RT Journal Article
SR Electronic
T1 Myeloperoxidase and Eosinophil Peroxidase Inhibit the <em>in vitro</em> Endotoxin Activities of Lipopolysaccharide (LPS) and Lipid A and Increase Survival in an <em>in vivo</em> Mouse LPS LD90 model
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 499855
DO 10.1101/499855
A1 Robert C. Allen
A1 Mary L. Henery
A1 John C. Allen
A1 Roger J. Hawks
A1 Jackson T. Stephens, Jr
YR 2018
UL http://biorxiv.org/content/early/2018/12/22/499855.abstract
AB Myeloperoxidase (MPO) and eosinophil peroxidase (EPO) are cationic leukocyte haloperoxidases with potent microbicidal and detoxifying activities. MPO selectively binds and kills specific Gram-positive bacteria (GPB) and all Gram-negative bacteria (GNB) tested. Endotoxin, i.e., lipopolysaccharide (LPS) comprising a toxic Lipid A component, is a characteristic of all GNB. The possibility that haloperoxidases bind to and inhibit the endotoxin of GBN was considered and tested by contacting MPO and EPO with LPS and Lipid A and measuring for inhibition of endotoxin activity using either the in vitro gel or chromogenic Limulus amebocyte lysate (LAL) assays. Contacting MPO and EPO with LPS purified from Escherichia coli O55:B5 and with diphosphoryl Lipid A purified from E. coli F583 inhibited their endotoxin activities in proportion to the natural log of the MPO or EPO concentration. Although MPO is less cationic than EPO, MPO consistently demonstrated inhibition of endotoxin activity that is about threefold superior to EPO. Haloperoxidase enzymatic activity was not required for inhibition, and MPO haloperoxidase action did not increase endotoxin inhibition. MPO and EPO inhibition of LPS endotoxin activity was also measured using a 90% lethal dose (LD90) mouse model studied over a five-day period. Based on Kaplan Meier survival analysis, MPO significantly increased mouse survival in a dose-dependent manner. EPO was less effective. In conclusion, contacting MPO and EPO with LPS and Lipid A inhibits in vitro endotoxin activities, but inhibition is independent of haloperoxidase enzymatic function. MPO significantly increases mouse survival against LPS in an in vivo LD90 endotoxin model.