Role of actin and calmodulin in migration and proliferation of rabbit gastric mucosal cells in culture

The Role of Calmodulin in Tumor Cell Migration, Invasiveness, and Metastasis

Calmodulin (CaM) is the principal Ca²⁺ sensor protein in all eukaryotic cells, that upon binding to target proteins transduces signals encoded by global or subcellular-specific changes of Ca²⁺ concentration within the cell. The Ca²⁺/CaM complex as well as Ca²⁺-free CaM modulate the activity of a vast number of enzymes, channels, signaling, adaptor and structural proteins, and hence the functionality of implicated signaling pathways, which control multiple cellular functions. A basic and important cellular function controlled by CaM in various ways is cell motility. Here we discuss the role of CaM-dependent systems involved in cell migration, tumor cell invasiveness, and metastasis development. Emphasis is given to phosphorylation/dephosphorylation events catalyzed by myosin light-chain kinase, CaM-dependent kinase-II, as well as other CaM-dependent kinases, and the CaM-dependent phosphatase calcineurin. In addition, the role of the CaM-regulated small GTPases Rac1 and Cdc42 (cell division cycle protein 42) as well as CaM-binding adaptor/scaffold proteins such as Grb7 (growth factor receptor bound protein 7), IQGAP (IQ motif containing GTPase activating protein) and AKAP12 (A kinase anchoring protein 12) will be reviewed. CaM-regulated mechanisms in cancer cells responsible for their greater migratory capacity compared to non-malignant cells, invasion of adjacent normal tissues and their systemic dissemination will be discussed, including closely linked processes such as the epithelial–mesenchymal transition and the activation of metalloproteases. This review covers as well the role of CaM in establishing metastatic foci in distant organs. Finally, the use of CaM antagonists and other blocking techniques to downregulate CaM-dependent systems aimed at preventing cancer cell invasiveness and metastasis development will be outlined.

Cell injury triggers actin polymerization to initiate epithelial restitution

The role of the actin cytoskeleton in the sequence of physiological epithelial repair in the intact epithelium has yet to be elucidated. Here, we explore the role of actin in gastric repair in vivo and in vitro gastric organoids (gastroids). In response to two-photon-induced cellular damage of either an in vivo gastric or in vitro gastroid epithelium, actin redistribution specifically occurred in the lateral membranes of cells neighboring the damaged cell. This was followed by their migration inward to close the gap at the basal pole of the dead cell, in parallel with exfoliation of the dead cell into the lumen. The repair and focal increase of actin was significantly blocked by treatment with EDTA or the inhibition of actin polymerization. Treatment with inhibitors of myosin light chain kinase, myosin II, trefoil factor 2 signaling or phospholipase C slowed both the initial actin redistribution and the repair. While Rac1 inhibition facilitated repair, inhibition of RhoA/Rho-associated protein kinase inhibited it. Inhibitors of focal adhesion kinase and Cdc42 had negligible effects. Hence, initial actin polymerization occurs in the lateral membrane, and is primarily important to initiate dead cell exfoliation and cell migration to close the gap.

The many faces of calmodulin in cell proliferation, programmed cell death, autophagy, and cancer

Calmodulin (CaM) is a ubiquitous Ca(2+) receptor protein mediating a large number of signaling processes in all eukaryotic cells. CaM plays a central role in regulating a myriad of cellular functions via interaction with multiple target proteins. This review focuses on the action of CaM and CaM-dependent signaling systems in the control of vertebrate cell proliferation, programmed cell death and autophagy. The significance of CaM and interconnected CaM-regulated systems for the physiology of cancer cells including tumor stem cells, and processes required for tumor progression such as growth, tumor-associated angiogenesis and metastasis are highlighted. Furthermore, the potential targeting of CaM-dependent signaling processes for therapeutic use is discussed.

Lansoprazole promotes gastric mucosal cell proliferation and migration by activating p44/p42 mitogen-activated protein kinase

