EGF promotes gastric mucosal restitution by activating Na(+)/H(+) exchange of epithelial cells

Treatment of gastric ulcer, traditional Chinese medicine may be a better choice

ETHNOPHARMACOLOGICAL RELEVANCE

Gastric ulcer (GU) is the injury of the gastric mucosa caused by the stimulation of various pathogenic factors penetrating the deep mucosal muscle layer. An increasing number of studies have shown that traditional Chinese medicine (TCM) is highly effective in treating GU due to its multitarget, multilevel, and multi-pathway effects.

AIM OF THE STUDY

To review the latest research progress in the treatment of GU by TCM, including clinical and experimental studies, focusing on the target and mechanism of action of drugs and providing a theoretical basis for the treatment of GU by natural herbs.

MATERIALS AND METHODS

Electronic databases (PubMed, Elsevier, Springer, Web of Science, and CNKI) were searched using the keywords "gastric ulcer", "gastric mucosal lesion", "TCM" and or paired with "peptic ulcer" and "natural drugs" for studies published in the last fifteen years until 2023.

RESULTS

TCM, including single components of natural products, Chinese patent medicines (CPM), and TCM decoction, is expected to treat GU by regulating various mechanisms, such as redox balance, inflammatory factors, angiogenesis, gastric mucosal protective factors, intestinal flora, apoptosis, and autophagy.

CONCLUSIONS

We discussed and summarized the mechanism of TCM in the treatment of GU, which provided a sufficient basis for TCM treatment of GU.

Lack of Association between Epidermal Growth Factor or Its Receptor and Reflux Esophagitis, Barrett’s Esophagus, and Esophageal Adenocarcinoma: A Case-Control Study

The epidermal growth factor (EGF) and its receptor (EGFR) gene-gene interactions were shown to increase the susceptibility to esophageal cancer. However, the role of the EGF/EGFR pathway in the development of gastroesophageal reflux disease (GERD) and its complications (reflux esophagitis (RE), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC)) remains unclear. This association study is aimed at investigating functional EGF and EGFR gene polymorphisms, their mRNA expression in esophageal tissues, and EGF plasma levels in relation to RE, BE, and EAC development in the Central European population. 301 patients with RE/BE/EAC (cases) as well as 98 patients with nonerosive reflux disease (NERD) and 8 healthy individuals (controls) were genotyped for +61 A>G EGF (rs4444903) and +142285 G>A EGFR (rs2227983) polymorphisms using the TaqMan quantitative polymerase chain reaction (qPCR). In random subgroups, the EGF and EGFR mRNA expressions were analyzed by reverse transcription qPCR in esophageal tissue with and without endoscopically visible pathological changes; and the EGF plasma levels were determined by enzyme-linked immunosorbent assay. None of the genotyped SNPs nor EGF-EGFR genotype interactions were associated with RE, BE, or EAC development (p > 0.05). Moreover, mRNA expression of neither EGF nor EGFR differed between samples of the esophageal tissue with and without endoscopically visible pathology (p > 0.05) nor between samples from patients with different diagnoses, i.e., RE, BE, or EAC (p > 0.05). Nevertheless, the lower EGF mRNA expression in carriers of combined genotypes AA +61 EGF (rs4444903) and GG +142285 EGFR (rs2227983; p < 0.05) suggests a possible direct/indirect effect of EGF-EGFR gene interactions on EGF gene expression. In conclusion, EGF and EGFR gene variants and their mRNA/protein expression were not associated with RE, BE or EAC development in the Central European population.

Wheat oligopeptides enhance the intestinal mucosal barrier and alleviate inflammation via the TLR4/Myd88/MAPK signaling pathway in aged mice

Background

Aging can induce oxidative stress, inflammation and mucosal impairment, and few works have been conducted to investigate the protective effects of WP on the natural intestinal aging process.

Objective

The present work aimed to examine the protective effect of wheat oligopeptides (WP) on intestine mucosal impairment in aged mice, and investigate the potential antioxidation, anti-inflammatory effects of WP.

Design

Seventy-two aged mice (24 months old) were randomly divided into six groups, 12 for each group. Twelve young mice (6 months old) were regarded as the young control group. WP (25, 50, 100, 200, or 400 mg/kg) or distilled water were administered daily by gavage for 30 days.

