Can anti-AQP4 antibody damage the blood-brain barrier?

BACKGROUND: Aquaporin 4 (AQP4) is a water-channel protein predominantly expressed in astrocyte end feet that make up the blood-brain barrier (BBB). Recently, anti-AQP4 antibody has been identified as a specific biomarker of neuromyelitis optica (NMO). However, whether anti-AQP4 antibodies damage the BBB is unclear. METHODS: We evaluated BBB damage in patients with NMO and multiple sclerosis by measuring albumin leakage (AL) and studied its correlation with anti-AQP4 antibody. RESULTS: No obvious difference in AL was observed between patients with and without anti-AQP4 antibodies. In the multivariate analysis, anti-AQP4 antibody was not associated with BBB damage. Of the anti-AQP4-positive patients, 58.0% had normal AL values, and the degree of BBB damage was unrelated to the anti-AQP4 antibody titer. In addition, 41.9% of anti-AQP4-positive patients showed no gadolinium enhancement of the MRI. CONCLUSION: These results indicate that the presence of anti-AQP4 antibody alone in plasma is insufficient to disrupt the BBB.

Molecular network analysis of T-cell transcriptome suggests aberrant regulation of gene expression by NF-kappaB as a biomarker for relapse of multiple sclerosis.

Molecular mechanisms responsible for acute relapse of multiple sclerosis (MS) remain currently unknown. The aim of this study is to identify the relapse-specific biomarker genes in T lymphocytes of relapsing-remitting MS (RRMS). Total RNA of CD3+ T cells isolated from six RRMS patients taken at the peak of acute relapse and at the point of complete remission was processed for DNA microarray analysis. We identified a set of 43 differentially expressed genes (DEG) between acute relapse and complete remission. By using 43 DEG as a discriminator, hierarchical clustering separated the cluster of relapse from that of remission. The molecular network of 43 DEG investigated by KeyMolnet, a bioinformatics tool for analyzing molecular interaction on the curated knowledge database, showed the most significant relationship with aberrant regulation of gene expression by the nuclear factor-kappa B (NF-kappaB) in T cells during MS relapse. These results support the logical hypothesis that NF-kappaB plays a central role in triggering molecular events in T cells responsible for induction of acute relapse of MS, and suggest that aberrant gene regulation by NF-kappaB on T-cell transcriptome might serve as a molecular biomarker for monitoring the clinical disease activity of MS.

Close association of water channel AQP1 with amyloid-beta deposition in Alzheimer disease brains.

Aquaporin-1 (AQP1), a membrane water channel protein, is expressed exclusively in the choroid plexus epithelium in the central nervous system under physiological conditions. However, AQP1 expression is enhanced in reactive astrocytes, accumulating in brain lesions of Creutzfeldt-Jakob disease and multiple sclerosis, suggesting a role of AQP1-expressing astrocytes in brain water homeostasis under pathological conditions. To clarify a pathological implication of AQP1 in Alzheimer disease (AD), we investigated the possible relationship between amyloid-beta (Abeta) deposition and astrocytic AQP1 expression in the motor cortex and hippocampus of 11 AD patients and 16 age-matched other neurological disease cases. In all cases, AQP1 was expressed exclusively in a subpopulation of multipolar fibrillary astrocytes. The great majority of AQP1-expressing astrocytes were located either on the top of or in close proximity to Abeta plaques in AD brains but not in non-AD cases, whereas those independent of Abeta deposition were found predominantly in non-AD brains. By Western blot, cultured human astrocytes constitutively expressed AQP1, and the levels of AQP1 protein expression were not affected by exposure to Abeta(1-42) peptide, but were elevated by hypertonic sodium chloride. By immunoprecipitation, the C-terminal fragment-beta (CTFbeta) of amyloid precursor protein interacted with the N-terminal half of AQP1 spanning the transmembrane helices H1, H2 and H3. These observations suggest the possible association of astrocytic AQP1 with Abeta deposition in AD brains.

Neuromyelitis optica/Devic's disease: gene expression profiling of brain lesions.

