A key claudin extracellular loop domain is critical for epithelial barrier integrity

Intercellular tight junctions (TJs) regulate epithelial barrier properties. Claudins are major structural constituents of TJs and belong to a large family of tetra-spanning membrane proteins that have two predicted extracellular loops (ELs). Given that claudin-1 is widely expressed in epithelia, we further defined the role of its EL domains in determining TJ function. The effects of several claudin-1 EL mimetic peptides on epithelial barrier structure and function were examined. Incubation of model human intestinal epithelial cells with a 27-amino acid peptide corresponding to a portion of the first EL domain (Cldn-1(53-80)) reversibly interfered with epithelial barrier function by inducing the rearrangement of key TJ proteins: occludin, claudin-1, junctional adhesion molecule-A, and zonula occludens-1. Cldn-1(53-80) associated with both claudin-1 and occludin, suggesting both the direct interference with the ability of these proteins to assemble into functional TJs and their close interaction under physiological conditions. These effects were specific for Cldn-1(53-80), because peptides corresponding to other claudin-1 EL domains failed to influence TJ function. Furthermore, the oral administration of Cldn-1(53-80) to rats increased paracellular gastric permeability. Thus, the identification of a critical claudin-1 EL motif, Cldn-1(53-80), capable of regulating TJ structure and function, offers a useful adjunct to treatments that require drug delivery across an epithelial barrier.

Ala657 and Conserved Active Site Residues Promote Fibroblast Activation Protein Endopeptidase Activity via Distinct Mechanisms of Transition State Stabilization

Fibroblast activation protein (FAP) and dipeptidyl peptidase-4 (DPP-4) are highly homologous serine proteases of the prolyl peptidase family and therapeutic targets for cancer and diabetes, respectively. Both proteases display dipeptidyl peptidase activity, but FAP alone has endopeptidase activity. FAP Ala657, which corresponds to DPP-4 Asp663, is important for endopeptidase activity; however, its specific role remains unclear, and it is unknown whether conserved DPP-4 substrate binding residues support FAP endopeptidase activity. Using site-directed mutagenesis and kinetic analyses, we show here that Ala657 and five conserved active site residues (Arg123, Glu203, Glu204, Tyr656, and Asn704) promote FAP endopeptidase activity via distinct mechanisms of transition state stabilization (TSS). The conserved residues provide marked TSS energy for both endopeptidase and dipeptidyl peptidase substrates, and structural modeling supports their function in binding both substrates. Ala657 also stabilizes endopeptidase substrate binding and additionally dictates FAP reactivity with transition state inhibitors, allowing tight interaction with tetrahedral intermediate analogues but not acyl-enzyme analogues. Conversely, DPP-4 Asp663 stabilizes dipeptidyl peptidase substrate binding and permits tight interaction with both transition state analogues. Structural modeling suggests that FAP Ala657 and DPP-4 Asp663 confer their contrasting effects on TSS by modulating the conformation of conserved residues FAP Glu204 and DPP-4 Glu206. FAP therefore requires the combined function of Ala657 and the conserved residues for endopeptidase activity.

Synthesis and structure–activity relationship of N-acyl-Gly-, N-acyl-Sar- and N-blocked-boroPro inhibitors of FAP, DPP4, and POP

The structure-activity relationship of various N-acyl-Gly-, N-acyl-Sar-, and N-blocked-boroPro derivatives against three prolyl peptidases was explored. Several N-acyl-Gly- and N-blocked-boroPro compounds showed low nanomolar inhibitory activity against fibroblast activation protein (FAP) and prolyl oligopeptidase (POP) and selectivity against dipeptidyl peptidase-4 (DPP4). N-Acyl-Sar-boroPro analogs retained selectivity against DPP4 and potent POP inhibitory activity but displayed decreased FAP inhibitory activity.

The familial risk of acne vulgaris in Chinese Hans ? a case-control study

BACKGROUND

Acne is a chronic inflammatory disease of the pilosebaceous follicles. Recent studies bring us increasing evidences that hereditary factors play an important but indirect role in acne.

OBJECTIVE

To investigate the possible role of genetic factors in the pathogenesis of acne vulgaris in Chinese Han ethnic group.

PATIENTS AND METHODS

Volunteers of 975 acne cases and 580 controls were included, contributing 3009 and 1825 first-degree relatives, respectively. One thousand and eighty-five first-degree relatives of acne cases were affected with facial acne. This compared with 223 first-degree relatives of non-acne controls. The odds ratio was used to estimate the relative risk for acne vulgaris associated with having an affected first-degree relative.

