Myeloid-Derived Suppressor Cell-Derived Arginase-1 Oppositely Modulates IL-17A and IL-17F Through the ESR/STAT3 Pathway During Colitis in Mice

Quercetin in Osteoporosis Treatment: A Comprehensive Review of Its Mechanisms and Therapeutic Potential

PURPOSE OF REVIEW

This review aims to provide a theoretical basis and insights for quercetin's clinical application in the prevention and treatment of osteoporosis (OP), analyzing its roles in bone formation promotion, bone resorption inhibition, anti-inflammation, antioxidant effects, and potential mechanisms.

RECENT FINDINGS

OP, a prevalent bone disorder, is marked by reduced bone mineral density and impaired bone architecture, elevating the risk of fractures in patients. The primary approach to OP management is pharmacotherapy, with quercetin, a phytochemical compound, emerging as a focus of recent interest. This natural flavonoid exerts regulatory effects on bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts and promotes bone health and metabolic equilibrium via anti-inflammatory and antioxidative pathways. Although quercetin has demonstrated significant potential in regulating bone metabolism, there is a need for further high-quality clinical studies focused on medicinal quercetin.

Role played by MDSC in colitis-associated colorectal cancer and potential therapeutic strategies

Colitis-associated colorectal cancer has been a hot topic in public health issues worldwide. Numerous studies have demonstrated the significance of myeloid-derived suppressor cells (MDSCs) in the progression of this ailment, but the specific mechanism of their role in the transformation of inflammation to cancer is unclear, and potential therapies targeting MDSC are also unclear. This paper outlines the possible involvement of MDSC to the development of colitis-associated colorectal cancer. It also explores the immune and other relevant roles played by MDSC, and collates relevant targeted therapies against MDSC. In addition, current targeted therapies for colorectal cancer are analyzed and summarized.

α-mangostin derivatives ameliorated mouse DSS-induced chronic colitis via regulating Th17/Treg balance

Th17 cell, an important subpopulation of helper T cell, plays an important role in the development of inflammatory bowel disease (IBD) and is thought to be a potential target for the treatment of IBD. In our previous study, we demonstrated that α-mangostin could relieve lupus nephritis via inhibiting Th17 cell function. In our preliminary study, we obtained four derivatives by adding chemical modification of α-mangostin which could also inhibit Th17 cell differentiation in vitro. In this study, we constructed a chronic IBD mouse model and demonstrated the therapeutic effects of α-mangostin and its derivatives as therapeutic agents for IBD. In compounds treating groups, intestinal inflammation showed significant improvement in symptoms which included weight loss, high disease activity index, colon length shorten and the change of intestinal flora. We also found that compounds could effectively either suppress the number of Th17 cell or increase the number of Treg cell detected by flow cytometry, thus reducing the Th17/Treg ratio and suppressing the level of intestinal inflammation. Notably, IL17-F levels, rather than IL17-A, were reduced in the colon of mice of compounds treating groups. Thus, α-mangostin and its derivatives ameliorate DSS-induced chronic colitis in mice by regulating Th17/Treg balance to alleviate intestinal inflammation and can modulate the intestinal microbial community. These results suggest that α-mangostin and its derivatives may be the new therapeutic option for chronic colitis.

Diverse functions of myeloid-derived suppressor cells in autoimmune diseases

Since myeloid-derived suppressor cells (MDSCs) were found suppressing immune responses in cancer and other pathological conditions, subsequent researchers have pinned their hopes on the suppressive function against immune damage in autoimmune diseases. However, recent studies have found key distinctions of MDSC immune effects in cancer and autoimmunity. These include not only suppression and immune tolerance, but MDSCs also possess pro-inflammatory effects and exacerbate immune disorders during autoimmunity, while promoting T cell proliferation, inducing Th17 cell differentiation, releasing pro-inflammatory cytokines, and causing direct tissue damage. Additionally, MDSCs could interact with surrounding cells to directly cause tissue damage or repair, sometimes even as an inflammatory indicator in line with disease severity. These diverse manifestations could be partially attributed to the heterogeneity of MDSCs, but not all. The different disease types, disease states, and cytokine profiles alter the diverse phenotypes and functions of MDSCs, thus leading to the impairment or obversion of MDSC suppression. In this review, we summarize the functions of MDSCs in several autoimmune diseases and attempt to elucidate the mechanisms behind their actions.

