Effects of chloroquine on lysosomal enzymes, NADPH-induced lipid peroxidation, and antioxidant enzymes of rat retina.
TL;DR: In contrast to the acute effect, chloroquine, given in 7- and 15-day treatment schedules, had no significant effect on the lysosomal enzyme system, while at the same time a normalization or a decrease in NADPH-induced lipid peroxidation, associated with a significant increase in tissue glutathione content, was noted.
Abstract: Chloroquine (1, 5 and 10 mg/kg), given in acute and in chronic (7 and 15 days) treatment schedules, caused characteristic alterations in the lysosomal enzyme system, antioxidant enzymes, NADPH-induced lipid peroxidation, and glutathione content in the retina of the rat. One-half hour and four hours after chloroquine administration, increased free activities of lysosomal enzymes and NADPH-induced lipid peroxidation were observed, associated with a decrease in tissue glutathione content. In contrast to the acute effect, chloroquine, given in 7- and 15-day treatment schedules, had no significant effect on the lysosomal enzyme system, while at the same time a normalization or a decrease in NADPH-induced lipid peroxidation, associated with a significant increase in tissue glutathione content, was noted. Catalase and peroxidase activities were decreased after both the acute and the daily treatment schedules. Superoxide dismutase activity, although increased in the high dose acute study, appeared otherwise little affected by chloroquine treatment.
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01 Jan 1985
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TL;DR: Injections of leupeptin or chloroquine into the brains of young rats induced the formation of lysosome-associated granular aggregates which closely resembled the ceroid-lipofuscin that accumulates in certain disease states and during aging.
Abstract: Injections of leupeptin (a thiol proteinase inhibitor) or chloroquine (a general lysosomal enzyme inhibitor) into the brains of young rats induced the formation of lysosome-associated granular aggregates (dense bodies) which closely resembled the ceroid-lipofuscin that accumulates in certain disease states and during aging The dense material increased in a dose- and time-dependent fashion and was differentially distributed across brain regions and cell types These observations provide clues to the origins of ceroid-lipofuscin and suggest means for studying the consequences of its accumulation
278 citations
TL;DR: Results suggest that Tam, by initially partitioning into the membranes, induces a generation of transmembrane signals and an oxidative stress to elicit the membrane association of PKC, followed by an irreversible activation, and subsequent down-regulation of this enzyme, which, in part, may lead to cell growth inhibition.
Abstract: Nonsteroidal agent tamoxifen (Tam), a therapeutic/chemopreventive agent for breast cancer, inhibits protein kinase C (PKC), which is considered to be one of its extra-estrogen receptor sites of action. This drug is required at higher (>100 microM) concentrations to inhibit PKC in the test tube, whereas it is required at lower (1-10 microM) concentrations to induce inhibition of cell growth in estrogen receptor-negative cell types. To identify additional mechanisms of action of Tam on PKC and cell growth, studies with MDA-MB-231, an estrogen receptor-negative breast carcinoma cell type, have been carried out. Upon treatment with 5-20 microM Tam, a cytosol to membrane translocation of PKC occurred within 30 min, which was then followed by a down-regulation of the enzyme within 2 h. A transient generation of Ca2+/lipid-independent activated form of PKC was observed during this period. Rapidly growing cells require nearly 2-3-fold lower concentrations (2-5 microM) of Tam than do confluent cells to induce changes in PKC. Furthermore, phorbol ester binding observed with intact cells also decreased in Tam-treated cells only under the conditions PKC was inactivated. Unlike phorbol esters, Tam did not directly support the membrane association of PKC. The release of arachidonic acid correlated with the PKC membrane translocation. Studies carried out with [3H]Tam revealed that Tam partitioned into the membrane, and there was no appreciable covalent association of [3H]Tam with cellular proteins within this limited time period (2 h). Various antioxidants (vitamin E, vitamin C, beta-carotene, catalase, and superoxide dismutase) inhibited all these cellular effects of Tam. Moreover, vitamin E strikingly blocked Tam-induced growth inhibition. To determine whether oxymetabolites of Tam can affect PKC permanently, OH-Tam was tested with purified PKC. In contrast to Tam, which reversibly inhibited PKC, OH-Tam permanently inactivated the enzyme by modifying the catalytic domain at lower concentrations. The vicinal thiols present within this domain were found to be required to induce this inactivation. This effect was partially blocked by various antioxidants. This is the first report showing the role of oxidative stress in mediating the actions of Tam. Taken together these results suggest that Tam, by initially partitioning into the membranes, induces a generation of transmembrane signals and an oxidative stress to elicit the membrane association of PKC, followed by an irreversible activation, and subsequent down-regulation of this enzyme, which, in part, may lead to cell growth inhibition.
157 citations
TL;DR: The present review provides a biochemical investigation of the mechanisms leading to deadly inflammation in severe COVID-19, counterbalanced by GSH, and discusses the current data about the feasibility of increasing GSH levels, which could be used to prevent and subdue the disease.
