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PubMed1985

Study of differentiation of fresh myelogenous leukemic cells by compounds that induce a human promyelocytic leukemic line (HL-60) to differentiate.

The human promyelocytic leukemia cell line known as HL-60 can be triggered to mature to functional granulocytes and/or macrophages after exposure to a variety of compounds. The findings have generated enthusiasm for possible therapy of leukemia using compounds that induce leukemic cell differentiation. We investigated whether five compounds known to trigger HL-60 differentiation to granulocytes could trigger the maturation of blast cells from 12 patients with myelogenous leukemia. Maturation was judged by morphology, superoxide production, phagocytosis, expression of Fc receptors, and development of alpha-napthyl acetate esterase activity. The blast cells from most patients showed little morphological, histological or functional maturation after exposure to the various compounds as compared to the blast cells cultured without the compounds. Actinomycin was able to induce significant maturation of leukemic cells of some patients when maturation was analyzed by several statistical methods. Our study suggests that many compounds which trigger differentiation of promyelocytic leukemia cells may not trigger differentiation of less mature myeloid leukemic cells.

Adult↗

PubMed1988

Induction of differentiation of human promyelocytic leukemia cells (HL60) by metabolites of hexamethylene bisacetamide.

We studied the ability of five metabolites of hexamethylene bisacetamide (HMBA), which we had previously identified in patient urine, to induce differentiation or to influence differentiation induced by HMBA of a human promyelocytic cell line. Differentiation of HL60 cells was quantified by morphological changes and by the ability to reduce nitroblue tetrazolium. N-Acetyl-1,6-diaminohexane (NADAH), the deacetylated, first metabolite of HMBA, was a more potent inducer of HL60 differentiation than was HMBA. NADAH produced 20-30% differentiation at 0.25 mM and 30-40% differentiation at 0.5 mM. NADAH (1 mM) induced 2-3-fold more differentiation than did 1 mM HMBA. HL60 differentiation, induced by various combinations of HMBA and NADAH, reflected a combined effect of the two compounds. In contrast, 1,6-diaminohexane, at 0.5-5 mM, failed to induce HL60 differentiation. Similarly, 0.5-5 mM 6-acetamidohexanoic acid, the major metabolite of HMBA, and 6-aminohexanoic acid failed to induce differentiation of HL60 cells. However, 6-acetamidohexanoic acid, when combined with HMBA or NADAH at various concentrations and ratios, enhanced the differentiation of HL60 cells induced by these two compounds. This enhancement was most apparent with addition of 0.50-3.0 mM 6-acetamidohexanoic acid to HL60 cells incubated with 1.0-3.0 mM HMBA or 0.25-1.0 mM NADAH. 6-Aminohexanoic acid similarly enhanced HMBA-induced differentiation of HL60 cells. These in vitro results have implications in terms of the clinical application of HMBA and interpretation of the results of clinical trials performed to date and may provide some insight into the mechanism of HMBA-induced cellular differentiation.

Acetamides↗

PubMed1999

Cytoprotection and iron mobilization in rat hepatocyte cultures by a new synthetic dihydroxamate chelator.

The cytoprotection and iron mobilization effect of a new dihydroxamate chelator 1,1 bis [(11-N-hydroxy)-2,5,11-triaza-1,6,10-trioxo dodecanyl] ethane or KD was studied in primary rat hepatocyte cultures exposed to iron-citrate. Lactate dehydrogenase (LDH) release and malondialdehyde (MDA) production were measured as indexes of cytotoxicity. Cell viability was evaluated using the [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyl tetrazolium bromide] (MTT) reduction test. To demonstrate that this chelator was able to decrease iron uptake or increase iron release from the hepatocytes, labelled cells were obtained by maintaining the cultures in the presence of 0.02 microM 55Fe-citrate. The efficacy of KD was compared to desferrioxamine B (DFO) at stoechiometry concentrations. After 24 h of exposure to 50 microM of iron-citrate, a significant release of LDH and MDA was observed. Cell viability was also significantly decreased. When 100 microM of KD were added at the same time as iron, LDH and MDA release was decreased and cell viability was improved. In the presence of the same chelator concentration, a net decrease of iron uptake by the cells was observed as attested by the low intracellular 55Fe level. Moreover, in the 55Fe loaded hepatocytes, the chelator increased the iron extracellular level indicating its iron release effect from the cells. In all tested experimental conditions, the efficacy of 100 microM of the dihydroxamate chelator KD was close to that of 50 microM of the trihydroxamate chelator DFO. In conclusion, KD is effective at a level comparable to DFO in protecting rat hepatocytes against the toxic effect of iron-citrate by decreasing the uptake of the metal and increasing its release from the cells. This synthetic compound appears to have some potential therapeutical interest and the results obtained encourage the synthesis of new hydroxamate ligands.

