Activation of peroxisome proliferator-activated receptor gamma suppresses inducible cyclooxygenase and nitric oxide synthase during oral mucosal ulcer healing.
BACKGROUND
Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a ligand-dependent transcription factor, belonging to the steroid hormone receptor family, known to play a pivotal role in the resolution of inflammation. In this study, we investigated the effect of a specific PPARgamma ligand, ciglitazone, on the course of buccal mucosal ulcer healing by analyzing mucosal activity of inducible nitric oxide synthase (NOS-2) and the expression cyclooxygenases (COX-1 and COX-2) responsible for prostaglandin (PG) generation.


METHODS
Groups of rats with experimentally induced buccal mucosal ulcers were administered twice daily for up to 10 days with ciglitazone at 5, 10, and 15 mg/kg or the vehicle, and their mucosal tissue subjected to assessment of ulcer healing rate and biochemical measurements.


RESULTS
The ulcer onset, characterized by up-regulation of NOS-2 and COX-2 protein expression, was reflected in a marked increase in the mucosal PGE2 generation and NOS-2 activity, whereas healing was accompanied by a drop in PGE2 and NOS-2 activity, and a decrease in COX-2 and NOS-2 protein expression. The mucosal expression of COX-1 protein, however, remained unchanged. Administration of ciglitazone led to a significant dose-dependent acceleration in the mucosal reduction of PGE2 generation and NOS-2 activity, and produced a marked decline in COX-2 and NOS-2 protein expression, but the rate of ulcer healing and the expression of COX-1 protein remained unaffected.


CONCLUSIONS
Our findings thus suggest that the products of induced NOS-2 and COX-2 enzymes, associated with mucosal inflammatory responses to injury, do not play a significant role in oral mucosal ulcer healing.
Research Center, University of Medicine and Dentistry of New Jersey, Newark 07103-2400, USA. slomiabr@umdnj.edu
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D000818:Animals; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000378:metabolism*; D015232:Dinoprostone / Q000096:biosynthesis; D004790:Enzyme Induction / Q000502:physiology; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins; D009061:Mouth Mucosa / Q000503:physiopathology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D019226:Oral Ulcer / Q000503:physiopathology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014945:Wound Healing / Q000502:physiology*
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D015232:Dinoprostone