Differential Gene Expression of Human Mast cell Activation Reveals Gene profiles of Innate and Adaptive Immunity.

High-density oligonucleotide microarray is a promising approach for high throughput analysis. It has been extensively used in many areas of biomedical research. Immunoglobulin E (IgE) mediated allergic response (type-1 hypersensitivity) is one of the most powerful reactions of the immune system. Tissue Mast Cells (MCs) and circulating basophils are the major effector cells in these reactions. By dissecting the regulatory circuitry of mast cells by analyzing the genome wide effects of antigen stimulation triggered by FcεRI, offers a potential for finding novel genes as ‘targets’ for therapeutic intervention. In this work, we tried to study the gene expression pattern in IgE sensitized and FcεRI cross linked cord blood derived MCs using one of the latest techniques, high density oligonucleotide expression probe array (HG-Focus array, Gene Chip, Affymetrix, Santa Clara, CA). Microarray hybridization of RNA from cord blood derived MCs revealed coordinated changes in gene expression in response to IgE stimulation and receptor cross linking at different time points. Among the most prominent findings, we observed 2 to 32-fold increased expression of different transcripts. Real-time PCR confirmed reliability of microarray data. This enabled us to classify and cluster genes by functional families as well as to understand known genes in signaling pathways. These results defined a list of primary candidates for finding novel genes as ‘targets’ for therapeutic intervention

siRNA knockdown of SPHK1 in vivo protects mice from systemic, type-I Allergy.

Systemic anaphylaxis is considered to be a typical immediate hypersensitivity response, determined by the activation of immune cells,
via antigen-induced aggregation of IgE-sensitized FcεRI cells. Perhaps most the important cells, in the immediate hypersensitivity responses, are mast cells. We have previously shown that SPHK1 plays a key role in the intracellular signaling pathways triggered by FceRI aggregation on human
mast cells. More recently, we performed a genome-wide gene expression profiling of human mast cells, sensitized with IgE alone, or stimulated by FcεRI aggregation. We found that sphingosine kinase 1 (SPHK1) was one
of genes activated at the earlier stages of mast cell activation, including during sensitization. Moreover, SPHK1 has been shown, by us and others, to be a key player in the intracellular signaling pathways triggered by
several immune-receptors, including fMLP, C5a, and Fcg- and Fcereceptors. Here we have investigated the in vivo role of SPHK1 in allergy, using a specific siRNA to knockdown SPHK1 in vivo. Our results support a role for
SPHK1 in the inflammatory responses that share clinical, immunological, and histological features of type I hypersensitivity. Thus, mice pretreated with the siRNA for SPHK1 were protected from the IgE mediated allergic
reactions including: temperature changes, histamine release, cytokine production, cell-adhesion molecule expression, and immune cell infiltration into the lungs

Phospholipase D1 Mediates TNFα-Induced Inflammation in a Murine Model of TNFα-Induced Peritonitis

<p><b>Background:</b> Tumor Necrosis Factor alpha (TNF alpha) is a pleiotropic cytokine extensively studied for its role in the pathogenesis of a variety of disease conditions, including in inflammatory diseases. We have recently shown that, in vitro, that TNF alpha utilizes PLD1 to mediate the activation of NF kappa B and ERK1/2 in human monocytes. The aim of this study was to investigate the role(s) played by phospholipase D1 (PLD1) in TNF alpha-mediated inflammatory responses in vivo.</p> <p><b>Methodology/Findings:</b> Studies were performed in vivo using a mouse model of TNF alpha-induced peritonitis. The role of PLD1 was investigated by functional genomics, utilizing a specific siRNA to silence the expression of PLD1. Administration of the siRNA against PLD1 significantly reduced PLD1 levels in vivo. TNF alpha triggers a rapid pyrogenic response, but the in vivo silencing of PLD1 protects mice from the TNFa-induced rise in temperature. Similarly TNF alpha caused an increase in the serum levels of IL-6, MIP-1 alpha and MIP-1 beta: this increase in cytokine/chemokine levels was inhibited in mice where PLD1 had been silenced. We then induced acute peritonitis with TNF alpha. Intraperitoneal injection of TNFa triggered a rapid increase in vascular permeability, and the influx of neutrophils and monocytes into the peritoneal cavity. By contrast, in mice where PLD1 had been silenced, the TNF alpha-triggered increase in vascular permeability and phagocyte influx was substantially reduced. Furthermore, we also show that the TNF alpha-mediated upregulation of the cell adhesion molecules VCAM and ICAM1, in the vascular endothelium, were dependent on PLD1.</p> <p><b>Conclusions:</b> These novel data demonstrate a critical role for PLD1 in TNF alpha-induced inflammation in vivo and warrant further investigation. Indeed, our results suggest PLD1 as a novel target for treating inflammatory diseases, where TNF alpha play key roles: these include diseases ranging from sepsis to respiratory and autoimmune diseases; all diseases with considerable unmet medical need.</p&gt

