Macrophage migration inhibitory factor induces cell death and decreases neuronal nitric oxide expression in spinal cord neurons

Immunomodulation of streptozotocin induced Type 1 diabetes mellitus in mouse model by Macrophage migration inhibitory factor-2 (MIF-2) homologue of human lymphatic filarial parasite, Wuchereria bancrofti

Helminth parasites modulate the host immune system to ensure a long-lasting asymptomatic form of infection generally, mediated by the secretion of immunomodulatory molecules and one such molecule is a homologue of human host cytokine, Macrophage migratory Inhibitory Factor (hMIF). In this study, we sought to understand the role of homologue of hMIF from the lymphatic filarial parasite, Wuchereria bancrofti (Wba-MIF2), in the immunomodulation of the Streptozotocin (STZ)-induced Type1 Diabetes Mellitus (T1DM) animal model. Full-length recombinant Wba-MIF2 was expressed and found to have both oxidoreductase and tautomerase activities. Wba-MIF2 recombinant protein was treated to STZ induced T1DM animals, and after 5 weeks pro-inflammatory (IL-1, IL-2, IL-6, TNF-α, IFN-γ) and anti-inflammatory (IL-4, IL-10) cytokines and gene expressions were determined in sera samples and spleen respectively. Pro-inflammatory and anti-inflammatory cytokine levels were significantly (p<0.05) up-regulated and down-regulated respectively, in the STZ-T1DM animals, as compared to treated groups. Histopathology showed macrophage infiltration and greater damage of islets of beta cells in the pancreatic tissue of STZ-T1DM animals, than Wba-MIF2 treated STZ-T1DM animals. The present study clearly showed the potential of Wba-MIF2 as an immunomodulatory molecule, which could modulate the host immune system in the STZ-T1DM mice model from a pro-inflammatory to anti-inflammatory milieu.

Astaxanthin ameliorates serum level and spinal expression of macrophage migration inhibitory factor following spinal cord injury

Astaxanthin (AST) is a lipid-soluble carotenoid with antioxidant and anti-inflammatory properties. Previous reports demonstrated the promising effects of AST on spinal cord injury (SCI)-induced inflammation and sensory-motor dysfunction. Macrophage migration inhibitory factor (MIF), as a cytokine, plays a critical role in the inflammatory phase of SCI. The aim of this study was to evaluate the effects of AST on post-SCI levels of MIF in serum and spinal cord. The possible correlation between MIF and mechanical pain threshold was also assessed. Adult male rats were subjected to a severe compression spinal injury and 30 min later were treated with AST (Intrathecal, 2 nmol) or vehicle. Neuropathic pain was assessed by von Frey filaments before the surgery, and then on days 7, 14, 21, and 28 post-SCI. Western blot and ELISA were used to measure the serum level and spinal expression of MIF following SCI in the same time points. AST treatment significantly attenuated the SCI-induced dysregulations in the serum levels and tissue expression of MIF. A negative correlation was observed between mechanical pain threshold and serum MIF level (r = -0.5463, P < 0.001), as well as mechanical pain threshold and spinal level of MIF (r = -0.9562; P < 0.001). AST ameliorates SCI-induced sensory dysfunction, probably through inhibiting MIF-regulated inflammatory pathways.

Altered Circulating Immune Cell Distribution in Traumatic Spinal Cord Injury Patients in Relation to Clinical Parameters

