Cytoprotection by metallothionein against gastroduodenal mucosal injury caused by ethanol in mice

Human Infrapatellar Fat Pad Mesenchymal Stem Cell-Derived Extracellular Vesicles Inhibit Fibroblast Proliferation by Regulating MT2A to Reduce Knee Arthrofibrosis

Knee arthrofibrosis is one of the most serious complications of knee surgery; however, its pathogenesis is unclear, and current treatment methods have not achieved satisfactory results. Mesenchymal stem cells (MSCs) have good anti-inflammatory and antifibrotic properties, and studies have reported that human infrapatellar fat pad-derived MSCs (IPFSCs) have the advantages of strong proliferative and differentiating ability, ease of acquisition, and minimal harm to the donor. Increasing evidence has shown that MSCs function through their paracrine extracellular vesicles (EVs). Our study is aimed at exploring the effects of human IPFSC-derived EVs (IPFSC-EVs) on knee arthrofibrosis and the underlying mechanisms in vivo and in vitro. In the in vivo study, injecting IPFSC-EVs into the knee joint cavity effectively reduced surgery-induced knee arthrofibrosis in rats. In the in vitro study, IPFSC-EVs were found to inhibit the proliferation of fibroblasts in the inflammatory environment. Additionally, we screened a potential IPFSC-EV molecular target, metallothionein 2A (MT2A), using RNA sequencing. We found that silencing MT2A partially reversed the inhibitory effect of IPFSC-EVs on fibroblast proliferation in the inflammatory environment. In conclusion, IPFSC-EVs inhibit the progression of knee arthrofibrosis by regulating MT2A, which inhibits fibroblast proliferation in the inflammatory environment.

Effects of Cadmium Exposure on Gut Villi in Danio rerio

In aquatic organisms, cadmium exposure occurs from ovum to death and the route of absorption is particularly wide, being represented by skin, gills and gastrointestinal tract, through which contaminated water and/or preys are ingested. It is known that cadmium interferes with the gut; however, less information is available on cadmium effects on an important component of the gut, namely goblet cells, specialized in mucus synthesis. In the present work, we studied the effects of two sublethal cadmium concentrations on the gut mucosa of Danio rerio. Particular attention was paid to changes in the distribution of glycan residues, and in metallothionein expression in intestinal cells. The results show that cadmium interferes with gut mucosa and goblet cells features. The effects are dose- and site-dependent, the anterior gut being more markedly affected than the midgut. Cadmium modifies the presence and/or distribution of glycans in the brush border and cytoplasm of enterocytes and in the goblet cells’ cytoplasm and alters the metallothionein expression and localization. The results suggest a significant interference of cadmium with mucosal efficiency, representing a health risk for the organism in direct contact with contamination and indirectly for the trophic chain.

Metallothionein 2 activation by pravastatin reinforces epithelial integrity and ameliorates radiation-induced enteropathy

Background

Radiotherapy or accidental exposure to ionizing radiation causes severe damage of healthy intestinal tissues. Intestinal barrier function is highly sensitive to ionizing radiation, and loss of epithelial integrity results in mucosal inflammation, bacterial translocation, and endotoxemia. Few studies have of epithelial integrity as a therapeutic target to treat radiation toxicity. Here, we examined the effects of pravastatin (PS) and the molecular mechanisms underlying epithelial integrity on radiation-induced enteropathy.

Methods

The radio-mitigative effects of PS were evaluated in a minipig model by quantifying clinical symptoms, and performing histological and serological analyses and mRNA sequencing in intestinal tissues. To evaluate the role of intercellular junctions on radiation damage, we used tight junction regulator and metallothionein 2 (MT2) as treatments in a mouse model of radiation-induced enteropathy. Caco-2 monolayers were used to examine functional epithelial integrityand intercellular junction expression.

Finding

Using a minipig model of pharmaceutical oral bioavailability, we found that PS mitigated acute radiation-induced enteropathy. PS-treated irradiated minipigs had mild clinical symptoms, lower intestinal inflammation and endotoxin levels, and improved gastrointestinal integrity, compared with control group animals. The results of mRNA sequencing analysis indicated that PS treatment markedly influenced intercellular junctions by inhibiting p38 MAPK signaling in the irradiated intestinal epithelium. The PS-regulated gene MT2 improved the epithelial barrier via enhancement of intercellular junctions in radiation-induced enteropathy.

Interpretation

PS regulated epithelial integrity by modulating MT2 in radiation-damaged epithelial cells. These findings suggested that maintenance of epithelial integrity is a novel therapeutic target for treatment of radiation-induced gastrointestinal damage.

Funding

As stated in the Acknowledgments

Effect of moxibustion stimulation on repair of gastric mucosal lesions in rats after peroneal neurotomy

AIM: To explore the mechanism underlying the protective effect of moxibustion on gastric mucosal lesions by investigating the relationship between endogenetic information started by moxibustion and the peroneal nerve pathways.

METHODS: Forty-eight SD rats were randomly and equally divided into four groups: a normal group (A), a model group (B), a gastric mucosal injury + moxibustion group (C), and a gastric mucosa injury + moxibustion + surgery group (D). Groups C and D were given 3 days of recovery after reroneal neurotomy. Group A was given saline and the other 3 groups were administered absolute ethanol and aspirin to induce gastric mucosa injury. After that, moxibustion was applied on Zusanli (ST36) in groups C and D, twice a day for 3 days. Finally, gastric ulcer index (UI) was assessed by gastric biopsy, gastric mucosa repair related cytokines such as epidermal growth factor (EGF) and prostaglandin E₂ (PGE₂) were detected, and mucosal apoptosis index (AI) was evaluated.

