Recovery of acute renal failure following bilateral renal artery angioplasty and stenting

Atherosclerotic renovascular disease commonly coexists with chronic kidney disease, and its optimal management remains unsettled. In this case report, we describe a 75-year-old woman with chronic kidney disease and critical atherosclerotic bilateral renal artery stenosis, who presented with a hypertensive emergency and developed acute renal failure following antihypertensive treatment. Bilateral percutaneous transluminal renal angioplasties (PTRA) with stent placement were performed and resulted in immediate recovery of renal function. The existing literature on this impressive response to PTRA is reviewed and discussed.

Chronic kidney disease as a global public health problem: approaches and initiatives - a position statement from Kidney Disease Improving Global Outcomes

Chronic kidney disease (CKD) is increasingly recognized as a global public health problem. There is now convincing evidence that CKD can be detected using simple laboratory tests, and that treatment can prevent or delay complications of decreased kidney function, slow the progression of kidney disease, and reduce the risk of cardiovascular disease (CVD). Translating these advances to simple and applicable public health measures must be adopted as a goal worldwide. Understanding the relationship between CKD and other chronic diseases is important to developing a public health policy to improve outcomes. The 2004 Kidney Disease Improving Global Outcomes (KDIGO) Controversies Conference on 'Definition and Classification of Chronic Kidney Disease' represented an important endorsement of the Kidney Disease Outcome Quality Initiative definition and classification of CKD by the international community. The 2006 KDIGO Controversies Conference on CKD was convened to consider six major topics: (1) CKD classification, (2) CKD screening and surveillance, (3) public policy for CKD, (4) CVD and CVD risk factors as risk factors for development and progression of CKD, (5) association of CKD with chronic infections, and (6) association of CKD with cancer. This report contains the recommendations from the meeting. It has been reviewed by the conference participants and approved as position statement by the KDIGO Board of Directors. KDIGO will work in collaboration with international and national public health organizations to facilitate implementation of these recommendations.

CREB transcription factor modulates Bcl2 transcription in response to C5a in HL-60-derived neutrophils

BACKGROUND

Complement fragment C5a and neutrophils have been implicated in the pathogenesis of renal disease and C5a has also been shown to delay apoptosis of human neutrophils via a transcription-independent pathway. However, transcription-dependent pathways have not been well described. The present study examined whether activation of HL-60-derived neutrophils by C5a modulates the transcription of two members of the Bcl2 family, Bax (pro-apoptotic) and Bcl2 (anti-apoptotic) molecules, and whether the cAMP-response element-binding protein (CREB) transcription factor mediates these effects through the phosphatidylinositol 3-kinase (PI3K)/Akt and extra-cellular signal-regulated kinase (ERK) signalling pathways.

MATERIALS AND METHODS

The human promyelocytic leukaemia HL-60 cell line was differentiated into neutrophils using 1.25% DMSO. Differentiated cells were incubated with recombinant human C5a for 30-120 min with, or without, pretreatment with wortmannin or PD98059. The cells were lysed and quantified for gene-specific Bax and Bcl2 mRNA. In separate experiments, cells were incubated with C5a for 5-30 min with, or without, pretreatment with wortmannin, PD98059, or alkaline phosphatase. Cells were then lysed and immunoblotted using antihuman phospho-CREB (Ser133) antibody. Apoptosis was assessed by measuring active caspase-3 in differentiated HL-60 cells.

RESULTS

C5a inhibited caspase-3 activation in HL-60-derived neutrophils (P=0.003). C5a significantly increased the expression of Bcl2 mRNA (P=0.028), which was time-dependent, peaking at 30 min, and was abrogated in the presence of either wortmannin or PD98059 (both P=0.028). The C5a had no impact on Bax mRNA expression. The Bax : Bcl2 mRNA ratio markedly decreased at 30 min (P=0.028). Time-dependent effect of C5a on CREB phosphorylation was demonstrable and rapid, peaking at 5 min, and was abrogated by either wortmannin or PD98059 (both P=0.028). Phosphorylation of CREB, but not of Akt and ERK, was inhibited by alkaline phosphatase (P=0.028). The effect of C5a on Bcl2 mRNA expression was abrogated by alkaline phosphatase (P=0.028). The Bax : Bcl2 mRNA ratio markedly increased in the presence of alkaline phosphatase (P=0.046).

CONCLUSIONS

This study demonstrates that C5a induces Bcl2 mRNA transcription in HL-60-derived neutrophils, which is mediated in part by CREB through the convergence of the PI3K/Akt and ERK-signalling pathways.

Biocompatible hemodialysis membranes for acute renal failure

BACKGROUND

Acute renal failure (ARF) is associated with substantial morbidity and mortality. Some trials have reported a survival advantage among patients dialyzed with biocompatible membranes (BCM) compared to bioincompatible membranes (BICM). These findings were not consistently observed in subsequent studies.

OBJECTIVES

To ascertain whether the use of BCM confers an advantage in either survival or recovery of renal function over the use of BICM in adult patients with ARF requiring intermittent hemodialysis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library - Issue 1, 2004), MEDLINE (1966 to January 2004), EMBASE (1980 to January 2004), the Mexican Index of Latin American Biomedical Journals IMBIOMED (1990 to January 2004), the Latin American and Caribbean Health Sciences Literature Database LILACS (1982 to January 2004), and reference lists of articles.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing the use of a BCM with a BICM in patients > 18 years of age with ARF requiring intermittent hemodialysis.

DATA COLLECTION AND ANALYSIS

Two authors extracted the data independently. Cellulose-derived dialysis membranes were classified as BICM, and synthetic dialyzers were considered as BCM. The main outcomes were all-cause mortality and recovery of renal function by type of dialyzer. We further explored these outcomes according to the flux properties (high-flux or low-flux) of each of these dialyzers. A meta-analysis was conducted by combining data using a random-effects model.

MAIN RESULTS

Nine studies were included in the primary analysis of mortality, with a total of 1062 patients. None of the pooled RR's reached statistical significance. The pooled relative risk (RR) for mortality was 0.93 (95% confidence interval (CI) = 0.81 to 1.07). The overall RR for recovery of renal function, inclusive of 1038 patients from nine studies was 1.09 (95% CI 0.90 to 1.31). The pooled RR for mortality by dialyzer flux property was 1.03 (95% CI 0.82 to 1.30). The RR for recovery of renal function by flux property was 0.85 (95% CI 0.55 to 1.31). A meta-analysis of mortality of kidney transplant recipients was not possible, but the analysis of recovery of renal function in this patient population was 1.09 (95% CI 0.91to 1.31). Results of sensitivity analyses did not differ significantly from the primary analyses.

AUTHORS' CONCLUSIONS

There is no demonstrable clinical advantage to the use of BCM versus BICM in patients with ARF who require intermittent hemodialysis.

Ribavirin monotherapy for hepatitis C virus-associated membranous nephropathy

Glomerular diseases associated with hepatitis C virus (HCV) infection are increasingly being recognized. Antiviral therapy with interferon-alpha (IFN-alpha) and ribavirin eradicate viral activity in a significant proportion of patients with chronic active hepatitis, often with amelioration of extrahepatic manifestations, including glomerular pathology. Unfortunately, adverse effects often preclude the use of IFN-alpha. We describe a patient with refractory nephrotic syndrome secondary to HCV-associated membranous nephropathy who sustained a complete remission following the initiation of ribavirin monotherapy. The existing literature on the association between these two disorders and therapy with ribavirin is reviewed.

Anti-oxidants reverse uraemia-induced down-regulation of mitochondrial membrane potential and interleukin-10 production

BACKGROUND

The anti-inflammatory cytokine, interleukin-10 (IL-10), has potent immunomodulatory effects. We hypothesized that previously reported defective synthesis of IL-10 by immunocompetent cells exposed to a uraemic milieu may be due to impaired mitochondrial membrane potential (MMP).

MATERIALS AND METHODS

The human promonocytic THP-1 cell line was differentiated to monocytes and incubated with pooled control or uraemic plasma with and without catalase or N-acetyl L-cysteine (NAC). Basal hydrogen peroxide (H(2)O(2)) production was measured by flow cytometry. To measure MMP, cells were stained with rhodamine 123 (Rh123) and the uptake of Rh123 assessed by flow cytometry. To assess the relative contribution of the NADPH oxidase and mitochondrial electron transport chain (ELT) to endotoxin (ET)-stimulated IL-10 production among monocytic cells, cells were incubated with and without a selective NADPH oxidase inhibitor, apocynin and mitochondrial ELT inhibitors, diphenyliodinium and rotenone, washed and ET-stimulated IL-10 production was measured. In other experiments, cells were incubated with pooled control or uraemic plasma in the presence or absence of antioxidants followed by overnight incubation with ET. IL-10 production by monocytes in the cell supernatant was then quantified.

