Atsushi Isshiki

Plasma fibronectin supports neuronal survival and reduces brain injury following transient focal cerebral ischemia but is not essential for skin-wound healing and hemostasis

Fibronectin performs essential roles in embryonic development and is prominently expressed during tissue repair. Two forms of fibronectin have been identified: plasma fibronectin (pFn), which is expressed by hepatocytes and secreted in soluble form into plasma; and cellular fibronectin (cFn), an insoluble form expressed locally by fibroblasts and other cell types and deposited and assembled into the extracellular matrix. To investigate the role of pFn in vivo, we generated pFn-deficient adult mice using Cre-loxP conditional gene-knockout technology. Here we show that pFn-deficient mice show increased neuronal apoptosis and larger infarction areas following transient focal cerebral ischemia. However, pFn is dispensable for skin-wound healing and hemostasis.

Neuroprotective properties of propofol and midazolam, but not pentobarbital, on neuronal damage induced by forebrain ischemia, based on the GABAA receptors

Background: The mechanism of the neuroprotective effects of propofol was compared to two other types of intravenous (i.v.) anesthetics (i.e., benzodiazepine; midazolam and barbiturate; pentobarbital) using Mongolian gerbils focusing on GABA receptor subtypes.

Involvement of the brain-derived neurotrophic factor/TrkB pathway in neuroprotecive effect of cyclosporin A in forebrain ischemia

Recent studies have shown that cyclosporin A, a specific antagonist of calcineurin, a phosphatase, ameliorates neuronal cell death in the CA1 sector of the hippocampus after forebrain ischemia in animal models. The mechanism of this neuroprotective effect, however, has not yet been established. Brain-derived neurotrophic factor (BDNF), a member of the neurotrophins, is one of the potent survival and developmental factors whose expression is regulated by cyclic AMP-response element-binding protein (CREB). Activation of CREB is dependent on its phosphorylation at Ser(133), and calcineurin has been reported to dephosphorylate CREB via protein phosphatase 1. Based on these observations, we attempted to investigate how cyclosporin A treatment would affect the changes of phosphorylated CREB (pCREB), BDNF and its receptor tyrosine kinase B (TrkB) after forebrain ischemia in rats. Phosphorylation of CREB was kept augmented throughout the time course examined in cyclosporin A-treated animals, while it ceased without cyclosporin A. Reverse transcription-polymerase chain reaction revealed prolonged maintenance of BDNF mRNA expression in the CA1 sector of cyclosporin A-treated animals. The protein expression of BDNF and TrkB appeared to be up-regulated in cyclosporin A-treated animals, whereas it was transiently up-regulated but decreased to the marginal level of expression without cyclosporin A.From these results we suggest that cyclosporin A induces pCREB by an inhibition of calcineurin, resulting in the induction of BDNF. The mechanisms by which cyclosporin A protects the CA1 region from neuronal cell death in forebrain ischemia may involve the interaction of pCREB, BDNF and TrkB.

Protein Kinase C-γ and Calcium/Calmodulin-Dependent Protein Kinase II-α Are Persistently Translocated to Cell Membranes of the Rat Brain during and after Middle Cerebral Artery Occlusion

The levels of protein kinase C-γ (PKC-γ) and the calcium/calmodulin-dependent kinase II-α (CaMKII-α) were measured in crude synaptosomal (P2), particulate (P3), and cytosolic (S3) fractions of the neocortex of rats exposed to 1-hour and 2-hour middle cerebral artery occlusion (MCAO) and 2-hour MCAO followed by 2-hour reperfusion. During MCAO, PKC levels increased in P2 and P3 in the most severe ischemic areas concomitantly with a decrease in S3. In the penumbra, PKCγ decreased in S3 without any significant increases in P2 and P3. Total PKC-γ also decreased in the penumbra but not in the ischemic core, suggesting that the protein is degraded by an energy-dependent mechanism, possibly by the 26S proteasome. The CaMKII-α levels increased in P2 but not P3 during ischemia and reperfusion in all ischemic regions, particularly in the ischemic core. Concomitantly, the levels in S3 decreased by 20% to 40% in the penumbra and by approximately 80% in the ischemic core. There were no changes in the total levels of CaMKII-α during MCAO. The authors conclude that during and after ischemia, PKC and CaMKII-α are translocated to the cell membranes, particularly synaptic membranes, where they may modulate cellular function, such as neurotransmission, and also affect cell survival. Drugs preventing PKC and/or CaMKII-α translocation may prove beneficial against ischemic cell death.

Restricted clinical efficacy of cyclosporin A on rat transient middle cerebral artery occlusion

The immunosuppressant cyclosporin A (CsA) has been shown to have neuroprotective action. The inhibition of both calcineurin activation and mitochondrial permeability transition pore (mtPTP) opening are considered the primary neuroprotective mechanisms of CsA. Here we have evaluated the effect of CsA on significantly reducing infarct size induced by transient middle cerebral artery occlusion (MCAO) in rats, and examined variable therapeutic applications for brain infarction. Experimental rats were divided into 12 groups according to: CsA administration time (immediately after occlusion or immediately after reperfusion); dosage (between 10 and 50 mg/kg); route (i.v. or i.p.); and with or without needle insertion, which hypothetically disrupts the blood brain barrier (BBB). Neuroprotective effects of CsA were hardly noticeable when administered immediately after occlusion or by i.v. injection. By needle insertion, CsA administration significantly reduced infarct size, although vehicle treatment also reduced infarct size compared with nontreatment animals, i.e. no needle insertion. These results suggest that needle insertion allows endogenous neuroprotective substances to pass into the brain. Furthermore, single dosages over 30 mg/kg CsA were excessive and negated potential neuroprotective effects. However, two i.p. administrations of 20 mg/kg CsA immediately and 24 hrs after reperfusion significantly ameliorated the infarct size compared to the vehicle-treated group. We conclude that CsA exhibits significant neuroprotective activity, although its therapeutic application for stroke may be limited by very strict and precise management requirements.

