Protective role of metallothionein in stress-induced gastric ulcer in rats

Protective effect of the solvent extracts of Portulacca oleracea against acidified ethanol induced gastric ulcer in rabbits

Portulacca oleracea L. has been used for treatment of different ailments. The aim of this study was to investigate the effectiveness and possible mechanism of action involved in the anti gastric ulcerogenic effect of Portulacca oleracea. Methanolic extract & subsequent fractions (100, 200 and 400 mg/kg) of Portulacca oleracea (P. oleracea) were administered orally to experimental rabbits one hour before oral administration of HCl/ethanol (40:60). Anti gastric ulcerogenic potential of P. oleracea was evaluated by assessment of gastric pH, pepsin, free acidity, ulcer index, mucus content and total acidity. For the investigation of possible mechanism of action malondialdehyde (MDA), histamine, and H + K + ATPase content were determined in the stomach homogenate. Histopathological study of stomach tissue was carried out by H&E dye. Ethyl acetate fraction (EAF) of P. oleracea was the most potent fraction among all fractions that exhibited efficient protection against acidified ethanol mediated gastric-ulcer. The ethyl acetate fraction (EAF) significantly increased the pH of gastric juice, while pepsin and histamine was observed to decrease significantly in comparison to acidified ethanol group (***p ≤ 0.001). The EAF showed moderately H + K + ATPase inhibitory activity. Moreover, it was also observed that EAF decreased the malondialdehyde (MDA) level in the stomach tissue homogenate showing antioxidant effect. Histopathological studies showed that among the tested fractions, EAF significantly prevented acidified ethanol induced gastric mucosal damage. These results showed that mechanism of anti gastric ulcerogenic potential of P. oleracea could be associated with the reduction in histamine level, H + K + ATPase inhibition and reduced MDA level.

The critical role of microRNAs in stress response: Therapeutic prospect and limitation

Stress response refers to the systemic nonspecific response upon exposure to strong stimulation or chronic stress, such as severe trauma, shock, infection, burn, major surgery or improper environment, which disturb organisms and damage their physical and psychological health. However, the pathogenesis of stress induced disorder remains complicated and diverse under different stress exposure. Recently, studies have revealed a specific role of microRNAs (miRNAs) in regulating cellular function under different types of stress, suggesting a significant role in the treatment and prevention of stress-related diseases, such as stress ulcer, posttraumatic stress disorder, stress-induced cardiomyopathy and so on. This paper have reviewed the literature on microRNA related stress diseases in different databases including PubMed, Web of Science, and the MiRbase. It considers only peer-reviewed papers published in English between 2004 and 2018. This review summarizes new advances in principles and mechanisms of miRNAs regulating stress signalling pathway and the role of miRNAs in human stress diseases. This comprehensive review is to provide an integrated account of how different stresses affect miRNAs and how stress-miRNA pathways may, in turn, be linked with disease, which offers some potential strategies for stress disorder treatment. Furthermore, the limitation of current studies and challenges for clinical use are discussed.

Effects of the IGF-1/PTEN/Akt/FoxO signaling pathway on male reproduction in rats subjected to water immersion and restraint stress

The aim of the present study was to determine the effects of the insulin-like growth factor 1 (IGF-1)/phosphatase and tensin homologue deleted on chromosome 10 (PTEN)/Akt/forkhead box (FoxO) signaling pathway on male reproduction in rats subjected to water immersion and restraint stress (WRS). Sperm morphology, sperm malformation rate, and serum testosterone concentration were analyzed following WRS. In addition, the expression levels and immunolocalization of IGF-1, PTEN, Akt and FoxO proteins, as well as the rate of cell apoptosis in rat testes, were investigated. The results indicated that sperm malformation rate, serum testosterone concentration, and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were increased in the testes after WRS. Furthermore, IGF-1 and FoxO1 proteins were predominantly localized in the sperm cytoplasm during the late stages of spermatogenesis. FoxO1 protein was also localized in Leydig cell cytoplasm. PTEN and total Akt proteins were predominantly expressed in the cytoplasm of Leydig cells and spermatogonia. PTEN protein was also detected in vascular endothelial cells. In addition, IGF-1, PTEN, Akt1, Akt2, FoxO3 and FoxO4 gene expression levels were upregulated following WRS, and peaked after 7 h of WRS. During the recovery period, the expression levels of these genes gradually returned to normal levels. The present study demonstrated that WRS induced sperm damage in the testes. In addition, the results indicated that the IGF-1/PTEN/Akt/FoxO signaling pathway may serve an anti-stress role in the testes of rats subjected to WRS.

