Hideki Houzen

Tumor necrosis factor enhancement of transient outward potassium currents in cultured rat cortical neurons

The effect of recombinant human tumor necrosis factor‐α (TNF) on voltage‐gated membrane currents of cultured neurons derived from embryonic rat cerebral cortex was studied using the whole‐cell patch‐clamp technique. Treatment of neurons with TNF resulted in an increase in outward potassium current density, dependent upon the concentration of TNF and the incubation time, without affecting other membrane currents such as barium and N‐methyl‐D‐aspartate (NMDA). Long exposures (12–48 hr) to TNF (10–100 ng/ml) increased transient outward potassium current (A‐current) density without affecting the parameters of activation and inactivation of the current. Prolonged exposures to TNF diminished its increasing effect on the A‐current. Since the increase of A‐current density induced by TNF is inhibited by both the anti‐TNF receptor antibody and cycloheximide treatment, the effect of TNF might be mediated through receptors and by de novo synthesis of the channel protein itself and/or modulating proteins associated with the channel activities. Results indicate that phosphatidylcholine‐specific phospholipase C and protein kinase C, but not ceramide, are involved in the signal transduction. In toxicological experiments, TNF had no neurotoxicity. Moreover, a 12 hr pretreatment of TNF protected neurons against NMDA‐induced neurotoxicity. This protective effect of TNF was canceled by 4‐aminopyridine, an A‐current blocker, suggesting that the increase of A‐current densities induced by TNF contributes to the neuroprotection. J. Neurosci. Res. 50:990–999, 1997. © 1997 Wiley‐Liss, Inc.

Increasing prevalence and incidence of multiple sclerosis in northern Japan

Background We previously reported that prevalence of multiple sclerosis (MS) in Japan was 8.6/100,000 individuals in 2001. This was much higher than prevalence previously reported from Asian countries. A second epidemiologic survey was conducted to assess changes in MS prevalence and incidence over the last 30 years in Tokachi province of Hokkaido, the northernmost island of Japan. Methods The authors studied the frequency of MS in the community of Tokachi Province, where the population has stabilized between 350,000 and 360,000 over the last 30 years. The survey was conducted at the same institutions using the same methods as the first survey in 2001. Results On March 31, 2006, 47 subjects satisfied Poser’s criteria for MS. The prevalence rate increased from 8.6 to 13.1/100,000 individuals between 2001 and 2006. The prevalence of conventional MS (C-MS) increased in five years although the prevalence of optic-spinal MS (OS-MS) did not increase. The mean annual incidence increased from 0.15 (1975–1989) to 0.68 (1990–2004). Conclusions The results show the highest MS prevalence in Asia; the increase in MS prevalence in Tokachi Province may be due to increased incidence after 1990.

Increased prevalence, incidence, and female predominance of multiple sclerosis in northern Japan

OBJECTIVE To carry out the third epidemiologic surveillance of multiple sclerosis (MS) in Tokachi province, on the northernmost island of Japan, and to compare the results of the present survey on the prevalence, incidence, and characteristics of MS and neuromyelitis optica (NMO) with those of previous surveys performed in 2001 and 2006. METHODS A data processing sheet was sent to all MS-related institutions in Tokachi province, and all sheets were collected in March 2011. The criteria of Poser were used for diagnosing MS and the criteria proposed by Wingerchuk for diagnosing NMO. We then compared the results of the present survey with those of previous surveys performed in 2001 and 2006 in the same community. RESULTS Fifty-seven patients diagnosed with MS according to the criteria of Poser were identified. The prevalence was 16.2/100,000 in 2011, which was higher than in the previous studies. The female/male ratio of MS was 2.63, 2.75, and 3.38 in 2001, 2006, and 2011, respectively. Three patients fulfilled the criteria for diagnosis of NMO in 2011; the prevalence of NMO was 0.9/100,000. CONCLUSIONS The results of this study suggest that the prevalence and the female predominance of MS have been increasing, due to an increase in the incidence after 1990, and that the prevalence of NMO is relatively low in northern Japan.

A novel D104G mutation in the adenine nucleotide translocator 1 gene in autosomal dominant progressive external ophthalmoplegia patients with mitochondrial DNA with multiple deletions

Autosomal dominant progressive external ophthalmoplegia is a mitochondrial disorder characterized by multiple large deletions of mitochondrial DNA. A recent study showed pathogenic heterozygous missense mutations in the heart/skeletal muscle isoform of the adenine nucleotide translocator 1 gene in autosomal dominant progressive external ophthalmoplegia patients. In one Japanese autosomal dominant progressive external ophthalmoplegia family, we found a novel A‐to‐G heterozygous mutation at nucleotide 311 of the adenine nucleotide translocator 1 gene, which segregated with affected individuals and could not be detected in the genomic DNA sequence of 120 normal controls. This mutation converted a highly conserved aspartic acid into a glycine at codon 104. Polymerase chain reaction analysis of single muscle fibers showed the presence of one type of deletion in each fiber, suggesting clonal expansion of mitochondrial DNA with deletions. These findings support the pathogenesis of the adenine nucleotide translocator 1 gene mutation in human disease.

