Zinc oxide nanoparticles cause nephrotoxicity and kidney metabolism alterations in rats

Although zinc oxide nanoparticles (ZnO NPs) have been widely used, their potential hazards on mammalian and human remain largely unknown. In this study, the biochemical compositions of urine and kidney from the rats treated with ZnO NPs (100, 300 and 1000 mg/kg, respectively) were investigated using (1)H nuclear magnetic resonance (NMR) technique with the pattern recognition of partial least squares-discriminant analysis. Hematology, clinical biochemistry and kidney histopathological examinations were also performed. Metabolic profiles from rats treated with ZnO NP(S) exhibited increases in the levels of taurine, lactate, acetate, creatine, phosphocholine, trimethylamine-N-oxide, α-glucose, and 3-D-hydroxybutyrate, as well as decreases in lipid, succinate, citrate, α-ketoglutarate, hippurate and 4-hydroxyphenylacetic acid in urine after ZnO NPs treatment for 14 days. A similar alteration pattern was also identified in kidney. Urine choline and phosphocholine increased significantly shortly after ZnO NPs treatment, moreover, some amino acids and glucose also increased during the experimental period. However, succinate, citrate and α-ketoglutarate in urine exhibited a different alteration trend, which showed increases on the first day after ZnO NPs treatment, but decreases gradually until the termination of the study. A similar alteration pattern of urinary (1)H NMR spectra was also detected in kidney. Moreover, ZnO NPs (1000 mg/kg) resulted in significant increases in serum creatine and blood urea nitrogen, decreases in hemoglobin, haematocrit and mean corpuscular hemoglobin concentration, and overt tubular epithelial cell necrosis. These findings show that ZnO NPs can disturb the energy metabolism and cause mitochondria and cell membrane impairment in rat kidney, which may contribute to ZnO NPs-induced nephrotoxicity.