A Novel Long Noncoding RNA in Osteocytes Regulates Bone Formation through the Wnt/β-Catenin Signaling Pathway

The vast majority of transcribed RNAs are noncoding RNAs. Among noncoding RNAs, long noncoding RNAs (lncRNAs), which contain hundreds to thousands of bases, have received attention in many fields. The vast majority of the constituent cells in bone tissue are osteocytes, but their regulatory mechanisms are incompletely understood. Considering the wide range of potential contributions of lncRNAs to physiological processes and pathological conditions, we hypothesized that lncRNAs in osteocytes, which have not been reported, could be involved in bone metabolism. Here, we first isolated osteocytes from femurs of mice with osteocyte-specific GFP expression. Then, through RNA-sequencing, we identified osteocyte-specific lncRNAs and focused on a novel lncRNA, 9530026P05Rik (lncRNA953Rik), which strongly suppressed osteogenic differentiation. In the IDG-SW3 osteocyte line with lncRNA953Rik overexpression, the expression of Osterix and its downstream genes was reduced. RNA pull-down and subsequent LC-MS/MS analysis revealed that lncRNA953Rik bound the nuclear protein CCAR2. We demonstrated that CCAR2 promoted Wnt/β-catenin signaling and that lncRNA953Rik inhibited this pathway. lncRNA953Rik sequestered CCAR2 from HDAC1, leading to deacetylation of H3K27 in the Osterix promoter and consequent transcriptional downregulation of Osterix. This research is the first to clarify the role of a lncRNA in osteocytes. Our findings can pave the way for novel therapeutic options targeting lncRNAs in osteocytes to treat bone metabolic diseases such as osteoporosis.

Three-dimensional visualization of neural networks inside bone by Osteo-DISCO protocol and alteration of bone remodeling by surgical nerve ablation

Bone is one of the largest organ systems in humans and is considered to regulate whole-body homeostasis in cooperation with other organs. We have previously reported that a sympathetic or sensory nervous system inside bone regulates bone homeostasis. However, the detailed regulatory mechanism, including the distribution of nerves inside bone, remains unknown. Although a two-dimensional histological analysis has been widely used to evaluate the structure of nerves or blood vessels, the actual structure is more complex, suggesting that it should be evaluated three-dimensionally. Here, we established a novel bone tissue clearing technique (Osteo-DISCO) for murine bones which enabled us to visualize the detailed distribution of nerves or blood vessels inside bone. Interestingly, we found that there is a specific nerve entry site in each long bone and that surgical ablation of the specific nerve fibers entering bone tissue led to decreased bone formation and impaired bone regeneration. Furthermore, we revealed that the administration of calcitonin gene-related peptide (CGRP), which is primarily released from sensory nerves, suppressed the bone loss caused by surgical nerve ablation. An in vitro study also indicated that CGRP directly promotes osteoblast activity, suggesting that sensory nerves inside bone can regulate osteogenesis via the secretion of CGRP.

55Identification of celastramycin as a novel therapeutic agent for pulmonary arterial hypertension - high-throughput screening of 5,562 compounds

Background

Pulmonary arterial hypertension (PAH) is characterized by enhanced proliferation of pulmonary artery smooth muscle cells (PASMCs) accompanying increased production of inflammatory factors and adaptation of mitochondrial metabolism to a hyperproliferative state. However, at present, since all the drugs in clinical use target pulmonary vascular dilatation, they may not be so effective for patients with advanced PAH.

Purposes

We aimed to discover a novel drug for PAH that inhibits PASMC proliferation.

Methods

In the first screening, we examined 5,562 compounds from our original library using high-throughput screening system to discover a compound that inhibits proliferation of PASMCs from PAH patients (PAH-PASMCs). In the second screening, we performed concentration-dependent assays and counter assays with PAH-PASMCs and PASMCs from healthy donors. We also performed apoptosis assays and mechanistic analysis for inflammation, reactive oxygen species (ROS), and mitochondrial function.

Results

We found that celastramycin, a benzoyl pyrrole-type compound originally found in a bacteria extract, inhibited the proliferation of PAH-PASMCs in a dose-dependent manner with minimal effects on PASMCs from healthy donors. Moreover, celastramycin inhibited proliferation with minimal increase in apoptosis and low rate of cell death. Then, we synthesized 25 analogues of celastramycin, and finally selected the lead compound that significantly inhibited proliferation of PAH-PASMCs and reduced cytosolic ROS levels. Mechanistic analysis demonstrated that celastramycin reduced the protein levels of hypoxia-inducible factor-1α, which was abnormally activated in PAH-PASMCs and impaired aerobic metabolism, and nuclear factor-κB, which induces pro-inflammatory signals, in PAH-PASMCs compared with vehicle controls, leading to reduced secretion of inflammatory cytokines. Importantly, celastramycin treatment reduced the ROS levels in PAH-PASMCs with increased protein levels of NF-E2-related factor 2 (Nrf2), a master regulator of cellular response against oxidative stress. Furthermore, celastramycin treatment improved mitochondrial energy metabolism with recovered mitochondrial network formation in PAH-PASMCs. We also discovered that celastramycin-mediated effects on these transcriptional modulators could be regulated by zinc finger C3H1 domain-containing protein, which is a binding partner of celastramycin. Finally, celastramycin treatment ameliorated pulmonary hypertension in three experimental animal models of PH in mice and rats, accompanied by reduced inflammatory changes in the lungs.

