血清氧化-还原态的监测及其与细胞损伤的关系

目的 :探讨如何评价体内的氧化还原状态及细胞的氧化还原态改变对细胞增殖、凋亡、损伤等的影响。方法 :测定正常人血清的NADPH/NADP+ 和GSH/GSSG比值 ,以了解该两项指标对机体氧化还原态的监测能力。并在培养的内皮细胞中加入各种浓度的氧化剂过氧化氢 (H2 O2 )和 /或还原剂N 乙酰 L 半胱氨酸(NAC) ,观察NADPH/NADP+ 和GSH/GSSG比值的变化与细胞活力及损伤之间的关系。以LDH释放率 ,细胞培养液中脂质过氧化物 (LPO)的浓度 ,细胞增殖活性、细胞凋亡率 ,观察细胞的增殖、损伤及其与氧化 还原态变化的关系。结果 :①在培养的内皮细胞中加入H2 O2 后 ,GSH/GSSG和NADPH/NADP+ 比值明显降低 ,细胞氧化还原状态偏向氧化应激方向 ,细胞出现氧化应激损伤 ;脂质过氧化物 (LPO)生成增多 ;LDH释放率增加 ;细胞增殖活力下降 ;凋亡率增高。氧化应激性损伤程度与GSH/GSSG和NADPH/NADP+ 比值呈负相关 ( p <0 .0 5 )。②在各浓度H2 O2 组中加入 0 .5mmol·L 1NAC ,GSH/GSSG和NADPH/NADP+ 比值恢复至接近对照组 ,上述氧化应激性损害也受到了不同程度的抑制 ,并在一定范围内呈量效关系。③单独加入NAC ,在高浓度NAC1mmol·L 1M和 2mmol·L 1时 ,GSH/GSSG和NADPH/NADP+ 比值明显升高 (VSControl,p <0 .0 1 ) ,细胞的氧化     

成都地区青年人群中血浆和红细胞还原/氧化型谷胱甘肽的含量及其氧化-还原电位的分布

目的 :测量谷胱甘肽还原型和氧化型在血浆内和红细胞内的含量 ,探讨GSH/GSSG及其氧化还原电位在健康人群的分布情况。方法 :在组织内谷胱甘肽荧光测量法的基础上 ,加以改进 ,对血浆和红细胞内的GSH/GSSG进行测定 ,并计算出GSH/GSSH的氧化还原电位。同时 ,探讨了冷冻保存和去蛋白处理对血浆和红细胞内GSH和GSSG的影响。结果 :改进后的方法具重复性好 ;准确性高 ,回收率在 98.7%和 97.5 % ;标准曲线呈明显线性等良好的测定效率。用本法对 42名年青年健康志愿者的新鲜血浆和红细胞液的谷胱甘肽进行测定 ,结果为 :血浆内GSH的范围为 8.64± 1 .40 μmol/L ,GSSG的范围为 1 .0 8± 0 .2 4μmol/L ,GSH/GSSG的比值为1 0 .2 7± 1 .5 4;红细胞内GSH的范围为 6.81± 1 .3 8μmol/LRBC ,红细胞内GSSG的范围为 0 .77± 0 .3 9μmol/LR BC ,GSH/GSSG的比值为 9.0 2± 3 .61。血浆GSH/GSSG的氧化还原电位为Eh =-2 1 3 .9mV± 4.94mV ;RBC液的Eh =-2 2 1 .4mV± 3 .1 6mV ,血浆内和红细胞内的GSH/GSSG比值以及电位值都呈正态分布。血浆和红细胞在 -80℃条件下保存后对GSH和GSSG的测定有一定影响 (p <0 .0 5 )。结论 :本文建立的GSH/GSSG测定方法具有良好的重复性、准确性 ;测得的青年人血浆和RBC液的GSH/GSSG比值以及     

苯的代谢产物氢醌改变细胞氧化还原状态诱导TNF-α表达

目的:研究苯的代谢产物氢醌(HQ)对HL-60细胞TNF-α产生和细胞活性的影响,并探讨这种影响是否通过氧化还原调节来实现.方法:HL-60细胞用不同浓度HQ刺激24 h后,收集细胞及培养液上清,检测细胞内活性氧、氧化型/还原型谷胱甘肽含量,CCK8检测细胞增殖,流式细胞术(FCM)检测细胞凋亡,ELISA法检测TNF-α含量.结果:5 μmol/L HQ即可诱导GSH水平增高,抑制HL-60细胞增殖,但对GSH/GSSG比例,TNF-α表达及细胞凋亡无显著影响.50、 100 μmol/L HQ可破坏细胞内氧化还原状态,GSH/GSSG比例下降,TNF-α表达增高,显著抑制HL-60细胞增殖,诱导细胞凋亡,抗氧化剂N-乙酰半胱氨酸能拮抗HQ诱导的TNF-α表达、增殖抑制及细胞凋亡.结论:HQ可通过改变HL-60细胞内氧化还原状态诱导TNF-α表达,导致细胞凋亡.     

