Free radical recycling and intramembrane mobility in the antioxidant properties of alpha-tocopherol and alpha-tocotrienol

d-Alpha-tocopherol (2R,4'R,8'R-Alpha-tocopherol) and d-alpha-tocotrienol are two vitamin E constituents having the same aromatic chromanol "head" but differing in their hydrocarbon "tail": tocopherol with a saturated and toctrienol with an unsaturated isoprenoid chain. d-Alpha-tocopherol has the highest vitamin E activity, while d-alpha-tocotrienol manifests only about 30% of this activity. Since vitamin E is considered to be physiologically the most important lipid-soluble chain-breaking antioxidant of membranes, we studied alpha-tocotrienol as compared to alpha-tocopherol under conditions which are important for their antioxidant function. d-Alpha-tocotrienol possesses 40-60 times higher antioxidant activity against (Fe2+ + ascorbate)- and (Fe2+ + NADPH)-induced lipid peroxidation in rat liver microsomal membranes and 6.5 times better protection of cytochrome P-450 against oxidative damage than d-alpha-tocopherol. To clarify the mechanisms responsible for the much higher antioxidant potency of d-alpha-tocotrienol compared to d-alpha-tocopherol, ESR studies were performed of recycling efficiency of the chromanols from their chromanoxyl radicals. 1H-NMR measurements of lipid molecular mobility in liposomes containing chromanols, and fluorescence measurements which reveal the uniformity of distribution (clusterizations) of chromanols in the lipid bilayer. From the results, we concluded that this higher antioxidant potency of d-alpha-tocotrienol is due to the combined effects of three properties exhibited by d-alpha-tocotrienol as compared to d-alpha-tocopherol: (i) its higher recycling efficiency from chromanoxyl radicals, (ii) its more uniform distribution in membrane bilayer, and (iii) its stronger disordering of membrane lipids which makes interaction of chromanols with lipid radicals more efficient. The data presented show that there is a considerable discrepancy between the relative in vitro antioxidant activity of d-alpha-tocopherol and d-alpha-tocotrienol with the conventional bioassays of their vitamin activity.

Enzymic and non-enzymic antioxidants in epidermis and dermis of human skin

We measured enzymic and non-enzymic antioxidants in human epidermis and dermis from six healthy volunteers undergoing surgical procedures. Epidermis was separated from dermis by curettage and antioxidants were measured by high-performance liquid chromatography (HPLC) or standard spectrophotometric methods. The concentration of every antioxidant (referenced to skin wet weight) was higher in the epidermis than in the dermis. Among the enzymic antioxidants, the activities of superoxide dismutase, glutathione peroxidase, and glutathione reductase were higher in the epidermis compared to the dermis by 126, 61 and 215%, respectively. Catalase activity in particular was much higher (720%) in the epidermis. Glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase, which provide reduced nicotinamide adenine dinucleotide phosphate (NADPH), also showed higher activity in the epidermis than the dermis by 111% and 313%, respectively. Among the lipophilic antioxidants, the concentration of alpha-tocopherol was higher in the epidermis than the dermis by 90%. The concentration of ubiquinol 10 was especially higher in the epidermis, by 900%. Among the hydrophilic antioxidants, concentrations of ascorbic acid and uric acid were also higher in the epidermis than in the dermis by 425 and 488%, respectively. Reduced glutathione and total glutathione were higher in the epidermis than in the dermis by 513 and 471%. Thus the antioxidant capacity of the human epidermis is far greater than that of dermis. As the epidermis composes the outermost 10% of the skin and acts as the initial barrier to oxidant assault, it is perhaps not surprising that it has higher levels of antioxidants.

Mitochondrial respiratory chain-dependent generation of superoxide anion and its release into the intermembrane space

It has been generally accepted that superoxide anion generated by the mitochondrial respiratory transport chain are vectorially released into the mitochondrial matrix, where they are converted to hydrogen peroxide through the catalytic action of Mn-superoxide dismutase. Release of superoxide anion into the intermembrane space is a controversial topic, partly unresolved by the reaction of superoxide anion with cytochrome c, which faces the intermembrane space and is present in this compartment at a high concentration. This study was aimed at assessing the topological site(s) of release of superoxide anion during respiratory chain activity. To address this issue, mitoplasts were prepared from isolated mitochondria by digitonin treatment to remove portions of the outer membrane along with portions of cytochrome c. EPR analysis in conjunction with spin traps of antimycin-supplemented mitoplasts revealed the formation of a spin adduct of superoxide anion. The EPR signal was (i) abrogated by superoxide dismutase, (ii) decreased competitively by exogenous ferricytochrome c and (iii) broadened by the membrane-impermeable spin-broadening agent chromium trioxalate. These results confirm the production and release of superoxide anion towards the cytosolic side of the inner mitochondrial membrane. In addition, co-treatment of mitoplasts with myxothiazol and antimycin A, resulting in an inhibition of the oxidation of ubiquinol to ubisemiquinone, abolished the EPR signal, thus suggesting that ubisemiquinone autoxidation at the outer site of the complex-III ubiquinone pool is a pathway for superoxide anion formation and subsequent release into the intermembrane space. The generation of superoxide anion towards the intermembrane space requires consideration of the mitochondrial steady-state values for superoxide anion and hydrogen peroxide, the decay pathways of these oxidants in this compartment and the implications of these processes for cytosolic events.