Integrated network pharmacology and metabolomics analyses of the mechanism underlying the efficacy of Ma-Mu-Ran Antidiarrheal Capsules against dextran sulfate sodium-induced ulcerative colitis

The current study utilizes a comprehensive network pharmacology and metabolomics analysis to investigate the mechanism of action of Ma-Mu-Ran Antidiarrheal Capsules (MMRAC) for the treatment of ulcerative colitis (UC). In this study, we established a mouse model of UC using dextran sulfate sodium. Colonic tissues were collected from mice and then subjected to hematoxylin and eosin staining, as well as histopathological analysis, to assess the therapeutic effect of MMRAC. Furthermore, we assessed the mechanisms through which MMRAC combats UC by employing integrated metabolomics and network pharmacology strategies. Lastly, we validated the key targets identified through western blot and molecular docking. An integrated network of metabolomics and network pharmacology was constructed using Cytoscape to identify eight endogenous metabolites involved in the therapeutic action of MMRAC on UC. Further comprehensive analyses were focused on four key targets and their associated core metabolites and pathways. The results of western blot and molecular docking demonstrated that MMRAC could modulate key targets and their expression levels. The cumulative results indicated that MMRAC restored intestinal function in UC, reduced inflammatory responses, and alleviated oxidative stress by influencing the methionine and cysteine metabolic pathways, as well as the urea cycle. In addition, it had an impact on arginine, proline, glutamate, aspartate, and asparagine metabolic pathways and their associated targets.

Polyamines from myeloid-derived suppressor cells promote Th17 polarization and disease progression

Myeloid-derived suppressor cells (MDSCs) are a group of immature myeloid cells that play an important role in diseases. MDSCs promote Th17 differentiation and aggravate systemic lupus erythematosus (SLE) progression by producing arginase-1 to metabolize arginine. However, the metabolic regulators remain unknown. Here, we report that MDSC derivative polyamines can promote Th17 differentiation via miR-542-5p in vitro. Th17 polarization was enhanced in response to polyamine treatment or upon miR-542-5p overexpression. The TGF-β/SMAD3 pathway was shown to be involved in miR-542-5p-facilitated Th17 differentiation. Furthermore, miR-542-5p expression positively correlated with the levels of polyamine synthetases in peripheral blood mononuclear cells of patients with SLE as well as disease severity. In humanized SLE model mice, MDSC depletion decreased the levels of Th17 cells, accompanied by reduced expression of miR-542-5p and these polyamine synthetases. In addition, miR-542-5p expression positively correlated with the Th17 level and disease severity in both patients and humanized SLE mice. Together, our data reveal a novel molecular pathway by which MDSC-derived polyamine metabolism enhances Th17 differentiation and aggravates SLE.

Low-dose decitabine modulates myeloid-derived suppressor cell fitness via LKB1 in immune thrombocytopenia

Myeloid-derived suppressor cells (MDSCs) are heterogeneous immature cells and natural inhibitors of adaptive immunity. Metabolic fitness of MDSCs is fundamental for its suppressive activity toward effector T cells. Our previous studies showed that the number and inhibitory function of MDSCs were impaired in patients with immune thrombocytopenia (ITP) compared with healthy controls. In this study, we analyzed the effects of decitabine on MDSCs from patients with ITP, both in vitro and in vivo. We found that low-dose decitabine promoted the generation of MDSCs and enhanced their aerobic metabolism and immunosuppressive functions. Lower expression of liver kinase 1 (LKB1) was found in MDSCs from patients with ITP, which was corrected by decitabine therapy. LKB1 short hairpin RNA (shRNA) transfection effectively blocked the function of MDSCs and almost offset the enhanced effect of decitabine on impaired MDSCs. Subsequently, anti-CD61 immune-sensitized splenocytes were transferred into severe combined immunodeficient (SCID) mice to induce ITP in murine models. Passive transfer of decitabine-modulated MDSCs significantly raised platelet counts compared with that of phosphate buffered saline-modulated MDSCs. However, when LKB1 shRNA-transfected MDSCs were transferred into SCID mice, the therapeutic effect of decitabine in alleviating thrombocytopenia was quenched. In conclusion, our study suggests that the impaired aerobic metabolism of MDSCs is involved in the pathogenesis of ITP, and the modulatory effect of decitabine on MDSC metabolism contributes to the improvement of its immunosuppressive function. This provides a possible mechanism for sustained remission elicited by low-dose decitabine in patients with ITP.

