MIF Promotes Classical Activation and Conversion of Inflammatory Ly6C(high) Monocytes into TipDCs during Murine Toxoplasmosis

Paracrine rescue of MYR1-deficient Toxoplasma gondii mutants reveals limitations of pooled in vivo CRISPR screens

Toxoplasma gondii is an intracellular parasite that subverts host cell functions via secreted virulence factors. Up to 70% of parasite-controlled changes in the host transcriptome rely on the MYR1 protein, which is required for the translocation of secreted proteins into the host cell. Mice infected with MYR1 knock-out (KO) strains survive infection, supporting a paramount function of MYR1-dependent secreted proteins in Toxoplasma virulence and proliferation. However, we have previously shown that MYR1 mutants have no growth defect in pooled in vivo CRISPR-Cas9 screens in mice, suggesting that the presence of parasites that are wild-type at the myr1 locus in pooled screens can rescue the phenotype. Here, we demonstrate that MYR1 is not required for the survival in IFN-γ-activated murine macrophages, and that parasites lacking MYR1 are able to expand during the onset of infection. While ΔMYR1 parasites have restricted growth in single-strain murine infections, we show that the phenotype is rescued by co-infection with wild-type (WT) parasites in vivo, independent of host functional adaptive immunity or key pro-inflammatory cytokines. These data show that the major function of MYR1-dependent secreted proteins is not to protect the parasite from clearance within infected cells. Instead, MYR-dependent proteins generate a permissive niche in a paracrine manner, which rescues ΔMYR1 parasites within a pool of CRISPR mutants in mice. Our results highlight an important limitation of otherwise powerful in vivo CRISPR screens and point towards key functions for MYR1-dependent Toxoplasma-host interactions beyond the infected cell.

The role of macrophage migration inhibitory factor family and CD74 in the pathogenesis of melanoma

Melanoma is an aggressive tumour with poor prognosis that arises from the malignant transformation of melanocytes. Over the past few decades, intense research into the pathogenesis of melanoma has led to the development of BRAF and immune checkpoint inhibitors, including antibodies against programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4), which have shown clinically significant efficacy. However, some tumours do not respond to these therapies initially or become treatment resistant. Most melanoma tissues appear to possess biological characteristics that allow them to evade these treatments, and identifying these characteristics is one of the major challenges facing cancer researchers. One such characteristic that has recently gained attention is the role of macrophage migration inhibitory factor (MIF) and its receptor CD74. This review outlines the cellular and molecular functions of CD74, MIF and their family of proteins. We then review their roles in tumours based on previous reports, highlight their pathological significance in melanoma and discuss their potential as therapeutic targets.

Origin and Function of Monocytes in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a chronic disease resulting from the interaction of various factors such as social elements, autoimmunity, genetics, and gut microbiota. Alarmingly, recent epidemiological data points to a surging incidence of IBD, underscoring an urgent imperative: to delineate the intricate mechanisms driving its onset. Such insights are paramount, not only for enhancing our comprehension of IBD pathogenesis but also for refining diagnostic and therapeutic paradigms. Monocytes, significant immune cells derived from the bone marrow, serve as precursors to macrophages (Mφs) and dendritic cells (DCs) in the inflammatory response of IBD. Within the IBD milieu, their role is twofold. On the one hand, monocytes are instrumental in precipitating the disease's progression. On the other hand, their differentiated offsprings, namely moMφs and moDCs, are conspicuously mobilized at inflammatory foci, manifesting either pro-inflammatory or anti-inflammatory actions. The phenotypic spectrum of these effector cells, intriguingly, is modulated by variables such as host genetics and the subtleties of the prevailing inflammatory microenvironment. Notwithstanding their significance, a palpable dearth exists in the literature concerning the roles and mechanisms of monocytes in IBD pathogenesis. This review endeavors to bridge this knowledge gap. It offers an exhaustive exploration of monocytes' origin, their developmental trajectory, and their differentiation dynamics during IBD. Furthermore, it delves into the functional ramifications of monocytes and their differentiated progenies throughout IBD's course. Through this lens, we aspire to furnish novel perspectives into IBD's etiology and potential therapeutic strategies.

