RENAL RESEARCH INSTITUTE SYMPOSIUM: Longitudinal Study of Apoptosis in Chronic Uremic Patients

Induction of Vesicular Trafficking and JNK-Mediated Apoptotic Signaling in Mononuclear Leukocytes Marks the Immuno-Proteostasis Response to Uremic Proteins

INTRODUCTION

Uremic retention solutes have been alleged to induce the apoptotic program of different cell types, including peripheral blood mononuclear leukocytes (PBL), which may contribute to uremic leukopenia and immune dysfunction.

METHODS

The molecular effects of these solutes were investigated in uremic PBL (u-PBL) and mononuclear cell lines (THP-1 and K562) exposed to the high molecular weight fraction of uremic plasma (u-HMW) prepared by in vitro ultrafiltration with 50 kDa cut-off microconcentrators.

RESULTS

u-PBL show reduced cell viability and increased apoptotic death compared to healthy control PBL (c-PBL). u-HMW induce apoptosis both in u-PBL and c-PBL, as well as in mononuclear cell lines, also stimulating cellular H2O2 formation and secretion, IRE1-α-mediated endoplasmic reticulum stress signaling, and JNK/cJun pathway activation. Also, u-HMW induce autophagy in THP-1 monocytes. u-PBL were characterized by the presence in their cellular proteome of the main proteins and carbonylation targets of u-HMW, namely albumin, transferrin, and fibrinogen, and by the increased expression of receptor for advanced glycation end-products, a scavenger receptor with promiscuous ligand binding properties involved in leukocyte activation and endocytosis.

CONCLUSIONS

Large uremic solutes induce abnormal endocytosis and terminal alteration of cellular proteostasis mechanisms in PBL, including UPR/ER stress response and autophagy, ultimately activating the JNK-mediated apoptotic signaling of these cells. These findings describe the suicidal role of immune cells in facing systemic proteostasis alterations of kidney disease patients, a process that we define as the immuno-proteostasis response of uremia.

Procalcitonin and Conventional Markers of Inflammation in Peritoneal Dialysis Patients and Peritonitis

Objectives

To determine the significance of a newly described marker of inflammation procalcitonin (PCT), and to investigate its relationship to conventional markers of inflammation, such as C-reactive protein (CRP), fibrinogen, and erythrocyte sedimentation rate (ESR), in patients on peritoneal dialysis (PD) and with peritonitis.

Design

A prospective, observational clinical study.

Setting

The Nephrology Division of a University-affiliated teaching hospital.

Patients and Methods

51 consecutive patients on PD were included in the study. Of this number, 16 developed peritonitis during the observational period. Baseline PCT, CRP, and fibrinogen concentrations and ESR of 51 PD patients were determined at a time point (TB) prior to any evidence of infection. These results were compared with laboratory values from 74 hemodialysis patients and 34 nonuremic control subjects. All PD patients then were followed prospectively for evidence of peritonitis. In addition to routine blood tests, including hemoglobin and leukocyte count, and routine biochemical tests, blood samples were taken to measure PCT, CRP, and fibrinogen concentrations and ESR at the time (T0) when patients first were diagnosed with PD peritonitis and also on the 4th (T4) and the 14th (T14) days after treatment for peritonitis was initiated. PCT was assayed by immunoluminometry.

Results

No significant difference was observed between baseline median serum PCT concentrations in PD and hemodialysis patients; however, in both groups, baseline median PCT concentrations were significantly higher than those of nonuremic controls ( p < 0.05). The 16 patients on PD who developed peritonitis had 21 PD peritonitis episodes during the study period. The increased PCT concentration observed at T0 in PD peritonitis episodes decreased with therapy, and this change was statistically significant ( p < 0.05). In a receiver operating characteristic curve analysis for peritonitis, the area under the curve (AUC) for PCT was 0.80, which was significantly lower than the AUC for CRP and greater than the AUCs for fibrinogen and ESR. The sensitivity of PCT for peritonitis was lower than the sensitivity of conventional markers of inflammation; however, the specificity of PCT was higher.

Conclusions

Median serum PCT concentration in PD patients was significantly higher than in nonuremic controls but not hemodialysis patients. Serum PCT concentrations may serve as a useful adjunct to traditional markers of inflammation in detecting and monitoring inflammation and peritonitis in PD patients.