The paradoxical role of MDSCs in inflammatory bowel diseases: From bench to bedside

Myeloid-derived suppressor cells (MDSCs) are a group of bone marrow derived heterogeneous cells, which is known for their immunosuppressive functions especially in tumors. Recently, MDSCs have receiving increasing attention in pathological conditions like infection, inflammation and autoimmune diseases. Inflammatory bowel diseases (IBD) are a series of immune-dysfunctional autoimmune diseases characterized by relapsing intestinal inflammation. The role of MDSCs in IBD remains controversial. Although most studies in vitro demonstrated its anti-inflammatory effects by inhibiting the proliferation and function of T cells, it was reported that MDSCs failed to relieve inflammation but even promoted inflammatory responses in experimental IBD. Here we summarize recent insights into the role of MDSCs in the development of IBD and the potential of MDSCs-targeted therapy.

MDSCs and T cells in solid tumors and non-Hodgkin lymphomas: an immunosuppressive speech

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous subset of cells expanded during multiple pathological settings, including cancers. In tumors, MDSCs are dominant drivers of T-cell immunosuppression. To accomplish their job, they exploit multiple mechanisms ultimately leading to the paralysis of anti-tumor immunity. Among the variety of MDSC-ways of working within the tumor microenvironment, the generation of reactive species and the metabolic reprogramming have emerged as pivotal determinants of their immunosuppressive power. In this review we will overview integral mechanisms of MDSC-mediated immunosuppression in solid tumors, with a particular focus on Non-Hodgkin lymphoma.

Mitochondrial damage-associated molecular patterns trigger arginase-dependent lymphocyte immunoregulation

Tissue damage leads to loss of cellular and mitochondrial membrane integrity and release of damage-associated molecular patterns, including those of mitochondrial origin (mitoDAMPs). Here, we describe the lymphocyte response to mitoDAMPs. Using primary cells from mice and human donors, we demonstrate that natural killer (NK) cells and T cells adopt regulatory phenotypes and functions in response to mitoDAMPs. NK cell-mediated cytotoxicity, interferon gamma (IFN-γ) production, T cell proliferation, and in vivo anti-viral T cell activation are all interrupted in the presence of mitoDAMPs or mitoDAMP-rich irradiated cells in in vitro and in vivo assays. Mass spectrometry analysis of mitoDAMPs demonstrates that arginase and products of its enzymatic activity are prevalent in mitoDAMP preparations. Functional validation by arginase inhibition and/or arginine add-back shows that arginine depletion is responsible for the alteration in immunologic polarity. We conclude that lymphocyte responses to mitoDAMPs reflect a highly conserved mechanism that regulates inflammation in response to tissue injury.

Myeloid-Derived Suppressor Cells in Solid Tumors

Myeloid-derived suppressor cells (MDSCs) are one of the main suppressive cell population of the immune system. They play a pivotal role in the establishment of the tumor microenvironment (TME). In the context of cancers or other pathological conditions, MDSCs can differentiate, expand, and migrate in large quantities during circulation, inhibiting the cytotoxic functions of T cells and NK cells. This process is regulated by ROS, iNOS/NO, arginase-1, and multiple soluble cytokines. The definition of MDSCs and their phenotypes in humans are not as well represented as in other organisms such as mice, owing to the absence of the cognate molecule. However, a comprehensive understanding of the differences between different species and subsets will be beneficial for clarifying the immunosuppressive properties and potential clinical values of these cells during tumor progression. Recently, experimental evidence and clinical investigations have demonstrated that MDSCs have a close relationship with poor prognosis and drug resistance, which is considered to be a leading marker for practical applications and therapeutic methods. In this review, we summarize the remarkable position of MDSCs in solid tumors, explain their classifications in different models, and introduce new treatment approaches to target MDSCs to better understand the advancement of new approaches to cancer treatment.

Role of Myeloid-derived suppressor cell (MDSC) in autoimmunity and its potential as a therapeutic target

Myeloid suppressor cells (MDSCs) are an important class of immune-regulating cells that can suppress T cell function. Most of our knowledge about the function of MDSC comes from studies of cancer models. Recent studies, however, have greatly contributed to the description of MDSC involvement in autoimmune diseases. They are known as a cell population that may negatively affect immune responses by regulating the function of CD4⁺ and CD8⁺ cells, which makes them an attractive target for autoimmune diseases therapy. However, many questions about MDSC activation, differentiation, and inhibitory functions remain unanswered. In this study, we have summarized the role of MDSCs in various autoimmune diseases, and the potential of targeting them for therapeutic benefits has been discussed.

