Implications of reactive oxygen species and cytokines in gastroprotection against stress-induced gastric damage by nitric oxide releasing aspirin

BACKGROUND AND AIMS: Nitric oxide-releasing aspirin (NO-ASA) has been shown to inhibit cyclo-oxygenase and prostaglandin generation without causing mucosal damage, but the role of reactive oxygen species (ROS) and cytokines in the action of ASA and NO-ASA against acute gastric damage has been little studied. METHODS AND MATERIALS: We compared the effect of NO-ASA and ASA on gastric lesions provoked by water-immersion and restraint stress (WRS), ischemia-reperfusion, and 100% ethanol. We determined the number and area of gastric lesions, gastric blood flow (GBF), plasma concentration of proinflammatory cytokines IL-1beta and TNFalpha, expression of superoxide dismutase (SOD) and glutathione peroxidase (GPx), ROS generation, and the malondialdehyde (MDA) concentration as an index of lipid peroxidation. RESULTS: Pretreatment with NO-ASA attenuated dose-dependently gastric erosions provoked by WRS, ischemia-reperfusion, and ethanol. In contrast, ASA aggravated significantly WRS-induced lesions, and this was accompanied by a fall in the GBF, suppression of prostaglandin E(2) generation, and significant rise in ROS chemiluminescence and in plasma TNFalpha and IL-1beta levels. ASA also enhanced significantly the mucosal MDA content and downregulated SOD and GPx mRNA, and these effects were markedly reduced by NO-ASA. CONCLUSION: Coupling of NO to ASA attenuates stress, ischemia-reperfusion, and ethanol-induced damage due to mucosal hyperemia mediated by NO, which compensates for prostaglandin deficiency induced by ASA. ASA aggravates WRS damage via enhancement of ROS and cytokine generation and suppression of SOD and GPx, and these effects are counteracted by NO released from NO-ASA.     

Enhanced resistance of gastric mucosa to damaging agents in the rat stomach adapted to Helicobacter pylori lipopolysaccharide

BACKGROUND AND AIM: Lipopolysaccharide (LPS) has been proposed to act as one of numerous virulence factors in the Helicobacter pylori (HP)-infected stomach. However, little is known as to whether the gastric mucosa can withstand the repeated LPS insult, and how the possible adaptation to this endotoxin influences the damage induced by strong irritants. We determined the effect of a single or repeated parenteral administration of LPS obtained from HP on acute gastric lesions induced by intragastric application of 100% ethanol (1.5 ml) and by water immersion and restraint stress (WRS). METHODS: The area of the gastric lesions was measured by planimetry, mucosal gastric blood flow (GBF) was determined by H(2) gas clearance, and gastric luminal content was collected for the determination of luminal NO(2)(-)/NO(3)(-) levels by the Griess reaction. Biopsy samples were taken for the measurement of prostaglandin (PG) E(2) by radioimmunoassay and mucosal expression of constitutive and inducible nitric oxide synthase (cNOS and iNOS), constitutive (COX-1) and inducible cyclooxygenase (COX-2), heat shock protein 70 (HSP 70) mRNA and protein were analyzed by RT-PCR and Western blot. RESULTS: HP LPS (1 mg/kg i.p.) injected once or 5 times produced negligible macroscopic injury and failed to influence GBF significantly compared to the injuries recorded in vehicle-controlled rats. Single and repeated (5 times) administration of HP LPS significantly reduced ethanol- and WRS-induced lesions, these protective effects were accompanied by a rise in GBF and excessive luminal release of NO. The suppression of NOS activity by L-NAME (20 mg/kg i.p.), a nonspecific NOS inhibitor, or L-NIL (30 mg/kg i.g.), a specific iNOS inhibitor, and of COX-2 activity by NS-398 reversed the protective and hyperemic effects of single or repeated LPS administrations against ethanol and WRS damage and the accompanying rise in NO and PGE(2) production. These effects of L-NAME were significantly antagonized by the addition of L-arginine, a substrate for NO synthesis. The signals for cNOS, COX-1 and HSP 70 mRNA were detected by RT-PCR in the vehicle-treated gastric mucosa, whereas gene and protein expression of iNOS, COX-2 and HSP 70 mRNA were significantly increased only in rats treated with 1 or 5 applications of HP LPS. CONCLUSIONS: Repeated injections of HP LPS enhance gastric mucosal resistance to the mucosal damage induced by ethanol and WRS via a mechanism involving mucosal overexpression of iNOS, COX-2 and HSP 70 with subsequent excessive production of NO and PGE(2).     

