Carmen Correale

Unique role of junctional adhesion molecule-a in maintaining mucosal homeostasis in inflammatory bowel disease.

BACKGROUND & AIMS Junctional adhesion molecule-A (JAM-A) is localized at the tight junctions and controls leukocyte migration into the tissues. However, its functional role in inflammatory bowel disease (IBD) is unexplored. METHODS Control, Crohns disease (CD), and ulcerative colitis (UC) tissue specimens were studied for JAM-A expression, as well as the colon of mice given dextran sodium sulfate (DSS). Wild-type and JAM-A(-/-), Tie-2-Cre-JAM-A(-/-) (endothelial/hematopoietic-specific JAM inactivation) mice were studied for susceptibility to DSS. Disease activity and colonic inflammation were assessed using a disease activity index histology and endoscopy, and mucosal cytokines were measured by enzyme-linked immunosorbent assay. JAM-A function was investigated by RNA silencing in epithelial cells, and apoptosis was measured. RESULTS In both CD and UC, as well as in experimental colitis, there is a loss of epithelial but not endothelial JAM-A expression. Deletion of JAM-A results in a dramatic increase in susceptibility to DSS colitis, as assessed by weight loss, disease activity index, histologic and endoscopic severity, and strikingly high mortality rates. This is not caused by the absence of JAM-A in the endothelial or hematopoietic compartments because Tie-2-Cre-JAM-A(-/-) mice are no more susceptible to DSS colitis than wild-type animals. JAM-A(-/-) mice displayed increased intestinal permeability and inflammatory cytokine production, and marked epithelial apoptosis. Silencing of JAM-A in intestinal epithelial cells resulted in increased permeability in vitro. CONCLUSIONS Our results show a nonredundant and novel role of JAM-A in controlling mucosal homeostasis by regulating the integrity and permeability of epithelial barrier function.

The lymphatic system controls intestinal inflammation and inflammation-associated colon cancer through the chemokine decoy receptor D6

Background and aims Inflammatory CC chemokines have long been associated with cancer, but unequivocal evidence of a role in clinically relevant models of carcinogenesis is lacking. D6, a promiscuous decoy receptor that scavenges inflammatory CC chemokines, plays a non-redundant role in reducing the inflammatory response in various organs. As inflammation is a key player in the development of inflammatory bowel disease (IBD) and IBD-associated colorectal cancer, we investigated D6 expression in human colitis and colon cancer, and its role in experimental colitis and inflammation-associated colon cancer. Results In humans, D6 was mainly expressed by lymphatic vessels and leukocytes in the mucosa of individuals with IBD and colon cancer, as well as the mucosa of control individuals. Mice lacking expression of D6 were significantly more susceptible to experimental colitis than wild-type mice and failed to resolve colitis, with significantly higher levels of several pro-inflammatory chemokines. In bone marrow chimeric mice, the ability of D6 to regulate colitis was tracked to the stromal/lymphatic compartment, with no contribution of haemopoietic cells. Finally, after administration of the carcinogen azoxymethane, D6−/− mice showed increased susceptibility to colitis-associated cancer in the distal segment of the colon compared with wild-type mice. Conclusions D6 expressed on lymphatic vessels plays a key role in the control of intestinal inflammation and the development of inflammation-associated colon cancer. Our results reveal a new unexpected role for the lymphatic system in the pathogenesis of IBD and intestinal cancer, and candidate chemokines as novel players in tumour promotion and progression.