Effects of β-adrenoceptor stimulation on contractility, [Ca2+]i, and Ca2+ current in diabetic rat cardiomyocytes

The mechanism of the diminished inotropic response to β-adrenoceptor stimulation in diabetic hearts was studied in enzymatically isolated diabetic rat ventricular myocytes in comparison with age-matched controls. The increases in contractions and intracellular Ca2+ concentration ([Ca2+]i) transients produced by isoproterenol were markedly diminished in diabetic myocytes. The inotropic and [Ca2+]iresponses to forskolin and dibutyryl cAMP (DBcAMP) were also reduced. No significant difference was found in the stimulating effects of isoproterenol, forskolin, and DBcAMP on the L-type Ca2+ current ( I Ca) between control and diabetic myocytes. The rise of [Ca2+]iin response to rapid caffeine application, an index of sarcoplasmic reticulum (SR) Ca2+ content, was significantly decreased in diabetic myocytes. Isoproterenol, forskolin, and DBcAMP enhanced this [Ca2+]iresponse to caffeine in control myocytes more markedly than in diabetic myocytes. The changes in the isoproterenol responses observed in diabetic myocytes were prevented by insulin therapy. We conclude that 1) diabetes causes an impairment of the contractile and [Ca2+]iresponses of cardiac myocytes when stimulated at both β-adrenoceptors and the postreceptor level without affecting the I Ca response and 2) altered SR functions of uptake and/or release of Ca2+ may primarily contribute to the diminished β-adrenergic response.The mechanism of the diminished inotropic response to beta-adrenoceptor stimulation in diabetic hearts was studied in enzymatically isolated diabetic rat ventricular myocytes in comparison with age-matched controls. The increases in contractions and intracellular Ca2+ concentration ([Ca2+]i) transients produced by isoproterenol were markedly diminished in diabetic myocytes. The inotropic and [Ca2+]i responses to forskolin and dibutyryl cAMP (DBcAMP) were also reduced. No significant difference was found in the stimulating effects of isoproterenol, forskolin, and DBcAMP on the L-type Ca2+ current (ICa) between control and diabetic myocytes. The rise of [Ca2+]i in response to rapid caffeine application, an index of sarcoplasmic reticulum (SR) Ca2+ content, was significantly decreased in diabetic myocytes. Isoproterenol, forskolin, and DBcAMP enhanced this [Ca2+]i response to caffeine in control myocytes more markedly than in diabetic myocytes. The changes in the isoproterenol responses observed in diabetic myocytes were prevented by insulin therapy. We conclude that 1) diabetes causes an impairment of the contractile and [Ca2+]i responses of cardiac myocytes when stimulated at both beta-adrenoceptors and the postreceptor level without affecting the ICa response and 2) altered SR functions of uptake and/or release of Ca2+ may primarily contribute to the diminished beta-adrenergic response.

Effects of caffeine on the freezing of gait in Parkinson's disease.

Caffeine is a nonselective competitive blockade of adenosine A1 and A2A receptors. In this report, we studied the efficacy of 100 mg of caffeine per day on the freezing of gait (FOG) for patients with Parkinsons disease. Different subtypes of FOG showed different therapeutic responses to caffeine. Caffeine improved “total akinesia” type of FOG, but had no effect on “trembling in place.” Tolerance developed to the beneficial effect of caffeine on FOG within a few months, but a 2‐week caffeine withdrawal period could restore the effect of caffeine.

DNAJB6 myopathy in an Asian cohort and cytoplasmic/nuclear inclusions

DNAJB6, which encodes DnaJ homolog, subfamily B, member 6 (DNAJB6) was recently identified as a causative gene for limb-girdle muscular dystrophy type 1D (LGMD1D). DNAJB6 is a member of heat shock protein 40 and contains a J domain, G/F domain and C-terminal domain. Only three different mutations have been identified in 11 families. In this study, we identified seven Japanese individuals from four unrelated families who carried a DNAJB6 mutation. We found a novel p.Phe96Ile substitution and a previously reported p.Phe96Leu change in the G/F domain of DNAJB6. All affected individuals showed slowly progressive muscle weakness, mainly in their legs, and their muscle pathology showed cytoplasmic inclusions and rimmed vacuoles. Our immunohistochemical analysis detected cytoplasmic accumulations associated with chaperone-assisted selective autophagy together with intranuclear accumulations of DNAJB6 and heat shock 22-kD protein 8 (HSPB8). This is the first report of Asian patients with LGMD1D. Our new findings may contribute to understanding the pathological mechanisms of this myopathy.

