Biomedical subjects

Hui Bin Sun

Publications and source records attributed to Hui Bin Sun.

10 recordsLinked to original sources

PubMed2004

Oscillating Couette flow for in vitro cell loading.

Synovial joints are loaded by weight bearing, stretching, and fluid-driven shear. To simulate in vitro fluid-driven shear, we developed an "oscillating Couette flow mechanical shear loader". Oscillating Couette flow mimics relative motion of articular surfaces; hence, characterizing flow-induced shear by the loader enhances understanding of mechanotransduction in the joint tissue. Here, the analytical and computational models for an oscillating Couette flow were used to predict time-varying shear distribution on a plate surface, applying numerical simulation to evaluate the effects of finite plate dimension in a 2D flow. Shear stress on the plate was significantly different from that in simpler models (unbounded plates and viscous low-frequency flow). High-stress spots appeared near the leading and trailing edges of a moving plate, and a relatively uniform shear region was restricted to the interior area. Stress prediction in an example experimental geometry is presented, where the frequency and finite width effects are feasibly accounted.

Cells, Cultured↗

PubMed2003

CITED2-mediated regulation of MMP-1 and MMP-13 in human chondrocytes under flow shear.

CITED2 (CBP/p300-interacting transactivator with ED-rich tail 2) is a member of the Cited family of nuclear regulators, previously known as mrg1 (melanocyte-specific gene-related gene 1). CITED2 is inducible by varying stimuli including lipopolysaccharide, hypoxia, and cytokines such as interleukin 9 and interferon gamma. Using the immortalized human chondrocyte cell line, C-28/I2, we investigated whether CITED2 could be responsive to mechanical stimuli, and if so, whether CITED2 could mediate shear-driven regulation of matrix metalloproteinase (MMP) genes. The C-28/I2 cells were cultured under flow shear at 1-20 dyn/cm2, and the role of CIT-ED2 in regulation of MMPs was examined using the plasmids encoding sense and antisense CITED2 DNA sequences. The results showed that flow shear at 5 dyn/cm2 increased CITED2 mRNA and protein levels and down-regulated MMP-1 and MMP-13 mRNA and protein levels as well as enzyme activities. Consistent with the coordinated expression patterns of CITED2 and MMPs, overexpression of CITED2 repressed MMP-1 and MMP-13 mRNA levels and activities, whereas antisense CITED2 plasmids prevented the shear-induced down-regulation of MMP expression. Interleukin-1beta induced the formation of p300-Ets-1 complexes without affecting expression of CITED2. Transforming growth factor-beta as well as flow shear at 5 dyn/cm2 stimulated not only the expression of CITED2 but also the association of CIT-ED2 with p300 by dissociating Ets-1 from p300. These results indicate that CITED2 plays a major role in shear-induced down-regulation of MMP-1 and MMP-13 via a transforming growth factor-beta-dependent pathway.

Cell Line↗

PubMed2003

Synthesis of radiolabeled biphenylsulfonamide matrix metalloproteinase inhibitors as new potential PET cancer imaging agents.

Novel matrix metalloproteinase (MMP) inhibitor radiotracers, (S)-3-methyl-2-(2',3',4'-methoxybiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1a-c), (S)-3-methyl-2-(2',3',4'-fluorobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1d-f), and (S)-3-methyl-2-(4'-nitrobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1g), a series of substituted biphenylsulfonamide derivatives, have been synthesized for evaluation as new potential positron emission tomography (PET) cancer imaging agents.

Biphenyl Compounds↗

PubMed2003

Model-based analysis of matrix metalloproteinase expression under mechanical shear.

