• Fumitake Usui, Koumei Shirasuna, Hiroaki Kimura, Kazuki Tatsumi, Akira Kawashima, Tadayoshi Karasawa, Koichi Yoshimura, Hiroki Aoki, Hiroko Tsutsui, Tetsuo Noda, Junji Sagara, Shun'ichiro Taniguchi, and Masafumi Takahashi.
• From the Division of Inflammation Resesarch, Center for Molecular Medicine, Jichi Medical University, Tochigi, Japan (F.U., K.S., H.K., K.T., A.K., T.K., M.T.); Department of Molecular Oncology, Shinshu University Graduate School of Medicine, Matsumoto, Japan (J.S., S.T.); Department of Surgery and Clinical Science, Yamaguchi University Graduate School of Medicine, Ube, Japan (K.Y.); Cardiovascular Research Institute, Kurume University, Kurume, Japan (H.A.); Department of Microbiology, Hyogo College of Medicine, Nishinomiya, Japan (H.T.); and Department of Cell Biology, Japanese Foundation for Cancer Research, Cancer Institute, Tokyo, Japan (T.N.).
• Arterioscler. Thromb. Vasc. Biol. 2015 Jan 1;35(1):127-36.

ObjectiveAbdominal aortic aneurysm (AAA) is considered a chronic inflammatory disease; however, the molecular basis underlying the sterile inflammatory response involved in the process of AAA remains unclear. We previously showed that the inflammasome, which regulates the caspase-1-dependent interleukin-1β production, mediates the sterile cardiovascular inflammatory responses. Therefore, we hypothesized that the inflammasome is a key mediator of initial inflammation in AAA formation.Approach And ResultsApoptosis-associated speck-like protein containing a caspase recruitment domain is highly expressed in adventitial macrophages in human and murine AAA tissues. Using an established mouse model of AAA induced by continuous infusion of angiotensin II in Apoe(-/-) mice, NLR family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 deficiency in Apoe(-/-) mice were shown to decrease the incidence, maximal diameter, and severity of AAA along with adventitial fibrosis and inflammatory responses significantly, such as inflammatory cell infiltration and cytokine expression in the vessel wall. NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 deficiency in Apoe(-/-) mice also reduced elastic lamina degradation and metalloproteinase activation in the early phase of AAA formation. Furthermore, angiotensin II stimulated generation of mitochondria-derived reactive oxygen species in the adventitial macrophages, and this mitochondria-derived reactive oxygen species generation was inhibited by NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 deficiency. In vitro experiments revealed that angiotensin II stimulated the NLRP3 inflammasome activation and subsequent interleukin-1β release in macrophages, and this activation was mediated through an angiotensin type I receptor/mitochondria-derived reactive oxygen species-dependent pathway.ConclusionsOur results demonstrate the importance of the NLRP3 inflammasome in the initial inflammatory responses in AAA formation, indicating its potential as a novel therapeutic target for preventing AAA progression.© 2014 American Heart Association, Inc.

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