Molecular pharmacology of the beta-adrenergic receptor on THP-1 cells

Fingerprinting heterocellular β-adrenoceptor functional expression in the brain using agonist activity profiles

Noradrenergic projections from the brainstem locus coeruleus drive arousal, attentiveness, mood, and memory, but specific adrenoceptor (AR) function across the varied brain cell types has not been extensively characterized, especially with agonists. This study reports a pharmacological analysis of brain AR function, offering insights for innovative therapeutic interventions that might serve to compensate for locus coeruleus decline, known to develop in the earliest phases of neurodegenerative diseases. First, β-AR agonist activities were measured in recombinant cell systems and compared with those of isoprenaline to generate Δlog(Emax/EC50) values, system-independent metrics of agonist activity, that, in turn, provide receptor subtype fingerprints. These fingerprints were then used to assess receptor subtype expression across human brain cell systems and compared with Δlog(Emax/EC50) values arising from β-arrestin activation or measurements of cAMP response desensitization to assess the possibility of ligand bias among β-AR agonists. Agonist activity profiles were confirmed to be system-independent and, in particular, revealed β2-AR functional expression across several human brain cell types. Broad β2-AR function observed is consistent with noradrenergic tone arising from the locus coeruleus exerting heterocellular neuroexcitatory and homeostatic influence. Notably, Δlog(Emax/EC50) measurements suggest that tested β-AR agonists do not show ligand bias as it pertains to homologous receptor desensitization in the system examined. Δlog(Emax/EC50) agonist fingerprinting is a powerful means of assessing receptor subtype expression regardless of receptor expression levels or assay readout, and the method may be applicable to future use for novel ligands and tissues expressing any receptor with available reference agonists.

Does oral salbutamol improve fatigue in multiple sclerosis? A pilot placebo-controlled study

BACKGROUND

Because MS-related fatigue could be associated with enhanced proinflammatory cytokine production, drugs with immunomodulatories properties, such as salbutamol, may represent an alternative treatment. We aimed to evaluate the effect of salbutamol on MS-related fatigue.

METHODS

Thirty patients with relapsing-remitting MS who were between 18 and 69 years old, and suffering from fatigue, were evaluated with the Fatigue Severity Scale (FSS) and the Brazilian version of the neurological fatigue index for multiple sclerosis (NFI/MS-BR). They received salbutamol 2 mg twice a day or a placebo in a pilot randomized, double-masked placebo-controlled trial. The primary outcome was the change in the FSS score at the end of 90 days. The secondary outcome was the efficacy, represented by changes in their scores on the NFI/MS-BR subdomains (in the same period) and the Expanded Disability Status Scale (EDSS) at the end of 90 days.

RESULTS

Thirty subjects were allocated to receive either salbutamol (14) or a placebo (16). There was no superiority of salbutamol over the placebo in the FSS outcome at 30 (p ==0.498), 60 (p = 0.854) and 90 (p = 0.240) days. There was no a significant decrease in the proportion of patients with severe or moderate fatigue in the salbutamol group at the end of the follow-up. The scores on the NFI/MS-BR and its subscales did not improve significantly with treatment. No significant difference was observed in the EDSS outcome (p = 0.313). No serious adverse events were found. An increase in heart rate was evident in the salbutamol group only in the first 30 days, but without statistical significance in relation to placebo (p = 0.077).

CONCLUSION

Treatment with salbutamol does not improve fatigue in patients with relapsing-remitting MS.

β-adrenergic receptors in the up-regulation of COX2 expression and prostaglandin production in testicular macrophages: Possible relevance to male idiopathic infertility

Catecholaminergic neuronal elements (CNE) and macrophages (MACs) are increased in testes of patients with idiopathic infertility. Now, we describe an anatomical proximity between CNE and MACs, expression of specific α- and β-adrenergic receptors (ADRs) subtypes in MACs, and a positive correlation between the number of MACs and cyclooxygenase (COX2) expression - key enzyme in prostaglandin (PG) synthesis and an inflammatory marker - in testes of infertile men. To examine a potential effect of adrenergic input on COX2 expression, we used two additional experimental models: non-testicular human MACs (THP1 cell line) and non-human testicular MACs purified from adult Syrian hamsters. We found that epinephrine and norepinephrine up-regulate COX2 expression and PGD2 production through β1-and β2-ADRs. Our results demonstrate the existence of a yet unknown link between CNE and MACs in the human testis that could trigger inflammation and tissue homeostatic dysregulation associated with pathogenesis or maintenance of infertility states.