RESULTS: The improvement of UI was better in group C than in group D (P = 0.014). Compared with group C, serum and gastric levels of EGF and PGE₂ (EGF in serum P = 0.003, EGF in tissue P = 0.000; PGE₂ in serum P = 0.002, PGE₂ in tissue P = 0.000), and mucosal AI (P = 0.000) did not significantly rise in group D.

CONCLUSION: Moxibustion on Zusanli can transmit information by peroneal nerve pathways to regulate the release of gastric mucosal protective factors and the expression of apoptosis-related proteins, thus achieving the effect of repairing the gastric mucosa.

Does oral exposure to cadmium and lead mediate susceptibility to colitis? The dark-and-bright sides of heavy metals in gut ecology

Although the heavy metals cadmium (Cd) and lead (Pb) are known environmental health concerns, their long-term impacts on gut ecology and susceptibility to gastrointestinal autoimmune diseases have not been extensively investigated. We sought to determine whether subchronic oral exposure to Cd or Pb is a risk factor for the development and progression of inflammatory bowel disease (IBD). Mice were exposed to various doses of CdCl2 or PbCl2 in drinking water for 1, 4 or 6 weeks prior to infection with Salmonella, the induction of colitis with dextran sodium sulfate (DSS) or trinitrobenzene sulfonic acid (TNBS). In human cell-based models, exposure to Cd and Pb is associated with reduced transepithelial electric resistance and changes in bacteria-induced cytokine responses. Although 1- and 6-week exposures did not have clear effects on the response to Salmonella infectious challenges, 1-week short-term treatments with CdCl2 tended to enhance intestinal inflammation in mice. Unexpectedly, subchronic exposure to Cd and (to a lesser extent) Pb significantly mitigated some of the symptoms of DSS-induced colitis and reduced the severity of TNBS colitis in a dose-dependent manner. The possible adaptive and immunosuppressive mechanisms by which heavy metals might reduce intestinal inflammation are explored and discussed.

Effects of pre-moxibustion at Zusanli (ST36) on heat shock protein 70 expression in rats with gastric mucosal lesions after neurotomy

Studies have shown that pre-moxibustion protects the gastric mucosa by up-regulating the expression of heat shock protein 70. However, the signaling pathway underlying this effect remains unclear. Rats were intragastrically administered absolute alcohol, causing obvious lesion of the gastric mucosa. Following pre-moxibustion at Zusanli (ST36) for 8 days, the ulcer index decreased to different degrees. The results of an enzyme linked immunosorbent assay and western blotting showed significant upregulation of heat shock protein 70 expression in the gastric mucosa and serum. None out of transection of the spinal cord, damage to the nucleus of the solitary tract, neurotomy of the vagal nerve and neurotomy of the common peroneal nerve affected the decrease in ulcer index or the increase in heat shock protein 70 expression in serum after pre-moxibustion at Zusanli, and heat shock protein 70 expression was obviously decreased in the gastric mucosa. These findings suggest that pre-moxibustion at Zusanli can protect the gastric mucosa against lesioning, and that the mechanism underlying this effect involves its induction of heat shock protein 70 expression. Neural pathways participate in the regulatory effects of moxibustion on heat shock protein 70 expression in the gastric mucosa.

Role of the nucleus tractus solitarii in the protection of pre-moxibustion on gastric mucosal lesions

Previous studies have shown that somatic sensation by acupuncture and visceral nociceptive stimulation can converge in the nucleus tractus solitarii where neurons integrate signals impacting on the function of organs. To explore the role of the nucleus tractus solitarii in the protective mechanism of pre-moxibustion on gastric mucosa, nucleus tractus solitarii were damaged in rats and pre-moxibustion treatment at the Zusanli (ST36) point followed. The gastric mucosa was then damaged by the anhydrous ethanol lavage method. Morphological observations, enzyme linked immunosorbent assays, and western immunoblot analyses showed that gastric mucosa surface lesion and the infiltration of inflammatory cells were significantly ameliorated after pre-moxibustion treatment. Furthermore, the gastric mucosal damage index and somatostatin level were reduced, and epidermal growth factor content in the gastric mucosa and heat-shock protein-70 expression were increased. These results were reversed by damage to the nucleus tractus solitarii. These findings suggest that moxibustion pretreatment at the Zusanli point is protective against acute gastric mucosa injury, and nucleus tractus solitarii damage inhibits these responses. Therefore, the nucleus tractus solitarii may be an important area for regulating the signal transduction of the protective effect of pre-moxibustion on gastric mucosa.

Effect of moxibustion pretreatment on the contents of PGE2 and EGF in gastric mucosal injury in rats after nucleus of the solitary tract or spinal cord damage

AIM: To observe the effect of moxibustion pretreatment on the contents of prostaglandin E2 (PGE₂) and epidermal growth factor (EGF) in acute gastric mucosal injury in rats after nucleus of the solitary tract (NTS) or spinal cord damage, and to discuss the relationship between the central nervous system and endogenous protective effect of moxibustion.

METHODS: Fifty SD rats were randomly divided into five groups: a blank group, a model group, a moxibustion group, a NTS damage group, and a spinal cord damage group. After spinal cord damage and NTS damage were induced in groups D and E, respectively, moxibustion at Zusanli point (ST36) was applied in groups C, D and E. After that, the rats were intragastrically given absolute ethanol to induce acute gastric mucosal injury. The contents of PGE₂ and EGF in the gastric mucosa were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS: Moxibustion pretreatment increased the contents of PGE₂ and EGF in the gastric mucosa (338.82 μg/L ± 19.87 μg/L vs 279.52 μg/L ± 16.53 μg/L, P < 0.01; 4037.12 μg/L ± 300.20 μg/L vs 2923.73 μg/L ± 251.23 μg/L, P < 0.05). NTS or spinal cord damage reduced the contents of PGE₂ and EGF compared to the moxibustion group, in which the NTS and spinal cord were normal (298.65 μg/L ± 12.89 μg/L, 317.56 μg/L ± 16.60 μg/L vs 338.82 μg/L ± 19.87 μg/L; 3176.21 μg/L ± 242.35 μg/L, 3337.43 μg/L ± 249.86 μg/L vs 4037.12 μg/L ± 300.20 μg/L, all P < 0.01). The content of PGE₂ in the NTS damage group was lower than that in the spinal cord damage group (P < 0.05).

