For the second animal model,14 aging (1-year-old) C57Bl/6 and Tph

For the second animal model,14 aging (1-year-old) C57Bl/6 and Tph (−/−) male mice on a background of C57Bl/64, 10 were fed carbon tetrachloride (4 mL/kg CCl4 mixed with an equal volume of soybean oil) three times per week for 6 weeks by gavage (10 animals per group). Data are given as mean and standard deviation (SD). Differences between the groups were assessed by 1-way or 2-way analysis of variance (ANOVA) using an appropriate post-test, including BMN 673 nmr Dunnett’s and Bonferroni post-hoc tests. Differences of tumor weight were assessed with a two-tailed t test. The level of statistical significance was set at P < 0.05. Statistical

analyses were performed with Prism 4.0 (GraphPad) The TMA was analyzed with an SPSS databank (SPSS 12.0). Association between categorical data was tested with the two-tailed χ2 test. Correlation between categorical and continuous data was measured with Kendall’s τ (two-tailed). To test whether 5HT is a mitogen for hepatocellular cancer cells we measured thymidine incorporation in two human hepatocellular cancer cell lines, Huh7 and HepG2. In the presence of 10% fetal calf serum (FCS) thymidine-incorporation was tripled compared to serum-free media (SFM) alone (Supporting Fig. 1A). A dose PD0325901 cost response over six log scales revealed a maximal incorporation of thymidine at 100 μM 5HT (in the absence of FCS), similar

to the activity in the presence of 10% FCS. Qualitative assessment of proliferating cells was performed

with staining of incorporated BrdU and Ki67 (Supporting Fig. 1B). The total number of cells, determined with nuclear Hoechst staining, was lower in SFM compared to media containing 10% FCS or 100 μM 5HT in the absence of serum (Supporting Fig. 1C). Interestingly, the percentage of BrdU- or Ki67-positive cells in relation Adenosine triphosphate to the total number of cells was the same in FCS, SFM, or 5HT. We concluded that the assays reported the number of viable cells, and not whether there was proliferation.16 Therefore, we tested whether 5HT treatment improved cell survival. After 72 hours of serum deprivation almost all cells (Huh7) underwent complete necrotic cell death as demonstrated by light microscopy, calcein/ethidium staining (green cells were alive, red cells were dead), and Hoechst/TUNEL staining (blue cells were alive, green cells were dead) (Fig. 1A). However, upon treatment with 100 μM 5HT, cell death could be prevented and viability was maintained to a similar degree as with standard culture conditions in the presence of 10% FCS. Thus, we concluded that 5HT promotes survival, which was also supported by two different viability assays with both cells lines, Huh7 and HepG2. MTT (Fig. 1B) and CytoTox-Fluor (Fig. 1C) exhibited a dose-dependent increase of vital cells or a decrease of dead cells after stimulation with 5HT.

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