Residual of Bacterial Dna in Hemodialyzers: The Proof of Subclinical Infection Sustaining Chronic Inflammation

Background and purpose

Inflammation and infection seem to be important causes of morbidity and mortality in Chronic Kidney Disease (CKD) patients. Subclinical infections have been proposed as an important cause of inflammatory syndrome but to date this hypothesis remains speculative. In this investigation, we developed a method for molecular detection of the presence of bacterial DNA in a population of chronic kidney disease patients in order to correlate molecular data with the degree and level of inflammation and to evaluate the usefulness of the method in the diagnosis of subclinical infection.

Design

The study was divided into two phases: the study of a population of 81 CKD patients for prevalence and level of inflammation and infection; and the molecular evaluation of a subgroup of 38 patients without evident clinical causes of inflammation for molecular evaluation of subclinical infection.

Results

Patients hemoculture negative turned out positive for the presence of bacterial DNA when molecular methods were used. We found a trend of correlation with the presence of bacterial DNA and the increase in hs-CRP, IL-6 and oxidative stress (AOPP) levels and a reduction in MFI DR+. Hemodialyzer membranes seem to have properties that are “sticky” to bacteria/bacterial DNA and work as concentrators. Moreover our data suggest that DNA can traverse hemodialysis membranes.

Conclusions

Molecular methods have turned out to be far more sensitive than standard methods in detecting subclinical infection. The presence of bacterial DNA seems to influence the variation of some parameters of inflammation and immunity. Apart from the limitations and pitfalls, a molecular method could be useful for the screening of subclinical infection and diagnosis of sepsis when the hemoculture is negative. The identification of the microorganism involved, however, must be done with species-specific primers. These results are preliminary and more investigations will have to be performed in order to confirm our results.

Expanded Haemodialysis Therapy of Chronic Haemodialysis Patients Prevents Calcification and Apoptosis of Vascular Smooth Muscle Cells in vitro

BACKGROUND

Vascular calcification is a common phenomenon in patients with chronic kidney disease and strongly associated with increased cardiovascular mortality. Vascular calcification is an active process mediated in part by inflammatory processes in vascular smooth muscle cells (VSMC). These could be modified by the insufficient removal of proinflammatory cytokines through conventional high-flux (HF) membranes. Recent trials demonstrated a reduction of inflammation in VSMC by use of dialysis membranes with a higher and steeper cut-off. These membranes caused significant albumin loss. Therefore, the effect of high retention Onset (HRO) dialysis membranes on vascular calcification and its implications in vitro was evaluated.

METHODS

In the PERCI II trial, 48 chronic dialysis patients were dialyzed using HF and HRO dialyzers and serum samples were collected. Calcifying VSMC were incubated with the serum samples. Calcification was determined using alizarin red staining (AZR) and determination of alkaline phosphatase (ALP) activity. Furthermore, apoptosis was evaluated, and release of matrix Gla protein (MGP), osteopontin (OPN) and growth differentiation factor 15 (GDF-15) were measured in cell supernatants.

RESULTS

Vascular calcification in vitro was significantly reduced by 24% (ALP) and 36% (AZR) after 4 weeks of HRO dialysis and by 33% (ALP) and 48% (AZR) after 12 weeks of dialysis using HRO membranes compared to HF dialysis. Apoptosis was significantly lower in the HRO group. The concentrations of MGP and OPN were significantly elevated after incubation with HF serum compared to HRO serum and healthy controls. Similarly, GDF-15 release in the supernatant was elevated after incubation with HF serum, an effect significantly ameliorated after treatment with HRO medium.

CONCLUSIONS

Expanded haemodialysis therapy reduces the pro-calcific potential of serum from dialysis patients in vitro. With a markedly reduced albumin filtration compared to high cut-off dialysis, use of the HRO dialyzers may possibly provide a treatment option for chronic dialysis patients to reduce the progression of vascular calcification.

