Redox regulation of macrophage migration inhibitory factor expression in rat neurons

The roles of macrophage migration inhibitory factor in retinal diseases

Macrophage migration inhibitory factor (MIF), a multifunctional cytokine, is secreted by various cells and participates in inflammatory reactions, including innate and adaptive immunity. There are some evidences that MIF is involved in many vitreoretinal diseases. For example, MIF can exacerbate many types of uveitis; measurements of MIF levels can be used to monitor the effectiveness of uveitis treatment. MIF also alleviates trauma-induced and glaucoma-induced optic nerve damage. Furthermore, MIF is critical for retinal/choroidal neovascularization, especially complex neovascularization. MIF exacerbates retinal degeneration; thus, anti-MIF therapy may help to mitigate retinal degeneration. MIF protects uveal melanoma from attacks by natural killer cells. The mechanism underlying the effects of MIF in these diseases has been demonstrated: it binds to cluster of differentiation 74, inhibits the c-Jun N-terminal kinase pathway, and triggers mitogen-activated protein kinases, extracellular signal-regulated kinase-1/2, and the phosphoinositide-3-kinase/Akt pathway. MIF also upregulates Toll-like receptor 4 and activates the nuclear factor kappa-B signaling pathway. This review focuses on the structure and function of MIF and its receptors, including the effects of MIF on uveal inflammation, retinal degeneration, optic neuropathy, retinal/choroidal neovascularization, and uveal melanoma.

Molecular profiling of sponge deflation reveals an ancient relaxant-inflammatory response

A hallmark of animals is the coordination of whole-body movement. Neurons and muscles are central to this, yet coordinated movements also exist in sponges that lack these cell types. Sponges are sessile animals with a complex canal system for filter-feeding. They undergo whole-body movements resembling "contractions" that lead to canal closure and water expulsion. Here, we combine live 3D optical coherence microscopy, pharmacology, and functional proteomics to elucidate the sequence and detail of shape changes, the tissues and molecular physiology involved, and the control of these movements. Morphometric analysis and targeted perturbation suggest that the movement is driven by the relaxation of actomyosin stress fibers in epithelial canal cells, which leads to whole-body deflation via collapse of the incurrent and expansion of the excurrent canal system. Thermal proteome profiling and quantitative phosphoproteomics confirm the control of cellular relaxation by an Akt/NO/PKG/PKA pathway. Agitation-induced deflation leads to differential phosphorylation of proteins forming epithelial cell junctions, implying their mechanosensitive role. Unexpectedly, untargeted metabolomics detect a concomitant decrease in antioxidant molecules during deflation, reflecting an increase in reactive oxygen species. Together with the secretion of proteinases, cytokines, and granulin, this indicates an inflammation-like state of the deflating sponge reminiscent of vascular endothelial cells experiencing oscillatory shear stress. These results suggest the conservation of an ancient relaxant-inflammatory response of perturbed fluid-carrying systems in animals and offer a possible mechanism for whole-body coordination through diffusible paracrine signals and mechanotransduction.

Molecular profiling of sponge deflation reveals an ancient relaxant-inflammatory response

A hallmark of animals is the coordination of whole-body movement. Neurons and muscles are central to this, yet coordinated movements also exist in sponges that lack these cell types. Sponges are sessile animals with a complex canal system for filter-feeding. They undergo whole-body movements resembling "contractions" that lead to canal closure and water expulsion. Here, we combine 3D optical coherence microscopy, pharmacology, and functional proteomics to elucidate anatomy, molecular physiology, and control of these movements. We find them driven by the relaxation of actomyosin stress fibers in epithelial canal cells, which leads to whole-body deflation via collapse of the incurrent and expansion of the excurrent system, controlled by an Akt/NO/PKG/A pathway. A concomitant increase in reactive oxygen species and secretion of proteinases and cytokines indicate an inflammation-like state reminiscent of vascular endothelial cells experiencing oscillatory shear stress. This suggests an ancient relaxant-inflammatory response of perturbed fluid-carrying systems in animals.

Multifaceted interconnections between macrophage migration inhibitory factor and psychiatric disorders

Inflammation is involved in the pathogenesis of psychiatric disorders. Many previous studies have defined the important roles of inflammatory factors in the pathogenesis, diagnosis, and treatment outcomes of psychiatric disorders. Macrophage migration inhibitory factor (MIF), a pro-inflammatory factor, has been gradually recognized to be involved in the development of neurological diseases in recent years. Our current review focuses on discussing the potential beneficial and detrimental roles of MIF in psychiatric disorders. We will provide new mechanistic insights for the development of potential diagnostic and therapeutic biomarkers based on MIF for psychiatric diseases.

