Role of cyclic AMP in the modulation of IgE production by the beta 2-adrenoceptor agonist, fenoterol

Activation of hepatic adenosine A1 receptor ameliorates MASH via inhibiting SREBPs maturation

Metabolic (dysfunction)-associated steatohepatitis (MASH) is the advanced stage of metabolic (dysfunction)-associated fatty liver disease (MAFLD) lacking approved clinical drugs. Adenosine A1 receptor (A1R), belonging to the G-protein-coupled receptors (GPCRs) superfamily, is mainly distributed in the central nervous system and major peripheral organs with wide-ranging physiological functions; however, the exact role of hepatic A1R in MAFLD remains unclear. Here, we report that liver-specific depletion of A1R aggravates while overexpression attenuates diet-induced metabolic-associated fatty liver (MAFL)/MASH in mice. Mechanistically, activation of hepatic A1R promotes the competitive binding of sterol-regulatory element binding protein (SREBP) cleavage-activating protein (SCAP) to sequestosome 1 (SQSTM1), rather than protein kinase A (PKA) leading to SCAP degradation in lysosomes. Reduced SCAP hinders SREBP1c/2 maturation and thus suppresses de novo lipogenesis and inflammation. Higher hepatic A1R expression is observed in patients with MAFL/MASH and high-fat diet (HFD)-fed mice, which is supposed to be a physiologically adaptive response because A1R agonists attenuate MAFL/MASH in an A1R-dependent manner. These results highlight that hepatic A1R is a potential target for MAFL/MASH therapy.

The β2-adrenoreceptor gene promoter polymorphisms may modulate β2-agonist- and glucocorticoid-induced IgE synthesis

BACKGROUND

β2-adrenoreceptor (β2-AR) agonists and glucocorticoids (GCS) were shown to induce IgE synthesis in human PBMCs. Serum total IgE levels are associated with single nucleotide polymorphisms (SNPs) of the β2-AR gene. We aimed to assess the association of the effect of fenoterol (β2-AR agonist) on IL-4-driven and budesonide-induced IgE synthesis with genetic variants of β2-AR.

METHODS

The study included 25 individuals: 13 with allergic asthma and/or allergic rhinitis and 12 healthy volunteers. PBMCs were cultured with IL-4, fenoterol and/or budesonide, and IgE concentrations in supernatants were assessed. Five SNPs in positions: -47, -20, 46, 79 and 252 of β2-AR were determined by direct DNA sequencing.

RESULTS

In -47 T/T and -20 T/T patients, incubation with fenoterol resulted in decreased IgE production, whereas in -47 C/T and -47 C/C as well as in -20 C/T and -20 C/C individuals, it was enhanced. In contrast to fenoterol, budesonide-induced IgE synthesis was significantly increased in -47 T/T and -20 T/T patients as compared to -47 C/T, -47 C/C, -20 C/T and -47 C/C individuals. Polymorphisms in positions 46, 79 and 252 were not associated with fenoterol- or budesonide-modulated IgE synthesis. No differences in the distribution of IgE synthesis was seen between atopic and non-atopic individuals carrying the same alleles.

CONCLUSIONS

The differential effect of β2-agonists and GCS on IgE synthesis may be associated with genetic variants of promoter region of the β2-AR gene.

Beta2-adrenergic agonist use and the risk of multiple sclerosis: a total population-based case-control study

OBJECTIVE

The aim of this study was to investigate whether the use of fenoterol, a beta2-adrenergic agonist, was associated with multiple sclerosis (MS) risk by conducting a total population-based case-control study in Taiwan.

METHODS

A total of 578 patients with newly diagnosed MS who had a severely disabling disease (SDD) certificate between January 1, 2002 and December 1, 2008 comprised the case group. These cases were compared with 2890 gender-, age-, residence-, and insurance premium-matched controls. Fenoterol use was analyzed using a conditional logistic regression model that controlled for asthma, chronic obstructive pulmonary disease (COPD), salbutamol and steroid use.

