Christopher A. Lamb

Signal interactions between nitric oxide and reactive oxygen intermediates in the plant hypersensitive disease resistance response.

Nitric oxide (NO) and reactive oxygen intermediates (ROIs) play key roles in the activation of disease resistance mechanisms both in animals and plants. In animals NO cooperates with ROIs to kill tumor cells and for macrophage killing of bacteria. Such cytotoxic events occur because unregulated NO levels drive a diffusion-limited reaction with O2− to generate peroxynitrite (ONOO−), a mediator of cellular injury in many biological systems. Here we show that in soybean cells unregulated NO production at the onset of a pathogen-induced hypersensitive response (HR) is not sufficient to activate hypersensitive cell death. The HR is triggered only by balanced production of NO and ROIs. Moreover, hypersensitive cell death is activated after interaction of NO not with O2− but with H2O2 generated from O2− by superoxide dismutase. Increasing the level of O2− reduces NO-mediated toxicity, and ONOO− is not a mediator of hypersensitive cell death. During the HR, superoxide dismutase accelerates O2− dismutation to H2O2 to minimize the loss of NO by reaction with O2− and to trigger hypersensitive cell death through NO/H2O2 cooperation. However, O2− rather than H2O2 is the primary ROI signal for pathogen induction of glutathione S-transferase, and the rates of production and dismutation of O2− generated during the oxidative burst play a crucial role in the modulation and integration of NO/H2O2 signaling in the HR. Thus although plants and animals use a similar repertoire of signals in disease resistance, ROIs and NO are deployed in strikingly different ways to trigger host cell death.

Abscisic acid has a key role in modulating diverse plant-pathogen interactions

We isolated an activation-tagged Arabidopsis (Arabidopsis thaliana) line, constitutive disease susceptibility2-1D (cds2-1D), that showed enhanced bacterial growth when challenged with various Pseudomonas syringae strains. Systemic acquired resistance and systemic PATHOGENESIS-RELATED GENE1 induction were also compromised in cds2-1D. The T-DNA insertion adjacent to NINE-CIS-EPOXYCAROTENOID DIOXYGENASE5 (NCED5), one of six genes encoding the abscisic acid (ABA) biosynthetic enzyme NCED, caused a massive increase in transcript level and enhanced ABA levels >2-fold. Overexpression of NCED genes recreated the enhanced disease susceptibility phenotype. NCED2, NCED3, and NCED5 were induced, and ABA accumulated strongly following compatible P. syringae infection. The ABA biosynthetic mutant aba3-1 showed reduced susceptibility to virulent P. syringae, and ABA, whether through exogenous application or endogenous accumulation in response to mild water stress, resulted in increased bacterial growth following challenge with virulent P. syringae, indicating that ABA suppresses resistance to P. syringae. Likewise ABA accumulation also compromised resistance to the biotrophic oomycete Hyaloperonospora arabidopsis, whereas resistance to the fungus Alternaria brassicicola was enhanced in cds2-1D plants and compromised in aba3-1 plants, indicating that ABA promotes resistance to this necrotroph. Comparison of the accumulation of salicylic acid and jasmonic acid in the wild type, cds2-1D, and aba3-1 plants challenged with P. syringae showed that ABA promotes jasmonic acid accumulation and exhibits a complex antagonistic relationship with salicylic acid. Our findings provide genetic evidence that the abiotic stress signal ABA also has profound roles in modulating diverse plant-pathogen interactions mediated at least in part by cross talk with the jasmonic acid and salicylic acid biotic stress signal pathways.

Etrolizumab as induction therapy for ulcerative colitis: a randomised, controlled, phase 2 trial

