Apoptotic signaling through the beta -adrenergic receptor. A new Gs effector pathway

β2-Adrenergic Receptor Mediated Inhibition of T Cell Function and Its Implications for CAR-T Cell Therapy

The microenvironment of most tumors is complex, comprising numerous aspects of immunosuppression. Several studies have indicated that the adrenergic system is vital for controlling immunological responses. In the context of the tumor microenvironment, nor-adrenaline (NA) is poured in by innervating nerves and tumor tissues itself. The receptors for nor-adrenaline are present on the surfaces of cancer and immune cells and are often involved in the activation of pro-tumoral signaling pathways. Beta2-adrenergic receptors (β2-ARs) are an emerging class of receptors that are capable of modulating the functioning of immune cells. β2-AR is reported to activate regulatory immune cells and inhibit effector immune cells. Blocking β2-AR increases activation, proliferation, and cytokine release of T lymphocytes. Moreover, β2-AR deficiency during metabolic reprogramming of T cells increases mitochondrial membrane potential and biogenesis. In the view of the available research data, the immunosuppressive role of β2-AR in T cells presents it as a targetable checkpoint in CAR-T cell therapies. In this review, we have abridged the contemporary knowledge about adrenergic-stress-mediated β2-AR activation on T lymphocytes inside tumor milieu.

A1 and A2A adenosine receptors play a protective role to reduce prevalence of autoimmunity following tissue damage

Adenosine is a potent modulator that has a tremendous effect on the immune system. Adenosine affects T cell activity, and is necessary in maintaining the T helper/regulatory T cell (Treg ) ratio. Adenosine signalling is also involved in activating neutrophils and the formation of neutrophil extracellular traps (NETs), which has been linked to autoimmune disorders. Therefore, adenosine, through its receptors, is extremely important in maintaining homeostasis and involved in the development of autoimmune diseases. In this study, we aim to evaluate the role of adenosine A1 and A2A receptors in involvement of autoimmune diseases. We studied adenosine regulation by NETosis in vitro, and used two murine models of autoimmune diseases: type I diabetes mellitus (T1DM) induced by low-dose streptozotocin and pristane-induced systemic lupus erythematosus (SLE). We have found that A1 R enhances and A2A R suppresses NETosis. In addition, in both models, A1 R-knock-out (KO) mice were predisposed to the development of autoimmunity. In the SLE model in wild-type (WT) mice we observed a decline of A1 R mRNA levels 6 h after pristane injection that was parallel to lymphocyte reduction. Following pristane, 43% of A1 R-KO mice suffered from lupus-like disease while WT mice remained without any sign of disease at 36 weeks. In WT mice, at 10 days A2A R mRNA levels were significantly higher compared to A1R-KO mice. Similar to SLE, in the T1DM model the presence of A1 R and A2A R was protective. Our data suggest that, in autoimmune diseases, the acute elimination of lymphocytes and reduction of DNA release due to NETosis depends upon A1 R desensitization and long-term suppression of A2A R.

Non-Selective Beta-Blockers Decrease Infection, Acute Kidney Injury Episodes, and Ameliorate Sarcopenic Changes in Patients with Cirrhosis: A Propensity-Score Matching Tertiary-Center Cohort Study

Background: Cirrhotic complications resulting from portal hypertension can be considerably reduced by non-selective beta-blockers (NSBBs); however, scarce studies have investigated therapeutic agents for other complications. We aimed to investigate the effects of NSBBs on common cirrhotic complications of infection, acute kidney injury (AKI), chronic renal function declination, and sarcopenic changes. Methods: Medical records of hospitalization for cirrhosis with at least a 4-year follow-up were analyzed and selected using propensity-score matching (PSM). Generalized estimating equation (GEE) was applied to assess the association of NSBBs with infection requiring hospitalization and AKI. Chronic renal function declination was evaluated by slope of regression lines derived from reciprocal of the serum creatinine level. The covariates of CT-measured skeletal muscle index (SMI) alterations were analyzed by generalized linear mixed model. Results: Among the 4946 reviewed individuals, 166 (83 NSBB group, 83 non-NSBB group) were eligible. Using GEE, Charlson comorbidity index, Child-Pugh score and non-NSBB were risk factors for infection; non-NSBB group revealed a robust trend toward AKI, showed no significant difference with chronic renal function declination of NSBB group, and was negatively associated with SMI alteration. Conclusion: Chronic NSBB use lowered the episodes of infection requiring hospitalization and AKIs, whereas non-NSBB was associated with sarcopenic changes.

Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle

Key points

Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity.

Although whole‐body glucose clearance is normal, 1‐month‐old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation.

Impaired glucose‐stimulated insulin secretion in IUGR lambs is due to lower intra‐islet insulin availability and not from glucose sensing.

We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole‐body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies.

IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose‐stimulated insulin secretion and insulin‐stimulated glucose oxidation, providing new insights into potential mechanisms for this risk.

Abstract

Placental insufficiency causes intrauterine growth restriction (IUGR) and disturbances in glucose homeostasis with associated β adrenergic receptor (ADRβ) desensitization. Our objectives were to measure insulin‐sensitive glucose metabolism in neonatal lambs with IUGR and to determine whether daily treatment with ADRβ2 agonist and ADRβ1/β3 antagonists for 1 month normalizes their glucose metabolism. Growth, glucose‐stimulated insulin secretion (GSIS) and glucose utilization rates (GURs) were measured in control lambs, IUGR lambs and IUGR lambs treated with adrenergic receptor modifiers: clenbuterol atenolol and SR59230A (IUGR‐AR). In IUGR lambs, islet insulin content and GSIS were less than in controls; however, insulin sensitivity and whole‐body GUR were not different from controls. Of importance, ADRβ2 stimulation with β1/β3 inhibition increases both insulin sensitivity and whole‐body glucose utilization in IUGR lambs. In IUGR and IUGR‐AR lambs, hindlimb GURs were greater but fractional glucose oxidation rates and ex vivo skeletal muscle glucose oxidation rates were lower than controls. Glucose transporter 4 (GLUT4) was lower in IUGR and IUGR‐AR skeletal muscle than in controls but GLUT1 was greater in IUGR‐AR. ADRβ2, insulin receptor, glycogen content and citrate synthase activity were similar among groups. In IUGR and IUGR‐AR lambs heart rates were greater, which was independent of cardiac ADRβ1 activation. We conclude that targeted ADRβ2 stimulation improved whole‐body insulin sensitivity but minimally affected defects in GSIS and skeletal muscle glucose oxidation. We show that risk factors for developing diabetes are independent of postnatal catch‐up growth in IUGR lambs as early as 1 month of age and are inherent to the islets and myocytes.

Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity.

Although whole‐body glucose clearance is normal, 1‐month‐old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation.

Impaired glucose‐stimulated insulin secretion in IUGR lambs is due to lower intra‐islet insulin availability and not from glucose sensing.

We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole‐body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies.

IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose‐stimulated insulin secretion and insulin‐stimulated glucose oxidation, providing new insights into potential mechanisms for this risk.

Synergistic Effects of Weightlessness, Isoproterenol, and Radiation on DNA Damage Response and Cytokine Production in Immune Cells

The implementation of rotating-wall vessels (RWVs) for studying the effect of lack of gravity has attracted attention, especially in the fields of stem cells, tissue regeneration, and cancer research. Immune cells incubated in RWVs exhibit several features of immunosuppression including impaired leukocyte proliferation, cytokine responses, and antibody production. Interestingly, stress hormones influence cellular immune pathways affected by microgravity, such as cell proliferation, apoptosis, DNA repair, and T cell activation. These pathways are crucial defense mechanisms that protect the cell from toxins, pathogens, and radiation. Despite the importance of the adrenergic receptor in regulating the immune system, the effect of microgravity on the adrenergic system has been poorly studied. Thus, we elected to investigate the synergistic effects of isoproterenol (a sympathomimetic drug), radiation, and microgravity in nonstimulated immune cells. Peripheral blood mononuclear cells were treated with the sympathomimetic drug isoproterenol, exposed to 0.8 or 2 Gy γ-radiation, and incubated in RWVs. Mixed model regression analyses showed significant synergistic effects on the expression of the β2-adrenergic receptor gene (ADRB2). Radiation alone increased ADRB2 expression, and cells incubated in microgravity had more DNA strand breaks than cells incubated in normal gravity. We observed radiation-induced cytokine production only in microgravity. Prior treatment with isoproterenol clearly prevents most of the microgravity-mediated effects. RWVs may be a useful tool to provide insight into novel regulatory pathways, providing benefit not only to astronauts but also to patients suffering from immune disorders or undergoing radiotherapy.

