Influence of Solvent on the Drug-Loading Process of Amphiphilic Nanogel Star Polymers

We present an all-atom molecular dynamics study of the effect of a range of organic solvents (dichloromethane, diethyl ether, toluene, methanol, dimethyl sulfoxide, and tetrahydrofuran) on the conformations of a nanogel star polymeric nanoparticle with solvophobic and solvophilic structural elements. These nanoparticles are of particular interest for drug delivery applications. As drug loading generally takes place in an organic solvent, this work serves to provide insight into the factors controlling the early steps of that process. Our work suggests that nanoparticle conformational structure is highly sensitive to the choice of solvent, providing avenues for further study as well as predictions for both computational and experimental explorations of the drug-loading process. Our findings suggest that when used in the drug-loading process, dichloromethane, tetrahydrofuran, and toluene allow for a more extensive and increased drug-loading into the interior of nanogel star polymers of the composition studied here. In contrast, methanol is more likely to support shallow or surface loading and, consequently, faster drug release rates. Finally, diethyl ether should not work in a formulation process since none of the regions of the nanogel star polymer appear to be sufficiently solvated by it.

Spatial Distribution of Hydrophobic Drugs in Model Nanogel-Core Star Polymers

Star polymers with a cross-linked nanogel core are promising carriers of cargo for therapeutic applications due to the synthetic control of amphiphilicity of arms and stability at infinite dilution. Three nanogel-core star polymers were investigated to understand how the arm-block chemical structure controls loading efficiency of a model drug, ibuprofen, and its spatial distribution. The spatial distribution profiles of hydrophobic core, hydrophilic corona, and encapsulated drug were determined by small-angle neutron scattering (SANS). SANS provides the nanometer-scale sensitivity to determine how the arm-block chemistry enhances the sequestering of ibuprofen. Validated molecular dynamics simulations capture the trends in drug profile and polymer segment distribution with further details on drug orientation distribution. This work provides a basis to study structure-function relationships in macromolecular-based carriers of cargo and represents a path toward validated and predictive simulation.

Hypochlorous acid-modified low-density lipoprotein inactivates the lysosomal protease cathepsin B: protection by ascorbic and lipoic acids

Unregulated uptake of oxidized LDL by the scavenger receptor(s) of macrophages is thought to be an early event in atherosclerotic lesion development. Accumulation of oxidized LDL within macrophages may result from resistance of the modified LDL to enzymatic hydrolysis or from direct inactivation of lysosomal enzymes by reactive LDL-associated moieties. Since HOCl-modified LDL has been detected in vivo, the effects of HOCI-modified LDL on the activities of the cysteine protease cathepsin B and the aspartyl protease cathepsin D were investigated. LDL (0.5 mg protein/ml), which had been exposed to HOCl (25-200 microM), caused rapid dose-dependent inactivation of cathepsin B, but not of cathepsin D. Exposure of LDL to HOCl results primarily in the formation of LDL-associated chloramines, and the model chloramine N(alpha)-acetyl-lysine chloramine also caused dose-dependent inactivation of cathepsin B. Incubation of HOCl-modified LDL with ascorbic and lipoic acids (25-200 microM) resulted in dose-dependent reduction of LDL-associated chloramines and concomitant protection against cathepsin B inactivation. Thus, the data indicate that HOCl-modified LDL inactivates cathepsin B by a chloramine-dependent mechanism, most likely via oxidation of the enzyme's critical cysteine residue. Furthermore, small molecule antioxidants, such as ascorbic and lipoic acids, may be able to inhibit this potentially pro-atherogenic process by scavenging LDL-associated chloramines.

Fatty acid chlorohydrins and bromohydrins are cytotoxic to human endothelial cells

Reaction of unsaturated lipids with the hypohalous acids (hypochlorous acid and hypobromous acid) results in the addition of the halide (X) across double bonds to form halohydrins (-CH2CH(OH)CH(X)CH2-). These modified lipids could be potentially destabilising to cell membranes due to their increased polarity. We have investigated the effect of pre-formed halohydrins on human umbilical vein endothelial cells (HUVEC) by incubating cultured cells with oleic acid micelles containing chlorohydrins or bromohydrins. Cell detachment and necrotic death were observed with increasing doses of halohydrins, whereas the cells were unaffected by equivalent doses of oleic acid. Bromohydrins caused more lysis than did chlorohydrins at equivalent doses. Complete lysis was seen with 200 microM fatty acid/chlorohydrin micelles and with 50 microM fatty acid/bromohydrin micelles. Chlorohydrin uptake was much less than the oleic acid control whereas bromohydrins were incorporated into the endothelial cells similarly to oleic acid. This difference or the bulkier nature of the bromohydrins could account for their increased toxicity. This study has demonstrated the potential toxicity of the halohydrins, and implications for their formation in inflammation are discussed.

