硫辛酸对2型糖尿病下肢血管病变患者血清8异前列腺素F2α水平的影响

目的 观察硫辛酸对2型糖尿病（T2DM）下肢血管病变患者血清8异前列腺素F2α（8 iso PGF2α）水平的影响。方法 选择T2DM患者288例,根据踝肱比（ABI）分为单纯T2DM组191例和下肢血管病变组97例,下肢血管病变组又分为常规治疗组和硫辛酸组。硫辛酸治疗剂量0.6 g/d,疗程2周。并设正常对照组100例。检测治疗前后血清8 iso PGF2α水平,记录治疗前后无痛行走距离和最大行走距离。结果 单纯T2DM组血清8 iso PGF2α水平明显高于正常对照组（P＜0.05）;下肢血管病变组血清8 iso PGF2α水平高于单纯T2DM组（P＜0.05）。经过2周的治疗,常规治疗组和硫辛酸组血清8 iso PGF2α水平均有所下降,硫辛酸组降低较为明显（P＜0.05）;两组无痛行走距离及最大行走距离均有所增加（P＜0.05）,硫辛酸组增加较为明显（P＜0.05）。结论 血清8 iso PGF2α水平与T2DM下肢血管病变程度有关,硫辛酸可以降低T2DM下肢血管病变患者的血清8 iso PGF2α水平,并改善临床症状。     

The impact of redox and thiol status on the bone marrow: Pharmacological intervention strategies

Imbalances in cancer cell redox homeostasis provide a platform for new opportunities in the development of anticancer drugs. The control of severe dose-limiting toxicities associated with redox regulation, including myelosuppression and immunosuppression, remains a challenge. Recent evidence implicates a critical role for redox regulation and thiol balance in pathways that control myeloproliferation, hematopoietic progenitor cell mobilization, and immune response. Hematopoietic stem cell (HSC) self-renewal and differentiation are dependent upon levels of intracellular reactive oxygen species (ROS) and niche microenvironments. Redox status and the equilibrium of free thiol:disulfide couples are important in modulating immune response and lymphocyte activation, proliferation and differentiation. This subject matter is the focus of the present review. The potential of redox modulating chemotherapeutics as myeloproliferative and immunomodulatory agents is also covered.     

Preclinical pharmacokinetic analysis of NOV-002, a glutathione disulfide mimetic

NOV-002 is a glutathione disulfide (GSSG) mimetic that is the subject of clinical investigation in oncology indications. GSSG is reduced by glutathione reductase (GR) to form glutathione (GSH), thereby maintaining redox homeostasis. The purpose of the study was to report the pharmacokinetic properties of NOV-002 and evaluate the effect that NOV-002 elicits in redox homeostasis. The pharmacokinetic analysis and tissue distribution of NOV-002 and GSH was evaluated in mice following a dose of 250 mg/kg, i.p. The redox potential and total protein thiol status was calculated. Here we show that NOV-002 is a substrate for GR and that GSH is a primary metabolite. Non-linear pharmacokinetic modeling predicted that the estimated absorption and elimination rate constants correspond to a half-life of ∼13 min with an AUC of 1.18 μg h/mL, a C_max of 2.16 μg/ml and a volume of distribution of 42.61 L/kg. In addition, measurement of the redox potential and total protein thiol status indicated the generation of a transient oxidative signal in the plasma compartment after administration of NOV-002. These results indicate that NOV-002 exerts kinetic and dynamic effects in mice consistent with the GSSG component as the active pharmacological constituent of the drug. A longer-lasting decrease in total plasma free thiol content was also seen, suggesting that the oxidative effect of the GSSG from NOV-002 was impacting redox homeostasis.     

