Tumor associated macrophages and 'NO'

Citrulline facilitates the glycolysis, proliferation, and metastasis of lung cancer cells by regulating RAB3C

Lung cancer (LC) is one of the major malignant diseases threatening human health. The study aimed to identify the effect of citrulline on the malignant phenotype of LC cells and to further disclose the potential molecular mechanism of citrulline in regulating the development of LC, providing a novel molecular biological basis for the clinical treatment of LC. The effects of citrulline on the viability, proliferation, migration, and invasion of LC cells (A549, H1299) were validated by CCK-8, colony formation, EdU, and transwell assays. The cell glycolysis was assessed via determining the glucose uptake, lactate production, ATP levels, extracellular acidification rate (ECAR), and oxygen consumption rate (OCR). RNA-seq and molecular docking were performed to screen for citrulline-binding target proteins. Western blotting experiments were conducted to examine the expression of related signaling pathway molecules. In addition, the impacts of citrulline on LC growth in vivo were investigated by constructing mouse models. Citrulline augmented the viability of LC cells in a concentration and time-dependent manner. The proliferation, migration, invasion, glycolysis, and EMT processes of LC cells were substantially enhanced after citrulline treatment. Bioinformatics analysis indicated that citrulline could bind to RAB3C protein. Western blotting results indicated that citrulline activated the IL-6/STAT3 pathway by binding to RAB3C. In addition, animal experiments disclosed that citrulline promoted tumor growth in mice. Citrulline accelerated the glycolysis and activated the IL6/STAT3 pathway through the RAB3C protein, consequently facilitating the development of LC.

Understanding Macrophage-Tumor Interactions: Insights from Single-Cell Behavior Monitoring in a Sessile Microdroplet System

Interaction between tumor-associated macrophages and tumor cells is crucial for tumor development, metastasis, and the related immune process. However, the macrophages are highly heterogeneous spanning from anti-tumorigenic to pro-tumorigenic, which needs to be understood at the single-cell level. Herein, a sessile microdroplet system designed for monitoring cellular behavior and analyzing intercellular interaction, demonstrated with macrophage-tumor cell pairs is presented. An automatic procedure based on the inkjet printing method is utilized for the precise pairing and co-encapsulation of heterotypic cells within picoliter droplets. The sessile nature of microdroplets ensures controlled fusion and provides stable environments conducive to adherent cell culture. The nitric oxide generation and morphological changes over incubation are explored to reveal the complicated interactions from a single-cell perspective. The immune response of macrophages under distinct cellular microenvironments is recorded. The results demonstrate that the tumor microenvironment displays a modulating role in polarizing macrophages from anti-tumorigenic into pro-tumorigenic phenotype. The approach provides a versatile and compatible platform to investigate intercellular interaction at the single-cell level, showing promising potential for advancing single-cell behavior studies.

New hope for tumor immunotherapy: the macrophage-related "do not eat me" signaling pathway

The "do not eat me" signaling pathway is extremely active in tumor cells, providing a means for these cells to elude macrophage phagocytosis and escape immune surveillance. Representative markers of this pathway, such as CD47 and CD24, are highly expressed in numerous tumors. The interaction of SIRPα with CD47 reduces the accumulation of non-myosin ⅡA on the cell membrane. The combination of CD24 and Siglec10 ultimately leads to the recruitment of SHP-1 or SHP-2 to reduce signal transduction. Both of them weaken the ability of macrophages to engulf tumor cells. Blocking the mutual recognition between CD47-SIRPα or CD24-Siglec10 using large molecular proteins or small molecular drugs represents a promising avenue for tumor immunotherapy. Doing so can inhibit signal transduction and enhance macrophage clearance rates of cancer cells. In this paper, we summarize the characteristics of the drugs that affect the "do not eat me" signaling pathway via classical large molecular proteins and small molecule drugs, which target the CD47-SIRPα and CD24-Siglec10 signaling pathways, which target the CD47-SIRPα and CD24-Siglec10 signaling pathways. We expect it will offer insight into the development of new drugs centered on blocking the "do not eat me" signaling pathway.

