BMP-2 up-regulates PTEN expression and induces apoptosis of pulmonary artery smooth muscle cells under hypoxia

Epithelial-mesenchymal interaction protects normal colonocytes from 4-HNE-induced phenotypic transformation

INTRODUCTION

Recent studies have shown that epithelial-stromal interactions could play a role in the development of colorectal cancer. Here, we investigated the role of fibroblasts in the transformation of normal colonocytes induced by 4-HNE.

METHODS

Normal Co colonocytes and nF fibroblasts from the same mouse colon were exposed, in monoculture (m) or coculture (c), to 4-HNE (5 μM) twice weekly for 3 weeks. Gene expression was then analysed and the ability of Co colonocytes to grow in anchorage-independent conditions was tested in soft agar. Fibroblasts previously treated or not with 4-HNE were also seeded in culture inserts positioned above the agar layers to allow paracrine exchanges with colonocytes.

RESULTS

First, 60% of the genes studied were modulated by coculture in Co colonocytes, with notably increased expression of BMP receptors. Furthermore, while 4-HNE increased the ability of monoculture-treated Co colonocytes to form colonies, this effect was not observed in coculture-treated Co colonocytes. Adding a selective BMPR1 inhibitor during the treatment phase abolished the protective effect of coculture. Conversely, addition of a BMP4 agonist to the medium of monoculture-treated Co colonocytes prevented phenotypic transformation by 4-HNE. Second, the presence of nF(m)-HNE fibroblasts during the soft agar assay increased the number and size of Co(m) colonocyte colonies, regardless of whether these cells had been previously treated with 4-HNE in monoculture. For soft agar assays performed with nF(c) and Co(c) cells initially treated in coculture, only the reassociation between Co(c)-HNE and nF(c)-HNE resulted in a small increase in the number of colonies.

CONCLUSIONS

During the exposure phase, the epithelial-mesenchymal interaction protected colonocytes from 4-HNE-induced phenotypic transformation via activation of the BMP pathway. This intercellular dialogue also limited the ability of fibroblasts to subsequently promote colonocyte-anchorage-independent growth. In contrast, fibroblasts pre-exposed to 4-HNE in monoculture strongly increased the ability of Co(m) colonocytes to form colonies.

Improving bone morphogenetic protein (BMP) production in CHO cells through understanding of BMP synthesis, signaling and endocytosis

Bone morphogenetic proteins (BMPs) are a group of growth factors with the clinical potential to regulate cartilage and bone formation. Functionally active mature recombinant human BMPs (rhBMPs), produced primarily in Chinese hamster ovary (CHO) cells for clinical applications, are considered difficult to express because they undergo maturation processes, signaling pathways, or endocytosis. Although BMPs are a family of proteins with similar mature domain sequence identities, their individual properties are diverse. Thus, understanding the properties of individual rhBMPs is essential to improve rhBMP production in CHO cells. In this review, we discuss various approaches to improve rhBMP production in CHO cells by understanding the overall maturation process, signaling pathways and endocytosis of individual rhBMPs.

A systematic summary of survival and death signalling during the life of hair follicle stem cells

Hair follicle stem cells (HFSCs) are among the most widely available resources and most frequently approved model systems used for studying adult stem cells. HFSCs are particularly useful because of their self-renewal and differentiation properties. Additionally, the cyclic growth of hair follicles is driven by HFSCs. There are high expectations for the use of HFSCs as favourable systems for studying the molecular mechanisms that contribute to HFSC identification and can be applied to hair loss therapy, such as the activation or regeneration of hair follicles, and to the generation of hair using a tissue-engineering strategy. A variety of molecules are involved in the networks that critically regulate the fate of HFSCs, such as factors in hair follicle growth and development (in the Wnt pathway, Sonic hedgehog pathway, Notch pathway, and BMP pathway), and that suppress apoptotic cues (the apoptosis pathway). Here, we review the life cycle, biomarkers and functions of HFSCs, concluding with a summary of the signalling pathways involved in HFSC fate for promoting better understanding of the pathophysiological changes in the HFSC niche. Importantly, we highlight the potential mechanisms underlying the therapeutic targets involved in pathways associated with the treatment of hair loss and other disorders of skin and hair, including alopecia, skin cancer, skin inflammation, and skin wound healing.

