Liposome-encapsulated aprotinin biodistribution in mice: Side-by-side comparison with free drug formulation.

Injuries of the respiratory system caused by viral infections (e.g., by influenza virus, respiratory syncytial virus, metapneumovirus, or coronavirus) can lead to long-term complications or even life-threatening conditions. The challenges of treatment of such diseases have become particularly pronounced during the recent pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One promising drug is the anti-fibrinolytic and anti-inflammatory protease inhibitor aprotinin, which has demonstrated considerable inhibition of the replication of some viruses. Encapsulation of aprotinin in liposomes can significantly improve the effectiveness of the drug, however, the use of nanoparticles as carriers of aprotinin can radically change its biodistribution in the body. Here we show that the liposomal form of aprotinin accumulates more efficiently in the lungs, heart, and kidneys than the molecular form by side-by-side comparison of the ex vivo biodistribution of these two fluorescently labeled formulations in mice using bioimaging. In particular, we synthesized liposomes of different compositions and studied their accumulation in various organs and tissues. Direct comparison of the biodistributions of liposomal and free aprotinin showed that liposomes accumulated in the lungs 1.82 times more effectively, and in the heart and kidneys - 3.56 and 2.00 times, respectively. This suggests that the liposomal formulation exhibits a longer residence time in the target organ and, thus, has the potential for a longer therapeutic effect. The results reveal the great potential of the aprotinin-loaded liposomes for the treatment of respiratory system injuries and heart- and kidney-related complications of viral infections.

A production platform for disulfide-bonded peptides in the periplasm of Escherichia coli.

BACKGROUND: Recombinant peptide production in Escherichia coli provides a sustainable alternative to environmentally harmful and size-limited chemical synthesis. However, in-vivo production of disulfide-bonded peptides at high yields remains challenging, due to degradation by host proteases/peptidases and the necessity of translocation into the periplasmic space for disulfide bond formation. RESULTS: In this study, we established an expression system for efficient and soluble production of disulfide-bonded peptides in the periplasm of E. coli. We chose model peptides with varying complexity (size, structure, number of disulfide bonds), namely parathyroid hormone 1-84, somatostatin 1-28, plectasin, and bovine pancreatic trypsin inhibitor (aprotinin). All peptides were expressed without and with the N-terminal, low molecular weight CASPON™ tag (4.1 kDa), with the expression cassette being integrated into the host genome. During BioLector™ cultivations at microliter scale, we found that most of our model peptides can only be sufficiently expressed in combination with the CASPON™ tag, otherwise expression was only weak or undetectable on SDS-PAGE. Undesired degradation by host proteases/peptidases was evident even with the CASPON™ tag. Therefore, we investigated whether degradation happened before or after translocation by expressing the peptides in combination with either a co- or post-translational signal sequence. Our results suggest that degradation predominantly happened after the translocation, as degradation fragments appeared to be identical independent of the signal sequence, and expression was not enhanced with the co-translational signal sequence. Lastly, we expressed all CASPON™-tagged peptides in two industry-relevant host strains during C-limited fed-batch cultivations in bioreactors. We found that the process performance was highly dependent on the peptide-host-combination. The titers that were reached varied between 0.6-2.6 g L-1, and exceeded previously published data in E. coli. Moreover, all peptides were shown by mass spectrometry to be expressed to completion, including full formation of disulfide bonds. CONCLUSION: In this work, we demonstrated the potential of the CASPON™ technology as a highly efficient platform for the production of soluble peptides in the periplasm of E. coli. The titers we show here are unprecedented whenever parathyroid hormone, somatostatin, plectasin or bovine pancreatic trypsin inhibitor were produced in E. coli, thus making our proposed upstream platform favorable over previously published approaches and chemical synthesis.

In Nordic countries 30-day mortality rate is half that estimated with EuroSCORE II in high-risk adult patients given aprotinin and undergoing mainly complex cardiac procedures.

