Different concentrations of 17β-estradiol modulates apoptosis induced by interleukin-1β in rat annulus fibrosus cells

Interleukin-1β (IL-1β) is a pleiotropic cytokine that mediates inflammatory and cell death activities. IL-1β has been previously reported to induce apoptosis of intervertebral disc (IVD) cells in IVD degeneration. Accumulating data have suggested that post-menopausal women have a high incidence of IVD degeneration. It has therefore been proposed that estrogen may have a close association with IVD degeneration. Whether estrogen is able to protect IVD cells from apoptosis remains unclear. The present study aimed to examine whether 17β-estradiol (17β-E2) inhibited IL-1β-induced apoptosis of rat annulus fibrosus (AF) cells. Additionally, the dose-response effect of 17β-E2 on cell apoptosis was investigated. AF cells were isolated from male Sprague Dawley rats and cultured in complete medium. Following approximately two weeks, the AF cells were treated with IL-1β (75 ng/ml) for 24 h, with a pretreatment of 17β-E2 for 1 h. Apoptosis of AF cells was analyzed by annexin V/propidium iodide binding assay and morphological changes, together with an assessment of caspase-3 activity. Cell viability of the AF cells was determined by MTT assay. The level of apoptosis and caspase-3 activity in the AF cells was increased whereas the cell viability was decreased following treatment with IL-1β (75 ng/ml), as compared with the control group. This effect was reversed by pretreatment with 17β-E2, in a dose-dependent manner. The protective effect of 17β-E2 was abolished by estrogen receptor antagonist ICI182, 780. These results indicate that 17β-E2 protects rat AF cells from apoptosis induced by IL-1β, in a dose-dependent manner.