A Novel Tool for the Assessment Oxidative Stress in Age-Related Macular Degeneration: Thiol/Disulfide Homeostasis Revisited

Thiol disulfide homeostasis in psychiatric disorders: A comprehensive review

Thiol-disulfide couple maintains an intracellular redox status. Dynamic thiol-disulfide homeostasis acts crucial parts in metabolic processes involving signal mechanisms, inflammation, antioxidant defense. Thiol-disulfide homeostasis have been implicated in numerous diseases. In this comprehensive review we identified the studies that examined the thiol-disulfide homeostasis in psychiatric disorders. Most cases demonstrated alterations in thiol-disulfide homeostasis and in most of them the thiol-disulfide balance tended to change direction to the disulfide side, that is, to the oxidative side. Currently, the fact that N-acetylcysteine, a thiol-containing compound, is of great interest as a new treatment approach in psychiatric disorders and the role of glutathione, the most abundant thiol, in the brain highlights the importance of evaluating the thiol-disulfide balance in psychiatric disorders.

The Pathomechanism, Antioxidant Biomarkers, and Treatment of Oxidative Stress-Related Eye Diseases

Oxidative stress is an important pathomechanism found in numerous ocular degenerative diseases. To provide a better understanding of the mechanism and treatment of oxidant/antioxidant imbalance-induced ocular diseases, this article summarizes and provides updates on the relevant research. We review the oxidative damage (e.g., lipid peroxidation, DNA lesions, autophagy, and apoptosis) that occurs in different areas of the eye (e.g., cornea, anterior chamber, lens, retina, and optic nerve). We then introduce the antioxidant mechanisms present in the eye, as well as the ocular diseases that occur as a result of antioxidant imbalances (e.g., keratoconus, cataracts, age-related macular degeneration, and glaucoma), the relevant antioxidant biomarkers, and the potential of predictive diagnostics. Finally, we discuss natural antioxidant therapies for oxidative stress-related ocular diseases.

Dynamic thiol disulphide homeostasis in patients with surfer's eye: a case-control study

PURPOSE

The role of oxidative stress in the pathogenesis of pterygium is still unclear. However, abnormal thiol disulfide homeostasis levels are involved in the pathogenesis of various systemic or ocular diseases. We aim to analyze dynamic thiol disulphide homeostasis in patients suffering from conjunctival pterygium using a contemporary technique.

METHODS

Thirty-eight subjects suffering from pterygium and 35 age-gender matched healthy volunteers were recruited for the study. For each case, total thiol, disulfide and native thiol levels in blood were obtained. Additionally, the ratio of disulfide over total thiol, native thiol over total thiol and disulfide over native thiol were computed.

RESULTS

The level of median native thiol was lower in pterygium group (318.2 µmol/L vs. 333.4 µmol/L) and median disulfide was slightly higher in pterygium group (24.3 µmol/L vs. 22.8 µmol/L) compared to control group. Both disulfide over total thiol and disulfide over native thiol ratios were higher in pterygium group, ratio of native thiol over total thiol was found to be higher in control group. Nevertheless, none of those differences were statistically significant at 95% confidence level. Notably, correlation test pointed to a negative correlation both between pterygium grade and native thiol and between total thiol and pterygium grade in pterygium group (P = 0.03 and 0.02, respectively).

CONCLUSION

A negative correlation hinting that slightly weakened dynamic thiol disulphide homeostasis in subjects with pterygium, a local ocular disease. Further studies with larger sample sizes may shed light on this potential relationship and justify systemic antioxidant therapies in these cases.

The Relationship between Choroidal Thickness and Intracellular Oxidised-reduced Glutathione and Extracellular Thiol-disulfide Homeostasis at Different Stages of Diabetic Retinopathy

Purpose: To evaluate the relationship between diabetic retinopathy and oxidative damage by measuring intracellular and extracellular thiol levels, and to compare intracellular and extracellular thiol levels. Method: In this prospective, cross-sectional, and comparative study, 25 healthy control participants (group 1), a total of 25 diabetic macular edema (DME) patients with non-proliferative diabetic retinopathy (DRP) and without DME (group 2), and 25 DME patients with non-proliferative DRP and with DME (group 3) were included. Choroidal thickness (ChT) and central macular thickness (CMT) were measured by spectral domain optic coherence tomography. For the evaluation of antioxidant/oxidant balance, intracellular GSH (reduced glutathione) and GSSG (oxidized glutathione), extracellular SH (thiol) and SS (disulfide) levels were measured and recorded. Results: Comparing intracellular and extracellular thiol levels between groups, intracellular GSSG level and GSSG/GSH percent ratio, and extracellular disulfide and SS/SH percent ratio values were higher in diabetic patients than healthy participants. Choroidal thicknesses were significantly thinner in DRP groups compared to the healthy population. When the relationship between choroidal thicknesses and thiol levels was investigated, there were significant relationships between choroidal thicknesses and thiol levels in group 3. Conclusion: Oxidative stress and impaired intracellular GSH/GSSG and serum SH/SS balances were observed to have an effect on DRP and DME pathogenesis. In addition, in groups with and without DME, thinning in choroidal thicknesses and the relationship between these thicknesses and intra/extracellular oxidative stress indicators can also be explained.