Gastroprotective effects (in rodents) of a flavonoid rich fraction obtained from Syngonanthus macrolepsis

Objectives

Syngonanthus macrolepis, popularly known in Brazil as ‘sempre-vivas’, is a plant from the family Eriocaulaceae, it is found in the states of Minas Gerais and Bahia. The species contains a variety of constituents, including flavonoids with gastroprotective effect. In this work, a flavonoid-rich fraction (Sm-FRF) obtained from scapes of S. macrolepis was investigated for preventing gastric ulceration in mice and rats.

Methods

The activity was evaluated in models of induced gastric ulcer (absolute ethanol, stress, non-steroidal anti-inflammatory drugs and pylorus ligation). The cytoprotective mechanisms of the Sm-FRF in relation to sulfhydryl (SH) groups, nitric oxide (NO) and antioxidant enzymes were also evaluated.

Key findings

The Sm-FRF (100 mg/kg, p.o.) significantly reduced gastric injury in all models, and did not alter gastric juice parameters after pylorus ligation.

Conclusions

The results indicate significant gastroprotective activity for the Sm-FRF, which probably involves the participation of both SH groups and the antioxidant system. Both are integral parts of the gastrointestinal mucosa's cytoprotective mechanisms against aggressive factors.

Metallothionein 2A inhibits NF-κB pathway activation and predicts clinical outcome segregated with TNM stage in gastric cancer patients following radical resection

Background

Metallothionein 2A (MT2A) as a stress protein, plays a protective role in gastric mucosal barrier. Its role in the development of gastric cancer (GC) is unclear. The mechanism of MT2A will be investigated in gastric tumorigenesis.

Methods

MT2A expression was detected in 973 gastric specimens. The biological function was determined through ectopic expressing MT2A in vitro and in vivo. The possible downstream effectors of MT2A were investigated in NF-κB signaling. The protein levels of MT2A, IκB-α and p-IκB-α (ser32/36) expression were analyzed in a subset of 258 patients by IHC staining. The prognostic effects of MT2A, status of IκB-α and TNM stage were evaluated using the Kaplan-Meier method and compared using the log-rank test.

Results

Decreased MT2A expression was detected in cell lines and primary tumors of GC. In clinical data, loss of MT2A (MT2A + in Normal (n =171, 76.0%); Intestinal metaplasia (n = 118, 50.8%); GC (n = 684. 22.4%, P < 0.001)) was associated with poor prognosis (P < 0.001), advanced TNM stage (P = 0.05), and down-regulation of IκB-α expression (P < 0.001). Furthermore, MT2A was the independent prognostic signature segregated from the status of IκB-α and pathological features. In addition, MT2A inhibited cell growth through apoptosis and G2/M arrest, which negatively regulated NF-κB pathway through up-regulation of IκB-α and down-regulation of p-IκB-α and cyclin D1 expression.

Conclusions

MT2A might play a tumor suppressive activity through inhibiting NF-κB signaling and may be a prognostic biomarker and potential target for individual therapy of GC patients.