Dynamic polarization of tumor-associated macrophages and their interaction with intratumoral T cells in an inflamed tumor microenvironment: from mechanistic insights to therapeutic opportunities

Immunotherapy has brought a paradigm shift in the treatment of tumors in recent decades. However, a significant proportion of patients remain unresponsive, largely due to the immunosuppressive tumor microenvironment (TME). Tumor-associated macrophages (TAMs) play crucial roles in shaping the TME by exhibiting dual identities as both mediators and responders of inflammation. TAMs closely interact with intratumoral T cells, regulating their infiltration, activation, expansion, effector function, and exhaustion through multiple secretory and surface factors. Nevertheless, the heterogeneous and plastic nature of TAMs renders the targeting of any of these factors alone inadequate and poses significant challenges for mechanistic studies and clinical translation of corresponding therapies. In this review, we present a comprehensive summary of the mechanisms by which TAMs dynamically polarize to influence intratumoral T cells, with a focus on their interaction with other TME cells and metabolic competition. For each mechanism, we also discuss relevant therapeutic opportunities, including non-specific and targeted approaches in combination with checkpoint inhibitors and cellular therapies. Our ultimate goal is to develop macrophage-centered therapies that can fine-tune tumor inflammation and empower immunotherapy.

The role of macrophages in the tumor microenvironment and tumor metabolism

The complexity and plasticity of the tumor microenvironment (TME) make it difficult to fully understand the intratumoral regulation of different cell types and their activities. Macrophages play a crucial role in the signaling dynamics of the TME. Among the different subtypes of macrophages, tumor-associated macrophages (TAMs) are often associated with poor prognosis, although some subtypes of TAMs can at the same time improve treatment responsiveness and lead to favorable clinical outcomes. TAMs are key regulators of cancer cell proliferation, metastasis, angiogenesis, extracellular matrix remodeling, tumor metabolism, and importantly immunosuppression in the TME by modulating various chemokines, cytokines, and growth factors. TAMs have been identified as a key contributor to resistance to chemotherapy and cancer immunotherapy. In this review article, we aim to discuss the mechanisms by which TAMs regulate innate and adaptive immune signaling in the TME and summarize recent preclinical research on the development of therapeutics targeting TAMs and tumor metabolism.

Genetic Programming by Nitric Oxide-Sensing Gene Switch System in Tumor-Targeting Bacteria

Recent progress in synthetic biology has enabled bacteria to respond to specific disease signals to perform diagnostic and/or therapeutic tasks. Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) colonization of tumors results in increases in nitric oxide (NO) levels, suggesting that NO may act as a candidate inducer of tumor-specific gene expression. The present study describes a NO-sensing gene switch system for triggering tumor-specific gene expression in an attenuated strain of S. Typhimurium. The genetic circuit was designed to sense NO via NorR, thus initiating the expression of FimE DNA recombinase. This was found to lead sequentially to the unidirectional inversion of a promoter region (fimS), which induced the expression of target genes. Target gene expression in bacteria transformed with the NO-sensing switch system was triggered in the presence of a chemical source of NO, diethylenetriamine/nitric oxide (DETA/NO) in vitro. In vivo results revealed that the gene expression is tumor-targeted, and specific to NO generated by inducible nitric oxide synthase (iNOS) after S. Typhimurium colonization. These results showed that NO was a promising inducer to finely tune the expression of target genes carried by tumor-targeting bacteria.

Immunometabolic attributes and mitochondria-associated signaling of Tumor-Associated Macrophages in tumor microenvironment modulate cancer progression

Macrophages are specialized immune cells, which have the capacity to phagocytize and destroy the target cells, including tumor cells. Some macrophages, however on their way to devour the cancer cells undergo a change due to a complex set of signaling pathways. They are induced to change into a polarized state known as M2. The M2 macrophages help in metastasis, tumor suppression, and angiogenesis. The macrophage which gets associated with this TME, are referred to as tumor-associated macrophages (TAMs). TAMS undergo a metabolic reprogramming toward oxidative metabolism for bioenergetic purposes (OXPHOS), fatty acid oxidation (FAO), decreased glycolysis, decreased metabolism via the PPP, and upregulation of arginase 1 (ARG1) which triggers immunosuppressive pro-tumor signaling in the tumor microenvironment (TME) in which mitochondria plays an instrumental role. Reports have suggested that a complex series of interactions and exchange of materials, such as cytokines, metabolic intermediates and sometimes even transfer of mitochondria take place between TAMS and other TME components most importantly cancer cells that reprogram their metabolism to encourage cell growth, division, epithelial to mesenchymal transition, that ultimately play an important role in tumor progression. This review will try to focus on the crosstalk between the TAMs with several other components of TME, what instrumental role mitochondria play in that and also try to explore some of the therapeutic options available in cancer patients.

Repurposing nitric oxide donating drugs in cancer therapy through immune modulation

BACKGROUND

Nitric oxide-releasing drugs are used for cardiovascular diseases; however, their effects on the tumor immune microenvironment are less clear. Therefore, this study explored the impact of nitric oxide donors on tumor progression in immune-competent mice.

