[Show abstract][Hide abstract] ABSTRACT: Iron is an important biological catalyst and is critical for DNA synthesis during cell proliferation. Cellular iron uptake
is enhanced in tumor cells to support increased DNA synthesis. Circadian variations in DNA synthesis and proliferation have
been identified in tumor cells, but their relationship with intracellular iron levels is unclear. In this study, we identified
a 24-hour rhythm in iron regulatory protein 2 (IRP2) levels in colon-26 tumors implanted in mice. Our findings suggest that
IRP2 regulates the 24-hour rhythm of transferrin receptor 1 (Tfr1) mRNA expression post-transcriptionally, by binding to RNA
stem-loop structures known as iron-response elements. We also found that Irp2 mRNA transcription is promoted by circadian
clock genes, including brain and muscle Arnt-like 1 (BMAL1) and the circadian locomotor output cycles kaput (CLOCK) heterodimer.
Moreover, growth in colon-26(Δ19) tumors expressing the clock-mutant protein (CLOCKΔ19) was low compared with that in wild-type
colon-26 tumor. The time-dependent variation of cellular iron levels, and the proliferation rate in wild-type colon-26 tumor
was decreased by CLOCKΔ19 expression. Our findings suggest that circadian organization contributes to tumor cell proliferation
by regulating iron metabolism in the tumor.
Preview · Article · Jan 2016 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Chronic kidney disease (CKD) is associated with an increase in serum retinol; however, the underlying mechanisms of this disorder are poorly characterized. Here, we found that the alteration of hepatic metabolism induced the accumulation of serum retinol in 5/6 nephrectomy (5/6Nx) mice. The liver is the major organ responsible for retinol metabolism; accordingly, microarray analysis revealed that the hepatic expression of most CYP genes was changed in 5/6Nx mice. In addition, D-box binding protein (DBP), which controls the expression of several CYP genes, was significantly decreased in these mice. Cyp3a11 and Cyp26a1, encoding key proteins in retinol metabolism, showed the greatest decrease in expression in 5/6Nx mice, a process mediated by the decreased expression of DBP. Furthermore, an increase of plasma transforming growth factor-β1 (TGF-β1) in 5/6Nx mice led to the decreased expression of the Dbp gene. Consistent with these findings, the alterations of retinol metabolism and renal dysfunction in 5/6Nx mice were ameliorated by administration of an anti-TGF-β1 antibody. We also show that the accumulation of serum retinol induced renal apoptosis in 5/6Nx mice fed a normal diet, whereas renal dysfunction was reduced in mice fed a retinol-free diet. These findings indicate that constitutive Dbp expression plays an important role in mediating hepatic dysfunction under CKD. Thus, the aggravation of renal dysfunction in patients with CKD might be prevented by a recovery of hepatic function, potentially through therapies targeting DBP and retinol. .
Preview · Article · Jan 2016 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: The biological activities of cannabidiol (CBD), a major non-psychotropic constituent of the fiber-type cannabis plant, have been examined in detail (e.g., CBD modulation of body weight in mice and rats). However, few studies have investigated the biological activities of cannabidiol-2’,6’-dimethyl ether (CBDD), a dimethyl ether derivative of the parent CBD. We herein focused on the effects of CBDD on body weight changes in mice, and demonstrated that it stimulated body weight gain in apolipoprotein E (ApoE)-deficient BALB/c. KOR/Stm Slc-Apoeshl mice, especially between 10 and 20 weeks of age.
Full-text · Article · Nov 2015 · The Journal of Toxicological Sciences
[Show abstract][Hide abstract] ABSTRACT: Bongkrekic acid (BKA), an antibiotic isolated from Pseudomonas cocovenans, is an inhibitory molecule of adenine nucleotide translocase. Since this translocase is a core component of the mitochondrial permeability transition pore (MPTP) formed by apoptotic stimuli, BKA has been used as a tool to abrogate apoptosis. However, the other biochemical properties of BKA have not yet been resolved. Although the definition of a fatty acid is a carboxylic acid (-COOH) with a long hydrocarbon chain (tail), when focused on the chemical structure of BKA, the molecule was revealed to be a branched unsaturated tricarboxylic acid that resembled the structure of polyunsaturated fatty acids (PUFAs). Peroxisome proliferator-activated receptors (PPARs) consist of a subfamily of three isoforms: α, β, and γ, the ligands of which include PUFAs. Using completely synthesized BKA together with simplified BKA derivatives (purity: > 98%), we herein demonstrated the utility of BKA as a selective activator of the human PPARγ isoform, which may not be associated with the anti-apoptotic nature of BKA. We also discussed the possible usefulness of BKA.
