Metabolomics in Nephrotoxicity

The later that a molecule or molecular class is lost from the drug development pipeline, the higher the financial cost. Minimizing attrition is therefore one of the most important aims of a pharmaceutical discovery programme. Novel technologies that increase the probability of making the right choice early save resources, and promote safety, efficacy and profitability. Metabonomics is a systems approach for studying in vivo metabolic profiles, which promises to provide information on drug toxicity, disease processes and gene function at several stages in the discovery-and-development process.

The clinical use of cisplatin (cis-diamminedichloroplatinum II) is highly limited by its nephrotoxicity. The precise mechanisms involved in cisplatin-induced mitochondrial dysfunction in kidney have not been completely clarified. Therefore, we investigated in vivo the effects of cisplatin on mitochondrial bioenergetics, redox state, and oxidative stress as well as the occurrence of cell death by apoptosis in cisplatin-treated rat kidney. Adult male Wistar rats weighing 200-220 g were divided into two groups. The control group (n = 8) was treated only with an intraperitoneal (i.p.) injection of saline solution (1 ml per 100 g body weight), and the cisplatin group (n = 8) was given a single injection of cisplatin (10 mg/kg body weight, i.p.). Animals were sacrificed 72 h after the treatment. The cisplatin group presented acute renal failure characterized by increased plasmatic creatinine and urea levels. Mitochondrial dysfunction was evidenced by the decline in membrane electrochemical potential and the substantial decrease in mitochondrial calcium uptake. The mitochondrial antioxidant defense system was depleted, as shown by decreased GSH and NADPH levels, GSH/GSSG ratio, and increased GSSG level. Moreover, cisplatin induced oxidative damage to mitochondrial lipids, including cardiolipin, and oxidation of mitochondrial proteins, as demonstrated by the significant decrease of sulfhydryl protein concentrations and increased levels of carbonylated proteins. Additionally, aconitase activity, which is essential for mitochondrial function, was also found to be lower in the cisplatin group. Renal cell death via apoptosis was evidenced by the increased caspase-3 activity. Results show the central role of mitochondria and the intensification of apoptosis in cisplatin-induced acute renal failure, highlighting a number of steps that might be targeted to minimize cisplatin-induced nephrotoxicity.

Peroxisome proliferator-activated receptor-alpha (PPARalpha) agonists such as fenofibrate are used to treat dyslipidemia. Although fenofibrate is considered safe in humans, it is known to cause hepatocarcinogenesis in rodents. To evaluate untargeted metabolic profiling as a tool for gaining insight into the underlying pharmacology and hepatotoxicology, Fischer 344 male rats were dosed with 300 mg/kg/day of fenofibrate for 14 days and the urine and plasma were analyzed on days 2 and 14. A combination of liquid and gas chromatography mass spectrometry returned the profiles of 486 plasma and 932 urinary metabolites. Aside from known pharmacological effects, such as accelerated fatty acid beta-oxidation and reduced plasma cholesterol, new observations on the drug's impact on cellular metabolism were generated. Reductions in TCA cycle intermediates and biochemical evidence of lactic acidosis demonstrated that energy metabolism homeostasis was altered. Perturbation of the glutathione biosynthesis and elevation of oxidative stress markers were observed. Furthermore, tryptophan metabolism was up-regulated, resulting in accumulation of tryptophan metabolites associated with reactive oxygen species generation, suggesting the possibility of oxidative stress as a mechanism of nongenotoxic carcinogenesis. Finally, several metabolites related to liver function, kidney function, cell damage, and cell proliferation were altered by fenofibrate-induced toxicity at this dose.