RESULTS

Basal H(2)O(2) production was significantly higher among differentiated THP-1 cells exposed to uraemic plasma compared with normal plasma (180.57 +/- 10.24 vs. 41.57 +/- 8.98 MCI; P = 0.02). Uraemic plasma also down regulated MMP (4.60 +/- 1.28 vs. 8.00 +/- 1.59 MCI with normal plasma; P = 0.03). Both diphenyliodinium and rotenone, selective inhibitors of the mitochondrial ELT, inhibited ET-stimulated IL-10 production. In contrast, apocynin, a selective NADPH oxidase inhibitor, did not inhibit ET-stimulated IL-10 production. Further, ET-stimulated IL-10 production by cells incubated with uraemic plasma was significantly lower when compared to cells exposed to normal plasma. Pre-incubation with catalase and NAC restored uraemia-induced down regulation of MMP. In addition, ET-stimulated IL-10 production by cells incubated with uraemic plasma was also restored by both catalase and NAC.

CONCLUSIONS

Our observations suggest that ET-stimulated IL-10 synthesis by monocytic cells is mitochondrial ELT-dependent and NADPH oxidase-independent. Monocytic cells exposed to a uraemic environment exhibit higher basal ROS production, lower MMP, and impaired ET-stimulated IL-10 synthesis. Anti-oxidants restore MMP and up-regulate ET-stimulated IL-10 synthesis.

Crescentic fibrillary glomerulonephritis associated with hepatitis C viral infection

Fibrillary glomerulonephritis (FGN) is a pathological diagnosis that is rarely associated with systemic disorders. In this case report, we describe a woman who presented with FGN of the crescentic type in association with hepatitis C viral infection. The existing literature on the association between these 2 disorders is reviewed, and postulated therapy is presented.

C5a delays apoptosis of human neutrophils via an extracellular signal-regulated kinase and Bad-mediated signalling pathway

AIMS

We recently demonstrated that complement fragment C5a delays apoptosis of human neutrophils via induction of the phosphatidylinositol-3 kinase (PI 3-K) pathway. In the present study, we examined whether C5a modulates neutrophil survival through the extracellular signal-regulated kinase (ERK) and Bad-mediated signalling pathway.

METHODS

Human neutrophils were isolated by percoll gradient and preincubated for 1 h with or without PD98059 (20 microM), a specific ERK inhibitor, followed by incubation with C5a (1 microg mL(-1)) for 24 h. Apoptosis was quantified by flow cytometry, using propidium iodide nuclear staining. Extracellular signal-regulated kinase downstream signalling events were evaluated by measuring the expression of cytosolic total and phosphorylated p44/p42 proteins, and Bad phosphorylation using immunoblot analyses. These time-dependent analyses were performed over a brief exposure to C5a (0-30 min). Modulation of cytosolic caspase-9 and caspase-3 activity was measured by Western blot analyses.

RESULTS

C5a inhibited neutrophil apoptosis (P=0.04), which was abrogated in the presence of PD98059 (P=0.04). Time-dependent effect of C5a on p44/p42 phosphorylation was rapid, peaked at 5 min, and was abrogated by the ERK inhibitor (P=0.04). In addition, brief stimulation of neutrophils with C5a induced phosphorylation of Bad, which was inhibited by the ERK inhibitor (P=0.03). Further, C5a suppressed the proteolytic cleavage of caspase-9 and caspase-3, which was reversed by ERK inhibition. Finally, blockade of both the ERK (with PD98059) and PI 3-K (with wortmannin) pathways did not induce additive inhibition of neutrophil apoptosis by C5a.

CONCLUSION

This study demonstrates that in addition to the PI 3-K pathway, C5a also inhibits neutrophil apoptosis via an ERK-signalling pathway, resulting in phosphorylation of Bad and blockade of proteolytic cleavage of caspases. The activation of this additional survival-signalling pathway may be another important cellular mechanism that enhances neutrophil survival in inflammatory states.

Quantification of Bax and Bcl2 in polymorphonuclear leukocytes from haemodialysis patients: relation to hydrogen peroxide

BACKGROUND

Bax and Bcl2 are two apoptosis-related molecules that play an important role in determining cell fate following oxidative injury. In the present study, we explored the relation of hydrogen peroxide (H2O2) generation by polymorphonuclear cells (PMNs) to the cytosolic expression of Bax and Bcl2 proteins and apoptosis in haemodialysis (HD) patients.

METHODS

Cytosolic generation of H2O2 by PMNs from control subjects and HD patients was measured by flow cytometry using the dichlorofluorescin diacetate assay. Bax and Bcl2 expression was detected by flow cytometry using FITC-conjugated antibodies. Apoptosis was quantified by flow cytometry using propidium iodide nuclear staining. To examine the effect of H2O2 on Bcl2 and Bax expression, PMNs from control subjects were briefly exposed to H2O2 (0.1-100 microM) for 10 min and then washed and cultured for 6 h, with or without catalase, a H2O2 detoxifying molecule. Bcl2 and Bax expression was determined by Western blot analysis.

RESULTS

Basal H2O2 generation by resting PMNs was significantly higher in HD patients compared with control subjects (211 +/- 115 vs. 23 +/- 5 MFI; P=0.002). However, PMNs from HD patients did not undergo accelerated programmed cell death compared with control subjects (58 +/- 7% vs. 46 +/- 5; P=0.14). Polymorphonuclear cells cytosolic Bcl2 was undetected in control subjects but detected in 25% of HD patients, and Bax was more frequently detected in PMNs from HD patients (75% vs. 67%; P=0.04). In the HD patients with detectable cytosolic Bax and Bcl2 proteins, the Bax to Bcl2 ratio inversely correlated with H2O2 levels (P<0.0001). Finally, brief exposure of PMNs to 0.1-100 microM of H2O2 resulted in a marked increase in Bcl2 expression (P=0.001), which was prevented by catalase (P=0.05). There was no apparent effect on Bax expression.

CONCLUSIONS

This study demonstrates that in HD patients, high-resting cytosolic H2O2 production by PMNs is not associated with accelerated in vitro apoptosis, and that the Bax/Bcl2 system may counter-balance the deleterious effects of reactive oxygen species in human PMNs.

Sleep quality and clinical correlates in patients on maintenance dialysis

BACKGROUND

Sleep quality is a subject of increasing interest to clinicians caring for dialysis patients. Self-assessed sleep disturbances have been associated with quality of life outcomes. The goal of this study was to identify clinical and laboratory parameters that are independently associated with overall sleep quality among prevalent dialysis patients.

METHODS

The Epworth Sleepiness Scale (ESS) and the Sleep Problems Index (SPI), a questionnaire derived from the Medical Outcomes Study, were administered to 71 dialysis patients and 68 subjects without known kidney disease (control group). The ESS and the SPI sleep item responses between the 2 groups were compared. The sleep items from the SPI were also aggregated into a sleep quality score. Multivariate linear regression analyses of sleep quality scores were used to identify clinical factors that were independently associated with poor sleep.

RESULTS

The ESS score was not significantly different between the 2 groups. However, the responses to the SPI sleep items demonstrated significantly impaired subjective sleep quality in dialysis patients compared with control subjects. In addition, overall sleep quality, as measured by the aggregated sleep score, was lower in dialysis patients compared with the control group (41 vs. 47, p < 0.001). In multivariate analyses, factors that were independently associated with poor sleep quality in dialysis patients were male gender (p = 0.006), history of coronary artery disease (p = 0.003), and high phosphate level (p = 0.05).

CONCLUSION

This study demonstrates that global sleep quality of dialysis patients is substantially impaired. Poor sleep quality was associated with male gender, coronary artery disease and high serum phosphate level, a modifiable factor. Future studies are needed to examine the relationship of serum phosphate level to sleep quality in dialysis patients.

