Innate immune environment in ileal pouch mucosa: α5 defensin up-regulation as predictor of chronic/relapsing pouchitis

Pouchitis: pathophysiology and management

Pouchitis is an acute or chronic inflammatory disease of the ileal reservoir. It is common after restorative proctocolectomy with ileal pouch-anal anastomosis, and treatment of chronic antibiotic-refractory pouchitis has proven challenging. Most cases of acute pouchitis evolve into chronic pouchitis. The aetiology of acute pouchitis is likely to be partly related to the gut microbiota, whereas the pathophysiology of chronic pouchitis involves abnormal interactions between genetic disposition, faecal stasis, the gut microbiota, dysregulated host immunity, surgical techniques, ischaemia and mesentery-related factors. Pouchoscopy with biopsy is the most valuable modality for diagnosis, disease monitoring, assessment of treatment response, dysplasia surveillance and delivery of endoscopic therapy. Triggering or risk factors, such as Clostridioides difficile infection and use of non-steroidal anti-inflammatory drugs, should be modified or eradicated. In terms of treatment, acute pouchitis usually responds to oral antibiotics, whereas chronic antibiotic-refractory pouchitis often requires induction and maintenance therapy with integrin, interleukin or tumour necrosis factor inhibitors. Chronic pouchitis with ischaemic features, fistulae or abscesses can be treated with hyperbaric oxygen therapy.

Oral administration of Lactobacillus casei DG® after ileostomy closure in restorative proctocolectomy: a randomized placebo-controlled trial (microbiota and immune microenvironment in pouchitis -MEP1)

Pouchitis is an idiopathic inflammatory disease that may occur in ileal pouches, and it can lead to ileal pouch failure. This was a single-center, randomized, double-blinded, placebo-controlled trial that assessed the effect of Lactobacillus casei (L. casei) DG®, a probiotic strain, on the ileal pouch mucosa to determine the crosstalk between microbiota and mucosal immune system. Fifty-two patients undergoing restorative proctocolectomy were recruited and randomly assigned to receive a daily oral supplementation of L. casei DG® (n = 26) or placebo (n = 26) for 8 weeks from the ileostomy closure (T0) to a pouch endoscopy after 8 weeks (T1) and 1 year (T2). Ileal pouch mucosa samples were collected at T0, T1, and T2. At T1, the L. casei DG®-supplemented group showed a significant reduction of inflammatory cytokines levels compared to T0 baseline levels in the pouch mucosa, whereas in the placebo group cytokines levels resulted stable. In conclusion, probiotic manipulation of mucosal microbiota by L. casei DG®-supplementation after stoma closure in patients who underwent restorative proctocolectomy has a beneficial impact on the ileal pouch microenvironment. Registration number: NCT03136419 (http://www.clinicaltrials.gov).

Pouchitis Is Associated with Paneth Cell Dysfunction and Ameliorated by Exogenous Lysosome in a Rat Model Undergoing Ileal Pouch Anal Anastomosis

BACKGROUND

Pouchitis is a common complication of restorative proctocolectomy and ileal pouch anal anastomosis (IPAA) for ulcerative colitis (UC), significantly affecting the postoperative quality of life. Paneth cells play an important role in the maintenance of gut homeostasis. This study aimed to investigate the role of Paneth cells in the pathogenesis of pouchitis.

METHOD

Endoscopic biopsies from the pouch body and terminal ileum of UC patients undergoing IPAA with or without pouchitis were obtained to analyze Paneth cell function. Acute pouchitis was induced with 5% dextran sulfate sodium (DSS) for seven consecutive days in a rat model of IPAA. The Paneth cell morphology was examined by immunofluorescence and electron microscopy. The effect of exogenous lysozyme supplementation on pouchitis was also investigated. The fecal microbiota profile after DSS and lysozyme treatment was determined by 16s rRNA ITS2 sequence analysis.

RESULT

Abnormal mucosal lysozyme expression was observed in patients with pouchitis. The rat model of pouchitis showed increased pouch inflammation, increased CD3+ and CD45+ T cell infiltration, and decreased tight junction proteins, including ZO-1 and Occludin. There is a significant deficiency of Paneth cell-derived lysozyme granules in the rat model of pouchitis. Supplementation with exogenous lysozyme significantly ameliorated pouchitis, lowering the levels of inflammatory cytokines such as TNF-α and IL-6 in the pouch tissue. 16s rRNA analysis revealed a higher Lachnospiraceae level after lysosome treatment.