Cell proliferation and migration are important repair mechanisms in cell defect type mucosal injuries, such as peptic ulcers. To evaluate the level of cell restitution in vitro, we established a normalized assay system for analyzing the area of a tissue defect created in the center of a cultured cell layer. Although proton pump inhibitors are known to be potently effective in the treatment of peptic ulcers by inducing acid suppression, they are also effective in low-acid conditions, such as in gastric ulcers associated with severe atrophic gastritis of the corpus. The present study was designed to examine the pH-independent effect of lansoprazole (LPZ) on cell restitution in vitro. The mouse gastric mucosal cell line, GSM06, was cultured to confluence. A 4-fluoric ethylene-tipped aluminum stick was then used to produce a cell-free area in the center of the culture well. After measuring the area of the cell defect using a digital analyzer equipped with an inverted microscope, LPZ was added to each well; the area of the residual cell defect was then measured 6 and 24 hours after LPZ administration. To investigate the involvement of the p44/p42 mitogen-activated protein kinase (MAPK) and p38 MAPK in this process, PD98059 (a MEK inhibitor) or FR167653 (a p38 MAPK inhibitor) was added to the cell cultures. In a separate experiment, GSM06 cells were cultured to the subconfluent level, each test agent was added, and the cell number in each well was measured using an MTT assay 16 hours after the administration of the agents. Six hours after the addition of LPZ, a slight but significant increase in the cell restitution rate was observed in the LPZ-treated groups compared with that in the control group. After 24 hours, a further significant increase in the cell restitution rate was observed in the LPZ groups compared with that in the control group. While the addition of PD98059 significantly attenuated the cell restitution rate in the LPZ groups, the addition of FR167653 had no such effect. The total cell number in the subconfluent cell cultures was significantly increased in the LPZ-treated groups compared with that in the control group. In conclusion, LPZ promotes the healing of injured gastric mucosal cells following injury by enhancing cell proliferation and migration. Furthermore, the mechanism by which cell proliferation and migration is promoted by LPZ may involve the activation of p44/p42 MAPK.

Protective effect of a novel rice extract against ethanol-induced gastric mucosal injury in rat

The aim of this study was to investigate the protective action of rice extract on ethanol-induced mucosal damage in vivo and wound healing of epithelial cells in vitro. Also, the effect of rice extract on gastric mucosal prostaglandin E(2) level, HSP72 expression, gastric acid secretion, and contribution of vanilloid receptor-mediated action was studied. In addition, using cultured gastric mucosal cells (RGM-1), the effect of rice extract on cytoprotection and wound healing of epithelial cells was evaluated. Rice extract significantly reduced gastric mucosal damage produced by ethanol in vivo, and heat treatment (80 degrees C, 3 min) of this agent did not alter its protective effect. Rice extract also protected RGM-1 from ethanol-induced damage in a dose-dependent manner. Rice extract accelerated wound healing of gastric epithelial cells. Our results demonstrate that rice extract could be an alternative ulcer treatment that provides cytoprotection and enhancement of wound healing not dependent on acid secretion, prostaglandin E(2) level, HSP72 expression, or vanilloid receptors.

Effect of the ulcerogenic agents ethanol, acetylsalicylic acid and taurocholate on actin cytoskeleton and cell motility in cultured rat gastric mucosal cells

AIM: To assess the effects of ulcerogenic agents on actin cytoskeleton and cell motility and the contribution of oxidative stress.

METHODS: Rat gastric mucosal cell monolayers were cultured on coverslips. The cells were exposed, with or without allopurinol (2 mmol/L), for 15 min to ethanol (10-150 mL/L), ASA (1-20 mmol/L) or taurocholate (1-20 mmol/L), then the cells were processed for actin and vinculin staining. Cell migration after wounding was also measured.

RESULTS: Exposure to 10 mL/L ethanol caused divergence of zonula adherens-associated actin bundles of adjacent cells and decreased rate of migration. These actions were opposed by xanthine oxidase inhibitor allopurinol. Exposure to 50 mL/L ethanol induced degradation and divergence of zonula adherens-associated vinculin from adjacent cells, which was, again, partially reverted by allopurinol. With 1 mmol/L ASA actin filaments became shorter and thicker. However, higher concentrations (10, 20 mmol/L) of ASA returned microfilaments thinner and longer, and decreased rate of migration. Zonula adherens-associated actin bundles were moderately distorted with 10 mmol/L ASA and with 10 mmol/L taurocholate. Exposure to taurocholate provoked changes resembling those of ASA. Taurocholate 5-20 mmol/L decreased the rate of migration dose dependently. The effects of ASA and taurocholate were not prevented by allopurinol.

CONCLUSION: All ulcerogenic agents decreased the rate of migration dose dependently and induced divergence of zonula adherens-associated actin bundles of adjacent cells. In addition, ethanol and ASA caused degradation of actin cytoskeleton. Oxidative stress seems to underlie ethanol, but not ASA or taurocholate, induced cytoskeletal damage.