Periodontitis exacerbation during pregnancy in mice: Role of macrophage migration inhibitory factor as a key inductor

OBJECTIVE

The present study was designed to investigate the role of macrophage migration inhibitory factor (MIF) in the exacerbation of pregestational periodontal disease (PGPD).

BACKGROUND

Periodontitis (PT) is a severe stage of periodontal disease characterized by inflammation of the supporting tissues of the teeth, which usually worsens during pregnancy. MIF is a proinflammatory cytokine that is significantly elevated in periodontitis, both at the beginning and at the end of pregnancy. Although periodontitis usually presents with greater severity during pregnancy, the participation of MIF in the evolution of periodontitis has not been established.

METHODS

To analyze the relevance of MIF in the exacerbation of PGPD, we employed a model of PGPD in WT and Mif-/- mice, both with a BALB/c genetic background. PT was induced with nylon suture ligatures placed supramarginally around the second upper right molar. For PGPD, PT was induced 2 weeks before mating. We evaluated histological changes and performed histometric analysis of the clinical attachment loss, relative expression of MMP-2 and MMP-13 by immunofluorescence, and relative expression of the cytokines mif, tnf-α, ifn-γ, and il-17 by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Our data revealed that periodontal tissue from PGPD WT mice produced a twofold increase in MIF compared with PT WT mice. Moreover, the evolution of periodontitis in Mif-/- mice was less severe than in PGDP WT mice. Periodontal tissue from Mif-/- mice with PGPD produced 80% less TNF-α and no IFN-γ, as well as 50% lower expression of matrix metalloproteinase (MMP)-2 and 25% less MMP-13 compared to WT PGDP mice.

CONCLUSIONS

Our study suggests that MIF plays an important role in the exacerbation of periodontitis during pregnancy and that MIF is partially responsible for the inflammation associated with the severity of periodontitis during pregnancy.

Macrophage migration inhibitory factor favors Neospora caninum infection in mice

Neospora caninum is a protozoan parasite with worldwide incidence, acting as a major cause of reproductive failures in ruminants and neuromuscular symptoms in dogs. Macrophage Migration Inhibitory Factor (MIF) is produced by several cell types and exhibits a central role in immune responses against intracellular pathogens. The present study aimed to comprehend the role of MIF in the relationship between N. caninum and its host. We used in vivo, in vitro and ex vivo experiments in a model of infection based on genetically deficient mice to analyze the infection kinetics and inflammatory markers. MIF production was measured in response to N. caninum during the acute and chronic phases of the infection. While Mif-/- mice survived lethal doses of NcLiv tachyzoites, sublethal infections in these mice showed that parasite burden was controlled in target tissues, alongside with reduced inflammatory infiltrates detected in lung and brain sections. TNF was increased at the initial site of the infection in genetically deficient mice and the MIF-dependent reduction was confirmed in vitro with macrophages and ex vivo with primed spleen cells. In sum, MIF negatively regulated host immunity against N. caninum, favoring disease progression.

Immunotoxicity Evaluation of Trihalophenolic Disinfection By-Products in Mouse and Human Mononuclear Macrophage Systems: The Role of RNA Epitranscriptomic Modification in Mammalian Immunity

BACKGROUND

2,4,6-Trichlorophenol (TCP), 2,4,6-tribromophenol (TBP) and 2,4,6-triiodophenol (TIP) are three widely detected trihalophenolic disinfection by-products (DBPs). Previous studies have mainly focused on the carcinogenic risk and developmental toxicity of 2,4,6-trihalophenols. Very little is known about their immunotoxicity in mammals.

OBJECTIVES

We investigated the effects of 2,4,6-trihalophenols on mammalian immunity using a mouse macrophage model infected with bacteria or intracellular parasites and aimed to elucidate the underlying mechanisms from an epitranscriptomic perspective. The identified mechanisms were further validated in human peripheral blood mononuclear cells (PBMCs).

METHODS

The mouse macrophage cell line RAW264.7 and primary mouse peritoneal macrophages were exposed to different concentrations of TCP, TBP, and TIP. The pro-inflammatory marker Ly6C, the survival of the bacterium Escherichia coli (E. coli), and the parasite burden of Toxoplasma gondii (T. gondii) were assessed. Furthermore, the global gene expression profiling of macrophages following exposure to 2,4,6-trihalophenols was obtained through RNA-sequencing (RNA-seq). The effects of 2,4,6-trihalophenols on RNA N 6 -methyladenosine (m 6 A ) methyltransferases and total RNA m 6 A levels were evaluated using Western blotting and dot blot, respectively. Transcriptome-wide m 6 A methylome was analyzed by m 6 A -seq . In addition, expression of m 6 A regulators and total RNA m 6 A levels in human PBMCs exposed to 2,4,6-trihalophenols were detected using quantitative reverse transcriptase polymerase chain reaction and dot blot, respectively.

