Genetic damage in chronic renal failure patients is associated with the glomerular filtration rate index

Genetic Variants Related to Increased CKD Progression-A Systematic Review

The incidence and prevalence of chronic kidney disease (CKD) are increasing worldwide. CKD is associated with high morbidity, premature mortality, and high healthcare costs. Genetic variants may influence CKD development and progression. This study aimed to identify the associations between allelic variants and CKD progression. We performed a systematic literature review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed, Embase, and Cochrane Central databases were used for data collection. Hereditary causes of CKD were excluded from the analysis. A total of 38 reports were included. The selected studies included cohort studies, case-control studies, and genome-wide association studies (GWASs). The studies involved patients of different ethnicities and with comorbid diseases. Several genetic variants were identified in genes that encode proteins related to metabolic processes, oxidative stress, immune regulation, the renin-angiotensin-aldosterone pathway, and epigenetics, among others. These genetic alterations can affect protein function and lead to renal damage, impacting CKD development and progression. Gene polymorphisms can influence CKD progression. Many of these are population-specific, and their relevance may be influenced by the presence of other diseases and environmental factors. Larger studies are needed to confirm the associations described here.

Accelerated Vascular Aging in Chronic Kidney Disease: The Potential for Novel Therapies

The pathophysiology of vascular disease is linked to accelerated biological aging and a combination of genetic, lifestyle, biological, and environmental risk factors. Within the scenario of uncontrolled artery wall aging processes, CKD (chronic kidney disease) stands out as a valid model for detailed structural, functional, and molecular studies of this process. The cardiorenal syndrome relates to the detrimental bidirectional interplay between the kidney and the cardiovascular system. In addition to established risk factors, this group of patients is subjected to a plethora of other emerging vascular risk factors, such as inflammation, oxidative stress, mitochondrial dysfunction, vitamin K deficiency, cellular senescence, somatic mutations, epigenetic modifications, and increased apoptosis. A better understanding of the molecular mechanisms through which the uremic milieu triggers and maintains early vascular aging processes, has provided important new clues on inflammatory pathways and emerging risk factors alike, and to the altered behavior of cells in the arterial wall. Advances in the understanding of the biology of uremic early vascular aging opens avenues to novel pharmacological and nutritional therapeutic interventions. Such strategies hold promise to improve future prevention and treatment of early vascular aging not only in CKD but also in the elderly general population.

Micronucleus frequency in chronic kidney disease patients: A review

BACKGROUND

Chronic kidney disease (CKD) is defined as a gradual loss of renal function progressing from very mild damage, with no obvious symptoms in stage one, to complete kidney failure in stage five, which ultimately requires kidney replacement therapy by organ transplantation or dialysis. Cancer incidence and other health problems, mainly diabetes and hypertension, are elevated in CKD, ultimately leading to elevated mortality.

METHODS

A literature search on the induction of micronuclei (MN) as endpoint for genomic damage in white blood cells and buccal mucosa cells of CKD patients was conducted. Possible associations with disease stage, treatment modalities, and vitamin or antioxidant supplementations were analyzed.

RESULTS

In total, 26 studies were enclosed in the data analysis. Patient groups in the predialysis or hemodialysis state of the disease exhibit higher levels of genomic damage, measured as micronucleus frequency in peripheral blood lymphocytes and buccal mucosa cells, than healthy control groups. Genomic damage seems to increase with the disease stage during the predialysis phase. The association with dialysis regimens or with years on dialysis is less clear, but there are indications that efficient removal of uremic toxins is beneficial. Patients with CKD receive a variety of medications, some of which could modulate genomic damage levels and thus contribute to the observed heterogeneity. In addition, supplementation with vitamins or antioxidants may in some cases lower the genomic damage. Meta-Analysis confirmed the high and significant levels of genomic damage present in CKD patients compared to matched healthy controls.

CONCLUSION

Genomic damage, as measured by the MN frequency, is elevated in CKD patients. Different strategies, including supplementation with antioxidants and optimizing dialysis processes, can reduce the levels of genomic damage and the different associated pathologies. Whether MN frequency can in the future also be used to assist in certain therapeutic decisions in CKD will have to be investigated further in larger studies.

