Effect of long-term Helicobacter felis infection in a mouse model of streptozotocin-induced diabetes

BACKGROUND: We previously REPORTED that mice with diabetes and short-term Helicobacter felis infection had an increase in glycated hemoglobin (HbA1c). Here we report the effect of long-term infection. MATERIALS AND METHODS: Six-week-old C57BL/6 mice were injected with streptozotocin to induce diabetes and started on daily insulin. Following streptozotocin injection, animals were paired according to their HbA1c values and randomized to orally receive either H. felis or culture medium alone. Weight and HbA1c were monitored monthly for 6 months. RESULTS: Thirty animals corresponding to 15 pairs were included in the study. H. felis-infected diabetic mice developed significantly more gastritis than uninfected animals. Sixteen mice died during the observation period. As compared to uninfected animals, infected mice died more frequently (40% versus 67%, p = .14) and earlier (160 versus 61 days, p = .20); both variables combined showed that H. felis infection significantly decreased the chances of survival during the study period (p = .045). In addition, infected mice showed a trend for higher increase in their HbA1c (0.97 +/- 2.5% versus - 0.22 +/- 3.0%; p = .21) and lower weight gain (2.0 +/- 3.4 g versus 2.9 +/- 2.0 g; p = .15) than uninfected mice. CONCLUSION: Long-term H. felis infection had a deleterious effect in mice with streptozotocin-induced diabetes resulting in increased mortality. If the same phenomenon occurs in humans this could lead to interventions to improve the long-term outcome of patients with diabetes.     

Helicobacter-induced gastritis in mice not expressing metallothionein-I and II

Background. Helicobacter pylori a primary cause of gastritis and peptic ulcer disease, is associated with increased production of reactive oxygen species within the gastric mucosa. Metallothionein (MT), a low‐molecular‐weight, cysteine‐rich, metal‐binding ligand, has been shown to sequester reactive oxygen species and reduce tissue damage. This study investigates the role of MT in H. pylori‐induced gastritis in mice. Materials and Methods. Control (MT+/+) and MT‐null (MT–/–) mice were inoculated with either 1 × 10⁸H. pylori or H. felis, and were infected for 4, 8 and 16 weeks or 8 weeks, respectively. H. pylori load was determined by culture. Myloperoxidase activity and MT levels were also determined. Results. The stomachs of H. felis‐infected mice were more severely inflamed than those of H. pylori‐infected mice. H. felis‐induced gastritis was more severe (p = .003) in MT–/– than in MT+/+ mice. MT–/– mice also had higher (60%; p < .05) H. pylori loads than MT+/+ mice 4 weeks after infection but not 8 or 16 weeks after infection. Myloperoxidase activity with H. pylori was similar between MT+/+ and MT–/– mice. Thirty‐three per cent greater (p < .05) myloperoxidase activity was observed in MT–/– than in MT+/+ mice infected with H. felis. In MT+/+ mice infected with H. pylori, liver MT was increased by 33 and 39% (p < .05) at 8 and 16 weeks, respectively, whereas gastric MT increased by 46% (p < .05) at 4 weeks and declined to baseline levels at 8 and 16 weeks. Conclusions. Mice lacking MT are more susceptible to H. pylori colonization and gastric inflammation, indicating that MT may be protective against H. pylori‐induced gastritis.     

Helicobacter felis infection causes an acute iron deficiency in nonpregnant and pregnant mice

