Inhibitory effect on TPA

EBV = inhibitory effect on TPA-induced Epstein-Banr virus early antigen [170] ... 

Inhibitory Effects on TPA, HHPA, and Croton Oil-Induced Inflammatory Edema... 

Inhibitory Effects on TPA Stimulated 32Pi Incorporation in HeLa Cells... 

Induction of epidermal ODC is a characteristic biochemical alteration elicited by TPA and may be representative of the effects of phorbol esters with strong tumor promoting activity [81]. A single application of TPA (5 pg) resulted in a substantial and transient increase of epidermal ODC activity in mice with a peak at about 4 h after TPA treatment, and the induction was potently inhibited by treatment (5 pM) of the mouse skin with sitosterol (33, 65% inhibition) and three lupane type triterpenoids betulin (255 79%), betulinic acid (257 89%), and lupeol (264,96%) [30]. The inhibitory effect on TPA-induced ODC activity was further reported for ursolic acid (210 45% inhibition at 2.0 pM/5nM of TPA) [31]. 

It has been reported that karounidiol and 7-oxo-dihydrokarounidiol have an inhibitory effect on TPA-induced inflammation [86]. Topically applied, they completely inhibited edema generation in a dose-dependent manner. The ID5o of karounidiol and 7-oxo-dihydrokarounidiol were 0.4 and 0.3 mg/ear, respectively. 

Epstein-Barr virus early antigen induction. Methanol extract of the dried leaf, in cell culture at a concentration of 1 pg/mL, was inactive. The assay was designed for tumor-promoting activity . Two diastere-oisomers of 2,7,1 l-cembratriene-4,6-diol (a- and 3-CBT) from the neutral fractions of cigarette smoke condensate, in Raji cells, produced potent inhibitory effects on the induction of Epstein-Barr virus (EBV)-EA by 12-0-tetradecanoylphorbol-13-acetate (TPA). The doses of a- and P-CBT required for 50% inhibition of EBV-EA induction by TPA were 7.7 and 6.7 mg/mL, respectively. Application of a- and P-CBT to mouse skin before treatment with TPA, inhibited TPA-induced ornithine decarboxylase activity in a dose-dependent manner. Application of 16.5 pM/mouse of a- and p-CBT resulted... 

The inhibitory effects of the sterols and triterpenoids on TPA-induced inflammatory ear edema in mice are shown in Table 2. The inhibitory effects of three reference compounds, quercetin (4), a known inhibitor of TPA-induced inflammation in mice, and of two commercially available anti-inflammatory drugs, indomethacin (5) and hydrocortisone (6), were included for comparison. As is evident from Table 2, most of the compounds examined exhibited activity almost equivalent to or higher than quercetin (4). Inhibitory effects on the other experimental models were also included in Table 2. 

Soyasapogenol B, soyasaponins I and II and wistariasaponins from Wistaria brachybotrys (wistariasaponin C corresponds to astragaloside VIII) decreased (20-30%) the Epstein-Barr Virus (EBV) activation induced by the tumor promoter TPA (12-O-tetradecanoylphorbol-13-acetate) in Raji cells at a concentration of lxlO2 mol ratio [151]. Soyasaponin I from the same plant exhibited remarkable inhibitory effects on mouse skin tumor promotion on the basis of the two-stage DMBA-TPA carcinogenesis test in vivo. Soyasaponin I reduced the number of papillomas per mouse at about 40% even at 20 weeks [152]. 

Several terpenoids have been evaluated for their inhibitory effects on EBV-EA activation induced by TPA. Table 6 shows the inhibitory effects of monoterpenoids [70,71], sesquiterpenoids [20,119-123], diterpenoids [21,123-131], and meroterpenoids [117] against TPA (32 pmol, 20 ng)-induced EBV-EA activation in Raji cells. The inhibitory effects were compared with that of [3-carotene, a vitamin A precursor that has been studied intensively in cancer chemoprevention using animal models [2,4]. All of the terpenoids tested caused higher viability (60-80%) of Raji cells even at mol ratio of compound to TPA = 1000 1 indicating their very low cytotoxicity at that high concentration (refer to Table 6). 

Abies sachalinensis (C.F.Schmidt) Mast, (bark) Spirobiflavonoids (abiesinols). All compounds exhibited potent inhibitory effects on ( )-(iI)-methyl-2-[( )-hydroxyimino]-5-nitro-6-methoxyhex-3-enamide (NOR 1) activation. A spirobiflavonoid showed remarkable anti-tumor-initiating activity in the in vivo two-stage mouse skin carcinogenesis test using peroxynitrite (ONOO PN) as the initiator and 12-O-tetradecanoyl-phorbol- 13-acetate (TPA) as the promoter. Wada et al., 2010[476]. 

