a reduction of the autophagy substrate sequestome 1. In summary, we report that T. solium EV from viable cysts attenuates the AKT-mTOR pathway thereby promoting apoptosis in macrophages, and this may exert immunosuppression during an early viable stage of the parasite in NCC, which is primarily asymptomatic. Further investigation on EV-mediated immune suppression revealed that the EV can protect the mice from DSS-induced colitis and improve colon architecture. These findings shed light on the previously unknown role of T. solium EV and the therapeutic role of their immune suppression potential.

Tumour-derived exosome SNHG17 induced by oestrogen contributes to ovarian cancer progression via the CCL13-CCR2-M2 macrophage axis

Oestrogen is known to be strongly associated with ovarian cancer. There was much work to show the importance of lncRNA SNHG17 in ovarian cancer. However, no study has revealed the molecular regulatory mechanism and functional effects between oestrogen and SNHG17 in the development and metastasis of ovarian cancer. In this study, we found that SNHG17 expression was significantly increased in ovarian cancer and positively correlated with oestrogen treatment. Oestrogen could promote M2 macrophage polarization as well as ovarian cancer cells SKOV3 and ES2 cell exosomal SNHG17 expression. When exposure to oestrogen, exosomal SNHG17 promoted ovarian cancer cell proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) in vitro, and tumour growth and lung metastasis in vivo by accelerating M2-like phenotype of macrophages. Mechanically, exosomal SNHG17 could facilitate the release of CCL13 from M2 macrophage via the PI3K-Akt signalling pathway. Moreover, CCL13-CCR2 axis was identified to be involved in ovarian cancer tumour behaviours driven by oestrogen. There results demonstrate a novel mechanism that exosomal SNHG17 exerts an oncogenic effect on ovarian cancer via the CCL13-CCR2-M2 macrophage axis upon oestrogen treatment, of which SNHG17 may be a potential biomarker and therapeutic target for ovarian cancer responded to oestrogen.

IL20Rb aggravates pulmonary fibrosis through enhancing bone marrow derived profibrotic macrophage activation

Idiopathic pulmonary fibrosis (IPF) is one of the most fatal chronic interstitial lung diseases with unknown pathogenesis, current treatments cannot truly reverse the progression of the disease. Pulmonary macrophages, especially bone marrow derived pro-fibrotic macrophages, secrete multiple kinds of profibrotic mediators (SPP1, CD206, CD163, IL-10, CCL18…), thus further promote myofibroblast activation and fibrosis procession. IL20Rb is a cell-surface receptor that belongs to IL-20 family. The role of IL20Rb in macrophage activation and pulmonary fibrosis remains unclear. In this study, we established a bleomycin-induced pulmonary fibrosis model, used IL4/13-inducing THP1 cells to induce profibrotic macrophage (M2-like phenotype) polarization models. We found that IL20Rb is upregulated in the progression of pulmonary fibrosis, and its absence can alleviate the progression of pulmonary fibrosis. In addition, we demonstrated that IL20Rb promote the activation of bone marrow derived profibrotic macrophages by regulating the Jak2/Stat3 and Pi3k/Akt signaling pathways. In terms of therapeutic strategy, we used IL20Rb neutralizing antibodies for animal administration, which was found to alleviate the progression of IPF. Our results suggest that IL20Rb plays a profibrotic role by promoting profibrotic macrophage polarization, and IL20Rb may become a potential therapeutic target for IPF. Neutralizing antibodies against IL20Rb may become a potential drug for the clinical treatment of IPF.

Novel insights into macrophage immunometabolism in nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), an inflammatory subtype of nonalcoholic fatty liver disease (NAFLD), is characterized by liver steatosis, inflammation, hepatocellular injury and different degrees of fibrosis, and has been becoming the leading cause of liver-related morbidity and mortality worldwide. Unfortunately, the pathogenesis of NASH has not been completely clarified, and there are no approved therapeutic drugs. Recent accumulated evidences have revealed the involvement of macrophage in the regulation of host liver steatosis, inflammation and fibrosis, and different phenotypes of macrophages have different metabolic characteristics. Therefore, targeted regulation of macrophage immunometabolism may contribute to the treatment and prognosis of NASH. In this review, we summarized the current evidences of the role of macrophage immunometabolism in NASH, especially focused on the related function conversion, as well as the strategies to promote its polarization balance in the liver, and hold promise for macrophage immunometabolism-targeted therapies in the treatment of NASH.

Microglia and macrophage metabolism: a regulator of cerebral gliomas

Reciprocal interactions between the tumor microenvironment (TME) and cancer cells play important roles in tumorigenesis and progression of glioma. Glioma-associated macrophages (GAMs), either of peripheral origin or representing brain-intrinsic microglia, are the majority population of infiltrating immune cells in glioma. GAMs, usually classified into M1 and M2 phenotypes, have remarkable plasticity and regulate tumor progression through different metabolic pathways. Recently, research efforts have increasingly focused on GAMs metabolism as potential targets for glioma therapy. This review aims to delineate the metabolic characteristics of GAMs within the TME and provide a summary of current therapeutic strategies targeting GAMs metabolism in glioma. The goal is to provide novel insights and therapeutic pathways for glioma by highlighting the significance of GAMs metabolism.