Loci associated with genomic damage levels in chronic kidney disease patients and controls

Chronic kidney disease (CKD) is a multifactorial disorder with an important genetic component, and several studies have demonstrated potential associations with allelic variants. In addition, CKD patients are also characterized by high levels of genomic damage. Nevertheless, no studies have established relationships between DNA damage, or genomic instability present in CKD patients, and gene polymorphisms. To fill in this gap, the potential role of polymorphisms in genes involved in base excision repair (OGG1, rs1052133; MUTYH, rs3219489; XRCC1, rs25487), nucleotide excision repair (ERCC2/XPD, rs1799793, rs171140, rs13181; ERCC4, rs3136166); phase II metabolism (GSTP1, rs749174; GSTO1, rs2164624; GSTO2, rs156697), and antioxidant enzymes (SOD1, rs17880135, rs1041740, rs202446; SOD2, rs4880; CAT, rs1001179; GPX1, rs17080528; GPX3, rs870406: GPX4, rs713041) were inquired. In addition, some genes involved in CKD (AGT, rs5050; GLO1, rs386572987; SHROOM3, rs17319721) were also evaluated. The genomic damage, the genomic instability, and oxidative damage were evaluated by using the micronucleus and the comet assay in 589 donors (415 CKD patients and 174 controls). Our results showed significant associations between genomic damage and genes directly involved in DNA repair pathways (XRCC1, and ERCC2), and with genes encoding for antioxidant enzymes (SOD1 and GPX1). GSTO2, as a gene involved in phase II metabolism, and MUTYH showed also an association with genomic instability. Interestingly, the three genes associated with CKD (AGT, GLO1, and SHROOM3) showed associations with both the high levels of oxidatively damaged DNA and genomic instability. These results support our view that genomic instability can be considered a biomarker of the CKD status.

Micronuclei and disease - Report of HUMN project workshop at Rennes 2019 EEMGS conference

The "Micronuclei and Disease" workshop was organized by the HUMN Project consortium and hosted by the European Environmental Mutagen and Genomics Society at their annual meeting in Rennes, France, on 23 May 2019. The program of the workshop focused on addressing the emerging evidence linking micronucleus (MN) frequency to human disease. The first objective was to review what has been published and evaluate the level and quality of evidence for the connection between MN frequency and various diseases through all life stages. The second objective was to identify the knowledge gaps and what else needs to be done to determine the clinical utility of MN assays as predictors of disease risk and of prognosis when disease is active. Speakers at the workshop discussed the association of MN frequency with inflammation, infertility, pregnancy complications, obesity, diabetes, cardiovascular disease, kidney disease, cervical and bladder cancer, oral head and neck cancer, lung cancer, accelerated ageing syndromes, neurodegenerative diseases, and a road-map on how to utilise this knowledge was proposed. The outcomes of the workshop indicated that there are significant opportunities for translating the application of MN assays into clinical practice to improve disease prevention and risk management and to inform public health policy.

Genetic Variants Associated with Chronic Kidney Disease in a Spanish Population

Chronic kidney disease (CKD) patients have many affected physiological pathways. Variations in the genes regulating these pathways might affect the incidence and predisposition to this disease. A total of 722 Spanish adults, including 548 patients and 174 controls, were genotyped to better understand the effects of genetic risk loci on the susceptibility to CKD. We analyzed 38 single nucleotide polymorphisms (SNPs) in candidate genes associated with the inflammatory response (interleukins IL-1A, IL-4, IL-6, IL-10, TNF-α, ICAM-1), fibrogenesis (TGFB1), homocysteine synthesis (MTHFR), DNA repair (OGG1, MUTYH, XRCC1, ERCC2, ERCC4), renin-angiotensin-aldosterone system (CYP11B2, AGT), phase-II metabolism (GSTP1, GSTO1, GSTO2), antioxidant capacity (SOD1, SOD2, CAT, GPX1, GPX3, GPX4), and some other genes previously reported to be associated with CKD (GLO1, SLC7A9, SHROOM3, UMOD, VEGFA, MGP, KL). The results showed associations of GPX1, GSTO1, GSTO2, UMOD, and MGP with CKD. Additionally, associations with CKD related pathologies, such as hypertension (GPX4, CYP11B2, ERCC4), cardiovascular disease, diabetes and cancer predisposition (ERCC2) were also observed. Different genes showed association with biochemical parameters characteristic for CKD, such as creatinine (GPX1, GSTO1, GSTO2, KL, MGP), glomerular filtration rate (GPX1, GSTO1, KL, ICAM-1, MGP), hemoglobin (ERCC2, SHROOM3), resistance index erythropoietin (SOD2, VEGFA, MTHFR, KL), albumin (SOD1, GSTO2, ERCC2, SOD2), phosphorus (IL-4, ERCC4 SOD1, GPX4, GPX1), parathyroid hormone (IL-1A, IL-6, SHROOM3, UMOD, ICAM-1), C-reactive protein (SOD2, TGFB1,GSTP1, XRCC1), and ferritin (SOD2, GSTP1, SLC7A9, GPX4). To our knowledge, this is the second comprehensive study carried out in Spanish patients linking genetic polymorphisms and CKD.

