The Effect of Dialysate Glucose on Phagocyte Superoxide Generation in Capd Patients

Objective

In the present study, we investigated the influence of dialysate glucose on superoxide (02) generation by peripheral and peritoneal phagocytes in continuous ambulatory peritoneal dialysis (CAPD) patients.

Design

Peripheral polymorphonuclear leukocytes (PMNL) and mononuclear leukocytes (MNL), and peritoneal cells were isolated from peripheral blood and peritoneal effluents, respectively, and their oxidative metabolism was assessed by measuring 02 generation after stimulation with a soluble stimulant [phorbol myristate acetate (PMA), 1 mg/mL, Sigma Chemical, St. Louis, MO, U.S.A.] using the chemiluminescence method. Dialysate glucose effect on 02 generation was also studied in vitro by exposing peripheral PMNL and MNL from healthy controls to peritoneal dialysis fluid (PDF) containing glucose or amino acids at a neutral pH for different time periods.

Results

The amount of 02 generation by both peripheral and peritoneal phagocytes in CAPD patients was significantly higher than that in the control, and the response was greater in patients who were dialyzed with high glucose dialysate than those using low glucose dialysate. In an in vitro study, all incubated cells, except the control, showed suppression of 02 generation in the early dwell time (2 hr), and subsequently showed increased responses (peaking at 6 hr), although lower in degree than those observed in vivo. In contrast, amino acid-based PDF exhibited no such effect on 02 generation at identical pH with similar or lower osmolality. Furthermore, the respective increased or decreased oxidative responses with the increased or decreased PDF glucose concentrations in the same patient confirmed the positive effect of PDF glucose on phagocyte 02 generation.

Conclusion

It is suggested that increased 02 generation by peritoneal and circulating phagocytes in CAPD patients is at least partly due to the enhancement of hexose monophosphate shunt activity by increasing glucose metabolism in phagocytes, and the increased 02 generation might be involved in long-term complications of CAPD. Therefore, a suitable alternative osmotic agent is needed to provide a more physiological environment to minimize the adverse effects of glucose on cell functions.

Absence of Modulating Effects of Cytokines on Antioxidant Enzymes in Peritoneal Mesothelial Cells

Objective

To investigate the modulation of superoxide dismutase, glutathione peroxidase, and catalase by cytokines and endotoxin in human peritoneal mesothelial cells.

Design

Cultured human peritoneal mesothelial cells were treated with various concentrations of interleu kin-1 α, tumor necrosis factor-α(TNFα), interleukin-6, interleukin-8, transforming growth factor-β (TGFβ), and lipopolysaccharide. Cell morphology was observed and the activities of superoxide dismutase, catalase, and glutathione peroxidase were assayed. The antioxidant enzyme activities of human peritoneal mesothelial cells were also compared with those of human liver and kidney tissues.

Results

Interleukin-1α, TNFα, TGFβ, and lipopolysaccharide caused dose-dependent cytotoxicities in mesothelial cells. The activities of these three antioxidant enzymes did not change after treatment with cytokines and endotoxin. The total superoxide dismutase activity of confluent human peritoneal mesothelial cells was found to be greater than that of human liver and kidney tissues and was composed mostly of manganese superoxide dismutase activity. Furthermore, glutathione peroxidase and catalase activities of human peritoneal mesothelial cells were lower than those of human liver and kidney tissues.

Conclusion

In human peritoneal mesothelial cells, lack of induction of antioxidant enzymes by inflammatory cytokines, as well as high superoxide dismutase activity accompanied by insufficient glutathione peroxidase and catalase activities may both contribute to the susceptibility of these cells to oxidative damage. Therefore, appropriate management to decrease oxidative injury to the peritoneum should be taken into consideration when treating long-term continuous ambulatory peritoneal dialysis patients.

Changes in Biocompatibility of Dialysis Fluid during Its Dwell in the Peritoneal Cavity

Objective

To evaluate the changes in biocompatibility of peritoneal dialysis solutions during intraperitoneal dwell.

Design

We studied the effect of the drained dialysates at time 0 and after 30, 60, 120, 240, and 360 minutes of intraperitoneal dwell on the growth of peritoneal mesothelial cells and fibroblasts and the synthesis of proteins by these cells. On one day the patients were dialyzed with glucose-based Dianeal and on alternate days with an amino acid-containing solution based on Travasol.