Impact of iron dextran on polymorphonuclear cell function among hemodialysis patients

BACKGROUND

Polymorphonuclear cell (PMN) dysfunction and the increased use of parenteral iron may be important contributory factors to bacterial infections among patients with end-stage renal disease (ESRD) on maintenance hemodialysis (HD). We compared the in vitro impact of a commonly used parenteral iron preparation, iron dextran, on PMN function and viability between a group of HD patients with normal iron indices and healthy subjects.

METHODS

Eleven patients with ESRD on HD and 10 healthy subjects were studied. PMN harvested from heparinized blood were incubated with iron dextran (0 - 20 mM) in culture medium (RPMI) for 24 hours at 37 degrees C with 5% CO2 following which function and viability were assessed by flow cytometry using appropriate fluorescent labels.

RESULTS

Unstimulated, S. aureus and N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated hydrogen peroxide (H2O2) production was significantly higher in PMN unexposed to iron dextran from HD patients compared to those from healthy subjects. Iron dextran had no impact on unstimulated PMN H2O2 production in either group. In the healthy group, the only significant change occurred with 4-beta-phorbol 12-beta-myristate 13-alpha-acetate (PMA) stimulation, where cells exposed to 0.2 and 2.0 mM iron dextran produced less H2O2 relative to PMN unexposed to iron dextran (p < 0.05). In the HD group, all concentrations of iron dextran significantly attenuated H2O2 production stimulated by S. aureus, fMLP and PMA compared to PMN unexposed to iron dextran. Although PMN phagocytosis decreased with exposure to increasing concentration of iron dextran in both healthy subjects and HD patients, these changes did not achieve statistical significance. No significant changes in PMN viability or apoptosis were seen in either group after exposure to iron dextran.

CONCLUSIONS

These results indicate that iron dextran, a standard parenteral iron preparation, attenuates PMN function in HD patients with normal iron indices at clinically relevant concentrations. Further studies are required to evaluate and compare the impact of newer preparations of parenteral iron, such as iron sucrose and ferric gluconate, on PMN function.

Effect of biocompatibility of hemodialysis membranes on mortality in acute renal failure: a meta-analysis

BACKGROUND

The effect of biocompatibility of hemodialysis membranes on mortality in acute renal failure (ARF) has been a subject of intense debate, with some, but not all studies reporting a lower risk of death among patients with ARF dialyzed with biocompatible membranes (BCM) compared to bioincompatible membranes (BICM).

OBJECTIVES

We performed a meta-analysis of group data extracted from previously published studies of controlled clinical trials to assess the impact of BCM on the mortality among patients with ARF who required intermittent hemodialysis (IHD).

METHODS

BCM and BICM were defined as synthetic and cellulose-derived membranes (cuprophan and cellulose acetate), respectively. All controlled clinical trials comparing the effect of BCM to BICM on clinical outcomes in the setting of ARF were included. Original articles as well as abstracts were included. Data in Tables, Figures, and text were independently extracted by 2 of the authors. Risk ratios (RR) for mortality were combined using the random-effects model.

RESULTS

Seven studies with a total of 722 patients met the inclusion criteria. One hundred seventy-two (45%) of 384 patients died in the BCM group, compared with 156 (46%) of 338 patients in the BICM group. The RRs for mortality ranged from 0.56-1.28. Overall, the pooled RR for mortality was 0.92 (95% CI = 0.76-1.13) in favor of the BCM group. However, the test for heterogeneity in RR among studies was significant (chi2 = 8.6, p < 0.05). One study accounted for this significance, and once removed from the model, the RR for mortality was 0.94 (95% CI = 0.79-1.12), and the test for heterogeneity among studies lost its significance. Subgroup analyses comparing BCM to cuprophan membranes revealed that the RR for mortality was 0.82 (95% CI = 0.62 - 1.08) in favor of the BCM group, whereas in the subgroup of studies comparing BCM to cellulose acetate, the RR for mortality was 1.11 (95% CI = 0.87-1.44) in favor of the BCM group.

CONCLUSION

This metaanalysis demonstrates that the use of BCM does not significantly affect mortality among patients with ARF who require IHD. However, subgroup analyses suggest that cellulose acetate membranes may offer a survival advantage when compared with synthetic membranes, which, in turn, may be more beneficial than cuprophan membranes. Available evidence does not permit a recommendation for or against the use of BCM in ARF. Large trials and pooled analyses of individual patient-level data will be required to assess sources of variability among studies and non-fatal outcomes of ARF.

Pyrogenic reactions following gentamicin therapy: an alternative explanation

A hypothesis is proposed, arguing that gentamicin administration in a single daily dose results in higher peak tissue concentration, marked bacteriolysis with endotoxin (ET) release and consequent ET-mediated febrile host responses, which resemble Jarisch-Herxheimer reactions.

Pulmonary infectious mortality among patients with end-stage renal disease

BACKGROUND

Infection is the second-leading cause of death among patients with end-stage renal disease (ESRD). This is due in part to advanced age, comorbid conditions, and immune dysfunction observed in uremic states. Although one may hypothesize that pulmonary infectious mortality is higher among patients with ESRD compared with the general population (GP), no such data are currently available.

METHODS

We compared annual pulmonary infectious mortality rates among patients with ESRD to those in the GP. The data were abstracted from the United States Renal Data System and the National Center for Health Statistics, respectively, and were stratified by age, gender, race, and presence or absence of diabetes mellitus (DM). In the GP, primary and multiple cause-of-death analyses were performed to account for potential limitations of the data sources.

RESULTS

Overall, pulmonary infectious mortality rate was 14-fold to 16-fold higher in dialysis patients and approximately twofold higher in renal transplant recipients compared with the GP. After stratification for age, differences between groups decreased but retained their magnitude.

CONCLUSION

Patients with ESRD treated with dialysis have higher pulmonary infectious mortality rates compared with the GP, even after stratification for age, race, and DM. Consequently, this patient population must be considered at high risk for the development of lethal pulmonary infections.

Interaction between cyclosporine and Hypericum perforatum (St. John's wort) after organ transplantation

The use of herbal medicine has become increasingly popular in the United States. Hypericum perforatum (St. John's wort) is an herbal extract that is used widely as a folk remedy for depression. In this case report, we describe a kidney transplant recipient who developed marked reduction of cyclosporine therapeutic activity after the self-initiation of St. John's wort. Postulated mechanisms for the ability of this herbal extract to interact with pharmaceutical medications are presented, and the existing literature is reviewed.

Hemodialysis in acute renal failure: does the membrane matter?

Patients who develop hospital-acquired acute renal failure (ARF) that require dialytic support have high mortality rates. The potential impact of dialyzer membrane biocompatibility on clinical outcomes in ARF has been a subject of ongoing controversy. This article summarizes the clinical trials published to date that have examined the effect of dialyzer membrane biocompatibility on clinical outcomes of patients with ARF who require intermittent hemodialysis. A redirection of research endeavors in the field of dialysis in ARF is also argued.

Mechanisms of neutrophil apoptosis in uremia and relevance of the Fas (APO-1, CD95)/Fas ligand system

The regulation of neutrophil apoptosis in chronic renal failure (CRF) has not been clearly defined. The Fas/FasL system is an important apoptotic regulatory pathway in a wide variety of cells. Fas is a widely expressed cell surface protein that transduces an apoptotic signal after interaction with its natural ligand FasL. In contrast to the extensive tissue distribution of Fas, constitutive expression of FasL is relatively limited. We examined Fas and FasL expression by neutrophils in healthy subjects, patients with CRF, and patients on hemodialysis (HD) and peritoneal dialysis (PD). Fas expression was significantly higher among patients with CRF compared with control subjects, HD patients, and PD patients. FasL expression was significantly higher among patients with CRF compared with control subjects. At 24 h, neutrophil apoptosis was higher among patients with CRF compared with control subjects. Furthermore, high-neutrophil Fas expression was paralleled by a higher sensitivity to Fas-mediated apoptosis. There was a strong correlation between Fas-stimulated apoptosis and creatinine clearance as well as Fas expression. Finally, we found that uremic serum increased the expression of neutrophil-associated Fas and FasL proteins, when compared with normal serum. Further studies are under way to examine the regulation of this pathway in the uremic environment.

