We nave examined the hypothesis that monocrotaline (MCT) independent of hepatocyte metaoolism and through the induction of oxidative stress stimulates cellular polyamine regulatory mechanisms and content which in turn is necessary for MCT to exert effects on PAEC. Confocal scanning laser microscopy showed an increase in the intensity of 2,7-dichlorofluorescin fluorescence (DCF) in MCT (2.5 mM) treated PAEC for 24 hr as compared to control cells, indicating ROS formation. MCT also increased the nuclear content of the oxygen radical associated nuclear protein NF-KB. Although MCT produced cytotoxicity, it failed to induce the degradation of genomic DNA to oligonucleosomal fragments a characteristic marker of apoptosis. MCT significantly increased PAEC cellular putrescine, spermidine and spermme content. A significant increase in abundance of ornithine decarboxylase (ODC) mRT>JA. was associated with upregulation of ODC activity and enhancement of 14C-spermidine import in MCT-treated PAEC. The depletion of cellular polyamine contents through the blockade of both de novq pplyamine biosynthesis and polyamine uptake system prevented MCT-induced increases in the expression of fibronectin in the conditioned medium of PAEC. Furthermore, cotreatment with dimethylthiourea (DMTU), an oxygen radical scavenger, attenuated MCT-induced increases in ÜCF fluorescence, NF-KB expression, cellular polyamine content. 14C-spermidine import and ODC activity. Relative to control cells, the expression of TGF-β1 growth factor was also increased in MCT-treated PAEC. These data support our hypothesis and are consistent with results of in vivo studies. (Supported by AHA).
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology