The role of macrophage polarization in infectious and inflammatory diseases

M2 Monocyte Polarization in Dialyzed Patients Is Associated with Increased Levels of M-CSF and Myeloperoxidase-Associated Oxidative Stress: Preliminary Results

Cardiovascular diseases represent a major issue in terms of morbidity and mortality for dialysis patients. This morbidity is due to the accelerated atherosclerosis observed in these patients. Atherosclerosis is a chronic inflammatory disease characterized by key players such as monocytes, macrophages, or oxidized LDLs. Monocytes-macrophages are classified into subsets of polarized cells, with M1 and M2 macrophages considered, respectively, as pro- and anti-inflammatory. (1) Methods: The monocyte subsets and phenotypes were analyzed by flow cytometry. These data were completed by the quantification of plasma M-CSF, IL-8, CRP, Mox-LDLs, Apo-B, Apo-AI, chloro-tyrosine, and homocitrulline concentrations. The statistical differences and associations between two continuous variables were assessed using the Mann-Whitney U test and Spearman's correlation coefficient, respectively. (2) Results: Hemodialyzed patients showed a significant increase in their concentrations of CRP, M-CSF, and IL-8 (inflammation biomarkers), as well as chloro-tyrosine and homocitrulline (myeloperoxidase-associated oxidative stress biomarkers). Moreover, we observed a higher percentage of M2 monocytes in the plasma of hemodialysis patients as compared to the controls. (3) Conclusions: Our data suggest that oxidative stress and an inflammatory environment, which is amplified in hemodialysis patients, seems to favor an increase in the concentration of circulating M-CSF, therefore leading to an increase in M2 polarization among circulating monocytes.

Hydrogen Promotes the M1 Macrophage Conversion During the Polarization of Macrophages in Necrotizing Enterocolitis

Background: Hydrogen is protective against intestinal injury in necrotizing enterocolitis (NEC), mainly through to alleviate inflammation response. The M1 macrophages can promote inflammation. We hypothesized that hydrogen would promote the M1 macrophages conversion during the polarization and reduce the inflammatory factors in NEC. Methods: We used M1 and M2 macrophages induced from RAW264.7 cells and bone marrow-derived macrophages, models of NEC and macrophages derived from spleens, abdominal lymph nodes and lamina propria in model mice. Cytokines, CD16/32 and CD206 were measured by quantitative PCR, flow cytometry. Nuclear factor-κB (NF-κB) p65 were determined by western blot. Histology staining were used to assess the severity of NEC. Results: Macrophages were successfully polarized to M1 or M2 by assessing the expression of inflammatory factors. Pro-inflammatory factors and CD16/32 in M1 macrophages were decreased, and the expression of CD16/32 in lamina propria were inhibited after treatment with hydrogen, but the changes has no effects in other tissues. Hydrogen inhibited the NF-κB p65 in M1 macrophages nucleus and distal ileum of NEC. HE staining showed hydrogen could attenuate the severity of NEC. Conclusion: Hydrogen could attenuate the severity of NEC through promoting M1 macrophages conversion by inhibited the expression of NF-κB p65 in the nucleus.

Modulation Effects of Toxoplasma gondii Histone H2A1 on Murine Macrophages and Encapsulation with Polymer as a Vaccine Candidate

Toxoplasma gondii (T. gondii) is the most common zoonotic protozoa and has infected about one-third of the population worldwide. Recombinant epitopes encapsulated in nanospheres have advantages over traditional T. gondii vaccines. For an efficient delivery system, poly (DL-lactide-co-glycolide) (PLGA) and chitosan are the most frequently used biodegradable polymeric nanospheres with strong safety profiles. In the present study, we first expressed and purified histone H2A1 of T. gondii using the prokaryotic expression system. The effects of recombinant TgH2A1 on the functions of murine macrophages were then studied. Purified recombinant TgH2A1 was then encapsulated in nanospheres with PLGA and chitosan. After subcutaneous vaccination in mice, the immune response was evaluated by double antibody sandwich ELISA kits. The results from this study showed that PLGA and chitosan loaded with rTgH2A1 could trigger a stronger Th1 oriented immune response and prolong the survival time of mice effectively. In conclusion, PLGA and chitosan nanospheres loaded with histone H2A1 are an effective method for the development of vaccines against T. gondii. Further studies should focus on evaluating the regulatory mechanism of TgH2A1, vaccine potency, and cellular response in chronic T. gondii infections.

Neural stem cells induce M2 polarization of macrophages through the upregulation of interleukin-4

Macrophages are divided into two types: M1- and M2-type macrophages. Both types of macrophages serve important roles during the process of inflammation. M1-type macrophages release various pro-inflammatory cytokines, such as IL-1, IFN-γ and other inflammatory mediators, such as nitric oxide, glutamate and reactive oxygen species to generate inflammation. In contrast, M2-type macrophages counteract the pro-inflammatory M1 conditions and promote tissue repair by secreting anti-inflammatory cytokines, such as IL-10. In spinal cord injury (SCI), an imbalance in M1/M2 macrophages leads to irreversible tissue destruction. Thus, it is crucial to increase the number of M2-type macrophages and promote M2 polarization of macrophages in SCI. Accordingly, in this study an in vitro co-culture system was established to investigate the effect of neural stem cells (NSCs) on macrophages. The results of the present study demonstrated that NSCs induced M2 polarization and suppressed M1 polarization of macrophages in an interleukin (IL)-4-dependent manner. Furthermore, the nuclear factor (NF)-κB/p65 signaling pathway was involved in the M1 polarization of macrophages and NSCs suppressed the activation of the NF-κB/p65 pathway in an IL-4-dependent manner to induce M2 macrophage polarization. These findings provide more insight into SCI and help to identify novel treatment strategies.

Intestinal Anti-Inflammatory Activity of Terpenes in Experimental Models (2010-2020): A Review

Inflammatory bowel diseases (IBDs) refer to a group of disorders characterized by inflammation in the mucosa of the gastrointestinal tract, which mainly comprises Crohn’s disease (CD) and ulcerative colitis (UC). IBDs are characterized by inflammation of the intestinal mucosa, are highly debilitating, and are without a definitive cure. Their pathogenesis has not yet been fully elucidated; however, it is assumed that genetic, immunological, and environmental factors are involved. People affected by IBDs have relapses, and therapeutic regimens are not always able to keep symptoms in remission over the long term. Natural products emerge as an alternative for the development of new drugs; bioactive compounds are promising in the treatment of several disorders, among them those that affect the gastrointestinal tract, due to their wide structural diversity and biological activities. This review compiles 12 terpenes with intestinal anti-inflammatory activity evaluated in animal models and in vitro studies. The therapeutic approach to IBDs using terpenes acts basically to prevent oxidative stress, combat dysbiosis, restore intestinal permeability, and improve the inflammation process in different signaling pathways.

Vitamin D3 as Potential Treatment Adjuncts for COVID-19

Severe acute respiratory syndrome coronavirus type (SARS-CoV2, also known as COVID-19), which is the latest pandemic infectious disease, constitutes a serious risk to human health. SARS-CoV2 infection causes immune activation and systemic hyperinflammation which can lead to respiratory distress syndrome (ARDS). ARDS victims are characterized by a significant increase in IL-6 and IL-1. Macrophage activation, associated with the "cytokine storm", promotes the dysregulation of the innate immunity. So far, without vaccines or specific therapy, all efforts to design drugs or clinical trials are worthwhile. Vitamin D and its receptor vitamin D receptor (VDR) exert a critical role in infections due to their remarkable impact on both innate and adaptive immune responses and on the suppression of the inflammatory process. The protective properties of vitamin D supplementation have been supported by numerous observational studies and by meta-analysis of clinical trials for prevention of viral acute respiratory infection. In this review, we compare the mechanisms of the host immune response to SARS-CoV2 infection and the immunomodulatory actions that vitamin D exerts in order to consider the preventive effect of vitamin D supplementation on SARS-CoV2 viral infection.

