Aim: Interleukin-1 receptor-associated kinase 1 (IRAK1) and IRAK4 play essential roles in the induction of inflammatory gene products. We aimed to investigate the effect of the inhibition of IRAK1 and IRAK4 kinase activities on neointimal formation in rats with carotid artery balloon injuries using the IRAK1/4 inhibitor N-(2-Morpholinylethyl)-2-(3-nitrobenzoylamido)-benzimidazole, a cell-permeable benzimidazole compound.
Methods: Wistar rats and vascular smooth muscle cells (VSMCs) isolated from the thoracic aortas were used. Toll-like receptor 4 (TLR4)-mediated nuclear factor kappa B (NFκB) signaling pathway was revealed by microarrays analysis. In addition, the differential expression of the TLR4 pathway genes, including TLR4, IRAK1, IκBα, and interleukin-1β (IL-1β), was confirmed by quantitative real-time polymerase chain reaction. Immunohistochemical staining, elastic-van Gieson and Masson staining, 5-ethynyl-2´-deoxyuridine staining, enzyme-linked immunosorbent assay, transwell migration assay and western blotting were also contributed for relevant detection.
Results: The expression of TLR4 protein gradually increased at days 1, 3, 7, and 21 after balloon injury compared with the uninjured group. The dual inhibition of IRAK1 and IRAK4 attenuated neointimal formation and fibrotic remodeling after injury in vivo and suppressed VSMC proliferation and migration in vitro. The production of mediators such as tumor necrosis factor-α and IL-1β in injured arteries were also reduced by the inhibition of IRAK1 and IRAK4. The expression of NFκB p65- and F4/80-positive cells in inhibitor rats were fewer than those in control rats at day 7, while IRAK1 expression was markedly higher at day 3 in inhibitor rats. Furthermore, western blotting analysis revealed that the IRAK1/4 inhibitor suppressed the IRAK1 and IRAK4 kinase activities and the activation of the TLR4-mediated NFκB pathway in vivo and in vitro.
Conclusions: This study suggested that IRAK1/4 could serve as a potential therapeutic target to suppress neointimal formation in carotid arteries after balloon injury through the TLR4/NFκB signaling pathway.