Hyun-Jeong Park

Enhanced IL-18 expression in common skin tumors

Interleukin-18 (IL-18) has been found to have multiple effects upon various cells involved in inflammatory response. Recently we reported that B16 murine melanoma cells are able to produce IL-18, which is involved in the regulation of intracellular reactive oxygen intermediates (ROI) and Fas-ligand expression, indicating that IL-18 plays key role in the tumor activity of melanoma. In this study, we investigated the pattern of IL-18 expression in the human system. IL-18 production was tested by enzyme linked immunosorbent assay (ELISA) assay in various tumor cell lines, including Raji (Burkitts lymphoma), IM-9 (B lymphoblast), Jurkat (acute T cell leukemia), SK-MES-1 (squamous cell carcinoma (SCC) cell line), SK-MEL-2, G-361, DM-4, and DX-3 (melanoma cell lines). ELISA tests showed that IL-18 was highly expressed in malignant skin tumors such as SK-MES-1, SK-MEL-2, G-361, DM-4, and DX-3 cell lines, thus suggesting that IL-18 production may be associated with the malignancy of skin tumors. Here, we report that enhanced IL-18 expression is positively correlated with malignant skin tumors such as SCC and melanoma, suggesting the importance role of IL-18 in malignancy of skin tumors. Taken together, expression of IL-18 by tumor cells in human skin tissue may provide an important clue to understand the pathogenesis of malignant skin tumors.

Does knowledge matter? Intentional medication nonadherence among middle-aged Korean Americans with high blood pressure

Aim: To examine predictors of intentional and unintentional nonadherence to antihypertensive medication regimens and their relationships to blood pressure outcomes. Background: Although poor adherence to medical regimens is a major concern in the care of patients with high blood pressure (HBP), our understanding of the complex behavior related to adherence is limited. Moreover, few studies have been devoted to understanding adherence issues in ethnic minority groups, such as the interplay between cultural beliefs and HBP medication-taking behaviors. Design: A cross-sectional analysis was performed to assess the factors affecting nonadherence to antihypertensive medication regimens. Methods: The data used in this analysis came from an ongoing HBP intervention trial involving middle-aged (40-64 years) Korean Americans with HBP. A total of 445 Korean Americans with HBP was enrolled in the trial at baseline. Of these, 208 participants who were on antihypertensive medication were included in the analysis. Using multivariate logistic regression, we examined theoretically selected variables to assess their relationships to intentional and unintentional nonadherence in this sample. Results: Approximately 53.8% of the subjects endorsed 1 or more types of nonadherent behaviors. After controlling for demographic variables, multivariate analysis revealed that a greater number of side effects from the medication (adjusted odds ratio [OR], 1.19; 95% confidence interval [CI], 1.07 to 1.33) and a lower level of HBP knowledge (adjusted OR, 0.89; 95% CI, 0.79 to 0.99) were significantly associated with intentional nonadherence. Unintentional nonadherence was less strongly associated with the study variables examined in the analysis. Conclusion: Our findings indicate that intentional nonadherence to antihypertensive medication that stems from incomplete knowledge of HBP treatment is prevalent among middle-aged Korean Americans with HBP. The results highlight the strong need for an intervention that focuses on increasing patient knowledge about HBP, including the benefits and side effects of antihypertensive medication. This type of focused intervention may help reduce intentional nonadherence to antihypertensive medications and ultimately result in achieving adequate BP control in this high-risk group.

Interleukin-18 is a critical factor for vascular endothelial growth factor-enhanced migration in human gastric cancer cell lines

Cell migration and angiogenesis are key steps in tumor metastasis. However, the mechanism of migration regulated by vascular endothelial growth factor (VEGF), a potent regulator of angiogenesis, is not completely understood. This study examined the relationship between VEGF and migration, along with the mechanism involved in the VEGF-regulated migration of human gastric cancer cells. The level of cell migration was increased by recombinant human (rh)VEGF-165 in the VEGF receptor-2-expressing SNU-601 cells. Interleukin (IL)-18 is associated with the malignant progression of tumors. Accordingly, this study examined the effect of IL-18 on the migration of cancer cells in order to identify the factors involved in VEGF-enhanced migration. Inhibiting IL-18 markedly reduced the level of VEGF-enhanced migration, and IL-18 increased cell migration directly through filamentous-actin polymerization and tensin downregulation. It was confirmed that rhVEGF-165 increased IL-18 production significantly. An antioxidant and an extracellular signal-regulated kinase (ERK)1/2-specific inhibitor blocked rhVEGF-165-enhanced IL-18 production. Accordingly, rhVEGF-165 increased the generation of region of interest (ROI) and activated the ERK1/2 pathway. These results suggest that rhVEGF-165 enhances IL-18 production via the generation of ROI and ERK1/2 phosphorylation, which results in the increased migration of gastric cancer cells.

