Effect of lesogaberan, a novel GABA(B)-receptor agonist, on transient lower oesophageal sphincter relaxations in male subjects.

BACKGROUND: Transient lower oesophageal sphincter relaxations (TLESRs) are a major mechanism behind gastro-oesophageal reflux disease (GERD). AIM: To assess the effect of lesogaberan (AZD3355) - a novel peripherally active GABA(B) receptor agonist - on TLESRs. METHODS: Twenty-four healthy men were enrolled in this single-blind, placebo-controlled, randomized, single-centre, three-period crossover phase 1 study. Subjects were randomized to receive single oral doses of lesogaberan (0.8 mg/kg), baclofen (40 mg) and placebo, separated by washout periods of < or = 7 days. Subjects finished a meal 1 h after the dose. Oesophageal manometry and pH-metry measurements were taken during the 3 h after the meal. RESULTS: Twenty-one subjects completed the study. Compared with placebo, lesogaberan 0.8 mg/kg significantly reduced the number of TLESRs by 36% [geometric mean ratio (GMR): 0.64; 95% confidence interval (CI): 0.51-0.82] and significantly reduced the number of acid reflux episodes (mean reduction: 1.6; 95% CI: 0.34-2.9). Lesogaberan also significantly increased lower oesophageal sphincter (LES) pressure by 39% compared with placebo (GMR: 1.39; 95% CI: 1.18-1.64). Comparable results were observed with baclofen. Similar numbers of adverse events were reported by subjects taking lesogaberan and placebo. CONCLUSION: Compared with placebo, lesogaberan significantly reduced TLESRs and acid reflux episodes and increased LES pressure.

The GABA(B) receptor agonist AZD9343 inhibits transient lower oesophageal sphincter relaxations and acid reflux in healthy volunteers: a phase I study.

BACKGROUND: Transient lower oesophageal sphincter relaxations (TLESRs) represent an interesting target for the treatment of gastro-oesophageal reflux. Baclofen reduces TLESRs and reflux episodes, but is not optimal for clinical application because of its central side effects. Therefore, new agents are required. AIM: To study the effect of AZD9343, a new selective GABA(B) receptor agonist, in healthy volunteers. METHODS: A total of 27 subjects participated in a placebo-controlled, randomized, two-centre phase I study. Subjects underwent oesophageal manometry and pH-metry for 3 h postprandially. Before meal ingestion, a single oral dose of placebo, 60 and 320 mg AZD9343 or 40 mg baclofen was given on four separate days. RESULTS: Somnolence was reported after 320 mg AZD9343 and baclofen. Reversible short-lasting paraesthesia was reported after AZD9343. AZD9343 320 mg and baclofen significantly reduced the number of TLESRs with 32% and 40% respectively. Acid reflux was significantly decreased by AZD9343 and baclofen. Like baclofen, AZD9343 increased LES pressure before meal intake. AZD9343 320 mg and baclofen significantly reduced the swallowing rate. CONCLUSIONS: Like baclofen, AZD9343 dose-dependently decreases the number of TLESRs and acid reflux episodes, increases LES pressure and reduces swallowing, extending the concept that GABA(B) agonists are potent reflux inhibitors. However, discovery of analogues with an improved side effect profile is warranted.

Reproducibility of meal-induced transient lower oesophageal sphincter relaxations in patients with gastro-oesophageal reflux disease.

AIM: To calculate the number of subjects required in trials investigating drugs reducing the number of transient lower oesophageal sphincter relaxations (TLOSRs), the inter- and intra-individual variability of TLOSRs were determined, using meal ingestion as a trigger of TLOSRs and reflux. METHODS: A total of 23 gastro-oesophageal reflux disease (GORD) patients with no to grade B oesophagitis and a hiatal hernia < or =3 cm underwent oesophageal manometry and pHmetry 1 h before and 3 h after ingestion of a solid meal on two separate days approximately 4 weeks apart. Reflux episodes and the underlying mechanisms and the number of TLOSRs were evaluated. RESULTS: The number of TLOSRs, reflux episodes and % time with pH < 4 after meal ingestion did not differ significantly between the two sessions. The intra-individual variation of TLOSRs in the 3 h postprandial period (24.4) was smaller compared with the inter-individual variation (47.5). Transient lower oesophageal sphincter relaxations were the predominant cause of reflux accounting for 61 +/- 7 and 70 +/- 5% of the reflux episodes in visits 1 and 2, respectively. CONCLUSIONS: These data for the first time provide information on the variability of TLOSRs and reflux evoked by meal ingestion, which is of crucial importance for the design and power calculations of future clinical studies evaluating the efficacy of new drugs targeting TLOSRs.

