Search

Background: The members of the family of heat shock factors coordinate the inducible transcription of heat shock genes in response to diverse stimuli. Any disturbances in signal transduction may lead to the attenuation of heat shock proteins synthesis and to cell death due to apoptosis. It has been shown by others that different nuclear factors, such as nuclear factor interleukin 6 or signal transducer and activator of transcription 3, co-operate with heat shock factors, mostly enhancing their activator effect on heat shock proteins genes expression. Therefore, we sought to determine whether apoptosis induced in the gastric epithelium exposed to live Helicobacter pylori might occur due to the elimination of HSP70 expression and deregulation of the heat shock response of the cell., Materials and Methods: Experiments were performed on KATO III gastric epithelial cells exposed to live cagA, vacA expressing Hp over different periods of time. Total cellular RNA, cytoplasmic and nuclear proteins were isolated for polymerase chain reaction, western-blot, electrophoretic mobility shift assay, decoy and co-immunoprecipitation studies., Results: We found that in human gastric epithelium exposed to Helicobacter pylori, heat shock factor 1 is bound and restrained in complexes by phosphorylated signal transducer and activator of transcription 3 protein. In consequence, heat shock factor 1 bound up with phosphorylated signal transducer and activator of transcription 3 protein is unable to activate HSP70 protein synthesis in KATO III cells under stress conditions. Helicobacter pylori also causes changes in bax/bcl-2 cellular equilibrium, leading to the induction of apoptosis., Conclusions: The observed phenomenon might be the mechanism whereby gastric epithelium adapts to the infection of Helicobacter pylori, eliminating cells which are damaged or altered by bacterial cytotoxic products from the tissue.

The interaction between Helicobacter pylori (H. pylori) and nonsteroidal anti-inflammatory drugs (NSAIDs) such as acetylsalicylic acid is still controversial. This study was designed to compare the effect of acetylsalicylic acid and vitamin C-releasing acetylsalicylic acid on the gastric mucosal damage and microbleeding before and after eradication of H. pylori in 10 young healthy volunteers. Acetylsalicylic acid induced significantly more gastric lesions and higher microbleeding than acetylsalicylic acid-vitamin C. After successful H. pylori eradication therapy, acetylsalicylic acid induced significantly higher mucosal lesions and microbleeding than before eradication. In contrast, after acetylsalicylic acid-vitamin C, gastric lesion index was significantly lower and eradication therapy failed to aggravate it. All H. pylori-positive subjects showed significant up-regulation of antioxidant enzyme (superoxide dismutase, catalase, glutathione peroxidase). Plain acetylsalicylic acid stronger than acetylsalicylic acid-vitamin C reduced gastric gene expression of these antioxidant enzymes. H. pylori eradication significantly decreased expression of these enzymes and this was further enhanced by plain acetylsalicylic acid, but not acetylsalicylic acid-vitamin C. Under plain acetylsalicylic acid therapy, the expression of proinflammatory cytokines was increased before and after eradication of H. pylori. We conclude that vitamin C combined with acetylsalicylic acid, unlike plain acetylsalicylic acid without vitamin C, protects gastric mucosa in man probably due the attenuation of oxidative stress and proinflammatory cytokines.

