Inhibition of macrophage migration inhibitory factor secretion from macrophages by vitamin E

Vitamin E is a MIF Inhibitor

Macrophage migration inhibitory factor (MIF) is known to contribute to the pathogenesis of inflammatory hyperalgesia and neuropathic pain. Prior studies have shown that Vitamin E treatment is associated with attenuated hyperalgesia and reduced neuropathic pain in rodents. Given these observations, we investigated the possibility that Vitamin E is a MIF inhibitor. Dopachrome tautomerase assays revealed that Vitamin E inhibits the enzymatic activity of purified human recombinant MIF (rhMIF) in a dose-dependent manner (45%, 74%, 92% and 100% inhibition at 3, 10, 30 and 100μM, respectively). Cell-free ELISA based assays showed that Vitamin E binds onto rhMIF thereby blocking its recognition (48% inhibition at 100μM). Circular dichroism studies indicated the Vitamin E has a strong affinity to bind to rhMIF (binding constant 19.52±1.4μM). In silico studies demonstrated that Vitamin E docks well in the active site of MIF with the long aliphatic chain of Vitamin E exhibiting strong van der Waals interactions with MIF. Most importantly, human cell-based assays revealed that Vitamin E significantly inhibits rhMIF-induced production of pro-inflammatory cytokines in a dose-dependent manner (77%, 80%, and 96% inhibition of IL-6 production, respectively, at 10, 30 and 100μM). Taken together, these results demonstrate that Vitamin E inhibits not only the enzymatic activity of MIF but more importantly the biological function of MIF. Our findings suggest that Vitamin E may be attenuating hyperalgesia and reducing neuropathic pain at least in part by inhibiting MIF activity.

Vitamin E ingestion improves several immune functions in elderly men and women

The effects of diet supplementation with the antioxidant vitamin E (200 mg daily) on several blood neutrophil, lymphocyte and natural killer cell functions have been investigated in healthy elderly men and women before supplementation, after 3 months of supplementation and 6 months after the end of supplementation (post-supplementation). In parallel, samples of healthy adult men and women were used as age controls. In elderly men and women, an impairment of immune functions was observed in comparison with the respective adult controls and the intake of vitamin E resulted in a significant enhancement of immune parameters in both elderly men and women, bringing their values close to those in the adults. These effects were not found in post-supplementation samples in several but not in all functions. The present findings suggest that supplementation with vitamin E can produce an improvement of immune functions and therefore of health in aged people.

Oxidoreductase Macrophage Migration Inhibitory Factor is simultaneously increased in leukocyte subsets of patients with severe sepsis

The oxidoreductase Macrophage Migration Inhibitory Factor (MIF) is discussed as a promising target for immunomodulatory therapy in patients with severe sepsis. Moreover, MIF expresses tautomerase as well as thiol-protein oxidoreductase activities and has a potential role in cellular redox homeostasis, apoptosis inhibition, endotoxin responsiveness as well as regulation of nuclear transcription factors. To further elucidate a potential role of intracellular MIF in severe sepsis, we assessed alterations of intracellular MIF content in peripheral blood leukocytes of patients with severe sepsis in comparison to healthy controls and non-septic patients after major surgery. Intracellular MIF was significantly elevated simultaneously in lymphocytes, B-cells, macrophages and granulocytes of patients with severe sepsis when compared to healthy control individuals (p < 0.05) and increased when compared to non-septic patients after major surgery. In parallel, plasma MIF levels were elevated in severe sepsis (p < 0.05). There was no difference of intracellular MIF in lymphocytes, B-cells, macrophages or granulocytes between surviving and non-surviving patients with severe sepsis (p > 0.05). However, in survivors LPS ex vivo stimulation increased MIF secretion but not in non-survivors of sepsis (p < 0.05). This finding underlines the role of intracellular MIF in inflammatory diseases. It suggests monitoring of intracellular MIF in further clinical and non-clinical research valuable.

