New psychoactive substances, including synthetic cannabinoids, pose a great threat to the health of the individuals and public health and represent a difficult challenge for drug policy regulations. Cumyl-derivative SGT-24 is an illegal synthetic cannabinoid, mainly used as an e-liquid in electronic cigarettes. Pharmacological properties of SGT-24 are poorly understood therefore we decided to investigate its direct impact on neuronal and astrocyte function. Neurons are the fundamental cells of the central nervous system, astrocytes on the other hand are the most ubiquitous glial cells offering metabolic and trophic support to neurons, modulating synaptic plasticity and participating in synaptic transmission.
The expression of cannabinoid receptor on primary cell cultures of rat cortical neurons and astrocytes was confirmed by quantitative real-time polymerase chain reaction. The cell cultures were then exposed to 0,5 µM SGT-24 for 1 to 24 hours to assess the change in cell viability, measure intracellular adenosine-5’-triphosphate (ATP) concentration and determine caspase 3/7 and lactate dehydrogenase (LDH) activity. Flow cytometry was performed to confirm viability test results and determine the percentage of early apoptotic and necroptotic cells. Using selective cannabinoid receptors agonists to block the neurotoxic activity of SGT-24 we determined their role in neurotoxic processes.
Neurons and astrocytes express cannabinoid receptor CB1, nuclear receptor PPAR γ, ionotropic receptor TRPV1 and GPR-55. SGT-24 significantly affects viability of neurons after 2 hours, yet the viability of astrocytes one hour later. Neuronal intracellular ATP concentration decreases after 2 hours whereas astrocytic only after 6. No significant effect on LDH was observed. SGT-24 induces different forms of cell death. Significantly more neurons undergo apoptosis while more astrocytes undergo necroptosis. The increase of caspase 3/7 activity in neurons after 2 hours and astrocytes after 4, confirms the occurrence of early apoptosis in both types of cells. The addition of selective cannabinoid receptors agonists of CB1 and TRPV1 to astrocytes and additionally PPAR γ to neurons, inhibited harmful effects of SGT-24 on cell viability.
SGT-24 is neurotoxic in acute exposure of central nervous system cells, and the process is receptor-mediated. Abuse of SGT-24 can impair the function of the central nervous system, so it is important to aggravate the access to it and to raise awareness of the possible consequences of the use of SGT-24 and synthetic cannabinoids in general.
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