The role of DNA damage as a therapeutic target in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disease and is caused by heterozygous germ-line mutations in either PKD1 (85%) or PKD2 (15%). It is characterised by the formation of numerous fluid-filled renal cysts and leads to adult-onset kidney failure in ~50% of patients by 60 years. Kidney cysts in ADPKD are focal and sporadic, arising from the clonal proliferation of collecting-duct principal cells, but in only 1-2% of nephrons for reasons that are not clear. Previous studies have demonstrated that further postnatal reductions in PKD1 (or PKD2) dose are required for kidney cyst formation, but the exact triggering factors are not clear. A growing body of evidence suggests that DNA damage, and activation of the DNA damage response pathway, are altered in ciliopathies. The aims of this review are to: (i) analyse the evidence linking DNA damage and renal cyst formation in ADPKD; (ii) evaluate the advantages and disadvantages of biomarkers to assess DNA damage in ADPKD and finally, (iii) evaluate the potential effects of current clinical treatments on modifying DNA damage in ADPKD. These studies will address the significance of DNA damage and may lead to a new therapeutic approach in ADPKD.

Micronuclei and Their Association with Infertility, Pregnancy Complications, Developmental Defects, Anaemias, Inflammation, Diabetes, Chronic Kidney Disease, Obesity, Cardiovascular Disease, Neurodegenerative Diseases and Cancer

Micronuclei (MN) are a strong cytogenetic indicator of a catastrophic change in the genetic structure and stability of a cell because they originate from either chromosome breaks or whole chromosomes that have been lost from the main nucleus during cell division. The resulting genetic abnormalities can to lead to cellular malfunction, altered gene expression and impaired regenerative capacity. Furthermore, MN are increased as a consequence of genetic defects in DNA repair, deficiency in micronutrients required for DNA replication and repair and exposure to genotoxic chemicals and ultraviolet or ionising radiation. For all of these reasons, the measurement of MN has become one of the best-established methods to measure DNA damage in humans at the cytogenetic level. This chapter is a narrative review of the current evidence for the association of increased MN frequency with developmental and degenerative diseases. In addition, important knowledge gaps are identified, and recommendations for future studies required to consolidate the evidence are provided. The great majority of published studies show a significant association of increased MN in lymphocytes and/or buccal cells with infertility, pregnancy complications, developmental defects, anaemias, inflammation, diabetes, cardiovascular disease, kidney disease, neurodegenerative diseases and cancer. However, the strongest evidence is from prospective studies showing that MN frequency in lymphocytes predicts cancer risk and cardiovascular disease mortality.

Influence of Carnicor, Venofer, and Sevelamer on the levels of genotoxic damage in end-stage renal disease patients

End-stage renal disease (ESRD) patients present high levels of phosphorus and calcium products in serum, which contribute to the development of vascular calcification and cardiovascular disease, and to low iron stores and carnitine deficiency. For these reasons, ESRD patients are generally supplemented with different medicines. Some of the most common treatments include the use of Carnicor, Venofer, and Sevelamer drugs. Carnicor is used as a source of L-carnitine, acting as antioxidant and neuroprotector. Venofer is used to reduce the deficit of iron. Sevelamer is used to treat hyperphosphatemia. To determine the potential harmful genotoxic effects of these drugs, a group of 214 patients included in a hemodialysis program with different intakes of Carnicor, Venofer, and Sevelamer were evaluated. The levels of basal and oxidative DNA damage, as well as chromosomal damage, were measured in all individuals using the comet and the micronucleus assays, respectively. Our results indicate that Carnicor administration was associated with low but significant increases in the frequency of basal DNA damage and micronuclei. Environ. Mol. Mutagen. 59:302-311, 2018. © 2018 Wiley Periodicals, Inc.

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. © 2017 Wiley Periodicals, Inc.

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.