Objectives. To describe current on- (isolated coronary arterty bypass grafting, iCABG) and off-label (non-iCABG) use of aprotinin and associated safety endpoints in adult patients undergoing high-risk cardiac surgery in Nordic countries. Design. Data come from 10 cardiac surgery centres in Finland, Norway and Sweden participating in the European Nordic aprotinin patient registry (NAPaR). Results. 486 patients were given aprotinin between 2016 and 2020. 59 patients (12.1%) underwent iCABG and 427 (87.9%) non-iCABG, including surgery for aortic dissection (16.7%) and endocarditis (36.0%). 89.9% were administered a full aprotinin dosage and 37.0% were re-sternotomies. Dual antiplatelet treatment affected 72.9% of iCABG and 7.0% of non-iCABG patients. 0.6% of patients had anaphylactic reactions associated with aprotinin. 6.4% (95 CI% 4.2%-8.6%) of patients were reoperated for bleeding. Rate of postoperative thromboembolic events, day 1 rise in creatinine >44µmol/L and new dialysis for any reason was 4.7% (95%CI 2.8%-6.6%), 16.7% (95%CI 13.4%-20.0%) and 14.0% (95%CI 10.9%-17.1%), respectively. In-hospital mortality and 30-day mortality was 4.9% (95%CI 2.8%-6.9%) and 6.3% (95%CI 3.7%-7.8%) in all patients versus mean EuroSCORE II 11.4% (95%CI 8.4%-14.0%, p < .01). 30-day mortality in patients undergoing surgery for aortic dissection and endocarditis was 6.2% (95%CI 0.9%-11.4%) and 6.3% (95%CI 2.7%-9.9%) versus mean EuroSCORE II 13.2% (95%CI 6.1%-21.0%, p = .11) and 14.5% (95%CI 12.1%-16.8%, p = .01), respectively. Conclusions. NAPaR data from Nordic countries suggest a favourable safety profile of aprotinin in adult cardiac surgery.

Efficacy and utility of antifibrinolytics in pediatric spine surgery: a systematic review and network meta-analysis.

Antifibrinolytics have gained increasing attention in minimizing blood loss and mitigating the risks associated with massive transfusions, including infection and coagulopathy in pediatric patients undergoing spine surgery. Nevertheless, the selection of optimal agent is still a matter of debate. We aim to review the utility of these agents and compare the efficacy of antifibrinolytics in pediatric and adolescent spine surgeries. A comprehensive search was performed in Scopus, Web of Science, and MEDLINE databases for relevant works. Studies providing quantitative data on predefined outcomes were included. Primary outcome was perioperative bleeding between the groups. Secondary outcomes included transfusion volume, rate of complications, and operation time. Twenty-eight studies were included in the meta-analysis incorporating 2553 patients. The use of Tranexamic acid (RoM: 0.71, 95%CI: [0.62-0.81], p < 0.001, I2 = 88%), Aprotinin (RoM: 0.54, 95%CI: [0.46-0.64], p < 0.001, I2 = 0%), and Epsilon-aminocaproic acid (RoM: 0.71, 95%CI: [0.62-0.81], p < 0.001, I2 = 60%) led to a 29%, 46%, and 29% reduction in perioperative blood loss, respectively. Network meta-analysis revealed higher probability of efficacy with Tranexamic acid compared to Epsilon-aminocaproic acid (P score: 0.924 vs. 0.571). The rate of complications was not statistically different between each two antifibrinolytic agent or antifibrinolytics compared to placebo or standard of care. Our network meta-analysis suggests a superior efficacy of all antifibrinolytics compared to standard of care/placebo in reducing blood loss and transfusion rate. Further adequately-powered randomized clinical trials are recommended to reach definite conclusion on comparative performance of these agents and to also provide robust objective assessments and standardized outcome data and safety profile on antifibrinolytics in pediatric and adolescent pediatric surgeries.

Aprotinin (I): Understanding the Role of Host Proteases in COVID-19 and the Importance of Pharmacologically Regulating Their Function.

