TSC1 controls macrophage polarization to prevent inflammatory disease

Ox-LDL-induced CD80+ macrophages expand pro-atherosclerotic NKT cells via CD1d in atherosclerotic mice and hyperlipidemic patients

Atherosclerosis is an inflammatory disease of blood vessels involving the immune system. Natural killer T (NKT) cells, as crucial components of the innate and acquired immune systems, play critical roles in the development of atherosclerosis. However, the mechanism and clinical relevance of NKT cells in early atherosclerosis are largely unclear. The study investigated the mechanism influencing NKT cell function in apoE deficiency-induced early atherosclerosis. Our findings demonstrated that there were higher populations of NKT cells and interferon-gamma (IFN-γ)-producing NKT cells in the peripheral blood of patients with hyperlipidemia and in the aorta, blood, spleen, and bone marrow of early atherosclerotic mice compared with the control groups. Moreover, we discovered that the infiltration of CD80+ macrophages and CD1d expression on CD80+ macrophages in atherosclerotic mice climbed remarkably. CD1d expression increased in CD80+ macrophages stimulated by oxidized low-density lipoprotein (ox-LDL) ex vivo and in vitro. Ex vivo coculture of macrophages with NKT cells revealed that ox-LDL-induced CD80+ macrophages presented lipid antigen α-Galcer (alpha-galactosylceramide) to NKT cells via CD1d, enabling NKT cells to express more IFN-γ. Furthermore, a greater proportion of CD1d+ monocytes and CD1d+CD80+ monocytes were found in peripheral blood of hyperlipidemic patients compared with that of healthy donors. Positive correlations were found between CD1d+CD80+ monocytes and NKT cells or IFN-γ+ NKT cells in hyperlipidemic patients. Our findings illustrated that CD80+ macrophages stimulated NKT cells to secrete IFN-γ via CD1d-presenting α-Galcer, which may accelerate the progression of early atherosclerosis. Inhibiting lipid antigen presentation by CD80+ macrophages to NKT cells may be a promising immune target for the treatment of early atherosclerosis.NEW & NOTEWORTHY This work proposed the ox-LDL-CD80+ monocyte/macrophage-CD1d-NKT cell-IFN-γ axis in the progression of atherosclerosis. The proinflammatory IFN-γ+ NKT cells are closely related to CD1d+CD80+ monocytes in hyperlipidemic patients. Inhibiting CD80+ macrophages to present lipid antigens to NKT cells through CD1d blocking may be a new therapeutic target for atherosclerosis.

BMSC-Derived Exosomes Attenuate Rat Osteoarthritis by Regulating Macrophage Polarization through PINK1/Parkin Signaling Pathway

OBJECTIVE

Exosomes derived from bone marrow mesenchymal stem cells (BMSC-Exos) may modulate the M1/M2 polarization of macrophages during osteoarthritis (OA). However, the underlying mechanisms of BMSC-Exos in this process still need to be elucidated. In this study, we explored the role of BMSC-Exos in the polarization of macrophages in vitro and the OA rats in vivo.

METHODS

The effects of BMSC-Exos on RAW264.7 cells were determined, including the production of reactive oxygen species (ROS) and the protein expression of Akt, PINK1, and Parkin. We prepared an OA model by resecting the anterior cruciate ligament and medial meniscus of Sprague-Dawley (SD) rats. Hematoxylin-eosin (H&E) and safranin O-fast green staining, immunohistochemistry and immunofluorescence analyses, and the examination of interleukin 6 (IL-6), interleukin 1β (IL-1β), tumor necrosis factor alpha (TNF-α), and interleukin 10 (IL-10) were performed to assess changes in cartilage and synovium.

RESULTS

BMSC-Exos inhibited mitochondrial membrane damage, ROS production, and the protein expression of PINK1 and Parkin. Akt phosphorylation was downregulated under lipopolysaccharide (LPS) induction but significantly recovered after treatment with BMSC-Exos. BMSC-Exos alleviated cartilage damage, inhibited M1 polarization, and promoted M2 polarization in the synovium in OA rats. The expression of PINK1 and Parkin in the synovium and the levels of IL-6, IL-1β, and TNF-α in the serum decreased, but the level of IL-10 increased when BMSC-Exos were used in OA rats.

CONCLUSION

BMSC-Exos ameliorate OA development by regulating synovial macrophage polarization, and one of the underlying mechanisms may be through inhibiting PINK1/Parkin signaling.

Crosstalk between P2Y receptors and cyclooxygenase activity in inflammation and tissue repair

The role of extracellular nucleotides as modulators of inflammation and cell stress is well established. One of the main actions of these molecules is mediated by the activation of purinergic receptors (P2) of the plasma membrane. P2 receptors can be classified according to two different structural families: P2X ionotropic ion channel receptors, and P2Y metabotropic G protein-coupled receptors. During inflammation, damaged cells release nucleotides and purinergic signaling occurs along the temporal pattern of the synthesis of pro-inflammatory and pro-resolving mediators by myeloid and lymphoid cells. In macrophages under pro-inflammatory conditions, the expression and activity of cyclooxygenase 2 significantly increases and enhances the circulating levels of prostaglandin E2 (PGE2), which exerts its effects both through specific plasma membrane receptors (EP1-EP4) and by activation of intracellular targets. Here we review the mechanisms involved in the crosstalk between PGE2 and P2Y receptors on macrophages, which is dependent on several isoforms of protein kinase C and protein kinase D1. Due to this crosstalk, a P2Y-dependent increase in calcium is blunted by PGE2 whereas, under these conditions, macrophages exhibit reduced migratory capacity along with enhanced phagocytosis, which contributes to the modulation of the inflammatory response and tissue repair.

Spermidine ameliorates osteoarthritis via altering macrophage polarization

OBJECTIVE

Spermidine (SPD) is an anti-aging natural substance, and it exerts effects through anti-apoptosis and anti-inflammation. However, the specific protective mechanism of SPD in osteoarthritis (OA) remains unclear. Here, we explored the role of SPD on the articular cartilage and the synovial tissue, and tested whether the drug would regulate the polarization of synovial macrophages by in vivo and in vitro experiments.

METHODS

By constructing an OA model in mice, we preliminarily explored the protective effect of SPD on the articular cartilage and the synovial tissue. Meanwhile, we isolated and cultured human primary chondrocytes and bone marrow-derived macrophages (BMDMs), and prepared a conditioned medium (CM) to explore the specific protective effect of SPD in vitro.

RESULTS

We found that SPD alleviated cartilage degeneration and synovitis, increased M2 polarization and decreased M1 polarization in synovial macrophages. In vitro experiments, SPD inhibited ERK MAPK and p65/NF-κB signaling in macrophages, and transformed macrophages from M1 to M2 subtypes. Interestingly, SPD had no direct protective effect on chondrocytes in vitro; however, the conditioned medium (CM) from M1 macrophages treated with SPD promoted the anabolism and inhibited the catabolism of chondrocytes. Moreover, this CM markedly suppressed IL-1β-induced p38/JNK MAPK signaling pathway activation in chondrocytes.

CONCLUSIONS

This work provides new perspectives on the role of SPD in OA. SPD does not directly target chondrocytes, but can ameliorate the degradation of articular cartilage through regulating M1/M2 polarization of synovial macrophages. Hence, SPD is expected to be the potential therapy for OA.

Empowering macrophages: the cancer fighters within the tumour microenvironment in mantle cell lymphoma

In Mantle Cell Lymphoma (MCL), the role of macrophages within the tumour microenvironment (TME) has recently gained attention due to their impact on prognosis and response to therapy. Despite their low absolute number in MCL tumour tissue, recent findings reveal an association between the levels of macrophages and prognosis, consistent with trends observed in other lymphoma subtypes. M2-like macrophages, identified by markers such as CD163, contribute to angiogenesis and suppression of the immune response. Clinical trials with MCL patients treated with chemoimmunotherapy and targeted treatments underscore the adverse impact of high levels of M2-like macrophages. Immunomodulatory drugs like lenalidomide reduce the levels of MCL-associated CD163+ macrophages and enhance macrophage phagocytic activity. Similarly, clinical approaches targeting the CD47 "don't eat me" signalling, in combination with the anti-CD20-antibody rituximab, demonstrate increased macrophage activity and phagocytosis of MCL tumour cells. Cell-based therapies such as chimeric antigen receptor (CAR) T-cell have shown promise but various challenges persist, leading to a potential interest in CAR-macrophages (CAR-M). When macrophages are recruited to the TME, they offer advantages including phagocytic function and responsiveness to microenvironment alterations, suggesting their potential as a manipulable and inducible alternative when CAR T-cell therapies fails in the complex landscape of MCL treatment.

