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Proteinuria is pathogenic to proximal tubular cells (PTC) and linked with progression to renal failure. The aim of this study was to determine the effects of human serum albumin (HSA) overload on the changes in gene and protein expression stimulated by oxidative stress in PTC and any interaction with ANG II that is pivotal in disease pathogenesis. Markers of oxidative stress, antioxidant defences, transcription factor activation, and the expression of stress-related genes were measured in human PTC (HK-2 cells) overloaded with either globulin-free fatty acid free (GF/FAF) HSA or globulin-free (GF) HSA. The effects of ANG II were also determined. HSA overload in HK-2 cells caused PTC hyperfunction, increased oxidative stress, and an upregulation of adaptive responses and stress-related genes. Some responses were common to both HSAs but others were unique to either HSA and unaffected by addition of ANG II or candesartan (a specific ANG II type 1 receptor blocker). ANG II also independently induced oxidative stress and upregulated other stress-related genes. HSA overload in HK-2 cells stimulated increased oxidative stress and upregulated changes in stress-related gene expression indicating new pathways of PTC injury that are not mediated via ANG II type 1 receptors.

Background: Ultraviolet radiation (UVR) generates reactive oxygen species in skin that can play a role in skin damage, but reports about the photoprotective properties of oral antioxidant supplements are conflicting., Objective: We examined the ability of 2 lipid-soluble antioxidants, vitamin E and beta-carotene, to reduce markers of oxidative stress and erythema in human skin exposed to UVR., Design: Sixteen healthy subjects took either alpha-tocopherol (n = 8; 400 IU/d) or beta-carotene (n = 8; 15 mg/d) for 8 wk. Biopsy samples before and after supplementation were taken from unexposed skin and skin 6 h after 120 mJ/cm(2) UVR. The effects of supplements on markers of oxidative stress in skin and the minimal erythema dose to UVR were assessed., Results: Supplementary vitamin E was bioavailable, the plasma concentration increased from 14.0 +/- 0.66 (x +/- SEM) to 18.2 +/- 0.64 mug/mL (P < 0.01), and the skin concentration increased from 0.55 +/- 0.09 to 1.6 +/- 0.19 ng/mg protein (P < 0.01). Supplementary beta-carotene increased plasma concentrations from 1 +/- 0.3 to 2.25 +/- 0.3 mug/mL (P < 0.05), but skin concentrations were undetectable. Before vitamin E supplementation, UVR increased the skin malondialdehyde concentration from 0.42 +/- 0.07 to 1.24 +/- 0.16 nmol/mg protein (P < 0.01), whereas oxidized or total glutathione increased from 9.98 +/- 0.4% to 12.0 +/- 1.0% (P < 0.05). Vitamin E supplementation significantly decreased the skin malondialdehyde concentration, but neither vitamin E nor beta-carotene significantly influenced other measures of oxidation in basal or UVR-exposed skin., Conclusions: Vitamin E or beta-carotene supplementation had no effect on skin sensitivity to UVR. Although vitamin E supplements significantly reduced the skin malondialdehyde concentration, neither supplement affected other measures of UVR-induced oxidative stress in human skin, which suggested no photoprotection of supplementation.

Chronic metabolic acidosis occurs commonly in chronic renal failure (CRF). The proximal renal tubular cell is the site in the kidney of high oxidative metabolic activity and in CRF is associated with adaptive hypertrophy and hypermetabolism. We hypothesised that chronic acidosis may lead to increased generation of reactive oxygen species due to increased oxidative activity. We developed a novel model of chronic acidosis in LLC-PK1 cells and measured markers of oxidative stress and metabolism. Acidosis led to a reduction in cellular total glutathione and protein thiol content and an increase in glutathione peroxidase activity and NH3 generation. The expression of constitutively expressed heat stress protein (HSP) HSC70 and HSP60 increased at pH 7.0., (Copyright 2003 S. Karger AG, Basel)

Background/Aims: Angiotensin II (AngII) is pivotal in the pathogenesis of progressive kidney disease. We have recently shown that AngII induced an increase in markers of oxidative stress, adaptive responses and upregulated stress-related gene expression in immortalised human proximal tubular (HK-2) cells. However, these observed effects of AngII were not mediated solely via AngII type 1 receptor (ATR1). Both HK-2 cells and primary human renal proximal tubular cells (RPTEC) are useful tools to investigate the renin-angiotensin system (RAS), but data on the local expression of the RAS in these cells remain limited. We therefore characterised RAS expression in RPTEC and HK-2 cells. Methods: The mRNA and protein expression of RAS in RPTEC and HK-2 cells was examined by RT-PCR, Western blotting and immunoprecipitation. Results: In both cell lines, mRNA for angiotensin-converting enzyme (ACE) and mRNA and protein expression for angiotensinogen, renin, ACE2, ATR1 and ATR4 were detected. Candesartan, a specific ATR1 blocker, effectively blocked the expression of 80% of the stress-related genes that were upregulated in HK-2 cells following exposure to AngII. Con clusion: These data support a role for AngII in mediating oxidative stress via other receptor types stimulated by AngII and confirm that it is possible to investigate ATR4 pathways of potential injury in RPTEC. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Ultraviolet radiation (UVR) generates reactive oxygen species in skin that can play a role in skin damage, but reports about the photoprotective properties of oral antioxidant supplements are conflicting. Objective: We examined the ability of 2 lipid-soluble antioxidants, vitamin E and β-carotene, to reduce markers of oxidative stress and erythema in human skin exposed to UVR. Design: Sixteen healthy subjects took either a-tocopherol (n = 8; 400 IU/d) or j3-carotene (n = 8; 15 mg/d) for 8 wk. Biopsy samples before and after supplementation were taken from unexposed skin and skin 6 h after 120 mJ/cm2 UVR. The effects of supplements on markers of oxidative stress in skin and the minimal erythema dose to UVR were assessed. Results: Supplementary vitamin E was bioavailable, the plasma concentration increased from 14.0 ± 0.66 (x ± SEM) to 18.2 ± 0.64 μg/mL (P < 0.01), and the skin concentration increased from 0.55 ± 0.09 to 1.6 ± 0.19 ng/mg protein (P < 0.01). Supplementary β-carotene increased plasma concentrations from 1 ± 0.3 to 2.25 ± 0.3 μg/mL (P < 0.05), but skin concentrations were undetectable. Before vitamin E supplementation, UVR increased the skin malon-dialdehyde concentration from 0.42 ± 0.07 to 1.24 ± 0.16nmol/mg protein (P < 0.01), whereas oxidized or total glutathione increased from 9.98 ± 0.4% to 12.0 ± 1.0% (P < 0.05). Vitamin E supplementation significantly decreased the skin malondialdehyde concentration, but neither vitamin E nor β-carotene significantly influenced other measures of oxidation in basal or UVR-exposed skin. Conclusions: Vitamin E or β-carotene supplementation had no effect on skin sensitivity to UVR. Although vitamin E supplements significantly reduced the skin malondialdehyde concentration, neither supplement affected other measures of UVR-induced oxidative stress in human skin, which suggested no photoprotection of supplementation. [ABSTRACT FROM AUTHOR]