Aims: To evaluate the specific role of the endocannabinoid/cannabinoid type-1 (CB1R) system in modulating mitochondrial dynamics in the metabolically active renal proximal tubular cells (RPTCs). Materials and methods: We utilized mitochondrially-targeted GFP in live cells (wild-type and null for the CB1R) and electron microscopy in kidney sections of RPTC-CB1R-/- mice and their littermate controls. In both in vitro and in vivo conditions, we assessed the ability of CB1R agonism or fatty acid flux to modulate mitochondrial architecture and function. Results: Direct stimulation of CB1R resulted in mitochondrial fragmentation in RPTCs. This process was mediated, at least in part, by modulating the phosphorylation levels of the canonical fission protein dynamin-related protein 1 on both S637 and S616 residues. CB1R-induced mitochondrial fission was associated with mitochondrial dysfunction, as documented by reduced oxygen consumption and ATP production, increased reactive oxygen species and cellular lactate levels, as well as a decline in mitochondrial biogenesis. Likewise, we documented that exposure of RPTCs to a fatty acid flux induced CB1R-dependent mitochondrial fission, lipotoxicity and cellular dysfunction. Conclusions: CB1R plays a key role in inducing mitochondrial fragmentation in RPTCs, leading to a decline in the organelle's function and contributing to the renal tubular injury associated with lipotoxicity and other metabolic diseases.
Bibliographical noteFunding Information:
information This work was supported by an ERC-2015-StG grant (#676841) as well as a grant from the Israel Science Foundation (ISF; 158/18) to J. T.We are grateful to Dr Yael Friedman from the Bio-Imaging Unit, The Alexander Silberman Institute of Life Science of the Hebrew University for her technical assistance with transmission electron microscopy. We also appreciate the insights and assistance of Mr Dekel Assaf in implementing the quantification methods of mitochondrial morphology described in this work as well as the technical assistance of Dr Liad Hinden and Mr Shahar Azar. The authors declare that no conflict of interest exists. A. D. conducted the experiments and analysed the data. A. P. assisted in conducting the experiments. S. U. conducted and analyzed the in vivo metabolic assessment. R. H. provided reagents and technical assistance. A. N. conducted the LC?MS/MS analysis. A. D. and J. T. designed and supervised the experiments and wrote the manuscript.
This work was supported by an ERC-2015-StG grant (#676841) as well as a grant from the Israel Science Foundation (ISF; 158/18) to J. T.
© 2018 The Authors. Diabetes, Obesity and Metabolism published by John Wiley & Sons Ltd.
- cellular research
- experimental pharmacology