Protection by polaprezinc, an anti-ulcer drug, against indomethacin-induced apoptosis in rat gastric mucosal cells

A randomised trial of topical polaprezinc to prevent oral mucositis in patients undergoing haematopoietic stem cell transplantation (ToPaZ study)

PURPOSE

Oral mucositis (OM) is a common complication in haematopoietic stem cell transplantation (HSCT). Polaprezinc, an anti-ulcer drug, has been shown to be effective to prevent OM in several studies when administered topically and systemically. This study aimed to evaluate the effectiveness of topical polaprezinc in patients undergoing HSCT.

METHODS

This was an open-label randomised clinical trial comparing polaprezinc and sodium bicarbonate mouthwashes for the prevention of severe OM in HSCT patients. Adult patients who received conditioning regimens at moderate to high risk of developing OM were included. The primary endpoint was the incidence of severe (WHO grades 3-4) OM. The secondary endpoints included duration of grades 3-4 OM, incidence and duration of grades 2-4 OM, patient-reported pain and functional limitations.

RESULTS

In total, 108 patients (55 test arm and 53 control arm) were randomised. There was no difference in the incidence of grades 3 to 4 OM (35% test arm versus 36% control arm). The secondary endpoints were not significantly different. In both arms, patients reported more throat pain compared to mouth pain.

CONCLUSIONS

Topical polaprezinc had no effect in the prevention of OM in HSCT patients. Further research is required to evaluate the effects of systemic polaprezinc. The OM assessment tool needs to be reviewed as throat mucositis was a main issue in this study.

TRIAL REGISTRATION

ACTRN12320001188921 (Date Registered: 10th November 2020).

Efficacy and Safety of Polaprezinc-Based Therapy versus the Standard Triple Therapy for Helicobacter pylori Eradication: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Helicobacter pylori (H. pylori) is the most prevalent etiology of gastritis worldwide. H. pylori management depends mainly on antibiotics, especially the triple therapy formed of clarithromycin, amoxicillin, and proton pump inhibitors. Lately, many antibiotic-resistant strains have emerged, leading to a decrease in the eradication rates of H. pylori. Polaprezinc (PZN), a mucosal protective zinc-L-carnosine complex, may be a non-antibiotic agent to treat H. pylori without the risk of resistance. We performed a systematic review and meta-analysis to evaluate the efficacy and safety of a PZN-based regimen for the eradication of H. pylori. This study used a systematic review and meta-analysis synthesizing randomized controlled trials (RCTs) from WOS, SCOPUS, EMBASE, PubMed, and Google Scholar until 25 July 2022. We used the odds ratio (OR) for dichotomous outcomes presented with the corresponding 95% confidence interval (CI). We registered our protocol in PROSPERO with ID: CRD42022349231. We included 3 trials with a total of 396 participants who were randomized to either PZN plus triple therapy (n = 199) or triple therapy alone (control) (n = 197). Pooled OR found a statistical difference favoring the PZN arm in the intention to treat and per protocol H. pylori eradication rates (OR: 2.01 with 95% CI [1.27, 3.21], p = 0.003) and (OR: 2.65 with 95% CI [1.55, 4.54], p = 0.0004), respectively. We found no statistical difference between the two groups regarding the total adverse events (OR: 1.06 with 95% CI [0.55, 2.06], p = 0.85). PZN, when added to the triple therapy, yielded a better effect concerning the eradication rates of H. pylori with no difference in adverse event rates, and thus can be considered a valuable adjuvant for the management of H. pylori. However, the evidence is still scarce, and larger trials are needed to confirm or refute our findings.

Exacerbation of Elastase-Induced Emphysema via Increased Oxidative Stress in Metallothionein-Knockout Mice

Although the pathogenesis of chronic obstructive pulmonary disease (COPD) is not yet fully understood, recent studies suggest that the disruption of the intracellular balance of oxidative (such as reactive oxygen species (ROS)) and antioxidant molecules plays an important role in COPD development and progression. Metallothionein is an endogenous metal-binding protein with reported ROS scavenging activity. Although there have been many publications on the protective effects of metallothionein in the kidney and liver, its role in COPD models such as elastase- or cigarette smoke (CS)-induced lung injury is unknown. Thus, in the present study, we analyzed the elastase-induced lung injury model using metallothionein-knockout (MT-KO; MT-1 and -2 gene deletion) mice. The expression of MT-1 and MT-2 in the lungs of MT-KO mice was markedly lower compared with that in the lungs of wildtype (WT) mice. Porcine pancreatic elastase (PPE)-induced lung injury (alveolar enlargement and respiratory impairment) was significantly exacerbated in MT-KO mice compared with WT mice. Additionally, PPE-induced increases in the number of inflammatory cells, inflammatory cytokines, and cell death in lung tissue were significantly more pronounced in MT-KO mice compared with WT mice. Finally, using an in vivo imaging system, we also found that PPE-induced ROS production in the lungs was enhanced in MT-KO mice compared with WT mice. These results suggest that metallothionein may act as an inhibitor against elastase-induced lung injury by suppressing ROS production. These results suggest that metallothionein protein, or compounds that can induce metallothionein, could be useful in the treatment of COPD.

