Cellular and molecular mechanisms of 17beta-estradiol postconditioning protection against gastric mucosal injury induced by ischemia/reperfusion in rats

Protective Effect of Tea Saponins on Alcohol-Induced Gastric Mucosal Injury in Mice

Excessive alcohol consumption harms the human body, particularly the digestive system, by causing damage to the gastric mucosa. Tea saponin is a natural active substance extracted from tea tree seeds that has gastroprotective potential against alcohol-induced mucosal damage. However, the protective mechanism of tea saponins is not fully understood. The current study aimed to explore the protective mechanism of tea saponins against alcohol-induced gastric mucosal injury in mice. Histopathological changes, immunohistochemistry, immunoblotting, and gastric mucosa-related cytokine levels were analyzed in three groups of male mice: model, control, and tea saponin-treated. Compared to the model group, the tea saponin group prominently ameliorated alcohol-induced gastric mucosal injury by improving cell necrosis, inflammatory cell infiltration, and edema. Downregulation of inflammation-related factors cluster of differentiation 68 (CD68), myeloperoxidase (MPO), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) was also found in the tea saponin group. These results suggest that tea saponins have a protective effect against alcohol-induced gastric mucosal damage in mice. Therefore, tea saponin may serve as a food additive for gastric mucosal protection.

Role of the antioxidant pathway in the healing of peptic ulcers induced by ischemia-reperfusion in male and female rats treated with Eugenia punicifolia

Ischaemia and reperfusion (I/R)-induced gastrointestinal disorders are caused by free radicals, resulting in organ damage and functional disarrangement. This study aimed to investigate the healing effects of hydroalcoholic extracts from the leaves of Eugenia punicifolia (Kunth) DC. (HEEP) in male and female Wistar rats with I/R-induced peptic injuries, and the role of antioxidants in improving this response. After I/R-induced gastric and duodenal injuries, male and female [intact (INT) and ovariectomized (OVZ)] rats were orally treated with HEEP for 6 days. Biochemical analysis was used to determine the catalase (CAT), superoxide dismutase (SOD), and myeloperoxidase (MPO) activities, as well as malondialdehyde and reduced glutathione levels, to measure the gastric and duodenal healing process. Six days of HEEP treatment significantly decreased the I/R-induced gastric [male (73.68%), INT (52.83%), and OVZ (43.13%)] and duodenal damage [male (57.03%), INT (56.04%), and OVZ (54.83%)] in all groups. In OVZ rats, the healing effect of HEEP occurred because of the increased activity of SOD (2x) and CAT (1.16x) in the gastric mucosa. In the duodenal mucosa of INT rats, the extract reduced MPO (20.83%) activity. The 6-day HEEP treatment improved the healing of I/R-induced peptic ulcer injury, with the system acting differently in males and females. The antioxidant system is an important component of the HEEP activity during post-I/R mucosal recovery. This result revealed the importance of antioxidant compounds in minimizing the severity of I/R-related events.

Protective effect of histamine microinjected into cerebellar fastigial nucleus on stress gastric mucosal damage in rats

In the study, we investigated the effect of histamine microinjected into cerebellar fastigial nucleus (FN) on stress gastric mucosal damage (SGMD), and its mechanisms in rats. The model of SGMD was established by restraining and water (21±1°C)-immersion for 3h. The gastric mucosal damage index (GMDI) indicated the severity of gastric mucosal damage. Histamine or receptor antagonist was microinjected into the FN. The decussation of superior cerebellar peduncle (DSCP) and the lateral hypothalamic area (LHA) were destroyed, respectively. The pathological changes of gastric mucosa were evaluated using biological signal acquisition system, Laser-Doppler flowmeter, and western blotting. We found that the microinjection of histamine (0.05, 0.5, and 5μg) into FN significantly attenuated the SGMD, in a dose-dependent manner, whereas, the microinjection of histamine H2 receptor antagonist, ranitidine, and glutamic acid decarboxylase antagonist, 3-mercaptopropionic acid (3-MPA) exacerbated the SGMD. The protective effect of histamine on SGMD was abolished by electrical lesion of DSCP or chemical ablation of LHA. The microinjection of histamine decreased the discharge frequency of the greater splanchnic nerve, and the gastric mucosal blood flow was increased. In addition, the cellular proliferation was enhanced, but the cellular apoptosis was reduced in the gastric mucosa. Also the pro-apoptosis protein, Bax, and caspase-3 were down-regulated, and the anti-apoptosis protein, Bcl-2 was up-regulated following microinjection of histamine. In conclusion, the FN participated in the regulation of SGMD after histamine microinjected into FN, and cerebellar-hypothalamic circuits (include: DSCP, LHA) contribute to the process, which may provide a new therapeutic strategy for SGMD.

