Postoperative ileus after digestive surgery: Network meta-analysis of pharmacological intervention

AIMS

Several medicinal treatments for avoiding postoperative ileus (POI) after abdominal surgery have been evaluated in randomized controlled trials (RCTs). This network meta-analysis aimed to explore the relative effectiveness of these different treatments on ileus outcome measures.

METHODS

A systematic literature review was performed to identify RCTs comparing treatments for POI following abdominal surgery. A Bayesian network meta-analysis was performed. Direct and indirect comparisons of all regimens were simultaneously compared using random-effects network meta-analysis.

RESULTS

A total of 38 RCTs were included in this network meta-analysis reporting on 6371 patients. Our network meta-analysis shows that prokinetics significantly reduce the duration of first gas (mean difference [MD] = 16 h; credible interval -30, -3.1; surface under the cumulative ranking curve [SUCRA] 0.418), duration of first bowel movements (MD = 25 h; credible interval -39, -11; SUCRA 0.25) and duration of postoperative hospitalization (MD -1.9 h; credible interval -3.8, -0.040; SUCRA 0.34). Opioid antagonists are the only treatment that significantly improve the duration of food recovery (MD -19 h; credible interval -26, -14; SUCRA 0.163).

CONCLUSION

Based on our meta-analysis, the 2 most consistent pharmacological treatments able to effectively reduce POI after abdominal surgery are prokinetics and opioid antagonists. The absence of clear superiority of 1 treatment over another highlights the limits of the pharmacological principles available.

S. aureus drives itch and scratch-induced skin damage through a V8 protease-PAR1 axis

Itch is an unpleasant sensation that evokes a desire to scratch. The skin barrier is constantly exposed to microbes and their products. However, the role of microbes in itch generation is unknown. Here, we show that Staphylococcus aureus, a bacterial pathogen associated with itchy skin diseases, directly activates pruriceptor sensory neurons to drive itch. Epicutaneous S. aureus exposure causes robust itch and scratch-induced damage. By testing multiple isogenic bacterial mutants for virulence factors, we identify the S. aureus serine protease V8 as a critical mediator in evoking spontaneous itch and alloknesis. V8 cleaves proteinase-activated receptor 1 (PAR1) on mouse and human sensory neurons. Targeting PAR1 through genetic deficiency, small interfering RNA (siRNA) knockdown, or pharmacological blockade decreases itch and skin damage caused by V8 and S. aureus exposure. Thus, we identify a mechanism of action for a pruritogenic bacterial factor and demonstrate the potential of inhibiting V8-PAR1 signaling to treat itch.

PAR-1 Antagonism to Promote Gut Mucosa Healing in Crohn's Disease Patients: A New Avenue for CVT120165

A new paradigm has been added for the treatment of inflammatory bowel diseases such as Crohn's disease and ulcerative colitis. In addition to resolving symptoms and inflammatory cell activation, the objective of tissue repair and mucosal healing is also now considered a primary goal. In the search of mediators that would be responsible for delayed mucosal healing, protease-activated receptor-1 (PAR-1) has emerged as a most interesting target. Indeed, in Crohn's disease, the endogenous PAR-1 agonist thrombin is drastically activated. Activation of PAR-1 is known to be associated with epithelial dysfunctions that hamper mucosal homeostasis. This review gathers the scientific evidences of a potential role for PAR-1 in mucosal damage and mucosal dysfunctions associated with chronic intestinal inflammation. The potential clinical benefits of PAR-1 antagonism to promote mucosal repair in CD patients are discussed. Targeted local delivery of a PAR-1 antagonist molecule such as CVT120165, a formulated version of the FDA-approved PAR-1 antagonist vorapaxar, at the mucosa of Crohn's disease patients could be proposed as a new indication for IBD that could be rapidly tested in clinical trials.

Increased Mucosal Thrombin is Associated with Crohn's Disease and Causes Inflammatory Damage through Protease-activated Receptors Activation

BACKGROUND AND AIMS

Thrombin levels in the colon of Crohn's disease patients have recently been found to be elevated 100-fold compared with healthy controls. Our aim was to determine whether and how dysregulated thrombin activity could contribute to local tissue malfunctions associated with Crohn's disease.

METHODS

Thrombin activity was studied in tissues from Crohn's disease patients and healthy controls. Intracolonic administration of thrombin to wild-type or protease-activated receptor-deficient mice was used to assess the effects and mechanisms of local thrombin upregulation. Colitis was induced in rats and mice by the intracolonic administration of trinitrobenzene sulphonic acid.

