Listeriolysin O mediates cytotoxicity against human brain microvascular

Authors: ZHANG, TING - Mississippi State University; BAE, DONGRYEOUL - Mississippi State University; WANG, CHINLING - Mississippi State University

Submitted to: FEMS Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary: Targeting and direct invasion of central nervous system (CNS) by L. monocytogenes has been documented by electron microscopic observation and in vitro experiments. Large numbers of bacteria circulate in the blood are needed to allow L. monocytogenes to invade CNS, Our data showed that a toxin, listeriolysin increased the permeability of the capillary walls and facilitated the penetration of brain cells by L. monocytogenes. This is a first report reveals a novel route of CNS infection and importance role of listeriolysin during the infection. Understanding this mechanism will help understand the biology and symptoms as infected this pathogen, and help prevent the infection and transmission of the pathogens in human population.

Technical Abstract: Penetration of the brain microvascular endothelial layer is one of the routes L. monocytogenes use to breach the blood-brain barrier. Because host factors in the blood severely limit direct invasion of human brain microvascular endothelial cells (HBMECs) by L. monocytogenes, alternative mechanisms might be used by this bacterium to penetrate the endothelial cell layer. In this study, we evaluated the cytotoxicity of proteins secreted by L. monocytogenes against HBEMCs using a live/dead staining method. Interestingly, the integrity of the plasma membrane of HBMECs was impaired by proteins secreted by the EGD wild type strain but not proteins secreted by the isogenic 'prfA strain. Therefore, we investigated the cytotoxicity of proteins secreted by several isogenic mutant strains ('plcA, 'mpl, and 'hly) incapable of producing the prfA-regulated bacterial products PlcA, Mpl, and LLO, respectively. Results from both fluorescent microscopy and flow cytometry analyses showed that proteins secreted by the 'hly strain were not cytotoxic to HBMECs, whereas those secreted by the 'plcA and 'mpl strains were cytotoxic. These results suggest that LLO-mediated cytotoxicity against brain microvascular endothelial cells enables L. monocytogenes cells to effectively penetrate the brain microvascular endothelial layer.