Protective influence of melatonin against acute esophageal lesions involves prostaglandins, nitric oxide and sensory nerves.

Melatonin (MT) is known to protect gastrointestinal mucosa against various types of injury but its effects on esophageal damage have not been studied. We examined the effects of MT on acute esophageal injury and the mechanism involved in the action of this indole. Acute esophageal lesions were induced by perfusion with acid-pepsin solution using tube inserted through the oral cavity into the mid of esophagus of anaesthetized rats with or without inhibition of prostaglandin (PG) generation by indomethacin (5 mg/kg/day), nitric oxide (NO) formation by N(G)-nitro-L-arginine (L-NNA, 20 mg/kg/day) or sensory nerves deactivation by capsaicin (125 mg/kg, sc). The esophageal injury was assessed by macroscopic score and histologic activity index. The esophageal mucosal blood flow (EBF) was determinated by H(2)-gas clearance method. The plasma TNF-alpha and nitrate/nitrite (NOx) levels and mucosal PGE(2) contents were assessed by immunoassays. Esophageal acid-pepsin perfusion induced noticeable esophageal mucosal injury as compared to perfusion with vehicle saline. The pretreatment with MT prevented significantly esophageal injury, raised EBF and mucosal content of PGE(2), while decreasing the levels of TNF-alpha. Inhibition of COX/PG and NOS/NO systems by indomethacin and L-NNA, respectively, or inactivation of sensory nerves by capsaicin, that manifested in further increase of esophageal injury, reduced the levels of EBF, markedly raised the levels TNF-alpha and reduced mucosal PGE(2), but the pretreatment with MT prevented significantly esophageal injury, improved EBF and raised mucosal PGE(2) contents. These studies suggest that MT can be considered as a novel esophagoprotector, acting, at least in part, through the COX/PG and NOS/NO systems and activation of sensory nerves.

Inflammatory response in visceral fat tissue and liver is prenatally programmed: experimental research.

To investigate the mechanisms of developmental programming we analyzed the effects of maternal stress and food intake on physiological activity of adipose tissue and hepatocellular organization in the offsprings. The experiments were conducted in nonlinear female rats (n=20) and their male offsprings (n=28). During their pregnancy female rats were exposed to social and emotional stress using Pratt's model, and nutritional insults: high sugar diet (HSD) with chronic access to 30% solution of saccharose in drinking water ad libitum, high fat diet (HFD) containing 45% calories from fat or their combination - high sugar and high fat diet (HSFD). The effects of maternal stress and nutrition on severity of visceral fat and liver changes were then examined in offsprings, along with changes in serum levels of the pro- and anti-inflammatory cytokines: IL-1b, IL-8 (in rats known as GRO/CINC-1), leptin and adiponectin, respectively. Maternal exposure to stress in combination with HSFD resulted in the most prominent changes in the offsprings: histological changes in the visceral fat tissue and liver with cell reorganization and signs of inflammation, 217% increase in IL-1ß level, 99% increase in GRO/CINC-1 level, 79% increase in leptin level and 41% decrease in adiponectin level. The leptin/adiponectin index was elevated in all study groups and reached 158% in HSD group, 138% in HFD group and was two times higher in HSFD group vs control. The rat model used in this study provides novel insight into development of nonalcoholic fatty liver disease. Expressed pro- and anti-inflammatory cytokines may indicate early changes in liver and adipose tissue functioning and leptin/adiponectin index could be a novel non-invasive marker of metabolic-related liver alteration. Healthy nutrition and stress management during prenatal period may serve as a valid strategy to prevent liver and adipose tissue inflammation/alteration and metabolic disorders in adulthood.

New insight into oseophageal injury and protection in physiologically relevant animal models.

