Proteomic analysis of circulating monocytes in Chinese premenopausal females with extremely discordant bone mineral density

Proteomic Biomarkers Associated with Low Bone Mineral Density: A Systematic Review

Osteoporosis is a globally relevant public health issue. Our study aimed to summarize the knowledge on the proteomic biomarkers for low bone mineral density over the last years. We conducted a systematic review following the PRISMA guidelines; the scoured databases were PubMed, Web of Sciences, Scopus, and EBSCO, from inception to 2 June 2023. A total of 610 relevant studies were identified and 33 were assessed for eligibility. Finally, 29 studies met the criteria for this systematic review. The risk of bias was evaluated using the Joanna Briggs Institute Critical Appraisal Checklist tool. From the studies selected, 154 proteins were associated with changes of bone mineral density, from which only 10 were reported in at least two articles. The protein-protein network analysis indicated potential biomarkers involved in the skeletal system, immune system process, regulation of protein metabolic process, regulation of signaling, transport, cellular component assembly, cell differentiation, hemostasis, and extracellular matrix organization. Mass spectrometry-based proteomic profiling has allowed the discovery of new biomarkers with diagnostic potential. However, it is necessary to compare and validate the potential biomarkers in different populations to determine their association with bone metabolism and evaluate their translation to the clinical management of osteoporosis.

Label-free quantitative proteomics in serum reveals candidate biomarkers associated with low bone mineral density in Mexican postmenopausal women

Postmenopausal osteoporosis is a public health problem leading to an increased risk of fractures, negatively impacting women's health. The absence of sensitive and specific biomarkers for early detection of osteoporosis represents a substantial challenge for improving patient management. Herein, we aimed to identify potential candidate proteins associated with low bone mineral density (BMD) in postmenopausal women from the Mexican population. Serum samples from postmenopausal women (40 with normal BMD, 40 with osteopenia (OS), and 20 with osteoporosis (OP)) were analyzed by label-free LC-MS/MS quantitative proteomics. Proteome profiling revealed significant differences between the OS and OP groups compared to individuals with normal BMD. A quantitative comparison of proteins between groups indicated 454 differentially expressed proteins (DEPs). Compared to normal BMD, 14 and 214 DEPs were found in OS and OP groups, respectively, while 226 DEPs were identified between OS and OP groups. The protein-protein interaction and enrichment analysis of DEPs were closely linked to the bone mineral content, skeletal morphology, and immune response activation. Based on their role in bone metabolism, a panel of 12 candidate biomarkers was selected, of which 1 DEP (RYR1) was found upregulated in the OS and OP groups, 8 DEPs (APOA1, SHBG, FETB, MASP1, PTK2B, KNG1, GSN, and B2M) were upregulated in OP and 3 DEPs (APOA2, RYR3, and HBD) were downregulated in OS or OP. The proteomic analysis described here may help discover new and potentially non-invasive biomarkers for the early diagnosis of osteoporosis in postmenopausal women.

Proteomics Profiling of Osteoporosis and Osteopenia Patients and Associated Network Analysis

Bone mass reduction due to an imbalance in osteogenesis and osteolysis is characterized by low bone mineral density (LBMD) and is clinically classified as osteopenia (ON) or osteoporosis (OP), which is more severe. Multiple biomarkers for diagnosing OP and its progression have been reported; however, most of these lack specificity. This cohort study aimed to investigate sensitive and specific LBMD-associated protein biomarkers in patients diagnosed with ON and OP. A label-free liquid chromatography-mass spectrometry (LC-MS) proteomics approach was used to analyze serum samples. Patients’ proteomics profiles were filtered for potential confounding effects, such as age, sex, chronic diseases, and medication. A distinctive proteomics profile between the control, ON, and OP groups (Q² = 0.7295, R² = 0.9180) was identified, and significant dysregulation in a panel of proteins (n = 20) was common among the three groups. A comparison of these proteins showed that the levels of eight proteins were upregulated in ON, compared to those in the control and the OP groups, while the levels of eleven proteins were downregulated in the ON group compared to those in the control group. Interestingly, only one protein, myosin heavy chain 14 (MYH14), showed a linear increase from the control to the ON group, with the highest abundance in the OP group. A significant separation in the proteomics profile between the ON and OP groups (Q² = 0.8760, R² = 0.991) was also noted. Furthermore, a total of twenty-six proteins were found to be dysregulated between the ON and the OP groups, with fourteen upregulated and twelve downregulated proteins in the OP, compared to that in the ON group. Most of the identified dysregulated proteins were immunoglobulins, complement proteins, cytoskeletal proteins, coagulation factors, and various enzymes. Of these identified proteins, the highest area under the curve (AUC) in the receiver operating characteristic (ROC) analysis was related to three proteins (immunoglobulin Lambda constant 1 (IGLC1), RNA binding protein (MEX3B), and fibulin 1 (FBLN1)). Multiple reaction monitoring (MRM), LC-MS, was used to validate some of the identified proteins. A network pathway analysis of the differentially abundant proteins demonstrated dysregulation of inflammatory signaling pathways in the LBMD patients, including the tumor necrosis factor (TNF), toll-like receptor (TL4), and interferon-γ (IFNG) signaling pathways. These results reveal the existence of potentially sensitive protein biomarkers that could be used in further investigations of bone health and OP progression.

A correlative studies between osteoporosis and blood cell composition: Implications for auxiliary diagnosis of osteoporosis

Osteoporosis is defined as a metabolic skeletal disease characterized by a decrease of the bone mass per unit volume, caused by a variety of reasons. Increasing evidence indicate that the host inflammatory response was correlated with the occurrence and development of osteoporosis, and it has been recognized that T lymphocytes and B lymphocytes play a critical role in pathogenesis of inflammatory bone disease. Between January 2018 and December 2018, retrospective analysis of 487 patients (exclusion of patients with recent infections and hematologic disorders whose leukocyte counts or classifications are markedly abnormal) who underwent bone mineral density (BMD) examinations in Huzhou Central Hospital. The patients were divided into normal bone density group, osteopenia group, and osteoporosis group according to the T score of BMD in the left femoral neck, respectively. Statistics of the lymphocyte ratio and the monocyte ratio in the blood routine examination results during the same period were performed so as to make a comparison of the differences among the groups. The correlation of the lymphocyte ratio and monocyte ratio with the T score of BMD in the left femoral neck was also analyzed. The difference between neutrocyte ratio lymphocyte ratio and the monocyte ratio was statistically significant in both males and females among the normal bone density group, osteopenia group and osteoporosis group (P < .01 or P < .05). Inflammation plays an important role in the progression of osteoporosis. By monitoring these three indicators in blood routine examination, early intervention for osteoporosis may become possible.

