Concerns about the risk of titanium dioxide nanoparticles (TiO2 NPs) to human health and environment are gradually increasing due to their wide range of applications. In this study, cytotoxicity, DNA damage, and apoptosis induced by TiO2 NPs (5 nm) in A549 cells were investigated. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays revealed the time- and concentration-dependent cytotoxic effects of TiO2 NPs in a concentration range of 50 to 200 μg/mL. A statistically significant (p < 0.05) induction in DNA damage was observed by the comet assay in cells exposed to 50 to 200 μg/mL TiO2 NPs for 48 h. A significant (p < 0.05) induction in micronucleus formation determined by 4,6-diamino-2-phenylindole (DAPI) staining was also observed at the above concentrations. Typical apoptotic morphological feature and apoptotic bodies in A549 cells induced by TiO2 NPs at the above concentrations were observed by scanning electron micrographs. Flow cytometric analysis demonstrated that the cells treated with TiO2 NPs at concentrations of 100 and 200 μg/mL showed a significant G2/M phase arrest and a significant increased proportion of apoptotic cells. TiO2 NPs also disrupted the mitochondrial membrane potential evaluated by rhodamine 123 staining. Further analysis by quantitative real-time PCR (qRT-PCR) indicated that the expression of caspase-3 and caspase-9 messenger RNA (mRNA) was increased significantly at the concentrations of 100 and 200 μg/mL TiO2 NPs for 48 h. Taken together, these findings suggest that TiO2 NPs can inhibit A549 cell proliferation, cause DNA damage, and induce apoptosis via a mechanism primarily involving the activation of the intrinsic mitochondrial pathway. The assay data provide strong evidence that TiO2 NPs can induce cytotoxicity, significant DNA damage, and apoptosis of A549 cells, suggesting that exposure to TiO2 NPs could cause cell injury and be hazardous to health.
Lead (Pb), a heavy metal which is widely recognized as an environmental toxicant, is transported from the earth's crust into the human body to a significant extent.
The effect of extracts
from four types
of tea made from Camelia sinensis (green,
white, black, and oolong) on in vitro amylolysis
of gelatinized starch and the underlying mechanisms were studied.
Of the four extracts, black tea extract (BTE) gave the strongest inhibition
of starch digestion and on α-amylase activity. Fluorescence
quenching and surface plasmon resonance (SPR) showed compounds in
BTE bound to α-amylase more strongly than those in the green,
white, and oolong tea extracts. Individual testing of five phenolic
compounds abundant in tea extracts showed that theaflavins had a greater
inhibitory effect than catechins on α-amylase. SPR showed that
theaflavins had much lower equilibrium dissociation constants and
therefore bound more tightly to α-amylase than catechins. We
conclude that BTE had a stronger inhibitory effect on in vitro enzymatic starch digestion than the other tea extracts, mainly due
to the higher content of theaflavins causing stronger inhibition of
α-amylase.
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