Glutathione transferase-mediated and non-enzymatic activation and detoxication of the N-hydroxy derivative of Trp-P-2, a potent pyrolysate promutagen

Glutathione (GSH) transferase-mediated and non-enzymatic activation and detoxication of 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole (N-OH-Trp-P-2) were studied in vitro. N-OH-Trp-P-2 is an active metabolite of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), a mutagenic and carcinogenic heterocyclic amine. The enzymatic GSH conjugation with N-OH-Trp-P-2 was catalysed by rat-liver GSH transferase and a rat-liver cytosol fraction to form three conjugates (CH-1, CH-2 and CH-3). The mutagenicities of the GSH conjugates were studied by using Salmonella typhimurium TA98 as the tester strain. The GSH conjugates except for CH-3 were completely detoxicated products, but CH-3 was found to be a more potent mutagen than N-OH-Trp-P-2. The mutagenicity of CH-3 seemed to be due to the direct action of the conjugate, but not to N-OH-Trp-P-2 formed from it.     

Metabolic activation of Trp-P-2, a tryptophan-pyrolysis mutagen, by isolated rat hepatocytes

Metabolic activation of a tryptophan-pyrolysis product, 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), by isolated rat hepatocytes was studied. The substrate (Trp-P-2) disappearance by hepatocytes from untreated rats was slow, but enhanced by 3-methylcholanthrene (MC) pretreatment of rats. The covalent binding of Trp-P-2 to cellular macromolecules was detected in hepatocytes from untreated rats. The amount of covalent binding of Trp-P-2 to protein and RNA was greater than that to DNA. The covalent binding to Trp-P-2 to DNA, RNA and protein in hepatocytes from untreated rats was about 5-10 times less than that in hepatocytes from MC-pretreated rats. 7,8-Benzoflavone strongly inhibited the substrate disappearance and the binding of Trp-P-2 to DNA in hepatocytes from MC-pretreated rats. These results indicate that Trp-P-2 is metabolically activated by the P-448 type of cytochrome P-450 which is induced by MC. Diethylmaleate enhanced by about 50% the binding of Trp-P-2 to DNA in hepatocytes from MC-pretreated rats. On the other hand, cysteine inhibited the binding of Trp-P-2 to DNA with a concomitant reduction in the accumulation of the active metabolite, N-hydroxy-Trp-P-2 (N-OH-Trp-P-2). Sulfhydryl compounds seemed to play important roles in the detoxification of Trp-P-2.     

Metabolic activation of Trp-P-2, a mutagenic amine from tryptophan-pyrolysate,by liver microsomes from 3-methylcholanthrene-responsive and non-responsive mice

1. The metabolic activation of a tryptophan pyrolysate, Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole), was studied using liver microsomes from mice of 3-methylcholanthrene-responsive, C57BL/6N (B6) strain and non-responsive, DBA/2N (D2) strain.

2. The formation of N-hydroxy-Trp-P-2 (3-hydroxylamino-1-methyl-5H-pyrido-[4,3-b]indole) by hepatic microsomes was markedly increased by the pretreatment with 3-methylcholanthrene in B6 mice, but not in D2 mice.

3. The same treatment increased the activity to convert Trp-P-2 to a mutagen(s) in the Salmonella/microsome test system in B6 mice, but not in D2 mice.

4. The formation of N-hydroxy-Trp-P-2 corresponded with the increase in the number of the revertants, and with the activities of aromatic hydrocarbon hydroxylase and biphenyl 2-hydroxylase.

5. Addition of α-naphthoflavone to microsomes from control and 3-methyl-cholanthrene-treated B6 mice effectively decreased the activities to convert Trp-P-2 to a mutagen(s) and to N-hydroxylate Trp-P-2.