A road map for understanding molecular and genetic determinants of osteoporosis

Osteoporosis is a highly prevalent disorder characterized by low bone mineral density and an increased risk of fracture, termed osteoporotic fracture. Notably, bone mineral density, osteoporosis and osteoporotic fracture are highly heritable; however, determining the genetic architecture, and especially the underlying genomic and molecular mechanisms, of osteoporosis in vivo in humans is still challenging. In addition to susceptibility loci identified in genome-wide association studies, advances in various omics technologies, including genomics, transcriptomics, epigenomics, proteomics and metabolomics, have all been applied to dissect the pathogenesis of osteoporosis. However, each technology individually cannot capture the entire view of the disease pathology and thus fails to comprehensively identify the underlying pathological molecular mechanisms, especially the regulatory and signalling mechanisms. A change to the status quo calls for integrative multi-omics and inter-omics analyses with approaches in 'systems genetics and genomics'. In this Review, we highlight findings from genome-wide association studies and studies using various omics technologies individually to identify mechanisms of osteoporosis. Furthermore, we summarize current studies of data integration to understand, diagnose and inform the treatment of osteoporosis. The integration of multiple technologies will provide a road map to illuminate the complex pathogenesis of osteoporosis, especially from molecular functional aspects, in vivo in humans.

Integrative Analyses of Genes Associated With Osteoporosis in CD16+ Monocyte

BACKGROUND

Osteoporosis is a metabolic bone disease characterized by decreased bone mineral density and abnormal bone quality. Monocytes can secret cytokines for bone resorption, resulting in bone mass loss. However, the mechanism by which monocytes subpopulations lead to osteoporosis remains unclear. The aim of this study was to identify genes associated with osteoporosis in monocytes subsets.

METHODS

Three microarray datasets including GSE7158 (transcription of low/high-peak bone mass), GSE101489 (transcription of CD16+/CD16- monocyte) and GSE93883 (miRNA expression profile of primary osteoporosis) were derived from the Gene Expression Omnibus (GEO) database and analyzed with GEO2R tool to identify differentially expressed genes (DEGs). Functional enrichment was analyzed using Metascape database and GSEA software. STRING was utilized for the Protein-Protein Interaction Network construct. The hub genes were screened out using the Cytoscape software. Related miRNAs were predicted in miRWalk, miRDB, and TargetScan databases.

RESULTS

Total 368 DEGs from GSE7158 were screened out, which were mostly enriched in signaling, positive regulation of biological process and immune system process. The hub genes were clustered into two modules by PPI network analysis. We identified 15 overlapping DGEs between GSE101489 and GSE7158 microarray datasets. Moreover, all of them were up-regulated genes in both datasets. Then, nine key genes were screened out from above 15 overlapping DEGs using Cytoscape software. It is a remarkable fact that the nine genes were all in one hub gene module of GSE7158. Additionally, 183 target miRNAs were predicted according to the above nine DEGs. After cross-verification with miRNA express profile dataset for osteoporosis (GSE93883), 12 DEmiRNAs were selected. Finally, a miRNA-mRNA network was constructed with the nine key genes and 12 miRNAs, which were involved in osteoporosis.

CONCLUSION

Our analysis results constructed a gene expression framework in monocyte subsets for osteoporosis. This approach could provide a novel insight into osteoporosis.

Melatonin restores the osteoporosis-impaired osteogenic potential of bone marrow mesenchymal stem cells by preserving SIRT1-mediated intracellular antioxidant properties

Postmenopausal osteoporosis (OP) is one of the most common bone diseases that affects millions of aging women. Reduced osteogenesis and increased oxidative stress have been implicated in bone marrow mesenchymal stem cells (BMMSCs) derived from OP patients. Melatonin has shown positive effects on osteoblast differentiation and bone formation; however, it was unknown whether melatonin could restore OP-impaired osteogenic potential of BMMSCs and what the underlying mechanisms entailed. The objective of this study is to investigate (1) whether melatonin can restore the impaired osteogenic potential of OP BMMSCs by preserving their antioxidant functions, and if so, (2) whether intravenous administration of melatonin can prevent OP-induced bone loss in ovariectomized (OVX) rats. Ovariectomies were performed in female rats and BMMSCs were isolated from the osteoporotic rats 3 months later. In vitro treatment with melatonin successfully improved the osteogenic differentiation of OP BMMSCs, as evidenced by increased levels of matrix mineralization and osteoblast-specific genes. In melatonin-treated OP BMMSCs, intracellular oxidative stress was significantly attenuated, while levels of intracellular antioxidant enzymes were noticeably up-regulated - particularly superoxide dismutase 2 (SOD2) and glutathione peroxidase 1 (GPX1). Silent information regulator type 1 (SIRT1) was involved in the melatonin-mediated recovery of osteogenesis and antioxidant functions. Meanwhile, in vivo injections of melatonin via the tail vein successfully ameliorated the bone micro-architecture in ovariectomized rat femurs. Further experiments confirmed that BMMSCs derived from melatonin-treated OVX rats exerted well-preserved antioxidant properties and osteogenic potential. Our findings demonstrate that the administration of melatonin is a promising strategy for treating patients with postmenopausal OP by preserving the antioxidant properties and osteogenic potential of their BMMSCs.

Serum Proteomic Analysis Reveals Vitamin D-Binding Protein (VDBP) as a Potential Biomarker for Low Bone Mineral Density in Mexican Postmenopausal Women

Osteoporosis is a skeletal disease mainly affecting women over 50 years old and it represents a serious public health problem because of the high socioeconomic burden. This disease is characterized by deterioration of bone microarchitecture, low bone mineral density (BMD), and increased risk of fragility fractures. This study aimed to identify serum useful proteins as biomarkers for the diagnosis and/or prognosis of osteoporosis and fracture risk. We collected 446 serum samples from postmenopausal women aged ≥45 years old. Based on the BMD measurement, we classified the participants into three groups: osteoporotic, osteopenic, and normal. In an initial discovery stage, we conducted a proteomic approach using two-dimensional differential gel electrophoresis (2D-DIGE). The peptides into the spots of interest were identified through matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF/TOF). Enzyme-linked immunosorbent assay (ELISA) was performed to validate the proteins of interest. We identified 27 spots of interest when comparing low BMD versus normal BMD postmenopausal women. Based on their relevance in bone metabolism, we analyzed three proteins: ceruloplasmin (CP), gelsolin (GSN), and vitamin D-binding protein (VDBP). Our results demonstrated that low serum VDBP levels correlate with low BMD (osteopenic and osteoporotic). Therefore, VDBP could be considered as a novel, potential, and non-invasive biomarker for the early detection of osteoporosis.

