Klebsiella pneumoniae induces an inflammatory response in human retinal-pigmented epithelial cells.
OBJECTIVE
The retinal pigment epithelium (RPE) is a barrier to Klebsiella pneumoniae infection in endogenous endophthalmitis. Nevertheless, the inflammatory response of RPE cells upon interaction with this pathogen has not been studied. Here we tested the hypothesis that K. pneumoniae induces an inflammatory response in human retinal epithelial cells.


METHODS
In this study we set out to investigate the effects of whole K. pneumoniae and of its lipopolysaccharide on RPE cells in vitro using bacterial invasion and cytotoxicity assays, fluorescent microscopy and ELISA. For that, we utilized K. pneumoniae strain ATCC 43816 and the continuous human retinal-pigmented epithelial cell line ARPE-19.


RESULTS
Stimulation of ARPE-19 with live K. pneumoniae for 24h induced a 31.5-fold (p=0.0132) increase in IL-6 and 6.5-fold (p=0.0004) increase in MCP-1 levels compared to the non-infected control cells. Purified K. pneumoniae LPS (1μgml(-1)) also induced cytokine levels, MCP-1 (1.7-fold upregulation; p=0.0006) and IL-6 (1.3-fold upregulation, p=0.065). The tested K. pneumoniae strain ATCC 43816 did not have a significant effect on the viability of ARPE-19 cells (11% decrease, p=0.096) and showed a low ability to invade the cells.


CONCLUSIONS
Both whole live K. pneumoniae and K. pneumoniae LPS exert a strong pro-inflammatory effect on retinal pigmented epithelial cells, consistent with clinical manifestations of disease. Bacterial pro-inflammatory effects are not likely related to host cell invasion. This is the first investigation of the interactions of a major endogenous endophthalmitis pathogen, K. pneumoniae with human retinal pigmented epithelial cells.
Section of Oral and Diagnostic Sciences, Columbia University College of Dental Medicine, 630 W 168 St., P&S Box 20, New York, NY 10032-3725, USA. andreas.pollreisz@gmail.com
Andreas
A
Pollreisz
Brian
B
Rafferty
Emil
E
Kozarov
Evanthia
E
Lalla
D002460:Cell Line; D018932:Chemokine CCL2 / Q000096:biosynthesis; D054884:Host-Pathogen Interactions / Q000276:immunology*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D007710:Klebsiella Infections / Q000276:immunology / Q000382:microbiology*; D007711:Klebsiella pneumoniae; D008070:Lipopolysaccharides / Q000276:immunology; D055213:Retinal Pigment Epithelium / Q000276:immunology / Q000382:microbiology*; D012173:Retinitis / Q000276:immunology / Q000382:microbiology*
C111835:CCL2 protein, human; D018932:Chemokine CCL2; D015850:Interleukin-6; D008070:Lipopolysaccharides