Antioxidant capacity and structural changes of human serum albumin from patients in advanced stages of diabetic nephropathy and the effect of the dialysis

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.

Label-Free Method Development for Hydroxyproline PTM Mapping in Human Plasma Proteome

Post-translational modifications (PTMs) impart structural heterogeneities that can alter plasma proteins' functions in various pathophysiological processes. However, the identification and mapping of PTMs in untargeted plasma proteomics is still a challenge due to the presence of diverse components in blood. Here, we report a label-free method for identifying and mapping hydroxylated proteins using tandem mass spectrometry (MS/MS) in the human plasma sample. Our untargeted proteomics approach led us to identify 676 de novo sequenced peptides in human plasma that correspond to 201 proteins, out of which 11 plasma proteins were found to be hydroxylated. Among these hydroxylated proteins, Immunoglobulin A1 (IgA1) heavy chain was found to be modified at residue 285 (Pro²⁸⁵ to Hyp²⁸⁵), which was further validated by MS/MS study. Molecular dynamics (MD) simulation analysis demonstrated that this proline hydroxylation in IgA1 caused both local and global structural changes. Overall, this study provides a comprehensive understanding of the protein profile containing Hyp PTMs in human plasma and shows the future perspective of identifying and discriminating Hyp PTM in the normal and the diseased proteomes.

Predictive value of three Inflammation-based Glasgow Prognostic Scores for major cardiovascular adverse events in patients with acute myocardial infarction during hospitalization: a retrospective study

Aim

Inflammation-based Glasgow Prognostic Scores (GPS) have been reported to predict the prognosis of patients with acute ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). The goal of this study was to investigate whether three kinds of GPSs can effectively predict major cardiovascular adverse events (MACEs) in STEMI or non-ST-segment elevation myocardial infarction (NSTEMI) patients undergoing PPCI, elective PCI (EPCI) or conservative drug therapy during hospitalization.

Methods

In this retrospective cohort study, patients with acute myocardial infarction (AMI) were divided into 0, 1 or 2 score according to the GPSs. Logistic regression and receiver operating characteristic (ROC) curve analysis were performed to assess the predictive value of GPSs for MACE and all-cause mortality during hospitalization. Three kinds of GPSs, Inflammation-based Glasgow Prognostic Score (GPS), modified GPS (MGPS) and high-sensitivity CRP-modified GPS (HS-MGPS) and Global Registry of Acute Coronary Events (GRACE) score were applied in this study.

Results

A total of 188 patients were enrolled. The ROC curve with MACE showed that the AUC of GPS (0.820 (95% confidence interval (CI) [0.754-0.885]), P < 0.001) was larger than that of MGPS (0.789 (95% CI [0.715-0.863]), P < 0.001), HS-MGPS (0.787 (95% CI [0.717-0.856]), P < 0.001) and GRACE score (0.743 (95% CI [0.672-0.814]), P < 0.001). The ROC curve with all-cause mortality showed that the AUC of GPS (0.696 (95% CI [0.561-0.831]), P = 0.005) was similar to the HS-MGPS (0.698 (95% CI [0.569-0.826]), P = 0.005) and higher than the MGPS (0.668 (95% CI [0.525-0.812]), P = 0.016), but lower than the GRACE score (0.812 (95% CI [0.734-0.889]), P < 0.001). Multivariate logistic regression analysis showed that the GPS was an independent risk factor for the incidence of MACE during hospitalization. Compared with the odds ratio (OR) value for a GPS of 0, the OR for a GPS of 1 was 7.173 (95% CI [2.425-21.216]), P < 0.001), and that for a GPS of 2 was 18.636 (95% CI [5.813-59.746]), P < 0.001), but not an independent risk factor for all-cause mortality (P = 0.302). GRACE score was an independent risk factor for MACE (1.019 (95% CI [1.004-1.035]), P = 0.015) and all-cause mortality (1.040 (95% CI [1.017-1.064]), P = 0.001). In the subgroups classified according to the type of AMI, the presence of disease interference GPSs and the type of PCI, the ability of GPS to predict the occurrence of MACE seemed to be greater than that of MGPS and HS-MGPS.

