Detection of oxidative DNA damage in oesophageal biopsies of patients with reflux symptoms and normal pH monitoring

Curcumin abrogates bile-induced NF-κB activity and DNA damage in vitro and suppresses NF-κB activity whilst promoting apoptosis in vivo, suggesting chemopreventative potential in Barrett's oesophagus

INTRODUCTION

Curcumin has been suggested to possess anti-neoplastic properties. As oesophageal adenocarcinoma (OA) and Barrett's oesophagus (BO) represent a neoplastic series, we postulated that curcumin supplementation may slow neoplastic progression at this site. Our aim was to investigate the effects of curcumin in vitro and in vivo on markers of oesophageal cancer progression.

METHODS

We investigated the in vitro ability of curcumin to prevent bile acid-induced DNA damage using micronucleus assay and nuclear factor-kappaB (NF-κB) activity in the oesophageal cell lines (OE33) using real-time PCR of the extracted RNA. We also analysed NF-κB p65 activation in curcumin-pre-treated OE33 cells exposed to deoxycholic acid (DCA) using ELISA. In another pilot study, BO patients took a daily 500 mg curcumin tablet for 7 days prior to their endoscopy. In biopsies collected from these patients (n=33, 16 curcumin, 17 control), we examined NF-κB-driven gene expression (interleukin (IL)-8, inhibitor- kappaB (I-κB)) using real-time PCR of the extracted RNA from the biopsy sample. The apoptotic frequency was assessed by counting the number of apoptotic bodies in the epithelial cells from the Barrett's tissue with and without curcumin.

RESULTS

In vitro, curcumin (50 μM) significantly abrogated DNA damage and NF-κB activity induced by bile. Pretreating OE33 cells with curcumin (50 μM) completely abolished the ability of DCA (300 μM) to activate NF-κB. In vivo, IL-8 expression was non-significantly suppressed in the curcumin-supplemented patients compared to the squamous control tissue, whilst also showing a doubling in the apoptotic frequency compared to non-supplemented control patients.

CONCLUSIONS

Curcumin abrogated bile-driven effects in vitro. The in vivo data also suggests that curcumin supplementation had beneficial effects (increased apoptosis, potentially reduced NF-κB activity) in the Barrett's tissues themselves, despite poor delivery of the curcumin to the oesophagus.

Immunochemical detection of oxidatively damaged DNA

Oxidatively damaged DNA is implicated in various diseases, including neurodegenerative disorders, cancer, diabetes, cardiovascular and inflammatory diseases as well as aging. Several methods have been developed to detect oxidatively damaged DNA. They include chromatographic techniques, the Comet assay, (32)P-postlabelling and immunochemical methods that use antibodies to detect oxidized lesions. In this review, we discuss the detection of 8-oxo-7,8-dihydro-29-deoxyguanosine (8-oxodG), the most abundant oxidized nucleoside. This lesion is frequently used as a marker of exposure to oxidants, including environmental pollutants, as well as a potential marker of disease progression. We concentrate on studies published between the years 2000 and 2011 that used enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry to detect 8-oxodG in humans, laboratory animals and in cell lines. Oxidative damage observed in these organisms resulted from disease, exposure to environmental pollutants or from in vitro treatment with various chemical and physical factors.

Functional heartburn: what it is and how to treat it

Functional heartburn is considered one of the most common functional esophageal disorders. The disorder is more common in young women and is associated with other functional bowel disorders and psychological co-morbidity, primarily somatization. The etiology of functional heartburn remains unknown. Most patients, however, demonstrate esophageal hypersensitivity. Functional heartburn has been identified as the main cause for proton pump inhibitor (PPI) failure in patients with heartburn. Treatment is still a challenge, and patients should be started with PPI treatment. In non-responders, escalation of the PPI dose could be attempted and, if unsuccessful, pain modulators should be prescribed.

p16 mutation spectrum in the premalignant condition Barrett's esophagus

Background

Mutation, promoter hypermethylation and loss of heterozygosity involving the tumor suppressor gene p16 (CDKN2a/INK4a) have been detected in a wide variety of human cancers, but much less is known concerning the frequency and spectrum of p16 mutations in premalignant conditions.

Methods and Findings

We have determined the p16 mutation spectrum for a cohort of 304 patients with Barrett's esophagus, a premalignant condition that predisposes to the development of esophageal adenocarcinoma. Forty seven mutations were detected by sequencing of p16 exon 2 in 44 BE patients (14.5%) with a mutation spectrum consistent with that caused by oxidative damage and chronic inflammation. The percentage of patients with p16 mutations increased with increasing histologic grade. In addition, samples from 3 out of 19 patients (15.8%) who underwent esophagectomy were found to have mutations.

Conclusions

The results of this study suggest the environment of the esophagus in BE patients can both generate and select for clones with p16 mutations.

Reactive oxygen species and chemokines: Are they elevated in the esophageal mucosa of children with gastroesophageal reflux disease?

AIM: To determine the role of inflammatory cytokines and reactive oxygen species (ROS) in childhood reflux esophagitis.

METHODS: A total of 59 subjects who had complaints suggesting GERD underwent esophagogastroduodenoscopy. Endoscopic and histopathologic diagnosis of reflux esophagitis was established by Savary-Miller and Vandenplas grading systems, respectively. Esophageal biopsy specimens were taken from the esophagus 20% proximal above the esophagogastric junction for conventional histopathological examination and the measurements of ROS and cytokine levels. ROS were measured by chemiluminescence, whereas IL-8 and MCP-1 levels were determined with quantitative immunometric ELISA on esophageal tissue. Esophageal tissue ROS, IL-8 and MCP-1 levels were compared among groups with and without endoscopic/histo-pathologic esophagitis.