甲基丙烯酸环氧丙酯对大鼠肝脏谷胱甘肽含量的影响及其可能的生物学意义

大鼠一次经胃给予50mg/kg剂量的GMA(Glycidyl Methacrylate),两周后测定显示,其肝脏还原型谷胱甘肽(GSH)含量显著降低,氧化型谷胱甘肽(GSSG)含量明显增加,总谷胱甘肽库(GSH+GSSG)和GSH/GSSG比值亦显著减小,实验还表明,上述改变可能与GMA对不同种类DNA的损伤和基因变异作用密切相关。     

一种简便、准确的血清氧化及还原型辅酶II的分光光度测定法的建立

由于辅酶II在正常细胞稳态及许多代谢异常中均非常重要,寻找一个简便而可靠的方法测定氧化型及还原型辅酶II对于了解机体的氧化还原稳态将非常有益.本法是对Nisselbam法稍加改进,运用一个敏感的酶循环反应以分光光度法测定血清中的辅酶II,结果显示标准曲线线性关系良好,加样回收较完全.用本法测定的27例健康献血员,血清NADPH、NADP+及其比值NADPH/NADP+分别为8.385±1.516nmol/ml,3.624±0.985nmol/ml,2.3612±0.805,男女性别无明显差异.本法灵敏、准确、重现性好、费用低、操作简便,是测定氧化型及还原型辅酶II的较佳选择.     

气功水的电导率变化及氧化还原电位的影响

本文研究了气功水的电导率变化及氧化还原电位的影响。发现外气容易被水吸收，水中的气含量依赖于水的电导率的氧化还原电位。气很容易被电导率为０．８￣８μｓｃｍ＾－１的蒸馏水吸收，并且发现，蒸馏水的氧化还原电位越低，气越容易被吸收。但是对于电导率值高于蒸馏水１０００倍以上的北京自来水，井水，有气较难进入的倾向。     

HSPB1对心肌细胞氧化应激时氧化还原状态的影响

目的:本研究主要探讨HSPB1如何调控细胞的氧化还原状态从而发挥抗心肌损伤的作用。方法:以过氧化氢(H_2O_2)诱导的H9c2心肌细胞氧化应激损伤为模型,转染HSP25表达质粒或小分子干扰RNA,观察细胞存活率、LDH水平、细胞凋亡、活性氧水平、谷胱甘肽含量和GSH/GSSG比值的变化,非还原变性蛋白质印迹检测谷氧还蛋白1(Trx1)、谷胱甘肽过氧化物酶(GR)氧化还原状态的改变。结果:HSPB1过表达抑制H_2O_2所致的LDH释放以及caspase 3和PARP的断裂;HSPB1过表达不能减少过氧化氢引起的活性氧水平增加和不能增加细胞内GSH的含量,但可抑制H_2O_2所致的GSH/GSSG比值的降低。非还原性蛋白质印迹显示HSPB1过表达明显减少了H_2O_2所致的GR和Trx1的氧化。HSPB1表达下调促进H_2O_2所致的细胞死亡、LDH释放以及caspase 3和PARP的断裂,以及GSH/GSSG比值的下降;同时,非还原性蛋白质印迹显示HSPB1表达下调明显增加了H_2O_2所致的GR和Trx1的氧化。结论:HSPB1在心肌细胞氧化应激损伤中通过调控GR和Trx1的氧化还原状态起到抗细胞凋亡的作用。     

