Endothelial TLR4 and the microbiome drive cerebral cavernous malformations

Area of Science:

• Neuroscience
• Immunology
• Microbiology

Background:

• Cerebral cavernous malformations (CCMs) are cerebrovascular lesions causing stroke and seizures.
• Current treatments for CCMs are lacking, necessitating research into underlying pathogenic mechanisms.
• The upstream activators of the MEKK3-KLF2/4 signaling pathway implicated in CCMs remain largely unidentified.

Purpose of the Study:

• To identify upstream activators of the disease pathway in cerebral cavernous malformations.
• To investigate the role of endothelial Toll-like receptor 4 (TLR4) and the gut microbiome in CCM pathogenesis.
• To explore potential therapeutic strategies targeting the identified pathways.

Main Methods:

• Utilized mouse models of CCMs.
• Investigated the effects of Toll-like receptor 4 (TLR4) activation and blockade.
• Examined the impact of germ-free conditions and antibiotic treatment on CCM formation.
• Analyzed human genetic data for associations between polymorphisms and CCM lesion burden.

Main Results:

• Endothelial TLR4 activation by Gram-negative bacteria or lipopolysaccharide accelerates CCM formation.
• Genetic or pharmacologic blockade of TLR4 signaling prevents CCM development in mice.
• Germ-free mice are protected from CCM formation, and antibiotic treatment alters susceptibility.
• Human genetic polymorphisms in TLR4 and CD14 correlate with increased CCM lesion burden.

Conclusions:

• Endothelial TLR4 and the gut microbiome are critical stimulants of cerebral cavernous malformation formation.
• Targeting TLR4 signaling and the microbiome presents a novel therapeutic strategy for CCMs.
• Innate immune signaling and the microbiome play unexpected roles in cerebrovascular disease pathogenesis.