Macrophage Migration Inhibitory Factor Knockout Mice Research Articles

Abstract 13208: A Small Molecule Macrophage Migration Inhibitory Factor Agonist Ameliorates Age-Related Myocardial Intolerance to Ischemia-Reperfusion Insults via Metabolic Regulation

Introduction: The macrophage migration inhibitory factor (MIF) is emerged as a critical mediator during myocardia ischemia and reperfusion (I/R). An impaired MIF signaling is occurred in aging. MIF agonist, MIF20, can argument cardiac MIF signaling through increasing the binding affinity between MIF and its receptor, CD74/CD44. Hypothesis: Administration of MIF20 can increase the resistance of aged myocardium to ischemic insults caused by I/R via modulating the MIF signaling regulated energy metabolism. Methods: Young (3-5 months) and aged (24-26 months) wild-type C57BL/6J mice, cardiomyocyte specific MIF knock out C57BL/6J mice (cMIF-/-) and wild type littermates (MIF flox/flox ) were injected with MIF20 (0.15 μg/kg, I.V.) 5 minutes before reperfusion after 45 minutes of ischemia. The left ventricular myocardium was for immunoblotting, NAD/NADH assay, and metabolomics analysis. The working heart perfusion and the SeaHorse system were for metabolic measurements. Results: The small molecule MIF agonist, MIF20, which binds to MIF to increase signaling through its cognate receptor CD74/CD44 not only decreases infarct size but also preserves cardiac systolic function in the aged versus young hearts. MIF20 contributes to the maintenance of mitochondrial fitness and preserves the contractility of cardiomyocytes under hypoxia and reoxygenation stress. These beneficial effects of MIF20 are reduced in cardiomyocyte-specific MIF knock-out (cMIF -/- ) versus littermates (MIF flox/flox ) mice, supporting the autocrine role of MIF in mediating ischemic cardiac protection. The age-related disruption of metabolic homeostasis in aged versus young hearts was modulated by MIF20’s ability to upregulate glucose oxidation and downregulate the oxidation of fatty acid. These actions were associated with an upregulation of pyruvate dehydrogenase kinase 4 (PDK4) and downregulation of Long-chain acyl-CoA dehydrogenase (LCAD). MIF20 as MIF signaling agonism modulation of metabolic adaptation in aged hearts further led to reduced generation of reactive oxygen species (ROS) in the myocardium. Conclusions: MIF agonists such as MIF20 may have a therapeutic role by limiting cardiac damage and rescuing cardiac dysfunctions of senescent hearts to I/R stress.

The impact of MIF deficiency on alterations of fecal microbiota in C57BL/6 mice induced by Trichinella spiralis infection.

Trichinellosis caused by Trichinella spiralis (T. spiralis) is a major food-borne parasitic zoonosis worldwide. Prevention of trichinellosis is an effective strategy to improve patient quality of life. Macrophage migration inhibitory factor (MIF) is closely related to the occurrence and development of several parasitic diseases. Studying the impact of MIF deficiency (Mif-/- ) on the alterations in host fecal microbiota due to T. spiralis infection may contribute to proposing a novel dual therapeutic approach for trichinellosis. To reveal the diversity and differences in fecal microbial composition, feces were collected from T. spiralis-uninfected and T. spiralis-infected wild-type (WT) and MIF knockout (KO) C57BL/6 mice at 0, 7, 14, and 35 days post-infection (dpi), and the samples were sent for 16S rRNA amplicon sequencing on the Illumina NovaSeq platform. Flow cytometry was used to determine the expression levels of IFN-γ and IL-4 in the CD4+ /CD8+ T-cell sets of mouse spleens. The results showed that operational taxonomic unit (OTU) clustering, relative abundance of microbial composition, alpha diversity, and beta diversity exhibited significant changes among the eight groups. The LEfSe analysis selected several potential biomarkers at the genus or species level, including Akkermansia muciniphila, Lactobacillus murinus, Coprococcus catus, Firmicutes bacterium M10_2, Parabacteroides sp. CT06, and Bacteroides between the KTs and WTs groups. The predicted bacterial functions of the fecal microbiota were mainly involved in metabolism, such as the metabolism of carbohydrates, amino acids, energy, cofactors, vitamins, nucleotides, glycans, and lipids. Flow cytometry revealed an increased CD3+ CD8- /CD3+ CD8+ T-cell ratio and increased IFN-γ and IL-4 levels in CD3+ CD8- T-cell sets from WT and MIF KO mice at 7 dpi. The results indicated that both MIF KO and infection time have a significant influence on the CD3+ CD8- IFN-γ+ and CD3+ CD8- IL-4+ response in mice after T. spiralis. In conclusion, this research showed alterations of the fecal microbiota and immune response in both WT and MIF KO mice before and after T. spiralis infection. These results revealed a potential role of MIF in regulating the pathogenesis of trichinellosis related to the intestinal microbiota. Importantly, the selected potential biomarkers combined with MIF will also offer a novel therapeutic approach to treat trichinellosis in the future.