Lipoic acid increases de novo synthesis of cellular glutathione by improving cystine utilization

Lipoic acid (thiotic acid) is being used as a dietary supplement, and as a therapeutic agent, and is reported to have beneficial effects in disorders associated with oxidative stress, but its mechanism of action remains unclear. We present evidence that lipoic acid induces a substantial increase in cellular reduced glutathione in cultured human Jurkat T cells human erythrocytes, C6 glial cells, NB41A3 neuroblastoma cells, and peripheral blood lymphocytes. The effect depends on metabolic reduction of lipoic acid to dihydrolipoic acid. Dihydrolipoic acid is released into the culture medium where it reduces cystine. Cysteine thus formed is readily taken up by the neutral amino acid transport system and utilized for glutathione synthesis. By this mechanism lipoic acid enables cystine to bypass the xc- transport system, which is weakly expressed in lymphocytes and inhibited by glutamate. Thereby lipoic acid enables the key enzyme of glutathione synthesis, gamma-glutamylcysteine synthetase, which is regulated by uptake-limited cysteine supply, to work at optimum conditions. Flow cytometric analysis of freshly prepared human peripheral blood lymphocytes, using monobromobimane labeling of cellular thiols, reveals that lipoic acid acts mainly to normalize a subpopulation of cells severely compromised in thiol status rather than to increase thiol content beyond physiological levels. Hence lipoic acid may have clinical relevance in restoration of severely glutathione deficient cells.

Protective effects of idebenone and alpha-tocopherol on beta-amyloid-(1-42)-induced learning and memory deficits in rats: implication of oxidative stress in beta-amyloid-induced neurotoxicity in vivo

Amyloid beta-peptide (A beta), the major constituent of the senile plaques in the brains of patients with Alzheimer's disease, is cytotoxic to neurons and has a central role in the pathogenesis of the disease. Previous studies have suggested that oxidative stress is involved in the mechanisms of A beta-induced neurotoxicity in vitro. In the present study, we examined whether oxidative stress contributes to learning and memory deficits caused by continuous intracerebroventricular infusion of A beta-(1-42). In the A beta-(1-42)-infused rats, spontaneous alternation behaviour in a Y-maze and spatial memory in a water maze task were significantly impaired, as compared with A beta-(40-1)-infused control rats. The retention of passive avoidance learning was also significantly impaired by treatment with A beta-(1-42). Potent antioxidants idebenone and alpha-tocopherol prevented the behavioural deficits in Y-maze and water maze, but not passive avoidance, tasks in A beta-(1-42)-infused rats when they were repeatedly administered by mouth once a day from 3 days before the start of A beta infusion to the end of behavioural experiments. Lipid peroxide levels in the hippocampus and cerebral cortex of A beta-(1-42)-infused rats did not differ from those in control animals, and neither idebenone nor alpha-tocopherol affected the lipid peroxide levels. These results suggest that treatment with antioxidants such as idebenone and alpha-tocopherol prevents learning and memory deficits caused by A beta.

Dose-response effects of acute ultraviolet irradiation on antioxidants and molecular markers of oxidation in murine epidermis and dermis

