Clearance of NT-proBNP and Procalcitonin during Continuous Venovenous Hemodialysis with the Medium Cutoff Filter in Patients with Rhabdomyolysis-Associated Early Acute Kidney Injury

INTRODUCTION

In polytrauma patients with AKI continuous venovenous hemodialysis (CVVHD) with medium cutoff membrane filters is commonly adopted to increase the removal of both myoglobin and inflammatory mediators, but its impact on increasing molecular weight markers of inflammation and cardiac damage is debated.

METHODS

Twelve critically ill patients with rhabdomyolysis (4 burns and 8 polytrauma patients) and early AKI requiring CVVHD with EMIc2 filter were tested for 72 h on serum and effluent levels for NT-proBNP, procalcitonin (PCT), myoglobin, C-reactive protein (CRP), alpha1-glycoprotein, albumin, and total protein.

RESULTS

The sieving coefficients (SCs) for proBNP and myoglobin were as higher as 0.5 at the start, decreased to 0.3 at the 2nd h, and then slowly declined to the final value of 0.25 and 0.20 at the 72nd h, respectively. PCT showed a negligible SC at the 1st h, a peak of 0.4 at the 12th h, and a final value of 0.3. SCs for albumin, alpha1-glycoprotein, and total protein were negligible. A similar trend was observed for the clearances (17-25 mL/min for proBNP and myoglobin; 12 mL/for PCT; <2 mL/min for albumin, alpha1-glycoprotein, and total protein). No correlation was found between systemic determinations and filter clearances of proBNP, PCT, and myoglobin. Net fluid loss/hour during CVVHD positively correlated with systemic myoglobin for all patients and NT-proBNP in the burn patients.

CONCLUSION

CVVHD with EMiC2 filter showed low clearances for NT-proBNP and procalcitonin. CVVHD did not significantly affect the serum levels of these biomarkers, which could be adopted in the clinical management of early CVVHD patients.

AB0199 GENES PREDICTIVE ON THE EFFICACY OF INFLIXIMAB IN THE TREATMENT OF RHEUMATOID ARTHRITIS: A PROSPECTIVE, MULTI-CENTRE, CLINICAL PERFORMANCE EVALUATION STUDY FOR AN IN-VITRO DIAGNOSTICS MEDICAL DEVICE

Background:

Approximately 30% of rheumatoid arthritis (RA) patients fail to respond to first biological therapy, thus treatment selection of biologic therapy for patients with RA is of high importance. The lack of biomarkers to predict specific biological treatment response, in the case of non-responder (NR) patients leads to unnecessary exposure, delay of adequate therapy, progression of the disease and therapy cost increase. Predicting the patient’s responsiveness to the first biological therapy is still an unmet need in the clinical setting. Predictive in vitro testing would have a significant effect on the administration of biological therapy, on the real life implementation of cost effective personalized therapy.

Objectives:

The purpose of this in vitro diagnostic medical device study was to demonstrate that particular gene expression profiles as genomic biomarkers (i.e. the IVD medical device) predict therapeutic response to infliximab, discriminate between responders and non-responders to infliximab treatment. Responders were defined if they reached DAS target value DAS28≤3.2 at 6 month (M6).

Methods:

110 bionaive patients were enrolled with moderate-high activity RA (DAS28-CRP >3.2), who have responded inadequately to DMARDs (including methotrexate), after they have been assigned to infliximab treatment. All patients received commercially available infliximab, procured according to SmPC, local guidelines and regulations in this non-interventional clinical study. The clinical response was evaluated according to the change from baseline in disease activity at M6. Clinical characteristics (RA duration, smoke, steroid treatment, etc.) and serological parameters (RF, ACPA, aCVM) were collected. A 3rdvisit scheduled around week 22 (M6) and change of DAS28-CRP value from the baseline has been evaluated. Gene expression profiling was performed from blood samples taken at month 0 (M0); - just before the first infliximab infusion. Global gene expression profiling was performed to identify differentially expressing genes using RNA sequencing. The set of differentially expressing genes were further reduced with a combination of machine learning modelling and various feature elimination methods. The expression of the reduced gene set was confirmed and further analysed using reverse-transcription and quantitative real-time PCR.

Results:

A total of 250 genes were identified by a combination of differential gene expression analyses, feature elimination techniques and various machine learning modelling methods of which 44 genes showed significant differences between NR and good responder groups. Preliminary interim analysis identified associations between gene expression and clinical response/ non-response to infliximab therapy.

