Kiichi Shirakawa

Renal redox dysregulation in AKI: application for oxidative stress marker of AKI

Oxidative stress is a major determinant of acute kidney injury (AKI); however, the effects of an AKI on renal redox system are unclear, and few existing AKI markers are suitable for evaluating oxidative stress. We measured urinary levels of the redox-regulatory protein thioredoxin 1 (TRX1) in patients with various kinds of kidney disease and in mice with renal ischemia-reperfusion injury. Urinary TRX1 levels were markedly higher in patients with AKI than in those with chronic kidney disease or in healthy subjects. In a receiver operating characteristic curve analysis to differentiate between AKI and other renal diseases, the area under the curve for urinary TRX1 was 0.94 (95% confidence interval, 0.90-0.98), and the sensitivity and specificity were 0.88 and 0.88, respectively, at the optimal cutoff value of 43.0 μg/g creatinine. Immunostaining revealed TRX1 to be diffusely distributed in the tubules of normal kidneys, but to be shifted to the brush borders or urinary lumen in injured tubules in both mice and humans with AKI. Urinary TRX1 in AKI was predominantly in the oxidized form. In cultured human proximal tubular epithelial cells, hydrogen peroxide specifically and dose dependently increased TRX1 levels in the culture supernatant, while reducing intracellular levels. These findings suggest that urinary TRX1 is an oxidative stress-specific biomarker useful for distinguishing AKI from chronic kidney disease and healthy kidneys.

Correlation between the Severity of Clinicopathological Parameters and Whole Blood Interferon-α Production Capacity in Active Phase IgA Nephropathy Patients

Background/Aims: Patients with IgA nephropathy (IgA-N) are thought to have immune system disorders that frequently result in high serum IgA levels and a relatively high susceptibility to upper respiratory infections. Aims: To clarify the influence of the specific immune response of IgA-N patients on the clinicopathological features of the disease, we measured the whole-blood-producing capacity of interferon-α (IFNα-PC). We then compared these findings with clinical and histopathological parameters, including tissue macrophage infiltration, during both histologically active and latent phases. Patients and Methods: Fifty-one inpatients with IgA-N and 70 healthy controls were examined. According to the histological findings, 32 patients had disease in the active phase (AP), and 19 were in the latent phase (LP). Results: In AP patients, IFNα-PC showed positive correlations to serum creatinine, blood urea nitrogen, serum β2-microglobulin (s-β2MG), urinary total protein (U-TP), and urinary β2MG, in addition to the number of infiltrated macrophages per area of interstitium. In LP patients, negative correlations were shown between IFNα-PC and s-β2MG, U-TP, and U-N-acetyl-β-D-glucosaminidase. Conclusion: A significant positive relationship exists between IFNα-PC and the clinicopathological parameters of deteriorated renal lesions in the AP but not in the LP. Thus, the immune status influencing the functional damage may differ between these two phase.