乙酰半胱氨酸对糖尿病大鼠心肌缺血再灌注损伤的保护作用及其机制

目的: 观察乙酰半胱氨酸对糖尿病大鼠心肌缺血/再灌注后导致的细胞凋亡的影响,探讨其机制.方法: 链尿佐菌素诱导糖尿病大鼠模型,随机分为假手术组、缺血/再灌注组和缺血/再灌注+乙酰半胱氨酸治疗组.组织匀浆检测心肌组织还原型谷胱甘肽(GSH)、氧化型谷胱甘肽(GSSG)含量和半胱氨酸天冬氨酸蛋白酶-3(Caspase-3)的活性;脱氧核糖核苷酸末端转移酶介导的缺口末端标记(TUNEL)和琼脂糖凝胶电泳检测DNA片段化两种方法检测心肌细胞凋亡并计算凋亡指数.结果: 缺血/再灌注后,糖尿病和非糖尿病组均出现明显的心肌细胞凋亡,同时伴有GSH含量降低,GSSG含量和Caspase-3的活性升高,上述变化糖尿病组比非糖尿病组更明显(P<0.05);乙酰半胱氨酸干预的糖尿病和非糖尿病大鼠的心肌细胞凋亡均减轻,同时伴有GSH含量上升,GSSG含量和Caspase-3的活性下降,上述变化非糖尿病组比糖尿病组更明显(P<0.05).结论: 乙酰半胱氨酸干预可以通过提高心肌GSH含量、降低Caspase-3的活性减轻糖尿病和非糖尿病大鼠缺血/再灌注引起的心肌细胞凋亡,对缺血/再灌注心肌有保护作用,但糖尿病组的疗效低于非糖尿病组.     

TIMP-3基因甲基化与结直肠癌临床病理的关系

目的：探讨TIMP-3基因甲基化与结直肠癌临床病理指标和转移复发的关系。 方法： 采用巢式甲基化特异性PCR技术（nMSP法）检测100例结直肠癌组织和100例癌旁非癌组织TIMP-3基因甲基化；采用RT-PCR检测100例结直肠癌组织和100例癌旁非癌组织TIMP-3 mRNA的表达。 结果： 肿瘤组织TIMP-3 mRNA的表达阳性率为64%，肿瘤组织TIMP-3 mRNA的表达率明显低于癌旁非癌组织（P＜0.01）；TIMP-3 mRNA的表达率无淋巴结转移组（34/42）高于淋巴结转移组（30/58）（P＜0.01），甲基化阳性率Duke’s C+D期伴淋巴结转移组明显高于Duke’s A+B期不伴淋巴结转移组（P＜0.05）。结肠近端、分化程度差的结直肠癌组织甲基化阳性率明显高于远端直肠和分化程度高者（P＜0.05）。 结论： TIMP-3基因甲基化容易发生在结肠近端、Duke’s C、D期、伴淋巴结转移、细胞分化差和浸润型结直肠癌患者。     

慢性乙型病毒性肝炎患者趋化因子IP-10、Rantes与氧化损伤的关系研究

目的 观察慢性乙型病毒性肝炎(CHB)患者血清趋化因子IP - 10、Rantes和氧化损伤的改变,探讨趋化因子和氧化应激在CHB发病机制中的作用.方法 采集70例CHB患者和10例健康志愿者血液标本,采用ELISA法检测血清趋化因子IFN-γ诱导蛋白10(IP-10)、正常T细胞表达分泌的活化调节因子(Rantes)表达水平及还原型谷胱甘肽(GSH)、氧化型谷胱甘肽(GSSG)水平,并进行相关性分析.结果 CHB患者血清IP-10、Rantes水平均明显高于健康对照者,并且IP-10、Rantes水平分别与丙氨酸转氨酶水平呈正相关.CHB患者GSH、GSH/GSSG水平均明显低于健康对照者,降低的GSH、GSH/GSSG水平分别与患者ALT水平呈负相关.IP-10、Rantes水平分别与GSH、GSH/GSSG呈负相关.结论 趋化因子和氧化应激相互作用,参与慢性乙型病毒性肝炎的发生和发展.     

Pentose phosphate shunt, pyridine nucleotides, glutathione, and insulin secretion of fetal islets

In rat fetal islets it was tested whether their failure to respond to glucose with insulin secretion might be due to inadequate changes of the redox state of pyridine nucleotides and of glutathione. In islets of newborn (5 days) and adult (3 mo) rats elevation of glucose produced an increase in insulin secretion, pentose phosphate shunt (PPS) activity, and NADPH/NADP, NADH/NAD, and GSH/GSSG ratios. An increase in the NADH/NAD ratio was also observed in islets of fetal rats, but in contrast to islets of newborns and adults no increase in insulin release, PPS activity, and the GSH/GSSG ratio was observed. However, at all glucose concentrations tested islets of fetal rats exhibited a high NADPH/NADP ratio similar to the ratio of adult rats in the presence of 16.7 mM glucose. It is suggested that in fetal islets there exists a lack of hydrogen transfer from NADPH to GSSG. The high NADPH/NADP ratio may in turn suppress PPS activity. It is possible that the missing insulin release of fetal islets in response to glucose is at least in part due to the fact that the oxidation-reduction state of the GSH/GSSG system also does not respond to the elevation of the glucose concentration.     

