# TLR4 and the microbiome in CCM disease

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2021 · $539,561

## Abstract

Cerebral cavernous malformation (CCM) is a cerebrovascular disease that affects over
200,000 individuals in the US and is a common cause of stroke and seizure in young
individuals. There are presently no medical therapies for CCM disease, and treatment is
limited to surgical resection and anti-seizure medications. We have recently
demonstrated that CCMs arise due to a gain of MEKK3 signaling and increased
expression of the KLF2 and KLF4 transcription factors in CCM-deficient brain endothelial
cells (ECs). These studies reveal the downstream signaling mechanism impacted in
CCM disease, but they do not identify strong therapeutic targets or address the question
of what activates MEKK3 in brain ECs. Our preliminary studies demonstrate that TLR4
is a critical upstream activator of endothelial MEKK3-KLF signaling that is required for
CCM formation, and that gram negative bacteria (GNB) in the gut microbiome are the
key in vivo ligand for this pathway in the mouse neonatal CCM model. Genetic analysis
of human CCM patients by our co-investigator Dr. Helen Kim has independently
identified TLR4 and its co-receptor CD14 as genes associated with CCM lesion number,
suggesting that our mouse findings extend to human CCM disease. This proposal will
further test the role of endothelial TLR4 signaling and the gut microbiome in CCM
disease pathogenesis using mouse and human studies. Aim 1 will (i) test the role of
TLR4 during CCM formation in adult mice, (ii) determine whether blocking ant-TLR4 and
anti-CD14 antibodies prevent CCM formation in the mouse model, (iii) use mouse
genetic approaches to determine the pathway by which TLR4 activates MEKK3 during
CCM formation, and (iv) apply genetic approaches to fully interrogate the TLR4-MEKK3-
KLF pathway in human patients with CCM disease due to a common mutation in KRIT1.
Aim 2 will test the role of GNB and the gut microbiome in CCM pathogenesis by (i)
determining whether CCM lesions arise in germ-free animals, (ii) defining microbiomes
that confer resistance or susceptibility to CCM disease in mice, and (iii) testing whether
breakdown of the gut epithelial barrier accelerates CCM formation in mice. These
studies will significantly expand our understanding of the molecular and physiologic
basis of CCM pathogenesis, and lay the foundation for translating these discoveries to
new therapies for CCM disease based on blocking TLR4 signaling (for which FDA
approved agents already exist) or altering the gut microbiome.

## Key facts

- **NIH application ID:** 10152688
- **Project number:** 5R01NS100949-05
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** MARK L KAHN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $539,561
- **Award type:** 5
- **Project period:** 2017-07-01 → 2022-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10152688

## Citation

> US National Institutes of Health, RePORTER application 10152688, TLR4 and the microbiome in CCM disease (5R01NS100949-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10152688. Licensed CC0.

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