Full-text · Article · Mar 2015 · The Journal of Toxicological Sciences
[Show abstract][Hide abstract] ABSTRACT: We previously identified cannabidiolic acid (CBDA), a major component of the fiber-type cannabis plant, as an inhibitor of MDA-MB-231 human breast cancer cell migration in vitro (Takeda et al., 2012). Although MDA-MB-231 is a widely used human breast cancer cell line in in vitro and in vivo studies, these cells have to be injected into nude mice (immunodeficient animals) in in vivo trials. Thus, we established the murine breast cancer cell line, 4T1E/M3, which is highly metastatic to bone in BALB/c mice (Takahashi et al., 2008, 2009; Sakai et al., 2012); this murine syngeneic tumor model may be useful for identifying molecular targets for therapeutic interventions. Prior to in vivo experiments using the murine tumor model, we herein performed DNA microarray analyses of 4T1E/M3 cells, treated with CBDA for 48 hr at a sub-toxic concentration (25 µM), in order to comprehensively analyze the effects of CBDA on the genes involved in the bone metastasis of breast cancers. The results obtained revealed that the expression of matrix metalloproteinase-9 (MMP-9), transforming growth factor-β (TGF-β) inducible gene H3 (BIGH3), and parathyroid hormone-related protein (PTHrP) was markedly down-regulated by 0.11-fold, 0.22-fold, and 0.15-fold, respectively; these molecules were mutually involved in the bone metastasis of breast cancer cells.
[Show abstract][Hide abstract] ABSTRACT: Sesquiterpene lactones exhibit toxicity in humans and animals by non-selectively interacting with cellular macromolecules. Among the sesquiterpene lactones identified to date, (–)-xanthatin, which was obtained in an extract from Xanthium strumarium (the Cocklebur plant), is reportedly less toxic to animals. Although we have shown that (–)-xanthatin has anti-proliferative effects, coupled with the induction of DNA damage-inducible GADD45γ, on highly aggressive human MDA-MB-231 breast cancer cells, the molecular mechanisms of anti-proliferative activity have not yet been elucidated in detail. Furthermore, evidence for the involvement of DNA damage is currently not sufficient. In the present study, we chemically synthesized pure (–)-xanthatin, and attempted to obtain more concrete evidence for DNA damage caused by (–)-xanthatin, which leads to cell death. The results obtained revealed the marked up-regulation of RhoB, which is up-regulated by DNA damage. We summarized the anti-proliferative effects of (–)-xanthatin in combination with our previous findings.
[Show abstract][Hide abstract] ABSTRACT: We recently reported that 9-tetrahydrocannabinol (9-THC), a major cannabinoid component in Cannabis Sativa (marijuana), significantly stimulated the expression of fatty acid 2-hydroxylase (FA2H) in human breast cancer MDA-MB-231 cells. Peroxisome proliferator-activated receptor (PPAR) was previously implicated in this induction. However, the mechanisms mediating this induction have not been elucidated in detail. We performed a DNA microarray analysis of 9-THC-treated samples and showed the selective up-regulation of the PPAR isoform coupled with the induction of FA2H over the other isoforms ( and ). 9-THC itself had no binding/activation potential to/on PPAR, and palmitic acid (PA), a PPAR ligand, exhibited no stimulatory effects on FA2H in MDA-MB-231 cells; thus, we hypothesized that the levels of PPAR induced were involved in the 9-THC-mediated increase in FA2H. In support of this hypothesis, we herein demonstrated that i) 9-THC activated the basal transcriptional activity of PPAR in a concentration-dependent manner, ii) the concomitant up-regulation of PPAR/FA2H was caused by 9-THC, iii) PA could activate PPAR after the PPAR expression plasmid was introduced, and iv) the 9-THC-induced up-regulation of FA2H was further stimulated by the co-treatment with L-663,536 (a known PPAR inducer). Taken together, these results support the concept that the induced levels of PPAR may be involved in the 9-THC up-regulation of FA2H in MDA-MB-231 cells.
