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PubMed1984

Benoxaprofen photosensitization of cell membrane disruption.

Benoxaprofen (BXP) is a nonsteroidal anti-inflammatory drug which causes cutaneous phototoxicity. Because the in vivo phototoxicity may involve photosensitized damage to mast cell membranes, the mechanism for photosensitized damage was studied in a single model system, the red blood cell. Oxygen-dependent and oxygen-independent mechanisms for membrane disruption were detected. Oxygen-dependent lysis was not quenched by superoxide dismutase and was quenched only at high sodium azide concentrations. A two-step mechanism is proposed involving initial photodecarboxylation of BXP to form a lipophilic photoproduct which subsequently photosensitizes membrane damage. Human serum albumin at 0.03% totally inhibited BXP-photosensitized lysis.

Anti-Inflammatory Agents↗

PubMed1990

Comparison of the intoxication pathways of tumor necrosis factor and diphtheria toxin.

The mechanism by which tumor necrosis factor alpha (TNF) initiates tumor cell destruction is unknown. Having established that a brief drop in extracellular pH enhances the killing activity of TNF, our next objective was to explore whether TNF-induced cell death is dependent on endosomal acidification. Diphtheria toxin (DTx), a well-characterized acid-dependent cytotoxin, served as an indicator of the effectiveness of each treatment condition. Studies with lysosomotropic agents demonstrated that the cytotoxic pathway of TNF can operate independently of low pH exposure in contrast to the lethal pathway of DTx. When NH4Cl-treated cells were exposed to TNF at low pH, the level of killing increased two- to threefold over that attained with cells maintained at neutral pH (either with or without NH4Cl). Furthermore, inhibition of metabolic processes by sodium azide in combination with 2-deoxyglucose severely reduced DTx killing but stimulated TNF killing. Despite these differences, TNF and DTx provoked extensive internucleosomal DNA cleavage in prelytic target cells. Inhibitor of nuclear poly(ADP-ribose) transferase also evoked similar levels of cellular resistance to both cytotoxins. Models for DTx- and TNF-induced cytolysis are discussed in view of these new discoveries.

Ammonium Chloride↗

PubMed1990

Transient inotropic effects of low extracellular sodium in perfused rat heart.

The inotropic effects of low concentrations of extracellular Na+ (35-110 mM) were studied using Langendorff-perfused rat hearts. Low Na+ induced an initial positive inotropic response proportional to the decrease of transsarcolemmal Na+ gradient. At 35 mM Na+, this effect was followed by a secondary fall in contractility and rise of resting force (RF) and then by a delayed positive inotropic effect and recovery of RF. The magnitude of these low Na(+)-induced transient changes was dependent on the extracellular Ca2+ concentration and was altered by amiloride (6 x 10(-4) and 2.5 x 10(-3) M), ouabain (5 x 10(-5) and 5 x 10(-4) M), ryanodine (2 x 10(-8), 1 x 10(-7) and 1 x 10(-6) M), and sodium azide (1 x 10(-3) and 5 x 10(-3) M) but not by verapamil (2 x 10(-8) and 1 x 10(-7) M) or vanadate (4 x 10(-6) M). The data indicate the initial positive inotropic response of the rat heart to low Na+ may be due to rapid loading of myocytes with Ca2+ through the Na(+)-Ca2+ exchange mechanism. The secondary depression of contractility and the rise of RF appear to be the consequence of the short-lived intracellular Ca2+ overload. Furthermore, the recovery of contractions and the delayed positive inotropic response may be the result of the intracellular redistribution of excessive Ca2+ into the sarcoplasmic reticulum with mitochondria and increased transsarcolemmal Ca2+ efflux apparently playing a more minor role.

Amiloride↗

PubMed1990

Possible roles of free radicals in alcoholic tissue damage.

