Human serum butyrylcholinesterase interactions with cisplatin and cyclophosphamide

Molecular and Computational Analysis Identify Statins as Selective Inhibitors of Human Butyrylcholinesterase

Cholinesterase enzyme family consists of acetylcholinesterase (AChE, 3.1.1.7), the major enzyme responsible for hydrolysis of acetylcholine at cholinergic synapses, and butyrylcholinesterase (BChE, 3.1.1.8) a detoxification enzyme of plasma. Statins are cholesterol-lowering medications utilized as protective medicaments in stroke and Alzheimer's disease, which cholinesterases are associated with. Thus, in this study, we characterized the inhibitory effects and mechanisms of common statins, rosuvastatin, atorvastatin, simvastatin and lovastatin, on human erythrocyte AChE and purified serum BChE using in vitro and in silico methods. Kinetic assays identified statins as selective non-competitive inhibitors of human serum BChE. The IC₅₀ and K_m values were found as 194.7 ± 55.2 µM and 1.03 ± 0.2 µM for rosuvastatin, 492.5 ± 55.1 µM and 7.2 ± 0.3 µM for atorvastatin, 14.2 ± 0.3 µM and 202.7 ± 23.2 µM for lovastatin, and 17.6 ± 0.1 µM and 207.2 ± 13.2 µM for simvastatin, respectively. The compounds did not display considerable inhibition against AChE. Molecular docking predicted good affinity and strong interactions with the BChE active site for atorvastatin and rosuvastatin. Current study identifies rosuvastatin as the most specific and selective inhibitor of human BChE among the tested statins. As selective inhibitors of BChE statins have the potential to be re-evaluated as medicaments due to their pleiotropic effects.

Novel activity of human BChE: Lipid hydrolysis

Acetylcholinesterase and butyrylcholinesterase (BChE) typically hydrolyze the neurotransmitter acetylcholine. The multifunctional enzyme BChE is associated with lipid metabolism through an undefined mechanism. Based on lipid-related studies and by comparing the structural similarities between lipases and BChE we postulated that the association of BChE with lipid metabolism could occur through hydrolytic activity. Utilizing purified BChE enzymes from different sources and several lipases as controls, the ability of BChE to hydrolyze 4-methylumbelliferyl (4-mu) palmitate is investigated. Using lectin affinity, inhibition kinetics, and molecular modeling, we demonstrated that purified BChE hydrolyzed 4-mu palmitate at pH 8 as effectively as wheat germ lipase. The affinity K_m value of the enzymes for 4-mu palmitate as substrate is found as 10.4 μM, 34.2 μM, 129.8 μM, and 186 μM for wheat germ lipase, purified BChE, pancreatic lipase, and commercial BChE, respectively. Analysis of the inhibitory effect of 4-mu palmitate on BChE using butyrylthiocholine as substrate revealed competitive inhibition with K_i and IC₅₀ values of 448 μM and 987.2 μM, respectively. The binding affinity and interactions of 4-mu palmitate with BChE and pancreatic lipase were predicted by molecular docking. These results suggest that BChE possesses lipolytic activity. The possibility that BChE hydrolyzes not only 4-mu palmitate but also other types of lipids will lead to a new approach to those disease states associated with increased BChE activity/expression.

Drop of Butyrylcholinesterase Activity after Cyclophosphamide Conditioning as a Predictive Marker of Liver Transplant-Related Complications and Its Correlation with Transplant-Related Mortality in Pediatric Hematopoietic Stem Cell Recipients

