Oxidative stress and thiol depletion in plasma and peripheral blood lymphocytes from HIV-infected patients: toxicological and pathological implications

Extracellular Calcium Receptor as a Target for Glutathione and Its Derivatives

Extracellular glutathione (GSH) and oxidized glutathione (GSSG) can modulate the function of the extracellular calcium sensing receptor (CaSR). The CaSR has a binding pocket in the extracellular domain of CaSR large enough to bind either GSH or GSSG, as well as the naturally occurring oxidized derivative L-cysteine glutathione disulfide (CySSG) and the compound cysteinyl glutathione (CysGSH). Modeling the binding energies (ΔG) of CySSG and CysGSH to CaSR reveals that both cysteine derivatives may have greater affinities for CaSR than either GSH or GSSG. GSH, CySSG, and GSSG are found in circulation in mammals and, among the three, CySSG is more affected by HIV/AIDs and aging than either GSH or GSSG. The beta-carbon linkage of cysteine in CysGSH may model a new class of calcimimetics, exemplified by etelcalcetide. Circulating glutathionergic compounds, particularly CySSG, may mediate calcium-regulatory responses via receptor-binding to CaSR in a variety of organs, including parathyroids, kidneys, and bones. Receptor-mediated actions of glutathionergics may thus complement their roles in redox regulation and detoxification. The glutathionergic binding site(s) on CaSR are suggested to be a target for development of drugs that can be used in treating kidney and other diseases whose mechanisms involve CaSR dysregulation.

Glutathione Deficiency in HIV-1-Infected Children with Short Stature

Objective This study was aimed to determine if glutathione (GSH) deficiency occurs in children with HIV infection and whether GSH deficiency is associated with HIV-related short stature.

Methods We conducted a cross-sectional study with two age-matched comparison groups in an inner city hospital-based pediatric AIDS/HIV outpatient clinic. Ten perinatally HIV-infected children aged 6 to 49 months with short stature (height–age percentile ≤5) were studied together with age-matched 10 HIV-infected children with normal height and 10 HIV-seronegative children with normal height. Total erythrocyte GSH (GSH and GSH disulfide) levels were determined by a modification of the 5,5′-dithiobis-2-nitrobenzoic acid glutathione disulfide reductase method. Other measures included complete blood counts, lymphocyte subset analysis, plasma albumin, cholesterol, vitamins A and E, and determination of HIV disease stage.

Discussion Erythrocyte GSH levels were lower in HIV-infected children with short stature (mean ± standard deviation [SD]: 0.639 µmol/mL ± 0.189) compared with HIV-infected children with normal height (mean ± SD: 0.860 µmol/mL ± 0.358; p < 0.05) and HIV-negative controls (mean ± SD: 0.990 µmol/mL ± 0.343; p < 0.05). Plasma levels of cholesterol, albumin, and vitamins A and E did not differ between the short-stature group and either the HIV-infected normal-height group or HIV-negative controls.

Conclusion These results demonstrate a GSH deficiency in HIV-infected children with short stature and support the hypothesis that GSH balance is important in growth among HIV-infected children.

Thiol/disulfide homeostasis as a novel indicator of oxidative stress during the treatment process of patients with septic arthritis

Objectives

This study aims to investigate dynamic thiol/disulfide homeostasis as a novel indicator of oxidative stress and to find out its association with standard inflammatory markers during the treatment of patients with septic arthritis (SA).

Patients and methods

In this prospective study, a new colorimetric method for measuring thiol/disulfide homeostasis was assessed between May 2013 and October 2014 in 24 patients with SA (14 males, 10 females; mean age 14.5±19.1 years; range, 1 to 80 years) at baseline and the end of the third week of the treatment, and in 24 healthy controls (14 males, 10 females; mean age 12.5±18.7 years; range, 1 to 85 years). Also, standard inflammatory markers such as C-reactive protein (CRP), erythrocyte sedimentation rate, and white blood cell count were evaluated.

Results

At baseline, serum disulfide was higher in SA group compared to the control group, whereas native thiol was lower (p<0.05 for all). At the end of the third week of the treatment, serum disulfide level was lower, whereas the native thiol was higher compared to baseline (p<0.05 for all). In addition, serum disulfide level was positively correlated with CRP (r=0.736, p<0.001) and disulfide/native thiol ratio (r=0.779, p<0.001). Furthermore, in multiple regression analyses, the disulfide level was independently associated with CRP (β=0.226, p=0.005).

Conclusion

Our results suggest that the elevated levels of serum disulfide and standard inflammatory markers at baseline in patients with SA and decreased levels of these parameters are related with oxidative stress. This homeostasis shifted towards disulfide formation due to thiol oxidation. Therefore, thiol/ disulfide homeostasis may be a helpful biomarker for the follow- up in patients with SA.

Plasma cysteine/cystine and glutathione/glutathione disulfide redox potentials in HIV and COPD patients

Chronic obstructive pulmonary disease (COPD) is prevalent in patients infected with HIV. The purpose of this study was to test the hypothesis that systemic oxidation correlates with loss of lung function in subjects with COPD, and that HIV infection can contribute to creating such an environment. Subjects were recruited at the University of Louisville in the following groups: HIV-infected (n = 36), COPD (n = 32), HIV and COPD (n = 28), and uninfected controls with normal lung function (n = 34). HIV infection was assessed by viral load and CD4 cell counts. Pulmonary function was determined by spirometry, and plasma was collected for measurement of cysteine (Cys), cystine (CySS), glutathione (GSH) and GSH disulfide (GSSG) by HPLC followed by estimation of redox potentials (E_h) using the Nernst equation. Results showed that patients with COPD had more oxidized plasma E_h Cys/CySS than patients with normal lung function, but plasma E_h GSH/GSSG was unaltered. In addition, there was a correlation between the extent of plasma E_h Cys/CySS oxidation and loss of lung function, and this correlation remained even after correcting for age, sex, race and body mass index. HIV infection per se was not associated with increased oxidation of plasma E_h Cys/CySS, but plasma E_h Cys/CySS was more oxidized in patients with lower CD4-positve T cell counts. In patients with both HIV infection and COPD, there was a significant correlation between CD4 cell counts and lung function. Thus, systemic oxidation correlated with decreased lung function in subjects with COPD and decreased CD4 counts in subjects infected with HIV. Thus, factors contributing to plasma E_h Cys/CySS may represent novel mechanisms underlying the increased prevalence of COPD in people living with HIV.

Cysteine/Glutathione Deficiency: A Significant and Treatable Corollary of Disease

Glutathione (GSH) deficiency may play a pivotal role in a variety of apparently unrelated clinical conditions and diseases. Orally administered N-acetylcysteine (NAC), which replenishes the cysteine required for GSH synthesis, has been tested in a large number of randomized placebo-controlled trials involving these diseases and conditions. This chapter focused on developing a base of evidence suggesting that NAC administration improves disease by increasing cysteine and/or GSH in a variety of diseases, thereby implying a significant role for GSH deficiency in the clinical basis of many diseases. To develop this base of evidence, we systematically selected studies which considered the hypothesis that the therapeutic efficacy for NAC is an indication that cysteine and/or GSH deficiency is a pathophysiological part of the diseases studied. In this manner we focus this chapter on explaining the biological mechanisms of NAC therapy in a wide variety of disorders and demonstrate its ubiquitous role in improving disease that involves disrupted GSH and/or cysteine metabolism.

