Roles of platelets and proteinase-activated receptors in gastric ulcer healing

Age-related changes in haematological parameters and biochemical markers of healing in the stomach of rats with acetic acid induced injury

This study examined the changes in haematological and biochemical variables in response to gastric mucosa injury in male Wistar rats divided into four groups according to their ages (3, 6, 12, and 18 months). 0.2 ml of acetic acid was injected intraluminal into the stomach glandular portion of each rat for 45 seconds under anaesthesia. Collection of blood and stomach samples occurred on days 3, 7, 14 and 21 post-induction of gastric ulcer. The results obtained from this study showed 100 % area of gastric mucosa healed in 3-month old rats, 91.72 %, 68.52 % and 62.81 % area of mucosa treated in 6, 12 and 18-month old rats respectively on day 21 post-induction of gastric ulcer. Increased circulation of blood cells in younger rats occurred, neutrophil-lymphocyte ratio (NLR) was decreased in younger rats (3 and 6 months) significantly (p < 0.05) when compared to older rats (12 and 18 months). Lipid peroxidation and glutathione (GSH) levels were elevated in older rats (12 and 18 months) significantly (p < 0.05) when compared to younger rats (3 and 6 months). In comparison, superoxide dismutase (SOD) and catalase levels were decreased in older rats (12 and 18 months) significantly (p < 0.05) when compared to younger rats (3 and 6 months). Histological evaluation showed evidence of early healing with re-epithelialisation and angiogenesis in younger rats, but older rats showed delayed healing. The study showed that the slower rate of healing of gastric ulcer with advancing age in rats might be due to reducing circulating blood cells and anti-inflammatory activities during healing via a lipid peroxidation-dependent mechanism.

Effectiveness of Autologous Platelet-Rich Plasma for the Healing of Ulcers after Endoscopic Submucosal Dissection

Background/Aims

Platelet-rich plasma (PRP) has been used for wound healing in various medical fields. The aim of this study was to evaluate the clinical efficacy and safety of local PRP injections after endoscopic submucosal dissection (ESD).

Methods

Patients were non-randomly divided into the following two groups: (1) control group in which patients were administered only an intravenous proton pump inhibitor (PPI), and (2) a study group in which patients were administered an intravenous PPI and a topical PRP injection. We assessed the reduction in the ulcer area and stage of the ulcer after the procedure (24 hours, 48 hours, and 28 days after endoscopic surgery).

Results

We enrolled 7 study and 7 control patients. In the study group, the rate of ulcer reduction was 59% compared to 52% in the control group (p=0.372), 28 days after ESD. There were 5 patients in the S stage and 2 patients in the H stage in the study group compared to no patient in the S stage and 7 patients in the H stage in the control group (p=0.05), 28 days after ESD. There were no serious complications in either group.

Conclusions

The local injection of PRP is a safe and effective procedure for ulcer healing after ESD.

Time-dependent course of gastric ulcer healing and molecular markers profile modulated by increased gastric mucosal content of carbon monoxide released from its pharmacological donor

BACKGROUND AND PURPOSE

Besides hydrogen sulfide (H₂S) and nitric oxide (NO), carbon monoxide (CO) contributes to the maintenance of gastric mucosal integrity. We investigated increased CO bioavailability effects on time-dependent dynamics of gastric ulcer healing mediated by particular growth factors, anti-inflammatory and molecular pathways.

EXPERIMENTAL APPROACH

Wistar rats with gastric ulcers induced by serosal acetic acid application (day 0) were treated i.g. throughout 3, 6 or 14 days with vehicle or CO-releasing tricarbonyldichlororuthenium (II) dimer (CORM-2, 2.5 mg/kg). Gross and microscopic alterations in gastric ulcer size and gastric blood flow (GBF) at ulcer margin were determined by planimetry, histology and laser flowmetry, respectively. Gastric mRNA/protein expressions of platelet derived growth factors (PDGFA-D), insulin-like growth factor (IGF-1), epidermal growth factor (EGF), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGFA) and their receptors, heme oxygenases (HMOX), nuclear factor (erythroid-derived 2)-like 2 (Nrf-2), cyclooxygenase (COX-2), hypoxia inducible factor (HIF)-1α, anti-inflammatory annexin-1 and transforming growth factor (TGF-β1) were assessed by real-time PCR or Western blot. TGF-β1-3 and IL-10 plasma concentration were measured using Luminex platform. Prostaglandin E₂ content at ulcer margin was assessed by ELISA.