Hepatic microsomes metabolize ethanol to a free radical metabolite which forms adducts with the spin trapping agents PBN (phenyl-N-t-butylnitrone) and DMPO (5,5-dimethyl-l-pyrroline N-oxide). This ethanol radical has been identified as the l-hydroxyethyl radical through the use of 13C-labelled ethanol. A role of the cytochrome P-450 enzymes in the generation of the l-hydroxyethyl radical was suggested by requirements for oxygen and NADPH, as well as inhibition in the presence of SKF 525-A and imidazole. In contrast, the ESR signal intensity of the l-hydroxyethyl radical was diminished when either catalase, or the iron chelating agent deferoxamine, was added to the microsomal incubations, and was increased by the addition of ADP-Fe. These observations suggest that the ethanol radicals may arise secondary to iron-catalyzed formation of hydroxyl radicals from hydrogen peroxide. This possibility was supported by enhanced rates of l-hydroxyethyl radical formation when microsomal catalase activity was inhibited by the addition of sodium azide, or by pretreatment of rats with aminotriazole. However, the reaction was relatively insensitive to scavengers of the hydroxyl radical. Thus, the mechanism of l-hydroxyethyl radical formation could involve two cytochrome P-450-dependent pathways: generation of hydrogen peroxide required for a Fenton reaction, as well as direct catalytic formation of the ethanol radical.

Animals↗

PubMed1991

The SOS-Chromo-spottest: evaluation of a short-term test for the determination of genotoxic compounds in contaminated environmental samples.

To evaluate the sensitivity of the SOS-Chromo-spottest towards genotoxic compounds 5 reference chemicals (4-nitroquinoline-1-oxide (4-NQO), methylmethansulfonate (MMS), 2,4,7-trinitro-9-fluorenone (TNF), sodium azide (SA) and daunomycin (DM) were tested by 3 different agar plate media (STA-plates: synthetic media containing Xgal, B-plates: synthetic media containing 1% lactose and bromocresolpurple, C-plates: 1% lactose bromocresolpurple media containing complex nutrients). Even 1 ng of 4-NQO showed genotoxic effects by using STA-plates. The threshold value for MMS was 80 nl, for TNF 160 ng and for DM 80 ng. Similarly the spottest with B-plates are positive results, but the sensitivity of this test procedure was 80 to 250 times lower than the STA-plate test. The C-plate test only reacted with high amounts of 4-NQO (1000 ng). Therefore, the SOS-chromo-spottest with STA-media described by Quillardet and Hofnung seems to be a sufficient procedure to detect genotoxic compounds in contaminated environmental samples directly without previous extraction procedures. The simpler B-plates can be used to examine the genotoxicity of certain compounds like industrial or household chemicals where the genotoxicants can be expected to be present in high doses.

4-Nitroquinoline-1-oxide↗

PubMed1990

Distribution and preservation of Schistosoma mansoni eggs in stools.

Thirty-eight stool samples were preserved with sodium azide, 5 mg g-1 of stool. Results show that after 12 weeks, all the samples with S. mansoni eggs remained positive with good egg morphology. Egg counts show an average decrease of about 20%. Given the logistic advantages provided by using a small quantity of dry preservative this method is acceptable for mass prevalence surveys where sensitivity is not critical. The distribution of eggs in the stool was studied in 10 samples. Results showed no significant differences between centre and surface of the stools.

Analysis of Variance↗

PubMed1989

Effects of DIDS on the chick retinal pigment epithelium. II. Mechanism of the light peak and other responses originating at the basal membrane.