[Show abstract][Hide abstract] ABSTRACT: Metastases are known to be responsible for approximately 90% of breast cancer-related deaths. Cyclooxygenase-2 (COX-2) is involved not only in inflammatory processes, but also in the metastasis of cancer cells; it is expressed in 40% of human invasive breast cancers. To comprehensively analyze the effects of cannabidiolic acid (CBDA), a selective COX-2 inhibitor found in the fiber-type cannabis plant (Takeda et al., 2008), on COX-2 expression and the genes involved in metastasis, we performed a DNA microarray analysis of human breast cancer MDA-MB-231 cells, which are invasive breast cancer cells that express high levels of COX-2, treated with CBDA for 48 hr at 25 µM. The results obtained revealed that COX-2 and Id-1, a positive regulator of breast cancer metastasis, were down-regulated (0.19-fold and 0.52-fold, respectively), while SHARP1 (or BHLHE41), a suppressor of breast cancer metastasis, was up-regulated (1.72-fold) and CHIP (or STUB1) was unaffected (1.03-fold). These changes were confirmed by real-time RT-PCR analyses. Taken together, the results obtained here demonstrated that i) CBDA had dual inhibitory effects on COX-2 through down-regulation and enzyme inhibition, and ii) CBDA may possess the ability to suppress genes that are positively involved in the metastasis of cancer cells in vitro.
No preview · Article · Sep 2014 · The Journal of Toxicological Sciences
[Show abstract][Hide abstract] ABSTRACT: Few studies have examined xanthocidin, a biotic isolated from Streptomyces xanthocidicus in 1966, because its supply is limited. Based on its chemical structure, xanthocidin has the potential to become a lead compound in the production of agrochemicals and anti-cancer drugs; however, it is unstable under both basic and acidic conditions. We recently established the total synthesis of xanthocidin using the FeCl3-mediated Nazarov reaction, and obtained two stable derivatives (#1 and #2). The results of the present study demonstrated that these derivatives exhibited the inhibitory activity of topoisomerase IIα, known as a molecular target for cancer chemotherapy, and this was attributed to the respective exo-methylene ketone group without DNA intercalation. The results obtained also suggest that these derivatives may have value as lead compounds in the synthesis of topoisomerase IIα inhibitors.
No preview · Article · Feb 2014 · Biological & Pharmaceutical Bulletin
[Show abstract][Hide abstract] ABSTRACT: We reported that (-)-xanthatin, a xanthanolide sesquiterpene lactone present in the Cocklebur plant, exhibited potent anti-proliferative effects on human breast cancer cells, in which GADD45γ, a novel tumor suppressor gene, was induced. Mechanistically, topoisomerase IIα (Topo IIα) inhibition by (-)-xanthatin was shown to be the upstream trigger that stimulated the expression of GADD45γ mRNA and concomitantly produced reactive oxygen species (ROS) to maintain this expression. Since the anti-cancer drug etoposide, a selective Topo IIα inhibitor, has also been shown to induce intracellular ROS, (-)-xanthatin may exert its anti-proliferative effects on cancer cells in a similar manner to those of etoposide. In the present study, to generalize its applicability to cancer therapy, we further investigated the biological activities of (-)-xanthatin by comparing its activities to those of the established anti-cancer drug etoposide. After the exposure of breast cancer cells to (-)-xanthatin or etoposide, a prolonged and marked up-regulation in the expression of c-fos, a proapoptotic molecule, was detected together with GADD45γ; and the expression of these molecules was stabilized by ROS and abrogated by the pretreatment with N-acetyl-L-cysteine (NAC), a potent ROS scavenger. (-)-Xanthatin in particular exhibited stronger anti-proliferative potential than that of etoposide, which underlies the marked induction of c-fos/GADD45γ and ROS production.
