Tsubasa Takizawa

High-mobility group box 1 is an important mediator of microglial activation induced by cortical spreading depression

Single episodes of cortical spreading depression (CSD) are believed to cause typical migraine aura, whereas clusters of spreading depolarizations have been observed in cerebral ischemia and subarachnoid hemorrhage. We recently demonstrated that the release of high-mobility group box 1 (HMGB1) from cortical neurons after CSD in a rodent model is dependent on the number of CSD episodes, such that only multiple CSD episodes can induce significant HMGB1 release. Here, we report that only multiple CSD inductions caused microglial hypertrophy (activation) accompanied by a greater impact on the transcription activity of the HMGB1 receptor genes, TLR2 and TLR4, while the total number of cortical microglia was not affected. Both an HMGB1-neurtalizing antibody and the HMGB1 inhibitor glycyrrhizin abrogated multiple CSD-induced microglial hypertrophy. Moreover, multiple CSD inductions failed to induce microglial hypertrophy in TLR2/4 double knockout mice. These results strongly implicate the HMGB1–TLR2/4 axis in the activation of microglia following multiple CSD inductions. Increased expression of the lysosomal acid hydrolase cathepsin D was detected in activated microglia by immunostaining, suggesting that lysosomal phagocytic activity may be enhanced in multiple CSD-activated microglia.

Temporal profiles of high-mobility group box 1 expression levels after cortical spreading depression in mice

Introduction Cortical spreading depression (CSD) has recently been shown to induce the release of the nuclear protein termed high-mobility group box 1 from neurons, causing activation of the trigeminovascular system. Here, we explored the effects of single and multiple cortical spreading depression inductions on high-mobility group box 1 (HMGB1) transcriptional activity relative to high-mobility group box 1 protein expression levels and intracellular localization in cortical neurons and astrocytes. Methods Single or multiple cortical spreading depression inductions were achieved by KCl application to the mouse cerebral cortex. The animals were sacrificed at 30 minutes, 3 hours and 24 hours after cortical spreading depression induction. High-mobility group box 1 expression levels were explored with in situ hybridization, Western blotting and immunostaining. Results Cortical spreading depression up-regulated high-mobility group box 1 transcriptional activity in neurons at 3 hours in a manner that was dependent on the number of cortical spreading depression inductions. At 24 hours, the high-mobility group box 1 transcriptional activity had returned to basal levels. Cortical spreading depression induced a reduction in high-mobility group box 1 protein expression at 3 hours, which was also dependent on the number of cortical spreading depression inductions. Following cortical spreading depression, the release of high-mobility group box 1 from the nucleus was observed in a small proportion of neurons, but not in astrocytes. Conclusion Cortical spreading depression induced translocation of high-mobility group box 1 from neuronal nuclei, driving transcriptional up-regulation of high-mobility group box 1 to maintain protein levels.

Repetitive trigeminal nociceptive stimulation in rats increases their susceptibility to cortical spreading depression.

We examined the ability of trigeminal nerve activation to induce cortical spreading depression in rats. Capsaicin was injected into the bilateral plantar or whisker pad for either 4 or 6 days in rats. The number and duration of cortical spreading depressions induced by potassium were significantly increased in animals injected with capsaicin in the bilateral whisker pad compared with animals injected in the bilateral plantar or in controls, while administration of a GABAA receptor agonist decreased these effects. Repetitive nociceptive stimulation of the trigeminal nerve lowers the threshold for the induction of cortical spreading depression by altering GABAergic neuronal activity.

Functional interactions between transient receptor potential M8 and transient receptor potential V1 in the trigeminal system: Relevance to migraine pathophysiology

Background Recent genome-wide association studies have identified transient receptor potential M8 (TRPM8) as a migraine susceptibility gene. TRPM8 is a nonselective cation channel that mediates cool perception. However, its precise role in migraine pathophysiology is elusive. Transient receptor potential V1 (TRPV1) is a nonselective cation channel activated by noxious heat. Both TRPM8 and TRPV1 are expressed in trigeminal ganglion (TG) neurons. Methods We investigated the functional roles of TRPM8 and TRPV1 in a meningeal inflammation-based migraine model by measuring the effects of facial TRPM8 activation on thermal allodynia and assessing receptor coexpression changes in TG neurons. We performed retrograde tracer labeling to identify TG neurons innervating the face and dura. Results We found that pharmacological TRPM8 activation reversed the meningeal inflammation-induced lowering of the facial heat pain threshold, an effect abolished by genetic ablation of TRPM8. No significant changes in the heat pain threshold were seen in sham-operated animals. Meningeal inflammation caused dynamic alterations in TRPM8/TRPV1 coexpression patterns in TG neurons, and colocalization was most pronounced when the ameliorating effect of TRPM8 activation on thermal allodynia was maximal. Our tracer assay disclosed the presence of dura-innervating TG neurons sending collaterals to the face. Approximately half of them were TRPV1-positive. We also demonstrated functional inhibition of TRPV1 by TRPM8 in a cell-based assay using c-Jun N-terminal kinase phosphorylation as a surrogate marker. Conclusions Our findings provide a plausible mechanism to explain how facial TRPM8 activation can relieve migraine by suppressing TRPV1 activity. Facial TRPM8 appears to be a promising therapeutic target for migraine.

