Pathobionts in Inflammatory Bowel Disease: Origins, Underlying Mechanisms, and Implications for Clinical Care.

The gut microbiota plays a significant role in the pathogenesis of both forms of inflammatory bowel disease (IBD), namely, Crohn's disease (CD) and ulcerative colitis (UC). Although evidence suggests dysbiosis and loss of beneficial microbial species can exacerbate IBD, many new studies have identified microbes with pathogenic qualities, termed "pathobionts," within the intestines of patients with IBD. The concept of pathobionts initiating or driving the chronicity of IBD has largely focused on the putative aggravating role that adherent invasive Escherichia coli may play in CD. However, recent studies have identified additional bacterial and fungal pathobionts in patients with CD and UC. This review will highlight the characteristics of these pathobionts and their implications for IBD treatment. Beyond exploring the origins of pathobionts, we discuss those associated with specific clinical features and the potential mechanisms involved, such as creeping fat (Clostridium innocuum) and impaired wound healing (Debaryomyces hansenii) in patients with CD as well as the increased fecal proteolytic activity (Bacteroides vulgatus) seen as a biomarker for UC severity. Finally, we examine the potential impact of pathobionts on current IBD therapies, and several new approaches to target pathobionts currently in the early stages of development. Despite recognizing that pathobionts likely contribute to the pathogenesis of IBD, more work is needed to define their modes of action. Determining whether causal relationships exist between pathobionts and specific disease characteristics could pave the way for improved care for patients, particularly for those not responding to current IBD therapies.

Clinicopathological features and prognosis of pyoderma gangrenosum in Korea: A single centre, retrospective, observational study over 20 years.

BACKGROUND: Pyoderma gangrenosum is a rare autoinflammatory neutrophilic dermatosis that rapidly evolves. However, little is known about the clinicopathological features and prognosis of pyoderma gangrenosum. AIMS: We aimed to document clinicopathologic and prognostic data of the patients with pyoderma gangrenosum. METHODS: In this retrospective observational study, we reviewed case records of patients diagnosed with pyoderma gangrenosum between 1999-2019. RESULTS: Fifty-three patients were identified by reviewing medical records for skin biopsy; of these, 37 were men and 16 were women. Mean age at onset was 43.3 ± 18.5 years. The most frequently affected area was the lower extremities (60.4%), followed by the head and neck (17.0%). The most common subtype was ulcerative (47.2%), followed by bullous (22.6%). 30 cases had underlying diseases and the most common were malignancy (24.5%), followed by inflammatory bowel diseases (18.9%). The proportion of cases with history of trauma were significantly higher in post-operative type (100%) as compared to the bullous type (8.3%). Histologic features of granulation tissue were frequently found in post-operative type (66.7%) and bullous type (58.3%). Granulomas were predominantly found in bullous type (58.3%). Age <60 years appeared to be significantly associated with multiple lesions. Partial-to-complete remission was observed in 40 cases (75.5%). Nine (17.0%) cases experienced recurrence with a median progression-free period of six months (interquartile range of 3.0-9.0 months). Cases with underlying hematologic disorders and the bullous subtype were significantly associated with early recurrence. LIMITATIONS: This study was a single-centre study with a retrospective design. CONCLUSION: Pyoderma gangrenosum appears to have ethnic differences. Underlying haematologic disorders and bullous subtype have a worse prognosis. However, the type of histopathology did not correlate with the clinical outcome of pyoderma gangrenosum.

Genome-wide association study of leprosy in Malawi and Mali.

