Biomedical subjects

R Bucala

Publications and source records attributed to R Bucala.

At least 127 records · Page 7Linked to original sources

PubMed1996

Prevention of cardiovascular and renal pathology of aging by the advanced glycation inhibitor aminoguanidine.

Human aging is impacted severely by cardiovascular disease and significantly but less overtly by renal dysfunction. Advanced glycation endproducts (AGEs) have been linked to tissue damage in diabetes and aging, and the AGE inhibitor aminoguanidine (AG) has been shown to inhibit renal and vascular pathology in diabetic animals. In the present study, the effects of AG on aging-related renal and vascular changes and AGE accumulation were studied in nondiabetic female Sprague-Dawley (S-D) and Fischer 344 (F344) rats treated with AG (0.1% in drinking water) for 18 mo. Significant increases in the AGE content in aged cardiac (P < 0.05), aortic (P < 0.005), and renal (P < 0.05) tissues were prevented by AG treatment (P < 0.05 for each tissue). A marked age-linked vasodilatory impairment in response to acetylcholine and nitroglycerine was prevented by AG treatment (P < 0.005), as was an age-related cardiac hypertrophy evident in both strains (P < 0.05). While creatinine clearance was unaffected by aging in these studies, the AGE/ creatinine clearance ratio declined 3-fold in old rats vs. young rats (S-D, P < 0.05; F344, P < 0.01), while it declined significantly less in AG-treated old rats (P < 0.05). In S-D but not in F344 rats, a significant (P < 0.05) age-linked 24% nephron loss was completely prevented by AG treatment, and glomerular sclerosis was markedly suppressed (P < 0.01). Age-related albuminuria and proteinuria were markedly inhibited by AG in both strains (S-D, P < 0.01; F344, P < 0.01). These data suggest that early interference with AGE accumulation by AG treatment may impart significant protection against the progressive cardiovascular and renal decline afflicting the last decades of life.

Acetylcholine↗

PubMed1996

Long-term assessment of glucose control by haemoglobin-AGE measurement.

BACKGROUND: Control of blood glucose is important in reducing both the incidence and the severity of complications in diabetes mellitus. One consequence of long- term hyperglycaemia is the formation and accumulation of advanced glycation end-products (AGEs) on tissue macromolecules. An AGE-modified form of human haemoglobin (Hb-AGE) present at high levels in the red cells of diabetic patients, differs from glucose-derived Amadori product HbA1c in being chemically irreversible and thus persisting for the circulating life of the red cell. We therefore compared Hb- AGE with HbA1c as indicators of long-term blood glucose control. METHODS: In an open study we measured circulating HbA1c and Hb-AGE concentrations in eight patients with poorly controlled non-insulin-dependent diabetes after a switch to subcutaneous insulin therapy and careful blood glucose monitoring. RESULTS: After 16 weeks of insulin therapy, the mean HbA1c had decreased from 13.3 (SD 1.2) to 7.3 (0.9)% and the mean Hb-AGE from 12.1 (1.5) to 7.3 (1.3) U/mg Hb. The rate of Hb-AGE decline was 23% slower than that of HbA1c (p=0.044). INTERPRETATION: The observation that Hb-AGE declines more slowly than HbA1c is consistent with the irreversible nature of the AGE product. Because of this property, Hb-AGE may prove superior to HbA1c as a long-term index of circulating glucose concentrations.

Blood Glucose↗

PubMed1996

Hydroxyalkenal formation induced by advanced glycosylation of low density lipoprotein.

Advanced glycosylation end products (AGEs) have been identified to be present on both the apolipoprotein and lipid components of low density lipoprotein (LDL) and to act to prevent its recognition and uptake by high affinity, tissue LDL receptors. Lipid-linked AGEs form readily in vitro by the covalent addition of glucose to the amine-containing head groups of phospholipids. This process is accompanied by oxidation of the unsaturated fatty acid side chains and occurs in the absence of exogenously added transition metals or free radical generating systems, suggesting that AGE formation may contribute significantly to lipid oxidation in vivo. To assess more precisely the chemical basis of AGE-induced oxidative modification, we performed gas chromatography-mass spectrometry analysis of the lipid products which form over time during LDL-advanced glycosylation in vitro. Negative ion chemical ionization mass spectroscopy of two major compounds that were identified were consistent with the structures of the fatty acid oxidation products 4-hydroxyhexenal and 4-hydroxynonenal. These data support the concept that AGE formation in close proximity to unsaturated fatty acyl groups leads to lipid oxidation and provide additional evidence that advanced glycosylation is an important pathogenic modification of the LDL particle in vivo.