CONCLUSION: NTS or spinal cord damage reduces the protective effect of moxibustion pretreatment at Zusanli point (ST36) on the gastric mucosa, suggesting that both the NTS and spinal cord are involved in the protective effect of moxibustion on the gastric mucosa.

Zinc supplementation attenuates metallothionein and oxidative stress changes in kidney of streptozotocin-induced diabetic rats

Zinc is an element that under physiological conditions preferentially binds to and is a potent inducer of metallothionein under physiological conditions. The present study was conducted to explore whether zinc supplementation morphologically and biochemically protects against diabetic nephropathy through modulation of kidney metallothionein induction and oxidative stress in streptozotocin-induced diabetic rats. Thirty-two Wistar albino male rats were equally divided into four groups. The first group was used as untreated controls and the second group was supplemented with 30 mg/kg/day zinc as zinc sulfate. The third group was treated with streptozotocin to induce diabetes and the fourth group was treated with streptozotocin and supplemented with zinc as described for group 2. The blood glucose and micro-albuminuria levels, body and kidney weights were measured during the 42-day experimental period. At the end of the experiment, the kidneys were removed from all animals from the four groups. Diabetes resulted in degenerative kidney morphological changes. The metallothionein immunoreactivity level was lower and the kidney lipid peroxidation levels were higher in the diabetes group than in the controls. The metallothionein immunoreactivity levels were higher in the tubules of the zinc-supplemented diabetic rats as compared to the non-supplemented diabetic group. The zinc and metallothionein concentrations in kidney tissue were higher in the supplemented diabetic group compared to the non-supplemented diabetes group. The activity of glutathione peroxidase did not change in any of the four groups. In conclusion, the present study shows that zinc has a protective effect against diabetic damage of kidney tissue through stimulation of metallothionein synthesis and regulation of the oxidative stress.

Effects of pre-moxibustion at Zusanli (ST36) on heat shock protein 70 expression in rats with gastric mucosal lesions after neurotomy

Studies have shown that pre-moxibustion protects the gastric mucosa by up-regulating the expression of heat shock protein 70. However, the signaling pathway underlying this effect remains unclear. Rats were intragastrically administered absolute alcohol, causing obvious lesion of the gastric mucosa. Following pre-moxibustion at Zusanli (ST36) for 8 days, the ulcer index decreased to different degrees. The results of an enzyme linked immunosorbent assay and western blotting showed significant upregulation of heat shock protein 70 expression in the gastric mucosa and serum. None out of transection of the spinal cord, damage to the nucleus of the solitary tract, neurotomy of the vagal nerve and neurotomy of the common peroneal nerve affected the decrease in ulcer index or the increase in heat shock protein 70 expression in serum after pre-moxibustion at Zusanli, and heat shock protein 70 expression was obviously decreased in the gastric mucosa. These findings suggest that pre-moxibustion at Zusanli can protect the gastric mucosa against lesioning, and that the mechanism underlying this effect involves its induction of heat shock protein 70 expression. Neural pathways participate in the regulatory effects of moxibustion on heat shock protein 70 expression in the gastric mucosa.

Toll-like receptor 4 participates in gastric mucosal protection through Cox-2 and PGE2

AIM

To elucidate the role of Toll-like receptors (TLRs) in gastric cytoprotection after ethanol injury.

METHODS

C57BL/6J, C3H/HeOuJ and C3H/HeJ mice were used. All mice were killed 4h after ethanol administration. TLR4, cyclooxygenase-2 (Cox-2) and prostaglandin E(2) (PGE(2)) expression were measured by immunohistochemistry, western blotting and enzyme-linked immunosorbent assay (ELISA) separately.

RESULTS

The expression of TLR4 increased in C57BL/6J mice stomach 4h after ethanol injury. The cells expressing TLR4 included Cox-2 expressing cells and macrophages. The injury in C3H/HeJ mice was more severe than in C3H/HeOuJ mice 4h after ethanol injury. The expression of Cox-2 and PGE(2) only increased in C3H/HeOuJ mice. The number of macrophages and the expression of macrophage-inflammatory protein-2 (MIP-2) also increased only in C3H/HeOuJ mice.

CONCLUSION

TLR4 signal is activated in mice stomach 4h after ethanol injury. The protective effects of TLR4 signalling are mediated through the induction of Cox-2 expression and the production of PGE(2).

Metallothionein as an anti-inflammatory mediator

The integration of knowledge concerning the regulation of MT, a highly conserved, low molecular weight, cystein-rich metalloprotein, on its proposed functions is necessary to clarify how MT affects cellular processes. MT expression is induced/enhanced in various tissues by a number of physiological mediators. The cellular accumulation of MT depends on the availability of cellular zinc derived from the diet. MT modulates the binding and exchange/transport of heavy metals such as zinc, cadmium, or copper under physiological conditions and cytoprotection from their toxicities, and the release of gaseous mediators such as hydroxyl radicals or nitric oxide. In addition, MT reportedly affects a number of cellular processes, such as gene expression, apoptosis, proliferation, and differentiation. Given the genetic approach, the apparently healthy status of MT-deficient mice argues against an essential biological role for MT; however, this molecule may be critical in cells/tissues/organs in times of stress, since MT expression is also evoked/enhanced by various stresses. In particular, because metallothionein (MT) is induced by inflammatory stress, its roles in inflammation are implied. Also, MT expression in various organs/tissues can be enhanced by inflammatory stimuli, implicating in inflammatory diseases. In this paper, we review the role of MT of various inflammatory conditions.

