Bacteriophage-based approach for treatment of urinary tract infections: a quick outlook

Urinary tract infections (UTIs) are among the most common bacterial infections affecting millions worldwide. The increasing emergence of antibiotic-resistant bacteria has become a serious concern in managing UTIs. Therefore, there is a growing interest in using bacteriophages as an alternative or adjunct therapy for UTIs. Bacteriophages are viruses that infect and kill bacteria, making them a promising tool for treating UTIs caused by antibiotic-resistant bacteria. This article provides a quick outlook on using bacteriophages to treat UTIs. We summarize the current understanding of the biology of bacteriophages, the challenges associated with developing phage-based therapies, and the promising results of several case reports and clinical trials. We also highlight the potential of phage therapy as a valuable tool in the fight against antibiotic-resistant UTIs. This quick outlook on a bacteriophage-based approach for treating UTIs offers a timely and informative summary of the current research in this field.

Advances in bacteriophage-mediated strategies for combating polymicrobial biofilms

Bacteria and fungi tend to coexist within biofilms instead of in planktonic states. Usually, such communities include cross-kingdom microorganisms, which make them harder to remove from abiotic surfaces or infection sites. Additionally, the produced biofilm matrix protects embedded microorganisms from antibiotics, disinfectants, or the host immune system. Therefore, classic therapies based on antibiotics might be ineffective, especially when multidrug-resistant bacteria are causative factors. The complexities surrounding the eradication of biofilms from diverse surfaces and the human body have spurred the exploration of alternative therapeutic modalities. Among these options, bacteriophages and their enzymatic counterparts have emerged as promising candidates, either employed independently or in synergy with antibiotics and other agents. Phages are natural bacteria killers because of mechanisms of action that differ from antibiotics, phages might answer worldwide problems with bacterial infections. In this review, we report the attempts to use bacteriophages in combating polymicrobial biofilms in in vitro studies, using different models, including the therapeutical use of phages. In addition, we sum up the advantages, disadvantages, and perspectives of phage therapy.

Response Surface Methodology Application for Bacteriophage-Antibiotic Antibiofilm Activity Optimization

Phage-antibiotic combination-based protocols are presently under heightened investigation. This paradigm extends to engagements with bacterial biofilms, necessitating novel computational approaches to comprehensively characterize and optimize the outcomes achievable via these combinations. This study aimed to explore the Response Surface Methodology (RSM) in optimizing the antibiofilm activity of bacteriophage-antibiotic combinations. We employ a combination of antibiotics (gentamicin, meropenem, amikacin, ceftazidime, fosfomycin, imipenem, and colistin) alongside the bacteriophage vB_AbaP_AGC01 to combat Acinetobacter baumannii biofilm. Based on the conducted biofilm challenge assays analyzed using the RSM, the optimal points of antibiofilm activity efficacy were effectively selected by applying this methodology, enabling the quantifiable mathematical representations. Subsequent optimization showed the synergistic potential of the anti-biofilm that arises when antibiotics are judiciously combined with the AGC01 bacteriophage, reducing biofilm biomass by up to 80% depending on the antibiotic used. The data suggest that the phage-imipenem combination demonstrates the highest efficacy, with an 88.74% reduction. Notably, the lower concentrations characterized by a high maximum reduction in biofilm biomass were observed in the phage-amikacin combination at cA = 0.00195 and cP = 0.38 as the option that required minimum resources. It is worth noting that only gentamicin antagonism between the phage and the antibiotic was detected.

Sulfhemoglobin under the spotlight - Detection and characterization of SHb and HbFeIII-SH

Sulfhemoglobinemia is an incurable disease caused by an overdose of sulfur-containing drugs with oxidizing properties. Its diagnosis remains hindered due to the similarity of symptoms to other pathological state - methemoglobinemia, as well as contradictory information on the structure and characteristics of sulfhemoglobin. Herein, we present sulfhemoglobinemia model on living functional human erythrocytes, designed to recreate processes which could take place in a patient body in order to complement missing information and highlight distinctiveness of two hemoglobin (Hb) adducts formed after interaction with sulfur donors. Employed techniques, UV-Vis absorption, Raman, Fourier transformed infrared (FT-IR) and electronic circular dichroism (ECD) spectroscopies, allowed to distinguish and characterize Hb adduct with sulfur atom bounded directly to the iron ion (HbFe^III-SH), and irreversibly connected to the porphyrin ring (SHb - sulfhemoglobin). Presented herein results provided also new evidence on formation of both these hemoglobin adducts inside functional erythrocytes under oxidative conditions and during sulfur-containing drug presence, what can be further translated into future physiological studies. Moreover, we found that sulfur attachment to the porphyrin ring altered Hb structure and lead to changes in protein packing inside RBCs, eventually. Interestingly, measurement of blood drop smear by Raman spectroscopy occurred the most accurate method to differentiate HbFe^III-SH and SHb, indicating potential of this technique in sulfhemoglobinemia diagnosis.