CONCLUSIONS

Paneth cell dysfunction is prominent in patients and rat models of pouchitis and may be one of its causes. The decrease in Lachnospiraceae, a characteristic of dysbiosis in pouchitis, could be reserved by lysosome treatment. Lysozyme supplementation shows promise as a novel treatment strategy for pouchitis.

Validation of the Padova Prognostic Score for Colitis in Predicting Long-Term Outcome After Restorative Proctocolectomy

BACKGROUND

In 10%-20% of cases it is impossible to make a differential diagnosis between ulcerative colitis and Crohn's colitis. A 50% failure rate of J pouch ilea-anal anastomosis is observed in Crohn's colitis. In 2009, we created the Padua Prognostic Score for Colitis (PPSC) to predict the long-term clinical and functional outcome and quality of life of patients undergoing restorative proctocolectomy with J pouch. The aim of the present study is to establish and validate the accuracy of a prognostic score for chronic inflammatory bowel diseases (IBD).

PATIENT POPULATION AND METHODS

The PPSC was created in 2009 by integrating clinical and histological information of patients undergoing RPC. It included preoperative perianal abscess or fistula, rectal sparing, terminal ileum involvement, skip lesions and histological diagnosis of indeterminate colitis or Crohn's colitis on the operative specimen. The validity of this score was tested in predicting postoperative abscess or fistula, anal canal disease, pouchitis, pouch failure and new diagnosis of Crohn's disease. Correlation analysis, ROC curve analysis and survival analysis were used to validate the PPSC in a different cohort from the previous one.

RESULTS

We retrospectively enrolled in this study 138 consecutive patients undergoing CPR for ulcerative colitis (n = 127) or indeterminate colitis (n = 11) in our institution since 2005 to 2020. In this period, we observed 11 patients with postoperative abscess or fistula, 3 with anal canal disease, 40 with pouchitis, 6 with pouch failure and 6 with new diagnosis of Crohn's disease. In the new validation cohort, the PPSC confirmed to have a good accuracy in predicting the onset of postoperative CD (AUC = 74.5%, p = 0.018). Kaplan Meier curves demonstrate how a PPSC over 1 can reliably predicts the long-term onset of, pouchitis (p = 0.002) and anal abscess or fistulae (p = 0.04).

CONCLUSIONS

In this validation study we confirmed the accuracy of the PPSC in predicting postoperative fistulas or abscesses and pouchitis. Therefore, we believe that in clinical practice patients with a PPSC score greater than 1 should be warned of this risk of possible Crohn's disease diagnosis and pouch failure.

NF-κB-dependent induction of porcine β-defensin 114 regulates intestinal epithelium homeostasis

Intestinal epithelial cells (IECs) offer a primary physical barrier against commensal and pathogenic microorganisms in the gastrointestine. However, the influence of IECs on the development and regulation of mucosal immunity to infection is unknown. Here, we show that the porcine β-defensin 114 (PBD114) is an endotoxin-responsive gene expressed in IECs. Analysis on expression profiling of PBD114 gene using an infected porcine model and IPEC-J2 cells unveiled a pattern of induction in response to stimulation of various toll-like receptors (TLRs). By means of promoter analysis, PBD114 was found to be a NF-κB-dependent gene. Importantly, PBD114 suppresses endotoxin-induced inflammation and apoptosis in IECs through downregulation of two critical inflammation-associated signaling proteins, NF-kappa-B inhibitor alpha (IkB-α) and extracellular signal-regulated kinase1/2 (ERK1/2). PBD114 also suppresses inflammation and IEC apoptosis in mice exposed to bacterial endotoxins. Thus, we propose that TLR-activated NF-kB rapidly increases the expression of PBD114 that operates a feedback control of the NF-kB-dependent inflammation. The NF-kB-dependent induction of PBD114 may be a key event through which the mammalian host maintains intestinal epithelium homeostasis in response to various infections or diseases.

Upregulated Expression of Intestinal Antimicrobial Peptide HD5 Associated with Renal Function in IgA Nephropathy

PURPOSE

It was reported that gut-kidney axis may play an important role in IgA nephropathy (IgAN). Previous five GWASs of different populations for IgAN have discovered several genes related to intestinal immunity, including DEFA gene. However, the roles of the encoded proteins of DEFA5/6 which were called intestinal antimicrobial peptides HD5 and HD6 were not clear in kidney disease, such as IgAN. The purpose of this study was to clarify the association of HD5 and HD6 with IgAN.