Remote ischemic postconditioning protects against gastric mucosal lesions in rats

AIM: To investigate the protective effects of remote ischemic postconditioning (RIP) against limb ischemia-reperfusion (IR)-induced gastric mucosal injury.

METHODS: Gastric IR was established in male Wistar rats by placing an elastic rubber band under a pressure of 290-310 mmHg on the proximal part of both lower limbs for 3 h followed by reperfusion for 0, 1, 3, 6, 12 or 24 h. RIP was performed using three cycles of 30 s of reperfusion and 30 s of reocclusion of the femoral aortic immediately after IR and before reperfusion for up to 24 h. Rats were randomly assigned to receive IR (n = 36), IR followed by RIP (n = 36), or sham treatment (n = 36). Gastric tissue samples were collected from six animals in each group at each timepoint and processed to determine levels of malondialdehyde (MDA), superoxide dismutase (SOD), xanthine oxidase (XOD) and myeloperoxidase (MPO). Additional samples were processed for histologic analysis by hematoxylin and eosin staining. Blood samples were similarly collected to determine serum levels of lactate dehydrogenase (LDH), creatine kinase (CK), tumor necrosis factor (TNF)-α and interleukin (IL)-10.

RESULTS: The pathologic changes in gastric tissue induced by IR were observed by light microscopy. Administration of RIP dramatically reduced the gastric damage score after 6 h of reperfusion (5.85 ± 0.22 vs 7.72 ± 0.43; P < 0.01). In addition, RIP treatment decreased the serum activities of LDH (3.31 ± 0.32 vs 6.46 ± 0.03; P < 0.01), CK (1.94 ± 0.20 vs 4.54 ± 0.19; P < 0.01) and the concentration of TNF-α (53.82 ± 0.85 vs 88.50 ± 3.08; P < 0.01), and elevated the concentration of IL-10 (101.46 ± 5.08 vs 99.77 ± 4.32; P < 0.01) induced by IR at 6 h. Furthermore, RIP treatment prevented the marked elevation in MDA (3.79 ± 0.29 vs 6.39 ± 0.81) content, XOD (7.81 ± 0.75 vs 10.37 ± 2.47) and MPO (0.47 ± 0.05 vs 0.82 ± 0.03) activities, and decrease in SOD (4.95 ± 0.32 vs 3.41 ± 0.38; P < 0.01) activity in the gastric tissue as measured at 6 h.

CONCLUSION: RIP provides effective functional protection and prevents cell injury to gastric tissue induced by limb IR via anti-inflammatory and antioxidant actions.

Glutamate microinjection into the hypothalamic paraventricular nucleus attenuates ulcerative colitis in rats

AIM

To investigate the effects of glutamate microinjection into hypothalamic paraventricular nucleus (PVN) on ulcerative colitis (UC) in rats and to explore the relevant mechanisms.

METHODS

2,4,6-Trinitrobenzenesulfonic acid (100 mg/kg in 50% ethanol) was instilled into the colon of adult male SD rats to induce UC. A colonic damage score (CDS) was used to indicate the severity of the colonic mucosal damage. The pathological changes in the colonic mucosa were evaluated using immunohistochemistry, Western blotting, biochemical analyses or ELISA. Ten minutes before UC induction, drugs were microinjected into the relevant nuclei in rat brain to produce chemical stimulation or chemical lesion.

