Induction of human ADAMTS-2 gene expression by IL-1 alpha is mediated by a multiple crosstalk of MEK/JNK and PI3K pathways in osteoblast like cells

Abstract

Up-regulation of ADAMTS genes with proinflammatory cytokines is important for some pathological conditions such as osteoarthritis (OA) that is a disease based on ECM degradation in cartilage. IL-1 alpha is a proinflammatory cytokine and important both to normal and pathophysiologic conditions in cartilage and bone. Effects of some proinflammatory cytokines such as TNF-alpha and IL-1 beta on the some members of ADAMTS family have been investigated in some chondrocyte tissues or cell lines. However the effect of the IL-1 alpha on the expression of ADAMTS-2 and ADAMTS-3 gene expression in osteoblast like cell lines, remains unclear. Therefore, the aim of this study is to investigate the effect of IL-1 alpha on ADAMTS-2 and ADAMTS-3 gene expression in osteoblast like cells, Saos-2 and MG-63.

The present study, for the first time, demonstrated that IL-1 alpha increases ADAMTS-2 and ADAMTS-3 gene expressions in both Saos-2 and MG-63 cells. Having correlation to mRNA induction, the upregulation of ADAMTS-2,-3 protein levels by IL-1 alpha stimulation is also observed. The inhibition studies showed that this upregulation occurred at the level of transcription, and there was no effect of IL-1 alpha on ADAMTS-2 mRNA half-life in Saos-2 cells. Transactivation potential of IL-1 alpha on ADAMTS-2 promoter was investigated by transient transfection assay. Specifically, IL-1 alpha strongly increased -658/+112 and -530/+112 ADAMTS-2 promoter constructs. Further, we analyzed signaling pathways involved in ADAMTS-2 induction. Pathway inhibition studies revealed that this upregulation depends on the activation of MEK, JNK and PI3K pathways. These findings suggested that IL-1 alpha is a strong positive regulator of ADAMTS-2 and ADAMTS-3 expression. These findings would provide novel insight into the pathophysiology of OA.