Influencing the inflammatory response of haemodialysis patients by cytokine elimination using large-pore membranes

Validation by Computer Simulation of Two Indirect Methods for Quantification of Free Water Transport in Peritoneal Dialysis

Background

In peritoneal dialysis, approximately 40% of the total osmotic ultrafiltration (UF) induced by glucose can be predicted to be due to “free” water transport across aquaporin-1 (APQ-1). Theoretically, it would be possible to assess the fraction of free water transport in the early phase of a hypertonic dwell, when UF rate is high and the relative contribution of Na+ diffusion is low. La Milia et al. [La Milia V. et al. Fast-fast peritoneal equilibration test (FAST-FAST-PET): a simple method for peritoneal hydraulic permeability study [Abstract]. Nephrol Dial Transplant 2002; 17 (Suppl 1):17–18] suggested a technique to assess sodium-associated water transport based on sodium removal (Na+R) divided by the plasma Na+ concentration during a “fast-fast” (60 minute) peritoneal equilibration test (PET) for 3.86% glucose, yielding an estimate of the UF passing through the small pores (UFSP). Free water transport (UF through ultrasmall pores; UFUSP) was obtained by subtracting UFSP from total UF. Although peritoneal Na+ transport is almost totally convective, this technique will slightly overestimate small-pore UF due to the presence of some small-pore Na+ diffusion from the circulation during the dwell. A way of dealing with this problem was presented recently by Smit (Smit W. et al. Quantification of free water transport in peritoneal dialysis. Kidney Int 2004; 66:849–854).

Methods

In the present study we used the three-pore model of peritoneal transport to predict the degree of overestimation of UFSP for the technique presented by La Milia et al., and any potential deviations from theory for the technique presented by Smit et al. Simulations were performed under ordinary conditions and during simulated UF failure for 3.86% glucose. The fractional UF coefficient accounted for by APQ-1 was set at 2%.

Results

Estimating the UFSP from the sodium-associated water transport according to the method by La Milia et al. consistently overestimated UFSP and underestimated UFUSP. These errors were, however, minimal for dwells lasting between 30 and 80 minutes. The technique by Smit et al. to calculate aquaporin-mediated water flow (UFUSP), using an elaborate correction for Na+ diffusion from the circulation during the dwell, seemed accurate in most situations but, in general, tended to moderately overestimate UFUSP at early dwell times (<30 minutes) and underestimate UFUSP at long dwell times (4 hours).

Conclusions

The technique presented by La Milia et al. to calculate free water transport during a fast-fast PET was found to be surprisingly accurate, although the procedure would further improve by the introduction of a correction algorithm. The technique by Smit is even more accurate for dwells up to 4 hours’ duration. However, since the Smit technique is elaborate, it is less practical for routine determinations of aquaporin-mediated water transport in peritoneal dialysis.

Cross-Talk between Inflammation, Coagulation/Fibrinolysis and Vascular access in Hemodialysis Patients

This work aimed to study the association between fibrinolytic/endothelial cell function and inflammatory markers in chronic kidney disease (CKD) patients undergoing hemodialysis (HD) and recombinant human erythropoietin (rhEPO) therapies, and its relationship with the type of vascular access (VA) used for the HD procedure. As fibrinolytic/endothelial cell function markers we evaluated plasminogen activator inhibitor type-1 (PAI-1), tissue plasminogen activator (tPA) and D-dimers, and as inflammatory markers; C-reactive protein (CRP), soluble interleukin (IL)-2 receptor (s-IL2R), IL-6 and serum albumin levels. The study was performed in 50 CKD patients undergoing regular HD, 11 with a central venous dialysis catheter (CVC) and 39 with an arteriovenous fistula (AVF), and in 25 healthy controls. Compared to controls, CKD patients presented with significantly higher levels of CRP, s-IL2R, IL-6 and D-dimers, and significantly lower levels of PAI-1. The tPA/PAI-1 ratio was significantly higher in CKD patients. We also found statistical significant correlations in CKD patients between D-dimers levels and inflammatory markers: CRP, albumin, s-IL2R and IL-6. When comparing the two groups of CKD patients, we found that those with a CVC presented statistically significant lower levels of hemoglobin concentration and albumin, and higher levels of CRP, IL-6, D-dimers and tPA. Our results showed an association between fibrinolytic/endothelial cell function and increased inflammatory markers in CKD patients. The increased levels of D-dimer, tPA and inflammatory markers in CKD patients using a CVC, led us to propose a relationship between the type of VA chosen for HD, and the risk of thrombogenesis.