Effect of the IGF-1/PTEN/Akt/FoxO signaling pathway on the development and healing of water immersion and restraint stress-induced gastric ulcers in rats

Insulin-like growth factor 1 (IGF-1) and Akt [also known as protein kinase B (PKB)] proteins have been reported to exhibit gastroprotective effects by reducing water immersion and restraint stress (WRS)-induced gastric mucosal cellular apoptosis. To confirm whether the IGF-1/PTEN/Akt/FoxO signaling pathway is effective in protecting against gastric ulcers, our current study was conducted to examine the expression and localization of IGF-1, phosphatase and tensin homologue deleted on chromosome 10 (PTEN), Akt and O subfamily of forkhead box (FoxO) proteins, caspase-3 activity and the number of apoptotic cells in gastric mucosa of rats subjected to WRS. Our results demonstrated that WRS induced gastric ulcers by enhancing cell apoptosis in rat gastric mucosa. In addition, in normal rat gastric mucosa, PTEN, total Akt and FoxO1 were found mainly in the cell cytoplasm of fundic glands in the lamina propria close to the muscularis mucosa. In addition, strong staining of IGF-1, FoxO3a and FoxO4 in the gastric mucosa was primarily concentrated in the cell cytoplasm of the fundic glands in whole lamina propria. However, in rat gastric ulcers, IGF-1, total Akt, FoxO3a and FoxO4 were localized in proximity to the base of the ulcer margin and were also present in the granulation tissues of the gastric ulcers. Moreover, in the rat gastric ulcers, the mRNA transcript levels of IGF-1, PTEN, Akt-1, Akt-2, FoxO3 and FoxO4 were upregulated in the gastric ulcer margin, with a peak between Days 4 and 8 following 7 h of WRS. In conclusion, our results imply that the IGF-1/PTEN/Akt/FoxO signaling pathway plays a certain role(s) in the protection against ulceration through the regulation of cellular apoptosis as observed in the development and healing of rat gastric ulcers.

Mitigating endoplasmic reticulum stress with revaprazan ameliorates stress-related mucosal disease

BACKGROUND AND AIM

The term "stress-related mucosal disease" (SRMD) represents conditions ranging from superficial mucosal damage to focal deep mucosal damage in the stomach, of which pathogenesis is deduced to be violent mucosal ischemia or excess oxidative stress, but not fully clarified yet. Under the hypothesis that mucosal cell apoptosis subsequent to endoplasmic reticulum (ER) stress might play a crucial role, we evaluated the efficacy and mechanism that novel acid pump antagonist (APA), revaprazan, alleviated water immersion restraint stress (WIRS) induced SRMD in rats.

METHODS

In order to define whether WIRS-induced SRMD is associated with ER stress, we checked the alteration in the expression of ER stress markers including GRP78, CHOP, XBP-1, BiP as well as apoptosis in WIRS-induced SRMD. The efficacy of revaprazan on either alleviating ER stress or attenuating SRMD was compared with proton pump inhibitor (PPI) and gastroprotectant.

RESULTS

Ten hours of WIRS induced a severe degree of SRMD, in which ER stress markers including CHOP, XBP1, and BiP were significantly overexpressed in the gastric tissues. However, these markers of ER stress were significantly decreased in the group pretreated with revaprazan compared to PPI or gastroprotectant, accompanied with a significant reduction in apoptotic index. In addition to ER stress, revaprazan imposed anti-inflammatory benefit to limit SRMD based on significant levels of inflammatory cell apoptosis.

CONCLUSION

Endoplasmic reticulum stress accompanied with drastic apoptosis was implicated in the development of SRMD, but revaprazan could rescue the stomach from SRMD through alleviating ER stress in epithelial cells much better than either PPI or gastroprotectant.

Metallothionein and brain inflammation

Since the seminal discoveries of Bert Vallee regarding zinc and metallothioneins (MTs) more than 50 years ago, thousands of studies have been published concerning this fascinating story. One of the most active areas of research is the involvement of these proteins in the inflammatory response in general, and in neuroinflammation in particular. We describe the general aspects of the inflammatory response, highlighting the essential role of the major cytokine interleukin-6, and review briefly the expression and function of MTs in the central nervous system in the context of neuroinflammation. Particular attention is paid to the Tg2576 Alzheimer disease mouse model and the preliminary results obtained in mice into which human Zn(7)MT-2A was injected, which suggest a reversal of the behavioral deficits while enhancing amyloid plaque load and gliosis.

