Macrophage migration inhibitory factor expression in human renal allograft rejection

Macrophage Migration Inhibitory Factor (MIF) as a Stress Molecule in Renal Inflammation

Renal inflammation is an initial pathological process during progressive renal injury regardless of the initial cause. Macrophage migration inhibitory factor (MIF) is a truly proinflammatory stress mediator that is highly expressed in a variety of both inflammatory cells and intrinsic kidney cells. MIF is released from the diseased kidney immediately upon stimulation to trigger renal inflammation by activating macrophages and T cells, and promoting the production of proinflammatory cytokines, chemokines, and stress molecules via signaling pathways involving the CD74/CD44 and chemokine receptors CXCR2, CXCR4, and CXCR7 signaling. In addition, MIF can function as a stress molecule to counter-regulate the immunosuppressive effect of glucocorticoid in renal inflammation. Given the critical position of MIF in the upstream inflammatory cascade, this review focuses on the regulatory role and molecular mechanisms of MIF in kidney diseases. The therapeutic potential of targeting MIF signaling to treat kidney diseases is also discussed.

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.

Blocking Macrophage Migration Inhibitory Factor Protects Against Cisplatin-Induced Acute Kidney Injury in Mice

Macrophage migration inhibitory factor (MIF) is elevated in patients with acute kidney injury (AKI) and is suggested as a potential predictor for renal replacement therapy in AKI. In this study, we found that MIF also plays a pathogenic role and is a therapeutic target for AKI. In a cisplatin-induced AKI mouse model, elevated plasma MIF correlated with increased serum creatinine and the severity of renal inflammation and tubular necrosis, whereas deletion of MIF protected the kidney from cisplatin-induced AKI by largely improving renal functional and histological injury, and suppressing renal inflammation including upregulation of cytokines such as interleukin (IL)-1β, tumor necrosis factor-alpha (TNF-α), IL-6, inducible nitric oxide synthase (iNOS), MCP-1, IL-8, and infiltration of macrophages, neutrophils, and T cells. We next developed a novel therapeutic strategy for AKI by blocking the endogenous MIF with an MIF inhibitor, ribosomal protein S19 (RPS19). Similar to the MIF-knockout mice, treatment with RPS19, but not the mutant RPS19, suppressed cisplatin-induced AKI. Mechanistically, we found that both genetic knockout and pharmacological inhibition of MIF protected against AKI by inactivating the CD74-nuclear factor κB (NF-κB) signaling. In conclusion, MIF is pathogenic in cisplatin-induced AKI. Targeting MIF with an MIF inhibitor RPS19 could be a promising therapeutic potential for AKI.

Macrophage-to-Myofibroblast Transition Contributes to Interstitial Fibrosis in Chronic Renal Allograft Injury

Interstitial fibrosis is an important contributor to graft loss in chronic renal allograft injury. Inflammatory macrophages are associated with fibrosis in renal allografts, but how these cells contribute to this damaging response is not clearly understood. Here, we investigated the role of macrophage-to-myofibroblast transition in interstitial fibrosis in human and experimental chronic renal allograft injury. In biopsy specimens from patients with active chronic allograft rejection, we identified cells undergoing macrophage-to-myofibroblast transition by the coexpression of macrophage (CD68) and myofibroblast (α-smooth muscle actin [α-SMA]) markers. CD68⁺/α-SMA⁺ cells accounted for approximately 50% of the myofibroblast population, and the number of these cells correlated with allograft function and the severity of interstitial fibrosis. Similarly, in C57BL/6J mice with a BALB/c renal allograft, cells coexpressing macrophage markers (CD68 or F4/80) and α-SMA composed a significant population in the interstitium of allografts undergoing chronic rejection. Fate-mapping in Lyz2-Cre/Rosa26-Tomato mice showed that approximately half of α-SMA⁺ myofibroblasts in renal allografts originated from recipient bone marrow-derived macrophages. Knockout of Smad3 protected against interstitial fibrosis in renal allografts and substantially reduced the number of macrophage-to-myofibroblast transition cells. Furthermore, the majority of macrophage-to-myofibroblast transition cells in human and experimental renal allograft rejection coexpressed the M2-type macrophage marker CD206, and this expression was considerably reduced in Smad3-knockout recipients. In conclusion, our studies indicate that macrophage-to-myofibroblast transition contributes to interstitial fibrosis in chronic renal allograft injury. Moreover, the transition of bone marrow-derived M2-type macrophages to myofibroblasts in the renal allograft is regulated via a Smad3-dependent mechanism.

The role of Krüppel-like factor 4 in transforming growth factor-β-induced inflammatory and fibrotic responses in human proximal tubule cells

Krüppel-like factor 4 (KLF4) is known to mitigate inflammation in several cell types. Using human proximal tubule cells, the present study aimed to investigate the role of KLF4 in regulating transforming growth factor (TGF)-β₁ induced inflammatory and fibrotic responses. Human kidney proximal tubular cells were exposed to high glucose, or TGF-β₁ and KLF4 expressions were determined. Cells were then transfected with empty vector or KLF4 and exposed to 2-ng/mL TGF-β₁ for up to 72 h. Inflammatory proteins (macrophage migration inhibitory factor and monocyte chemoattractant protein-1) and pro-fibrotic proteins (fibronectin and collagen IV) were measured after 72 h by enzyme-linked immunosorbent assay and western blot, respectively. To determine the relevance to in vivo models of chronic kidney disease, KLF4 protein expression in streptozotocin-induced diabetic mice was determined. Krüppel-like factor 4 messenger RNA (mRNA) levels were significantly reduced in high glucose-treated human kidney proximal tubular cells. High glucose increased TGF-β₁ mRNA expression, which significantly increased migration inhibitory factor and monocyte chemoattractant protein-1 protein secretion. Transforming growth factor-β₁ significantly increased fibronectin and collagen IV protein expression. The overexpression of KLF4 significantly reduced TGF-β-mediated increases in migration inhibitory factor and monocyte chemoattractant protein-1 but had no effect on TGF-β-mediated fibronectin and collagen IV mRNA and protein expression. The levels of KLF4 mRNA were significantly reduced in the diabetic kidney, and diabetic animals had a significant reduction in renal tubular expression of KLF4 proteins. This data suggest that KLF4 reduces inflammation induced by TGF-β₁, suggesting a therapeutic role for KLF4 in diabetic nephropathy.

Macrophages in renal transplantation: Roles and therapeutic implications

The presence of macrophages within transplanted renal allografts has been appreciated for some time, whereby macrophages were viewed primarily as participants in the process of cell-mediated allograft rejection. Recent insights into macrophage biology have greatly expanded our conceptual understanding of the multiple roles of macrophages within the allograft. Distinct macrophage subsets are present within the kidney and these sub-serve discrete functions in promoting and attenuating inflammation, immune modulation and tissue repair. Unraveling the complex roles macrophages play in transplantation will allow identification of potential therapeutic targets to prevent and treat allograft rejection and maximize graft longevity.

Macrophages in solid organ transplantation

Macrophages are highly plastic hematopoietic cells with diversified functions related to their anatomic location and differentiation states. A number of recent studies have examined the role of macrophages in solid organ transplantation. These studies show that macrophages can induce allograft injury but, conversely, can also promote tissue repair in ischemia-reperfusion injury and acute rejection. Therapeutic strategies that target macrophages to improve outcomes in solid organ transplant recipients are being examined in preclinical and clinical models. In this review, we discuss the role of macrophages in different types of injury and rejection, with a focus on macrophage-mediated tissue injury, specifically vascular injury, repair and remodeling. We also discuss emerging macrophage-centered therapeutic opportunities in solid organ transplantation.

