OBJECTIVE: To explore the mechanism of alpha-difluoromethylornithine (DFMO) inhibiting ODC activity in the cortex and hippocampus in rats. METHODS: Forty male rats was randomly divided into ischemal control group and DFMO pretreatment group. DFMO was given intravenously half an hour before global cerebral ischemia, and expression of ODC mRNA was measured by comparative reverse transcription-polymerase chain reaction (RT-PCR) in the cortex and hippocampus in rats after 2, 4, 6 h and 8 h of reperfusion. The variations of the expression of ODC mRNA were studied in the DFMO pretreatment group and the ischemal control group respectively. RESULTS: After 2, 4 and 6 h of reperfusion, the expression of ODC mRNA in the cortex and hippocampus in the pretreatment group was lower than that in the ischemia control group significantly (P <0.05, P <0.01), but not at 8 h reperfusion (P > 0.05). CONCLUSION DFMO suppressed the expression of ODC mRNA after different lengths of reperfusion following 10-minute global cerebral ischemia in rats and it may be one of the ways for DFMO to inhibit ODC activity.
Animals ; Brain Ischemia ; metabolism ; Cerebral Cortex ; metabolism ; Eflornithine ; pharmacology ; Hippocampus ; metabolism ; Male ; Ornithine Decarboxylase ; biosynthesis ; genetics ; Ornithine Decarboxylase Inhibitors ; RNA, Messenger ; biosynthesis ; genetics ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Reperfusion Injury ; metabolism

UV radiation is known to cause photoaging of the skin and is considered one of the leading cause of developing skin carcinogenesis. Melatonin which has a highly lipophilic molecular structure facilitating penetration of cell membranes and serving as an extra- and intracellular free radical scavenger has been demonstrated to protect photodamage of skin affected by UV exposure. In this study, we have examined the role of melatonin in response to UVB induced photodamaging process, using human skin fibroblasts in vitro. Cell survival curves after UVB irradiation showed dose-dependent decrease. Only 60% of fibroblasts were survived at 140 mJ/cm2 UVB irradiation. By pre-cultivation of cells with melatonin (100 nM), a significant number of cells remained unaffected. After UVB irradiation with 70 mJ/cm2, the level of putrescine was 1.7+/-0.3 fold increased compared to melatonin pre-treated group. In Northern analyses, the transcriptional level of ornithine decarboxylase (ODC) gene expression was increased by UVB irradiation and prohibited by melatonin. These results indicated that melatonin was effectively able to neutralize membrane peroxidation when present in relevant concentration during UVB irradiation and diminishes the UVB-induced increase of polyamine synthesis and ODC gene expression. Collectively, ODC response to UVB induced changes are possibly involves a melatonin or antioxidant sensitive regulatory pathway in normal human skin fibroblast.
Antioxidants/*pharmacology ; Apoptosis/drug effects/radiation effects ; Fibroblasts/*drug effects/*radiation effects ; Human ; Melatonin/*pharmacology ; Ornithine Decarboxylase/biosynthesis/genetics ; Polyamines/*metabolism ; *Ultraviolet Rays

Ornithine decarboxylase (ODC) is the rate-limiting enzyme in polyamine biosynthesis and a target for chemoprevention. Hydroxydibenzoylmethane (HDB), a derivative of dibenzoylmethane of licorice, is a promising chemopreventive agent. In this paper, we investigated whether HDB would inhibit the ODC pathway to enhance apoptosis in human promyelocytic leukemia HL-60 cells. We found ODC enzyme activity was reduced during HDB treatment. Overexpression of ODC in HL-60 parental cells could reduce HDB-induced apoptosis, which leads to loss of mitochondrial membrane potential (Deltapsim), through lessening intracellular ROS. Furthermore, ODC overexpression protected cytochrome c release and the activation of caspase-3 following HDB treatment. The results demonstrated HDB-induced apoptosis was through a mechanism of down-regulation of ODC and occurred along a ROS-dependent mitochondria-mediated pathway.
Apoptosis/*drug effects ; Caspase 3/metabolism ; Chalcones/metabolism/*pharmacology ; Chemoprevention ; Cytochromes c/biosynthesis/secretion ; Down-Regulation ; Gene Expression ; HL-60 Cells ; Humans ; Immunoblotting ; Leukemia, Myeloid/*enzymology/pathology ; Membrane Potential, Mitochondrial/drug effects ; Mitochondria/enzymology ; Ornithine Decarboxylase/antagonists & inhibitors/genetics/*metabolism ; Reactive Oxygen Species/analysis/metabolism ; Reverse Transcriptase Polymerase Chain Reaction