T-2 Toxin Induces Epiphyseal Plate Lesions via Decreased SECISBP2-Mediated Selenoprotein Expression in DA Rats, Exacerbated by Selenium Deficiency.

OBJECTIVE: Both selenium (Se) deficiency and mycotoxin T2 lead to epiphyseal plate lesions, similar to Kashin-Beck disease (KBD). However, regulation of selenoproteins synthesis mediated by SECISBP2, in response to these 2 environmental factors, remained unclear. The present study proposed to explore the mechanism behind the cartilage degradation resulting from Se deficiency and mycotoxin T2 exposure. DESIGN: Deep chondrocyte necrosis and epiphyseal plate lesions were replicated in Dark Agouti (DA) rats by feeding them T2 toxin/Se deficiency artificial synthetic diet for 2 months. RESULTS: Se deficiency led to decreased expression of COL2α1, while T2 treatment reduced the heparan sulfate 6-O-sulfotransferase 2 (HS6ST2) expression, both of which affected the cartilage extracellular matrix metabolism in the rat models. The expression of Col2α1, Acan, Hs6st2, Secisbp2, Gpx1, and Gpx4 were all significantly decreased in cartilage tissues from DA rats, fed a Se-deficient diet or exposed to T2 toxin, contrary to Adamts4, whose expression was increased in both conditions. In addition, T2 treatment led to the decreased expression of SBP2, GPX1, GPX4, and total GPXs activity in C28/I2 cells. CONCLUSION: DA rats exposed to T2 toxin and/or Se-deficient conditions serve as the perfect model of KBD. The 2 environmental risk factors of KBD, which serve as a "double whammy," can intensify the extracellular matrix metabolic imbalance and the antioxidant activity of chondrocytes, leading to articular cartilage degradation and epiphyseal plate abnormalities similar to those observed in KBD.

Selenium-sensitive miRNA-181a-5p targeting SBP2 regulates selenoproteins expression in cartilage.

Selenium (Se) deficiency brings about defects in the biosynthesis of several selenoproteins and has been associated with aberrant chondrogenesis. Selenocysteine (Sec) Insertion Sequence (SECIS) and SECIS binding protein 2 (SBP2) interaction is a very critical node for the metabolic balance between Se and selenoproteins. The Gpx1, Gpx4 and SelS have different binding affinities with SBP2 in cells. According to our results, both miR-181a-5p and SBP2 appeared to be selenium-sensitive and regulated the expression of selenoproteins in C28/I2 cells under Se sufficient environment. However, they showed significantly opposite expression trend in Se deficiency rats cartilage and SeD C28/I2 cells. The SBP2 is a direct target gene of miR-181a-5p in C28/I2 cells as determined by reporter gene and off-target experiments. And the miR-181a-5p could regulate SBP2 and the selenoproteins in C28/I2 cells. Depending upon the Se supply levels, C28/I2 cells were divided into three groups, that is normal Se, SeD and SeS, which underwent through a 7-day Se deprivation process, then SBP2 was knocked-down and overexpressed in all the groups. Moreover, the selected selenoproteins were down-regulated in second-generation low Se diet rat cartilage. The selenoproteins expression was decreased by Se deficiency which depended on the Selenium-sensitive miR-181a-5p to participate and regulate SBP2 at post-transcriptional level. It involves a series of antioxidant and ECM (extracellular matrix) genes, to overcome the ROS-related stress for the protection of essential physiological functions and to maintain the balance between anabolism and catabolism of the cartilage.

Abnormality of epiphyseal plate induced by selenium deficiency diet in two generation DA rats.

This study aimed to observe the effects of Se deficiency on epiphyseal plates of two generation DA rats fed with artificial total synthetic low Se diet. All F0 and F1 DA rats were fed with synthetic low Se diet (SeD group) and low Se diet supplied with Se (SeS group). The levels of selenium and enzyme activities of GPx were detected in plasma of the rats. General growth of bone and articular cartilage was measured macroscopically and microscopically. The epiphyseal plate of femur heads or tibia were obtained to histological and immunohistochemical examinations. The cartilage from left knee joints and femur heads was used to detect the gene expression of collagens, ADAMTSs and several selenoproteins by RT-qPCR. Two generation SeD rats showed Se insufficiency status. The thicknesses of the femur and tibial epiphyseal plates in both F0 and F1 SeD rats were significantly less than that of SeS rats. In F1 generation, SeD rats showed much fewer proliferative chondrocyte layers than SeS ones. Importantly, two generation SeD rats both showed significantly more serious pathological changes of epiphyseal plates. In two generation rats, gene expressions of COL II, GPx1 and GPx4 were significantly down-regulated in SeD rats than SeS ones; meanwhile ADAMTS-4 showed an up-regulated expression in cartilage. Dietary Se deficiency can apparently cause epiphyseal plate lesion and decrease cartilage type II collagen production and GPx1 activity in two generation DA rats fed with the artificial total synthesis low Se diet.