KEY RESULTS

CORM-2 decreased ulcer area and increased GBF after 6 and 14 days of treatment comparing to vehicle. CO donor upregulated HGF, HGFr, VEGFR1, VEGFR2, TGF-β1, annexin-1 and maintained increased IGF-1, PDGFC and EGF expression at various time-intervals of ulcer healing. TGF-β3 and IL-10 plasma concentration were significantly increased after COMR-2 vs. vehicle.

CONCLUSIONS

CO time-dependently accelerates gastric ulcer healing and raises GBF at ulcer margin by mechanism involving subsequent upregulation of anti-inflammatory, growth promoting and angiogenic factors response, not observed physiologically.

Autocrine extra-pancreatic trypsin 3 secretion promotes cell proliferation and survival in esophageal adenocarcinoma

Trypsin or Tumor associated trypsin (TAT) activation of Protease-activated receptor 2 (PAR-2) promotes tumor cell proliferation in gastrointestinal cancers. The role of the trypsin/PAR-2 network in esophageal adenocarcinoma (EA) development has not yet been investigated. The aim of this study is to investigate the role of trypsin/PAR-2 activation in EA tumorogenesis and therapy. We found that esophageal adenocarcinoma cells (EACs) and Barrett’s Metaplasia (BART) expressed high levels of type 3 extra-pancreatic trypsinogen (PRSS3), a novel type of TAT. Activity of secreted trypsin was detected in cultured media from EA OE19 and OE33 cultures but not from BART culture. Surface PAR-2 expression in BART and EACs was confirmed by both flow cytometry and immunofluorescence. Trypsin induced cell proliferation (∼ 2 fold; P<0.01) in all tested cell lines at a concentration of 10 nM. Inhibition of PAR-2 activity in EACs via the PAR-2 antagonist ENMD (500 µM), anti-PAR2 antibody SAM-11 (2 µg/ml), or siRNA PAR-2 knockdown, reduced cell proliferation and increased apoptosis by up to 4 fold (P<0.01). Trypsin stimulation led to phosphorylation of ERK1/2, suggesting involvement of MAPK pathway in PAR-2 signal transduction. Inhibition of PAR-2 activation or siRNA PAR-2 knockdown in EACs prior to treatment with 5 FU reduced cell viability of EACs by an additional 30% (P<0.01) compared to chemotherapy alone. Our data suggest that extra-pancreatic trypsinogen 3 is produced by EACs and activates PAR-2 in an autocrine manner. PAR-2 activation increases cancer cell proliferation, and promotes cancer cell survival. Targeting the trypsin activated PAR-2 pathway in conjunction with current chemotherapeutic agents may be a viable therapeutic strategy in EA.

Platelet aggregation measurement for assessment of hemostasis failure mechanisms in patients with gastroduodenal ulcer bleeding

Background

The purpose of this study was to identify factors associated with the risk of unsustainable hemostasis in patients with gastric and duodenal ulcer bleeding by in vitro assessment of platelet reactivity using artificial neural networks.

Methods

Patients with gastroduodenal ulcers complicated by bleeding were studied. Platelet aggregation was measured using aggregometry with adenosine diphosphate 5 μM, epinephrine 2.5 μM, 5-hydroxytryptophan 10 μM, collagen 1 μM, and thrombin 0.06 NIH Unit/mL as agonists. Multiple logistic regression was used to evaluate the independent relationship between demographic, clinical, endoscopic, and laboratory data and in vitro assessment of platelet reactivity and local parameters of hemostasis in patients with ulcer bleeding.

Results

Analysis of platelet aggregation in patients with gastroduodenal ulcer bleeding allowed the variability of platelet response to different agonists used in effective concentration which induces 50% platelet aggregation (EC₅₀) to be established. The relationship between platelet aggregation and the spatial-temporal characteristics of ulcers complicated by bleeding was demonstrated. Adrenoreactivity of platelets was associated with time elapsed since the start of ulcer bleeding and degree of hemorrhage. The lowest platelet response to collagen and thrombin was detected in patients with active bleeding (P < 0.001) and unsustainable recent bleeding (P < 0.01). Decreased adenosine diphosphate-induced platelet aggregation in patients with ulcer bleeding was correlated with the platelet response to thrombin (r = 0.714, P < 0.001) and collagen (r = 0.584, P < 0.01).

Conclusion

Estimation of platelet reactivity in vitro indicates the key mechanisms of failure of hemostasis in patients with ulcer bleeding. In addition to gender, an important determinant of unsustainable hemostasis was a decreased platelet response to thrombin and adenosine diphosphate.