RESULTS

Microinjection of glutamate (3, 6 and 12 μg) into the PVN dose-dependently decreased the CDS in UC rats. This protective effect was eliminated after kainic acid (0.3 μg) was microinjected into PVN or into the nucleus tractus solitarius (NTS) that caused chemical lesion of these nuclei. This protective effect was also prevented when the AVP-V1 receptor antagonist DPVDAV (200 ng) was microinjected into the NTS. The discharge frequency of the vagus was markedly decreased following microinjection of glutamate into the PVN. Microinjection of glutamate into the PVN in UC rats significantly increased the cell proliferation and anti-oxidant levels, and decreased the apoptosis and Bax and caspase 3 expression levels and reduced the pro-inflammatory factors in the colonic mucosa.

CONCLUSION

The activation of hypothalamic PVN exerts protective effects against UC, which is mediated by the NTS and vagus. The effects may be achieved via anti-oxidative, anti-apoptotic, and anti-inflammatory factors.

Protective effects of estrogen on ischemia/reperfusion-induced bladder dysfunction in female rabbits

OBJECTIVE

The present study investigated the effects of ovarian hormone depletion and estrogen administration on ischemia/reperfusion (I/R)-induced bladder damage in female rabbits.

METHODS

Female New Zealand white rabbits were divided into five groups. A sham surgical procedure was performed on rabbits in group 1. In group 2, both vesical arteries were clamped for 2 hours and then released (I/R surgical procedure). In group 3, 17β-estradiol (100 μg/kg/d) was injected intramuscularly before I/R surgical procedure. In group 4, ovariectomies were performed before I/R surgical procedure. Group 5 had ovariectomy, recovered for 2 weeks, and then received 17β-estradiol for 2 weeks. I/R surgical procedure was performed thereafter. Rabbits were killed 7 days after I/R surgical procedure. Masson's trichrome stain was used, and immunohistochemical experiments were performed to evaluate interstitial fibrosis and intramural nerve changes. Western immunoblots were examined to determine the expressions of markers for inflammation, fibrosis, and oxidative stress.

RESULTS

I/R surgical procedure decreased bladder contractile responses by 30% to 50%. Ovarian hormone depletion further reduced bladder contractile function by 45% to 55% compared with the I/R group members that retained their ovaries. Moreover, I/R surgical procedure significantly decreased intramural neurofilament staining by two thirds compared with the control group. Estrogen replacement after ovariectomy significantly increased the density of nerve terminals. In addition, the expression of transforming growth factor-β and fibronectin increased twofold and fivefold after I/R, respectively. Ovarian hormone depletion further increased the expression of these inflammatory and fibrosis markers. Ovariectomy significantly exacerbated oxidative damage, whereas estrogen replacement diminished oxidative stress to a level approaching that of the control group.

CONCLUSIONS

I/R surgical procedure increases oxidative damage, enhances interstitial fibrosis, and results in bladder denervation. Ovarian hormone deficiency exacerbates this I/R-induced bladder damage, whereas estrogen therapy after ovariectomy attenuates this injury. These results reveal estrogen's protective effects on bladders subjected to I/R injury and the potential benefits of estrogen therapy on I/R-induced bladder damage.

γ-Aminobutyric acid-mediated neurotransmission in cerebellar-hypothalamic circuit attenuates gastric mucosal injury induced by ischemia-reperfusion

BACKGROUND

Excessive greater splanchnic nerve (GSN) activation contributes to the progression of gastric ischemia-reperfusion (GI-R) injury. This study was designed to investigate the protective mechanism of cerebellar fastigial nucleus (FN) stimulation against GI-R injury.

METHODS

The GI-R injury model was induced in rats by clamping the celiac artery for 30 min, and then reperfusion for 30 min, 1, 3, 6, or 24 h, respectively.

