Different Epidemic Potentials of the HIV-1B and C Subtypes

HIV, the cause of AIDS in humans, is characterized by great genetic heterogeneity. In particular, HIV-1 group M subtypes are responsible for most of the infections worldwide. We investigate the demographic history of HIV-1B and HIV-1C subtypes in South Africa and Brazil using both a parametric and a nonparametric approach based on coalescent theory. Our results show that although both subtypes are spreading exponentially in Brazil, the HIV-1C growth rate is about twice that of Brazilian HIV-1B or South African HIV-1C, providing evidence, for the first time, of a different epidemic potential between two HIV-1 subtypes. The present study not only may have important consequences for devising future vaccination and therapeutic strategies, but also offers additional evidence that skyline plots are indeed a simple and powerful tool for monitoring and predicting the behavior of viral epidemics.Reviewing Editor: Dr. Yves Van de Peer     

Gene dosage-dependent effects of bcl-2 expression on cellular survival and redox status

The human oncogene bcl-2 exerts protective functions in numerous models of apoptotic cell death and increased oxidative stress. We investigated the effects of inducible bcl-2 overexpression on cellular survival and redox status in dopaminergic rat pheochromocytoma PC 12 cells. Induction of high-level expression of bcl-2 in PC 12 cells resulted in generation of oxidative stress and cessation of growth by cell cycle arrest. Cell cycle arrest in bcl-2-overexpressing PC 12 cells was prevented by an inhibitor of extracellular signal-related kinase (ERK 1/2) activation. Protective effects of bcl-2 expression against L-DOPA neurotoxicity decreased with increasing amounts of bcl-2. Furthermore, high-level bcl-2 overexpression sensitized cells towards oxidative stress and glutathione depletion. Our data suggest that bcl-2 expression is beneficial only in a limited gene dosage range and that high-level expression of bcl-2 exerts potential deleterious effects.     

HIV-1 C/B'亚型多价重组MVA病毒疫苗

目的：检测人类免疫缺陷病毒1型（HIV-1） C/B'亚型与痘苗病毒安卡拉株（MVA）的多价重组疫苗的免疫原性,此疫苗中包含HIV-1 C/B'CRF 株的五个基因,分别是env、gag、pol、nef、tat。方法：设105 pfu/mL 、106 pfu/mL、107 pfu/mL ADMVA三个剂量组,用ELISPOT方法检测细胞免疫反应。同时,以Gag蛋白作为包被抗原,使用间接ELISA的方法检测体液免疫反应。结果：免疫后的小鼠对插入基因env、gag、pol和nef所表达蛋白均产生了特异性细胞免疫应答,且免疫效果与免疫剂量呈正相关。ELISA结果表明, MVA重组疫苗免疫诱导产生了特异性体液免疫,抗HIV-1Gag的抗体滴度与免疫次数和免疫剂量都存在正相关性。结论：多价MVA重组疫苗能有效地诱导小鼠产生特异地细胞免疫和体液免疫反应。     

Glutathione redox dynamics and expression of glutathione-related genes in the developing embryo

Embryonic development involves dramatic changes in cell proliferation and differentiation that must be highly coordinated and tightly regulated. Cellular redox balance is critical for cell fate decisions, but it is susceptible to disruption by endogenous and exogenous sources of oxidative stress. The most abundant endogenous nonprotein antioxidant defense molecule is the tripeptide glutathione (γ-glutamylcysteinylglycine, GSH), but the ontogeny of GSH concentration and redox state during early life stages is poorly understood. Here, we describe the GSH redox dynamics during embryonic and early larval development (0–5 days postfertilization) in the zebrafish (Danio rerio), a model vertebrate embryo. We measured reduced and oxidized glutathione using HPLC and calculated the whole embryo total glutathione (GSH_T) concentrations and redox potentials (E_h) over 0–120 h of zebrafish development (including mature oocytes, fertilization, midblastula transition, gastrulation, somitogenesis, pharyngula, prehatch embryos, and hatched eleutheroembryos). GSH_T concentration doubled between 12 h postfertilization (hpf) and hatching. The GSH E_h increased, becoming more oxidizing during the first 12 h, and then oscillated around −190 mV through organogenesis, followed by a rapid change, associated with hatching, to a more negative (more reducing) E_h (−220 mV). After hatching, E_h stabilized and remained steady through 120 hpf. The dynamic changes in GSH redox status and concentration defined discrete windows of development: primary organogenesis, organ differentiation, and larval growth. We identified the set of zebrafish genes involved in the synthesis, utilization, and recycling of GSH, including several novel paralogs, and measured how expression of these genes changes during development. Ontogenic changes in the expression of GSH-related genes support the hypothesis that GSH redox state is tightly regulated early in development. This study provides a foundation for understanding the redox regulation of developmental signaling and investigating the effects of oxidative stress during embryogenesis.     