Conclusion

The GPS has a good predictive value for the occurrence of MACE during hospitalization in patients with AMI, regardless of STEMI or NSTEMI, the choice of PCI mode and the presence or absence of diseases that interfere with GPS. However, GPS is less predictive of all-cause mortality during hospitalization than GRACE score, which may be due to the interference of patients with other diseases.

Cell-culture growth conditions resulting in the oxidation of a recombinant antigen-binding fragment

Use of Quality-by-Design (QbD) tools is becoming an important part of the bioprocessing industry when developing a process for manufacturing operations to ensure the robustness and reproducibility of the biologic product. In the present study, a QbD tool, Design of Experiments (DOE), was utilized to optimize a bioprocess for the production of a CHO recombinant antigen-binding fragment (rFab) in small-scale bioreactors. DOE studies evaluated percent dissolved oxygen, temperature, and feeding strategy specific to this Chinese Hamster Ovary (CHO) clone. It was determined that these factors influenced cell viability, yield of the recombinant protein, and metabolic byproduct formation. To ensure the quality of the target molecule in the cell-culture process, small-scale purifications and analytical evaluation of the target molecule were completed prior to cell-culture scale-up to ensure that oxidation of the rFab, presence of free light chain, and truncation of thiol group were not observed. Analysis of the purified rFab by mass spectrometry indicated that rFab oxidation occurred under poor cell-culture conditions. PCR profile array results also revealed increased transcription of the oxidative genes Superoxide Dismutase 3, Myeloperoxidase, Dual Oxidase Like 2, Nuclear Receptor Coactivator 7, NADPH Oxidase Organizer 1, Mitochondria Uncouple Protein 3, Eosinophil Peroxidase, Lactoperoxidase Like, Serum Albumin Like, and Glutathione S-Transferase Pi 1 in this CHO strain. The present study suggests a mechanism and pathway for the oxidation of an rFab molecule during cell-culture bioprocess optimization. The present study also demonstrated the importance of utilizing the QbD tool of DOE to optimize the cell-culture bioprocess prior to scaling up into the large-scale production bioreactor.

Lysosomal dysfunction induced by changes in albumin's tertiary structure: Potential key factor in protein toxicity during diabetic nephropathy

AIMS

Increased amounts of protein, in particular albumin within renal tubular cells (TBCs), induce the expression of inflammatory and fibrogenic mediators, which are adverse prognostic factors in tubulointerstitial fibrosis and diabetic nephropathy (DN). We sought to assess the participation of the thiol-linked tertiary structure of albumin in the mechanism of protein toxicity in a model of TBCs.

MATERIALS AND METHODS

Cultured human renal proximal tubular cells, HK-2, were exposed to isolated albumin from patients with and without DN (Stages 0, 1 and 4). The magnitude of change of the albumin tertiary structure, cell viability (LDH leakage), apoptosis (Annexin V), transdifferentiation and reticulum endoplasmic stress (Western blot and flow cytometry) and lysosomal enzyme activity were assessed.

KEY FINDINGS

We found that albumin from Stage 4 patients presented >50% higher thiol-dependent changes of tertiary structure compared to Stages 0 and 1. Cells incubated with Stage 4 albumin displayed 5 times less viability, accompanied by an increased number of apoptotic cells; evidence of profibrogenic markers E-cadherin and vimentin and higher expression of epithelial-to-mesenchymal transition markers α-SMA and E-cadherin and of endoplasmic reticulum stress protein GRP78 were likewise observed. Moreover, we found that cathepsin B activity in isolated lysosomes showed a significant inhibitory effect on albumin from patients in advanced stages of DN and on albumin that was intentionally modified.

SIGNIFICANCE

Overall, this study showed that thiol-dependent changes in albumin's tertiary structure interfere with the lysosomal proteolysis of renal TBCs, inducing molecular changes associated with interstitial fibrosis and DN progression.