Urinary macrophage migration inhibitory factor serves as a potential biomarker for acute kidney injury in patients with acute pyelonephritis

Conventional markers of kidney function that are familiar to clinicians, including the serum creatinine and blood urea nitrogen levels, are unable to reveal genuine injury to the kidney, and their use may delay treatment. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine, and the predictive role and pathogenic mechanism of MIF deregulation during kidney infections involving acute kidney injury (AKI) are not currently known. In this study, we showed that elevated urinary MIF levels accompanied the development of AKI during kidney infection in patients with acute pyelonephritis (APN). In addition to the MIF level, the urinary levels of interleukin (IL)-1β and kidney injury molecule (KIM)-1 were also upregulated and were positively correlated with the levels of urinary MIF. An elevated urinary MIF level, along with elevated IL-1β and KIM-1 levels, is speculated to be a potential biomarker for the presence of AKI in APN patients.

Cytomegalovirus upregulates vascular endothelial growth factor and its second cellular kinase domain receptor in human fibroblasts

Human cytomegalovirus (HCMV) activation and elevated levels of vascular endothelial growth factor (VEGF) have been found to be associated with transplant rejection. However, information is lacking about whether elevated levels of this multifunctional factor are directly due to viral activation, or if they derive from impurities within the culture supernatant of infected cell cultures. We used purified as well as unpurified viral stocks to infect human fibroblasts in vitro and applied PCR, Western blot, ELISA, and immunofluorescence staining to investigate the expression of VEGF and its receptors. Our data suggest that HCMV infection triggers an early and sustained induction of VEGF and kinase insert domain receptor (KDR) mRNAs, whereas transcript levels of FLT-1 remain unchanged by viral infection. Analysis of the extracellular VEGF and cellular KDR protein expression after infection with purified and unpurified HCMV strains AD169 and TOLEDO showed, in clear contrast to UV-inactivated virus preparations, an increased release of VEGF and KDR proteins. In addition, immunofluorescence revealed that HCMV infection was also accompanied by a profound increase in intracellular VEGF and KDR levels. These results confirm that active HCMV infection is required to induce VEGF and the most important VEGF receptor KDR, and that the upregulation of VEGF and KDR are a direct viral effect and not a secondary effect mediated by inflammatory cytokines within the supernatant. The HCMV-dependent upregulation of VEGF and KDR contributes to the theory that viral-induced immune mediators play a key role in transplant rejection.

MIF, CD74 and other partners in kidney disease: tales of a promiscuous couple

Macrophage migration inhibitory factor (MIF) is increased in kidney and urine during kidney disease. MIF binds to and activates CD74 and chemokine receptors CXCR2 and CXCR4. CD74 is a protein trafficking regulator and a cell membrane receptor for MIF, D-dopachrome tautomerase (D-DT/MIF-2) and bacterial proteins. MIF signaling through CD74 requires CD44. CD74, CD44 and CXCR4 are upregulated in renal cells in diseased kidneys and MIF activation of CD74 in kidney cells promotes an inflammatory response. MIF or CXCR2 targeting protects from experimental kidney injury, CD44 deficiency modulates kidney injury and CXCR4 activation promotes glomerular injury. However, the contribution of MIF or MIF-2 to these actions of MIF receptors has not been explored. The safety and efficacy of strategies targeting MIF, CD74, CD44 and CXCR4 are under study in humans.

Evaluation of 131I-anti-MIF mAb as a reporter for allograft rejection

Finding a specific agent will be useful for monitoring allorejection in clinic. The macrophage migration inhibitory factor (MIF) was reported to be one of the major cytokines involved in allorejection. In this study, we evaluated whether (131)I-anti-MIF mAb could be an efficient imaging reporter for monitoring allorejection. (131)I-anti-MIF mAb or control (131)I-IgG was injected to skin allotransplantation mice and T/NT ratios were evaluated. The imaging changes of grafts were dynamically displayed by whole-body images. The results showed that up-regulation of MIF expression was found in allografts but not in isografts. During the whole progression of rejection, the T/NT ratio in the (131)I-anti-MIF mAb group was significantly higher than that in the (131)I-IgG group and markedly increased on the top of rejection. The graft-rejection could also be shown more clearly in the (131)I-anti-MIF mAb group by whole-body imaging. These results implied that (131)I-anti-MIF mAb may be a valid method for facilitating the development of protocols to monitor allorejection.

Macrophages and kidney transplantation

Macrophages are present within the transplanted kidney in varying numbers throughout its lifespan. Because of their prominence during acute rejection episodes, macrophages traditionally have been viewed as contributors to T-cell-directed graft injury. With growing appreciation of macrophage biology, it has become evident that different types of macrophages exist within the kidney, subserving a range of functions that include promotion or attenuation of inflammation, participation in innate and adaptive immune responses, and mediation of tissue injury and fibrosis, as well as tissue repair. A deeper understanding of how macrophages accumulate within the kidney and of what factors control their differentiation and function may identify novel therapeutic targets in transplantation.

Macrophage migration inhibitory factor plays a pivotal role in hepatocellular carcinoma and may be a noninvasive imaging target

Macrophage migration inhibitory factor (MIF) has emerged to play a central role in the control of the host inflammatory and immune response. Several reports have documented that MIF can inactivate the tumor suppresser activity of p53; overexpression of MIF was significantly higher in both the sera and the local lesions from patients with HCC than from patients with normal controls. These findings indicate that MIF may contribute to multiple aspects of tumor progression and neoplasia, thus MIF may be an effective therapeutic target molecule. We speculate that MIF is important for the development and progression of hepatocellular carcinoma, and can be used as a marker for tumor detection.

MicroRNAs in immune regulation--opportunities for cancer immunotherapy

Endogenously produced microRNAs are predicted to regulate the translation of over two-thirds all human gene transcripts. Certain microRNAs regulate expression of genes that are critically involved in both innate and adaptive immune responses. Immune cells represent a highly attractive target for microRNA gene therapy approaches, as these cells can be isolated, treated and then reintroduced into the patient. In this short review, we discuss how recent discoveries on the roles of microRNAs in immune-regulation will advance the field of cancer immunology and immunotherapy. Targets identified already in T cells include microRNAs, miR-17-92 family, miR-155, and miR-181a. In macrophages, miR-125b, miR-146, and miR-155 act as Pathogen Associated Molecular Pattern Molecule-associated microRNAs and miR-34C and miR-214 as Damage Associated Molecular Pattern Molecules-associated miRs. We have also demonstrated that the ability of tumors to serve as targets for cytolytic effectors is regulated by miR-222 and miR-339.

The role of macrophage migration inhibitory factor in mouse islet transplantation

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many tissues including pancreatic beta-cells.

METHODS

This study investigates the impact of MIF on islet transplantation using MIF knock-out (MIFko) mice.

RESULTS

Early islet function, assessed with a syngeneic marginal islet mass transplant model, was enhanced when using MIFko islets (P<0.05 compared with wild-type [WT] controls). This result was supported by increased in vitro resistance of MIFko islets to apoptosis (terminal deoxynucleotide tranferase-mediated dUTP nick-end labeling assay), and by improved glucose metabolism (lower blood glucose levels, reduced glucose areas under curve and higher insulin release during intraperitoneal glucose challenges, and in vitro in the absence of MIF, P<0.01). The beneficial impact of MIFko islets was insufficient to delay allogeneic islet rejection. However, the rejection of WT islet allografts was marginally delayed in MIFko recipients by 6 days when compared with WT recipient (P<0.05). This effect is supported by the lower activity of MIF-deficient macrophages, assessed in vitro and in vivo by cotransplantation of islet/macrophages. Leukocyte infiltration of the graft and donor-specific lymphocyte activity (mixed lymphocyte reaction, interferon gamma ELISPOT) were similar in both groups.