RESULTS

Compared with the group of people who did not use fenoterol, the adjusted odds ratios were 0.67 (95% confidence interval (CI) = 0.48-0.93, p = 0.016) for the group prescribed fenoterol below 2.25 cumulative defined daily dose (cDDD) and 0.49 (95% CI = 0.33-0.71, p < 0.001) for the group with a cumulative fenoterol use of more than 2.25 cDDD. The dose-response relationship was similar within the non-asthma patients. The associations were similar between males and females, but differences between age groups were observed.

CONCLUSIONS

The results of this study suggest that fenoterol use may reduce the risk of MS.

Phosphodiesterase 4 inhibitors and db-cAMP inhibit TNF-alpha release from human mononuclear cells. Effects of cAMP and cGMP-dependent protein kinase inhibitors

We investigated the effects of specific inhibitors of cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) on the inhibitory activity of phosphodiesterase (PDE) type 4 inhibitors and of the cell permeable analogue of cAMP, db-cAMP on LPS-induced TNF-alpha release from human mononuclear cells. Incubation from 30 min of mononuclear cells with dbcAMP (10(-5) to 10(-3) M), rolipram (10(-9) M to 10(-5) M) or Ro 20-1724 (10(-9) M to 10(-5) M) significantly inhibited LPS-induced TNF-alpha release. When mononuclear cells were preincubated for 30 min with the selective PKA inhibitor, H89 (10(-4) M), but not with the selective PKG inhibitor, Rp-8-pCPT-cGMPs (10(-4) M), a significant reduction of the inhibitory effect of db-cAMP was noted. Thirty min incubation of mononuclear cells with Rp-8-pCPT-cGMPs induced a significant reduction of the inhibitory activities of both rolipram and Ro 20-1724 (10(-9) to 10(-5) M) on LPS-induced TNF-alpha release, whereas H89 elicited a moderate, but significant inhibition. The present data indicate that db-cAMP inhibits TNF-alpha release from human mononuclear cells through a PKA-dependent mechanism. In contrast, PDE 4 inhibitors elicit their in vitro anti-inflammatory activities via a PKG-dependent rather than PKA-dependent activation.

A study of the bio-accessibility of welding fumes

The respiratory bio-accessibility of a substance is the fraction that is soluble in the respiratory environment and is available for absorption. In the case of respiratory exposure the amount of absorbed substance plays a main role in the biological effects. Extensive bio-accessibility studies have always been an essential requirement for a better understanding of the biological effects of different workplace aerosols, such as welding fumes. Fumes generated using three different welding techniques, manual metal arc (MMA) welding, metal inert gas (MIG) welding, and tungsten inert gas (TIG) welding were investigated in the present study. Each technique was used for stainless steel welding. Welding fumes were collected on PVC membrane filters in batches of 114 using a multiport air sampler. Three different fluids were applied for the solubility study: deionised water and two kinds of lung fluid simulants: lung epithelial lining fluid simulant (Gamble's solution) and artificial lung lining fluid simulant (Hatch's solution). In order to obtain sufficient data to study the tendencies in solubility change with time, seven different leaching periods were used (0.5, 1, 2, 4, 8, 16, 24 h), each of them with three replicates. The effect of dissolution temperature was also studied. The total amounts of selected metals in the three different welding fumes were determined after microwave-assisted digestion with the mixture of aqua regia and hydrofluoric acid. The most obvious observation yielded by the results is that the solubility of individual metals varies greatly depending on the welding technique, the composition of the leaching fluid and leaching time. This study shows that the most reasonable choice as a media for the bio-assessment of solubility might be Hatch's solution by a dissolution time of 24 h.