Targeted knockdown of PGAM5 in synovial macrophages efficiently alleviates osteoarthritis

Osteoarthritis (OA) is a common degenerative disease worldwide and new therapeutics that target inflammation and the crosstalk between immunocytes and chondrocytes are being developed to prevent and treat OA. These attempts involve repolarizing pro-inflammatory M1 macrophages into the anti-inflammatory M2 phenotype in synovium. In this study, we found that phosphoglycerate mutase 5 (PGAM5) significantly increased in macrophages in OA synovium compared to controls based on histology of human samples and single-cell RNA sequencing results of mice models. To address the role of PGAM5 in macrophages in OA, we found conditional knockout of PGAM5 in macrophages greatly alleviated OA symptoms and promoted anabolic metabolism of chondrocytes in vitro and in vivo. Mechanistically, we found that PGAM5 enhanced M1 polarization via AKT-mTOR/p38/ERK pathways, whereas inhibited M2 polarization via STAT6-PPARγ pathway in murine bone marrow-derived macrophages. Furthermore, we found that PGAM5 directly dephosphorylated Dishevelled Segment Polarity Protein 2 (DVL2) which resulted in the inhibition of β-catenin and repolarization of M2 macrophages into M1 macrophages. Conditional knockout of both PGAM5 and β-catenin in macrophages significantly exacerbated osteoarthritis compared to PGAM5-deficient mice. Motivated by these findings, we successfully designed mannose modified fluoropolymers combined with siPGAM5 to inhibit PGAM5 specifically in synovial macrophages via intra-articular injection, which possessed desired targeting abilities of synovial macrophages and greatly attenuated murine osteoarthritis. Collectively, these findings defined a key role for PGAM5 in orchestrating macrophage polarization and provides insights into novel macrophage-targeted strategy for treating OA.

Loss of macrophage TSC1 exacerbates sterile inflammatory liver injury through inhibiting the AKT/MST1/NRF2 signaling pathway

Tuberous sclerosis complex 1 (TSC1) plays important roles in regulating innate immunity. However, the precise role of TSC1 in macrophages in the regulation of oxidative stress response and hepatic inflammation in liver ischemia/reperfusion injury (I/R) remains unknown. In a mouse model of liver I/R injury, deletion of myeloid-specific TSC1 inhibited AKT and MST1 phosphorylation, and decreased NRF2 accumulation, whereas activated TLR4/NF-κB pathway, leading to increased hepatic inflammation. Adoptive transfer of AKT- or MST1-overexpressing macrophages, or Keap1 disruption in myeloid-specific TSC1-knockout mice promoted NRF2 activation but reduced TLR4 activity and mitigated I/R-induced liver inflammation. Mechanistically, TSC1 in macrophages promoted AKT and MST1 phosphorylation, and protected NRF2 from Keap1-mediated ubiquitination. Furthermore, overexpression AKT or MST1 in TSC1-knockout macrophages upregulated NRF2 expression, downregulated TLR4/NF-κB, resulting in reduced inflammatory factors, ROS and inflammatory cytokine-mediated hepatocyte apoptosis. Strikingly, TSC1 induction in NRF2-deficient macrophages failed to reverse the TLR4/NF-κB activity and production of pro-inflammatory factors. Conclusions: Macrophage TSC1 promoted the activation of the AKT/MST1 signaling pathway, increased NRF2 levels via reducing Keap1-mediated ubiquitination, and modulated oxidative stress-driven inflammatory responses in liver I/R injury. Our findings underscore the critical role of macrophage TSC1 as a novel regulator of innate immunity and imply the therapeutic potential for the treatment of sterile liver inflammation in transplant recipients. Schematic illustration of macrophage TSC1-mediated AKT/MST1/NRF2 signaling pathway in I/R-triggered liver inflammation. Macrophage TSC1 can be activated in I/R-stressed livers. TSC1 activation promotes phosphorylation of AKT and MST1, which in turn increases NRF2 expression and inhibits ROS production and TLR4/NF-κB activation, resulting in reduced hepatocellular apoptosis in I/R-triggered liver injury.

A Novel Cargo Delivery System-AnCar-ExoLaIMTS Ameliorates Arthritis via Specifically Targeting Pro-Inflammatory Macrophages

Macrophages are heterogenic phagocytic cells that play distinct roles in physiological and pathological processes. Targeting different types of macrophages has shown potent therapeutic effects in many diseases. Although many approaches are developed to target anti-inflammatory macrophages, there are few researches on targeting pro-inflammatory macrophages, which is partially attributed to their non-s pecificity phagocytosis of extracellular substances. In this study, a novel recombinant protein is constructed that can be anchored on an exosome membrane with the purpose of targeting pro-inflammatory macrophages via antigen recognition, which is named AnCar-ExoLaIMTS . The data indicate that the phagocytosis efficiencies of pro-inflammatory macrophages for different AnCar-ExoLaIMTS show obvious differences. The AnCar-ExoLaIMTS3 has the best targeting ability for pro-inflammatory macrophages in vitro and in vivo. Mechanically, AnCar-ExoLaIMTS3 can specifically recognize the leucine-rich repeat domain of the TLR4 receptor, and then enter into pro-inflammatory macrophages via the TLR4-mediated receptor endocytosis pathway. Moreover, AnCar-ExoLaIMTS3 can efficiently deliver therapeutic cargo to pro-inflammatory macrophages and inhibit the synovial inflammatory response via downregulation of HIF-1α level, thus ameliorating the severity of arthritis in vivo. Collectively, the work established a novel gene/drug delivery system that can specifically target pro-inflammatory macrophages, which may be beneficial for the treatments of arthritis and other inflammatory diseases.

Downregulation of nutrition sensor GCN2 in macrophages contributes to poor wound healing in diabetes

Poor skin wound healing, which is common in patients with diabetes, is related to imbalanced macrophage polarization. Here, we find that nutrition sensor GCN2 (general control nonderepressible 2) and its downstream are significantly upregulated in human skin wound tissue and mouse skin wound macrophages, but skin wound-related GCN2 expression and activity are significantly downregulated by diabetes and hyperglycemia. Using wound healing models of GCN2-deleted mice, bone marrow chimeric mice, and monocyte-transferred mice, we show that GCN2 deletion in macrophages significantly delays skin wound healing compared with wild-type mice by altering M1 and M2a/M2c polarization. Mechanistically, GCN2 inhibits M1 macrophages via OXPHOS-ROS-NF-κB pathway and promotes tissue-repairing M2a/M2c macrophages through eukaryotic translation initiation factor 2 (eIF2α)-hypoxia-inducible factor 1α (HIF1α)-glycolysis pathway. Importantly, local supplementation of GCN2 activator halofuginone efficiently restores wound healing in diabetic mice with re-balancing M1 and M2a/2c polarization. Thus, the decreased macrophage GCN2 expression and activity contribute to poor wound healing in diabetes and targeting GCN2 improves wound healing in diabetes.

Mycobacterium tuberculosis virulence protein ESAT-6 influences M1/M2 polarization and macrophage apoptosis to regulate tuberculosis progression

BACKGROUND

Tuberculosis (TB) is an infectious disease caused by infection with Mycobacterium tuberculosis (Mtb), and it remains one of the major threats to human health worldwide. To our knowledge, the polarization of M1/M2 macrophages were critical innate immune cells which play important roles in regulating the immune response during TB progression.

OBJECTIVE

We aimed to explore the potential mechanisms of M1/M2 macrophage polarization in TB development.

METHODS

THP-1 macrophages were treated with early secreted antigenic target of 6 kDa (ESAT-6) protein for an increasing time. The polarization profiles, apoptosis levels of M1 and M2 macrophages were detected by RT-qPCR, immunofluorescence, Western blot and flow cytometry.

RESULTS

ESAT-6 initially promoted the generation of pro-inflammatory M1-polarized macrophages in THP-1 cells within 24 h, which were suppressed by further ESAT-6 treatment at 30-42 h. Interestingly, ESAT-6 continuously promoted M2 polarization of THP-1 cells, thereby maintaining the anti-inflammatory response in a time-dependent manner. In addition, ESAT-6 promoted apoptotic cell death in M1-polarized macrophages, which had little effects on apoptosis of M2-phenotype of macrophages. Then, the potential underlying mechanisms were uncovered, and we verified that ESAT-6 increased the protein levels of TLR4, MyD88 and NF-κB to activate the TLR4/MyD88/NF-κB pathway within 24 h, and this signal pathway was significantly inactivated at 36 h post-treatment. Interestingly, the following experiments confirmed that ESAT-6 TLR4/MyD88/NF-κB pathway-dependently regulated M1/M2 polarization and apoptosis of macrophage in THP-1 cells.

CONCLUSION

Our study investigated the detailed effects and mechanisms of M1/M2 macrophages in regulating innate responses during TB development, which provided a new perspective on the development of treatment strategies for this disease.

CD206+ M2-like macrophages protect against intervertebral disc degeneration partially by targeting R-spondin-2

OBJECTIVE

This study aimed to explore the specific function of M2 macrophages in intervertebral disc degeneration (IDD).