NAD/NADH,NADP/NADPH und GSSG/GSH in menschlichen Erythrocyten

Zusammenfassung Die Gehalte menschlicher Erythrocyten an Pyridinnucleotiden wurden in kombinierten optischen Testen gemessen: NAD und NADP mit ADH und G-6-PDH, NADH und NADPH mit GDH-TIM und GlDH. Mittelwerte in nMol/ml Erythrocyten: NAD 42, NADH 22, NADP 24, NADPH 51. Diskussion der Ergebnisse im Hinblick auf Probleme der Regulation der direkten Glucoseoxydation, für die im Erythrocyten wahrscheinlich nicht der NADPH/NADP-Quotient, sondern der GSH/GSSG-Quotient (=99:1) eine regulative Funktion besitzt.

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Summary The pyridine nucleotide content of human erythrocytes, measured by combined optical tests with ADH and G-6-PDH (NAD, NADP) and GDH-TIM and GlDH (NADH, NADPH) is: NAD 42, NADH 22, NADP 24, NADPH 51 nMol/ml red cells (mean values). The results are discussed especially in respect to problems of regulation of the direct glucose oxydation. They support the suggestion, that not NADPH/NADP but GSH/GSSG (99:1) is responsible for this pathway.

     

Cathepsin B responsiveness to glutathione and lipoic acid redox

Some subcomponents of cell protein degradation exhibit an unexplained reductive energy requirement; and diverse cysteine proteases are among multiple effector mechanisms requiring reduction. Present studies investigated whether cathepsin B activity is graded in response to (a) reduced glutathione (GSH) and dihydrolipoic acid (DHLA) concentrations, (b) their redox ratios, and (c) their differential potencies and efficacies. Purified bovine cathepsin B activity was assayed with carbobenzyloxy-Arg-Arg-aminomethylcoumarin by standard methods following inactivation by spontaneous air oxidation. Endogenous GSH concentration (2-3 mM) maintained 30-40% of the maximal cathepsin B reaction rate observed under dithiothreitol (5 mM). Following activation with GSH, the cathepsin B reaction rate was inhibited in proportion to nonphysiologic GSH:GSSG redox ratio above 1% oxidized (e.g., 85% inhibited at 3 mM:2 mM). Thus, cathepsin B can be redox buffered by the GSH:GSSG ratio. DHLA was identified as a potent cathepsin activator with threshold near 1 microM and 80% maximal activation near 10 microM. Conversely, oxidized lipoamide disulfide inhibited cathepsin B over 5-250 microM. DHLA at 5-50 microM superimposed severalfold additional activation upon the stable submaximal cathepsin B reaction rate maintained by endogenous GSH concentration (2-3 mM). Cell protein degradation was bioassayed by release of [3H] leucine from the biosynthetically labeled rat heart under nonrecirculating perfusion. The pro-oxidant, diamide (100 microM), reversibly inhibited 80% of basal proteolysis. Supraphysiologic extracellular DHLA (80 microM) doubled the basal rate of averaged cell protein degradation in 15 min. Thus, the cell redox system buffers an intermediate rate of protein degradation, which can be decreased by supraphysiologic exposure to diamide pro-oxidant or increased by DHLA reductant.     

L-carnitine and DL-alpha-lipoic acid reverse the age-related deficit in glutathione redox state in skeletal muscle and heart tissues

In the present study, the glutathione redox system was evaluated as a function of age in rat heart and muscle. A decline in reduced glutathione (GSH) levels is associated with aging and many age-related diseases. The objective of this study was to determine whether L-carnitine and DL-alpha-lipoic acid could compensate for GSH depletion in protection against oxidative insults. In this study we determined reduced glutathione, oxidized glutathione (GSSG), glutathione peroxidase (GPx), glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G6PDH) in skeletal muscle and heart of young and aged rats. We also calculated GSH/GSSG molar ratio and glutathione redox system. GSH levels were significantly lowered in aged rats than young rats. Conversely, GSSG levels were significantly high in aged rats. GSH/GSSG molar ratio and redox index were found to decreased in aged rats. The activities of GPx, GR, and G6PDH were found to be decreased in aged rats when compared with young rats. Supplementation of carnitine and lipoic acid to aged rats significantly increased the GSH levels thereby increasing the activity of GPx, GR, and G6PDH in skeletal muscle and heart of aged rats. In conclusion, our study suggests that supplementation of carnitine and lipoic acid to aged rats improves the glutathione redox system.     

