Biomedical subjects

Zhiwen Liu

Publications and source records attributed to Zhiwen Liu.

9 recordsLinked to original sources

PubMed2006

Endogenous thrombospondin-1 is a cell-surface ligand for regulation of integrin-dependent T-lymphocyte adhesion.

Lymphocyte adhesion to cells and extracellular matrix (ECM) via integrins plays a pivotal role for the function of the immune system. We show here that endogenous thrombospondin-1 (TSP-1) is a cell-surface ligand for cis interaction of surface receptors in T lymphocytes controlled by integrins and the T-cell antigen receptor (TCR/CD3). Stimulation of CD3 triggers rapid surface expression of TSP-1 in quiescent T cells, whereas activated cells express TSP-1 constitutively. Endogenous TSP-1 is attached to lipoprotein receptor-related protein 1 (LRP1/CD91) and calreticulin (CRT) on the cell surface through its NH2-terminal domain. Adhesion via integrins to ICAM-1 or ECM components up-regulates TSP turnover dramatically from a low level in nonadherent cells, whereas CD3 stimulation inhibits TSP turnover through interference with CD91/CRT-mediated internalization. Integrin-associated protein (IAP/CD47) is essential for TSP turnover and adhesion through interaction with the C-terminal domain of TSP-1 in response to triggering signals delivered at the NH2-terminal. These results indicate that endogenous TSP-1 connects separate cell-surface receptors functionally and regulates T-cell adhesion.

Biotinylation↗

PubMed2006

Frequency division multiplexed multichannel high-speed fluorescence confocal microscope.

In this article, we report a new type of fluorescence confocal microscope: frequency division multiplexed multichannel fluorescence confocal microscope, in which we encode the spatial location information into the frequency domain. In this microscope, the exciting laser beam is first split into multiple beams and each beam is modulated at a different frequency. These multiple beams are focused at different locations of the target to form multiple focal points, which further generate multiple fluorescent emission spots. The fluorescent emissions from different focal points are also modulated at different frequencies, because the exciting beams are modulated at different frequencies (or difference carrier frequency). Then, all the fluorescent emissions (modulated at different frequencies) are collected together and detected by a highly sensitive, large-dynamic-range photomultiplier tube. By demodulating the detected signal (i.e., via the Fourier transform), we can distinguish the fluorescent light emitted from the different locations by the corresponding carrier frequencies. The major advantage of this unique fluorescence confocal microscope is that it not only has a high sensitivity because of the use of photomultiplier tube but also can get multiple-point data simultaneously, which is crucial to study the dynamic behavior of many biological process. As an initial step, to verify the feasibility of the proposed multichannel confocal microscope, we have developed a two-channel confocal fluorescence microscope and applied it to study the dynamic behavior of the changes of the calcium ion concentration during the single cardiac myocyte contraction. Our preliminary experimental results demonstrated that we could indeed realize multichannel confocal fluorescence microscopy by utilizing the frequency division multiplexed microscope, which could become an effective tool to study the dynamic behavior of many biological processes.

Animals↗

PubMed2005

Manipulation and spectroscopy of a single particle by use of white-light optical tweezers.

We demonstrate, for the first time to our knowledge, three-dimensional (3D) trapping and manipulation of microscopic objects by use of supercontinuum white light generated from photonic crystal fibers. Furthermore, we show that the supercontinuum white-light optical tweezers used have the unique capability to perform optical scattering spectroscopy of a single 3D trapped object over a broad wavelength range. These novel tweezers can potentially open a promising avenue toward simultaneous manipulation and characterization of microscopic objects.

Equipment Design↗

PubMed2004

Holographic recording of laser-induced plasma.

We report on a holographic probing technique that allows for measurement of free-electron distribution with fine spatial detail. Plasma is generated by focusing a femtosecond pulse in air. We also demonstrate the capability of the holographic technique of capturing the time evolution of the plasma-generation process.