Abstract: The novel COVID-19 pandemic is affecting the world’s population differently: mostly in the presence of conditions such as aging, diabetes and hypertension the virus triggers a lethal cytokine storm and patients die from acute respiratory distress syndrome, whereas in many cases the disease has a mild or even asymptomatic progression. A common denominator in all conditions associated with COVID-19 appears to be the impaired redox homeostasis responsible for reactive oxygen species (ROS) accumulation; therefore, levels of glutathione (GSH), the key anti-oxidant guardian in all tissues, could be critical in extinguishing the exacerbated inflammation that triggers organ failure in COVID-19. The present review provides a biochemical investigation of the mechanisms leading to deadly inflammation in severe COVID-19, counterbalanced by GSH. The pathways competing for GSH are described to illustrate the events concurring to cause a depletion of endogenous GSH stocks. Drawing on evidence from literature that demonstrates the reduced levels of GSH in the main conditions clinically associated with severe disease, we highlight the relevance of restoring GSH levels in the attempt to protect the most vulnerable subjects from severe symptoms of COVID-19. Finally, we discuss the current data about the feasibility of increasing GSH levels, which could be used to prevent and subdue the disease.
136 citations
Cites background from "Effects of chloroquine on lysosomal..."
...In addition to its prooxidant activity leading to GSH depletion [86], chloroquine accumulates into lysosomes leading to their alkalinization and to the impaired uptake of many nutrients from the blood, including transferrin-bound iron....
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TL;DR: It is suggested that parasite feeding on host cell cytosol is the primary target for the antimalarial action of these drugs, and the metabolically dependent acidification of this parasite organelle is involved in both processes.
Abstract: Intraerythrocytic malaria parasites feed on their host cell cytosol. We show that human red blood cells infected with the malaria parasite Plasmodium falciparum , produce free amino adds the composition of which resembles that of globin, the most abundant red blood cell protein. The rate of amino acid production is almost equal to the rate of efflux of these acids from the infected cell. Production of amino acids increases with parasite age: the rates of production at the young ring and the mature trophozoite stages were 3.3 and 13.5 nmol/10 8 infected cells per min at 37°, respectively, compared with 0.04 nmol/10 8 cells per min in uninfected cells. The quinoline-containing antimalarial drugs, chloroquine, quinine and mefloquine, inhibit amino acid production at the same concentrations at which they inhibit parasite growth, but have no effect on the endogenous parasite protein degradation. We suggest that parasite feeding on host cell cytosol is the primary target for the antimalarial action of these drugs. Chloroquine accumulation, the rate of amino add production by infected cells and the inhibitory effect of the drug, were determined simultaneously at the different stages of parasite development. At all stages the rate of amino add production and chloroquine accumulation were directly related and both were inversely related to the inhibitory effidency of the drug. The lysosomotropic agents methylamine and NH 4 Cl at millimolar concentrations also inhibit amino add production, suggesting that the process is pH dependent and localized in the vacuole. Host cytosol degradation and drug accumulation both ake place in the parasite food vacuole. Our observations imply that the metabolically dependent acidification of this parasite organelle is involved in both processes.
115 citations
References
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TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
Abstract: Since 1922 when Wu proposed the use of the Folin phenol reagent for the measurement of proteins, a number of modified analytical procedures utilizing this reagent have been reported for the determination of proteins in serum, in antigen-antibody precipitates, and in insulin. Although the reagent would seem to be recommended by its great sensitivity and the simplicity of procedure possible with its use, it has not found great favor for general biochemical purposes. In the belief that this reagent, nevertheless, has considerable merit for certain application, but that its peculiarities and limitations need to be understood for its fullest exploitation, it has been studied with regard to effects of variations in pH, time of reaction, and concentration of reactants, permissible levels of reagents commonly used in handling proteins, and interfering substances. Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
289,852 citations
TL;DR: A water-soluble (at pH 8) aromatic disulfide [5,5′-dithiobis(2-nitrobenzoic acid] has been synthesized and shown to be useful for determination of sulfhydryl groups.
Abstract: A water-soluble (at pH 8) aromatic disulfide [5,5′-dithiobis(2-nitrobenzoic acid)] has been synthesized and shown to be useful for determination of sulfhydryl groups. Several applications have been made to show its usefulness for biological materials. A study of the reaction of this disulfide with blood has produced some evidence for the splitting of disulfide bonds by reduced heme.
23,232 citations
TL;DR: The reduction of nitro blue tetrazolium (NitroBT) with NADH mediated by phenazine methosulfate (PMS) under aerobic conditions was inhibited upon addition ofsuperoxide dismutase, indicating the involvement of superoxide aninon radical in the reduction of NitroBT.
Abstract: Summary The reduction of nitro blue tetrazolium (NitroBT) with NADH mediated by phenazine methosulfate (PMS) under aerobic conditions was inhibited upon addition of superoxide dismutase. This observation indicated the involvement of superoxide aninon radical (O 2 − ) in the reduction of NitroBT, the radical being generated in the reoxidation of reduced PMS. Similarly, the reduction of NitroBT coupled to D-amino acid oxidase-PMS system under aerobic conditions was also inhibited by superoxide dismutase. A simple method for detecting superoxide dismutase is described.
3,331 citations
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01 Jan 1972TL;DR: This short review of free radicals discusses certain types of free radical, such as nitroxyl-radicals and free radicals stabilized by steric or derealization features, which are stable enough to be crystallised and stored at temperatures above 0°.
Abstract: Free radicals are molecules or molecular fragments containing a single unpaired electron. In general, free radicals are reactive chemically, some (e.g. HO•) being extremely reactive. However, certain types of free radical, such as nitroxyl-radicals and free radicals stabilized by steric or derealization features, are much less reactive and a few (e.g. diphenyl picryl hydrazyl) are stable enough to be crystallised and stored at temperatures above 0°. Table 1 gives the general structures of free radicals that will be discussed in this short review.
1,643 citations