The regulation of NLRP3 inflammasome expression during the development of cardiac contractile dysfunction in chronic kidney disease

Chronic inflammation plays a crucial role in the long-term complications in patients with chronic kidney disease (CKD). This study aimed to assess the role of NLR pyrin domain-containing protein (NLRP3) inflammasome in cardiac contractile dysfunctions in CKD. The cardiac contractile function was evaluated and the expression of NLRP3 inflammasome and related cytokines in the heart was assessed in a murine sham-operated and 5/6 nephrectomy CKD model in vivo. In vitro, H9c2 cells were treated with uremic toxin indoxyl sulfate (IS), with or without NLRP3 inflammasome inhibition, which was achieved by using small interfering RNA (siRNA)-mediated knockdown of the NLRP3 gene. Moreover, the activation of nuclear factor κB (NF-κB) signaling and apoptosis marker levels were assessed in the IS-treated H9c2 cells. The results demonstrated that CKD can lead to the development of cardiac contractile dysfunction in vivo associated with the upregulation of NLRP3 inflammasome, IL-1β, IL-18, and contribute to the myocardial apoptosis. In vitro experiments showed the upregulation of inflammasome, IL-1β, and IL-18 levels, and cell apoptosis in the IS-treated H9c2 cells through the activation of NF-κB signaling pathway. The transfection of cells with si-NLRP3 was shown to alleviate IL-1β, IL-18, and cell apoptosis. Moreover, decreased cell viability induced by IS was shown to be attenuated by IL-1β or IL-18-neutralizing antibody. In summary, CKD can result in the development of cardiac contractile dysfunction associated with the upregulation of NLRP3 inflammasome/IL-1β/IL-18 axis induced by the uremic toxins.

Role of Uremic Toxins on Apoptosis With Varying Periods of Hemodialysis

Increased apoptotic cell death in uremic patients has been confirmed by a variety of studies. The present study aimed to investigate the effect of uremic toxins and duration of hemodialysis (HD) therapy on apoptosis by means of measuring serum caspase cleaved CK18 (CCCK-18) levels. Seventy chronic HD patients were recruited and divided into three groups with differing periods of HD, from 6 months to 10 years. Twelve healthy subjects served as controls. Serum CCCK-18 level was found significantly higher in HD patient groups (Group 2; 189 ± 71 IU/L, Group 3; 182 ± 65 IU/L, Group 4; 204 ± 111 IU/L) as compared to the control group (122 ± 20 U/L) (P < 0.05). When all hemodialysis patients considered together serum CCCK-18 showed positive correlation with serum uric acid and phosphorus (P < 0.05). In conclusion, our results suggest that apoptosis is enhanced in HD patients, phosphorus and uric acid might play a role in this increment, but duration of HD therapy has no effect on apoptosis.

Risk of Tuberculosis Among Patients on Dialysis: The Predictive Value of Serial Interferon-Gamma Release Assay

Patients on long-term dialysis are at high risk for tuberculosis (TB). Although latent tuberculosis infection (LTBI) is good target for TB eradication, interferon-gamma release assay-defined LTBI has a high proportion of negative conversion and lacks active TB correlation among patients on dialysis.Patients on long-term dialysis were screened in multiple centers in Taiwan. QuantiFERON-TB Gold In-tube (QFT-GIT) was used to define LTBI and was performed thrice at 6-month intervals. The primary outcome was active TB diagnosed after LTBI screening. The incidence and predictive value of QFT-GIT were analyzed.The 940 dialysis patients enrolled had an average age of 59.3 years. The initial QFT-GIT results were positive in 193, including 49.6% with persistent positive results on second check. In an average follow-up period of 3 years, 7 patients had TB. Three (319.1 per 100,000 person-yrs) and 4 (141.8 per 100,000 person-yrs) of them were prevalent and incident TB cases, respectively. Persistent positive QFT-GIT for 2 and 3 times correlated with increased hazard ratio for TB (14.44 and 20.29, respectively) compared with a single positive result (hazard ratio 10.38). Among those with 3 positive QFT-GIT results, TB development rate was 4.5% and incidence rate was 1352.3 per 100,000 person-years. In contrast, none of the incident TB occurred in those with initial positive and then negative conversion of QFT-GIT.In an area of intermediate TB incidence, dialysis patients have high TB risk. LTBI status is a good predictor of TB development, especially for those with more than 1 positive result. After excluding prevalent TB cases, serial follow-up of LTBI may narrow the target population to reduce treatment costs.

Impact of anemia treatment with methoxy polyethylene glycol-epoetin beta on polymorphonuclear cells apoptosis in predialysis patients with chronic kidney disease

BACKGROUND

Some data in literature indicate increased apoptosis of polymorphonuclear cells (PMNs) in chronic kidney disease (CKD), what seems to be connected with anemia. Erythropoiesis-stimulating agents, used in anemia treatment in CKD may affect cells apoptosis. Aim of this study was to investigate impact of anemia treatment with methoxy polyethylene glycol-epoetin beta (CERA) on PMNs apoptosis in predialysis patients with CKD.