1615-P: The Peripheral and Central Cross Talk Mediated by Adipose MIF—A Novel Mechanism of Hyperphagia following Olanzapine Treatment

Olanzapine is one of the first-line antipsychotic medications but it usually induces metabolic side effects, characterized by obesity. We previously indicated that olanzapine leads to hyperphagia through the effects of a proinflammatory cytokine, macrophage migration inhibitory factor (MIF) in the hypothalamus. However, whether olanzapine's upregulated peripheral MIF could affect the central mechanism is currently unknown. Our present study found that olanzapine increases ectopic expression of dopamine receptor 1 (DRD1) in adipocytes which relatively upregulates MIF expression and release through a PKA/CREB signaling pathway. In global MIF knockout mice, MIF accumulation appears in the hypothalamus following peripheral injection of recombinant MIF proteins, suggesting that peripheral MIF indeed travels to the hypothalamus. Mif Lung Tg mice (MIF overexpression in the lung) with increased circulating MIF levels had hyperphagia and activation of the CaMKKβ/AMPK/AgRP signaling pathway in the hypothalamus. Overall, our study for the first time proved that adipose-derived MIF is a crucial factor in regulating metabolic side effects induced by olanzapine. Disclosure X.Chen: None. Y.Huang: None. Y.Qi: None. L.Chen: None. L.Li: None. P.Gao: None. D.Cui: None. D.Qi: None. Funding National Sciences and Engineering Research Council of Canada (RGPIN-2017-04542); Canadian Institutes of Health Research (PJT-156116); China Scholarship Council (202106230212)

Inhibition of macrophage migration inhibitory factor (MIF) suppresses apoptosis signal-regulating kinase 1 to protect against liver ischemia/reperfusion injury.

Background: Hepatic ischemia–reperfusion (I/R) injury is a major complication leading to surgical failures in liver resection, transplantation, and hemorrhagic shock. The role of cytokine macrophage migration inhibitory factor (MIF) in hepatic I/R injury is unclear. Methods: We examined changes of MIF expression in mice after hepatic I/R surgery and hepatocytes challenged with hypoxia–reoxygenation (H/R) insult. Subsequently, MIF global knock-out mice and mice with adeno-associated-virus (AAV)-delivered MIF overexpression were subjected to hepatic I/R injury. Hepatic histology, the inflammatory response, apoptosis and oxidative stress were monitored to assess liver damage. The molecular mechanisms of MIF function were explored in vivo and in vitro. Results: MIF was significantly upregulated in the serum whereas decreased in liver tissues of mice after hepatic I/R injury. MIF knock-out effectively attenuated I/R -induced liver inflammation, apoptosis and oxidative stress in vivo and in vitro, whereas MIF overexpression significantly aggravated liver injury. Via RNA-seq analysis, we found a significant decreased trend of MAPK pathway in MIF knock-out mice subjected hepatic I/R surgery. Using the apoptosis signal-regulating kinase 1 (ASK1) inhibitor NQDI-1 we determined that, mechanistically, the protective effect of MIF deficiency on hepatic I/R injury was dependent on the suppressing of the ASK1-JNK/P38 signaling pathway. Moreover, we found MIF inhibitor ISO-1 alleviate hepatic I/R injury in mice. Conclusion: Our results confirm that MIF deficiency suppresses the ASK1-JNK/P38 pathway and protects the liver from I/R -induced injury. Our findings suggest MIF as a novel biomarker and therapeutic target for the diagnosis and treatment of hepatic I/R injury.

Macrophage migration inhibitory factor contributes to immunopathogenesis during Plasmodium yoelii 17XL infection.

