An exuberant inflammatory response to E coli: implications for the pathogenesis of ulcerative colitis and pyoderma gangrenosum

Ambroxol, a mucolytic agent, boosts HO-1, suppresses NF-κB, and decreases the susceptibility of the inflamed rat colon to apoptosis: A new treatment option for treating ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease of unknown etiology that increases the risk of developing colorectal cancer and imposes a lifelong healthcare burden on millions of patients worldwide. Current treatment strategies are associated with significant risks and have been shown to be fairly effective. Hence, discovering new therapies that have better efficacy and safety profiles than currently exploited therapeutic strategies is challenging. It has been well delineated that NF-κB/Nrf2 crosstalk is a chief player in the interplay between oxidative stress and inflammation. Ambroxol hydrochloride, a mucolytic agent, has shown antioxidant and anti-inflammatory activity in humans and animals and has not yet been examined for the management of UC. Therefore, our approach was to investigate whether ambroxol could be effective to combat UC using the common acetic acid rat model. Interestingly, a high dose of oral ambroxol (200 mg/kg/day) reasonably improved the microscopic and macroscopic features of the injured colon. This was linked to low disease activity and a reduction in the colonic weight/length ratio. In the context of that, ambroxol boosted Nrf2 activity and upregulated HO-1 and catalase to augment the antioxidant defense against oxidative damage. Besides, ambroxol inactivated NF-κB signaling and its consequent target pro-inflammatory mediators, IL-6 and TNF-α. In contrast, IL-10 is upregulated. Consistent with these results, myeloperoxidase activity is suppressed. Moreover, ambroxol decreased the susceptibility of the injured colon to apoptosis. To conclude, our findings highlight the potential application of ambroxol to modify the progression of UC by its anti-inflammatory, antioxidant, and antiapoptotic properties.

Acute Experimental Barrier Injury Triggers Ulcerative Colitis-Specific Innate Hyperresponsiveness and Ulcerative Colitis-Type Microbiome Changes in Humans

BACKGROUND AND AIMS

The trigger hypothesis opens the possibility of anti-flare initiation therapies by stating that ulcerative colitis (UC) flares originate from inadequate responses to acute mucosal injuries. However, experimental evidence is restricted by a limited use of suitable human models. We thus aimed to investigate the acute mucosal barrier injury responses in humans with and without UC using an experimental injury model.

METHODS

A standardized mucosal break was inflicted in the sigmoid colon of 19 patients with UC in endoscopic and histological remission and 20 control subjects. Postinjury responses were assessed repeatedly by high-resolution imaging and sampling to perform Geboes scoring, RNA sequencing, and injury niche microbiota 16S ribosomal RNA gene sequencing.

RESULTS

UC patients had more severe endoscopic postinjury inflammation than did control subjects (P < .01), an elevated modified Geboes score (P < .05), a rapid induction of innate response gene sets (P < .05) and antimicrobial peptides (P < .01), and engagement of neutrophils (P < .01). Innate lymphoid cell type 3 (ILC3) markers were increased preinjury (P < .01), and ILC3 activating cytokines were highly induced postinjury, resulting in an increase in ILC3-type cytokine interleukin-17A. Across groups, the postinjury mucosal microbiome had higher bacterial load (P < .0001) and lower α-diversity (P < .05).

CONCLUSIONS

UC patients in remission respond to mucosal breaks by an innate hyperresponse engaging resident regulatory ILC3s and a subsequent adaptive activation. The postinjury inflammatory bowel disease-like microbiota diversity decrease is irrespective of diagnosis, suggesting that the dysbiosis is secondary to host injury responses. We provide a model for the study of flare initiation in the search for antitrigger-directed therapies.