Aldehydes↗

PubMed1996

An essential role for macrophage migration inhibitory factor in the tuberculin delayed-type hypersensitivity reaction.

30 years ago, investigations into the molecular basis of the delayed-type hypersensitivity reaction (DTH) provided evidence for the first lymphokine activity: a lymphocyte-derived mediator called macrophage migration inhibitory factor (MIF), which inhibited the random migration of peritoneal macrophages. Despite the long-standing association of MIF with the DTH reaction and the cloning of a human protein with macrophage migration inhibitory activity, the precise role of MIF in this classic cell-mediated immune response has remained undefined. This situation has been further complicated by the fact that two other cytokines, interferon gamma and IL-4, similarly inhibit macrophage migration and by the identification of mitogenic contaminants in some preparations of cloned human MIF. Using recently developed molecular probes for mouse MIF, we have examined the role of this protein in a classical model of DTH, the tuberculin reaction in mice. Both MIF messenger RNA and protein were expressed prominently in DTH lesions, as assessed by reverse transcription polymerase chain reaction, in situ hybridization, and immunostaining with anti-MIF antibody. The predominant cellular origin of MIF appeared to be the monocyte/macrophage, a cell type identified recently to be a major source of MIF release in vivo. The administration of neutralizing anti-MIF antibodies to mice inhibited significantly the development of DTH, thus affirming the central role of MIF in this classic immunological response.

Animals↗

PubMed1996

NMR characterization of structure, backbone dynamics, and glutathione binding of the human macrophage migration inhibitory factor (MIF).

Human macrophage migration inhibitory factor is a 114 amino acid protein that belongs to the family of immunologic cytokines. Assignments of 1H, 15N, and 13C resonances have enabled the determination of the secondary structure of the protein, which consists of two alpha-helices (residues 18-31 and 89-72) and a central four-stranded beta-sheet. In the beta-sheet, two parallel beta-sheets are connected in an antiparallel sense. From the total of three cysteines present in the primary structure of MIF, none was found to form disulfide bridges. 1H-15N heteronuclear T1, T2, and steady-state NOE measurements indicate that the backbone of MIF exists in a rigid structure of limited conformational flexibility (on the nanosecond to picosecond time scale). Several residues located in the loop regions and at the N termini of two helices exhibit internal motions on the 1-3 ns time scale. The capacity to bind glutathione was investigated by titration of a uniform 15N-labeled sample and led us to conclude that MIF has, at best, very low affinity for glutathione.

Amino Acid Sequence↗

PubMed1996

MIF re-discovered: pituitary hormone and glucocorticoid-induced regulator of cytokine production.

The protein mediator known as macrophage migration inhibitory factor (MIF) was one of the first cytokine activities to be discovered and was described 30 years ago to be a T cell-derived factor that inhibited the random migration of macrophages. Despite the long-standing association of MIF with activated lymphocytes, the precise role of MIF in host responses remained undefined. Recent studies however, have led to the description of a pituitary mediator that appears to act as the natural, counter-regulatory hormone for glucocorticoid action within the immune system. Isolated as a product of an anterior pituitary cell line, this protein was sequenced and found to have the same structure as MIF. The major role of MIF appears to be to act at an inflammatory site or lymph node to counter-balance the inhibitory effects of steroids on the primary immune response, which must necessarily be mounted to eliminate the source of infection or tissue invasion.

Animals↗

PubMed1996

What is the effect of hyperglycemia on atherogenesis and can it be reversed by aminoguanidine?

