Heme oxygenase 1 expression in young uremic patients on hemodialysis

Nrf2 Plays a Protective Role Against Intravascular Hemolysis-Mediated Acute Kidney Injury

Massive intravascular hemolysis is associated with acute kidney injury (AKI). Nuclear factor erythroid-2-related factor 2 (Nrf2) plays a central role in the defense against oxidative stress by activating the expression of antioxidant proteins. We investigated the role of Nrf2 in intravascular hemolysis and whether Nrf2 activation protected against hemoglobin (Hb)/heme-mediated renal damage in vivo and in vitro. We observed renal Nrf2 activation in human hemolysis and in an experimental model of intravascular hemolysis promoted by phenylhydrazine intraperitoneal injection. In wild-type mice, Hb/heme released from intravascular hemolysis promoted AKI, resulting in decreased renal function, enhanced expression of tubular injury markers (KIM-1 and NGAL), oxidative and endoplasmic reticulum stress (ER), and cell death. These features were more severe in Nrf2-deficient mice, which showed decreased expression of Nrf2-related antioxidant enzymes, including heme oxygenase 1 (HO-1) and ferritin. Nrf2 activation with sulforaphane protected against Hb toxicity in mice and cultured tubular epithelial cells, ameliorating renal function and kidney injury and reducing cell stress and death. Nrf2 genotype or sulforaphane treatment did not influence the severity of hemolysis. In conclusion, our study identifies Nrf2 as a key molecule involved in protection against renal damage associated with hemolysis and opens novel therapeutic approaches to prevent renal damage in patients with severe hemolytic crisis. These findings provide new insights into novel aspects of Hb-mediated renal toxicity and may have important therapeutic implications for intravascular hemolysis-related diseases.

Oxidative stress in children on hemodialysis: value of autoantibodies against oxidized low-density lipoprotein

The principal causes of morbidity and mortality in children with chronic renal failure on maintenance hemodialysis are cardiovascular complications. Recently, it has been suggested that oxidative stress, chronic inflammation and malnutrition are risk factors for cardiovascular disease. However, to date, biomarkers of oxidative stress have not been well studied in children. The aim of this study was to investigate the relationship between oxidative stress and cardiovascular risk factors in children on hemodialysis therapy. Twenty-eight hemodialysis patients (13 females, 15 males; mean age 15.1 +/- 2.5 years) and 20 healthy children (13 females, seven males; mean age 14.3 +/- 2.7 years) were included in the study. Levels of antibodies to oxidized low-density lipoprotein (oLABs), high sensitivity C-reactive protein (hs-CRP), albumin, prealbumin, transferrin, and ferritin were measured. Antibodies to oxidized low-density lipoprotein (LDL) in hemodialysis patients were lower than those in the controls (P < 0.05). The patients with lower oLAB titers had higher levels of hs-CRP and ratio of erythropoietin to hematocrit (EPO/Htc), and lower levels of albumin, prealbumin, apolipoprotein A-1 (ApoA(1)), and high-density lipoprotein (P < 0.05). Antibodies to oxidized LDL in hemodialysis patients with dyslipidemia were lower than those of patients with normal lipid profile (P < 0,05). This study showed that children treated by hemodialysis are exposed to oxidative stress and chronic inflammation. We suggest that oLAB levels are decreased in children on hemodialysis as a result of severe oxidative stress and that these antibodies are related to inflammation, anemia, malnutrition and dyslipidemia.

Influence of oxidative stress and inflammation on rHuEPO requirements of hemodialysis patients with CRP values "in normal range"

AIMS

We sought to evaluate influences of oxidative stress (OS) on rHuEPO requirements in hemodialysis patients without chronic inflammation.

METHODS

Sixty-eight hemodialysis patients and 46 healthy controls underwent measurements plasma levels of antioxidative agents, such as glutathione peroxidase (GPX), superoxide dismutase (SOD), and oxidative compounds including malonyldialdehyde (MDA). We retrospectively analyzed the last 3 months' rHuEPO requirements, iron indices, and CRP levels.

RESULTS

Plasma levels for SOD, GPX, and MDA were 974.4+/-216.4 U/gHb, 44.4+/-13.6 U/gHb, 10.0+/-2.0 nmol/mL, respectively yielding results that were different from healthy controls (P<.0001). Increased OS negatively correlated with hemoglobin levels (P<.0001) and positively correlated with rHuEPO requirements (P<.01). Increased antioxidative capacity positively correlated with hemoglobin levels (P<.0001) and negatively correlated with rHuEPO requirements (P<.0001). For further analyses, hemodialysis patients were subgrouped according to rHuEPO requirements as group I (lowest 1/3, n=23), group II (moderate 1/3, n=23) and group III (highest 1/3, n=22). Group III displayed the highest MDA (P<.05), the lowest SOD (P<.0001), and comparable GPX (P<.05) levels. Group III also had the highest CRP and the lowest albumin levels compared with the others (P<.01).

CONCLUSION

OS has strong adverse influences on rHuEPO responses of HD patients with "normal" CRP levels, but it should not be forgotten that CRP levels in the "normal" range may still reflect ongoing microinflammation.

Oxidatively-modified and glycated proteins as candidate pro-inflammatory toxins in uremia and dialysis patients

End stage renal disease (ESRD) patients accumulate blood hallmarks of protein glycation and oxidation. It is now well established that these protein damage products may represent a heterogeneous class of uremic toxins with pro-inflammatory and pro-oxidant properties. These toxins could be directly involved in the pathogenesis of the inflammatory syndrome and vascular complications, which are mainly sustained by the uremic state and bioincompatibility of dialysis therapy. A key underlying event in the toxicity of these proteinaceous solutes has been identified in scavenger receptor-dependent recognition and elimination by inflammatory and endothelial cells, which once activated generate further and even more pronounced protein injuries by a self-feeding mechanism based on inflammation and oxidative stress-derived events. This review examines the literature and provides original information on the techniques for investigating proteinaceous pro-inflammatory toxins. We have also evaluated therapeutic - either pharmacological or dialytic - strategies proposed to alleviate the accumulation of these toxins and to constrain the inflammatory and oxidative burden of ESRD.