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Background: Ultraviolet A (UVA) is known to induce the expression of many stress responsive genes due to the generation of reactive oxygen species (ROS). However, UVA's role in inducing metallothionein (MT) gene expression has not been studied. Furthermore, our group demonstrated that UVA enhanced 12-O-tetradecanoylphorbol-13-acetate (TPA)-mediated induction of ornithine decarboxylase (ODC) activity in mouse skin (1)., Methods: We examined the interaction of UVA, TPA and antioxidants on the induction of MT and ODC mRNA in mouse skin. Female CD-1 mice were exposed to UVA (19 J/cm2) and total RNA was isolated from the skin. Northern blot analysis for MT and ODC mRNAs was performed. ODC activity in mouse epidermis was also determined in some experiments., Results: UVA induced MT mRNA in mouse skin; however, it did not increase ODC mRNA. 1,4-Diazabicylo-[2,2,2]-octane (DABCO), a singlet oxygen scavenger, reduced UVA-mediated induction of MT mRNA by 40%. The data suggest that ROS produced by UVA exposure may contribute to its ability to induce MT mRNA. UVA slightly enhanced TPA-mediated ODC mRNA induction, while it enhanced ODC enzyme activity 70%. UVA additively intensified TPA-mediated MT mRNA induction. alpha-Tocopherol pretreatment inhibited the induction of ODC enzyme activity by TPA treatment combined with UVA exposure (TPA + UVA); however, alpha-tocopherol had less of an inhibitory effect on ODC mRNA induction by TPA + UVA. Curcumin, a plant pigment, dramatically inhibited both TPA- and TPA + UVA-induced expression of ODC and MT genes., Conclusions: These results demonstrate that UVA can induce MT gene expression and enhance TPA-induced ODC and MT gene expression. The data further suggest that these effects are partially mediated by ROS.

Oleanolic acid (OA) has been shown to inhibit mouse skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA). This study was designed to examine the effect of OA on the TPA-induced expression of the ornithine decarboxylase (ODC) gene as well as other genes. OA inhibited the induction of ODC activity and mRNA level produced by TPA in the skin of female CD-1 mice. Preapplication of OA (10 mumol) to the mouse dorsal skin produced an approximately 50% decrease in TPA (8 nmol)-induced epidermal ODC activity, as well as ODC gene expression. These results suggest that OA inhibits TPA-induced ODC mainly at the transcriptional level. In addition to ODC, TPA also stimulated metallothionein (MT) gene expression in mouse skin. A dose of 2.5 mumol of OA diminished the TPA-induced MT mRNA 50%. Treatment with OA (10 mumol) after TPA (8 nmol) application also inhibited ODC and MT gene expression which suggests that OA does not compete with TPA for its receptor. OA pretreatment also prevented c-fos gene expression. All of these findings suggest that OA diminishes some signal transduction pathways of TPA to suppress target gene expression in mouse skin. This study suggests that OA might be a general inhibitor against TPA-stimulated gene expression in mouse skin.

Background: Previous studies have demonstrated appreciable tumor induction in mouse skin by daily irradiation with high-power long-wavelength ultraviolet A (UVA)., Object: The aim of the present study was to examine the enhancing effects of UVA on changes in mouse skin mediated by the tumor promoter 12-o-tetradecanoylphorbol-13-acetate (TPA) by measurement of ornithine decarboxylase (ODC) activity and morphometric analysis. In addition, we examined the inhibitory effects of curcumin, a component of turmeric, on these changes., Method: ODC activity in the epidermis of CD-1 mice was determined by the method of Russell and Snyder. Epidermal and dermal thickness, and the number of dermal infiltrating inflammatory cells were quantified using a computer-assisted image analyzer., Results: A combination of topical TPA application and UVA irradiation produced a greater increment of ODC activity at 4 h than TPA alone (p < 0.05). Histopathologically, TPA plus UVA tended to increase the dermal infiltrating inflammatory cells in contrast to TPA alone. Pretreatment of mice with curcumin significantly abrogated the TPA-induced changes in ODC activity and the dermal infiltrating inflammatory cells as well as the TPA plus UVA-mediated enhancement of these changes., Conclusion: Our data indicate that UVA irradiation (18.72 J/cm2) significantly enhances ODC induction at an early stage (4-6 h) after topical application of TPA, and aggravates the dermatitis elicited by TPA. Pretreatment with curcumin significantly inhibits these enhancing effects.

Trans-Stilbene oxide (TSO, 2 mmol/kg, ip.) induced ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) to 60-fold and 5-fold of the controls, respectively, in the liver of rats. Parallel to ODC induction, there was a marked increase in putrescine content to 50-fold of the control levels. Cis-Stilbene oxide (CSO), a stereoisomer of TSO, also produced the induction of ODC and SAMDC and the increase in putrescine content. There was no difference in the ability to induce ODC and SAMDC between TSO and CSO with respect to the extents of induction and the time needed to reach maximal levels. Trans-Stilbene (TS), a mother compound of TSO, did not show such an effect on ODC, while cis-stilbene (CS) induced both ODC and SAMDC. Treatment with glutathione inhibited TSO- and CSO-mediated induction of ODC and SAMDC. These findings add new information concerning the abilities of TSO, CSO and CS on hepatic polyamine metabolism.

