Human serum albumin （HSA） is a plasma protein responsible for the binding and transport of fatty acids and a variety of exogenous chemicals such as drugs and environmental pollutants. Such binding plays a crucial role in determining the ADME （absorption, distribution, metabolism, and excretion） and bioavailability of the pollutants. The binding interaction between HSA and acetic acid （C2）, octanoic acid （C8） and dodecanoic acid （C12） has been investigated by the combination of site-specific fluorescent probe, tryptophan intrinsic fluorescence and tyrosine electrochemistry. For the study of the fatty acid interaction with the two drug-binding sites on HSA, two fluorescent probes, dansylamide and dansyl-L-proline were employed in the displacement measurements. Intrinsic fluorescence of tryptophan in HSA was monitored upon addition of the fatty acids into HSA. Electrocatalyzed response of the tyrosine residues in HSA by a redox mediator was used to investigate the binding interaction. Qualitatively, observations from these three approaches were very similar. HSA did not show any change in the fluorescence and electrochemical experiments after mixing with C2, suggesting there is no significant interaction with the short-chain fatty acid. For C8, the measured signal dropped in a single-exponential mode, indicating an independent and non-cooperative binding. The calculated association constant and binding ratio were 3.1 × 10^6 L/mol and 1 with drug binding Site Ⅰ, 1.1 × 107 L/mol and 1 with Site Ⅱ, and 7.0× 0^4 L/mol and 4 with the tryptophan site, respectively. The measurements with C12 displayed multiple phases of fluorescence change, suggesting cooperativity and allosteric effect of the C12 binding. These results correlate well with those obtained by the established methods, and validate the new approach as a viable tool to study the interactions of environmental pollutants with biological molecules.
CHEN Yan-Min,GUO Liang-Hong State Key Laboratory of Environmental Chemistry and Ecotoxicology,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences,Beijing 100085,China.
Objective In order to investigate the potential mechanisms in troglitazone-induced apoptosis in HT29 cells,the effects of PPARγ and POX-induced ROS were explored.Methods [3-（4,5）-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide （MTT） assay,Annexin V and PI staining using FACS,plasmid transfection,ROS formation detected by DCFH staining,RNA interference,RT-PCR RT-QPCR,and Western blotting analyses were employed to investigate the apoptotic effect of troglitazone and the potential role of PPARγ pathway and POX-induced ROS formation in HT29 cells.Results Troglitazone was found to inhibit the growth of HT29 cells by induction of apoptosis.During this process,mitochondria related pathways including ROS formation,POX expression and cytochrome c release increased,which were inhibited by pretreatment with GW9662,a specific antagonist of PPARγ.These results illustrated that POX upregulation and ROS formation in apoptosis induced by troglitazone was modulated in PPARγ-dependent pattern.Furthermore,the inhibition of ROS and apoptosis after POX siRNA used in troglitazone-treated HT29 cells indicated that POX be essential in the ROS formation and PPARγ-dependent apoptosis induced by troglitazone.Conclusion The findings from this study showed that troglitazone-induced apoptosis was mediated by POX-induced ROS formation,at least partly,via PPARγ activation.
The fate of the high production volume,currently in use,and not regulated non-polybrominated diphenyl ether(PBDE) flame retardants,such as tetrabromobisphenol A(TBBPA) ,hexabromocyclododecane(HBCD) and dechlorane plus(DP),and the alternative flame retardants of PBDE,such as BTBPE and DBDPE,in the environment has attracted increasing attention and aroused concern due to the increasing regulation and phasing-out of PBDEs.This paper reviews the distribution,bioaccumulation,human exposure and environmental behavior of those non-PBDE flame retardants in various environmental compartments.The data gaps and needs for future research are discussed.
LUO XiaoJun,CHEN SheJun,MAI BiXian & FU JiaMo State Key Laboratory of Organic Geochemistry
