MiR-133a in human circulating monocytes: a potential biomarker associated with postmenopausal osteoporosis

Background

Osteoporosis mainly occurs in postmenopausal women, which is characterized by low bone mineral density (BMD) due to unbalanced bone resorption by osteoclasts and formation by osteoblasts. Circulating monocytes play important roles in osteoclastogenesis by acting as osteoclast precursors and secreting osteoclastogenic factors, such as IL-1, IL-6 and TNF-α. MicroRNAs (miRNAs) have been implicated as important biomarkers in various diseases. The present study aimed to find significant miRNA biomarkers in human circulating monocytes underlying postmenopausal osteoporosis.

Methodology/Principal Findings

We used ABI TaqMan® miRNA array followed by qRT-PCR validation in circulating monocytes to identify miRNA biomarkers in 10 high and 10 low BMD postmenopausal Caucasian women. MiR-133a was upregulated (P=0.007) in the low compared with the high BMD groups in the array analyses, which was also validated by qRT-PCR (P=0.044). We performed bioinformatic target gene analysis and found three potential osteoclast-related target genes, CXCL11, CXCR3 and SLC39A1. In addition, we performed Pearson correlation analyses between the expression levels of miR-133a and the three potential target genes in the 20 postmenopausal women. We did find negative correlations between miR-133a and all the three genes though not significant.

Conclusions/Significance

This is the first in vivo miRNA expression analysis in human circulating monocytes to identify novel miRNA biomarkers underlying postmenopausal osteoporosis. Our results suggest that miR-133a in circulating monocytes is a potential biomarker for postmenopausal osteoporosis.     

Aerobic degradation of diethyl phthalate by Sphingomonas sp

An aerobic diethyl phthalate (DEP) degrading bacterium, DEP-AD1, was isolated from activated sludge. Based on its 16S rDNA sequence, this isolate was identified belonging to Sphingomonas genus with 99% similarity to Sphingomonas sp. strain C28242 and 98% similarity to S. capsulate. The specific degradation rate of DEP was concentration dependent with a maximum of 14 mg-DEP/(Lh). Results of degradation tests showed that DEP-AD1 could also degrade monoethyl phthalate (MEP), dimethyl phthalate (DMP), dibutyl phthalate (DBP), and diethylhexyl phthalate (DEHP), but not phthalate and benzoate.     

Trapping and characterization of covalent intermediates of mutant retaining glycosyltransferases

The enzymatic mechanism by which retaining glycosyltransferases (GTs) transfer monosaccharides with net retention of the anomeric configuration has, so far, resisted elucidation. Here, direct detection of covalent glycosyl-enzyme intermediates for mutants of two model retaining GTs, the human blood group synthesizing α-(1 → 3)-N-acetylgalactosaminyltransferase (GTA) and α-(1 → 3)-galactosyltransferase (GTB) mutants, by mass spectrometry (MS) is reported. Incubation of mutants of GTA or GTB, in which the putative catalytic nucleophile Glu(303) was replaced with Cys (i.e. GTA(E303C) and GTB(E303C)), with their respective donor substrate results in a covalent intermediate. Tandem MS analysis using collision-induced dissociation confirmed Cys(303) as the site of glycosylation. Exposure of the glycosyl-enzyme intermediates to a disaccharide acceptor results in the formation of the corresponding enzymatic trisaccharide products. These findings suggest that the GTA(E303C) and GTB(E303C) mutants may operate by a double-displacement mechanism.     

Study of the restitution of action potential duration using the artificial neural network

It is widely accepted that the APD (action potential duration) restitution plays a key role in the initializing and maintaining of the reentry arrhythmias. The Luo-Rudy II models paced with different protocols showed that the current APD had a complex relation with the previous APDs and diastole intervals (DIs). This relation could not be accurately described by a single exponential function. We used an artificial neural network to formularize this relation. The results suggested that back-propagation (BP) network could predict the current APD from the information of the first three previous beats. This would help provide a target for potential anti-arrhythmic therapies.     

Biochemical mechanisms leading to tryptophan 2,3-dioxygenase activation

Tryptophan 2,3-dioxygenase (TDO) is the first enzyme in the tryptophan oxidation pathway. It is a hemoprotein and its heme prosthetic group is present as a heme-ferric (heme-Fe(3+)) form that is not active. To be able to oxidize tryptophan, the heme-Fe(3+) form of the enzyme must be reduced to a heme-ferrous (heme-Fe(2+)) form and this study describes conditions that promote TDO activation. TDO is progressively activated upon mixing with tryptophan in a neutral buffer, which leads to an impression that tryptophan is responsible for TDO activation. Through extensive analysis of factors resulting in TDO activation during incubation with tryptophan, we conclude that tryptophan indirectly activates TDO through promoting the production of reactive oxygen species. This consideration is supported by the virtual elimination of the initial lag phase when either pre-incubated tryptophan solution was used as the substrate or a low concentration of superoxide or hydrogen peroxide was incorporated into the freshly tryptophan and TDO mixture. However, accumulation of these reactive oxygen species also leads to the inactivation of TDO, so that both TDO activation and inactivation proceed with the specific outcome depending greatly on the concentrations of superoxide and hydrogen peroxide. As a consequence, the rate of TDO catalysis varies depending upon the proportion of the active to inactive forms of the enzyme, which is in a dynamic relationship in the reaction mixture. These data provide some insight towards elucidating the molecular regulation of TDO in vivo.     