Chronic diseases of lifestyle (CDL), the most common chronic group of non-infectious and non-transmissible diseases worldwide, which share the similar risk factors of unhealthy lifestyle, have become most recognized as a serious trigger in the genesis of oesophageal injury. Non-erosive oesophageal lesions (NEOL) are found more frequently than erosive or ulcer lesions in patients with reflux oesophagitis (RO) related to CDL. They also have restricted healing options, which often leads to carcinogenesis. Therefore, developing a physiologically relevant animal model of NEOL remains an urgent priority. One of triggers of CDL, postprandial hyperglycemia (PHG), which is characterized by hyperglycemic spikes, and overloading nitro-compounds leading to oxidative stress that may predispose to NEOL. The present study was designed to set up a model of RO related to CDL in rodents to understand mechanisms of oesophageal preulcerogenic injury under such conditions as food-associated long-term PHG, restrained water-immersion stress (WIS), and imbalance of entero-salivary nitrites recirculation (ESNR). Beneficial effects of L-tryptophan (L-Try) have already been described by many activities in kynurenine and melatonin (Mel) synthesis, redox reactions, which play a key role for cytoprotection and proliferation. Nevertheless, the effect of L-Try and Mel on NEOL under PHG is still unknown. An extract of Cucurbita maxim sweet seed (eCMS), which contains a high amount of antioxidants, also appear to play an important role in foregut cytoprotection. Thus, the second aim was to observe the effects of eCSE on oesophageal mucosa (OEM) in modification of ESNR (mESNR). Rats were used with without/with pre-treatment L-Try, Mel during WIS and PHG. In the second series of experiments rats were used with without/with CSE pre-treatment in mESNR; oral and OEM lesions were determined by histology; inflammation of OEM by lectin histochemistry; esophageal NO2(-), cNOS and iNOS via bioassays; interleukin 1ß (IL-1ß), interleukin-8 (IL-8) via ELISA. PHG caused destructive lesions in the OEM accompanied by the up-regulation of iNOS and down-regulation of cNOS expressions, excessive NO2(-) while COX significantly aggravated the severity of these lesions; L-Try prevented ulcerogenic response to PHG with potent up-regulation of cNOS but did not affect synthesis NO2(-). Mannose (Man)-containing specific a-DMan glycoconjugates labelled by lectins GNA, PSL, LCA, ConA and fucose (Fuc)-rich Fuc-α1 glycoconjugates - PFA, LABA are contributed in OEM integrity. It was shown that the changes of subepithelial and epithelial structures labelled by GNA, PSL, LCA displayed their highest exposure in the surface layer, whereas in the intima of microvasculature and nerve fibres of serosa membrane of the oesophagus by ConA during PHG NEOL. Also, the overexpression of Fuc glycans was present in OEM pre-epithelial and epithelial layers labelled by LABA and in the epithelial-glial-endothelial activity by PFA. Thus, initial changes in endothelial metabolism via iNOS and eNOS can be diagnostic and prognostic markers of NEOL in RO. Our mESNR studies also documented an early increase in pro-inflammatory mediators in the initial stage of oesophageal ulcerogenesis and repair and it can be a model for both proximal and distal oesophageal reflux diseases, as determinate by NEOL in oral mucosa and OEM. These findings suggest that endothelial metabolism is deeply involved in pathogenesis of NEOL. These models may be useful for detecting a new therapeutic strategy NERD, testing anti-ulcer drugs against RO and impaired healing OEM. Our results suggest that L-Try and Mel prevent OEM damage inducted by PHG and oesophagoprotective effect via modulation NO/NOS activity. The anti-inflammatory effect of eCMS could be used to protect oral mucosa and OEM against mESNR.

Effects of nitrosative stress and reactive oxygen-scavenging systems in esophageal physiopathy under streptozotocin-induced experimental hyperglycemia.

Experimental and clinical gastrointestinal data reported that nitrosative stress development involved in impaired barrier function, altered motility and a lowered threshold to noxious stimuli, but its pathogenetic role in diabetic esophagopathy remains unexplored. We tested the hypothesis that an imbalance in nonenzymatic glycation and glycooxidation, enhanced peroxynitrite formation, may play an important role in development esophageal mucosa (EM) lesions during streptozotocin-induced experimental hyperglycemia (EHG). To understand the biological significance of EM resistance in vivo used a glycomic approach to identification of lectin receptors glycosylation pattern. Were enrolled rat groups without/with EHG & modification of NO/NOS activity by L-arginine (L-arg) and indomethacin pre-treatment. Survival rate, destruction occurrence ratio, the size of EM lesions, and the number of EM lesions was investigated. To access the oligosaccharide residues the peroxidase conjugated lectin (HPA, SNA, WGA, PNA)-diaminobenzidine procedure was performed to EM sections. EHG was monitored daily by glucometer. Content of NO (NO(n)) was determinated by Griess reagent and reactive oxygen-scavenging systems (ROSS) activity - generally accepted biochemical methods. In EHG and L-arg pretreatment group reduced NO(n) and EM injury with markedly rise ROSS activity significantly vs to control; in the group with indomethacin pretreatment existed different ROSS activity. Presence of heterogeneous glycosylation pattern in different layers of EM was shown. In EHG staining with PNA and SNA were strongly positive. NS and ROSS play a critical role in esophagoprotection induced by EHG, because both involved increases in iNOS expression. These results indicate the usefulness of glycomic approach as multifunctional substrate of early evaluation of NS in esophageal physiopathy.

Influence of Viburnum opulus proanthocyanidins on stress-induced gastrointestinal mucosal damage.

