Objective-Aortic calcification is prevalent in type II diabetes (T2DM), enhancing morbidity and tracking metabolic syndrome parameters. Ldlr Ϫ/Ϫ mice fed high-fat "Westernized" diets (HFD) accumulate aortic calcium primarily in the tunica media, mediated via osteogenic morphogens and transcriptional programs that induce aortic alkaline phosphatase (ALP). Because elevated TNF-␣ is characteristic of obesity with T2DM, we examined contributions of this inflammatory cytokine. Methods and Results-HFD promoted obesity, hyperglycemia, and hyperlipidemia, and upregulated serum TNF-␣ in Ldlr Ϫ/Ϫ mice. Serum haptoglobin (inflammatory marker) was increased along with aortic expression of BMP2, Msx2, Wnt3a, and Wnt7a. Dosing with the TNF-␣ neutralizing antibody infliximab did not reduce obesity, hypercholesterolemia, or hyperglycemia; however, haptoglobin, aortic BMP2, Msx2, Wnt3a, and Wnt7a and aortic calcium accumulation were downregulated by infliximab. Mice with vascular TNF-␣ augmented by a transgene (SM22-TNF␣Tg) driven from the SM22 promoter upregulated aortic Msx2, Wnt3a, and Wnt7a. Furthermore, SM22-TNF␣Tg;TOPGAL mice exhibited greater aortic ␤-galactosidase reporter staining versus TOPGAL sibs, indicating enhanced mural Wnt signaling. In aortic myofibroblast cultures, TNF-␣ upregulated Msx2, Wnt3a, Wnt7a, and ALP. ALP induction was inhibited by Dkk1, an antagonist of paracrine Wnt actions. Conclusions-TNF-␣ promote aortic Msx2-Wnt programs that contribute to aortic calcium accumulation in T2DM.

Abstract-Osteopontin (OPN) is a cytokine upregulated in diabetic vascular disease. To better understand its role in vascular remodeling, we assessed how OPN controls metalloproteinase (MMP) activation in aortic adventitial myofibroblasts (AMFs) and A7r5 vascular smooth muscle cells (VSMCs). By zymography, OPN and tumor necrosis factor (TNF)-␣ preferentially upregulate pro-matrix metalloproteinase 9 (pro-MMP9) activity. TNF-␣ upregulated pro-MMP9 in AMFs isolated from wild-type (OPN ϩ/ϩ ) mice, but pro-MMP9 induction was abrogated in AMFs from OPN Ϫ/Ϫ mice. OPN treatment of VSMCs enhanced pro-MMP9 activity, and TNF-␣ induction of pro-MMP9 was inhibited by anti-OPN antibody and apocynin. Superoxide and the oxylipid product 8-isoprostaglandin F 2 ␣-isoprostane

Studies of fracture repair have revealed that paracrine endothelial-mesenchymal interactions direct bone formation that restores osseous integrity. Angiogenic growth factors and specific members of the bone morphogenetic protein (BMP) family mediate these interactions. Recently, these same signals have been shown to be critical in the vascular pathobiology of hypertension, diabetes, and atherosclerosis. In the arterial vasculature, mechanical and inflammatory redox signals, characteristic of hypertension and diabetes have emerged as a secretagogues for BMP production-with downstream activation of endothelial NADPH oxidases (Nox). Preliminary data now indicate that the paracrine signals provided by BMP and reactive oxygen species augment aortic myofibroblast Msx2-Wnt signaling and matrix turnover. The net mural response to these stimuli promotes osteogenic differentiation of calcifying vascular cells, moreover, oxidation of vascular LDL cholesterol generates oxysterols that trigger Runx2 activity via hedgehog pathways. Thus, BMP, Wnt, and hedgehog gene expression programs-osteogenic pathways highly familiar to the bone biologist-are elaborated in the arterial vasculature via redox-regulated mechanisms. In the brief review, we recount mounting evidence that points to oxidative stress as a major contributor to the pathobiology of diabetic arterial calcification.

