Yongmin Xiong
Director of the Endemic Institute of Xian Jiaotong University, China
Title: The Study on the Relationship between Selenium and Kashin-Beck Disease
Biography
Biography: Yongmin Xiong
Abstract
Background: Kashin-Beck disease (KBD) is an endemic, disabling and deforming osteoarthropathy, and mainly affects children or teenagers in growth and development period. The mainly pathological changes in KBD are degeneration and necrosis in joint cartilage and epiphyseal plate cartilage. The disease has been found over 160 years, but, its etiology remains unclear. Epidemiological investigation of environmental risks has shown that selenium deficiency may contribute to the etiopathogenesis of KBD and Se supplementation could significantly decrease the incidence of KBD. Thus, it is considered that Se deficiency is a main environmental factor of KBD, however, the exact molecular mechanism for KBD treatment with Se is still obscure.
Objective: Screening of KBD susceptibility genes and related functional experiments were conducted in order to illuminate molecular mechanism of selenoprotein on cartilage cell oxidative stress, inflammation and apoptosis signaling pathway, and further search new molecular targets for the early diagnosis, warning and treatment of KBD.
Methods: Selenoprotein gene transcription level, protein expression level and enzymatic activity in KBD and normal blood and cartilage samples were detected by using qRT-PCR, ELISA and Western blot. Selenoprotein single nucleotide polymorphisms (SNPs) were detected by using PCR-RFLP and ARMS-PCR. The protein expression levels of inflammation and oxidative stress signaling molecules in whole blood and chondrocytes were detected by western blot. The chondrocyte oxidative damage model was established using hydrogen peroxide tert butyl alcohol (tBHP), and the oxidative damage effects on apoptosis and oxidative stress, inflammation signaling pathways in chondrocyte were observed in the model to explore protective mechanism of selenium.
Results：1. The mRNA expression levels of 9 selenoprotein genes in blood and 4 in cartilage were detected, among which mRNA expression of GPx1, GPx4, SEPP, TrxR and DIO2 in whole blood decreased in the KBD group compared to controls, and mRNA expression of GPx1, GPx4 and DIO2 in cartilage decreased in the KBD group compared to controls. 2. In this experiment, 11 SNPs from 7 important selenoprotein genes were screened, the results showed that GPx1Pro198Leu, GPx4Haplotype(rs713041, rs4807542), SEPS1(rs28665122, rs34713741), SEP15 rs5859 displayed significant differences in genotypic and allelic frequency between the KBD and control groups, while TrxR2(rs5748469, rs1139793, rs5746841)，SEPP1(rs7579) and DIO2 (rs225014) showed no significant differences. 3. The protein expression levels of inflammation and oxidative stress signal transduction pathways were observed between KBD patients and controls. The protein expression levels of PI3K/AKt, ERK, JNK, Nrf2-ARE, NFκB and AP1 signal molecule in KBD group were significantly higher than that in control group, while protein expression levels of ERK in KBD patients was decreased than that in control group, indicating that signaling pathways related to oxidative stress, inflammation, apoptosis were disordered in KBD patients. 4. In genotype subgroup analyses, GPx enzyme activity decreased in the variant genotype GPx1Pro198Leu, and PI3K/AKt signaling pathway were up-regulated in the variant genotype (AA) individual in SEPS1-105G>A (rs28665122). These suggested that selenoprotein polymorphism had important role in regulating GPx enzyme activity and PI3K/AKt signaling. 5. 300 μmol/L tBHP could induce apoptosis and suppress cell survival in human chondrocyte C28 cells, the up-regulation of protein expression levels of c-jun, p-c-jun, MEKK1, p-JNK, AP-1 and the down-regulation of Bcl-2 were observed. Pre-protection with Na2SeO3 (0.05 μg/mL, 0.1 μg/mL) could ameliorate the cell apoptosis, inhibit the ROS generation, and regulate the protein expression levels of the signaling molecular.
Conclusions: The results indicated that some important SNPs of selenoprotein are associated with the risk of development of KBD, including GPX1Pro198Leu, GPx4 (rs713041, rs4807542), SEPS1G-105A, sep15rs5859, which might influence inflammation or oxidative stress signal pathways in KBD patients. Furthermore, chondrocyte apoptosis induced by oxidative stress might be mediated via up-regulation of PI3K/Akt, JNK, NFκB and AP1 signaling pathways related to inflammation and oxidative stress, and Na2SeO3 has an effect of anti-apoptosis by down-regulating the signaling pathways.