The content of elements in rainwater and its relation to the frequency of hospitalization for gastric and duodenal peptic ulcers in Opole Voivodship, Poland, during 2000-2002

The relationship between chemical elements in rainwater and the frequency of hospitalizations for gastric and duodenal peptic ulcers was studied on the population of the province (Voivodship) of Opole, Poland, during the years 2000-2002. There is a high positive correlation between hospitalized cases of gastric peptic ulcers with chromium in rainwater (r = 0.71), cadmium (r = 0.63), and lead (r = 0.70). Mild positive correlations were found with zinc (r = 0.55), copper (r = 0.56), iron (r = 0.57), chloride (r = 0.60), and sulfate (r = 0.52). These correlations were higher on men, suggesting that there are gender correlations involved. In duodenal peptic ulcers, we observed a high positive correlation between chromium in rainwater and hospitalized cases (r = 0.61) and mild positive correlations with lead (r = 0.57), copper (r = 0.52), and cadmium (r = 0.51). Significant gender differences were not found. These positive correlations may be due to the biological activity of the elements, such as their cytotoxic activity, enhanced local adrenergic stimulation on mucosal vasculature, ion channel (mainly calcium channels) remodeling, and, for example promoting infection by Helicobacter pylori.

Modulation of protein tyrosine phosphorylation in gastric mucosa during re-epithelization processes

AIM: To investigate the role of protein tyrosine phosphorylation in gastric wound formation and repair following ulceration.

METHODS: Gastric lesions were induced in rats using restraint cold stress. To investigate the effect of oxidative and nitrosative cell stress on tyrosine phosphorylation during wound repair, total activity of protein tyrosine kinase (PTK), protein tyrosine phosphatase (PTP), antioxidant enzymes, nitric oxide synthase (NOS), 2’,5’-oligoadenylate synthetase, hydroxyl radical and zinc levels were assayed in parallel.

RESULTS: Ulcer provocation induced an immediate decrease in tyrosine kinase (40% in plasma membranes and 56% in cytosol, P < 0.05) and phosphatase activity (threefold in plasma membranes and 3.3-fold in cytosol), followed by 2.3-2.4-fold decrease (P < 0.05) in protein phosphotyrosine content in the gastric mucosa. Ulceration induced no immediate change in superoxide dismutase (SOD) activity, 30% increase (P < 0.05) in catalase activity, 2.3-fold inhibition (P < 0.05) of glutathione peroxidase, 3.3-fold increase (P < 0.05) in hydroxyl radical content, and 2.3-fold decrease (P < 0.05) in zinc level in gastric mucosa. NOS activity was three times higher in gastric mucosa cells after cold stress. Following ulceration, PTK activity increased in plasma membranes and reached a maximum on day 4 after stress (twofold increase, P < 0.05), but remained inhibited (1.6-3-fold decrease on days 3, 4 and 5, P < 0.05) in the cytosol. Tyrosine phosphatases remained inhibited both in membranes and cytosol (1.5-2.4-fold, P < 0.05). NOS activity remained increased on days 1, 2 and 3 (3.8-, 2.6-, 2.2-fold, respectively, P < 0.05). Activity of SOD increased 1.6 times (P < 0.05) days 4 and 5 after stress. Catalase activity normalized after day 2. Glutathione peroxidase activity and zinc level decreased (3.3- and 2-fold, respectively, P < 0.05) on the last day. Activity of 2’,5’-oligoadenylate synthethase increased 2.8-fold (P < 0.05) at the beginning, and 1.6-2.3-fold (P < 0.05) during ulcer recuperation, and normalized on day 5, consistent with slowing of inflammation processes.

CONCLUSION: These studies show diverse changes in total tyrosine kinase activity in gastric mucosa during the recovery process. Oxidative and nitrosative stress during lesion formation might lead to the observed reduction in tyrosine phosphorylation during ulceration.

