Very early onset inflammatory bowel disease: Investigation of the IL-10 signaling pathway in Iranian children

Background & aimComparing to adult inflammatory bowel disease (IBD), those with early onset manifestations have different features in terms of the underlying molecular pathology, the course of disease and the response to therapy. We investigated the IL-10 signaling pathway previously reported as an important cause of infantile (Very Early Onset) IBD to find any possible variants.MethodWith the next generation sequencing technique we screened IL-10, IL-10RA and IL10RB genes of 15 children affected by very early onset-GI (gastrointestinal) disorders. Additionally, we analyzed them based on Thermo Fisher immune deficiency panel for genes either having a known role in IBD pathogenesis or cause the disorders with overlapping manifestations. We performed multiple functional analyses only for the cases showing variants in IL-10- related genes.ResultIn 3 out of 15 patients we identified variants including a homozygous and heterozygote mutations in IL-10RA and a novel homozygous mutation in IL-12RB1. Our functional studies reveal that in contrast to the IL-10RA heterozygote mutation that does not have deleterious effects, the homozygous mutation abrogates the IL-10 signaling pathway.ConclusionOur study suggests we need to modify the classical diagnostic approach from functional assays followed by candidate- gene or genes sequencing to the firstly parallel genomic screening followed by functional studies.     

Pediatric inflammatory bowel disease: specificity of very early onset

Introduction: The incidence of inflammatory bowel disease (IBD) has increased over the last 50 years. It is now recognized that several genetic defects can express an IBD-like phenotype at very early onset (<6 years).

Areas covered: The aim of this review was to update knowledge concerning the specificity of IBD at onset <6 years, which can include conventional/standard IBD as well as monogenic IBD-like diseases.

Expert commentary: We found that females are less prone than males to develop monogenic disorders, which have X-linked heritability in several cases. Furthermore, the Crohn’s Diseases (CD) subtype seems to be suggestive of monogenic disorders while Unclassified IBD (IBDU) subtype is predominantly found in conventional/standard IBD at onset <6 years. Isolated colonic location is prevalent in both the subsets of IBD at onset <6 years if compared to IBD at later onset. Monogenic disorders require more aggressive medical and surgical treatments and can be complicated by the occurrence of lymphomas.     

Hermansky-Pudlak syndrome with early onset inflammatory bowel disease due to loss of dysbindin expression

Hermansky-Pudlak syndrome (HPS) is a heterogeneous group of autosomal recessive genetic disorders characterized by oculocutaneous albinism, bleeding diathesis, and variable presentation of immune deficiency and dysregulation. The pathogenesis of HPS involves mutations in genes responsible for biogenesis and trafficking of lysosome-related organelles, essential for the function of melanosomes, platelet granules, and immune cell granules. Eleven genes coding for proteins in the BLOC-1, BLOC-2, BLOC-3 and AP-3 complexes have been implicated in the pathogenesis of HPS. To date, the rare subtype HPS-7 associated with bi-allelic mutations in DTNBP1 (dysbindin) has only been reported in 9 patients. We report a novel DTNBP1 splicing mutation in a 15-month-old patient with HPS-7 phenotype and severe inflammatory bowel disease (IBD). This patient's leukocytes have undetectable dysbindin protein. We also identify dysregulated expression of several genes involved in activation of the adaptive immune response. This case underscores the emerging immunological consequences of dysbindin deficiency and suggests that DTNBP1 mutations may underlie some rare cases of very early onset IBD.     

Neutrophil–T cell crosstalk in inflammatory bowel disease

Neutrophils are the most abundant leucocytes in human blood, promptly recruited to the site of tissue injury, where they orchestrate inflammation and tissue repair. The multifaceted functions of neutrophils have been more appreciated during the recent decade, and these cells are now recognized as sophisticated and essential players in infection, cancer and chronic inflammatory diseases. Consequently, our understanding of the role of neutrophils in inflammatory bowel disease (IBD), their immune responses and their ability to shape adaptive immunity in the gut have been recognized. Here, current knowledge on neutrophil responses in IBD and their capacity to influence T cells are summarized with an emphasis on the role of these cells in human disease.     

