Evidence That p-Cresol and IL-6 Are Adsorbed by the HFR Cartridge: Towards a New Strategy to Decrease Systemic Inflammation in Dialyzed Patients?

Introduction Hemodialysis (HD) and hemodiafiltration clear only with a low efficiency the plasma from interleukin-6 and p-cresol, two protein-bound uremic toxins associated with high cardiovascular risk in end stage renal disease. HFR Supra is a double-chamber hemodiafiltration system in which the ultrafiltrate returns to the patient after its regeneration through a resin cartridge that binds hydrophobic and protein-bound solutes. In the present study, we evaluated whether the HFR cartridge can also bind total p-cresol and IL-6 and remove them from the ultrafiltrate. Methods We compared the levels of IL-6 and p-cresol in ultrafiltrate samples collected at the inlet (UFin) and at the outlet (UFout) of the cartridge at the start or at the end of a 240 min HFR session in 12 inflamed chronic HD patients. The pro-inflammatory activity of the ultrafiltrate samples was also determined by evaluating the changes that they induced in IL-6 mRNA expression and protein release in peripheral blood mononuclear cells from 12 healthy volunteers. IL-6 and p-cresol circulating levels were also assessed in peripheral plasma blood samples collected before and after HFR and, for comparison, a control HD. Results p-Cresol and IL-6 were lower in UFout than in UFin both at the start and at the end of the HFR session, suggesting that they were retained by the cartridge. IL-6 mRNA expression and release were lower in PBMC incubated with UFout collected at the end than with UFin collected at the start of HFR, suggesting that passage through the cartridge reduced UF pro-inflammatory activity. Plasma total p-cresol decreased by about 53% after HFR, and 37% after HD. IL-6 circulating values were unmodified by either these dialysis procedures. Conclusions This study shows that the HFR-Supra cartridge retains total p-cresol and IL-6 in the ultrafiltrate and lowers plasma total p cresol but not IL-6 levels. Trial Registration ClinicalTrials.gov NCT0186577

Add-On Aliskiren in Non-Dialysis CKD Patients Treated with Dual Blockade of Renin-Angiotensin System (RAS): A Prospective Pilot Study

The additive antiproteinuric effects of CEI+ARB are limited in most CKD pts possibly due to escape mechanisms. We evaluated antiproteinuric efficacy of direct renin inhibitor aliskiren in CKD pts with residual proteinuria after dual RAS blockade. We selected consecutive adult CKD stage 1-4 (no transplant) pts with proteinuria >0.5 g/d treated with CEI+ ARB at maximal tolerated dose unchanged in the previous 3 months. Immunosuppressive therapy, sK >5.5 mEq/L and eGFR change >30% in the previous 6 months were exclusion criteria. Patients were evaluated before (baseline) and during 6 months of aliskiren at a dose titrated to 300 mg/d. Out of the 50 selected pts, 5 did not complete the study (immunosuppressive therapy, n=2; no assumption of aliskiren, n=3). Age was 57±15 yrs and BMI 30±6 kg/m2; prevalence of males, diabetes and prior CV disease was 78%, 49% and 33%, respectively. Main changes in the 45 pts studied Basal month 1 month 3 month 6 P Systolic BP (mmHg) 146±13 139±13 139±16 141±19 0.0002 Diastolic BP (mmHg) 86±8 83±7 82±9 80±9 0.005 eGFR (mL/min/1.73 m2) 47.7±26.5 46.6±27.3 45.7±27.8 44.2±26.3 0.004 sK (mEq/L) 4.7±0.5 4.8±0.5 4.8±0.5 4.8±0.6 0.167 Proteinuria (g/d) 3.39±2.25 2.94±2.07 2.99±2.41 2.69±1.98 0.03

Antiproteinuric Response to Add-on Aliskiren in Proteinuric Patients Treated With Dual Blockade of the Renin-Angiotensin System: A 12-Month Prospective Uncontrolled Study

This pilot study shows that aliskiren with ACE-inhibitor/ARB therapy allows a clinically significant (22% at month 6) and persistent (up to month 12) decrease in proteinuria. The antiproteinuric effect was at least in part unrelated to the antihypertensive effect and small decrease in eGFR and instead may depend on enhanced suppression of intrarenal angiotensin II with more effective correction of glomerular hypertension.The magnitude of antiproteinuric response was greater in younger patients and those with higher sodium excretion and therefore intake

Effect of UF_in-15 and UF_out-225 on IL-6 gene expression and on IL-6 release in PBMC cultures from healthy subjects.

<p>A Mean ± SD of the fold increase in IL-6 gene expression respect to controls observed in PBMC cultures from 12 healthy volunteers, exposed to UF_in-15 (black) and UF_out-225 (dark gray). Data were normalized to β-actin mRNA expression and expressed as percent increase respect to those obtained in control cultures, set at 1, in which no UF was added. B, Mean ± SD of immunoreactive IL-6 concentrations in culture media of PBMCs from twelve healthy volunteers after a 24 h incubation with saline (basal condition, white), UF_in-15 (black), or and UF_out-225 (dark gray). *p<0.05vs control; °p<0.05 vscontrol and UF_in-15, at Kruskal-Wallis one way analysis of variance on ranks followed by Student-Newman-Keuls post hoc test.</p

Sequence of the IL-6 and β-actin primers used in the study.

<p>Sequence of the IL-6 and β-actin primers used in the study.</p

Albumin, total-cresol and IL-6 concentrations in ultrafiltrate samples collected before and after the HFR sorbent cartridge at the beginning and at the end of the dialysis session.

<p>The data shown in the Table are the mean ± standard deviation of albumin, total cresol and IL-6 measured in samples of the UF collected before and after being adsorbed by the sorbent cartridge of the convection stage of the HFR Supra apparatus. Note the very low concentrations of albumin in pre-sorbent UF samples that is consistent with the low sieving coefficient (about 0.02 for albumin) of the polyphenylene membrane of the system. The values of total cresol concentration shown are the sum of p-cresol and p-cresol metabolite concentrations because, as we detail in the methods section, the acidic extraction method that we used converts all p-cresol derivatives in p-cresol.</p><p>*p<0.05 vs 15 min pre-cartridge and ^†p<0.05 vs 225 min pre-cartridge, at repeated measure ANOVA followed by the Student-Newman-Keuls post-hoc test.</p

Schematic representation of the HFR apparatus.

<p>The figure shows the main components of the HFR Supra system (Bellco, Mirandola, Italy) used in the study. 1-The blood of the patient is pumped into the top filter (the convection stage). 2-In this stage of the HFR apparatus, the blood is filtered by a high flux polyethersulfone membrane. 3-The ultrafiltrate produced in the convection stage is pumped by a second pump through a sorbent cartridge where hydrophobic waste solutes are retained. The small syringes indicate the points of the systems where rubber stopper for UF sample collection are located. 4-The blood coming from the convection stage and the UF coming from the cartridge are mixed in a chamber located between the two filters 5-This “reconstituted” blood enters the bottom filter (the diffusion stage) where it is undergoes dialytic treatment (both diffusion and ultrafiltration for weight loss) with a low flux polyethersulfone membrane. 6-The cleared blood is returned to the patient. (Modified form an original image kindly provided by Dr. G. Palladino, Bellco, Mirandola, Italy).</p