engleski

Immunohistochemistry of the HNE-protein adducts in colon of rats: Study on the dietary influences on lipid peroxidation in colon carcinogenesis

Meta-analysis of epidemiological studies have demonstrated a moderate but significant association between red meat intake and colorectal cancer risk. A recent epidemiological study and experimental studies in rats have associated this increased risk to haem iron of red meat. There are several reasons for this, among which oxidative stress and consequential lipid peroxidation may be considered as an essential pathological background of thus supported carcinogenesis. Since 4-hydroxynonenal (HNE) is also commonly considered as the end product of lipid peroxidation acting as a “ second toxic messenger of free radicals” as well as a growth regulating substance we analyzed presence of HNE-protein adducts in the colon tissues of rats fed on different types of diet. Usual PAP-DAB staining was applied for genuine HNE-histidine monoclonal antibodies used on formalin-fixed paraffin embedded specimens of rats fed on various diets for 14 weeks. The control AIN76-based group (CD) was a low-calcium diet (20 µ mol/g) containing 5% safflower oil. The effect of haem was studied with a haemin-supplemented diets (HH: 1.5 µ mol/g) and diet with haemoglobin (HG: 0.36 µ mol/g). The effect of antioxidants was investigated with a HH diet supplemented with 0.05% butylated hydroxyanisole and rutin (HH+AO). The effect of oil was investigated by replacing safflower oil with olive oil (5%) in a HH diet given (HH+OO). A group of rats received control diet, supplemented with olive oil (CD+OO). The immunohistochemistry of HNE-protein adducts revealed that CD group had slight domination of HNE positivity in proximal colon in comparison to distal and in particular central part. In most cases connective tissue was more positive than epithelium. In HG major positivity seemed to be in colon medium, but there were no obvious differences between CD and HG for proximal and distal part. In HH group there were no regional distributions of the HNE-positivity (unlike CD). In CD + OO indices of “ lack of HNE” in central part of colon were obtained, while HNE was less present than in CD without OO. In HH + OO the proximal part was more positive than the other parts indicating the loss of HNE-immunopositivity due to the olive oil diet, while the samples of the HH + AO group were also entirely negative for HNE. Since it is known that HNE immunopositivity is often found in colon it seems that in the colon tissues HNE-protein adducts might disappear in early stages of carcinogenesis. Interestingly, regional distribution of HNE-protein adducts in normal and altered colon tissues of the rats studied resembled this usual frequency of distribution of colon malignancies in humans. However, it has yet to be evaluated what are the basis of disappearance and reappearance of HNE-protein adducts in colon tissues during carcinogenesis and in dependence of specific diets. The findings of effectiveness of specific diets with olive oil and antioxidants might further indicate usefulness of the HNE-immunohistochemistry to evaluate not only carcinogenesis itself but also efficiency of cancer therapy and cancer prevention protocols.

lipid peroxidation; colon carcinogenesis

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