Abl interactor 1: A novel biomarker for osteoporosis in Chinese elderly men

Low bone mineral density (BMD) is a high-risk factor of osteoporosis (OP) and osteoporotic fracture (OF). Peripheral blood monocytes (PBM) can give birth to osteoclasts to resorb bone. Herein, we attempted to identify OP susceptible proteins in human PBM and characterize their functions in bone. Employing the label-free quantitative proteomics methodology (Easy-nLC1000 and Q-exactive) and traditional Western Blotting (WB), we discovered and validated that a key protein, i.e. Abl Interactor 1(ABI1), was significantly down-regulated in PBM in Chinese elderly men with extremely low vs. high BMD (n = 18, p < .05), as well as in OF patients vs. non-fractured (NF) subjects (n = 36, p < .05). The above down-regulation tendency was also observed in Chinese elderly women (n = 51, P < .05). For translational purpose, plasma ABI1 protein was assessed by ELISA in Chinese elderly men, which was found significantly down-regulated in OF (n = 20) vs. NF (n = 64) subjects (Mean: 0.41 vs. 1.03 ng/ml, FC = 0.39, p = .039), as well as in low (n = 32) vs. high (n = 32) BMD subjects (Mean: 0.5 vs. 1.57 ng/ml, FC = 0.32,p = .0012). ROC analyses in another independent study sample (n = 75) showed that the plasma ABI1 protein has superior performance in discriminating osteopenia and healthy subjects (AUC = 0.755, 95% CI: 0.632-0.877, p = .001). Follow-up cellular functional studies revealed that ABI1 protein significantly promoted osteoblast growth (optimal concentration 2.0 ng/ml), osteoblastic gene expression (OPN, ALP, COL1A1, p < .05) and osteoblast differentiation.ABI1 protein also significantly attenuated monocyte trans-endothelial migration and osteoclast differentiation and activity. In conclusion, ABI1 is a novel protein biomarker for OP in Chinese elderly. ABI1 protein, via promoting osteoblast growth, differentiation and activity, and attenuating monocyte trans-endothelial migration and osteoclast differentiation, influences BMD variation and fracture risk in humans. SIGNIFICANCE: Previous plentiful studies indicated that protein ABI1 played an essential role in the progression of several malignancies, including hepatoma, colon cancer and epithelial ovarian cancer. However, there was relatively limited understandings regarding its molecular and cellular functions relevant to bone phenotypes. Employing the label-free quantitative proteomics methodology (Easy-nLC1000 and Q-exactive) and traditional Western Blotting (WB), we discovered and validated that ABI1 was significantly down-regulated in PBM in Chinese elderly men with extremely low BMD as well as in OF patients. The down-regulation trend was consistent in plasma samples in Chinese elderly men. Follow-up cellular functional studies revealed that, on the one hand, ABI1 protein significantly promoted osteoblast growth, osteoblastic gene expression and osteoblast differentiation; on the other hand, it also significantly attenuated monocyte trans-endothelial migration and osteoclast differentiation and activity. It suggested that ABI1 is a promising biomarker with translational value.

Screening pathways and hub genes involved in osteoclastogenesis by gene expression analysis of circulating monocytes based on Gibbs sampling

Differential expression pathways and hub genes in circulating monocytes from healthy Chinese women with high peak bone mass (PBM) vs. low PBM were explored using a Markov chain Monte Carlo (MCMC) algorithm. Human circulating monocytes transcription profiling (containing 14 samples with high PBM and 12 samples with low PBM) and KEGG pathways were all downloaded from the public database. Initial state of all the pathways were constructed and Gibbs sampling was performed to obtain a Markov chain and the posterior values of all the pathways were calculated. The probability (α) of occurrence of each pathway was calculated based on the posterior value and it was adjusted by taking gene expression variation into account. Pathways with α_adj >0.8 were considered as differentially expressed pathways. Then, these steps were performed again on all the genes in the differentially expressed pathways to find the hub genes in the differential pathways. After Gibbs sampling, neuroactive ligand-receptor interaction (hsa04080) with α_adj = 0.986 was screened out as the differentially expressed pathway. Analyzing the genes in this pathway, three genes (neurotensin, tachykinin receptor 3 and follicle-stimulating hormone receptor) with α_adj >0.8 were identified as hub genes in circulating monocytes which may associate with osteoporosis development. One pathway and three genes which may possess close relationship with osteoporosis development were found in this study. These results provide insights into our understanding of the role of circulating monocytes in osteoporosis development.

Association of Plasma Irisin with Bone Mineral Density in a Large Chinese Population Using an Extreme Sampling Design

Irisin, a myokine produced by skeletal muscle in response to physical exercise, promotes trans-differentiation of white adipose tissue into brown adipose tissue. Recent evidences suggested that irisin also plays an important role in the control of bone metabolism. This study aimed to ascertain the relationship between plasma irisin and bone mineral density (BMD) in Chinese population by adoption of an extreme sampling method. Based on a large and screened Chinese elderly population (N = 6308), two subgroups with extremely high and low hip BMD were selected for discovery (N = 80, high vs. low BMD = 44:36) and validation (N = 60, high vs. low BMD = 30:30), respectively. Plasma irisin, P1NP, and β-CTx were measured using commercially available ELISA kits. Other metabolic parameters (e.g., blood glucose, total cholesterol and triglycerides) were collected. Student's t test and Spearman correlation analyses were conducted in SPSS. Significant difference was discovered for plasma irisin between females and age-matched males (N = 80, male vs. female = 42:38, P = 0.002). The plasma irisin levels were significantly higher in high BMD subjects than in low BMD subjects, which was observed in both discovery (P = 0.012) and validation samples (P = 0.022). However, such observation was limited to males only. Further correlation analyses in males showed that plasma irisin was correlated with BMD (r = 0.362, P = 0.025) and triglyceride (r = - 0.354, P = 0.032). Plasma irisin levels were associated with hip BMD in Chinese elderly men. This study represented the first effort of investigating the relationship of plasma irisin and BMD in elderly population. The positive correlation between plasma irisin and BMD hints intrinsic communication between muscle and bone.

Plasma gelsolin is associated with hip BMD in Chinese postmenopausal women

Gelsolin (GSN) protein, expressed in circulating monocytes, was previously reported to be associated with osteoporosis in both Chinese and Caucasian women. This study aims to test if plasma GSN protein level is associated with hip bone mineral density (BMD) in Chinese population. Based on two study Groups containing 6,308 old Chinese, we adopted extreme sampling scheme and selected 3 independent samples (Subgroups 1-3) for discovery, replication, and validation purposes. We tested plasma GSN concentration, and analyzed whether plasma GSN level differs between subjects with extremely low vs. high hip BMD. In Group 1 (N = 1,860), the plasma GSN level increased in the female with low BMD, which was discovered in the Subgroup 1 (N = 42, p = 0.093) and replicated in the Subgroup 2 (N = 39, p = 0.095). With more extreme sampling for the Subgroup 3 from the Group 2 (N = 4,448), the difference of plasma GSN level in the female with low BMD vs. high BMD is more significant (N = 45, p = 0.037). After the subjects were pooled from Subgroups 2 and 3, the difference in plasma GSN between low and high BMD subjects became even more significant (p = 0.016). The plasma GSN level was negatively correlated with total hip BMD (r = -0.26, p = 0.033). We concluded that plasma GSN was associated with hip BMD in Chinese postmenopausal women and plasma GSN might be a potential risk biomarker for osteoporosis.