Studies on patients establish Crohn's disease as a manifestation of impaired innate immunity

The fruitless search for the cause of Crohn's disease has been conducted for more than a century. Various theories, including autoimmunity, mycobacterial infection and aberrant response to food and other ingested materials, have been abandoned for lack of robust proof. This review will provide the evidence, obtained from patients with this condition, that the common predisposition to Crohn's is a failure of the acute inflammatory response to tissue damage. This acute inflammation normally attracts large numbers of neutrophil leucocytes which engulf and clear bacteria and autologous debris from the inflamed site. The underlying predisposition in Crohn's disease is unmasked by damage to the bowel mucosa, predominantly through infection, which allows faecal bowel contents access to the vulnerable tissues within. Consequent upon failure of the clearance of these infectious and antigenic intestinal contents, it becomes contained, leading to a chronic granulomatous inflammation, producing cytokine release, local tissue damage and systemic symptoms. Multiple molecular pathologies extending across the whole spectrum of the acute inflammatory and innate immune response lead to the common predisposition in which defective monocyte and macrophage function plays a central role. Family linkage and exome sequencing together with GWAS have identified some of the molecules involved, including receptors, molecules involved in vesicle trafficking, and effector cells. Current therapy is immunosuppressant, which controls the symptoms but accentuates the underlying problem, which can only logically be tackled by correcting the primary lesion/s by gene therapy or genome editing, or through the development of drugs that stimulate innate immunity.

Pirfenidone prevents and reverses hepatic insulin resistance and steatohepatitis by polarizing M2 macrophages

Nonalcoholic steatohepatitis (NASH) is associated with lipotoxic liver injury, leading to insulin resistance, inflammation, and fibrosis. Despite its increased global incidence, very few promising treatments for NASH are available. Pirfenidone is an antifibrotic agent used to treat pulmonary fibrosis; it suppresses the pulmonary influx of T cells and macrophages. Here, we investigated the effect of pirfenidone in a mouse model of lipotoxicity-induced NASH via a high-cholesterol and high-fat diet. After 12 weeks of feeding, pirfenidone administration attenuated excessive hepatic lipid accumulation and peroxidation by reducing the expression of genes related to lipogenesis and fatty acid synthesis and enhancing the expression of those related to fatty acid oxidation. Flow cytometry indicated that pirfenidone reduced the number of total hepatic macrophages, particularly CD11c⁺CD206^-(M1)-type macrophages, increased the number of CD11c^-CD206⁺(M2)-type macrophages, and subsequently reduced T-cell numbers, which helped improve insulin resistance and steatohepatitis. Moreover, pirfenidone downregulated the lipopolysaccharide (LPS)-induced mRNA expression of M1 marker genes and upregulated IL-4-induced M2 marker genes in a dose-dependent manner in RAW264.7 macrophages. Importantly, pirfenidone reversed insulin resistance, hepatic inflammation, and fibrosis in mice with pre-existing NASH. These findings suggest that pirfenidone is a potential candidate for the treatment of NASH.

Pyoderma gangrenosum and tumour necrosis factor alpha inhibitors: A semi-systematic review

Pyoderma gangrenosum (PG) is a rare ulcerative skin disease that presents a therapeutic challenge. Tumour necrosis factor alpha (TNFα) inhibitors have been reported to successfully control PG. Our aim was to systematically evaluate and compare the clinical effectiveness of TNFα inhibitors in adults with PG. A literature search including databases such as PubMed, Embase, Scopus, and Web of Science was conducted, using search terms related to PG and TNFα inhibitors. Studies and case reports were included if patients were diagnosed with PG, over the age of 18 and administered TNFα inhibitor. A total of 3212 unique citations were identified resulting in 222 articles describing 356 patients being included in our study. The study we report found an 87% (95% CI: 83%-90%) response rate and a 67% (95% CI: 62%-72%) complete response rate to TNFα inhibitors. No statistically significant differences in the response rates (P = 0.6159) or complete response rates (P = 0.0773) to infliximab, adalimumab, and etanercept were found. In our study TNFα inhibitors demonstrated significant effectiveness with response and complete response rates supporting the use of TNFα inhibitors to treat PG in adults. Our study suggests that there is no significant difference in effectiveness among infliximab, adalimumab, and etanercept.

Treatment of inflammatory bowel disease associated E. coli with ciprofloxacin and E. coli Nissle in the streptomycin-treated mouse intestine

Background

E. coli belonging to the phylogenetic group B2 are linked to Inflammatory Bowel Disease (IBD). Studies have shown that antimicrobials have some effect in the treatment of IBD, and it has been demonstrated that E. coli Nissle has prophylactic abilities comparable to 5-aminosalicylic acid (5-ASA) therapy in ulcerative colitis. The objective of this study was to test if ciprofloxacin and/or E. coli Nissle could eradicate IBD associated E. coli in the streptomycin-treated mouse intestine.

