LUNG MATRIX DEPOSITION OF NORMAL AND ALKYLATED PLASMA FIBRONECTIN - RESPONSE TO POSTSURGICAL SEPSIS

Plasma fibronectin (Fn) can both enhance phagocytic clearance of micro particulate debris by macrophages as well as incorporate it into the l ung extracellular matrix (ECM). The goal of this study was to document that N-ethylmaleimide (NEM)-treated human plasma Fn (HFn) would lose its ability to incorporate into the lung ECM in vivo even though it wo uld retain its ability to stimulate test particle phagocytosis and bin d to fibrin. Using dual-label immunofluorescence, we compared the lung deposition of purified normal HFn and NEM-alkylated HFn (NEM-HFn) aft er their intravenous injection into postoperative nonbacteremic and ba cteremic sheep in relationship to the localization of endogenous sheep Fn. Two days after a sterile surgical thoracotomy, sheep were infused with either 5 x 10(8) Pseudomonas aeruginosa (postsurgical bacteremic model) or the diluent (nonbacteremic model). They also received a bol us 100-mg injection (5 min) of either HFn or NEM-HFn. Analysis of seri al lung biopsies harvested at 2-h intervals demonstrated little deposi tion of NEM-HFn compared with HFn in the lung interstitial matrix of p ostoperative nonbacteremic sheep. In contrast, enhanced deposition of both HFn and NEM-HFn was observed in the lungs of postoperative bacter emic sheep. However, in the lungs of bacteremic sheep, HFn displayed a diffuse fibrillar deposition pattern in the lung characteristic of EC M incorporation, whereas the enhanced NEM-HFn deposition, especially i n the interstitial ECM region of the lung, was primarily focal and pun ctate, with very Little fibrillar incorporation. Immunofluorescent ana lysis with antibodies specific to fibrinogen, Fn, and lung macrophage surface antigens coupled with immunoperoxidase staining for HFn antige n revealed that the punctate fluorescence pattern was due to both the binding of HFn to fibrin and its colocalization with inflammatory cell s. Thus treatment of plasma Fn with low concentrations of NEM mill lim it its normal in vivo fibrillar incorporation into the interstitial EC M region of the lung.