TARGET OF RAPAMYCIN signaling plays a role in Arabidopsis growth promotion by Azospirillum brasilense Sp245

Azospirillum brasilense colonizes plant roots and improves productivity, but the molecular mechanisms behind its phytostimulation properties remain mostly unknown. Here, we uncover an important role of TARGET OF RAPAMYCIN (TOR) signaling on the response of Arabidopsis thaliana to A. brasilense Sp245. The effect of the bacterium on TOR expression was analyzed in the transgenic line TOR/tor-1, which carries a translational fusion with the GUS reporter protein, and the activity of TOR was assayed thought the phosphorylation of its downstream signaling target S6K protein. Besides, the role of TOR on plant growth in inoculated plants was assessed using the ATP-competitive inhibitor AZD-8055. A decrease in growth of the primary root correlates with an improved branching and absorptive capacity via lateral root and root hair proliferation 6 days after transplant to different concentrations of the bacterium (10³ or 10⁵ CFU/mL). Bacterization increased the expression of TOR in shoot and root apexes and promoted phosphorylation of S6K 3 days after transplant. The TOR inhibitor AZD-8055 (1 μM) inhibited plant growth and cell division in root meristems and in lateral root primordia, interfering with the phytostimulation by A. brasilense. In addition, the role of auxin produced by the bacterium to stimulate TOR expression was explored. Noteworthy, the A. brasilense mutant FAJ009, impaired in auxin production, was unable to elicit TOR signaling to the level observed for the wild-type strain, showing the importance of this phyhormone to stimulate TOR signaling. Together, our findings establish an important role of TOR signaling for the probiotic traits elicited by A. brasilense in A. thaliana.

Autolytic enzymes are responsible for increased melanization of carbon stressed Aspergillus nidulans cultures

Melanization of carbon stressed Aspergillus nidulans cultures were studied. Melanin production showed strong positive correlation with the activity of the secreted chitinase and ß-1,3-glucanase. Deletion of either chiB encoding an autolytic endochitinase or engA encoding an autolytic ß-1,3-endoglucanase, or both, almost completely prevented melanization of carbon stressed cultures. In contrast, addition of Trichoderma lyticase to cultures induced melanin production. Synthetic melanin could efficiently inhibit the purified ChiB chitinase activity. It could also efficiently decrease the intensity of hyphal fragmentation and pellet disorganization in Trichoderma lyticase treated cultures. Glyphosate, an inhibitor of L-3,4-dihydroxyphenylalanine-type melanin synthesis, could prevent melanization of carbon-starved cultures and enhanced pellet disorganization, while pyroquilon, a 1,8-dihydroxynaphthalene-type melanin synthesis inhibitor, enhanced melanization, and prevented pellet disorganization. We concluded that cell wall stress induced by autolytic cell wall hydrolases was responsible for melanization of carbon-starved cultures. The produced melanin can shield the living cells but may not inhibit the degradation and reutilization of cell wall materials of dead hyphae. Controlling the activity of autolytic hydrolase production can be an efficient approach to prevent unwanted melanization in the fermentation industry, while applying melanin synthesis inhibitors can decrease the resistance of pathogenic fungi against the chitinases produced by the host organism.

ARQ-197, an oral small-molecule inhibitor of c-Met for the treatment of solid tumors

ARQ-197 is an oral, selective c-Met inhibitor under development by ArQule Inc, in partnership with Daiichi Sankyo Co Ltd and Asian licensee Kyowa Hakko Kirin Co Ltd, for the potential treatment of solid tumors, including NSCLC, hepatocellular carcinoma and pancreatic cancer, as well as microphthalmia transcription factor-driven tumors. c-Met, a key cell surface receptor tyrosine kinase involved in diverse regulatory functions, is often aberrantly activated in human cancers. While the precise mechanism of action of ARQ-197 remains undefined, data from preclinical studies have demonstrated that ARQ-197 inhibits c-Met activation in numerous human tumor cell lines and specifically targets c-Met in various cancer types; uniquely, ARQ-197 inhibits c-Met in a non-ATP-competitive manner. Phase I/II clinical trials demonstrated promise in terms of both tolerability and tumor response. Intriguingly, dose-limiting adverse effects were hematological in nature. Combinational trials are also ongoing to take advantage of the signaling crosstalk between c-Met and other oncogenic signaling systems. Prioritization of the clinical development of c-Met inhibitors, such as ARQ-197, among different tumor disease types is a key challenge at present; an improved understanding of the prediction of molecular determinants in tumors with respect to c-Met kinase as the driver oncogenic receptor, and of the prediction of tumor response, is still urgently needed.

CYP2C76-mediated species difference in drug metabolism: A comparison of pitavastatin metabolism between monkeys and humans

The monkey is often used to predict metabolism of drugs in humans since it generally shows a metabolic pattern similar to humans. However, metabolic profiles different from humans are occasionally seen in monkeys for some drugs including pitavastatin. Recently, we have successfully identified a monkey-specific cytochrome P450 (CYP) 2C76, which possibly accounts for a species difference between monkeys and humans because of its sequence and functional uniqueness. The present study on the role of CYP2C76 and other monkey CYP2Cs in pitavastatin metabolism, as an example, has revealed that CYP2C76 is important for the metabolism of the lactone form, indicating a major role of CYP2C76 for the difference in the metabolism of pitavastatin and possibly other drugs between monkeys and humans. The current investigation on the involvement of CYP2C76 in the metabolism of other drugs is expected to reveal further the further importance of this monkey-specific drug-metabolizing enzyme.

Larvicidal activity of sterol carrier protein-2 inhibitor in four species of mosquitoes

A previous report has shown that mosquito sterol carrier protein-2 inhibitors (SCPIs) are larvicidal to larvae of the yellowfever mosquito, Aedes aegypti (L.) (J. Lipid Res. 46: 650-657, 2005). In the current study, we tested SCPI-1 in an additional four mosquito species for larvicidal activities: Culex pipiens pipiens, Anopheles gambiae, Culex restuans, and Aedes vexans. Cholesterol accumulation in SCPI-treated Ae. aegypti fourth instars was examined. SCPI-1 is lethal to all tested mosquito species, with the LC50 value ranging from 5.2 to 15 microM when treatments started at the first to third instar. However, LC50 values increase to from 5.2 to 38.7 microM in treatments started at first and fourth instar, respectively. The results indicate that the lethal effect of SCPI-1 decreases with the growth of larvae, which suggests that SCPI-1 is more effective before the larvae reach final growth period (the last instar). SCPI-1 suppressed cholesterol uptake in Ae. aegypti fourth instars, suggesting that one of the modes of action of SCPI-1 is via reduction in cholesterol absorption.

Rifampicin Reduces Plasma Concentrations of Moxifloxacin in Patients with Tuberculosis

BACKGROUND

The long duration of the current tuberculosis (TB) treatment is demanding and warrants the development of new drugs. Moxifloxacin shows promising results and may be combined with rifampicin to shorten the duration of TB treatment. Rifampicin induces the phase II metabolic enzymes that are involved in the biotransformation of moxifloxacin. Therefore, the interaction between rifampicin and moxifloxacin should be investigated.

PATIENTS AND METHODS

Nineteen Indonesian patients with pulmonary TB who were in the last month of their TB treatment completed a 1-arm, 2-period, fixed-order pharmacokinetic study. In phase 1 of the study, they received 400 mg of moxifloxacin every day for 5 days in addition to 450 mg of rifampicin and 600 mg of isoniazid 3 times per week. In phase 2 of the study, after a 1-month washout period, patients received moxifloxacin for another 5 days (without rifampicin and isoniazid). A 24-h pharmacokinetic curve for moxifloxacin was recorded on the last day of both study periods, and its pharmacokinetic parameters were evaluated for an interaction with rifampicin, using a bioequivalence approach.

RESULTS

Coadministration of moxifloxacin with rifampicin and isoniazid resulted in an almost uniform decrease in moxifloxacin exposure (in 18 of 19 patients). The geometric means for the ratio of phase 1 area under the curve to phase 2 area under the curve and for the ratio of phase 1 peak plasma concentration to phase 2 peak plasma concentration were 0.69 (90% confidence interval, 0.65-0.74) and 0.68 (90% confidence interval, 0.64-0.73), respectively. The median time to reach peak plasma concentration for moxifloxacin was prolonged from 1 h to 2.5 h when combined with rifampicin and isoniazid (P=.003).

CONCLUSIONS

Coadministration of moxifloxacin with intermittently administered rifampicin and isoniazid results in reduced moxifloxacin plasma concentrations, which is most likely the result of induced glucuronidation or sulphation by rifampicin. Further studies are warranted to evaluate the impact of the interaction on the outcome of TB treatment.

Participation of ATP in nonadrenergic, noncholinergic relaxation of longitudinal muscle of wistar rat jejunum

A role of ATP in nonadrenergic, noncholinergic (NANC) relaxations was examined in the Wistar rat jejunum. Electrical field stimulation (EFS) induced NANC relaxation of longitudinal muscle of the jejunal segments in a frequency-dependent manner. A purinoceptor antagonist, adenosine 3'-phosphate 5'-phosphosulfate (A3P5PS, 100 muM) inhibited the relaxation: relaxations induced by EFS at lower or higher frequencies were either completely or partially inhibited, respectively. After the jejunal segments had been desensitized to ATP, the relaxations were decreased to the same extent as those inhibited by A3P5PS. An inhibitor of small conductance Ca(2+)-activated K(+) channels (SK channels), apamin (100 nM), completely inhibited EFS-induced relaxations. Treatment of the segments with an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase, thapsigargin (1 muM), significantly inhibited the relaxations. The exogenous ATP-induced relaxation of longitudinal muscle occurred with a concomitant decrease in intracellular Ca(2+) levels. Apamin and thapsigargin abolished these ATP-induced responses. A3P5PS significantly inhibited the inhibitory junction potentials which were induced in the longitudinal muscle cells. In addition, apamin significantly inhibited the hyperpolarization that was induced by exogenous ATP in the cells. These findings in the Wistar rat jejunum suggest that ATP participates in the NANC relaxation via activation of SK channels induced by Ca(2+) ions that are released from the thapsigargin-sensitive store site.

