Interaction of a cyclic peptide, Ro09-0198, with phosphatidylethanolamine in liposomal membranes.

Ro09-0198 is a cyclic peptide isolated from Streptoverticillium griseoverticillatum. This peptide caused permeability increase and aggregation of liposomes containing phosphatidylethanolamine. Liposomes containing phosphatidylserine, phosphatidylinositol or cardiolipin instead of phosphatidylethanolamine were, however, not appreciably reactive with the peptide. Among the structural analogs of phosphatidylethanolamine, dialkylphosphatidylethanolamine and 1-acylglycerophosphoethanolamine incorporated into liposomes could interact with Ro09-0198 to cause a permeability increase, whereas liposomes consisting of alkylphosphoethanolamine or phosphatidyl-N-monomethylethanolamine were insensitive to the peptide. These findings indicate that a glycerol backbone and a primary amino group of phosphatidylethanolamine are necessary for interaction with Ro09-0198 to cause membrane damage. Ro09-0198 induced a selective permeability change on liposomes. Glucose and umbelliferyl phosphate were effluxed significantly, but sucrose was only slightly permeable and inulin could not be released. Consequently, the permeability increase induced by Ro09-0198 is rather specific to molecules smaller than sucrose. Line broadening of electron spin resonance signals of spin-labeled phosphatidylethanolamine was observed upon treatment of liposomes with Ro09-0198. It was suggested from these results that Ro09-0198 can alter the physical organization of phosphatidylethanolamine in membranes, thus providing a basis for changes in membrane permeability.

Hemolytic activity of a cyclic peptide Ro09-0198 isolated from Streptoverticillium.

Ro09-0198, a cyclic peptide isolated from culture filtrates of Streptoverticillium griseoverticillatum, induced lysis of erythrocytes. Preincubation of the peptide with phosphatidylethanolamine reduced the hemolytic activity, whereas other phospholipids present in erythrocytes in nature had no effect. A study of the structural requirements on phosphatidylethanolamine necessary for interaction with the peptide indicates that Ro09-0198 recognizes strictly a particular chemical structure of phosphatidylethanolamine: dialkylphosphoethanolamine as well as 1-acylglycerophosphoethanolamine showed the same inhibitory effect on hemolysis induced by Ro09-0198 as diacylphosphatidylethanolamine, whereas phosphoethanolamine gave no inhibitory effect. Neither phosphatidyl-N-monomethylethanolamine nor alkylphosphopropanolamine had an inhibitory effect. Consequently, the hydrophobic chain is necessary for the interaction and the phosphoethanolamine moiety is exactly recognized by the peptide. Ro-09-0198-induced hemolysis was temperature-dependent and the sensitivity of hemolysis differed greatly among animal species.

Quantitative assessment of estrogenic activity in the water environment of Korea by the E-SCREEN assay.

In this study, the E-SCREEN assay was optimized and validated for the sensitive quantitative determination of the total estrogenicity in river samples. River water and sediment samples were collected and analyzed with the E-SCREEN. River water (10 l) was extracted using combined solid-phase extraction in static adsorption mode with Soxhlet extraction. Estrogenic pollutants adsorbed to the XAD-4 resin were recovered with 98.24 +/- 5.90% efficiency by elution with ethyl acetate and dichloromethane (1:9). The detection limit by 17beta-estradiol equivalent concentration (EEQ) of the E-SCREEN assay was 8.03 pg EEQ/l. Among the water samples, the estrogenic activity was observed to be higher downstream of the Kumho river (7.43 ng EEQ/l) and upstream of Kum river (2.05 ng EEQ/l) than in other samples. More than 3 mg of equivalent sediment samples from the Kumho river, Kum river and Miho stream showed partial agonistic effects, and the Mankyung river showed a partial agonistic effect with only 1.5 mg of sediment. The highest value of RPE was 83.34 downstream of the Kumho river, and the lowest value of RPE was 6.52 downstream of the Miho stream. Full estrogen agonistic activities were observed downstream of the Kumho river and upstream of the Kum river. The partial agonistic activity was observed in upstream of the Kumho river, downstream of the Mankyung river, and upstream of the Miho stream, and no agonistic action was observed downstream of the Kum river or Miho stream, or upstream of the Mankyung river. The total estrogenic activity in the river water and sediment samples was between 0.50 pg/L and 7.4 ng/L, 3.39 pg/g and 10.70 pg/g.

Induction of differentiation of U-937 cells by 2-chloro-3-amino-1,4-naphthoquinone.