Thiol-disulfide homeostasis: an integrated approach with biochemical and clinical aspects

Dynamic thiol-disulfide homeostasis (TDH) is a new area has begun to attract more scrutiny. Dynamic TDH is reversal of thiol oxidation in proteins and represents the status of thiols (-SH) and disulfides (-S-S-). Organic compounds containing the sulfhydryl group is called thiol, composed of sulfur and hydrogen atoms. Disulfides are the most important class of dynamic, redox responsive covalent bonds build in between two thiol groups. For many years, thiol levels were analyzed by several methods. During last years, measurements of disulfide levels have been analyzed by a novel automated method, developed by Erel and Neselioglu. In this method, addition to thiol (termed as native thiol) levels, disulfide levels were also measured and sum of native thiol and disulfide levels were termed as total thiol. Therefore, TDH was begun to be understood in organism. In healthy humans, TDH is maintained within a certain range. Dysregulated dynamic TDH has been implicated several disorders with unknown etiology. A growing body of evidence has demonstrated that the thiol-disulfide homeostasis is involved in variety diseases, such as diabetes mellitus, hypertension, nonsmall cell lung cancer, familial Mediterranean fever (FMF), inflammatory bowel diseases, occupational diseases, gestational diabetes mellitus and preeclampsia. These results may elucidate some pathogenic mechanism or may be a predictor indicating diagnostic clue, prognostic marker or therapeutic sign. In conclusion, protection of the thiol-disulfide homeostasis is of great importance for the human being. Evidence achieved so far has proposed that thiol-disulfide homeostasis is an important issue needs to elucidate wholly.

Ischemia-Modified Albumin Levels and Thiol-Disulphide Homeostasis in Diabetic Macular Edema in Patients with Diabetes Mellitus Type 2

PURPOSE

It was aimed to assess the role of thiol-disulphide homeostasis and ischemia-modified albumin (IMA) level in the development of diabetic macular edema (DME) in patients with diabetes mellitus type 2 (T2DM).

MATERIALS AND METHODS

Sixty-six study patients were divided into two groups. Group I included 43 patients with T2DM and DME, and Group 2 included 23 patients with T2DM without eye involvement. A novel colorimetric method was used to assess thiol-disulphide homeostasis. Between the two groups IMA, total anti-oxidant, and total oxidant levels were measured and compared.

RESULTS

In Group 1, total and native thiol levels and disulphide levels were lower compared to Group 2 (p = .025, p < .001 and p = .013, respectively). Disulphide/native thiol, disulphide/total thiol ratios and native thiol/total thiol were similar between the groups. Total anti-oxidant level (TAL) reduced whereas total oxidant level (TOL) increased in Group 1 compared to Group 2 (p = .001, p = .002, respectively). Albumin level decreased, whereas IMA level increased in Group 1 compared to Group 2 (p < .001 for both).

CONCLUSIONS

The disruption in thiol/disulphide homeostasis, increased IMA and oxidative stress have an impact on the development of diabetic macular edema.

Protective Effects of Boron on Cyclophosphamide-Induced Bladder Damage and Oxidative Stress in Rats