Cardiac Autoimmunity: Myocarditis

Myocarditis is the inflammation of the muscle tissues of the heart (myocardium). After a pathologic cardiac-specific inflammatory process, it may progress to chronic damage and dilated cardiomyopathy. The latter is characterized by systolic dysfunction, whose clinical correlate is heart failure. Nevertheless, other acute complications may arise as consequence of tissue damage and electrophysiologic disturbances. Different etiologies are involved in triggering myocarditis. In some cases, such as giant cell myocarditis or eosinophilic necrotizing myocarditis, it is an autoimmune process. Several factors predispose the development of autoimmune myocarditis such as systemic/local primary autoimmunity, viral infection, HLA and gender bias, exposure of cryptic antigens, mimicry, and deficient thymic training/Treg induction. Once the anti-myocardium autoimmune process is triggered, several components of the immune response orchestrate a sustained attack toward myocardial tissues with particular timing and immunopathogenic features. Innate response mediated by monocytes/macrophages, neutrophils, and eosinophils parallels the adaptive response, playing a final effector role and not only a priming function. Stromal cells like fibroblast are also involved in the process through specific cytokines. Furthermore, adaptive T cell responses have anti-paradigmatic features, as Th17 response is dispensable for acute myocarditis but is the main driver of the process leading to dilated cardiomyopathy. Humoral response, thought to be a bystander, is important in the appearance of late-stage hemodynamic complications. The complexity of that process, as well as the unspecific and variable clinical presentation, had generated difficulties for diagnosis and treatment, which remain suboptimal. In this chapter, we will discuss the most relevant immunopathogenic findings from a basic science and clinical perspective.

Prolyl hydroxylase domain enzymes and their role in cell signaling and cancer metabolism

The prolyl hydroxylase domain (PHD) enzymes regulate the stability of the hypoxia-inducible factor (HIF) in response to oxygen availability. During oxygen limitation, the inhibition of PHD permits the stabilization of HIF, allowing the cellular adaptation to hypoxia. This adaptation is especially important for solid tumors, which are often exposed to a hypoxic environment. However, and despite their original role as the oxygen sensors of the cell, PHD are currently known to display HIF-independent and hydroxylase-independent functions in the control of different cellular pathways, including mTOR pathway, NF-kB pathway, apoptosis and cellular metabolism. In this review, we summarize the recent advances in the regulation and functions of PHD in cancer signaling and cell metabolism.

Edaravone, a potent free radical scavenger and a calcium channel blocker attenuate isoproterenol induced myocardial infarction by suppressing oxidative stress, apoptotic signaling and ultrastructural damage

OBJECTIVES

In the present study, we investigated whether combination therapy of low-dose benidipine with the potent free radical scavenger edaravone has a cardioprotective effect against isoproterenol (ISO)-induced myocardial infarction (MI) in Wistar rats.

METHODS

Rats were pretreated with concurrent doses of benidipine and edaravone (1 μg/kg/day + 1 mg/kg/day and 3 μg/kg/day + 3 mg/kg/day) by intravenous (i.v.) and intraperitoneal (i.p.) routes respectively for 28 days, followed by MI induction using ISO (85 mg/kg) by subcutaneous route for two days at 24 h intervals. After the treatment period, blood was withdrawn and the heart was preserved for biochemical estimations.

RESULTS

The activities of the cardiac biomarkers (lactate dehydrogenase and creatine kinase-MB), and the level of malondialdehyde (MDA) significantly increased, while antioxidant markers (reduced glutathione, catalase, superoxidase dismutase, glutathione peroxidase, glutathione reductase) were significantly decreased in the ISO intoxicated group compared with the control group. Moreover, the level of C-reactive protein (CRP) and Caspase-3 activity significantly increased in ISO-intoxicated group. An ultrastructure study was also carried out. Pretreatment with a combination of benidipine and edaravone significantly attenuated the activities of the cardiac biomarkers and the level of MDA, and significantly increased the antioxidant markers compared with the ISO-intoxicated group. Furthermore, pretreatment with the combination of benidipine and edaravone significantly decreased the level of CRP and Caspase-3 activity as compared to the ISO-treated group. The ultrastructure study of myocardium revealed that pretreated groups preserved the mitochondrial shape, the membrane and its internal structures.

CONCLUSION

Taken together these results suggest that the combination of benidipine and edaravone showed significant protective effect in ISO-induced MI.

Cardiovascular Dysfunction Following Burn Injury: What We Have Learned from Rat and Mouse Models

Severe burn profoundly affects organs both proximal and distal to the actual burn site. Cardiovascular dysfunction is a well-documented phenomenon that increases morbidity and mortality following a massive thermal trauma. Beginning immediately post-burn, during the ebb phase, cardiac function is severely depressed. By 48 h post-injury, cardiac function rebounds and the post-burn myocardium becomes tachycardic and hyperinflammatory. While current clinical trials are investigating a variety of drugs targeted at reducing aspects of the post-burn hypermetabolic response such as heart rate and cardiac work, there is still a paucity of knowledge regarding the underlying mechanisms that induce cardiac dysfunction in the severely burned. There are many animal models of burn injury, from rodents, to sheep or swine, but the majority of burn related cardiovascular investigations have occurred in rat and mouse models. This literature review consolidates the data supporting the prevalent role that β-adrenergic receptors play in mediating post-burn cardiac dysfunction and the idea that pharmacological modulation of this receptor family is a viable therapeutic target for resolving burn-induced cardiac deficits.

Role of host β1- and β2-adrenergic receptors in a murine model of B16 melanoma: functional involvement of β3-adrenergic receptors

Complex interactions between tumor cells and their surrounding compartment are strongly influenced by the host in which the tumor grows. In melanoma, for instance, stress-associated norephinephrine (NE), acting at β-adrenergic receptors (β-ARs), stimulates melanoma cell proliferation and tumor angiogenesis. Among β-ARs, β3-ARs play a role acting not only at tumor cells but also at non-neoplastic stromal cells within the melanoma. In the present study, we used a murine model of B16 melanoma to evaluate the role of the host β1- and β2-ARs in melanoma growth and we determined whether the role of β3-ARs can be influenced by the absence of stromal β1- and β2-ARs. As compared to wild-type mice, β1/2-AR knockout mice displayed (i) increased intratumoral levels of both NE and β3-ARs, as evidentiated at both messenger and protein levels; (ii) increased tumor vascularization; (iii) decreased tumor cell proliferation but increased tumor cell apoptosis; and (iv) increased responsiveness to intratumoral injection of the β3-AR blocker L-748,337 in terms of decrease in tumor growth, tumor vascular response, tumor cell proliferation, and increase in tumor cell death. These findings together validate the role of β-AR signaling in melanoma microenvironment suggesting that non-neoplastic stromal cells may be targeted by β-AR-related drugs. The additional fact that β3-ARs play an important role in melanoma growth suggests selective β3-AR antagonists as important proapoptotic agents.

Prolyl hydroxylase domain enzymes: important regulators of cancer metabolism

The hypoxia-inducible factor (HIF) prolyl hydroxylase domain enzymes (PHDs) regulate the stability of HIF protein by post-translational hydroxylation of two conserved prolyl residues in its α subunit in an oxygen-dependent manner. Trans-4-prolyl hydroxylation of HIFα under normal oxygen (O₂) availability enables its association with the von Hippel-Lindau (VHL) tumor suppressor pVHL E3 ligase complex, leading to the degradation of HIFα via the ubiquitin-proteasome pathway. Due to the obligatory requirement of molecular O₂ as a co-substrate, the activity of PHDs is inhibited under hypoxic conditions, resulting in stabilized HIFα, which dimerizes with HIFβ and, together with transcriptional co-activators CBP/p300, activates the transcription of its target genes. As a key molecular regulator of adaptive response to hypoxia, HIF plays important roles in multiple cellular processes and its overexpression has been detected in various cancers. The HIF1α isoform in particular has a strong impact on cellular metabolism, most notably by promoting anaerobic, whilst inhibiting O₂-dependent, metabolism of glucose. The PHD enzymes also seem to have HIF-independent functions and are subject to regulation by factors other than O₂, such as by metabolic status, oxidative stress, and abnormal levels of endogenous metabolites (oncometabolites) that have been observed in some types of cancers. In this review, we aim to summarize current understandings of the function and regulation of PHDs in cancer with an emphasis on their roles in metabolism.