RESULTS

Mouse macrophages exposed to TCP, TBP, or TIP had lower expression of the pro-inflammatory marker Ly6C, with a greater difference from control observed for TIP-exposed cells. Consistently, macrophages exposed to such DBPs, especially TIP, were susceptible to infection with the bacterium E. coli and the intracellular parasite T. gondii, indicating a compromised ability of macrophages to defend against pathogens. Intriguingly, macrophages exposed to TIP had significantly greater m 6 A levels, which correlated with the greater expression levels of m 6 A methyltransferases. Macrophages exposed to each of the three 2,4,6-trihalophenols exhibited transcriptome-wide redistribution of m 6 A . In particular, the m 6 A peaks in genes associated with immune-related pathways were altered after exposure. In addition, differences in m 6 A were also observed in human PBMCs after exposure to 2,4,6-trihalophenols.

DISCUSSION

These findings suggest that 2,4,6-trihalophenol exposure impaired the ability of macrophages to defend against pathogens. This response might be associated with notable differences in m 6 A after exposure. To the best of our knowledge, this study presents the first m 6 A landscape across the transcriptome of immune cells exposed to pollutants. However, significant challenges remain in elucidating the mechanisms by which m 6 A mediates immune dysregulation in infected macrophages after 2,4,6-trihalophenol exposure. https://doi.org/10.1289/EHP11329.

Digital Cell Atlas of Mouse Uterus: From Regenerative Stage to Maturational Stage

Endometrium undergoes repeated repair and regeneration during the menstrual cycle. Previous attempts using gene expression data to define the menstrual cycle failed to come to an agreement. Here we used single-cell RNA sequencing data of C57BL/6J mice uteri to construct a novel integrated cell atlas of mice uteri from the regenerative endometrium to the maturational endometrium at the single-cell level, providing a more accurate cytological-based elucidation for the changes that occurred in the endometrium during the estrus cycle. Based on the expression levels of proliferating cell nuclear antigen, differentially expressed genes, and gene ontology terms, we delineated in detail the transitions of epithelial cells, stromal cells, and immune cells that happened during the estrus cycle. The transcription factors that shaped the differentiation of the mononuclear phagocyte system had been proposed, being Mafb, Irf7, and Nr4a1. The amounts and functions of immune cells varied sharply in two stages, especially NK cells and macrophages. We also found putative uterus tissue-resident macrophages and identified potential endometrial mesenchymal stem cells (high expression of Cd34, Pdgfrb, Aldh1a2) in vivo. The cell atlas of mice uteri presented here would improve our understanding of the transitions that occurred in the endometrium from the regenerative endometrium to the maturational endometrium. With the assistance of a normal cell atlas as a reference, we may identify morphologically unaffected abnormalities in future clinical practice. Cautions would be needed when adopting our conclusions, for the limited number of mice that participated in this study may affect the strength of our conclusions.

Protective Effect Against Toxoplasmosis in BALB/c Mice Vaccinated With Recombinant Toxoplasma gondii MIF, CDPK3, and 14-3-3 Protein Cocktail Vaccine