YTHDC1 mitigates ischemic stroke by promoting Akt phosphorylation through destabilizing PTEN mRNA

YTH Domain Containing 1 (YTHDC1) is one of the m⁶A readers that is essential for oocyte development and tumor progression. The role of YTHDC1 in neuronal survival and ischemic stroke is unknown. Here, we found that YTHDC1 was unregulated in the early phase of ischemic stroke. Knockdown of YTHDC1 exacerbated ischemic brain injury and overexpression of YTHDC1 protected rats against brain injury. Mechanistically, YTHDC1 promoted PTEN mRNA degradation to increase Akt phosphorylation, thus facilitating neuronal survival in particular after ischemia. These data identify YTHDC1 as a novel regulator of neuronal survival and modulating m⁶A reader YTHDC1 may provide a potential therapeutic target for ischemic stroke.

MEIS1 regulated proliferation and migration of pulmonary artery smooth muscle cells in hypoxia-induced pulmonary hypertension

AIM

Proliferation and migration of pulmonary artery smooth muscle cells (PASMCs) are regarded as the primary factors resulting in pulmonary arterial remodeling in pulmonary hypertension (PH). Myeloid ecotropic viral integration site 1 (MEIS1) has been positioned as a negative cardiomyocyte cell cycle regulator and regulates proliferation of multiple kinds of cancer cells. Whether MESI1 is involved in the proliferation and migration of PASMCs deserves to be identified.

MAIN METHODS

Sprague Dawley rats were exposed to hypoxia condition (10% O₂) for 4 weeks to induce PH and primary rat PASMCs were cultured in hypoxia condition (3% O₂) for 48 h to induce proliferation and migration. Immunohistochemistry, immunofluorescence, reverse transcription PCR and Western blot analysis were performed to detect the expressions of target mRNAs and proteins. EDU, CCK8 and wound healing assays were conducted to measure the proliferation and migration of PASMCs.

KEY FINDINGS

Hypoxia down-regulated the expression of MEIS1 (both mRNA and protein) in pulmonary arteries and PASMCs. Over-expression of MEIS1 inhibited the proliferation and migration of PASMCs afforded by hypoxia. In contrast, knockdown of MEIS1 under normoxia condition like hypoxia induced the proliferation and migration of PASMCs. MEIS1 mediated hypoxia-induced the proliferation and migration of PASMCs via METTL14/MEIS1/p21 signaling.

SIGNIFICANCE

The present study revealed that MEIS1 regulated the proliferation and migration of PASMCs during hypoxia-induced PH. Thus, MEIS1 may be a potential target for PH therapy.

BMP2-mediated PTEN enhancement promotes differentiation of hair follicle stem cells by inducing autophagy

The proliferation and differentiation of hair follicle stem cells (HFSCs) is regulated by several signaling pathways, including BMP and PTEN. Therefore, this study intended to clarify the potential effects of two such regulators, BMP2 and PTEN, on HFSC differentiation. HFSCs were subjected to BMP2, noggin (BMP2 ligand inhibitor), rapamycin (Rapa, autophagy inducer), 3-methyladenine (3-MA, autophagy inhibitor), or shRNA against PTEN. The differentiation of HFSCs was evaluated using oil red O staining and autophagy was assessed using the transmission electron microscope. Then expression of epidermal differentiation marker (K10 and involucrin), adipogenic markers (PPAR-γ2, aP2, perilipin2, and Adipoq), keratinocyte-specific marker (K15), proliferation-related markers (PCNA and Ki67) and autophagy-related factors (Atg5, Atg7, Atg12, Beclin-1 and LC3-II/LC3-I) was examined by RT-qPCR and Western blot analysis. Next, HFSCs were treated with 3-MA, or shRNA against Atg5 or Atg7 to verify the effect of autophagy on differentiation of BMP2-treated HFSCs. Finally, the effect of BMP2 on HFSC differentiation was verified by a mouse wound model. HFSCs overexpressing BMP2 exhibited elevated expression of epidermal differentiation marker, adipogenic markers and autophagy-related factors but inhibited expression of keratinocyte-specific marker and proliferation-related markers. Furthermore, we found that PTEN promoted the differentiation of BMP2-treated HFSCs by inducing autophagy. In vivo experiments further confirmed the roles of BMP2/PTEN on differentiation of HFSCs. Taken together, BMP2 up-regulated PTEN and consequently induced autophagy to facilitate HFSC differentiation.