Micronuclei and other nuclear anomalies in buccal epithelial cells of children with chronic kidney disease

The objective of this study was to reveal the likely genomic instability in children with chronic kidney disease (CKD) using micronucleus (MN) assay on buccal epithelial cells (BEC). We investigated the frequencies of micronuclei and other nuclear anomalies, such as nuclear buds, binucleated cells, condensed chromatin, and karyorrhectic and pyknotic cells in BEC. Children with CKD were grouped as follows: children in the pre-dialysis (PreD) stage (N=17), children on regular haemodialysis (HD) (N=14), and children who have undergone transplantation (Tx) (N=17). As a control group, twenty age- and gender-matched healthy children were selected. The MN frequency in BEC of all groups of children with CKD was significantly elevated (5- to 7-fold) as compared to the control group (p<0.001). In contrast, the frequencies of nuclear buds were not significantly higher in the study groups compared to the control group. The frequencies of binucleated cells and condensed chromatin cells were significantly higher in all subgroups of children with CKD relative to the control group (p<0.001). Our results show that the BEC of pediatric PreD, HD, and Tx patients with CKD display increased cytogenetic, cytokinetic, and cytotoxic effects. They also point to the sensitivity and usefulness of the BEC MN assay in the assessment of genetic susceptibility of patients with CKD.

DNA Damage in Chronic Kidney Disease: Evaluation of Clinical Biomarkers

Patients with chronic kidney disease (CKD) exhibit an increased cancer risk compared to a healthy control population. To be able to estimate the cancer risk of the patients and to assess the impact of interventional therapies thereon, it is of particular interest to measure the patients' burden of genomic damage. Chromosomal abnormalities, reduced DNA repair, and DNA lesions were found indeed in cells of patients with CKD. Biomarkers for DNA damage measurable in easily accessible cells like peripheral blood lymphocytes are chromosomal aberrations, structural DNA lesions, and oxidatively modified DNA bases. In this review the most common methods quantifying the three parameters mentioned above, the cytokinesis-block micronucleus assay, the comet assay, and the quantification of 8-oxo-7,8-dihydro-2′-deoxyguanosine, are evaluated concerning the feasibility of the analysis and regarding the marker's potential to predict clinical outcomes.

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.

Radiosensitivity in patients suffering from chronic kidney disease

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.

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.

Genetic damage in patients with chronic kidney disease, peritoneal dialysis and haemodialysis: a comparative study

Patients with chronic kidney disease (CKD) have signs of genomic instability and, as a consequence, extensive genetic damage, possibly due to accumulation of uraemic toxins, oxidative stress mediators and other endogenous substances with genotoxic properties. We explored factors associated with the presence and background levels of genetic damage in CKD. A cross-sectional study was performed in 91 CKD patients including pre-dialysis (CKD patients; n = 23) and patients undergoing peritoneal dialysis (PD; n = 33) or haemodialysis (HD; n = 35) and with 61 healthy subjects, divided into two subgroups with the older group being in the age range of the patients, serving as controls. Alkaline comet assay and cytokinesis-block micronucleus assay in peripheral blood lymphocytes were used to determine DNA and chromosome damage, respectively, present in CKD. Markers of oxidative stress [malondialdehyde (MDA), advanced glycation end products (AGEs), thiols, advanced oxidation protein products and 8-hydroxy-2'-deoxyguanosine] and markers of inflammation (C-reactive protein, interleukin-6 and tumour necrosis factor alpha) were also measured. Micronucleus (MN) frequency was significantly higher (P < 0.05) in the CKD group (46±4‰) when compared with the older control (oC) group (27.7±14). A significant increase in MN frequency (P < 0.05) was also seen in PD patients (41.9±14‰) versus the oC group. There was no statistically significant difference for the HD group (29.7±15.6‰; P = NS) versus the oC group. Comet assay data showed a significant increase (P < 0.001) of tail DNA intensity in cells of patients with CKD (15.6±7%) with respect to the total control (TC) group (11±1%). PD patients (14.8±7%) also have a significant increase (P < 0.001) versus the TC group. Again, there was no statistically significant difference for the HD group (12.5±3%) compared with the TC group. Patients with MN values in the upper quartile had increased cholesterol, triglycerides, AGEs and MDA levels and lower albumin levels. Multiple logistic regression analysis showed that male gender, diabetes and treatment modality were independently associated with higher levels of DNA damage. Our results suggest that oxidative stress, diabetes, gender and dialysis modality in CKD patients increased DNA and chromosome damage. To confirm these data, prospective clinical trials need to be performed.

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.