Mesalazine granules promote disease clearance in patients with mild-to-moderate ulcerative colitis.

BACKGROUND: Over the past decade, treatment targets for ulcerative colitis (UC) have become more stringent, incorporating multiple parameters. Recently, the concept of 'disease clearance'-defined as combined clinical, endoscopic, and histological remission-has been proposed as an ultimate endpoint in treating UC. OBJECTIVE: To determine the rates of disease clearance in patients with mild-to-moderate UC treated with different doses of mesalazine granules as induction therapy. METHODS: In a post hoc analysis, data were pooled from four randomised, active-controlled, phase 3 clinical trials in patients with mild-to-moderate UC receiving 8-week induction therapy with mesalazine granules at daily doses of 1.5, 3.0 or 4.5 g. Rates of clinical, endoscopic, and histological remission were determined using stringent criteria and used to calculate rates of the composite endpoints of clinical plus endoscopic remission, endoscopic plus histological remission, and disease clearance (clinical plus endoscopic plus histological remission). RESULTS: A total of 860 patients were included in the analysis. Among the total population, 20.0% achieved disease clearance with mesalazine granules: 13.1% in patients receiving 1.5 g mesalazine granules/day, 21.8% in those receiving 3.0 g/day and 18.9% in those receiving 4.5 g/day. Among patients with moderate UC, 16.8% achieved disease clearance: 7.1% with 1.5 g/day, 18.8% with 3.0 g/day and 16.2% with 4.5 g/day. CONCLUSION: Disease clearance, proposed to be predictive of improved long-term outcomes, can be achieved in a clinically meaningful proportion of mild-to-moderate UC patients treated with mesalazine granules. A daily dose of 3.0 g appears optimal to reach this target.

Membrane Fusion Mediated by Non-covalent Binding of Re-engineered Cholera Toxin Assemblies to Glycolipids.

Membrane fusion is essential for the transport of macromolecules and viruses across membranes. While glycan-binding proteins (lectins) often initiate cellular adhesion, subsequent fusion events require additional protein machinery. No mechanism for membrane fusion arising from simply a protein binding to membrane glycolipids has been described thus far. Herein, we report that a biotinylated protein derived from cholera toxin becomes a fusogenic lectin upon cross-linking with streptavidin. This novel reengineered protein brings about hemifusion and fusion of vesicles as demonstrated by mixing of fluorescently labeled lipids between vesicles as well as content mixing of liposomes filled with fluorescently labeled dextran. Exclusion of the complex at vesicle-vesicle interfaces could also be observed, indicating the formation of hemifusion diaphragms. Discovery of this fusogenic lectin complex demonstrates that new emergent properties can arise from simple changes in protein architecture and provides insights into new mechanisms of lipid-driven fusion.

The Lectin LecB Induces Patches with Basolateral Characteristics at the Apical Membrane to Promote Pseudomonas aeruginosa Host Cell Invasion.

The opportunistic bacterium Pseudomonas aeruginosa can infect mucosal tissues of the human body. To persist at the mucosal barrier, this highly adaptable pathogen has evolved many strategies, including invasion of host cells. Here, we show that the P. aeruginosa lectin LecB binds and cross-links fucosylated receptors at the apical plasma membrane of epithelial cells. This triggers a signaling cascade via Src kinases and phosphoinositide 3-kinase (PI3K), leading to the formation of patches enriched with the basolateral marker phosphatidylinositol (3,4,5)-trisphosphate (PIP3) at the apical plasma membrane. This identifies LecB as a causative bacterial factor for activating this well-known host cell response that is elicited upon apical binding of P. aeruginosa. Downstream from PI3K, Rac1 is activated to cause actin rearrangement and the outgrowth of protrusions at the apical plasma membrane. LecB-triggered PI3K activation also results in aberrant recruitment of caveolin-1 to the apical domain. In addition, we reveal a positive feedback loop between PI3K activation and apical caveolin-1 recruitment, which provides a mechanistic explanation for the previously observed implication of caveolin-1 in P. aeruginosa host cell invasion. Interestingly, LecB treatment also reversibly removes primary cilia. To directly prove the role of LecB for bacterial uptake, we coated bacterium-sized beads with LecB, which drastically enhanced their endocytosis. Furthermore, LecB deletion and LecB inhibition with l-fucose diminished the invasion efficiency of P. aeruginosa bacteria. Taken together, the results of our study identify LecB as a missing link that can explain how PI3K signaling and caveolin-1 recruitment are triggered to facilitate invasion of epithelial cells from the apical side by P. aeruginosa. IMPORTANCE An intriguing feature of the bacterium P. aeruginosa is its ability to colonize highly diverse niches. P. aeruginosa can, besides forming biofilms, also enter and proliferate within epithelial host cells. Moreover, research during recent years has shown that P. aeruginosa possesses many different mechanisms to invade host cells. In this study, we identify LecB as a novel invasion factor. In particular, we show that LecB activates PI3K signaling, which is connected via a positive feedback loop to apical caveolin-1 recruitment and leads to actin rearrangement at the apical plasma membrane. This provides a unifying explanation for the previously reported implication of PI3K and caveolin-1 in host cell invasion by P. aeruginosa. In addition, our study adds a further function to the remarkable repertoire of the lectin LecB, which is all brought about by the capability of LecB to recognize fucosylated glycans on many different niche-specific host cell receptors.

Bacterial lectin BambL acts as a B cell superantigen.