Journal Article↗

PubMed2002

Effects of cyclosporin A on the levels of intercellular adhesion molecule-1 expressed by oral fibroblasts.

OBJECTIVE: To investigate the effects of cyclosporin A (CSA) on the level of intercellular adhesion molecule-1 (ICAM-1) expressed by oral fibroblasts (FB). METHODS: The fibroblasts were obtained from normal buccal mucosa (NM-FB) and cultured in vitro. Then the levels of ICAM-1 expressed by fibroblasts incubated with or without CSA in the presence of 10% fetal calf serum for 48 hours at 37 degrees C in 5% CO(2) and air were monitored by using cell-based ELISA for ICAM-1. RESULTS: We demonstrated that NM-FB had ICAM-1 expression (A = 0.324 +/- 0.030), and after 48 hours incubated with CSA the ICAM-1 levels expressed by oral buccal mucosa fibroblasts were dose-dependently decreased. CONCLUSIONS: CSA reduces the levels of ICAM-1 expressed by oral mucosal FB, and may be useful in the treatment of some oral mucosal disorders.

Cells, Cultured↗

PubMedDate not supplied

Inhibition of proliferation, migration, and matrix metalloprotease production in malignant mesothelioma cells by tyrosine kinase inhibitors.

The epidermal growth factor receptor (EGFR) is expressed in a variety of human solid tumors, including malignant mesothelioma. EGFR has been implicated in regulation of cell proliferation, survival, angiogenesis, and metastasis, making it an ideal target for drug development. ZD1839 (gefitinib) and OSI-774 (erlotinib) are new, low-molecular-weight, EGFR-selective tyrosine kinase (TK) inhibitors, whereas CI-1033 is a pan-EGFR family TK inhibitor. In the present study, we used ZD1839, OSI-774, and CI-1033 and investigated the effect of these drugs on proliferation, migration, and matrix metalloprotease (MMP) production in three malignant mesothelioma cell lines (M14K, ZL34, and SPC212). Using [3H]thymidine incorporation, DNA synthesis assay, we found that all three drugs inhibited transforming growth factor-alpha (TGF-alpha)-induced cellular proliferation in a dose-dependent manner. In addition, all three drugs induced apoptosis in ZL34 cells as determined by flow cytometry using annexin-V staining. Furthermore, all three drugs inhibited TGF-alpha-induced cell migration (chemotaxis) in a dose-dependent manner as determined by Boyden chamber assay. TGF-alpha-induced MMP-9 production was also inhibited in a dose-dependent manner as determined by gelatin zymography in three cell lines tested. In conclusion, our study demonstrates inhibitory effectiveness of EGFR-TK inhibitors in malignant mesothelioma cells and suggests that these drugs may be an effective treatment strategy for malignant mesothelioma.

Antineoplastic Agents↗

PubMedDate not supplied

Growth factor-enhanced expression and activity of matrix metalloproteases in human non-small cell lung cancer cell lines.

Growth factors secreted by either host or tumour cells play a major role in tumour cell progression. Besides stimulating cell division, growth factors may also stimulate cell migration and modulate matrix metalloprotease (MMP) production. MMPs are enzymes involved in a variety of physiological and pathological processes including tumour cell invasion and metastasis. We have previously shown that different growth factors regulate the motile behaviour of human lung cancer cell lines. In order to further advance our knowledge of the role the different growth factors play in lung cancer, we investigated their effect on two key enzymes belonging to the MMP family of enzymes, namely MMP-9 and MMP-2. Serum-free cultures of three human non-small cell lung cancer cell lines were exposed to five different growth factors: insulin-like growth factor I (IGF I) and II (IGF II), hepatocyte growth factor (HGF), epidermal growth factor (EGF) and stem cell factor (SCF). The expression of MMP-9 and MMP-2 in growth factor-treated and untreated cell lines was evaluated using gelatine zymography and quantified using computer-assisted image analyses. We found heterogeneous expression and activity of MMP-9 and MMP-2 in all three lung cancer cell lines. The most important finding in our study is that HGF and EGF are capable of stimulating the conversion of MMP-9 from a latent to an active form in human large cell lung cancer cell line U-1810 [corrected]. IGF I, IGF II, HGF and EGF stimulated an enhanced expression and activity of the latent form of MMP-2 and MMP-9. SCF did not enhance MMP activity in any of the cell lines tested. Our previous studies have shown that IGF I, IGF II, HGF, EGF and SCF induce migration of human non-small cell lung cancer cells in the presence of extracellular matrix (ECM) components. In the present study we show that growth factors can also enhance the expression of MMP's in these cells. Taken together these results indicate that certain growth factors may promote invasiveness through their ability to induce not only cell migration, but also by enhancing the expression and activity of matrix degrading MMP-2 and MMP-9.

