The Role Of ER Stress And Oxidative Stress In Kidney Injury Induced By Overdose Of Fluoride

Objective Discussion in the mRNA level of ER stress with chronic fluorosis whether was occurred or not with kidney injury and the degree of occurrence. To discuss the mechanisms of kidney injury in the mRNA level of oxidative stress with chronic fluorosis. To verify the level of gene and protein levels detected by a variety of changes in antioxidant enzymes are consistent.Methods 48 male Wistar rats, weighing 90 g ~ 140 g (average 120 g), according to the weight evenly divided into 4 groups and each group 12. The establishment of normal breeding and low calcium food calcium keep the two groups. Normal feeding large group was divided into control group of normal food and normal food (the concentration of F- is 100 mg/L) group. The low calcium food large group was divided into low calcium control group and low calcium food (the concentration of F- is 100 mg/L) group. The body weight was measured and the general state of rats and dental changes were observed once a week during the experimental period of three months. Rats were sacrificed after the choice of bilateral kidney tissue three months later. The one was preserved with liquid nitrogen for RT-PCR experimental study. Another one was used to preserve with polyformaldehyde for pathological section.The content of the uric acid (UA) and malondialdehyde (MDA) and the vitality of the antioxidant enzyme superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the serum were determined by the methods of biochemical assay. These are phosphotungstic acid method, thiobarbituric acid (TBA) method, pyrogallol autoxidation method and dual-dithio nitrobenzoic acid (DTNB) method. Total RNA was extracted from kidney tissue and the expression of mRNA of GSH-Px, SOD, thioredoxin (Trx), GRP78, CHOP, PDI and XBP-1 were determined in the kidney tissue by the methods of RT-PCR. Identifying the product of their fragments length used agarose gel electrophoresis. The GAPDH was as a reference to the relative content of each observation. Through HE staining of the pathological observes the changes in kidney tissue.Results The content of the GSH-Px, SOD and MDA were increased in serum when the rats were exposed to fluoride with normal diet and the rising of GSH-Px was statistical significance (P<0.05). As compared with control group, the content of MDA in serum with fluoride treated was significantly increased than that respective control group, but only the differences between groups with low calcium was statistical significance (P<0.05). As compared with the corresponding control group, the content of uric acid in serum in the normal diet (the concentration of F- is 100 mg/L) (P<0.05) and low calcium (the concentration of F- is 100 mg/L) (P<0.01) group was decreased. It is suggest that the content of uric acid in serum has an important relationship with low calcium diet.The SOD, GSH-Px, Trx and GAPDH fragments of DNA were gone with RT-PCR method. Then they were electrophoresed through the agarose gel. We can see the product of fragment length and the gene in the gene pool (the United States National Library of Genebank) was consisitent with the retrieved by the number of fragments with base. The content of GSH-Px, SOD and Trx at the level of mRNA were increased significantly and the gene expression of SOD was significant (P<0.05) in the kidney tissue treated with fluoride. As compared with the control normal diet group, the level of gene expression of content of SOD was increased significantly in the kidney tissue in the low calcium control group either. In the same treated fluoride conditions, the Trx gene expression in low calcium group was significantly lower than in normal diet group in kidney tissue in rats(P<0.05).The GRP78, XBP-1, CHOP, PDI and GAPDH fragments of DNA were gone with RT-PCR method. Then they were electrophoresed through the agarose gel. We can see the product of fragment length and the gene in the gene pool (the United States National Library of Genebank) was consisitent with the retrieved by the number of fragments with base. The content of GRP78, XBP-1, CHOP and PDI at the level of mRNA were increased significantly but was not significant in the kidney tissue treated with fluoride in the normal diet group. XBP-1 appeared in the editing and its expression was significantly enhanced with statistical significance in the normal diet group (P<0.05) and in the low calcium group (P<0.05) when treated with fluoride. In the same treated fluoride conditions, the PDI gene expression in low calcium group was significantly higher than in normal diet group in kidney tissue in rats(P<0.05) and the same as GRP78 (P<0.05). The results show that both before and after fluoridation, CHOP changed not significantly.The pathological examination of kidney in the experimental period of three months showed that: 1) As compared with normal food control group, the low calcium and fluoride exposed rats showed that the proximal tubule and distal tubule present cellular edema and vacuolar degeneration and sporadic necrosis, mild regeneration recovery and hyperemia of kidney interstitium. 2) As compared with normal food control group, the low calcium exposed rats showed that the proximal tubule and distal tubule present cellular edema and vacuolar degeneration and congestion of kidney interstitium and glomcrulus. 3) As compared with normal food control group, the fluoride exposed rats showed that the proximal tubule and distal tubule present cellular edema and vacuolar degeneration and with characteristics of apoptosis of endothelial cell occasionally.Conclusions The pathological examination of kidney showed that low calcium could aggravate the kidney damage of fluorosis. As compared with normal food control group, the fluoride exposed rats showed that the proximal tubule and distal tubule present cellular edema and vacuolar degeneration. The normal food and fluoride exposed group presented the characteristics of apoptosis of endothelial cell occasionally and the low calcium food and fluoride exposed rats presented the sporadic necrosis and mild regeneration recovery and hyperemia of kidney interstitium in kidney of rats.Uric acid might relieve oxidative stress caused by fluoride. It is suggested that the uric acid may be an indicator to determine the antioxidant to be a chronic fluorosis prompt detection. A certain concentration of fluoride stimulated the antioxidant enzyme gene expression in kidney. It is coincident that antioxidant enzyme activity increased in the serum. Just as arouse the body of oxidative stress and stimulate the body of oxidant/antioxidant response. The oxidative stress may be aggravated when fluoride toxicity combined with low calcium.The ER stress occurred in the kidney tissue of rats through 3 months feeding the high fluoride. It is suggested that ER stress injury of fluorosis was in the protective effect of stage. This was the same as mentioned in front of the damage effects of oxidative stress in the stage. PDI played a role in antagonisted fluoride induced ER stress. To sum up, a certain degree of ER stress through the activation of protective mechanisms such as molecular chaperone gene expression and the closure of a number of harmful cells play a protective effect.It is suggested that both oxidative stress and endoplasmic reticulum stress play a role in the pathogenesy of kidney damage of fluorosis through the pathological picture of kidney tissue, associating with the results of biochemical assay in the serum and the results of molecular biology of correlation factor in kidney.