The diverse roles of myeloid derived suppressor cells in mucosal immunity

The mucosal immune system plays a vital role in protecting the host from the external environment. Its major challenge is to balance immune responses against harmful and harmless agents and serve as a 'homeostatic gate keeper'. Myeloid derived suppressor cells (MDSCs) are a heterogeneous population of undifferentiated cells that are characterized by an immunoregulatory and immunosuppressive phenotype. Herein we postulate that MDSCs may be involved in shaping immune responses related to mucosal immunity, due to their immunomodulatory and tissue remodeling functions. Until recently, MDSCs were investigated mainly in cancerous diseases, where they induce and contribute to an immunosuppressive and inflammatory environment that favors tumor development. However, it is now becoming clear that MDSCs participate in non-cancerous conditions such as chronic infections, autoimmune diseases, pregnancy, aging processes and immune tolerance to commensal microbiota at mucosal sites. Since MDSCs are found in the periphery only in small numbers under normal conditions, their role is highlighted during pathologies characterized by acute or chronic inflammation, when they accumulate and become activated. In this review, we describe several aspects of the current knowledge characterizing MDSCs and their involvement in the regulation of the mucosal epithelial barrier, their crosstalk with commensal microbiota and pathogenic microorganisms, and their complex interactions with a variety of surrounding regulatory and effector immune cells. Finally, we discuss the beneficial and harmful outcomes of the MDSC regulatory functions in diseases affecting mucosal tissues. We wish to illuminate the pivotal role of MDSCs in mucosal immunity, the limitations in our understanding of all the players and the intricate challenges stemming from the complex interactions of MDSCs with their environment.

Control of T-Cell Activation and Signaling by Amino-Acid Catabolizing Enzymes

Amino acids are essential for protein synthesis, epigenetic modification through the methylation of histones, and the maintenance of a controlled balance of oxidoreduction via the production of glutathione and are precursors of certain neurotransmitters. T lymphocytes are particularly sensitive to fluctuations in amino acid levels. During evolution, the production of amino-acid catabolizing enzymes by mainly antigen-presenting cells has become a physiological mechanism to control T-cell activation and polarization. The action of these enzymes interferes with TCR and co-stimulation signaling, allowing tuning of the T-cell response. These capacities can be altered in certain pathological conditions, with relevant consequences for the development of disease.

L-Arginine/Nitric Oxide Pathway Is Altered in Colorectal Cancer and Can Be Modulated by Novel Derivatives from Oxicam Class of Non-Steroidal Anti-Inflammatory Drugs

L-arginine/nitric oxide pathway metabolites are altered in colorectal cancer (CRC). We evaluated underlying changes in pathway enzymes in 55 paired tumor/tumor-adjacent samples and 20 normal mucosa using quantitative-PCR and assessed the impact of classic and novel oxicam analogues on enzyme expression and intracellular metabolite concentration (LC-MS/MS) in Caco-2, HCT116, and HT-29 cells. Compared to normal mucosa, ARG1, PRMT1, and PRMT5 were overexpressed in both tumor and tumor-adjacent tissue and DDAH2 solely in tumor-adjacent tissue. Tumor-adjacent tissue had higher expression of ARG1, DDAH1, and DDAH2 and lower NOS2 than patients-matched tumors. The ARG1 expression in tumors increased along with tumor grade and reflected lymph node involvement. Novel oxicam analogues with arylpiperazine moiety at the thiazine ring were more effective in downregulating DDAHs and PRMTs and upregulating ARG2 than piroxicam and meloxicam. An analogue distinguished by propylene linker between thiazine's and piperazine's nitrogen atoms and containing two fluorine substituents was the strongest inhibitor of DDAHs and PRMTs expression, while an analogue containing propylene linker but no fluorine substituents was the strongest inhibitor of ARG2 expression. Metabolic reprogramming in CRC includes overexpression of DDAHs and PRMTs in addition to ARG1 and NOS2 and is not restricted to tumor tissue but can be modulated by novel oxicam analogues.