Apoptosis of leukocytes: basic concepts and implications in uremia

Circulating blood leukocytes have short life expectancies and end their lives by committing programmed cell death or apoptosis. Apoptosis is an active form of cell death that is initiated by a number of stimuli and is intricately regulated. Apoptosis in both excessive and reduced amounts has pathological implications. Evidence suggests that apoptosis may play a role in the pathophysiology of immune dysfunction in uremia. Indeed, accelerated programmed cell death has been observed in lymphocytes, monocytes, and polymorphonuclear leukocytes among patients with chronic renal failure. This may be due in part to the retention of uremic toxins. The aim of this article is to review the evidence for accelerated leukocyte apoptosis, key regulatory apoptotic pathways, and the possible role of this highly organized process in the pathogenesis of immune dysfunction in uremia.

Mortality caused by sepsis in patients with end-stage renal disease compared with the general population

BACKGROUND

In the United States, infection is second to cardiovascular disease as the leading cause of death in patients with end-stage renal disease (ESRD), and septicemia accounts for more than 75% of this category. This increased susceptibility to infections is partly due to uremia, old age, and comorbid conditions. Although it is intuitive to believe that mortality caused by sepsis may be higher in patients with ESRD compared with the general population (GP), no such data are currently available.

METHODS

We compared annual mortality rates caused by sepsis in patients with ESRD (U.S. Health Care Financing Administration 2746 death notification form) with those in the GP (death certificate). Data were abstracted from the U.S. Renal Data System (1994 through 1996 Special Data request) and the National Center for Health Statistics. Data were stratified by age, gender, race, and diabetes mellitus (DM). Sensitivity analyses were performed to account for potential limitations of the data sources.

RESULTS

Overall, the annual percentage mortality secondary to sepsis was approximately 100- to 300-fold higher in dialysis patients and 20-fold higher in renal transplant recipients (RTRs) compared with the GP. Mortality caused by sepsis was higher among diabetic patients across all populations. After stratification for age, differences between groups decreased but retained their magnitude. These findings remained robust despite a wide range of sensitivity analyses. Indeed, mortality secondary to sepsis remained approximately 50-fold higher in dialysis patients compared with the GP, using multiple cause-of-death analyses; was approximately 50-fold higher in diabetic patients with ESRD compared with diabetic patients in the GP, when accounting for underreporting of DM on death certificates in the GP; and was approximately 30-fold higher in RTRs compared with the GP, when accounting for the incomplete ascertainment of cause of death among RTRs. Furthermore, despite assignment of primary cause-of-death to major organ infections in the GP, annual mortality secondary to sepsis remained 30- to 45-fold higher in the dialysis population.

CONCLUSIONS

Patients with ESRD treated by dialysis have higher annual mortality rates caused by sepsis compared with the GP, even after stratification for age, race, and DM. Consequently, this patient population should be considered at high-risk for the development of lethal sepsis.

Serum soluble Fas (CD95) and Fas ligand profiles in chronic kidney failure

Apoptosis, or programmed cell death, is an active form of cell death that is initiated by a number of stimuli and is intricately regulated. Apoptosis in both excessive and reduced amounts has pathophysiologic implications. Accelerated programmed cell death has been observed in leukocytes among patients with chronic renal failure (CRF). This has been ascribed in part to the retention of uremic toxins. The Fas/Fas ligand (FasL) system is a key regulatory apoptotic pathway. Membrane-bound Fas is a cell-surface receptor that transduces apoptosis after interaction with membrane-bound or soluble FasL (sFasL). By contrast, soluble Fas (sFas) binds sFasL and inhibits its activity. In an attempt to examine the balance between these soluble factors in uremia, we measured soluble sFas and sFasL levels in the serum of healthy control subjects and patients with various degrees of CRF and examined the distribution of the various molecular mass fractions of these proteins in uremic serum. In brief, serum was obtained from 15 healthy volunteers, 17 patients with CRF, 11 patients undergoing maintenance hemodialysis (HD), and 7 patients undergoing peritoneal dialysis (PD). Serum sFas and sFasL were measured by enzyme-linked immunosorbent assay, and their molecular distribution was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblot. Compared with results in healthy control subjects, sFas levels were significantly higher in patients with CRF and in patients undergoing dialysis. There was a significant inverse correlation between sFas levels and creatinine clearance. Serum sFasL levels were not different among the four groups. However, the sFas-to-sFasL ratio was significantly lower in healthy control subjects as compared with patients with CRF and patients undergoing dialysis. Immunoblots and densitometric analyses of sFas and sFasL depicted a known 48-kd sFas, a known 27-kd sFasL, and a 60-kd sFas-sFasL protein aggregate signal. In conclusion, serum sFas levels are increased in patients with various degrees of CRF and may bind circulating sFasL, thereby minimizing mediation of cellular apoptosis.

New polyether sulfone dialyzers attenuate passage of cytokine-inducing substances from pseudomonas aeruginosa contaminated dialysate

The use of bicarbonate dialysate and high-flux and reprocessed dialyzers has raised concerns about the reverse transfer of dialysate contaminants into the blood compartment. This in vitro study was performed to investigate the reverse transfer of soluble Pseudomonas aeruginosa bacterial products across a polyether sulfone (PES), a newly developed synthetic polymer dialyzer. In vitro dialysis was carried out at 37 degreesC in a closed countercurrent recirculating loop dialysis circuit with a new PES dialyzer. An equal mixture of heparinized whole blood (from healthy volunteers) with pyrogen-free tissue culture medium was circulated in the blood compartment, and bicarbonate dialysate was circulated in the dialysate compartment. After 15 min of dialysis, the dialysate was challenged sequentially with 10(-4), 10(-3), and 10(-2) dilutions of a P. aeruginosa culture supernatant. 1-ml samples were drawn from the blood compartment 5 and 15 min after each challenge and incubated upright at 37 degrees C. At the end of 24 h, Triton X-100 was added, in order to extract total interleukin (IL) 6 and IL-8 production by the whole-blood mixture. These cytokines were measured by electrochemiluminescence assays. At dilutions of 10(-4) and 10(-3), the reverse transfer of soluble bacterial products across the dialyzer was negligible. Five and 15 min after contaminating the dialysate with the highest concentration (10(-2) dilution), the increase in IL-6 production was 239 +/- 170% (p = 0.06) and 886 +/- 444% (p = 0.02), respectively. However, comparing the IL-6-inducing potency of the 10(-2) bacterial supernatant dilution to the spontaneous IL-6 production in the blood compartment during dialysis with the same dilution of dialysate contaminant, there was a dramatic reduction in IL-6 production by 94 and 89% at 5 and 15 min, respectively. Similarly, 5 and 15 min after contaminating the dialysate with the 10(-2) dilution, the increase in IL-8 production was 357 +/- 147% (p = 0.07) and 630 +/- 229% (p = 0.04), respectively. However, comparing the IL-8-inducing potency of the 10(-2) bacterial supernatant dilution to the spontaneous IL-8 production in the blood compartment during dialysis with the same dilution of dialysate contaminant, there was a dramatic reduction in IL-8 production by 93 and 92% at 5 and 15 min, respectively. These results demonstrate that PES dialyzers markedly attenuate passage of cytokine-inducing substances from contaminated dialysate, using a method that detects the entire cytokine synthetic output in the blood compartment.

Impact of intermittent hemodialysis variables on clinical outcomes in acute renal failure

When hospital-acquired acute renal failure (ARF) is severe enough to require renal replacement therapy, mortality rates are extremely high, exceeding 50%. The potential impact of renal replacement therapy on clinical outcomes in ARF remains a subject of ongoing investigation and controversy. This article reviews in depth all of the clinical trials that have examined the effect of dialysis-related variables on clinical outcomes in patients with ARF requiring intermittent hemodialysis. In particular, the role of biocompatibility of dialyzer membranes, and timing, intensity, and adequacy of dialysis are discussed.

Dialysis disequilibrium syndrome: an unusual cause of respiratory failure in the medical intensive care unit

We describe a case of the dialysis disequilibrium syndrome (DDS) that was marked by the rapid onset of cerebral edema and the subsequent development of acute respiratory failure. The patient was treated successfully with a combination of mechanical hyperventilation and mannitol. The clinical presentation, pathogenesis, prevention and treatment of the entity are discussed.

Impact of dialyzer membrane selection on cellular responses in acute renal failure: a crossover study

BACKGROUND

When acute renal failure (ARF) is severe enough to require dialysis, in-hospital mortality rates approach 60%. These alarming figures have been ascribed in part to advanced age and the high prevalence of comorbid conditions. In the past several years, a number of attempts have been made to investigate the impact of dialyzer membrane type on clinical outcomes. Unfortunately, to date, clinical studies addressing this question have reported conflicting results.

