Combinatorial interference of toll-like receptor 2 and 4 synergistically stabilizes atherosclerotic plaque in apolipoprotein E-knockout mice.

To test the hypothesis that combinatorial interference of toll-like receptor 2 (TLR2) and TLR4 is superior to isolated interference of TLR2 or TLR4 in stabilizing atherosclerotic plaques, lentiviruses carrying small interfering RNA of TLR2 or TLR4 were constructed and proved efficacious for knocking down mRNA and protein expression of TLR2 or TLR4 significantly in vitro. One hundred and fifty apolipoprotein E(-/-) mice fed a high-fat diet were divided into the control, mock, TLR2i, TLR4i and TLR2 + 4i subgroups and a constrictive collar was placed around carotid artery of these mice to induce plaque formation. TLR2i and TLR4i viral suspension was transfected into carotid plaques, respectively, in TLR2i and TLR4i subgroups, or in combination in TLR2 + 4i subgroup. Four weeks after lentivirus transfection, mRNA and protein expression of TLR2 or TLR4 was attenuated markedly in carotid plaques, leading to reduced local inflammatory cytokine expression and plaque content of lipid and macrophages, increased plaque content of collagen and lowered plaque vulnerability index. Factorial ANOVA analysis revealed that there was a synergistic effect between TLR4i and TLR2i in stabilizing plaques. In conclusion, combinatorial interference of TLR2 and TLR4 reduces local inflammation and stabilizes plaques more effectively than interference of TLR2 or TLR4 alone.

A causal relationship between shear stress and atherosclerotic lesions in apolipoprotein E knockout mice assessed by ultrasound biomicroscopy.

The present study was undertaken to examine the hemodynamic state using the latest ultrasound biomicroscopy (UBM) technique and to investigate the effect of local shear stress on the development of atherosclerosis in the constrictive collar-treated carotid arteries of apolipoprotein E-deficient (apoE(-/-)) mice. Fifty-six male apoE(-/-) mice fed a high-lipid diet were divided into an interventional group (n = 48) and the control group (n = 8). Constrictive and nonconstrictive collars were placed around the carotid artery of the mice in the interventional group and the control group, respectively. The carotid lumen diameters and flow velocities were measured by UBM, and shear stress in the lesion region was calculated. Histopathology and electron microscopy were performed to observe the morphological changes in the carotid artery. In the region proximal to the constrictive collar, shear stress was significantly reduced 2 days after collar placement and remained low over time compared with the baseline level. In contrast, within the constrictive collar region, shear stress was increased significantly. Although endothelial permeability was enhanced in both regions, monocyte chemotaxis protein-1 (MCP-1) expression, macrophage infiltration, and atherosclerotic lesions were more prominent in the region proximal to the constrictive collar. Moreover, increased MCP-1 expression was observed as early as 2 days after constrictive collar placement, which preceded the morphological changes of the vessel wall. In conclusion, UBM offers a noninvasive and reliable technique for measuring shear stress in apoE(-/-) mice. Persistent low shear stress promotes endothelial permeability and enhances MCP-1 expression and macrophage recruitment, which were essential in the pathogenesis of atherosclerosis in apoE(-/-) mice.

Enhanced stabilization of atherosclerotic plaques in apolipoprotein E-knockout mice by combinatorial Toll-like receptor-1 and -2 gene silencing.

Because both Toll-like receptor-1 (TLR1) and TLR2 are expressed in atherosclerotic plaques, we hypothesized that TLR1 and TLR2 may play different roles in the formation of vulnerable plaques and that combinatorial knockdown of TLR1 and TLR2 genes may enhance the effects of isolated knockdown of the TLR1 or TLR2 gene on plaque stabilization. Lentiviruses carrying small interfering RNAs of TLR1 or TLR2 were constructed, which knocked down mRNA and protein expression of TLR1 or TLR2 significantly in vitro. One hundred and forty apolipoprotein E-deficient (apoE(-/-)) mice were randomly allocated to control, mock, TLR1 interference (TLR1i), TLR2 interference (TLR2i), and TLR1+2 interference (TLR1+2i) subgroups and a constrictive collar was placed around the carotid artery of these mice to induce plaque formation. TLR1i and TLR2i viral suspension was transfected into the carotid plaques separately in the TLR1i and TLR2i subgroups or together in the TLR1+2i subgroup. Four weeks after lentivirus transfection, expression of both TLR1 and TLR2 in the carotid plaques was remarkably attenuated. Plaques of the TLR1i subgroup showed lower macrophage content and interleukin (IL)-6 expression and a thicker fibrous cap compared with the control or mock subgroups. Plaques of the TLR2i subgroup showed a higher content of collagen and lower content of lipid and macrophages, a thicker fibrous cap, lower vulnerability index, and lower mRNA expression of IL-6 and monocyte chemoattractant protein-1 than the TLR1i subgroup. In the TLR1+2i subgroup, the macrophage and smooth muscle cell content, and the vulnerability index, were ameliorated as compared with those in the TLR2i subgroup. Lentivirus-mediated RNA interference can be used to efficiently knock down TLR1 and TLR2 genes in carotid plaques of apoE(-/-) mice. Although isolated knockdown of TLR1 or TLR2 is effective in attenuating plaque vulnerability, combinatorial interference with TLR1 and TLR2 exhibits enhanced improvement of plaque stability, and thus provides a useful approach to the stabilization of vulnerable plaques.