The diminished expression of proangiogenic growth factors and their receptors in gastric ulcers of cirrhotic patients

Objectives

The pathogenesis of the higher occurrence of peptic ulcer disease in cirrhotic patients is complex. Platelets can stimulate angiogenesis and promote gastric ulcer healing. We compared the expressions of proangiogenic growth factors and their receptors in the gastric ulcer margin between cirrhotic patients with thrombocytopenia and those of non-cirrhotic patients to elucidate possible mechanisms.

Methods

Eligible cirrhotic patients (n = 55) and non-cirrhotic patients (n = 55) who had gastric ulcers were enrolled. Mucosa from the gastric ulcer margin and non-ulcer areas were sampled and the mRNA expressions of the proangiogenic growth factors (vascular endothelial growth factor [VEGF], platelet derived growth factor [PDGF], basic fibroblast growth factor [bFGF]) and their receptors (VEGFR1, VEGFR2, PDGFRA, PDGFRB, FGFR1, FGFR2) were measured and compared. Platelet count and the expressions of these growth factors and their receptors were correlated with each other.

Results

The two groups were comparable in terms of gender, ulcer size and infection rate of Helicobacter pylori. However, the cirrhotic group were younger in age, had a lower platelet count than those in the non-cirrhotic group (p<0.05). The cirrhotic patients had diminished mRNA expressions of PDGFB, VEGFR2, FGFR1, and FGFR2 in gastric ulcer margin when compared with those of the non-cirrhotic patients (p<0.05). Diminished expressions of PDGFB and VEGFR2, FGFR1, and FGFR2 were well correlated with the degree of thrombocytopenia in these cirrhotic patients (ρ>0.5, p<0.001).

Conclusions

Our findings implied that diminished activity of proangiogenic factors and their receptors may contribute to the pathogenesis of gastric ulcers in cirrhotic patients.

Platelet proteome and tumor dormancy: can platelets content serve as predictive biomarkers for exit of tumors from dormancy?

Although tumor dormancy is highly prevalent, the underling mechanisms are still mostly unknown. It is unclear which lesions will progress and become a disseminated cancer, and which will remain dormant and asymptomatic. Yet, an improved ability to predict progression would open the possibility of timely treatment and improvement in outcomes. We have recently described the ability of platelets to selectively uptake angiogenesis regulators very early in tumor growth, and proposed their use as an early marker of malignancy. In this review we will summarize current knowledge about these processes and will discuss the possibility of using platelet content to predict presence of occult tumors.

A randomized, placebo-controlled study of the effects of naproxen, aspirin, celecoxib or clopidogrel on gastroduodenal mucosal healing

BACKGROUND

Many individuals with gastroduodenal ulcers require on-going, non-steroidal anti-inflammatory drug (NSAID) or anti-platelet therapy.

AIMS

To evaluate the effects of these agents on gastroduodenal mucosal healing.

METHODS

Helicobacter pylori-negative volunteers were randomized to receive naproxen, celecoxib, aspirin, clopidogrel or placebo. Antral and duodenal lesions were created endoscopically with a biopsy forceps. After 7 days of medication dosing, each lesion was scored [from 0 (low) to 8 (high)] using a validated methodology. The primary endpoint was the mean injury score. The secondary endpoint was the percentage of subjects with > or = 1 unhealed lesion.

RESULTS

In all, 108 subjects completed the study. Naproxen impaired antral lesion healing more than placebo, clopidogrel, aspirin or celecoxib (mean injury score of 4.3 vs. 3.0, 2.7, 3.2, and 3.2, respectively, P < 0.05). Naproxen impaired duodenal lesion healing more than placebo, clopidogrel or aspirin (mean injury score of 4.0 vs. 2.4, 2.6, and 2.2, respectively, P < 0.05). More subjects taking naproxen than placebo or clopidogrel had > or =1 unhealed antral lesions (72.2% vs. 36.0% and 32.0%, respectively, P < 0.05) and unhealed duodenal lesions (61.1% vs. 16.0% and 28.0%, respectively, P < 0.05).

CONCLUSIONS

Naproxen may impair gastroduodenal healing more than aspirin or celecoxib in H. pylori negative subjects. Clopidogrel did not impair mucosal healing.

