The Effects Of Chronic Trace Chromium (â…¥) On Oxidative Stress Of Mice Liver Cells

BackgroundSince1988the second-generation metal on metal (Metal-on-Metal MOM) joint was used by B.G.Weber clinically, over275,000cases Metasul joint was implanted in humans worldwide, which is considered to be more applicable for the young and active patients. According to whether retaining the femoral neck,Metal on metal hip prostheses can be divided into the metal on metal total hip prosthesis and the surface joint prosthesis.Because of its good stiffness and strength, superior abrasion resistance and corrosion resistance, the Metasul joint is considered to have a good prospect. However, the metal prosthesis implanted in the body withstands bending, impact and friction, mechanical force constantly, which may be result in the destruction of the joint prosthesis surface inert oxide layer and continuous release of metal ions. It is generally believed that the MOM prosthesis implantation will cause the rise of human metal ion concentration. Sauve, etc. found that the serum cobalt and chromium concentration of patients implanted in Metasul joints were higher than the control group3-5times after30years of follow-up study. Maezawa, K.found that the metal ion concentration in the blood of44patients which were implanted in Metasul joints gradually increased at fisrt three years, and then25%of the metal ion concentration in patients decreased after4years, although16.3%of metal ion concentration gradually increased after7years of follow-up study. Chinese scholars had researched25surface hip replacement with a2-year follow-up.The results showed that the metal ion concentration gradually increased after postoperative6months, then decreased gradually and stabilized, but still higher than normal. Multi-center clinical studies have confirmed:compared to metal on polyethylene prostheses MOM would produce less wear particles, but higher metal ion concentration in the periprosthetic blood and tissue.With the development of modern metallurgy technology and biological materials, The cobalt-chromium alloy (which the chromium content of about50-70%) dues to better science and mechanical properties and becomes the main material of contemporary metal on metal hip prosthesis. With the implantation of the prosthesis, chromium will continue to slow release. The most research has focused on metal ions in the periprosthetic bone, soft tissue and immune cells Currently:①The effects of continuous releasion of metal ions from prosthesis on the surrounding soft tissue,Such as the cause of inflammatory pseudotumor.②prosthesis aseptic loosening. The loosening of the prosthesis is one of the major complications after surgery. And most scholars believe that the reasonof loosening of the prosthesis is periprosthetic osteolysis.③The metal ions can induce monocytes and macrophages release a variety of cytokines, causing immune responses. The liver is the body’s largest detoxifying glands, with its complex and diverse biochemical functions. The most metal ions, including chromium are required for biological conversion in the liver cells. But the current study of effects of chronic trace chromium on liver cells is not enough.Chromium is one of the essential trace element in the body and gradually reduces with increasing age. Physiological doses of chromium has an important role in the regulation of blood sugar and cholesterol.The exist form of chromium are trivalent and hexavalent in the body. Toxicology and environmental health research has confirmed that a large number of chromium ions in a short time can cause changes in the hepatocyte cell signal transduction pathways, which led to the enzymology, morphology, and irreversible damage and even apoptosis. The toxicity of chromium ions related with their valence state greatly. The toxicity of hexavalent chromium is more100times than trivalent chromium.The hexavalent chromium enters cells through nonspecific anionic channels and is reduced to Cr(III)both enzymatically and nonenzymatically.This process will cause the cell oxidative stress, resulting in a large number of peroxides.The large of peroxides lead to a cascading waterfall of reaction, causing lipid peroxidation and DNA damage. Meanwhile,in order to fight the oxidative stress reaction cells will start anti-oxidative stress system to maintain the stability of the intracellular environment. These anti-oxidative stress enzymes, include superoxide dismutase (SOD), glutathione a (GSH), glutathione reductase (GR) and glutamate cysteine ligase (GCL).Chromium exists mainly in the form of hexavalent in the current metal on metal hip prosthesis. Toxicology and Environmental Health Research, the MOM hip joint prosthesis implanted in the body, chromium (VI) ion release is a slow and traces the process. Corrosion of the metal prosthesis usually0.15-0.3μg/cm2/h or30μ/d, or11mg/y.The blood chromium content of literature reported