METHODS

Intervertebral disc (IVD) samples from normal (n = 4) and IDD (n = 6) patients were collected, and the expression of M2-polarized macrophage marker, CD206, was investigated using immunohistochemical staining. Nucleus pulposus cells (NPCs) in a TNF-α environment were obtained, and a mouse caudal IVD puncture model was established. Mice with Rheb deletions, specifically in the myeloid lineage, were generated and subjected to surgery-induced IDD. IDD-induced damage and cell apoptosis were measured using histological scoring, X-ray imaging, immunohistochemical staining, and TdT-mediated dUTP nick end labeling (TUNEL) assay. Finally, mice and NPCs were treated with R-spondin-2 (Rspo2) or anti-Rspo2 to investigate the role of Rspo2 in IDD.

RESULTS

Accumulation of CD206 in human and mouse IDD tissues was detected. Rheb deletion in the myeloid lineage (RheBcKO) increased the number of CD206+ M2-like macrophages (mean difference 18.6% [15.7-21.6%], P < 0.001), decreased cell apoptosis (mean difference -15.6% [-8.9 to 22.2%], P = 0.001) and attenuated the IDD process in the mouse IDD model. NPCs treated with Rspo2 displayed increased extracellular matrix catabolism and apoptosis; co-culture with a conditioned medium derived from RheBcKO mice inhibited these changes. Anti-Rspo2 treatment in the mouse caudal IVD puncture model exerted protective effects against IDD.

CONCLUSIONS

Promoting CD206+ M2-like macrophages could reduce Rspo2 secretion, thereby alleviating experimental IDD. Rheb deletion may help M2-polarized macrophages accumulate and attenuate experimental IDD partially by inhibiting Rspo2 production. Hence, M2-polarized macrophages and Rspo2 may serve as therapeutic targets for IDD.

N6-methyladenosine modification of TSC1 mRNA contributes to macrophage polarization regulated by Coptisine in DSS-induced ulcerative colitis

BACKGROUND AND PURPOSE

Ulcerative colitis (UC) is a global refractory disease characterized by recurrent episodes. Coptisine (COP) is an isoquinoline alkaloid derived from Coptis chinensis, which has strong anti-inflammatory activity. Macrophages are key cells mediating inflammation. It is reported that N6-methyladenosine (m6A) RNA methylation regulates the polarization of macrophages and affects the development of inflammation. COP exerts an exact inhibitory effect on macrophages inflammation, while the specific mechanism remains unclear. The current study is designed to conduct a further investigation into the protective mechanism of COP against dextran sulfate sodium (DSS) -induced UC in mice.

METHODS

Using a DSS-induced UC model, we evaluated the pharmacodynamic effect of COP on UC mice, and verified the regulatory mechanism of COP on macrophage polarization in vivo and in vitro. The methylation level of m6A was detected by methylated RNA immunoprecipitation sequence (MeRIP) -qPCR, and the expression level of Methyltransferase Like (METTL)14 was determined by western blotting. Then METTL14 was knocked down in macrophages, and its effects on Tuberous sclerosis complex (TSC1) mRNA and m6A methylation regulation were observed.

RESULTS

COP improved the symptoms, alleviated tissue damage and reduced inflammation levels in DSS-induced UC mice. COP increased TSC1 expression, inhibited the Mitogen-activated protein kinase (MEK) / Extracellular regulated protein kinases (ERK) signaling pathway, and thus inhibited macrophage M1 polarization, whereas COP increased CCAAT Enhancer Binding Protein beta (c/EBPβ) expression, and thus promoted macrophage M2 polarization. COP also significantly increased the expression of METTL14, which enhanced m6A methylation and ultimately improved the stability of TSC1 mRNA.

CONCLUSIONS

COP was effective in treating UC and could regulate the polarization of macrophages. The possible mechanisms might be related to m6A modification-mediated TSC1.

Ceria-vesicle nanohybrid therapeutic for modulation of innate and adaptive immunity in a collagen-induced arthritis model

Commencing with the breakdown of immune tolerance, multiple pathogenic factors, including synovial inflammation and harmful cytokines, are conjointly involved in the progression of rheumatoid arthritis. Intervening to mitigate some of these factors can bring a short-term therapeutic effect, but other unresolved factors will continue to aggravate the disease. Here we developed a ceria nanoparticle-immobilized mesenchymal stem cell nanovesicle hybrid system to address multiple factors in rheumatoid arthritis. Each component of this nanohybrid works individually and also synergistically, resulting in comprehensive treatment. Alleviation of inflammation and modulation of the tissue environment into an immunotolerant-favourable state are combined to recover the immune system by bridging innate and adaptive immunity. The therapy is shown to successfully treat and prevent rheumatoid arthritis by relieving the main symptoms and also by restoring the immune system through the induction of regulatory T cells in a mouse model of collagen-induced arthritis.

Immunomodulatory functions of microorganisms in tissue regenerative healing

External pathogenic microorganisms and commensal microorganisms in the body have either harmful or beneficial impacts on the regenerative repair of tissues, and the immune system plays a crucial regulatory role in this process. This review summarises our current understanding of microorganism-immune system interactions, with a focus on how these interactions impact the renewal and repair ability of tissues, including skin, bone, gut, liver, and nerves. This review concludes with a discussion of the mechanisms by which microbes act on various types of immune cells to affect tissue regeneration, offers potential strategies for using microbial therapies to enhance the regenerative repair function of tissues, and suggest novel therapeutic approaches for regenerative medicine. STATEMENT OF SIGNIFICANCE: Microbiological communities have crucial impacts on human health and illness by participating in energy collection and storage and performing various metabolic processes. External pathogenic microorganisms and commensal microorganisms in the body have either harmful or beneficial impacts on the regenerative repair of tissues, and the immune system plays a critical regulatory role in this process. This study reviews the important correlation between microorganisms and the immune system and investigates the mechanism of various microorganism that participate in the regeneration and repair of tissues and organs by modulating immune system.

Emodin inhibits bladder inflammation and fibrosis in mice with interstitial cystitis by regulating JMJD3

PURPOSE

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a devastating urological chronic pelvic pain condition. In search of a potential treatment, we investigated the effect of emodin on IC/BPS inflammation and fibrosis, and explore the potential mechanism.

METHODS

An experimental model of interstitial cystitis was induced by cyclophosphamide, and human bladder smooth muscle cells were treated with lipopolysaccharide to establish the cell model in vitro. In both models, inflammation- and fibrosis-related indexes were measured after emodin administration. Furthermore, the specific antagonists were used to dig for the mechanisms underlying the response to emodin treatment.

RESULTS

Emodin significantly ameliorated management of cystitis, reduced the amount of inflammatory cytokines (tumor necrosis factor-α, monocyte chemoattractant protein-1, interleukin-1β, interleukin-8, and interleukin-6) in models, as well as reducing the synthesis of fibrosis marker including collagen1, collagen3, vimentin, fibronectin and α-smooth muscle actin. Further mechanism studies demonstrated that emodin inhibited inflammatory reaction and fibrosis through blocking lysine-specific demethylase 6B (JMJD3) expression via JAK/STAT, NF-κB and TGF-β/SMAD pathways.

CONCLUSIONS

Our study reveals the critical role of emodin-JMJD3 signaling in interstitial cystitis by regulating inflammation, fibrosis, and extracellular matrix deposition in cells and tissues, and these findings provide an avenue for effective treatment of patients with cystitis.

Reprogramming tumor-associated macrophages to outcompete endovascular endothelial progenitor cells and suppress tumor neoangiogenesis

Tumors develop by invoking a supportive environment characterized by aberrant angiogenesis and infiltration of tumor-associated macrophages (TAMs). In a transgenic model of breast cancer, we found that TAMs localized to the tumor parenchyma and were smaller than mammary tissue macrophages. TAMs had low activity of the metabolic regulator mammalian/mechanistic target of rapamycin complex 1 (mTORC1), and depletion of negative regulator of mTORC1 signaling, tuberous sclerosis complex 1 (TSC1), in TAMs inhibited tumor growth in a manner independent of adaptive lymphocytes. Whereas wild-type TAMs exhibited inflammatory and angiogenic gene expression profiles, TSC1-deficient TAMs had a pro-resolving phenotype. TSC1-deficient TAMs relocated to a perivascular niche, depleted protein C receptor (PROCR)-expressing endovascular endothelial progenitor cells, and rectified the hyperpermeable blood vasculature, causing tumor tissue hypoxia and cancer cell death. TSC1-deficient TAMs were metabolically active and effectively eliminated PROCR-expressing endothelial cells in cell competition experiments. Thus, TAMs exhibit a TSC1-dependent mTORC1-low state, and increasing mTORC1 signaling promotes a pro-resolving state that suppresses tumor growth, defining an innate immune tumor suppression pathway that may be exploited for cancer immunotherapy.

