The Endocannabinoid System Mediates Cystogenesis in Tuberous Sclerosis Kidney Disease

Background: Tuberous Sclerosis Complex disease (TSC) is caused by an inactivating mutations in TSC genes, leading to mTOR pathway hyperactivation. CKD secondary to angiomyolipoma and renal cysts is a leading cause of morbidity in TSC. The endocannabinoid (eCB) system is involved in kidney pathophysiology. Its ligands act mainly through endocannabinoid receptors, CB1R and CB2R. Here we aimed to explore eCB ligands and receptors involvement in TSC cystic kidney disease.

Methods: We used a TSC mouse model with TSC1 deletion in nephron progenitor cells as well as HK2 cell line with TSC1 deletion using Crispr/cas9. eCB system characterization was performed using western blotting, immunofluorescence staining of kidney sections, real-time PCR for RNA expression and liquid chromatography/inline tandem mass spectrometry analysis for ligand level measurements.

Results: eCB ligands level in TSC kidneys changed significantly with an elevation of N-arachidonoyl ethanolamide and a decline in 2-arachidonoyl levels compared to control. These changes in the eCB ligands were associated with pertubations in the expression level of enzymes involved in their biosynthesis and degradation. The expression and protein level of CB1R was upregulated, and down regulated for CB2R, in TSC1 mouse model and TSC1 null HK2 cell. Furthermore, incubation of HK2 cells with CB1R antagonists prevented the mTOR pathway hyperactivation.

Conclusion: TSC1 deletion in the kidney modifies the eCB system, including ligands, enzymes, and receptors profile. The role of the endocannabinoid system in cystic kidney disease may be mediated by mTORC1 activity and inflammation. CB1R inhibition may ameliorate these TSC associated cell signaling with a beneficial therapeutic potential.