Naphthoquinone compounds have various pharmacological effects such as antiviral, antifungal and anticancer activities. We demonstrated the differentiation of the inducing effect of a naphthoquinone derivative, 2-chloro-3-amino-1,4-nahpthoquinone (NQCA) on the human leukemia cell line U-937. When U-937 cells were treated with NQCA for 4 days, phenotypes indicative of differentiation such as nitroblue tetrazolium (NBT)-reducing activity and phagocytosis were induced. To evaluate the route of differentiation of U-937 cells induced by NQCA, we determined naphthol AS-D chloroacetate esterase and alpha-naphthyl acetate esterase activities. Four days treatment of U-937 cells with NQCA increased alpha-naphthyl acetate esterase activity about 63.5% but naphthol AS-D chloroacetate esterase was not detected. These results indicate that NQCA caused differentiation of U-937 cells into macrophage-like cells. Since protein kinase C (PKC) and protein kinase A (PKA) have important roles in cell-differentiation and proliferation, we employed a PKC inhibitor NA-382 and a PKA inhibitor H-89 to examine the effects of each kinase on the differentiation of U-937 cells. The PKC inhibitor NA-382 decreased the effect of NQCA on U-937 cells, while the PKA inhibitor H-89 did not. Also glutathione (GSH) inhibited the effect of NQCA. It is concluded that the differentiation-inducing effect of NQCA on U-937 cells may be attributed to PKC activation followed by production of free radicals.

Differentiation inducing effects of 2-chloro-3-amino-1,4-naphthoquinone on human leukemia HL-60.

There are some highly cytotoxic anticancer compounds inducing differentiation of cancer cells to normal cells at below highly cytotoxic concentration. Naphthoquinone derivatives having cytotoxic effects on cancer cell were tested to learn whether they have differentiation inducing activity in human leukemia HL-60 cells or not. When HL-60 cells were treated with 2-chloro-3-amino-1,4-naphthoquinone (CANQ) for four days, differentiation-related phenotypes such as nitrobluetetrazolium (NBT)-reducing ability and phagocytosis were induced. These differentiation markers were increased by cotreatment with 1,25-dihydroxyvitamin D3 which is a well-known inducer of differentiation in HL-60 cells. To evaluate the route of differentiation induced by CANQ, we examined naphthol AS-D chloroacetate esterase and alpha-naphthylacetate esterase activities and changes in cellular size and granulation. Treatment of HL-60 cells with CANQ for four days resulted in an 82.4% increase in alpha-naphthylacetate esterase activity in spite of a 0.2% increase in naphthol AS-D chloroacetate esterase activity. The size of cells in cell mass was larger and granulation was more decreased than untreated cells. These results indicate that HL-60 cells were induced to differentiate into macrophage-like cells.

Alteration in the biliary and urinary excretion of acetaminophen metabolites by nephrotoxicants in rats.

It has been shown that ureter ligation increases the biliary excretion of acetaminophen (AA) conjugates, mainly as the sulfate in rats. This study was conducted to examine the effect of nephrotoxicants-that induce renal damage without liver injury on the biliary and urinary excretion of AA metabolites. Renal damage was produced in male S.D. rats, 1 day after dosing with 200 mg/kg p.o. of hexachloro-1,3-butadiene (HCBD), or 3 day after the dosage of 7.5 mg/kg iv of cisplatin (CIS). Renal damage without liver injury was confirmed by measuring serum enzymes, creatinine and BUN levels. AA and its metabolites were measured for 3 hr by HPLC in rats injected iv with 150 mg/kg of AA. The excreted amounts of AA-glucuronide (AA-G), AA-sulfate (AA-S) and AA-glutathione into bile were reduced to 57, 18 and 73% of control rats, respectively, by HCBD. HCBD pretreatment also altered the urinary excretion of AA-G, AA-S and AA-mercapturate to 75, 14 and 118% of controls. CIS drastically reduced the urinary excretion of AA metabolites, whereas this compound significantly enhanced the biliary excretion of AA-S. However, CIS did not cause an increase in the percentage of the dose excreted as AA-G in bile. Both HCBD and CIS caused marked elevations in the blood concentrations of AA-G and AA-S. These findings suggest that: 1) not all renal malfunction results in increased biliary excretion of AA metabolites to compensate for the lack of renal elimination, and 2) the selective reduction in biliary and urinary excretion of AA-S by HCBD appears to occur by mechanism(s) other than through alteration of AA and its metabolites.

Complex formation of peptide antibiotic Ro09-0198 with lysophosphatidylethanolamine: 1H NMR analyses in dimethyl sulfoxide solution.

Ro09-0198 is a peptide antibiotic and immunopotentiator produced by Streptoverticillium griseoverticillatum which exhibits antitumor and antimicrobial activities. The chemical structure has been determined [Kessler et al. (1988) Helv. Chim. Acta 71, 1924-1929; Wakamiya et al. (1988) Tetrahedron Lett. 37, 4771-4772]. This peptide specifically interacts with (lyso)phosphatidylethanolamine, causing hemolysis and enhancing permeability in phosphatidylethanolamine-containing vesicles [Choung et al. (1988) Biochim. Biophys. Acta 940, 171-179, 180-187]. The highly specific nature of the interaction was studied by two dimensional proton NMR analyses. Proton resonances of the peptide were observed in dimethyl sulfoxide solution in the presence of 1-dodecanoyl-sn-glycerophosphoethanolamine. By comparison to the chemical shifts in the absence of lysophosphatidylethanolamine and by analysis of intermolecular cross-peaks in NOESY spectra, amino acid residues involved in the binding with the phospholipid were identified. The ammonium group of the phospholipid interacts with the carboxylate group of beta-hydroxyaspartic acid-15 but not with that of the carboxylate terminus. The secondary ammonium group of lysinoalanine-19/6 is probably bound to the phosphate group of the lipid. The peptide does not interact strongly with the fatty acid chain of the lipid. A folded structure of the central part [from Phe7 to Ala(S)14] of the peptide opens on binding with the phospholipid and accommodates the glycerophosphoethanolamine head group.

Transcriptional induction of Nur77 by indomethacin that results in apoptosis of colon cancer cells.

Non-steroidal anti-inflammatory drugs (NSAIDs) have cancer preventive and tumor regressive effects in the human colon, perhaps due to their capability to induce apoptosis of the colon cancer cells. Here, we report that indomethacin induced the expression of Nur77 which has been implicated in activation-induced apoptosis of T-lymphocytes, in a colon cancer cell line, HCT-15. The transcript- and protein-level, the transcriptional activity of Nur77 promoter, and the DNA binding of Nur77 were significantly induced following indomethacin treatment. Among the two potential trans-acting factors that activate Nur77-promoter, indomethacin induced DNA binding and reporter gene activity of AP-1, but not that of related serum response factor (RSRF), suggesting that the transcriptional induction of Nur77 may be mediated through activation of AP-I. Further, we showed that all trans-RA repressed the induction of Nur77 as well as the apoptosis-induced by indomethacin, providing evidence that transcriptional induction of Nur77 may be an important mechanism by which indomethacin induces apoptosis in colon cancer cells.

Alteration of acetaminophen metabolism by sulfate and steroids in primary monolayer hepatocyte cultures of rats and mice.

Sulfotransferase (ST) is considered to be generally not induced by xenobiotics. However, it has been reported that steroids such as dexamethasone (DEX) and pregnenolone-16a-carbonitrile (PCN) are effective ST inducers in rats, and sulfation of xenobiotics is quite different in rats and mice. The present study is primarily aimed at determining the effect of sulfate and steroids on the metabolism of acetaminophen (AA) in vitro using monolayer cultured hepatocytes of Sprague-Dawley rats and ICR mice. Hepatocytes of rats and mice were incubated with inorganic sulfate (0.25, 0.5, 1.0, 2.0, 4.0 mM) and AA in SO4-depleted media. AA sulfation rates increased as the sulfate concentration was raised to 1.0 mM in rats, whereas the addition of inorganic sulfate to the media had a lesser effect in mice hepatocytes. After pretreatment with DEX (0.1, 1.0, 10, 100 microM) and PCN (0.1, 1.0, 10 microM) for 3 d, hepatocytes were incubated with AA in media containing 4.0 mM SO4-. Pretreatment of the hepatocytes with DEX caused an increase in the glucuronidation and sulfation of AA by 2-3 folds in rats, but to a lesser extent in mice. PCN significantly enhanced the formation of AA-glucuronide and AA-sulfate in mice, but had a minimal effect on rat hepatocytes. In summary, sulfate and DEX markedly enhanced the formation of AA-sulfate in rats hepatocytes, and DEX and PCN increased the sulfation of AA in mice hepatocytes. These results partially support the claim that DEX and PCN are effective ST and uridine diphosphate-glucuronyltransferase inducers in vivo.

Activation of NF-kappaB determines the sensitivity of human colon cancer cells to TNFalpha-induced apoptosis.

Tumor necrosis factor alpha (TNFalpha) generates a potent cytotoxic effect, however many cancer cells are resistant to TNFalpha-mediated killing and the cause of the differential sensitivity remains to be elucidated. In this study, we demonstrated that TNFalpha induced cell death in four different human colon cancer cell lines. The degree of cytotoxic effect was different in each cell line, in that HCT-15 was relatively sensitive, while DLD-1, HT-29 and WiDr were relatively resistant. TNFalpha induced apoptotic changes such as morphological changes, DNA fragmentation and activation of caspase-3 in HCT-15, but to a lesser degree in the others. Transcriptional expression of TNFR1(p55), as well as that of FLICE, Fas, FADD, DR3, FAF, TRADD, and RIP was similar in these cell lines, indicating that the susceptibility to TNFalpha-induced apoptosis may not be determined by the constitutive expression level of these factors. Interestingly, the cytotoxic effect of TNFalpha was well correlated with the DNA binding activity of NF-kappaB in the colon cancer cell lines. Further, the overexpression of a non-phosphorylated mutant form of IkappaBalpha enhanced the cytotoxicity of TNFalpha in the resistant cell line, DLD-1, indicating that NF-kappaB activity may determine the sensitivity of colon cancer cells to TNFalpha-induced apoptosis. Thus, our results indicate that modulation of NF-kappaB activity may provide a useful tool to sensitize colon cancer cells to TNFalpha treatment.