Biotherapy of experimental acute kidney injury: emerging novel therapeutic strategies

Acute kidney injury (AKI) is a complex and heterogeneous disease with high incidence and mortality, posing a serious threat to human life and health. Usually, in clinical practice, AKI is caused by crush injury, nephrotoxin exposure, ischemia-reperfusion injury, or sepsis. Therefore, most AKI models for pharmacological experimentation are based on this. The current research promises to develop new biological therapies, including antibody therapy, non-antibody protein therapy, cell therapy, and RNA therapy, that could help mitigate the development of AKI. These approaches can promote renal repair and improve systemic hemodynamics after renal injury by reducing oxidative stress, inflammatory response, organelles damage, and cell death, or activating cytoprotective mechanisms. However, no candidate drugs for AKI prevention or treatment have been successfully translated from bench to bedside. This article summarizes the latest progress in AKI biotherapy, focusing on potential clinical targets and novel treatment strategies that merit further investigation in future pre-clinical and clinical studies.

Mechanistic target of rapamycin (mTOR): a potential new therapeutic target for rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by systemic synovitis and bone destruction. Proinflammatory cytokines activate pathways of immune-mediated inflammation, which aggravates RA. The mechanistic target of rapamycin (mTOR) signaling pathway associated with RA connects immune and metabolic signals, which regulates immune cell proliferation and differentiation, macrophage polarization and migration, antigen presentation, and synovial cell activation. Therefore, therapy strategies targeting mTOR have become an important direction of current RA treatment research. In the current review, we summarize the biological functions of mTOR, its regulatory effects on inflammation, and the curative effects of mTOR inhibitors in RA, thus providing references for the development of RA therapeutic targets and new drugs.

mTORC2 orchestrates monocytic and granulocytic lineage commitment by an ATF5-mediated pathway

Myeloid hematopoiesis is a finely controlled consecutive developmental process, which is essential to maintain peripheral innate immune homeostasis. Herein, we found that Rictor deletion caused the remarkable reduction of granulocyte-monocyte progenitors (GMPs), monocytes, and macrophages, while the levels of neutrophils were unaffected. Adoptive transfer of Rictor-deleted GMPs or common myeloid progenitors (CMPs) in syngeneic mice showed poor re-constitution of monocytes compared to wild-type GMPs or CMPs. In addition to decreasing the proliferation of CMPs/GMPs, Rictor deletion preferentially inhibited Ly6C+ monocyte differentiation, while enhancing neutrophil differentiation, as determined by colony formation assays. mTORC2 promotes monocyte development by downregulation of the AKT-Foxo4-activating transcription factor 5 (ATF5)-mitochondrial unfolded protein response (mtUPR) pathway. Genetic overexpression of ATF5 or exposure to ethidium bromide significantly rescued monocyte/macrophage differentiation defects of Rictor-deficient myeloid progenitors. Therefore, Rictor is required for CMP/GMP proliferation and acts as an important switch to balance monocytic and granulocytic lineage commitment in bone marrow.

Mesenchymal stromal cells regulate THP-1-differentiated macrophage cytokine production by activating Akt/mammalian target of rapamycin complex 1 pathway

BACKGROUND AIMS

The Akt/mammalian target of rapamycin (mTOR) pathway in macrophages converges inflammatory and metabolic signals from multiple receptors to regulate a cell's survival, metabolism and activation. Although mesenchymal stromal cells (MSCs) are well known to modulate macrophage activation, the effects of MSCs on the Akt/mTOR pathway in macrophages have not been elucidated.

METHODS

We herein investigated whether MSCs affect the Akt/mTOR complex 1 (mTORC1) pathway to regulate macrophage polarization.

RESULTS

Results showed that human bone marrow-derived MSCs induced activation of Akt and its downstream mTORC1 signaling in THP-1-differentiated macrophages in a p62/sequestosome 1-independent manner. Inhibition of Akt or mTORC1 attenuated the effects of MSCs on the suppression of tumor necrosis factor-α and interleukin-12 production and the promotion of interleukin-10 and tumor growth factor-β1 in macrophages stimulated by lipopolysaccharide/ATP. Conversely, activation of Akt or mTORC1 reproduced and potentiated MSC effects on macrophage cytokine production. MSCs with cyclooxygenase-2 knockdown, however, failed to activate the Akt/mTORC1 signaling in macrophages and were less effective in the modulation of macrophage cytokine production than control MSCs.

CONCLUSIONS

These data demonstrate that MSCs control THP-1-differentiated macrophage activation at least partly through upregulation of the Akt/mTORC1 signaling in a cyclooxygenase-2-dependent manner.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.

Impaired PPARγ activation by cadmium exacerbates infection-induced lung injury

Emerging data indicate an association between environmental heavy metal exposure and lung disease, including lower respiratory tract infections (LRTIs). Here, we show by single-cell RNA sequencing an increase in Pparg gene expression in lung macrophages from mice exposed to cadmium and/or infected with Streptococcus pneumoniae. However, the heavy metal cadmium or infection mediated an inhibitory posttranslational modification of peroxisome proliferator-activated receptor γ (PPARγ) to exacerbate LRTIs. Cadmium and infection increased ERK activation to regulate PPARγ degradation in monocyte-derived macrophages. Mice harboring a conditional deletion of Pparg in monocyte-derived macrophages had more severe S. pneumoniae infection after cadmium exposure, showed greater lung injury, and had increased mortality. Inhibition of ERK activation with BVD-523 protected mice from lung injury after cadmium exposure or infection. Moreover, individuals residing in areas of high air cadmium levels had increased cadmium concentration in their bronchoalveolar lavage (BAL) fluid, increased barrier dysfunction, and showed PPARγ inhibition that was mediated, at least in part, by ERK activation in isolated BAL cells. These observations suggest that impaired activation of PPARγ in monocyte-derived macrophages exacerbates lung injury and the severity of LRTIs.

In Situ Sustained Macrophage-Targeted Nanomicelle-Hydrogel Microspheres for Inhibiting Osteoarthritis

There are still challenges in applying drug nanocarriers for in situ sustained macrophage targeting and regulation, due to the rapid clearance of nanocarriers and burst drug release in vivo. Herein, a nanomicelle-hydrogel microsphere, characterized by its macrophage-targeted nanosized secondary structure that allows it to accurately bind to M1 macrophages through active endocytosis, is employed for in situ sustained macrophage targeting and regulation, and addresses the insufficient osteoarthritis therapeutic efficacy caused by rapid clearance of drug nanocarriers. The 3-dimensional structure of a microsphere can prevent the rapid escape and clearance of a nanomicelle, thus keeping it in joints, while the ligand-guided secondary structure can carry drugs to accurately target and enter M1 macrophages, and release drugs via the transition from hydrophobicity to hydrophilicity of nanomicelles under inflammatory stimulation inside the macrophages. The experiments show that the nanomicelle-hydrogel microsphere can in situ sustainably target and regulate M1 macrophages for more than 14 days in joints, and attenuate local "cytokine storm" by continuous M1 macrophage apoptosis promotion and polarization inhibition. This micro/nano-hydrogel system shows excellent ability to sustainably target and regulate macrophage, realizes the improvement of drug utilization and efficacy inside the macrophage, and thereby can be a potential platform for treating macrophage-related diseases.

Enhancer of zeste homolog 2 promotes renal fibrosis after acute kidney injury by inducing epithelial-mesenchymal transition and activation of M2 macrophage polarization

Long-term follow-up data indicates that 1/4 patients with acute kidney injury (AKI) will develop to chronic kidney disease (CKD). Our previous studies have demonstrated that enhancer of zeste homolog 2 (EZH2) played an important role in AKI and CKD. However, the role and mechanisms of EZH2 in AKI-to-CKD transition are still unclear. Here, we demonstrated EZH2 and H3K27me3 highly upregulated in kidney from patients with ANCA-associated glomerulonephritis, and expressed positively with fibrotic lesion and negatively with renal function. Conditional EZH2 deletion or pharmacological inhibition with 3-DZNeP significantly improved renal function and attenuated pathological lesion in ischemia/reperfusion (I/R) or folic acid (FA) mice models (two models of AKI-to-CKD transition). Mechanistically, we used CUT & Tag technology to verify that EZH2 binding to the PTEN promoter and regulating its transcription, thus regulating its downstream signaling pathways. Genetic or pharmacological depletion of EZH2 upregulated PTEN expression and suppressed the phosphorylation of EGFR and its downstream signaling ERK1/2 and STAT3, consequently alleviating the partial epithelial-mesenchymal transition (EMT), G2/M arrest, and the aberrant secretion of profibrogenic and proinflammatory factors in vivo and vitro experiments. In addition, EZH2 promoted the EMT program induced loss of renal tubular epithelial cell transporters (OAT1, ATPase, and AQP1), and blockade of EZH2 prevented it. We further co-cultured macrophages with the medium of human renal tubular epithelial cells treated with H₂O₂ and found macrophages transferred to M2 phenotype, and EZH2 could regulate M2 macrophage polarization through STAT6 and PI3K/AKT pathways. These results were further verified in two mice models. Thus, targeted inhibition of EZH2 might be a novel therapy for ameliorating renal fibrosis after acute kidney injury by counteracting partial EMT and blockade of M2 macrophage polarization.

