Involvement of PAF (Platelet-Activating Factor) in chloroquine-induced retinopathy]

Chloroquine retinopathy is a severe toxic retinal impairment which may result in loss of vision by alterations of the pigmentary epithelium and photoreceptors. Currently, there is no specific treatment for this retinopathy. In order to test the possible involvement of Platelet-Activating Factor (PAF) in chloroquine-induced retinopathy and the use of PAF antagonists for prevention of this condition, we have examined the effect of these substances on the electroretinogram (ERG) of isolated rat retina. When retinas from normal rats were perfused with chloroquine (10(-6) M), a marked and rapid decrease in ERG b-wave amplitude was observed. In contrast, chloroquine had no effect on the ERG of retina isolated from animals pretreated with the PAF antagonist, BN 50730 (30 mg/kg/day i.p., 5 days). The results obtained indicate that (i) chloroquine is a toxic drug for retinal function, (ii) PAF plays a key role in chloroquine retinopathy and (iii) PAF antagonists may constitute valuable agents for the treatment of this retinal impairment.     

Antioxidative effect of o-benzoquinone derivatives during CCl4-induced lipid peroxidation in the rat liver

It was found that o-benzoquinones (oBQ) inhibit the CCl4-dependent lipid peroxidation (LPO) in rat liver microsomes in vitro. The experimental data suggest that the antioxidant effect of oBQ is not due to the ability of these substances to shunt the NADPH-dependent electron transport pathways. More likely, oBQ inhibit LPO due to the ability of their reduced forms to scavenge the free radicals which induce LPO. Based on the experimental data, it was concluded that the increasing absorption of liver lipids at 230-236 nm after administration of CCl4 is due to the accumulation of reduced hydroperoxides. This process was shown to be inhibited by oBQ.     

Chloroquine and Hydroxychloroquine Increase Retinal Pigment Epithelial Layer Permeability

Antimalarials chloroquine (CQ) and hydroxychloroquine (HCQ) are widely used as antiinflammatory drugs, but side effects include retinopathy and vision loss. The objective of this study was to examine the effect of CQ and HCQ on the barrier integrity of retinal pigment epithelial (RPE) cell monolayers in vitro. Permeability of ARPE‐19 cell monolayers was determined using Fluorescein isothiocyanate (FITC)‐labeled dextran. The influence of CQ and HCQ on cell death and the expression tight junction molecules was examined. CQ and HCQ significantly increased ARPE‐19 monolayer permeability after 3 and 18 h, respectively, and enhanced mRNA levels for claudin‐1 and occludin. Cytotoxicity was only observed after 18 h exposure. Thus, CQ and HCQ rapidly enhance RPE barrier permeability in vitro, independent of cytotoxicity or loss of zonula occludens‐1, claudin‐1, and occludin expression. Our findings suggest that CQ/HCQ‐induced permeability of the RPE layer may contribute to blood–retinal barrier breakdown in case of CQ/HCQ‐induced retinopathy.     

Modification of an enzymic system of Ca2+ transport in sarcoplasmic reticulum during lipid peroxidation. In vivo damages in the development of pathological changes

The role of lipid peroxidation (LPO) in the damages of the enzymic system of Ca2+ transport in sarcoplasmic reticulum (SR) membranes of skeletal and cardiac muscles under conditions of vitamin E deficiency, ischemia and limb reoxygenation as well as in emotional-pain stress was investigated. It was shown that these processes are associated with activation of endogenous LPO in SR membranes "in vivo" and with simultaneous inhibition of Ca2+ transport, (i. e. decrease of the Ca2+/ATP ratio) and inactivation of Ca-ATPase. The degree of damage of the Ca2+ transport system was correlated with the concentration of LPO products accumulated in SR membranes "in vivo and during LPO induction by the Fe2+ + ascorbate system 'in vitro". Injection of natural and synthetic free radical scavengers (e. g. 4-methyl-2.6-ditretbutylphenol, alpha-tocopherol) to experimental animals resulted in practically complete suppression of LPO activation "in vivo" and in partial protection of the Ca2+-transporting capacity of SR membranes. A comparison of experimental results allowed to estimate the role of LPO in SR damage under pathological conditions. Model experiments with "contraction-relaxation" cycles including isolated components of muscle fibers (SR fragments and myofibrils) demonstrated that LPO induction in SR membranes by the Fe2+ + ascorbate system results in complete elimination of the relaxation step in myofibrils due to the loss of the SR affinity to decrease the concentration of Ca2+ in the incubation medium. This effect can be removed by free radical scavengers. The role of LPO in pathological changes of muscle contractility is discussed.     