Photobiomodulation enhances the Th1 immune response of human monocytes

This study aims to evaluate the effects of photobiomodulation (PBM) on human monocytes, assessing the oxidative burst and ultimate fungicidal potential of these cells, as well as the gene expression at the mRNA level of CD68, CD80, CD163, CD204, IL-6, TNF-α and IL-10 in derived macrophages. Primary cultures of human monocytes were irradiated with an InGaAlP (660 nm)/GaAlAs (780 nm) diode laser (parameters: 40 mW, 0.04 cm², 1 W/cm²; doses: 200, 400 and 600 J/cm²). Cells were submitted to the chemiluminescence assay, and a microbicidal activity assay against Candida albicans was performed. Reactive oxygen species (ROS) and nitric oxide (NO) production were measured, and cell viability was assessed by the exclusion method using 0.2% Trypan blue reagent. Irradiated monocytes were cultured for 72 h towards differentiation into macrophages. Total RNA was extracted, submitted to reverse transcription and real-time PCR. The results were analysed by ANOVA and the Tukey test (α = 0.05). Irradiated monocytes revealed a significant increase in their intracellular and extracellular ROS (P < 0.001). The 660 nm wavelength and 400 J/cm² dose were the most relevant parameters (P < 0.001). The fungicidal capacity of the monocytes was shown to be greatly increased after PBM (P < 0.001). PBM increased the expression of TNF-α (P = 0.0302) and the production of NO (P < 0.05) and did not impair monocyte viability. PBM induces a pro-inflammatory Th1-driven response in monocytes and macrophages.

Role of M2-like macrophages in the progression of ovarian cancer

In this study, we noninvasively assessed whether M2-like macrophages accelerate the progression of ovarian cancer by performing molecular imaging of ovarian cancer cells expressing enhanced firefly luciferase (Effluc) in living mice. First, murine ovarian cancer ID8 cells expressing Effluc (ID8/Effluc cells) were established by retroviral infection. Subsequently, macrophages were isolated from the peritoneal exudate of mice injected with thioglycollate medium and differentiated into M2-like macrophages by adding interleukin 4. To characterize these M2-like macrophages, F4/80 and cluster of differentiation 206 expression levels were determined. Then, the M2-like macrophages were co-cultured with the ID8/Effluc cells and bioluminescence imaging (BLI) of signals from the ID8/Effluc cells was completed. Additionally, migration and wound healing were assessed to evaluate the effects of conditioned medium (CM) from M2-like macrophages on ID8/Effluc cell motility. In the in vivo study, mice were first given either liposome-phosphate-buffered saline or liposome-clodronate (lipo-clodronate). After 24 h, ID8/Effluc cells were intraperitoneally injected into the mice and BLI was completed at the designed time points. Next, histological analysis was conducted to characterize the infiltrated tumor. Flow cytometric analysis revealed high levels of CD206 expression in the differentiated M2-like macrophages. Meanwhile, ID8/Effluc cells co-cultured with these M2-like macrophages proliferated rapidly in an M2-like macrophage, number-dependent manner. The migration of the ID8/Effluc cells was also increased by the application of CM from M2-like macrophages. In vivo BLI revealed that the growth rate of intraperitoneally injected ovarian cancer cells was inhibited following macrophage depletion by treatment with lipo-clodronate. M2-like macrophages accelerated the progression of ovarian cancer, suggesting they are a new therapeutic target for ovarian cancer and that ovarian cancer could be managed by altering the nature of communication between ovarian cancer and macrophages.

Excretory/Secretory Products From Trichinella spiralis Adult Worms Attenuated DSS-Induced Colitis in Mice by Driving PD-1-Mediated M2 Macrophage Polarization

Helminth-modulated macrophages contribute to attenuating inflammation in inflammatory bowel diseases. The programmed death 1 (PD-1) plays an important role in macrophage polarization and is essential in the maintenance of immune system homeostasis. Here, we investigate the role of PD-1-mediated polarization of M2 macrophages and the protective effects of excretory/secretory products from Trichinella spiralis adult worms (AES) on DSS-induced colitis in mice. Colitis in mice was induced by oral administration of dextran sodium sulfate (DSS) daily. Mice with DSS-induced colitis were treated with T. spiralis AES intraperitoneally, and pathological manifestations were evaluated. Macrophages in mice were depleted with liposomal clodronate. Markers for M1-type (iNOS, TNF-α) and M2-type (CD206, Arg-1) macrophages were detected by qRT-PCR and flow cytometry. Macrophage expression of PD-1 was quantified by flow cytometry; RAW 264.7 cells and peritoneal macrophages were used for in vitro tests, and PD-1 gene knockout mice were used for in vivo investigation of the role of PD-1 in AES-induced M2 macrophage polarization. Macrophage depletion was found to reduce DSS-induced colitis in mice. Treatment with T. spiralis AES significantly increased macrophage expression of CD206 and Arg-1 and simultaneously attenuated colitis severity. We found T. spiralis AES to enhance M2 macrophage polarization; these findings were confirmed studying in vitro cultures of RAW264.7 cells and peritoneal macrophages from mice. Further experimentation revealed that AES upregulated PD-1 expression, primarily on M2 macrophages expressing CD206. The AES-induced M2 polarization was found to be decreased in PD-1 deficient macrophages, and the therapeutic effects of AES on colitis was reduced in PD-1 knockout mice. In conclusion, the protective effects of T. spiralis AES on DSS-induced colitis were found to associate with PD-1 upregulation and M2 macrophage polarization. Thus, PD-1-mediated M2 macrophage polarization is a key mechanism of helminth-induced modulation of the host immune system.

Up-regulation of MiR-145-5p promotes the growth and migration in LPS-treated HUVECs through inducing macrophage polarization to M2

MiR-145-5p is high-expressed in human vascular endothelial cells (HUVECs) and alternatively activated macrophages (M2). However, whether miR-145-5p can reduce HUVEC damage by regulating macrophage immunophenotype is less reported. THP-1 was stimulated by Phorbolate-12-myristate-13-acetate, LPS and IFN-γ, and IL-4 to differentiate into macrophages (M0, M1 and M2). The expressions of macrophage markers were detected by Western blotting, and the expressions of miR-145-5p and kruppel-like factor-14 (KLF14) were detected by qRT-PCR. Dual-luciferase reporter assay was used to analyze the targeted relationship of miR-145-5p and KLF14. HUVEC injury was induced by LPS and then co-cultured with M1 transfected by miR-145-5p mimic. The effect of miR-145-3p on proliferation and metastasis of LPS-induced HUVECs was detected by MTT, clone formation, scratch assay and Transwell. We found that the expression of miR-145-5p was higher in M2 than that in M1. MiR-145-5p expression was down-regulated during M2-to-M1, but up-regulated during M1-to-M2. The expressions of IL-1β and iNOS were down-regulated, while the protein expressions of CCL17 and Arg-1 were up-regulated by miR-145-5p mimic in M0. The viability, proliferation, migration and invasion of HUVECs were promoted, however, LDH activity of the HUVECs was inhibited by mimics. In addition, KLF14 was predicted as the target gene for miR-145-5p in HUVECs. Collectively, our results demonstrate that miR-145-5p inhibited cell proliferation of LPS-treated HUVECs possibly through regulating macrophage polarization to M2.

Long non-coding RNA FENDRR regulates IFNγ-induced M1 phenotype in macrophages

Macrophages play an essential role in host defense and display remarkable plasticity in switching between classically (pro-inflammatory-M1) and alternatively activated (anti-inflammatory-M2) phenotypes. The molecular mechanisms of macrophage polarization are not fully understood. Long non-coding RNAs (lncRNAs) with a length of > 200 nucleotides have been shown to play diverse roles in biological processes. Aberrant expression of lncRNAs is associated with a variety of pathophysiological conditions such as cancer, diabetes, cardiovascular, pulmonary diseases, and tissue fibrosis. In this study, we investigated the role of lncRNA FENDRR in human and mouse macrophage polarization. Human THP-1 monocytes were activated with phorbol-12-myristate-13-acetate (PMA) and differentiated into M1 macrophages with IFNγ or M2 macrophages with IL4. Real-time PCR analysis revealed that FENDRR was expressed 80-fold higher in M1 macrophages than that in M2 macrophages. Overexpression of FENDRR in PMA-activated THP-1 cells increased the IFNγ-induced expression of M1 markers, including IL1β and TNFα at both mRNA and protein levels. Knockdown of FENDRR had an opposite effect. Similarly, FENDRR overexpression in primary mouse bone marrow-derived macrophages increased mRNA expression of M1 markers. FENDRR overexpression increased, while FENDRR knock-down decreased, the IFNγ-induced phosphorylation of STAT1 in PMA-activated THP-1 cells. Our studies suggest that FENDRR enhances IFNγ-induced M1 macrophage polarization via the STAT1 pathway.