METHODS

The effects of three different nitric oxide-releasing compounds (SNAP, SNP, and ISMN) on tumor growth were studied in tumor-bearing mouse models. Three mouse tumor models were used: B16F1 melanoma and LL2 lung carcinoma in C57BL/6 mice, CT26 colon cancer in BALB/c mice, and LL2 lung carcinoma in NOD/SCID mice. After nitric oxide treatment, splenic cytokines and lymphocytes were analyzed by cytokine array and flow cytometry, and tumor-infiltrating lymphocytes in the TME were analyzed using flow cytometry and single-cell RNA sequencing.

RESULTS

Low doses of three exogenous nitric oxide donors inhibited tumor growth in two immunocompetent mouse models but not in NOD/SCID immunodeficient mice. Low-dose nitric oxide donors increase the levels of splenic cytokines IFN-γ and TNF-α but decrease the levels of cytokines IL-6 and IL-10, suggesting an alteration in Th2 cells. Nitric oxide donors increased the number of CD8⁺ T cells with activation gene signatures, as indicated by single-cell RNA sequencing. Flow cytometry analysis confirmed an increase in infiltrating CD8⁺ T cells and dendritic cells. The antitumor effect of nitric oxide donors was abolished by depletion of CD8⁺ T cells, indicating the requirement for CD8⁺ T cells. Tumor inhibition correlated with a decrease in a subtype of protumor macrophages and an increase in a subset of Arg1-positive macrophages expressing antitumor gene signatures. The increase in this subset of macrophages was confirmed by flow cytometry analysis. Finally, the combination of low-dose nitric oxide donor and cisplatin induced an additive cancer therapeutic effect in two immunocompetent animal models. The enhanced therapeutic effect was accompanied by an increase in the cells expressing the gene signature of NK cell.

CONCLUSIONS

Low concentrations of exogenous nitric oxide donors inhibit tumor growth in vivo by regulating T cells and macrophages. CD8⁺ T cells are essential for antitumor effects. In addition, low-dose nitric oxide donors may be combined with chemotherapeutic drugs in cancer therapy in the future.

The markers to delineate different phenotypes of macrophages related to metabolic disorders

Macrophages have a wide variety of roles in physiological and pathological conditions, making them promising diagnostic and therapeutic targets in diseases, especially metabolic disorders, which have attracted considerable attention in recent years. Owing to their heterogeneity and polarization, the phenotypes and functions of macrophages related to metabolic disorders are diverse and complicated. In the past three decades, the rapid progress of macrophage research has benefited from the emergence of specific molecular markers to delineate different phenotypes of macrophages and elucidate their role in metabolic disorders. In this review, we analyze the functions and applications of commonly used and novel markers of macrophages related to metabolic disorders, facilitating the better use of these macrophage markers in metabolic disorder research.

EGCG Prevents the Transcriptional Reprogramming of an Inflammatory and Immune-Suppressive Molecular Signature in Macrophage-like Differentiated Human HL60 Promyelocytic Leukemia Cells

Simple Summary

Scientists are increasingly harnessing the power of the immune system to prevent cancer. While macrophages are a major component of the tumor microenvironment where they orchestrate various aspects of immunity, dysregulated immune and inflammatory responses will play a key role in cancer initiation and progression. Depending on their activation status, macrophages can have a dual impact on tumorigenesis by either antagonising cytotoxic immune cells or enhancing antitumor responses. Increased infiltration of tumor-associated macrophages has long been associated with poor patient prognosis in most solid cancers, highlighting their value as potential diagnostic and prognostic biomarkers in cancer. A variety of macrophage-centered approaches to cancer therapy have been investigated, including strategies to prevent tumor-promoting activities. In this study, we highlight the chemopreventive properties of EGCG derived from green tea that underpin its ability to re-program macrophage molecular signature and function.

Abstract

Background: The promyelocytic leukemia cell differentiation process enables recapitulation of the polarized M1 or M2 macrophage-like phenotype with inflammatory and immune-suppressive properties. While evidence supports the anti-inflammatory effect of dietary-derived epigallocatechin-3-gallate (EGCG), its impact on the onset of immune phenotype molecular signature remains unclear. Methods: Human HL60 promyelocytic cells grown in suspension were differentiated into CD11b^High/CD14^Low adherent macrophages with phorbol 12-myristate 13-acetate (PMA). Gelatin zymography was used to assess the levels of matrix metalloproteinase (MMP)-9, and total RNA was isolated for RNAseq and RT-qPCR assessment of differentially expressed gene levels involved in inflammation and immunity. Protein lysates were used to assess the phosphorylation status of signaling intermediates involved in macrophage-like cell differentiation. Results: Cell adhesion and induction of MMP-9 were indicative of HL60 cell differentiation into a macrophage-like phenotype. The extracellular signal-regulated kinase (ERK), glycogen synthase kinase (GSK)-3, p90 ribosomal S6 kinases (RSK), and cAMP-response-element-binding protein (CREB) were all phosphorylated, and EGCG reduced such phosphorylation status. Increases in inflammation and immunity genes included, among others, CCL22, CSF1, CSF2, IL1B, and TNF, which inductions were prevented by EGCG. This was corroborated by unbiased transcriptomic analysis which further highlighted the capacity of EGCG to downregulate the hematopoietic stem cell regulator CBFA2T3. Conclusion: EGCG inhibits inflammatory signaling crosstalk and prevents the onset of an immune phenotype in macrophage-like differentiated cells.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

