Low-Salt Diet and Cyclosporine Nephrotoxicity: Changes in Kidney Cell Metabolism

Abstract

Cyclosporine (CsA) is a highly effective immunosuppressant used in patients after transplantation; however its use is limited by nephrotoxicity. Salt depletion is known to enhance CsA-induced nephrotoxicity in the rat, but the underlying molecular mechanisms are not completely understood. The goal of our study was to identify the molecular effects of salt depletion alone and in combination with CsA on the kidney using a proteo metabolomic strategy. Rats (n=6) were assigned to four study groups: 1) normal controls, 2) low-salt fed controls, 3) 10 mg/kg/d CsA for 28 days on a normal diet, 4) 10 mg/kg/d CsA for 28 days on low-salt diet. Low-salt diet redirected kidney energy metabolism towards mitochondria as indicated by a higher energy charge than in normal-fed controls. Low-salt diet alone reduced phospho-AKT and phospho-STAT3 levels, and changed the expression of ion transporters PDZK1 and CLIC1. CsA induced macro- and microvesicular tubular epithelial vacuolization and reduced energy charge; changes that were more significant in low-salt fed animal, probably because of their more pronounced dependence on mitochondria. Here, CsA increased phospho-JAK2 and phospho-STAT3 levels and reduced the phospho-IKKγ and p65 proteins, thus activating NF-κB signaling. Decreased expression of lactate transport regulator CD147 and phospho-AKT was also observed after CsA exposure in low-salt rats, indicating a decrease in glycolysis. In summary, our study suggests a key role for PDZK1, CD147, JAK/STAT and AKT signaling in CsA-induced nephrotoxicity and proposes mechanistic explanations on why rats fed a low-salt diet have higher sensitivity to CsA.

Function of CD147 in Atherosclerosis and Atherothrombosis

“…CD147 is known to be involved in the JAK/STAT pathway, which participates in atherosclerosis development [80]. JAK/STAT is an important signaling pathway that regulates initiation/progression of atherosclerosis and remodeling in response to injury.…”

Metabolomics in Nephrotoxicity

“…Low-salt diet and CsA nephrotoxicity were also evaluated using 1 H NMR metabolomics in Klawitter's research group [36]. The study showed that proximal tubular injury was associated with increased urinary acetate, lactate, glucose, amino acids and decreased hippurate, creatinine, 2-oxoglutarate, succinate, and citrate.…”

Proteomic approaches to the study of renal mitochondria

“…In low salt animals, CsA treatment decreased the level of TCA cycle and ETS proteins. CsA more strongly affected the kidneys of rats fed with a low-salt diet due to their higher dependence on the energy production by mitochondrial respiration 99 . In hyperoxaluria, renal tubular epithelial cells are exposed to oxalate which lead to the activation of intracellular responses, including overproduction of free radicals and reactive oxygen species.…”

“…Effect of cyclosporine A (CsA) nephrotoxicity was studied on the kidney of normal and salt-depleted rat models by combined strategy employing proteomics and metabolomics 99 . CsA is used after renal transplantation to prevent organ rejection.…”