Role of Ginkgolides in the Inflammatory Immune Response of Neurological Diseases: A Review of Current Literatures

The inflammatory immune response (IIR) is a physiological or excessive systemic response, induced by inflammatory immune cells according to changes in the internal and external environments. An excessive IIR is the pathological basis for the generation and development of neurological diseases. Ginkgolides are one of the important medicinal ingredients in Ginkgo biloba. Many studies have verified that ginkgolides have anti-platelet-activating, anti-apoptotic, anti-oxidative, neurotrophic, and neuroimmunomodulatory effects. Inflammatory immunomodulation is mediated by inhibition of the mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways. They also inhibit the platelet-activating factor (PAF)-mediated signal transduction to attenuate the inflammatory response. Herein, we reviewed the studies on the roles of ginkgolides in inflammatory immunomodulation and suggested its potential role in novel treatments for neurological diseases.

miR-106b-5p Inhibits IRF1/IFN-β Signaling to Promote M2 Macrophage Polarization of Glioblastoma

Purpose

The microRNA (miRNA) profile changes in the tumor-associated macrophages. However, the role of miR-106b-5p in the glioblastoma-associated macrophages is poorly understood.

Materials and Methods

In our study, miR-106b-5p and M2 macrophage markers were detected by qRT-PCR and Western blotting in THP1 cells, with the conditioned medium from U251 cells or M2 macrophages in response to IL-4 stimulation and M1 macrophages stimulated by LPS and IFN-γ. IFN regulatory factor (IRF1) was identified as a target of miR-106b-5p in the glioma infiltrating macrophages by luciferase reporter assay. The molecular mechanisms involved in the miR-106b-5p-mediated regulation of M2 polarization were clarified by shRNA knockdown assay.

Results

Our results showed miR-106b-5p expression was upregulated in glioma-infiltrating macrophages. miR-106b-5p regulated M2 polarization of glioma infiltrating macrophages and enhanced the growth of glioma-infiltrating macrophages. IRF1 was identified as a target of miR-106b-5p. Furthermore, miR-106b-5p inhibited IRF1 expression by targeting IRF1/IFN-β pathway to promote M2 polarization of macrophages.

Conclusion

miR-106b-5p may inhibit IRF1/IFN-β signaling to promote M2 macrophage polarization of glioblastoma, and it may become a novel target for the treatment of glioblastoma.

Regulating the Polarization of Macrophages: A Promising Approach to Vascular Dermatosis

Macrophages, a kind of innate immune cells, derive from monocytes in circulation and play a crucial role in the innate and adaptive immunity. Under the stimulation of the signals from local microenvironment, macrophages generally tend to differentiate into two main functional phenotypes depending on their high plasticity and heterogeneity, namely, classically activated macrophage (M1) and alternatively activated macrophage (M2). This phenomenon is often called macrophage polarization. In pathological conditions, chronic persistent inflammation could induce an aberrant response of macrophage and cause a shift in their phenotypes. Moreover, this shift would result in the alteration of macrophage polarization in some vascular dermatoses; e.g., an increase in proinflammatory M1 emerges from Behcet's disease (BD), psoriasis, and systemic lupus erythematosus (SLE), whereas an enhancement in anti-inflammatory M2 appears in infantile hemangioma (IH). Individual polarized phenotypes and their complicated cytokine networks may crucially mediate in the pathological processes of some vascular diseases (vascular dermatosis in particular) by activation of T cell subsets (such as Th1, Th2, Th17, and Treg cells), deterioration of oxidative stress damage, and induction of angiogenesis, but the specific mechanism remains ambiguous. Therefore, in this review, we discuss the possible role of macrophage polarization in the pathological processes of vascular skin diseases. In addition, it is proposed that regulation of macrophage polarization may become a potential strategy for controlling these disorders.

Nanomedicine therapies modulating Macrophage Dysfunction: a potential strategy to attenuate Cytokine Storms in severe infections

Cytokine storms, defined by the dysregulated and excessive production of multiple pro-inflammatory cytokines, are closely associated with the pathology and mortality of several infectious diseases, including coronavirus disease 2019 (COVID-19). Effective therapies are urgently needed to block the development of cytokine storms to improve patient outcomes, but approaches that target individual cytokines may have limited effect due to the number of cytokines involved in this process. Dysfunctional macrophages appear to play an essential role in cytokine storm development, and therapeutic interventions that target these cells may be a more feasible approach than targeting specific cytokines. Nanomedicine-based therapeutics that target macrophages have recently been shown to reduce cytokine production in animal models of diseases that are associated with excessive proinflammatory responses. In this mini-review, we summarize important studies and discuss how macrophage-targeted nanomedicines can be employed to attenuate cytokine storms and their associated pathological effects to improve outcomes in patients with severe infections or other conditions associated with excessive pro-inflammatory responses. We also discuss engineering approaches that can improve nanocarriers targeting efficiency to macrophages, and key issues should be considered before initiating such studies.

Trophoblast-derived IL-6 serves as an important factor for normal pregnancy by activating Stat3-mediated M2 macrophages polarization

Macrophages are major components of decidual microenvironment that play an important role in human implantation and placentation. Trophoblasts which migrate into the endometrium and interplay with decidual cells, have been reported to participate in the polarization of macrophages. However, the potential mechanisms of trophoblasts modulating M2 macrophages polarization still need further exploration. Herein, we used the co-cultured model to investigate the interaction between macrophages and trophoblasts. Our results illustrated that when co-cultured with trophoblasts, macrophages tended to polarize to M2-subtype, accompanied by increased expression of multiple M2 markers including CD206 and CCL18 mRNA expression and IL-10 and TGF-β protein level. Further experiments identified that trophoblast-derived IL-6, as the major contributor, promoted M2 macrophages polarization by activating Stat3 pathway. Moreover, activated M2 macrophages exerted a promoting role in the invasion and migration of trophoblasts in a feedback manner. Clinically, results from histology demonstrated that IL-6 expression in placental villous tissues was positive correlated with CD206-positive macrophage infiltration in decidua in normal pregnancy patients. Altogether, our findings indicate that trophoblasts induce M2 macrophages polarization via IL-6/Stat3 signal pathway, which in turn promote the invasion and migration of trophoblasts. These results provide insights into the crosstalk between macrophages and trophoblasts at maternal-fetal microenvironment in normal pregnancy.

Highly Water-Preserving Zwitterionic Betaine-Incorporated Collagen Sponges With Anti-oxidation and Anti-inflammation for Wound Regeneration

A core problem in wound healing – with both fundamental and technological significance – concerns the rational design of bioactive and moist microenvironments. Here, we design a new class of zwitterionic betaine-incorporated collagen sponges (BET@COL) with integrated anti-oxidation and anti-inflammatory properties for promoting wound healing in a full-thickness wound model. The presence of zwitterionic betaine in a 3D network structure of collagen enables tightly bound and locked water molecules inside sponges via ionic solvation and confinement effect, while the integration of this amino acid also empowers the sponge with anti-oxidation and anti-inflammatory functions. In vitro results demonstrated that BET@COL collagen sponges strongly preserved water content up to 33.78 ± 0.78% at the 80th min at 37°C (only 0.44 ± 0.18% in control), and also exhibited high cell biocompatibility. Further, BET@COL collagen sponges with different betaine contents were applied to a full-thickness cutaneous wound model in mice, followed by a systematical evaluation and comparison of the effect of preserved water on wound healing efficiency in vivo. The optimal BET@COL collagen sponges were able to maintain high water content (e.g., moist microenvironment), suppress oxidative stress, improve anti-inflammation, all of which impose synergetic healing effects to promote wound closure, granulation formation, re-epithelization, collagen deposition and angiogenesis. This work demonstrates a new material as a promising candidate for wound dressing.