Leprosy is a chronic infection of the skin and peripheral nerves caused by Mycobacterium leprae. Despite recent improvements in disease control, leprosy remains an important cause of infectious disability globally. Large-scale genetic association studies in Chinese, Vietnamese and Indian populations have identified over 30 susceptibility loci for leprosy. There is a significant burden of leprosy in Africa, however it is uncertain whether the findings of published genetic association studies are generalizable to African populations. To address this, we conducted a genome-wide association study (GWAS) of leprosy in Malawian (327 cases, 436 controls) and Malian (247 cases, 368 controls) individuals. In that analysis, we replicated four risk loci previously reported in China, Vietnam and India; MHC Class I and II, LACC1 and SLC29A3. We further identified a novel leprosy susceptibility locus at 10q24 (rs2015583; combined p = 8.81 × 10-9; OR = 0.51 [95% CI 0.40 - 0.64]). Using publicly-available data we characterise regulatory activity at this locus, identifying ACTR1A as a candidate mediator of leprosy risk. This locus shows evidence of recent positive selection and demonstrates pleiotropy with established risk loci for inflammatory bowel disease and childhood-onset asthma. A shared genetic architecture for leprosy and inflammatory bowel disease has been previously described. We expand on this, strengthening the hypothesis that selection pressure driven by leprosy has shaped the evolution of autoimmune and atopic disease in modern populations. More broadly, our data highlights the importance of defining the genetic architecture of disease across genetically diverse populations, and that disease insights derived from GWAS in one population may not translate to all affected populations.

Transvaginal hybrid-NOTES vs. traditional laparoscopic sigmoid resection for diverticulitis: a short-term comparative study.

The aim was to compare short-term results of transvaginal hybrid-NOTES (NSR) with traditional laparoscopic technique in sigmoid resection (LSR) in cases of diverticulitis. Natural Orifice Transluminal Endoscopic Surgery has been evolved as a minimally invasive procedure to reduce the operative trauma due to the absence of specimen extraction through the abdominal wall causing less postoperative pain, and shorter hospital stay. Despite the increasing use and published case series of NSR for diverticulitis as a laparoscopic procedure with transvaginal stapling and specimen extraction, there are no studies comparing this procedure with LSR. Twenty NSR patients operated at the Cologne-Merheim Medical Center have been documented and compared with 20 female LSR patients matched for body mass index, American Society of Anesthesiologists-classification (ASA), Hansen/Stock classification, and age. To ensure comparability regarding peri- and postoperative care, only procedures performed by the same surgeon were included. Procedural time, intra- and postoperative complications, conversion rate, postoperative pain, the duration of an epidural catheter, analgesic consumption, and postoperative length of hospital stay were analyzed. There were no significant differences in the sum of pain levels (p = 0.930), length of procedure (p = 0.079), intra- and postoperative complications, as well as duration of an epidural catheter. On the contrary, there were significant positive effects for NSR on morphine requirement at day seven and eight (p = 0.019 and p = 0.035 respectively) as well as the postoperative length of hospital stay (p = 0.031). This retrospective study reveals significant positive effects for NSR compared to LSR regarding length of hospital stay as well as morphine consumption after removal of the epidural catheter, whereas there were no significant differences in complication rate and procedural time. In summary, NSR is an adequate alternative to traditional laparoscopic sigmoid resection considering the surgeons experience and the patient's personal preferences.

Psoriasis increases the risk of concurrent inflammatory bowel disease: A population-based nationwide study in Korea.

BACKGROUND: The epidemiology of the association between psoriasis and inflammatory bowel disease is poorly defined and remains controversial. AIM: To evaluate the prevalence of inflammatory bowel disease in patients with psoriasis compared with the general population. METHODS: We searched the nationwide health claims database between 2011 and 2015 and evaluated the prevalence of inflammatory bowel disease, including Crohn's disease and ulcerative colitis. RESULTS: Prevalence of inflammatory bowel disease, Crohn's disease and ulcerative colitis in patients with psoriasis vs the general population in 2011 were 0.16, 0.05 and 0.12% vs 0.08, 0.03 and 0.06%, respectively, which increased significantly with time between 2011 and 2015. Patients with psoriasis consistently revealed higher standardized prevalence (age and sex adjusted) of inflammatory bowel disease, Crohn's disease and ulcerative colitis compared with the general population. Subgroup analysis revealed the highest risk of prevalent inflammatory bowel disease in patients younger than 19 years (crude odds ratio 5.33, 95% confidence interval 3.74-7.59). Severe psoriasis demonstrated higher odds of inflammatory bowel disease (odds ratio 2.96, 95% confidence interval 2.54-3.45) than mild psoriasis (odds ratio 1.68, 95% confidence interval 1.51-1.88). LIMITATIONS: Limited data for doing adjustment and cross-sectional study design. CONCLUSIONS: Psoriasis patients revealed higher risk of inflammatory bowel disease. In particular, young patients and those with severe psoriasis may require closer monitoring and comprehensive management.