Limitation of ischemic necrosis by the use of antioxidant ionol

Inhibitory effect of Ionol on lipid peroxidation (LPO) in the infarction zone and out of it after experimental myocardial infarction in the experiments on rats was investigated. The results of measurements, performed by two independent methods: point counting and the computer image analysis were compared. It was shown that LPO activation out of the ischaemic zone was prevented and dimensions of the ischaemic necrosis were limited by Ionol, which did not influence LPO activation in the ischaemic zone. Data obtained by both methods coincide qualitatively, the computer image analysis being more sensitive and effective.     

Electro-Oculograms in the Early Diagnosis of Chloroquine Retinopathy

Funduscopy, electro-oculography and electroretinography are all valuable in early detection of chloroquine retinopathy, which is reversible if detected early. Simplified instrumentation for electro-oculography was utilized in testing 12 normal controls, one patient with diabetic retinopathy and 15 patients with potential or actual cases of chloroquine retinopathy. Normal controls, and all but one of the patients without clinical evidence of retinopathy, had electro-oculographic ratios above 180. All patients having evidence of retinopathy had ratios below 180.     

Stabilizing effect of hydroxybenzimidazole and its derivatives on biological membranes during activation of lipid peroxidation

Inhibition of lipid peroxidation (LPO) by oxybenzimidazole (OBI) and its derivatives--alkyloxybenzimidazole (AOBI) and alkylethoxybenzimidazole (AEBI) was studied in liver microsomes and brain synaptosomes. It has been shown that both OBI and AOBI strongly inhibit LPO in microsomes and not synaptosomes. AEBI failed to inhibit LPO in microsomes. AOBI is more potent than OBI both in ascorbate- and NADPH-dependent LPO of microsomes. An antioxidant effect of both compounds is more marked in ascorbate-dependent LPO. The investigation of the possible use of AOBI for the protection of liver membranes in various pathological conditions associated with LPO activation seems promising.     

The in vitro pharmacology of chloroquine and quinacrine

The effects of guanethidine, chloroquine and quinacrine on noradrenergic nerves have been compared in vitro using the isolated expansor secundariorum muscle of chicks. The effect of chloroquine on alpha-methyl-noradrenaline uptake by noradrenergic nerve terminals in various tissues were studied. The inhibitory action of guanethidine and quinacrine on noradrenergic nerves appeared to be mediated intraneuronally. The inhibitory action of chloroquine was readily reversible and unaffected by dexamphetamine. Chloroquine caused supersensitivity of the expansor muscle to noradrenaline by blocking its neuronal reuptake since the supersensitivity caused by denervation was not further increased by chloroquine. This was confirmed by the finding that chloroquine inhibited alpha-methylnoradrenaline uptake (Uptake1). Quinacrine did not cause supersensitivity to noradrenaline, possibly due to its direct depressant action on the expansor secundariorum muscle.     

