Increased serum anti-CYP2E1 IgG autoantibody levels may be involved in the pathogenesis of occupational trichloroethylene hypersensitivity syndrome: a case-control study.

Occupational exposure to trichloroethylene (TCE) causes a systemic skin disorder with hepatitis known as TCE hypersensitivity syndrome (TCE-HS). Human Leukocyte Antigen (HLA)-B*13:01 is its susceptibility factor; however, the immunological pathogenesis of TCE-HS remains unknown. We herein examined the hypothesis that autoantibodies to CYP2E1 are primarily involved in TCE-HS. A case-control study of 80 TCE-HS patients, 186 TCE-tolerant controls (TCE-TC), and 71 TCE-nonexposed controls (TCE-nonEC) was conducted to measure their serum anti-CYP2E1 antibody (IgG) levels. The effects of TCE exposure indices, such as 8-h time-weighted-average (TWA) airborne concentrations, urinary metabolite concentrations, and TCE usage duration; sex; smoking and drinking habits; and alanine aminotransferase (ALT) levels on the antibody levels were also analyzed in the two control groups. There were significant differences in anti-CYP2E1 antibody levels among the three groups: TCE-TC > TCE-HS patients > TCE-nonEC. Antibody levels were not different between HLA-B*13:01 carriers and noncarriers in TCE-HS patients and TCE-TC. The serum CYP2E1 measurement suggested increased immunocomplex levels only in patients with TCE-HS. Multiple regression analysis for the two control groups showed that the antibody levels were significantly higher by the TCE exposure. Women had higher antibody levels than men; however, smoking, drinking, and ALT levels did not affect the anti-CYP2E1 antibody levels. Anti-CYP2E1 antibodies were elevated at concentrations lower than the TWA concentration of 2.5 ppm for TCE exposure. Since HLA-B*13:01 polymorphism was not involved in the autoantibody levels, the possible mechanism underlying the pathogenesis of TCE-HS is that TCE exposure induces anti-CYP2E1 autoantibody production, and HLA-B*13:01 is involved in the development of TCE-HS.

CEBPγ facilitates lamellipodia formation and cancer cell migration through CERS6 upregulation.

Ceramide synthase 6 (CERS6) promotes lung cancer metastasis by stimulating cancer cell migration. To examine the underlying mechanisms, we performed luciferase analysis of the CERS6 promoter region and identified the Y-box as a cis-acting element. As a parallel analysis of database records for 149 non-small-cell lung cancer (NSCLC) cancer patients, we screened for trans-acting factors with an expression level showing a correlation with CERS6 expression. Among the candidates noted, silencing of either CCAAT enhancer-binding protein γ (CEBPγ) or Y-box binding protein 1 (YBX1) reduced the CERS6 expression level. Following knockdown, CEBPγ and YBX1 were found to be independently associated with reductions in ceramide-dependent lamellipodia formation as well as migration activity, while only CEBPγ may have induced CERS6 expression through specific binding to the Y-box. The mRNA expression levels of CERS6, CEBPγ, and YBX1 were positively correlated with adenocarcinoma invasiveness. YBX1 expression was observed in all 20 examined clinical lung cancer specimens, while 6 of those showed a staining pattern similar to that of CERS6. The present findings suggest promotion of lung cancer migration by possible involvement of the transcription factors CEBPγ and YBX1.

Involvement of MCL1, c-myc, and cyclin D2 protein degradation in ponatinib-induced cytotoxicity against T315I(+) Ph+leukemia cells.

