Takahiro Maruta

Autoimmune Targets of Heart and Skeletal Muscles in Myasthenia Gravis

OBJECTIVE To investigate the clinical, histological, and immunological features of patients with myasthenia gravis (MG) who also developed myocarditis and/or myositis. DESIGN Observational and retrospective case series. SETTING Keio University, Hanamaki General Hospital, Kanazawa University, Nagasaki University, and Juntendo University. PATIENTS A cohort of 8 patients with MG with clinically defined inflammatory myopathies. INTERVENTIONS Clinical and histological features were described. Serological analyses included MG-related antistriational autoantibodies (those to titin, ryanodine receptor, muscular voltage-gated potassium channel Kv1.4) and myositis-specific autoantibodies. RESULTS Of 924 patients with MG, 8 (0.9%) had inflammatory myopathies. The mean (SD) onset age of MG was 55.3 (10.3) years. All patients showed severe symptoms with bulbar involvement; 5 patients had myasthenic crisis and 4 had invasive thymoma. Myocarditis was found in 3 patients and myositis in 6. Myocarditis, developing 13 to 211 months after the MG onset, was characterized by heart failure and arrhythmias. Myositis, developing before or at the same time as MG, affected limb and paraspinal muscles. Histological findings of skeletal muscles showed CD8(+) lymphocyte infiltration. Seven patients had 1 of these antistriational autoantibodies but not myositis-specific autoantibodies. Immunomodulatory therapy was required for all patients and was effective for both MG and inflammatory myopathies, although 1 patient died. CONCLUSIONS Heart and skeletal muscles are autoimmune targets in some patients with MG. This autoimmunity has a broad clinical spectrum with antistriational autoantibodies.

Lambert-Eaton myasthenic syndrome as an autoimmune calcium-channelopathy.

Lambert-Eaton myasthenic syndrome, often associated with small-cell lung carcinoma, is a disease of neuromuscular transmission in which antibodies directed against voltage-gated calcium channel (VGCC)(P/Q-type) in the motor nerve terminal play a crucial role in causing a deficient quantal release of acetylcholine. The motor nerve terminal and carcinoma cell may share a common antigen. The study using synthetic peptides and recombinant protein specified the extracellular S5-S6 linker regions in 3 of 4 domains as immunodominant sites in the molecular structure of P/Q-type VGCC alpha1 subunit. Also, the study by use of peptides and recombinant protein corresponding to synaptotagmin I suggested that in this functionally VGCC-associated presynaptic protein, the segment which exposes extracellularly during exocytosis can be immunogenic for the syndrome.

Voglibose inhibits postprandial hypotension in neurologic disorders and elderly people

The authors examined blood pressure, glucose, insulin, and neurotensin before and after intake of 75 g glucose with or without voglibose in 28 neurologic patients and 20 healthy controls. Voglibose significantly prevented hypotension and neurotensin increment after glucose intake and had no influence on glucose or insulin increment. These results suggest that voglibose benefits postprandial hypotension.

Autoantibody to dihydropyridine receptor in myasthenia gravis.

To investigate autoantibodies related to excitation-contraction (E-C) coupling in patients with myasthenia gravis (MG), we developed a novel method to detect autoantibodies against dihydropyridine receptor (DHPR). Using this method, we detected DHPR antibody in 37% (11 out of 30) of MG patients with thymoma. Antibodies were not detected in normal nor disease controls. The titer of DHPR antibodies showed no significant correlation with autoantibodies to acetylcholine nor ryanodine receptors. The DHPR antibody is another marker for thymoma in MG, and it might have some role in clinical symptoms related to E-C coupling.

Inhibition by human sera of botulinum neurotoxin-A binding to synaptosomes: a new assay for blocking and non-blocking antibodies.

The mouse protection assay (MPA), which is an in vivo assay, is currently the most widely used method for monitoring blocking antibodies (Abs) in botulinum neurotoxin (BoNT)-treated patients. In recent studies we found that a number of the regions on the heavy (H) subunit of BoNT/A that bind blocking mouse Abs coincided, or overlapped, with the regions that bind to mouse synaptosomes (snps). This suggested that blocking anti-BoNT/A Abs would be expected to inhibit BoNT/A binding to snps. In the present work, we analyzed sera from 58 cervical dystonia (CD) patients who had been treated with BOTOX (a preparation of BoNT/A serotype) for blocking Abs by MPA and by their abilities to inhibit in vitro the binding of 125I-labeled active BoNT/A or inactive toxin (toxoid) to mouse brain snps. With active 125I-labeled BoNT/A-snps binding, the MPA-positive sera (n = 30) displayed inhibition levels that were distinctly higher (mean = 21.1 +/- 5.8) than those obtained with MPA-negative sera (n = 28) (mean = -1.3 +/- 3.9; p < 0.0001) or control sera (n = 19) (mean = -3.4 +/- 2.8; p < 0.0001). Similarly, inhibition levels by MPA-positive sera of 125I-labeled toxoid snp-binding (mean = 48.6 +/- 8.7) were distinctly higher than inhibition by MPA-negative sera (mean=10.0+/-7.6; p < 0.0001) or control sera (mean = 1.8 +/- 6.9; p < 0.0001). Thus, using labeled active toxin or toxoid, the inhibition assay correlated very well with the MPA. The inhibitory activity of the non-protective sera generally correlated with the duration of survival after toxin challenge (correlation coefficients of inhibition: active toxin = 0.445; p = 0.0167; inactive toxoid = 0.774; p < 0.0001). It is concluded that the snp-inhibition assay reported here is reliable, reproducible and correlates very well with the MPA. It requires much less serum (0.75% of the amount needed for the MPA) and is considerably less costly than the MPA. With either 125I-labeled active toxin or toxoid, it is possible to distinguish CD sera that have blocking Abs from those that lack such Abs. Since the results with the toxoid were as discriminating as those of the active toxin, it would not even be necessary to use active toxin in these assays.

