Involvement of ionic interactions in cytokine adsorption of polyethyleneimine-coated polyacrylonitrile and polymethyl methacrylate membranes in vitro

In Vitro Evaluation of Liposomal Amphotericin B Adsorption With Different Hemofilters for Continuous Hemofiltration

BACKGROUND

Fungemia is an infectious disease with a poor prognosis. Continuous hemofiltration (CHF) is widely used for the treatment of acute kidney injury associated with fungemia. However, the effect of hemofiltration membranes for CHF on antifungal drug concentrations remains poorly understood. Therefore, clarifying the adsorption of antifungal drugs onto these membranes is important. We investigated the adsorption properties of liposomal amphotericin B on different hemofiltration membranes using closed-circulation hemofiltration.

METHODS

We performed hemofiltration with each solution adjusted to liposomal amphotericin B as a closed circulatory circuit using polyacrylonitrile (AN69ST), polymethyl methacrylate (PMMA), and polysulfone (PS) membranes. Only this circuit was used as a control. Amphotericin B concentration at the inlet and in the effluent of the hemofiltration membrane was measured. The adsorption rate (Ra) of amphotericin B was then calculated.

RESULTS

The concentration of amphotericin B decreased in the PS membranes compared to that in the controls after 15 min (p = 0.03). The Ra of amphotericin B was higher in PS membranes than in the controls (p = 0.02). Amphotericin B was not adsorbed onto the PMMA or AN69ST membranes. The concentration of amphotericin B in these membranes showed no change compared with that in the control after 1440 min. Liposomal amphotericin B was temporarily absorbed on PS membranes, but at clinical doses, it did not appear to affect the antifungal doses.

CONCLUSIONS

Different blood purification membranes can be used to treat CHF without affecting the administration of antifungal drugs.

Enhanced Bioactive Compound Absorption on PMMA Microwell Plates via Fine Controlling Air Plasma Treatment Time for Disease Diagnosis Applications

Microwell plates absorb bioactive compounds and are commonly used for disease prediction, diagnosis, and monitoring. Chemical absorption is more effective than physical absorption for stabilizing these compounds. This study systematically investigates the fundamental mechanisms of air plasma-induced surface modifications in poly(methyl methacrylate) (PMMA), focusing on carboxyl group formation kinetics, morphological evolution, and optical property changes. Air plasma treatment enhances the hydrophilicity and surface roughness of the PMMA plates. Light transmission remains comparable to untreated plates for 10 min treatment durations. Treatment for 3 min significantly increases the large-molecular-weight carboxyl compounds, with minimal loss after wash buffer rinsing. Thus, a 3 min air plasma treatment optimally enhances PMMA microwell plates for effective bioactive compound absorption.

Investigation of Inflammatory Reduction During Extracorporeal Membrane Oxygenation Using a Novel Cytokine Adsorption Column: A Rat Model Study

Background: Cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) are widely used. Previous methods to reduce inflammation have shown inconsistent results. We developed a cytokine adsorption column using polymethyl methacrylate (PMMA) and investigated its anti-inflammatory effects during ECMO. Materials and Methods: Male Sprague-Dawley rats were divided into three groups (seven rats in each group): SHAM, ECMO, and ECMO with PMMA (PMMA group). Experiments comprised 180 min of cannulation only in the SHAM group and 60 min of ECMO followed by 120 min of observation in the ECMO and PMMA groups. PMMA adsorption was conducted from 30 min after ECMO initiation to completion in the PMMA group. Blood parameters and cytokines were measured during experiments. Lung tissues were collected after the experiment for evaluation of tissue edema. Results: The PMMA group showed significantly lower levels of tumor necrosis factor alpha (TNF-α) and interleukin(IL)-6 compared to the ECMO group at 120 min after completing ECMO. However, there were no significant differences in IL-10 levels between the ECMO group and the PMMA group at the same time points. Lung edema incidence was significantly lower in the PMMA group. Conclusions: The PMMA column effectively suppressed systemic inflammatory reactions during ECMO.