T315I mutation found in chronic myelogenous leukemia (CML) and Ph + ALL patients is the most serious one among resistance against BCR/ABL kinase inhibitors including imatinib and is only responsive to ponatinib (PNT). However, the novel strategy is required to reduce life-threatening adverse effects of PNT including ischemic cardiovascular disease. We examined the mechanism of PNT-induced cytotoxicity against a T315I(+) Ph + ALL cell line, TccY/Sr. PNT induced apoptosis (increased sub G1 cells, and cleaved caspase3 and PARP), and suppressed protein expression of MCL1, cyclin D2 and c-myc, which were reversed by a proteasome inhibitor, MG132, suggesting enhanced proteasomal degradation by PNT. Among BCL2 family inhibitors, MCL1 inhibitors (maritoclax and AZD5991) robustly induced cell death, showing the MCL1-dependent survival of TccY/Sr cells. Decreased MCL1 and c-myc expression by PNT was also observed in T315I(+) MEGA2/STIR cells. PNT suppressed PI3K activation followed by AKT inhibition and GSK3 dephosphorylation. PI3K/AKT inhibitors mimicked PNT, suggesting that PI3K/AKT signaling is important for survival of TccY/Sr cells. Moreover, GSK3 inhibitor (SB216763) reduced PNT-induced cytotoxicity and degradation of c-myc and MCL1. AZD5991 exhibited the synergistic action with PNT, anti-cancer drugs and venetoclax (BCL2 inhibitor), suggesting the utility of MCL1 inhibitor alone or in combination as a future clinical option for Ph + leukemia patients.

Myonectin Is an Exercise-Induced Myokine That Protects the Heart From Ischemia-Reperfusion Injury.

RATIONALE: Physical exercise provides benefits for various organ systems, and some of systemic effects of exercise are mediated through modulation of muscle-derived secreted factors, also known as myokines. Myonectin/C1q (complement component 1q)/TNF (tumor necrosis factor)-related protein 15/erythroferrone is a myokine that is upregulated in skeletal muscle and blood by exercise. OBJECTIVE: We investigated the role of myonectin in myocardial ischemic injury. METHODS AND RESULTS: Ischemia-reperfusion in myonectin-knockout mice led to enhancement of myocardial infarct size, cardiac dysfunction, apoptosis, and proinflammatory gene expression compared with wild-type mice. Conversely, transgenic overexpression of myonectin in skeletal muscle reduced myocardial damage after ischemia-reperfusion. Treadmill exercise increased circulating myonectin levels in wild-type mice, and it reduced infarct size after ischemia-reperfusion in wild-type mice, but not in myonectin-knockout mice. Treatment of cultured cardiomyocytes with myonectin protein attenuated hypoxia/reoxygenation-induced apoptosis via S1P (sphingosine-1-phosphate)-dependent activation of cAMP/Akt cascades. Similarly, myonectin suppressed inflammatory response to lipopolysaccharide in cultured macrophages through the S1P/cAMP/Akt-dependent signaling pathway. Moreover, blockade of S1P-dependent pathway reversed myonectin-mediated reduction of myocardial infarct size in mice after ischemia-reperfusion. CONCLUSIONS: These data indicate that myonectin functions as an endurance exercise-induced myokine which ameliorates acute myocardial ischemic injury by suppressing apoptosis and inflammation in the heart, suggesting that myonectin mediates some of the beneficial actions of exercise on cardiovascular health.

Modulation of the sphingolipid rheostat is involved in paclitaxel resistance of the human prostate cancer cell line PC3-PR.

Taxoids are anti-cancer drugs frequently used to treat solid tumors, but they are sometimes ineffective and tumors may become resistant to their action. Here, we examined the involvement of sphingolipid metabolic enzymes in paclitaxel (PTX) resistance using a human prostate cancer cell line, PC3, and its PTX-resistant subline, PC3-PR. PTX (20 nM) suppressed cell proliferation and increased various ceramide species in PC3, but not PC3-PR, cells. PC3-PR contained higher S1P levels than did PC3, regardless of PTX treatment. Western blotting revealed that PC3-PR cells expressed higher levels of sphingosine kinase 1 (SPHK1) and glucosylceramide synthase (GCS) but lower levels of acid sphingomyelinase (ASMase) and neutral sphingomyelinase 2 than did PC3 cells. Inhibition of SPHK1 using siRNA or a pharmacological inhibitor decreased S1P levels in PC3-PR cells and inhibited proliferation in the presence or absence of PTX, suggesting that SPHK1 is at least partially responsible for PTX resistance. Similarly, GCS inhibitors (PDMP and PPMP) increased cellular ceramides and suppressed the proliferation of PC3-PR. However, inhibition of proteasome function or histone deacetylase activity increased SMase and ceramide levels and suppressed PC3-PR proliferation. These results suggest that modulation of metabolic enzyme expression and alteration of the sphingolipid rheostat protects cancer cells against PTX.