We report the development of a model-based analysis for identification of the role of transcription factor (TF) binding motifs. A nonlinear mathematical model was formulated to establish the quantitative relationship between the temporal expression profiles and the distribution of known TF binding motifs on regulatory DNA regions. In order to evaluate biological meaning of the nonlinear model, the role of TF binding motifs predicted by the model was examined by a promoter competition assay where specific TF binding motifs were inactivated by a transient transfer of the DNA fragments consisting of the TF binding motifs. Using the shear stress responses of a family of matrix metalloproteinases in human synovial cells as a model system, we showed that the nonlinear formulation was able to approximate the experimentally observed expression profile better than the linear formulation, and the stimulatory and inhibitory roles of TF binding motifs extracted from the model were validated by the competition assay. The results support that an integrated usage of the nonlinear model and the biochemical evaluation assay would contribute to identifying critical regulatory DNA elements in mechanical responses in connective tissue.

Amino Acid Motifs↗

PubMed2003

Expression and activities of matrix metalloproteinases under oscillatory shear in IL-1-stimulated synovial cells.

Matrix metalloproteinases (MMPs) are known to play a critical role in tissue disintegration, and an elevated level of MMPs is observed in synovium and synovial fluid of joints with rheumatoid arthritis. During joint movement, synovial tissue receives various mechanical stimuli, but effects of mechanical challenges on regulation of MMPs in rheumatic synovium are poorly understood. Focusing on cellular responses to oscillatory fluid shear in human synovial cells, we determined the expression of MMP-1 and MMP-13 by polymerase chain reaction and immunoblotting as well as proteolytic activities of total MMPs by a fibril degradation assay and zymography. The results revealed that approximately 0.5 dyn/cm2 oscillatory shear at 1 Hz not only reduced an mRNA level and a protein level of MMP-1 and MMP-13, but it also decreased collagenase and gelatinase activities of total MMPs. Furthermore, the induction of the MMP expression and activities by interleukin-1 was suppressed by the oscillatory shear. Interestingly, the oscillatory shear upregulated the mRNA expression of TIMP-1 and TIMP-2. Our results support a potential role of oscillatory shear in regulating expression and activities of MMPs in the presence and the absence of proinflammatory cytokine.

Arthritis, Rheumatoid↗

PubMed2002

Involvement of the calcium-independent receptor for alpha-latrotoxin in brain ischemia.

Cerebral ischemia is caused by a reduced blood supply to neurons, and vulnerability to neurodegeneration varies considerably among neuronal types. In hippocampus, neurons in the CA1 region are more susceptible to ischemia-induced neuronal death than neurons in the CA3 region, and in response to transient forebrain ischemia a family of calcium-dependent receptors for alpha-latrotoxin is differentially expressed in the two regions. Here, we report that an ischemic insult up-regulated a family of calcium-independent receptors for alpha-latrotoxin (CIRL) mRNAs in CA1 neurons and down-regulated their mRNAs in CA3 neurons. Furthermore, antisense oligonucleotides complementary to CIRL-1 mRNA or CIRL-3 mRNA suppressed neuronal death associated with hypoxia in hippocampal and cortical cell cultures. The observed region-specific CIRL mRNA expression in hippocampus and an in vitro rescue experiment by antisense oligonucleotides against CIRL mRNAs suggest a functional importance of CIRL in neurodegeneration.

Animals↗

PubMed2002

Promoter competition assay for analyzing gene regulation in joint tissue engineering.

We describe a new biochemical technique, "promoter competition assay," for examining the role of cis-acting DNA elements in tissue cultures. Recent advances in tissue engineering permit the culture of a variety of cells. Many tissues are engineered, however, without an appropriate understanding of molecular machinery that regulates gene expression and cellular growth. For elucidating the role of cis-acting regulatory elements in cellular differentiation and growth, we developed the promoter competition assay. This assay uses a transient transfer into cells of double-stranded DNA fragments consisting of cis-acting regulatory elements. The transferred DNA fragments act as a competitor and titrate the function of their genomic counterparts. Using synovial cells derived from a rheumatoid arthritis patient, we examined a role of NF-kappa B binding sites in the regulation of the expression of matrix metalloproteinase (MMP) genes. The results support a stimulatory role of NF-kappa B in transcriptional regulation of MMP-1 and MMP-13.

Arthritis, Rheumatoid↗

PubMed2002

Systems analysis of matrix metalloproteinase mRNA expression in skeletal tissues.

