Phorbol Ester-induced Ornithine Decarboxylase Activity Research Articles

Inhibitory effects of the standardized extract (DA‐9601) of Artemisia asiatica Nakai on phorbol ester–induced ornithine decarboxylase activity, papilloma formation, cyclooxygenase‐2 expression, inducible nitric oxide synthase expression and nuclear transcription factor κB activation in mouse skin

Artemisia asiatica Nakai has been used in traditional Asian medicine for the treatment of inflammatory and other disorders. Previous studies have revealed that the formulated ethanol extract (DA-9601) of A. asiatica has pronounced antioxidative and antiinflammatory activities and exhibits cytoprotective effects against experimentally induced gastrointestinal, hepatic and pancreatic damage. In the present study, we assessed the inhibitory effect of DA-9601 on tumor promotion, which is closely linked to inflammatory tissue damage. As an initial approach to evaluating the possible antitumor-promoting potential of DA-9601, its effects on TPA-induced ear edema were examined in female ICR mice. Pretreatment of the inner surface of the mouse ear with DA-9601 30 min prior to topical application of TPA inhibited ear edema at 5 hr. TPA-stimulated expression of epidermal COX-2 and iNOS was also mitigated by topical application of the same extract. Moreover, DA-9601 abrogated the TPA-mediated activation of NF-kappa B/Rel and AP-1 in mouse epidermis. Suppression of epidermal NF-kappa B by DA-9601 appeared to be mediated in part through inhibition of I kappa B alpha degradation, thereby blocking the nuclear translocation of p65, the functional subunit of NF-kappa B. DA-9601 also significantly suppressed TPA-induced ODC activity and papilloma formation in mouse skin. Taken together, these findings suggest that DA-9601 derived from A. asiatica possesses potential chemopreventive activities.

Cubé resin insecticide: identification and biological activity of 29 rotenoid constituents.

Cubé resin, the root extract from Lonchocarpus utilis and urucu, is an important insecticide, acaricide, and piscicide. The four major active ingredients are rotenone, deguelin, rotenolone, and tephrosin, totaling 77 wt %. As a commercial pesticide, the minor constituents are also of chemical interest and toxicological relevance. This study identifies 25 minor rotenoids in cubé resin "brittle" of which 12 are new compounds, the most unusual being 7'-chloro-5'-hydroxy-4',5'-dihydrodeguelin (the first chlororotenoid from a plant extract) and four isomers of 4',5'-dihydro-4', 5'-dihydroxytephrosin. Several of the minor rotenoids may be decomposition products from free radical processes during sample preparation, extraction with trichloroethylene, and processing the resin. Assays of the 29 rotenoids as inhibitors of NADH:ubiquinone oxidoreductase activity (primary target for toxicity) and phorbol ester-induced ornithine decarboxylase activity (indicator of cancer chemopreventive action) and for cytotoxicity establish similar structure-activity relationships in each system and the importance of the overall molecular conformation and the E-ring substituents.

New bioactive flavonoids and stilbenes in cubé resin insecticide.

Fractionation of cubé resin from Lonchocarpus utilus and L. urucu roots led to the isolation and identification of 11 minor flavonoids and stilbenes containing the gem-dimethylpyran moiety or a dihydrodiol derivative thereof. The eight new compounds were as follows: the isoflavonoid cis-4'',5''-dihydro-4'',5' '-dihydroxylonchocarpusone (2); four (2S)-6-(gamma, gamma-dimethylallyl)-6'',6''-dimethylpyran[2'',3'':7, 8]flavanones with substituents of 5-hydroxy-3',4'-dimethoxy (3), 5, 3'-dihydroxy-4'-methoxy (4), 5,4'-dihydroxy-3'-methoxy (5), and 3', 4'-dimethoxy (6); and three 6'',6''-dimethylpyran[2'',3'':3', 4']stilbenes with 4-hydroxy-5'-methoxy (9), 3,5'-dimethoxy-4-hydroxy (10) and 3,4,5-trimethoxy (11) substitution patterns. Structure-activity relationships for inhibition of NADH:ubiquinone oxidoreductase activity (bovine heart electron transport particles) and phorbol ester-induced ornithine decarboxylase activity (cultured MCF-7 cells) generally parallel those for cytotoxicity (MCF-7 and Hepa 1clc7 cells).

Rotenoids and chalcones from Mundulea sericea that inhibit phorbol ester-induced ornithine decarboxylase activity

Two novel rotenoids, (−)-13α-hydroxydeguelin and (−)-13α-hydroxytephrosin, and a new chalcone, munsericin, were isolated from the bark of Mundulea sericea, and their structures were elucidated by spectroscopic methods. Also obtained were the parent rotenoids, deguelin and tephrosin, and the known chalcone, 4-hydroxy-lonchocarpin. The rotenoids and chalcones exhibited potent inhibitory activity against phorbol ester-induced ornithine decarboxylase activity in cultured mouse 308 epidermal cells.

