19 research outputs found
Decadal Changes in Seasonal Variation of Atmospheric Haze over the Eastern United States: Connections with Anthropogenic Emissions and Implications for Aerosol Composition
The
current seasonal summer maximum in surface fine particulate
matter (PM<sub>2.5</sub>) over the eastern United States has been
well established. We find that this seasonality has historically changed
substantially, based on long-term quality assured inverse visibility
(1/Vis) data over 1946ā1998. The median summer/winter 1/Vis
ratio increased from about 0.8 over both the southeastern and northeastern
United States in the late 1940s to 1.24 over the southeastern United
States and to 1.04 over the northeastern United States in the mid-1970s.
This ratio exhibits weaker changes in both regions afterward. The
observed PM<sub>2.5</sub> seasonality after the year 2000 has similar
spatial distribution as that in 1/Vis over the mid-1990s, with systematically
higher summer/winter ratios which rapidly weaken after the mid-2000s.
From 1956 to 1975, stronger increases in 1/Vis occurred in summer
than in winter in both regions, associated with increases in sulfur
dioxide emissions and reductions in anthropogenic carbonaceous emissions.
Over the southeastern United States, the changes in aerosol seasonality,
i.e., both the strengthened summer maxima over 1946ā1975 and
dampened summer maxima after 2007, suggest historical changes in anthropogenic
influence on secondary organic aerosol (SOA) formation and suggest
the prospect of reducing summer SOA through controls on anthropogenic
emissions
Bak and Bax mediate apoptosis in Ras/E1A-transformed MEF cells.
<p>(<b>A</b>) Expression of both anti-apoptotic and pro-apoptotic Bcl-2 proteins in the indicated cell lines were examined by western blot. (<b>B</b>) The indicated MEF cells were cultured in soft agar and representative images are shown. (<b>C</b>) The number of foci shown in (B). Data represent meanĀ±S.D. of three independent measurements. Asterisks (*) indicate <i>P</i><0.05, Studentās unpaired t test. (<b>D</b>) Both untransformed and transformed Bak<sup>ā/ā</sup>Bax<sup>ā/ā</sup> MEF cells were resistant to apoptotic stimuli. The indicated cells were treated with 0.5 ĀµM thapsigargin and 5 ĀµM etoposide, and cell viability was measured 48 hours later. MeanĀ±S.D. of three independent experiments are shown. Asterisks (*) indicate <i>P</i><0.05, ānsā indicates no significance (P>0.05), Studentās unpaired t test.</p
Intracellular nanoparticles colocalize with lysosomes.
<p>The indicated cell lines were first cultured with 0.1 mg/ml nanoparticles for 24 hours, then incubated with 2 ĀµM acridine orange (A) or 50 nM LysoTracker Red (B). Bright field and fluorescence images were acquired through a fluorescence microscope. Representative images are shown. While lysosomes labeled with acridine orange or LysoTracker Red are shown in red (the middle panels), TiO<sub>2</sub> nanoparticles inside cells are observed as dark-colored aggregates (the left panels).</p
Oncogenic transformation does not affect fluid phase endocytosis.
<p>(<b>A</b>) Untransformed and transformed Wild-type or Bak<sup>ā/ā</sup>Bax<sup>ā/ā</sup> MEF cells were incubated with 10 Āµg/ml or 30 Āµg/ml 10 kDa Dextran conjugated to Alexa Fluor 647 (Invitrogene). The uptake of Dextran into cells was measured by flow cytometry. (<b>B</b>) The intracellular levels of Dextran were measured as the intensities of Dextran fluorescence. MeanĀ±S.D. of three independent experiments are shown. ānsā indicates no significance (P>0.05), Studentās unpaired t test.</p
Selective cytotoxicity of TiO<sub>2</sub> nanoparticles is related to an oncogenic transformation-induced increase of lysosomal activities.
