Mitsuru Kakihana

A Noncompetitive BACE1 Inhibitor TAK-070 Ameliorates Aβ Pathology and Behavioral Deficits in a Mouse Model of Alzheimer's Disease

We discovered a nonpeptidic compound, TAK-070, that inhibited BACE1, a rate-limiting protease for the generation of Aβ peptides that are considered causative for Alzheimers disease (AD), in a noncompetitive manner. TAK-070 bound to full-length BACE1, but not to truncated BACE1 lacking the transmembrane domain. Short-term oral administration of TAK-070 decreased the brain levels of soluble Aβ, increased that of neurotrophic sAPPα by ∼20%, and normalized the behavioral impairments in cognitive tests in Tg2576 mice, an APP transgenic mouse model of AD. Six-month chronic treatment decreased cerebral Aβ deposition by ∼60%, preserving the pharmacological efficacy on soluble Aβ and sAPPα levels. These results support the feasibility of BACE1 inhibition with a noncompetitive inhibitor as disease-modifying as well as symptomatic therapy for AD.

Effects of idebenone on neurological deficits, local cerebral blood flow, and energy metabolism in rats with experimental cerebral ischemia

Improvement of energy metabolism in ischemic cerebral tissue benefits the therapy of occlusive cerebrovascular disorders. In the present study, the effects of 6-(10-hydroxydecyl)-2,3-dimethoxy-5-methyl-1,4-benzoquinone (idebenone) on neurological signs, such as ischemic seizures, lactate and ATP contents of the cerebral cortex, and local cerebral blood flow, were assessed in stroke-prone spontaneously hypertensive rats (SHRSP) with experimentally induced cerebral ischemia. Experimental cerebral ischemia was caused by bilateral carotid artery occlusion (BCAO) in male SHRSP (8-10 weeks old). Pretreatment with idebenone (10-100 mg/kg, p.o.) for 3 or 10 days delayed the onset of ischemic seizure (acute stroke) and prolonged survival time in SHRSP roughly in a dose-dependent manner. When the compound (100 mg/kg, i.p.) was given once 30 min after BCAO, it exerted similar ameliorating effects on the neurological deficits. When idebenone (100 mg/kg for 3 days) was given orally, it did not significantly inhibit the decrease in regional cerebral blood flow induced by BCAO. However, the same treatment markedly inhibited increases in the lactate content and lactate/pyruvate ratio and the decrease in ATP content of the cerebral cortex. The compound did not affect cerebral blood flow in normal rats. These results suggest that idebenone ameliorates the neurological deficits related to cerebral ischemia, and that this effect is mediated by improving cerebral energy metabolism.

Recombinant human basic fibroblast growth factor (rhbFGF) induces secretion of nerve growth factor (NGF) in cultured rat astroglial cells

Recombinant human basic fibroblast growth factor (rhbFGF) was found to induce secretion of nerve growth factor (NGF) in cultured astrocytes from rat brain. The induction was concentration dependent; a maximum increase of 2-fold was observed at concentrations of 3-10 ng/ml or rhbFGF. When rhbFGF was added to the astrocytes, the induction occurred within 8 h and leveled off after 12 h. Antiserum against rhbFGF completely blocked the induction. Maximum induction occurred under serum-free culture conditions and in cultures with a high cell density. These results suggest that rhbFGF may exert a neurotrophic effect on the central nervous system through the induction of NGF secretion by astrocytes.

Effects of idebenone on neurological deficits following cerebrovascular lesions in stroke-prone spontaneously hypertensive rats

The effects of 6-(10-hydroxydecyl)-2,3-dimethoxy-5-methyl-1,4-benzoquinone (idebenone) on neurological deficits following cerebrovascular lesions were examined in stroke-prone spontaneously hypertensive rats (SHRSP). The SHRSP were maintained on a 1% NaCl solution as drinking water to shorten the onset time of cerebrovascular lesions (stroke). After the onset of stroke, the salt solution was exchanged for tap water, and idebenone (30 and 100 mg/kg) was administered orally once daily for 3 weeks. The neurological deficits were evaluated by a specially designed scoring system or by an open-field test. Idebenone decreased the severity of the neurological deficits in a dose-dependent manner and this was statistically significant in the high-dose group. The severity of neurological changes was inversely related to the motor activity in the open-field test performed when the experiment was terminated, indicating the appropriateness of the scoring system. Moreover, the compound (100 mg/kg) significantly ameliorated a decrease in food intake (anorexia) that followed the onset of stroke. These results suggest that idebenone may be useful to treat patients with cerebrovascular lesions.