NOX1 loss-of-function genetic variants in patients with inflammatory bowel disease

Genetic defects that affect intestinal epithelial barrier function can present with very early-onset inflammatory bowel disease (VEOIBD). Using whole-genome sequencing, a novel hemizygous defect in NOX1 encoding NAPDH oxidase 1 was identified in a patient with ulcerative colitis-like VEOIBD. Exome screening of 1,878 pediatric patients identified further seven male inflammatory bowel disease (IBD) patients with rare NOX1 mutations. Loss-of-function was validated in p.N122H and p.T497A, and to a lesser degree in p.Y470H, p.R287Q, p.I67M, p.Q293R as well as the previously described p.P330S, and the common NOX1 SNP p.D360N (rs34688635) variant. The missense mutation p.N122H abrogated reactive oxygen species (ROS) production in cell lines, ex vivo colonic explants, and patient-derived colonic organoid cultures. Within colonic crypts, NOX1 constitutively generates a high level of ROS in the crypt lumen. Analysis of 9,513 controls and 11,140 IBD patients of non-Jewish European ancestry did not reveal an association between p.D360N and IBD. Our data suggest that loss-of-function variants in NOX1 do not cause a Mendelian disorder of high penetrance but are a context-specific modifier. Our results implicate that variants in NOX1 change brush border ROS within colonic crypts at the interface between the epithelium and luminal microbes.     

Very early premature ovarian failure in two sisters compound heterozygous for the FMR1 premutation

Expansion of the CGG trinucleotide repeat in the 5′ untranslated region of the fragile X mental retardation 1 (FMR1) gene within the premutation range is one of the known genetic factors associated with premature ovarian failure and earlier age at menopause. Studies have shown that approximately 16–26% of female carriers will develop premature ovarian failure, and current research is focussed on the identification of molecular factors that predict its occurrence in female carriers. In this report we present two sisters who are compound heterozygous for a premutation, and who were referred because of very early menopause, occurring at the age of 17 years in the youngest sister. Premature ovarian failure associated with FMR1 premutation at such an early age has not been reported in the literature before.     

CEDNIK syndrome in a Brazilian patient with compound heterozygous pathogenic variants

CEDNIK (Cerebral Dysgenesis, Neuropathy, Ichthyosis, and Keratoderma) syndrome is a neuro ichthyotic syndrome characterized by a clinical constellation of features including severe developmental delay, microcephaly, and facial dysmorphism. Here, we report the clinical and molecular characterization of a patient with CEDNIK syndrome harboring two compound heterozygous variants in the SNAP29 gene. The patient presents a combination of a loss-of-function SNAP29 mutation and a ～370 kb 22q11.2 deletion, each of these genetic variants inherited from one of the parents. This report provides detailed data of a patient with unprecedented genetic events leading to the CEDNIK phenotype and may contribute to the elucidation of this rare condition.     

Genetic variants and monoallelic expression of surfactant protein-D in inflammatory bowel disease

Surfactant protein-D (SP-D) is expressed on mucosal surfaces and functions in the innate immune response to microorganisms. We studied the genetic association of the two nonsynonymous SP-D single nucleotide polymorphisms (SNPs) rs721917 and rs2243639 in 256 inflammatory bowel disease (IBD) cases (123 CD and 133 UC) and 376 unrelated healthy individuals from an IBD population from Central Pennsylvania. Case-control analysis revealed a significant association of rs2243639 with susceptibility to Crohn's disease (CD) (p= 0.0036), but not ulcerative colitis (UC) (p= 0.883), and no association of rs721917 with CD (p= 0.328) or UC (p= 0.218). Using intestinal tissues from 19 individuals heterozygous for each SNP, we compared allelic expression of these two SNPs between diseased and matched normal tissues. rs2243639 exhibited balanced biallelic (BB) expression; while rs721917 exhibited differential allelic expression (BB 37%, imbalanced biallelic [IB] 45%, and dominant monoallelic [DM] 18%). Comparison of allelic expression pattern between diseased and matched normal tissues, 13 of 19 individuals (14 UC, 5 CD) showed a similar pattern. The six patients exhibiting a different pattern were all UC patients. The results suggest that differential allelic expression may affect penetrance of the SNP rs721917 disease-susceptibility allele in IBD. The potential impact of SP-D monoallelic expression on incomplete penetrance is discussed.     

T cell receptor repertoire and mitotic responses of lamina propria T lymphocytes in inflammatory bowel disease.

Human intestinal lamina propria T lymphocytes (LPL-T) physiologically exhibit minimal proliferation in response to antigen receptor stimulation in vitro. This is thought to occur as a consequence of regulatory influences which are exerted by the mucosal microenvironment. The present study is aimed at investigating whether proliferative responses of intestinal LPL-T to antigen receptor stimulation are altered in patients with inflammatory bowel disease. Accordingly, proliferative responses of LPL-T in patients with Crohn's disease and ulcerative colitis to stimulation with CD3 MoAb plus IL-2 were examined and compared with controls. In addition, T cell receptor (TCR) repertoires of LPL-T and peripheral blood T lymphocytes were determined by indirect immunofluorescence using a panel of 11 TCR V beta specific antibodies. In most patients with inflammatory bowel disease, LPL-T showed enhanced proliferation to antigen receptor stimulation compared with controls. Moreover, perhaps as a consequence, an enhanced frequency of in vivo preactivated T cells was seen as judged from an increased spontaneous proliferative response to low concentrations of exogenous IL-2. LPL-T and peripheral blood T lymphocytes exhibited similar percentages of TCR V beta gene usage both in controls and in patients. In summary, polyclonal activation of LPL-T due to impairment of local adjustment, i.e. insufficient down-regulation of TCR/CD3-dependent signalling processes, may contribute to the pathogenesis of inflammatory bowel disease.     

