Lara Rodríguez-Ribera

Genomic damage as a biomarker of chronic kidney disease status

Patients suffering from chronic kidney disease (CKD) exhibit a high incidence of cancer and cardiovascular diseases, as well as high levels of genomic damage. To confirm the association of CKD with genomic damage we have carried out the largest study to date addressing this issue, using a total of 602 subjects (187 controls, 206 pre‐dialysis CKD patients and 209 CKD patients in hemodialysis). DNA oxidative damage was measured in all individuals using the comet assay. Our results indicate that CKD patients have significantly higher levels of DNA damage than controls, but no significant differences were observed between pre‐hemodialysis (pre‐HD) and hemodialysis (HD) patients. When oxidative damage was measured, no differences were observed between patients and controls, although HD patients showed significantly higher levels of oxidative damage than pre‐HD patients. In addition, a positive relationship was demonstrated between genomic damage and all‐cause mortality. Our study confirms that genomic damage can be predictive of prognosis in CKD patients, with high levels of DNA damage indicating a poor prognosis in HD patients. Environ. Mol. Mutagen. 56:301–312, 2015.

Genomic Instability in Chronic Renal Failure Patients

Patients suffering chronic renal failure (CRF) exhibit a high incidence of cancer, as well as high levels of genetic damage. We hypothesized that these patients show genomic instability as measured by increased radiosensitivity to the induction of genetic damage. The background levels of genetic damage and the net genetic damage after in vitro irradiation with 0.5 Gy were analyzed using the micronucleus assay in peripheral blood lymphocytes of 174 CRF patients and 53 controls. The net radiation‐induced genetic damage was significantly higher in CRF patients with respect to controls. Among CRF patients, the levels of genetic damage were higher in those with prior incidence of cancer than in those without cancer; in addition, those CRF patients undergoing hemodialysis presented with higher levels of genetic damage than those in the advanced Stages (4–5) of the pathology. A positive association was observed between basal and net micronucleus frequency among CFR patients. However, no association was found between net genetic damage and parameters linked to the different stages of the pathology, such as urine creatinine levels and glomerular filtration rate. Our results indicate that CRF patients show increased radiosensitivity and that the degree of radiosensitivity is associated with the progression of the pathological stage of the disease. Environ. Mol. Mutagen., 2012.

Genomic damage as an independent predictor marker of mortality in hemodialysis patients.

AIM Hemodialysis (HD) patients present an enhanced mortality. Since oxidative DNA damage can be considered a biomarker of genomic instability our aim was to evaluate the influence of this genetic biomarker in all-cause mortality in a group of HD patients followed for 4 years. MATERIAL AND METHODS 123 chronic HD patients were included. Overall genomic damage was analyzed using the Comet assay. Oxidative DNA damage was measured using the Comet assay complemented with the use of Endo-III and FPG enzymes. Follow-up was carried out from January 2007 to July 2011. RESULTS Selected HD patients had a mean age of 62 ± 15 years. During the follow-up 36% of patients died (48% due to cardiovascular disease) and 23% were transplanted. Older patients, with high CRP levels, low levels of cholesterol-HDL and albumin, and higher genetic damage at the beginning of the study showed an increased risk for mortality. Multivariate analysis showed that only genomic damage, age and CRP were independently associated with mortality. CONCLUSIONS Our study shows for the first time that, in HD patients, the presence of high levels of genomic damage is a strong predictor of all-cause mortality. This association remains significant after adjustment for relevant covariates.

Time in hemodialysis modulates the levels of genetic damage in hemodialysis patients

It is assumed that hemodialysis treatment can diminish the levels of genetic damage in circulating lymphocytes by cleaning the blood of uremic toxins that cause oxidative stress. However, the hemodialysis process by itself may also induce genomic damage by producing reactive oxygen species (ROS). We conducted a follow‐up study in a group of 70 hemodialysis patients followed for a mean time of 15 months. We investigated the effect of exposure time in hemodialysis on the levels of genetic damage in peripheral blood lymphocytes using the micronucleus assay. In addition, genetic damage after in vitro irradiation with 0.5 Gy was also analyzed to evaluate changes in radiosensitivity. Our results showed that, at the end of the study, there was a decrease in both the basal levels of genetic damage (9.9 ± 1.0 vs. 7.6 ± 0.7) and radiosensitivity values (38.5 ± 3.0 vs. 27.6 ± 2.4). We conclude that hemodialysis procedures may act as an ameliorating factor reducing the genetic damage present in chronic kidney disease patients. Environ. Mol. Mutagen. 55:363–368, 2014.

Genetic damage in patients moving from hemodialysis to online hemodiafiltration

End-stage renal failure patients exhibit a high incidence of genetic damage and genomic instability. Part of this genetic damage is assumed to be caused by the hemodialysis (HD) procedure. To reduce these effects, different alternative HD procedures have been proposed, such as the use of high efficiency convective therapies to improve the reactive oxygen species/antioxidant ratio. To determine the efficiency of online hemodiafiltration (HDF) technique on the levels of DNA damage, we have measured the frequency of micronucleus in peripheral blood lymphocytes of 33 individuals moving from low-flux HD to post-dilution online HDF. In addition to basal levels of genetic damage, potential changes in radiosensitivity were measured as indicators of genomic instability. Plasma antioxidant capacity was also determined. Second samples were obtained after 6 months on the HDF protocol. Results indicate that moving to online HDF therapy produce a significant reduction of the basal levels of genetic damage, but does not affect the genomic instability status. In addition, a greater increase in plasma antioxidant capacity was observed. In spite of the lack of correlation between these parameters, our results confirm the usefulness of the online HDF technique as a way to reduce DNA damage in HD patients.

Radiosensitivity in patients suffering from chronic kidney disease.