TLR4 and TLR9 Polymorphisms Effect on Inflammatory Response in End-Stage Renal Disease Patients

Toll-like receptors (TLRs) play a key role in the response of innate and adaptive immune system to microbial and endogenous ligands. Inflammation is a common feature in end-stage renal disease (ESRD) patients; however, the mechanisms/factors triggering the inflammatory process are still poorly clarified. Our aim was to analyze the impact of the c.-1486T>C and c.896A>G polymorphisms in TLR9 and TLR4 genes, respectively, on the inflammatory response of ESRD patients. Clinical and laboratory evaluation was carried out on 184 ESRD patients. Polymerase chain reaction followed by restriction fragmens length polymorphisms (PCR-RFLP) was employed for genotyping of TLR-4 c.896A>G and TLR-9 c.-1486T>C polymorphisms. The prevalence of AA and AG of TLR4 c.896A>G polymorphism in ESRD patients was 97.8% and 2.2%, respectively. None of the individuals showed a homozygous TLR4 polymorphism. Concerning the TLR9 c.-1486T>C polymorphism, we found that ESRD patients showed a prevalence of TC and CC genotypes of 57.1% and 20.6%, respectively. We found that the heterozygous patients for the TLR4 c.896A>G polymorphism presented an increased level in lymphocyte count, a decrease in neutrophil/lymphocyte ratio and in serum levels of hepcidin. Regarding the TLR9 c.-1486T>C polymorphism, we found that it is associated with decreased white blood cell and neutrophil counts, ferritin and CRP serum levels, and with an increase in serum levels of creatinine. Our data suggest that the presence of the studied polymorphisms is associated with a decreased inflammatory response in ESRD patients under hemodialysis, and, thus its presence might have beneficial effects in ESRD patients. Moreover, our data provide new insights in the role of TLR polymorphisms in renal disease, which might have impact in the near future for the development of innovative therapies.

Association of secondary hyperparathyroidism with hemoglobin level in patients with chronic kidney disease

PURPOSE

Secondary hyperparathyroidism (SHPT) is one of the less recognized reasons of anemia in chronic kidney disease (CKD). In this study, we evaluated the role of SHPT as a cause of anemia and correlation of intact parathyroid hormone (iPTH) and hemoglobin (Hb) level in hemodialysis (HD) patients.

METHODS

This cross-sectional study was carried out in 63 individuals admitted in HD unit of the institute. Serum samples were collected and urea, creatinine, Hb, ferritin and iPTH levels were measured. Statistical analysis was carried out using the SPSS software (IBM, NY, USA).

RESULTS

Mean ± standard deviation for serum urea, creatinine, Hb, ferritin and intact PTH were 177 ± 15.52, 15.16 ± 2.28 mg/dl, 7.03 ± 2.26 g/dl, 654.7 ± 563.4 ng/ml, 539.18 ± 493.59 pg/ml respectively. A reverse correlation was found between intact PTH and Hb level.

CONCLUSIONS

A variety of postulated pathophysiological mechanisms linking SHPT and anemia in CKD are discussed. An efficient control of parathyroid hormone hypersecretion may be required to achieve a better management of anemia in HD patients.

Cardiac antiapoptotic and proproliferative effect of recombinant human erythropoietin in a moderate stage of chronic renal failure in the rat

Objective:

Recombinant human erythropoietin (rhEPO) therapy under circumstances of moderate chronic renal failure (CRF), with yet lower kidney and heart lesion, may have a protective cardiac effect beyond the correction of anemia, whose mechanism deserves better elucidation, namely by clarifying the impact on gene expression profile of markers of apoptosis, inflammation, proliferation, angiogenesis, and lesion/stress in the heart.

Materials and Methods:

Four groups of rats were studied over a period of 15 weeks (n=7 each): control—without surgery and without drug treatment; rhEPO—treated with 50 IU/kg/week of rhEPO—beta; CRF—submitted to partial nephrectomy (3/4); CRF + rhEPO—CRF with rhEPO treatment after the 3rd week of surgery. The heart was collected in order to evaluate the gene expression, by real-time qPCR, of markers of apoptotic machinery, inflammation/immunology, proliferation/angiogenesis, and lesion/stress.