METHODS

This crossover study examined the effect of dialyzer membrane type on cytokine synthesis by peripheral blood mononuclear cells (PBMCs), superoxide release by neutrophils, and apoptosis or programmed cell death of neutrophils in 24 patients with ARF requiring intermittent hemodialysis. The patients were assigned in an alternate order to a low-flux cellulose acetate (CA) or polysulfone (PS) dialyzer. After three consecutive dialysis sessions, patients were crossed over to the second dialyzer for three additional treatments. These cellular responses were measured upon dialyzer assignment and at the third and sixth dialysis session in relationship to the dialyzer type.

RESULTS

The results of the study showed no impact of dialyzer biocompatibility on synthesis of tumor necrosis factor-alpha (TNF-alpha) or interleukin 10 (IL-10) by PBMCs, superoxide release by neutrophils, or neutrophil apoptosis. This held true regardless of the initial dialyzer assignment. Furthermore, there was no correlation between dialysis adequacy (measured by single-pool Kt/V) and postdialysis cellular responses.

CONCLUSIONS

In summary, this study refines the question of biocompatibility by comparing a substituted cellulose rather than unsubstituted cellulose dialyzer to a PS dialyzer in the setting of ARF. The results failed to demonstrate a dialyzer advantage on the selected cellular responses.

Dialysis adequacy in patients with acute renal failure

Measurement of dialysis adequacy in patients with end-stage renal disease involves the use of urea kinetic modeling, which is a reflection of both dietary protein intake and efficiency of small solute clearance. Different dialytic modalities are available for patients in acute renal failure, including intermittent hemodialysis, continuous renal replacement therapies and peritoneal dialysis. In recent years, there has been a growing effort to measure dialysis adequacy in patients with acute renal failure using urea kinetic modeling. This initiative has been driven by the persistently high mortality rates in patients with dialysis-requiring acute renal failure, which may partly be related to inadequate dialysis dosing. In the setting of acute renal failure, dialysis adequacy has been measured using both single-pool and double-pool urea kinetics, as well as blood-based and dialysate-based urea kinetic modeling. Unfortunately, current goals and methods of measuring dialysis adequacy have been extrapolated from the end-stage renal disease patient population. These extrapolations are problematic because of differences in total body water, protein catabolic rate, and vascular access. Continuous renal replacement therapy has theoretical advantages over intermittent hemodialysis, including a decreased tendency to induce hypotension, and improved solute clearance and fluid removal, while allowing intensive nutritional support, and a better clearance of medium- to large-size molecules. The latter may play a significant role in patients with sepsis-associated acute renal failure. To date, comparative studies are scant and equivocal in establishing the superiority of a particular dialysis dose or modality.

Hematopoietic effect of Radix angelicae sinensis in a hemodialysis patient

The primary cause of anemia of chronic renal failure (CRF) is insufficient production of erythropoietin by the diseased kidneys. Although most patients receiving hemodialysis (HD) respond to recombinant human erythropoietin (rHuEPO) treatment, 4% prove to be rHuEPO resistant. The patient presented in this case study suffered from anemia of CRF that was resistant to rHuEPO therapy. He experienced marked improvement in the anemia after self-initiating regular consumption of the Chinese herb Dang qui (botanical name: Radix angelicae sinensis). The significant hematologic amelioration occurred in the face of a major decrease in the amount of rHuEPO administered. The causes and mechanisms of inadequate response to rHuEPO, as well as the possible beneficial hematopoietic effects of this herbal preparation, are discussed.

Modulation of neutrophil apoptosis by uremic plasma during hemodialysis

During hemodialysis (HD), blood-membrane interactions lead to activation of several circulating cells and plasma proteins. The resultant activation and/or release of mediators can modulate the structure, function and survival of circulating neutrophils. Little is known of plasma factors that influence apoptosis of neutrophils in hemodialyzed patients. Hence, we investigated the effect of uremic plasma obtained during HD on the survival of neutrophils obtained from healthy volunteers. Neutrophils harvested from healthy volunteers were incubated in ultrafiltered culture medium supplemented with either 50% heterologous normal plasma obtained from healthy volunteers (n = 15) or 50% uremic plasma collected from long-term HD patients dialyzed with cuprophan (CU) (n = 8), cellulose triacetate (CTA) (n = 8) or polysulfone (PS) (n = 8) dialyzers. Plasma samples were drawn predialysis, 15 min after starting dialysis, and postdialysis. After 24-hour incubation, neutrophil aliquots were processed for quantification of apoptosis by flow cytometry, using propidium iodide DNA staining. In addition, tumor necrosis factor alpha (TNFalpha) and interleukin-10 (IL-10) were measured in normal and predialysis uremic plasma samples. Neutrophils from healthy volunteers exposed to heterologous normal plasma samples exhibited 10.3 +/- 1.2% apoptosis. In contrast, the proportion of apoptosis was significantly higher among neutrophils exposed to predialysis (28.5 +/- 2.3%, p < 0.0001), 15 min (23.0 +/- 2.4%, p < 0.0001), or postdialysis uremic plasma samples (25.7 +/- 2. 3%, p < 0.0001). Compared to neutrophils exposed to predialysis uremic plasma samples, a significantly lower proportion of apoptosis was observed in neutrophils exposed to the 15-min plasma samples among patients dialyzed with CU (26.4 +/- 2.9 vs. 18.2 +/- 3.5%; p < 0.001) but not with CTA or PS dialyzers. Further, CU membranes induced the greatest percentage decrease in neutrophil apoptosis at 15 min. There was a direct correlation between neutrophil apoptosis and plasma levels of TNFalpha (r = 0.424, p = 0.02) and IL-10 (r = 0. 744, p < 0.0001). The results of the study suggest that normal neutrophils exposed to uremic plasma undergo accelerated in vitro apoptosis compared to those incubated with normal plasma. Further, during HD, the apoptosis-inducing activity of uremic plasma is modulated by the use of dialyzers with different degrees of biocompatibility. The identification of soluble factors that are responsible for the increased apoptosis-inducing activity of uremic plasma needs to be further investigated.

Neutrophil apoptosis and dysfunction in uremia

The high prevalence of bacterial infections among patients with end-stage renal disease suggests that "professional" phagocytes such as neutrophils are functionally impaired. This dysfunction has been ascribed to uremic toxins, malnutrition, and dialysis. The aim of this study was to investigate the contribution of apoptosis to neutrophil dysfunction in uremia. Neutrophils harvested from uremic patients (n = 6) and age-/gender-matched healthy control subjects (n = 6) were incubated with either 50% autologous plasma or 10% fetal calf serum. After 24-h incubation, apoptosis was quantified by flow cytometry by using propidium iodide nuclear staining. Neutrophils from healthy volunteers were also incubated with either 50% heterologous normal or uremic plasma. After 24-h incubation, apoptosis was quantified by flow cytometry and transmission electron microscopy. In addition, superoxide production was determined by measuring the capacity to reduce ferri- to ferro-cytochrome C by using 4-beta-phorbol 12-beta-myristate 13-alpha-acetate or N-formyl methionyl-leucyl-phenylalanine (fMLP) for stimulus. Phagocytosis was determined by the uptake of 14C-labeled heat-killed Staphylococcus aureus. Compared with normal neutrophils, uremic neutrophils demonstrated greater apoptosis in the presence of autologous plasma (9 +/- 4 versus 19 +/- 6%, P = 0.01) as well as 10% fetal calf serum (19 +/- 7 versus 31 +/- 6%, P = 0.03). Furthermore, compared with normal neutrophils exposed to heterologous normal plasma, those exposed to heterologous uremic plasma exhibited higher apoptosis rates (19 +/- 3 versus 40 +/- 5%, P = 0.002), lower tMLP-stimulated superoxide production (22.6 +/- 2.5 versus 15.5 +/- 1.1 nmol O2*-/3.12 x 10(5) cells/30 min, P = 0.01), and a lower phagocytosis index (38 +/- 3% versus 27 +/- 5%, P = 0.04). Apoptosis correlated inversely with fMLP-stimulated superoxide production (r = -0.60, P = 0.04) and phagocytosis (r = -0.57, P = 0.05). These results suggest that uremic neutrophils undergo accelerated in vitro apoptosis. Furthermore, uremic plasma accelerates apoptosis of normal neutrophils, resulting in a dysfunctional pattern that is similar to that observed in uremia.