Abstract Purpose: Patients suffering from chronic kidney disease (CKD) exhibit a high incidence of cancer, as well as high levels of genetic damage. We hypothesized that these patients show genomic instability detected as an increased chromosomal radiosensitivity in front of the genetic damage induced by ionizing radiation. Material and methods: The background levels of genetic damage and the net genetic damage after in vitro irradiation with 0.5 Gy were analyzed using the micronucleus (MN) assay in peripheral blood lymphocytes. A total number of 552 individuals (179 controls and 373 CKD patients) were included in the study. Results: The net radiation-induced genetic damage was significantly higher in CKD patients than in controls; but no differences between those patients submitted to hemodialysis and those in pre-dialytic stages were detected. A positive correlation was observed between basal and net micronucleus frequencies in CKD patients what would indicate an underlying genetic background modulating DNA damage levels. Conclusions: Our results indicate that CKD patients present genomic instability, measured as an increased chromosomal radiosensitivity in front of ionizing radiation.

Vitamin E-coated dialysis membranes reduce the levels of oxidative genetic damage in hemodialysis patients

End-stage renal disease patients present oxidative stress status that increases when they are submitted to hemodialysis (HD). This increase in oxidative stress can affect their genetic material, among other targets. The objective of this study was to evaluate the effect of using polysulfone membranes coated with vitamin E, during the HD sessions, on the levels of genetic damage of HD patients. Forty-six patients were followed for 6 months, of whom 29 changed from conventional HD to the use of membranes coated with vitamin E. The level of genetic damage was measured using the micronucleus and the comet assays, both before and after the follow-up period. Serum vitamin E concentration was also checked. The obtained results showed that 24% of our patients presented vitamin E deficiency, and this was normalized in those patients treated with vitamin E-coated membranes. Patients with vitamin E deficiency showed higher levels of oxidative DNA damage. After the use of vitamin E-coated membranes we detected a significant decrease in the levels of oxidative damage. Additionally, hemoglobin values increased significantly with the use of vitamin E-coated membranes. In conclusion, the use of vitamin E-coated membranes supposes a decrease on the levels of oxidative DNA damage, and improves the uremic anemia status. Furthermore, the use of this type of membrane was also effective in correcting vitamin E deficiency.

Levels of DNA damage in peripheral blood lymphocytes of patients undergoing standard hemodialysis vs on-line hemodiafiltration: A comet assay investigation.

Chronic kidney disease (CKD) patients exhibit high levels of genetic damage. Part of this genetic damage is supposed to be caused by the hemodialysis (HD) therapy. Different and more efficient HD procedures could reduce the genetic damage and improve health status of CKD patients. In the present study, we analyzed if changing to online hemodiafiltration (OL-HDF) has a beneficial effect on the levels of genetic damage. The levels of genetic damage (DNA breaks and oxidatively damaged DNA) were analyzed in peripheral blood lymphocytes by using the comet assay. Forty-nine patients submitted to HD, 34 of them changing to OL-HDF and 15 patients continuing in low-flux HD, were included in the study. Plasma antioxidant capacity was also determined. Second sampling period was established after 6 months on the new or traditional HD protocol. A slight decrease in the levels of DNA damage was observed in patients who switched to OL-HDF (P=0.048) in relation to the reference group. This reduction is indicative that OL-HDF shows greater efficiency than low-flux HD in the reduction of basal levels of genetic damage.

Unfermented grape juice reduce genomic damage on patients undergoing hemodialysis.

Chronic kidney disease (CKD) patients in dialysis (HD) are considered to be submitted to a continuous oxidative stress. This stress can cause damage on DNA and, consequently, contribute to the high levels of DNA damage observed in these patients. Due to the well-known role of polyphenols as antioxidant agents we proposed its use to reduce the levels of genotoxicity present in HD-CKD patients. The objective of this study was to evaluate the antigenotoxic effects of unfermented grape juice (UGJ) on HD-CKD patients. The levels of DNA damage were analyzed using different biomarkers, such as breaks and oxidized DNA bases by the comet assay, chromosome damage by the micronucleus test. In addition, TEAC (Trolox equivalent antioxidant capacity) was also evaluated. Thirty-nine patients were followed for six months, of whom 25 were supplemented by UGJ and 14 were not supplemented. The obtained results showed a significant decrease in the underlying levels of oxidative DNA damage, in the supplemented group. Regarding the clinical parameters, LDL and cholesterol, were significantly reduced in the patients studied after the supplementation period, although cholesterol was also decreased in the non-supplemented patients. In conclusion, in our studied group the supplementation with UGJ reduced the levels of oxidative DNA damage of HD-CKD patients.

DNA damage in kidney transplant patients. Role of organ origin

Chronic kidney disease (CKD) patients are characterized by elevated levels of genomic damage. This damage increases when kidney function decreases being maximum in hemodialysis patients. As kidney transplantation improves renal function, and it is related with better survival, the aim of our study was to evaluate potential changes in DNA damage levels after kidney transplantation, and comparing living donor recipients with cadaveric donor recipients. The alkaline comet assay was used to determine DNA breaks and oxidative damaged DNA; and the micronucleus assay was used to determine chromosomal breakage and/or aneuploidy. Fifty CKD patients were followed up after 6 and 12 months of their kidney transplantation. All patients increased their genomic damage levels after 6 and 12 months of renal transplantation, compared with those observed before transplantation, despite of the improvement of their metabolic functions. Donor advanced age correlated positively with higher DNA damage. Genomic damage was lower in living donor transplants with respect to cadaveric donor transplants. Our conclusion is that DNA damage increased in kidney transplantation patients, whereas their renal function improved. Higher levels of DNA damage were found in cadaveric donor transplants when compared to living donor transplants. Environ. Mol. Mutagen. 58:712–718, 2017.