Ganoderic acids alleviate atherosclerosis by inhibiting macrophage M1 polarization via TLR4/MyD88/NF-κB signaling pathway

BACKGROUND AND AIMS

Atherosclerosis (AS) is a chronic inflammatory disease characterized by lipid infiltration and plaque formation in blood vessel walls. Ganoderic acids (GA), a class of major bioactive compounds isolated from the Chinese traditional medicine Ganoderma lucidum, have multiple pharmacological activities. This study aimed to determine the anti-atherosclerotic effect of GA and reveal the pharmacological mechanism.

METHODS

ApoE-/- mice were fed a high-cholesterol diet and treated with GA for 16 weeks to induce AS and identify the effect of GA. Network pharmacological analysis was performed to predict the anti-atherosclerotic mechanisms. An invitro cell model was used to explore the effect of GA on macrophage polarization and the possible mechanism involved in bone marrow dereived macrophages (BMDMs) and RAW264.7 cells stimulated with lipopolysaccharide or oxidized low-density lipoprotein.

RESULTS

It was found that GA at 5 and 25 mg/kg/d significantly inhibited the development of AS and increased plaque stability, as evidenced by decreased plaque in the aorta, reduced necrotic core size and increased collagen/lipid ratio in lesions. GA reduced the proportion of M1 macrophages in plaques, but had no effect on M2 macrophages. In vitro experiments showed that GA (1, 5, 25 μg/mL) significantly decreased the proportion of CD86+ macrophages and the mRNA levels of IL-6, IL-1β, and MCP-1 in macrophages. Experimental results showed that GA inhibited M1 macrophage polarization by regulating TLR4/MyD88/NF-κB signaling pathway.

CONCLUSIONS

This study demonstrated that GA play an important role in plaque stability and macrophage polarization. GA exert the anti-atherosclerotic effect partly by regulating TLR4/MyD88/NF-κB signaling pathways to inhibit M1 polarization of macrophages. Our study provides theoretical basis and experimental data for the pharmacological activity and mechanisms of GA against AS.

RNA Expression of MMP12 Is Strongly Associated with Inflammatory Bowel Disease and Is Regulated by Metabolic Pathways in RAW 264.7 Macrophages

Macrophage metalloelastase or matrix metalloproteinase-12 (MMP12) is a macrophage-specific proteolytic enzyme involved in the physiopathology of many inflammatory diseases, including inflammatory bowel disease. Although previously published data suggested that the modulation of MMP12 in macrophages could be a determinant for the development of intestinal inflammation, scarce information is available on the mechanisms underlying the regulation of MMP12 expression in those phagocytes. Therefore, in this study, we aimed to delineate the association of MMP12 with inflammatory bowel disease and the molecular events leading to the transcriptional control of this metalloproteinase. For that, we used publicly available transcriptional data. Also, we worked with the RAW 264.7 macrophage cell line for functional experiments. Our results showed a strong association of MMP12 expression with the severity of inflammatory bowel disease and the response to relevant biological therapies. In vitro assays revealed that the inhibition of mechanistic target of rapamycin complex 1 (mTORC1) and the stimulation of the AMP-activated protein kinase (AMPK) signaling pathway potentiated the expression of Mmp12. Additionally, AMPK and mTOR required a functional downstream glycolytic pathway to fully engage with Mmp12 expression. Finally, the pharmacological inhibition of MMP12 abolished the expression of the proinflammatory cytokine Interleukin-6 (Il6) in macrophages. Overall, our findings provide a better understanding of the mechanistic regulation of MMP12 in macrophages and its relationship with inflammation.

Leucine alleviates cytokine storm syndrome by regulating macrophage polarization via the mTORC1/LXRα signaling pathway

Cytokine storms are associated with severe pathological damage and death in some diseases. Excessive activation of M1 macrophages and the subsequent secretion of pro-inflammatory cytokines are a major cause of cytokine storms. Therefore, promoting the polarization of M2 macrophages to restore immune balance is a promising therapeutic strategy for treating cytokine storm syndrome (CSS). This study was aimed at investigating the potential protective effects of leucine on lipopolysaccharide (LPS)-induced CSS in mice and exploring the underlying mechanisms. CSS was induced by LPS administration in mice, which were concurrently administered leucine orally. In vitro, bone marrow derived macrophages (BMDMs) were polarized to M1 and M2 phenotypes with LPS and interleukin-4 (IL-4), respectively, and treated with leucine. Leucine decreased mortality in mice treated with lethal doses of LPS. Specifically, leucine decreased M1 polarization and promoted M2 polarization, thus diminishing pro-inflammatory cytokine levels and ameliorating CSS in mice. Further studies revealed that leucine-induced macrophage polarization through the mechanistic target of rapamycin complex 1 (mTORC1)/liver X receptor α (LXRα) pathway, which synergistically enhanced the expression of the IL-4-induced M2 marker Arg1 and subsequent M2 polarization. In summary, this study revealed that leucine ameliorates CSS in LPS mice by promoting M2 polarization through the mTORC1/LXRα/Arg1 signaling pathway. Our findings indicate that a fundamental link between metabolism and immunity contributes to the resolution of inflammation and the repair of damaged tissues.