RESULTS: Of 59 patients 28 (47.5%) had normal esophagus whereas 31 (52.5%) had endoscopic esophagitis. In histopathological evaluation, almost 73% of the cases had mild and 6.8% had moderate degree of esophagitis. When ROS and chemokine levels were compared among groups with and without endoscopic esophagitis, statistical difference could not be found between patients with and without esophagitis. Although the levels of ROS, IL-8 and MCP-1 were found to be higher in the group with histopathological reflux esophagitis, this difference was not statistically significant.

CONCLUSION: These results suggest that the grade of esophagitis is usually mild or moderate during childhood and factors apart from ROS, IL-8 and MCP-1 may be involved in the pathogenesis of reflux esophagitis in children.

Duodenal Reflux Leads to Down Regulation of DNA Mismatch Repair Pathway in an Animal Model of Esophageal Cancer

BACKGROUND

Gastroduodenal reflux is implicated in esophageal carcinogenesis. This effect is mediated by reactive oxygen species. We hypothesized that this is mediated by DNA mismatch lesion 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxoG), which is repaired by the Mut Y homologue (MYH). We tested the effect of reflux, either alone or in combination with the human dietary mutagen methyl-n-amyl nitrosamine (MNAN), on DNA damage in adenocarcinoma and squamous cell cancer of the esophagus in a rat model.

METHODS

Reflux was promoted in male Sprague-Dawley rats by duodenoesophageal anastomosis (8 weeks) without gastric bypass. MNAN treatment (25 mg/kg per week intraperitoneally for four doses) commenced at 10 weeks age. Ten animals served as controls. Quantification of 8-oxoG was performed by using immunohistochemistry, and MYH was analyzed by Western blot. Apoptosis was assessed by terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling (TUNEL), cytochrome C, and caspase.

RESULTS

Tumors (adenocarcinoma) developed in 15 (50%) of 30 animals with reflux alone; this increased to 26 (86.6%) of 30 when reflux was combined with MNAN treatment, with tumor histology consistent with adenosquamous and squamous cell cancer. DNA damage, as reflected by positive 8-oxoG staining in reflux groups, was significantly increased compared with control (p < 0.01), and this was maximal in tissues with malignant transformation. Protein levels of the DNA repair enzyme MYH were significantly less in tissues subjected to reflux compared with controls (p < 0.05). TUNEL, cytochrome C, and caspase positivity confirmed increased apoptosis in cancer lesions.

CONCLUSIONS

Gastroduodenal reflux leads to increased DNA damage and downregulation of the DNA mismatch repair pathway. This pathway has an important role in esophageal carcinogenesis in rats.

Selective decrease in the DNA base excision repair pathway in squamous cell cancer of the esophagus

OBJECTIVES

Oxidative damage can lead to a highly mutagenic 8-oxoguanine lesion, which mispairs with adenosine residues, leading to G:C-->T:A transversions. In mammalian cells 8-oxoguanine glycosylase initiates the DNA base excision repair pathway to repair the 8-oxoguanine lesion. To date, there is no information regarding oxidative DNA damage and repair pathways in esophageal cancer. Therefore we designed the current study to demonstrate the DNA damage and repair pathways in esophageal cancer by expression of 8-oxoguanine glycosylase in reflux-induced and mutagen (methyl-n-amyl nitrosamine)-induced DNA damage and apoptosis in esophageal tumors.

METHODS

Gastroduodenal reflux was surgically created in male Sprague Dawley rats (n = 120). Half of the animals received methyl-n-amyl nitrosamine. Animals not undergoing operations served as control animals (n = 10). The experiment concluded 30 weeks postoperatively. Immunohistochemistry for 8-oxoguanine and 8-oxoguanine glycosylase was assessed by 2 independent observers. Protein expression was assessed by using the Western blot method.

RESULTS

There was significantly more DNA damage in both adenocarcinoma (n = 15) and squamous cell carcinoma (n = 19), as exemplified by positive 8-oxoguanine expression compared with that seen in control animals (P < .05). 8-Oxoguanine glycosylase was several folds upregulated in adenocarcinoma (P < .05), but there was significantly decreased expression in squamous cell carcinoma (P < .01). The apoptosis was assessed as caspase-dependent and caspase-independent pathways, and both were active and correlated well with 8-oxoguanine expression.

CONCLUSION

These results demonstrate the selective decrease in the DNA base excision repair pathway in combined reflux and methyl-n-amyl nitrosamine-induced squamous cell cancer of the esophagus.

Differential gene expression profiling of vocal fold polyps and Reinke's edema by complementary DNA microarray

OBJECTIVES

Our purpose was to determine whether complementary DNA (cDNA) microarray analysis (MA) can establish distinct gene expression profiles for 2 phenotypically similar vocal fold lesions: Reinke's edema (RE) and polyps. Established transcript profiles can provide insight into the molecular and cellular processes involved in these diseases.

METHODS

Eleven RE specimens and 17 polyps were analyzed with MA for 8,745 genes. Further MA profiling was attempted within each lesion group to identify molecular markers for reflux exposure and smoking. Prediction analysis was used to predict lesion classification for 2 unclassified samples. A real-time polymerase chain reaction was performed to corroborate MA transcript levels for selected significant genes.

RESULTS

Sixty-five genes were found to differentiate RE and polyps (p = .0088). For RE, 19 genes were differentiated for reflux exposure (p = .016). No genes were found to differentiate smokers from nonsmokers. For polyps, no genes were found to differentiate for reflux (p = .16) and smoking (p = .565). Categorization of unclassified lesions was possible with a minimum of 13 genes.

CONCLUSIONS

We demonstrate the feasibility of benign lesion classification based on MA. Microarray analysis is useful not only for improving diagnosis and classification of such lesions, but also for potentially generating prognostic indicators and targets for therapy.