BACKGROUND: The role of Helicobacter pylori infection in iron deficiency during pregnancy is limited. The aim of the present study was to assess the relationship between Helicobacter infection and levels of iron stores in pregnant mice. MATERIALS AND METHODS: Female C57BL/6 mice were either inoculated with 10(8) H. pylori, Helicobacter felis or water. In the nonpregnant study, 15 mice from each group were sacrificed after 4 and 20 weeks of infection. In the pregnancy study, after 6 weeks of infection all female mice were mated and approximately 2 weeks after mating, half of the pregnant mice (n = 9/group) from each group were sacrificed. The remaining mice were allowed to give birth, and approximately 4 weeks after birth, mice were asphyxiated with CO2, followed by heart puncture, and killed by cervical dislocation. Serum ferritin and iron were determined with a micro-particle enzyme immunoassay method and by a timed-endpoint method. RESULTS: Serum iron levels in mice infected with H. felis were significantly (p < .05) lowered compared to control (24%) and H. pylori (27%)-infected mice at 4 weeks of infection. Serum iron in the control, H. pylori and H. felis groups were significantly (p < .05) elevated at 20 weeks by 39, 26 and 77%, respectively, compared to 4 weeks of infection. H. felis-infected mice had a significantly (p < .05) decreased serum ferritin level during pregnancy (61%) compared to H. pylori-infected mice. CONCLUSION: These results suggest that H. felis but not H. pylori infection causes an acute iron deficiency in normal and pregnant mice.     

Human group IIA secretory phospholipase A2 potentiates Ca2+ influx through L-type voltage-sensitive Ca2+ channels in cultured rat cortical neurons

Mammalian group IIA secretory phospholipase A2 (sPLA2-IIA) generates prostaglandin D2 (PGD2) and triggers apoptosis in cortical neurons. However, mechanisms of PGD2 generation and apoptosis have not yet been established. Therefore, we examined how second messengers are involved in the sPLA2-IIA-induced neuronal apoptosis in primary cultures of rat cortical neurons. sPLA2-IIA potentiated a marked influx of Ca2+ into neurons before apoptosis. A calcium chelator and a blocker of the L-type voltage-sensitive Ca2+ channel (L-VSCC) prevented neurons from sPLA2-IIA-induced neuronal cell death in a concentration-dependent manner. Furthermore, the L-VSCC blocker ameliorated sPLA2-IIA-induced morphologic alterations and apoptotic features such as condensed chromatin and fragmented DNA. Other blockers of VSCCs such as N type and P/Q types did not affect the neurotoxicity of sPLA2-IIA. Blockers of L-VSCC significantly suppressed sPLA2-IIA-enhanced Ca2+ influx into neurons. Moreover, reactive oxygen species (ROS) were generated prior to apoptosis. Radical scavengers reduced not only ROS generation, but also the sPLA2-IIA-induced Ca2+ influx and apoptosis. In conclusion, we demonstrated that sPLA2-IIA potentiates the influx of Ca2+ into neurons via L-VSCC. Furthermore, the present study suggested that eicosanoids and ROS generated during arachidonic acid oxidative metabolism are involved in sPLA2-IIA-induced apoptosis in cooperation with Ca2+.     

The molecular mechanism of human group IIA phospholipase A2 inactivation by bolinaquinone

The molecular basis of the human group IIA secretory phospholipase A₂ inactivation by bolinaquinone (BLQ), a hydroxyquinone marine terpenoid, has been investigated for the comprehension of its relevant antiinflammatory properties, through the combination of spectroscopic techniques, biosensors analysis, mass spectrometry (MS) and molecular docking. Indeed, sPLA₂s are well known to be implicated in the pathogenesis of inflammation such as rheumatoid arthritis, septic shock, psoriasis and asthma. Our results suggest a mechanism of competitive inhibition guided by a non‐covalent molecular recognition event, disclosing the key role of the BLQ hydroxyl‐quinone moiety in the chelation of the catalytic Ca²⁺ ion inside the enzyme active site. The understanding of the sPLA₂‐IIA inactivation mechanism by BLQ could be useful for the development of a new chemical class of PLA₂ inhibitors, able to specifically target the enzyme active site. Copyright © 2009 John Wiley & Sons, Ltd.     