Animals↗

PubMed2003

Synergistic protection of PC12 cells from beta-amyloid toxicity by resveratrol and catechin.

beta-Amyloid peptide (beta-AP) elicits a toxic effect on neurons in vitro and in vivo. Many environmental factors including antioxidants, metal ions and proteoglycans modify beta-AP toxicity. We have investigated on PC12 cells, the protective effect from beta-AP (1-41) of two plant polyphenols, resveratrol and catechin. PC12 cells treated with 10(-6)M beta-AP (1-41) for 16h decrease the cell viability at 24% of the control with an IC(50) value of 1.1+/-0.14 x 10(-8)M. Twenty-five micromolar resveratrol and 50 microM catechin protect PC12 cells from beta-AP (1-41) toxicity with the IC(50) value increased at 2.2+/-0.19 x 10(-7)M and at 8.9+/-0.7 x 10(-8)M, respectively. While the protective effect is concentration dependent for catechin, resveratrol shows a concentration-dependent biphasic effect. Up to 50 microM concentration, resveratrol protects PC12 cells from beta-AP (1-41) toxicity. At concentration higher than 50 microM, an inhibitory activity on cell proliferation appears. This antiproliferative effect is shown also in the absence of beta-AP (1-41). Resveratrol and catechin have a synergistic protective action. In the presence of 50 microM catechin and 10 microM resveratrol or 25 microM resveratrol and 10 microM catechin, the toxicity determined by 10(-7)M beta-AP (1-41) is almost completely abolished. Catechin is more effective than resveratrol in protecting PC12 cells from the toxicity of hydrogen peroxide. The protection from Oxygen Reactive Species (ROS) toxicity is concentration dependent for both resveratrol and catechin. In this case the protection is merely additive and the synergistic effect is not observed. These results demonstrate that resveratrol and catechin protect PC12 cells from beta-AP (1-41) toxicity and that their protective effect is synergistic. Such a protective effect probably is not due only to their antioxidant activity. The different chemical and biological activity shown by these compounds on several cell types and the complexity of the beta-AP (1-41) toxicity may explain the synergistic protective effect and suggest that the utilization of different compounds with synergistic activity may protect more effectively from complex mechanisms of toxicity.

Amyloid beta-Peptides↗

PubMed2005

The AMPA-antagonist talampanel is neuroprotective in rodent models of focal cerebral ischemia.

Cerebroprotection after administration of glutamate receptor antagonists has been well documented. The present study is intended to determine whether the non-competitive alpha-amino-3-hydroxy-methyl-4-isoxazolyl-propionic acid (AMPA) receptor antagonist talampanel, known as antiepileptic drug, has neuroprotective effects in stroke models in rodents. The infarct size was measured in three models of stroke by 2,3,5-triphenyltetrazolium chloride staining. Therapeutic time window was also examined in rats subjected to 1h middle cerebral artery occlusion. The degree of neuroprotection was tested in mice, using 1.5, 2 h or permanent middle cerebral artery occlusions. Effect on photochemically induced thrombosis was investigated in rats applying 30 min time window after brain irradiation. Talampanel reduced the infarct size by 47.3% (p<0.01) after a 30 min delay and 48.5% (p<0.01) after 2 h delay following middle cerebral artery occlusion in rats. In mice, talampanel reduced the extension of the infarcted tissue at the levels of striatum and hippocampus by 44.5% (p<0.05) and 39.3% (p<0.01) after 1.5 h transient ischemia and still caused 37.0% (p<0.05) and 37.0% (p<0.05) inhibitions when 2 h occlusion was applied. In photothrombosis talampanel showed a 40.1% (p<0.05) inhibition. Protective actions of talampanel in various stroke models, in rats and mice, suggest a possible therapeutic role of the compound in stroke patients.

Animals↗

PubMed2004

Madhucosides A and B, protobassic acid glycosides from Madhuca indica with inhibitory activity on free radical release from phagocytes.

