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Ki-Beom Suhr

Publications and source records attributed to Ki-Beom Suhr.

8 recordsLinked to original sources
PubMed2005

Involvement of urokinase-type plasminogen activator in sphingosylphosphorylcholine-induced angiogenesis.

Sphingosylphosphorylcholine (SPC) has been shown to accelerate wound healing. As angiogenesis is fundamental to proper wound healing, we examined the effect of SPC on angiogenesis using a well-established rat aortic ring assay. SPC significantly stimulated the sprouting of endothelial cells from rat aortic ring. Recognizing its potential effect on angiogenesis, we further investigated the action of SPC using human umbilical vein endothelial cells (HUVECs) cultured in vitro. SPC significantly accelerated the closure of in vitro wound. In addition, SPC markedly enhanced the chemotactic migration and capillary-like tube formation. Subsequently, we examined whether SPC affected the production of urokinase-type plasminogen activator (uPA), an important regulator of angiogenesis, and found that SPC stimulated the expression of uPA at both the transcriptional and translational levels. Consistent with these results, SPC increased the activity of cell-surface-associated plasminogen activator. Pretreatment with antiuPA antibody significantly diminished both the chemotactic migration and capillary-like tube formation, indicating the potential importance of uPA in SPC-induced angiogenesis. Together, these results suggest that SPC may affect angiogenesis in the wound-healing process via regulation of uPA production.

Animals↗
PubMed2005

Induction of connective tissue growth factor expression by sphingosylphosphorylcholine in cultured human skin fibroblasts.

Sphingosylphosphorylcholine (SPC) is a bioactive sphingolipid metabolite that can enhance wound healing. In an effort to find downstream effectors of SPC, we performed microarray analysis and found that the expression of the gene for connective tissue growth factor (CTGF) was significantly affected in human skin fibroblasts cultured in vitro. Northern blot analysis showed that SPC markedly induced CTGF mRNA expression in a dose- and time-dependent manner. Consistent with this result, Western blot analysis also showed that SPC significantly induced the CTGF production. Pretreatment with cycloheximide did not prevent the CTGF induction by SPC, indicating that SPC stimulates CTGF mRNA expression without the increased synthesis of a regulatory protein. Inhibition by pretreatment with Y27632, but not by PD98059 (a mitogen-activated protein kinase 1/2 inhibitor) and LY294002 (a phosphatidylinositol 3-kinase inhibitor), indicated that rho-kinase pathway was involved in SPC-induced CTGF expression. Together, these results reveal the potential importance of CTGF induction as a downstream event in SPC-induced cellular responses.

Base Sequence↗
PubMed2004

Signaling events during induction of plasminogen activator inhibitor-1 expression by sphingosylphosphorylcholine in cultured human dermal fibroblasts.

Sphingosylphosphorylcholine (SPC) is a bioactive sphingolipid metabolite that can enhance wound healing. In a search for effectors downstream of SPC in the wound-healing process, we found that the expression of the gene for plasminogen activator inhibitor-1 (PAI-1) was significantly affected. ELISA and western blot analyses showed that SPC markedly induced PAI-1 production in human dermal fibroblasts cultured in vitro. Inhibition by pre-treatment with pertussis toxin (PTx), but not by tyrphostin A47 (a receptor tyrosine kinase inhibitor), indicated that PTx-sensitive G proteins were involved in SPC-induced PAI-1 expression. SPC elicited a rapid and transient increase in intracellular calcium levels ([Ca2+]i), measured using laser scanning confocal microscopy, which was partly mediated through PTx-sensitive G proteins. Pre-treatment with thapsigargin, but not with EGTA, abolished SPC-induced PAI-1 expression, indicating the importance of Ca2+ release from internal stores. Phorbol-12-myristate-13-acetate (PMA) induced the expression of PAI-1, and pre-treatment with Ro 31-8220 (a PKC inhibitor) markedly suppressed SPC-induced PAI-1 expression. SPC-induced PAI-1 expression was also significantly suppressed by PD98059 (a specific MAPK kinase 1/2 inhibitor). Consistent with this result, SPC stimulated the phosphorylation of p42/44 extracellular signal-regulated kinase (ERK). Together, these results suggest that SPC induces PAI-1 production through a G protein-coupled calcium increase and downstream kinase signaling events in cultured human dermal fibroblasts.

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PubMed2003

The G protein-coupled receptor GPR4 suppresses ERK activation in a ligand-independent manner.