FAM76B regulates PI3K/Akt/NF-κB-mediated M1 macrophage polarization by influencing the stability of PIK3CD mRNA

Macrophage polarization is closely related to inflammation development, yet how macrophages are polarized remains unclear. In our study, the number of M1 macrophages was markedly increased in Fam76b knockout U937 cells vs. wild-type U937 cells, and FAM76B expression was decreased in M1 macrophages induced from different sources of macrophages. Moreover, Fam76b knockout enhanced the mRNA and protein levels of M1 macrophage-associated marker genes. These results suggest that FAM76B inhibits M1 macrophage polarization. We then further explored the mechanism by which FAM76B regulates macrophage polarization. We found that FAM76B can regulate PI3K/Akt/NF-κB pathway-mediated M1 macrophage polarization by stabilizing PIK3CD mRNA. Finally, FAM76B was proven to protect against inflammatory bowel disease (IBD) by inhibiting M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vivo. In summary, FAM76B regulates M1 macrophage polarization through the PI3K/Akt/NF-κB pathway in vitro and in vivo, which may inform the development of future therapeutic strategies for IBD and other inflammatory diseases.

Deficiency of INPP4A promotes M2 macrophage polarization in eosinophilic chronic rhinosinusitis with nasal polyps

OBJECTIVE

The treatment of eosinophilic chronic rhinosinusitis with nasal polyps (E-CRSwNP) remains a challenge due to its complex pathogenesis. Inositol polyphosphate-4-phosphatase type IA (INPP4A), a lipid phosphatase, has been implicated in allergic asthma. However, the expression and function of INPP4A in E-CRSwNP remain unclear. This study aims to investigate the role of INPP4A in macrophages in E-CRSwNP.

METHODS

We assessed the expression of INPP4A in human and mouse nasal mucosal tissues via immunofluorescence staining. THP-1 cells were cultured and exposed to various cytokines to investigate the regulation of INPP4A expression and its functional role. Additionally, we established a murine nasal polyp (NP) model and administrated an INPP4A-overexpressing lentivirus evaluate its impact on NP.

RESULTS

The percentage of INPP4A + CD68 + macrophages among total macrophages decreased in the E-CRSwNP group compared to the control and the non-eosinophilic CRSwNP (NE-CRSwNP) groups, exhibiting an inverse correlation with an increased percentage of CD206 + CD68 + M2 macrophages among total macrophages. Overexpression of INPP4A led to a reduced percentage of THP-1 cells polarizing towards the M2 phenotype, accompanied by decreased levels of associated chemotactic factors including CCL18, CCL22, CCL24, and CCL26. We also validated the involvement of the PI3K-AKT pathway in the function of INPP4A in vitro. Furthermore, INPP4A overexpression in the murine NP model resulted in the attenuation of eosinophilic inflammation in the nasal mucosa.

CONCLUSIONS

INPP4A deficiency promotes macrophage polarization towards the M2 phenotype, leading to the secretion of chemokines that recruit eosinophils and Th2 cells, thereby amplifying eosinophilic inflammation in E-CRSwNP. INPP4A may exert a suppressive role in eosinophilic inflammation and could potentially serve as a novel therapeutic strategy.

Inhibition of PTEN promotes osteointegration of titanium implants in type 2 diabetes by enhancing anti-inflammation and osteogenic capacity of adipose-derived stem cells

Background: The low osteogenic differentiation potential and attenuated anti-inflammatory effect of adipose-derived stem cells (ADSCs) from animals with type 2 diabetes mellitus (T2DM) limits osseointegration of the implant. However, the underlying mechanisms are not fully understood. Methods: Western blotting and qRT-PCR analyses were performed to investigate the effects of PTEN on the osteogenic capacity of ADSCs of T2DM rats (TADSCs). We conducted animal experiments in T2DM-Sprague Dawley (SD) rats to evaluate the osteogenic capacity of modified TADSC sheets in vivo. New bone formation was assessed by micro-CT and histological analyses. Results: In this study, adipose-derived stem cells of T2DM rats exhibited an impaired osteogenic capacity. RNA-seq analysis showed that PTEN mRNA expression was upregulated in TADSCs, which attenuated the osteogenic capacity of TADSCs by inhibiting the AKT/mTOR/HIF-1α signaling pathway. miR-140-3p, which inhibits PTEN, was suppressed in TADSCs. Overexpression or inhibition of PTEN could correspondingly reduce or enhance the osteogenic ability of TADSCs by regulating the AKT/mTOR/HIF-1α signaling pathway. TADSCs transfected with PTEN siRNA resulted in higher and lower expressions of genes encoded in M2 macrophages (Arg1) and M1 macrophages (iNOS), respectively. In the T2DM rat model, PTEN inhibition in TADSC sheets promoted macrophage polarization toward the M2 phenotype, attenuated inflammation, and enhanced osseointegration around implants. Conclusion: Upregulation of PTEN, which was partially due to the inhibition of miR-140-3p, is important for the attenuated osteogenesis by TADSCs owing to the inhibition of the AKT/mTOR/HIF-1α signaling pathway. Inhibition of PTEN significantly improves the anti-inflammatory effect and osteogenic capacity of TADSCs, thus promoting peri-implant bone formation in T2DM rats. Our findings offer a potential therapeutic approach for modifying stem cells derived from patients with T2DM to enhance osseointegration.