Coenzyme Q10 in Neuromuscular and Neurodegenerative Disorders

Coenzyme Q10 (CoQ10, or ubiquinone) is an electron carrier of the mitochondrial respiratory chain (electron transport chain) with antioxidant properties. In view of the involvement of CoQ10 in oxidative phosphorylation and cellular antioxidant protection a deficiency in this quinone would be expected to contribute to disease pathophysiology by causing a failure in energy metabolism and antioxidant status. Indeed, a deficit in CoQ10 status has been determined in a number of neuromuscular and neurodegenerative disorders. Primary disorders of CoQ10 biosynthesis are potentially treatable conditions and therefore a high degree of clinical awareness about this condition is essential. A secondary loss of CoQ10 status following HMG-Coa reductase inhibitor (statins) treatment has be implicated in the pathophysiology of the myotoxicity associated with this pharmacotherapy. CoQ10 and its analogue, idebenone, have been widely used in the treatment of neurodegenerative and neuromuscular disorders. These compounds could potentially play a role in the treatment of mitochondrial disorders, Parkinsons disease, Huntingtons disease, amyotrophic lateral sclerosis, Friedreichs ataxia, and other conditions which have been linked to mitochondrial dysfunction. This article reviews the physiological roles of CoQ10, as well as the rationale and the role in clinical practice of CoQ10 supplementation in different neurological and muscular diseases, from primary CoQ10 deficiency to neurodegenerative disorders. We also briefly report a case of the myopathic form of CoQ10 deficiency.

Multiple Pathogenic Roles of Microvasculature in Inflammatory Bowel Disease: A Jack of All Trades

The etiology of Crohns disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD), is still largely unknown. However, it is now clear that the abnormalities underlying pathogenesis of intestinal inflammation are not restricted to those mediated by classic immune cells but also involve nonimmune cells. In particular, advances in vascular biology have outlined a central and multifaceted pathogenic role for the microcirculation in the initiation and perpetuation of IBD. The microcirculation and its endothelial lining play a crucial role in mucosal immune homeostasis through tight regulation of the nature and magnitude of leukocyte migration from the intravascular to the interstitial space. Chronically inflamed IBD microvessels display significant alterations in microvascular physiology and function compared with vessels from healthy and uninvolved IBD intestine. The investigation into human IBD has demonstrated how endothelial activation present in chronically inflamed IBD microvessels results in a functional phenotype that also includes leakiness, chemokine and cytokine expression, procoagulant activity, and angiogenesis. This review contemplates the newly uncovered contribution of intestinal microcirculation to pathogenesis and maintenance of chronic intestinal inflammation. In particular, we assess the multiple roles of the microvascular endothelium in innate immunity, leukocyte recruitment, coagulation and perfusion, and immune-driven angiogenesis in IBD.

VEGF-C–dependent stimulation of lymphatic function ameliorates experimental inflammatory bowel disease

Crohns disease (CD) and ulcerative colitis (UC) are chronic inflammatory bowel diseases (IBDs) of unknown etiology that are associated with an aberrant mucosal immune response. Neoangiogenesis and vascular injury are observed in IBD along with increased lymphangiogenesis. While the pathogenic role of angiogenesis in IBD is well characterized, it is not clear how or if increased lymphangiogenesis promotes disease. Here, we determined that enhancing lymphangiogenesis and lymphatic function reduces experimental IBD. Specifically, we demonstrated that adenoviral induction of prolymphangiogenic factor VEGF-C provides marked protection against the development of acute and chronic colitis in 2 different animal models. VEGF-C-dependent protection was observed in combination with increased inflammatory cell mobilization and bacterial antigen clearance from the inflamed colon to the draining lymph nodes. Moreover, we found that the VEGF-C/VEGFR3 pathway regulates macrophage (MΦ) plasticity and activation both in cultured MΦs and in vivo, imparting a hybrid M1-M2 phenotype. The protective function of VEGF-C was meditated by the so-called resolving MΦs during chronic experimental colitis in a STAT6-dependent manner. Together, these findings shed light on the contribution of lymphatics to the pathogenesis of gut inflammation and suggest that correction of defective lymphatic function with VEGF-C has potential as a therapeutic strategy for IBD.