Macrophage migration inhibitory factor derived from spinal cord is involved in activation of macrophages following gecko tail amputation

Macrophages and their initiation of acute inflammation have been defined to be functionally important in tissue repair and regeneration. In injury-induced production of macrophage migration inhibitory factor (MIF), which has been described as a pleiotropic protein that participates in multiple cellular and biologic processes, it is unknown whether it is involved in the regulation of macrophage events during the epimorphic regeneration. In the model of gecko tail amputation, the protein levels of gecko MIF (gMIF) have been determined to be significantly increased in the nerve cells of the spinal cord in association with the recruitment of macrophages to the lesion site. gMIF has been shown to interact with the CD74 receptor to promote the migration of macrophages through activation of Ras homolog gene family member A and to trigger inflammatory responses through MAPK signaling pathways. The determination of microsphere phagocytosis also indicated that gMIF could enhance macrophage phagocytosis. gMIF-mediated recruitment and activation of macrophages have been found to be necessary for gecko tail regeneration, as evidenced by the depletion of macrophages using clodronate liposomes. The results present a novel function of MIF during the epimorphic regeneration, which is beneficial for insights into its pleiotropic property.-Wang, Y., Wei, S., Song, H., Zhang, X., Wang, W., Du, N., Song, T., Liang, H., Chen, X., Wang, Y. Macrophage migration inhibitory factor derived from spinal cord is involved in activation of macrophages following gecko tail amputation.

Macrophage migration inhibitory factor activates inflammatory responses of astrocytes through interaction with CD74 receptor

Astrocytes, the major glial cell population of the central nervous system (CNS), play important physiological roles related to CNS homeostasis. Growing evidence demonstrates that astrocytes trigger innate immune responses under challenge of a variety of proinflammatory cytokines. Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine mainly secreted from monocytes/macrophages, is involved in inflammation-associated pathophysiology. Here, we displayed that expression of MIF significantly increased following spinal cord injury, in colocalization with microglia and astrocytes. MIF elicited inflammatory responses of astrocytes via activation of CD74 receptor and extracellular signal-related kinase (ERK) pathway. Transcriptome analysis revealed that inflammation-related factors cholesterol 25-hydroxylase (Ch25h) and phospholipase A2-IIA (Pla2g2a), downstream of MIF/CD74 axis, were potentially implicated in the mediating inflammatory response of astrocytes. Our results provided a new target for interference of CNS inflammation after insults.

Macrophage migration inhibitory factor: A multifaceted cytokine implicated in multiple neurological diseases

Macrophage migration inhibitory factor (MIF) is a conserved cytokine found as a homotrimer protein. It is found in a wide spectrum of cell types in the body including neuronal and non-neuronal cells. MIF is implicated in several biological processes; chemo-attraction, cytokine activity, and receptor binding, among other functions. More recently, a chaperone-like activity has been added to its repertoire. In this review, we focus on the implication of MIF in the central nervous system and peripheries, its role in neurological disorders, and the mechanisms by which MIF is regulated. Numerous studies have associated MIF with various disease settings. MIF plays an important role in advocating tumorigenic processes, Alzheimer's disease, and is also upregulated in autism-spectrum disorders and spinal cord injury where it contributes to the severity of the injured area. The protective effect of MIF has been reported in amyotrophic lateral sclerosis by its reduction of aggregated misfolded SOD1, subsequently reducing the severity of this disease. Interestingly, a protective as well as pathological role for MIF has been implicated in stroke and cerebral ischemia, as well as depression. Thus, the role of MIF in neurological disorders appears to be diverse with both beneficial and adversary effects. Furthermore, its modulation is rather complex and it is regulated by different proteins, either on a molecular or protein level. This complexity might be dependent on the pathophysiological context and/or cellular microenvironment. Hence, further clarification of its diverse roles in neurological pathologies is warranted to provide new mechanistic insights which may lead in the future to the development of therapeutic strategies based on MIF, to fight some of these neurological disorders.

Novel mechanism within the paraventricular nucleus reduces both blood pressure and hypothalamic pituitary-adrenal axis responses to acute stress