METHODS

We measured HD5 and HD6 in serum, urine, and kidney of IgAN patients and normal controls by ELISA, Western blot, and immunofluorescence. The association of HD5 or HD6 levels with clinical and pathologic phenotypes was analyzed.

RESULTS

Serum levels of HD5 and HD6 were significantly higher in IgAN patients than those in normal controls. Baseline serum HD5 levels were significantly associated with eGFR (P = 0.002) and tubular atrophy/interstitial fibrosis (P = 0.002) and tubular atrophy/interstitial fibrosis (P = 0.002) and tubular atrophy/interstitial fibrosis (P = 0.002) and tubular atrophy/interstitial fibrosis (.

CONCLUSIONS

In IgAN patients, an elevated serum HD5 level at the time of renal biopsy was associated with poor renal outcomes. HD5 rather than HD6 was probably associated with renal function of IgAN patients.

Alzheimer's Disease-Associated β-Amyloid Is Rapidly Seeded by Herpesviridae to Protect against Brain Infection

Amyloid-β peptide (Aβ) fibrilization and deposition as β-amyloid are hallmarks of Alzheimer's disease (AD) pathology. We recently reported Aβ is an innate immune protein that protects against fungal and bacterial infections. Fibrilization pathways mediate Aβ antimicrobial activities. Thus, infection can seed and dramatically accelerate β-amyloid deposition. Here, we show Aβ oligomers bind herpesvirus surface glycoproteins, accelerating β-amyloid deposition and leading to protective viral entrapment activity in 5XFAD mouse and 3D human neural cell culture infection models against neurotropic herpes simplex virus 1 (HSV1) and human herpesvirus 6A and B. Herpesviridae are linked to AD, but it has been unclear how viruses may induce β-amyloidosis in brain. These data support the notion that Aβ might play a protective role in CNS innate immunity, and suggest an AD etiological mechanism in which herpesviridae infection may directly promote Aβ amyloidosis.

Fecal microbiota transplantation and bacterial consortium transplantation have comparable effects on the re-establishment of mucosal barrier function in mice with intestinal dysbiosis

Fecal microbiota transplantation (FMT) is a promising therapy, despite some reports of adverse side effects. Bacterial consortia transplantation (BCT) for targeted restoration of the intestinal ecosystem is considered a relatively safe and simple procedure. However, no systematic research has assessed the effects of FMT and BCT on immune responses of intestinal mucosal barrier in patients. We conducted complementary studies in animal models on the effects of FMT and BCT, and provide recommendations for improving the clinical outcomes of these treatments. To establish the dysbiosis model, male BALB/c mice were treated with ceftriaxone intra-gastrically for 7 days. After that, FMT and BCT were performed on ceftriaxone-treated mice for 3 consecutive days to rebuild the intestinal ecosystem. Post-FMT and post-BCT changes of the intestinal microbial community and mucosal barrier functions were investigated and compared. Disruption of intestinal microbial homeostasis impacted the integrity of mucosal epithelial layer, resulting in increased intestinal permeability. These outcomes were accompanied by overexpression of Muc2, significant decrease of SIgA secretion, and overproduction of defensins and inflammatory cytokines. After FMT and BCT, the intestinal microbiota recovered quickly, this was associated with better reconstruction of mucosal barriers and re-establishment of immune networks compared with spontaneous recovery (SR). Although based on a short-term study, our results suggest that FMT and BCT promote the re-establishment of intestinal microbial communities in mice with antibiotic-induced dysbiosis, and contribute to the temporal and spatial interactions between microbiota and mucosal barriers. The effects of BCT are comparable to that of FMT, especially in normalizing the intestinal levels of Muc2, SIgA, and defensins.