Grapefruit-seed extract attenuates ethanol-and stress-induced gastric lesions via activation of prostaglandin, nitric oxide and sensory nerve pathways

AIM: Grapefruit-seed extract (GSE) containing flavonoids, possesses antibacterial and antioxidative properties but whether it influences the gastric defense mechanism and gastroprotection against ethanol- and stress-induced gastric lesions remains unknown. METHODS: We compared the effects of GSE on gastric mucosal lesions induced in rats by topical application of 100% ethanol or 3.5 h of water immersion and restraint stress (WRS) with or without (A) inhibition of cyclooxygenase (COX)-1 activity by indomethacin and rofecoxib, the selective COX-2 inhibitor, (B) suppression of NO-synthase with L-NNA (20 mg/kg ip), and (C) inactivation by capsaicin (125 mg/kg sc) of sensory nerves with or without intragastric (ig) pretreatment with GSE applied 30 min prior to ethanol or WRS. One hour after ethanol and 3.5 h after the end of WRS, the number and area of gastric lesions were measured by planimetry, the gastric blood flow (GBF) was assessed by H2-gas clearance technique and plasma gastrin levels and the gastric mucosal generation of PGE2, superoxide dismutase (SOD) activity and malonyldialdehyde (MDA) concentration, as an index of lipid peroxidation were determined. RESULTS: Ethanol and WRS caused gastric lesions accompanied by the significant fall in the GBF and SOD activity and the rise in the mucosal MDA content. Pretreatment with GSE (8-64 mg/kg i g) dose-dependently attenuated gastric lesions induced by 100% ethanol and WRS; the dose reducing these lesions by 50% (ID50) was 25 and 36 mg/kg, respectively, and this protective effect was similar to that obtained with methyl PGE2 analog (5 μg/kg i g). GSE significantly raised the GBF, mucosal generation of PGE2, SOD activity and plasma gastrin levels while attenuating MDA content. Inhibition of PGE2 generation with indomethacin or rofecoxib and suppression of NO synthase by L-NNA or capsaicin denervation reversed the GSE-induced protection and the accompanying hyperemia. Co-treatment of exogenous calcitonine gene-related peptide (CGRP) with GSE restored the protection and accompanying hyperemic effects of GSE in rats with capsaicin denervation. CONCLUSION: GSE exerts a potent gastroprotective activity against ethanol and WRS-induced gastric lesions via an increase in endogenous PG generation, suppression of lipid peroxidation and hyperemia possibly mediated by NO and CGRP released from sensory nerves.     

Role ofl-arginine, a substrate for nitric oxide-synthase, in gastroprotection and ulcer healing