Following a spinal cord injury (SCI), an inflammatory immune reaction is triggered which results in advanced secondary tissue damage. The systemic post-SCI immune response is poorly understood. This study aimed to extensively analyse the circulating immune cell composition in traumatic SCI patients in relation to clinical parameters. High-dimensional flow cytometry was performed on peripheral blood mononuclear cells of 18 traumatic SCI patients and 18 healthy controls to determine immune cell subsets. SCI blood samples were collected at multiple time points in the (sub)acute (0 days to 3 weeks post-SCI, (s)aSCI) and chronic (6 to &gt;18 weeks post-SCI, cSCI) disease phase. Total and CD4+ T cell frequencies were increased in cSCI patients. Both CD4+ T cells and B cells were shifted towards memory phenotypes in (s)aSCI patients and cSCI patients, respectively. Most profound changes were observed in the B cell compartment. Decreased immunoglobulin (Ig)G+ and increased IgM+ B cell frequencies reflected disease severity, as these correlated with American Spinal Injury Association (ASIA) impairment scale (AIS) scores. Post-SCI B cell responses consisted of an increased frequency of CD74+ cells and CD74 expression level within total B cells and B cell subsets. Findings from this study suggest that post-SCI inflammation is driven by memory immune cell subsets. The increased CD74 expression on post-SCI B cells could suggest the involvement of CD74-related pathways in neuroinflammation following SCI. In addition, the clinical and prognostic value of monitoring circulating IgM+ and IgG+ B cell levels in SCI patients should be further evaluated.

Thrombin acts as inducer of proinflammatory macrophage migration inhibitory factor in astrocytes following rat spinal cord injury

BACKGROUND

The danger-associated molecular patterns (DAMPs) are critical contributors to the progressive neuropathology and thereafter affect the functional outcomes following spinal cord injury (SCI). Up to now, the regulatory mechanisms on their inducible production from the living cells remain elusive, aside from their passive release from the necrotic cells. Thrombin is immediately activated by the damaged or stressed central nervous system (CNS), which potently mediates inflammatory astrocytic responses through proteolytic cleavage of protease-activated receptors (PARs). Therefore, SCI-activated thrombin is conceived to induce the production of DAMPs from astrocytes at lesion site.

METHODS

Rat SCI model was established by the cord contusion at T8-T10. The expression of thrombin and macrophage migration inhibitory factor (MIF) was determined by ELISA and Western blot. The PAR1, PAR3, and PAR4 receptors of thrombin were examined by PCR and immunohistochemistry. Primary astrocytes were isolated and purified from the spinal cord, followed by stimulation with different concentrations of thrombin either for transcriptome sequencing or for analysis of thrombin-mediated expression of MIF and related signal pathways in the presence or absence of various inhibitors. The post-injury locomotor functions were assessed using the Basso, Beattie, and Bresnahan (BBB) locomotor scale.

RESULTS

MIF protein levels were significantly elevated in parallel with those of thrombin induced by SCI. Immunostaining demonstrated that PAR1 receptor, together with MIF, was abundantly expressed in astrocytes. By transcriptome sequencing and bioinformatical analysis of thrombin-stimulated primary astrocytes, MIF was identified to be dynamically regulated by the serine protease. Investigation of the underlying mechanism using various inhibitors revealed that thrombin-activated PAR1 was responsible for the MIF production of astrocytes through modulation of JNK/NFκB pathway. Administration of PAR1 inhibitor at lesion sites following SCI significantly reduced the protein levels of MIF and ameliorated functional deficits of rat locomotion.

CONCLUSION

SCI-activated thrombin is a robust inducer of MIF production from astrocytes. Exploring the roles of thrombin in promoting the production of DAMPs from astrocytes at lesion site will provide an alternative strategy for the clinical therapy of CNS inflammation.

Determining the Optimal Administration Conditions under Which MIF Exerts Neuroprotective Effects by Inducing BDNF Expression and Inhibiting Apoptosis in an In Vitro Stroke Model

Macrophage migration inhibitory factor (MIF) exerts neuroprotective effects against cerebral ischemia/reperfusion injury by inhibiting neuronal apoptosis and inducing the expression of brain-derived neurotrophic factor (BDNF). However, the optimal administration conditions of MIF are currently unknown. Here, we aimed to identify these conditions in an in vitro model. To determine the optimal concentration of MIF, human neuroblastoma cells were assigned to one of seven groups: control, oxygen and glucose deprivation/reperfusion (OGD/R), and OGD/R with different concentrations (1, 10, 30, 60, and 100 ng/mL) of MIF. Six groups were studied to investigate the optimal administration time: control, OGD/R, and OGD/R with MIF administered at different times (pre-OGD, OGD-treat, post-OGD, and whole-processing). Water-soluble tetrazolium salt-1 assay, Western blot analysis, and immunocytochemistry were used to analyze cell viability and protein expression. We found that 60 ng/mL was the optimal concentration of MIF. However, the effects of administration time were not significant; MIF elicited similar neuroprotective effects regardless of administration time. These findings correlated with the expression of BDNF and apoptosis-related proteins. This study provides detailed information on MIF administration, which offers a foundation for future in vivo studies and translation into novel therapeutic strategies for ischemic stroke.

