Miyuki Fukuda

Critical role of TNF-alpha-TNFR1 signaling in intracranial aneurysm formation

BackgroundIntracranial aneurysm (IA) is a socially important disease due to its high incidence in the general public and the severity of resultant subarachnoid hemorrhage that follows rupture. Despite the social importance of IA as a cause of subarachnoid hemorrhage, there is no medical treatment to prevent rupture, except for surgical procedures, because the mechanisms regulating IA formation are poorly understood. Therefore, these mechanisms should be elucidated to identify a therapeutic target for IA treatment. In human IAs, the presence of inflammatory responses, such as an increase of tumor necrosis factor (TNF)-alpha, have been observed, suggesting a role for inflammation in IA formation. Recent investigations using rodent models of IAs have revealed the crucial role of inflammatory responses in IA formation, supporting the results of human studies. Thus, we identified nuclear factor (NF)-kappaB as a critical mediator of inflammation regulating IA formation, by inducing downstream pro-inflammatory genes such as MCP-1, a chemoattractant for macrophages, and COX-2. In this study, we focused on TNF-alpha signaling as a potential cascade that regulates NF-kappaB-mediated IA formation.ResultsWe first confirmed an increase in TNF-alpha content in IA walls during IA formation, as expected based on human studies. Consistently, the activity of TNF-alpha converting enzyme (TACE), an enzyme responsible for TNF-alpha release, was induced in the arterial walls after aneurysm induction in a rat model. Next, we subjected tumor necrosis factor receptor superfamily member 1a (TNFR1)-deficient mice to the IA model to clarify the contribution of TNF-alpha-TNFR1 signaling to pathogenesis, and confirmed significant suppression of IA formation in TNFR1-deficient mice. Furthermore, in the IA walls of TNFR1-deficient mice, inflammatory responses, including NF-kappaB activation, subsequent expression of MCP-1 and COX-2, and infiltration of macrophages into the IA lesion, were greatly suppressed compared with those in wild-type mice.ConclusionsIn this study, using rodent models of IAs, we clarified the crucial role of TNF-alpha-TNFR1 signaling in the pathogenesis of IAs by inducing inflammatory responses, and propose this signaling as a potential therapeutic target for IA treatment.

Prostaglandin E2-EP2-NF-κB signaling in macrophages as a potential therapeutic target for intracranial aneurysms

Inhibition of prostaglandin E2 signaling in macrophages may be a pharmacological option for treating intracranial aneurysms. A receptor target for intracranial aneurysms The rupture of intracranial aneurysms is life-threatening. Unfortunately, surgery is currently the only therapeutic option. Inflammation mediated by macrophages that infiltrate the arterial wall both causes intracranial aneurysms and promotes their progression. Aoki et al. delineated a self-amplifying signaling pathway in macrophages that would be expected to aggravate the inflammation that underlies the formation and progression of intracranial aneurysms. They found that signaling through the prostaglandin E receptor subtype 2 (EP2) activated the transcription factor NF-κB to induce the expression of the genes encoding COX-2, the enzyme that synthesizes the ligand for EP2, and MCP-1, an attractant for macrophages. Administering an EP2 antagonist to rats prevented the formation and progression of intracranial aneurysms, suggesting that targeting the EP2 receptor could be a pharmacological alternative to treat developing intracranial aneurysms. Intracranial aneurysms are common but are generally untreated, and their rupture can lead to subarachnoid hemorrhage. Because of the poor prognosis associated with subarachnoid hemorrhage, preventing the progression of intracranial aneurysms is critically important. Intracranial aneurysms are caused by chronic inflammation of the arterial wall due to macrophage infiltration triggered by monocyte chemoattractant protein-1 (MCP-1), macrophage activation mediated by the transcription factor nuclear factor κB (NF-κB), and inflammatory signaling involving prostaglandin E2 (PGE2) and prostaglandin E receptor subtype 2 (EP2). We correlated EP2 and cyclooxygenase-2 (COX-2) with macrophage infiltration in human intracranial aneurysm lesions. Monitoring the spatiotemporal pattern of NF-κB activation during intracranial aneurysm development in mice showed that NF-κB was first activated in macrophages in the adventitia and in endothelial cells and, subsequently, in the entire arterial wall. Mice with a macrophage-specific deletion of Ptger2 (which encodes EP2) or macrophage-specific expression of an IκBα mutant that restricts NF-κB activation had fewer intracranial aneurysms with reduced macrophage infiltration and NF-κB activation. In cultured cells, EP2 signaling cooperated with tumor necrosis factor–α (TNF-α) to activate NF-κB and synergistically induce the expression of proinflammatory genes, including Ptgs2 (encoding COX-2). EP2 signaling also stabilized Ccl2 (encoding MCP-1) by activating the RNA-stabilizing protein HuR. Rats administered an EP2 antagonist had reduced macrophage infiltration and intracranial aneurysm formation and progression. This signaling pathway in macrophages thus facilitates intracranial aneurysm development by amplifying inflammation in intracranial arteries. These results indicate that EP2 antagonists may therefore be a therapeutic alternative to surgery.