Macrophage migration inhibitory factor (MIF) is a cytokine recognized regulator of the inflammatory immune response associated with several immune cells that produce inflammatory cytokines such as IL-1β, IL-6, IL-12, IL-18, and TNF-α. This study aimed to understand the effect of MIF on the immune response and pathogenesis during Plasmodium infection. Wild-type (Wt) and MIF knockout (Mif -/-) mice were intravenously infected with 1×103 Plasmodium yoelii (Py) 17XL-parasitized red blood cells. Our data showed that Py17XL-infected Wt mice died 11 days postinfection, while Mif -/- mice showed reduced parasitemia and an increase in their survival at day 11 up to 58%, importantly they succumb up to day 21 postinfection. The increased survival rate in Mif -/- mice was associated with less severe cachexia and anemia as a result of a mixed Th1/Th2 cytokine profile, high levels of IL-12, IL-17/IL-4, and IL-10 in serum; and high levels of IL-4 and IL-10, and low levels of IFN-γ in spleen cells compared to Py17XL infected Wt mice. Moreover, macrophages (Mφs) from Mif -/- mice exhibited higher concentrations of IL-10 and IL-12 and reduced levels of TNF-α and nitric oxide (NO) compared to Py17XL-infected Wt mice. These results demonstrate that MIF has an important role in regulating the immune response associated with host pathogenesis and lethality, which is relevant to consider in preventing/reducing complications in Plasmodium infections.

MIF promotes neurodegeneration and cell death via its nuclease activity following traumatic brain injury.

Traumatic brain injury (TBI), often induced by sports, car accidents, falls, or other daily occurrences, is a primary non-genetically related risk factor for the development of subsequent neurodegeneration and neuronal cell death. However, the molecular mechanisms underlying neurodegeneration, cell death, and neurobehavioral dysfunction following TBI remain unclear. Here, we found that poly(ADP-ribose) polymerase-1 (PARP-1) was hyperactivated following TBI and its inhibition reduced TBI-induced brain injury. Macrophage migration inhibitory factor (MIF), a newly identified nuclease involved in PARP-1-dependent cell death, was translocated from the cytosol to the nucleus in cortical neurons following TBI and promoted neuronal cell death in vivo. Genetic deletion of MIF protected neurons from TBI-induced dendritic spine loss, morphological complexity degeneration, and subsequent neuronal cell death in mice. Moreover, MIF knockout reduced the brain injury volume and improved long-term animal behavioral rehabilitation. These neuroprotective effects in MIF knockout mice were reversed by the expression of wild-type MIF but not nuclease-deficient MIF mutant. In contrast, genetic deletion of MIF did not alter TBI-induced neuroinflammation. These findings reveal that MIF mediates TBI-induced neurodegeneration, neuronal cell death and neurobehavioral dysfunction through its nuclease activity, but not its pro-inflammatory role. Targeting MIF's nuclease activity may offer a novel strategy to protect neurons from TBI.

MIF inhibits myeloid derived suppressor cell mediated immunosuppression by promoting an inflammatory M1 phenotypic shift

Cancers of the oral cavity and pharynx contribute 3% of yearly cancer cases in the United States, primarily as head and neck squamous cell carcinoma (HNSCC). HNSCC presents with a five-year survival rate of 66.2%, with primary risk factors being alcohol abuse or human papillomavirus infection. Myeloid derived suppressor cells (MDSC) are a myeloid lineage cell population known to accumulate within HNSCC tumors and promote a pro-tumor microenvironment by suppressing the host immune response against tumor cells. Macrophage migration inhibitory factor (MIF) is a cytokine released by immune cells and mediates inflammatory and chemotactic effects upon interaction with its receptor, CD74, expressed by antigen presenting cells (APC), including MDSC. Given their role in promoting tumor growth, our group sought to elucidate the function of host versus tumor cell derived MIF on MDSC. Given the chemotactic effects of MIF upon APC, we hypothesized that knockdown of Mif gene expression would result in a better outcome and reduced tumor burden as a result of reduced MDSC accumulation within the primary tumor microenvironment. Using murine HNSCC cell lines LY2 and MOC2 in conjunction with Mif+/+, Mif-/- and myeloid specific MIF knockout mice (m-Mif-/-), our group has revealed an anti-immunosuppressive role for host-derived MIF through its interaction with MDSC, with tumor derived MIF being immunosuppressive in nature. After injection of the tumor cell lines into the buccal mucosa of age matched mice, we monitored tumor development until terminal sacrifice. At this point, we extracted tumor cells for flow cytometric analysis and isolated tumor associated Gr-1+ MDSC. Extracted MDSC were co-cultured with naïve T cells fluorescently labeled with CFSE, to enable quantification of suppression of T cell proliferation. Furthermore, we extracted isolated MDSC RNA for analysis by RT-qPCR. Unexpectedly, our initial finding ran contrary to our hypothesis, as we found that Mif-/- mice had a mean tumor burden of 108.3 mg compared to Mif+/+ mice who presented with a mean tumor of only 64 mg (p = 0.00624). Flow cytometry revealed increased CD11b+ F4/80+ macrophages in mice expressing MIF. Interestingly, a smaller proportion of these cells were identified as MDSC in Mif+/+ and m-Mif-/- compared to Mif-/-, determined by expression of MDSC markers Ly6G and Ly6C. Our group found that both Mif+/+ and m-Mif-/- demonstrated reduced suppression of T cell proliferation compared to Mif-/-. Gene expression analysis revealed in Mif-/- MDSC upregulation of immunosuppressive genes Arg1, Ptgs2, S100a8 and S100a9. Seeing that both Mif+/+ and m-Mif-/- demonstrate similar anti-tumor phenotypic and molecular responses to HNSCC, our group has concluded that in response to host derived, but not tumor derived, MIF, MDSC at the tumor site shift towards a more anti-tumor M1 phenotype and additionally that MIF derived from non-myeloid host sources within the tumor microenvironment are sufficient to stimulate this response.

