CD8+ T-cell deficiency protects mice from abdominal aortic aneurysm formation in response to calcium chloride2

Abdominal aortic aneurysm (AAA) is an aneurysm-like dilated and highly fatal cardiovascular disease. CD8(+) T cells have been shown to be critical for vascular pathological processes, but the contribution of these lymphocytes to vascular diseases remains elusive. Methods and results: Eight-week-old male wildtype (CD8(+/+)) and Cd8a knockout (CD8(-/-)) mice were used in a calcium chloride(2) (CaCl2)-induced experimental AAA model. At 6 weeks after surgery, CD8(+) T-cell deletion prevented the formation of AAA, accompanied by reductions of the levels of inflammatory (interferon-gamma [IFN-gamma], interleukin-1 beta, monocyte chemoattractant protein-1, intracellular adhesion molecule-1, vascular cell adhesion molecule-1, NOD-like receptor protein 3, caspase-1), oxidative stress [NADPH oxidase and gp91(phox)], and proteolysis (cathepsin S, cathepsin K, matrix metalloproteinase-2 [MMP-2] and MMP-9) proteins and/or genes in plasma and/or AAA tissues. Immunoreactivities of MMP-2 and MMP-9 were observed in macrophages. An injection of IFN-gamma and adoptive transfer of CD8(+) T cells of IFN-gamma(+/+) mice diminished CD8(-/-)-mediated vasculoprotective actions in the AAA mice. In vitro, IFN-gamma enhanced MMP-2 and MMP-9 gelatinolytic activities in macrophage and/or vascular smooth muscle cells. Conclusion: The vasculoprotective effects of CD8(+) T-cell deletion in a mouse CaCl2-induced AAA model were likely attributable to, at least in part, the attenuation of IFN-gamma-dependent inflammation action, oxidative stress production, and proteolysis, suggesting a novel therapeutic target for AAA formation by regulating CD8(+) T-cell-derived IFN-gamma secretion.