Comparison of Different Membranes for Continuous Renal Replacement Therapies: An In Vitro Study

Inflammatory mediators play a major role in the development and progression of acute kidney injury (AKI). Continuous renal replacement therapy (CRRT) removes these mediators from the blood using AN69-M, AN69-ST, and HF1400 filters to target low and middle-molecular weight molecules. We characterized the in vitro removal performance of each filter in a 72 hour simulated CRRT procedure. Urea clearance with AN69-M and AN69-ST remained stable (52.4 and 51.2 ml/minute, respectively) but decreased with HF1400 (47.0 ml/minute; p < 0.001). Vancomycin clearance remained stable for AN69 filters but decreased for HF1400. Interleukin (IL)-8 was removed primarily via adsorption with the AN69 filters (92.2 and 91.2 ml/minute for AN69-M and AN69-ST, respectively), but clearance was significantly lower with HF1400 (8.4 ml/minute). Tumor necrosis factor (TNF)-α clearance was higher with AN69-ST compared with AN69-M or HF1400 (10.3, 1.8, and 2.3 ml/minute, respectively). β2-microglobulin clearance was higher with both AN69-based filters. The hydrogel water repartition of AN69 filters was different, with a higher percentage of bound water in AN69-ST versus AN69-M (30.5% ± 0.2% and 19.3% ± 1.5%, respectively; p < 0.05). These results suggest that clearance profiles of CRRT filters differ according to their properties; further investigation is needed to translate this into clinical improvements.

Unveiling cytokine charge disparity as a potential mechanism for immune regulation

Cytokines are small signaling proteins that regulate the immune responses to infection and tissue damage. Surface charges of cytokines determine their in vivo fate in immune regulation, e.g., half-life and distribution. The overall negative charges in the extracellular microenvironment and the acidosis during inflammation and infection may differentially impact cytokines with different surface charges for fine-tuned immune regulation via controlling tissue residential properties. However, the trend and role of cytokine surface charges has yet to be elucidated in the literature. Interestingly, we have observed that most pro-inflammatory cytokines have a negative charge, while most anti-inflammatory cytokines and chemokines have a positive charge. In this review, we extensively examined the surface charges of all cytokines and chemokines, summarized the pharmacokinetics and tissue adhesion of major cytokines, and analyzed the link of surface charge with cytokine biodistribution, activation, and function in immune regulation. Additionally, we identified that the general trend of charge disparity between pro- and anti-inflammatory cytokines represents a unique opportunity to develop precise immune modulation approaches, which can be applied to many inflammation-associated diseases including solid tumors, chronic wounds, infection, and sepsis.

Blood Purification in Patients with Sepsis Associated with Acute Kidney Injury: A Narrative Review

Sepsis leads to organ dysfunction. Acute kidney injury, a common type of organ dysfunction, is associated with a high mortality rate in patients with sepsis. Kidney replacement therapy can correct the metabolic, electrolyte, and fluid imbalances caused by acute kidney injury. While this therapy can improve outcomes, evidence of its beneficial effects is lacking. Herein, we review the indications for blood purification therapy, including kidney replacement therapy, and the current knowledge regarding acute kidney injury in terms of renal and non-renal indications. While renal indications have been well-documented, indications for blood purification therapy in sepsis (non-renal indications) remain controversial. Excessive inflammation is an important factor in the development of sepsis; blood purification therapy has been shown to reduce inflammatory mediators and improve hemodynamic instability. Given the pathophysiology of sepsis, blood purification therapy may decrease mortality rates in these patients. Further trials are needed in order to establish the effectiveness of blood purification therapy for sepsis.

Comparison of the cytokine adsorption ability in continuous renal replacement therapy using polyethyleneimine-coated polyacrylonitrile (AN69ST) or polymethylmethacrylate (PMMA) hemofilters: a pilot single-center open-label randomized control trial

BACKGROUND

Sepsis occurs as a result of dysregulated host response to infection. However, cytokine adsorption therapy may restore the balance of proinflammatory and anti-inflammatory mediator responses in patients with sepsis. This study aimed to determine the cytokine adsorption ability of two different types of continuous renal replacement therapy (CRRT) hemofilters for polyethyleneimine-coated polyacrylonitrile (AN69ST) (surface-treated) and polymethylmethacrylate (PMMA) CRRT.

METHODS

We performed a randomized controlled trial among sepsis patients undergoing CRRT, who were randomly assigned (1:1) to receive either AN69ST or PMMA-CRRT. The primary outcome was cytokine clearance of hemofilter adsorption (CHA). The secondary endpoints were the intensive care unit (ICU) and 28-day mortalities.

RESULTS

We randomly selected 52 patients. Primary outcome data were available for 26 patients each in the AN69ST-CRRT and PMMA-CRRT arms. The CHA of high-mobility group box 1, tumor necrosis factor, interleukin (IL)-8, monokine induced by interferon-γ, and macrophage inflammatory protein were significantly higher in the AN69ST-CRRT group than in the PMMA-CRRT group (P < 0.001, P < 0.01, P < 0.001, P < 0.001 and P < 0.001, respectively). In contrast, the CHA of IL-6 was significantly higher in the PMMA-CRRT group than in the AN69ST-CRRT group (P < 0.001). In addition, the 28-day mortality was not significantly different between the two groups (50% in AN69ST-CRRT vs. 30.8% in PMMA-CRRT, P = 0.26).