Role of metallothionein in lung inflammation induced by ozone exposure in mice

Metallothionein (MT) is a free radical scavenger induced by inflammatory stimuli; however, its roles in inflammation have not been fully investigated. In the present study, we genetically determined the role of MT in ozone (O(3))-induced lung inflammation using MT-I/II null (-/-) mice. Subacute (65 h) exposure to O(3) (0.3 ppm) induced lung inflammation and enhanced vascular permeability, which was significantly greater in MT(-/-) than in corresponding wild-type mice. Electron microscopically, O(3) exposure induced vacuolar degeneration of pulmonary endothelial and epithelial cells, and interstitial edema with focal loss of the basement membrane, which was more prominent in MT(-/-) than in wild-type mice. O(3) -induced lung expression of interleukin-6 was significantly greater in MT(-/-) than in wild-type mice; however, lung expression of the chemokines examined was comparable in both genotypes of mice in the presence of O(3). Following O(3) exposure, the formation of oxidative stress-related molecules/adducts, such as heme oxidase-1, inducible nitric oxide synthase, 8-hydroxy-2'-deoxyguanosine, and nitrotyrosine, in the lung was significantly greater in MT(-/-) than in wild-type mice. Collectively, MT protects against O(3)-induced lung inflammation, at least partly, via the regulation of pulmonary endothelial and epithelial integrity and its antioxidative property.

Role of metallothionein in Helicobacter pylori-positive gastric mucosa with or without early gastric cancer and the effect on its expression after eradication therapy

BACKGROUND AND AIM

Metallothionein (MT) has a proven relationship with various kinds of cancer and reduces tissue damage. Helicobacter pylori (H. pylori) infection is associated with the alteration of gastric epithelial cell cycle events, a condition implicated in the initiation and development of gastric cancer. This study investigates the role of MT in H. pylori-induced gastritis with or without early gastric cancer (ECG) and evaluates the effect on MT expression after eradication therapy.

METHODS

Gastric biopsy samples were immunohistochemically examined for MT expression in 36 H. pylori-negative patients without ECG and 98 positive patients with or without ECG. Real time polymerase chain reaction was performed in 14 antral biopsy samples with or without H. pylori. The severity of gastritis was also evaluated according to the updated Sydney System. In 31 successfully eradicated patients, the above assessment was repeated for two consecutive years.

RESULTS

MT expression was higher in H. pylori-negative patients than in positive patients (P < 0.01). Moreover, in the corpus it was higher in H. pylori-positive patients without ECG compared to those with ECG (P < 0.05). The MT labeling index had a negative correlation with the severity of gastritis (P < 0.01). A positive correlation was shown between the MT labeling index and apoptosis: proliferation ratio (r = 0.41, P < 0.01). The MT labeling index in H. pylori-positive patients was gradually recovered after eradication (P < 0.05).

CONCLUSION

The decrease of MT expression cannot prevent tissue damage in H. pylori-positive gastric mucosa and leads to more severe gastritis. This phenomenon may be attributed to gastric carcinogenesis. H. pylori eradication increases MT expression and may reduce the risk of ECG.

Metallothionein is a crucial protective factor against Helicobacter pylori-induced gastric erosive lesions in a mouse model

Infection with the gastric pathogen Helicobacter pylori (H. pylori) causes chronic gastritis, peptic ulcer, and gastric adenocarcinoma. These diseases are associated with production of reactive oxygen species (ROS) from infiltrated macrophages and neutrophiles in inflammatory sites. Metallothionein (MT) is a low-molecular-weight, cysteine-rich protein that can act not only as a metal-binding protein, but also as a ROS scavenger. In the present study, we examined the role of MT in the protection against H. pylori-induced gastric injury using MT-null mice. Female MT-null and wild-type mice were challenged with H. pylori SS1 strain, and then histological changes were evaluated with the updated Sydney grading system at 17 and 21 wk after challenge. Although the colonization efficiency of H. pylori was essentially the same for MT-null and wild-type mice, the scores of activity of inflammatory cells were significantly higher in MT-null mice than in wild-type mice at 17 wk after challenge. Histopathological examination revealed erosive lesions accompanied by infiltration of inflammatory cells in the infected MT-null mice but not in wild-type mice. Furthermore, activation of NF-kappaB and expression of NF-kappaB-mediated chemokines such as macrophage inflammatory protein-1alpha and monocytes chemoattractant protein-1 in gastric cells were markedly higher in MT-null mice than in wild-type mice. These results suggest that MT in the gastric mucosa might play an important role in the protection against H. pylori-induced gastric ulceration.

[Analysis of toxicity using metallothionein knockout mice]

Two research groups produced metallothionein (MT)-I/II knockout mice with null mutation of MT-I and MT-II genes. In 1993, Choo et al. produced MT-I/II knockout mice with a mixed genetic background of 129 Ola and C57BL/6 strains. Palmiter et al. also produced MT-I/II knockout mice with a genetic background of 129/Sv strain in 1994. Subsequently, MT-I/II knockout mice have been used to clarify the biological function and physiological role of MT by many research groups. We were also provided MT-I/II knockout mice from Dr. Choo (Australia). F1 hybrid mice were mated with C57BL/6, and their offspring were back-crossed to C57BL/6 for ten generations. MT-I/II knockout (MT(-/-)) mice and wild-type (MT(+/+)) mice were obtained by mating of those heterozygous (MT(+/-)) mice. We have been investigating the susceptibility of MT-I/II knockout mice to toxicity of harmful factors and some diseases. Our present studies found that MT-I/II knockout mice have an increased sensitivity to harmful metals such as cadmium, mercury, and arsenic, oxidative stress, chemical carcinogenesis and neurodegenerative diseases. These results clearly indicate that MT plays an important role in defense of these toxicities. In this review, we present our findings and summarize recent reports with MT-I/II knockout mice concerning the role of MT as a biological protective factor.