Conclusions

These results indicate that celastramycin ameliorates pulmonary hypertension through inhibition of excessive proliferation of PAH-PASMCs, for which its anti-inflammatory and beneficial effects on mitochondrial energy metabolism may be involved. Thus, celastramycin could be a novel drug for PAH as it exerts anti-proliferative effects on PAH-PASMCs.

P6479Diagnostic and prognostic significance of serum levels of selenoprotein P in patients with pulmonary arterial hypertension

Background

Despite the recent progress in upfront combination therapy for pulmonary arterial hypertension (PAH), a useful biomarker for the disorder still remains to be developed. Selenoprotein P (SeP) is a glycoprotein secreted mainly from hepatocytes but also from other various kinds of cells, including pulmonary artery smooth muscle cells (PASMCs), to maintain selenium homeostasis and cellular energy metabolism. We have recently demonstrated that SeP expression in PASMCs is markedly up-regulated in PAH patients and plays crucial roles in the pathogenesis of the disorder. In this study, we thus examined whether serum levels of SeP could be a useful biomarker for the disorder.

Methods

In the experimental study, we performed gene expression microarray and in silico analyses to identify a novel therapeutic target for PAH. We also used the lung, serum, and cultured PAMSCs derived from patients with PAH for mechanistic experiments. In the clinical study, we enrolled a total of 65 consecutive patients with PAH who underwent right heart catheterization for hemodynamic assessment. We measured serum SeP levels and evaluated their prognostic impacts during follow-up (mean 1,520 days, IQR: 1,393–1,804 days). Serum SeP level was measured using a newly developed sol particle homogeneous immunoassay. As controls, we collected serum samples from 20 controls without any known cardiac disorders evaluated by hematological examination, echocardiography, and coronary angiography. In PAH patients, we examined the relationship between baseline SeP levels and composite endpoint of all-cause death and lung transplantation. The correlation between the absolute changes in SeP and those in hemodynamic parameters during follow-up were also examined.

Results

In the experimental study, SeP promoted PASMC proliferation through increased oxidative stress and mitochondrial metabolic dysfunction, which were associated with activated HIF-1α and dysregulated glutathione metabolism. In the clinical study, PAH patients showed significantly higher levels of serum SeP compared with controls (3.07±0.57 vs. 2.43±0.25 mg/L, P<0.0001). Higher SeP levels (cut-off point, 3.47 mg/L) were significantly associated with the composite endpoint of all-cause death and lung transplantation in PAH patients [HR: 4.85 (1.42 to 16.6), P<0.01]. Importantly, we found that absolute changes in SeP levels in PAH patients significantly correlated with those in mean pulmonary artery pressure, pulmonary vascular resistance, and cardiac index in response to PAH-specific therapy (R=0.78, 0.76, and −0.71, respectively, all P<0.0001). Furthermore, the increases in SeP levels during follow-up predicted the poor outcome in PAH patients [Figure, HR: 4.29 (1.27 to 14.4), P<0.05].

Figure 1

Conclusions

These results indicate that SeP is a novel therapeutic target of PAH and that serum SeP levels are a novel biomarker for diagnosis and assessment of treatment efficacy and long-term prognosis in PAH patients.

Acknowledgement/Funding

Grants-in-aid for Scientific Research from the Japan Agency for Medical Research and Development, Tokyo, Japan (16ek0109176h0001, 17ek0109227h0001).

P836Glasgow Prognostic Score predicts the readmission caused by acute decompensated heart failure after myocardial infarction

Purpose

The Glasgow Prognostic Score (GPS), combination of C-reactive protein (CRP) and serum albumin concentration, provides predictions of prognosis in patients with heart failure. We evaluated the GPS of patients with acute myocardial infarction (MI).

Methods

We investigated the prognosis of 1182 patients with acute MI in our institution. These patients were classified into three groups by GPS at admission. GPS was defined as follows: patients with both elevated CRP (>1.0mg/dL) and hypoalbuminemia (<3.5 g/dL) were allocated a score of 2, patients with only one of these biochemical abnormalities were allocated a score of 1, and patients with neither of these abnormalities were allocated a score of 0.

