Antioxidant capacity and protein oxidation in cerebrospinal fluid of amyotrophic lateral sclerosis.

BACKGROUND: The causes of Amyotrophic Lateral Sclerosis (ALS) are unknown. A bulk of evidence supports the hypothesis that oxidative stress and mitochondrial dysfunction can be implicated in ALS pathogenesis. METHODS =: We assessed, in cerebrospinal fluid (CSF) and in plasma of 49 ALS patients and 8 controls, the amount of oxidized proteins (AOPP, advanced oxidation protein products), the total antioxidant capacity (FRA, the ferric reducing ability), and, in CSF, two oxidation products, the 4-hydroxynonenal and the sum of nitrites plus nitrates. RESULTS: The FRA was decreased (p = 0.003) in CSF, and AOPP were increased in both CSF (p = 0.0039) and plasma (p = 0.001) of ALS patients. The content of AOPP was differently represented in CSF of ALS clinical subsets, resulting in increase in the common and pseudopolyneuropathic forms (p < 0.001) and nearly undetectable in the bulbar form, as in controls. The sum of nitrites plus nitrates and 4-hydroxynonenal were unchanged in ALS patients compared with controls. CONCLUSION: Our results, while confirming the occurrence of oxidative stress in ALS, indicate how its effects can be stratified and therefore implicated differently in the pathogenesis of different clinical forms of ALS.

Loss of lipid peroxidation as a histochemical marker for preneoplastic hepatocellular foci of rats.

Since it is known that tumor cell membranes have lost the capacity to undergo lipid peroxidation, it seemed of interest to investigate whether the loss of susceptibility to lipid peroxidation represents a tumoral marker appearing in preneoplastic cells together with the other known tumoral markers. A histochemical technique was developed to detect lipid peroxidation in individual cells of liver sections exposed to effective prooxidants. The technique was based on the detection of protein-bound aldehydes (alkenals) with the use of the Schiff's reagent. The latter reagent can also detect carbonyl function present in acyl residues of peroxidized phospholipids of cellular membranes. Liver preneoplastic foci were obtained in rats by the i.p. administration of diethylnitrosamine and of 2-acetylaminofluorene in the diet. Frozen sections of the liver, incubated in the presence of reduced nicotinamide adenine dinucleotide phosphate:iron revealed the presence of areas in which lipid peroxidation had not been induced (Schiff-negative areas). These areas corresponded strictly, in serial sections, to areas that were strongly positive to gamma-glutamyltranspeptidase.

Synergistic antiproliferative activity of suramin and alpha 2A-interferon against human colorectal adenocarcinoma cell lines: in vitro studies.

Suramin, a polysulphonated naphthylurea proven to be an effective anticancer agent against selected tumours, and alpha 2A-interferon (alpha 2A-IFN) were investigated for their combined effects on HCT-8, HCT-15, CL-D, SW-480 and SW-620 human colorectal adenocarcinoma cell lines. All lines were sensitive to clinically achievable concentrations of suramin in a dose-dependent manner, while alpha 2A-IFN alone induced only a modest reduction of cell growth. Concomitant treatment with suramin and alpha 2A-IFN resulted in a synergistic inhibition of cell viability in each cell line at all doses tested. However, when suramin and alpha 2A-IFN were administered sequentially, inhibition of cell viability was clearly dependent on the timing of treatment schedule, with maximum effect obtained when alpha 2A-IFN was administered prior to suramin. In contrast, pretreatment with suramin was markedly inferior to the former one. In conclusion, suramin and alpha 2A-IFN exert a synergistic effect on human colorectal cell proliferation in vitro at clinically achievable concentrations. This observation may have clinical relevance although the mechanisms of interaction remain to be elucidated.

Azidothymidine in combination with 5-fluorouracil in human colorectal cell lines: in vitro synergistic cytotoxicity and DNA-induced strand-breaks.