Nitric oxide (NO) synthesized froml-arginine interacts with prostaglandins (PG) and sensory neuropeptides in the regulation of mucosal integrity, but the role ofl-arginine, a substrate for NO-synthase, in gastroprotection and healing of chronic gastric ulcers has been little studied. In this study we compared the effects of intragastric (i.g.) and systemic (i.v.) administration ofl-arginine ord-arginine on gastric secretion and acute gastric lesions provoked in rats by i.g. application of 100% ethanol, acidified aspirin (ASA), or the exposure to 3.5h of water immersion and restraint stress (WRS). In addition, the effects ofl-arginine on ulcer healing and the formation of new vessels (angiogenesis) were determined, using monoclonal antibody (MAb E-9).l-arginine (10–200 mg/kg i.g.) failed to significantly affect gastric secretion but dose-dependently reduced the gastric lesions induced by 100% ethanol, ASA, and WRS, the doses inhibiting 50% of these lesions being 65, 94, and 72 mg/kg, respectively. This protection was accompanied by a significant rise in the gastric blood flow (GBF), whereasl-arginine given i.v. failed to affect the ethanol-lesions and the GBF.d-arginine or the NO-related amino acids—l-glutamine,l-citrulline, orl-ornithine—failed to significantly influence these lesions. Suppression of the generation of mucosal PG by indomethacin or capsaicin-denervation attenuated the protection and hyperemia induced byl-arginine. The inhibition of constitutive NO synthase byl-NNA had no significant effect on the protection afforded byl-arginine, but reduced the gastric hyperemia accompanying this protection.l-arginine (150 mg/kg per day, i.g.) accelerated the ulcer healing and increased GBF at the ulcer margin, and angiogenesis, whereas treatment with L-NNA had an opposite effect.l-arginine added to N^G-nitro-l-arginine (L-NNA) restored the ulcer healing, hyperemia, and angiogenesis. We conclude that: (1) the protective activity ofl-arginine involves gastric hyperemia mediated by NO and a mild irritant effect due to enhanced generation of endogenous PG, and (2) the ulcer healing properties ofl-arginine depend upon its hyperemic and angiogenic actions, possibly involving NO.     

左旋精氨酸甲酯及左旋精氨酸对应激状态下胃黏膜耐受性细胞保护作用的影响

目的：探讨内源性一氧化氮（NO）在应激状态下胃黏膜耐受性细胞保护中的作用及其可能的机制。方法：以重复浸水束缚应激（WRS）制作动物模型,以左旋精氨酸甲酯（L－NAME）或左旋精氨酸（L－Arg）抑制或促进内源性NO的合成,动态检测胃黏膜血流量（GMBF）、溃疡指数（UI）、黏膜一化氮含量的变化。结果：重复应激后,实验对照组大鼠UI明显下降,同时GMBF上升,黏膜内NO含量增高;L－NAME使WWRS引起的胃黏膜损伤加重,消除了GMBF的递增趋势,黏膜NO含量下降;而L－Arg可减轻WRS造成的黏膜损伤,GMBF、黏膜NO含量增相应增加;GMBF、UI、黏膜NO含量变化之间有相关关系。结论：内源性NO通过调节GMBF而介导耐受性细胞保护作用,L－NAME抑制其合成,延缓这一作用,L－Arg增加其合成,促进该作用。     

Effects of Cyclooxygenase-2 Selective and Nitric Oxide-Releasing Nonsteroidal Antiinflammatory Drugs on Mucosal Ulcerogenic and Healing Responses of the Stomach

Effects of selective cyclooxygenase-2 (COX-2)inhibitors (NS-398) and nitric oxide (NO)-releasingaspirin (NO-ASA) on gastric ulcerogenic and healingresponses were examined in comparison with nonselective COX inhibitors such as indomethacin and aspirin(ASA). Hypothermic stress (28-30°C, 4 hr) inducedgastric lesions in anesthetized rats with an increase ofacid secretion. The lesions induced by hypothermic stress were markedly worsened by subcutaneousadministration of both indomethacin and ASA but were notaffected by either NS-398 or NO-ASA, although theincreased acid secretion during hypothermia was not affected by any of the drugs. On the otherhand, the healing of gastric ulcers induced in mice bythermal cauterization (70°C, 15 sec) wassignificantly delayed by daily subcutaneousadministration of indomethacin and ASA as well as NS-398, but not by NO-ASA.COX-2 mRNA was not detected in the intact mucosa but waspositively expressed in the ulcerated mucosa, mostpotently on day 3 after ulceration. Prostaglandin contents in the intact mouse stomach werereduced by indomethacin, ASA, and NO-ASA, while theincreased prostaglandin generation in the ulceratedmucosa was inhibited by all drugs including NS-398.After subcutaneous administration of NO-ASA topylorus-ligated rats and mice, high amounts ofNO_x were detected in both the gastriccontents and serum. In addition, both NS-398 and NO-ASAshowed an equipotent antiinflammatory effect againstcarrageenan-induced paw edema in rats as compared withindomethacin and ASA. These results suggest that bothindomethacin and ASA not only increased the mucosalulcerogenic response to stress but impaired the healingresponse of gastric ulcers as well. The former actionwas due to inhibition of COX-1, while the latter effectwas accounted for by inhibition of COX-2 and was mimicked by the COX-2-selective inhibitorNS-398. NO-ASA, although it inhibited both COX-1 andCOX-2 activity, had no deleterious effects on gastriculcerogenic and healing responses.     