Oral administration of γ-glutamylcysteine increases intracellular glutathione levels above homeostasis in a randomised human trial pilot study

Objective

To determine if orally dosed γ-glutamylcysteine (γ-GC) can increase cellular glutathione (GSH) levels above homeostasis. Many chronic and age-related disorders are associated with down-regulation, or impairment, of glutamate cysteine ligase (GCL). This suggests that γ-GC supply may become limiting for the maintenance of cellular GSH at the normal levels required to effectively protect against oxidative stress and any resulting physiological damage.

Methods

GSH levels were measured in lymphocytes of healthy, non-fasting participants before and after single oral doses (2 and 4 g) of γ-GC. Blood samples were immediately processed using high speed fluorescence-activated cell sorting to isolate 10⁶ lymphocytes that were then assayed for GSH content.

Results

A single 2 g dose of γ-GC increased lymphocyte GSH content above basal levels (53±47%, p<0.01, n=14) within 90 min of administration. A randomized dosage (2 and 4 g γ-GC) crossover design was used to explore the pharmacokinetics of this GSH increase. In general, for both dose levels (n=9), GSH increased from initial basal levels over 3 h (t_max) before reaching maximum GSH concentrations (C_max) that were near two (2 g γ-GC) to three (4 g γ-GC) fold basal levels (0.4 nmol/10⁶ lymphocytes). Beyond t_max, GSH levels progressively declined reaching near basal levels by 5 h. The GSH half-life was between 2 and 3 h with exposure (AUC) to increased GSH levels of 0.7 (2 g γ-GC) and 1.8 (4 g γ-GC) nmol.h/10⁶ lymphocytes.

Conclusions

Oral γ-GC is a non-toxic form of cysteine that can be directly taken up by cells and transiently increase lymphocyte GSH above homeostatic levels. Our findings that γ-GC can increase GSH levels in healthy subjects suggests that it may have potential as an adjunct for treating diseases associated with chronic GSH depletion. This trial was registered at anzctr.org.au as ACTRN12612000952842.

Alteration of thiol-disulphide homeostasis in acute tonsillopharyngitis

OBJECTIVE

Thiol-disulphide homeostasis (TDH) has a critical role in various clinical disorders. We aimed to assess the association of TDH with acute tonsillopharyngitis (AT) in children.

METHODS

This study included 94 (73 viral and 21 bacterial) tonsillopharyngitis patients and 88 control children. Their native thiol, total thiol, and disulphide levels were measured.

RESULTS

Viral and bacterial tonsillopharyngitis patients had lower native thiol levels compared with healthy children (P < 0.001 and P = 0.008, respectively). Both groups had lower total thiol levels compared with control children (P = 0.002 for viral, P = 0.011 for bacterial). The disulphide levels were lower in bacterial than in viral tonsillopharyngitis patients (P = 0.04), and there was a significant difference between viral tonsillopharyngitis patients and the control group (P < 0.001). The native/total thiol ratio in each patient group was lower than in the control group (P < 0.001 for viral, P = 0.017 for bacterial). The disulphide/native thiol and disulphide/total thiol ratios were significantly higher in viral (P < 0.001 for both) and bacterial tonsillopharyngitis patients (P = 0.017 for both) than in healthy children. In all patients, a correlation was found between the levels of C-reactive protein (CRP) and native thiol (r = -0.211, P = 0.04), CRP and total thiol (r = -0.217, P = 0.036), white blood cell (WBC) and native thiol (r = -0.228, P = 0.002), WBC and total thiol (r = -0.191, P = 0.01), and WBC and disulphide (r = 0.160, P = 0.03).

DISCUSSION

TDH is altered in AT in children. The alteration is more prominent in viral than in bacterial tonsillopharyngitis.

Aging and HIV/AIDS: pathogenetic role of therapeutic side effects

The intersection of aging and HIV/AIDS is a looming 'epidemic within an epidemic.' This paper reviews how HIV/AIDS and its therapy cause premature aging or contribute mechanistically to HIV-associated non-AIDS illnesses (HANA). Survival with HIV/AIDS has markedly improved by therapy combinations containing nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors, and protease inhibitors (PIs) called HAART (highly active antiretroviral therapy). Because NRTIs and PIs together prevent or attenuate HIV-1 replication, and prolong life, the population of aging patients with HIV/AIDS increases accordingly. However, illnesses frequently associated with aging in the absence of HIV/AIDS appear to occur prematurely in HIV/AIDS patients. Theories that help to explain biological aging include oxidative stress (where mitochondrial oxidative injury exceeds antioxidant defense), chromosome telomere shortening with associated cellular senescence, and accumulation of lamin A precursors (a nuclear envelop protein). Each of these has the potential to be enhanced or caused by HIV/AIDS, antiretroviral therapy, or both. Antiretroviral therapy has been shown to enhance events seen in biological aging. Specifically, antiretroviral NRTIs cause mitochondrial dysfunction, oxidative stress, and mitochondrial DNA defects that resemble features of both HANA and aging. More recent clinical evidence points to telomere shortening caused by NRTI triphosphate-induced inhibition of telomerase, suggesting telomerase reverse transcriptase (TERT) inhibition as being a pathogenetic contributor to premature aging in HIV/AIDS. PIs may also have a role in premature aging in HIV/AIDS as they cause prelamin A accumulation. Overall, toxic side effects of HAART may both resemble and promote events of aging and are worthy of mechanistic studies.

T cell responses to drugs and drug metabolites

Understanding the chemical mechanisms by which drugs and drug metabolites interact with cells of the immune system is pivotal to our knowledge of drug hypersensitivity as a whole.In this chapter, we will discuss the currently accepted mechanisms where there is scientific and clinical evidence to support the ways in which drugs and their metabolites interact with T cells. We will also discuss bioanalytical platforms, such as mass spectrometry, and in vitro test assays such as the lymphocyte transformation test that can be used to study drug hypersensitivity; the combination of such techniques can be used to relate the chemistry of drug antigen formation to immune function. Ab initio T cell priming assays are also discussed with respect to predicting the potential of a drug to cause hypersensitivity reactions in humans in relation to the chemistry of the drug and its ability to form haptens, antigens and immunogens in patients.

Idiosyncratic adverse drug reactions: current concepts

Idiosyncratic drug reactions are a significant cause of morbidity and mortality for patients; they also markedly increase the uncertainty of drug development. The major targets are skin, liver, and bone marrow. Clinical characteristics suggest that IDRs are immune mediated, and there is substantive evidence that most, but not all, IDRs are caused by chemically reactive species. However, rigorous mechanistic studies are very difficult to perform, especially in the absence of valid animal models. Models to explain how drugs or reactive metabolites interact with the MHC/T-cell receptor complex include the hapten and P-I models, and most recently it was found that abacavir can interact reversibly with MHC to alter the endogenous peptides that are presented to T cells. The discovery of HLA molecules as important risk factors for some IDRs has also significantly contributed to our understanding of these adverse reactions, but it is not yet clear what fraction of IDRs have a strong HLA dependence. In addition, with the exception of abacavir, most patients who have the HLA that confers a higher IDR risk with a specific drug will not have an IDR when treated with that drug. Interindividual differences in T-cell receptors and other factors also presumably play a role in determining which patients will have an IDR. The immune response represents a delicate balance, and immune tolerance may be the dominant response to a drug that can cause IDRs.

