Tumor necrosis factor-α induces aortic intima-media thickening via perivascular adipose tissue inflammation.

BACKGROUND/AIMS: Neointimal thickening results from inflammation in association with vascular smooth muscle cell (VSMC) proliferation. We studied the role of perivascular adipose tissue (PVAT) on VSMC proliferation and intima-media thickening (IMT) in a rodent model of chronic inflammation. METHODS: The abdominal aorta and surrounding PVAT of tumour necrosis factor (TNF)-α-injected mice were examined 28 days after administration. Plasma and PVAT cytokines were measured with Milliplex™ assays. Inflammatory cells were examined with immunofluorescence. Expression of transforming growth factor (TGF)-ß1, matrix metalloproteinase (MMP)-2, MMP-9 and MMP-12 was examined with immunohistochemistry, immunoblotting and zymography. IMT was determined. Cell proliferation and TGF-ß1 mRNA levels were examined after treating VSMC with PVAT homogenates ± MMP-2 inhibitors (batimastat, ARP 100 or TIMP-2) and SB-431542, a selective inhibitor of the TGF-ß-type 1 receptor. RESULTS: Significant increases in CD3, CD68, neutrophils, vascular cell adhesion molecule-1 and MMP-2 in PVAT, and TGF-ß1 and IMT of the aorta of TNF-α-injected mice were observed. PVAT of TNF-α-injected mice significantly up-regulated TGF-ß1 and increased cell proliferation in a dose-dependent manner and was attenuated by SB-431542, batimastat, ARP 100 and TIMP-2. CONCLUSIONS: Our study shows that chronic PVAT inflammation leads to MMP-mediated increase in TGF-ß1 and hence VSMC proliferation.

Role of tumor necrosis factor-α in the pathogenesis of atrial fibrosis and development of an arrhythmogenic substrate.

BACKGROUND: Although tumor necrosis factor-α (TNF-α) levels are increased in patients with atrial fibrillation (AF), its role in the pathogenesis of AF is unclear. We investigated whether direct delivery of TNF-α could induce atrial fibrosis. METHODS AND RESULTS: TNF-α (4 µg/kg) was injected into the tail vein of 20 male Swiss albino mice (TNF group) and saline into 20 control mice (CON group). The dose was carefully chosen to avoid any significant decrease in left ventricular (LV) function. Animals were killed after 16 weeks and their atria examined for fibrosis. We found increased atrial fibrosis in the TNF group compared with the CON group [372.8±21.5 arbitrary units (a.u.) vs. 56.9±6.5 a.u., respectively, mean±SEM; P<0.0001] and decreased connexin-40 immunofluorescence [7.5±0.4 a.u vs. 40.4±1.9 a.u, respectively; P<0.0001]. Transforming growth factor-ß [TGF-ß: 95.6±1.8 a.u vs. 29.4±5.8 a.u; P<0.001], α-smooth muscle actin (α-SMA: 97.9±13.0 a.u vs. 50.1±18.5 a.u; P<0.05] and matrix metalloproteinase 2 (MMP-2)/GAPDH levels [157.3±26.4 a.u vs. 105.8±13.3 a.u; P<0.05] were also increased in the TNF group. CONCLUSIONS: TNF-α is involved in the pathogenesis of atrial fibrosis and altered connexin-40 expression in mice through the TGF-ß signaling pathway, activation of myofibroblasts and increased secretion of MMPs. Collectively, these changes may contribute to the arrhythmogenic substrate and development of AF.

Tumor necrosis factor-α-induced nuclear factor-kappaB activation in human cardiomyocytes is mediated by NADPH oxidase.

An elevated level of tumor necrosis factor (TNF)-α is implicated in several cardiovascular diseases including heart failure. Numerous reports have demonstrated that TNF-α activates nuclear factor (NF)-kappaB, resulting in the upregulation of several genes that regulate inflammation, proliferation, and apoptosis of cardiomyocytes. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, a major source of reactive oxygen species (ROS), is also activated by TNF-α and plays a crucial role in redox-sensitive signaling pathways. The present study investigated whether NADPH oxidase mediates TNF-α-induced NF-kappaB activation and NF-kappaB-mediated gene expression. Human cardiomyocytes were treated with recombinant TNF-α with or without pretreatment with diphenyleneiodonium (DPI) and apocynin, inhibitors of NADPH oxidase. TNF-α-induced ROS production was measured using 5-(and-6)-chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate assay. TNF-α-induced NF-kappaB activation was also examined using immunoblot; NF-kappaB binding to its binding motif was determined using a Cignal reporter luciferase assay and an electrophoretic mobility shift assay. TNF-α-induced upregulation of interleukin (IL)-1ß and vascular cell adhesion molecule (VCAM)-1 was investigated using real-time PCR and immunoblot. TNF-α-induced ROS production in cardiomyocytes was mediated by NADPH oxidase. Phosphorylation of IKK-α/ß and p65, degradation of IkappaBα, binding of NF-kappaB to its binding motif, and upregulation of IL-1ß and VCAM-1 induced by TNF-α were significantly attenuated by treatment with DPI and apocynin. Collectively, these findings demonstrate that NADPH oxidase plays a role in regulation of TNF-α-induced NF-kappaB activation and upregulation of proinflammatory cytokines, IL-1ß and VCAM-1, in human cardiomyocytes.

Tumor necrosis factor-alpha-induced nuclear factor-kappaB activation in human cardiomyocytes is mediated by NADPH oxidase

An elevated level of tumor necrosis factor (TNF)-α is implicated in several cardiovascular diseases including heart failure. Numerous reports have demonstrated that TNF- alfa activates nuclear factor (NF)-kappaB, resulting in the upregulation of several genes that regulate inflammation, proliferation, and apoptosis of cardiomyocytes. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, a major source of reactive oxygen species (ROS), is also activated by TNF- alfa and plays a crucial role in redox-sensitive signaling pathways. The present study investigated whether NADPH oxidase mediates TNF-alfa-induced NF-kappaB activation and NF-kappaB-mediated gene expression. Human cardiomyocytes were treated with recombinant TNF- alfa with or without pretreatment with diphenyleneiodonium (DPI) and apocynin, inhibitors of NADPH oxidase. TNF-α-induced ROS production was measured using 5-(and-6)-chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate assay. TNF- alfa-induced NF-kappaB activation was also examined using immunoblot; NF-kappaB binding to its binding motif was determined using a Cignal reporter luciferase assay and an electrophoretic mobility shift assay. TNF- alfa -induced upregulation of interleukin (IL)-1β and vascular cell adhesion molecule (VCAM)-1 was investigated using real-time PCR and immunoblot. TNF- alfa -induced ROS production in cardiomyocytes was mediated by NADPH oxidase. Phosphorylation of IKK- alfa /β and p65, degradation of IkappaBalfa, binding of NF-kappaB to its binding motif, and upregulation of IL-1β and VCAM-1 induced by TNF- alfa were significantly attenuated by treatment with DPI and apocynin. Collectively, these findings demonstrate that NADPH oxidase plays a role in regulation of TNF- alfa -induced NF-kappaB activation and upregulation of proinflammatory cytokines, IL-1β and VCAM-1, in human cardiomyocytes