LACC1 Regulates TNF and IL-17 in Mouse Models of Arthritis and Inflammation.

Both common and rare genetic variants of laccase domain-containing 1 (LACC1, previously C13orf31) are associated with inflammatory bowel disease, leprosy, Behcet disease, and systemic juvenile idiopathic arthritis. However, the functional relevance of these variants is unclear. In this study, we use LACC1-deficient mice to gain insight into the role of LACC1 in regulating inflammation. Following oral administration of Citrobacter rodentium, LACC1 knockout (KO) mice had more severe colon lesions compared with wildtype (WT) controls. Immunization with collagen II, a collagen-induced arthritis (CIA) model, resulted in an accelerated onset of arthritis and significantly worse arthritis and inflammation in LACC1 KO mice. Similar results were obtained in a mannan-induced arthritis model. Serum and local TNF in CIA paws and C. rodentium colons were significantly increased in LACC1 KO mice compared with WT controls. The percentage of IL-17A-producing CD4+ T cells was elevated in LACC1 KO mice undergoing CIA as well as aged mice compared with WT controls. Neutralization of IL-17, but not TNF, prevented enhanced mannan-induced arthritis in LACC1 KO mice. These data provide new mechanistic insight into the function of LACC1 in regulating TNF and IL-17 during inflammatory responses. We hypothesize that these effects contribute to immune-driven pathologies observed in individuals carrying LACC1 variants.

A genome wide association study identifies a lncRna as risk factor for pathological inflammatory responses in leprosy.

Leprosy Type-1 Reactions (T1Rs) are pathological inflammatory responses that afflict a sub-group of leprosy patients and result in peripheral nerve damage. Here, we employed a family-based GWAS in 221 families with 229 T1R-affect offspring with stepwise replication to identify risk factors for T1R. We discovered, replicated and validated T1R-specific associations with SNPs located in chromosome region 10p21.2. Combined analysis across the three independent samples resulted in strong evidence of association of rs1875147 with T1R (p = 4.5x10-8; OR = 1.54, 95% CI = 1.32-1.80). The T1R-risk locus was restricted to a lncRNA-encoding genomic interval with rs1875147 being an eQTL for the lncRNA. Since a genetic overlap between leprosy and inflammatory bowel disease (IBD) has been detected, we evaluated if the shared genetic control could be traced to the T1R endophenotype. Employing the results of a recent IBD GWAS meta-analysis we found that 10.6% of IBD SNPs available in our dataset shared a common risk-allele with T1R (p = 2.4x10-4). This finding points to a substantial overlap in the genetic control of clinically diverse inflammatory disorders.

Understanding inflammatory bowel disease via immunogenetics.

The major inflammatory bowel diseases, Crohn's disease and ulcerative colitis, are both debilitating disorders of the gastrointestinal tract, characterized by a dysregulated immune response to unknown environmental triggers. Both disorders have an important and overlapping genetic component, and much progress has been made in the last 20 years at elucidating some of the specific factors contributing to disease pathogenesis. Here we review our growing understanding of the immunogenetics of inflammatory bowel disease, from the twin studies that first implicated a role for the genome in disease susceptibility to the latest genome-wide association studies that have identified hundreds of associated loci. We consider the insight this offers into the biological mechanisms of the inflammatory bowel diseases, such as autophagy, barrier defence and T-cell differentiation signalling. We reflect on these findings in the context of other immune-related disorders, both common and rare. These observations include links both obvious, such as to pediatric colitis, and more surprising, such as to leprosy. As a changing picture of the underlying genetic architecture emerges, we turn to future directions for the study of complex human diseases such as these, including the use of next generation sequencing technologies for the identification of rarer risk alleles, and potential approaches for narrowing down associated loci to casual variants. We consider the implications of this work for translation into clinical practice, for example via early therapeutic hypotheses arising from our improved understanding of the biology of inflammatory bowel disease. Finally, we present potential opportunities to better understand environmental risk factors, such as the human microbiota in the context of immunogenetics.

