Biomedical subjects

Chuanshu Huang

Publications and source records attributed to Chuanshu Huang.

At least 37 records · Page 2Linked to original sources

PubMed2006

Effects of polycyclic aromatic hydrocarbons (PAHs) on vascular endothelial growth factor induction through phosphatidylinositol 3-kinase/AP-1-dependent, HIF-1alpha-independent pathway.

Previous studies have demonstrated that exposure to polycyclic aromatic hydrocarbons (PAHs) and its derivatives is associated with an increased risk of skin cancers, and the carcinogenic effect of PAHs is thought to involve both tumor initiation and promotion. Whereas PAH tumor initiation is well characterized, the mechanisms involved in the tumor promotion of PAHs remain elusive. In the present study, we investigated the effects of PAHs on vascular endothelial growth factor (VEGF) expression by comparison of its induction between the active metabolite and its parent compound (B[a]PDE versus B[a]P) or between active compound and its relatively inactive analog (5-MCDE versus CDE). We found that exposure of cells to (+/-)-anti-benzo-[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE) or (+/-)-anti-5-methylchrysene-1,2-diol-3,4-epoxide (5-MCDE) led to marked induction of VEGF in Cl41 cells, whereas benzo[a]pyrene (B[a]P) or chrysene-1,2-diol-3,4-epoxide (CDE) did not exhibit significant inductive effects. Exposure of cells to B[a]PDE and 5-MCDE did not induce HIF-1alpha activation, whereas AP-1 was significantly activated. Moreover, overexpression of TAM67 (a dominant-negative mutant c-Jun) dramatically blocked that VEGF induction. Electrophoretic mobility shift assay showed that AP-1 was only able to specifically recognize and bind to its AP-1 potential binding site within -1136 and -1115 of the VEGF promoter region. Site-directed mutation of this AP-1 binding site eliminated the VEGF transcriptional activity induced by B[a]PDE, suggesting that the AP-1 binding site between -1136 and -1115 in the VEGF promoter region is critical for VEGF induction by B[a]PDE. In addition, overexpression of Deltap85 (a dominant-negative mutant PI-3K) impaired B[a]PDE- and 5-MCDE-induced VEGF induction. Considering our previous findings that PI-3K is an upstream mediator for c-Jun/AP-1 activation, we conclude that the VEGF induction by B[a]PDE and 5-MCDE is through PI-3K/AP-1-dependent and HIF-1alpha-independent pathways. These findings may help us to understand the mechanisms involved in PAH carcinogenic effects.

Animals↗

PubMed2006

Black raspberry extracts inhibit benzo(a)pyrene diol-epoxide-induced activator protein 1 activation and VEGF transcription by targeting the phosphotidylinositol 3-kinase/Akt pathway.

Previous studies have shown that freeze-dried black raspberry extract fractions inhibit benzo(a)pyrene [B(a)P]-induced transformation of Syrian hamster embryo cells and benzo(a)pyrene diol-epoxide [B(a)PDE]-induced activator protein-1 (AP-1) activity in mouse epidermal Cl 41 cells. The phosphotidylinositol 3-kinase (PI-3K)/Akt pathway is critical for B(a)PDE-induced AP-1 activation in mouse epidermal Cl 41 cells. In the present study, we determined the potential involvement of PI-3K and its downstream kinases on the inhibition of AP-1 activation by black raspberry fractions, RO-FOO3, RO-FOO4, RO-ME, and RO-DM. In addition, we investigated the effects of these fractions on the expression of the AP-1 target genes, vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS). Pretreatment of Cl 41 cells with fractions RO-F003 and RO-ME reduced activation of AP-1 and the expression of VEGF, but not iNOS. In contrast, fractions RO-F004 and RO-DM had no effect on AP-1 activation or the expression of either VEGF or iNOS. Consistent with inhibition of AP-1 activation, the RO-ME fraction markedly inhibited activation of PI-3K, Akt, and p70 S6 kinase (p70(S6k)). In addition, overexpression of the dominant negative PI-3K mutant delta p85 reduced the induction of VEGF by B(a)PDE. It is likely that the inhibitory effects of fractions RO-FOO3 and RO-ME on B(a)PDE-induced AP-1 activation and VEGF expression are mediated by inhibition of the PI-3K/Akt pathway. In view of the important roles of AP-1 and VEGF in tumor development, one mechanism for the chemopreventive activity of black raspberries may be inhibition of the PI-3K/Akt/AP-1/VEGF pathway.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2006

Inflammation, a key event in cancer development.