Oxidant-antioxidant imbalance in horses infected with equine infectious anaemia virus

This study assesses the impact of equine infectious anaemia virus (EIAV) infection on the oxidant/antioxidant equilibrium of horses. Blood samples from 96 Romanian horses aged 1-25 years, were divided into different groups according to their EIAV-infection status, age, and time post-seroconversion. The effect of infection on oxidative stress was estimated by measuring enzymatic antioxidants (superoxide dismutase [SOD], glutathione peroxidase [GPx] and catalase), non-enzymatic antioxidants (uric acid and carotenoids), and lipid peroxidation (malondialdehyde [MDA]). Infection modified the oxidant/antioxidant equilibrium in the horses, influencing GPx and uric acid levels (P<0.05). Time post-seroconversion also contributed to oxidative stress imbalance, exhibiting a significant influence on both SOD and MDA concentrations in the blood (P<0.05). Animal age did not have a significant influence on oxidative stress. Recently infected horses (<1 year following seroconversion), and horses >5 years old, represented the most vulnerable category in terms of oxidative stress, followed by recently infected animals <5 years old. The results of this study are novel in implicating EIAV infection in the development of oxidative stress in horses.

Inhibitory effects of glutathione on dengue virus production

Reduced glutathione (GSH) is the most powerful intracellular antioxidant and also involved in viral infections. The pathogenesis of dengue virus (DV) infection has not been completely clarified. This study investigated the relationship between DV serotype 2 (DV2) infections and host intracellular GSH content. Results showed infection with DV2 resulted in a decrease in intracellular GSH, which caused NF-kappaB activation and increased DV2 production. Supplemental GSH significantly inhibited activation of NF-kappaB, resulting in a decreased production of DV2 in HepG2 cells. Furthermore, high activity of NF-kappaB and increased production of DV2 was observed in HepG2 cells treated with buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. In conclusion, DV2 infection could reduce host intracellular GSH concentration and benefited from this process. Supplemental GSH could inhibit viral production, indicating GSH might be valuable in the prevention and treatment of DV2 infection.

Combined ascorbate and glutathione deficiency leads to decreased cytochrome b5 expression and impaired reduction of sulfamethoxazole hydroxylamine

Sulfonamide antimicrobials such as sulfamethoxazole (SMX) have been associated with drug hypersensitivity reactions, particularly in patients with AIDS. A reactive oxidative metabolite, sulfamethoxazole-nitroso (SMX-NO), forms drug-tissue adducts that elicit a T-cell response. Antioxidants such as ascorbic acid (AA) and glutathione (GSH) reduce SMX-NO to the less reactive hydroxylamine metabolite (SMX-HA), which is further reduced to the non-immunogenic parent compound by cytochrome b (5) (b5) and its reductase (b5R). We hypothesized that deficiencies in AA and GSH would enhance drug-tissue adduct formation and immunogenicity toward SMX-NO and that these antioxidant deficiencies might also impair the activity of the b5/b5R pathway. We tested these hypotheses in guinea pigs fed either a normal or AA-restricted diet, followed by buthionine sulfoximine treatment (250 mg/kg SC daily, or vehicle); and SMX-NO (1 mg/kg IP 4 days per week, or vehicle), for 2 weeks. Guinea pigs did not show any biochemical or histopathologic evidence of SMX-NO-related toxicity. Combined AA and GSH deficiency in this model did not significantly increase tissue-drug adduct formation, or splenocyte proliferation in response to SMX-NO. However, combined antioxidant deficiency was associated with decreased mRNA and protein expression of cytochrome b (5), as well as significant decreases in SMX-HA reduction in SMX-NO-treated pigs. These results suggest that SMX-HA detoxification may be down-regulated in combined AA and GSH deficiency. This mechanism could contribute to the higher risk of SMX hypersensitivity in patients with AIDS with antioxidant depletion.

TNF, LTA, HSPA1L and HLA-DR gene polymorphisms in HIV-positive patients with hypersensitivity to cotrimoxazole

AIMS

Sulfamethoxazole in combination with trimethoprim (cotrimoxazole) is used for prophylaxis and treatment of several opportunistic infections in HIV-infected patients. It is associated with a high incidence of hypersensitivity reactions, which is thought to have an immune basis. Genetic polymorphisms in MHC are known to predispose to hypersensitivity reactions to a structurally diverse group of drugs in HIV-positive patients. The aim of the study was to determine whether functional polymorphisms in TNF, LTA, HSPA1L and HLA-DRB1 genes influence the risk of cotrimoxazole hypersensitivity in HIV-infected patients.

METHODS

We genotyped 136 HIV-positive patients with (n = 53) and without (n = 83) cotrimoxazole hypersensitivity using a combination of PCR-based techniques, including PCR-restriction fragment length polymorphisms, PCR-sequence specific oligonucleotides and real-time PCR. Genotypes and the haplotype frequencies were analyzed using the chi(2) test in the Haploview and CLUMP programs.

RESULTS

No statistically significant difference in SNP or haplotype frequencies were found in HIV-infected sulfamethoxazole hypersensitive patients compared with controls.

CONCLUSION

Our data show that MHC polymorphisms are not major predisposing factors for cotrimoxazole hypersensitivity, although we cannot exclude a minor contribution. An environmental factor (i.e., HIV infection) seems to predominate over any of the genetic factors so far investigated in increasing the risk of cotrimoxazole hypersensitivity.

HIV Tat potentiates cell toxicity in a T cell model for sulphamethoxazole-induced adverse drug reactions

HIV infection results in severe immune dysfunction with ensuing sequelae that includes characteristic opportunistic infections. Pneumocystis pneumonia (PCP) is one of the most common of these infections and is routinely treated with sulphamethaxazole (SMX). Although this drug is known to cause hypersensitivity adverse drug reactions (ADRs) in 0.1% of the general population, the incidence of these ADRs increases tenfold in the HIV-positive population. The HIV-1 trans-activator of transcription (HIV-1 Tat) together with the drug metabolite sulphamethaxazole-hydroxylamine (SMX-HA) have both been reported to be factors in these hypersensitivity ADRs. In this study, we use an inducible, Tat-expressing vector system to show that the level of Tat expression contributes to the cellular sensitivity of Jurkat T cells to SMX-HA. We further demonstrated that apoptosis is the likely mechanism by which this occurs. Thus, our data provide insight into the significant increase of SMX-related ADRs during the transition between HIV-1 infection and AIDS.

Nonvitamin, nonmineral dietary supplementation in HIV-positive people

BACKGROUND

Many consumers with chronic diseases attempt to take control of their health by using dietary supplements. The objective of this study was to describe current nonvitamin, nonmineral (NVNM) supplement use of HIV-infected persons in the Nutrition for Healthy Living (NFHL) cohort, the financial burden that buying these supplements might pose to this population, and to review current literature on potential interactions between NVNM supplements.

METHODS

At baseline visit, participants were educated by a registered dietitian on keeping a complete 3-day food record (including all supplements) for 2 weekdays and 1 weekend day. Seventy-two subjects reported consumption of NVNM supplements, and their food records were reviewed in detail.