Mechanism of paclitaxel resistance in a human prostate cancer cell line, PC3-PR, and its sensitization by cabazitaxel.

Paclitaxel (PTX) is a microtubule-targeting drug widely used for the treatment of a variety of cancers. However, drug resistance can emerge after a series of treatments, and this can seriously affect the patient's prognosis. Here, we analyzed the mechanism of PTX resistance using a human prostate cancer cell line, PC3, and its PTX-resistant subline, PC3-PR. Compared with PC3, PC3-PR exhibited some unique phenotypes that might be associated with PTX resistance, including decreased expression of acetylated α-tubulin and the cell cycle regulator p21, and increased expression of ßIII tubulin, histone deacetylase 6 (HDAC6), and the anti-apoptotic protein Bcl2. The drug exporters MDR1 and MRP1 were not involved in PTX resistance. Although cabazitaxel (CTX), a novel taxoid, has been reported to overcome PTX resistance, its mechanism of action is unknown. We found that treatment of PC3-PR cells with CTX induced expression of acetylated α-tubulin and p21, but not the related regulators p27, p15, and p16 or the Bcl2 family proteins. The pan-HDAC inhibitors trichostatin A and suberanilohydroxamic acid and the HDAC6-specific inhibitor tubacin inhibited PC3-PR proliferation and increased expression of p21 and acetylated α-tubulin in a manner similar to CTX. Our data shed light on the cellular response to PTX and CTX.

Resveratrol-induced transcriptional up-regulation of ASMase (SMPD1) of human leukemia and cancer cells.

Resveratrol (RSV) is a plant-derived phytoalexin present in plants, whose pleiotropic effects for health benefits have been previously reported. Its anti-cancer activity is among the current topics for novel cancer treatment. Here, effects of RSV on cell proliferation and the sphingolipid metabolism of K562, a human leukemia cell line, were analyzed. Some experiments were also performed in HCT116, a human colon cancer cell line. RSV inhibited cell proliferation of both cell lines. Increased cellular ceramide and decreased sphingomyelin and S1P by RSV were observed in RSV-treated K562 cells. Further analysis revealed that acid sphingomyelinase mRNA and enzyme activity levels were increased by RSV. Desipramine, a functional ASMase inhibitor, prevented RSV-induced ceramide increase. RSV increased ATF3, EGR1, EGR3 proteins and phosphorylated c-Jun and FOXO3. However, co-transfection using these transcription factor expression vectors and ASMase promoter reporter vector revealed positive effects of EGR1 and EGR3 but not others. Electrophoresis mobility shift assay (EMSA) and Chromatin immunoprecipitation (ChIP) assay demonstrated the direct binding of EGR1/3 transcription factors with ASMase 5'-promoter. These results indicate that increased EGR1/3 and ASMase expression play an important role in cellular ceramide increase by RSV treatment.

Increased SPHK2 Transcription of Human Colon Cancer Cells in Serum-Depleted Culture: The Involvement of CREB Transcription Factor.

Sphingosine kinases (SPHK) are important to determine cells' fate by producing sphingosine 1-phosphate. Reportedly, exogenous SPHK2 overexpression induces cell cycle arrest or cell death. However, the regulatory mechanism of SPHK2 expression has not been fully elucidated. Here, we analyzed this issue using human colon cancer cell lines under various stress conditions. Serum depletion (FCS(-)) but not hypoxia and glucose depletion increased mRNA, protein and enzyme activity of SPHK2 but not SPHK1. In HCT116 cells mostly used, SPHK2 activity was predominant over SPHK1, and serum depletion increased both nuclear and cytoplasmic SPHK2 activity. Based on previous reports analyzing cellular response after serum depletion, the temporal changes of intracellular signaling molecules and candidate transcription factors for SPHK2 were examined using serum-depleted HCT116 cells, and performed transfection experiments with siRNA or cDNA of candidate transcription factors. Results showed that the rapid and transient JNK activation followed by CREB activation was the major regulator of increased SPHK2 transcription in FCS(-) culture. EMSA and ChIP assay confirmed the direct binding of activated CREB to the CREB binding site of 5' SPHK2 promoter region. Colon cancer cells examined continued to grow in FCS(-) culture, although mildly, while hypoxia and glucose depletion suppressed cell proliferation or induced cell death, suggesting the different role of SPHK2 in different stress conditions. Because of the unique relationship observed after serum depletion, we examined effects of siRNA for SPHK2, and found the role of SPHK2 as a growth or survival factor but not a cell proliferation inhibitor in FCS(-) culture.

