Adjuvant effect of inhaled particulate matter containing free radicals following house-dust mite induction of asthma in mice.

INTRODUCTION: Exposures to particulate matter (PM) from combustion sources can exacerbate preexisting asthma. However, the cellular and molecular mechanisms by which PM promotes the exacerbation of asthma remain elusive. We used a house dust mite (HDM)-induced mouse model of asthma to test the hypothesis that inhaled DCB230, which are PM containing environmentally persistent free radicals (EPFRs), will aggravate asthmatic responses. METHODS: Groups of 8-10-week-old C57BL/6 male mice were exposed to either air or DCB230 aerosols at a concentration of 1.5 mg/m3 4 h/day for 10 days with or without prior HDM-induction of asthma. RESULTS: Aerosolized DCB230 particles formed small aggregates (30-150 nm). Mice exposed to DCB230 alone showed significantly reduced lung tidal volume, overexpression of the Muc5ac gene, and dysregulation of 4 inflammation related genes, Ccl11, Ccl24, Il-10, and Tpsb2. This suggests DCB230 particles interacted with the lung epithelium inducing mucous hypersecretion and restricting lung volume. In addition to reduced lung tidal volume, compared to respective controls, the HDM + DCB230-exposed group exhibited significantly increased lung tissue damping and up-regulated expression of Muc5ac, indicating that in this model, mucous hypersecretion may be central to pulmonary dysfunction. This group also showed augmented lung eosinophilic inflammation accompanied by an up-regulation of 36 asthma related genes. Twelve of these genes are part of IL-17 signaling, suggesting that this pathway is critical for DCB230 induced toxicity and adjuvant effects in lungs previously exposed to HDM. CONCLUSION: Our data indicate that inhaled DCB230 can act as an adjuvant, exacerbating asthma through IL-17-mediated responses in a HDM mouse model.

Inhalation of particulate matter containing free radicals leads to decreased vascular responsiveness associated with an altered pulmonary function.

Airborne particulate matter (PM) is associated with an increased risk for cardiovascular diseases. Although the goal of thermal remediation is to eliminate organic wastes through combustion, when incomplete combustion occurs, organics chemisorb to transition metals to generate PM-containing environmentally persistent free radicals (EPFRs). Similar EPFR species have been detected in PM found in diesel and gasoline exhaust, woodsmoke, and urban air. Prior in vivo studies demonstrated that EPFRs reduce cardiac function secondary to elevations in pulmonary arterial pressures. In vitro studies showed that EPFRs increase ROS and cytokines in pulmonary epithelial cells. We thus hypothesized that EPFR inhalation would promote lung inflammation and oxidative stress, leading to systemic inflammation, vascular endothelial injury, and a decline in vascular function. Mice were exposed to EPFRs for either 4 h or for 4 h/day for 10 days and lung and vascular function were assessed. After a 4-h exposure, plasma nitric oxide (NO) was reduced while endothelin-1 (ET-1) was increased, however lung function was not altered. After 10 day, plasma NO and ET-1 levels were again altered and lung tidal volume was reduced. These time course studies suggested the vasculature may be an early target of injury. To test this hypothesis, an intermediate time point of 3 days was selected. Though the mice exhibited no marked inflammation in either the lung or the blood, we did note significantly reduced endothelial function concurrent with a reduction in lung tidal volume and an elevation in annexin V protein levels in the lung. Although vascular dysfunction was not dependent upon inflammation, it may be associated with an injury at the air-blood interface. Gene expression analysis suggested roles for oxidative stress and aryl hydrocarbon receptor (Ahr) signaling. Studies probing the relationship between pulmonary oxidative stress and AhR signaling at the air-blood interface with vascular dysfunction seem warranted.NEW & NOTEWORTHY Particulate matter (PM) resulting from the combustion of organic matter is known to contribute to cardiopulmonary disease. Despite hypotheses that cardiovascular dysfunction occurring after PM exposures is secondary to lung or systemic inflammation, these studies investigating exposures to PM-containing environmentally persistent free radicals (EPFRs) demonstrate that cardiovascular dysfunction precedes pulmonary inflammation. The cardiopulmonary health consequences of EPFRs have yet to be thoroughly evaluated, especially in healthy, adult mice. Our data suggest the vasculature as a direct target of PM exposure, and our studies aimed to elucidate the mechanisms contributing to EPFR-induced vascular dysfunction.

Particulate matter containing environmentally persistent free radicals induces AhR-dependent cytokine and reactive oxygen species production in human bronchial epithelial cells.