Proteases are produced and released in the mucosal cells of the respiratory tract and have important physiological functions, for example, maintaining airway humidification to allow proper gas exchange. The infectious mechanism of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), takes advantage of host proteases in two ways: to change the spatial conformation of the spike (S) protein via endoproteolysis (e.g., transmembrane serine protease type 2 (TMPRSS2)) and as a target to anchor to epithelial cells (e.g., angiotensin-converting enzyme 2 (ACE2)). This infectious process leads to an imbalance in the mucosa between the release and action of proteases versus regulation by anti-proteases, which contributes to the exacerbation of the inflammatory and prothrombotic response in COVID-19. In this article, we describe the most important proteases that are affected in COVID-19, and how their overactivation affects the three main physiological systems in which they participate: the complement system and the kinin-kallikrein system (KKS), which both form part of the contact system of innate immunity, and the renin-angiotensin-aldosterone system (RAAS). We aim to elucidate the pathophysiological bases of COVID-19 in the context of the imbalance between the action of proteases and anti-proteases to understand the mechanism of aprotinin action (a panprotease inhibitor). In a second-part review, titled "Aprotinin (II): Inhalational Administration for the Treatment of COVID-19 and Other Viral Conditions", we explain in depth the pharmacodynamics, pharmacokinetics, toxicity, and use of aprotinin as an antiviral drug.

Aprotinin (II): Inhalational Administration for the Treatment of COVID-19 and Other Viral Conditions.

Aprotinin is a broad-spectrum inhibitor of human proteases that has been approved for the treatment of bleeding in single coronary artery bypass surgery because of its potent antifibrinolytic actions. Following the outbreak of the COVID-19 pandemic, there was an urgent need to find new antiviral drugs. Aprotinin is a good candidate for therapeutic repositioning as a broad-spectrum antiviral drug and for treating the symptomatic processes that characterise viral respiratory diseases, including COVID-19. This is due to its strong pharmacological ability to inhibit a plethora of host proteases used by respiratory viruses in their infective mechanisms. The proteases allow the cleavage and conformational change of proteins that make up their viral capsid, and thus enable them to anchor themselves by recognition of their target in the epithelial cell. In addition, the activation of these proteases initiates the inflammatory process that triggers the infection. The attraction of the drug is not only its pharmacodynamic characteristics but also the possibility of administration by the inhalation route, avoiding unwanted systemic effects. This, together with the low cost of treatment (≈2 Euro/dose), makes it a good candidate to reach countries with lower economic means. In this article, we will discuss the pharmacodynamic, pharmacokinetic, and toxicological characteristics of aprotinin administered by the inhalation route; analyse the main advances in our knowledge of this medication; and the future directions that should be taken in research in order to reposition this medication in therapeutics.

Cost analysis study comparing the impact of treatment with aprotinin versus tranexamic acid in cardiac surgery under cardiopulmonary bypass.

OBJECTIVES: An increased risk of mortality and postoperative side effects led to aprotinin (Trasylol®) withdrawal from the market in 2008, but since 2018 aprotinin has again been used in France. The French retrospective multicentre APACHE study (AProtinin versus tranexamic Acid in Cardiac surgery patients with High-risk for Excessive bleeding) compared the efficacy of tranexamic acid versus half-dose aprotinin. The aim of this study, ancillary to the APACHE study, is to carry out a medico-economic analysis of the use of these two antifibrinolytics on an APACHE subpopulation. METHODS: Economic data on reimbursement by the French health insurance system were extracted from the program for the data processing of medical information, and quantitative data on the cost of healthcare products were obtained from the hospital pharmacy software. RESULTS: The main analysis of costs for the population shows that the global valuation was not significantly different between the two treatment groups (P=0.60), but the costs of blood products included in the related hospital stay group (Groupe Homogène de séjour [GHS]) (whole blood, platelets and plasma) were higher for the tranexamic acid group (P=0.007). In a sub-analysis of patients alive at discharge, the costs of blood products in addition to GHS (blood-derived medicines) and the costs of blood products in the GHS were higher for the tranexamic acid group (P=0.04 and 0.001, respectively). CONCLUSIONS: The additional cost of aprotinin at the time of purchase is offset by the additional costs of blood products in the tranexamic acid group.

Aprotinin-Drug against Respiratory Diseases.