Isolation of a hemidesmosome-rich fraction from a human squamous cell carcinoma cell line.

Hemidesmosomes are cell-to-matrix adhesion complexes anchoring keratinocytes to basement membranes. For the first time, we present a method to prepare a fraction from human cultured cells that are highly enriched in hemidesmosomal proteins. Using DJM-1 cells derived from human squamous cell carcinoma, accumulation of hemidesmosomes was observed when these cells were cultured for more than 10 days in a commercial serum-free medium without supplemental calcium. Electron microscopy demonstrated that numerous electron-dense adhesion structures were present along the basal cell membranes of DJM-1 cells cultured under the aforementioned conditions. After removing cellular materials using an ammonia solution, hemidesmosomal proteins and deposited extracellular matrix were collected and separated by electrophoresis. There were eight major polypeptides, which were determined to be plectin, BP230, BP180, integrin α6 and ß4 subunits, and laminin-332 by immunoblotting and mass spectrometry. Therefore, we designated this preparation as a hemidesmosome-rich fraction. This fraction contained laminin-332 exclusively in its unprocessed form, which may account for the promotion of laminin deposition, and minimal amounts of Lutheran blood group protein, a nonhemidesmosomal transmembrane protein. This hemidesmosome-rich fraction would be useful not only for biological research on hemidesmosomes but also for developing a serum test for patients with blistering skin diseases.

Crucial roles of exosomes secreted from ganglioside GD3/GD2-positive glioma cells in enhancement of the malignant phenotypes and signals of GD3/GD2-negative glioma cells.

Neuroectoderm-derived tumors characteristically express gangliosides such as GD3 and GD2. Many studies have reported that gangliosides GD3/GD2 enhance malignant phenotypes of cancers. Recently, we reported that human gliomas expressing GD3/GD2 exhibited enhanced malignant phenotypes. Here, we investigated the function of GD3/GD2 in glioma cells and GD3/GD2-expressing glioma-derived exosomes. As reported previously, transfectant cells of human glioma U251 MG expressing GD3/GD2 showed enhanced cancer phenotypes compared with GD3/GD2-negative controls. When GD3/GD2-negative cells were treated with exosomes secreted from GD3/GD2-positive cells, clearly increased malignant properties were observed. Furthermore, increased phosphorylation of signaling molecules was detected after 5-15 min of exosome treatment, ie, higher tyrosine phosphorylation of platelet-derived growth factor receptor, focal adhesion kinase, and paxillin was found in treated cells than in controls. Phosphorylation of extracellular signal-regulated kinase-1/2 was also enhanced. Consequently, it is suggested that exosomes secreted from GD3/GD2-positive gliomas play important roles in enhancement of the malignant properties of glioma cells, leading to total aggravation of heterogenous cancer tissues, and also in the regulation of tumor microenvironments.

LASP1, CERS6, and Actin Form a Ternary Complex That Promotes Cancer Cell Migration.