Results

After successful colonization with the IBD associated E. coli strains in mice the introduction of E. coli Nissle did not result in eradication of either IBD associated strains or an E. coli from a healthy control, instead, co-colonization at high levels were obtained. Treatment of mice, precolonized with IBD associated E. coli, with ciprofloxacin for three days alone apparently resulted in effective eradication of tested E. coli. However, treatment of precolonized mice with a combination of ciprofloxacin for 3 days followed by E. coli Nissle surprisingly allowed one IBD associated E. coli to re-colonize the mouse intestine, but at a level 3 logs under E. coli Nissle. A prolonged treatment with ciprofloxacin for 7 days did not change this outcome.

Conclusions

In the mouse model E. coli Nissle can not be used alone to eradicate IBD associated E. coli; rather, 3 days of ciprofloxacin are apparently efficient in eradicating these strains, but surprisingly, after ciprofloxacin treatment (3 or 7 days), the introduction of E. coli Nissle may support re-colonization with IBD associated E. coli.

Defective innate immunity in inflammatory bowel disease: a Crohn's disease exclusivity?

PURPOSE OF REVIEW

This review summarizes the recent developments in support of the immunodeficiency model of Crohn's disease.

RECENT FINDINGS

The demonstration of impaired acute inflammation in Crohn's disease provides a novel mechanism for its pathogenesis, with diminished macrophage cytokine production and neutrophil recruitment leading to reduced bacterial clearance. The innate immune response may be further overwhelmed by other factors. The mucosal barrier in Crohn's patients is disrupted, with abnormal ultrastructure as well as antibacterial defensin deficiency. Specific bacterial agents may contribute and one promising candidate, adherent-invasive Escherichia coli, has recently been described. An interaction between Nod2 and the autophagy system has been elucidated, with direct consequences for bacterial clearance, and the most recent genome-wide association study meta-analysis has extended the number of Crohn's disease susceptibility loci to 71. The spectrum of congenital immunodeficiency disorders recognized to develop Crohn's-like inflammatory bowel disease is also expanding. Conversely, no specific immunodeficiency has so far been observed in ulcerative colitis, in which the defect appears to be failure of inflammation termination and resolution.

SUMMARY

Recent advances continue to highlight defects in innate immunity in Crohn's patients. Similar abnormalities may extend to other granulomatous disorders, but not diseases such as ulcerative colitis.

Crohn's disease: an immune deficiency state

Crohn's disease is a chronic inflammatory disorder primarily affecting the gastrointestinal tract. Its clinical manifestations arise from a substantial infiltration of the intestinal mucosa by activated leukocytes and the downstream consequences of chronic inflammation. The underlying cause driving this immunological reaction remains poorly understood. A number of hypotheses have been proposed, most of which postulate a primary over-activation of the immune response, based on the pathological appearances of active Crohn's lesions. Interestingly, none of these theories have been mechanistically proven. It is possible that the immunological events responsible for disease initiation are quite different from those contributing to its persistence and propagation. A substantial body of data has emerged in recent years to suggest that the primary defect in Crohn's disease is actually one of relative immunodeficiency. This review considers the evidence for such a phenomenon in contrast to alternative prevailing hypotheses and attempts to address some of the potential paradoxes that it generates.

Delayed resolution of acute inflammation in ulcerative colitis is associated with elevated cytokine release downstream of TLR4

Background

Ulcerative colitis (UC) is widely viewed as a leukocyte-mediated disorder. Although strong evidence implicates an exuberant response to microbial components in its pathogenesis, no intrinsic immune defect has been identified and the underlying pathogenic mechanisms remain obscure.

