Hormetic effects of a cannabinoid system component, 2-arachidonoyl glycerol, on cell viability and expression profile of growth factors in cultured mouse Sertoli cells: Friend or foe of male fertility?

The generally undesired effects of exocannabinoids on male reproduction include alterations in testicular cell proliferation and function, as well as apoptosis induction. However, this paradigm has been challenged by the ability of endocannabinoids to regulate reproductive function. The present study addresses these paradoxical facts by investigating the effects of the endocannabinoid 2-arachidonoyl glycerol (2-AG) on mouse Sertoli cells' survival and apoptosis, with a mechanistic insight into Sertoli cell-based growth factors' production. The Mus musculus Sertoli cell line (TM4) was exposed to different concentrations of 2-AG, and cell viability was evaluated using MTT assay. Growth factors' gene and protein expressions were analyzed through RT-PCR and western blotting. 2-AG concentration dependently increased TM4 viability, with a slight increase starting at 0.0001 µM, a peak of 190% of the control level at 1 µM, and a decrease at 3 µM. Moreover, 2-AG paradoxically altered mRNA expression of caspase-3 and growth factors. Caspase-3 mRNA expression was down-regulated, and growth factors mRNA and protein expression were up-regulated when using a low concentration of 2-AG (1 μM). Opposite effects were observed by a higher concentration of 2-AG (3 μM). These paradoxical effects of 2-AG can be explained through the concept of hormesis. The results indicate the pivotal role of 2-AG in mediating Sertoli cell viability and apoptosis, at least in part, through altering growth factors secretion. Furthermore, they suggest the involvement of endocannabinoids in Sertoli cell-based physiological and pathological conditions and reflect the ability of abnormally elevated 2-AG to mimic the actions of exocannabinoids in reproductive dysfunction.