Anxa2 attenuates osteoblast growth and is associated with hip BMD and osteoporotic fracture in Chinese elderly

Low bone mineral density (BMD) is a risk factor of osteoporotic fracture (OF). Peripheral blood monocytes (PBM) can differentiate into osteoclasts to resorb bone. It was known that PBM-expressed Anxa2 protein is associated with BMD, and extracellular Anxa2 protein promotes osteoclastogenesis. This study aimed to test 1) whether Anxa2 protein level in PBM differs significantly between subjects with OF and without fracture history (NF); 2) whether Anxa2 level in plasma is associated with BMD; 3) how Anxa2 protein at various concentrations would affect osteoblastic activity in vitro. All the study subjects were Chinese Han elderly. Firstly, Anxa2 protein in PBM was identified and quantitated by LC-MS/MS and compared between 45 OF cases and 42 healthy controls. Secondly, plasma Anxa2 protein level was quantitated by ELISA and compared between unrelated subjects with extremely low vs. high hip BMD (0.63±0.10 vs. 1.05±0.10 g/cm², n = 75). Furthermore, in vitro functional assay was utilized to test the effects of extracellular Anxa2 protein on osteoblastic growth. We found that Anxa2 protein expression in PBM was significantly up-regulated in OF vs. NF subjects (fold change [FC)] = 1.16, P<0.05). Plasma Anxa2 protein concentration (range: 31.69–227.35ng/ml) was significantly elevated in low vs. high BMD subjects (84.85 vs. 66.15ng/ml, FC = 1.28, P<0.05). Cellular dynamical monitoring demonstrated that the general shape of dose-response relationship is the inverse U-shaped curve. Specifically, lower dose of Anxa2 protein may promote osteoblast growth and the optimal concentration for osteoblastic growth was around 50ng/ml, but even higher concentration could attenuate hFOB1.19 osteoprogenitor cell growth. We concluded that Anxa2 protein could attenuate osteoblast growth and be associated with hip BMD and OF in Chinese elderly.

"Omics" Signatures in Peripheral Monocytes from Women with Low BMD Condition

Postmenopausal osteoporosis (PMO) is a result of increased bone resorption compared to formation. Osteoclasts are responsible for bone resorption, which are derived from circulating monocytes that undertake a journey from the blood to the bone for the process of osteoclastogenesis. In recent times, the use of high throughput technologies to explore monocytes from women with low versus high bone density has led to the identification of candidate molecules that may be deregulated in PMO. This review provides a list of molecules in monocytes relevant to bone density which have been identified by "omics" studies in the last decade or so. The molecules in monocytes that are deregulated in low BMD condition may contribute to processes such as monocyte survival, migration/chemotaxis, adhesion, transendothelial migration, and differentiation into the osteoclast lineage. Each of these processes may be crucial to the overall route of osteoclastogenesis and an increase in any/all of these processes can lead to increased bone resorption and subsequently low bone density. Whether these molecules are indeed the cause or effect is an arena currently unexplored.

Identification of microRNAs in human circulating monocytes of postmenopausal osteoporotic Mexican-Mestizo women: A pilot study

MicroRNAs (miRNAs or miRs) are a class of short non-coding RNAs that serve an important regulatory role in living organisms. These molecules are associated with multiple biological processes and are potential biomarkers in multiple diseases. The present study aimed to further identify miRNAs that are differentially expressed in circulating monocytes (CMCs) from postmenopausal Mexican-Mestizo women. Microarray analyses of monocytes using Affymetrix miRNA 4.0 and Human Genome U133 Plus 2.0 arrays were performed in 6 normal and 6 osteoporotic women, followed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) validation. The overexpression of miR-1270, miR-548×-3p and miR-8084 were detected in the osteoporosis compared with the normal group according to the microarray analysis; miR-1270, a miRNA with several target genes associated with bone remodeling, was validated by RT-qPCR. Bioinformatics analysis identified that interferon regulatory factor 8 (IRF8) is the most likely target gene of miR-1270, which is associated with osteoclastogenesis. Furthermore, the findings of the present study demonstrate that an upregulation of miR-1270 may reduce the gene expression of IRF8 in CMCs (osteoclast precursors), implicating its potential role in leading to low bone mineral density and contributing to osteoporosis development in postmenopausal women.

Network based subcellular proteomics in monocyte membrane revealed novel candidate genes involved in osteoporosis

In this study, label-free-based quantitative subcellular proteomics integrated with network analysis highlighted several candidate genes including P4HB, ITGB1, CD36, and ACTN1 that may be involved in osteoporosis. All of them are predicted as significant membrane proteins with high confidence and enriched in bone-related biological process. The results were further verified in transcriptomic and genomic levels.

INTRODUCTION

Osteoporosis is a metabolic bone disease mainly characterized by low bone mineral density (BMD). As the precursors of osteoclasts, peripheral blood monocytes (PBMs) are supported to be important candidates for identifying genes related to osteoporosis. We performed subcellular proteomics study to identify significant membrane proteins that involved in osteoporosis.

METHODS

To investigate the association between monocytes, membrane proteins, and osteoporosis, we performed label-free quantitative subcellular proteomics in 59 male subjects with discordant BMD levels, with 30 high vs. 29 low BMD subjects. Subsequently, we performed integrated gene enrichment analysis, functional annotation, and pathway and network analysis based on multiple bioinformatics tools.

RESULTS

A total of 1070 membrane proteins were identified and quantified. By comparing the proteins' expression level, we found 36 proteins that were differentially expressed between high and low BMD groups. Protein localization prediction supported the notion that the differentially expressed proteins, P4HB (p = 0.0021), CD36 (p = 0.0104), ACTN1 (p = 0.0381), and ITGB1 (p = 0.0385), are significant membrane proteins. Functional annotation and pathway and network analysis highlighted that P4HB, ITGB1, CD36, and ACTN1 are enriched in osteoporosis-related pathways and terms including "ECM-receptor interaction," "calcium ion binding," "leukocyte transendothelial migration," and "reduction of cytosolic calcium levels." Results from transcriptomic and genomic levels provided additional supporting evidences.

CONCLUSION

Our study strongly supports the significance of the genes P4HB, ITGB1, CD36, and ACTN1 to the etiology of osteoporosis risk.

The Role of Monocyte Percentage in Osteoporosis in Male Rheumatic Diseases

Osteoporosis is easily overlooked in male patients, especially in the field of rheumatic diseases mostly prevalent with female patients, and its link to pathogenesis is still lacking. Attenuated monocyte apoptosis from a transcriptome-wide expression study illustrates the role of monocytes in osteoporosis. This study tested the hypothesis that the monocyte percentage among leukocytes could be a biomarker of osteoporosis in rheumatic diseases. Eighty-seven males with rheumatic diseases were evaluated in rheumatology outpatient clinics for bone mineral density (BMD) and surrogate markers, such as routine peripheral blood parameters and autoantibodies. From the total number of 87 patients included in this study, only 15 met the criteria for diagnosis of osteoporosis. Both age and monocyte percentage remained independently associated with the presence of osteoporosis. Steroid dose (equivalent prednisolone dose) was negatively associated with BMD of the hip area and platelet counts were negatively associated with BMD and T score of the spine area. Besides age, monocyte percentage meets the major requirements for osteoporosis in male rheumatic diseases. A higher monocyte percentage in male rheumatic disease patients, aged over 50 years in this study, and BMD study should be considered in order to reduce the risk of osteoporosis-related fractures.

Identification of crucial genes related to postmenopausal osteoporosis using gene expression profiling

BACKGROUND

Postmenopausal osteoporosis is a common bone disease and characterized by low bone mineral density.

AIM

This study aimed to reveal key genes associated with postmenopausal osteoporosis (PMO), and provide a theoretical basis for subsequent experiments.

METHODS

The dataset GSE7429 was obtained from Gene Expression Omnibus. A total of 20 B cell samples (ten ones, respectively from postmenopausal women with low or high bone mineral density (BMD) were included in this dataset. Following screening of differentially expressed genes (DEGs), coexpression analysis of all genes was performed, and key genes in the coexpression network were screened using the random walk algorithm. Afterwards, functional and pathway analyses were conducted. Additionally, protein-protein interactions (PPIs) between DEGs and key genes were analyzed.

