Thiol/Disulfide Ratios, HOMA Score, and Quality of Sleep in Renal Transplant Recipients Without Diabetes

OBJECTIVES

Thiols play an important role in defense against reactive oxygen species. We aimed to evaluate the relation between oxidative stress, glucose tolerance, and sleep quality in kidney transplant recipients without diabetes.

MATERIALS AND METHODS

We enrolled 95 kidney transplant recipients without diabetes from living and deceased donors with stable allograft function and 60 healthy controls. We included recipients who received a kidney from a living donor with a first-degree relation. Insulin resistance was determined using the Homeostasis Model Assessment score. Native thiol, total thiol, and disulfide levels were measured, and disulfide versus native thiol/total thiol ratios were calculated from all patients. We used the Pittsburg Sleep Quality Index to assess sleeping patterns. According to standard cutoff value of the index (≤5 indicates good quality sleep; >5 indicates poor sleep quality), we stratified kidney transplant recipients as group 1 (Pittsburg Sleep Quality Index ≤5; n = 41) and group 2 (Pittsburg Sleep Quality Index >5; n = 54).

RESULTS

In correlation analysis, Pittsburg Sleep Quality Index was positively correlated with age, the Homeostasis Model Assessment score, body mass index, serum disulfide levels, disulfide/total thiol ratio, and native/total thiol ratio. The Pittsburgh Sleep Quality Index was negatively correlated with total thiol levels. In subgroup analysis, the Homeostasis Model Assessment score, disulfide levels, and disulfide/total thiol and native/total thiol ratios were significantly lower in group 1; however, total thiol level was significantly higher in this group. In multivariate regression analysis, age, the Homeostasis Model Assessment score, disulfide/total thiol ratio, and renal resistivity index were detected as predictors of sleep quality score.

CONCLUSIONS

Sleep quality moderates oxidative stress identified by thiol-disulfide homeostasis and insulin resistance in renal transplant recipients without diabetes.

Thiol reductive stress activates the hypoxia response pathway

Owing to their capability to disrupt the oxidative protein folding environment in the endoplasmic reticulum (ER), thiol antioxidants, such as dithiothreitol (DTT), are used as ER-specific stressors. We recently showed that thiol antioxidants modulate the methionine-homocysteine cycle by upregulating an S-adenosylmethionine-dependent methyltransferase, rips-1, in Caenorhabditis elegans. However, the changes in cellular physiology induced by thiol stress that modulate the methionine-homocysteine cycle remain uncharacterized. Here, using forward genetic screens in C. elegans, we discover that thiol stress enhances rips-1 expression via the hypoxia response pathway. We demonstrate that thiol stress activates the hypoxia response pathway. The activation of the hypoxia response pathway by thiol stress is conserved in human cells. The hypoxia response pathway enhances thiol toxicity via rips-1 expression and confers protection against thiol toxicity via rips-1-independent mechanisms. Finally, we show that DTT might activate the hypoxia response pathway by producing hydrogen sulfide. Our studies reveal an intriguing interaction between thiol-mediated reductive stress and the hypoxia response pathway and challenge the current model that thiol antioxidant DTT disrupts only the ER milieu in the cell.

The association of fasting plasma thiol fractions with body fat compartments, biomarker profile, and adipose tissue gene expression

People with high plasma total cysteine (tCys) have higher fat mass and higher concentrations of the atherogenic apolipoprotein B (apoB). The disulfide form, cystine, enhanced human adipogenesis and correlated with total fat mass in a Middle-Eastern cohort. In 35 European adults with overweight (88.6% women) and with dual-X-ray absorptiometry measurements of regional fat, we investigated how cystine compared to other free disulfides in their association with total regional adiposity, plasma lipid and glucose biomarkers, and adipose tissue lipid enzyme mRNA (n = 19). Most total plasma homocysteine (tHcy) (78%) was protein-bound; 63% of total glutathione (tGSH) was reduced. tCys was 49% protein-bound, 30% mixed-disulfide, 15% cystine, and 6% reduced. Controlling for age and lean mass, cystine and total free cysteine were the fractions most strongly associated with android and total fat: 1% higher cystine predicted 1.97% higher android fat mass (95% CI 0.64, 3.31) and 1.25% (0.65, 2.98) higher total fat mass (both p = 0.005). A positive association between tCys and apoB (β: 0.64%; 95% CI 0.17, 1.12%, p = 0.009) was apparently driven by free cysteine and cystine; cystine was also inversely associated with the HDL-associated apolipoprotein A1 (β: -0.57%; 95% CI -0.96, -0.17%, p = 0.007). No independent positive associations with adiposity were noted for tGSH or tHcy fractions. Plasma cystine correlated with CPT1a mRNA (Spearman's r = 0.68, p = 0.001). In conclusion, plasma cystine-but not homocysteine or glutathione disulfides-is associated with android adiposity and an atherogenic plasma apolipoprotein profile. The role of cystine in human adiposity and cardiometabolic risk deserves investigation. ClinicalTrials.gov identifiers: NCT02647970 and NCT03629392.

Perturbed gut microbiome and fecal and serum metabolomes are associated with chronic kidney disease severity

BACKGROUND

Chronic kidney disease (CKD) is a severe public health problem associated with a disordered gut microbiome. However, the functional alterations of microbiota and their cross talk with metabolism pathways based on disease severity remain unclear.

RESULTS

We performed metagenomics and untargeted metabolomics in a cohort of 68 patients with CKD of differing severities and 20 healthy controls to characterize the complex interplay between the gut microbiome and fecal and serum metabolites during CKD progression. We identified 26 microbial species that significantly changed in patients with CKD; 18 species changed as the disease progressed, and eight species changed only in a specific CKD group. These distinct changes in gut microbiota were accompanied by functional alterations in arginine and proline, arachidonic acid, and glutathione metabolism and ubiquinone and other terpenoid-quinone biosynthesis pathways during CKD progression. Further metabolomic analyses revealed that the distributions of toxic and pro-oxidant metabolites from these four essential metabolic pathways varied in the feces and serum as CKD progressed. Furthermore, we observed a complex co-occurrence between CKD severity-related bacteria and the characterized metabolites from the four essential metabolic pathways. Notably, Ruminococcus bromii, fecal hydroquinone, and serum creatinine were identified as the main contributors to the integrated network, indicating their key roles in CKD progression. Moreover, a noninvasive model including R. bromii and fecal hydroquinone, L-cystine, and 12-keto-tetrahydro-LTB4 levels classified the CKD severity (area under the curve [AUC]: > 0.9) and had better performance than the serum creatinine level for mild CKD (AUC: 0.972 vs. 0.896).

CONCLUSIONS

Perturbed CKD severity-related gut microbiota may contribute to unbalanced toxic and pro-oxidant metabolism in the gut and host, accelerating CKD progression, which may be an early diagnostic and therapeutic target for CKD. Video Abstract.

