Activation of both nuclear factor of activated T cells and inhibitor of nuclear factor-kappa B kinase beta-subunit-/nuclear factor-kappa B is critical for cyclooxygenase-2 induction by benzo[a]pyrene in human bronchial epithelial cells

BPDE-DNA adduct formation and alterations of mRNA, protein, and DNA methylation of CYP1A1, GSTP1, and GSTM1 induced by benzo[a]pyrene and the intervention of aspirin in mice

Benzo[a]pyrene (B[a]P), one typical environmental pollutant, the toxicity mechanisms, and potential prevention remain perplexing. Available evidence suggests cytochrome P450 1A1 (CYP1A1) and glutathione S-transferases (GSTs) metabolize B[a]P, resulting in metabolic activation and detoxification of B[a]P. This study aimed to reveal the impact of B[a]P exposure on trans-7,8-diol-anti-9,10-epoxide DNA (BPDE-DNA) adduct formation, level of CYP1A1, glutathione S-transferase pi (GSTP1) and glutathione S-transferase mu1 (GSTM1) mRNA, protein and DNA methylation in mice, and the potential prevention of aspirin (ASP). This study firstly determined the BPDE-DNA adduct formation in an acute toxicity test of a large dose in mice induced by B[a]P, which subsequently detected CYP1A1, GSTP1, and GSTM1 at levels of mRNA, protein, and DNA methylation in the organs of mice in a subacute toxicity test at appropriate doses and the potential prevention of ASP, using the methods of real-time quantitative PCR (QPCR), western blotting, and real-time methylation-specific PCR (MSP), respectively. The results verified that B[a]P induced the formation of BPDE-DNA adduct in all the organs of mice in an acute toxicity test, and the order of concentration of which was lung > kidney > liver > brain. In a subacute toxicity test, following B[a]P treatment, mice showed a dose-dependent slowdown in body weight gain and abnormalities in behavioral and cognitive function and which were alleviated by ASP co-treatment. Compared to the controls, following B[a]P treatment, CYP1A1 was significantly induced in all organs in mice at mRNA level (P < 0.05), was suppressed in the lung and cerebrum of mice at protein level, and inhibited at DNA methylation level in the liver, lung, and cerebrum, whereas GSTP1 and GSTM1 at mRNA, protein, and DNA methylation levels showed organ-specific changes in mice following B[a]P treatment, which was generally alleviated by ASP intervention. In conclusion, B[a]P induced BPDE-DNA adduct formation in all organs in mice and altered the mRNA, protein, and DNA methylation levels in CYP1A1, GSTP1, and GSTM1 in an organ-dependent pattern, which could be related to the organ toxicity and mechanism of B[a]P. ASP intervention may be an effective measure to prevent B[a]P toxicity. The findings provide scientific evidence for further study on the organ toxicity and mechanisms of B[a]P.

Alterations of DNA methylation and mRNA levels of CYP1A1, GSTP1, and GSTM1 in human bronchial epithelial cells induced by benzo[a]pyrene

Benzo[a]pyrene (B[a]P) is a known human carcinogen and plays a major function in the initiation of lung cancer at its first proximity. However, the underlying molecular mechanisms are less well understood. In this study, we investigated the impact of B[a]P treatment on the DNA methylation and mRNA levels of CYP1A1, GSTP1, and GSTM1 in human bronchial epithelial cells (16HBEs), and provide scientific evidence for the mechanism study on the carcinogenesis of B[a]P. We treated 16HBEs with DMSO or concentrations of B[a]P at 1, 2, and 5 mmol/L for 24 h, observed the morphological changes, determined the cell viability, DNA methylation, and mRNA levels of CYP1A1, GSTP1, and GSTM1. Compared to the DMSO controls, B[a]P treatment had significantly increased the neoplastic cell number and cell viability in 16HBEs at all three doses (1, 2, and 5 mmol/L), and had significantly reduced the CYP1A1 and GSTP1 DNA promoter methylation levels. Following B[a]P treatment, the GSTM1 promoter methylation level in 16HBEs was profoundly reduced at low dose group compared to the DMSO controls, yet it was significantly increased at both middle and high dose groups. The mRNA levels of CYP1A1, GSTP1, and GSTM1 were significantly decreased in 16HBEs following B[a]P treatment at all three doses. The findings demonstrate that B[a]P promoted cell proliferation in 16HBEs, which was possibly related to the altered DNA methylations and the inhibited mRNA levels in CYP1A1, GSTP1, and GSTM1.