The structures of madhucosides A (1) and B (2), isolated from the bark of Madhuca indica, were established as 3-O-beta-D-apiofuranosyl(1-->2)-beta-D-glucopyranosyl-28-O-[beta-D-xylopyranosyl(1-->2)-[alpha-L-rhamnopyranosyl(1-->4)]-beta-D-glucopyranosyl(1--> 3)-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranosyl]protobassic acid and 3-O-beta-D-apiofuranosyl(1-->2)-beta-D-glucopyranosyl-28-O-[beta-D-xylopyranosyl(1-->2)-[alpha-L-rhamnopyranosyl(1-->4)]-beta-D-glucopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopyranosyl]protobassic acid, respectively. These two compounds showed significant inhibitory effects on both superoxide release from polymorphonuclear cells in a NBT reduction assay and hypochlorous acid generation from neutrophils assessed in a luminol-enhanced chemiluminescence assay.

Glycosides↗

PubMed1987

Superoxide dismutase-like activities of copper(II) complexes tested in serum.

The superoxide dismutase-like activities of a series of coordination complexes of copper were evaluated and compared to the activities of bovine erythrocyte superoxide dismutase (superoxide: superoxide oxidoreductase, EC 1.15.1.1) in serum using the nitroblue tetrazolium chloride (NBT)-reduction assay and electron paramagnetic resonance (EPR) spectroscopy. A 40% inhibition was observed for the initial rate of the NBT reduction by superoxide dismutase in serum, but more than 40% inhibition was achieved with CuSO4, Cu(II)-dimethylglyoxime, Cu(II)-3,8-dimethyl-4,7-diazadeca-3,7-dienediamide, Cu2[N,N'-(2-(O-hydroxy-benzhydrylidene)amino)ethyl]2-1,2-ethane dia mine), Cu(II)-(diisopropylsalicylate)2, Cu(II)-(p-bromo-benzoate)2, Cu(II)-(nicotinate)2 and Cu(II)-(1,2-diamino-2-methylpropane)2. The electron paramagnetic resonance technique of spin trapping was used to detect the formation of superoxide (O2-.) and other free radicals in the xanthine-xanthine oxidase system under a variety of conditions. Addition of the spin trapping agent 5,5-dimethylpyrroline 1-oxide (DMPO) to the xanthine-xanthine oxidase system in fetal bovine serum produced the O2-.-spin adduct of DMPO (herein referred to as superoxide spin adduct, DMPO-OOH) as the well known short-lived nitroxyl whose characteristic EPR spectrum was recorded before its rapid decay to undetectable levels. The hydroxyl radical (HO.) adduct of the spin trap DMPO (herein referred to as DMPO-OH) was detected to a very small extent. When CuSO4, or the test complexes of copper, were added to the xanthine-xanthine oxidase system in serum containing the spin trap, the yield of DMPO-OOH was negligible. In addition to their superoxide dismutase-like activity, CuSO4 and the copper complexes also behaved as Fenton-type catalysts as seen by the accumulation of varying amounts of the hydroxyl spin adduct DMPO-OH. Both the Fenton-type catalysis and the superoxide dismutase-like action of these compounds were lost when a chelator such as EDTA was included in the xanthine-xanthine oxidase incubation mixture. Addition of superoxide dismutase instead of the copper compounds to this enzyme system abolished the formation of superoxide adduct DMPO-OOH, and no hydroxyl adduct DMPO-OH was detected. This effect of superoxide dismutase remained unaltered by EDTA.

Animals↗

PubMed2002

Prevention of the areca nut extract-induced unscheduled DNA synthesis of gingival keratinocytes by vitamin C and thiol compounds.

There are about 600 million betel quid (BQ) chewers in the world. BQ chewing is the major risk factor of oral cancer in India, Taiwan, South Africa and numerous other countries. Areca nut (AN) extract, the main component of BQ, exerts cytotoxicity and genotoxicity to several types of cells. In the present study, AN extract induced the unscheduled DNA synthesis (UDS) of gingival keratinocytes (GK). Vitamin C, at concentration of 50 and 200 microg/ml prevented the AN-induced UDS by 41 and 56%, respectively. Glutathione (GSH, 1-3 mM) and N-acetyl-L-cysteine (NAC, 1-3 mM) also protected the AN-induced UDS by 89-100 and 76-90%. These preventive effects were not due to cytotoxicity as analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Deferoxamine (20 and 30 mM), an iron chelator and a free radical scavenger, also prevented AN extract induced UDS of GK by 30-55%. On the contrary, banthocuproine (50-200 microM, a copper chelator) and 1,10-phenanthroline (50, 100 microM, a lipid permeable iron chelator), lacked preventive effects. Specific reactive oxygen species scavengers such as dimethyl-sulfoxide (2%), mannitol (10-20 mM), dimethylthiourea (10-20 mM), pyruvate (10 mM), catalase (200 and 400 U/ml), and superoxide dismutase (50 and 200 U/ml) also lacked these preventive effects. Moreover, higher concentrations of H(2)O(2) (0.5-1 mM) inhibited the basal levels of UDS by 19-37%. Interestingly, NAC, GSH, Vitamin C and deferoxamine cannot prevent the AN-induced morphological changes of GK at similar concentrations. These results reveal that AN extract-induced UDS of GK is associated with free radical reactions. Possibly different ingredients of AN is responsible for genotoxicity and cytotoxicity. Vitamin C, GSH and NAC may be potentially used in the future for chemoprevention of BQ chewing related oral mucosal lesions.