Toxoplasma gondii can infect almost all endotherm organisms including humans and cause life-threatening toxoplasmosis in immunocompromised individuals, which leads to serious public health problems. Developing an excellent vaccine against this disease is impending. In present study, we formulated a cocktail protein vaccine including the TgMIF, TgCDPK3, and Tg14-3-3 proteins, which play critical roles in T. gondii infection. The recombinant protein vaccines were constructed and assessed by vaccination in BALB/c mice. We organized the mice in various protein combination groups of vaccines, and all mice were immunized with corresponding proteins at 0, 2, and 4 weeks. The specific protective effects of the vaccines on mice against T. gondii were analyzed by the mensuration of cytokines, serum antibodies, splenocyte proliferation assay, survival time, and parasite cyst burden of mice after the challenge. The study indicated that mice immunized with all three multicomponent proteins vaccine triggered a strong immune response with highest levels of IFN-γ production and IgG antibody compared with the other two protein combinations and controls. Moreover, there was an increase in IL-4 production and antigen-specific lymphocyte proliferation. The parasite cysts were significantly reduced (resulting in an 82.7% reduction), and survival time was longer in immunized mice with three multicomponent proteins compared with the other groups of mice. The enhanced humoral and cell-mediated immunity indicated that the protein cocktail vaccine containing three antigens provided effective protection for mice. These results indicated that recombinant TgMIF, TgCDPK3, and Tg14-3-3 multicomponent proteins were potential candidates for vaccine against toxoplasmosis.

17β-estradiol modulates the expression of hormonal receptors on THP-1 T. gondii-infected macrophages and monocytes in an AKT and ERK-dependent manner

Toxoplasma gondii (T. gondii) is a parasite common in pregnancy. Monocytes and macrophages are a significant immunologic barrier against T. gondii by boosting up inflammation. This outcome is highly regulated by signaling pathways such as MAPK (ERK1/2) and PI3K (AKT), necessary in cell growth and proliferation. It may be associated with the hormonal receptors' modulation by T. gondii (Estrogen Receptor (ER)-α, ERβ, G Protein-coupled ER (GPER), and Prolactin Receptor (PRLR)), as previously reported by our research group. 17β-estradiol also activates MAPK and PI3K; however, its combined effect in THP-1 monocytes and macrophages, infected with T. gondii, has not yet been evaluated. This study aimed to evaluate the combined effect of 17β-estradiol in the activation of signaling pathways using a model of THP-1 monocytes and macrophages infected with T. gondii. THP-1 monocytes were cultured and differentiated into macrophages. Inhibition of AKT and ERK1/2 was performed with specific inhibitors. Stimuli were performed with 17β-estradiol (10 nM), T. gondii (20,000 tachyzoites), and both conditions for 48 h. Proteins were extracted and quantified, and Western Blot assays were performed. 17β-estradiol performed activation of ERK1/2 and AKT in T. gondii-infected macrophages. 17β-estradiol modulated the expression of hormonal receptors in infected cells: increases the PRLR and PrgR in T. gondii-infected macrophages and decreases the PRLR and ERα in T. gondii-infected monocytes. As for GPER, its expression is abolished by T. gondii, and 17β-estradiol cannot restore it. Finally, the blockage of ERK and AKT pathways modified the expression of hormonal receptors. In conclusion, 17β-estradiol modifies the receptors of T. gondii-infected THP1 macrophages and monocytes in an ERK/AKT dependent manner.

The Role of MIF in Hepatic Function, Oxidative Stress, and Inflammation in Thioacetamide-induced Liver Injury in Mice: Protective Effects of Betaine

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a multipotent cytokine that contributes to the inflammatory response to chemical liver injury. This cytokine exhibits pro- and anti-inflammatory effects depending on the etiology and stage of liver disease.

OBJECTIVE

Our study aimed to investigate the role of MIF in oxidative stress and inflammation in the liver, and modulatory effects of betaine on MIF in thioacetamide (TAA)-induced chronic hepatic damage in mice.

METHODS

The experiment was performed on wild type and knockout MIF-/- C57BL/6 mice. They were divided into the following groups: control; Bet-group that received betaine (2% wt/v dissolved in drinking water); MIF-/- mice group; MIF-/-+Bet; TAA-group that received TAA (200 mg/kg b.w.), intraperitoneally, 3x/week/8 weeks); TAA+Bet; MIF-/-+TAA, and MIF-/-+TAA+Bet. In TAA- and Bet-treated groups, animals received the same doses. After eight weeks of treatment, blood samples were collected for biochemical analysis, and liver specimens were prepared for the assessment of parameters of oxidative stress and inflammation.

RESULTS

In MIF-/-mice, TAA reduced transaminases, γ-glutamyltranspeptidase, bilirubin, malondialdehyde (MDA), oxidative protein products (AOPP), total oxidant status (TOS), C-reactive protein (CRP), IL-6, IFN-γ, and increased thiols and total antioxidant status (TAS). Betaine attenuated the mechanism of MIF and mediated effects in TAA-induced liver injury, reducing transaminases, γ-glutamyltranspeptidase, bilirubin, MDA, AOPP, TOS, CRP, IL-6, IFN-g, and increasing thiols.

