Activin A is stimulated by tumor necrosis factor-alpha and modulates collagen gene expression in human amniotic cells.

BACKGROUND: Accumulating evidence supports the idea of activin A as a modulator of inflammation. In human pregnancy, elevated activin A concentrations in amniotic fluid are reported in women with intra-amniotic infection and inflammation- induced pre-term birth. AIM: To test the hypothesis that activin A was involved in the pathophysiology of amnionitis, we evaluated the effects of tumor necrosis factor-α and lipopolysaccharide on activin A production in human amniotic epithelial cells, and the effects of activin A on the expression of collagen mRNA in amniotic mesenchymal cells. MATERIALS AND METHODS: Amniotic membranes were obtained from patients without systemic disease, signs of premature delivery or fetal complications, during elective cesarean sections at term. Amniotic epithelial cells and mesenchymal cells were separately obtained by enzymatic digestion and cultured. Activin A was measured by enzyme-linked immunosorbent assay and collagen mRNA levels were assessed by quantitative PCR. RESULTS: Amniotic epithelial cells produced activin A in a cell density- and time-dependent manner. Tumor necrosis factor- α enhanced activin A production in a time-dependent (48-120 h) and dose-dependent (10-300 ng/ml) manner in amniotic epithelial cells. Lipopolysaccharide also stimulated activin A production, but the effect was less prominent. In amniotic mesenchymal cells, the effect of activin A on the expression of type I and type III collagen mRNA was suppressive. CONCLUSIONS: Tumor necrosis factor-α and lipopolysaccharide stimulated activin A production in amniotic epithelial cells, and activin A modulated expression of collagen mRNA in amniotic mesenchymal cells. These results support the idea that activin A is involved in the pathophysiology of amnionitis.

Cimetidine enhances the antiproliferative effect of 5-fluorouracil on colon carcinoma SW620.

We investigated the effects of cimetidine on p-glycoprotein and on the antiproliferative effect of various anticancer drugs which are recognized by p-glycoprotein. We used colon carcinoma SW620 cells and their doxorubicin resistant SW620 Ad300 derived cells, the latter express p-glycoprotein and have multidrug resistance phenotype. To assess the effect of cimetidine on the efflux activity of p-glycoprotein, we examined its effects on the accumulation of rhodamine123 which is recognized by p-glycoprotein. Cimetidine had no effect on rhodamine123 accumulation on either cell line. Cimetidine did not enhance the antiproliferative effect of any of the anticancer drugs investigated. This indicates that cimetidine was not recognized by p-glycoprotein. However, cimetidine remarkably enhanced the antiproliferation effects of 5-fluorouracil on SW620 cells, not those of 5-fluorouracil on SW620 Ad300, whereas cimetidine itself showed little effect on antiproliferation. This finding indicates that combination therapy using 5-fluorouracil and cimetidine might be useful for cancer patients.

In archaebacteria, there is a doxorubicin efflux pump similar to mammalian P-glycoprotein.

We selected for study an anthracycline-resistant mutant from the archaebacteria Haloferax volcanii. This resistance was reversed by a Ca(2+)-channel antagonist, nifedipine (NDP). This resistance and its reversal by NDP suggest P-glycoprotein (Pgp) to be responsible for maintaining an anticancer drug concentration below the cytotoxic level. Using rhodamine 123 (RH123) as a substrate for Pgp, we then examined whether the resistance to anthracyclines in this bacteria might involve a Pgp-like anthracycline efflux pump. RH123 accumulation by the bacteria was determined with flow cytometry. A steady-state RH123 accumulation by the resistant cells revealed approx. one-fifteenth of that by the wild-type cells, which could be remarkably enhanced by NDP. The other modulators of Pgp, diltiazem and verapamil, also enhanced RH123 accumulation in resistant cells. The uncoupler FCCP completely restored RH123 accumulation in resistant cells to the wild-type cell level. RH123 unidirectional efflux from resistant cells after its preloading revealed much greater than that from wild-type cells, which was remarkably inhibited by FCCP. These confirmed that RH123 low accumulation involves its active efflux mechanism. Taken together, the present study indicated that lower evolutionary archaebacteria might also express a Pgp-like protein very similar to mammalian Pgp.