The in vitro cytotoxicity of the combination of azidothymidine (AZT) and 5-fluorouracil (5-FU) against the human colorectal cancer cells SW-480, SW-620 and COLO-320DM was evaluated. The cytotoxic effects of 5-FU and AZT were determined by the assay using 2,3-bis(2-methoxy-4-nitro-5-sulfophenil)-2H-tetrazolium-5-carbo xanilide inner salt (XXT), while drug-induced DNA strand-breaks were measured using a fluorometric analysis of DNA unwinding. After an exposure of 72 h, 5-FU and AZT induced a dose-dependent cytotoxicity against each cell line. The addition of 3, 10 and 30 microM AZT to various concentrations of 5-FU, as well as the addition of 0.5, 1 and 3 microns 5-FU to various concentrations of AZT, resulted in an enhanced cytotoxic effect. Isobologram analysis and the combination index (CI) method demonstrated that the interaction between 5-FU and AZT was clearly synergistic in each cell line, except for the 30% level of effect in SW-620, where borderline synergism was observed. The evaluation of DNA strand-breaks after an exposure of 16 h to 5-FU, AZT or 5-FU + AZT demonstrated that the 5-FU + AZT combination produced the greatest DNA damage, and that this interaction was synergistic in each cell line. In conclusion, our study supports the evidence that the potential antitumour activity of AZT can be modulated by combining it with agents which inhibit thymidylate (dTMP) formation, such as 5-FU, and that the increased cytotoxicity is related to enhanced DNA damage. These findings should encourage further experimental and clinical studies of the potential use of AZT in combination with inhibitors of de novo dTMP synthesis.

Localization of a glutathione-dependent dehydroascorbate reductase within the central nervous system of the rat.

In this study, we describe for the first time the occurrence, within the central nervous system of the rat, of a dehydroascorbate reductase analogous to the one we recently described in the liver. Dehydroascorbate reductase plays a pivotal role in regenerating ascorbic acid from its oxidation product, dehydroascorbate. In a first set of experiments, we showed that a dehydroascorbate reductase activity is present in brain cytosol; immunoblotting analysis confirmed the presence of an immunoreactive cytosolic protein in selected brain areas. Immunotitration showed that approximately 65% of dehydroascorbate reductase activity of brain cytosol which was recovered in the ammonium sulphate fraction can be attributed to this enzyme. Using immunohistochemistry, we found that a variety of brain areas expresses the enzyme. Immunoreactivity was confined to the gray matter. Amongst the several brain regions, the cerebellum appears to be the most densely stained. The enzyme was also abundant in the hippocampus and the olfactory cortex. The lesion of norepinephrine terminals following systemic administration of DSP-4 markedly decreased immunoreactivity in the cerebellum. Apart from the possible co-localization of the enzyme with norepinephrine, the relative content of dehydroascorbate reductase in different brain regions might be crucial in conditioning regional sensitivity to free radical-induced brain damage. Given the scarcity of protective mechanisms demonstrated in the brain, the discovery of a new enzyme with antioxidant properties might represent a starting-point to increase our knowledge about the antioxidant mechanisms operating in several central nervous system disorders.

Defective natural killer cell cytotoxic activity in feline immunodeficiency virus-infected cats.

Flow cytometry has been employed to study NK cell cytotoxic activity in cats infected with feline immunodeficiency virus. The results show that animals infected for 12 months or more have decreased levels of NK cell cytotoxic activity in their blood. The impairment could not be overcome by in vitro treatment of effector cells with interleukin 2. Additional results suggest that the NK cells of infected cats are defective, in that they are still able to bind to target cells but have a reduced ability to kill them.

Evaluation of resistance index of several anticancer agents on parental and resistant P-388 cell lines.

Multidrug resistance is frequently detected in haematological malignancies and in acute leukaemias with a poor prognosis. In the last few years, several reports seem to suggest that the new anthracycline derivative idarubicin and the anthraquinone mitoxantrone have some advantages in the management of untreated or relapsed acute leukaemias compared with older anthracyclines. This could be due to a different interaction of these drugs with multidrug resistance. To evaluate this possibility, we compared the activity of doxorubicin (DOXO), epirubicin (EPI), idarubicin (IDA) and mitoxantrone (MITO) on a murine, multidrug resistant, leukaemic cell line (P-388/Dx) cultured in vitro. ID50 of IDA and MITO was in the ng range whereas that of DOXO and EPI was in the microgram(s) range. Moreover, IDA has a resistance index of 50 whereas DOXO has one of 250. Verapamil is able to almost completely abolish the resistance to IDA. Efflux experiments confirm that verapamil increases IDA intracellular concentration. IDA and MITO appear to be less involved in multidrug resistance than older anthracyclines.

DNA repair systems in early and persistent hepatocyte nodules in the rat.

The repair of three DNA lesions, namely O6-methylguanine, 7-methylguanine, and 3-methyladenine, was investigated within early and persistent hepatocyte nodules generated in Fischer 344 rats by a modified Solt-Farber procedure (diethylnitrosamine initiation followed by a 2-acetylaminofluorene/CCl4 cycle). The O6-methylguanine-DNA methyltransferase concentration within both hepatocyte nodule types was always higher than that found in age-matched controls (normal, initiated-only and promoted-only livers). As far as 3-methyladenine and 7-methylguanine-DNA glycosylases are concerned, the early hepatocyte nodules showed far higher activities for both enzymes than were found in the controls, whereas in the persistent ones they underwent a significant decrease. In conclusion hepatocyte nodules are endowed with a high DNA repair activity, which is partly adaptive, partly constitutive; along with others, such a defence mechanism could allow transformed cells to resist many cytotoxic drugs.