CONCLUSION

These data indicate that targeting MIF has the potential to improve early function after syngeneic islet transplantation, but has only a marginal impact on allogeneic rejection.

The role of macrophage migration inhibitory factor on glucose metabolism and diabetes

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in many inflammatory reactions and disorders, and it has become evident that it also affects glucose homeostasis. The protein is produced by pancreatic beta cells and can promote the release of insulin. It also modulates glucose uptake, glycolysis and insulin resistance in insulin target cells such as the adipocyte, myocyte and cardiomyocyte. Possessing both immunological and endocrinological properties, MIF has been associated with the development of type 1 and type 2 diabetes, and it may be important in the setting of islet transplantation. The present review summarises our current knowledge, based on clinical and research data, on the impact of MIF on both physiological and pathological aspects of glucose metabolism.

Overexpression of macrophage migration inhibitory factor induces angiogenesis in human breast cancer

Macrophage migration inhibitory factor (MIF) is known to be an important contributor to tumor progression. Overexpression of MIF has been reported in different types of tumors. However, the correlation between MIF expression and tumor pathologic features in patients with breast cancer has not been elucidated. In this study, we examined the expression of MIF, vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) in human tissues with or without tumor. In addition, we investigated the expression of MIF in MDA-MB-231, MCF-7 (breast cancer cell lines) and MCF-10A (epithelial cell line) cells, and its effect on VEGF and IL-8. We found that MIF was overexpressed in breast cancer tissues compared with normal ones. The level of MIF showed the positive correlation between the expression of IL-8 and tumor microvessel density (MVD). The patients with positive MIF expression in tumor tissues showed a significantly worse disease-free survival compared with negative ones. Increased MIF serum levels were also found to correlate with higher levels of IL-8 in the sera of the patients with breast cancer. In vitro experiments successfully detected MIF in breast cell lines. However, the expression level of it by normal epithelial cells was much less than that of cancer cells. Exogenous MIF did not cause endothelial tube formation and migration but induced a dose dependent increase in VEGF and IL-8 secretion in breast cancer cell lines. In summary, our studies show that human breast cancer tissue expresses MIF. Its in vitro effect on VEGF and IL-8 indicates that MIF may contribute to tumor in angiogenesis and thus play an important role in the pathogenesis of breast cancer.

Serum macrophage migration inhibitory factor (MIF) levels after allogeneic hematopoietic stem cell transplantation

Macrophage migration inhibitory factor (MIF) may play an important role in the pathogenesis of acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT), as MIF plays an important role to regulate the production of tumor necrosis factor-alpha (TNF-alpha), one of the inflammatory cytokines which induces and exacerbates aGVHD. We examined the association between serum MIF levels and aGVHD vs. chronic GVHD (cGVHD) in allo-SCT patients in this study. We found a significant increase in the peak serum MIF (14.46 ng +/- 1.47 ng/ml) at onset in patients that developed aGVHD (n = 23, P = 0.009). We also found that mean serum MIF levels in patients who developed extensive type cGVHD within 6 months (12.58 +/- 2.18 ng/ml, n = 13) were significantly higher than MIF levels before allo-HSCT (7.86 +/- 1.17 ng/ml, n = 19, P = 0.04). Therefore, we speculated that serum MIF levels increase during the active phase of both aGVHD and cGVHD.

Interleukin-1beta and macrophage migration inhibitory factor (MIF) in dermal fibroblasts mediate UVA-induced matrix metalloproteinase-1 expression

BACKGROUND

Exposure to solar UV radiation is the main environmental factor that causes premature aging of the skin. Matrix metalloproteinases (MMP)-1 is a member of the MMP family and degrades types I and III collagens, which are the major structural components of the dermis.

OBJECTIVE

We evaluated the involvement IL-1beta and macrophage migration inhibitory factor (MIF) in MMP-1 expression under ultraviolet A (UVA) irradiation.

METHODS

IL-1beta and MIF in MMP-1 expression in cultured human dermal fibroblasts and the UVA effects on MMPs production using IL-1alpha/beta-deficient mice were analyzed. Furthermore, fibroblasts derived from MIF-deficient mice were used to analyze the effect of IL-1beta-induced MMPs production.

RESULTS

IL-1beta-enhanced MIF expression and induced MMP-1 in cultured human dermal fibroblasts. IL-1beta-induced MMP-1 expression is inhibited by neutralizing anti-MIF antibody. Dermal fibroblasts of IL-1alpha/beta-deficient mice produced significantly decreased levels of MMPs compared to wild-type mice after UVA irradiation. Furthermore, fibroblasts of MIF-deficient mice were much less sensitive to IL-1beta-induced MMPs production. On the contrary, IL-1beta produced significantly decreased levels of MMPs in MIF-deficient mice fibroblasts. The up-regulation of MMP-1 mRNA by IL-1beta stimulation was found to be inhibited by a p38 inhibitor and a JNK inhibitor. In contrast, the MEK inhibitor and inhibitor were found to have little effect on expression of MMP-1 mRNA.

CONCLUSIONS

IL-1beta is involved in the up-regulation of UVA-induced MMP-1 in dermal fibroblasts, and IL-1beta and MIF cytokine network induce MMP-1 and contribute to the loss of interstitial collagen in skin photoaging.

Macrophage migration inhibitory factor induces MMP-9 expression in macrophages via the MEK-ERK MAP kinase pathway

We have shown previously that macrophage migration inhibitory factor (MIF) may play a role in the destabilization of atherosclerotic plaques by activating matrix metalloproteinase protein-9 (MMP-9). The aim of this study is to investigate the signaling mechanism by which MIF induces MMP-9 expression and activation in a murine macrophage line (RAW264.7). MIF was able to activate extracellular signal-regulated kinase 1/2 (ERK1/2), to a less extent JNK, but not p38 mitogen-activated protein (MAP), MAP kinase to induce MMP9 mRNA and protein expression in RAW264.7 murine macrophages. This was confirmed by the findings that addition of an ERK MAP kinase inhibitor (PD98059) but not a p38 inhibitor (SB203589) abolished MIF-induced MMP-9 expression and activation, whereas addition of a JNK inhibitor (SP600125) produced a partially inhibitory effect. The functional role of mitogen-activated protein kinase kinase (MEK)-ERK MAP kinase in MIF-induced MMP-9 expression was further confirmed by overexpressing dominant negative MEK (DN-MEK) and DN-ERK MAP kinases. Interestingly, constitutive expression of a wild-type (WT)-MEK alone was also capable of inducing a low, but significant MMP-9 mRNA and protein expression but did not cause a further increase in MMP-9 in response to MIF. MIF activates the MEK-ERK MAP kinase pathway to induce MMP-9 expression by murine macrophages. Activation of this pathway is necessary for MMP-9 expression and activation in response to MIF stimulation.

