Neuroimmune phenotypes in brain aneurysms and neurodegenerative diseases.

Aneurysmal subarachnoid hemorrhage is a devastating neurological disease that occurs downstream of abnormal dilation of cerebral vessels and weakening of the vessel wall due to underlying inflammation. Vascular endothelial inflammation has been identified as a critical driver of aneurysm growth and progression, with numerous immune cell populations proposed to have a role in this process. The innate immune cells that partake in the process of aneurysm growth, primarily macrophages, can adopt pro-inflammatory or anti-inflammatory phenotypes. A recent line of work implicates an imbalance in macrophage phenotypes as a critical feature in the progression of cerebral aneurysmal disease. An imbalance in immune cell states is also observed in neurodegenerative processes, where the inflammatory phenotypes of microglia and astrocytes appear to be involved in disease progression. Understanding cerebral aneurysms and neurodegeneration as processes that involve inflammatory imbalances may provide a window for future research and identification of therapeutic targets, where modulating immune phenotypes has the potential to reduce both aneurysm rupture risk and neurodegenerative progression. Further, advances in treatments for one disease could be cautiously applied in preclinical models for the other.