Influence of β2 adrenergic receptor genotype on risk of nocturnal ventilation in patients with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease resulting in severe respiratory derangements. As such, DMD patients are at a high risk of nocturnal hypoventilation, thereby requiring nocturnal ventilation (NV). To this end, NV is an important clinical milestone in the management of DMD. Emerging evidence suggests that ß₂ adrenergic receptors (ADRB2) may play a role in determining respiratory function, whereby more functional ADRB2 genotype variants (e.g., Gly16) are associated with improved pulmonary function and respiratory muscle strength. These findings suggest that the more functional ADRB2 genotype may help to preserve respiratory function in patients with DMD. The purpose of this study was to identify the influence of ADRB2 genotype on the risk of NV use in DMD. Data from the CINRG Duchenne Natural History Study including 175 DMD patients (3–25 yrs) were analyzed focusing on ADRB2 genotype variants. Time-to-event analyses were used to examine differences in the age at prescription of full-time NV use between genotypes. There were no differences between genotype groups in age, height, weight, corticosteroid use, proportion of ambulatory patients, or age at loss of ambulation. DMD patients expressing the Gly16 polymorphism had a significantly (P < 0.05) lower mean age at NV prescription compared with those patients expressing the Arg16 polymorphism (21.80 ± 0.59 yrs. vs 25.91 ± 1.31 yrs., respectively). In addition, a covariate-adjusted Cox model revealed that the Gly16 variant group possessed a 6.52-fold higher risk of full-time NV use at any given age compared with the Arg16 polymorphism group. These data suggest that genetic variations in the ADRB2 gene may influence the age at which DMD patients are first prescribed NV, whereby patients with the Gly16 polymorphism are more likely to require NV assistance at an earlier age than their Arg16 counterparts.

Differential modulation of innate immune response by epinephrine and estradiol

Background Although it is widely accepted that catecholamines and estrogens influence immunity and have consequences for health, their effect on innate immunity (e.g. monocytes and neutrophils) is still not fully investigated. Materials and methods Our study aimed to analyze the production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, monocyte chemoattractant protein (MCP)-1 and IL-8 by whole blood cells following short-term exposure to epinephrine (Epi) and 17β-estradiol (E2) in the presence or absence of lipopolysaccharide (LPS). We also evaluated the in vitro effect of these hormones on expression of β2 integrin (CD11b/CD18) and L-selectin (CD62L) by circulating neutrophils and monocytes in the blood of healthy subjects. Results Epi has shown a potential to modulate the production of pro-inflammatory mediators. Its exposure resulted in significantly increased production of IL-8 in a dose-dependent manner. On the contrary, a dose-dependent suppression of LPS-induced production of IL-1β, IL-8, and MCP-1 by Epi was observed. In neutrophils, a modest rise in CD11b expression was observed after Epi exposure. Simultaneously, Epi suppressed LPS-induced expression of CD11b and CD18. In monocytes, Epi suppressed LPS-induced expression of C11b. E2 inhibited LPS-induced TNF-α production and caused a significant decrease in CD62L expression in both cell populations. No significant changes were observed after double exposure of cells with Epi and E2. Conclusions Thus, our results show that Epi and E2 differentially modulate the innate immune response and have a dual effect on cytokine modulation. The findings suggest that the observed immunoregulatory role of Epi and E2 may influence the outcome in endotoxin responses and can be critical in the regulation of inflammatory responses.

Effect of β-agonist on the dexamethasone-induced expression of aromatase by the human monocyte cells