Features of chronic allograft rejection on rat small intestine transplantation

The aim of this study was to develop a model of chronic rejection of the entire small intestine transplantation and to analyze the features of chronic rejection. Allogenic small bowel transplantation was performed in a rat combination of Lewis to F344. Intestines were procured at the 60th and the 90th day after operation. We compared the semiquantitative score of histological parameters. The immunological components involved in the chronic rejection process were evaluated by immunohistochemical staining and the cytokine levels in grafts. The significant characteristics of the allograft on histology were changes of villous architecture, interstitial fibrosis, leukocyte infiltration, and obliterative arteriopathy. Allografts on the 60th day post-transplantation had more score in inflammatory events, while the grafts on the 90th day after operation had more values in ischemia/fibrotic events. The number of infiltrating CD4, CD8 and macrophage cells in allografts progressively decreased over time. The level of intragraft cytokines such as IL-6, TNF-alpha and IL-10 in the 90th day after transplantation also decreased compared with that in the 60th day. These data suggested that in the early stage (POD 60), there were more active and intense inflammatory events; later (POD 90) allografts manifested less inflammation and more arterial obliteration and fibrosis.

Gastric epithelial expression of macrophage migration inhibitory factor is not altered by Helicobacter pylori infection in humans

BACKGROUND

Recent reports have shown an upregulation of macrophage migration inhibitory factor (MIF) during gastric ulcer development in a rat model and elevated counts of MIF-positive cells in biopsies from Helicobacter pylori-infected patients. H. pylori infection is a proven cofactor in humans causing gastritis and gastric ulcers. The aim of this study was to characterize MIF expression in human gastric epithelial cells in response to H. pylori.

METHODS

MIF mRNA and MIF protein expression was detected in human gastric epithelial cell lines after stimulation with proinflammatory cytokines or infection with H. pylori (cagA+/vacA+) using real-time reverse transcriptase-polymerase and enzyme-linked immunosorbent assay. Interleukin-8 secretion was measured as positive control. MIF mRNA and MIF protein expression was assessed in H. pylori-positive and -negative human gastric biopsy samples.

RESULTS

While interleukin-8 mRNA expression and interleukin-8 secretion were upregulated in gastric epithelial cells in vitro after H. pylori infection, no changes in MIF mRNA expression and MIF secretion could be detected. We found no significant differences in MIF expression in total RNA extracted from gastric biopsy tissue when comparing H. pylori-positive to control patients. Likewise, MIF protein expression in gastric epithelium was unaffected by H. pylori infection as compared to uninfected tissue.

CONCLUSIONS

While an increased MIF expression and positive effects of MIF blockade in ulcer healing have been shown in a rodent model and elevated numbers of MIF-positive cells have been found in H. pylori-infected human tissue, we herein could not confirm any differences in human gastric epithelial MIF expression and secretion after H. pylori infection in vitro and in vivo.

Effect of macrophage migration inhibitory factor (MIF) on acute graft-versus-host disease in a murine model of allogeneic stem cell transplantation

Macrophage migration inhibitory factor (MIF) may play an important role in the pathogenesis of acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). We examined whether MIF has an influence on the development of aGVHD and survival using BALB/c-based MIF knock-out (MIF KO) mice. Although MIF expression was observed in lymphocytes that had infiltrated the liver during aGVHD in both wild-type (WT) and MIF KO mice that received bone marrow cells (BM) and spleen cells (SP) from C57BL/6N mice, no significant difference was found in severity of aGVHD or survival rate between the two groups of mice. However, MIF level had decreased at 1 week after HSCT when MIF KO mice were used as the recipients. In the experiment using MIF KO mice as the donors, the recipient mice transplanted with BM and SP from MIF KO mice had significantly lower aGVHD scores on days 14, 21, and 35 than those in the recipient mice transplanted with BM and SP from WT-BALB/c mice. Histopathological findings supported these observations, showing that the bile ducts and lobules in the liver were destroyed by infiltrating MIF-expressing lymphocytes in the recipients of BM and SP from WT-BALB/c mice, while the bile ducts were not destroyed even by infiltrating MIF-deficient lymphocytes in the recipients of BM and SP from MIF KO mice. Therefore, these findings suggest that MIF has an effect on the development of aGVHD in a murine model of allogeneic stem cell transplantation.

The role of macrophages in allograft rejection

Macrophage accumulation has long been recognized as a feature of allograft rejection, yet the role of macrophages in rejection remains underappreciated. Macrophages contribute to both the innate and acquired arms of the alloimmune response and thus may be involved in all aspects of acute and chronic allograft rejection. Recent advances in macrophage biology have allowed a better understanding of the mechanisms of macrophage accumulation, their state of activation and the pleuripotent roles they play in allograft rejection. Therapeutic attention to macrophages, in addition to T lymphocytes, may lead to improved outcomes in organ transplantation.

Blockage of the macrophage migration inhibitory factor expression by short interference RNA inhibited the rejection of an allogeneic tracheal graft

We investigated the inhibitory effect of blocking the macrophage migration inhibitory factor (MIF) on the fibrous obstruction of a transplanted allograft in a murine model of obstructive bronchiolitis (OB). Tracheal grafts from C57BL/6 mice were transplanted into a subcutaneous pouch of BALB/c. Three days after transplantation, liposome including short interference (si) RNA for MIF was injected into the lumen of the grafts. The allografts were then harvested 7, 14 or 28 days after transplantation for an evaluation of the morphological changes. The MIF expression, which was ubiquitously recognized in the epithelium of allografts, decreased after the in vivo transfection of MIF siRNA. OB formation was therefore inhibited significantly more by the treatment with MIF siRNA than the allografts injected with empty liposome on the 14th day, however, no difference was observed between them on the 28th day. Treatment with MIF siRNA inhibits the destruction of tracheal allografts and OB formation in the early phase, and MIF was thus found to be one of the major cytokines involved in the rejection of the allogeneic trachea.

Macrophage migration inhibitory factor stimulates angiogenic factor expression and correlates with differentiation and lymph node status in patients with esophageal squamous cell carcinoma

OBJECTIVE

The objectives of this study were: 1) to examine the expression of macrophage migration inhibitory factor (MIF) in esophageal squamous cell carcinoma (ESCC); 2) to see if a relationship exists between MIF expression, clinicopathologic features, and long-term prognosis; and 3) to ascertain the possible biologic function of MIF in angiogenesis.

SUMMARY BACKGROUND DATA

MIF has been linked to fundamental processes such as those controlling cell proliferation, cell survival, angiogenesis, and tumor progression. Its role in ESCC, and the correlation of MIF expression and tumor pathologic features in patients, has not been elucidated.

METHODS

The expression of MIF in tumor and nontumor tissues was examined by immunohistochemical staining. Concentrations of MIF, vascular endothelial growth factor (VEGF), and interleukin-8 (IL-8) in patients' sera and in the supernatant of tumor cells culture were examined by ELISA. Correlations with clinicopathologic factors were made.

RESULTS

In 72 patients with ESCC, intracellular MIF was overexpressed in esophagectomy specimens. The expression of MIF correlated with both tumor differentiation and lymph node status. The median survival in the low-MIF expression group (<50% positively stained cancer cells on immunohistochemistry) and high expression group (>/=50% positively stained cancer cells) was 28.3 months and 15.8 months, respectively (P = 0.03). The 3-year survival rates for the 2 groups were 37.7% and 12.1%, respectively. MIF expression was related to microvessel density; increased MIF serum levels also correlated with higher serum levels of VEGF. In addition, in vitro MIF stimulation of esophageal cancer cell lines induced a dose-dependent increase in VEGF and IL-8 secretion.

CONCLUSIONS

These results demonstrate, for the first time, that human esophageal carcinomas express and secrete large amounts of MIF. Through its effects on VEGF and IL-8, MIF may serve as an autocrine factor in angiogenesis and thus play an important role in the pathogenesis of ESCC.