Clostridium difficile infection in the postcolectomy patient

Clostridium difficile infection (CDI) after total colectomy has been increasingly recognized over the past decade. C. difficile enteritis (CDE) is a rare occurrence, whereas C. difficile pouchitis (CDP) has been reported in approximately 10% of symptomatic patients seen at a referral center for pouch dysfunction. Similar to colonic CDI in the general population, antibiotic use and comorbid diseases may be risk factors for CDE. In contrast, the postoperative use of antibiotics does not seem to be associated with CDP, whereas male gender, recent hospitalization, and presurgery antibiotic use were shown to be risk factors for CDP. C. difficile is capable of colonizing all intestinal sites, including the ileal pouch. Similarities with the colon at physiological and cellular levels may contribute to the susceptibility of the ileal pouch to CDI. Postcolectomy CDI likely represents a disease spectrum from asymptomatic colonization to severe symptomatic infection. CDI should be considered in ostomy patients with fever and increased ileostomy output and in ileal pouch patients with a change in "normal" symptom pattern or chronic antibiotic-refractory pouchitis. Sensitive and specific methods for detection of CDI are available, and endoscopy is useful in evaluating the patient with suspected CDE or CDP, although pseudomembranes are typically absent. Vancomycin is used as the first-line therapy for CDP and may be warranted for patients with inflammatory bowel disease with CDE. Fecal microbiota transplantation has found its use in the management of severe or antibiotic refractory CDP, but this approach requires evaluation for the management of refractory CDE.

Relationship between pouch microbiota and pouchitis following restorative proctocolectomy for ulcerative colitis

Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) has become the surgical treatment of choice for many patients with medically refractory ulcerative colitis (UC) and familial adenomatous polyposis (FAP). UC patients with IPAA (UC-IPAA) are, nevertheless, susceptible to inflammatory and noninflammatory sequelae such as pouchitis, which is only rarely noted in FAP patients with IPAA. Pouchitis is the most frequent long-term complication of UC-IPAA patients, with a cumulative prevalence of up to 50%. Although the aetiology of pouchitis remains unclear, accumulating evidence suggests that a dysbiosis of the pouch microbiota and an abnormal mucosal immune response are implicated in its pathogenesis. Studies using culture and molecular techniques have detected a dysbiosis of the pouch microbiota in patients with pouchitis. Risk factors, genetic associations, and serological markers suggest that interactions between the host immune response and the pouch microbiota underlie the aetiology of this idiopathic inflammatory condition. This systematic review focuses on the dysbiosis of the microbiota that inhabit the pouch in UC and FAP patients and its interaction with the mucosal immune system. A meta-analysis was not attempted due to the highly heterogeneous microbiota composition and the different detection methods used by the various studies. Although no specific bacterial species, genus, or family has as yet been identified as pathogenic, there is evidence that a dysbiosis characterized by decreased gut microbiota diversity in UC-IPAA patients may, in genetically predisposed subjects, lead to aberrant mucosal immune regulation triggering an inflammatory process.

Pouchitis: what every gastroenterologist needs to know

Pouchitis is the most common complication among patients with ulcerative colitis who have undergone restorative proctocolectomy with ileal pouch-anal anastomosis. Pouchitis is actually a spectrum of diseases that vary in etiology, pathogenesis, phenotype, and clinical course. Although initial acute episodes typically respond to antibiotic therapy, patients can become dependent on antibiotics or develop refractory disease. Many factors contribute to the course of refractory pouchitis, such as the use of nonsteroidal anti-inflammatory drugs, infection with Clostridium difficile, pouch ischemia, or concurrent immune-mediated disorders. Identification of these secondary factors can help direct therapy.

Inflammatory bowel disease: an impaired barrier disease

BACKGROUND

The intestinal barrier is a delicate structure composed of a single layer of epithelial cells, the mucus, commensal bacteria, immune cells, and antibodies. Furthermore, a wealth of antimicrobial peptides (AMPs) can be found in the mucus and defend the mucosa. Different lines of investigations now point to a prominent pathophysiological role of defensins, an important family of AMPs, in the pathogenesis of inflammatory bowel disease and, particularly, in small intestinal Crohn's disease.

PURPOSE

In this review, we introduce the different antimicrobial peptides of the intestinal mucosa and describe their function, their expression pattern along the gastrointestinal tract, and their spatial relationship to the mucus layer. We then focus on the alterations found in inflammatory bowel disease. Small intestinal Crohn's disease (CD) is closely linked to defects in Paneth cells (specialized secretory epithelial cells at the bottom crypts) which secrete α-defensin human defensin (HD)-5 in huge quantities in healthy individuals. Decreased expression of these antimicrobial peptides is found in ileal CD, and single nucleotide polymorphisms with the highest linkage to CD affect genes involved in Paneth cell biology and defensin secretion. Additionally, antimicrobial peptides have a role in ulcerative colitis, where the depleted mucus layer cannot fulfill its crucial function of binding defensins and other AMPs to their proper site of action.

CONCLUSION

Inflammatory bowel disease arises when the mucosal barrier is compromised in its defense against challenges from the intestinal microbiota. In ileal CD, a strong association can be found between diminished expression or defective function of defensins and the advent of intestinal inflammation.