Table.

Three models containing gene expression + clinical data sets illustrates some statistical characteristics

Modell building_IDAccuracySensitivitySpecificityModell VerificationAccuracySensitivitySpecificity00232100.00100.00100.00002328888.8987.5000249 98.82 96.55100.00002498477.7887.5000270 98.82 96.55100.00002708877.7893.75

Conclusion:

Our preliminary analysis shows that this set of genes and selected clinical parameters are predictive markers for infliximab specific response in RA patients. Ongoing work involves the clinical validation of these results in an independent patient cohort (n=60). This approach provides the opportunity to develop an in vitro diagnostic test method for the prediction of infliximab treatment responsiveness in bionaive rheumatod arthritis patients, hence to personalize infliximab therapy for these patients.

Disclosure of Interests:

Emese Kiss Consultant of: EK has received consultancy fees from Egis., Gyula Poór Consultant of: GyP has received consultancy fees from Egis and he was the coordinating investigator in this study, Gábor Zahuczky Grant/research support from: Egis, Katalin Tauberné Jakab Employee of: Egis., Miklós Sebeszta Employee of: Egis., Tamás Ponyi Employee of: Egis., Zsolt Holló Employee of: Egis.

Calcein assay for multidrug resistance reliably predicts therapy response and survival rate in acute myeloid leukaemia

In this study, we evaluated the suitability of the calcein assay as a routine clinical laboratory method for the identification of multidrug-resistant phenotype in acute leukaemia. This study presents the results of the calcein tests obtained in two large haematological centres in Hungary. Assays were performed with blast cells of 93 de novo acute leukaemia patients, including 65 patients with acute myeloid leukaemia (AML). Results were expressed as multidrug resistance activity factor (MAF) values. AML patients were divided into responders and non-responders and MAF values were calculated for each group. In both centres, responder patients displayed significantly lower MAF values than non-responders (P = 0.0045 and P = 0.0454). Cut-off values were established between the MAFR + SEM and MAFNR - SEM values. On the basis of these cut-off levels, multidrug resistance (MDR) negativity showed a 72% predictive value for the response to chemotherapy, whereas MDR positivity was found to have an average predictive value of 69% for therapy failure. MDR activity was a prognostic factor for survival rate and the test was suitable for detecting patients at relapse. The calcein assay can be used as a quantitative, standardized, inexpensive screening test in a routine clinical laboratory setting. The assay detects both P-glycoprotein and multidrug resistance-associated protein activities, and identifies AML patients with unfavourable therapy responses.

Parallel functional and immunological detection of human multidrug resistance proteins, P-glycoprotein and MRP1

The proper assessment of the expression and drug extrusion activity of multidrug resistance proteins in various tumor cells is a challenging clinical laboratory problem. Recently, we have introduced a fluorescent dye (calcein) accumulation assay for the estimation of the functional expression of both P-glycoprotein (MDR1) and the multidrug resistance-associated protein (MRP1). Since both MDR1 and MRP1 decrease the intracellular accumulation of the fluorescent free calcein, by applying appropriate inhibitors of MDR1 and MRP1, the transport activity of these proteins could be quantitatively and selectively estimated in fluorometry or flow-cytometry assays. In the present work single-cell fluorescence digital imaging has been applied to characterize the kinetics and inhibitor-sensitivity of calcein accumulation in a mixture of HL60 MRP1 and NIH 3T3 MDR1 cells. Subsequent immunofluorescence labeling was performed by the anti-MDR1 monoclonal antibody (mAb) UIC2 in the same cell population. We report that the double labeling approach, based on the single cell calcein accumulation assay and an immunofluorescence detection, provides good sensitivity and selectivity for the simultaneous functional and immunological detection of cellular MDR1 and MRP1.

[Significance of multidrug resistance in the therapy of malignant tumors]