Annexin-I as a potential target for green tea extract induced actin remodeling

Using a multistep human urothelial model, we previously showed that green tea extract (GTE) selectively modulates actin remodeling in transformed cells (MC-T11), which resulted in increased cell adhesion and reduced cell motility (Lu et al., Clin Cancer Res 2005;11:1675-83). This study further analyzed which actin binding proteins (ABPs) might be involved in this process. Proteomic profiles of GTE treated and untreated MC-T11 cells using two-dimensional gel electrophoresis coupled with liquid chromatography tandem mass spectrometry (LC/MS/MS) and matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) identified 20 GTE-induced proteins. Among them, 3 were ABPs (tropomodulin, cofilin and annexin-I), and only annexin-I showed a dose- and time-dependent expression. The increased annexin-I correlated with actin remodeling, and was the result of transcription level up-regulation, as determined by RT-PCR, pull-down immunoblot and siRNA analyses. 5-Azacytidine, a DNA methylation inhibitor, exhibited no effect on annexin-I expression when used alone, but had an additive effect for GTE-induced annexin-I expression. Immunohistochemistry of bladder cancer tissue array showed a decrease of annexin-I expression in carcinoma in situ and low grade papillary carcinoma (n = 32, 0% positive) compared to nontumor urothelium (n = 18, 89% positive) (p < 0.001 by Fisher exact test), but increased in some (6 of 15, 40%) high-grade tumors. Together, GTE induced annexin-I expression plays a role in regulating actin remodeling and decreased annexin-I expression is a common event in early stage of bladder cancer development.

The role of zinc sulfate and metallothionein in protection against ethanol-induced gastric damage in rats

In this study, the effects of zinc sulfate against ethanol-induced acute gastric damage in rats were investigated, morphologically and biochemically. In addition, the present investigation has demonstrated the distribution of metallothionein stimulated by zinc in gastric mucosal tissues, immunohistochemically. The gastric damage was induced by intragastric administration of 1 ml absolute ethanol per rat. Rats received zinc sulfate (100 mg/kg/day) for 3 consecutive days 2 hr prior to the administration of absolute ethanol. Acute ethanol exposure caused degenerative morphological changes, a decrease in metallothionein immunreactivity; an increase in lipid peroxidation (LPO) levels, and a decrease in reduced glutathione (GSH) levels in gastric mucosa. On the other hand, zinc sulfate administration to ethanol-treated rats caused a significant reduction in the histological damage, an increase in metallothionein immunreactivity, a decrease in LPO levels, and an increase in GSH levels in gastric mucosa. As a result, the present study indicates that zinc sulfate has a protective effect against ethanol-induced acute gastric damage. In addition, we might say that the zinc given as exogenous protection against acute gastric damage has a protective effect both by stimulation of metallothionein synthesis and through GSH as well as having antioxidative potential.

Integrative roles of transforming growth factor-alpha in the cytoprotection mechanisms of gastric mucosal injury

Background

Transforming growth factor α (TGFα) protects against gastric mucosal injury and facilitates wound healing. However, its overexpression is known to induce hypertrophic gastropathy resembling Menetrier's disease in transgenic (TG) mice on an FVB background, as one of the authors reported previously. We studied another TGFα-expressing mouse line on a CD1 background, whose gastric mucosa appears normal. Since this TG mouse had a strong resistance to ethanol-induced gastric injury, we considered the long-term effect of TGFα on several gastric protection mechanisms.

Methods

TGFα-expressing transgenic (TG) mouse lines bearing human TGFα cDNA under the control of the mouse metallothionein gene I promoter were generated on a CD1 mouse background, and analyzed their ethanol injury-resistant phenotypes produced by TGFα.

Results

In the TG mucosa, blood flow was well maintained after ethanol injury. Further, neural and inducible types of NO synthases were consistently and widely expressed in the TG mucosa, compared with the limited distribution of neural type NO synthase in the luminal pit region of the wild-type (WT) mucosa. COX-2 and its upstream transcription factor NfkB were constitutively elevated in the TG mucosa even before ethanol administration, whereas they were induced in the same region of the WT mucosa only after ethanol injury. Two anti-apoptotic proteins, HSP70 and Bcl-2, were upregulated in the TG mucosa even before ethanol administration, while they were not expressed in the WT mucosa before the injury. Furthermore, pro-caspase 3 activation was inhibited in the TG mucosa, while it was converted to the active form in the WT mucosa following ethanol administration.

Conclusion

We conclude that TGFα maintains the gastric mucosal defense against gastric injury by integrating other cytoprotective mechanisms.

Nitric oxide and zinc homeostasis in acute lung injury

Among putative small molecules that affect sensitivity to acute lung injury, zinc and nitric oxide are potentially unique by virtue of their interdependence and dual capacities to be cytoprotective or injurious. Nitric oxide and zinc appear to be linked via an intracellular signaling pathway involving S-nitrosation of metallothoinein--itself a small protein known to be an important inducible gene product that may modify lung injury. In the present article, we summarize recent efforts using genetic and fluorescence optical imaging techniques to: (1) demonstrate that S-nitrosation of metallothionein affects intracellular zinc homeostasis in intact pulmonary endothelial cells; and (2) reveal a protective role for this pathway in hyperoxic and LPS-induced injury.