Studies of saturated absorption and measurements of optical frequency for lines in the nu1 + nu3 and nu1 + 2nu4 bands of ammonia at 1.5 microm

A cavity-enhanced absorption spectrometer was used to saturate several lines of ammonia in the 1510 nm - 1560 nm region. Analysis of power broadening of the saturated absorption feature for one of the ammonia lines yielded a dipole moment value comparable to that of the lines in the nu(1)+nu(3) band in acetylene. Highly reproducible frequency measurements of four ammonia line centres were carried out using a frequency comb generated by a mode-locked Cr(4+):YAG laser. These results demonstrate the possible application of ammonia saturated absorption lines for frequency metrology and calibration in a spectral region lacking strong absorbers. To our knowledge, this is the first frequency measurement of saturated absorption lines in ammonia at near infrared frequencies and the first reported observation of saturated absorption lines in the nu(1)+2nu(4) band.

Ultrashort pulse Cr4+:YAG laser for high precision infrared frequency interval measurements

A cavity stabilized, SESAM mode-locked Cr4+:YAG laser capable of generating sub-100 fs pulses has been developed. Locking the 130-MHz pulse repetition frequency to that of a hydrogen maser-referenced frequency synthesizer provides a 30-nm wide frequency comb for the 1530-nm wavelength region. In conjunction with a pair of acetylene stabilized, external cavity diode lasers, this laser provides a high precision measurement tool for the determination of acetylene transition frequencies.

Comparison of the efficacy and safety of ebrotidine in the treatment of duodenal ulcer. A multicentre, double-blind, placebo-controlled phase II study

Ebrotidine (N-[(E)-[[2-[[[2-[(diaminomethylene)amino]-4 -thiazoly]methyl]thio]ethyl]amino]methylene]-4-bromo-benzenesulfon amide, CAS 100981-43-9, FI-3542) is a new H2-receptor antagonist characterized by its high receptor affinity and gastroprotective effect. This Phase II study has been undertaken to establish the efficacy and safety of ebrotidine, administered in four dosages as a single evening dose versus placebo in the treatment of duodenal ulcer. A total of 110 duodenal ulcer patients were studied in a randomized, double-blind, placebo-controlled, multicentre clinical trial. The patients were assigned to 5 groups: placebo, 200 mg, 400 mg, 600 mg and 800 mg of ebrotidine once daily. Controls were performed at baseline and every two weeks at four follow-up visits unless ulcer healed before. Endoscopic examination was the main parameter for the assessment of treatment efficacy and ulcer healing rate. Vital signs and blood/ urine analysis were used to establish safety. The three groups treated with higher dosages (400 to 800 mg of ebrotidine daily) showed an endoscopic ulcer healing rate of 90-95%, significantly higher than 55% achieved with placebo (p < 0.05), whilst the differences between these three dosages of ebrotidine were not statistically significant. Healing rate in the group treated with 200 mg of ebrotidine daily was not significantly different from that in the placebo group. The development of symptoms, number of episodes of ulcer-related pain, total ulcerated surface area or subjective ratings by the patients and investigators also differed significantly between ebrotidine (400, 600 and 800 mg daily) and placebo, and again, no marked differences were found between these three doses of ebrotidine. As far as tolerance is concerned, no clinically or statistically significant changes were observed in vital signs and analytical parameters. The incidence of side effects was less than that presented by the placebo group, possibly due to a greater consumption of antacids in this group. Results showed that a daily dose of 400 mg ebrotidine is effective and safe in the treatment of duodenal ulcers.

