Basic actions of transforming growth factor-alpha and related peptides

Modelling the erythroblastic island niche of dyserythropoietic anaemia type IV patients using induced pluripotent stem cells

Introduction: Congenital dyserythropoietic anaemia (CDA) type IV has been associated with an amino acid substitution, Glu325Lys (E325K), in the transcription factor KLF1. These patients present with a range of symptoms, including the persistence of nucleated red blood cells (RBCs) in the peripheral blood which reflects the known role for KLF1 within the erythroid cell lineage. The final stages of RBCs maturation and enucleation take place within the erythroblastic island (EBI) niche in close association with EBI macrophages. It is not known whether the detrimental effects of the E325K mutation in KLF1 are restricted to the erythroid lineage or whether deficiencies in macrophages associated with their niche also contribute to the disease pathology. Methods: To address this question, we generated an in vitro model of the human EBI niche using induced pluripotent stem cells (iPSCs) derived from one CDA type IV patient as well as two iPSC lines genetically modified to express an KLF1-E325K-ERT2 protein that could be activated with 4OH-tamoxifen. The one patient iPSC line was compared to control lines from two healthy donors and the KLF1-E325K-ERT2 iPSC line to one inducible KLF1-ERT2 line generated from the same parental iPSCS. Results: The CDA patient-derived iPSCs and iPSCs expressing the activated KLF1-E325K-ERT2 protein showed significant deficiencies in the production of erythroid cells with associated disruption of some known KLF1 target genes. Macrophages could be generated from all iPSC lines but when the E325K-ERT2 fusion protein was activated, we noted the generation of a slightly less mature macrophage population marked by CD93. A subtle trend in their reduced ability to support RBC enucleation was also associated with macrophages carrying the E325K-ERT2 transgene. Discussion: Taken together these data support the notion that the clinically significant effects of the KLF1-E325K mutation are primarily associated with deficiencies in the erythroid lineage but it is possible that deficiencies in the niche might have the potential to exacerbate the condition. The strategy we describe provides a powerful approach to assess the effects of other mutations in KLF1 as well as other factors associated with the EBI niche.

Inflammatory changes of the gastric mucosa and serum concentration of chosen growth factors in children

PURPOSE

To assess whether there is a correlation between the severity of gastritis and concentration of chosen growth factors in the serum of children infected with H. pylori.

MATERIAL AND METHODS

The study included 64 children of whom 50% (Group I) were infected with H. pylori and had gastritis; 18.7% (Group II) of the examined children had a positive titre of IgG against H. pylori and normal gastric mucosa. Controls (Group III) comprised 31.3%. The gastric mucosa was evaluated histopathologically according to the Sydney System. The serum concentrations of growth factors: EGF, TGF-alpha, VEGF, were determined using ELISA.

RESULTS

Mean concentrations of the growth factors were also the highest in Group I compared to Group II and Group III (EGF - 137.3+/-10.4 pg/mL, TGF-alpha - 0.4+/-1.2 pg/mL, VEGF - 146.8 pg/mL). Analysis of correlations between growth factors and the severity of gastritis as well as the activity of antral gastric mucosa inflammation proved that mean EGF concentration in H. pylori infected children was the highest (149.5+/-84.8 pg/mL) in severe gastritis, whereas mean concentrations of TGF-alpha (2.0+/-4.3 pg/mL) and of VEGF (148.1+/-92.6 pg/mL) were the highest in moderate gastritis. Mean concentrations of EGF (155.1+/-116.4 pg/mL) and of VEGF (156.0+/-118.9 pg/mL) were the highest in high activity antral gastritis, whereas the mean concentration of TGF-alpha was the highest (2.0+/-4.2 pg/ml) in moderate activity gastritis.

CONCLUSIONS

In the children with H. pylori infection, serum concentrations of EGF, TGF-alpha, VEGF were the highest in moderate and severe antral gastritis.