Patients

Dialysates were collected from 4 patients during continuous ambulatory peritoneal dialysis (CAPD) training.

Results

Unused dialysis solutions containing glucose or amino acids inhibit growth of mesothelial cells and fibroblasts. Dialysates obtained after 30 or 60 minutes of intraperitoneal dwell support the growth of these cells in a way similar to 10% fetal calf serum, but dialysates drained after a longer dwell of 120 360 minutes had a stronger effect on growth of these cells than did serum. All glucose-based dialysates stimulate the synthesis of collagen in mesothelial cells, whereas they reduce the synthesis of non-collagen proteins. All glucose-based dialysates reduce the synthesis of collagen and noncollagen proteins in fibroblasts compared with the production of these proteins in the presence of serum.

Conclusion

Changes in the properties of the dialysis solutions during their intraperitoneal dwells do not seem to increase their biocompatibility. Indeed, excessive mitogenic effect and the stimulation of collagen synthesis of the dialysates may induce pathological changes in the peritoneum.

Oxidative Stress in Patients Undergoing Peritoneal Dialysis: A Current Review of the Literature

Peritoneal dialysis (PD) patients manifest excessive oxidative stress (OS) compared to the general population and predialysis chronic kidney disease patients, mainly due to the composition of the PD solution (high-glucose content, low pH, elevated osmolality, increased lactate concentration and glucose degradation products). However, PD could be considered a more biocompatible form of dialysis compared to hemodialysis (HD), since several studies showed that the latter results in an excess accumulation of oxidative products and loss of antioxidants. OS in PD is tightly linked with chronic inflammation, atherogenesis, peritoneal fibrosis, and loss of residual renal function. Although exogenous supplementation of antioxidants, such as vitamins E and C, N-acetylcysteine, and carotenoids, in some cases showed potential beneficial effects in PD patients, relevant recommendations have not been yet adopted in everyday clinical practice.

How has peritoneal dialysis changed over the last 30 years: experience of the Verona dialysis center

Background

The last decade has witnessed considerable improvement in dialysis technology and changes in clinical management of patients in peritoneal dialysis (PD) with a significant impact on long term clinical outcomes. However, the identification of factors involved in this process is still not complete.

Methods

Therefore, to assess this objective, we retrospectively analyzed clinical records of 260 adult patients who started PD treatment from 1983 to 2012 in our renal unit. For the analysis, we divided them into three groups according to the time of starting dialysis: GROUP A (n: 62, 1983–1992), GROUP B (n: 66, 1993–2002) and GROUP C (n: 132, 2003 to 2012).

Results

Statistical analysis revealed that patients included in the GROUP C showed a reduction in mean patients’ age (p = 0.03), smoking habit (p = 0.001), mean systolic blood pressure (p < 0.0001) and an increment in hemoglobin levels (p < 0.0001) and residual diuresis (p = 0.016) compared to the other two study groups. Additionally, patients included in GROUP C, mainly treated with automated peritoneal dialysis, showed a reduced risk of all-causes mortality and a decreased risk to develop acute myocardial infarction and cerebrovascular disease. Patients’ age, diabetes mellitus and smoking habit were all positively associated with a significant increased risk of mortality in our PD patients, while serum albumin levels and residual diuresis were negatively correlated.

Conclusions

Therefore, the present study, revealed that in the last decade there has been a growth of our PD program with a concomitant modification of our patients’ characteristics. These changes, together with the evident technical advances, have caused a significant improvement of patients’ survival and a decrement of the rate of hospitalization. Moreover, it reveals that our pre-dialysis care, modifying the above-mentioned factors, has been a major cause of these clinical improvements.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0051-3) contains supplementary material, which is available to authorized users.

Association between blood cadmium levels and malnutrition in peritoneal dialysis

Background

Malnutrition is associated with an increased risk of cardiovascular death and may cause protein-energy wasting in individuals with chronic kidney disease. A previous study demonstrated that blood cadmium levels (BCLs) were associated with malnutrition in maintenance hemodialysis (MHD) patients. However, the correlation between cadmium exposure and malnutrition remains unclear in chronic peritoneal dialysis (CPD) patients. This study examined the possible adverse effects of environmental cadmium exposure in CPD patients.