Particulate Matter and Traffic-Related Exposures in Relation to Breast Cancer Survival

BACKGROUND

Although particulate matter (PM) has not been consistently associated with breast cancer risk, two studies have reported harmful associations for breast cancer survival. We examined PM exposures and breast cancer survival in two U.S.-based prospective cohort studies.

METHODS

The Nurses' Health Study (NHS) and NHSII are cohorts with detailed data on medical history, lifestyle factors, and causes of death. Women with Stage I-III breast cancer (n = 8,936) were followed through June 2014. Residential PM was estimated using spatio-temporal models. We performed Cox regression to estimate hazard ratios (HR) of breast cancer-specific mortality and all-cause mortality for 10 μg/m³ increases in post-diagnosis PM.

RESULTS

There were 1,211 breast cancer-specific deaths. Overall, PM was not associated with breast cancer-specific mortality [PM_2.5: HR, 1.09; 95% confidence interval (CI), 0.87-1.36; PM_2.5-10: HR, 1.03; 95% CI, 0.85-1.24; PM₁₀: HR, 1.05; 95% CI, 0.89-1.24], but was associated with modest increases in all-cause mortality (PM_2.5: HR, 1.12; 95% CI, 0.96-1.30; PM_2.5-10: HR, 1.12; 95% CI, 1.00-1.24; PM₁₀: HR, 1.09; 95% CI, 1.01-1.18). However, among participants with Stage I disease, PM_2.5 was associated with higher breast cancer-specific mortality (HR, 1.64; 95% CI, 1.11-2.43).

CONCLUSIONS

PM was not associated with breast cancer-specific death overall; however, higher PM was associated with all-cause mortality. Higher PM_2.5 was associated with higher breast cancer-specific mortality among patients with Stage I breast cancer even after adjustment.

IMPACT

Studies on ambient PM and breast cancer survival demonstrate that PM_2.5 may have broader health effects than previously recognized and warrants further research on breast tumor progression.

NFATc2 enhances tumor-initiating phenotypes through the NFATc2/SOX2/ALDH axis in lung adenocarcinoma

Tumor-initiating cells (TIC) are dynamic cancer cell subsets that display enhanced tumor functions and resilience to treatment but the mechanism of TIC induction or maintenance in lung cancer is not fully understood. In this study, we show the calcium pathway transcription factor NFATc2 is a novel regulator of lung TIC phenotypes, including tumorspheres, cell motility, tumorigenesis, as well as in vitro and in vivo responses to chemotherapy and targeted therapy. In human lung cancers, high NFATc2 expression predicted poor tumor differentiation, adverse recurrence-free and cancer-specific overall survivals. Mechanistic investigations identified NFATc2 response elements in the 3’ enhancer region of SOX2, and NFATc2/SOX2 coupling upregulates ALDH1A1 by binding to its 5’ enhancer. Through this axis, oxidative stress induced by cancer drug treatment is attenuated, leading to increased resistance in a mutation-independent manner. Targeting this axis provides a novel approach for the long-term treatment of lung cancer through TIC elimination.

DOI:http://dx.doi.org/10.7554/eLife.26733.001

Cancer develops when cells become faulty and start to grow uncontrollably. They eventually form lumps or tumors, which may spread to surrounding tissues or even to other areas in the body. One of the reasons why cancer treatment remains a challenge is that there are over 200 types of cells in the body, and there are a lot of moments in the life cycle of a cell when things could go wrong. Researchers have shown that many cancers, including lung cancer, are not only extremely different from patient to patient, but also display great differences between cancer cells within the same tumor.

