The discovery of diazepinone-based 5-HT3 receptor partial agonists.

Serotonin type 3 (5-HT3) receptor partial agonists have been targeted as potential new drugs for the symptomatic relief of irritable bowel syndrome (IBS). Multiple diazepinone-based compounds have been discovered, which exhibit nanomolar binding affinity for the h5-HT3A receptor and display a range of intrinsic activities (IA=7-87% of 5-HT Emax) in HEK cells heterologously expressing the h5-HT3A receptor. Favorable physicochemical properties and in vitro ADME profile coupled with oral activity in the murine von Bezold-Jarisch reflex model demonstrates the series has promise for producing low to moderate IA partial agonists suitable for an IBS indication.

Visual eyes: a quantitative analysis of the photoreceptor layer in deep-sea sharks.

The marine environment presents unique visual challenges for a range of organisms, particularly those dwelling at great depths, where sunlight may either be absent or drop to very low levels. Under these environmental conditions, the visual system must maximise light absorption in order to enhance the detection of prey, predators and potential mates. Using stereological analysis of retinal wholemounts, the distribution and number of photoreceptors (rods) was determined for 5 deep-sea shark species from a range of depths (46-1,500 m). All species possessed areas of increased photoreceptor density (with peaks between 41,000 and 82,000 rods/mm(2)) within discrete regions of the retina. The total number of rods in the photoreceptor layer also varied between 17 × 10(6) and 63 × 10(6). It is evident that increasing sensitivity of the retina is an important adaptation to life in the deep sea. The location of discrete areas of high cell density within the photoreceptor layer of the retina corresponds to discrete areas of the visual field that are sampled at a higher intensity, hence increasing sensitivity. The location of these areas of increased sensitivity differed between the species of this study. The disparity of areas of increased sensitivity seen between species is thought to reflect distinctive predator avoidance and prey capture strategies. This study reveals that the visual demands of deep-sea sharks vary interspecifically and that sampling of each species' visual field is not solely determined by its habitat.

The identification of N-glycosylated residues of the human 5-HT3B receptor subunit: importance for cell membrane expression.

The 5-hydroxytryptamine 3 (5-HT(3)) receptor is a pentameric ligand-gated ion channel with potential molecular isoforms arising from different subunit combinations and/or different post-translational modifications of the individual subunits. Since N-glycosylation of the 5-HT3A subunit impacts cell surface trafficking, the presence of N-glycosylation of the human (h) 5-HT3B subunit and the influence upon cell membrane expression was investigated. Following transient expression of the h5-HT3B subunit by human embryonic kidney cells (HEK293 cells) stably expressing the h5-HT3A subunit, the N-glycosylation inhibitor tunicamycin reduced the size of the predominant h5-HT3B-immunoreactive protein (∼ 55 kDa reduced to ∼ 40 kDa). Disruption of each consensus N-glycosylation sequences in the h5-HT3B subunit (N31S, N75S, N117S, N147S and N182S) resulted in a reduced molecular weight (by ∼ 2-4 kDa) of each mutant when expressed by HEK293 cells stably expressing the h5-HT3A subunit. Immunocytochemical studies demonstrated that disruption of each of the N-glycosylation sequences (individually or combined) reduced the expression of the mutant h5-HT3B subunit protein in the cell membrane when co-expressed with the h5-HT3A subunit. The present study has identified utilised N-glycosylation sites of the h5-HT3B subunit and demonstrated that they promote subunit expression in the cell membrane; a prerequisite for 5-HT(3) receptor function.

Inosine Acedoben Dimepranol promotes an early and sustained increase in the natural killer cell component of circulating lymphocytes: A clinical trial supporting anti-viral indications.

Inosine Acedoben Dimepranol (IAD), licensed for the treatment of cell-mediated immune deficiencies associated with viral infections, has been reported to impact a variety of immune parameters both in vitro and in vivo. Here we report the results from a clinical trial where multiple lymphocyte subsets - CD19+ B cells, CD3+ T cells, CD4+ T-helper cells, FoxP3hi/CD25hi/CD127lo regulatory T cells (Tregs), CD3-/CD56+ NK cells, and CD3+/CD56+ NKT cells - were, together with serum immunoglobulins and IgG subclasses, followed during 14days of IAD administration to ten healthy volunteers; these selected from 27 individuals pre-screened in vitro for their capacity to respond to IAD as gauged by increases in the percentage of Treg and/or NKT cells arising in PHA-stimulated cultures. While a transient spike and dip in Treg and T-helper fractions, respectively, was noted, the outstanding consequence of IAD administration (1g po, qds) was an early and durable rise in NK cells. For half the cohort, NK cells increased as a percentage of total peripheral blood lymphocytes within 1.5h of receiving drug. By Day 5, all but one of the volunteers displayed higher NK cell percentages, such elevation - effectively a doubling or greater - being maintained at termination of study. The IAD-induced populations were as replete in Granzyme A and Perforin as basal NK cells. The novel finding of IAD boosting phenotypically competent NK numbers in healthy individuals supports the drug's indicated benefit in conditions associated with viral infection and reinforces the potential for uplift where immune performance may be compromised.

5-Chloroindole: a potent allosteric modulator of the 5-HT3 receptor.

BACKGROUND AND PURPOSE: The 5-HT3 receptor is a ligand-gated ion channel that is modulated allosterically by various compounds including colchicine, alcohols and volatile anaesthetics. However the positive allosteric modulators (PAMs) identified to date have low affinity, which hinders investigation because of non-selective effects at pharmacologically active concentrations. The present study identifies 5-chloroindole (Cl-indole) as a potent PAM of the 5-HT3 receptor. EXPERIMENTAL APPROACH: 5-HT3 receptor function was assessed by the increase in intracellular calcium and single-cell electrophysiological recordings in HEK293 cells stably expressing the h5-HT3A receptor and also the mouse native 5-HT3 receptor that increases neuronal contraction of bladder smooth muscle. KEY RESULTS: Cl-indole (1-100 µM) potentiated agonist (5-HT) and particularly partial agonist [(S)-zacopride, DDP733, RR210, quipazine, dopamine, 2-methyl-5-HT, SR57227A, meta chlorophenyl biguanide] induced h5-HT3A receptor-mediated responses. This effect of Cl-indole was also apparent at the mouse native 5-HT3 receptor. Radioligand-binding studies identified that Cl-indole induced a small (≈ twofold) increase in the apparent affinity of 5-HT for the h5-HT3A receptor, whereas there was no effect upon the affinity of the antagonist, tropisetron. Cl-indole was able to reactivate desensitized 5-HT3 receptors. In contrast to its effect on the 5-HT3 receptor, Cl-indole did not alter human nicotinic α7 receptor responses. CONCLUSIONS AND IMPLICATIONS: The present study identifies Cl-indole as a relatively potent and selective PAM of the 5-HT3 receptor; such compounds will aid investigation of the molecular basis for allosteric modulation of the 5-HT3 receptor and may assist the discovery of novel therapeutic drugs targeting this receptor.