Abstract MicroRNAs (miRNAs) play an important role in insulin signaling and insulin secretion, but the role of miRNAs in the association between obesity and hepatic insulin resistance is largely unknown. This study reports that saturated fatty acid (SFA) and high fat diet (HFD) significantly induce miR-195 expression in hepatocytes, and that the insulin receptor (INSR), not insulin receptor substrate-1 (IRS-1), is a direct target of miR-195. Furthermore, the ectopic expression of miR-195 suppresses the expression of INSR, thereby impairing the insulin signaling cascade and glycogen synthesis in HepG2 cells. These findings suggest that the dysregulation of miR-195 by SFA is a detrimental factor for hepatic insulin sensitivity.

Abstract Ceramide-1-phosphate (Cer-1-P) is emerging as a novel bioactive sphingolipid. It is formed by phosphorylation of ceramide catalyzed by ceramide kinase, and has been implicated in different cellular processes. Cer-1-P is mitogenic for fibroblasts, blocks apoptosis in macrophages, controls phagocytosis in neutrophils, and mediates inflammatory responses. Only recently have we started to uncover the signaling pathways that are affected by Cer-1-P. Recent work has demonstrated that cytosolic phospholipase A2 and acid sphingomyelinase are direct intracellular targets of Cer-1-P, and that it may also induce phosphorylation of extracellular signal-regulated kinase-2 and calcium mobilization. These actions of Cer-1-P seem to be cell type-specific.

Abstract The contributions of membrane type-1 matrix metalloproteinase (MT1-MMP) and of the glucose-6-phosphate transporter (G6PT) in sphingosine-1-phosphate (S1P)-mediated Ca2+ mobilization were assessed in glioblastoma cells. We show that gene silencing of MT1-MMP or G6PT decreased the extent of S1P-induced Ca2+ mobilization, chemotaxis, and extracellular signal-related kinase phosphorylation. Chlorogenic acid and (−)-epigallocatechin-3-gallate, two diet-derived inhibitors of G6PT and of MT1-MMP, respectively, reduced S1P-mediated Ca2+ mobilization. An intact MT1-MMP/G6PT signaling axis is thus required for efficient Ca2+ mobilization in response to bioactive lipids such as S1P. Targeted inhibition of either MT1-MMP or G6PT may lead to reduced infiltrative and invasive properties of brain tumor cells.

Abstract The ovaries of many species contain catecholamines and β-adrenergic receptors. The present studies were done to determine if catecholamines play a role in the regulation of androgen production by porcine theca cells. Basal and luteinizing hormone (LH)-stimulated androstenedione production was significantly inhibited by noradrenaline and isoproterenol. The inhibitory effects were dose-dependent and were enhanced when the cultures contained the carboxy-O-methyl transferase inhibitor, U-0521. The inhibitory effect of isoproterenol was reversed by the β-adrenergic antagonist, metoprolol. Isoproterenol caused a generalized inhibition of LH-stimulated steroidogenesis, decreasing the accumulation of pregnenolone, progesterone, androstenedione and estradiol in the culture medium. These studies suggest that catecholamines may be important regulators of thecal androgen production.

Abstract NADPH oxidase has been shown to play an important role in cardiovascular biology. The goal of the present study was to determine whether NADPH oxidase activity is important for endothelial cell growth and migration. In proliferation assays, growth factor- or serum-induced DNA synthesis in three different types of human endothelial cells was abrogated by inhibitors of NADPH oxidase, but not by inhibitors of xanthine oxidase or nitric oxide synthase. Moreover, vascular endothelial growth factor-induced migration of human endothelial cells was suppressed in the presence of NADPH oxidase inhibitors. These results support a potential role for NADPH oxidase in mediating angiogenesis.