Essential and Non-Essential Amino Acids in Dogs at Different Stages of Chronic Kidney Disease

Abnormalities of serum amino acid profile, mostly characterized by a reduction in essential amino acids (EAAs) and an increase in non-essential amino acids (NEAAs), have been documented in human chronic kidney diseases (CKD). Amino acid disorders have been associated with CKD complications, such as metabolic acidosis and malnutrition. The aim of the present study was to evaluate EAAs and NEAAs in dogs affected by CKD at different IRIS stages, with particular reference to calcium−phosphate abnormalities, metabolic acidosis, and protein-energy wasting syndrome (PEW). Serum EAAs (L-histidine, L-isoleucine, L-leucine, L-lysine, methionine, L-phenylalanine, L-threonine, tryptophan, L-valine, and L-arginine) and serum NEAAs (L-alanine, L-aspartic acid, L-cysteine, L-glutamic acid, glycine, proline, L-serine, and L-tyrosine) were analyzed with HPLC in a group of dogs with CKD (n = 62), and in a group of healthy dogs (n = 25). CKD dogs showed significantly lower serum levels of histidine (p < 0.000), isoleucine (p < 0.000), tryptophan (p < 0.000), alanine (p = 0.013), cysteine (p < 0.000), and serine (p = 0.002), and significantly higher levels of proline (p < 0.000), leucine (p = 0.001), lysine (p < 0.000), valine (p < 0.000), arginine (p = 0.002), glutamic acid (p = 0.002), and glycine (p = 0.010) compared to healthy dogs. Dogs with abnormal calcium x phosphate values showed significantly higher levels of cysteine (p = 0.003), and lower levels of tryptophan (p = 0.025) compared to CKD dogs with normal CaxP. Dogs with metabolic acidosis showed significantly higher levels of phenylalanine (p = 0.035) and leucine (p = 0.034) compared to CKD dogs without metabolic acidosis. Dogs with PEW showed significantly lower levels for most of amino acids. In PEW dogs, the median distribution of both EAAs (p = 0.000) and NEAAs (p = 0.001) was significantly lower. The serum pattern of both EAAs and NEAAs was significantly different in CKD dogs compared to healthy dogs, although no association with the progression of the IRIS stage was found.

Evaluation of serum thiol-disulphide homeostasis parameters as oxidative stress markers in epilepsy patients

The present study focuses on the investigation of the dynamic thiol-disulphide homeostasis in patients with epilepsy and understanding the effects of antiepileptic drugs on thiol levels. A total of 148 participants, 75 of whom had epilepsy and 73 were healthy volunteers, were included in the study. Total thiol and native thiol levels of all epilepsy patients and healthy volunteers were measured. Disulphide level, disulphide/native thiol, disulphide/total thiol and native/total thiol ratios were calculated from these values. The results were compared between epilepsy patients and healthy volunteers. A statistically significant difference was found between native thiol level, total thiol level, disulphide level, disulfide/total thiol, disulphide/native thiol and native/total thiol ratios between patients with epilepsy and healthy volunteers (p = 0.002, p = 0.035, p < 0.001, p < 0.001, p < 0.001, p < 0.001, respectively). The drugs used had a significant effect on disulphide, disulphide/total thiol, native/total thiol levels (p values 0.004, 0.009, 0.009, respectively). Decreased levels of serum native, total thiol and increased disulfide levels as parameters of oxidative stress may be considered as parameters to explain the pathogenesis or consequences of epilepsy.

Thiol/disulfide homeostasis in medication-naive children and adolescents with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) causes significant psychic distress and affects children's social and academic functioning. Approximately 80% of OCD cases begin in childhood. Earlier onset is associated with more severe OC symptoms, poorer treatment response, and a more unfavorable clinical course. A particular oxidative stress marker, thiol/disulfide homeostasis, using a new, comparatively inexpensive, easily calculated, easily accessible, repeatable, and fully automated method was investigated between pediatric patients diagnosed with OCD and a healthy control group in this study. This study is the first to address this subject in pediatric patients with OCD and aims to contribute to our knowledge of the etiopathogenesis and treatment of pediatric OCD. The study included children with OCD (n = 35, 52.2%) (drug free, comorbidity free) between 11 and 18 years of age and age- and sex-matched healthy controls (n = 32, 47.8%). The total thiol (p = 0.025) and disulfide (p = 0.001) levels and the disulfide/native thiol (p = 0.001) and disulfide/total thiol ratios (p = 0.001) were significantly different between the groups. Also, in the patient group, biochemical analysis revealed that the disulfide level (p = 0.05) and the disulfide/native thiol (p = 0.034) and disulfide/total thiol ratios (p = 0.039) differed significantly according to the presence of a family history of psychiatric disorders. Consequently, the results of our study show that thiol/disulfide homeostasis may affect the etiopathogenesis of pediatric OCD and can be utilized as a new method when evaluating oxidative stress.

The association of dynamic thiol-disulphide balance with white-coat hypertension

OBJECTIVE

Dynamic thiol-disulphide homeostasis is an indicator of the antioxidant system that interacts early with the oxidative environment. This study aimed to assess the dynamic thiol/disulphide balance in individuals with white-coat hypertension (WCH).

METHODS

This cross-sectional study included a total of 117 individuals who presented to our outpatient cardiology clinic. Seventy patients were diagnosed with WCH. All blood samples were obtained from the patients after a minimum of 8 h of fasting, centrifuged immediately, stored in Eppendorf tubes, and protected at -80°C.

RESULTS

The two groups were well-balanced in terms of age, gender, and BMI. Native thiol and total thiol levels were lower in the WCH group than in normotensive individuals. However, disulphide levels were higher in the former. Serum disulphide concentration positively correlated with 24-h SBP, and 24-h DBP. In backward stepwise logistic regression analysis, serum disulphide [odds ratio (OR) = 1.165 (1.089-1.245), 95% confidence interval (CI), P < 0.001] and serum total thiol levels [OR = 0.992 (0.984-1.000), 95% CI, P = 0.050] were independently associated with WCH.

CONCLUSION

We demonstrated that dynamic thiol/disulphide balance shifted strongly towards disulphide formation due to thiol oxidation in patients with WCH.

Simultaneous Determination of Human Serum Albumin and Low-Molecular-Weight Thiols after Derivatization with Monobromobimane

Biothiols are extremely powerful antioxidants that protect cells against the effects of oxidative stress. They are also considered relevant disease biomarkers, specifically risk factors for cardiovascular disease. In this paper, a new procedure for the simultaneous determination of human serum albumin and low-molecular-weight thiols in plasma is described. The method is based on the pre-column derivatization of analytes with a thiol-specific fluorescence labeling reagent, monobromobimane, followed by separation and quantification through reversed-phase high-performance liquid chromatography with fluorescence detection (excitation, 378 nm; emission, 492 nm). Prior to the derivatization step, the oxidized thiols are converted to their reduced forms by reductive cleavage with sodium borohydride. Linearity in the detector response for total thiols was observed in the following ranges: 1.76–30.0 mg mL⁻¹ for human serum albumin, 0.29–5.0 nmol mL⁻¹ for α-lipoic acid, 1.16–35 nmol mL⁻¹ for glutathione, 9.83–450.0 nmol mL⁻¹ for cysteine, 0.55–40.0 nmol mL⁻¹ for homocysteine, 0.34–50.0 nmol mL⁻¹ for N-acetyl-L-cysteine, and 1.45–45.0 nmol mL⁻¹ for cysteinylglycine. Recovery values of 85.16–119.48% were recorded for all the analytes. The developed method is sensitive, repeatable, and linear within the expected ranges of total thiols. The devised procedure can be applied to plasma samples to monitor biochemical processes in various pathophysiological states.

