Integrin α2β1 is involved in T-2 toxin-induced decrease of type II collagen in C28/I2 chondrocytes

MiR-140 is involved in T-2 toxin-induced matrix degradation of articular cartilage

T-2 toxin is one of the most toxic mycotoxins contaminating various grains. It is considered an environmental risk factor for Kashin-Beck disease (KBD), an endemic degenerative osteochondrosis. Currently, the underlying molecular mechanisms of articular cartilage damage caused by T-2 toxin have not been elucidated. Studies have shown that miR-140 is essential for cartilage formation, and extracellular matrix (EMC) synthesis and degradation. The objective of this study was to investigate the mechanism of miR-140 involvement in T-2 toxin-induced articular cartilage damage. Two treatment groups, each containing wild-type mice and miR-140 knockout mice were administered with T-2 toxin (200 ng/g BW/day) or a normal diet for 1 month, 3 months, and 6 months. Results showed that T-2 toxin caused articular cartilage and growth plate damage in mice. The expression of miR-140 decreased in articular cartilage of wild-type mice treated with T-2 toxin, and miR-140 deficiency aggravated T-2 toxin-induced knee cartilage damage. T-2 toxin-caused the reduction of miR-140 expression was consistent with collagen type II (COL2A1), aggrecan (ACAN), and SRY-box containing gene 9 (SOX9) and opposite to matrix metalloproteinase 13 (MMP13), a disintegrin and metalloproteinase with thrombospondin motif 5 (ADAMTS-5), and v-ral simian leukemia viral oncogene homolog A (RALA). In addition, we collected finger joints cartilage and knee joints cartilage from KBD patients and controls for paraffin embedding and sectioning. Results found that the expression of miR-140 in the articular cartilage of the KBD group was lower than that of the control group. The expression of COL2A1, ACAN, and SOX9 decreased, whereas ADAMTS-5, MMP13, and RALA increased in the articular cartilage of the KBD group. These results revealed that miR-140 might be involved in T-2 toxin-induced degradation of the ECM of articular cartilage. Moreover, the occurrence of KBD might be related to the decreased expression of miR-140 in articular cartilage.

Transforming growth factor-β receptors mediates matrix degradation and abnormal hypertrophy in T-2 toxin-induced hypertrophic chondrocytes

This study investigated whether transforming growth factor-β receptor I (TGF-βRI) and TGF-βRII mediate matrix degradation and abnormal hypertrophy in T-2 toxin-induced hypertrophic chondrocytes. Hypertrophic chondrocytes were exposed to TGF-βRI and TGF-βRII binding inhibitor (GW788388) for 24 h prior to exposure to different concentrations of T-2 toxin (0, 10, 25, and 50 ng/mL for 48 h). Hypertrophic chondrocytes were assessed based on the expression of matrix-degrading and terminal differentiation-related genes and cell viability. Matrix metalloproteinases (MMPs, MMP-13, MMP-1, and MMP-9) were reduced in the GW788388+T-2 toxin group compared to the T-2 toxin group. The expression of terminal differentiation-related genes (MMP-2, MMP-10, and collagen X) was increased in hypertrophic chondrocytes in the inhibited groups compared to that in the T-2 toxin group. The survival rate of chondrocytes decreased significantly in a dose-dependent manner. GW788388 did not significantly block the reduced cell viability in hypertrophic chondrocytes exposed to T-2 toxin. The upregulated expression of TGF-βRI and TGF-βRII mediates the abnormal chondrocyte hypertrophy and extracellular matrix degeneration observed in T-2 toxin-induced hypertrophic chondrocytes.