Recent advances on polaprezinc for medical use (Review)

The present study described the chemical and biological properties of zinc complex of L-carnosine (L-CAZ; generic name, polaprezinc; chemical name, catena-(S)-[µ-[N(α)-(3-aminopropionyl) histidinato (2-) N1, N2, O: N(τ)]-zinc], molecular formula, C₉H₁₄N₄O₃Zn; molecular weight, 291.6404; CAS registry number, 107667-60-7). Characterized as a white or yellowish white crystalline powder, this drug is insoluble in glacial acetic acid and almost insoluble in water, methanol, ethanol and ether. It is soluble in dilute hydrochloric acid, dilute nitric acid and sodium hydroxide solution, and its melting point is 260-270˚C. Polaprezinc is an anti-ulcer drug that was jointly studied and developed by Hamari Chemicals Co., Ltd. and Zeria Pharmaceutical Co., Ltd., and was first approved in Japan in 1994. This review article summarizes the research advances of polaprezinc, including the patents, preparations, synthetic routes, pharmacokinetics, pharmacological effects and application in clinical research.

Indomethacin can induce cell death in rat gastric parietal cells through alteration of some apoptosis- and autophagy-associated molecules

In clinical medicine, indomethacin (IND, a non-steroidal anti-inflammatory drug) is used variously in the treatment of severe osteoarthritis, rheumatoid arthritis, gouty arthritis or ankylosing spondylitis. A common complication found alongside the therapeutic characteristics is gastric mucosal damage. This complication is mediated through apoptosis and autophagy of the gastrointestinal mucosal epithelium. Apoptosis and autophagy are critical homeostatic pathways catalysed by caspases downstream of the gastrointestinal mucosal epithelial injury. Both act through molecular signalling pathways characterized by the initiation, mediation, execution and regulation of the cell regulatory cycle. In this study we hypothesized that dysregulated apoptosis and autophagy are associated with IND-induced gastric damage. We examined the spectra of in vivo experimental gastric ulcers in male Sprague-Dawley rats through gastric gavage of IND. Following an 18-hour fast, IND was administered to experimental rats. They were sacrificed at 3-, 6- and 12-hour intervals. Parietal cells (H⁺ , K⁺ -ATPase β-subunit assay) and apoptosis (TUNEL assay) were determined. The expression of apoptosis-signalling caspase (caspases 3, 8, 9 and 12), DNA damage (anti-phospho-histone H2A.X) and autophagy (MAP-LC3, LAMP-1 and cathepsin B)-related molecules in gastric mucosal cells was examined. The administration of IND was associated with gastric mucosal erosions and ulcerations mainly involving the gastric parietal cells (PCs) of the isthmic and upper neck regions and a time-dependent gradual increase in the number of apoptotic PCs with the induction of both apoptotic (upregulation of caspases 3 and 8) cell death and autophagic (MAP-LC3-II, LAMP-1 and cathepsin B) cell death. Autophagy induced by fasting and IND 3 hours initially prompted the degradation of caspase 8. After 6 and 12 hours, damping down of autophagic activity occurred, resulting in the upregulation of active caspase 8 and its nuclear translocation. In conclusion we report that IND can induce time-dependent apoptotic and autophagic cell death of PCs. Our study provides the first indication of the interactions between these two homeostatic pathways in this context.

Ultra-structural study of the indomethacin-induced apoptosis and autophagy in rat gastric parietal cells

BACKGROUND AND AIM OF THE WORK

Indomethacin (IND), a non-steroidal anti-inflammatory drug, can induce gastric mucosal ulcerations. To date, the ultra-structural changes in the parietal cells (PCs) of the gastric mucosa following the intake of IND are mostly unknown. We carried out the current investigation to get insights into this issue.

MATERIALS AND METHODS

We established an animal model consisting of 35 adult male Sprague Dawley rats. The animals were divided into three groups, including; control (normal feeding), fasting, and indomethacin-treated groups. After treatment of 18-h fasting rats with IND, they were sacrificed at 3, 6, and 12-h intervals. The morphological features, including the apoptotic, and autophagic changes in the gastric mucosa PCs were examined using transmission electron microscopy.

RESULTS

In normal feeding animals (control group), the gastric PCs were present in various stages of activity. Fasting was associated with the predominance of the inactive parietal cells with features of up-regulated autophagy. In the IND -treated animals (at 3-h interval), PCs showed prominent autophagic changes, and subtle apoptotic cell death. In the IND -treated animals (at 6-12-h interval), PCs showed prominent apoptotic changes, and subtle autophagic features.

