Bacterial induction of Snail1 contributes to blood-brain barrier disruption
Brandon J. Kim, … , David Traver, Kelly S. Doran
Brandon J. Kim, … , David Traver, Kelly S. Doran
Published May 11, 2015
Citation Information: J Clin Invest. 2015;125(6):2473-2483. https://doi.org/10.1172/JCI74159.
View: Text | PDF
Research Article Vascular biology

Bacterial induction of Snail1 contributes to blood-brain barrier disruption

Abstract

Bacterial meningitis is a serious infection of the CNS that results when blood-borne bacteria are able to cross the blood-brain barrier (BBB). Group B Streptococcus (GBS) is the leading cause of neonatal meningitis; however, the molecular mechanisms that regulate bacterial BBB disruption and penetration are not well understood. Here, we found that infection of human brain microvascular endothelial cells (hBMECs) with GBS and other meningeal pathogens results in the induction of host transcriptional repressor Snail1, which impedes expression of tight junction genes. Moreover, GBS infection also induced Snail1 expression in murine and zebrafish models. Tight junction components ZO-1, claudin 5, and occludin were decreased at both the transcript and protein levels in hBMECs following GBS infection, and this repression was dependent on Snail1 induction. Bacteria-independent Snail1 expression was sufficient to facilitate tight junction disruption, promoting BBB permeability to allow bacterial passage. GBS induction of Snail1 expression was dependent on the ERK1/2/MAPK signaling cascade and bacterial cell wall components. Finally, overexpression of a dominant-negative Snail1 homolog in zebrafish elevated transcription of tight junction protein–encoding genes and increased zebrafish survival in response to GBS challenge. Taken together, our data support a Snail1-dependent mechanism of BBB disruption and penetration by meningeal pathogens.

Authors

Brandon J. Kim, Bryan M. Hancock, Andres Bermudez, Natasha Del Cid, Efren Reyes, Nina M. van Sorge, Xavier Lauth, Cameron A. Smurthwaite, Brett J. Hilton, Aleksandr Stotland, Anirban Banerjee, John Buchanan, Roland Wolkowicz, David Traver, Kelly S. Doran

×

Figure 2

GBS disrupts tight junctions of brain endothelium.

Options: View larger image (or click on image) Download as PowerPoint
GBS disrupts tight junctions of brain endothelium. GBS decreased transcr...
GBS decreased transcript abundance of zo-1 (A), occludin (B), and claudin 5 (C) in confluent hBMECs (A and B) or bEND3 (C) following GBS infection for 5 hours at an MOI of 10. qPCR experiments were performed at least 3 times in triplicate. Error bars represent the SEM of at least 3 biological replicates (A–C). Protein levels of ZO-1 and occludin in hBMECs (D, F, and G) or bEND3 (E and H) during GBS infection were determined by Western blot analysis. Lysates were probed for ZO-1, occludin, or claudin 5. Western blot analysis was normalized to GAPDH (D–H). Experiments were performed at least 3 times in triplicate. Error bars represent the SD of a representative experiment (F–H). hBMECs were stained for ZO-1 and visualized by immunofluorescence (scale bars: 20 μm) (I). Mice (n = 8/group) were infected i.v. with GBS or vehicle control. Upon sacrifice, brain tissue was collected and endothelial cells isolated for RNA extraction and qPCR analysis (J and K). Student’s t test was used for image analysis. *P < 0.05; **P < 0.01; ***P < 0.001.