Adult-onset recurrent painful ophthalmoplegic neuropathy displaying atypical oculomotor nerve gadolinium-enhancement pattern in the orbit and cavernous sinus

Dear Editor, We read with great interest the review article in Cephalalgia entitled ‘Ophthalmoplegic migraine: From questions to answers’ by Ambrosetto et al. (1). The authors pointed out that, in adult-onset recurrent painful ophthalmoplegic neuropathy (RPON, code 13.9 of ICHD-3 beta), the magnetic resonance imaging (MRI) finding shows no gadolinium enhancement or nerve thickening. We experienced an adult-onset case of RPON in which fat-suppressed post-contrast T1weighted imaging (T1WI) and T2-weighted imaging (T2WI) were useful in detecting lesions within the orbit and cavernous sinus. A 42-year-old woman presented with recurrent throbbing headaches in the right occiput followed by right ptosis and ophthalmoparesis of inward and vertical movements. She experienced these symptoms approximately 30 times in the 22 years since the first attack. The symptoms resolved within two months. After excluding cerebral aneurysm, Tolosa–Hunt syndrome, sarcoidosis, diabetes, thyroid dysfunction, collagen diseases and meningitis, we diagnosed RPON. Ten cranial MRI examinations were conducted over six years using a 1.5-T unit. High spatial resolution thin-slice fat-suppressed T2WI was added to conventional whole brain MRI in six examinations. Only one conventional whole-brain MRI detected slight abnormal enhancement of the right oculomotor nerve at the root exit zone that was performed one week after the onset of oculomotor symptoms (Figure 1(a)). In contrast, obvious enhancement of the right oculomotor nerve within the orbit and cavernous sinus was identified in all high-resolution fat-suppressed postcontrast T1WIs of the orbit performed during an ictal period (Figure 1(b)). The magnitude of enhancement was greater 1 week after the onset of the oculomotor symptoms compared with that after three and eight weeks. The enhancement disappeared during the interictal period. Further, fat-suppressed T2WIs of the orbit and cavernous sinus showed swelling and abnormal hyperintensities of the oculomotor nerve during a paroxysmal period (Figure 1(c)). These alterations emerged in parallel with the disease activity. It is noteworthy that conventional whole-brain T2WIs did not detect such abnormalities. RPON, formerly known as ophthalmoplegic migraine, is a rare disorder and its onset occurs usually

New onset of myasthenia gravis after intravesical Bacillus Calmette-guerin: A case report and literature review

Rationale: Recently, drug-related myasthenia gravis (MG) has received attention, because the number of reported cases involving MG associated with immune checkpoint inhibitors, a new immunotherapy, is increasing. We present a case involving the new onset of MG, in which the symptoms started shortly after intravesical Bacillus Calmette-Guerin (BCG) for bladder cancer. Patient concerns: A 69-year-old male with bladder cancer developed ptosis and diplopia 4 days after the completion of a treatment regimen with intravesical BCG weekly for 6 weeks. Diagnoses: Ocular MG was confirmed by a positive serum anti-acetylcholine receptor antibody test. Interventions: Treatment with high-dose methylprednisolone pulse therapy was given, after insufficient treatment with pyridostigmine bromide and 10 mg/d prednisolone. Outcomes: Symptoms resolved completely 12 days after high-dose methylprednisolone pulse therapy. Lessons: Intravesical BCG could be listed as a novel drug that may induce a new onset of MG along with drugs such as D-penicillamine and immune checkpoint inhibitors.

Alterations in the threshold of the potassium concentration to evoke cortical spreading depression during the natural estrous cycle in mice.

Cortical spreading depression (CSD) has been implicated in a variety of neurological disorders. However, the relationship between serum sex hormones and susceptibility to the development of CSD in naturally estrous cycling female animals is largely unknown. The natural estrous cycle of mice consists of four stages, namely, proestrus, estrus, metestrus and diestrus. We measured the serum concentration of estradiol and progesterone in estrus and diestrus and compared the minimum potassium concentrations necessary to evoke CSD in each stage and in males. In diestrus, the minimum potassium concentration required to evoke CSD was significantly lower compared to the other three phases and male animals. The serum level of estradiol is significantly higher and serum level of progesterone is significantly lower in diestrus compared to estrus. Furthermore, when we administered an estrogen receptor antagonist, the susceptibility to the development of CSD was decreased. Conversely, the administration of a progesterone receptor antagonist increased the susceptibility to CSD. Our results demonstrated that neuronal excitability related to CSD induction differs among the natural estrous phases in mice.