Several recent studies have identified nuclear factor-kappaB as a key modulator in driving inflammation to cancers. Besides this transcription factor, essential in regulating inflammation and cancer development, an inflammatory microenvironment inhabiting various inflammatory cells and a network of signaling molecules are also indispensable for the malignant progression of transformed cells, which is attributed to the mutagenic predisposition of persistent infection-fighting agents at sites of chronic inflammation. As a subverted host response to inflammation-induced tumors, the inflammatory cells and regulators may facilitate angiogenesis and promote the growth, invasion, and metastasis of tumor cells. Thus far, research regarding inflammation-associated cancer development has focused on cytokines and chemokines as well as their downstream targets in linking inflammation and cancer. Moreover, other proteins with extensive roles in inflammation and cancer, such as signal transducers and activators of transcription, Nrf2, and nuclear factor of activated T cells, are also proposed to be promising targets for future studies. The elucidation of their specific effects and interactions will accelerate the development of novel therapeutic interventions against cancer development triggered by inflammation.

Animals↗

PubMed2006

Molecular mechanisms involved in chemoprevention of black raspberry extracts: from transcription factors to their target genes.

Berries have attracted attention for their chemopreventive activities in last a few years. Dietary freeze-dried blackberries have been shown to reduce esophagus and colon cancer development induced by chemical carcinogen in rodents. To elucidate molecular mechanisms involved in chemoprevention by berry extracts, we employed mouse epidermal Cl 41 cell line, a well-characterized in vitro model in tumor promotion studies. Pretreatment of Cl 41 cells with methanol-extracted blackberry fraction RO-ME resulted in a dramatical inhibition of B(a)PDE-induced activation of AP-1 and NFkB, and expression of VEGF and COX-2. The inhibitory effects of RO-ME on B(a)PDE-induced activation of AP-1 and NFkappaB appear to be mediated via inhibition of MAPKs and IkappaBalpha phosphorylation, respectively. In view of the important roles of AP-1, NFkappaB, VEGF and COX-2 in tumor promotion/progression, and VEGF and COX-2 are target of AP-1 and NFkappaB, we anticipate that the ability of black raspberries to inhibit tumor development may be mediated by impairing signal transduction pathways leading to activation of AP-1 and NFkappaB, subsequently resulting in down-regulation of VEGF and COX-2 expression. The RO-ME fraction appears to be the major fraction responsible for the inhibitory activity of black raspberries.

Animals↗

PubMed2006

Ionizing radiation synergistic induction of cyclooxygenase-2 with benzo[a]pyrene diol-epoxide through nuclear factor of activated T cells in mouse epidermal Cl 41 cells.

Carcinogenic effects of ionizing radiation and benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE), a major metabolite of benzo[a]pyrene (B[a]P), have been well demonstrated both in vitro and in vivo. Two-stage carcinogenesis results indicate that mouse skin is highly susceptible to both ionizing radiation and benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE), a major metabolite of benzo[a]pyrene (B[a]P). It is believed that signaling pathways leading to the regulation of gene expression play a significant role in the development of skin cancers. The NFAT family of proteins are important transcription factors involved in the regulation of various target genes, such as IL-1 and TNF-alpha, which play key roles in the regulation of inflammation and carcinogenesis. Thus, the effect of ionizing radiation and B[a]PDE on COX-2 induction and NFAT3 activation, and their relationship, was investigated in mouse epidermal Cl 41 cells. We found that B[a]PDE exposure induced a very high level of NFAT activation in mouse epidermal Cl 41 cells. Ionizing radiation exhibited a synergistic effect with B[a]PDE on NFAT activation and COX-2 induction, while ionizing radiation alone had no effect. By stably knocking down NFAT3 protein expression by means of the specific interfering RNA (siRNA) technique, we found that COX-2 induction by B[a]PDE and the synergistic effect of ionizing radiation with B[a]PDE was totally blocked. These results indicate that ionizing radiation acts synergistically with B[a]PDE on COX-2 induction, and the synergism is dependent on the NFAT3 pathway.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2005