CONCLUSIONS

Our study indicates that IND treatment could induce gastropathy through time-dependent alterations in the autophagic and apoptotic machinery of PCs. Further studies are needed to examine the underlying molecular mechanisms.

Carnosine and Lung Disease

Carnosine (β-alanyl-L-histidine) is a small dipeptide with numerous activities, including antioxidant effects, metal ion chelation, proton buffering capacity, and inhibitory effects on protein carbonylation and glycation. Carnosine has been mostly studied in organs where it is abundant, including skeletal muscle, cerebral cortex, kidney, spleen, and plasma. Recently, the effect of supplementation with carnosine has been studied in organs with low levels of carnosine, such as the lung, in animal models of influenza virus or lipopolysaccharide-induced acute lung injury and pulmonary fibrosis. Among the known protective effects of carnosine, its antioxidant effect has attracted increasing attention for potential use in treating lung disease. In this review, we describe the in vitro and in vivo biological and physiological actions of carnosine. We also report our recent study and discuss the roles of carnosine or its related compounds in organs where carnosine is present in only small amounts (especially the lung) and its protective mechanisms.

Protective effect of polaprezinc on cadmium-induced injury of lung epithelium

Cadmium is a toxic metal contained in food, water and the atmosphere, and exposure to cadmium can cause respiratory diseases in humans. Various health problems caused by cadmium result from oxidative stress-dependent cellular injury. Metallothioneins are intracellular, cysteine-rich, metal-binding proteins that have a detoxifying action on heavy metals such as cadmium in various organs. In addition, expression of metallothioneins is induced by metals with low biological toxicity, such as zinc. Therefore, in this study we examined whether polaprezinc, a chelate compound consisting of carnosine and zinc, can suppress cadmium-induced lung epithelial cell death. We found that cell viability markers (intracellular ATP levels and mitochondrial activity) and cytotoxicity (lactate dehydrogenase release) were decreased and increased, respectively by cadmium treatment; however, polaprezinc significantly reversed these changes. Moreover, cadmium-dependent endoplasmic reticulum stress responses were suppressed by polaprezinc treatment. We then examined the protective mechanisms of polaprezinc, focusing on oxidative stress. Cadmium induced the production of reactive oxygen species (ROS) in A549 cells in a dose-dependent manner and polaprezinc significantly suppressed this cadmium-induced ROS production. Finally, we examined whether polaprezinc exerts an antioxidative action by inducing metallothioneins. We found that polaprezinc dose-dependently induced metallothioneins using real-time RT-PCR, ELISA, and western blotting analyses. These results indicate that polaprezinc can suppress cadmium-induced lung epithelial cell death and oxidative stress by inducing metallothioneins. We therefore suggest that polaprezinc may have therapeutic effects against respiratory diseases, such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis.

The Gastrointestinal Exertional Heat Stroke Paradigm: Pathophysiology, Assessment, Severity, Aetiology and Nutritional Countermeasures

Exertional heat stroke (EHS) is a life-threatening medical condition involving thermoregulatory failure and is the most severe condition along a continuum of heat-related illnesses. Current EHS policy guidance principally advocates a thermoregulatory management approach, despite growing recognition that gastrointestinal (GI) microbial translocation contributes to disease pathophysiology. Contemporary research has focused to understand the relevance of GI barrier integrity and strategies to maintain it during periods of exertional-heat stress. GI barrier integrity can be assessed non-invasively using a variety of in vivo techniques, including active inert mixed-weight molecular probe recovery tests and passive biomarkers indicative of GI structural integrity loss or microbial translocation. Strenuous exercise is strongly characterised to disrupt GI barrier integrity, and aspects of this response correlate with the corresponding magnitude of thermal strain. The aetiology of GI barrier integrity loss following exertional-heat stress is poorly understood, though may directly relate to localised hyperthermia, splanchnic hypoperfusion-mediated ischemic injury, and neuroendocrine-immune alterations. Nutritional countermeasures to maintain GI barrier integrity following exertional-heat stress provide a promising approach to mitigate EHS. The focus of this review is to evaluate: (1) the GI paradigm of exertional heat stroke; (2) techniques to assess GI barrier integrity; (3) typical GI barrier integrity responses to exertional-heat stress; (4) the aetiology of GI barrier integrity loss following exertional-heat stress; and (5) nutritional countermeasures to maintain GI barrier integrity in response to exertional-heat stress.