Methodology/Principal Findings

The acute immune response to bacterial injection was determined in UC patients with quiescent disease and directly compared to healthy control subjects. Monocyte-derived macrophages were used to investigate bacterial recognition mechanisms in vitro. An exuberant and protracted acute inflammatory response to bacteria was evident in patients with UC, which coincides with increased systemic levels of CXCL10. Macrophages stimulated with bacteria and Toll-like receptor (TLR) ligands revealed a specific defect in the TLR4 response in UC. The defect resulted in the over-expression of a number of pro-inflammatory molecules under transcriptional control of the adaptor TIR-domain containing adaptor inducing interferon-β (TRIF).

Conclusion

These findings highlight a dysregulated innate immune response with over-expression of molecules associated with leukocyte recruitment and activation that may eventuate in the hallmark chronic immune-mediated inflammation of UC.

A phylogenetic group of Escherichia coli associated with active left-sided inflammatory bowel disease

Background

Escherichia coli have been found in increased numbers in tissues from patients with Inflammatory Bowel Disease (IBD) and adherent-invasive E. coli have been found in resected ileum from patients with Crohn's disesae. This study aimed to characterize possible differences in phylogenetic group (triplex PCR), extraintestinal pathogenic E. coli (ExPEC) genes and multilocus sequence type (MLST) between E. coli strains isolated from IBD patients with past or present involvement of the left side of the colon and from controls.

Results

Fecal samples were collected from 18 patients and from 10 healthy controls. Disease activity was evaluated by sigmoidoscopy. Interestingly, E. coli strains of the phylogenetic group B2 were cultured from 60% of patients with IBD compared to 11% of healthy controls (p < 0.05). Furthermore, when comparing the number of E. coli B2 strains with at least one positive ExPEC gene among different groups, 86% were found positive among active IBD patients, significantly more than 13% among inactive IBD patients (p < 0.05), and 11% among healthy controls (p < 0.05). The B2 phylogenetic group was found in a specific cluster based on MLST, but no further separation between E. coli strains associated with active compared to inactive IBD was achieved.

Conclusion

In conclusion, E. coli of the phylogenetic group B2 were isolated more frequently from IBD patients with past or present involvement of the left side of the colon compared to healthy controls, and B2 strains with ExPEC genes were found more frequently among IBD patients with active disease compared to patients with inactive disease.

Dysregulation of human beta-defensin-2 protein in inflammatory bowel disease

Background

Human β-defensin-2 (HBD2) is an antimicrobial peptide implicated in the pathogenesis of inflammatory bowel disease (IBD). Low copy number and concomitant low mRNA expression of the HBD2 gene have been implicated in susceptibility to colonic Crohn's Disease (CD). We investigated the colonic distribution of HBD2 mRNA expression, and the contributions of genetic and environmental factors on HBD2 protein production.

Methodology/Principal Findings

We examined HBD2 mRNA expression at three colonic locations by microarray analysis of biopsies from 151 patients (53 CD, 67 ulcerative colitis [UC], 31 controls). We investigated environmental and genetic influences on HBD2 protein production using ex vivo cultured sigmoid colon biopsies from 69 patients (22 CD, 26 UC, 21 controls) stimulated with lipopolysaccharide (LPS) and/or nicotine for 24 hours. HBD2 and cytokines were measured in culture supernatants. Using DNA samples from these patients, regions in the HBD2 gene promoter were sequenced for NF-κB binding-sites and HBD2 gene copy number was determined. HBD2 mRNA expression was highest in inflamed (vs. uninflamed p = 0.0122) ascending colon in CD and in inflamed (vs. uninflamed p<0.0001) sigmoid colon in UC. HBD2 protein production was increased in inflamed UC biopsies (p = 0.0078). There was no difference in HBD2 protein production from unstimulated biopsies of CD, UC and controls. LPS-induced HBD2 production was significantly increased in CD (p = 0.0375) but not UC (p = 0.2017); this LPS-induced response was augmented by nicotine in UC (p = 0.0308) but not CD (p = 0.6872). Nicotine alone did not affect HBD2 production. HBD2 production correlated with IL8 production in UC (p<0.001) and with IL10 in CD (p<0.05). Variations in the HBD2 promoter and HBD2 gene copy number did not affect HBD2 production.

Significance/Conclusions

Colonic HBD2 was dysregulated at mRNA and protein level in IBD. Inflammatory status and stimulus but not germline variations influenced these changes.