Antioxidants↗

PubMed2004

Acidic oligosaccharide sugar chain, a marine-derived acidic oligosaccharide, inhibits the cytotoxicity and aggregation of amyloid beta protein.

In this paper, we investigated interactions of the acidic oligosaccharide sugar chain (AOSC), derived from brown algae Echlonia kurome OKAM, with amyloid beta protein (Abeta). We observed that AOSC inhibited the toxicity induced by Abeta in both primarily cortical cells and the SH-SY5Y cell line. We also observed that AOSC inhibited the apoptosis induced by Abeta in SH-SY5Y by reducing the elevated level of intracellular calcium concentration ([Ca(2+)](i)) and suppressing the generation of reactive oxygen species. Surface plasmon resonance analysis demonstrated that AOSC had affinity for both freshly-dissolved Abeta and 48-h incubated Abeta. Furthermore, AOSC blocked the fibril formation of Abeta, which may be responsible for its anti-cytotoxic effects. Thus, our results indicate that AOSC might be a potentially therapeutic compound for Alzheimer's disease.

Amyloid beta-Peptides↗

PubMed2005

Cytotoxicity, antitumoral and antimycobacterial activity of tetrazole and oxadiazole derivatives.

In this study, the antimycobacterial activity of mono and di-substituted tetrazole and oxadiazole derivatives and their precursors was assayed on Mycobacterium tuberculosis H37Rv, and cytotoxicity was evaluated on J774 macrophages and on tumoral cell lines. Structure Activity Relationship (SAR) analysis was performed using Principal Component Analysis (PCA) to determine the relationship between these compounds and their biological activities.

Anti-Bacterial Agents↗

PubMed2006

Phenolic glycosides from Exostema mexicanum leaves.

Phytochemical investigation of the leaves of Exostema mexicanum led to the isolation of two novel acylated flavonol glycosides 6, 7 and three glycosides 1-4 structurally belonging to the group of 4-phenylcoumarins. One of them, 5-O-beta-D-glucopyranosyl-4'-hydroxy-7-methoxy-4-phenylcoumarin (2), turned out to be new. Furthermore, the 4-phenylcoumarin aglycone 3'-hydroxy-4',5,7-trimethoxy-4-phenylcoumarin (5) was obtained. The in vitro cytotoxicity of 3-5 against the cell line ECV-304 was evaluated; the aglycone 5 was highly cytotoxic, whereas the glycosidic compounds 3 and 4 were inactive.

Antineoplastic Agents, Phytogenic↗

PubMed1993

Schedule-dependent synergism of edatrexate and cisplatin in combination in the A549 lung-cancer cell line as assessed by median-effect analysis.

The methotrexate analog edatrexate has been shown to have greater antitumor activity and an improved therapeutic index as compared with its parent compound in preclinical systems. These studies suggest that edatrexate may have a broad role in the treatment of solid tumors. Information regarding edatrexate in combination with other chemotherapeutic agents is limited. We evaluated the interaction of edatrexate with cisplatin in vitro as assessed by median-effect analysis in the A549 human lung-cancer cell line. The effects of dose, exposure time, and schedule dependence were assessed. Cytotoxicity was evaluated using the tetrazolium-based colorimetric (MTT) assay. The inhibitory concentration producing 50% absorbance (IC50 for edatrexate with 1 h exposure was 1.4 microM. For all combination experiments, the edatrexate dose was fixed at 0.2 microM (IC10) whereas cisplatin (CDDP) concentrations were varied for 1-, 3-, and 24-h exposures either before or after edatrexate treatment. Drug interactions were assessed using the combination-index method as defined by median-effect analysis. A synergistic interaction was documented in experiments when edatrexate was applied prior to CDDP (combination index, < 1). The combination studies in which edatrexate was used prior to CDDP resulted in significant reduction of all three CDDP IC50 values: 1-h IC50, from 30.0 to 3.9 microM; 3-h IC50, from 21.3 to 1.4 microM; and 24-h IC50, from 1.7 to 0.03 microM. In contrast, synergism was not observed in experiments in which edatrexate treatment occurred after cisplatin exposure. Median-effect analysis is a useful method of determining drug interactions. In the present study, the combination of edatrexate and CDDP demonstrated schedule-dependent synergism, with the synergism being observed only in the setting of edatrexate treatment before CDDP exposure. Due to the potential broad spectrum of activity of edatrexate plus CDDP, further studies are warranted to determine the mechanism responsible for the synergism and to investigate this combination in a variety of tumor models.