Results

Histological observations showed that intestinal mucosal degeneration was attenuated by WP pretreatment. WP exhibited remarkable antioxidant activity via increasing superoxide dismutase, glutathione peroxidase, total antioxidant capacity and catalase activities, and decreasing the malondialdehyde levels in small intestine mucosa. WP pretreatment significantly suppressed intestinal mucosa inflammation through the reduction of TNF-α, TGF-β, IFN-γ IL-1β and IL-6. WP markedly protect the intestinal mucosal barrier by decreasing the ICAM-1 level, and increasing ZO-1 and JAMA-A levels. WP significantly down-regulated protein expression levels of TLR4, Myd88, and MAPK, suggesting that WP have a potential effect on inhibiting aging-induced inflammatory responses by blocking TLR4/Myd88/MAPK signal transduction.

Conclusion

WP administration effectively alleviated intestinal mucosal impairment in aged mice. The potential mechanism was associated with enhancement of antioxidation and anti-inflammatory action and protection of the intestinal mucosal barrier.

Traditional Chinese medicine for precancerous lesions of gastric cancer: A review

Gastric cancer (GC) is the fifth most common type of cancer and the third leading cause of death due to cancer worldwide. The gastric mucosa often undergoes many years of precancerous lesions of gastric cancer (PLGC) stages before progressing to gastric malignancy. Unfortunately, there are no effective Western drugs for patients with PLGC. In recent years, traditional Chinese medicine (TCM) has been proven effective in treating PLGC. Classical TCM formulas and chemical components isolated from some Chinese herbal medicines have been administered to treat PLGC, and the main advantage is their comprehensive intervention with multiple approaches and multiple targets. In this review, we focus on recent studies using TCM treatment for PLGC, including clinical observations and experimental research, with a focus on targets and mechanisms of drugs. This review provides some ideas and a theoretical basis for applying TCM to treat PLGC and prevent GC.

Deficient Active Transport Activity in Healing Mucosa After Mild Gastric Epithelial Damage

BACKGROUND

Peptic ulcers recur, suggesting that ulcer healing may leave tissue predisposed to subsequent damage. In mice, we have identified that the regenerated epithelium found after ulcer healing will remain abnormal for months after healing.

AIM

To determine whether healed gastric mucosa has altered epithelial function, as measured by electrophysiologic parameters.

METHOD

Ulcers were induced in mouse gastric corpus by serosal local application of acetic acid. Thirty days or 8 months after ulcer induction, tissue was mounted in an Ussing chamber. Transepithelial electrophysiologic parameters (short-circuit current, I_sc. resistance, R) were compared between the regenerated healed ulcer region and the non-ulcerated contralateral region, in response to luminal hyperosmolar NaCl challenge (0.5 M).

RESULTS

In unperturbed stomach, luminal application of hyperosmolar NaCl transiently dropped I_sc followed by gradual recovery over 2 h. Compared to the starting baseline I_sc, percent I_sc recovery was reduced in 30-day healing mucosa, but not at 8 months. Prior to NaCl challenge, a lower baseline I_sc was observed in trefoil factor 2 (TFF2) knockout (KO) versus wild type (WT), with no I_sc recovery in either non-ulcerated or healing mucosa of KO. Inhibiting Na/H exchanger (NHE) transport in WT mucosa inhibited I_sc recovery in response to luminal challenge. NHE2-KO baseline I_sc was reduced versus NHE2-WT. In murine gastric organoids, NHE inhibition slowed recovery of intracellular pH and delayed the repair of photic induced damage.

CONCLUSION

Healing gastric mucosa has deficient electrophysiological recovery in response to hypertonic NaCl. TFF2 and NHE2 contribute to I_sc regulation, and the recovery and healing of transepithelial function.

Trefoil factor 2 activation of CXCR4 requires calcium mobilization to drive epithelial repair in gastric organoids

KEY POINTS

Determining the signalling cascade of epithelial repair, using murine gastric organoids, allows definition of regulatory processes intrinsic to epithelial cells, at the same time as validating and dissecting the signalling cascade with more precision than is possible in vivo Following single cell damage, intracellular calcium selectively increases within cells adjacent to the damage site and is essential for promoting repair. Trefoil factor 2 (TFF2) acts via chemokine C-X-C receptor 4 and epidermal growth factor receptor signalling, including extracellular signal-regulated kinase activation, to drive calcium mobilization and promote gastric repair. Sodium hydrogen exchanger 2, although essential for repair, acts downstream of TFF2 and calcium mobilization.

