Somatostatin receptors in the immune system and immune-mediated disease

The veitebrate body has at its disposal three different systems, which together help it to maintain homeostasis and to respond to environmental signals: the nervous system. the endocrine system and the immune system. Traditionally, these systems have been studied as separate entities. However, in the interest of stability of the organism, it is essential that these different systems be able to communicate and reciprocally regulate each other's activities [I]. Communication can take place via direct cell-cell contact or through soluble signalling molecules and their specific receptors on target cells. It is hypothesised that the signalling molecules, which are shared between the three systems, are evolutionarily ancient [2]. Among others, endorphins [3, 4], cytokines such as interleukin-l (IL-l) and IL-6 [5-7], honnones such as corticotrophin-releasing factor (CRF) [8, 9] and adrenocorticotrophic hormone (ACTH) [3, 4] and neuropeptides such as substance P and somatostatin [2, to] have been identified as signalling molecules with effects on many different cell types and effector systems. Through its effects on vasodilatation and blood flow the nervous system can modulate the local immune microenvironment in any tissue. All specialised lymphoid tissues are densely innervated by neurons of the sympathetic nervous system and by sensory neurons containing peptide neurotransmitters. Hormones with an endocrine or paracrine mode of action also modulate the tissue microenvironment [11, 12]. This chapter will fiuther focus on the role of the ubiquitous neuropeptide somatostatin as an intersystem signalling molecule, with emphasis on the immune system

The case for hypervirulence through gene deletion in Mycobacterium tuberculosis.

Deletion of genes in a pathogen is commonly associated with a reduction in its ability to cause disease. However, some rare cases have been described in the literature whereby deletion of a gene results in an increase in virulence. Recently, there have been several reports of hypervirulence resulting from gene deletion in Mycobacterium tuberculosis. Here, we explore this phenomenon in the context of the interaction between the pathogen and the host response

Somatostatin receptor subtype expression in cells of the rat immune system during adjuvant arthritis

Somatostatin is a neuropeptide that is widely distributed throughout the body. It acts as a neurohormone and a neurotransmitter an

Characterisation of a putative AraC transcriptional regulator from Mycobacterium smegmatis

MSMEG_0307 is annotated as a transcriptional regulator belonging to the AraC protein family and is located adjacent to the arylamine N-acetyltransferase (nat) gene in Mycobacterium smegmatis, in a gene cluster, conserved in most environmental mycobacterial species. In order to elucidate the function of the AraC protein from the nat operon in M. smegmatis, two conserved palindromic DNA motifs were identified using bioinformatics and tested for protein binding using electrophoretic mobility shift assays with a recombinant form of the AraC protein. We identified the formation of a DNA:AraC protein complex with one of the motifs as well as the presence of this motif in 20 loci across the whole genome of M. smegmatis, supporting the existence of an AraC controlled regulon. To characterise the effects of AraC in the regulation of the nat operon genes, as well as to gain further insight into its function, we generated a ΔaraC mutant strain where the araC gene was replaced by a hygromycin resistance marker. The level of expression of the nat and MSMEG_0308 genes was down-regulated in the ΔaraC strain when compared to the wild type strain indicating an activator effect of the AraC protein on the expression of the nat operon genes

A highly conserved transcriptional repressor controls a large regulon involved in lipid degradation in Mycobacterium smegmatis and Mycobacterium tuberculosis

The Mycobacterium tuberculosis TetR-type regulator Rv3574 has been implicated in pathogenesis as it is induced in vivo, and genome-wide essentiality studies show it is required for infection. As the gene is highly conserved in the mycobacteria, we deleted the Rv3574 orthologue in Mycobacterium smegmatis (MSMEG_6042) and used real-time quantitative polymerase chain reaction and microarray analyses to show that it represses the transcription both of itself and of a large number of genes involved in lipid metabolism. We identified a conserved motif within its own promoter (TnnAACnnGTTnnA) and showed that it binds as a dimer to 29 bp probes containing the motif. We found 16 and 31 other instances of the motif in intergenic regions of M. tuberculosis and M. smegmatis respectively. Combining the results of the microarray studies with the motif analyses, we predict that Rv3574 directly controls the expression of 83 genes in M. smegmatis, and 74 in M. tuberculosis. Many of these genes are known to be induced by growth on cholesterol in rhodococci, and palmitate in M. tuberculosis. We conclude that this regulator, designated elsewhere as kstR, controls the expression of genes used for utilizing diverse lipids as energy sources, possibly imported through the mce4 system

The Role of Lipid Metabolism in T Lymphocyte Differentiation and Survival

The differentiation and effector functions of both the innate and adaptive immune system are inextricably linked to cellular metabolism. The features of metabolism which affect both arms of the immune system include metabolic substrate availability, expression of enzymes, transport proteins, and transcription factors which control catabolism of these substrates, and the ability to perform anabolic metabolism. The control of lipid metabolism is central to the appropriate differentiation and functions of T lymphocytes, and ultimately to the maintenance of immune tolerance. This review will focus on the role of fatty acid (FA) metabolism in T cell differentiation, effector function, and survival. FAs are important sources of cellular energy, stored as triglycerides. They are also used as precursors to produce complex lipids such as cholesterol and membrane phospholipids. FA residues also become incorporated into hormones and signaling moieties. FAs signal via nuclear receptors and their channeling, between storage as triacyl glycerides or oxidation as fuel, may play a role in survival or death of the cell. In recent years, progress in the field of immunometabolism has highlighted diverse roles for FA metabolism in CD4 and CD8 T cell differentiation and function. This review will firstly describe the sensing and modulation of the environmental FAs and lipid intracellular signaling and will then explore the key role of lipid metabolism in regulating the balance between potentially damaging pro-inflammatory and anti-inflammatory regulatory responses. Finally the complex role of extracellular FAs in determining cell survival will be discussed

Bystander Macrophage Apoptosis after Mycobacterium tuberculosis H37Ra Infection▿

Human macrophages infected with Mycobacterium tuberculosis may undergo apoptosis. Macrophage apoptosis contributes to the innate immune response against M. tuberculosis by containing and limiting the growth of mycobacteria and also by depriving the bacillus of its niche cell. Apoptosis of infected macrophages is well documented; however, bystander apoptosis of uninfected macrophages has not been described in the setting of M. tuberculosis. We observed that uninfected human macrophages underwent significant bystander apoptosis 48 and 96 h after they came into contact with macrophages infected with avirulent M. tuberculosis. The bystander apoptosis was significantly greater than the background apoptosis observed in uninfected control cells cultured for the same length of time. There was no evidence of the involvement of tumor necrosis factor alpha, Fas, tumor necrosis factor-related apoptosis-inducing ligand, transforming growth factor β, Toll-like receptor 2, or MyD88 in contact-mediated bystander apoptosis. This newly described phenomenon may further limit the spread of M. tuberculosis by eliminating the niche cells on which the bacillus relies

Immune Senescence and Vaccination in the Elderly

Vaccines are powerful public health tools that have been of tremendous benefit in protecting vulnerable populations worldwide from many pathogens. However, vaccine- preventable diseases still remain a considerable burden and this is particularly true among aging and aged populations in industrialized countries. The predicted demographic shift in the population landscape towards an ever-increasing aging population and the evidence suggesting that older individuals mount less-than optimal immune response to vaccination have raised the question of improving vaccine responses in older individuals. This review presents recent progress in the understanding at the cellular and molecular levels of age related immune decline and strategies to translate current knowledge into the development of immunization strategies to promote healthy aging, keeping older members of our society autonomous and independent