RESULTS

The risk of acne vulgaris occurring in a relative of a patient with acne vulgaris was significantly greater than for the relative of an unaffected individual (odds ratio 4.05, 95% confidence interval (CI): 3.45-4.76, P<0.001).

CONCLUSION

Our study suggests that familial factors are important in determining individual susceptibility to acne vulgaris.

A prospective investigation of outcomes after hospital discharge for endemic, community-acquired methicillin-resistant and -susceptible Staphylococcus aureus skin infection

BACKGROUND

Although community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection has become increasingly common, prospective data on outcomes of patients with skin infection remain poorly defined.

METHODS

We prospectively observed a cohort of 201 patients discharged after hospitalization for CA-MRSA infection or community-acquired methicillin-susceptible S. aureus (CA-MSSA) infection. Patients were interviewed 30 and 120 days after they received a diagnosis. Our primary outcome was clinical response, defined as no relapse, new S. aureus infection, or need for antibiotics at day 30.

RESULTS

Among 117 patients with skin infection, the nonresponse rate at day 30 was similar among patients with CA-MRSA infection and those with CA-MSSA infection (23 [33%] of 70 vs. 13 [28%] of 47 patients; P=.55). Lack of incision and drainage was associated with nonresponse at day 30 (P=.005), but other clinical factors, including receipt of antibiotics inactive against the infecting strain, were not. Patients with CA-MSSA infection were more likely to be rehospitalized (P=.003) and to believe subjectively that they had not been cured (P=.002) at day 30. At day 30, there was a trend for close contacts of CA-MRSA-infected patients to develop a similar infection (13% vs. 4%; odds ratio, 3.3; 95% confidence interval, 0.7-15.8; P=.2).

CONCLUSION

Although it is believed patients with CA-MRSA skin infection may have more serious outcomes than those with CA-MSSA skin infection, we found similar outcomes in these 2 groups after hospital discharge. Clinical nonresponse at day 30 was associated with a lack of receipt of incision and drainage. Our data also suggest that close contacts of persons with CA-MRSA skin infection may have a higher likelihood of acquiring an infection.

Sensitivity and inter-observer variability for capsule endoscopy image analysis in a cohort of novice readers

AIM: To determine the performance of novice readers (4^th year medical students) for detecting capsule endoscopy findings.

METHODS: Ten capsule endoscopy cases of small bowel lesions were administered to the readers. Gold standard findings were pre-defined by gastroenterologists. Ten gold standard “targets” were identified among the 10 cases. Readers were given a 30-min overview of Rapid Reader software and instructed to mark any potential areas of abnormalities. A software program was developed using SAS to analyze the thumbnailed findings.

RESULTS: The overall sensitivity for detecting the gold standard findings was 80%. As a group, at least 5 out of 10 readers detected each gold standard finding per recording. All the gold standard targets were identified when the readers’ results were combined. Incidental finding/false positive rate ranged between 8.2-59.8 per reader.

CONCLUSION: A panel of medical students with minimal endoscopic experience can achieve high sensitivity in detecting lesions on capsule endoscopy. A group of novice readers can pre-screen recordings to thumbnail potential areas of small bowel lesions for further review. These thumbnails must be reviewed to determine the clinical relevance. Further studies are ongoing to assess other cohorts.

Peptide substrate profiling defines fibroblast activation protein as an endopeptidase of strict Gly(2)-Pro(1)-cleaving specificity

Fibroblast activation protein (FAP) is a serine protease of undefined endopeptidase specificity implicated in tumorigenesis. To characterize FAP's P(4)-P(2)(') specificity, we synthesized intramolecularly quenched fluorescent substrate sets based on the FAP cleavage site in alpha(2)-antiplasmin (TSGP-NQ). FAP required substrates with Pro at P(1) and Gly or d-amino acids at P(2) and preferred small, uncharged amino acids at P(3), but tolerated most amino acids at P(4), P(1)(') and P(2)('). These substrate preferences allowed design of peptidyl-chloromethyl ketones that inhibited FAP, but not the related protease, dipeptidyl peptidase-4. Thus, FAP is a narrow specificity endopeptidase and this can be exploited for inhibitor design.