Emerging evidence suggests that sex steroids are important for human skin health. In particular, estrogen improves skin thickness, elasticity and moisture of older women. The major source of circulating estrogen is the ovary; however, local estrogen synthesis and secretion have important roles in, for example, bone metabolism and breast cancer development. We hypothesized that infiltrated peripheral monocytes are one of the sources of estrogen in skin tissues. We also hypothesized that, during atopic dermatitis under stress, a decline in the hypothalamus-pituitary-adrenal axis (HPA) and facilitation of the (hypothalamus)-sympathetic-adrenomedullary system (SAM) attenuates estrogen secretion from monocytes. Based on this hypothesis, we tested aromatase expression in the human peripheral monocyte-derived cell line THP-1 in response to the synthetic glucocorticoid dexamethasone (Dex), the synthetic β-agonist isoproterenol (Iso) and the β-antagonist propranolol (Pro). Dex mimics glucocorticoid secreted during excitation of the HPA, and Iso mimics catecholamine secreted during excitation of the SAM. We found that aromatase activity and the CYP19A1 gene transcript were both upregulated in THP-1 cells in the presence of Dex. Addition of Iso induced their downregulation and further addition of Pro rescued aromatase expression. These results may suggest that attenuation of estrogen secretion from peripheral monocytes could be a part of the pathology of stress-caused deterioration of atopic dermatitis. Further examination using an in vitro human skin model including THP-1 cells might be a valuable tool for investigating the therapeutic efficacy and mechanism of estrogen treatment for skin health.

Psychiatric comorbidity in the treatment of patients with inflammatory bowel disease

Ulcerative colitis and Crohn’s disease, commonly known as inflammatory bowel disease (IBD), draw attention from specialists of various disorders, including gastroenterology, psychiatry, and radiology. The involvement of a cortical influence in the brain-gut axis as well as the interaction of the hypothalamic-pituitary-adrenal axis and the peripheral nervous system provide an initial explanation of the psychological symptoms associated with IBD. The involvement of structures the limbic system, such as the anterior cingulate cortex, the prefrontal cortex, and the amygdala, paves the way for the discovery of the mechanisms underlying depression depression, anxiety, alexithymia, personality traits, and other psychological impairments following the onset of IBD. Psychiatric therapy in IBD patients is almost as important as the gastroenterological approach and consists of pharmacological treatment and psychotherapy. Neither of the available psychiatric treatment methods is considered the golden standard because both methods have side effects, and psychotropic medication can provoke the worsening of IBD symptoms. Thus, both approaches must be applied with awareness of the possibility of side effects. We suggest that psychiatrists and gastroenterologists work together to reach a consensus on IBD therapy to ensure success and to reduce side effects and relapse to the lowest possible rates.

Two High Throughput Screen Assays for Measurement of TNF-α in THP-1 Cells

Tumor Necrosis Factor-α (TNF-α), a secreted cytokine, plays an important role in inflammatory diseases and immune disorders, and is a potential target for drug development. The traditional assays for detecting TNF-α, enzyme linked immunosorbent assay (ELISA) and radioimmunoassay, are not suitable for the large size compound screens. Both assays suffer from a complicated protocol, multiple plate wash steps and/or excessive radioactive waste. A simple and quick measurement of TNF-α production in a cell based assay is needed for high throughput screening to identify the lead compounds from the compound library. We have developed and optimized two homogeneous TNF-α assays using the HTRF (homogeneous time resolved fluorescence) and AlphaLISA assay formats. We have validated the HTRF based TNF-α assay in a 1536-well plate format by screening a library of 1280 pharmacologically active compounds. The active compounds identified from the screen were confirmed in the AlphaLISA TNF-α assay using a bead-based technology. These compounds were also confirmed in a traditional ELISA assay. From this study, several beta adrenergic agonists have been identified as TNF-α inhibitors. We also identified several novel inhibitors of TNF-α, such as BTO-1, CCG-2046, ellipticine, and PD 169316. The results demonstrated that both homogeneous TNF-α assays are robust and suitable for high throughput screening.

Pro-inflammatory responses in human monocytes are beta1-adrenergic receptor subtype dependent

Stress induced circulating catecholamines are hypothesized to selectively activate adrenergic receptors (ARs) on immunocompetent cells modulating their inflammatory response to trauma or environmental toxins. We characterized changes in expression of a pro-inflammatory cytokine modulated by beta-AR activation in human primary and immortalized monocytes that had been simultaneously stimulated with lipopolysaccharide (LPS). Results from cytokine antibody arrays demonstrated that half-maximal effective concentrations of the selective beta-AR agonist isoproterenol (Iso) qualitatively increased LPS-mediated expression of the soluble cytokine, interleukin-1beta (IL-1beta). Semi-quantitative immunoblot techniques confirmed a synergistic increase of IL-1beta production in both LPS stimulated THP-1 cells and primary human monocytes co-incubated with Iso. Immunoblot techniques as well as radioligand binding studies were also used to characterize the heterogeneous expression of beta(1)- and beta(2)-AR subtypes on THP-1 cells. beta-AR activation is classically associated with generation of cAMP in many tissues and cell types. Therefore, using the method of Schild, we generated Iso concentration-response curves in the presence of fixed subtype-selective beta-AR antagonist concentrations to demonstrate that beta(1)-AR activation was exclusively linked with the generation of cAMP in THP-1 cells. Furthermore, use of a selective kinase inhibitor demonstrated that Iso potentiated the expression of soluble IL-1beta through activation of cAMP-dependent protein kinase A. Finally, discriminating concentrations of subtype-selective beta-AR antagonists revealed that beta(1)-AR stimulation alone accounted for the synergistic production of IL-1beta in LPS stimulated monocytes co-incubated with Iso. These results demonstrate a unique synergistic pro-inflammatory response mediated through a beta(1)-AR cAMP-dependent mechanism in LPS-challenged monocytic cells.