Results

Of the patients, 70.3% (n=831), 19.2% (n=227), and 10.5% (n=124) had GPS of 0, 1, and 2, respectively. In-hospital mortality of GPS 0, GPS 1, and GPS 2 were 4.7%, 18.1%, and 31.5%, respectively (p<0.0001). Relative to a GPS of 0, the hazard ratios for the readmission caused by acute decompensated heart failure (ADHF) were 3.27 (95% CI: 2.04–5.18) for a GPS of 1 and 3.62 (95% CI: 1.93–6.42) for a GPS of 2 in the age- and sex- adjusted Cox proportional hazard model. After propensity score matching, baseline characteristics were balanced, and 250 paired patients constituted GPS 0 group and GPS 1–2 group. Patients with GPS1 or 2 had a higher risk of the development of ADHF compared with patients with GPS 0 (Hazard ratio: 1.96, 95% confidence interval: 1.13–3.47, p=0.017).

Conclusions

The GPS, which is based on systemic inflammation, is useful for predicting the development of acute decompensated heart failure after myocardial infarction.

Circadian Clock Regulates Bone Resorption in Mice

The circadian clock controls many behavioral and physiological processes beyond daily rhythms. Circadian dysfunction increases the risk of cancer, obesity, and cardiovascular and metabolic diseases. Although clinical studies have shown that bone resorption is controlled by circadian rhythm, as indicated by diurnal variations in bone resorption, the molecular mechanism of circadian clock-dependent bone resorption remains unknown. To clarify the role of circadian rhythm in bone resorption, aryl hydrocarbon receptor nuclear translocator-like (Bmal1), a prototype circadian gene, was knocked out specifically in osteoclasts. Osteoclast-specific Bmal1-knockout mice showed a high bone mass phenotype due to reduced osteoclast differentiation. A cell-based assay revealed that BMAL1 upregulated nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 (Nfatc1) transcription through its binding to an E-box element located on the Nfatc1 promoter in cooperation with circadian locomotor output cycles kaput (CLOCK), a heterodimer partner of BMAL1. Moreover, steroid receptor coactivator (SRC) family members were shown to interact with and upregulate BMAL1:CLOCK transcriptional activity. Collectively, these data suggest that bone resorption is controlled by osteoclastic BMAL1 through interactions with the SRC family and binding to the Nfatc1 promoter. © 2016 American Society for Bone and Mineral Research.

Histone deacetylase inhibitor panobinostat induces calcineurin degradation in multiple myeloma

Multiple myeloma (MM) is a relapsed and refractory disease, one that highlights the need for developing new molecular therapies for overcoming of drug resistance. Addition of panobinostat, a histone deacetylase (HDAC) inhibitor, to bortezomib and dexamethasone improved progression-free survival (PFS) in relapsed and refractory MM patients. Here, we demonstrate how calcineurin, when inhibited by immunosuppressive drugs like FK506, is involved in myeloma cell growth and targeted by panobinostat. mRNA expression of PPP3CA, a catalytic subunit of calcineurin, was high in advanced patients. Panobinostat degraded PPP3CA, a degradation that should have been induced by inhibition of the chaperone function of heat shock protein 90 (HSP90). Cotreatment with HDAC inhibitors and FK506 led to an enhanced antimyeloma effect with a greater PPP3CA reduction compared with HDAC inhibitors alone both in vitro and in vivo. In addition, this combination treatment efficiently blocked osteoclast formation, which results in osteolytic lesions. The poor response and short PFS duration observed in the bortezomib-containing therapies of patients with high PPP3CA suggested its relevance to bortezomib resistance. Moreover, bortezomib and HDAC inhibitors synergistically suppressed MM cell viability through PPP3CA inhibition. Our findings underscore the usefulness of calcineurin-targeted therapy in MM patients, including patients who are resistant to bortezomib.

MicroRNA-145 regulates osteoblastic differentiation by targeting the transcription factor Cbfb

Osteoblastic differentiation is regulated by various factors, including hormones and transcription factors. Runt-related transcription factor 2 (Runx2) is an essential player in osteoblastogenesis and transactivates its molecular target by creating a protein complex with its hetero-dimeric partner core binding factor beta (Cbfb). However, the molecular regulation of Cbfb expression remains unknown. Here, we identified miR-145 as a crucial regulator of Cbfb expression. The expression of miR-145 increased during osteoblastogenesis, indicating that miR-145 works as an inhibitor of osteoblastogenesis. Stable expression of miR-145 decreased endogenous Cbfb expression and inhibited osteoblastogenesis, in cooperation with miR-34c. Furthermore, miR-145 decreased bone regeneration in vivo. Our results indicate that miR-145 physiologically regulates osteoblast differentiation and bone formation via Cbfb expression by forming a regulatory microRNA network.