| Background and objectiveThe serious environmental pollution caused by heavy metals has become more and more serious,and the long-term accumulation of cadmium in the human body,especially in the kidney,can cause serious toxic damage to the human body.Therefore,we used transcriptomics,proteomics and metabolomics to detect the change of expression level of mRNA,protein,metabolin,to investigate the toxicity of cadmium on the kidney and revel the toxicity-damage mechinanism on systermic biological level.Methods1.Cadmium-induced nephrotoxicity in rats:SD rats were injected subcutaneously with cadmium chloride 0.6mg/kg for 6 weeks and 12 weeks to establish low-dose cadmium chronic toxicity rat model,to observe the toxic effects of cadmium on rat kidney and assess degree of renal impairment.2.Transcriptomics:Affymatrix RTA1.0 full expression of the chip of rat kidney was used to identificate and detect expressed change of mRNA of kidney after renal injury induced by cadmium in rats,screen differentially expressed mRNA.3.Proteomics:iTRAQ proteomics was used to identificate and detect expressed change of protein profilings after renal injury induced by cadmium in rats,screen differentially expressed protein.4.Metabolomics:Ultra-High Performance Liquid Chromatography-Mass Spectrometry of non-targeted metabolites was used to identify cadmium-induced renal toxicity in rats after renal damage changes,screen for different changes in metabolic compounds.5.Bioinformatics analysis:The differentially expressed mRNA,protein,metabolic compounds from transcriptomics,proteomics,metabolomics,respectively,were used to enrichment analyse on the mRNA,protein,final metabolite level,respectively.The systematic analysis to revel one integrated chain pathway or one key gene/protein.6.qPCR,Western blot:Validate the expression level of the identified key gene/protein on mRNA and protein level,respectively.7.The cadmium toxicity model of rat renal proximal tubule NRK-52E cell and of humal proximal renal tubule HK-2 cell:rat and human proximal tubule cells were used to validte the expression change of key gene/protein after cadmium treated,and revel the function mechanism.Results1.After 6 weeks and 12 weeks exposure to cadmium chloride,there were no significant change of renal cell necrosis were observed in HE staining microscope,but the apoptosis level of kidney cell were significanty increased by TUNEL test.The urinary cdmium of rats were significantly increased.The expression ofβ2-microglobulin,renal injury molecule-1 and N-acetyl-β-D-glucosidase were significantly increased in the urine of rats.2.The transcriptomics of 6week and 12week screened out 1153,906 differentially expressed genes,and 782 genes in the integrated data of 6 week and 12 week.43 6,176 differentially expressed proteins were screened out in 6 week and 12 week of proteomics data,and 866 proteins in the integrated data of 6 week and 12 week.75,45 differentially expressed metabolic compounds were screened out in 6 week,12 week of metabolomics.3.GO enrichment and KEGG enrichment analysis of differential genes,differential proteins,differential metabolites from transcriptomics,proteomics,metabolomics reveal three integrated pathways:Fc gamma R-mediated phagocytosis,Glutathione metabolism,Metabolism of xenobiotics by cytochrome P450,they play a consistent role on the level of mRNA,protein,metabolites.4.qPCR and Western blot validate the expression of Fc gamma R-mediated phagocytosis pathway and key protein PLD1 in kidney of cadmium-treated rats.The expression trendency were consistent with the transcriptomics and proteomics.5.The cadmium-induced model of renal proximal tubule epithelial cell rat NRK-52E cell and human HK-2 cell validate the expression tendency of key protein PLD1 of Fc gamma R-mediated phagocytosis pathway were consistent with the tendency of rat model and transcriptomics and protomics.Conclusion1.Chronic low-dose cadmium exposure caused obvious toxicity of rat kidney and renal dysfunction.2.Fc gamma R-mediated phagocytosis pathway and the key protein,PLD1,may play a role in the mechanism of cadmium-induced renal injury in renal proximal tubules.3.Transcriptomics,proteomics and metabolomics can accurately reflect the changes and results of cadmium-induced renal injury from mRNA,protein and metabolite levels,and may systemic revel and explain the mechanism of cadmium-induced renal toxicity from the system level. |
