Arsenic represses airway epithelial mucin expression by affecting retinoic acid signaling pathway.

Arsenic is a ubiquitous environmental toxicant, found in high concentrations worldwide. Although abundant research has dealt with arsenic-induced cancers, studies on mechanisms of non-malignant lung diseases have not been complete. In addition, decades of research have mostly concentrated on high-dose arsenic exposure, which has very limited use in modeling the biological effects of today's low-dose exposures. Indeed, accumulated evidence has shown that low-dose arsenic exposure (i.e. ≤100 ppb) may also alter lung homeostasis by causing host susceptibility to viral infection. However, the underlying mechanism of this alteration is unknown. In this study, we found that low-dose sodium arsenite (As (III)) repressed major airway mucins-MUC5AC and MUC5B at both mRNA and protein levels. We further demonstrated that this repression was not caused by cellular toxicity or mediated by the reduction of a common mucin-inducing pathway-EGFR. Other established mucin activators- dsRNA, IL1ß or IL17 were not able to override As (III)-induced mucin repression. Interestingly, the suppressing effect of As (III) appeared to be partially reversible, and supplementation of all trans retinoic acid (t-RA) doses dependently restored mucin gene expression. Further analyses indicated that As (III) treatment significantly reduced the protein level of retinoic acid receptors (RARα, γ and RXRα) as well as RARE promoter reporter activity. Therefore, our study fills in an important knowledge gap in the field of low-dose arsenic exposure. The interference of RA signaling, and mucin gene expression may be important pathogenic factors in low-dose arsenic induced lung toxicity.

Tanshinone I activates the Nrf2-dependent antioxidant response and protects against As(III)-induced lung inflammation in vitro and in vivo.

AIMS: The NF-E2 p45-related factor 2 (Nrf2) signaling pathway regulates the cellular antioxidant response and activation of Nrf2 has recently been shown to limit tissue damage from exposure to environmental toxicants, including As(III). In an attempt to identify improved molecular agents for systemic protection against environmental insults, we have focused on the identification of novel medicinal plant-derived Nrf2 activators. RESULTS: Tanshinones [tanshinone I (T-I), tanshinone IIA, dihydrotanshinone, cryptotanshinone], phenanthrenequinone-based redox therapeutics derived from the medicinal herb Salvia miltiorrhiza, have been tested as experimental therapeutics for Nrf2-dependent cytoprotection. Using a dual luciferase reporter assay overexpressing wild-type or mutant Kelch-like ECH-associated protein-1 (Keap1), we demonstrate that T-I is a potent Keap1-C151-dependent Nrf2 activator that stabilizes Nrf2 by hindering its ubiquitination. In human bronchial epithelial cells exposed to As(III), T-I displays pronounced cytoprotective activity with upregulation of Nrf2-orchestrated gene expression. In Nrf2 wild-type mice, systemic administration of T-I attenuates As(III) induced inflammatory lung damage, a protective effect not observed in Nrf2 knockout mice. INNOVATION: Tanshinones have been identified as a novel class of Nrf2-inducers for antioxidant tissue protection in an in vivo As(III) inhalation model, that is relevant to low doses of environmental exposure. CONCLUSION: T-I represents a prototype Nrf2-activator that displays cytoprotective activity upon systemic administration targeting lung damage originating from environmental insults. T-I based Nrf2-directed systemic intervention may provide therapeutic benefit in protecting other organs against environmental insults.

Chronic arsenic exposure in nanomolar concentrations compromises wound response and intercellular signaling in airway epithelial cells.

Paracrine ATP signaling in the lung epithelium participates in a variety of innate immune functions, including mucociliary clearance, bactericide production, and as an initiating signal in wound repair. We evaluated the effects of chronic low-dose arsenic relevant to U.S. drinking water standards (i.e., 10 ppb [130nM]) on airway epithelial cells. Immortalized human bronchial epithelial cells (16HBE14o-) were exposed to 0, 130, or 330nM arsenic (as Na-arsenite) for 4-5 weeks and examined for wound repair efficiency and ATP-mediated Ca(2+) signaling. We found that chronic arsenic exposure at these low doses slows wound repair and reduces ATP-mediated Ca(2+) signaling. We further show that arsenic compromises ATP-mediated Ca(2+) signaling by altering both Ca(2+) release from intracellular stores (via metabotropic P2Y receptors) and Ca(2+) influx mechanisms (via ionotropic P2X receptors). To better model the effects of arsenic on ATP-mediated Ca(2+) signaling under conditions of natural exposure, we cultured tracheal epithelial cells obtained from mice exposed to control or 50 ppb Na-arsenite supplemented drinking water for 4 weeks. Tracheal epithelial cells from arsenic-exposed mice displayed reduced ATP-mediated Ca(2+) signaling dynamics similar to our in vitro chronic exposure. Our findings demonstrate that chronic arsenic exposure at levels that are commonly found in drinking water (i.e., 10-50 ppb) alters cellular mechanisms critical to airway innate immunity.