RESULTS

Active forms of thrombin were increased in Crohn's disease patient tissues. Elevated thrombin expression and activity were associated with intestinal epithelial cells. Increased thrombin activity and expression were also a feature of experimental colitis in rats. Colonic exposure to doses of active thrombin comparable to what is found in inflammatory bowel disease tissues caused mucosal damage and tissue dysfunctions in mice, through a mechanism involving both protease-activated receptors -1 and -4. Intracolonic administration of the thrombin inhibitor dabigatran, as well as inhibition of protease-activated receptor-1, prevented trinitrobenzene sulphonic acid-induced colitis in rodent models.

CONCLUSIONS

Our data demonstrated that increased local thrombin activity, as it occurs in the colon of patients with inflammatory bowel disease, causes mucosal damage and inflammation. Colonic thrombin and protease-activated receptor-1 appear as possible mechanisms involved in mucosal damage and loss of function and therefore represent potential therapeutic targets for treating inflammatory bowel disease.

A48 COLITIS FAVORS THE EXPANSION OF BACTERIA THAT ACTIVATE PAR2 AMPLIFYING INFLAMMATORY RESPONSE

Background

Proteolytic imbalance has been described in patients with inflammatory bowel disease (IBD) and in different models of experimental colitis. Although the proteases reported to be increased are mainly from the host, the role of bacterial proteases has recently emerged, as they can promote inflammation, in part, through activation of Protease-activated receptors (PARs). PAR2 deficient mice are resistant to inflammation and PAR2 activation affects multiple aspects of the tissue response to injury. However, PAR2 communicates with other receptors such as toll-like and other PARs, which are important in multiple immune signaling pathways. Thus, the direct implication of PAR2 in colitis, and specifically the activation of the external domain by microbial proteases, remains unclear.

Aims

To study the role of PAR2 and bacterial proteases in experimental colitis.

Methods

C57BL/6 and protease-resistant PAR2 (R38E-PAR2) mice, in which activation site of PAR2 is missing, were given 3.5% dextran sodium sulfate (DSS) in drinking water for 5 days followed by 2 days of water. Control C57BL/6 (wild-type) and R38E-PAR2 mice received only water. Percent weight change was evaluated along the study. Fecal microbiota (16S Ilumina), expression of proinflammatory genes (Nanostring), gut permeability (Ussing chamber), proteolytic activities (colorimetric assay) and bacterial translocation (plating) were measured in all mice at sacrifice. Inflammation was determined by analyzing stool consistency, fecal blood and by microscopic scores (Cooper score). Bacteria with proteolytic activity were isolated using agar-media with protein as main nutrient and bacterial capacity to release the external domain of PAR2 was tested in cells harbouring luciferase at the PAR2 N terminus.

Results

Wild-type, but not R38E-PAR2 mice, had increased expression of several pro-inflammatory genes, such as tnf, map3k and tlr, gut dysfunction and increased intestinal permeability, increased bacterial translocation into spleen and altered microbiota profiles following DSS treatment. DSS induced colitis in both mouse strains, but clinical and microscopic scores were significantly lower in R38E-PAR2 compared with wild-type mice. DSS increased the abundance of opportunistic pathogens such as Enterococcus and Staphylococcus only in wild-type mice. Proteolytic phenotype of these bacteria, and their capacity to cleave the external domain of PAR2, was confirmed.

Conclusions

Mice lacking the activation site of PAR2 are protected from DSS-induced colitis. DSS treatment leads to expansion of bacteria releasing active proteases, which may mediate injury through PAR2. These results suggest that intestinal injury promotes microbial proteolytic imbalance which in turn, exacerbates inflammation.

Funding Agencies

CAG, CCC, CIHR

Epithelial expression and function of trypsin-3 in irritable bowel syndrome

OBJECTIVES

Proteases are key mediators of pain and altered enteric neuronal signalling, although the types and sources of these important intestinal mediators are unknown. We hypothesised that intestinal epithelium is a major source of trypsin-like activity in patients with IBS and this activity signals to primary afferent and enteric nerves and induces visceral hypersensitivity.

DESIGN

Trypsin-like activity was determined in tissues from patients with IBS and in supernatants of Caco-2 cells stimulated or not. These supernatants were also applied to cultures of primary afferents. mRNA isoforms of trypsin (PRSS1, 2 and 3) were detected by reverse transcription-PCR, and trypsin-3 protein expression was studied by western blot analysis and immunohistochemistry. Electrophysiological recordings and Ca²⁺ imaging in response to trypsin-3 were performed in mouse primary afferent and in human submucosal neurons, respectively. Visceromotor response to colorectal distension was recorded in mice administered intracolonically with trypsin-3.