Comparison of the Rate of Uptake and Biologic Effects of Retinol Added to Human Keratinocytes Either Directly to the Culture Medium or Bound to Serum Retinol-Binding Protein

Retinol circulates in the plasma bound to retinol-binding protein (RBP), but the mechanism by which retinol is transferred from RBP to target cells is not known. To study retinol delivery, human keratinocytes (HKc) were incubated with [3H]retinol added directly to the culture medium or bound to RBP and the uptake of [3H]retinol was determined at various times. During the first hour of incubation, the rate of [3H]retinol accumulation by HKc was about 40 times greater when the vitamin was added directly to the media rather than bound to RBP. Although maximal uptake of [3H]retinol added directly to the culture medium occurred at 3 h, the uptake of [3H]retinol from RBP was linear with time for at least 72 h. By 57 h, cell-associated [3H]retinol was the same whether it was added directly to the culture medium or bound to RBP. Excess unlabeled retinol or pretreatment of HKc with retinol had no effect on the uptake of [3H]retinol added directly to the culture medium or bound to RBP. Apo- but not holo-RBP was capable of competing with HKc for the uptake of [3H]retinol from RBP. No specific or saturable binding of 125I-labeled RBP to HKc cultured in the absence or the presence of retinol was found. The dose response of retinol inhibition of cholesterol sulfate synthesis and phorbol ester-induced ornithine decarboxylase activity or retinol modulation of keratin expression was the same whether the retinol was delivered to HKc bound to RBP or added directly to the medium. Our data support a mechanism for retinol delivery from RBP to HKc that does not involve cell-surface RBP receptors but instead suggest that the vitamin is first slowly released from RBP and then becomes cell-associated from the aqueous phase. This mechanism is consistent with the finding that HKc respond identically to retinol whether or not it is delivered to them bound to RBP.

Novel heteroarotinoids: synthesis and biological activity

In this study, 13 heteroarotinoids were synthesized. The key step in each preparation was the condensation of the appropriate chroman-, thiochroman-, or benzothienyl-substituted phosphorus ylide, obtained from the independent synthesis of the corresponding phosphonium salts, with selected polyene-substituted aldehyde esters. Nine of these heterocycles contained a thiochroman group, two had a chroman group, and two others had a benzothienyl system. Screening of the compounds was with one of two assays. One assay measured the ability of a retinoid to inhibit the phorbol ester induced increase of mouse epidermal ornithine decarboxylase (ODC) activity. The other assay measured retinoid-induced differentiation of the human myoloid leukemia cell line HL-60. In the ODC assay, all thirteen compounds were screened. The most active heteroarotinoids were ester 10 [methyl (E)-4-[2-(2,2,4,4-tetramethylthiochroman-6-yl)-1- propenyl]benzoate] and acid 11 [(E)-4-[2-(2,2,4,4-tetramethyl-3,4- dihydro-2H-1- benzothiopyran-6-yl)-1-propenyl]benzoic acid]. Both of these retinoids had ID50 values (dose required for half-maximal inhibition of phorbol ester induced ODC activity) of about 0.3 nmol. In comparison, the ID50 value for trans-retinoic acid (1) was 0.12 nmol while the ID50 values for acids 7 and 9, namely (2Z,4E,6E)-3,7-dimethyl-7-(4,4-dimethyl-thiochroman -6-yl)-2,4,6-heptatrienoic acid and (2E,4E,6E)-3,7-dimethyl-7-(2,2,4,4-tetramethylthiochroman -6-yl)-2,4,6- heptatrienoic acid, respectively, were about 3.5 nmol. Heteroarotinoids 8 and 12-17 had ID50 values of 35 nmol or greater. With a thiochroman unit, the most active acids in decreasing order of activity in the ODC assay were 7 greater than 9 greater than 8. Thus, simple replacement of the terminal propenyl system [C(16,17,18)] in 7 with a cyclopropyl group produced acid 8 [(2E,4E,6E)-7-methyl-7-(4,4-dimethylthiochroman-6-yl)- 2,3-methylene-4,6-heptadienoic acid with markedly reduced activity. With a benzoic acid group as part of the structure attached to the thiochroman unit, the ODC activity was enhanced as shown in 10 and 11. The combination of the 2,2,4,4-tetramethylthiochroman group and the benzoic acid (or ester) terminal group seemed to enhance the biological action which resembles that found with (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)- 1-propenyl]benzoic acid (TTNPB, 6b), a well-known model system.(ABSTRACT TRUNCATED AT 400 WORDS)

Epidermal cell proliferation and modulation of the protective potency of dexamethasone against phorbol ester-induced ornithine decarboxylase activity.

Treating mouse skin with dexamethasone (DXME, 1 mumol) after a single TPA (3.25 nmol) application, inhibited both the dermal inflammatory reaction and the induction of epidermal ornithine decarboxylase (ODC) activity. At the hyperplastic stage, DXME was active against inflammation, though inhibited weakly the induction of ODC. In DXME-protected skin, the hyperplastic stage was delayed; unexpectedly, before that stage, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced strongly ODC activity in the epidermal cell layer. Provided that the proliferation process was induced, epidermal cells were increasingly sensitive toward TPA action; they may have been less dependent on inflammatory factors which may modulate the induction of ODC.