CERS6 is associated with metastasis and poor prognosis in non-small cell lung cancer (NSCLC) patients through d18:1/C16:0 ceramide (C16 ceramide)-mediated cell migration, though the detailed mechanism has not been elucidated. In the present study, examinations including co-immunoprecipitation, liquid chromatography, and tandem mass spectrometry analysis were performed to identify a novel binding partner of CERS6. Among the examined candidates, LASP1 was a top-ranked binding partner, with the LIM domain possibly required for direct interaction. In accord with those findings, CERS6 and LASP1 were found to co-localize on lamellipodia in several lung cancer cell lines. Furthermore, silencing of CERS6 and/or LASP1 significantly suppressed cell migration and lamellipodia formation, whereas ectopic addition of C16 ceramide partially rescued those phenotypes. Both LASP1 and CERS6 showed co-immunoprecipitation with actin, with those interactions markedly reduced when the LASP1-CERS6 complex was abolished. Based on these findings, it is proposed that LASP1-CERS6 interaction promotes cancer cell migration.

Proteomic identification of hippocampal proteins vulnerable to oxidative stress in excitotoxin-induced acute neuronal injury.

Excitotoxicity is involved in seizure-induced acute neuronal death, hypoxic-ischemic encephalopathy, and chronic neurodegenerative conditions such as Alzheimer's disease. Although oxidative stress has been implicated in excitotoxicity, the target proteins of oxidative damage during the course of excitotoxic cell death are still unclear. In the present study, we performed 2D-oxyblot analysis and mass spectrometric amino acid sequencing to identify proteins that were vulnerable to oxidative damage in the rat hippocampus during kainic acid (KA)-induced status epilepticus. We first investigated the time course in which oxidative protein damage occurred using immunohistochemistry. Carbonylated proteins, a manifestation of protein oxidation, were detected in hippocampal neurons as early as 3h after KA administration. Immunoreactivity for 8-hydroxy-2'-deoxyguanosine (8-OHdG) was also elevated at the same time point. The increase in oxidative damage to proteins and DNA occurred concomitantly with the early morphological changes in KA-treated rat hippocampus, i.e., changes in chromatin distribution and swelling of rough endoplasmic reticulum and mitochondria, which preceded the appearance of morphological features of neuronal death such as pyknotic nuclei and hypereosinophilic cytoplasm. Proteomic analysis revealed that several hippocampal proteins were consistently carbonylated at this time point, including heat shock 70kDa protein 4, valosin-containing protein, mitochondrial inner membrane protein (mitofilin), α-internexin, and tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein (14-3-3 protein). We propose that oxidative damage to these proteins may be one of the upstream events in the molecular pathway leading to excitotoxic cell death in KA-treated rat hippocampus, and these proteins may be targets of therapeutic intervention for seizure-induced neuronal death.

The combination therapy of targeting both paclitaxel and Dendrophthoe pentandra leaves extract nanoparticles for improvement breast cancer treatment efficacy by reducing TUBB3 and MAP4 expressions.

The aim of this study is to investigate the combination treatments of paclitaxel and chitosan-Dendrophthoe pentandra leaves extract nanoparticles (NPDP) on MCF-7 breast cancer cells. Chitosan-NPDP nanoparticles were characterized by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), and assessed by using immunofluorescence microscopy. MCF-7 cells are cultured and divided into six groups: group 1 was a negative control (without paclitaxel or NPDP); group 2 was treated with paclitaxel alone; groups 3-5 were treated with NPDP (2, 4, and 8 mg/mL, respectively) and group 6 was treated only by 8 mg/mL of chitosan-NPDP nanoparticles. The proliferation and cell cycle were analyzed by flow cytometry and the expression of TUBB3 and MAP4 were assessed by immunofluorescence microscopy. The combinations of paclitaxel-NPDP significantly inhibit proliferation of cells (P<0.001) and it is able to induce G2/M cell cycle arrest (P<0.001). The combination of paclitaxel-NPDP significantly decreases the expressions of TUBB3 (P<0.001) and MAP4 (P<0.001) in MCF-7 cells. These results indicate that the combination of NPDP nanoparticles could reduce the expressions of TUBB3 and MAP4. This research may provide possible sources of new therapy for NPDP.

A redox-linked novel pathway for arsenic-mediated RET tyrosine kinase activation.