Ornithine-A urea cycle metabolite enhances autophagy and controls Mycobacterium tuberculosis infection

Macrophages are professional phagocytes known to play a vital role in controlling Mycobacterium tuberculosis (Mtb) infection and disease progression. Here we compare Mtb growth in mouse alveolar (AMs), peritoneal (PMs), and liver (Kupffer cells; KCs) macrophages and in bone marrow-derived monocytes (BDMs). KCs restrict Mtb growth more efficiently than all other macrophages and monocytes despite equivalent infections through enhanced autophagy. A metabolomics comparison of Mtb-infected macrophages indicates that ornithine and imidazole are two top-scoring metabolites in Mtb-infected KCs and that acetylcholine is the top-scoring in Mtb-infected AMs. Ornithine, imidazole and atropine (acetylcholine inhibitor) inhibit Mtb growth in AMs. Ornithine enhances AMPK mediated autophagy whereas imidazole directly kills Mtb by reducing cytochrome P450 activity. Intranasal delivery of ornithine or imidazole or the two together restricts Mtb growth. Our study demonstrates that the metabolic differences between Mtb-infected AMs and KCs lead to differences in the restriction of Mtb growth.

Kupffer cells are more resistant to M. tuberculosis when compared with alveolar macrophages. Here the authors show that this distinction is caused by the presence of ornithine and imidazole in Kupffer cells and that these metabolites can drive autophagy and M. tuberculosis killing in alveolar macrophages when given intranasally to infected mice.

Unraveling the regulatory role of endoplasmic-reticulum-associated degradation in tumor immunity

During malignant transformation and cancer progression, tumor cells face both intrinsic and extrinsic stress, endoplasmic reticulum (ER) stress in particular. To survive and proliferate, tumor cells use multiple stress response pathways to mitigate ER stress, promoting disease aggression and treatment resistance. Among the stress response pathways is ER-associated degradation (ERAD), which consists of multiple components and steps working together to ensure protein quality and quantity. In addition to its established role in stress responses and tumor cell survival, ERAD has recently been shown to regulate tumor immunity. Here we summarize current knowledge on how ERAD promotes protein degradation, regulates immune cell development and function, participates in antigen presentation, exerts paradoxical roles on tumorigenesis and immunity, and thus impacts current cancer therapy. Collectively, ERAD is a critical protein homeostasis pathway intertwined with cancer development and tumor immunity. Of particular importance is the need to further unveil ERAD's enigmatic roles in tumor immunity to develop effective targeted and combination therapy for successful treatment of cancer.

Suppressors of Cytokine Signaling (SOCS)1 and SOCS3 Proteins Are Mediators of Interleukin-10 Modulation of Inflammatory Responses Induced by Chlamydia muridarum and Its Major Outer Membrane Protein (MOMP) in Mouse J774 Macrophages

The immunopathology of chlamydial diseases is exacerbated by a broad-spectrum of inflammatory mediators, which we reported are inhibited by IL-10 in macrophages. However, the chlamydial protein moiety that induces the inflammatory mediators and the mechanisms by which IL-10 inhibits them are unknown. We hypothesized that Chlamydia major outer membrane protein (MOMP) mediates its disease pathogenesis, and the suppressor of cytokine signaling (SOCS)1 and SOCS3 proteins are mediators of the IL-10 inhibitory actions. Our hypothesis was tested by exposing mouse J774 macrophages to chlamydial stimulants (live Chlamydia muridarum and MOMP) with and without IL-10. MOMP significantly induced several inflammatory mediators (IL-6, IL-12p40, CCL5, CXCL10), which were dose-dependently inhibited by IL-10. Chlamydial stimulants induced the mRNA gene transcripts and protein expression of SOCS1 and SOCS3, with more SOCS3 expression. Notably, IL-10 reciprocally regulated their expression by reducing SOCS1 and increasing SOCS3. Specific inhibitions of MAPK pathways revealed that p38, JNK, and MEK1/2 are required for inducing inflammatory mediators as well as SOCS1 and SOCS3. Chlamydial stimulants triggered an M1 pro-inflammatory phenotype evidently by an enhanced nos2 (M1 marker) expression, which was skewed by IL-10 towards a more M2 anti-inflammatory phenotype by the increased expression of mrc1 and arg1 (M2 markers) and the reduced SOCS1/SOCS3 ratios. Neutralization of endogenously produced IL-10 augmented the secretion of inflammatory mediators, reduced SOCS3 expression, and skewed the chlamydial M1 to an M2 phenotype. Inhibition of proteasome degradation increased TNF but decreased IL-10, CCL5, and CXCL10 secretion by suppressing SOCS1 and SOCS3 expressions and dysregulating their STAT1 and STAT3 transcription factors. Our data show that SOCS1 and SOCS3 are regulators of IL-10 inhibitory actions, and underscore SOCS proteins as therapeutic targets for IL-10 control of inflammation for Chlamydia and other bacterial inflammatory diseases.

The activation of IL-17 signaling pathway promotes pyroptosis in pneumonia-induced sepsis

Background

Pyroptosis is closely relevant to sepsis. However, the molecular mechanisms of pyroptosis in pneumonia-induced sepsis are still not fully understood. Thus, this study aimed to find the specific molecular pathways associated with pyroptosis and explore their relationship in pneumonia-induced sepsis.

Methods

First, significant signaling pathways related to pneumonia-induced sepsis were screened by bioinformatics analysis based on GSE48080. The peripheral blood samples from patients with pneumonia-induced sepsis and healthy subjects were collected. Pneumonia-induced sepsis rat models were also established. Then, inflammatory response, pyroptosis, and regulatory T cells (Tregs)/T-helper 17 (Th17), Th1/Th2, and M1/M2 cell ratios in pneumonia-induced sepsis were evaluated.

Results

IL-17 signaling pathway was significantly related to pneumonia-induced sepsis by bioinformatics analysis. Compared with healthy groups, the higher of Th17/Treg, Th1/Th2 and M1/M2 cell radios in the patients and sepsis rat model indicated that pneumonia-induced sepsis caused a severe inflammatory response. This result was confirmed by higher levels of pro-inflammatory factors (IL-6, TNF-α, IL-1β, and IL-18) and an inflammation indicator (LDH), as well as pyroptosis occurrence in sepsis. Additionally, the up-regulation of key molecules (HMGB1, RAGE, IL-17A, TRAF6 and NK-κB) in the IL-17 signaling pathway suggested the IL-17 pathway was activated. Moreover, the release of IL-1β and IL-18 and the levels of the molecules (NLRP3, NLRC4, Cleaved caspase-1, and Cleaved GSDMD) associated with caspase-1-dependent pyroptosis were up-regulated in pneumonia-induced sepsis.

Conclusions

As NK-κB activation can promote the development of caspase-1-dependent pyroptosis, these findings suggested that the activation of the IL-17 signaling pathway could promote pyroptosis in pneumonia-induced sepsis.

Metabolic Reprogramming of Mouse Bone Marrow Derived Macrophages Following Erythrophagocytosis

Reticuloendothelial macrophages engulf ∼0.2 trillion senescent erythrocytes daily in a process called erythrophagocytosis (EP). This critical mechanism preserves systemic heme-iron homeostasis by regulating red blood cell (RBC) catabolism and iron recycling. Although extensive work has demonstrated the various effects on macrophage metabolic reprogramming by stimulation with proinflammatory cytokines, little is known about the impact of EP on the macrophage metabolome and proteome. Thus, we performed mass spectrometry-based metabolomics and proteomics analyses of mouse bone marrow-derived macrophages (BMDMs) before and after EP of IgG-coated RBCs. Further, metabolomics was performed on BMDMs incubated with free IgG to ensure that changes to macrophage metabolism were due to opsonized RBCs and not to free IgG binding. Uniformly labeled tracing experiments were conducted on BMDMs in the presence and absence of IgG-coated RBCs to assess the flux of glucose through the pentose phosphate pathway (PPP). In this study, we demonstrate that EP significantly alters amino acid and fatty acid metabolism, the Krebs cycle, OXPHOS, and arachidonate-linoleate metabolism. Increases in levels of amino acids, lipids and oxylipins, heme products, and RBC-derived proteins are noted in BMDMs following EP. Tracing experiments with U-¹³C₆ glucose indicated a slower flux through glycolysis and enhanced PPP activation. Notably, we show that it is fueled by glucose derived from the macrophages themselves or from the extracellular media prior to EP, but not from opsonized RBCs. The PPP-derived NADPH can then fuel the oxidative burst, leading to the generation of reactive oxygen species necessary to promote digestion of phagocytosed RBC proteins via radical attack. Results were confirmed by redox proteomics experiments, demonstrating the oxidation of Cys152 and Cys94 of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and hemoglobin-β, respectively. Significant increases in early Krebs cycle and C₅-branched dibasic acid metabolites (α-ketoglutarate and 2-hydroxyglutarate, respectively) indicate that EP promotes the dysregulation of mitochondrial metabolism. Lastly, EP stimulated aminolevulinic acid (ALA) synthase and arginase activity as indicated by significant accumulations of ALA and ornithine after IgG-mediated RBC ingestion. Importantly, EP-mediated metabolic reprogramming of BMDMs does not occur following exposure to IgG alone. In conclusion, we show that EP reprograms macrophage metabolism and modifies macrophage polarization.

