Chemoresistance in Malignant Intracranial Tumors: Longer Survival with Negative MDR1 Expression

AIM

To analyze the Glutathione S-transferase (GST)-P, GST-M, cytochrome p450 (CYP)1-A1, CYP1-B1, and multidrug resistance (MDR)-1 expressions in malignant intracranial tumor (ICT)s, and to elicit their role on patient survival.

MATERIAL AND METHODS

GST-P, GST-M, CYP1-A1, CYP1-B1, and MDR-1 expressions were analyzed using immunostaining in 149 samples from 141 patients with preoperative ICT diagnosis. The case characteristics were reviewed, and the enzyme expressions were equated based on the age, gender, and tumor type. Then, 77 of 141 patients with malignant ICT and complete medical records postoperative were also investigated in detail for the relationship between the diagnosis, enzyme expression, and overall survival.

RESULTS

The average age was 49.44 years, with 83 (58.45%) male patients. Among the 77 malignant ICTs, 38 (49.3%) and 29 were glial tumors and metastases, respectively, with a 13.35-month overall survival. Patients with metastatic tumor have approximately threefold higher GSTP level than those with glial tumors. MDR-1 expression was approximately twofold higher in > 60-year-old patients. No statistically significant association was found between patients? smoking behaviors, alcohol consumption, and overall survival. Only MDR-1 expression was correlated with overall survival. Better overall survival was observed in patients with a negative MDR-1 expression than those with a positive one.

CONCLUSION

MDR-1 is an important indicator of survival in malignant intracranial tumor patients. Longer survival is associated with negative MDR-1 expression.

Synthesis and antioxidant properties of substituted 2-phenyl-1H-indoles

In this study, we report the design, synthesis and antioxidant activity of a series of substituted 2-(4-aminophenyl)-1H-indoles and 2-(methoxyphenyl)-1H-indoles. The new compounds are structurally related to the known indole-based antioxidant lead compound melatonin (MLT), and the antitumour 2-(4-aminophenyl)benzothiazole and 2-(3,4-dimethoxyphenyl)benzothiazole series. Efficient access to the target 2-phenylindoles was achieved via Fischer indole synthesis between substituted phenylhydrazines and acetophenones. 2-(4-Aminophenyl)indoles (such as the 6-fluoro analogue 3b) in particular showed potent antioxidant activity in the DPPH and superoxide radical scavenging assays (80% and 81% inhibition at 1mM concentration of 3b, respectively), at a level comparable with the reference standard MLT (98% and 75% at 1 mM).

Synthesis and comparison of antioxidant properties of indole-based melatonin analogue indole amino Acid derivatives

Increased levels of reactive oxygen species attributed to oxidative stress have been found to be responsible for the development of some vital diseases such as cardiovascular, neurodegenerative and autoimmune diseases. Recently, it was observed that melatonin is a highly important antioxidant, and melatonin analogues are under investigation to find out improved antioxidant activity. In this study, 14 melatonin -based analogue indole amino acid and N-protected amino acid derivatives were synthesized and elucidated spectrometrically. To investigate the antioxidant activity of the synthesized compounds and to compare with melatonin, butylhydroxytoluene and vitamin E, lipid peroxidation inhibition and 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activities were tested. The results indicated that the synthesized new indole amino acid derivatives have similar activities to melatonin in 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity assay but more potent activities in lipid peroxidation inhibition assay.

GST isoenzymes in matched normal and neoplastic breast tissue

The potential to metabolize endogenous and exogenous substances may influence breast cancer development and tumor growth. Therefore we investigated GST activity and the protein expression of glutathione S-transferases (GSTs) isoenzymes known to be involved in the metabolism of endogenous and exogenous carcinogens in breast cancer tissue to obtain new information on their possible role in tumor progression. The interindividual variation in the conjugation of 1-chloro-2,4-dinitrobenzene (CDNB) and of 1,2-epoxy-3-(p-nitrophenoxy) propane (EPNP) with glutathione (GSH) by cytosolic glutathione S-transferases (GSTs) were investigated in human breast matched normal and tumor samples. The GSTA, GSTM, GSTP and GSTT isoenzymes from the crude extracts of matched breast normal and tumor tissues in terms of their immunological properties using western blotting were compared. In most of the samples, the GST activities were higher in the tumor than in the normal cytosolic fractions against both CDNB and EPNP. In the western blotting analysis, it was proved statistically that in normal and tumor epithelial cells, there was difference between GST pi and theta isoenzymes expressions (p0.05). In normal epithelium there was a stronger GST theta expression than in invasive tumor tissues (p=0.013). However, the stronger GST pi expression was observed in tumor epithelium than in normal epithelium in human breast cancers (p=0.000). We found the GSTP protein level and GST activities were higher in the breast tumor than in the normal cytosolic fractions against both CDNB and EPNP, thus implicating a certain biological importance.