Red wine antioxidants bind to human lipoproteins and protect them from metal ion-dependent and -independent oxidation

Plant-derived polyphenols may exert beneficial effects on atherosclerosis and cardiovascular diseases, in part, because of their antioxidant properties. In this study we compared the effects of unbound (free) and lipoprotein-associated red wine components on in vitro antioxidant protection of human low-density lipoprotein (LDL). Preincubation of LDL (1 mg protein/mL) with 0-2.5% (v/v) red wine for 3 h at 37 degrees C followed by gel filtration to remove unbound red wine components resulted in a dose-dependent, up to 4-fold increase in LDL-associated antioxidant capacity (measured as Trolox equivalents). Similar results were obtained with high-density lipoprotein (HDL) and bovine serum albumin (BSA). Furthermore, LDL was subjected to oxidation by copper and aqueous peroxyl radicals (2,2'-azobis[2-amidinopropane] dihydrochloride, AAPH). Under both types of oxidative stress, LDL-associated and free red wine components significantly decreased oxidation of the lipoprotein's protein moiety (assessed by tryptophan fluorescence) and lipid moiety (assessed by thiobarbituric acid-reactive substances and conjugated dienes). Similar protective effects of red wine components were observed against HDL oxidation. In contrast, red wine exerted a pro-oxidant effect on copper-induced oxidation of BSA tryptophan residues, while protecting them from AAPH-induced oxidation. Ascorbate strongly enhanced the protective effect of red wine against copper-induced LDL oxidation, and had an additive effect against AAPH-induced oxidation. Our data indicate that red wine components bind to LDL and HDL and protect these lipoproteins from metal ion-dependent and -independent protein and lipid oxidation.

Comparison of low-density lipoprotein modification by myeloperoxidase-derived hypochlorous and hypobromous acids

Myeloperoxidase (MPO), a heme enzyme secreted by activated phagocytes, catalyzes the oxidation of halides to hypohalous acids. At plasma concentrations of halides, hypochlorous acid (HOCl) is the major strong oxidant produced. In contrast, the related enzyme eosinophil peroxidase preferentially generates hypobromous acid (HOBr). Since reagent and MPO-derived HOCl converts low-density lipoprotein (LDL) to a potentially atherogenic form, we investigated the effects of HOBr on LDL modification. Compared to HOCl, HOBr caused 2-3-fold greater oxidation of tryptophan and cysteine residues of the protein moiety (apoB) of LDL and 4-fold greater formation of fatty acid halohydrins from the lipids in LDL. In contrast, HOBr was 2-fold less reactive than HOCl with lysine residues and caused little formation of N-bromamines. Nevertheless, HOBr caused an equivalent increase in the relative electrophoretic mobility of LDL as HOCl, which was not reversed upon subsequent incubation with ascorbate, in contrast to the shift in mobility caused by HOCl. Similar apoB modifications were observed with HOBr generated by MPO/H(2)O(2)/Br(-). In the presence of equivalent concentrations of Cl(-) and Br(-), modifications of LDL by MPO resembled those seen in the presence of Br(-) alone. Interestingly, even at physiological concentrations of the two halides (100 mM Cl(-), 100 microM Br(-)), MPO utilized a portion of the Br(-) to oxidize apoB cysteine residues. MPO also utilized the pseudohalide thiocyanate to oxidize apoB cysteine residues. Our data show that even though HOBr has different reactivities than HOCl with apoB, it is able to alter the charge of LDL, converting it into a potentially atherogenic particle.

Ldl modified by hypochlorous acid is a potent inhibitor of lecithin-cholesterol acyltransferase activity

Modification of low density lipoprotein (LDL) by myeloperoxidase-generated HOCl has been implicated in human atherosclerosis. Incubation of LDL with HOCl generates several reactive intermediates, primarily N-chloramines, which may react with other biomolecules. In this study, we investigated the effects of HOCl-modified LDL on the activity of lecithin-cholesterol acyltransferase (LCAT), an enzyme essential for high density lipoprotein maturation and the antiatherogenic reverse cholesterol transport pathway. We exposed human LDL (0.5 mg protein/mL) to physiological concentrations of HOCl (25 to 200 micromol/L) and characterized the resulting LDL modifications to apolipoprotein B and lipids; the modified LDL was subsequently incubated with apolipoprotein B-depleted plasma (density >1.063 g/mL fraction), which contains functional LCAT. Increasing concentrations of HOCl caused various modifications to LDL, primarily, loss of lysine residues and increases in N-chloramines and electrophoretic mobility, whereas lipid hydroperoxides were only minor products. LCAT activity was extremely sensitive to HOCl-modified LDL and was reduced by 23% and 93% by LDL preincubated with 25 and 100 micromol/L HOCl, respectively. Addition of 200 micromol/L ascorbate or N-acetyl derivatives of cysteine or methionine completely prevented LCAT inactivation by LDL preincubated with </=200 micromol/L HOCl. Protecting the free thiol groups of LCAT with 5,5'-dithio-bis-(2-nitrobenzoic acid) before exposure to HOCl-modified LDL, which inhibits lipid hydroperoxide-mediated inactivation of LCAT, failed to prevent the loss of enzyme activity. Our data indicate that N-chloramines from HOCl-modified LDL mediate the loss of plasma LCAT activity and provide a novel mechanism by which myeloperoxidase-generated HOCl may promote atherogenesis.

Relative reactivities of N-chloramines and hypochlorous acid with human plasma constituents

Hypochlorous acid (HOCl), the major strong oxidant produced by the phagocyte enzyme myeloperoxidase, reacts readily with free amino groups to form N-chloramines. Since different N-chloramines have different stabilities and reactivities depending on their structures, we investigated the relative reactivities of three model N-chloramines and HOCl with human plasma constituents. TheN-chloramines studied were N(alpha)-acetyl-lysine chloramine (LysCA, a model of protein-associated N-chloramines), taurine chloramine (TaurCA, the primary N-chloramine produced by activated neutrophils), and monochloramine (MonoCA, a lipophilic N-chloramine). Addition of these chlorine species (100--1000 microM each) to plasma resulted in rapid loss of thiols, with the extent of thiol oxidation decreasing in the order TaurCA = LysCA > MonoCA = HOCl. The single reduced thiol of albumin was the major target. Loss of plasma ascorbate also occurred, with the extent decreasing in the order HOCl > LysCA > TaurCA > MonoCA. Experiments comparing equimolar albumin thiols and ascorbate showed that while HOCl caused equivalent loss of thiols and ascorbate, theN-chloramines reacted preferentially with thiols. The chlorine species also inactivated alpha(1)-antiproteinase, implicating oxidation of methionine residues, and ascorbate provided variable protection depending on the chlorine species involved. Together, our data indicate that in biological fluids N-chloramines react more readily with protein thiols than with methionine residues or ascorbate, and thus may cause biologically relevant, selective loss of thiol groups.