Indomethacin delays gastric restitution: association with the inhibition of focal adhesion kinase and tensin phosphorylation and reduced actin stress fibers

Repair of superficial gastric mucosal injury is accomplished by the process of restitution-migration of epithelial cells to restore continuity of the mucosal surface. Actin filaments, focal adhesions, and focal adhesion kinase (FAK) play crucial roles in cell motility essential for restitution. We studied whether epidermal growth factor (EGF) and/or indomethacin (IND) affect cell migration, actin stress fiber formation, and/or phosphorylation of FAK and tensin in wounded gastric monolayers. Human gastric epithelial monolayers (MKN 28 cells) were wounded and treated with either vehicle or 0.5 mM IND for 16 hr followed by EGF. EGF treatment significantly stimulated cell migration and actin stress fiber formation, and increased FAK localization to focal adhesions, and phosphorylation of FAK and tensin, whereas IND inhibited all these at the baseline and EGF-stimulated conditions. IND-induced inhibition of FAK phosphorylation preceded changes in actin polymerization, indicating that actin depolymerization might be the consequence of decreased FAK activity. In in vivo experiments, rats received either vehicle or IND (5 mg/kg i.g.), and 3 min later, they received water or 5% hypertonic NaCl; gastric mucosa was obtained at 1, 4, and 8 hr after injury. Four and 8 hr after hypertonic injury, FAK phosphorylation was induced in gastric mucosa compared with controls. IND pretreatment significantly delayed epithelial restitution in vivo, and reduced FAK phosphorylation and recruitment to adhesion points, as well as actin stress fiber formation in migrating surface epithelial cells. Our study indicates that FAK, tensin, and actin stress fibers are likely mediators of EGF-stimulated cell migration in wounded human gastric monolayers and potential targets for IND-induced inhibition of restitution.

Nicotine suppresses gastric wound repair via the inhibition of polyamine and K(+) channel expression

Nicotine is one of the most representative components in cigarette smoke leading to gastric ulceration. Both ornithine decarboxylase and potassium ion (K(+)) channels are essential for cell growth and wound repair. The aim of the present study is to elucidate the causative relationship of these two factors during wound healing and the influence of nicotine on this healing process in rat gastric mucosal epithelial cells (RGM-1). Nicotine markedly inhibited cell migration and proliferation in RGM-1 cells. The latter effect was significantly antagonized by a nicotinic receptor blocker, mecamylamine. Nicotine also suppressed ornithine decarboxylase activity significantly. Our data showed that inhibition of cell proliferation and ornithine decarboxylase activity by nicotine was accompanied with a reduction in K(+) channel protein expression, all of which were significantly alleviated by spermidine pretreatment. These results suggested that there was a cause/effect link between ornithine decarboxylase and K(+) channel on wound repair. Nicotine in cigarette smoke inhibited this healing process and delayed wound repair in gastric epithelial cells.

Inhibition of proliferation of gastric epithelial cells by a cyclooxygenase 2 inhibitor, JTE522, is also mediated by a PGE2-independent pathway

BACKGROUND

Cyclooxygenase-2 (COX-2) is one of the rate-limiting enzymes for prostaglandin synthesis from arachidonic acid. Although it is known that inhibition of cyclooxygenase activity delays ulcer healing, the regulatory relationship between COX-2 and its metabolites in gastric epithelial cell proliferation is not well known.

AIM

To investigate whether COX-2 has an effect on gastric mucosal cell proliferation and further studied whether such effect is mediated only by prostaglandin E2 (PGE2), a representative metabolite of arachidonates in the gastric mucosa.

METHODS

Artificial wounds of defined area size were created on complete monolayer cell sheets of isolated rat gastric epithelial cells and rat gastric cell line RGM1 under the addition of arachidonic acid or a COX-2 selective inhibitor, JTE522. Repair of wounds was assessed by monitoring wound size, with cell proliferation detected using 5-bromodeoxyuridine staining. Quantity of secreted PGE2 was measured by enzyme immunoassay.

RESULTS

Stimulation of foetal calf serum increased the expression of COX-2 protein and inhibition of COX-2 retarded wound healing with reduction of cell proliferation. Arachidonic acid increased PGE2 production and accelerated restoration. Combination of JTE522 and arachidonic acid resulted in a marked retardation of wound healing compared to the control, but JTE522 did not completely suppress the increase in cellular PGE2 content following the addition of arachidonate.

CONCLUSIONS

The difference in the effects of JTE522 on PGE2 production and on wound healing suggest that the involvement of COX-2 in gastric epithelial cell proliferation is not mediated solely by PGE2.