There has not as yet been an integrated, comprehensive study of the responses of dermis and epidermis in vivo to a wide range of ultraviolet (UV) doses, encompassing all major antioxidants and a sensitive marker of oxidative damage. We have irradiated hairless mice with simulated solar light at doses of 2, 5, 12.5, and 25 J/cm2 combined UVA and UVB (0.8 to 10 MED) and measured enzymic and non-enzymic antioxidants as well as lipid hydroperoxides in both epidermis and dermis to elucidate the response of cutaneous antioxidant defense mechanisms to UV stress. Among the nonenzymic antioxidants two different dose-response patterns were seen. Ascorbate was rapidly depleted at doses between 0 and 5 J/cm2 but was less affected between 5 and 25 J/cm2. In contrast, glutathione, ubiquinol/one, and alpha-tocopherol levels remained approximately equal to control levels between 0 and 5 J/cm2, then decreased to varying degrees from 5 to 25 J/cm2; ubiquinol was almost completely depleted, whereas alpha-tocopherol dropped only 30%. The concentration of lipid hydroperoxides increased throughout the dose range. These results may be explained partly by direct destruction of some antioxidants by UV light, partly by the separate antioxidant functions of the compounds, and partly by recycling of some antioxidants (e.g., alpha-tocopherol) at the expense of others (e.g., ubiquinol). Even at the lowest dose (0.8 MED) lipid hydroperoxide formation was observed. Among the enzymic antioxidants, superoxide dismutase activity decreased significantly (to 63.6% of initial activity for epidermis and 51.5% for dermis at 25 J), whereas activities of glutathione peroxidase and glutathione reductase decreased slightly. Catalase activity decreased dramatically at doses above 5 J (to 11.8% of initial activity in epidermis and 27.7% in dermis at 25 J). The dramatic loss of catalase is almost entirely accounted for by direct destruction by the simulated solar light, but superoxide dismutase was unaffected by direct exposure; hence its destruction must be due to indirect effects, either mediated by free radicals or other harmful species formed upon irradiation. At low doses of UV light many components of the cutaneous antioxidant system were damaged, whereas at high doses all components were damaged and some were almost completely destroyed.

Long-term survival and function of intrahepatic islet allografts in baboons treated with humanized anti-CD154

Clinical islet cell transplantation has resulted in insulin independence in a limited number of cases. Rejection, recurrence of autoimmunity, and impairment of normal islet function by conventional immunosuppressive drugs, e.g., steroids, tacrolimus, and cyclosporin A, may all contribute to islet allograft loss. Furthermore, intraportal infusion of allogeneic islets results in the activation of intrahepatic macrophages and endothelial cells, followed by production of proinflammatory mediators that can contribute to islet primary nonfunction. We reasoned that the beneficial effects of anti-CD154 treatment on autoimmunity, alloreactivity, and proinflammatory events mediated by macrophages and endothelial cells made it an ideal agent for the prevention of islet allograft failure. In this study, a nonhuman primate model (Papio hamadryas) was used to assess the effect of humanized anti-CD154 (hu5c8) on allogeneic islet engraftment and function. Nonimmunosuppressed and tacrolimus-treated recipients were insulin independent posttransplant, but rejected their islet allografts in 8 days. Engraftment and insulin independence were achieved in seven of seven baboon recipients of anti-CD154 induction therapy administered on days -1, 3, and 10 relative to the islet transplant. Three of three baboons treated with 20 mg/kg anti-CD154 induction therapy experienced delayed rejection episodes, first detected by elevations in postprandial blood glucose levels, on postoperative day (POD) 31 for one and on POD 58 for the other two. Re-treatment with three doses of anti-CD154 resulted in reversal of rejection in all three animals and in a return to normoglycemia and insulin independence in two of three baboons. It was possible to reverse multiple episodes of rejection with this approach. A loss of functional islet mass, as detected by reduced first-phase insulin release in response to intravenous glucose tolerance testing, was observed after each episode of rejection. One of two baboons treated with 10 mg/kg induction therapy became insulin independent post-transplant but rejected the islet graft on POD 10; the other animal experienced a reversible rejection episode on POD 58 and remained insulin independent and normoglycemic until POD 264. Two additional baboon recipients of allogeneic islets and donor bone marrow (infused on PODs 5 and 11) were treated with induction therapy (PODs -1, 3, 10), followed by initiation of monthly maintenance therapy (for a period of 6 months) on POD 28. Rejection-free graft survival and insulin independence was maintained for 114 and 238 days, with preservation of functional islet mass observed in the absence of rejection. Prevention and reversal of rejection, in the absence of the deleterious effects associated with the use of conventional immunosuppressive drugs, make anti-CD154 a unique agent for further study in islet cell transplantation.

Evolution of proneural atonal expression during distinct regulatory phases in the developing Drosophila eye

BACKGROUND

Receptors of the Notch family affect the determination of many cell types. In the Drosophila eye, Notch antagonises the basic helix-loop-helix (bHLH) protein atonal, which is required for R8 photoreceptor determination. Similar antagonism between Notch and proneural bHLH proteins regulates most neural cell determination, however, it is uncertain whether the mechanisms are similar in all cases. Here, we have analyzed the sensitivity of atonal expression to Notch signalling using a temperature-sensitive Notch allele, by the expression of activated Notch or of the ligand Serrate, and by monitoring expression of the atonal-dependant gene scabrous and of the Notch-dependent Enhancer of split genes.