RESULTS

Each of the 72 subjects in this study used a mean of 6 NVNM supplements, which may have been in the form of a pill, powder, bar, or liquid. The 6 most common were glutamine (51%), N-acetyl-cysteine (36%), fish oil (33%), alpha-lipoic acid (32%), acetyl-l-carnitine (28%), and coenzyme Q10 (28%). Participants were also taking an average of 4 vitamin/mineral supplements; the 6 most common were multivitamin/multimineral (83%), vitamin E (51%), vitamin C (47%), vitamin B complex (43%), calcium (29%), and selenium (28%).

CONCLUSIONS

With a total of 107 different types of NVNM supplements, our estimated cost examples indicated a weekly supplement regimen cost of between $25 and $40 dollars. According to literature review, taking an NVNM supplement may involve some risk because many components have not been studied and these products are not tightly regulated.

Interaction of SIV/SHIV infection and morphine on plasma oxidant/antioxidant balance in macaque

A homeostatic balance exists between the cellular generation of oxidant species and endogenous antioxidants under normal physiological conditions. Human Immunodeficiency Virus (HIV) infection is known to affect this balance causing oxidative stress. However, the interaction of HIV infection with a substance abuse on cellular oxidant/antioxidant system is sparse. This study was designed in order to investigate the interactive effect of morphine abuse and Simian Immunodeficiency Virus/ Simian Human Immunodeficiency Virus (SIV/SHIV) infection on plasma oxidant/antioxidant balance in rhesus macaques. Six rhesus macaques adapted to morphine dependence (20 weeks) along with three controls were infected with mixture of SHIV(KU-1B), SHIV(89.6P), and SIV(17E-Fr). Plasma samples from morphine-dependent and control macaques were analyzed for an array of oxidative stress indices after 16 weeks of infection. Morphine-dependence significantly increased plasma malondialdehyde (MDA) and 8-isoprostane levels (8-fold and 2-fold), but these animals showed higher MDA and 8-isoprostane levels after viral infection (18-fold and 4-fold) which was directly correlated with increase in viral load and decline in CD4+ cells. Plasma glutathione (GSH) level depleted (55%) with morphine dependence that was further depleted (25%) by the infection. Activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were increased by 30% and 110%, respectively with morphine dependence, but that was decreased by the infection. Catalase (CAT) activity declined (25%) with morphine dependence that was further declined by infection. Our results clearly suggest that morphine interaction with SIV/SHIV infection causes higher oxidative tissue injury that might have implication in the pathogenesis of AIDS in morphine-dependent macaques.

Drug hypersensitivity in HIV

PURPOSE OF REVIEW

Drug hypersensitivity has been reported to occur 100 times more commonly in those living with HIV. In the first decade of HIV treatment, this mainly involved drugs used to treat HIV-related infections but now primarily includes drugs used to treat HIV. This review focuses on the current knowledge of the epidemiology, pathophysiology and clinical features of drug hypersensitivity reactions of drugs used in the management of the HIV-infected patient.

RECENT FINDINGS

Our understanding of the immunogenetics and host predisposition to drug hypersensitivity has been advanced considerably by the antiretroviral drugs abacavir and nevirapine. The association of abacavir hypersensitivity reaction with HLA-B*5701 has been particularly important and provides a basis for genetic screening in the clinic setting.

SUMMARY

The increased predisposition of drug hypersensitivity disease in HIV will continue to provide a fertile ground for study of the diverse and complex processes that drive its pathophysiology. Our knowledge of drug hypersensitivity will also increase as the expanding armentarium of antiretroviral therapy is applied to more diverse populations in the developing world. The potential for widespread implementation of HLA-B*5701 screening for abacavir hypersensitivity will set an important precedent for bringing individualized medicine to the clinic and the use of genetic testing to improve drug safety.

Morphine-mediated deterioration of oxidative stress leads to rapid disease progression in SIV/SHIV-infected macaques

Oxidative stress is well documented in HIV infection, but the effect of concomitant substance abuse is largely unknown. We studied oxidative stress in our macaque model of morphine abuse and AIDS. In plasma, we found an approximately 50% decrease in catalase activity with morphine dependence that was exacerbated by infection in rapid progressors. Superoxide dismutase was decreased by a similar degree, but only in the presence of both morphine and viral infection. The loss of these antioxidant systems was coincident with significantly increased plasma malondialdehyde upon viral infection that displayed a synergistic increase in conjunction with morphine and rapid disease.

Immunological principles of T-cell-mediated adverse drug reactions in skin

Drug hypersensitivity reactions in skin are an immune-mediated phenomenon associated with significant patient mortality and morbidity. Antigen-specific T cells, which have been isolated from the peripheral circulation and target organs of hypersensitive patients, are thought to propagate and regulate the development of clinical symptoms. The investigation of clinical cases with respect to the basic cellular and chemical mechanisms that underpin drug hypersensitivity has resulted in: i) the need to redress some aspects of present immunological dogma; and ii) additional fundamental immunological questions. Thus, the aim of this review article is to summarise present opinion on how and why drugs initiate a pathogenic T-cell response in a small section of the population and subsequently reflect on gaps in basic immunology and where future research might lead.

Role of bioactivation in drug-induced hypersensitivity reactions

Drug-induced hypersensitivity reactions are a major problem in both clinical treatment and drug development. This review covers recent developments in our understanding of the pathogenic mechanisms involved, with special focus on the potential role of metabolism and bioactivation in generating a chemical signal for activation of the immune system. The possible role of haptenation and neoantigen formation is discussed, alongside recent findings that challenge this paradigm. Additionally, the essential role of costimulation is examined, as are the potential points whereby costimulation may be driven by reactive metabolites. The relevance of local generation of metabolites in determining the location and character of a reaction is also covered.

Role of Lymphocyte Multidrug Resistance Protein 1 in HIV Infection

The multidrug resistance protein 1 (MRP1) is a drug transporter that protects cells from oxidative stress, which increases HIV-1 replication. The aim of this study was to characterize the expression, function, and role of lymphocyte MRP1 in HIV-1 infection and its modulation by antiretroviral drugs such as the protease inhibitors (PIs). Peripheral blood mononuclear cells (PBMCs) from HIV-positive individuals do not show significant alterations of MRP1 expression despite highly active antiretroviral therapy and HIV plasma viral load levels; however, they exhibit different intracellular MRP1 expression as compared with healthy subjects. By contrast, MRP efflux function is increased in subjects with primary HIV infection and becomes defective in later stages of the infection. PI- and probenecid (PBCD)-mediated inhibition of MRP lowers the in vitro stress-induced response of lymphoid cells by reducing the level of the specific reactive oxygen species superoxide anion and hydrogen peroxide. Finally, the blockade of MRP by PBCD and PIs down-modulates HIV-1 replication by a mechanism independent of inhibition of the HIV-1 protease. Our results are consistent with a model wherein HIV replication is favored by the MRP1-related oxidative stress and inhibition of MRP1 may contribute to the antiviral activity of PIs.

Micronutrient supplementation in children and adults with HIV infection

BACKGROUND

The scale and impact of the HIV/AIDS pandemic has made the search for simple, affordable, safe, and effective public health interventions all the more urgent. Micronutrient supplements hold the promise of meeting these criteria, but their widespread use needs to be based on sound scientific evidence of effectiveness and safety.

