Jeongwon Sohn

Increased expression of pro-inflammatory cytokines and metalloproteinase-1 by TGF-β1 in synovial fibroblasts from rheumatoid arthritis and normal individuals

Transforming growth factor (TGF)‐β1 is expressed abundantly in the rheumatoid synovium. In this study, the inflammatory effect of TGF‐β1 in rheumatoid arthritis (RA) was investigated using cultured fibroblast‐like synoviocytes (FLS) from RA and osteoarthritis (OA) patients, as well as non‐arthritic individuals. mRNA expressions of IL‐1β, tumour necrosis factor (TNF)‐α, IL‐8, macrophage inflammatory protein (MIP)‐1α and metalloproteinase (MMP)‐1 were increased in RA and OA FLS by TGF‐β1 treatment, but not in non‐arthritic FLS. Enhanced protein expression of IL‐1β, IL‐8 and MMP‐1 was also observed in RA FLS. Moreover, TGF‐β1 showed a synergistic effect in increasing protein expression of IL‐1β and matrix metalloproteinase (MMP)‐1 with TNFα and IL‐1β, respectively. Biological activity of IL‐1 determined by mouse thymocyte proliferation assay was also enhanced by 50% in response to TGF‐β1 in the culture supernatant of RA FLS. DNA binding activities of nuclear factor (NF)‐κB and activator protein (AP)‐1 were shown to increase by TGF‐β1 as well. These results suggest that TGF‐β1 contributes for the progression of inflammation and joint destruction in RA, and this effect is specific for the arthritic synovial fibroblasts.

Glycogen synthase kinase 3β phosphorylates p21WAF1/CIP1 for proteasomal degradation after UV irradiation

ABSTRACT UV irradiation has been reported to induce p21WAF1/CIP1 protein degradation through a ubiquitin-proteasome pathway, but the underlying biochemical mechanism remains to be elucidated. Here, we show that ser-114 phosphorylation of p21 protein by glycogen synthase kinase 3β (GSK-3β) is required for its degradation in response to UV irradiation and that GSK-3β activation is a downstream event in the ATR signaling pathway triggered by UV. UV transiently increased GSK-3β activity, and this increase could be blocked by caffeine or by ATR small interfering RNA, indicating ATR-dependent activation of GSK-3β. ser-114, located within the putative GSK-3β target sequence, was phosphorylated by GSK-3β upon UV exposure. The nonphosphorylatable S114A mutant of p21 was protected from UV-induced destabilization. Degradation of p21 protein by UV irradiation was independent of p53 status and prevented by proteasome inhibitors. In contrast to the previous report, the proteasomal degradation of p21 appeared to be ubiquitination independent. These data show that GSK-3β is activated by UV irradiation through the ATR signaling pathway and phosphorylates p21 at ser-114 for its degradation by the proteasome. To our knowledge, this is the first demonstration of GSK-3β as the missing link between UV-induced ATR activation and p21 degradation.

Prostaglandin E2 augments IL-10 signaling and function.

In inflamed joints of rheumatoid arthritis, PGE2 is highly expressed, and IL-10 and IL-6 are also abundant. PGE2 is a well-known activator of the cAMP signaling pathway, and there is functional cross-talk between cAMP signaling and the Jak-STAT signaling pathway. In this study, we evaluated the modulating effect of PGE2 on STAT signaling and its biological function induced by IL-10 and IL-6, and elucidated its mechanism in THP-1 cells. STAT phosphorylation was determined by Western blot, and gene expression was analyzed using real-time PCR. Pretreatment with PGE2 significantly augmented IL-10-induced STAT3 and STAT1 phosphorylation, as well as suppressors of cytokine signaling 3 (SOCS3) and IL-1R antagonist gene expression. In contrast, PGE2 suppressed IL-6-induced phosphorylation of STAT3 and STAT1. These PGE2-induced modulating effects were largely reversed by actinomycin D. Pretreatment with dibutyryl cAMP augmented IL-10-induced, but did not change IL-6-induced STAT3 phosphorylation. Misoprostol, an EP2/3/4 agonist, and butaprost, an EP2 agonist, augmented IL-10-induced STAT3 phosphorylation and SOCS3 gene expression, but sulprostone, an EP1/3 agonist, had no effect. H89, a protein kinase A inhibitor, and LY294002, a PI3K inhibitor, diminished PGE2-mediated augmentation of IL-10-induced STAT3 phosphorylation. In this study, we found that PGE2 selectively regulates cytokine signaling via increased intracellular cAMP levels and de novo gene expression, and these modulating effects may be mediated through EP2 or EP4 receptors. PGE2 may modulate immune responses by alteration of cytokine signaling in THP-1 cells.

