The role of the peroxisome proliferator-activated receptor-α (PPAR-α) in the regulation of acute inflammation

The peroxisome proliferator-activated receptor-α (PPAR-α) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors related to retinoid, steroid, and thyroid hormone receptors. The aim of the present study was to evaluate the role of the PPAR-α receptor on the development of acute inflammation. To address this question, we used two animal models of acute inflammation (carrageenan-induced paw edema and carrageenan-induced pleurisy). We report here that when compared with PPAR-α wild-type mice, PPAR-α knockout mice (PPAR-αKO) mice experienced a higher rate of the extent and severity when subjected to carrageenan injection in the paw edema model or to carrageenan administration in the pleurisy model. In particular, the absence of a functional PPAR-α gene in PPAR-αKO mice resulted in a significant augmentation of various inflammatory parameters (e.g., enhancement of paw edema, pleural exudate formation, mononuclear cell infiltration, and histological injury) in vivo. Furthermore, the absence of a functional PPAR-α gene enhanced the staining (immunohistochemistry) for FAS ligand in the paw and in the lung and the expression of tumor necrosis factor α and interleukin-1β in the lungs of carrageenan-treated mice. In conclusion, the increased inflammatory response observed in PPAR-αKO mice strongly suggests that a PPAR-α pathway modulates the degree of acute inflammation in the mice.