NovelN-acyl dehydroalanine derivatives as antioxidants: Studies on rat liver lipid peroxidation levels and DPPH free radical scavenging activity

Oxidative stress has been implicated in the development of many neurodegenerative diseases such as Parkinson and Alzhemier's disease and is also responsible for aging, artherosclerosis, rheumatoid arthritis and carcinogenesis. Olefins such as dehydroalanines have been shown to inactivate free radicals by forming stabilized free radical adducts. Among these molecules N-acyl dehydroalanines react with and scavenge oxygen and hydroxyl radicals. This study describes the synthesis, characterization and in vitro effects on rat liver lipid peroxidation levels, and DPPH free radical scavenging activities of some N-acyl dehydroalanine derivatives. Compounds c, f and j slightly scavenged the level of DPPH radical at 10(-3) M concentration by about 27, 46, and 56%, respectively while compounds a, d, e, f, g, h showed a strong inhibitory effect on lipid peroxidation at 10(-3)M and 10(-4)M concentrations and inhibition was in the range of 76-90%. The possible antioxidant mechanism of the compounds was discussed.

Screening and evaluation of antioxidant activity of some pyridazine derivatives

Antioxidants are compounds that can delay, inhibit, or prevent the oxidation of materials that can be oxidized by scavenging free radicals and help in diminishing oxidative stress. They belong to different chemical classes. Recently there are studies related to pyridazinone derivatives for their antioxidant activities. Since there are evidences implicates reactive oxygen species and nitric oxide as mediators of inflammation and/or tissue damage in inflammatory and arthritic disorders it was though that compounds that have both antioxidant and anti-inflammatory activities would have been essential for the inflammatory diseases. Based on these findings a series of 2H-pyridazine-3-one and 6-chloropyridazine analogues that have anti-inflammatory activity was tested in vitro on superoxide formation and effects on lipid peroxidation were determined against alpha-tocopherol. Most of the compounds have strong inhibitory effect on superoxide anion (between 84% - 99%) at 10(- 3) M concentration. In addition, these compounds showed similar activity to alpha-tocopherol at 10(- 3) M concentrations.

Synthesis and evaluation of novel N-H and N-substituted indole-2- and 3-carboxamide derivatives as antioxidants agents

We have previously reported on the synthesis of novel indole derivatives where some compounds showed significant antioxidant activity. Here, we report the synthesis of novel N-H and N-substituted indole-2- and 3-carboxamide derivatives and investigated their antioxidant role in order to identify structural characteristics responsible for activity. Although all compounds showed a strong inhibitory (95-100%) effect on superoxide anion (SOD) only compounds 4, 5 and 6 showed simliar potency for the inhibition of lipid peroxidation (81-94%) which revealed that compounds 4, 5 and 6 possessed highly potent antioxidant properties. Substitution in the 1-position of the indole ring caused the significant differences between the activity results regarding lipid peroxidation inhibition.

Synthesis of N-substituted indole-2-carboxamides and investigation of their biochemical responses against free radicals

The antioxidant role of novel N-substituted indole-2-carboxamides (I2CDs) was investigated for their inhibitory effects on superoxide anion (O2-) and lipid peroxidation (LP). Among the synthesized I2CDs, 3, 4, 6, 8 and 9 significantly inhibited O2*- with an inhibition range at 70-98%. Examination of substituent effects on activity showed that both the ortho- and para- positions of the benzamide residue needs to be dichlorinated in order to get a maximum inhibitory effect on superoxide anion. In general, halogenated derivatives were found more active then the non-halogenated ones. However, none of the I2CDs had a significant inhibitory effects on the level of lipid peroxidation; only compounds 7 and 10 moderately decreased LP levels by over 50% at 10(-3) M concentrations.

Investigation of the in vitro antioxidant behaviour of some 2-phenylindole derivatives: discussion on possible antioxidant mechanisms and comparison with melatonin

Oxidative stress has been implicated in the development of many neurodegenerative diseases and also responsible from aging and some cancer types. Indolic compounds are a broad family of substances present in microorganisms, plants and animals. They are mainly related to tryptophan metabolism, and present particular properties that depend on their respective chemical structures. Due to free radical scavenger and antioxidant properties of indolic derivatives such as indolinic nitroxides and melatonin, a series of 2-phenyl indole derivatives were prepared and their in vitro effects on rat liver lipid peroxidation levels, superoxide formation and DPPH stable radical scavenging activities were determined against melatonin, BHT and alpha-tocopherol. The compounds significantly inhibited (72-98%) lipid peroxidation at 10(-3) M. These values were similar to that observed with BHT (88%). Possible structure-activity relationships of the compounds were discussed.

A study on the antioxidant activities of some new benzazole derivatives

The in vitro antioxidant properties of some new benzazole derivatives (1-10) such as benzoxazoles, benzimidazoles, and benzothiazoles were determined by their effects on the rat liver microsomal NADPH-dependent lipid peroxidation (LP) level, the scavenging of superoxide anion and the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). Compounds 1, 2, 4 and 6, showed potent scavenging effect on superoxide radical at 10(-3) M. Compound 8, 5-nitro-2-(phenoxymethyl)benzimidazole, strongly inhibited lipid peroxidation at 10(-3) M concentration.