Pulmonary responses to welding fumes: role of metal constituents

It is estimated that more than 1 million workers worldwide perform some type of welding as part of their work duties. Epidemiology studies have shown that a large number of welders experience some type of respiratory illness. Respiratory effects seen in full-time welders have included bronchitis, siderosis, asthma, and a possible increase in the incidence of lung cancer. Pulmonary infections are increased in terms of severity, duration, and frequency among welders. Inhalation exposure to welding fumes may vary due to differences in the materials used and methods employed. The chemical properties of welding fumes can be quite complex. Most welding materials are alloy mixtures of metals characterized by different steels that may contain iron, manganese, chromium, and nickel. Animal studies have indicated that the presence and combination of different metal constituents is an important determinant in the potential pneumotoxic responses associated with welding fumes. Animal models have demonstrated that stainless steel (SS) welding fumes, which contain significant levels of nickel and chromium, induce more lung injury and inflammation, and are retained in the lungs longer than mild steel (MS) welding fumes, which contain mostly iron. In addition, SS fumes generated from welding processes using fluxes to protect the resulting weld contain elevated levels of soluble metals, which may affect respiratory health. Recent animal studies have indicated that the lung injury and inflammation induced by SS welding fumes that contain water-soluble metals are dependent on both the soluble and insoluble fractions of the fume. This article reviews the role that metals play in the pulmonary effects associated with welding fume exposure in workers and laboratory animals.

Pulmonary effects of welding fumes: review of worker and experimental animal studies

BACKGROUND

Approximately one million workers worldwide perform welding as part of their work duties. Electric arc welding processes produce metal fumes and gases which may be harmful to exposed workers.

METHODS

This review summarizes human and animals studies which have examined the effect of welding fume exposure on respiratory health. An extensive search of the scientific and occupational health literature was performed, acquiring published articles which examined the effects of welding on all aspects of worker and laboratory animal health. The databases accessed included PubMed, Ovid, NIOSHTIC, and TOXNET.

RESULTS

Pulmonary effects observed in full-time welders have included metal fume fever, airway irritation, lung function changes, susceptibility to pulmonary infection, and a possible increase in the incidence of lung cancer. Although limited in most cases, animal studies have tended to support the findings from epidemiologic studies.

CONCLUSIONS

Despite the numerous studies on welding fumes, incomplete information still exists regarding the causality and possible underlying mechanisms associated with welding fume inhalation and pulmonary disease. The use of animal models and the ability to control the welding fume exposure in toxicology studies could be utilized in an attempt to develop a better understanding of how welding fumes affect pulmonary health.

Stimulation of the B cell receptor, CD86 (B7-2), and the beta 2-adrenergic receptor intrinsically modulates the level of IgG1 and IgE produced per B cell

Our findings using B cells from either wild-type, CD86-deficient, or beta 2-adrenergic receptor (beta2AR)-deficient mice suggest three mechanisms by which the level of IgG1 and IgE production can be increased on a per cell basis. Trinitrophenyl-specific B cells enriched from unimmunized mouse spleens were pre-exposed to Ag and/or the beta 2AR ligand terbutaline for 24 h before being activated by either a beta 2AR-negative Th2 cell clone or CD40 ligand/Sf9 cells and IL-4 in the presence or absence of an anti-CD86 Ab. Data suggest that the first mechanism involves a B cell receptor (BCR)-dependent up-regulation of CD86 expression that, when CD86 is stimulated, increases the amount of IgG1 and IgE produced in comparison to unstimulated cells. The second mechanism involves a BCR- and beta 2AR-dependent up-regulation of CD86 to a level higher than that induced by stimulation of either receptor alone that, when CD86 is stimulated, further increases the amount of IgG1 and IgE produced. The third mechanism is BCR-independent and involves a beta 2AR-dependent increase in the ability of a B cell to respond to IL-4. Flow cytometric and limiting dilution analyses suggest that the increase in IgG1 and IgE occurs independently from the isotype switching event. These findings suggest that the BCR, the beta 2AR, and CD86 are involved in regulating IL-4-dependent IgG1 and IgE production.

