Identification of Soluble Supramolecular FN-fibrin Complexes in Human Plasma

Abstract

SDS-agarose FN immunoblotting of 257 normal and pathological human plasma samples revealed the ladder pattern of multiple plasma FN bands which corresponded to FN monomer and dimer, and 5 FN-fibrin bands with increasing molecular masses. The FN-fibrin bands of about 750 kDa, 1000 kDa, 1300 kDa, 1600 kDa, and 1900 kDa appeared more frequently and in significantly higher relative amounts in the pathological samples (P < 0.000) than in relatively healthy individuals. The revealing of high-molecular FN-fibrin complexes by SDS-agarose FN immunobloting might have the potential to become a laboratory biomarker of some diseases in which the coagulation system is triggered.

Occurrence of soluble supra-molecular FN–fibrin complexes in the plasma of children with recurrent respiratory infection

“…We have previously shown that the FN-fibrin complexes, particularly those with lower molecular masses of $750 kDa and $1000 kDa, can occur in some normal samples taken from physically healthy individuals and having normal biochemical and haematological parameters. 15 Whilst RRI can cause either acute, chronic or transitional destruction states of the structure of the respiratory epithelium, our results show the molecular consequences of respiratory infections at the level of activation of inflammatory and coagulation systems. The occurrence of a 280-kDa FN-fibrin reduced form and multiple FN-fibrin complexes seems to be a dynamic and transient process related to pathophysiological events probably connected with normal haemostasis.…”

“…As discussed earlier, 15 these FN-fibrin complexes differed from the adjacent one by $280 kDa, which corresponded to the mass of one Note: The FN reduced forms (240 kDa and 280 kDa) were detected by Western immunoblotting (Figure 1). RRI groups were stratified as described in legend to Table 1 …”

“…6,21 The FN can be covalently crosslinked by factor XIII a through an isopeptide bond to the carboxyl terminal compact and flexible aC-domain of fibrin, 21,22 creating soluble FN-fibrin hetero-complexes easily revealed by agarose immunoblotting. 15 In contrast, in healthy individuals, FN and fibrinogen circulate in the blood independently (binding sites on fibrinogen for FN are concealed); thus they are unable to interact and therefore the FN-fibrin complexes should not be observed. 21 Indeed, such FN-fibrin complexes were absent in most of the normal adult samples, 15 although in this study, they were present in a few samples taken from children in the normal group, Group5.…”

“…15 In contrast, in healthy individuals, FN and fibrinogen circulate in the blood independently (binding sites on fibrinogen for FN are concealed); thus they are unable to interact and therefore the FN-fibrin complexes should not be observed. 21 Indeed, such FN-fibrin complexes were absent in most of the normal adult samples, 15 although in this study, they were present in a few samples taken from children in the normal group, Group5. However, it should be realized that samples within our normal group were collected from children visiting a doctor for noninfection events.…”

“…5 These FN forms were identified as the subunits of soluble supra-molecular plasma FN-fibrin complexes, which were easily revealed by SDS-agarose immunoblotting. 15 The present study was undertaken to determine whether the soluble supra-molecular FN-fibrin complexes occurred in the plasma of children suffering from RRI. The frequency of occurrence and relative amounts of supra-molecular FN-fibrin forms in the plasma of children with RRI, during the period of recovery, stratified by immunoglobulin concentration and number of natural killer (NK) cells were compared to their frequency in those children with acute infection and to their frequency in healthy children.…”