Yukie Matsuyama

Dialyzable Uremic Solutes Contribute to Enhanced Oxidation of Serum Albumin in Regular Hemodialysis Patients

Background: Oxidative stress (OS) is reportedly enhanced in patients receiving regular hemodialysis (HD). However, the in vivo redox state of HD patients, particularly after HD sessions, remains unclear. This study aimed to clarify the influence of HD on OS using the albumin redox state as a marker. Method: Blood samples of 8 regular HD patients were obtained during the course of study. The redox state of albumin was determined using high-performance liquid chromatography. Results: The mean fraction of reversibly oxidized albumin [f(HNA-1)] declined significantly over the course of the session and reached a minimum 4 h after the session had ended (pre-HD, 36.16 ± 7.50%; 4 h after HD, 25.71 ± 6.41%), then gradually rose to predialytic levels. The proportion of irreversibly oxidized albumin did not change significantly over time. Positive correlations were demonstrated between f(HNA-1) and uremic small solutes in each case. Conclusion: Accumulation of dialyzable uremic solutes may contribute to OS in HD patients.

Human astrocytes and aortic endothelial cells actively convert the oxidized form of albumin to the reduced form: reduced albumin might participate in redox regulation of nerve and blood vessel systems.

Human serum albumin (HSA) is a mixture of mercaptalbumin (HMA, reduced form) and nonmercaptalbumin (HNA, oxidized form), i.e., a protein-thiol redox couple in the extracellular fluid (ECF), and it might have antioxidant properties. Forty-two patients with orthopedic disorders participated in this study and were divided into two groups according to their age (young and older groups). By using HPLC to separate HSA into HMA and HNA, we analyzed the percentages of HMA and HNA in serum and lumbar cerebrospinal fluid (CSF). We also examined the redox activity of cultured normal human astrocytes, aortic endothelial cells, and dermal fibroblasts for HSA-thiol. The mean HMA value from the serum of the older group was significantly lower than that of the young group, whereas that from CSF was not significantly different between the two groups; CSF albumin is almost completely in the reduced form, and no age-related differences were observed. Cultured astrocytes and aortic endothelial cells showed conversion of HNA to HMA, whereas dermal fibroblasts showed no such redox activity. From the results obtained from in-vivo and in-vitro studies, HMA is considered to participate in redox regulation in the ECF, for example in the CSF that surrounds the central nervous system (CNS), and in blood serum.

Effect of a hydrogen (H2)-enriched solution on the albumin redox of hemodialysis patients

Elevated oxidative stress (OS) is associated with severe cardiovascular disease and premature death among patients treated with hemodialysis (HD). Oxidative stress is enhanced by contact between blood and dialysis membranes during HD sessions. This study aimed to clarify whether hydrogen (H2), which is a known antioxidant, is capable of suppressing increased OS induced during HD sessions. Eight patients on regular HD treatment were studied. Two HD sessions were performed in a cross‐over design trial using standard and hydrogen‐enriched solutions (mean of 50 p.p.b. H2; H2‐HD). Blood samples were obtained from the inlet and outlet of the dialyzer during HD to determine changes in plasma levels of glutathione, hydrogen peroxide, and albumin redox state as a marker of OS. Comparison of inlet and outlet blood revealed significant decreases in total glutathione and reduced glutathione, as well as significant increases in hydrogen peroxide in both HD treatments. However, the mean proportion of reversibly oxidized albumin in outlet serum was significantly lower than that in inlet serum following the H2‐HD session, whereas no significant changes were found in the standard solution session, suggesting that “intra‐dialyzer” OS is reduced by H2‐HD. In conclusion, the application of H2‐enriched solutions could ameliorate OS during HD.

Close relationship between redox state of human serum albumin and serum cysteine levels in non-diabetic CKD patients with various degrees of renal function.

