# Childhood arterial ischemic stroke: role of TLR4-neutrophil axis in injury and hemorrhagic transformation

> **NIH NIH R56** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2024 · $523,382

## Abstract

Abstract
Reperfusion of cerebral microcirculation after cerebral artery blockage can have dual roles —
neuroprotection if reperfusion is early but adverse events and increased neurological disability if
reperfusion is delayed. Mechanical thrombectomy has revolutionized care in adult stroke and is of proven
benefit in multiple randomized clinical trials with time windows gradually increasing from 4.5 to 24 or more
hours. In children with arterial ischemic stroke, retrospective case series suggest safety and possible
benefit of thrombectomy, however selection bias, lack of non-treated control outcomes and insufficient
knowledge of when it is safe to remove thrombus in childhood arterial ischemic stroke (CAIS) raise
concerns on whether children can safely benefit from endovascular thrombectomy. Knowledge of
mechanisms of adverse effects of late recanalization/thrombectomy in CAIS is essentially inexistent. We
will fill this gap in knowledge using novel CAIS mice models and explore novel therapeutic agent.
Central Hypothesis: TLR4-neutrophil axis mediates injury and hemorrhagic transformation in
childhood arterial ischemic stroke (CAIS).
In a model of late reperfusion/recanalization in juvenile male and female mice, following 8h transient
middle cerebral artery occlusion, we will examine whether pharmacologic neutrophil elastase (NE)
inhibition attenuates the magnitude of hemorrhagic transformation, brain edema, injury, the inflammatory
response, and alters leukocyte phenotypes. Using multimodality MRI, we will examine effects on
secondary hemorrhagic transformation and chronic injury in relation to new vessel formation, vessel
complexity in vivo, myelination and long-term functional outcomes. We will examine efficacy of NE
inhibition in a model of local thrombus formation in the juvenile brain (Aim 1). We will use loss-of-function
experiments to determine if disrupted TLR4 signaling in neutrophils attenuates acute hemorrhagic
transformation and inflammation and improves long-term functional outcomes of CAIS (Aim 2). We will
examine beneficial effects of ApTOLL, a novel TLR4-binding DNA aptamer shown protective in a Ib/IIa
acute adult stroke clinical trial, and determine if ApTOLL protects by disrupting TLR4 signaling in
neutrophils and altering neutrophil phenotypes (Aim 3).
 The proposed studies will serve as proof-of-principle in CAIS models in defining the mechanisms of
hemorrhagic transformation following late recanalization or thrombus formation. The proposal is novel
conceptually, uses novel animal models and state-of-the art methodologies, and examines if ApTOLL, the
first successful neuroprotectant in humans in a long time, can protect children who suffer stroke and
alleviate adverse effects of late recanalization.

## Key facts

- **NIH application ID:** 11045096
- **Project number:** 2R56NS103483-06
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Zinaida S Vexler
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $523,382
- **Award type:** 2
- **Project period:** 2018-04-15 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11045096

## Citation

> US National Institutes of Health, RePORTER application 11045096, Childhood arterial ischemic stroke: role of TLR4-neutrophil axis in injury and hemorrhagic transformation (2R56NS103483-06). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/11045096. Licensed CC0.

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