Chronic liver injury by thioacetamide and promotion of hepatic carcinogenesis.

To verify whether a mild, but prolonged liver injury by chemicals needing bioactivation causes both hepatic cirrhosis and the appearance of hepatocyte nodules and tumors (providing the liver has been exposed previously to initiating stimuli), diethylnitrosamine-initiated and uninitiated rats were administered thioacetamide at low dose (250 mg/l drinking water) for 6 months. Hepatocyte nodule incidence as well as changes in the drug-metabolizing system were followed at monthly intervals. In the uninitiated rats a micronodular liver cirrhosis slowly developed upon thioacetamide chronic administration; a few hepatocyte focal lesions of small size were seen from the 3rd month onward. By contrast in the diethylnitrosamine-initiated thioacetamide-treated rats the liver was macronodular because of the appearance and growth of many hepatocyte nodules; some hepatomas were also seen. During thioacetamide administration both uninitiated and diethylnitrosamine-initiated rats underwent a progressive decrease of the cytochrome P-450 liver content as well as of the activity of aminopyrine N-demethylase, ethoxycoumarin O-deethylase and ethoxyresorufin O-deethylase. On the other hand, most components of the phase II of the drug-metabolizing system were markedly enhanced. In conclusion, chronic administration of thioacetamide at low doses provided strong promoting stimuli for previously initiated hepatocytes.

Detection of feline immunodeficiency virus p24 antigen and p24-specific antibodies by monoclonal antibody-based assays.

A panel of monoclonal antibodies (mAbs) detecting distinct B-cell epitopes on p24 core viral protein of feline immunodeficiency virus (FIV) were employed to develop immunoassays to measure p24 concentration in culture and serum samples, to localize p24 in FIV-infected cells and tissues, and to detect anti-p24 antibodies in cat sera. In its optimized configuration the p24 capture assay detected as little as 0.25 ng/ml of protein. The assay was found at least as sensitive as the reverse transcriptase activity assay in FIV-infected lymphocyte cultures and proved capable of detecting p24 antigen in acid pretreated sera from a high proportion of FIV-infected cats. The mAbs were also successfully used to detect the p24 antigen in permeated FIV-infected cells by flow cytometry and in tissue sections from FIV-infected cats by immunohistochemical staining. Anti-p24 antibodies in FIV-infected cat sera were assayed by a competitive capture ELISA which readily identified occasional false positive results provided by a standard ELISA using purified whole FIV-coated wells.

Reduced cardiotoxicity and increased cytotoxicity in a novel anthracycline analogue, 4'-amino-3'-hydroxy-doxorubicin.

The acute and chronic cardiotoxicity and cytotoxicity of the novel doxorubicin (DXR) derivative 4'-amino-3'-hydroxy-DXR were compared with those of 4'-deoxy-DXR and DXR. In the acute cardiotoxicity study, the ECG and hemodynamic changes recorded in anesthetized rats that had been treated i.v. with 10 mg/kg 4'-amino-3'-hydroxy-DXR or 8.6 mg/kg 4'-deoxy-DXR were significantly less severe than those caused by 13 mg/kg DXR. In the chronic cardiotoxicity study, rats received 3 weekly i.v. injections of 3 mg/kg DXR, 3 mg/kg 4'-amino-3'-hydroxy-DXR, or 2 mg/kg 4'-deoxy-DXR during the first 14 days of the study and were observed for an additional 35-day period. DXR induced severe cardiomyopathy that was characterized by ECG changes in vivo (S alpha T-segment widening and T-wave flattening) and by impairment of the contractile responses (Fmax, +/- dF/dtmax) to adrenaline of hearts isolated from treated animals. 4'-Deoxy-DXR caused a progressive enlargement of the S alpha T segment in vivo and a significant impairment of the -dF/dtmax value in vitro, which were less severe than those produced by DXR. The least cardiotoxic drug was 4'-amino-3'-hydroxy-DXR, which induced minor ECG changes without causing significant alterations in the contractile responses of isolated hearts to adrenaline. On the basis of the drug concentration required to inhibit 50% of the colony formation (IC50) of cell lines in vitro, 4'-amino-3'-hydroxy-DXR was less active than 4'-deoxy-DXR but at least twice as active as DXR against human cancer and murine transformed cell lines. These data indicate that 4'-amino-3'-hydroxy-DXR is significantly less cardiotoxic and more cytotoxic than DXR.