Lipid metabolism reprogramming in tumor-associated macrophages and implications for therapy

The tumormicroenvironment (TME) plays a key role in tumor progression. Tumor-associated macrophages (TAMs), which are natural immune cells abundantin the TME, are mainly divided into the anti-tumor M1 subtype and pro-tumor M2 subtype. Due to the high plasticity of TAMs, the conversion of the M1 to M2 phenotype in hypoxic and hypoglycemic TME promotes cancer progression, which is closely related to lipid metabolism. Key factors of lipid metabolism in TAMs, including peroxisome proliferator-activated receptor and lipoxygenase, promote the formation of a tumor immunosuppressive microenvironment and facilitate immune escape. In addition, tumor cells promote lipid accumulation in TAMs, causing TAMs to polarize to the M2 phenotype. Moreover, other factors of lipid metabolism, such as abhydrolase domain containing 5 and fatty acid binding protein, have both promoting and inhibiting effects on tumor cells. Therefore, further research on lipid metabolism in tumors is still required. In addition, statins, as core drugs regulating cholesterol metabolism, can inhibit lipid rafts and adhesion of tumor cells, which can sensitize them to chemotherapeutic drugs. Clinical studies on simvastatin and lovastatin in a variety of tumors are underway. This article provides a comprehensive review of the role of lipid metabolism in TAMs in tumor progression, and provides new ideas for targeting lipid metabolism in tumor therapy.

Transcriptome Sequencing Reveals the Mechanism behind Chemically Induced Oral Mucositis in a 3D Cell Culture Model

Oral mucositis is a common side effect of cancer treatment, and in particular of treatment with the mTORC1 inhibitor everolimus. Current treatment methods are not efficient enough and a better understanding of the causes and mechanisms behind oral mucositis is necessary to find potential therapeutic targets. Here, we treated an organotypic 3D oral mucosal tissue model consisting of human keratinocytes grown on top of human fibroblasts with a high or low dose of everolimus for 40 or 60 h and investigated (1) the effect of everolimus on microscopic sections of the 3D cell culture for evidence of morphologic changes and (2) changes in the transcriptome by high throughput RNA-Seq analysis. We show that the most affected pathways are cornification, cytokine expression, glycolysis, and cell proliferation and we provide further details. This study provides a good resource towards a better understanding of the development of oral mucositis. It gives a detailed overview of the different molecular pathways that are involved in mucositis. This in turn provides information about potential therapeutic targets, which is an important step towards preventing or managing this common side effect of cancer treatment.

Macrophage Biology in Human Granulomatous Skin Inflammation

Cutaneous granulomatoses represent a heterogeneous group of diseases, which are defined by macrophage infiltration in the skin. Skin granuloma can be formed in the context of infectious and non-infectious conditions. Recent technological advances have deepened our understanding of the pathophysiology of granulomatous skin inflammation, and they provide novel insights into human tissue macrophage biology at the site of ongoing disease. Here, we discuss findings on macrophage immune function and metabolism derived from three prototypic cutaneous granulomatoses: granuloma annulare, sarcoidosis, and leprosy.

CD146+ Umbilical Cord Mesenchymal Stem Cells Exhibit High Immunomodulatory Activity and Therapeutic Efficacy in Septic Mice

Background

Several studies have shown that MSCs can significantly improve the survival of sepsis animals. CD146+ mesenchymal stem cells (MSCs) correlate with high therapeutic potency. However, their therapeutic effect on sepsis and detail mechanisms have not been explored.

Methods

The effect of CD146±MSCs on differentiation of Treg, Th1, Th17 subsets was evaluated by flow cytometry. The effects of CD146±MSCs on RAW264.7 phagocytosis and LPS-stimulated polarization were studied using a co-culture protocol. Luminex bead array and RNA sequencing were employed to determine the mechanisms of MSCs on LPS-stimulated RAW264.7. The Arg1 protein was detected by Western blot. CD146±MSCs were injected into LPS-induced sepsis mice by tail vein. The therapeutic effect was assessed by organ HE staining, T-cell subsets, cytokine in plasma, peritoneal macrophages, infiltrating monocytes subpopulations.

Results

In vitro, CD146+MSCs could significantly increase the proportion of Treg cells. Co-culture with CD146+MSCs increase the phagocytic rate of RAW264.7. CD146+MSCs regulate M2-type macrophages production more rapidly. The transcript profile differences between the CD146+MSCs and CD146-MSCs groups were clustered in arginine metabolism pathways. CD146+MSCs decreased NO production and increased ARG1 expression. CD146+MSCs secreted higher level of IL15,IFNγ, VEGF and lower level of IL1β, IL8 under LPS stimuli. In vivo, The level of IL10 at 24h and CXCL1, IFNγ at 12h in CD146+MSCs group was the highest. CD146+MSCs treatment enhances the phagocytic capacity of peritoneal macrophages. CD146+MSCs also increases the ratios of CD11b+Ly6C^lo reparative monocytes and CD11b+Ly6C^hi inflammatory monocytes until 24h.

Conclusion

Compared with CD146-MSCs, CD146+MSCs can accelerate the end of the inflammatory response and have robust anti-inflammatory effects, by increasing the Treg cells, promoting macrophage phagocytosis, enhancing the reparative macrophage, secreting more VEGF, etc.

The Role of PGK1 in Promoting Ischemia/Reperfusion Injury-Induced Microglial M1 Polarization and Inflammation by Regulating Glycolysis

Stroke is a leading cause of death, with a continuously increasing incidence. As a metabolic process that catabolizes glucose pyruvate and provides adenosine triphosphate (ATP), glycolysis plays a crucial role in different diseases. Phosphoglycerate kinase 1 (PGK1) facilitates energy production with biosynthesis in many diseases, including stroke. However, the exact role of PGK1/glycolysis in stroke remains to be elucidated. A rat model of middle cerebral artery occlusion (MCAO) was used to mimic ischemia/reperfusion injuries. Oxygen glucose deprivation/re-oxygenation (OGD/R) was used to induce injury to highly aggressively proliferating immortalized (HAPI) rat microglial cells. The extracellular acidification rate (ECAR) was determined using an XFe24 Extracellular Flux Analyzer. ATP, lactate dehydrogenase, tumor necrosis factor-alpha, and interleukin-6 levels were measured using commercial kits. Chromatin immunoprecipitation assay was performed to examine the interaction between H3K27ac or p300 and the PGK1 promoter region. PGK1 was either knocked down or overexpressed by lentivirus. Thus, to examine its role in stroke, real-time polymerase chain reaction and immunoblotting were used to measure gene expression. The expression of PGK1 was increased and associated with M1 polarization and glycolysis in MCAO rat models. OGD/R promoted M1 polarization and HAPI microglial cell inflammation by regulating glycolysis. Silencing PGK1 reduced OGD/R-increased M1 polarization, inflammation, and glycolysis. Conversely, the overexpression of PGK1 promoted HAPI microglial cell inflammation by regulating glycolysis. The mechanism showed that histone acetyltransferase p300 promoted PGK1 expression through H3K27 acetylation. Finally, data indicated that silencing PGK1 inhibited microglia M1 polarization, inflammation, and glycolysis in MCAO rat models. PGK1 could promote ischemia/reperfusion injury-induced microglial M1 polarization and inflammation by regulating glycolysis, which might provide a novel direction in developing new therapeutic medications for preventing or treating stroke.

Microgravity and immune cells

The microgravity environment experienced during spaceflight severely impaired immune system, making astronauts vulnerable to various diseases that seriously threaten the health of astronauts. Immune cells are exceptionally sensitive to changes in gravity and the microgravity environment can affect multiple aspects of immune cells through different mechanisms. Previous reports have mainly summarized the role of microgravity in the classification of innate and adaptive immune cells, lacking an overall grasp of the laws that microgravity effects on immune cells at different stages of their entire developmental process, such as differentiation, activation, metabolism, as well as function, which are discussed and concluded in this review. The possible molecular mechanisms are also analysed to provide a clear understanding of the specific role of microgravity in the whole development process of immune cells. Furthermore, the existing methods by which to reverse the damage of immune cells caused by microgravity, such as the use of polysaccharides, flavonoids, other natural immune cell activators etc. to target cell proliferation, apoptosis and impaired function are summarized. This review will provide not only new directions and ideas for the study of immune cell function in the microgravity environment, but also an important theoretical basis for the development of immunosuppression prevention and treatment drugs for spaceflight.

Effects of Total Saponins from Dioscorea Nipponica Makino on Monosodium Urate-Induced M1-Polarized Macrophages through Arachidonic Acid Signaling Pathway: An in vitro Study

OBJECTIVE

To investigate and reveal the underlying mechanism of the effect of total saponins from Dioscoreae nipponica Makino (TSDN) on the arachidonic acid pathway in monosodium urate (MSU) crystal-induced M1-polarized macrophages.