Interleukin 26 Skews Macrophage Polarization Towards M1 Phenotype by Activating cJUN and the NF-κB Pathway

Interleukin 26 (IL-26) is a new member of the IL-10 family that is highly expressed in rheumatoid arthritis (RA). However, the functions of IL-26 produced by macrophages in RA have not been elucidated. In the present work, we evaluated the effects and the mechanisms of IL-26 on M1 and M2 macrophage differentiation. Human or mouse macrophage cells were treated with lipopolysaccharides (LPS), interferon gamma (IFNγ), or IL-4 alone or concurrently treated with IL-26 to monitor M1 or M2 macrophage subtypes. The expression level of M1 or M2 macrophage genes was evaluated by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The molecular mechanisms of downstream signaling activation during differentiation were investigated by immunoblotting assay. Our results found that IL-26 promoted macrophage cells from CD80⁺ M1 macrophage differentiation, not from the CD206⁺ M2 phenotype. The messenger RNA of M1-type macrophage markers tumor necrosis factor alpha (TNFα) and inducible nitric oxide synthase (iNOS) was up-regulated in the IL-26-treated group. Also, the M1-related proinflammatory cytokines TNFα and IL-6 were induced after IL-26 stimulation. Interestingly, IL-10, a cytokine marker of M2 macrophage, was also elevated after IL-26 stimulation. Moreover, the M1-like macrophage stimulated by IL-26 underwent cJUN, nuclear factor kappa B (NF-κB), and signal transducer and activator of transcription 1 (STAT1) activation. Our findings suggested the role of IL-26 in synovial macrophages of active rheumatoid arthritis and provided a new insight into IL-26 as a candidate therapeutic target in rheumatoid arthritis.

Paradoxical Pro-inflammatory Responses by Human Macrophages to an Amoebae Host-Adapted Legionella Effector

Legionella pneumophila has co-evolved with amoebae, their natural hosts. Upon transmission to humans, the bacteria proliferate within alveolar macrophages causing pneumonia. Here, we show L. pneumophila injects the effector LamA, an amylase, into the cytosol of human macrophage (hMDMs) and amoebae to rapidly degrade glycogen to generate cytosolic hyper-glucose. In response, hMDMs shift their metabolism to aerobic glycolysis, which directly triggers an M1-like pro-inflammatory differentiation and nutritional innate immunity through enhanced tryptophan degradation. This leads to a modest restriction of bacterial proliferation in hMDMs. In contrast, LamA-mediated glycogenolysis in amoebae deprives the natural host from the main building blocks for synthesis of the cellulose-rich cyst wall, leading to subversion of amoeba encystation. This is non-permissive for bacterial proliferation. Therefore, LamA of L. pneumophila is an amoebae host-adapted effector that subverts encystation of the amoebae natural host, and the paradoxical hMDMs' pro-inflammatory response is likely an evolutionary accident.

Sea Hare Hydrolysate-Induced Reduction of Human Non-Small Cell Lung Cancer Cell Growth through Regulation of Macrophage Polarization and Non-Apoptotic Regulated Cell Death Pathways

Sea hare-derived compounds induce macrophage activation and reduce asthmatic parameters in mouse models of allergic asthma. These findings led us to study the role of sea hare hydrolysates (SHH) in cancer pathophysiology. SHH treatment-induced M1 macrophage activation in RAW264.7 cells, peritoneal macrophages, and THP-1 cells, as did lipopolysaccharide (LPS) (+ INF-γ), whereas SHH reduced interleukin (IL)-4 (+IL-13)-induced M2 macrophage polarization. In addition, SHH treatment inhibited the actions of M1 and M2 macrophages, which have anticancer and pro-cancer effects, respectively, in non-small cell lung cancer cells (A549 and HCC-366) and tumor-associated macrophages (TAMs). Furthermore, SHH induced G2/M phase arrest and cell death in A549 cells. SHH also downregulated STAT3 activation in macrophages and A549 cells, and the down-regulation was recovered by colivelin, a STAT3 activator. SHH-induced reduction of M2 polarization and tumor growth was blocked by colivelin treatment. SHH-induced cell death did not occur in the manner of apoptotic signaling pathways, while the death pattern was mediated through pyroptosis/necroptosis, which causes membrane rupture, formation of vacuoles and bleb, activation of caspase-1, and secretion of IL-1β in SHH-treated A549 cells. However, a combination of SHH and colivelin blocked caspase-1 activation. Z-YVAD-FMK and necrostatin-1, pyrotosis and necroptosis inhibitors, attenuated SHH's effect on the cell viability of A549 cells. Taken together, SHH showed anticancer effects through a cytotoxic effect on A549 cells and a regulatory effect on macrophages in A549 cells. In addition, the SHH-induced anticancer effects were mediated by non-apoptotic regulated cell death pathways under STAT3 inhibition. These results suggest that SHH may be offered as a potential remedy for cancer immunotherapy.

Macrophages: First guards in the prevention of cardiovascular diseases

Cardiovascular diseases (CVD) remain one of the leading causes of mortality worldwide, especially in developing countries. It is widely known that severe inflammation can lead to atherosclerosis, which can cause various downstream pathologies, including myocardial injury and viral myocarditis. To date, several strategies have been proposed to prevent and cure CVD. The use of targeting macrophages has emerged as one of the most effective therapeutic approaches. Macrophages play a crucial role in eliminating senescent and dead cells while maintaining myocardial electrical activity and repairing myocardial injury. They also contribute to tissue repair and remodeling and plaque stabilization. Targeting macrophage pathways can, therefore, be advantageous in CVD care since it can lead to decreased aggregation of mononuclear cells at the injured site in the heart. Furthermore, it inhibits the development of pro-inflammatory factors, facilitates cholesterol outflow, and reduces the lipid concentration. More in-depth studies are still needed to formulate a comprehensive classification of phenotypes for different macrophages and determine their roles in the pathogenesis of CVD. In this review, we summarize the recent advances in the understanding of the role of macrophages in the prevention and cure of CVD.

Macrophage-secreted Lipocalin-2 Promotes Regeneration of Injured Primary Murine Renal Tubular Epithelial Cells

Lipocalin-2 (Lcn-2) is rapidly upregulated in macrophages after renal tubular injury and acts as renoprotective and pro-regenerative agent. Lcn-2 possesses the ability to bind and transport iron with high affinity. Therefore, the present study focuses on the decisive role of the Lcn-2 iron-load for its pro-regenerative function. Primary mouse tubular epithelial cells were isolated from kidney tissue of wildtype mice and incubated with 5μM Cisplatin for 24h to induce injury. Bone marrow-derived macrophages of wildtype and Lcn-2^-/- mice were isolated and polarized with IL-10 towards an anti-inflammatory, iron-release phenotype. Their supernatants as well as recombinant iron-loaded holo-Lcn-2 was used for stimulation of Cisplatin-injured tubular epithelial cells. Incubation of tubular epithelial cells with wildtype supernatants resulted in less damage and induced cellular proliferation, whereas in absence of Lcn-2 no protective effect was observed. Epithelial integrity as well as cellular proliferation showed a clear protection upon rescue experiments applying holo-Lcn-2. Notably, we detected a positive correlation between total iron amounts in tubular epithelial cells and cellular proliferation, which, in turn, reinforced the assumed link between availability of Lcn-2-bound iron and recovery. We hypothesize that macrophage-released Lcn-2-bound iron is provided to tubular epithelial cells during toxic cell damage, whereby injury is limited and recovery is favored.