Aprotinin (APR) was discovered in 1930. APR is an effective pan-protease inhibitor, a typical "magic shotgun". Until 2007, APR was widely used as an antithrombotic and anti-inflammatory drug in cardiac and noncardiac surgeries for reduction of bleeding and thus limiting the need for blood transfusion. The ability of APR to inhibit proteolytic activation of some viruses leads to its use as an antiviral drug for the prevention and treatment of acute respiratory virus infections. However, due to incompetent interpretation of several clinical trials followed by incredible controversy in the literature, the usage of APR was nearly stopped for a decade worldwide. In 2015-2020, after re-analysis of these clinical trials' data the restrictions in APR usage were lifted worldwide. This review discusses antiviral mechanisms of APR action and summarizes current knowledge and prospective regarding the use of APR treatment for diseases caused by RNA-containing viruses, including influenza and SARS-CoV-2 viruses, or as a part of combination antiviral treatment.

Aprotinin treatment against SARS-CoV-2: A randomized phase III study to evaluate the safety and efficacy of a pan-protease inhibitor for moderate COVID-19.

BACKGROUND: SARS-CoV-2 virus requires host proteases to cleave its spike protein to bind to its ACE2 target through a two-step furin-mediated entry mechanism. Aprotinin is a broad-spectrum protease inhibitor that has been employed as antiviral drug for other human respiratory viruses. Also, it has important anti-inflammatory properties for inhibiting the innate immunity contact system. METHODS: This was a multicentre, double-blind, randomized trial performed in four Spanish hospitals comparing standard treatment versus standard treatment + aprotinin for patients with COVID-19 between 20 May 2020 and 20 October 2021. The primary efficacy outcomes were length of hospital stay and ICU admission. The secondary endpoints were each of the primary efficacy outcomes and a composite of oxygen therapy, analytical parameters and death. Safety outcomes included adverse reactions to treatment during a 30-day follow-up period. Treatment was given for 11 days or till discharge. RESULTS: With almost identical analytical profiles, significant differences were observed in treatment time, which was 2 days lower in the aprotinin group (p = .002), and length of hospital admission, which was 5 days shorter in the aprotinin group (p = .003). The incidence of discharge was 2.19 times higher (HR: 2.188 [1.182-4.047]) in the aprotinin group than in the placebo group (p = .013). In addition, the aprotinin-treated group required less oxygen therapy and had no adverse reactions or side effects. CONCLUSION: Inhaled aprotinin may improve standard treatment and clinical outcomes in hospitalized patients with COVID-19, resulting in a shorter treatment time and hospitalization compared with the placebo group. The administration of aprotinin was safe.

Renal effects of the serine protease inhibitor aprotinin in healthy conscious mice.

Treatment with aprotinin, a broad-spectrum serine protease inhibitor with a molecular weight of 6512 Da, was associated with acute kidney injury, which was one of the reasons for withdrawal from the market in 2007. Inhibition of renal serine proteases regulating the epithelial sodium channel ENaC could be a possible mechanism. Herein, we studied the effect of aprotinin in wild-type 129S1/SvImJ mice on sodium handling, tubular function, and integrity under a control and low-salt diet. Mice were studied in metabolic cages, and aprotinin was delivered by subcutaneously implanted sustained release pellets (2 mg/day over 10 days). Mean urinary aprotinin concentration ranged between 642 ± 135 (day 2) and 127 ± 16 (day 8) µg/mL . Aprotinin caused impaired sodium preservation under a low-salt diet while stimulating excessive hyperaldosteronism and unexpectedly, proteolytic activation of ENaC. Aprotinin inhibited proximal tubular function leading to glucosuria and proteinuria. Plasma urea and cystatin C concentration increased significantly under aprotinin treatment. Kidney tissues from aprotinin-treated mice showed accumulation of intracellular aprotinin and expression of the kidney injury molecule 1 (KIM-1). In electron microscopy, electron-dense deposits were observed. There was no evidence for kidney injury in mice treated with a lower aprotinin dose (0.5 mg/day). In conclusion, high doses of aprotinin exert nephrotoxic effects by accumulation in the tubular system of healthy mice, leading to inhibition of proximal tubular function and counterregulatory stimulation of ENaC-mediated sodium transport.