Helicobacter felis does not stimulate human neutrophil oxidative burst in contrast to 'Gastrospirillum hominis' and Helicobacter pylori

Helicobacter pylori is a human pathogen, whereas the natural hosts for 'Gastrospirillum hominis' and Helicobacter felis are animals. 'G. hominis' is occasionally found to cause infection in humans, whereas H. felis only rarely infects humans. The pathogenesis of H. pylori infection is not completely understood and in order to reveal differences in immune response to the three Helicobacter species, the upregulation of adherence molecule CD11b/CD18, chemotactic activity and oxidative burst response of neutrophils after stimulation with H. pylori, 'G. hominis' and H. felis sonicates, were compared. Like H. pylori, 'G. hominis' and H. felis induced upregulation of CD11b/CD18 and chemotaxis of neutrophils. 'G. hominis' demonstrated a more pronounced upregulation of CD11b/CD18, whereas H. felis was the strongest stimulant of neutrophil chemotaxis. H. felis was unable to stimulate neutrophils to oxidative burst response, whereas 'G. hominis' activated neutrophils in a dose-dependent way similar to H. pylori. 'G. hominis' and H. felis were both able to prime neutrophils for oxidative burst response similar to H. pylori. In conclusion, we observed clear differences in neutrophil responses to different Helicobacter species, which indicates that bacterial virulence factors may be important for the diversity in the pathogenetic outcome of Helicobacter infections.     

The role of propeptide in the refolding of human group IB phospholipase A2

Phospholipase A2 (PLA2, EC 3.1.1.4) catalyzes the hy-drolysis of the 2-acyl ester bond of sn-3-phosphoglycerides,producing a free fatty acid and a lysophospholipid [1].Mammalian secretory phospholipase A2 is tentatively sug-gested to be involved in the in…     

A novel method for assessing gastritis in the murine model demonstrates genetically determined variation in response to Helicobacter felis infection

Background. In murine Helicobacter infection it has been demonstrated that the degree of gastric mucosal inflammation is determined by mouse strain. This is a valuable tool for investigating genetic, immunological or bacterial determinants for the outcome of human Helicobacter infection. This study aims to devise a robust method to facilitate these investigations. Materials and Methods. C57BL/6, BALB/c and (C57BL/6 × BALB/c) F1 mice were given 10⁸H. felis by gavage on days 1, 3 and 5 of the experiment Sections of the lesser and greater curve of stomach were examined at 12 weeks to assess active gastritis using a semi‐quantitative and a quantitative method by counting neutrophils in glands in four zones of the mucosa. Results. Semi‐quantitative scoring for active inflammation, based on the Sydney System, was inadequate with little discrimination between strains. Quantifying the level of active inflammation, counting the number of neutrophils in inflamed gastric glands and taking the total number of neutrophils in three inflamed pits within each zone (cardia, body, transitional zone and antrum) showed clear differences between the two parental strains for the degree of active gastritis and furthermore, using this system the phenotype of the (C57BL/6 × BALB/c) F1 was found to be between the two parental extremes. Conclusions. This novel method provides a numerical value for active inflammation in the stomach that is accurate, reproducible and discriminatory.     

Molecular dynamics simulations reveal structural insights into inhibitor binding modes and functionality in human Group IIA phospholipase A2

Human Group IIA phospholipase A₂ (hGIIA) promotes inflammation in immune‐mediated pathologies by regulating the arachidonic acid pathway through both catalysis‐dependent and ‐independent mechanisms. The hGIIA crystal structure, both alone and inhibitor‐bound, together with structures of closely related snake‐venom‐derived secreted phospholipase enzymes has been well described. However, differentiation of biological and nonbiological contacts and the relevance of structures determined from snake venom enzymes to human enzymes are not clear. We employed molecular dynamics (MD) and docking approaches to understand the binding of inhibitors that selectively or nonselectively block the catalysis‐independent mechanism of hGIIA. Our results indicate that hGIIA behaves as a monomer in the solution environment rather than a dimer arrangement that is in the asymmetric unit of some crystal structures. The binding mode of a nonselective inhibitor, KH064, was validated by a combination of the experimental electron density and MD simulations. The binding mode of the selective pentapeptide inhibitor FLSYK to hGIIA was stipulated to be different to that of the snake venom phospholipases A₂ of Daboia russelli pulchella (svPLA₂). Our data suggest that the application of MD approaches to crystal structure data is beneficial in evaluating the robustness of conclusions drawn based on crystal structure data alone. Proteins 2017; 85:827–842. © 2016 Wiley Periodicals, Inc.     

