Brain Activation by Peptide Pro-Leu-Gly-NH2 (MIF-1)

MIF-1 (Pro-Leu-Gly-NH2) is a tripeptide for which the therapeutic potential in Parkinson's disease and depression has been indicated by many studies. However, the cellular mechanisms of action of MIF-1 are not yet clear. Here, we show the specific brain regions responsive to MIF-1 treatment by c-Fos mapping, and determine the kinetics of cellular signaling by western blotting of pERK, pSTAT3, and c-Fos in cultured neurons. The immunoreactivity of c-Fos was increased 4 hours after MIF-1 treatment in brain regions critically involved in the regulation of mood, anxiety, depression, and memory. The number of cells activated was greater after peripheral treatment (intravenous delivery) than after intracerebroventricular injection. In cultured SH-SY5Y neuronal cells, c-Fos was induced time- and dose-dependently. The activation of cellular c-Fos was preceded by a transient increase of mitogen-activated protein kinase pERK but a reduction of phosphorylated Signal Transducer and Activator of Transcription (pSTAT3) initially. We conclude that MIF-1 can modulate multiple cellular signals including pERK, and pSTAT3 to activate c-Fos. The cellular activation in specific brain regions illustrates the biochemical and neuroanatomical basis underlying the therapeutic effect of MIF-1 in Parkinson's disease and depression

Lower cerebrospinal fluid/plasma fibroblast growth factor 21 (FGF21) ratios and placental FGF21 production in gestational diabetes

Objectives: Circulating Fibroblast Growth Factor 21 (FGF21) levels are increased in insulin resistant states such as obesity, type 2 diabetes mellitus and gestational diabetes mellitus (GDM). In addition, GDM is associated with serious maternal and fetal complications. We sought to study human cerebrospinal fluid (CSF) and corresponding circulating FGF21 levels in women with gestational diabetes mellitus (GDM) and in age and BMI matched control subjects. We also assessed FGF21 secretion from GDM and control human placental explants. Design: CSF and corresponding plasma FGF21 levels of 24 women were measured by ELISA [12 GDM (age: 26–47 years, BMI: 24.3–36.3 kg/m2) and 12 controls (age: 22–40 years, BMI: 30.1–37.0 kg/m2)]. FGF21 levels in conditioned media were secretion from GDM and control human placental explants were also measured by ELISA. Results: Glucose, HOMA-IR and circulating NEFA levels were significantly higher in women with GDM compared to control subjects. Plasma FGF21 levels were significantly higher in women with GDM compared to control subjects [234.3 (150.2–352.7) vs. 115.5 (60.5–188.7) pg/ml; P<0.05]. However, there was no significant difference in CSF FGF21 levels in women with GDM compared to control subjects. Interestingly, CSF/Plasma FGF21 ratio was significantly lower in women with GDM compared to control subjects [0.4 (0.3–0.6) vs. 0.8 (0.5–1.6); P<0.05]. FGF21 secretion into conditioned media was significantly lower in human placental explants from women with GDM compared to control subjects (P<0.05). Conclusions: The central actions of FGF21 in GDM subjects maybe pivotal in the pathogenesis of insulin resistance in GDM subjects. The significance of FGF21 produced by the placenta remains uncharted and maybe crucial in our understanding of the patho-physiology of GDM and its associated maternal and fetal complications. Future research should seek to elucidate these points

Interleukin-15 receptor is essential to facilitate GABA transmission and hippocampal-dependent memory

Interleukin-15 (IL15) is a cytokine produced by normal brain, but the functions of the IL15 system in normal adults are not yet clear. The hypothesis that the hippocampal IL15 system is essential for memory consolidation was tested by use of IL15Rα knockout mice in behavioral, biochemical, immunohistological, and electron microscopic analyses. The knockout mice showed deficits in memory, determined by the Stone T-maze and fear conditioning. In their hippocampi, the concentration of γ-aminobutyric acid (GABA) was significantly lower. There were region specific changes of the GABA synthesizing enzyme glutamic acid decarboxidase (GAD), with increased GAD-67 immunopositive interneurons in the stratum oriens of the CA1 region of the hippocampus, accompanied by non-significant reduction of GAD-67 synapses in the CA3 region. Western blotting showed an increase of GAD-65, but not GAD-67, in the hippocampal homogenate. The ultrastructure of the hippocampus remained intact in the knockout mice. To further test the hypothesis that IL15 directly modulates GABA turnover by reuptake mechanisms, the dose-response relationship of IL15 on (3)H-GABA uptake was determined in two neuronal cell lines. The effective and non-toxic dose was further used in the synaptosomal uptake studies. IL15 decreased the uptake of (3)H-GABA in synaptosomes from the forebrain of wildtype mice. Consistent with this, IL15Rα knockout mice had increased synaptosomal uptake of (3)H-GABA. Overall, the results show novel functions of a unique cytokine in normal hippocampal activity by regulating GABA transmission

Unique leptin trafficking by a tailless receptor

Impairment in blood-to-brain transport of leptin is a major cause as well as consequence of obesity. Leptin crosses the blood-brain barrier by transcytosis rather than undergoing intracellular degradation. Results from previous studies have indicated that the membrane juxtapositional cytoplasmic sequence of the leptin receptor ObR is responsible for leptin transport. To identify the specific structural domains, we generated a series of ObR truncates with different lengths of the intracellular sequence, overexpressed them in 3 types of mammalian cells including cerebral endothelia, and quantified leptin binding and endocytosis. All mutant ObRs were able to bind and mediate the internalization of leptin. Surprisingly, ObR860, a construct with no cytoplasmic sequence, could act like the classical ObRa transporter in internalizing leptin. There were some cell type-dependent variations in the intracellular trafficking of Alexa-labeled leptin when mediated by ObR860 or ObRa because of differential involvement of membrane microdomains, as shown by use of the clathrin inhibitor chlorpromazine and the dynamin inhibitor Dynasore. The clathrin- and dynamin-mediated endocytosis of leptin contrasts with the lack of effect of the caveolae inhibitors nystatin and filipin. Thus, leptin-induced internalization of the ligand-receptor complex can occur without specific sorting signals in the cytoplasmic region of ObR. This novel finding may have significant implications for leptin transport.—Tu, H., Hsuchou, H., Kastin, A. J., Wu, X., Pan, W. Unique leptin trafficking by a tailless receptor