T-2 toxin induces articular cartilage damage by increasing the expression of MMP-13 via the TGF-β receptor pathway

T-2 toxin pre-disposes individuals to osteoarthritis, Kashin-Beck disease (KBD). The major pathological change associated with KBD is the degradation of the articular cartilage matrix. Herein, we investigated the key molecules that regulate T-2 toxin-mediated cartilage degradation. Potential KBD treatments were also investigated. Sprague Dawley rats were divided into the T-2 toxin group and the control group. The T-2 toxin group received 100 ng/g BW/day, whereas the control group received a similar dose of PBS. The expression of matrix metalloproteinase-13 (MMP-13) and TGF-β receptor I/II (TGF-βRI/II) was analyzed using immunohistochemical staining. C28/I2 chondrocytes were exposed to TGF-βRI/II binding inhibitor (GW788388) for 24 h before incubation in different T-2 toxin concentrations (0, 6, 12, and 24 ng/mL for 72 h). The expression of mRNA for TGF-βRI/II, MMP-13 and proteins for MMP-13, and Smad-2 in chondrocytes were analyzed using RT-PCR and western blot, respectively. Safranin O staining revealed that T-2 toxin treatment modulated the expression of articular cartilage matrix. On the other hand, T-2 toxin treatment sharply increased the expression of MMP-13, TGF-βRI, and TGF-βRII in the rat cartilages. Interestingly, blocking the TGF-βRs-smad 2 signaling pathway using GW788388 abrogated the effect of T-2 toxin on upregulating MMP-13 expression. The expression of MMP-13 in chondrocytes induced with T-2 toxin is regulated via the TGF-βRs signaling pathway. As such, inhibiting the expression of TGF-βRs is a potential KBD treatment.

Downregulation of Insulin-Like Growth Factor-1 Receptor Mediates Chondrocyte Death and Matrix Degradation in Kashin-Beck Disease

PURPOSE

To explore the relationship between insulin-like growth factor (IGF)-1R expression and the pathological progression of Kashin-Beck disease (KBD).

DESIGN

KBD cartilage samples were collected from 5 patients. Additionally, T-2 toxin was administered to rats fed a selenium (Se)-deficient diet, and their knee joints were collected. Human C28/I2 chondrocytes and mouse hypertrophic ATDC5 chondrocytes were cultured in vitro and treated with T-2 toxin and Se supplementation. Subsequently, the cultured human and mouse chondrocytes were treated with the IGF-1R inhibitor, picropodophyllin. Chondrocyte death and caspase-3 activity were analyzed using flow cytometry and a specific kit, respectively. Protein and mRNA expression levels of IGF-1R and matrix molecules were measured using immunohistochemistry, western blotting, and quantitative real-time reverse transcription-polymerase chain reaction analyses.

RESULTS

The cartilages from patients with KBD and T-2 toxin-treated rats on a Se-deficient diet showed significantly decreased expression of IGF-1R compared to cartilages from controls. T-2 toxin decreased IGF-1R mRNA and protein levels in both C28/I2 and hypertrophic ATDC5 chondrocytes in a dose-dependent manner; however, Se supplementation reduced the decrease of IGF-1R induced by T-2 toxin. Furthermore, inhibition of IGF-1R resulted in chondrocyte death of C28/I2 and hypertrophic ATDC5 chondrocytes, as well as decreased type II collagen expression and increased MMP-13 expression at the mRNA and protein levels.

CONCLUSION

Downregulation of IGF-1R was associated with KBD cartilage destruction. Therefore, inhibition of IGF-1R may mediate chondrocyte death and extracellular matrix degeneration related to the pathological progression of KBD.

Endoplasmic reticulum stress pathway mediates T-2 toxin-induced chondrocyte apoptosis

