Surfactant proteins A and D inhibit the growth of Gram-negative bacteria by increasing membrane permeability
Huixing Wu, … , Kwang Sik Kim, Francis X. McCormack
Huixing Wu, … , Kwang Sik Kim, Francis X. McCormack
Published May 15, 2003
Citation Information: J Clin Invest. 2003;111(10):1589-1602. https://doi.org/10.1172/JCI16889.
View: Text | PDF
Article Pulmonology

Surfactant proteins A and D inhibit the growth of Gram-negative bacteria by increasing membrane permeability

Abstract

The pulmonary collectins, surfactant proteins A (SP-A) and D (SP-D), have been reported to bind lipopolysaccharide (LPS), opsonize microorganisms, and enhance the clearance of lung pathogens. In this study, we examined the effect of SP-A and SP-D on the growth and viability of Gram-negative bacteria. The pulmonary clearance of Escherichia coli K12 was reduced in SP-A–null mice and was increased in SP-D–overexpressing mice, compared with strain-matched wild-type controls. Purified SP-A and SP-D inhibited bacterial synthetic functions of several, but not all, strains of E. coli, Klebsiella pneumoniae, and Enterobacter aerogenes. In general, rough E. coli strains were more susceptible than smooth strains, and collectin-mediated growth inhibition was partially blocked by coincubation with rough LPS vesicles. Although both SP-A and SP-D agglutinated E. coli K12 in a calcium-dependent manner, microbial growth inhibition was independent of bacterial aggregation. At least part of the antimicrobial activity of SP-A and SP-D was localized to their C-terminal domains using truncated recombinant proteins. Incubation of E. coli K12 with SP-A or SP-D increased bacterial permeability. Deletion of the E. coli OmpA gene from a collectin-resistant smooth E. coli strain enhanced SP-A and SP-D–mediated growth inhibition. These data indicate that SP-A and SP-D are antimicrobial proteins that directly inhibit the proliferation of Gram-negative bacteria in a macrophage- and aggregation-independent manner by increasing the permeability of the microbial cell membrane.

Authors

Huixing Wu, Alexander Kuzmenko, Sijue Wan, Lyndsay Schaffer, Alison Weiss, James H. Fisher, Kwang Sik Kim, Francis X. McCormack

×

Figure 9

Options: View larger image (or click on image) Download as PowerPoint
Growth inhibition of smooth and rough laboratory strains of E. coli and ...
Growth inhibition of smooth and rough laboratory strains of E. coli and other Gram-negative isolates by pulmonary collectins. The effect of hSP-A (100 μg/ml) and rSP-D (10 μg/ml) on 3H-uridine uptake by laboratory strains and clinical isolates was assessed (a) and correlated with the LPS profile on SDS-PAGE analysis (b). The following rough E. coli strains are shown: an E. coli K12 strain containing an empty pGEM vector (F9+), and isogenic strains with pGEM-driven expression of glycosyltransferases that add two (OS4) and five (OS7) sugars to the core oligosaccharide; a K12 mutant with a defective lipid A missing an acyl chain (MLK217); E. coli J5; two luminescent E. coli HB101 strains (101a and 101b); and LCD25, an E. coli K12 acetate auxotroph. The following smooth E. coli strains are shown: 0111:K58 (B4) and 055:K59 (B5). Clinical isolates shown include four E. coli isolates, three smooth variants (Ec1, Ec2, and Ec3) and one rough variant (Ec4); two K. pneumoniae strains (Kp1 and Kp2); and two E. aerogenes strains (Ea1 and Ea2). Data shown are mean ± SEM; n = 3; *P < 0.01, #P < 0.05.