Clinical features of spinal cord sarcoidosis: analysis of 17 neurosarcoidosis patients

The diagnosis of neurosarcoidosis is often difficult; the imaging signs of spinal cord sarcoidosis sometimes mimic those of cervical spondylotic myelopathy, which is common in elderly persons. We examined the characteristics of spinal cord sarcoidosis in Japanese patients with neurosarcoidosis. This case series identified patients with neurosarcoidosis at four general hospitals and one university hospital from April 1998 to September 2010. All diagnoses were based on the diagnostic criteria proposed by Zajicek et al. Seventeen patients (nine men and eight women) were involved: six patients with spinal cord lesions accompanied by cervical spondylosis, five with cerebral lesions, three with cranial nerve lesions, two with meningitis, and one with nerve root lesions. Patients with spinal cord sarcoidosis had a higher onset age, longer duration from onset to diagnosis, reduced leukocytosis in the cerebrospinal fluid (CSF), and lower angiotensin-converting enzyme (ACE) levels in the CSF. The results of this study indicate that diagnosis of spinal cord sarcoidosis requires careful evaluation.

Clinical characterization and successful treatment of 6 patients with Churg-Strauss syndrome-associated neuropathy

OBJECTIVE To confirm the reported findings and clarify unknown clinical features of Churg-Strauss syndrome (CSS)-associated neuropathy and design appropriate treatment. PATIENTS AND METHODS We assessed the clinical features of 6 patients with CSS-associated neuropathy. RESULTS Mononeuritis multiplex was present in 4 cases and polyneuropathy in the remaining cases. Both groups progressed to sensori-motor polyneuropathy in an acute or subacute course. All cases showed bronchial asthma and eosinophilia. Two cases with serum antineutrophil cytoplasmic antibodies to myeloperoxidase (MPO-ANCA) had an acute clinical course and severe symptoms. Nerve conduction studies (NCS) of these 2 cases revealed conduction blocks at the initial stage, although NCS finally indicated sensori-motor axonopathy at the involved extremities. For treatment, high-dose corticosteroid therapy for 4 cases, and cyclophosphamide combined with corticosteroids for 1 case, were effective. For the remaining case, intravenous immunoglobulin (IVIg) at the chronic phase resulted in a slow improvement of neuropathy in the symptomatic aspect. There was no relapse of neuropathy with low-dose corticosteroid treatment for 14-24 months after the initial treatment, except 1 case. There was also no relapse in the other case that was treated with moderate-dose steroids. CONCLUSION Our study showed that CSS-associated neuropathy is a treatable disorder and that the first choice therapy is high-dose corticosteroid. In cases where corticosteroids are ineffective or for severe cases, immunosuppressive therapy (cyclophosphamide) with steroids should be considered, and IVIg might be a treatment option.

Thiamine and its derivatives inhibit delayed rectifier potassium channels of rat cultured cortical neurons

We examined the effects of thiamine and its derivatives on voltage-gated ion channels of neuronal cells isolated from fetal forebrain cortex and cultured for 6-14 days. Under the whole-cell voltage clamp, thiamine tetrahydrofurfuryl disulfide (TTFD), a membrane-permeable derivative of thiamine, inhibited the delayed rectifier K+ current (IK) in a concentration-dependent manner (10(-4)-10(-3) M). The IK-suppressing effect was also observed by internal perfusion with 1 mM thiamine, but not by the external application of thiamine, indicating the poor permeability of thiamine through the cell membrane. However, thiamine which was applied directly to the intracellular side of patch membranes in the inside-out configuration failed to decrease the open probability of the single IK channel. In contrast, thiamine diphosphate decreased both the open probability and the open-time of the channel without changing the single channel conductance. These results suggest that phosphorylated thiamine can function as an endogenous K+ channel blocker in neuronal cells. TTFD, when applied extracellularly at a concentration of 1 mM, prolonged the action potential (AP) duration of neurons (172.8 +/- 6.6%) without changing the resting membrane potential or AP amplitude, while the same concentration of thiamine did not influence any parameters of the AP, implying that TTFD may cause the potentiation of neuronal AP through the inhibition of IK.