Macrophage migration inhibitory factor inhibition as a novel therapeutic approach against triple-negative breast cancer

Triple-negative breast cancer (TNBC), defined as loss of estrogen, progesterone, and Her2 receptors, is a subtype of highly aggressive breast cancer with worse prognosis and poor survival rate. Macrophage migration inhibitory factor (MIF) is a pleiotropic pro-inflammatory cytokine aberrantly expressed in many solid tumors and known to promote tumor progression and metastasis. However, its role in TNBC progression and metastasis is unexplored. Here we have shown that in TNBC patients, MIF expression was significantly enriched in the tumor compared to adjacent normal tissue. Using publically available patient datasets, we showed that MIF overexpression correlates with worse survival in TNBC compared to other hormonal status. Orthotopic implantation of TNBC cells into MIF knockout mice showed reduced tumor growth compared to wild-type mice. In addition, we have shown that MIF downregulation inhibits TNBC growth and progression in a syngeneic mouse model. We further showed that CPSI-1306, a small-molecule MIF inhibitor, inhibits the growth of TNBC cells in vitro. Mechanistic studies revealed that CPSI-1306 induces intrinsic apoptosis by alteration in mitochondrial membrane potential, cytochrome c (Cyt c) release, and activation of different caspases. In addition, CPSI-1306 inhibits the activation of cell survival and proliferation-related molecules. CPSI-1306 treatment also reduced the tumor growth and metastasis in orthotopic mouse models of mammary carcinoma. CPSI-1306 treatment of tumor-bearing mice significantly inhibited TNBC growth and pulmonary metastasis in a dose-dependent manner. Histological analysis of xenograft tumors revealed a higher number of apoptotic cells in CPSI-1306-treated tumors compared to vehicle controls. Our studies, for the first time, show that MIF overexpression in TNBC enhances growth and metastasis. Taken together, our results indicate that using small molecular weight MIF inhibitors could be a promising strategy to inhibit TNBC progression and metastasis.

Identification of molecules associated with disease progression of autoimmune myocarditis to dilated cardiomyopathy

Abstract Myocarditis is an inflammatory disease characterized by immune infiltrates into the myocardium. In many patients, the disease progresses to a chronic phase dilated cardiomyopathy (DCM) in which there is extensive fibrosis leading to ventricular dilation and impaired cardiac function. Less than 50% of these patients survive more than 5 years. Immunosuppressive treatments such as corticosteroids (CSs) are effective in managing the acute phase of the disease, but do not prevent progression to the DCM. Using the experimental autoimmune myocarditis (EAM) animal model, we previously demonstrated that the inflammatory cytokine macrophage migration inhibitory factor (MIF) plays a role in resistance to CS treatment. MIF knockout mice were treated with the corticosteroid Dexamethasone (Dex) and proved to be resistant to both EAM and DCM. We also observed that treatment with MIF inhibitors and Dex decreased the expression of chemokines and adhesion molecules and implicated these molecules in the progression of disease. Within these, osteopontin (OPN), a powerful chemoattractant, was downregulated. We hypothesized that OPN plays a role in the disease process and investigated its role in EAM and DCM using OPN knockout mice. Our results show that OPN knockout mice developed EAM, but that progression to DCM was impaired. Furthermore, we observed a decrease in CD45+CD133+ fibroblast progenitor cells infiltrating the myocardium in the absence of OPN, which could contribute to attenuated disease in KO mice. This study may provide insights into the mechanisms driving progression of EAM to DCM and point to potential therapeutic targets.