No preview · Article · Aug 2013 · The Journal of Toxicological Sciences
[Show abstract][Hide abstract] ABSTRACT: Δ(9)-Tetrahydrocannabinol (Δ(9)-THC) has been reported as possessing anti-estrogenic activity, although the mechanisms underlying these effects are poorly delineated. In this study, we used the estrogen receptor α (ERα)-positive human breast cancer cell line, MCF-7, as an experimental model and show that Δ(9)-THC exposures markedly suppress 17β-estradiol (E2)- induced MCF-7 cell proliferation. We demonstrate that these effects result from Δ(9)-THC's ability to inhibit E2-liganded ERα activation. Mechanistically, the data obtained from biochemical analyses revealed that: i) Δ(9)-THC up-regulates ERβ, a repressor of ERα, inhibiting the expression of E2/ERα-regulated genes that promote cell growth, and that ii) Δ(9)-THC induction of ERβ modulates E2/ERα signaling in the absence of direct interaction with the E2 ligand binding site. Therefore, the data presented support the concept that Δ(9)-THC's anti-estrogenic activities are mediated by the ERβ disruption of E2/ERα signaling. αααααααααα
No preview · Article · May 2013 · Chemical Research in Toxicology
[Show abstract][Hide abstract] ABSTRACT: To investigate gene(s) being regulated by ∆(9)-tetrahydrocannabinol (∆(9)-THC), we performed DNA microarray analysis of human breast cancer MDA-MB-231 cells, which are poorly differentiated breast cancer cells, treated with ∆(9)-THC for 48 hr at an IC50 concentration of approximately 25 µM. Among the highly up-regulated genes (> 10-fold) observed, fatty acid 2-hydroxylase (FA2H) was significantly induced (17.8-fold). Although the physiological role of FA2H has not yet been fully understood, FA2H has been shown to modulate cell differentiation. The results of Oil Red O staining after ∆(9)-THC exposure showed the distribution of lipid droplets (a sign of the differentiated phenotype) in cells. Taken together, the results obtained here indicate that FA2H is a novel ∆(9)-THC-regulated gene, and that ∆(9)-THC induces differentiation signal(s) in poorly differentiated MDA-MB-231 cells.
No preview · Article · Mar 2013 · The Journal of Toxicological Sciences
[Show abstract][Hide abstract] ABSTRACT: Previously, we reported that (-)-xanthatin, a naturally occurring xanthanolide present in the Cocklebur plant, exhibits potent anti-proliferative effects on human breast cancer cells, accompanied by an induction of the growth arrest and DNA damage-inducible gene 45γ (GADD45γ), recognized recently as a novel tumor suppressor gene. However, the mechanisms mediating this activation were unknown. Topoisomerase IIα (Topo IIα) inhibition has been reported to produce a cell death response accompanied by an atypical DNA laddering fragmentation profile, similar to that noted previously for (-)-xanthatin. Therefore we hypothesized that (-)-xanthatin's GADD45γ activation was mediated through the Topo IIα pathway. Here, we identify that (-)-xanthatin does function as a catalytic inhibitor of Topo IIα, promoting DNA damage. In addition, reactive oxygen species (ROS) were elevated in cells treated with this agent. Mechanistically, it was determined that the induced levels of GADD45γ mRNA resulting from (-)-xanthatin exposures were stabilized by coordinately produced ROS, and that the consequent induction of GADD45γ mRNA, GADD45γ protein and ROS generation were abrogated by co-treatment with N-acetyl-L-cysteine. Taken together, the data support the concept that Topo IIα inhibition by (-)-xanthatin is a trigger that stimulates expression of DNA damage-inducible GADD45γ mRNA and that concomitantly produced ROS act downstream to further enhance the GADD45γ mRNA/GADD45γ protein induction process, resulting in breast cancer cell death.