Macrophage migration inhibitory factor as a therapeutic target after traumatic spinal cord injury: a systematic review

PURPOSE

Macrophages play an important role in mediating damage after Spinal cord injury (SCI) by secreting macrophage migration inhibitory factor (MMIF) as a secondary injury mediator. We aimed to systematically review the role of MMIF as a therapeutic target after traumatic SCI.

METHODS

Our systematic review has been performed according to the PRISMA 2009 Checklist. A systematic search in the scientific databases was carried out for studies published before 20 February 2019 from major databases. Two researchers independently screened titles. The risk of bias of eligible articles was assessed, and data were extracted. Finally, we systematically analyzed and interpreted related data.

RESULTS

785 papers were selected for the title and abstract screening. 12 papers were included for data extraction. Eight animal studies were of high quality and the remaining two were of medium quality. One of the two human studies was of poor quality and the other was of fair quality. MMIF as a pro-inflammatory mediator can cause increased susceptibility to glutamate-related neurotoxicity, increased nitrite production, increased ERK activation, and increased COX2/PGE2 signaling pathway activation and subsequent stimulation of CCL5-related chemotaxis. Two human studies and six animal studies demonstrated that MMIF level increases after SCI. MMIF inhibition might be a potential therapeutic target in SCI by multiple different mechanisms (6/12 studies).

CONCLUSION

Most animal studies demonstrate significant neurologic improvement after administration of MMIF inhibitors, but these inhibitors have not been studied in humans yet. Further clinical trials are need to further understand MMIF inhibitor utility in acute or chronic SCI.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

CCL3 contributes to secondary damage after spinal cord injury

Background

Secondary damage after spinal cord injury (SCI) is characterized by a cascade of events including hemorrhage, apoptosis, oxidative stress, and inflammation which increase the lesion size which can influence the functional impairment. Thus, identifying specific mechanisms attributed to secondary injury is critical in minimizing tissue damage and improving neurological outcome. In this work, we are investigating the role of CCL3 (macrophage inflammatory protein 1-α, MIP-1α), a chemokine involved in the recruitment of inflammatory cells, which plays an important role in inflammatory conditions of the central and peripheral nervous system.

Methods

A mouse model of lower thoracic (T11) spinal cord contusion injury was used. We assessed expression levels of CCL3 and its receptors on the mRNA and protein level and analyzed changes in locomotor recovery and the inflammatory response in the injured spinal cord of wild-type and CCL3^−/− mice.

Results

The expression of CCL3 and its receptors was increased after thoracic contusion SCI in mice. We then examined the role of CCL3 after SCI and its direct influence on the inflammatory response, locomotor recovery and lesion size using CCL3^−/− mice. CCL3^−/− mice showed mild but significant improvement of locomotor recovery, a smaller lesion size and reduced neuronal damage compared to wild-type controls. In addition, neutrophil numbers as well as the pro-inflammatory cytokines and chemokines, known to play a deleterious role after SCI, were markedly reduced in the absence of CCL3.

Conclusion

We have identified CCL3 as a potential target to modulate the inflammatory response and secondary damage after SCI. Collectively, this study shows that CCL3 contributes to progressive tissue damage and functional impairment during secondary injury after SCI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02037-3.