Adenocarcinoma↗

PubMed1994

Purpurogallin, a scavenger of polymorphonuclear leukocyte-derived oxyradicals.

Purpurogallin (PPG) is a phenolic compound extracted from nutgalls formed on oak trees. It has been used as an additive to edible or nonedible oils or fats, and to hydrocarbon fuels or lubricants to retard their oxidation. We investigated by luminol-dependent chemiluminescence (PMNL-CL), the ability of PPG to scavenge oxygen free radicals (OFRs) generated by zymosan-activated polympophonuclear leukocytes (PMNLs). Its OFR-scavenging ability was also investigated by the use of nitro blue tetrazolium (NBT). We also investigated by the dye-exclusion method, if PPG affects the viability of PMNLs. PPG in the concentrations of 0.005-0.4 mM was used in this study. PPG scavenged OFRs produced by zymosan-activated PMNLs in a concentration-dependent manner. Almost complete scavenging was observed at a concentration of 0.2 mM. The NBT test indicated that PPG (0.2 mM) did not completely prevent the activation of PMNLs by zymosan. Viability of PMNLs in the absence or presence of PPG (0.4 mM) were 95.77 +/- 0.56% and 96.78 +/- 0.60% respectively. The results suggest that PPG scavenges OFRs produced from activated PMNLs in a concentration-dependent manner and that the cell viability is not affected by PPG. PPG is a potent scavenger of OFRs and should be of value in the prevention and treatment of diseases in the pathophysiology of which OFRs are invovled.

Animals↗

PubMed2006

Comparison of inhibitory action of candesartan and enalapril on brain ischemia through inhibition of oxidative stress.

The effects of an angiotensin II type 1 (AT1) receptor blocker (ARB) on ischemic brain damage induced by middle cerebral artery (MCA) occlusion were compared with those of an angiotensin converting enzyme (ACE) inhibitor. Treatment of male C57BL/6J mice with an ARB, candesartan, reduced the brain ischemic area and neurological deficit after MCA occlusion at a non-hypotensive dose. In contrast, an ACE inhibitor, enalapril, did not reduce the brain ischemic area, and neurological deficit even at a hypotensive dose. Candesartan improved the reduction of brain surface blood flow after MCA occlusion, and inhibited the increase in superoxide production both in the cortex and brain arterial wall at non-hypotensive and hypotensive doses. However, enalapril did not affect the changes in blood flow and superoxide production in the brain after MCA occlusion. AT2 receptor expression in the ischemic area was increased at 3 h after MCA occlusion by pretreatment with candesartan, but not that with enalapril. AT1 receptor expression was neither affected by candesartan nor by enalapril. These results suggest that candesartan attenuated ischemic brain damage, at least partly, through inhibition of oxidative stress.

Analysis of Variance↗

PubMed2004

Angiotensin receptor gene expression in candesartan mediated neuroprotection.

Male Wistar rats were treated with an angiotensin AT1 receptor antagonist, candesartan cilexetil (TCV-116, 1 mg/kg/day) over a 4-week period. Systolic blood pressure was significantly reduced by 14% after 1 week and remained stable for the next 3 weeks compared with controls. Up-regulation of AT2, but not AT1, receptor gene expression by 3.4-fold and 5.0-fold was observed 1 and 4 weeks after treatment. Middle cerebral artery occlusion caused significantly reduced infarct volumes in TCV-116-treated rats, by about 30% when compared with control rats. Neurological scores were also improved in treated rats. These results suggest that the neuroprotective effects of TCV-116 may be mediated through AT1 receptor antagonism and AT2 receptor up-regulation.

Analysis of Variance↗

PubMed1993

Stimulation of endogenous prostacyclin protects the reperfused pig myocardium from ischemic injury.