The nitric oxide congener nitrite inhibits myeloperoxidase/H2O2/ Cl- -mediated modification of low density lipoprotein

Nitric oxide, a pivotal molecule in vascular homeostasis, is converted under aerobic conditions to nitrite. Recent studies have shown that myeloperoxidase (MPO), an abundant heme protein released by activated leukocytes, can oxidize nitrite (NO(2-)) to a radical species, most likely nitrogen dioxide. Furthermore, hypochlorous acid (HOCl), the major strong oxidant generated by MPO in the presence of physiological concentrations of chloride ions, can also react with nitrite, forming the reactive intermediate nitryl chloride. Since MPO and MPO-derived HOCl, as well as reactive nitrogen species, have been implicated in the pathogenesis of atherosclerosis through oxidative modification of low density lipoprotein (LDL), we investigated the effects of physiological concentrations of nitrite (12.5-200 microm) on MPO-mediated modification of LDL in the absence and presence of physiological chloride concentrations. Interestingly, nitrite concentrations as low as 12.5 and 25 microm significantly decreased MPO/H2O2)/Cl- -induced modification of apoB lysine residues, formation of N-chloramines, and increases in the relative electrophoretic mobility of LDL. In contrast, none of these markers of LDL atherogenic modification were affected by the MPO/H2O2/NO2-) system. Furthermore, experiments using ascorbate (12.5-200 microm) and the tyrosine analogue 4-hydroxyphenylacetic acid (12.5-200 microm), which are both substrates of MPO, indicated that nitrite inhibits MPO-mediated LDL modifications by trapping the enzyme in its inactive compound II form. These data offer a novel mechanism for a potential antiatherogenic effect of the nitric oxide congener nitrite.

Myeloperoxidase binds to low-density lipoprotein: potential implications for atherosclerosis

Myeloperoxidase (MPO), an abundant heme enzyme released by activated phagocytes, catalyzes the formation of a number of reactive species that can modify low-density lipoprotein (LDL) to a form that converts macrophages into lipid-laden or 'foam' cells, the hallmark of atherosclerotic lesions. Since MPO has been shown to bind to a number of different cell types, we investigated binding of MPO to LDL. Using the precipitation reagents phosphotungstate or isopropanol, MPO co-precipitated with LDL, retaining its catalytic activity. The association of MPO with LDL was confirmed using native gel electrophoresis. MPO was also found to co-precipitate with apolipoprotein B-100-containing lipoproteins in whole plasma. No precipitation of MPO was observed in lipoprotein-deficient plasma, and there was a dose-dependent increase in precipitation following addition of LDL to lipoprotein-deficient plasma. Binding of MPO to LDL could potentially enhance site-directed oxidation of the lipoprotein and limit scavenging of reactive oxygen species by antioxidants.

Vitamin C suppresses oxidative lipid damage in vivo, even in the presence of iron overload

Ascorbate is a strong antioxidant; however, it can also act as a prooxidant in vitro by reducing transition metals. To investigate the in vivo relevance of this prooxidant activity, we performed a study using guinea pigs fed high or low ascorbate doses with or without prior loading with iron dextran. Iron-loaded animals gained less weight and exhibited increased plasma beta-N-acetyl-D-glucosaminidase activity, a marker of tissue lysosomal membrane damage, compared with control animals. The iron-loaded animals fed the low ascorbate dose had decreased plasma alpha-tocopherol levels and increased plasma levels of triglycerides and F(2)-isoprostanes, specific and sensitive markers of in vivo lipid peroxidation. In contrast, the two groups of animals fed the high ascorbate dose had significantly lower hepatic F(2)-isoprostane levels than the groups fed the low ascorbate dose, irrespective of iron load. These data indicate that 1) ascorbate acts as an antioxidant toward lipids in vivo, even in the presence of iron overload; 2) iron loading per se does not cause oxidative lipid damage but is associated with growth retardation and tissue damage, both of which are not affected by vitamin C; and 3) the combination of iron loading with a low ascorbate status causes additional pathophysiological changes, in particular, increased plasma triglycerides.

Potential antiatherogenic mechanisms of ascorbate (vitamin C) and alpha-tocopherol (vitamin E)

The premise that oxidative stress, among several other factors, plays an important role in atherogenesis implies that the development and progression of atherosclerosis can be inhibited by antioxidants. In this minireview we discuss several mechanisms by which the antioxidants ascorbate (vitamin C) and alpha-tocopherol (vitamin E) may protect against atherosclerosis. These mechanisms include inhibition of LDL oxidation and inhibition of leukocyte adhesion to the endothelium and vascular endothelial dysfunction. Overall, ascorbate appears to be more effective than alpha-tocopherol in mitigating these pathophysiological processes, most likely as a result of its abilities to effectively scavenge a wide range of reactive oxygen and nitrogen species and to regenerate alpha-tocopherol, and possibly tetrahydrobiopterin, from its radical species. In contrast, alpha-tocopherol can act either as an antioxidant or a pro-oxidant to inhibit or facilitate, respectively, lipid peroxidation in LDL. However, this pro-oxidant activity of alpha-tocopherol is prevented by ascorbate acting as a coantioxidant. Therefore, an optimum vitamin C intake or body status may help protect against atherosclerosis and its clinical sequelae, whereas vitamin E may only be effective in combination with vitamin C.