Phenotypic changes of Helicobacter pylori components during an experimental infection in mice

The bacterial pathogen Helicobacter pylori is highly adapted to the human stomach and the clinical isolates show a high diversity which could be due to adaptative changes of the strains passing from one host to another. In order to study these variations, experimental infection of mice was developed and provided three out of the eleven tested strains able to infect C57BL/6 mice: the Sydney strain which is known to be well adapted to mice and two freshly isolated strains from infected patients. Mice were orally infected with one of these three strains (infecting strains) and were killed 45 days later. H. pylori strains were isolated from the stomachs of mice (emerging strains). The three infecting strains were compared to the three emerging strains for protein and lipopolysaccharide profiles, antigenic profiles revealed by Western blot with monospecific sera and genetic status by testing for the cagA gene and the vacA genotype. During the 45 days of infection, H. pylori underwent phenotypic variations which may be attributed to the adaptation from a human to a mouse environment or from an in vitro to a mouse environment. Those variations consisted of an over-expression at the cell surface of a 180-kDa protein and of a decreased expression of proteins of 260 and 120 kDa. Moreover, antigenic variations were shown for the two freshly isolated strains from human: the CagA and VacA antigens were in the saline extracts of the infecting strains only while the UreA, UreB, HspA and HspB were in the saline extracts of both the infecting and the emerging strains. These variations may contribute to the adaptation of the strains to the mouse environment.     

The role of interleukin-17 in the Helicobacter pylori induced infection and immunity

Background: Helicobacter pylori infection is regarded as the major cause of various gastric diseases and induces the production of several cytokines including interleukin‐17 (IL‐17) recently recognized as an important player in the mammalian immune system. Objective: This review deals with the role of IL‐17 on the H. pylori‐induced infection and immunity in humans and experimental animals. Results: H. pylori infection increases IL‐17 in the gastric mucosa of humans and experimental animals. In humans, IL‐17 induces the secretion of IL‐8 by activating the ERK 1/2 MAP kinase pathway and the released IL‐8 attracts neutrophils promoting inflammation. IL‐23 is increased in patients with H. pylori‐related gastritis and regulates IL‐17 secretion via STAT3 pathway. Studies in H. pylori‐infected mice indicate that IL‐17 is primarily associated with gastric inflammation. The early events in the immune response of immunized and challenged mice include the recruitment of T cells and the production of IL‐17. Neutrophil attracting chemokines are released, and the bacterial load is considerably reduced. IL‐17 plays a dual role in infection and vaccination. In infection, T regulatory cells (Tregs) suppress the inflammatory reaction driven by IL‐17 thereby favoring bacterial persistence. Immunization produces Helicobacter‐specific memory T‐helper cells that can possibly alter the ratio between T‐helper 17 and Treg responses so that the IL‐17‐driven inflammatory reaction can overcome the Treg response leading to bacterial clearance. Conclusion: IL‐17 plays an important role in H. pylori‐related gastritis and in the reduction of Helicobacter infection in mice following immunization.     