BACKGROUND Etrolizumab is a humanised monoclonal antibody that selectively binds the β7 subunit of the heterodimeric integrins α4β7 and αEβ7. We aimed to assess etrolizumab in patients with moderately-to-severely active ulcerative colitis. METHODS In this double-blind, placebo-controlled, randomised, phase 2 study, patients with moderately-to-severely active ulcerative colitis who had not responded to conventional therapy were recruited from 40 referral centres in 11 countries. Eligible patients (aged 18-75 years; Mayo Clinic Score [MCS] of 5 of higher [or ≥6 in USA]; and disease extending 25 cm or more from anal verge) were randomised (1:1:1) to one of two dose levels of subcutaneous etrolizumab (100 mg at weeks 0, 4, and 8, with placebo at week 2; or 420 mg loading dose [LD] at week 0 followed by 300 mg at weeks 2, 4, and 8), or matching placebo. The primary endpoint was clinical remission at week 10, defined as MCS of 2 or less (with no individual subscore of >1), analysed in the modified intention-to-treat population (mITT; all randomly assigned patients who had received at least one dose of study drug, had at least one post-baseline disease-activity assessment, and had a centrally read screening endoscopic subscore of ≥2). This study is registered with ClinicalTrials.gov, number NCT01336465. FINDINGS Between Sept 2, 2011, and July 11, 2012, 124 patients were randomly assigned, of whom five had a endoscopic subscore of 0 or 1 and were excluded from the mITT population, leaving 39 patients in the etrolizumab 100 mg group, 39 in the etrolizumab 300 mg plus LD group, and 41 in the placebo group for the primary analyses. No patients in the placebo group had clinical remission at week 10, compared with eight (21% [95% CI 7-36]) patients in the etrolizumab 100 mg group (p=0·0040) and four (10% [0·2-24]) patients in the 300 mg plus LD group (p=0·048). Adverse events occurred in 25 (61%) of 41 patients in the etrolizumab 100 mg group (five [12%] of which were regarded as serious), 19 (48%) of 40 patients in the etrolizumab 300 mg plus LD group (two [5%] serious), and 31 (72%) of 43 patients in the placebo group (five [12%] serious). INTERPRETATION Etrolizumab was more likely to lead to clinical remission at week 10 than was placebo. Therefore, blockade of both α4β7 and αEβ7 might provide a unique therapeutic approach for the treatment of ulcerative colitis, and phase 3 studies have been planned. FUNDING Genentech.

Genetic Elucidation of Nitric Oxide Signaling in Incompatible Plant-Pathogen Interactions

Recent experiments indicate that nitric oxide (NO) plays a pivotal role in disease resistance and several other physiological processes in plants. However, most of the current information about the function of NO in plants is based on pharmacological studies, and additional approaches are therefore required to ascertain the role of NO as an important signaling molecule in plants. We have expressed a bacterial nitric oxide dioxygenase (NOD) in Arabidopsis plants and/or avirulent Pseudomonas syringae pv tomato to study incompatible plant-pathogen interactions impaired in NO signaling. NOD expression in transgenic Arabidopsis resulted in decreased NO levels in planta and attenuated a pathogen-induced NO burst. Moreover, NOD expression in plant cells had very similar effects on plant defenses compared to NOD expression in avirulent Pseudomonas. The defense responses most affected by NO reduction during the incompatible interaction were decreased H2O2 levels during the oxidative burst and a blockage of Phe ammonia lyase expression, the key enzyme in the general phenylpropanoid pathway. Expression of the NOD furthermore blocked UV light-induced Phe ammonia lyase and chalcone synthase gene expression, indicating a general signaling function of NO in the activation of the phenylpropanoid pathway. NO possibly functions in incompatible plant-pathogen interactions by inhibiting the plant antioxidative machinery, and thereby ensuring locally prolonged H2O2 levels. Additionally, albeit to a lesser extent, we observed decreases in salicylic acid production, a diminished development of hypersensitive cell death, and a delay in pathogenesis-related protein 1 expression during these NO-deficient plant-pathogen interactions. Therefore, this genetic approach confirms that NO is an important regulatory component in the signaling network of plant defense responses.

Faecal calprotectin or lactoferrin can identify postoperative recurrence in Crohn's disease

Identifying Crohns disease recurrence in symptomatic patients after ileocaecal resection is difficult. The aim of this study was to evaluate faecal concentrations of granulocyte degradation products in this setting.

