Masamichi Ikawa

PET imaging of redox and energy states in stroke-like episodes of MELAS

In stroke-like episodes of patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), changes in oxidative stress and glucose metabolism and their sequence remain obscure. We developed a novel double imaging method using positron emission tomography (PET) with [(62)Cu]-diacetyl-bis(N4-methylthiosemicarbazone) ((62)Cu-ATSM) and [(18)F]-fluorodeoxyglucose ((18)FDG) to visualize the regional oxidative stress, glucose metabolism and blood flow in brain lesions of stroke-like episodes non-invasively and rapidly. These PET imagings were performed on a MELAS patient with stroke-like lesions, and clearly demonstrated that oxidative stress following hyperemia along with increased glucose metabolism plays crucial roles in the pathogenesis of MELAS stroke-like episodes.

Evaluation of striatal oxidative stress in patients with Parkinson's disease using [62Cu]ATSM PET.

INTRODUCTION To clarify the role of oxidative stress and mitochondrial dysfunction in the pathogenesis of Parkinsons disease (PD) in living patients, positron emission tomography (PET) with [(62)Cu]diacetyl-bis(N(4)-methylthiosemicarbazone) ([(62)Cu]ATSM) was applied to functional imaging of oxidative stress mainly due to mitochondrial dysfunction in the striata of patients with PD. METHODS Fifteen PD patients who presented with lateral dominant symptoms at onset and six healthy controls underwent [(62)Cu]ATSM PET. Dynamic PET data acquisition was performed, and standardized uptake values (SUVs) were obtained from the delayed phase of dynamic data by means of region of interest analysis. The striatum-to-cerebellum SUV ratio (S/C ratio) was calculated from the SUV in all subjects of the striatum and the cerebellar cortex. RESULTS The mean S/C ratio of the bilateral striata of the patients (1.15±0.10) was significantly increased compared with that of the controls (1.08±0.02) (P<.05). In the patients, the S/C ratio of the bilateral striata showed a positive correlation with the Unified Parkinsons Disease Rating Scale (UPDRS) rating (r=0.52, P<.05), and the S/C ratio of the striatum contralateral to the initially affected body side showed a strong positive correlation with the UPDRS rating (r=0.62, P<.05). CONCLUSIONS [(62)Cu]ATSM PET imaging demonstrated that striatal oxidative stress was enhanced in PD patients compared with the controls and increased with the progression of disease severity, particularly in the contralateral striatum. These findings indicated that oxidative stress associates with striatal neurodegeneration in PD.

Statins and myotoxic effects associated with anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase autoantibodies: an observational study in Japan

AbstractStatins have a variety of myotoxic effects and can trigger the development of inflammatory myopathies or myasthenia gravis (MG) mediated by immunomodulatory properties. Autoantibodies to 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) have been identified in patients with statin-associated myopathy. The purpose of the present study is to develop an enzyme-linked immunosorbent assay (ELISA) of anti-HMGCR antibodies and to elucidate the clinical significance of anti-HMGCR antibodies in Japanese patients with inflammatory myopathies or MG.We enrolled 75 patients with inflammatory myopathies, who were all negative for anti-signal recognition particle and anti-aminoacyl transfer RNA synthetase antibodies. They were referred to Keio University and National Center of Neurology and Psychiatry between October 2010 and September 2012. We also studied 251 patients with MG who were followed at the MG Clinic at Keio University Hospital. Anti-HMGCR antibodies were detected by ELISA. We investigated demographic, clinical, radiological, and histological findings associated with anti-HMGCR antibodies.We established the anti-HMGCR ELISA with the recombinant protein. Protein immunoprecipitation detected autoantigens corresponding to HMGCR. Immunohistochemistry using muscle biopsy specimens revealed regenerating muscle fibers clearly stained by polyclonal anti-HMGCR antibodies and patients’ serum. Anti-HMGCR autoantibodies were specifically detected in 8 patients with necrotizing myopathy. The seropositivity rate in the necrotizing myopathy patients was significantly higher than those in the patients with other histological diagnoses of inflammatory myopathies (31% vs 2%, P = 0.001). Statins were administered in only 3 of the 8 anti-HMGCR-positive patients. Myopathy associated with anti-HMGCR antibodies showed mild limb weakness and favorable response to immunotherapy. All 8 patients exhibited increased signal intensities on short T1 inversion recovery of muscle MRI. Of the 251 patients with MG, 23 were administered statins at the onset of MG. One late-onset MG patient experienced MG worsening after 4-wk treatment with atorvastatin. However, anti-HMGCR antibodies were not detected in the 251 MG patients except for one early-onset MG patient with no history of statin therapy.Anti-HMGCR antibodies are a relevant clinical marker of necrotizing myopathy with or without statin exposure, but they are not associated with the onset or deterioration of MG.