Transplant-related liver complications are a potentially fatal condition of hematopoietic stem cell transplantation (HSCT) in pediatric patients, actually representing one of the main factors involved in transplant-related mortality (TRM). The search for a specific marker capable of predicting the development of this condition is a relevant clinical issue. We have observed a variable reduction in serum butyrylcholinesterase (BChE) activity after a cyclophosphamide-containing conditioning regimen. This study aims to determine the cutoff of BChE activity reduction that might be a specific prognostic marker for liver complications after HSCT. Our results show that the reduction of BChE values below 2000 U/L the day before the transplantation is an indicator strongly associated with the transplant-related liver complications (p < 0.0001). The incidence of overall survival at 1 year was significantly higher in the BChE > 2000 U/L group compared to the BChE < 2000 U/L group (84.7% versus 58.5%, p < 0.001), while the TRM rate was significantly lower (8.1% versus 23.1%, p < 0.05). None of the patients undergoing prophylaxis with defibrotide developed severe liver complications. Starting defibrotide treatment at the first signs of hepatic dysfunction in patients with particularly low BChE activity levels reduces severe liver transplant-related complications.

Reversal of succinylcholine induced apnea with an organophosphate scavenging recombinant butyrylcholinesterase

BACKGROUND

Concerns about the safety of paralytics such as succinylcholine to facilitate endotracheal intubation limit their use in prehospital and emergency department settings. The ability to rapidly reverse paralysis and restore respiratory drive would increase the safety margin of an agent, thus permitting the pursuit of alternative intubation strategies. In particular, patients who carry genetic or acquired deficiency of butyrylcholinesterase, the serum enzyme responsible for succinylcholine hydrolysis, are susceptible to succinylcholine-induced apnea, which manifests as paralysis, lasting hours beyond the normally brief half-life of succinylcholine. We hypothesized that intravenous administration of plant-derived recombinant BChE, which also prevents mortality in nerve agent poisoning, would rapidly reverse the effects of succinylcholine.

METHODS

Recombinant butyrylcholinesterase was produced in transgenic plants and purified. Further analysis involved murine and guinea pig models of succinylcholine toxicity. Animals were treated with lethal and sublethal doses of succinylcholine followed by administration of butyrylcholinesterase or vehicle. In both animal models vital signs and overall survival at specified intervals post succinylcholine administration were assessed.

RESULTS

Purified plant-derived recombinant human butyrylcholinesterase can hydrolyze succinylcholine in vitro. Challenge of mice with an LD100 of succinylcholine followed by BChE administration resulted in complete prevention of respiratory inhibition and concomitant mortality. Furthermore, experiments in symptomatic guinea pigs demonstrated extremely rapid succinylcholine detoxification with complete amelioration of symptoms and no apparent complications.

CONCLUSIONS

Recombinant plant-derived butyrylcholinesterase was capable of counteracting and reversing apnea in two complementary models of lethal succinylcholine toxicity, completely preventing mortality. This study of a protein antidote validates the feasibility of protection and treatment of overdose from succinylcholine as well as other biologically active butyrylcholinesterase substrates.

Anandamide and its congeners inhibit human plasma butyrylcholinesterase. Possible new roles for these endocannabinoids?

Butyrylcholinesterase (BChE), a serine hydrolase biochemically related to the cholinergic enzyme Acetylcholinesterase (AChE), is found in many mammalian tissues, such as serum and central nervous system, but its physiological role is still unclear. BChE is an important human plasma esterase, where it has detoxifying roles. Furthermore, recent studies suggest that brain BChE can have a role in Alzheimer's disease (AD). The endocannabinoid arachidonoylethanolamide (anandamide) and other acylethanolamides (NAEs) are almost ubiquitary molecules and are physiologically present in many tissues, including blood and brain, where they show neuroprotective and anti-inflammatory properties. This paper demonstrates that they are uncompetitive (oleoylethanolamide and palmitoylethanolamide) or non competitive (anandamide) inhibitors of BChE (Ki in the range 1.32-7.48 nM). On the contrary, NAEs are ineffective on AChE kinetic features. On the basis of the X-ray crystallographic structure of human BChE, and by using flexible docking procedures, an hypothesis on the NAE-BChE interaction is formulated by molecular modeling studies. Our results suggest that anandamide and the other acylethanolamides studied could have a role in the modulation of the physiological actions of BChE.