Fast-track DRESSA: a bioassay for fast, sensitive, and selective detection of halogenated and polycyclic aromatic hydrocarbons

Sensitive detection and monitoring of senescence-associated secretory phenotype by SASP-RAP assay

Senescence-associated secretory phenotype (SASP) is characterized by abundant secretion of various proteins in senescent cells and implicated in tumor progression and inflammatory responses. However, the profile of secreted proteins in SASP is different from cell type to cell type, and currently, universal markers for SASP have not been reported. In the present investigation, we show that SASP-responsive alkaline phosphatase (SASP-RAP) serves as a sensitive, general and convenient marker for SASP. Etoposide-treated cells exhibited a senescent phenotype characterized by senile morphology, positive staining for senescence-associated β-galactosidase, growth arrest and induction of p53 and p21^WAF1/CIP1. In SASP-RAP-transfected cells, exposure to etoposide increased secretion of SASP-RAP time-dependently. The kinetics of secretion was closely correlated with that of activation of the p21^WAF1/CIP1 promoter and the p16^INK4a promoter. The enhanced secretion of SASP-RAP by senescence was also observed in cells treated with other senescence inducers such as trichostatin A, doxorubicin and 4-phenylbutylic acid. The induction of SASP-RAP by senescence was similarly observed in natural replicative senescence. To confirm selectivity of the SASP-RAP response, cells were treated with senescence-related and -unrelated stimuli (IL-1β, LPS, TNF-α and TGF-β), and induction of senescence markers and activity of SASP-RAP were evaluated in parallel. Unlike etoposide, senescence-unrelated stimuli did not induce p53 and p21^WAF1/CIP1, and it was correlated with lack of induction of SASP-RAP. In contrast, senescence-unrelated stimuli up-regulated conventional indicators for SASP, e.g., MMP-3, IL-6 and TIMP, without induction of senescence. SASP-RAP thus serves as a selective, convenient and general marker for detection and monitoring of SASP during cellular senescence.

Lactobacillus bulgaricus OLL1181 activates the aryl hydrocarbon receptor pathway and inhibits colitis

Increasing evidence suggests that the aryl hydrocarbon receptor (AhR) pathway has an important role in the regulation of inflammatory responses. Most recently, we have shown that the activation of the AhR pathway by a potent AhR agonist inhibits the development of dextran sodium sulfate (DSS)-induced colitis, a model of human ulcerative colitis, by the induction of prostaglandin E2 (PGE2) in the large intestine. Because several strains of probiotic lactic acid bacteria have been reported to inhibit DSS-induced colitis by unidentified mechanisms, we hypothesized that particular strains of lactic acid bacterium might have the potential to activate the AhR pathway, thereby inhibiting DSS-induced colitis. This study investigated whether there are specific lactic acid bacterial strains that can activate the AhR pathway, and if so, whether this AhR-activating potential is associated with suppression of DSS-induced colitis. By using AhR signaling reporter cells, we found that Lactobacillus bulgaricus OLL1181 had the potential to activate the AhR pathway. OLL1181 also induced the mRNA expression of cytochrome P450 family 1A1 (CYP1A1), a target gene of the AhR pathway, in human colon cells, which was inhibited by the addition of an AhR antagonist, α-naphthoflavon (αNF). In addition, mice treated orally with OLL1181 showed an increase in CYP1A1 mRNA expression in the large intestine and amelioration of DSS-induced colitis. Thus, OLL1181 can induce activation of the intestinal AhR pathway and inhibit DSS-induced colitis in mice. This strain of lactic acid bacterium has therefore the potential to activate the AhR pathway, which may be able to suppress colitis.