Efficacy of a potent and safe vitamin D receptor agonist for the treatment of inflammatory bowel disease

Deficiency in 1alpha,25-dihydroxyvitamin D(3) (1,25D(3)) has been suggested as an important environmental factor for immuno-mediated disorders including inflammatory bowel diseases (IBD), comprising Crohns disease and ulcerative colitis, both characterized by chronic intestinal inflammation. Administration of vitamin D receptor (VDR) agonists can ameliorate spontaneous and induced animal models of colitis, but hypercalcemia is a dose-limiting adverse event. Previous work in our laboratory has identified 1alpha,25(OH)(2)-16-ene-20-cyclopropyl-vitamin D(3) (BXL-62) as a potent anti-inflammatory VDR agonist with a low calcemic activity. In the present study, we confirm the marked anti-inflammatory properties of BXL-62 and show its capacity to induce VDR primary response genes, like CYP24A1 and CAMP, at lower concentrations than 1,25D(3), in PBMCs from IBD patients. Its higher anti-inflammatory potency compared to 1,25D(3) was demonstrated by the significantly more potent inhibition in PBMCs and in lymphocyte-enriched lamina propria mononuclear cells of the pro-inflammatory cytokines TNF-alpha, IL-12/23p40, IL-6 and IFN-gamma, both at mRNA and protein level. The therapeutic efficacy of intra-rectal administration of BXL-62 in experimental IBD is shown by its beneficial effects, significantly higher than 1,25D(3), to induce recovery of clinical symptoms of colitis at normocalcemic doses in mice undergoing dextran sodium sulfate-induced colitis. These results confirm the therapeutic efficacy of VDR agonists in experimental colitis, and suggest BXL-62 as a promising compound for IBD treatment.

The role of MAPK in governing lymphocyte adhesion to and migration across the microvasculature in inflammatory bowel disease

Lymphocyte recruitment is a key pathogenic event in inflammatory bowel disease (IBD). Adhesion of T cells to human intestinal microvascular endothelial cells (HIMEC) is mediated by ICAM‐1, VCAM‐1 and fractalkine (FKN), but the signaling molecules that orchestrate this process have yet to be identified. Because MAPK play an important role in the response of many cell types to pro‐inflammatory stimuli, we assessed the functional role of p38 MAPK, p42/44 MAPK and JNK in the regulation of lymphocyte adhesion to and chemotaxis across the microvasculature in IBD. We found that the MAPK were phosphorylated in the bowel microvasculature and human intestinal fibroblasts of patients with IBD but not of healthy individuals. Stimulation of HIMEC with TNF‐α triggered phosphorylation of the MAPK, and up‐regulation of VCAM‐1, FKN and ICAM‐1. Blockade of p38 decreased the expression of all MAPK by 50% (p<0.01), whereas inhibition of p42/44 decreased the expression of ICAM‐1 and FKN by 50% (p<0.01). Treatment of human intestinal fibroblasts with TNF‐α elicited production of IL‐8 and MCP‐1, which was reduced (p<0.05) by blockade of p38 and p42/44. Finally, blockade of p38 and p42/44 reduced lymphocyte adhesion to (p<0.05) and transmigration across (p<0.05) HIMEC monolayers. These findings suggest a critical role for MAPK in governing lymphocyte influx into the gut in IBD patients, and their blockade may offer a molecular target for blockade of leukocyte recruitment to the intestine.

Infliximab Therapy Inhibits Inflammation-Induced Angiogenesis in the Mucosa of Patients With Crohn's Disease