Selective inhibition of fibroblast activation protein protease based on dipeptide substrate specificity

Fibroblast activation protein (FAP) is a transmembrane serine peptidase that belongs to the prolyl peptidase family. FAP has been implicated in cancer; however, its specific role remains elusive because inhibitors that distinguish FAP from other prolyl peptidases like dipeptidyl peptidase-4 (DPP-4) have not been developed. To identify peptide motifs for FAP-selective inhibitor design, we used P(2)-Pro(1) and acetyl (Ac)-P(2)-Pro(1) dipeptide substrate libraries, where P(2) was varied and substrate hydrolysis occurs between Pro(1) and a fluorescent leaving group. With the P(2)-Pro(1) library, FAP preferred Ile, Pro, or Arg at the P(2) residue; however, DPP-4 showed broad reactivity against this library, precluding selectivity. By contrast, with the Ac-P(2)-Pro(1) library, FAP cleaved only Ac-Gly-Pro, whereas DPP-4 showed little reactivity with all substrates. FAP also cleaved formyl-, benzyloxycarbonyl-, biotinyl-, and peptidyl-Gly-Pro substrates, which DPP-4 cleaved poorly, suggesting an N-acyl-Gly-Pro motif for inhibitor design. Therefore, we synthesized and tested the compound Ac-Gly-prolineboronic acid, which inhibited FAP with a K(i) of 23 +/- 3 nm. This was approximately 9- to approximately 5400-fold lower than the K(i) values for other prolyl peptidases, including DPP-4, DPP-7, DPP-8, DPP-9, prolyl oligopeptidase, and acylpeptide hydrolase. These results identify Ac-Gly-BoroPro as a FAP-selective inhibitor and suggest that N-acyl-Gly-Pro-based inhibitors will allow testing of FAP as a therapeutic target.

Production of phytase in a low phosphate medium by a novel yeast Candida krusei

A yeast strain producing high levels of phytase was isolated from soil and identified as Candida krusei. The phytase was located on the yeast cell wall and was a glucanase-extractable protein. The phytase production was controlled by the phosphate concentration in the medium used. The maximum production of phytase occurred in a medium containing 0.5 mg of phosphorus per 100 ml, and most of the cells were ellipsoid-shaped and did not exhibit budding. Increasing the concentration of phosphorus in the medium to more than 5 mg of phosphorus per 100 ml caused inhibition of phytase production and 90% of the cells exhibited budding. On the other hand, transferring cells grown in the high-phosphate medium into a phosphate-free one derepressed the phytase production. For example, transferring cells grown in 2 mg of phosphorus per 100 ml into the phosphate-free medium, enhanced the total phytase activity up to 5.5-fold that in the medium containing 0.5 mg of phosphorus per 100 ml. The phytase showed two optimum pHs of 2.5 and 5.5, an optimum temperature of 40 degrees C and the K(m) value for Na-phytate was 0.03 mM. Using in vitro experiments that simulated the conditions of the digestive tract, 50-80% phosphorus was liberated from different plant samples (wheat bran, rice bran and feeds) by the strain.

Association of upper and lower gastrointestinal tract symptoms with body mass index in an Australian cohort

Food modulates gastrointestinal (GI) function and GI symptoms could alter food intake, but it is not established whether or not obese people experience more or less GI symptoms. We aimed at evaluating the association between body mass index (BMI) and specific GI symptoms in the community. Population-based random samples from Sydney, Australia (n = 777) completed a validated questionnaire. The association of each GI symptom with BMI (kg m(-2)) categories was assessed using logistic regression analysis adjusting for potential confounders. The prevalence of obesity (BMI > or =30 kg m(-2)) was 22%. There were univariate associations (adjusting for age, sex, education level, alcohol and smoking) between increased BMI category and heartburn (OR = 1.9, 95% CI 1.4, 2.5), acid regurgitation (OR = 2.1, 95% CI 1.4, 2.9), increased bloating (OR = 1.3, 95%CI 1.1, 1.6), increased stool frequency (OR = 1.4, 95% CI 1.1, 1.7), loose and watery stools (OR = 1.5, 95% CI 1.1, 2.0) and upper abdominal pain (OR = 1.3, 95% CI 1.03, 1.6). Early satiety was associated with a lower BMI category but this was not significant after adjustment (OR = 0.8, 95% CI 0.6, 1.1). Lower abdominal pain, postprandial fullness, nausea and vomiting were not associated with BMI category. In a regression model adjusting for sex, education, smoking, alcohol and all GI symptoms, older age, less early satiety and increased stool frequency and heartburn were all independently associated with increasing BMI (all P < 0.01). Heartburn and diarrhoea were associated with increased BMI, while early satiety was associated with a lower BMI in this population.

Non-destructive characterization of resin-based filling materials using Electronic Speckle Pattern Interferometry

OBJECTIVES

The aim of this study was to develop a non-destructive test for characterizing the modulus of resin-based filling materials.