METHODS

M1 polarization of RAW264.7 cells were induced by 1 µ g/mL lipopolysaccharide (LPS). The methylthiazolyldiphenyl-tetrazolium bromide method was then used to screen the concentration of TSDN. MSU (500 µ g/mL) was used to induce the gouty arthritis model. Afterwards, 10 µ g/L TSDN and 8 µ mol/L celecoxib, which was used as a positive control, were added to the above LPS and MSU-induced cells for 24 h. The mRNA and protein expressions of cyclooxygenase (COX) 2, 5-lipoxygenase (5-LOX), microsomal prostaglandin E synthase derived eicosanoids (mPGES)-1, leukotriene B (LTB)4, cytochrome P450 (CYP) 4A, and prostaglandin E2 (PGE₂) were tested by real-time polymerase chain reaction and Western blotting, respectively. The enzyme-linked immunosorbent assay was used to test the contents of M1 markers, including inducible nitric oxid synthase (NOS) 2, CD80, and CD86.

RESULTS

TSDN inhibited the proliferation of M1 macrophages and decreased both the mRNA and protein expressions of COX2, 5-LOX, CYP4A, LTB4, and PGE₂ (P<0.01) while increased the mRNA and protein expression of mPGES-1 (P<0.05 or P<0.01). TSDN could also significantly decrease the contents of NOS2, CD80, and CD86 (P<0.01).

CONCLUSION

TSDN has an anti-inflammation effect on gouty arthritis in an in vitro model by regulating arachidonic acid signaling pathway.

Engineered Nanoprobes for Immune Activation Monitoring

The activation of the immune system is critical for cancer immunotherapy and treatments of inflammatory diseases. Non-invasive visualization of immunoactivation is designed to monitor the dynamic nature of the immune response and facilitate the assessment of therapeutic outcomes, which, however, remains challenging. Conventional imaging modalities, such as positron emission tomography, computed tomography, etc., were utilized for imaging immune-related biomarkers. To explore the dynamic immune monitoring, probes with signals correlated to biomarkers of immune activation or prognosis are urgently needed. These emerging molecular probes, which turn on the signal only in the presence of the intended biomarker, can improve the detection specificity. These probes with "turn on" signals enable non-invasive, dynamic, and real-time imaging with high sensitivity and efficiency, showing significance for multifunctionality/multimodality imaging. As a result, more and more innovative engineered nanoprobes combined with diverse imaging modalities were developed to assess the activation of the immune system. In this work, we comprehensively review the recent and emerging advances in engineered nanoprobes for monitoring immune activation in cancer or other immune-mediated inflammatory diseases and discuss the potential in predicting the efficacy following treatments. Research on real-time in vivo immunoimaging is still under exploration, and this review can provide guidance and facilitate the development and application of next-generation imaging technologies.

CCL3 aggravates intestinal damage in NEC by promoting macrophage chemotaxis and M1 macrophage polarization

BACKGROUND

NEC is a life-threatening gastrointestinal disease in neonates, the pathogenesis of which remains poorly understood.

METHODS

CCL3 levels in intestinal tissue of mice were measured and analyzed. HE staining was used to assess pathological changes in intestinal tissue. FCM was used to detect the proportion and phenotype of macrophages. RNA-seq and RT-PCR were used to evaluate the effect of CCL3 on macrophages.

RESULTS

CCL3 was highly expressed in the intestinal tissues of mice with NEC and induced macrophage infiltration. Transcriptome data showed that CCL3 strongly induced a transition in the phenotype of macrophages into a proinflammatory one. Mechanistically, in vivo experiments confirmed that CCL3 induced M1 macrophage polarization in NEC intestinal tissue, thereby aggravating inflammatory injury of intestinal tissue, which was alleviated by anti-CCL3 treatment. In addition, in vitro experiments showed that CCL3 significantly enhances the expression of M1-related genes in both PMφ and BMDM while inhibiting the expression of M2-related genes, which was also alleviated by anti-CCl3 treatment.

CONCLUSIONS

Our data elucidated the involvement of CCL3 in the pathogenesis of NEC, in which upregulated CCL3 expression exacerbated inflammatory intestinal damage by regulating macrophage chemotaxis and M1 phenotype polarization, suggesting that blocking CCL3 may be a potential strategy for effective intervention in NEC.

IMPACT

Our study represents an important conceptual advancement that CCL3 may be one of the key culprits of intestinal tissue damage in patients with NEC. CCL3 aggravates inflammatory intestinal injury and intestinal mucosal barrier imbalance by regulating the chemotaxis, polarization, and function of macrophages. Blocking CCL3 significantly reduced NEC-mediated intestinal injury, suggesting a new potential therapeutic strategy.

The PI3K/Akt Pathway in Meta-Inflammation

Obesity is a global epidemic representing a serious public health burden as it is a major risk factor for the development of cardiovascular disease, stroke and all-cause mortality. Chronic low-grade systemic inflammation, also known as meta-inflammation, is thought to underly obesity's negative health consequences, which include insulin resistance and the development of type 2 diabetes. Meta-inflammation is characterized by the accumulation of immune cells in adipose tissue, a deregulation in the synthesis and release of adipokines and a pronounced increase in the production of proinflammatory factors. In this state, the infiltration of macrophages and their metabolic activation contributes to complex paracrine and autocrine signaling, which sustains a proinflammatory microenvironment. A key signaling pathway mediating the response of macrophages and adipocytes to a microenvironment of excessive nutrients is the phosphoinositide 3-kinase (PI3K)/Akt pathway. This multifaceted network not only transduces metabolic information but also regulates macrophages' intracellular changes, which are responsible for their phenotypic switch towards a more proinflammatory state. In the present review, we discuss how the crosstalk between macrophages and adipocytes contributes to meta-inflammation and provide an overview on the involvement of the PI3K/Akt signaling pathway, and how its impairment contributes to the development of insulin resistance.

FABP5 Deficiency Impaired Macrophage Inflammation by Regulating AMPK/NF-κB Signaling Pathway

Fatty acid binding protein 5 (FABP5) is mainly involved in the uptake, transport, and metabolism of fatty acid in the cytoplasm, and its role in immune cells has been recognized in recent years. However, the role of FABP5 in macrophage inflammation and its underlying mechanisms were not fully addressed. In our study, the acute liver injury and sepsis mouse models were induced by i.p. injection of LPS and cecal contents, respectively. Oleic acid (0.6 g/kg) was injected four times by intragastric administration every week, and this lasted for 1 wk before the LPS or cecal content challenge. We found that myeloid-specific deletion of FABP5 mitigated LPS-induced acute liver injury with reduced mortality of mice, histological liver damage, alanine aminotransferase, and proinflammatory factor levels. Metabolic analysis showed that FABP5 deletion increased the intracellular unsaturated fatty acids, especially oleic acid, in LPS-induced macrophages. The addition of oleic acid also decreased LPS-stimulated macrophage inflammation in vitro and reduced acute liver injury in LPS-induced or cecal content-induced sepsis mice. RNA-sequencing and molecular mechanism studies showed that FABP5 deletion or oleic acid supplementation increased the AMP/ATP ratio and AMP-activated protein kinase (AMPK) activation and inhibited the NF-κB pathway during the inflammatory response to LPS stimulation of macrophages. Inhibiting AMPK activation or expression by chemical or genetic approaches significantly rescued the decreased NF-κB signaling pathway and inflammatory response in LPS-treated FABP5-knockout macrophages. Our present study indicated that inhibiting FABP5 or supplementation of oleic acid might be used for the treatment of sepsis-caused acute liver injury.

LysM-positive neurons drive Tuberous Sclerosis Complex (TSC)-associated brain lesions

Mutations of Tsc1 or Tsc2 can lead to excessive activation of mTORC1 and cause Tuberous Sclerosis Complex (TSC), which is an autosomal dominant genetic disease prominently characterized by seizures, mental retardation and multiorgan hamartoma. In TSC, pathological changes in the central nervous system are the leading cause of death and disability. In decades, series of rodent models have been established by mutating Tsc1 or Tsc2 genes in diverse neural cell lineages to investigate the underlying cellular and molecular mechanisms, however, the cellular origin triggering neural pathological changes in TSC is undetermined. In this study, we generated a novel mouse model involving conditional deletion of Tsc1 in lysozyme 2 (Lyz2)-positive cells which replicated several features of brain lesions including epileptic seizures, megalencephaly, highly enlarged pS6-positive neurons and astrogliosis. In addition, we confirmed that bone marrow-derived myeloid cells including microglia with Tsc1 deficiency are not the decisive lineage in the cerebral pathologies in TSC. These histological assays in our murine model indicate an essential contribution of Lyz2-positive neurons to TSC progression. The Lyz2-positive neural population-specific onset of Tsc1 loss in murine postnatal brain might be the key to pathological phenotypes. Our findings thus provided evidences supporting new insights into the role of Lyz2-positive neurons in TSC events.