Synthesis and Antioxidant Activity of New Tetrahydro-Naphthalene-Indole Derivatives as Retinoid and Melatonin Analogs

A number of retinoid-related compounds represent classes of antioxidative and proapoptotic agents with promising potential in the treatment of neoplastic diseases. Indeed, the synthetic retinoid amide fenretinide [N-(4-hydroxyphenyl)retinamide] induces apoptosis of cancer cells and acts as a chemotherapeutic drug in cancer therapy. In the present work, and as a continuation of our studies on retinoid-type compounds, the synthesis of melatonin retinamide derivatives was studied as a novel series of melatonin retinoids, using the condensation reaction sequence involving tetrahydrotetramethylnaphthalene carboxylic acid and appropriate melatonin-type moieties. Despite of the weak DPPH inhibition activity pattern of the synthesized compounds, some of them showed a strong inhibition on lipid peroxidation (IVa-b, Va, and VIIa-c, 88, 96, 90, 94, 93, and 86%, respectively at 10(-4) M concentration) when melatonin (85% at 10(-4) M concentration) was used as a reference compound.

Comparison of NAT1, NAT2 and GSTT2-2 activities in normal and neoplastic human breast tissues

In this study, arylamine N-acetyltransferases, NATs (E.C.2.3.1.5) and glutathione-S-transferase-T2-2, GSTT2-2 (E.C.2.5.1.18) enzyme activities in the breast tumor and surrounding tumor-free tissues of 22 female breast cancer patients with infiltrating ductal carcinoma were measured. The possible impacts of grade of malignancy, chemotherapy treatment, estrogen receptor status and menopausal status on all enzyme activities were evaluated. The results showed that, both NAT2 and GSTT2-2 display significant differences between tumor and tumor-free breast tissues, while no difference was observed in NAT1. Grade of malignancy seems to be positively associated with NAT1 and negatively associated with GSTT2-2. Though, both NAT2 and GSTT2-2 have increased mean tumor activities, the grade of malignancy, chemotherapy status, menopausal status or estrogen receptor status are not correlated statistically.

Antioxidant properties of Ballota species growing in Turkey

In the present study, the antioxidant properties of ethanol extracts of 16 Ballota species belonging to the Lamiaceae family and growing in Turkey on superoxide anion formation and lipid peroxidation were investigated. All extracts inhibited superoxide anion formation but to different extents. The extracts of Ballota antalyense, Ballota macrodonta, Ballota glandulosissima, Ballota larendana, Ballota pseudodictamnus, Ballota nigra subsp. anatolica, Ballota saxatilis subsp. saxatilis, Ballota rotundifolia, and Ballota saxatilis subsp. brachyodonta exhibited remarkable anti-superoxide anion formation with IC(50) values from 0.50 to 0.87 mg/ml. The extracts of Ballota antalyense, Ballota macrodonta and Ballota glandulosissima have the lowest IC(50) values (0.50, 0.51 and 0.51 mg/ml, respectively) which were rather close to the well-known superoxide anion scavenger alpha-tocopherol (IC(50): 0.22 mg/ml). The extracts of Ballota inaequidens, Ballota glandulosissima, Ballota saxatilis subsp. saxatilis, Ballota macrodonta and Ballota antalyense inhibited lipid peroxidation with IC(50) values from 12 to 20 mg/ml. The extracts of Ballota inaequidens (IC(50): 12 mg/ml) and Ballota glandulosissima (IC(50): 15 mg/ml) exhibited the strongest inhibitory effects on lipid peroxidation compared with alpha-tocopherol (IC(50): 3 mg/ml). The results show that Ballota glandulosissima is the best antioxidant source among these 16 Ballota species.

Antioxidant Properties of Novel Benzimidazole Retinoids

Our approach was to examine the antioxidant activity of novel retinoid derivatives containing the benzimidazole moiety. Their in vitro effects on rat liver microasomal, NADPH-dependent lipid peroxidation levels and superoxide anion formation were determined. Lipid peroxidation in rat liver microsomes was reduced by some of the compounds in a dose-dependent manner.

Expression of CYP3A4 in human breast tumour and non-tumour tissues

Cytochrome P450 3A4 (CYP3A4), a member of multigene superfamily of enzymes, plays a major role in the activation of procarcinogens such as polycyclic hydrocarbon dihydrodiols, aflatoxins and heterocyclic amines as well as of several drugs including tamoxifen which is used in breast cancer therapy. Using immunohistochemistry, the cellular distribution and the level of expression of CYP3A4 was assessed in breast tumour and surrounding tumour free (control) breast tissue in 25 pairs of samples obtained from females with infiltrating ductal carcinoma. Cells staining with the CYP3A4 antibody showed only cytoplasmic positivity with varying intensities in 100% (25/25) of tumours and 68% (17/25) of normal breast tissues. Cytoplasmic staining was present in invasive ductal carcinoma cells but not in tumour stroma. CYP3A4 was detected in normal epithelium and myoepithelium. Only focal staining was noted in some of the non-epithelial cells (e.g. endothelial cells) in normal breast tissues. When CYP3A4 staining was assessed semiquantitatively the mean staining score values of CYP3A4 were found to be significantly higher in tumours compared to that of normal breast tissues. These results show that CYP3A4 protein is expressed in both tumour and normal breast tissue with an increased expression in tumours.