Increased oxidative stress is related to disease severity in the ALS motor cortex: A PET study

Objective: To investigate cerebral oxidative stress based on an over-reductive state caused by mitochondrial dysfunction and its relationship to disease severity in patients with amyotrophic lateral sclerosis (ALS) using PET with [62Cu]diacetyl-bis(N4-methylthiosemicarbazone) (62Cu-ATSM). Methods: Twelve patients with ALS and 9 age-matched healthy controls underwent a 20-minute dynamic brain PET scan after 62Cu-ATSM injection. The standardized uptake value (SUV) images obtained from the last 10 minutes of frames were normalized by the global mean (nSUV). Regional 62Cu-ATSM retention in the nSUV images was compared between groups using statistical parametric mapping (SPM) and region of interest (ROI) analysis. Secondary analyses evaluated the correlations between regional nSUVs and the clinical characteristics of the participants. Results: In SPM mapping, patients with ALS showed a significantly greater accumulation of 62Cu-ATSM compared to controls in the bilateral cortices around the central sulcus, including the motor cortex, and the right superior parietal lobule. ROI analysis also revealed significantly greater nSUVs in patients than controls in these regions. Increases in nSUV for these regions were associated with decreases in the revised ALS Functional Rating Scale score, suggesting a good correlation with the severity of ALS. In controls, age was correlated with nSUV for the bilateral cortices around the central sulcus, although this correlation was not observed in patients with ALS. Conclusions: 62Cu-ATSM PET imaging demonstrated increased oxidative stress based on an over-reductive state, primarily in the motor cortex, in patients with ALS. The magnitude of oxidative stress correlated well with clinical severity, indicating that it may be associated with neurodegenerative changes in ALS.

Pathophysiologic evaluation of MELAS strokes by serially quantified MRS and CASL perfusion images

PURPOSE To clarify the roles of serial MR spectroscopy (MRS) and continuous arterial spin labeling (CASL) perfusion images for evaluating cerebral lesions in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). MATERIALS AND METHODS Two cases of MELAS followed up serially using MRS and CASL images in addition to routine MR imaging were enrolled. RESULTS Newly appeared lesions assessed by MRS revealed increased lactate doublets which correlated well with CSF lactate level, and these showed a decreasing trend after treatment, although conventional T2 weighted images revealed hyper-intensity in both phases. Spectra from normally appearing white matter depicted slight lactate peaks during clinical exacerbation periods with marked elevation of CSF lactate and showed a decreasing NAA concentration during the prolonged course. In CASL images, acute lesions of the disease were clearly visible as hyper-perfusion foci, and chronic lesions were demonstrated as hypo- or iso-perfusion regions. CONCLUSION The detection of lactate peaks in the MR spectrum from normally appearing white matter may be considered as systemic lactic acidosis or an exacerbation of MELAS, and active lesions can be distinguished from chronic inactive lesions by the increase of lactate peaks in MRS or the state of hyper-perfusion in CASL images.

Hashimoto’s Encephalopathy as a Treatable Adult-Onset Cerebellar Ataxia Mimicking Spinocerebellar Degeneration

Background: Hashimoto’s encephalopathy (HE) presents with a variety of neurologic and neuropsychiatric features. In this study, we investigated the clinical and immunological profiles of the cerebellar ataxic form of HE. Methods: The clinical features, treatments, laboratory features, brain imaging, and serum anti-NH2-terminal of α-enolase autoantibodies (anti-NAE Abs), a useful diagnostic marker for HE, were investigated in 13 patients who presented with sporadic adult-onset cerebellar ataxia and fulfilled the HE diagnostic criteria (antithyroid Abs and responsiveness to immunotherapy). Results: All of the patients presented with truncal ataxia, but nystagmus was uncommon (17%). Eight patients had an insidious onset that mimicked spinocerebellar degeneration (SCD), but brain imaging showed little or no cerebellar atrophy in all of the patients. Those patients with serum anti-NAE Abs (n = 8) did not have nystagmus and tended to respond better to immunotherapy than the anti-NAE Ab-negative patients. Conclusion: The present study suggests that insidious adult-onset and truncal ataxia are common in the cerebellar ataxic form of HE, which mimics SCD, but that nystagmus and severe cerebellar atrophy are uncommon. Antithyroid and anti-NAE Abs may be useful for diagnosing cerebellar ataxic HE.