Uptake and reduction of alpha-lipoic acid by human erythrocytes

OBJECTIVES: The reducing capacity of erythrocytes has been used clinically as to estimate resistance to oxidant stress. In this work we targeted the antioxidant capacity of pyridine nucleotide disulfide reductases of these cells by measuring their ability to reduce the disulfide alpha-lipoic acid. METHODS: Erythrocyte reduction of alpha-lipoic acid and related disulfides was measured as reduction of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) outside the cells. RESULTS: Lipoic acid-dependent DTNB reduction by human erythrocytes required d-glucose and consumed NADPH, but not NADH. This activity was inhibited by carmustine and phenylarsine oxide, as expected if alpha-lipoic acid is reduced by the glutathione and thioredoxin reductase systems. Reduction of hydroxyethyl disulfide, which provides an estimate of total erythrocyte disulfide reduction capacity, was similar to that of alpha-lipoic acid. Erythrocytes incubated with alpha-lipoic acid also reduced extracellular ferricyanide, although rates of dehydroascorbate reduction were several-fold greater, probably because intracellular GSH can recycle ascorbate but not alpha-lipoic acid in erythrocytes. CONCLUSION: These results show that alpha-lipoic acid-dependent DTNB reduction provides a simple method to selectively assess the capacity of pyridine nucleotide disulfide reductases of human erythrocytes. When coupled with other non-destructive assays, such as reduction of hydroxyethyl disulfide and ferricyanide, this assay provides a comprehensive approach to assessing erythrocyte reducing capacity in a variety of clinical conditions associated with oxidant stress.     

Disulfide bond based polymeric drug carriers for cancer chemotherapy and relevant redox environments in mammals

Increasing numbers of disulfide linkage‐employing polymeric drug carriers that utilize the reversible peculiarity of this unique covalent bond have been reported. The reduction‐sensitive disulfide bond is usually employed as a linkage between hydrophilic and hydrophobic polymers, polymers and drugs, or as cross‐linkers in polymeric drug carriers. These polymeric drug carriers are designed to exploit the significant redox potential difference between the reducing intracellular environments and relatively oxidizing extracellular spaces. In addition, these drug carriers can release a considerable amount of anticancer drug in response to the reducing environment when they reach tumor tissues, effectively improving antitumor efficacy. This review focuses on various disulfide linkage‐employing polymeric drug carriers. Important redox thiol pools, including GSH/GSSG, Cys/CySS, and Trx1, as well as redox environments in mammals, will be introduced.     

Coenzyme Q10 and α-lipoic acid: antioxidant and pro-oxidant effects in plasma and peripheral blood lymphocytes of supplemented subjects

Reactive oxygen species not only cause damage but also have a physiological role in the protection against pathogens and in cell signalling. Mitochondrial nutrients, such as coenzyme Q₁₀ and α-lipoic acid, beside their acknowledged antioxidant activities, show interesting features in relation to their redox state and consequent biological activity. In this study, we tested whether oral supplementation with 200 mg/day of coenzyme Q₁₀ alone or in association with 200 mg/die of α-lipoic acid for 15 days on 16 healthy subjects was able to modulate the oxidative status into different compartments (plasma and cells), in basal condition and following an oxidative insult in peripheral blood lymphocytes exposed in vitro to H₂O₂. Data have shown that tested compounds produced antioxidant and bioenergetic effects improving oxidative status of the lipid compartment and mitochondrial functionality in peripheral blood lymphocytes. Simultaneously, an increased intracellular reactive oxygen species level was observed, although they did not lead to enhanced DNA oxidative damage. Coenzyme Q₁₀ and α-lipoic acid produced beneficial effects also steering intracellular redox poise toward a pro-oxidant environment. In contrast with other antioxidant molecules, pro-oxidant activities of tested mitochondrial nutrients and consequent oxidant mediated signalling, could have important implications in promoting adaptive response to oxidative stress.     

