Persistent systemic inflammation and atypical enterocolitis in patients with NEMO syndrome

Dendritic cells from humans with hypomorphic mutations in IKBKG/NEMO have impaired mitogen-activated protein kinase activity

The covalent attachment of lysine 63-linked polyubiquitin to the zinc-finger domain of IKBKG/NEMO (also known as IKKγ) is necessary for full activation of NF-κB. Impairments of this biochemical mechanism explain the deleterious effects of hypomorphic NEMO mutations on NF-κB signaling function in humans suffering from X-linked ectodermal dysplasia and immunodeficiency. Nevertheless, the biological function of the NEMO zinc-finger domain in the regulation of mitogen-activated protein kinase (MAPK) activity is poorly understood. Here we show that dendritic cells from patients with EDI caused by a C-terminal E391X deletion of the zinc finger of NEMO exhibit impaired MAPK activation in response to lipopolysaccharide (LPS) stimulation. Interestingly, DCs from patients with a C417R missense mutation within the zinc finger domain of NEMO in which ubiquitination of NEMO is preserved are also defective in JNK and ERK activity following LPS stimulation. Our findings indicate that the structural integrity of the NEMO ZF domain is more important than its polyubiquitination for full activation of the MAPK. Furthermore, phosphorylation and polyubiquitination of upstream TAK1 were significantly reduced in the E391X zinc-finger deleted patients, indicating that the NEMO zinc finger may play an important role in assembling the proximal signaling complex for MAPK activation.

NEMO syndrome (incontinentia pigmenti) and systemic lupus erythematosus: a new disease association

Congenital diseases are increasingly being recognised in adults because of clinical mimicry, variable clinical picture or rarity of the disease; pregnancy is a valuable diagnostic occasion. The present case is the first report of an association report between NEMO syndrome (an acronym of the mutated, non-functioning gene, NF-kB essential modulator), a rare X-linked disease, characterised by developmental anomalies, immunodepression and skin lesions, and systemic lupus erythematosus (SLE). A 35-year-old patient affected by SLE sought clinical advice in the 8th week of gestation. The diagnosis of SLE dated back to the age of 24, when multisystemic manifestations (pleuropericarditis, weight loss, alopecia, skin involvement, joint pain, kidney involvement) were observed. She had been treated with steroids since 1999; immunosuppressive drugs had been added for short periods. Developmental anomalies were present, including oligodontia, retinal problems, anomalies of the corpus callosum and pes planovalgus. Family history included multiple miscarriages, dental malformations and oligodontia and skin blistering in the first months of life. On these bases, incontinentia pigmenti (IP; or NEMO syndrome) was diagnosed and confirmed by genetic testing. The NEMO gene is implicated in immune deficiencies as well as in autoimmune diseases. This report may suggest a role for NF-kB essential modulator in the pathogenesis of SLE, in the context of the complex immunologic deficiencies increasingly associated with autoimmune diseases.

Successful treatment with infliximab for inflammatory colitis in a patient with X-linked anhidrotic ectodermal dysplasia with immunodeficiency

X-linked anhidrotic ectodermal dysplasia with immunodeficiency (X-EDA-ID) is caused by hypomorphic mutations in the gene encoding nuclear factor-κB essential modulator protein (NEMO). Patients are susceptibile to diverse pathogens due to insufficient cytokine and frequently show severe chronic colitis. An 11-year-old boy with X-EDA-ID was hospitalized with autoimmune symptoms and severe chronic colitis which had been refractory to immunosuppressive drugs. Since tumor necrosis factor (TNF) α is responsible for the pathogenesis of NEMO colitis according to intestinal NEMO and additional TNFR1 knockout mice studies, and high levels of TNFα-producing mononuclear cells were detected in the patient due to the unexpected gene reversion mosaicism of NEMO, an anti-TNFα monoclonal antibody was administered to ameliorate his abdominal symptoms. Repeated administrations improved his colonoscopic findings as well as his dry skin along with a reduction of TNFα-expressing T cells. These findings suggest TNF blockade therapy is of value for refractory NEMO colitis with gene reversion.

Epithelial-specific blockade of MyD88-dependent pathway causes spontaneous small intestinal inflammation

Accumulating evidence suggests a role for Toll-like receptor (TLR) signaling at the intestinal epithelial cells (IECs) level for intestinal protection against exogenous injury or pathogenic infection. We hypothesized that MyD88 dependent TLR signaling at intestinal epithelium is critical for mucosal immune homeostasis. In the current study, a transgenic mouse model was generated in which a dominant-negative mutant of MyD88 (dnMyD88) was driven by an intestinal epithelial-specific murine villin promoter. Aged transgenic mice spontaneously developed chronic small intestinal inflammation, as revealed by increased CD4+ and CD8+ lymphocytes, neutrophil and macrophage infiltration, increased production of cytokines as TNF-alpha, IFN-gamma, IL-1beta, and IL-17, crypt abscesses, lymphedema, and Goblet cell depletion. The chronic inflammation was not due to increased epithelial apoptosis or permeability, but to a decreased Paneth cell-derived alpha-defensins (cryptdins) and RegIII-gamma and increased commensal bacteria translocation. Thus, epithelial MyD88-dependent pathway plays an essential role in limiting mucosal microflora penetration and preventing mucosal immunoregulation disturbance in vivo.