Antiproliferative and proapoptotic effects of tocopherol and tocol on activated hepatic stellate cells

A bioactive product lipoxin A4 attenuates liver fibrosis in an experimental model by regulating immune response and modulating the expression of regeneration genes

BACKGROUND/AIMS

Lipoxin A4 (LXA4), an anti-inflammatory lipid mediator, regulates leukocyte cellular activity and activates gene transcription. The therapeutic effect of LXA4 on liver fibrosis and its mechanism on the immune system are largely unknown. Because the regenerative capacity of hepatocytes in acute and chronic liver failure models of mouse increases by silencing MKK4, we aimed to investigate the effect of parenteral administration of LXA4 on the genes responsible for regeneration of liver, namely MKK4, MKK7, and ATF2, and visualize the therapeutic effects in an experimental model.

MATERIALS AND METHODS

Fibrosis was induced in mice by administration of thioacetamide (TAA). LXA4 was administered during the last two weeks of fibrosis induction. The fibrosis level was measured by Knodell scoring. The liver function was measured by analyzing serum ALT, AST, and AP levels. Expression levels of genes responsible for liver fibrosis (TGF-α) and cell regeneration (MKK4, MKK7, and ATF2) have been measured by RT-PCR analysis. Inflammatory and anti-inflammatory cytokine levels were measured in serum samples and liver homogenates by Enzyme Linked Immunosorbent Assay (ELISA). Ultrathin sections were examined using a transmission electron microscope and analyzed.

RESULTS

We observed significant healing in liver of the LXA4-treated group, histologically. This finding was in parallel with reduction of serum ALT, AST, but not AP levels. TGF-α and MKK4 expressions were significantly reduced in the LXA4-treated group. Administration of LXA4 caused significant elevation of IL-10 in systemic circulation; however, that elevation was not detected in liver homogenates. Nevertheless, significant reductions in TNF-α and IL-17 have been observed.

CONCLUSION

The anti-inflammatory effect of LXA4 maintains the regenerative capacity of liver during fibrosis in an experimental liver fibrosis model. LXA4 may be therapeutically beneficial in liver fibrosis.

Induction of Anoikis in Human Colorectal Cancer Cells by Fucoxanthinol

Fucoxanthin (Fx), one of the major xanthophylls in brown algae, is known to be effective for colorectal cancer (CRC) chemoprevention through inhibiting cell growth, cell cycle and caspase activation. Recently, we observed fucoxanthinol (FuOH), an anti-cancer active metabolite of Fx, treatment of human CRC cells resulted in plenty of living floating cells several hours after exposure, and induced apoptosis. In the present study, we investigated whether FuOH induced anchorage-dependent apoptosis, that is "anoikis", along with integrin signal suppression in human CRC cells. We found that cells exposed to 2.5 μM FuOH clearly showed anti-proliferative and apoptotic effects to DLD-1 cells, human CRC cells. FuOH treatment of DLD-1 cells led to an increase in anoikis-like changes represented by Calcein AM negative/ethidium homodimer-1 positive cell and living floating cells. Moreover, FuOH decreased FAK activation, and altered integrin β1 expression and distribution after 6 h treatment. After 24 h, the cells decreased PPARγ expression and Akt activation and increased integrin β1 expression. Our findings suggested that FuOH can induce anoikis in CRC cells through suppression of integrin signals in human CRC cells.