硫辛酸联合缬沙坦治疗早期糖尿病肾病及改善炎症进程的疗效观察

目的探讨硫辛酸联合缬沙坦对早期糖尿病肾病患者氧化应激及炎症水平的影响。 方法收集潍坊市人民医院2016年12月至2017年6月入院的128例早期糖尿病肾病患者,按入院时间随机分为4组。对照组患者给予常规治疗,实验组3组患者分别加用硫辛酸静脉滴注、缬沙坦口服及硫辛酸联合缬沙坦治疗,比较4组患者治疗前后糖代谢、尿蛋白水平、氧化应激水平及炎症水平,治疗前后比较采用配对样本t检验,组间比较首先进行方差分析,再采用LSD-t检验分别进行组间的两两比较。 结果硫辛酸组、缬沙坦组及联合组患者治疗后尿白蛋白、尿白蛋白/尿肌酐、丙二醛（MDA）、超敏C反应蛋白（hs-CRP）、8-异前列腺素F2α（8-iso-PGF2α）水平组间比较低于对照组[（20.36±4.32）mg/L vs （23.35±5.38）mg/L vs （16.48±3.37）mg/L vs （44.57±7.78）mg/L;（42.13±21.52）mg/g vs （45.78±16.47）mg/g vs （34.62±23.58）mg/g vs （74.72±15.33）mg/g;（4.71±0.78）mol/ml vs （5.17±0.84）mol/ml vs （3.87±1.31）mol/ml vs （5.96±0.96）mol/ml;（2.24±0.98）mg/L vs （2.35±1.17）mg/L vs （1.76±1.26）mg/L vs （2.93±1.15）mg/L;（34.98±6.51）ng/L vs （36.78±9.46）ng/L vs （30.19±13.25）ng/L vs （44.38±12.27）ng/L],差异具有统计学意义（t=19.815、17.373、22.992,P均<0.001;t=10.029、8.906、12.026,P均<0.001;t=6.514、4.128、10.848,P均<0.001;t=5.769、4.999、7.721,P均<0.001;t=4.004、3.238、6.043,P<0.001、=0.001、<0.001）;超氧化物歧化酶（SOD）水平高于对照组[（78.62±5.31）U/ml vs （75.28±9.24）U/ml vs （83.31±6.18）U/ml vs （72.13±7.35）U/ml],差异具有统计学意义（t=4.879、2.365、8.412,P<0.001、=0.019、<0.001）。且缬沙坦联合硫辛酸组较单用缬沙坦组或单用硫辛酸组患者治疗后尿白蛋白、尿白蛋白/尿肌酐、MDA、hs-CRP、8-iso-PGF2α水平低、SOD水平高,差异具有统计学意义（t=3.177、5.619,P=0.002、<0.001;t=1.996、3.120,P=0.047、<0.001;t=4.333、6.719,P=0.002、<0.001;t=1.981、2.478,P=0.049、=0.007;t=2.039、2.806,P=0.043、=0.006;t=3.533、6.047,P=0.001、<0.001）。 结论硫辛酸联合缬沙坦治疗可以改善早期糖尿病肾病患者氧化应激及炎症状态,具有治疗指导意义。     

Knockout Studies Reveal an Important Role of Plasmodium Lipoic Acid Protein Ligase A1 for Asexual Blood Stage Parasite Survival

Lipoic acid (LA) is a dithiol-containing cofactor that is essential for the function of α-keto acid dehydrogenase complexes. LA acts as a reversible acyl group acceptor and ‘swinging arm’ during acyl-coenzyme A formation. The cofactor is post-translationally attached to the acyl-transferase subunits of the multienzyme complexes through the action of octanoyl (lipoyl): N-octanoyl (lipoyl) transferase (LipB) or lipoic acid protein ligases (LplA). Remarkably, apicomplexan parasites possess LA biosynthesis as well as scavenging pathways and the two pathways are distributed between mitochondrion and a vestigial organelle, the apicoplast. The apicoplast-specific LipB is dispensable for parasite growth due to functional redundancy of the parasite's lipoic acid/octanoic acid ligases/transferases. In this study, we show that LplA1 plays a pivotal role during the development of the erythrocytic stages of the malaria parasite. Gene disruptions in the human malaria parasite P. falciparum consistently were unsuccessful while in the rodent malaria model parasite P. berghei the LplA1 gene locus was targeted by knock-in and knockout constructs. However, the LplA1⁽⁻⁾ mutant could not be cloned suggesting a critical role of LplA1 for asexual parasite growth in vitro and in vivo. These experimental genetics data suggest that lipoylation during expansion in red blood cells largely occurs through salvage from the host erythrocytes and subsequent ligation of LA to the target proteins of the malaria parasite.     

Modulation of extracellular homocysteine concentration in human cell lines

BACKGROUND: Despite the growing evidence that plasma homocysteine is a cardiovascular risk factor, the mechanism behind the vascular injuries is still unknown. Information about the metabolism of homocysteine is, therefore, essential for an understanding of its role in atherogenesis, thereby enabling a modulation of that risk. METHODS: In the present study, we have examined the modulation of extracellular homocysteine in HeLa and hepatoma cell cultures in relation to a changed extracellular thiol redox status and in the presence of specific inhibitors of amino acid transporters. RESULTS: The findings in the present study show that a changed thiol redox status by copper ions, copper chelator or the monothiol, N-acetylcysteine (NAC), affects extracellular homocysteine in the same way in hepatoma cell cultures, but not to the same extent as observed in HeLa cell cultures. However, the dithiols, dithiothreitol (DTT) and alpha-lipoic acid (LA), which lowered extracellular homocysteine concentration in HeLa cell cultures, increased the extracellular total homocysteine concentration in hepatoma cell cultures, probably mainly as a result of increased release of homocysteine extracellularly. Studies with specific inhibitors of amino acid transporters in HeLa cell cultures showed that homocysteine uptake occurred mainly by system A and glutamate transporters. Hepatoma cells seemed to have a much smaller uptake capacity of homocysteine compared to HeLa cells. CONCLUSION: The lack of uptake capacity of homocysteine in hepatoma cells indicates that hepatocytes only play a small role in the elimination of homocysteine from circulation. Intracellular metabolism, cellular export and the complex pattern of homocysteine uptake in different cells are important to examine further in order to possibly be able to lower plasma homocysteine levels.     