Influence of NG‐nitro‐L‐arginine methyl ester and L‐arginine on gastric mucosal tolerant cytoprotection under stress

OBJECTIVE : To determine the role of endogenous nitric oxide (NO) in gastric mucosal tolerant cytoprotection under stress and its possible mechanism. METHODS : Sprague–Dawley rats were exposed to repeated water immersion and restraint stress (WRS), during which N^G‐nitro‐L ‐arginine methyl ester (L ‐NAME), a non‐selective NO synthase inhibitor, and L ‐arginine (L ‐Arg), a substrate for NO synthesis, were administered to inhibit or promote the synthesis of endogenous NO, respectively. Gastric mucosal blood flow (GMBF) was measured with an LDF‐3 Flowmeter (Electronic Instrument Factory of Nankai University, Tianjin, China), the NO level in the gastric mucosa was monitored by the Griess reaction and gastric mucosal lesions were evaluated using the ulcer index (UI). The relationships between changes in GMBF, UI and NO content in the gastric mucosa were analyzed by linear correlation analysis. RESULTS : Repeated WRS induced gastric mucosal tolerant cytoprotection and this was accompanied by increased GMBF and NO levels in the gastric mucosa. Inhibition of endogenous NO synthesis by L ‐NAME worsened mucosal lesions induced by single WRS and, after repeated WRS, the adaptive incremence in GMBF was abolished and the NO content in the gastric mucosa was significantly reduced. In contrast, enhancement of endogenous NO synthesis by L ‐Arg attenuated mucosal erosions caused by single WRS. After repeated WRS, GMBF and the NO content in the mucosa increased gradually. Mucosal lesions were negligible after rats were exposed to the fourth WRS. CONCLUSIONS : During the tolerant cytoprotection, GMBF, UI and the NO content showed regular changes and there were good relationships between them. L ‐NAME and L ‐Arg changed the levels of endogenous NO, which, accordingly, affected GMBF and the gastric tolerance. By regulating GMBF, endogenous NO may play an important role in the gastric mucosal tolerant cytoprotection under stress. Inhibition of the synthesis of NO delayed the induction of tolerant cytoprotection, whereas increased NO synthesis promoted cytoprotection.     

