Role Of Autophagy And Ferroptosis In The Mechanism Underlying Rat Kidney Injury Caused By Hexavalent Chromium

Objective:Chromium is widely used in industry and manufacturing industry in China.Hexavalent chromium is one of the main forms of chromium,which is toxic to kidney.This study aimed to observe the damage to the kidney of rats caused by hexavalent chromium(VI),explore the role of autophagy and ferroptosis and further explore the toxic effect mechanism of Cr(Ⅵ)-induced kidney injury,which will lay an experimental foundation for the clinical therapy of kidney injury caused by Cr(Ⅵ).Methods:32 rats were randomly divided into the control group,low dose group,medium dose group and high dose group according to the exposure dose of 0.0,0.2,0.4,0.8mg/kg·bw potassium dichromate.Rats were intraperitoneally injected with different doses of potassium dichromate solution five days a week for five weeks,and rats in the control group were administered the equal volume of saline.After Cr(Ⅵ)didn’t administer to rats,blood was collected from the abdominal aorta and serum was separated.The rat kidney function indexes including the serum creatinine(CR)and urea nitrogen(URE)were measured by automatic biochemical analyzer.The kidneys were taken out and weighed,the viscera coefficient was calculated and subsequently the pathological section was prepared.The expression of autophagy-related proteins BNIP3,Beclin-1,LC3 B and ferroptosis-related proteins GPX4 and Tf R1 was detected by immunohistochemistry.The expression of autophagy-related proteins BNIP3,Beclin-1,LC3 B,ferroptosis-related proteins GPX4,Tf R1 and endoplasmic reticulum stress(ERs)protein Grp78 was detected by Western blot.The iron content in kidney tissue was detected by the iron ion detection kit.Results:Compared with the control group,the rats in the model group showed anorexia and poor mental state.After Cr(Ⅵ)didn’t administer to rats,the renal viscera coefficient of rats in the medium and the high dose group significantly increased compared with the control group(P<0.05).The level of serum CR in the medium and high dose groups were significantly higher than that in the control group(P<0.05).There was significantly different in the blood URE content among all the groups(P<0.05).HE staining results showed that in the low-dose group,there was a small amount of inflammatory cell infiltration and cytoplasmic vacuolization in the kidneys of the rats;in the medium-dose group,there was inflammatory cell infiltration and glomerular cystic stenosis with severe cytoplasmic vacuolization;in the high-dose group,there was a large amount of inflammatory cell infiltration with severe cellular structure deformation and more severe glomerular cystic stenosis.According to the results of immunohistochemistry and Western blot,the expression of Beclin-1 in the low dose group was significantly elevated compared with that in the control group(P<0.05),and the expression of Beclin-1 in the middle and high dose group was significantly elevated compared with that in the control group and low dose group(P<0.05).And the expression of BNIP3,LC3 B and endoplasmic reticulum(ER)stress protein Grp78 in the model groups was significantly elevated compared with the control group(P<0.05),and there was a significant difference among all the exposure groups(P<0.05).The expression of ferroptosis-related protein GPX4 in the model group was significantly decreased compared with the control group(P<0.05),and there was a significant difference among all the exposure dose groups(P < 0.05).The expression of Tf R1 protein in the middle dose group was significantly elevated compared with the control and low dose group(P < 0.05).The expression of Tf R1 protein in the high dose group was significantly elevated compared with other groups(P < 0.05).The iron content test results showed that the iron content in the medium-dose group was significantly higher than that in the control group and low dose group(P < 0.05),and the iron content in the high-dose group was higher than that in the other groups(P<0.05).Conclusion:1.Cr(Ⅵ)can cause the damage to kidney and endoplasmic reticulum stress in rats.2.Cr(Ⅵ)can result in over-autophagy by up-regulating the expressions of BNIP3,Beclin-1 and LC3 B proteins,which may be one of the mechanisms that Cr(Ⅵ)causes the damage to kidney.3.Cr(Ⅵ)can result in ferroptosis by down-regulating the expression of ferroptosis-related protein GPX4 and up-regulating the expression of Tf R1,resulting in increased iron content,which may be one of the mechanisms that Cr(Ⅵ)causes the damage to kidney.