Abstract

UR-144, a cannabinoid receptor agonist, is widely used alone or in combination with other synthetic cannabinoids (SCs) all over the world. At overdose, cardiovascular symptoms have been reported and the underlying molecular mechanisms of these adverse effects are not known. It is highly important to clarify the toxic effects of UR-144 for the treatment of poisoning. In the present study, the molecular mechanism of cytotoxic effects of UR-144 is evaluated on a cardiomyoblastic cell line using WST-1 and LDH assays. Apoptosis/necrosis, autophagy, and ROS (reactive oxygen species) levels were determined using flow cytometry. Cytoplasmic Ca²⁺ levels were measured by using a fluorogenic calcium-binding dye. Released and cytoplasmic troponin T levels, a specific marker of cardiotoxicity, were examined with western blot. For the evaluation of the role of DAPK1, on UR-144-induced cell death, DAPK1 activity and DAPK1 protein level were investigated. Its cytotoxic effects increased in a dose-dependent manner for WST-1 and LDH assays, while membrane damage, one of the signs of necrotic cell death, was more remarkable than damage to mitochondria. Cytoplasmic Ca²⁺ levels rose after high-dose UR-144 treatment and inhibition of DAPK1 activity ameliorated UR-144-induced cytotoxicity. Released troponin T significantly increased at a dose of 200 µM. ROS and total antioxidant capacity of cells were both reduced following high dose UR-144 treatment. The results indicated that UR-144-induced autophagic and necrotic cell death might be a consequence of elevated cytoplasmic Ca²⁺ levels and DAPK1 activation. However, in vivo/clinical studies are needed to identify molecular mechanisms of cardiotoxic effects of UR-144.