Mare's colostrum globules stimulate fibroblast growth in vitro: a biochemical study

The wound repair function of mare's milk and colostrum was investigated. Mare's colostrum improved wound healing in vivo; thus fibroblast growth activation by mare's milk and colostrum was examined. As expected, colostrum was more effective than milk. To establish the biochemical nature of the bioactive molecules involved, colostrum was fractionated into whey, casein, and fat globules, and the efficacy of these fractions on fibroblast proliferation was studied. The fat globule fraction provided the strongest stimulation; its composition was studied and compared with the less-active milk fat globule fraction. The lipid pattern highlighted several differences between mare's colostrum and milk; in particular, total lipid, linoleic acid, linolenic acid, ganglioside, and glycolipid contents were higher in colostrum. A proteomic investigation revealed some differences between the protein composition of colostrum and milk fat globules. Adipophylin and lactadherin were significantly overexpressed in colostrum fat globules. The role of specific lipids on skin wound repair and that of the epidermal growth factor-like domain, embedded within the lactadherin molecule and probably released in conditions stimulating proteolysis, are discussed.

Impaired gastric ulcer healing in diabetic rats: role of heat shock protein, growth factors, prostaglandins and proinflammatory cytokines

Gastric mucosa of diabetic rats is highly vulnerable to acute injury, but little is known about the influence of diabetic conditions on the healing of gastric ulcers. In this study, streptozotocin (70 mg/kg injected intraperitoneally) was used to induce diabetes mellitus in rats. Four weeks after streptozotocin injection, gastric ulcers were induced using the acetic acid method, and 10 days later, the healing rate and the gastric blood flow (GBF) were measured by planimetry and hydrogen (H(2))-gas clearance method, respectively. Six major groups of rats with gastric ulcers were used: (1) vehicle (saline); (2) streptozotocin alone; (3) insulin (4 IU/day intraperitoneally); (4) streptozotocin plus insulin; (5) pentoxifylline, an inhibitor of synthesis and release of tumor necrosis factor-alpha (TNF alpha); and (6) aspirin, a non-selective inhibitor of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), and rofecoxib, the highly selective COX-2. In the diabetic rats, a significant delay in ulcer healing ( approximately by 300%), accompanied by a decrease in the gastric mucosal blood flow was observed. The prolongation of the healing in diabetic animals was associated with an increase in gastric mucosal expression and release of TNFalpha, interleukin-1 beta (IL-1 beta), suppression of the vascular endothelial growth factor (VEGF), platelet endothelial cell adhesion molecule-1 (PECAM-1) and the mucosal overexpression of heat shock protein 70 (HSP 70). Administration of insulin reversed the delay in ulcer healing and significantly decreased the expression of IL-1 beta and TNF-alpha, while producing the rise in the expression of VEGF and PECAM. Pentoxifylline, an inhibitor of TNF-alpha, which by itself accelerated ulcer healing in non-diabetic rats, counteracted the increase in the area of gastric ulcer induced by streptozotocin, raised significantly gastric blood flow and suppressed the plasma TNF-alpha levels. Aspirin and rofecoxib, that significantly suppressed the mucosal prostaglandin E(2) generation in ulcer area, delayed significantly the rate of ulcer healing and decreased the GBF at ulcer margin in non-diabetic rats, and these changes were significantly augmented in diabetic animals. We conclude that: (1) Experimental diabetes dramatically impairs ulcer healing, depending upon the increased release of proinflammatory cytokines and the attenuation of angiogenesis that can limit the ulcer healing effects of locally produced HSP 70 and TNF-alpha. (2) Insulin reversed this impairment of ulcer healing in diabetic rats, mainly due to the enhancement of angiogenesis and reduction in expression of cytokines in the ulcer area. (3) Classic non-steroidal anti-inflammatory drugs such as aspirin prolonged ulcer healing under diabetic conditions due to suppression of endogenous prostaglandins and the fall in the microcirculation at the ulcer margin and these effects were mimicked by selective, so called "safe" COX-2 inhibitor, rofecoxib, suggesting that both COX isoforms are important sources of prostaglandins that are essential in the ulcer healing in diabetes.

