Inhibition of diacylglycerol lipase α as a novel strategy to mitigate the nephrotoxicity of cisplatin

Cisplatin is a potent first-line therapy for many solid malignancies such as breast, ovarian, lung, testicular and head and neck cancer. Nephrotoxicity is a primary dose-limiting toxicity and the major obstacle for the clinical use of cisplatin. Approximately 30% of patients that receive cisplatin treatment (either alone or in combination with other chemotherapeutics) will develop kidney damage and that ∼50% of cancer patients showed signs of nephrotoxicity 4 years posttreatment with cisplatin The mechanistic basis for cisplatin-induced kidney damage is not fully understood and no efficient management strategies are currently available. The endocannabinoid (EC) system, which has been initially focused on the central nervous system, also plays important roles in the peripheral organs, including the kidneys. The most well-characterized ECs are anandamide (AEA) and 2- arachidonoylglycerol (2-AG). The biosynthesis of AEA is through the hydrolysis of N-arachidonoyl-phosphatidyl- ethanolamines via at least three distinct biosynthetic routes. The 2-AG is produced by diacylglycerol lipases (DAGLα and DAGLβ), which hydrolyze 2-arachidonoyl-containing diacylglycerols (DAG) to generate 2-AG. After production, ECs bind to the local cannabinoid receptors (CB1 and CB2) in an autocrine or paracrine manner. It has been shown that EC system participates in different kidney diseases, including cisplatin nephrotoxicity, and that interventions of CB receptors are promising therapeutic strategies. Surprisingly, the majority of studies focus on CB receptors, and little is known about roles of ECs metabolic enzymes in kidney damages. It is important to address this significant gap and imperative to investigate the role of ECs enzymes in kidney diseases. Given the fact that 2-AG is 50-fold more abundant than AEA in kidneys and has a similar affinity to CB receptors, we focused on the 2-AG-producing enzyme DAGLs. Our preliminary data showed that DAGLα gene KO protected the kidneys against cisplatin nephrotoxicity in mice, while no difference was observed in DAGLβ KO mice. Furthermore, a selective DAGL inhibitor, DO34, protected against cisplatin-induced damages in human kidney tubular cell line HK-2 cells. Based on the above information, the hypothesis to be tested is that over produced 2-AG contributes to the cisplatin nephrotoxicity and that inhibition of DAGLα protects the kidneys against cisplatin-induced nephrotoxicity. Two Aims are proposed. Aim 1: To determine whether inhibition of DAGLα protects the kidneys against cisplatin-induced nephrotoxicity. Aim 2: To establish that inhibition of DAGL will not interfere with the antitumor actions of cisplatin. Studies will involve both pharmacological and genetic interventions as well as systemic and kidney-targeted approaches for DAGLα inhibition. The findings from these proposed studies will identify that the activation of DAGL/2-AG production is a novel molecular mechanism in cisplatin-induced nephrotoxicity and suggest new therapeutic strategies for the prevention and treatment of cisplatin-induced nephrotoxicity by inhibition of DAGLα, either using DAGL inhibitor DO34 or kidney-targeted delivery of DAGLα siRNA, given that FDA has recently approved several siRNA-based drugs.