6. These results indicate that N-hydroxy-Trp-P-2 is a proximate or ultimate mutagenic principle of Trp-P-2.     

Neuroprotective effects of PMC, a potent alpha-tocopherol derivative, in brain ischemia-reperfusion: reduced neutrophil activation and anti-oxidant actions

2,2,5,7,8-Pentamethyl-6-hydroxychromane (PMC) is the most potent analogue of alpha-tocopherol for anti-oxidation. It is more hydrophilic than other alpha-tocopherol derivatives and has potent free radical-scavenging activity. In the present study, PMC significantly attenuated middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia in rats. Administration of PMC at 20mg/kg, showed marked reductions in infarct size compared with that of control rats. MCAO-induced focal cerebral ischemia was associated with increases in HIF-1alpha, active caspase-3, iNOS, and nitrotyrosine expressions in ischemic regions. These expressions were markedly inhibited by treatment with PMC (20mg/kg). In addition, PMC (4-12 microM) inhibited respiratory bursts in human neutrophils stimulated by fMLP (800 nM) and PMA (320 nM). Furthermore, PMC (6, 12, and 60 microM) also significantly inhibited neutrophil migration stimulated by leukotriene B(4) (160 nM). An electron spin resonance (ESR) method was conducted on the scavenging activity of PMC on the free radicals formed. PMC (12 microM) greatly reduced the ESR signal intensities of superoxide anion, hydroxyl radical, and methyl radical formation. In conclusion, we demonstrate a potent neuroprotective effect of PMC on MCAO-induced focal cerebral ischemia in vivo. This effect may be mediated, at least in part, by inhibition of free radical formation, followed by inhibition of HIF-1alpha activation, apoptosis formation (active caspase-3), neutrophil activation, and inflammatory responses (i.e., iNOS and nitrotyrosine expressions), resulting in a reduction in the infarct volume in ischemia-reperfusion brain injury. Thus, PMC treatment may represent a novel approach to lowering the risk or improving function in ischemia-reperfusion brain injury-related disorders.     

Pharmacological profile of a potent,efficacious fentanyl derivative in rhesus monkeys

The recent synthesis of fentanyl derivatives, some of which appear to have novel profiles of pharmacological effects, has provided compelling evidence that opioid efficacy might be altered systematically by modifications in the parent compound fentanyl. In the present study a new 4-(heteroanilido)-piperidine, compound 28, was studied for its effects in rhesus monkeys. In self-administration studies compound 28 maintained rates of lever pressing similar to those maintained by alfentanil; the reinforcing effects of compound 28 were attenuated by the opioid antagonist quadazocine. In drug discrimination studies compound 28 did not substitute for the agonist ethylketocyclazocine and did substitute for the agonist alfentanil. In morphine-treated subjects discriminating between saline and naltrexone, compound 28 did not substitute for naltrexone; however, in morphine-abstinent subjects compound 28 reversed naltrexone lever responding. Moreover, this discriminative stimulus effect in morphine-abstinent subjects was antagonized by naltrexone and by quadazocine in a manner consistent with receptor mediation. Compound 28 also was an effective analgesic in a warm-water, tail-withdrawal procedure and it decreased markedly respiratory function. The analgesic effects as well as the respiratory depressant effects of compound 28 were antagonized by quadazocine. Together, these results show compound 28 to be a potent, efficacious agonist of similar potency to alfentanil. Large differences in apparent efficacy at receptors between compound 28 and another compound in this series (mirfentanil), clearly demonstrate that, within this chemical family, small chemical changes can confer significant differences in pharmacologic effect.Supported by USPHS Grants DA 05018 and DA 00254. Portions of these results were presented at the 53rd Annual Scientific Meeting of the Committee on Problems of Drug Dependence, Palm Beach (France et al. 1992). Animals used in these studies were maintained in accordance with the University Committee on the Use and Care of Animals, Louisiana State University Medical Center and University of Michigan, and guidelines of the Committee on the Care and Use of Laboratory Animals of the Institute of Laboratory Animal Resources, National Research Council (Department of Health, Education and Welfare, Publication No. (NIH) 85-23, revised 1983).     