Dual suppression of adipogenesis by cigarette smoke through activation of the aryl hydrocarbon receptor and induction of endoplasmic reticulum stress

Cigarette smoking decreases body weight, whereas molecular mechanisms underlying this phenomenon have not been elucidated. In this report, we investigated regulation of adipogenesis by cigarette smoke and involvement of aryl hydrocarbon receptor (AhR) and endoplasmic reticulum (ER) stress. We found that cigarette smoke extract (CSE) inhibited differentiation of preadipocytes into adipocytes dose dependently. It was associated with a decrease in lipid accumulation, blunted expression of adipocyte markers (adiponectin, PPAR-gamma, and C/EBPalpha), and sustained expression of a preadipocyte marker MCP-1. CSE markedly induced activation of AhR, and AhR agonists (2,3,7,8-tetrachlorodibenzo-p-dioxin, benzo[a]pyrene and 3-methylcholanthrene) reproduced the inhibitory effect of CSE on adipocyte differentiation. Furthermore, knockout of the AhR gene or blockade of AhR by a dominant-negative mutant attenuated the suppressive effects of CSE on adipocyte differentiation. We also found that CSE induced ER stress in preadipocytes, and ER stress inducers (thapsigargin, tunicamycin, and A23187) reproduced the suppressive effect of CSE on the differentiation of preadipocytes. Interestingly, AhR agonists did not cause ER stress, and ER stress inducers did not activate AhR. These results suggested that cigarette smoke has the potential to inhibit adipocyte differentiation via dual, independent mechanisms, i.e., through activation of the AhR pathway and induction of the unfolded protein response.

Suppression of adipocyte differentiation by Cordyceps militaris through activation of the aryl hydrocarbon receptor

Mycelial extracts have a wide range of biological activities that modulate functions of mammalian cells. In this report, we sought to identify antiadipogenic mycelia with the use of 3T3-L1 cells and found that the extract of Cordyceps militaris exclusively suppressed differentiation of 3T3-L1 preadipocytes into mature adipocytes without affecting cell viability. This inhibitory effect was dose dependent, reversible, and associated with 1) a decrease in lipid accumulation, 2) blunted induction of adipocyte markers including adiponectin, peroxisome proliferator-activated receptor-gamma, and CCAAT/enhancer binding protein-alpha, and 3) sustained expression of a preadipocyte marker, monocyte chemoattractant protein-1. C. militaris also significantly decreased accumulation of lipid and hypertrophy in mature adipocytes and preserved their response to insulin (phosphorylation of Akt) during prolonged culture. Subsequent experiments revealed that C. militaris has the potential to activate the aryl hydrocarbon receptor (AhR). In 3T3-L1 cells, treatment with AhR agonists including benzo[a]pyrene and 3-methylcholanthrene reproduced the antiadipogenic effect of C. militaris. Furthermore, dominant-negative inhibition of AhR abrogated the suppressive effect of C. militaris on adipocyte differentiation. These results suggest that C. militaris has the potential to interfere with adipocyte differentiation through activation of AhR.

Blockade of the aryl hydrocarbon receptor pathway triggered by dioxin, polycyclic aromatic hydrocarbons and cigarette smoke by Phellinus linteus

Environmental pollutants including halogenated and polycyclic aromatic hydrocarbons activate the aryl hydrocarbon receptor (AhR) and thereby cause a wide range of pathological changes. Development of AhR antagonists will be useful for prevention and treatment of diseases related to AhR activation. Towards this end, we aimed in the present study at seeking for potential inhibitors of the AhR pathway in mycelial extracts using the dioxin responsive element-based sensing via secreted alkaline phosphatase (DRESSA). Through the screening of 13 mycelia, extracts prepared from Phellinus linteus, Cordyceps militaris and Hericium erinaceum inhibited activation of AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin, benzo[a]pyrene or 3-methylcholanthrene. Subsequent studies revealed that only Phellinus linteus suppressed activation of AhR and AhR-dependent gene expression triggered by all of these agonists. Cigarette smoke is known to contain a number of halogenated and polycyclic aromatic hydrocarbons. We found that Phellinus linteus has the potential to block activation of AhR and AhR-dependent gene expression triggered by cigarette smoke. Furthermore, the inhibitory effect of Phellinus linteus on the AhR pathway was independent of; 1) depression of AhR or AhR nuclear translocator, and 2) induction of AhR repressor. We conclude that Phellinus linteus contains potent inhibitor(s) of AhR activation and may be useful for prevention of pathologies associated with aberrant activation of AhR.