Microglial autophagy defect causes parkinson disease-like symptoms by accelerating inflammasome activation in mice

Microglial activation-induced neuroinflammation is closely associated with the development of Parkinson disease (PD). Macroautophagy/autophagy regulates many biological processes, but the role of autophagy in microglial activation during PD development remains largely unclear. In this study, we showed that deletion of microglial Atg5 caused PD-like symptoms in mice, characterized by impairment in motor coordination and cognitive learning, loss of tyrosine hydroxylase (TH) neurons, enhancement of neuroinflammation and reduction in dopamine levels in the striatum. Mechanistically, we found that inhibition of autophagy led to NLRP3 (NLR family pyrin domain containing 3) inflammasome activation via PDE10A (phosphodiesterase 10A)-cyclic adenosine monophosphate (cAMP) signaling in microglia, and the sequential upregulation of downstream IL1B/IL-1β in turn increased the expression of MIF (macrophage migration inhibitory factor [glycosylation-inhibiting factor]), a pro-inflammatory cytokine. Inhibition of NLRP3 inflammasome activation by administration of MCC950, a specific inhibitor for NLRP3, decreased MIF expression and neuroinflammatory levels, and rescued the loss of TH neurons in the substantial nigra (SN). Interestingly, we found that serum MIF levels in PD patients were significantly elevated. Taken together, our results reveal an important role of autophagy in microglial activation-driven PD-like symptoms, thus providing potential targets for the clinical treatment of PD. Abbreviations: ATG: autophagy related; cAMP: cyclic adenosine monophosphate; cKO: conditional knockout; NOS2/INOS: nitric oxide synthase 2, inducible; IL1B: interleukin 1 beta; ITGAM/CD-11b: integrin alpha M/cluster of differentiation molecule 11B; MAP1LC3: microtubule-associated protein 1 light chain 3; MIF: macrophage migration inhibitory factor (glycosylation-inhibiting factor); NLRP3: NLR family pyrin domain containing 3; PBS: phosphate-buffered saline; PD: parkinson disease; PDE10A: phosphodiesterase 10A; SN: substantial nigra; TH: tyrosine hydroxylase; TNF: tumor necrosis factor; WT: wild type.

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.

AAV2/9-mediated overexpression of MIF inhibits SOD1 misfolding, delays disease onset, and extends survival in mouse models of ALS

Mutations in superoxide dismutase (SOD1) cause amyotrophic lateral sclerosis (ALS), a neurodegenerative disease characterized by the loss of upper and lower motor neurons. Transgenic mice that overexpress mutant SOD1 develop paralysis and accumulate misfolded SOD1 onto the cytoplasmic faces of intracellular organelles, including mitochondria and endoplasmic reticulum (ER). Recently, macrophage migration inhibitory factor (MIF) was shown to directly inhibit mutant SOD1 misfolding and binding to intracellular membranes. In addition, complete elimination of endogenous MIF accelerated disease onset and late disease progression, as well as shortened the lifespan of mutant SOD1 mice with higher amounts of misfolded SOD1 detected within the spinal cord. Based on these findings, we used adeno-associated viral (AAV) vectors to overexpress MIF in the spinal cord of mutant SOD1^G93A and loxSOD1^G37R mice. Our data show that MIF mRNA and protein levels were increased in the spinal cords of AAV2/9-MIF-injected mice. Furthermore, mutant SOD1^G93A and loxSOD1^G37R mice injected with AAV2/9-MIF demonstrated a significant delay in disease onset and prolonged survival compared with their AAV2/9-GFP-injected or noninjected littermates. Moreover, these mice accumulated reduced amounts of misfolded SOD1 in their spinal cords, with no observed effect on glial overactivation as a result of MIF up-regulation. Our findings indicate that MIF plays a significant role in SOD1 folding and misfolding mechanisms and strengthen the hypothesis that MIF acts as a chaperone for misfolded SOD1 in vivo and may have further implications regarding the therapeutic potential role of up-regulation of MIF in modulating the specific accumulation of misfolded SOD1.