RESULTS

The atonal expression pattern evolves from general "prepattern' expression, through transient "intermediate groups' to R8 precursor-specific expression. Successive phases of atonal expression differ in sensitivity to Notch. Prepattern expression of atonal is not inhibited. Inhibition begins at the intermediate group stage, corresponding to the period when atonal gene function is required for its own expression. At the transition to R8 cell-specific expression, Notch is activated in all intermediate group cells except the R8 cell precursor. R8 cells remain sensitive to inhibition in columns 0 and 1, but become less sensitive thereafter; non-R8 cells do not require Notch activity to keep atonal expression inactive. Thus, Notch signaling is coupled to atonal repression for only part of the atonal expression pattern. Accordingly, the Enhancer-of-split m delta protein is expressed reciprocally to atonal at the intermediate group and early R8 stages, but is expressed in other patterns before and after.

CONCLUSIONS

In eye development, inhibition by Notch activity is restricted to specific phases of proneural gene expression, beginning when prepattern decays and is replaced by autoregulation. We suggest that Notch signalling inhibits atonal autoregulation, but not expression by other mechanisms, and that a transition from prepattern to autoregulation is necessary for patterning neural cell determination. Distinct neural tissues might differ in their proneural prepatterns, but use Notch in a similar mechanism.

Vitamin E reduces oxidant injury to mitochondria and the hepatotoxicity of taurochenodeoxycholic acid in the rat

BACKGROUND & AIMS

Hydrophobic bile acids have been implicated in the pathogenesis of cholestatic liver injury. The hypothesis that hydrophobic bile acid toxicity is mediated by oxidant stress in an in vivo rat model was tested in this study.

METHODS

A dose-response study of bolus intravenous (i.v.) taurochenodeoxycholic acid (TCDC) in rats was conducted. Rats were then pretreated with parenteral alpha-tocopherol, and its effect on i.v. TCDC toxicity was evaluated by liver blood tests and by assessing mitochondrial lipid peroxidation.

RESULTS

Four hours after an i.v. bolus of TCDC (10 mumol/100 g weight), serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels peaked, hepatic mitochondria showed evidence of increased lipid peroxidation, and serum bile acid analysis was consistent with a cholestatic injury. Liver histology at 4 hours showed hepatocellular necrosis and swelling and mild portal tract inflammation. Treatment with parenteral alpha-tocopherol was associated with a 60%-70% reduction in AST and ALT levels, improved histology, and a 60% reduction in mitochondrial lipid peroxidation in rats receiving TCDC.

CONCLUSIONS

These data show that hepatocyte injury and oxidant damage to mitochondria caused by i.v. TCDC can be significantly reduced by pretreatment with the antioxidant vitamin E. These in vivo findings support the role for oxidant stress in the pathogenesis of bile acid hepatic toxicity.

Alpha-lipoic acid reduction by mammalian cells to the dithiol form, and release into the culture medium

Lipoic acid has been reported recently to be an effective antioxidant in biological systems. It may act in vivo through reduction to its dithiol form, dihydrolipoic acid. Using a dual Hg/Au electrode, and HPLC with electrochemical detection, a method was developed which allowed simultaneous measurement of lipoic acid and dihydrolipoic acid, at nanomolar levels. (RS)-alpha-Lipoic acid was added to human cells in tissue culture (Jurkat T-lymphocytes and primary neonatal diploid fibroblasts). Lipoic acid was converted rapidly by the cells to dihydrolipoic acid, which accumulated in the cell pellet. Monitored over a 2-hr interval, dihydrolipoic acid was released, and several-fold more dihydrolipoic acid could be found in the medium than in the pellet.

Topical application of alpha-tocopherol modulates the antioxidant network and diminishes ultraviolet-induced oxidative damage in murine skin

The aim of this study was to investigate the effects of topical alpha-tocopherol application on epidermal and dermal antioxidants and its ability to prevent ultraviolet (UV)-induced oxidative damage. Hairless mice received topical applications of alpha-tocopherol 24 h before a single, acute UV irradiation (10 x minimal erythemal dose). The four major antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase), hydrophilic and lipophilic antioxidants, and lipid hydroperoxides, markers of oxidative damage, were assayed in both epidermis and dermis of hairless mice. Topical alpha-tocopherol treatment increased dermal superoxide dismutase activity by 30% (P < 0.01) and protected epidermal glutathione peroxidase and superoxide dismutase from depletion after UV irradiation. Total and reduced glutathione levels in the epidermis increased by 50% after the topical treatment (P < 0.05), as did dermal ascorbate levels (by 40%: P < 0.01). The topical treatment increased alpha-tocopherol levels both in the epidermis (62-fold) and the dermis (22-fold: P < 0.001 in each layer). Furthermore, alpha-tocopherol treatment significantly reduced the formation of epidermal lipid hydroperoxides after UV irradiation (P < 0.05). These results demonstrate that topical administration of alpha-tocopherol protects cutaneous tissues against oxidative damage induced by UV irradiation in vivo, and suggest that the underlying mechanism of this effect involves the up-regulation of a network of enzymatic and non-enzymatic antioxidants.