The Efficacy of Aprotinin Combinations with Selected Antiviral Drugs in Mouse Models of Influenza Pneumonia and Coronavirus Infection Caused by SARS-CoV-2.

The efficacy of aprotinin combinations with selected antiviral-drugs treatment of influenza virus and coronavirus (SARS-CoV-2) infection was studied in mice models of influenza pneumonia and COVID-19. The high efficacy of the combinations in reducing virus titer in lungs and body weight loss and in increasing the survival rate were demonstrated. This preclinical study can be considered a confirmatory step before introducing the combinations into clinical assessment.

Synergistic Effect of ß-alanine and Aprotinin on Mesenteric Ischemia.

BACKGROUND: Acute mesenteric ischemia arises through sudden interruption of mesenteric blood flow, mostly due to an occlusion of the superior mesenteric artery and is associated with a high mortality of approximately 50% to 90%. In previous studies, the single application of ß-alanine or aprotinin caused an ameliorated intestinal damage but without any systemic effects. METHODS: To analyze the combined effect of ß-alanine and aprotinin on acute ischemia and reperfusion of the small intestine, a model with anesthetized rats was used. Ischemia and reperfusion were initiated by occluding and reopening the superior mesenteric artery. After 120 min of ischemia and 180 min of reperfusion, the intestine was analyzed for tissue damage, the activity of the saccharase, and accumulation of granulocytes. In addition, systemic and metabolic as well as inflammatory parameters were measured in blood at certain points in time. RESULTS: The combination of ß-alanine and aprotinin resulted in a clearly stabilized mean arterial blood pressure and blood glucose level during the reperfusion period. Furthermore, the combined administration resulted in significantly reduced tissue damage parameters, cytokine and cell-free hemoglobin concentrations in blood plasma. In addition, the damage to the small intestine was significantly attenuated, so that the animals ultimately survived the entire test period because of the administration of both substances. CONCLUSIONS: Overall, the simultaneous application of both substances leads to a synergistic protection without the occurrence of undesirable side effects. The combined usage of ß-alanine and aprotinin can be seen as a promising approach to inhibit the onset of acute mesenteric ischemia.

Cardiothoracic Anesthesia and Critical Care in the United Kingdom (UK) Part 1: Some Insights Into the History and Development.

This review is intended to highlight some of the historic events that contributed to the development of thoracic and cardiac anesthesia and surgery in Great Britain and Northern Ireland (UK). The aim of this first of two parts is to concentrate on the development of techniques, facilities, and pharmacology that allowed progress and advancement in patient management that were developed primarily in the UK. However, progress usually requires input from a wide variety of sources of knowledge, and cardiothoracic practice is no exception. Reference is, thus, made to sources outside of the UK that guided, influenced, or inspired changes in practice, such as the techniques of operating on the heart and great vessels in war casualties, developed by Dr. Dwight Harken, or the demonstration of the Blalock-Thomas-Taussig shunt by Alfred Blalock. In addition to advances in medical equipment, such as computed tomography, the UK contributed greatly to pharmacologic interventions that were unique at the time in such varied areas as nonflammable volatile anesthetic agents, heart failure treatments, and neuromuscular blocking agents for both cardiac and thoracic surgical practice.

Establishment and development of a CZE-UV method for rapid measurement of aprotinin potency.

A new method for the measurement of aprotinin potency by CZE-UV detector was established for the first time. The on-line mixing of substrate, trypsin and aprotinin using at-inlet technology was realized by the established method. Enzymatic reaction, separation, and detection of substrate and product can be performed simultaneously online. The aprotinin potency can be measured within 4 min. The response surface methodology was used to optimize the incubation conditions of trypsin and substrate, and the optimized conditions were obtained under 17.39 mM phosphate buffer at pH 7.6, 1.40 min of incubation time. The repeatability of proposed method was evaluated in three different systems of capillary zone electrophoresis: (i) only substrate; (ii) trypsin and substrate; (iii) aprotinin, trypsin and substrate, and the RSDs of migration times and peak areas of substrate were less than 2.7 and 3.1%, respectively. The RSDs of migration times and peak areas of product were less than 2.1 and 3.0%, respectively. A formula was also developed to calculate the aprotinin potency in this method. In a word, the established CZE-UV method was convenient, fast, and environmentally friendly for the measurement of aprotinin potency.