Function and dysfunction of leucine-rich repeat kinase 2 (LRRK2): Parkinson's disease and beyond.

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of familial Parkinson's disease (PD). As such, functions and dysfunctions of LRRK2 in PD have been the subject of extensive investigation. In addition to PD, increasing evidence is suggesting that LRRK2 is associated with a wide range of diseases. Genome-wide association studies have implicated LRRK2 in Crohn's disease (CD) and leprosy, and the carriers with pathogenic mutations of LRRK2 show increased risk to develop particular types of cancer. LRRK2 mutations are rarely found in Alzheimer's disease (AD), but LRRK2 might play a part in tauopathies. The association of LRRK2 with the pathogenesis of apparently unrelated diseases remains enigmatic, but it might be related to the yet unknown diverse functions of LRRK2. Here, we reviewed current knowledge on the link between LRRK2 and several diseases, including PD, AD, CD, leprosy, and cancer, and discussed the possibility of targeting LRRK2 in such diseases.

Panniculitis with vasculitis.

Panniculitides encompass a great number of different entities; however, once a vasculitis has been detected histopathologically within the subcutaneous tissue, the differential diagnosis is mainly restricted to polyarteritis (panarteritis) nodosa (PAN), nodular vasculitis (NV), and Bazin's erythema induratum (EI). Patients with PAN may have the disease confined to the skin, but must be followed over a long period because many of them develop late systemic disease. The NV/EI group represents by far the most common type of lobular panniculitis with vasculitis; we prefer keeping the distinction between the two entities by underlining the equation NV positive tuberculin skin test = EI. Other lobular panniculitides with vasculitis are exceedingly rare and set in a systemic background which can be infectious (lepromatous leprosy panniculitides) or autoimmune/dysreactive (neutrophilic lobular panniculitis in rheumatoid arthritis, lobular panniculitis in inflammatory bowel disease).

The role of TL1A and DR3 in autoimmune and inflammatory diseases.

TNF-like ligand 1A (TL1A), which binds its cognate receptor DR3 and the decoy receptor DcR3, is an identified member of the TNF superfamily. TL1A exerts pleiotropic effects on cell proliferation, activation, and differentiation of immune cells, including helper T cells and regulatory T cells. TL1A and its two receptors expression is increased in both serum and inflamed tissues in autoimmune diseases such as inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and ankylosing spondylitis (AS). Polymorphisms of the TNFSF15 gene that encodes TL1A are associated with the pathogenesis of irritable bowel syndrome, leprosy, and autoimmune diseases, including IBD, AS, and primary biliary cirrhosis (PBC). In mice, blocking of TL1A-DR3 interaction by either antagonistic antibodies or deletion of the DR3 gene attenuates the severity of multiple autoimmune diseases, whereas sustained TL1A expression on T cells or dendritic cells induces IL-13-dependent small intestinal inflammation. This suggests that modulation of TL1A-DR3 interaction may be a potential therapeutic target in several autoimmune diseases, including IBD, RA, AS, and PBC.

Identification of IL18RAP/IL18R1 and IL12B as leprosy risk genes demonstrates shared pathogenesis between inflammation and infectious diseases.

