Synthesis of Nα,Nδ-dicarbobenzoxy-L-ornithyl-β-alanine benzyl ester,a derivative of salty peptide,in 1,1,1-trichloroethane with polyethylene glycol-modified papain

Summary N,N-Dicarbobenzoxy-L-ornithyl--alanine benzyl ester, a derivative of salty peptide, was synthesized from N,N-dicarbobenzoxy-L-ornithine ethyl ester and -alanine benzyl ester in 1,1,1-trichloroethane using papain modified with polyethylene glycol. The peptide bond formation proceeded in a transparent organic solvent at room temperature and the product was obtained as precipitates from the reaction system.     

The Effects of Different Repetitive Transcranial Magnetic Stimulation (rTMS) Protocols on Cortical Gene Expression in a Rat Model of Cerebral Ischemic-Reperfusion Injury

Although repetitive Transcranial Magnetic Stimulation (rTMS) in treatment of stroke in humans has been explored over the past decade the data remain controversial in terms of optimal stimulation parameters and the mechanisms of rTMS long-term effects. This study aimed to explore the potential of different rTMS protocols to induce changes in gene expression in rat cortices after acute ischemic-reperfusion brain injury. The stroke was induced by middle cerebral artery occlusion (MCAO) with subsequent reperfusion. Changes in the expression of 96 genes were examined using low-density expression arrays after MCAO alone and after MCAO combined with 1Hz, 5Hz, continuous (cTBS) and intermittent (iTBS) theta-burst rTMS. rTMS over the lesioned hemisphere was given for two weeks (with a 2-day pause) in a single daily session and a total of 2400 pulses. MCAO alone induced significant upregulation in the expression of 44 genes and downregulation in 10. Two weeks of iTBS induced significant increase in the expression of 52 genes. There were no downregulated genes. 1Hz and 5Hz had no significant effects on gene expression, while cTBS effects were negligible. Upregulated genes included those involved in angiogenesis, inflammation, injury response and cellular repair, structural remodeling, neuroprotection, neurotransmission and neuronal plasticity. The results show that long-term rTMS in acute ischemic-reperfusion brain injury induces complex changes in gene expression that span multiple pathways, which generally promote the recovery. They also demonstrate that induced changes primarily depend on the rTMS frequency (1Hz and 5Hz vs. iTBS) and pattern (cTBS vs. iTBS). The results further underlines the premise that one of the benefits of rTMS application in stroke may be to prime the brain, enhancing its potential to cope with the injury and to rewire. This could further augment its potential to favorably respond to rehabilitation, and to restore some of the loss functions.     

Utilization of [11C]phosgene for radiosynthesis of N-(2-{3-[3,5-bis(trifluoromethyl)]phenyl[11C]ureido}ethyl)glycyrrhetinamide, an inhibitory agent for proteasome and kinase in tumors

N-(2-{3-[3,5-Bis(trifluoromethyl)]phenylureido}ethyl)glycyrrhetinamide (2), an ureido-substituted derivative of glycyrrhetinic acid (1), has been reported to display potent inhibitory activity for proteasome and kinase, which are overexpressed in tumors. In this study, we labeled this unsymmetrical urea 2 using [(11)C]phosgene ([(11)C]COCl(2)) as a labeling agent with the expectation that [(11)C]2 could become a positron emission tomography ligand for the imaging of proteasome and kinase in tumors. The strategy for the radiosynthesis of [(11)C]2 was to react hydrochloride of 3,5-bis(trifluoromethyl)aniline (4·HCl) with [(11)C]COCl(2) to possibly give isocyanate [(11)C]6, followed by the reaction of [(11)C]6 with N-(2-aminoethyl)glycyrrhetinamide (3).     

Autotaxin is overexpressed in glioblastoma multiforme and contributes to cell motility of glioblastoma by converting lysophosphatidylcholine to lysophosphatidic acid

Autotaxin (ATX) is a multifunctional phosphodiesterase originally isolated from melanoma cells as a potent cell motility-stimulating factor. ATX is identical to lysophospholipase D, which produces a bioactive phospholipid, lysophosphatidic acid (LPA), from lysophosphatidylcholine (LPC). Although enhanced expression of ATX in various tumor tissues has been repeatedly demonstrated, and thus, ATX is implicated in progression of tumor, the precise role of ATX expressed by tumor cells was unclear. In this study, we found that ATX is highly expressed in glioblastoma multiforme (GBM), the most malignant glioma due to its high infiltration into the normal brain parenchyma, but not in tissues from other brain tumors. In addition, LPA1, an LPA receptor responsible for LPA-driven cell motility, is predominantly expressed in GBM. One of the glioblastomas that showed the highest ATX expression (SNB-78), as well as ATX-stable transfectants, showed LPA1-dependent cell migration in response to LPA in both Boyden chamber and wound healing assays. Interestingly these ATX-expressing cells also showed chemotactic response to LPC. In addition, knockdown of the ATX level using small interfering RNA technique in SNB-78 cells suppressed their migratory response to LPC. These results suggest that the autocrine production of LPA by cancer cell-derived ATX and exogenously supplied LPC contribute to the invasiveness of cancer cells and that LPA1, ATX, and LPC-producing enzymes are potential targets for cancer therapy, including GBM.     