Biphasic firing response of nucleus accumbens neurons elicited by THPB-18 and its correlation with DA receptor subtypes

AIM

To investigate the possibility whether THPB-18 (l-12-shloroscoulerine) possesses the D1 agonist-D2 antagonist action on meso-accumbens-mPFC DA system.

METHODS

Single unit spontaneous firing activity was recorded in the nucleus accumbens (NAc) neurons of naive and unilateral-6-hydroxydopamine (6-OHDA)-lesioned Sprague-Dawley rats. The effects of drugs applied intravenously or iontophoretically were determined by the change of firing rates.

RESULTS

Under normal conditions, the systemic administration of THPB-18 produced a decrease-increase biphasic firing pattern in the NAc neurons during cumulative doses. High dose of THPB-18 was capable of reversing the inhibition induced by both D2 agonist LY171555 and D1/D2 agonist APO on NAc firing activity. Spiperone pretreatment could not block the high dose of THPB-18-induced firing rate increase, which was reversed by the D1 selective antagonist SCH23390. The tested NAc neurons were effectively inhibited by iontophoretically applied THPB-18 in 90 % of 6-OHDA-lesioned rats, while THPB-18 caused variable effects on the firing of NAc neurons in the neurons of unlesioned rats. The inhibitory effect of THPB-18 was blocked by iontophoretic application of SCH23390, but not D2 antagonist spiperone.

CONCLUSION

Similar to L-stepholidine, THPB-18 also possesses the D1 agonistic-D2 antagonistic dual action on the VTA-NAc DA system.

Modulation of the locomotor activating effects of the noncompetitive NMDA receptor antagonist MK801 by dopamine D2/3 receptor agonists in mice

The noncompetitive NMDA receptor antagonist MK801 (dizocilpine) produces behavioral stimulation mediated, in part, through indirect activation of the dopamine (DA) system. Previous reports indicate that D2/3 agonists inhibit MK801-induced stereotypies; however, it is unclear if these agonists also attenuate MK801-induced locomotion. As such, the ability of the D2/3 agonists, quinelorane and quinpirole, and the partial D3 agonist, BP897, to attenuate the locomotor activating effects of MK801 was examined in mice. MK801 (0.1-1.0 mg/kg) produced a biphasic effect on total distance traveled with the intermediate dose of 0.3 mg/kg producing the greatest stimulation. The increase in MK801-induced total distance traveled was attenuated by the coadministration of quinelorane and quinpirole at doses that alone had no effect on activity. Similarly, the partial D3 agonist, BP897, blocked the effects of MK801. The D3-preferring antagonist, nafadotride, reversed the attenuation of quinelorane and partially reversed the attenuation of quinpirole. The D2-preferring antagonist, eticlopride, reversed the attenuating effects of quinelorane, but was not effective against quinpirole. Nafadotride and eticlopride were ineffective against the attenuating effects of BP897 on MK801-induced locomotion. Because BP897 is a partial agonist it was tested against quinelorane/MK801 and quinpirole/MK801 combinations. BP897 reversed the attenuating effects of quinelorane, but not those of quinpirole on MK801's effects. These results demonstrate that the DA system, through D2/3 receptor activation, modulates the locomotor activating effects produced by noncompetitive NMDA receptor blockade.

Metabolic stability and uptake by human hepatocytes of pitavastatin, a new inhibitor of HMG-CoA reductase

To gain a better understanding of the metabolic stability and transport of pitavastatin (CAS 147526-32-7), a new and potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, experiments were conducted using human hepatocytes and oocytes of Xenopus laevis expressing human organic anion transporting polypeptide-2 (OATP2), respectively. Almost the entire radioactivity was from the unchanged substance or lactone form in human hepatocytes, and the cytochrome P450 (CYP)-mediated metabolism of pitavastatin was negligible. The results suggested that CYPs are not critically involved in determining the metabolic fate of pitavastatin. The hepatic uptake of pitavastatin reached saturation with a Km of 2.99 +/- 0.79 micromol/L. Also, the uptake of pitavastatin was mediated by OATP2 expressed in oocytes with a Km of 5.53 +/- 1.70 micromol/L. These results indicated that OATP2 plays a major role in the distribution of pitavastatin in liver. Furthermore, to elucidate the increase in the plasma concentration of pitavastatin in a clinical setting, the inhibitory effect of ciclosporin (cyclosporin A, CAS 59865-13-3) on the uptake of pitavastatin was examined. The uptake of pitavastatin was inhibited in the presence of cyclosporin A and the apparent IC50 value was 2.91 +/- 0.78 micromol/L. This result may at least partly explain the drug-drug interaction between pitavastatin and cyclosporin A. In conclusion, the characterization of transporters needs to be taken into account to avoid transporter-mediated drug-drug interaction.

Pitavastatin, a Potent Hydroxymethylglutaryl Coenzyme a Reductase Inhibitor, Increases Cholesterol 7 .ALPHA.-Hydroxylase Gene Expression in HepG2 Cells

BACKGROUND

The effect of pitavastatin on the mRNA levels of apolipoprotein (apo) A-I, peroxisome proliferator-activated receptor alpha (PPARalpha), cholesterol 7alpha-hydroxylase (CYP7A1), and farnesoid X receptor (FXR) in HepG2 cells was examined to establish whether pitavastatin affects bile acid synthesis and if so, to determine a possible molecular mechanism.

METHODS AND RESULTS

HepG2 cells were cultured in serum-free Dulbecco's modified Eagle medium for 18 h before drug treatment. Total RNA was extracted at set times and mRNA levels were quantified by reverse transcription-real time polymerase chain reaction. Pitavastatin at 0.1, 1, 5, and 10 micromol/L increased the mRNA levels of apo A-I, PPARalpha, CYP7A1, and FXR in a dose-dependent manner. The mRNA levels of apo A-I, PPAR alpha, CYP7A1, and FXR similarly increased with increasing doses of pitavastatin. Coincubation of mevalonate (4 mmol/L) with pitavastatin (5 micromol/L) reversed the inductive effects of pitavastatin on the mRNA levels of these genes, indicating that the inductive effects of pitavastatin were related to its inhibition of HMG-CoA reductase.

CONCLUSIONS

Pitavastatin increased the mRNA levels of CYP7A1 in HepG2 cells, suggesting that increased conversion of cholesterol to bile acids may be the mechanism for its potent low-density lipoprotein cholesterol-lowering effects.

Effect of Gemfibrozil on the Metabolism of Pitavastatin - Determining the Best Animal Model for Human CYP And UGT Activities

A series of studies was conducted to determine the best animal model for human CYP and UGT activities. The investigation focused primarily on the interactions occurring in the CYP- or UGT-mediated metabolism of pitavastatin, and involved in vitro and in vivo experiments. We found that the best animal models for human CYP-mediated hydroxylation and UGT-mediated lactonization of pitavastatin were rats and dogs, respectively. In addition, a large difference in the metabolic properties of pitavastatin was found between monkeys and humans. In the presence of gemfibrozil, the CYP- or UGT-mediated metabolism of pitavastatin was inhibited in vitro. However, gemfibrozil treatment had no inhibitory effect on the AUC of pitavastatin and its lactone form in rats and dogs. We conclude that the plasma level of pitavastatin would not be increased by co-administration of gemfibrozil in humans.

Precautions for Use and Adverse Effects of Vesnarinone Potential Mechanisms and Future Therapies

This article reviews the precautions and adverse effects associated with vesnarinone use, and the potential mechanisms responsible for these complications as well as suggested treatment strategies. Vesnarinone, a quinolinone derivative, improves the haemodynamics and quality of life in patients with congestive heart failure (CHF); however, it is associated with the adverse effects of increased sudden cardiac death and neutropenia. These adverse effects have limited the application of vesnarinone to the general population but perhaps with continued research into vesnarinone-induced neutropenia and advances in arrhythmia management, the risk/ benefit ratio of vesnarinone may become favourable. For now, the use of vesnarinone should be limited to patients with CHF who have demonstrated a poor response to other cardiac medications and devices. These patients should be closely monitored for both cardiac and non-cardiac adverse effects.

Influence of milk on the antimutagenic potential of green and black teas

BACKGROUND

The objective of this study was to evaluate whether addition of milk to green, black and decaffeinated black teas alters their antimutagenic activity.

MATERIALS AND METHODS

Two model mutagens were used, the direct-acting N'-methyl-N'-nitro-nitrosoguanidine (MNNG) and the indirect-acting 2-amino-3-methylimidazo-[4,5-flquinoline (IQ), and their mutagenic activity was determined in the Ames test, in the presence of tea and milk/tea mixtures. Solids from the milk/tea mixtures were removed by centrifugation and the supernatant analysed by HPLC for individual catechins and gallic acid in green tea, and thearubigins, theaflavins and flavonol glycosides in black teas.