ABSTRACT

The gastric mucosa of the stomach is continually exposed to environmental and physiological stress factors that can cause local epithelial damage. Although much is known about the complex nature of gastric wound repair, the stepwise process that characterizes epithelial restitution remains poorly defined. The present study aimed to determine the effectors that drive gastric epithelial repair using a reductionist culture model. To determine the role of trefoil factor 2 (TFF2) and intracellular calcium (Ca2+ ) mobilization in gastric restitution, gastric organoids were derived from TFF2 knockout (KO) mice and yellow Cameleon-Nano15 (fluorescent calcium reporter) transgenic mice, respectively. Inhibitors and recombinant protein were used to determine the upstream and downstream effectors of gastric restitution following photodamage (PD) to single cells within the gastric organoids. Single cell PD resulted in parallel events of dead cell exfoliation and migration of intact neighbouring cells to restore a continuous epithelium in the damage site. Under normal conditions following PD, Ca2+ levels increased within neighbour migrating cells, peaking at ∼1 min, suggesting localized Ca2+ mobilization at the site of cell protrusion/migration. TFF2 KO organoids exhibit delayed repair; however, this delay can be rescued by the addition of exogenous TFF2. Inhibition of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK)1/2 or a TFF2 receptor, chemokine C-X-C receptor 4 (CXCR4), resulted in significant delay and dampened Ca2+ mobilization. Inhibition of sodium hydrogen exchanger 2 (NHE2) caused significant delay but did not affect Ca2+ mobilization. A similar delay was observed in NHE2 KO organoids. In TFF2 KO gastric organoids, the addition of exogenous TFF2 in the presence of EGFR or CXCR4 inhibition was unable to rescue repair. The present study demonstrates that intracellular Ca2+ mobilization occurs within gastric epithelial cells adjacent to the damage site to promote repair by mechanisms that involve TFF2 signalling via CXCR4, as well as activation of EGFR and ERK1/2. Furthermore NHE2 is shown to be important for efficient repair and to operate via a mechanism either downstream or independent of calcium mobilization.

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.

SLC9 Gene Family: Function, Expression, and Regulation

The Slc9 family of Na⁺ /H⁺ exchangers (NHEs) plays a critical role in electroneutral exchange of Na⁺ and H⁺ in the mammalian intestine as well as other absorptive and secretory epithelia of digestive organs. These transport proteins contribute to the transepithelial Na⁺ and water absorption, intracellular pH and cellular volume regulation as well as the electrolyte, acid-base, and fluid volume homeostasis at the systemic level. They also influence the function of other membrane transport mechanisms, affect cellular proliferation and apoptosis as well as cell migration, adherence to the extracellular matrix, and tissue repair. Additionally, they modulate the extracellular milieu to facilitate other nutrient absorption and to regulate the intestinal microbial microenvironment. Na⁺ /H⁺ exchange is inhibited in selected gastrointestinal diseases, either by intrinsic factors (e.g., bile acids, inflammatory mediators) or infectious agents and associated bacterial toxins. Disrupted NHE activity may contribute not only to local and systemic electrolyte imbalance but also to the disease severity via multiple mechanisms. In this review, we describe the cation proton antiporter superfamily of Na⁺ /H⁺ exchangers with a particular emphasis on the eight SLC9A isoforms found in the digestive tract, followed by a more integrative description in their roles in each of the digestive organs. We discuss regulatory mechanisms that determine the function of Na⁺ /H⁺ exchangers as pertinent to the digestive tract, their regulation in pathological states of the digestive organs, and reciprocally, the contribution of dysregulated Na⁺ /H⁺ exchange to the disease pathogenesis and progression. © 2018 American Physiological Society. Compr Physiol 8:555-583, 2018.

Na+ /H+ exchanger NHE1 and NHE2 have opposite effects on migration velocity in rat gastric surface cells