Carcinoma, Non-Small-Cell Lung↗

PubMedDate not supplied

Expression of hyaluronan synthases and hyaluronan in malignant mesothelioma cells.

BACKGROUND: Hyaluronan is one of the main components of the extracellular matrix. It is synthesized at the cell plasma membrane by specific hyaluronan synthases (HAS). Although a large number of studies have described hyaluronan in pleural effusion from malignant mesothelioma, the source of hyaluronan in malignant mesothelioma has been subject to controversy. MATERIALS AND METHODS: The mRNA expression of all three HAS in malignant mesothelioma cells was studied using RT-PCR. The hyaluronan production in culture medium of malignant mesothelioma cells was also examined using high-performance liquid chromatography (HPLC). RESULTS: We found that 9/10 malignant mesothelioma cell lines and one primary culture of malignant mesothelioma cells expressed HAS-1, while 10/10 malignant mesothelioma cell lines and one primary culture of malignant mesothelioma cells expressed HAS-2 and HAS-3. In addition, we demonstrated hyaluronan in the culture medium of 6 out of 10 malignant mesothelioma cell lines and one primary culture of malignant mesothelioma cells. CONCLUSION: Our results show that malignant mesothelioma cells express all three HAS and synthesize hyaluronan. The expression of HAS isoforms and hyaluronan in malignant mesothelioma cells in cultures and previous observations by other investigators indicate that these cells are, at least in part, responsible for hyaluronan synthesis in vivo.

Cell Line, Tumor↗

PubMedDate not supplied

Chemotaxis and chemokinesis of malignant mesothelioma cells to multiple growth factors.

BACKGROUND: Chemotaxis is defined as directional cell movement of cells towards concentration gradients of solubilized attractants, whereas chemokinesis is defined as random cell movement in the absence of chemoattractant gradients. Since tumor cell motility plays an important role in the process of tumor invasion and metastasis, we investigated these two distinct motile behaviors in highly invasive tumor, malignant mesothelioma. MATERIALS AND METHODS: Chemotaxis and chemokinesis of mesothelioma cells were assayed using Boyden chambers fitted with filters coated with collagen type IV and different growth factors and cytokines were used as chemoattractants. RESULTS: We found that growth factors such as epidermal growth factor, transforming growth factor-alpha, amphiregulin, heparin-binding epidermal growth factor-like growth factor, beta-cellulin, insulin-like growth factor-I, insulin-like growth factor-II and stem cell factor stimulated directional (chemotactic) and/or random (chemokinetic) motility in all mesothelioma cell lines tested, whereas none of acidic fibroblast growth factor, basic fibroblast growth factor, granulocyte-macrophage colony-stimulating factor or interleukin-6 induced migration in the same mesothelioma cells. CONCLUSION: These findings provide evidence that: (i) multiple growth factors can induce chemotaxis and chemokinesis in malignant mesothelioma cell lines, and (ii) may contribute to our understanding of the highly invasive behavior of malignant mesotheliomas in vivo.

Cell Line, Tumor↗