Functional characterization of human IL-8 in vascular stenosis using a novel humanized transgenic mouse model

IL-8 (aka interleukin 8, CXCL8) is a prototypic cytokine that is highly expressed in the diseased vessel wall and its plasma concentration is strongly associated with cardiovascular events. However, whether IL-8 plays a causative role in cardiovascular diseases remains largely unknown. In this study we used a human IL-8 transgenic (Tg) mouse strain with a bacterial artificial chromosome (BAC) integrated into its genome. This BAC encompasses 166 kb of sequence encompassing the human IL-8 gene locus as well as upstream and downstream DNA sequences containing regulatory elements. This BAC ensured a pathophysiologically regulated, rather than forced constitutive, expression of human IL-8 in the mouse. Tg mice were subjected to complete carotid ligation injury. IL-8 was highly expressed in the ligation-injured carotid artery from 3 days until 2 weeks after injury. As a result, exacerbated neointimal hyperplasia and increased Mac2 and PCNA positive cells were observed in Tg mice. To further confirm its role in promoting neointimal formation, IL-8 was neutralized by anti-IL8 treatment at the ligation site. Consequently, the size of neointima was significantly reduced. Our results provided new insights into the regulation and function of IL-8 in response to vascular insult and during neointima formation.