Enhancement in the protective qualities of gastric mucus by ebrotidine during duodenal ulcer healing

1. Gastric mucus from duodenal ulcer patients before and following therapy with a new antiulcer agent, ebrotidine, at 400, 600 and 800 mg dose was examined for changes in the physicochemical qualities and anti-H. pylori activity. 2. The results of physical measurements revealed that successful therapy with ebrotidine was accompanied by a 25% increase in gastric mucus viscosity, and a 20% increase in H+ retardation capacity, while its hydrophobicity increased by 11%. 3. The enhancement in the physical properties of mucus with ebrotidine therapy were also reflected in a marked (2.6-2.9-fold) increase in the proportion of the high molecular weight form of mucin. Furthermore, following therapy with ebrotidine, the gastric mucins showed a 36% higher content of sulfate as compared to that before the therapy. 4. Assays on the H. pylori aggregating titer of gastric mucin revealed that ebrotidine therapy at all three doses evoked a 4-fold increase in mucin anti-H. pylori activity. 5. The data demonstrate that duodenal ulcer therapy with ebrotidine leads to a marked improvement in the protective qualities of gastric mucus essential for the maintenance of mucosal integrity and enhances the inherent mucosal defense against H. pylori infection.

Inhibition of gastric mucosal mucin receptor by Helicobacter pylori lipopolysaccharide: effect of sulglycotide

1. A receptor for mucin was isolated from the solubilized gastric epithelial cell membrane by affinity chromatography on Sepharose-bound wheat germ agglutinin. 2. The receptor protein displayed a molecular weight of 97 kDa and exhibited specific affinity towards mucin-coated surfaces. The optimum for mucin binding occurred at 60-100 micrograms/ml, while the values for the receptor were 2.0-3.1 micrograms/ml. 3. The mucin binding to the receptor was susceptible to Helicobacter pylori lipopolysaccharide which caused maximum inhibition of 91% at 30 mu/ml. This inhibitory effect of the lipopolysaccharide was abolished by a gastroprotective agent, sulglycotide. 4. The effect of sulglycotide was dose dependent and at 50 micrograms/ml produced a 94% restoration in receptor-mucin binding. Furthermore, sulglycotide was also capable of enhancing (97%) the mucin binding to its receptor in the absence of the lipopolysaccharide. 5. The results demonstrate that H. pylori through its lipopolysaccharide interferes in the interaction of mucin with gastric epithelial surfaces and that a gastroprotective agent, sulglycotide, counteracts this effect, and hence is capable of preventing the loss of mucin coat continuity occurring with H. pylori infection.

Gastric mucosal EGF and PDGF receptor expression with ulcer healing by ebrotidine

OBJECTIVES

Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) play important roles in the process of mucosal repair and restitution, and their biological effects are mediated by receptors located on the target cell surfaces. The purpose of this study was to assess the effect of the antiulcer agent, ebrotidine, on the expression of EGF and PDGF receptors with chronic ulcer healing.

METHODS

Chronic gastric ulcers were developed in the rat by acetic acid technique. The animal were divided into two groups and were treated twice daily for 14 consecutive days, either with ebrotidine at 100 mg/kg, or placebo. At different stages of treatment, the animals were sacrificed and used for the isolation and quantification of gastric mucosal EGF and PDGF receptors.

RESULTS

The binding assays revealed that ulcer healing was accompanied by an increase in mucosal expression of both types of receptors. A 1.7-1.8-fold increase in PDGF and EGF receptors occurred by the 4th day after the development of ulcer and reached a maximum of 3-fold increase by the 14th day, when the ulcer was essentially healed. Treatment with ebrotidine caused accelerated ulcer healing (7 days) which was accompanied by a significant enhancement in receptor expression. Compared to the controls, a 1.5-fold increase in EGF and 1.7-fold increase in PDGF receptor expression occurred by the 7th day of ebrotidine treatment, and a 1.4- to 1.5-fold increase was still observed at the 14th day of treatment.

CONCLUSIONS

The results suggest that ebrotidine is capable of enhancement of gastric mucosal proliferative activities associated with ulcer healing through the stimulation of EGF and PDGF receptor expression.

Gastric mucosal laminin receptor expression with ulcer healing by ebrotidine

1. The effect of antiulcer agent, ebrotidine, on the expression of gastric mucosal laminin receptor during ulcer healing was investigated. 2. Rats with acetic acid-induced chronic gastric ulcers were treated twice daily for 14 consecutive days either with ebrotidine at 100 mg/kg or placebo, and then at different stages of treatment used for the isolation and quantitation of gastric mucosal laminin receptor. 3. The binding assays revealed that the ulcer healing was accompanied by an increase in mucosal expression of laminin receptor. A 2.7-fold increase in the receptor expression occurred by 4th day following the development of ulcer and reached a maximum of 8.6-fold increase by the 14th day when the ulcer was essentially healed. 4. Treatment with ebrotidine caused accelerated ulcer healing (7 days), which was accompanied by a remarkable enhancement in the laminin receptor expression. A 2.5-fold increase in the receptor expression over that of controls occurred by the 4th day of ebrotidine treatment, and a 1.7-fold increase was still observed at the 14th day of treatment. 5. The results suggest that ebrotidine, by evoking enhanced mucosal cell laminin receptor expression, promotes reepithelization and, hence, hastens the ulcer healing.