Role of metallothionein in coagulatory disturbance and systemic inflammation induced by lipopolysaccharide in mice

Although metallothionein (MT) can be induced by inflammatory mediators, its roles in coagulatory disturbance during inflammation are poorly defined. We determined whether MT protects against coagulatory and fibrinolytic disturbance and systemic inflammation induced by intraperitoneal administration of lipopolysaccharide (LPS) in MT-I/II null (-/-) and wild-type (WT) mice. As compared with WT mice, MT (-/-) mice revealed significant prolongation of prothrombin and activated partial thromboplastin time, a significant increase in the levels of fibrinogen and fibrinogen/fibrin degradation products, and a significant decrease in activated protein C, after LPS treatment. LPS induced inflammatory organ damages in the lung, kidney, and liver in both genotypes of mice. The damages, including neutrophil infiltration, were more prominent in MT (-/-) mice than in WT mice after LPS treatment. In both genotypes of mice, LPS enhanced protein expression of interleukin (IL)-1beta, IL-6, granulocyte/macrophage-colony-stimulating factor, macrophage inflammatory protein (MIP)-1alpha, MIP-2, macrophage chemoattractant protein-1, and keratinocyte chemoattractant in the lung, kidney, and liver and circulatory levels of IL-1beta, IL-6, MIP-2, and KC. In overall trends, however, the levels of these proinflammatory proteins were greater in MT (-/-) mice than in WT mice after LPS challenge. Our results suggest that MT protects against coagulatory and fibrinolytic disturbance and multiple organ damages induced by LPS, at least partly, via the inhibition of the expression of proinflammatory proteins.

DSCR1 (ADAPT78) lethality: Evidence for a protective effect of trisomy 21 genes?

Over the last several years, suggestive evidence has accrued supporting a possible involvement for DSCR1 (ADAPT78) in Down syndrome. Toward testing this, we attempted to generate DSCR1 transgenic mice. Surprisingly, in almost every case, embryonic lethality was observed. In C57Bl/6 mice, DSCR1 human transgene was identified in developing embryos prior to lethality and up to day 9.5. Its mRNA expression was also observed and varied relative to control. In rare instances (twice) where transgenics survived to term, no mRNA expression was observed, suggesting that expression is required for lethality. This lethal phenotype contrasted with, and was surprising in light of, mouse models of Down syndrome where multiple chromosome 21 genes including Dscr1 are overexpressed and survive to term. To explain the seemingly contradictory lethal effect of DSCR1 by itself but not in combination with other trisomy genes, we propose that some trisomy genes (including DSCR1) confer lethality, but others suppress it.

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

AIM: To illustrate the pathophysiological role of metallothionein (MT) in gastric ulcer induced by stress.

METHODS: Wistar rats underwent water-immersion-restraint (WIR) stress, ZnSO₄ (an MT inducer) treatment, WIR+ZnSO₄ or WIR+MT, and the ulcer index (UI) was estimated in excised stomach and liver tissues. The mRNA level of gastric MT was determined by semi-quantitative RT-PCR. The MT content in gastric and hepatic tissues was determined by Cd/hemoglobin affinity assay. The lipid peroxidation products malondialdehyde (MDA) and conjugated dienes (CD) were estimated by use of thiobarbituric acid reactive species and ultraviolet spectrophotometry.

RESULTS: WIR stress induced severe gastric mucosal lesions in rats. Compared with control rats, stressed rats had increased lipid peroxide content in serum and stomach and liver tissues. MDA content was increased by 34%, 21% and 29% and CD level by 270%, 83% and 28%, respectively. MT content in the stomach and liver was increased by 0.74- and 1.8-fold, and the MT-mRNA level in the stomach was increased by 26%. Pretreatment with ZnSO₄ prevented gastric lesion development (the UI was 87% lower than that without pretreatment), and the MDA and CD content in serum and tissues was lower. The MT content in the liver was double in rats that were not pretreated, and the MT mRNA level in the stomach was 35% higher. MT administration 1 h before the WIR stress prevented gastric lesion development (the UI decreased by 47% compared with that in rats not pretreated), and the MDA and CD content in serum and tissues was significantly lower.

CONCLUSION: In WIR-stressed rats, the MT level was increased in serum and in stomach and liver tissues. Pre-administration of exogenous MT or pre-induction of endogenous MT can protect the gastric mucosa against stress-induced ulcers and inhibits the formation of stress-induced lipid peroxide. MT could have a gastroprotective effect and might be a new interventive and therapeutic target in stress-induced gastric ulcers.

Role of metallothionein in antigen-related airway inflammation

Metallothionein (MT) is a protein that can be induced by inflammatory mediators and participates in cytoprotection. However, its role in antigen-related inflammation remains to be established. We determined whether intrinsic MT protects against antigen-related airway inflammation induced by ovalbumin (OVA) in MT-I/II null (MT [-/-]) mice and in corresponding wild-type (WT) mice. MT (-/-) mice and WT mice were intratracheally challenged with OVA (1 mug per body) biweekly four times. Twenty-four hours after the last OVA challenge, significant increases were shown in the numbers of total cells, eosinophils, and neutrophils in bronchoalveolar lavage fluid from MT (-/-) mice than in those from WT mice. The protein level of interleukin-1beta (IL-1beta) was significantly greater in MT (-/-) mice than in WT mice after OVA challenge. Immunohistochemical analysis showed that the formations of 8-oxy-deoxyguanosine and nitrotyrosine in the lung were more intense in MT (-/-) mice than in WT mice after OVA challenge. These results indicate that endogenous MT is a protective molecule against antigen-related airway inflammation induced by OVA, at least partly, via the suppression of enhanced lung expression of IL-1beta and via the antioxidative properties. Our findings suggest that MT may be a therapeutic target for the treatment of antigen-related airway inflammatory diseases such as bronchial asthma.

Protective role of metallothionein in acute lung injury induced by bacterial endotoxin

BACKGROUND

Metallothionein (MT) is a protein that can be induced by inflammatory mediators and participate in cytoprotection. However, its role in inflammation remains to be established. A study was undertaken to determine whether intrinsic MT protects against acute inflammatory lung injury induced by bacterial endotoxin in MT-I/II knock out (-/-) and wild type (WT) mice.