RESULTS

Addition of skimmed milk to all the teas failed to influence their antimutagenic activity towards the two mutagens. Addition of milk to green tea resulted primarily in loss of (-)-epigallocatechin gallate whereas in the black teas it primarily reduced theaflavins levels.

CONCLUSION

The antimutagenic activity of green and black teas is not modulated by the presence of skimmed milk, even at high concentrations.

Effect of high sucrose diet on cytochrome P450 1A and heterocyclic amine mutagenesis

To assess the effect of dietary sucrose on liver cytochrome P450 1A content and activity, male F344 rat weanlings were randomized into two diet groups for a period of 90 days. One group was fed a diet containing 65% of total calories from sucrose (HSD) while the other was fed standard lab chow (0% sucrose). Microsomal fractions from each of 10 animals in each group were used in Western immunoblot, mutagenesis and 7-alkoxyresorufin-0-deethylase (AROD) assays. No statistically significant difference in the mean quantity of liver CYP 1A2 was detected by Western blot analysis, while a significant decrease in mean liver CYP 1A1 was observed in the rats fed the HSD. Liver microsomal-dependent mutagenesis of two heterocyclic amines (HCAs), 2-amino-3,8-dimethyl-imadazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), in Salminella typhimurium TA98 was decreased in animals on the HSD compared to those on the control diet by 33% (p < 0.001) and 25% (p < 0.001), respectively. In addition, rats on the HSD had significantly decreased ethoxyresorufin-0-deethylase (EROD) and methoxyresorufin-0-deethylase (MROD) activity over a range of substrate concentrations. These results show that a HSD alters hepatic CYP 1A content and activity and suggests that the metabolism of substrates for this P450 subfamily may be significantly altered.

Flavonoids inhibit genetic toxicity produced by carcinogens in cells expressing CYP1A2 and CYP1A1

The effects of the flavonoids quercetin, apigenin and chrysin (10 microM) on the genetic toxicity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and benzo[a]pyrene (BaP) was investigated at sub-cytotoxic concentrations in Chinese hamster V79 cells expressing human or rat cytochromes P450. In V79 r1A2-NH and V79 h1A1-MZ cells, none of the flavonoids increased DNA strand breaks (SB) (measured by the Comet assay) or produced detectable DNA adducts (measured by 32P-post-labelling). Neither IQ nor BaP produced DNA damage in the absence of expressed CYP1A2 or CYP1A1, respectively. DNA damage measured as SB and DNA adducts was detectable in V79 r1A2-NH cells expressing rat CYP1A2 when treated with IQ (2.5-50 microM) and this was inhibited by quercetin. Likewise, DNA damage (SB and DNA adducts) was elevated in V79 h1A1-MZ cells expressing human CYP1A1 when treated with BaP (0.1-0.5 microM) and this was inhibited by chrysin and apigenin, but not by quercetin. The specificity of CYP1A1 inhibition by chrysin and apigenin and CYP1A2 inhibition by quercetin was confirmed by ethylresorufin O-deethylase assay.

Efficacy of leukotriene receptor antagonist in chronic urticaria. A double-blind, placebo-controlled comparison of treatment with montelukast and cetirizine in patients with chronic urticaria with intolerance to food additive and/or acetylsalicylic acid

BACKGROUND

The cause and pathogenesis of chronic urticaria are still poorly understood. IgE-independent reactions, are common in adult patients with chronic urticaria, who have daily spontaneous occurrence of weals. H(1)-receptor antagonists (antihistamines) are the major class of therapeutic agents used in the management of urticaria and angioedema. Nevertheless, chronic urticaria is often difficult to treat and may not be controlled by antihistamines alone. It has been postulated that mediators other than histamine, such as kinins, prostaglandin and leukotrienes, may be responsible for some of the symptoms in urticaria which are not controlled by antihistamines. In this study, which was randomized double-blind, placebo-controlled, we compare the clinical efficacy and safety of montelukast (MT) 10 mg given once a day and cetirizine (CET) 10 mg given once a day with placebo (PLA), in the treatment of patients with chronic urticaria who have positive challenge to acetylsalicylic acid (ASA) and/or food additives.

PATIENTS AND METHODS

A group of 51 patients, ranging in age from 15 to 71 years, with chronic urticaria and positive challenge to food additives and/or ASA, participated in this study for a period of 4 weeks, starting from a 3-day run-in. The assessment of the efficacy was based on scores of daily urticaria symptoms.

RESULTS

MT significantly increased the percentage of symptom-free days for hive and itch. Analysis of frequency distribution of urticaria scores for each symptom gave similar results (MT vs. CET and MT vs. PLA, P < 0.001). The interference with sleep due to their skin condition was also lower in the group treated with MT (P < 0.001). In addition, the median number of days without the rescue medication was significantly higher in the MT group (24 days) than both the CET and the PLA groups (18 days, P < 0.001, and 20 days, P < 0.001, respectively). Finally, a low incidence of adverse events was observed in this study.

CONCLUSION

The results of this comparative study demonstrate that montelukast orally administered once a day is very effective for the treatment of cutaneous symptoms in patients with chronic urticaria due to food additives and/or ASA.

BW373U86, a delta opioid agonist, partially mediates delayed cardioprotection via a free radical mechanism that is independent of opioid receptor stimulation

Opioids have been shown to produce both an early and delayed phase of cardioprotection; however, the signaling pathways involved, particularly in the delayed response, have not been well defined. Therefore, we investigated the potential of BW373U86 (BW), a potent delta opioid agonist, to produce delayed cardioprotection and characterized the role of opioid receptors and oxygen-derived free radicals (OFRs) in this delayed response. All rats underwent 30 min of ischemia followed by 2 h of reperfusion. The rats were divided into four groups. First, rats were pretreated with selective opioid receptor antagonists or the antioxidant, 2-mercaptopropionyl glycine (2-MPG), in the presence of BW and allowed to recover for 24 h before the ischemia-reperfusion protocol. Second, rats were pretreated with BW, allowed to recover for 24 h, and subsequently treated with either opioid antagonists or 2-MPG, 10 min prior to the ischemia-reperfusion protocol. Third, rats underwent ischemic preconditioning (IPC) (1x5 min occlusion) both with and without 2-MPG to determine the role of OFRs in acute cardioprotection. Fourth, rats were pretreated with TAN-67, an opioid agonist known to signal through the delta1 opioid receptor in the presence and absence of 2-MPG. Control rats were injected with saline and allowed to recover for 24 h. BW produced a bell-shaped dose-related reduction in infarct size with a maximal reduction observed at 0.1 mg/kg v control (16+/-3%v 60+/-3%, P<0.001). Surprisingly, the delayed protection induced by BW was only partially blocked by pretreatment with the delta1-selective antagonist, BNTX; however, it was completely blocked by pretreatment with 2-MPG (47+/-5%, P<0.001). Only naloxone given acutely inhibited the protective effects of BW; however, at the dose used, 2-MPG partially reduced the protective effect of acute IPC. TAN-67 (0.1 mg/kg) also produced a significant reduction in infarct size compared to control (18+/-4%v 60+/-3%, P<0.001). This protection was blocked by pretreatment with 2-MPG (42+/-4%, P<0.001). These data suggest that BW and TAN-67 mediate delayed cardioprotection via a free radical mechanism that appears to be only partially dependent on delta opioid receptor stimulation. Furthermore, it is the early burst in OFRs that is crucial to initiating the protective effect.

Effect of a specific cysteinyl leukotriene-receptor 1-antagonist (montelukast) on the transmigration of eosinophils across human umbilical vein endothelial cells

BACKGROUND

Leukotrienes have been implicated in the selective infiltration of eosinophils into the bronchial mucosa in asthma.

OBJECTIVE

We studied whether eosinophil transmigration through cultured human umbilical vein endothelial cells (HUVECs) can be blocked by a specific cysteinyl LT1-receptor-antagonist.

METHODS

Unstimulated and stimulated eosinophils from patients with asthma and normal controls were subjected to confluent human umbilical vein endothelial cell (HUVEC) monolayers separating the upper and lower chamber of Transwell culture plates. Unstimulated eosinophils or cells pre-incubated in the presence of the eosinophil activating cytokines GM-CSF or IL-13 were placed in the upper chambers while PAF, a potent chemoattractant factor for eosinophils, was added to the lower chamber. Migration of eosinophils was quantified by a beta-glucuronidase assay.

RESULTS

The assumption that eosinophils express CysLT1 (cysteinyl-leukotriene 1)-receptors was based on our demonstration of mRNA-expression for the CysLT-1-receptor by polymerase chain reaction on purified eosinophils. The chemotactic response to PAF was significantly reduced when eosinophils were pre-incubated with montelukast for 15 min. When eosinophils were pre-incubated with GM-CSF and/or IL-13, the migratory response to PAF was also significantly reduced by montelukast.

CONCLUSION

From these data we conclude that the specific cysteinyl LT1-receptor antagonist montelukast can inhibit PAF-induced eosinophil transmigration through cultured HUVEC monolayers.

Long-term asthma control with oral montelukast and inhaled beclomethasone for adults and children 6 years and older

BACKGROUND

Leukotriene receptor antagonists have demonstrated clinical benefits in chronic asthma studies of up to 3 months in duration. The effects of these agents over extended periods of time have not been reported.

OBJECTIVE

To describe the long-term effect of oral montelukast, a potent and specific cysteinyl leukotriene receptor antagonist, compared with inhaled corticosteroids in both adult and paediatric patients with chronic asthma.