Thiol-disulphide homoeostasis as a novel oxidative stress biomarker in lung tuberculosis patient

AIMS OF STUDY

To compare a novel oxidative stress biomarker dynamic thiol/disulphide homoeostasis between patients with lung tuberculosis and healthy controls.

METHODS

Our study included 50 patients with active lung tuberculosis and 50 healthy controls. Serum thiol/disulphide was measured with a new automated spectrometric method developed and results were compared statistically.

RESULTS

We found that native and total thiol levels were significantly decreased in patients with lung tuberculosis, disulphide/native thiol and disulphide/total thiol levels were found to be higher in lung tuberculosis patients when compared with the control group. However, disulphide levels were higher in the control group than in the patient group.

CONCLUSIONS

Based on the results of this study, it can be said that oxidative stress is closely associated with lung tuberculosis pathogenesis. There is a need for new studies that will show the possible effects of oxidative stress on lung tuberculosis pathogenesis.

The Significance of Thiol/Disulfide Homeostasis and Ischemia-modified Albumin Levels in Assessing Oxidative Stress in Obese Children and Adolescents

Objective

There is an association between obesity and several inflammatory and oxidative markers in children. In this study, we analyzed thiol/disulfide homeostasis and serum ischemia-modified albumin (IMA) levels for the first time in order to clarify and determine the oxidant/antioxidant balance in metabolically healthy and unhealthy children.

Methods

This study included obese children and healthy volunteers between 4-18 years of age. The obese patients were divided into two groups: metabolically healthy obese (MHO) and metabolically unhealthy obese (MUO). Biochemical parameters including thiol/disulfide homeostasis, and IMA concentrations were analyzed.

Results

There were 301 recruits of whom 168 (55.8%) were females. The obese children numbered 196 (MHO n=58 and MUO n=138) and healthy controls numbered 105. No statistically significant difference could be found in ages and genders of the patients among all groups (p>0.05, for all). Native thiol (SH), total thiol (SH+SS), and native thiol/total thiol (SH/SH+SS) ratio were statistically significantly lower in the MUO group than the control group (p<0.001, p=0.005, and p=0.005; respectively). Disulfide (SS), disulfide/native thiol (SS/SH), disulfide/total thiol (SS/SH+SS) and IMA levels were statistically significantly higher in the MUO group than the control group (p=0.002, p<0.001, p<0.001, and p=0.001, respectively).

Conclusion

Chronic inflammation due to oxidative stress induced by impaired metabolic parameters in MUO children caused impairment in thiol redox homeostasis. Our data suggested that the degree of oxidant imbalance in obese children worsened as obesity and metabolic abnormalities increased. It is hypothesized that thiol/disulfide homeostasis and high serum IMA levels may be reliable indicators of oxidant-antioxidant status in MUO children.

Thiol-disulfide as a novel indicator of obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) is an oxidative stress disease, which has been considered to be a notable risk and associated with increased cardiovascular morbidity and mortality. Thiol-disulfide homeostasis is as a novel indicator of oxidative stress.

OBJECTIVES

We aimed to evaluate thiol-disulfide homeostasis in a large patient population with OSA.

METHODS

A total of 230 with OSA and 40 healthy controls were included in the study. Inclusion criteria for OSA patients are having apnoea-hypopnoea index of ≥5/hour, being more than 18 years of age and having no previous treatment for OSA. Thiol-disulfide analysis was done for the patients and control group. Blood thiol-disulfide homeostasis was analysed using the new automatic method, developed by Erel and Neşelioğlu.

RESULTS

Among all OSA subjects, 149 (64.8%) were males and the mean ages of the patients were 53.38 ± 10.22. Total thiol, native thiol (SH) and disulfide (SS) levels were significantly lower in OSA group compared to the control group (P < .001, P < .001 and P = .039 respectively). Also, total thiol and native thiol (SH) were significantly different between the groups according to OSA severity (mild-moderate to severe OSA) (P < .001 and P < .001 respectively). Thiol-disulfide redox parameters were correlated with apnoea-hypopnoea index (AHI) scores.

CONCLUSION

The present prospective study showed that thiol/disulfide homeostasis was unbalanced in OSA patients. Especially, in OSA patients have low level of thiol/disulfide redox parameters when compared to healthy subjects. Evaluating thiol-disulfide homeostasis in OSA may be a contributing aspect to assessment and monitoring of the patient.

An investigation of thiol/disulfide homeostasis in patients with Behçet's disease

INTRODUCTION

Behçet's disease (BD) is a relapsing systemic inflammatory disorder. The diagnosis of BD is primarily based on clinical findings. Current biomarkers are not yet sufficient to diagnose and cannot anticipate the course of the disease and response to treatment. The aim of this study was to evaluate the relationship between the thiol-disulfide balance and disease activity and organ involvement in BD.

MATERIAL AND METHODS

A hundred fifty patients with BD and 100 age- and gender-matched healthy controls were included in the study. Disease activity was assessed with the BD Current Activity form score. Serum levels of native thiol (NT), total thiol (TT), and disulfide were measured and the disulfide/native thiol, disulfide/total thiol and native thiol/total thiol levels were calculated for the patient and control groups.

RESULTS

Native thiol, total thiol, native thiol/total thiol values of the BD patients were significantly lower than those of the control group. The disulfide/native thiol, disulfide/total thiol values of BD patients were higher compared to the control group and the disulfide value of the BD group was slightly higher compared to the control group. No correlation was determined between thiol levels and disease activity and organ involvement in BD.

CONCLUSIONS

In patients with Behcet's disease, the thiol-disulfide homeostasis balance shifted towards disulfide formation due to thiol oxidation. It may be used as a novel marker in BD because it is easy, practical, fully automated and relatively inexpensive.

Commensal Microbiota Regulation of Metabolic Networks During Olfactory Dysfunction in Mice

INTRODUCTION

Recently, an increasing number of studies have focused on commensal microbiota. These microorganisms have been suggested to impact human health and disease. However, only a small amount of data exists to support the assessment of the influences that commensal microbiota exert on olfactory function.

METHODS

We used a buried food pellet test (BFPT) to investigate and compare olfactory functions in adult, male, germ-free (GF) and specific-pathogen-free (SPF) mice, then examined and compared the metabolomic profiles for olfactory bulbs (OBs) isolated from GF and SPF mice to uncover the mechanisms associated with olfactory dysfunction.