CONCLUSION

AN69ST and PMMA membranes have different cytokine CHA in patients with sepsis. Therefore, these two hemofilters may have to be used depending on the target cytokine.

TRIAL REGISTRATION NUMBER

This study was registered in the University Hospital Medical Information Network on November 1, 2017 (Trial No: UMIN000029450, https://center6.umin.ac.jp ).

Targeting circulating high mobility group box-1 and histones by extracorporeal blood purification as an immunomodulation strategy against critical illnesses

Both high mobility group box-1 (HMGB1) and histones are major damage-associated molecular patterns (DAPMs) that mediate lethal systemic inflammation, activation of the complement and coagulation system, endothelial injury and multiple organ dysfunction syndrome in critical illnesses. Although accumulating evidence collectively shows that targeting HMGB1 or histones by their specific antibodies or inhibitors could significantly mitigate aberrant immune responses in multiple critically ill animal models, routine clinical use of such agents is still not recommended by any guideline. In contrast, extracorporeal blood purification, which has been widely used to replace dysfunctional organs and remove exogenous or endogenous toxins in intensive care units, may also exert an immunomodulatory effect by eliminating inflammatory mediators such as cytokines, endotoxin, HMGB1 and histones in patients with critical illnesses. In this review, we summarize the multiple immunopathological roles of HMGB1 and histones in mediating inflammation, immune thrombosis and organ dysfunction and discuss the rationale for the removal of these DAMPs using various hemofilters. The latest preclinical and clinical evidence for the use of extracorporeal blood purification to improve the clinical outcome of critically ill patients by targeting circulating HMGB1 and histones is also gathered.

Rationale for sequential extracorporeal therapy (SET) in sepsis

Sepsis and septic shock remain drivers for morbidity and mortality in critical illness. The clinical picture of patients presenting with these syndromes evolves rapidly and may be characterised by: (a) microbial host invasion, (b) establishment of an infection focus, (c) opsonisation of bacterial products (e.g. lipopolysaccharide), (d) recognition of pathogens resulting in an immune response, (e) cellular and humoral effects of circulating pathogen and pathogen products, (f) immunodysregulation and endocrine effects of cytokines, (g) endothelial and organ damage, and (h) organ crosstalk and multiple organ dysfunction. Each step may be a potential target for a specific therapeutic approach. At various stages, extracorporeal therapies may target circulating molecules for removal. In sequence, we could consider: (a) pathogen removal from the circulation with affinity binders and cartridges (specific), (b) circulating endotoxin removal by haemoperfusion with polymyxin B adsorbers (specific), (c) cytokine removal by haemoperfusion with sorbent cartridges or adsorbing membranes (non-specific), (d) extracorporeal organ support with different techniques for respiratory and cardiac support (CO₂ removal or extracorporeal membrane oxygenation), and renal support (haemofiltration, haemodialysis, or ultrafiltration). The sequence of events and the use of different techniques at different points for specific targets will likely require trials with endpoints other than mortality. Instead, the primary objectives should be to achieve the desired action by using extracorporeal therapy at a specific point.

A Larger Membrane Area Increases Cytokine Removal in Polymethyl Methacrylate Hemofilters

Blood purification is performed to control cytokines in critically ill patients. The relationship between the clearance (CL) and the membrane area during adsorption is not clear. We hypothesized that the CL increases with the hydrophobic area when hydrophobic binding contributes to cytokine adsorption. We investigated the relationship between the hemofilter membrane area and the CL of the high mobility group box 1 protein (HMGB-1) and interleukin-6 (IL-6). We performed experimental hemofiltration in vitro using polymethyl methacrylate membranes CH-1.8W (1.8 m²) and CH-1.0N (1.0 m²), as well as polysulfone membrane NV-18X (1.8 m²). After adding 100 mg of HMGB1 or 10 μg of IL-6 into the test solution, experimental hemofiltration was conducted for 360 min in a closed-loop circulation system, and the same amount of HMGB1 and IL-6 was added after 180 min. With CH-1.8W and CH-1.0N, both HMGB-1 and IL-6 showed a rapid concentration decrease of more than 70% at 180 min and 360 min after the re-addition. At 15 min, the CL of HMGB-1 was CH-1.8W: 28.4 and CH-1.0N: 19.8, and that of IL-6 was CH-1.8W: 41.1 and CH-1.0N: 25.4. CH-1.8W and CH-1.0N removed HMGB1 and IL-6 by adsorption and CH-1.8W was superior in CL, which increased with a greater membrane area.

