Blood-borne fragments of fibronectin after thermal injury
P La Celle, FA Blumenstock and TM Saba
Department of Physiology and Cell Biology, Albany Medical College, NY.
Fibronectin is an adhesive protein that can promote phagocytosis and
endothelial cell adhesion. Plasma fibronectin declines following burn in
animals and patients, potentially due to its complexing with circulating
collagenous debris as well as its rapid binding to sites of tissue injury.
Such depletion of fibronectin initiates an opsonic deficiency of the
plasma. In view of the sensitivity of fibronectin to proteolytic enzymes,
an additional factor that could contribute to the decrease of plasma
opsonic activity after burn is the proteolytic fragmentation of fibronectin
in the blood. In the current study, we determined if fibronectin fragments
appear in the blood of anesthetized rats after a sublethal full-thickness
skin burn of 15% to 16% of body surface. Plasma fibronectin concentration
was quantified by enzyme- linked immunosorbent assay and the presence of
fibronectin fragments in plasma was determined by immunoblot analysis. All
blood was collected in an antiprotease mixture to yield final plasma
concentrations of 0.15% EDTA, 3mmol/L phenylmethylsulfonyl fluoride, and 3
mmol/L iodoacetate to prevent degradation of fibronectin after sampling.
Plasma fibronectin decreased 60% to 70% within 30 minutes post-burn, and
this low level lasted for at least 4 hours. Within 30 minutes post- burn,
two prominent fragments of fibronectin with a molecular weight of 110 +/-
2.2 kd and 122 +/- 3.3 Kd, respectively, were also detected in the plasma.
Peak concentration of these fragments was detected at 60 minutes post-burn,
but their level declined by 4 hours. By 4 hours, both bands appeared to
resolve into doublets. To rule out the possibility that the fragments of
fibronectin detected in the plasma were actually generated by coagulation
enzymes activated at the site of peripheral blood sampling, rapid direct
inferior vena cava sampling was performed, which also yield the presence of
the fragments. Thus, fibronectin fragments exist in the plasma following
thermal injury. Because fragments of fibronectin can compete with the
intact fibronectin molecule with respect to its ability to stimulate
macrophage phagocytosis, such fragments may contribute to altered systemic
phagocytic host defense following thermal injury. Furthermore, because
fibronectin peptides can compete with matrix fibronectin and impair
adhesion of cultured endothelial cells, such circulating fragments may also
influence the integrity of the vascular barrier.
Volume 77,
Issue 9,
pp. 2037-2041,
05/01/1991
Copyright © 1991 by The American Society of Hematology