d-ribose- l-cysteine abrogates testicular maladaptive responses induced by polychlorinated bisphenol intoxication in rats via activation of the mTOR signaling pathway mediating inhibition of apoptosis, inflammation, and oxidonitrergic flux

Male reproductive maladaptive responses are becoming a global health concern and also a social issue. Polychlorinated biphenyls (PCBs) are a member of halogenated aromatic environmental pollutants with diverse environmental matrices. This study was conducted to explore the mechanisms of PCBs-induced testicular maladaptive responses and the potential reversal effects of d-ribose- l-cysteine (DRLC) on testicular injury induced by administration of PCBs (2 mg/kg) for 30 days. DRLC (50 mg/kg) was administered orally for 15 days starting from Days 16 to 30 after the initial 15 days of treatment with PCB. All assays were carried out using established protocols. Administration of DRLC at 50 mg/kg after treatment with PCBs enhances body and testicular weights, gonadotropins (luteinizing hormone and follicle-stimulating hormone), testosterone and poor sperm quality. DRLC also reduced testicular injury score, improved spermatogenesis scoring, reduced oxidative stress biomarkers (malondialdehyde), as well as restored the reduced activities of antioxidant enzymes (glutathione peroxidase, superoxide dismutase, and catalase) and decreases pro-inflammatory response (tumor necrosis factor-alpha and NO). More so, DRLC treatment abrogates testicular DNA fragmentation and downregulated p53 and caspase 3 activities and upregulated the concentration of autophagy-related protein (mammalian target of rapamycin [mTOR] and Atg7). DRLC abates testicular deficit induced by PCBs intoxicated rats via activation of the mTOR signaling pathway mediating inhibition of apoptosis, Inflammation and oxidative flux.

Blockading a new NSCLC immunosuppressive target by pluripotent autologous tumor vaccines magnifies sequential immunotherapy

The presence of multiple immunosuppressive targets and insufficient activation and infiltration of cytotoxic T lymphocytes (CTLs) allow tumor cells to escape immune surveillance and disable anti-PD-1/PD-L1 immunotherapy. Nanobiotechnology-engineered autologous tumor vaccines (ATVs) that were camouflaged by tumor cell membrane (TCM) were designed to activate and facilitate CTLs infiltration for killing the unprotected lung tumor cells, consequently realizing the sequential immunotherapy. PDE5 was firstly screened out as a new immunosuppressive target of lung cancer in clinical practice. Immediately afterwards, phosphodiesterase-5 (PDE5) and programmed cell death 1 ligand 1 (PD-L1) dual-target co-inhibition was proposed to unfreeze the immunosuppressive microenvironment of NSCLC. Systematic studies validated that this ATVs-unlocked sequential immunotherapy after co-encapsulating PDE5 inhibitor and NO donor (i.e., l-arginine) exerted robust anti-tumor effects through increasing inducible nitric oxide synthase (iNOS) expression, blockading PDE5 pathway and activating systematic immune responses, which synergistically eradicated local and abscopal lung cancers in either orthotopic or subcutaneous models. The pluripotent ATVs that enable PDE5 inhibition and sequential immunotherapy provide a new avenue to mitigate immunosuppressive microenvironment and magnify anti-PD-1/PD-L1 immunotherapy.

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A clinically-screened NSCLC immunosuppressive target (PDE5) is experimentally validated available for designing new drugs.

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Pluripotent ATVs unlock sequential immunotherapy via PDE5&PD-L1 co-inhibition and TCM antigens-arised immune activation.

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NO donor loaded in ATVs augmented PDE5i efficacy and magnified sequential immunotherapy along with TCM-enabled tumor tropism.