Comprehensive analysis of cytokine adsorption properties of polymethyl methacrylate (PMMA) membrane material

In acute kidney injury caused by sepsis (septic AKI), excessive production of inflammatory mediators is believed to be involved in deterioration of the disease. Renal replacement therapy using a polymethyl methacrylate (PMMA) membrane hemofilter improves the pathological condition of septic AKI by adsorbing and removing inflammatory cytokines. However, the adsorption properties of the PMMA membrane are unclear. In this study, we comprehensively analyzed the adsorption of 48 different cytokines in human plasma to PMMA and polysulfone (PS) membranes. Seventy-nine percent (38/48) of the cytokines were adsorbed more efficiently to the PMMA membrane than the PS membrane, which indicates that the PMMA membrane has high cytokine adsorption ability. The adsorption rate tended to be higher for the cytokines with lower molecular weight, and there was a significant correlation between the molecular weight of the cytokines and the adsorption rates. Electron microscopy showed that the PMMA hollow fiber membrane had a uniform internal structure from the inner to the outer layers of the membrane and had nano-pores inside the membrane that may have contributed to the adsorption of proteins with a specific molecular weight range. The clinical efficacy of a PMMA membrane hemofilter with cytokine adsorption properties against septic AKI needs further investigation including the evaluation of filtration performance of the hemofilters.

Replication of fouling in vitro in hollow fiber dialyzers by albumin immobilization

For designing and evaluating the dialyzer and investigating the optimal therapeutic conditions, in vitro studies bring us many useful findings. In hemodialysis, however, the membrane fouling due to protein molecules reduces solute removal performance. Therefore, we investigated a method for replicating the fouling in dialyzers in aqueous experiments. After the albumin solution was circulated in the test circuit with a dialyzer, a glutaraldehyde solution was pumped into the dialyzer to immobilize albumin on the hollow fiber membrane. Under various immobilization conditions, the permeability of creatinine and vitamin B₁₂ was evaluated by dialysis experiments. The creatinine clearance after immobilization of albumin was decreased, suggesting pore plugging by our fouling replication method. The glutaraldehyde crosslinked albumin molecules that adhered them to the membrane firmly. Moreover, the degree of fouling may be controlled by changing the concentration of albumin solution and the volume of glutaraldehyde solution used for immobilization. Our fouling replication method was applied to three types of polyester polymer alloy (PEPA) dialyzers and one polysulfone (PSf) dialyzer. This method enables to evaluate the permeability of various dialyzers with fouling in vitro that will be of great help in collecting data for designing dialyzers.

Early High-dose Continuous Veno-venous Hemofiltration Alleviates the Alterations of CD4+ T Lymphocyte Subsets in Septic Patients Combined with Acute Kidney Injury

BACKGROUND

This study aims to determine whether early high-dose continuous venous-venous hemofiltration (CVVH) alleviates the alterations in CD4⁺ T lymphocyte subsets in septic patients combined with acute kidney injury.

METHODS

Enrolled septic patients combined with acute kidney injury were randomized into CVVH (n = 50) and conventional treatment (non-CVVH, n = 53) groups. Healthy volunteers (n = 21) were enrolled. CVVH was initiated within 12 h of intensive care unit (ICU) admission with the doses of 35 ~ 60 mL/kg/h and maintained for at least 72 h. Th1, Th2, Th17 and T_reg were measured by flow cytometry on days 1, 3 and 7 of ICU admission. Sequential organ failure assessment (SOFA) scores were calculated.

RESULTS

Th1 percentages and Th1/Th2 ratios were lower, and Th2, Th17 and T_reg percentages and Th17/T_reg ratios were higher in septic patients compared to healthy volunteers. CVVH significantly increased Th1 percentages and Th1/Th2 ratios, and significantly decreased Th2, Th17 and T_reg percentages and Th17/T_reg ratios compared to non-CVVH. Th1 percentages and Th1/Th2 ratios were negatively correlated with SOFA scores, while Th2, Th17 and T_reg percentages and Th17/T_reg ratios were positively correlated with SOFA scores. Patients with CVVH had significantly lower SOFA scores on day 7 of ICU admission and a shorter ICU stay compared to those with non-CVVH.