Cigarette smoke extracts delay wound healing in the stomach: involvement of polyamine synthesis

The association between cigarette smoking and peptic ulcer diseases has been well established. Ornithine decarboxylase (ODC) is crucial for the gastroprotective and mucosal growth promoting effects in gastric ulcer healing. The aim of this study is to elucidate the possible mechanism of how inhibition of ODC activity is involved in the delay of ulcer healing, if any, by cigarette smoke extracts (CSE). CSE were fractionated into chloroform extract (CE) and ethanol extract (EE). In in vivo study, rats with acetic acid-induced ulcers were given CE or EE intragastrically (2.5 or 5 mg/kg) once daily for 3 days. Ulcer sizes were significantly larger after CE or EE administration, followed by an increase in myeloperoxidase activity and a reduction in cell proliferation. However, both CSE stimulated the number of microvessels following the increase of basic fibroblast growth factor. In in vitro studies, the effect of CE or EE (10, 40, or 100 microg/ml) on cell migration and cell proliferation were measured using an in vitro wound model and [(3)H]-thymidine incorporation assay, respectively. Both CSE delayed cell migration and decreased cell proliferation, which were accompanied with a reduction in ODC activity. Exogenous spermidine (5 or 10 microM) could reverse the inhibitory action on cell proliferation and ODC activity induced by CSE. In conclusion, both CSE significantly delayed ulcer healing as a result of reduction in cell proliferation and cell migration. All these effects are, in part, related to the reduction of polyamine synthesis.

Nitric oxide donors retard wound healing in cultured rabbit gastric epithelial cell monolayers

Effects of nitric oxide (NO) on gastric wound healing were investigated in primary rabbit gastric epithelial cell cultures. We analyzed the speed of cell migration, proliferation, and apoptosis after creating a round wound on the cell cultures. The monolayers were incubated with or without the NO donor sodium nitroprusside, oxatriazolimine 1,2,3,4-oxatriazolium, 5amino-3-(3,4-dichlorophenylchloride), or the peroxynitrite generator 3-morpholinosydnomine-N-ethylcarbamide. The possible role of cGMP as a second messenger of NO was investigated with 8-bromo-cGMP. The role of O2(-*) was evaluated using diethyldithiocarbamate and pyrogallol. The effects of superoxide dismutase and allopurinol were also investigated. NO inhibited the speed of cell migration and proliferation and induced cell apoptosis in a dose- and time-dependent manner. The effects were augmented with O2(-*) generators and ameliorated by O2-(8) scavengers, whereas cGMP had no significant effect on wound healing. NO donors retard gastric wound healing by inhibiting migration and proliferation and inducing cell apoptosis. These effects do not seem to be mediated via cGMP, but O2(-*). or peroxynitrites may be involved.

A mechanistic study of proliferation induced by Angelica sinensis in a normal gastric epithelial cell line

It has been reported that an extract from Angelica sinensis mainly consisting of polysaccharides (95%) prevented ethanol- or indomethacin-induced gastric mucosal damage (Cho CH et al. Planta Med 2000;66:348-51). However, it is not known whether Angelica sinensis has a direct stimulatory effect on the healing of gastric mucosal lesions. To study the hypothesis that Angelica sinensis has a direct mucosal healing effect in rats and in isolated gastric epithelial cells, we assessed the wound repair in both animals and normal cell culture (RGM-1), as well as [3H]thymidine incorporation, ornithine decarboxylase (ODC) activity, and ODC protein and c-Myc protein expression after different treatments in RGM-1 cells. We found that Angelica sinensis crude extract (ASCE) dose-dependently enhanced gastric ulcer healing in rats and promoted wound repair in RGM-1 cells. It also significantly stimulated [3H]thymidine incorporation and ODC activity in RGM-1 cells in a concentration-dependent manner. ODC and c-Myc protein expression was also increased as a result of this process. DL-alpha-difluoromethyl-ornithine repressed the [3H]thymidine incorporation and ODC activity induced by ASCE. Pretreatment with c-Myc antisense oligodeoxynucleotides blocked the stimulatory action of ASCE on [3H]thymidine incorporation and ODC protein expression. These data suggest that ASCE has a direct mucosal healing effect on gastric epithelial cells, while ODC and c-Myc are closely associated with this effect.

Characterization and application of a gastric surface mucous cell line GSM06 established from temperature-sensitive simian virus 40 large T-antigen transgenic mice

It has been indicated that transgenic mouse harboring a temperature-sensitive simian virus 40 large T-antigen gene is useful for establishing cell lines from tissues that have proved difficult to culture in vitro. The gastric surface mucous cell line GSM06 was established from a primary culture of gastric fundic mucosal cells of the transgenic mice. GSM06 cells showed temperature-sensitive growth in culture and expressed large T-antigen at a permissive temperature (33 degrees C) but not at a nonpermissive temperature (39 degrees C). At 39 degrees C, the cells produced periodic acid-Schiff positive glycoconjugates that formed a mucous sheet like the gastric surface mucosa in the stomach. Insulin markedly increased the production of glycoconjugates. In addition, proprotein-processing endoprotease furin suppression retarded cell growth, but accelerated cell differentiation. An air-liquid interface promoted the differentiation of GSM06 cells in a reconstruction culture with nitrocellulose membrane and collagen gel. The gastric surface mucous cell line GSM06 with unique characteristics, therefore, should be useful as an in vitro model of the gastric mucosa for physiological and pharmacological investigations. Moreover, experiments using immortalized cells established in vitro and having specific functions may offer an alternative to experiments using living animals and thereby offer a solution to this ethical issue.