Persistent phosphorylation of synaptic proteins following middle cerebral artery occlusion.

Transient cerebral ischemia following 1 to 2 hours of middle cerebral artery occlusion (MCAO) in the rat leads to infarction, which can be diminished by synaptic transmission modulators, implying aberrant cell signaling in the pathogenetic process. The authors report here changes in the levels of tyrosine phosphorylated proteins (PTyr) and calcium calmodulin kinase II (CaMKII) phosphorylation of Thr 286, in synaptosomal, particulate, and cytosolic fractions of different cortical areas following 1 or 2 hours of MCAO, or 2 hours of MCAO followed by 2 hours of reperfusion. At the end of 2-hour MCAO, PTyr, and in particular the pp180, indicative of NR2A/B subunit, increased in the synaptosomal fraction in less ischemic areas while it decreased in more severe ischemic regions. During reperfusion, phosphorylation increased at least 2-fold in all reperfused areas. During 2 hours of MCAO, the phosphorylation of CaMKII increased 8- to 10-fold in the synaptosomal fraction in all ischemic brain regions. During reperfusion, the phospho-CaMKII levels remained elevated by approximately 300% compared with the contralateral hemisphere (control). There was no increase in phospho-CaMKII in the cytosolic fraction at any time during or following ischemia in any of the brain regions examined. The authors conclude that both tyrosine kinase coupled pathways, as well as CaMKII-mediated cellular processes associated with synaptic activity, are strongly activated during and particularly following MCAO. These results support the hypothesis that aberrant cell signaling may contribute to ischemic cell death and dysfunction, and that selective modulators of cell signaling may be targets for pharmacological intervention against ischemic brain damage.

The Effectiveness of the Fukuhara Laryngeal Mask Airway Holding Forceps (F Forceps)

The laryngeal mask airway (LMA) was introduced more than two decades ago cl), and a comprehensive review article on the LMA has been published (2). The LMA has many advantages over the endotracheal tube (3), including increased speed in establishing an airway, reduced anesthetic requirements for airway tolerance, and lower frequency of coughing during emergence. Insertion of the LMA is performed blindly so that the LMA cuff is placed to cover the laryngeal inlet. The technique of LMA insertion described by Brain (4,5) has been widely accepted and used. Fukuhara (6) had designed and developed the J-shaped LMA holding forceps, named the Fukuhara (F) forceps, for easy and accurate placement of the LMA. The current study was undertaken to evaluate the effectiveness of the F forceps, which have been approved by the Food and Drug Administration.

Isoflurane Inhibits Protein Kinase Cγ and Calcium/Calmodulin Dependent Protein Kinase II-α Translocation to Synaptic Membranes in Ischemic Mice Brains

Volatile anesthetics isoflurane possibly improves the ischemic brain injury. However, its molecular actions are still unclear. In ischemia, protein kinase C (PKC)γ and calcium/calmodulin dependent protein kinase II (CaMKII)-α are persistently translocated from cytosol to cell membranes, and diminish these translocation suggested to be neuroprotective. We thus tested a hypothesis that isoflurane inhibits PKCγ and CaMKII-α translocation after ischemic brain insults. C57Bl/6J male mice were made to inhale 1 or 2 MAC isoflurane, after which 3 or 5 min cerebral ischemia was induced by decapitation. The sampled cerebrum cortex was then homogenized and centrifuged into crude synaptosomal fractions (P2), cytosolic fractions (S3), and particulate fractions (P3). CaMKII-α and PKCγ levels of these fractions were analyzed by immunoblotting. PKCγ and CaMKII-α are translocated to synaptic membrane from cytosol by cerebral ischemia, although isoflurane significantly inhibited such translocation. These results may explain in part the cellular and molecular mechanisms of neuroprotective effects of isoflurane.

An atypical case of fulminant interstitial pneumonitis induced by carbamazepine.

Carbamazepine is a therapeutic anticonvulsant, used to manage pain. We often use it to treat trigeminal and post-herpes zoster neuralgias. Interstitial pneumonitis (IP) is a known adverse consequence of using carbamazepine, with bronchiolitis obliterans and organizing pneumonitis. (BOOP) drug-induced IP as typical examples. Here we described a patient with post-herpes zoster neuralgia, who suffered from drug-induced acute IP that differed from cases typically induced by carbamazepine.

Reduction of Brain Infarction Induced by a Transient Brain Ischemia in mdr1a Knockout Mice

In order to evaluate the functional role of P-glycoprotein (P-gp) in cerebral ischemia, both multidrug resistance 1a knockout (KO) mice and wild-type mice were subjected to transient focal ischemia under a constant body and brain temperature about 37°C. The results showed that the volume of brain infarction induced by middle cerebral artery occlusion in KO mice was significantly smaller than that seen in wild-type mice, although there were no significant differences in cerebral blood flow, physiological data and on anatomical analysis of cerebrovasculature between both groups. We suggest that multidrug resistance 1a P-gp plays a role for adjusting the expressions of endogenous neuronal cell modulating substances, such as cytokines, neuronal peptides, and others, in the brain, which is consistent with a previous paper (Bobrov et al. Neurosci Lett 24: 6–11, 2008).