Interleukin-1 receptor antagonist synthesis by peripheral blood mononuclear cells in hemodialysis patients

BACKGROUND

Pro-inflammatory cytokines like interleukin (IL)-1 beta and tumor necrosis factor-alpha (TANF-alpha) are believed to play a significant role in dialysis-related morbidity. It has been previously demonstrated that the endogenous synthesis of interleukin-1 receptor antagonist (IL-1Ra) is a reliable marker of the level of IL-1 beta synthesis in hemodialysis (HD) patients. In this study, we assessed the impact of clinical and laboratory variables on IL-1Ra synthesis by peripheral blood mononuclear cells (PBMC) in patients on HD with unsubstituted cellulose dialyzers.

METHODS

IL-1Ra by PBMC was measured by a specific non-cross-reactive radioimmunoassay. Day to day variation in cytokine synthesis, the correlation between cytokine synthesis under different in vitro stimulatory conditions, and the influence of clinical and laboratory variables on cytokine synthesis were studied.

RESULTS

Although there was a trend towards greater IL-1Ra synthesis by unstimulated, endotoxin-stimulated and IgG-stimulated PBMC drawn before the second and third dialysis sessions of the week when compared to the first dialysis treatment, this was not statistically significant. There was a strong correlation between IL-1Ra synthesis by PBMC cultured under different stimulatory conditions that was best observed between IL-1Ra cell content and from endotoxin-stimulated PBMC (r = 0.51, P = 0.0001), and endotoxin- and IgG-stimulated PBMC (r = 0.44, P = 0.0001). In addition, there was a close correlation between total synthesis (cell associated and secreted) and secreted levels of IL-1Ra in unstimulated (r = 0.59, P = 0.0001) and endotoxin-stimulated PBMC (r = 0.69, P = 0.0001). Interestingly, there was an inverse correlation between IL-1Ra synthesis and duration of dialysis that was strongest for secreted IL-1Ra from unstimulated (r = -0.50, P = 0.002) and endotoxin-stimulated PBMC (r = -0.34, P = 0.04). There was no significant correlation between IL-1Ra synthesis by PBMC and other clinical and laboratory indices.

CONCLUSIONS

The observations from this study indicate that: (1) in HD patients, there were no significant differences in cytokine synthesis by PBMC drawn before the three different dialysis treatments during the week; (2) there is a close relationship between IL-1Ra synthesis from PBMC cultured under different stimulatory conditions; (3) the secreted levels of IL-1Ra correlate directly with total synthesis (cell-associated and secreted); (4) with the exception of duration of dialysis, none of the other clinical or laboratory parameters correlated with cytokine synthesis; and (5) the diminished endotoxin- or IgG-stimulated IL-1Ra synthesis with increasing time on dialysis is possibly another sign of the impaired host-defense system in patients on long-term hemodialysis.

Polymyxin-B stimulates tumor necrosis factor-alpha production by human peripheral blood mononuclear cells

Gram-negative bacterial lipopolysaccharide (LPS) is a well known stimulus for cytokine production, particularly interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha). Polymyxin B (PMX-B) is a cationic polypeptide that binds to LPS, neutralizing its biological effects. PMX-B also disrupts gram-negative bacterial cell membrane phospholipids but is highly toxic to mammalian cells, therefore is of limited use. PMX-B is used as additive to media, as a way to handle LPS contamination. To derive benefit from the ability of PMX-B to neutralize lipid A in vivo while avoiding its systemic toxicity, PMX-B was covalently bound to polystyrene-derivative fibers, creating a hemoperfusion column (PMX-F) for the selective removal of circulating ET. In vitro PMX-F hemoperfusion studies have demonstrated effective ET removal, using either the Limulus amebocyte lysate assay or TNF alpha production by peripheral blood mononuclear cells (PBMC) as an index of ET removal. However, the question whether PMX-B itself could stimulate human PBMC to produce cytokines has not been adequately addressed. We examined the effect of increasing concentrations of PMX-B on cytokine production by PBMC in vitro. PBMC harvested from healthy volunteers were incubated for 24 hours at 37 degrees C with control (tissue culture media RPMI), or 5 microg/ml, 10 microg/ml, 20 microg/ml or 100 microg/ml PMX-B. At the end of 24 hours, PBMC were subjected to three freeze-thaw cycles, and total TNF alpha production (pg/2.5x10(6) PBMC) was measured by radioimmunoassay. Total TNF alpha production by PBMC was 163 +/- 3 pg, 171 +/- 9 pg, 164 +/- 4 pg, 323 +/- 63 pg and 331 +/- 58 pg, in the control, PMX-B 5 microg/ml, 10 microg/ml, 20 microg/ml and 100 microg/ml conditions, respectively. Compared to controls (RPMI), the percentage increase in TNF alpha production by PBMC was 5 +/- 6% (P=0.23), 1 +/- 3% (P=0.45), 99 +/- 40% (P=0.03) and 103 +/- 36% (P=0.02) in the presence of 5 microg/ml, 10 microg/ml, 20 microg/ml and 100 microg/ml of PMX-B, respectively. Furthermore, total TNF alpha production correlated significantly with increasing concentrations of PMX-B (R=0.53, P=0.007). We conclude that the use of PMX-B in in vitro studies as an LPS-neutralizing agent, or in the experimental treatment of endotoxic or septic shock can lead to erroneous interpretations of cytokine production by PBMC, and should be used cautiously in in vitro systems at high concentrations.

Effect of formaldehyde/bleach reprocessing on in vivo performances of high-efficiency cellulose and high-flux polysulfone dialyzers

Among the several disadvantages of reprocessed dialyzers is the concern that reuse could decrease the clearance of uremic toxins, leading to a decrease in the delivered dose of dialysis. To examine this possibility in the clinical setting, the clearances of small molecular weight solutes (urea and creatinine) and middle molecular weight substances (beta 2 microglobulin) were compared during dialysis with "high-efficiency" cellulose (T220L) and "high-flux" polysulfone (F80B) dialyzers reprocessed with formaldehyde and bleach. In a crossover study, six chronic hemodialysis patients were alternately assigned to undergo 21 dialysis treatments with a single T220L dialyzer or F80B dialyzer. Each patient was studied during first use (0 reuse), 2nd reuse (3rd use), and 5th, 10th, 15th, and 20th reuse of each dialyzer. Urea, creatinine, and beta 2 microglobulin clearances were measured at blood flow rates of 300 ml/min (Qb 300) and 400 ml/min (Qb 400). Total albumin loss into the dialysate was measured during each treatment. Urea or creatinine clearance of new T220L dialyzers was not significantly different from that of new F80B dialyzers at either Qb. Urea clearance of F80B dialyzers at Qb 300 decreased from 241 +/- 2 ml/min for new dialyzers to 221 +/- 5 ml/min after 20 reuses (P < 0.001), and Qb 400 from 280 +/- 4 ml/min for new dialyzers to 253 +/- 7 ml/min after 20 reuses (P = 0.001). Similarly, with reuse, creatinine clearance of F80B dialyzers also decreased at Qb 300 (P = 0.07) and Qb 400 (P = 0.03). In contrast, urea or creatinine clearance of T220L dialyzers did not decrease with reuse at either Qb. Urea clearance of T220L dialyzers was significantly higher than that of F80B at Qb 300 at the 5th, 10th, 15th, and 20th reuse (P < 0.001, = 0.005, = 0.004, and = 0.006, respectively), and Qb 400 at the 2nd, 5th, 10th, 15th, and 20th reuse (P = 0.04, 0.008, 0.03, 0.02, and 0.008, respectively). Beta 2 microglobulin clearance of T220L dialyzers was < 5.0 ml/min across the reuses studied. Beta 2 microglobulin clearance of F80B was < 5.0 ml/min for new dialyzers, but increased to 21.2 +/- 5.3 ml/min (Qb 300) and 23.6 +/- 3.3 ml/min (Qb 400) after 20 reuses (P < 0.001). Throughout the study, albumin was undetectable in the dialysate with T220L dialyzers. With F80B dialyzers, albumin was detected in the dialysate in four instances (total loss during dialysis, 483 mg to 1.467 g). In summary, the results of this study emphasize the greater need for information on dialyzer clearances during clinical dialysis, especially with reprocessed dialyzers. A more accurate knowledge of dialyzer performance in vivo would help to ensure that the dose of dialysis prescribed is indeed delivered to the patients.