Role of the microsomal FAD-containing monooxygenase in the liver toxicity of thioacetamide S-oxide.

To evaluate the different contributions of either microsomal FAD-containing ( FADM ) or cytochrome P-450 dependent monooxygenases in the bioactivation and liver toxicity of thioacetamide-S-oxide ( TASO ) (a proximate metabolite of the liver toxin and carcinogen thioacetamide), this compound: (i) was given to rats pretreated with methimazole (a substrate and inhibitor of FADM ), SKF 525-A (an inhibitor of cytochrome P-450) and cobalt protoporphyrin IX (a synthetic porphyrin which induces a long-lasting depletion of the hepatic cytochrome P-450); and (ii) was added to liver microsomes performing oxidation of model FADM or cytochrome P-450 substrates. Whereas the prior administration of methimazole alleviated the TASO induced liver necrosis, SKF 525-A was almost ineffective. Also pretreatment with cobalt protoporphyrin IX prevented liver necrosis. However, this porphyrin derivative was found to depress both cytochrome P-450 dependent and the FADM dependent biotransformations. On the other hand, addition of TASO to liver microsomes in vitro induced changes in the kinetics of S-oxidation of thiobenzamide and of N-oxidation of dimethylaniline, whereas the O-deethylation of ethoxycoumarin was unchanged. The overall results show the necessity of TASO bioactivation by mixed-function monooxygenases for the toxic action to be apparent; at the same time, the findings suggest FADM as the system mainly involved in TASO metabolism.

Early biochemical liver changes following thiobenzamide poisoning.

Administration of thiobenzamide in a single dose (25 mg/100 g body wt by stomach tube) to male rats induced centrilobular necrosis, which became evident 10 h after the poisoning. In the meantime liver weight and water content underwent changes, glycogen was lost, triglycerides accumulated in the liver while decreasing in serum, [3H] leucine uptake in proteins was impaired and the activity of glucose-6-phosphatase and aminopyrine demethylase decreased. The activity of NADPH-cytochrome c reductase remained unchanged, whereas a reduction of the microsomal cytochrome P-450 occurred. The liver amount of reduced glutathione underwent no significant changes. Pretreatment of the animals with cobalt chloride or 20-methylcholanthrene decreased the liver damage caused by the drug. The in vitro addition of thiobenzamide to liver microsomes resulted in a spectral change. The appearance of conjugated dienes among microsomal lipids from drug-treated rats indicated for a lipoperoxidation taking place in vivo.

Methimazole-induced modulation of thiobenzamide bioactivation and toxicity.

The formation of thiobenzamide-S-oxide (TBSO) from thiobenzamide (TB) by rat liver microsomes was competitively inhibited by methimazole (MMI; 1-methyl-2-mercaptoimidazole), a known substrate and inhibitor of the microsomal FAD-containing monooxygenase. S-oxidation was also temporarily depressed in liver microsomes obtained from MMI-treated rats. When administered in vivo, MMI alleviated TB-induced liver necrosis in a dose-dependent manner; moreover, a significant decrease in the serum concentration of TBSO was observed. The protective effect of MMI against the necrogenic effect of TB could arise from competition of these two chemicals for the same bioactivating system, leading to a lower production of the liver damaging metabolite, TBSO.

The hepatotoxicity of thiobenzamide-S-oxide.

Administration of thiobenzamide (TB) (0.18 mmol/100 g b.w.) to rats caused the appearance in serum and urine of a compound identified as thiobenzamide-S-oxide. When synthesized and given by oral administration, this compound induced the early appearance of liver centrilobular necrosis, impairment of glucose-6-phosphatase and aminopyrine demethylase activities, and diminished cytochrome P-450 content. Liver necrosis was suppressed by the prior administration of 20-methylcholanthrene. It is concluded that TB-S-oxide is involved, possibly as a proximate precursor, in TB-induced liver damage.

Liver cell proliferation induced by single administration of thiobenzamide.

After administration of thiobenzamide (TB) (2.5 mg/100 g b.w.) by stomach tube to male rats, an increase of liver weight was evident within 2 days. It was associated with an increase of hepatic DNA, in the incorporation of [3H]thymidine into nuclei of both hepatocytes and bile duct cells and also in the mitotic index of both types of cells. Liver water content and morphology as well as serum GPT activity were unchanged. In conclusion, TB administration in a single dose below the necrotic threshold stimulates multiplication of liver cells without evidence of damage.

Biological effects of PEMF (pulsing electromagnetic field): an attempt to modify cell resistance to anticancer agents.

