Stimulation Of Adenylate Cyclase Research Articles

Striatal ERK is Activated in Response to L‐DOPA Administration in a Knock‐in Mouse Model of DOPA‐Responsive Dystonia

Abnormal dopamine (DA) neurotransmission is associated with many dystonic disorders; however, the precise nature of the defects in DA transmission that result in dystonia are not known. To address this question, we used a knock‐in mouse model of L‐DOPA‐responsive dystonia (DRD). DRD mice display the core features of the human disorder, including reduced striatal DA levels and abnormal movement that improves in response to L‐DOPA, the precursor to DA. In the striatum, DA promotes movement by activating D1 receptors (D1Rs) expressed on direct pathway spiny projection neurons (SPNs) and inhibits movement by activating D2 receptors (D2Rs) expressed on indirect pathway SPNs. D1Rs stimulate adenylate cyclase (AC) activity and D2Rs inhibit AC; however, in DRD mice, D1Rs display an exaggerated AC response to D1 agonist stimulation and D2Rs exhibit a change in valence whereby D2R agonists increase AC. Our objective was to determine signaling alterations in both SPN subtypes downstream of AC, specifically phosphorylated ERK (p‐ERK), that contribute to the alleviation of dystonia by L‐DOPA to identify downstream targets that may serve as novel therapeutic targets. DRD and control mice were subcutaneously injected with L‐DOPA (10 mg/kg), the D1R agonist SKF 81297 (0.2 mg/kg), the D2R agonist quinpirole (0.1 mg/kg), or saline. Mice were perfused 45 min after drug treatment and striatal sections were immunostained for p‐ERK. DRD mice showed a significant and robust increase in p‐ERK levels in the dorsal striatum in response to L‐DOPA treatment compared to controls and saline‐treated mice. In contrast, SKF 81297 or quinpirole treatment evoked only modest changes in p‐ERK. The L‐DOPA specific increase in p‐ERK suggests that D1R and D2R co‐activation may regulate p‐ERK and/or that p‐ERK may serve as a coincidence detector for convergent DA and glutamatergic signaling that occurs when endogenous DA signaling is restored in the striatum. Future studies are aimed to elucidate cell‐type specific mechanisms underlying increased p‐ERK in response to L‐DOPA in DRD mice to refine downstream signaling mechanisms that are instrumental to the therapeutic effects.Support or Funding InformationThis work was supported by the United States National Institute of Health grant R01 NS088528 and T32 NS007480‐17.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Induction of Pro-Apoptotic Endoplasmic Reticulum Stress in Multiple Myeloma Cells by NEO214, Perillyl Alcohol Conjugated to Rolipram.

Despite the introduction of new therapies for multiple myeloma (MM), many patients are still dying from this disease and novel treatments are urgently needed. We have designed a novel hybrid molecule, called NEO214, that was generated by covalent conjugation of the natural monoterpene perillyl alcohol (POH), an inducer of endoplasmic reticulum (ER) stress, to rolipram (Rp), an inhibitor of phosphodiesterase-4 (PDE4). Its potential anticancer effects were investigated in a panel of MM cell lines. We found that NEO214 effectively killed MM cells in vitro with a potency that was over an order of magnitude stronger than that of its individual components, either alone or in combination. The cytotoxic mechanism of NEO214 involved severe ER stress and prolonged induction of CCAAT/enhancer-binding protein homologous protein (CHOP), a key pro-apoptotic component of the ER stress response. These effects were prevented by salubrinal, a pharmacologic inhibitor of ER stress, and by CHOP gene knockout. Conversely, combination of NEO214 with bortezomib, a drug in clinical use for patients with MM, resulted in synergistic enhancement of MM cell death. Combination with the adenylate cyclase stimulant forskolin did not enhance NEO214 impact, indicating that cyclic adenosine 3′,5′-monophosphate (AMP) pathways might play a lesser role. Our study introduces the novel agent NEO214 as a potent inducer of ER stress with significant anti-MM activity in vitro. It should be further investigated as a potential MM therapy aimed at exploiting this tumor’s distinct sensitivity to ER stress.

