Hitoshi Nakayama

Induction of CHOP and apoptosis by nitric oxide in p53-deficient microglial cells

Excessive nitric oxide (NO) has been implicated in neurotoxicity after stresses such as ischemia. NO toxicity is generally thought to be mediated by the DNA damage–p53 pathway or mitochondrial dysfunction. We investigated the mechanism of NO toxicity by using murine microglial MG5 cells established from p53‐deficient mice. When MG5 cells were exposed to bacterial lipopolysaccharide plus interferon‐γ, mRNA and protein for inducible NO synthase (iNOS) were markedly induced, and apoptosis occurred. Under these conditions, we found that mRNA and protein for CHOP/GADD153, a C/EBP family transcription factor which is involved in endoplasmic reticulum (ER) stress‐induced apoptosis, are induced. iNOS mRNA was induced 2 h after treatment, whereas CHOP mRNA began to increase at 6 h with a time lag. CHOP mRNA was also induced by NO donors S‐nitroso‐N‐acetyl‐DL‐penicillamine (SNAP) or NOC18, or a peroxynitrite generator 3‐(4‐morpholinyl)‐sydnonimine hydrochloride (SIN‐1). Bip/GRP78, an ER chaperone which is known to be induced by ER stress, was also induced by SNAP or SIN‐1, indicating that NO causes ER stress. These results suggest that NO‐induced apoptosis in MG5 cells occurs through the ER stress pathway involving CHOP, but is independent of p53.

Scavenger Receptors that Recognize Advanced Glycation End Products

Scavenger receptors recognize modified low-density lipoproteins (LDLs) such as acetylated LDL and oxidized LDL. Advanced glycation end products (AGE), which are generated through long-term exposure of proteins to glucose, also behave as active ligands for some scavenger receptors, including class A scavenger receptor (SR-A) and class B scavenger receptors such as CD36 and scavenger receptor, class B, type I (SR-BI). SR-BI, the first identified high-density lipoprotein (HDL) receptor, plays key roles in reverse cholesterol transport by promoting selective uptake of cholesteryl esters (CE) in HDL by hepatocytes, and cholesterol efflux of unesterified cholesterol from peripheral cells to HDL. Using Chinese hamster ovary cells overexpressing SR-BI (CHO-SR-BI cells), it was demonstrated that AGE-bovine serum albumin binds to SR-BI and inhibits selective uptake of HDL-CE by CHO-SR-BI cells as well as cholesterol efflux from CHO-SR-BI cells to HDL, suggesting potential roles of AGE in diabetic dyslipidemia and accelerated atherosclerosis in diabetes.

Studies of magnetic cores for JHF synchrotrons

Magnetic cores suited for the RF cavities of JHF (Japanese Hadron Facility) synchrotrons have been studied. The shunt impedance of the cavity is required about 2 k/spl Omega//m because of the high acceleration voltage of more than 10 kV/m. The permeability of the core should meet with the RF frequencies of the 3 GeV booster and the 50 GeV ring. Characteristics of several ferrites and a Fe-based soft magnetic alloy composed of amorphous and ultra-fine grain structure have been measured with a test bench. The shunt impedance of the soft magnetic core named FINEMET is high enough. It is stable when input RF power is increased, while those of samples of ferrites drop rapidly. The permeability of FINEMET strongly depends on the bias current. Because of its low Q value, the bias current is not necessary for its new material. FINEMET is considered as one of the most probable candidate for JHF synchrotrons.

Sphingolipids Metabolism Following Cerebral Ischemia

It has been well known that ischemic insults induced the hydrolytic breakdown of polyphosphoinositides by calcium-dependent phospholipase C, and diacylglycerol (DAG) was hydrolyzed to free fatty acids (FFAs) by DAG lipase [1, 2, 11, 22, 26]. The composition of FFAs consists mainly of stearic (C18:0) and arachidonic acids (C20:4). These processes are thought to act at early phase of the ischemia. Prolonged ischemia induces the degradation of membrane phospholipids, and the level of various phospholipids decrease at late phase of the ischemia. To determine a therapeutic time window of the ischemic penumbra, it is essential to evaluate the time course of the degradation of glycerophospholipids.

The Protective Effect of DY9760e, a Novel Calmodulin Antagonist, on Rat Permanent Middle Cerebral Artery Occlusion

A newly synthesized calmodulin antagonist, DY9760e (3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1(-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate), has been shown to possess a cytoprotective effect against cytotoxicity induced by Ca2+ overload [1]. Since Ca2+ overload is suspected to be one of the major causes of ischemic neuronal cell damage [2], we examined the effect of this drug on infarct volume in the rat permanent focal ischemia model.