Effect of alpha‐lipoic acid on endometrial implants in an experimental rat model

To investigate the antioxidant and anti‐inflammatory effects of alpha‐lipoic acid (ALA) in the treatment of endometriosis in an experimental rat model by evaluating biochemical and histopathologic parameters. Experimental endometriosis was induced by the peritoneal implantation of autologous endometrial tissue. The rats were randomly divided into two groups with eight rats each. Group I was intraperitoneally administered ALA 100 mg/kg/day for 14 days. Group II was intraperitoneally administered saline solution at the same dosage and over the same period. Endometrial implant volume was measured in both groups both pre‐ and post‐treatment. Tumor necrosis factor alpha (TNF‐α) was measured in peritoneal fluid. Total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) were assessed in serum. The implants were histopathologically evaluated. In the ALA group, the serum TOS and OSI levels, the endometrial implant volumes, the TNF‐α levels in serum and peritoneal fluid, and the histopathologic scores were significantly lower compared to the control group (P < 0.05). Alpha‐lipoic acid may have a therapeutic potential in the treatment of endometriosis due to its antioxidant and anti‐inflammatory effects.     

前列地尔联合硫辛酸辅助治疗糖尿病足的临床研究

目的:探讨前列地尔联合硫辛酸治疗糖尿病足的临床效果和安全性。方法:将2009年1月至2012年12月收治的糖尿病足患者101例随机分为对照组(n=49)和治疗组(n=52),对照组予以严格控制血糖、血压、清创、改善循环、抗感染等常规治疗,治疗组在对照组治疗的基础上加用前列地尔10 ug加入生理盐水100 ml中静脉滴注,每日一次,硫辛酸300 mg加入生理盐水250 ml中静脉滴注,每日一次,2周为一疗程,比较2疗程后两组的临床疗效和不良反应。结果:治疗组总有效率92.3%(48/52)明显高于对照组的67.4%(33/49),P0.01;两组均未发现明显毒副作用。结论:在常规治疗的基础上,加用前列地尔和硫辛酸治疗糖尿病足能提高疗效,且无明显副作用。     

Allosteric disulfide bonds in thrombosis and thrombolysis

Allosteric disulfide bonds control protein function by mediating conformational change when they undergo reduction or oxidation. The known allosteric disulfide bonds are characterized by a particular bond geometry, the -RHStaple. A number of thrombosis and thrombolysis proteins contain one or more disulfide bonds of this type. Tissue factor (TF) was the first hemostasis protein shown to be controlled by an allosteric disulfide bond, the Cys186-Cys209 bond in the membrane-proximal fibronectin type III domain. TF exists in three forms on the cell surface: a cryptic form that is inert, a coagulant form that rapidly binds factor VIIa to initiate coagulation, and a signaling form that binds FVIIa and cleaves protease-activated receptor 2, which functions in inflammation, tumor progression and angiogenesis. Reduction and oxidation of the Cys186-Cys209 disulfide bond is central to the transition between the three forms of TF. The redox state of the bond appears to be controlled by protein disulfide isomerase and NO. Plasmin(ogen), vitronectin, glycoprotein 1balpha, integrin beta(3) and thrombomodulin also contain -RHStaple disulfides, and there is circumstantial evidence that the function of these proteins may involve cleavage/formation of these disulfide bonds.     

