Marie M, Stickney K, VanBuecken D, Vellek B, Webber C, Allen L, Bollyk J, Hilderman N, Ismail H, Lamola S, Sanda S, Vendettuoli H, Tridgell D, Monzavi R, Bock M, Fisher L, Halvorson M, Jeandron D, Kim M, Wood J, Geffner M, Kaufman F, Parkman R, Salazar C, Goland R, Clynes R, Cook S, Freeby M, Gallagher MP, Gandica R, Greenberg E, Kurland A, Pollak S, Wolk A, Chan M, Koplimae L, Levine E, Smith K, Trast J, DiMeglio L, Blum J, Evans-Molina C, Hufferd R, Jagielo B, Kruse C, Patrick V, Rigby M, Spall M, Swinney K, Terrell J, Christner L, Ford L, Lynch S, Menendez M, Merrill P, Pescovitz M, Rodriguez H, Alleyn C, Baidal D, Fay S, Gaglia J, Resnick B, Szubowicz S, Weir G, Benjamin R, Conboy D, deManbey A, Jackson R, Jalahej H, Orban T, Ricker A, Wolfsdorf J, Zhang HH, Wilson D, Aye T, Baker B, Barahona K, Buckingham B, Esrey K, Esrey T, Fathman G, Snyder R, Aneja B, Chatav M, Espinoza O, Frank E, Liu J, Perry J, Pyle R, Rigby A, Riley K, Soto A, Gitelman S, Adi S, Anderson M, Berhel A, Breen K, Fraser K, Gerard-Gonzalez A, Jossan P, Lustig R, Moassesfar S, Mugg A, Ng D, Prahalod P, Rangel-Lugo M, Sanda S, Tarkoff J, Torok C, Wesch R, Aslan I, Buchanan J, Cordier J, Hamilton C, Hawkins L, Ho T, Jain A, Ko K, Lee T, Phelps S, Rosenthal S, Sahakitrungruang T, Stehl L, Taylor L, Wertz M, Wong J, Philipson L, Briars R, Devine N, Littlejohn E, Grant T, Gottlieb P, Klingensmith G, Steck A, Alkanani A, Bautista K, Bedoy R, Blau A, Burke B, Cory L, Dang M, Fitzgerald-Miller L, Fouts A, Gage V, Garg S, Gesauldo P, Gutin R, Hayes C, Hoffman M, Ketchum K, Logsden-Sackett N, Maahs D, Messer L, Meyers L, Michels A, Peacock S, Rewers M, Rodriguez P, Sepulbeda F, Sippl R, Steck A, Taki I, Tran BK, Tran T, Wadwa RP, Zeitler P, Barker J, Barry S, Birks L, Bomsburger L, Bookert T, Briggs L, Burdick P, Cabrera R, Chase P, Cobry E, Conley A, Cook G, Daniels J, DiDomenico D, Eckert J, Ehler A, Eisenbarth G, Fain P, Fiallo-Scharer R, Frank N, Goettle H, Haarhues M, Harris S, Horton L, Hutton J, Jeffrrey J, Jenison R, Jones K, Kastelic W, King MA, Lehr D, Lungaro J, Mason K, Maurer H, Nguyen L, Proto A, Realsen J, Schmitt K, Schwartz M, Skovgaard S, Smith J, Vanderwel B, Voelmle M, Wagner R, Wallace A, Walravens P, Weiner L, Westerhoff B, Westfall E, Widmer K, Wright H, Schatz D, Abraham A, Atkinson M, Cintron M, Clare-Salzler M, Ferguson J, Haller M, Hosford J, Mancini D, Rohrs H, Silverstein J, Thomas J, Winter W, Cole G, Cook R, Coy R, Hicks E, Lewis N, Marks J, Pugliese A, Blaschke C, Matheson D, Sanders-Branca N, Sosenko J, Arazo L, Arce R, Cisneros M, Sabbag S, Moran A, Gibson C, Fife B, Hering B, Kwong C, Leschyshyn J, Nathan B, Pappenfus B, Street A, Boes MA, Eck SP, Finney L, Fischer TA, Martin A, Muzamhindo CJ, Rhodes M, Smith J, Wagner J, Wood B, Becker D, Delallo K, Diaz A, Elnyczky B, Libman I, Pasek B, Riley K, Trucco M, Copemen B, Gwynn D, Toledo F, Rodriguez H, Bollepalli S, Diamond F, Eyth E, Henson D, Lenz A, Shulman D, Raskin P, Adhikari S, Dickson B, Dunnigan E, Lingvay I, Pruneda L, Ramos-Roman M, Raskin P, Rhee C, Richard J, Siegelman M, Sturges D, Sumpter K, White P, Alford M, Arthur J, Aviles-Santa ML, Cordova E, Davis R, Fernandez S, Fordan S, Hardin T, Jacobs A, Kaloyanova P, Lukacova-Zib I, Mirfakhraee S, Mohan A, Noto H, Smith O, Torres N, Wherrett D, Balmer D, Eisel L, Kovalakovska R, Mehan M, Sultan F, Ahenkorah B, Cevallos J, Razack N, Ricci MJ, Rhode A, Srikandarajah M, Steger R, Russell WE, Black M, Brendle F, Brown A, Moore D, Pittel E, Robertson A, Shannon A, Thomas JW, Herold K, Feldman L, Sherwin R, Tamborlane W, Weinzimer S, Toppari J, Kallio T, Kärkkäinen M, Mäntymäki E, Niininen T, Nurmi B, Rajala P, Romo M, Suomenrinne S, Näntö-Salonen K, Simell O, Simell T, Bosi E, Battaglia M, Bianconi E, Bonfanti R, Grogan P, Laurenzi A, Martinenghi S, Meschi F, Pastore M, Falqui L, Muscato MT, Viscardi M, Castleden H, Farthing N, Loud S, Matthews C, McGhee J, Morgan A, Pollitt J, Elliot-Jones R, Wheaton C, Knip M, Siljander H, Suomalainen H, Colman P, Healy F, Mesfin S, Redl L, Wentworth J, Willis J, Farley M, Harrison L, Perry C, Williams F, Mayo A, Paxton J, Thompson V, Volin L, Fenton C, Carr L, Lemon E, Swank M, Luidens M, Salgam M, Sharma V, Schade D, King C, Carano R, Heiden J, Means N, Holman L, Thomas I, Madrigal D, Muth T, Martin C, Plunkett C, Ramm C, Auchus R, Lane W, Avots E, Buford M, Hale C, Hoyle J, Lane B, Muir A, Shuler S, Raviele N, Ivie E, Jenkins M, Lindsley K, Hansen I, Fadoju D, Felner E, Bode B, Hosey R, Sax J, Jefferies C, Mannering S, Prentis R, She J, Stachura M, Hopkins D, Williams J, Steed L, Asatapova E, Nunez S, Knight S, Dixon P, Ching J, Donner T, Longnecker S, Abel K, Arcara K, Blackman S, Clark L, Cooke D, Plotnick L, Levin P, Bromberger L, Klein K, Sadurska K, Allen C, Michaud D, Snodgrass H, Burghen G, Chatha S, Clark C, Silverberg J, Wittmer C, Gardner J, LeBoeuf C, Bell P, McGlore O, Tennet H, Alba N, Carroll M, Baert L, