Metabolomics and transcriptomics indicated the molecular targets of copper to the pig kidney

Copper poses huge environmental and public health concerns due to its widespread and persistent use in the past several decades. Although it is well established that at higher levels copper causes nephrotoxicity, the exact mechanisms of its toxicity is not fully understood. Therefore, this experimental study for the first time investigates the potential molecular mechanisms including transcriptomics, metabolomics, serum biochemical, histopathological, cell apoptosis and autophagy in copper-induced renal toxicity in pigs. A total of 14 piglets were randomly assigned to two group (7 piglets per group) and treated with a standard diet (11 mg CuSO₄ per kg of feed) and a high copper diet (250 mg CuSO₄ per kg of feed). The results of serum biochemical tests and renal histopathology suggested that 250 mg/kg CuSO₄ in the diet significantly increased serum creatinine (CREA) and induced renal tubular epithelial cell swelling. Results on transcriptomics and metabolomics showed alteration in 804 genes and 53 metabolites in kidneys of treated pigs, respectively. Combined analysis of transcriptomics and metabolomics indicated that different genes and metabolism pathways in kidneys of treated pigs were involved in glycerophospholipids metabolism and glycosphingolipid metabolism. Furthermore, copper induced mitochondrial apoptosis characterized by increased bax, bak, caspase 3, caspase 8 and caspase 9 expressions while decreased bcl-xl and bcl2/bax expression. Exposure to copper decreased the autophagic flux in terms of increased number of autophagosomes, beclin1 and LC3b/LC3a expression and p62 accumulation. These results indicated that the imbalance of glycosphingolipid metabolism, the impairment of autophagy and increase mitochondrial apoptosis play an important role in copper induced renal damage and are useful mechanisms to understand the mechanisms of copper nephrotoxicity.