The Mechanistic Target of Rapamycin Complex 1 Pathway Contributes to the Anti-Tumor Effect of Granulocyte-Macrophage-Colony-Stimulating Factor-Producing T Helper Cells in Mouse Colorectal Cancer

INTRODUCTION

The role of granulocyte-macrophage-colony-stimulating factor-producing T helper (ThGM) cells in colorectal cancer (CRC) development remains unclear. This study characterizes the function of ThGM cells in mouse CRC.

METHODS

Mouse CRC was induced by administrating azoxymethane and dextran sulfate sodium. The presence of ThGM cells in CRC tissues and the mechanistic target of rapamycin complex 1 (mTORC1) signaling in ThGM cells was detected by flow cytometry. The impact of mTORC1 signaling on ThGM cell function was determined by in vitro culture. The effect of ThGM cells on CRC development was evaluated by adoptive transfer assays.

RESULTS

ThGM cells, which expressed granulocyte-macrophage-colony-stimulating factor (GM-CSF), accumulated in CRC tissues. mTORC1 signaling is activated in CRC ThGM cells. mTORC1 inhibition by rapamycin suppressed ThGM cell differentiation and proliferation and resulted in the death of differentiating ThGM cells. mTORC1 inhibition in already differentiated ThGM cells did not induce significant cell death but decreased the expression of GM-CSF, interleukin-2, and tumor necrosis factor-alpha while impeding cell proliferation. Furthermore, mTORC1 inhibition diminished the effect of ThGM cells on driving macrophage polarization toward the M1 type, as evidenced by lower expression of pro-inflammatory cytokines, major histocompatibility complex class II molecule, and CD80 in macrophages after co-culture with rapamycin-treated ThGM cells. Lentivirus-mediated knockdown/overexpression of regulatory-associated protein of mTOR (Raptor) confirmed the essential role of mTORC1 in ThGM cell differentiation and function. Adoptively transferred ThGM cells suppressed CRC growth whereas mTORC1 inhibition abolished this effect.

CONCLUSION

mTORC1 is essential for the anti-CRC activity of ThGM cells.

Enhancement of Macrophage Immunity against Chlamydial Infection by Natural Killer T Cells

Lung macrophage (LM) is vital in host defence against bacterial infections. However, the influence of other innate immune cells on its function, including the polarisation of different subpopulations, remains poorly understood. This study examined the polarisation of LM subpopulations (monocytes/undifferentiated macrophages (Mo/Mφ), interstitial macrophages (IM), and alveolar macrophages (AM)). We further assessed the effect of invariant natural killer T cells (iNKT) on LM polarisation in a protective function against Chlamydia muridarum, an obligate intracellular bacterium, and respiratory tract infection. We found a preferentially increased local Mo/Mφ and IMs with a significant shift to a type-1 macrophage (M1) phenotype and higher expression of iNOS and TNF-α. Interestingly, during the same infection, the alteration of macrophage subpopulations and the shift towards M1 was much less in iNKT KO mice. More importantly, functional testing by adoptively transferring LMs isolated from iNKT KO mice (iNKT KO-Mφ) conferred less protection than those isolated from wild-type mice (WT-Mφ). Further analyses showed significantly reduced gene expression of the JAK/STAT signalling pathway molecules in iNKT KO-Mφ. The data show an important role of iNKT in promoting LM polarisation to the M1 direction, which is functionally relevant to host defence against a human intracellular bacterial infection. The alteration of JAK/STAT signalling molecule gene expression in iNKT KO-Mφ suggests the modulating effect of iNKT is likely through the JAK/STAT pathway.

Ghrelin regulating liver activity and its potential effects on liver fibrosis and Echinococcosis

Ghrelin widely exists in the central nervous system and peripheral organs, and has biological activities such as maintaining energy homeostasis, regulating lipid metabolism, cell proliferation, immune response, gastrointestinal physiological activities, cognition, memory, circadian rhythm and reward effects. In many benign liver diseases, it may play a hepatoprotective role against steatosis, chronic inflammation, oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress and apoptosis, and improve liver cell autophagy and immune response to improve disease progression. However, the role of Ghrelin in liver Echinococcosis is currently unclear. This review systematically summarizes the molecular mechanisms by which Ghrelin regulates liver growth metabolism, immune-inflammation, fibrogenesis, proliferation and apoptosis, as well as its protective effects in liver fibrosis diseases, and further proposes the role of Ghrelin in liver Echinococcosis infection. During the infectious process, it may promote the parasitism and survival of parasites on the host by improving the immune-inflammatory microenvironment and fibrosis state, thereby accelerating disease progression. However, there is currently a lack of targeted in vitro and in vivo experimental evidence for this viewpoint.