Antiglaucoma drug GLC756 and its effect on cellular cAMP and tumor necrosis factor alpha release in vitro of activated human monocytic leukemia cells

PURPOSE

GLC756, a putative antiglaucoma drug with dopamine D(2) agonist and D(1) antagonist properties, significantly decreases tumor necrosis factor alpha (TNF-alpha) levels in lipopolysaccharide (LPS)-induced rats. The present study describes the effects of GLC756 on cellular adenosine 3', 5'-cyclic monophosphate (cAMP) in relation to TNF-alpha production on LPS-stimulated human acute monocytic leukemia cells.

METHODS

A human peripheral blood acute monocytic leukemia cell line (THP-1) was activated via LPS. THP-1 cells were incubated with GLC756 or betamethasone (positive control) at concentrations of 1, 10, and 30 microM. The TNF-alpha concentration in supernatant and cAMP levels in cellular extract were measured by enzyme-linked immunosorbent assay 0,1, 2.5, 4.5, 7, and 24 h post-activation.

RESULTS

Compared with LPS controls, both GLC756 at 30 muM and betamethasone at > or =1 microM had a significant inhibitory effect on TNF-alpha release from THP-1 cells 2.5 to 24 h post-activation. Parallel to the TNF-alpha decrease, GLC756 induced significant increases of cellular cAMP 2.5 and 7 h post-activation. Betamethasone had no effect on the cellular cAMP level.

CONCLUSION

Intracellular signaling pathway leading to inhibition of the production of the proinflammatory cytokine TNF-alpha after GLC756 treatment might be mediated through the second messenger cAMP.

Dual ligand stimulation of RAW 264.7 cells uncovers feedback mechanisms that regulate TLR-mediated gene expression

To characterize how signaling by TLR ligands can be modulated by non-TLR ligands, murine RAW 264.7 cells were treated with LPS, IFN-gamma, 2-methyl-thio-ATP (2MA), PGE(2), and isoproterenol (ISO). Ligands were applied individually and in combination with LPS, for 1, 2, and 4 h, and transcriptional changes were measured using customized oligo arrays. We used nonadditive transcriptional responses to dual ligands (responses that were reproducibly greater or less than the expected additive responses) as a measure of pathway interaction. Our analysis suggests that cross-talk is limited; <24% of the features with significant responses to the single ligands responded nonadditively to a dual ligand pair. PGE(2) and ISO mainly attenuated, while 2MA enhanced, LPS-induced transcriptional changes. IFN-gamma and LPS cross-regulated the transcriptional response induced by each other: while LPS preferentially enhanced IFN-gamma-induced changes in gene expression at 1 h, IFN-gamma signaling primarily attenuated LPS-induced changes at 4 h. Our data suggest specific cross-talk mechanisms: 1) LPS enhances the expression of IFN-gamma-response genes by augmenting STAT1 activity and by activating NF-kappaB, which synergizes with IFN-gamma-induced transcriptional factors; 2) IFN-gamma attenuates the late LPS transcriptional response by increasing the expression of suppressor of cytokine signaling 1 and cytokine-inducible SH2-containing protein expression; 3) 2MA modulates LPS secondary transcriptional response by increasing IFN-beta and inhibiting IL-10 gene expression; 4) PGE(2) and ISO similarly regulate the LPS transcriptional response. They increase IL-10 transcription, resulting in attenuated expression of known IL-10-suppressed genes.