RESULTS

A set of 308 DEGs (170 up-regulated ones and 138 down-regulated ones) between low BMD and high BMD samples were identified, and 101 key genes in the coexpression network were screened out. In the coexpression network, some genes had a higher score and degree, such as CSTA. The key genes in the coexpression network were mainly enriched in GO terms of the defense response (e.g., SERPINA1 and CST3), immune response (e.g., IL32 and CLEC7A); while, the DEGs were mainly enriched in structural constituent of cytoskeleton (e.g., CYLC2 and TUBA1B) and membrane-enclosed lumen (e.g., CCNE1 and INTS5). In the PPI network, CCNE1 interacted with REL; and TUBA1B interacted with ESR1.

CONCLUSIONS

A series of interactions, such as CSTA/TYROBP, CCNE1/REL and TUBA1B/ESR1 might play pivotal roles in the occurrence and development of PMO.

Mass spectrometry based proteomics profiling of human monocytes

Human monocyte is an important cell type which is involved in various complex human diseases. To better understand the biology of human monocytes and facilitate further studies, we developed the first comprehensive proteome knowledge base specifically for human monocytes by integrating both in vivo and in vitro datasets. The top 2000 expressed genes from in vitro datasets and 779 genes from in vivo experiments were integrated into this study. Altogether, a total of 2237 unique monocyte-expressed genes were cataloged. Biological functions of these monocyte-expressed genes were annotated and classified via Gene Ontology (GO) analysis. Furthermore, by extracting the overlapped genes from in vivo and in vitro datasets, a core gene list including 541 unique genes was generated. Based on the core gene list, further gene-disease associations, pathway and network analyses were performed. Data analyses based on multiple bioinformatics tools produced a large body of biologically meaningful information, and revealed a number of genes such as SAMHD1, G6PD, GPD2 and ENO1, which have been reported to be related to immune response, blood biology, bone remodeling, and cancer respectively. As a unique resource, this study can serve as a reference map for future in-depth research on monocytes biology and monocyte-involved human diseases.

P4 medicine and osteoporosis: a systematic review

BACKGROUND

Osteoporosis is the most frequent bone metabolic disease. In order to improve early detection, prediction, prevention, diagnosis, and treatment of the disease, a new model of P4 medicine (personalized, predictive, preventive, and participatory medicine) could be applied. The aim of this work was to systematically review the publications of four different types of "omics" studies related to osteoporosis, in order to discover novel predictive, preventive, diagnostic, and therapeutic targets for better management of the geriatric population.

METHODS

To systematically search the PubMed database, we created specific groups of criteria for four different types of "omics" information on osteoporosis: genomic, transcriptomic, proteomic, and metabolomic. We then analyzed the intersections between them in order to find correlations and common pathways or molecules with important roles in osteoporosis, and with a potential application in disease prediction, prevention, diagnosis, or treatment.

RESULTS

Altogether, 180 publications of "omics" studies in the field of osteoporosis were found and reviewed at first selection. After introducing the inclusion and exclusion criteria (the secondary selection), 46 papers were included in the systematic review.

CONCLUSIONS

The intersection of reviewed papers identified five genes (ESR1, IBSP, CTNNB1, SOX4, and IDUA) and processes like the Wnt pathway, JAK/STAT signaling, and ERK/MAPK, which should be further validated for their predictive, diagnostic, or other clinical value in osteoporosis. Such molecular insights will enable us to fit osteoporosis into the P4 strategy and could increase the effectiveness of disease prediction and prevention, with a decrease in morbidity in the geriatric population.

Molecular mechanisms of osteoporotic hip fractures in elderly women

A common manifestation of age-related bone loss and resultant osteoporosis are fractures of the hip. Age-related osteoporosis is thought to be determined by a number of intrinsic factors including genetics, hormonal changes, changes in levels of oxidative stress, or an inflammatory status associated with the aging process. The aim of this study was to investigate gene expression and bone architecture in bone samples derived from elderly osteoporotic women with hip fractures (OP) in comparison to bone samples from age matched women with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 10 women with low-trauma hip fractures (mean age 83±6) and consecutive surgical hip replacement. Ten bone samples from patients undergoing hip replacement due to osteoarthritis (mean age 80±5) served as controls. One half of each bone sample was subjected to gene expression analysis. The second half of each bone sample was analyzed by microcomputed tomography. From each half, samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. We could show a significantly decreased expression of the osteoblast related genes RUNX2, Osterix, Sclerostin, WNT10B, and Osteocalcin, a significantly increased ratio of RANKL to Osteoprotegerin, and a significantly increased expression of the enzymes superoxide dismutase 2 (SOD2) and glutathione peroxidase GPX3, and of the inflammatory cytokine IL6 in bone samples from hip fracture patients compared to controls. Major microstructural changes in OP bone were seen in the neck and were characterized by a significant decrease of bone volume, trabecular number, and connectivity density and a significant increase of trabecular separation. In conclusion, our data give evidence for a decreased expression of osteoblast related genes and increased expression of osteoclast related genes. Furthermore, increased expression of SOD2 and GPX3 suggest increased antioxidative activity in bone samples from elderly osteoporotic women with hip fractures.

The Sirt1 Activators SRT2183 and SRT3025 Inhibit RANKL-Induced Osteoclastogenesis in Bone Marrow-Derived Macrophages and Down-Regulate Sirt3 in Sirt1 Null Cells

Increased osteoclast-mediated bone resorption is characteristic of osteoporosis, malignant bone disease and inflammatory arthritis. Targeted deletion of Sirtuin1 (Sirt1), a key player in aging and metabolism, in osteoclasts results in increased osteoclast-mediated bone resorption in vivo, making it a potential novel therapeutic target to block bone resorption. Sirt1 activating compounds (STACs) were generated and were investigated in animal disease models and in humans however their mechanism of action was a source of controversy. We studied the effect of SRT2183 and SRT3025 on osteoclastogenesis in bone-marrow derived macrophages (BMMs) in vitro, and discovered that these STACs inhibit RANKL-induced osteoclast differentiation, fusion and resorptive capacity without affecting osteoclast survival. SRT2183 and SRT3025 activated AMPK, increased Sirt1 expression and decreased RelA/p65 lysine310 acetylation, critical for NF-κB activation, and an established Sirt1 target. However, inhibition of osteoclastogenesis by these STACs was also observed in BMMs derived from sirt1 knock out (sirt1^-/-) mice lacking the Sirt1 protein, in which neither AMPK nor RelA/p65 lysine 310 acetylation was affected, confirming that these effects require Sirt1, but suggesting that Sirt1 is not essential for inhibition of osteoclastogenesis by these STACs under these conditions. In sirt1 null osteoclasts treated with SRT2183 or SRT3025 Sirt3 was found to be down-regulated. Our findings suggest that SRT2183 and SRT3025 activate Sirt1 and inhibit RANKL-induced osteoclastogenesis in vitro however under conditions of Sirt1 deficiency can affect Sirt3. As aging is associated with reduced Sirt1 level and activity, the influence of STACs on Sirt3 needs to be investigated in vivo in animal and human disease models of aging and osteoporosis.