RESULTS

We found that the absence of commensal microbiota was able to influence olfactory function and the metabolic signatures of OBs, with 38 metabolites presenting significant differences between the two groups. These metabolites were primarily associated with disturbances in glycolysis, the tricarboxylic acid (TCA) cycle, amino acid metabolism, and purine catabolism. Finally, the commensal microbiota regulation of metabolic networks during olfactory dysfunction was identified, based on an integrated analysis of metabolite, protein, and mRNA levels.

CONCLUSION

This study demonstrated that the absence of commensal microbiota may impair olfactory function and disrupt metabolic networks. These findings provide a new entry-point for understanding olfactory-associated disorders and their potential underlying mechanisms.

Uremic toxins promote accumulation of oxidized protein and increased sensitivity to hydrogen peroxide in endothelial cells by impairing the autophagic flux

Chronic kidney disease (CKD) is associated with high mortality rates, mainly due to cardiovascular diseases (CVD). Uremia has been considered a relevant risk factor for CVD in CKD patients, since uremic toxins (UTs) promote systemic and vascular inflammation, oxidative stress and senescence. Here, we demonstrate that uremic toxins indoxyl sulfate (IxS), p-cresyl sulfate (pCS) and indole acetic acid (IAA) are incorporated by human endothelial cells and inhibit the autophagic flux, demonstrated by cellular p62 accumulation. Moreover, isolated and mixed UTs impair the lysosomal stage of autophagy, as determined by cell imaging of the mRFP-GFP-LC3 protein. Endothelial cells exposed to UTs display accumulation of carbonylated proteins and increased sensitivity to hydrogen peroxide. Rapamycin, an autophagy activator which induces both autophagosome formation and clearance, prevented these effects. Collectively, our findings demonstrate that accumulation of oxidized proteins and enhanced cell sensitivity to hydrogen peroxide are consequences of impaired autophagic flux. These data provide evidence that UTs-induced impaired autophagy may be a novel contributor to endothelial dysfunction.

Role of native Thiol, total Thiol and dynamic Disulphide in diagnosis of patient with prostate cancer and prostatitis

BACKGROUND

Our study investigates whether Native Thiol, Total Thiol and disulphide levels measured in serum of patients with prostate cancer and prostatitis and of healthy subjects, have any role in differential diagnosis.

MATERIALS AND METHODS

Patients followed up for histopathologically verified diagnosis of prostate cancer and prostatitis in 2016-2017 at the Medicalpark Gaziantep Hospital Urology Clinic were included in the study. Native Thiol (NT), Total Thiol (TT), Dynamic Disulphide (DD) levels in serum were measured by a novel automated method.

RESULTS

NT, TT, DD, NT / TT ratios, DD / TT ratio and DD / NT ratio were measured as 118.4 ± 36.8μmoL / L, 150.3 ± 45.3μmoL / L, 15.9 ± 7μmoL / L, 78.8 ± 7μmoL / L, 10.5 ± 3.5μmoL / L, 13.8 ± 5.8μmoL / L respectively in patients with prostate cancer; as 116.4 ± 40.5μmoL / L, 147.5 ± 50.1μmoL / L, 15.5 ± 8.7μmoL / L, 79.7 ± 9μmoL / L, 10.1 ± 4.5μmoL / L, 13.5 ± 7.2μmoL / L in patients with prostatitis and as 144.1 ± 21.2μmoL / L, 191 ± 32.3μmoL / L, 23.4 ± 10.1μmoL / L, 76.1 ± 98.3μmoL / L, 11.9 ± 4.1μmoL / L, 16.4 ± 6.9μmoL / L in healthy subjects. Significant difference was detected between groups of NT, TT and DD levels (p = 0.008, p = 0.001, p = 0.002). No significant difference was detected in terms of the NT / TT, DD / TT and DD / NT rates (p = 0.222, p = 0.222, p = 0.222).

CONCLUSIONS

Serum NT, TT, DD levels in patients with prostatitis and prostate cancer were found significantly lower compared to the control group. This indicates that just as inflammation, prostate cancer also increases oxidative stress on tissues.

Effects of antiepileptic drugs on dynamic thiol/disulphide homeostasis in children with idiopathic epilepsy

PURPOSE

Anti-epileptic drugs have been widely used in children with epilepsy. Although several studies have investigated the role of oxidative stress and the effects of antiepileptic drugs on several oxidative markers in epilepsy, adequate information is not available on this issue. This study aimed to investigate the changes in thiol disulphide homeostasis in children with epilepsy under two commonly prescribed AED monotherapies, carbamazepine and valproic acid.

METHODS

A hundred and one children with epilepsy using valproic acid or carbamazepine and 58 healthy children were included in this study. Of the 101 patients with idiopathic epilepsy, 58 were on valproic acid monotherapy and 43 patients were on carbamazepine monotherapy. The total thiol, native thiol, and disulphide levels were measured and the disulphide/native thiol, disulphide/total thiol and native thiol/total thiol ratios were calculated in both groups.

RESULTS

The total thiol and native thiol levels of the valproic acid treated group were significantly lower than the control group (p < 0.05). The native thiol level of carbamazepine treated group was lower than the control group without a significance (p = 0.123). Disulphide level, disulphide/native thiol and disulphide/total thiol ratios were significantly higher and native thiol/total thiol ratio was significantly lower in both valproic acid and carbamazepine treated group compared with the control group.

CONCLUSION

Thiol/disulphide homeostasis is impaired in children with idiopathic epilepsy using valproic acid or carbamazepine. Valproic acid which is frequently used in childhood epilepsy may modify this balance more than carbamazepine monotherapy. More importantly, the new method used in our study proposes a promising, practical and daily applicable test for evaluating oxidative stress in these patien.

Thiol/disulphide homeostasis in manic episode and remission phases of bipolar disorder

PURPOSE

Bipolar disorder (BD) is a chronical psychiatric disorder of which pathophysiology was demonstrated to be related with oxidative stress. Thiol-disulphide homeostasis is an indicator of oxidative balance. This study aims to investigate thiol-disulphide homeostasis in BD.

MATERIALS AND METHODS

27 patients in manic episode (MA), 29 patients in remission (RE) and 60 healthy participants (HC) were included to the study. Serum native thiol and total thiol levels were measured with a novel colorimetric, automated method. The disulphide levels and disulphide/native thiol ratios were also calculated from these measured parameters.

RESULTS

Native thiol levels and total thiol levels of both MA and RE groups were lower than HC. No significant difference detected between MA and RE in terms of native thiol levels and total thiol levels. Disulphide levels and disulphide/native thiol ratio was detected statistically similar between three groups.

CONCLUSION

Our results support the oxidative imbalance theory in pathophysiology of BD. Further studies with larger sample sizes are needed for being able to understand these pathways in detail and use them as a target of treatment.

Does extracorporeal shockwave lithotripsy therapy affect thiol-disulfide homeostasis?

Objective:

Extracorporeal Shockwave Lithotripsy (ESWL) is a non-invasive method that is effective at crushing stones in the upper urinary tract. Disturbance of the thiol/disulfide homeostasis, in favor of the disulfide, has been shown to be involved in the disease pathogenesis.