The Role of Vitamin K and Its Related Compounds in Mendelian and Acquired Ectopic Mineralization Disorders

Ectopic mineralization disorders comprise a broad spectrum of inherited or acquired diseases characterized by aberrant deposition of calcium crystals in multiple organs, such as the skin, eyes, kidneys, and blood vessels. Although the precise mechanisms leading to ectopic calcification are still incompletely known to date, various molecular targets leading to a disturbed balance between pro- and anti-mineralizing pathways have been identified in recent years. Vitamin K and its related compounds, mainly those post-translationally activated by vitamin K-dependent carboxylation, may play an important role in the pathogenesis of ectopic mineralization as has been demonstrated in studies on rare Mendelian diseases, but also on highly prevalent disorders, like vascular calcification. This narrative review compiles and summarizes the current knowledge regarding the role of vitamin K, its metabolism, and associated compounds in the pathophysiology of both monogenic ectopic mineralization disorders, like pseudoxanthoma elasticum or Keutel syndrome, as well as acquired multifactorial diseases, like chronic kidney disease. Clinical and molecular aspects of the various disorders are discussed according to the state-of-the-art, followed by a comprehensive literature review regarding the role of vitamin K in molecular pathophysiology and as a therapeutic target in both human and animal models of ectopic mineralization disorders.

Upregulation of microRNA-17-5p contributes to hypoxia-induced proliferation in human pulmonary artery smooth muscle cells through modulation of p21 and PTEN

BACKGROUND

Pulmonary arterial smooth muscle cell (PASMC) proliferation in response to hypoxia plays an important role in the vascular remodelling that occurs in hypoxic pulmonary hypertension. MicroRNAs (miRs) are emerging as important regulators in the progression of pulmonary hypertension. In this study, we investigated whether the expression of miR-17-5p is modulated by hypoxia and is involved in the hypoxia-induced proliferation of PASMCs.

METHODS

Human PASMCs were cultured under hypoxic conditions. miR-17-5p expression was determined by real-time RT-PCR. A BrdU incorporation assay and time-lapse recording were utilized to determine cell proliferation and migration.

RESULTS

PASMC proliferation was increased by moderate hypoxia (3% oxygen) but was reduced by severe hypoxia (0.1% oxygen) after 48 h. Moderate hypoxia induced miR-17-5p expression. Overexpression of miR-17-5p by transfection with miR-17-5p enhanced cell proliferation and migration in normoxia, whereas knockdown of miR-17-5p with anti-miR-17-5p inhibitors significantly reduced cell proliferation and migration. The expression of miR-17-5p target genes, specifically phosphatase and tensin homologue (PTEN) and cyclin-dependent kinase inhibitor 1 (p21WAF1/Cip1, p21), was reduced under moderate hypoxia in PASMCs. Under normoxia, overexpression of miR-17-5p in PASMCs reduced the expression of PTEN and p21.

CONCLUSION

Our data indicate that miR-17-5p might play a significant role in hypoxia-induced pulmonary vascular smooth muscle cell proliferation by regulating multiple gene targets, including PTEN and p21, and that miR-17-5p could be a novel therapeutic target for the management of hypoxia-induced PH.

Sumoylation of SMAD 4 ameliorates the oxidative stress-induced apoptosis in osteoblasts

Oxidative stress-induced mitochondrial function and cell apoptosis to osteoblasts, plays a critical role in the pathophysiology of osteoporosis. However, mechanisms underlying such process remain not yet clear. We aims in this study to investigate a possible role of SMAD (the mothers against decapentaplegic homolog 4 (SMAD4) in the oxidative stress-induced apoptosis, in homo sapiens osteoblast hFOB1.19 cells. Results demonstrated that the treatment with more than 100μM H₂O₂ significantly downregulated the cellular viability, whereas markedly induced apoptosis in hFOB1.19 cells. The SMAD4 was markedly reduced in both mRNA and protein levels in the H₂O₂ -treated hFOB1.19 cells, along with the reduction of Small ubiquitin-related modifier 1 (SUMO 1) and SUMO 2/3. The immunoprecipitation assay confirmed indicated the interaction between SUMO 1 (or SUMO 2/3) and SMAD4. Moreover, the SMAD4 overexpression markedly ameliorated the H₂O₂-resulted viability reduction and apoptosis induction in hFOB1.19 cells. Interestingly, such amelioration was blocked by the knockdown of SUMO 2/3. Taken together, we conclued that SMAD4 inhibits the H₂O₂-induced apoptosis in osteoblast hFOB1.19 cells; such inhibition might depend on the SUMOylation by SUMO 2/3. It implies a promising role of SMAD4 in oxidative stress-promoted damage to osteoblasts.