Sodium Ascorbate (Vitamin C) Induces Apoptosis in Melanoma Cells via the Down-Regulation of Transferrin Receptor Dependent Iron Uptake

Sodium ascorbate (vitamin C) has a reputation for inconsistent effects upon malignant tumor cells, which vary from growth stimulation to apoptosis induction. Melanoma cells were found to be more susceptible to vitamin C toxicity than any other tumor cells. The present study has shown that sodium ascorbate decreases cellular iron uptake by melanoma cells in a dose‐ and time‐dependent fashion, indicating that intracellular iron levels may be a critical factor in sodium ascorbate‐induced apoptosis. Indeed, sodium ascorbate‐induced apoptosis is enhanced by the iron chelator, desferrioxamine (DFO) while it is inhibited by the iron donor, ferric ammonium citrate (FAC). Moreover, the inhibitory effects of sodium ascorbate on intracellular iron levels are blocked by addition of transferrin, suggesting that transferrin receptor (TfR) dependent pathway of iron uptake may be regulated by sodium ascorbate. Cells exposed to sodium ascorbate demonstrated down‐regulation of TfR expression and this precedes sodium ascorbate‐induced apoptosis. Taken together, sodium ascorbate‐mediated apoptosis appears to be initiated by a reduction of TfR expression, resulting in a down‐regulation of iron uptake followed by an induction of apoptosis. This study demonstrates the specific mechanism of sodium ascorbate‐induced apoptosis and these findings support future clinical trial of sodium ascorbate in the prevention of human melanoma relapse.

L-ascorbic acid (vitamin C) induces the apoptosis of B16 murine melanoma cells via a caspase-8-independent pathway.

Abstractl-Ascorbic acid (vitamin C) has been reported to play a role in the treatment and prevention of cancer. However, its specific mechanistic pathways remain obscure. This study was carried out to identify the sodium ascorbate–induced apoptotic pathway in B16F10 murine melanoma cells. Sodium ascorbate was found to induce the apoptosis of B16F10 murine melanoma in a time- and dose-dependent manner, and this was prevented by pretreatment with N-acetyl-l-cysteine (NAC), a well-known antioxidant. In fact, sodium ascorbate–treated B16F10 melanoma cells showed increased intracellular reactive oxygen species generation (ROS) levels. These results indicate that sodium ascorbate induced apoptosis in B16F10 murine melanoma cells by acting as a prooxidant. We examined the involvement of caspase-8 using a specific caspase-8 inhibitor (z-IETD-fmk) on the sodium ascorbate–induced apoptotic pathway. Cell death was found not to be inhibited by z-IETD-fmk treatment, indicating that sodium ascorbate–induced apoptosis is not mediated by caspase-8. In addition, we detected a reduction in the mitochondrial membrane potential during apoptosis and confirmed cytochrome-c release from mitochondria by immunoblotting. Taken together, it appears that the induction of a prooxidant state by sodium ascorbate and a subsequent reduction in mitochondrial membrane potential are involved in the apoptotic pathway of B16F10 murine melanoma cells, and that this occurs in a caspase-8–independent manner.

The enhanced IL-18 production by UVB irradiation requires ROI and AP-1 signaling in human keratinocyte cell line (HaCaT)

Based on our recent observation that enhanced IL-18 expression positively correlates with malignant skin tumors, such as SCC and melanoma, we examined the possible role of UVB, known to be associated with skin cancer development, in the enhancement of IL-18 production using primary human epidermal keratinocytes and human keratinocyte cell line HaCaT. After cells were exposed to UVB irradiation in vitro, IL-18 production was examined by Northern blot analysis and ELISA, and it was found that IL-18 production is enhanced by UVB irradiation in a dose- and time-dependent manner. In addition, we confirmed that it is functionally active form of IL-18 using the inhibitor of caspase-1. The effect of UVB irradiation was blocked by antioxidant, N-acetyl-L-cysteine (NAC), which suggested the involvement of reactive oxygen intermediates (ROI) in the signal transduction of UVB irradiation-enhanced IL-18 synthesis. We also found that UVB irradiation increased AP-1 binding activity by using EMSA with AP-1-specific oligonucleotide. Furthermore, inhibitors of UVB-induced AP-1 activity, such as PD98059, blocked enhanced IL-18 production, indicating that AP-1 activation is required for UVB-induced IL-18 production. Taken together, our results suggest that UVB irradiation-enhanced IL-18 production is selectively mediated through the generation of ROI and the activation of AP-1.