CONCLUSIONS

Septic patients combined with acute kidney injury exhibit different alterations of CD4⁺ T lymphocyte subsets. Early high-dose CVVH alleviates the alterations, which may be one of factors associated with improved sepsis severity.

Contribution of diafiltration and adsorption to vancomycin clearance in a continuous hemodiafiltration circuit model in vitro

BACKGROUND

Vancomycin (VCM) is eliminated mainly by diafiltration under continuous hemodiafiltration (CHDF), but the contribution of adsorption to CHDF clearance (CL_CHDF ) of VCM using a polyacrylonitrile and sodium methallyl sulfonate copolymer membrane coated with polyethylenimine (AN69ST) or a polymethylmethacrylate (PMMA) membrane is unknown. This study sought to investigate the contribution of diafiltration and adsorption to the CL_CHDF of VCM using AN69ST and PMMA membranes in vitro.

METHODS

An in vitro CHDF circuit model was developed. The initial concentration of VCM was 50 μg/mL and human serum albumin (HSA) was prepared at a concentration of 0, 2.5, or 5.0 g/dL. The effluent flow rate (Qe) was set at 800, 1500, or 3000 mL/h. The CL_CHDF , diafiltration rate, and adsorption rate of VCM were calculated.

RESULTS

Total CL_CHDF of VCM using the AN69ST membrane increased and decreased with increasing Qe and HSA concentration, respectively. Diafiltration and adsorption rates were 82.1 ± 9.8% and 12.1 ± 6.1% under all conditions, respectively. Total CL_CHDF using the PMMA membrane increased with increasing Qe. Diafiltration and adsorption rates were 89.2 ± 20.4% and 4.6 ± 17.0% under all conditions, respectively. The observed CL_CHDF values significantly correlated with the predicted CL_CHDF , calculated according to a previous study as the product of Qe and the plasma unbound fraction.

CONCLUSIONS

Diafiltration predominantly contributed to CL_CHDF of VCM using AN69ST and PMMA membranes. When diafiltration rather than adsorption mainly contributes to the CL_CHDF of VCM, the CL_CHDF could be predicted from the Qe and HSA concentration, at least in vitro.

Targeting Cytokines, Pathogen-Associated Molecular Patterns, and Damage-Associated Molecular Patterns in Sepsis via Blood Purification

Sepsis is characterized by a dysregulated immune response to infections that causes life-threatening organ dysfunction and even death. When infections occur, bacterial cell wall components (endotoxin or lipopolysaccharide), known as pathogen-associated molecular patterns, bind to pattern recognition receptors, such as toll-like receptors, to initiate an inflammatory response for pathogen elimination. However, strong activation of the immune system leads to cellular dysfunction and ultimately organ failure. Damage-associated molecular patterns (DAMPs), which are released by injured host cells, are well-recognized triggers that result in the elevation of inflammatory cytokine levels. A cytokine storm is thus amplified and sustained in this vicious cycle. Interestingly, during sepsis, neutrophils transition from powerful antimicrobial protectors into dangerous mediators of tissue injury and organ dysfunction. Thus, the concept of blood purification has evolved to include inflammatory cells and mediators. In this review, we summarize recent advances in knowledge regarding the role of lipopolysaccharides, cytokines, DAMPs, and neutrophils in the pathogenesis of sepsis. Additionally, we discuss the potential of blood purification, especially the adsorption technology, for removing immune cells and molecular mediators, thereby serving as a therapeutic strategy against sepsis. Finally, we describe the concept of our immune-modulating blood purification system.

Comparison of myoglobin clearance in three types of blood purification modalities

Myoglobin, which can cause acute kidney injury, has a relatively high molecular weight and is poorly cleared by diffusion. We compared and examined myoglobin clearance by changing the blood purification membrane and modality in patients with a myoglobin blood concentration ≥ 1000 ng/ml. We retrospectively analyzed three patient groups based on the following three types of continuous hemofiltration (CHF): AN69ST membrane, polymethylmethacrylate (PMMA) membrane, and high-flow hemodiafiltration (HDF) with increased dialysate flow rate using the PMMA membrane. There was no significant difference in clearance in CHF between AN69ST and PMMA membranes. However, the high-flow HDF group showed the highest myoglobin clearance (p = 0.003). In the PMMA membrane, changing the treatment modality to high-flow HDF increased clearance above the theoretical value, possibly due to internal filtration. To remove myoglobin by kidney replacement therapy from patients with hypermyoglobinemia, a modality such as high-flow HDF would be desirable.