Essential roles of PI-3K/Akt/IKKbeta/NFkappaB pathway in cyclin D1 induction by arsenite in JB6 Cl41 cells.

Skin is a major target of carcinogenic trivalent arsenic (arsenite, As3+). It has been thought that cell proliferation is one of the central events involved in the carcinogenic effect of arsenite. Cyclin D1, a nuclear protein playing a pivotal role in cell proliferation and cell cycle transition from G1 to S phases, has been reported to be induced in human fibroblast by arsenite via uncertain molecular mechanisms. In the present study, the potential roles of PI-3K/Akt/IKKbeta/NFkappaB signal pathway in cyclin D1 induction by arsenite were addressed in mouse epidermal Cl41 cells. We found that exposure of Cl41 cells to arsenite was able to induce cell proliferation, activate PI-3K-->Akt/p70(S6k) signal pathway and increase cyclin D1 expression at both transcription and protein levels. Pre-treatment of Cl41 cells with PI-3K inhibitor, wortmannin, significantly inhibited the phosphorylation of Akt and p70(S6k) and thereby dramatically impaired the cyclin D1 induction by arsenite, implicating the importance of the PI-3K signal pathway in the cyclin D1 induction by arsenite. Furthermore, inhibition of PI-3K/Akt by overexpression of Deltap85 or DN-Akt blocked arsenite-induced IKK phosphorylation, IkappaBalpha degradation and cyclin D1 expression, indicating that IKK/NFkappaB is the downstream transducer of arsenite-triggered PI-3K/Akt cascade. Moreover, inhibition of IKKbeta/NFkappaB signal pathway by overexpression of its dominant negative mutant, IKKbeta-KM, also significantly blocked arsenite-induced cyclin D1 expression. Overall, arsenite exposure triggered PI-3K/Akt/IKKbeta/NFkappaB signal cascade which in turn plays essential roles in inducing cyclin D1 expression.

Animals↗

PubMed2005

Cyclin D1 induction through IkappaB kinase beta/nuclear factor-kappaB pathway is responsible for arsenite-induced increased cell cycle G1-S phase transition in human keratinocytes.

Environmental and occupational exposure to arsenite is associated with an increased risk of human cancers, including skin, urinary bladder, and respiratory tract cancers. Although much evidence suggests that alterations in cell cycle machinery are implicated in the carcinogenic effect of arsenite, the molecular mechanisms underlying the cell cycle alterations are largely unknown. In the present study, we observed that exposure of human keratinocyte HaCat cells to arsenite resulted in the promotion of cell cycle progression, especially G(1)-S transition. Further studies found that arsenite exposure was able to induce cyclin D1 expression. The induction of cyclin D1 by arsenite required nuclear factor-kappaB (NF-kappaB) activation, because the inhibition of IkappaB phosphorylation by overexpression of the dominant-negative mutant, IKKbeta-KM, impaired arsenite-induced cyclin D1 expression and G1-S transition. The requirement of IkappaB kinase beta (IKKbeta) for cyclin D1 induction was further confirmed by the findings that arsenite-induced cyclin D1 expression was totally blocked in IKKbeta knockout (IKKbeta(-/-)) mouse embryo fibroblasts. In addition, knockdown of cyclin D1 expression using cyclin D1-specific small interference RNA significantly blocked arsenite-induced cell cycle progression in HaCat cells. Taken together, our results show that arsenite-induced cell cycle from G(1) to S phase transition is through IKKbeta/NF-kappaB/cyclin D1-dependent pathway.