OBJECTIVES

To assess whether micronutrient supplements are effective in reducing morbidity and mortality in adults and children with HIV infection.

SEARCH STRATEGY

The Cochrane Library (CENTRAL), EMBASE, MEDLINE, AIDSearch, CINAHL, and conference proceedings were searched, and pharmaceutical manufacturers and researchers in the field were contacted to locate any ongoing or unpublished trials.

SELECTION CRITERIA

Randomised controlled trials comparing the effects of micronutrient supplements (vitamins, trace elements, and combinations of these) with placebo or no treatment on mortality and morbidity in HIV-infected individuals.

DATA COLLECTION AND ANALYSIS

Two reviewers independently appraised trial quality and extracted data. Study authors were contacted for additional data where necessary. A meta-analysis was not deemed appropriate due to significant heterogeneity between trials.

MAIN RESULTS

Fifteen trials were included. Six trials comparing vitamin A/beta-carotene with placebo in adults failed to show any effects on mortality, morbidity, CD4 and CD8 counts, or on viral load. Four trials of other micronutrients in adults did not affect overall mortality, although there was a reduction in mortality in a low CD4 subgroup. In a large Tanzanian trial in pregnant and lactating women, daily multivitamin supplementation was associated with a number of benefits to both mothers and children: a reduction in maternal mortality from AIDS-related causes; a reduced risk of progression to stage four disease; fewer adverse pregnancy outcomes; less diarrhoeal morbidity; and a reduction in early-child mortality among immunologically- and nutritionally-compromised women. Vitamin A alone reduced all-cause mortality and improved growth in a small sub-group of HIV-infected children in one hospital-based trial, and reduced diarrhoea-associated morbidity in a small HIV-infected sub-group of infants in another trial.

AUTHORS' CONCLUSIONS

There is no conclusive evidence at present to show that micronutrient supplementation effectively reduces morbidity and mortality among HIV-infected adults. It is reasonable to support the current WHO recommendations to promote and support adequate dietary intake of micronutrients at RDA levels wherever possible. There is evidence of benefit of vitamin A supplementation in children. The long-term clinical benefits, adverse effects, and optimal formulation of micronutrient supplements require further investigation.

Hypersensitivity of HIV-1-Infected Cells to Reactive Sulfonamide Metabolites Correlated to Expression of the HIV-1 Viral Protein Tat

Impairment of human immunodeficiency virus (HIV)-infected cells to deal with reactive drug metabolites may be a mechanism for the increased rate of adverse drug reactions seen in AIDS. HIV Tat protein expression may be associated with increased oxidative stress within HIV-infected cells. To determine the relationship between expression of HIV Tat and sensitivity to reactive drug metabolites, we studied toxicity of sulfamethoxazole (SMX) and its reactive hydroxylamine intermediate (SMX-HA) in lymphocytes transfected with the HIV tat gene. Over a concentration range from 0 to 400 microM SMX-HA, there was a significant concentration-dependent increase in cell death in transfected cell lines expressing Tat compared with controls. Jurkat T cells transfected with a dose-dependent inducible tat gene showed increased toxicity in response to SMX-HA as more Tat expression was induced. Enhanced sensitivity to SMX-HA was accompanied by significantly lower concentrations of total intracellular glutathione compared with controls (P < 0.05). Sensitivity to reactive drug metabolites in HIV-infected cells seems to be mediated by the viral protein Tat.

Sulfonamide hypersensitivity

Sulfonamide antibiotics can result in a wide variety of hypersensitivity reactions. No validated diagnostic tests are available for sulfonamide reactions; therefore, clinicians must rely on the combination of a careful patient history, review of medical records, and a sound knowledge base regarding the common clinical manifestations of sulfonamide hypersensitivity reactions. Although HIV-infected individuals have a high risk for hypersensitivity reactions to sulfamethoxazole, readministering the drug can usually be performed safely by using a desensitization protocol. Sulfonamide-containing medications that are not antibiotics also have the capacity for causing hypersensitivity reactions. Whether the sulfa moiety confers a risk of cross-reaction is controversial. The preponderance of available evidence suggests that sulfonamide antibiotics probably do not cross-react with sulfonamide nonantibiotics.

Likelihood and Mechanisms of Cross-Allergenicity Between Sulfonamide Antibiotics and Other Drugs Containing a Sulfonamide Functional Group

Concerns about cross-allergenicity between sulfonamide antibiotics and nonantibiotic, sulfonamide-containing drugs persist and can complicate patients' drug therapy unnecessarily. No interaction between the human immune system and the sulfonamide functional group has been demonstrated. The immunologic determinant of type I, immediate hypersensitivity responses to sulfonamide antibiotics is the N1 heterocyclic ring. Nonantibiotic sulfonamides do not contain this structural feature. Non-type I hypersensitivity responses to sulfonamide antibiotics are largely attributable to reactive metabolites that may cause either direct cytotoxicity or immunologic response. Formation of these metabolites is a stereospecific process that occurs at the N4 amino nitrogen of the sulfonamide antibiotics, a structure also not found on any nonantibiotic sulfonamide drugs. The stereospecificity of these reactions implies that cross-reactivity with nonantibiotic sulfonamide-containing drugs is highly unlikely; this assertion is supported by recent literature. However, T-cell recognition of unmetabolized, nonhaptenated parent sulfonamide antibiotic appears to occur in a small subset of hypersensitive patients. Several of the severe cutaneous reactions associated with sulfonamide antibiotics are mediated by T cells. It is not known whether T-cell recognition of antibiotic is related to the sulfonamide functional group. Until the mechanism of this recognition is elucidated, cross-reactivity with nonantibiotic sulfonamides appears to remain at least theoretically possible.

Plant substances as anti-HIV agents selected according to their putative mechanism of action

Despite the continuous advances made in antiretroviral combination therapy, AIDS has become the leading cause of death in Africa and the fourth worldwide. Today, many research groups are exploring the biodiversity of the plant kingdom to find new and better anti-HIV drugs with novel mechanisms of action. In this review, plant substances showing a promising anti-HIV activity are discussed according to the viral targets with which they interact. Most of these compounds, however, interfere with early steps in the HIV replication, such as the virus entry steps and the viral enzymes reverse transcriptase and integrase, whereas until now almost no plant compounds have been found to interact with the many other viral targets. Since some plant substances are known to modulate several cellular factors, such as NF-kappa B and TNF-alpha, which are also involved in the replication of HIV, their role as potential anti-HIV products is also discussed. In conclusion, several plant-derived antiviral agents are good candidates to be further studied for their potential in the systemic therapy and/or prophylaxis of HIV infections, most probably in combination with other anti-HIV drugs.