Neuromyelitis optica (NMO), also known as Devic's disease, is an inflammatory demyelinating disease that affects selectively the optic nerves and the spinal cord, possibly mediated by an immune mechanism distinct from that of multiple sclerosis (MS). Recent studies indicate that NMO also involves the brain. Here, we studied gene expression profile of brain lesions of a patient with NMO by using DNA microarray, along with gene expression profile of the brains of Parkinson disease and amyotrophic lateral sclerosis patients. We identified more than 200 genes up-regulated in NMO brain lesions. The top 20 genes were composed of the molecules closely associated with immune regulation, among which marked up-regulation of interferon gamma-inducible protein 30 (IFI30), CD163, and secreted phosphoprotein 1 (SPP1, osteopontin) was validated by real time RT-PCR, Northern blot and Western blot analysis. Pathologically, CD68(+) macrophages and microglia expressed intense immunoreactivities for IFI30 and CD163 in NMO lesions, consisting of inflammatory demyelination, axonal loss, necrosis, cavity formation, and vascular fibrosis. KeyMolnet, a bioinformatics tool for analyzing molecular interaction on the curated knowledge database, suggested that the molecular network of up-regulated genes in NMO brain lesions involves transcriptional regulation by the nuclear factor-kappaB (NF-kappaB) and B-lymphocyte-induced maturation protein-1 (Blimp-1). These results suggest that profound activation of the macrophage-mediated proinflammatory immune mechanism plays a pivotal role in development of NMO brain lesions.

[Tailored therapy for multiple sclerosis].

Multiple sclerosis (MS) is considered as an autoimmune disease targeted to myelin and oligodendrocytes, which leads to inflammatory demyelination in the central nervous system (CNS). MS is possibly a polygenetic and multifactorial disorder in which the interaction between various genetic and environmental factors could cause clinically and pathologically heterogeneous phenotypes. Most of the previous efforts to predict clinical courses, therapeutic responses, and prognosis of MS have been unsuccessful. However, pharma-cogenomic approach by using DNA microarray, protein chip, genome-wide analysis of single nucleotide polymorphism, and bioinformatics technology has been recently established. It would help us to understand the disease mechanisms, and to identify diagnostic markers and novel therapeutic targets, and to precisely predict therapeutic responses and adverse events. This comprehensive approach promotes the development of tailored therapy in MS as well as in other neurological disorders of complex etiology.

[Anti-VGKC antibody-associated limbic encephalitis/Morvan syndrome].

Anti-voltage-gated potassium channel antibodies (anti-VGKC-Ab) cause hyperexcitability of the peripheral nerve and central nervous system. Peripheral nerve hyperexcitability is the chief manifestation of Issacs syndrome and cramp-fasciculation syndrome. Morvan syndrome is characterized by neuromyotonia with autonomic and CNS involvement. Manifestations involving the CNS without peripheral involvement are characteristic of limbic encephalitis and epilepsy. The clinical features of anti-VGKC-Ab-associated limbic encephalitis are subacute onset of episodic memory impairment, disorientation and agitation. Hyponatremia is also noted in most patients. Cortico-steroid therapy, plasma exchange and intravenous immunoglobulin are effective in treating to not only the clinical symptoms but also hyponatremia. Unlike other anti-VGKC-Ab-associated neurological disorders, paraneoplastic cases are rare. Thus, anti-VGKC-Ab-associated limbic encephalopathy is considered to be an autoimmune, non-paraneoplastic, potentially treatable encephalitis. Morvan syndrome is characterized by widespread neurological symptoms involving the peripheral nervous system (neuromyotonia), autonomic system (hyperhidrosis, severe constipation, urinary incontinence, and cardiac arrhythmia) and the CNS (severe insomnia, hallucinations, impairment of short-term memory and epilepsy). Many patients have an underlying tumor, for example thymoma, lung cancer, testicular cancer and lymphoma; this indicates the paraneoplastic nature of the disease. Needle electro-myography reveals myokimic discharge. In nerve conduction study, stimulus-induced repetitive descharges are frequently demonstrated in involved muscles. Plasma exchange is an effective treatment approach, and tumor resection also improves symptoms. Both VGKC-Ab-associated limbic encephalitis and Morvan syndrome can be successfully treated. Therefore, when these diseases are suspected, it's important to measure the anti-VGKC-Ab level.