B cell superantigens crosslink conserved domains of B cell receptors (BCRs) and cause dysregulated, polyclonal B cell activation irrespective of normal BCR-antigen complementarity. The cells typically succumb to activation-induced cell death, which can impede the adaptive immune response and favor infection. In the present study, we demonstrate that the fucose-binding lectin of Burkholderia ambifaria, BambL, bears functional resemblance to B cell superantigens. By engaging surface glycans, the bacterial lectin activated human peripheral blood B cells, which manifested in the surface expression of CD69, CD54 and CD86 but became increasingly cytotoxic at higher concentrations. The effects were sensitive to BCR pathway inhibitors and excess fucose, which corroborates a glycan-driven mode of action. Interactome analyses in a model cell line suggest BambL binds directly to glycans of the BCR and regulatory coreceptors. In vitro, BambL triggered BCR signaling and induced CD19 internalization and degradation. Owing to the lectin's six binding sites, we propose a BCR activation model in which BambL functions as a clustering hub for receptor glycans, modulates normal BCR regulation, and induces cell death through exhaustive activation.

Efficacy and safety of prolonged release budesonide granules in mesalazine-refractory ulcerative colitis: A multi-centre Phase IIa study (TOPICAL-1).

BACKGROUND: In patients with mesalazine-refractory ulcerative colitis, systemic corticosteroids are the treatment of choice. OBJECTIVE: To evaluate the efficacy and safety of prolonged release budesonide granules for the induction of remission in patients with mesalazine-refractory ulcerative colitis. METHODS: Patients with mesalazine-refractory ulcerative colitis discontinued mesalazine at baseline and received 9 mg prolonged release budesonide granules daily for 8 weeks in this open-label, phase IIa study, followed by a 2-week follow-up phase wherein patients continued treatment on alternate days (EudraCT number 2014-005635-14; ClinicalTrials.gov identifier NCT02550418). The primary endpoint was clinical remission (Clinical Activity Index ≤4; stool frequency <18 per week; absence of rectal bleeding) at Week 8. Secondary endpoints included clinical, endoscopic and histological measures of disease at Week 8. A post hoc analysis assessed histo-endoscopic mucosal healing. Treatment-emergent adverse events and morning cortisol levels were assessed throughout the treatment and follow-up phases. RESULTS: A total of 61 patients were included in the intention-to-treat population; 50 were included in the follow-up analysis set. Clinical remission was achieved in 29 patients (47.5%; 95% confidence interval: 34.6-60.7%) by Week 8. Mean stool and bloody stool frequency decreased significantly from 32.5 to 22.9 per week (p<0.0001) and from 17.6 to 8.1 per week (p<0.0001), respectively. Rates of mucosal healing, endoscopic remission and histological remission were 58.0%, 54.0% and 36.0%, respectively. Histo-endoscopic mucosal healing was achieved by 34.0% of patients. Twenty-four patients (39.3%) experienced treatment-emergent adverse events, of which gastrointestinal disorders (16.4%) were the most common. Mean morning cortisol levels were not significantly suppressed by Week 8. CONCLUSIONS: Treatment with prolonged release budesonide granules for 8 weeks was associated with clinical, endoscopic and histological remission and demonstrated a favourable safety profile in patients with mesalazine-refractory ulcerative colitis. These results warrant further investigation into the potential of prolonged release budesonide granules as an alternative treatment for this patient population.

The Pseudomonas aeruginosa Lectin LecB Causes Integrin Internalization and Inhibits Epithelial Wound Healing.

The opportunistic bacterium Pseudomonas aeruginosa produces the fucose-specific lectin LecB, which has been identified as a virulence factor. LecB has a tetrameric structure with four opposing binding sites and has been shown to act as a cross-linker. Here, we demonstrate that LecB strongly binds to the glycosylated moieties of ß1-integrins on the basolateral plasma membrane of epithelial cells and causes rapid integrin endocytosis. Whereas internalized integrins were degraded via a lysosomal pathway, washout of LecB restored integrin cell surface localization, thus indicating a specific and direct action of LecB on integrins to bring about their endocytosis. Interestingly, LecB was able to trigger uptake of active and inactive ß1-integrins and also of complete α3ß1-integrin-laminin complexes. We provide a mechanistic explanation for this unique endocytic process by showing that LecB has the additional ability to recognize fucose-bearing glycosphingolipids and causes the formation of membrane invaginations on giant unilamellar vesicles. In cells, LecB recruited integrins to these invaginations by cross-linking integrins and glycosphingolipids. In epithelial wound healing assays, LecB specifically cleared integrins from the surface of cells located at the wound edge and blocked cell migration and wound healing in a dose-dependent manner. Moreover, the wild-type P. aeruginosa strain PAO1 was able to loosen cell-substrate adhesion in order to crawl underneath exposed cells, whereas knockout of LecB significantly reduced crawling events. Based on these results, we suggest that LecB has a role in disseminating bacteria along the cell-basement membrane interface.IMPORTANCEPseudomonas aeruginosa is a ubiquitous environmental bacterium that is one of the leading causes of nosocomial infections. P. aeruginosa is able to switch between planktonic, intracellular, and biofilm-based lifestyles, which allows it to evade the immune system as well as antibiotic treatment. Hence, alternatives to antibiotic treatment are urgently required to combat P. aeruginosa infections. Lectins, like the fucose-specific LecB, are promising targets, because removal of LecB resulted in decreased virulence in mouse models. Currently, several research groups are developing LecB inhibitors. However, the role of LecB in host-pathogen interactions is not well understood. The significance of our research is in identifying cellular mechanisms of how LecB facilitates P. aeruginosa infection. We introduce LecB as a new member of the list of bacterial molecules that bind integrins and show that P. aeruginosa can move forward underneath attached epithelial cells by loosening cell-basement membrane attachment in a LecB-dependent manner.