叶酸、硫辛酸联合足底穴位按摩对高危糖尿病足患者的疗效观察

目的探讨联合应用叶酸、静脉加口服硫辛酸序贯治疗及足底穴位按摩对高危糖尿病足(DF)的康复效果。方法120例高危DF患者随机分为4组,对照组采用糖尿病基础治疗,叶酸组在对照组基础上加用叶酸,硫辛酸组在叶酸组基础上加用α-硫辛酸静脉滴注2周后口服,按摩组在硫辛酸组基础上加用足底穴位按摩治疗,疗程6个月。比较干预前后4组多伦多症状体征评分、肱踝脉搏波传导速度(ba PWV)、踝肱比(ABI)以及生活质量评分变化。结果叶酸组、硫辛酸组、按摩组同型半胱氨酸、ba PWV较对照组显著下降(P0.01);多伦多症状体征评分除叶酸组外均较对照组显著降低(P0.01);ABI除叶酸组外均较对照组显著升高(P0.01);生活质量评分除叶酸组外均较对照组显著降低(P0.01);硫辛酸组、按摩组氧化型低密度脂蛋白显著低于未用硫辛酸组(P0.01)。结论叶酸、硫辛酸联合足底按摩可以改善DF治疗效果。     

Genetic rescue of nonclassical ERα signaling normalizes energy balance in obese Erα-null mutant mice

In addition to its role in reproduction, estradiol-17β is critical to the regulation of energy balance and body weight. Estrogen receptor α-null (Erα-/-) mutant mice develop an obese state characterized by decreased energy expenditure, decreased locomotion, increased adiposity, altered glucose homeostasis, and hyperleptinemia. Such features are reminiscent of the propensity of postmenopausal women to develop obesity and type 2 diabetes. The mechanisms by which ERα signaling maintains normal energy balance, however, have remained unclear. Here we used knockin mice that express mutant ERα that can only signal through the noncanonical pathway to assess the role of nonclassical ERα signaling in energy homeostasis. In these mice, we found that nonclassical ERα signaling restored metabolic parameters dysregulated in Erα-/- mutant mice to normal or near-normal values. The rescue of body weight and metabolic function by nonclassical ERα signaling was mediated by normalization of energy expenditure, including voluntary locomotor activity. These findings indicate that nonclassical ERα signaling mediates major effects of estradiol-17β on energy balance, raising the possibility that selective ERα agonists may be developed to reduce the risks of obesity and metabolic disturbances in postmenopausal women.     

Vicinal thiols are required for activation of the αIIbβ3 platelet integrin

Summary. Background: Closely spaced thiols in proteins that interconvert between the dithiol form and disulfide bonds are called vicinal thiols. These thiols provide a mechanism to regulate protein function. We previously found that thiols in both αIIb and β3 of the αIIbβ3 fibrinogen receptor were required for platelet aggregation. Methods and Results: Using p‐chloromercuribenzene sulfonate (pCMBS) we provide evidence that surface thiols in αIIbβ3 are exposed during platelet activation. Phenylarsine oxide (PAO), a reagent that binds vicinal thiols, inhibits platelet aggregation and labeling of sulfhydryls in both αIIb and β3. For the aggregation and labeling studies, binding of PAO to vicinal thiols was confirmed by reversal of PAO binding with the dithiol reagent 2,3‐Dimercapto‐1‐propanesulfonic acid (DMPS). In contrast, the monothiol β‐mercaptoethanol did not reverse the effects of PAO. Additionally, PAO did not inhibit sulfhydryl labeling of the monothiol protein albumin, confirming the specificity of PAO for vicinal thiols in αIIbβ3. As vicinal thiols represent redox sensitive sites that can be regulated by reducing equivalents from the extracellular or cytoplasmic environment, they are likely to be important in regulating activation of αIIbβ3. Additionally, when the labeled integrin was passed though a lectin column containing wheat germ agglutinin and lentil lectin a substantial amount of non‐labeled αIIbβ3 eluted separately from the labeled receptor. This suggests that two populations of integrin exist on platelets that can be distinguished by thiol labeling. Conclusion: A vicinal thiol‐containing population of αIIbβ3 provides redox sensitive sites for regulation of αIIbβ3.     

Thiol redox status influences extracellular concentration of homocysteine in HeLa cell cultures.

We have recently shown that low concentrations of copper ions increased the extracellular concentration of homocysteine in a HeLa cell culture system. This increase might be attributed to copper-induced oxidation of extracellular homocysteine, since earlier reports suggest that the oxidized fraction of homocysteine seems to be less available for cellular uptake than the reduced fraction. To investigate further this mechanism we have therefore, in the present study, determined intra- and extracellular concentrations of homocysteine and their relations to the extracellular thiol redox status. The results of this study show that the redox status of homocysteine is important for its extracellular concentration. Increased oxidation of thiols catalyzed by copper ions resulted in an increased extracellular concentration of homocysteine, whereas the addition of antioxidant agents (N-acetylcysteine or dithiothreitol) or a specific copper(I) ion chelator (bathocuproinedisulfonic acid) was accompanied by a decreased extracellular concentration of homocysteine. These effects are probably dependent on differences in cellular uptake between reduced and oxidized homocysteine.     