Effect of glucose concentration, osmolality, and sterilization process of peritoneal dialysis fluids on cytokine production by peripheral blood mononuclear cells and polymorphonuclear cell functions in vitro

We sought to investigate the effects of high glucose concentration, osmolality, and heat sterilization of peritoneal dialysis fluids on tumor necrosis factor-alpha (TNF-alpha) production by peripheral blood mononuclear cells (PBMC) and polymorphonuclear cell (PMN) functions. Blood samples were obtained from eight healthy volunteers. PBMCs and PMNs were harvested by centrifugation with Ficoll-Hypaque (Sigma, St Louis, MO). PBMC were incubated with an equal volume of test fluids and RPMI for 4 hours (pH equilibrated), followed by incubation for 20 hours in RPMI with or without endotoxin (10 ng/mL). Total TNF-alpha production was measured by radioimmunoassay. PMNs were incubated with pH-adjusted test fluids for 30 minutes. After incubation, phagocytosis was determined by the uptake of 14C-labeled Staphylococcus aureus, oxidative burst by reduction of ferricytochrome C to ferrouscytochrome C on stimulation with phorbol myristate acetate, and enzyme release by measurement of endotoxin-stimulated bactericidal/permeability increasing factor. To study the effects of increasing glucose concentration and osmolality on PBMC and PMN functions, we compared conventional 1.5% Dianeal (1.5%D), (Baxter Healthcare Corp, Deerfield, IL) 2.5% Dianeal (2.5%D), 4.25% Dianeal (4.25%D), and control (RPMI for PBMCs and Hank's balanced salt solution for PMNs). PMNs exposed to 4.25%D exhibited an inhibition of phagocytosis, phorbol myristate acetate (PMA)-stimulated oxidative burst, and bactericidal/permeability increasing factor release compared with control, 1.5%D, or 2.5%D. To study the effects of increased osmolality when controlled for glucose concentration, we compared 1.5%D with 1.5%D in which osmolality was increased to that of 4.25%D with the addition of either sodium chloride (1.5%D+NaCl) or mannitol (1.5%D+M). High osmolality induced higher TNF-alpha production by unstimulated PBMCs and decreased TNF-alpha production by endotoxin-stimulated PBMCs. PMN functions were also inhibited by high osmolality. To study the effects of increased glucose concentration when controlled for osmolality, we compared 4.25%D with 1.5%D+NaCl and 1.5%D+M. High glucose concentration induced an increase in TNF-alpha production by unstimulated PBMCs, a decrease in TNF-alpha production by endotoxin-stimulated PBMCs, and an inhibition of PMN functions. Finally, to investigate the effects of heat sterilization, we compared 4.25%D (heat sterilized) to a filter-sterilized 4.25%D (4.25%D-F). The filter-sterilized fluid induced less changes in PBMC and PMN functions compared with the heat-sterilized fluid. These data suggest that the high glucose concentration, high osmolality, and heat sterilization of peritoneal dialysis fluids adversely affect PBMC and PMN functions. These effects could predispose continuous ambulatory peritoneal dialysis patients to peritonitis, compromise host defense during infection, and jeopardize long-term survival of the peritoneal membrane.

Removal of cytokine inducing substances by polymyxin-B immobilized polystyrene-derivative fibers during in vitro hemoperfusion of 10% human plasma containing Staphylococcus aureus challenge

Staphylococcus aureus (S. aureus) is frequently isolated from blood cultures in the hospital setting. The pathogenesis of S. aureus bacteremia probably replicates mechanisms implicated in gram negative bacterial infections. Cell wall components, such as peptidoglycans and lipoteichoic acids (LTA), can trigger cytokine production. Polymyxin-B (PMX-B) is a cationic peptide that binds endotoxin (ET) and inhibits its activity. Based on this principle, PMX-B was incorporated in polystyrene-derivative fibers, creating a hemoperfusion column (PMX-20R) that removes ET. The authors assessed whether S. aureus possesses PMX-B suppressible cytokine-inducing substances, and whether LTA, an anionic molecule, is one such substance. Heparinized blood was obtained from healthy volunteers, peripheral blood mononuclear cells (PBMC) were isolated by Ficoll-Hypaque separation, and 10% human plasma prepared. PBMC were incubated with 1, 5, or 10 microg/ml of S. aureus LTA, with and without 10 microg/ml of PMX-B. Also, using PMX-20R, in vitro hemoperfusion (IVH) was performed with 10% human plasma containing a 1:1,000 dilution of S. aureus challenge at 100 ml/min for 2 hours at 37 degrees C, and plasma obtained before and after IVH was incubated with PBMC. After a 24 hour incubation at 37 degrees C, PBMC were subjected to three freeze-thaw cycles, and total TNFalpha was measured by radioimmunoassay. TNFalpha production by PBMC incubated with LTA was 164+/-4 pg, 324+/-54 pg, 657+/-55 pg, and 1143+/-215 pg in control, and LTA 1, 5, and 10 microg/ml, respectively. The addition of PMX-B resulted in a 40+/-12% (p = 0.02), 61+/-6% (p = 0.002), and 62+/-14% (p = 0.02) decrease in TNFalpha production, respectively. Before IVH, TNFalpha production by PBMC incubated with 10% plasma containing S. aureus challenge was 1275+/-70 pg. After 2 hours of IVH, the decrease in TNFalpha production was 20+/-4% (p = 0.002). In conclusion, S. aureus LTA induces TNFalpha production that is significantly suppressed by PMX-B. Consequently, S. aureus cytokine-inducing substances are removed during IVH with PMX-20R, and this may be due to stoichiometric binding of LTA to PMX-B.

Endotoxin Removal by Polymyxin-B Immobilized Polystyrene-Derivative Fibers During In Vitro Hemoperfusion of 10% Human Plasma

During gram-negative bacterial sepsis, lipid A, the biologically active moiety of endotoxin (ET), activates monocytes and induces the release of cytokines. PMX-B, a cationic peptide, binds to lipid A and inhibits its activity. Based on this principle, PMX-B was incorporated in polystyrene-derivative fibers, creating a hemoperfusion column (PMX-20R) that removes ET. After in vitro characterization of the cytokine inducing potency of three gram-negative bacterial challenges, the authors evaluated the in vitro efficacy of PMX-20R in a model using 10% human plasma. Cytokine production by peripheral blood mononuclear cells (PBMC) incubated with plasma before and after in vitro hemoperfusion (IVH) was used as the index of ET removal. One hundred forty milliliters of heparinized blood were obtained from healthy volunteers. Forty milliliters were used to harvest PBMC at baseline, and 10% plasma prepared from the rest, was challenged with: 1) 0.01, 1, or 100 ng/ml of purified Escherichia coli ET; or 2) 1:1,000 dilution of E. coli, Pseudomonas aeruginosa, or Klebsiella pneumoniae. IVH was performed at 100 ml/min at 37 degrees C for up to 6 hours. One half milliliter samples, drawn before and at designated time intervals after the start of IVH, were mixed with a 0.5 ml suspension of 5 x 10(6) PBMC/ml from the same donor, and incubated for 24 hours at 37 degrees C. PBMC were subjected to three freeze-thaw cycles, and total tumor necrosis factor alpha (TNFalpha) was measured by radioimmunoassay. Before IVH, TNFalpha production by PBMC incubated with 10% plasma containing 0.01, 1, or 100 ng/ml of purified E. coli ET was 1905+/-391 pg, 2076+/-552 pg, and 5304+/-1001 pg, respectively. After 2 hours of IVH, the respective decrease in TNFalpha production was 82+/-5% (p = 0.005), 78+/-10% (p = 0.01), and 95+/-1% (p = 0.002). Before IVH, TNFalpha production by PBMC incubated with 10% plasma containing 1:1,000 dilution of E. coli, P. aeruginosa or K. pneumoniae was 2896+/-273 pg, 1816+/-122 pg, and 1131+/-125 pg, respectively. After 2 hours of IVH, the respective decrease in TNFalpha production was 83+/-4% (p < 0.001), 53+/-4% (p < 0.001), and 70+/-5% (p < 0.001). When IVH was extended to 6 hours, the further decrease in TNFalpha production was not statistically significant. These results suggest an impressive in vitro removal of ET by PMX-20R from 10% human plasma containing either purified E. coli ET or E. coli, P. aeruginosa, or K. pneumoniae. Further in vitro studies are required, using whole blood challenged with gram-negative bacteria.