Continuous Albuterol Treatments may Lead to Lactic Acidosis in Children with Status Asthmaticus

Asthma is a chronic inflammatory condition of the airways characterized by airflow obstruction, caused by bronchoconstriction, airway edema, acute inflammation and increased secretions, most commonly treated with albuterol. Albuterol functions by activating beta-2-adrenergic receptors on airway smooth muscles stimulating adenyl cyclase and increasing production of C-AMP causing relaxation of the smooth muscle and bronchodilation. It has been our observation that lactic acid levels tend to increase with the use of continuous albuterol treatments in pediatric patients.

Anoctamin 9/TMEM16J is a cation channel activated by cAMP/PKA signal

Anoctamins (ANOs) are multifunctional membrane proteins that consist of 10 homologs. ANO1 (TMEM16A) and ANO2 (TMEM16B) are anion channels activated by intracellular calcium that meditate numerous physiological functions. ANO6 is a scramblase that redistributes phospholipids across the cell membrane. The other homologs are not well characterized. We found ANO9/TMEM16J is a cation channel activated by a cAMP-dependent protein kinase A (PKA). Intracellular cAMP-activated robust currents in whole cells expressing ANO9, which were inhibited by a PKA blocker. A cholera toxin that persistently stimulated adenylate cyclase activated ANO9 as did the application of PKA. The cAMP-induced ANO9 currents were permeable to cations. The cAMP-dependent ANO9 currents were augmented by intracellular Ca2+. Ano9 transcripts were predominant in the intestines. Human intestinal SW480 cells expressed high levels of Ano9 transcripts and showed PKA inhibitor-reversible cAMP-dependent currents. We conclude that ANO9 is a cation channel activated by a cAMP/PKA pathway and could play a role in intestine function.

Mechanisms of electromechanical and electrochemical coupling in olfactory cilia of the frog (Rana temporaria)

The mechanisms of electromechanical and electrochemical coupling in olfactory cilia of the frog (Rana temporaria) have been investigated. High-resolution optical television microscopy of live tissue and pharmacological analysis have been used to reveal the regulation of the motility of olfactory cilia in the absence of odorants; the entry of Ca2+ ions mediated by three types of ion channels (mechanosensitive, cyclic nucleotide gated, and voltage-gated) was shown to determine the motility of cilia. Stimulation of the olfactory adenylate cyclase by movements of the cilia in the absence of odors has been demonstrated and the regulation of cilia motility by membrane potential has been revealed. Membrane potential can affect olfactory acuity and the ability to perceive weak olfactory stimuli in the absence of adequate stimulation.

Engineering a minimal G protein to facilitate crystallisation of G protein-coupled receptors in their active conformation.

G protein-coupled receptors (GPCRs) modulate cytoplasmic signalling in response to extracellular stimuli, and are important therapeutic targets in a wide range of diseases. Structure determination of GPCRs in all activation states is important to elucidate the precise mechanism of signal transduction and to facilitate optimal drug design. However, due to their inherent instability, crystallisation of GPCRs in complex with cytoplasmic signalling proteins, such as heterotrimeric G proteins and β-arrestins, has proved challenging. Here, we describe the design of a minimal G protein, mini-Gs, which is composed solely of the GTPase domain from the adenylate cyclase stimulating G protein Gs. Mini-Gs is a small, soluble protein, which efficiently couples GPCRs in the absence of Gβγ subunits. We engineered mini-Gs, using rational design mutagenesis, to form a stable complex with detergent-solubilised β1-adrenergic receptor (β1AR). Mini G proteins induce similar pharmacological and structural changes in GPCRs as heterotrimeric G proteins, but eliminate many of the problems associated with crystallisation of these complexes, specifically their large size, conformational dynamics and instability in detergent. They are therefore novel tools, which will facilitate the biochemical and structural characterisation of GPCRs in their active conformation.