Altered glutathione redox state in schizophrenia

Altered antioxidant status has been reported in schizophrenia. The glutathione (GSH) redox system is important for reducing oxidative stress. GSH, a radical scavenger, is converted to oxidized glutathione (GSSG) through glutathione peroxidase (GPx), and converted back to GSH by glutathione reductase (GR). Measurements of GSH, GSSG and its related enzymatic reactions are thus important for evaluating the redox and antioxidant status. In the present study, levels of GSH, GSSG, GPx and GR were assessed in the caudate region of postmortem brains from schizophrenic patients and control subjects (with and without other psychiatric disorders). Significantly lower levels of GSH, GPx, and GR were found in schizophrenic group than in control groups without any psychiatric disorders. Concomitantly, a decreased GSH:GSSG ratio was also found in schizophrenic group. Moreover, both GSSG and GR levels were significantly and inversely correlated to age of schizophrenic patients, but not control subjects. No significant differences were found in any GSH redox measures between control subjects and individuals with other types of psychiatric disorders. There were, however, positive correlations between GSH and GPx, GSH and GR, as well as GPx and GR levels in control subjects without psychiatric disorders. These positive correlations suggest a dynamic state is kept in check during the redox coupling under normal conditions. By contrast, lack of such correlations in schizophrenia point to a disturbance of redox coupling mechanisms in the antioxidant defense system, possibly resulting from a decreased level of GSH as well as age-related decreases of GSSG and GR activities.     

Oxidation of plasma cysteine/cystine redox state in endotoxin-induced lung injury

Several lines of evidence indicate that perturbations in the extracellular thiol/disulfide redox environment correlate with the progression and severity of acute lung injury (ALI). Cysteine (Cys) and its disulfide Cystine (CySS) constitute the most abundant, low-molecular-weight thiol/disulfide redox couple in the plasma, and Cys homeostasis is adversely affected during the inflammatory response to infection and injury. While much emphasis has been placed on glutathione (GSH) and glutathione disulfide (GSSG), little is known about the regulation of the Cys/CySS couple in ALI. The purpose of the present study was to determine whether endotoxin administration causes a decrease in Cys and/or an oxidation of the plasma Cys/CySS redox state (E(h) Cys/CySS), and to determine whether these changes were associated with changes in plasma E(h) GSH/GSSG. Mice received endotoxin intraperitoneally, and GSH and Cys redox states were measured at time points known to correlate with the progression of endotoxin-induced lung injury. E(h) in mV was calculated using Cys, CySS, GSH, and GSSG values by high-performance liquid chromatography and the Nernst equation. We observed distinct effects of endotoxin on the GSH and Cys redox systems during the acute phase; plasma E(h) Cys/CySS was selectively oxidized early in response to endotoxin, while E(h) GSH/GSSG remained unchanged. Unexpectedly, subsequent oxidation of E(h) GSH/GSSG and E(h) Cys/CySS occurred as a consequence of endotoxin-induced anorexia. Taken together, the results indicate that enhanced oxidation of Cys, altered transport of Cys and CySS, and decreased food intake each contribute to the oxidation of plasma Cys/CySS redox state in endotoxemia.     

Glutathione-dependent redox status of frataxin-deficient cells in a yeast model of Friedreich's ataxia

Friedreich's ataxia is a neurodegenerative disease caused by reduced expression of the mitochondrial protein frataxin. The main phenotypic features of frataxin-deficient human and yeast cells include iron accumulation in mitochondria, iron-sulphur cluster defects and high sensitivity to oxidative stress. Glutathione is a major protective agent against oxidative damage and glutathione-related systems participate in maintaining the cellular thiol/disulfide status and the reduced environment of the cell. Here, we present the first detailed biochemical study of the glutathione-dependent redox status of wild-type and frataxin-deficient cells in a yeast model of the disease. There were five times less total glutathione (GSH+GSSG) in frataxin-deficient cells, imbalanced GSH/GSSG pools and higher glutathione peroxidase activity. The pentose phosphate pathway was stimulated in frataxin-deficient cells, glucose-6-phosphate dehydrogenase activity was three times higher than in wild-type cells and this was coupled to a defect in the NADPH/NADP(+) pool. Moreover, analysis of gene expression confirms the adaptative response of mutant cells to stress conditions and we bring evidence for a strong relation between the glutathione-dependent redox status of the cells and iron homeostasis. Dynamic studies show that intracellular glutathione levels reflect an adaptation of cells to iron stress conditions, and allow to distinguish constitutive stress observed in frataxin-deficient cells from the acute response of wild-type cells. In conclusion, our findings provide evidence for an impairment of glutathione homeostasis in a yeast model of Friedreich's ataxia and identify glutathione as a valuable indicator of the redox status of frataxin-deficient cells.     