Sustained expression of MCP-1 by low wall shear stress loading concomitant with turbulent flow on endothelial cells of intracranial aneurysm

IntroductionEnlargement of a pre-existing intracranial aneurysm is a well-established risk factor of rupture. Excessive low wall shear stress concomitant with turbulent flow in the dome of an aneurysm may contribute to progression and rupture. However, how stress conditions regulate enlargement of a pre-existing aneurysm remains to be elucidated.ResultsWall shear stress was calculated with 3D-computational fluid dynamics simulation using three cases of unruptured intracranial aneurysm. The resulting value, 0.017 Pa at the dome, was much lower than that in the parent artery. We loaded wall shear stress corresponding to the value and also turbulent flow to the primary culture of endothelial cells. We then obtained gene expression profiles by RNA sequence analysis. RNA sequence analysis detected hundreds of differentially expressed genes among groups. Gene ontology and pathway analysis identified signaling related with cell division/proliferation as overrepresented in the low wall shear stress–loaded group, which was further augmented by the addition of turbulent flow. Moreover, expression of some chemoattractants for inflammatory cells, including MCP-1, was upregulated under low wall shear stress with concomitant turbulent flow. We further examined the temporal sequence of expressions of factors identified in an in vitro study using a rat model. No proliferative cells were detected, but MCP-1 expression was induced and sustained in the endothelial cell layer.ConclusionsLow wall shear stress concomitant with turbulent flow contributes to sustained expression of MCP-1 in endothelial cells and presumably plays a role in facilitating macrophage infiltration and exacerbating inflammation, which leads to enlargement or rupture.

Molecular basis for intracranial aneurysm formation.

Intracranial aneurysm (IA) is a socially important disease both because it has a high prevalence and because of the severity of resultant subarachnoid hemorrhages after IA rupture. The major concern of current IA treatment is the lack medical therapies that are less invasive than surgical procedures for many patients. The current situation is mostly caused by a lack of knowledge regarding the regulating mechanisms of IA formation. Hemodynamic stress, especially high wall shear stress, loaded on arterial bifurcation sites is recognized as a trigger of IA formation from studies performed in the field of fluid dynamics. On the other hand, many studies using human specimens have also revealed the presence of active inflammatory responses, such as the infiltration of macrophages, in the pathogenesis of IA. Because of these findings, recent experimental studies, mainly using animal models of IA, have revealed some of the molecular mechanisms linking hemodynamic stress and long-lasting inflammation in IA walls. Currently, we propose that IA is a chronic inflammatory disease regulated by a positive feedback loop consisting of the cyclooxygenase (COX)-2 - prostaglandin (PG) E2 - prostaglandin E receptor 2 (EP2) - nuclear factor (NF)-κB signaling pathway triggered under hemodynamic stress and macrophage infiltration via NF-κB-mediated monocyte chemoattractant protein (MCP)-1 induction. These findings indicate future directions for the development of therapeutic drugs for IAs.

Dipeptidyl Peptidase‐4 Inhibitor Anagliptin Prevents Intracranial Aneurysm Growth by Suppressing Macrophage Infiltration and Activation

Background Chronic inflammation plays a key role in the pathogenesis of intracranial aneurysms (IAs). DPP‐4 (dipeptidyl peptidase‐4) inhibitors have anti‐inflammatory effects, including suppressing macrophage infiltration, in various inflammatory models. We examined whether a DPP‐4 inhibitor, anagliptin, could suppress the growth of IAs in a rodent aneurysm model. Methods and Results IAs were surgically induced in 7‐week‐old male Sprague Dawley rats, followed by oral administration of 300 mg/kg anagliptin. We measured the morphologic parameters of aneurysms over time and their local inflammatory responses. To investigate the molecular mechanisms, we used lipopolysaccharide‐treated RAW264.7 macrophages. In the anagliptin‐treated group, aneurysms were significantly smaller 2 to 4 weeks after IA induction. Anagliptin inhibited the accumulation of macrophages in IAs, reduced the expression of MCP‐1 (monocyte chemotactic protein 1), and suppressed the phosphorylation of p65. In lipopolysaccharide‐stimulated RAW264.7 cells, anagliptin treatment significantly reduced the production of tumor necrosis factor α, MCP‐1, and IL‐6 (interleukin 6) independent of GLP‐1 (glucagon‐like peptide 1), the key mediator in the antidiabetic effects of DPP‐4 inhibitors. Notably, anagliptin activated ERK5 (extracellular signal–regulated kinase 5), which mediates the anti‐inflammatory effects of statins, in RAW264.7 macrophages. Preadministration with an ERK5 inhibitor blocked the inhibitory effect of anagliptin on MCP‐1 and IL‐6 expression. Accordingly, the ERK5 inhibitor also counteracted the suppression of p65 phosphorylation in vitro. Conclusions A DPP‐4 inhibitor, anagliptin, prevents the growth of IAs via its anti‐inflammatory effects on macrophages.