Effects of growth factors on aspirin-induced inhibition of wound repair in a rabbit gastric epithelial cell model

BACKGROUND

Aspirin is known to cause adverse effects, including gastric mucosal injury, and to retard gastric wound healing. Growth factors including hepatocyte growth factor (HGF), epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) have been shown to play an important role in the repair of gastric mucosal injury.

AIM

To employ the cultured gastric epithelial cell model to elucidate the effects of aspirin, as well as several growth factors (HGF, EGF and IGF-I), on gastric wound repair.

METHODS

Isolated rabbit gastric epithelial cells (92% mucous cells) were cultured in F-12 medium and formed a complete monolayer cell sheet in 48 h. A wound with a cell-free area of constant size (2 mm2) was then created and the wound repair process was monitored by measuring wound size every 12 h. Proliferating cells were detected by BrdU staining. Effects of aspirin (8 mM), HGF (10 ng/mL), EGF (10 ng/mL) and IGF-I (30 ng/mL) were assessed.

RESULTS

Aspirin significantly retarded wound healing, but simultaneous addition of growth factors significantly accelerated wound repair compared with aspirin alone. Growth factors reversed the aspirin-induced inhibition of cell proliferation.

CONCLUSION

Growth factors, including HGF, EGF and IGF-I, reversed the aspirin-induced inhibition of wound repair through their cytoprotective effects on gastric epithelial cells.

Models for use in wound healing research: a survey focusing on in vitro and in vivo adult soft tissue

Many different factors must be considered before selecting a wound healing model to use for a specific study. A wide variety of models have been developed that examine different aspects of the repair response, both in vitro and in vivo. In this review article, we focus on those systems that are most widely used for studies on adult soft tissue healing. Advantages and disadvantages of each are discussed, along with relevant background information to help guide decision-making.

Role of epidermal growth factor receptor in basal and stimulated colonic epithelial cell migration in vitro

Colonic mucosal wounds are repaired, in part, by epithelial migration. Signaling mechanisms regulating this migration are poorly characterized. This study aimed to examine the role that the epidermal growth factor (EGF) receptor (EGF-R) and its ligands, EGF and transforming growth factor-alpha (TGF-alpha), play in migration in wounded in vitro models of colonic epithelium. Migration was assessed over 24 h in circular wounds made in confluent monolayers of LIM1215 human colon cancer cells. EGF and TGF-alpha stimulated migration twofold from 4 h after wounding. Basal migration and the motogenic effects of short chain fatty acids and hepatocyte growth factor were mediated through enhanced binding of TGF-alpha to EGF-R, while trefoil peptide-mediated motogenesis required EGF-R activation independently of TGF-alpha binding. Activation of protein kinase C (PKC) stimulated migration, an effect more potent than, and independent of, EGF-R activation. However, neither inhibition of PKC by Ro 31-8220 nor depletion of PKC by pretreatement with phorbol myristate acetate attenuated EGF-R-mediated motogenesis. In conclusion, EGF-R activation via TGF-alpha binding, or intracellularly, mediates basal LIM1215 migration and the effects of several motogens, with the exception of PKC activators. Since EGF-R and PKC have physiological activators in vivo, they may control colonic mucosal repair processes following injury.

Effect of temperature and mechanical strain on gastric epithelial cell line GSM06 wound restoration in vitro

BACKGROUND

The influence of the degree of cell differentiation and of physical stimulation on gastric mucosal wound healing is not completely understood.

METHODS

A gastric mucosal cell line, GSM06, derived from the gastric mucosal cells of transgenic mice harbouring the simian virus 40 large T antigen, was cultured at 33 degrees C to make a confluent cell sheet. Artificial wounds of constant size were created. Wound healing was monitored at different temperatures (33, 37 and 39 degrees C), which altered the degree of differentiation. Cell proliferation was detected by bromodeoxyuridine staining. Mechanical strain was applied to adherent GSM06 cells after wounding in order to increase their length by an average of 5 or 10% at 5 cycles/min for 60 h. Repair of the wound was monitored every 12 h.

RESULTS

Differentiated gastric epithelial cells showed a higher speed of migration. The number of proliferating cells around the wound was greatest at 33 degrees C and barely detectable at 39 degrees C. Under conditions of mechanical strain, the migration speed of differentiated cells (at 39 degrees C) slowed in a strain strength-dependent manner.

CONCLUSIONS

It is suggested that cell differentiation status and physical stimulants might play a role in gastric wound healing in vivo by modifying cellular migration.

