AJP - Lung Cellular and Molecular Physiology, Vol 269, Issue 2 248-L260, Copyright © 1995 by American Physiological Society
Fibronectin attenuates increased endothelial monolayer permeability after RGD peptide, anti-alpha 5 beta 1, or TNF-alpha exposure
T. M. Curtis, P. J. McKeown-Longo, P. A. Vincent, S. M. Homan, E. M. Wheatley and T. M. Saba
Department of Physiology and Cell Biology, Albany Medical College, New York 12208, USA.
Endothelial permeability can be altered by tumor necrosis factor-alpha
(TNF-alpha), a cytokine released in association with inflammation-induced
tissue injury. In the subendothelial matrix, fibronectin (Fn) influences
endothelial cell adhesion by the interaction of integrins with RGD and
non-RGD attachment sites in Fn. We compared the effect of TNF-alpha,
RGD-containing peptides (GRGDSP), or antibody to alpha 5 beta 1-integrins
on the protein permeability of bovine lung endothelial monolayers as
assessed by transendothelial 125I-labeled albumin clearance. We also
examined the influence of purified human plasma fibronectin (hFn) on this
permeability response. TNF-alpha, RGD peptides, and antibodies to alpha 5
beta 1-integrins elicited a dose- and time-dependent increase in protein
permeability as well as a reorganization and/or disruption of the
endogenous Fn matrix. A control RGE peptide (GRGESP) as well as
immunoglobulin G purified from nonimmune rabbit serum did not increase
endothelial protein permeability or disrupt the endogenous fibrillar Fn
pattern in the matrix. Likewise, a LDV peptide derived from the
alternatively spliced type III connecting segment (IIICS) within bovine Fn
(bFn) was unable to increase permeability of the bovine endothelial
monolayer. Co-incubation of purified soluble hFn (300 or 600 micrograms/ml)
with either TNF-alpha, the RGD peptide, or the antibody to alpha 5 beta
1-integrins prevented the increase in endothelial permeability. This
protective effect was also observed when the purified hFn (600
micrograms/ml) was added after the TNF-alpha-induced increase in
endothelial permeability had taken place. Immunofluorescent analysis
confirmed the incorporation of the hFn into the subendothelial matrix and
its co-localization with the endogenous bFn. The similar alteration of the
subendothelial matrix after exposure to RGD peptides, anti-alpha 5 beta
1-antibodies, or TNF-alpha, coupled with the ability for hFn to attenuate
the permeability increase typically elicited by all three agents, suggests
that disruption of cell-matrix interactions may be the mechanism by which
TNF-alpha alters endothelial permeability.