RESULTS

We showed that stimulated intestinal epithelial cells released trypsin-like activity specifically from the basolateral side. This activity was able to activate sensory neurons. In colons of patients with IBS, increased trypsin-like activity was associated with the epithelium. We identified that trypsin-3 was the only form of trypsin upregulated in stimulated intestinal epithelial cells and in tissues from patients with IBS. Trypsin-3 was able to signal to human submucosal enteric neurons and mouse sensory neurons, and to induce visceral hypersensitivity in vivo, all by a protease-activated receptor-2-dependent mechanism.

CONCLUSIONS

In IBS, the intestinal epithelium produces and releases the active protease trypsin-3, which is able to signal to enteric neurons and to induce visceral hypersensitivity.

Protectin D1n-3 DPA and resolvin D5n-3 DPA are effectors of intestinal protection

The resolution of inflammation is an active process orchestrated by specialized proresolving lipid mediators (SPM) that limit the host response within the affected tissue; failure of effective resolution may lead to tissue injury. Because persistence of inflammatory signals is a main feature of chronic inflammatory conditions, including inflammatory bowel diseases (IBDs), herein we investigate expression and functions of SPM in intestinal inflammation. Targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics was used to identify SPMs from n-3 polyunsaturated fatty acids in human IBD colon biopsies, quantifying a significant up-regulation of the resolvin and protectin pathway compared with normal gut tissue. Systemic treatment with protectin (PD)1n-3 DPA or resolvin (Rv)D5n-3 DPA protected against colitis and intestinal ischemia/reperfusion-induced inflammation in mice. Inhibition of 15-lipoxygenase activity reduced PD1n-3 DPA and augmented intestinal inflammation in experimental colitis. Intravital microscopy of mouse mesenteric venules demonstrated that PD1n-3 DPA and RvD5n-3 DPA decreased the extent of leukocyte adhesion and emigration following ischemia-reperfusion. These data were translated by assessing human neutrophil-endothelial interactions under flow: PD1n-3 DPA and RvD5n-3 DPA reduced cell adhesion onto TNF-α-activated human endothelial monolayers. In conclusion, we propose that innovative therapies based on n-3 DPA-derived mediators could be developed to enable antiinflammatory and tissue protective effects in inflammatory pathologies of the gut.

Transgenic kallikrein 5 mice reproduce major cutaneous and systemic hallmarks of Netherton syndrome

Netherton syndrome (NS) is a severe genetic skin disease in which absence of a key protease inhibitor causes congenital exfoliative erythroderma, eczematous-like lesions, and atopic manifestations. Several proteases are overactive in NS, including kallikrein-related peptidase (KLK) 5, KLK7, and elastase-2 (ELA2), which are suggested to be part of a proteolytic cascade initiated by KLK5. To address the role of KLK5 in NS, we have generated a new transgenic murine model expressing human KLK5 in the granular layer of the epidermis (Tg-KLK5). Transgene expression resulted in increased proteolytic activity attributable to KLK5 and its downstream targets KLK7, KLK14, and ELA2. Tg-KLK5 mice developed an exfoliative erythroderma with scaling, growth delay, and hair abnormalities. The skin barrier was defective and the stratum corneum was detached through desmosomal cleavage. Importantly, Tg-KLK5 mice displayed cutaneous and systemic hallmarks of severe inflammation and allergy with pruritus. The skin showed enhanced expression of inflammatory cytokines and chemokines, infiltration of immune cells, and markers of Th2/Th17/Th22 T cell responses. Moreover, serum IgE and Tslp levels were elevated. Our study identifies KLK5 as an important contributor to the NS proteolytic cascade and provides a new and viable model for the evaluation of future targeted therapies for NS or related diseases such as atopic dermatitis.

Engineering lactococci and lactobacilli for human health

Food-grade lactic acid bacteria (LAB) are good candidates for the development of oral vectors, and are attractive alternatives to attenuated pathogens, for mucosal delivery strategies. In this review, we summarize recent results on the use of LAB as mucosal delivery vectors for therapeutic proteins and DNA vaccines. Most of this work has been based on the model LAB, Lactococcus lactis, which is suitable for the heterologous expression of therapeutic proteins. Recombinant lactococci and lactobacilli strains expressing antiproteases and antioxidant enzymes have been tested successfully for their prophylactic and therapeutic effects in murine models of colitis. Recombinant lactococci secreting autoantigens have been found to be effective for the treatment of type 1 diabetes. Also, recombinant lactococci delivering DNA were able to prevent a bovine β-lactoglobulin (BLG)-allergic reaction in mice. We believe that these various coherent findings demonstrate the potential value of using LAB, particularly lactococci and lactobacilli strains, to develop novel vectors for the therapeutic delivery of proteins to mucosal surfaces. Further tests and in particular human clinical trials are now important next steps to conclude on the benefit of these approaches for human health.