β-Adrenergic response is counteracted by extremely-low-frequency pulsed electromagnetic fields in beating cardiomyocytes

Proper β-adrenergic signaling is indispensable for modulating heart frequency.Studies on extremely-low-frequency pulsed electromagnetic field (ELF-PEMF) effects in the heart beat function are contradictory and no definitive conclusions were obtained so far.To investigate the interplay between ELF-PEMF exposure and β-adrenergic signaling, cultures of primary murine neonatal cardiomyocytes and of sinoatrial node were exposed to ELF-PEMF and short and long-term effects were evaluated. The ELF-PEMF generated a variable magnetic induction field of 0–6mT at a frequency of 75Hz.Exposure to 3mT ELF-PEMF induced a decrease of contraction rate, Ca2+ transients, contraction force, and energy consumption both under basal conditions and after β-adrenergic stimulation in neonatal cardiomyocytes. ELF-PEMF exposure inhibited β-adrenergic response in sinoatrial node (SAN) region.ELF-PEMF specifically modulated β2 adrenergic receptor response and the exposure did not modify the increase of contraction rate after adenylate cyclase stimulation by forskolin.In HEK293T cells transfected with β1 or β2 adrenergic receptors, ELF-PEMF exposure induced a rapid and selective internalization of β2 adrenergic receptor. The β-adrenergic signaling, was reduced trough Gi protein by ELF-PEMF exposure since the phosphorylation level of phospholamban and the PI3K pathway were impaired after isoproterenol stimulation in neonatal cardiomyocytes.Long term effects of ELF-PEMF exposure were assessed in cultures of isolated cardiomyocytes. ELF-PEMF counteracts cell size increase, the generation of binucleated of cardiomyocytes and prevents the up-regulation of hypertrophic markers after β-adrenergic stimulation, indicating an inhibition of cell growth and maturation.These data show that short and long term exposure to ELF-PEMF induces a reduction of cardiac β-adrenergic response at molecular, functional and adaptative levels.

Evaluation of Cytotoxicity and Hypoxic Effect of Nitroimidazole Embedded Nanoparticles.

Adenylate cyclase is a key intracellular enzyme involved in energy imbalance leading to tumor hypoxia and cytotoxicity. In this study, adenylate cyclase activities in isolated hepatocytes and Kupffer cells were compared in the presence of several metabolic stimulators. In cultured hepatocyte cells, adenylate cyclase was stimulated by guanylyl imidotriphosphate (GITP), guanosine triphosphate (GTP), progesterone and nitroimidazole embedded nanoparticle (NNP) effectors, while prostaglandin E2 and F2α were used as effectors in cultured Kupffer cells. The results showed that NNPs decreased adenylate cyclase specific activity in a dose-dependent manner after preincubation of hepatocytes with NNPs. The NNPs stimulated adenylate cyclase activities in hepatocytes were evaluated based on measurement of cyclic adenosine monophosphate (cAMP). The stimulatory effects of NNPs on adenylate cyclase were independent of the presence of GTP and may have been due to a direct effect on the catalytic subunit of adenylate cyclase. In addition, basal cAMP generation in hepatocyte cells was efficiently suppressed by the NNPs. In conclusion, NNPs exerted direct effects on the catalytic subunit of the adenylate cyclase system, and adenylate cyclase was hormone sensitive in liver cells.

Cyclic AMP-elevating Agents Promote Cumulus Cell Survival and Hyaluronan Matrix Stability, Thereby Prolonging the Time of Mouse Oocyte Fertilizability

Cumulus cells sustain the development and fertilization of the mammalian oocyte. These cells are retained around the oocyte by a hyaluronan-rich extracellular matrix synthesized before ovulation, a process called cumulus cell-oocyte complex (COC) expansion. Hyaluronan release and dispersion of the cumulus cells progressively occur after ovulation, paralleling the decline of oocyte fertilization. We show here that, in mice, postovulatory changes of matrix are temporally correlated to cumulus cell death. Cumulus cell apoptosis and matrix disassembly also occurred in ovulated COCs cultured in vitro. COCs expanded in vitro with FSH or EGF underwent the same changes, whereas those expanded with 8-bromo-adenosine-3',5'-cyclic monophosphate (8-Br-cAMP) maintained integrity for a longer time. It is noteworthy that 8-Br-cAMP treatment was also effective on ovulated COCs cultured in vitro, prolonging the vitality of the cumulus cells and the stability of the matrix from a few hours to >2 days. Stimulation of endogenous adenylate cyclase with forskolin or inhibition of phosphodiesterase with rolipram produced similar effects. The treatment with selective cAMP analogues suggests that the effects of cAMP elevation are exerted through an EPAC-independent, PKA type II-dependent signaling pathway, probably acting at the post-transcriptional level. Finally, overnight culture of ovulated COCs with 8-Br-cAMP significantly counteracted the decrease of fertilization rate, doubling the number of fertilized oocytes compared with control conditions. In conclusion, these studies suggest that cAMP-elevating agents prevent cumulus cell senescence and allow them to continue to exert beneficial effects on oocyte and sperm, thereby extending in vitro the time frame of oocyte fertilizability.