Anti-invasive effects of CXCR4 and FAK inhibitors in non-small cell lung carcinomas with mutually inactivated p53 and PTEN tumor suppressors

Non-small cell lung carcinoma (NSCLC) is the most common type of lung cancer. At the time of diagnosis, a large percentage of NSCLC patients have already developed metastasis, responsible for extremely high mortality rates. CXCR4 receptor and focal adhesion kinase (FAK) are known to regulate such invasive cancer behavior. Their expression is downregulated by p53 and PTEN tumor suppressors which are commonly co-inactivated in NSCLC patients and contribute to metastasis. Therefore, targeting CXCR4 or FAK seems to be a promising strategy in suppressing metastatic spread of p53/PTEN deficient NSCLCs. In this study, we first examined the invasive characteristics of NSCLC cells with suppressed p53 and PTEN activity using wound healing, gelatin degradation and invasion assays. Further, changes in the expression of CXCR4 and FAK were evaluated by RT-qPCR and Western Blot analysis. Finally, we tested the ability of CXCR4 and FAK inhibitors (WZ811 and PF-573228, respectively) to suppress the migratory and invasive potential of p53/PTEN deficient NSCLC cells, in vitro and in vivo using metastatic models of human NSCLC. Our results showed that cells with mutually inactive p53 and PTEN have significantly increased invasive potential associated with hyperactivation of CXCR4 and FAK signaling pathways. Treatments with WZ811 and PF-573228 inhibitors significantly reduced migratory and invasive capacity in vitro and showed a trend of improved survival in vivo. Accordingly, we demonstrated that p53/PTEN deficient NSCLCs have extremely invasive phenotype and provided a rationale for the use of CXCR4 or FAK inhibitors for the suppression of NSCLC dissemination.

BMP-7 induces apoptosis in human germinal center B cells and is influenced by TGF-β receptor type I ALK5

Selection and maturation of B cells into plasma cells producing high-affinity antibodies occur in germinal centers (GC). GCs form transiently in secondary lymphoid organs upon antigen challenge, and the GC reaction is a highly regulated process. TGF-β is a potent negative regulator, but the influence of other family members including bone morphogenetic proteins (BMPs) is less known. Studies of human peripheral blood B lymphocytes showed that BMP-6 suppressed plasmablast differentiation, whereas BMP-7 induced apoptosis. Here, we show that human naïve and GC B cells had a strikingly different receptor expression pattern. GC B cells expressed high levels of BMP type I receptor but low levels of type II receptors, whereas naïve B cells had the opposite pattern. Furthermore, GC B cells had elevated levels of downstream signaling components SMAD1 and SMAD5, but reduced levels of the inhibitory SMAD7. Functional assays of GC B cells revealed that BMP-7 suppressed the viability-promoting effect of CD40L and IL-21, but had no effect on CD40L- and IL-21-induced differentiation into plasmablasts. BMP-7-induced apoptosis was counteracted by a selective TGF-β type I receptor (ALK4/5/7) inhibitor, but not by a selective BMP receptor type I inhibitor. Furthermore, overexpression of truncated ALK5 in a B-cell line counteracted BMP-7-induced apoptosis, whereas overexpression of truncated ALK4 had no effect. BMP-7 mRNA and protein was readily detected in tonsillar B cells, indicating a physiological relevance of the study. Altogether, we identified BMP-7 as a negative regulator of GC B-cell survival. The effect was counteracted by truncated ALK5, suggesting greater complexity in regulating BMP-7 signaling than previously believed.

