Title

 

Authors

 D. Cerretani¹, A.I.Fiaschi¹, G.G. Franchi¹, G. Fiore<sup>1

1</sup>Dept. of Neurological, Neurosurgical and Behavioural Sciences, "G. Segre" Pharmacology Unit, School of Medicine,  University of Siena. 

 

Abstract

Cannabinoids, Δ⁹-tetrahydrocannabinol (Δ⁹-THC) and cannabidiol (CAN), have been found to exert antiproliferative effects upon a variety of cancer cells, including glioma cell lines (Massi et al., 2006). Specifically, activation of the two cannabinoid receptors, CB1 and CB2, by  Δ⁹-THC can lead to the inhibition of cell proliferation, invasion, and induction of apoptosis in cancer cell lines. However, the molecular basis of these actions were not fully understood. Furthermore CBD, a non-psychotropic cannabinoid, has also been reported to induce apoptosis in several transformed or immortalized cells including C6 glioma. Ample evidence supports a crucial role of reactive oxygen species (ROS) in the regulation of apoptosis and  the production of ROS during apoptosis has been described in various models of apoptotic cell death. Oxidative stress, resulting from excessive production of ROS, damages cells by lipid peroxidation and by alteration of protein and nucleic acid structures. This study investigated a possible involvement of Δ⁹-THC and CANin the induction of oxidative stress in DBTRG-05MG glioblastoma cells lines in presence  and without specific CB1 and CB2 antagonists, AM251 and AM630. In this contest we measured the parameters of oxidative stress:  reduced (GSH) and oxidized glutathione (GSSG), glutathione reductase (GR), Catalase (CAT), ascorbic acid (AA) and the malondhyaldehyde (MDA) an indicator of lipid peroxidation,in glioblastoma cells after 6 hour of exposition to Δ⁹-THC (40µM) and CAN (20µM). The results showed that 6 hours of cells exposition  to CAN and Δ⁹-THC produced a significant reduction of GSH/GSSG ratio of about 4 (p<0.05) and 2 (p<0.05) times respectively; the antioxidant enzymes CAT and GR showed a decrease of activities of 15% (p<0.02) and 7% (p<0.05) respectively; the non enzymatic antioxidant AA showed a significantly reduction of 17% (p<0.05) and 27% (p<0.05)  respectively. At last CAN and Δ⁹-THC treatment for 6 h induces a significant increase of MDA levels, which were not modified by the pre-treatment of the cells with AM251, whereas the pre-treatment with AM630 partially antagonized the effect both CAN and Δ⁹-THC.In conclusion the present study demonstrates that CAN and Δ⁹-THC impaired the antioxidant cellular defence system in glioblastoma cells, and these events could be correlated to an oxidative stress pathway where lipid peroxidation represents the last step of the cell injury. We observed at our experimental conditions employing high concentration of cannabinoids, that the oxidative stress produced by CAN and Δ⁹-THC were only partially dependent on CB2 receptor activation and not dependent on CB1 activation. In fact, evidence suggest that cannabinoids may induce apoptosis in astrocytoma cells when applied at high concentrations (> 10uM) that bypass CB1 and CB2 receptors with a mechanism that may depend on ERK signaling (Cudaback et al., 2010). Basing onthe effects observed in this study, CAN and Δ⁹-THC could represent a potential antitumoural agent for treating malignant glioblastoma.

Massi et al. (2006). Cell Moll Life Sci. 63: 2057-2066
Cudaback et al. (2010). Plos ONE. 5 (1): e8702