METHODS

Male and female patients with chronic, stable asthma (adults aged 15-85 years, children aged 6-14 years), who had completed double-blind, placebo-controlled clinical studies, participated in three extension studies with oral montelukast taken once daily (10 mg tablet for adults, 5 mg chewable tablet for paediatric patients) or inhaled corticosteroids (beclomethasone 200 microg twice daily for adults, beclomethasone 100 microg or equivalent three times daily for children). A double-blind adult extension study was 37 weeks in duration; open-label adult extension studies were 156 (adults) and 112 (paediatric) weeks in duration. A total of 436, 374, and 245 patients entered these extension studies, respectively.

RESULTS

Treatment with both montelukast and inhaled corticosteroids resulted in improvement in multiple parameters of asthma control. Improvements in daytime symptom scores were generally comparable among treatment groups. No tachyphylaxis to the effects of montelukast was evident. In the adult open-label study, however, the effect of beclomethasone on mean forced expiratory volume in 1 second (FEV1) gradually decreased from start of the study to the end of the follow-up treatment period.

CONCLUSION

Both montelukast and inhaled corticosteroids were effective in controlling mild to moderate chronic asthma; the relative effectiveness of montelukast and beclomethasone were similar in open-label conditions. The hypothesis, that clinical practice conditions (e.g., adherence) may have a significant impact on the effectiveness of these therapies, should be tested in future clinical trials.

NK-104, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, reduces osteopontin expression by rat aortic smooth muscle cells

1. It has been suggested that osteopontin promotes the development of atherosclerosis, especially under diabetic conditions. 2. In the present study, we found that NK-104, a new potent synthetic inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, reduced osteopontin expression both at protein and mRNA levels in cultured rat aortic smooth muscle cells. 3. The inhibitory effect of NK-104 was almost completely reversed by mevalonate, suggesting that mevalonate or its metabolites play important roles in the regulation of osteopontin expression. 4. Furthermore, oral administration of NK-104 (3 mg kg(-1) day(-1) for 7 days) effectively suppressed abnormally upregulated expression of osteopontin mRNA in the aorta and kidney of streptozotocin-induced diabetic rats. 5. These data support a notion that NK-104 is a suitable drug for the treatment of diabetic patients with hypercholesterolaemia.

Modulation of NMDA- and (+)TAN-67-induced nociception by GABA(B) receptors in the mouse spinal cord

The present study was designed to investigate the effect of a selective GABA(B) receptor agonist baclofen on the pain-like nociceptive behavior (scratching, biting and licking) induced by intrathecal (i.t.) injection of N-methyl-D-aspartate (NMDA) or (+)TAN-67, the enantiomorphs of 2-methyl-4aalpha-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12aalpha-octahydro-quinolino[2,3,3g]isoquinoline (TAN-67), in the mouse. NMDA (0.05-0.2 microg/mouse) given i.t. immediately caused nociception in a dose-dependent manner. The nociception was significantly antagonized by i.t. co-injection with dizocilipine (0.1-1.0 microg/mouse), a non-competitive NMDA receptor antagonist. I.t. co-injection with baclofen (37.5-150 ng/mouse) significantly reduced the NMDA-induced nociceptive behavior in a dose-dependent fashion. The inhibition produced by baclofen was completely reversed by a selective GABA(B) receptor antagonist 2-hydroxysaclofen (0.15 and 0.3 microg/mouse). An i.t. injection of (+)TAN-67 at doses of 3.75-15 microg/mouse elicited a long-lasting and a dose-related nociception. The nociceptive behavior induced by (+)TAN-67 given i.t. was markedly suppressed by i.t. co-injection with baclofen (3-30 ng/mouse), and the inhibitory effect of baclofen was prevented by i.t. injection of 2-hydroxysaclofen (1 and 3 microg/ mouse). In addition, the (+)TAN-67-induced nociception was also attenuated by i.t. co-injection with dizocilipine (0.1-1.0 microg/mouse). These results suggest that spinal GABA(B) receptors may be implicated in the expression of nociception elicited by i.t. injection of either NMDA or (+)TAN-67 in the mouse.

Effects of citrus flavonoids on the mutagenicity of heterocyclic amines and on cytochrome P450 1A2 activity

Heterocyclic amines (HCA's) are promutagens produced by high temperature cooking of meat products and are activated by cytochrome P450 (CYP) lA2. Using Aroclor 1254 induced rat liver S9 we tested four citrus flavonoids diosmin, naringenin, naringin and rutin for their effects on the mutagenicity of HCA's MeIQx, Glu-P-1*, IQ and PhIP in Salmonella typhimurium TA98. The effects of the citrus flavonoids on CYPlA2 activity was determined by measuring demethylation of methoxyresorufin (MROD). MeIQx induced mutagenesis in S. typhimurium was significantly inhibited by all four flavonoids in a concentration dependent manner at 0.25, 0.5 and 1.0 mumole. Glu-P-1 induced mutagenesis was inhibited by rutin and naringenin. IQ induced mutagenesis was significantly inhibited by each flavonoid except diosmin at all three doses. With the exception of diosmin and naringin at 0.25 mumole all four flavonoids at all three doses significantly inhibited PhlP induced mutagenesis. The inhibition of MROD activity by the citrus flavonoids correlated best with the inhibition of MeIQx induced mutagenesis but also correlated with the inhibition of IQ induced mutagenesis except for diosmin and with the inhibition of PhlP induced mutagenesis except for the 0.25 mumole dose of diosmin and naringin. Our data suggest a chemopreventive potential for diosmin, naringin, naringenin and rutin towards CYPlA2 mediated mutagenesis of HCA's.

Opioid-induced cardioprotection against myocardial infarction and arrhythmias: mitochondrial versus sarcolemmal ATP-sensitive potassium channels

We examined the role of the sarcolemmal and mitochondrial ATP-sensitive potassium (K(ATP)) channel in a rat model of myocardial infarction after stimulation with the selective delta(1)-opioid receptor agonist TAN-67. Hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Infarct size was expressed as a percentage of the area at risk. TAN-67 significantly reduced infarct size/area at risk (29.6 +/- 3.3) versus control (63. 1 +/- 2.3). The sarcolemmal-selective K(ATP) channel antagonist HMR 1098, administered 10 min before TAN-67, did not significantly attenuate cardioprotection (26.0 +/- 7.3) at a dose (3 mg/kg) that had no effect in the absence of TAN-67 (56.3 +/- 4.3). Pretreatment with the mitochondrial selective antagonist 5-hydroxydecanoic acid (5-HD) 5 min before the 30-min occlusion completely abolished TAN-67-induced cardioprotection (54.3 +/- 2.7), but had no effect in the absence of TAN-67 (62.6 +/- 4.1), suggesting the involvement of the mitochondrial K(ATP) channel. Additionally, we examined the antiarrhythmic effects of TAN-67 in the presence or absence of 5-HD and HMR 1098 during 30 min of ischemia. Control animals had an average arrhythmia score of 10.40 +/- 2.41. TAN-67 significantly reduced the arrhythmia score during 30 min of ischemia (2.38 +/- 0. 85). 5-HD and HMR 1098 in the absence of TAN-67 produced an insignificant decrease in the arrhythmia score (8.80 +/- 2.56 and 4. 20 +/- 1.07, respectively). 5-HD administration before TAN-67 treatment abolished its antiarrhythmic effect (4.71 +/- 1.11). However, HMR 1098 did not abolish TAN-67-induced protection against arrhythmias (1.67 +/- 0.80). These data suggest that delta(1)-opioid receptor stimulation is cardioprotective against myocardial ischemia and sublethal arrhythmias and suggest a role for the mitochondrial K(ATP) channel in mediating these cardioprotective effects.

Vesnarinone suppresses TNF-induced activation of NF-kappa B, c-Jun kinase, and apoptosis

Vesnarinone, a synthetic quinolinone derivative used in the treatment of cardiac failure, exhibits immunomodulatory, anti-inflammatory, and cell growth regulatory properties. The mechanisms underlying these properties are not understood, but due to the critical role of nuclear transcription factor NF-kappa B in these responses, we hypothesized that vesnarinone must modulate NF-kappa B activation. We investigated the effect of vesnarinone on NF-kappa B activation induced by inflammatory agents. Vesnarinone blocked TNF-induced activation of NF-kappa B in a concentration- and time-dependent manner. This effect was mediated through inhibition of phosphorylation and degradation of I kappa B alpha, an inhibitor of NF-kappa B. The effects of vesnarinone were not cell type specific, as it blocked TNF-induced NF-kappa B activation in a variety of cells. NF-kappa B-dependent reporter gene transcription activated by TNF was also suppressed by vesnarinone. The TNF-induced NF-kappa B activation cascade involving TNF receptor 1-TNF receptor associated death domain-TNF receptor associated factor 2 NF-kappa B-inducing kinase-IKK was interrupted at the TNF receptor associated factor 2 and NF-kappa B-inducing kinase sites by vesnarinone, thus suppressing NF-kappa B reporter gene expression. Vesnarinone also blocked NF-kappa B activation induced by several other inflammatory agents, inhibited the TNF-induced activation of transcription factor AP-1, and suppressed the TNF-induced activation of c-Jun N-terminal kinase and mitogen-activated protein kinase kinase. TNF-induced cytotoxicity, caspase activation, and lipid peroxidation were also abolished by vesnarinone. Overall, our results indicate that vesnarinone inhibits activation of NF-kappa B and AP-1 and their associated kinases. This may provide a molecular basis for vesnarinone's ability to suppress inflammation, immunomodulation, and growth regulation.