The sympathetic nervous system modulates CD4(+)Foxp3(+) regulatory T cells via noradrenaline-dependent apoptosis in a murine model of lymphoproliferative disease

The sympathetic nervous system (SNS) plays a crucial role in the course and development of autoimmune disease in Fas-deficient lpr/lpr mice. As regulatory T cells (Tregs) are considered important modulators of autoimmune processes, we analyzed the interaction between the SNS and Tregs in this murine model of lymphoproliferative disease. We found that the percentage of Tregs among CD4(+) T cells is increased in the spleen, lymph nodes, and thymus of lpr/lpr mice as compared to age-matched C57Bl/6J (B6) mice. Furthermore, noradrenaline (NA), the main sympathetic neurotransmitter, induced apoptosis in B6- and lpr/lpr-derived Tregs. NA also reduced the frequency of Foxp3(+) cells and Foxp3 mRNA expression via β2-adrenoceptor (β2-AR)-mediated mechanisms in a concentration and time-dependent manner. Destruction of peripheral sympathetic nerves by 6-hydroxydopamine significantly increased the percentage of Tregs in B6 control mice to an extent comparable to aged-matched lpr/lpr mice. The concentration of splenic NA negatively correlated with the frequency of CD4(+)Foxp3(+) Tregs. Additionally, 60days after sympathectomy, a partial recovery of NA concentrations led to Treg percentages comparable to those of intact, vehicle-treated controls. Immunohistochemical analysis of the spleen revealed localization of single Foxp3(+) Tregs in proximity to NA-producing nerve fibers, providing an interface between Tregs and the SNS. Taken together, our data suggest a relation between the degree of splenic sympathetic innervation and the size of the Treg compartment. While there are few examples of endogenous substances capable of affecting Tregs, our results provide a possible explanation of how the magnitude of the Treg compartment in the spleen can be regulated by the SNS.

Effects of catecholamines on thymocyte apoptosis and proliferation depend on thymocyte microenvironment

The present study, through quantification of tyrosine hydroxylase (TH) expression and catecholamine (CA) content in the presence and in the absence of α-methyl-p-tyrosine (AMPT), a TH inhibitor, in adult thymic organ (ATOC) and thymocyte culture, demonstrated that thymic cells produce CAs. In addition, in ATOC an increase in β2-adrenoceptor (AR) mRNA expression and β2-AR thymocyte surface density was registered. Furthermore, AMPT (10(-4)M), as propranolol (10(-4)M), augmented thymocyte apoptosis and diminished thymocyte proliferation in ATOC. Propranolol exerted these effects acting on CD3(high) thymocytes. However, in thymocyte cultures, propranolol (10(-6)M) acting on the same thymocyte subset exerted the opposing effect on thymocyte apoptosis and ConA-stimulated proliferation. This suggested that, depending on thymocyte microenvironment, differential effects can be induced through the same type of AR. Additionally, arterenol (10(-8) to 10(-6)M), similar to propranolol, diminished apoptosis, but increased ConA-stimulated thymocyte proliferation in thymocyte culture. However, differently from propranolol, arterenol affected manly CD3- thymocyte subset, which harbors majority of α1-AR+thymocytes. Additionally, arterenol showed a dose-dependent decrease in efficiency of thymocyte apoptosis and proliferation modulation with the rise in its concentration. Considering greater affinity of arterenol for α1-ARs than for β2-ARs, the previous findings could be attributable to increased engagement of β2-ARs with the rise of arterenol concentration. Consistently, in the presence of propranolol (10(-6)M), a β-AR blocker, the arterenol (10(-8)M) effects on thymocytes were augmented. In conclusion, thymic endogenous CAs, acting through distinct AR types and, possible, the same AR type (but in different cell microenvironment) may exert the opposing effects on thymocyte apoptosis/proliferation.

Sodium/calcium exchanger is upregulated by sulfide signaling, forms complex with the β1 and β3 but not β2 adrenergic receptors, and induces apoptosis

Hydrogen sulfide (H2S) as a novel gasotransmitter regulates variety of processes, including calcium transport systems. Sodium calcium exchanger (NCX) is one of the key players in a regulation calcium homeostasis. Thus, the aims of our work were to determine effect of sulfide signaling on the NCX type 1 (NCX1) expression and function in HeLa cells, to investigate the relationship of β-adrenergic receptors with the NCX1 in the presence and/or absence of H2S, and to determine physiological importance of this potential communication. As a H2S donor, we used morpholin-4-ium-4-methoxyphenyl(morpholino) phosphinodithioate-GYY4137. We observed increased levels of the NCX1 mRNA, protein, and activity after 24 h of GYY4137 treatment. This increase was accompanied by elevated cAMP due to the GYY4137 treatment, which was completely abolished, when NCX1 was silenced. Increased cAMP levels would point to upregulation of β-adrenergic receptors. Indeed, GYY4137 increased expression of β1 and β3 (but not β2) adrenergic receptors. These receptors co-precipitated, co-localized with the NCX1, and induced apoptosis in the presence of H2S. Our results suggest that sulfide signaling plays a role in regulation of the NCX1, β1 and β3 adrenergic receptors, their co-localization, and stimulation of apoptosis, which might be of a potential importance in cancer treatment.

Anti-M(3) peptide IgG from Sjögren's syndrome triggers apoptosis in A253 cells

Primary Sjögren's syndrome (pSS) is an autoimmune disease that targets salivary and lachrymal glands, characterized by anti-cholinergic autoantibodies directed against the M(3) muscarinic acetylcholine receptor (mAChR). The aim of this work was to evaluate if cholinergic autoantibodies contained in IgG purified from Sjögren sera could trigger apoptosis of A253 cell line. We also determined if caspase-3 and matrix metalloproteinase-3 (MMP-3) are involved in the induction of A253 cell death. Our results demonstrated that anti-cholinergic autoantibodies stimulate apoptosis and inositol phosphate (InsP) accumulation accompanied by caspase-3 activation and MMP-3 production. All of these effects were blunted by atropine and J104794, indicating that M(3) mAChRs are impacted by the anti-cholinergic autoantibodies. The intracellular pathway leading to autoantibody-induced biological effects involves phospholipase C (PLC), calcium/calmodulin (CaM) and extracellular calcium as demonstrated by treatment with U-73122, W-7, verapamil, BAPTA and BAPTA-AM, all of which blocked the effects of the anti-cholinergic autoantibodies. In conclusion, anti-cholinergic autoantibodies in IgG purified from pSS patient's sera mediates apoptosis of the A253 cell line in an InsP, caspase-3 and MMP-3 dependent manner.

Dark cell change of the cerebellar Purkinje cells induced by terbutaline under transient disruption of the blood-brain barrier in adult rats: morphological evaluation

This study aimed to establish a cerebellar degeneration animal model and to characterize the dark cell change of Purkinje cells. We hypothesized that terbutaline, a β2-adrenoceptor agonist, induces cerebellar degeneration not only in neonatal rats, but also in adult rats. Nine-week-old adult male Sprague-Dawley rats were anesthetized and infused with 25% mannitol via the left common carotid artery. Thirty seconds later, terbutaline was infused via the same artery. Dark-stained Purkinje cells were observed in the entire cerebellum on day 3. Prominent Bergmann glial cells accompanied by swelling of the glial processes were present, and were closely associated with the dark-stained Purkinje cells. These findings were found continuously throughout day 30. Ultrastructurally, dilated Golgi vesicles and/or endoplasmic reticulum and large lamella bodies were present in both severely changed and slightly changed Purkinje cells. Bergmann glial cells in the area of synaptic contacts of the severely changed Purkinje cells showed swelling. The Bergmann glial process in close contact with the slightly changed Purkinje cell dendrite in molecular layer showed slight swelling, and large lamella bodies in the dendrite were observed close to the dendritic spines. These findings may suggest that terbutaline induced a failure of Bergmann glial cell and resulted in dark cell degeneration of the Purkinje cells due to glutamate excitotoxicity.

The role of the sympathetic nervous system in the thymus in health and disease

The existence of a network of immunoneuroendocrine interactions that results in the reciprocal modulation of the classical functions of each system is well established at present. Most of the evidence derives from studies on secondary lymphoid organs, such as the spleen and lymph nodes. In this article, several aspects relevant to understand the role of the sympathetic nervous system in the establishment of these interactions in the thymus are discussed. At present, the sympathetic innervation of the thymus, the expression of adrenergic receptors in thymic cells, particularly of β-adrenergic receptors, and the effect of sympathetic neurotransmitters, although mainly derived from in vitro or pharmacological studies, seem to be relatively well studied. However, other aspects, such as the relevance that immune-sympathetic interactions at the thymic level may have for certain diseases, specially autoimmune or other diseases that primarily involve the activation of the immune system, as well as how the integration of sympathetic and hormonal signals at local levels may affect thymic functions, certainly deserve further investigation.

Promoter polymorphisms in the β-2 adrenergic receptor are associated with drug-induced gene expression changes and response in acute lymphoblastic leukemia

We investigated whether genetic polymorphisms in the promoter region of the proapoptotic β-2 adrenergic receptor gene (ADRB2) influence treatment-induced changes in ADRB2 expression in leukemia cells and response to chemotherapy. The ADRB2 promoter region was genotyped in germline DNA from 369 children with acute lymphoblastic leukemia (ALL). For 95 of the patients, sufficient RNA was available before and after in vivo treatment to assess treatment-induced gene expression changes in ALL cells. After treatment, the median ADRB2 mRNA expression was ninefold lower in leukemia cells of patients who ultimately relapsed as compared with patients who remained in continuous complete remission (CCR). Polymorphisms in the ADRB2 promoter were significantly linked to methotrexate (MTX)-induced upregulation in ADRB2 gene expression in ALL cells. Moreover, the ADRB2 promoter haplotype was significantly related to early treatment response in 245 children with ALL who received uniform treatment. We conclude that germline polymorphisms in ADRB2 are linked to the antileukemic effects of ALL chemotherapy.