ZJU-6, a novel derivative of Erianin, shows potent anti-tubulin polymerisation and anti-angiogenic activities

ZJU-6 was designed to enhance anti-angiogenesis and anti-tumour activity of its parent compound Erianin, a clinic anti-tumour agent. This study investigated the detailed biological mechanism of ZJU-6 in comparison with that of Erianin. Both ZJU-6 and Erianin substantially reduced cell viability and induced apoptosis in human cancer cell lines. Profound G2/M cell arrest was observed 24 h after treatment of MCF-7 cells with ZJU-6 (≥ 2.5 μM) or Erianin (≥ 0.1 μM); being consistent with mitotic collapse. 0.5 μM of Erianin or ZJU-6 failed to stabilise tubulin. Pre-G1 MCF-7 cell accumulating 24 h post treatment indicated apoptosis. Caspase-3 activity, PARP cleavage and Annexin V?+?ve /PI -ve populations correlate the apoptotic destiny of cells exposed to either ZJU-6 or Erianin. Furthermore ZJU-6 showed potent anti-angiogenetic property and demonstrated radical scavenging capacity. Due to its potent anti-proliferative, pro-apoptotic and anti-angiogenic activities ZJU-6 is an attractive chemotherapeutic agent to be developed.     

Synthesis, chiral resolution, and enantiopharmacology of a potent 2,3-benzodiazepine derivative as noncompetitive AMPA receptor antagonist

This paper describes the synthesis of racemic 3,5-dihydro-5-methyl-7,8-methylenedioxy-4H-2,3-benzodiazepin-4-one (+/-)-5, attempted stereoselective synthesis of its enantiomers, chiral HPLC resolution of the racemate, and assignment of the absolute configuration. Enantiomer (5S)-(-)-5 is provided with an in vivo anticonvulsant activity 8 times higher than its enantiomer (5R)-(+)-5. This result is confirmed in the in vitro test by the ability to inhibit the kainate-induced increase of the [Ca(2+)](i) in a primary culture of rat cerebellar granule cells which express alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. Binding affinity of compound (+/-)-5 at the AMPA and N-methyl-d-aspartic acid (NMDA) receptors was also evaluated.     

Pharmacological action and clinical effects of falecalcitriol,a highly potent derivative of active vitamin D3

Much effort has been made to create highly potentiated active vitamin D for better clinical applications and falecalcitriol was successfully synthesized as one of such candidates with highly potent and long-lasting effects. Its chemical structure has a calcitriol side chain modification in which both methyls at positions C-26 and C-27 are substituted by tri-fluoromethyls. The mechanism for its strong and long-lasting effects is probably due to altered side chain metabolism and decreased inactivation. Although C-24 position hydroxylation catalyzed by Cyp24 inactivates calcitriol, falecarcitriol is metabolized to C-23S hydroxylated metabolite by the same enzyme Cyp24 and this metabolite still has strong activity. Stronger action of falecalcitriol has been shown in target organs or cells of active vitamin D such as bone, parathyroid cells, and keratinocytes, when compared with calcitriol, the endogenous active form of vitamin D. Daily oral administration of falecalcitriol at doses lower than those required for calcitriol has been shown to have clinical effects for the treatment of diseases such as hyperparathyroidism due to chronic renal failure (2 degrees HPT), rickets, osteomalacia and hypoparathyroidism. The comparative study with alfacalcidol showed its specific action on parathyroid hormone suppression and better improvement of bone metabolism markers in 2 degrees HPT patients.     

Pharmacological characterization of a novel sulfonylureid-pyrazole derivative, SM-19712, a potent nonpeptidic inhibitor of endothelin converting enzyme

We describe the pharmacological characteristics of SM-19712 (4-chloro-N-[[(4-cyano-3-methyl-1-phenyl-1H-pyrazol-5-yl)amino]carbonyl] benzenesulfonamide, monosodium salt). SM-19712 inhibited endothelin converting enzyme (ECE) solubilized from rat lung microsomes with an IC50 value of 42 nM and, at 10 - 100 microM, had no effect on other metalloproteases such as neutral endopeptidase 24.11 and angiotensin converting enzyme, showing a high specificity for ECE. In cultured porcine aortic endothelial cells, SM-19712 at 1 - 100 microM concentration-dependently inhibited the endogenous conversion of big endothelin-1 (ET-1) to ET-1 with an IC50 value of 31 microM. In anesthetized rats, either intravenous (1-30 mg/kg) or oral (10-30 mg/kg) administration of SM-19712 dose-dependently suppressed the pressor responses induced by big ET-1. In acute myocardial infarction of rabbits subjected to coronary occlusion and reperfusion, SM-19712 reduced the infarct size, the increase in serum concentration of ET-1 and the serum activity of creatinine phosphokinase. The present study demonstrates that SM-19712 is a structurally novel, nonpeptide, potent and selective inhibitor of ECE, and SM-19712 is a valuable new tool for elucidating the pathophysiological role of ECE.     

