Our findings suggest that a low dose of THC produces subjective stress-relieving effects in line with those commonly reported among cannabis users, but that higher doses may non-specifically increase negative mood.

The alpha7 nicotinic acetylcholine receptor (nAChR) is a potential target in neuroinflammation. Screening a plant extract library identified Solidago nemoralis as containing methyl-quercetin derivatives that are relatively selective ligands for the alpha7 nAChR. Flavonoids are not known for this activity, so we screened a small library of pure flavonoids to confirm our findings. Some flavonoids, e.g. rhamnetin, displaced a selective alpha7 nAChR radioligand from rat brain membranes whereas similar structures e.g. sakuranetin, did not. To evaluate the contribution of this putative nAChR activity to the known anti-inflammatory properties of these flavonoids, we compared their effects on lipopolysaccharide induced release of inflammatory mediators from BV2 microglia. Both rhamnetin and sakuranetin reduced mediator release, but differed in potency (rhamnetin>sakuranetin) and the Hill slope of their concentration response curves. For rhamnetin the Hill coefficient was >3.0 whereas for sakuranetin the coefficient was 1.0, suggesting that effects of rhamnetin are mediated through more than one mechanism, whereas sakuranetin has a single mechanism. nACHR antagonists decreased the Hill coefficient for rhamnetin toward unity, which suggests that a nAChR-mediated mechanism contributes cooperatively to its overall anti-inflammatory effect. In contrast nAChR antagonists had no effect on the potency or Hill coefficient for sakuranetin, but a concentration of nicotine (1μM) that had no effect alone, significantly increased the Hill coefficient of this flavonoid. In conclusion, the anti-inflammatory effects of rhamnetin benefit cooperatively from a nAChR-mediated mechanism. This action, together with potent free radical scavenging activity, suggests that flavonoids with alpha7 nAChR activity have therapeutic potential in neuroinflammatory conditions.

Background Ethanol causes neurotoxicity by several mechanisms including excitotoxicity and neuroinflammation, but little is known about the interaction between these mechanisms. Because neuroinflammation is known to enhance excitotoxicity, we hypothesized that neuroinflammation contributes to the enhanced excitotoxicity which is associated with ethanol withdrawal (EWD). The aim of this study was to evaluate the lipopolysaccharide (LPS)-induced inflammatory response of cultured hippocampal tissue during EWD and its effects on the enhanced N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity which occurs at this time. Methods Using a neonatal organotypic hippocampal slice culture (OHSC) model, we assessed the effects of NMDA and LPS (separately or combined) during EWD after 10 days of ethanol exposure. Neurotoxicity was assessed using propidium iodide uptake and the inflammatory response was evaluated by measuring the release of TNF-alpha (quantified by ELISA) and nitric oxide (quantified by the Griess reaction) into culture media. Furthermore, we explored the potential role of the microglial cell type using immortalized BV2 microglia treated with ethanol for 10 days and challenged with LPS during EWD. Results As predicted, NMDA-induced toxicity was potentiated by LPS under control conditions. However, during EWD the reverse was observed and LPS inhibited peak NMDA-induced toxicity. Additionally, LPS-induced release of TNF-alpha and nitric oxide during EWD was reduced compared to control conditions. In BV2 microglia, following ethanol exposure, LPS-induced release of nitric oxide was reduced whereas TNF-alpha release was potentiated. Conclusions During EWD following chronic ethanol exposure, OHSC exhibited a desensitized inflammatory response to LPS and the effects of LPS on NMDA toxicity were reversed. This might be explained by a change in microglia to an anti-inflammatory and neuroprotective phenotype. In support, studies on BV2 microglia indicate that ethanol exposure and EWD does alter the response of these cells to LPS, but this cannot fully explain the changes observed in the OHSC. The data suggest that neuroinflammation and excitotoxicity do interact during EWD. However, the interaction is not as simple as we originally proposed. This in turn illustrates the need to assess the extent, importance and relation of these mechanisms in models of ethanol exposure producing neurotoxicity.

By screening a native plant extract library we identified Solidago nemoralis as a novel source of agonists for alpha7 nicotinic receptors for acetylcholine with therapeutic potential. The next phase of our drug discovery strategy is to increase the yields of active compounds in the plant species by gain of function mutations in hairy root cultures [1]. Here we report a protocol for Agrobacterium rhizogenes-mediated genetic transformation of hairy root cultures of Solidago nemoralis which will enable this. Leaf explants of this species were successfully transformed with a frequency of 30% -35% using A. rhizogenes strain R1000 harboring the binary vector pCambia 1301. Transformation was confirmed using the β-glucuronidase (GUS) histochemical assay. Transformed hairy roots showed spontaneous regeneration of adventitious shoots in media without the addition of cytokines, albeit at very low frequency. However, media supplementation with auxin (α-naphthaleneacetic acid, NAA) increased shoot regeneration frequency to 35% and resulted in viable adventitious shoots. Transformation was confirmed at all phases of plant regeneration by GUS staining. Hairy root transformation of Solidago altissima has been previously reported, but this is the first report of genetic transformation of S. nemoralis. The protocol will allow for a large population of activation tagged mutants of S. nemoralis to be generated which will be then screened for the presence of stable mutants which are over-producing metabolites with activity at alpha7 nicotinic receptors. These over-producing mutant cultures will then be regenerated into intact mutant plants.

No abstract