Genome-wide association study implicates immune activation of multiple integrin genes in inflammatory bowel disease

Genetic association studies have identified 215 risk loci for inflammatory bowel disease, thereby uncovering fundamental aspects of its molecular biology. We performed a genome-wide association study of 25,305 individuals and conducted a meta-analysis with published summary statistics, yielding a total sample size of 59,957 subjects. We identified 25 new susceptibility loci, 3 of which contain integrin genes that encode proteins in pathways that have been identified as important therapeutic targets in inflammatory bowel disease. The associated variants are correlated with expression changes in response to immune stimulus at two of these genes (ITGA4 and ITGB8) and at previously implicated loci (ITGAL and ICAM1). In all four cases, the expression-increasing allele also increases disease risk. We also identified likely causal missense variants in a gene implicated in primary immune deficiency, PLCG2, and a negative regulator of inflammation, SLAMF8. Our results demonstrate that new associations at common variants continue to identify genes relevant to therapeutic target identification and prioritization.

Adult malnutrition screening, prevalence and management in a United Kingdom hospital: cross-sectional study.

The objectives of the present cross-sectional study were to assess the screening, prevalence and management of malnutrition and identify any co-existence with obesity in adult hospital in-patients. The Malnutrition Universal Screening Tool (MUST) was applied to all medical, surgical, orthopaedic and critical care in-patients in an acute hospital in North-East England on a single day in 2007. An audit was also performed of malnutrition screening using a locally developed tool. Patients were excluded from study if they had been an in-patient less than 24 h or if discharged on the day of study. Of 328 patients meeting inclusion criteria, 100% had full data collection (143 males, 185 females, median length of stay 8 d (range 1-90 d), median age 76 years (range 17-101 years)). Only 226 patients (68.9%) had been screened for malnutrition and thirty-one (13.7%) were at highest malnutrition risk, of which only 45.2% were appropriately referred to nutrition and dietetic services. The prevalence of malnutrition (MUST > or = 1) was 44%. The prevalence of highest risk (MUST > or = 2) increased with age (20.6% < 60 years, 29.7% 60-79 years and 39.4% > or = 80 years). In total 37.8% (n 70) of female patients had a MUST score of > or = 2 compared with 24.5% (n 35) of males. Obesity (BMI > 30 kg/m2) was identified in 9.5% of those with a MUST score > or = 2. We have shown that malnutrition is a common problem affecting over 40% of patients in this hospital-wide study. Currently malnutrition is often unrecognised and undertreated in clinical practice. Hospitals must develop comprehensive strategies to both identify and treat in-patients with this common condition.

Chemokine receptor CXCR3 agonist prevents human T-cell migration in a humanized model of arthritic inflammation

The recruitment of T lymphocytes during diseases such as rheumatoid arthritis is regulated by stimulation of the chemokine receptors expressed by these cells. This study was designed to assess the potential of a CXCR3-specific small-molecule agonist to inhibit the migration of activated human T cells toward multiple chemokines. Further experiments defined the molecular mechanism for this anti-inflammatory activity. Analysis in vitro demonstrated agonist induced internalization of both CXCR3 and other chemokine receptors coexpressed by CXCR3+ T cells. Unlike chemokine receptor-specific antagonists, the CXCR3 agonist inhibited migration of activated T cells toward the chemokine mixture in synovial fluid from patients with active rheumatoid arthritis. A humanized mouse air-pouch model showed that intravenous treatment with the CXCR3 agonist prevented inflammatory migration of activated human T cells toward this synovial fluid. A potential mechanism for this action was defined by demonstration that the CXCR3 agonist induces receptor cross-phosphorylation within CXCR3-CCR5 heterodimers on the surface of activated T cells. This study shows that generalized chemokine receptor desensitization can be induced by specific stimulation of a single chemokine receptor on the surface of activated human T cells. A humanized mouse model was used to demonstrate that this receptor desensitization inhibits the inflammatory response that is normally produced by the chemokines present in synovial fluid from patients with active rheumatoid arthritis.

Anti-tissue transglutaminase antibodies in the follow-up of adult coeliac disease.

Background  The detection of auto antibodies directed against tissue transglutaminase (anti‐tTG antibodies) has a well‐established role in the diagnosis of coeliac disease, but the value of these antibodies in long‐term follow‐up is controversial.

Thiopurine withdrawal during sustained clinical remission in inflammatory bowel disease: relapse and recapture rates, with predictive factors in 237 patients

Thiopurines (azathioprine and mercaptopurine) remain integral to most medical strategies for maintaining remission in Crohns disease (CD) and ulcerative colitis (UC). Indefinite use of these drugs is tempered by long‐term risks. While clinical relapse is noted frequently following drug withdrawal, there are few published data on predictive factors.