Effects of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) on the expression of inflammatory cytokines and apoptosis induction in rheumatoid synovial fibroblasts and monocytes
Jd. Ji et al., Effects of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) on the expression of inflammatory cytokines and apoptosis induction in rheumatoid synovial fibroblasts and monocytes, J AUTOIMMUN, 17(3), 2001, pp. 215-221
This study was performed to investigate whether peroxisome proliterator-act
ivated receptor-gamma (PPAR-gamma) exerted an anti-inflammatory effect on r
heumatoid synovial cells and inhibited dysregulated proliferation. The expr
ession of PPAR-gamma mRNA in cultured human synoviocytes and THP-1 cells wa
s analysed by RT-PCR. PPAR-gamma was expressed in normal, osteoarthritis (O
A), rheumatoid arthritis (RA) synovial cells as well as a human monocytic c
ell line, THP-1. In RA and OA synoviocytes, the induction of inflammatory c
ytokine mRNA expression such as TNF-a and IL-1 beta was significantly inhib
ited by the natural PPAR-gamma agonist 15 deoxy-Delta (12,14) prostaglandin
J(2), (15d-PGJ,). The effect of PPAR-y on the nuclear factor (NF)-KB activ
ity was tested by electrophoretic mobility shift assay (EMSA). Both troglit
azone and 15d-PGJ(2) markedly inhibited TNF-a-induced NF-KB activation at 3
0 muM. However, PPAR-y agonist neither reduced proliferation nor induced ap
optosis in RA synoviocytes when measured by XTT assay and fluorescence acti
vated cell sorter (FACS) analysis. In contrast, it induced apoptosis in a d
ose-dependent manner in THP-1 cells and augmented INF-related apoptosis-ind
ucing ligand (TRAIL)-induced apoptosis as well. In conclusion, these data d
emonstrate that PPAR-gamma is expressed in human synoviocytes and THP-1 cel
ls, and the PPAR-7 activation inhibits expression of inflammatory cytokines
in RA synoviocytes. Furthermore, PPAR-y activation induces apoptosis by it
self and augments TRAIL/ Apo2L-induced apoptosis in THP-1 cells. These resu
lts suggest that PPAR-7 agonists may provide a new therapeutic approach for
RA. (C) 2001 Academic Press.