Smad4 Deficiency in Smooth Muscle Cells Initiates the Formation of Aortic Aneurysm

RATIONALE

Aortic aneurysm is a life-threatening cardiovascular disorder caused by the predisposition for dissection and rupture. Genetic studies have proved the involvement of the transforming growth factor-β (TGF-β) pathway in aortic aneurysm. Smad4 is the central mediator of the canonical TGF-β signaling pathway. However, the exact role of Smad4 in smooth muscle cells (SMCs) leading to the pathogenesis of aortic aneurysms is largely unknown.

OBJECTIVE

To determine the role of smooth muscle Smad4 in the pathogenesis of aortic aneurysms.

METHODS AND RESULTS

Conditional gene knockout strategy combined with histology and expression analysis showed that Smad4 or TGF-β receptor type II deficiency in SMCs led to the occurrence of aortic aneurysms along with an upregulation of cathepsin S and matrix metallopeptidase-12, which are proteases essential for elastin degradation. We further demonstrated a previously unknown downregulation of matrix metallopeptidase-12 by TGF-β in the aortic SMCs, which is largely abrogated in the absence of Smad4. Chemotactic assay and pharmacologic treatment demonstrated that Smad4-deficient SMCs directly triggered aortic wall inflammation via the excessive production of chemokines to recruit macrophages. Monocyte/macrophage depletion or blocking selective chemokine axis largely abrogated the progression of aortic aneurysm caused by Smad4 deficiency in SMCs.

CONCLUSIONS

The findings reveal that Smad4-dependent TGF-β signaling in SMCs protects against aortic aneurysm formation and dissection. The data also suggest important implications for novel therapeutic strategies to limit the progression of the aneurysm resulting from TGF-β signaling loss-of-function mutations.

PPARγ Ligands Attenuate Hypoxia-Induced Proliferation in Human Pulmonary Artery Smooth Muscle Cells through Modulation of MicroRNA-21

Pulmonary hypertension (PH) is a progressive and often fatal disorder whose pathogenesis involves pulmonary artery smooth muscle cell (PASMC) proliferation. Although modern PH therapies have significantly improved survival, continued progress rests on the discovery of novel therapies and molecular targets. MicroRNA (miR)-21 has emerged as an important non-coding RNA that contributes to PH pathogenesis by enhancing vascular cell proliferation, however little is known about available therapies that modulate its expression. We previously demonstrated that peroxisome proliferator-activated receptor gamma (PPARγ) agonists attenuated hypoxia-induced HPASMC proliferation, vascular remodeling and PH through pleiotropic actions on multiple targets, including transforming growth factor (TGF)-β1 and phosphatase and tensin homolog deleted on chromosome 10 (PTEN). PTEN is a validated target of miR-21. We therefore hypothesized that antiproliferative effects conferred by PPARγ activation are mediated through inhibition of hypoxia-induced miR-21 expression. Human PASMC monolayers were exposed to hypoxia then treated with the PPARγ agonist, rosiglitazone (RSG,10 μM), or in parallel, C57Bl/6J mice were exposed to hypoxia then treated with RSG. RSG attenuated hypoxic increases in miR-21 expression in vitro and in vivo and abrogated reductions in PTEN and PASMC proliferation. Antiproliferative effects of RSG were lost following siRNA-mediated PTEN depletion. Furthermore, miR-21 mimic decreased PTEN and stimulated PASMC proliferation, whereas miR-21 inhibition increased PTEN and attenuated hypoxia-induced HPASMC proliferation. Collectively, these results demonstrate that PPARγ ligands regulate proliferative responses to hypoxia by preventing hypoxic increases in miR-21 and reductions in PTEN. These findings further clarify molecular mechanisms that support targeting PPARγ to attenuate pathogenic derangements in PH.

A method to control phosphoinositides and to analyze PTEN function in living cells using voltage sensitive phosphatases