Diacylglycerol Kinase �� Augments C-Raf Activity and B-Raf/C-Raf Heterodimerization

The Ras/B-Raf/C-Raf/MEK/ERK signaling cascade is critical for the control of many fundamental cellular processes, including proliferation, survival, and differentiation. This study demonstrated that small interfering RNA-dependent knockdown of diacylglycerol kinase η (DGKη) impaired the Ras/B-Raf/C-Raf/MEK/ERK pathway activated by epidermal growth factor (EGF) in HeLa cells. Conversely, the overexpression of DGKη1 could activate the Ras/B-Raf/C-Raf/MEK/ERK pathway in a DGK activity-independent manner, suggesting that DGKη serves as a scaffold/adaptor protein. By determining the activity of all the components of the pathway in DGKη-silenced HeLa cells, this study revealed that DGKη activated C-Raf but not B-Raf. Moreover, this study demonstrated that DGKη enhanced EGF-induced heterodimerization of C-Raf with B-Raf, which transmits the signal to C-Raf. DGKη physically interacted with B-Raf and C-Raf, regulating EGF-induced recruitment of B-Raf and C-Raf from the cytosol to membranes. The DGKη-dependent activation of C-Raf occurred downstream or independently of the already known C-Raf modifications, such as dephosphorylation at Ser-259, phosphorylation at Ser-338, and interaction with 14-3-3 protein. Taken together, the results obtained strongly support that DGKη acts as a novel critical regulatory component of the Ras/B-Raf/C-Raf/MEK/ERK signaling cascade via a previously unidentified mechanism.The Ras/Raf/MEK³/ERK signaling pathway is critical for the transduction of the extracellular signals to the nucleus, regulating diverse physiological processes such as cell proliferation, differentiation, and survival (1, 2). The binding of extracellular ligands, such as growth factors and cytokines, to cell surface receptors activates Ras. The Raf serine/threonine kinase transmits signals from activated Ras to the downstream protein kinases, MEK1 and MEK2, subsequently leading to activation of ERK1 and ERK2.In mammals, the Raf kinase consists of three isoforms, A-Raf, B-Raf, and C-Raf (Raf-1). It is clinically known that both B-Raf and C-Raf mutations are associated with human cancers (3–5). Knock-out mouse studies demonstrated that each individual Raf isoform has distinct functions, although the three Raf isoforms have high homology in the amino acid sequence (6). The mechanisms underlying C-Raf activation are complicated and thus are not completely understood (3). In response to extracellular signals, C-Raf is initially recruited from cytosol to the plasma membrane and undergo conformational changes by binding directly to the active Ras (7). In addition, other modifications and factors are required for the sufficient activation of C-Raf. For example, dephosphorylation of Ser-259 and phosphorylation of Ser-338, Tyr-341, Thr-491, and Ser-494 are critical for the activation of C-Raf (8–11). Feedback phosphorylation of C-Raf by ERK was also reported to be important for the modulation of C-Raf activity (12, 13). C-Raf activity is regulated by the interaction with 14-3-3 protein (14). Moreover, the heterodimerization of C-Raf with B-Raf, which transmits the signal to C-Raf, has been reported to play an essential role in the activation of the MEK-ERK signaling pathway (15–17). Although B-Raf and C-Raf are the central regulatory components in the Ras/B-Raf/C-Raf/MEK/ERK signaling cascade involved in a variety of pathophysiological events, the activation mechanisms of C-Raf by B-Raf are still unclear.Diacylglycerol kinase (DGK) catalyzes the phosphorylation of diacylglycerol to generate phosphatidic acid. DGK has been recently recognized as an emerging key regulator in a wide range of cell signaling systems (18–20). To date, 10 mammalian DGK isozymes have been identified. They characteristically contain two or three protein kinase C-like C1 domains and a catalytic region and are subdivided into five subtypes according to their structural features (18–20). Their structural variety and distinct expression patterns in tissues allow us to presume that each DGK isozyme has its own biological functions. Indeed, recent studies have revealed that individual DGK isozymes play distinct roles in cell functions through interactions with unique partner proteins such as protein kinase C (21, 22), Ras guanyl nucleotide-releasing protein (23, 24), phosphatidylinositol-4-phosphate 5-kinase (25), chimerins (26, 27), AP-2 (28), and PSD-95 (29).DGKη belongs to the type II DGKs containing a pleckstrin homology domain at the N terminus and the separated catalytic region (19, 30). Two alternative splicing products of DGKη have been identified as DGKη1 and -η2 (31). DGKη2 possesses a sterile α-motif (SAM) domain at the C terminus, whereas DGKη1 does not. This study demonstrated that the expression levels of DGKη1 and -η2 were regulated differently by glucocorticoid, and that they were translocated from the cytoplasm to endosomes in response to stress stimuli as osmotic shock and oxidative stress (31). However, the physiological roles of DGKη remain unknown.This study showed that siRNA-dependent knockdown of DGKη inhibits cell proliferation of the HeLa cells. In addition, DGKη is required for the Ras/B-Raf/C-Raf/MEK/ERK signaling cascade activated by epidermal growth factor (EGF). Intriguingly, DGKη regulates recruitment of B-Raf and C-Raf from cytosol to membranes and their heterodimerization. Moreover, this study demonstrated that DGKη activates C-Raf but not B-Raf in an EGF-dependent manner. The data show DGKη as a novel key regulator of the Ras/B-Raf/C-Raf/MEK/ERK signaling pathway.     

[18F]FEAC and [18F]FEDAC: Two novel positron emission tomography ligands for peripheral-type benzodiazepine receptor in the brain

[¹⁸F]FEAC ([¹⁸F]4a) and [¹⁸F]FEDAC ([¹⁸F]4b) were developed as two novel positron emission tomography (PET) ligands for peripheral-type benzodiazepine receptor (PBR). [¹⁸F]4a and [¹⁸F]4b were synthesized by fluoroethylation of precursors 8a and 8b with [¹⁸F]FCH₂CH₂Br ([¹⁸F]9), respectively. Small-animal PET scan for a neuroinflammatory rat model showed that the two radioligands had high uptakes of radioactivity in the kainic acid-infused striatum, a brain region where PBR density was increased.