Particulate matter (PM) is emitted during the combustion of fuels and wastes. PM exposure exacerbates pulmonary diseases, and the mechanism may involve oxidative stress. At lower combustion temperatures such as occurs in the cool zone of a flame, aromatic compounds chemisorb to the surface of metal-oxide-containing PM, resulting in the formation of surface-stabilized environmentally persistent free radicals (EPFR). Prior studies showed that PM-containing EPFR redox cycle to produce reactive oxygen species (ROS), and after inhalation, EPFR induce pulmonary inflammation and oxidative stress. Our objective was to elucidate mechanisms linking EPFR-induced oxidant injury with increased cytokine production by pulmonary epithelial cells. We thus treated human bronchial epithelial cells with EPFR at sub-toxic doses and measured ROS and cytokine production. To assess aryl hydrocarbon receptor (AhR) activity, cells were transfected with a luciferase reporter for xenobiotic response element activation. To test whether cytokine production was dependent upon AhR activation or oxidative stress, some cells were co-treated with an antioxidant or an AhR antagonist. EPFR increased IL-6 release in an ROS and AhR- and oxidant-dependent manner. Moreover, EPFR induced an AhR activation that was dependent upon oxidant production, since antioxidant co-treatment blocked AhR activation. On the other hand, EPFR treatment increased a cellular ROS production that was at least partially attenuated by AhR knockdown using siRNA. While AhR activation was correlated with an increased expression of oxidant-producing enzymes like cytochrome P450 CYP1A1, it is possible that AhR activation is both a cause and effect of EPFR-induced ROS. Finally, lipid oxidation products also induced AhR activation. ROS-dependent AhR activation may be a mechanism for altered epithelial cell responses after EPFR exposure, potentially via formation of bioactive lipid or protein oxidation products.

New Insight into the Origin of the Red/Near-Infrared Intense Fluorescence of a Crystalline 2-Hydroxychalcone Derivative: A Comprehensive Picture from the Excited-State Femtosecond Dynamics.

Fluorescence upconversion and transient absorption techniques are used to explain the source of the intense red/near-infrared emission of crystalline 4-dimethylamino-2'-hydroxychalcone. We found that the initially excited enol form undergoes tautomerization in 3 ps to form the keto tautomer. The latter is stable in the ground state as a consequence of J-type aggregation in the crystal packing and is manifested in an absorption peak at 550 nm that spectrally overlaps with the short-lived enol emission, leading to self-reabsorption and adding a factor to the complete depletion of the enol emission. Relaxation of the keto tautomer takes place in the form of intense fluorescence (600-750 nm) with 1.7 ns lifetime. The different spectroscopy in solution is due to vibrational cooling (300 fs), followed by solvation dynamics (5 ps in methanol) and twisting of the hydroxyphenyl ring (16 ps), before relaxation of the enol tautomer in the form of weak green fluorescence with 350 ps lifetime.

Aqueous-based initiator attachment and ATRP grafting of polymer brushes from poly(methyl methacrylate) substrates.

Many polymers, such as PMMA, are very susceptible to swelling or dissolution by organic solvents. Growing covalently attached polymer brushes from these surfaces by atom-transfer radical polymerization (ATRP) is challenging because of the typical requirement of organic solvent for initiator immobilization. We report an unprecedented, aqueous-based route to graft poly(N-isopropylacrylamide), PNIPAAm, from poly(methyl methacrylate), PMMA, surfaces by ATRP, wherein the underlying PMMA is unaffected. Successful attachment of the ATRP initiator, N-hydroxysuccinimidyl-2-bromo-2-methylpropionate, on amine-bearing PMMA surfaces was confirmed by XPS. From this surface-immobilized initiator, thermoresponsive PNIPAAm brushes were grown by aqueous ATRP to yield optically transparent PNIPAAm-grafted PMMA surfaces. This procedure is valuable, as it can be applied for the aqueous-based covalent attachment of ATRP initiator on any amine-functionalized surface, with subsequent polymerization of a variety of monomers.

Surface modification of droplet polymeric microfluidic devices for the stable and continuous generation of aqueous droplets.

Droplet microfluidics performed in poly(methyl methacrylate) (PMMA) microfluidic devices resulted in significant wall wetting by water droplets formed in a liquid-liquid segmented flow when using a hydrophobic carrier fluid such as perfluorotripropylamine (FC-3283). This wall wetting led to water droplets with nonuniform sizes that were often trapped on the wall surfaces, leading to unstable and poorly controlled liquid-liquid segmented flow. To circumvent this problem, we developed a two-step procedure to hydrophobically modify the surfaces of PMMA and other thermoplastic materials commonly used to make microfluidic devices. The surface-modification route involved the introduction of hydroxyl groups by oxygen plasma treatment of the polymer surface followed by a solution-phase reaction with heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane dissolved in fluorocarbon solvent FC-3283. This procedure was found to be useful for the modification of PMMA and other thermoplastic surfaces, including polycyclic olefin copolymer (COC) and polycarbonate (PC). Angle-resolved X-ray photoelectron spectroscopy indicated that the fluorination of these polymers took place with high surface selectivity. This procedure was used to modify the surface of a PMMA droplet microfluidic device (DMFD) and was shown to be useful in reducing the wetting problem during the generation of aqueous droplets in a perfluorotripropylamine (FC-3283) carrier fluid and could generate stable segmented flows for hours of operation. In the case of PMMA DMFD, oxygen plasma treatment was carried out after the PMMA cover plate was thermally fusion bonded to the PMMA microfluidic chip. Because the appended chemistry to the channel wall created a hydrophobic surface, it will accommodate the use of other carrier fluids that are hydrophobic as well, such as hexadecane or mineral oils.