Prostaglandin E2 Synthesis In Cells Research Articles

Regulation of prostaglandin E2 synthesis in cells derived from chondrocytes of patients with osteoarthritis

BackgroundOsteoarthritis (OA) is a disorder that causes pain and degeneration of the joint over a chronic time course. Chondrocytes in OA play important roles in maintaining the homeostasis of the joint while they produce many cytokines and pathological mediators, including interleukin-1 P (IL-1β), cyclooxygenases (COX), and prostaglandin E2 (PGE2). To elucidate the mechanisms of pain due to OA, the pathway of PGE2 synthesis was analyzed using cells derived from chondrocytes obtained from patients with OA. MethodsChondrocytes were isolated from cartilage samples obtained at the time of joint replacement surgery from patients with OA. The chondrocytes at the second passage were cultured with or without IL-1β, dexamethasone (DEX), or COX inhibitors such as NS-398, meloxicam, and indomethacin. Reverse transcription-polymerase chain reaction and Western blotting analysis were performed to study the levels of mRNA and protein, respectively. An enzyme-linked immunosorbent assay was performed to investigate the translocation of nuclear factor-KB (NF-ΚB) to the nucleus, and Western blotting analysis was performed to study the phosphorylation of mitogen-activated protein kinases. ResultsIL-1β markedly enhanced the expression of COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) at both the mRNA and protein levels. The up-regulation was suppressed by DEX or COX inhibitors. IL-1β strongly increased the translocation of NF-ΚB to the nucleus and the phosphorylation of extracellular-signal-regulated kinase, p38, and c-Jun amino-terminal kinase; but the up-regulation was not inhibited by DEX or COX inhibitors. Interestingly, in a dose-dependent manner, PGE2 recovered mPGES-i expression from suppression by DEX, whereas it did not restore the expression of COX-2 in the presence of DEX and IL-1β. ConclusionsThese results suggested that in cells derived from OA chondrocytes different mechanisms of regulation exist between mPGES-1 and COX-2, and the expression of mPGES-1 was, at least partially, regulated through the autocrine positive feedback by PGE2.

Sustained activation of PGE2 synthesis in mesangial cells cocultured with glomerular endothelial cells.

Glomerular endothelial cells synthesize and release endothelin-1 (ET-1), and mesangial cells, normally closely apposed to endothelial cells in vivo, respond to ET-1 with contraction, proliferation, and prostaglandin E2 (PGE2) release. This study sought to determine whether chronic coculture of mesangial cells with glomerular endothelial cells alters mesangial cell PGE2 synthesis. Mesangial cells cocultured with endothelial cells were found to release PGE2 at rates much greater than those observed in mesangial cells not cocultured with endothelial cells. This effect persisted for at least 24 h after the mesangial cells were removed from coculture with endothelial cells. The increase in basal mesangial cell PGE2 synthesis was dependent on endothelial cell-derived ET-1. Despite the increase in basal PGE2 synthesis after coculture with endothelial cells, acute ET-1-stimulated PGE2 release was markedly blunted in mesangial cells that had been cocultured with endothelial cells when compared with mesangial cells in solo-culture. This lack of responsiveness was specific for ET-1 and resulted from a profound downregulation of mesangial cell endothelin receptors. Thus coculture with endothelial cells produces two apparently opposing and ET-1-dependent effects in mesangial cells, namely a sustained increase in basal PGE2 synthesis by the cells and a loss of responsiveness to further stimulation with ET-1. It is postulated that the induction of sustained PGE2 synthesis may also occur in vivo if endothelin release from endothelial cells is stimulated and may explain, in part, the extraordinary sensitivity of some patients with glomerular disease to cyclooxygenase inhibitors.

Aluminum enhances the stimulatory effect of NaF on prostaglandin E2 synthesis in a clonal osteoblast-like cell line, MOB 3-4, in vitro.

The effect of NaF on prostaglandin E2 (PGE2) synthesis in a clonal osteoblast-like cell line, MOB 3-4, was examined in the presence of Al3+. The MOB 3-4 cell line, which was derived from neonatal mouse calvaria, displays many osteoblastic characteristics, including the biosynthesis of PGE2. In the absence of Al3+, 1 mM NaF increased PGE2 synthesis (per well) to about 340% of the control level, whereas NaF at lower concentrations (below 0.1 mM) did not show such a significant effect. In the presence of 10 microM Al3+, NaF concentrations ranging from 0.01 to 1 mM increased PGE2 synthesis in a dose-dependent manner, though 10 microM Al3+ had no effect by itself. Similar effects were observed on alkaline phosphatase (ALP) activity per well, but a stimulatory effect of NaF on protein synthesis was observed only in the presence of 10 microM Al3+. These data demonstrated that PGE2 synthesis per protein was increased by NaF alone, and this effect was markedly enhanced by the addition of AlCl3. ALP activity per protein was, however, significantly increased by NaF in the absence of AlCl3. Taken together with our previous finding that Al3+ enhances the NaF-induced Ca2+ mobilization in MOB 3-4 cells, these results suggest that F- combined with Al3+ (i.e., AlF4-) is a more potent stimulator of PGE2 synthesis in cells than F- alone, and that the AlF4- -enhanced PGE2 synthesis may be caused by an increase in cytosolic free Ca2+ concentration during activation of the G protein by AlF4-.