Effect of polaprezinc on experimental corrosive esophageal burns in rats

Unconsciously caustic ingestion is one of the most common causes of serious esophageal strictures in children. The aim of this study is to determine the efficiency of polaprezinc in preventing stricture formation after corrosive esophageal burns (CEB); this was the first time it has been used to treat experimental CEB in rats. Twenty-four rats were divided into four groups, three of which received CEB by the instillation of 1 mL of 10% NaOH solution into their isolated esophageal segments for three minutes. Group C (control) was uninjured and untreated. Group B (esophageal burn) received CEB but were left untreated. Groups PT1 and PT2 had CEB and received 100 mg/kg/day and 200 mg/kg/day, respectively, of intraperitoneal polaprezinc treatment (PT) for the first two weeks, then oral PT for another two weeks. We assessed the treatment's efficiency of the treatment after the fourth week by evaluating the stenosis index (SI) and the histopathological damage score, determining tissue hydroxyproline content (HP), and measuring the weight of the rats before and after the experiment. Mean SI was statistically lower in the groups PT1 and PT2 when compared with Group B (p = 0.006, 0.004, respectively). HP levels were highest in Group B, but it was insignificant (P> 0.05). In terms of histopathological damage score, treatment groups demonstrated less collagen deposition, mucosal, and submucosal damage than both Group B (p = 0.01) and Group C (p = 0.02). Group PT1 and Group PT2 (P> 0.05) showed similar results, indicating the treatment's effectiveness was independent of dosage. Outside of Group C, weight gain was detected only in Group PT2, though it was statistically insignificant. In Group PT1, weight loss was lower than in Group B. Polaprezinc, with its antifibrotic, antioxidant, anti-inflammatory, wound-healing and antiapoptotic effects, was efficient in reducing stricture formation by decreasing HP levels and histopathologic damage, preventing stenosis, and weight gain in higher dosages in the treatment group.

Evaluation of anti-inflammatory and ulcerogenic potential of zinc-ibuprofen and zinc-naproxen complexes in rats

Because of numerous indications and high availability, non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed and used medicines in the world. However, long-term therapy with and improper use of NSAIDs may lead to gastrointestinal damage. Therefore, improving the therapeutic index of the existing drugs has become a priority over the past decades. Considerable attention in the field has been concentrated on metal complexes of non-steroidal anti-inflammatory drugs. The aim of this study is to evaluate the effect of complexation with zinc on the anti-inflammatory and ulcerogenic effects of ibuprofen and naproxen after single and triple intragastric administration to rats. The anti-inflammatory effect was assessed in carrageenan-induced inflammatory edema in the hind paw of male albino Wistar rats. The mucosal lesions were inspected and evaluated for gross pathology. Single administration of both the investigated complexes, namely zinc-ibuprofen and zinc-naproxen (20 mg/kg equivalent to ibuprofen and naproxen, respectively) and their parent drugs and physical mixtures with zinc hydroaspartate (ZHA doses: 16.05 and 14.37 mg/kg), caused a significant reduction of the edema after the same time from the carrageenan injection in comparison to the control groups. However, no statistically significant differences between the investigated drugs were observed after their single administration. The mean ulceration score for the mixture of ibuprofen and ZHA was statistically lower than the mean score achieved in rats after treatment with ibuprofen alone. On the other hand, triple intragastric administration of the ZHA-ibuprofen and ZHA-naproxen combination showed substantial enhancement of the anti-inflammatory activity against control groups, as well as against the parent NSAIDs. The most potent anti-inflammatory activity was demonstrated after 2 h from the carrageenan injection in animals receiving ZHA together with naproxen. The edema growth was reduced in these animals by 80.9% as compared to the control group. This result was significantly higher than the results achieved in animals receiving zinc-naproxen (50.2%) or naproxen alone (47.9%). Both NSAID complexes with zinc and mixtures with ZHA alleviated ulcerations caused by parent NSAIDs; however, the mixtures of both ibuprofen and naproxen with ZHA after triple administration were the least damaging. In view of the above results, zinc supplementation during NSAID therapy may have a beneficial effect on ulcer prevention and healing by reducing the effective dose of the parent drug and increasing its potency.

A Zinc Morpholine Complex Prevents HCl/Ethanol-Induced Gastric Ulcers in a Rat Model

Zinc is a naturally occurring element with roles in wound healing and rescuing tissue integrity, particularly in the gastrointestinal system, where it can be detected in the mucosal and submucosal layers. Zinc chelates are known to have beneficial effects on the gastrointestinal mucosa and in cases of gastric ulcer. We synthesized complexes of zinc featuring a heterocyclic amine binding amino acids then investigated their ability to enhance the gastric self-repair. Zinc-morpholine complex, Zn(L)SCN, namely showed strong free-radical scavenging, promotion of the DNA and RNA polymerases reconstruction and suppression of cell damage. The complex's mode of action is proposed to involve hydrogen bond formation via its bis(thiocyanato-k)zinc moiety. Zn(L)SCN complex had potent effects on gastric enzymatic activity both in vitro and in vivo. The complex disrupted the ulcerative process as demonstrated by changes in the intermediate metabolites of the oxidative pathway - specifically, reduction in the MDA levels and elevation of reduced glutathione together with an attenuation of oxidative DNA damage. Additionally, Zn(L)SCN restored the gastric mucosa, inhibited the production of pro-inflammatory cytokines (IL-6, TNF and the caspases), and preserved the gastric mucous balance. Zn(L)SCN thus exhibited anti-oxidative, anti-inflammatory and anti-apoptotic activities, all of which have cytoprotective effects on the gastric lining.