Characterization of cell deformation and migration using a parametric estimation of image motion

This paper deals with the spatio-temporal analysis of two-dimensional deformation and motion of cells from time series of digitized video images. A parametric motion approach based on an affine model has been proposed for the quantitative characterization of cellular movements in different experimental areas of cellular biology including spontaneous cell deformation, cell mitosis, individual cell migration and collective migration of cell populations as cell monolayer. The accuracy and robustness of the affine model parameter estimation, which is based on a multiresolution algorithm, has been established from synthesized image sequences. A major interest of our approach is to follow with time the evolution of a few number of parameters characteristic of cellular motion and deformation. From the time-varying eigenvalues of the affine model square matrix, a precise quantification of the cell pseudopodial activity, as well as of cell division has been performed. For migrating cells, the motion quantification confirms that cell body deformation has a leading role in controlling nucleus displacement, the nucleus itself undergoing a larger rotational motion. At the cell population level, image motion analysis of in vitro wound healing experiments quantifies the heterogeneous cell populations dynamics.

A neurotrophic pyrimidine compound, MS-818, enhances EGF-induced restoration of gastric epithelial wounds in vitro

MS-818 is a novel synthetic pyrimidine compound that stimulates nerve regeneration and promotes synthesis of various growth factors and differentiation of astrocytes. Effects of MS-818 on gastric epithelial cells were assessed using a wound repair model with primary cultured gastric epithelial cells from rabbits. A round wound with a constant cell-free area was created and the process of restoration was monitored by measuring wound size every 12 h. Cell proliferation was monitored by sequential staining with BrdU. As previously reported, EGF (10 ng/ml) accelerated wound repair by promoting cell migration and proliferation. Although MS-818 alone had no effects, MS-818 (10-100 microM) enhanced EGF-induced acceleration of gastric epithelial restoration, including cell migration and proliferation. Although the detailed mechanism of action of this agent is still unclear, MS-818 might have favorable effects on in vivo gastric mucosal repair.

The novel histamine H2 receptor antagonist FRG-8813 prevents delay of wound repair induced by hydrogen peroxide in a rabbit gastric epithelial cell system

The effects of a novel histamine H₂ receptor antagonist (FRG-8813) on the restoration process of gastric epithelial wounds were assessed using an in vitro wound healing model. FRG-8813 (1, 10 mol/L) was added to a complete confluent monolayer cell sheet after artificial wounding. The restoration process was analysed by a time-lapse video system and cell migration, proliferation and apoptosis were assessed. Hydrogen peroxide (1, 3 mmol/L) inhibited restoration after wounding by suppressing cell migration and proliferation and induced epithelial cell apoptosis around the wound. The addition of FRG-8813 abolished the hydrogen peroxide-induced retardation and prevented apoptosis, although FRG-8813 itself did not enhance wound healing. FRG-8813 may act as a radical scavenger as well as having an anti-secretory action and may have favourable effects on peptic ulcer healing.

Insulin-like growth factor I plays a role in gastric wound healing: evidence using a zinc derivative, polaprezinc, and an in vitro rabbit wound repair model

BACKGROUND

Although the detailed mechanism is unclear, zinc and its derivative, polaprezinc, have been reported to accelerate gastric ulcer healing in vivo.

AIM

To investigate the detailed cellular mechanism of polaprezinc on gastric epithelial cells and fibroblasts with special attention to insulin-like growth factor I (IGF-I).

METHODS

Isolated rabbit gastric epithelial cells formed a complete monolayer, from which a circular artificial wound with constant size was made. The restoration process was monitored by measuring wound size up to 48 h. Either polaprezinc, IGF-I, fibroblast conditioned medium or neutralized medium conditioned by anti-IGF-I antibody was added at the time of wounding. The expression of mRNA of IGF-I, hepatocyte growth factor (HGF) and transforming growth factor alpha (TGF-alpha) in fibroblasts with or without polaprezinc treatment was tested using reverse transcription polymerase chain reaction (RT-PCR). Gastric epithelial cell proliferation was also examined by bromodeoxyuridine (BrdU) staining.

RESULTS

IGF-I and fibroblast conditioned medium treatment accelerated gastric epithelial restoration which included cell migration and proliferation. However, polaprezinc and neutralized conditioned medium treatment did not accelerate epithelial repair. RT-PCR for growth factor mRNA revealed the IGF-I mRNA expression in fibroblasts was increased after treatment with polaprezinc.

CONCLUSION

Polaprezinc induced IGF-I production from mesenchymal cells, resulting in stimulation of epithelial cell restoration through a paracrine pathway. IGF-I may play an important role in gastric wound repair.