The macrophage infiltration index and matrix metalloproteinase-II expression as a predictor of chronic allograft rejection

The presence of macrophages on renal biopsy specimens is considered an important cofactor in the development of chronic allograft nephropathy (CAN). Macrophages can activate the expression of matrix metalloproteinases (MMP), which induce glomerulosclerosis, arteriosclerosis, and interstitial fibrosis. The aim of our study was to demonstrate if they were related to the development of CAN. We analyzed matrix metalloproteinase (MMP) expression with specific monoclonal antibodies on 53 kidney biopsies performed due to the suspicion of a first acute rejection (AR) episode: 24 of the grafts have been lost due to CAN and the rest are still functioning. The group with CAN showed worse graft function and greater proteinuria from the beginning. The macrophage infiltration index (MI) expression was significantly higher in that group also (18.8 +/- 12 vs 12.5 +/- 9.15; P < .05), with a more important presence of macrophages in the interstitium and tubules. We observed a positive correlation between MI and tubular infiltration (r(2) = 0.52; P < .001) and between MMP-II and MI in the interstitium (r(2) = 0.3; P < .05) and with the global MI (r(2) = 0.3; P < 0.05). The last correlation was more powerful in the group with CAN (r(2) = 0.4; P < .05). According to our experience, global MI and tubular infiltration during an AR episode are good markers of long-term graft survival. The correlation between MI and MMP-II supports the role of macrophages in the development of CAN, although further studies are needed to clarify the nature of this relationship.

Macrophage accumulation and renal fibrosis are independent of macrophage migration inhibitory factor in mouse obstructive nephropathy

BACKGROUND AND AIM

The progression of renal injury, initiated by either an immune or non-immune insult, is closely associated with the accumulation of leucocytes and fibroblasts in the damaged kidney. Macrophage migration inhibitory factor (MIF) regulates leucocyte activation and fibroblast proliferation in vitro. Studies have identified a pathological role for MIF in immune-initiated renal injury in the rat. In this study, we examined the role of MIF in obstructive nephropathy, where renal injury is initiated by a non-immune insult.

METHODS AND RESULTS

Unilateral ureteric ligation was performed on MIF wildtype (+/+) and MIF deficient (-/-) mice. Groups of five mice were killed at days 0, 1, 5 or 10 after obstruction, and kidneys were examined via immunohistochemistry and northern blotting. In MIF +/+ mice, expression of the MIF protein increased in obstructed kidneys compared to normal control kidneys. Interstitial macrophage and T cell accumulation was significantly increased in obstructed kidneys at day 5 and 10, but was unaffected by MIF deficiency. Osteopontin and macrophage colony stimulating factor (M-CSF) mRNA expression in obstructed kidneys were equally increased in both genotypes, indicating that expression of these chemokines is not influenced by MIF. No difference was detected in the development of renal fibrosis in obstructed MIF +/+ and MIF -/- kidneys, as assessed by myofibroblast accumulation and proliferation and expression of profibrotic molecules (transforming growth factor-beta 1(TGF-beta1) and collagen).

CONCLUSION

These results demonstrate that MIF expression is increased in obstructive nephropathy without affecting kidney leucocyte accumulation or the development of renal fibrosis. This suggests that the progression of renal injury in obstructive nephropathy is independent of MIF.

Up-regulation of macrophage migration inhibitory factor in infants with acute neonatal necrotizing enterocolitis

AIMS

To investigate the role of macrophage migration inhibitory factor (MIF) and its downstream cytokine cascade in necrotizing enterocolitis (NEC).

METHODS AND RESULTS

The expression of MIF mRNA and protein in NEC guts was assayed by in situ hybridization and immunohistochemistry, respectively. Concentrations of MIF, interleukin (IL)-6 and IL-8 in the serum and in the supernatant of macrophage cultures were examined by ELISA. Increased expression of MIF mRNA and protein was observed in the NEC guts, mainly in the infiltrating macrophages in the mucosa and submucosal layers. Up-regulation of MIF was associated with the accumulation of macrophages and T cells. In addition, serum levels of MIF, IL-6 and IL-8 in NEC patients during the acute stage of the disease were significantly increased. The expression of MIF decreased both locally and systemically after the disease was resolved. MIF was also found to increase the secretion of IL-6 and IL-8 by macrophages isolated from healthy individuals in vitro in NEC.

CONCLUSIONS

MIF acts by stimulating macrophage production of IL-6 and IL-8. This further aggravates the inflammatory process by increasing the infiltration of neutrophils and activating inflammatory cells. The results of this study suggest that MIF plays an important role in the pathogenesis of NEC and may serve as a target for therapeutic intervention in NEC.

Macrophage migration inhibitory factor induces MMP-9 expression: implications for destabilization of human atherosclerotic plaques

Macrophage migration inhibitory factor (MIF) has been shown to participate in both experimental and human atherogenesis. Expression of MMP-9 has been shown to play a role in the instability of atherosclerotic plaque. Thus, we hypothesize that MIF may participate in the destabilization of atherosclerotic plaques by stimulating MMP-9 expression. This hypothesis was investigated by examining the expression of MIF and MMP-9 in human atherosclerotic plaques using two-color immunostaining and by determining the potential role of MIF in the induction of MMP-9 expression in vascular smooth muscle cells (VSMC) and macrophages in vitro. Two-color immunohistochemistry demonstrated that MIF was strongly upregulated by macrophages and VSMCs. This was associated with marked increase in MMP-9 expression in vulnerable atheromatous plaques, but not in the fibrous lesions. Upregulation of MIF and MMP-9 in vulnerable atheromatous plaques was associated with the weakening of fibrous caps. The role of MIF in MMP-9 expression was demonstrated by the ability of MIF to directly induce MMP-9 mRNA and protein expression in macrophages and in VSMCs in a dose and time-dependent manner, which was blocked by a neutralizing MIF antibody. In conclusion, MIF and MMP-9 are markedly upregulated in vulnerable atheromatous plaques. The ability of MIF to induce MMP-9 expression in VSMCs and macrophages suggests that MIF may play a role in the destabilization of human atherosclerotic plaques.

Elevated macrophage migration inhibitory factor (MIF) levels in the urine of patients with focal glomerular sclerosis

The pathogenesis of focal glomerular sclerosis (FGS) is poorly understood. Macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine released from T cells and macrophages, and is a key molecule in inflammation. To examine further the possible role of MIF in FGS, we measured MIF levels in the urine. The purpose of the present study was to evaluate the involvement of MIF in FGS. Urine samples were obtained from 20 FGS patients. The disease controls included 40 patients with minimal-change nephrotic syndrome (MCNS) and membranous nephropathy (MN). A group of healthy subjects also served as controls. Biopsies were performed in all patients prior to entry to the study. The samples were assayed for MIF protein by a sandwich enzyme-linked immunosorbent assay (ELISA). The levels of MIF in the urine of FGS patients were significantly higher than those of the normal controls and patients with MCNS and MN. In contrast, the levels of urinary MIF (uMIF) in patients with MCNS and MN did not differ significantly from normal values. In the present study, attention also focused on the relationship between uMIF levels and pathological features. Among the patients with FGS, uMIF levels were significantly correlated with the grade of mesangial matrix increase and that of interstitial fibrosis. There was also a significant correlation between uMIF levels and the number of both intraglomerular and interstitial macrophages. Although the underlying mechanisms remain to be determined, our study presents evidence that urinary excretion of MIF is increased in FGS patients with active renal lesions.