Changes in macrophage and lymphocyte functions in guinea-pigs after different amounts of vitamin E ingestion

Vitamin E is the main biological lipid-soluble antioxidant and plays a crucial role in the maintenance of the immune system. In the present work, twenty-one guinea-pigs (3-weeks-old) were distributed into three groups, which during 5 weeks ingested different amounts of vitamin E (/kg diet): 15 mg (low vitamin E diet), 150 mg (medium vitamin E diet; control) or 1500 mg (high vitamin E diet). The function of lymphocytes and macrophages were then studied. In macrophages obtained from the peritoneum several steps of the phagocytic process (chemotaxis, ingestion and superoxide anion production) were assayed, as well as chemotaxis and proliferation of peritoneal and spleen lymphocytes. The results indicate that with respect to the medium vitamin E diet, low ingestion of vitamin E causes a decrease in chemotaxis and production of superoxide anion by macrophages and an increase in the phagocytic capacity. With the high vitamin E diet an increase in macrophage and lymphocyte chemotaxis, superoxide anion production and lymphoproliferative capacity, as well as a decrease in phagocytosis, were observed. Therefore, diet supplementation with higher than usual levels of vitamin E appears to be beneficial for the immune system.

Ursolic acid promotes the release of macrophage migration inhibitory factor via ERK2 activation in resting mouse macrophages

Macrophage migration inhibitory factor (MIF) plays some pivotal roles in innate immunity and inflammation. Ursolic acid (UA), an anti-inflammatory triterpene carboxylic acid, was recently reported to induce the release of pro-inflammatory mediators in resting macrophages (Mvarphi). We investigated the effects of UA on MIF protein release in resting RAW264.7 mouse Mvarphi, and found that it decreased intracellular MIF protein levels and promoted the release of MIF into the culture media in dose- and time-dependent manners, without affecting mRNA levels. Further, the triterpene strikingly induced activation of mitogen-activated protein kinase kinase 1/2 (MEK1/2) and extracellular signal-regulated kinase 1/2 (ERK1/2) within 30min, whereas no phosphorylation of p38 MAPK or JNK protein was observed. In addition, UA-promoted MIF release was significantly inhibited by PD98059, a MEK1/2 inhibitor, while siRNA for ERK2, but not ERK1, significantly decreased the amount of MIF protein released. These results suggest that UA triggers the release of intracellular MIF protein through the ERK2 activation.

Link between macrophage migration inhibitory factor and cellular redox regulation

Macrophage migration inhibitory factor (MIF) is an evolutionary conserved 12.5-kDa protein mediator with multiple functions in innate and acquired immunity. Upon leaderless secretion, MIF acts as a typical inflammatory cytokine, but there is no structural homology between MIF and any of the known cytokine protein families. Also, MIF is unique among cytokines in that it exhibits certain endocrine properties and has enzymatic activity. The catalytic thiol-protein oxidoreductase (TPOR) activity of MIF is mediated by a Cys-Ala-Leu-Cys active site between residues 57 and 60 that can undergo reversible intramolecular disulfide formation. Such a redox motif is typically found in TPORs of the thioredoxin (Trx) family of proteins. MIF seems to act as a disulfide reductase, and structure-function analyses of the redox site indicate that this activity is not only observed in vitro, but plays a role in cellular redox homeostasis, apoptosis inhibition, MIF-mediated monocyte/macrophage activation, and possibly the modulation of the activity of MIF-binding proteins. In this Forum review, the biochemical and biological evidence for a role of the TPOR activity for various MIF functions is summarized and discussed. In particular, the marked functional homologies with Trx proteins, the MIF redox/MHC II link, and recent attempts to discern the intra- versus extracellular roles of the MIF TPOR activity are dealt with.

Aerosol-administered alpha-tocopherol attenuates lung inflammation in rats given lipopolysaccharide intratracheally

Intrapulmonary administration of bacterial lipopolysaccharide (LPS) induces a well-characterized lung inflammatory response involving alveolar macrophage activation, proinflammatory cytokine elaboration, and neutrophil influx. Vitamin E, a lipophilic antioxidant consisting of a family that includes tocopherols and tocotrienols, has previously been shown to have a variety of anti-inflammatory effects, raising interest in its possible uses in disease prevention or therapy. Because aerosol delivery is a specific and rapid way to administer agents to the lungs, the authors undertook to determine whether inhaled vitamin E aerosols would have an anti-inflammatory effect in the lungs. Using a rat model of acute lung inflammation caused by intratracheally administered LPS (10 microg Pseudomonas aeruginosa LPS), the authors examined the effect of aerosol-administered vitamin E, in this case alpha-tocopherol, on several indices of lung inflammation which are increased by LPS treatment. It was found that inhaled alpha-tocopherol aerosol, but not inhaled alpha-tocopherol acetate aerosol, decreased tumor necrosis factor alpha (TNFalpha) and cytokine-induced neutrophil chemoattractant-1 (CINC-1) mRNA levels in lung tissue, TNFalpha and CINC-1 immunoreactive protein levels in lung lavage, and the number of neutrophils recoverable by lung lavage from rats given LPS intratracheally. These results contribute to the increasing body of work describing immunomodulatory functions of alpha-tocopherol, and support the idea that direct aerosol administration of alpha-tocopherol may play a beneficial role in strategies to control inflammatory lung illnesses.