Oxidation of LDL by myeloperoxidase and reactive nitrogen species: reaction pathways and antioxidant protection

Oxidative modification of low density lipoprotein (LDL) appears to play an important role in atherogenesis. Although the precise mechanisms of LDL oxidation in vivo are unknown, several lines of evidence implicate myeloperoxidase and reactive nitrogen species, in addition to ceruloplasmin and 15-lipoxygenase. Myeloperoxidase generates a number of reactive species, including hypochlorous acid, chloramines, tyrosyl radicals, and nitrogen dioxide. These reactive species oxidize the protein, lipid, and antioxidant components of LDL. Modification of apolipoprotein B results in enhanced uptake of LDL by macrophages with subsequent formation of lipid-laden foam cells. Nitric oxide synthases produce nitric oxide and, under certain conditions, superoxide radicals. Numerous other sources of superoxide radicals have been identified in the arterial wall, including NAD(P)H oxidases and xanthine oxidase. Nitric oxide and superoxide readily combine to form peroxynitrite, a reactive nitrogen species capable of modifying LDL. In this review, we examine the reaction pathways involved in LDL oxidation by myeloperoxidase and reactive nitrogen species and the potential protective effects of the antioxidant vitamins C and E.

Vitamin C protects against and reverses specific hypochlorous acid- and chloramine-dependent modifications of low-density lipoprotein

Activated phagocytes produce the highly reactive oxidant hypochlorous acid (HOCl) via the myeloperoxidase-catalysed reaction of hydrogen peroxide with chloride ions. HOCl reacts readily with a number of susceptible targets on apolipoprotein B-100 of low-density lipoprotein (LDL), resulting in uncontrolled uptake of HOCl-modified LDL by macrophages. We have investigated the effects of vitamin C (ascorbate), an effective water-soluble antioxidant, on the HOCl- and chloramine-dependent modification of LDL. Co-incubation of vitamin C (25-200 microM) with LDL resulted in concentration-dependent protection against HOCl (25-200 microM)-mediated oxidation of tryptophan and lysine residues, formation of chloramines and increases in the relative electrophoretic mobility of LDL. Vitamin C also partially protected against oxidation of cysteine residues by HOCl, and fully protected against oxidation of these residues by the low-molecular-mass chloramines, N(alpha)-acetyl-lysine chloramine and taurine chloramine, and to a lesser extent monochloramine (each at 25-200 microM). Further, we found that HOCl (25-200 microM)-dependent formation of chloramines on apolipoprotein B-100 was fully reversed by 200 microM vitamin C; however, the loss of lysine residues and increase in relative electrophoretic mobility of LDL were only partially reversed, and the loss of tryptophan and cysteine residues was not reversed. Time-course experiments showed that the reversal by vitamin C of HOCl-dependent modifications became less efficient as the LDL was incubated for up to 4 h at 37 degrees C. These data show that vitamin C not only protects against, but also reverses, specific HOCl- and chloramine-dependent modifications of LDL. As HOCl-mediated LDL modifications have been strongly implicated in the pathogenesis of atherosclerosis, our data indicate that vitamin C could contribute to the anti-atherogenic defence against HOCl.

Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans

The current recommended dietary allowance (RDA) for vitamin C for adult nonsmoking men and women is 60 mg/d, which is based on a mean requirement of 46 mg/d to prevent the deficiency disease scurvy. However, recent scientific evidence indicates that an increased intake of vitamin C is associated with a reduced risk of chronic diseases such as cancer, cardiovascular disease, and cataract, probably through antioxidant mechanisms. It is likely that the amount of vitamin C required to prevent scurvy is not sufficient to optimally protect against these diseases. Because the RDA is defined as "the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all healthy individuals in a group," it is appropriate to reevaluate the RDA for vitamin C. Therefore, we reviewed the biochemical, clinical, and epidemiologic evidence to date for a role of vitamin C in chronic disease prevention. The totality of the reviewed data suggests that an intake of 90-100 mg vitamin C/d is required for optimum reduction of chronic disease risk in nonsmoking men and women. This amount is about twice the amount on which the current RDA for vitamin C is based, suggesting a new RDA of 120 mg vitamin C/d.

Increased prevalence of antithyroid antibodies identified in women with recurrent pregnancy loss but not in women undergoing assisted reproduction

OBJECTIVE

To assess the prevalence of antibodies to thyroglobulin and thyroid peroxidase (or microsomal) in women with recurrent pregnancy loss and women undergoing assisted reproductive techniques (ART) compared with healthy controls.

DESIGN

Retrospective, two-centered study.

SETTING

University-affiliated private patient centers.

PATIENT(S)

Included were 700 women with a history of two or more consecutive pregnancy losses, 688 women with a history of infertility who were undergoing ART, and 200 healthy, reproductive-aged female controls.

INTERVENTION(S)

Blood was collected before ART cycles, frozen, and assayed.

MAIN OUTCOME MEASURE(S)

Standardized ELISAs were used to measure antithyroid antibodies and TSH levels. Statistical analysis was performed with use of the two-tailed Fisher's exact test.

