TITLE

CHROMOENDOSCOPY WITH METHYLENE BLUE IN BARRETT'S OESOPHAGUS: ADDING INSULT TO INJURY?

AUTHOR(S)
Olliver, J.R.; Wild, C.P.; Sahay, P.; Dexter, S.P.L.; Hardie, L.J.
PUB. DATE
April 2003
SOURCE
Gut;Apr2003 Supplement 1, Vol. 52, pA5
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Chromoendoscopy with methylene blue (MB) is increasingly being applied during endoscopic examination of Barrett's oesophagus (BO). MB selectively stains specialised intestinal metaplasia as it is specifically absorbed by the goblet cells characterising this tissue. Experimental studies show that photosensitisation of MB with visible light stimulates the formation of singlet oxygen species leading to the generation of single strand breaks and oxidative alterations to guanine residues of which the promutagenic DNA adduct, 8-hydroxydeoxyguanosine (8-OHdG) predominates. We hypothesised that the application of MB to the oesophagus followed by exposure to endoscopic light may stimulate high levels of DNA damage in BO. Biopsies were collected before and after MB exposure from immediately adjacent sites within BO mucosa from 15 patients. Biopsies were subject to DNA damage analysis using the comet assay to detect strand breaks and alkali-labile sites. In addition the enzyme Fapy-DNA glycosylase (FpG) was incorporated into the assay to allow the detection of FpG sensitive sites, including 8-OHdG. For every patient studied, DNA damage levels increased (range 6.0-71.9%) following MB chromoendoscopy. Statistical comparison of matched biopsies revealed a significant difference (p < 0.005) in the DNA damage level before (28.8% (24.6-32.4%), median percentage tail DNA (1st-3rd quartile)) compared to after chromoendoscopy (36.5% (32.1-42.7%)). Following MB chromoendoscopy the percentage of cells with highly damage DNA attributable to FpG sensitive sites, approximately doubled. Barrett's mucosa is a recognised preneoplastic tissue, which exhibits many genetic and epigenetic alterations. Exposing this and any associated dysplasia to further promutagenic DNA damage, via MB chromoendoscopy warrants caution as it could potentially accelerate the carcinogenic process.
ACCESSION #
9747278

 

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