We examined the biochemical effects of arsenic on the activities of RET proto-oncogene (c-RET protein tyrosine kinases) and RET oncogene (RET-MEN2A and RET-PTC1 protein tyrosine kinases) products. Arsenic activated c-RET kinase with promotion of disulfide bond-mediated dimerization of c-RET protein. Arsenic further activated RET-MEN2A kinase, which was already 3- to 10-fold augmented by genetic mutation compared with c-RET kinase activity, with promotion of disulfide bond-mediated dimerization of RET-MEN2A protein (superactivation). Arsenic also increased extracellular domain-deleted RET-PTC1 kinase activity with promotion of disulfide bond-mediated dimerization of RET-PTC1 protein. Arsenic increased RET-PTC1 kinase activity with cysteine 365 (C365) replaced by alanine with promotion of dimer formation but not with cysteine 376 (C376) replaced by alanine. Our results suggest that arsenic-mediated regulation of RET kinase activity is dependent on conformational change of RET protein through modulation of a special cysteine sited at the intracellular domain in RET protein (relevant cysteine of C376 in RET-PTC1 protein). Moreover, arsenic enhanced the activity of immunoprecipitated RET protein with increase in thiol-dependent dimer formation. As arsenic (14.2 microM) was detected in the cells cultured with arsenic (100 microM), direct association between arsenic and RET in the cells might modulate dimer formation. Thus, we demonstrated a novel redox-linked mechanism of activation of arsenic-mediated RET proto-oncogene and oncogene products.

Essential roles of CD8+CD122+ regulatory T cells in the maintenance of T cell homeostasis.

Regulation of immune system is of paramount importance to prevent immune attacks against self-components. Mice deficient in the interleukin (IL)-2/IL-15 receptor beta chain, CD122, are model animals of such immune attacks and characteristically have a high number of abnormally activated T cells. Here, we show that the transfer of CD8+CD122+ cells into CD122-deficient neonates totally prevented the development of abnormal T cells. Furthermore, recombination activating gene-2-/- mice that received wild-type mice-derived CD8+CD122- cells died within 10 wk after cell transfer, indicating that normal CD8+CD122- cells become dangerously activated T cells in the absence of CD8+CD122+ T cells. CD8+CD122+ cells could control activated CD8+ or CD4+ T cells both in vivo and in vitro. Our results indicate that the CD8+CD122+ population includes naturally occurring CD8+ regulatory T cells that control potentially dangerous T cells.

Peptides containing the MXXCW motif inhibit oncogenic RET kinase activity with a novel mechanism of action.

REarranged during Transition (RET) is a tyrosine kinase associated with the development of several malignancies. Identification of RET kinase inhibitors promises valuable therapeutic tools for the intervention of RET-driven tumors. Most currently available tyrosine kinase inhibitors target the ATP binding site, but there are several drawbacks of these ATP-competitive drugs. Therefore, there is a need to develop new kinase inhibitors with alternative mechanisms of action. We have previously reported that a conserved cysteine in the MXXCW motif of RET is crucial to the disulfide-bonded dimerization-linked activation of RET kinases. Reagents which bind to this cysteine may inhibit the activity of RET kinases through disulfide-bond mediated dimerization. Here, we examine the potential of MXXCW motif-containing peptides as candidate kinase inhibitors. We demonstrate that MXXCW motif-containing peptides bind to RET in a redox-sensitive manner and block enzymatic activity, causing inhibition of the RET-dependent activity of extracellular signal-regulated kinases and effectively reducing the malignant potential of RET-papillary thyroid carcinoma-1 (PTC)-expressing cells. These motif-containing peptides were also found to be effective against the drug resistant mutant of RET. The inhibition of RET kinase activity by these peptides resulted in suppression of RET-PTC-1-mediated cancer growth. The great potency of these cysteine targeted peptides could indicate promising approaches for novel molecular-targeted therapies for RET-associated cancers.

Oxidized Perilla and Linseed Oils Induce Neuronal Apoptosis by Caspase-Dependent and -Independent Pathways.