Regulation of macrophage function by the antioxidant N-acetylcysteine in mouse-oxidative stress by endotoxin

Changes in several functions of peritoneal macrophages from mice with oxidative stress caused by intraperitoneal injection of endotoxin (Escherichia coli lipopolysaccharide, LPS) (100 mg/kg), and associated with a high production of reactive oxygen species (ROS), have been observed in our previous studies. Antioxidants such as N-acetylcysteine (NAC) are free radical scavengers that improve and modulate the immune response, especially in oxidative stress situations. Therefore, in the present work, we have studied the effects of the administration of NAC (150 mg/kg i.p.) on different functions of peritoneal macrophages from Swiss mice suffering that oxidative stress, caused by LPS (100 mg/kg). NAC was injected 30 min after LPS injection, and the peritoneal macrophages were obtained at 2, 4, 12, and 24 h after endotoxin injection. The following functions, key stages of the phagocytic process, were studied: adherence to substrate, chemotaxis, ingestion of particles, and production of ROS (reactive oxygen species), as well as tumor necrosis factor (TNFalpha) release. The decrease in chemotaxis and the increase in adherence, ingestion, superoxide anion production, and TNFalpha release shown by macrophages from animals with oxidative stress were counteracted by NAC injection. These data suggest that NAC administration may be useful for the treatment of oxidative stress-linked endotoxic shock, modulating the function of macrophages, specifically in decreasing the production of ROS and of inflammatory cytokines such as TNFalpha.

Secretion of macrophage migration inhibitory factor differs from interleukin-6 in hydrogen peroxide- and LPS-stimulated human fibroblasts

To investigate the mechanism for secretion of macrophage migration inhibitory factor (MIF) in cultured human fibroblasts, we compared it with the secretion of interleukin-6 (IL-6) after stimulation with lipopolysaccharides (LPS) and H2O2. MIF content of the medium of 2.0 x 10(6) cells/20 ml after 20 h culture of nonstimulated fibroblasts was 0.30 +/- 0.06 ng/ml, whereas LPS-stimulation (10 microg/ml) only led to a 1.5-fold increase as compared with the nonstimulated cells. In contrast, a significant increase of IL-6 was induced by LPS-stimulation (6048 +/- 488 pg/ml in LPS-stimulated cells vs. 58 +/- 36 pg/ml in control cells). On the other hand, higher concentrations of H2O2 (0.6-1.2 mM) caused an increase of MIF secretion into the culture medium irrespective of LPS-stimulation; with 1.2 mM H2O2-stimulation for 20 h, it was increased to 40-fold as compared with the nonstimulated cells. However, lower concentrations (0.1-0.4 mM) did not cause this. Interestingly, H2O2-stimulation not only failed to increase IL-6 production from fibroblasts, but also repressed induction of IL-6 by LPS-stimulation in a dose-dependent manner. Genistein, a tyrosine kinase inhibitor, and H-7, a protein kinase C inhibitor, also inhibited IL-6 secretion but not MIF secretion in both LPS- and H2O2-stimulated fibroblasts. From analysis of trypan blue exclusion, formazan formation, morphological changes, and intracellular MIF content by Western blotting, we found that MIF secretion by H2O2 seemed to be mainly due to cell death and subsequent leakage of intracellular MIF. Taken together, these results suggest that MIF secretion differs from IL-6 via LPS-mediated signaling pathways.