CONCLUSION

MIF is a mediator in hepatotoxic, pro-oxidative, and proinflammatoryeffects of TAA-induced liver injury. MIF-targeted therapy can potentially mitigate oxidative stress and inflammation in the liver, but the exact mechanism of its action requires further investigation. Betaine increases anti-oxidative defense and attenuates hepatotoxic effects of MIF, suggesting that betaine can be used for the prevention and treatment of liver damage.

Reparative System Arising from CCR2(+) Monocyte Conversion Attenuates Neuroinflammation Following Ischemic Stroke

Monocytes recruitment from the blood to inflamed tissues following ischemic stroke is an important immune response to wound healing and tissue repair. Mouse monocytes can be endogenously divided into two distinct populations: pro-inflammatory or classical monocytes that express CCR2^highCX3CR1^low and circulate in blood, and anti-inflammatory or non-classical monocytes that express CCR2^lowCX3CR1^high and patrol locally. In this study of transgenic mice with functional CX3CR1^GFP/+ or CX3CR1^GFP/+-CCR2^RFP/+, we found that CCR2^highCX3CR1^low monocytes recruited to the injured brain were cytokine-dependently converted into CCR2^lowCX3CR1^high macrophages, especially under the influence of IL-4 and IL-13, thereby attenuating the neuroinflammation following sterile ischemic stroke. The overall data suggest that (1) the regulation of monocyte-switching is one of the ultimate reparative strategies in ischemic stroke, and (2) the adaptation of monocytes in a locally inflamed milieu is vital to alleviating the effects of ischemic stroke through innate immunity.

Immune modulation by the macrophage migration inhibitory factor (MIF) family: D-dopachrome tautomerase (DDT) is not (always) a backup system

Human macrophage migration inhibition factor (MIF) is a protein with cytokine and chemokine properties that regulates a diverse range of physiological functions related to innate immunity and inflammation. Most research has focused on the role of MIF in different inflammatory diseases. D-dopachrome tautomerase (DDT), a different molecule with structural similarities to MIF, which shares receptors and biological functions, has recently been reported, but little is known about its roles and mechanisms. In this review, we sought to understand the similarities and differences between these molecules by summarizing what is known about their different structures, receptors and mechanisms regulating their expression and biological activities with an emphasis on immunological aspects.

Tumor-Associated Macrophages (TAMs): A Critical Activator In Ovarian Cancer Metastasis

Tumor-associated macrophages (TAMs) that appear in every stage of cancer progression are usually tumor-promoting cells and are present abundantly in the tumor-associated microenvironment. In ovarian cancer, the overall and intratumoral M1/M2 ratio is a relatively efficient TAM parameter for predicting the prognosis of patients, especially for serous tissue type cancer. TAMs exhibit immunological checkpoint modulators, such as the B7 family and programmed death-ligand 1 (PD-L1), and play a key role in the development, metastasis and invasion of ovarian cancer, but the underlying mechanism is barely understood. Ovarian cancer is a severe gynecological malignancy with high mortality. Ovarian cancer-associated death can primarily be attributed to cancer metastasis. The majority of patients are diagnosed with wide dissemination in the peritoneum and omentum, limiting the effectiveness of surgery and chemotherapy. In addition, unlike other well-documented cancers, metastasis through vasculature is not a usual dissemination pathway in ovarian cancer. This review sheds light on TAMs and the main process and mechanism of ovarian cancer metastasis.

Macrophage Migration Inhibitory Factor Promotes the Interaction between the Tumor, Macrophages, and T Cells to Regulate the Progression of Chemically Induced Colitis-Associated Colorectal Cancer