Alpha-linolenic acid (ALA), a polyunsaturated fatty acid, is involved in bioregulatory functions. In recent years, the health-promoting effects of vegetable-derived edible oils rich in ALA have attracted attention. ALA has a variety of physiological effects such as anti-arteriosclerotic and antiallergic properties, but is prone to oxidation. Therefore, safety concerns exist with regard to adverse effects on humans induced by its oxides. However, the effects on neuronal cells induced by oxidized ALA-rich oils, such as perilla and linseed oils, have not been fully investigated. This information is very important from the viewpoint of food safety. In this study, we investigated the effects of oxidized perilla and linseed oils, which are rich in ALA, on the toxicity of neuronal SH-SY5Y cells. Perilla and linseed oils were significantly oxidized compared with other edible vegetable oils. These oxidized oils induce neuronal cell death and apoptosis via caspase-dependent and -independent pathways through reactive oxygen species (ROS) generation. Furthermore, they suppressed neurite outgrowth. These results suggest that oxidized perilla and linseed oils have the potential to cause neuronal loss and ROS-mediated apoptosis, and thus may affect the onset and progression of neurodegenerative disorders and other diseases.

Vaticanol C, a phytoalexin, induces apoptosis of leukemia and cancer cells by modulating expression of multiple sphingolipid metabolic enzymes.

Resveratrol (RSV) has recently attracted keen interest because of its pleiotropic effects. It exerts a wide range of health-promoting effects. In addition to health-promoting effects, RSV possesses anti-carcinogenic activity. However, a non-physiological concentration is needed to achieve an anti-cancer effect, and its in vivo bioavailability is low. Therefore, the clinical application of phytochemicals requires alternative candidates that induce the desired effects at a lower concentration and with increased bioavailability. We previously reported a low IC50 of vaticanol C (VTC), an RSV tetramer, among 12 RSV derivatives (Ito T. et al, 2003). However, the precise mechanism involved remains to be determined. Here, we screened an in-house chemical library bearing RSV building blocks ranging from dimers to octamers for cytotoxic effects in several leukemia and cancer cell lines and their anti-cancer drug-resistant sublines. Among the compounds, VTC exhibited the highest cytotoxicity, which was partially inhibited by a caspase 3 inhibitor, Z-VAD-FMK. VTC decreased the expression of sphingosine kinase 1, sphingosine kinase 2 and glucosylceramide synthase by transcriptional or post-transcriptional mechanisms, and increased cellular ceramides/dihydroceramides and decreased sphingosine 1-phosphate (S1P). VTC-induced sphingolipid rheostat modulation (the ratio of ceramide/S1P) is thought to be involved in cellular apoptosis. Indeed, exogenous S1P addition modulated VTC cytotoxicity significantly. A combination of SPHK1, SPHK2, and GCS chemical inhibitors induced sphingolipid rheostat modulation, cell growth suppression, and cytotoxicity similar to that of VTC. These results suggest the involvement of sphingolipid metabolism in VTC-induced cytotoxicity, and indicate VTC is a promising prototype for translational research.

1,4-butanediyl-bismethanethiosulfonate (BMTS) induces apoptosis through reactive oxygen species-mediated mechanism.

Although methane sulfonate compounds are widely used for the protein modification for their selectivity of thiol groups in proteins, their intracellular signaling events have not yet been clearly documented. This study demonstrated the methane sulfonate chemical 1,4-butanediyl-bismethanethiosulfonate (BMTS)-induced cascades of signals that ultimately led to apoptosis of Jurkat cells. BMTS induced apoptosis through fragmentation of DNA, activation of caspase-9 and caspase-3, and downregulation of Bcl-2 protein with reduction of mitochondrial membrane potential. Moreover, BMTS intensely and transiently induced intracellular reactive oxygen species (ROS) production and ROS produced by BMTS was mediated through mitochondria. We also found that a reducing agent dithiothreitol (DTT) and an anti-oxidant N-acetyl cysteine (NAC) inhibited BMTS-mediated caspase-9 and -3 activation, ROS production and induction of Annexin V/propidium iodide double positive cells, suggesting the involvement of ROS in the apoptosis process. Therefore, this study further extends our understanding on the basic mechanism of redox-linked apoptosis induced by sulfhydryl-reactive chemicals.