ABSTRACT
Aberrant elevation in the levels of the pro-inflammatory cytokine interleukin-1β (IL-1β) contributes to neuroinflammatory diseases. Blood–brain barrier (BBB) dysfunction is a hallmark phenotype of neuroinflammation. It is known that IL-1β directly induces BBB hyperpermeability but the mechanisms remain unclear. Claudin-5 (Cldn5) is a tight junction protein found at endothelial cell–cell contacts that are crucial for maintaining brain microvascular endothelial cell (BMVEC) integrity. Transcriptional regulation of Cldn5 has been attributed to the transcription factors β-catenin and forkhead box protein O1 (FoxO1), and the signaling molecules regulating their nuclear translocation. Non-muscle myosin light chain kinase (nmMlck, encoded by the Mylk gene) is a key regulator involved in endothelial hyperpermeability, and IL-1β has been shown to mediate nmMlck-dependent barrier dysfunction in epithelia. Considering these factors, we tested the hypothesis that nmMlck modulates IL-1β-mediated downregulation of Cldn5 in BMVECs in a manner that depends on transcriptional repression mediated by β-catenin and FoxO1. We found that treating BMVECs with IL-1β induced barrier dysfunction concomitantly with the nuclear translocation of β-catenin and FoxO1 and the repression of Cldn5. Most importantly, using primary BMVECs isolated from mice null for nmMlck, we identified that Cldn5 repression caused by β-catenin and FoxO1 in IL-1β-mediated barrier dysfunction was dependent on nmMlck.
Footnotes
Competing interests
The authors declare no competing interests.
Author contributions
This study was conceived and designed by R.S.B.J. and S.Y.Y. Experiments were designed, executed and interpreted by all listed authors. The manuscript was prepared by R.S.B.J., R.J.H. and S.Y.Y.
Funding
This work was supported in part by the National Institutes of Health Research Project Grants [grant numbers GM097270, HL070752, HL096640 and HL061507]. Deposited in PMC for release after 12 months.
Supplementary material available online at http://jcs.biologists.org/lookup/suppl/doi:10.1242/jcs.144550/-/DC1
- Received October 11, 2013.
- Accepted January 12, 2014.
- © 2014. Published by The Company of Biologists Ltd