Characterisation of the expression of the Renin-Angiotensin system in primary and immortalised human renal proximal tubular cells.

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.