Anti-inflammatory actions of 15-deoxy-Δ 12,14-prostaglandin J2 and troglitazone -: Evidence for heat shock-dependent and -independent inhibition of cytokine-induced inducible nitric oxide synthase expression

In this study, the anti-inflammatory actions of the peroxisome proliferator-activated receptor (PPAR)-gamma agonists 15-deoxy-Delta (12,14)-prostaglandin J(2) (15-d-Delta (12,14)-PGJ(2)) and troglitazone have been examined. Treatment of RAW 264.7 cells and CD-1 mouse peritoneal macrophages with lipopolysaccharide (LPS) + interferon-gamma (IFN-gamma) results in inducible nitric oxide synthase (iNOS), inducible cyclooxygenase (COX-2) and interleukin-1 (IL-1) expression, increased production of nitric oxide, and the release of IL-1, In a concentration-dependent manner, 15-d-Delta (12,14)-PGJ(2) inhibits each of these proinflammatory actions of LPS + IFN-gamma, with half-maximal inhibition at -0.5 mu g/ml and complete inhibition at 1-5 mu g/ml, The inhibitory actions of 15-d-Delta (12,14)-PGJ(2) on LPS + IFN-gamma-induced inflammatory events are not associated with the inhibition of iNOS enzymatic activity or macrophage cell death, but appear to result from an inhibition of iNOS and IL-1 transcription. In addition, the anti-inflammatory actions of 15-d-Delta (12,14)-PGJ(2) are not limited to peritoneal macrophages, as 15-d-Delta (12,14)-PGJ(2) prevents TNF-alpha + LPS-induced resident islet macrophage expression of IL-1 beta and beta-cell expression of iNOS stimulated by the local release of IL-1 in rat islets, 15-d-Delta (12,14)-PGJ(2) appears to be similar to 10-fold more effective at inhibiting resident islet macrophage activation (in response to TNF + LPS) than IL-1-induced nitrite production by beta-cells. Two mechanisms appear to be associated with the antiinflammatory actions of both 15-d-Delta (12,14)-PGJ(2) and troglitazone: 1) the direct inhibition of cytokine- and endotoxin-stimulated iNOS and IL-1 transcription; and 2) the inhibition of IL-1 signaling, an event associated with PPAR-gamma agonist-induced activation of the heat shock response (as assayed by heat shock protein 70 expression). These findings indicate that the PPAR-gamma agonists, troglitazone and the J series of prostaglandins, are potent anti-inflammatory agents that prevent cytokine- and endotoxin-stimulated activation of peripheral and resident tissue macrophages and cytokine-induced iNOS expression by beta-cells by the inhibition of transcriptional activation and induction of the heat shock response.