Protective effect of estrogen receptors (ERα/β) against the intervertebral disc degeneration involves activating CCN5 via the promoter.

Abstract

Due to the decrease of estrogen and estrogen receptor (ER) in postmenopausal women, they have a higher risk of intervertebral disc degeneration (IDD) than men. This study aims to explore how ERα and ERb interact with CCN5 and protect IDD. We used Chromatin immunoprecipitation (ChIP) and Luciferase reporter assay to determine whether the ERα/b protein binds to CCN5 promoter and activates its expression. We used TNF-α to induce nucleus pulposus (NP) cell degeneration to simulate the IDD process. The change of the expression of ERα/β and CCN5 was measured in the degenerated NP cells. To understand the function of ERα/β in the NP cells degeneration, we upregulated the ERα/b gene expression by vector transfection or 17b-estradiol (E2) stimulation. Besides, we also used the CCN5 gene-silenced NP cells by siRNA transfection as a comparison to determine the role of CCN5. We tested the cell proliferation and principal components of the extracellular matrix (ECM) to value the degree of NP cell degeneration. ERα and ERβ protein can bind to the same promoter regions of CCN5 and activate its expression, respectively. TNF-α degraded NP cells with a reduction of cell proliferation, collagen II, ACAN, ERα, ERβ, and CCN5 expression, and increased collagen I/III, and MMP-13 expression. Upregulated ERα or ERβ resulted in the maintains of CCN5 and alleviated the NP cell degeneration. Besides, 17β-E2 supplement increased the ERα, ERβ, and CCN5 expression, as well as stable NP cells phenotype. However, it was partly abolished by the silencing of CCN5. Upregulation of ERα and ERβ protects the NP cell degeneration during IDD through the activation of CCN5 by binding to its promoter.