Aortic Msx2-Wnt Calcification Cascade Is Regulated by TNF-α–Dependent Signals in Diabetic Ldlr ^−/− Mice

Abstract

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.

Cell-specific effects of TNF-α and IL-1β on alkaline phosphatase: implication for syndesmophyte formation and vascular calcification

“…This is in marked contrast with the published effects of TNF-a on TNAP expression and activity in VSMCs 22,23 and on vascular calcification in diabetic mice. 24 In this context, we aimed at deciphering the mechanisms responsible for the different Cell-specific effects of TNF-a on TNAP P Lencel et al effect of TNF-a on TNAP in chondrocytes and VSMCs. We first confirm that TNF-a stimulates both TNAP expression and activity in human VSMCs.…”

“…Indeed, whereas TNF-a and IL-1b may be direct inhibitors of ectopic bone formation in patients with AS, TNF-a is strongly suspected to be a direct activator of vascular calcification that develops in association with diabetes mellitus, 24 and probably also in the context of atherosclerosis. 41,42 Indeed, several independent groups have shown that TNF-a stimulates the expression and activity of TNAP in VSMCs.…”

“…41,42 Indeed, several independent groups have shown that TNF-a stimulates the expression and activity of TNAP in VSMCs. [22][23][24] Since TNAP overexpression in mouse under the control of the a2col1 promoter of the collagen type I induces vascular calcification, 20 we have recently proposed that TNF-a may induce vascular calcification by the mere stimulation of TNAP. 25 In the present study, we first confirm that TNF-a stimulates TNAP expression and activity in human VSMCs, [22][23][24] and further suggest that like in human osteoblasts, 29 TNF-a may act by inhibiting PPARg activity.…”

“…21 This hypothesis was conceivable since TNF-a stimulates TNAP expression in vascular smooth muscle cells (VSMCs), 22,23 and since blockade of TNF-a with infliximab specifically inhibits vascular calcification in the LdlrÀ/À diabetes mellitus mouse model, without reducing obesity, hypercholesterolemia or hyperglycemia. 24 In this hypothesis, cytokines may stimulate ectopic collagen calcification by the mere stimulation of TNAP activity, and this calcified matrix, may in turn induce the ossification process, in the arterial wall, 25 and in entheseal fibro-cartilage during AS. 4,5 MATERIALS AND METHODS Chemicals Cell culture plastic ware was purchased from D Dutscher (Brumath, France).…”

Triple play: Promoting neurovascular longevity with nicotinamide, WNT, and erythropoietin in diabetes mellitus

“…Clinical observations in patients with coronary artery disease and the combined metabolic syndrome with hypertension, hyperlipidemia, and DM have observed impaired Wnt signaling through a missense mutation in LRP-6 [193]. Experimental studies in mice that develop hyperglycemia through a high fat diet also demonstrate increased expression of some Wnt family members, such as Wnt3a and Wnt7a [194]. Yet, intact Wnt family members may offer glucose tolerance and increased insulin sensitivity [195] as well as protect glomerular mesangial cells from elevated glucose induced apoptosis [196].…”