Expression profile of immune response genes in patients with Severe Acute Respiratory Syndrome

BACKGROUND: Severe acute respiratory syndrome (SARS) emerged in later February 2003, as a new epidemic form of life-threatening infection caused by a novel coronavirus. However, the immune-pathogenesis of SARS is poorly understood. To understand the host response to this pathogen, we investigated the gene expression profiles of peripheral blood mononuclear cells (PBMCs) derived from SARS patients, and compared with healthy controls. RESULTS: The number of differentially expressed genes was found to be 186 under stringent filtering criteria of microarray data analysis. Several genes were highly up-regulated in patients with SARS, such as, the genes coding for Lactoferrin, S100A9 and Lipocalin 2. The real-time PCR method verified the results of the gene array analysis and showed that those genes that were up-regulated as determined by microarray analysis were also found to be comparatively up-regulated by real-time PCR analysis. CONCLUSIONS: This differential gene expression profiling of PBMCs from patients with SARS strongly suggests that the response of SARS affected patients seems to be mainly an innate inflammatory response, rather than a specific immune response against a viral infection, as we observed a complete lack of cytokine genes usually triggered during a viral infection. Our study shows for the first time how the immune system responds to the SARS infection, and opens new possibilities for designing new diagnostics and treatments for this new life-threatening disease

Water and Ion Channels: Crucial in the Initiation and Progression of Apoptosis in Central Nervous System?

Programmed cell death (PCD), is a highly regulated and sophisticated cellular mechanism that commits cell to isolated death fate. PCD has been implicated in the pathogenesis of numerous neurodegenerative disorders. Countless molecular events underlie this phenomenon, with each playing a crucial role in death commitment. A precedent event, apoptotic volume decrease (AVD), is ubiquitously observed in various forms of PCD induced by different cellular insults. Under physiological conditions, cells when subjected to osmotic fluctuations will undergo regulatory volume increase/decrease (RVI/RVD) to achieve homeostatic balance with neurons in the brain being additionally protected by the blood-brain-barrier. However, during AVD following apoptotic trigger, cell undergoes anistonic shrinkage that involves the loss of water and ions, particularly monovalent ions e.g. K+, Na+ and Cl-. It is worthwhile to concentrate on the molecular implications underlying the loss of these cellular components which posed to be significant and crucial in the successful propagation of the apoptotic signals. Microarray and real-time PCR analyses demonstrated several ion and water channel genes are regulated upon the onset of lactacystin (a proteosomal inhibitor)-mediated apoptosis. A time course study revealed that gene expressions of water and ion channels are being modulated just prior to apoptosis, some of which are aquaporin 4 and 9, potassium channels and chloride channels. In this review, we shall looked into the molecular protein machineries involved in the execution of AVD in the central nervous system (CNS), and focus on the significance of movements of each cellular component in affecting PCD commitment, thus provide some pharmacological advantages in the global apoptotic cell death

Sphingosine kinase signalling in immune cells: potential as novel therapeutic targets

