Researchers from Japan and the United States have identified a potential contributor to the earliest stages of brain injury after subarachnoid hemorrhage, a severe form of stroke that commonly follows the rupture of a cerebral aneurysm. Their study points to RAGE, short for receptor for advanced glycation end products, in neutrophils as a driver of inflammation and injury around cerebral arteries after the bleed.
The work, led by researchers at Kanazawa University and published in the Journal of Cerebral Blood Flow & Metabolism, focuses on events that can continue to damage the brain even after the source of bleeding has been secured. The results were reported in mice, so they do not establish a treatment for people. But they offer a more detailed account of how early vascular dysfunction and inflammation may be linked after this type of hemorrhagic stroke.
A dangerous period after bleeding
Subarachnoid hemorrhage, or SAH, occurs when bleeding enters the space surrounding the brain. It is often caused by a ruptured cerebral aneurysm and can produce sudden, serious neurological damage. Managing the initial bleeding is essential, but it does not necessarily end the threat to the brain.
Reduced cerebral blood flow, narrowing of cerebral arteries known as vasospasm, inflammation and brain swelling can all contribute to worsening neurological outcomes after SAH. The connections among these early processes have remained incompletely understood.
The new research builds on earlier work by the same group. In 2023, the researchers reported that sympathetic hyperactivity immediately after SAH could impair cerebral circulation and worsen neurological outcome. Their latest study proposes that a subsequent inflammatory phase follows that immediate response.
In the researchers’ model, sympathetic stimulation and alpha1-mediated constriction of cerebral arteries occur immediately after hemorrhage. A neutrophil RAGE-dependent inflammatory injury then develops during the hyperacute-to-acute period. That sequence matters because it suggests there may be multiple early processes to understand, rather than a single mechanism operating from the moment bleeding begins.
What the mouse experiments found
The team compared outcomes after SAH in wild-type mice and in mice lacking RAGE. In wild-type animals, SAH was associated with neurological deterioration, pronounced vasospasm in major cerebral arteries and a substantial reduction in cortical vascular perfusion.
RAGE-knockout mice showed markedly better neurological function and cortical perfusion, while arterial vasospasm was reduced. These findings support the idea that RAGE signaling is involved in the vascular and neurological damage observed in the model.
The researchers also examined neutrophils, immune cells that can respond rapidly to injury and inflammation. They found that MPO-positive neutrophils accumulated around cerebral arteries early after SAH, with a prominent rise by six hours. This perivascular accumulation was strongly suppressed in RAGE-knockout mice.
That observation is central to the study’s proposed mechanism. Rather than treating inflammation as a broad and undifferentiated consequence of brain bleeding, the researchers identify a specific immune-cell-associated pathway that may help connect early inflammation to arterial narrowing, impaired cortical circulation and neurological dysfunction.
Why RAGE is of interest
RAGE is the receptor for advanced glycation end products. In this study, the emphasis is not simply on whether the receptor is present after injury, but on its role in neutrophils during the early response to SAH.
The results suggest that neutrophil RAGE promotes the buildup of neutrophils around cerebral arteries. In the reported mouse experiments, that process was associated with vasospasm and loss of cortical perfusion. When RAGE was absent, neutrophil accumulation around the vessels was reduced and several measures of injury improved.
This makes RAGE a candidate for further research into early cerebrovascular injury after SAH. It does not mean that blocking RAGE will necessarily improve outcomes in patients. The evidence described in the study comes from animal experiments, and translating a mechanism from mice to clinical care requires additional work.
Still, the findings narrow the question for future studies. Researchers can investigate whether the same timing and cellular behavior occur in people, whether RAGE activity can be measured in clinically useful ways, and whether intervening in this pathway can be done safely without disrupting needed immune responses.
From mechanism to possible treatment research
The most immediate value of the study is mechanistic. SAH can trigger a cascade of harmful events, and the report places neutrophil RAGE within a proposed timeline: immediate sympathetic and arterial effects are followed by inflammatory vascular injury during the early acute phase.
A clearer timeline can help researchers decide when to test interventions. If perivascular neutrophil accumulation rises early, as it did in the mouse model, any strategy directed at this process may need to be evaluated in a correspondingly early treatment window. The research also raises the possibility that treatments aimed at circulation and treatments aimed at inflammatory injury could address different parts of the same evolving problem.
For now, the study should be read as a preclinical advance rather than a change in medical practice. It identifies associations and improvements in RAGE-deficient mice after experimentally modeled SAH. It does not demonstrate that a RAGE-targeted therapy is available, effective or safe for people who experience subarachnoid hemorrhage.
Even so, the work adds a specific target to the search for ways to limit damage after aneurysmal bleeding. By linking neutrophil RAGE with early arterial inflammation, vasospasm, perfusion loss and neurological dysfunction, the researchers have outlined a pathway that can now be tested more directly in future laboratory and clinical research.
This article is based on reporting by Medical Xpress. Read the original article.
Originally published on medicalxpress.com