Ossification of the Yellow Ligament Combined with Ossification of the Posterior Longitudinal Ligament at the Cervicothoracic Junction

BACKGROUND Both ossification of the yellow ligament (OYL) and the ossification of the posterior longitudinal ligament are relatively rare clinical entities. We report a extremely rare case of the spinal canal stenosis because of OYL, OPLL and listhesis at the cervicothoracic junction. CASE DESCRIPTION A 69-year-old man had progressive pain over his bilateral axillar portion and right lower extremity for 1 year. Radiology showed cervical canal stenosis with ossification of OYL, OPLL, and listhesis at the cervicothoracic junction. Posterior decompression therapy was performed, and he recovered entirely from his symptoms. CONCLUSIONS Triple factors of OYL, OPLL and listhesis contributed the cervical canal stenosis limited at cervicothoracic junction. Early diagnosis and surgical therapy is recommended for the good prognosis of this pathologic condition, as well as careful long-term follow-up for the early detection of its recurrence.

A sphingosine‐1‐phosphate receptor type 1 agonist, ASP4058, suppresses intracranial aneurysm through promoting endothelial integrity and blocking macrophage transmigration

Intracranial aneurysm (IA), common in the general public, causes lethal subarachnoid haemorrhage on rupture. It is, therefore, of utmost importance to prevent the IA from rupturing. However, there is currently no medical treatment. Recent studies suggest that IA is the result of chronic inflammation in the arterial wall caused by endothelial dysfunction and infiltrating macrophages. The sphingosine‐1‐phosphate receptor type 1 (S1P1 receptor) is present on the endothelium and promotes its barrier function. Here we have tested the potential of an S1P1 agonist, ASP4058, to prevent IA in an animal model.

An S1P1 agonist, ASP4058, suppresses intracranial aneurysm through promoting endothelial integrity and blocking macrophage transmigration.

Intracranial aneurysm (IA), common in the general public, causes lethal subarachnoid haemorrhage on rupture. It is, therefore, of utmost importance to prevent the IA from rupturing. However, there is currently no medical treatment. Recent studies suggest that IA is the result of chronic inflammation in the arterial wall caused by endothelial dysfunction and infiltrating macrophages. The sphingosine‐1‐phosphate receptor type 1 (S1P1 receptor) is present on the endothelium and promotes its barrier function. Here we have tested the potential of an S1P1 agonist, ASP4058, to prevent IA in an animal model.

Arsenic trioxide sensitizes glioblastoma to a myc inhibitor.

Glioblastoma multiforme (GBM) is associated with high mortality due to infiltrative growth and recurrence. Median survival of the patients is less than 15 months, increasing requirements for new therapies. We found that both arsenic trioxide and 10058F4, an inhibitor of Myc, induced differentiation of cancer stem-like cells (CSC) of GBM and that arsenic trioxide drastically enhanced the anti-proliferative effect of 10058F4 but not apoptotic effects. EGFR-driven genetically engineered GBM mouse model showed that this cooperative effect is higher in EGFRvIII-expressing INK4a/Arf-/- neural stem cells (NSCs) than in control wild type NSCs. In addition, treatment of GBM CSC xenografts with arsenic trioxide and 10058F4 resulted in significant decrease in tumor growth and increased differentiation with concomitant decrease of proneural and mesenchymal GBM CSCs in vivo. Our study was the first to evaluate arsenic trioxide and 10058F4 interaction in GBM CSC differentiation and to assess new opportunities for arsenic trioxide and 10058F4 combination as a promising approach for future differentiation therapy of GBM.

Correction: Arsenic Trioxide Sensitizes Glioblastoma to a Myc Inhibitor

Fig 7 is incorrect. Panel E was incorrectly labeled. The authors have provided a corrected version here. Fig 7 Arsenic trioxide and 10058F4 combination treatment efficiently regressed established gliomas.