4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) appears to block a Cl- conductance in the basal membrane of the chick retinal pigment epithelium (RPE) (Gallemore and Steinberg, 1989). The present paper describes the effect of DIDS, as well as effects of anion movement blockade with other pharmacological agents, on 3 responses that originate as depolarizations of the RPE basal membrane: the light peak of the DC electroretinogram, the response to sodium azide, and the response to a small transtissue hyperosmotic gradient. Intracellular and extracellular potentials, and measurements of subretinal [K+]o were obtained from an in vitro preparation of chick retina-RPE-choroid. Choroidal perfusion with each of 4 anion transport and Cl- channel blockers (DIDS, 4-acetamido-4'-isothiocyanostilbene, phenylanthranylic acid, and thiocyanate) suppressed the light peak. DIDS, the most potent agent, abolished the basal membrane light-peak depolarization. Choroidal perfusion with azide depolarized the basal membrane and decreased its apparent resistance, Rba, as in cat (Linsenmeier and Steinberg, 1987). The basal membrane depolarization, recorded extracellularly as an increase in the transtissue potential (TTP), was blocked by DIDS. Azide also increased RPE c-wave amplitude, which could be explained by the decrease in Rba, and it suppressed the light peak. As previously described (Shirao and Steinberg, 1987), a 25 mOsm transtissue hyperosmotic load (retinal side hyperosmotic) increased the TTP, increased the c-wave and decreased the transtissue resistance. DIDS suppressed each of these effects. We conclude that the light peak, the response to azide, and the response to a retinal hyperosmotic load may each originate as an increase in a basal membrane anion conductance that may be permeable to chloride.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1988

Modulation of human polymorphonuclear leukocyte function by the flavonoid silybin.

The effect in vitro of the naturally occurring flavonoid silybin on human polymorphonuclear leukocyte (PMN) functions has been studied. Preincubation of PMNs for 10 min at 37 degrees C with silybin inhibited, in a dose-dependent way, the luminol-enhanced chemiluminescence (CL) generated by stimulated cells without affecting the non-enhanced CL or superoxide anion production evaluated by the cytochrome C reduction assay. No significant effect of silybin on PMN phagocytic or chemotactic activities were found. Silybin did not absorb light at the wavelength of luminol-enhanced CL and was not toxic to PMNs at the concentrations used. Catalase, a scavenger of H2O2, inhibited luminol-enhanced CL to a similar degree as silybin; moreover, when incubated together with PMNs, silybin and catalase did not produce an additive inhibition of CL. On the contrary, the simultaneous addition of silybin and sodium azide, an inhibitor of myeloperoxidase, further increased inhibition over that seen with azide alone. These results suggest that inhibition of H2O2 may be the mechanism by which silybin inhibits the luminol-enhanced CL generated by stimulated PMNs. Such results indicate a possible anti-inflammatory activity for silybin even if their clinical relevance remains to be elucidated.

Azides↗

PubMed1985

Spin trapping of the azidyl radical in azide/catalase/H2O2 and various azide/peroxidase/H2O2 peroxidizing systems.

The azidyl radical is formed during the oxidation of sodium azide by the catalase/hydrogen peroxide system, as detected by the ESR spin-trapping technique. The oxidation of azide by horseradish peroxidase, chloroperoxidase, lactoperoxidase, and myeloperoxidase also forms azidyl radical. It is suggested that the evolution of nitrogen gas and nitrogen oxides reported in the azide/catalase/hydrogen peroxide system results from reactions of the azidyl radical. The azide/horseradish peroxidase/hydrogen peroxide system consumes oxygen, and this oxygen uptake is inhibited by the spin trap 5,5-dimethyl-1-pyrroline-N-oxide, presumably due to the competition with oxygen for the azidyl radical. Although azide is used routinely as an inhibitor of myeloperoxidase and catalase, some consideration should be given to the biochemical consequences of the formation of the highly reactive azidyl radical by the peroxidase activity of these enzymes.

Azides↗

PubMed1986

Multiple effects of the phenylhydrazone derivative FCCP on the secretory pathway in rat plasma cells.