Levonantradol, a potent cannabinoid-related analgesic, antagonizes haloperidol-induced activation of striatal dopamine synthesis

Levonantradol antagonized the compensatory acceleration of striatal dopamine synthesis induced by haloperidol. This effect was stereospecific, since the pharmacologically less active enantiomer, dextronantradol was approximately 30 times less effective. delta 9-Tetrahydrocannabinol at a dose 320 times higher than levonantradol also attenuated the haloperidol effect, but cannabidiol was inactive at a dose 750 times higher. GABA-like actions of levonantradol may be responsible for this responsible for this antagonism of haloperidol, but anticholinergic effects may also contribute.     

Pharmacological profile of AS-9705, a novel benzotriazolecarboxamide derivative,as a gastroprokinetic agent with potent anti-emetic activity

The pharmacological profile of AS-9705 ((R)-N-(1-ethyl-1H-hexahydroazepin-3- yl)-6- methoxy-1H-benzotriazole-5-carboxamide fumarate monohydrate, CAS 219622-61-4), a novel gastroprokinetic agent with potent anti-emetic activity, was investigated in the present study. AS-9705 inhibited [3H]spiperone binding to human dopamine D2.long receptors, and [3H]R(+)-7-OH-DPAT binding to human dopamine D3 receptors (IC50 values of 58.5 +/- 14.0 and 60.8 +/- 7.8 (nmol/l), respectively) and had negligible affinity (IC50 > 10 mumol/l) for other neurotransmitter recognition sites examined. Moreover, in ferrets or dogs, AS-9705 dose-dependently inhibited emesis induced by R(+)-7-OH-DPAT and apomorphine with ID50 values of 0.05 mg/kg p.o. and 0.04 mg/kg p.o., respectively. AS-9705 dose-dependently enhanced normal gastric emptying and potently inhibited the delay in gastric empting induced by apomorphine, morphine, cisplatin, clonidine and cholecystokinin in rats. Furthermore, in conscious fasting dogs, AS-9705 dose-dependently stimulated gastric motility. In conclusion, AS-9705 is a novel gastroprokinetic agent with potent antiemetic activity and minimal CNS adverse effects and is, therefore, worthy of clinical investigation.     

Dialdehyde derivative of 5'-deoxyinosine as a more potent analog of the dialdehyde derivative of inosine (NSC 118994).

The dialdehyde derivative of 5′-deoxyinosine (5′-deoxyinox) was prepared from 5′-deoxyadenosine by HNO₂ deamination and periodate oxidation. 5′-Deoxyinox was shown to inhibit ribonucleotide reductase activity in cell-free extracts and to inhibit RNA and DNA syntheses in intact cells. Further, 5′-deoxyinox inhibited the conversion of cytidine nucleotides to deoxycytidine nucleotides in intact cells. In comparative studies with the dialdehyde derivative of inosine (Inox), 5′-deoxyinox was shown to be more active on a molar basis in inhibiting RNA or DNA synthesis in intact cells. In addition, 5′-deoxyinox was more inhibitory to the growth of Novikoff hepatoma cells in culture than was Inox. 5′-Deoxyinox, in addition to being more active than Inox, also differed from Inox in its biochemical properties. Inox did not inhibit RNA polymerase activity when added to isolated nuclei. On the other hand, 5′-deoxyinox showed a marked inhibition of the RNA polymerase activity when added to the isolated nuclei. Further, inhibition of the RNA polymerase activity in the nuclei from Inox-treated cells was reversed completely by the addition of exogenous polydeoxyadenylate-deoxythymidylate as template, whereas the inhibition caused by 5′-deoxyi nox was not reversed by this treatment. These studies show that, in addition to the variation in activity caused by altering the purine component, the nature of the dialdehyde moiety also plays a role in the mode of action of this class of compounds.     

Metabolism of norcocaine, N-hydroxy norcocaine and cocaine-N-oxide in the rat.