Animals↗

PubMed2005

Involvement of protein kinase C in crystalline silica-induced activation of the MAP kinase and AP-1 pathway.

Crystalline silica has long been well established as a fibrogenic agent, and recent evidence has implicated it as a potential human carcinogen. However, the mechanisms of silica-induced disease development and progression are not well understood. Our previous studies demonstrated that crystalline silica is able to activate activator protein-1 (AP-1) through mitogen-activated protein kinase (MAPK) pathways. The present study investigates the possible involvement of protein kinase C (PKC) in silica-induced activation of the MAPK/AP-1 signal transduction pathway. Treatment of mouse epidermal cells (JB6 cell line) with freshly fractured silica stimulated translocation of PKCalpha and PKCepsilon from the cytosol to the membrane and activated AP-1 transcription activity. Pretreatment of cells with PKC inhibitors, including RO-32-0432, calphostin C, and bisindolylmaleimide I, inhibited silica-induced AP-1 activation and phosphorylation of ERKs and p38 kinase. These inhibitory effects by PKC inhibitors were dose dependent. Furthermore, overexpression of dominant negative mutant (DNM) of PKCalpha or PKCepsilon markedly blocked AP-1 activation as well as phosphorylation of ERKs and p38 kinase induced by freshly fractured silica. These results demonstrate that PKCalpha and PKCepsilon are essential in silica-induced AP-1 activation through the MAP kinase (ERKs and p38 kinases) pathway.

Animals↗

PubMed2005

Overexpression of cyclin D1-CDK4 in silica-induced transformed cells is due to activation of ERKs, JNKs/AP-1 pathway.

Silica has been known to be a factor inducing acute injury and chronic pulmonary fibrosis. Silica has also been listed as a human carcinogen in 1996 by International Agency for Research on Cancer (IARC). However, the molecular mechanisms involved its pathologic effects are not well understood. In these studies, we found that exposure of human embryonic lung fibroblasts (HELF) to crystalline silica could cause increases in activation of extracellular signal-regulated kinases (ERKs), p38K, and c-Jun NH2-terminal amino kinases (JNKs), and HELF transformation. Interestingly, silica-induced transformation of HELF (S-HELF) led to increases in activated levels of ERKs and p46 of JNKs, and decrease in p38K activation, and no effect on activation of p54 of JNKs, as compared with those in parental HELF. Further studies showed that there are differential effects of ERKs, JNKs and p38K, as well as their downstream transcription factor AP-1, in regulation of expression of cyclin D1 and CDK4 and cell cycle alternations induced by silica. Cyclin D1 and CDK4 were increased in S-HELF as compared with those in HELF. Inhibition of ERKs activation by AG126, JNK by SP600125, and AP-1 by curcumin could reduced the induction of cyclin D1 and CDK4. There is no significant difference for cell cycle distribution between groups. These results demonstrate that ERKs and JNKs, but not p38K is responsible for induction of cyclin D1 and CDK4 in S-HELF, suggesting that overexpression of cyclin D1 and CDK4 caused by silica is mediated by ERK, JNK/AP-1signaling pathway.

Blotting, Western↗

PubMed2005

Loss of tumor suppressor p53 decreases PTEN expression and enhances signaling pathways leading to activation of activator protein 1 and nuclear factor kappaB induced by UV radiation.