Sympathetic skin response and heart rate variability as diagnostic tools for the differential diagnosis of Lewy body dementia and Alzheimer's disease: a diagnostic test study.

Objective The purpose of this study is to investigate the usefulness of sympathetic skin response (SSR) and heart rate variability (HRV) for the differential diagnosis of patients with dementia with Lewy bodies (DLB). Design A diagnostic test study. Setting Single centre in Japan. Participants We examined 20 patients with probable Alzheimers disease (AD) diagnosed with NINCDS-ADRDA criteria and 20 with probable DLB diagnosed with the criteria of the third international DLB workshop. Methods For the SSR measurement, surface electrodes were used: the active recording electrode was placed on the palm of the hand and the reference electrode was placed on the dorsum of the same hand. SSR was induced by a median nerve electrical stimulation at an amplitude of 20 mA. For the HRV measurement, the A–A intervals were measured twice for 2 min with an interval of 5 min in a sitting position after a rest of 5 min. From the low-frequency power (LF; 0.02–0.15 Hz) and high-frequency power (HF; 0.15–0.50 Hz), the ratio of LF to HF power (LF/HF) was calculated using the maximal entropy method. Results SSR and HRV could detect the abnormality of autonomic function in patients with DLB at sensitivities of 85% and 90%, respectively. On the other hand, SSR and HRV detected an abnormality of autonomic function in patients with AD at sensitivities of 15% and 25% (p<0.05). The combination of the SSR and the HRV (double-positive) indicated abnormal autonomic function was recorded in only 1 of 20 patients (5%) with AD. In contrast, this combination indicated autonomic abnormality in 15 of 20 patients with DLB by our criteria (75%). Conclusions SSR and HRV can be applied to differentiate DLB from AD.

Up-regulation of MHC class I and class II in the skeletal muscles of myasthenia gravis

The up-regulation of MHC in muscles is thought to be associated with inflammatory myopathies. The expression of MHC class I and class II was examined in muscles of myasthenia gravis (MG). MG muscle specimens from all 5 patients with thymoma and 2 of 5 without thymoma showed MHC class I up-regulation and 3 of 5 with thymoma showed MHC class II. The up-regulation of MHC in MG muscles is thus considered to be a common phenomenon. MG muscles expressed not only MHC class I but also class II, and these muscles could thus act as immunoregulating cells in MG.

Vaccination with a MHC class II peptide in Alum and inactive pertussis strongly ameliorates clinical MG in C57BL/6 mice

We have investigated the efficacy of immunization against peptides from predisposing MHC class II molecules in human-compatible adjuvants for ameliorating experimental autoimmune myasthenia gravis (EAMG). C57BL/6 mice were immunized three times with the peptide I-Abetab62-76 in Alum+killed pertussis organisms (PT) prior to two injections with tAChR. The treatment greatly reduced the occurrence and severity of clinical MG relative to controls that received saline/Alum+PT or none. It also reduced antibody and T-cell responses against tAChR. The results have important implications for the possible immunotherapy of MG by targeting disease-associated MHC.

Autoantibody-induced internalization of nicotinic acetylcholine receptor α3 subunit exogenously expressed in human embryonic kidney cells.

Autoantibody against nicotinic acetylcholine receptor (nAChR) α3 subunit has been implicated in the pathogenesis of paraneoplastic neurological syndrome. To examine the effect of anti-α3 subunit autoantibody on cell-surface nAChRs, we established human embryonic kidney 293 cells stably co-expressing α3 and β4 subunits. Upon incubation with seropositive patients serum, this cell line showed co-accumulation of patients IgG and α3 subunits in the cytoplasm. These data support the hypothesis that anti-α3 subunit autoantibody induces internalization of cell-surface nAChRs and thereby impairs synaptic transmission.

Spectral Analyses of Heart Rate Variability by Acceleration Plethysmography for Diagnostic Support of Migraine: Clinical Research

It is suspected that the pathophysiology of migraine has a relation to the autonomic dysfunction. We studied to assess the autonomic function in migraine using the spectral analysis of heart rate variability (HRV) by accelerated plethysmography (APG). Five-hundred-twenty-four patients received the health check-ups in an affiliated hospital since September, 2011 to April, 2013. Eighty-three patients with headache and 38 controls were enrolled in this study. The patients were subdivided into 19 with migraine (19 female), 26 with tension-type headache (TTH) (7 male, 19 female) and 31 of other headaches using a questionnaire based on the International Classification of Headache Disorders 2nd Edition. Patients with migraine or tension-type headache underwent examinations using APG with an orthostatic load. Twenty-four controls without headache received same examinations. As a result, the standing/sitting ratio of spectral power of high-frequency (HF) in the migraine group was higher than those of TTH (p=0.0277) and normal controls (p=0.0104). The cut-off value of 1.058 could separate migraine from TTH with sensitivity of 0.632 and specificity of 0.846. The results suggested that the parasympathetic activity accentuated by orthostatic load in patients with migraine, on the contrarily the parasympathetic activities diminished by orthostatic load in patients with TTH or normal controls. This study showed that spectral analysis of HRV by APG is a supportive tool to distinguish migraine from TTH.