Development and evaluation of a DNA vaccine based on Helicobacter pylori urease B: failure to prevent experimental infection in the mouse model

BACKGROUND: The development of a vaccine against Helicobacter pylori has become a priority to prevent major morbidity and mortality associated with this infection. Our goal was to prepare and evaluate a DNA vaccine based on the urease B gene (ureB). METHODS: The ureB gene of H. pylori was amplified and cloned into the eukaryotic expression vector pcDNA3.1/TOPO. Plasmid DNA was purified from transformed Escherichia coli cells and used to immunize mice by the intragastric, intramuscular, intrarectal (40 micro g each) and intranasal (16 micro g) route, three doses every 2 weeks, with CpG oligodeoxynucleotide (ODN) as adjuvant. Four weeks after the third dose, animals were orally challenged with Helicobacter felis and were sacrificed 6 weeks later. The stomach was stained to detect the presence of infection. RESULTS: Despite in vitro confirmation of successful cloning and functionality of the ureB gene with expression of a protein morphologically and antigenically identical to urease B, the DNA vaccine did not perform well in vivo. Immunization of mice produced a weak immune response. Overall, intrarectal and intranasal administration seemed more immunogenic than other routes. Protection against challenge was modest and nonsignificant, and slightly better on animals immunized by the intramuscular and intranasal route. CONCLUSION: A DNA vaccine based on H. pylori urease B was poorly immunogenic and nonprotective at the conditions evaluated. Higher doses, better adjuvants or a prime-boost approach may circumvent these limitations.     

Role of Lewis A and Lewis B blood group antigens in Helicobacter pylori infection

BACKGROUND AND AIMS: We investigated the prevalence of Helicobacter pylori infection in a large group of women to determine whether there was an association of current infection status with Lewis blood group antigen A and B phenotype. METHODS: Between November 2000 and November 2001, mothers were recruited after delivery of their offspring at the Department of Gynecology and Obstetrics at the University of Ulm, Ulm, Germany. The H. pylori infection status of the women was determined by 13C urea breath test. Their Lewis A and Lewis B phenotype was determined using standard laboratory techniques. RESULTS: In total, 22.2% of the 712 women included in the study (mean age 30.7 years) had a current H. pylori infection. The prevalence of infection varied from 15.5% in women of German nationality to 75.0% in women of Turkish nationality (p < .001). Most women (68.1%) had a Le(a-b+) phenotype. The prevalence of H. pylori infection in women with Le(a-b+) phenotypes was lower than in other women (p = .02). In multivariate analysis, the odds ratio (OR) for a current H. pylori infection given Le(a-b+) was 0.56 [95% confidence interval (CI) 0.33-0.95] compared to women with Le(a-b-). CONCLUSION: Le(a-b+) blood group phenotype in combination with secretor status may hinder colonization of H. pylori in the population studied.     

Pharmacokinetics of radioiodinated human and ovine growth hormones in transgenic mice expressing bovine growth hormone

Pharmacokinetics of radioiodinated human growth hormone (hGH) and ovine growth hormone (oGH) were studied in normal mice and in transgenic mice carrying the bovine growth hormone (bGH) gene fused to phosphoenolpyruvate carboxykinase promoter/regulator (PEPCK-bGH). Multiexponential plasma decay curves were obtained in both normal and transgenic mice after a¹²⁵I-oGH injection and pharmacokinetic parameters were estimated by fitting blood concentration data to a three compartment model. The half-life for the rapid compartment was shorter in transgenic than in normal mice (t_1/2:1.2±0.3 vs. 2.2±0.5 min). The slow compartment had a t_1/2 of 160±23 min for transgenic and 70±8 min for normal mice while the middle compartment had a t_1/2 of approximately 10 min for both groups of mice. The mean residence times were 167±24 and 55±5 min for transgenic and normal mice, respectively. Specific liver uptake of radioactivity after injection of¹²⁵I-oGH or¹²⁵I-hGH was found in both groups of animals. Specificity studies indicated that, similarly to normal mice, livers of transgenic mice possess a mixed population of somatotropic and lactogenic receptors. Uptake of labelled hGH by the liver was dose-dependent and the doses that prevented 50% of liver uptake (ED_50%) were 8 and 165 g per 50 g body weight for normal and transgenic mice, respectively. Thesein vivo results confirm and extend previousin vitro findings that a life-long excess of bGH increases hepatic somatotropic and lactogenic receptors. Since elevation in growth hormone (GH) receptors was reported to be associated with an increase in GH binding protein (GHBP), we suspect that both the increase in the mean residence time and the reduction in specific uptake of GH in the livers of transgenic mice may be the result of an increase in GHBP levels.     