This study aims to investigate protective effects of boron against cyclophosphamide-induced bladder toxicity that produces oxidative stress and leads to apoptosis of the cells. In total, 24 rats were divided into 4 equal groups. The control group received saline. The 2nd experimental group received 200 mg kg of cyclophosphamide i.p. on the 4th day while the 3rd group was given only boron (200 mg kg, i.p.) for 6 days. In the 4th group, boron was given for 6 days and cyclophosphamide (200 mg kg, i.p.) was administrated on the 4th day. Twenty-four hours after the last boron or cyclophosphamide administration, rats were sacrificed under anesthesia. Bladder tissues of rats were taken for histological and immunohistochemical (apoptotic markers such as caspase-3, bcl-2, and bax) and blood was taken for the biochemical (serum total thiol, serum natural thiol, serum thiol-disulfide) analysis. Transient epithelial thinning, edema, marked inflammatory reaction, and bleeding were observed in bladders of the group that received cyclophosphamide. Also, the activity of bax and caspase-3-positive cells increased while the number of bcl-2-positive cells decreased. In the same group, serum natural thiol and total thiol levels decreased while serum disulfide levels increased, which indicates oxidative stress. On the other hand, in the boron+cyclophosphamide group pretreatment with boron protected, the bladder tissue and the number of bcl-2-positive cells increased, and bax and caspase-3-positive cells decreased, showing antiapoptotic effects of boron against cyclophosphamide-induced toxicity. In parallel with the findings of this group, native thiol and total thiol levels increased and serum disulfide levels decreased pointing out to a decreased oxidative stress. Our results indicate that boron pretreatment significantly protects rat bladder against cyclophosphamide-induced bladder damage due to its antiapoptotic and antioxidant properties.

Thiol/disulfide homeostasis in patients with ocular-active and ocular-inactive Behçet disease

PURPOSE

To evaluate thiol/disulfide homeostasis in ocular-active (OA) and ocular-inactive (OI) Behçet disease (BD) patients and compare the data with healthy subjects.

METHODS

Twenty OABD patients, 20 OIBD patients and 20 healthy control subjects were included into the study. The BD ocular attack score 24 (BOS24) scoring system was used to assess the activity of disease in ocular BD patients. Systemic activity was also evaluated using BD current activity form (BDCAF). The native thiol (NT), total thiol (TT) and disulfide levels and NT/TT, disulfide/NT and disulfide/TT ratios were measured via using an innovative and automated method.

RESULTS

BOS24 and BDCAF scores were 13.25 ± 2.32 and 4.18 ± 2.06 in OABD patients and 0.31 ± 0.47 and 2.14 ± 1.98 in OIBD patients, respectively. The NT, TT levels and NT/TT ratio were significantly reduced; in contrast, the disulfide levels, disulfide/NT and disulfide/TT ratios were significantly increased in OABD and OIBD patients compared to the healthy control subjects (p < 0.05). Moreover, while the levels of NT and TT were significantly reduced, the disulfide levels as well as disulfide/NT and disulfide/TT ratios were significantly elevated between OABD and OIBD patients (p < 0.05). However, the ratio of NT/TT did not significantly differ between OABD and OIBD patients (p = 0.449). The multiple regression model including BOS24 and BDCAF score statistically significantly predicted NT level, TT level and disulfide level (p < 0.001 for all).

CONCLUSION

Thiol oxidation in BD patients resulted in a change of the thiol/disulfide balance. Therefore, thiol/disulfide homeostasis in BD patients can be used an innovative oxidative stress marker.

The significance of thiol/disulfide homeostasis and ischemia-modified albumin levels to assess the oxidative stress in patients with different stages of diabetes mellitus

This study investigated the value of Thiol/Disulfide homeostasis and ischemia-modified albumin (IMA) levels in discriminating diabetic cases with different stages of retinopathy and without retinopathy. In total, 122 patients with type 2 diabetes mellitus (DM) were enrolled in this prospective cross-sectional study. These patients were separated into three subgroups: Group 1 included 42 patients with DM and no diabetic retinopathy (DR), Group 2 included 40 patients with DM having non-proliferative DR and the Group 3 had 40 patients with DM having proliferative DR. The native thiol, total thiol, and disulfide levels and disulfide-native thiol, disulfide-total thiol, and native thiol-total thiol ratios as well as the IMA levels were analyzed and compared among the groups. There were no statistically significant differences regarding the ages and genders of the patients between the groups. The native thiol level, the total thiol level and the native thiol-total thiol ratio showed a statistically significantly reduction, while the disulfide level, the disulfide-native thiol ratio, and the disulfide-total thiol ratio showed a statistically significantly elevation in the Group 3 compared with the Group 1 and Group 2. Additionally, the mean IMA levels were statistically significantly higher in Group 3 when compared to Group 1 and Group 2 (p = .003 and p = .014, respectively). In conclusion, both Thiol/Disulfide homeostasis parameters and IMA levels increase with the progression of DR. Thiol/Disuldife homeostasis balance and IMA levels may be used a biomarker to monitor the tissue ischemia in DM and to discriminate the different stages of DR, in the future.