Intracranial aneurysm pathogenesis

Intracranial aneurysm pathogenesis

Until now, the exact etiology of intracranial aneurysms formation remains unclear.

Time-dependent and site-dependent morphological changes and the level of degradation molecules may be indicative of the vulnerability of aneurysm rupture 1).

Miyata et al. proposed the contribution of a structural change in an adventitia, i.e., vasa vasorum formation, to the rupture of IAs 2).

Intracranial aneurysm risk factors.

see Intracranial aneurysm genetics.

see Intracranial aneurysm pathophysiology.

see Intracranial aneurysm hemodynamics.

In addition to ambiental factors (smoking, excessive alcohol consumption and hypertension), epidemiological studies have demonstrated a familiar influence contributing to the pathogenesis of intracranial aneurysms, with increased frequency in first- and second-degree relatives of people with subarachnoid hemorrhage.

Data suggest that macrophage-derived Matrix metalloproteinase 2 and Matrix metalloproteinase 9, may play an important role in the progression of intracranial aneurysms. The findings will shed a new light into the pathogenesis of cerebral aneurysms and highlight the importance of inflammatory response causing the degeneration of extracellular matrix in the process of this disease 3).

Investigations strongly suggest that the pathophysiology is closely associated with chronic inflammation in vascular walls. Nuclear factor kappaB (NF-kappaB) has a key role in the formation and progression.

Children with Sickle Cell Disease (SCD) are at risk for developing multiple intracranial aneurysms, and a high index of suspicion must be maintained during the interpretation of routine magnetic resonance imaging or angiography of the brain 4).

Dental bacterial DNA can be found using a quantitative polymerase chain reaction in both ruptured and unruptured aneurysm walls, suggesting that bacterial DNA plays a role in the pathogenesis of cerebral aneurysms in general, rather than only in ruptured aneurysms 5).

Thrombospondin type-1 domain-containing protein 1 is a protein that in humans is encoded by the THSD1 gene.

The protein encoded by this gene contains a type 1 thrombospondin domain, which is found in thrombospondin, a number of proteins involved in the complement pathway, as well as extracellular matrix proteins. Alternatively spliced transcript variants encoding distinct isoforms have been observed.

As illustrated by THSD1 research, cell adhesion may play a significant role in IA 6).

A study discovered that harmful variants in THSD1 (Thrombospondin type-1 domain-containing protein 1) likely cause intracranial aneurysm and subarachnoid hemorrhage in a subset of both familial and sporadic patients with supporting evidence from two vertebrate models 7).

A report identified THSD1 mutations in familial and sporadic IA patients and shows that THSD1 loss results in cerebral bleeding in 2 animal models. This finding provides new insight into IA and subarachnoid hemorrhage pathogenesis and provides new understanding of THSD1 function, which includes endothelial cell to extracellular matrix adhesion 8).

Toll‑like receptor (TLR) 2/4 serves an important regulatory role in nerve tissue injury. However, the downstream and potential mechanisms remain to be elucidated. The present study was designed to investigate the roles of the TLR2/4‑major myeloid differentiation response gene 88 (MyD88)‑NF‑κB signaling pathway in the development of an intracranial aneurysm. The expression of TLR2, TLR4, and MyD88 in the blood of normal controls and patients with intracranial aneurysms were detected by quantitative PCR and ELISA. Human brain vascular smooth muscle cells were treated by Angiotensin II (Ang II) to evaluate the involvement of the TLR2/4‑MyD88‑NF‑κB signaling pathway in the process. The in vitro experiment was divided into four groups: The control group, an Ang Ⅱ group, an Ang Ⅱ + small interfering (si)RNA control group, and an Ang Ⅱ + TLR2‑group. Cell viability, migration, apoptosis, and expression of TLR2, TLR4, MyD88, NF‑κB, and phosphorylated (p‑)p65 expression was detected. The results demonstrated that the expression of TLR2, TLR4, MyD88, and NF‑κB at mRNA and protein levels in patients with an intracranial aneurysm was significantly higher compared with corresponding protein in normal controls (P&lt;0.05). <em>In vitro</em> experiments demonstrated that Ang Ⅱ treatment increased the cell proliferation and migration rate but reduced the apoptotic rate compared with the control (P&lt;0.05). The expression of TLR2, TLR4, MyD88, NF‑κB, and p‑p65 was significantly increased in the Ang II group (vs. control; P&lt;0.05). By contrast, TLR2‑short interfering RNA reduced the cell proliferation and migration rate and reduced the expression of TLR2, TLR4, MyD88, NF‑κB, and p‑p65 (vs. Ang Ⅱ + short interfering RNA control; P&lt;0.05). In conclusion, the data of the present study indicated that the TLR2/4‑MyD88‑NF‑κB signaling pathway is involved in the intracranial aneurysm pathogenesis 9).