Several attempts have been undertaken to reduce the severity of ischemic myocardial injury by exogenous administration of eicosanoids and by modification of endogenous eicosanoid production. The present study investigates whether defibrotide, a compound that stimulates endogenous prostacyclin (PGI2), has a beneficial effect in experimental ischemic myocardial injury. Anesthetized, open-chest minipigs were subjected to 1 h of coronary artery occlusion, followed by 3 h of reperfusion. Defibrotide (32 mg/kg x h) or its vehicle were infused i.v. throughout the experiment. Defibrotide increased cardiac PGI2 formation 3- to 4-fold greater than control (P < .05). Thromboxane levels remained unchanged. Irreversible ischemic injury, as identified by negative tetrazolium staining, amounted to 44 +/- 6% of the area at risk in pigs receiving vehicle but was reduced to 23 +/- 4% by defibrotide (P < .05). This reduced tissue injury in defibrotide-treated pigs was associated with improved functional recovery (left ventricular pressure, + dP/dtmax), during early reperfusion. Recovery did not occur in vehicle-treated pigs. Collagen (2 micrograms/ml)-induced platelet aggregation ex vivo was increased in vehicle-treated pigs during ischemia and reperfusion, but not in animals treated with defibrotide. Polymorphonuclear neutrophil leukocyte accumulation in the ischemic border zone was reduced from 59 +/- 17 cells/mm2 in vehicle-treated pigs to 17 +/- 9 cells/mm2 by defibrotide (P < .05). Pretreatment of the animals with indomethacin (3 mg/kg) prevented the reduction of infarct size and polymorphonuclear neutrophil leukocyte infiltration by defibrotide. Indomethacin increased infarct size in vehicle- and defibrotide-treated pigs by 71 and 59%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMed1997

N-deacetyl ketoconazole-induced hepatotoxicity in a primary culture system of rat hepatocytes.

Ketoconazole (KT) is an azole antifungal agent that has been associated with hepatotoxicity. The mechanism of its hepatotoxicity has not yet been resolved. It has been suggested that a reactive metabolite may be the cause of toxicity because the hepatic injury does not appear to be mediated through an immunoallergic mechanism. Several metabolites of KT have been reported in the literature of which the deacetylated metabolite, N-deacetyl ketoconazole (DAK), is the major metabolite which undergoes further metabolism by the flavin-containing monooxygenases (FMO) to form a potentially toxic dialdehyde. The objective of this study was to evaluate DAK's cytotoxicity and the role of FMO in a primary culture system of rat hepatocytes. Cytotoxicity was evaluated by measuring the leakage of the cytosolic enzyme, lactate dehydrogenase (LDH), into the medium and by assessing mitochondrial reduction of 3-(4,5-dimethythiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT). The cultures were exposed to various concentrations of DAK (20-160 microM) for 0.5-4 h. There was a significant increase (P < 0.05) in LDH leakage and an immediate decrease in MTT reduction (P < 0.05) as early as 0.5 h. The MTT reduction assay appeared to be more sensitive than the LDH assay in that lower concentrations were needed to observe a 50% reduction of MTT (107, 90, 75, 58 microM DAK at 0.5, 1.0, 2.0 and 4.0 h, respectively). The concentrations to observe 50% LDH leakage from the hepatocytes were 155, 133, 100, 70 microM DAK at 0.5, 1.0, 2.0 and 4.0 h, respectively. Moreover, co-treatment with methimazole, a competitive substrate for FMO, produced a significant decrease (P < 0.05) in % LDH leakage as early as 0.5 h, when compared to cells treated solely with DAK. Also, the toxicity was significantly (P < 0.05) enhanced as early as 0.5 h by n-octylamine, a known positive effector for FMO. These results demonstrate that DAK is a more potent cytotoxicant than its parent compound, KT, as reported previously by our laboratory (Rodriguez and Acosta, Toxicology, 96: 83-92, 1995) and its toxicity was expressed in a dose- and time-dependent manner. Furthermore, DAK's cytotoxicity was enhanced with n-octylamine and suppressed with methimazole, suggesting a role for FMO in the toxicity of the metabolite.

Animals↗

PubMed1999

Excavatolides F-M, new briarane diterpenes from the gorgonian Briareum excavatum.

Eight new briarane-type diterpenes, excavatolides F-M (1-8), have been isolated from the gorgonian Briareum excavatum. The structures and relative stereochemistry of these compounds were established by spectral analysis and chemical methods. The cytotoxicity of these compounds toward various cancer cell lines has also been determined.

Animals↗