OBJECTIVES:Inflammation-driven angiogenesis contributes to the pathogenesis of inflammatory bowel disease (IBD). In line with this, the efficacy of inhibitors of angiogenesis has been demonstrated in experimental models of colitis. Currently, the ability of infliximab, an anti-tumor necrosis factor-α (TNF-α) agent that is highly beneficial in patients with IBD, to affect mucosal angiogenesis in patients with Crohns disease (CD) and ulcerative colitis (UC) is unknown.METHODS:Patients with active CD (n=14) were treated with infliximab for 1 year, and peripheral blood and intestinal mucosa samples were collected before and after treatment. Mucosal angiogenesis was evaluated by CD31 and Ki-67 staining in endoscopic biopsies at baseline (week 0) and at week 54. The release of vascular endothelial growth factor-A (VEGF-A) by cultured mucosal extracts was measured by enzyme-linked immunosorbent assay (ELISA), before and after administration of infliximab, as well as in cultures of human intestinal fibroblasts (HIFs) stimulated with TNF-α in the presence or absence of infliximab. Migration of human intestinal microvascular endothelial cells (HIMECs) was investigated by migration assays.RESULTS:Microvessel density was significantly higher in the mucosa from patients with CD compared with tissue from healthy control individuals. Of the 14 patients, 8 (57%) showed a clinical remission in response to infliximab, which was associated with a significant reduction of microvascular density. Morphometric vessel analysis further confirmed the significant reduction of the area of vascular section after administration of infliximab. Furthermore, the expression levels of the proliferation marker Ki-67 in endothelial cells were significantly reduced after treatment. The mucosal concentration of VEGF-A was also significantly decreased, whereas in vitro exposure of HIF to infliximab virtually abolished TNF-α-induced VEGF-A production. These phenomena did not occur in patients who showed no clinical response to infliximab.CONCLUSIONS:Administration of infliximab downregulates mucosal angiogenesis in patients with CD and restrains production of VEGF-A by mucosal fibroblasts. It is proposed that this ameliorates inflammation-driven angiogenesis in the gut mucosa and contributes to the therapeutic efficacy of blockade of TNF-α.

Unexpected role of anticoagulant protein C in controlling epithelial barrier integrity and intestinal inflammation

The protein C (PC) pathway is a well-characterized coagulation system. Endothelial PC receptors and thrombomodulin mediate the conversion of PC to its activated form, a potent anticoagulant and anti-inflammatory molecule. Here we show that the PC pathway is expressed on intestinal epithelial cells. The epithelial expression of PC and endothelial PC receptor is down-regulated In patients with inflammatory bowel disease. PC−/−/PC(Tg) mice, expressing only 3% of WT PC, developed spontaneous intestinal inflammation and were prone to severe experimental colitis. These mice also demonstrated spontaneous elevated production of inflammatory cytokines and increased intestinal permeability. Structural analysis of epithelial tight junction molecules revealed that lack of PC leads to decreased JAM-A and claudin-3 expression and an altered pattern of ZO-1 expression. In vitro, treatment of epithelial cells with activated PC led to protection of tight junction disruption induced by TNF-α, and in vivo, topical treatment with activated PC led to mucosal healing and amelioration of colitis. Taken together, these findings demonstrate that the PC pathway is a unique system involved in controlling intestinal homeostasis and inflammation by regulating epithelial barrier function.

Intestinal fibrosis in Crohn's disease: medical treatment or surgery?

Crohns disease (CD) is a chronic panenteric disease of unknown aethiology tending to progress, inspite medical or surgical treatment. Intestinal fibrosis is among the most common complications of CD, resulting in stricture formation in the small intestine and colon. About 75% of CD patients will undergo surgery at least once over the course of their disease and fibrotic strictures represents the main indication for surgery and the first cause of hospitalization and costs for CD patients. Clinical management of intestinal strictures depends on the type of stricture: inflammatory strictures are treated medically and are usually responsive to treatment, while fibrotic strictures require surgery. Clinical decisions regarding the right treatment choice for such conditions require proper knowledge on what to expect from the emerging drug strategies and surgical techniques. To achieve optimal results in patients management an approach combining the expertise of both gastroenterologist and colorectal surgeon is essential. This review aims at providing clinicians with an overview on fibrotic strictures in CD patients particular focus will be placed on the principal imaging modalities, and the medical, endoscopic and surgical treatment options with relative indications, according to the most recent evidence available.