Effect of Dietary Lipids on Endotoxemia Influences Postprandial Inflammatory Response

Metabolic syndrome (MetS) results in postprandial metabolic alterations that predisposes one to a state of chronic low-grade inflammation and increased oxidative stress. We aimed to assess the effect of the consumption of the quantity and quality of dietary fat on fasting and postprandial plasma lipopolysaccharides (LPS). A subgroup of 75 subjects with metabolic syndrome was randomized to receive 1 of 4 diets: HSFA, rich in saturated fat; HMUFA, rich in monounsaturated fat; LFHCC n-3, low-fat, rich in complex carbohydrate diet supplemented with n-3 polyunsaturated fatty acids; LFHCC low-fat, rich in complex carbohydrate diet supplemented with placebo, for 12 weeks each. We administered a fat challenge reflecting the fatty acid composition of the diets at postintervention. We determined the plasma lipoproteins and glucose and gene expression in peripheral blood mononuclear cells (PBMC) and adipose tissue. LPS and LPS binding protein (LBP) plasma levels were determined by ELISA, at fasting and postprandial (4 h after a fat challenge) states. We observed a postprandial increase in LPS levels after the intake of the HSFA meal, whereas we did not find any postprandial changes after the intake of the other three diets. Moreover, we found a positive relationship between the LPS plasma levels and the gene expression of IkBa and MIF1 in PBMC. No statistically significant differences in the LBP plasma levels at fasting or postprandial states were observed. Our results suggest that the consumption of HSFA diet increases the intestinal absorption of LPS which, in turn, increases postprandial endotoxemia levels and the postprandial inflammatory response.

Human decidual natural killer cells as a source and target of macrophage migration inhibitory factor

The human uterine mucosa of early pregnancy is largely populated by CD56(bright) natural killer (NK) cells (uterine (u) NK cells). The specific functions of these cells are still unknown, but their interaction and response to foetal trophoblasts are thought to be important for the establishment of a successful pregnancy. The study reported herein shows that uNK cells respond to, and produce, macrophage migration inhibitory factor (MIF), a cytokine highly expressed in the human placenta and in the cyclic and pregnant endometrium. Recombinant human MIF reduced in a dose-dependent manner the cytolytic activity of purified uNK cells against K562 cells. RT-PCR, Western blot analysis and ELISA demonstrated the synthesis and secretion of the cytokine by uNK cells. Double immunofluorescence staining showed the presence of MIF in uterine CD56 + cells. Finally, neutralization of the endogenous cytokine by a polyclonal antibody resulted in a sharp increase in the cytolytic activity of uNK cells. These findings indicate the existence of a previously unrevealed paracrine and autocrine action of MIF on uNK cells and support its contribution to the immune privilege at the maternal-foetal interface.

Role of macrophage migration inhibitory factor in bleomycin-induced lung injury and fibrosis in mice

Macrophage migration inhibitory factor (MIF) is a unique cytokine that reportedly overrides the anti-inflammatory effect of endogenous glucocorticoids. MIF has been demonstrated to be involved in a variety of inflammatory diseases. In this study, we examined the role of MIF in bleomycin (BLM)-induced lung injury and fibrosis. The levels of MIF in lung tissues and bronchoalveolar lavage fluids were significantly increased in the period 5-10 days after intratracheal administration of BLM. Treatment with the anti-MIF antibody significantly reduced the mortality at 14 days and the histopathological lung injury score at 10 days. These effects were accompanied with significant suppression of the accumulation of inflammatory cells in the alveolar space and tumor necrosis factor-alpha in the lungs at 7 days. However, the anti-MIF antibody did not affect either the content of lung hydroxyproline or the histopathological lung fibrosis score at 21 days after BLM. These data provide further evidence for the crucial role of MIF in acute lung inflammation but do not support the involvement of MIF in lung fibrosis induced by BLM in mice.

Age- and sex-related changes in Tyr-MIF-1-like immunoreactivity in rat plasma

The concentrations in plasma of the biologically active endogenous peptide Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) have not been measured during development or in female rats. By radioimmunoassay, we found that Tyr-MIF-1-like immunoreactivity (Tyr-MIF-1-LI) was first consistently detectable in plasma when the rat was 5 days old, and then gradually increased to adult concentrations by day 15. In male rats, the levels remained relatively constant for the next 21 months. In female rats, plasma concentrations of Tyr-MIF-1-LI at day 15 were about the same as in male rats. At 6 months of age, however, the concentrations in females decreased by half and by 21 months of life were only about a third of the concentrations found at day 15 or in age-matched males. The differences with age were not due to the length of time of storage of the samples, because another group of rats 1 month old was killed on the same day as 5-day-old rats and still showed several times more Tyr-MIF-1-LI in the plasma; again, no differences were found between male and female rats at either 5 days or 1 month. A single injection of estradiol followed by progesterone lowered the concentrations in 1-month-old male rats. In female rats that were either ovariectomized or sham-ovariectomized, the expected similarity in their plasma concentrations of Tyr-MIF-1-LI was found at 1 month of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunochemical recognition of oxytocin by antiserum to L-prolyl-leucyl-glycine amide

Antisera were raised in rabbits against Pro-Leu-Gly-NH2 (PLG)-bovine thyroglobulin conjugates. Specificity of the antisera towards oxytocin was evaluated by a radioimmunoassay as well as by immunohistochemical procedures on hypothalamic tissue and hormone bound to Sepharose beads. It was concluded that immunization with PLG can raise antisera that are specific to oxytocin.

Radioimmunoassayable N-Tyr-MIF-1-like activity in rat brain is increased by pinealectomy

Levels of N-Tyr-MIF-1-like immunoreactivity were measured in rat brain by radioimmunoassay (RIA). Although the highest levels were found in the pineal and hypothalamus, the striatum and thalamus also contained significantly more immunoreactivity than the other parts of the brain. Since oxytocin cross-reacts 5.4% with the antibody for N-Tyr-MIF-1, oxytocin-like immunoreactivity was also measured by RIA, but could not account for the levels of radioimmunoassayable N-Tyr-MIF-1 found in these experiments. There was a significant increase in N-Tyr-MIF-1-like immunoreactivity after pinealectomy, a tendency for a decrease after stress, but essentially no change after hypophysectomy. A diurnal rhythm was observed with the highest levels at night and lowest levels during the day. The results demonstrate the presence in brain tissue of a novel immunoreactive peptide, the levels of which can be altered by neuroendocrine manipulations.

Radioimmunoassay of MIF-1/Tyr-MIF-1-like material in rat pineal

The hypothalamic peptide MIF-1 (Pro-Leu-Gly-NH2) was coupled to thyroglobulin and injected into rabbits. The resulting antiserum reacted with the tetrapeptide Tyr-MIF-1 to a greater extent than with the tripeptide MIF-1, presumably because of a better conformation for antibody binding. By radioimmunoassay (RIA), immunoreactive MIF-1/Tyr-MIF-1-like material was found in the pineal gland of each of the 100 rats examined. The tendencies for slightly higher levels in pineals obtained from rats kept in constant darkness for two weeks, from rats in a normal light cycle decapitated at noon, or from rats which had been hypophysectomized were not statistically significant. Gel filtration of pineal extracts on a column of Sephadex G-10 revealed that by RIA one immunoreactive peak eluted near MIF-1 and oxytocin, and another peak near Tyr-MIF-1. The results suggest the presence in pineal tissue of an MIF-1-like material as well as a novel peptide containing Tyr-Pro-Leu-Gly-NH2 or a closely related structure for which oxytocin is unlikely to be the precursor.