Following superficial injury, neighbouring gastric epithelial cells close the wound by rapid cell migration, a process called epithelial restitution. Na⁺/H⁺ exchange (NHE) inhibitors interfere with restitution, but the role of the different NHE isoforms expressed in gastric pit cells has remained elusive. The role of the basolaterally expressed NHE1 (Slc9a1) and the presumably apically expressed NHE2 (Slc9a2) in epithelial restitution was investigated in the nontransformed rat gastric surface cell line RGM1. Migration velocity was assessed by loading the cells with the fluorescent dye DiR and following closure of an experimental wound over time. Since RGM1 cells expressed very low NHE2 mRNA and have low transport activity, NHE2 was introduced by lentiviral gene transfer. In medium with pH 7.4, RGM1 cells displayed slow wound healing even in the absence of growth factors and independently of NHE activity. Growth factors accelerated wound healing in a partly NHE1‐dependent fashion. Preincubation with acidic pH 7.1 stimulated restitution in a NHE1‐dependent fashion. When pH 7.1 was maintained during the restitution period, migratory speed was reduced to ∼10% of the speed at pH 7,4, and the residual restitution was further inhibited by NHE1 inhibition. Lentiviral NHE2 expression increased the steady‐state pH_i and reduced the restitution velocity after low pH preincubation, which was reversible by pharmacological NHE2 inhibition. The results demonstrate that in RGM1 cells, migratory velocity is increased by NHE1 activation, while NHE2 activity inhibit this process. A differential activation of NHE1 and NHE2 may therefore, play a role in the initiation and completion of the epithelial restitution process.

Trefoil Factor Peptides and Gastrointestinal Function

Trefoil factor (TFF) peptides, with a 40-amino acid motif and including six conserved cysteine residues that form intramolecular disulfide bonds, are a family of mucin-associated secretory molecules mediating many physiological roles that maintain and restore gastrointestinal (GI) mucosal homeostasis. TFF peptides play important roles in response to GI mucosal injury and inflammation. In response to acute GI mucosal injury, TFF peptides accelerate cell migration to seal the damaged area from luminal contents, whereas chronic inflammation leads to increased TFF expression to prevent further progression of disease. Although much evidence supports the physiological significance of TFF peptides in mucosal defenses, the molecular and cellular mechanisms of TFF peptides in the GI epithelium remain largely unknown. In this review, we summarize the functional roles of TFF1, 2, and 3 and illustrate their action mechanisms, focusing on defense mechanisms in the GI tract.

Pathophysiology of Intestinal Na+/H+ exchange

Several members of the SLC9A family of Na⁺/H⁺ exchangers are expressed in the gut, with varying expression patterns and cellular localization. Not only do they participate in the regulation of basic epithelial cell functions, including control of transepithelial Na⁺ absorption, intracellular pH (pH _i ), cell volume, and nutrient absorption, but also in cellular proliferation, migration, and apoptosis. Additionally, they modulate the extracellular milieu in order to facilitate other nutrient absorption and to regulate the intestinal microbial microenvironment. Na⁺/H⁺ exchangers are frequent targets of inhibition in gastrointestinal pathologies, either by intrinsic factors (e.g. bile acids, inflammatory mediators) or infectious agents and associated microbial toxins. Based on emerging evidence, disruption of NHE activity via impaired expression or function of respective isoforms may contribute not only to local and systemic electrolyte imbalance, but also to the disease severity via multiple mechanisms. Here, we review the current state of knowledge about the roles Na⁺/H⁺ exchangers play in the pathogenesis of disorders of diverse origin and affecting a range of GI tissues.

Calmodulin kinase II constitutively binds, phosphorylates, and inhibits brush border Na+/H+ exchanger 3 (NHE3) by a NHERF2 protein-dependent process

The epithelial brush border (BB) Na(+)/H(+) exchanger 3 (NHE3) accounts for most renal and intestinal Na(+) absorption. Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibits NHE3 activity under basal conditions in intact intestine, acting in the BB, but the mechanism is unclear. We now demonstrate that in both PS120 fibroblasts and polarized Caco-2BBe cells expressing NHE3, CaMKII inhibits basal NHE3 activity, because the CaMKII-specific inhibitors KN-93 and KN-62 stimulate NHE3 activity. This inhibition requires NHERF2. CaMKIIγ associates with NHE3 between aa 586 and 605 in the NHE3 C terminus in a Ca(2+)-dependent manner, with less association when Ca(2+) is increased. CaMKII inhibits NHE3 by an effect on its turnover number, not changing surface expression. Back phosphorylation demonstrated that NHE3 is phosphorylated by CaMKII under basal conditions. This overall phosphorylation of NHE3 is not affected by the presence of NHERF2. Amino acids downstream of NHE3 aa 690 are required for CaMKII to inhibit basal NHE3 activity, and mutations of the three putative CaMKII phosphorylation sites downstream of aa 690 each prevented KN-93 stimulation of NHE3 activity. These studies demonstrate that CaMKIIγ is a novel NHE3-binding protein, and this association is reduced by elevated Ca(2+). CaMKII inhibits basal NHE3 activity associated with phosphorylation of NHE3 by effects requiring aa downstream of NHE3 aa 690 and of the CaMKII-binding site on NHE3. CaMKII binding to and phosphorylation of the NHE3 C terminus are parts of the physiologic regulation of NHE3 that occurs in fibroblasts as well as in the BB of an intestinal Na(+)-absorptive cell.