Alteration in T lymphocyte subpopulations in inflammatory bowel disease.

Peripheral blood mononuclear cells from thirty-one patients with inflammatory bowel disease (ulcerative colitis and Crohn's disease) were analysed for the proportions and absolute numbers of total T cells, and for the T cell subpopulations carrying Fc receptors for either IgM (Tmu cells) or IgG (T gamma cells). Twenty-six control subjects were studied simultaneously. Total T cell numbers were normal in patients with inflammatory bowel disease but there was a marked reduction in the proportion and absolute numbers of Tmu cells in patients, whether their disease was active or in remission. T gamma cells were normal. Simultaneous assessment of lymphocyte response to mitogens in vitro was performed in a group of patients. Responses to phytohaemagglutinin, concanavalin A and pokeweed mitogen were decreased and a positive correlation was found between the number of circulating Tmu cells and the responses to mitogens in vitro. These studies demonstrate that despite the presence of normal numbers of total T cells in inflammatory bowel disease, there is a marked imbalance in T cell subpopulations that correlates with mitogen responsiveness. This imbalance provides a possible cellular basis for the defect in cell-mediated immunity seen in these patients.     

Association of CTLA-4 variants with susceptibility to inflammatory bowel disease: A meta-analysis

Objective

The aim of this study was to determine whether CTLA-4 gene variants were associated with susceptibility to inflammatory bowel disease (IBD).

Methods

Meta-analysis was conducted on the association between CTLA-4 variants and IBD using: (1) allelic contrast, (2) the recessive model, and (3) the dominant model.

Results

A total of 9 relevant studies including 1739 Crohn’s disease (CD) cases, 10 relevant studies containing 1017 ulcerative colitis (UC) cases and 2685 healthy controls were involved in this meta-analysis. Overall, CTLA-4+49A/G, −318C/T and CT60 variants were not associated with IBD susceptibility in all genetic models (P > 0.05). Stratification by ethnicity indicated a significant association between the CTLA-4+49A/G variant and CD in Caucasian group (GG vs. GA + AA: OR = 0.723, 95% CI = 0.564–0.926, P = 0.010). In Asian group, meta-analysis showed a significant association between the CTLA-4 CT60 variant and UC (AA vs. AG + GG: OR = 0.375, 95% CI = 0.163–0.861, P = 0.021).

Conclusions

Based on the published literature, this meta-analysis suggests that the CTLA-4+49A/G variant may be related to CD susceptibility in Caucasians, and the CTLA-4 CT60 variant may be associated with UC susceptibility in Asians.     

Environmental influences on T regulatory cells in inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic, idiopathic inflammation of the intestine. The disease is thought to result from a combination of genetic and environmental factors which ultimately leads to a mucosal immune system that overreacts to normal constituents of the mucosal microbiota. The inflammation in IBD is primarily mediated by inappropriate production of proinflammatory cytokines by CD4(+) T effector cells, effects that are suppressed by CD4(+) T regulatory cells. Defects in both the function of T regulatory cells, and the ability of T effector cells to be suppressed, have been implicated in IBD. In this review we will discuss environmental factors, including cytokines, vitamins A and D, and commensal bacteria, which influence the phenotype and function of regulatory T cells and thereby alter the course of IBD. We will also discuss how these environmental signals can be manipulated therapeutically in order to improve the function of regulatory T cells and ultimately restore mucosal homeostasis in patients with IBD.     

A novel neurodevelopmental disorder associated with compound heterozygous variants in the huntingtin gene

We report compound heterozygous variants in HTT, the gene encoding huntingtin, in association with an autosomal recessive neurodevelopmental disorder. Three siblings presented with severe global developmental delay since birth, central hypotonia progressing to spastic quadraparesis, feeding difficulties, dystonia (2/3 sibs), prominent midline stereotypies (2/3), bruxism (1/3), high myopia (2/3), and epilepsy (1/3). Whole exome sequencing identified compound heterozygous variants in HTT that co-segregated in the three affected sibs and were absent in an unaffected sib. There were no additional variants in other genes that could account for the reported phenotype. Molecular analysis of HTT should be considered, not just for Huntington''s disease, but also in children with a Rett-like syndrome who test negative for known Rett and Rett-like syndrome genes.     