The lysophospholipids, lysophosphatidic acid, sphingosine-1-phosphate, and sphingosylphosphorylcholine (SPC), are bioactive lipid molecules that regulate diverse biological processes. Although the specific G protein-coupled receptors for lysophosphatidic acid and sphingosine-1-phosphate have been well-characterized, much less is known of the SPC receptors. It has been reported that ovarian cancer G protein-coupled receptor 1 (OGR1) is a high affinity receptor for SPC, and its closely related homologue GPR4 is a high affinity receptor for SPC with low affinity for lysophosphatidylcholine (LPC). However, in a functional assay to examine the specificity of ligand binding, we found that neither SPC nor LPC, or other related lysophospholipids, induced internalization of GPR4 from the plasma membrane. In agreement, these lysolipids also did not induce translocation of beta-arrestin2-GFP from the cytosol to the plasma membrane in GPR4 expressing cells. However, when these cells were cotransfected with G protein-coupled receptor kinase 2, in the absence of added ligands, beta-arrestin2-GFP accumulated in cytoplasmic vesicles, reminiscent of vesicular labeling usually observed after agonist stimulation of GPCRs. In addition, neither SPC nor LPC stimulated the binding of GTPgammaS to membranes prepared from GPR4 expressing cells and did not activate ERK1/2. Surprisingly, enforced expression of GPR4 inhibited activation of ERK1/2 induced by several stimuli, including SPC, sphingosine-1-phosphate, and even EGF. Collectively, our results suggest that SPC and LPC are not the ligands for GPR4 and that this receptor may constitutively inhibit ERK1/2 activation.

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PubMed2002

Sphingosylphosphorylcholine stimulates cellular fibronectin expression through upregulation of IL-6 in cultured human dermal fibroblasts.

Sphingosylphosphorylcholine (SPC) has been reported to stimulate wound healing by its potent mitogenic effect. Fibronectin (FN) is a cell-adhesion protein that plays an important role in cell migration and collagen deposition during wound healing. In order to elucidate further the mechanism involved in the accelerated wound healing stimulated by SPC, we studied the role of SPC in FN production in cultured human dermal fibroblasts. We demonstrated that SPC dose- and time-dependently enhanced the expression of FN in human dermal fibroblast at the protein and mRNA levels. IL-6 is known to stimulate the production of FN in fibroblasts. SPC also markedly induced IL-6 production in cultured human dermal fibroblasts in a dose- and time-dependent manner. We also demonstrated that FN mRNA expression in human dermal fibroblasts was upregulated 4 h after IL-6 treatment. Moreover, pretreatment with neutralizing anti-IL-6 antibodies partially blocked the upregulation of FN mRNA expression induced by SPC in human dermal fibroblasts. These results indicate that SPC may stimulate FN synthesis through IL-6 production in cultured human dermal fibroblasts.

Antibodies↗
PubMed2002

Identification of calcium-induced genes in HaCaT keratinocytes by polymerase chain reaction-based subtractive hybridization.

Suppression subtractive hybridization, a PCR-based method for cDNA subtraction, was used to identify differentially expressed genes in keratinocytes. Differentiation was induced by elevating the calcium level in the cell culture medium. Using HaCaT immortalized keratinocytes cultured in the presence of a high calcium concentration, we isolated 60 clones representing 48 different genes. By reverse Northern analysis, 13 genes were scored as overexpressed in these HaCaT cells. Northern blot analysis was used to confirm differential gene expression. Six genes, keratin 1, plasminogen activator inhibitor type 2 (PAI-2), ferritin H, peroxiredoxin 5 (PRDX5), insulin-like growth factor binding protein-3 (IGFBP-3), and one EST gene, were differentially expressed in HaCaT cells cultured in the presence of a high calcium concentration. Two of these genes, keratin 1 and PAI-2, are differentially expressed during keratinocyte terminal differentiation. IGFBP-3, which has reduced expression during epidermal differentiation, was increased after culture in a high-calcium medium for 2 or 5 days. Overexpression of the ferritin H and PRDX5 genes due to elevated calcium has not been reported in keratinocytes. We demonstrated the expression of IGFBP-3, ferritin H, PRDX5, and one gene of a matching sequence from the EST database during differentiation in primary cultured normal human keratinocytes. The EST gene expressed two transcripts of 1.8 kb and 2.5 kb in HaCaT cells, and the transcripts were confirmed to increase in keratinocytes cultured in a high-calcium medium.

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PubMedDate not supplied

Quantification of the wound healing using polarization-sensitive optical coherence tomography.

We use polarization-sensitive optical coherence tomography (PS-OCT) to monitor the wound healing process in vitro and in vivo, which are affected by various drugs. Five rabbit subjects are used for in vitro studies and another five are used for in vivo studies. The in vitro studies are conducted to compare the PS-OCT images with histopathology. For each subject, three biopsy lesions are created on each ear: one site is not treated (control); the second site is treated with sphingosylphosphorylcholine, which is expected to promote healing; and the last is administered with tetraacetylphytosphingosine, which negatively affects the healing process. Each site is examined with a PS-OCT system at 1, 4, 7, 10, and 14- days after wound generation. The variations of phase retardation values caused by the collagen morphology changes on wound sites are quantified for all cases. Our results suggest that PS-OCT may be a useful tool for visualization of collagen fiber regeneration and for quantification of various drug effects during the wound healing process.

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