Compensatory mechanisms enhance hippocampal acetylcholine release in transgenic mice expressing human acetylcholinesterase

Central cholinergic neurotransmission was studied in learning-impaired transgenic mice expressing human acetylcholinesterase (hAChE-Tg). Total catalytic activity of AChE was approximately twofold higher in synaptosomes from hippocampus, striatum and cortex of hAChE-Tg mice as compared with controls (FVB/N mice). Extracellular acetylcholine (ACh) levels in the hippocampus, monitored by microdialysis in the absence or presence of 10(-8)-10(-3) M neostigmine in the perfusion fluid, were indistinguishable in freely moving control and hAChE-Tg mice. Muscarinic receptor functions were unchanged as indicated by similar effects of scopolamine on ACh release and of carbachol on inositol phosphate formation. However, when the mice were anaesthetized with halothane (0.8 vol. %), hippocampal ACh reached significantly lower levels in AChE-Tg mice as compared with controls. Also, the high-affinity choline uptake (HACU) in hippocampal synaptosomes from awake hAChE-Tg mice was accelerated but was reduced by halothane anaesthesia. Moreover, hAChE-Tg mice displayed increased motor activity in novel but not in familiar environment and presented reduced anxiety in the elevated plus-maze test. Systemic application of a low dose of physostigmine (100 microgram/kg i.p.) normalized all of the enhanced parameters in hAChE-Tg mice: spontaneous motor activity, hippocampal ACh efflux and hippocampal HACU, attributing these parameters to the hypocholinergic state due to excessive AChE activity. We conclude that, in hAChE-Tg mice, hippocampal ACh release is up-regulated in response to external stimuli thereby facilitating cholinergic neurotransmission. Such compensatory phenomena most likely play important roles in counteracting functional deficits in mammals with central cholinergic dysfunctions.     

Induction of secretory phospholipase A2 in reactive astrocytes in response to transient focal cerebral ischemia in the rat brain

Although mRNA expression of group IIA secretory phospholipase A2 (sPLA2-IIA) has been implicated in responses to injury in the CNS, information on protein expression remains unclear. In this study, we investigated temporal and spatial expression of sPLA2-IIA mRNA and immunoreactivity in transient focal cerebral ischemia induced in rats by occlusion of the middle cerebral artery. Northern blot analysis showed a biphasic increase in sPLA2-IIA mRNA expression following 60-min of ischemia-reperfusion: an early phase at 30 min and a second increase at a late phase ranging from 12 h to 14 days. In situ hybridization localized the early-phase increase in sPLA2-IIA mRNA to the affected ischemic cortex and the late-phase increase to the penumbral area. Besides sPLA2-IIA mRNA, glial fibrillary acidic protein (GFAP) and cyclo-oxygenase-2 mRNAs, but not cytosolic PLA2, also showed an increase in the penumbral area at 3 days after ischemia-reperfusion. Immunohistochemistry of sPLA2-IIA indicated positive cells in the penumbral area similar to the GFAP-positive astrocytes but different from the isolectin B4-positive microglial cells. Confocal microscopy further confirmed immunoreactivity of sPLA2-IIA in reactive astrocytes but not in microglial cells. Taken together, these results demonstrate for the first time an up-regulation of the inflammatory sPLA2-IIA in reactive astrocytes in response to cerebral ischemia-reperfusion.     