Knockout of macrophage migration inhibitory factor accentuates side-stream smoke exposure-induced myocardial contractile dysfunction through dysregulated mitophagy

Second hand smoke exposure increases the prevalence of chronic diseases partly attributed to inflammatory responses. Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, is involved in the pathogenesis of multiple diseases although its role in second hand smoke exposure-induced cardiac anomalies remains elusive. This study evaluated the impact of MIF knockout on side-stream smoke exposure-induced cardiac pathology and underlying mechanisms. Adult WT and MIF knockout (MIFKO) mice were placed in a chamber exposed to cigarette smoke for 1 h daily for 60 consecutive days. Echocardiographic, cardiomyocyte function and intracellular Ca2+ handling were evaluated. Autophagy, mitophagy and apoptosis were examined using western blot. DHE staining was used to evaluate superoxide anion (O2−) generation. Masson trichrome staining was employed to assess interstitial fibrosis. Our data revealed that MIF knockout accentuated side-stream smoke-induced cardiac anomalies in fractional shortening, cardiomyocyte function, intracellular Ca2+ homeostasis, myocardial ultrastructure and mitochondrial content along with overt apoptosis and O2− generation. In addition, unfavorable effects of side-stream smoke were accompanied by excessive formation of autophagolysosome and elevated TFEB, the effect of which was exacerbated by MIF knockout. Recombinant MIF rescued smoke extract-induced myopathic anomalies through promoting AMPK activation, mitophagy and lysosomal function. Taken together, our data suggest that MIF serves as a protective factor against side-stream smoke exposure-induced myopathic changes through facilitating mitophagy and autophagolysosome formation.

The role of MIF in chronic lung diseases: looking beyond inflammation.

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that has been associated with many diseases. Most studies found in literature describe MIF as a proinflammatory cytokine involved in chronic inflammatory conditions, but evidence from last years suggests that many of its key effects are not directly related to inflammation. In fact, MIF is constitutively expressed in most human tissues and in some cases in high levels, which does not reflect the pattern of expression of a classic proinflammatory cytokine. Moreover, MIF is highly expressed during embryonic development and decreases during adulthood, which point toward a more likely role as growth factor. Accordingly, MIF knockout mice develop age-related spontaneous emphysema, suggesting that MIF presence (e.g., in younger individuals and wild-type animals) is part of a healthy lung. In view of this new line of evidence, we aimed to review data on the role of MIF in the pathogenesis of chronic lung diseases.

Mitochondrial DNA alterations in aged macrophage migration inhibitory factor-knockout mice

The age-induced, exponential accumulation of mitochondrial DNA (mtDNA) deletion mutations contributes to muscle fiber loss. The causes of these mutations are not known. Systemic inflammation is associated with decreased muscle mass in older adults and is implicated in the formation of sporadic mtDNA deletions. Macrophage migration inhibitory factor knockout (MIF-KO) mice are long-lived with decreased inflammation. We hypothesized that aged MIF-KO mice would have lower mtDNA deletion frequencies and fewer electron transport chain (ETC) deficient fibers.We measured mtDNA copy number and mutation frequency as well as the number and length of ETC deficient fibers in 22-month old MIF-KO and F2 hybrid control mice. We also measured mtDNA copy number and deletion frequency in female UM-HET3 mice, a strain whose lifespan matches the MIF-KO mice.We did not observe a significant effect of MIF ablation on muscle mtDNA deletion frequency. There was a significantly lower mtDNA copy number in the MIF-KO mice and the lifespan-matched UM-HET3 mice compared to the F2 hybrids, suggesting the importance of genetic background in mtDNA copy number control. Our data do not support a definitive role for MIF in age-induced mtDNA deletions.

Macrophage migration inhibitory factor promotes renal injury induced by ischemic reperfusion.

