We have investigated the effects of isoflavone
supplementation on NF-jB activation in vivo in
human volunteers [53]. Genistein is an antioxidant
as indicated earlier, thus, soy isoflavone supplementation
is expected to inhibit NF-jB activation and,
in turn, may reduce the oxidative damage in human
lymphocytes. The lymphocytes from healthy male
subjects were harvested from peripheral blood and
cultured for 24 h in the absence and presence of genistein.
EMSA revealed that genistein treatment
inhibited basal levels of NF-jB DNA binding activity
by 56% and abrogated TNF-a induced NF-jB
activity by 50%. Furthermore, when human volunteers
received 50 mg of soy isoflavone supplements
(NovasoyTM) twice daily for 3 weeks, TNF-a failed
to activate NF-jB activity in lymphocytes harvested
from these volunteers, however lymphocytes from
these volunteers collected prior to soy isoflavone
intervention showed activation of NF-jB DNAbinding
activity upon TNF-a treatment ex vivo
[53]. These results demonstrate that soy isoflavone
supplementation has a protective effect against
TNF-a induced NF-jB activation in humans
in vivo. We have also measured the levels of oxidative
DNA damage in the blood of the six subjects
before and after supplementation with NovasoyTM. The results demonstrate that isoflavone supplementation reduced the levels of the 5-OhmdU and decreased oxidative damage in human subjects,which provided strong evidence that soy isoflavone functions as antioxidant, and these effects of genistein could be responsible for its chemopreventive activity [53].