During the last few years, it has become clear that sphingolipids are sources of important signalling molecules. Particularly, the sphingolipid metabolites, ceramide and S1P, have emerged as a new class of potent bioactive molecules, implicated in a variety of cellular processes such as cell differentiation, apoptosis, and proliferation. Sphingomyelin (SM) is the major membrane sphingolipid and is the precursor for the bioactive products. Ceramide is formed from SM by the action of sphingomyelinases (SMase), however, ceramide can be very rapidly hydrolysed, by ceramidases to yield sphingosine, and sphingosine can be phosphorylated by sphingosine kinase (SphK) to yield S1P. In immune cells, the sphingolipid metabolism is tightly related to the main stages of immune cell development, differentiation, activation, and proliferation, transduced into physiological responses such as survival, calcium mobilization, cytoskeletal reorganization and chemotaxis.<p></p> Several biological effectors have been shown to promote the synthesis of S1P, including growth factors, cytokines, and antigen and G-protein-coupled receptor agonists. Interest in S1P focused recently on two distinct cellular actions of this lipid, namely its function as an intracellular second messenger, capable of triggering calcium release from internal stores, and as an extracellular ligand activating specific G protein-coupled receptors. Inhibition of SphK stimulation strongly reduced or even prevented cellular events triggered by several proinflammatory agonists, such as receptor-stimulated DNA synthesis, Ca<sup>2+</sup> mobilization, degranulation, chemotaxis and cytokine production. Another very important observation is the direct role played by S1P in chemotaxis, and cellular escape from apoptosis. As an extracellular mediator, several studies have now shown that S1P binds a number of G-protein-coupled receptors (GPCR) encoded by endothelial differentiation genes (EDG), collectively known as the S1P-receptors. Binding of S1P to these receptors trigger an wide range of cellular responses including proliferation, enhanced extracellular matrix assembly, stimulation of adherent junctions, formation of actin stress fibres, and inhibition of apoptosis induced by either ceramide or growth factor withdrawal. Moreover, blocking S1P1-receptor inhibits lymphocyte egress from lymphatic organs. This review summarises the evidence linking SphK signalling pathway to immune-cell activation and based on these data discuss the potential for targeting SphKs to suppress inflammation and other pathological conditions.<p></p&gt

Role of Cell Adhesion Molecules and Immune-Cell Migration in the Initiation, Onset and Development of Atherosclerosis

Atherosclerosis is currently the leading factor of death in developed countries. It is now recognized as a chronic immune-inflammatory disease, whose initial stages involve the interaction of leukocytes with the endothelial monolayer. The initial stage of atherosclerosis requires the interplay of various cell adhesion molecules and immune cells to trigger leukocyte and lymphocyte migration from the circulating blood into the arterial intima. Studies have unveiled the role of inflammatory mediators in the initiation, onset and progression of the disease. During the last few years we have gained a greater understanding of the mechanism that modulates monocyte, macrophage and T cell infiltration, the role these cells play in the atherosclerotic lesion, in the formation of the fibrous plaque formation with the consequent narrowing of the arteries and the mechanisms that lead to plaque rupture and the formation of thrombi and emboli. This review talks about the leukocyte recruitment in early atherosclerosis, the formation of the plaque, and the mechanisms that lead to thrombosis in advanced atherosclerosis. Finally, we discuss the potential for novel therapies to treat this disease

Recent trials for FTY720 (fingolimod): a new generation of immunomodulators structurally similar to sphingosine

Most of the conventional immunosuppressive drugs act by inhibiting the activation of enzymes, production of cytokines or proliferation of immune cells. Recently much attention is given to a new class of inhibitors that act by counteracting the functions of the lysophospholid sphingosine-1-phosphate (S1P). S1P is emerging as a potent stimulator of several immune cells and is critical for lymphocyte migration. The sphingosine analogue, FTY720 (fingolimod), a high affinity agonist of sphingosine-1-phosphate type-1 receptor (S1P-1), acts primarily by sequestering lymphocytes within peripheral lymphoid organs rendering them incapable of migrating to the sites of inflammation. Phase I, II and III, clinical trials comparing the efficacy of FTY720 containing regimens to conventional immunosuppressive regimens in de novo renal transplant patients, have been conducted. Moreover, clinical trials are also on-going in patients with relapsingremitting multiple sclerosis showing obvious benefit for patients receiving FTY720. In this review, we focus on the transition of this novel compound from bench to clinical trials, and discuss the clinical potential of this drug in autoimmune diseases and in transplantation immunology

New developments on the TNFα-mediated signalling pathways

TNFα (tumour necrosis factor α) is an extensively studied pleiotropic cytokine associated with the pathogenesis of a variety of inflammatory diseases. It elicits a wide spectrum of cellular responses which mediates and regulates inflammation, immune response, cell survival, proliferation and apoptosis. TNFα initiates its responses by binding to its receptors. TNFα-induced effector responses are mediated by the actions and interactions among the various intracellular signalling mediators in the cell. TNFα induces both survival and apoptotic signal in a TRADD (TNF receptor-associated DD)-dependent and -independent way. The signals are further transduced via a variety of signalling mediators, including caspases, MAPKs (mitogen-activated protein kinases), phospholipid mediators and miRNA/miR (microRNA), whose roles in specific functional responses is not fully understood. Elucidating the complexity and cross talks among signalling mediators involved in the TNFα-mediated responses will certainly aid in the identification of molecular targets, which can potentially lead to the development of novel therapeutics to treat TNFα-associated disorders and in dampening inflammation