Reducing sugars such as glucose react non-enzymatically with the amino groups of proteins and lipids to initiate a chemical modification pathway known as advanced glycosylation. Recent progress in our understanding of this process has affirmed the hypothesis that advanced glycosylation endproducts (AGEs) play an important role in the evolution of both diabetic and non-diabetic vascular disease. Utilizing newly developed AGE-specific ELISA techniques, AGEs have been identified to be present on a variety of vascular wall, lipoprotein, and lipid constituents. Vascular wall AGEs contribute to vascular pathology by acting to increase vascular permeability, enhance subintimal protein and lipoprotein deposition, and inactivate the endothelium-derived relaxing factor, nitric oxide. Lipid-linked AGEs also have been shown to initiate oxidative modification, thus promoting the formation of oxidized low-density lipoprotein. AGE-specific ELISA analysis has demonstrated a significantly increased level of AGE-modified LDL in the plasma of diabetic patients when compared to normal controls. Furthermore, LDL which has been modified by advanced glycosylation exhibits markedly impaired clearance kinetics in vivo. Thus, AGE-modification impairs LDL-receptor-mediated clearance mechanisms and contributes to elevated LDL levels in patients with diabetes. This concept has been substantiated recently by the clinical observation that administration of the advanced glycosylation inhibitor aminoguanidine to diabetic patients significantly decreases circulating LDL levels.

Animals↗

PubMed1996

Effects of aminoguanidine in preventing experimental diabetic nephropathy are related to the duration of treatment.

It has been postulated that the accumulation of advanced glycation end products (AGEs) in the kidney is important in the pathogenesis of diabetic nephropathy. Previously, aminoguanidine has been shown to inhibit the accumulation of renal AGEs and to retard the development of experimental diabetic nephropathy. The present study serially assessed the accumulation of AGEs in the aorta and kidney, as well as renal functional and structural parameters over 32 weeks of experimental diabetes in the absence and presence of aminoguanidine. In addition, it was determined if aminoguanidine was more effective if administered earlier or later in the evolution of diabetic nephropathy by treating diabetic rats with aminoguanidine in the first or second half of the 32-week study period. In the serial studies, glomerular and renal tubular fluorescence increased over the 32 week period and this increase was attenuated by aminoguanidine treatment. Concomitant with the effects of aminoguanidine on fluorescence, there was a retardation in the rise in urinary albumin excretion and prevention of mesangial expansion. Early or late administration of aminoguanidine in diabetic rats reduced tissue fluorescence in glomeruli and renal tubules. At 32 weeks, renal AGEs were increased in diabetic rats as assessed by tissue fluorescence. Using a specific RIA, renal AGEs were increased in diabetic rats and decreased by aminoguanidine treatment, administered over the entire 32 weeks or in the first or latter half of the 32-week study period. Aminoguanidine therapy for the entire 32-week study period retarded the rise in albuminuria in the diabetic rats and was more effective than 16 weeks of treatment either in the first or second half of the study. Early and late aminoguanidine administration were similar in their capacity to retard the development of albuminuria in diabetic rats. Similar effects were observed on mesangial expansion. The increased glomerular basement thickness in diabetic rats was not affected by aminoguanidine, irrespective of duration or timing of therapy. This study confirms that in vivo generation of AGEs in the kidney is time dependent and closely linked to the development of experimental diabetic nephropathy. The renoprotective effects of aminoguanidine in diabetes appear to be related to the duration but not to the timing of treatment.

Animals↗

PubMed1996

Site-specific modification of apolipoprotein B by advanced glycosylation end-products: implications for lipoprotein clearance and atherogenesis.

An AGE-modified form of LDL (AGE-LDL) circulates in patients with diabetes mellitus or renal insufficiency and shows impaired plasma clearance kinetics when injected into transgenic mice that express the human LDL receptor. The advanced glycosylation inhibitor aminoguanidine decreases plasma LDL in diabetic patients, further suggesting that the AGE modification of LDL contributes significantly to increased LDL in vivo. We utilized AGE-specific antibodies to identify the major site(s) of AGE modification within apolipoprotein B (apoB), which impairs the binding of AGE-LDL by human fibroblast LDL receptors. Despite the large size of apoB (4536 amino acid residues) and its high content of potentially reactive lysines, the predominant site of AGE-immunoreactivity was found to lie within a single 67 amino acid domain located 1791 residues N-terminal to the LDL receptor binding site. These data point to the high specificity and reactivity of this site toward AGE formation and to a significant structural interaction between this region of apoB and the LDL receptor binding domain. A low but detectable degree of AGE modification was found to affect this site in LDL which was isolated from normal, non-diabetic individuals, suggesting that advanced glycosylation may contribute to elevated LDL in the general population as well.

Amino Acid Sequence↗

PubMed1996

The role of advanced glycosylation end-products in the pathogenesis of atherosclerosis.