Enhancement in gastric mucosal epidermal growth factor receptor expression by sulglycotide

The effect of intragastric administration of sulglycotide, a cytoprotective sulfated glycopeptide, on the expression of gastric mucosal epidermal growth factor receptor was investigated. The experiments were conducted with groups of rats, one receiving twice daily for 5 consecutive days a dose of 200mg/kg sulglycotide, and the other only vehicle. Mucosal cell membranes were isolated from the stomachs at 16, 40 and 88h after the last dose, and used for EGF receptor assays. The binding assays revealed a marked increase in mucosal EGF receptor expression with sulglycotide. Compared to the controls, the sulglycotide-treated group showed a 4-fold increase in the EGF receptor expression at 16h after the last dose of sulglycotide, a 4.7-fold increase in the EGF receptor was observed by the 40h, and a 4.2-fold increase was still evident at 88h following the treatment. The results demonstrate that sulglycotide exhibits remarkable ability to enhance the gastric mucosal expression of EGF receptor.

Association of salivary bacterial aggregating activity with sulfomucin

The requirements of human salivary mucins for aggregating potential towards the common cariogenic oral bacteria, S. mutans and S. sanguis, were investigated. Agglutination inhibition assays demonstrated that the aggregating capacity towards bacteria resides in the acidic mucin fraction. The inhibitory activity of the acidic mucin decreased only 2-4-fold following removal of sialic acid, whereas the desulfation caused a complete loss of the inhibitory potential against both bacteria. Furthermore, the aggregating capacity of mucin-derived sulfated oligosaccharide was found to be 16-fold higher than that of the sialic acid containing oligosaccharide. The results point towards the importance of salivary sulfomucins as a predominant factor in the defense of oral cavity against cariogenic bacteria.

Regulation of gastric mucosal calcium channel activity by an antiulcer agent, ebrotidine

Ebrotidine is a new H2-receptor antagonist also known for its gastroprotective effect against ethanol-induced mucosal injury. In this study, we investigated the effect of ebrotidine on the activity of the gastric mucosal calcium channels. The channel complex was isolated from the solubilized gastric epithelial cell membranes by affinity chromatography on wheat germ agglutinin. The complex following labeling with [3H] PN200-110 was reconstituted into phosphatidylcholine vesicles which exhibited active 45Ca2+ uptake into intravesicular space and responded in a concentration-dependent manner to calcium channel activator, BAY K8644, as well as to calcium channel antagonist, PN200-100. The 45Ca2+ uptake was inhibited by ebrotidine which caused maximum inhibitory effect of 54.9% at 50 micrograms/ml. The gastric mucosal calcium channels on epidermal growth factor binding (EGF) in the presence of ATP responded by an increase in tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels displayed a 48% greater 45Ca2+ uptake. This phosphorylation process was inhibited by ebrotidine which also interfered with the binding of EGF to calcium channel protein. The results point towards the importance of EGF in the maintenance of gastric mucosal calcium homeostasis, and suggest that ebrotidine has the ability to protect the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastic mucosal calcium channel phosphorylation.

Sulglycotide effect on the proteolytic and lipolytic activities of Helicobacter pylori toward gastric mucus

OBJECTIVES

Infection with Helicobacter pylori is now recognized as a major factor in the etiology of gastric disease, and among the detrimental effects this bacterium exerts on the mucosal integrity is the elaboration of extracellular protease and lipase enzymes capable of mucus protein and lipids degradation. We present here evidence that the activities of these enzymes are inhibited by an gastroprotective agent, sulglycotide.

METHODS

The grown colonies of bacterium were washed with saline, filtered through sterilization filter, and the filtrate used as the enzyme source.

RESULTS

In the absence of sulglycotide, the H. pylori protease caused extensive degradation of human gastric mucus, while free fatty acids, glycerol monooleate and lysophosphatidylcholine were produced by the action of H. pylori lipase and phospholipase A enzymes. Introduction of sulglycotide to the incubation systems led to the reduction in the rate of mucus protein and lipid degradation. The rate of proteolysis inhibition was proportional to sulglycotide concentration up to 45 micrograms/ml, at which point a 43% reduction in mucus degradation was attained, whereas the maximum inhibition of lipase (39%) and phospholipase A (98%) activities occurred at a sulglycotide concentration of 100 micrograms/ml.

