Burn-induced heart failure: lipopolysaccharide binding protein improves burn and endotoxin-induced cardiac contractility deficits.
BACKGROUND
Burn injury is frequently complicated by bacterial infection. Following burn injury, exposure to endotoxin produces a measurable decrease in cardiomyocyte sarcomere contractile function. Lipopolysaccharide-binding protein (LBP) is an acute phase protein that potentiates the recognition of lipopolysaccharide (LPS) by binding to the lipid A moiety of LPS. In this study, we sought to determine the effect of recombinant rat LBP (rLBP) on cardiomyocyte sarcomere function after burn or sham injury in the presence or absence of bacterial endotoxin.


METHODS
Rats underwent a full-thickness 30% total body surface area scald or sham burn. At 24 h post-injury, cardiomyocytes were isolated, plated at 50,000 cells/well, and incubated with 50 μg/mL LPS and rLBP or chloramphenicol acetyltransferase (BVCat, an irrelevant control protein produced using the same expression system as rLBP) at concentrations by volume of 1%, 5%, 10%, and 30%. Subsets of cardiomyocytes were incubated with 5% rat serum or 30% rLBP and blocking experiments were conducted using an LBP-like synthetic peptide (LBPK95A). In vitro sarcomere function was measured using a variable rate video camera system with length detection software.


RESULTS
Co-culture of burn and sham injury derived cardiomyocytes with high-dose rLBP in the presence of LPS resulted in a significant reduction to the functional impairment observed in peak sarcomere shortening following exposure to LPS alone. LBP-like peptide LBPK95A at a concentration of 20 μg/mL, in the presence of LPS, abolished the ability of 30% rLBP and 5% rat serum to restore peak sarcomere shortening of cardiomyocytes isolated following burn injury to levels of function exhibited in the absence of endotoxin exposure.


CONCLUSIONS
In the setting of LPS challenge following burn injury, rLBP at high concentrations restores cardiomyocyte sarcomere contractile function in vitro. Rather than potentiating the recognition of LPS by the cellular LPS receptor complex, rLBP at high concentrations likely results in an inhibitory binding effect that minimizes the impact of endotoxin exposure on cardiomyocyte function following thermal injury.
Niederbichler
Andreas D
AD
Department of Surgery, University of Michigan Medical School, Ann Arbor, Michigan 48109-5033, USA. mhemmila@umich.edu
Hoesel
Laszlo M
LM
Ipaktchi
Kyros
K
Olivarez
Leovigildo
L
Erdmann
Martin
M
Vogt
Peter M
PM
Su
Grace L
GL
Arbabi
Saman
S
Westfall
Margaret V
MV
Wang
Stewart C
SC
Hemmila
Mark R
MR
D000209:Acute-Phase Proteins / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D002056:Burns / Q000150:complications* / Q000503:physiopathology; D002352:Carrier Proteins / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006333:Heart Failure / Q000209:etiology*; D020287:In Situ Nick-End Labeling; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009200:Myocardial Contraction / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D012518:Sarcomeres / Q000187:drug effects / Q000502:physiology; D000099231:Lipopolysaccharide-Binding Protein
D000209:Acute-Phase Proteins; D002352:Carrier Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D000099231:Lipopolysaccharide-Binding Protein