Vascular calcification (VC) is often associated with cardiovascular and metabolic diseases. However, the molecular mechanisms linking VC to these diseases have yet to be elucidated. Here we report that MDM2-induced ubiquitination of histone deacetylase 1 (HDAC1) mediates VC. Loss of HDAC1 activity via either chemical inhibitor or genetic ablation enhances VC. HDAC1 protein, but not mRNA, is reduced in cell and animal calcification models and in human calcified coronary artery. Under calcification-inducing conditions, proteasomal degradation of HDAC1 precedes VC and it is mediated by MDM2 E3 ubiquitin ligase that initiates HDAC1 K74 ubiquitination. Overexpression of MDM2 enhances VC, whereas loss of MDM2 blunts it. Decoy peptide spanning HDAC1 K74 and RG 7112, an MDM2 inhibitor, prevent VC in vivo and in vitro. These results uncover a previously unappreciated ubiquitination pathway and suggest MDM2-mediated HDAC1 ubiquitination as a new therapeutic target in VC.

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Obesity is a serious and increasing health problem worldwide, and the inhibition of adipogenesis is considered to be a potential therapeutic target for it. Bergamottin (BGM), a component of grapefruit juice, has been reported to regulate lipolysis. However, the physiological role of BGM in obesity has not been evaluated so far. In the present study, we investigated the effects of BGM on obesity in 3T3-L1 cells and in mice fed a high-fat diet (HFD). BGM inhibited adipogenic differentiation of 3T3-L1 cells along with a significant decrease in the lipid content by downregulating the expression of two critical adipogenic factors, CCAAT enhancer-binding protein-alpha (C/EBP[Formula: see text]) and peroxisome proliferator activated receptor-gamma (PPAR[Formula: see text]). The expressions of target proteins such as adipocyte fatty acid-binding protein (aP2), adiponectin, and resistin were also decreased by BGM. It activated AMP-activated protein kinase (AMPK) by increasing phosphorylation of AMPK and the downstream target acetyl-CoA carboxylase (ACC), indicating that BGM exerted its antiadipogenic effect through AMPK activation. In the HFD-induced obese mouse model, BGM administration significantly reduced the weight and sizes of white adipose tissue as well as the weight gain of mice fed HFD. Moreover, UCP1 and PGC1[Formula: see text] expressions, well-known as brown adipocyte marker genes, were higher in the BGM-treated HFD mice than that in the HFD-induced obese mice. This study suggests that BGM suppress adipogenesis by AMPK activation in vitro and reduces body weight in vivo.

Bone mineralization is a normal physiological process, whereas ectopic calcification of soft tissues is a pathological process that leads to irreversible tissue damage. We have established a coxsackievirus B3 (CVB3)–infected mouse model that manifests both osteoporosis and ectopic calcification specifically in heart, pancreas, and lung. The CVB3-infected mice showed increased serum concentrations of both cytokines including IL-1β, TNF-α, and the receptor activator of NF-κB ligand (RANKL) that stimulate osteoclast formation and of the osteoclast-derived protein tartrate-resistant acid phosphatase 5b. They exhibited more osteoclasts in bone, with no change in the number of osteoblasts, and a decrease in bone formation and the serum concentration of osteoblast-produced osteocalcin. These results indicate that CVB3-induced osteoporosis is likely due to upregulation of osteoclast formation and function, in addition to decreased osteoblast activity. In addition, the serum in the CVB3-infected mice contained a high inorganic phosphate content, which causes ectopic calcification. RANKL treatment induced an increase in the in vitro cardiac fibroblast calcification by inorganic phosphate via the upregulation of osteogenic BMP2, SPARC, Runx2, Fra-1, and NF-κB signaling. We finally observed that i.p. administration of RANK-Fc, a recombinant antagonist of RANKL, prevented bone loss as well as ectopic calcification in CVB3-infected mice. Thus, our results indicate that RANKL may contribute to both abnormal calcium deposition in soft tissues and calcium depletion in bone. In addition, our animal model should provide a tool for the development of new therapeutic agents for calcium disturbance in soft and hard tissues.

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