The tumour
necrosis factor-alpha (TNF) inhibitory activity of
hamamelitannin from Hamamelis virginiana was investigated by assessing the TNF-mediated EAhy926 endothelial cell death and adhesiveness to monocytes. Treatment of the cells by TNF (25 ng/ml) and
actinomycin D (0.1ng/ml) resulted in significant DNA fragmentation (34+/-0.6, n=4) and cytotoxicity (97+/-4.5%, n=6) following treatment for 8 and 24h, respectively. One to 100 microM concentrations of
hamamelitannin inhibited the TNF-mediated endothelial cell death and DNA fragmentation in a dose-dependent manner. One hundred % protection against TNF-induced DNA fragmentation and cytotoxicity was obtained for
hamamelitannin concentrations higher than 10 microM. The protective effect of
hamamelitannin was comparable with that of a related compound
epigallocatechin gallate while
gallic acid was a weak
protective agent (<40% protection). EAhy926 endothelial cells upregulated (by 4- to 7-fold) the surface expression of
intercellular adhesion molecule-1 (ICAM-1) and adhesiveness to monocytic U937 cells
after treatment with TNF (0.5ng/ml) for 6 or 24h. Concentrations (1-100 microM) of
hamamelitannin that inhibited the TNF-mediated cell death and DNA fragmentation, however, failed to inhibit the TNF-induced
ICAM-1 expression and EAhy926 cell adhesiveness to U937 cells. Thus,
hamamelitannin inhibits the TNF-mediated endothelial cell death without altering the TNF-induced upregulation of endothelial adhesiveness. The observed anti-TNF activity of
hamamelitannin may explain the antihamorrhaegic use of H. virginiana in
traditional medicine and its claimed use as a
protective agent for UV radiation.