Identification of potential lung cancer biomarkers using an in vitro carcinogenesis model

Lung cancer is one of the deadliest and commonly diagnosed neoplasms. Early diagnosis of this disease is critical for improving clinical outcome and prognosis. Because the early stages of lung cancer often produce no symptoms, it is necessary to identify biomarkers for early detection, prognostic evaluation, and recurrence monitoring of the cancer. To identify potential lung cancer biomarkers, we analyzed the differential protein secretion from transformed bronchial epithelial cells (1198 and 1170-I) as compared to immortalized normal bronchial epithelial cells (BEAS-2B) and non-transformed cells (1799) all of which are derived from BEAS-2B and represent multistage bronchial epithelial carcinogenesis. The proteins recovered from the conditioned media of the cells were separated on two-dimensional gels. There was little difference between the secretome of the BEAS-2B and 1799 cells, whereas the patterns between the transformed 1198 and 1170-I cells and non-transformed 1799 cells were significantly different. Using mass spectrometry and database search, we identified 20 proteins including protein gene product 9.5 (PGP9.5), translationally controlled tumor protein (TCTP), tissue inhibitors of metalloproteinases-2 (TIMP-2), and triosephosphate isomerase (TPI), that were either increased or decreased simultaneously in conditioned media of both 1198 and 1170-I cells. Furthermore, levels of PGP9.5, TCTP, TIMP-2, and TPI were significantly increased not only in the conditioned media of both transformed cell lines when compared to those of BEAS-2B and 1799 cells, but also in plasmas and tissues from lung cancer patients when compared to those in normal controls. We suggest the PGP9.5, TCTP, TIMP-2, and TPI as promising candidates for lung cancer serum biomarkers.

Signaling pathway for 2,3,7,8-tetrachlorodibenzo- p-dioxin-induced TNF-alpha production in differentiated THP-1 human macrophages.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a prototypic halogenated aromatic hydrocarbon (HAH), is known as one of the most potent toxicants. At least a part of its toxic effects appears to be derived from its ability to induce TNF-α production. However, the signaling pathway of TCDD that leads to TNF-α expression has not been elucidated. In this study, we investigated the signaling mechanism of TCDD-induced TNF-α expression in PMA-differentiated THP-1 macrophages. TCDD induced both mRNA and protein expression of TNF-α in a dose- and time-dependent manner. Alpha-Naphthoflavone (NF), an aryl hydrocarbon receptor (AhR) inhibitor, prevented the TCDD-induced expression of TNF-α at both mRNA and protein levels. Genistein, a protein tyrosine kinase (PTK) inhibitor, and PD153035, an EGFR inhibitor, also blocked the increase of TNF-α expression by TCDD, indicating the role of EGFR in TCDD-induced TNF-α expression. On the other hand, PP2, a c-Src specific inhibitor, did not affect TCDD-induced TNF-α expression. EGFR phosphorylation was detected as early as 5 min after TCDD treatment. TCDD-induced EGFR activation was AhR-dependent since co-treatment with α-NF prevented it. ERK was found to be a downstream effector of EGFR activation in the signaling pathway leading to TNF-α production after TCDD stimulation. Activation of ERK was observed from 30 min after TCDD treatment. PD98059, an inhibitor of the MEK-ERK pathway, completely prevented the TNF-α mRNA and protein expression induced by TCDD, whereas inhibitors of JNK and p38 MAPK had no effect. PD153035, an EGFR inhibitor, as well as α-NF significantly reduced ERK phosphorylation, suggesting that ERK activation by TCDD was mediated by both EGFR and AhR. These results indicate that TNF-α production by TCDD in differentiated THP-1 macrophages is AhR-dependent and involves activation of EGFR and ERK, but not c-Src, JNK, nor p38 MAPK. A signaling pathway is proposed where TCDD induces sequential activation of AhR, EGFR and ERK, leading to the increased expression of TNF-α.

