Background: In CKD, atherogenesis is accelerated, compared to the general population. Heme-oxygenase 1 (HO-1), an inducible heme-degrading enzyme, with anti-oxidative and anti-inflammatory properties, results in protection against atherogenesis. We investigated whether oxidative stress affects HO-1 induction differentially uremic or control conditions.

Methods: HUAECs were conditioned in 30% human serum conditions (pooled from 40 hemodialysis patients or 10 healthy volunteers) for 72h, followed by exposure to increasing concentrations of peroxynitrite (0.1–1mM) for 10 minutes in 100mM phosphatebuffer, pH 7.5. Additionally, HUAECs were incubated with 100μM Hemin during 6h. Cell viability was measured by MTT assay, 30 minutes after peroxynitrite exposure with or without hemin (50μM for 6h).

HO-1 expression was evaluated by RT-PCR, Western blot and ELISA.

Results: Equal cell viability was found when conditioned in uremic or control serum. Hemin treatment did not affect cell viability, but peroxynitrite treatment reduced cell viability by 23% and 43 % in control and uremic serum (P<0.05 vs. control). Hemin induced a 250-fold increase in HO-1 expression in both conditions. Consistent with mRNA induction, WB and ELISA confirm the induction of HO-1 by hemin in uremic and control conditions.

Conclusion: Although uremia is considered pro-oxidative, pro-inflammatory state, uremic serum per se does not affect cell viability. Oxidative stress however affects endothelial cell viability to a larger extent in uremic conditions compared to control. More work will be needed to determine whether the induction of HO-1 by Hemin is capable of abrogating oxidative-stress-induced processes, implicated in atherogenesis, in cells exposed to uremic toxins in the circulation.