FR190997, a novel bradykinin B2 agonist, expresses longer action than bradykinin in paw edema formation and hypotensive response

Biological actions of a novel non-peptide B2 receptor agonist, FR190997, were examined by comparing them with those of bradykinin. The paw edema was induced by subcutaneous injection of 30 microl of solution of bradykinin (0.3, 0.6, and 1.2 nmol) or FR190997 (0.1, 0.3, and 0.9 nmol) into the right hind paw of ICR male mice. Bradykinin caused a dose-dependent edema formation, which peaked at 15 min and ceased after 150 min. FR190997 also formed a dose-dependent edema, peaking at 15-30 min with a slight delay compared to bradykinin and this response continued over 200 min. The edema formed by bradykinin or FR190997 was inhibited by pretreatment with HOE140 (1 mg/kg) injected intraperitoneally 30 min before the injection of each agonist. A novel non-peptide B2 antagonist, FR173657 (30 mg/kg, i.p. 30 min before the agonist), also diminished these responses by bradykinin and FR190997 dose-dependently. Indomethacin (10 mg/kg, i.p. 30 min before) inhibited the response to FR190997, suggesting that release of prostaglandins induced by the B2 agonistic action might be involved in this inflammatory process induced by FR190997. The hypotensive action of FR190997 was also examined. Intravenously injected FR190997 caused the systemic hypotensive response in Sprague-Dawley male rats anesthetized with pentobarbital. The potency of FR190997 was weaker than that of bradykinin, when compared with the maximal hypotension. Duration of the hypotensive response of FR190997 was significantly longer than that of bradykinin. These results indicate that FR190997 has the B2 agonistic action similar to bradykinin and is also a good tool for in vivo examination of the B2 receptor.

Modulation of the potency of promutagens and direct acting mutagens in bacteria by inhibitors of the multidrug resistance mechanism

Multiple drug resistance (MDR) mechanisms are known to limit the effectiveness of some cancer chemotherapies, probably through enhancing P-glycoprotein-mediated drug efflux from mammalian cells. Similar mechanisms appear to act in other organisms, including bacteria, and may affect not only the toxicity but also the mutagenicity of certain chemicals. At least in some experimental situations, MDR can be overcome through concomitant treatment of the cells with various types of inhibitors. Two MDR inhibitors, verapamil, a calcium channel blocker, and trifluoperazine, a calmodulin inhibitor, were assayed for their ability to modulate the potency of nine mutagens with varying mechanisms of action in various Salmonella typhimurium his- strains. Neither verapamil nor trifluoperazine affected the direct mutagenicity of sodium dichromate and 2-methoxy-6-chloro-9[3-(2-chloroethyl)amino-propyl-amino] dihydrochloride (ICR 191) or the S9-mediated mutagenicity of benzo[a]pyrene and 2-amino-3,4-dimethyl-amidazo[4,5-f]quinoline (MeIQ). Both modulators enhanced the direct mutagenicity of doxorubicin. Moreover, trifluoperazine sharply increased the S9-mediated mutagenicity of cyclophosphamide and 2-aminofluorene, while it consistently decreased the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). The contrasting effect towards the aromatic amine 2-aminofluorene and the heterocyclic amine Trp-P-2, representative of important chemical families responsible for the bacterial mutagenicity of cigarette smoke, may explain the observed lack of influence of trifluoperazine on the mutagenicity of a cigarette smoke condensate. These observations extend the known range of chemical types whose mutagenicity can be modulated by inhibitors of MDR and suggest that there may be value in adding MDR inhibitors, especially trifluoperazine, to optimize the detection of mutagenicity by certain types of chemicals in the Salmonella/mammalian microsome mutagenicity test.

Possible mechanisms of antimutagens by various teas as judged by their effects on mutagenesis by 2-amino-3-methylimidazo[4,5-f]quinoline and benzo[a]pyrene

Possible mechanisms of antimutagenicity of various tea extracts (green, pouchong, oolong and black tea) toward 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and benzo[a]pyrene (B[a]P) were investigated using a Salmonella/microsome assay. Tea extracts exhibited no inhibitory effects toward IQ and B[a]P in bio-antimutagenic assays, indicating that their antimutagenic activity is desmutagenic in nature. The mutagenicities of IQ and B[a]P decreased as the reaction periods of tea extracts with promutagens, S9 mix, or mutagen metabolites increased. The antimutagenicity of tea extracts toward IQ could be attributed (primarily) to an interaction between tea extracts and S9 mix. Apart from their interaction with S9 mix, tea extracts also exhibited antimutagenicity by markedly decreasing the mutagenicity of B[a]P metabolites. These results suggest that tea extracts: (1) inhibit the cytochrome P-450-mediated metabolism of IQ and B[a]P to their ultimate mutagenic metabolite form; and (2) interact with both promutagens and their metabolites in such a way as to reduce their mutagenic potentials. Therefore, the antimutagenic actions of tea extracts are due to a combination of the above distinctive mechanisms, and can vary with the type of mutagen under test.

The inhibition by flavonoids of 2-amino-3-methylimidazo[4,5-f]quinoline metabolic activation to a mutagen: a structure-activity relationship study

The mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in Salmonella typhimurium TA98 is inhibited by flavonoids with distinct structure-antimutagenicity relationships (Edenharder, R., I. von Petersdorff I. and R. Rauscher (1993). Antimutagenic effects of flavonoids, chalcones and structurally related compounds on the activity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and other heterocyclic amine mutagens from cooked food, Mutation Res., 287, 261-274). With respect to the mechanism(s) of antimutagenicity, the following results were obtained here. (1) 7-Methoxy- and 7-ethoxyresorufin-O-dealkylase activities in rat liver microsomes, linked to cytochrome P-450-dependent 1A1 and 1A2 monooxygenases catalyzing oxidation of IQ to N-hydroxy-IQ (N-OH-IQ), were effectively inhibited by 16 flavonoids (IC50: 0.4-9.8 microM). Flavones and flavonols are in general more potent enzyme inhibitors than flavanones, isoflavones, and chalcones. Among flavones the presence of hydroxyl or methoxyl groups resulted in minor changes only. However, among flavonols and flavanones the parent compounds exerted the strongest inhibitory effects, which decreased in dependence on number and position of hydroxyl functions. Contrary to the results obtained in the Salmonella assay in the tests with alkoxyresorufins no extraordinary counteracting effects of isoflavones, of hydroxyl groups at carbons 6 or 2' or of the elimination of ring B (benzylideneacetone) were detected. (2) No effects of flavonoids on NADPH-dependent cytochrome P-450 reductase activity could be detected. (3) The effects of 30 flavonoids on mutagenicity induced by N-OH-IQ in S. typhimurium TA98NR were again structure dependent. The most striking feature was the, in principle, reverse structure-antimutagenicity pattern as compared to IQ: non-polar compounds were inactive and a 50% inhibition was achieved only by some flavones and flavonols (IC50: 15.0-148 nmol/ml top agar). Within the flavone and flavonol subgroups inhibitory effects increased in dependence on number and position of hydroxyl functions. Isoflavones and flavanones, however, as well as glycosides, were inactive. Hydroxyl groups at carbons 7, 3', 4', and 5' generated antimutagenic compounds, a hydroxyl function at C5 was ineffective, but hydroxyls at C3 and 6 as well as methoxyl groups at C3' (isorhamnetin) or 4' (diosmetin) generated comutagenic compounds. 4. Cytosolic activation of IQ to mutagenic metabolites as determined by experiments with the hepatic S105 fraction comprises about 10% of the mutagenicity after activation by the combined microsomal and cytosolic fractions (S9). The pattern of inhibition as produced by 20 flavonoids was closely similar to that observed with the S9 fraction. 5. In various experiments designed for modulation of the mutagenic response, it could be shown that further mechanisms of flavonoid interaction with the overall mutagenic process may exist, such as interactions with biological membranes (luteolin, fisetin) and effects on fixation and expression of.DNA damage (flavone, fisetin).

Neuroprotective effects of the GABA(A) receptor partial agonist U-101017 in 3-acetylpyridine-treated rats

The neuroprotective effects of U-101017, [7-chloro-5-[cis-3,5-dimethylpiperazine)carbonyl]-imidazole[1,5a]quinoli ne-3-carboxylate], a GABA(A) receptor partial agonist, were investigated in 3-acetylpyridine (3-AP) treated Wistar rats. A significant (P < 0.01) reduction in both cGMP and ATP in the cerebellum was observed at 96 h after treatment with 3-AP (500 micromol/kg i.p.). Oral administration of U-101017 before and after treatment with 3-AP significantly attenuated 3-AP-induced decreases in cGMP and ATP, and this effect was dose related. Consistent with the neurochemical effect, U-101017 prevented 3-AP-induced loss of motor coordination. Treatment with U-101017 partially, but significantly (P < 0.01) prevented the loss of inferior olivary neurons. U-101017 had no significant effect on body temperature. Thus, hypothermia was not involved in neuroprotective effects of U-101017. Co-administration of flumazenil with each treatment of U-101017 blocked the neuroprotective effect of U-101017, indicating that it mediated neuroprotection via the benzodiazepine binding sites on the GABA(A) receptor complex. Delayed administration of U-101017 at various time intervals after treatment with 3-AP demonstrated a significant neuroprotective effect even at 8 h, suggesting that this drug has a wide therapeutic window.