The administration of sulfobromophthalein (BSP, 0.5 mmol/kg, ip.) increased ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) activities to 30-fold and 5-fold, respectively, of the controls at 12 hr in the liver of rats. Parallel to the increase in ODC, there was an increase in hepatic putrescine content. However, spermine content tended to decrease. BSP increased ODC and SAMDC activities and putrescine content, but decreased spermine content, in a dose-dependent manner. Pretreatment of rats with actinomycin D and cycloheximide almost completely blocked the BSP-mediated increase of ODC and SAMDC activities. Pretreatment with glutathione (GSH) failed to inhibit BSP-mediated increase of ODC and SAMDC activities. In addition, the administration of BSP-GSH conjugate (0.5 mmol/kg, iv.) did not produce the increase of ODC and SAMDC activities. Pretreatment with phenobarbital and 3-methylcholanthrene did not inhibit BSP-mediated increase of ODC and SAMDC. The results indicate that BSP could cause changes in hepatic polyamine content due to the induction of ODC and SAMDC.

The administration of Phorone (diisopropylidene acetone, 250 mg/kg, ip.), a glutathione (GSH) depletor, markedly induced (400-fold of the control at 12 hr) ornithine decarboxylase (ODC) in the liver of rats. Parallel to ODC induction there was a marked increase in hepatic putrescine content. Phorone also produced an increase in spermidine content and a decrease in spermine content. The effects of phorone on ODC and putrescine content occurred dose-dependently with more than a 1000-fold increase in ODC activity over the controls at a dose of 500 mg/kg. Pretreatment of rats with buthionine sulfoximine, a GSH depletor by inhibition of biosynthesis, failed to inhibit phorone-mediated induction of ODC. In contrast, pretreatment with GSH, but not post-treatment, blocked the induction of ODC by phorone.

Co-protoporphyrin, like Co2+, produced a significant and persistent induction of hepatic ornithine decarboxylase (ODC) as well as its known inducing effect on heme oxygenase and the decreasing effects on drug-metabolizing enzymes. The induction of ODC and heme oxygenase by Co-protoporphyrin occurred dose-dependently with the lowest effective dose of 6.25 mumol/kg. Although Co-protoporphyrin produced similar effects on ODC and heme oxygenase to Co2+, there were differences in the mode of ODC induction. In particular, pretreatment with diethyl maleate failed to augment the induction of ODC by Co-protoporphyrin. Moreover, multiple administrations of Co2+, but not Co-protoporphyrin, caused super-additive induction of ODC to about 1000-fold over the controls. This super-additive induction of ODC by Co2+ was dependent on the doses and time intervals between two administrations. In parallel with a large induction of ODC evoked by two administrations of Co2+, hepatic putrescine content was increased markedly, while spermine content was decreased as compared to the control levels. Pretreatment with Co2+ led to super-additive induction of ODC by subsequent administration of the metal ion itself or diethyl maleate, but not by other ODC inducers, such as Co-protoporphyrin and thioacetamide, and not by subsequent partial hepatectomy. Under these experimental conditions, the magnitudes of heme oxygenase induction were similar. ODC induced by two doses of Co2+ was insensitive to exogenous putrescine, but sensitive to alpha-difluoromethylornithine and 1,3-diaminopropane. These findings add new insight into the effects of Co2+ and Co-protoporphyrin on hepatic polyamine metabolism; and the results suggest that the metal ion could cause extensive derangement of the ODC regulatory system in a manner different from the metalloporphyrin.

Diethyl maleate (DEM), a well-known glutathione (GSH) depletor, causes a dose-dependent increase in hepatic ornithine decarboxylase (ODC) activity as well as heme oxygenase activity in rats. Considering the important role ODC has in polyamine biosynthesis in response to endogenous and exogenous stimuli, further extensive studies on the effect of DEM on ODC in relation to its GSH-depleting effect were carried out. Specifically, concomitant with the profound decrease in GSH content, the higher dose of DEM (1284 mg/kg) caused a marked increase in ODC activity (about 1000 times that of the control) at 12 hr after its administration. DEM at this dose also caused a marked increase in heme oxygenase activity, but the effects on cytochrome P-450 content and aminopyrine demethylase activity were less extensive. The increases in ODC and heme oxygenase activities evoked by DEM were almost completely blocked by pretreatment of rats with either actinomycin D or cycloheximide. Parallel to the increase in ODC activity, DEM caused a profound increase in putrescine content in the liver, while the agent reduced spermine content. The administrations of alpha-difluoromethylornithine and 1,3-diaminopropane resulted in the inhibition of DEM-mediated induction of ODC, but not heme oxygenase. In contrast, methylglyoxal bis(guanylhydrazone) inhibited the induction of both ODC and heme oxygenase evoked by DEM. The DEM-induced ODC exhibited two phases of decay with the prolonged half-lives of 26 and 223 min. Additionally, the elution profile from DEAE-Sepharose CL-6B column chromatography of cytoplasmic fraction from DEM-treated rat liver exhibited two peaks of ODC activity. These findings add new insight into the biochemical effect of DEM on hepatic polyamine metabolism in addition to its GSH-depleting effect.

The level of rat hepatic ornithine decarboxylase (ODC) induced by repetitive administration of Co2+ was determined by affinity labeling with [3H]difluoromethylornithine. Such a treatment with Co2+ ion induced ODC level to a 10-fold greater extent than single dose of the metal ion or well-known inducers of the enzyme, such as thioacetamide or carbon tetrachloride. The half life of ODC activity induced by repetitive treatment with Co2+ (95 min) was substantially increased to about 10-fold over the value obtained from the enzyme induced by single treatment with the metal ion (10 min). ODC activity induced by repetitive treatment with Co2+ was separated into two peaks by DEAE-Sepharose column chromatography. The two independently collected fractions of ODC peaks exhibited different affinity for pyridoxal 5'-phosphate in vitro and sensitivity to cycloheximide in vivo.