Actions of Prostaglandins on Human Nucleus Pulposus Metabolism Inferred by Cyclooxygenase 2 Inhibition of Cytokine Activated Cells

OBJECTIVE: Low back pain is frequently treated with nonsteroidal anti-inflammatory drugs (NSAIDs), but little is known about intervertebral disc metabolism of the prostaglandins that are diminished by these drugs. Hence, this study aimed at delineating prostaglandin actions in cytokine activated disc cells by comparing the response of nucleus pulposus (NP) cells to the pro-inflammatory cytokine interleukin (IL)-1β with and without cyclooxygenase 2 (COX-2) inhibition. METHODS: NP cells cultured in alginate beads were activated with IL-1β ± the COX-2 inhibitor Sc-58125. Media harvested from cultured cells were analyzed for prostaglandin E2 (PGE(2)), prostaglandin F2 alpha (PGF(2α)), IL-6, and matrix metalloproteinase (MMP)-3 by enzyme-linked immunosorbent assay and nitric oxide by Griess Reaction. Gene expression along with proteoglycan, collagen, and total protein synthesis were also measured. RESULTS: IL-1β increased culture media PGE(2) and PGF(2α), but decreased proteoglycan and collagen syntheses as well as mRNA expression of the matrix genes aggrecan, versican, collagen I, and collagen II. COX-2 inhibition partially rescued proteoglycan and collagen syntheses and collagen I mRNA, but decreased collagen II mRNA IL-1β activated NP cells. COX-2 inhibition initially enhanced and subsequently reduced IL-1β induced inducible nitric oxide synthase, without altering medium nitrite. IL-1β induction of MMP-3 mRNA was increased by COX-2 inhibition at 24 and 48 hours. CONCLUSION: COX-2 inhibition alters the response of NP cells to IL-1β, suggesting IL-1β action on disc cells is mediated at least in part through COX-2 and its prostaglandins. COX-2 inhibition produces minimal effects on several key catabolic mediators, with the exception of MMP-3. Blocking COX-2 might be beneficial for maintaining disc matrix since it provides an overall rescue of IL-1 induced loss of matrix protein synthesis.