Colitis-associated colorectal cancer (CRC) development has been shown to be related to chronically enhanced inflammation. Macrophage migration inhibitory factor (MIF) is an inflammatory mediator that favors inflammatory cytokine production and has chemotactic properties for the recruitment of macrophages (Møs) and T cells. Here, we investigated the role of MIF in the inflammatory response and recruitment of immune cells in a murine model of chemical carcinogenesis to establish the impact of MIF on CRC genesis and malignancy. We used BALB/c MIF-knockout (MIF^-/-) and wild-type (WT) mice to develop CRC by administering intraperitoneal (i.p.) azoxymethane and dextran sodium sulfate in drinking water. Greater tumor burdens were observed in MIF^-/- mice than in WT mice. Tumors from MIF^-/- mice were histologically identified to be more aggressive than tumors from WT mice. The localization of MIF suggests that it is also involved in cell differentiation. The relative gene expression of il-17, measured by real-time PCR, was higher in MIF^-/- CRC mice, compared to the WT CRC and healthy MIF^-/- mice. Importantly, compared to the WT intestinal epithelium, lower percentages of tumor-associated Møs were found in the MIF^-/- intestinal epithelium. These results suggest that MIF plays a role in controlling the initial development of CRC by attracting Møs to the tumor, which is a condition that favors the initial antitumor responses.

Increased Toxoplasma gondii Intracellular Proliferation in Human Extravillous Trophoblast Cells (HTR8/SVneo Line) Is Sequentially Triggered by MIF, ERK1/2, and COX-2

Macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine, which mediates the regulation of diverse cellular functions. It is produced by extravillous trophoblastic cells and has been found to be involved in the pathogenesis of diseases caused by some protozoa, including Toxoplasma gondii. Previous studies demonstrated the ability of T. gondii to take advantage of MIF action in human trophoblast cells. However, MIF action in T. gondii-infected extravillous trophoblastic cells (HTR8/SVneo cell line) has not been fully investigated. The present study aimed to investigate the role of MIF in T. gondii-infected HTR8/SVneo cells and verify the intracellular signaling pathways triggered by this cytokine. We found that T. gondii increased MIF production by HTR8/SVneo cells, and by contrast, MIF inhibition, by ISO-1, led to a significant decrease in T. gondii proliferation and CD74 expression in HTR8/SVneo cells. Moreover, in infected HTR8/SVneo cells, the addition of recombinant MIF (rMIF) increased CD44 co-receptor expression, ERK1/2 phosphorylation, COX-2 expression, and IL-8 production, which favored T. gondii proliferation. Our findings indicate that T. gondii can use MIF to modulate important factors in HTR8/SVneo cells, being a possible explanation for the higher susceptibility of extravillous trophoblast cells than other trophoblast cell populations.

The Protection of Midazolam Against Immune Mediated Liver Injury Induced by Lipopolysaccharide and Galactosamine in Mice

Objectives: Liver macrophages agitated by Lipopolysaccharide (LPS) can enhance immuno-inflammatory responses in the liver which mediate liver injury and result in dysfunction. Midazolam has been reported to have inhibitory effects on activated immunity and escalated inflammation, however, what the effects of midazolam on the liver injury caused by excessive immuno-inflammatory response in sepsis, and what influence it will exert on inflamed liver macrophages need to be elucidated.

Methods: In the present study, LPS and galactosamine-induced acute liver injury mice were used to observe the effect of midazolam in vivo. LPS-stimulated bone marrow cells were used to evaluate the influence of midazolam on monocytes in vitro.

Results: Midazolam prevented liver tissue injury and decreased serum alanine transaminase (ALT) level in LPS plus galactosamine treated mice. Mechanistically, midazolam suppressed tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) produced by LPS stimulated liver macrophages in vivo and bone marrow monocytes in vitro, and reduced the expression of major histocompatibility complex class II (MHC II), cluster of differentiation 40 and 86 (CD40 and CD86) on the cell surface. These results could be reversed by PK-11195, a peripheral benzodiazepine receptor (PBR) blocker.

Conclusion: Midazolam can prevent liver from LPS-induced immune mediated liver injury by inhibiting inflammation and immune activation in liver macrophages.

