The General Toxicity Research Of Nano-coppers And Its Effects On Rat Hepatic Cytochrome P450 Enzymes

Nano-copper has good antibacterial and growth promotion effects,so it is expected to become a new type of feed additive.However,since the toxicological effect of nano-coppers are different from the conventional copper sources,and there is no report about the effect of nano-copper on cytochrome P450（CYP450）enzymes,which will increase the risk of nano-copper used as feed additive or in combination using with other drugs.So,we carried out the general toxicity study of nano-coppers with various particle sizes,and its effect and preliminary mechanism on the expression of CYP450 enzyme in rat liver in the case of sub-chronic exposure.1.Characterization of nano-copper particles:The results showed that the average particle diameters of the four copper particles were 27.6±9.5 nm（30 nm）,53.2±17.6 nm（50 nm）,and89.5±33.4 nm（80nm）,and 987.4±436.7（1μm）perspectively.2.Acute toxicity study of nano-copper in rats:The LD₅₀ of different sources of copper were tested by the up and down method.The results were 133.8 mg/kg（Cu ions）,1022.0 mg/mg（30 nm Cu NPs）,1750.0 mg/kg（50 nm Cu NPs）,2075.0 mg/kg（80 nm Cu NPs）and>5000 mg/kg（1μm Cu MPs）.The results of acute toxicity showed that the LD₅₀ was positively correlated with particle size.The smaller the particle size have shown the greater acute toxicity.The doses of 50,100 and 400 mg/kg were chosen to evaluate the 7 days repeat oral exposure toxicity of nano-copper particles with different particle sizes based on the acute toxicity tests results.The blood hematology and biochemical indicators showed that the nano-copper of different particle sizes caused similar toxic effects.The results shown that nano-copper caused significant increase in the number of white blood cells,significantly reduced the number of red blood cells and lymphocytes.The liver damage indicators also increased.The Cu NPs（80 nm）significantly increased the levels of oxidative stress and inflammation.3.Toxicity and changes of liver CYP450 enzymes after sub-chronic exposure to Cu NPs:Rats were exposure to 80 nm nanao-copper for 28 days at the doses of 50 mg/kg(1/40 LD₅₀),100mg/kg(1/20 LD₅₀)and 200 mg/kg(1/10 LD₅₀)to establish a sub-chronic exposure model.The results showed that nano-copper caused a dose-dependent decrease in body weight and absolute liver weight.High doses（200 mg/kg）of nano-copper significantly increased serum levels of AST and ALP.High doses of nano-copper（200 mg/kg）significantly increased the level of oxidative stress and inflammation cytokines,but the mRNA and protein expression of CYP450 1A2,2C11,2D6 and 3A1 were decreased in liver of rat.At the same time,the enzyme activities of CYP450 1A2,2C11,2D6,2E1 and 3A1 were reduced in a dose-dependent manner.4.Mechanism of CYP450 enzymes down regulation by Cu NPs in liver of rat:We analyzed the nuclear receptors and signaling pathways involved in the regulation of CYP450 enzymes in rat liver,which indicated that Cu NPs（80 nm）significantly reduced the mRNA and protein expression of CAR,PXR and AHR in the liver.The signal pathways of NF-κB,MAPK and STAT5 were also activated by nano-copper.In summary,the smaller size of Cu NPs induced the smaller LD₅₀ and similar toxic symptoms,but the symptoms were in different degree.Sub-chronic toxicity test showed that80 nm of copper particles significantly altered the normal physiological and biochemical functions of rat liver.Nano-copper activated NF-κB,MAPK,and STAT5 signaling pathways by inducing inflammatory responses and oxidative stress,which interaction with nuclear receptors to reduce the expression of drug-metabolizing enzymes.