Interaction of specific and innate factors of immunity: IgA enhances the antimicrobial effect of the lactoperoxidase system against Streptococcus mutans

The antimicrobial effect of the lactoperoxidase (LPO) system (enzyme with the thiocyanate ion and hydrogen peroxide) on Streptococcus mutans NCTC 10449 (serotype c) was significantly enhanced when the system was combined with secretory IgA. Similar enhancement was observed with LPO-myeloma IgA1 or IgA2 combinations. This enhancement of the antimicrobial efficiency was not dependent on the presence of specific antibodies to S. mutans in the IgA preparation, but seemed to require binding between LPO and immunoglobulin. However, neither human polyclonal nor myeloma IgG or IgM nor rabbit IgG enhanced the antibacterial activity of the LPO system. None of the immunoglobulins, when added alone, produced antimicrobial effects. LPO was shown to bind to colostral secretory IgA, myeloma IgA1, IgA2, and to a lesser degree to monoclonal and polyclonal IgG and monoclonal IgM. This binding had a stabilizing effect on the enzyme activity. Our results suggest that IgA significantly enhances the antibacterial efficiency of one of the innate immune factors--the LPO system.     

Plasmodium falciparum: in vitro drug interaction between chloroquine and enantiomers of amlodipine

Both enantiomers of amlodipine, whose calcium antagonist action resides almost exclusively in the R(-) enantiomer, reversed chloroquine resistance in Plasmodium falciparum in vitro. R(-) enantiomer was slightly more effective than the S(+) enantiomer in potentiating chloroquine action against chloroquine-resistant strains of parasites. No potentiating effect was observed in chloroquine-sensitive parasites. Both enantiomers entered rapidly into parasitized erythrocytes to the same extent. Reversal of chloroquine resistance by the enantiomers of amlodipine was related to dose-dependent increase in the accumulation of chloroquine inside the erythrocytes parasitized by resistant parasites. These results suggest that the potentiating effect on chloroquine is independent of calcium metabolism of malaria parasites.     

Lipid peroxidation as a major factor in the modification of the catalytic function of Ca-ATPase of the sarcoplasmic reticulum in hypercholesterolemia

A comparative study of the effect of an experimental hypercholesterolemia and in vitro induced lipid peroxidation (LPO) on the temperature dependence of the activity of sarcoplasmic reticular Ca-ATPase from rabbit skeletal muscle (SR) has been performed. A control Arrhenius plot of ATPase activity determined in the presence of alamethicin was characterized by discontinuity in the 20 degrees C area. Both in vitro induced LPO and hypercholesterolemia resulted in a shift of discontinuity to 30 degrees C area. The replacement of lipid Ca-ATPase membrane environment by egg yolk lecithin did not affect the temperature dependence of the activity in control SR and failed to restore the original nature of the Arrhenius plot for Ca-ATPase modified by hypercholesterolemia or the in vitro induced LPO.     

The pathogenetic bases for chemotherapy in an experimental Salmonella infection]

The effect of etiotropic (polymyxin and adriblastin) and pathogenetic (levamisole and vitamin E) chemotherapy on lipid peroxidation (LPO), phagocyte functional activity and the process and outcomes of Salmonella infection was studied in rabbits. It was shown that development of salmonellosis was accompanied by activation of LPO which was phase-by-phase. There was synchronism in changing of LPO and neutrophilic phagocytic activity. Adriblastin and levamisole stimulated LPO and increased the neutrophilic phagocytic activity. Vitamin E inhibited LPO and had an unfavourable effect on the process and outcomes of the infection. The problem in differential use of the chemotherapeutic drugs with an account of their modulating effect on LPO is discussed.     

In-vitro venous prostacyclin production,plasma 6-keto-prostaglandin F1 alpha concentrations,and diabetic retinopathy.