High hepatocyte growth factor levels in faeces during acute infectious gastroenteritis

Hepatocyte growth factor (HGF) is a potent mitogen of mature epithelial cells which is produced after organ injuries and acts as a trigger for regeneration in the impaired organ. The aim of the present study was to investigate local production of HGF during infectious gastroenteritis. We measured the concentration of HGF in serum and faeces in 49 patients with acute infectious gastroenteritis (bacterium = 30, virus = 10, amoebae = 1, and probable infection = 8) at the time of referral to hospital and at convalescence (n = 31). The values were compared with normal healthy vaccination volunteers (n = 11) as well as patients with acute non-infectious diarrhoea (n = 10). The presence of HGF in faeces was confirmed by ELISA and Western immunoblot. HGF concentrations in faeces was significantly higher in the patients with infectious gastroenteritis compared to the control groups (p < 0.0001). Using a cut-off concentration of 20 ng/g, the overall sensitivity of faeces HGF to distinguish infectious gastroenteritis (bacterial, viral, probable infection) was 98% with a specificity of 100%. At convalescence all patients had normal values. There was no significant correlation between HGF concentrations in faeces and serum. Determination of faeces HGF may identify cases of transmittable diarrhoea requiring isolation at an early stage.

Importance of nitric oxide and capsaicin-sensitive afferent nerves in healing of stress lesions induced by epidermal growth factor

Epidermal growth factor (EGF) is a potent mitogen implicated in gastroprotection and ulcer healing, but its possible interaction with nitric oxide (NO) and sensory nerves on healing after acute gastric damage has not been assessed. We examined the effects of topical application of a small dose (0.5 mg/kg) of capsaicin to stimulate sensory nerves and a larger parenteral dose of capsaicin (125 mg/kg s.c.) to deactivate these neurons or the effect of systemic administration of NG-nitro-L-arginine methyl ester (L-NAME) (20 mg/kg i.v.) to suppress NO synthase on healing of gastric lesions induced by 3.5 h of water immersion and restraint stress (WRS) in rats without or with EGF administration. Rats were sacrificed at 0, 6, 12, or 24 h after WRS and the gastric blood flow (GBF) was measured by the H2 gas clearance technique. Exposure to WRS produced many gastric lesions, with a marked decrease in GBF, but at 12 h these lesions started to heal and the lesion number was reduced by 75% after 24 h. This was accompanied by progressive increase in the GBF and an increase in expression of EGF mRNA in gastric mucosa, as detected by RT-PCR. Pretreatment with L-NAME or functional ablation of sensory nerves by capsaicin significantly delayed the healing of WRS lesions and accompanying hyperemia. In contrast, pretreatment with EGF (100 micrograms/kg s.c.) or glyceryl trinitrate (10 mg/kg i.g.), a donor of NO, or stimulation of sensory nerves by topical capsaicin significantly enhanced the healing of these lesions and increased the GBF. The acceleration of the healing and accompanying hyperemia induced by EGF at 12 h after WRS were completely reversed in rats pretreated with L-NAME or in those with capsaicin denervation. Addition of L-arginine but not D-arginine to L-NAME restored the healing of stress lesions and gastric hyperemia induced by this peptide. Removal of salivary glands, which reduced luminal content of EGF and DNA synthesis by about fourfold compared to rats with intact glands, produced a significant delay in healing, and this was further aggravated by capsaicin denervation. We conclude that EGF, sensory nerves, and NO play an important role in the healing of gastric mucosa from lesions induced by stress and that sensory nerves and NO appear to interact with EGF in the mechanism of mucosal recovery from stress lesions.

