Inhibition of inducible nitric oxide synthase by peroxisome proliferator-activated receptor agonists: correlation with induction of heme oxygenase 1.
Genetic knock-out in mice of peroxisome proliferator-activated receptor-alpha (PPAR alpha) can prolong inflammation in response to leukotriene B4. Although cyclooxygenase 2 has been shown to be induced by PPAR activation, the effect of PPAR agonists on the key inflammatory enzyme systems of nitric oxide synthase (NOS) and stress proteins has not been investigated. The effect on these of naturally occurring eicosanoid PPAR agonists (leukotriene B4 and 8(S)-hydroxyeicosatetraenoic acid, which are PPAR alpha selective; PGA2, PGD2, PGJ2, and delta12PGJ2, which are PPAR gamma selective) and the synthetic PPAR alpha agonist Wy14,643 was examined in activated RAW264.7 murine macrophages. Leukotriene B4 and 8(S)-hydroxyeicosatetraenoic acid stimulated nitrite accumulation, indicative of enhanced NOS activity. PGA2, PGD2, PGJ2, delta12PGJ2, and Wy14,643 reduced nitrite accumulation, with delta12PGJ2 being the most effective. The mechanism behind this reduction was examined using Western blotting. Inhibition of nitrite accumulation was associated with a fall in inducible NOS protein and an induction of heme oxygenase 1, correlating both dose dependently and temporally. Other proteins examined (cyclooxygenase 2, heme oxygenase 2, heat shock protein 70, and glucose-regulated protein 78) were unaffected. The data suggest that naturally occurring PPAR agonists can inhibit the inducible NOS enzyme pathway. This inhibition may be mediated by modulation of the stress protein, heme oxygenase 1. Thus, the generation of eicosanoid breakdown products during inflammation may contribute to its eventual resolution by activation of the PPAR system. This system may thus represent a novel target for therapeutic intervention in inflammatory disease.
Department of Experimental Pathology, St. Bartholomew's and The Royal London School of Medicine and Dentistry, United Kingdom.
P R
PR
Colville-Nash
S S
SS
Qureshi
D
D
Willis
D A
DA
Willoughby
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004306:Dose-Response Relationship, Immunologic; D004790:Enzyme Induction / Q000187:drug effects; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis*; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D008830:Microbodies / Q000201:enzymology* / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000037:antagonists & inhibitors / Q000378:metabolism; D015230:Prostaglandin D2 / Q000031:analogs & derivatives / Q000494:pharmacology; D011465:Prostaglandins, Synthetic / Q000494:pharmacology; D011524:Protoporphyrins / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists*; D013997:Time Factors; D014157:Transcription Factors / Q000819:agonists*
D009573:Nitrites; D011465:Prostaglandins, Synthetic; D011524:Protoporphyrins; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; C017803:zinc protoporphyrin; C037112:9-deoxy-delta-9-prostaglandin D2; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D006419:Heme Oxygenase (Decyclizing); D015230:Prostaglandin D2