Recent studies demonstrated that the proanthocyanidins (PA), the polymers of flavan-3-ols, naturally occurring plant metabolites widely available in fruits, vegetables, nuts, seeds, flowers and bark, have anti-inflammatory, anticarcinogenic, anti-allergic, antioxidant and vasodilatory actions. We hypothesized that Viburnum opulus PA (VOPA, Caprifoliaceae), due to activation of multifactorial gastrointestinal mucosal defense mechanisms, exert gastroduodenoprotective effects. The aim of the study was: 1) to investigate VOPA effects on gastroduodenal mucosal integrity and pattern of carbohydrate binding proteins and nitric oxide (NO) content in intact mucosa and that exposed to non-topical ulcerogens (stress) in rats without and with capsaicin (125 mg/kg, sc) denervation; and 2), to assess the role of activity of antioxidizing enzymes superoxide dismutase (SOD), catalase (CAT), gluthatione peroxidase (GPx) in VOPA-induced gastroduodenoprotection against water immersion and restraint stress (WRS) in rats. VOPA was administered orally in dose of 25, 50 or 75 mg/kg body weight. Gastroduodenal mucosal damage detected by routine light microscopic investigation and lectin histochemistry set, purified from plant and animal sources of Carpatian region. NO content, pro-and antioxidant system were determined by routine laboratory methods. Pretreatment with VOPA afforded gastroduodenoprotection and was accompanied by an increase in NO expression, both changes being reversed by sensory denervation, as well as by the rise of SOD, CAT activity and fall in MDA content. Our study shows that VOPA exerts a potent gastroduodenoprotective activity via an increase in endogenous NO generation, suppression of lipid peroxidation and mobilization of antioxidant activity and changes in glycoconjugate content of the gastroduodenal mucosa of rat.

Gastroprotective effects of flavonoids in plant extracts.

The purpose of this paper is to overview the relations between plant-originated substances and their bioactivity measured in terms of antioxidant, cytoprotective and antiulcer activities. In addition, we assessed whether these compounds are capable of affecting the gastric mucosal lesions induced by absolute ethanol applied intragastrically (i.g.). The following plant-originated flavonoid substances were considered; Solon (Sophoradin extract), Amaranth seed extract, grapefruit-seed extract (GSE) and capsaicin (extract of chilly pepper). The area of gastric mucosa lesions and gastric blood flow were measured in rats with ethanol-induced lesions without (control) and with one of the tested substances without and with capsaicin denervation of afferent nerves or administration of L-nitro-arginine (L-NNA), an inhibitor of nitric oxide synthase (NOS). Male Wistar rats, weighing 180-220 g fasted for 24 h before the study where used 100% ethanol was applied i.g. to induce gastric lesions, whose area was determined by planimetry. Gastric blood flow was assessed using electrolytic regional blood flowmeter. All tested plant-originated substances afforded gastroprotection against ethanol-induced damage and this was accompanied by increase in gastric microcirculation, both changes being reversed by pretreatment with neurotoxic dose of capsaicin or by pretreatment with L-NNA. We conclude that plant-originated flavonoid substances are highly gastroprotective probably due to enhancement of the expression of constitutive NOS and release of NO and neuropeptides such as calcitonin gene related peptide (CGRP) released from sensory afferent nerves increasing gastric microcirculation.

Influence of plant-originated gastroproteciive and antiulcer substances on gastric mucosal repair.

UNLABELLED: Fundamental basis of cellular and molecular mechanisms involved in mucosal injury and repair in gastrointestinal tract helps to develop new therapeutic approaches to various gut mucosal injury- related diseases. The study was aimed to assess the relations between plant-originated substances and their bioactivity measured in terms of antioxidant, cytoprotective and antiulceric activities and to deteminate if these effects are capable of affecting the gastric mucosal lesions induced by absolute ethanol applied intragastrically. The following plant-originated substances were considered: Solon, capsaicin, grapefruit-seed extract and amaranth. The area of gastric mucosa lesions and gastric blood flow were measured in rats with ethanol-induced lesions without (control) and with one of the tested substances without and with capsaicin denervation of afferent nerves or administration of L-nitro-arginine (L-NNA), an inhibitor of nitric oxide synthase (NOS). MATERIAL/METHODS: male Wistar rats, weighing 180-220 g fasted for 24 h before the study, 100% ethanol was applied ig to induced gastric lesions, whose area was determined by planimetry. Gastric blood flow was assessed using electrolytic regional blood flowmeter. RESULTS: All tested plant-originated substances afforded gastroprotection against ethanol-induced damage and this was accompanied by an increase in gastric microcirculation, both changes being reversed by pretreatment with neurotoxic dose of capsaicin or by pretreatment-with L-NNA. CONCLUSIONS: Plant-originated substances are highly gastroprotective probably due to enhancement of the expression of NOS I, NO release and an increase in gastric microcirculation.