Effects of different doses of fluoride on expression of IRE1α-ASK1-JNK proteins in rat renal cortex / 中华地方病学杂志

ABSTRACT

Objective:To investigate the expression and significance of endoplasmic reticulum stress apoptosis pathway related proteins in renal cortex of rats with chronic fluorosis.Methods:Twenty four healthy SD rats were divided into 4 groups (6 rats/group, half male and half female) according to their body mass (100 - 120 g) by random number table method, rats in control group drank tap water (fluoride content < 0.5 mg/L), and in low, medium and high fluoride groups drank tap water with fluoride content (sodium fluoride) of 10, 50 and 100 mg/L, respectively. After 180 days of feeding, dental fluorosis was examined, 24-hour urine sample was collected and the content of fluoride in urine was detected by fluoride ion selective electrode method. Renal tissue was taken after anesthesia, and the pathological changes of renal cortex were observed by hematoxylin-eosin (HE) staining. The expressions of endoplasmic reticulum stress apoptosis pathway related proteins [inositol-requiring enzyme 1α (IRE1α), apoptosis signal-regulating kinase 1 (ASK1), C-Jun N-terminal kinase (JNK) and phosphorylated JNK (P-JNK)] were determined by immunohistochemical staining in rat renal cortex.Results:No dental fluorosis was found in control group. The incidence of dental fluorosis in low, medium and high fluoride groups were 2/6, 5/6 and 6/6, respectively. Compared with control group [(5.707 ± 1.190) mg/L], the urinary fluoride in low, medium and high fluoride groups [(17.028 ± 3.006), (34.378 ± 12.045), (94.759 ± 31.773) mg/L] was significantly higher ( P < 0.05), and the urinary fluoride in high fluoride group was higher than that in low and medium fluoride groups ( P < 0.05). HE staining showed that, compared with control group, the cell volume of renal tubules and glomeruli in medium and high fluoride groups increased, the cells arranged closely, and the eosinophilia of the cytoplasm increased. The immunohistochemical staining results showed that there was no significant difference in the expression of JNK protein in rat renal cortex between control group and low, medium and high fluoride groups ( F = 0.07, P > 0.05). The expressions of IRE1α, ASK1 and P-JNK proteins in rat renal cortex in high fluoride group were higher than those of control, low and medium fluoride groups ( P < 0.05), and the expressions of IRE1α and ASK1 proteins in medium fluoride group were significantly higher than those in control and low fluoride groups ( P < 0.05). Conclusion:Long-term excessive fluoride intake can lead to renal cortex injury in rats, and the mechanism of injury may be related to the activation of IRE1α-ASK1-JNK endoplasmic reticulum stress apoptosis pathway.