Necrosis and apoptosis of polymorphonuclear cells exposed to peritoneal dialysis fluids in vitro

Conventional peritoneal dialysis (PD) fluids are known to inhibit polymorphonuclear cells (PMN) phagocytosis, oxidative burst and enzyme release. However, the relative contributions of apoptosis and/or necrosis to this dysfunction have not been examined. We investigated the effects of osmolality, glucose concentration and heat-sterilization of PD fluids on necrosis and apoptosis of PMN. Polymorphonuclear cells were isolated from 8 healthy volunteers and exposed to different PD fluids for four hours. PMN were then double-stained with Hoechst 33342 and propidium iodide to study the proportion of viable, apoptotic and necrotic cells. Transmission electron microscopy (TEM) was performed to confirm the results obtained with flow cytometry. The fluids studied were conventionally heat-sterilized 1.5% Dianeal (1.5% D), conventionally heat-sterilized 4.25% Dianeal (4.25% D), 1.5% D in which the osmolality was increased to that of 4.25% D by adding mannitol (1.5% D + M), a filter-sterilized version of 4.25% D (4.25% D-F) and a 1.1% amino acid PD fluid (AA) (Nutrineal PD4). All PD fluids had their pH equilibrated (pH = 7.4) by the addition of sodium bicarbonate. Compared to PMN exposed to culture medium, a significantly higher proportion of necrosis was observed in PMN exposed to 1.5% D (P = 0.04). The 4.25% D induced greater necrosis than 1.5% D (P = 0.001), and the 4.25% D also induced significantly more necrosis (P = 0.002) compared to 4.25% D-F. These data suggest that the consequences of heat-sterilization, rather than high glucose concentration are responsible for the necrosis observed. Indeed, the proportion of necrotic PMN with 4.25% D-F was not significantly different from 1.5% D. The 1.5% D + M and AA induced significantly more apoptosis compared to 1.5% D (P = 0.006 and P < 0.05, respectively), suggesting that apoptosis can be induced by the high osmolality of PD fluids. However, 1.5% D +/- M also induced significantly more apoptosis (P = 0.007) compared to 4.25% D-F. This suggests that the apoptosis effect is specific for the osmolyte present in PD fluids, and that mannitol and amino acids induce more apoptosis than glucose. In summary, the different non-physiological components of conventional PD fluids evaluated in this study had a differential effect on PMN survival. Heat sterilization of high glucose-containing PD fluids was associated predominantly with necrosis of PMN, and high osmolality with apoptosis.

Effect of two-chambered bicarbonate lactate-buffered peritoneal dialysis fluids on peripheral blood mononuclear cell and polymorphonuclear cell function in vitro

Low pH, high osmolality, increasing glucose concentration, and glucose degradation products (GDP) formed during heat sterilization of conventional peritoneal dialysis (PD) fluids have been shown to have a detrimental effect on cells involved in peritoneal host defense. The two-chambered PD fluid bag in which glucose at pH approximately 3 is separated from a bicarbonate (25 mmol/L)-lactate (15 mmol/L) buffer during heat sterilization permits PD fluids with lower GDP to be delivered to the patient at neutral pH. To establish the possible benefit of two-chambered bag PD fluids on peripheral blood mononuclear cell (PBMC) and polymorphonuclear (PMN) cell function, we compared conventional 1.5% Dianeal (1.5%D) with 1.5% two-chambered bag bicarbonate-lactate (1.5%D-B), and conventional 4.25% Dianeal (4.25%D) with 4.25% two-chambered bag bicarbonate-lactate (4.25%D-B). Furthermore, to study the effect of the sterilization process on PBMC and PMN function, we compared filter-sterilized 4.25%D (4.25%D-F) with 4.25%D and 4.25%D-B. PBMC were harvested by Ficoll-Hypaque separation, and 2.5 x 10(6) cells in RPMI were incubated with an equal volume of the test fluids for 4 hours, pelleted, and resuspended in RPMI containing 10 ng endotoxin for a further 20 hours. Tumor necrosis factor alpha (TNF-alpha) production by endotoxin-stimulated PBMC was not significantly different (P = 0.10) between 1.5%D-B and 1.5%D, but was significantly higher (P = 0.01) with 4.25%D-B compared with 4.25%D. PBMC exposed to filter-sterilized fluid (4.25%D-F) showed significantly higher endotoxin-stimulated TNF-alpha production compared with 4.25%D (P = 0.02), but was not significantly different from 4.25%D-B (P = 0.40). PMN were harvested by Ficoll-Hypaque separation and 10 x 10(6) cells incubated with test fluids for 30 minutes. After incubation, phagocytosis (phagocytosis index) was determined by the uptake of 14C-labeled Staphylococcus aureus, oxidative burst by reduction of ferricytochrome C to ferrocytochrome C on stimulation with PMA, and enzyme release by measurement of endotoxin-stimulated bactericidal/permeability increasing protein (BPI). Bicarbonate-lactate two-chambered fluids of similar osmolality and glucose concentration conferred a significant improvement in phagocytosis (P = 0.02 for 1.5%D-B and P < 0.001 for 4.25%D-B). Oxidative burst and BPI release were significantly higher in 4.25%D-B compared with 4.25%D (P < 0.001). Filter-sterilized 4.25%D-F conferred a significant improvement in phagocytosis and oxidative burst compared with 4.25%D (P < 0.001) or 4.25%D-B (P < 0.001). Furthermore, conventional 4.25%D was associated with significantly lower BPI release compared with 4.25%D-F (P = 0.01). GDP's acetaldehyde and 5-HMF were analyzed in 4.25%D-B, 4.25%D, and 4.25%D-F. Acetaldehyde was below the lower limit (0.79 ppm) of the standard curve in 4.25%D-B and 4.25%D-F fluids but was detected (3.76 to 5.12 ppm) in all of the 4.25%D fluids. Relative levels of 5-HMF in the 4.25%D-B (0.032 to 0.041 Abs @ 284 nm) and 4.25%D (0.031 to 0.036 Abs @ 284 nm) were similar. The lowest levels (0.001 Abs @ 284 nm) were observed in the filter-sterilized 4.25%D-F. The beneficial effects of two-chambered bicarbonate lactate-buffered PD fluids on PBMC and PMN function are probably related to reduction of GDP from heat sterilization of glucose in a separate chamber at a lower pH. This improvement in biocompatibility could have a beneficial affect on peritoneal defenses.

Extracorporeal adsorbent-based strategies in sepsis

Gram-negative bacterial sepsis remains a challenging diagnostic and therapeutic dilemma to the practicing clinician. Bacterial-derived products (eg, gram-negative bacterial lipopolysaccharide or endotoxin) and host inflammatory mediators (eg, tumor necrosis factor-alpha and interleukin-1) are believed to play a pivotal role in the pathogenesis of sepsis and septic shock. Despite the many advances in the treatment of sepsis, mortality rates in septic patients remain high. Indeed, numerous clinical trials using biologically engineered immunotherapies targeting specific inflammatory mediators have proven unsuccessful. This lack of success has led to a renewed interest in blood purification techniques using extracorporeal therapies. During sepsis, circulating bacterial-derived products as well as inflammatory mediators can be reduced and/or eliminated by various extracorporeal adjunctive therapies such as plasma exchange, continuous renal replacement, and adsorbent-based therapies. Adsorbents have commonly been used orally for gastrointestinal removal of toxins or drugs. However, their potential use in sepsis has received little attention. The incorporation of adsorbents in hemoperfusion columns has allowed their use for the removal of toxic compounds from the circulatory system. Adsorbents developed for use in sepsis can bind toxins in a nonselective (eg, charcoal), selective (eg, polymyxin B-immobilized polystyrene-derivative fiber), or specific (eg, antibody-coated microsphere-based detoxification system) way. However, despite an explosive development in the experimental use of these promising therapies, randomized clinical trials are currently lacking. In summary, a multi-disciplinary complex therapeutic approach remains a prerequisite to the successful treatment of sepsis.

Marked dilutional acidosis complicating management of right ventricular myocardial infarction

Dilutional acidosis is a poorly recognized cause of metabolic acidosis. Indeed, the prevailing view has been that even massive expansion of the extracellular fluid volume with non-bicarbonate-containing solutions would not lead to clinically significant hypobicarbonatemia. We describe the development of marked dilutional acidosis as a complication of management of right ventricular myocardial infarction. The pathogenesis, clinical significance, prevention, and treatment of the entity are discussed.