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

Aoki T, Fukuda M, Nishimura M, Nozaki K, Narumiya S - Acta Neuropathol Commun (2014)

Bottom Line: 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.In 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Innovation Center for Immunoregulation Technologies and Drugs (AK project), Kyoto University Graduate School of Medicine, Konoe-cho Yoshida, Sakyo-ku, Kyoto City, Kyoto 606-8501, Japan. tomoaoki@kuhp.kyoto-u.ac.jp.

ABSTRACT

Background: Intracranial 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.

Results: We 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.

Conclusions: In 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.

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Suppression of IA formation in TNFR1-deficient mice. (A) Incidence of IAs in wild-type (WT), TNFR1-heterozygous (hetero), and TNFR1-deficient (KO) mice. IA was defined as a lesion with disrupted internal elastic lamina by Elastica van Gieson staining. The number of mice used for each genotype is shown in parentheses. *indicates p < 0.05. (B) Systemic blood pressure in each genotype (WT, wild-type mouse; Het, TNFR1-heterozygous mouse; KO, TNFR1-deficient mouse) after aneurysm induction. Systemic blood pressure (SBP, systolic blood pressure; MBP, mean blood pressure) was measured by the tail-cuff method. All bars indicate the mean ± SEM.
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Figure 2: Suppression of IA formation in TNFR1-deficient mice. (A) Incidence of IAs in wild-type (WT), TNFR1-heterozygous (hetero), and TNFR1-deficient (KO) mice. IA was defined as a lesion with disrupted internal elastic lamina by Elastica van Gieson staining. The number of mice used for each genotype is shown in parentheses. *indicates p < 0.05. (B) Systemic blood pressure in each genotype (WT, wild-type mouse; Het, TNFR1-heterozygous mouse; KO, TNFR1-deficient mouse) after aneurysm induction. Systemic blood pressure (SBP, systolic blood pressure; MBP, mean blood pressure) was measured by the tail-cuff method. All bars indicate the mean ± SEM.

Mentions: Immunohistochemical analyses were performed as previously described [19]. Briefly, at the indicated period after aneurysm induction, 5-um-thick frozen sections were made as described above. After blocking with 3% donkey or goat serum (Jackson ImmunoResearch, Baltimore, MD, USA), slices were incubated with primary antibodies followed by incubation with fluorescence-labeled secondary antibodies (Jackson ImmunoResearch). Finally, fluorescent images were acquired through a confocal fluorescence microscope system (CTR6500, Leica Microsystems, Tokyo, Japan). Representative images from at least 3 independent samples are shown in Figures 1 and 2. The relative intensity of positive staining in IA walls from each experiment was measured by imaging software and statistically analyzed.


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

Aoki T, Fukuda M, Nishimura M, Nozaki K, Narumiya S - Acta Neuropathol Commun (2014)

Suppression of IA formation in TNFR1-deficient mice. (A) Incidence of IAs in wild-type (WT), TNFR1-heterozygous (hetero), and TNFR1-deficient (KO) mice. IA was defined as a lesion with disrupted internal elastic lamina by Elastica van Gieson staining. The number of mice used for each genotype is shown in parentheses. *indicates p < 0.05. (B) Systemic blood pressure in each genotype (WT, wild-type mouse; Het, TNFR1-heterozygous mouse; KO, TNFR1-deficient mouse) after aneurysm induction. Systemic blood pressure (SBP, systolic blood pressure; MBP, mean blood pressure) was measured by the tail-cuff method. All bars indicate the mean ± SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3974421&req=5

Figure 2: Suppression of IA formation in TNFR1-deficient mice. (A) Incidence of IAs in wild-type (WT), TNFR1-heterozygous (hetero), and TNFR1-deficient (KO) mice. IA was defined as a lesion with disrupted internal elastic lamina by Elastica van Gieson staining. The number of mice used for each genotype is shown in parentheses. *indicates p < 0.05. (B) Systemic blood pressure in each genotype (WT, wild-type mouse; Het, TNFR1-heterozygous mouse; KO, TNFR1-deficient mouse) after aneurysm induction. Systemic blood pressure (SBP, systolic blood pressure; MBP, mean blood pressure) was measured by the tail-cuff method. All bars indicate the mean ± SEM.
Mentions: Immunohistochemical analyses were performed as previously described [19]. Briefly, at the indicated period after aneurysm induction, 5-um-thick frozen sections were made as described above. After blocking with 3% donkey or goat serum (Jackson ImmunoResearch, Baltimore, MD, USA), slices were incubated with primary antibodies followed by incubation with fluorescence-labeled secondary antibodies (Jackson ImmunoResearch). Finally, fluorescent images were acquired through a confocal fluorescence microscope system (CTR6500, Leica Microsystems, Tokyo, Japan). Representative images from at least 3 independent samples are shown in Figures 1 and 2. The relative intensity of positive staining in IA walls from each experiment was measured by imaging software and statistically analyzed.

Bottom Line: 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.In 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Innovation Center for Immunoregulation Technologies and Drugs (AK project), Kyoto University Graduate School of Medicine, Konoe-cho Yoshida, Sakyo-ku, Kyoto City, Kyoto 606-8501, Japan. tomoaoki@kuhp.kyoto-u.ac.jp.

ABSTRACT

Background: Intracranial 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.

Results: We 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.

Conclusions: In 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.

Show MeSH
Related in: MedlinePlus