Activation of p38 mitogen-activated protein kinase by norepinephrine in T-lineage cells

The catecholamine norepinephrine (NE) stimulates T lymphocytes through a beta-adrenergic receptor (βAR)/adenylyl cyclase (AC)/cyclic AMP (cAMP)/protein kinase A (PKA) pathway, leading to altered cell responsiveness and apoptosis. p38 Mitogen-activated protein kinase (MAPK), a major intracellular signalling mediator for cellular and environmental stressors, is involved in the production of immune modulators and in the regulation of T-cell development, survival and death. In these studies we investigated the relationship among NE signalling, p38 MAPK activity and T-cell death. We showed that NE stimulation of BALB/c mouse thymocytes and S49 thymoma cells selectively increases the dual phosphorylation and activity of p38α MAPK. p38 MAPK activation involves the βAR, Gs protein, AC, cAMP and PKA, as determined through the use of a βAR antagonist, activators of AC and cAMP, and S49 clonal mutants deficient in Gs and PKA. Dual phosphorylation of p38 MAPK is also dependent on its own catalytic activity. Inhibition of p38 MAPK activity revealed its involvement in cAMP-mediated activating transcription factor-2 (ATF-2) phosphorylation, Fas ligand messenger RNA (mRNA) up-regulation, and cell death. These results identify a mechanism through which NE stimulation of the βAR/Gs/PKA pathway activates p38 MAPK, which can be potentiated by autophosphorylation, and leads to changes in T-cell dynamics, in part through the regulation of Fas ligand mRNA expression.

Muscarinic cholinoceptor activation by pilocarpine triggers apoptosis in human skin fibroblast cells

The aim of the present work was to examine the role of muscarinic acetylcholine receptors (mAChRs) on apoptosis in human skin fibroblast cells. Neonatal human skin fibroblast cultures were stimulated with pilocarpine in the presence or absence of specific antagonists. Pilocarpine stimulates apoptosis, total inositol phosphates (InsP) accumulation and nitric oxide synthase (NOS) activity. All these effects were inhibited by atropine, mustard hydrochloride (4-DAMP) and pirenzepine, indicating that M(1) and M(3) mAChRs are implicated in pilocarpine action. Pilocarpine apoptotic action is accompanied by caspase-3 and JNK activation. The intracellular pathway leading to pilocarpine-induced biological effects involved phospholipase C, calcium/calmodulin and extracellular calcium as U-73122, W-7, verapamil, BAPTA and BAPTA-AM blocked pilocarpine effects. L-NMMA, a NOS inhibitor, had no effect, indicating that the enzyme does not participate in the apoptosis phenomenon. These results may contribute to a better understanding of the modulatory role of the parasympathetic muscarinic system on the apoptotic human skin fibroblast process.

Stimulatory heterotrimeric G protein augments gamma ray-induced apoptosis by up-regulation of Bak expression via CREB and AP-1 in H1299 human lung cancer cells

Stimulatory heterotrimeric GTP-binding proteins (Gs protein) stimulate cAMP generation in response to various signals, and modulate various cellular phenomena such as proliferation and apoptosis. This study aimed to investigate the effect of Gs proteins on gamma ray-induced apoptosis of lung cancer cells and its molecular mechanism, as an attempt to develop a new strategy to improve the therapeutic efficacy of gamma radiation. Expression of constitutively active mutant of the alpha subunit of Gs (GalphasQL) augmented gamma ray-induced apoptosis via mitochondrial dependent pathway when assessed by clonogenic assay, FACS analysis of PI stained cells, and western blot analysis of the cytoplasmic translocation of cytochrome C and the cleavage of caspase-3 and ploy(ADP-ribose) polymerase (PARP) in H1299 human lung cancer cells. GalphasQL up-regulated the Bak expression at the levels of protein and mRNA. Treatment with inhibitors of PKA (H89), SP600125 (JNK inhibitor), and a CRE-decoy blocked GalphasQL-stimulated Bak reporter luciferase activity. Expression of GalphasQL increased basal and gamma ray-induced luciferase activity of cAMP response element binding protein (CREB) and AP-1, and the binding of CREB and AP-1 to Bak promoter. Furthermore, prostaglandin E2, a Galphas activating signal, was found to augment gamma ray-induced apoptosis, which was abolished by treatment with a prostanoid receptor antagonist. These results indicate that Galphas augments gamma ray-induced apoptosis by up-regulation of Bak expression via CREB and AP-1 in H1299 lung cancer cells, suggesting that the efficacy of radiotherapy of lung cancer may be improved by modulating Gs signaling pathway.

Stimulatory heterotrimeric GTP-binding protein augments cisplatin-induced apoptosis by upregulating Bak expression in human lung cancer cells

The present study aimed to investigate the effect of the stimulatory heterotrimeric GTP-binding (Gs) protein signaling system on cisplatin-induced apoptosis of lung cancer cells and its underlying mechanism as an attempt to develop a novel strategy to improve the therapeutic efficacy of cisplatin. Overexpression of the constitutively active alpha subunit of Gs (GalphasQL) in A549 human lung cancer cells increased cisplatin-induced apoptosis, and knockdown of Galphas with small hairpin RNA decreased the percentage of apoptotic cells. GalphasQL increased the expression of the proapoptotic proteins B-cell leukemia/lymphoma-2 genes (Bcl-2) homologous antagonist killer protein (Bak) and Bcl-2 associated X protein (Bax), and decreased the expression of the antiapoptotic proteins Bcl-2 and Bcl-Xlong protein. Knockdown of Bak blocked the augmentative effects of GalphasQL. GalphasQL decreased the degradation rate of the Bak protein, and increased Bak mRNA transcript levels. GalphasQL increased Bak-luciferase activity in a protein kinase A and cyclic AMP response element-dependent manner. GalphasQL also augmented cisplatin-induced apoptosis of H1299 human lung cancer cells that lack functional p53. From this study, it is concluded that Galphas augments cisplatin-induced apoptosis of lung cancer cells partially through upregulating Bak expression by increasing transcription and by decreasing the rate of protein degradation.

Heterotrimeric G proteins and apoptosis: intersecting signaling pathways leading to context dependent phenotypes

Apoptosis, a programmed cell death mechanism, is a fundamental process during the normal development and somatic maintenance of all multicellular organisms and thus is highly conserved and tightly regulated through numerous signaling pathways. Apoptosis is of particular clinical importance as its dysregulation contributes significantly to numerous human diseases, primarily through changes in the expression and activation of key apoptotic regulators. Each of the four families of heterotrimeric G proteins (G(s), G(i/o), G(q/11) and G(12/13)) has been implicated in numerous cellular signaling processes, including proliferation, transformation, migration, differentiation, and apoptosis. Heterotrimeric G protein signaling is an important but not widely studied mechanism regulating apoptosis. G protein Signaling and Apoptosis broadly cover two large bodies of literature and share numerous signaling pathways. Examination of the intersection between these two areas is the focus of this review. Several studies have implicated signaling through each of the four heterotrimeric G protein families to regulate apoptosis within numerous disease contexts, but the mechanism(s) are not well defined. Each G protein family has been shown to stimulate and/or inhibit apoptosis in a context-dependent fashion through regulating numerous downstream effectors including the Bcl-2 family, NF-kappaB, PI3 Kinase, MAP Kinases, and small GTPases. These cell-type specific and G protein coupled receptor dependent effects have led to a complex body of literature of G protein regulation of apoptosis. Here, we review the literature and summarize apoptotic signaling through each of the four heterotrimeric G protein families (and the relevant G protein coupled receptors), and discuss limitations and future directions for research on regulating apoptosis through G protein coupled mechanisms. Continued investigation in this field is essential for the identification of important targets for pharmacological intervention in numerous diseases.

The heterotrimeric G-protein alpha-subunit Galphaq regulates TCR-mediated immune responses through an Lck-dependent pathway

Here, we examined the functional involvement of heterotrimeric G-proteins in TCR-induced immune responses. TCR/CD3 crosslinking resulted in activation of both Galphaq and Galphas, but not Galphai-2. Targeting of Galphas, Galphai-2 and Galphaq using siRNA demonstrated a specific role of Galphaq in TCR signaling. Jurkat TAg T cells with Galphaq knockdown displayed reduced activation of Lck and LAT phosphorylation, but paradoxically showed sustained ERK1/2 phosphorylation and increased NFAT-AP-1-reporter activity implicating Galphaq in the negative control of downstream signaling and IL-2-promoter activity. Primary T cells isolated from Galphaq-deficient mice had a similar TCR signaling response with reduced proximal LAT phosphorylation, sustained ERK1/2 phosphorylation and augmented immune responses including increased secretion of IL-2, IL-5, IL-12 and TNF-alpha. The effects on NFAT-AP-1-reporter activity were sensitive to the Src family kinase inhibitor PP2 and were reversed by transient expression of constitutively active Lck. Furthermore, expression of constitutively active Galphaq Q209L elevated Lck activity and Zap-70 phosphorylation. Together these data argue for a role of Galphaq in the fine-tuning of proximal TCR signals at the level of Lck and a negative regulatory role of Galphaq in transcriptional activation of cytokine responses.