Antioxidant Defenses Influence HIV-1 Replication and Associated Cytopathic Effects

HIV-infected cells often exhibit reduced levels of antioxidant enzymes and thiols. To investigate the role of cellular antioxidant defenses in the progression of an acutely spreading HIV-1 infection, human Sup-T1 T cells were engineered to overexpress the selenium-dependent glutathione peroxidase, GSHPx-1. This enzyme represents a major cellular defense mechanism against toxicity associated with reactive oxygen species (ROS). T cells engineered to produce elevated GSHPx-1 activity displayed accelerated viral replication and associated cytopathic effects compared to control cells. Conversely, the inhibition of the synthesis of glutathione with buthione sulfoximine (BSO) resulted in the attenuation of viral replication in Sup-T1 cells. Similarly, exposure of human peripheral blood lymphocytes (PBLs) to low, nontoxic levels of BSO resulted in an approximately 80% decline in HIV-1 replication as indicated by Western blot analysis of viral proteins.     

Evaluation of a dithiocarbamate derivative as a model of thiol oxidative stress in H9c2 rat cardiomyocytes

Thiol redox state (TRS) refers to the balance between reduced thiols and their corresponding disulfides and is mainly reflected by the ratio of reduced and oxidized glutathione (GSH/GSSG). A decrease in GSH/GSSG, which reflects a state of thiol oxidative stress, as well as thiol modifications such as S-glutathionylation, has been shown to have important implications in a variety of cardiovascular diseases. Therefore, research models for inducing thiol oxidative stress are important tools for studying the pathophysiology of these disease states as well as examining the impact of pharmacological interventions on thiol pathways. The purpose of this study was to evaluate the use of a dithiocarbamate derivative, 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA), as a pharmacological model of thiol oxidative stress by examining the extent of thiol modifications induced in H9c2 rat cardiomyocytes and its impact on cellular functions. The extent of thiol oxidative stress produced by 2-AAPA was also compared to other models of oxidative stress including hydrogen peroxide (H₂O₂), diamide, buthionine sulfoximine, and N,N׳-bis(2-chloroethyl)-N-nitroso-urea. Results indicated that 2-AAPA effectively inhibited glutathione reductase and thioredoxin reductase activities and decreased the GSH/GSSG ratio by causing a significant accumulation of GSSG. 2-AAPA also increased the formation of protein disulfides as well as S-glutathionylation. The alteration in TRS led to a loss of mitochondrial membrane potential, release of cytochrome c, and increase in reactive oxygen species production. Compared to other models, 2-AAPA is more potent at creating a state of thiol oxidative stress with lower cytotoxicity, higher specificity, and more pharmacological relevance, and could be utilized as a research tool to study TRS-related normal and abnormal biochemical processes in cardiovascular diseases.     

Blood as a reactive species generator and redox status regulator during exercise

The exact origin of reactive species and oxidative damage detected in blood is largely unknown. Blood interacts with all organs and tissues and, consequently, with many possible sources of reactive species. In addition, a multitude of oxidizable substrates are already in blood. A muscle-centric approach is frequently adopted to explain reactive species generation, which obscures the possibility that sources of reactive species and oxidative damage other than skeletal muscle may be also at work during exercise. Plasma and blood cells can autonomously produce significant amounts of reactive species at rest and during exercise. The major reactive species generators located in blood during exercise may be erythrocytes (mainly due to their quantity) and leukocytes (mainly due to their drastic activation during exercise). Therefore, it is plausible to assume that oxidative stress/damage measured frequently in blood after exercise or any other experimental intervention derives, at least in part, from the blood.     

Interaction of plasma glutathione redox and folate deficiency on arsenic methylation capacity in Bangladeshi adults

Inorganic arsenic(As) is metabolized through a series of methylation reactions catalyzed by arsenic(III)-methyltransferase (AS3MT), resulting in the generation of monomethylarsonic (MMAs) and dimethylarsinic acids (DMAs). AS3MT activity requires the presence of the methyl donor S-adenosylmethionine, a product of folate-dependent one-carbon metabolism, and a reductant. Although glutathione (GSH), the primary endogenous antioxidant, is not required for As methylation, GSH stimulates As methylation rates in vitro. However, the relationship between GSH redox and As methylation capacity in humans is unknown. We wished to test the hypothesis that a more oxidized plasma GSH redox status is associated with decreased As methylation capacity and examine whether these associations are modified by folate nutritional status. Concentrations of plasma GSH and GSSG, plasma folate, total blood As (bAs), total urinary As (uAs), and uAs metabolites were assessed in a cross-sectional study of n=376 Bangladeshi adults who were chronically exposed to As in drinking water. We observed that a decreased plasma GSH/GSSG ratio (reflecting a more oxidized redox state) was significantly associated with increased urinary %MMA, decreased urinary %DMA, and increased total bAs in folate-deficient individuals (plasma folate ≤9.0 nmol/L). Concentrations of plasma GSH and GSSG were independently associated with increased and decreased As methylation capacity, respectively. No significant associations were observed in folate-sufficient individuals, and interactions by folate status were statistically significant. Our findings suggest that GSH/GSSG redox regulation might contribute to the large interindividual variation in As methylation capacity observed in human populations.     

