Activation of PPAR alpha or gamma reduces secretion of matrix metalloproteinase 9 but not interleukin 8 from human monocytic THP-1 cells

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated tr anscription factors that directly control numerous genes of lipid metabolis m by binding to response elements in the promoter. It has recently been pro posed that PPAR gamma may also regulate genes for proinflammatory proteins, not through PPRE binding but by interaction with transcription factors AP- 1, STAT, and NF-kappa B. Recent studies with cultured human monocytes, howe ver, have failed to observe an inhibitory effect of PPAR gamma agonists on induced expression of TNF alpha and IL-6, genes known to be controlled by A P-1, STAT, and NF-kappa B. In a similar fashion, we show here that PPAR alp ha (fenofibrate) or PPAR gamma (rosiglitazone) agonists failed to modulate LPS-induced secretion of IL-8 in THP-1 cells. When we made parallel observa tions on another gene, matrix metalloproteinase 9 (MMP-9), we were surprise d to find profound downregulation of LPS-induced secretion by both PPAR alp ha or PPAR gamma agonists, These findings suggest that PPAR may regulate on ly a subset of the proinflammatory genes controlled by AP-1, STAT, and NF-k appa B. Effects of PPARs on MMP-9 may account for the beneficial effect of PPAR agonists in animal models of atherosclerosis. (C) 2000 Academic Press.