Transcription factor p53 and phosphatase PTEN are two tumor suppressors that play essential roles in suppression of carcinogenesis. However, the mechanisms by which p53 mediates anticancer activity and the relationship between p53 and PTEN are not well understood. In the present study, we found that pretreatment of mouse epidermal Cl41 cells with pifithrin-alpha, an inhibitor for p53-dependent transcriptional activation, resulted in a marked increase in UV-induced activation of activator protein 1 (AP-1) and nuclear factor kappaB (NF-kappaB). Consistent with activation of AP-1 and NF-kappaB, pifithrin-alpha was also able to enhance the UV-induced phosphorylation of c-Jun-NH2-kinases (JNK) and p38 kinase, whereas it did not show any effect on phosphorylation of extracellular signal-regulated kinases. Furthermore, the UV-induced signal activation, including phosphorylation of JNK, p38 kinase, Akt, and p70S6K, was significantly enhanced in p53-deficient cells (p53-/-), which can be reversed by p53 reconstitution. In addition, knockdown of p53 expression by its small interfering RNA also caused the elevation of AP-1 activation and Akt phosphorylation induced by UV radiation. These results show that p53 has a suppressive activity on the cell signaling pathways leading to activation of AP-1 and NF-kappaB in cell response to UV radiation. More importantly, deficiency of p53 expression resulted in a decrease in PTEN protein expression, suggesting that p53 plays a critical role in the regulation of PTEN expression. In addition, overexpression of wild-type PTEN resulted in inhibition of UV-induced AP-1 activity. Because PTEN is a well-known phosphatase involved in the regulation of phosphatidylinositol 3-kinase (PI-3K)/Akt signaling pathway, taken together with the evidence that PI-3K/Akt plays an important role in the activation of AP-1 and NF-kappaB during tumor development, we anticipate that inhibition of AP-1 and NF-kappaB by tumor suppressor p53 seems to be mediated via PTEN, which may be a novel mechanism involved in anticancer activity of p53 protein.

Animals↗

PubMed2005

Nickel carcinogenesis: epigenetics and hypoxia signaling.

Both water soluble and insoluble nickel compounds have been implicated in the etiology of human lung and nasal cancers. Water insoluble nickel compounds have been shown to enter cells by phagocytosis and are contained in cytoplasmic vacuoles, which are acidified thus accelerating the dissolution of soluble nickel from the particles. Using Newport Green, a dye that fluoresces when ionic nickel is bound, we have shown that following exposure (48-72 h) of human lung (A549) cells to NiS particles, most of the nickel is contained in the nucleus, while cells exposed to soluble NiCl2 exhibit most of the ions localized in the cytoplasm. This effect is consistent with previously published reports showing that short-term exposure of cells to crystalline nickel particles (1-3 days) is able to epigenetically silence target genes placed near heterochromatin, while similar short-term exposure to soluble nickel compounds are not able to induce silencing of genes placed near heterochromatin. However, a 3 week exposure of cells to soluble NiCl2 is also able to induce gene silencing. A similar effect was found in yeast cells where nickel was able to silence the URA-3 gene placed near (1.3 kb) a telomere silencing element, but not when the gene was placed farther away from the silencing element (2.0 kb). In addition to epigenetic effects, nickel compounds activate hypoxia signaling pathways. The mechanism of this effect involves the ability of either soluble or insoluble nickel compounds to block iron uptake leading to cellular iron depletion, directly affect iron containing enzymes, or both. This results in the inhibition of a variety of iron-dependent enzymes, such as aconitase and the HIF proline hydroxylases (PHD1-3). The inhibition of the HIF proline hydroxylases stabilizes the HIF protein and activates hypoxic signaling. Additional studies have shown that nickel and hypoxia decrease histone acetylation and increase the methylation of H3 lysine 9. These events are involved in gene silencing and hypoxia can also cause these effects in human cells. It is hypothesised that the state of hypoxia either by low oxygen tension or as a result of agents that signal hypoxia under normal oxygen tension (iron chelation, nickel and cobalt) results in low levels of acetyl CoA, which is a substrate for histone and other protein acetylation. This effect may in part be responsible for the gene silencing following nickel exposure and during hypoxia.

Carcinogens↗

PubMed2005

The role of epidermal growth factor receptor in ethanol-mediated inhibition of activator protein-1 transactivation.