Results:

The main findings obtained were (a) CRF rats have demonstrated overexpression of EPO-R in the heart without changes on EPO expression, together with overexpression of Bax/Bcl2 ratio, PCNA, and IL-2; (b) rhEPO therapy on the heart of the rats with CRF induced by partial 3/4 nephrectomy promoted nonhematopoietic protection, demonstrated by the apoptosis prevention, viewed by the Bax/Bcl2 balance, by the promotion of proliferation, due to PCNA increment, and by the immunomodulatory action, expressed by a trend to prevent the IL-2 increment.

Conclusion:

In this model of moderate CRF, rhEPO treatment showed important cardiac nonhematopoietic effects, expressed mainly by the antiapoptotic and the proproliferative action, suggesting that early rhEPO therapy in moderate stages of CRF might have further therapeutic benefits.

Vascular Access versus the Effect of Statins on Inflammation and Fibrinolysis in Renal Dialysis Patients

Purpose

The aim of this work was to assess the effect of statin therapy on inflammatory and fibrinolytic/endothelial (dys)function markers in end-stage renal disease (ESRD) patients under hemodialysis (HD), according to the type of vascular access.

Methods

This transversal study includes 191 ESRD patients under regular HD, divided into four groups according to vascular access and statin therapy: 87 patients with arteriovenous fistula (AVF) and no statins (AVF-NS), 61 with AVF and statins (AVF-S), 27 with central venous dialysis catheter (CVC) and no statins (CVC-NS) and 16 with CVC and statins (CVC-S). The basic lipid profile and fibrinolytic/endothelial cell function markers were assessed.

Results

Patients with CVC presented significantly higher levels of D-dimers compared with AVF groups. CVC-NS patients also presented the highest IL-6 values, which were significantly higher than those presented by CVC-S patients. AVF-S patients presented significantly higher t-PA and PAI-1 values and lower adiponectin levels compared with AVF-NS.

Conclusions

Our results demonstrate that patients with CVC, particularly those not under statin therapy, present a higher production and turnover of fibrin. We also found that statin therapy decreases inflammation in CVC patients but is associated with a reduction of adiponectin and increased endothelial function marker levels in AVF patients.

Inflammation, T-cell phenotype, and inflammatory cytokines in chronic kidney disease patients under hemodialysis and its relationship to resistance to recombinant human erythropoietin therapy

BACKGROUND

Resistance to recombinant human erythropoietin (rhEPO) occurs in some chronic kidney disease (CKD) patients, which may be due to enhanced systemic inflammatory response and to the erythropoiesis-suppressing effect of pro-inflammatory cytokines, some of which are produced by T cells.

AIM OF STUDY

The aim of this study was to investigate the relationship between resistance to rhEPO therapy in hemodialysis CKD patients and inflammatory markers [C-reactive protein (CRP), soluble interleukin (IL)-2 receptor (sIL2R), and serum albumin levels], blood cell counts, T-cell phenotype, cytokine production by T cells, and serum cytokine levels.

MATERIALS AND METHODS

We studied 50 hemodialysis CKD patients, 25 responders and 25 nonresponders to rhEPO, and compared them to each other and with 25 healthy controls. When compared to controls, CKD patients showed increased serum levels of CRP, IL-6, and sIL2R and a T-cell lymphopenia, due to decreased numbers of both CD4+ and CD8+ T cells. T cells from CKD patients had an immunophenotype compatible with chronic T-cell stimulation as shown by the increased percentage of CD28-, CD57+, HLA-DR+, CD28-HLA-DR+, and CD57+ HLA-DR+ T cells and produce higher levels of IL-2, INF-gamma, and TNF-alpha after short-term in vitro stimulation, although Th1 cytokines were not detectable in serum. Statistically significant differences were found between responders and nonresponders to rhEPO therapy for total lymphocyte and CD4+ T-lymphocyte counts, albumin (lower in nonresponders) and CRP (higher in nonresponders) levels.

CONCLUSION

CKD patients under hemodialysis present with raised inflammatory markers and decrease of total lymphocyte and CD4+ T-lymphocyte counts when compared with controls. Some of those markers are even further enhanced in nonresponders to rhEPO therapy patients, but resistance to this therapy cannot be justified by a Th1 polarized T-cell response.