Hyperhomocysteinemia in renal transplant patients as independent cause of endothelial damage and cardiovascular disease

Oxidative stress and 'monocyte reprogramming' after kidney transplant: a longitudinal study

Uremia has been implicated in increased oxidative stress (OS) and decreased monocyte HLA-DR expression in chronic kidney disease (CKD) patients. Thus, one would expect normalization of these parameters after successful kidney transplant (KTx). Our aim was to describe patterns of OS and HLA-DR expression after KTx and to explore the effect of renal function and different immunosuppression regimens. 30 KTx patients (20 male; 48 +/- 11 years) were enrolled and compared with 20 healthy controls. We measured advanced oxidation protein products (AOPP) and the percentage of monocytes expressing HLA-DR (%DR+) before (preKTx) and after KTx (on days 2, 30, 90, 180 and after 1 year). Compared to controls, patients had a higher preKTx AOPP (152.6 vs. 69.3 micromol/l; p < 0.001). AOPP decreased at 48 h after KTx, achieving values similar to controls. Thereafter, it increased again and remained significantly higher compared to controls, returning to preKTx levels at 90 days. Prior to KTx there was a trend for lower %DR+ in KTx patients compared to controls (96 vs. 98%; NS). Following KTx, patients had a lower %DR+ in the 1st month; then it gradually returned to preKTx levels during the 1st year; at no time did it reach a value similar to controls. Cyclosporine (CyA)-treated patients had a significantly higher AOPP (161.5 vs. 99.5 micromol/l; p = 0.03) and a lower %DR+ (91.7 vs. 96.4; p < 0.05) at 30 days than patients on tacrolimus (FK). Patients on mycophenolate mofetil (MMF) showed a low AOPP (106.9 vs. 168.1 micromol/l; p = 0.05) and a high %DR+ (96.7 vs. 88.2%; p = 0.001) than those on everolimus. After 3 months, CyA-treated patients had a non-significant increase in AOPP levels, whereas those on FK showed a decrease (p < 0.05) as did those treated with MMF (p < 0.05). Successful KTx reduced but did not normalize AOPP, suggesting ongoing OS, perhaps due to persistent mild renal dysfunction and the effects of immunosuppression. HLA-DR expression remained low after KTx, which may be a possible contributing factor to infectious complications after transplantation. Immunosuppressive agents appear to have diverse effects on OS and HLA-DR expression.

Oxidative stress in kidney transplant patients1

BACKGROUND

Little information is available about the role of oxidative stress in renal transplant patients. To evaluate the prevalence and severity of oxidative stress in renal transplantation, the authors conducted a cross-sectional study.

METHODS

In 112 cadaver or living-donor kidney transplant recipients with a follow-up of at least 6 months and with plasma creatinine less than or equal to 2.5 mg/dL, complete blood count, serum vitamin B12, serum folate (s-F), reactive oxygen species (ROS), thiol groups (-SH), total antioxidant activity (TAOC), serum homocysteine (Hcy), and intraerythrocyte folate (ery-F) were measured.

RESULTS

The mean levels of Hcy (21.1 microM vs. <10 microM), ROS (302.7 U. Carr (Carratelli units) vs. 250-300 U. Carr), and TAOC (410.6 micromol/HclO/mL vs. >350 micromol/HclO/mL), were higher than the reference interval, whereas -SH groups, vitamin B12, s-F, and ery-F were within the normal range. In the multivariate model, plasma creatinine (P=0.0062), vitamin B12 (P=0.0121), and TAOC (P=0.0007) were independently associated with oxidative stress. At multiple regression analysis, -SH groups and ROS were directly and inversely related to hematocrit (P=0.0007 and P=0.0073). There was also a negative correlation between -SH groups and blood pressure levels (P=0.0095).

CONCLUSIONS

Renal transplant patients have a pattern of increased oxidant stress that is counterbalanced by an enhancement of the antioxidant mechanisms. Besides the well-known risk factors, the authors found that anemia is an independent risk factor for an increase of ROS. Further studies are needed to evaluate whether the correction of anemia might prevent or reduce the oxidative stress in renal transplant patients.