Methods:

A total of 36 individuals that underwent ESWL had blood samples collected before ESWL (0hrs), 6hrs, and one week after the ESWL. Sera native and total as wells as disulfide amount was measured using an automated method sodium borohydrate (NaBH₄) reduction. In addition, Ischemia Modified Albumin (IMA) levels were measured using colorimetric assay method.

Results:

Native thiol level was reduced at the 6th hour following ESWL compared to baseline. While the ratios of disulfide level, Disulfide/Total Thiol (DTT), Disulfide/Native Thiol (DNT) and IMA level were increased at the 6th hour following ESWL compared to baseline, they were found to be similar with their baseline values at the end of 1st week. Total thiol and native /total thiol did not show any significant change.

Conclusions:

ESWL treatment disrupts thiol/disulfide homeostasis and the structure of albumin at the acute term. Therefore, it increases protein oxidation and leads to increased oxidative stress. However, this state is transient and returns to normal within the proceeding days.

Effects of Hemodialysis on Thiol-Disulphide Homeostasis in Critically Ill Pediatric Patients with Acute Kidney Injury

Aim

To evaluate thiol/disulphide homeostasis as a new indicator of oxidative stress in AKI patients and to determine the effect of HD on antioxidant balance and oxidative stress through plasma thiols.

Methods

This study was performed in patients aged between 12 months and 18 years prospectively who underwent hemodialysis due to AKI and were followed up for a year in a 22-bed tertiary pediatric intensive care unit. 20 patients and 39 controls were included.

Results

No difference was present between the groups in terms of age and gender. Median values of plasma native thiol, total thiol, and percent thiol were significantly lower in AKI group both before and after dialysis when compared to control group. The median dynamic disulphide values were significantly lower in the AKI group of predialysis compared to the controls. When pre- and postdialysis values were compared, disulphide values were statistically higher after dialysis. When pre- and postdialysis native thiol, dynamic disulphide, total thiol, and percent thiol median values were compared, postdialysis values were significantly higher than the predialysis values. There was a positive correlation between albumin, total thiol, and native thiol values before dialysis in the patient group.

Conclusion

AKI patients have low levels of thiol species showing the presence of oxidative stress and hemodialysis has a positive effect on thiol/disulphide balance. This new method may be an inexpensive and simple tool suitable for clinical studies and can be used in routine screening as a useful indicator to show oxidative stress.

Dynamic thiol/disulfide homeostasis in patients with lichen planus

OBJECTIVE

Lichen planus (LP) is an autoimmune inflammatory disease of the mucocutaneous tissue, whose exact pathological course remains unclear. Abnormal thiol/disulfide homeostasis has been postulated to be responsible for a number of diseases predominated by chronic inflammation. To be able to contribute complicated and unclear pathogenesis of LP, we aimed to investigate dynamic thiol/disulfide homeostasis in patients with LP, using an original automated method developed by Erel and Neselioglu in this study.

METHODS

The study group consisted of 81 unrelated patients with LP and 80 unrelated healthy controls with no LP lesions in their personal history or on clinical examination. Thiol/disulphide homeostasis tests have been measured with a novel automatic spectrophotometric method developed and the results have been compared statistically.

RESULTS

Native thiol and total thiol levels were found as significantly higher in patients with LP than the control group (P = 0.026 and 0.035, respectively). There was no significant difference between the disulfide levels of the patients with LP and the control group.

CONCLUSIONS

We provide evidence that that thiol/disulphide homeostasis impaired in favor of thiol levels in LP patients compared to the control group based on the data of our study. To the best of our knowledge, the present study is the first examination on the correlation between thiol and disulfide homeostasis in patients with LP.

Plasma Cystine Levels and Cardiovascular and All-Cause Mortality in Hemodialysis Patients

Oxidative stress accelerates the development of cardiovascular disease. Plasma cystine, a thiol oxidative stress marker, is related to several established factors for cardiovascular disease risk and prognosis. Although a comprehensive oxidative stress index is clinically required for hemodialysis patients with high oxidative stress, there are few reports concerning thiol oxidative stress markers predicting their prognosis. We investigated the relationship between plasma amino acids including cystine levels and cardiovascular disease-related and all-cause mortality in 132 maintenance hemodialysis patients. Higher cystine levels were associated with old age, longer hemodialysis duration, hemodialysis-associated hypotension, higher cardiothoracic ratio, higher blood urea nitrogen, and lower ankle-brachial index. Multivariate Cox regression analysis revealed that high plasma cystine was independently related with both cardiovascular disease mortality and all-cause mortality. Thus, high plasma cystine levels predict the prognosis of hemodialysis patients. High cystine levels necessitate a careful investigation for the cause of oxidative stress and comorbidities like vascular injury.

The change in serum Thiol/Disulphide homeostasis after transrectal ultrasound guided prostate biopsy

Objectives

The aim of this prospective clinical study was to investigate variations in a novel oxidative stress marker (thiol/disulphide homeostasis) in men who underwent transrectal ultrasound guided prostate biopsy (TRUSB).

Materials and Methods

A total of 22 men undergoing TRUSB of the prostate were enrolled in the study. Patients with abnormal digital rectal examination and/or total prostate specific antigen (PSA) over 4ng/mL underwent TRUSB with 12 cores. Serum samples were obtained before and just after the procedure to evaluate the possible changes in thiol/disulphide homeostasis. Mean age, total PSA and free PSA, prostate volume and histopathological data were also recorded.

Results

Mean age of the study population was 65.05±8.89 years. Significant decreases in native and total thiol levels were documented after the biopsy procedure. However, serum disulphide levels and disulphide/native thiol, disulphide/total thiol and native/total thiol ratios did not significantly change after TRUSB. No correlation was observed between oxidative parameters and total PSA and free PSA levels, prostate volume and histopathology of the prostate. However, mean patient age was significantly correlated with mean native and total thiol levels.

Conclusion

Significant decreases in serum native and total thiol levels related to the prostate biopsy procedure suggest that TRUSB causes acute oxidative stress in the human body. Since our trial is the first in the current literature to investigate these oxidative stress markers in urology practice, additional studies are warranted.

Investigation of dynamic thiol-disulphide homoeostasis in age-related cataract patients with a novel and automated assay

PURPOSE

The aim of this study was to determine plasma thiol-disulphide homoeostasis in patients with age-related cataract (ARC) and compare the results of the patients with healthy subjects. Plasma malondialdehyde (MDA) levels and catalase (CAT) activity were also investigated.

METHODS

The study included 53 cataract patients and 52 healthy volunteers. Native thiol-disulphide exchanges were determined using a novel and automated method. CAT activity was determined using the method described by Aebi, and MDA levels were calculated using the thiobarbituric acid method.

