Characterisation of Interleukin-8 and monocyte chemoattractant protein-1 expression within the abdominal aortic aneurysm and their association with mural inflammation.

Abstract

Abdominal aortic aneurysms (AAAs) are characterised by chronic transmural inflammation. This study investigated the expression of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) within the AAA, and their relationship with mural inflammation. Biopsies were obtained from 25 AAAs, 15 abdominal aortas, and 10 atherosclerotic thoracic aortas. IL-8 and MCP-1 expression was measured in homogenised specimens by ELISA. Infiltrate composition and localised expression of IL-8 and MCP-1 were determined through immunohistochemistry. ELISA analysis demonstrated that IL-8 and MCP-1 were raised in the AAA compared to the controls [(IL-8, AAA vs. abdominal aorta: >28-fold, P<.001; AAA vs. thoracic aorta: >28-fold, P<.001) (MCP-1, AAA vs. abdominal aorta: 9-fold, P<.001; AAA vs. thoracic aorta: 19-fold, P<.001)]. Immunohistochemistry revealed that IL-8 was localised to the inflammatory infiltrate, which consisted predominantly of CD3(+) T- and CD20(+) B-lymphocytes. MCP-1 was predominantly expressed by CD68(+) macrophages. Increasing IL-8 expression was associated with an increase in mural inflammation, and an increase in CD3(+) T-lymphocytes of CD4(+) phenotype within the infiltrate population. Pathways involving IL-8 and MCP-1 may be involved in AAA pathogenesis. IL-8 may be directly involved in the chemotaxis of T(H)-lymphocytes into the AAA wall.