Methods

A total of 301 CPD patients were enrolled and divided into 3 study groups based on the following BCL tertiles: low (<0.19 μg/L), middle (0.19–0.39 μg/L), and high (>0.39 μg/L). Demographic, hematological, biochemical, and dialysis-related data were obtained for analysis. The analysis also included values of nutritional and inflammatory markers.

Results

The BCLs of CPD patients were lower than those of MHD patients. At baseline, patients in the high BCL group were older and had a higher prevalence of diabetes mellitus but lower serum albumin, creatinine, and phosphate levels than the patients in the other 2 groups. After adjusting for potential variables, stepwise backward multiple linear regression analysis revealed that age and alanine aminotransferase levels were positively associated with logarithmic transformation of BCLs (log BCLs), while serum albumin levels were negatively associated with log BCLs in CPD patients. The log BCLs were a significant determinant (beta coefficient ± standard error = -0.185 ± 0.074; P = 0.013) of nutritional status and significantly associated with the presence of malnutrition (odds ratio = 2.64; 95% confidence interval: 1.07–6.48; P = 0.035) in CPD patients after adjustment for related variables.

Conclusions

BCL is significantly associated with nutritional status and malnutrition in CPD patients. Therefore, it is important for CPD patients to avoid environmental exposure to cadmium such as through smoking and consumption of cadmium-rich foods.

Downregulation of nuclear-encoded genes of oxidative metabolism in dialyzed chronic kidney disease patients

Background

Mitochondria, essential eukaryotic cells organelles defined as the “powerhouse of the cell” because of their ability to produce the vast majority of energy necessary for cellular metabolism, may have a primary role in the oxidative stress-related intracellular machinery associated to chronic kidney disease (CKD).

Methods

To better assess this research assumption, we decided to study the key factors regulating mitochondrial oxidative metabolism in CKD patients in peritoneal dialysis (PD, n = 15) using several bio-molecular methodologies.

Results

RT-PCR experiments demonstrate that the expression level of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) and nuclear respiratory factor-1 (NRF-1), two genes primarily involved in mitochondrial biogenesis and functions, were significantly hypo-expressed in peripheral blood mononuclear cells of PD patients compared to healthy subjects (HS, n = 15). Additionally, mRNA levels of several PGC1-α downstream target genes (TFAM, COX6C,COX7C, UQCRH and MCAD) were profoundly down-regulated in PD cells. TFAM protein analysis confirmed gene-expression results. High plasmatic concentration of Malondialdehyde found in PD patients, confirmed the contribution of the oxidative stress to these biological effects. Finally, Nuclear factor erythroid-derived 2-like 2 (NRF2 or NFE2L2), a transcription factor for numerous antioxidant/detoxifying enzymes and one of its target genes, superoxide dismutase-2 mitochondrial (SOD2) were up-regulated in PD compared to HS.

Conclusions

Our results revealed, for the first time, that CKD-PD patients’ PBMC, through a complex intracellular biochemical machinery, are able to modulate their mitochondrial functions probably in the attempt to reduce oxidative metabolic damage and to turn on a valuable defense cellular strategy against oxidative stress.

Increased oxidative damage to peripheral blood leukocyte DNA in chronic peritoneal dialysis patients