Macrophage migration inhibitory factor and the risk of myocardial infarction or death due to coronary artery disease in adults without prior myocardial infarction or stroke: the EPIC-Norfolk Prospective Population study

PURPOSE

To determine whether plasma levels of macrophage migration inhibitory factor, a proinflammatory cytokine involved in atherogenesis, are predictive of myocardial infarction or death from coronary artery disease.

METHODS

We performed a prospective case-control study nested in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk cohort. We selected men and women who did not report a history of myocardial infarction or stroke at baseline. Baseline concentrations of macrophage migration inhibitory factor were measured among 777 patients who had a myocardial infarction or died of coronary artery disease during follow-up, and 1554 matched controls who remained free of coronary artery disease.

RESULTS

Baseline macrophage migration inhibitory factor concentrations were higher in cases than controls (median, 107.4 microg/L vs. 90.7 microg/L, P = 0.001). The risk of myocardial infarction or death from coronary artery disease increased with increasing quartiles of macrophage migration inhibitory factor (P for linearity <0.0001). Patients in the highest quartile had the greatest likelihood of myocardial infarction or death due to coronary artery disease (unadjusted odds ratio [OR] = 1.6; 95% confidence interval [CI]: 1.2 to 2.0). After adjustment for traditional risk factors and C-reactive protein level, the odds ratio decreased slightly (OR = 1.3; 95% CI: 1.0 to 1.7). Upon additional adjustment for white cell count, this association was no longer statistically significant.

CONCLUSION

Prospective data suggest that the relation between macrophage migration inhibitory factor and the risk of myocardial infarction or death due to coronary artery disease in adults without a history of myocardial infarction or stroke is not very strong. However, the data support a regulatory role for macrophage migration inhibitory factor in the process of atherosclerosis.

Long-Term Treatment With a Specific Rho-Kinase Inhibitor Suppresses Cardiac Allograft Vasculopathy in Mice

Cardiac allograft vasculopathy (CAV) continues to be a major cause of late graft failure after cardiac transplantation. We have demonstrated that Rho-kinase, an effector of the small GTPase Rho, plays an important role in the pathogenesis of arteriosclerosis. In this study, we examined whether the Rho-kinase–mediated pathway is also involved in the pathogenesis of CAV using a specific Rho-kinase inhibitor and a dominant-negative Rho-kinase. Hearts from AKR mice were heterotopically transplanted to C3H/He (allograft) or AKR mice (isograft), and the effects of long-term oral treatment with fasudil, which is metabolized to a specific Rho-kinase inhibitor hydroxyfasudil, on CAV were examined at 2 and 4 weeks after the transplantation. Coronary remodeling in the allografts characterized by intimal thickening and perivascular fibrosis was dose-dependently suppressed in the fasudil group compared with the control group ( P <0.01, n=9 to 10). The inhibitory effects of hydroxyfasudil were mimicked by in vivo gene transfer of dominant-negative Rho-kinase ( P <0.05, n=4). Among the proinflammatory cytokines examined, those of macrophage migration inhibitory factor, interferon-γ, and transforming growth factor-β1 were upregulated in the control group and were dose-dependently inhibited in the fasudil group ( P <0.01, n=5). Vascular inflammation in the allografts, as evidenced by accumulation of inflammatory cells (macrophages and T cells), was also significantly inhibited in the fasudil group ( P <0.05, n=5 to 10). These results indicate that long-term treatment with fasudil suppresses CAV in mice, suggesting that Rho-kinase is an important therapeutic target for the prevention of CAV.

Ultraviolet A-induced Production of Matrix Metalloproteinase-1 Is Mediated by Macrophage Migration Inhibitory Factor (MIF) in Human Dermal Fibroblasts

Matrix metalloproteinases (MMPs) are thought to be responsible for dermal photoaging in human skin. In the present study, we evaluated the involvement of macrophage migration inhibitory factor (MIF) in MMP-1 expression under ultraviolet A (UVA) irradiation in cultured human dermal fibroblasts. UVA (20 J/cm(2)) up-regulates MIF production, and UVA-induced MMP-1 mRNA production is inhibited by an anti-MIF antibody. MIF (100 ng/ml) was shown to induce MMP-1 in cultured human dermal fibroblasts. We found that MIF (100 ng/ml) enhanced MMP-1 activity in cultured fibroblasts assessed by zymography. Moreover, we observed that fibroblasts obtained from MIF-deficient mice were much less sensitive to UVA regarding MMP-13 expression than those from wild-type BALB/c mice. Furthermore, after UVA irradiation (10 J/cm(2)), dermal fibroblasts of MIF-deficient mice produced significantly decreased levels of MMP-13 compared with fibroblasts of wild-type mice. Next we investigated the signal transduction pathway of MIF. The up-regulation of MMP-1 mRNA by MIF stimulation was found to be inhibited by a PKC inhibitor (GF109203X), a Src-family tyrosine kinase inhibitor (herbimycin A), a tyrosine kinase inhibitor (genistein), a PKA inhibitor (H89), a MEK inhibitor (PD98089), and a JNK inhibitor (SP600125). In contrast, the p38 inhibitor (SB203580) was found to have little effect on expression of MMP-1 mRNA. We found that PKC-pan, PKC alpha/beta II, PKC delta (Thr505), PKC delta (Ser(643)), Raf, and MAPK were phosphorylated by MIF. Moreover, we demonstrated that phosphorylation of PKC alpha/beta II and MAPK in response to MIF was suppressed by genistein, and herbimycin A as well as by transfection of the plasmid of C-terminal Src kinase. The DNA binding activity of AP-1 was significantly up-regulated 2 h after MIF stimulation. Taken together, these results suggest that MIF is involved in the up-regulation of UVA-induced MMP-1 in dermal fibroblasts through PKC-, PKA-, Src family tyrosine kinase-, MAPK-, c-Jun-, and AP-1-dependent pathways.

Macrophage migration inhibitory factor: a regulator of innate immunity

Cytokines are essential effector molecules of innate immunity that initiate and coordinate the cellular and humoral responses aimed, for example, at the eradication of microbial pathogens.

Discovered in the late 1960s as a product of activated T cells, the cytokine macrophage migration inhibitory factor (MIF) has been discovered recently to carry out important functions as a mediator of the innate immune system.

Constitutively expressed by a broad spectrum of cells and tissues, including monocytes and macrophages, MIF is rapidly released after exposure to microbial products and pro-inflammatory mediators, and in response to stress. After it is released, MIF induces pro-inflammatory biological responses that act as a regulator of immune responses.

MIF activates the extracellular signal-regulated kinase 1 (ERK1)/ERK2–mitogen-activated protein kinase pathway, inhibits the activity of JUN activation domain-binding protein 1 (JAB1) — a co-activator of the activator protein 1 (AP1) — upregulates the expression of Toll-like receptor 4 to promote the recognition of endotoxin-expressing bacterial pathogens, sustains pro-inflammatory function by inhibiting p53-dependent apoptosis of macrophages and counter-regulates the immunosuppressive effects of glucocorticoids on immune cells.

As a pro-inflammatory mediator, MIF has been shown to be implicated in the pathogenesis of severe sepsis and septic shock, acute respiratory distress syndrome, and several other inflammatory and autoimmune diseases, including rheumatoid arthritis, glomerulonephritis and inflammatory bowel diseases.

Given its crucial role as a regulator of innate and acquired immunity, pharmacological or immunological modulation of MIF activity might offer new treatment opportunities for the management of acute and chronic inflammatory diseases.

