Bacillus cereus Induces Permeability of an in vitro Blood Retinal Barrier

Department of Microbiology and Immunology, Oklahoma Center for Neuroscience, Department of Ophthalmology, Oklahoma Christian University, University of Oklahoma Health Sciences Center, Dean McGee Eye Institute, Oklahoma City, Oklahoma

^* To whom correspondence should be addressed. Email: michelle-callegan{at}ouhsc.edu.

	Abstract

Most Bacillus cereus toxin production is controlled by the quorum sensing-dependent, pleiotropic global regulator plcR, which contributes to the organism's virulence in the eye. The purpose of this study was to analyze the effects of B. cereus infection and plcR-regulated toxins on barrier function of the retinal pigment epithelium (RPE), the primary cell of the BRB. Human ARPE-19 cells were apically inoculated with wild type or quorum-sensing-deficient B. cereus and cell cytotoxicity was analyzed. PlcR-regulated toxins were not required for B. cereus-induced RPE cytotoxicity, but these toxins did increase the rate of cell death, primarily by necrosis. B. cereus infection of polarized RPE monolayers resulted in increased barrier permeability, independent of plcR-regulated toxins. Loss of both occludin and ZO-1 expression occurred by 8 h postinfection, but alterations in tight junctions appeared to precede cell cytotoxicity. Of several proinflammatory cytokines analyzed, only IL-6 was produced in response to B. cereus infection. These results demonstrate the deleterious effects of B. cereus infection on RPE barrier function and suggest that plcR-regulated toxins may not contribute significantly to RPE barrier permeability during infection.