Effects of caffeoylquinic acid derivatives and C-flavonoid from Lychnophora ericoides on in vitro inflammatory mediator production.

In this study we aimed at evaluating the effect of the major polar constituents of the medicinal plant Lychnophora ericoides on the production of inflammatory mediators produced by LPS-stimulated U-937 cells. The 6,8-di-C-beta-glucosylapigenin (vicenin-2) presented no effect on tumor necrosis factor (TNF)-alpha production, but inhibited, in a dose-dependent manner, the production of prostaglandin (PG) E2 without altering the expression of cyclooxygenase (COX)-2 protein. 3,5-Dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid, at lower concentrations, had small but significant effects on reducing PGE2 levels; at higher doses these compounds stimulated PGE2 and also TNF-alpha production by the cells. All the caffeoylquinic acid derivatives, in a dose-dependent fashion, were able to inhibit monocyte chemoattractant protein-3 synthesis/release, with 4,5-DCQ being the most potent at the highest tested concentration. These results add important information on the effects of plant natural polyphenols, namely vicenin-2 and caffeoylquinic acid derivatives, on the production of inflammatory mediators by cultured cells.

Efficacy and mechanism of action of turmeric supplements in the treatment of experimental arthritis.

OBJECTIVE: Scientific evidence is lacking for the antiarthritic efficacy of turmeric dietary supplements that are being promoted for arthritis treatment. Therefore, we undertook studies to determine the antiarthritic efficacy and mechanism of action of a well-characterized turmeric extract using an animal model of rheumatoid arthritis (RA). METHODS: The composition of commercial turmeric dietary supplements was determined by high-performance liquid chromatography. A curcuminoid-containing turmeric extract similar in composition to these supplements was isolated and administered intraperitoneally to female Lewis rats prior to or after the onset of streptococcal cell wall-induced arthritis. Efficacy in preventing joint swelling and destruction was determined clinically, histologically, and by measurement of bone mineral density. Mechanism of action was elucidated by analysis of turmeric's effect on articular transcription factor activation, microarray analysis of articular gene expression, and verification of the physiologic effects of alterations in gene expression. RESULTS: A turmeric fraction depleted of essential oils profoundly inhibited joint inflammation and periarticular joint destruction in a dose-dependent manner. In vivo treatment prevented local activation of NF-kappaB and the subsequent expression of NF-kappaB-regulated genes mediating joint inflammation and destruction, including chemokines, cyclooxygenase 2, and RANKL. Consistent with these findings, inflammatory cell influx, joint levels of prostaglandin E(2), and periarticular osteoclast formation were inhibited by turmeric extract treatment. CONCLUSION: These translational studies demonstrate in vivo efficacy and identify a mechanism of action for a well-characterized turmeric extract that supports further clinical evaluation of turmeric dietary supplements in the treatment of RA.

Turmeric extracts containing curcuminoids prevent experimental rheumatoid arthritis.

Turmeric has been used for centuries in Ayurvedic medicine as a treatment for inflammatory disorders including arthritis. On the basis of this traditional usage, dietary supplements containing turmeric rhizome and turmeric extracts are also being used in the western world for arthritis treatment and prevention. However, to our knowledge, no data are available regarding antiarthritic efficacy of complex turmeric extracts similar in composition to those available for use as dietary supplements. Therefore, the studies described here were undertaken to determine the in vivo efficacy of well-characterized curcuminoid-containing turmeric extracts in the prevention or treatment of arthritis using streptococcal cell wall (SCW)-induced arthritis, a well-described animal model of rheumatoid arthritis (RA). Arthritic index, a clinical measure of joint swelling, was used as the primary endpoint for assessing the effect of extracts on joint inflammation. An essential oil-depleted turmeric fraction containing 41% of the three major curcuminoids was efficacious in preventing joint inflammation when treatment was started before, but not after, the onset of joint inflammation. A commercial sample containing 94% of the three major curcuminoids was more potent in preventing arthritis than the essential oil-depleted turmeric fraction when compared by total curcuminoid dose per body weight. In conclusion, these data (1) document the in vivo antiarthritic efficacy of an essential oil-depleted turmeric fraction and (2) suggest that the three major curcuminoids are responsible for this antiarthritic effect, while the remaining compounds in the crude turmeric extract may inhibit this protective effect.