[Show abstract][Hide abstract] ABSTRACT: Cannabidiol (CBD), a major non-psychotropic constituent of fiber-type cannabis plant, has been reported to possess diverse biological activities, including anti-proliferative effect on cancer cells. Although CBD is obtained from non-enzymatic decarboxylation of its parent molecule, cannabidiolic acid (CBDA), few studies have investigated whether CBDA itself is biologically active. Results of the current investigation revealed that CBDA inhibits migration of the highly invasive MDA-MB-231 human breast cancer cells, apparently through a mechanism involving inhibition of cAMP-dependent protein kinase A, coupled with an activation of the small GTPase, RhoA. It is established that activation of the RhoA signaling pathway leads to inhibition of the mobility of various cancer cells, including MDA-MB-231 cells. The data presented in this report suggest for the first time that as an active component in the cannabis plant, CBDA offers potential therapeutic modality in the abrogation of cancer cell migration, including aggressive breast cancers.
No preview · Article · Sep 2012 · Toxicology Letters
[Show abstract][Hide abstract] ABSTRACT: A repressor composed of homodimeric subunits, as is often found in bacteria, possesses two effector-binding sites per molecule, enabling sophisticated regulation by the cooperative binding of two effector molecules. Positive cooperativity generates a narrower region of effector concentration for switching, but little is known about the role of negative cooperativity. d-camphor, an inducer for Pseudomonas putida cytochrome P450cam hydroxylase operon (camDCAB), binds to the homodimeric cam repressor (CamR). Here, we report solid evidence that the complex of CamR and an operator DNA is not dissociated by the first binding of d-camphor but, at a higher concentration, is dissociated by the second binding. d-camphor thus binds to the CamR in two steps with negative cooperativity, yielding two distinct dissociation constants of K(d1 ) =( ) 0.064 ± 0.030 and K(d2 ) =( ) 14 ± 0.3 μm, as well as the Hill coefficient of 0.56 ± 0.05 (<1). The first binding guarantees the high specificity of the inducer by the high affinity, although the second binding turns on the gene expression at a 200-fold higher concentration, a more suitable switching point for the catabolism of d-camphor.
[Show abstract][Hide abstract] ABSTRACT: 15-Lipoxygenase (15-LOX) is one of the key enzymes responsible for the formation of oxidized low-density lipoprotein (ox-LDL), a major causal factor for atherosclerosis. Both enzymatic (15-LOX) and non-enzymatic (Cu(2+)) mechanisms have been proposed for the production of ox-LDL. We have recently reported that cannabidiol-2',6'-dimethyl ether (CBDD) is a selective and potent inhibitor of 15-LOX-catalyzed linoleic acid oxygenation (Takeda et al., Drug Metab. Dispos., 37, 1733-1737 (2009)). In the LDL, linoleic acid is present as cholesteryl linoleate, the major fatty acid esterified to cholesterol, and is susceptible to oxidative modification by 15-LOX or Cu(2+). In this investigation, we examined the efficacy of CBDD on i) 15-LOX-catalyzed oxygenation of cholesteryl linoleate, and ii) ox-LDL formation catalyzed by 15-LOX versus Cu(2+)-mediated non-enzymatic generation of this important mediator. The results obtained demonstrate that CBDD is a potent and selective inhibitor of ox-LDL formation generated by the 15-LOX pathway. These studies establish CBDD as both an important experimental tool for characterizing 15-LOX-mediated ox-LDL formation, and as a potentially useful therapeutic agent for treatment of atherosclerosis.
[Show abstract][Hide abstract] ABSTRACT: exo-Methylene lactone group-containing compounds, such as (--)-xanthatin, are present in a large variety of biologically active natural products, including extracts of Xanthium strumarium (Cocklebur). These substances are reported to possess diverse functional activities, exhibiting anti-inflammatory, antimalarial, and anticancer potential. In this study, we synthesized six structurally related xanthanolides containing exo-methylene lactone moieties, including (--)-xanthatin and (+)-8-epi-xanthatin, and examined the effects of these chemically defined substances on the highly aggressive and farnesyltransferase inhibitor (FTI)-resistant MDA-MB-231 cancer cell line. The results obtained demonstrate that (--)-xanthatin was a highly effective inhibitor of MDA-MB-231 cell growth, inducing caspase-independent cell death, and that these effects were independent of FTase inhibition. Further, our results show that among the GADD45 isoforms, GADD45γ was selectively induced by (--)-xanthatin and that GADD45γ-primed JNK and p38 signaling pathways are, at least in part, involved in mediating the growth inhibition and potential anticancer activities of this agent. Given that GADD45γ is becoming increasingly recognized for its tumor suppressor function, the results presented here suggest the novel possibility that (--)-xanthatin may have therapeutic value as a selective inducer of GADD45γ in human cancer cells, in particular in FTI-resistant aggressive breast cancers.