Intracellular mechanisms involved in copper-gonadotropin-releasing hormone (Cu-GnRH) complex-induced cAMP/PKA signaling in female rat anterior pituitary cells in vitro.

The copper-gonadotropin-releasing hormone molecule (Cu-GnRH) is a GnRH analog, which preserves its amino acid sequence, but which contains a Cu(2+) ion stably bound to the nitrogen atoms including that of the imidazole ring of Histidine(2). A previous report indicated that Cu-GnRH was able to activate cAMP/PKA signaling in anterior pituitary cells in vitro, but raised the question of which intracellular mechanism(s) mediated the Cu-GnRH-induced cAMP synthesis in gonadotropes. To investigate this mechanism, in the present study, female rat anterior pituitary cells in vitro were pretreated with 0.1 μM antide, a GnRH antagonist; 0.1 μM cetrorelix, a GnRH receptor antagonist; 0.1 μM PACAP6-38, a PAC-1 receptor antagonist; 2 μM GF109203X, a protein kinase C inhibitor; 50 mM PMA, a protein kinase C activator; the protein kinase A inhibitors H89 (30 μM) and KT5720 (60 nM); factors affecting intracellular calcium activity: 2.5 mM EGTA; 2 μM thapsigargin; 5 μM A23187, a Ca(2+) ionophore; or 10 μg/ml cycloheximide, a protein synthesis inhibitor. After one of the above pretreatments, cells were incubated in the presence of 0.1 μM Cu-GnRH for 0.5, 1, and 3 h. Radioimmunoassay analysis of cAMP confirmed the functional link between Cu-GnRH stimulation and cAMP/PKA signal transduction in rat anterior pituitary cells, demonstrating increased intracellular cAMP, which was reduced in the presence of specific PKA inhibitors. The stimulatory effect of Cu-GnRH on cAMP production was partly dependent on GnRH receptor activation. In addition, an indirect and Ca(2+)-dependent mechanism might be involved in intracellular adenylate cyclase stimulation. Neither activation of protein kinase C nor new protein synthesis was involved in the Cu-GnRH-induced increase of cAMP in the rat anterior pituitary primary cultures. Presented data indicate that conformational changes of GnRH molecule resulting from cooper ion coordination affect specific pharmacological properties of Cu-GnRH molecule including specific pattern of intracellular activity induced by complex in anterior pituitary cells in vitro.

Regulation of the Melanocortin-Sensitive Adenylate Cyclase System by N-Acylated Peptide 71-82 of Type 4 Melanocortin Receptor.

The peptides structurally corresponding in to cytoplasmic loops of G protein-coupled receptors (GPCR) are able to control functional activity of homologous receptors and the corresponding signaling pathways. Modification of these peptides with hydrophobic radicals enhances their biological activity due to penetration of lipophilic derivatives through the membrane and anchoring near their targets, GPCR. We synthesized an N-palmitoylated peptide Palm-Val-[Lys-Asn-Lys-Asn-Leu-His-Ser-Pro-(Nle)-Tyr-Phe-Phe71-82]-amide-Palm-Val-(71-82) structurally corresponding to cytoplasmic loop 1 of melanocortin 4 receptor (M4R). We found that in micromolar concentrations it very effectively suppresses stimulation of basal adenylate cyclase activity and basal level of GppNHp binding of heterotrimeric G proteins produced by THIQ and α-melanocyte stimulating hormone (α-MSH), agonists of M4R homologous to the peptide, in synaptosomal membranes of rat brain. The peptide Palm-Val-(71-82) also reduced, albeit to a significantly less extent, stimulation of adenylate cyclase and G-proteins by M3R agonist of γ-MSH, due to high homology of the peptide primary structure to M3R cytoplasmic loop 1. The synthesized peptide with activity of M4R/M3R antagonist can be used for the development of regulators of M4R and M3R and the corresponding biochemical and physiological processes.