Macrophage migration inhibitory factor (MIF) is pleiotropic cytokine that has multiple effects in many inflammatory and immune diseases. This study reveals a potential role of MIF in acute kidney injury (AKI) in patients and in kidney ischemic reperfusion injury (IRI) mouse model in MIF wild‐type (WT) and MIF knockout (KO) mice. Clinically, plasma and urinary MIF levels were largely elevated at the onset of AKI, declined to normal levels when AKI was resolved and correlated tightly with serum creatinine independent of disease causes. Experimentally, MIF levels in plasma and urine were rapidly elevated after IRI‐AKI and associated with the elevation of serum creatinine and the severity of tubular necrosis, which were suppressed in MIF KO mice. It was possible that MIF may mediate AKI via CD74/TLR4‐NF‐κB signalling as mice lacking MIF were protected from AKI by largely suppressing CD74/TLR‐4‐NF‐κB associated renal inflammation, including the expression of MCP‐1, TNF‐α, IL‐1β, IL‐6, iNOS, CXCL15(IL‐8 in human) and infiltration of macrophages, neutrophil, and T cells. In conclusion, our study suggests that MIF may be pathogenic in AKI and levels of plasma and urinary MIF may correlate with the progression and regression of AKI.

Macrophage migration inhibitory factor plays an essential role in ischemic preconditioning-mediated cardioprotection.

Ischemic preconditioning (IPC) is an endogenous protection strategy against myocardial ischemia-reperfusion (I/R) injury. Macrophage migration inhibitory factor (MIF) released from the myocardium subjected to brief periods of ischemia confers cardioprotection. We hypothesized that MIF plays an essential role in IPC-induced cardioprotection. I/R was induced either ex vivo or in vivo in male wild-type (WT) and MIF knockout (MIFKO) mice with or without proceeding IPC (three cycles of 5-min ischemia and 5-min reperfusion). Indices of myocardial injury, regional inflammation and cardiac function were determined to evaluate the extent of I/R injury. Activations of the reperfusion injury salvage kinase (RISK) pathway, AMP-activated protein kinase (AMPK) and their downstream components were investigated to explore the underlying mechanisms. IPC conferred prominent protection in WT hearts evidenced by reduced infarct size (by 33-35%), myocyte apoptosis and enzymatic markers of tissue injury, ROS production, inflammatory cell infiltration and MCP1/CCR2 expression (all P<0.05). IPC also ameliorated cardiac dysfunction both ex vivo and in vivo These protective effects were abolished in MIFKO hearts. Notably, IPC mediated further activations of RISK pathway, AMPK and the membrane translocation of GLUT4 in WT hearts. Deletion of MIF blunted these changes in response to IPC, which is the likely basis for the absence of protective effects of IPC against I/R injury. In conclusion, MIF plays a critical role in IPC-mediated cardioprotection under ischemic stress by activating RISK signaling pathway and AMPK. These results provide an insight for developing a novel therapeutic strategy that target MIF to protect ischemic hearts.

MIF mediates bladder pain, not inflammation, in cyclophosphamide cystitis

Macrophage migration inhibitory factor (MIF), a proinflammatory mediator, is recognized as a player in inflammatory and neuropathic pain. Cyclophosphamide (CYP) results in bladder inflammation and pain and it’s a frequently used animal model of interstitial cystitis/bladder pain syndrome (IC/BPS). Because pretreatment with a MIF inhibitor (ISO-1) prevented both CYP-induced bladder pain and inflammation we used genetic MIF knockout (KO) mice to further investigate MIF’s role in CYP-induced bladder pain and inflammation. Abdominal mechanical threshold measured bladder pain induced by CYP in wild type (WT) and MIF KO mice at several time points (0–48 h). End-point (48 h) changes in micturition parameters and histological signs of bladder inflammation were also evaluated. Abdominal mechanical hypersensitivity developed within 4 h after CYP injection (and lasted for the entire observation period: 48 h) in WT mice. MIF KO mice, on the other hand, did not develop abdominal mechanical hypersensitivity suggesting that MIF is a pivotal molecule in mediating CYP-induced bladder pain. Both WT and MIF KO mice treated with CYP showed histological signs of marked bladder inflammation and showed a significant decrease in micturition volume and increase in frequency. Since both changes were blocked in MIF KO mice by pretreatment with a MIF inhibitor (ISO-1) it is likely these are non-specific effects of ISO-1. MIF mediates CYP-induced bladder pain but not CYP-induced bladder inflammation. The locus of effect (bladder) or central (spinal) for MIF mediation of bladder pain remains to be determined.

Macrophage migration inhibitory factor knockout attenuates endotoxin-induced cardiac dysfunction in mice.