Notch/NICD/RBP-J signaling axis regulates M1 polarization of macrophages mediated by advanced glycation end products

Advanced glycation end products (AGEs) aggregation and macrophages polarization are identified as the main factors contributing to bone diseases caused by aging or diabetes, such as senile or diabetic osteoporosis. Here, we aimed to elucidate the involvement and potential mechanism of AGEs in macrophages polarization and osteoclastogenesis. Firstly, AGEs-treated RAW264.7 macrophages were observed to up-regulate the release of nitric oxide (NO), the expression of M1-associated genes and the surface antigen marker CD86. The detection of osteoclast-related markers and TRAP staining revealed that the osteoclastogenic ability of M1 macrophages was markedly enhanced by AGEs. Further, AGEs were found to effectively activate the transduction of Notch signaling pathway and promote the nuclear translocation of NICD1. In addition, with the signals transduction of Notch pathway blocked by γ-secretase inhibitor DAPT and siRNA targeting silencing RBP-J, AGEs-induced M1 polarization was significantly mitigated. Collectively, we defined a critical role for AGEs in inducing M1 polarization and osteoclastogenesis of macrophages, and further identified Notch/NICD/RBP-J signaling axis as an essential mechanism regulating AGEs-mediated M1 polarization.

Angiotensin-(1-7) improves diabetes mellitus-induced erectile dysfunction in rats by regulating nitric oxide synthase levels

This study explores the role of inducible nitric oxide synthase (iNOS) in the pathogenesis of diabetes mellitus-induced erectile dysfunction (DMED) and the effect of angiotensin 1-7 (Ang- [1-7]) on NOS levels. A type 2 diabetes mellitus (DM) rat model was established. Erectile function was assessed by measuring intracavernous pressure and mean arterial pressure after electrical stimulation. The expression of iNOS, endothelial NOS (eNOS), eNOS phosphorylated at Ser 1177 (p-eNOS [Ser 1177]), and AKT/p-AKT in corpus cavernosum smooth muscle cells (CCSMCs) was measured by Western blotting and immunofluorescence. The plasma levels of NO, SOD, malondialdehyde, and peroxynitrite were calculated. Intracellular calcium content was determined by flow cytometry. DMED rats exhibited decreased erectile function and severe oxidative stress. Ang-(1-7) treatment improved erectile response and suppressed oxidative stress by upregulating p-eNOS/eNOS and downregulating iNOS levels. Silencing iNOS in CCSMCs decreased oxidative stress and intracellular calcium levels induced by high glucose. In turn, iNOS overexpression increased oxidative stress and intracellular calcium level. Treatment with the MAS receptor antagonist A779 and the Akt antagonist LY294002 reversed the effects of Ang-(1-7) on iNOS. Ang-(1-7) improved DMED through the MAS/AKT signaling pathway.

Production of NOS2 and inflammatory cytokines is reduced by selected protein kinase inhibitors with partial repolarization of HL-60 derived and human blood macrophages

JAK/STAT pathway plays a well-known role in macrophage polarization, but other signaling routes may also be involved. The aim of this study was to identify new signaling pathways and repolarize macrophages by selected protein kinase inhibitors. HL-60 derived macrophages were chosen as model cells and human blood macrophages were used for comparison. M1 and M2 polarization of HL60 derived and human blood macrophages was promoted by LPS + IFNγ (LIF) and IL-4 treatments, respectively. In HL-60 derived macrophages, M1 polarization was mediated by Erk1/2 and p38 phosphorylation, while HSP27 phosphorylation was involved in M2 polarization. The inhibition of both MAPK and JAK/STAT pathways reduced the expression of NOS2, IP-10 and TNFα, IL-8 production was decreased by the inhibition of AMPK and PKD, the upstream kinase of HSP27. HSP27 phosphorylation was inhibited by NB 142, a PKD inhibitor. The expression of CD80 (M1 marker) was reduced by MAPK and JAK/STAT inhibitors, without increasing CD206 (M2 marker). On the other hand, CD206 was reduced by PKD and AMPK inhibitors, without increasing CD80 marker. Phagocytic capacity of HL-60 derived macrophages was higher in M1 macrophages and decreased by trametinib and a p38 inhibitor, while in human blood macrophages, where AT 9283, a JAK/STAT inhibitor also caused a significant decrease in M1 polarized macrophages, no difference was observed between M1 and M2 macrophages. Our results suggest that the repolarization of macrophages cannot be achieved by inhibiting their signaling pathways; nevertheless, the expression of certain polarization markers was decreased, therefore a "depolarization" could be observed both in M1 and M2 polarized cells. Selected protein kinase inhibitors of M1 polarization, decreasing NOS 2 and inflammatory cytokines may be potential candidates for therapeutical trials against inflammatory diseases.