Antidepressants and inflammatory bowel disease: a systematic review

Background

A number of studies have suggested a link between the patient's psyche and the course of inflammatory bowel disease (IBD). Although pharmacotherapy with antidepressants has not been widely explored, some investigators have proposed that treating psychological co-morbidities with antidepressants may help to control disease activity. To date a systematic analysis of the available studies assessing the efficacy of antidepressants for the control of somatic symptoms in IBD patients has not been performed.

Methods

We searched electronic databases, without any language restriction. All relevant papers issued after 1990 were examined.

Results

12 relevant publications were identified. All of them referred to non-randomised studies. Antidepressants reported in these publications included paroxetine, bupropion, amitriptyline, phenelzine, and mirtazapine. In 10 articles, paroxetine, bupropion, and phenelzine were suggested to be effective for treating both psychological and somatic symptoms in patients suffering from IBD. Amitriptyline was found ineffective for treating somatic symptoms of IBD. Mirtazapine was not recommended for IBD patients.

Conclusion

Although most of reviewed papers suggest a beneficial effect of treatment with antidepressants in patients with IBD, due to the lack of reliable data, it is impossible to judge the efficacy of antidepressants in IBD. Properly designed trials are justified and needed based upon the available uncontrolled data.

Norepinephrine inhibits human immunodeficiency virus type-1 infection through the NF-κB inactivation

Exercise or acute stress can exert significant effects on immune system as well as cardiovascular and respiratory systems through catecholamines. In this study, we investigated effects of norepinephrine (NE), a catecholamine neurotransmitter on human immunodeficiency virus type-1 (HIV-1) infection. NE inhibited in vitro HIV-1 infection of peripheral blood mononuclear cells (PBMC) from healthy donors and ex vivo HIV-1 replication in patients' PBMC. In transient expression assays, NE downregulated HIV-1 long terminal repeat, but site-directed mutagenesis on NF-kappaB-binding sites or cotreatment with H89 (a protein kinase A inhibitor) abrogated the NE-mediated effect. Gel-shift assays showed suppression of NF-kappaB activity in NE-treated cells. NE increased cytoplasmic levels of IkappaB-alpha, a natural inhibitor of NF-kappaB. Thus, NE apparently inhibits HIV-1 infection, at least in part through NF-kappaB inactivation.

Bupropion for fatigue and as a tumor necrosis factor-α lowering agent in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic disease which can often be severe, progressive and necessitate liver transplantation. The cause of PBC is not known, and treatments other than liver transplantation are often not effective. Among the more common and troublesome symptoms of PBC is fatigue. The etiology of fatigue in PBC is not well-understood, and there is no known treatment for it. Here, we suggest that for a number of reasons that the safe and commonly used oral antidepressant bupropion might be effective for fatigue in PBC: (1) increased monoaminergic and dopaminergic tone to combat fatigue, (2) treatment of concomitant depression, (3) in general for PBC as a tumor necrosis factor-alpha (TNF) lowering agent, if TNF is eventually found to play a role in PBC pathogenesis.

Dobutamine Inhibits Phorbol-Myristate-Acetate-Induced Activation of Nuclear Factor-??B in Human T Lymphocytes In Vitro

Adrenergic drugs are often used for hemodynamic support of cardiac output and vasomotor tone in critically ill patients. Recent evidence shows that the administration of these vasoactive drugs may affect cytokine release and could influence the inflammatory response. However, the mechanism of this immunomodulatory effect remains unknown. The nuclear transcription factor-kappaB (NF-kappaB) regulates the expression of many cytokines and plays a central role in the immune response. Therefore, we examined the effects of various adrenergic drugs (dobutamine, xamoterol, clenbuterol, epinephrine, norepinephrine, and phenylephrine) on the activation of NF-kappaB, on the NF-kappaB-driven reporter gene activity, and on the expression of the NF-kappaB target gene interleukin (IL)-8. In addition, we quantified the amount of the NF-kappaB inhibitors IkappaBalpha and IL-10. Here we report that dobutamine inhibited the activation of NF-kappaB in primary human CD3(+) T lymphocytes. Suppression of NF-kappaB involved the stabilization of its inhibitor, IkappaBalpha. The effect appears to be beta(2)-receptor specific, because beta(1)-adrenergic and alpha-adrenergic substances (i.e., xamoterol, epinephrine, norepinephrine, and phenylephrine) did not affect NF-kappaB activation and because dobutamine-mediated inhibition of NF-kappaB could be prevented by a specific beta(2)-antagonist. Our results demonstrate that dobutamine is a potent and specific inhibitor of NF-kappaB, and they thus provide a possible molecular mechanism for the immunomodulation associated with beta-adrenergic therapy.