LEKTI fragments specifically inhibit KLK5, KLK7, and KLK14 and control desquamation through a pH-dependent interaction

LEKTI is a 15-domain serine proteinase inhibitor whose defective expression underlies the severe autosomal recessive ichthyosiform skin disease, Netherton syndrome. Here, we show that LEKTI is produced as a precursor rapidly cleaved by furin, generating a variety of single or multidomain LEKTI fragments secreted in cultured keratinocytes and in the epidermis. The identity of these biological fragments (D1, D5, D6, D8-D11, and D9-D15) was inferred from biochemical analysis, using a panel of LEKTI antibodies. The functional inhibitory capacity of each fragment was tested on a panel of serine proteases. All LEKTI fragments, except D1, showed specific and differential inhibition of human kallikreins 5, 7, and 14. The strongest inhibition was observed with D8-D11, toward KLK5. Kinetics analysis revealed that this interaction is rapid and irreversible, reflecting an extremely tight binding complex. We demonstrated that pH variations govern this interaction, leading to the release of active KLK5 from the complex at acidic pH. These results identify KLK5, a key actor of the desquamation process, as the major target of LEKTI. They disclose a new mechanism of skin homeostasis by which the epidermal pH gradient allows precisely regulated KLK5 activity and corneodesmosomal cleavage in the most superficial layers of the stratum corneum.

Cloning and characterization of a gut-specific cathepsin L from the aphid Aphis gossypii

We have characterized proteinase activities in gut extracts from the cotton-melon aphid (Aphis gossypii Glover), an insect feeding strictly on protein-poor phloem. The major, if not exclusive, intestinal proteinases of this aphid are of the cysteine type. A cDNA has been cloned from a gut library and codes for the cysteine proteinase AgCatL, a cathepsin L-like cysteine proteinase. The AgCatL protein shows high sequence similarity with mammalian and some arthropod cathepsin L-like proteinases, but can be reliably distinguished from the secreted (digestive) proteinases identified in other arthropods. AgCatL is widely expressed in aphid intestinal cells. Immunolocalization of AgCatL showed an intense signal at the level of the anterior 'stomach' part of the midgut, and especially at intracellular localization. Although the precise role of AgCatL in aphid midgut physiology is still unclear, this enzyme could be involved in the processing of exogenous ingested polypeptides.

Midgut adaptation and digestive enzyme distribution in a phloem feeding insect, the pea aphid Acyrthosiphon pisum

Transmission electron micrographs of the pea aphid midgut revealed that its anterior region has cells with an apical complex network of lamellae (apical lamellae) instead of the usual regularly-arranged microvilli. These apical lamellae are linked to one another by trabeculae. Modified perimicrovillar membranes (MPM) are associated with the lamellae and project into the lumen. Trabeculae and MPM become less conspicuous along the midgut. The most active A. pisum digestive enzymes are membrane-bound. An aminopeptidase (APN) is described elsewhere. An alpha-glucosidase (alpha-Glu) has a molecular mass of 72 kDa, pH optimum 6.0 and catalyzes in vitro transglycosylations in the presence of an excess of the substrate sucrose. There is a major cysteine proteinase activity (CP) on protein substrates that has a molecular mass of 40 kDa, pH optimum 5.5, is inhibited by E-64 and chymostatin and is activated by EDTA+cysteine. The enzyme is more active against carbobenzoxy-Phe-Arg-4-methylcoumarin-7-amide (ZFRMCA) than against ZRRMCA. These features identify the purified CP as a cathepsin-L-like cysteine proteinase. Most CP is found in the anterior midgut, whereas alpha-Glu and APN predominate in the posterior midgut. With the aid of antibodies, alpha-Glu and CP were immunolocalized in cell vesicles and MPM, whereas APN was localized in vesicles, apical lamellae and MPM. The data suggest that the anterior midgut is structurally reinforced to resist osmotic pressures and that the transglycosylating alpha-Glu, together with CP and APN are bound to MPM, thus being both distributed over a large surface and prevented from excretion with honeydew. alpha-Glu frees glucose from sucrose without increasing the osmolarity, and CP and APN may process toxins or other proteins occasionally present in phloem.