Monocyte Proteomics Reveals Involvement of Phosphorylated HSP27 in the Pathogenesis of Osteoporosis

Peripheral monocytes, precursors of osteoclasts, have emerged as important candidates for identifying proteins relevant to osteoporosis, a condition characterized by low Bone Mineral Density (BMD) and increased susceptibility for fractures. We employed 4-plex iTRAQ (isobaric tags for relative and absolute quantification) coupled with LC-MS/MS (liquid chromatography coupled with tandem mass spectrometry) to identify differentially expressed monocyte proteins from premenopausal and postmenopausal women with low versus high BMD. Of 1801 proteins identified, 45 were differentially abundant in low versus high BMD, with heat shock protein 27 (HSP27) distinctly upregulated in low BMD condition in both premenopausal and postmenopausal categories. Validation in individual samples (n = 80) using intracellular ELISA confirmed that total HSP27 (tHSP27) as well as phosphorylated HSP27 (pHSP27) was elevated in low BMD condition in both categories (P < 0.05). Further, using transwell assays, pHSP27, when placed in the upper chamber, could increase monocyte migration (P < 0.0001) and this was additive in combination with RANKL (receptor activator of NF_kB ligand) placed in the lower chamber (P = 0.05). Effect of pHSP27 in monocyte migration towards bone milieu can result in increased osteoclast formation and thus contribute to pathogenesis of osteoporosis. Overall, this study reveals for the first time a novel link between monocyte HSP27 and BMD.

Attenuated monocyte apoptosis, a new mechanism for osteoporosis suggested by a transcriptome-wide expression study of monocytes

BACKGROUND

Osteoporosis is caused by excessive bone resorption (by osteoclasts) over bone formation (by osteoblasts). Monocytes are important to osteoporosis by serving as progenitors of osteoclasts and produce cytokines for osteoclastogenesis.

AIM

To identify osteoporosis-related genes, we performed microarray analyses of monocytes using Affymetrix 1.0 ST arrays in 42 (including 16 pre- and 26 postmenopausal) high hip BMD (bone mineral density) vs. 31 (including 15 pre- and 16 postmenopausal) low hip BMD Caucasian female subjects. Here, high vs. low BMD is defined as belonging to top vs. bottom 30% of BMD values in population.

METHOD

Differential gene expression analysis in high vs. low BMD subjects was conducted in the total cohort as well as pre- and post-menopausal subjects. Focusing on the top differentially expressed genes identified in the total, the pre- and the postmenopausal subjects (with a p <5E-03), we performed replication of the findings in 3 independent datasets of microarray analyses of monocytes (total N = 125).

RESULTS

We identified (in the 73 subjects) and successfully replicated in all the 3 independent datasets 2 genes, DAXX and PLK3. Interestingly, both genes are apoptosis induction genes and both down-regulated in the low BMD subjects. Moreover, using the top 200 genes identified in the meta-analysis across all of the 4 microarray datasets, GO term enrichment analysis identified a number of terms related to induction of apoptosis, for which the majority of component genes are also down-regulated in the low BMD subjects. Overall, our result may suggest that there might be a decreased apoptosis activity of monocytes in the low BMD subjects.

CONCLUSION

Our study for the first time suggested a decreased apoptosis rate (hence an increased survival) of monocytes, an important osteoclastogenic cell, as a novel mechanism for osteoporosis.

Manganese superoxide dismutase is required to maintain osteoclast differentiation and function under static force

Bone homeostasis is maintained by the balance of osteoblasts (OBs) and osteoclasts (OCs). Increased activity of OCs not only contributes to pathological bone resorption, such as osteoporosis and periodontitis, but also is responsible for physiological conditions like orthodontic tooth movement (OTM). However, the detailed mechanism by which orthodontic force promotes the formation of OCs is still poorly understood. In this study, we confirmed that static force promoted the differentiation of human cord monocytes (HMNCs) into OCs depending on loading time and magnitude. Protein expression profiles among HMNCs, HMNCs subjected to static force and mature OCs were established via 2-DE and MALDI-TOF-MS analyses. Total respective protein spot numbers of 549 ± 13, 612 ± 19 and 634 ± 16 were detected in each of the gels by image analysis. The five proteins identified were plasminogen activator inhibitor 2 (PAI-2, Spot 1), peroxiredoxin-6 (PRD-6, Spot 3), manganese superoxide dismutase (SOD2, Spot 6), Rho GDP-dissociation inhibitor 2 (Rho-GDI2, Spot 11) and L-lactate dehydrogenase B chain (L-LDH, Spot 15). More importantly, we revealed that SOD2 was required to maintain monocyte differentiation into functional OCs and may become a potential target for regulating the efficiency of OTM in the future.

Genome-wide Association Studies for Osteoporosis: A 2013 Update

In the past few years, the bone field has witnessed great advances in genome-wide association studies (GWASs) of osteoporosis, with a number of promising genes identified. In particular, meta-analysis of GWASs, aimed at increasing the power of studies by combining the results from different study populations, have led to the identification of novel associations that would not otherwise have been identified in individual GWASs. Recently, the first whole genome sequencing study for osteoporosis and fractures was published, reporting a novel rare nonsense mutation. This review summarizes the important and representative findings published by December 2013. Comments are made on the notable findings and representative studies for their potential influence and implications on our present understanding of the genetics of osteoporosis. Potential limitations of GWASs and their meta-analyses are evaluated, with an emphasis on understanding the reasons for inconsistent results between different studies and clarification of misinterpretation of GWAS meta-analysis results. Implications and challenges of GWAS are also discussed, including the need for multi- and inter-disciplinary studies.

Plant polyphenols in the treatment of age-associated diseases: revealing the pleiotropic effects of icariin by network analysis

Polyphenols are a broad class of compounds. Some are ingested in substantial quantities from nutritional sources, more are produced by medicinal plants, and some of them are taken as drugs. It is becoming clear, that a single polyphenol is impacting several cellular pathways. Thus, a network approach is becoming feasible, describing the interaction of a single polyphenol with cellular networks. Here we have selected icariin to draw a prototypic network of icariin activities. Icariin appears to be a promising drug to treat major age-related diseases, like neurodegeneration, memory and depressive disorders, chronic inflammation, diabetes, and osteoporosis. It interacts with several relevant pathways, like PDE, TGF-ß, MAPK, PPAR, NOS, IGF, Sirtuin, and others. Such networks will be useful to future comparative studies of complex effects of polyphenols.

Characterization of the DNA methylome and its interindividual variation in human peripheral blood monocytes

AIM

Peripheral blood monocytes (PBMs) play multiple and critical roles in the immune response, and abnormalities in PBMs have been linked to a variety of human disorders. However, the DNA methylation landscape in PBMs is largely unknown. In this study, we characterized epigenome-wide DNA methylation profiles in purified PBMs.

MATERIALS & METHODS

PBMs were isolated from freshly collected peripheral blood from 18 unrelated healthy postmenopausal Caucasian females. Epigenome-wide DNA methylation profiles (the methylome) were characterized by using methylated DNA immunoprecipitation combined with high-throughput sequencing.