Macrophage migration inhibitory factor (MIF) counteracts pressor effects of angiotensin II (ANG II) in the paraventricular nucleus of the hypothalamus (PVN) in normotensive rats, but this mechanism is absent in spontaneously hypertensive rats (SHRs) due to a lack of MIF in PVN neurons. Since endogenous ANG II in the PVN modulates stress reactivity, we tested the hypothesis that replacement of MIF in PVN neurons would reduce baseline blood pressure and inhibit stress-induced increases in blood pressure and plasma corticosterone in adult male SHRs. Radiotelemetry transmitters were implanted to measure blood pressure, and then an adeno-associated viral vector expressing either enhanced green fluorescent protein (GFP) or MIF was injected bilaterally into the PVN. Cardiovascular responses to a 15-min water stress (1-cm deep, 25°C) and a 60-min restraint stress were evaluated 3-4 wk later. MIF treatment in the PVN attenuated average restraint-induced increases in blood pressure (37.4 ± 2.0 and 27.6 ± 3.5 mmHg in GFP and MIF groups, respectively, P < 0.05) and corticosterone (42 ± 2 and 36 ± 3 μg/dl in GFP and MIF groups, respectively, P < 0.05). MIF treatment in the PVN also reduced stress-induced elevations in the number of c-Fos-positive cells in the rostral ventrolateral medulla (71 ± 5 in GFP and 47 ± 5 in MIF SHRs, P < 0.01) and corticotropin-releasing factor mRNA expression in the PVN. However, MIF had no significant effects on the cardiovascular responses to water stress in SHRs or to either stress in Sprague-Dawley rats. Therefore, viral vector-mediated restoration of MIF in PVN neurons of SHRs attenuates blood pressure and hypothalamic pituitary adrenal axis responses to stress.

Expression of macrophage migration inhibitory factor in the mouse neocortex and posterior piriform cortices during postnatal development

Macrophage migration inhibitory factor (MIF) functions as a pleiotropic protein, participating in a vast array of cellular and biological processes. Abnormal expression of MIF has been implicated in many neurological diseases, including Parkinson's disease, epilepsy, Alzheimer's Disease, stroke, and neuropathic pain. However, the expression patterns of mif transcript and MIF protein from the early postnatal period through adulthood in the mouse brain are still poorly understood. We therefore investigated the temporal and spatial expression of MIF in the mouse neocortex during postnatal development in detail and partially in posterior piriform cortices (pPC). As determined by quantitative real-time PCR (qPCR), mif transcript gradually increased during development, with the highest level noted at postnatal day 30 (P30) followed by a sharp decline at P75. In contrast, Western blotting results showed that MIF increased constantly from P7 to P75. The highest level of MIF was at P75, while the lowest level of MIF was at P7. Immunofluorescence histochemistry revealed that MIF-immunoreactive (ir) cells were within the entire depth of the developed neocortex, and MIF was heterogeneously distributed among cortical cells, especially at P7, P14, P30, and P75; MIF was abundant in the pyramidal layer within pPC. Double immunostaining showed that all the mature neurons were MIF-ir and all the intensely stained MIF-ir cells were parvalbumin positive (Pv +) at adult. Moreover, it was demonstrated that MIF protein localized in the perikaryon, processes, presynaptic structures, and the nucleus in neurons. Taken together, the developmentally regulated expression and the subcellular localization of MIF should form a platform for an analysis of MIF neurodevelopmental biology and MIF-related nerve diseases.

Brain miffed by macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a cytokine which also exhibits enzymatic properties like oxidoreductase and tautomerase. MIF plays a pivotal role in innate and acquired immunity as well as in the neuroendocrine axis. Since it is involved in the pathogenesis of acute and chronic inflammation, neoangiogenesis, and cancer, MIF and its signaling components are considered suitable targets for therapeutic intervention in several fields of medicine. In neurodegenerative and neurooncological diseases, MIF is a highly relevant, but still a hardly investigated mediator. MIF operates via intracellular protein-protein interaction as well as in CD74/CXCR2/CXCR4 receptor-mediated pathways to regulate essential cellular systems such as redox balance, HIF-1, and p53-mediated senescence and apoptosis as well as multiple signaling pathways. Acting as an endogenous glucocorticoid antagonist, MIF thus represents a relevant resistance gene in brain tumor therapies. Alongside this dual action, a functional homolog-annotated D-dopachrome tautomerase/MIF-2 has been uncovered utilizing the same cell surface receptor signaling cascade as MIF. Here we review MIF actions with respect to redox regulation in apoptosis and in tumor growth as well as its extracellular function with a focus on its potential role in brain diseases. We consider the possibility of MIF targeting in neurodegenerative processes and brain tumors by novel MIF-neutralizing approaches.

Murine macrophages response to iron

Macrophages play a critical role at the crossroad between iron metabolism and immunity, being able to store and recycle iron derived from the phagocytosis of senescent erythrocytes. The way by which macrophages manage non-heme iron at physiological concentration is still not fully understood. We investigated protein changes in mouse bone marrow macrophages incubated with ferric ammonium citrate (FAC 10 μM iron). Differentially expressed spots were identified by nano RP-HPLC-ESI-MS/MS. Transcriptomic, metabolomics and western immunoblotting analyses complemented the proteomic approach. Pattern analysis was also used for identifying networks of proteins involved in iron homeostasis. FAC treatment resulted in higher abundance of several proteins including ferritins, cytoskeleton related proteins, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) at the membrane level, vimentin, arginase, galectin-3 and macrophage migration inhibitory factor (MIF). Interestingly, GAPDH has been recently proposed to act as an alternative transferrin receptor for iron acquisition through internalization of the GAPDH-transferrin complex into the early endosomes. FAC treatment also induced the up-regulation of oxidative stress-related proteins (PRDX), which was further confirmed at the metabolic level (increase in GSSG, 8-isoprostane and pentose phosphate pathway intermediates) through mass spectrometry-based targeted metabolomics approaches. This study represents an example of the potential usefulness of "integarated omics" in the field of iron biology, especially for the elucidation of the molecular mechanisms controlling iron homeostasis in normal and disease conditions. This article is part of a Special Issue entitled: Integrated omics.