RESULT

Native thiol and total thiol levels were significantly lower in the cataract patients compared with the controls (p < 0.001, p = 0.002, respectively). The disulphide levels of the cataract patients were significantly higher than the controls (p = 0.002). The ratios of disulphide/native thiol and disulphide/total thiol were statistically higher in the cataract patients compared with the control group (p < 0.001, p < 0.001, respectively). Furthermore, CAT activity was significantly lower in the cataract patient group compared with the control group (p < 0.001), and MDA levels were insignificantly higher in the patient group (p = 0.581).

CONCLUSIONS

Our study showed that dynamic thiol-disulphide homoeostasis has shifted towards disulphide formation, as a result of thiol oxidation in ARC patients. The present study is the first to measure thiol-disulphide homoeostasis in ARC patients with a novel automated assay. This study supports the hypothesis that cataract is an oxidative disorder. Further studies are required in order to examine the relationship between oxidative stress and the development of cataract formation.

A novel marker in acute central serous chorioretinopathy: thiol/disulfide homeostasis

PURPOSE

The aim of this study was to compare dynamic thiol/disulfide homeostatic status in acute central serous chorioretinopathy (CSCR) patients by using a novel and automated assay determining dynamic thiol/disulfide homeostasis.

METHODS

Fifty-one patients with acute CSCR (study group) and 65 healthy individuals (control group) were enrolled in this study. Diagnosis of acute CSCR was made clinically and using spectral-domain RTVue OCT (optical coherence tomography) (Optovue, Fremont, CA). Fluorescein angiography confirmed the diagnosis of acute CSCR in all subjects. Total thiol, native thiol, disulfide amount, and native thiol/disulfide ratio (TDR) were calculated in the blood samples.

RESULTS

Mean total thiol, native thiol, and native TDR values were lower in patients with acute CSCR (364.2 ± 14.1, 326.4 ± 13.2, 17.14 ± 1.9, respectively) than in healthy eyes (441.2 ± 16.3, 398.5 ± 16.4, 22.70 ± 2.15, respectively; mean total thiol, p = 0.017; native thiol, p = 0.011; native TDR, p = 0.031).

CONCLUSIONS

Total thiol, native thiol, and native TDR were significantly lower statistically in patients with acute CSCR when compared with healthy controls.

Dynamic Thiol/Disulphide Homeostasis in Patients With Fibromyalgia

Objectives

This study aims to investigate dynamic thiol/disulphide homeostasis in patients with fibromyalgia syndrome (FMS).

Patients and methods

Fifty female patients with FMS (mean age 40.5±7.2 years; range 21 to 55 years) and 40 healthy female controls (mean age 39±9.4 years, range 22 to 55 years) were included in the study. Pain visual analog scale, tender points, Fibromyalgia Impact Questionnaire, and Beck Depression Inventory were evaluated. Age, body mass index (BMI), and symptom durations were also recorded. Native thiol, disulphide and total thiol levels were measured with a novel automated method.

Results

Serum disulphide levels were 14.7±3.4 μmol/L and 22.2±3.6 μmol/L in the FMS and control groups, respectively (p<0.001). Native thiol levels were 452.1±33.8 μmol/L and 433.5±37.6 μmol/L in the FMS and control groups, (p=0.015), while total thiol levels were 481.7±35.6 μmol/L and 477.5±38.9 μmol/L in the FMS and control groups, respectively (p=0.593). In the FMS group, disulphide/native thiol percent ratios and disulphide/ total thiol percent ratios were statistically significantly lower and native/total thiol percent ratios were statistically significantly higher than those of the control group. There were no correlations between serum thiol/disulphide profiles and pain scores & clinical variables in patients with FMS.

Conclusion

Because of the decreased disulphide and increased native thiol levels, the thiol/disulphide balance has shifted to the reductive side. This metabolic disturbance may have a role in the pathogenesis of FMS.

Dynamic thiol-disulfide homeostasis in acute ischemic stroke patients

Dynamic thiol-disulfide homeostasis plays a critical role in the cellular protection provided by antioxidation. The aim of this study was to investigate whether there is a change in thiol-disulfide homeostasis in acute ischemic stroke patients. Patients diagnosed with acute ischemic stroke that had undergone magnetic resonance diffusion-weighted imaging within the first 24 h were prospectively included in this study. The thiol, disulfide, and total thiol levels were measured during the first 24 and 72 h, and the National Institutes of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS), and Barthel Index (BI) of the patients were recorded. Overall, the relationships between the thiol-disulfide levels of the patients and the infarct volumes, NIHSS, mRS, and BI scores were investigated. In this study, 54 patients and 53 healthy controls were included. The mean of the native thiol levels in the stroke group was 356.572 ± 61.659 μmol/L (min/max 228.00/546.40), while it was 415.453 ± 39.436 μmol/L (min/max 323.50/488.70) in the control group (p < 0.001). A negative, significant correlation was observed between the infarct volumes and native thiol levels (ρ = -0.378; p = 0.005), and the disulfide levels were similar between the groups (Z = 0.774; p = 0.439). Significant difference was found between the thiol levels of the mild and moderate-severe NIHSS groups (p = 0.026). The changes in the thiol levels under oxidative stress may be associated with the severity of the stroke. Substitution of thiol deficiency and correction of thiol-disulfide imbalance may be beneficial in ischemic stroke.

Dynamic thiol/disulfide homeostasis in patients with autoimmune subclinical hypothyroidism

OBJECTIVE

The aim of this study was to investigate dynamic thiol/disulfide homeostasis in autoimmune subclinical hypothyroidism.

METHODS

Forty-eight patients with a new diagnosis of subclinical hypothyroidism due to Hashimoto thyroiditis who were not yet under medical therapy, and 48 healthy control subjects were enrolled. Thiol/disulfide homeostasis [native thiol-disulfide exchanges] was measured in both groups using the automated method developed by Erel and Neselioglu. An absolute difference of 0.5 between the total thiol and native thiol concentrations revealed the disulfide bond amount.

RESULTS

The native thiol level (p = 0.014) and native thiol/total thiol ratio (p = 0.001) were lower in patients with subclinical hypothyroidism than in the control group. Meanwhile, the disulfide level (p = 0.004), disulfide/native thiol ratio (p = 0.001), and disulfide/total thiol (p = 0.001) ratio were higher in patients with subclinical hypothyroidism than in the control group. The antithyroid peroxidase and anti-thyroglobulin levels were positively correlated with the disulfide/native thiol ratio (r = 0.339, p = 0.019; r = 0.243, p = 0.023, respectively) and the disulfide/total thiol ratio (r = 0.133, p = 0.019; r = 0.238, p = 0.026, respectively) and negatively correlated with the native thiol/total thiol ratio (r = -0.292, p = 0.004; r = -0.233, p = 0.022, respectively).

CONCLUSION

We found that thiol/disulfide homeostasis shifted to disulfide formation in patients with subclinical hypothyroidism and that thyroid autoantibodies were positively correlated with thiol oxidation. It is not clear whether abnormal thiol/disulfide homeostasis is a cause or a consequence in Hashimoto thyroiditis. Further studies are required.