Coronary artery disease and cerebrovascular disease due to the rapid progression of atherosclerosis is the principal cause of death in diabetes mellitus. Modification of low-density lipoproteins (LDL) by advanced glycosylation end-products (AGE) may play a central role in the development of atherosclerosis, especially in diabetic patients. An AGE-modified form of LDL (AGE-LDL) has been found to circulate in human plasma, and AGE modifications have been identified as being present on both the apoprotein (ApoB) and the phospholipid components of LDL. By utilizing an AGE-specific ELISA, we measured the AGE attached to the ApoB and lipid components of LDL from normal controls and diabetic patients with or without end-stage renal disease (ESRD), as well as lipid oxidation. AGE-ApoB, AGE-lipid and oxidized LDL (Ox-LDL) in diabetic patients were significantly higher than those in patients without diabetes. The correlation between AGE-ApoB and AGE-lipid were highly significant. An especially marked elevation of AGE-LDL was found in diabetic patients with ESRD. The correlation between the serum total cholesterol and the AGE-LDL (AGE-ApoB and AGE-lipid) was significant. In addition, based on the known biological properties of AGE-modified peptide (AGE-peptide), we have proposed that these chemically reactive circulating AGE-peptides contribute to tissue injury by reattaching to susceptible target proteins both within and outside the vasculature, and that this process accelerates vascular pathology in diabetic patients. These data indicate that AGE-modified LDLs may represent a particularly atherogenic form of LDL, and AGE-LDLs as well as AGE-peptides are likely to contribute to the development of atherosclerosis in diabetic patients.

Apolipoproteins B↗

PubMed1996

The subunit structure of human macrophage migration inhibitory factor: evidence for a trimer.

The subunit structure of human macrophage migration inhibitory factor (MIF) has been studied by preliminary X-ray analysis of wild-type and selenomethionine-MIF and dynamic light scattering. Crystal form I of MIF belongs to space group P2(1)2(1)2(1) and is grown from 2 M ammonium sulfate at pH 8.5. A native data set has been collected to 2.4 A resolution. Self-rotation studies and Van values indicate that three molecules per asymmetric unit are present. A data set to 2.8 A resolution has been collected for crystal form II, which belongs to space group P3(1)21 or P3(2)21 and grows from 2 M ammonium sulfate, 2% polyethylene glycol (average molecular mass 400) 0.1 M HEPES, pH 7.5. Three, four, five or six monomers in the asymmetric unit are consistent with Van values for this crystal form. Analysis of crystal form II containing selenomethionine-MIF indicates nine selenium sites are present per asymmetric unit. Dynamic light scattering of MIF suggests that the major form of the protein in solution is a trimer. The results of these studies are in contrast to previous reports indicating that MIF is a monomer or dimer. The subunit arrangement of MIF is similar to that of tumor necrosis factor and suggests that signal transduction might require trimerization of receptor subunits.

Crystallization↗

PubMed1996

MIF rediscovered: cytokine, pituitary hormone, and glucocorticoid-induced regulator of the immune response.

The protein that has been historically called macrophage migration inhibitory factor (MIF) was one of the first cytokine activities to be discovered and was originally described to be a T lymphocyte product that inhibited the random migration of macrophages. Over the years, additional molecules with MIF "activity" have been described and the precise role of the original MIF "protein" remained enigmatic. Recent studies have led to the discovery of a pituitary mediator that appears to act as the counterregulatory hormone for glucocorticoid action within the immune system. Isolated as a product of murine anterior pituitary cells, this peptide was sequenced and found to be the mouse homolog of MIF. MIF has the unique property of being released from macrophages and T cells in response to physiological concentrations of glucocorticoids. The secretion of MIF is tightly regulated and decreases at high, anti-inflammatory steroid concentrations. Once released, MIF "overrides" or counterregulates the immunosuppressive effects of steroids on immune cell activation and cytokine production. These observations suggest that MIF fills an important gap in our understanding of how the host initiates and controls immunity. Because glucocorticoids are an integral part of the host's global response to infection or tissue invasion, the physiological role of MIF is to act at an inflammatory site or lymph node to counterbalance the profound inhibitory effects of steroids on the immune response.

Animals↗

PubMed1996

Macrophage migration inhibitory factor production by Leydig cells: evidence for a role in the regulation of testicular function.

