Macrophage-derived IL-18 and increased fibrinogen deposition are age-related inflammatory signatures of vascular remodeling

Abstract

Padron RI. Macrophage-derived IL-18 and increased fibrinogen deposition are age-related inflammatory signatures of vascular remodeling. Am J Physiol Heart Circ Physiol 306: H641-H653, 2014. First published January 10, 2014; doi:10.1152/ajpheart.00641.2013.-Aging has been associated with pathological vascular remodeling and increased neointimal hyperplasia. The understanding of how aging exacerbates this process is fundamental to prevent cardiovascular complications in the elderly. This study proposes a mechanism by which aging sustains leukocyte adhesion, vascular inflammation, and increased neointimal thickness after injury. The effect of aging on vascular remodeling was assessed in the rat balloon injury model using microarray analysis, immunohistochemistry, and LINCOplex assays. The injured arteries in aging rats developed thicker neointimas than those in younger animals, and this significantly correlated with a higher number of tissue macrophages and increased vascular IL-18. Indeed, IL-18 was 23-fold more abundant in the injured vasculature of aged animals compared with young rats, while circulating levels were similar in both groups of animals. The depletion of macrophages in aged rats with clodronate liposomes ameliorated vascular accumulation of IL-18 and significantly decreased neointimal formation. IL-18 was found to inhibit apoptosis of vascular smooth muscle cells (VSMC) and macrophages, thus favoring both the formation and inflammation of the neointima. In addition, injured arteries of aged rats accumulated 18-fold more fibrinogen-␥ than those of young animals. Incubation of rat peritoneal macrophages with immobilized IL-18 increased leukocyte adhesion to fibrinogen and suggested a proinflammatory positive feedback loop among macrophages, VSMC, and the deposition of fibrinogen during neointimal hyperplasia. In conclusion, our data reveal that concentration changes in vascular cytokine and fibrinogen following injury in aging rats contribute to local inflammation and postinjury neointima formation. inflammation; vascular injury; aging; neointima; vascular smooth muscle cells AGING IS RECOGNIZED AS A MAJOR and independent risk factor for the development of vascular restenosis (29). This risk can be explained by profound, age-dependent changes in vascular structure and physiology that lead to endothelial dysfunction (18) and a chronic inflammatory stage (53), which impair healing and render a vascular system prone to develop occlusive neointimas in response to injury. However, even when this notion is largely accepted, the mechanisms by which aging alters vascular physiology and repair have remained understudied to date.The process of aging increases and sustains inflammation within the vascular wall (52). Macrophages are commonly recognized as the most important cell type in the chronicity of this process (37). Indeed, inflammation in arteries of aged individuals is evidenced by an excessive accumulation of macrophages in the inner layer of the arterial wall (intima), and this occurs in the presence o...

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