Macrophage Migration Inhibitory Factor Promotes Chemotaxis of Astrocytes through Regulation of Cholesterol 25-Hydroxylase Following Rat Spinal Cord Injury

Oxysterol derived from cholesterol metabolism is involved in the inflammatory activation, and consequently in development of major chronic diseases. Multiple cytokines have been found to induce the expression of cholesterol metabolism-related enzymes. Several studies have shown that the protein level of cholesterol-25-hydroxylase (CH25H) is remarkably increased in response to injury of central nervous system (CNS), but little is known about the mechanisms of cytokine-induced expression of CH25H in specific cell types, and the resultant effects. In the present study, we demonstrated that ch25h expression was significantly upregulated in the astrocytes of rat injured spinal cord, in parallel with those of MIF. Administration of MIF inhibitor 4-IPP in the lesion sites attenuated injury-induced ch25h expression. MIF facilitated ch25h expression of astrocytes through interaction with CD74 membrane receptor, which in turn promoted production of chemokines, as identified by transcriptome profiles. MIF-induced release of oxysterol 25-hydroxycholesterol (25-HC) from astrocytes affects cell migration, but inhibited cell viability in dose-dependent manner, suggesting that MIF aggravates progressive neuropathology through regulation of cholesterol metabolism following CNS injury. These results have provided a novel mechanism and a potential therapeutic strategy for injured CNS.

Macrophage migration inhibitory factor facilitates production of CCL5 in astrocytes following rat spinal cord injury

Background

Astrocytes act as immune effector cells with the ability to produce a wide array of chemokines and cytokines in response to various stimuli. Macrophage migration inhibitory factor (MIF) is inducibly expressed in injured spinal cord contributing to excessive inflammation that affects motor functional recovery. Unknown is whether MIF can facilitate inflammatory responses through stimulating release of chemokines from astrocytes following spinal cord injury.

Methods

Following the establishment of the contusion spinal cord injury rat model, the correlation of chemokine (C-C motif) ligand 5 (CCL5) expression with that of MIF was assayed by Western blot, ELISA, and immunohistochemistry. Immunoprecipitation was used to detect MIF interaction with membrane CD74 receptor. Intracellular signal transduction of MIF/CD74 axis was analyzed by transcriptome sequencing of primary astrocytes and further validated by treatment of various inhibitors. The effects of CCL5 released by astrocytes on macrophage migration were performed by transwell migration assay. The post-injury locomotor functions were assessed using the Basso, Beattie, and Bresnahan (BBB) locomotor scale.

Results

The protein levels of chemokine CCL5/RANTES were remarkably increased in the astrocytes of rat injured spinal cord, in parallel with the expression of MIF. Treatment of MIF inhibitor 4-IPP in the lesion sites resulted in a significant decrease of CCL5 protein levels. In vitro study revealed MIF was capable of facilitating CCL5 production of astrocytes through interaction with CD74 membrane receptor, and knockdown of this receptor attenuated such effects. Production of CCL5 in astrocytes was significantly blocked by inhibitor of c-Jun N-terminal kinase, rather than by those of ERK and P38. Recombinant CCL5 protein was found to be more effective in promoting migration of M2- compared to M1-type macrophages.

Conclusion

Collectively, these data reveal a novel function of MIF in regulation of CCL5 release from astrocytes, which in turn favors for recruitment of inflammatory cells to the injured site of the spinal cord, in association with activation of excessive inflammation.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1297-z) contains supplementary material, which is available to authorized users.

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.

Macrophage polarization: a key event in the secondary phase of acute spinal cord injury

Acute spinal cord injury (SCI) has become epidemic in modern society. Despite advances made in the understanding of the pathogenesis and improvements in early recognition and treatment, it remains a devastating event, often producing severe and permanent disability. SCI has two phases: acute and secondary. Although the acute phase is marked by severe local and systemic events such as tissue contusion, ischaemia, haemorrhage and vascular damage, the outcome of SCI are mainly influenced by the secondary phase. SCI causes inflammatory responses through the activation of innate immune responses that contribute to secondary injury, in which polarization‐based macrophage activation is a hallmarker. Macrophages accumulated within the epicentre and the haematoma of the injured spinal cord play a significant role in this inflammation. Depending on their phenotype and activation status, macrophages may initiate secondary injury mechanisms and/or promote CNS regeneration and repair. When it comes to therapies for SCI, very few can be performed in the acute phase. However, as macrophage activation and polarization switch are exquisitely sensitive to changes in microenvironment, some trials have been conducted to modulate macrophage polarization towards benefiting the recovery of SCI. Given this, it is important to understand how macrophages and SCI interrelate and interact on a molecular pathophysiological level. This review provides a comprehensive overview of the immuno‐pathophysiological features of acute SCI mainly from the following perspectives: (i) the overview of the pathophysiology of acute SCI, (ii) the roles of macrophage, especially its polarization switch in acute SCI, and (iii) newly developed neuroprotective therapies modulating macrophage polarization in acute SCI.