Vitamin E suppression of microglial activation is neuroprotective

Neurotoxic microglial-neuronal interactions have been implicated in the pathogenesis of various neurodegenerative diseases such as Alzheimer's disease, and vitamin E has been shown to have direct neuroprotective effects. To determine whether vitamin E also has indirect neuroprotective effects through suppression of microglial activation, we used a microglial-neuronal coculture. Lipopolysaccharide (LPS) treatment of a microglial cell line (N9) induced a time-dependent activation of both p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-kappaB (NFkappaB), with consequent increases in interleukin-1alpha (IL-1alpha), tumor necrosis factor-alpha (TNF-alpha), and nitric oxide (NO) production. Differentiated neuronal cells (PC12 cells treated with nerve growth factor) exhibited marked loss of processes and decreased survival when cocultured with LPS-activated microglia. Preincubation of microglia with vitamin E diminished this neurotoxic effect, independently of direct effects of the antioxidant on the neuronal cells. Microglial NO production and the induction of IL-1alpha and TNFalpha expression also were attenuated by vitamin E. Such antiinflammatory effects of vitamin E were correlated with suppression of p38 MAPK and NFkappaB activation and were mimicked by an inhibition of either p38 MAPK (by SB203580) or NFkappaB (by decoy oligonucleotides). These results suggest that, in addition to the beneficial effects of providing direct antioxidant protection to neurons reported by others, vitamin E may provide neuroprotection in vivo through suppression of signaling events necessary for microglial activation.

Effect of coffee consumption on bone metabolism

The effects of coffee on bone metabolism are still controversial, although several studies have suggested that caffeine and/or heavy coffee consumption is associated with a significant increase in risk of fracture, osteoporosis, and periodontal disease. Therefore, we sought to clarify the relationship between coffee consumption and bone metabolism using male Wistar rats. Forty-eight male Wistar rats were assigned to three treatment groups including a control-diet group (control, n = 16, coffee-free diet), a 0.62% coffee-diet group (low caffeine, n = 16, diet supplemented with 6.2 g/kg of the control diet), and a 1.36% coffee-diet group (high caffeine, n = 16, diet supplemented with 13.6 g/kg of the control diet), and animals were maintained on an experimental diet for 140 days. Although caffeine in serum was not detected in rats fed the control diet, low-intake coffee for 140 days led to an increase in caffeine concentration to 0.53 +/- 0.11 microg/mL and high-intake coffee led to an increase of 1.77 +/- 0.22 microg/mL. No significant differences in body weight change, serum and urinary biochemical markers of bone metabolism, and bone histomorphometry were found between the coffee-diet groups and the control-diet group, except that urinary phosphorus excretion after 140 days of both coffee diets was significantly increased compared with controls (p < 0.05). In addition, the coffee diets were not associated with differences in tumor necrosis factor-alpha and interleukin-6, which have been implicated in the pathogenesis of bone loss together with interleukin-1beta. In conclusion, the present study strongly indicates that coffee does not stimulate bone loss in rats.

T-kininogen and a 45 kda proteinase from Porphyromonas gingivalis

To clarify the pathogenic role of proteinases from Porphyromonas gingivalis, a 45 kDa proteinase was isolated from P. gingivalis culture medium by a combination of gel filtration (Bio-Gel A-0.5 m) and ion-exchange chromatographies (DEAE-Sephacel and SP-Sepharose FF). The enzyme was found to have a molecular mass of 45 kDa by SDS-PAGE and to require mercaptoethanol for its activation. The 45 kDa proteinase cleaved T-kininogen into small fragments, but failed to release kinin. In contrast, T-kininogen inhibited the Arg-amidolytic activity of the 45 kDa proteinase with a Ki of 2 nM. On the other hand, the 45 kDa proteinase did not stimulate the production of PGE2, IL-1beta, and TNF-alpha from the macrophages.

Modulation of murine macrophage function by N-acetylcysteine in a model of endotoxic shock

In previous studies we have observed changes in several functions of peritoneal macrophages from BALB/c mice with irreversible endotoxic shock caused by intraperitoneal injection of E. coli lipopolysaccharide (LPS) (100 mg/kg), which were associated with a high production of superoxide anion. Since antioxidants, such as N-acetylcysteine (NAC), are free radical scavengers that improve the immune response, in the present work we have studied different functions of peritoneal macrophages from BALB/c mice suffering the endotoxic shock above indicated and administered N-acetylcysteine (150 mg/kg i.p.) at 30 minutes after LPS injection. In the peritoneal macrophages obtained at 2, 4, 12 and 24 h after LPS injection, the following functions were studied: adherence to substrate, mobility, ingestion of particles, and production of superoxide anion and tumour necrosis factor (TNF alpha). The increase in adherence, ingestion and superoxide anion and TNF alpha production shown by macrophages from animals with endotoxic shock was counteracted by NAC injection. Moreover, the survival time of mice with endotoxic shock was increased in the presence of NAC. These data suggest that NAC, administered intraperitoneally, may be useful for the treatment of irreversible endotoxic shock by modulation of the function of macrophages with decreased superoxide anion and TNF alpha production and concomitant increase of survival time.