KEY RESULTS

Microinjection of L-Glu (3, 6, 12 μg) into the FN dose-dependently attenuated GI-R injury and GSN activity. In addition, there was an enhancement of gastric mucosal blood flow in GI-R rats. Pretreatment with the glutamic acid decarboxylase antagonist into the FN, the GABAA receptor antagonist into the lateral hypothalamic area or lesion of superior cerebellar peduncle all reversed the protective effects of the FN stimulation. Furthermore, the FN stimulation reduced the TUNEL-positive gastric mucosal cell and Bax-positive gastric mucosal cell in GI-R rats.

CONCLUSIONS & INFERENCES

These results indicate that the protective effects of the FN stimulation against GI-R injury may be mediated by attenuation of the excessive GSN activation, gastric mucosal cell apoptosis, and Bax expression in GI-R rats.

In vivo intranasal anti-CD23 treatment inhibits allergic responses in a murine model of allergic rhinitis

Although CD23-dependent transcytosis of IgE and IgE-derived immune complexes across respiratory epithelial cells is likely to play a pivotal role in the initiation and development of airway allergic inflammation, there is currently a lack of physiological support for this phenomena to suggest that the targeting of CD23 could be used as a means of therapeutic intervention. The present study was designed to detect the CD23 expression in the nasal mucosa of allergic rhinitis (AR) murine model by immunohistochemistry and western blotting, and to investigate whether intranasal anti-CD23 treatment could inhibit allergen-induced upper airway inflammation in the AR model. This is the first report to show that CD23 was constitutively expressed in murine nasal epithelial cells, and its expression was significantly up-regulated in the AR murine model. In vivo, the up-regulation of CD23 expression was correlated with increased serum IL-4 levels. Following intranasal anti-CD23 treatment, nasal symptoms were alleviated and histopathologic examination showed a significant decrease in eosinophilic infiltration. Meanwhile, ELISA analysis showed levels of serum leukotriene C4 (LTC4), eosinophil cation protein (ECP), ovalbumin (OVA)-specific IgE and IL-4 also significantly decreased, as were LTC4 and OVA-specific IgE in the nasal lavage fluid. Furthermore, Western blotting analysis showed that ECP expression in the nasal mucosa was down-regulated. Finally, flow cytometric analysis revealed anti-CD23 treatment inhibited Th2 cell responses. These results indicate that intranasal anti-CD23 treatment can reduce allergic responses in a murine model of allergic rhinitis.

Muscimol microinjection into cerebellar fastigial nucleus exacerbates stress-induced gastric mucosal damage in rats

AIM

To investigate the effects of microinjection of the GABA(A) receptor agonist muscimol into cerebellar fastigial nucleus (FN) on stress-induced gastric mucosal damage and the underlying mechanism in rats.

METHODS

Stress-induced gastric mucosal damage was induced in adult male SD rats by restraining and immersing them in cold water for 3 h. GABA(A) receptor agonist or antagonist was microinjected into the lateral FN. The decussation of superior cerebellar peduncle (DSCP) was electrically destroyed and the lateral hypothalamic area (LHA) was chemically ablated by microinjection of kainic acid. The pathological changes in the gastric mucosa were evaluated using TUNEL staining, immunohistochemistry staining and Western blotting.

RESULTS

Microinjection of muscimol (1.25, 2.5, and 5.0 μg) into FN significantly exacerbated the stress-induced gastric mucosal damage in a dose-dependent manner, whereas microinjection of GABA(A) receptor antagonist bicuculline attenuated the damage. The intensifying effect of muscimol on gastric mucosal damage was abolished by electrical lesion of DSCP or chemical ablation of LHA performed 3 d before microinjection of muscimol. Microinjection of muscimol markedly increased the discharge frequency of the greater splanchnic nerve, significantly increased the gastric acid volume and acidity, and further reduced the gastric mucosal blood flow. In the gastric mucosa, further reduced proliferation cells, enhanced apoptosis, and decreased anti-oxidant levels were observed following microinjection of muscimol.