Previous studies have shown that vessels from diabetics produce less prostacyclin in vitro than those from normal controls. To determine whether this decreased production is related to complications elective biopsy of a superficial forearm vein was performed on 12 insulin-dependent male diabetics, six with nil or minimal and six with proliferative retinopathy, and seven male controls. Vein segments from the diabetics and controls produced similar amounts of prostacyclin in vitro (medians 0.11 and 0.19 ng/mg tissue respectively), but the segments from the diabetics with nil or minimal retinopathy produced less than those from the diabetics with proliferative retinopathy (medians 0.09 and 0.18 ng/mg respectively). Preoperative plasma immunoreactive concentrations of 6-keto-prostaglandin F1 alpha were not significantly different between the controls and the diabetics (medians 101 and 116 pg/ml respectively). In a separate study, however, 11 diabetics with duration of disease of over 10 years and nil or minimal retinopathy had significantly lower concentrations than a matched group of 16 with background or proliferative retinopathy (medians 79 and 121 pg/ml respectively). These results do not support an association between reduced prostacyclin production and diabetic retinopathy.     

Antioxidant effect of diphenyl diselenide against sodium nitroprusside (SNP) induced lipid peroxidation in human platelets and erythrocyte membranes: an in vitro evaluation

An in vitro evaluation on the antioxidant effect of diphenyl diselenide (PhSe)(2), an organochalcogenide, against sodium nitroprusside (SNP)-induced lipid peroxidation (LPO) was conduced. Human platelets and erythrocyte membranes (ghosts), as well as rat brain homogenates (S(1)), were pre-incubated with different concentrations of SNP (0-10 microM). All SNP concentrations tested significantly increased LPO in human platelets and S(1). Platelets were more sensitive to SNP-induced peroxidative damage when compared to S(1). SNP 10 microM decreased glutathione peroxidase (GPx) activity and did not affect glutathione reductase (GR) and catalase (CAT) activities in human platelets. However, ghosts were insensitive to SNP-induced LPO and no changes on GPx, GR and CAT activities were observed. Diphenyl diselenide significantly protected human platelets against SNP-induced LPO and recovered GPx inactivation. This effect was more evident at (PhSe)(2) concentrations above 2 microM. The presented results indicate that (PhSe)(2) exerts protective effects on SNP-induced oxidative damage in human blood components and in rat brain. These phenomena seem to be related to its thiol peroxidase-like activity and to a possible direct interaction with SNP and derivatives. Based on our results and on literature, diphenyl diselenide can be pointed as a promising antioxidant molecule.     

Lipid peroxidation in microsomes of murine bone marrow after low-doseγ-irradiation

The principal aim of the study was to investigate the effect of low-dose-irradiation on lipid peroxidation (LPO) in murine bone marrow. To this end, the degree of LPO in suspensions of microsomes of murine bone marrow cells (BMC) was determined in terms of malondialdehyde (MDA) formation after whole-body or in vitro exposure to various doses of-radiation. These effects were compared to some extent with similar effects in liver and spleen preparations. As to the effect of-irradiation on LPO in BMC, the response depends on the dose level and on whether whole-body or in vitro exposures are involved. Whole-body irradiation did not result in an increase in LPO in BMC microsomes, even at such high doses as 15 Gy, although hepatic microsomes showed a marked increase. In contrast, in vitro irradiation of BMC microsomes with 0.1, 10 and 50 Gy brought about an increase in LPO. This increase was already significant (P <0.05) at 0.1 Gy following a post-irradiation incubation and substantial at 50 Gy, even without subsequent incubation. The results show that low doses of-irradiation are able to induce an elevation of LPO in murine BMC microsomes, but only after in vitro irradiation. In the case of whole-body irradiation cellular radical scavengers and other metabolic reactions may prevent a measurable increase in LPO. This is partly illustrated by the case of vitamin-E deficiency, where a substantial increase in LPO in BMC microsomes is observed even without-irradiation in comparison with euvitaminotic mice because normally occurring radicals are not scavenged sufficiently.On leave from the University of Rochester, School of Medicine and Dentistry, Rochester, NY 14678, USA     

In vitro chloroquine resistance modulation study on fresh isolates of Brazilian Plasmodium falciparum: intrinsic antimalarial activity of phenothiazine drugs

