Comparative studies of the effects of stilbene compounds on hepatic ornithine decarboxylase and S-adenosylmethionine decarboxylase induction in rats

Organosulfur compounds from alliaceae in the prevention of human pathologies

A strong association between elevated plasma low-density-lipoprotein (LDL) and the development of cardiovascular diseases (CVD) has been established. Oxidation of LDL (Ox-LDL) promotes vascular dysfunction, enhances the production and release of inflammatory mediators such as reactive oxygen species and contribute to the initiation and progression of atherosclerosis. In addition, Ox-LDL enhances the production and release of tumor necrosis factor (TNF-alpha), interleukin (IL)-6, arachidonic acid metabolites and nitric oxide (NO) that are responsible for various human pathologies including cancer. Organosulfur compounds (OSC) from alliaceae modulate the glutathione (GSH) redox cycle and inhibits NFkappa-B activation in human T cells. Furthermore, OSC bioactivities include antioxidant, antibacterial, anticarcinogenic, antiatherogenic, immunostimulatory, and liver protection potential.

Cooperative induction of c-fos and heme oxygenase gene products under oxidative stress in human fibroblastic cells

Heme oxygenase-1 is a stress responsive enzyme and implicated in a protective function of cellular damage. We investigated cellular events leading to the heme oxygenase-1 gene expression induced by sublethal concentrations of glutathione depletors, phorone and diethyl maleate, in human fibroblastic cells. Accumulation of heme oxygenase-1 mRNA by glutathione depletors was canceled by simultaneous treatment with cycloheximide, an inhibitor of protein synthesis; however, the inhibitory effect decreased when the inhibitor was added 30 min later. Among the inducible early response genes, the c-fos expression was significantly elevated with a peak at 30 min after the agents. Accumulation of heme oxygenase-1 and c-fos transcripts was abrogated in cells pretreated with 1,4-diazabicyclo[2.2.2]octane, an oxygen-free radical quencher. Decrease in glutathione levels preferentially activated extracellular-signal regulated kinases rather than other stress-activated protein kinases such as c-Jun N-terminal kinases and p38 MAP kinase. Pretreatment of cells with PD 98059, an inhibitor of the extracellular-signal regulated kinase cascade, or the c-fos antisense oligodeoxynucleotide inhibited the heme oxygenase-1 induction elicited by glutathione depletion. These observations indicated that c-Fos protein plays a role in heme oxygenase-1 gene expression induced by glutathione depletion-mediated oxidative stress in human fibroblasts.

Induction of metallothionein synthesis by glutathione depletion after trans- and cis-stilbene oxide administration in rats

To investigate the relationship between glutathione (GSH) depletion and metallothionein (MT) synthesis, the effects of substrates and an inhibitor of GSH S-transferases on concentrations of hepatic GSH, zinc (Zn) and MT were studied in rats. Trans-stilbene oxide (TSO) is an inducer of drug metabolizing enzymes and also a substrate of GSH S-transferase, whereby it covalently reacts with and depletes GSH. The hepatic GSH level was decreased to 25% of the control 2 h after injection of TSO, and returned to the control level by 24 h. TSO significantly increased hepatic concentrations of Zn and MT in a dose-dependent manner. Two isoforms of MT (MT-I and MT-II) were increased by TSO; MT-II was the dominant form. Pretreatment with buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, enhanced MT synthesis itself as well as that induced by TSO and cis-stilbene oxide (CSO). On the contrary, infection into rats of perfluorodecanoic acid (PFDA), an inhibitor of GSH S-transferase, resulted in a decrease in basal levels of Zn, and prevented the increase in MT synthesis by TSO and CSO. These results suggest that the decrease of GSH concentration in the liver which causes oxidative stress conditions may be related to MT induction.