Supraspinal delta 1-opioid receptor-mediated antinociceptive properties of (-)-TAN-67 in diabetic mice

The antinociceptive potencies of the enantiomorphs of TAN-67 (2-methyl-4-alpha alpha-(3-hydroxyphenyl)-1,2,3,4,4 a 5, 12, 12 a alpha-octahydroquinolino[2,3,3,-g]isoquinoline), (-)-TAN-67 and (+)-TAN-67, given intracerebroventricularly (i.c.v.) on the antinociceptive response were studied in streptozotocin-induced diabetic mice using the tail-flick test. (-)-TAN-67 at doses of 3-10 micrograms given i.c.v. produced dose-dependent inhibition of the tail-flick response in both non-diabetic and diabetic mice. The antinociceptive effect of (-)-TAN-67 in the tail-flick test in diabetic mice was greater than that in non-diabetic mice. The antinociceptive effect of (-)-TAN-67 was not antagonized by pretreatment with either beta-funaltrexamine, a selective mu-opioid receptor antagonist, or nor-binaltorphimine, a selective kappa-opioid receptor antagonist. When 7-benzylidenenaltrexone, a selective delta 1-opioid receptor antagonist, was administered 10 min before treatment with (-)-TAN-67, the antinociceptive effect of (-)-TAN-67 was significantly antagonized. However, naltriben, a selective delta 2-opioid receptor antagonist, had no significant effect on the antinociceptive effect of (-)-TAN-67. On the other hand, in the tail-flick test. (+)-TAN-67 at doses of 3-30 micrograms given i.c.v. did not produce dose-dependent inhibition of the tail-flick response in either non-diabetic or diabetic mice. In conclusion, (-)-TAN-67, but not its enantiomer (+)-TAN-67, produced an antinociceptive effect through the activation of delta 1-opioid receptors.

Protection by green tea, black tea, and indole-3-carbinol against 2-amino-3-methylimidazo[4,5-f]quinoline-induced DNA adducts and colonic aberrant crypts in the F344 rat

Male F344 rats were exposed for 8 weeks to extracts of green tea (2% w/v) or black tea (1% w/v), or to 0.1% dietary indole-3-carbinol (I3C). In weeks 3 and 4 of the study, rats were given 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) every other day by oral gavage (50 mg/kg body wt) in order to induce aberrant crypt foci (ACF) in the colon. Compared with controls given IQ alone, all three inhibitors reduced the number of total aberrant crypts per colon, and green tea and I3C inhibited significantly the mean number of ACF (P < 0.05). Rats pre-treated with green tea, black tea, or I3C and given a single p.o. injection of 50 mg IQ/kg body wt 24-48 h before sacrifice had reduced levels of IQ-DNA adducts in the liver, and excreted lower amounts of IQ and other promutagens in the urine and feces. Inhibitors also reduced the excretion of IQ-sulfamate in the urine, but increased the relative amounts of IQ-5-O-sulfate and IQ-5-O-glucuronide. Western blotting together with assays for 7-ethoxyresorufin O-deethylase and methoxyresorufin O-demethylase established that I3C preferentially induced cytochrome P4501A1 over 1A2, consistent with the altered profile of urinary metabolites. However, both teas caused slight induction of cytochrome P4501A2 versus 1A1, which would be predicted to enhance the activation of IQ. Thus, green tea and black tea are likely to protect against IQ-DNA adducts and ACF by mechanisms other than induction of cytochromes P450, such as inhibition of enzymes which activate IQ or the scavenging of reactive intermediates.

Protection of conjugated linoleic acids against 2-amino-3- methylimidazo[4,5-f]quinoline-induced colon carcinogenesis in the F344 rat: a study of inhibitory mechanisms

Grilled ground beef contains a number of heterocyclic amine carcinogens, such as 2-amino-3-methylimidazo[4,5-f] quinoline (IQ), as well as anticarcinogenic conjugated linoleic acids (CLA). In the present study, CLA was administered to male F344 rats by gavage on alternating days in weeks 1-4, while IQ was given by gavage every other day in weeks 3 and 4 (100 mg/kg body wt). Rats were killed 6 h after the final carcinogen dose 16 in order to score colonic aberrant crypt foci (ACF). In the ACF study, CLA had no effect on the size of the foci, but inhibited significantly (P < 0.05) the number of ACF/colon, from 4.3 +/- 2.4 in controls to 1.1 +/- 1.3 in CLA-treated rats (mean +/- SD, n = 10). Rats given CLA also had significantly lower IQ-DNA adducts in the colon as determined by 32P-postlabeling analysis; relative adduct labeling levels (RAL x 10(7) for the major adduct were 9.13 +/- 2.6 in controls versus 5.42 +/- 1.8 in CLA-treated animals (P < 0.05). Mechanism studies indicated that CLA and other fatty acids interact with certain heterocyclic amines in a manner consistent with substrate-ligand binding. However, no such interaction occurred with IQ, and CLA failed to inhibit significantly the mutagenicity of N-hydroxy-IQ in the Salmonella assay. Liver microsomes from CLA-treated rats exhibited lower activities for dealkylation of 7-ethoxyresorufin and methoxyresorufin and activated IQ to DNA binding species less effectively than microsomes from control animals. Direct addition of CLA to the in vitro incubation inhibited IQ-DNA binding and was associated with increased recovery of unmetabolized parent compound. In the Salmonella assay, CLA inhibited the mutagenic activity of IQ in the presence of S9 or ram seminal vesicle microsomes. Collectively, these results support a mechanism involving inhibition of carcinogen activation by CLA, as opposed to direct interaction with the procarcinogen, scavenging of electrophiles or selective induction of phase I detoxification pathways.

Inhibition by chlorophyllin of 2-amino-3-methylimidazo-[4,5-f]quinoline-induced tumorigenesis in the male F344 rat

This report describes a 1-year carcinogenicity bioassay in which male F344 rats received 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) by gavage 2-3 times per week throughout the first 35 weeks of study, while 0.1% sodium/copper chlorophyllin (CHL) was given concomitantly in the drinking water. The carcinogen dose was calculated to provide an average exposure of 4.2 mg IQ/rat per day, equivalent to that reported in previous carcinogenicity study in which rats were given 0.03% IQ in the diet. Adjusted for length of follow-up, inhibition was highly significant for total tumor burden (P < 0.001), and for specific sites was significant in the small intestine and Zymbal's gland (P < or = 0.1), and in the liver (P < 0.01). In rats given CHL, the first onset of tumors in the Zymbal's gland was delayed from week 20 to 36, but was shortened from week 31 to 26 in the skin (P < 0.05). These results support a chemopreventive role for CHL in several of the major target organs for IQ tumorigenesis in the rat, but raise concerns over possible deleterious effects in the skin.

Structure-activity relationships of anthraquinones as inhibitors of 7-ethoxycoumarin O-deethylase and mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline

The antimutagenicity of 17 natural and synthetic anthraquinones was determined using Salmonella typhimurium TA98 against 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in the presence of Aroclor 1254-induced rat hepatic S9. In general, the relationship between the chemical structures of anthraquinones and their antimutagenicity was found to contain one or more of the following features: (i) C9 carbonyl group, (ii) hydroxyl group at C1 and C4, (iii) C2 ethyl group, and (iv) C3 methyl group. The inhibitory effect of anthraquinones on 7-ethoxycoumarin O-deethylase (ECD) of Aroclor, 1254-induced hepatic microsomes was also examined. In addition, we studied the effect of anthraquinones on the metabolism of IQ by Aroclor 1254-induced microsomes using high-performance liquid chromatography. The antimutagenicity correlated with the inhibition of cytochrome P-450IA2-linked ECD activity in hepatic microsomes, and with the inhibition of N-hydroxy-IQ formation of IQ metabolism by hepatic microsomes. Moreover, we also examined the antimutagenicity of anthraquinones against synthetic N-hydroxy-IQ. Quinizarin and anthraflavic acid were shown to have more effect on the direct mutagenicity of N-hydroxy-IQ than that of the anthraquinones tested. This might explain why both anthraquinones showed higher antimutagenicity; although they inhibited ECD less. These results suggest that there exist at least two mechanisms of action in modifying roles of anthraquinones on the mutagenicity of IQ: (i) mediation through interaction with microsomal activating enzymes to inhibit the major active metabolite of N-hydroxy-IQ formation and (ii) direct interaction with the proximate metabolite of IQ, N-hydroxy-IQ, to block its attack on DNA.