Tuberous Sclerosis Complex 1 Deficiency in Macrophages Promotes Unclassical Inflammatory Response to Lipopolysaccharide In Vitro and Dextran Sodium Sulfate-Induced Colitis in Mice

Human tuberous sclerosis (TSC) is mainly caused by genetic mutations of tuberous TSC1or TSC2. Recent studies found that TSC1 deficiency promoted classical M1 macrophage polarization. However, whether TSC1 regulates other inflammatory cytokine expression in lipopolysaccharidem (LPS)-stimulated macrophages is unknown. Herein, we studied the cytokine expression profile of wild-type (WT) and TSC1-deleted macrophages after LPS stimulation in vitro and the pathogenesis of dextran sodium sulfate (DSS)-induced colitis in mice with myeloid-specific TSC1 deletion (TSC1cKO mice). We found that TSC1-deficient macrophages exhibited the enhanced secretion of interleukin-17A (IL-17A), IL-17F, and interferon-gamma (IFN-γ) in response to LPS stimulation in vitro. This is in contrast to LPS-stimulated WT macrophages, which usually do not. Importantly, TSC1cKO mice exhibited exacerbated DSS-induced acute colitis with severer symptoms. MTOR deletion or rapamycin treatment significantly reversed the enhanced expressions of IL-17A, IL-17F, and IFN-γ in LPS-stimulated TSC1-deficient macrophages in vitro and rescued the enhanced DSS-induced colitis in TSC1cKO mice, indicating that TSC1 deficiency increased these cytokine productions in an mTOR-dependent manner. RNA-sequencing and molecular studies indicated that TSC1 deficiency enhanced the aerobic glycolysis process and the activities of mTOR-STAT3-RORγT pathway in LPS-stimulated macrophages. Inhibition of aerobic glycolysis, STAT3, or RORγT reversed IL-17 and IFN-γ expression in LPS-treated TSC1-deficient macrophages. Thus, TSC1 is essential for macrophages to shut down IL-17A, IL-17F, and IFN-γ expression during LPS stimulation by suppressing the aerobic glycolysis process and mTOR-STAT3, RORγT, and T-bet pathways. The present study uncovered the key role of TSC1 in shutting down IL-17A, IL-17F, and IFN-γ expressions in LPS-treated macrophages.

Liposome cocktail activator modulates hepatocytes and remodels the microenvironment to mitigate acute liver failure

Acute liver failure (ALF) is a mortal and critical hepatic disease, in which oxidative stress, inflammation storm and hepatocyte death are crucial in the pathogenesis. Hence, in contrast to the control of a single link, a combination therapy targeting multiple pathogenic links of the disease will be a favorable means to control the progression of the disease. In this study, we constructed dimethyl itaconate-loaded liposomes modified with dodecyl gallate as a cocktail activator to investigate its functional role in acetaminophen (APAP)-induced ALF. Our results demonstrated that the cocktail activator acted on hepatocytes and triggered cocktail efficacy, thereby simultaneously attenuating APAP-induced hepatocyte damage and remodeling the damage microenvironment. The cocktail activator could effectively scavenge reactive oxygen species, inhibit excessive inflammatory responses and reduce cell death in impaired hepatocytes for detoxification. More importantly, the cocktail activator could remodel the damage microenvironment, thus further promoting hepatocyte expansion and specifically switching macrophages from the M1 to M2 phenotype for a favorable liver regeneration of ALF. Furthermore, in APAP-induced ALF mouse model, the cocktail activator improved liver function, alleviated histopathological damage and increased survival rate. In summary, these findings indicate that the cocktail activator may provide a promising therapeutic approach for ALF treatment as a nanomedicine.

CCAAT/Enhancer-Binding Proteins in Fibrosis: Complex Roles Beyond Conventional Understanding

CCAAT/enhancer-binding proteins (C/EBPs) are a family of at least six identified transcription factors that contain a highly conserved basic leucine zipper domain and interact selectively with duplex DNA to regulate target gene expression. C/EBPs play important roles in various physiological processes, and their abnormal function can lead to various diseases. Recently, accumulating evidence has demonstrated that aberrant C/EBP expression or activity is closely associated with the onset and progression of fibrosis in several organs and tissues. During fibrosis, various C/EBPs can exert distinct functions in the same organ, while the same C/EBP can exert distinct functions in different organs. Modulating C/EBP expression or activity could regulate various molecular processes to alleviate fibrosis in multiple organs; therefore, novel C/EBPs-based therapeutic methods for treating fibrosis have attracted considerable attention. In this review, we will explore the features of C/EBPs and their critical functions in fibrosis in order to highlight new avenues for the development of novel therapies targeting C/EBPs.

Metformin-dependent variation of microglia phenotype dictates pericytes maturation under oxygen-glucose deprivation

Blood-brain barrier resident cells are in the frontline of vascular diseases. To maintain brain tissue homeostasis, a series of cells are integrated regularly to form the neurovascular unit. It is thought that microglia can switch between M1/M2 phenotypes after the initiation of different pathologies. The existence of transition between maturity and stemness features in pericytes could maintain blood-brain barrier functionality against different pathologies. In the current study, the effect of metformin on the balance of the M1/M2 microglial phenotype under oxygen-glucose deprivation conditions and the impact of microglial phenotype changes on pericyte maturation have been explored. Both microglia and pericytes were isolated from the rat brain. Data showed that microglia treatment with metformin under glucose- and oxygen-free conditions suppressed microglia shifting into the M2 phenotype (CD206+ cells) compared to the control (p < .01) and metformin-treated groups (p < .05). Incubation of pericytes with microglia-conditioned media pretreated with metformin under glucose- and oxygen-free conditions or normal conditions increased pericyte maturity. These changes coincided with the reduction of the Sox2/NG2 ratio compared to the control pericytes (p < .05). Data revealed the close microglial-pericytic interplay under the ischemic and hypoxic conditions and the importance of microglial phenotype acquisition on pericyte maturation.

Engineered Bacterial Outer Membrane Vesicles as Controllable Two-Way Adaptors to Activate Macrophage Phagocytosis for Improved Tumor Immunotherapy

The most immune cells infiltrating tumor microenvironment (TME), tumor-associated macrophages (TAMs) closely resemble immunosuppressive M2-polarized macrophages. Moreover, tumor cells exhibit high expression of CD47 "don't eat me" signal, which obstructs macrophage phagocytosis. The precise and efficient activation of TAMs is a promising approach to tumor immunotherapy; however, re-education of macrophages remains a challenge. Bacteria-derived outer membrane vesicles (OMVs) are highly immunogenic nanovesicles that can robustly stimulate macrophages. Here, an OMV-based controllable two-way adaptor is reported, in which a CD47 nanobody (CD47nb) is fused onto OMV surface (OMV-CD47nb), with the outer surface coated with a polyethylene glycol (PEG) layer containing diselenide bonds (PEG/Se) to form PEG/Se@OMV-CD47nb. The PEG/Se layer modification not only mitigates the immunogenicity of OMV-CD47nb, thereby remarkedly increasing the dose that can be administered safely through intravenous injection, but also equips the formulation with radiation-triggered controlled release of OMV-CD47nb. Application of radiation to tumors in mice injected with the nanoformulation results in remodeling of TME. As two-way adaptors, OMV-CD47nb activates TAM phagocytosis of tumor cells via multiple pathways, including induction of M1 polarization and blockade of "don't eat me" signal. Moreover, this activation of TAMs results in the stimulation of T cell-mediated antitumor immunity through effective antigen presentation.

Research progress of neoantigens in gynecologic cancers

The incidence and mortality of gynecological cancers have increased over the past decade. In the absence of effective treatment strategies, many advanced patients develop resistance to conventional therapies and have poor prognosis. Neoantigens have emerged as a novel tumor-specific antigen (TSA) that arises from genomic mutations in tumor cells. With higher immunogenicity than tumor-associated antigens (TAA), they have no risk of developing autoimmune response, leading them an attractive candidate for tumor therapeutic vaccines. With the development of next-generation sequencing (NGS) technology, the identification of neoantigens has been gradually improved, and the scope of application of neoantigen vaccines has continued to expand. Combined with other therapies such as immune-checkpoint inhibitors (ICIs) or adoptive cell therapy (ACT), the application of neoantigen in gynecological cancers has extended to clinical practice. Here, we reviewed the preclinical and clinical studies of neoantigens in gynecological cancers.

Integrated genomic, transcriptomic, and epigenetic analyses identify a leukotriene synthesis-related M2 macrophage gene signature that predicts prognosis and treatment vulnerability in gliomas

The pathological implications of tumor-associated macrophages in the glioma microenvironment have been highlighted, while there lacks a gene signature to characterize the functional status and clinical implications of these cells. Comprehensive bioinformatics approaches were employed to develop an M2 macrophage-associated gene signature at bulk-tumor and single-cell levels and explore immunological and metabolic features. Consequently, the PI3K pathway and fatty acid metabolism were correlated with the M2 fraction. Further distilling the pathway members resulted in a leukotriene synthesis-related gene signature (Macro index), including PIK3R5, PIK3R6, ALOX5, ALOX5AP, and ALOX15B, that was primarily expressed by monocytes/macrophages. Increased Macro index predicted IL13-induced macrophages, and was associated with T-cell dysfunction at both transcriptional and epigenetic levels and predicted an unfavorable outcome. Besides, the Macro index was proportional with PAI1 at the protein level, with high levels of the latter suggesting a decreased progression-free interval of glioblastoma. Notably, the monocytes/macrophages in the glioma environment contribute to the expression of immune checkpoints and the Macro index predicts glioma responsiveness to anti-PD1 treatment. Together, our study proposed a leukotriene synthesis-related M2 macrophage gene signature, which may provide insights into the role of these cells in the glioma microenvironment and facilitate individually tailored therapeutic strategies for the disease.