Blockade of the dioxin pathway by herbal medicine Formula Bupleuri Minor: identification of active entities for suppression of AhR activation

Environmental pollutants including dioxins activate the aryl hydrocarbon receptor (AhR) and cause a wide range of pathologies. Development of AhR antagonists will be useful for prevention and treatment of the diseases related to AhR activation. Towards this goal, we aimed at seeking for potential AhR antagonists in herbal medicines using the dioxin responsive element-based sensing via secreted alkaline phosphatase (DRESSA). Through initial rough screening, 4 formulae were selected from 20 herbal medicines and subjected to the second, detailed screening. We found that only Formula bupleuri minor (TJ-9) significantly inhibited activation of AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Among 7 raw herb extracts in TJ-9, Glycyrrhizae Radix and Scutellariae Radix were responsible for the antagonistic effect of TJ-9 against dioxin. Some constituents including Bupleuri Radix and Zingiberis Rhizoma rather activated AhR. Among 12 major constituents of Glycyrrhizae Radix and Scutellariae Radix, we identified that licopyranocoumarin, glycyrrhizic acid and genistein in Glycyrrhizae Radix and baicalein, wogonin and daidzein in Scutellariae Radix had substantial antagonistic effects on AhR. Among these, baicalein most effectively blocked activation of AhR triggered by cigarette smoke, a strong activator of AhR. The antagonistic substances identified here may be useful for prevention from diseases associated with aberrant activation of AhR.

Direct, continuous monitoring of air pollution by transgenic sensor mice responsive to halogenated and polycyclic aromatic hydrocarbons

BACKGROUND

The aryl hydrocarbon receptor (AhR, also called the dioxin receptor) plays crucial roles in toxicologic responses of animals to environmental pollutants, especially to halogenated and polycyclic aromatic hydrocarbons. To achieve direct, continuous risk assessment of air pollution using biological systems, we generated transgenic sensor mice that produce secreted alkaline phosphatase (SEAP) under the control of AhR.

METHODS

To characterize responses of the mice to AhR agonists, sensor mice were orally administered 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3-methylcholanthrene (3MC), benzo[a]pyrene (B[a]P), or beta-naphthoflavone (BNF), and serum levels of SEAP were evaluated. To monitor air pollution caused by cigarette smoke, we placed the mice each day in an experimental smoking room, and evaluated activity of serum SEAP for up to 4 days. Activation of AhR in individual organs was also examined by reverse transcription-polymerase chain reaction (RT-PCR) analysis of SEAP.

RESULTS

In response to oral exposure to TCDD, sensor mice exhibited dramatic and sustained activation of AhR. The mice also responded sensitively to 3MC, B[a]P, and BNF. Activation of AhR was dose dependent, and the liver was identified as the main responding organ. After exposure to the smoking environment, sensor mice consistently exhibited transient, reversible activation of AhR. RT-PCR analysis of SEAP revealed that activation of AhR occurred predominantly in the lung.

CONCLUSION

We are the first laboratory to demonstrate successfully direct, comprehensive monitoring of air pollution using genetically engineered mammals. The established system would be useful for real risk assessment of halogenated and polycyclic aromatic hydrocarbons in the air, especially in smoking environments.

Cigarette smoke as a trigger for the dioxin receptor-mediated signaling pathway

Dioxins and dioxin-like chemicals cause a wide range of pathologies including carcinogenesis, immune dysfunction, and developmental/reproductive abnormalities. Most of these toxic effects are mediated by aryl hydrocarbon receptor (AhR; also called the dioxin receptor), a ligand-activated transcription factor. Constitutive activation of AhR via genetic manipulation causes development of cancers, inflammation and immune abnormality in mice even without exposure to xenobiotic ligands. Recent investigation disclosed that cigarette smoke contains high levels of agonists for AhR and strongly activates the dioxin signaling pathway. In this review, we describe and discuss possible roles of AhR activation in cigarette smoke-related pathologies, especially focusing on carcinogenesis, inflammation, atherosclerosis, immune dysfunction and teratogenesis.