Modifying actions of solvent extracts from fruit and vegetable residues on 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoxaline (MeIQx) induced mutagenesis in Salmonella typhimurium TA 98

The edible parts of 13 fruits--apples, apricots, bananas, blackberries, sweet cherries, red currants, white grapes, oranges, peaches, pears, plums, raspberries, and strawberries--and of 12 vegetables--asparagus, green beans, broccoli, brussels sprouts, red and white cabbage, carrots, cauliflower, onions, green peppers, spinach, and tomatoes--were squeezed in order to separate juices and residues. The residues were washed, lyophilized, and extracted sequentially with n-hexane, dichloromethane, acetone, and 2-propanol. Solvent extracted materials were tested in Salmonella typhymurium TA 98 for antimutagenicity against IQ and MeIQx. We found antimutagenic activities in 96% of the n-hexane extracts, 64% of the dichloromethane extracts, 44% of the acetone extracts, and 36% of the 2-propanol extracts. Since no or only minor differences were seen between the mutagens IQ and MeIQx investigations were continued with IQ only. Additional antimutagenic activities were detected in a total of 29.6% of extracts tested when an enzyme preparation with glycosidase-activities (fecalase) was included in the assay. These activities were found in originally inactive or less active dichloromethane, acetone, and 2-propanol extracts, and are therefore strongly suggestive for the liberation of antimutagenic aglycones from inactive glycosides. The existence of possibly a multitude of antimutagenic factors in fruits and vegetables was further substantiated by: (1) solvent partitioning of the n-hexane extracts of cauliflower, peaches, and spinach; (2) separation of the n-hexane and dichloromethane extracts of cauliflower, peaches, and spinach into acidid, neutral, and basic compounds; (3) chromatographic analysis of the n-hexane and dichloromethane extracts of spinach. Taken together, antimutagenic activities were present in 32 of 36 subfractions, corresponding to 88.9%. In the green vegetables beans, broccoli, and spinach the known antimutagen chlorophyll was proven to contribute considerably to antimutagenic potency. Other important contributions may be caused by various fibers: (I) antimutagenicity of fruit and vegetable solvent extracts was extensively heat stable; (II) heating surprisingly caused an increase of antimutagenic potencies or generated new antimutagenic activities in several solvent fractions, especially of broccoli, white and red cabbage. Indeed, mutagenicity induced by IQ was strongly reduced by lignin, weakly by alginic acid and pectin A, while cellulose, gum arabic, gum guar, and xylan were ineffective. With respect to the mechanisms of antimutagenicity binding of IQ by various fibers and inhibition of cytochrome P-450-dependent monooxygenases might be of major importance since no solvent fraction of any fruit or vegetable was able to reduce mutagenic activity induced by N-OH-IQ in S. typhimurium TA 98NR.

Antimutagenicity of Maillard reaction products from amino acid/sugar model systems against 2-amino-3-methylimidazo-[4,5-f]quinoline: the role of pyrazines

The antimutagenicity of dichloromethane extracts from eight amino acid/sugar model systems was determined using Salmonella typhimurium TA98 against 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ) in the presence of Aroclor 1254-induced rat hepatic S9. The Maillard reaction products in the dichloromethane extracts were then quantified and qualified by capillary gas chromatography and gas chromatography-mass spectrometry, respectively. Pyrazines and furans were found to be the major Maillard reaction products yielded in the extracts. Moreover, the antimutagenicity of dichloromethane extracts correlated positively with the total amounts of pyrazines and furans. To elucidate the mechanism of antimutagenicity of dichloromethane extracts, the inhibitory effect of pyrazines on ethoxycoumarin deethylase activity in Aroclor 1254-induced hepatic microsomes was examined. We also studied the effects of pyrazines on IQ metabolism by Aroclor 1254-induced microsomes using high-performance liquid chromatography. The antimutagenicity of pyrazines correlated positively with both the inhibition of cytochrome P-450 IA2-linked ethoxycoumarin deethylase in hepatic microsomes and the inhibition of N-hydroxy-IQ formation from IQ metabolism by hepatic microsomes. Thus we concluded that pyrazines in dichloromethane extracts from eight amino acid/sugar model systems play an important role in the antimutagenicity of IQ. Moreover, we concluded that the modifying effect of pyrazines on the mutagenicity of IQ is mediated through interaction with microsomal activating enzymes to inhibit the major active metabolite in N-hydroxy-IQ formation.

Evaluation of the antimutagenic potential of anthracene: in vitro and ex vivo studies

The present study was undertaken in order to evaluate the in vitro and ex vivo antimutagenicity of anthracene against the food-borne carcinogen IQ (2-amino-3-methylimidazo[4,5-f]quinoline). Anthracene caused a marked, concentration-dependent decrease in the mutagenicity of IQ in the Ames test, whether hepatic S9 or isolated microsomes from Aroclor 1254-induced rats served as the activation systems. Anthracene gave rise to a concentration-dependent inhibition of the 0-deethylation of ethoxyresorufin, a diagnostic probe for CYP1A (cytochrome P450 family 1, subfamily A) activity, and of the metabolic activation of Glu-P-1 (2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole, a diagnostic probe for CYP1A2. When microsomal metabolism of IQ was terminated by menadione, incorporation of anthracene into the incubation mixture once again inhibited the mutagenicity of IQ. All the above observations indicate that anthracene owes its antimutagenic response against IQ to: (a) inhibition of its CYP1A-mediated activation and (b) direct interaction between anthracene and the reactive intermediate(s) of IQ leading to their inactivation. Treatment of rats with anthracene did not greatly influence the ability of hepatic preparations to bioactivate IQ to mutagens. Similarly, administration of anthracene 2 h before sacrifice to Aroclor 1254-pretreated rats, did not modulate the hepatic activation of IQ. These findings demonstrate that the in vitro mechanisms of the antimutagenicity of anthracene are not operative in vivo, and further illustrate the inadequacy of in vitro studies, conducted in isolation, in predicting such effects.

In vitro effect of vegetable and fruit juices on the mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline

The antimutagenic potencies of the juices of 28 fruits and 34 vegetables commonly consumed in Germany were investigated with respect to the mutagenic activities induced by 2-amino-3-methyl[4,5-f]-quinoline (IQ), and in part by 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) or 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in Salmonella typhimurium TA98 and TA100. With IQ, weak to strong antimutagenic activities were found in 68% of the fruits and 73% of the vegetables that were tested. In fruits, strong antimutagenic activities were detected in bananas, blackberries, blueberries, sweet and sour cherries, blackcurrants and redcurrants, pineapple and watermelon. Moderate antimutagenic activities were detected in greengage, kiwi, mangos, honeydew melons and plums. Weak antimutagenic activities were detected in apple, apricot, mirabelle, pears, peaches and strawberries, whereas white and red grapes and raspberries were inactive, and gooseberries and citrus fruits in general possessed marginal or no antimutagenic activities. In vegetables, strong to moderate antimutagenic activities were found for all cruciferous vegetables, except Chinese cabbage, which had only weak antimutagenic activity. Other vegetables with strong antimutagenic activities were beets, chives, horseradish, onions, rhubarb and spinach. Moderate antimutagenic activities were found with green beans and tomatoes, weak activities in eggplant, garden cress, many lettuces, leeks, mangold, cucumber, pumpkin, radish and summer squash. Asparagus, carrots, fennel leaves, parsley, green peppers and radishes were inactive. When fruit and vegetable juices were heated, a considerable reduction of antimutagenic potencies was seen with apple, apricot, kiwi, pineapple, beets, cabbage (Chinese, Savoy, red and white), cauliflower, leafy lettuce, cucumber, onions, radish and rhubarb. Antimutagenic factors in blackberries, blueberries, sweet and sour cherries, honeydew melons, mirabelle, plums, strawberries, Brussels sprouts, chicory greens, eggplant, garden cress, mangold, pumpkin, lamb's lettuce and spinach were, however, remarkably heat stable. Antimutagenic potencies in bananas, blackcurrants and redcurrants, greengages, gooseberries, mangos, watermelon, green beans, kohlrabi, horseradish, tomatoes and chives were partially reduced. Antimutagenic activities in the juices of eight apple cultivars were moderate in two, weak in four, and marginal or absent in two. No major differences, however, were detected in five batches of oranges and three batches each of grapefruits, asparagus, green beans, broccoli, cauliflower, spinach and tomatoes. No (or only minor) differences were seen between IQ, MeIQ and MeIQx and tester strains TA98 and TA100. Pineapple and celeriac juices inhibited the enzymatic system responsible for the activation of IQ, but had no desmutagenic activity. Peroxidase activity found to be present in broccoli, cauliflower, green beans and tomatoes may contribute to antimutagenic activities in these vegetables.

The structure-activity relationships of flavonoids as inhibitors of cytochrome P-450 enzymes in rat liver microsomes and the mutagenicity of 2-amino-3-methyl-imidazo[4,5-f]quinoline

The antimutagenicity of 19 naturally occurring flavonoids and their derivatives including flavones, flavonols, flavanones, isoflavones and flavanols were determined using Salmonella typhimurium TA98 against 2-amino-3-methylimidazo[4,5-f] quinoline (IQ) in the presence of Aroclor 1254-induced rat hepatic S9. In general, a relationship between the chemical structure of flavonoids and their antimutagenicity was found for compounds containing one or more of the following features: (i) C4 keto group, (ii) aglycone, (iii) double bond at positions C2 and C3, (iv) phenyl group at position C2, and (v) three hydroxy substituents at positions C4', C5 and C7. The inhibitory effects of flavonoids on activities of 7-ethoxycoumarin deethylase (ECD) and 7-ethoxyresorufin deethylase (ESD) of Aroclor 1254-induced hepatic microsomes were also examined. In addition, we studied the effects of flavonoids on the metabolism of IQ by Aroclor 1254-induced microsomes using high-performance liquid chromatography. The antimutagenicity correlated with the inhibition of cytochrome P-450IA1-linked ESD and P-450IA2-linked ECD activity in hepatic microsomes, and with an inhibition of N-hydroxy-IQ formation from IQ metabolism by hepatic microsomes. These results indicated that flavones or flavonols that contain C5, C7 and C4' hydroxyl groups are potent inhibitors of P-450 enzyme activities induced by Aroclor 1254 (P-450IA1 and P-450IA2), and may potentially be useful as chemopreventive agents against heterocyclic amine-induced mutagenesis or carcinogenesis.

