Evaluation of the heme oxygenase-1 expression in esophagitis and esophageal cancer induced by different reflux experimental models and diethylnitrosamine

Estrogen-Dependent Nrf2 Expression Protects Against Reflux-Induced Esophagitis

BACKGROUND

Gastroesophageal reflux disease is more common in males than in females. The enhanced antioxidative capacity of estrogen in females might account for the gender difference. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a pivotal role in the host defense mechanism against oxidative stress.

AIMS

This study aimed to clarify the role of Nrf2 in reflux-induced esophageal inflammation, focusing on the gender difference and nitric oxide.

METHODS

Gastroesophageal reflux was surgically induced in male and female rats. Nitrite and ascorbic acid were administered for 1 week to provoke nitric oxide in the esophageal lumen. Male rats with gastroesophageal reflux were supplemented with 17β-estradiol or tert-butylhydroquinone, an Nrf2-inducing reagent. Esophageal squamous cell carcinoma KYSE30 cells were treated with 17β-estradiol. Nrf2 expression was examined by Western blotting and quantitative real-time PCR. Antioxidant gene expression profiles were examined by a PCR array.

RESULTS

In the presence of nitric oxide, reflux-induced esophageal damage was less evident, whereas esophageal expression of Nrf2 and its target genes such as Nqo1 was more evident in female or male rats supplemented with 17β-estradiol than in male rats. 17β-Estradiol increased nuclear Nrf2 expression in KYSE30 cells. tert-Butylhydroquinone increased tissue Nqo1 mRNA expression, leading to a reduction in reflux-induced esophageal damage.

CONCLUSIONS

Estrogen-dependent Nrf2 expression might contribute to protection against the development of gastroesophageal reflux disease in females.

Protective role of hemeoxygenase-1 in gastrointestinal diseases

Disorders and diseases of the gastrointestinal system encompass a wide array of pathogenic mechanisms as a result of genetic, infectious, neoplastic, and inflammatory conditions. Inflammatory diseases in general are rising in incidence and are emerging clinical problems in gastroenterology and hepatology. Hemeoxygenase-1 (HO-1) is a stress-inducible enzyme that has been shown to confer protection in various organ-system models. Its downstream effectors, carbon monoxide and biliverdin have also been shown to offer these beneficial effects. Many studies suggest that induction of HO-1 expression in gastrointestinal tissues and cells plays a critical role in cytoprotection and resolving inflammation as well as tissue injury. In this review, we examine the protective role of HO-1 and its downstream effectors in modulating inflammatory diseases of the upper (esophagus and stomach) and lower (small and large intestine) gastrointestinal tract, the liver, and the pancreas. Cytoprotective, anti-inflammatory, anti-proliferative, antioxidant, and anti-apoptotic activities of HO-1 make it a promising if not ideal therapeutic target for inflammatory diseases of the gastrointestinal system.

Nrf2 deficiency impairs the barrier function of mouse oesophageal epithelium

OBJECTIVE

As a major cellular defence mechanism, the Nrf2/Keap1 pathway regulates expression of genes involved in detoxification and stress response. Here we hypothesise that Nrf2 is involved in oesophageal barrier function and plays a protective role against gastro-oesophageal reflux disease (GERD).

DESIGN

Human oesophageal biopsy samples, mouse surgical models and Nrf2(-/-) mice were used to assess the role of the Nrf2/Keap1 pathway in oesophageal barrier function. Trans-epithelial electrical resistance (TEER) was measured with mini-Ussing chambers. HE staining and transmission electron microscopy were used to examine tissue morphology, while gene microarray, immunohistochemistry, western blotting and chromatin immunoprecipitation (ChIP) analysis were used to assess gene expression.

RESULTS

Nrf2 was expressed in normal oesophageal epithelium and activated in GERD of both humans and mice. Nrf2 deficiency and gastro-oesophageal reflux in mice, alone or in combination, reduced TEER and increased intercellular space in oesophageal epithelium. Nrf2 target genes and gene sets associated with oxidoreductase activity, mitochondrial biogenesis and energy production were downregulated in the oesophageal epithelium of Nrf2(-/-) mice. Consistent with the antioxidative function of Nrf2, a DNA oxidative damage marker (8OHdG) dramatically increased in oesophageal epithelial cells of Nrf2(-/-) mice compared with those of wild-type mice. Interestingly, ATP biogenesis, Cox IV (a mitochondrial protein) and Claudin 4 (Cldn4) expression were downregulated in the oesophageal epithelium of Nrf2(-/-) mice, suggesting that energy-dependent tight junction integrity was subject to Nrf2 regulation. ChIP analysis confirmed the binding of Nrf2 to Cldn4 promoter.

CONCLUSIONS

Nrf2 deficiency impairs oesophageal barrier function through disrupting energy-dependent tight junction.

Expression and function of heme oxygenase-1 in human gastric cancer

Heme oxygenase-1 (HO-1) potently influences tumor growth and metastasis. To date, no study has been performed on HO-1 expression pattern and its clinicopathological significance in human gastric cancer (GC) cases. In this study, the expression of HO-1 in human GC tissues (n = 74) and matched non-tumoral adjacent parenchyma (n = 46) was investigated by immunohistochemistry. The correlation of HO-1 with the clinicopathological characteristics was analyzed. Results showed that HO-1 was expressed in 62 GC tissues from 74 cases (83.8%), which is significantly higher than non-tumoral adjacent parenchyma (20/46, 43.8%, P < 0.05). A high HO-1 expression rate showed a close association with well/moderate histological differentiation and negative lymph node metastasis (P < 0.05). The expression of matrix metallopeptidase 9 (MMP9) and vascular endothelial growth factor A (VEGF-A) as well as chemosensitivity to cisplatin of MKN-45 cell lines with genetically altered HO-1 status were then determined by realtime polymerase chain reaction and 3-(4,5 dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), respectively. Whether the induction or inhibition of HO-1 by cobalt-protoporphyrin-IX (CoPP) or zinc-protoporphyrin-IX (ZnPP) could affect the sensitivity of MKN-45 cells to cisplatin was also studied. Results showed that the expression of MMP9 and VEGF-A were up-regulated in MKN-45 cells overexpressing HO-1, and down-regulated in HO-1 interfered cells. HO-1 overexpression could lead to an increased resistance to cisplatin, whereas down-regulation of HO-1 expression by siRNA or chemical inhibition of HO-1 could lead to increased chemosensitivity to cisplatin in MKN-45 cells. HO-1 may have multiple effects on protection against carcinogenesis and progression in GC.