CONCLUSION

Cerebellar FN participates in the regulation of stress-induced gastric mucosal damage, and cerebello-hypothalamic circuits contribute to the process.

Lateral hypothalamic area mediated the aggravated effect of microinjection of Baclofen into cerebellar fastigial nucleus on stress gastric mucosal damage in rats

Cerebellum, primarily believed as a subcortical somatic motor center, is increasingly considered to be implicated in visceral activities. However, little is known about its regulation on gastrointestinal organs. In this research, we investigated the aggravated effect of microinjection of gamma-aminobutyric acid receptor subtype B (GABA(B)R) agonist, Baclofen into cerebellar fastigial nucleus (FN) on stress gastric mucosal damage (SGMD) and its possible regulatory mechanism. The gastric mucosal damage index was chosen to indicate the severity of gastric mucosal injure. Immunohistochemistry and transferase-mediated dUTP-biotin nick-endlabeling (TUNEL) methods were used to detect the variations of lateral hypothalamic area (LHA) and gastric mucosa. It had been demonstrated that FN participates in regulation of SGMD via its GABA(B)R and GABA neural pathway, which passes through the decussation of superior cerebellar peduncle and projects to the GABA receptors in LHA. Meanwhile, celiac sympathetic nerve involves in this process via mediating neural discharge, which results in the decrease of gastric mucosal blood flow. Additionally, apoptosis, proliferation and oxidation in gastric mucosa, and gastric acid contribute in the mechanism. It could be expected that these results might suggest insights to the cerebellar and hypothalamic function, and the treatment of gastrointestinal diseases.

Gastroprotective activity of Zanthoxylum rhoifolium Lam. in animal models

ETHNOPHARMACOLOGICAL RELEVANCE

The stem barks of Zanthoxylum rhoifolium Lam. (Rutaceae), locally known as "mamica de cadela", are popularly used in dyspepsies, stomachic, tonic, antitumoral, antipyretic and are used in treating flatulence and colic. The objective of this study was to evaluate the gastroprotective effect of the ethanolic extract of Zanthoxylum rhoifolium (EEZR) stem barks in acute gastric lesion models, investigating their possible mechanisms.

MATERIALS AND METHODS

Mice were used for the evaluation of the acute toxicity, and mice and rats to study the gastroprotective activity. The gastroprotective action of EEZR was analyzed in the absolute ethanol, HCl/ethanol and indomethacin-induced gastric lesion models in mice, hypothermic-restraint stress, and ischemia/reperfusion in rats. In the investigation of the gastroprotective mechanisms of EEZR, the participation of the NO-synthase pathway, ATP-sensitive potassium channels (K(ATP)), the levels of the non-protein sulfhydril groups (NP-SH) and the catalase activity using the ethanol-induced gastric mucosa lesion model and the quantification of the gastric mucus and the antisecretory activity through pylorus ligature model in rats were analyzed.

RESULTS

The animals did not present any signs of acute toxicity for the EEZR (up to the 4 g/kg dose, po), and it was not possible to calculate the DL(50). EEZR (125-500 mg/kg) exhibited a significant gastroprotective effect in absolute ethanol, HCl/ethanol, hypothermic-restraint stress, and ischemia/reperfusion-induced gastric lesion models. EEZR (250 and 500 mg/kg) exhibited still a gastroprotective activity in the indomethacin-induced ulcer model. Gastroprotection of EEZR was significantly decreased in pre-treated mice with l-NAME or glibenclamide, the respective nitric oxide synthase and K(ATP) channels inhibitors. Our studies revealed that EEZR (500 mg/kg) prevented the decrease of the non-protein sulfhydril groups (NP-SH) and increased the catalase levels in ethanol-treated animals. Furthermore, the extract (500 mg/kg) significantly increased the mucus production, however, the gastric secretion parameters (volume, [H(+)], pH) did not show any alteration.