LncRNA Dnmt3aos regulates Dnmt3a expression leading to aberrant DNA methylation in macrophage polarization

Long non-coding RNAs (lncRNAs) play key roles in various biological processes. However, the roles of lncRNAs in macrophage polarization remain largely unexplored. In this study, thousands of lncRNAs were identified that are differentially expressed in distinct polarized bone marrow-derived macrophages. Among them, Dnmt3aos (DNA methyltransferase 3A, opposite strand), as a known lncRNA, locates on the antisense strand of Dnmt3a. Functional experiments further confirmed that Dnmt3aos were highly expressed in M(IL-4) macrophages and participated in the regulation of Dnmt3a expression, and played a key role in macrophage polarization. The DNA methylation profiles between the Dnmt3aos knockdown group and the control group in M(IL-4) macrophages were determined by MeDIP-seq technique for the first time, and the Dnmt3aos-Dnmt3a axis-mediated DNA methylation modification-regulated macrophage polarization- related gene IFN-γ was identified. Our study will help to enrich our knowledge of the mechanism of macrophage polarization.

Soluble PTX3 of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Attenuates Hyperoxic Lung Injury by Activating Macrophage Polarization in Neonatal Rat Model

Therapeutic treatment of various inflammation-related diseases using mesenchymal stem cells (MSCs) has increased in recent years because of the paracrine action of these cells but shows several limitations. First, MSC-based therapies exhibit varying efficacies; thus, biomarkers should be determined to identify who may benefit from these candidate therapeutic agents. Second, the mechanism underlying the therapeutic effects is poorly understood. To evaluate the effects of human umbilical cord blood-derived MSCs (UCB-MSCs) on macrophages, the macrophage cell line NR8383 stimulated with lipopolysaccharide (LPS) was cocultured by UCB-MSCs. We found that UCB-MSCs mediated changes in macrophage polarization towards M2 from M1 macrophages. To identify the paracrine action underlying the anti-inflammation effect of UCB-MSCs, the secretion of UCB-MSCs exposed to LPS-stimulated NR8383 cells was tested using a biotin label-based 507 antibody array. Among the secreted proteins, we selected pentraxin-related protein PTX3/tumor necrosis factor-inducible gene 14 protein (PTX3) to investigate its association with UCB-MSCs in macrophage polarization. We found that human PTX3 was secreted from UCB-MSCs under inflammation condition and reinforced the M2 macrophage marker via the Dectin-1 receptor by activating MSK1/2 phosphorylation signaling in NR8383 cells. Accordingly, knockdown of PTX3 in UCB-MSCs significantly attenuated their therapeutic effects in a neonatal hyperoxic lung injury resulting in reduced survival, lung alveolarization, M2 marker expression, Dectin-1 levels, anti-inflammatory cytokines, and improved M1 marker expression and inflammatory cytokines compared to control MSC-injected rats. UCB-MSCs show therapeutic potential by controlling macrophage polarization. Interestingly, higher PTX3 levels in UCB-MSCs induced greater improvement in the therapeutic effects than lower PTX3 levels. Collectively, PTX3 is a potential marker with critical paracrine effects for predicting the therapeutic potential of MSC therapy in inflammatory diseases; quality control assessments using PTX3 may be useful for improving the therapeutic effects of UCB-MSCs.

Polarization of Human Monocyte-Derived Cells With Vitamin D Promotes Control of Mycobacterium tuberculosis Infection

Background: Understanding macrophage behavior is key to decipher Mycobacterium tuberculosis (Mtb) pathogenesis. We studied the phenotype and ability of human monocyte-derived cells polarized with active vitamin D [1,25(OH)₂D₃] to control intracellular Mtb infection compared with polarization of conventional subsets, classical M1 or alternative M2.

Methods: Human blood-derived monocytes were treated with active vitamin D or different cytokines to obtain 1,25(OH)₂D₃-polarized as well as M1- and M2-like cells or fully polarized M1 and M2 subsets. We used an in vitro macrophage Mtb infection model to assess both phenotype and functional markers i.e., inhibitory and scavenger receptors, costimulatory molecules, cytokines, chemokines, and effector molecules using flow cytometry and quantitative mRNA analysis. Intracellular uptake of bacilli and Mtb growth was monitored using flow cytometry and colony forming units.

Results: Uninfected M1 subsets typically expressed higher levels of CCR7, TLR2, and CD86, while M2 subsets expressed higher CD163, CD200R, and CD206. Most of the investigated markers were up-regulated in all subsets after Mtb infection, generating a mixed M1/M2 phenotype, while the expression of CD206, HLADR, and CD80 was specifically up-regulated (P < 0.05) on 1,25(OH)₂D₃-polarized macrophages. Consistent with the pro-inflammatory features of M1 cells, Mtb uptake and intracellular Mtb growth was significantly (P < 0.01–0.001 and P < 0.05–0.01) lower in the M1 (19.3%) compared with the M2 (82.7%) subsets 4 h post-infection. However, infectivity rapidly and gradually increased in M1 cells at 24–72 h. 1,25(OH)₂D₃-polarized monocyte-derived cells was the most potent subset to inhibit Mtb growth at both 4 and 72 h (P < 0.05–0.01) post-Mtb infection. This ability was associated with high mRNA levels of pro-inflammatory cytokines and the antimicrobial peptide LL-37 but also anti-inflammatory IL-10, while expression of the immunosuppressive enzyme IDO (indoleamine 2,3-dioxygenase) remained low in Mtb-infected 1,25(OH)₂D₃-polarized cells compared with the other subsets.

Conclusions: Mtb infection promoted a mixed M1/M2 macrophage activation, and 1,25(OH)₂D₃-polarized monocyte-derived cells expressing LL-37 but not IDO, were most effective to control intracellular Mtb growth. Macrophage polarization in the presence of vitamin D may provide the capacity to mount an antimicrobial response against Mtb and simultaneously prevent expression of inhibitory molecules that could accelerate local immunosuppression in the microenvironment of infected tissue.

Combination Immunotherapy with Passive Antibody and Sulfasalazine Accelerates Fungal Clearance and Promotes the Resolution of Pneumocystis-Associated Immunopathogenesis

The pulmonary immune response protects healthy individuals against Pneumocystis pneumonia (PcP). However, the immune response also drives immunopathogenesis in patients who develop severe PcP, and it is generally accepted that optimal treatment requires combination strategies that promote fungal killing and also provide effective immunomodulation. The anti-inflammatory drug sulfasalazine programs macrophages for enhanced Pneumocystis phagocytosis and also suppresses PcP-related immunopathogenesis. Anti-Pneumocystis antibody opsonizes Pneumocystis organisms for greater phagocytosis and may also mask antigens that drive immunopathogenesis. Thus, we hypothesized that combining antibody and sulfasalazine would have the dual benefit of enhancing fungal clearance while dampening immunopathogenesis and allow the rescue of severe PcP. To model a clinically relevant treatment scenario in mice, therapeutic interventions were withheld until clear symptoms of pneumonia were evident. When administered individually, both passive antibody and sulfasalazine improved pulmonary function and enhanced Pneumocystis clearance to similar degrees. However, combination treatment with antibody and sulfasalazine produced a more rapid improvement, with recovery of body weight, a dramatic improvement in pulmonary function, reduced lung inflammation, and the rapid clearance of the Pneumocystis organisms. Accelerated fungal clearance in the combination treatment group was associated with a significant increase in macrophage phagocytosis of Pneumocystis Both passive antibody and sulfasalazine resulted in the suppression of Th1 cytokines and a marked increase in lung macrophages displaying an alternatively activated phenotype, which were enhanced by combination treatment. Our data support the concept that passive antibody and sulfasalazine could be an effective and specific adjunctive therapy for PcP, with the potential to accelerate fungal clearance while attenuating PcP-associated immunopathogenesis.

Cyclic AMP Regulates Key Features of Macrophages via PKA: Recruitment, Reprogramming and Efferocytosis

Macrophages are central to inflammation resolution, an active process aimed at restoring tissue homeostasis following an inflammatory response. Here, the effects of db-cAMP on macrophage phenotype and function were investigated. Injection of db-cAMP into the pleural cavity of mice induced monocytes recruitment in a manner dependent on PKA and CCR2/CCL2 pathways. Furthermore, db-cAMP promoted reprogramming of bone-marrow-derived macrophages to a M2 phenotype as seen by increased Arg-1/CD206/Ym-1 expression and IL-10 levels (M2 markers). Db-cAMP also showed a synergistic effect with IL-4 in inducing STAT-3 phosphorylation and Arg-1 expression. Importantly, db-cAMP prevented IFN-γ/LPS-induced macrophage polarization to M1-like as shown by increased Arg-1 associated to lower levels of M1 cytokines (TNF-α/IL-6) and p-STAT1. In vivo, db-cAMP reduced the number of M1 macrophages induced by LPS injection without changes in M2 and Mres numbers. Moreover, db-cAMP enhanced efferocytosis of apoptotic neutrophils in a PKA-dependent manner and increased the expression of Annexin A1 and CD36, two molecules associated with efferocytosis. Finally, inhibition of endogenous PKA during LPS-induced pleurisy impaired the physiological resolution of inflammation. Taken together, the results suggest that cAMP is involved in the major functions of macrophages, such as nonphlogistic recruitment, reprogramming and efferocytosis, all key processes for inflammation resolution.

