Pharmacological profile of DA-6886, a novel 5-HT4 receptor agonist to accelerate colonic motor activity in mice.

DA-6886, the gastrointestinal prokinetic benzamide derivative is a novel 5-HT4 receptor agonist being developed for the treatment of constipation-predominant irritable bowel syndrome (IBS-C). The purpose of this study was to characterize in vitro and in vivo pharmacological profile of DA-6886. We used various receptor binding assay, cAMP accumulation assay, organ bath experiment and colonic transit assay in normal and chemically constipated mice. DA-6886 exhibited high affinity and selectivity to human 5-HT4 receptor splice variants, with mean pKi of 7.1, 7.5, 7.9 for the human 5-HT4a, 5-HT4b and 5-HT4d, respectively. By contrast, DA-6886 did not show significant affinity for several receptors including dopamine D2 receptor, other 5-HT receptors except for 5-HT2B receptor (pKi value of 6.2). The affinity for 5-HT4 receptor was translated into functional agonist activity in Cos-7 cells expressing 5-HT4 receptor splice variants. Furthermore, DA-6886 induced relaxation of the rat oesophagus preparation (pEC50 value of 7.4) in a 5-HT4 receptor antagonist-sensitive manner. The evaluation of DA-6886 in CHO cells expressing hERG channels revealed that it inhibited hERG channel current with an pIC50 value of 4.3, indicating that the compound was 1000-fold more selective for the 5-HT4 receptor over hERG channels. In the normal ICR mice, oral administration of DA-6886 (0.4 and 2mg/kg) resulted in marked stimulation of colonic transit. Furthermore, in the loperamide-induced constipation mouse model, 2mg/kg of DA-6886 significantly improved the delay of colonic transit, similar to 10mg/kg of tegaserod. Taken together, DA-6886 is a highly potent and selective 5-HT4 receptor agonist to accelerate colonic transit in mice, which might be therapeutic agent having a favorable safety profile in the treatment of gastrointestinal motor disorders such as IBS-C and chronic constipation.

Altered activity of cytochrome P450 in alcoholic fatty liver exposed to ischemia/reperfusion.

Ischemia/reperfusion (I/R) injury is a major cause of morbidity and mortality in liver surgery and transplantation, and fatty livers are susceptible to greater I/R injury and a higher incidence of primary graft nonfunction after transplantation. Because alcohol intake and obesity are major causes of fatty liver, this study was initiated to investigate the effect of chronic ethanol consumption on hepatic microsomal cytochrome P450 (CYP) activity after I/R. Rats were fed an alcohol liquid diet or a control isocaloric diet for 4 weeks, and then subjected to 60 min of hepatic ischemia and 5 h of reperfusion. It was found that, chronic ethanol consumption significantly increased liver weight, serum triglyceride (TG), liver TG, and serum aminotransferase activities. Moreover, alcoholic fatty livers exposed to I/R showed significantly higher levels of aminotransferase activities than the controls. No significant differences in microsomal CYP content or CYP1A1 activity were found between I/R treated animals fed a control diet (the CD + I/R group) and I/R treated animals fed an ethanol containing diet (the ED + I/R group). Moreover, whereas CYP1A2 activity was decreased in the ED + I/R group versus the CD + I/R group, CYP2E1 activity was elevated. Additionally, chronic alcohol consumption up-regulated TNF-alpha and IL-6 mRNA levels immediately after I/R. In conclusion, chronic ethanol consumption was found to potentiate hepatocellular damage as indicated by abnormalities in microsomal drug metabolizing function during I/R.