Trefoil factor 2 requires Na/H exchanger 2 activity to enhance mouse gastric epithelial repair

Trefoil factor (TFF) peptides are pivotal for gastric restitution after surface epithelial damage, but TFF cellular targets that promote cell migration are poorly understood. Conversely, Na/H exchangers (NHE) are often implicated in cellular migration but have a controversial role in gastric restitution. Using intravital microscopy to create microscopic lesions in the mouse gastric surface epithelium and directly measure epithelial restitution, we evaluated whether TFFs and NHE isoforms share a common pathway to promote epithelial repair. Blocking Na/H exchange (luminal 10 μm 5-(N-ethyl-N-isopropyl) amiloride or 25 μm HOE694) slows restitution 72-83% in wild-type or NHE1(-/-) mice. In contrast, HOE694 has no effect on the intrinsically defective gastric restitution in NHE2(-/-) mice or TFF2(-/-) mice. In TFF2(-/-) mice, NHE2 protein is reduced 23%, NHE2 remains localized to apical membranes of surface epithelium, and NHE1 protein amount or localization is unchanged. The action of topical rat TFF3 to accelerate restitution in TFF2(-/-) mice was inhibited by AMD3100 (CXCR4 receptor antagonist). Furthermore, rat TFF3 did not rescue restitution when NHE2 was inhibited [TFF2(-/-) mice +HOE694, or NHE2(-/-) mice]. HOE694 had no effect on pH at the juxtamucosal surface before or after damage. We conclude that functional NHE2, but not NHE1, is essential for mouse gastric epithelial restitution and that TFFs activate epithelial repair via NHE2.

Amiloride inhibits macropinocytosis by lowering submembranous pH and preventing Rac1 and Cdc42 signaling

Inhibitors of Na⁺/H⁺ exchange proteins block macropinocytosis by lowering the pH near the plasma membrane, which in turn inhibits actin remodeling by Rho family GTPases.

Macropinocytosis is differentiated from other types of endocytosis by its unique susceptibility to inhibitors of Na⁺/H⁺ exchange. Yet, the functional relationship between Na⁺/H⁺ exchange and macropinosome formation remains obscure. In A431 cells, stimulation by EGF simultaneously activated macropinocytosis and Na⁺/H⁺ exchange, elevating cytosolic pH and stimulating Na⁺ influx. Remarkably, although inhibition of Na⁺/H⁺ exchange by amiloride or HOE-694 obliterated macropinocytosis, neither cytosolic alkalinization nor Na⁺ influx were required. Instead, using novel probes of submembranous pH, we detected the accumulation of metabolically generated acid at sites of macropinocytosis, an effect counteracted by Na⁺/H⁺ exchange and greatly magnified when amiloride or HOE-694 were present. The acidification observed in the presence of the inhibitors did not alter receptor engagement or phosphorylation, nor did it significantly depress phosphatidylinositol-3-kinase stimulation. However, activation of the GTPases that promote actin remodelling was found to be exquisitely sensitive to the submembranous pH. This sensitivity confers to macropinocytosis its unique susceptibility to inhibitors of Na⁺/H⁺ exchange.

Clinical study of external application of Qiyu oil gauze for promoting post-operational healing in patients with anal fistula

OBJECTIVE

To observe the effects of the external application of Qiyu oil gauze (QYOG) for promoting post-operational healing in patients with anal fistula and to explore its mechanism of action so as to provide a beneficial scientific basis for its wide use.

METHODS

Sixty patients with anal fistula scheduled to receive simple low anal fistulectomy were equally assigned, according to the sequence of hospitalization, to the tested group and the control group, and their wounds were classified according to longitudinal diameter into three grades (Grade I with a diameter below 2 cm; Grade II, 2-5 cm; and Grade III, over 5 cm). After the operation was completed and the operational wound was sterilized with benzalkonium bromide, the wound substratum was packed with QYOG in the test group and with vaseline gauze in the control group. The packing gauze was changed every day till the wound was healed. The healing time of the patients was observed, and the number of capillaries and positive cell percentages of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF) in wound granulation tissues were counted on the 5th day after the operation.