Adenosine A2b receptor promotes progression of human oral cancer.

BackgroundAdenosine A2b receptor (ADORA2B) encodes an adenosine receptor that is a member of the G protein-coupled receptor superfamily. This integral membrane protein stimulates adenylate cyclase activity in the presence of adenosine. Little is known about the relevance of ADORA2B to human malignancy including oral squamous cell carcinoma (OSCC). We aimed to characterize the expression state and function of ADORA2B in OSCC.MethodsThe ADORA2B expression levels in nine OSCC-derived cells were analyzed by quantitative reverse transcriptase-polymerase chain reaction and immunoblotting analyses. Using an ADORA2B knockdown model, we assessed cellular proliferation and expression of hypoxia-inducible factor1α (HIF-1α). We examined the adenosine receptor expression profile under both normoxic and hypoxic conditions in the OSCC-derived cells. In addition to in vitro data, the clinical correlation between the ADORA2B expression levels in primary OSCCs (n = 100 patients) and the clinicopathological status by immunohistochemistry (IHC) also was evaluated.ResultsADORA2B mRNA and protein were up-regulated significantly (p < 0.05) in seven OSCC-derived cells compared with human normal oral keratinocytes. Suppression of ADORA2B expression with shRNA significantly (p < 0.05) inhibited cellular proliferation compared with the control cells. HIF-1α also was down-regulated in ADORA2B knockdown OSCC cells. During hypoxia, ADORA2B expression was induced significantly (p < 0.05) in the mRNA and protein after 24 hours of incubation in OSCC-derived cells. IHC showed that ADORA2B expression in primary OSCCs was significantly (p < 0.05) greater than in the normal oral counterparts and that ADORA2B-positive OSCCs were correlated closely (p < 0.05) with tumoral size.ConclusionOur results suggested that ADORA2B controls cellular proliferation via HIF-1α activation, indicating that ADORA2B may be a key regulator of tumoral progression in OSCCs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1577-2) contains supplementary material, which is available to authorized users.

Modification of the β-Adrenoceptor Stimulation Pathway in Zucker Obese and Obese Diabetic Rat Myocardium.

Although metabolic syndrome is associated with increased sympathetic activity that chronically stimulates β-adrenoceptors, the β-adrenoceptor signaling pathway has been poorly studied in this situation. We studied the β-adrenoceptor signaling pathway in Zucker lean, obese, and obese diabetic rats. Experimental, prospective study. University medical research laboratory. Adult male Zucker lean (control), obese, and obese diabetic rats. The effects of β-adrenoceptor stimulation were investigated in vitro in isolated left ventricular papillary muscles in control, obese, and obese diabetic rats. β1-, β2-, and β3-adrenoceptors and multidrug resistance-associated protein 4 were quantified by Western Blotting. Triglyceride, cholesterol, leptin, adiponectin, and C-peptide plasma concentrations were measured. Data are mean ± SD. Hyperlipidemia, high leptin, and C-peptide concentrations were observed in obese and obese diabetic strains, whereas hyperglycemia occurred only in the diabetic strain. The positive inotropic effect of isoproterenol was slightly reduced in obese rats (183% ± 11% of baseline; p = 0.003; n = 7) and markedly reduced in obese diabetic rats (137% ± 18% of baseline; p < 0.001; n = 10) when compared with control rats (210% ± 17% of baseline; n = 9). β1-adrenoceptors were down-regulated in obese (-41%; p = 0.02) and diabetic (-54%; p = 0.003) when compared with control rats, whereas β3-adrenoceptors and multidrug resistance-associated protein expression remained unchanged. Direct stimulation of adenylate cyclase with forskolin or administration of 3',5'-cyclic adenosine monophosphate suggests that subtle impairments also occurred beside the down-regulation of β1-adrenoceptor. The positive inotropic effect of β-adrenoceptor stimulation is slightly decreased in Zucker obese rats and was more markedly decreased in Zucker diabetic rats. These decreases are mainly related to β1-adrenoceptor down-regulation.