Panaxydol induces apoptosis through an increased intracellular calcium level, activation of JNK and p38 MAPK and NADPH oxidase-dependent generation of reactive oxygen species

Panaxydol, a polyacetylenic compound derived from Panax ginseng roots, has been shown to inhibit the growth of cancer cells. In this study, we demonstrated that panaxydol induced apoptosis preferentially in transformed cells with a minimal effect on non-transformed cells. Furthermore, panaxydol was shown to induce apoptosis through an increase in intracellular Ca2+ concentration ([Ca2+]i), activation of JNK and p38 MAPK, and generation of reactive oxygen species (ROS) initially by NADPH oxidase and then by mitochondria. Panaxydol-induced apoptosis was caspase-dependent and occurred through a mitochondrial pathway. ROS generation by NADPH oxidase was critical for panaxydol-induced apoptosis. Mitochondrial ROS production was also required, however, it appeared to be secondary to the ROS generation by NADPH oxidase. Activation of NADPH oxidase was demonstrated by the membrane translocation of regulatory p47phox and p67phox subunits and shown to be necessary for ROS generation by panaxydol treatment. Panaxydol triggered a rapid and sustained increase of [Ca2+]i, which resulted in activation of JNK and p38 MAPK. JNK and p38 MAPK play a key role in activation of NADPH oxidase, since inhibition of their expression or activity abrogated membrane translocation of p47phox and p67phox subunits and ROS generation. In summary, these data indicate that panaxydol induces apoptosis preferentially in cancer cells, and the signaling mechanisms involve a [Ca2+]i increase, JNK and p38 MAPK activation, and ROS generation through NADPH oxidase and mitochondria.

Polymorphisms of the CTLA-4 exon 1 and promoter gene in systemic lupus erythematosus.

The objective of this study was to determine whether the polymorphisms of the CTLA-4 exon 1 (/49) and promoter (7318) are associated with susceptibility to systemic lupus erythematosus (SLE) and its clinical features. Polymerase chain reaction of genomic DNA-restriction fragment length polymorphism was used to determine genotypes of the CTLA-4 exon 1 (/49) and promoter (7318) in 80 SLE patients and 86 healthy control subjects. The genotype distribution of the CTLA-4 exon 1 (/49) differed between SLE patients and controls (w2 = 6.74, 2 degrees of freedom (d.f.), P = 0.03). The CTLA-4 AG genotype occurred more frequently in patients with SLE (46.3% vs 33.7% controls). On the other hand, the CTLA-4 AA genotype as well as the CTLA-4 GG genotype was less frequent among SLE patients than among control subjects (1.3% vs 9.3% and 52.5% vs 57.0%, respectively). The genotype distribution of the CTLA-4 promoter (-318) different between SLE patients and control subjects (CT, TT, CC; genotype 27.5%, 0%, 72.5% vs 16.3%, 4.7%, 79.1% controls respectively, w2 = 6.36 2 d.f., P = 0.04). However, Fishers exact or w2 P-values for each genotypes of the CTLA-4 exon l (+49) and promoter (-318) between SLE and control group < 0.05. Clinically, in the lupus patients there was no significant difference according to the CTLA-4 polymorphism. In conclusion, no correlation was found between CTLA-4 exon 1 (+49) and promoter (-318) polymorphisms and SLE in our study.