Roles of vitamin A in the regulation of fatty acid synthesis

Dietary macronutrients and micronutrients play important roles in human health. On the other hand, the excessive energy derived from food is stored in the form of triacylglycerol. A variety of dietary and hormonal factors affect this process through the regulation of the activities and expression levels of those key player enzymes involved in fatty acid biosynthesis such as acetyl-CoA carboxylase, fatty acid synthase, fatty acid elongases, and desaturases. As a micronutrient, vitamin A is essential for the health of humans. Recently, vitamin A has been shown to play a role in the regulation of glucose and lipid metabolism. This review summarizes recent research progresses about the roles of vitamin A in fatty acid synthesis. It focuses on the effects of vitamin A on the activities and expression levels of mRNA and proteins of key enzymes for fatty acid synthesis in vitro and in vivo. It appears that vitamin A status and its signaling pathway regulate the expression levels of enzymes involved in fatty acid synthesis. Future research directions are also discussed.     

Inhibiting Rotavirus Infection by Membrane-Impermeant Thiol/Disulfide Exchange Blockers and Antibodies against Protein Disulfide Isomerase

Objectives: Determining the effect of membrane-impermeant thiol/disulfide exchange inhibitors on rhesus rotavirus infectivity in MA104 cells and investigating protein disulfide isomerase (PDI) as a potential target for these inhibitors. Methods: Cells were treated with DTNB [5,5-dithio-bis-(2-nitrobenzoic acid)], bacitracin or anti-PDI antibodies and then infected with virus. Triple-layered particles (TLPs) were also pretreated with inhibitors before inoculation. The effects of these inhibitors on α-sarcin co-entry, virus binding to cells and PDI-TLP interaction were also examined. FACS analysis, cell-surface protein biotin-labeling, lipid-raft isolation and ELISA were performed to determine cell-surface PDI expression. Results: Infectivity became reduced by 50% when cells or TLPs were treated with 1 or 6 mM DTNB, respectively; infectivity became reduced by 50% by 20 mM bacitracin treatment of cells whereas TLPs were insensitive to bacitracin treatment; anti-PDI antibodies decreased viral infectivity by about 45%. The presence of DTNB (2.5 mM) or bacitracin (20 mM) was unable to prevent virus binding to cells and rotavirus-induced α-sarcin co-entry. Conclusions: It was concluded that thiol/disulfide exchange was involved in rotavirus entry process and that cell-surface PDI was at least a potential target for DTNB and bacitracin-induced infectivity inhibition.     

Alteration in the redox state of plasma in heart-transplant patients with moderate hyperhomocysteinemia

Hyperhomocysteinemia has recently been suggested to contribute to the progression of the so-called chronic rejection or cardiac allograft vasculopathy (CAV) in heart-transplant patients in which the major determinant of the increase in homocysteine (Hcy) was the progressive decline of renal function. The exact mechanisms of tissue injury by Hcy is unknown, but some aspects of its toxicity have been related to its capacity for altering the redox state of plasma and forming protein adducts by intermediate lactone. To study the relationships between Hcy levels and variations in the redox state governed by thiols, plasma levels of Hcy, cysteine, glutathione, cysteinylglycine, and corresponding disulfides and protein-mixed disulfides were evaluated in subjects with moderate hyperhomocysteinemia represented by heart-transplant patients with (HTRF) and without (HT) renal failure, as well as patients with renal failure of different origin (RF), and compared with those of a control group (C) of normal subjects matched for age and sex. Plasma levels of Hcy and the corresponding protein mixed disulfides increased progressively in HTs, RFs, and HTRFs with respect to control. These changes were correlated with cysteine variations (as cystine and protein-mixed disulfides) but not with glutathione or cysteinylglycine that varied only as disulfides with a similar tendency. Moreover, an alteration in the plasma redox was evidenced by the decrease in thiol/disulfide ratios of cysteine, Hcy, and cysteinylglycine. In all groups, cysteine was directly correlated with Hcy but not with glutathione or cysteinylglycine, which in turn were correlated each other. Therefore levels of plasma cysteine were more linked to Hcy than to metabolism of glutathione. The clinical meaning of cysteine changes remains undefined and requires further study.