Hp and NSAID are the most common pathogens in the stomach, but their interaction on gastro-duodenal mucosa has been little studied. Hp infection in humans does not interfere with NSAID-induced gastric ulcer healing by omeprazole, therefore, there is no rationale to eradicate the germ. Hp infection induces COX-2 expression resulting in excessive biosynthesis of gastroprotective prostaglandin (PG), which should in turn counteract NSAID-induced gastropathy and contribute to healing of existing ulcers. Some investigators claim that Hp infection acts synergistically with NSAID on ulcerogenesis and propose that Hp should be eradicated, particularly at the onset of long-term NSAID therapy. Our studies in about 6500 dyspeptic patients undergoing upper endoscopy and 13C-urea breath test revealed that about 70% of these patients are Hp positive and 31% of these develop gastro-duodenal ulcers. Of these ulcers, 66% were Hp positive and NSAID negative, 3%--NSAID positive and Hp negative, 8% were both Hp positive and NSAID positive, while 23% ulcers were Hp and NSAID negative. An evidence was obtained for negative interaction between Hp infection and NSAID on risk of gastro-duodenal ulcers suggesting that Hp may attenuate the peptic ulcerogenesis. Our results support the concept 1) the interaction between Hp infection and NSAID on gastro-duodenal ulcerations is antagonistic, 2) the Hp and NSAID are independent risk factors for peptic ulcerations in humans, 3) there is no need for the Hp eradication in NSAID-treated patients, and 4) the rate of ulcer complications (hemorrhage and perforation) remains constant despite the decrease in Hp and ulcer prevalence.

Background/aim: Nitric oxide (NO) releasing nonsteroidal anti-inflammatory drugs do not cause gastric mucosal damage, despite inhibition of the cyclooxygenase activity to a similar extent as conventional nonsteroidal anti-inflammatory drugs that induce such damage. We compared the effects of native aspirin (ASA) with those of NO-releasing ASA (NO-ASA) on the development and healing of acute gastric lesions induced by water immersion and restraint stress (WRS) and the mucosal expression of heat shock protein 70 (HSP70)., Methods: Wistar rats received: (1). vehicle; (2). ASA (40 mg/kg i.g), and (3). NO-ASA (2.5-40 mg/kg i.g.), followed 0.5 h later by 3.5 h of WRS with or without glyceryl trinitrate, the donor of NO, and carboxy-PTIO, a NO scavenger. Healing of WRS lesions was assessed 0-24 h after termination of WRS. Number of gastric lesions, gastric mucosal blood flow (GBF), malondialdehyde (MDA) content, and RT-PCR expression of HSP70 mRNA were determined., Results: WRS caused typical bleeding erosions that were aggravated by aspirin and this was accompanied by a fall in the GBF and a significant rise in the mucosal MDA concentrations. In contrast, NO-ASA, which raised significantly the luminal content of NO(x), reduced number of WRS lesions and mucosal MDA levels while increasing significantly the GBF. These protective and hyperemic effects of NO-ASA against WRS lesions were mimicked by addition of glyceryl trinitrate to native ASA and significantly attenuated by carboxy-PTIO added to NO-ASA. HSP70 mRNA was significantly upregulated by WRS, and this was significantly attenuated by ASA, but not by NO-ASA. NO-ASA decreased significantly the MDA content and induced overexpression of HSP70 mRNA during healing of WRS lesions., Conclusion: NO-ASA exhibits mucosal protective and healing effects against WRS-induced gastric lesions due to the release of NO, which induces gastric hyperemia, and the attenuation of lipid peroxidation and counteracts the inhibition of HSP70 expression induced by native ASA., (Copyright 2002 S. Karger AG, Basel)

Reactive oxygen species (ROS) have high chemical reactivity, due to the presence of an uncoupled electron in their molecules. Therefore, they cause tissue damages, especially by lipid peroxidation. Lipid peroxides are metabolized to malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). The increase of MDA and 4-HNE concentration indicates ROS-dependent tissue damage. Superoxide dismutase (SOD) is a main enzyme which neutralizes ROS into less noxious hydrogen peroxide. The decrease of SOD activity is related to impairment of protective mechanisms and leads to tissue injury. The hydrogen peroxide is further metabolized to water in the presence of reduced glutathione (GSH). The decrease of GSH level has detrimental consequences for cellular properties of antioxidative defence. Gastric mucosa, under stress conditions, exhibits intensification of lipid peroxidation (increase of MDA and 4-HNE), as well as the decrease of SOD activity and GSH concentration. This parameters appear to be useful for understanding of pathomechanisms of the origin of gastric mucosa damage in stress conditions. [ABSTRACT FROM AUTHOR]