Arrestin-3 is essential for the activation of Fyn by the luteinizing hormone receptor (LHR) in MA-10 cells

Recent studies showed that Fyn is a mediator of the LHR-induced activation of the ERK1/2 cascade in MA-10 cells. Since the LHR is a G protein-coupled receptor and the Src family of kinases can be activated by some Galpha subunits and by the non-visual arrestins we investigated the role of these signaling molecules in the LHR-provoked activation of Fyn. Small interfering RNAs (siRNAs) that target two Galpha subunits that participate in LHR signaling (Galpha(s) and Galpha(11)) and one that targets arrestin-3 were co-transfected with the hLHR in MA-10 cells. We then determined the effects of these siRNAs on the LHR-provoked activation of Fyn, the phosphorylation of FAK (a prominent Fyn substrate) and the release of EGF-like growth factors (a Fyn-mediated process). Expression of the siRNA against Galpha(s) decreased the level of Galpha(s) and LHR-stimulated cAMP production by approximately 50% but did not affect LHR-stimulated Fyn activation or FAK phosphorylation. Likewise, expression of the siRNA against Galpha(11) decreased the level of Galpha(11) and LHR-stimulated inositol phosphate production by approximately 50% but did not affect LHR-stimulated Fyn activation or FAK phosphorylation. Expression of the siRNA against arrestin-3 decreased the level of arrestin-3 and the rate of internalization of hCG by approximately 50% and it also inhibited the LHR-provoked stimulation of Fyn, the phosphorylation of FAK and the release of EGF-like growth factors. These results show that, in MA-10 cells, the hLHR activates Fyn through an arrestin-3-dependent pathway and that this pathway is a mediator of the hLHR-provoked release of EGF-like growth factors.

Fetal mechanisms in neurodevelopmental disorders

Normal development of the central nervous system depends on complex, dynamic mechanisms with multiple spatial and temporal components during gestation. Neurodevelopmental disorders may originate during fetal life from genetic as well as intrauterine and extrauterine factors that affect the fetal-maternal environment. Fetal neurodevelopment depends on cell programs, developmental trajectories, synaptic plasticity, and oligodendrocyte maturation, which are variously modifiable by factors such as stress and endocrine disruption, exposure to pesticides such as chlorpyrifos and to drugs such as terbutaline, maternal teratogenic alleles, and premature birth. Current research illustrates how altered fetal mechanisms may affect long-term physiological and behavioral functions of the central nervous system more significantly than they affect its form, and these effects may be transgenerational. This research emphasizes the diversity of such prenatal mechanisms and the need to expand our understanding of how, when altered, they may lead to disordered development, the signs of which may not appear until long after birth.

Heterodimers of adenylyl cyclases 2 and 5 show enhanced functional responses in the presence of Galpha s

Recent studies have demonstrated that adenylyl cyclase isoforms can form both homo- and heterodimers and that this may be the basic functional unit of these enzymes (see Cooper, D.M.F. and Crossthwaite, A.J. (2006) Trends. Pharmacol. Sci. 8:426-431). Here, we show that adenylyl cyclases 2 and 5 can form a functional heterodimeric complex in HEK293 cells using a combination of BRET, confocal imaging, co-immunoprecipitation and assays of adenylyl cyclase activity. The AC2/5 complex is formed constitutively and is stable in the presence of receptor or forskolin stimulation. The complex formed by AC2/5 is also much more sensitive to the presence of Galpha(s) and forskolin than either of the parent AC isoforms themselves. Finally, we also show that this complex can be detected in native tissues as AC2 and AC5 were localized to the same structures in adult mouse ventricular myocytes and neonatal mouse cardiac fibroblasts and could be co-immunoprecipitated from lysates of mouse heart.

Intracellular mediators of CXCR4-dependent signaling in T cells

The signaling pathways induced in T lymphocytes by CXCR4-CXCL12 interaction, which lead to the cytoskeletal macro-rearrangements observable in migrating cells, are as yet largely uncharacterized. The aim of this review is to briefly summarize the current knowledge of the signaling machinery which controls the process of chemotaxis in CXCL12-stimulated T lymphocytes.

Prostaglandin E2 activates HPK1 kinase activity via a PKA-dependent pathway

Hematopoietic progenitor kinase 1 (HPK1) is a hematopoietic cell-restricted member of the Ste20 serine/threonine kinase super family. We recently reported that the immunosuppressive eicosanoid, prostaglandin E(2) (PGE(2)), is capable of activating HPK1 in T cells. In this report, we demonstrate that unlike the TCR-induced activation of HPK1 kinase activity, the induction of HPK1 catalytic activity by PGE(2) does not require the presence of phosphotyrosine-based signaling molecules such as Lck, ZAP-70, SLP-76, and Lat. Nor does the PGE(2)-induced HPK1 activation require the intermolecular interaction between its proline-rich regions and the SH3 domain-containing adaptor proteins, as required by the signaling from the TCR to HPK1. Instead, our study reveals that PGE(2) signal to HPK1 via a 3' -5 '-cyclic adenosine monophosphate-regulated, PKA-dependent pathway. Consistent with this observation, changing the serine 171 residue that forms the optimal PKA phosphorylation site within the "activation loop" of HPK1 to alanine completely prevents this mutant from responding to PGE(2)-generated stimulation signals. Moreover, the inability of HPK1 to respond to PGE(2) stimulation in PKA-deficient S49 cells further supports the importance of PKA in this signaling pathway. We speculate that this unique signaling pathway enables PGE(2) signals to engage a proven negative regulator of TCR signal transduction pathway and uses it to inhibit T cell activation.

Impaired antibody synthesis after spinal cord injury is level dependent and is due to sympathetic nervous system dysregulation

Individuals with spinal cord injury (SCI) are highly susceptible to infection. This post-traumatic immune suppression is thought to occur via alterations in sympathetic nervous system (SNS) or hypothalamic-pituitary-adrenal (HPA) axis function. Normally, the HPA axis and SNS help coordinate proper immune function. After SCI, the HPA axis becomes activated and descending input to sympathetic preganglionic neurons (SPNs) is impaired. Because lymphoid organs are innervated by SPNs distributed throughout the thoracolumbar spinal cord, we predicted level-dependent immune suppression after SCI due to activation of the HPA axis and loss of descending input to SPNs. We tested this hypothesis by measuring indices of HPA (circulating corticosterone; CORT) and SNS function (norepinephrine (NE) in spleen) as well as antigen-specific antibody synthesis against an exogenous non-self protein following high- or low-level SCI. Using a mid-thoracic (T9) spinal contusion injury model, we found that CORT was elevated after SCI with aberrant patterns of diurnal CORT synthesis evident through at least the first 24 h post-injury. However, splenic NE and antibody synthesis were similar to uninjured controls. Injury severity did not change these parameters. Indeed, CORT, NE and antibody synthesis were similar after T9 contusion or transection SCI. In contrast, high-level SCI (T3) caused sustained increases in CORT and splenic NE along with impaired antibody synthesis and elevated splenocyte apoptosis. The immunosuppressive effects of T3 SCI were caused by NE acting at beta2-adrenergic receptors (beta2AR) and could be reversed using beta2AR blockers. Interestingly, impaired antibody after T3 SCI could be mimicked after T9 SCI with a beta2AR agonist. These data illustrate the immunosuppressive effects of the SNS after high-level SCI and indicate that immune deficits may be overcome using beta-blockers.

beta2-Adrenergic receptor gene variants and risk for autism in the AGRE cohort

The beta2-adrenergic receptor is part of the catecholamine system, and variants at two polymorphic sites in the gene coding for the receptor (ADRB2) confer increased activity. Overstimulation of this receptor may alter brain development, and has been linked to autism in non-identical twins. The objective of this study was to determine whether alleles in ADRB2 are associated with diagnosis of autism in the Autism Genetic Resource Exchange (AGRE) population. Three hundred and thirty-one independent autism case-parent trios were included in the analysis. Subjects were genotyped at activity-related polymorphisms rs1042713 (codon 16) and rs1042714 (codon 27). Association between autism and genotypes at each polymorphic site was tested using genotype-based transmission disequilibrium tests, and effect modification by family and pregnancy characteristics was evaluated. Sensitivity to designation of the proband in each family was assessed by performing 1000 repeats of the analysis selecting affected children randomly. A statistically significant OR of 1.66 for the Glu27 homozygous genotype was observed. Increased associations with this genotype were observed among a subset of Autism Diagnostic Observation Schedule confirmed cases and a subset reporting experience of pregnancy-related stressors. In conclusion, the Glu27 allele of the ADRB2 gene may confer increased risk of autism and shows increased strength with exposure to pregnancy related stress.