Efficacy of zinc-carnosine chelate compound, Polaprezinc, enemas in patients with ulcerative colitis

OBJECTIVES

Ulcerative colitis (UC) is a chronic, relapsing and remitting intestinal inflammatory disorder. Zinc is known to be efficacious for the repair of damaged tissue and has been shown to protect against gastric ulceration. This study focused on Polaprezinc (PZ), N-(3-aminopropionyl)-L-histidinato zinc, which accelerates ulcer healing through actions such as prostaglandin-independent cytoprotection and antioxidative activity.

METHODS

In this randomized, placebo-controlled, investigator-blinded trial, 28 patients with active UC at The Jikei University Hospital were randomly divided into two groups: one treated with a 150 mg PZ enema (n = 18) and the other not treated with a PZ enema (n = 10). All patients received usual induction therapy. Clinical symptoms, endoscopic findings and histological findings were evaluated at entry and one week later.

RESULTS

In the PZ group, modified Matts' endoscopic scores were significantly improved after treatment compared to baseline in the rectum (p = 0.004), sigmoid colon (p = 0.03) and descending colon (p = 0.04). In the non-PZ group, scores were not significantly improved in the rectum (p = 0.14) and descending colon (p = 0.34), but were improved in the sigmoid colon (p = 0.04). In the PZ group, the Mayo scores at baseline and at Day 8 were 9.1 ± 1.6 and 5.8 ± 2.7 (p = 0.00004), respectively, and in the placebo group, the scores were 8.9 ± 1.7 and 7.4 ± 2.1 (p = 0.009), respectively. Clinical response or remission was significantly better in the PZ group (71%) than in the placebo group (10%).

CONCLUSIONS

A zinc-carnosine chelate compound, PZ, enema may become a useful new add-on treatment to accelerate mucosal healing in UC.

Effectiveness of polaprezinc for low-dose aspirin-induced small-bowel mucosal injuries as evaluated by capsule endoscopy: a pilot randomized controlled study

Background

Treatment of low-dose aspirin (LDA)-induced small-bowel injury has not been established. Polaprezinc, a chelate of zinc and L-carnosine, may be efficacious for such injury. We conducted a pilot randomized controlled study to investigate whether polaprezinc is effective against LDA-induced small-bowel injuries.

Methods

Consecutive patients under long-term (>3 months) LDA treatment and who agreed to participate in our study underwent initial capsule endoscopy (CE). Patients with LDA-induced small-bowel injury apparent upon initial CE (n = 20) were randomized into a polaprezinc (150 mg/day for 4 weeks) group and a control (no polaprezinc treatment) group. All underwent follow-up CE after 4 weeks. Changes in the number and characteristics of small-bowel mucosal injuries were compared within and between the two groups.

Results

The median number of reddened lesions and erosions/ulcers upon follow-up CE in the polaprezinc group significantly decreased (P < 0.05). However, there was no significant difference in the median number of reddened lesions and erosions/ulcers upon follow-up CE in the control group.

Conclusions

Co-administration of polaprezinc may be effective against small-bowel mucosal injury associated with long-term LDA therapy.

Trial registration

UMIN Clinical Trials Registry UMIN000003687.

Rebamipide ameliorates indomethacin-induced small intestinal injury in rats via the inhibition of matrix metalloproteinases activity

BACKGROUND AND AIM

The pathogenesis of non-steroidal anti-inflammatory drugs (NSAIDs)-induced small intestinal lesions remains unclear, although it is considered to be quite different from that of upper gastrointestinal tract ulcers due to the absence of acid and the presence of bacteria and bile in the small intestine. The aim of this study was to characterize specific gene expression profiles of intestinal mucosa in indomethacin-induced small intestinal injury, and to investigate the effects of rebamipide on the expression of these genes.

METHODS

Intestinal injury was induced in male Wistar rats by subcutaneous administration of indomethacin. Total RNA of the intestinal mucosa was extracted 24 h after indomethacin administration, gene expression was investigated using microarray analysis, and the identified genes were confirmed by real-time polymerase chain reaction (PCR). In addition, we investigated whether the treatment with rebamipide altered the expression of these identified genes.

RESULTS

The administration of indomethacin induced small intestine injuries, and these lesions were significantly inhibited by the treatment with rebamipide. Microarray analysis showed that the genes for several matrix metalloproteinases (MMPs) and several chemokine-related genes were significantly upregulated, and metallothionein 1a (MT1a) was downregulated in the intestinal mucosa after administration of indomethacin. The expressions of these genes were reversed by the treatment with rebamipide.