1. The metabolism of [3H]norcocaine, N-hydroxy[3H]norcocaine and cocaine-N-oxide has been investigated in rats after i.v. injection. 2. The biological t 1/2 of norcocaine (dose 2 mg/kg i.v.) in plasma, liver and brain were 0.4, 1.6, 0.5 h, respectively and the compound was not detectable in the central nervous system 6 h after injection. The % dose of norcocaine excreted unchanged in urine and faeces in 96 h were 0.7 and 1.0, respectively. Benzoylnorecgonine, norecgonine, norecgonine methyl ester and an unidentified compound were excreted in urine. 3. The biological t 1/2 of N-hydroxynorcocaine (5 mg/kg i.v.) in brain and plasma were 0.3, 1.6 h respectively and only 1.3 and 1.6% of dose were excreted unchanged in urine and faeces in 96 h. N-Hydroxybenzoylnorecgonine and N-hydroxynorecgonine methyl ester were the major urinary metabolites. N-hydroxynorcocaine was not metabolized to norcocaine in vitro by liver microsomes. Doses of greater than 7.5 mg/kg i.v. resulted in death of rats by cardiorespiratory arrest. 4. Cocaine-N-oxide (50 mg/kg i.v.) yielded ecgonine-N-oxide methyl ester as its major metabolite; other minor metabolites were cocaine (0.5%), norcocaine (1%), benzoylecgonine, ecgonine, ecgonine-N-oxide, along with minor amounts of unmetabolized compound. Lethality of cocaine-N-oxide (100 mg/kg i.v.) was possibly due to metabolism to norcocaine and cocaine.     

BU74, a complex oripavine derivative with potent kappa opioid receptor agonism and delayed opioid antagonism

In the search for opioid agonists with delayed antagonist actions as potential treatments for substance abuse, the bridged morphinan BU74 (17-cyclopropylmethyl-3-hydroxy-[5beta,7beta,3',5']-pyrrolidino-2'[S]-phenyl-7alpha-methyl-6,14-endoetheno morphinan) (3f) was synthesized. In isolated tissue and [35S]GTPgammaS opioid receptor functional assays BU74 was shown to be a potent long-lasting kappa opioid receptor agonist, delta opioid receptor partial agonist and mu opioid receptor antagonist. In antinociceptive tests in the mouse, BU74 showed high efficacy and potent kappa opioid receptor agonism. When its agonist action had waned BU74 became an antagonist of kappa and mu opioid receptor agonists in the tail flick assay and of delta, kappa and mu opioid receptor agonists in the acetic acid writhing assay. The slow onset, long-duration kappa opioid receptor agonist effects of BU74 suggests that it could be a lead compound for the discovery of a treatment for cocaine abuse.     

Emodin, a naturally occurring anthraquinone derivative, suppresses IgE-mediated anaphylactic reaction and mast cell activation

The high-affinity receptor for IgE (Fc?RI)-mediated activation of mast cells plays an important role in allergic diseases such as asthma, allergic rhinitis and atopic dermatitis. Emodin, a naturally occurring anthraquinone derivative in oriental herbal medicines, has several beneficial pharmacologic effects, such as anti-cancer and anti-diabetic activities. However, the anti-allergic effect of emodin has not yet been investigated. To assess the anti-allergic activity of emodin, in vivo passive anaphylaxis animal model and in vitro mouse bone marrow-derived mast cells were used to investigate the mechanism of its action on mast cells. Our results showed that emodin inhibited degranulation, generation of eicosanoids (prostaglandin D₂ and leukotriene C₄), and secretion of cytokines (TNF-α and IL-6) in a dose-dependent manner in IgE/Ag-stimulated mast cells. Biochemical analysis of the Fc?RI-mediated signaling pathways demonstrated that emodin inhibited the phosphorylation of Syk and multiple downstream signaling processes including mobilization of intracellular Ca²⁺ and activation of the mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and NF-κB pathways. When administered orally, emodin attenuated the mast cell-dependent passive anaphylactic reaction in IgE-sensitized mice. Thus, emodin inhibits mast cell activation and thereby the anaphylactic reaction through suppression of the receptor-proximal Syk-dependent signaling pathways. Therefore, emodin might provide a basis for development of a novel anti-allergic drug.     