MIF and D-DT are potential disease severity modifiers in male MS subjects

Little is known about mechanisms that drive the development of progressive multiple sclerosis (MS), although inflammatory factors, such as macrophage migration inhibitory factor (MIF), its homolog D-dopachrome tautomerase (D-DT), and their common receptor CD74 may contribute to disease worsening. Our findings demonstrate elevated MIF and D-DT levels in males with progressive disease compared with relapsing-remitting males (RRMS) and female MS subjects, with increased levels of CD74 in females vs. males with high MS disease severity. Furthermore, increased MIF and D-DT levels in males with progressive disease were significantly correlated with the presence of two high-expression promoter polymorphisms located in the MIF gene, a -794CATT_5-8 microsatellite repeat and a -173 G/C SNP. Conversely, mice lacking MIF or D-DT developed less-severe signs of experimental autoimmune encephalomyelitis, a murine model of MS, thus implicating both homologs as copathogenic contributors. These findings indicate that genetically controlled high MIF expression (and D-DT) promotes MS progression in males, suggesting that these two factors are sex-specific disease modifiers and raising the possibility that aggressive anti-MIF treatment of clinically isolated syndrome or RRMS males with a high-expresser genotype might slow or prevent the onset of progressive MS. Additionally, selective targeting of MIF:CD74 signaling might provide an effective, trackable therapeutic approach for MS subjects of both sexes.

NADPH oxidase 4 is required for the generation of macrophage migration inhibitory factor and host defense against Toxoplasma gondii infection

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox) are an important family of catalytic enzymes that generate reactive oxygen species (ROS), which mediate the regulation of diverse cellular functions. Although phagocyte Nox2/gp91phox is closely associated with the activation of host innate immune responses, the roles of Nox family protein during Toxoplasma gondii (T. gondii) infection have not been fully investigated. Here, we found that T. gondii-mediated ROS production was required for the upregulation of macrophage migration inhibitory factor (MIF) mRNA and protein levels via activation of mitogen-activated protein kinase and nuclear factor-κB signaling in macrophages. Interestingly, MIF knockdown led to a significant increase in the survival of intracellular T. gondii in bone marrow-derived macrophages (BMDMs). Moreover, Nox4 deficiency, but not Nox2/gp91phox and the cytosolic subunit p47phox, resulted in enhanced survival of the intracellular T. gondii RH strain and impaired expression of T. gondii-mediated MIF in BMDMs. Additionally, Nox4-deficient mice showed increased susceptibility to virulent RH strain infection and increased cyst burden in brain tissues and low levels of MIF expression following infection with the avirulent ME49 strain. Collectively, our findings indicate that Nox4-mediated ROS generation plays a central role in MIF production and resistance to T. gondii infection.

Monocyte Conversion During Inflammation and Injury

Monocytes are circulating leukocytes important in both innate and adaptive immunity, primarily functioning in immune defense, inflammation, and tissue remodeling. There are 2 subsets of monocytes in mice (3 subsets in humans) that are mobilized from the bone marrow and recruited to sites of inflammation, where they carry out their respective functions in promoting inflammation or facilitating tissue repair. Our understanding of the fate of these monocyte subsets at the site of inflammation is constantly evolving. This brief review highlights the plasticity of monocyte subsets and their conversion during inflammation and injury.

Altered Macrophage and Dendritic Cell Response in Mif-/- Mice Reveals a Role of Mif for Inflammatory-Th1 Response in Type 1 Diabetes

Macrophage migration inhibitory factor (Mif) is highly expressed in type 1 diabetes mellitus (T1DM). However, there is limited information about how Mif influences the activation of macrophages (Mφ) and dendritic cells (DC) in T1DM. To address this issue, we induced T1DM by administering multiple low doses of streptozotocin (STZ) to Mif-/- or wild-type (Wt) BALB/c mice. We found that Mif-/- mice treated with STZ (Mif-/-STZ) developed lower levels of hyperglycemia, inflammatory cytokines, and specific pancreatic islet antigen- (PIAg-) IgG and displayed reduced cellular infiltration into the pancreatic islets compared to Wt mice treated with STZ (WtSTZ). Moreover, Mφ and DC from Mif-/-STZ displayed lower expression of MHC-II, costimulatory molecules CD80, CD86, and CD40, Toll-like receptor- (TLR-) 2, and TLR-4 than WtSTZ. These changes were associated with a reduced capacity of Mφ and DC from Mif-/-STZ to induce proliferation in ovalbumin-specific T cells. All the deficiencies observed in Mif-/-STZ were recovered by exogenous administration of recombinant Mif. These findings suggest that Mif plays a role in the molecular mechanisms of Mφ and DC activation and drives T cell responses involved in the pathology of T1DM. Therefore, Mif is a potential therapeutic target to reduce the pathology of T1DM.