Some human malignant tumours respond poorly to initial chemotherapy, indicating that they possess intrinsic resistance. On the other hand, in a significant portion of tumours after early promising results of therapy, the patients relapse, metastases appear, and acquired resistance to chemotherapy develops. The broad spectrum-resistance against chemotherapy is called multidrug resistance (MDR), and due to its clinical significance, studying of proteins responsible for multidrug resistance has become one of the most active research areas in biomedicine. There are several molecular mechanisms responsible for multidrug resistance. A group of filogenetically conservative plasmamembrane proteins actively extrudes different toxic compounds, xenobiotics, and also cytotoxic drugs from drug-resistant cells by using the energy of ATP. The clinically and biochemically most thoroughly characterized member of these proteins is the P-glycoprotein, which pumps hydrophobic drugs of natural origin and different chemical structure out of the cells. The recently cloned multidrug resistance associated protein (MRP) has also a broad substrate specificity, thus resembling P-glycoprotein. However, besides hydrophobic compounds, organic anions, glucuronide and glutathione conjugates are also excellent substrates of the MRP. The basic and clinically relevant properties of proteins causing multidrug resistance and the state of the art of current diagnostic approaches are summarized in this literature review. The different malignancies are characterized from the point of view of their multidrug resistance and recent clinical and biochemical data concerning therapeutic approaches for reversal of multidrug resistance are also presented.

The multidrug transporters--proteins of an ancient immune system

The multidrug resistance proteins, discovered as membrane transporters producing chemotherapy-resistance in cancer, are functioning as complex cellular defence systems through recognition and energy-dependent removal of a large variety of toxic agents. The multidrug transporters belong to the ATP-binding cassette (ABC) transporters, present both in prokaryotes and eukaryotes and built from a combination of characteristic membrane-spanning helices and cytoplasmic ATP-binding domains. In mammals the MDR1 (P-glycoprotein) extrudes large hydrophobic compounds and provides the basis of the blood-brain and the blood-testis barrier for such molecules. The multidrug resistance-associated protein (MRP) and its homologues have a major role in the cellular export of large organic anions, including e.g. conjugated bile salts and glutathione-conjugates. The substrate recognition, that is the self and non-self discrimination and the ATP-dependent foreign agent extrusion are directly coupled within the structure of these large plasma membrane proteins. Here we suggest that the multidrug transporters are essential parts of our immune-defence system, working as 'cellular antitoxic' mechanisms.

Membrane topology and glycosylation of the human multidrug resistance-associated protein

The membrane topology of the human multidrug resistance-associated protein (MRP) was examined by flow cytometry phenotyping, immunoblotting, and limited proteolysis in drug-resistant human and baculovirus-infected insect cells, expressing either the glycosylated or the underglycosylated forms of this protein. Inhibition of N-linked glycosylation in human cells by tunicamycin did not inhibit the transport function or the antibody recognition of MRP, although its apparent molecular mass was reduced from 180 kDa to 150 kDa. Extracellular addition of trypsin or chymotrypsin had no effect either on the function or on the molecular mass of MRP, while in isolated membranes limited proteolysis produced three large membrane-bound fragments. These experiments and the alignment of the MRP sequence with the human cystic fibrosis transmembrane conductance regulator (CFTR) suggest that human MRP, similarly to CFTR, contains a tandem repeat of six transmembrane helices, each followed by a nucleotide binding domain, and that the C-terminal membrane-bound region is glycosylated. However, the N-terminal region of MRP contains an additional membrane-bound, glycosylated area with four or five transmembrane helices, which seems to be a characteristic feature of MRP-like ATP-binding cassette transporters.

Transport properties of the multidrug resistance-associated protein (MRP) in human tumour cells

In this paper we demonstrate that the expression of the multidrug resistance-associated protein (MRP) in a variety of intact human tumour cells results in the ATP-dependent, mutually exclusive extrusion of both the acetoxymethyl ester and the free anion forms of the fluorescent dye calcein, as well as that of a fluorescent pyrenemaleimide-glutathione conjugate. The MRP-dependent transport of all these three model compounds closely correlates with the expression level of MRP and is cross-inhibited by hydrophobic anticancer drugs, by reversing agents for MDR1, and also by compounds not influencing MDR1, such as hydrophobic anions, alkylating agents, and inhibitors of organic anion transporters. Cellular glutathione depletion affects neither the MRP-dependent extrusion of calcein AM or free calcein, nor its modulation by most hydrophobic or anionic compounds, although eliminating the cross-inhibitory effect of glutathione conjugates. These results suggest that the outward pumping of both hydrophobic uncharged and water-soluble anionic compounds, including glutathione conjugates, is an inherent property of MRP, and offer sensitive methods for the functional diagnostics of this transport protein as well as for the rapid screening of drug-resistance modulating agents.