METHODS

Percentage of early and late apoptotic PMNs was measured by flow cytometry based on annexin V and propidium iodide binding. CD90 (Fas), CD95L (FasL), CD16 and CD11b expression on PMNs were evaluated by flow cytometry after incubation with respective monoclonal antibody.

RESULTS

Percentage of PMNs in early and late apoptosis in CKD patients before CERA treatment was significantly higher to control group, which was accompanied by significantly higher Fas and Fas-L expression and significantly lower expression of CD16. CERA treatment downregulated significantly percentage of early, apoptotic PMNs but percentage of late apoptotic cells did not change and was still significantly higher to control group. In all investigated groups we observed a significant negative correlation between hemoglobin concentration and percentage of apoptotic PMNs, as well as Fas and FasL expression and significant positive correlation between Hb and CD16 expression.

CONCLUSIONS

Our results indicate that PMNs apoptosis is increased in predialysis patients with CKD and anemia treatment with CERA may diminish readiness of PMNs to undergo apoptosis. This antiapoptotic impact of anemia treatment with CERA seems to concern early apoptotic PMNs before they undergo to late, irreversible stage of apoptosis.

Effects of an astragalus polysaccharide and rhein combination on apoptosis in rats with chronic renal failure

Objective. To investigate the effects and to analyze the mechanism of the combination of Astragalus polysaccharide (APS) and Rhein on apoptosis in rats with chronic renal failure (CRF). Methods. Thirty-seven male Wistar rats were randomly divided into a control group, a model group, a low-dose APS and Rhein combination group, and a high-dose APS and Rhein combination group. CRF was induced by orogastric gavage with adenine. Rats were observed for renal function, electrolyte, and pathological changes for 7 weeks after administration. Renal tubular cell apoptosis was assessed by TUNEL and protein expressions of IRE1 and CHOP were detected by Western-blotting. Results. The combination of APS and Rhein decreased the kidney weight and index, improved renal pathological injury, maintained the stability of serum electrolytes, and reduced SCr and BUN levels in rat models. Moreover, APS and Rhein combination could effectively inhibit the apoptosis and reduce the protein expressions of IRE1and CHOP of renal tubular cells. Conclusions. The combination of APS and Rhein could improve renal function and reduce renal cell apoptosis to protect against further progression of CRF, whose mechanism may be related to alleviate endoplasmic reticulum stress (ERS) in the renal cells.

Pullulan-histone antibody nanoconjugates for the removal of chromatin fragments from systemic circulation

The billions of cells that die in the adult human body daily release considerable amounts of fragmented chromatin in the form of mono- and oligonucleosomes into the circulation in normal individuals, and in higher quantities in many disease conditions. Recent results suggest that circulating chromatin fragments (Cfs) especially from abnormal cells can spontaneously enter into healthy cells to damage their DNA and induce genomic instability. Furthermore, Cfs isolated from cancer patients may induce oncogenic transformation in the recipients' cells. Thus, it follows that if such Cfs emanating from apoptotic cells could be prevented from reaching other cells, it could potentially inhibit pathological conditions, including cancer. Here we have developed pullulan based histone antibody nanoconjugates for the removal of Cfs. Nanoconjugates were developed and various physico-chemical characterizations were carried out. The efficacy of these nanoconjugates on removing Cfs was evaluated both in vitro and in vivo. Our results indicate that nanoconjugates may have therapeutic value in the efficient removal of Cfs, reducing inflammation and fatality in a mouse model of sepsis, and in preventing neutropenia following treatment with Adriamycin.

Cardiorenal Syndrome Type 1 May Be Immunologically Mediated: A Pilot Evaluation of Monocyte Apoptosis