RESULTS

The wound healing time was 17.80+/-5.46 days in the test group, which was significantly shorter than that in the control group (21.90+/-6.32 days, P<0.01). The number of capillaries and positive cell percentages of VEGF and bFGF in wound granulation tissues on the 5th day in the tested group were higher than those in the control group (P<0.01), though the difference in EGF between the two groups was insignificant (P>0.05).

CONCLUSION

QYOG could shorten the wound healing time after anal fistulectomy, which suggests that it participates in the stimulation of wound granulation tissues to produce VEGF and bFGF, and thus promotes capillary genesis and improves blood circulation in wounds so as to promote wound healing.

Plant cysteine proteinases: evaluation of the pharmacological activity

Cysteine proteinases are involved in virtually every aspect of plant physiology and development. They play a role in development, senescence, programmed cell death, storage and mobilization of germinal proteins, and in response to various types of environmental stress. In this review, we focus on a group of plant defensive enzymes occurring in germinal tissue of Caricaceae. These enzymes elicit a protective response in the unripe fruit after physical stress. We propose that these enzymes follow a strategy similar to mammalian serine proteinases involved in blood clotting and wound healing. We show evidence for the pharmacological role of plant cysteine proteinases in mammalian wound healing, immunomodulation, digestive conditions, and neoplastic alterations.

The gastric ulcer protective and healing role of cysteine proteinases from Carica candamarcensis

Latex from Caricaceae contains proteolytic enzymes localized in the fruit, which are used ethnopharmacologically to treat digestive disorders. Some of these proteins display proliferative properties when probed with mammalian cells, suggesting a role in the reconstruction of wounded tissue. We tested the efficacy of a proteolytic fraction derived from Carica candamarcensis, designated as P1G10 in experimental rodent models, to protect and heal chemically induced gastric ulcers. The protective effect of oral administration of P1G10 fraction was analyzed in indomethacin-treated Wistar animals. The healing effect of P1G10 was studied following sub-serous injection of acetic acid in a Wistar rat model. The results show that P1G10 between 0.1 and 10 mg/kg protect indomethacin but not ethanol-induced gastric ulcers. The maximal protection attained was 67% with 10 mg/kg of P1G10. The healing rate by 10 mg/kg of P1G10 using the acetic acid ulcerogenic model is similar to that of omeprazole (10 mg/kg) or ranitidine (100 mg/kg). The effect of P1G10 at 10 mg/kg seems to be mediated by an increase in the mucus content by 25% and stimulation of angiogenesis by 64% in a manner similar to growth factors. These results confirm the protective and healing role of proteinases from C. candamarcensis.

Complications after oesophagectomy with possible contribution of neoadjuvant therapy including an EGFR-antibody to a fatal outcome

Background

Different molecular therapies like the EGFR-inhibiting antibody cetuximab have come into clinical practice. Cetuximab is EMEA-approved for metastatic colorectal cancer and advanced squamous-cell head and neck cancer. Administration is said to be safe and well tolerated with common, usually mild dermatologic side effects.

Case presentation

We present the case of a patient with fatal complications after oesophagectomy and neoadjuvant chemotherapy including cetuximab for squamous-cell esophageal cancer. A transthoracic en-bloc oesophagectomy was performed. Few days later the patient died due to gas exchange dysfunction and circulation instability after a previously unseen combination of drain-erosion of the stomach with subsequent pleurisy and air leak of the left main bronchus.

Conclusion

So far we have never observed this fatal combination of drain erosion of the stomach with fibrinous pleurisy and unmanageable progressive tracheal defect before. The role of cetuximab in the multifactorial aetiology of damages of stomach and trachea after oesophagectomy remains unclear since we are not able to link the complication directly to cetuximab or definitely exclude it as a sole surgical complication. Clinicians should be aware of the possibility of fatal side effects and careful recording of all complications is necessary in ongoing and planned studies to obtain more evidence about safety and tolerance of targeted therapies.

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

BACKGROUND

Transforming growth factor alpha (TGFalpha) 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 TGFalpha-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 TGFalpha on several gastric protection mechanisms.

METHODS

TGFalpha-expressing transgenic (TG) mouse lines bearing human TGFalpha 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 TGFalpha.