RESULTS

Distinct patterns were revealed at different genomic features. For instance, promoters were commonly (∼58%) found to be unmethylated; whereas protein coding regions were largely (∼84%) methylated. Although CpG-rich and -poor promoters showed distinct methylation patterns, interestingly, a negative correlation between promoter methylation levels and gene transcription levels was consistently observed across promoters with high to low CpG densities. Importantly, we observed substantial interindividual variation in DNA methylation across the individual PBM methylomes and the pattern of this interindividual variation varied between different genomic features, with highly variable regions enriched for repetitive DNA elements. Furthermore, we observed a modest but significant excess (p < 2.2 × 10(-16)) of genes showing a negative correlation between interindividual promoter methylation and transcription levels. These significant genes were enriched in biological processes that are closely related to PBM functions, suggesting that alteration in DNA methylation is likely to be an important mechanism contributing to the interindividual variation in PBM function, and PBM-related phenotypic and disease-susceptibility variation in humans.

CONCLUSION

This study represents a comprehensive analysis of the human PBM methylome and its interindividual variation. Our data provide a valuable resource for future epigenomic and multiomic studies, exploring biological and disease-related regulatory mechanisms in PBMs.

Inhibition of transketolase by oxythiamine altered dynamics of protein signals in pancreatic cancer cells

Oxythiamine (OT), an analogue of anti-metabolite, can suppress the nonoxidative synthesis of ribose and induce cell apoptosis by causing a G1 phase arrest in vitro and in vivo. However, the molecular mechanism remains unclear yet. In the present study, a quantitative proteomic analysis using the modified SILAC method (mSILAC) was performed to determine the effect of metabolic inhibition on dynamic changes of protein expression in MIA PaCa-2 cancer cells treated with OT at various doses (0 μM, 5 μM, 50 μM and 500 μM) and time points (0 h, 12 h and 48 h). A total of 52 differential proteins in MIA PaCa-2 cells treated with OT were identified, including 14 phosphorylated proteins. Based on the dynamic expression pattern, these proteins were categorized in three clusters, straight down-regulation (cluster 1, 37% of total proteins), upright "V" shape expression pattern (cluster 2, 47.8% total), and downright "V" shape pattern (cluster 3, 15.2% total). Among them, Annexin A1 expression was significantly down-regulated by OT treatment in time-dependent manner, while no change of this protein was observed in OT dose-dependent fashion. Pathway analysis suggested that inhibition of transketolase resulted in changes of multiple cellular signaling pathways associated with cell apoptosis. The temporal expression patterns of proteins revealed that OT altered dynamics of protein expression in time-dependent fashion by suppressing phosphor kinase expression, resulting in cancer cell apoptosis. Results from this study suggest that interference of single metabolic enzyme activity altered multiple cellular signaling pathways.

Detection of significant pathways in osteoporosis based on graph clustering

Osteoporosis is the most common and serious skeletal disorder among the elderly, characterized by a low bone mineral density (BMD). Low bone mass in the elderly is highly dependent on their peak bone mass (PBM) as young adults. Circulating monocytes serve as early progenitors of osteoclasts and produce significant molecules for bone metabolism. An improved understanding of the biology and genetics of osteoclast differentiation at the pathway level is likely to be beneficial for the development of novel targeted approaches for osteoporosis. The objective of this study was to explore gene expression profiles comprehensively by grouping individual differentially expressed genes (DEGs) into gene sets and pathways using the graph clustering approach and Gene Ontology (GO) term enrichment analysis. The results indicated that the DEGs between high and low PBM samples were grouped into nine gene sets. The genes in clusters 1 and 8 (including GBP1, STAT1, CXCL10 and EIF2AK2) may be associated with osteoclast differentiation by the immune system response. The genes in clusters 2, 7 and 9 (including SOCS3, SOD2, ATF3, ADM EGR2 and BCL2A1) may be associated with osteoclast differentiation by responses to various stimuli. This study provides a number of candidate genes that warrant further investigation, including DDX60, HERC5, RSAD2, SIGLEC1, CMPK2, MX1, SEPING1, EPSTI1, C9orf72, PHLDA2, PFKFB3, PLEKHG2, ANKRD28, IL1RN and RNF19B.

Monocyte/macrophage proteomics: recent findings and biomedical applications

Macrophages, originating from the migration and differentiation of circulating monocytes into virtually all tissues, are extremely flexible and plastic cells that play vital homeostatic roles, but also contribute to the pathophysiology of many human diseases. For these reasons, they are intensively studied by different approaches, recently including proteomics. Macrophage cells can be taken from a range of different sources, including blood monocytes and macrophages from tissues. Macrophages can also be generated by in vitro culture from blood monocytes, and cell lines derived from this lineage can be used. Similarly, many different proteomic techniques can be used, ranging from classic approaches based on 2D gel electrophoresis to more recent high-throughput gel-free techniques essentially based on mass spectrometry. Here, we review the application of such techniques to the study of monocytes/macrophages, and summarize some results potentially relevant to two paradigmatic conditions - atherosclerosis and disorders of iron metabolism.

Smoke-induced signal molecules in bone marrow cells from altered low-density lipoprotein receptor-related protein 5 mice

Mechanism underlying smoke-induced loss of bone mass is unknown. In this study, we hypothesized that protein signals induced by smoking in bone marrow may be associated with the loss of bone mass. Using a proteomics approach, we identified 38 proteins differentially expressed in bone marrow cells from low-density lipoprotein receptor-related protein 5 (Lrp5) mice exposed to cigarette smoking. Smoking effects on protein expression in bone marrow among three genotypes (Lrp5(+/+), Lrp5(G171V), and Lrp5(-/-)) varied. On the basis of the ratio of protein expression induced by smoking versus nonsmoking, smoke induced protein expression significantly in wild-type mice compared to the other two genotypes (Lrp5(G171V) and Lrp5(-/-)). These proteins include inhibitors of β-catenin and proteins associated with differentiation of osteoclasts. We observed that S100A8 and S100A9 were overexpressed in human smokers compared to nonsmokers, which confirmed the effect of smoking on the expression of two proteins in Lrp5 mice, suggesting the role of these proteins in bone remodeling. Smoke induced expression of S100A8 and S100A9 in a time-dependent fashion, which was opposite of the changes in the ratio of OPG/RANKL in bone marrow cells, suggesting that the high levels of S100A8 and S100A9 may be associated with smoke-induced bone loss by increasing bone resorption.