Immunohistochemical demonstration of the expression of CYP2E1 in human breast tumour and non-tumour tissues

Environmental chemicals are one of the risk factors in breast cancer genesis. Cytochrome P450 2E1 (CYP2E1), a member of multigene superfamily of enzymes, plays a major role in the activation of some of these chemicals such as tobacco-derived N-nitrosamines. Using immunohistochemistry, the cellular distribution and the level of expression of CYP2E1 was assessed in breast tumour and surrounding tumour free (control) breast tissue in 25 pairs of samples obtained from females with infiltrating ductal carcinoma. Cells staining with the CYP2E1 antibody showed only cytoplasmic positivity with varying intensities in 100% (25/25) of tumours and 96% (24/25) of normal breast tissues. Cytoplasmic staining was present in invasive ductal carcinoma cells but not in tumour stroma. CYP2E1 was detected in normal epithelial, myoepithelial and to a lesser degree in some of the non-epithelial cells (e.g. endothelial cells). No positive staining was detected in other non-epithelial cells such as fibroblasts in normal breast tissues. When CYP2E1 staining was assessed semiquantitatively the mean staining score values of CYP2E1 was found to be significantly higher in tumours compared to that of normal breast tissues. These results show that CYP2E1 protein is expressed in both tumour and normal breast tissue with an increased expression in breast tumours.

Synthesis and antioxidative properties of novel thiazolidinedione/imidazolidinedione compounds as retinoids

The general term "retinoids" refers to both naturally occurring as well as synthetic compounds which exhibit biological activity similar to vitamin A (retinol). Vitamin A and its two metabolites, retinaldehyde and retinoic acid, are fat-soluble unsaturated isoprenoids necessary for the growth, differentiation and maintenance of epithelial tissues. In this study, we have synthesized thiazolidinedione/imidazolidinedione compounds as retinoids. Their in vitro effects on rat liver microsomal NADPH-dependent lipid peroxidation (LP) levels and superoxide anion formation were determined.

The organochlorine pesticide residues and antioxidant enzyme activities in human breast tumors: is there any association?

The levels of some organochlorine pesticides (OCP)s (hexachlorobenzene, HCB, alpha-hexachlorocyclohexane, alpha-HCH, beta-HCH, gamma-HCH, heptachlorepoxide, HE, bis (4-chlorophenyl)-1,1-dichloroethene, p.p'DDE, bis (4-chlorophenyl)-1,1,1-trichloroethane, p.p' DDT and total DDT (E-DDT) and antioxidant enzyme activities namely Cu, Zn superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathione peroxidase (Se-GSH-Px), total glutathione peroxidase (T-GSH-Px), selenium independent glutathione peroxidase (GSH-Px II), glutathione reductase (GRd), level of reduced glutathione (GSH) and lipid peroxidation (LP), glutathione S-transferase (GST) activity toward several substrates including 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), ethacrynic acid (EAA), 1,2-epoxy-3-(p-nitrophenoxy)-propane (ENPP) were measured in tumor and surrounding tumor free tissues of 24 female breast cancer patients and was evaluated whether there exist any association between the levels of OCPs and antioxidants. The mean levels of GSH, alpha-BHC, gamma-BHC and HE, and activities of SOD, Se-GSH-Px, T-GSH-Px, GSH-Px II,GRd, GST CDNB, and GST DCNB were significantly higher in tumors than in controls. In tumors, significant correlations were noted between: SOD and y-BHC; Se-GSH-Px and gamma-BHC; T-GSH-Px and gamma-BHC; GSH-Px II and alpha-BHC, gamma-BHC; GSH and alpha-BHC, gamma-BHC, HE; GRd and alpha-BHC; CDNB GST and alpha-BHC, gamma-BHC. These results show that free-radical mediated oxidative stress is, at least partly, associated with some of these OCP residues in human breast tumors.

The expression of cytochrome P450 enzymes in human breast tumours and normal breast tissue

Environmental chemicals are one of the risk factors in breast cancer genesis. Cytochrome P450 (CYP) enzymes play a major role in the activation of these chemicals. Using highly specific and sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. the expression profile of all major xenobiotic metabolizing CYP forms was screened in breast tumour and surrounding tumour free (control) breast tissue in a series of 20 sample pairs obtained from females with infiltrating ductal carcinoma. The levels of CYPIAI mRNA were very low in both tumour and normal tissue. CYP1B1, CYP2B6, CYP2C, CYP2D6, CYP2E1, CYP4B1, and CYP11A1 expressions were positive in both tumours and control tissue. CYP2A6, CYP2A7, CYP2A13, CYP2F1, CYP3A4, CYP3A5. and CYP3A7 mRNAs were expressed neither in tumours nor in control tissue. These results show that several CYPs. responsible for the activation of a quite large number of procarcinogens and genotoxic estrogen metabolites. are expressed in breast tissue with a lack of qualitative differences in CYP expression at mRNA level between breast tumours and surrounding normal breast.