Bupropion for Blau syndrome

Blau syndrome (BS) is an autosomal dominantly inherited disease characterized by granulomas and arthritis. The gene mutated in BS was recently found to be CARD15. Mutations in this gene also occur in about 20% of patients with Crohn's disease (CD), though with different mutations than in the Crohn's patients. We are not aware of any cure or specific treatment for BS. We have found that bupropion is effective for CD, and we now suggest that bupropion be considered for treatment of BS.

Effects of a beta3-adrenergic agonist on the immune response in diet-induced (cafeteria) obese animals

Molecules with affinity for beta3-adrenoceptors are not only effective anti-obesity agents in rodent models, but may play a role in the regulation of the immune response. The aim of the current investigation was to analyse the effects of trecadrine on the immune response in diet-induced (cafeteria) obese rats. Male Wistar rats were divided into 2 groups, the control group (C, n=9) was fed with the standard pelleted chow laboratory diet, while the other group was fed with a high-fat (cafeteria) diet. Cafeteria-fed rats were divided into two new subgroups (n=9 each), which received either i.p. saline (obese, O) or trecadrine (1mg/kg/day) (obese+trecadrine, O+T) daily for 5 weeks. Lymphocyte subpopulations and the proliferative response were determined by validated procedures. The administration of trecadrine was able to prevent the onset of obesity in cafeteria-fed rats. Trecadrine-treatment to obese animals appeared to improve the number of lymphocyte subpopulations (CD4+ and CD8+) as compared to those animals only receiving the high-fat diet, being the values of the trecadrine-treated animals on the high-fat diet similar to the control rats. However, the lymphoproliferative response when stimulated with several mitogens was markedly reduced by the cafeteria intake and was further decreased by the beta3-adrenergic administration. The spleen mRNA expression level of UCP2, PPARgamma and Ob-Rb were not affected by the trecadrine treatment. Summing up, at the immune system level, trecadrine administration increased the proportion of CD4+ spleen lymphocytes, although it was not able to restore the lymphocyte proliferative response which was depressed.

Combination of bupropion, paroxetine and quetiapine as adjuvant treatment for multiple myeloma

Multiple myeloma is a severe plasma dyschrasia with no known treatment or cure, even bone marrow transplantation. Cytokines such as tumor necrosis factor-alpha (TNF) and interleukin-6 (Il-6) are thought to be important trophic factors for the malignant plasma cells. In turn, histamine and nitric oxide are positive regulatory factors for Il-6. Here we note that the safe, approved and commonly used psychiatric medicines bupropion (Wellbutrin), paroxetine (Paxil) and quetiapine (Seroquel) are respectively potent TNF, nitric oxide and histamine antagonists and thus might find some use in treatment of multiple myeloma.

Contribution of the adrenal glands and splenic nerve to LPS-induced splenic cytokine production in the rat

Both the hypothalamic pituitary adrenal axis (HPAA) and the sympathetic nervous system (SNS) can inhibit immune function and are regarded as the primary efferent pathways for neural-immune interactions. To determine if this relationship is maintained in vivo in response to an inflammatory stimulus, rats were injected intravenously (iv) with various doses of lipopolysaccharide (LPS) and splenic cytokine mRNA and protein levels were measured at several dose and time intervals post-injection. The spleen was chosen as the target organ because both the neural and hormonal inputs to the spleen can be selectively removed by splenic nerve cut (SNC) and adrenalectomy (ADX), respectively. Data from our dose response studies established that maximum levels of splenic cytokines were induced in response to relatively low doses of LPS. Minimal changes in LPS-induced splenic cytokine levels were observed in response to ADX, SNC, or a combination of the two procedures across several doses of LPS. These results suggest that there are aspects of immune regulation that are functionally removed from these central modulatory systems and that the counter-regulatory responses induced by LPS have minimal impact on the concurrent induction of cytokines by this inflammatory stimulus. The conceptual model of neural-immune regulation as an inhibitory feedback system, at least with regards to the early activational effects induced by an inflammatory stimulus, was not supported by these studies.