CONCLUSIONS

This study indicates that sulglycotide is capable of counteracting the mucolytic activity of H. pylori, and thus may be of value in the therapy of H. pylori-associated gastric diseases.

Characterization of gastric mucosal mucin receptor

Mucin receptor was isolated from gastric epithelial cell membrane by a procedure involving membrane solubilization with octylglucoside followed by affinity chromatography on Sepharose-bound wheat germ agglutinin. The receptor protein yielded on SDS-PAGE a single 97kDa band and displayed specific affinity, in a concentration-dependent manner, towards the mucin-coated surface. The receptor showed requirement for carbohydrate chains in mucin for binding, as their removal caused a marked (87%) reduction in binding capacity. Scatchard analysis revealed a linear plot with a single class of high affinity binding (Kd = 43.8 nM; Bmax = 140 pmol/mg protein) sites. The results demonstrate for the first time the presence in gastric mucosa of a specific receptor for mucin.

Helicobacter pylori lipopolysaccharide inhibition of gastric mucosal laminin receptor: effect of sulglycotide

1. The effect of cell-wall lipopolysaccharide from Helicobacter pylori, a bacterium implicated in the etiology of gastric disease, on the gastric mucosal laminin-receptor was investigated. 2. The receptor, isolated from gastric epithelial cell membrane by affinity chromatography on laminin-coupled Sepharose, was radioiodinated and incorporated into liposomes which exhibited specific affinity towards laminin-coated surface. 3. The binding of liposomal receptor to laminin-coated surface was inhibited by H. pylori lipopolysaccharide, which at 50 micrograms/ml caused a nearly complete (97%) inhibition in binding. 4. The inhibitory effect of the lipopolysaccharide was prevented by a cytoprotective agent, sulglycotide, that evoked a 92% restoration in binding at 40 micrograms/ml. 5. The results demonstrate that through its lipopolysaccharide H. pylori is capable of disrupting the gastric mucosal integrity and that this detrimental effect could be successfully countered by sulglycotide.

Inhibition of Helicobacter pylori glycosulfatase activity towards human gastric sulfomucin by a gastroprotective agent, sulglycotide

1. A glycosulfatase activity towards human gastric sulfomucin was identified in the extracellular material elaborated by Helicobacter pylori, a pathogen implicated in the etiology of gastric disease. 2. The purified enzyme displayed an apparent molecular weight of 30 kDa, and exhibited maximum activity at pH 5.7 in the presence of 0.3% Triton X-100 and 100 mM CaCl2. 3. The H. pylori glycosulfatase activity towards human gastric sulfomucin was inhibited by a gastroprotective agent, sulglycotide. The inhibitory effect was proportional to the concentration of sulglycotide up to 20 micrograms/ml, at which a 98% decrease in mucin desulfation occurred. However, the drug lost the inhibitory effect following its chemical desulfation. 4. The results demonstrate that sulglycotide is a potent inhibitor of H. pylori glycosulfatase and, hence, may be of value in the treatment of gastric disease associated with this bacterial infection.

Enhancement in gastric mucosal laminin receptor expression with ulcer healing

The expression of gastric mucosal laminin receptor with chronic ulcer healing was investigated. The receptor protein was isolated from gastric epithelial cell membrane of rats at various stages of ulcer healing and following radioiodination incorporated into vesicles which exhibited specific affinity towards laminin-coated surface. The binding assays revealed that the ulcer healing was accompanied by an increase in laminin receptor expression. A significant increase (2.5-fold) in the receptor expression occurred by the third day following the development of ulcer, reached a maximum of 8.6-fold increase by the 14th day when the ulcer was virtually healed, and its high level remained for at least 20 days. The results demonstrate the importance of laminin receptor as an indice of gastric mucosal repair in ulcer healing.