Uranyl acetate induces hprt mutations and uranium-DNA adducts in Chinese hamster ovary EM9 cells.

Questions about possible adverse health effects from exposures to uranium have arisen as a result of uranium mining, residual mine tailings and use of depleted uranium in the military. The purpose of the current study was to measure the toxicity of depleted uranium as uranyl acetate (UA) in mammalian cells. The activity of UA in the parental CHO AA8 line was compared with that in the XRCC1-deficient CHO EM9 line. Cytotoxicity was measured by clonogenic survival. A dose of 200 microM UA over 24 h produced 3.1-fold greater cell death in the CHO EM9 than the CHO AA8 line, and a dose of 300 microM was 1.7-fold more cytotoxic. Mutagenicity at the hypoxanthine (guanine) phosphoribosyltransferase (hprt) locus was measured by selection with 6-thioguanine. A dose of 200 microM UA produced approximately 5-fold higher averaged induced mutant frequency in the CHO EM9 line relative to the CHO AA8 line. The generation of DNA strand breaks was measured by the alkaline comet assay at 40 min and 24 h exposures. DNA strand breaks were detected in both lines; however a dose response may have been masked by U-DNA adducts or crosslinks. Uranium-DNA adducts were measured by inductively coupled plasma optical emission spectroscopy (ICP-OES) at 24 and 48 h exposures. A maximum adduct level of 8 U atoms/10(3) DNA-P for the 300 microM dose was found in the EM9 line after 48 h. This is the first report of the formation of uranium-DNA adducts and mutations in mammalian cells after direct exposure to a depleted uranium compound. Data suggest that uranium could be chemically genotoxic and mutagenic through the formation of strand breaks and covalent U-DNA adducts. Thus the health risks for uranium exposure could go beyond those for radiation exposure.

Commercially processed dry ginger (Zingiber officinale): composition and effects on LPS-stimulated PGE2 production.

Using techniques previously employed to identify ginger constituents in fresh organically grown Hawaiian white and yellow ginger varieties, partially purified fractions derived from the silica gel column chromatography and HPLC of a methylene chloride extract of commercially processed dry ginger, Zingiber officinale Roscoe, Zingiberaceae, which demonstrated remarkable anti-inflammatory activity, were investigated by gas chromatography-mass spectrometry. In all, 115 compounds were identified, 88 with retention times (R(t)) >21 min and 27 with <21 min. Of those 88 compounds, 45 were previously reported by us from fresh ginger, 12 are cited elsewhere in the literature and the rest (31) are new: methyl [8]-paradol, methyl [6]-isogingerol, methyl [4]-shogaol, [6]-isoshogaol, two 6-hydroxy-[n]-shogaols (n=8 and 10), 6-dehydro-[6]-gingerol, three 5-methoxy-[n]-gingerols (n=4, 8 and 10), 3-acetoxy-[4]-gingerdiol, 5-acetoxy-[6]-gingerdiol (stereoisomer), diacetoxy-[8]-gingerdiol, methyl diacetoxy-[8]-gingerdiol, 6-(4'-hydroxy-3'-methoxyphenyl)-2-nonyl-2-hydroxytetrahydropyran, 3-acetoxydihydro-[6]-paradol methyl ether, 1-(4'-hydroxy-3'-methoxyphenyl)-2-nonadecen-1-one and its methyl ether derivative, 1,7-bis-(4'-hydroxy-3'-methoxyphenyl)-5-methoxyheptan-3-one, 1,7-bis-(4'-hydroxy-3'-methoxyphenyl)-3-hydroxy-5-acetoxyheptane, acetoxy-3-dihydrodemethoxy-[6]-shogaol, 5-acetoxy-3-deoxy-[6]-gingerol, 1-hydroxy-[6]-paradol, (2E)-geranial acetals of [4]- and [6]-gingerdiols, (2Z)-neral acetal of [6]-gingerdiol, acetaldehyde acetal of [6]-gingerdiol, 1-(4-hydroxy-3-methoxyphenyl)-2,4-dehydro-6-decanone and the cyclic methyl orthoesters of [6]- and [10]-gingerdiols. Of the 27 R(t)<21 min compounds, we had found 5 from fresh ginger, 20 others were found elsewhere in the literature, and two are new: 5-(4'-hydroxy-3'-methoxyphenyl)-pent-2-en-1-al and 5-(4'-hydroxy-3'-methoxyphenyl)-3-hydroxy-1-pentanal. Most of the short R(t) compounds are probably formed by thermal degradation during GC (which mimics cooking) and/or commercial drying. The concentrations of gingerols, the major constituents of fresh ginger, were reduced slightly in dry ginger, while the concentrations of shogaols, the major gingerol dehydration products, increased.