Mast cell tryptase release and asthmatic responses to allergen increase with regular use of salbutamol

BACKGROUND

Increased asthmatic responses to allergen, both early and late, have been demonstrated after regular use of beta(2)-agonists in as few as 7 days. Desensitization of beta(2)-adrenergic receptors on airway mast cells may contribute to this effect by allowing greater release of mast cell mediator on allergen-induced degranulation. Tryptase released from lung mast cells can be measured in serum 1 hour after allergen challenge and serves as a marker of mast cell degranulation.

OBJECTIVE

To examine the effect of regular treatment with salbutamol, a beta(2)-agonist, on mast cell mediator release after allergen challenge and its influence on the early asthmatic response (EAR) and the late allergic response, we measured the EAR, serum tryptase levels, the 7-hour FEV(1), and sputum tryptase levels and cell profiles.

METHODS

We conducted a placebo-controlled, double-blind, randomized cross-over comparison of treatments for 10 days with either a salbutamol metered-dose inhaler (100 microgram, 2 puffs 4 times daily) or a matched placebo inhaler with at least a 7-day washout between treatments. Atopic subjects (n = 14) with mild-to-moderate asthma performed same-dose allergen inhalation tests after both treatments 12 to 15 hours after the last dose of study inhaler. Baseline and 7-hour FEV(1) and the EAR to allergen were measured by using spirometry; venous blood was drawn at 1 hour for analysis of serum tryptase; and sputum was induced and collected at 1 and 7 hours.

RESULTS

Salbutamol treatment resulted in a significantly greater EAR (20% +/- 1.6% [SEM] vs 15% +/- 2.1%; P =.047); increased 1-hour serum tryptase levels (9.09 +/- 1.57 vs 7.52 +/- 1.12 microgram/L; P =. 011); increased proportions of eosinophils in the 7-hour sputum sample (39.1% +/- 5.1% vs 28.4% +/- 4.4%; P <.05); increased proportion of metachromatic cells in the 7-hour sputum sample (4.4% +/- 1.1% vs 2.2% +/- 0.6%; P =.032); and lower 7-hour FEV(1) (2.77 +/- 0.18 vs 2.97 +/- 0.20 L; P =.014). Baseline FEV(1) was not significantly different after salbutamol treatment compared with values after placebo treatment (2.90 +/- 0.20 vs 3.00 +/- 0.19 L; P =.11).

CONCLUSION

Regular 10-day treatment with salbutamol increases the allergen-induced release of mediator from airway mast cells, and this is reflected in an increased EAR to allergen. Late-phase responses to allergen were also enhanced, as demonstrated by decreased 7-hour FEV(1) and increased eosinophilia and percentage of metachromatic cells in the 7-hour sputum sample. Increased allergen-induced mast cell degranulation could, in part, explain the increased asthmatic responses to allergen after beta(2)-agonist treatment and could contribute to the deterioration of asthma control that is associated with regular use of beta(2)-agonist by potentiating allergic inflammation.

Beta-adrenergic modulation of human type-1/type-2 cytokine balance

BACKGROUND

Neuroendocrine mediators are increasingly recognized as immunomodulatory agents. Lymphocytes and monocytes express receptors for a variety of neuroendocrine mediators, including catecholamines. It has been reported that beta-adrenergic agonists decrease IFN-gamma production, with varying effects on IL-4 and IL-5 production.

OBJECTIVE

Our purpose was to determine the effects of catecholamines (including beta-adrenergic agonists) on the type-1/type-2 cytokine balance in tetanus-stimulated human PBMCs.

METHOD

Human PBMCs were stimulated with tetanus in the presence of epinephrine (EPI), norepinephrine, or terbutaline. IFN-gamma, IL-4, IL-5, and IL-10 levels in the supernatants were determined by ELISA.

RESULTS

PBMCs stimulated in the presence of EPI produced decreased levels of IFN-gamma and increased levels of IL-10, IL-4, and IL-5. A small decrease in IFN-gamma production and an increase in IL-10, IL-4, and IL-5 production were also observed with norepinephrine. Terbutaline induced similar alterations in the type-1/type-2 cytokine balance compared with EPI, indicating that the beta(2)adrenergic receptor is involved in these cytokine alterations. Furthermore, these cytokine alterations were blocked by propranolol. Finally, IL-12p70 prevented the cytokine alterations, suggesting that the mechanism of beta-adrenergic-induced cytokine alterations involves a decrease in IL-12.