The role of the cytoskeleton in migration and proliferation of a cultured human gastric cancer cell line using a new metastasis model

Using an in vitro model for investigating the mechanism of migration and proliferation of a cultured human gastric cancer cell line which we established recently, we studied the suppressive effect of inhibitors of the cytoskeleton proteins, actin and myosin, on the migration and proliferation of cancer cells. These inhibitors suppressed the capacity of cancer cells to migrate and proliferate dose-dependently. Thus the integrity of the cytoskeletal system may play an important role in the mechanism of metastasis of gastric cancer cells.

Effects of epidermal growth factor and insulin on migration and proliferation of primary cultured rabbit gastric epithelial cells

We assessed the influence of epidermal growth factor (EGF) and insulin on gastric epithelial restoration in vitro. Rabbit gastric epithelial cells were cultured and formed a complete monolayer cell sheet in 2 days. We created a wound (1.8 +/- 0.05 mm2) by denuding an area of cells, and EGF (0.1-30 ng/ml) and/or insulin (1 nM-1 microM) was added. The restoration process, which included cell migration and proliferation, was monitored by measuring the cell-free area every 12 h for 2 days. Proliferating cells were detected by sequential staining with bromodeoxyuridine (BrdU). Control cells showed complete repair in 36-48 h and restoration was accelerated dose-dependently by EGF or insulin. EGF plus insulin further accelerated restoration, which was then completed in 12-24 h. EGF and/or insulin increased the number of BrdU- positive cells. The results indicated that EGF and insulin additively accelerated gastric epithelial wound repair by stimulating both the migration and the proliferation of gastric epithelial cells (particularly the former).

In vitro dynamics of chromatin organization and migration

The organization of eukaryotic chromatin is not static but changes as a function of cell status during processes such as proliferation, differentiation, and migration. DNA quantification has not been used extensively to investigate chromatin dynamics in combination with cellular migration. In this context, an optimized DNA-specific, nonperturbant method has been developed for studying chromatin organization, using the fluorescent vital bisbenzimidazole probe Hoechst 33342: this property has been described by Hamori et al. (1980). Computer-assisted image analysis was used to follow migratory activity and chromatin organization of L929 fibroblasts during in vitro wound healing. Cell movements were analyzed using an optical flow technique, which consists in the calculation of the velocity field of cells and nuclear movements in the frame. This system allows the correlation of cell migration and position in the cell cycle. It makes it possible to study chromatin dynamics using a quantitative analysis of nuclear differentiation reorganization (nuclear texture) and to correlate this with migration characteristics. The present system would be of interest for studying cell-extracellular matrix interactions using differing substrates, and also the migratory response to chemotactic factors. Such a model is a prerequisite for gaining better understanding of drug action.

Ethanol retards gastric epithelial restoration in monolayer cultures

The purpose of this study was to clarify the effect of ethanol on confluent monolayer gastric epithelial cells that had a round cell-free area in the center of the culture dish. Restoration of such "wounding" was evaluated quantitatively every 12 hr using a computer image analyzer with and without ethanol. Without ethanol, restoration was achieved within 48 hr. Exposure to ethanol retarded cellular restoration significantly. Staining for actin and myosin in the control group revealed the presence of lamellipodia and stress fibers. However, in the ethanol group narrowed lamellipodia and few stress fibers were observed. In conclusion, ethanol retarded the migration and proliferation of cultured gastric mucosal cells after in vitro wounding, possibly by damaging the cytoskeletal system.

Acidic calponin cloned from neural cells is differentially expressed during rat brain development

Calponin is an actin-, tropomyosin- and Ca2+ calmodulin-binding protein that inhibits in vitro the actomyosin MgATPase. Basic and acidic variants of calponin have been described to date. Although the cerebral expression of calponin remained controversial for some time, transcripts encoding acidic calponin in the adult rat brain and in cultured cerebellar cells have been reported. In the present work, we report the expression of acidic calponin mRNAs and the isolation of cDNAs encoding the full-length acidic calponin in cultured neuronal and glial cells and in adult rat brain. Sequence analysis reveals that acidic calponin in the brain is identical to that previously described in rat aortic vascular smooth muscle. In situ hybridization shows that calponin is highly expressed during ontogenesis in granule cells of the dentate gyrus of the hippocampus, in all layers of the olfactory bulb and in cerebellar granule neurons of the external and internal layers. In the adult rat brain, calponin expression decreased in these fields, but increased in choroid plexus cells. Bergmann glial cells were also labelled by a calponin probe. The reverse transcription-coupled polymerase chain reaction confirms that calponin mRNA levels are highest in the early stages of hippocampal development and that expression levels are low in adult hippocampi. The developmental expression pattern of brain acidic calponin suggests that calponin could be involved in contractile activity associated with neural cell proliferation or neuronal migration.