Catheter-based Renal Denervation as a Treatment for Pulmonary Hypertension: Hope or Hype?

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary vascular resistance (PVR) that causes right ventricular (RV) failure and premature death. This hypertensive condition leads to precapillary pulmonary hypertension, defined as a mean pulmonary artery pressure (mPAP) 25 mmHg, pulmonary capillary wedge pressure 15 mmHg, and PVR > 3 Wood units at rest. The prevalence of PAH is estimated to range from 15 to 50 patients/million, with a female predominance (men:women, 1:2) and 1-year and 5-year survival rates of 85% and 57%, respectively. During the last 15 years, treatments for PAH have been studied in multiple clinical trials, with approval subsequently granted for 9 distinct drugs belonging to 4 pharmacological families: prostanoids (epoprostenol, iloprost, treprostinil), endothelin receptor antagonists (bosentan, ambrisentan, macitentan), phosphodiesterase-5 inhibitors (sildenafil, tadalafil), and adenylate cyclase stimulators (riociguat). Despite these therapeutic advances, many patients with PAH show disabling symptoms and an ominous prognosis, underscoring the need for new therapeutic strategies to combat PAH. The pathophysiology of PAH involves excessive vasoconstriction and vascular remodeling. The increased PVR is initially reversible and is due to an imbalance between vasodilatory and vasoconstrictive agents, but can become permanent in later stages. The vascular remodeling is characterized by intimal thickening and fibrosis and the proliferation and migration of vascular smooth muscle cells, with hypertrophy and fibrosis of the tunica media, inflammation, and in situ thrombosis, which trigger the formation of plexiform and obstructive lesions (the most characteristic finding of PAH), all of which lead to RV remodeling. Given our poor understanding of the pathophysiology of PAH, the development of new preclinical models of PAH and their evaluation using appropriate imaging techniques are essential to further our understanding of PAH.

PAC1‐Gs Coupling Through AC6 Mediates NCS/Rapgef2‐dependent ERK Activation in Neuroendocrine Cells

The neuritogenic cAMP sensor (NCS), the protein product of the Rapgef2 gene, couples GPCR‐Gs‐dependent elevation of cAMP to ERK activation required for neuritogenesis, while additional aspects of cAMP‐dependent cell differentiation are mediated through PKA (pro‐survival effects) and Epac2 (growth arrest) (Emery et al., JBC 289: 10126, 2014). Functional full‐length Rapgef2 is expressed in cell lines of neuroendocrine lineage, but not in several non‐neuroendocrine cell lines commonly used for high‐throughput GPCR ligand and antagonist screening (Emery et al., Sci. Sig. 6: ra51, 2013). In a series of NS‐1 cell sublines into which Gs‐coupled GPCRs were introduced as single‐copy genes under the control of the CMV promoter, some (e.g. ADCYAP1R1, ADBR1, DRD1), but not others (ADBR2, ADORA2A), engage NCS/Rapgef2 and induce neuritogenesis when stimulated with the appropriate ligand. All are coupled to adenylate cyclase and cause stimulation of Epac and PKA. To determine the mechanism of coupling specificity between GPCRs and NCS/Rapgef2, we are evaluating the membranous adenylate cyclase (AC) specificity for NCS/Rapgef2 coupling. In PC12 cells, which express ACs 3, 4, 6, 7, and 9, PACAP‐initiated signaling through ADCYAP1R1 (cAMP elevation, ERK phosphorylation, and neuritogenesis) is greatly attenuated by knockdown of AC6, but not AC7, achieved by stable lentiviral‐mediated shRNA expression, with no significant effects of either knock‐down on forskolin‐induced downstream cAMP‐dependent signaling events (ERK activation and neuritogenesis). These data suggest that the ADCYAP1R1 (PAC1) receptor is preferentially coupled to AC6, and this AC preference is linked to engagement of NCS/Rapgef2, ERK activation, and neuritogenesis.