A potential mechanism underlying ethanol-induced alterations in gene expression is the disruption of transcription factor activity. Growth factor receptors, particularly receptor tyrosine kinases, play an important role in modulating many biological effects of ethanol. We demonstrated here that the expression of epidermal growth factor receptor (EGFR) mediated the effect of ethanol on the activity of transcription factor activator protein-1 (AP-1). Ethanol had little effect on AP-1 activity in the fibroblast cells devoid of EGFR (B82); however, it significantly suppressed AP-1 activity in B82 cells that were stably transfected with either a wild-type EGFR (B82L) or a kinase-deficient receptor (B82M721) in a concentration-dependent manner. EGF activated AP-1 only in B82L cells; the activation was mediated primarily by Akt and ERK. Ethanol inhibited EGF-induced EGFR autophosphorylation, phosphorylation of ERK as well as Akt and its substrate GSK-3beta, and subsequently blocked EGF-stimulated AP-1 activation in B82L cells. On the other hand, ethanol had little effect on EGF-stimulated JNK activation. Phorbol ester 12-O-teradecanoyl-phorbol-13-acetate (TPA) activated AP-1 in B82L and B82M721 cells, but not B82 cells. TPA-induced activation of ERK and PKCdelta was dependent on the expression of EGFR although the intrinsic kinase activity of EGFR was not required. In contrast, TPA-induced phosphorylation of p38 MAPK, JNKs and other PKC isoforms was independent of EGFR. Ethanol selectively inhibited TPA-induced phosphorylation of ERK and PKCdelta, and modestly suppressed TPA-stimulated AP-1 activation in B82L and B82M721 cells. Thus, EGFR plays a critical role in the interaction between ethanol and AP-1.

Animals↗

PubMed2005

Differential requirement of signal pathways for benzo[a]pyrene (B[a]P)-induced nitric oxide synthase (iNOS) in rat esophageal epithelial cells.

Overexpression of inducible nitric oxide synthase (iNOS) has been reported in several human cancers, including esophageal squamous cell carcinoma (SCC). Benzo[a]pyrene (B[a]P), a polycyclic hydrocarbon carcinogen found in tobacco smoke and in the environment, induces cancer in multiple organ sites in animals and may be a causative agent for certain human cancers, such as esophageal cancer. In the present study, the effects of B[a]P on the induction of iNOS and the signaling pathways that lead to the induction were investigated in cultured rat esophageal epithelial (RE-149) cells. Treatment of RE-149 cells with B[a]P led to a marked increase in the expression of iNOS. The induction of iNOS by B[a]P was found to occur through an extracellular signal-regulated protein kinases (ERKs)-dependent pathway, since inhibition of ERKs by either pretreatment of RE-149 cells with PD98059, an inhibitor of ERKs upstream kinase MEK1/2, or overexpression of DN-ERK2, blocked the induction of iNOS by B[a]P. Furthermore, impairing nuclear factor-kappaB (NFkappaB) activation by either NEMO-BDBP, an NFkappaB specific inhibitor, or overexpression of DN-IkappaBalpha or IKK-KM markedly inhibited the expression of B[a]P-induced iNOS, suggesting that the NFkappaB pathway is also required for the induction of iNOS by B[a]P. In addition, treatment of RE-149 cells with either SB202190, a p38 kinase inhibitor, or c-JunN-terminal kinase inhibitor II, resulted in an increased induction of iNOS. Pretreatment of RE-149 cells with wortmannin, a PI-3K inhibitor, or with rapamycin, an mTOR/p70S6K pathway inhibitor, had no effect on the expression of iNOS. These results suggest that B[a]P initiates the signaling pathways leading to the induction of iNOS in cultured rat esophageal epithelial cells. In view of the potential role of iNOS in the development of esophageal SCC in humans, we speculate that the induction of iNOS by B[a]P may be one mechanism by which B[a]P could produce carcinogenic effects in the human esophagus.

