Correlations between Environmental Variables and Bacterial Community Structures Suggest Fe(III) and Vinyl Chloride Reduction As Antagonistic Terminal Electron-Accepting Processes

Natural attenuation of anaerobic aquifers contaminated with tetrachloroethene (PCE) often results in the accumulation of the intermediates <i>cis</i>-dichloroethene and vinyl chloride (VC) which are even more toxic than the parent compound. Reasons for this accumulation were investigated in a PCE-contaminated aquifer in which VC accumulation has previously been shown to occur using stable isotope techniques. Multifactorial analysis of bacterial community structure data and environmental variables showed that in general terminal electron-accepting processes were shaping the bacterial community structures. Both VC and Fe­(III) reduction were key but antagonistic terminal electron-accepting processes. The phylogenetic affiliation of terminal restriction fragments (T-RFs), together with correlation analyses, showed that T-RFs having significant correlation with VC reduction were closely affiliated to the genus <i>Dehalococcoides</i> and to uncultured bacteria belonging to the “Lahn Cluster” within the class <i>Dehalococcoidetes</i>. A T-RF that negatively correlated with a “Lahn Cluster” T-RF was affiliated to the genus <i>Rhodoferax</i> that contains members identified as iron-reducing bacteria. The higher affinity of Fe­(III)-reducing bacteria for hydrogen compared with VC-reducing bacteria might explain why VC accumulated locally at the studied site. In conclusion, the combination of molecular and numerical ecology approaches was helpful to identify reasons for the accumulation of toxic dechlorination intermediates and could become a useful tool for characterizing contaminated sites in general

Fn14•TRAIL induces death of HCC cell lines in a dose dependent manner.

<p>SK-HEP-1 (<b>A</b>) HCC cells were incubated with indicated concentrations of Fn14•TRAIL for 72 [left panel], 48 and 24 hours [right panel]. (<b>B</b>,<b>C</b>) HepG2 [B, left panel] and Huh7 [B, right panel] HCC cell lines, as well as NKNT3 [C, left panel] and FHB [C, right panel] hepatocyte cell lines, were incubated with indicated concentrations of Fn14•TRAIL for 48 and 24 hours. Viable cells were stained with trypan blue and counted. Results represent the mean +/- SE of 3 independent experiments (* <i>p</i> < 0.05 ** <i>p</i> < 0.01 vs no Fn14•TRAIL). </p

Fn14•TRAIL is more potent than soluble forms of Trail and Fn14 alone or in combination.

<p>(<b>A</b>) SK-HEP-1 [A, left panel], HepG2 [A, middle panel] and Huh7 [A, right panel] HCC cell lines, as well as NKNT3 [B, left panel] and FHB [B, right panel] hepatocyte cell lines, were incubated with 0, 3, 30 or 300 ng/ml of Fn14•TRAIL, TRAIL, Fn14-Fc or combination of the later two for 48 hours. Viable cells were stained with trypan blue and counted. The results represent the mean +/- SD of three independent experiments (* <i>p</i> ≤ 0.05). (<b>B</b>) HepG2 HCC cells were incubated with 30ng/ml Fn14•TRAIL for 24 hours, in the presence or absence of anti Fn14 or anti TRAIL blocking antibodies. Treated cells were stained by Annexin V-FITC and Propidium Iodide, and counted by flow cytometer (2x10⁴ cells per sample). The results represent the mean +/- SD of two independent experiments (* p ≤ 0.05).</p

HCC and hepatocyte cell lines express TRAIL, TRAIL receptors, Fn14 and TWEAK.

<p>(<b>A</b>) The mRNA expression level of TRAIL, TRAIL receptors (DR4, DR5, DCR-1, DCR-2, OPG), Fn14 and TWEAK was determined by quantitive real-time PCR analysis. A representative experiment of three independent experiments is shown. Data are shown as average of triplicates (SD < 0.3), normalized against two endogenous control human genes, TBP and Actin-B, as calculated by Dataassist v2.0 software. (<b>B</b>,<b>C</b>) Protein expression of TRAIL, TRAIL receptors (DR4, DR5, DcR1, DcR2), Fn14 and TWEAK was determined by flow cytometeric analysis. (<b>D</b>) Fn14•TRAIL binds to HCC cells – HepG2 cells were incubated with Fn14•TRAIL, soluble TRAIL, Fn14 or the combination of the latter for 30 min at 4°c, immune-stained with PE-conjugated anti-Fn14, and analyzed by flow-cytometry. The results represent the mean +/- SD of triplicates (* <i>p</i> ≤ 0.05). </p

Molecular analysis of the Fn14•TRAIL.

<p>(A) The amino-acid sequence of the Fn14-TRAIL protein. The amino-acid sequence of the extra-cellular domain of human Fn14 (amino-acids 1-52 of the mature protein, marked in bold letters) are directly linked to the extra-cellular domain of human TRAIL (amino-acids 53-217 of the mature protein, non-bold letters). The underlined sequence represents the signal-peptide of the human Urokinase protein, utilized to secrete Fn14-TRAIL out of the cell and removed from the mature protein. (B) Fn14-TRAIL separated at denaturizing conditions on SDS-PAGE, Coomassie gel staining. (C) Western blot analysis with anti-TRAIL and anti-Fn14 primary antibodies. </p

No hepatotoxicty is observed in Fn14•TRAIL treated mice.

<p>HepG2 Nude mice were treated daily with subcutaneous injections of 200μg of Fn14•TRAIL (n=4) or vehicle (n=4) for 8 days. One hour after last injection blood counts (<b>A</b>) liver enzymes and urea (<b>B</b>) were measured. Livers were harvested and H&E stained sections were tested (<b>C</b>). Data are presented as mean +/- S.E. </p