Increasing evidence suggest that these differences may be caused by a type of cells called tumor initiating cells, or TICs for short. These TICs behave like stem cells and can renew themselves or mature into different types of cells. They are thought to help cancers grow and spread, and even make them resistant to treatments. Previous research has shown that in many types of cancer, the protein NFATc2 helps cancer cells to grow and spread. Until now, however, it was not known if NFATc2 is also important in TICs in lung cancer.

Using human lung cancer cell lines and animal models, Xiao et al. show that the protein NFATc2 stimulates the stem-cell like behavior of TICs. The results showed that TICs had higher levels of the NFATc2 protein than other lung cancer cells that were not TICs. Tumors with higher levels were also more aggressive. When NFATc2 was removed from the cells, they formed smaller tumors and were more sensitive to drug treatment compared to cancer cells with NFATc2.

Further experiments revealed that NFATc2 helped to increase the levels of a protein called Sox2, which gives cells the ability to renew or develop into different cell types. Together, these two proteins stimulated the production of another protein that was already known to play a crucial role in TIC maintenance.

A better understanding of the mechanisms regulating TICs in lung cancer will help scientists tackle new questions about how this cancer progresses and resists to therapy. In the longer-term, combining classic cancer treatments with new therapeutic strategies targeting NFATc2 could make treatments for lung cancer patients more effective.

DOI:http://dx.doi.org/10.7554/eLife.26733.002

Resolvin D1 down-regulates CYP1A1 and PTGS2 gene in the HUVEC cells treated with benzo(a)pyrene

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) can interact with lipids and their derivatives and have been known to induce atherosclerosis. The aim of this study was to evaluate the impact of Resolvin D1 (RvD1) on inflammatory-state realted proteins and genes in the human primary umbilical vein endothelial HUVEC cells exposed to benzo(a)pyrene (BaP).

METHODS

We analyzed the influence of RvD1 and/or BaP on cyclooxygenase-2 (COX-2), cytosolic prostaglandine E2 synthase (cPGES), glutathione S transferase (GSTM1) and aryl hydrocarbon receptor (AhR) protein expression by Western blot. Additionaly, phospholipase A2 (cPLA2) and cytochrome P450 (CYP1A1) activity, as well as AhR, CYP1A1, phospholipase A2 (PLA2G4A) and prostaglandin synthase 2 (PTGS2) gene expression by qRT-PCR was studied.

RESULTS

RvD1 down-regulates cytochrome P450 (CYP1A1) and prostaglandin synthase 2 (PTGS2) gene expression in HUVEC cells exposed to BaP. Repressesion of COX-2, cPGES and overexpressesion of GSTM1 protein was noted after co-treatment with RvD1 and BaP. After incubation with RvD1 an increase of cPLA2 and a decrease of CYP1A1 activity was observed when compared to BaP treated alone endothelial cells.

CONCLUSIONS

Our data suggests that RvD1 can significantly contributes on vascular function and alleviates the harmful effects caused by BaP, which might potentially aid in the repair of the injured endothelium.

Nuclear factor of activated T-cell isoform expression and regulation in human myometrium

BACKGROUND

During pregnancy, myometrial gene and protein expression is tightly regulated to accommodate fetal growth, promote quiescence and ultimately prepare for the onset of labour. It is proposed that changes in calcium signalling, may contribute to regulating gene expression and that nuclear factor of activated T-cell (NFAT) transcription factors (isoforms c1-c4) may be involved. Currently, there is little information regarding NFAT expression and regulation in myometrium.

METHODS

This study examined NFAT isoform mRNA expression in human myometrial tissue and cells from pregnant women using quantitative PCR. The effects of the Ca(2+) ionophore A23187 and in vitro stretch (25 % elongation, static strain; Flexercell FX-4000 Tension System) on NFAT expression were determined in cultured human myometrial cells.

