Kazutaka Haraguchi

Suppression of experimental crescentic glomerulonephritis by peroxisome proliferator-activated receptor (PPAR)γ activators

AbstractBackground. It has been recently reported that peroxisome proliferator-activated receptors (PPARs)γ exist in various tissues and that they exibit anti-inflammatory effects. Methods. We investigated the effects of PPARγ activators on the development of crescentic glomerulonephritis. Crescentic glomerulonephritis was induced by the injection of rabbit anti-rat glomerular basement membrane antibody in WKY rats. Results. Administration of troglitazone suppressed urinary protein excretion and crescent formation as indicated by crescent scores. Pioglitazone, a PPARγ activator, mimicked the effect of troglitazone, but bezafibrate, a PPARα-activator, did not. Immunohistology revealed that troglitazone and pioglitazone inhibited the infiltration of ED-1-positive monocyte/macrophages and CD8-positive cells into glomeruli. Conclusions. In the present study, we demonstrated that PPARγ activators exert antinephritic effects by suppressing the recruitment of inflammatory cells via a PPARγ-dependent mechanism.

Tumor Necrosis Factor-α and Interferon-γ Suppress Both Gene Expression and Deoxyribonucleic Acid-Binding of TTF-2 in FRTL-5 Cells

Tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) are cytokines that can individually or additively suppress thyroid cell function and the expression of thyroid-specific genes, such as thyroglobulin (TG) and thyroperoxidase (TPO). Thyroid transcription factor-2 (TTF-2) is a DNA-binding protein that modulates the expression of TG and TPO genes. In the present study, we examine the effects of TNF-α and IFN-γ on TTF-2 gene expression, as well as the DNA-binding activity of TTF-2. FRTL-5 cells were maintained in 5H medium containing 0.2% calf serum for 7 days, then incubated with TNF-α, IFN-γ, or TNF-α plus IFN-γ. Total RNA was isolated and Northern blotted. TNF-α (50 ng/ml) only slightly suppressed (61± 2% compared with control), whereas IFN-γ (100 U/ml) modestly decreased TTF-2 messenger RNA (mRNA) levels (34 ± 4%). TNF-α and IFN-γ simultaneously caused a marked decrease in TTF-2 mRNA levels (13 ± 2%). The suppressive effects of TNF-α and IFN-γ on TTF-2 mRNA levels were concentration dependent and ma...

Activation of Peroxisome Proliferator-Activated Receptor-g Inhibits Apoptosis Induced by Serum Deprivation in LLC-PK1 Cells

Peroxisome proliferator-activated receptor-γ (PPARγ) belongs to a superfamily of nuclear receptors, which plays important roles in lipid and glucose metabolism. However, expression of PPARγ in extra-adipose tissues and stimulation of apoptosis by PPARγ activators has been previously reported. We investigated the functions of PPARγ using a clonal kidney cell line (LLC-PK1). RT-PCR revealed the expression of PPARγ in LLC-PK1 cells. The cells accumulated fat droplets and increased β-oxidation of free fatty acids in response to troglitazone, a ligand for PPARγ. At physiological concentrations, ligands for PPARγ including troglitazone, BRL49653, and 15-deoxy-δ-12,14-prostaglandin J2 inhibited serum-deprivation-induced apoptosis of the cells. On the other hand, PPARα activators did not inhibit the apoptosis. Apoptosis of LLC-PK1 cells was determined by a cell viability assay, condensation of the nucleus on fluorescent and electron microscopy, and DNA fragmentation as indicated by the appearance of nucleosomal ladders on an agarose gel. Troglitazone also suppressed serum-deprivation-induced activation of Caspase 3. However, troglitazone did not suppress apoptosis induced by ATP deprivation. Anti-apoptotic effects of troglitazone were partially blocked by a phosphatidylinositol-3-kinase (PI3K) inhibitor, wortmannin, but not by other kinase inhibitors such as PD98059 and AG490. These results suggest that PPARγ is functionally expressed in LLC-PK1 cells, and its activation inhibits apoptosis induced by serum deprivation, at least in part, through the PI3K pathway.