Spontaneous activation of the NF-κB signaling pathway in isolated normal glomeruli

In this report, we describe that NF-κB is spontaneously activated in isolated, normal glomeruli. Ex vivo incubation of isolated rat glomeruli triggered expression of a NF-κB-dependent gene, monocyte chemoattractant protein-1 (MCP-1), in parallel with downregulation of IκBα and IκBβ proteins and activation of the p65 NF-κB subunit. The induction of MCP-1 was also observed in mesangial cells coincubated with isolated glomeruli or exposed to media conditioned by isolated glomeruli (GCM), which was abrogated by inhibition of NF-κB. The activation of NF-κB by glomerulus-derived factors was confirmed using reporter mesangial cells that produce secreted alkaline phosphatase (SEAP) under the control of the κB enhancer element. When the reporter cells were adoptively transferred into normal glomeruli, expression of SEAP mRNA and activity of SEAP were also upregulated in the explanted glomeruli. The molecular weight of factors responsible for activation of NF-κB was >50 kDa, and TNF-α was identified as one of glomerulus-derived activators. To examine upstream events involved, we focused on MAP kinases that are spontaneously activated in explanted glomeruli. Selective suppression of ERK or p38 MAP kinase significantly attenuated activation of NF-κB in mesangial cells triggered by coculture with isolated glomeruli. Interestingly, the suppressive effects by MAP kinase inhibitors were not observed in mesangial cells treated with GCM. These data suggested that NF-κB was spontaneously activated in explanted glomeruli via autocrine/paracrine factors including TNF-α and that the production of NF-κB activators by glomeruli was, at least in part, through MAP kinase pathways.

High levels of dioxin-like potential in cigarette smoke evidenced by in vitro and in vivo biosensing

Cigarette smoke contains low levels of agonists for the aryl hydrocarbon receptor (AhR; also called the dioxin receptor). However, little is understood about the whole potential of cigarette smoke for activating AhR. In this report, we evaluated the total "dioxin-like" activity of cigarette smoke using in vitro and in vivo reporter systems. Cigarette smoke extract (CSE) was prepared from seven cigarette brands (1-20 mg tar content) and subjected to in vitro bioassay based on the xenobiotic-responsive element (XRE) as the sensor and secreted alkaline phosphatase (SEAP) as the reporter. Exposure of reporter cells to CSE triggered activation of XRE in a dose-dependent manner, which was suppressed by functional inhibition of AhR. Direct, brief exposure of the cells to cigarette smoke similarly induced activation of XRE. Using 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) as the standard, the XRE-activating potential (XAP) of individual smoke was evaluated quantitatively. Positive correlation was observed between the tar content and XAP values. The XAP values estimated were extremely high with a range from 18.5 to 51.2 ng 2,3,7,8-TCDD equivalent per cigarette. To further estimate XAP of cigarette smoke in vivo, we generated transgenic reporter mice that secrete SEAP under the control of XRE. After exposure of the mice to smoke, serum levels of SEAP were significantly elevated within 12 hours, peaked at 24 hours, and declined thereafter. These results evidenced for the first time that cigarette smoke has unexpectedly high dioxin-like potential that triggers the AhR-XRE pathway in vitro and in vivo.

Biosensors as useful tools for environmental analysis and monitoring

Recent advances in the development and application of biosensors for environmental analysis and monitoring are reviewed in this article. Several examples of biosensors developed for relevant environmental pollutants and parameters are briefly overviewed. Special attention is paid to the application of biosensors to real environmental samples, taking into consideration aspects such as sample pretreatment, matrix effects and validation of biosensor measurements. Current trends in biosensor development are also considered and commented on in this work. In this context, nanotechnology, miniaturisation, multi-sensor array development and, especially, biotechnology arise as fast-growing areas that will have a marked influence on the development of new biosensing strategies in the near future.

Profiling of functional phosphodiesterase in mesangial cells using a CRE-SEAP-based reporting system