基于补体C5a在炎症性肠病中的作用研究

目的探索2,4,6-三硝基苯磺酸(TNBS)诱导炎症性肠病(IBD)发病机制中补体C5a的作用。方法选择SPF级雄性Sprague-Dawley(SD)大鼠60只,鼠龄6~8周,体质量180~220 g。随机分为3组,即空白对照组、TNBS IBD组、TNBS+抗C5a单克隆抗体干预组(简称治疗组)。IBD大鼠建模方法采用TNBS联合乙醇诱导灌肠法。治疗组在建模后立即每只腹腔注射抗C5a单克隆抗体1.5 mg干预。利用酶联免疫吸附分析(ELISA)法检测不同时间段大鼠血清中炎性介质C5a和白细胞介素(IL)-6、肿瘤坏死因子α(TNF-α)的表达水平;另给予C5a拮抗剂后,再次检测大鼠血清中IL-6、TNF-α的表达水平。结果C5a、IL-6、TNF-α伴随着炎症的进展而增高,伴随炎症的转归出现下降趋势,即血清中C5a、IL-6、TNF-α的变化趋势与炎症反应程度呈正向相关性;给予C5a拮抗剂后,TNBS IBD组与治疗组相比,IL-6、TNF-α的表达水平有明显下调趋势,差异有统计学意义(P<0.05)。结论初步判断抗C5a单克隆抗体可能通过抑制IL-6、TNF-α的表达,有效地降低了IBD炎症反应,提示C5a在IBD发病机制中发挥着重要作用。     

T cell mimicry in inflammatory heart disease

Inflammatory heart diseases such as myocarditis and rheumatic heart disease result from the infiltration of the myocardium or valve with T cells and macrophages that result in scarring of the myocardium or valve and alteration in cardiac function. Our studies of T cells from these diseases have identified cardiac myosin in both rheumatic carditis and myocarditis as an important autoantigen. In rheumatic heart disease, streptococcal M protein specific T cells migrate to valves. By investigating streptococcal M protein and cardiac myosin in the Lewis rat model of myocarditis and valvulitis, T cell mimicry is supported as a potential mechanism in disease. Structural and immunological mimicry between the streptococcal M protein and cardiac myosin is shown directly in the Lewis rat model. Rat T cell lines demonstrate mimicry between cardiac myosin and M protein, and T cells isolated directly from inflammatory lesions in myocarditis respond to streptococcal M protein peptides. Studies in BALB/c mice also support the immunological crossreactivity of T cells primed against cardiac myosin with streptococcal M protein peptides containing cardiac myosin homologies. T cell lines produced from the Lewis rat specific to the cardiac myosin like sequences of streptococcal M protein migrated to the valves after passive transfer of the M protein specific T cell lines. In coxsackieviral myocarditis in the MRL mouse strain, cardiac myosin mimicking M protein peptide NT4 was found to induce tolerance and prevent coxsackieviral induced myocarditis, suggesting T cell mimicry between coxsackievirus and streptococcal M protein, both of which are associated with inflammatory heart disease. T cell mimicry between cardiac myosin and microbial antigens such as the streptococcal M protein may prime the immune system for inflammatory heart disease.     

Decreased suppressor cell activity in inflammatory bowel disease.

Studies were performed on eleven patients with inflammatory bowel disease to determine if there was an alteration in concanavalin A (Con A) induced suppressor cell activity. Similar investigations were also performed on twenty-one control subjects and five patients with other inflammatory conditions. Supressor cells were generated by pre-incubation of peripheral blood mononuclear cells with a mitogenic concentration of Con A, followed by treatment with mitomycin C and alpha-methyl mannoside. Under these conditions, cells obtained from normal individuals are then capable of suppressing the Con A-stimulated blast transformation responses of fresh allogeneic lymphocytes in new cultures. We found that in twenty out of twenty-one control subjects, and all five patients with other inflammatory disorders, Con A-stimulated suppressor cell activity was demonstrable. Four patients with inflammatory bowel disease, whose disease was mildly active or was in clinical remission, had elicitable suppressor cell activity which fell within the normal range. In contrast, suppressor cell activity was markedly diminished or absent in seven patients with severe and active inflammatory bowel disease. These studies suggest that an alternation in Con A-stimulated suppressor cells exists in patients with active inflammatory bowel disease, which may contribute, in part, to the persistent inflammation in the gastrointestinal tract.