Drug-stimulated ATPase activity of a deletion mutant of the human multidrug-resistance protein (MDR1)

The baculovirus-insect cell system has been used for the functional expression of the human multidrug resistance protein (MDR1) and a mutant MDR1 variant lacking a twenty amino acid segment from the first extracellular loop (delta aa78-97 MDR1). Both MDR1 proteins were found to be correctly inserted into the insect cell membrane as indicated by their interaction with MRK 16 antibody. The removal of the 78-97 segment from the first extracellular loop dramatically altered drug-stimulated ATPase activity. Rhodamine 123 or vinblastine were not able to stimulate the mutant protein and Calcein AM had also little effect. In contrast, verapamil increased the ATPase activity of the mutant almost to the same maximal level as that of the wild type. However, the verapamil concentration needed for the half maximal stimulation of the ATPase activity was found to be about hundred times higher than that for the wild type MDR1. These results indicate that a partial deletion of an extracellular loop modulates the affinity of MDR1 for its transportable substrates in a variable fashion.

Interaction of bioactive hydrophobic peptides with the human multidrug transporter

In this report we demonstrate that various biologically active hydrophobic peptide derivatives, e.g., proteinase inhibitors, chemoattractants, ionophores, enkephalins, and immunosuppressants, stimulate a membrane ATPase activity associated with the human multidrug transporter (MDR1). The stimulation of the MDR1-ATPase by these agents does not correlate with their known biochemical or pharmacological activities but rather with their hydrophobicity. The peptides that show high-affinity interaction with the MDR1-ATPase also interfere strongly with fluorescent dye extrusion catalyzed by the multidrug transporter in intact cells and some have been shown to reverse drug resistance in cultured cells. These data suggest that several hydrophobic peptides behave as substrates of the multidrug transporter and may be used to modulate the chemotherapy resistance of tumor cells.

Calcein accumulation as a fluorometric functional assay of the multidrug transporter

Acetoxymethyl ester (AM) derivatives of various fluorescent indicators (fura-2, fluo-3, indo-1, BCECF, calcein) are actively extruded by the multidrug transporter (MDR1, P-glycoprotein-Homolya, L. et al. (1993) J. Biol. Chem. 268, 21493-21496). In the present paper we show that the measurement of the accumulation of a fluorescent cell viability marker, calcein, can be effectively used as a rapid and sensitive fluorometric and flow cytometric assay for studying P-glycoprotein function. The rate of calcein accumulation in human MDR1-expressing cells is significantly lower than in the control cells, while various drug-resistance reversing agents (verapamil, vinblastine, oligomycin, cyclosporin A and UIC2 monoclonal antibody) greatly increase calcein trapping only in the MDR1-expressing cells. Since calcein-AM is not fluorescent and free calcein is not a substrate of the multidrug transporter, the assay is readily applicable for rapid kinetic studies of the MDR1 function. Calcein has a high fluorescence intensity in the visible range, thus changes in calcein uptake can be easily visualised and MDR1-expressing and control cells separated by conventional flow cytometry.

Fluorescent cellular indicators are extruded by the multidrug resistance protein

In this report we show that NIH-3T3 mouse fibroblasts stably expressing the human multidrug transporter (MDR1 or P-glycoprotein), in contrast to the control NIH-3T3 cells, actively extrude the hydrophobic acetoxymethyl ester (AM) derivatives used for cellular loading of various fluorescent calcium and pH indicators. This dye extrusion is blocked by competing substrates and inhibitors of the multidrug transporters, e.g. by verapamil, vincristine, sodium orthovanadate, oligomycin, and a monoclonal anti-MDR1 antibody. The hydrophilic free acid forms of the indicators are not exported by MDR1. We also demonstrate that in isolated cell membranes the MDR1-ATPase, similar to that by known substrates of the transporter, is stimulated by the AM derivatives of fluorescent dyes whereas the free acid forms of the dyes are without effect. Since (i) the AM derivatives of the fluorescent indicators rapidly permeate the cell membrane and are readily cleaved by high activity and large capacity cytoplasmic esterases and (ii) the free acid forms are not substrates for export by MDR1, the observations above suggest that dye extrusion by MDR1 may occur without a cytoplasmic appearance of the AM compounds. These data also call attention to the possible interaction of widely used hydrophobic fluorescent indicators with MDR1 and offer an efficient detection of MDR1-expressing tumor cells as well as a screening method for examining drug interactions with the multidrug transporter.