We studied the sensitivity of the last steps of the secretory process of antibody-producing cells to carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP) and sodium azide (NaN3), agents which lower the cellular ATP content by inhibiting oxidative phosphorylation and mitochondrial electron transport, respectively. Popliteal lymph node cells or purified plasma cells from rats immunized against horseradish peroxidase were incubated with the drugs. The rate of secretion of anti-HRP antibodies was measured by an enzyme-linked immunoadsorbent assay or after biosynthetic labeling with L-[3H]fucose. FCCP as well as NaN3 were shown to rapidly inhibit (in less than 5 min) the secretion of immunoglobulins (Ig) and to partially block the release of fucosylated Ig. This indicates that the drugs inhibit the transport of Ig from the Golgi apparatus (GA) (where fucose is added to Ig) to the plasma membrane. However, the degree of inhibition reached 40 to 50% with NaN3 and 70 to 80% with FCCP, whereas both drugs similarly depleted ATP stores by 45 to 55%. These results are consistent with multiple effects of FCCP on the secretion pathway of Ig. As a tentative explanation, we suggest that FCCP, because of its protonophore properties, not only reduces cellular ATP levels but may also neutralize the Golgi or post-Golgi acidic compartments recently shown to be involved in the transport of plasma membrane and secretory proteins.

Adenosine Triphosphate↗

PubMed1994

In vitro phototoxic activities of new quinolone antibacterial agents: lipid peroxidative potentials.

To determine the fundamental photochemical properties of new quinolones that can induce photosensitivity, the in vitro phototoxicity of these drugs (enoxacin, norfloxacin, ofloxacin, ciprofloxacin, and lomefloxacin) was examined with respect to photosensitizing ability to peroxidize unsaturated lipid squalene in ethanol solution. Lomefloxacin and ciprofloxacin showed the highest efficiency in sensitization of peroxidation of the lipid. Moderate repression of peroxidation occurred by addition of sodium azide (a quencher of singlet molecular oxygen), suggesting that the nonsinglet oxygen mechanism is operative in addition to the singlet oxygen mechanism.

Absorption↗

PubMed2002

An expedient route to the tetrazole analogues of alpha-amino acids.

[reaction: see text] Convenient conditions are described for the transformation of alpha-aminonitriles to the tetrazole analogues of alpha-amino acids. Refluxing the starting material in water/2-propanol at 80 degrees C with sodium azide and catalytic zinc bromide affords the tetrazole product in yields generally exceeding 90%.

Amino Acids↗

PubMed1995

Is reduced accumulation of Hoechst 33342 in multidrug resistant cells related to P-glycoprotein activity?

Although bisbenzimidazole-DNA interactions have been studied in solution, little information has been available in living cells. The reduced accumulation of the nuclear dye Hoechst 33342 (H342) in cells with multidrug resistant (MDR) phenotype suggested its possible use in a functional test for detection of these cells. We performed experiments to elucidate the mechanisms involved in the H342-exclusion from resistant cells. As contradictory results have been reported in literature, we compared the entire fluorescence spectra of H342 in solution and in intact living cells under different experimental conditions. The study was performed by fluorescence image cytometry. This technique allow accurate quantification of the amount of H342 bound to DNA in living cells. The dye uptake was followed in sensitive and resistant cells, a lymphoblastoid cell line, CCRF-CEM, and its resistant variant selected with vinblastine CEM/VLB100 under conditions that could modulate H342-cell binding. Competition experiments with sodium azide, verapamil, and vinblastine indicated that resistant cells did not differ in the number of possible binding sites for H342. The obtained results ruled out the possibility of discriminating cells on the basis of a spectral shift. Two modes of binding, differing in their affinity for the dye, seem to co-exist in intact cells. Although it clearly appeared that the P-glycoprotein expressed in MDR cells was mainly responsible for the H342-exclusion, other mechanisms might also be involved.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1992

Transport and hydrolysis of maltose by Schwanniomyces castellii.

Hydrolysis and transport of maltose into Schwanniomyces castellii was studied under aerobic and anaerobic conditions. Amylase and glucosidase were not synthetized in presence of maltose in anaerobic conditions. Maltose permease was synthesized in anaerobiosis and its functioning is not inhibited. Glucose strongly repressed induction. The half-saturation constant for uptake of maltose was 0.06 mM. The rate of uptake of maltose was decreased by 2,4-dinitrophenol, antimycin or sodium azide. The significance of these results in relation to the Kluyver effect is discussed.

2,4-Dinitrophenol↗

PubMed1994

Comparison of the ATPase activities of bovine heart and liver mitochondrial ATP synthases with different tissue-specific gamma subunit isoforms.