7-ethoxyresorufin O-deethylase (EROD) activity is not capable of reflecting the overall malignant potential of breast cancer tissue

7-Ethoxylesorufin O-deethylase (EROD) (mainly catalyzed by cytochrome P450 (CYP) 1A1 and used as a marker for CYP 1A1) activity was measured in the breast tumor and surrounding tumor free (normal) tissues of 37 female breast cancer patients with infiltrating ductal carcinoma. About 11% of the tumor and normal breast tissue samples lacked the enzyme activity. Large interindividual variations in the activities of EROD were found in both tumor and normal tissues ranging from 0 to 283 and 0 to 801 fmol/mg/min, respectively. However, no significant difference was noted between the mean EROD activities of tumor and normal breast tissues. This tendency did not change with the stage and grade of the malignancy and menopausal status. No significant correlation was observed between the EROD activity and stage or grade of malignancy (p > 0.05). Thus, it appears that EROD activity is not capable of reflecting the overall malignant potential of breast cancer tissue.

Xenobiotic metabolizing and antioxidant enzymes in normal and neoplastic human breast tissue

An investigation was made of ethoxyresorufin O-deethylase (EROD) activity, a cytochrome P450 (CYP) dependent enzyme mainly catalyzed by CYP1A1, glutathione S-transferase (GST) activity toward the substrates 1-chloro-2,4- dinitrobenzene (CDNB) and ethacrynic acid (EAA), reduced glutathione (GSH) levels, and antioxidant enzyme (AOE) activity namely catalase (CAT) and selenium- dependent glutathione peroxidase (Se-GPx) in tumor and surrounding tumor-free (normal) tissues in female breast cancer patients. Wide interindividual variations were found in the enzyme activities in both tumor and normal breast tissues. No significant differences were noted between mean EROD and CAT activities in tumor and normal breast tissues. The mean activities of CDNB GST, EAA GST and Se-GPx and GSH levels in tumor tissue were significantly higher than those in normal breast tissue. These results show that CYP, GST and AOE behave differentially in breast tumors.

Glutathione and lipid peroxidation levels in human breast tumors

The levels of reduced glutathione (GSH) and lipid peroxidation (LP) of breast tumor and surrounding tumor free (normal) tissues of 39 breast cancer female patients with infiltrating ductal carcinoma and the relationship between these two parameters were investigated. Large interindividual variations in the levels of GSH and LP were found in both tumor and normal tissues. The mean GSH levels of tumors were significantly higher than those of normal tissues. This tendency did not change with the stage and grade (excluding grade 1) of the malignancy, menopausal status and chemotherapy treatment. No correlation was found between GSH level and stage or grade of malignancy (p > 0.05). However, although more than half of the tumor samples (23/39, 59%) had higher LP levels than their corresponding normal tissues, no significant difference was noted between the mean LP levels of tumor and normal tissues. This tendency did not change with the stage and grade of the malignancy, and menopausal status and chemotherapy treatment. No relationship was observed between the LP level and stage or grade of malignancy (p > 0.05). Overall, no association existed between the levels of GSH and LP in tumors (p > 0.05). These results reveal that the GSH, but not LP, could be a marker of breast malignancy and that the increase in GSH level is not sufficient to lower the LP level in human breast tumors.

Neuronal overexpression of heme oxygenase-1 correlates with an attenuated exploratory behavior and causes an increase in neuronal NADPH diaphorase staining

Heme oxygenase isozymes, HO-1 (also known as hsp32) and HO-2, are the source for the formation of the putative messenger molecule carbon monoxide (CO), reactive iron, and the in vitro antioxidant bilirubin. We have developed and characterized transgenic (Tg) mice that overexpress the stress protein in neurons in various brain regions. The Tg mice were generated by the use of rat HO-1 cDNA under the control of the neuron-specific enolase promoter. Except for a tendency to have an enlarged spleen, Tg mice did not show gross anatomical changes. Increase in HO-1 mRNA, which was demonstrated by northern blot analysis and in situ hybridization, was accompanied by an increase in neuronal HO-1 protein expression, shown by immunohistochemistry and western blotting, and an increase in HO activity. Expression of the transgene correlated with an attenuation of exploratory behavior and increased circling activity and coincided with enhanced neuronal NADPH diaphorase staining. Those changes were not accompanied by an increase in DNA damage or significant change in whole-brain NO synthase activity. The HO-1 Tg mice potentially represent a good model to examine the function of CO as a neuromodulator, iron as a gene regulator, and bile pigments as in vivo antioxidants.