Color and power Doppler twinkling artifacts from urinary stones: clinical observations and phantom studies

OBJECTIVE

The purpose of this study was to determine whether color and power Doppler twinkling artifacts could be considered an additional diagnostic sonographic feature of urinary stones.

SUBJECTS AND METHODS

A prospective study was performed in 32 patients with 20 renal stones and 16 ureteral stones to assess how often urinary stones show twinkling artifacts on Doppler sonography. Gray-scale images and color, power, and spectral Doppler images were obtained in all patients. All sonographic examinations were performed with a 3.5- or 5-MHz curvilinear phased array probe. The images were then analyzed for the presence, appearance, and intensity of the artifacts. Phantom experiments were performed with various kinds of urinary stones with high-megahertz linear phased array probes. The effects on the artifacts of the composition of the stones, of the Doppler velocity scale, and of the focal zone were investigated.

RESULTS

Thirty (83%) of 36 urinary stones showed color and power Doppler twinkling artifacts, which appeared as a rapidly changing color complex seen persistently behind stones like a comet's tail. Twenty-two of 30 stones with the twinkling artifacts showed strong intensity artifacts. Spectra with saturated amplitude were obtained from all 30 stones showing color Doppler artifacts. In phantom experiments, the artifacts originated from all stones. The velocity range did not affect the artifacts, whereas focal zone did.

CONCLUSION

Color Doppler twinkling artifacts from urinary stones occur frequently and may be considered an additional sonographic feature of urinary stones. The observation of these artifacts may be helpful in determining the presence of urinary stones.

MiR-181a confers resistance of cervical cancer to radiation therapy through targeting the pro-apoptotic PRKCD gene

The purpose of this study was to define the roles of miR-181a in determining sensitivity of cervical cancer to radiation therapy, to explore the underlying mechanism and to evaluate the potential of miR-181a as a biomarker for predicting radio-sensitivity. Tumor specimens from 18 patients with a histological diagnosis of squamous cervical carcinoma (stage IIIB) were used in the micro-RNA profiling and comparison. These patients never received any chemotherapy before radiation therapy. Human cervical cancer cell lines, SiHa and Me180, were used in vitro (cell culture) and in vivo (animal) studies. Transfection of tumor cells with the mimic or inhibitor of miR-181a, and reporter gene assay, were performed to investigate the role of miR-181a in determining radio-sensitivity and the target gene. Higher expression of miR-181a was observed in human cervical cancer specimens and cell lines that were insensitive to radiation therapy, as compared with sensitive cancer specimens and the cell lines. We also found that miR-181a negatively regulated the expression of PRKCD, a pro-apoptotic protein kinase, via targeting its 3'-untranslated region (UTR), thereby inhibiting irradiation-induced apoptosis and decreasing G2/M block. The role of miR-181a in conferring cellular resistance to radiation treatment was validated both in cell culture models and in mouse tumor xenograft models. The effect of miR-181a on radio-resistance was mediated through targeting the 3'-UTR of PRKCD gene. Thus, the expression level of miR-181a in cervical cancer may serve as a biomarker for sensitivity to radiation therapy, and targeting miR-181a may represent a new approach to sensitizing cervical cancer to radiation treatment.

Cytosolic and mitochondrial systems for NADH- and NADPH-dependent reduction of alpha-lipoic acid

In cellular, tissue, and organismal systems, exogenously supplied alpha-lipoic acid (thioctic acid) has a variety of significant effects, including direct radical scavenging, redox modulation of cell metabolism, and potential to inhibit oxidatively-induced injury. Because reduction of lipoate to dihydrolipoate is a crucial step in many of these processes, we investigated mechanisms of its reduction. The mitochondrial NADH-dependent dihydrolipoamide dehydrogenase exhibits a marked preference for R(+)-lipoate, whereas NADPH-dependent glutathione reductase shows slightly greater activity toward the S(-)-lipoate stereoisomer. Rat liver mitochondria also reduced exogenous lipoic acid. The rate of reduction was stimulated by substrates which increased the NADH content of the mitochondria, and was inhibited by methoxyindole-2-carboxylic acid, a dihydrolipoamide dehydrogenase inhibitor. In rat liver cytosol, NADPH-dependent reduction was greater than NADH, and lipoate reduction was inhibited by glutathione disulfide. In rat heart, kidney, and brain whole cell-soluble fractions, NADH contributed more to reduction (70-90%) than NADPH, whereas with liver, NADH and NADPH were about equally active. An intact organ, the isolated perfused rat heart, reduced R-lipoate six to eight times more rapidly than S-lipoate, consistent with high mitochondrial dihydrolipoamide dehydrogenase activity and results with isolated cardiac mitochondria. On the other hand, erythrocytes, which lack mitochondria, somewhat more actively reduced S- than R-lipoate. These results demonstrate differing stereospecific reduction by intact cells and tissues. Thus, mechanisms of reduction of alpha-lipoate are highly tissue-specific and effects of exogenously supplied alpha-lipoate are determined by tissue glutathione reductase and dihydrolipoamide dehydrogenase activity.