Arginine and Arginases Modulate Metabolism, Tumor Microenvironment and Prostate Cancer Progression

Arginine availability and activation of arginine-related pathways at cancer sites have profound effects on the tumor microenvironment, far beyond their well-known role in the hepatic urea cycle. Arginine metabolism impacts not only malignant cells but also the surrounding immune cells behavior, modulating growth, survival, and immunosurveillance mechanisms, either through an arginase-mediated effect on polyamines and proline synthesis, or by the arginine/nitric oxide pathway in tumor cells, antitumor T-cells, myeloid-derived suppressor cells, and macrophages. This review presents evidence concerning the impact of arginine metabolism and arginase activity in the prostate cancer microenvironment, highlighting the recent advances in immunotherapy, which might be relevant for prostate cancer. Even though further research is required, arginine deprivation may represent a novel antimetabolite strategy for the treatment of arginine-dependent prostate cancer.

Decreased nitric oxide content mediated by asymmetrical dimethylarginine and protein l-arginine methyltransferase 3 in macrophages induces trophoblast apoptosis: a potential cause of recurrent miscarriage

STUDY QUESTION

Is the protein l-arginine methyltransferase 3 (PRMT3)/asymmetrical dimethylarginine (ADMA)/nitric oxide (NO) pathway involved in the development of recurrent miscarriage (RM), and what is the potential mechanism?

SUMMARY ANSWER

Elevated levels of PRMT3 and ADMA inhibit NO formation in the decidua, thereby impairing the functions of trophoblast cells at the maternal-foetal interface.

WHAT IS KNOWN ALREADY

Decreased NO bioavailability is associated with RM. ADMA, an endogenous inhibitor of nitric oxide synthase (NOS), is derived from the methylation of protein arginine residues by PRMTs and serves as a predictor of mortality in critical illness.

STUDY DESIGN, SIZE, DURATION

A total of 145 women with RM and 149 healthy women undergoing elective termination of an early normal pregnancy were enrolled. Ninety-six female CBA/J, 24 male DBA/2 and 24 male BALB/c mice were included. CBA/J × DBA/2 matings represent the abortion group, while CBA/J × BALB/c matings represent the normal control group. The CBA/J pregnant mice were then categorised into four groups: (i) normal + vehicle group (n = 28), (ii) abortion + vehicle group (n = 28), (iii) normal + SGC707 (a PRMT3 inhibitor) group (n = 20) and (iv) abortion + SGC707 group (n = 20). All injections were made intraperitoneally on Days 0.5, 3.5 and 6.5 of pregnancy. Decidual tissues were collected on Days 8.5, 9.5 and 10.5 of gestation. The embryo resorption rates were calculated on Day 9.5 and Day 10.5 of gestation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

NO concentration, ADMA content, NOS activity, expression levels of NOS and PRMTs in decidual tissues were determined using conventional assay kits or western blotting. PRMT3 expression was further analysed in decidual stromal cells, macrophages and natural killer cells. A co-culture system between decidual macrophages (DMs) and HTR-8/SVneo trophoblasts was constructed to study the roles of the PRMT3/ADMA/NO signalling pathway. Trophoblast apoptosis was analysed via Annexin V-fluorescein isothiocyanate/propidium iodide staining. CBA/J × DBA/2 mouse models were used to investigate the effects of SGC707 on embryo resorption rates.

MAIN RESULTS AND THE ROLE OF CHANCE

Our results show that NO concentration and NOS activity were decreased, but ADMA content and PRMT3 expression were increased in the decidua of RM patients. Moreover, compared with the normal control subjects, PRMT3 expression was significantly up-regulated in the macrophages but not in the natural killer cells or stromal cells of the decidua from RM patients. The inhibition of PRMT3 results in a significant decrease in ADMA accumulation and an increase in NO concentration in macrophages. When co-cultured with DMs, which were treated with SGC707 and ADMA, trophoblast apoptosis was suppressed and induced, respectively. In vivo experiments revealed that the administration of SGC707 reduced the embryo resorption rate of CBA/J × DBA/2 mice.

LIMITATIONS, REASONS FOR CAUTION

All sets of experiments were not performed with the same samples. The main reason is that each tissue needs to be reserved for clinical diagnosis and only a small piece of each tissue can be cut and collected for this study.