The availability of human genome sequences provides life scientists and biomedical engineers with a challenging opportunity to develop computational and experimental tools for quantitatively analyzing biological processes. In response to a growing need to integrate experimental mRNA expression data with human genome sequences, we present here a unique analysis named "Promoter-Based Estimation (PROBE)" analysis. The PROBE analysis is "systems analysis" of transcriptional processes using control and estimation theories. A linear model was built in order to estimate the mRNA levels of a group of genes from their regulatory DNA sequences. The model was also used to interpret two independent datasets in skeletal tissues. The results demonstrated that the mRNA levels of a family of matrix metalloproteinases can be modeled from a distribution of cis-acting elements on regulatory DNA sequences. The model accurately predicted a stimulatory role of cis-acting elements such as AP1, NFY, PEA3, and Sp1 as well as an inhibitory role of AP2. These predictions are consistent with biological observations, and a specific assay for testing such predictions is proposed. Although eukaryotic transcription is a complex mechanism, the two examples presented here support the potential use of the described analysis for elucidating the functional significance of DNA regulatory elements.

Algorithms↗

PubMed2002

Reduction of cytokine-induced expression and activity of MMP-1 and MMP-13 by mechanical strain in MH7A rheumatoid synovial cells.

Excessive mechanical load induces harmful outcomes for joint diseases, such as osteoarthritis and rheumatoid arthritis, but physical stimuli at appropriate intensity are essential for growth and maintenance of bone and articular cartilage. Using a fibroblast-like synoviocyte cell line derived from a patient with rheumatoid arthritis, we examined the effects of gentle cyclic strain, focusing on the expression and activity of matrix metalloproteinase-1 (MMP-1) and MMP-13. Synovial cells were cultured on a collagen-coated agar block and exposed to 2% cyclic strain at 6 rev./min for 1 h. Expression of MMP-1 and MMP-13 was assayed using semi-quantitative and real-time PCR, as well as immunoblotting. Their activity was measured using spectrofluorometry and zymography. The results showed that the cyclic strain reduced the mRNA and protein levels of MMP-1 and MMP-13, and that both collagenase and gelatinase activity was decreased under the strain. The reduction in MMP activity by the cyclic strain was not achieved by the transcriptional inhibitor, actinomycin D. In the presence of proinflammatory cytokines, such as IL-1 beta and TNF-alpha, the strain reduced the cytokine-induced expression and activities of MMPs. Interestingly, the strain elevated the mRNA level of tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2. These results support a potential role of mechanical strain in down-regulating the cytokine-mediated proteolytic processes in synoviocytes.

Arthritis, Rheumatoid↗

PubMed2002

Synthesis and preliminary biological evaluation of MMP inhibitor radiotracers [11C]methyl-halo-CGS 27023A analogs, new potential PET breast cancer imaging agents.

A series of [11C]methyl-halo-CGS 27023A analogs (2-F, 1a; 4-F, 1b; 2-Cl, 1c; 3-Cl, 1d; 4-Cl, 1e; 2-Br, 1f; 3-Br, 1g; 4-Br, 1h; 4-I, 1i), novel radiolabeled matrix metalloproteinase (MMP) inhibitors, have been synthesized for evaluation as new potential positron emission tomography (PET) breast cancer imaging agents. The precursors halo-CGS 27023A analogs (2-F, 6a; 4-F, 6b; 2-Cl, 6c; 3-Cl, 6d; 4-Cl, 6e; 2-Br, 6f; 3-Br, 6g; 4-Br, 6h; 4-I, 6i) for radiolabeling were obtained in four steps from starting material amino acid D-valine with moderate to excellent chemical yields. Precursors were labeled by [11C]methyl triflate through 11C-O-methylation method at the aminohydroxyl position under basic conditions and isolated by solid-phase extraction (SPE) purification to produce pure target compounds in 40-60% radiochemical yields (decay corrected to end of bombardment), in 20-25 min synthesis time.

Animals↗