Immunomodulation in diabetic wounds healing: The intersection of macrophage reprogramming and immunotherapeutic hydrogels

Diabetic wound healing presents a significant clinical challenge due to the interplay of systemic metabolic disturbances and local inflammation, which hinder the healing process. Macrophages undergo a phenotypic shift from M1 to M2 during wound healing, a transition pivotal for effective tissue repair. However, in diabetic wounds, the microenvironment disrupts this phenotypic polarization, perpetuating inflammation, and impeding healing. Reprograming macrophages to restore their M2 phenotype offers a potential avenue for modulating the wound immune microenvironment and promoting healing. This review elucidates the mechanisms underlying impaired macrophage polarization toward the M2 phenotype in diabetic wounds and discusses novel strategies, including epigenetic and metabolic interventions, to promote macrophage conversion to M2. Hydrogels, with their hydrated 3D cross-linked structure, closely resemble the physiological extracellular matrix and offer advantageous properties such as biocompatibility, tunability, and versatility. These characteristics make hydrogels promising candidates for developing immunomodulatory materials aimed at addressing diabetic wounds. Understanding the role of hydrogels in immunotherapy, particularly in the context of macrophage reprograming, is essential for the development of advanced wound care solutions. This review also highlights recent advancements in immunotherapeutic hydrogels as a step toward precise and effective treatments for diabetic wounds.

Nutrient-sensing growth hormone secretagogue receptor in macrophage programming and meta-inflammation

OBJECTIVE

Obesity-associated chronic inflammation, aka meta-inflammation, is a key pathogenic driver for obesity-associated comorbidity. Growth hormone secretagogue receptor (GHSR) is known to mediate the effects of nutrient-sensing hormone ghrelin in food intake and fat deposition. We previously reported that global Ghsr ablation protects against diet-induced inflammation and insulin resistance, but the site(s) of action and mechanism are unknown. Macrophages are key drivers of meta-inflammation. To unravel the role of GHSR in macrophages, we generated myeloid-specific Ghsr knockout mice (LysM-Cre;Ghsrf/f).

METHODS

LysM-Cre;Ghsrf/f and control Ghsrf/f mice were subjected to 5 months of high-fat diet (HFD) feeding to induce obesity. In vivo, metabolic profiling of food intake, physical activity, and energy expenditure, as well as glucose and insulin tolerance tests (GTT and ITT) were performed. At termination, peritoneal macrophages (PMs), epididymal white adipose tissue (eWAT), and liver were analyzed by flow cytometry and histology. For ex vivo studies, bone marrow-derived macrophages (BMDMs) were generated from the mice and treated with palmitic acid (PA) or lipopolysaccharide (LPS). For in vitro studies, macrophage RAW264.7 cells with Ghsr overexpression or Insulin receptor substrate 2 (Irs2) knockdown were studied.

RESULTS

We found that Ghsr expression in PMs was increased under HFD feeding. In vivo, HFD-fed LysM-Cre;Ghsrf/f mice exhibited significantly attenuated systemic inflammation and insulin resistance without affecting food intake or body weight. Tissue analysis showed that HFD-fed LysM-Cre;Ghsrf/f mice have significantly decreased monocyte/macrophage infiltration, pro-inflammatory activation, and lipid accumulation, showing elevated lipid-associated macrophages (LAMs) in eWAT and liver. Ex vivo, Ghsr-deficient macrophages protected against PA- or LPS-induced pro-inflammatory polarization, showing reduced glycolysis, increased fatty acid oxidation, and decreased NF-κB nuclear translocation. At molecular level, GHSR metabolically programs macrophage polarization through PKA-CREB-IRS2-AKT2 signaling pathway.

CONCLUSIONS

These novel results demonstrate that macrophage GHSR plays a key role in the pathogenesis of meta-inflammation, and macrophage GHSR promotes macrophage infiltration and induces pro-inflammatory polarization. These exciting findings suggest that GHSR may serve as a novel immunotherapeutic target for the treatment of obesity and its associated comorbidity.

Advances in the regulatory mechanisms of mTOR in necroptosis

The mammalian target of rapamycin (mTOR), an evolutionarily highly conserved serine/threonine protein kinase, plays a prominent role in controlling gene expression, metabolism, and cell death. Programmed cell death (PCD) is indispensable for maintaining homeostasis by removing senescent, defective, or malignant cells. Necroptosis, a type of PCD, relies on the interplay between receptor-interacting serine-threonine kinases (RIPKs) and the membrane perforation by mixed lineage kinase domain-like protein (MLKL), which is distinguished from apoptosis. With the development of necroptosis-regulating mechanisms, the importance of mTOR in the complex network of intersecting signaling pathways that govern the process has become more evident. mTOR is directly responsible for the regulation of RIPKs. Autophagy is an indirect mechanism by which mTOR regulates the removal and interaction of RIPKs. Another necroptosis trigger is reactive oxygen species (ROS) produced by oxidative stress; mTOR regulates necroptosis by exploiting ROS. Considering the intricacy of the signal network, it is reasonable to assume that mTOR exerts a bifacial effect on necroptosis. However, additional research is necessary to elucidate the underlying mechanisms. In this review, we summarized the mechanisms underlying mTOR activation and necroptosis and highlighted the signaling pathway through which mTOR regulates necroptosis. The development of therapeutic targets for various diseases has been greatly advanced by the expanding knowledge of how mTOR regulates necroptosis.