Voltage sensitive phosphatases (VSPs), including engineered voltage sensitive PTEN, are excellent tools to rapidly and reversibly alter the phosphoinositide (PI) content of the plasma membrane in vivo and study the tumor suppressor PTEN. However, widespread adoption of these tools is hampered by the requirement for electrophysiological instrumentation to control the activity of VSPs. Additionally, monitoring and quantifying the PI changes in living cells requires sophisticated microscopy equipment and image analysis. Here we present methods that bypass these obstacles. First, we explore technically simple means for activation of VSPs via extracellularly applied agents or light. Secondly, we characterize methods to monitor PI(4,5)P₂ and PI(3,4,5)P₃ levels using fluorescence microscopy or photometry in conjunction with translocation or FRET based PI probes, respectively. We then demonstrate the application of these techniques by characterizing the effect of known PTEN mutations on its enzymatic activity, analyzing the effect of PTEN inhibitors, and detecting in real time rapid inhibition of protein kinase B following depletion of PI(3,4,5)P₃. Thus, we established an approach that does not only allow for rapidly manipulating and monitoring PI(4,5)P₂ and PI(3,4,5)P₃ levels in a population of cells, but also facilitates the study of PTEN mutants and pharmacological targeting in mammalian cells.

Commentary: Bone morphogenetic protein's contribution to pulmonary artery hypertension: Should this raise concern for patients undergoing spinal fusions with bone morphogenetic protein?

BACKGROUND

Congenital pulmonary artery hypertension (PAH) has been clinically correlated in 70-80% of cases with mutations at the bone morphogenetic protein receptor 2 (BMPR2) genetic site. However, there is also clinical and basic science/laboratory literature indicating a dose-response relationship between BMP signaling and the evolution of PAH (e.g., increased endothelial, smooth muscle, and progenitor cell production, with calcifications).

METHODS

Clinical PAH, characterized by pulmonary artery remodeling, elevated right ventricular pressures, increased vascular constriction, and inflammation, is largely due to congenital mutations at the BMPR2 site. Both clinical and laboratory studies have confirmed the correlation between dysfunction at the BMPR2 genetic site and PAH. However, additional basic science and clinical studies suggest a dose-response relationship between BMP signaling and the evolution of PAH.

RESULTS

Laboratory studies found that pulmonary artery smooth muscle cells (PASMCs) under hypoxic conditions proliferated in response to BMP-2 in a dose-dependent fashion. Others noted that PASMCs extracted from patients with Primary Pulmonary Hypertension (PPH) demonstrated abnormal growth responses to transforming growth factor-beta (TGF-β) in a dose-related manner.

CONCLUSIONS

The clinical/basic science literature appears to document a dose-dependent relationship between BMP and PAH (independent of the congenital lesions). Does this mean patients undergoing lumbar fusions with BMP are at risk for PAH?

Deficiency of Akt1, but not Akt2, attenuates the development of pulmonary hypertension

Pulmonary vascular remodeling, mainly attributable to enhanced pulmonary arterial smooth muscle cell proliferation and migration, is a major cause for elevated pulmonary vascular resistance and pulmonary arterial pressure in patients with pulmonary hypertension. The signaling cascade through Akt, comprised of three isoforms (Akt1-3) with distinct but overlapping functions, is involved in regulating cell proliferation and migration. This study aims to investigate whether the Akt/mammalian target of rapamycin (mTOR) pathway, and particularly which Akt isoform, contributes to the development and progression of pulmonary vascular remodeling in hypoxia-induced pulmonary hypertension (HPH). Compared with the wild-type littermates, Akt1(-/-) mice were protected against the development and progression of chronic HPH, whereas Akt2(-/-) mice did not demonstrate any significant protection against the development of HPH. Furthermore, pulmonary vascular remodeling was significantly attenuated in the Akt1(-/-) mice, with no significant effect noted in the Akt2(-/-) mice after chronic exposure to normobaric hypoxia (10% O2). Overexpression of the upstream repressor of Akt signaling, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), and conditional and inducible knockout of mTOR in smooth muscle cells were also shown to attenuate the rise in right ventricular systolic pressure and the development of right ventricular hypertrophy. In conclusion, Akt isoforms appear to have a unique function within the pulmonary vasculature, with the Akt1 isoform having a dominant role in pulmonary vascular remodeling associated with HPH. The PTEN/Akt1/mTOR signaling pathway will continue to be a critical area of study in the pathogenesis of pulmonary hypertension, and specific Akt isoforms may help specify therapeutic targets for the treatment of pulmonary hypertension.