AIMS Human mercaptalbumin (HMA) acts as a covalent-carrier protein for sulfur-containing amino acids, cysteine, and glutathione. In addition, its sulfhydryl residue reacts with peroxyl radicals. In this study, we evaluated the redox state of human serum albumin and its relationship with serum amino thiol levels in non-diabetic chronic kidney disease (CKD) patients with various degrees of renal function. MATERIALS AND METHODS High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring were used to analyze serum samples collected from 37 non-dialysis patients with primary glomerulonephritis without diabetes mellitus (DM) or other systemic diseases (non-diabetic CKD patients). RESULTS Total cysteine and homocysteine plasma levels increased with decreasing renal function and showed a significant negative correlation with glomerular filtration rate. The protein-bound ratio of serum cysteine also changed with the degree of renal dysfunction. The HPLC fraction of human mercaptalbumin (HMA) (%) was significantly lower in nondiabetic CKD patients than in healthy subjects. The redox state of human serum albumin (i.e., HMA %) correlated significantly with the total serum cysteine level. CONCLUSION The HPLC fraction of HMA (%) closely correlated with the serum cysteine level in non-diabetic CKD patients. An increase in oxidized cysteine with impaired renal function and a reduced plasma redox capacity associated with a decrease in the reduced form of serum albumin (HMA %) may be important risk factors for promoting long-term complications in patients with renal dysfunction.

The influence of the redox state of follicular fluid albumin on the viability of aspirated human oocytes

A number of reports have suggested that the oxidative state of human albumin in serum and in some body fluids is associated with cell damage. However there are no reports on the redox state of human follicular fluid (FF) and its influence on oocyte viability. The aim of this study was to examine the relationship between the redox state of FF and serum on oocyte viability. The cytoplasmic condition of oocytes was evaluated microscopically at collection in 117 women. Deteriorating oocytes were recognized by degenerative changes in their cytoplasm. The redox state of FFs that yielded degenerated oocytes was evaluated and compared with fluids containing normal oocytes. The redox state of the corresponding FF and serum, at the time of oocyte retrieval, was analyzed by high performance liquid chromatography. The redox state of FF that contained degenerated oocytes was found to have a significantly elevated oxidized state compared with the FFs that yielded normal oocytes. Also the albumin in the FF of patients was found to be predominantly in the reduced state compared with that in their serum at the time of oocyte retrieval. In addition, increasing age and endometriosis were found to shift the redox of serum to the oxidative state. We propose that the reduced state of albumin in FF may play an important role in protecting oocytes from oxidative damage.

Transperitoneal administration of dissolved hydrogen for peritoneal dialysis patients: a novel approach to suppress oxidative stress in the peritoneal cavity

BackgroundOxidative stress (OS) related to glucose degradation products such as methylglyoxal is reportedly associated with peritoneal deterioration in patients treated with peritoneal dialysis (PD). However, the use of general antioxidant agents is limited due to their harmful effects. This study aimed to clarify the influence of the novel antioxidant molecular hydrogen (H2) on peritoneal OS using albumin redox state as a marker.MethodsEffluent and blood samples of 6 regular PD patients were obtained during the peritoneal equilibrium test using standard dialysate and hydrogen-enriched dialysate. The redox state of albumin in effluent and blood was determined using high-performance liquid chromatography.ResultsMean proportion of reduced albumin (ƒ(HMA)) in effluent was significantly higher in H2-enriched dialysate (62.31 ± 11.10%) than in standard dialysate (54.70 ± 13.08%). Likewise, serum ƒ(HMA) after administration of hydrogen-enriched dialysate (65.75 ± 7.52%) was significantly higher than that after standard dialysate (62.44 ± 7.66%).ConclusionsTrans-peritoneal administration of H2 reduces peritoneal and systemic OS.

