geranylgeranylacetone and benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone

Although heat shock protein 72 kDa (HSP72) protects tubular epithelium from a variety of acute insults, its role in chronic renal injury and fibrosis is poorly characterized. In this study, we tested the hypothesis that HSP72 reduces apoptosis and epithelial-to-mesenchymal transition (EMT), important contributors to tubular cell injury in vitro and in vivo. In rats, orally administered geranylgeranylacetone (GGA), an agent that selectively induces HSP72, markedly reduced both apoptosis and cell proliferation in tubular epithelium and decreased both interstitial fibroblast accumulation and collagen I deposition after unilateral ureteric obstruction, a model of chronic renal tubulointerstitial fibrosis and dysfunction. In cultured renal NRK52E cells, exposure to TGF-beta1 induced EMT and apoptosis, major causes of renal fibrosis and tubular atrophy, respectively. Exposure to a pan-caspase inhibitor (ZVAD-FMK) prevented TGF-beta1-induced apoptosis but did not reduce EMT. In contrast, selective HSP72 expression in vitro inhibited EMT caused by TGF-beta1 as indicated by preserving the E-cadherin expression level and alpha-smooth muscle actin induction. Small interfering RNA directed against HSP72 blocked the cytoprotective effects of HSP72 overexpression on EMT in TGF-beta1-exposed cells. Taken together, our data indicate that HSP72 ameliorates renal tubulointerstitial fibrosis in obstructive nephropathy by inhibiting both renal tubular epithelial cell apoptosis and EMT.

Topics: Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Cell Line; Cell Proliferation; Cell Transdifferentiation; Diterpenes; Epithelial Cells; Fibrosis; HSP72 Heat-Shock Proteins; Kidney Failure, Chronic; Kidney Tubules, Proximal; Male; Mesenchymal Stem Cells; Rats; Rats, Sprague-Dawley; Transforming Growth Factor beta1

Geranylgeranylacetone (GGA) induces apoptosis in human leukemia HL-60 cells in a dose- and time-dependent manner. This effect was completely prevented by the pan-caspase inhibitor z-Val-Ala-Asp(OMe) fluoromethylketone, thereby implicating the caspase cascade in the process. Prior to DNA fragmentation, GGA treatment markedly activated caspase-3(-like) proteases, which might be responsible for the observed apoptosis. In addition, GGA treatment interfered with the processing and membrane localization of Rap1 and Ras, and these changes may be a result of apoptosis. Moreover, nitric oxide donors significantly accentuated the GGA-induced apoptosis, suggesting that the apoptotic pathway induced by GGA might be regulated by a redox-sensitive mechanism. Taken together, these data suggest that the isoprenoid, GGA, is an effective inducer of apoptotic cell death in HL-60 cells.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; bcl-2-Associated X Protein; Blotting, Western; Caspases; Diterpenes; DNA Fragmentation; DNA-Binding Proteins; Dose-Response Relationship, Drug; HL-60 Cells; Humans; Multigene Family; Nitroso Compounds; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; ras Proteins; Subcellular Fractions