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Activation of Invariant Natural Killer T Cells by α-Galactosylceramide Attenuates the Development of Angiotensin II-Mediated Abdominal Aortic Aneurysm in Obese ob/ob Mice.

ABSTRACT: The infiltration and activation of macrophages as well as lymphocytes within the aorta contribute to the pathogenesis of abdominal aortic aneurysm (AAA). Invariant natural killer T (iNKT) cells are unique subset of T lymphocytes and have a crucial role in atherogenesis. However, it remains unclear whether iNKT cells also impact on the development of AAA. Ob/ob mice were administered angiotensin II (AngII, 1,000 ng/kg/min) or phosphate-buffered saline (PBS) by osmotic minipumps for 4 weeks and further divided into 2 groups; α-galactosylceramide (αGC; PBS-αGC; n = 5 and AngII-αGC; n = 12), which specifically activates iNKT cells, and PBS (PBS-PBS; n = 10, and AngII-PBS; n = 6). Maximal abdominal aortic diameter was comparable between PBS-PBS and PBS-αGC, and was significantly greater in AngII-PBS than in PBS-PBS. This increase was significantly attenuated in AngII-αGC without affecting blood pressure. αGC significantly enhanced iNKT cell infiltration compared to PBS-PBS. The ratio of F4/80-positive macrophages or CD3-positive T lymphocytes area to the lesion area was significantly higher in AngII-PBS than in PBS-PBS, and was significantly decreased in AngII-αGC. Gene expression of M2-macrophage specific markers, arginase-1 and resistin-like molecule alpha, was significantly greater in aortic tissues from AngII-αGC compared to AngII-PBS 1 week after AngII administration, and this increase was diminished at 4 weeks. Activation of iNKT cells by αGC can attenuate AngII-mediated AAA in ob/ob mice via inducing anti-inflammatory M2 polarized state. Activation of iNKT cells by the bioactive lipid αGC may be a novel therapeutic target against the development of AAA.

SUBMITTER: Saito A

PROVIDER: S-EPMC8141584 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:RATIONALE:Abdominal aortic aneurysms (AAAs) are a chronic inflammatory vascular disease for which pharmacological treatments are not available. A mouse model of AAA formation involves chronic infusion of angiotensin II (AngII), and previous studies indicated a primary role for the AngII type 1a receptor in AAA formation. ?-arrestin (?arr)-2 is a multifunctional scaffolding protein that binds G-protein-coupled receptors such as AngII type 1a and regulates numerous signaling pathways and pathophysiological processes. However, a role for ?arr2 in AngII-induced AAA formation is currently unknown. OBJECTIVE:To determine whether ?arr2 played a role in AngII-induced AAA formation in mice. METHODS AND RESULTS:Treatment of ?arr2(+/+) and ?arr2(-/-) mice on the hyperlipidemic apolipoprotein E-deficient (apoE(-/-)) background or on normolipidemic C57BL/6 background with AngII for 28 days indicated that ?arr2 deficiency significantly attenuated AAA formation. ?arr2 deficiency attenuated AngII-induced expression of cyclooxygenase-2, monocyte chemoattractant protein-1, macrophage inflammatory protein 1?, and macrophage infiltration. AngII also increased the levels of phosphorylated extracellular signal-regulated kinase 1/2 in apoE(-/-)/?arr2(+/+) aortas, whereas ?arr2 deficiency diminished this increase. Furthermore, inhibition of extracellular signal-regulated kinase 1/2 activation with CI1040 (100 mg/kg per day) reduced the level of AngII-induced cyclooxygenase-2 expression in apoE(-/-)/?arr2(+/+) mice to the level observed in apoE(-/-)/?arr2(-/-) mice. AngII treatment also increased matrix metalloproteinase expression and disruption of the elastic layer in apoE(-/-)/?arr2(+/+) aortas, and ?arr2 deficiency reduced these effects. CONCLUSIONS:?arr2 contributes to AngII-induced AAA formation in mice by phosphorylated extracellular signal-regulated kinase 1/2-mediated cyclooxygenase-2 induction and increased inflammation. These studies suggest that for the AngII type 1a receptor, G-protein-independent, ?arr2-dependent signaling plays a major role in AngII-induced AAA formation.

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Activation of Invariant Natural Killer T Cells by α-Galactosylceramide Attenuates the Development of Angiotensin II-Mediated Abdominal Aortic Aneurysm in Obese ob/ob Mice.

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