Impaired Thiol-Disulfide Balance in Acute Brucellosis

The objective of this study was to examine a novel profile: thiol-disulfide homeostasis in acute brucellosis. The study included 90 patients with acute brucellosis, and 27 healthy controls. Thiol-disulfide profile tests were analyzed by a recently developed method, and ceruloplasmin levels were determined. Native thiol levels were 256.72 ± 48.20 μmol/L in the acute brucellosis group and 461.13 ± 45.37 μmol/L in the healthy group, and total thiol levels were 298.58 ± 51.78 μmol/L in the acute brucellosis group and 504.83 ± 51.05 μmol/L in the healthy group (p < 0.001, for both). The disulfide/native thiol ratios and disulfide/total thiol ratios were significantly higher, and native thiol/total thiol ratios were significantly lower in patients with acute brucellosis than in the healthy controls (p < 0.001, for all ratios). There were either positive or negative relationships between ceruloplasmin levels and thiol-disulfide parameters. The thiol-disulfide homeostasis was impaired in acute brucellosis. The strong associations between thiol-disulfide parameters and a positive acute-phase reactant reflected the disruption of the balance between the antioxidant and oxidant systems. Since thiol groups act as anti-inflammatory mediators, the alteration in the thiol-disulfide homeostasis may be involved in brucellosis.

Thiol/disulphide homeostasis in Bell's palsy as a novel pathogenetic marker

OBJECTIVES

The aim of this study was to investigate the relationship between Bell's palsy and a novel oxidative stress parameter, thiol/disulphide homeostasis.

DESIGN

A prospective study evaluating oxidative stress in Bell's palsy.

SETTING

This research took place in the department of Otorhinolaryngology, Ataturk Training and Research Hospital.

PARTICIPANTS

Totally, 77 patients with Bell's palsy and 38 healthy controls were included in this study.

MAIN OUTCOME MEASURES

The blood levels of total and native thiol and disulphide activity were assessed, and their levels were compared in the patients and controls.

RESULTS

There were statistically significant differences between the patients and controls regarding thiol/disulphide parameters. The mean native thiol and total thiol were significantly lower and disulphide levels were higher in the Bell's palsy than controls. On binary logistic regression analysis, the created model showed 45.3% variation. The cut-off value was 18.95 for disulphides.

CONCLUSION

Native and total thiol levels were low in the Bell's palsy. This metabolic disturbance may have a role in the pathogenesis of Bell's palsy.

Lipoic acid does not improve renal function markers in 5/6 nephrectomy model: possible role of Nrf2 inactivation

Chronic kidney disease (CKD) progression and complications are associated with increased oxidative stress, as well as with Nrf2 inactivation. Lipoic acid (LA) has been considered an inducer of Nrf2 antioxidant response. We tested whether oral administration of LA provides beneficial effects in experimental CKD in rats. Wistar rats underwent 5/6 nephrectomy (CKD group) or sham laparotomy. Seven days later, CKD group was divided into three subgroups that received: (i) LA continuously in the drinking water (100 mg/kg/day), (ii) LA by gavage every other day (100 mg/kg), or (iii) no LA treatment. LA treatment lasted until day 60. Plasma urea and creatinine, 24 h-proteinuria, glomerulosclerosis, interstitial fibrosis/tubular atrophy, and Nrf2 activation were analyzed. All parameters measured were significantly altered in the untreated CKD group, compared with the sham group, as expected. Oral LA administration, either in the drinking water or by gavage, did not improve significantly any parameter, comparing the treated-groups with the untreated CKD group. These results indicate that oral LA administration for 53 days was ineffective to reactivate Nrf2 in the remnant kidney of uremic rats, likely preventing improvements in biochemical and histopathological markers of renal function.

Determination of thiol/disulphide homeostasis in type 1 diabetes mellitus and the factors associated with thiol oxidation

In this study, we aimed to examine dynamic thiol/disulfide homeostasis in type 1 diabetes mellitus (T1DM) and identify the factors associated with thiol oxidation. Thirty-eight subjects (18 male, 20 female) diagnosed with T1DM and 38 (17 male, 21 female) healthy volunteers without any known diseases were included in the study. Thiol/disulfide homeostasis concentrations were measured by a newly developed method (Erel & Neselioglu) in this study. After native thiol, total thiol and disulfide levels were determined; measures such as disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol were calculated. In T1DM patients, compared to the control group, disulfide (p = 0.024), disulfide/native thiol (p < 0.001), and disulfide/total thiol (p < 0.001) were determined higher, while native thiol (p = 0.004) and total thiol (p < 0.001) levels were much lower. In the patient group, a positive correlation was determined between c-reactive protein (r = 325, p = 0.007; r = 316, p = 0.010, respectively), fasting blood glucose (r = 279, p = 0.018; r = 251, p = 0.035, respectively), and glycosylated hemoglobin (r = 341, p = 0.004; r = 332, p = 0.005, respectively) and rates of disulfide/native thiol and disulfide/total thiol. We determined that thiol oxidation increase in T1DM patients compared to the control group. We thought that hyperglycemia and chronic inflammation might be the major cause of increase in oxide thiol form. In order to determine the relationship between the status of autoimmunity and dynamic thiol/disulfide in T1DM, dynamic thiol/disulfide homeostasis in newly diagnosed-antibody positive-T1DM patients is required to be investigated.

Dynamic thiol-disulfide homeostasis in hyperemesis gravidarum

OBJECTIVE

To determine serum thiol-disulfide homeostasis in hyperemesis gravidarum.

STUDY DESIGN

Twenty-six pregnant women with hyperemesis gravidarum and 37 healthy pregnant women were included in the study. Native thiol, disulfide and total thiol concentrations were measured with a novel automated method.

RESULTS

Serum disulfide levels were 15.68±4.41 μmol l(-1) in the hyperemesis gravidarum group and 13.49±2.81 μmol l(-1) in the healthy group (P=0.031). Native thiol levels were 213.86±26.29 μmol l(-1) in the hyperemesis gravidarum group and 232.18±19.21 μmol l(-1) in healthy group (P=0.004), and total thiol levels were 245.23±28.58 μmol l(-1) in the hyperemesis gravidarum group and 259.17±19.94 μmol l(-1) in the healthy group (P=0.038).

CONCLUSION

Native and total thiol were deficient in the hyperemesis gravidarum group and this deficiency was correlated with the severity of the disease. The thiol-disulfide balance has shifted to the oxidative side. This metabolic disturbance may have a role in the pathogenesis of hyperemesis gravidarum.

Is disulphide/thiol ratio related to blood pressure in masked hypertension?

