Active alpha 2 and beta adrenoceptors in lymphocytes from patients with chronic lymphocytic leukemia

Adrenergic receptor gene expression in bovine leukocytes

The α- and β-adrenergic receptors (ARs) bind the stress hormones epinephrine (E), norepinephrine (NE), and dopamine and activate diverse physiological responses. A lack of information on AR gene expression in leukocytes limits our understanding of how stress alters immune function. Quantitative analyses of AR gene expression was completed for bovine leukocytes. Individual leukocyte lineages and subpopulations within lineages were isolated with high-speed cell sorting to facilitate a targeted analysis of AR gene expression. These analyses confirmed all 9 AR genes were expressed in bovine leukocytes with marked differences in AR gene expression when comparing among leukocyte lineages. Furthermore, separation of polymorphonuclear cells into neutrophils and eosinophils revealed these key innate immune cells also differ significantly in AR gene expression. This study provides the first comprehensive survey of AR gene expression in immune cells of any mammalian species and provides insight into conflicting reports that stress can either activate or suppress immune function.

Adrenergic Signaling in Circadian Control of Immunity

Circadian rhythms govern a multitude of physiologic processes, both on a cell-intrinsic level and systemically, through the coordinated function of multi-organ biosystems. One such system-the adrenergic system-relies on the catecholamine neurotransmitters, adrenaline and noradrenaline, to carry out a range of biological functions. Production of these catecholamines is under dual regulation by both neural components of the sympathetic nervous system and hormonal mechanisms involving the hypothalamus-pituitary-adrenal axis. Importantly, both neural and hormonal arms receive input from the body's central clock, giving rise to the observed rhythmic variations in catecholamine levels in blood and peripheral tissues. Oscillations in catecholamine signals have the potential to influence various cellular targets expressing adrenergic receptors, including cells of the immune system. This review will focus on ways in which the body's central master clock regulates the adrenergic system to generate circadian rhythms in adrenaline and noradrenaline, and will summarize the existing literature linking circadian control of the adrenergic system to immunologic outcomes. A better understanding of the complex, multi-system pathways involved in the control of adrenergic signals may provide immunologists with new insight into mechanisms of immune regulation and precipitate the discovery of new therapeutics.

The role of G protein-coupled receptors in lymphoid malignancies

B cell lymphoma consists of multiple individual diseases arising throughout the lifespan of B cell development. From pro-B cells in the bone marrow, through circulating mature memory B cells, each stage of B cell development is prone to oncogenic mutation and transformation, which can lead to a corresponding lymphoma. Therapies designed against individual types of lymphoma often target features that differ between malignant cells and the corresponding normal cells from which they arise. These genetic changes between tumor and normal cells can include oncogene activation, tumor suppressor gene repression and modified cell surface receptor expression. G protein-coupled receptors (GPCRs) are an important class of cell surface receptors that represent an ideal target for lymphoma therapeutics. GPCRs bind a wide range of ligands to relay extracellular signals through G protein-mediated signaling cascades. Each lymphoma subgroup expresses a unique pattern of GPCRs and efforts are underway to fully characterize these patterns at the genetic level. Aberrations such as overexpression, deletion and mutation of GPCRs have been characterized as having causative roles in lymphoma and such studies describing GPCRs in B cell lymphomas are summarized here.

Impact of stress on cancer metastasis

The influence of psychosocial factors on the development and progression of cancer has been a longstanding hypothesis since ancient times. In fact, epidemiological and clinical studies over the past 30 years have provided strong evidence for links between chronic stress, depression and social isolation and cancer progression. By contrast, there is only limited evidence for the role of these behavioral factors in cancer initiation. Recent cellular and molecular studies have identified specific signaling pathways that impact cancer growth and metastasis. This article provides an overview of the relationship between psychosocial factors, specifically chronic stress, and cancer progression.

Potential clozapine target sites on peripheral hematopoietic cells and stromal cells of the bone marrow

The antipsychotic drug clozapine, acts via interaction with selective neurotransmitter receptor systems. Its use however, is associated with life-threatening agranulocytosis. The mechanism by which this occurs and its possible relationship with the drug's atypicality remain unclear. As a first step in identifying mechanistic pathways involved, profiling of neurotransmitter receptors on human neutrophils, mononuclear and bone marrow stromal cells as putative targets for clozapine-mediated toxicity was undertaken. Expression of mRNA encoding dopaminergic d2, d3, d4; serotonergic 5ht2a, 5ht2c, 5ht3, 5ht6, 5ht7; adrenergic alpha1a, alpha2; histaminergic h1 and muscarinic m1, m2, m3, m4, m5 receptors was analyzed by reverse transcription-polymerase chain reaction methods. While 5ht2c, 5ht6, m1 and m2 mRNA were undetected, the presence of the other receptors indicates sites at which clozapine could bind and induce toxicity of neutrophils and stromal components which regulate granulopoiesis. The functional significance of differential receptor expression while unknown, may argue for neural regulation of hematopoiesis.