CONCLUSION

These data suggest that MMPs, chemokines, and MT1a may play an important role in the intestinal mucosal injury induced by indomethacin. In particular, the inhibition of MMP genes and chemokine-related genes by rebamipide may be important for the therapeutic effect against NSAIDs-induced small intestinal injury.

Effect of a zinc L-carnosine compound on acid-induced injury in canine gastric mucosa ex vivo

OBJECTIVE

To examine whether a zinc L-carnosine compound used for treatment of suspected gastric ulcers in dogs ameliorates acid-induced injury in canine gastric mucosa.

SAMPLE

Gastric mucosa from 6 healthy dogs.

PROCEDURES

Mucosa from the gastric antrum was harvested from 6 unadoptable shelter dogs immediately after euthanasia and mounted on Ussing chambers. The tissues were equilibrated for 30 minutes in neutral Ringer's solution prior to incubation with acidic Ringer's solution (HCl plus Ringer's solution [final pH, 1.5 to 2.5]), acidic Ringer's solution plus zinc L-carnosine compound, or zinc L-carnosine compound alone. Tissues were maintained for 180 minutes in Ussing chambers, during which permeability was assessed by measurement of transepithelial electrical resistance. After the 180-minute treatment period, tissues were removed from Ussing chambers and labeled with immunofluorescent anti-active caspase-3 antibody as an indicator of apoptosis.

RESULTS

Permeability of the gastric mucosa was significantly increased in a time-dependent manner by addition of HCl, whereas control tissues maintained viability for the study period. Change in permeability was detected within the first 15 minutes after acid application and progressed over the subsequent 150 minutes. The zinc L-carnosine compound had no significant effect on this increase in permeability. Apoptosis was evident in acid-treated tissues but not in control tissues. The zinc L-carnosine compound did not protect against development of apoptosis.

CONCLUSIONS AND CLINICAL RELEVANCE

Addition of HCl caused a dose-dependent increase in gastric permeability over time and apparent induction of apoptosis as determined on the basis of immunofluorescence. However, there was no significant protective effect of a zinc L-carnosine compound. Nonetheless, results suggested the utility of this method for further studies of canine gastric injury.

Carnosine prevents apoptosis of glomerular cells and podocyte loss in STZ diabetic rats

BACKGROUND/AIMS

We identified carnosinase-1 (CN-1) as risk-factor for diabetic nephropathy (DN). Carnosine, the substrate for CN-1, supposedly is a protective factor regarding diabetic complications. In this study, we hypothesized that carnosine administration to diabetic rats might protect the kidneys from glomerular apoptosis and podocyte loss.

METHODS

We examined the effect of oral L-carnosine administration (1g/kg BW per day) on apoptosis, podocyte loss, oxidative stress, AGEs and hexosamine pathway in kidneys of streptozotocin-induced diabetic Wistar rats after 3 months of diabetes and treatment.

RESULTS

Hyperglycemia significantly reduced endogenous kidney carnosine levels. In parallel, podocyte numbers significantly decreased (-21% compared to non-diabetics, p<0.05), apoptotic glomerular cells numbers increased (32%, compared to non-diabetic, p<0.05) and protein levels of bax and cytochrome c increased (175% and 117%). Carnosine treatment restored carnosine kidney levels, prevented podocytes loss (+23% compared to diabetic, p<0.05), restrained glomerular apoptosis (-34% compared to diabetic; p<0.05) and reduced expression of bax and cytochrome c (-63% and -54% compared to diabetics, both p<0.05). In kidneys of all diabetic animals, levels of ROS, AGEs and GlcNAc-modified proteins were increased.

CONCLUSION

By inhibition of pro-apoptotic signaling and independent of biochemical abnormalities, carnosine protects diabetic rat kidneys from apoptosis and podocyte loss.

Heat shock protein 70-dependent protective effect of polaprezinc on acetylsalicylic acid-induced apoptosis of rat intestinal epithelial cells