Role of TFF in healing of stress-induced gastric lesions

AIM: To determine the changes of pS2 and ITF of TFF expression in gastric mucosa and the effect on ulcer healing of pS2, ITF to Water-immersion and restraint stress (WRS)in rats.METHODS: Wistar rats were exposed to single or repeated WRS for 4 h every other day for up to 6 days. Gastric mucosal blood flow (GMBF) was measured by LDF-3 flowmeter and the extent of gastric mucosal lesions were evaluated grossly and histologically. Expression of pS2 and ITF mRNA was determined by RT-PCR. Immunohistochemistry was used to further detect the expression of pS2 and ITF.RESULTS: WRS applied once produced numerous gastric mucosal erosions, but the number of these lesions gradually declined and GMBF restored at 2, 4, 8 h after stress. The area of gastric mucosal lesion was reduced by 64.9 % and GMBF was increased by 89.8 % at 8 h. The healing of stress-induced ulcerations was accompanied by increased expression of pS2 (0.51±0.14 vs0.77±0.11, P＜0.01) and ITF (0.022±0.001 vs 0.177±0.010, P＜0.01). The results were demonstrated further by immunohistochemistry of pS2(0.95±0.11 vs1.41±0.04, P＜0.01) and ITF (0.134±0.001 vs 0.253±0.01,P＜0.01). With repeated WRS, adaptation to this WRS developed, the area of gastric mucosal lesions was reduced by 22.0 % after four consecutive WRS. This adaptation to WRS was accompanied by increased GMBF (being increased by 94.2 %), active cell proliferation in the neck region of gastric glands, and increased expression of pS2 (0.37±0.02 vs 0.77±0.01, P＜0.01) and ITF (0.040±0.001 vs0.372±0.010, P＜0.01). The result was demonstrated further by immunohistochemistry of pS2 (0.55±0.04 vs 2.46±0.08, P＜0.01) and ITF (0.134±0.001 vs0.354±0.070,P＜0.01).CONCLUSION: TFF may not only participate in the early phase of epithelial repair known as restitution(maked by increased cell migration),but also play an important role in the subsequent, protracted phase of glandular renewal(made by cell proliferation).     

Low gastric toxicity of nitric oxide-releasing aspirin, NCX-4016, in rats with cirrhosis and arthritis

The gastric toxic effects of aspirin (ASA) and NCX-4016, a nitric oxide (NO)-releasing ASA, were compared in normal, cirrhotic, and arthritic rats. Oral administration of ASA (100 mg/kg) produced hemorrhagic lesions on the gastric mucosa in normal rats. The gastric ulcerogenic response to ASA was significantly worsened in both cirrhotic rats induced by N-nitrosodiethylamine and in arthritic rats induced by Freund's complete adjuvant. By contrast, NCX-4016 at 190 mg/kg (a dose equimolar to 100 mg/kg of ASA) did not induce damage in normal rat stomachs but caused slight lesions in the gastric mucosa of both cirrhotic and arthritic rats. Plasma salicylate levels following administration of ASA or NCX-4016 were not different between normal, cirrhotic, and arthritic rats, although the latter drug gave significantly lower values in any group of rats as compared to the former. Acid secretion was significantly increased in both cirrhotic and arthritic rats. ASA with 150 mM HCl caused severe gastric lesions in normal rats, the degree of damage being significantly greater than that induced by ASA alone. Coadministration of NOR-3, a NO donor, significantly prevented the development of gastric lesions induced by ASA, irrespective of whether or not ASA was given together with HCl. Gastric mucosal application of ASA (100 mg/kg) for 30 min caused a marked reduction of transmucosal potential difference (PD) with a minimal effect on gastric mucosal blood flow in both normal and cirrhotic rats, while that of NCX-4016 did not cause a PD reduction and produced a marked increase in the mucosal blood flow in both groups of rats. These results suggest that gastric mucosal susceptibility to ASA-induced damage is increased in both cirrhotic and arthritic rats (the process being partly accounted for by acid hypersecretion in these animals), NCX-4016 has even less gastric toxicity in both cirrhotic and arthritic rats, and the gastric-sparing effect of NCX-4016 is due, at least partly, to an increase of gastric mucosal blood flow, mediated by NO released from this drug.     

Lack of gastric toxicity of nitric oxide-releasing indomethacin, NCX-530, in experimental animals

