Marine cyanobacteria-derived serotonin receptor 2C active fraction induces psychoactive behavioral effects in mice

Abstract

Context Marine cyanobacteria offer a robust resource for natural products drug discovery due to the secondary metabolites they produce. Objective To identify novel cyanobacterial compounds that exhibit CNS psychoactive effects. Materials and methods Cyanobacteria were collected from Las Perlas Archipelago, Panama and subjected to dichloromethane/methanol extraction and fractionation by column chromatography before being screened for affinity against a panel of CNS targets. A 50:50 ethyl acetate:methanol fraction of one cyanobacterial extract (2064H) was subjected to HPLC and the major peak was isolated (2064H3). At a dose of 20 μg per animal, 2064H and 2064H3 were tested in mice using behavioral assays that included the forced swim, open field, and formalin tests. Results 2064H was shown to bind to the serotonin 2C (5-HT2C) receptor, a known target for depression and pain treatment. 2064H showed 59.6% inhibition of binding of [3H]-mesulergine with an IC50 of 179 ng/mL and did not show inhibition of binding greater than 45% with any other receptors tested. Both 2064H and 2064H3 decreased immobility time in the first min of the tail suspension test. 2064H increased time, distance and number of entries in the center region in the first half of the open field test. 2064H increased overall nocifensive behaviors in the formalin test. Discussion and Conclusion Overall, manipulating the 5-HT2C receptor with these receptor-specific ligands derived from cyanobacteria altered pain, depression and anxiety-like behaviors, illustrating the importance of this receptor in affective behaviors. These results demonstrate the potential of cyanobacteria as a source for CNS active compounds.

Cyanobacterial extract with serotonin receptor subtype 7 (5‐HT7R) affinity modulates depression and anxiety‐like behavior in mice

“…prior to use. We have previously shown no behavioral effect of this vehicle preparation in mice compared to 100% aCSF vehicle (Lax et al, 2016). Microinjections were performed using a 32-gauge injector that extended 0.5 mm beyond the tip of the ICV or CA1 cannulas.…”

“…Cyanobacterial extracts and commercial compounds for behavioral characterization were prepared as described previously (Lax et al, 2016). Briefly, samples from collection DUQ0002, fraction I (DUQ0002I), the known 5-HT 7 R antagonist SB258719 (SB258719 hydrochloride, Tocris) and subfractions isolated from the parent fraction (DUQ0002I-1A-C, 2–4) were dissolved in a mixture of 50% DMSO and 50% artificial cerebrospinal fluid (aCSF) containing the following (in mM): 125 NaCl, 2.5 KCl, 1.25 NaH 2 PO 4 , 25 NaHCO 3 , 2.0 CaCl 2 , 1.0 MgCl 2 and 25 D-glucose, bubbled with 95% O 2 /5% CO 2 for 20 min.…”

“…For all injections, fraction DUQ0002I and subfractions DUQ0002I-1A-C, DUQ0002-2-4 were administered at a dose of 40 μg per cannula and SB258719 was administered at a dose of 5 μg based on previously literature (Zhao et al, 2014). The fraction dose was based on PDSP screening at 4 mg/mL and adjusted for ICV injections and intra-amygdala injections that we have done previously (Kolber et al, 2010; Lax et al, 2016). _ENREF_19 50%/50% aCSF/DMSO was used as a vehicle control in all experiments.…”

“…These include extracts from the genus Moorea (formerly Lyngbya (N. Engene et al, 2012)) acting on the cannabinoid receptors (Gutierrez et al, 2011; Han, McPhail, Ligresti, Di Marzo, & Gerwick, 2003; Montaser, Paul, & Luesch, 2012; Sitachitta & Gerwick, 1998) and an extract from the genus Oscillatoria acting on the serotonin system identified in our previous publication (Lax et al, 2016). The goal of the present research was to further probe metabolites extracted from cyanobacteria against GPCRs found in the CNS.…”

Evaluating Marine Cyanobacteria as a Source for CNS Receptor Ligands

“…Because of this, there is an opportunity to explore marine cyanobacteria for leads targeting these receptors to treat associated diseases. Our previous work [ 11 , 12 ] has shown in vivo activity in models of depression and anxiety from marine cyanobacterial extracts and fractions targeting serotonin receptors (5-HTRs). By utilizing a broad GPCR screen we believe additional leads can be discovered but hits must be followed up with additional in vitro and in vivo assays examining specificity, efficacy, and toxicity.…”