Cholinergic neuromuscular transmission mediated by interstitial cells of Cajal in the myenteric layer in mouse ileal longitudinal smooth muscles

Serotoninergic Mechanisms of Action in the Relaxant Properties of Saccharomyces boulardii CNCM I-745 on the Intestine

BACKGROUND

Perturbations of intestinal serotonergic neurotransmission seem to be involved in bowel dysmotility associated with irritable bowel syndrome (IBS) with diarrhea. Oral administration of probiotics is an emerging strategy to improve IBS symptoms, possibly via influencing local serotonin metabolism and neurotransmission. In the present study, we evaluated the effects of the yeast Saccharomyces boulardii CNCM I-745 (S. boulardii) on intestinal motility and serotonergic receptors.

METHODS

Isolated rat ileum was contracted in a cumulative concentration way by serotonin (5-HT), various 5-HT agonists or by acetylcholine to determine their effective concentration 50% (EC50). Single concentrations of S. boulardii or 5-HT antagonists were added before agonists to identify the receptors targeted by S. boulardii.

RESULTS

The serotonin antagonists 5-HT1A WAY100635, 5-HT2A ketanserin and 5-HT4 GR113808 inhibited 5-HT-induced contractions in a concentration-dependent manner. S. boulardii between 0.05 and 1.5 mg/mL increased the EC50 value of 5-HT suggesting an inhibitory effect against serotonin-induced contraction. Ileum contractions induced by the serotonin agonist 5-HT1 carboxamidotryptamine or by the serotonin agonist 5-HT2 alpha-methyl-5-HT were significantly reduced by S. boulardii at 1.5 mg/mL. The yeast did not affect acetylcholine-induced ileum contraction.

CONCLUSION

S. boulardii CNCM I-745 possesses relaxant properties on the rat ileum involving the inhibition of 5-HT and more specifically 5-HT1A and 5-HT2A/2B/2C receptor-induced contractions. These data suggest that the attenuation of 5-HT-induced ileal contractions by S. boulardii represents a probable mechanism of action sustaining its efficacy in patients affected by IBS with diarrhea.

G protein coupled signal transduction mechanisms in malfunction of smooth muscle relaxation and contraction in functional dyspepsia

Functional dyspepsia (FD) is a heterogeneous disease associated with gastrointestinal dysmotility, and it relates to malfunction of smooth muscle relaxation and contraction that is mainly mediated by G protein coupled signal transduction mechanisms involving phosphatidyl inositol (PI) signal transduction pathway, cyclic nucleus signal transduction pathway and small G protein signal transduction pathway. By discussing different components and signal pathways of G protein coupled signal transduction system and their associations with malfunction of smooth muscle relaxation and contraction in FD, this review aims to provide a new thought about the treatment of FD through the regulation of gastrointestinal motility from a microcosmic perspective.

β3-Adrenoceptor agonists for overactive bladder syndrome: Role of translational pharmacology in a repositioning clinical drug development project

β3-Adrenoceptor agonists were originally considered as a promising drug class for the treatment of obesity and/or type 2 diabetes. When these development efforts failed, they were repositioned for the treatment of the overactive bladder syndrome. Based on the example of the β3-adrenoceptor agonist mirabegron, but also taking into consideration evidence obtained with ritobegron and solabegron, we discuss challenges facing a translational pharmacology program accompanying clinical drug development for a first-in-class molecule. Challenges included generic ones such as ligand selectivity, species differences and drug target gene polymorphisms. Challenges that are more specific included changing concepts of the underlying pathophysiology of the target condition while clinical development was under way; moreover, a paucity of public domain tools for the study of the drug target and aspects of receptor agonists as drugs had to be addressed. Nonetheless, a successful first-in-class launch was accomplished. Looking back at this translational pharmacology program, we conclude that a specifically tailored and highly flexible approach is required. However, several of the lessons learned may also be applicable to translational pharmacology programs in other indications.