The effects of a nitric oxide (NO) releasing derivative of indomethacin (NCX-530) on gastric ulcerogenic and healing responses were evaluated in rats and mice, in comparison with the parent compound indomethacin. Indomethacin (per os) produced damage in the rat stomach in a dose-dependent manner. NCX-530 (per os) itself, however, was not ulcerogenic and even showed a dose-dependent protection against HCl/ethanol-induced lesions in the rat stomach. Likewise, indomethacin given repeatedly delayed healing of gastric ulcers induced in mice by thermal cauterization, while NCX-530 did not affect the healing response and significantly promoted the healing as compared to indomethacin. These actions of NCX-530 were mimicked by the combined administration of a NO donor NOR-3 with indomethacin. The amount of NO metabolites was increased in both the gastric contents and serum when NCX-530, but not indomethacin, was given in pylorus-ligated stomachs. Neither indomethacin nor NCX-530 influenced gastric acid secretion and transmucosal potential difference, yet NCX-530 caused a marked increase of gastric mucosal blood flow, which was preventable by carboxy-PTIO, a scavenger of NO. Gastric motility was increased by indomethacin but not by NCX-530. In addition, NCX-530 inhibited PGE₂ generation in both the intact and ulcerated gastric mucosa and showed antiinflammatory action on carrageenan-induced rat paw edema, as effectively as indomethacin. These results suggest that unlike indomethacin, NCX-530 caused neither an irritating action on the stomach nor healing impairment effect on the preexisting gastric ulcers, but conferred gastric protection against HCl/ethanol, despite causing cyclooxygenase inhibition and antiinflammatory action, as effectively as indomethacin. This NO-releasing indomethacin, probably by releasing NO, exerts protective influences, such as an increase of gastric mucosal blood flow, that counteract the potential damaging effects of cyclooxygenase inhibition by indomethacin.     

Dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress in rats

AIM: To investigate the dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress (WRS) in rats. METHODS: WRS model of Sprague-Dawley (SD) rats was established. Fifty-six male SD rats were randomly divided into control group, stress group and post-stress group. The stress group was divided into 1, 2 and 4 h stress subgroups. The post-stress group was divided into 24, 48 and 72 h subgroups. The pH value of gastric juice, ulcer index (UI) of gastric mucosa and H , K -ATPase activity of gastric parietal cells were measured. Ultrastructural change of parietal cells was observed under transmission electron microscope (TEM). RESULTS: The pH value of gastric juice decreased time-dependently in stress group and increased in post-stress group. The H , K -ATPase activity of gastric parietal cells and the UI of gastric mucosa increased time-dependently in stress group and decreased in post-stress group. Compared to control group, the pH value decreased remarkably (P = 0.0001), the UI and H , K -ATPase activity increased significantly (P = 0.0001, P = 0.0174) in 4 h stress subgroup. UI was positively related with stress time (r = 0.9876, P < 0.01) but negatively with pH value (r = -0.8724, P < 0.05). The parietal cells became active in stress group, especially in 4 h stress subgroup, in which plenty of intracellular canalicular and mitochondria were observed under TEM. In post-stress group, the parietal cells recovered to resting state. CONCOUSION: The acid secretion of parietal cells is consistent with their ultrastructural changes during the development and healing of stress ulcer induced by WRS and the degree of gastric mucosal lesions, suggesting gastric acid play an important role in the development of stress ulcer and is closely related with the recovery of gastric mucosal lesions induced by WRS.     

Mechanisms of curcumin-induced gastroprotection against ethanol-induced gastric mucosal lesions

Background

Curcumin, a pleiotropic substance used for centuries in traditional medicine, exhibits antioxidant, anti-inflammatory and antiproliferative efficacy against various tumours, but the role of curcumin in gastroprotection is little studied. We determined the effect of curcumin against gastric haemorrhagic lesions induced by 75% ethanol and alterations in gastric blood flow (GBF) in rats with cyclooxygenase-1 (COX-1) and COX-2 activity inhibited by indomethacin, SC-560 or rofecoxib, inhibited NO-synthase activity, capsaicin denervation and blockade of TRPV1 receptors by capsazepine.

Methods

One hour after ethanol administration, the gastric mucosal lesions were assessed by planimetry, the GBF was examined by H₂ gas clearance, plasma gastrin was determined by radioimmunoassay, and the gastric mucosal mRNA expression of Cdx-2, HIF-1α, HO-1 and SOD 2 was analysed by RT-PCR.