A subpopulation of dopamine D1 receptors mediate repetitive jaw movements in rats

Repetitive jaw movements (RJM) in rats, a potentially useful animal model of tardive dyskinesia, appears to be mediated by the dopamine D1 receptor as evidenced in part by their induction and inhibition with D1 agonists and D1 antagonists, respectively. Selective destruction of 60-90% of D1 receptors by EEDQ, measured in several CNS dopaminergically innervated areas, preceded by protection of D2, 5-HT2, alpha 1 and alpha 2 receptors, however, failed to reduce D1 agonist-augmentable RJM. Further, the affinity of dopamine toward displacement of 3H-SCH-23390 binding from striatal D1 receptors was significantly decreased by administered EEDQ, a counter-intuitive result in relation to D1 responsitivity and RJM. Thus, at present it is suggested that an EEDQ-resistant D1 receptor subpopulation may exist.

Differential effects of the optical isomers of EMD 53998 on contraction and cytoplasmic Ca2+ in isolated ferret cardiac muscle

EMD 53998 (a thiadiazinone) is a novel inotropic substance that increases the Ca2+ sensitivity of the myofilaments in skinned cardiac fibers and has been found to have similar effects in intact cardiac muscle. However, the compound also possesses the ability to inhibit phosphodiesterase III, indicating that its actions in intact cardiac muscle are likely to be complex. The present study was carried out to investigate the possibility that the optical isomers of EMD 53998--(+)EMD 57033 and (-)EMD 57439--which have recently been shown to possess a separation of sensitization and phosphodiesterase inhibition in subcellular preparations, might also demonstrate this separation of activities in intact cardiac muscle. The experiments were performed on isolated ferret papillary muscles, which were contracting isometrically. In some preparations, the photoprotein aequorin was injected into superficial cells to measure intracellular Ca2+ as well as force. (+)EMD 57033 caused a substantial positive inotropic effect that was associated with prolongation of the twitch, reduction in the amplitude of the Ca2+ transient, and abbreviation of the Ca2+ transient. This is the profile expected of a Ca(2+)-sensitizing compound. Conversely, (-)EMD 57439 caused a less marked positive inotropic effect that was associated with an abbreviation of the twitch, an increase in the amplitude of the Ca2+ transient, and an abbreviation of the Ca2+ transient. This is the profile expected of an agent producing its inotropic effect by increasing cAMP (e.g., phosphodiesterase inhibition). The results indicate that the optical isomers of EMD 53998 possess a remarkable separation of Ca(2+)-sensitizing and phosphodiesterase-inhibiting activities in intact cardiac muscle. These actions were additive and could account for the effects observed with EMD 53998. (+)EMD 57033 appears to be the first inotropic agent that acts predominantly by increasing myofilament calcium sensitivity.

Antimutagenic effects of flavonoids, chalcones and structurally related compounds on the activity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and other heterocyclic amine mutagens from cooked food

Sixty-four flavonoids were tested for their antimutagenic potencies with respect to IQ in Salmonella typhimurium TA98 and in part also towards MeIQ, MeIQx, Trp-P-2, and Glu-P-1 and in S. typhimurium TA100. Antimutagenic potencies were quantified by the inhibitory dose for 50% reduction of mutagenic activity (ID50). A carbonyl function at C-4 of the flavane nucleus seems to be essential for antimutagenicity: two flavanols and four anthocyanidines were inactive. Again, five isoflavons, except biochanin A, were inactive. Within the other groups of 21 flavones, 16 flavonols and 16 flavanones the parent compounds flavone, flavonol, and flavanone possessed the highest antimutagenic potencies (ID50: 4.1, 2.5, 5.5 nmoles). Increasing polarity by introduction of hydroxyl functions reduced antimutagenic potency. Reducing polarity of hydroxy flavonoids by methyl etherification, however, increased antimutagenic potency again. 6-Hydroxy- and 2'-hydroxy substituted flavonoids were considerably less potent antimutagens. Of 11 flavonoid glycosides tested all compounds except apigenin- and luteolin-7-glucoside (ID50:74, 115 nmoles) were inactive or only weakly antimutagenic. Rings C and A of the nucleus were not essential for antimutagenicity: chalcone and three derivatives were nearly as active as comparable flavones while antimutagenicity of benzylidenacetone was considerably reduced (ID50: 95 nmoles). Cinnamylaldehyde and cinnamoates, however, were inactive. A planar structure in the vicinity of the carbonyl group may also be important for antimutagenicity. Flavanones were less potent antimutagens than the corresponding flavones, but dihydrochalcones and 14 structurally related saturated aromatic carbonyl compounds were inactive. Fisetin and 6-hydroxyflavone were competitive inhibitors, but luteolin was a mixed type inhibitor. The inhibition mechanisms of flavone, kaempferol, morin, flavanone, and 2'-hydroxyflavanone were concentration dependent, being competitive at low concentrations and mixed or non-competitive (2'-hydroxyflavanone) at concentrations about the ID50 value. No fundamental differences between the two tester strains and no clear influence of mutagen structure on antimutagenic potency could be detected.

Antimutagenicity of ellagic acid towards the food mutagen IQ: investigation into possible mechanisms of action

The ability of the plant phenol ellagic acid to inhibit the mutagenicity of the food mutagen IQ was evaluated using Salmonella typhimurium strain TA98 in the Ames mutagenicity test. Ellagic acid caused a concentration-dependent decrease in the S-9- and microsome-mediated mutagenicity of IQ. The plant phenol did not interact directly with the IQ-derived mutagenic species and did not modify the cytosol-mediated activation of the promutagen. At the concentrations used in the mutagenicity studies, ellagic acid failed to inhibit microsomal mixed-function oxidase activity, including that mediated by the P450I family responsible for the bioactivation of IQ, despite being an essentially planar molecule as indicated by computer-graphic analysis. The inhibitory effect of ellagic acid was independent of its ability to chelate Mg2+. However, pre-incubation of ellagic acid with the bacteria, followed by removal of the plant phenol, did not completely prevent the inhibitory effect of the phenol on the mutagenicity of IQ. Intraperitoneal administration of ellagic acid to rats caused a decrease in total cytochrome P-450 levels and related activities as well as in cytosolic glutathione S-transferase activity. Finally, the possibility that the reported anticarcinogenic action of ellagic acid reflects nothing more than non-selective destruction of hepatic cytochromes P-450, and thus reduced chemical activation, is considered.

Inhibition of 2-amino-3-methylimidazo[4,5-f]quinoline-DNA adduct formation in CDF1 mice by heat-altered derivatives of linoleic acid

Grilled ground beef contains a number of carcinogens, including aminoimidazoazaarenes, such as 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), as well as anticarcinogenic substances, such as heat-generated derivatives of linoleic acid (CLA). In the present study, CLA was administered by gavage every other day to young adult CDF1 mice for a period of 45 days (50 microliters/48 hr for days 1-24 and 100 microliters/48 hr for days 25-45), using trioctanoin as a control. On day 46 all animals received a single oral dose (50 mg/kg) of IQ and tissues were collected 24 hr later. Tissue DNA was purified and analysed for IQ-DNA adducts by 32P-postlabelling assays. Compared with controls, CLA treatment caused a 43.1 and 31.8% inhibition of adduct formation in the livers of male and female mice, respectively. In the lung and large intestine CLA had a 74.2 and 39.4% inhibitory effect, respectively, in the female only, whereas there was no effect in the stomach or small intestine of either sex. In the kidneys of females, CLA treatment inhibited IQ-DNA adduct formation almost completely (95.2%), whereas in the kidneys of males CLA had no effect. It is concluded that CLA inhibits IQ-DNA adduct formation in certain IQ target organs (liver and lung) and non-target organs (large intestine, kidney), but is inactive in other target organs (stomach) and non-target organs (small intestine) of the CDF1 mouse.

Effect of emodin on cooked-food mutagen activation

The herbs Rheum palmatum B and Polygonum cuspidatum S are frequently used as laxatives and anticancer drugs in Chinese medicine. The antimutagenic activity of these herbs as well as their active component emodin was examined in Salmonella typhimurium TA98. The crude extracts and emodin induced a dose-dependent decrease in the mutagenicity of benzo[a]pyrene (B[a]P), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). Furthermore, emodin reduced the mutagenicity of IQ by direct inhibition of the hepatic microsomal activation and not by interaction with proximate metabolites of IQ and/or by modification of DNA repair processes in the bacterial cell.

Studies on the antimalarial mode of action of quinoline-containing drugs: time-dependence and irreversibility of drug action, and interactions with compounds that alter the function of the parasite's food vacuole

The quinoline-containing antimalarial drugs chloroquine, quinine and mefloquine exert an irreversible inhibitory effect on erythrocytic stages of Plasmodium falciparum grown in culture. Inhibition is time- and concentration-dependent and the full effect is observed after 2-6 hours of exposure to the drug. Washing of infected cells after drug exposure in the presence of NH4Cl to accelerate drug efflux, intensifies the inhibitory effect of chloroquine, probably due to the pH-dependent release of highly concentrated drug from the acidic food vacuole of the parasite. When both antimalarials and NH4Cl are present in the culture, drug effect is reduced, as expected from the demonstrable alkalinization of the food vacuole and the consequent reduction in drug accumulation. The protease inhibitor leupeptin inhibits digestion of ingested host cell cytosol, and thus inhibits parasite growth, though reversibly so (Rosenthal et al, J. Clin. Invest. 82 1560-1566 (1988)). Thus, although the antimalarials also inhibit the feeding process, this is not the cause of their irreversible action. Leupeptin is found to be antagonistic to antimalarials' action, suggesting that the drugs form complexes with products of host cell digestion that are responsible for irreversible inhibition of parasite growth.