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 TGFalpha maintains the gastric mucosal defense against gastric injury by integrating other cytoprotective mechanisms.

Epidermal growth factor enhances intracellular pH regulation via calcium signaling in acid-exposed primary cultured rabbit gastric epithelial cells

We have elucidated the role of different ion transporters and epidermal growth factor(EGF) during luminal acid exposure in primary cultured rabbit surface epithelial cells by measuring intracellular calcium and pH. Amiloride, DIDS, or sodium or bicarbonate substitutions were used to inhibit ion transport. During luminal acid exposure the dominant intracellular pH regulator is the Na+/H+ antiport, and bicarbonate transport has only a secondary role, which is uncovered as the Na+/H+ function fails. The decrease in intracellular pH caused by luminal acid was significantly smaller in serosal EGF-treated epithelia than in controls. This defensive function of EGF was abolished by verapamil, BAPTA, and calmidazolium but not by TMB-8. EGF increased intracellular calcium, which was prevented by verapamil but not by TMB-8. EGF enhances gastric epithelial defense against luminal acid by inducing intracellular calcium signaling via plasma membrane verapamil-sensitive calcium channels and thereby enhancing the function of the Na+/H+ antiport.

Roles of epidermal growth factor and Na+/H+ exchanger-1 in esophageal epithelial defense against acid-induced injury

Epidermal growth factor (EGF) is predominantly secreted by salivary glands and activates Na(+)/H(+) exchanger-1 (NHE-1), which regulates intracellular pH (pH(i)). We investigated the roles of EGF and NHE-1 in esophageal epithelial defense against acid using human esophageal epithelial cell lines and a rat chronic esophagitis model. Esophageal epithelial cells were incubated with acidified medium in the absence or presence of EGF. Cell viability and changes in pH(i) were measured. Chronic acid reflux esophagitis was induced in rats with and without sialoadenectomy. Esophageal lesion index, epithelial proliferation, and expression of EGF receptors and NHE-1 were examined. EGF protected esophageal epithelial cells against acid in a dose-dependent manner, and the cytoprotective effect of EGF was completely blocked by treatment with NHE-1 inhibitors. Tyrosine kinase, calmodulin, and PKC inhibitors significantly inhibited cytoprotection by EGF, whereas MEK, phosphatidylinositol 3-kinase, and PKA inhibitors had no effect. EGF significantly increased pH(i) recovery after NH(4)Cl pulse acidification, and this increase in pH(i) recovery was significantly blocked by inhibitors of calmodulin and PKC. Sialoadenectomy led to an increase in the severity of chronic esophagitis but affected neither epithelial proliferation nor expression of EGF receptors. Expression of NHE-1 mRNA was increased in esophagitis and upregulated in rats with sialoadenectomy. The increasing severity of esophagitis in rats with sialoadenectomy was prevented by exogenous administration of EGF. In conclusion, EGF protects esophageal epithelial cells against acid through NHE activation via Ca(2+)/calmodulin and the PKC pathway. Deficiency in endogenous EGF is associated with increased severity of esophagitis. EGF and NHE-1 play crucial roles in esophageal epithelial defense against acid.

Regulation of restitution after superficial injury in isolated guinea pig gastric mucosa