Results

Curcumin, in a dose-dependent manner, reduced ethanol-induced gastric lesions and significantly increased GBF and plasma gastrin levels. Curcumin-induced protection was completely reversed by indomethacin and SC-560, and significantly attenuated by rofecoxib, L-NNA, capsaicin denervation and capsazepine. Curcumin downregulated Cdx-2 and Hif-1α mRNA expression and upregulated HO-1 and SOD 2, and these effects were reversed by L-NNA and further restored by co-treatment of L-NNA with l-arginine.

Conclusions

Curcumin-induced protection against ethanol damage involves endogenous PG, NO, gastrin and CGRP released from sensory nerves due to activation of the vanilloid TRPV1 receptor. This protective effect can be attributed to the inhibition of HIF-1α and Cdx-2 expression and the activation of HO-1 and SOD 2 expression.

     

热休克蛋白70对肝硬化门静脉高压性胃病大鼠胃黏膜损伤的保护作用

背景:临床上重度门静脉高压性胃病(PHG)常可引起上消化道致命性大出血。热休克蛋白70(HSP70)是加强胃黏膜防御功能的主要热休克蛋白。目的:探讨HSP70对肝硬化PHG大鼠胃黏膜损伤的保护作用及其机制。方法:以CCl_4制备肝硬化PHG大鼠模型,实验分为正常对照组、PHG组和三组热处理组。以酶联免疫吸附测定(ELISA)检测胃黏膜HSP70和肿瘤坏死因子(TNF)-α水平,并观察胃黏膜病理变化。结果:与正常对照大鼠相比,PHG大鼠胃黏膜HSP70水平明显降低而TNF-α水平明显升高,胃黏膜出现明显病理损伤;热处理组正常大鼠胃黏膜HSP70水平明显升高,TNF-α水平无变化,胃黏膜无明显损伤。与PHG大鼠相比,热处理组PHG大鼠胃黏膜HSP70水平明显升高,TNF-α水平明显降低,胃黏膜损伤明显减轻。结论:HSP70能减轻肝硬化PHG大鼠胃黏膜损伤,其保护作用可能与胃黏膜TNF-α水平降低有关。     

Role of melatonin in mucosal gastroprotection against aspirin‐induced gastric lesions in humans

Abstract: Melatonin and its precursor, l ‐tryptophan, have been shown to exert gastroprotective effects in animals, but their influence on the gastric damage by aspirin (ASA) in humans has been sparingly investigated. In this study, we designed to determine the effects of melatonin and l ‐tryptophan on ASA‐induced gastric mucosal damage, gastric microbleeding, mucosal generation of prostaglandin E₂, and plasma melatonin, and gastrin levels. Three groups of healthy male volunteers (n = 30) with intact gastric mucosa received daily for 11 days either ASA alone or that combined with melatonin or tryptophan. Gastric blood loss and mucosal damage were evaluated at 3rd, 7th, and 11th days of ASA administration by endoscopy using Lanza score. ASA alone caused a marked rise of gastric damage and gastric blood loss, mainly at day 3rd and 7th, but they were significantly reduced at 11th day. Pretreatment with melatonin or tryptophan remarkably reduced ASA‐induced gastric lesions and microbleeding. Gastric mucosal generation of PGE₂ was suppressed by about 90% in all subjects treated with ASA alone without or with addition of melatonin or tryptophan. Plasma melatonin was markedly increased after treatment with melatonin or tryptophan plus ASA, but it was also raised significantly after application of ASA alone. Plasma gastrin levels were raised in subjects given melatonin or tryptophan plus ASA, but not in those with ASA alone. We conclude that melatonin and its precursor tryptophan given orally significantly reduce gastric lesions induced by ASA possibly due to (a) direct gastroprotective action of exogenous melatonin or that generated from tryptophan and (b) gastrin released from the gastric mucosa by melatonin or tryptophan.     

