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Endothelial TLR4 and the microbiome drive cerebral cavernous malformations.

ABSTRACT: Cerebral cavernous malformations (CCMs) are a cause of stroke and seizure for which no effective medical therapies yet exist. CCMs arise from the loss of an adaptor complex that negatively regulates MEKK3-KLF2/4 signalling in brain endothelial cells, but upstream activators of this disease pathway have yet to be identified. Here we identify endothelial Toll-like receptor 4 (TLR4) and the gut microbiome as critical stimulants of CCM formation. Activation of TLR4 by Gram-negative bacteria or lipopolysaccharide accelerates CCM formation, and genetic or pharmacologic blockade of TLR4 signalling prevents CCM formation in mice. Polymorphisms that increase expression of the TLR4 gene or the gene encoding its co-receptor CD14 are associated with higher CCM lesion burden in humans. Germ-free mice are protected from CCM formation, and a single course of antibiotics permanently alters CCM susceptibility in mice. These studies identify unexpected roles for the microbiome and innate immune signalling in the pathogenesis of a cerebrovascular disease, as well as strategies for its treatment.

SUBMITTER: Tang AT

PROVIDER: S-EPMC5757866 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Endothelial TLR4 and the microbiome drive cerebral cavernous malformations.

Tang Alan T AT Choi Jaesung P JP Kotzin Jonathan J JJ Yang Yiqing Y Hong Courtney C CC Hobson Nicholas N Girard Romuald R Zeineddine Hussein A HA Lightle Rhonda R Moore Thomas T Cao Ying Y Shenkar Robert R Chen Mei M Mericko Patricia P Yang Jisheng J Li Li L Tanes Ceylan C Kobuley Dmytro D Võsa Urmo U Whitehead Kevin J KJ Li Dean Y DY Franke Lude L Hart Blaine B Schwaninger Markus M Henao-Mejia Jorge J Morrison Leslie L Kim Helen H Awad Issam A IA Zheng Xiangjian X Kahn Mark L ML

Nature 20170510 7654

Cerebral cavernous malformations (CCMs) are a cause of stroke and seizure for which no effective medical therapies yet exist. CCMs arise from the loss of an adaptor complex that negatively regulates MEKK3-KLF2/4 signalling in brain endothelial cells, but upstream activators of this disease pathway have yet to be identified. Here we identify endothelial Toll-like receptor 4 (TLR4) and the gut microbiome as critical stimulants of CCM formation. Activation of TLR4 by Gram-negative bacteria or lipop ...[more]

PMID: 28489816

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Project description:RATIONALE:Vascular malformations arise in vessels throughout the entire body. Causative genetic mutations have been identified for many of these diseases; however, little is known about the mutant cell lineage within these malformations. OBJECTIVE:We utilize an inducible mouse model of cerebral cavernous malformations (CCMs) coupled with a multicolor fluorescent reporter to visualize the contribution of mutant endothelial cells (ECs) to the malformation. METHODS AND RESULTS:We combined a Ccm3 mouse model with the confetti fluorescent reporter to simultaneously delete Ccm3 and label the mutant EC with 1 of 4 possible colors. We acquired Z-series confocal images from serial brain sections and created 3-dimensional reconstructions of entire CCMs to visualize mutant ECs during CCM development. We observed a pronounced pattern of CCMs lined with mutant ECs labeled with a single confetti color (n=42). The close 3-dimensional distribution, as determined by the nearest neighbor analysis, of the clonally dominant ECs within the CCM was statistically different than the background confetti labeling of ECs in non-CCM control brain slices as well as a computer simulation ( P<0.001). Many of the small (<100 ?m diameter) CCMs consisted, almost exclusively, of the clonally dominant mutant ECs labeled with the same confetti color, whereas the large (>100 ?m diameter) CCMs contained both the clonally dominant mutant cells and wild-type ECs. We propose of model of CCM development in which an EC acquires a second somatic mutation, undergoes clonal expansion to initiate CCM formation, and then incorporates neighboring wild-type ECs to increase the size of the malformation. CONCLUSIONS:This is the first study to visualize, with single-cell resolution, the clonal expansion of mutant ECs within CCMs. The incorporation of wild-type ECs into the growing malformation presents another series of cellular events whose elucidation would enhance our understanding of CCMs and may provide novel therapeutic opportunities.

Dataset Information

Endothelial TLR4 and the microbiome drive cerebral cavernous malformations.

Publications

Endothelial TLR4 and the microbiome drive cerebral cavernous malformations.

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