Recombinant Human Epidermal Growth Factor Alleviates Gastric Antral Ulcer Induced by Naproxen: A Non-steroidal Anti Inflammatory Drug

BACKGROUND

To study the effect (s) of recombinant human Epidermal Growth Factor (rhEGF) on naproxen induced gastric ulcer in Wistar NIN rats.

METHODS

Male Wistar NIN rats were randomly divided into six experimental groups: Group I - Control, Group II - Naproxen treated, Group III - Naproxen with rhEGF/7 days, Group IV - Naproxen without rhEGF/7 days, Group V - Naproxen with rhEGF/14 days, and Group VI - Naproxen without rhEGF/14 days. Gastric ulcer was induced with naproxen at a concentration of 80 mg/kg by oral administration. After 24 hours of induction of ulcer, rhEGF treatment was started at a concentration of 100 µg/kg. Ulcer presence and healing were confirmed by histopathology study and molecular markers.

RESULTS

Naproxen per se induced gastric antral ulcers in Wistar NIN rats. Compared with control rats, naproxen induced rats had increased lipid peroxide content in serum. Subsequent decrease in lipid peroxide was observed in rhEGF treated groups. Treatment with rhEGF significantly resulted in healing of the ulcers, which was evident by 7 days of rhEGF treatment with total healing seen by 14 days. Significant increase in immunoreactivity for Cox-2 was observed when compared to control groups, whereas less immunoreactivity of Cox-2 was observed in rhEGF treated group. Compared with control group, naproxen induced group exhibited more gene expression of both Cox-2 and TGF beta while gene expression of Cox-2 and TGF beta in rhEGF group was comparable to control group.

CONCLUSIONS

The beneficial effects of rhEGF in the management of ulcer healing can be understood. Oral rhEGF can promote healing of the rats with gastric ulcer by stimulating Cox-2 and TGF-beta expression.

Effects of exogenous metallothionein against thallium-induced oxidative stress in rat liver

Metallothionein (MT) is a low-molecular weight sulfur-rich protein that plays role in metal homeostasis/detoxification and radical scavenging. The following study investigated the ability of exogenous MT to protect against oxidative damage induced by thallium (TI) in rat liver. Male Wistar rats were divided into four groups; a control and three experimental groups. The control group received physiological saline. Group 1 animals were injected with thallium acetate intraperitoneally (i.p.) at a single dose of LD(50) (32 mg/kg). In group 2 and group 3, metallothionein I was administrated once at two different doses (1 or 2.5mg/kg i.p., respectively) 1h before TI intoxication. Levels of endogenous antioxidants, oxidative stress markers were measured and histopathological examinations were performed 4 days after TI administration. TI accumulation in liver decreased related to the dose of MT. Mostly all of the alterations in the levels antioxidants restored to normal levels in MT administrated animals. H(2)O(2) levels and lipid peroxidation decreased, integrity of hepatocytes and membranous structures inside the cells were preserved. The toxic effects of TI were modulated in MT administrated animals particularly at the dose of 2.5mg/kg. These findings suggest an active role of exogenous MT against TI-induced oxidative stress in rat liver.

Hydrogen sulphide-induced hypothermia attenuates stress-related ulceration in rats

1. Hydrogen sulphide (H(2)S) acts as a gaseous cellular messenger and has recently been reported to induce a suspended animation-like state in mice. The aim of the present study was to investigate the protective role of H(2)S exposure in stress gastric ulcer. 2. In the present study, we used a rat model of water immersion and restraint stress (WRS) to induce the typical stress disease, namely stress gastric ulcer. Rats were treated with WRS for 4 h, with or without pre-exposure to H(2)S (160 p.p.m. H(2)S for 2.5 h). 3. In H(2)S-exposed rats, body temperature was significantly reduced by 2.5C (P < 0.01) and oxygen consumption was reduced by 37.1% (P < 0.01) compared with control rats. Plasma levels of H(2)S were increased by 20.8% (P < 0.01) following pre-exposure. Pre-exposure to H(2)S significantly reduced the gastric ulcer index, from 24 +/- 9 to 9 +/- 2 (P < 0.01), in WRS rats. In addition, WRS increased plasma levels of adrenocorticotropin (ACTH) and corticosterone 4.7- and 4.8-fold, respectively (both P < 0.01). Pre-exposure to H(2)S markedly suppressed plasma ACTH and corticosterone level by 34.4 and 53.2%, respectively (both P < 0.01), and reduced WRS-elevated myeloperoxidase (MPO) activity by 19%. In the present study, WRS increased gastric malondialdehyde and conjugated diene content by 42 and 68%, respectively (both P < 0.01), and H(2)S exposure reduced lipid peroxide production. Finally, H(2)S exposure inhibited the WRS-elevated expression of glucose-regulated protein 78 and caspase 12, markers of endoplasmic reticulum stress. 4. In conclusion, a low concentration of H(2)S may be a new pharmacological tool for induced hypothermia to prevent severe stress-induced diseases and multifarious trauma in the clinical setting.