Influence of gastric colonization with Candida albicans on ulcer healing in rats: effect of ranitidine, aspirin and probiotic therapy

OBJECTIVE: Candida albicans frequently inhabits the gastrointestinal tract of humans leading to gastrointestinal candidiasis, especially following suppression of gastric acidity, but studies on the relation between this fungal infection and gastric pathology are limited due to lack of convenient animal models resembling Candida infection in humans. MATERIAL AND METHODS. We compared the effects of C. albicans and vehicle inoculation on gastric secretion and healing of gastric ulcers induced by acetic acid in rats treated with 1) ranitidine (30 mg kg(-1) day(-1) s.c.) and 2) aspirin (ASA) (60 mg kg(-1) day(-1) i.g.) with or without probiotic bacteria Lactobacillus acidophillus. At day 0 and at 4, 15 and 25 days after ulcer induction, the ulcer area, the gastric blood flow (GBF), the quantitative gastric cultures of Candida and the expression of mRNAs for pro-inflammatory cytokines IL-1beta and TNF-alpha and growth factors EGF and TGFalpha were assessed in the gastric mucosa. RESULTS: Gastric acid output was reduced by over 40% soon after Candida inoculation and this effect persisted during all time intervals tested. The area of ulcers in control rats significantly decreased at day 15 and the ulcers disappeared almost completely after 25 days of their induction. In contrast, the ulcers were present until day 25 in Candida-inoculated rats followed by a fall in GBF and a rise in plasma gastrin levels, these effects being significantly attenuated by the co-treatment with Lactobacillus. Candidiasis was accompanied by up-regulation of mRNA for IL-1beta, TNF-alpha, EGF and TGFalpha and a significant increment in plasma IL-1beta and TNF-alpha levels. CONCLUSIONS: 1) Persistent colonization with Candida could be achieved in rats treated with antisecretory agents or non-steroidal anti-inflammatory drugs (NSAIDs) such as ASA; 2) candidiasis reduces gastric acid secretion, while delaying ulcer healing possibly due to the impairment in GBF in the ulcer area and enhanced expression and release of IL-1beta and TNFalpha and 3) probiotic therapy could be useful in the treatment against the deleterious action of fungal infection on the healing of pre-existing gastric ulcers.     

Expression and immunolocalization of heat shock proteins in the healing of gastric ulcers in rats

BACKGROUND: Heat shock proteins are induced when cells are subjected to noxious stimuli. They afford cytoprotection and increase the resistance of the tissue to damage. However, their roles in the healing of gastric ulcers have not been well established. In this study, the expression and immunolocalization of three heat shock proteins (HSPs); namely inducible HSP70 (iHSP70), HSP47, and HSP32 during ulcer healing were investigated in rats with gastric ulcer. METHODS: Gastric ulcers (kissing ulcers) were induced by luminal application of acetic acid solution. Gastric tissue samples were obtained from the ulcer base, ulcer margin, and non-ulcerated area around the ulcer margin at different time intervals after ulcer induction. The protein levels and distributions of HSPs were analyzed with Western blotting and immunohistochemical methods, respectively. RESULTS: It was found that all HSPs were expressed in normal, non-ulcerated, and gastric ulcer tissues. HSP32 was elevated during inflammation (1-8 days after ulcer induction), while HSP47 expression was exacerbated at the ulcer base and margin during ulcer healing (3-12 days). Decreased expression of iHSP70 was observed at the ulcer base immediately after ulcer induction, but returned to normal level by the end of the healing stage (8-12 days). Inducible HSP70 was found distributed in the gastric glands and injured tissues in the inflamed areas. Wide distribution of HSP47 was detected in granulation tissues and collagen producing cells, while HSP32 was localized in the gastric glands and inflammatory cells. CONCLUSIONS: The findings indicate that iHSP70, HSP47, and HSP32 play different roles during ulcer healing. HSP32 seems to act as an inflammatory defensive factor, and HSP47 as a collagen-specific molecular chaperon contributing significantly to gastric ulcer healing. However, the role of iHSP70 in the ulcer healing process is still undefined.