Redistribution of Gαs in mouse salivary glands following β-adrenergic stimulation

ObjectiveSignalling via β-adrenergic receptors activates heterotrimeric G-proteins, which dissociate into α and βγ subunits. In salivary glands, the α subunit of Gs stimulates adenylate cyclase, increasing cyclic AMP levels and promoting exocytosis. The goals of this study were to determine Gαs localization in salivary glands and whether it undergoes redistribution upon activation. MethodsMouse parotid and submandibular (SMG) glands were fixed with paraformaldehyde and prepared for immunofluorescence labelling with anti-Gαs. ResultsIn unstimulated parotid and SMG acinar cells, Gαs was localized mainly to basolateral membranes. Some parotid acinar cells also exhibited cytoplasmic fluorescence. Isoproterenol (IPR) stimulation resulted in decreased membrane fluorescence and increased cytoplasmic fluorescence, which appeared relatively uniform by 30min. Beginning about 2h after IPR, cytoplasmic fluorescence decreased and membrane fluorescence increased, approaching unstimulated levels in SMG acini by 4h. Some parotid acini exhibited cytoplasmic fluorescence up to 8h after IPR. The IPR-induced redistribution of Gαs was prevented (SMG) or reduced (parotid) by prior injection of propranolol. Striated duct cells of unstimulated mice exhibited general cytoplasmic fluorescence, which was unchanged after IPR. ConclusionsGαs is localized to basolateral membranes of unstimulated salivary acinar cells. Activation of Gαs causes its release from the cell membrane and movement into the cytoplasm. Reassociation of Gαs with the membrane begins about 2h after stimulation in the SMG, but complete reassociation takes several hours in the parotid gland. The presence of Gαs in striated duct cells suggests a role in signal transduction of secretion and/or electrolyte transport processes.

Current optimization of combined therapy for chronic obstructive pulmonary disease

Testing the new combined bronchodilator Anoro Ellipta in different clinical trials gives to its high clinical efficacy and safety in chronic obstructive pulmonary disease. The drug contains the molecules of sustained-release selective β2-adrenergic receptor agonist (vilanterol) and a muscarinic cholinergic receptor antagonist (umeclidinium bromide). The bronchodilating mechanisms of umeclidinium bromide are in the competitive inhibition of the binding of acetylcholine with muscarinic acetylcholine receptors of airway smooth muscles whereas in those of vilanterol are in that with the stimulation of intracellular adenylate cyclase. On days 1 and 24 after inhalation of the first dose of vilanterol and umeclidinium bromide, there was a significant increase in the forced expiratory volume in one second as compared to placebo. No clinical effects on QT interval on an electrocardiogram and cardiac rhythm were found. The benefits of an inhalation device (Ellipta) are its innovation design ensuring the effective delivery of an aerosol dose into the airway, convenience, and simplicity.

Role of Cholera Toxin in &lt;i&gt;Vibrio cholerae&lt;/i&gt; Infection in Humans - A Review

Vibrio cholerae, the causative agent of Asiatic cholera, is a gram-negative motile bacterial species acquired via oral ingestion of contaminated food or water sources. Cholera has spread from the Indian subcontinent where it is endemic to involve nearly the whole world seven times during the past 185 years. V. cholerae serogroup O1, biotype El Tor, has moved from Asia to cause pandemic disease in Africa and South America during the past 35 years. A new serogroup, O139, appeared in south Asia in 1992, has become endemic there, and threatens to start the next pandemic. The facultative human pathogen V. cholerae represents a paradigm that evolved from environmental non-pathogenic strains by acquisition of virulence genes. The major virulence factors of V. cholerae, cholera toxin (CTX) encoded by the ctxAB genes residing in the genome of filamentous lysogenic bacteriophage (CTXɸ) and toxin coregulated pilus (TCP) encoded by vibrio pathogenicity island (VPI). CTX, a potent stimulator of adenylate cyclase, causes the intestine to secrete watery fluid rich in sodium, bicarbonate, and potassium, in volumes far exceeding the intestinal absorptive capacity, by ADP-ribosylation of the alpha subunit of the GTP-binding protein. Thus intestinal infection with V. cholerae results in the loss of large volumes of watery stool, leading to severe and rapidly progressing dehydration and shock. Without adequate and appropriate rehydration therapy, severe cholera kills about half of affected individuals. Today, cholera still remains a burden mainly for underdeveloped countries, which cannot afford to establish or to maintain necessary hygienic and medical facilities. During the last three decades, intensive research has been undertaken to unravel the virulence properties and to study the epidemiology of this significant human pathogen. This review provides an overview of the role of CTX in the occurrence of this disease in humans.