Macrophage polarization in spinal cord injury repair and the possible role of microRNAs: A review

The prevention, treatment, and rehabilitation of spinal cord injury (SCI) have always posed significant medical challenges. After mechanical injury, disturbances in microcirculation, edema formation, and the generation of free radicals lead to additional damage, impeding effective repair processes and potentially exacerbating further dysfunction. In this context, inflammatory responses, especially the activation of macrophages, play a pivotal role. Different phenotypes of macrophages have distinct effects on inflammation. Activation of classical macrophage cells (M1) promotes inflammation, while activation of alternative macrophage cells (M2) inhibits inflammation. The polarization of macrophages is crucial for disease healing. A non-coding RNA, known as microRNA (miRNA), governs the polarization of macrophages, thereby reducing inflammation following SCI and facilitating functional recovery. This study elucidates the inflammatory response to SCI, focusing on the infiltration of immune cells, specifically macrophages. It examines their phenotype and provides an explanation of their polarization mechanisms. Finally, this paper introduces several well-known miRNAs that contribute to macrophage polarization following SCI, including miR-155, miR-130a, and miR-27 for M1 polarization, as well as miR-22, miR-146a, miR-21, miR-124, miR-223, miR-93, miR-132, and miR-34a for M2 polarization. The emphasis is placed on their potential therapeutic role in SCI by modulating macrophage polarization, as well as the present developments and obstacles of miRNA clinical therapy.

Phenylalanine diminishes M1 macrophage inflammation

Emerging evidence suggests that amino acids dictate the effector functions of immune cells; however, whether and how phenylalanine (Phe) orchestrates the polarization of macrophages is not understood. Here, we determined that Phe attenuated lipopolysaccharide (LPS) and P. multocida serotype A strain CQ2 (PmCQ2) infection-induced inflammation in vivo. Furthermore, we demonstrated that Phe inhibited the production of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in proinflammatory (M1) macrophages. Phe reprogrammed the transcriptomic and metabolic profiles and enhanced oxidative phosphorylation in M1 macrophages, which reduced the activation of caspase-1. Notably, the valine-succinyl-CoA axis played a critical role in Phe-mediated inhibition of IL-1β production in M1 macrophages. Taken together, our findings suggest that manipulating the valine-succinyl-CoA axis provides a potential target for preventing and/or treating macrophage-related diseases.

Effects of Everolimus in Modulating the Host Immune Responses against Mycobacterium tuberculosis Infection

The phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (P13K/AKT/mTOR) pathway plays a key role in tuberculosis (TB) pathogenesis and infection. While the activity levels of this pathway during active infection are still debated, manipulating this pathway shows potential benefit for host-directed therapies. Some studies indicate that pathway inhibitors may have potential for TB treatment through upregulation of autophagy, while other studies do not encourage the use of these inhibitors due to possible host tissue destruction by Mycobacterium tuberculosis (M. tb) and increased infection risk. Investigating further clinical trials and their use of pathway inhibitors is necessary in order to ascertain their potential for TB treatment. This paper is particularly focused on the drug everolimus, an mTOR inhibitor. One of the first clinical trials sponsored by the Aurum Institute showed potential benefit in using everolimus as an adjunctive therapy for tuberculosis. Infection with tuberculosis is associated with a metabolic shift from oxidative phosphorylation towards glycolysis. The everolimus arm in the clinical trial showed further reduction than the control for both maximal and peak glycolytic activity. Compared with control, those receiving everolimus demonstrated increased lung function through forced expiratory volume in 1 s (FEV1) measurements, suggesting that everolimus may mitigate inflammation contributing to lung damage.

Local administration of liposomal-based Plekhf1 gene therapy attenuates pulmonary fibrosis by modulating macrophage polarization

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease with limited therapeutic options. Macrophages, particularly alternatively activated macrophages (M2), have been recognized to contribute to the pathogenesis of pulmonary fibrosis. Therefore, targeting macrophages might be a viable therapeutic strategy for IPF. Herein, we report a potential nanomedicine-based gene therapy for IPF by modulating macrophage M2 activation. In this study, we illustrated that the levels of pleckstrin homology and FYVE domain containing 1 (Plekhf1) were increased in the lungs originating from IPF patients and PF mice. Further functionality studies identified the pivotal role of Plekhf1 in macrophage M2 activation. Mechanistically, Plekhf1 was upregulated by IL-4/IL-13 stimulation, after which Plekhf1 enhanced PI3K/Akt signaling to promote the macrophage M2 program and exacerbate pulmonary fibrosis. Therefore, intratracheal administration of Plekhf1 siRNA-loaded liposomes could effectively suppress the expression of Plekhf1 in the lungs and notably protect mice against BLM-induced lung injury and fibrosis, concomitant with a significant reduction in M2 macrophage accumulation in the lungs. In conclusion, Plekhf1 may play a crucial role in the pathogenesis of pulmonary fibrosis, and Plekhf1 siRNA-loaded liposomes might be a promising therapeutic approach against pulmonary fibrosis.