The effect of baclofen on gastro-oesophageal reflux, lower oesophageal sphincter function and reflux symptoms in patients with reflux disease.

BACKGROUND: Baclofen decreases gastro-oesophageal reflux episodes in healthy subjects by reducing the incidence of transient lower oesophageal sphincter relaxations. AIM: To investigate the effect of baclofen on reflux symptoms, oesophageal pH and lower oesophageal sphincter manometry in patients with gastro-oesophageal reflux disease. METHODS: A double-blind, placebo-controlled, two-way crossover design was used to study the effect of baclofen on heartburn and regurgitation 3 h after a provocation test meal in 37 patients with gastro-oesophageal reflux disease. Additionally, in 20 of these patients, the effect of baclofen on oesophageal pH, transient lower oesophageal sphincter relaxations and basal lower oesophageal sphincter pressure was studied. RESULTS: Baclofen significantly decreased the acid reflux time and the incidence of gastro-oesophageal reflux episodes (8.3 +/- 8.8% vs. 12.4 +/- 12.0%, P = 0.03 and 10.9 +/- 7.3 per 3 h vs. 18.7 +/- 12.4 per 3 h). The incidence of transient lower oesophageal sphincter relaxations was significantly lower with baclofen than with placebo (15.1 +/- 6.4 per 3 h vs. 22.8 +/- 5.4 per 3 h, P < 0.0001). Lower oesophageal sphincter pressure and the percentage of transient lower oesophageal sphincter relaxations associated with reflux were not affected by baclofen. No significant effect on symptom scores was observed. CONCLUSIONS: Baclofen decreases post-prandial acid reflux in patients with gastro-oesophageal reflux disease by reducing the incidence of transient lower oesophageal sphincter relaxations. No effect of a single dose of baclofen on reflux symptoms could be demonstrated in this 3-h post-prandial study.

Baclofen-mediated gastro-oesophageal acid reflux control in patients with established reflux disease.

AIM: To explore the effect of baclofen on oesophageal acid exposure in patients with gastro-oesophageal reflux disease. METHODS AND MATERIALS: Twenty patients with established reflux disease were included in this double-blind, randomized, crossover study. Baclofen, 40 mg, or placebo was given as a single dose with a washout period of 4 weeks. Symptoms were assessed by a visual analogue scale. Oesophageal pH was registered for 12 h and analysed for the whole period and for the 0-4-h, 4-8-h, 8-12-h and 2-h post-prandial periods. RESULTS: Baclofen significantly reduced the number of reflux episodes during the 0-4-h (7.9 vs. 16.5, P < 0.0001; post-prandially: 6.0 vs. 11.2, P < 0.0001) and 0-12-h (46.5 vs. 73, P=0.0001; post-prandially: 18.8 vs. 29.3, P < 0.0001) periods. The fraction of time with pH < 4 was significantly lowered during the 0-4-h period (9.3 vs. 15.6, P=0.0019; post-prandially: 16.1 vs. 23.5, P=0.0083). Similar results were also obtained in patients with a hiatus hernia (n=13). Belching was significantly reduced (32 vs. 69 episodes, P < 0.01). CONCLUSIONS: A single oral dose of 40 mg baclofen significantly reduced both the number of reflux episodes and the fraction of time with pH < 4, an effect primarily found during the first 4 h after dosing.

Thrombin signal transduction of the fibrinolytic system in human adult venous endothelium in vitro.

Thrombin can regulate the-fibrinolytic system by increasing the endothelial production of both tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1). The thrombin receptor transducts signals through the GTP-binding protein system, the classical pathway being the Galpha q-protein. The purpose of the present study was to examine the roles of Galpha i-protein and tyrosine kinases in the thrombin signal transduction of t-PA and PAI-1 production from human adult vein endothelial cells (HAVEC). t-PA and PAI-1 antigen were analysed in conditioned medium from cultured HAVEC after 16 h incubation. Data are expressed as percentages of basal release (100%), means +/- 95% confidence intervals. Thrombin increased t-PA and PAI-1 production (234 +/- 42% and 211 +/- 42%, respectively). Pertussis toxin (PTX) (inhibiting Galpha i-pathway) reduced basal PAI-1 (66 +/- 8%), but had only a weak influence on basal t-PA production. Pertussis toxin and genistein (inhibiting tyrosine kinase) significantly reduced the thrombin induction of both t-PA and PAI-1 (PTX: 142 +/- 23% and 146 +/- 19%, respectively, genistein: 156 +/- 42% and 76 +/- 24%, respectively). The present study demonstrated that thrombin can increase the production of t-PA and PAI-1 by transducting signals through the Galpha i and tyrosine kinase pathway, in addition to the Galpha q/protein kinase C pathway as has been found previously.