The association of psychotropic medication use with the cognitive, functional, and neuropsychiatric trajectory of Alzheimer's disease

OBJECTIVE

The use of psychotropic medications in Alzheimer's disease (AD) has been associated with both deleterious and potentially beneficial outcomes. We examined the longitudinal association of psychotropic medication use with cognitive, functional, and neuropsychiatric symptom (NPS) trajectories among community-ascertained incident AD cases from the Cache County Dementia Progression Study.

METHODS

A total of 230 participants were followed for a mean of 3.7 years. Persistency index (PI) was calculated for all antidepressants, selective serotonin reuptake inhibitors (SSRIs), antipsychotics (atypical and typical), and benzodiazepines as the proportion of observed time of medication exposure. Mixed-effects models were used to examine the association between PI for each medication class and Mini-Mental State Exam (MMSE), Clinical Dementia Rating Sum of Boxes (CDR-Sum), and Neuropsychiatric Inventory - Total (NPI-Total) trajectories, controlling for appropriate demographic and clinical covariates.

RESULTS

At baseline, psychotropic medication use was associated with greater severity of dementia and poorer medical status. Higher PI for all medication classes was associated with a more rapid decline in MMSE. For antidepressant, SSRI, benzodiazepine, and typical antipsychotic use, a higher PI was associated with a more rapid increase in CDR-Sum. For SSRIs, antipsychotics, and typical antipsychotics, a higher PI was associated with more rapid increase in NPI-Total.

CONCLUSIONS

Psychotropic medication use was associated with more rapid cognitive and functional decline in AD, and not with improved NPS. Clinicians may tend to prescribe psychotropic medications to AD patients at risk of poorer outcomes, but one cannot rule out the possibility of poorer outcomes being caused by psychotropic medications.

Regulation of cellular thiols in human lymphocytes by alpha-lipoic acid: a flow cytometric analysis

Modulation of cellular thiols is an effective therapeutic strategy, particularly in the treatment of AIDS. Lipoic acid, a metabolic antioxidant, functions as a redox modulator and has proven clinically beneficial effects. It is also used as a dietary supplement. We utilized the specific capabilities of N-ethylmaleimide to block total cellular thiols, phenylarsine oxide to block vicinal dithiols, and buthionine sulfoximine to deplete cellular GSH to flow cytometrically investigate how these thiol pools are influenced by exogenous lipoate treatment. Low concentrations of lipoate and its analogue lipoamide increased Jurkat cell GSH in a dose-dependent manner between 10 (25 microM for lipoamide) to 100 microM. This was also observed in mitogenically stimulated peripheral blood lymphocytes (PBL). Studies with Jurkat cells and its Wurzburg subclone showed that lipoate dependent increase in cellular GSH was similar in CD4+ and - cells. Chronic (16 week) exposure of cells to lipoate resulted in further increase of total cellular thiols, vicinal dithiols, and GSH. High concentration (2 and 5 mM) of lipoate exhibited cell shrinkage, thiol depletion, and DNA fragmentation effects. Based on similar effects of octanoic acid, the cytotoxic effects of lipoate at high concentration could be attributed to its fatty acid structure. In certain diseases such as AIDS and cancer, elevated plasma glutamate lowers cellular GSH by inhibiting cystine uptake. Low concentrations of lipoate and lipoamide were able to bypass the adverse effect of elevated extracellular glutamate. A heterogeneity in the thiol status of PBL was observed. Lipoate, lipoamide, or N-acetylcysteine corrected the deficient thiol status of cell subpopulations. Hence, the favorable effects of low concentrations of lipoate treatment appears clinically relevant.