Hippo-YAP/TAZ signaling in osteogenesis and macrophage polarization: Therapeutic implications in bone defect repair

Bone defects caused by diseases or surgery are a common clinical problem. Researchers are devoted to finding biological mechanisms that accelerate bone defect repair, which is a complex and continuous process controlled by many factors. As members of transcriptional costimulatory molecules, Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) play an important regulatory role in osteogenesis, and they affect cell function by regulating the expression of osteogenic genes in osteogenesis-related cells. Macrophages are an important group of cells whose function is regulated by YAP/TAZ. Currently, the relationship between YAP/TAZ and macrophage polarization has attracted increasing attention. In bone tissue, YAP/TAZ can realize diverse osteogenic regulation by mediating macrophage polarization. Macrophages polarize into M1 and M2 phenotypes under different stimuli. M1 macrophages dominate the inflammatory response by releasing a number of inflammatory mediators in the early phase of bone defect repair, while massive aggregation of M2 macrophages is beneficial for inflammation resolution and tissue repair, as they secrete many anti-inflammatory and osteogenesis-related cytokines. The mechanism of YAP/TAZ-mediated macrophage polarization during osteogenesis warrants further study and it is likely to be a promising strategy for bone defect repair. In this article, we review the effect of Hippo-YAP/TAZ signaling and macrophage polarization on bone defect repair, and highlight the regulation of macrophage polarization by YAP/TAZ.

SGLT2 inhibitors prevent LPS-induced M1 macrophage polarization and alleviate inflammatory bowel disease by downregulating NHE1 expression

BACKGROUND

Classically activated M1 macrophages, characterized by aberrant glycolysis and secretion of inflammatory cytokines, play pivotal roles in inflammatory diseases, including inflammatory bowel disease (IBD). Recently, sodium-glucose co-transporter 2 (SGLT2) inhibitors were shown to suppress Na+/H+ exchanger 1 (NHE1) and Na+/Ca2+ exchanger 1 (NCX1) activity, regulating downstream intracellular Ca2+ concentrations in cardiomyocytes. However, whether SGLT2 inhibitors regulate M1 macrophage polarization by downregulating NHE1 and NCX1 remains unknown.

METHODS

We analyzed cellular responses to SGLT2 inhibitors using mouse bone marrow-derived macrophages and peritoneal macrophages treated with lipopolysaccharide (LPS). To induce IBD, we used a dextran sulfate sodium salt-induced colitis mouse model.

RESULTS

We observed that NHE1 and NCX1 were overexpressed in LPS-treated macrophages, leading to M1 macrophage polarization. Mechanistically, NHE1 and NCX1-mediated Ca2+ accumulation in the macrophage resulted in enhanced glycolysis by promoting PI3K/AKT/mTORC1 signaling. SGLT2 inhibitors suppressed both the expression levels and activities of NHE1 and NCX1, and consequently downregulated PI3K/AKT/mTORC1 signaling and glycolysis in LPS-treated macrophages. We observed inhibition of LPS-stimulated M1 polarization and cytokine production by SGLT2 inhibitors in vitro, ex vivo, and in an IBD mouse model.

CONCLUSIONS

NHE1 promotes M1 macrophage polarization and SGLT2 inhibitors are a novel strategy to treat M1 macrophage-mediated inflammatory diseases, including IBD.

Upregulation of exosome secretion from tumor-associated macrophages plays a key role in the suppression of anti-tumor immunity

Macrophages play a pivotal role in tumor immunity. We report that reprogramming of macrophages to tumor-associated macrophages (TAMs) promotes the secretion of exosomes. Mechanistically, increased exosome secretion is driven by MADD, which is phosphorylated by Akt upon TAM induction and activates Rab27a. TAM exosomes carry high levels of programmed death-ligand 1 (PD-L1) and potently suppress the proliferation and function of CD8+ T cells. Analysis of patient melanoma tissues indicates that TAM exosomes contribute significantly to CD8+ T cell suppression. Single-cell RNA sequencing analysis showed that exosome-related genes are highly expressed in macrophages in melanoma; TAM-specific RAB27A expression inversely correlates with CD8+ T cell infiltration. In a murine melanoma model, lipid nanoparticle delivery of small interfering RNAs (siRNAs) targeting macrophage RAB27A led to better T cell activation and sensitized tumors to anti-programmed cell death protein 1 (PD-1) treatment. Our study demonstrates tumors use TAM exosomes to combat CD8 T cells and suggests targeting TAM exosomes as a potential strategy to improve immunotherapies.

Molecular Mechanisms Underpinning Immunometabolic Reprogramming: How the Wind Changes during Cancer Progression

Metabolism and the immunological state are intimately intertwined, as defense responses are bioenergetically expensive. Metabolic homeostasis is a key requirement for the proper function of immune cell subsets, and the perturbation of the immune-metabolic balance is a recurrent event in many human diseases, including cancer, due to nutrient fluctuation, hypoxia and additional metabolic changes occurring in the tumor microenvironment (TME). Although much remains to be understood in the field of immunometabolism, here, we report the current knowledge on both physiological and cancer-associated metabolic profiles of immune cells, and the main molecular circuits involved in their regulation, highlighting similarities and differences, and emphasizing immune metabolic liabilities that could be exploited in cancer therapy to overcome immune resistance.

