C5a-C5AR1 axis as a potential trigger of the rupture of intracranial aneurysms
Subarachnoid hemorrhage due to rupture of intracranial aneurysm (IA) still has poor prognosis once after the onset in spite of modern technical advancement in medical care. The development of the novel therapeutic strategy based on molecular machineries regulating the rupture is thus mandatory for social health. Here, recent studies have clarified the potential role of neutrophil-mediated inflammatory responses in the process leading to rupture. Thereby, factors mediating the recruitment of neutrophils in situ could be the therapeutic targets to prevent rupture of IAs. In the present study, complement C5a receptor 1 (C5AR1) was picked up as the candidates from comprehensive gene expression profile data. The induction of C5AR1 in IA lesions exclusively in rupture-prone or ruptured lesions was then confirmed in immunohistochemistry. The ligand of C5AR1, C5a, was induced through the enzymatic digestion by tissue-type Plasminogen Activator and, intriguingly, forms the auto-amplification in C5a-C5AR1 axis to exacerbate neutrophil infiltration and resultant neutrophil-mediated inflammation in situ, which triggers rupture of IAs. In conclusion, we have, in the present study, examined potential factors mediating the infiltration of neutrophils into IA lesions and then identified C5a-C5AR1 axis. This cascade could become the therapeutic target to prevent rupture of IAs. Overall design: To investigate the difference of gene expression patterns between intracranial aneurysms and normal intracranial arteries in rats