This study focuses on the extent of oxidative DNA damage in peripheral blood leukocytes of chronic peritoneal dialysis (CPD) patients. 8-Hydroxy 2'-deoxyguanosine (8-OHdG) contents in peripheral leukocyte DNA were measured by an HPLC-electrochemical detection method in 24 age- and sex-matched healthy subjects, 22 nondialyzed patients with advanced renal failure, and 42 CPD patients. Mean 8-OHdG content was the highest in CPD patients, followed by the nondialyzed patients, and then by the healthy subjects (19.4 versus 11.9 versus 8.3/10(6) dG; ANOVA P < 0.001). In nondialyzed subjects, peripheral leukocyte 8-OHdG contents inversely correlated with renal creatinine clearance (r = -0.772; P < 0.001). Deficiency of blood antioxidants in CPD and nondialyzed patients was expressed by the lower plasma levels of ascorbate, cholesterol-standardized alpha-tocopherol and whole-blood reduced glutathione, and the higher levels of whole-blood oxidized glutathione as compared with healthy subjects (ANOVA P < 0.05). Mean serum ferritin and iron levels and transferrin saturation were higher in the CPD patients than those in the nondialyzed patients and controls (ANOVA P < 0.05). Flow cytometric analyses of intracellular reactive oxygen species production of peripheral leukocytes showed that spontaneous production by granulocytes, as well as phorbol-12-myristate-13-acetate (PMA)-induced production by granulocytes, lymphocytes and monocytes, were the highest from CPD patients, followed by nondialyzed patients, and then by the healthy subjects (ANOVA P < 0.05). Forward stepwise multiple regression disclosed that uremia, PD treatment, spontaneous and PMA-induced reactive oxygen species production in leukocytes, and serum iron were the independent determinants of peripheral leukocyte 8-OHdG content (R(2) = 0.769; P < 0.001). In conclusion, profound increased 8-OHdG levels in peripheral leukocyte DNA occur in the course of chronic renal failure, gradually increase with its progression, and are further exacerbated by PD treatment.

Ex vivo low-density lipoprotein oxidizability and in vivo lipid peroxidation in patients on CAPD

BACKGROUND

Chronic renal failure is associated with accelerated atherosclerosis and a high incidence of cardiovascular disease. Oxidative modification of low-density lipoprotein (LDL) is considered a key event in atherogenesis.

METHODS

We studied the ex vivo oxidizability of LDL exposed to Cu2+ ions (lag time, rate of propagation, maximum conjugated diene formation) and its relationship with LDL density, fatty acids, and antioxidants, along with plasma malondialdehyde (MDA) and autoantibodies against Cu2+-, MDA-, and hypochlorous acid-modified LDL and plasma antioxidants in 17 continuous ambulatory peritoneal dialysis (CAPD) patients and 21 healthy control subjects.

RESULTS

LDL alpha- and gamma-tocopherol and total polyunsaturated fatty acid (PUFA) concentrations were significantly higher in the CAPD patients. LDL density was shifted to small, dense LDL. LDL oxidizability was comparable to that of healthy subjects. Lag time correlated positively with LDL alpha-tocopherol and inversely with both total PUFA concentrations and density; the rate of oxidation and LDL density correlated positively with total PUFA and total fatty acid concentrations, respectively. Ratios of autoantibody titers against oxidized to native LDL did not differ between the two groups. While plasma alpha- and gamma-tocopherol concentrations and tocopherol to cholesterol ratios were significantly higher, vitamin C concentrations were very low in the CAPD patients. MDA concentrations were 1.7 times higher than in healthy subjects.

CONCLUSIONS

(1) Ex vivo LDL oxidizability is normal in CAPD patients as a result of efficient protection by LDL-associated lipophilic antioxidants, although the LDL composition is altered toward high oxidizability; and (2) the plasma antioxidant screen is insufficient due to impaired vitamin C status.

Peritoneal dialysis solutions for the 21st century

Existing peritoneal dialysis (PD) solutions were formulated for the maintenance of fluid and electrolyte balance, correction of metabolic acidosis, and the removal of metabolic waste products. Solutions currently in development are designed to improve biocompatibility by neutralizing pH and reducing glucose degradation products. PD solutions developed for the 21st century will address major clinical needs related to the maintenance of adequate nutrition, improvement of cardiovascular comorbidity, preservation of peritoneal membrane function, and adequacy of dialysis. Nutrineal is the first example of a PD solution to address such a clinical need. Another example is a low sodium solution to improve sodium balance thereby reducing the incidence of hypertension and the need for antihypertensive medication. New solutions under investigation will employ additives to protect the peritoneal membrane during peritonitis and chronic PD and to optimize PD therapy via improvements in ultrafiltration and solute clearances. Examples include the use of antioxidants to reduce oxidative damage during peritonitis and the use of glycosaminoglycans or other additives to enhance ultrafiltration. Future concepts include remodeling of the peritoneum, for example, the use of mesothelial gene therapy to introduce metabolic and anabolic machinery to remove or perpetually recycle metabolic wastes. The 21st century promises to be an exciting and fruitful time for the investigation and development of new products for the improvement of PD therapy.