Protection of the small intestine from mucosal injury induced by nonsteroidal anti-inflammatory drugs including acetylsalicylic acid is a critical issue in the field of gastroenterology. Polaprezinc an anti-ulcer drug, consisting of zinc and L-carnosine, provides gastric mucosal protection against various irritants. In this study, we investigated the protective effect of polaprezinc on acetylsalicylic acid-induced apoptosis of the RIE1 rat intestinal epithelial cell line. Confluent rat intestinal epithelial cells were incubated with 70 µM polaprezinc for 24 h, and then stimulated with or without 15 mM acetylsalicylic acid for a further 15 h. Subsequent cellular viability was quantified by fluorometric assay based on cell lysis and staining. Acetylsalicylic acid-induced cell death was also qualified by fluorescent microscopy of Hoechst33342 and propidium iodide. Heat shock proteins 70 protein expression after adding polaprezinc or acetylsalicylic acid was assessed by western blotting. To investigate the role of Heat shock protein 70, Heat shock protein 70-specific small interfering RNA was applied. Cell viability was quantified by fluorometric assay based on cell lysis and staining and apoptosis was analyzed by fluorescence-activated cell sorting. We found that acetylsalicylic acid significantly induced apoptosis of rat intestinal epithelial cells in a dose- and time-dependent manner. Polaprezinc significantly suppressed acetylsalicylic acid-induced apoptosis of rat intestinal epithelial cells at its late phase. At the same time, polaprezinc increased Heat shock protein 70 expressions of rat intestinal epithelial cells in a time-dependent manner. However, in Heat shock protein 70-silenced rat intestinal epithelial cells, polaprezinc could not suppress acetylsalicylic acid -induced apoptosis at its late phase. We conclude that polaprezinc-increased Heat shock protein 70 expression might be an important mechanism by which polaprezinc suppresses acetylsalicylic acid-induced small intestinal apoptosis, a hallmark of acetylsalicylic acid-induced enteropathy.

Reactive oxygen species-quenching and anti-apoptotic effect of polaprezinc on indomethacin-induced small intestinal epithelial cell injury

BACKGROUND

To protect the small intestine from mucosal injury induced by nonsteroidal anti-inflammatory drugs is one of the critical issues in the field of gastroenterology. Polaprezinc (PZ), a gastric muco-protecting agent, has been widely used for the treatment of gastric ulcer and gastritis for its unique effects, such as its strong reactive oxygen species (ROS)-quenching effect. The aim of this study was to clarify the mechanism by which indomethacin-induced small intestinal mucosal injury occurs, by using a rat intestinal epithelial cell line (RIE-1). In addition, the protective role of PZ and the possible mechanism of its effect on indomethacin-induced small intestinal injury were investigated.

METHODS

Cell death was evaluated by methyl thiazolyl tetrazolium (MTT) assay and a double-staining method with Hoechst33342 dye and propidium iodide. Indomethacin-induced ROS production was evaluated by detecting the oxidation of a redox-sensitive fluorogenic probe, RedoxSensor, and the oxidation of cysteine residues of proteins (protein S oxidation). The activation of cytochrome c, smac/DIABLO, and caspase-3 was assessed by western blotting. In some experiments, PZ or its components, L: -carnosine and zinc, were used.

RESULTS

We found that indomethacin caused apoptosis in RIE-1 cells in a dose- and time-dependent manner. Indomethacin also induced ROS production and an increase in the protein S oxidation of RIE-1. Pretreatment of RIE-1 with PZ or zinc sulfate, but not L: -carnosine, significantly reduced the indomethacin-induced apoptosis. PZ prevented ROS production and the increase in protein S-oxidation. PZ inhibited indomethacin-induced cytochrome c and smac/DIABLO release and subsequent caspase-3 activation.

CONCLUSIONS

The protective effect of PZ on indomethacin-induced small intestinal injury may be dependent on its ROS-quenching effect.

Polaprezinc Protects Mice against Endotoxin Shock

Polaprezinc (PZ), a chelate compound consisting of zinc and l-carnosine (Car), is an anti-ulcer drug developed in Japan. In the present study, we investigated whether PZ suppresses mortality, pulmonary inflammation, and plasma nitric oxide (NO) and tumor necrosis factor (TNF)-α levels in endotoxin shock mice after peritoneal injection of lipopolysaccharide (LPS), and how PZ protects against LPS-induced endotoxin shock. PZ pretreatment inhibited the decrease in the survival rate of mice after LPS injection. PZ inhibited the increases in plasma NO as well as TNF-α after LPS. Compatibly, PZ suppressed LPS-induced inducible NO synthase mRNA transcription in the mouse lungs. PZ also improved LPS-induced lung injury. However, PZ did not enhance the induction of heat shock protein (HSP) 70 in the mouse lungs after LPS. Pretreatment of RAW264 cells with PZ suppressed the production of NO and TNF-α after LPS addition. This inhibition likely resulted from the inhibitory effect of PZ on LPS-mediated nuclear factor-κB (NF-κB) activation. Zinc sulfate, but not Car, suppressed NO production after LPS. These results indicate that PZ, in particular its zinc subcomponent, inhibits LPS-induced endotoxin shock via the inhibition of NF-κB activation and subsequent induction of proinflammatory products such as NO and TNF-α, but not HSP induction.