TcpC Inhibits M1 but Promotes M2 Macrophage Polarization via Regulation of the MAPK/NF-κB and Akt/STAT6 Pathways in Urinary Tract Infection

Abstract

TcpC is a multifunctional virulence factor of Uropathogenic Escherichia coli (UPEC). Macrophages can differentiate into two different subsets M1 and M2 that play distinct roles in anti-infection immunity. Here, we investigate the influence of TcpC on M1/M2 polarization and the potential mechanisms. Our data showed that M1 markers CD86 and iNOS were significantly inhibited, while the M2 markers CD163, CD206 and Arg-1 were enhanced in macrophages in kidneys from the TcpC-secreting wild-type CFT073 (CFT073^wt)-infected pyelonephritis mouse model, compared with those in macrophages in kidneys from TcpC knockout CFT073 mutant (CFT073^Δtcpc)-infected mice. CFT073^wt or recombinant TcpC (rTcpC) treatment inhibits LPS + IFN-γ-induced CD80, CD86, TNF-α and iNOS expression, but promotes IL-4-induced CD163, CD206, Arg-1 and IL-10 expression in both human and mouse macrophage cell lines THP-1 and J774A.1. Moreover, rTcpC significantly attenuated LPS + IFN-γ-induced phosphorylation of p38, ERK, p50 and p65 but enhanced IL-4-induced phosphorylation of Akt and STAT6. These data suggest that TcpC inhibits M1 but promotes M2 macrophage polarization by down-regulation of p38, ERK/NF-κB and up-regulation of the Akt/STAT6 signaling pathway, respectively. Our findings not only illuminate the regulatory effects of TcpC on macrophage M1/M2 polarization and its related signaling pathways, but also provide a novel mechanism underlying TcpC-mediated immune evasion of macrophage-mediated innate immunity.

Simple Summary

We investigate the influence of TcpC, a multifunctional virulence factor of Uropathogenic Escherichia coli (UPEC), on M1/M2 macrophage polarization and the potential mechanisms. TcpC-secreting wild-type CFT073 (CFT073^wt) or recombinant TcpC (rTcpC) treatment inhibits LPS + IFN-γ-induced CD80, CD86, TNF-α and iNOS expression, but promotes IL-4-induced CD163, CD206, Arg-1 and IL-10 expression in CFT073^wt-infected pyelonephritis model mouse and both human and mouse macrophage cell lines THP-1 and J774A.1, respectively. Moreover, rTcpC significantly attenuated LPS + IFN-γ-induced phosphorylation of p38, ERK, p50 and p65 but en-hanced IL-4-induced phosphorylation of Akt and STAT6. These data suggest that TcpC inhibits M1 but promotes M2 macrophage polarization by down-regulation of p38, ERK/NF-κB and up-regulation of the Akt/STAT6 signaling pathway, respectively. Our findings not only illuminate the regulatory effects of TcpC on macrophage M1/M2 polarization and its related signaling pathways, but also provide a novel mechanism underlying TcpC-mediated immune evasion of macrophage-mediated innate immunity.

Modulation of mTOR Signaling in Cardiovascular Disease to Target Acute and Chronic Inflammation

Inflammation is a key component in the pathogenesis of cardiovascular diseases causing a significant burden of morbidity and mortality worldwide. Recent research shows that mammalian target of rapamycin (mTOR) signaling plays an important role in the general and inflammation-driven mechanisms that underpin cardiovascular disease. mTOR kinase acts prominently in signaling pathways that govern essential cellular activities including growth, proliferation, motility, energy consumption, and survival. Since the development of drugs targeting mTOR, there is proven efficacy in terms of survival benefit in cancer and allograft rejection. This review presents current information and concepts of mTOR activity in myocardial infarction and atherosclerosis, two important instances of cardiovascular illness involving acute and chronic inflammation. In experimental models, inhibition of mTOR signaling reduces myocardial infarct size, enhances functional remodeling, and lowers the overall burden of atheroma. Aside from the well-known effects of mTOR inhibition, which are suppression of growth and general metabolic activity, mTOR also impacts on specific leukocyte subpopulations and inflammatory processes. Inflammatory cell abundance is decreased due to lower migratory capacity, decreased production of chemoattractants and cytokines, and attenuated proliferation. In contrast to the generally suppressed growth signals, anti-inflammatory cell types such as regulatory T cells and reparative macrophages are enriched and activated, promoting resolution of inflammation and tissue regeneration. Nonetheless, given its involvement in the control of major cellular pathways and the maintenance of a functional immune response, modification of this system necessitates a balanced and time-limited approach. Overall, this review will focus on the advancements, prospects, and limits of regulating mTOR signaling in cardiovascular disease.

Metabolic Reprogramming Induces Macrophage Polarization in the Tumor Microenvironment

Macrophages are one of the most important cells in the innate immune system, they are converted into two distinct subtypes with completely different molecular phenotypes and functional features under different stimuli of the microenvironment: M1 macrophages induced by IFN-γ/lipopolysaccharides(LPS) and M2 macrophages induced by IL-4/IL-10/IL-13. Tumor-associated macrophages (TAMs) differentiate from macrophages through various factors in the tumor microenvironment (TME). TAMs have the phenotype and function of M2 macrophages and are capable of secreting multiple cytokines to promote tumor progression. Both tumor cells and macrophages can meet the energy needs for rapid cell growth and proliferation through metabolic reprogramming, so a comprehensive understanding of pro-tumor and antitumor metabolic switches in TAM is essential to understanding immune escape mechanisms. This paper focuses on the functions of relevant signaling pathways and cytokines during macrophage polarization and metabolic reprogramming, and briefly discusses the effects of different microenvironments and macrophage pathogenicity, in addition to describing the research progress of inhibitory drugs for certain metabolic and polarized signaling pathways.

Sinomenine inhibits macrophage M1 polarization by downregulating α7nAChR via a feedback pathway of α7nAChR/ERK/Egr-1

BACKGROUND

Sinomenine (SIN) is an anti-inflammatory drug that has been used for decades in China to treat arthritis. In a previous study, SIN acted on α7 nicotinic acetylcholine receptor (α7nAChR) to inhibit inflammatory responses in macrophages, which indicates a new anti-inflammatory mechanism of SIN. However, the level of α7nAChR was increased in the inflammatory responses and was downregulated by SIN in vitro, so the underlying mechanisms of SIN acting on α7nAChR remain unclear.

PURPOSE

To analyze the role of α7nAChR in inflammation and the effect and mechanism of SIN regulation of α7nAChR.

METHODS

The effects of SIN on α7nAChR in endotoxemic mice and LPS-stimulated macrophages were observed. Nicotine (Nic) was used as a positive control, and berberine (Ber) was used as a negative control targeting α7nAChR. The antagonists of α7nAChR, α-bungarotoxin (BTX) and mecamylamine (Me), were used to block α7nAChR. In RAW264.7 macrophage cells in vitro, α7nAChR short hairpin RNA (shRNA) was used to knock down α7nAChR. Macrophage polarization was analyzed by the detection of TNF-α, IL-6, iNOS, IL-10, Arg-1, and Fizz1. U0126 was used to block ERK phosphorylation. The cytokines α7nAChR, ERK1/2, p-ERK1/2 and Egr-1 were detected.

RESULTS

SIN decreased the levels of TNF-α, IL-6 and the expression of α7nAChR increased by LPS in endotoxemic mice. The above effects of SIN were attenuated by BTX. In the α7nAChR shRNA transfected RAW264.7 cells, compared with the control, α7nAChR was knocked down, and M1 phenotype markers (including TNF-α, IL-6, and iNOS) were significantly downregulated, whereas M2 phenotype markers (including IL-10, Arg-1, and Fizz1) were significantly upregulated when stimulated by LPS. SIN inhibited the expression of p-ERK1/2 and the transcription factor Egr-1 induced by LPS in RAW264.7 cells, and the above effects of SIN were attenuated by BTX. The expression of α7nAChR was suppressed by U0126, which lessened the expression of p-ERK1/2 and Egr-1.

CONCLUSIONS

SIN acts on α7nAChR to inhibit inflammatory responses and downregulates high expression of α7nAChR in vivo and in vitro. The increase of α7nAChR expression is correlated with inflammatory responses and participates in macrophage M1 polarization. SIN downregulates α7nAChR via a feedback pathway of α7nAChR/ERK/Egr-1, which contributes to inhibiting macrophage M1 polarization and inflammatory responses.