Dobutamine modulates lipopolysaccharide-induced macrophage inflammatory protein-1alpha and interleukin-8 production in human monocytes

Chemokines mediate the migration of leukocytes to sites of inflammation. The CC chemokine macrophage inflammatory protein (MIP)-1alpha and the CXC chemokine interleukin (IL)-8 are reported to play an important role in early inflammatory stages, wound healing, sepsis, and some cardiovascular diseases, including acute coronary syndromes and congestive heart failure. We conducted this study to investigate the effect of dobutamine on lipopolysaccharide (LPS)-induced MIP-1alpha and IL-8 production by human monocytic THP-1 cells. Monocytes were incubated in vitro with LPS for 4 or 16 h at 37 degrees C in the presence or absence of dobutamine. The effect of dobutamine on MIP-1alpha and IL-8 synthesis was examined by using an enzyme-linked immunosorbent assay, and MIP-1alpha and IL-8 messenger RNA (mRNA) were examined by using reverse transcriptase-polymerase chain reaction. Dobutamine significantly inhibited LPS-induced MIP-1alpha and IL-8 production by THP-1 cells in a dose-dependent manner. Salbutamol had a similar suppressive effect on LPS-stimulated MIP-1alpha and IL-8 production. MIP-1alpha mRNA was also suppressed by 10 micro M dobutamine, whereas, at the same concentration, dobutamine had no significant effect on the IL-8 mRNA level. Moreover, we found that dobutamine suppressed the MIP-1alpha-induced chemotaxis in THP-1 differentiated macrophages. These findings suggest that dobutamine may inhibit macrophage chemotaxis, as well as MIP-1alpha and IL-8 production by monocytes. The site of chemokine regulation is at the transcriptional level for MIP-1alpha and might be at the posttranscriptional level for IL-8.

IMPLICATIONS

Macrophage inflammatory protein (MIP)-1alpha and interleukin (IL)-8 are reported to play an important role in early inflammatory stages, wound healing, sepsis, and some cardiovascular diseases. Our study suggests that dobutamine may inhibit macrophage chemotaxis, as well as lipopolysaccharide-induced MIP-1alpha and IL-8 production by human monocytes.

Monoamine oxidase inhibitors for IgA nephropathy

IgA nephropathy (IgAN), characterized by renal mesangial deposits of antibodies (of the IgA subtype), is the most common glomerulonephritis worldwide. The cause of IgAN is not known. IgAN can often lead to end stage renal disease (ESRD), and there is no known treatment proven to prevent ESRD in IgAN. Long term use of steroids or other immunosuppressant drugs carry severe toxicities and other risks. IgAN patients have high serum levels of tumor necrosis factor-alpha (TNF). Increased monoamine levels, via increased cellular cyclic AMP, can decrease TNF elaboration. Monoamine oxidase inhibitors (MAO-Is) have been found effective in case studies for a number of diseases, e.g. rheumatoid arthritis and Crohn's disease, characterized by high TNF levels. Here I suggest that MAO-Is might be of utility in IgAN by decreasing TNF levels.

beta-adrenergic agonists exert their "anti-inflammatory" effects in monocytic cells through the IkappaB/NF-kappaB pathway

In addition to their well-studied bronchodilatory and cardiotonic effects, beta-adrenergic agonists carry anti-inflammatory properties by inhibiting cytokine production by human mononuclear cells. In a model of human promonocytic THP-1 cells stimulated with lipopolysaccharide (LPS), we showed that beta-agonists inhibited tumor necrosis factor-alpha and interleukin-8 production predominantly via the beta(2)-adrenergic receptor through the generation of cAMP and activation of protein kinase A. This effect was reproduced by other cAMP-elevating agents such as prostaglandins and cAMP analogs. Activation and nuclear translocation of the transcription factor nuclear factor-kappaB induced by LPS were inhibited with treatment with beta-agonists, an effect that was prominent at late time points (>1 h). Although the initial IkappaB-alpha degradation induced by LPS was minimally affected by beta-agonists, the latter induced a marked rebound of the cytosolic IkappaB-alpha levels at later time points (>1 h), accompanied by an increased IkappaB-alpha cytoplasmic half-life. This potentially accounts for the observed nuclear factor-kappaB sequestration in the cytoplasmic compartment. We postulate that the anti-inflammatory effects of beta-agonists reside in their capacity to increase cytoplasmic concentrations of IkappaB-alpha, possibly by decreasing its degradation.