BACKGROUND: Cardiorenal syndrome (CRS) type 1 is characterized by a rapid worsening of cardiac function leading to acute kidney injury (AKI). An immune-mediated damage and alteration of immune response have been postulated as potential mechanisms involved in CRS type 1. In this pilot study, we examined the possible role of the immune-mediated mechanisms in the pathogenesis of this syndrome. The main objective was to analyze in vitro that plasma of CRS type 1 patients was able to trigger a response in monocytes resulting in apoptosis. The secondary aim was to evaluate TNF-α and IL-6 plasma levels of CRS type 1 patients. METHODS: Fifteen patients with acute heart failure (AHF) and CRS type 1 were enrolled and 20 healthy volunteers without AHF or AKI were recruited as control group. Plasma from these two groups was incubated with monocytes and, subsequently, cell apoptosis was evaluated. In addition, the activity of caspase-8 was assessed after 24 h incubation. Quantitative determination of TNF-α and IL-6 levels was performed. RESULTS: Plasma-induced apoptosis was significantly higher in CRS type 1 patients compared with healthy controls at 72 h (78 vs. 11%) and 96 h (81 vs. 11%). At 24 h, the activity of caspase-8 was significantly higher in monocytes incubated with plasma from the CRS type 1 group. TNF-α (2.39 vs. 28.49 pg/ml) and IL-6 (4.8 vs. 16.5 pg/ml) levels were significantly elevated in the CRS type 1 group (p < 0.01). CONCLUSIONS: In conclusion, there is a defective regulation of monocyte apoptosis in CRS type 1 patients, and inflammatory pathways may have a central role in the pathogenesis of CRS type 1 and may be fundamental in damage to distant organs.

HLA-DR expression and apoptosis: a cross-sectional controlled study in hemodialysis and peritoneal dialysis patients

BACKGROUND

Altered HLA-DR expression and apoptosis have been described to reflect a state of immunological dysfunction in uremia. Here, we performed a cross-sectional, controlled study to evaluate monocyte HLA-DR expression and apoptosis in dialyzed chronic kidney disease patients.

METHODS

Monocyte HLA-DR expression was determined in 81 hemodialysis (HD) and 51 peritoneal dialysis (PD) patients and 40 healthy controls. By triple-color flow cytometry, we analyzed the percentage of monocytes in whole blood, the percentage of HLA-DR+ monocytes and the mean fluorescence intensity. Using U937 cell line incubated with the patients' plasma, we analyzed the percentage of apoptosis induced after 96 h.

RESULTS

Both HD and PD patients had lower, but statistically not significant, monocyte HLA-DR expression compared to controls (96.47 +/- 3.83% and 96.64 +/- 3.29% respectively, versus 98.42 +/- 1.05%). However, mean fluorescence intensity of HLA-DR was significantly higher in PD (149.35 +/- 80.96) than in HD (99.20 +/- 40.46), and controls (73.25 +/- 27.78, p < 0.001). Apoptosis was higher in both HD and PD (35.14 +/- 6.77 and 14.37 +/- 5.03%) compared to controls (11.30 +/- 2.03%, p < 0.001), and significantly higher in HD compared to PD.

CONCLUSION

A reduced inflammatory state and the continuous solute removal in PD may attenuate immune dysfunction in uremia. In HD but not in PD patients, there was a significant correlation between the percentage of HLA-DR+ monocytes with apoptosis (R = 0.230, p = 0.04).

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.

Inflammation and Subclinical Infection in Chronic Kidney Disease: A Molecular Approach

Inflammation and infection seem to be important causes of morbidity and mortality in chronic kidney disease (CKD) patients; subclinical infections have been proposed as an important cause of inflammatory syndrome, but to date this hypothesis remains speculative. We developed a method for the molecular detection of the presence of bacterial DNA in a population of CKD patients in order to correlate the molecular data with the degree and level of inflammation and to evaluate its usefulness in the diagnosis of subclinical infection. The study was divided into two phases: (1) a population of 81 CKD patients was screened for the prevalence and level of inflammation and the presence of possible infection, and (2) a subgroup of 38 patients, without evident clinical causes of inflammation, underwent complete molecular evaluation for subclinical infection using bacterial DNA primers for sequencing. Additionally, complete analysis was carried out in the blood and dialysate compartments of the hemodialyzers used. The general population showed a certain degree of subclinical inflammation and no difference was found between patients with and without evident causes of inflammation. Hemoculture-negative patients were positive for the presence of bacterial DNA when molecular methods were used. We found a correlation trend between the presence of bacterial DNA and the increase in hs-CRP, IL-6 and oxidative stress (advanced oxidation protein product) levels and a reduction in the mean fluorescence intensity for HLA-DR. Hemodialyzer membranes seem to have properties that stick to bacteria/bacterial DNA and work as concentrators. In fact, patients with negative bacterial DNA in the circulating blood displayed positivity in the blood compartment of the dialyzer. The dialysate was negative for bacterial DNA but the dialysate compartment of the hemodialyzers used was positive in a high percentage. Moreover our data suggest that bacterial DNA can traverse hemodialysis membranes. Molecular methods have been found to be far more sensitive than standard methods in detecting subclinical infection. The presence of bacterial DNA seems to influence the variation in some parameters of inflammation and immunity. Apart from the limitations and pitfalls, the molecular method could be useful to screen for subclinical infection and diagnose subclinical sepsis when the hemoculture is negative. However, the identification of the microorganism implicated must be done with species-specific primers.

