渡邉 知佳

Originally, apomorphine was a broad-spectrum dopamine agonist with an affinity for all subtypes of the Dopamine D1 receptor to the D5 receptor. We previously identified apomorphine as a potential therapeutic agent for mitochondrial diseases by screening a chemical library of fibroblasts from patients with mitochondrial diseases. In this study, we showed that apomorphine prevented ferroptosis in fibroblasts from various types of mitochondrial diseases as well as in normal controls. Well-known biomarkers of ferroptosis include protein markers such as prostaglandin endoperoxide synthase 2 (PTGS2), a key gene for ferroptosis-related inflammation PTGS2, lipid peroxidation, and reactive oxygen species. Our findings that apomorphine induced significant downregulation of PTSG2 and suppressed lipid peroxide to the same extent as other inhibitors of ferroptosis also indicate that apomorphine suppresses ferroptosis. To our knowledge, this is the first study to report that the anti-ferroptosis effect of apomorphine is not related to dopamine receptor agonist action and that apomorphine is a potent inhibitor of ferroptotic cell death independent of dopaminergic receptors.

Coenzyme Q10 (CoQ10) is involved in ATP production through electron transfer in the mitochondrial respiratory chain complex. CoQ10 receives electrons from respiratory chain complex I and II to become the reduced form, and then transfers electrons at complex III to become the oxidized form. The redox state of CoQ10 has been reported to be a marker of the mitochondrial metabolic state, but to our knowledge, no reports have focused on the individual quantification of reduced and oxidized CoQ10 or the ratio of reduced to total CoQ10 (reduced/total CoQ10) in patients with mitochondrial diseases. We measured reduced and oxidized CoQ10 in skin fibroblasts from 24 mitochondrial disease patients, including 5 primary CoQ10 deficiency patients and 10 respiratory chain complex deficiency patients, and determined the reduced/total CoQ10 ratio. In primary CoQ10 deficiency patients, total CoQ10 levels were significantly decreased, however, the reduced/total CoQ10 ratio was not changed. On the other hand, in mitochondrial disease patients other than primary CoQ10 deficiency patients, total CoQ10 levels did not decrease. However, the reduced/total CoQ10 ratio in patients with respiratory chain complex IV and V deficiency was higher in comparison to those with respiratory chain complex I deficiency. Measurement of CoQ10 in fibroblasts proved useful for the diagnosis of primary CoQ10 deficiency. In addition, the reduced/total CoQ10 ratio may reflect the metabolic status of mitochondrial disease.

Glucose transporter 1 deficiency syndrome (GLUT1DS) is caused by haplo-insufficiency of SLC2A1, which encodes GLUT1, resulting in impaired hexose transport into the brain. Previously, we generated a tyrosine-mutant AAV9/3 vector in which SLC2A1 was expressed under the control of the endogenous GLUT1 promoter (AAV-GLUT1), and confirmed the improved motor function and cerebrospinal fluid glucose levels of Glut1-deficient mice after cerebroventricular injection of AAV-GLUT1. In preparation for clinical application, we examined the expression of transgenes after intra-cisterna magna injection of AAV-GFP (tyrosine-mutant AAV9/3-GFP with the CMV promoter) and AAV-GLUT1. We injected AAV-GFP or AAV-GLUT1 (1.63 × 1012 vector genomes/kg) into the cisterna magna of pigs to compare differential promoter activity. After AAV-GFP injection, exogenous GFP was expressed in broad areas of the brain and peripheral organs. After AAV-GLUT1 injection, exogenous GLUT1 was expressed predominantly in the brain. At the cellular level, exogenous GLUT1 was mainly expressed in the endothelium, followed by glia and neurons, which was contrasted with the neuronal-predominant expression of GFP by the CMV promotor. We consider intra-cisterna magna injection of AAV-GLUT1 to be a feasible approach for gene therapy of GLUT1DS.

Alexander disease (AxD) is a progressive neurodegenerative disease caused by a mutation in the glial fibrillary acid protein (GFAP) gene. A 4-year-old boy presented several times with hemiclonic seizures with eye deviation for a few minutes at 28 days after birth. Electroencephalogram showed independent sharp waves in the right and left temporal area. Magnetic resonance imaging showed high intensity T1-weighted images in the white matter of the frontal lobe and basal ganglia. He showed no head control at 4 years of age, and his weight gain was insufficient. He did not show macrocephaly. At 4 years of age, he died of bacterial pneumonia and septic shock. He was diagnosed with AxD, and direct sequencing revealed a de novo known mutation, c. 239 T > C, p.(F80S), in GFAP. Hela and U2-OS cells transfected with GFAP cDNA with c. 239 T > C showed dot-like cytoplasmic aggregation, similar to R239C, a common mutation found in severe infantile AxD. Aggregation in the cytoplasm caused by a GFAP mutation is a hallmark of AxD. Although there is only one previous report of a patient with an F80S mutation, our data support that F80S can cause the severe, infantile form of AxD.