Novel potent (dihydro)benzofuranyl piperazines as human histamine receptor ligands - Functional characterization and modeling studies on H3 and H4 receptors.

Histamine acts through four different receptors (H1R-H4R), the H3R and H4R being the most explored in the last years as drug targets. The H3R is a potential target to treat narcolepsy, Parkinson's disease, epilepsy, schizophrenia and several other CNS-related conditions, while H4R blockade leads to anti-inflammatory and immunomodulatory effects. Our group has been exploring the dihydrobenzofuranyl-piperazines (LINS01 series) as human H3R/H4R ligands as potential drug candidates. In the present study, a set of 12 compounds were synthesized from adequate (dihydro)benzofuran synthons through simple reactions with corresponding piperazines, giving moderate to high yields. Four compounds (1b, 1f, 1g and 1h) showed high hH3R affinity (pKi > 7), compound 1h being the most potent (pKi 8.4), and compound 1f showed the best efficiency (pKi 8.2, LE 0.53, LLE 5.85). BRET-based assays monitoring Gαi activity indicated that the compounds are potent antagonists. Only one compound (2c, pKi 7.1) presented high affinity for hH4R. In contrast to what was observed for hH3R, it showed partial agonist activity. Docking experiments indicated that bulky substituents occupy a hydrophobic pocket in hH3R, while the N-allyl group forms favorable interactions with hydrophobic residues in the TM2, 3 and 7, increasing the selectivity towards hH3R. Additionally, the importance of the indole NH in the interaction with Glu5.46 from hH4R was confirmed by the modeling results, explaining the affinity and agonistic activity of compound 2c. The data reported in this work represent important findings for the rational design of future compounds for hH3R and hH4R.

Antidepressant-like Effect of Insulin in Streptozotocin-induced Type 2 Diabetes Mellitus Rats.

This study evaluated the antidepressant-like effect of insulin compared to sertraline and a combination of insulin and sertraline in streptozotocin (STZ)-induced type 2 diabetes mellitus (T2DM) rats submitted to the forced swim test (FST). Male Wistar rats were daily treated for 21 days with insulin (1 or 2 IU/kg, i.p.), with the selective serotonin reuptake inhibitor (SSRI), sertraline (10 mg/kg, i.p.), or with a combination of insulin (1 or 2 IU/kg, i.p.) and sertraline (10 mg/kg, i.p.) and submitted to the FST. We also evaluated the water and food intake, urine volume and weight gain of the rats. Rats treated with STZ showed impaired glucose tolerance. Chronic treatment with sertraline showed an antidepressant-like effect in non-diabetic and diabetic rats. Furthermore, sertraline promoted lower weight gain in diabetic rats. Insulin reduced the immobility behaviour in T2DM rats with impaired glucose tolerance. In conclusion, our results showed that insulin has an antidepressant-like effect comparable to that of sertraline. Sertraline is effective as an antidepressant and reduces weight gain, which reinforces its superiority over other SSRIs in the treatment of major depression disorder in patients with T2DM.