Significance of 11C-PIB PET/CT in cardiac amyloidosis compared with 99mTc-aprotinin scintigraphy: A pilot study.

BACKGROUND: This study was to investigate the significance of 11C-Pittsburgh B (PIB) PET/CT in patients with suspected cardiac amyloidosis compared with 99mTc-aprotinin scintigraphy. METHODS: Thirteen consecutive patients with suspected cardiac amyloidosis were considered for enrolment in this prospective pilot study. Participants were scheduled to undergo a series of 11C-PIB PET/CT and 99mTc-aprotinin within a 2-month period. Finally, we evaluated nine cases who underwent both imaging modalities, and compared imaging results with clinical and pathological results and prognosis. RESULTS: Six of the 9 patients who underwent both imaging modalities were diagnosed with amyloidosis, of whom 3 patients were diagnosed with cardiac amyloidosis from endomyocardial biopsy. These 3 patients with positive 11C-PIB uptake at the left ventricle wall showed worsening of cardiac function progressing in the short term or death caused by acute exacerbation of chronic heart failure. Six of 8 patients with positive uptake on 99mTc-aprotinin presented with amyloid deposition in the left ventricle wall, but symptoms remained stable if results of 11C-PIB were not positive. CONCLUSION: In a small sample of subjects, the present study showed that 11C-PIB accumulation in myocardium indicated cardiac amyloidosis with poor prognosis. Uptake of 11C-PIB may be related to progressive amyloid deposition to the heart and can predict patient prognosis.

Performance of 99mTc-aprotinin scintigraphy for diagnosing light chain (AL) cardiac amyloidosis confirmed by endomyocardial biopsy.

BACKGROUND: Light chain (AL) cardiac amyloidosis is associated with a poor prognosis. Diagnosing at an early stage is critical for treatment and the management of cardiac complication. PURPOSE: We aimed to evaluate the diagnostic performance of 99mTc-aprotinin images in patients with AL cardiac amyloidosis. METHODS AND RESULTS: 99mTc-aprotinin scintigraphy and endomyocardial biopsy were performed in 10 patients with suspected amyloidosis. Endomyocardial biopsy showed amyloid deposits in 5 of 10 patients. 99mTc-aprotinin (planer image) was positive in 4 of 5 patients who had amyloid deposits in endomyocardial biopsy. On the other hand, all 5 patients without amyloid deposits were negative in planer image. 99mTc-aprotinin (SPECT/CT image) was positive in all 5 patients who had amyloid deposits. CONCLUSIONS: 99mTc-aprotinin scintigraphy is valuable for the non-invasive diagnosis of AL cardiac amyloidosis.

Comparison of botulinum toxin type A and aprotinin monotherapy with combination therapy in healing of burn wounds in an animal model.

Burns are one of the most common injuries that are complicated by many challenges including infection, severe inflammatory response, excessive expression of proteases, and scar formation. The aim of this study was to investigate the effect of botulinum toxin type A (BO) and aprotinin (AP) separately or in combination (BO-AP) in healing process. Four burn wounds were created in each rat and randomly filled with silver sulfadiazine (SSD), BO, AP and BO-AP. The rats were euthanized after 7, 14, and 28 days, and their harvested wound samples were evaluated by gross pathology, histopathology, gene expression, biochemical testing, and scanning electron microscopy. Both BO and AP significantly reduced expression of interleukin-1ß (IL-1ß) and transforming growth factor-ß1 (TGF-ß1) at the 7th post wounding day. Moreover, they inhibited scar formation by reducing the TGF-ß1 level and increasing basic fibroblast growth factor (bFGF) at the 28th day. AP by decreasing protease production showed more effective role than BO in wound regeneration. AP increased tissue organization and maturation and improved cosmetic appearance of wounds, at 28 days. The best results gained when combination of BO and AP were used in healing of burn wounds. Treatment by BO-AP significantly subsided inflammation compared to the BO, AP, and SSD treated wounds. Treatment with BO-AP also reduced collagen density and led to minimal scar formation. Combination of botulinum toxin type A and aprotinin considerably increased structural and functional properties of the healing wounds by reducing scar formation and decreasing production of proteases.