Denopamine, a beta1-adrenergic agonist, prolongs survival in a murine model of congestive heart failure induced by viral myocarditis: suppression of tumor necrosis factor-alpha production in the heart

OBJECTIVES

This study was designed to examine the effects of denopamine, a selective beta1-adrenergic agonist, in a murine model of congestive heart failure (CHF) due to viral myocarditis.

BACKGROUND

Positive inotropic agents are used to treat severe heart failure due to myocarditis. However, sympathomimetic agents have not been found beneficial in animal models of myocarditis.

METHODS

In vitro: The effects of denopamine on lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-alpha) production was studied in murine spleen cells. In vivo: Four-week-old DBA/2 mice were inoculated with the encephalomyocarditis virus (day 0). Denopamine (14 micromol/kg), denopamine (14 micromol/kg) with a selective beta1-blocker metoprolol (42 micromol/kg), or denopamine (14 micromol/kg) with metoprolol (84 micromol/kg) was given daily, and control mice received the vehicle only. Survival and myocardial histology on day 14 and TNF-alpha levels in the heart on day 6 were examined.

RESULTS

In the in vitro study, TNF-alpha levels in treated cells were significantly lower than in controls (p < 0.05). In the in vivo study treatment with denopamine significantly improved the survival of the animals (14 of 25 (56%) treated, vs 5 of 25 (20%) control mice), attenuated myocardial lesions, and suppressed TNF-alpha production (66.5+/-7.5 pg/mg of heart in treated mice vs 113.5+/-15.1 pg/mg of heart in control mice, mean+/-SE). There was a strong linear relationship between mortality and TNF-alpha levels (r=0.98, n=4, p < 0.05). These in vitro and in vivo effects of denopamine were significantly inhibited by metoprolol.

CONCLUSIONS

These results suggest that denopamine may exert its beneficial effects, in part, by suppressing the production of TNF-alpha via beta1-adrenoceptors.

Tumor necrosis factor alpha gene expression in human monocytic THP-1 cells exposed to beryllium

Chronic beryllium disease, which results from occupational exposure to particulate beryllium, is characterized by the development of lung granulomas and progressive pulmonary fibrosis. Increased production of proinflammatory cytokines (e.g., tumor necrosis factor alpha and interleukin-1 beta) by pulmonary alveolar macrophages occurs in many chronic fibrotic lung diseases and is thought to contribute to the disease process. The purpose of the present study was to investigate cytokine production by human monocytic cells exposed to beryllium in vitro. The results indicated that such cells respond to beryllium ions in the presence of fluoride by accumulation of messenger ribonucleic acid for both tumor necrosis factor alpha and interleukin-1 beta. These findings suggest that inhaled beryllium may directly stimulate the production of these cytokines by alveolar macrophages in vitro.

Selective coupling of beta 2-adrenergic receptor to hematopoietic-specific G proteins

The coupling of the beta 2-adrenergic receptor (AR) to the alpha subunits of the Gq class of G proteins was investigated in a cotransfection system. COS-7 cells cotransfected with the beta 2-AR cDNA and the G alpha 15 or G alpha 16 cDNA showed marked norepinephrine-induced increases in accumulation of inositol phosphates in a concentration-dependent manner. However, cells cotransfected with the cDNA encoding G alpha q, G alpha 11, or G alpha 14 instead of G alpha 16 gave no ligand-dependent activation of phospholipase C (PLC). The facts that the beta-AR agonist isoprenaline can also induce activation of PLC in cells coexpressing beta 2-AR and G alpha 16 and that the beta 2-AR-specific antagonist propranolol can block norepinephrine-induced activation of PLC in these cotransfected cells further indicate that it is the beta 2-AR that mediates the activation of phospholipase C in these cotransfected cells. To test the possibility of involvement of G beta gamma, a G beta gamma antagonist, G gamma 3 mutant with substitution of a Ser residue for the C-terminal Cys residue, was used because this protein, when expressed in COS-7 cells, can inhibit only G beta gamma-mediated but not G alpha-mediated activation of PLC. The result that the G gamma 3 mutant could not inhibit beta 2-adrenergic receptor-mediated activation of PLC in cells cotransfected with the G alpha 16 cDNA suggests that G beta gamma is unlikely to be a major mediator of beta 2-adrenergic receptor-induced activation of PLC. Thus, we conclude that the beta 2-adrenergic receptor can specifically couple to G alpha 15 and G alpha 16, but not to G alpha q, G alpha 11, or G alpha 14 to activate PLC.