CONCLUSION

beta-Adrenergic agonists induce a shift in the human type-1/type-2 cytokine balance toward a type-2 response. These data provide a potential mechanism to explain the paradoxical increase in asthma morbidity and mortality associated with the chronic use of scheduled dosing of short-acting beta-adrenergic agonists.

Association studies on beta2-adrenoceptor polymorphisms and enhanced IgE responsiveness in an atopic population

The beta2 adrenergic receptor 2 represents a cell surface receptor responsible for the binding of endogenous catecholamines and their exogenously administered agonists and antagonists, mediating their effects to the interior of the cell. On the basis of these functions, the observed association of two of its polymorphisms, Gly16 and Gln27, with nocturnal- and steroid-dependent asthma has been discussed. It has recently been suggested that Gln27 contributes to IgE variability in families with asthma. The aim of this study was to investigate possible influences of the polymorphisms Arg16Gly and Glu27Gln on IgE levels in families recruited through an atopic index case without regard to the presence of clinical symptoms. We employed linkage analysis in affected sibpairs characterized by elevated total IgE concentrations or sensitization to common inhalant allergens. Furthermore, we tested 258 children for association of any of the polymorphisms with enhanced IgE responsiveness. We could find neither linkage at the locus 5q31 nor significant association of the polymorphisms with elevated total IgE concentrations or specific sensitization. We conclude from our data that the polymorphisms Gln27Glu and Arg16Gly of the beta2-adrenergic receptor do not play a significant role in the pathogenesis of enhanced IgE responsiveness in an atopic population in general.

Oral food challenge increases in vitro IL-4 production by peripheral blood mononuclear cells in allergic patients

The aim of this study was to investigate interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) production by peripheral blood mononuclear cells (PBMC) in response to oral challenge in patients with food allergy. Thirty-one patients were compared with 10 healthy subjects. Cell cultures were prepared before and 150 min after single-blind, placebo-controlled, oral food challenge. In vitro production of cytokines was observed after stimulation with phytohemagglutinin (PHA) plus phorbol myristate acetate (PMA). Patients were characterized according to their reactions. In vitro IL-4 production was significantly greater in patients with food sensitization than in controls. The 18 patients with positive food challenge presented significantly greater IL-4 production after food challenge than before. IFN-gamma production was not modified. In the 10 control subjects and in 13 patients with negative food challenge, IL-4 and IFN-gamma production was comparable before and after food challenge. The increased IL-4 production in patients with positive oral food challenge could account for the development of polysensitization. This situation might be relevant to other allergic diseases and to treatments.

Phosphodiesterase profile of human B lymphocytes from normal and atopic donors and the effects of PDE inhibition on B cell proliferation

