MicroRNA-203 up-regulates nitric oxide expression in temporomandibular joint chondrocytes via targeting TRPV4

Objective: MicroRNAs (miRNAs) are recognised as important regulators of a variety of fundamental biologic processes. Our study was undertaken to examine the role of MicroRNA-203 (miR-203) in modulating nitric oxide (NO) expression in female Sprague-Dawley rat mandibular condylar chondrocytes (MCCs) via targeting transient receptor potential vanilloid 4 (TRPV4) and to demonstrate the possible mechanism of NO inhibition by chondroprotective factor 17 beta-oestradiol (E2). Methods: The expression of TRPV4 in mandibular condylar cartilage tissue and MCCs was detected by immunohistochemistry, immunofluorescence (IF), RT-PCR and Western blot, respectively. Primary SD rat MCCs were exposed to lipopolysaccharide (LPS), plus Ruthenium Red, 4 alpha-phorbol 12,13-didecanoate (4 alpha PDD), over-expressed miR-203 or E2 (10(-9) to 10(-6) M), the cellular supernatants were used for NO assay, miR-203 levels were measured by quantitative RT-PCR while TRPV4 expression changes were analysed by Western blot. The dual luciferase activity assay was performed to identify the target gene of miR-203. Results: TRPV4 and miR-203 were stably expressed in MCCs. The MCCs' expression of NO evoked by LPS could be enhanced or depressed by Ruthenium Red or 4 alpha PDD. The dual luciferase assay suggested that TRPV4 was the direct target gene of miR-203. Over-expression of miR-203 inhibited the expression of TRPV4 and increased NO expression in MCCs. E2 inhibited NO expression by inhibition of miR-203, which was concurrent with the up-regulation of TRPV4 expression level in MCCs. Conclusion: Our findings first suggested that miR-203 could up-regulate NO expression in female rat MCCs via targeting TRPV4. Moreover, the inhibition of NO by E2 might be at least in part through this mechanism. (C) 2012 Elsevier Ltd. All rights reserved.