Lactoferrin and desferrioxamine are ineffective in the treatment of Helicobacter pylori infection and may enhance H. pylori growth and gastric inflammation in mice

Aims:  To evaluate the efficacy of bovine lactoferrin (BLf), recombinant human lactoferrin (rHLf) and desferrioxamine against Helicobacter pylori in vitro and in mice and also to determine whether BLf or rHLf alter gastric inflammation.
Methods and Results:  In vitro: Broth dilution susceptibility tests were performed using different concentrations of desferrioxamine, BLf and rHLf. Murine trials: In the prevention trial, C57BL/6 female mice were treated with BLf or rHLF, and then infected with the SS1 strain of H. pylori . In the treatment trial, mice were gavaged with either BLf, rHLf or desferrioxamine. In addition, gastric myeloperoxidase activity (MPO) was measured to assess gastric inflammation. Desferoxamine was found to have a direct bactericidal effect, while BLf and rHLf only partially suppressed H. pylori growth in vitro . However, in both prevention and treatment trials all three forms of treatment failed to reduce H. pylori load in mice. Gastric MPO activity and H. pylori load were noted to be higher with lactoferrin treatments.
Conclusions:  Our study does not support the use of BLf or rHLF in the treatment of human H. pylori infection. Interestingly, H. pylori growth and gastric inflammation appear to be enhanced by lactoferrin treatment.
Significance and Impact of the Study:  The mouse model is ideal for testing novel H. pylori eradicating agents.     

Epidemiology of Helicobacter pylori infection in the Czech Republic

BACKGROUND: Prevalence of Helicobacter pylori infection has been estimated to range from 60 to 95% in the former communist countries of Central and Eastern Europe. The aim of this study was to evaluate H. pylori infection prevalence in a representative sample of the Czech population. The second objective was to describe difference of H. pylori prevalence between different social groups of children and adults. MATERIALS AND METHODS: A total of 2509 persons aged 5-100 years, randomly selected out of 30,012 persons of the general population, took part in the study. H. pylori infection was investigated by means of 13C-urea breath test. Breath samples were analyzed by isotope ratio mass spectrometry. Social and demographic characteristics were based on data from self-completed questionnaires. RESULTS: Using the total Czech population as a standard, we estimated the age-standardized prevalence of H. pylori in males aged 5+ years at 41.9% (95% CI 39.0%, 44.8%) and in females aged 5+ years at 41.4% (95% CI 38.6%, 44.3%) in 2001. Prevalence of H. pylori increased with age but was not related to gender. Children of mothers with basic or lower education, living in crowded accommodations, without access to running warm water, and residing in smaller towns appear to be at the highest risk. Low education and heavy smoking are most strongly associated with prevalence of H. pylori positivity in adults and adolescents. CONCLUSIONS: This is a unique study based on a representative sample of the general population in a Central European country. The overall prevalence of H. pylori is lower than previously assumed and could partly reflect a substantial recent decrease in H. pylori prevalence in the Czech Republic. Consistent with earlier studies, H. pylori infection is strongly influenced by socioeconomic conditions and childhood poverty.     

Bimodal regulatory effect of melittin and phospholipase A2-activating protein on human type II secretory phospholipase A2

Melittin and phospholipase A2-activating protein (PLAP) are known as efficient activators of secretory phospholipase A2(sPLA2) types I, II, and III when phospholipid liposomes are used as substrate. The present study demonstrates that both peptides can either inhibit or activate sPLA2 depending on the peptide/phospholipid ratio when erythrocyte membranes serve as a biologically relevant substrate. Low concentrations of melittin and PLAP were observed to inhibit sPLA2-triggered release of fatty acids from erythrocyte membranes. The inhibition was reversed at melittin concentrations above 1 microM. PLAP-induced inhibition of sPLA2 persisted steadily throughout the used concentration range (0-150 nM). The two peptides induced a dose-dependent activation of sPLA2 at low concentrations, followed by inhibition when model membranes were used as substrate. This opposite modulatory effect on biological membranes and model membranes is discussed with respect to different mechanisms the interaction of the regulatory peptides with the enzyme molecules and the substrate vesicles.