1. Phosphodiesterases (PDEs) are critically implicated in the regulation of mesangial cell function, but profile of functional PDEs in mesangial cells is still unclear. In this study, we investigated roles of individual PDEs in the regulation of mesangial cell behavior by the cAMP pathway. 2. Reporter mesangial cells that express secreted alkaline phosphatase (SEAP) under the control of the cAMP response element (CRE) were exposed to selective PDE inhibitors in the presence or absence of cAMP, and activity of CRE, expression of CRE-regulated protein, mitogenesis and cell survival were examined. 3. Exposure of reporter cells to cAMP-elevating agents resulted in time- and concentration-dependent activation of CRE. Treatment of the cells with any PDE inhibitors alone did not induce CRE activation. Under stimulation with 8-bromo-cAMP or 8-bromo-cGMP, however, inhibitors of PDE2, PDE3, PDE4 and PDE5 enhanced activation of CRE. Inhibition of PDE1 or PDE6 did not affect the CRE activation. 4. Among different combinations tested, only inhibitors of PDE3 and PDE4 cooperatively increased the level of intracellular cAMP, activity of protein kinase A, activation of CRE, and CRE-regulated protein, connexin43. 5. Concomitant inhibition of PDE3 and PDE4 attenuated mitogen-induced activation of extracellular signal-regulated kinases and cell proliferation. Under serum deprivation, combinational inhibition of PDE3 and PDE4 exclusively caused activation of caspase-3 and apoptosis. 6. The present data elucidated that PDE3 and PDE4 play critical roles in the regulation of mesangial cell function. PDE3 and PDE4 were identified as the novel, antiapoptotic machinery that supports survival of mesangial cells.

Recent advances in biosensor techniques for environmental monitoring

Biosensors for environmental applications continue to show advances and improvements in areas such as sensitivity, selectivity and simplicity. In addition to detecting and measuring specific compounds or compound classes such as pesticides, hazardous industrial chemicals, toxic metals, and pathogenic bacteria, biosensors and bioanalytical assays have been designed to measure biological effects such as cytotoxicity, genotoxicity, biological oxygen demand, pathogenic bacteria, and endocrine disruption effects. This article is intended to discuss recent advances in the area of biosensors for environmental applications.

Bioassay-based screening of microorganisms that degrade dioxin using substrate-immobilized microtubes

In the current study, we attempted to develop a method for bioassay-based screening of microorganisms that degrade dioxin. However, a crucial problem encountered was that the standard dioxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) added to bacterial medium immediately disappeared from the liquid phase due to its adsorption onto polypropylene (PP) tubes. Among other aromatic hydrocarbons, adsorption onto PP tubes was also observed in beta-naphthoflavone but not in benzo[a]pyrene. Adsorption of TCDD was observed not only onto PP tubes but also onto polystyrene, glass, and PP tubes with low affinity for DNA or protein. Silanization was not effective at preventing adsorption of TCDD. TCDD immobilized onto PP tubes was recovered by organic solvents, including ethanol, methanol, and dimethyl sulfoxide (DMSO). The elution efficiency of the immobilized TCDD by DMSO was approximately 85%. Based on these findings, screening of bacteria that degrade dioxin was attempted as follows. First, TCDD was immobilized onto PP tubes. Second, bacterial suspension was added to the tubes and incubated for biodegradation of TCDD. Third, remaining, immobilized TCDD was eluted by DMSO and subjected to a reporter bioassay to evaluate the level of TCDD. Using this method, we demonstrated successful screening of bacteria that have the potential for degradation of dioxin.

Influence of cAMP on reporter bioassays for dioxin and dioxin-like compounds

In reporter assays for detection of dioxins, the dioxin-responsive element (DRE) is generally used as a sensor sequence. In several systems, the CYP1A1 promoter containing DREs (DRE(cyp)) is inserted into a part of the long terminal repeat of mouse mammary tumor virus (LTR(MMTV)) to improve sensitivity of assays. We found that DRE(cyp)-LTR(MMTV) responds not only to dioxins and dioxin-like compounds but also to forskolin, a cAMP-elevating agent. This effect was dose-dependent and reproduced by other cAMP-elevating agents including 8-bromo-cAMP and 3-isobutyl-methylxanthine. The cAMP response element (CRE) and CRE-like sequences were absent in DRE(cyp)-LTR(MMTV) and not involved in this process. In contrast to the effect of dioxin, the activation of DRE(cyp)-LTR(MMTV) by cAMP was independent of the aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor for DRE. Furthermore, neither DRE(cyp), LTR(MMTV) nor the consensus sequence of DRE alone was activated in response to cAMP. These data elucidated for the first time that the combination of DRE(cyp) with LTR(MMTV) causes a peculiar response to cAMP and suggested that use of AhR antagonists is essential to exclude false-positive responses of DRE(cyp)-LTR(MMTV)-based bioassays for detection and quantification of dioxins and dioxin-like compounds.