Study of the Involvement of Mitochondria in Dent's Disease Using a Mice Model.

Dent's disease is a rare renal tubular disorder characterized by low-molecular-weight-proteinuria, hypercalciuria with nephrocalcinosis or nephrolithiasis, and progressive renal failure. It is frequently associated with inactivating mutations of the CLCN5gene coding for the 2Cl /H exchanger ClC-5. In the kidney, ClC-5 is mainly expressed in early endosomes of proximal tubules (PT) cells where it optimizes the function of the vacuolar H -ATPase to ensure proper endocytosis of low-molecular-weight-proteins. To better understand the cellular mechanisms involved in Dent's disease, we have generated a novel Knock-In mouse model carrying the ClC-5 N340K pathogenic mutation. We have previously demonstrated that these mice display similar clinical features to those observed in patients with Dent's disease. Interestingly, we observed an increase of oxidative stress in their kidney, as evidenced by higher expression of the NADPH oxidase 4, increased H O production, and ROS-related total protein damage in PT cells. Such cellular stress may arise from dysfunctional mitochondria in PT. Here, we therefore investigated the aspect of these organelles in PT cells of WT and N340K 3 month old mice using transmission electron microscopy. Compared to WT mice, mitochondria from mice carrying the N340K mutation exhibited morphologic alterations such as increased roundness, indicating that their function may be altered. Furthermore, to identify potential markers whose urinary excretion could be associated with the progression of Dent's disease, using mass spectrometry, we performed metabolomic analyses of urine form WT and transgenic mice aged of 4, 7 and 10 months. We demonstrated changes in the excretion of metabolites that are crucial of mitochondrial metabolism (tryptophan, quinolinic acid, malate, oxaloadipate, linolenic acid and butyric acid), suggesting that the NAD synthesis pathway, the citric acid cycle, and beta oxidation are affected. The present study shed more light on the pathophysiology of Dent's disease by suggesting that a mitochondrial dysfunction is involved in this disorder.