Accumulated evidence suggests that macrophage migration inhibitory factor (MIF) plays a key role not only in acute and chronic inflammatory diseases but also in cardiovascular disease. The cardiac dysfunction is related to lipopolysac-charide (LPS) in sepsis. This study was designed to examine whether MIF mediates LPS-induced cardiac dysfunction and address the mechanisms. Echocardiography, immunohistochemical analysis, cell shortening/re-lengthening, and intracellular Ca2+ fluores-cence evaluation were performed in whole hearts and isolated cardiomyocytes from C57 and MIF knockout mice treated with or without LPS. Reactive oxygen species and protein carbonyl formation were measured. Activation of mitogen-activated protein kinases and endoplasmic reticulum stress markers were evaluated using Western blot analysis. Human umbilical vein endothelial cells (HUVECs) were transfected with lentiviruses carrying short hairpin RNA (shRNA) to inhibit MIF. Echocardiography revealed that cardiac function was impaired and macrophage infiltration was increased in LPS-treated C57 mice. Peak shortening and maximal velocity of shortening/re-lengthening were significantly reduced and the duration of re-lengthening was prolonged in LPS-treated C57 mice. Reactive oxygen species and protein carbonyl levels were increased in LPS-treated C57 mice. These dysfunctional changes were attenuated in MIF knockout mice that were challenged with LPS. Western blot analysis revealed that activated p-JNK, p-ERK, and endoplasmic reticulum stress protein marker expression was decreased in LPS-treated MIF knockout mice. p-ERK and p-JNK levels were knocked down in MIF shRNA-transfected HUVECs. The data collectively suggest that MIF mediates LPS-induced cardiac dysfunction in murine cardiomyocytes, which was attenuated by MIF knockout, and the therapeutic option with regard to MIF may aid the management of cardiac dysfunction in sepsis.

Macrophage migration inhibitory factor mediates protease-activated receptor 4-induced bladder pain through urothelial high mobility group box 1.

Macrophage migration inhibitory factor (MIF) mediates pain although the mechanisms are not well understood. Urothelial activation of protease activated receptor 4 (PAR4) results in urothelial MIF release, urothelial high mobility group box 1 (HMGB1) release and bladder pain in mice without bladder inflammation. All three effects are prevented by MIF inhibition while intravesical disulfide HMGB1 alone can induce bladder pain. This study utilizes genetic MIF deletion to determine whether MIF mediates PAR4‐induced bladder pain and is upstream of HMGB1‐induced bladder pain. Wild type (C57/BL6) and MIF knockout (KO) mice were treated with intravesical PAR4 activating peptide or disulfide HMGB1 and tested for abdominal mechanical hypersensitivity at baseline (before treatment) and 24 h after injection. Micturition parameters and bladder histology were examined after behavioral test. Real‐time PCR and western blotting measured HMGB1 mRNA and protein levels in the bladders of naïve wild type and MIF KO mice, while immunofluorescence measured HMGB1 protein levels in the urothelium of both strains. Intravesical PAR4 activation resulted in abdominal mechanical hypersensitivity in wild‐type mice but not MIF KO mice. Intravesical disulfide HMGB1 induced abdominal mechanical hypersensitivity in both strains. Neither treatment resulted in significant changes in micturition or bladder histology in either strain. HMGB1 mRNA and protein levels were higher in MIF KO mouse bladders and the urothelium of MIF KO bladder had greater immunostaining than the wild‐type strain. MIF is a pivotal molecule mediating PAR4‐induced bladder pain and regulating urothelial HMGB1 production and release to elicit bladder pain.

Macrophage Migration Inhibitory Factor (MIF) Deficiency Exacerbates Aging-Induced Cardiac Remodeling and Dysfunction Despite Improved Inflammation: Role of Autophagy Regulation.

Aging leads to unfavorable geometric and functional sequelae in the heart. The proinflammatory cytokine macrophage migration inhibitory factor (MIF) plays a role in the maintenance of cardiac homeostasis under stress conditions although its impact in cardiac aging remains elusive. This study was designed to evaluate the role of MIF in aging-induced cardiac anomalies and the underlying mechanism involved. Cardiac geometry, contractile and intracellular Ca2+ properties were examined in young (3–4 mo) or old (24 mo) wild type and MIF knockout (MIF−/−) mice. Our data revealed that MIF knockout exacerbated aging-induced unfavorable structural and functional changes in the heart. The detrimental effect of MIF knockout was associated with accentuated loss in cardiac autophagy with aging. Aging promoted cardiac inflammation, the effect was attenuated by MIF knockout. Intriguingly, aging-induced unfavorable responses were reversed by treatment with the autophagy inducer rapamycin, with improved myocardial ATP availability in aged WT and MIF−/− mice. Using an in vitro model of senescence, MIF knockdown exacerbated doxorubicin-induced premature senescence in H9C2 myoblasts, the effect was ablated by MIF replenishment. Our data indicated that MIF knockout exacerbates aging-induced cardiac remodeling and functional anomalies despite improved inflammation, probably through attenuating loss of autophagy and ATP availability in the heart.