RESULT(S)

Antithyroid antibodies were identified in 29 of 200 (14.5%) of controls and 158 of 700 (22.5%) of women with recurrent pregnancy loss and 132 of 688 (19.2%) of women undergoing ART. Less than 20% of the women with antithyroid antibodies were clinically hypothyroid.

CONCLUSION(S)

Antithyroid antibodies are identified more frequently in women with recurrent pregnancy loss than in controls but not in women undergoing ART. These autoantibodies may be markers of autoimmune activation and have been associated with an increased risk of pregnancy loss and postpartum thyroid disease.

Differential reactivities of hypochlorous and hypobromous acids with purified Escherichia coli phospholipid: formation of haloamines and halohydrins

Hypochlorous (HOCl) and hypobromous (HOBr) acids are strong oxidants derived from myeloperoxidase and eosinophil peroxidase, the major antimicrobial enzymes of neutrophils and eosinophils, respectively. These oxidants are highly reactive with a wide range of biomolecules. At physiological pH, both HOCl and HOBr react readily with amines to form haloamines and with the unsaturated bonds of fatty acids to form halohydrins. We have investigated which of these reactions occur with phosphatidylethanolamine (PE), the predominant phospholipid of Escherichia coli. The formation of haloamines was determined by TLC and colorimetrically and the formation of halohydrins was determined by TLC and GC-MS. With HOCl, chloramines were much the preferred product and chlorohydrins were formed in substantial amounts only when HOCl was in excess of the amount required to convert the amine to the dichloramine. With HOBr at all concentrations, bromamines and bromohydrins were formed concurrently, indicating a greater relative reactivity with unsaturated fatty acids than with HOCl. The bromamine derivatives of PE, and other primary amines, were found to be more reactive than the equivalent chloramines, and were able to brominate the unsaturated bonds of fatty acids. Bromohydrins (formed directly or through the action of bromamines) may, therefore, be suitable biomarkers for the production of HOBr in vivo.

Comparison of human red cell lysis by hypochlorous and hypobromous acids: insights into the mechanism of lysis

Human red blood cells are lysed by the neutrophil-derived oxidant hypochlorous acid (HOCl), although the mechanism of lysis is unknown. Hypobromous acid (HOBr), a similarly reactive oxidant, lysed red cells approx. 10-fold faster than HOCl. Therefore we compared the effects of these oxidants on thiols, membrane lipids and proteins to determine which reactions are associated with lysis. There was no difference in the loss of reduced glutathione or membrane thiols with either oxidant, but HOBr reacted more readily with membrane lipids and proteins. Bromohydrin derivatives of phospholipids and cholesterol were seen at approx. one-tenth the level of oxidant than chlorohydrins were. However, these products were detected only with high concentrations of HOCl or HOBr, which caused instant haemolysis. Membrane protein modification occurred at much lower doses of oxidant and was more closely correlated with lysis. SDS/PAGE analysis showed that band 3, the anion transport protein, was lost at the lowest dose of HOBr and at the higher concentrations of HOCl. Labelling the red cells with eosin 5-maleimide, a fluorescent label for band 3, suggested possible clustering of this protein in oxidant-exposed cells. There was also irreversible cross-linking of all the major membrane proteins; this reaction occurred more readily with HOBr. The results indicate that membrane protein modification is the reaction responsible for HOCl-mediated lysis. These effects, and particularly cross-link formation, might result in clustering of band 3 and other membrane and cytoskeletal proteins to form haemolytic pores.

Modification of red cell membrane lipids by hypochlorous acid and haemolysis by preformed lipid chlorohydrins

Hypochlorous acid (HOCl), a strong oxidant generated by the myeloperoxidase system of neutrophils and monocytes, has been implicated in inflammatory tissue damage by these cells. Reaction of HOCl with the double bonds of unsaturated lipids produces alpha, beta-chlorohydrin isomers. We have exposed red cell membranes to HOCl and used thin layer chromatography (TLC) of the extracted lipids and enzyme-linked immunosorbent assay (ELISA), using an antichlorohydrin monoclonal antibody, to show that fatty acyl chlorohydrins are formed. The ELISA was approximately 25 fold more sensitive than TLC, and chlorohydrins were detected when membranes from 10(6) cells were treated with > or = 0.16 nmoles HOCl. Lipid chlorohydrins are more polar and bulky than their parent lipids and as such could affect membrane stability and function. To determine the effect of incorporation of lipid chlorohydrins into cell membranes, preformed fatty acid and cholesterol chlorohydrins were incubated with red cells. Lysis was measured as release of haemoglobin and incorporation of lipids was determined by 14C scintillation counting. Addition of HOCl-treated oleic acid to red cells resulted in rapid lysis of a fraction of the cells in a concentration dependent manner. HOCl-treated cholesterol also caused a small amount of cell lysis that was predominantly due to chlorohydrin 3, one of the three major cholesterol chlorohydrin products. Chlorohydrin 3, which has a decreased planarity and polarity, was also primarily responsible for altering the critical micelle concentration of HOCl-treated cholesterol-containing liposomes.