Of eight leprosy susceptibility loci identified by genome-wide association studies, five have been implicated in Crohn disease, suggesting a common genetic fingerprint between leprosy and inflammatory bowel disease (IBD). Here, we conducted a multiple-stage genetic association study of 133 IBD susceptibility loci in multiple leprosy samples (totaling 4,971 leprosy cases and 5,503 controls) from a Chinese population and discovered two associations at rs2058660 on 2q12.1 (p = 4.57 × 10(-19); odds ratio [OR] = 1.30) and rs6871626 on 5q33.3 (p = 3.95 × 10(-18); OR = 0.75), implicating IL18RAP/IL18R1 and IL12B as susceptibility genes for leprosy. Our study reveals the important role of IL12/IL18-mediated transcriptional regulation of IFN-γ production in leprosy, and together with previous findings, it demonstrates the shared genetic susceptibility between infectious and inflammatory diseases.

Deciphering the function of leucine-rich repeat kinase 2 and targeting its dysfunction in disease.

LRRK2 (leucine-rich repeat kinase 2) is a gene of unknown function that has been linked to a number a human diseases, including PD (Parkinson's disease), IBD (inflammatory bowel disease), leprosy and cancer. The papers from the LRRK2: Function and Dysfunction meeting in this issue of Biochemical Society Transactions explore our growing knowledge of LRRK2's normal function, the role that it plays in disease and emerging strategies to exploit LRRK2 as a therapeutic target.

Conference Scene: T-cell subset phenotype and function.

Organized by Euroscicon, this meeting focused on the complex and fast-paced research field of T-cell subset phenotype and function. During the past 20 years, this field has moved on from the simple Th1-Th2 paradigm to the discovery of a range of T-cell subsets, including Tregs and Th17 cells. The meeting brought together a variety of researchers currently exploring this field, to give insight into what we know, what we need to know and the potential implications of this research in the medical setting.

Therapeutic role of rifaximin in inflammatory bowel disease: clinical implication of human pregnane X receptor activation.

Human pregnane X receptor (PXR) has been implicated in the pathogenesis of inflammatory bowel disease (IBD). Rifaximin, a human PXR activator, is in clinical trials for treatment of IBD and has demonstrated efficacy in Crohn's disease and active ulcerative colitis. In the current study, the protective and therapeutic role of rifaximin in IBD and its respective mechanism were investigated. PXR-humanized (hPXR), wild-type, and Pxr-null mice were treated with rifaximin in the dextran sulfate sodium (DSS)-induced and trinitrobenzene sulfonic acid (TNBS)-induced IBD models to determine the protective function of human PXR activation in IBD. The therapeutic role of rifaximin was further evaluated in DSS-treated hPXR and Pxr-null mice. Results demonstrated that preadministration of rifaximin ameliorated the clinical hallmarks of colitis in DSS- and TNBS-treated hPXR mice as determined by body weight loss and assessment of diarrhea, rectal bleeding, colon length, and histology. In addition, higher survival rates and recovery from colitis symptoms were observed in hPXR mice, but not in Pxr-null mice, when rifaximin was administered after the onset of symptoms. Nuclear factor κB (NF-κB) target genes were markedly down-regulated in hPXR mice by rifaximin treatment. In vitro NF-κB reporter assays demonstrated inhibition of NF-κB activity after rifaximin treatment in colon-derived cell lines expressing hPXR. These findings demonstrated the preventive and therapeutic role of rifaximin on IBD through human PXR-mediated inhibition of the NF-κB signaling cascade, thus suggesting that human PXR may be an effective target for the treatment of IBD.

On the prevalence of M. avium subspecies paratuberculosis DNA in the blood of healthy individuals and patients with inflammatory bowel disease.