Role of Cholera Toxin in &lt;i&gt;Vibrio cholerae&lt;/i&gt; Infection in Humans - A Review

Vibrio cholerae, the causative agent of Asiatic cholera, is a gram-negative motile bacterial species acquired via oral ingestion of contaminated food or water sources. Cholera has spread from the Indian subcontinent where it is endemic to involve nearly the whole world seven times during the past 185 years. V. cholerae serogroup O1, biotype El Tor, has moved from Asia to cause pandemic disease in Africa and South America during the past 35 years. A new serogroup, O139, appeared in south Asia in 1992, has become endemic there, and threatens to start the next pandemic. The facultative human pathogen V. cholerae represents a paradigm that evolved from environmental non-pathogenic strains by acquisition of virulence genes. The major virulence factors of V. cholerae, cholera toxin (CTX) encoded by the ctxAB genes residing in the genome of filamentous lysogenic bacteriophage (CTXɸ) and toxin coregulated pilus (TCP) encoded by vibrio pathogenicity island (VPI). CTX, a potent stimulator of adenylate cyclase, causes the intestine to secrete watery fluid rich in sodium, bicarbonate, and potassium, in volumes far exceeding the intestinal absorptive capacity, by ADP-ribosylation of the alpha subunit of the GTP-binding protein. Thus intestinal infection with V. cholerae results in the loss of large volumes of watery stool, leading to severe and rapidly progressing dehydration and shock. Without adequate and appropriate rehydration therapy, severe cholera kills about half of affected individuals. Today, cholera still remains a burden mainly for underdeveloped countries, which cannot afford to establish or to maintain necessary hygienic and medical facilities. During the last three decades, intensive research has been undertaken to unravel the virulence properties and to study the epidemiology of this significant human pathogen. This review provides an overview of the role of CTX in the occurrence of this disease in humans.

PI3Kγ integrates cAMP and Akt signalling of the μ‐opioid receptor

The μ-opioid receptor has been characterized as the main mediator of opioid signalling in neuronal cells. Opioid-induced pain suppression was originally proposed to be mediated by μ-opioid receptor-induced inhibitory effects on cAMP, which is known to mediate inflammatory hypernociception. Recent investigations revealed PI3Kγ and Akt (PKB) as additional elements of μ-opioid receptor signalling. Hence, we investigated the interaction between pronociceptive cAMP and antinociceptive PI3K/Akt signalling pathways. The human neuroblastoma cell line SK-N-LO and primary dorsal root ganglia (DRG) cells from mice were used to elucidate mediators of μ-opioid receptor signalling. In both cellular systems cAMP was manipulated by stimulation of adenylate cyclase and consequent effects on PI3K/Akt signalling were analysed. Morphine stimulated Akt phosphorylation on Ser(473) and Thr(308) in a dose- and time-dependent manner indicating a functional μ-opioid receptor/Akt signalling pathway in μ-SK-N-LO cells. This effect of morphine was suppressed by the μ-opioid receptor inhibitor, naloxone, Pertussis toxin, an inhibitor of Gi heterotrimeric G-proteins, and the pan PI3K inhibitor wortmannin. cAMP-elevating agents also suppressed μ-opioid receptor-dependent stimulation of PI3Kγ lipid kinase and Akt activities in SK-N-LO cells and DRG. The data unveil a hitherto unknown interaction of pronociceptive cAMP and antinociceptive PI3K/Akt signalling pathways in neuronal cells. PI3Kγ was identified as a mediator of the inhibitory action of cAMP on Akt in SK-N-LO cells and DRG. The data indicate that PI3Kγ has a critical role in cAMP-mediated inflammatory hypernociception and analgesic signalling via μ-opioid receptors and PI3K/Akt in neuronal cells.