Parenting style, parenting stress, and children's health-related behaviors.

Objective: Parental guidance is critical to the development of childrens health-related behaviors. The purpose of this study was to look at the relationship between parenting factors, including parenting style and parenting stress, and childrens health-related behaviors. Methods: In this descriptive, correlational study, 284 parents of preschool children were interviewed using the Child Rearing Questionnaire and the Korean Parenting Stress Index-Short Form. Results: Parent distress, authoritative and permissive parenting styles, family income, and mothers education were significantly associated with childrens health-related behaviors. Conclusions: These findings suggest that higher levels of warmth, characteristics of both parenting styles, may be a critical factor in the development of health-related behaviors.

Expression of ADAM33 Is a Novel Regulatory Mechanism in IL-18-Secreted Process in Gastric Cancer

IL-18 has recently been reported to play a critical role in tumor migration, invasion, and metastasis. Because IL-18 has various biological activities after its secretion as an 18 kDa mature form, the regulation of the IL-18 secretion process is an important step in tumor progression. This study investigated the implication of IL-18 in vascular endothelial growth factor (VEGF)-D-regulated migration, along with the role of the IL-18 secretion process. VEGF-D enhanced cell migration, which was then blocked by inhibiting IL-18. VEGF-D increased IL-18 expression and secretion, suggesting that IL-18 is a critical mediator for VEGF-D-enhanced migration. VEGF-D induced a disintegrin and metalloprotease 33 (ADAM33) expression, which has a metalloproteinase domain. VEGF-D-enhanced IL-18 secretion and cell migration were inhibited by ADAM33 knock-down. Moreover, cell proliferation was considerably reduced in ADAM33 small interfering RNA transfectants. In conclusion, ADAM33 has a key role in gastric cancer pathogenesis by up-regulating IL-18 secretion process, resulting in increased cell migration and proliferation.

Vitamin C downregulates interleukin-18 production by increasing reactive oxygen intermediate and mitogen-activated protein kinase signalling in B16F10 murine melanoma cells.

We recently reported that interleukin-18 (IL-18) is highly expressed in malignant skin tumours such as melanomas, and may play a key role in the malignancy of such tumours. This study was designed to investigate the mechanisms of IL-18 regulation by vitamin C in B16F10 murine melanoma cells. Cells were treated with vitamin C, and the expression of IL-18 was measured by reverse transcription-polymerase chain reaction and intracellular flow cytometry analysis. Decreased IL-18 production and a significant reduction in IL-18 mRNA transcript were detected in cells treated with vitamin C. The effect of vitamin C treatment was blocked by the antioxidant N-acetyl-l-cysteine, suggesting that vitamin C affects IL-18 expression by up-regulating intracellular reactive oxygen intermediate (ROI) levels. To investigate whether the mitogen-activated protein kinase (MAPK) signalling pathway is involved in the downregulation of IL-18 production, cells were pretreated with SB203580, an inhibitor of p38 MAPK, prior to the addition of vitamin C. This pretreatment blocked the decrease in IL-18 production. However, vitamin C treatment enhanced the expression of phosphorylated p38 MAPK. Taken together, we conclude that vitamin C increases intracellular ROI levels, and regulates IL-18 production through the MAPK signalling pathway.

Enhancement of cell migration by corticotropin-releasing hormone through ERK1/2 pathway in murine melanoma cell line, B16F10.

Abstract:  Melanoma is a malignant skin cancer that displays a high rate of tumor cell migration and metastasis. This study examined how corticotropin‐releasing hormone (CRH) affects the migration of melanoma cells in order to further understand the relationship between stress and tumor cell migration. The migration assay data showed that CRH treatment increased the level of B16F10 cell migration in a dose‐ and time‐dependent manner. To determine whether the extracellular signal‐regulated protein kinase 1/2 (ERK1/2) signaling pathway is involved in the upregulation of melanoma migration, cells were pretreated with an inhibitor of ERK1/2 (PD098059). The pretreatment of PD098059 blocked the increase in cell migration. Furthermore, CRH induced the phosphorylation of ERK1/2. The maximum activation of ERK1/2 by CRH was observed at 15 min. Taken together, these results suggest that CRH is an important mediator that regulates the migration of melanoma cells in the skin during stress through the ERK1/2 signaling pathway.