Capillary electrophoretic reactor for estimation of spontaneous dissociation rate of Trypsin-Aprotinin complex.

A capillary electrophoretic reactor was used to analyze the dissociation kinetics of an enzyme-inhibitor complex in a homogeneous solution without immobilization. The complex consisting of trypsin (Try) and aprotinin (Apr) was used as the model. Capillary electrophoresis provided a reaction field for Try-Apr complex to dissociate through the steady removal of free Try and Apr from the Try-Apr zone. By analyzing the dependence of peak height of Try-Apr on separation time, the dissociation rate kdH was obtained as 2.73 × 10-4 s-1 (298 K) at pH 2.46. The dependence of kdH on the proton concentration (pH = 2.09-3.12) revealed a first-order dependence of kdH on [H+]; kdH = kd + k1[H+], where kd is the spontaneous dissociation rate and was 5.65 × 10-5 s-1, and k1 is the second-order rate constant and was 5.07 × 10-2 M-1 s-1. From the kd value, the half-life of the Try-Apr complex at physiological pH was determined as 3.4 h. The presence of the proton-assisted dissociation can be explained by the protonation of -COO- of the Asp residue in Try, which breaks the salt bridge with the -NH3+ group of Lys in Apr.

Three consecutive cases of fatal intraoperative intracardiac thrombosis associated with the initiation of venoarterial extracorporeal membrane oxygenation in the presence of aprotinin.

Central venoarterial extracorporeal membrane oxygenation has been used since the 1970s to support patients with cardiogenic shock following cardiac surgery. Despite this, in-hospital mortality is still high, and although rare, thrombus within the cardiac chambers or within the extracorporeal membrane oxygenation circuit is often fatal. Aprotinin is an antifibrinolytic available in Europe and Canada, though not currently in the United States. Due to historical safety concerns, use of aprotinin is generally limited and is commonly reserved for patients with the highest bleeding risk. Given the limited availability of aprotinin over the last decade, it is not surprising to find a complete absence of literature describing the use of venoarterial extracorporeal membrane oxygenation in the presence of aprotinin. We present three consecutive cases of rapid fatal intraoperative intracardiac thrombosis associated with post-cardiotomy central venoarterial extracorporeal membrane oxygenation in patients receiving aprotinin.

Aprotinin prevents proteolytic epithelial sodium channel (ENaC) activation and volume retention in nephrotic syndrome.

Volume retention in nephrotic syndrome has been linked to activation of the epithelial sodium channel (ENaC) by proteolysis of its γ-subunit following urinary excretion of serine proteases such as plasmin. Here we tested whether pharmacological inhibition of urinary serine protease activity might protect from ENaC activation and volume retention in nephrotic syndrome. Urine from both nephrotic mice (induced by doxorubicin injection) and nephrotic patients exhibited high aprotinin-sensitive serine protease activity. Treatment of nephrotic mice with the serine protease inhibitor aprotinin by means of subcutaneous sustained-release pellets normalized urinary serine protease activity and prevented sodium retention, as did treatment with the ENaC inhibitor amiloride. In the kidney cortex from nephrotic mice, immunofluorescence revealed increased apical γ-ENaC staining, normalized by aprotinin treatment. In Xenopus laevis oocytes heterologously expressing murine ENaC, aprotinin had no direct inhibitory effect on channel activity but prevented proteolytic channel activation. Thus, our study shows that volume retention in experimental nephrotic syndrome is related to proteolytic ENaC activation by proteasuria and can be prevented by treatment with aprotinin. Hence, inhibition of urinary serine protease activity might become a therapeutic approach to treat patients with nephrotic-range proteinuria.