Radiolabeled Cu-ATSM as a novel indicator of overreduced intracellular state due to mitochondrial dysfunction: studies with mitochondrial DNA-less ρ0 cells and cybrids carrying MELAS mitochondrial DNA mutation.

OBJECTIVES Radiolabeled Cu-diacetyl-bis (N(4)-methylthiosemicarbazone) (*Cu-ATSM), including (60/62/64)Cu-ATSM, is a potential imaging agent of hypoxic tumors for positron emission tomography (PET). We have reported that *Cu-ATSM is trapped in tumor cells under intracellular overreduced states, e.g., hypoxia. Here we evaluated *Cu-ATSM as an indicator of intracellular overreduced states in mitochondrial disorders using cell lines with mitochondrial dysfunction. METHODS Mitochondrial DNA-less ρ(0)206 cells; the parental 143B human osteosarcoma cells; the cybrids carrying mutated mitochondria from a patient of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) (2SD); and that carrying wild-type one (2SA) were used. Cells were treated under normoxia or hypoxia, and (64)Cu-ATSM uptake was examined to compare it with levels of biological reductant NADH and NADPH. RESULTS ρ(0)206 cells showed higher (64)Cu-ATSM uptake than control 143B cells under normoxia, whereas (64)Cu-ATSM uptake was not significantly increased under hypoxia in ρ(0)206 cells. Additionally, (64)Cu-ATSM uptake showed correlate change to the NADH and NADPH levels, but not oxygenic conditions. 2SD cells showed increased (64)Cu-ATSM uptake under normoxia as compared with the control 2SA, and (64)Cu-ATSM uptake followed NADH and NADPH levels, but not oxygenic conditions. CONCLUSIONS (64)Cu-ATSM accumulated in cells with overreduced states due to mitochondrial dysfunction, even under normoxia. We recently reported that (62)Cu-ATSM-PET can visualize stroke-like episodes maintaining oxygen supply in MELAS patients. Taken together, our data indicate that *Cu-ATSM uptake reflects overreduced intracellular states, despite oxygenic conditions; thus, *Cu-ATSM would be a promising marker of intracellular overreduced states for disorders with mitochondrial dysfunction, such as MELAS, Parkinsons disease and Alzheimers disease.

Detection of preclinically latent hyperperfusion due to stroke-like episodes by arterial spin-labeling perfusion MRI in MELAS patients.

In stroke-like episodes (SEs) of patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS), the detection of preclinically latent lesions is a challenge. We report regional cerebral hyperperfusion observed on arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) in the preclinical phase more than 3 months before the clinical onset of SEs in 3 MELAS patients. These hyperperfused areas were not detected by conventional MRI in the preclinical phase and developed into acute lesions at the clinical onset of SEs, suggesting that ASL imaging has the potential for predicting the emergence of SEs.

Lymphomatosis cerebri: clinical characteristics, neuroimaging, and pathological findings

Lymphomatosis cerebri is a rare variant of primary central nervous system lymphoma. We present a case involving a 56-year-old immunocompetent woman who complained of rapid deterioration of her higher brain function over a 4-month period. Magnetic resonance imaging showed extensive white-matter lesions. During brain biopsy, a diffusely infiltrating lymphoma with distinctive immunohistochemical features was detected. Awareness of this unique presentation and early tissue diagnosis provide the best hope for instituting appropriate treatments.

In vivo functional brain imaging and a therapeutic trial of L-arginine in MELAS patients.

BACKGROUND Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is the most common type of mitochondrial disease and is characterized by stroke-like episodes (SEs), myopathy, lactic acidosis, diabetes mellitus, hearing-loss and cardiomyopathy. The causal hypotheses for SEs in MELAS presented to date are angiopathy, cytopathy and neuronal hyperexcitability. L-arginine (Arg) has been applied for the therapy in MELAS patients. SCOPE OF REVIEW We will introduce novel in vivo functional brain imaging techniques such as MRI and PET, and discuss the pathogenesis of SEs in MELAS patients. We will further describe here our clinical experience with L-arg therapy and discuss the dual pharmaceutical effects of this drug on MELAS. MAJOR CONCLUSIONS Administration of L-arg to MELAS patients has been successful in reducing neurological symptoms due to acute strokes and preventing recurrences of SEs in the chronic phase. L-Arg has dual pharmaceutical effects on both angiopathy and cytopathy in MELAS. GENERAL SIGNIFICANCE In vivo functional brain imaging promotes a better understanding of the pathogenesis and potential therapies for MELAS patients. This article is part of a Special Issue entitled Biochemistry of Mitochondria, Life and Intervention 2010.