Dynamic thiol/disulphide homeostasis plays a critical role in numerous intracellular enzymatic pathways including antioxidant defence and detoxification. In this study, we sought to investigate dynamic thiol/disulphide homeostasis in patients with masked hypertension (MHT) and its relationship with blood pressure. Forty patients (23 men, 17 women) with newly diagnosed MHT and not yet on medical therapy, and 40 healthy volunteers (21 men, 19 women) were enrolled. Blood thiol/disulphide homeostasis was measured in both groups. Serum native and total thiol levels were measured using the novel, fully automated colorimetric method developed by Erel et al. Serum disulphide level was calculated as (serum total thiol - serum native thiol)/2. Native and total thiol levels (p = 0.001) and native thiol/total thiol ratio (p = 0.023) were found to be lower in patients with MHT when compared to those of the control group. Disulphide level and ratios of disulphide/native thiol and disulphide/total thiol were higher in patients with MHT than in the control group (p = 0.001). A positive correlation of systolic blood pressure (SBP) and diastolic blood pressure (DBP) was observed with disulphide/native thiol ratio (p < 0.001). Stepwise multivariable regression analysis showed disulphide/native thiol ratio to be an independent risk factor of SBP and DBP, and SBP to be an independent risk factor of disulphide/thiol ratio (p = 0.001). In this study, we found that dynamic thiol/disulphide homeostasis shifted towards disulphide formation due to thiol oxidation in patients with MHT. Prospective randomised controlled studies are required to elucidate whether abnormal thiol/disulphide status lies in the pathogenesis of MHT or is a consequence of MHT.

Physiological Roles and Adverse Effects of the Two Cystine Importers of Escherichia coli

When cystine is added to Escherichia coli, the bacterium becomes remarkably sensitive to hydrogen peroxide. This effect is due to enlarged intracellular pools of cysteine, which can drive Fenton chemistry. Genetic analysis linked the sensitivity to YdjN, a secondary transporter that along with the FliY-YecSC ABC system is responsible for cystine uptake. FliY-YecSC has a nanomolar Km and is essential for import of trace cystine, whereas YdjN has a micromolar Km and is the predominant importer when cystine is more abundant. Oddly, both systems are strongly induced by the CysB response to sulfur scarcity. The FliY-YecSC system can import a variety of biomolecules, including diaminopimelate; it is therefore vulnerable to competitive inhibition, presumably warranting YdjN induction under low-sulfur conditions. But the consequence is that if micromolar cystine then becomes available, the abundant YdjN massively overimports it, at >30 times the total sulfur demand of the cell. The imported cystine is rapidly reduced to cysteine in a glutathione-dependent process. This action avoids the hazard of disulfide stress, but it precludes feedback inhibition of YdjN by cystine. We conjecture that YdjN possesses no cysteine allosteric site because the isostructural amino acid serine might inappropriately bind in its place. Instead, the cell partially resolves the overaccumulation of cysteine by immediately excreting it, completing a futile import/reduction/export cycle that consumes a large amount of cellular energy. These unique, wasteful, and dangerous features of cystine metabolism are reproduced by other bacteria. We propose to rename ydjN as tcyP and fliY-yecSC as tcyJLN.

IMPORTANCE

In general, intracellular metabolite pools are kept at steady, nontoxic levels by a sophisticated combination of transcriptional and allosteric controls. Surprisingly, in E. coli allosteric control is utterly absent from the primary importer of cystine. This flaw allows massive overimport of cystine, which causes acute vulnerability to oxidative stress and is remedied only by wasteful cysteine efflux. The lack of import control may be rationalized by the unusual properties of cysteine itself. This phenomenon justifies the existence of countervailing cysteine export systems, whose purpose is otherwise hard to understand. It also highlights an unexpected link between sulfur metabolism and oxidative damage. Although this investigation focused upon E. coli, experiments confirmed that similar phenomena occur in other species.

Homocysteine in Chronic Kidney Disease

Hyperhomocysteinemia occurs in chronic- and end-stage kidney disease at the time when dialysis or transplant becomes indispensable for survival. Excessive accumulation of homocysteine (Hcy) aggravates conditions associated with imbalanced homeostasis and cellular redox thereby resulting in severe oxidative stress leading to oxidation of reduced free and protein-bound thiols. Thiol modifications such as N-homocysteinylation, sulfination, cysteinylation, glutathionylation, and sulfhydration control cellular responses that direct complex metabolic pathways. Although cysteinyl modifications are kept low, under Hcy-induced stress, thiol modifications persist thus surpassing cellular proteostasis. Here, we review mechanisms of redox regulation and show how cysteinyl modifications triggered by excess Hcy contribute development and progression of chronic kidney disease. We discuss different signaling events resulting from aberrant cysteinyl modification with a focus on transsulfuration.

N-acetylcysteine as a potential strategy to attenuate the oxidative stress induced by uremic serum in the vascular system

AIMS

Chronic kidney disease (CKD) progression is accompanied by systemic oxidative stress, which contributes to an increase in the risk of cardiovascular diseases (CVDs). N-acetylcysteine (NAC) is among the most studied antioxidants, but its therapeutic benefits in CKD-associated CVDs remain controversial. Here, we investigated whether NAC could inhibit the oxidative stress induced by uremia in vitro and in vivo.

MAIN METHODS

Endothelial and smooth muscle cells were challenged with human uremic or non-uremic sera, and the effects of a pre-treatment with 2mM NAC were evaluated. Reactive oxygen species (ROS) production, protein oxidation and total glutathione/glutathione disulfide (tGSH/GSSG) ratios were measured. Five-sixths nephrectomized or sham-operated rats were orally treated (in the drinking water) with 60 mg/kg/day NAC or not treated for 53 days. Plasma cysteine/cystine reduction potential Eh(Cyss/2Cys) was determined as a novel marker of the systemic oxidative stress.

KEY FINDINGS

NAC inhibited all the determined oxidative stress parameters, likely by increasing the tGSH/GSSG ratio, in both cell lines exposed to uremic serum. Orally administered NAC attenuated the systemic oxidative stress in uremic rats.

SIGNIFICANCE

The present results indicate that NAC, by preventing GSH depletion in vascular cells exposed to uremic serum and by attenuating the systemic oxidative stress during CKD progression, emerges as a potential strategy to prevent the oxidative stress induced by uremic toxicity in the vascular system.

A novel and automated assay for thiol/disulphide homeostasis

OBJECTIVES

To develop a novel and automated assay determining plasma thiol/disulphide homeostasis, which consists of thiol-disulphide exchanges.

DESIGN AND METHODS

Native thiol and total thiol concentrations were synchronously measured as a paired test. In the first vessel, the amount of native thiol groups was measured by a modified Ellman reagent. At the parallel run, first, dynamic disulphide bonds were reduced to free thiol groups by NaBH(4). The unused reductant remnants were completely removed by formaldehyde. Thus, the total thiol amount could be accurately measured. Mercaptoethanol solutions were used as calibrators. The half value of the difference between total thiol and native thiol amounts gave the disulphide bond amount.

RESULTS

No separation step for the assay was needed. All processes were performed using an automated analyser within about 10 min. Plasma disulphide levels were 17.29±5.32 μmol/L, native thiol levels were 397±62 μmol/L and disulphide/native thiol per cent ratios were 4.32±1.49 in healthy subjects. Plasma disulphide levels were higher in patients with degenerative diseases and lower in patients with proliferative diseases.

CONCLUSION

An easy, inexpensive, practical, fully automated and also optionally manual spectrophotometric assay can be used to determine plasma dynamic thiol/disulphide homeostasis.