RESULTS

Human myometrial tissue and cultured cells expressed NFATc1-c4 mRNA. NFATc2 gene expression in cultured cells was increased in response to 6 h stretch (11.5 fold, P < 0.001, n = 6) and calcium ionophore (A23187, 5 μM) treatment (20.6 fold, P < 0.001, n = 6). This response to stretch was significantly reduced (90 %, P < 0.001, n = 10) in the presence of an intracellular calcium chelator, BAPTA-AM (20 μM).

CONCLUSIONS

These data suggest that NFATc2 expression is regulated by intracellular calcium and in vitro stretch, and that the stretch response in human myometrial cells is dependent upon intracellular calcium signalling pathways. Our findings indicate a potentially unique role for NFATc2 in mediating stretch-induced gene expression per se and warrant further exploration in relation to the mechanisms promoting uterine smooth muscle growth in early pregnancy and/or labour.

The effect of benzo[α]pyrene on expression and signaling cross talk of aryl hydrocarbon receptor and NFATc1 in mouse lung tissue

OBJECTIVE

Polycyclic aromatic hydrocarbons (PAHs) are potent environmental pollutants. Benzo[α]pyrene (B[α]P) is the major compound of PAHs that acts by activating aryl hydrocarbon receptor (AhR) in cells. B[α]P is a known carcinogen and an immunotoxicant; however, its role with regard to nuclear factor of activated T cell (NFAT) pathway is unclear. AhR and NFAT signaling pathways have common roles in pathological functions in immunotoxicity and lung cancer. In this study, the effect of AhR activation on expression and signaling cross talk of AhR and NFATc1 pathways in mouse lung tissue has been investigated.

METHODS

Swiss albino mice were randomly allocated to five groups and administered with cyclosporin A (CsA) and B[α]P for seven constitutive days. Animals were then killed, and lung tissues were obtained after washing the whole blood. Paraffin-embedded blocks were prepared, and 5 µm sections were cut for histopathological and immunohistochemical assessments. The results were scored by observer and digitally analyzed using ImageJ software.

RESULTS

Our data showed that CsA administration resulted in a significant reduction of AhR expression. This effect was partly blocked in mice coadministrated with B[α]P and CsA. NFATc1 expression was also reduced in CsA-treated animals. Furthermore, CsA inhibited the pathological effects of B[α]P in mouse lung tissue.

CONCLUSION

AhR expression is dependent on NFATc1 activation, and NFATc1 inhibition remarkably decreases AhR expression. However, it seems that total expression of NFATc1 is not dependent on AhR expression or activation. Moreover, CsA can prevent B[α]P-induced lung tissue damage, and it remarkably decreases NFATc1 expression. The results from this study point toward the molecular interactions of AhR and NFATc1 activation in lung tissue and the benefit of CsA treatment in B[α]P-induced lung damage.

Endotoxin induces proliferation of NSCLC in vitro and in vivo: role of COX-2 and EGFR activation

Lung cancer is frequently complicated by pulmonary infections which may impair prognosis of this disease. Therefore, we investigated the effect of bacterial lipopolysaccharides (LPS) on tumor proliferation in vitro in the non-small cell lung cancer (NSCLC) cell line A549, ex vivo in a tissue culture model using human NSCLC specimens and in vivo in the A549 adenocarcinoma mouse model. LPS induced a time- and dose-dependent increase in proliferation of A549 cells as quantified by MTS activity and cell counting. In parallel, an increased expression of the proliferation marker Ki-67 and cyclooxygenase (COX)-2 was detected both in A549 cells and in ex vivo human NSCLC tissue. Large amounts of COX-2-derived prostaglandin (PG)E(2) were secreted from LPS-stimulated A549 cells. Pharmacological interventions revealed that the proliferative effect of LPS was dependent on CD14 and Toll-like receptor (TLR)4. Moreover, blocking of the epidermal growth factor receptor (EGFR) also decreased LPS-induced proliferation of A549 cells. Inhibition of COX-2 activity in A549 cells severely attenuated both PGE(2) release and proliferation in response to LPS. Synthesis of PGE(2) was also reduced by inhibiting CD14, TLR4 and EGFR in A549 cells. The proliferative effect of LPS on A549 cells could be reproduced in the A549 adenocarcinoma mouse model with enhancement of tumor growth and Ki-67 expression in implanted tumors. In summary, LPS induces proliferation of NSCLC cells in vitro, ex vivo in human NSCLC specimen and in vivo in a mouse model of NSCLC. Pulmonary infection may thus directly induce tumor progression in NSCLC.