Drug hypersensitivity reactions in skin: understanding mechanisms and the development of diagnostic and predictive tests

Cutaneous manifestations of drug hypersensitivity can be serious and potentially life threatening and may prevent effective drug therapy. T cells play an important role in the pathology of drug hypersensitivity reactions. Classical studies suggest that T-cell activation requires drug bioactivation, covalent binding to protein and antigen processing to stimulate an immune response. Recent studies have shown that drugs can also be presented to T cells in the absence of antigen processing and drug metabolism. In this article, sulfamethoxazole is used as a paradigm to describe the chemical mechanisms involved in the initiation and maintenance of an aberrant drug antigen specific T-cell response. Presentation of the same drug to different individuals can cause a variety of skin diseases. Such reactions have been classified according to the phenotype and functionality of the T-cell response. This review summarises the different forms of cutaneous hypersensitivity reactions and describes how T-cell clones generated from hypersensitive patients have been used to study the cellular mechanisms of anticonvulsant hypersensitivity. Potential uses of in vitro cell culture assays for patient diagnosis and drug evaluation are also discussed.

Characterization of sulfamethoxazole and sulfamethoxazole metabolite-specific T-cell responses in animals and humans

Sulfamethoxazole (SMX) is associated with hypersensitivity reactions. Identification of drug-specific lymphocytes from hypersensitive patients suggests involvement of the immune system. Lymphocytes from humans recognize SMX and nitroso-SMX (SMX-NO), whereas cells from sensitized rats recognize only SMX-NO. In this investigation, we study the nature of SMX-specific T cells in four species. Male rats, mice, and rabbits were immunized with SMX (50 mg kg-1) or SMX-NO (1 mg kg-1). Lymphocytes and/or splenocytes were isolated and incubated with SMX, SMX-hydroxylamine or SMX-NO and proliferation were measured. Lymphocytes were also isolated from SMX-hypersensitive patients (n = 3) and drug-specific proliferation was measured. In addition, rabbits were bled fortnightly for 4 months to determine whether SMX-NO-specific T cells cross-react with SMX. To confirm that SMX-NO responses were due to covalent binding and not cross-reactivity, cells were pulsed with SMX-NO and/or coincubated with glutathione. Splenocytes from mice, rats, and rabbits proliferated when stimulated with SMX-NO, but not SMX. A 2-h pulse with SMX-NO was sufficient for proliferation, whereas cells coincubated with SMX-NO and glutathione did not proliferate. Rabbit lymphocytes proliferated in the presence of SMX-NO and SMX-hydroxylamine, but not SMX. SMX-hydroxylamine was converted to SMX-NO in culture. The SMXNO-specific response of rabbit lymphocytes was maintained for at least 4 months and the cells did not cross-react with SMX. Human lymphocytes from hypersensitive patients proliferated in the presence of SMX and both metabolites. These results highlight important differences in T-cell recognition of drug (metabolite) antigens in animals that have been sensitized against a drug metabolite and patients with hypersensitivity to the drug.

Monitoring adverse drug reactions to sulfonamide antibiotics in human immunodeficiency virus-infected individuals

Patients infected with the human immunodeficiency virus (HIV) are at higher risk for adverse drug reactions from trimethoprim-sulfamethoxazole (TMP-SMX) than the HIV-negative population. Studying the HIV-positive population the authors aimed to validate the predictive and diagnostic value of the lymphocyte toxicity assay (LTA) for adverse drug reactions. Patient lymphocytes were analyzed for toxicity to SMX and TMP. Of 35 enrolled HIV patients, 18 had TMP-SMX hypersensitivity syndrome reaction (HSR); 10 tolerated the drug; and 5 had never received the drug. When cases with HSR were compared with controls that tolerated the drugs, cytotoxicity was higher for cases: 29.5% +/- 10.1% versus 19.3% +/- 11.2% for SMX (P < 0.022) and 25.0% +/- 11.9% versus 16.3% +/- 11.0% for TMP (P < 0.04). The authors' proposed threshold value for assigning positive results for TMP and SMX hypersensitivities was 22.5%. The LTA has a strong potential for use as a diagnostic tool to assess TMP-SMX hypersensitivity in HIV-infected individuals. Larger patient populations, as well as in vitro studies are needed to further address the reasons for elevated results in immunocompromised patients and to validate the usefulness of the test.

Associations between dietary antioxidant intake and oxidative stress in HIV-seropositive and HIV-seronegative men and women

OBJECTIVE

To describe the relationship between dietary antioxidant intake and oxidative stress in clinically stable HIV-positive and HIV-negative adults.

DESIGN

A cross-sectional study.

METHODS

Average total daily dietary intakes of vitamin C, beta-carotene, alpha-tocopherol, selenium, and zinc from foods and nutritional supplements were estimated in noninstitutionalized individuals using the dietary history method. Plasma malondialdehyde (MDA) concentrations were measured by high-performance-liquid-chromatography (HPLC) whereas peripheral blood mononuclear cell glutathione (PBMC GSH) concentrations were determined spectrophotometrically by an enzymatic recycling assay. Data were analyzed in multiple linear regression models to investigate these relationships.

RESULTS

Regression analysis revealed an inverse relationship between selenium intake and plasma MDA in a model that included the five dietary antioxidants ( R 2 = 0.25; p < .02) and with selenium only ( R 2 = 0.19; p < .01). Both models were adjusted for gender, smoking status, and HIV seropositivity. Antioxidant intake was not associated with PBMC GSH ( R 2 = 0.12, p = .36). In univariate analyses, oxidative stress did not significantly differ between clinically stable HIV-positive and healthy HIV-negative study subjects.

CONCLUSIONS

This is the first study to characterize the relationship between dietary antioxidant intake from food and supplements with oxidative stress. The results suggested dietary selenium intake was strongly and inversely associated with plasma MDA, but dietary antioxidant intakes were not related to PBMC GSH. This study also provides evidence that HIV infection was not specifically associated with oxidative stress among clinically stable individuals.

Antigenicity and immunogenicity of sulphamethoxazole: demonstration of metabolism-dependent haptenation and T-cell proliferation in vivo

Sulphamethoxazole has been associated with the occurrence of hypersensitivity reactions. There is controversy as to whether the immune response is metabolism-dependent or -independent. We have therefore investigated the site of antigen formation and the nature of the drug signal presented to the immune system in vivo. Male Wistar rats were dosed with sulphamethoxazole, sulphamethoxazole hydroxylamine or nitroso sulphamethoxazole. Antigen formation on cell surfaces was determined by flow cytometry using a specific anti-sulphamethoxazole antibody. Immunogenicity was determined by assessment of ex vivo T-cell proliferation. Administration of nitroso sulphamethoxazole, but not sulphamethoxazole or sulphamethoxazole hydroxylamine, resulted in antigen formation on the surface of lymphocytes, splenocytes and epidermal keratinocytes, and a strong proliferative response of splenocytes on re-stimulation with nitroso sulphamethoxazole. Rats dosed with sulphamethoxazole or sulphamethoxazole hydroxylamine did not respond to any of the test compounds. CD4+ or CD8+ depleted cells responded equally to nitroso sulphamethoxazole. The proliferative response to nitroso sulphamethoxazole was seen even after pulsing for only 5 min, and was not inhibited by glutathione. Responding cells produced IFN-gamma, but not IL-4. Haptenation of cells by sulphamethoxazole hydroxylamine was seen after depletion of glutathione by pre-treating the rats with diethyl maleate. Splenocytes from the glutathione-depleted sulphamethoxazole hydroxylamine-treated rats responded weakly to nitroso sulphamethoxazole, but not to sulphamethoxazole or sulphamethoxazole hydroxylamine. Dosing of rats with sulphamethoxazole produced a cellular response to nitroso sulphamethoxazole (but not to sulphamethoxazole or its hydroxylamine) when the animals were primed with complete Freund's adjuvant. These studies demonstrate the antigenicity of nitroso sulphamethoxazole in vivo and provide evidence for the role of drug metabolism and cell surface haptenation in the induction of a cellular immune response in the rat.