Animals↗

PubMed2005

ERKs activation and calcium signaling are both required for VEGF induction by vanadium in mouse epidermal Cl41 cells.

The previous studies have demonstrated that vanadium exposure can cause a variety of biological effects. However, the mechanisms involved in the biological effects caused by vanadium are not well understood. Our previous studies have shown that exposure of mouse epidermal Cl 41 cells to vanadate stimulated the phosphorylation of both ERKs and p38K, and calcium signaling leading NFAT activation. In view of the evidence that ERKs and p38 kinase contribute to VEGF induction, we investigated in the present study the potential roles of ERKs, p38K, and calcium signaling in VEGF induction caused by vanadium exposure. Exposure of Cl 41 cells to vanadium led to VEGF induction in both time- and dose-dependent manners. Pre-treatment of Cl 41 cells with PD98059, an inhibitor of MEK1/2-ERKs pathway, but not SB202190, an inhibitor for p38K pathway, resulted in a dramatic inhibition of VEGF induction by vanadium. More interesting, pre-treatment of Cl 41 cells with intracellular calcium chelator, but not calcium channel blocker, resulted in a dramatic decrease in VEGF induction by vanadium. However, both PI-3K inhibitors and overexpression of Deltap85, a dominant negative PI-3K mutant, resulted in only a marginal decrease in VEGF induction by vanadium. Moreover, mTOR, as a downstream molecule of PI-3K, did not attribute to VEGF induction by vanadium because rapamycin pre-treatment did not show any inhibitory effect on VEGF induction. These results indicate that ERKs and intracellular stored calcium release play a critical role in VEGF induction by vanadium. PI-3K is partially involved in VEGF induction by vanadium, while p38K and mTOR are not involved. Those results will help us to understand the molecular mechanisms involved in vanadium-induced biological effects.

Animals↗

PubMed2005

Essential role of PI-3K, ERKs and calcium signal pathways in nickel-induced VEGF expression.

Exposure to a highly nickel-polluted environment has the potential to cause a variety of adverse health effects, such as the respiratory tract cancers. Since numerous studies have demonstrated that nickel generally has weak mutagenic activity, research focus had turned to cell signalling activation leading to gene modulation and epigenetic changes as a plausible mechanism of carcinogenesis. Previous studies have revealed that nickel compounds can induce the expression of vascular endothelial growth factor (VEGF), which is a key mediator of angiogenesis both in physiological and pathologic conditions. In the present study, we investigated the potential roles of PI-3K, ERKs, p38 kinase and calcium signalling in VEGF induction by nickel in Cl 41 cells. Exposure of Cl 41 cells to nickel compounds led to VEGF induction in both time- and dose-dependent manners. Pre-treatment of Cl 41 cells with PI-3K inhibitor, wortmannin or Ly294002, resulted in a striking inhibition of VEGF induction by nickel compounds, implicating the role of PI-3K in the induction. However, mTOR, one of downstream molecules of PI-3K, may not contribute to the induction because pre-treatment of Cl 41 cells with its inhibitor, rapamycin, did not show obvious decrease in nickel-induced VEGF expression. Furthermore, pre-treatment of Cl 41 cells with MEK1/2-ERKs pathway inhibitor, PD98059, significantly inhibited VEGF induction by both NiCl2 and Ni3S2, whereas p38 kinase inhibitor, SB202190, did not impair the induction. Pre-treatment of Cl 41 cells with intracellular calcium chelator, but not calcium channel blocker, inhibited VEGF induction by nickel. Collectively these data demonstrate that PI-3K, ERKs and cytosolic calcium, but not p38 kinase, play essential roles in VEGF induction by nickel compounds.

Animals↗

PubMed2005

Carcinogenic effect of nickel compounds.