Oxidation of neutrophil glutathione and protein thiols by myeloperoxidase-derived hypochlorous acid

Neutrophils, when stimulated, generate reactive oxygen species including myeloperoxidase-derived HOCl. There is an associated decrease in reduced glutathione (GSH) concentration. We have shown that neutrophil GSH levels decrease on exposure to reagent HOCl, whereas the equivalent concentration of H2O2 had no effect. GSH loss occurred without cell lysis, was not reversible, and was accompanied by the loss of an equivalent proportion of the total protein thiols. No glutathione disulphide was formed. Studies with 35S-labelled cells indicated that much of the GSH lost was accounted for by mixed disulphides with protein and a product that co-migrated on HPLC with a novel compound formed in the reaction of HOCl and pure GSH. The properties of this compound are consistent with an intramolecular sulphonamide. Neutrophils stimulated with PMA lost 30-40% of their GSH and a similar proportion of protein thiols. Little glutathione disulphide was formed and the products were the same as seen with HOCl-treated cells. From the results and studies with inhibitors and scavengers, we conclude that HOCl was responsible for the GSH loss. Propargylglycine and buthionine sulphoximine, inhibitors of glutathione synthesis, enhanced GSH loss, but their effects were due to the production of long-lived chloramines that oxidized GSH with greater efficiency than HOCl, rather than to the inhibition of GSH synthesis. The lack of thiol selectivity by HOCl and irreversibility of oxidation means that GSH will provide limited antioxidant protection for thiol enzymes in stimulated neutrophils.

Nuclear magnetic resonance characterization of 6 alpha-chloro-5 beta-cholestane-3 beta,5-diol formed from the reaction of hypochlorous acid with cholesterol

Hypochlorous acid generated by neutrophil myeloperoxidase has been shown to convert cholesterol into three different chlorohydrin isomers which previously had not been fully characterized. We have reacted hypochlorous acid with cholesterol/1,2-dipalmitoyl phosphatidylcholine liposomes to give these three major products and established that they are 6 beta-chloro-5 alpha-cholestane-3 beta,5-diol (chlorohydrin 1), 5 alpha-chloro-6 beta-cholestane-3,6-diol (chlorohydrin 2) and 6 alpha-chloro-5 beta-cholestane-3 beta,5-diol (chlorohydrin 3). These products were separated by thin-layer chromatography and fully characterized by 1H, 13C, attached proton test, doublequantum correlation spectroscopy, total correlation spectroscopy, heteronuclear multiple bond correlation and heteronuclear multiple quantum coherence nuclear magnetic resonance spectroscopy.

Chlorination of cholesterol in cell membranes by hypochlorous acid

Neutrophils and monocytes produce the highly cytotoxic hypochlorous acid (HOCl) via the myeloperoxidase (MPO)-catalyzed reaction of H2O2 with Cl-. We have investigated the reaction of reagent and MPO-derived HOCl with cholesterol in a purified liposome system, as well as progressively more complex biological systems. The products were identified by thin-layer chromatography (TLC) and characterized by mass spectrometry (MS). TLC of the HOCl-treated samples gave four major cholesterol products with color development typical of oxysterols. Two of the products coeluted with authentic alpha- and beta-chlorohydrin standards. As was the case with the standards, they were readily converted into their respective epoxides during analysis by MS. Gas chromatography-mass spectrometry analysis of the other major product (band 3) gave peaks consistent with epoxides as well as a lateeluting peak with a distinct mass spectrum. Electrospray MS of this product confirmed its identity as a chlorohydrin based on the presence of the predicted molecular ion and 3:1 Cl isotope ratios. Lipids extracted from red cells and isolated red cell membranes were exposed to HOCl and gave identical products to the purified cholesterol liposome system as determined by TLC and MS. Higher concentrations of HOCl were required due to competition by other unsaturated lipids and protein molecules. When intact red cells, neutrophils, and MCF7 mammary carcinoma cells were exposed to HOCl, cholesterol chlorohydrins were formed, as detected by TLC. The formation of cholesterol chlorohydrins could be potentially disruptive to cell membranes and result in cell lysis and death. They could also be potential biomarkers for oxidative damage associated with neutrophil/monocyte activation.

Peroxidase-mediated bromination of unsaturated fatty acids to form bromohydrins

Eosinophil peroxidase and myeloperoxidase (MPO) catalyze the oxidation of bromide by hydrogen peroxide to produce hypobromous acid (HOBr). Hypochlorous acid, which is also generated by MPO, reacts with unsaturated fatty acids to form chlorohydrins. In this study the equivalent reaction of HOBr, produced from MPO, bromide, and hydrogen peroxide, with oleic (18:1), linoleic (18:2), and arachidonic (20:4) acids has been investigated. Thin-layer chromatography detected one major product of higher polarity than the unmodified fatty acids and additional more polar products with the polyunsaturated fatty acids. Similar results were observed with N-bromosuccinimide-derived HOBr. Gas chromatography-mass spectrometry (GC-MS) and electrospray MS identified the major products of 18:1 as the isomeric 9,10-bromohydrins based on retention time and mass spectrometric isotope and fragmentation patterns. The products of 18:2 and 20:4 were too unstable for analysis by GC-MS. Electrospray MS identified the mono- and bisbromohydrins formed from 18:2 and 20:4 based on mass/charge ratios of the molecular ions and the presence of bromine isotope patterns. Other oxidation products not containing bromine, such as dihydroxy derivatives, were detected as well. Fatty acid bromohydrins could contribute to the antimicrobial activity and inflammatory tissue damage by eosinophils and neutrophils, and could potentially be useful specific markers for HOBr production in vivo.

Vitamin A and E status in very low birth weight infants: development of an improved parenteral delivery system

Plasma vitamin A and E levels were inadequate in very low birth weight infants receiving a continuous infusion of a parenteral multivitamin preparation, 1.5 ml/kg per day, in dextrose-amino acid solution. A new delivery system using 2 ml/kg per day, infused for 6 hours from the first day of life, avoided loss during infusion and significantly improved plasma vitamin A and E levels during the first 28 days of life in very low birth weight infants.