Zinc Supplementation with Polaprezinc Protects Mouse Hepatocytes against Acetaminophen-Induced Toxicity via Induction of Heat Shock Protein 70

Polaprezinc, a chelate compound consisting of zinc and l-carnosine, is clinically used as a medicine for gastric ulcers. It has been shown that induction of heat shock protein (HSP) is involved in protective effects of polaprezinc against gastric mucosal injury. In the present study, we investigated whether polaprezinc and its components could induce HSP70 and prevent acetaminophen (APAP) toxicity in mouse primary cultured hepatocytes. Hepatocytes were treated with polaprezinc, zinc sulfate or l-carnosine at the concentration of 100 microM for 9 h, and then exposed to 10 mM APAP. Polaprezinc or zinc sulfate increased cellular HSP70 expression. However, l-carnosine had no influence on it. Pretreatment of the cells with polaprezinc or zinc sulfate significantly suppressed cell death as well as cellular lipid peroxidation after APAP treatment. In contrast, pretreatment with polaprezinc did not affect decrease in intracellular glutathione after APAP. Furthermore, treatment with KNK437, an HSP inhibitor, attenuated increase in HSP70 expression induced by polaprezinc, and abolished protective effect of polaprezinc on cell death after APAP. These results suggested that polaprezinc, in particular its zinc component, induces HSP70 expression in mouse primary cultured hepatocytes, and inhibits lipid peroxidation after APAP treatment, resulting in protection against APAP toxicity.

Rescue strategies against non-steroidal anti-inflammatory drug-induced gastroduodenal damage

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most commonly prescribed drugs worldwide, which attests to their efficacy as analgesic, antipyretic and anti-inflammatory agents as well as anticancer drugs. However, NSAID use also carries a risk of major gastroduodenal events, including symptomatic ulcers and their serious complications that can lead to fatal outcomes. The development of "coxibs" (selective cyclooxygenase-2 [COX-2] inhibitors) offered similar efficacy with reduced toxicity, but this promise of gastroduodenal safety has only partially been fulfilled, and is now dented with associated risks of cardiovascular or intestinal complications. Recent advances in basic science and biotechnology have given insights into molecular mechanisms of NSAID-induced gastroduodenal damage beyond COX-2 inhibition. The emergence of newer kinds of NSAIDs should alleviate gastroduodenal toxicity without compromising innate drug efficacy. In this review, novel strategies for avoiding NSAID-associated gastroduodenal damage will be described.

Polaprezinc (Zinc L-carnosine) is a potent inducer of anti-oxidative stress enzyme, heme oxygenase (HO)-1 - a new mechanism of gastric mucosal protection

Heme oxygenase (HO)-1 is implicated in cytoprotection in various organs. We tested a possibility that polaprezinc (PZ), an anti-ulcer drug, could induce HO-1 in the gastric mucosa. Male 6-week-old Wistar rats were intragastrically administered PZ. Gastric expression of HO-1 was assessed by real time RT-PCR and western blotting, and localization of HO-1 was observed by in situ hybridization and immunohistochemistry. The levels of HO-1 mRNA were increased in a dose-dependent manner. The levels of HO-1 mRNA were increased 4-fold by PZ at the dose of 200 mg/kg at 3 h as compared with control levels. The levels of immunoreactive HO-1 were increased 3-fold at 6 h. Signals for HO-1 mRNA and immunoreactivity were detected strongly in the surface gastric mucosal cells and moderately in the gastric macrophages. Treatment with an HO-1 inhibitor, stannous mesoporphyrin (SnMP) significantly worsened the HCl-induced acute gastric mucosal lesions and increased the apoptosis of mucosal cells. Mucosal lesions were decreased by pretreatment with PZ, while they were increased by co-administration with SnMP. These data indicate for the first time that PZ is an effective inducer of HO-1 in the stomach. PZ-induced HO-1 functions as a part of the mucosal protective effects of PZ.

Protection by polaprezinc against radiation-induced apoptosis in rat jejunal crypt cells

Polaprezinc, an anti-ulcer drug, is a chelate compound consisting of zinc and L-carnosine. Polaprezinc has been shown to prevent gastric mucosal injury. The anti ulcer effects of polaprezinc have been ascribed to its antioxidative property. The effect of polaprezinc on ionizing radiation-induced apoptosis was studied in the jejunal epithelial crypt cells of rats. Seven-to eight week-old Wistar rats, which were treated with 100 mg/kg of polaprezinc orally 1h before irradiation or 2% carboxymethyl cellulose sodium in controls, were exposed to whole body X-ray irradiation at 2 Gy. The number of apoptotic cells per jejunum crypt was counted in haematoxylin and eosin stained sections at 0-6 h after irradiation. TUNEL positive cells and immunopositive cells for active caspase-3 per crypt were also counted. Accumulation of p53, p21(WAF1/CIP1) and Bax expression in the jejunum after irradiation were examined by Western blot analyses. Polaprezinc treatment given prior to radiation resulted in a significant reduction in numbers of apoptotic cells, TUNEL positive cells and active caspase-3 immunopositive cells in jejunal crypt cells. Polaprezinc treatment resulted in decreases of p53 accumulation, p21(WAF1/CIP1) and Bax expression after irradiation. Polaprezinc has a protective effect against ionizing radiation induced apoptosis in rat jejunal crypt cells.