Restored antioxidant capacity parallels the immunologic and virologic improvement in children with perinatal human immunodeficiency virus infection receiving highly active antiretroviral therapy

CD3+CD4+ T-lymphocyte numbers, viral load, and serum antioxidant capacity were evaluated in 20 children with perinatal human immunodeficiency virus (HIV) infection one month (T = -1) and one day (T = 0) before and one month (T = 1) and two months (T = 2) after a treatment switch to highly active antiretroviral therapy (HAART). Antioxidant capacity micromol/L) was evaluated by measuring the cuprous ion deriving from a known amount of cupric ion. Compared to control values (998 +/- 113 micromol/L), values in HIV-infected children were lower before HAART (T = -1, 848 +/- 211 micromol/L, P = 0.008; T = 0, 732 +/- 131 micromol/L, P < 0.0001), but similar during HAART (T = 1, 914 +/- 121 micromol/L, P = 0.089; T = 2; 957 +/- 155 micromol/L, P = 0.528; T = 1 and T = 2 vs T = 0, P < 0.0001). Immunologic and virologic improvement paralleled the restored antioxidant capacity. HAART may restore antioxidant capacity suppressing HIV, which inhibits antioxidant capacity. A positive feedback may be triggered since restored antioxidant capacity counterbalances the oxidative stress, which enhances lymphocyte apoptosis and HIV replication.

Plasma cysteine deficiency and decreased reduction of nitrososulfamethoxazole with HIV infection

The aim of these studies was to determine whether HIV-infected patients have a plasma thiol deficiency and whether this is associated with decreased detoxification of the toxic metabolites of sulfamethoxazole. Reduced, oxidized, protein-bound, and total thiol levels were measured in 33 HIV-positive patients and 33 control subjects by an HPLC method utilizing the fluorescent probe bromobimane. The reduction of sulfamethoxazole hydroxylamine and nitrososulfamethoxazole by plasma and the plasma redox balance in the presence of nitrososulphamethoxazole were also determined by HPLC. Reduced plasma cysteine was significantly (p<0.0001) lower in HIV-positive patients (13.0+/-3.0 microM) when compared with control subjects (16.9+/-3.0 microM). Although there was no difference in oxidized, protein-bound, and total cysteine, the thiol/disulfide ratios were lower in HIV-positive patients. Reduced homocysteine was elevated in patients. Plasma from HIV-positive patients was less able to detoxify nitrososulfamethoxazole than control plasma. These findings show that the disturbance in redox balance in HIV-positive patients may alter metabolic detoxification capacity, and thereby predispose to sulfamethoxazole hypersensitivity.

Glutathione and immune function

The immune system works best if the lymphoid cells have a delicately balanced intermediate level of glutathione. Even moderate changes in the intracellular glutathione level have profound effects on lymphocyte functions. Certain functions, such as the DNA synthetic response, are exquisitely sensitive to reactive oxygen intermediates and, therefore, are favoured by high levels of the antioxidant glutathione. Certain signal pathways, in contrast, are enhanced by oxidative conditions and favoured by low intracellular glutathione levels. The available evidence suggests that the lymphocytes from healthy human subjects have, on average, an optimal glutathione level. There is no indication that immunological functions such as resistance to infection or the response to vaccination may be enhanced in healthy human subjects by administration of glutathione or its precursor amino acid cysteine. However, immunological functions in diseases that are associated with a cysteine and glutathione deficiency may be significantly enhanced and potentially restored by cysteine supplementation. This factor has been studied most extensively in the case of human immunodeficiency virus (HIV)-infected patients who were found to experience, on average, a massive loss of S equivalent to a net loss of approximately 4 g cysteine/d. Two randomized placebo-controlled trials have shown that treatment of HIV-infected patients with N-acetyl-cysteine caused in both cases a significant increase in all immunological functions under test, including an almost complete restoration of natural killer cell activity. It remains to be tested whether cysteine supplementation may be useful also in other diseases and conditions that are associated with a low mean plasma cystine level and impaired immunological functions.

N-acetylcysteine replenishes glutathione in HIV infection

BACKGROUND

Glutathione (GSH) deficiency is common in HIV-infected individuals and is associated with impaired T cell function and impaired survival. N-acetylcysteine (NAC) is used to replenish GSH that has been depleted by acetaminophen overdose. Studies here test oral administration of NAC for safe and effective GSH replenishment in HIV infection.

DESIGN

Oral NAC administration in a randomized, 8-week double-blind, placebo-controlled trial followed by optional open-label drug for up to 24 weeks.

SUBJECTS

HIV-infected, low GSH, CD4 T cells < 500 micro L(-1), no active opportunistic infections or other debilitation; n = 81. Study conducted prior to introduction of protease inhibitors.

RESULTS

Whole blood GSH levels in NAC arm subjects significantly increased from 0.88 mM to 0.98 mM, bringing GSH levels in NAC-treated subjects to 89% of uninfected controls (P = 0.03). Baseline GSH levels in the placebo group (0.91) remained essentially the same during the 8 week placebo-controlled trial. T cell GSH, adjusted for CD4 T cell count and beta2-microglobulin levels, also increased in the NAC-treated subjects (P = 0.04). Adverse effects were minimal and not significantly associated with NAC ingestion.

CONCLUSION

NAC treatment for 8 weeks safely replenishes whole blood GSH and T cell GSH in HIV-infected individuals. Thus, NAC offers useful adjunct therapy to increase protection against oxidative stress, improve immune system function and increase detoxification of acetaminophen and other drugs. These findings suggest that NAC therapy could be valuable in other clinical situations in which GSH deficiency or oxidative stress plays a role in disease pathology, e.g. rheumatoid arthritis, Parkinson's disease, hepatitis, liver cirrhosis, septic shock and diabetes.

Decreased antioxidant defence in individuals infected by the human immunodeficiency virus

BACKGROUND

The oxidative stress associated with HIV infection may be important for the progression of the disease because reactive oxygen species activate the nuclear transcription factor NF-kappaB, which is obligatory for HIV replication.

PATIENTS AND METHODS

The activities of the antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1) and glutathione peroxidase (GPx, EC 1.11.1.9) of blood plasma and peripheral blood mononuclear cells, as well as the plasma levels of ascorbate, alpha-tocopherol and beta-carotene, were measured in 75 subjects with HIV infection and in 26 controls. The HIV-infected patients were classified according to the Walter Reed Army Institute criteria.

RESULTS

The extracellular SOD (EC-SOD) of blood plasma activity was decreased in HIV-infected patients compared to controls, while the SOD activity of mononuclear cells decreased with the HIV-associated disease progression. GPx activities and alpha-tocopherol concentration of HIV-infected patients neither differed as compared to controls nor in relation to disease progression. Lower concentrations of ascorbate and beta-carotene were found in HIV-infected patients than in controls. A positive correlation between CD4 lymphocyte counts and the SOD activities of plasma and mononuclear cells was found.