Broussonin E suppresses LPS-induced inflammatory response in macrophages via inhibiting MAPK pathway and enhancing JAK2-STAT3 pathway

Macrophages play an important role in inflammation, and excessive and chronic activation of macrophages leads to systemic inflammatory diseases, such as atherosclerosis and rheumatoid arthritis. In this paper, we explored the anti-inflammatory effect of broussonin E, a novel phenolic compound isolated from the barks ofBroussonetia kanzinoki, and its underlying molecular mechanisms. We discovered that Broussonin E could suppress the LPS-induced pro-inflammatory production in RAW264.7 cells, involving TNF-α, IL-1β, IL-6, COX-2 and iNOS. And broussonin E enhanced the expressions of anti-inflammatory mediators such as IL-10, CD206 and arginase-1 (Arg-1) in LPS-stimulated RAW264.7 cells. Further, we demonstrated that broussonin E inhibited the LPS-stimulated phosphorylation of ERK and p38 MAPK. Moreover, we found that broussonin E could activate janus kinase (JAK) 2, signal transducer and activator of transcription (STAT) 3. Downregulated pro-inflammatory cytokines and upregulated anti-inflammatory factors by broussonin E were abolished by using the inhibitor of JAK2-STAT3 pathway, WP1066. Taken together, our results showed that broussonin E could suppress inflammation by modulating macrophages activation statevia inhibiting the ERK and p38 MAPK and enhancing JAK2-STAT3 signaling pathway, and can be further developed as a promising drug for the treatment of inflammation-related diseases such as atherosclerosis.

Vitamin D and microbiota: Two sides of the same coin in the immunomodulatory aspects

The gut microbiota is crucial for host immune response, vitamin synthesis, short chain fatty acids (SCFAs) production, intestinal permeability, nutrient digestion energy metabolism and protection from pathogens. Therefore, gut microbiota guarantees the host's predisposition to gastrointestinal diseases. Intestinal microbiota may be damaged by environmental components with negative health conditions. Dysbiosis consisting in alteration in the gut microbiota has been involved in several disorders including inflammation, allergic reactions, autoimmune diseases, heart diseases, obesity, and metabolic syndrome and even in the state of malignant carcinogenesis existing in humans. Several epidemiological studies have shown that inadequate solar exposure results in vitamin D insufficiency/deficiency which has a strong impact on different immune responses and the occurrence of a wide range of pathological conditions. Additionally, new evidence indicates that the vitamin D pathway plays a key role in gut homeostasis. Due to the strong connection between vitamin D and microbiota, herein we focus on the new findings about intestinal bacteria-immune crosstalk and the impact of vitamin D in gut microbiota regulation, in order to offer new clarifications on their interaction. Understanding the mechanism by which vitamin D can affect the gut microbiota composition and its dynamic activities, as well as the innate and adaptive state of the immune system, is not only a fundamental research but also an opportunity to improve health status.

IL-4/IL-13 polarization of macrophages enhances Ebola virus glycoprotein-dependent infection

BACKGROUND

Ebolavirus (EBOV) outbreaks, while sporadic, cause tremendous morbidity and mortality. No therapeutics or vaccines are currently licensed; however, a vaccine has shown promise in clinical trials. A critical step towards development of effective therapeutics is a better understanding of factors that govern host susceptibility to this pathogen. As macrophages are an important cell population targeted during virus replication, we explore the effect of cytokine polarization on macrophage infection.

METHODS/MAIN FINDINGS

We utilized a BSL2 EBOV model virus, infectious, recombinant vesicular stomatitis virus encoding EBOV glycoprotein (GP) (rVSV/EBOV GP) in place of its native glycoprotein. Macrophages polarized towards a M2-like anti-inflammatory state by combined IL-4 and IL-13 treatment were more susceptible to rVSV/EBOV GP, but not to wild-type VSV (rVSV/G), suggesting that EBOV GP-dependent entry events were enhanced by these cytokines. Examination of RNA expression of known surface receptors that bind and internalize filoviruses demonstrated that IL-4/IL-13 stimulated expression of the C-type lectin receptor DC-SIGN in human macrophages and addition of the competitive inhibitor mannan abrogated IL-4/IL-13 enhanced infection. Two murine DC-SIGN-like family members, SIGNR3 and SIGNR5, were upregulated by IL-4/IL-13 in murine macrophages, but only SIGNR3 enhanced virus infection in a mannan-inhibited manner, suggesting that murine SIGNR3 plays a similar role to human DC-SIGN. In vivo IL-4/IL-13 administration significantly increased virus-mediated mortality in a mouse model and transfer of ex vivo IL-4/IL-13-treated murine peritoneal macrophages into the peritoneal cavity of mice enhanced pathogenesis.

SIGNIFICANCE

These studies highlight the ability of macrophage polarization to influence EBOV GP-dependent virus replication in vivo and ex vivo, with M2a polarization upregulating cell surface receptor expression and thereby enhancing virus replication. Our findings provide an increased understanding of the host factors in macrophages governing susceptibility to filoviruses and identify novel murine receptors mediating EBOV entry.

Toxoplasma ROP16I/III ameliorated inflammatory bowel diseases via inducing M2 phenotype of macrophages

BACKGROUND

Inflammatory bowel disease (IBD) is characterized by chronic and non-specific inflammation of the intestinal mucosa and mainly includes ulcerative colitis and Crohn's disease.

AIM

To explore the beneficial effect of ToxoROP16_I/III-induced M2 phynotype macrophages in homeostasis of IBDs through downregulation of M1 inflammatory cells.

METHODS

RAW264.7 macrophages stimulated by lipopolysaccharide (LPS) (M1 cells) were co-cultured with Caco-2 cells as an inflammatory model of IBD in vitro. The expression of ToxoROP16_I/III was observed in RAW264.7 macrophages that were transfected with pEGFP-rop16_I/III. The phenotypes of M2 and M1 macrophage cells were assessed by quantitative real-time reverse transcriptase polymerase chain reaction and the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, transforming growth factor (TGF)-β1, IL-10, inducible nitric oxide synthase (iNOS), and arginase-1 (Arg-1) was detected. The expression of iNOS, Arg-1, signal transducer and activator of transcription 3 (Stat3), p-Stat3, Stat6, p-Stat6, programmed death ligand-2 (PD-L2), caspase-3, -8, and -9 was analyzed by Western blotting, and Griess assays were performed to detect nitric oxide (NO). TNF-α, IL-1β, IL-6, TGF-β1, and IL-10 expression in the supernatants was detected by enzyme-linked immunosorbent assay, and Caco-2 cell apoptosis was determined by flow cytometry after mixing M1 cells with M2 cells in a Caco-2 cell co-culture system.

RESULTS

M1 cells exhibited significantly increased production of iNOS, NO, TNF-α, IL-1β, and IL-6, while ToxoROP16_I/III induced macrophage bias to M2 cells in vitro, showing increased expression of Arg-1, IL-10 and TGF-β1 and elevated production of p-Stat3 and p-Stat6. The mixed M1 and M2 cell culture induced by ToxoROP16_I/III exhibited decreased production of NO and iNOS and upregulated expression of Arg-1 and PD-L2. Accordingly, Caco-2 cells became apoptotic, and apoptosis-associated proteins such as caspase-3, -8 and -9 were dampened during co-culture of M1 and M2 cells. Flow cytometry analysis showed that co-culture of M1 cells with Caco-2 cells facilitated the apoptosis of Caco-2 cells, but co-culture of M1 and M2 cells alleviated Caco-2 cell apoptosis.

CONCLUSION

ToxoROP16_I/III-induced M2 macrophages inhibited apoptosis of Caco-2 cells caused by M1 macrophages. This finding may help gain a better understanding of the underlying mechanism and represent a promising therapeutic strategy for IBDs.