Modulation of H2O2-induced mitogen-activated protein kinases activation and cell death in SK-N-MC cells by EUK134, a salen derivative

Alzheimer's disease is a neurodegenerative disorder that is characterized by the accumulation of senile plaques containing amyloid β (Aβ) and neurofibrillary tangles composed of hyperphosphorylated tau protein in the brain. Oxidative stress has been proposed to mediate Aβ-induced neurotoxicity. In that regard, we evaluated the ability of EUK134, a superoxide dismutase and catalase mimics, to protect human neuroblastoma cell line SK-N-MC against H(2)O(2) -induced oxidative stress. Our data clearly indicated that cell death induced by H(2)O(2) was reversed by EUK134. Likewise, lipid peroxidation, caspase-3 activation and intracellular reactive oxygen species formation all returned to control levels following pre-treatments with EUK134. Elevated phosphorylation of mitogen-activated protein kinases (MAPK) induced by H(2)O(2) in SK-N-MC cells was lowered by EUK134 in a dose-dependent manner. In addition, EUK134 decreased expression of pro-apoptotic genes p53 and Bax and enhanced expression of anti-apoptotic Bcl-2 gene. Taken together, these results suggest that EUK134 protects neuronal cells against H(2)O(2) toxicity by attenuating oxidative stress through inhibition of MAPK phosphorylation cascade.     

H1, a derivative of Tetrandrine, exerts anti-MDR activity by initiating intrinsic apoptosis pathway and inhibiting the activation of Erk1/2 and Akt1/2

Currently, multi-drug resistance (MDR) to anticancer drugs is a major obstacle to successful treatment of cancer. Looking for novel compounds with anti-MDR activity is an effectively way to overcome cancer drug resistance. Here, we found that H1, a novel derivate of Tetrandrine, displayed anti-MDR activity in vitro and in vivo. Average resistant factor of H1 is only 1.6. In KB and KBv200 cancer cells xenograft mice, H1 also displayed favorable anti-MDR activity. It could induce typical apoptosis as indicated by morphologic changes, DNA fragmentation in sensitive and resistant cancer cells. Further studies showed that H1 treatment resulted in the increase of ROS generation, elevation of the Bax/Bcl-2 ratio, loss of mitochondrial transmembrane potential (ΔΨ_m), release of cytochrome c and AIF from mitochondria into cytosol, and activation of caspase-9 and caspase-3, but had no effect on activation of caspase-8 and the expression of Fas/FasL. On the other hand, H1 also inhibited survival pathways such as the activation of Erk1/2 and Akt1/2. In conclusion, H1 exerts good anti-MDR activity in vitro and in vivo, its mechanisms may be associated with initiating intrinsic apoptosis pathway and inhibiting the activation of Erk1/2 and Akt1/2. These findings further support the potential of H1 to be used in clinical trial of MDR cancer treatment.     

Licochalcone A is a potent inhibitor of TEL-Jak2-mediated transformation through the specific inhibition of Stat3 activation

Aberrant activation of Jak/Stat signaling causes a number of hematopoietic disorders and oncogenesis, and therefore the effective inhibitors of the Jak/Stat signaling pathway may be therapeutically useful. TEL-Jak2 gene fusion, which has been identified in human leukemia, encodes a chimeric protein endowed with constitutive tyrosine kinase activity. Expression of TEL-Jak2 protects Ba/F3 cells from IL-3 withdrawal-induced apoptotic cell death and leads to IL-3-independent growth. However, its mechanisms remain to be only partially understood. Here, we first found that Licochalcone A, one of the flavonoids isolated from the root of Glycyrrhiza inflate, inhibited TEL-Jak2-mediated cell proliferation and survival in the absence of IL-3. Licochalcone A failed to inhibit the activity of TEL-Jak2, however, this induced apoptosis of TEL-Jak2-transformed cells with a much lower concentration in the absence of IL-3 than in the presence of IL-3. Interestingly, Licochalcone A significantly inhibited the phosphorylation and nuclear localization of Stat3, which is essential for TEL-Jak2-induced cell transformation. These data suggest that Licochalcone A is a specific inhibitor for Stat3 and would be employed for the treatment of various diseases caused by disorders of the Jak/Stat pathway.