News on biomarkers in CKD-MBD

The increased awareness of the potential role played by mineral and bone disorder in the appearance of cardiovascular disease in renal patients has produced research efforts aimed at discovering possible pathogenic links. Accordingly, the diagnostic significance of the classic bone markers of mineral disorders and of the new markers in the setting of chronic kidney disease-mineral and bone disorders (CKD-MBD) needs to be re-evaluated along with increasing information. In this article we include classic markers of bone metabolism and some of the noncollagenous bone proteins that are gaining experimental and clinical significance in CKD-MBD. Among classic markers of secondary hyperparathyroidism and of renal osteodystrophy, we analyzed parathyroid hormone, alkaline phosphatase, tartrate-resistant acid phosphatase, and bone collagen-derived peptides. We underlined, for each, the relevance of parent proteins (peptides or isoforms) that affect assay methods and, eventually, the diagnostic or prognostic significance. Also, we considered their relationship with cardiovascular mortality. Among the numerous noncollagenous bone proteins, we examined matrix Gla protein (MGP), osteocalcin (OC), osteoprotegerin, and the small integrin-binding ligand N-linked glycoprotein family. For MGP and OC we report the relevant involvement with the process of calcification (MGP) and with glucose and energy metabolism (OC). Both of these proteins require vitamin K to become active and this is a specific problem in renal patients who frequently are deficient of this vitamin. Finally, recent acquisitions on the fascinating family of the small integrin-binding ligand N-linked glycoprotein proteins are recapitulated briefly to underline their potential clinical interest and their complex involvement with all aspects of CKD-MBD. Their diagnostic role in clinical practice awaits further studies.

Role of miR-17 family in the negative feedback loop of bone morphogenetic protein signaling in neuron

Bone morphogenetic protein (BMP) signaling is active in many tissues including the central nervous system, in which it regulates cell proliferation, differentiation and maturation. The modulation of BMP pathway is crucial since abnormality of BMP signaling may cause cellular malfunction such as apoptosis. There are evidences indicating that miR-17 family is involved in the BMP signaling. In the present study, we demonstrated that BMP2 stimulation directly increased the transcription of miR-17-92 and miR-106b-25 cluster via Smad activation, which leads to the up-regulation of mature miR-17/20a/93. In addition, we provided evidence that BMP2 activation repressed BMPRII expression through modulating miR-17 family in primary neurons. Furthermore, we proved that such negative regulation protected neurons from apoptosis induced by abnormal BMP signaling. Taken together, these results suggest a regulatory pathway of BMP-miR-17 family-BMPRII, which consist a negative feedback loop that balances BMP signaling and maintains cell homeostasis in neurons.

Vitamin K-dependent carboxylation of matrix Gla-protein: a crucial switch to control ectopic mineralization

Vascular mineralization has recently emerged as a risk factor for cardiovascular morbidity and mortality. Previously regarded as a passive end-stage process, vascular mineralization is currently recognized as an actively regulated process with cellular and humoral contributions. The discovery that the vitamin K-dependent matrix Gla-protein (MGP) is a strong inhibitor of vascular calcification has propelled our mechanistic understanding of this process and opened novel avenues for diagnosis and treatment. This review focuses on molecular mechanisms of vascular mineralization involving MGP and discusses the potential for treatments and biomarkers to monitor patients at risk for vascular mineralization.

In-depth characterization of the secretome of colorectal cancer metastatic cells identifies key proteins in cell adhesion, migration, and invasion

Liver metastasis in colorectal cancer is the major cause of cancer-related deaths. To identify and characterize proteins associated with colon cancer metastasis, we have compared the conditioned serum-free medium of highly metastatic KM12SM colorectal cancer cells with the parental, poorly metastatic KM12C cells using quantitative stable isotope labeling by amino acids in cell culture (SILAC) analyses on a linear ion trap-Orbitrap Velos mass spectrometer. In total, 1337 proteins were simultaneously identified in SILAC forward and reverse experiments. For quantification, 1098 proteins were selected in both experiments, with 155 proteins showing >1.5-fold change. About 52% of these proteins were secreted directly or using alternative secretion pathways. GDF15, S100A8/A9, and SERPINI1 showed capacity to discriminate cancer serum samples from healthy controls using ELISAs. In silico analyses of deregulated proteins in the secretome of metastatic cells showed a major abundance of proteins involved in cell adhesion, migration, and invasion. To characterize the tumorigenic and metastatic properties of some top up- and down-regulated proteins, we used siRNA silencing and antibody blocking. Knockdown expression of NEO1, SERPINI1, and PODXL showed a significant effect on cellular adhesion. Silencing or blocking experiments with SOSTDC1, CTSS, EFNA3, CD137L/TNFSF9, ZG16B, and Midkine caused a significant decrease in migration and invasion of highly metastatic cells. In addition, silencing of SOSTDC1, EFNA3, and CD137L/TNFSF9 reduced liver colonization capacity of KM12SM cells. Finally, the panel of six proteins involved in invasion showed association with poor prognosis and overall survival after dataset analysis of gene alterations. In summary, we have defined a collection of proteins that are relevant for understanding the mechanisms underlying adhesion, migration, invasion, and metastasis in colorectal cancer.