METHODS

Five different visible-light-cured composites (Filtek A110 [AO], Z100 [ZO], Filtek Z250 [ZT], F2000 [FT] and Filtek Flow [FF]; 3M-ESPE) were selected for this study. An ESPI (Electronic Speckle Pattern Interferometry) apparatus involving cantilever beam specimens (28 mm long, 8 mm wide and 2 mm thick) was developed for determining modulus. Out-of-plane displacement upon force application was measured using two focus region lengths (22 mm [EI1]; 11 mm [EI2]) and modulus (n = 7) was subsequently computed based on cantilever beam equations. Data was compared to those obtained from three-point-bend flexural testing (n = 7) based on ISO4049:2000 specifications [ISO]. Specimens were stored in distilled water at 37 degrees C for 1 week prior to evaluation for all tests. Results were analyzed using ANOVA/Scheffe's post-hoc tests (p < 0.05) and Pearson's correlation (p < 0.01).

RESULTS

Modulus ranged from 5.53 to 13.99, 5.78 to 14.24 and 4.26 to 11.30 GPa for EI1, EI2 and ISO, respectively. For all three tests, the modulus of ZO and FT was significantly greater than ZT, which in turn was significantly greater than AO and FF. Correlation of EI1 and EI2 to ISO was significant, positive and very strong (r = 0.94 for EI1 and EI2).

SIGNIFICANCE

ESPI may be a viable method of characterizing the modulus of resin-based filling materials. As it is a non-destructive test, time-dependent effects of composites can be determined using the same specimens leading to substantial time and material savings.

Development and validation of the Diabetes Bowel Symptom Questionnaire

BACKGROUND

Although gastrointestinal symptoms occur frequently, there is no validated measure of gastrointestinal symptoms in patients with diabetes mellitus.

AIM

To develop the Diabetes Bowel Symptom Questionnaire.

METHODS

A questionnaire derived from previously validated symptom measures was compiled to assess all relevant gastrointestinal and diabetes items. Face and content validity were ascertained by expert review. One hundred and sixty-eight patients with diabetes mellitus completed the instrument, and reliability was evaluated by a test-re-test procedure 1 week later. Concurrent validity was evaluated by an independent physician interview (n = 33). Measures of glycaemic control (glycated haemoglobin and plasma glucose) were compared with self-reported glycaemic control on a five-point Likert scale in diabetic out-patients (n = 166).

RESULTS

The questionnaire had adequate face and content validity. There was good to excellent test-re-test reliability for the gastrointestinal and diabetes items (median kappa: 0.63 and 0.79, respectively); concurrent validity was good to excellent (median kappa: 0.47 and 0.65, respectively), except for the items assessing the severity of gastrointestinal symptoms. Both glycated haemoglobin (P < 0.0001) and plasma glucose (P = 0.005) correlated significantly with self-reported glycaemic control.

CONCLUSION

The Diabetes Bowel Symptom Questionnaire appears to be a useful measure of gastrointestinal symptoms and glycaemic control in diabetes mellitus, and should have applicability in epidemiological and clinical studies.

Review article: Helicobacter pylori and nonulcer dyspepsia

Although up to 50% of patients diagnosed with nonulcer dyspepsia (NUD) have Helicobacter pylori infection and underlying chronic gastritis, it remains controversial whether any causal relationship exists. The results of worldwide epidemiological studies have been unconvincing. No clear-cut link has been documented between H. pylori and any specific symptom profile or pathophysiological mechanism in NUD. In the randomized controlled trials, methodological weaknesses may explain in part the conflicting results, but even in the well-conducted trials controversy persists. Although meta-analyses have attempted to resolve the issue, inherent methodological difficulties with meta-analysis remain a problem. Moreover, even the methodologically sound meta-analyses have reported conflicting results. In addition, predictors of treatment response remain obscure, and there continue to be theoretical concerns about the treatment of H. pylori infection in all patients with NUD. Hence, the management of these patients is challenging, but eradication of H. pylori infection may be beneficial in a small subgroup of cases with NUD that cannot be identified before treatment.

[Properties of mucosal antibodies]

Mucosal antibodies consist of a variety of molecules, including secretory IgA and local IgG, involved in the first immune barrier of defence against pathogens. They account for the majority of daily synthesized immunoglobulins in the body and mostly depend on the secretory immune system which is independent from its systemic counterpart. Acting by immune exclusion and immune elimination, these immunoglobulins correspond to preimmune poly-reactive natural antibodies and to antigen-induced antibodies. Recent progress in this field have suggested new approaches of mucosal vaccines preventing the entry of pathogens in the body.