that between2.6-26μg/L, and the life of the prosthesis over10years.May the slow release of trace chromium (VI) cause the oxidative stress of liver cells? How the liver cells against oxidative stress reaction? It is a great significance for assessing the security of MOM prostheses to confirm the effects of chronic trace chromium (VI) on oxidativestress of liver cells.Objectivel.To build chronic trace chromium (VI) in mice to simulate metal on metal hip implanted in the body caused by chromium (VI) slow release.2.To explore wether chronic trace chromium (VI) can cause oxidative stress in mouse liver cells.3. To explore wether chronic trace chromium (VI) can cause anti-oxidative stress in mouse liver cellsand what type of changes.4.Investigate the security of the distant target organ liver for the metal on metal prosthesis.Materials and MethodsAccording to the experimental design, the80NIH mice were randomly divided into four groups and were injected intraperitonealy with CrO3at a dose of Omg/kg,5mg/kg,10mg/kg and2Omg/kg every other day.The experiment lasted16weeks. Every four weeks, five mice were killed by cervical dislocation The blood was collected to detect blood chromium content by extirpating the eyeballs and the tissue of livers was quickly dissected off after the mice were sacrificed. One part of liver tissue was used by HE staining and transmission electron microscopy, the remaining liver tissue was washed by ice-cold saline, and was frozen in liquid nitrogen for elevation of the activity level of oxygen free radicals (ROS), lipid peroxidation malondialdehyde content (MDA), superoxide dismutase (SOD), glutathione activity (GSH), glutathione reductase (GR),and aslo for the expression of glutamate cysteine ligase (GCL)Results:1. The blood chromium content of5mg/kg and10mg/kg groups reached its peak, and then maintained at a certain concentration, reaching a plateau. For the high dose group, blood chromium concentration continues to rise, no significant plateau.2. ROS values of5mg/kg and10mg/kg groups groups were higher than the control group, and the difference was statistically significant, with the extension of exposure time,two groups gradually approaching a plateau.For the high dose group, ROS continues to rise, no obvious plateau. This is similar to the results of1.3.At each time point, the MDA content of20mg/kg group was higher than Omg/kg group, but the difference was not statistically significant.4、Compared with the control group, the CAT levels of5mg/kg,10mg/kg groups had no significant reduction, and then reduced significantly in the next each time point,. With the extension of exposure time,the CAT level20mg/kg group reduced and the difference was statistically significant.5.Compared with the control group, the activity of SOD of20mg/kg group reduced, and had a significant difference. With the extension of exposure time, the SOD activity significantly decreased.6.Compared with the control group, the GSH levels of5mg/kg,10mg/kg groups had no significant reduction, and then reduced significantly in the next each time point. With the extension of exposure time.the GSH level20mg/kg group reduced and the difference was statistically significant. 7. Compared with the control group, the GR activity of5mg/kg,10mg/kg groups increased and20mg/kg group significantly decreased, and differences were statistically significant. With the extension of exposure time, the GR activity of all groups decreased compared with the control group, and the difference was statistically significant8.The protein bands of GCL expression was analysed by image-proPlus image.The scan results:compared with the control group, The GCL expressions of5mg/kg and10mg/kg groups were significantly increased at each time point20mg/kg group GCL expression significantly decreased after8weeks.And all differences were statistically significant.9. HE staining of liver cells:Compared with the control group,5mg/kg group and10mg/kg group had no obvious abnormalities.20mg/kg group liver cells can be seen a small amount of vacuolar degeneration, the membrane is slightly wrinkled at16weeks. Transmission electron microscopy revealed:compared with the control,20mg/kg group had apoptosis changes at16weeks:nuclei shrinkage, chromatin condensation and the occurrence of side dimerization; And mitochondria became dense, steep disappeared, had vacuolization change.conclusions:1. Chronic trace chromium (Ⅵ) exposure can cause oxidative stress of mouse liver cells, and showed a certain amount of time and concentration-dependent.2. Chronic trace chromium (Ⅵ) caused oxidative stress in mouse liver cells.It prompted the release of chromium ion from MOM prosthesis caused oxidative stress distant target organs liver3Chronic trace chromium (VI) cause the changes of anti-oxidative stress system of mice liver cells.4metal on metal prosthesis to the safety of distant target organ liver still needs to further assessment.