BACKGROUND: Mycobacteria, such as M. leprae and M. tuberculosis infect billions of humans. However, because of appropriate immune responses and antibiotic therapy, overt mycobacterial diseases occur far less frequently. M. avium subspecies paratuberculosis (MAP) causes Johne's disease in ruminants, an affliction evocative of inflammatory bowel disease (IBD). Several agents used to treat IBD (5-ASA, methotrexate, azathioprine and its metabolite 6-MP) have recently been shown to be antiMAP antibiotics. We herein evaluate the prevalence of MAP DNA in healthy individuals and compare them with IBD patients on antiMAP antibiotics. METHODS: We studied 100 healthy individuals (90 blood donors) and 246 patients with IBD. IS900 MAP DNA was identified using a nested primer PCR in the buffy coat of blood. Positive signal was confirmed as MAP by DNA sequence analysis. PCR positive results frequencies were compared according to medications used. Significance was accepted at p<0.05. RESULTS: 47% (47/100) healthy controls and 16% (40/246) IBD patients were IS900 positive (p<0.0001). MAP DNA was identified in 17% of 143 patients receiving mesalamine and 6% of 16 receiving sulfasalazine. None of the IBD patients receiving methotrexate (n = 9), 6-MP (n = 3), ciprofloxacin (n = 5) or Tacrolimus (n = 3) had MAP DNA detectable in their blood. DISCUSSION: We found a disquietingly large percentage of healthy individuals have MAP DNA in their blood, the significance of which remains to be determined. Counter-intuitively, the incidence of MAP DNA was significantly lower in patients with IBD. Agents with the most potent in vitro antiMAP activity were associated with clearance of blood MAP DNA. We posit that the use antiMAP antibiotics was responsible for the decreased prevalence of MAP DNA in patients with IBD.

Cutaneous manifestations in 404 Iranian patients with inflammatory bowel disease: a retrospective study.

BACKGROUND: Cutaneous manifestations of inflammatory bowel disease are relatively common, although they vary widely. AIMS: The aim of this study was to determine the prevalence of cutaneous manifestations in inflammatory bowel disease according to their location, age, gender, activity, and type of underlying disease in an Iranian population during a 10-year period. METHODS: The medical records of 404 inpatients with inflammatory bowel disease were extracted retrospectively to detect cutaneous manifestations. RESULTS: In this study, the prevalence of cutaneous manifestations was 5.9%. These manifestations were higher in Crohn's disease (7.29%) than in ulcerative colitis (4.07%), and more frequent in females (52%) than in males (48%). Aphthous stomatitis was observed more frequently in Crohn's disease; however, pyoderma gangrenosum was seen more often in ulcerative colitis. Erythema nodosum was diagnosed only in female patients with Crohn's disease. Manifestations secondary to nutritional deficiency or associated conditions including psoriasis and other autoimmune disorders were less frequent. CONCLUSIONS: Aphthous stomatitis, pyoderma gangrenosum, and erythema nodosum were the most common skin disorders related to inflammatory bowel disease (IBD), which mainly occurred in women.

Culture of Mycobacterium avium subspecies paratuberculosis from the blood of patients with Crohn's disease.

BACKGROUND: Crohn's disease, a form of inflammatory bowel disease, resembles some aspects of tuberculosis, leprosy, and paratuberculosis. The role of Mycobacterium avium subspecies paratuberculosis (MAP) in Crohn's disease is controversial. METHODS: We tested for MAP by PCR and culture in buffy coat preparations from 28 individuals with Crohn's disease, nine with ulcerative colitis, and 15 without inflammatory bowel disease. FINDINGS: MAP DNA in uncultured buffy coats was identified by PCR in 13 (46%) individuals with Crohn's disease, four (45%) with ulcerative colitis, and three (20%) without inflammatory bowel disease. Viable MAP was cultured from the blood of 14 (50%) patients with Crohn's disease, two (22%) with ulcerative colitis, and none of the individuals without inflammatory bowel disease. Current use of immunosuppressive medication did not correlate with a positive MAP culture. Sequencing of PCR products from MAP cultures confirmed the presence of the MAP-specific IS900 fragment. Among 11 MAP isolates assessed, we identified nine strains that were not identical. INTERPRETATION: We detected viable MAP in peripheral blood in a higher proportion of individuals with Crohn's disease than in controls. These data contribute to the evidence that MAP might be a cause of Crohn's disease.