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.

Non-oncotic properties of albumin. A multidisciplinary vision about the implications for critically ill patients

INTRODUCTION

Effective resuscitation with human albumin solutions is achieved with less fluid than with crystalloid solutions. However, the role of albumin in today's critical care unit is also linked to its multiple pharmacological effects. Areas covered: The potential clinical benefits of albumin in select populations of critically ill patients like sepsis seem related to immunomodulatory and anti-inflammatory effects, antibiotic transportation and endothelial stabilization. Albumin transports many drugs used in critically ill patients. Such binding to albumin is frequently lessened in critically ill patients with hypoalbuminemia. These changes could result in sub-optimal treatment. Albumin has immunomodulatory capacity by binding several bacterial products. Albumin also influences vascular integrity, contributing to the maintenance of the normal capillary permeability. Moreover, the albumin molecule encompasses several antioxidant properties, thereby significantly reducing re-oxygenation injury, which is especially important in sepsis. In fact, most studies of albumin administration are a combination of a degree of resuscitation with a degree of maintenance or supplementation of albumin. Expert commentary: The potential clinical benefits of the use of albumin in selected critically ill patients such as sepsis seem related to its immunomodulatory and anti-inflammatory effects, antioxidant properties, antibiotic transportation and endothelial stabilization. Additional studies are warranted to further elucidate the underlying physiologic and molecular rationale.

Hyperglycemia induced structural and functional changes in human serum albumin of diabetic patients: a physico-chemical study

Structural and functional changes in glycated-HSA, isolated from diabetic patients, suggests it has a significant role in diabetes progression and kidney dysfunction.

Influence of Hemodialysis on Lipid Peroxidation, Enzymatic and Non-Enzymatic Antioxidant Capacity in Chronic Renal Failure Patients

BACKGROUND

Free radical induced damages are thought to be involved in chronic kidney disease (CKD), especially in patients who are on hemodialysis (HD) for prolonged periods. Hemodialysis can influence multiple biochemical factors, several of which are useful, although the rest can be harmful and increase the severity of disease.

OBJECTIVES

The purpose of this study was to evaluate the effect of the HD membrane polysulfone on oxidative stress markers, by measuring the level of lipid peroxidation and total antioxidant activity (TAC), in the blood of HD patients.

PATIENTS AND METHODS

This study was carried out on 31 HD patients and 31 healthy persons, matched for age and sex, as control group. Blood samples were drawn before and after HD from arteriovenous fistulas, and once from the controls. Superoxide dismutase (SOD), catalase (CAT) and thiobarbituric acid-reactive substance (TBARS) in blood hemolyzate, Glutathione peroxidase (GpX) of whole blood and TAC of plasma were measured, respectively. Then, we investigated the association between TAC of plasma, measured by ferric reducing antioxidant power (FRAP), and lipid peroxidation level with its related parameters, in HD patients.

RESULTS

The SOD, GpX and CAT were decreased after HD (P < 0.05). Also, FRAP was shown to decrease after HD (P < 0.05). However, erythrocyte TBARS levels (μmol/gr of Hb) were increased after HD, in comparison with controls, and before HD (P < 0.05). There was a significant negative correlation between TBARS and antioxidant indices, such as SOD (r = -0.67, P = 0.001), GpX (r = -0.76, P = 0.001), CAT (r = -0.63, P = 0.001) and FRAP (r = -0.84, P = 0.001). The FRAP was significantly and directly correlated with uric acid (r = +0.62, P = 0.001), SOD (r = +0.72, P = 0.001), GpX (r = +0.87, P = 0.001) and CAT (r = +0.84, P = 0.001).

CONCLUSIONS

The results of our study proposed that there is a loss or inactivation of antioxidant factors, coupled with increased lipid peroxidation during the procedure of HD, possibly through the dialyzer membrane, with probable consequences on the severity of illness.