Failure of catecholamines to shift T-cell cytokine responses toward a Th2 profile in patients with rheumatoid arthritis

To further understand the role of neuro-immunological interactions in the pathogenesis of rheumatoid arthritis (RA), we studied the influence of sympathetic neurotransmitters on cytokine production of T cells in patients with RA. T cells were isolated from peripheral blood of RA patients or healthy donors (HDs), and stimulated via CD3 and CD28. Co-incubation was carried out with epinephrine or norepinephrine in concentrations ranging from 10(-5) M to 10(-11) M. Interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, interleukin (IL)-4, and IL-10 were determined in the culture supernatant with enzyme-linked immunosorbent assay. In addition, IFN-gamma and IL-10 were evaluated with intracellular cytokine staining. Furthermore, basal and agonist-induced cAMP levels and catecholamine-induced apoptosis of T cells were measured. Catecholamines inhibited the synthesis of IFN-gamma, TNF-alpha, and IL-10 at a concentration of 10(-5) M. In addition, IFN-gamma release was suppressed by 10(-7) M epinephrine. Lower catecholamine concentrations exerted no significant effect. A reduced IL-4 production upon co-incubation with 10(-5) M epinephrine was observed in RA patients only. The inhibitory effect of catecholamines on IFN-gamma production was lower in RA patients as compared with HDs. In RA patients, a catecholamine-induced shift toward a Th2 (type 2) polarised cytokine profile was abrogated. Evaluation of intracellular cytokines revealed that CD8-positive T cells were accountable for the impaired catecholaminergic control of IFN-gamma production. The highly significant negative correlation between age and catecholamine effects in HDs was not found in RA patients. Basal and stimulated cAMP levels in T-cell subsets and catecholamine-induced apoptosis did not differ between RA patients and HDs. RA patients demonstrate an impaired inhibitory effect of catecholamines on IFN-gamma production together with a failure to induce a shift of T-cell cytokine responses toward a Th2-like profile. Such an unfavorable situation is a perpetuating factor for inflammation.

Galpha(s) sensitizes human SH-SY5Y cells to apoptosis independently of the protein kinase A pathway

Disturbances in Galpha(s-L) levels and function have been implicated in the pathophysiology of bipolar disorder, but the role of these changes in the development of the illness is not clear. In view of the critical role of Galpha(s)-mediated cAMP signaling in regulating cell survival, we investigated the potential role of Galpha(s-L) in modulating susceptibility to cellular stressors in human SH-SY5Y neuroblastoma cells. Overexpression of Galpha(s-L) to a level twice that of the vector-transfected cells did not directly affect cell viability but significantly increased the sensitivity to induction of cell death by serum deprivation and other apoptotic stimuli, including staurosporine, H(2)O(2), and tunicamycin. This enhanced sensitivity was associated with increased caspase-3 activation and appearance of fragmented nuclei (Hoechst 33342 staining). The broad-spectrum caspase inhibitor z-VAD-fmk completely suppressed cell death evoked by these apoptotic insults in both vector-transfected and Galpha(s-L)-overexpressing cells. The increased vulnerability conferred by increased Galpha(s-L) expression was neither mimicked by cAMP analogs 8-Br-cAMP, 8-CPT-cAMP, and 8-CPT-2Me-cAMP nor attenuated by PKA inhibitors Rp-cAMPS and KT5720. These data indicate that Galpha(s-L) may modulate apoptotic processes in a caspase-dependent manner through a signaling cascade that is independent of the cAMP/PKA or cAMP/Epac pathway. These results suggest that enhanced Galpha(s-L) expression, as was observed in post-mortem brain of bipolar patients, may impair cellular resilience in response to intracellular stress signals resulting from mitochondrial and/or endoplasmic reticulum dysfunction implicated in this disorder.

Transneuronal mapping of the CNS network controlling sympathetic outflow to the rat thymus

The thymus is a primary immune organ that is essential for the development of functional T cells. The thymus receives sympathetic innervation, and thymocytes and thymic epithelial cells express functional adrenergic receptors. In this study, we employed retrograde, transneuronal virus tracing to identify the CNS cell groups that regulate sympathetic outflow to the thymus. Pseudorabies virus (PRV) was injected into the thymus, and the pattern of PRV infection in sympathetic regulatory centers of the CNS was determined at 72 and 120 h post-inoculation. PRV infection within the CNS first appeared within the spinal cord at 72 h post-inoculation and was confined to neurons within the intermediolateral cell column at levels T1-T7. At 120 h post-inoculation infection had spread within the spinal cord to include the central autonomic nucleus, intercalated cell nucleus and light infection within the cells of the lateral funiculus. Within the brain, PRV positive cells were found within nuclei of the medulla oblongata, pons and hypothalamus. Infection in the hypothalamus was observed within the arcuate nucleus, dorsal, lateral, and posterior hypothalamus and in all parvicellular subdivisions of the paraventricular hypothalamic nucleus. None of the infected animals exhibited labeling of the dorsal motor nucleus of the vagus. In summary, this study provides the first anatomic map of CNS neurons involved in control of sympathetic outflow to the thymus.

The Role of Noradrenergic Nerves in the Development of the Lymphoproliferative Disease in Fas-Deficient, lpr/lpr Mice

Lpr/lpr mice develop a lymphoproliferative, autoimmune, lupus-like disease. These mice lack functional Fas (CD95) expression and are resistant to Fas ligand (CD178)-mediated apoptosis, a critical mechanism for the maintenance of peripheral tolerance. In this study, we show that noradrenaline (NA), the main sympathetic neurotransmitter, can induce apoptosis of lymphoid cells independently of functional Fas. Based on this finding, we used lpr/lpr mice as model to study the role of noradrenergic nerves in the expression of a lymphoproliferative disease. Early in ontogeny, the concentration of NA was significantly increased in the spleen of lpr/lpr mice, compared with normal littermates. However, splenic sympathetic innervation gradually declined as the disease progressed, and IgM blood levels and splenic NA concentration inversely correlated when the disease was overtly manifested. When the loss of noradrenergic fibers that occurred naturally during adult life in lpr/lpr mice was experimentally advanced by neonatal sympathectomy, the concentration of IgM and IgG2a in blood was markedly higher than that of control lpr/lpr mice, and the appearance of lymphadenopathy was accelerated. Furthermore, although neonatal denervation did not affect the life span of normal animals, it shortened significantly the survival time of lpr/lpr mice. These data show that, in addition to defects in the Fas pathway, an altered sympathetic innervation in lpr/lpr mice also contributes to the pathogenesis of the autoimmune disease, and strongly support the hypothesis that the sympathetic nervous system can modulate the expression of lymphoproliferative diseases.

The anti-apoptotic effect of leukotriene B4 in neutrophils: A role for phosphatidylinositol 3-kinase, extracellular signal-regulated kinase and Mcl-1

The constitutive commitment of neutrophils to apoptosis is a key process for the control and resolution of inflammation and it can be delayed by various inflammatory mediators including leukotriene B4 (LTB4). The mechanisms by which LTB4 contributes to neutrophil survival are still unclear and the present work aims at identifying intracellular pathways underlying this effect. Inhibition of human neutrophil apoptosis by LTB4 was abrogated by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin and by the specific MEK inhibitor PD98059. In contrast, inhibitors of p38 MAPK, Jak2/3 and Src did not hinder the anti-apoptotic effect of LTB4. We also investigated the effects of members of the Bcl-2 family as they play a crucial role in the regulation of programmed cell death. When neutrophils were incubated with LTB4 for 1 to 6 h, the mRNA levels of the anti-apoptotic protein Mcl-1 were upregulated approximately 2-fold, while those of the pro-apoptotic protein Bax were downregulated 3- to 4-fold, as determined by real-time PCR. Accordingly, Western blot analysis revealed that the expression of Mcl-1 was upregulated in presence of LTB4, while flow cytometric analysis revealed that Bax protein was downregulated. Furthermore, the modulatory effects of LTB4 on Mcl-1 and Bax proteins were abolished in the presence of either wortmannin or PD98059. Taken together, these results demonstrate the participation of PI3-K and MEK/ERK kinases, as well as regulatory apoptotic proteins such as Mcl-1 and Bax, in the anti-apoptotic effects of LTB4 in human neutrophils.