Association between life-span extension by caloric restriction and thiol redox state in two different strains of mice

The hypothesis that the life-extending effect of caloric restriction (CR) is associated with an attenuation of the age-related pro-oxidant shift in the thiol redox state was tested employing a novel experimental design. Amounts of GSH, GSSG, and protein mixed disulfides (Pr-SSG) in the skeletal muscle and liver were compared between two strains of mice that have similar life spans when fed ad libitum (AL), but different life spans under the standard CR regimen. The life span of one strain, C57BL/6, is extended under CR, whereas it remains unaffected in the other strain, DBA/2. Mice were fed AL or 40% less food starting at 4 months and compared at 6 and 24 months of age. The amounts of GSSG and Pr-SSG increased and the GSH:GSSG ratios decreased with age in both strains of AL-fed mice. CR prevented these age-related changes in the C57BL/6, whose life span is extended by CR, but not in the DBA/2 mice, in which it remains unaffected. CR enhanced the activity of glutamate-cysteine ligase in the C57BL/6, but not in the DBA/2 mice. The results suggest that longevity extension by CR may be associated with the attenuation of age-related pro-oxidizing shifts in the thiol redox state.     

Coreceptor Switching in HIV-1 Subtype B and Subtype C

We use a mathematical model to determine the factors affecting the delayed or rare coreceptor switch in HIV-1 subtype C infected individuals. The model takes into account the two main target cells for the CXCR4-tropic and CCR5-tropic virus and includes the the lytic and non-lytic immune responses. Computer-based simulations and a sensitivity analysis of the model predict that a persistent immune response suppresses the CXCR4-tropic virus to low levels and hence preventing a phenotypic switch. However, not only should the immune response be persistent, but it should have an efficient lytic immune response rather that an efficient non-lytic response. In addition, we also find that the availability of macrophage cells and enhanced viral kinetics are also crucial for the dominance of the R5 strain. We suggest that an altered host environment probably as a result of immune activation may explain the difference in coreceptor switching kinetics between HIV-1 subtype B and subtype C individuals.     

HIV-1复制型DNA疫苗与非复制型重组痘苗病毒疫苗在小鼠体内细胞免疫效果的研究

目的:用HIV-1复制型DNA疫苗和非复制型重组痘苗病毒疫苗(rNTV-C)进行单独免疫和联合免疫的研究(2种疫苗分别包含HIV-1 B’/C亚型的gp160、gag-pol、rev-tat-nef等6种基因),以了解这2种新型HIV疫苗单独免疫及联合免疫的效果,并为临床免疫方案的制定提供实验依据。方法:将HIV-1 DNA疫苗和rNTV-C疫苗免疫BALB/c小鼠,设计rNTV-C单独免疫组、DNA单独免疫组,以及DNA初免、rNTV-C加强的联合免疫组,并设计不同免疫途径和不同剂量的各种组合。用IFN-γELISPOT检测各组的细胞免疫效果,用统计学方法分析比较各组细胞免疫效果的差异。结果:DNA疫苗和rNTV-C疫苗单独免疫时,二者都能诱发针对各抗原的特异性免疫反应;联合免疫能够诱发比DNA或rNTV-C单独免疫都强的特异性细胞免疫反应。统计分析显示,2种疫苗采用肌肉注射途径的免疫效果显著高于皮内注射,1μg和5μg DNA疫苗的免疫效果差异不显著,而1×108 PFU的rNTV-C比2×107PFU的免疫效果要强。结论:联合免疫策略能够显著增强HIV-1疫苗各抗原的免疫原性,通过对2种HIV-1疫苗单独免疫及二者联合免疫的细胞免疫反应的分析比较,确定了较好的免疫方案,为疫苗临床前免疫效果评价和临床方案的制定提供了实验依据。     