Endoplasmic reticulum stress response is involved in the pathogenesis of stress induced gastric lesions in rats

Stress gastric ulcer is a serious complication, but the mechanism involved is not fully clarified. It is well known that mucosal cell apoptosis plays a crucial role in the pathogenesis of gastric ulceration. Recent studies have shown that endoplasmic reticulum (ER) stress is an important pathway leading to cellular apoptosis. To investigate the role of ER stress in the pathogenesis of stress gastric ulcer, we studied the alteration in the expression of ER stress markers GRP78 (glucose-regulated protein 78) and caspase-12 (an ER stress-specific proapoptotic molecule) and their relations with gastric mucosal apoptosis during development of stress gastric lesions in the water-immersion and restraint stress (WRS) model in rats. Rats developed severe gastric lesions after 6 h of WRS. Typical apoptosis was observed at the edge cells of WRS induced gastric lesions. Western blot analysis showed that GRP78 and activated caspase-12 were over-expressed in the gastric tissues of WRS rats. Immunohistochemical analysis demonstrated that increased GRP78 and caspase-12 were distributed only under the lesions. In addition, dithiothreitol and tunicamycin (ER stress inducers), which increased the expression of GRP78 and activated caspase-12, caused gastric mucosal injury and mucosal cell apoptosis in vitro. These findings suggest that ER stress might be involved in the development of stress gastric ulcer through an apoptotic mechanism.

Pathological quantification of experimental gastric ulcer in mice

AIM: To develop a method of quantifying the pathological changes gastric ulcer in the experimental mice.

METHODS: The experimental mice were fed with alcohol to establish the model of gastric ulcer. The area of the ulcer was quantified by weight and picture integration. Then the ratio of ulcer area to total stomach area (ulcer area ratio, UAR) was calculated to assess the degrees of the ulcers on the stomach wall. Furthermore, the methods of weighing, picture integration, marking, and grading were compared.

RESULTS: The mark indexes and the UAR by weight and picture integration were significantly different between different grading groups (Grade 4 vs Grade 2 vs Grade 1: 84.0±27.8 vs 19.6±8.1 vs 4.0±1.0, P<0.05; 40.74±0.26% vs 4.22±0.01%vs 1.03±0.01%, P<0.05; 31.57 ±0.16% vs 4.36±0.02% vs 2.43±0.02%, P<0.05) respectively, but the petechiae have no significant difference (P>0.05). Except in one mouse, the differences of UAR between by weight and picture integration in other five mice were 0.69, 4.89, 7.41, 1.26 and 2.76 respectively, which showed UAR had no marked difference between the two methods. In comparison of model I with model II, there were no obvious differences in the mark indexes, grading indexes and the numbers of petechiae while the UARs between by weight and picture integration were significantly different (6.14±0.08%vs 27.64±0.31%, P<0.05; 6.56±0.07% vs 21.22±0.21%, P<0.05).

CONCLUSION: The degrees of the gastric ulcer can be accessed by weight, picture integration, marking and grading. Weighing is better for measuring the ulcer over the fourth grade while picture integration can be used in all the degrees. The sensitivity and accuracy of picture integration and weighing are higher than those of traditional marking and grading.