Abstract Monocyte-derived dendritic cells (moDCs) are increasingly used in clinical settings to stimulate tumor immunity. Prostaglandin E2 (PGE2), which is a member of the eicosanoid family of oxygenated arachidonic acid derivatives generated through the action of cyclooxygenases (COXs), is frequently used to enhance the tumor necrosis factor-α-induced terminal maturation of moDCs. We show here that one effect of interleukin (IL)-4, which is used together with GM-CSF to generate moDCs, is the suppression of endogenous PGE2 production in moDCs. IL-4 inhibits the cytoplasmic form of phospholipase A2, the enzyme that specifically liberates arachidonic acid from membrane phospholipids. Although moDCs failed to mobilize endogenous arachidonic acid, they converted exogenous arachidonic acid into PGE2 in a COX-1- and COX-2-dependent fashion. IL-4-mediated suppression of PGE2 biosynthesis in human moDCs explains the previously reported maturation-enhancing effect of exogenous PGE2. The general suppression of eicosanoid biosynthesis may, however, limit the immunological efficacy of moDCs generated with IL-4.

Abstract The crawling locomotion and shape of eukaryotic cells have been associated with the stochastic molecular dynamics of actin and its protein regulators, chiefly Arp2/3 and Rho family GTPases, in making a cytoskeleton meshwork within cell extensions. However, the cell’s actin-dependent oscillatory shape and extension dynamics may also yield insights into locomotory mechanisms. Confocal observations of live Dictyostelium cells, expressing a green fluorescent protein–actin fusion protein, demonstrate oscillating supramolecular patterns of filamentous actin throughout the cell, which generate pseudopodia at the cell edge. The distinctively dissipative spatio-temporal behavior of these structures provides strong evidence that reversible actin filament assembly propagates as a self-organized, chemical reaction–diffusion wave.

Abstract The Drosophila ATP7 copper transporter has sequence homology to the human copper transporters ATP7A and ATP7B, which are defective in Menkes and Wilson disease, respectively. We show here that in Drosophila ATP7 is expressed by many peptidergic neurons. As C-terminal amidation of neuropeptides depends on the copper-containing enzyme PHM, it seemed likely that in the absence of ATP7 the activity of PHM might be compromised. Indeed, inhibition of ATP7 expression by RNAi led to a decrease in mature amidated neuropeptides and the appearance of C-terminally Gly-extended neuropeptides. The strength of this effect differed from one cell type to another; it was very pronounced for AKH and corazonin, but much less so for SIFamide and myosuppressin. Nevertheless, down-regulation of ATP7 specifically in the SIFamide-expressing neurons resulted in male–male courtship behavior.

Abstract The aim of the present study was to analyse the alterations of Cyclin dependent kinase 5 (Cdk5) expression and phosphorylation in PC12 cells overexpressing Amyloid precursor protein (APP). Our results demonstrated enhanced cell death and increased levels of mRNA for the Cdk5 gene in APP-transfected cells. Significantly decreased phosphorylation of Cdk5 at Tyr15 was observed in APPsw cells, which is responsible for a reduction in Cdk5 activity. Cdk5-dependent phosphorylation of Glycogen synthase kinase-3β (Gsk-3β) at Ser9 was also decreased, which can lead to the increase of Gsk-3β activity and hyperphosphorylation of MAP tau. Our results demonstrate for the first time, a deregulation of Cdk5 phosphorylation in APP-transfected cells.

Abstract Roles of Nurr1 and neurogenin 2 (Ngn2) have been shown in midbrain dopamine (DA) neuron development. We present here rat and mouse species-dependent differences of Nurr1 and Ngn2 actions in DA neuron differentiation. Nurr1 exogene expression caused an efficient generation of tyrosine hydroxylase (TH)-positive DA cells from rat neural precursor cells (NPCs). Nurr1-induced TH+ cell yields were low and highly variable depending on the origins of NPCs in mouse cultures. Coexpression of Ngn2 repressed Nurr1-induced generation of TH+ cells in rat cultures. In clear contrast, a robust enhancement in Nurr1-induced DA cell yields was observed in mouse NPCs by Ngn2. These findings imply that DA neurons may develop differently in the midbrains of these two species.