T-2 toxin leads to chondrocyte apoptosis and excessive extracellular matrix degradation. The aim of this study is to investigate if endoplasmic reticulum stress (ERS) - initiated apoptosis is involved in the chondrocyte damage induced by T-2 toxin. In vivo, rats were divided into a control group, T-2 toxin 200 ng/g BW/d group, the protein levels of GRP78, CHOP, and caspase-12 were detected using immunohistochemistry in articular cartilage tissues. In vitro, C28/I2 and ATDC5 chondrocytes were treated with various concentrations of T-2 toxin. For the salubrinal protection assay, cells were pretreated with 20 μM salubrinal for 1 h, and treated with and without T-2 toxin for 24 h. The cell viability was determined using the MTT assay; and the cell apoptosis was determined using the Flow Cytometry Assay; the mRNA and protein levels of the ERS markers and ECM were determined using RT-PCR and western blotting. This study found that the expressions of GRP78, CHOP, and caspase-12 is higher in T-2 toxin group than in control group both in vivo and in vitro, and the T-2 toxin administration promoted chondrocyte apoptosis, suppressed matrix synthesis, and accelerated cellular catabolism via the ERS signaling pathway. In addition, this study found that salubrinal prevented chondrocyte injury by inhibiting ERS-mediated apoptosis via the PERK-eIF2α-ATF4-CHOP signaling pathway. Collectively, this study provides a new clue to elucidate the mechanism of T-2 toxin-induced chondrocyte damage, and presents a novel therapeutic possibility of salubrinal for Osteoarthropathy such as osteoarthritis (OA) and Kaschin-Beck disease (KBD).

Identification of HIF-1α/VEGFA signaling pathway and transcription factors in Kashin-Beck disease by integrated bioinformatics analysis

Kashin-Beck disease (KBD) is a chronic and endemic osteoarthropathy. The pathogenesis of KBD has yet to be fully elucidated, although previous studies have shown that its etiology may be associated with low selenium abundance and high exposure to mycotoxins, such as T-2 toxin. In the present study, the Comparative Toxicogenomics Database was used to identify key genes associated with KBD, T-2 toxin and selenium. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used to identify the biological processes and pathways that key genes may be associated with. By searching the Search Tool for the Retrieval of Interacting Genes database and the Molecular Complex Detection plug-in with Cytoscape, it was possible to construct a KBD-associated protein-protein interaction (PPI) network, and screen the core modules and genes. Western blot analysis was subsequently used to verify the expression levels of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor A (VEGFA), two components that are associated with the HIF-1 signaling pathway in KBD disease. Via this approach, a total of 301 key genes were identified that were associated with KBD, T-2 toxin and selenium. The results of the GO and KEGG enrichment analyses demonstrated that these key genes were mainly involved in the process of apoptosis. Previous studies have demonstrated that excessive apoptosis of chondrocytes plays a crucial role in the pathophysiology of KBD, and that HIF-1α has an important role in chondrocyte apoptosis; therefore, the present study was focused on the expression level of HIF-1α in KBD. By analyzing the PPI network constructed from the key genes, a total of 10 core genes were obtained that may be associated with KBD. The results of western blotting experiments revealed that, after treating chondrocytes with different concentrations of T-2 toxin, the expression levels of HIF-1α and VEGFA were markedly downregulated. The iRegulon plug-in for Cytoscape was used to predict the transcription factors that may regulate HIF-1α and VEGFA in the HIF-1 signaling pathway. Using this approach, 10 core genes and 15 transcription factors were obtained. These results may help to clarify the pathogenesis of KBD, thereby providing further avenues for the therapeutic treatment of KBD.

The decreased expression of integrin αv is involved in T-2 toxin-induced extracellular matrix degradation in chondrocytes

T-2 toxin is one of the most toxic and common mycotoxins in grains and related products. It is considered a risk factor for Kashin-Beck disease (KBD), an endemic osteoarthritis. Both in vitro and in vivo studies have shown that T-2 toxin can cause extracellular matrix degradation; however, the underlying mechanism is unclear. Integrins have been found to regulate the expression of matrix metalloproteinases (MMPs), the 'scissors' of matrix proteins. In this study, we investigated whether integrin αv played a role in T-2 toxin-induced matrix degradation. Results from our study showed that the expression of integrin αv in the cartilage of rats fed T-2 toxin was reduced compared to that in rats fed a normal diet. Integrin αv was downregulated in T-2 toxin-treated C28/I2 chondrocytes, and selenium was found to have a protective effect. The expression of MMP-1, -3, -10, and -13 increased whereas that of type II collagen (Col II) protein decreased in C28/I2 cells treated with an integrin αv inhibitor. In conclusion, T-2 toxin can downregulate integrin αv expression in chondrocytes. Reduced integrin αv signalling could induce the release of MMPs, leading to matrix degradation.