Fresh organically grown ginger (Zingiber officinale): composition and effects on LPS-induced PGE2 production.

Gas chromatography in conjunction with mass spectrometry, a technique previously employed to analyze non-volatile pungent components of ginger extracts modified to trimethylsilyl derivatives, was applied successfully for the first time to analyze unmodified partially purified fractions from the dichloromethane extracts of organically grown samples of fresh Chinese white and Japanese yellow varieties of ginger, Zingiber officinale Roscoe (Zingiberaceae). This analysis resulted in the detection of 20 hitherto unknown natural products and 31 compounds previously reported as ginger constituents. These include paradols, dihydroparadols, gingerols, acetyl derivatives of gingerols, shogaols, 3-dihydroshogaols, gingerdiols, mono- and diacetyl derivatives of gingerdiols, 1-dehydrogingerdiones, diarylheptanoids, and methyl ether derivatives of some of these compounds. The thermal degradation of gingerols to gingerone, shogaols, and related compounds was demonstrated. The major constituent in the two varieties was [6]-gingerol, a chemical marker for Z. officinale. Mass spectral fragmentation patterns for all the compounds are described and interpreted. Anti-inflammatory activities of silica gel chromatography fractions were tested using an in vitro PGE2 assay. Most of the fractions containing gingerols and/or gingerol derivatives showed excellent inhibition of LPS-induced PGE2 production.

Correlation between in vivo and in vitro pulmonary responses to jet propulsion fuel-8 using precision-cut lung slices and a dynamic organ culture system.

In tissue slice models, interactions between the heterogeneous cell types comprising the lung parenchyma are maintained thus providing a controlled system for the study of pulmonary toxicology in vitro. However, validation of the model in vitro system must be affirmed. Previous reports, in in vivo systems, have demonstrated that Clara cells and alveolar type II cells are the targets following inhalation of JP-8 jet fuel. We have utilized the lung slice model to determine if cellular targets are similar following in vitro exposure to JP-8. Agar-filled adult rat lung explants were cored and precision cut, using the Brende/Vitron tissue slicer. Slices were cultured on titanium screens located as half-cylinders in cylindrical Teflon cradles that were loaded into standard scintillation vials and incubated at 37 degrees C. Slices were exposed to JP-8 jet fuel (0.5 mg/ml, 1.0 mg/ml, and 1.5 mg/ml in medium) for up to 24 hours. We determined ATP content using a luciferin-luciferase bioluminescent assay. No significant difference was found between the JP-8 jet fuel doses or time points, when compared to controls. Results were correlated with structural alterations following aerosol inhalation of JP-8. As a general observation, ultrastructural evaluation of alveolar type cells revealed an apparent increase in the number and size of surfactant secreting lamellar bodies that was JP-8 jet fuel-dose dependent. These results are similar to those observed following aerosol inhalation exposure. Thus, the lung tissue slice model appears to mimic in vivo effects of JP-8 and therefore is a useful model system for studying the mechanisms of lunginjury following JP-8 exposure.

Enhanced activity of human IL-10 after nitration in reducing human IL-1 production by stimulated peripheral blood mononuclear cells.

Nitric oxide and superoxide form the unstable compound, peroxynitrite, which can nitrate proteins and compromise function of proinflammatory cytokines at sites of inflammation. Reduced function of proinflammatory proteins such as IL-8, macrophage inflammatory protein-1alpha, and eotaxin suggest an anti-inflammatory effect of nitration. The effects of nitration on anti-inflammatory cytokines such as IL-10 are unknown. We hypothesized that peroxynitrite would modify the function of anti-inflammatory cytokines like IL-10. To test this hypothesis, the capacity of recombinant human IL-10 to inhibit production of human IL-1beta (IL-1) from LPS-stimulated human PBMC was evaluated. Human IL-10 was nitrated by incubation with peroxynitrite or by incubation with 3-morpholinosydnonimine, a peroxynitrite generator, for 2 h and then incubated with LPS-stimulated PBMC for 6 h, and IL-1 was measured in the culture supernatant fluids. Human IL-1 production was significantly lower in the peroxynitrite- or 3-morpholinosydnonimine-nitrated IL-10 group than in the IL-10 controls (p < 0.05, all comparisons). This finding demonstrates that although peroxynitrite inhibits proinflammatory cytokines, it may augment anti-inflammatory cytokines and further point to an important role for peroxynitrite in the regulation of inflammation.