Regulation of buccal mucosal calcium channel activity by salivary mucins

1. The effect salivary mucins on the activity of calcium channel isolated from buccal mucosal cell membranes was investigated. The uptake of 45Ca2+ while only moderately (15%) affected by the intact low and high molecular weight mucin forms, was significantly inhibited, by the acidic low and high molecular weight salivary mucins which evoked 64 and 60% inhibition, respectively. 2. The inhibitory effect of salivary mucins was associated with the sialic acid and sulfate ester groups of the carbohydrate chains, as the removal of either group caused partial loss in the glycoproteins inhibition, and the complete loss in the inhibitory effect occurred following desialylation and desulfation. 3. The channel in the presence of epidermal growth factor (EGF) and ATP responded by an increase in tyrosine phosphorylation of 55 and 170 kDa proteins, and the phosphorylated channels showed a 46% increase in 45Ca2+ uptake. The phosphorylation and the calcium uptake were susceptible to inhibition by a specific tyrosine kinase inhibitor, genistein. 4. The binding of EGF to calcium channel receptor protein was inhibited by the low and high molecular weight acidic mucins, causing 41.2 and 36.1% reduction, respectively. This reduction in binding was dependent upon the presence of sulfate ester and sialic acid groups, as evidenced by the loss of the glycoproteins' inhibitory capacity following removal of these groups. 5. The results for the first time demonstrate that salivary mucins actively participate in the modulation of the EGF-controlled buccal mucosal calcium channel activity expression, a process of importance to the preservation of oral tissue integrity.

Effect of ebrotidine on gastric mucosal EGF and PDGF receptor expression

The effect of ebrotidine, a new H2-blocker with gastroprotective properties, on the expression of gastric mucosal epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) receptors, was investigated. Mucosal cell membranes were isolated from rats receiving twice daily for 5 days a dose of 100mg/kg ebrotidine or 100mg/kg ranitidine or vehicle only. Assays for EGF and PDGF revealed the presence of both types of receptors, activation of which led to enhanced tyrosine kinase activity. The receptor binding values in the control group were 2.4 fmol for EGF and 1.45 fmol/mg protein for PDGF, whereas the values in the ebrotidine group increased for EGF by 65.7% and 38.6% for PDGF, but no such effect was observed with ranitidine. The results suggest that the gastroprotective properties of ebrotidine stem from its ability to stimulate the epithelial proliferative activities through the enhancement of EGF and PDGF receptors expression.

Differential expression of salivary mucin bacterial aggregating activity with caries status

1. The low and high mol. wt mucin forms were isolated from saliva of caries-resistant (CR) and caries-susceptible (CS) individuals, and assessed for their bacterial aggregating potential towards S. mutans and S. sanguis, the common cariogenic microorganisms encountered in the oral cavity. 2. The high mol. wt mucin from both groups of subjects exhibited similar protein and carbohydrate content, but the level of covalently bound fatty acids was significantly lower in the CR group. The mucin from CR group showed only a weak inhibitory potential, and no inhibitory activity was observed with the mucin of CS group. 3. The low mol. wt mucins from both groups, while displaying compositional similarities, showed a marked variation in the bacterial aggregating activity. With both bacteria, the activity of the mucin from CR group was at least 128-fold greater than that of CS group. 4. The conversion of the high mol. wt mucin to a low mol. wt form through the action of salivary protease produced in both groups enhancement in mucin's bacterial aggregating capacity. This enhancement was, however, considerably less pronounced in the case of mucin from CS group. 5. The results for the first time demonstrate that the bacterial aggregating epitope of salivary mucins is expressed to a greater extent in CR individuals, and that this epitope is apparently more accessible to bacteria in the low mol. wt mucin form.

Effect of ebrotidine on gastric mucosal calcium channel activity

Ebrotidine is a new H2-receptor antagonist also known for its gastroprotective effect against ethanol-induced mucosal injury. In this study, we investigated the effect of ebrotidine on the activity of the gastric mucosal calcium channels. The channel complex was isolated from the solubilized gastric epithelial cell membranes by affinity chromatography on wheat germ agglutinin. After being labeled with [3H]PN200-110, the complex was reconstituted into phosphatidylcholine vesicles which exhibited active 45Ca2+ uptake into intravesicular space and responded in a concentration-dependent manner to calcium channel activator, BAY K8644, as well as to calcium channel antagonist, PN200-110. The 45Ca2+ uptake was inhibited by ebrotidine. Maximum inhibitory effect was attained at 50 micrograms/ml ebrotidine, at which point a 54.9% decrease in uptake occurred. The gastric mucosal calcium channels, on epidermal growth factor binding (EGF) in the presence of ATP, responded by an increase in tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels displayed a 48% greater 45Ca2+ uptake. This phosphorylation process was inhibited by ebrotidine. Furthermore, ebrotidine also interfered with the binding of EGF to calcium channel protein. The results point toward the importance of EGF in the maintenance of gastric mucosal calcium homeostasis, and suggest that ebrotidine has the ability to protect the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastric mucosal calcium channel phosphorylation.