WIDER IMPLICATIONS OF THE FINDINGS

Our results indicate that the PRMT3/ADMA/NO pathway is a potential marker and target for the clinical diagnosis and therapy of RM.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Key Research and Development Program of China (2017YFC1001401), National Natural Science Foundation of China (81730039, 82071653, 81671460, 81971384 and 82171657) and Shanghai Municipal Medical and Health Discipline Construction Projects (2017ZZ02015). The authors have declared no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Macrophage Reprogramming and Cancer Therapeutics: Role of iNOS-Derived NO

Nitric oxide and its production by iNOS is an established mechanism critical to tumor promotion or suppression. Macrophages have important roles in immunity, development, and progression of cancer and have a controversial role in pro- and antitumoral effects. The tumor microenvironment consists of tumor-associated macrophages (TAM), among other cell types that influence the fate of the growing tumor. Depending on the microenvironment and various cues, macrophages polarize into a continuum represented by the M1-like pro-inflammatory phenotype or the anti-inflammatory M2-like phenotype; these two are predominant, while there are subsets and intermediates. Manipulating their plasticity through programming or reprogramming of M2-like to M1-like phenotypes presents the opportunity to maximize tumoricidal defenses. The dual role of iNOS-derived NO also influences TAM activity by repolarization to tumoricidal M1-type phenotype. Regulatory pathways and immunomodulation achieve this through miRNA that may inhibit the immunosuppressive tumor microenvironment. This review summarizes the classical physiology of macrophages and polarization, iNOS activities, and evidence towards TAM reprogramming with current information in glioblastoma and melanoma models, and the immunomodulatory and therapeutic options using iNOS or NO-dependent strategies.

Ferroptosis-Strengthened Metabolic and Inflammatory Regulation of Tumor-Associated Macrophages Provokes Potent Tumoricidal Activities

Modulation of tumor-associated macrophages (TAMs) holds promise for cancer treatment, mainly relying on M1 signaling activation and pro-inflammatory promotion. Nevertheless, the antitumor activity is often limited by the anti-inflammatory factors in the tumor microenvironment. Moreover, the metabolic function of TAMs is also critical to tumor progression. However, there are a few strategies that can simultaneously regulate both inflammatory and metabolic functions to achieve safe and potent antitumor activation of TAMs. Herein, we demonstrate that an iron-based metal organic framework nanoparticle and a ferroptosis-inducing agent synergistically induce mitochondrial alternation in TAMs, resulting in a radical metabolic switch from mitochondrial oxidative phosphorylation to glycolysis, which is resistant to anti-inflammatory stimuli challenge. The ferroptosis stress strengthened by the nanoformulation also drives multiple pro-inflammatory signaling pathways, enabling macrophage activation with potent tumoricidal activities. The ferroptosis-strengthened macrophage regulation strategy present in this study paves the way for TAM-centered antitumoral treatment to overcome the limitations of conventional methods.

Blocking the CCL5-CCR5 Axis Using Maraviroc Promotes M1 Polarization of Macrophages Cocultured with Irradiated Hepatoma Cells

Purpose

The C-C chemokine ligand 5 (CCL5)–C-C chemokine receptor (CCR5) axis facilitates tumor progression via multiple mechanisms. Herein, we elucidated the effect of a CCR5 antagonist (maraviroc [MVC]; blocking the CCL5–CCR5 axis) on the phenotype of macrophages cocultured with irradiated hepatoma cells. In addition, we investigated whether modulation of macrophage polarization can alter tumor cell sensitivity to radiation.

Materials and Methods

Quantitative reverse-transcription polymerase chain reaction, Western blotting, and enzyme-linked immunosorbent assays were applied to examine the levels of macrophage-associated markers. The mechanisms of macrophage polarization were explored by Western blotting in an in vitro model of coculture of human hepatoma cells with macrophages. The radiation sensitivity was examined in a clonogenic radiosensitivity assay. Tumor cell apoptosis was detected by Western blotting and flow cytometry. A mouse model of a subcutaneous tumor was also established.

Results

CCL5 skewed THP-1 M0 macrophages toward an M2-like phenotype. In coculture with hepatoma cells, macrophages manifested high levels of interleukin (IL) 10, IL-12, tumor necrosis factor α (TNF-α), transforming growth factor β1 (TGF-β1), arginase 1 (ARG1), and IL-1β. Tumor cell irradiation further upregulated these markers in macrophages. After incubation of macrophages with MVC for 24 h, levels of M1 cytokines significantly increased, whereas those of M2 phenotype factors ARG1, TGF-β1, and IL-10 decreased, accompanied by the activation of signal transducer and activator of transcription 3 (STAT3) and downregulation of suppressor of cytokine signaling 3 (SOCS3). The macrophage phenotype reverted to M2 states after treatment with a STAT3 inhibitor. The shift of macrophages toward the M1 phenotype enhanced the radiosensitivity and apoptosis of hepatoma cells. Mice receiving a combination of X-ray irradiation and MVC experienced a better antitumor effect than those receiving either MVC or irradiation alone did.