The physiological and behavioral effects of subchronic intracisternal administration of TGF-β in rats: comparison with the effects of CRF

We studied the physiological and behavioral effects of subchronic intracisternal administration of transforming growth factor-beta (TGF-beta) for 7 days. Subchronic intracisternal administration of TGF-beta significantly inhibited the increase in body weight of rats but did not affect food intake. In the measurement of locomotor activity after the final intracisternal administration on day 7, the total count for 1.5 h increased significantly in the TGF-beta group compared with the vehicle group. However, that for 10 h was not different between both groups. Furthermore, significant elevations in oxygen consumption were observed in the TGF-beta group during both light and dark phase. Subchronic TGF-beta treatment induced a significant decrease in the number of total leukocytes and lymphocytes and the relative weight of the thymus, and a significant increase in brown adipose tissue weight. Corticotropin-releasing factor (CRF) is the primary neuroendocrine factor released in response to stress. Subchronic treatment with CRF, as a positive control, significantly affected body weight, food intake, oxygen consumption, total leukocyte and lymphocyte counts, and thymus and adrenal weight. Subchronic TGF-beta administration partially mimicked the stress responses, implicating a role for TGF-beta in the brain in stress.

Activation of the lutropin/choriogonadotropin receptor in MA-10 cells leads to the tyrosine phosphorylation of the focal adhesion kinase by a pathway that involves Src family kinases

We show that activation of the endogenous or recombinant lutropin/choriogonadotropin receptor (LHR) in mouse Leydig tumor cells (MA-10 cells) leads to the tyrosine phosphorylation of the focal adhesion kinase (FAK) and one of its substrates (paxillin). Using specific antibodies to the five tyrosine residues of FAK that become phosphorylated, we show that activation of the LHR increases the phosphorylation of Tyr576 and Tyr577, but it does not affect the phosphorylation of Tyr397, Tyr861, or Tyr925. Because FAK is a prominent substrate for the Src family of tyrosine kinases (SFKs) we tested for their involvement in the LHR-mediated phosphorylation of FAK-Tyr576. Src is not detectable in MA-10 cells, but two other prominent members of this family (Fyn and Yes) are present. The LHR-mediated phosphorylation of FAK-Tyr576 is readily inhibited by PP2 (a pharmacological inhibitor of SFKs) and by dominant-negative mutants of SKFs. Moreover, activation of the LHR in MA-10 cells results in the stimulation of the activity of Fyn and Yes, and overexpression of either of these two tyrosine kinases enhances the LHR-mediated phosphorylation of FAK-Tyr576. Studies involving activation of other G protein-coupled receptors, overexpression of the different Galpha-subunits, and the use of second messenger analogs suggest that the LHR-induced phosphorylation of FAK-Tyr576 in MA-10 cells is mediated by SFKs, and that this family of kinases is, in turn, independently or cooperatively activated by the LHR-induced stimulation of Gs and Gq/11-mediated pathways.

Disruption of rat forebrain development by glucocorticoids: critical perinatal periods for effects on neural cell acquisition and on cell signaling cascades mediating noradrenergic and cholinergic neurotransmitter/neurotrophic responses

Glucocorticoids are the consensus treatment for the prevention of respiratory distress in preterm infants, but there is evidence for increased incidence of neurodevelopmental disorders as a result of their administration. We administered dexamethasone (Dex) to developing rats at doses below or within the range of those used clinically, evaluating the effects on forebrain development with exposure in three different stages: gestational days 17-19, postnatal days 1-3, or postnatal days 7-9. At 24 h after the last dose, we evaluated biomarkers of neural cell acquisition and growth, synaptic development, neurotransmitter receptor expression, and synaptic signaling mediated by adenylyl cyclase (AC). Dex impaired the acquisition of neural cells, with a peak effect when given in the immediate postnatal period. In association with this defect, Dex also elicited biphasic effects on cholinergic presynaptic development, promoting synaptic maturation at a dose (0.05 mg/kg) well below those used therapeutically, whereas the effect was diminished or lost when doses were increased to 0.2 or 0.8 mg/kg. Dex given postnatally also disrupted the expression of adrenergic receptors known to participate in neurotrophic modeling of the developing brain and evoked massive induction of AC activity. As a consequence, disparate receptor inputs all produced cyclic AMP overproduction, a likely contributor to disrupted patterns of cell replication, differentiation, and apoptosis. Superimposed on the heterologous AC induction, Dex impaired specific receptor-mediated cholinergic and adrenergic signals. These results indicate that, during a critical developmental period, Dex administration leads to widespread interference with forebrain development, likely contributing to eventual, adverse neurobehavioral outcomes.

Expression of beta adrenergic receptors in mouse oocytes and preimplantation embryos

Accumulating evidence indicates the role of endogenous catecholamines in mammalian embryogenesis. We searched public databases containing nucleotide sequences derived from mouse preimplantation cDNA libraries and found a partial sequence homology between a cDNA clone from mouse blastocysts and the mouse beta 2-adrenergic receptor sequence. No significant sequence homology was found for other mouse adrenergic and dopamine receptors. Using RT-PCR, we showed that beta 2-adrenoceptor is transcribed not only at blastocyst stage but also at earlier stages of preimplantation development as well as in oocytes. Moreover, we demonstrated that transcripts encoding both isoforms of the beta 3-adrenoceptor (beta 3a- and beta 3b-) are expressed in mouse oocytes and preimplantation embryos as well. We did not detect the beta 1-adrenoceptor transcript either in oocytes or in preimplantation embryos. Using an antibody against the mouse beta 2-adrenergic receptor, we showed that the receptor protein is expressed in oocytes and preimplantation embryos; in blastocysts, the immufluorescence labeling was stronger in the inner cell mass than in throphectodermal cells. The cell number of the in vitro cultured mouse preimplantation embryos exposed to isoproterenol (a potent beta adrenoceptor agonist) was lower than in control embryos, suggesting that activation of beta adrenergic receptors by appropriate agonist concentration can influence cell proliferation in mouse pre-implantation embryos. Thus, our results indicate that beta adrenergic receptors are expressed in mouse oocytes and preimplantation embryos and that ligands for the receptors can affect the mouse embryo even in the very early stages of development.

Beta2-adrenergic receptors mediate the differential effects of catecholamines on cytokine production of PBMC

We determined characteristics of beta2-adrenergic receptors (beta2R) on peripheral blood mononuclear cells (PBMC) and cytokine production after mitogenic stimulation and coincubation with catecholamines. PBMCs were stimulated with interleukin-2 (IL-2), tetanus toxoid (TT), anti-CD3 antibody, or phytohemagglutinin (PHA). The cytokines interferon-gamma (IFN-gamma), IL-4, and IL-6 were determined by ELISA following coincubation with high-dose (10(-5) M) and low-dose (10(-9) M) epinephrine (EPI) and norepinephrine (NE). Intracellular IFN-gamma and IL-4 were studied by FACS analysis. The beta2R density was investigated using a radioligand binding assay. The stimuli induced various cytokine profiles in PBMCs. Synthesis of IFN-gamma was induced by all mitogens and could be suppressed by catecholamines (26%-85% reduction). In PHA-stimulated PBMCs, IL-4 synthesis was decreased by high-dose catecholamines (24%-28% reduction). Adding a beta-blocking agent attenuated most catecholamine effects. A highly significant negative correlation between the density of beta2R with IFN-gamma and IL-6 levels of PHA-activated PBMCs (r = -0.88 to -0.96, p < 0.01-< 0.001) was observed. The results indicate that the density of beta2R on PBMC plays a role in mediating the differential catecholamine effects on cytokine production of PBMC. Furthermore, changes in cytokine expression induced by catecholamines favor Th2 responses.

Isoproterenol induces actin depolymerization in human airway smooth muscle cells via activation of an Src kinase and GS

In a previous study, we showed that isoproterenol induced actin depolymerization in human airway smooth muscle cells by both protein kinase A (PKA)-dependent and -independent signaling pathways. We now investigate the signaling pathway of PKA-independent actin depolymerization induced by isoproterenol in these cells. Cells were briefly exposed to isoproterenol or PGE1 in the presence and absence of specific inhibitors of Src-family tyrosine kinases, phosphatidylinositol-3-kinase (PI3 kinase), or MAP kinase, and actin depolymerization was measured by concomitant staining of filamentous actin with FITC-phalloidin and globular actin with Texas red DNase I. Isoproterenol, cholera toxin, and PGE1 induced actin depolymerization, indicated by a decrease in the intensity of filamentous/globular fluorescent staining. Pretreatment with the Src kinase inhibitors 4-amino-5-(4-chlorophenyl)-7-( t-butyl)pyrazolo[3,4-d]pyriimidine (PP2) or geldanamycin or the PKA inhibitor Rp-cAMPS only partly inhibited isoproterenol- or PGE1-induced actin depolymerization. In contrast, PP2 and geldanamycin did not inhibit forskolin-induced actin depolymerization, and AG-213 (an EGF receptor tyrosine kinase inhibitor) did not inhibit isoproterenol- or PGE1-induced actin depolymerization. PI3 kinase or MAP kinase inhibition did not inhibit isoproterenol-induced actin depolymerization. Moreover, isoproterenol but not forskolin induced tyrosine phosphorylation of an Src family member at position 416. These results further confirm that both PKA-dependent and PKA-independent pathways mediate actin depolymerization in human airway smooth muscle cells and that the PKA-independent pathway by which isoproterenol induces actin depolymerization in human airway smooth muscle cells involves Src protein tyrosine kinases and the Gs protein.