METHODS

MT (-/-) and WT mice were given vehicle or lipopolysaccharide (LPS, 125 microg/kg) intratracheally and the cellular profile of the bronchoalveolar lavage (BAL) fluid, pulmonary oedema, lung histology, expression of proinflammatory molecules, and nuclear localisation of nuclear factor-kappaB (NF-kappaB) in the lung were evaluated.

RESULTS

MT (-/-) mice were more susceptible than WT mice to lung inflammation, especially to lung oedema induced by intratracheal challenge with LPS. After LPS challenge, MT deficiency enhanced vacuolar degeneration of pulmonary endothelial cells and type I alveolar epithelial cells and caused focal loss of the basement membrane. LPS treatment caused no significant differences in the enhanced expression of proinflammatory cytokines and chemokines nor in the activation of the NF-kappaB pathway in the lung between the two genotypes. Lipid peroxide levels in the lungs were significantly higher in LPS treated MT (-/-) mice than in LPS treated WT mice.

CONCLUSIONS

Endogenous MT protects against acute lung injury related to LPS. The effects are possibly mediated by the enhancement of pulmonary endothelial and epithelial integrity, not by the inhibition of the NF-kappaB pathway.

Preservation of intestinal structural integrity by zinc is independent of metallothionein in alcohol-intoxicated mice

Intestinal-derived endotoxins are importantly involved in alcohol-induced liver injury. Disruption of intestinal barrier function and endotoxemia are common features associated with liver inflammation and injury due to acute ethanol exposure. Zinc has been shown to inhibit acute alcohol-induced liver injury. This study was designed to determine the inhibitory effect of zinc on alcohol-induced endotoxemia and whether the inhibition is mediated by metallothionein (MT) or is independent of MT. MT knockout (MT-KO) mice were administered three oral doses of zinc sulfate (2.5 mg zinc ion/kg body weight) every 12 hours before being administered a single dose of ethanol (6 g/kg body weight) by gavage. Ethanol administration caused liver injury as determined by increased serum transaminases, parenchymal fat accumulation, necrotic foci, and an elevation of tumor necrosis factor (TNF-alpha). Increased plasma endotoxin levels were detected in ethanol-treated animals whose small intestinal structural integrity was compromised as determined by microscopic examination. Zinc supplementation significantly inhibited acute ethanol-induced liver injury and suppressed hepatic TNF-alpha production in association with decreased circulating endotoxin levels and a significant protection of small intestine structure. As expected, MT levels remained undetectable in the MT-KO mice under the zinc treatment. These results thus demonstrate that zinc preservation of intestinal structural integrity is associated with suppression of endotoxemia and liver injury induced by acute exposure to ethanol and the zinc protection is independent of MT.

Helicobacter-induced gastritis in mice not expressing metallothionein-I and II

BACKGROUND

Helicobacter pylori a primary cause of gastritis and peptic ulcer disease, is associated with increased production of reactive oxygen species within the gastric mucosa. Metallothionein (MT), a low-molecular-weight, cysteine-rich, metal-binding ligand, has been shown to sequester reactive oxygen species and reduce tissue damage. This study investigates the role of MT in H. pylori-induced gastritis in mice.

MATERIALS AND METHODS

Control (MT+/+) and MT-null (MT-/-) mice were inoculated with either 1 x 108H. pylori or H. felis, and were infected for 4, 8 and 16 weeks or 8 weeks, respectively. H. pylori load was determined by culture. Myloperoxidase activity and MT levels were also determined.

RESULTS

The stomachs of H. felis-infected mice were more severely inflamed than those of H. pylori-infected mice. H. felis-induced gastritis was more severe (p =.003) in MT-/- than in MT+/+ mice. MT-/- mice also had higher (60%; p <.05) H. pylori loads than MT+/+ mice 4 weeks after infection but not 8 or 16 weeks after infection. Myloperoxidase activity with H. pylori was similar between MT+/+ and MT-/- mice. Thirty-three per cent greater (p <.05) myloperoxidase activity was observed in MT-/- than in MT+/+ mice infected with H. felis. In MT+/+ mice infected with H. pylori, liver MT was increased by 33 and 39% (p <.05) at 8 and 16 weeks, respectively, whereas gastric MT increased by 46% (p <.05) at 4 weeks and declined to baseline levels at 8 and 16 weeks.

CONCLUSIONS

Mice lacking MT are more susceptible to H. pylori colonization and gastric inflammation, indicating that MT may be protective against H. pylori-induced gastritis.

Use of proteomics to demonstrate a hierarchical oxidative stress response to diesel exhaust particle chemicals in a macrophage cell line

Epidemiological studies demonstrate an association between short term exposure to ambient particulate matter (PM) and cardiorespiratory morbidity and mortality. Although the biological mechanisms of these adverse effects are unknown, emerging data suggest a key role for oxidative stress. Ambient PM and diesel exhaust particles (DEP) contain redox cycling organic chemicals that induce pro-oxidative and pro-inflammatory effects in the lung. These responses are suppressed by N-acetylcysteine (NAC), which directly complexes to electrophilic DEP chemicals and exert additional antioxidant effects at the cellular level. A proteomics approach was used to study DEP-induced responses in the macrophage cell line, RAW 264.7. We demonstrate that in the dose range 10-100 microg/ml, organic DEP extracts induce a progressive decline in the cellular GSH/GSSG ratio, in parallel with a linear increase in newly expressed proteins on the two-dimensional gel. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry and electrospray ionization-liquid chromatography/mass spectrometry/mass spectrometry analysis, 32 newly induced/NAC-suppressed proteins were identified. These include antioxidant enzymes (e.g. heme oxygenase-1 and catalase), pro-inflammatory components (e.g. p38MAPK and Rel A), and products of intermediary metabolism that are regulated by oxidative stress. Heme oxygenase-1 was induced at low extract dose and with minimal decline in the GSH/GSSG ratio, whereas MAP kinase activation required a higher chemical dose and incremental levels of oxidative stress. Moreover, at extract doses >50 microg/ml, there is a steep decline in cellular viability. These data suggest that DEP induce a hierarchical oxidative stress response in which some of these proteins may serve as markers for oxidative stress during PM exposures.