Investigating Macrophages Plasticity Following Tumour-Immune Interactions During Oncolytic Therapies

Over the last few years, oncolytic virus therapy has been recognised as a promising approach in cancer treatment, due to the potential of these viruses to induce systemic anti-tumour immunity and selectively killing tumour cells. However, the effectiveness of these viruses depends significantly on their interactions with the host immune responses, both innate (e.g., macrophages, which accumulate in high numbers inside solid tumours) and adaptive (e.g., \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CD8}^{+}$$\end{document}CD8+ T cells). In this article, we consider a mathematical approach to investigate the possible outcomes of the complex interactions between two extreme types of macrophages (M1 and M2 cells), effector \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CD8}^{+}$$\end{document}CD8+ T cells and an oncolytic Vesicular Stomatitis Virus (VSV), on the growth/elimination of B16F10 melanoma. We discuss, in terms of VSV, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CD8}^{+}$$\end{document}CD8+ and macrophages levels, two different types of immune responses which could ensure tumour control and eventual elimination. We show that both innate and adaptive anti-tumour immune responses, as well as the oncolytic virus, could be very important in delaying tumour relapse and eventually eliminating the tumour. Overall this study supports the use mathematical modelling to increase our understanding of the complex immune interaction following oncolytic virotherapies. However, the complexity of the model combined with a lack of sufficient data for model parametrisation has an impact on the possibility of making quantitative predictions.

MiR-495 regulates macrophage M1/M2 polarization and insulin resistance in high-fat diet-fed mice via targeting FTO

MicroRNA 495 (miR-495) has been discovered to be involved in the metabolism and immune response in human body. The purpose of this study was to investigate the effect of miR-495 on macrophage M1/M2 polarization and insulin resistance in type 2 diabetes (T2D). A T2D mouse model was established by feeding C57BL/6 mice with a high-fat diet (HFD). The expressions of M1/M2 polarization markers and miR-495 in peritoneal macrophages were determined by qRT-PCR or Western blot. Mouse insulin tolerance test (ITT) and glucose tolerance test (GTT) were performed, and the targeted binding effect between miR-495, fat mass, and obesity-associated gene (FTO) was verified by double luciferase gene reporter assay. The body weight, blood glucose content, and miR-495 expression in macrophages of the HFD group were remarkably higher than those of the normal diet (ND) group. Besides, miR-495 induced the transformation of macrophages into M1-type pro-inflammatory macrophages and enhanced the insulin resistance of T2D mice. More importantly, FTO was proved to be a direct target gene of miR-495 and silencing FTO could induce the transformation of macrophages into M1-type pro-inflammatory macrophages. These results demonstrated that miR-495 could promote the transformation of macrophages into M1-type pro-inflammatory macrophages by inhibiting the expression of its target gene FTO, and aggravate the insulin resistance and adipose tissue inflammation in T2D mice, which provided a certain theoretical basis for the targeted treatment of T2D.

Impact of infection on transplantation tolerance

Allograft tolerance is the ultimate goal of organ transplantation. Current strategies for tolerance induction mainly focus on inhibiting alloreactive T cells while promoting regulatory immune cells. Pathogenic infections may have direct impact on both effector and regulatory cell populations, therefore can alter host susceptibility to transplantation tolerance induction as well as impair the quality and stability of tolerance once induced. In this review, we will discuss existing data demonstrating the effect of infections on transplantation tolerance, with particular emphasis on the role of the stage of infection (acute, chronic, or latent) and the stage of tolerance (induction or maintenance) in this infection-tolerance interaction. While the deleterious effect of acute infection on tolerance is mainly driven by proinflammatory cytokines induced shortly after the infection, chronic infection may generate exhausted T cells that could in fact facilitate transplantation tolerance. In addition to pathogenic infections, commensal intestinal microbiota also has numerous significant immunomodulatory effects that can shape the host alloimmunity following transplantation. A comprehensive understanding of these mechanisms is crucial for the development of therapeutic strategies for robustly inducing and stably maintaining transplantation tolerance while preserving host anti-pathogen immunity in clinically relevant scenarios.

PE_PGRS62 promotes the survival of Mycobacterium smegmatis within macrophages via disrupting ER stress-mediated apoptosis

Mycobacterium tuberculosis, the leading causative agent of tuberculosis, remains one of the most deadly infectious pathogens. PE_PGRS proteins become a new focus as their species specificity in mycobacteria, especially in pathogenic mycobacteria. Despite intensive research, PE_PGRS proteins are still a mysterious aspect of mycobacterial pathogenesis with unknown mechanism. Herein, we focused on a PE_PGRS member from M. tuberculosis, PE_PGRS62, characterized by a surface-exposed protein function in disrupting phagolysosome maturation. Expression of PE_PGRS62 in Mycobacterium smegmatis, a nonpathogenic species naturally deficient in PE_PGRS genes, resulted in enhanced resistance to various in vitro stresses and cellular survival in macrophage. As a consequence, the cytokine profiles of macrophage were disturbed and cell apoptosis were inhibited via decreasing endoplasmic reticulum stress response.

Decorin Secreted by Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Induces Macrophage Polarization via CD44 to Repair Hyperoxic Lung Injury

Bronchopulmonary dysplasia (BPD), caused by hyperoxia in newborns and infants, results in lung damage and abnormal pulmonary function. However, the current treatments for BPD are steroidal and pharmacological therapies, which cause neurodevelopmental impairment. Treatment with umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) is an efficient alternative approach. To prevent pulmonary inflammation in BPD, this study investigated the hypothesis that a key regulator was secreted by MSCs to polarize inflammatory macrophages into anti-inflammatory macrophages at inflammation sites. Lipopolysaccharide-induced macrophages co-cultured with MSCs secreted low levels of the inflammatory cytokines, IL-8 and IL-6, but high levels of the anti-inflammatory cytokine, IL-10. Silencing decorin in MSCs suppressed the expression of CD44, which mediates anti-inflammatory activity in macrophages. The effects of MSCs were examined in a rat model of hyperoxic lung damage. Macrophage polarization differed depending on the levels of decorin secreted by MSCs. Moreover, intratracheal injection of decorin-silenced MSCs or MSCs secreting low levels of decorin confirmed impaired alveolarization of damaged lung tissues by down-regulation of decorin. In tissues, a decrease in the anti-inflammatory macrophage marker, CD163, was observed via CD44. Thus, we identified decorin as a key paracrine factor, inducing macrophage polarization via CD44, a master immunoregulator in mesenchymal stem cells.

Roles of Neuropeptide Y in Neurodegenerative and Neuroimmune Diseases

Neuropeptide Y (NPY) is a neurotransmitter or neuromodulator that mainly exists in the nervous system. It plays a neuroprotective role in organisms and widely participates in the regulation of various physiological processes in vivo. Studies in both humans and animal models have been revealed that NPY levels are altered in some neurodegenerative and neuroimmune disorders. NPY plays various roles in these diseases, such as exerting a neuroprotective effect, increasing trophic support, decreasing excitotoxicity, regulating calcium homeostasis, and attenuating neuroinflammation. In this review, we will focus on the roles of NPY in the pathological mechanisms of neurodegenerative and neuroimmune diseases, highlighting NPY as a potential therapeutic target in these diseases.

Establishment of BV2 microglia polarization model and its effect on Toxoplasma gondii proliferation

Toxoplasma gondii is an intracellular opportunistic, parasitic protozoan. Microglia have been classified into two main types: M1 (classically activated macrophages) and M2 (alternatively activated macrophages). BV2 cells were used in this study, together with lipopolysaccharide (LPS) and interferon (IFN)-γ or interleukin (IL)-4, which were used to induce resting microglia. Expression levels of M1/M2 markers were determined at both mRNA and protein levels, using PCR, western blot, and flow cytometry. Furthermore, cells were infected with T. gondii PLK strain, and the dynamic changes in M1/M2 marker expression levels were determined. An in vitro polarization model was successfully established. Expression of Nos2 and M1-associated markers was significantly upregulated at 12 h post-infection in BV2 cells. Further, the JAK/STAT1 and NF-κB signaling pathways were also activated following T. gondii infection. This demonstrated that T. gondii infection induces M1-type microglial polarization in vitro. The present study demonstrated that T. gondii infection affects microglial activation in vitro and elucidated the effects of activated microglia on T. gondii proliferation. This data may serve as a useful reference for more detailed elucidation of interactions between T. gondii and the innate immune system.