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(1) Background: Over the past 10 years, a number of scientific studies have demonstrated the therapeutic potential of cannabinoid compounds present in the Cannabis Sativa and Indica plants. However, their role in mechanisms leading to neurodegeneration following cerebral ischemia is yet unclear. (2) Methods: We investigated the effects of Cannabis extracts (Bedrocan, FM2) or selected cannabinoids (Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabigerol) in rat organotypic hippocampal slices exposed to oxygen-glucose deprivation (OGD), an in vitro model of forebrain global ischemia. Cell death in the CA1 subregion of slices was quantified by propidium iodide fluorescence, and morphological analysis and tissue organization were examined by immunohistochemistry and confocal microscopy. (3) Results: Incubation with the Bedrocan extract or THC exacerbated, whereas incubation with the FM2 extract or cannabidiol attenuated CA1 injury induced by OGD. Δ9-THC toxicity was prevented by CB1 receptor antagonists, the neuroprotective effect of cannabidiol was blocked by TRPV2, 5-HT1A, and PPARγ antagonists. Confocal microscopy confirmed that CBD, but not THC, had a significant protective effect toward neuronal damage and tissue disorganization caused by OGD in organotypic hippocampal slices. (4) Conclusions: Our results suggest that cannabinoids play different roles in the mechanisms of post-ischemic neuronal death. In particular, appropriate concentrations of CBD or CBD/THC ratios may represent a valid therapeutic intervention in the treatment of post-ischemic neuronal death.

Thymoquinone (TQ) is the main constituent of Nigella sativa L. essential oil. In vitro studies have shown its protective effect against H2O2-induced oxidative stress in human retinal pigment epithelium cells, and in vivo experiments have demonstrated its effect in decreasing corneal neovascularization and reducing the inflammation in an experimental dry eye model in mice. Its therapeutic use is limited by poor bioavailability, low solubility, and scarce permeability. In this study, two liposomal formulations have been developed, both of which consist of phosphatidylcholine and Plurol Oleique, a liquid lipid, and one of which is coated with 0.1% w/v hyaluronic acid (HA) to increase both TQ solubility and its ocular therapeutic potential. Each formulation has a size <200 nm and an EE% around 70%, determined by scattering techniques and the HPLC-DAD analytical method, respectively, and they result in a 2-fold increase in TQ solubility. HA-coated liposomes are stable over 2 months at +4 °C, and coated and uncoated liposomes present a gradual and prolonged release of TQ. Two cell lines, human corneal epithelial cells (HCEC-2) and human conjunctival epithelial cells (HConEC) were used to investigate the safety of the liposomal formulations. Uptake studies were also performed using fluorescent liposomes. Both liposomes and, in particular, HA-coated liposomes reduce the TQ toxicity observed at high doses in both HCEC-2 and HConEC cells, and both formulations increase the absorption at the cellular level and especially at the nucleus level, with a more pronounced effect for HA-coated liposomes.

Experimental evidence indicates that the activation of ionotropic glutamate receptors plays an important role in neurological disorders’ models such as epilepsy, cerebral ischemia and trauma. The glutamate receptor agonist kainic acid (KA) induces seizures and excitotoxic cell death in the CA3 region of the hippocampus. Thymoquinone (TQ) is the most important component of the essential oil obtained from black cumin (Nigella sativa L.) seeds. It has many pharmacological actions including antioxidant, anti-inflammatory, and anti-apoptotic effects. TQ was used in an in vitro experimental model of primary cultures where excitotoxicity was induced. Briefly, rat organotypic hippocampal slices were exposed to 5 µM KA for 24 h. Cell death in the CA3 subregions of slices was quantified by measuring propidium iodide fluorescence. The cross-talk between TQ, ER stress and apoptotic pathways was investigated by Western blot. In untreated slices TQ (10 µM) induced a significant increase on the PSD95 levels and it decreased the excitotoxic injury induced by KA. Additionally, TQ was able to ameliorate the KA-induced increase in unfolded proteins GRP78 and GRP94 expression. Finally, TQ was able to partially rescue the reduction of the KA-induced apoptotic pathway activation. Our results suggest that TQ modulates the processes leading to post-kainate neuronal death in the CA3 hippocampal area.

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