For more than a quarter of a century, macrophage migration inhibitory factor (MIF) has been a mysterious cytokine. In recent years, MIF has assumed an important role as a pivotal regulator of innate immunity. MIF is an integral component of the host antimicrobial alarm system and stress response that promotes the pro-inflammatory functions of immune cells. A rapidly increasing amount of literature indicates that MIF is implicated in the pathogenesis of sepsis, and inflammatory and autoimmune diseases, suggesting that MIF-directed therapies might offer new treatment opportunities for human diseases in the future.

Blockade of macrophage migration inhibitory factor does not prevent acute renal allograft rejection

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory molecule involved in cell-mediated immunity and delayed-type hypersensitivity (DTH). We inhibited systemic and local MIF production to determine its contribution to acute rejection (AR). Skin DTH response and acute rejection of skin and kidney allografts were examined using MIF gene knockout (MIF -/-) and wild-type mice (MIF +/+) with anti-MIF or control antibody. MIF-Ab reduced skin DTH by 60% (p < 0.01), but absence of the MIF gene (MIF -/-) had no effect. Local absence of MIF had no effect on the survival of skin grafted onto BALB/c recipients. Similarly MIF +/+ and MIF -/- kidneys transplanted into BALB/c recipients showed a similar degree of histological rejection, graft dysfunction and cellular infiltrate suggesting that AR is not dependent on local MIF production. To investigate the influence of systemic MIF, BALB/c donor skin was grafted onto MIF +/+ and MIF -/- mice. The tempo of AR was not altered by systemic absence of MIF (MIF-Ab or MIF -/-). BALB/c kidneys transplanted into MIF +/+ (with or without MIF-Ab) and MIF -/- mice showed similar parameters of rejection. MIF blockade reduces the DTH response; however, neither local nor systemic MIF are required for the rejection of fully mismatched skin and renal allografts.

Cardiac allograft rejection in the absence of macrophage migration inhibitory factor

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a secreted proinflammatory lymphokine essential for elicitation of delayed-type hypersensitivity (DTH) reactions in vivo. We tested whether MIF blockade-absence affected acute or chronic murine cardiac allograft rejection.

METHODS

Wild-type (WT) C57BL/6 (B6) mice underwent transplantation with BALB/c hearts with or without blocking anti-MIF antibody, and MIF knockout (KO) B6 mice underwent transplantation with MIF KO BALB/c hearts. Chronic immune injury was induced in WT and KO recipients using donor-specific transfusion and anti-CD40L antibody.

RESULTS

Unexpectedly, the blockade or genetic absence of MIF did not prolong graft survival even if recipient T-cell cytotoxicity was additionally impaired. The histologic manifestations of acute and chronic immune injury to the allograft were similar between groups.

CONCLUSIONS

MIF is not required for acute or chronic allograft rejection in mice. The findings raise questions about the role of DTH as an important mediator of cardiac allograft injury.

Expression of macrophage migration inhibitory factor in acute ischemic myocardial injury

Macrophage migration inhibitory factor (MIF) is a key mediator in inflammatory or immune-mediated diseases, although its role in heart diseases is unknown. This study investigated the expression of MIF in the myocardium in the development of acute myocardial infarction (AMI). By use of immunohistochemistry, Western blotting, RT-PCR, and in situ hybridization, the gene and protein expression of MIF in the heart at 6 hr, 1 day, 3 days, 1 week, and 2 weeks after AMI was studied. In both normal and sham-operated rats, MIF mRNA and protein were expressed constitutively at low levels by the myocytes. By contrast, MIF mRNA was rapidly upregulated by the surviving myocytes in the infarcted region and, to a lesser extent, the non-infarcted region, accounting for a sevenfold increase at 6 hr after AMI (p<0.001). This was followed by a fourfold increase in MIF protein expression at day 1 after AMI (p<0.05). Macrophages were found accumulated in the infarcted region, being significant at day 1 (p<0.01) and progressive increased over the 2-week time course (p<0.01) in which MIF was found expressed in these cells. The results indicated that the infiltrating macrophages and myocytes were sources of MIF in the infarcted region. The latter cells became activated and involved in the amplification of inflammatory response in AMI. Therefore, upregulation of myocardial MIF may contribute to macrophage accumulation in the infarcted region and their pro-inflammatory role may participate in the myocyte damage seen in AMI.

Monocytes and peritubular capillary C4d deposition in acute renal allograft rejection

BACKGROUND

Peritubular capillary (PTC) deposition of complement split factor C4d in renal allografts has been shown to be closely associated with circulating antidonor antibodies and a marker for relatively poor graft survival. Monocyte/macrophage (MO) infiltration of renal allografts has been shown to adversely affect graft survival. The purpose of this study was to assess whether the two phenomena are related.

METHODS

Twenty-three biopsies (from 15 patients) demonstrated diffuse strong staining of PTC for C4d (C4d+ group) and acute tubular injury with or without significant cellular rejection, while 28 biopsies (with acute rejection) but negative for PTC C4d served as controls (C4d- group).

RESULTS

The C4d+ group demonstrated significantly greater glomerular and interstitial MO infiltration than did the C4d- group [3.4 +/- 2.0 vs. 0.2 +/- 0.3 MO/glomerulus, P < 0.0001; 12.9 +/- 9.2 vs. 6.5 +/- 5.0 MO/high power field (hpf), P = 0.0030]. Neutrophilic (PMN) infiltration of glomeruli and PTC was also significantly greater in the C4d+ group than in the C4d- one (0.8 +/- 0.6 vs. 0.3 +/- 0.3 PMN/glomerulus, P = 0.0003; 0.9 +/- 0.8 vs. 0.4 +/- 0.3 PTC PMN/hpf, P = 0.0035).

CONCLUSION

The results indicate a close association between PTC C4d deposition and MO infiltration, particularly glomerular, and confirm previous observations regarding the correlation of PTC C4d staining and PMN infiltration.

Macrophage migration inhibitory factor exhibits a pronounced circadian rhythm relevant to its role as a glucocorticoid counter-regulator

In humans, maximal expression of T helper 1 cytokines coincide with the nocturnal nadir of plasma cortisol, whereas T helper 2 cytokine responses are dominant during day-time. The pro-inflammatory cytokine, macrophage migration inhibitory factor counter-regulates glucocorticoid-mediated immune suppression. To determine the relationship between cortisol and macrophage migration inhibitory factor, healthy volunteers had blood drawn hourly for 24 h for measurement of plasma cortisol and basal- and stimulated-macrophage migration inhibitory factor. Similar to cortisol, macrophage migration inhibitory factor peaked during the late morning whereas interferon-gamma, tumour necrosis factor-alpha, interleukin-1 and interleukin-12 demonstrated a nocturnal peak. After oral cortisone, plasma macrophage migration inhibitory factor rose 2-4-fold, whereas the other cytokines decreased. There was no correlation between cortisol during the insulin tolerance test and plasma macrophage migration inhibitory factor. The late morning peak of macrophage migration inhibitory factor, by antagonizing cortisol-mediated pro-inflammatory cytokine suppression may prolong the duration of early morning inflammation. These observations explain the beneficial role of macrophage migration inhibitory factor neutralization in models of inflammatory arthritis.

Induction of MIF synthesis and secretion by tubular epithelial cells: a novel action of angiotensin II

BACKGROUND

Angiotensin II (Ang II) plays an important role in the development of renal injury through its vasoactive and proinflammatory activities. We investigated whether some of the effects of Ang II could be mediated through the production of macrophage migration inhibitory factor (MIF).

METHODS

Groups of rats underwent sham surgery (sham), subtotal nephrectomy (STNx), or STNx plus treatment with irbesartan. Renal tissue was examined 12 weeks postsurgery for MIF mRNA expression and leukocyte accumulation. To determine whether Ang II had a direct effect on MIF production, mRNA synthesis and protein secretion were examined in proximal tubular epithelial (NRK52E and MCT) cell lines.