Protein disulfide isomerase in redox cell signaling and homeostasis

Thiol proteins may potentially act as redox signaling adaptor proteins, adjusting reactive oxygen species intermediates to specific signals and redox signals to cell homeostasis. In this review, we discuss redox effects of protein disulfide isomerase (PDI), a thioredoxin superfamily oxidoreductase from the endoplasmic reticulum (ER). Abundantly expressed PDI displays ubiquity, interactions with redox and nonredox proteins, versatile effects, and several posttranslational modifications. The PDI family contains >20 members with at least some apparent complementary actions. PDI has oxidoreductase, isomerase, and chaperone effects, the last not directly dependent on its thiols. PDI is a converging hub for pathways of disulfide bond introduction into ER-processed proteins, via hydrogen peroxide-generating mechanisms involving the oxidase Ero1α, as well as hydrogen peroxide-consuming reactions involving peroxiredoxin IV and the novel peroxidases Gpx7/8. PDI is a candidate pathway for coupling ER stress to oxidant generation. Emerging information suggests a convergence between PDI and Nox family NADPH oxidases. PDI silencing prevents Nox responses to angiotensin II and inhibits Akt phosphorylation in vascular cells and parasite phagocytosis in macrophages. PDI overexpression spontaneously enhances Nox activation and expression. In neutrophils, PDI redox-dependently associates with p47phox and supports the respiratory burst. At the cell surface, PDI exerts transnitrosation, thiol reductase, and apparent isomerase activities toward targets including adhesion and matrix proteins and proteases. Such effects mediate redox-dependent adhesion, coagulation/thrombosis, immune functions, and virus internalization. The route of PDI externalization remains elusive. Such multiple redox effects of PDI may contribute to its conspicuous expression and functional role in disease, rendering PDI family members putative redox cell signaling adaptors.

Proteomic analysis of blood cells in fish exposed to chemotherapeutics: evidence for long term effects

Proteomics technology are increasingly used in ecotoxicological studies to characterize and monitor biomarkers of exposure. The present study aims at identifying long term effects of malachite green (MG) exposure on the proteome of peripheral blood mononuclear cells (PBMC) from the Asian catfish, Pangasianodon hypophthalmus. A common (0.1 ppm) concentration for therapeutic treatment was applied twice with a 72 h interval. PBMC were collected directly at the end of the second bath of MG (T1) and after 1 month of decontamination (T2). Analytical 2D-DIGE gels were run and a total of 2551±364 spots were matched. Among them, MG induced significant changes in abundance of 116 spots with no recovery after one month of decontamination. Using LC-MS/MS and considering single identification per spot, we could identify 25 different proteins. Additionally, MG residues were measured in muscle and in blood indicating that leuco-MG has almost totally disappeared after one month of decontamination. This work highlights long term effects of MG treatment on the PBMC proteome from fish intended for human consumption.

Post-genomics of bone metabolic dysfunctions and neoplasias

Post-genomic research on osteoblastic and osteoclastic cells, in contrast to that on many other cell types, has only been undertaken recently. Nevertheless, important information has been gained from these investigations on the mechanisms involved in osteoblast differentiation and on markers relevant for tissue regeneration and therapeutic validation of drugs, hormones and growth factors. These protein indicators may also have a diagnostic and prognostic value for bone dysfunctions and tumors. Some reviews have already focused on the application of transcriptomics and/or proteomics for exploring skeletal biology and related disorders. The main goal of the present review is to systematically summarize the most relevant post-genomic studies on various metabolic bone diseases (osteoporosis, Paget's disease and osteonecrosis), neoplasias (osteosarcoma) and metabolic conditions that indirectly affect bone tissue, such as alkaptonuria.

An integrative study ascertained SOD2 as a susceptibility gene for osteoporosis in Chinese

Osteoporosis is characterized by low BMD and has strong genetic determination. However, specific genetic variants influencing BMD and contributing to the pathogenesis of osteoporosis are largely uncharacterized. Current genetic studies in bone, which are aimed at identification of osteoporosis risk genes, are focused mostly on DNA, RNA, or the protein level individually, lacking integrative evidence from the three levels of genetic information flow to confidently ascertain the significance of genes for osteoporosis. Our previous proteomics study discovered that superoxide dismutase 2 (SOD2) in circulating monocytes (CMCs, ie, potential osteoclast precursors) was significantly upregulated at protein level in vivo in Chinese with low versus high hip BMD. Herein, at mRNA level, we found that SOD2 gene expression also was upregulated in CMCs (p < 0.05) in Chinese with low versus high hip BMD. At the DNA level, in 1627 unrelated Chinese subjects, we identified eight single-nucleotide polymorphisms (SNPs) at the SOD2 gene locus that were suggestively associated with hip BMD (peak signal at rs11968525, p = 0.048). Among the eight SNPs, three SNPs (rs7754103, rs7754295, and rs2053949) were associated with the SOD2 mRNA expression level (p < 0.05), suggesting that they are expression quantitative trait loci (eQTLs) regulating SOD2 gene expression. In conclusion, this integrative evidence from DNA, RNA, and protein levels support SOD2 as a susceptibility gene for osteoporosis.

Peripheral blood monocyte-expressed ANXA2 gene is involved in pathogenesis of osteoporosis in humans

Low bone mineral density (BMD) is a risk factor of osteoporosis and has strong genetic determination. Genes influencing BMD and fundamental mechanisms leading to osteoporosis have yet to be fully determined. Peripheral blood monocytes (PBM) are potential osteoclast precursors, which could access to bone resorption surfaces and differentiate into osteoclasts to resorb bone. Herein, we attempted to identify osteoporosis susceptibility gene(s) and characterize their function(s), through an initial proteomics discovery study on PBM in vivo, and multiscale validation studies in vivo and in vitro. Utilizing the quantitative proteomics methodology LC-nano-ESI-MS(E), we discovered that a novel protein, i.e. ANXA2, was up-regulated twofold in PBM in vivo in Caucasians with extremely low BMD (cases) versus those with extremely high BMD (controls) (n = 28, p < 0.05). ANXA2 gene up-regulation in low BMD subjects was replicated at the mRNA level in PBM in vivo in a second and independent case-control sample (n = 80, p < 0.05). At the DNA level, we found that SNPs in the ANXA2 gene were associated with BMD variation in a 3(rd) and independent case-control sample (n = 44, p < 0.05), as well as in a random population sample (n = 997, p < 0.05). The above integrative evidence strongly supports the concept that ANXA2 is involved in the pathogenesis of osteoporosis in humans. Through a follow-up cellular functional study, we found that ANXA2 protein significantly promoted monocyte migration across an endothelial barrier in vitro (p < 0.001). Thus, elevated ANXA2 protein expression level, as detected in low BMD subjects, probably stimulates more PBM migration through the blood vessel walls to bone resorption surfaces in vivo, where they differentiate into higher number of osteoclasts and resorb bone at higher rates, thereby decreasing BMD. In conclusion, this study identified a novel osteoporosis susceptibility gene ANXA2, and suggested a novel pathophysiological mechanism, mediated by ANXA2, for osteoporosis in humans.

Molecular genetic studies of gene identification for osteoporosis: the 2009 update

Osteoporosis is a complex human disease that results in increased susceptibility to fragility fractures. It can be phenotypically characterized using several traits, including bone mineral density, bone size, bone strength, and bone turnover markers. The identification of gene variants that contribute to osteoporosis phenotypes, or responses to therapy, can eventually help individualize the prognosis, treatment, and prevention of fractures and their adverse outcomes. Our previously published reviews have comprehensively summarized the progress of molecular genetic studies of gene identification for osteoporosis and have covered the data available to the end of September 2007. This review represents our continuing efforts to summarize the important and representative findings published between October 2007 and November 2009. The topics covered include genetic association and linkage studies in humans, transgenic and knockout mouse models, as well as gene-expression microarray and proteomics studies. Major results are tabulated for comparison and ease of reference. Comments are made on the notable findings and representative studies for their potential influence and implications on our present understanding of the genetics of osteoporosis.