The kinetics of heart and liver mitochondrial ATPase (FoF1) were examined using submitochondrial particles (SMPs) purified from the two tissues to obtain information on the role of gamma subunit isoforms. The F1 portion is mainly composed of the catalytic, common alpha beta subunits and tissue-specific gamma subunits. In contrast to the previous reports on the kinetics and crystallography of various F1's, the Vmax and Km of the two isoforms of FoF1 were identical although the SMPs were prepared from different tissues. Moreover sodium azide inhibited the two equally. The ATPase activity of liver SMP showed slightly steeper pH-dependency than that of heart SMP but the pH optima of the two were the same (pH 8).

Animals↗

PubMed1990

Rapid induction of acetylcholine receptor aggregates by a neural factor and extracellular Ca2+.

A soluble fetal brain extract (EBX) induces acetylcholine receptor (AChR) aggregation in cultured rat myotubes within 4 hr at 36 degrees C in a defined medium containing 1.8 mM (normal) extracellular Ca2+ (Olek et al., 1983). The activity of EBX was Ca2+ dependent; reducing extracellular Ca2+ significantly inhibited EBX-induced AChR aggregation and a 15-50% increase in extracellular Ca2+ synergistically enhanced the activity of EBX. Synergism was specific for Ca2+ as increases in other divalent cations (Ba2+, Co2+, Mg2+, Mn2+, Sr2+) had no effect. A large increase (300-500%) in extracellular Ca2+ alone also induced AChR aggregation within 4 hr at 36 degrees C. An equivalent increase in other cations (Ba2+, Co2+, Mg2+, Mn2+, Sr2+) did not promote AChR aggregation. An initial 15-min pulse of increased extracellular Ca2+ alone or with EBX was adequate to induce AChR aggregation. Aggregates induced by EBX, Ca2+ alone, or EBX/Ca2+ were found predominantly on the top surface of the myotube. These treatments did not detectably alter preexisting aggregates present at substrate contact sites on the bottom surface of myotubes. AChR aggregation induced by any treatment was not inhibited by cycloheximide, Ca2+ channel blockers, or protease inhibitors but was blocked by Co2+ and sodium azide.

Animals↗

PubMed1988

Unexpected stimulation of mitochondrial ADP-ribosylation by cyanide.

Cyanide, the classical inhibitor of the mitochondrial respiratory chain at site III, stimulates ADP-ribosylation of a number of mitochondrial proteins, the major protein being the 50-55 kDa band. Sodium azide, sharing the same inhibitory site, does not have the same effect. Rotenone or antimycin A have no influence on mitochondrial ADP-ribosylation. Data suggest that no apparent correlation exists between oxidoreductase function and protein ADP-ribosylation. Purified nuclear poly(ADP-ribose) polymerase activity was not affected by cyanide. The cyanide effect on mitochondrial ADP-ribosylation seems intriguing and may be attributed to NAD+-CN complex formation, since NAD reacts with cyanide at pH greater than 8 with N-substituted nicotinamide which may prevent inhibition of ADP-ribosylation.

Adenosine Diphosphate Ribose↗

PubMed1994

Arabidopsis assay for mutagenicity.

Four laboratories, two in the Czech Republic (Brno and Prague) and two in the CIS (Moscow and Duschanbe), participated in the International Programme on Chemical Safety's (IPCS) collaborative study to evaluate the utility of the most commonly used plant test systems, including the Arabidopsis thaliana assay, for assessing the mutagenic potential of environmental agents. Out of the five compounds evaluated in the Arabidopsis assay, three compounds, i.e., ethyl methanesulfonate, N-methyl-N-nitrosourea, and azidoglycerol, were reported to be mutagenic by all four participating laboratories. Sodium azide (NaN3) demonstrated a negative response in all four laboratories, whereas maleic hydrazide was reported to be weakly mutagenic by one laboratory and nonmutagenic by the other three laboratories.

Arabidopsis↗