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This study was designed to determine the prevalence of depression among hemodialysis (HD) patients from urban hospitals in Korea, to illustrate demographic factors and biomarkers associated with depression and health-related quality of life (HRQOL), and to demonstrate association between depression and HRQOL.For this multicenter, cross-sectional study, 160 HD patients from 3 university teaching hospitals and 3 local dialysis units in Korea were enrolled. Korean Beck's depression inventory and Korean version of Kidney Disease Quality of Life short form, version 1.3 (KDQOL-SFTM 1.3) were used to evaluate depression and quality of life, respectively.Depression was found in 51 out of 160 (31.9%) patients. Old age (60 years old), low hemoglobin level (10 g/dl), and low economic status were associated with depression, and old age (OR 6.138, p = 0.001) was the most important risk factor among them. Old age, female gender, presence of diabetes mellitus, high comorbidity index score (modified Charlson comorbidity indexor = 6), hypoalbuminemia (4.0 g/dl), and high CRP (0.5 mg/dl) were common factors associated with decreased HRQOL. Depression and HRQOL showed inverse linear relationship.Moderate to severe depression was common in maintenance HD patients in Korea. Among factors associated with depression and decreased HRQOL, some characteristics are potentially modifiable by social and medical intervention. Further prospective studies are warranted to see whether depression and HRQOL can be improved by modifying these factors.

According to the amyloid cascade hypothesis, Alzheimer's disease is the consequence of neuronal cell death induced by beta-amyloid (Abeta), which accumulates by abnormal clearance or production. On the other hand, recent studies have shown cell death-induced alteration in amyloid precursor protein (APP) processing, suggesting potential mutual interactions between APP processing and cell death. We have shown previously that the cell death caused by DNA damage-inducing agents (DDIAs) facilitated gamma-secretase activity and Abeta generation in a Bax/Bcl-2-dependent, but caspase-independent manner. Here, we attempted to elucidate the downstream mechanism that modulates gamma-secretase activity in DDIA-treated cells. N-acetyl cysteine, a potent antioxidant, attenuated DDIA-induced enhancement of gamma-secretase activity but failed to rescue cell death. Overexpression of heat shock protein 70, which blocks cytochrome c release from mitochondria, also reduced gamma-secretase activity. Moreover, glutathione depletion significantly facilitated gamma-secretase activity and Abeta generation by enhancing the formation of higher molecular weight gamma-secretase complex before signs of cell death developed. Finally, Abeta treatment, a known inducer of oxidative stress, also increased gamma-secretase activity. Taken together, these results indicate that DDIA-induced gamma-secretase activation is dependent on augmented oxidative stress, and that Abeta and gamma-secretase may activate each other. On the basis of these results, we propose a feed-back loop between oxidative stress and Abeta generation mediated by gamma-secretase activation.