Histidine-rich glycoprotein plus zinc reverses growth inhibition of vascular smooth muscle cells by heparin

Vascular smooth muscle cell (SMC) hyperplasia is known to be an important component in the pathogenesis of arteriosclerosis and restenosis. Although heparin has been well recognized as the representative molecule suppressing SMC growth in vitro, attempts to use heparin as a therapeutic anti-restenosis drug have not favorably influenced the angiographic or clinical outcome after angioplasty in some clinical trials. In this study, we have examined the effect of histidine-rich glycoprotein (HRG), a relatively abundant serum glycoprotein (~100 micrograms/ml in human serum), on the growth inhibition of cultured vascular SMC by heparin. Vascular SMC growth was significantly inhibited by heparin, giving nearly 85% inhibition with 100 micrograms/ml heparin. HRG reversed heparin-induced SMC growth inhibition in a dose dependent manner; 75% restoration of cell growth was observed when 100 micrograms/ml of HRG was co-added with 100 micrograms/ml heparin. Interestingly, micromolar concentrations of the zinc ion (0-10 microM), compatible with concentrations released from activated platelets, were found to enhance the restorative action of HRG. Western blot experiment demonstrated no significant amounts of the HRG moiety in fetal bovine serum, eliminating the possible contribution of contaminant HRG from culture media. These findings indicate that HRG, in combination with the zinc ion, plays a role in modulating the SMC growth response in pathophysiological states and explain the lack of success of heparin as a therapeutic anti-restenosis drug in clinical trials.     

Formalin removal from archival tissue by critical point drying

The extraction of high-quality nucleic acid may be problematic in formalin-fixed tissues because of cross-linking between proteins and DNA. Old fixed tissue specimens do produce fragmented DNA (<1.2 kb), which is only used for PCR amplification. Here we show that high molecular weight DNA (>194 kb) can be successfully extracted from fixed tissue samples (16-70 years old) by gradual dehydration and critical point drying. The reliability of extracted DNA was measured by its ability to serve as a template for the amplification of mtDNA fragments (403 and 1198 bp) and an nDNA fragment (1844 bp). In addition, fingerprinting analysis was performed using DNA from fixed human tissue to ensure the ability of extracted DNA to hybridize with the DNA probe. DNA derived by this method can be subject to amplification, complete digestion by restriction endonuclease, and hybridization.     

Human T-cell leukemia virus type 1 (HTLV-1) infection of mice: proliferation of cell clones with integrated HTLV-1 provirus in lymphoid organs

Human T-cell leukemia virus type 1 (HTLV-1) is suggested to cause adult T-cell leukemia after 40 to 50 years of latency in a small percentage of carriers. However, little is known about the pathophysiology of the latent period and the reservoir organs where polyclonal proliferation of cells harboring integrated provirus occurs. The availability of animal models would be useful to analyze the latent period of HTLV-1 infection. At 18 months after HTLV-1 infection of C3H/HeJ mice inoculated with the MT-2 cell line, which is an HTLV-1-producing human T-cell line, HTLV-1 provirus was detected in spleen DNA from eight of nine mice. No more than around 100 proviruses were found per 10(5) spleen cells. Cellular sequences flanking the 3' long terminal repeat (LTR) and the clonalities of the cells which harbor integrated HTLV-1 provirus were analyzed by linker-mediated PCR. The results showed that the flanking sequences are of mouse genome origin and that polyclonal proliferation of the spleen cells harboring integrated HTLV-1 provirus had occurred in three mice. A sequence flanking the 5' LTR was isolated from one of the mice and revealed the presence of a 6-nucleotide duplication of cellular sequences, consistent with typical retroviral integration. Moreover, PCR was performed on DNA from infected tissues, with LTR primers and primers derived from seven novel flanking sequences of the three mice. Data revealed that the expected PCR products were found from lymphatic tissues of the same mouse, suggesting that the lymphatic tissues were the reservoir organs for the infected and proliferating cell clones. The mouse model described here should be useful for analysis of the carrier state of HTLV-1 infection in humans.