Gender dependent effects of cigarette smoke on hepatic and pulmonary xenobiotic metabolizing enzymes in rats

The adult male and female rats were exposed to cigarette smoke (CS) 5 times a day, with 1 h intervals, for 3 days in a chamber where smoke and fresh air lead alternatively and were killed 16 h after the last treatments and hepatic and pulmonary monooxygenase (MO) activities (aniline-4-hydroxylase, AH; aminopyrine-N-demethylase, AMND; 7-ethoxyresorufin-O-deethylase, EROD; p-nitroanisole-O-demethylase, p-NAOD), lipid peroxidation (LP) and reduced glutathione (GSH) levels and glutathione-S-transferases (GSTs) activities toward several substrates (1-chloro-2,4-dinitrobenzene, CDNB; 1,2-dichloro-4-nitrobenzene, DCNB; ethacrynic acid, EAA; 1,2-epoxy-3-(p-nitrophenoxy)-propane, ENPP) were determined. CS significantly increased hepatic AMND, EROD and p-NAOD activities whereas it unaltered AH activity in both genders as compared with controls. In the lung, EROD and p-NAOD activities were also significantly increased by CS in both genders. Pulmonary AH activity, however, significantly increased in males but remained unchanged in females. Pulmonary AMND activity significantly increased in females but remained unaltered in males. A significant decrease was noted in the LP level of males, while that of females was unaltered by CS in the liver. Pulmonary GSH and LP, and hepatic GSH levels were significantly increased by CS in both genders. In males, GST activities toward CDNB and DCNB did not alter, whereas GST activities toward EAA and ENPP significantly increased and decreased, respectively, in the liver. In females, CS significantly increased hepatic GST activity toward DCNB but it was ineffective on the other hepatic GST activities. All pulmonary GST activities of males were significantly depressed by CS. In females, however, CS significantly increased pulmonary GST activities toward CDNB and DCNB but was ineffective on GST activities toward EAA and ENPP. These results suggest that gender related differences exist in the modulations of hepatic GST, and pulmonary MO and GST activities but not in those of hepatic MO activities, by CS in rats.

Allosteric modulation of Torpedo nicotinic acetylcholine receptor ion channel activity by noncompetitive agonists

Similar to other neuroreceptors of the vertebrate central nervous system, the nicotinic acetylcholine receptor (nAChR) is subject to modulatory control by allosterically acting ligands. Of particular interest in this regard are allosteric ligands that enhance the sensitivity of the receptor to its natural agonist acetylcholine (ACh), as such ligands could be useful as drugs in diseases associated with impaired nicotinic neurotransmission. Here we discuss the action of a novel class of nAChR ligands which act as allosterically potentiating ligands (APL) on the nicotinic responses induced by ACh and competitive agonists. In addition, APLs also act as noncompetitive agonists of very low efficacy, and as direct blockers of ACh-activated channels. These actions are observed with nAChRs from brain, muscle and electric tissue, and they depend on the structure of the APL and the concentration range applied. We focus here on Torpedo nAChR because (i) the unusual pharmacology of these ligands was first discovered with this system, and (ii) large quantities of this receptor are readily available for biochemical studies.

Differential responses of hepatic monooxygenases and glutathione S-transferases of mice to a combination of cadmium and nickel

The acute combined effects of cadmium (Cd) and nickel (Ni) on hepatic monooxygenase activities (ethylmorphine N-demethylase, EMND; aminopyrine N-demethylase, AMND; aniline 4-hydroxylase, AH), cytochrome P-450, cytochrome b5, microsomal heme and reduced glutathione (GSH) levels and glutathione S-transferase (GST) activities toward several substrates (1-chloro-2,4-dinitrobenzene, CDNB; 1,2-dichloro-4-nitrobenzene, DCNB; ethacrynic acid, EAA; 1,2-epoxy-3-(p-nitrophenoxy)-propane, ENPP) were determined and compared with those of Cd or Ni alone in mice. Male adult mice (25-30 g) were administered either a single dose of Cd (3.58 mg CdCl2.H2O/kg, i.p.) 48 hr prior to killing or a single dose of Ni (59.5 mg NiCl2.H2O/kg, s.c.) 16 hr prior to killing. For the combined treatment, the animals received the single dose of Ni 32 hr after the single dose of Cd and were then killed 16 hr later. Cd treatment alone significantly decreased EMND, AMND, and AH activities and cytochrome P-450 and heme levels as compared with controls. Cytochrome b5 level was not altered by Cd treatment. Cd also inhibited GSH level and the GST activities toward CDNB, EAA and ENPP significantly. No significant change was observed in the GST activity for DCNB by Cd. Ni treatment alone, however, decreased the monooxygenase and GST activities studied, and cytochrome P-450, cytochrome b5, heme and GSH levels significantly. Combined treatment significantly depressed the monooxygenase activities and cytochromes and heme levels. GSH level was not significantly altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential combined effect of cadmium and nickel on hepatic and renal glutathione S-transferases of the guinea pig

