Protective Effect Of Nano-selenium On Cadmium Chloride Induced Liver Injury In Male Mice

The heavy metal cadmium(Cd)is widely used in manufacturing,agriculture and materials because of its extended flexibility.With the increasing use of cadmium-containing products,the accompanying environmental pollution and public health problems become more and more prominent.Cadmium into the human or animal,will be in the liver,kidney,bone and lung and other tissues deposition,causing toxicity.Liver is one of the target organs of cadmium toxicity.Exposure to high concentrations of cadmium can induce strong oxidative stress and cause irreversible damage to the liver.It is very important to find effective antagonists for cadmium toxicity because it can damage the body’s defense system and induce oxidative damage of liver,apoptosis and excessive autophagy under sustained exposure to low concentrations of cadmium.As a trace essential element,selenium can effectively exert heavy metal antagonism,but its safe dose range is narrow,so it is necessary to explore the application of new selenides in heavy metal antagonism.Nano-selenium is a kind of small size,high bioactivity elemental metal material,which has advantages over ordinary inorganic selenium in antioxidant,anti-cancer and anti-diabetes.In the field of antagonistic heavy metal toxicity,nano-selenium can reduce the accumulation of heavy metals in tissues and promote their excretion,but the specific antagonistic mechanism is still unknown.Therefore,this experiment aims to synthesize and characterize chitosan coated nano-selenium,and study its protective effect on liver injury induced by single high concentration cadmium exposure and multiple low concentration cadmium exposure in mice,mainly including the following contents:(1)In this study,chitosan coated nano-selenium was prepared by chemical combination of inorganic selenium and vitamin C,and its physical properties were detected by transmission electron microscopy,scanning electron microscopy,infrared and X-ray diffraction methods.The results show that the nano-selenium synthesized in this experiment is zero-valent elemental selenium,which is bonded with chitosan by hydrogen bond and has uniform size spherical structure.(2)This study investigated the protective effect of nano-selenium on liver injury induced by a single high concentration of cadmium exposure(126 mg/kg)in mice.64 SPF Kunming male mice were randomly divided into blank control group(Con group),cadmium chloride group(Cd group),sodium selenite group(SSe group),nano selenium group(NSe group),and 16 mice per group.On the 14 th day,high concentration of cadmium(126 mg/kg)was given by gavage.The results showed that high concentration of cadmium exposure can cause mental burnout,slow movement,anorexia,anorexia and other toxic symptoms in mice.By inhibiting Nrf2 pathway,the mRNA expressions of Nrf2,HO-1,NQO-1,GSH-Px,CAT,SOD and GST in liver tissue were significantly down-regulated by high concentration cadmium stress(P < 0.05),the ROS content in liver cells was increased,and the GSH content in mice was significantly decreased.Significantly decreased T-AOC activity in mice(P < 0.05),and induced oxidative stress to cause liver congestion and hepatocyte degeneration.Nano selenium and sodium selenite(0.2 mg/kg)can increase the activity of T-SOD and the content of GSH,reduce the level of MDA,and alleviate the liver damage induced by high cadmium exposure in mice by activating Nrf2 pathway,and the antagonistic effect of nano selenium is better than that of sodium selenite.(3)This study investigated the protective effect of nano-selenium on liver injury induced by multiple low concentration cadmium exposure(5 mg/kg)in mice.108 SPF Kunming male mice,They were randomly divided into 6 groups(blank control group),cadmium chloride group(Cd group),low-dose nano-cadmium selenide group(LNSe+Cd group),medium-dose nano-cadmium selenide group(MNSe+Cd group),high-dose nano-cadmium selenide group(HNSe+Cd group)and single high-dose nano-selenium group(HNSe group),with 18 animals per group.Sterile distilled water,cadmium solution and nano-selenium solution at low(0.5 mg/kg),medium(1 mg/kg)and high(2 mg/kg)doses were administered,respectively.The experiment period was 28 days.The results showed that multiple exposure to low concentrations of cadmium significantly inhibited the growth of mice,decreased liver index(P < 0.05),increased the accumulation of cadmium in liver,induced the production of large amounts of ROS in liver,and significantly decreased the activities of CAT and GSH-Px in serum and liver(P < 0.05).The mRNA expression levels of Nrf2,HO-1,NQO-1,GSH-Px,CAT and GST in Nrf2 pathway were significantly down-regulated(P < 0.05),which induced oxidative damage of liver.Cadmium significantly increased mitochondrial depolarization,up-regulated the protein and mRNA expression levels of pro-apoptotic factors(Bax,Cytc1,Caspase-9 and Caspase-3)in liver(P < 0.05),down-regulated the protein and mRNA expression levels of anti-apoptotic factor Bcl-2(P < 0.05),and induced liver apoptosis.Cadmium significantly up-regulated the protein and mRNA expression levels of Atg7,LC3 II/I,and Beclin1 in liver(P < 0.05),and down-regulated the mRNA and protein expression levels of p62 in liver(P < 0.05),resulting in a large number of autophagy lysosomes in mouse liver cells,leading to excessive autophagy in liver.In addition,the activities of ALT,AST,AKP and GGT in serum were significantly increased(P < 0.05),while the activity of ALB was significantly decreased(P < 0.05),indicating that cadmium could damage liver tissue structure and cause liver dysfunction in mice.However,low,medium and high concentrations of nano-selenium can reduce ROS,protect mitochondrial structure integrity,reduce liver cell apoptosis rate,inhibit excessive autophagy,enhance the antioxidant capacity of the body and resist the liver damage induced by cadmium stress in mice by activating Nrf2 pathway.High dose of nano-selenium has the best protective effect.In conclusion,the nano-selenium synthesized in this study has good bioactivity against cadmium toxicity.On the one hand,0.2 mg/kg nano-selenium can alleviate liver injury induced by single high cadmium exposure(126 mg/kg)by reducing oxidative damage pathway.On the other hand,low(0.5 mg/kg),medium(1 mg/kg)and high concentration(2 mg/kg)nano-selenium can effectively resist liver injury induced by multiple low concentration cadmium exposure(5 mg/kg)by clearing ROS,reducing hepatocyte apoptosis and inhibiting excessive autophagy.