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Regulation of prostaglandin endoperoxide synthase gene expression in rat mesangial cells by interleukin-1 beta
D Rzymkiewicz1, K Leingang, N Baird
1Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Abstract:
In primary cultures of rat mesangial cells from passage 3 to 6, interleukin-1 beta (IL-1) induced a time-dependent increase in prostaglandin E2 (PGE2) formation and release into the extracellular medium. This increase was associated with a dramatic upregulation of the steady-state levels of mRNA for the prostaglandin endoperoxide synthetase (PES)-2 gene transcript as demonstrated by Northern analysis. In contrast, there did not appear to be a significant increase in the mRNA levels for a 2.8-kb transcript for the PES-1 gene. At 18 h of exposure to IL-1, the steady-state level of message for PES-2 remained elevated at 50% of the 2-h time point. Culturing the cells in the presence of cycloheximide and IL-1 demonstrated a superinduction of the PES-2 message without any change in PES-1 message. The tumor-promoting phorbol ester, phorbol myristate acetate (PMA), was also associated with an upregulation of the message for the PES-2 gene and did not influence the levels of the message for the PES-1 gene as demonstrated by Northern analysis. Dexamethasone (Dex) inhibited to control levels the induction by PMA, but the induction of the message by IL-1 was only inhibited 30%. Despite 70% of the message being present by 2 h of induction, Dex was capable of totally inhibiting the inductive effect of IL-1 with respect to PGE2 biosynthesis. Immunocytochemical studies demonstrated a dramatic induction of PES-2 protein by IL-1, which was inhibited by Dex. The data suggest that Dex inhibits the translation of the PES-2 protein.
Insights
Interleukin-1 beta (IL-1) upregulates prostaglandin endoperoxide synthetase-2 (PES-2) in rat mesangial cells, increasing prostaglandin E2 (PGE2) production. Dexamethasone (Dex) inhibits PES-2 protein translation, reducing PGE2 levels.
Area of Science:
- Molecular biology
- Cell biology
- Biochemistry
Background:
- Prostaglandin E2 (PGE2) plays a role in renal inflammation.
- Interleukin-1 beta (IL-1) is a key inflammatory cytokine.
- Prostaglandin endoperoxide synthetase (PES) enzymes are crucial for PGE2 synthesis.
Purpose of the Study:
- To investigate the effects of IL-1 on PES gene expression and PGE2 production in rat mesangial cells.
- To determine the role of PES-2 in IL-1-induced PGE2 formation.
- To examine the regulatory effects of dexamethasone (Dex) on PES-2 expression and function.
Main Methods:
- Primary culture of rat mesangial cells.
- Northern blot analysis to quantify mRNA levels of PES-1 and PES-2.
- Measurement of PGE2 formation and release.
- Treatment with IL-1, phorbol myristate acetate (PMA), cycloheximide, and dexamethasone (Dex).
- Immunocytochemical studies to detect PES-2 protein.
Main Results:
- IL-1 time-dependently increased PGE2 formation and release.
- IL-1 significantly upregulated steady-state mRNA levels of PES-2, but not PES-1.
- PMA also upregulated PES-2 mRNA, while Dex inhibited PMA-induced PES-2 upregulation.
- Dex partially inhibited IL-1-induced PES-2 mRNA levels but completely inhibited IL-1-induced PGE2 biosynthesis.
- IL-1 dramatically induced PES-2 protein, an effect inhibited by Dex, suggesting translational inhibition.
Conclusions:
- IL-1-induced PGE2 production in rat mesangial cells is mediated by the upregulation of PES-2.
- Dexamethasone inhibits IL-1-induced PGE2 biosynthesis primarily by suppressing the translation of PES-2 protein.
- PES-2 is a key target for anti-inflammatory strategies in the kidney.