CONCLUSION

These results suggest that abnormalities of antioxidant defence, mainly of SOD activity, are related to the progression of the HIV infection.

Genetic and metabolic control of the mitochondrial transmembrane potential and reactive oxygen intermediate production in HIV disease

Redox mechanims play important roles in replication of human immunodeficiency virus type 1 (HIV-1) and cellular susceptibility to apoptosis signals. Viral replication and accelerated turnover of CD4+ T cells occur throughout a prolonged asymptomatic phase in patients infected by HIV-1. Disease development is associated with steady loss of CD4+ T cells by apoptosis, increased rate of opportunistic infections and lymphoproliferative diseases, disruption of energy metabolism, and generalized wasting. Such pathological states are preceded by: (i) depletion of intracellular antioxidants, glutathione (GSH) and thioredoxin (TRX), (ii) increased reactive oxygen species (ROS) production, and (iii) changes in mitochondrial transmembrane potential (deltapsi(m)). Disruption of deltapsi(m) appears to be the point of no return in the effector phase of apoptosis. Viral proteins Tat, Nef, Vpr, protease, and gp120, have been implicated in initiation and/or intensification of oxidative stress and disruption of deltapsi(m). Redox-sensitive transcription factors, NF-kappaB, AP-1, and p53, support expression of viral genes and proinflammatory lymphokines. ROS regulate apoptosis signaling through Fas, tumor necrosis factor (TNF), and related cell death receptors, as well as the T-cell receptor. Oxidative stress in HIV-infected donors is accompanied by increased glucose utilization both on the cellular and organismal levels. Generation of GSH and TRX from their corresponding oxidized forms is dependent on NADPH provided through the pentose phosphate pathway of glucose metabolism. This article seeks to delineate the genetic and metabolic bases of HIV-induced oxidative stress. Such understanding should lead to development of effective antioxidant therapies in HIV disease.

N-acetyl-cysteine in the therapy of HIV-positive patients

Randomly selected asymptomatic HIV-positive persons reveal, on average, a massive daily loss of sulphur, which appears to represent in first approximation the mean loss throughout the asymptomatic stage, and may explain the widely observed decrease in cyst(e)ine and glutathione levels. This sulphur loss is reasonably expected to lead, within a few years, to a life-threatening condition and may, therefore, contribute decisively to disease progression. Importantly, the rate of sulphur loss is not ameliorated by highly active antiretroviral therapy and may contribute to antiretroviral treatment failure. Several clinical trials on N-acetyl-cysteine treatment of HIV-positive patients have revealed various therapeutic effects, but did not meet the rigorous standards for approval by the health authorities.

Detection of a ferrylhemoglobin intermediate in an endothelial cell model after hypoxia-reoxygenation

A cell culture model of bovine aortic endothelial cells attached to microcarrier beads was used to study the interaction of diaspirin cross-linked hemoglobin (an oxygen-carrying blood substitute) with hypoxia-reoxygenation. Hemoglobin (200 microM) and hypoxia-volume restriction (3-5 h), together and separately, caused toxicity in this model, as measured by decreased cellular replating efficiency. Hemoglobin (60 microM) caused a reduction in hydrogen peroxide concentration and an increase in lipid peroxidation above that induced by hypoxia alone. Incubation of hemoglobin with endothelial cells caused transient oxidation of hemoglobin to its highly reactive and toxic ferryl species after >/=3 h of hypoxia, followed by 1 h of reoxygenation. Lipid peroxidation, which may occur in the presence of ferrylhemoglobin, also occurred after 1 h of reoxygenation. Hemoglobin caused a dose-dependent decrease in intracellular glutathione concentration, suggesting that it caused an oxidative stress to the cells. However, addition of ascorbate, alpha-tocopherol, or trolox did not decrease hemoglobin oxidation in the presence of normal or hypoxic cells. It is concluded that diaspirin cross-linked hemoglobin forms a ferryl intermediate in the absence of any exogenously added oxidant and contributes to the oxidative burden experienced by endothelial cells after hypoxia-reoxygenation, a condition that is likely to be encountered during trauma and surgery when hemoglobin solutions are used as perfusion agents.

Cellular disposition of sulphamethoxazole and its metabolites: implications for hypersensitivity

1. Bioactivation of sulphamethoxazole (SMX) to chemically-reactive metabolites and subsequent protein conjugation is thought to be involved in SMX hypersensitivity. We have therefore examined the cellular metabolism, disposition and conjugation of SMX and its metabolites in vitro. 2. Flow cytometry revealed binding of N-hydroxy (SMX-NHOH) and nitroso (SMX-NO) metabolites of SMX, but not of SMX itself, to the surface of viable white blood cells. Cellular haptenation by SMX-NO was reduced by exogenous glutathione (GSH). 3. SMX-NHOH and SMX-NO were rapidly reduced back to the parent compound by cysteine (CYS), GSH, human peripheral blood cells and plasma, suggesting that this is an important and ubiquitous bioinactivation mechanism. 4. Fluorescence HPLC showed that SMX-NHOH and SMX-NO depleted CYS and GSH in buffer, and to a lesser extent, in cells and plasma. 5. Neutrophil apoptosis and inhibition of neutrophil function were induced at lower concentrations of SMX-NHOH and SMX-NO than those inducing loss of membrane viability, with SMX having no effect. Lymphocytes were significantly (P<0.05) more sensitive to the direct cytotoxic effects of SMX-NO than neutrophils. 6. Partitioning of SMX-NHOH into red blood cells was significantly (P<0.05) lower than with the hydroxylamine of dapsone. 7. Our results suggest that the balance between oxidation of SMX to its toxic metabolites and their reduction is an important protective cellular mechanism. If an imbalance exists, haptenation of the toxic metabolites to bodily proteins including the surface of viable cells can occur, and may result in drug hypersensitivity.

A randomized trial of N-acetylcysteine for prevention of trimethoprim-sulfamethoxazole hypersensitivity reactions in Pneumocystis carinii pneumonia prophylaxis (CTN 057). Canadian HIV Trials Network 057 Study Group

Hydroxylamine derivatives of sulfamethoxazole may be the reactive metabolites that cause adverse reactions to trimethoprim-sulfamethoxazole (TMP-SMX). The increased frequency of reactions observed in HIV-positive individuals is hypothesized to be due to systemic glutathione deficiency and a decreased ability to scavenge these metabolites. Two hundred and thirty-eight patients were randomized to receive or not receive N-acetylcysteine (3 g of the 20% liquid solution) 1 hour before each dose of TMP-SMX (trimethoprim 80 mg, sulfamethoxazole 400 mg) twice daily, which was initiated as primary Pneumocystis carinii pneumonia prophylaxis. Forty-five patients had to discontinue TMP-SMX within 2 months because of fever, rash, or pruritus including 25 of 102 patients (25%) who were receiving TMP-SMX alone and 20 of 96 patients (21%) who were randomized to TMP-SMX and N-acetylcysteine. The difference between treatment groups is 4% (95% confidence interval [CI]: -16%, +9%). No independent association was found with the hypersensitivity reaction and age, gender, race, HIV risk factor, prior AIDS, concurrent use of fluconazole, or baseline CD4. N-acetylcysteine at a dose of 3 g twice daily could not be shown to prevent TMP-SMX hypersensitivity reactions in patients with HIV infection.