Pilot study: elevated circulating levels of the proinflammatory cytokine macrophage migration inhibitory factor in patients with chronic spinal cord injury

OBJECTIVE

To test the hypothesis that the proinflammatory cytokine macrophage migration inhibitory factor (MIF) is elevated in the circulation of patients with chronic spinal cord injury (SCI) relative to uninjured subjects, and secondarily to identify additional immune mediators that are elevated in subjects with chronic SCI.

DESIGN

Prospective, observational pilot study.

SETTING

Outpatient clinic of a department of physical medicine and rehabilitation and research institute in an academic medical center.

PARTICIPANTS

Individuals with chronic (>1y from initial injury) SCI (n=22) and age- and sex-matched uninjured subjects (n=19).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Plasma levels of MIF, as determined by a commercially available multiplex suspension immunoassay. The relationship between MIF levels and clinical/demographic variables was also examined. As a secondary outcome, we evaluated other cytokines, chemokines, and growth factors.

RESULTS

Plasma MIF levels were significantly higher in subjects with chronic SCI than in control subjects (P<.001). Elevated MIF levels were not correlated significantly with any one clinical or demographic characteristic. Subjects with SCI also exhibited significantly higher plasma levels of monokine induced by interferon-gamma/chemokine C-X-C motif ligand 9 (P<.03), macrophage colony stimulating factor (P<.035), interleukin-3 (P<.044), and stem cell growth factor beta (SCGF-β) (P<.016). Among subjects with SCI, the levels of SCGF-β increased with the time from initial injury.

CONCLUSIONS

These data confirm the hypothesis that MIF is elevated in subjects with chronic SCI and identify additional novel immune mediators that are also elevated in these subjects. This study suggests the importance of examining the potential functional roles of MIF and other immune factors in subjects with chronic SCI.

Macrophage migration inhibitory factor acts as a neurotrophin in the developing inner ear

This study is the first to demonstrate that macrophage migration inhibitory factor (MIF), an immune system 'inflammatory' cytokine that is released by the developing otocyst, plays a role in regulating early innervation of the mouse and chick inner ear. We demonstrate that MIF is a major bioactive component of the previously uncharacterized otocyst-derived factor, which directs initial neurite outgrowth from the statoacoustic ganglion (SAG) to the developing inner ear. Recombinant MIF acts as a neurotrophin in promoting both SAG directional neurite outgrowth and neuronal survival and is expressed in both the developing and mature inner ear of chick and mouse. A MIF receptor, CD74, is found on both embryonic SAG neurons and adult mouse spiral ganglion neurons. Mif knockout mice are hearing impaired and demonstrate altered innervation to the organ of Corti, as well as fewer sensory hair cells. Furthermore, mouse embryonic stem cells become neuron-like when exposed to picomolar levels of MIF, suggesting the general importance of this cytokine in neural development.

Spinal macrophage migration inhibitory factor contributes to the pathogenesis of inflammatory hyperalgesia in rats

Pro-inflammatory cytokine production after nociceptive stimuli is pivotal for hyperalgesia. As macrophage migration inhibitory factor (MIF), a pleiotropic cytokine produced mainly by nonneuronal tissue, has been involved in the regulation of neuronal functions, herein we examined the role for MIF in formalin-induced inflammatory pain model. MIF critically contributed to nociceptive behaviors following formalin injection. Specifically, spinal administration of a MIF inhibitor (ISO-1) prevented and reversed flinching responses in rats. Further examination showed that levels of both MIF and the MIF receptor CD74 were substantially increased within the ipsilateral spinal cord dorsal horn after formalin administration. Mechanistic studies revealed that MIF upregulated the expression of the spinal NMDA receptor subunit NR2B via the MAPK signaling pathway. Moreover, microglial cells were found to be the major source of spinal MIF after formalin administration by fluorescence colocalization. These data highlight spinal MIF plays a critical role in the pathogenesis of formalin-induced inflammatory pain and suggest MIF may be a potential target for therapy of such pathological condition.