Free radical inactivation of rabbit muscle creatinine kinase: catalysis by physiological and hydrolyzed ICRF-187 (ICRF-198) iron chelates

Creatine kinase is a sulfhydryl containing enzyme that is particularly susceptible to oxidative inactivation. This enzyme is potentially vulnerable to inactivation under conditions when it would be used as a diagnostic marker of tissue damage such as during cardiac ischemia/reperfusion or other oxidative tissue injury. Oxidative stress in tissues can induce the release of iron from its storage proteins, making it an available catalyst for free radical reactions. Although creatinine kinase inactivation in a heart reperfusion model has been documented, the mechanism has not been fully described, particularly with regard to the role of iron. We have investigated the inactivation of rabbit muscle creatine kinase by hydrogen peroxide and by xanthine oxidase generated superoxide or Adriamycin radicals in the presence of iron catalysts. As shown previously, creatine kinase was inactivated by hydrogen peroxide. Ferrous iron enhanced the inactivation. In addition, micromolar levels of iron and iron chelates that were reduced and recycled by superoxide or Adriamycin radicals were effective catalysts of creatinine kinase inactivation. Of the physiological iron chelates studied, Fe(ATP) was an especially effective catalyst of inactivation by what appeared to be a site-localized reaction. Fe(ICRF-198), a non-physiological chelate of interest because of its putative role in alleviating Adriamycin-induced cardiotoxicity, also catalyzed the inactivation. Scavenger studies implicated hydroxyl radical as the oxidant involved in iron-dependent creatine kinase inactivation. Loss of protein thiols accompanied loss of creatine kinase activity. Reduced glutathione (GSH) provided marked protection from oxidative inactivation, suggesting that enzyme inactivation under physiological conditions would occur only after GSH depletion.

Assays using horseradish peroxidase and phenolic substrates require superoxide dismutase for accurate determination of hydrogen peroxide production by neutrophils

We used horseradish peroxidase and either scopoletin, homovanillic acid, or phenol red to measure hydrogen peroxide generated by human neutrophils. With these assays, superoxide dismutase significantly increased the amount of hydrogen peroxide detected. In contrast, it had no effect when the accumulation of hydrogen peroxide was measured with a hydrogen peroxide electrode. We propose that superoxide interferes with horseradish peroxidase-dependent assays so that hydrogen peroxide is underestimated. Thus, when using these assays, superoxide dismutase must be added to neutrophils to ensure that all the hydrogen peroxide they produce is detected.

Myeloperoxidase-dependent loss of malondialdehyde: a limitation for detecting neutrophil-mediated lipid peroxidation

Lipid peroxidation is commonly measured using the thiobarbituric acid (TBA) assay. We have examined how this assay is affected by hypochlorite, which is generated by the neutrophil enzyme myeloperoxidase. The TBA reactivity of phospholipid liposomes that had been partially peroxidized with iron/ascorbate was destroyed by low concentrations of sodium hypochlorite. Since most of the TBA reactivity in peroxidized liposomes is due to malondialdehyde, its reactivity was investigated. Addition of sodium hypochlorite destroyed the uv absorbance of malondialdehyde with a 2:1 stoichiometry and eliminated its TBA reactivity. The TBA reactivity of malondialdehyde and peroxidized liposomes was also lost after treatment with myeloperoxidase. The reaction with myeloperoxidase required chloride and was inhibited by catalase and methionine, indicating the involvement of hypochlorite. Neutrophils stimulated with phorbol myristate acetate or N-formyl-methionyl-leucyl-phenylalanine destroyed the TBA reactivity of malondialdehyde and peroxidized liposomes by a hypochlorite-dependent mechanism. The ability of hypochlorite to break down malondialdehyde explains why lipid peroxidation by stimulated neutrophils, as measured with TBA, is apparently inhibited by myeloperoxidase. Myeloperoxidase may not, however, inhibit the peroxidation process. The TBA assay and other assays of malondialdehyde may be of limited value, therefore, for assessing lipid peroxidation in systems where neutrophils or myeloperoxidase are involved.

Treatment-resistant depression: a survey of practice habits of Canadian psychiatrists

Treatment-resistant depression is a fascinating yet poorly defined condition. The various management strategies in use are a source of controversy. The objective of this survey was to determine how Canadian psychiatrists treat patients with "intractable depression." This information may be used to plan future research into the management of treatment-resistant depression. It may also provide information about the practices of Canadian psychiatrists and help direct residency training. Confidential questionnaires were mailed to all psychiatrists residing in Canada registered with the Canadian Psychiatric Association. Respondents indicated that 12.4% of their depressed patients were "resistant to treatment." Respondents were asked to rank a list of treatment choices in the order they would use them to treat patients with treatment-resistant depression. Ninety-five point eight percent of respondents used tricyclics as the first treatment of choice. Almost equal portions of respondents chose a second tricyclic, a monoamine oxidase inhibitor (MAOI) or a combination of lithium and tricyclics as their treatment of second choice.

Assessment of adult relatedness: a review of empirical findings from object relations and attachment theories

Assessment techniques designed to measure adult behavior and mental representation that emphasize relatedness constructs are reviewed. These measures grow out of two traditions, object relations and attachment theories. Although these two paradigms are fairly well elucidated theoretically, the relevant assessment literature is only more recently expanding, especially that focusing directly on adult attachment as opposed to childhood attachment. In addition to a presentation of various projective and objective measures, this review highlights the clinical and research implications for integration of these two paradigms around the cognitive, affective, and behavioral vicissitudes of adult relatedness.