Role of antioxidant systems in induced nutritional pancreatic atrophy in chicken

One-day-old chicks were reared using diets differing in their vitamin E and/or selenium content. The purpose of this research was to detect any possible imbalance in the antioxidant defense system, which could be related to development of nutritional pancreatic atrophy. Mitochondrial membranes from animals deficient in both nutrients, or just vitamin E, submitted to peroxidizability ‘in vitro’ had the production of TBARS greatly enhanced. Measurements of the 2-GSH/GSSG ratio suggested that selenium and vitamin E, the latter in higher magnitude, were responsible for maintenance of the reducing capacity of the cell. Enzymatic defense systems against oxidative stress were also studied. The results indicated that the total antioxidant enzymatic activity of pancreatic cells was not sufficient to scavenge all the ROS generated in the nutritionally deficient animals. The present study suggests that nutritional deficiency of selenium and/or vitamin E generates one imbalance between pro-oxidant and antioxidant systems in chicken pancreas, leading to oxidative stress and pancreatic atrophy.     

The dendritic and T cell responses to herpes simplex virus-1 are modulated by dietary vitamin E

Previous studies from our laboratory have shown that dietary α-tocopherol (vitamin E, or VE) is essential for regulating the cytokine and chemokine response in the brain to herpes simplex virus-1 (HSV-1) infection. The timing of T cell infiltration is critical to the resolution of central nervous system HSV-1 infections. Specifically, the appearance of “neuroprotective” CD8⁺IFN-γ⁺ T cells is crucial. During CNS infection, CD8⁺ T cell priming and expansion in the draining lymph node, followed by recruitment and expansion, occurs in the spleen with subsequent accumulation in the brain. Weanling male BALB/cByJ mice were placed on VE-deficient (Def) or -adequate diets for 4 weeks followed by intranasal infection with HSV-1. VE-Def mice had fewer CD8⁺IFN-γ⁺ T cells trafficking to the brain despite increased CD8⁺IFN-γ⁺ T cells and activated dendritic cells in the periphery. VE-Def mice had increased T regulatory cells (Tregs) in the periphery and brain, and the increase in Tregs decreased CD8⁺ T cell numbers in the brain. Our results demonstrate that adequate levels of VE are important for trafficking antigen-specific T cells to the brain, and dietary VE levels modulate T regulatory and dendritic cells in the periphery.     

Resveratrol protects SR-B1 levels in keratinocytes exposed to cigarette smoke

Cigarette smoking (CS) has been strongly linked to several health conditions including heart disease, lung cancer, and other respiratory and circulatory ailments. Deleterious effects of cigarette smoking on skin have also been well documented, but unlike effects on other organs, damage does not depend upon inhalation. The upper layer of the skin, the stratum corneum (rich in cholesterol fatty acids and ceramide), is very susceptible to damage induced by exposure to environmental stressors that can modify its lipid composition and thereby affect its function of protecting skin from dehydration. Scavenger receptor B1 (SR-B1) is involved in the uptake of cholesterol in several tissues including skin. We previously demonstrated that CS exposure induces formation of aldehyde (HNE) adducts that decrease SR-B1 expression. As topical resveratrol, a well-known polyphenolic stilbene, has been demonstrated to show benefits against skin disorders, we investigated its possible role as a protective agent against CS-induced reduction of SR-B1 expression in cutaneous tissue. In this study, we demonstrate that resveratrol at doses ranging from 0.5 to 10 μM is not toxic and is able to increase SR-B1 protein levels in a dose-dependent manner in human keratinocytes. Moreover, when the cells that were pretreated with various doses of resveratrol were exposed to CS, the loss of SR-B1 was prevented in a dose-dependent manner. In addition, in keratinocytes, resveratrol was also able to prevent an increase in HNE–protein adducts induced by CS. In particular resveratrol was able to prevent HNE–SR-B1 adduct formation. Thus, resveratrol seems to be a natural compound that could provide skin with a defense against exogenous stressors by protecting the essential cholesterol receptor, SR-B1.     

Role of Auf1 in elimination of oxidatively damaged messenger RNA in human cells

In aerobically growing cells, in which reactive oxygen species are produced, the guanine base of RNA is oxidized to 8-oxo-7,8-dihydroguanine, which induces alterations in gene expression. Here we show that the human Auf1 protein, also called HNRNPD, binds specifically to RNA containing this oxidized base and may be involved in cellular processes associated with managing the problems caused by RNA oxidation. Auf1-deficient cells were constructed from human HeLa and Nalm-6 lines using two different targeting procedures. Both types of Auf1-deficient cells are viable, but exhibit growth retardation. The stability of messenger RNA for four different housekeeping genes was determined in Auf1-deficient and -proficient cells, treated with or without hydrogen peroxide. The level of oxidized messenger RNA was considerably higher in Auf1-deficient cells than in Auf1-proficient cells. Auf1 may play a role in the elimination of oxidized RNA, which is required for the maintenance of proper gene expression under conditions of oxidative stress.