Comparative studies on the heterogeneity of plasma-derived and recombinant human albumins in laboratory use

We investigated the thiol-redox state, and the relationship between structural characteristics, such as thermal stability, and functional properties, such as cell growth activity, of commercial plasma-derived (pHSA) and recombinant human serum albumin (rHSA) products. In this study, 5 pHSA products (A1653, A9511, A1887, A8763, and A3782) and 2 rHSA products (A9731 and A9986) were obtained from Sigma-Aldrich. Among them, three kinds of HSA products [A1653 (an initial fractionation product), A3782 (a final purified product), and A9731 (recombinant albumin expressed in rice)] were selected for experiments on the thermal stabilities, analyzed by thermal denaturation curves, and cell growth activities of U937 and THP-1 cell lines using the WST-1 reagent. The secondary and tertiary structures of HSA products were similar, whereas a marked difference was observed in their thermal stabilities. The degree of thermal stability of the three representative products was in the order of A9731 (rHSA)>A1653 (pHSA)>A3782 (pHSA), as was the degree of cell growth activity of these products. One possible explanation for the present results is that albumin-bound fatty acids may have influenced the thermal stabilities and cell growth activities of U937 and THP-1 cells.

The redox state of recombinant human serum albumin and its optimal concentration for mouse embryo culture

Albumin has multiple physiological functions in embryo culture, such as a chelator of heavy metals, free radical scavenger, pH and osmotic regulator, a stabilizer, growth factor carrier, a surfactant, and a nutrient. However, the commercially available human serum albumin (HSA) products may not be completely safe since they could be contaminated with viruses and prions. Recombinant human serum albumin (rHSA) has been reported to be as efficient as commercial HSA for fertilization and embryo development. Despite the possible benefits of rHSA, it has not been widely used for embryo culture due to its high cost of production. Our objective was to analyze the redox state of different types of HSA products and rHSA to define oxidative status batch variations of HSA and rHSA and to evaluate the optimal concentration of rHSA for mouse embryo culture. The redox state of the HSA and rHSA used in embryo culture media was found to vary widely. Redox variations were found among different HSA batches as well as among rHSA batches. The highest blastocyst development and hatching rates were obtained with rHSA used at a concentration of 0.05 mg/mL. We showed that very low concentrations of rHSA were most favorable for advanced mouse embryo development in culture.

Difference in redox status of serum and aqueous humor in senile cataract patients as monitored via the albumin thiol-redox state.

PurposeTo clarify the redox states of the aqueous humor and serum in senile cataract patients.MethodsWe analyzed the reduced and oxidized albumin fractions in 58 patients. The patients had no detectable evidence of other eye or systemic diseases and were divided into two age groups (53–75 and 76-96 years). Analysis was performed with a high-performance liquid chromatographic system with a fluorescence detector.ResultsExtremely small amounts of reduced albumin (3.8% and 3.6% in the younger and older groups, respectively) and markedly large amounts of oxidized albumin (96.2% and 96.4%, respectively) were found in the aqueous humor. Moreover, a higher percentage of oxidized albumin, particularly a highly oxidized irreversible form of albumin, was found in the aqueous humor (12.3% and 12.0%) than in the serum (2.4% and 3.0%).ConclusionsIn senile cataract patients with no complications, the redox state of albumin in the aqueous humor differs considerably, both quantitatively and qualitatively, from that in the serum.

Pigment Epithelium-Derived Factor as a New Predictor of Mortality Among Chronic Kidney Disease Patients Treated With Hemodialysis

Pigment epithelium‐derived factor (PEDF) plays a protective role against atherosclerosis. Although serum PEDF level is increased in patients undergoing regular hemodialysis (HD), the pathophysiological role of PEDF in HD patients is unknown. We measured serum PEDF levels in 74 HD patients, and the association between serum PEDF and adverse events such as all‐cause death and cardiovascular accident was evaluated prospectively. During the follow up of 45.4 ± 25.1 months, 24 patients (32.4%) experienced cardiovascular accident and 18 (24.3%) died. Significantly higher incidences of all‐cause mortality and cardiovascular accident were observed in the lower PEDF group than in the higher PEDF group. After adjusting for propensity score calculated from multiple confounding factors (age, gender, systolic blood pressure, history of previous cardiovascular disease, level of carbonyl content, albumin, hemoglobin, total cholesterol, creatinine, C‐reactive protein, dialysis vintage, Kt/V‐urea and history of diabetes), lower predialytic PEDF was a significant risk factor for all‐cause mortality (relative hazard = 6.060, standard error = 0.68467, P = 0.0085). Lower levels of predialytic PEDF was associated with an increased risk of mortality.