No preview · Article · Jun 2011 · Chemical Research in Toxicology
[Show abstract][Hide abstract] ABSTRACT: 15-Lipoxygenase (15-LOX) is one of the key enzymes responsible for the formation of oxidized low-density lipoprotein, a major causal factor for atherosclerosis. Δ(9)-Tetrahydrocannabinol (Δ(9)-THC), a major component of marijuana, has suggested to suppress atherosclerosis. Although Δ(9)-THC seems to be attractive for the prevention of atherosclerosis, there is no information about whether or not 15-LOX isoform can be inhibited by Δ(9)-THC. In the present study, Δ(9)-THC was found to be a direct inhibitor for 15-LOX with an IC(50) (50% inhibition concentration) value of 2.42 μM. Furthermore, Δ(9)-THC-11-oic acid, a major and nonpsychoactive metabolite of Δ(9) -THC, but not another Δ(9)-THC metabolite 11-OH-Δ(9)-THC (psychoactive), was revealed to inhibit 15-LOX. Taken together, it is suggested that Δ(9) -THC can abrogate atherosclerosis via direct inhibition of 15-LOX, and that Δ(9)-THC-11-oic acid is shown to be an "active metabolite" of Δ(9) -THC in this case.
No preview · Article · Mar 2011 · Journal of Pharmaceutical Sciences
[Show abstract][Hide abstract] ABSTRACT: In clinical practice, glucocorticoids are often used with the aim of modulating the efficacy and toxicity of chemotherapeutic agents. However, how glucocorticoids modulate the pharmacological action of chemotherapeutic agents remains to be clarified. In this study, we generated glucocorticoid receptor (GR)-deficient rat-1 cells to investigate the role of GR in the regulation of cellular sensitivity to irinotecan hydrochloride (CPT-11). Treatment of wild-type rat-1 cells with dexamethasone (DEX) significantly enhanced the cytotoxic effect of CPT-11, whereas the treatment had little effect on the cytotoxicity of CPT-11 in GR-deficient cells. Topoisomerase-I activity in wild-type cells after concomitant treatment with DEX and CPT-11 was significantly lower than that after treatment with CPT-11 alone. DEX treatment also enhanced the inhibitory action of CPT-11 on the phosphatidylinositol 3-kinase-Akt signaling pathway in wild-type cells, accompanied by facilitating caspase-3 activity. These modulatory effects of DEX on the CPT-11-induced cytotoxicity were not observed in GR-deficient cells. Our present findings reveal the underlying mechanism by which GCs enhance the chemotherapeutic effect of CPT-11 and indicate the possibility that the dosage of CPT-11 could be reduced by the combination treatment with GCs, which may attenuate the adverse effect without decreasing anti-tumor activity.
No preview · Article · Mar 2009 · Journal of Pharmacological Sciences
[Show abstract][Hide abstract] ABSTRACT: Altered homeostatic regulation, including the disturbance of circadian rhythms, is often observed in patients undergoing interferon (IFN) therapy. We reported previously that IFN-alpha has the ability to modulate the circadian clock function at the molecular level and that the alteration of clock function could be overcome by changing the dosing schedule. In this study, we investigated the influence of IFN-alpha on the intrinsic biological rhythms in mice by comparing two dosing schedules, continuous administration and repetitive injection. Continuous administration of IFN-alpha to mice decreased the rhythm amplitude of locomotor activity, body temperature, leukocyte counts, and plasma corticosterone levels. The treatment also suppressed the oscillation in the expression of clock genes in the liver. On the other hand, modulation effects were scarcely observed in mice treated with repetitive injection of IFN-alpha. These results indicate that treatment with IFN-alpha does not always modulate the circadian clock function. This notion was also supported by in vitro findings that the inhibitory action of IFN-alpha on the expression of clock genes was dependent on its exposure time to cells. The alteration of clock function induced by IFN-alpha could be avoided by optimizing the dosing schedule.