1. CD19+ B lymphocytes were purified from the peripheral blood of normal and atopic subjects to analyse and compare the phosphodiesterase (PDE) activity profile, PDE mRNA expression and the importance of PDE activity for the regulation of B cell function. 2. The majority of cyclic AMP hydrolyzing activity of human B cells was cytosolic PDE4, followed by cytosolic PDE7-like activity; marginal PDE3 activity was found only in the particulate B cell fraction. PDE1, PDE2 and PDE5 activities were not detected. 3. By cDNA-PCR analysis mRNA of the PDE4 subtypes A, B (splice variant PDE4B2) and D were detected. In addition, a weak signal for PDE3A was found. 4. No differences in PDE activities or mRNA expression of PDE subtypes were found in B cells from either normal or atopic subjects. 5. Stimulation of B lymphocytes with the polyclonal stimulus lipopolysaccharide (LPS) induced a proliferative response in a time- and concentration-dependent manner, which was increased in the presence of interleukin-4 (IL-4). PDE4 inhibitors (rolipram, piclamilast) led to an increase in the cellular cyclic AMP concentration and to an augmentation of proliferation, whereas a PDE3 inhibitor (motapizone) was ineffective, which is in accordance with the PDE profile found. The proliferation enhancing effect of the PDE4 inhibitors was partly mimicked by the cyclic AMP analogues dibutyryl (db) cyclic AMP and 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-3',5'-cyclic monophosphorothioate, Sp-isomer (dcl-cBIMPS), respectively. However, at concentrations exceeding 100 microM db-cyclic AMP suppressed B lymphocyte proliferation, probably as a result of cytotoxicity. Prostaglandin E2 (PGE2, 1 microM) and forskolin (10 microM) did not affect B cell proliferation, even when given in combination with rolipram. 6. Inhibition of protein kinase A (PKA) by differentially acting selective inhibitors (KT 5720, Rp-8-Br-cyclic AMPS) decreased the proliferative response of control cells and reversed the proliferation enhancing effects of rolipram. 7. Importantly, PDE4 activity in LPS/IL-4-activated B lymphocytes decreased by about 50% compared to unstimulated control values. 8. We conclude that an increase in cyclic AMP, mediated by down-regulation of PDE4 activity, is involved in the stimulation of B cell proliferation in response to LPS/IL-4. B cell proliferation in response to a mitogenic stimulus can be further enhanced by pharmacological elevation of cyclic AMP.

Differential Coupling of Membrane Ig and CD40 to the Extracellularly Regulated Kinase Signaling Pathway

Coupling of membrane Ig (mIg) and CD40 to the extracellularly regulated kinase (ERK) signal transduction pathway was examined in the WEHI-231 B lymphoma and normal mouse B cells. Cross-linking mIg induces ERK activation in both WEHI-231 and normal B cells. In contrast, CD40 cross-linking failed to induce ERK activation in WEHI-231, but signals through CD40 were more effective than mIg as a stimulus for ERK activation in normal B cells. However, several lines of evidence suggest that CD40 and the B cell Ag regulate ERK through distinct pathways that converge at the level of MEK-1, mitogen-activated protein kinase kinase. Abs to mIg or CD40 induced MEK-1 activation with different kinetics. Cross-linking of mIg, but not CD40, induced tyrosine phosphorylation of the SHC adapter molecule that couples receptors to Ras-dependent signaling pathways. Finally, agents that elevate cAMP, causing protein kinase A-mediated inhibition of Raf-1, inhibited activation of ERK in response to mIg cross-linking, but had no affect on ERK activation in response to anti-CD40 or Jun N-terminal kinase activation by signals through either receptor. Thus, CD40 uses an unidentified protein kinase A-insensitive MEK kinase, rather than Raf-1, to regulate ERK activity.

Interactions between cAMP- and cGMP-dependent protein kinase inhibitors and phosphodiesterase IV inhibitors on arachidonate release from human monocytes

The effects of specific inhibitors of cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) on the inhibitory activity of phosphodiesterase (PDE) type IV inhibitors and of the cell permeable analogue of cAMP, db-cAMP, were investigated on fMLP-induced arachidonate release from human monocytes. When monocytes were preincubated with the combined PKA/PKG inhibitor H8 (10(-6) to 10(-4) M) or the selective PKG inhibitor Rp-8-cpt-cGMPs (10(-6) to 10(-4) M) a concentration-dependent reduction of the inhibitory effect of db-cAMP (10(-3) M), rolipram (10(-5) M) and Ro 20-1724 (10(-5) M) was noted. When monocytes were preincubated with the selective PKA inhibitor H89 (10(-6) to 10(-4) M), only a small inhibition of the effect of db-cAMP and no inhibition of the effects of rolipram and Ro 20-1724 were observed. The present data indicate that db-cAMP and PDE IV inhibitors elicit an in vitro anti-inflammatory activity by a PKA-independent mechanism, which do not appear to be mainly mediated via the PKG activation.