RESULTS

MIF mRNA was strongly expressed in 5.4%+/- 1.1% (mean +/- SD) of cortical tubules of sham-operated rats. This was significantly up-regulated in STNx rats (44.9%+/- 22.6%) and was abrogated by administration of irbesartan (2.8%+/- 2.4%). STNx resulted in significant glomerular and interstitial accumulation of macrophages and T cells, which correlated with glomerular and tubular MIF mRNA expression, respectively. In vitro studies of tubular epithelial cells revealed that Ang II caused a twofold increase in MIF mRNA expression in NRK52E and MCT cells, which was abrogated by irbesartan. In addition, Ang II induced a rapid release of 50% of MIF protein from NRK52E cells within 20 minutes.

CONCLUSION

This study has demonstrated that Ang II up-regulates MIF mRNA production and MIF protein secretion by tubular epithelial cells. Ang II may promote accumulation and activation of interstitial leukocytes via induction of MIF synthesis and secretion in renal tubular epithelial cells. This may be an important mechanism by which Ang II mediates renal injury.

Blockade of macrophage colony-stimulating factor reduces macrophage proliferation and accumulation in renal allograft rejection

Macrophage accumulation within an acutely rejecting allograft occurs by recruitment and local proliferation. To determine the importance of M-CSF in driving macrophage proliferation during acute rejection, we blocked the M-CSF receptor, c-fms, in a mouse model of acute renal allograft rejection. C57BL/6 mouse kidneys (allografts, n = 20) or BALB/c kidneys (isografts, n = 5) were transplanted into BALB/c mice. Anti-c-fms antibody (AFS98) or control Ig (50 mg/kg/day, i.p.) was given daily to allografts from days 0-5. All mice were killed day 6 postoperatively. Expression of the M-CSF receptor, c-fms, was restricted to infiltrating CD68+ macrophages. Blockade of c-fms reduced proliferating (CD68+/BrdU+) macrophages by 82% (1.1 v 6.2%, p < 0.001), interstitial CD68+ macrophage accumulation by 53% (595 v 1270/mm2, p < 0.001), and glomerular CD68+ macrophage accumulation by 71% (0.73 V 2.48 CD68+ cells per glomerulus, p < 0.001). Parameters of T-cell involvement (intragraft CD4+, CD8+ and CD25+ lymphocyte numbers) were not affected. The severity of tubulointerstitial rejection was reduced in the treatment group as shown by decreased tubulitis and tubular cell proliferation. Macrophage proliferation during acute allograft rejection is dependent on the interaction of M-CSF with its receptor c-fms. This pathway plays a significant and specific role in the accumulation of macrophages within a rejecting renal allograft.

Macrophage migratory inhibitory factor (MIF) expression in acute graft-versus-host disease (GVHD) in allogeneic hemopoietic stem cell transplant recipients

Graft-versus-host disease (GVHD) is a major complication after hemopoietic stem cell transplantation (HSCT), but its pathogenesis remains uncertain. Macrophage migratory inhibitory factor (MIF) is an important mediator in the allo-immune reaction during renal transplantation, yet its role in hemopoietic stem cell transplantation (HSCT) remains unexplored. This study investigated the potential role of MIF in acute graft-versus-host disease (aGVHD) following allogeneic HSCT. Forty-six randomly selected patients undergoing autologous or allogeneic HSCT were studied. Immunohistochemistry and in situ hybridization were performed to examine tissue MIF mRNA and protein expression on skin and colonic biopsy specimens. The associated T cell and macrophage activation was also studied by immunohistochemical studies. A semi-quantitative method was used to assess MIF staining, as well as T cell and macrophage staining. Serial blood samples were analyzed by ELISA for serum MIF levels. Immunohistochemistry and in situ hybridization performed in 15 skin and 19 colonic biopsies from 17 patients who developed moderate to severe aGVHD showed a significant increase in MIF mRNA and protein expression compared with normal controls (seven skin and five colonic biopsies). MIF was localized within the epidermis and the vascular area of skin, but diffusely expressed in the entire thickness of colon. Macrophage and T lymphocyte infiltration was confined to areas of strong MIF expression. Serial analysis by ELISA showed that only patients who developed aGVHD (n = 19) exhibited an increase (two- to three-fold) in serum MIF during HSCT, but not in the allogeneic HSCT recipients without aGVHD (n = 7) or those who received autologous HSCT (n = 8). In 14 out of 19 patients, serum MIF peaked before the onset of aGVHD. Local and systemic up-regulation of MIF expression is associated with the occurrence of acute GVHD. Its pathogenetic role remains to be further determined.

Human cytomegalovirus-mediated induction of MIF in fibroblasts

Human cytomegalovirus (HCMV) infection of fibroblasts induces the proinflammatory mediator macrophage migration inhibitory factor (MIF). Our in vitro experiments show that active HCMV infection alone is required to induce an early and sustained induction of MIF mRNA and protein production. Unlike in other infection models, in which MIF has been described to be released from preformed stores, our data conclusively show that HCMV infection triggers de novo synthesis and subsequent secretion of MIF. The kinetics of MIF protein production during HCMV infection points to an efficacious immune modulation, in which lymphocytes and monocytes are initially recruited by the early release of chemokines to sites of infection and locally activated by increasing concentrations of MIF.

Transferrin up-regulates chemokine synthesis by human proximal tubular epithelial cells: implication on mechanism of tubuloglomerular communication in glomerulopathic proteinura

BACKGROUND

The pathogenesis of glomerulosclerosis and tubulointerstitial fibrosis in proteinuric renal disease is obscure. We recently showed that transferrin, a key proteinuric component, mediates proximal tubular epithelial cell (PTEC) C3 synthesis. To further examine whether proteinuric tubular injury may induce glomerular inflammation and to characterize the role of transferrin in activating PTEC, glomerular mesangial cells (MC) were exposed to transferrin-activated PTEC culture supernatant and their proliferative and profibrotic responses analyzed.

METHODS

Human PTEC and MC were obtained by primary culture. Confluent, transferrin-stimulated PTEC were grown in serum-free medium to produce a "conditioned" medium that was incubated with quiescent MC. The proliferative response of MC was then assessed by thymidine uptake, and the expression of fibrogenic factors measured by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The chemokine profile in PTEC after transferrin treatment was examined by RT-PCR and ELISA.

RESULTS

"Conditioned" supernatant from PTEC, which contained the highest amounts of platelet-derived growth factor (PDGF), stimulated MC proliferation compared with serum-free (P = 0.03) or transferrin-containing (P = 0.009) control media. This proliferative response was partially abrogated by treating MC with anti-PDGF. MC expression of PDGF, but not transforming growth factor-beta or intercellular cell adhesion molecule-1, was up-regulated by conditioned PTEC medium. Transferrin up-regulated monocyte chemoattractant peptide-1, interleukin-8, and macrophage migration inhibitory factor expression in a time- and dose-dependent fashion, but had no effect on RANTES expression by PTEC.

CONCLUSIONS

These results provide experimental evidence suggesting that there is a tubuloglomerular "cross-talk" mechanism in the proteinuric state. PTEC-secreted PDGF, which further induces mesangial PDGF, could partially account for the mesangial proliferation frequently observed in proteinuric renal disease. Transferrin is one of the culprit nephrotic proteins leading to tubular overexpression of various proinflammatory chemokines, which may explain the interstitial changes observed in proteinuric states.