Epidermal growth factor and transforming growth factor alpha in duodenal ulcer and non-ulcer dyspepsia patients before and after Helicobacter pylori eradication

BACKGROUND

Epidermal growth (EGF) and transforming growth factor alpha (TGFalpha) are potent gastric secretory inhibitors, mitogens, and mucosal protectors, but the impact of Helicobacter pylori infection on their mucosal expression and luminal release has not been clarified.

METHODS

In this study, gene and immunoreactive and immunohistochemical expressions of EGF and TGFalpha were assessed in the gastric mucosa of 15 H. pylori-negative healthy normals, in 22 H. pylori-positive duodenal ulcer patients (DU) and in 24 H. pylori-positive non-ulcer dyspepsia patients (NUD). All studies in DU and NUD patients were repeated after 2 weeks of triple therapy (amoxicillin + clarithromycin + omeprazole) and 4 weeks and 2 years later.

RESULTS

Immunohistochemical expression of EGF and TGFalpha in H. pylori-positive DU and NUD was significantly higher than in H. pylori-negative normals, and this increase persisted at 2 and 4 weeks after therapy but normalized 2 years later. EGF mRNA was detected in the gastric mucosa of H. pylori-positive DU before and at 2 and 4 weeks after H. pylori eradication, but it was not found 2 years after the eradication of H. pylori or in gastric mucosa of H. pylori-negative control subjects. TGFalpha mRNA was detected in the gastric mucosa independently of H. pylori status, with the stronger expression observed in the gastric mucosa of H. pylori-positive DU and NUD before eradication than after this procedure. Plasma gastrin, which was significantly increased in H. pylori-positive DU, normalized already after 2 weeks of triple therapy. The eradication rate as determined by histology after triple therapy reached 86.3% in DU patients and 90.5% in NUD patients. Two years after the eradication the H. pylori reinfection rate was 4.5% among DU patients and 4.2% among NUD. Treatment of DU patients with triple therapy resulted in complete ulcer healing.

CONCLUSIONS

1) Chronic H. pylori infection and resulting antral gastritis are associated with increased plasma gastrin and increased mucosal cell proliferation, probably due to enhanced expression of EGF and TGFalpha, and 2) the H. pylori eradication results in a decrease in plasma gastrin, but the increase in gastric TGFalpha and EGF content is sustained, suggesting that they may be involved in ulcer healing.

The role of epidermal growth factor (EGF) and its receptor in mucosal protection, adaptation to injury, and ulcer healing: involvement of EGF-R signal transduction pathways

Growth factors and their receptors are known to play important roles in normal cell proliferation, morphogenesis, tissue repair, and ulcer healing. Epidermal growth factor (EGF) inhibits acid secretion, exerts a trophic effect on gastroduodenal mucosa, protects gastric mucosa against injury, mediates mucosal adaptation, and accelerates gastroduodenal ulcer healing by stimulating cell migration and proliferation. EGF exerts its actions by binding to its receptor, EGF-R, a transmembrane protein tyrosine kinase, which triggers receptor dimerization, autophosphorylation, and recruitment of kinase substrates. These events result in Ras (GTP-binding protein) activation of the Ras/Raf/MAP kinase pathway, leading to phosphorylation of regulatory proteins and transcription factors and culminating in cell proliferation. Other pathways potentially activated by EGF include the phosphatidylinositol pathway and the JAK/STAT signaling pathway. Recent studies demonstrated that EGF-R-associated tyrosine kinase plays an essential role in regulating gastric mucosal cell proliferation after acute injury and further demonstrated activation of the EGF-R gene, EGF-R phosphorylation, and increased MAP kinase activity during early stages of experimental gastric ulcer healing. Finally, experimental data indicate that Helicobacter pylori vacuolating cytotoxin inhibits healing of experimental gastric ulcers, cell proliferation, binding of EGF to its receptor, EGF-induced EGF-R phosphorylation, and MAP kinase (ERK-2) activation. These H. pylori actions can explain its interference with the ulcer healing process.