CONCLUSIONS

Our results indicate that the ethanolic extract of Zanthoxylum rhoifolium exhibits a significant gastroprotection, because it inhibits the formation of gastric lesions using different models. The release of the nitric oxide, the opening of the K(ATP) channels, the participation of the non-protein sulfhydril groups (NP-SH), catalase and the increase of mucous secretion seem to be involved in the gastroprotection activity of the EEZR. Nevertheless, this activity does not seem to be related to antisecretory mechanisms.

Differential expression of Bcl-2 and Bax during gastric ischemia-reperfusion of rats

AIM: To investigate expression of Bcl-2 and Bax in gastric ischemia-reperfusion (GI-R) and involvement of extracellular signal-regulated kinase (ERK) 1/2 activation.

METHODS: The GI-R model was established by ligature of the celiac artery for 30 min and reperfusion in Sprague-Dawley rats. Rats were assigned to groups in accordance with their evaluation period: control, 0, 0.5, 1, 3, 6, 24, 48, and 72 h. Expression and distribution of Bcl-2 and Bax proteins were analyzed by immunohistochemistry and western blotting in gastric tissue samples after sacrifice.

RESULTS: Compared with controls, the percentage of positive cells and protein levels of Bcl-2 decreased in the early phases of reperfusion, reached its minimum at 1 h (P < 0.05); it then increased, reaching its peak at 24 h of reperfusion (P < 0.05). The pattern of Bax expression was opposite to that of Bcl-2. Bax expression increased after reperfusion, with its peak at 1 h of reperfusion (P < 0.05), and then it decreased gradually to a minimum at 24 h after reperfusion (P < 0.05). On the other hand, inhibition of activation of ERK1/2 induced by PD98059, a specific upstream MEK inhibitor, had significant effects on Bcl-2 and Bax in GI-R. Compared with GI-R treatment only at 3 h of reperfusion, PD98059 reduced the number of Bcl-2 positive cells (0.58% of R3h group, P < 0.05) and Bcl-2 protein level (74% of R3h group, P < 0.05) but increased the number of Bax-positive cells (1.33-fold vs R3h group, P < 0.05) and Bax protein level (1.35-fold of R3h group, P < 0.05).

CONCLUSION: These results indicated that the Bcl-2 and Bax played a pivotal role in the gastric mucosal I-R injury and repair by activation of ERK1/2.

The protective effect of 17beta-estradiol postconditioning against hypoxia/reoxygenation injury in human gastric epithelial cells

The purpose of this study was to investigate the effects and mechanisms of 17beta-estradiol pharmacological postconditioning on gastric epithelial cells hypoxia/reoxygenation injury by using an in vitro model of human gastric epithelial cells. The model of hypoxia/reoxygenation was established with human gastric epithelial cell line. The gastric epithelial cell viability was detected by 3-(4, 5-dimethylthazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assays. Gastric epithelial cellular apoptosis was determined by Hoechst 33258 fluorochrome staining and flow cytometric analysis. Contents of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) were measured by Colorimetry analysis. The protein expression of Bcl-2 and Bax in different groups was determined by Western blot analyses and immunocytochemistry assay. 17beta-estradiol (10(-8), 10(-7) and 10(-6)mol/l) inhibited hypoxia/reoxygenation injury and 17beta-estradiol (10(-6)mol/l) obviously attenuated hypoxia/reoxygenation injury 3h hypoxia followed by 4h reoxygenation. 17beta-estradiol promoted gastric epithelial cell viability and inhibited the gastric epithelial cell apoptosis, and meanwhile, decreased the MDA content and increased SOD activity. The level of Bcl-2 protein was restored to the normal level by 17beta-estradiol pharmacological postconditioning. In contrast, the Bax protein level was markedly reduced by 17beta-estradiol pharmacological postconditioning. These effects of 17beta-estradiol were inhibited by pretreatment with fulvestrant. These data suggested that 17beta-estradiol seems involved in regulation of gastric hypoxia/reoxygenation injury and gastroprotection, and its protective effects were strongly related to estrogen receptor.