Inhibition of AKT enhances mitotic cell apoptosis induced by arsenic trioxide

Accumulated evidence has revealed a tight link between arsenic trioxide (ATO)-induced apoptosis and mitotic arrest in cancer cells. AKT, a serine/threonine kinase frequently over-activated in diverse tumors, plays critical roles in stimulating cell cycle progression, abrogating cell cycle checkpoints, suppressing apoptosis, and regulating mitotic spindle assembly. Inhibition of AKT may therefore enhance ATO cytotoxicity and thus its clinical utility. We show that AKT was activated by ATO in HeLa-S3 cells. Inhibition of AKT by inhibitors of the phosphatidyl inositol 3-kinase/AKT pathway significantly enhanced cell sensitivity to ATO by elevating mitotic cell apoptosis. Ectopic expression of the constitutively active AKT1 had no effect on ATO-induced spindle abnormalities but reduced kinetochore localization of BUBR1 and MAD2 and accelerated mitosis exit, prevented mitotic cell apoptosis, and enhanced the formation of micro- or multi-nuclei in ATO-treated cells. These results indicate that AKT1 activation may prevent apoptosis of ATO-arrested mitotic cells by attenuating the function of the spindle checkpoint and therefore allowing the formation of micro- or multi-nuclei in surviving daughter cells. In addition, AKT1 activation upregulated the expression of aurora kinase B (AURKB) and survivin, and depletion of AURKB or survivin reversed the resistance of AKT1-activated cells to ATO-induced apoptosis. Thus, AKT1 activation suppresses ATO-induced mitotic cell apoptosis, despite the presence of numerous spindle abnormalities, probably by upregulating AURKB and survivin and attenuating spindle checkpoint function. Inhibition of AKT therefore effectively sensitizes cancer cells to ATO by enhancing mitotic cell apoptosis.

Delayed administration of a PTEN inhibitor BPV improves functional recovery after experimental stroke

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) inhibitors administered prior to or immediately after experimental stroke confer acute neuroprotection. However, it remains unclear if delayed treatment with a PTEN inhibitor improves long-term functional recovery after stroke. We addressed the issue in this study. Adult male mice were subjected to 1h of middle cerebral artery occlusion (MCAO) followed by treatment with a well-established PTEN inhibitor BPV or saline daily for 14 days, starting at 24h after MCAO. Functional recovery was assessed with behavioral tests and acute infarct volumes were analyzed histologically. Delayed BPV treatment did not reduce infarction during the acute phase, but significantly improved long-term functional recovery after MCAO. Since PTEN is a critical intrinsic inhibitory factor in axonal regeneration, we further examined BPV effects on axonal densities following MCAO using bielschowsky silver staining and immunohistochemistry with antibodies against myelin basic protein. Delayed BPV treatment significantly increased axon densities in the ischemic brain at 14 days after MCAO. Moreover, PTEN expression persistently remained high in the ischemic brain over 14 days after MCAO, and BPV treatment increased post-ischemic activation of Akt and mTOR in the ischemic brain. Akt and mTOR activation are the well-established cascades downstream to PTEN inhibition and have been shown to contribute to post-injury axonal regrowth in response to PTEN inhibition. Consistently, in an in vitro neuronal ischemia model, BPV enhanced axonal outgrowth of primary cortical neurons after oxygen-glucose deprivation and the enhancing effects were abolished by Akt/mTOR inhibition. In conclusion, delayed BPV treatment improved functional recovery from experimental stroke possibly via enhancing axonal growth and Akt/mTOR activation contributed to BPV-enhanced post-stroke axon growth.