When male guinea pigs were given a single dose of Cd (2.0 mg Cd2+/kg, ip) 72 hr prior to sacrifice, the hepatic reduced glutathione (GSH) level did not change although glutathione S-transferase (GST) activities toward the substrates 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), ethacrynic acid (EAA), and 1,2-epoxy-3-(p-nitrophenoxy) propane (ENPP) increased significantly as compared to controls. Cd did not change the renal GSH level and GST activities toward CDNB and EAA. However, significant increase was observed in the GST activity for DCNB whereas GST activity for ENPP was significantly inhibited by Cd. When the animals were given a single dose of Ni (14.8 mg Ni2+/kg, sc) 16 hr prior to sacrifice, significant increases were observed in hepatic GSH level and GST activities toward CDNB, DCNB, EAA and ENPP. Ni, however, depressed the renal GSH level and GST activities toward CDNB, DCNB and ENPP significantly. The renal GST activity toward EAA remained unaltered. For the combined treatment, guinea pigs received the single dose of Ni 56 hr after the single dose of Cd and then they were killed 16 hr later. In these animals, no significant alteration was observed in the hepatic GSH level. The augmentation of elevation was observed in hepatic GST activities toward CDNB and DCNB. Combined metal treatment did not potentiate the elevation of hepatic GST activities toward EAA and ENPP to any greater degree. The depression of renal GSH level was significantly ameliorated by the combined treatment. Combination treatment potentiated the depression of renal GST activity for ENPP but not for CDNB.(ABSTRACT TRUNCATED AT 250 WORDS)

The responses of hepatic monooxygenases of guinea pig to cadmium and nickel

When Cd (3.58 mg CdCl2.H2O/kg, ip) was administered to male guinea pigs 72 h prior to sacrifice, the metal significantly inhibited the aniline 4-hydroxylase (AH) (16%), ethylmorphone N-demethylase (EMND) (26%), and aminopyrine N-demethylase (AMND) (18%) activities and cytochrome P-450 (12%) and cytochrome b5 (10%) levels. Cd did not alter the hepatic microsomal heme level. Cd, however, significantly increased the hepatic microsomal p-nitroanisole O-demethylase (p-NAOD) (53%) activity. When Ni (59.5 mg NiCl2 x 6H2O/kg, sc) was administered to the guinea pigs 16 h prior to sacrifice, the metal significantly depressed AH (49%), p-NAOD (66%), EMND (47%), and AMND (37%) activities, and cytochrome P-450 (15%), cytochrome b5 (24%), and microsomal heme (28%) levels. For the combined treatment, animals received the single dose of Ni 56 h after the single dose of Cd and then were killed 16 h later. In these animals, significant inhibitions were noted in AH (51%), EMND (47%), and AMND (30%) activities, and cytochrome P-450 (15%), cytochrome b5 (26%), and microsomal heme (30%) compared to those of controls. In the case of p-NAOD activity, the influence was in favor of Ni, i.e., the inhibition was about 61% by the combined treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Physostigmine and neuromuscular transmission

Single channel studies carried out in cultured rat myoballs and cultured hippocampal neurons, and ion flux studies performed on Torpedo electrocyte membrane vesicles, showed that physostigmine (Phy), a well-established acetylcholinesterase inhibitor, interacts directly with nicotinic acetylcholine receptors (nAChR). Low concentrations (0.1 microM) of Phy activate the receptor integral channel, whereas higher concentrations blocked the channel in its opened state. In contrast to channel activation by acetylcholine (ACh) and classical cholinergic agonists, however, Phy was capable of activating the nAChR channel even when the ACh binding sites were blocked by competitive antagonists, such as alpha-neurotoxins and d-tubocurarine, or when the nAChR was desensitized by preincubation with high concentrations of ACh. The binding site at which Phy binds and activates the nAChR was mapped. It was located within the N-terminal extracellular region of the alpha-polypeptide, in close proximity to the binding site of the natural transmitter. These data identify a novel binding site at nAChRs from many species and tissues that may be involved in receptor regulatory processes.

Combined effects of cadmium and nickel on hepatic glutathione S-transferases in rats

1. The acute combined effects of cadmium (Cd) and nickel (Ni) on rat hepatic glutathione S-transferase (GST) activities toward the substrates 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB) and ethacrynic acid (EAA) were determined and compared to those of Cd or Ni alone. 2. Male adult rats (225-275 g) were administered either a single dose of Cd (3.58 mg CdCl2.H2O/kg, i.p.) 72 hr prior to sacrifice or a single dose of Ni (59.5 mg NiCl2.6H2O/kg, s.c.) 16 hr prior to sacrifice. For the combined treatment, animals received the single dose of Ni 56 hr after the single dose of Cd and they were killed 16 hr later. 3. Cd treatment alone did not produce any changes in the hepatic GST activities toward the substrates studied. 4. Ni treatment alone, however, significantly increased hepatic GST activity toward EAA whereas it was ineffective on GST activities for CDNB and DCNB. 5. Combined treatment of metals did not alter hepatic GST activities toward the substrates CDNB and DCNB. Hepatic GST activity for EAA, however, was significantly increased by the combined treatment. Nevertheless, the combined treatment did not augment the increase in GST activity for EAA noted by Ni treatment alone.