1)

Yamaguchi T, Miyamoto T, Kitazato KT, Shikata E, Yamaguchi I, Korai M, Shimada K, Yagi K, Tada Y, Matsuzaki Y, Kanematsu Y, Takagi Y. Time-dependent and site-dependent morphological changes in rupture-prone arteries: ovariectomized rat intracranial aneurysm model. J Neurosurg. 2019 Sep 13:1-9. doi: 10.3171/2019.6.JNS19777. [Epub ahead of print] PubMed PMID: 31518986.
2)

Miyata H, Imai H, Koseki H, Shimizu K, Abekura Y, Oka M, Kawamata T, Matsuda T, Nozaki K, Narumiya S, Aoki T. Vasa vasorum formation is associated with rupture of intracranial aneurysms. J Neurosurg. 2019 Aug 16:1-11. doi: 10.3171/2019.5.JNS19405. [Epub ahead of print] PubMed PMID: 31419795.
3)

Aoki T, Kataoka H, Morimoto M, Nozaki K, Hashimoto N. Macrophage-derived matrix metalloproteinase-2 and -9 promote the progression of cerebral aneurysms in rats. Stroke. 2007 Jan;38(1):162-9. Epub 2006 Nov 22. PubMed PMID: 17122420.
4)

Saini S, Speller-Brown B, Wyse E, Meier ER, Carpenter J, Fasano RM, Pearl MS. Unruptured Intracranial Aneurysms in Children With Sickle Cell Disease: Analysis of 18 Aneurysms in 5 Patients. Neurosurgery. 2015 Feb 12. [Epub ahead of print] PubMed PMID: 25710108.
5)

Pyysalo MJ, Pyysalo LM, Pessi T, Karhunen PJ, Lehtimäki T, Oksala N, Öhman JE. Bacterial DNA findings in ruptured and unruptured intracranial aneurysms. Acta Odontol Scand. 2016 May;74(4):315-20. doi: 10.3109/00016357.2015.1130854. Epub 2016 Jan 18. PubMed PMID: 26777430.
6)

Xu Z, Rui YN, Hagan JP, Kim DH. Intracranial Aneurysms: Pathology, Genetics, and Molecular Mechanisms. Neuromolecular Med. 2019 May 4. doi: 10.1007/s12017-019-08537-7. [Epub ahead of print] Review. PubMed PMID: 31055715.
7)

Rui YN, Xu Z, Fang X, Menezes MR, Balzeau J, Niu A, Hagan JP, Kim DH. The Intracranial Aneurysm Gene THSD1 Connects Endosome Dynamics to Nascent Focal Adhesion Assembly. Cell Physiol Biochem. 2017;43(6):2200-2211. doi: 10.1159/000484298. Epub 2017 Oct 25. PubMed PMID: 29069646.
8)

Santiago-Sim T, Fang X, Hennessy ML, Nalbach SV, DePalma SR, Lee MS, Greenway SC, McDonough B, Hergenroeder GW, Patek KJ, Colosimo SM, Qualmann KJ, Hagan JP, Milewicz DM, MacRae CA, Dymecki SM, Seidman CE, Seidman JG, Kim DH. THSD1 (Thrombospondin Type 1 Domain Containing Protein 1) Mutation in the Pathogenesis of Intracranial Aneurysm and Subarachnoid Hemorrhage. Stroke. 2016 Dec;47(12):3005-3013. Epub 2016 Nov 15. Erratum in: Stroke. 2017 Aug;48(8):e240. PubMed PMID: 27895300; PubMed Central PMCID: PMC5134902.
9)

Zhang X, Wan Y, Feng J, Li M, Jiang Z. Involvement of TLR2/4‑MyD88‑NF‑κB signaling pathway in the pathogenesis of intracranial aneurysm. Mol Med Rep. 2021 Jan 26. doi: 10.3892/mmr.2021.11869. Epub ahead of print. PMID: 33655339.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

WhatsApp WhatsApp us
%d bloggers like this: