Search

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., Conclusion: 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.)

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: Chronic allograft nephropathy (CAN) is commonly associated with proteinuria. In native nephropathies, proteinuria is linked with proximal renal tubular damage. This study uses regression analysis to link proteinuria with urinary N-acetyl-beta-d-glucosaminidase (NAG) as a marker of tubular injury or hyperfunction in renal transplant patients., Methods: Proteinuria and urinary NAG were measured and regression analysis applied in 105 transplant patients (42 with CAN). Most were receiving calcineurin inhibitor-based immunosuppression (cyclosporine, n=60; tacrolimus, n=26; and neither drug, n=19). Patients with native nephropathies (n=96) and volunteers (n=21) were also studied., Results: Urinary NAG increased with increasing proteinuria. However, patients taking calcineurin inhibitors had higher urinary NAG at any level of urinary protein than those on alternative therapy, or in native nephropathies., Conclusions: In groups of transplant patients taking different immunosuppressive regimens, regression analysis of urinary NAG against urinary protein can identify the separate effects of drug-related tubular injury or hyperfunction from that of proteinuria.