Induction of G1 cell cycle arrest and p27KIP1 increase by panaxydol isolated from Panax ginseng

Polyacetylenic compounds of Panax ginseng roots have been shown to inhibit growth of several human malignant tumor cell lines. Panaxydol is known to be one of the cytotoxic polyacetylenic compounds of P. ginseng. In this study, we first showed that panaxydol decreased markedly the proliferation, and to a lesser extent, the number of cells in a human melanoma cell line, SK-MEL-1. Next, the effect of panaxydol on cell cycle progression and its mechanism of action were investigated. Cell cycle analysis revealed that panaxydol inhibited cell cycle progression of a human malignant melanoma cell line, SK-MEL-1, at G(1)-S transition. At the same time, panaxydol increased the protein expression of p27(KIP1) as early as 1 hr after treatment. Cyclin-dependent kinase 2 (Cdk2) activity was decreased in a dose-dependent manner after 24 hr of panaxydol treatment. Protein levels of p21(WAF1), p16(INK4a), p53, pRb (retinoblastoma protein), and E2F-1 were not changed. It was also found that cycloheximide reversed the growth inhibition induced by panaxydol and partially abrogated the increase in p27(KIP1) expression. These results indicate that panaxydol induces G(1) cell cycle arrest by decreasing Cdk2 activity and up-regulating p27(KIP1) protein expression.

Genome-wide expression profiling of 8-chloroadenosine- and 8-chloro-cAMP-treated human neuroblastoma cells using radioactive human cDNA microarray

Previous reports raised question as to whether 8-chloro-cyclic adenosine 3,5-monophosphate (8-Cl-cAMP) is a prodrug for its metabolite, 8-Cl-adenosine which exerts growth inhibition in a broad spectrum of cancer cells. The present study was carried out to clarify overall cellular affects of 8-Cl-cAMP and 8-Cl-adenosine on SK-N-DZ human neuroblastoma cells by ystematically characterizing gene expression using radioactive human cDNA microarray. Microarray was prepared with PCR-amplified cDNA of 2,304 known genes spotted on nylon membranes, employing (33)P-labeled cDNAs of SK-N-DZ cells as a probe. the expression levels of approximately 100 cDNAs, representing about 8% of the total DNA elements on the array, were altered in 8-Cl-adenosine- or 8-Cl-cAMP-treated cells, respectively. The genome-wide expression of the two samples exhibited partial overlaps; different sets of up-regulated genes but the same set of down-regulated genes. 8-Cl-adenosine treatment up- egulated genes involved in differentiation and development (LIM protein, connexin 26, neogenin, neurofilament triplet L protein and p21(WAF1/CIP1)) and immune response such as natural killer cells protein 4, and down-regulated ones involved in proliferation and transformation (transforming growth factor-β, DYRK2, urokinase-type plasminogen activator and proteins involved in transcription and translation) which were in close parallel with those by 8-Cl-cAMP. Our results indicated that the two drugs shared common genomic pathways for the down-regulation of certain genes, but used distinct pathways for the up-regulation of different gene clusters. Based on the findings, we suggest that the anti-cancer activity of 8-Cl-cAMP results at least in part through 8-Cl-adenosine. Thus, the systematic use of DNA arrays can provide insight into the dynamic cellular pathways involved in anticancer activities of chemotherapeutics.

Effect of petroleum ether extract of Panax ginseng roots on proliferation and cell cycle progression of human renal cell carcinoma cells

Panax ginseng roots have long been used as a medicinal herb in oriental countries. We have investigated anti-proliferative effects of lipid soluble Panax ginseng components on human renal cancer cell lines. Petroleum ether extract of Panax ginseng roots (GX-PE) or its partially purified preparation (7:3 GX) was added to cultures of three human renal cell carcinoma (RCC) cell lines, A498, Caki-1, and CURC II. Proliferation of RCC cells was estimated by a [3H]thymidine incorporation assay and cell cycle distribution was analyzed by flow cytometry. GX-PE, 7:3 GX, panaxydol and panaxynol inhibited proliferation of all three RCC cell lines in a dose dependent manner in vitro with an order of potency, 7:3 GX > panaxydol > panaxynol = GX-PE. Additive effect of interleukin 4 was also demonstrated, most prominently in Caki-1 which responded poorly to GX-PE alone. Analysis of cell cycle in CURC II and Caki-1 treated with GX-PE demonstrated increase in G1 phase population and corresponding decrease in S phase population. The present study demonstrated that proliferation of human RCC cell lines were inhibited by lipid soluble components of Panax ginseng roots by blocking cell cycle progression at G1 to S phase transition.