Stimulatory effects of sucralfate on secretion and synthesis of mucus by rabbit gastric mucosal cells. Involvement of phospholipase C

We examined the effects of sucralfate on the secretion and synthesis of mucus by cultured rabbit gastric mucosal cells, and the underlying intracellular mechanism. Treatment of mucosal cells with sucralfate (>0.5 mg/ml) for 4 and 8 hr caused a significant increase in the inositol triphosphate (IP3) content in the cells. Neomycin (a phospholipase C inhibitor) at 1 mM markedly inhibited the sucralfate-induced increases in both the IP3 content and mucus secretion and synthesis. Neither 10 nM staurosporine, 1 mM H-7 (protein kinase C inhibitors), nor 5 microM indomethacin (a cyclooxygenase inhibitor) affected the stimulatory effects of sucralfate on mucus secretion and synthesis, but 10 microM TMB-8 (an antagonist of intracellular Ca2+ mobilization)abolished its effects. Taken together, these results demonstrate that sucralfate acts directly an gastric mucosal cells, inducing increases in mucus secretion and synthesis, and that sucralfate causes an increase in the IP3 content, probably through activation of phospholipase C, and the subsequent IP3-elicited Ca2+ mobilization may be involved in the stimulatory effects of sucralfate.

Effects of transforming growth factors on the wound repair of cultured rabbit gastric mucosal cells

We have evaluated the role of two different transforming growth factors in the restoration of rabbit primary cultured gastric mucosal cells using a new wound repair model. After forming confluent monolayer cell sheets, a wound with a constant size (2 mm2) was made using a rotating silicon tip. Either TGF alpha (0.1 - 100 ng/mL or TGF beta 1 (0.1 - 10 ng/mL) was added to the medium and the process of wound repair was monitored and analysed quantitatively by an image analyser. Cell proliferation was examined by BrdU staining. After wounding, the cells fronting the wound formed lamellipodia and migrated towards the centre of the wound. In the control group, the wound healed completely 48 h after wounding. TGF alpha promoted wound healing and wound healed within 36 h in the presence of TGF alpha. TGF alpha increased the number of proliferative cells and they appeared in an earlier phase of healing than in controls. TGF beta did not have any effect on the wound repair process. In conclusion, TGF alpha promotes mucosal cell repair processes in the rabbit primary cultured gastric mucosal wound repair model in a dose-dependent manner by accelerating migration and proliferation. TGF alpha may modulate the healing process of a gastric ulcer or erosion in vivo.

Evaluation of ethanol on gastric epithelial restoration in vitro

Ethanol exerts damaging effects on gastric mucosa and delays ulcer healing. To investigate the effect of ethanol on the wound repairing process, we used a wound repair model using primary cultured gastric mucosal cells. A confluent monolayer gastric mucosal cell sheet consisting mainly of mucous cells was wounded to make a cell-free area of constant size. Cell-free area was restored with time after wounding and monitored every 12 hr using a computer image analyzer to observe epithelial cell restoration quantitatively in the presence and absence of ethanol (2.0%). It was found that, although the control wound was completely repaired in 36 to 48 hr, the group treated with 2.0% ethanol showed a significant delay of repair. In the control, 5-bromodeoxyuridine-positive cells appeared around the wound in 24 to 36 hr. In contrast, the group treated with 2.0% ethanol showed no 5-bromodeoxyuridine-positive cells during the experiment. In conclusion, 2.0% ethanol retarded the repair of gastric mucosal restoration by inhibiting the initial gastric cell migration, followed by inhibition of proliferation of cells.

Basic fibroblast growth factor accelerates gastric mucosal restoration in vitro by promoting mesenchymal cell migration and proliferation

It has been generally accepted that basic fibroblast growth factor is a potent stimulator of duodenal ulcer healing. However, the detailed mechanism and mode of action of growth factor on gastric ulcer healing is still controversial. Therefore, in the present study, the effects of basic fibroblast growth factor on gastric mucosal repair were studied using an in vitro cultured cell system. Artificial wounds were made in confluent monolayer rabbit gastric fibroblast and epithelial cell sheets by mechanical denudation. Changes in the size of the cell-free area were analysed quantitatively. Cell proliferation was assessed by BrdU staining. For both cell types, mucosal restoration involved cell migration and proliferation. Although the speed of restoration of epithelial cells was not affected by the addition of basic fibroblast growth factor, it was much faster for epithelial cells than for fibroblasts. Basic fibroblast growth factor accelerated wound repair of fibroblasts but not epithelial cells. Basic fibroblast growth factor accelerated wound repair by stimulating both cell migration and proliferation. Therefore, the effects of basic fibroblast growth factor in peptic ulcer diseases may be mainly due to the stimulation of mesenchymal cells.