Serial changes of corticospinal tract hyperintensity on magnetic resonance imaging from the preclinical stage in amyotrophic lateral sclerosis

Serial changes of corticospinal tract hyperintensity on magnetic resonance imaging from the preclinical stage in amyotrophic lateral sclerosis Tsubasa Takizawa, Gen Shiihashi, Junki Maehara, Koichi Oki, Mayuko Osaka, Hirokazu Fujiwara, Hidenori Ojima, Yuichi Ichinose, Mamoru Shibata, Shinichi Takahashi and Norihiro Suzuki Departments of Neurology, 2 Pathology, 3 Diagnostic Radiology, Keio University School of Medicine, and Department of Internal Medicine, International Catholic Hospital, Tokyo, Japan

Signaling Pathways Relevant to Nerve Growth Factor-induced Upregulation of Transient Receptor Potential M8 Expression

Transient receptor potential melastatin 8 (TRPM8) is a nonselective cation channel that primarily detects the innocuous cold. In pathological conditions, TRPM8 plays a role in the development of cold hyperalgesia/allodynia. Nerve growth factor (NGF) is an important mediator involved in various pain disorders. In the present study, the NGF-TrkA pathway increased TRPM8 expression by stabilizing TRPM8 mRNA through the actions of phosphatidylinositol 3-kinase and p38 MAP kinase. Moreover, c-Jun N-terminal kinase and Src tyrosine kinase were identified as a positive and negative regulator of TRPM8 expression, respectively, via post-transcriptional mechanisms independent of mRNA stabilization. PTEN activity was found to increase protein TRPM8 expression. Calcium imaging confirmed that NGF induced TRPM8 functional upregulation. Time-lapse fluorescence microscopic analysis and a cell fractionation assay revealed that NGF promoted the trafficking of TRPM8 to the plasma membrane. In the presence of NGF, lysosome-associated membrane protein-2 (LAMP-2) was localized to TRPM8-positive dot-like and linear structures, the latter of which were observed in the periphery of the cytoplasm. It was inferred that LAMP-2 was involved in the vesicular transport of TRPM8. Pharmacological blockade of the proteasome with MG132 led to a further increase in NGF-induced TRPM8 expression, indicating that the proteasome system played a pivotal role in the degradation of TRPM8. Our findings provide novel insight into the signaling pathways involved in NGF-mediated TRPM8 upregulation and its reversion to the normal state.

Low-signal intensity rims along the cerebral cortex and u-fibers on susceptibility-weighted imaging in progressive multifocal leukoencephalopathy

Recent reports described that low-signal intensity (LSI) rims along the cerebral cortex and U-fibers adjacent to the white matter lesions of progressive multifocal leukoencephalopathy (PML) on susceptibility-weighted imaging (SWI) might be a potential new characteristic finding.1 We herein present a case of PML in which the SWI finding of LSI rims provides a clue to the early diagnosis. A previously healthy male in his 40s visited a nearby hospital because of acute visual impairment. Initial brain MRI revealed high signal intensities in the subcortical white matter of the bilateral occipital lobes on T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR) imaging and diffusion-weighted imaging (DWI). He was referred to a neurologist in our hospital due to his exacerbation of visual impairment. MRI at 3T (Signa Pioneer, GE Healthcare Japan, Hino, Japan) showed relatively symmetrical hyperintense lesions on T2WI and FLAIR imaging in the subcortical white matter of the bilateral occipital lobes (Fig. 1a). The lesions showed LSIs on T1-weighted imaging (T1WI) and peripheral hyperintensities on DWI. SWI revealed LSI rims along the cerebral cortex and U-fibers adjacent to the lesions (Fig. 1b), which suggested PML. No mass effect was detected in these lesions. Serological blood tests revealed human immunodeficiency virus (HIV) infection. Definitive diagnosis of PML was made by the detection of John Cunningham virus DNA in the cerebrospinal fluid. Although highly active antiretroviral therapy was performed, visual impairment progressed from 20/500 vision to sensus luminis. MRI at 3T 2 months after the second MRI showed expanded hyperintense lesions on T2WI and FLAIR imaging (Fig. 2a), and expanded LSI rims on SWI, which showed lower signal intensities than the previous MRI. These findings were associated with exacerbation of visual impairment. Also, the sulci of the brain around the lesions expanded with time, which reflected mild progression of the lesions’ atrophy (Fig. 2b). Hodel et al. reported that these susceptibility changes were observed in all patients at the chronic stage, and in relatively high frequency (75%) even at the pre-symptomatic stage.2 Umino et al. reported that LSI rims could be observed infrequently in infarct and encephalitis.3 Sensitivity, specificity and underlying cause of LSI rims on SWI remain unclear. Further investigation must be done to reveal these important issues. In conclusion, characteristic LSI rims on SWI was identified in our case of PML. These findings apparently progressed with disease progression. Although further investigation with a larger-scale study is needed, these new findings may suggest an early diagnosis of PML and can be a helpful clue in follow-up and appropriate clinical practice.