Dialysis Membrane-Induced Oxidative Stress: Role of Heme Oxygenase-1

Dialysis membranes have been reported to induce monocyte apoptosis. We studied the role of oxidative stress in the induction of dialysis membrane-induced monocyte apoptosis. Superoxide dismutase, a superoxide scavenger, prevented dialysis membrane-induced monocyte apoptosis. Similarly, other antioxidants also inhibited dialysis membrane- induced apoptosis. In addition, the interaction of dialysis membranes with monocytes was associated with the generation of molecules leading to oxidative stress such as superoxide and TBARS. Interestingly, pre-induction of heme oxygenase (HO)-1 by hemin prevented dialysis membrane-induced monocyte apoptosis, whereas inhibition of HO-1 activity (treatment with tin protoporphyrin, SN-P) enhanced dialysis membrane-induced monocyte apoptosis. We suggest that oxidative injury associated with dialysis membrane and monocyte interaction plays a role in monocyte injury. Pre-induction of HO-1 may attenuate dialysis membrane-induced monocyte apoptosis.

Cell-Free Plasma DNA: A Marker for Apoptosis during Hemodialysis

Background: We evaluated whether cell-free plasma DNA might be an appropriate marker for cell damage during hemodialysis (HD) and whether it correlated with annexin V expression and 7-amino-actinomycin D (7AAD) nuclear staining of blood leukocytes.

Methods: Circulating DNA, annexin V, and 7AAD were measured in HD patients before HD, 20 min after start of HD, and after HD had ended. Healthy volunteers provided control measurements. Necrosis and apoptosis were monitored by gel electrophoresis.

Results: Plasma DNA concentrations were not significantly different between controls and patients before HD. Circulating DNA increased significantly (P &lt;0.05) after 20 min of treatment with HD. Post-HD concentrations of DNA were significantly higher compared with pre-HD and controls (P &lt;0.005). Agarose gel electrophoresis showed ladders typical of apoptosis in post-HD samples. Two subpopulations of CD45+ leukocytes were defined by flow cytometry: annexin V+/7AAD+ population for apoptosis, and annexin V+/7AAD− for early apoptosis. Compared with healthy controls, mean fluorescence (MF) of 7AAD+ apoptotic cells in the annexin V+/7AAD+ subpopulation before HD was not significantly increased. HD increased MF of 7AAD+ cells in the annexin V+/7AAD+ subpopulation. In this subpopulation, MF of annexin V+ cells was significantly higher (P &lt;0.01). MF of annexin V+ cells in the annexin V+/7AAD+ subpopulation increased during HD.

Conclusions: During HD, cell-free plasma DNA concentrations, annexin V expression, and 7AAD uptake in leukocytes increases. The increase in plasma DNA, appearing as ladders typical of apoptosis, and the 7AAD uptake in leukocytes demonstrate that the predominant portion of circulating DNA in HD patients originates from apoptotic leukocytes.

Oxidant and Carbonyl Stress-Related Apoptosis in End-Stage Kidney Disease: Impact of Membrane Flux

Apoptosis is a highly regulated process which mostly affects cell-mediated immunity. In this open-label, randomized, prospective clinical study, we determined the impact in 10 hemodialysis patients treated with high-, medium-, and low-flux membranes on spontaneous or plasma-induced apoptosis, on monocytes, as well as on oxidant and carbonyl stress. High- and medium-flux membranes significantly reduced patients' plasma-dependent proapoptotic activity on U937 monocytic cell lines. Patients who had the highest levels of plasma-induced proapoptotic activity exhibited the highest plasma levels of advanced oxidation protein products (AOPPs) and carbonyls. Plasma carbonyl residues but not AOPPs were significantly lowered. Finally, a significant correlation could be drawn between the extent of plasma-induced proapoptotic activity and both plasma carbonyl and AOPP levels.