Macrophage migration inhibitory factor (MIF), described originally as a product of activated T lymphocytes, recently has been found to be released by monocytes/macrophages and the anterior pituitary gland. Immunohistochemical studies of the adult rat testis using an affinity-purified polyclonal antimurine MIF antibody demonstrated strong staining for MIF in Leydig cells and their putative precursors. Peritubular myoid cells and the seminiferous epithelium were negative for MIF staining; however, a weak reaction around the heads of elongated spermatids also was observed. The expression of MIF messenger RNA and protein in whole rat testis was demonstrated by Northern blot and Western blot analyses, respectively. Both MIF messenger RNA and protein immunoreactivity in Leydig cells was observed in testes obtained from long term hypophysectomized rats. Significant concentrations of intracellular MIF were detected in lysates of the TM3 Leydig cell line (7.23 +/- 2.6 pg/microgram protein), and testicular interstitial fluid contained 14.7 +/- 1.6 ng/ml MIF protein, as measured by MIF-specific enzyme-linked immunosorbent assay. To gain insight into the possible biological role of MIF in the testis, cultures of adult rat seminiferous tubules and purified Leydig cells were incubated together with recombinant murine MIF (rMIF). Neither rMIF (50 ng/ml) nor a neutralizing anti-MIF antiserum was found to affect basal or LH-stimulated Leydig cell steroidogenesis in vitro. However, a dose-dependent decrease in the secretion of inhibin by the seminiferous tubules was observed at rMIF concentrations ranging from 10-100 ng/ml. Taken together, these data indicate that Leydig cells produce MIF in vivo and suggest an important regulatory role for this newly discovered mediator of testicular function.

Animals↗

PubMed1996

Recent progress in advanced glycation and diabetic vascular disease: role of advanced glycation end product receptors.

Advanced glycosylation end products (AGEs) form principally from the rearrangement of early glycation products, i.e., Amadori products, which produce a class of stable moieties that possess distinctive chemical crosslinking and biological properties. It has been generally believed that proteins with half-lives of longer than a few weeks are most susceptible to advanced glycosylation and that the highest levels of AGEs occur on proteins that comprise the long-lived structural components of connective tissue matrix and basement membrane.

Animals↗

PubMed1996

De Novo renal expression of macrophage migration inhibitory factor during the development of rat crescentic glomerulonephritis.

Macrophage migration inhibitory factor (MIF), a key mediator of the delayed-type hypersensitivity response, was originally thought to be produced by activated T cells. However, recent studies have found that MIF is produced in many cell types including monocytes/macrophages and anterior pituitary cells. The current study has examined MIF expression in normal and diseased kidney using in situ hybridization, immunohistochemistry, and Northern blotting. MIF mRNA and protein are constitutively expressed in normal kidney, being largely restricted to tubular epithelial cells and some glomerular visceral and parietal epithelial cells. During the development of rat anti-glomerular basement membrane glomerulonephritis, a model of macrophage-mediated renal injury, there was marked de novo expression of MIF by intrinsic kidney cells including endothelium and glomerular and tubular epithelial cells. Up-regulation of MIF expression correlated with macrophage accumulation within the glomerulus (P < 0.001) and tubulointerstitium (P < 0.001). Of significance, the accumulation of macrophages was exclusively localized to areas of strong MIF expression, contributing to focal glomerular and tubulointerstitial lesion formation. In addition, up-regulation of MIF expression by parietal epithelial cells was associated with macrophage accumulation within Bowman's space and crescent formation. Combined in situ hybridization and immunostaining also demonstrated MIF expression by macrophages, T cells, and fibroblast-like cells within renal lesions. In conclusion, these data provide the first demonstration that renal epithelial cells are a major source of MIF in both normal and diseased kidney. Furthermore, the up-regulation of MIF expression may play an important role in macrophage accumulation and progressive renal injury in rat crescentic glomerulonephritis.

Animals↗

PubMed1996

Effect of alpha-tocopherol on LDL oxidation and glycation: in vitro and in vivo studies.