Reaction time impairment in schizophrenia and affective illness: the role of attention

A young but chronic group of schizophrenic and affective disorders patients was tested for simple reaction time (RT) and RT while engaged in a concurrent task. The affective disorders patients were subdivided by the presence of psychotic features. The results show that extreme slowing of RT is due to psychoticism and is not characteristic of nonpsychotic affective illness. Extreme intrasubject variability, however, was specific to schizophrenia, and may be a trait marker of the disorder.

Computer-supervised exposure treatment for phobias

Twenty phobic outpatients were treated by 9 weekly "interviews" at the console of a desk computer. Using a conversational style and multiple choice questions, the computer assessed the symptoms and agreed a hierarchy of self-exposure tasks. Each week the patient was given a diary sheet of tasks to practise daily. At his next visit his progress and motivation were assessed, and if he was succeeding he was encouraged to accept progressively more difficult tasks. This group was compared with a group of 20 patients (matched for age, sex and type of phobia) treated conventionally by a therapist in the preceding year. Progress was measured on standardized scales (both self- and clinician-rated). The two groups showed significant improvement on all the scales, and 75-80% of each group were much improved (scores reduced by 50%). The therapist treated group tended to be more severely ill at entry and to show greater improvement during treatment. Improvement was maintained at 6 month follow-up in both groups.

Therapist contact and outcome of self-exposure treatment for phobias. A controlled study

Eighty-four chronic phobic patients were randomly assigned to self-exposure in vivo instructed by either a psychiatrist, a computer or a book; mean therapy time per patient was respectively 3.1, 3.2 and 0 hours. Seventy-one patients completed treatment. All three groups improved substantially and similarly to 6 months follow-up, with no significant difference between them; self-exposure treatment was effective even without therapist contact. Among the three groups, initial expectation of help and positive attitude to the psychiatrist were equally high and related to subsequent rating of help received. All three groups rated the psychiatrist as more tolerant, reliable, and understanding than the computer or book, but these attitudes did not relate to outcome, were initially similar among all three groups, and changed minimally at 6 months follow-up.

Borderline Defenses and Rorschach Responses: A Critique of Lerner, Albert, and Walsh

Collapsing DSM-III schizotypal and borderline groups to form a borderline population is unwarranted when the results are then related to borderline personality organization. In a comparison of overlapping scoring systems for inferring defensive operations, Lerner, Albert, and Walsh intertwine fact and theory extravagantly and are not justified by their chosen populations nor their assumptions about the theories involved.

Automated cognitive assessment of elderly patients: a comparison of two types of response device

Groups of 14 cognitively impaired elderly people were tested on two automated cognitive tests on several occasions. Patients registered their responses using either a touch-sensitive screen or a board with illuminated response buttons. The results indicate that the touch-sensitive screen is probably a more suitable response device than the button-board. Suggestions that it would prove disadvantageous to elderly patients were not supported, and its continued use is recommended.

Comparison of computerised self-rating scales for depression with conventional observer ratings

Highly significant correlations are demonstrated between a microcomputer-delivered self-rating Hamilton Rating Scale and conventional Observer Hamilton Rating Scales. These results demonstrate that self-rating using a microcomputer can provide a clinically useful tool in assessing the severity of depressive illness and monitoring progress with treatment.

Content interpretation re: Salley and Teiling's "Dissociated rage attacks in a Vietnam veteran: a Rorschach study"

Not necessarily belying usual symbolic interpretation of Rorschach content, Rorschach responses may represent a concrete experience reflecting a traumatic incident in the patient's past. This possibility should be considered particularly when the response in any way suggests undue preoccupation with the integrity of the body.

Controlled Study of Self-Exposure Treatment for Phobics: Preliminary Communication

Patients with phobic disorder (mainly agoraphobics) of minimum one year duration were treated by self-administered exposure in vivo treatment. Seventyone patients were randomly assigned to one of three groups: (A) book-instructed, (B) computer-instructed, or (C) therapist-instructed. All three groups improved significantly to a similar extent on various phobic measures at the end of the treatment and maintained their treatment gains at 6-month follow up. Mean clinicians' time spent with each patient was 40 minutes, 4.2 hours and 3.2 hours in group A, B and C respectively. Similar small numbers of patients defaulted from each group.

The WAIS and Rorschach test in diagnosing borderline personality

This study assesses the degree to which indicators from the Rorschach and the WAIS discriminate between the two groups of psychiatric inpatients diagnosed as having either borderline or psychotic personality organization by means of Kernberg's structural interview. A combination of WAIS scores focusing on the Picture Completion subtest, and Rorschach form level proved to be discriminators. These were interpreted as primarily reflecting reality testing. A linear combination of WAIS scale scores was identified that discriminated at least as well as the clinical WAIS-Rorschach comparisons.

DSM-III and structural diagnosis of borderline patients

This study compared diagnoses arrived at through a structural interview developed by Kernberg which assesses levels of personality organization with those arrived at using DSM-III criteria of signs and symptoms among a group of hospitalized patients. Complete agreement was reached in 61 percent of the cases. Among the cases in which there was disagreement, 39 percent could nevertheless be considered to be compatible within the two systems, while the remaining cases were not. Discussion is directed to the different facets of clinical material addressed with each of these two diagnostic approaches, their discrepancies, and the underlying relationship between the two systems.