Huntington disease phenocopy is a familial prion disease

Huntington disease (HD) is a common autosomal dominant neurodegenerative disease with early adult-onset motor abnormalities and dementia. Many studies of HD show that huntingtin (CAG)n repeat-expansion length is a sensitive and specific marker for HD. However, there are a significant number of examples of HD in the absence of a huntingtin (CAG)n expansion, suggesting that mutations in other genes can provoke HD-like disorders. The identification of genes responsible for these "phenocopies" may greatly improve the reliability of genetic screens for HD and may provide further insight into neurodegenerative disease. We have examined an HD phenocopy pedigree with linkage to chromosome 20p12 for mutations in the prion protein (PrP) gene (PRNP). This reveals that affected individuals are heterozygous for a 192-nucleotide (nt) insertion within the PrP coding region, which encodes an expanded PrP with eight extra octapeptide repeats. This reveals that this HD phenocopy is, in fact, a familial prion disease and that PrP repeat-expansion mutations can provoke an HD "genocopy." PrP repeat expansions are well characterized and provoke early-onset, slowly progressive atypical prion diseases with an autosomal dominant pattern of inheritance and a remarkable range of clinical features, many of which overlap with those of HD. This observation raises the possibility that an unknown number of HD phenocopies are, in fact, familial prion diseases and argues that clinicians should consider screening for PrP mutations in individuals with HD-like diseases in which the characteristic HD (CAG)n repeat expansions are absent.

Diagnostic accuracy of 18 F-FDG and 11 C-PIB-PET for prediction of short-term conversion to Alzheimer's disease in subjects with mild cognitive impairment

In recent years, the role of PET imaging in the prediction of mild cognitive impairment (MCI) to Alzheimer's disease (AD) conversion has been the subject of many longitudinal studies. The purpose of this study was to perform a meta-analysis to estimate the diagnostic accuracy of (18) F-fluoro-2-deoxyglucose-positron emission tomography (FDG-PET) and (11) C-Pittsburgh Compound B-positron emission tomography (PIB-PET) for prediction of short-term conversion to AD in patients with MCI. The MEDLINE and EMBASE databases were systematically searched for relevant studies. Methodological quality of the included studies was assessed. Sensitivities and specificities of PET in individual studies were calculated and meta-analysis was undertaken with a random-effects model. A summary receiver operating characteristic (SROC) curve was constructed with the Moses-Shapiro-Littenberg method. Heterogeneity was tested, and the presence of publication bias was assessed. Potential sources for heterogeneity were explored by assessing whether or not certain covariates significantly influenced the relative diagnostic odds ratio (DOR). Pooled estimates of sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-), DOR and the SROC curve of each PET imaging were determined. A total of 13 research studies (seven FDG-PET and six PIB-PET) met inclusion criteria and had sufficient data for statistical analysis. FDG-PET pooled estimates had 78.7% sensitivity (95% CI, 68.7-86.6%),74.0% specificity (95% CI, 67.0-80.3%), 18.1 LR+(95% CI, 7.3-45.0) and 0.32 LR-(95% CI, 0.16-0.61); and PIB-PET pooled estimates had 93.5% sensitivity (95%CI, 71.3-99.9%), 56.2% specificity (95% CI, 47.2-64.8%), 2.01 LR+ (95% CI, 1.57-2.58) and 0.17 LR-(95% CI, 0.08-0.36). Overall DOR was 17.3 (95% CI, 5.08-59.2) for FDG-PET and 12.8 (95% CI, 5.35-30.54) for PIB-PET. Area under the SROC curve was 0.88 ± 0.05 for FDG-PET and 0.85 ± 0.04 for PIB-PET. The data from FDG-PET research studies had high heterogeneity and funnel plot suggested a publication bias. The diagnostic accuracy determined for both FDG-PET and PIB-PET in this meta-analysis suggests that they are potentially valuable techniques for prediction of progression in patients with MCI. Both have their advantages and their combined use is a promising option for prediction purposes depending on availability and experience.

Alpha-lipoic acid increases intracellular glutathione in a human T-lymphocyte Jurkat cell line

The addition of exogenous alpha-lipoic acid to cellular medium causes a rapid increase of intracellular unbound thiols in Jurkat cells, a human T-lymphocyte cell line. The rise of cellular thiols is a result of the cellular uptake and reduction of lipoic acid to dihydrolipoic acid and a rise in intracellular glutathione. Although the level of dihydrolipoic acid is 100-fold lower than glutathione, the cellular concentration of dihydrolipoic acid might be responsible for the modulation of total cellular thiol levels. Rises in glutathione correlate with the levels of intracellular dihydrolipoic acid (p < .01). This increase in glutathione is not the result of expression of new proteins like gamma-glutamylcysteine synthetase, since the rise in glutathione was not inhibited by cycloheximide, a protein synthesis inhibitor. Lipoic acid administration is therefore a potential therapeutic agent in an array of diseases with glutathione anomalies including HIV infection.