Sex steroid regulation of macrophage migration inhibitory factor in normal and inflamed colon in the female rat

BACKGROUND AND AIMS

Sex steroids influence IBD symptoms. Macrophage migration inhibitory factor (MIF), a target of sex steroids in other inflammatory models, promotes interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha release in colitis. We investigated whether estradiol and progesterone influence MIF, IL-1beta, and TNF-alpha production in experimental colitis.

METHODS

Colonic MIF, IL-1beta, and TNF-alpha levels were measured in cyclic and ovariectomized rats, with or without estradiol benzoate (EB) or progesterone (P) replacement. MIF distribution was assessed by immunohistochemistry. Cytokines, myeloperoxidase activity, macroscopic damage, and plasma corticosterone were assessed 24 hours after intrarectal trinitrobenzene sulfonic acid (TNBS), with and without neutralizing anti-MIF antibody. Effects of EB and P on myeloperoxidase activity and MIF concentration were also assessed at 7 days in dextran sulfate sodium-induced colitis.

RESULTS

Basal IL-1beta and TNF-alpha contents did not fluctuate during the estrous cycle, while MIF concentrations increased from estrus (estrogen dominance) to metestrus (P dominance; P < .05). EB and P treatment mimicked these effects in ovariectomized rats, and similarly altered MIF immunostaining. Progesterone dominance aggravated TNBS colitis in comparison with estrogen. Progesterone enhanced TNBS-induced MIF (P < .001) and TNF-alpha (P < .01) production, while EB decreased MIF (P < .01) and IL-beta levels (P < .01). Anti-MIF antibody prevented P-mediated up-regulation of TNF-alpha, improved TNBS colitis, and enhanced plasma corticosterone. At 7 days after dextran sulfate sodium, EB decreased myeloperoxidase activity and MIF concentration, while P had no effect.

CONCLUSIONS

Estrogen decreases while progesterone increases MIF production in the female rat colon. Changes in basal MIF contents may affect colon susceptibility to inflammation, by modulating TNF-alpha and IL-1beta production during early stages of colitis.

Lipopolysaccharide-induced protein kinase D activation mediated by interleukin-1beta and protein kinase C

Protein kinase D (PKD), a newly described serine/threonine kinase, has been implicated in many signal transduction pathways. The present study was designed to determine whether and how PKD is activated in inflammation. The results demonstrated that lipopolysaccharide (LPS, 30 microg/ml) stimulated PKD and protein kinase C (PKC) phosphorylation in spinal neurons within 0.5 h, and the activation reached a maximum at 3 or 8 h and declined at 12 h. The phosphorylation could be inhibited by the selective inhibitors for PKC (100 nM), mainly for PKCalpha and PKCbeta, suggesting the involvement of the PKC pathway. Particularly, PKCalpha might be critical for LPS-induced PKD activation since the PKCbeta inhibitor (100 nM) observed no effect on the phosphorylation of PKD. Furthermore, the expression of interleukin-1beta (IL-1beta) was significantly induced by LPS within 0.5 h, and reached a maximum at 8 h. IL-1 receptor antagonist inhibited PKD and PKCs activation induced by LPS at a concentration of 50 nM and achieved maximum at 1000 nM. These results demonstrated for the first time that PKD could be activated by LPS in spinal neurons, might via the IL-1beta/PKCalpha pathway. Additionally, immunostaining showed an increase in number of phosphorylated PKD-immunoreactive cells of adult spinal dorsal horn induced by intraplantar injected carrageenan (2 microg/100 microl), and antisense oligodeoxynucleotide to IL-1 receptor type I (50 microg/10 microl, intrathecal injected) inhibited the PKD activation, suggesting an involvement of IL-1beta/PKD pathway in inflammation in adult spinal cord.