Glutathione redox regulates lipopolysaccharide-induced IL-12 production through p38 mitogen-activated protein kinase activation in human monocytes: role of glutathione redox in IFN-gamma priming of IL-12 production

We examined whether changes in intracellular reduced (GSH) or oxidized (GSSG) glutathione of human monocytes regulate lipopolysaccharide (LPS)-induced IL-12 production and defined the molecular mechanism that underlies glutathione redox regulation. Monocytes exposed to glutathione reduced form ethyl ester (GSH-OEt) or maleic acid diethyl ester (DEM) increased or decreased the intracellular GSH/GSSG ratio, respectively. LPS-induced IL-12 production and p38 mitogen-activated protein (MAP) kinase activation were enhanced by GSH-OEt but suppressed by DEM. Selective p38 inhibitors showed that p38 promoted GSH-OEt-enhanced IL-12 production. Furthermore, IFN-gamma priming increased the GSH/GSSG ratio and enhanced IL-12 production through p38, and DEM negated the priming effect of IFN-gamma on p38 activation and IL-12 production as well as on the GSH/GSSG ratio. These findings reveal that glutathione redox regulates LPS-induced IL-12 production from monocytes through p38 MAP kinase activation and that the priming effect of IFN-gamma on IL-12 production is partly a result of the glutathione redox balance.     

Redefining oxidative stress

Oxidative stress is often defined as an imbalance of pro-oxidants and antioxidants, which can be quantified in humans as the redox state of plasma GSH/GSSG. Plasma GSH redox in humans becomes oxidized with age, in response to oxidative stress (chemotherapy, smoking), and in common diseases (type 2 diabetes, cardiovascular disease). However, data also show that redox of plasma GSH/GSSG is not equilibrated with the larger plasma cysteine/cystine (Cys/CySS) pool, indicating that the "balance" of pro-oxidants and antioxidants cannot be defined by a single entity. The major cellular thiol/disulfide systems, including GSH/GSSG, thioredoxin- 1 (-SH(2)/-SS-), and Cys/CySS, are not in redox equilibrium and respond differently to chemical toxicants and physiologic stimuli. Individual signaling and control events occur through discrete redox pathways rather than through mechanisms that are directly responsive to a global thiol/disulfide balance such as that conceptualized in the common definition of oxidative stress. Thus, from a mechanistic standpoint, oxidative stress may be better defined as a disruption of redox signaling and control. Adoption of such a definition could redirect research to identify key perturbations of redox signaling and control and lead to new treatments for oxidative stress-related disease processes.     

Molecular mechanisms and potential clinical significance of S-glutathionylation

Protein S-glutathionylation, the reversible binding of glutathione to protein thiols (PSH), is involved in protein redox regulation, storage of glutathione, and protection of PSH from irreversible oxidation. S-Glutathionylated protein (PSSG) can result from thiol/disulfide exchange between PSH and GSSG or PSSG; direct interaction between partially oxidized PSH and GSH; reactions between PSH and S-nitrosothiols, oxidized forms of GSH, or glutathione thiyl radical. Indeed, thiol/disulfide exchange is an unlikely intracellular mechanism for S-glutathionylation, because of the redox potential of most Cys residues and the GSSG export by most cells as a protective mechanism against oxidative stress. S-Glutathionylation can be reversed, following restoration of a reducing GSH/GSSG ratio, in an enzyme-dependent or -independent manner. Currently, definite evidence of protein S-glutathionylation has been clearly demonstrated in few human diseases. In aging human lenses, protein S-glutathionylation increases; during cataractogenesis, some of lens proteins, including alpha- and beta-crystallins, form both mixed disulfides and disulfide-cross-linked aggregates, which increase with cataract severity. The correlation of lens nuclear color and opalescence intensity with protein S-glutathionylation indicates that protein-thiol mixed disulfides may play an important role in cataractogenesis and development of brunescence in human lenses. Recently, specific PSSG have been identified in the inferior parietal lobule in Alzheimer's disease. However, much investigation is needed to clarify the actual involvement of protein S-glutathionylation in many human diseases.