Cyclooxygenase-2 (COX-2) mediates arsenite inhibition of UVB-induced cellular apoptosis in mouse epidermal Cl41 cells

Inorganic arsenic is an environmental human carcinogen, and has been shown to act as a co-carcinogen with solar ultraviolet (UV) radiation in mouse skin tumor induction even at low concentrations. However, the precise mechanism of its co-carcinogenic action is largely unknown. Apoptosis plays an essential role as a protective mechanism against neoplastic development in the organism by eliminating genetically damaged cells. Thus, suppression of apoptosis is thought to contribute to carcinogenesis. It is known that cyclooxygenase-2 (COX-2) can promote carcinogenesis by inhibiting cell apoptosis under stress conditions; and our current studies investigated the potential contribution of COX-2 to the inhibitory effect of arsenite in UV-induced cell apoptosis in mouse epidermal Cl41 cells. We found that treatment of cells with low concentration (5 μM) arsenite attenuated cellular apoptosis upon UVB radiation accompanied with a coinductive effect on COX-2 expression and nuclear factor-κB (NFκB) transactivation. Our results also showed that the COX-2 induction by arsenite and UVB depended on an NFκB pathway because COX-2 co-induction could be attenuated in either p65-deficient or p50-deficient cells. Moreover, UVB-induced cell apoptosis could be dramatically reduced by the introduction of exogenous COX-2 expression, whereas the inhibitory effect of arsenite on UVB-induced cell apoptosis could be impaired in COX-2 knockdown C141 cells. Our results indicated that COX-2 mediated the anti-apoptotic effect of arsenite in UVB radiation through an NFκB-dependent pathway. Given the importance of apoptosis evasion during carcinogenesis, we anticipated that COX-2 induction might be at least partially responsible for the co-carcinogenic effect of arsenite on UVB-induced skin carcinogenesis.

Hexavalent chromium Cr(VI) up-regulates COX-2 expression through an NFκB/c-Jun/AP-1-dependent pathway

BACKGROUND

Hexavalent chromium [Cr(VI)] is recognized as a human carcinogen via inhalation. However, the molecular mechanisms by which Cr(VI) causes cancers are not well understood.

OBJECTIVES

We evaluated cyclooxygenase-2 (COX-2) expression and the signaling pathway leading to this induction due to Cr(VI) exposure in cultured cells.

METHODS

We used the luciferase reporter assay and Western blotting to determine COX-2 induction by Cr(VI). We used dominant negative mutant, genetic knockout, gene knockdown, and chromatin immunoprecipitation approaches to elucidate the signaling pathway leading to COX-2 induction.

RESULTS

We found that Cr(VI) exposure induced COX-2 expression in both normal human bronchial epithelial cells and mouse embryonic fibroblasts in a concentration- and time-dependent manner. Deletion of IKKβ [inhibitor of transcription factor NFκB (IκB) kinase β; an upstream kinase responsible for nuclear factor κB (NFκB) activation] or overexpression of TAM67 (a dominant-negative mutant of c-Jun) dramatically inhibited the COX-2 induction due to Cr(VI), suggesting that both NFκB and c-Jun/AP-1 pathways were required for Cr(VI)-induced COX-2 expression. Our results show that p65 and c-Jun are two major components involved in NFκB and AP-1 activation, respectively. Moreover, our studies suggest crosstalk between NFκB and c-Jun/AP-1 pathways in cellular response to Cr(VI) exposure for COX-2 induction.