Conclusion

M2 polarization of macrophages induced by CCL5–CCR5 signaling can be inhibited using MVC via the STAT3–SOCS3 pathway. The shift of macrophages toward the M1 phenotype promotes the sensitivity of human hepatoma cells to X-ray irradiation.

Natural Compounds as Metabolic Modulators of the Tumor Microenvironment

The tumor microenvironment (TME) is a heterogenous assemblage of malignant and non-malignant cells, including infiltrating immune cells and other stromal cells, together with extracellular matrix and a variety of soluble factors. This complex and dynamic milieu strongly affects tumor differentiation, progression, immune evasion, and response to therapy, thus being an important therapeutic target. The phenotypic and functional features of the various cell types present in the TME are largely dependent on their ability to adopt different metabolic programs. Hence, modulating the metabolism of the cells in the TME, and their metabolic crosstalk, has emerged as a promising strategy in the context of anticancer therapies. Natural compounds offer an attractive tool in this respect as their multiple biological activities can potentially be harnessed to ‘(re)-educate’ TME cells towards antitumoral roles. The present review discusses how natural compounds shape the metabolism of stromal cells in the TME and how this may impact tumor development and progression.

The Regulatory Role of α-Ketoglutarate Metabolism in Macrophages

Macrophages are multifunctional immune cells whose functions depend on polarizable phenotypes and the microenvironment. Macrophages have two phenotypes, including the M1 proinflammatory phenotype and the M2 anti-inflammatory phenotype, which play important roles in many inflammatory responses and diseases. α-Ketoglutarate is a key metabolite of the TCA cycle and can regulate the phenotype of macrophage polarization to exert anti-inflammatory effects in many inflammation-related diseases. In this review, we primarily elucidate the metabolism, regulatory mechanism, and perspectives of α-ketoglutarate on macrophages. The regulation of macrophage polarization by α-ketoglutarate may provide a promising target for the prevention and therapy of inflammatory diseases and is beneficial to animal health.

Rutin pretreatment promotes microglial M1 to M2 phenotype polarization

Microglial cells are important resident innate immune components in the central nervous system that are often activated during neuroinflammation. Activated microglia can display one of two phenotypes, M1 or M2, which each play distinct roles in neuroinflammation. Rutin, a dietary flavonoid, exhibits protective effects against neuroinflammation. However, whether rutin is able to influence the M1/M2 polarization of microglia remains unclear. In this study, in vitro BV-2 cell models of neuroinflammation were established using 100 ng/mL lipopolysaccharide to investigate the effects of 1-hour rutin pretreatment on microglial polarization. The results revealed that rutin pretreatment reduced the expression of the proinflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6 and increased the secretion of interleukin-10. Rutin pretreatment also downregulated the expression of the M1 microglial markers CD86 and inducible nitric oxide synthase and upregulated the expression of the M2 microglial markers arginase 1 and CD206. Rutin pretreatment inhibited the expression of Toll-like receptor 4 and myeloid differentiation factor 88 and blocked the phosphorylation of I kappa B kinase and nuclear factor-kappa B. These results showed that rutin pretreatment may promote the phenotypic switch of microglia M1 to M2 by inhibiting the Toll-like receptor 4/nuclear factor-kappa B signaling pathway to alleviate lipopolysaccharide-induced neuroinflammation.

Nitric Oxide in Macrophage Immunometabolism: Hiding in Plain Sight

Nitric Oxide (NO) is a soluble endogenous gas with various biological functions like signaling, and working as an effector molecule or metabolic regulator. In response to inflammatory signals, immune myeloid cells, like macrophages, increase production of cytokines and NO, which is important for pathogen killing. Under these proinflammatory circumstances, called “M1”, macrophages undergo a series of metabolic changes including rewiring of their tricarboxylic acid (TCA) cycle. Here, we review findings indicating that NO, through its interaction with heme and non-heme metal containing proteins, together with components of the electron transport chain, functions not only as a regulator of cell respiration, but also a modulator of intracellular cell metabolism. Moreover, diverse effects of NO and NO-derived reactive nitrogen species (RNS) involve precise interactions with different targets depending on concentration, temporal, and spatial restrictions. Although the role of NO in macrophage reprogramming has been in evidence for some time, current models have largely minimized its importance. It has, therefore, been hiding in plain sight. A review of the chemical properties of NO, past biochemical studies, and recent publications, necessitates that mechanisms of macrophage TCA reprogramming during stimulation must be re-imagined and re-interpreted as mechanistic results of NO exposure. The revised model of metabolic rewiring we describe here incorporates many early findings regarding NO biochemistry and brings NO out of hiding and to the forefront of macrophages immunometabolism.