Behavioural and neurobiological consequences of macrophage migration inhibitory factor gene deletion in mice.

BackgroundEvidence from clinical studies and animal models show that inflammation can lead to the development of depression. Macrophage migration inhibitory factor (MIF) is an important multifunctional cytokine that is synthesized by several cell types in the brain. MIF can increase production of other cytokines, activates cyclooxygenase (COX)-2 and can counter-regulate anti-inflammatory effects of glucocorticoids. Increased plasma levels of MIF are associated with hypothalamic–pituitary–adrenal (HPA) axis dysregulation and depressive symptoms in patients. In contrast, MIF knockout (KO) mice have been found to exhibit increased depressive-like behaviour. The exact role for MIF in depression is therefore still controversial. To further understand the role of MIF in depression, we studied depressive-like behaviour in congenic male and female MIF KO mice and wild-type (WT) littermates and the associated neurobiological mechanisms underlying the behavioural outcome.MethodsMIF KO and WT mice were tested for spontaneous locomotor activity in the open-field test, anhedonia-like behaviour in the sucrose preference test (SPT), as well as behavioural despair in the forced swim test (FST) and tail suspension test (TST). Brain and serum levels of cytokines, the enzymes COX-2 and indoleamine-2,3-dioxygenase (IDO) and the glucocorticoid hormone corticosterone were measured by RT-qPCR and/or high-sensitivity electrochemiluminescence-based multiplex immunoassays. Monoamines and metabolites were examined using HPLC.ResultsWe found that MIF KO mice of both sexes displayed decreased depressive-like behaviour as measured in the FST. In the TST, a similar, but non-significant, trend was also found. IFN-γ levels were decreased, and dopamine metabolism increased in MIF KO mice. Decreased brain IFN-γ levels predicted higher striatal dopamine levels, and high dopamine levels in turn were associated with reduced depressive-like behaviour. In the SPT, there was a sex-specific discrepancy, where male MIF KO mice showed reduced anhedonia-like behaviour whereas female KO mice displayed increased anhedonia-like behaviour. Our results suggest that this relates to the increased corticosterone levels detected in female, but not male, MIF KO mice.ConclusionsOur findings support that MIF is involved in the generation of depressive-like symptoms, potentially by the effects of IFN-γ on dopamine metabolism. Our data further suggests a sex-specific regulation of the involved mechanisms.

Macrophage migration inhibitory factor promotes resistance to glucocorticoid treatment in EAE.

Objective:Glucocorticoids (GCs) are used as standard treatment for acute attacks of multiple sclerosis (MS). However, GCs eventually lose efficacy and do not prevent disease progression. Macrophage migration inhibitory factor (MIF) is the only known proinflammatory cytokine induced by GCs that inhibits their anti-inflammatory effects. Therefore, we investigated whether MIF plays a role in resistance to GC treatment in experimental autoimmune encephalomyelitis (EAE), an animal model of MS.Methods:EAE was induced in wild-type (Wt) and MIF knockout (MIF−/−) mice followed by treatment with dexamethasone (Dex) before or upon disease onset. Splenocytes and brain mononuclear cells were harvested for cytokine ELISPOT assay and flow cytometry analysis.Results:Treatment of EAE with Dex was substantially more efficacious in MIF−/− mice than Wt mice. Dex treatment decreased MOG35-55–induced cytokine production by Wt or MIF−/− CD4+ T cells only at the onset of EAE but inhibited upregulation of T-bet during acute and chronic phases of disease, particularly in MIF−/− mice. Furthermore, passive EAE induced by adoptive transfer of T cells showed that Dex was highly effective in ameliorating disease induced by MIF−/− CD4+ T cells but not by Wt CD4+ T cells. The expression of T-bet and VLA-4 was decreased in CD4+ T cells in MIF−/− mice compared with Wt mice.Conclusions:Our data establish MIF as a key molecule in resistance of pathogenic CD4+ T cells to GC treatment in EAE and as a potential target to enhance the effectiveness of steroid treatment in neuroinflammatory disorders.