Modulation of the activity of the NADPH oxidase system by reactive oxygen species: influence of catalase

The nicotinamide adenine dinucleotide phosphate oxidase complex (Nox) is a major source of non-mitochondrial reactive oxygen species in cells. Nox contains both membrane (Cytb(558)) and cytosolic (p40(phox), p47(phox), p67(phox) and Rac) components. Nox has been submitted to a combination of oxygen free radicals produced by irradiation and to hydrogen peroxide. Irradiation of a single component with high doses led to partial inactivation; however, the irradiation of the whole system during its assembly phase with lower doses (2-10 Gy) led either to activation (2.7 Gy) or to strong inactivation if irradiation took place during the first minute of the assembly. Incubation of the membrane fractions or of p67(phox) with H(2)O(2) led to fast inactivation. Catalase protected weakly p67(phox) from H(2)O(2). Conversely, incubation of the membrane fractions with catalase led to over-activation of the system.

Association of the novel non-AT1, non-AT2 angiotensin binding site with neuronal cell death

We have discovered a non-AT(1), non-AT(2) angiotensin binding site in rodent and human brain membranes, which, based on its pharmacological/biochemical properties and tissue distribution, is different from angiotensin receptors and key proteases processing angiotensins. In this study, the novel angiotensin binding site was localized to a specific brain cell type by using radioligand receptor binding assays. Our results indicate that the novel binding site is expressed in mouse primary cortical neuronal membranes but not in primary cortical astroglial and bEnd.3 brain capillary endothelial cell membranes. Whole-cell binding assays in neurons showed that the binding site faces the outer side of the plasma membrane. Consistent with our previous observations, the novel binding site was unmasked by the sulfhydryl reagent p-chloromercuribenzoate. This effect had a bell-shaped curve and was reversed by reduced glutathione, indicating that the function of the binding site might be regulated by the redox state of the environment. Density of the novel binding site measured by saturation binding assays was significantly increased in neuronal membranes of cells challenged in four in vitro models of cell death (oxygen-glucose deprivation, sodium azide-induced hypoxia, N-methyl-D-aspartate neurotoxicity, and hydrogen peroxide neurotoxicity). In addition, our in vivo data from developing mouse brains showed that the density of the novel angiotensin binding site changes similarly to the pattern of neuronal death in maturating brain. This is the first time that evidence is provided on the association of the novel angiotensin binding site with neuronal death, and future studies directed toward understanding of the functions of this protein are warranted.

Hypoxia stimulates the expression of macrophage migration inhibitory factor in human vascular smooth muscle cells via HIF-1alpha dependent pathway

Background

Hypoxia plays an important role in vascular remodeling and directly affects vascular smooth muscle cells (VSMC) functions. Macrophage migration inhibitory factor (MIF) is a well known proinflammatory factor, and recent evidence suggests an important role of MIF in the progression of atherosclerosis and restenosis. However, the potential link between hypoxia and MIF in VSMC has not been investigated. The current study was designed to test whether hypoxia could regulate MIF expression in human VSMC. The effect of modulating MIF expression on hypoxia-induced VSMC proliferation and migration was also investigated at the same time.

Results

Expression of MIF mRNA and protein was up-regulated as early as 2 hours in cultured human VSMCs after exposed to moderate hypoxia condition (3% O₂). The up-regulation of MIF expression appears to be dependent on hypoxia-inducible transcription factor-1α(HIF-1α) since knockdown of HIF-1α inhibits the hypoxia induction of MIF gene and protein expression. The hypoxia induced expression of MIF was attenuated by antioxidant treatment as well as by inhibition of extracellular signal-regulated kinase (ERK). Under moderate hypoxia conditions (3% O₂), both cell proliferation and cell migration were increased in VSMC cells. Blocking the MIF by specific small interference RNA to MIF (MIF-shRNA) resulted in the suppression of proliferation and migration of VSMCs.

Conclusion

Our results demonstrated that in VSMCs, hypoxia increased MIF gene expression and protein production. The hypoxia-induced HIF-1α activation, reactive oxygen species (ROS) generation and ERK activation might be involved in this response. Both MIF and HIF-1α mediated the hypoxia response of vascular smooth muscle cells, including cell migration and proliferation.