CONCLUSION

We demonstrate for the first time that Cr(VI) is able to induce COX-2 expression via an NFκB/c-Jun/AP-1-dependent pathway. Our results provide novel insight into the molecular mechanisms linking Cr(VI) exposure to lung inflammation and carcinogenesis.

A cross-talk between NFAT and NF-κB pathways is crucial for nickel-induced COX-2 expression in Beas-2B cells

Cyclooxygenase-2 (COX-2) is a critical enzyme implicated in chronic inflammation-associated cancer development. Our studies have shown that the exposure of Beas-2B cells, a human bronchial epithelial cell line, to lung carcinogenic nickel compounds results in increased COX-2 expression. However, the signaling pathways leading to nickel-induced COX-2 expression are not well understood. In the current study, we found that the exposure of Beas-2B cells to nickel compounds resulted in the activation of both nuclear factor of activated T cell (NFAT) and nuclear factor-κB (NF-κB). The expression of COX-2 induced upon nickel exposure was inhibited by either a NFAT pharmacological inhibitor or the knockdown of NFAT3 by specific siRNA. We further found that the activation of NFAT and NF-κB was dependent on each other. Since our previous studies have shown that NF-κB activation is critical for nickel-induced COX-2 expression in Beas-2B cells exposed to nickel compounds under same experimental condition, we anticipate that there might be a cross-talk between the activation of NFAT and NF-κB for the COX-2 induction due to nickel exposure in Beas-2B cells. Furthermore, we showed that the scavenging of reactive oxygen species (ROS) by introduction of mitochondrial catalase inhibited the activation of both NFAT and NF-κB, and the induction of COX-2 due to nickel exposure. Taken together, our results defining the evidence showing a key role of the cross-talk between NFAT and NF-κB pathways in regulating nickel-induced COX-2 expression, further provide insight into the understanding of the molecular mechanisms linking nickel exposure to its lung carcinogenic effects.

Celecoxib inhibits the growth of gastric cancer cells not expressing COX-2 in vitro

AIM: To investigate whether celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, can induce the apoptosis of human gastric cancer MGC-803 cells not expressing COX-2 and explore potential mechanisms involved.

METHODS: Cell proliferation was measured by methyl thiazolyl tetrazolium (MTT) assay. Cell cycle distribution was measured by flow cytometry. The expression of Bax and Bcl-2 proteins was detected by immunohistochemistry. The secretion of vascular endothelial growth factor (VEGF) protein was detected by enzyme-linked immunosorbant assay (ELISA). The expression of COX-2 and nuclear factor-κB (NF-κB) proteins was examined by Western blot.

RESULTS: The expression of COX-2 protein was not detected in MGC-803 cells. Celecoxib could inhibit the proliferation and induce the apoptosis of MGC-803 cells in a dose- and time-dependent manner. The reduced rates of growth in cells treated with celecoxib at concentrations of 25, 50, 75 and 100 μmol/L for 24 h were 48.4%, 54.9%, 58.69% and 63.80%, respectively. Flow cytometry analysis showed that the apoptotic rate of MGC-803 cells treated with celecoxib was 4%, and a sub-G1 cell peak was present. Celecoxib inhibited the secretion of VEGF protein in MGC-803 cells. With the prolongation of the duration of incubation with celecoxib, the level of secreted VEGF decreased. Celecoxib could also inhibit the secretion of NF-κB protein by inhibiting its expression in a time-dependent manner.

CONCLUSION: Celecoxib inhibits growth and induces apoptosis of MGC-803 cells in a COX-2-independent manner. Celecoxib exerts its antitumor effects possibly by inhibiting the expression of NF-κB protein.

