DNA Damaging Effects, Oxidative Stress Responses and Cholinesterase Activity in Blood and Brain of Wistar Rats Exposed to Δ9-Tetrahydrocannabinol

Abstract

Currently we are faced with an ever-growing use of Δ⁹-tetrahydrocannabinol (THC) preparations, often used as supportive therapies for various malignancies and neurological disorders. As some of illegally distributed forms of such preparations, like cannabis oils and butane hash oil, might contain over 80% of THC, their consumers can become intoxicated or experience various detrimental effects. This fact motivated us for the assessments of THC toxicity in vivo on a Wistar rat model, at a daily oral dose of 7 mg/kg which is comparable to those found in illicit preparations. The main objective of the present study was to establish the magnitude and dynamics of DNA breakage associated with THC exposure in white blood and brain cells of treated rats using the alkaline comet assay. The extent of oxidative stress after acute 24 h exposure to THC was also determined as well as changes in activities of plasma and brain cholinesterases (ChE) in THC-treated and control rats. The DNA of brain cells was more prone to breakage after THC treatment compared to DNA in white blood cells. Even though DNA damage quantified by the alkaline comet assay is subject to repair, its elevated level detected in the brain cells of THC-treated rats was reason for concern. Since neurons do not proliferate, increased levels of DNA damage present threats to these cells in terms of both viability and genome stability, while inefficient DNA repair might lead to their progressive loss. The present study contributes to existing knowledge with evidence that acute exposure to a high THC dose led to low-level DNA damage in white blood cells and brain cells of rats and induced oxidative stress in brain, but did not disturb ChE activities.

Keywords: acetylcholinesterase; antioxidative enzymes; brain cells; butyrylcholinesterase; comet assay; genotoxicity; glutathione; lipid peroxidation; white blood cells.

Figure 1

The levels of DNA damage measured using the alkaline comet assay in white blood cells and brain cells of male Wistar rats after 1-, 3-, and 7-day (d) treatments with Δ⁹-tetrahydrocannabinol (THC) and in the respective controls. The daily THC dose was 7 mg/kg b.w.; it was dissolved in sesame oil and administered per os. Control rats (CON) received the same daily volume of sesame oil as the THC group. Data represent mean ± standard deviation. There were five rats per group, and 200 comets per rat were scored on duplicate slides (altogether one thousand independent comet measurements per each experimental group were made). * p < 0.05 vs. control (Mann–Whitney U test).