The studies were carried out on a primary screening test using their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol- 13-acetate (TPA), a strong promoter, in Raji cells. 

G (25) and soyasaponins I (26) exhibited remarkable inhibitory effects on EBV-EA activation but A and G have strong cytotoxicities on Raji cells. In these experiments the remarkable effect of soyasaponin I (more than 55-47% inhibition of activation at 5 x 102 mol ratio/TPA) was stronger than that of glycyrrhetic acid (23a) which is known as a strong antitumor promoter and it preserved the high viability of Raji cells [29, 30]. 

Many compounds that inhibit EBV-EA induction by TPA have been shown to act as inhibitors of tumor promotion in vivo [28]. Soyasaponin I (26) exhibited remarkable inhibitory effects on mouse skin tumor promotion on the basis of the two stage (DMBA-TPA) carcinogenesis... 

In a similar screening, Konoshima et al. [72] studied the inhibitory effects of twenty-four 29-nor-cucurbitacin glucosides isolated from the roots of Cayaponia tayuya and found that five of them, cayaponosides B, B3, D, D3b, and C2, exhibited significant inhibitory effects on EBV activation induced by the tumor promoter TPA. Moreover, two of the cucurbitacins shown to be active in vitro, cayaponosides B and C2, Fig. (14), inhibited mouse skin tumor promotion in a two-stage in vivo carcinogenesis test. 

Gomisin C has an inhibitory effect on the respiratory burst of rat neutrophils in vitro [243], The mechanism of action may be mediated partly by the suppression of NADPH oxidase and partly by the decrease in cytosolic Ca2+ released from an agonist-sensitive intracellular store. In fact, gomisin C attenuated the activity of TPA-activated neutrophil particulate NADPH oxidase in a concentration-dependent manner and reduced the increase in cytosolic free Ca2+ in neutrophils stimulated by fMLP in presence or absence of ethylenediaminetetraacetic acid (EDTA). In addition, this study suggests that the gomisin C mechanism is not mediated by changes in cellular cAMP or in inositol phosphates, or by scavenging... 

And, many compounds which showed strong inhibitory effects on the induction of EBV-EA by TPA have been shown to act as inhibitors of tumor promotion on two-stage carcinogenesis test in vivo [15-21, 27-29]. The one of two-stage carcinogenesis test is on mouse skin tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a... 

As shown in Table 3, the rotenoids 33,34 and 38 exhibited inhibitory effects on EBV-EA activation (more than 60% inhibition at 5 x 10 mol ratio/TPA), and 33 and 34 showed more remarkable inhibitory effects (about 30% inhibition even at a 1 x 10 mol ratio/TPA) than other rotenoids. The effects of 33 and 34 on the cell cycle of Raji cells were also examined, and it was concluded that the treatment of these compounds decreased the percentage of S phase and increased the percentage of the Gi phase in comparison with the positive control. Therefore, it was deduced that compounds 33 and 34 arrested Raji cells in the Gi phase, and consequently the percentage of G] phase in Raji cells was restored to normal value [21]. 

Also, the radix of A. heterotropoides var. mandshuricumm has been used in Chinese and Japanese traditional medicine and is also the important component of prescriptions. From the active -hexane fraction obtained from original MeOH extract of the radix of A. heterotropoides var. mandshuricum, six compounds (42 - 47) were isolated and their inhibitory effects on EBV-EA activation were examined. Of these compounds, lignans (46 and 47) exhibited more remarkable effects (more than 70% and 30% inhibitions at 5 x ICF mol ratio/TPA and 1 x 10 mol ratio/TPA, respectively) than phenylpropanoids (42 - 45) and preserved high viability of the Raji cells even at the highest concentration as shown in Table 5. Further, the effect of 46 on the cell cycle of Raji cells treated with TPA was also examined. 

On the basis of the results of the in vitro assays (inhibitory effects on EBV-EA activation and effects on the cell cycle of Raji cells induced by the promoter, TPA), the anti-tumor-promoting activities of 59 and 66 on the two-stage carcinogenesis test would be expected. 

Among these saponins, gymnocladussaponin G (95) exhibited the most significant inhibitory effects on EBV-EA activation (more than 85% and 60% inhibition at 1 x 10 and 1 x 10 mol ratio/TPA, respectively) and preserved high viability of Raji cells as shown in Table 11. Further, gleditsiasaponin C (79) and its prosapogenin C (75) showed week inhibitory effects on EBV-EA activation at 1 x 10 mol ratio/TPA. 

Many kinds of steroids and their glycosides were tested for their inhibitory effects on EBV-EA activation induced by TPA [63]. Of these steroids, though cardiac steroids and their glycosides had strong cytotoxicities against Raji cells at 1 x 10 mol ratio/TPA, they exhibited stronger inhibitory effects at lower concentration than other steroids. 

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