Different fibrinolytic potentials between human umbilical vein endothelial cells and human adult vein endothelial cells.

Endothelial cells play a central role in fibrinolysis due to their production of both tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1). The purpose of this study was to test the hypothesis that the production of t-PA and PAI-1 from human umbilical vein endothelial cells (HUVEC) and from human adult vein endothelial cells (HAVEC) adopt the same pathways for the regulation of fibrinolysis, and that differences in PAI-1 and t-PA production are only quantitative. HUVEC and HAVEC cultures were exposed to phorbol ester (PMA), endotoxin (LPS) or thrombin, singly or in combination with forskolin or H7. The conditioned medium was collected after 16 h and analyzed for t-PA and PAI-1 antigens. The basal production of both t-PA and PAI-1 was significantly higher from HUVEC than from HAVEC. Exposure to PMA, thrombin or forskolin gave a similar response from the two cell types. In contrast, the results from HUVEC and HAVEC differed significantly, not only in magnitude but also in direction, when the cells were exposed to forskolin coincubated with PMA, LPS or thrombin, and in magnitude alone when exposed to LPS only. The results indicate that there are not only quantitative but also qualitative differences in the production of t-PA and PAI-1 from HUVEC and HAVEC. These differences must be taken into account when data from cells of different origin are compared.

Complex intracellular signal transduction regulates tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1) synthesis in cultured human umbilical vein endothelium.

Endothelial cells are central in fibrinolysis because of their high production of both activators (t-PA, uPA) and inhibitors (PAI-1). The t-PA and PAI-1 synthesis could be regulated by signals transduction at several cellular levels. The purpose of this in vitro study, on cultured endothelial cells, was to explore the receptor/second messenger regulation of the t-PA and PAI-1 synthesis. Quiescent confluent human umbilical vein endothelial cells, cultured in passage 1, were exposed to different test substances. Samples from the conditioned medium were collected after 16 and 24 h and analysed for t-PA and PAI-1 antigen. All data presented were related to the data from control dishes (= 100%), in the same experiment. The results from the present study (mean +/- 95% confidence interval) demonstrated the following. (1) Forskolin, with a documented direct cAMP-inducing effect, decreased the basal PAI-1 production to 61 +/- 15%, and Na-nitroprusside, with a documented cGMP-inducing effect, increased the basal PAI-1 production to 141 +/- 38% without affecting the basal t-PA production. The surface receptor agonists isoprenalin or ephedrine, which indirectly affect adenylate cyclase, had no effect on t-PA or PAI-1 production. (2) Phorbolester (PMA), which directly activates proteinkinase C (PKC), increased the basal t-PA and PAI-1 production to 350 +/- 71%, and 163 +/- 35% respectively. (3) Thrombin, but not endothelin-1 (ET-1), increased the basal t-PA and PAI-1 production to 195 +/- 34% and 136 +/- 18%, respectively, indicating an PKC-mediated thrombin effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelial prostacyclin production, synergistic effect between adrenergic stimulating and blocking drugs.

Endothelial cells (EC) produce prostacyclin (PGI2) in high quantities which at the luminal surface decreases platelet aggregation and adhesion and basal to the cell relaxes smooth muscle cells (SMC). Connections have been reported between prostacyclin production, hypertension and the degree of adrenergic activation. The present study tested the hypothesis that prostacyclin production by EC could be regulated by adrenergic mechanisms. EC were isolated from human umbilical cord veins. Washed cells were seeded and grown to confluency on tissue culture dishes. The test drugs were simultaneously added to parallel dishes. Samples were collected from the conditioned medium and analyzed for 6-keto-PGF1a with RIA technique. Endothelial cells pretreated with the betaadrenoceptor blocking drugs metoprolol or propranolol synergistically increased basal prostacyclin production when exposed to betaadrenergic stimulation. However, using isomers with high or low betaadrenoblocking effect, this synergism was demonstrated not to be associated to the betaadrenoceptor blocking effect of the drugs per se. These findings may have implications on the arterial hypertensive state characterized by high sympathetic tonus and low PGI2 production. The data may offer an explanation why hypertensive individuals react with increased PGI2 production, upon betaadrenoceptor blocking therapy.