Measurement of superoxide dismutase-like activity of natural antioxidants

The superoxide dismutase (SOD)-like activity of natural antioxidants was evaluated by measuring the inhibition of pyrogallol autoxidation that is catalyzed by the superoxide radical. Among 22 water-soluble antioxidants tested, L-ascrobic acid, L-ascorbic acid 6-palmitate, glutathione (reduced form), (+)-catechin, and (-)-epicatechin showed effective SOD-like activity. To analyze lipophilic antioxidants, an optically clear organic system composed of diethyl ether, surfactant (dioctyl sulfosuccinate, AOT) and water, called reverse micelles, was developed. The optimum concentrations of AOT, water and pyrogallol for determining SOD-like activity were found to be 50 mM, 1.3 M, and 40 mM, respectively. After proving that pyrogallol autoxidation was mediated by the superoxide anion in that system, the SOD-like activity of 24 lipophilic antioxidants was measured. Cinnamon oil, gamma-oryzanol, extract of rosemary leaf, L-alpha-lecithin, and L-alpha-cephalin exhibited activity, although the activity of some antioxidants could not be measured because of the intense color or low solubility.

Dominant-negative inhibition of prion formation diminished by deletion mutagenesis of the prion protein

Polymorphic basic residues near the C terminus of the prion protein (PrP) in humans and sheep appear to protect against prion disease. In heterozygotes, inhibition of prion formation appears to be dominant negative and has been simulated in cultured cells persistently infected with scrapie prions. The results of nuclear magnetic resonance and mutagenesis studies indicate that specific substitutions at the C-terminal residues 167, 171, 214, and 218 of PrP(C) act as dominant-negative, inhibitors of PrP(Sc) formation (K. Kaneko et al., Proc. Natl. Acad. Sci. USA 94:10069-10074, 1997). Trafficking of substituted PrP(C) to caveaola-like domains or rafts by the glycolipid anchor was required for the dominant-negative phenotype; interestingly, amino acid replacements at multiple sites were less effective than single-residue substitutions. To elucidate which domains of PrP(C) are responsible for dominant-negative inhibition of PrP(Sc) formation, we analyzed whether N-terminally truncated PrP(Q218K) molecules exhibited dominant-negative effects in the conversion of full-length PrP(C) to PrP(Sc). We found that the C-terminal domain of PrP is not sufficient to impede the conversion of the full-length PrP(C) molecule and that N-terminally truncated molecules (with residues 23 to 88 and 23 to 120 deleted) have reduced dominant-negative activity. Whether the N-terminal region of PrP acts by stabilizing the C-terminal domain of the molecule or by modulating the binding of PrP(C) to an auxiliary molecule that participates in PrP(Sc) formation remains to be established.

Confinement effect on dipole-dipole interactions in nanofluids

Intermolecular dipole-dipole interactions were once thought to average to zero in gases and liquids as a result of rapid molecular motion that leads to sharp nuclear magnetic resonance lines. Recent papers have shown that small residual couplings survive the motional averaging if the magnetization is nonuniform or nonspherical. Here, we show that a much larger, qualitatively different intermolecular dipolar interaction remains in nanogases and nanoliquids as an effect of confinement. The dipolar coupling that characterizes such interactions is identical for all spin pairs and depends on the shape, orientation (with respect to the external magnetic field), and volume of the gas/liquid container. This nanoscale effect is useful in the determination of nanostructures and could have unique applications in the exploration of quantum space.

Spectroscopic and kinetic studies of lipases solubilized in reverse micelles

The conformation and activity of three different lipases have been studied in reverse micelles formed by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in isooctane. In the case of human pancreatic lipase, the conformation of the polypeptide chain--as judged from far-UV circular dichroism measurements--is only slightly altered after the enzyme is transferred from a bulk aqueous solution into the microenvironment of reverse micelles. Significant spectral changes in the near-UV circular dichroism and fluorescence spectrum indicate, however, that the solvation of aromatic amino acid side chains is considerably different in reverse micelles. Conversely, the circular dichroism spectra of the lipases from Candida rugosa and Pseudomonas sp. are considerably different in reverse micelles, compared with the spectra in aqueous solution, indicating that both enzymes loose the native structure at the water/AOT/oil interface. Bound substrate and/or product can prevent this denaturation. While Pseudomonas sp. and human pancreatic lipase are inhibited by tetrahydrolipstatin (THL), the lipase from Candida rugosa is not. These data, together with additional activity and inhibition data, indicate that the micellar microenvironment accentuates the difference between the different enzymes in terms of the relation structure/activity.