In LDLR(-/-) mice fed high-fat diabetogenic diets, osteogenic gene-regulatory programs are ectopically activated in vascular myofibroblasts and smooth muscle cells that promote arteriosclerotic calcium deposition. Msx2-Wnt signaling pathways previously identified as important for craniofacial skeletal development are induced in the vasculature by TNF, a prototypic cytokine mediator of the low-grade systemic inflammation of diabesity. To better understand this biology, we studied TNF actions on Msx2 in aortic myofibroblasts. TNF up-regulated Msx2 mRNA 4-fold within 3 h but did not regulate Msx1. Although IL-1β could also induce Msx2 expression, TNF-related apoptosis inducing ligand, receptor activator of nuclear factor-κB ligand, and IL-6 were inactive. Inhibition of nicotinamide adenine dinucleotide phosphate oxidase (Nox) activity and genetically induced Nox deficiency (p47phox(-/-)) reduced Msx2 induction, indicating contributions of reactive oxygen species (ROS) and redox signaling. Consistent with this, rotenone, an antagonist of mitochondrial complex I, inhibited TNF induction of Msx2 and Nox2, whereas pyruvate, an anapleurotic mitochondrial metabolic substrate, enhanced induction. Moreover, the glutathione peroxidase-mimetic ebselen abrogated this TNF response. Treatment of aortic myofibroblasts with hydrogen peroxide up-regulated Msx2 mRNA, promoter activity, and DNA-protein interactions. In vivo, SM22-TNF transgenic mice exhibit increased aortic Msx2 with no change in Msx1. Dosing SM22-TNF mice with either 20 ng/g Nox1 + 20 ng/g Nox2 antisense oligonucleotides or low-dose rotenone reduced arterial Msx2 expression. Aortic myofibroblasts from TNFR1(-/-) mice expressed levels of Msx2 that were 5% that of wild-type and were not inducible by TNF. Wnt7b and active β-catenin levels were also reduced. By contrast, TNF-inducible Msx2 expression was not reduced in TNFR2(-/-) cells. Finally, when cultured under mineralizing conditions, TNFR1(-/-) aortic myofibroblasts exhibited reduced calcification compared with wild-type and TNFR2(-/-) cells. Thus, ROS metabolism contributes to TNF induction of Msx2 and procalcific responses in myofibroblasts via TNFR1. Strategies that reduce vascular Nox- or mitochondrially activated ROS signals may prove useful in mitigating arteriosclerotic calcification.

FHL2, a molecule that interacts with many integrins and transcription factors, was found to play an important role in osteoblast differentiation. Overexpression of FHL2 increases the accumulation of osteoblast differentiation markers and matrix mineralization, whereas FHL2 deficiency results in inhibition of osteoblast differentiation and decreased bone formation.Introduction: Integrin-matrix interaction plays a critical role in osteoblast function. It has been shown that the cytoplasmic domains of integrin ␤ subunits mediate signal transduction induced by integrin-matrix interaction. We reasoned that the identification of proteins interacting with ␤-cytoplasmic tails followed by analysis of the function of these proteins would enhance our understanding on integrin signaling and the roles of these proteins in osteoblast activities. Materials and Methods: Yeast two hybrid assay was used to identify proteins interacting with the cytoplasmic domain of integrin ␤5 subunit. The association of these proteins with integrin ␣v␤5 was confirmed by confocal analysis and co-immunoprecipitation. A stable MC3T3-E1 cells line overexpressing Four and Half Lim Protein 2 (FHL2) and mouse osteoblasts deficient in FHL2 were used to study the roles of FHL2 in osteoblast differentiation and bone formation. Matrix protein expression was determined by mRNA analysis and Western blotting. Matrix mineralization was detected by Alizarin red staining. Alkaline phosphatase activity was also measured. CT was used to determine bone histomorphometry. Results and Conclusions: FHL2 and actin-binding proteins, palladin and filamin A, were identified as proteins interacting with ␤5 cytoplasmic domain. FHL2 co-localized with ␣v␤5 at the focal adhesion sites in association with palladin and filamin A. FHL2 was also present in nuclei. Osteoblasts overexpressing FHL2 exhibited increased adhesion to and migration on matrix proteins. Conversely, FHL2 stimulation of CREB activity was dependent on integrin function because it was inhibited by Gly-Arg-Gly-Asp-Ser (GRGDS) peptide. The expression of osteoblast differentiation markers and Msx2 was upregulated, and bone matrix mineralization was increased in FHL2 overexpressing cells. In contrast, FHL2-deficient bone marrow cells and osteoblasts displayed decreased osteoblast colony formation and differentiation, respectively, compared with wildtype cells. Moreover, FHL2-deficient female mice exhibited greater bone loss than the wildtype littermates after ovariectomy. Thus, FHL2 plays an important role in osteoblast differentiation and bone formation.