Much data support a role for both low density lipoprotein (LDL) oxidation and glycation in atherogenesis. While alpha-tocopherol decreases the oxidative susceptibility of LDL, its role in decreasing LDL glycation is unclear. Hence we tested the effect of alpha-tocopherol both in vitro and in vivo on LDL oxidation and glycation. LDL was isolated after enrichment of plasma with alpha-tocopherol. This resulted in a 2-fold increase in alpha-tocopherol in LDL (AT-LDL). During a 6-day incubation of control LDL (C-LDL) and AT-LDL with 25 mM glucose, there were no significant differences in the degree of glycation on days 1, 3, and 6. Also, apoB advanced glycosylation end product levels were not significantly different between C-LDL and AT-LDL. There was a progressive increase in the susceptibility of LDL to oxidation with increasing LDL glycation as evidenced by reduced lag time of copper-catalyzed LDL oxidation. However, AT-LDL was more resistant to copper-catalyzed oxidation. Similar findings were observed when the LDLs were incubated with endothelial cells. The data from the alpha-tocopherol supplementation study confirmed our in vitro findings that alpha-tocopherol significantly decreases oxidative susceptibility of LDL, but does not affect its glycation. Therefore, while glycation increases LDL oxidative susceptibility, alpha-tocopherol decreases the oxidation of glycated LDL but not LDL glycation.

Arteriosclerosis↗

PubMed1996

The immunoregulatory mediator macrophage migration inhibitory factor (MIF) catalyzes a tautomerization reaction.

BACKGROUND: Recent studies of melanin biosynthesis have uncovered an unusual enzymatic activity which converts the non-naturally occurring D-isomer of 2-carboxy-2,3-dihydroindole-5,6-quinone (dopachrome) into 5,6-dihydroxyindole-2-carboxylic acid (DHICA). The aim of the present investigation was to isolate and characterize the enzyme catalyzing this tautomerization reaction. MATERIALS AND METHODS: After we performed a tissue survey of D-dopachrome tautomerase activity, 10 bovine lenses were homogenized and used as a source of enzyme. A soluble fraction was obtained by high-speed centrifugation and subjected to successive FPLC chromatography on Phenyl-sepharose, Mono S cation-exchange, and Superdex gel-filtration. The isolated enzyme was electrophoresed, blotted onto PVDF membrane, and the N terminus analyzed by gas phase micro-sequencing. RESULTS: The protein catalyzing the conversion of D-dopachrome to DHICA was purified to homogeneity in 14% yield and showed a molecular weight of 12 kD when analyzed by SDS-PAGE. The first 27 amino acid residues of this protein were sequenced and found to be identical with those of bovine macrophage migration inhibitory factor (MIF). The catalytic activity of native MIF was confirmed by studies of purified recombinant human MIF, which showed the same tautomerase activity. While L-dopachrome was not a substrate for this reaction, the methyl esters of the L- and D-isomers were found to be better substrates for MIF than D-dopachrome. CONCLUSIONS: MIF has been described recently to be an anterior pituitary hormone and to be released from immune cells stimulated by low concentrations of glucocorticoids. Once secreted, MIF acts to control, or counter-regulate, the immunosuppressive effects of glucocorticoids on the immune system. Although the tested substrate, D-dopachrome, does not occur naturally, the observation that MIF has tautomerase activity suggests that MIF may mediate its biological effects by an enzymatic reaction. These data also offer a potential approach for the design of small molecule pharmacological inhibitors of MIF that may modulate its potent immunoregulatory effects in vivo.

Amino Acid Sequence↗

PubMed1996

Crystal structure of macrophage migration inhibitory factor (MIF), a glucocorticoid-induced regulator of cytokine production, reveals a unique architecture.

The mediator originally described as a macrophage migration inhibitory factor (MIF) has been identified recently to be a novel anterior pituitary hormone and the first protein to be released from immune cells upon stimulation with glucocorticoids. Once released, MIF acts to override or counter-regulate the immunosuppressive effects of glucocorticoids on cytokine production in vitro and on LPS lethality in vivo. MIF also has been described to catalyze a tautomerization reaction, suggesting that an enzymatic activity may underlie certain of its biological properties. The three-dimensional crystal structure of human MIF has been solved at 2.6A resolution. The X-ray crystal structure reveals MIF to be a trimer of identical subunits. Each monomer contains two antiparallel alpha-helices that pack against a four-stranded beta-sheet. The monomer has an additional two beta-strands that interact with the beta-sheets of adjacent subunits to form the interface between monomers. The three beta-sheets are arranged to form a barrel containing a solvent-accessible channel that runs through the center of the protein along a molecular three-fold axis. Electrostatic potential maps reveal that the channel has a positive potential, suggesting that it binds negatively charged molecules. The elucidated structure for MIF is unique among cytokines or hormones and suggests that this glucocorticoid-induced counter-regulatory hormone has a novel mechanism of action.

Animals↗