<p>(<b>A</b>) The expression levels of lysosomal protein LAMP1 in the indicated cells were determined by western blot. (<b>B</b>) The expression levels of LAMP1 are higher in transformed cells than their untransformed counterparts. The intensities of LAMP1 and actin shown in (A) were quantified using ImageJ software (NIH). The relative LAMP1 levels were calculated with the intensity of LMAP1 normalized to that of actin in the same sample. Data represent meanĀ±S.D. of three independent experiments. * p<0.05, Studentās unpaired t test. (<b>C</b>) The enzymatic activities of lysosomal acid phosphatase were measured. MeanĀ±S.D. of three independent experiments are shown. ā*ā indicates P<0.05, Studentās unpaired t test. (<b>D</b>) Chloroquine alleviates death of transformed cells induced by TiO<sub>2</sub> nanoparticles. The indicated cells were cultured in the absence or presence of chloroquine or TiO<sub>2</sub> nanoparticles. Cell viability was measured 24 hour after the treatments using TOTO-3 DNA dye exclusion approach. Data represent meanĀ±S.D. of three independent experiments. ā*ā indicates P<0.05; ānsā indicates no significance (P>0.05), Studentās unpaired t test. The viabilities of TiO<sub>2</sub> nanoparticle-treated transformed cell lines in the presence of chloroquine are significantly higher than those in the absence of chloroquine (p<0.05, Studentās unpaired t test), whereas the differences in the viabilities of untransformed cells with and without chloroquine exposure are not statistically significant (Studentās unpaired t test).</p
TiO<sub>2</sub> nanoparticles preferentially induce cell death in transformed cells.
<p>(<b>A</b>) The indicated cell lines were treated with various concentrations of P25 TiO<sub>2</sub> nanoparticles for 24 hours, and viability of cells was measured using TOTO-3 DNA dye exclusion method. Data represent meanĀ±S.D. of three independent experiments. * p<0.05, Studentās unpaired t test. (<b>B</b>) Effects of TiO<sub>2</sub> nanoparticles on cellular metabolic activities were determined by measuring Alamar Blue fluorescence. The indicated MEF cells were treated with 0.5 mg/ml or 1 mg/ml TiO<sub>2</sub> nanoparticles for 24 hours. The cellular reducing activities of treated cells were normalized to that of corresponding untreated cell lines. MeanĀ±S.D. of three independent experiments are shown. * p<0.05, Studentās unpaired t test. (<b>C</b>) Effects of TiO<sub>2</sub> nanoparticles on long-term cell viability were determined by clonogenicity assay. The normalized cell survival was calculated by dividing the number of wells with viable treated cells with that of untreated cells. Data represent meanĀ±S.D. of three independent experiments. * p<0.05, Studentās unpaired t test.</p
Heme exposure of HO-1KO A549 cells leads to lysosomal rupture and loss of viability which is prevented by pre-incubation with DFO.
<p>A549 cells were challenged with 100 Ī¼M heme for 24 hours and then stained with 5 Ī¼g/ml AO. <b>(A)</b> A549 cells deficient in intact lysosomes (āpaleā cells) were measured by flow cytometry. <b>(B)</b> The summary of data shown in (A). Data are means Ā± SEM of 3 independent experiments. *pā¤0.01. <b>(C)</b> A549 cells were pre-treated with 1 mM DFO for 2 hours and then challenged with 100 Ī¼M heme for 24 hours. Cell viability was measured using alamar blue. Data are means Ā± SEM of 3 independent experiments. *pā¤0.05.</p
TLR4 knockdown suppresses heme accumulation in HO-1KO A549 cells.
<p>Following 24 hour transfections with both 10 nM TLR4 and HO-1 siRNAs, the cells were challenged with 100 Ī¼M heme for 6 hours, detached with 0.05% trypsin, washed twice and lysed using snap freezing and thawing. Heme was measured spectrophotometrically. Data are means Ā± SEM of 3 independent experiments. *pā¤0.01.</p
Knockdown of TLR4 in A549 cells suppresses heme-induced intracellular ROS generation.
<p>Following 24 hour transfection with both HO-1 and TLR4 siRNAs the cells were challenged with 100 Ī¼M heme for a further 24 hours. The cells were then detached with 0.05% trypsin and stained with 10 Ī¼M DCFDA at 37Ā°C for 30 minutes. ROS was measured using flow cytometry. Data are means Ā± SEM of 3 independent experiments. *pā¤0.05.</p
HO-1KO in A549 cells sensitizes the cells to heme-mediated cytotoxicity.
<p><b>(A)</b> A549 cells were transfected with the indicated HO-1 siRNA for 24 hours, then treated with or without 100 Ī¼M heme for 36 hours. Western blot shows substantial reduction in HO-1 mRNA expression in cells transfected with HO-1 siRNA. <b>(B)</b> Cells were exposed to 100 Ī¼M heme for 36 hours and viability was assessed with Alamar blue reduction. Data are means Ā± SEM of 6 independent experiments. *pā¤0.01. <b>(C)</b> Human bronchial epithelial cells (HBEC) were transfected with the indicated HO-1 siRNA for 24 hours, and HO-1 expression was measured by western blot. <b>(D)</b> HBEC were transfected with the indicated HO-1 siRNA for 24 hours, then treated with or without 25 Ī¼M heme for 24 hours. Cell viability was measured by Alamar blue reduction.</p