Role of ceramide in Ca2+-sensing receptor-induced apoptosis

Increased extracellular Ca(2+) ([Ca(2+)](o)) can damage tissues, but the molecular mechanisms by which this occurs are poorly defined. Using HEK 293 cell lines that stably overexpress the Ca(2+)-sensing receptor (CaR), a G protein-coupled receptor, we demonstrate that activation of the CaR leads to apoptosis, which was determined by nuclear condensation, DNA fragmentation, caspase-3 activation, and increased cytosolic cytochrome c. This CaR-induced apoptotic pathway is initiated by CaR-induced accumulation of ceramide which plays an important role in inducing cell death signals by distinct G protein-independent signaling pathways. Pretreatment of wild-type CaR-expressing cells with pertussis toxin inhibited CaR-induced [(3)H]ceramide formation, c-Jun phosphorylation, and caspase-3 activation. The ceramide accumulation, c-Jun phosphorylation, and caspase-3 activation by the CaR can be abolished by sphingomyelinase and ceramide synthase inhibitors in different time frames. Cells that express a nonfunctional mutant CaR that were exposed to the same levels of [Ca(2+)](o) showed no evidence of activation of the apoptotic pathway. In conclusion, we report the involvement of the CaR in stimulating programmed cell death via a pathway involving GTP binding protein alpha subunit (Galpha(i))-dependent ceramide accumulation, activation of stress-activated protein kinase/c-Jun N-terminal kinase, c-Jun phosphorylation, caspase-3 activation, and DNA cleavage.

Adenylate cyclase regulation via proteasome-mediated modulation of Galphas levels

The adenylate cyclase (AC)/cyclic AMP (cAMP)/cAMP-dependent protein kinase pathway controls many biological phenomena. The ubiquitin/proteasome system, controlling the levels of many proteins, modulates important cellular processes such as cell cycle and cell growth. Here we describe a novel mechanism for AC regulation by proteasome pathway. Pharmacological inhibition of proteasome function in human osteosarcoma U2OS cells results in up-regulation of AC activity, increase of levels of alpha subunit of heterotrimeric stimulatory GTP-binding proteins (alphas) and, remarkably, also in preventing of beta-adrenergic receptor-mediated down-regulation of alphas protein levels. Accumulation of alphas protein is also accompanied by the appearance of polyubiquitinated alphas species. Our results: (1) identify alphas protein as a novel proteasome substrate in mammalian cells; (2) indicate that proteasome might play a physiological role in controlling AC/cAMP mediated pathways by modulating the levels of Galphas protein; (3) suggest a role for the proteasome also in controlling alphas-mediated signaling pathways other than those affecting AC complex.

Intravenous catecholamine administration affects mouse intestinal lymphocyte number and apoptosis

The purposes of this study were to determine plasma and intestinal epinephrine (E) and norepinephrine (NE) concentrations in mice after exercise stress and, the effect of intravenous injection of E and NE (at concentrations during exercise) on viability of intestinal lymphocytes (IL). Exhaustive exercise significantly elevated plasma E and NE, and intestinal E, compared with sedentary animals. Twenty-four hours after intravenous NE administration, IL counts were higher (p<0.001) and % apoptotic IL were lower (p<0.001) than saline conditions. E resulted in fewer apoptotic IL at 24 h compared to saline controls. E and NE differentially influence IL numbers at 24 h after injection although both result in fewer % apoptotic IL relative to mice given saline only.

Identification of T cell death-associated gene 8 (TDAG8) as a novel acid sensing G-protein-coupled receptor

T cell death-associated gene 8 (TDAG8) is a G-protein-coupled receptor mainly expressed in lymphoid organs and cancer tissues. TDAG8 shares high amino acid sequence homologies with recently reported proton-sensing G-protein-coupled receptors, G2A, OGR1, and GPR4. Here we have identified TDAG8 as a novel proton-sensing receptor. Upon acid stimulation, stably expressed TDAG8 was internalized from the plasma membrane. As a signaling pathway downstream of TDAG8, accumulation of cyclic AMP was observed in response to solutions with a pH value lower than 7.2. Furthermore, RhoA activation and actin rearrangement were elicited by acid-stimulated TDAG8. These results suggest that TDAG8 may play biological roles in immune response and cellular transformation under conditions accompanying tissue acidosis.

[Beta 2-adrenoceptor function in the kidney]

The majority of beta(2)-adrenoceptor (beta(2)-AR) agonists is eliminated via the kidneys as an unchanged substance. It is likely that such agents will exert pharmacological effects during their passage through the nephron. However, these pharmacological effects have, to our knowledge, not been taken into consideration when using these compounds in clinical practice because the role of beta(2)-AR in the regulation of renal function remains unclear. Renal beta(2)-ARs are predominantly localized to the proximal tubular epithelia and the membranes of smooth muscle cells from renal arteries. From this morphologic evidence, it is proposed that beta(2)-AR activation may regulate glomerular function and thereby sodium and water balance in the nephron segments. Actually, beta(2)-AR agonists given acutely cause a marked decrease in glomerular filtration rate. On the other hand, beta(2)-AR agonists inhibit the renal production of inflammatory cytokines such as TNF-alpha. Furthermore, the administration of beta(2)-AR agonists is found to attenuate apoptosis associated with shigatoxin in the hemolytic uremic syndrome (HUS). Increased understanding of the pharmacological basis of beta(2)-AR function in the kidney provides important new information relevant to the clinical use of beta(2)-AR agonists in airway diseases and potential applications of these drugs in renal inflammation and injury associated with sepsis or HUS.

Kinin B1 receptors stimulate nitric oxide production in endothelial cells: signaling pathways activated by angiotensin I-converting enzyme inhibitors and peptide ligands

We reported previously a novel mode of action of angiotensin I-converting enzyme (kininase II; ACE) inhibitors mediated through the direct activation of bradykinin B(1) receptor, independent of endogenous kinins or ACE (J Biol Chem 277:16847-16852, 2002). We aimed to further clarify the mechanism of activation of B(1) receptor, which leads to prolonged nitric oxide (NO) release. The ACE inhibitor enalaprilat and the peptide ligand desArg(10)-kallidin (in nanomolar concentrations) release NO by activating endothelial NO synthase (eNOS) in bovine and inducible NO synthase (iNOS) in stimulated human endothelial cells. The peptide and the ACE inhibitor ligands activate eNOS by facilitating different signaling pathways. DesArg(10)-kallidin enhances inositol-phosphate generation and elevates [Ca(2+)](i) by first augmenting intracellular release and then the influx of extracellular Ca(2+). In contrast, enalaprilat stimulates only the influx of extracellular Ca(2+) through rare earth-sensitive channels, and its effect is blocked by cholera toxin or protein kinase C inhibitors. In addition, unlike desArg(10)-kallidin, enalaprilat can also release NO independent of Ca(2+) in bovine endothelial cells. The inflammatory cytokines interleukin-1beta and interferon-gamma induce both B(1) receptor and iNOS in human endothelial cells. In contrast to eNOS, B(1) ligands activate iNOS similarly. Both desArg(10)-kallidin and ACE inhibitors enhance arginine uptake and release NO independent of [Ca(2+)](i) elevation. This is the first report on the direct activation of B(1) receptor by ACE inhibitors in human endothelial cells. This interaction leads to prolonged NO release and possibly contributes to the documented benefits of the use of ACE inhibitors.

Distinct roles for Src tyrosine kinase in beta2-adrenergic receptor signaling to MAPK and in receptor internalization

G protein-coupled receptors form the largest family of membrane receptors and transmit diverse ligand signals to modulate various cellular responses. After activation by their ligands, some of these G protein-coupled receptors are desensitized, internalized (endocytosed), and down-regulated (degraded). In HEK 293 cells, the G(s)-coupled beta2-adrenergic receptor was postulated to initiate a second wave of signaling, such as the activation of the mitogen-activated protein kinase (MAPK) pathway after the receptor is internalized. The tyrosine kinase c-Src plays a critical role in these events. Here we used mouse embryonic fibroblast (MEF) cells deficient in Src family tyrosine kinases to examine the role of Src in beta2-adrenergic receptor signaling to the MAPK pathway and in receptor internalization. We found that in Src-deficient cells the beta2-adrenergic receptor could activate the MAPK pathway. However, the internalization of beta2-adrenergic receptors was blocked in Src-deficient MEF cells. Furthermore, we observed that in MEF cells deficient in beta-arrestin 2 the internalization of the beta2-adrenergic receptor was impaired, whereas the activation of the MAPK pathway by the beta2-adrenergic receptor was normal. Our data demonstrate that although Src and beta-arrestin 2 play essential roles in beta2-adrenergic receptor internalization, they are not required for the activation of the MAPK pathway by the beta2-adrenergic receptor. In other words, our finding suggests that receptor internalization is not required for beta2-adrenergic receptor signaling to the MAPK pathway in MEF cells.