Peripheral adrenergic system and hypertension

Hypertension is a condition where adrenergic responsiveness, sympathetic activity and adrenoceptors are somewhat altered. Many techniques are available to assess human sympathetic nervous system activity. They each present limitations and disadvantages. Characterization and subdivision of the alpha and beta-adrenoceptors, according to their localization and answer to different agonists, was facilitated in recent years by the extensive use of pharmacological and molecular biology techniques. Some adrenoceptor studies were conducted on animal models, human tissues and peripheral blood cells to assess their changes in various forms and stages of hypertension. Our group has pointed out that alpha1-adrenergic receptors expressed by human peripheral blood lymphocytes underwent changes of density in essential hypertensives, compared to normotensive control subjects. The importance of these findings could provide an assessment of alpha1-peripheral receptors with possible future clinical implications in the pathophysiology and treatment of hypertension.

In situ hybridization and immunocytochemistry of alpha1-adrenoceptors in human peripheral blood lymphocytes

1 alpha1-Adrenoceptor subtypes were investigated in cytospin centrifuged preparations of human peripheral blood lymphocytes by in situ hybridization and immunocytochemistry. 2 In situ hybridization cytochemistry revealed alpha1A-, alpha1B-, and alpha1D-receptor mRNA in human peripheral blood lymphocytes. Lymphocytes hybridized for alpha1A receptor subtype represented approximately 30% of total lymphocytes, those hybridized for alpha1Beta- and alpha1D-receptor subtypes averaged 42 and 25% of total lymphocytes, respectively. 3 Cytospin centrifuged lymphocytes exposed to anti-alpha1A-, alpha1Beta- or alpha1D-receptor protein antibodies, developed specific immunostaining. Approximately 27% of total lymphocytes were immunoreactive for alpha1A-receptor protein, 40% displayed alpha1B-receptor protein immunoreactivity and 22% alpha1D-receptor protein immunoreactivity. Analysis of percentages as well as of lymphocyte morphology of in situ hybridized and immunolabelled lymphocytes suggests the co-expression of mRNA receptor signal and protein receptor immunostaining in the same lymphocyte. 4 The demonstration of both alpha1-adrenoceptor mRNA and receptor protein subtypes suggests that alpha1-adrenoceptors may have a role in regulating lymphocyte function. 5 The possibility of demonstrating receptor protein immunoreactivity in a small amount of blood, such as that required for preparing cytospin-centrifuged lymphocytes, may stimulate research to evaluate the role of these receptors in lymphocytes and to establish if assessment of lymphocyte alpha1-adrenoceptors may represent a marker of their status in health and disease.

alpha1-adrenergic receptor subtypes in human peripheral blood lymphocytes

We investigated the expression of alpha1-adrenergic receptor subtypes in intact human peripheral blood lymphocytes using reverse transcription-polymerase chain reaction (RT-PCR) and radioligand binding assay techniques combined with antibodies against the three subtypes of alpha1-adrenergic receptors (alpha1A, alpha1B, and alpha1D). RT-PCR amplified in peripheral blood lymphocytes a 348-bp alpha1A-adrenergic receptor fragment, a 689-bp alpha1B-adrenergic receptor fragment, and a 540-bp alpha1D-adrenergic receptor fragment. Radioligand binding assay with [3H]prazosin as radioligand revealed a high-affinity binding with a dissociation constant value of 0. 65+/-0.05 nmol/L and a maximum density of binding sites of 175. 3+/-20.5 fmol/10(6) cells. The pharmacological profile of [3H]prazosin binding to human peripheral blood lymphocytes was consistent with the labeling of alpha1-adrenergic receptors. Antibodies against alpha1A-, alpha1B-, and alpha1D-receptor subtypes decreased [3H]prazosin binding to a different extent. This indicates that human peripheral blood lymphocytes express the three alpha1-adrenergic receptor subtypes. Of the three different alpha1-adrenergic receptor subtypes, the alpha1B is the most represented and the alpha1D, the least. Future studies should clarify the functional relevance of alpha1-adrenergic receptors expressed by peripheral blood lymphocytes. The identification of these sites may represent a step for evaluating whether they represent a marker of alpha1-adrenergic receptors in cardiovascular disorders or for assessing responses to drug treatment on these receptors.

The role of adrenoceptor-mediated signals in the modulation of lymphocyte function

Adrenoceptors are heterotrimeric glycoproteins that bind specific endogenous ligands, such as the sympathetic neurotransmitter norepinephrine and the neurohormone epinephrine. Ligand binding to an adrenoceptor expressed on the cell surface initiates a cascade of biochemical and molecular responses inside the cell that lead to a change in cellular activity. Initially, the stimulation of an adrenoceptor directly activates G proteins that stimulate enzymes to induce the production of second messengers. The cascade continues as the second messengers activate serine/threonine protein kinases, resulting in either an inhibition or enhancement of cellular activity. The resulting changes in cellular activity are mediated by changes in gene expression that are induced by the phosphorylation of specific transcription factors. Adrenoceptor subtypes are expressed by both T and B lymphocytes. The aim of this review is to summarize and discuss the results from the many studies that have examined the role of adrenoceptor-mediated intracellular signals in the modulation of lymphocyte function. Another aim of this review is to discuss how these studies have advanced our understanding of the mechanisms by which the sympathetic nervous system transmits information to both T and B lymphocytes to maintain immune homeostasis.