Modulation of gastric mucosal calcium channel activity by mucus glycoprotein

1. The effect of gastric mucus glycoprotein on the activity of calcium channel isolated from gastric epithelial cell membrane was investigated. The 45Ca2+ uptake into the vesicle-reconstituted channels, while only moderately (14%) affected by the intact mucus glycoprotein, was found significantly inhibited (59%) by the acidic glycoprotein fraction. This effect was associated with the sialic acid and sulfate ester groups of the glycoprotein, as their removal caused a loss in the inhibition. 2. The channel complex in the presence of epidermal growth factor (EGF) and ATP responded by an increase in protein tyrosine phosphorylation of 55 and 170 kDa proteins, and the vesicles containing the phosphorylated channels showed a 50% increase in 45Ca2+ uptake. The phosphorylation and the calcium uptake were susceptible to inhibition by a specific tyrosine kinase inhibitor, genistein. 3. The channel protein phosphorylation was inhibited by the acidic mucus glycoprotein, which also interfered with the binding of EGF to the channel protein. The inhibitory effect was dependent upon the presence of sulfate ester and sialic acid groups, as evidenced by the loss of the glycoprotein inhibitory capacity following their removal. 4. The results suggest that the acidic gastric mucus glycoproteins, by modulating the EGF-controlled calcium channel phosphorylation, play a major role in gastric mucosal calcium homeostasis.

Control of mucin molecular forms expression by salivary protease: differences with caries

1. A protease activity capable of degradation of the high mol. wt salivary mucus glycoprotein to a low mol. wt glycoprotein form was identified in human submandibular gland secretion. 2. The protease exhibited optimum activity at pH 7.0-7.4, and gave on SDS-PAGE under reducing conditions two major protein bands of 48 and 53 kDa. The enzyme showed susceptibility to PMSF, alpha 1antitrypsin, and egg white and soybean inhibitors, a characteristic typical to serine proteases. 3. The activity of the protease towards the high mol. wt mucus glycoprotein was found to be 3.8-fold higher in submandibular gland secretion of caries-resistant individuals than that of caries-susceptible. Furthermore, the enzyme from both groups displayed greater activity against the mucus glycoprotein of caries-resistant subjects. 4. Since the low mol. wt salivary mucus glycoprotein form is more efficient in bacterial clearance than the high mol. wt mucin, the enhanced expression of this indigenous salivary protease activity towards mucin may be the determining factor in the resistance to caries.

Inhibition of Helicobacter pylori colonization by an antiulcer agent, sulglycotide

Sulglycotide, a potent antiulcer agent derived from duodenal mucus glycopeptide through sulfation of the carbohydrate moieties, was evaluated with respect to its ability to interfere with H. pylori mucosal attachment. H. pylori cells were incubated with sulglycotide or human gastric mucin and then examined for their inhibitory capacity of H. pylori attachment to erythrocytes. Titration data revealed that the mucin inhibitory activity was confined to its sulfomucin fraction, the titer of which was found to be 16-fold higher than that of intact mucin. The data with sulglycotide showed that the inhibitory titer of this agent against H. pylori attachment was at least 30-fold higher than that of the sulfated gastric mucin fraction. The results point towards the involvement of sulfomucins in the protection of gastric mucosa from H. pylori colonization and demonstrate that sulglycotide, because of structural similarities, is ideally suited to augment the inherent mucosal defenses against this pathogen.

Expression of salivary mucin bacterial aggregating activity: difference with caries

The low and high molecular weight mucin forms were isolated from saliva of individuals with different caries status and assessed for their bacterial aggregating potential towards S. mutans and S. sanguis. The high molecular weight mucin from both groups exhibited similar protein and carbohydrate content, but the level of covalently bound fatty acids was lower in the caries-resistant group. The mucin from caries-resistant group showed only a weak inhibitory potential, while no inhibitory activity was observed with the mucin of caries-susceptible group. The low molecular weight mucins from both groups, while displaying compositional similarities, showed a marked variation in the bacterial aggregating activity, and the titer of the mucin from caries-resistant group was at least 128-fold greater than that of caries-susceptible group. The results demonstrate that the bacterial aggregating epitope of salivary mucins is expressed to a greater extent in caries-resistant individuals, and that this epitope is apparently more accessible to bacteria in the low molecular weight mucin form.

