Impaired fibrinolytic activity within the lung is a common manifestation of acute and chronic inflammatory lung diseases. Because the fibrinolytic system is active during repair processes that restore injured tissues to normal, reduced fibrinolytic activity may contribute to the subsequent development of pulmonary fibrosis. To examine the relationship between the fibrinolytic system and pulmonary fibrosis, lung inflammation was induced by bleomycin in transgenic mice that either overexpressed or were completely deficient in murine plasminogen activator inhibitor-1 (PAI-1). 2 wk after 0.075 U of bleomycin, the lungs of transgenic mice overexpressing PAI-1 contained significantly more hydroxyproline (118 Ϯ 8 g) than littermate controls (70.5 Ϯ 8 g, P Ͻ 0.005). 3 wk after administration of a higher dose of bleomycin (0.15 U), the lung hydroxyproline content of mice completely deficient in PAI-1 (49 Ϯ 8 g) was not significantly different ( P ϭ 0.63) than that of control animals receiving saline (37 Ϯ 1 g), while hydroxyproline content was significantly increased in heterozygote (77 Ϯ 12 g, P ϭ 0.06) and wild-type (124 Ϯ 19 g, P Ͻ 0.001) littermates. These data demonstrate a direct correlation between the genetically determined level of PAI-1 expression and the extent of collagen accumulation that follows inflammatory lung injury. These results strongly support the hypothesis that alterations in fibrinolytic activity influence the extent of pulmonary fibrosis that occurs after inflammatory injury.

Three prokaryotic-derived probes to identify and study the temporal expression of oligo-or poly(sialic acid) also recognized rat brain membranes, further substantiating the presence of poly(sialic acid) in rat brain. This conclusion was confirmed by using a mutant of E. coli K1 that was defective in the synthesis of poly(sialic acid) and could only transfer sialic acid to exogenous acceptors of oligo-or poly(sialic acid). Sialyl polymer synthesis was restored in the mutant when brain membranes were added as exogenous acceptor.Sialic acid occurs primarily as the terminal, nonreducing sugar on N-asparaginyl-linked glycoproteins often attached to galactosyl residues of bi-, tri-, or tetraantennary sugar chains. Rarely, however, sialic acid exists internally to form polysialosyl chains of various lengths. A well-characterized poly(sialic acid) is a capsular polysaccharide, the K1 anti-

One of the major obstacles to pulmonary-directed gene therapy using adenoviral vectors is the induction of inflammation. We investigated whether the adenoviral particles that constitute the initial inoculum can serve as an inflammatory stimulus, independent of their ability to express genes that they contain. Viral particles were prepared that are defective in gene expression by (i) isolating particles that have incomplete genomes by selecting those that have buoyant densities on CsCl density gradients lighter than complete viruses; and (ii) cross-linking viral DNA by exposure to ultraviolet light in the presence of 8-methoxypsoralen. The defective particles retained their icosahedral appearance when viewed by electron microscopy but lost their plaque-forming ability on 293 cells. High doses of intact, incomplete, or inactivated viral particles were instilled intratracheally into CBA/J mice, and after 6 days the amount of inflammation was quantified by counting inflammatory cells contained within lung tissue. We found that the inflammatory responses induced by the incomplete or inactivated viral vectors were quantitatively similar to those caused by intact, competent viral vectors. We conclude that high doses of adenoviral vectors that are used for gene therapy can induce pulmonary inflammation, independent of expressing the genes they contain.

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