The modifying effects of dietary feeding of a polyisoprenylated benzophenon
e, garcinol, isolated from Garcinia indica fruit rind on the development of
azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were investig
ated in male F344 rats. We also assessed the effects of garcinol on prolife
rating cell nuclear antigen (PCNA) index in ACF and activities of detoxifyi
ng enzymes of glutathione S-transferase (GST) and quinone reductase (QR) in
liver. In addition, we examined the effects of garcinol on 12-O-tetradecan
oylphorbol-13-acetate-induced O-2(-) generation in differentiated human pro
myelocytic HL-60 cells and lipopolysaccharide (LPS)- and interferon (IFN)-g
amma-induced nitric oxide (NO) generation in mouse macrophage RAW 264.7 cel
ls. Western blotting analysis of inducible nitric oxide synthase (iNOS) and
cyclooxygenase-2 (COX-2) expression was done in LPS- and IFN-gamma-treated
mouse macrophage RAW 264.7 cells. Rats were given subcutaneous injections
of AOM (15 mg/kg body wt) once a week for 3 weeks to induce ACF, They also
received the experimental diet containing 0.01 or 0.05% garcinol for 5 week
s, starting 1 week before the first dosing of AOM, AOM exposure produced 97
+/- 15 ACF/rat at the end of the study (week 5), Dietary administration of
garcinol caused significant reduction in the frequency of ACF: 72 +/- 15 (
26% reduction, P < 0.01) at a dose of 0.01% and 58 +/- 8 (40% reduction, P
< 0.001) at a dose of 0.05%. Garcinol administration significantly lowered
PCNA index in ACF. Feeding of garcinol significantly elevated liver GST and
QR activities. In addition, garcinol could suppress O-2(-) and NO generati
on and expression of iNOS and COX-2 proteins. These findings might suggest
possible chemopreventive ability of garcinol, through induction of liver GS
T and QR, inhibition of O-2(-) and NO generation and/or suppression of iNOS
and COX-2 expression, on colon tumorigenesis.