Identification of human salivary protease activity toward mucin: differences with caries

A protease activity directed toward high molecular weight salivary mucus glycoprotein was identified in the secretion of human submandibular salivary gland. The protease exhibited maximum activity at pH 7.0-7.4, and following ammonium sulfate fractionation yielded an active enzyme at 60% saturation which on SDS-PAGE gave 48 and 53kDa protein bands. The enzyme exhibited serine-protease properties by showing susceptibility to phenyl methyl sulfonyl fluoride, alpha 1-antitrypsin, and egg white and soybean inhibitors. The protease activity in submandibular saliva of caries-resistant subjects was found to be 3.8-fold greater than that in saliva of caries-susceptible individuals, thus suggesting that the enzyme expression may be linked to the resistance to caries.

Does feedback regulation of pancreatic enzyme secretion by duodenal trypsin exist in cholecystectomized patients?

Recent studies have supported the existence of a feedback regulation of pancreatic enzyme secretion in man. The aim of present study was to evaluate whether a feedback regulation of pancreatic enzyme secretion exists in cholecystectomized patients. The study was carried out in 12 healthy volunteers and in 6 cholecystectomized patients, 7-14 years (mean 9 years) after the operation. Pancreatic secretion was stimulated by intraduodenal infusion of L-phenylalanine (100 mmo 1.1-1). The calculated outputs of pancreatic alpha-amylase and lipase were estimated. The feedback phenomenon was studied using consecutive intraduodenal infusion of trypsin (300 mg/h) and aprotinin (1.5 x 10(6) KIU/30 min). In 6 healthy persons, the infusion of trypsin caused a significant decrease (35-45%) in phenylalaninestimulated alpha-amylase and lipase outputs (p less than 0.05). This effect was completely reversed by intraduodenal aprotinin infusion. In contrast, the increase or the inhibition of tryptic activity in the duodenum was without any effect on pancreatic secretion in cholecystectomized patients. A feedback control of pancreatic secretion could not be demonstrated in patients 6-14 years after cholecystectomy.

Effect of duodenal trypsin on pancreatic secretion in men

The effect of tryptic activity in duodenum on L-phenylalanine (100 mmol.1-1 intraduodenally) stimulated pancreatic secretion in 18 healthy volunteers has been evaluated. Intraduodenal infusion of trypsin (150 mg) during 1 h caused the reduction of alpha-amylase and lipase output by ca 30%. The infusion of aprotinin at the dose of 0.5.10(6) KIU during 30 min caused return of the alpha-amylase and lipase output to the pretryptic values. The infusion of trypsin in higher dose (300 mg) caused more pronounced decrease of amylase and lipase output (ca 45%). Our data indicate that active trypsin in duodenum is responsible for the inhibition of L-phenylalanine stimulated pancreatic enzyme secretion in man. These results corroborate the existence of feedback regulation of stimulated pancreatic secretion by intraduodenal trypsin in man.

Feedback regulation of stimulated pancreatic enzyme secretion during intraduodenal perfusion of trypsin in man

The pancreatic enzyme secretion in several species is controlled by a negative feedback mechanism induced by the presence of active proteases in the duodenum. The existence of this mechanism in man is controversial. The purpose of the present study was to evaluate the effect of tryptic activity in the duodenum on phenylalanine-stimulated pancreatic enzyme secretion in healthy volunteers. A double-balloon, multi-lumen tube was used for the collection of duodenal juice containing pancreatic enzymes. The continuous infusion of phenylalanine (100 mM) into the duodenum evoked an almost constant secretion of trypsin, amylase and lipase for 160 min. The infusion of trypsin (150 mg h-1; 1.25 g l-1) caused a reduction of phenylalanine-stimulated amylase and lipase output by 25%. The subsequent infusion of aprotinin at a dose of 1.5 X 10(6) KIU for 30 min led to an almost complete inhibition of trypsin. Simultaneously, the amylase and lipase output returned to the values seen before trypsin perfusion. Infusion of a higher dose of trypsin (300 mg h-1; 2.5 g l-1) caused a more pronounced decrease in phenylalanine-stimulated amylase and lipase output by 45%. These data indicate that active trypsin in the duodenum is responsible for the inhibition of phenylalanine-stimulated pancreatic enzyme secretion in man in a dose-dependent fashion, thus confirming the existence of a feedback control of pancreatic secretion regulated by the amount of proteases in the gut.