Biochemical characterization of a novel channel-activating site on nicotinic acetylcholine receptors

We have studied the interaction of the reversible acetylcholine esterase inhibitor (-)physostigmine and several structurally related compounds with the nicotinic acetylcholine receptor (nAChR) from Torpedo marmorata electric tissue by means of ligand-induced ion flux into nAChR-rich membrane vesicles, direct binding studies and photoaffinity labeling. (-)Physostigmine acts as a channel-activating ligand at low concentrations and as a direct channel blocker at elevated concentrations. Channel activation is not inhibited by desensitizing concentrations of ACh or ACh-competitive ligands (including alpha-bungarotoxin and D-tubocurarine) but is inhibited by antibody FK1 and several other compounds. From photoaffinity labeling using tritiated physostigmine and mapping of the epitope for the Phy-competitive antibody FK1, the binding site for physostigmine is located within the alpha-subunit of the Torpedo nAChR and is distinct from the acetylcholine binding site. Our data suggest a second pathway of nAChR channel activation that may function physiologically as an allosteric control of receptor activity.

Responses of hepatic xenobiotic metabolizing enzymes of mouse, rat and guinea-pig to nickel

The effects of nickel (Ni) on hepatic monooxygenase activities (aniline 4-hydroxylase, AH; ethylmorphine N-demethylase, EMND; aminopyrine N-demethylase, AMND), cytochrome P-450, cytochrome b5, microsomal haem and reduced glutathione (GSH) levels, and glutathione S-transferase (GST) activities toward several substrates (1, chloro-2-4-dinitrobenzene, CDNB; 1,2 dichloro-4-nitrobenzene, DCNB; ethacrynic acid, EAA) in mice, rats and guinea-pigs were studied. Ni (59.50 mg NiCl2.6H2O/kg, subcutaneously) was administered to the animals 16 hr prior to sacrifice. Ni significantly inhibited AH, EMND, AMND activities, and decreased cytochrome P-450, cytochrome b5 (except in the livers of rats), and microsomal haem levels in the livers of all the animal species examined. However, the depressions were more profound in livers of mice than in those of the other two species. The hepatic GSH level was significantly inhibited in mice whereas no alteration was observed in rats. In guinea-pigs, the hepatic GSH level was significantly increased by Ni. The hepatic GST activity toward the substrate CDNB was significantly depressed in mice, unaltered in rats and significantly increased in guinea-pigs by Ni. The hepatic GST activity toward DCNB was significantly inhibited in mice whereas no significant alteration was observed in rats. In guinea-pigs, Ni caused significant increase in hepatic GST activity for DCNB. However, hepatic GST activity toward EAA was significantly inhibited in mice whereas significantly increased in rats and guinea-pigs. These results seem to indicate that i) there exists quantitative, but not qualitative, differences among the hepatic monooxygenases of rodents in response to Ni, mice being more sensitive than rats and guinea-pigs, ii) the influence of Ni on hepatic GSH level varies depending on the animal species and iii) the hepatic GSTs of rodents are differentially regulated by Ni.

Combined effect of cadmium and nickel on rat hepatic monooxygenases: possible stimulation of certain cytochrome P-450 isozymes

When male rats were given either a single dose of cadmium (3.58 mg CdCl2.6H2O/kg, i.p.) 72 h prior to sacrifice or a single dose of nickel (59.5 mg NiCl2.6H2O/kg, s.c.) 16 h prior to sacrifice, the activities of ethylmorphine N-demethylase, aminopyrine N-demethylase and aniline 4-hydroxylase, and the levels of cytochrome P-450 and microsomal heme were significantly decreased. Cadmium decreased the cytochrome b5 level significantly, whereas it did not alter the NADPH-cytochrome c reductase activity significantly. In contrast, Ni did not alter the cytochrome b5 level significantly but decreased the NADPH-cytochrome c reductase activity significantly. For the combined treatment, animals received the single dose of nickel 56 h after the single dose of cadmium and then they were killed 16 h later. In these animals ethylmorphine N-demethylase, aminopyrine N-demethylase and NADPH-cytochrome c reductase activities and cytochromes P-450 and b5 levels increased significantly as compared to those of controls, whereas aniline 4-hydroxylase activity and microsomal heme level remained unaltered. In concordance with the increase in the enzyme activities, certain P-450 protein bands were observed to be elevated when studied on SDS-polyacrylamide gel electrophoresis. Furthermore, when the monooxygenase activities and SDS-polyacrylamide gel electrophoresis profiles of combined metal-treated animals were compared with those of the animals treated with classic inducers such as phenobarbital (75 mg/kg i.p., 72, 48 and 24 h prior to sacrifice) and 3-methylcholanthrene (20 mg/kg i.p., 72, 48 and 24 h prior to sacrifice), the combination of metals seemed to have tendency to stimulate certain phenobarbital and 3-methylcholanthrene inducible cytochrome P-450 isozymes.