Student Number : 9902006N -
MSc(Med) Dissertation -
School of Medicine -
Faculty of Health Sciences / Hepatocellular carcinoma (HCC) is the most common primary malignant tumour of
the liver. Aflatoxin B1 (AFB1) is a potent hepatocarcinogen, and dietary iron overload
has been shown to contribute to HCC development in black africans. Both are well
studied hepatotoxins. The aim of this study was to use a Wistar rat model over a 12
month period to investigate synergy and the extent thereof between AFB1 ingestion
and dietary iron overload. 25ug/day of AFB1, reconstituted in DMSO, was
administered by gavaging the animals, over a period of 10 days with a 2 day interval
in between. The chow diet was supplemented with 0.75% (w/w) ferrocene iron.
Experimental subjects were divided into 4 groups. Group 1 was fed the normal chow
diet. Group 2 was fed 0.75% (w/w) ferrocene iron alone. Group 3 was gavaged 250μg
AFB1 alone. Group 4 was fed the 0.75% (w/w) ferrocene iron and gavaged 250μg
AFB1. A number of assays were conducted to investigate synergy. Colorimetric assays
were used to measure serum iron, total-iron binding capacity, ALT, AST, GGT, nitrite
production, lipid peroxidation and hydroxyproline concentrations. ELISA’s were used
to determine ferritin, 8-isoprostane and 8-hydroxyguanosine concentrations. Nontransferrin
bound iron was measured using an HPLC method. A chemiluminescent
assay was used to measure superoxide anion production. Cytokines were measured
using a suspension array system. Mutagenicity was assessed using the Ames
mutagenicity assay using salmonella typhimirium strains TA97, TA98, TA100 and
TA102. Iron profiling indicated that iron overloading occurred with the ingestion of
the ferrocene diet. Biomarkers of oxidative stress, as illustrated by the measurement
of 8-hydroxyguanosine and lipid peroxidation, showed additive synergistic effects
between the two carcinogens. The anti-inflammatory interleukin-10 was shown to be
markedly elevated with the co-administration of the two carcinogens, indicating the elevated inflammatory processes. Additive synergistic effects were noted in terms of
the liver disease marker ALT. The salmonella typhimirium strain TA102 used in the
Ames mutagenicity test showed increased colony counts with respect to the coadministration
of carcinogens (P<0.05), although no synergistic effect was noted. In a
few of the presented parameters, the AFB1 group was not significantly different to the
control group, although significant differences between the Fe group and the Fe +
AFB1 groups were noted. The implication of which is that the presence of AFB1 is
increasing the activity of Fe as a carcinogen, thereby acting as a co-carcinogen.
Examples of such parameters illustrating this are presented in the results section
including serum ALT, serum nitrite, liver and serum lipid peroxidation, liver and
serum 8-hydroxyguanosine, some of the mutagenicity assays, and interleukin-10.
The conclusion of this study suggests that AFB1 acts as a co-carcinogen in the
presence of iron overloading, implying that a synergistic relationship between these
two toxins exists.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/2093 |
| Date | 22 February 2007 |
| Creators | Bronze, Michelle Saltao |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 4190980 bytes, application/pdf, application/pdf |
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