Presence of thrombin-activatable fibrinolysis inhibitor in Helicobacter pylori-associated gastroduodenal disease

Thrombin-activatable fibrinolysis inhibitor (TAFI) plays a role in the regulation of coagulation and inflammation. In addition to inhibiting the fibrinolytic system, TAFI may also regulate the bradykinin and complement systems. We hypothesized that TAFI also plays a role in defense mechanisms of the gastric mucosa during Helicobacter pylori infection. This study comprised 65 patients with gastroduodenal disorders: 41 patients with H. pylori infection, 13 without, and 11 patients with cured H. pylori infection. The gastric intramucosal concentrations of TAFI were measured by enzyme immunoassay. The gastric levels of TAFI and plasminogen activator inhibitor-1 were significantly increased in patients with H. pylori compared to those without infection or cured H. pylori. The presence of TAFI was detected in gastric mucosal epithelial cells. The concentration of TAFI was correlated with the degree of gastric mucosal atrophy, inflammation, and disease activity. These results show that TAFI is present in the gastric mucosa and that it may play a role in the pathogenesis of H. pylori infection-associated gastroduodenal disorders.

Biochemical mechanism of healing activity of the natural phenolic, allylpyrocatechol against indomethacin-induced gastric ulceration in mice

Indomethacin caused maximum stomach ulceration in mice on the 3rd day, which was associated with reduction of plasma total antioxidant status (TAS), COX-1, COX-2, mucosal PGE(2), VEGF, and vWF, along with an increase in endostatin levels. Treatment with the phytochemical allylpyrocatechol (5 mg/kg, p.o. for 3 days) provided significant ulcer healing by reversing these biochemical parameters, as well as increasing the EGF expression more than that observed due to ulceration. Omeprazole (3 mg/kg, p.o. for 3 days) provided a similar healing by improving TAS and mucin levels, without significantly altering the other parameters.

Proteinase-activated receptor 2 (PAR-2) in gastrointestinal and pancreatic pathophysiology, inflammation and neoplasia

Of all the body systems, the gastrointestinal (GI) tract is the most exposed to proteinases. Proteolytic activity must thus be tightly regulated in the face of diverse environmental challenges, because unrestrained or excessive proteolysis leads to pathological GI conditions. The protease-activated receptor-2 (PAR-2) is expressed in numerous cell types within the GI tract, suggesting both multiple functions and numerous modes of receptor activation. Although best known as a pancreatic digestive enzyme, trypsin has also been found in other tissues and various cancers. Of interest, trypsin and PAR-2 act together in an autocrine loop that promotes proliferation, invasion and metastasis in neoplasia through various mechanisms. Trypsin and PAR-2 seem to act both directly and indirectly through activation of other proteinase cascades, including metalloproteinases. PAR-2 activation can participate in inflammatory reactions, be protective to mucosal surfaces, send or inhibit nociceptive messages, modify gut motility or secretory functions, and stimulate cell proliferation and motility. Several studies point to a role for the PARs in disease processes of the GI tract and pancreas ranging from inflammatory bowel disease, symptoms associated with irritable bowel syndrome, pain in pancreatitis, development of colon and other GI cancers, and even infectious colitis. Proteinases should not only be considered from the traditional view as digestive or degradative enzymes in the gut, but additionally as signalling molecules that actively participate in the spectrum of physiology and diseased states of the GI tract.

Platelets accelerate gastric ulcer healing through presentation of vascular endothelial growth factor

1. Platelets contain an array of growth factors that can modulate healing processes, including both pro- (e.g., vascular endothelial growth factor (VEGF)) and antiangiogenic (e.g., endostatin) factors. Previous studies have shown that circulating platelets contribute significantly to gastric ulcer healing, acting as a delivery system for these growth factors to the site of injury. In this study, we examined the effects of orally administered human platelets on the healing of gastric ulcers in rats, and determined the contribution of VEGF and endostatin to healing in this model. 2. Twice-daily administration of human platelets significantly accelerated ulcer healing, but platelet-poor plasma (PPP), lysed platelets and serum failed to produce this effect. There was no correlation between ulcer healing and the levels of VEGF or endostatin in serum, PPP or platelet-rich plasma (PRP). 3. Accelerated ulcer healing could not be produced by oral administration of the angiogenic factors themselves, at concentrations matching those in PRP. 4. The accelerated healing induced by platelets could be reversed by immuno-neutralization of VEGF. In contrast, immuno-neutralization of endostatin did not affect PRP-induced ulcer healing. 5. These studies indicate that VEGF released from platelets accounts for the accelerated healing of gastric ulcers. However, as intact (rather than lysed) platelets were required for the accelerated healing, the presentation of VEGF by the platelet at the site of injury appears to be crucial for enhancement of the healing process.