The immediate response of the gastrointestinal epithelium to superficial (i.e. microscopic) injury is primarily directed towards restoring the disturbed epithelial continuity. Both structural (i.e. cytoskeleton) and humoral (i.e. growth factors and cytokines) involvement in the process has recently been documented. Yet it is unclear whether humoral signaling regulating mucosal recovery after superficial injury is associated with tyrosine phosphorylation, and whether there are other signs of downstream activation of the signaling pathway. To evaluate the effects of exogenous genistein and phorbol-myristate acetate in the assessment of the role of tyrosine receptor-mediated signaling in the immediate repair of gastric mucosa after superficial injury. Guinea pig gastric mucosa was mounted in a Ussing chamber, injured with 1.25 M NaCl, and perfused for 4 h. Simultaneously, potential difference and tissue resistance were recorded. In some sets of experiments the tissue was exposed bilaterally either to genistein in order to inhibit tyrosine receptor-mediated signaling or to 4-phorbol-myristate 13-acetate (PMA) in order to enhance PKC signaling during the 4 h recovery. Phosphotyrosine (PTYR) and protein kinase C (PKC) immunoreactivity were assessed by immunoblotting and by immunohistochemistry. Proliferative activity was determined morphometrically after staining of the tissue for Ki-67 nuclear antigen and expressed as proliferative index (PI). The inhibition of tyrosine kinases with exogenous genistein resulted in a significant decrease of the PTYR and the stimulation of PKC with PMA increased the PTYR. Nevertheless, no change in the PTYR was observed by immunoblotting after superficial injury alone. Several PKC isoenzymes were found in the guinea pig gastric mucosa, including PKC-alpha, -epsilon, -zeta and -iota. They were unaffected either by the injury or the PMA treatment. The mean PI of tissues subjected to NaCl-injury was higher than that of uninjured control tissues (p<0.05) (n=7). Exposure of tissue to genistein during recovery decreased the PI, while stimulation with PMA increased it (p<0.05 for both) (n=6). Both electrophysiologic and morphologic restitution were sensitive to genistein, but not to PMA. Superficial injury alone does not influence tyrosine phosphorylation to a degree which could be assessed by immunoblotting. Nevertheless, exogenous modulation of tyrosine receptor-mediated signaling results in downstream signaling effects. The injury-associated induction of proliferation is sensitive to modulation of tyrosine phosphorylation and PKC, suggesting that superficial epithelial injury results in endogenous activation of the epithelium, presumably after paracrine stimulation of the neighboring cells.

Restitution of the bullfrog gastric mucosa is dependent on a DIDS-inhibitable pathway not related to HCO3- ion transport

This study was conducted to determine the contribution of ion transport to restitution after injury in the gastric mucosa. For this, intact sheets of stomach from the bullfrog, Rana catesbeiana, were mounted in Ussing chambers. Restitution was evaluated in the presence or absence of ion transport inhibitors amiloride, DIDS, and bumetanide to block Na(+)/H(+) exchange, Cl(-)/HCO(3)(-) exchange and Na(+)/HCO(3)(-) co-transport, and Na(+)-K(+)-2Cl(-) cotransport, respectively. Ion substitution experiments with Na(+)-free, Cl(-)-free, and HCO(3)(-)-free solutions were also performed. Injury to the mucosa was produced with 1 M NaCl, and restitution was evaluated by recovery of transepithelial resistance (TER), mannitol flux, and morphology. Amiloride, bumetanide, Cl(-)-free, or HCO(3)(-)-free solutions did not affect restitution. In Na(+)-free solutions, recovery of TER and mannitol flux did not occur because surface cells did not attach to the underlying basement membrane. In contrast, all aspects of restitution were inhibited by DIDS, a compound that inhibits Na(+)-dependent HCO(3)(-) transport. Because HCO(3)(-)-free solutions did not inhibit restitution, it was concluded that DIDS must block a yet undefined pathway not involved in HCO(3)(-) ion transport but essential for cell migration after injury and restitution in the gastric mucosa.

Preventive effect of hydrotalcite on gastric mucosal injury in rats induced by taurocholate

AIM: To study the preventive effect of hydrotalcite on gastric mucosal injury in rat induced by taurocholate, and to investigate the relationship between the protective mechanism of hydrotalcite and the expression of trefoil factor family 2 (TFF2) mRNA and c-fos protein.

METHODS: Forty five male Wistar rats were randomly divided into hydrotalcite group, ranitidine group and control group. Gastric mucosal injury was induced by introgastric acidified taurocholate. OD value of TFF2 mRNA expression in gastric mucous cells was determined by hybridization and computer image analysis system. OD value of c-fos protein expression in gastric mucous cells was measured by immunohistochemistry and computer image analysis system.

RESULTS: The gross mucosal injury index in hydrotalcite group was significantly lower than that in ranitidine group and control group (8.60 ± 2.20 vs 16.32 ± 4.27, 29.53 ± 5.39; P < 0.05, P < 0.01). The expression level of TFF2 mRNA in hydrotalcite group was markedly higher than that in ranitidine group and control group (0.56 ± 0.09 vs 0.30 ± 0.05, 0.28 ± 0.03, P < 0.05). The OD value of c-fos protein in hydrotalcite group was higher than that in ranitidine group and control group (0.52 ± 0.07 vs 0.31 ± 0.04, 0.32 ± 0.05, P < 0.05).

CONCLUSION: Hydrotalcite can protect gastric mucosal injury in rats induced by taurocholate, which may be related to the increased expression of TFF2 and c-fos protein.