Pulsing Electromagnetic Field (PEMF) effects lead to a modification of the multidrug resistance (MDR) of cells in vitro and in vivo. The murine leukemic doxorubicin-resistant cell line, P388/Dx, subjected to PEMF irradiation in vitro, showed a significant difference in thymidine incorporation when the concentration of doxorubicin reached a level of 1 microgram/mL, which corresponds to the inhibition dose 50 (ID50). The human lymphoblastic leukemia vinblastine-resistant cell line, CEM/VLB100, also showed a significant modification under the same experimental conditions at the in vitro ID50 corresponding to a vinblastine concentration of 100 ng/mL. BDF1 mice transplanted with P388/Dx cells also had an increase in their life span when doxorubicin was injected intraperitoneally in fractionated doses, while being subjected to PEMF irradiation.

Dry weight, triglycerides content and glucose-6-phosphatase activity of hepatocytes separated by sedimentation.

1) Isolated rat-hepatocytes were subfractionated by isopycnic or velocity sedimentation, and dry mass, triglycerides content and Glucose-6-Phosphatase activity of different subpopulations were determined. 2) Distribution of the cell dry masses and dry mass per average cell were substantially similar in all the fractions separated by isopycnic sedimentation. Velocity sedimentation allowed a satisfactory separation of cells of different dry mass. 3) Triglycerides content and Glucose-6-Phosphatase activity of cells of the different fractions obtained by isopycnic sedimentation showed no statistically significant difference. Subpopulations fractionated by velocity sedimentation differed in both triglycerides content and Glucose-6-Phosphatase activity, which were substantially parallel to the cell dry mass.

Circadian rhythm of dry mass and weight-class-pattern of the rat hepatocytes--effects of light-dark and feeding regimens.

1. Dry weight has been determined of individual hepatocytes isolated from rats kept at natural or at reversed daily light-dark cycle, and from rats under time-restricted feeding. Behaviours of liver weight, mitotic activity and binuclearity frequency of the hepatocytes and serum corticosterone have been also investigated. 2. At natural light-dark cycle, liver weight, hepatocyte mitotic activity, and serum corticosterone were higher during the day than during the night. In accordance, dry weight and class number of the hepatocytes were both higher by day than by night. 3. By reversal of the light-dark cycle, circadian rhythms of liver weight, hepatocyte mitotic activity and serum corticosterone underwent a reversal. In accordance, circadian rhythm also reversed of both dry mass of the hepatocytes, which became heavier by night than by day, and pattern of the hepatocyte weight-classes, which became sharper, more discrete and more numerous by night, less defined and lower in number by day. 4. Feeding restriction to early morning or to late afternoon did not affect substantially the circadian rhythms of the parameters examined. 5. Binuclear cell frequency did never differ significantly at midnight with respect to midday, irrespectively to the experimental condition. 6. Regulation of the circadian rhythm of both weight-class pattern and dry mass of the hepatocytes appears to be mainly acted by the light-dark regimen likely via modulation of the plasma glucocorticoids (corticosterone) concentration, and increase/decrease of which causes a decrease/increase of the total solid content of hepatocytes, with redistribution of cells in the weight-classes. 7. Feeding rhythm and time elapsed from food intake mainly influence definition of the individual weight-classes and weight range of the hepatocytes.

A quantitative cytochemical study of isolated epithelial cells of the hamster cheek pouch.

1. Dissociation of the hamster cheek pouch epithelium by a method combining trypsin attack and EDTA exposure, yielded a mixture f highly viable isolated cells (basal, spinous, and granular cells). 2. Such heterogeneous cell population was reproducibly separated into 4 fractions by pycnic sedimentation: in order of increasing density, Fraction I and Fraction II predominantly contained cells of the basal layer (93% and 76%, respectively), Fraction III basal, spinous and granular cells in equivalent concentration, Fraction IV mainly granular cells (69%). Horny squamae sedimented at the bottom of the tube. 3. Individual cells of the whole population and those of the population fractions separated by density gradient, were analyzed and charcterized as regards morphology, viability, volume, dry mass, density and DNA synthesizing ability. 4. A positive correlation was found between morphology, dry mass and density of the cells, showing that differentiation occurs by increments in mass and density. The weights of the basal, spinous and granular cells were distributed within ranges well defined and scantily overlapping, and were positively correlated with cell differentiation. Also cell density increased with differentiation degree. On the contrary, volume distribution of the various types of cells showed differences of minor importance, indicating for an increase of solids concentration in the more differentiated cells. 5. DNA synthesis took place only in basal cells, the density of which was generally very low.