Effects of idebenone on the levels of acetylcholine, choline, free fatty acids, and energy metabolites in the brains of rats with cerebral ischemia

Cerebral ischemia was induced by a 200-s occlusion of both common carotid arteries in rats in which both vertebral arteries had been permanently cauterized. In the ischemic rats, a significant decrease in acetylcholine (ACh) and a marked increase in choline were observed in the cerebral cortex, hippocampus, striatum, and diencephalon. A slight increase in choline was also observed in the cerebellum and brain stem. Pretreatment with idebenone (10 mg/kg, i.p.) inhibited the decrease in ACh and the increase in choline in the forebrain regions. In addition, the same dose of idebenone inhibited the increments of lactate and free fatty acid contents and tended to inhibit the decrement of the ATP content in the cerebral cortex of the cerebral ischemic rats. These results indicate that idebenone inhibits the alteration of the ACh level and the disruption of membrane phospholipids in the brain of ischemic rats; these effects may be mediated by improved cerebral energy metabolism.

Mechanism of increased sensitivity to cerebral ischemia following carotid artery occlusion in stroke-prone spontaneously hypertensive rats: importance of genetic factors.

Neurological symptoms and cerebral metabolism following bilateral carotid artery occlusion (BCAO) were observed in stroke-prone spontaneously hypertensive rats (SHRSP), stroke-resistant SHR (SHRSR), normal Wistar-Kyoto rats (WKY) and the F1 and F2 hybrids between SHRSP and SHRSR or WKY. Systolic blood pressure recorded before BCAO was found to rank in the following order: SHRSP greater than F1 (SHRSP X SHRSR) greater than SHRSR greater than F1 (SHRSP X WKY) greater than WKY. The effect of BCAO in these rats tended to be proportional to the blood pressure. F1 (SHRSP X WKY) was more sensitive to brain ischemia than SHRSR. In addition, though none of the SHRSR (average blood pressure 155 mm Hg) developed acute stroke symptoms, many animals of the F2 generation, in which the blood pressure was equal to or lower than that of SHRSR, developed stroke symptoms. Lactate and ATP changes in the F2 generations did not correlate with the blood pressure. The results suggest that genetic factors may play an important ro...

The novel compound TDN-345 induces synthesis/secretion of nerve growth factor in C6-10A glioma cells

A novel compound, TDN-345, not bearing catechol moiety, induced NGF synthesis/secretion in C6-10A glioma cells. Both intracellular and extracellular nerve growth factor (NGF) protein levels increased within 3 h and reached a maximum around 12 h after the addition of TDN-345. The induction of NGF synthesis/secretion by TDN-345 occurred in a concentration-dependent manner, beginning with about 0.1 microM and reaching a maximum at 10 microM. The ED50 was 0.88 microM. The induction was accompanied by an increase in NGF mRNA but not beta-actin mRNA. In a time-course study, the NGF mRNA level was found to reach a maximum 2-3 h after the addition of TDN-345 and then to return to control levels. The induction occurred dose-dependently. The catecholaminergic compound epinephrine, which induces NGF synthesis/secretion, increased the intracellular cyclic AMP content by more than 1000-times at 10 microM. In contrast, TDN-345 did not cause such a prominent increase in cAMP even at 100 microM. These results indicate that TDN-345 induces NGF synthesis/secretion by increasing NGF mRNA expression, and the action of TDN-345 clearly differs from that of epinephrine, as it does not seem to involve cAMP as a second messenger. The results of the present study suggest the existence of a signal transduction pathway for NGF synthesis/secretion which is not mediated by cAMP.

Effects of idebenone on metabolism of monoamines and cyclic AMP formation in rats

Idebenone, 6-(10-hydroxydecyl)-2,3-dimethoxy-5-methyl-1,4-benzoquinone, at a dose of 100 mg/kg (i.p.) markedly increased the level of 5-hydroxyindole-3-acetic acid (5-HIAA) in several brain regions without affecting monoamine contents in normal rats. In rats with cerebral ischemia, idebenone (10 mg/kg, i.p.) normalized the decreased levels of 5-HIAA in the cerebral cortex, hippocampus, diencephalon and brain stem. A 5-hydroxytryptamine (serotonin, 5-HT) biosynthesis inhibitor, DL-p-chlorophenylalanine (PCPA, 150 mg/kg, i.p.) decreased the levels of 5-HT to one-third of the control level 24 h after administration. Idebenone (10, 30, or 100 mg/kg, i.p.), administered 24 h after the treatment with PCPA, accelerated the PCPA-induced 5-HT decreased in the hippocampus, diencephalon and brain stem in a dose-dependent manner. Idebenone (100 mg/kg, i.p.) stimulated the release of 5-HT in the dorsal hippocampus as determined by in vivo differential pulse voltammetry. Idebenone, like p-chloroamphetamine (PCA), stimulated 5-HT release from slices of hippocampus and diencephalon, and the formation of cyclic AMP in a concentration-dependent manner in rat diencephalon slice. This stimulation was almost completely blocked by methysergide, a 5-HT receptor blocker. Idebenone slightly and PCA markedly inhibited 5-HT uptake into hippocampus slices. The mechanism of the 5-HT releasing actions of idebenone in the hippocampal slices may be mediated through endogenous calcium. These results suggest that idebenone has an enhancing effect on the turnover of 5-HT in the hippocampus, diencephalon, and brain stem of rats.