Etiology of lipid-laden macrophages in the lung

Uniquely positioned as sentinel cells constantly exposed to the environment, pulmonary macrophages are vital for the maintenance of the lung lining. These cells are responsible for the clearance of xenobiotics, pathogen detection and clearance, and homeostatic functions such as surfactant recycling. Among the spectrum of phenotypes that may be expressed by macrophages in the lung, the pulmonary lipid-laden phenotype is less commonly studied in comparison to its circulatory counterpart, the atherosclerotic lesion-associated foam cell, or the acutely activated inflammatory macrophage. Herein, we propose that lipid-laden macrophage formation in the lung is governed by lipid acquisition, storage, metabolism, and export processes. The cellular balance of these four processes is critical to the maintenance of homeostasis and the prevention of aberrant signaling that may contribute to lung pathologies. This review aims to examine mechanisms and signaling pathways that are involved in lipid-laden macrophage formation and the potential consequences of this phenotype in the lung.

Signaling pathways in macrophages: molecular mechanisms and therapeutic targets

Macrophages play diverse roles in development, homeostasis, and immunity. Accordingly, the dysfunction of macrophages is involved in the occurrence and progression of various diseases, such as coronavirus disease 2019 and atherosclerosis. The protective or pathogenic effect that macrophages exert in different conditions largely depends on their functional plasticity, which is regulated via signal transduction such as Janus kinase-signal transducer and activator of transcription, Wnt and Notch pathways, stimulated by environmental cues. Over the past few decades, the molecular mechanisms of signaling pathways in macrophages have been gradually elucidated, providing more alternative therapeutic targets for diseases treatment. Here, we provide an overview of the basic physiology of macrophages and expound the regulatory pathways within them. We also address the crucial role macrophages play in the pathogenesis of diseases, including autoimmune, neurodegenerative, metabolic, infectious diseases, and cancer, with a focus on advances in macrophage-targeted strategies exploring modulation of components and regulators of signaling pathways. Last, we discuss the challenges and possible solutions of macrophage-targeted therapy in clinical applications. We hope that this comprehensive review will provide directions for further research on therapeutic strategies targeting macrophage signaling pathways, which are promising to improve the efficacy of disease treatment.

Functional polarization of tumor-associated macrophages dictated by metabolic reprogramming

Macrophages are highly plastic in different tissues and can differentiate into functional subpopulations under different stimuli. Tumor-associated macrophages (TAMs) are one of the most important innate immune cells implicated in the establishment of an immunosuppressive tumor microenvironment (TME). Recent evidence pinpoints the critical role of metabolic reprogramming in dictating pro-tumorigenic functions of TAMs. Both tumor cells and macrophages undergo metabolic reprogramming to meet energy demands in the TME. Understanding the metabolic rewiring in TAMs can shed light on immune escape mechanisms and provide insights into repolarizing TAMs towards anti-tumorigenic function. Here, we discuss how metabolism impinges on the functional divergence of macrophages and its relevance to macrophage polarization in the TME.

Can Exercise Enhance the Efficacy of Checkpoint Inhibition by Modulating Anti-Tumor Immunity?

Immune checkpoint inhibition (ICI) has revolutionized cancer therapy. However, response to ICI is often limited to selected subsets of patients or not durable. Tumors that are non-responsive to checkpoint inhibition are characterized by low anti-tumoral immune cell infiltration and a highly immunosuppressive tumor microenvironment. Exercise is known to promote immune cell circulation and improve immunosurveillance. Results of recent studies indicate that physical activity can induce mobilization and redistribution of immune cells towards the tumor microenvironment (TME) and therefore enhance anti-tumor immunity. This suggests a favorable impact of exercise on the efficacy of ICI. Our review delivers insight into possible molecular mechanisms of the crosstalk between muscle, tumor, and immune cells. It summarizes current data on exercise-induced effects on anti-tumor immunity and ICI in mice and men. We consider preclinical and clinical study design challenges and discuss the role of cancer type, exercise frequency, intensity, time, and type (FITT) and immune sensitivity as critical factors for exercise-induced impact on cancer immunosurveillance.

TRAF Family Member 4 Promotes Cardiac Hypertrophy Through the Activation of the AKT Pathway

Background Pathological cardiac hypertrophy is a major cause of heart failure morbidity. The complex mechanism of intermolecular interactions underlying the pathogenesis of cardiac hypertrophy has led to a lack of development and application of therapeutic methods. Methods and Results Our study provides the first evidence that TRAF4, a member of the tumor necrosis factor receptor-associated factor (TRAF) family, acts as a promoter of cardiac hypertrophy. Here, Western blotting assays demonstrated that TRAF4 is upregulated in cardiac hypertrophy. Additionally, TRAF4 deletion inhibits the development of cardiac hypertrophy in a mouse model after transverse aortic constriction surgery, whereas its overexpression promotes phenylephrine stimulation-induced cardiomyocyte hypertrophy in primary neonatal rat cardiomyocytes. Mechanistically, RNA-seq analysis revealed that TRAF4 promoted the activation of the protein kinase B pathway during cardiac hypertrophy. Moreover, we found that inhibition of protein kinase B phosphorylation rescued the aggravated cardiomyocyte hypertrophic phenotypes caused by TRAF4 overexpression in phenylephrine-treated neonatal rat cardiomyocytes, suggesting that TRAF4 may regulate cardiac hypertrophy in a protein kinase B-dependent manner. Conclusions Our results revealed the regulatory function of TRAF4 in cardiac hypertrophy, which may provide new insights into developing therapeutic and preventive targets for this disease.