Thapsigargin-induced increase in cytoplasmic Ca2+ concentration and aldosterone production in rat adrenal glomerulosa cells: interaction with potassium and angiotensin-II

Thapsigargin (Tg), a microsomal Ca2+ pump inhibitor, dose-dependently increases the cytoplasmic Ca2+ concentration and aldosterone production without having any striking effect on the formation of inositol phosphates in isolated rat adrenal glomerulosa cells. The interaction of Tg with the major Ca2(+)-mediated stimuli of glomerulosa cells on aldosterone production was also examined. The effects of Tg and the Ca2(+)-mobilizing angiotensin-II (AII) were additive. The aldosterone production stimulatory effect of potassium, which induces Ca2+ influx via voltage-operated Ca2+ channels, was potentiated by Tg. The positive interaction between Tg and potassium on aldosterone production raises the possibility that stimuli generating Ca2+ signal by depleting intracellular Ca2+ stores, such as Tg or AII, enhance the response of the cell to depolarization. Such an interaction between AII and potassium may have an important role in the physiological control of aldosterone production.

Angiotensin II inhibits K(+)-induced Ca2+ signal generation in rat adrenal glomerulosa cells

The Ca2(+)-mobilizing hormone angiotensin II (AII) dose-dependently inhibited the K(+)-induced sustained increase of cytoplasmic Ca2+ concentration in adrenal glomerulosa cells and caused a rapid decrease of cytoplasmic Ca2+ when added to cells already stimulated with K+. These effects of AII on the K(+)-induced Ca2+ signal were mimicked, although less effectively, by other Ca2(+)-mobilizing agonists such as [Arg8]vasopressin (AVP) and thapsigargin. Phorbol esters did not show such effects, nor did corticotropin (ACTH), a secretagogue acting via cyclic AMP. The K(+)-stimulated initial 45Ca2+ uptake, a measure of Ca2+ entry into glomerulosa cells, was also prevented by AII pretreatment, and was inhibited by AVP, but not by ACTH. The stimulatory effect of K+ on aldosterone production, however, was not inhibited by AII, and the AII-induced aldosterone production was further increased by increasing K+. These data indicate that AII is able to inhibit static increases in cytoplasmic Ca2+ by inhibiting Ca2+ entry through voltage-sensitive Ca2+ channels and, possibly, by activating Ca2+ extrusion from the cells. It is also concluded that the Ca2+ signal evoked by AII is very efficient in stimulating hormone secretion, and the secretory response of the cells becomes more sensitive to any further increase of Ca2+ entry through voltage-sensitive Ca2+ channels.

Effects of high potassium concentration and dihydropyridine Ca2(+)-channel agonists on cytoplasmic Ca2+ and aldosterone production in rat adrenal glomerulosa cells

The aldosterone secretory response of isolated rat adrenal glomerulosa cells to potassium was studied in a cell-perifusion system. Increasing the potassium concentration from 3.6 to 5.4 mM in the perifusion medium caused a rapid 40-fold stimulation of aldosterone production which was maintained during the 2 h period of stimulation. A dose of 8.4 mM potassium elicited a 100-fold increase of hormone production with rapid onset and a slowly decreasing plateau. When the potassium concentration was further increased to 18 mM, there was a rapid stimulation of aldosterone production comparable to that evoked by 8.4 mM potassium; however, the response declined very rapidly to levels still above basal. The dihydropyridine-agonist BAY-K 8644 (100 nM) greatly enhanced the aldosterone response to 5.4 mM potassium but did not significantly modify the response evoked by 8.4 mM potassium. The effect of BAY-K 8644 on the aldosterone response was inhibitory at 18 mM potassium concentration, suggesting that the character of dihydropyridine modulation of the secretory response was voltage dependent, showing reversal at relatively negative potentials. When the cytoplasmic Ca2+ concentration was monitored in glomerulosa cells by the fluorescent Ca2(+)-probe Fura-2, potassium evoked a rapid dose-dependent increase in free Ca2+, with elevated steady-state Ca2(+)-levels throughout stimulation, even at potassium concentrations higher than 18 mM. Moreover, BAY-K 8644 (100 nM) enhanced the cytoplasmic Ca2+ response to all potassium concentrations tested up to 30 mM. The initial 30 sec 45Ca2+ uptake, an indicator of potassium-stimulated voltage-sensitive Ca2+ influx into these cells, showed a fast increase and only an initial inactivation in response to 18 mM potassium. This response was enhanced by 100 nM BAY-K 8644, with no sign of enhanced inactivation or inhibition caused by the dihydropyridine agonist. These results indicate that the correlation between Ca2+ influx, cytoplasmic Ca2+ levels, and the secretory response in adrenal glomerulosa cells is lost at potassium concentrations higher than 8 mM, especially in the presence of the dihydropyridine agonist, BAY-K 8644.