Prevention of alterations in intestinal permeability is involved in zinc inhibition of acute ethanol-induced liver damage in mice

Acute ethanol exposure causes liver injury in experimental animals, and accumulating evidence suggests that a major responsible factor for the pathogenesis is endotoxemia, which results from bacterial endotoxin leakage from the small intestine due to increased intestinal permeability under alcohol challenge. The purpose of this study was to examine whether zinc pretreatment would inhibit acute ethanol-induced liver injury through prevention of intestinal permeability changes. Male 129 SvPCJ mice were treated with three intragastric doses of ZnSO4 at 5 mg of zinc ion per kg each dosing prior to acute ethanol challenge with a single oral dose of 6 g/kg ethanol. The zinc treatment did not alter the elevation of serum concentrations of alcohol. The acute ethanol exposure caused an elevation in serum alanine aminotransferase levels as well as fatty liver and hepatic degenerative necrotic foci as determined by biochemical assay and histochemical analysis, respectively. A significant increase in liver tumor necrosis factor-alpha (TNF-alpha) levels was detected by enzyme-linked immunosorbent assay. These pathological effects correlated well with increases in serum endotoxin levels. Importantly, acute ethanol treatment caused significant damage to the small intestine as determined by morphological analysis of intestinal sections and permeability assay. These alcohol-induced hepatic pathological changes and TNF-alpha elevation were significantly inhibited in the zinc-pretreated animals. The inhibitory action of zinc on alcohol-induced liver damage and activation of inflammation was associated with zinc suppression of alcohol-induced intestinal permeability changes. These results thus demonstrate that zinc prevention of increased intestinal permeability is importantly involved in the inhibition of acute ethanol-induced liver damage in mice.

Strain-specific brain metallothionein II (MT-II) gene expression, its ethanol responsiveness, and association with ethanol preference in mice

BACKGROUND

Metallothioneins (MTs) are ubiquitously expressed intracellular proteins that bind heavy metals such as zinc, copper, and cadmium. Although their specific function has yet to be discovered, they are known to regulate the metabolism of these metals as well as respond to cellular stress agents, particularly oxidants.

METHODS

Brain RNA from experimental (8 g/kg 25% ethanol injection) and control (saline injection) mice from four strains (A/J, BALB/cJ, C57BL/6J, DBA/2J) that are known to differ with respect to ethanol preference was used in differential displays. This report includes molecular results on one gene (MT-II) identified.

RESULTS

Our results on differential displays suggest that a proportion of genes are differentially expressed across pair-wise strain comparisons. We identified MT-II as a strain-specific and ethanol-responsive gene. The level of MT-II messenger RNA (mRNA) in control mice of A/J, BALB/cJ, C57BL/6J, and DBA/2J strains was variable (0.50, 0.51, 0.90, and 0.14 times G3PDH expression, respectively). The degree of up-regulation in experimental mice was also somewhat variable among strains, ranging from 2.5 to 3.2 times expression over the matched controls. Experiments indicate that the promoter and genomic organization of the MT-II gene is identical in sequence for all four strains, and methylation studies revealed that the MT-II promoter region is unmethylated in the brains of these mice. Interestingly, MT-II expression in control mice demonstrated a positive correlation with the ethanol preference phenotype.

CONCLUSION

An increase in MT-II mRNA levels after injection of ethanol is attributed to the antioxidant properties of MT-II. The differential mRNA levels of this gene among four strains are not accounted for by the genomic organization, DNA sequence, or methylation status of this gene. Furthermore, the observed correlation between MT-II mRNA levels and ethanol preference raises an interesting hypothesis about the possible role of MT-II in ethanol effects and preference in mice.

Metallothionein-independent zinc protection from alcoholic liver injury

Previous studies using metallothionein (MT)-overexpressing transgenic mice have demonstrated that MT protects the liver from oxidative injury induced by alcohol. The mechanism of action of MT is unknown. Because MT primarily binds to zinc under physiological conditions and releases zinc under oxidative stress and zinc is an antioxidant element, it is likely that zinc mediates the protective action of MT. The present study was undertaken to determine the distinct role of zinc in hepatic protection from alcoholic injury. MT I/II-knockout (MT-KO) mice along with their wild-type controls were treated with three gastric doses of ethanol at 5 g/kg at 12-hour intervals. Zinc sulfate was injected intraperitoneally in a dosage of 5 mg/kg/day for 3 days before ethanol treatment. MT concentrations in MT-KO mice were very low and zinc concentrations in MT-KO mice were lower than in wild-type mice. Zinc treatment significantly elevated hepatic MT concentrations only in wild-type mice and increased zinc concentrations in both MT-KO and wild-type mice. Ethanol treatment caused degenerative morphological changes and necrotic appearance in the livers of MT-KO mice. Microvesicular steatosis was the only ethanol-induced change in the liver of wild-type mice. Ethanol treatment decreased hepatic glutathione concentrations and increased hepatic lipid peroxidation, and the concentrations of lipid peroxide products in the wild-type mice were lower than in the MT-KO mice. All of these alcohol-induced toxic responses were significantly suppressed by zinc treatment in both MT-KO and wild-type mouse livers. These results demonstrate that zinc, independent of MT, plays an important role in protection from alcoholic liver injury. However, MT is required to maintain high levels of zinc in the liver, suggesting that the protective action of MT in the liver is likely mediated by zinc.