Nickel is a widely distributed metal that is industrially applied in many forms. Accumulated epidemiological evidence confirms that exposures to nickel compounds are associated with increased nasal and lung cancer incidence, both in mostly occupational exposures. Although the molecular mechanisms by which nickel compounds cause cancer are still under intense investigation, the carcinogenic actions of nickel compounds are thought to involve oxidative stress, genomic DNA damage, epigenetic effects, and the regulation of gene expression by activation of certain transcription factors related to corresponding signal transduction pathways. The present review summarizes our current knowledge on the molecular mechanisms of nickel carcinogenesis, with special emphasis on the role of nickel induced reactive oxygen species (ROS) and signal transduction pathways.

Animals↗

PubMed2004

Iron-induced interleukin-6 gene expression: possible mediation through the extracellular signal-regulated kinase and p38 mitogen-activated protein kinase pathways.

Increased iron store in the body may increase the risk of many diseases such as cancer and inflammation. However, the precise pathogenic mechanism of iron has not yet been elucidated. In the present study, the early biological responses of cells to iron treatment were investigated in AP-1 luciferase reporter stably transfected mouse epidermal JB6 cells and primary rat hepatocytes. It was shown that water-soluble iron compounds, such as FeSO4 and Fe2(SO4)3, were more active in inducing AP-1 in JB6 cells than water-insoluble iron compounds, such as Fe2O3 and FeS. Iron stimulated mitogen-activated protein kinase (MAPK) family members of extracellular signal-regulated kinases (ERKs) and p38 MAPK but not c-jun NH2 terminal kinases (JNKs), both in JB6 cells and in primary rat hepatocytes, as determined by the phosphorylation assay. Interestingly, the increase in AP-1 luciferase activity by iron was inhibited by the pretreatment of the cells with PD98059, a specific MEK1 inhibitor, and SB202190, a p38 kinase inhibitor. Levels of interleukin-6 (IL-6), a pro-inflammatory cytokine, were increased in JB6 cells by iron in a dose-dependent manner. The increase in IL-6 and its mRNA by iron was also eliminated by the pretreatment of the cells with PD98059 and SB202190. Since the IL-6 promoter contains an AP-1 binding site, our studies indicate that the iron-induced IL-6 gene expression may be mediated through ERKs and p38 MAPK pathways, possibly one of the important mechanisms for the pathogenesis of iron overload.

Animals↗

PubMed2004

A critical role of PI-3K/Akt/JNKs pathway in benzo[a]pyrene diol-epoxide (B[a]PDE)-induced AP-1 transactivation in mouse epidermal Cl41 cells.

Mouse skin tumorigenicity studies indicate that benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE) contributes to carcinogenesis as both a tumor initiator and promoter. However, the mechanisms that mediate B[a]PDE tumor promotion effects remain unclear. Our results demonstrated that in mouse epidermal Cl41 cells, B[a]PDE treatment resulted in marked activation of AP-1 and its upstream MAPKs, including ERKs, JNKs and p38K. B[a]PDE exposure also led to activation of phosphotidylinositol 3-kinase (PI-3K), Akt and p70 S6 kinase (p70S6k). B[a]PDE-induced AP-1 transactivation was inhibited by pretreatment of cells with PI-3K inhibitors, wortmannin or Ly294002. In contrast, inhibition of p70S6k with rapamycin did not show any inhibitory effects. An overexpression of dominant-negative mutant of PI-3K, Deltap85, impaired B[a]PDE-induced activation of PI-3K, Akt and AP-1 transactivation. Furthermore, an overexpression of dominant-negative Akt mutant, Akt-T308A/S473A, blocked B[a]PDE-induced activation of Akt, AP-1 and JNKs, while it did not affect the activation of p70S6k, ERKs and p38 kinase. These results demonstrated that B[a]PDE was able to induce AP-1 transactivation and this AP-1 induction was specific through PI-3K/Akt/JNKs-dependent and p70S6k-independent pathways. This study also indicated that Akt-T308A/S473A blocks B[a]PDE-induced AP-1 activation specific through impairing JNK pathway. These findings will help us to understand the signal transduction pathways involved in the carcinogenic effects of B[a]PDE.

Animals↗