PTGS2-899G>C and prostate cancer risk: a population-based nested case-control study (ProtecT) and a systematic review with meta-analysis

Prostaglandin endoperoxidase synthase 2 is a key regulator of inflammation and may play a role in prostate carcinogenesis. The polymorphism, -899G>C (rs20417), alters a transcription factor-binding site and is associated with a reduced risk of colorectal adenoma. We tested the hypothesis that rs20417 may influence prostate cancer risk, using a large case-control study (n(cases)=1608, n(controls)=3058). We found no evidence that rs20417 alters prostate cancer risk (odds ratio (OR(CC & GC v GG)=1.05, 95% confidence interval (CI)=0.91-1.20). A meta-analysis of three studies also found little evidence that rs20417 alters risk (pooled OR(CC & GC v GG)=1.04, 95% CI=0.93-1.17), making it unlikely that rs20417 contributes in any major way to prostate cancer aetiology.

Modification of cysteine residue in p65 subunit of nuclear factor-kappaB (NF-kappaB) by picroliv suppresses NF-kappaB-regulated gene products and potentiates apoptosis

Picroliv, an iridoid glycoside derived from the plant Picrorhiza kurroa, is used traditionally to treat fever, asthma, hepatitis, and other inflammatory conditions. However, the exact mechanism of its therapeutic action is still unknown. Because nuclear factor-kappaB (NF-kappaB) activation plays a major role in inflammation and carcinogenesis, we postulated that picroliv must interfere with this pathway by inhibiting the activation of NF-kappaB-mediated signal cascade. Electrophoretic mobility shift assay showed that pretreatment with picroliv abrogated tumor necrosis factor (TNF)-induced activation of NF-kappaB. The glycoside also inhibited NF-kappaB activated by carcinogenic and inflammatory agents, such as cigarette smoke condensate, phorbol 12-myristate 13-acetate, okadaic acid, hydrogen peroxide, lipopolysaccharide, and epidermal growth factor. When examined for the mechanism of action, we found that picroliv inhibited activation of IkappaBalpha kinase, leading to inhibition of phosphorylation and degradation of IkappaBalpha. It also inhibited phosphorylation and nuclear translocation of p65. Further studies revealed that picroliv directly inhibits the binding of p65 to DNA, which was reversed by the treatment with reducing agents, suggesting a role for a cysteine residue in interaction with picroliv. Mutation of Cys(38) in p65 to serine abolished this effect of picroliv. NF-kappaB inhibition by picroliv leads to suppression of NF-kappaB-regulated proteins, including those linked with cell survival (inhibitor of apoptosis protein 1, Bcl-2, Bcl-xL, survivin, and TNF receptor-associated factor 2), proliferation (cyclin D1 and cyclooxygenase-2), angiogenesis (vascular endothelial growth factor), and invasion (intercellular adhesion molecule-1 and matrix metalloproteinase-9). Suppression of these proteins enhanced apoptosis induced by TNF. Overall, our results show that picroliv inhibits the NF-kappaB activation pathway, which may explain its anti-inflammatory and anticarcinogenic effects.

Benzo[a]pyrene induces expression of matrix metalloproteinases and cell migration and invasion of vascular smooth muscle cells

Benzo[a]pyrene (B[a]P) has been shown to accelerate atherosclerosis development in animal models. However, the mechanisms that B[a]P induces atherogenesis are unclear. Abnormal migration and invasion of vascular smooth muscle cells (VSMCs) is a major contributor to the development of atherosclerotic lesions. In this article, we demonstrated that B[a]P promoted the migration and invasion of rat VSMCs. B[a]P increased the mRNA levels of matrix metalloproteinase (MMP) 1, 2, 3, and 9. The MMPs inhibitor GM6001 inhibited B[a]P-induced invasion of VSMCs. Among the MMPs mentioned above, MMP-3 had the maximal induction. Mechanistic studies indicate that B[a]P-induced transcriptional activation of MMP-3 is not mediated by AP-1, NF-kappaB. B[a]P-induced expression of MMPs was attenuated by alpha-naphthoflavone, the aryl hydrocarbon receptor antagonist. In addition, alpha-naphthoflavone inhibited B[a]P-induced migration and invasion of VSMCs. These results suggest that the aryl hydrocarbon receptor plays an important role in B[a]P-induced expression of MMPs and migration and invasion of VSMC. Our findings may reveal a novel role of B[a]P in inducing atherogenesis.