Phenothiazine drugs - fluphenazine, chlorpromazine, methotrimeprazine and trifluoperazine - were evaluated as modulating agents against Brazilian chloroquine-resistant fresh isolates of Plasmodium falciparum. Aiming to simulate therapeutic schedules, chloroquine was employed at the concentration used for sensitive falciparum malaria treatment and anti-psychotic therapeutic concentrations of the phenothiazine drugs were adopted in two-fold serial dilutions. The in vitro microtechnique for drug susceptibility was employed. Unlike earlier reported data, the phenothiazine modulating effect was not observed. However, all the drugs demonstrated intrinsic antiplasmodial activity in concentrations lower than those described in the literature. In addition, IC50 estimates have been shown to be inferior to the usual anti-psychotic therapeutic concentrations. Statistical analysis also suggested an increase in the parasitaemia rate or, even, a predominant antiparasitic effect of phenothiazine over chloroquine when used in combination.     

Endocytosis by liver cells during suppression of intralysosomal proteolysis.

The lysosomotropic agent chloroquine is widely used as a specific inhibitor of intralysosomal proteolysis in isolated hepatocytes. It was shown that in vitro chloroquine reversibly inhibited purified cathepsins H, B, L in concentrations less than those observed inside lysosomes in vivo. However, administration of high doses of chloroquine to rats (30-50 mg/kg i.p. as a single or repeated injections) was followed by increased cathepsin D and cysteine proteinase activities, as well as other lysosomal enzymes. Chloroquine administration did not induce any changes of carbon particles phagocytosis by liver cells (macrophages); modifications of fluid-phase (125I-PVP uptake) and receptor-mediated endocytosis (125I-asialo-fetuin uptake) were noted. Chloroquine administered in vivo reproduced some symptoms of lysosomal storage diseases (especially during repeated drug administration).     

Participation of oxygen activated species in enzymatic lipid peroxidation in biomembranes]

The participation of oxygen activated species in the induction of lipid peroxidation (LPO) in the membrane systems containing cytochrome P-450 (liver microsomes) and in the membrane fragments devoid of this hemoprotein (brain and skeletal muscle microsomes) was studied. It was shown that the rate of NADH-dependent LPO does not depend on the presence of hemoproteins and the activity of NADH-specific flavoprotein in the membranes. On the other hand, the microsomal membranes of the liver with high specific contents of b5 and P-450 cytochromes and NADPH-specific flavoprotein, had the highest rates of NADPH-dependent LPO. It was found that the most effective inhibitors of free oxygen activated species in the case of NADPH- and NADH-dependent LPO in the microsomal fractions of liver, brain and skeletal muscles are the superoxide (O ./2) anion radical inhibitors. The singlet oxygen (1O2) quenchers inhibit only NADPH-dependent LPO in the liver, however, in a far lesser degree. The hydroxyl radical (OH) scavengers had no effect on enzymatic LPO in all systems studied.     

Chloroquine retinopathy and secondary trauma

This report describes a patient who initially presented with established chloroquine retinopathy resulting in reduced distance visual acuity, color vision anomalies and maculopathy in each eye. Subsequent trauma to the left side of the head produced a further decline in vision, accompanied by iritis and macula edema. A differential diagnosis, classification and treatment plan for patients with chloroquine retinopathy is presented.     

Effect of conditioned-reflex bilateral avoidance learning on lipid components of the rat brain

The active avoidance training of rats resulted in a depletion of lipid peroxidation (LPO) products in cerebral cortex. LPO inhibition was also shown in cerebral cortex of "active control" group receiving +non-combined stimuli (the effect of short-term stress). LPO inhibition was more pronounced in rats staining a training criterion compared to rats which received combined stimuli but did not reach the criterion. In the active control group LPO inhibition was accompanied by total phospholipids accumulation and cholesterol depletion in cortical lipid extracts. Irrespective of attaining the criterion in all rats trained for active avoidance the accumulation of cholesterol was seen. Active avoidance training affected also the phospholipid composition of cerebral cortex.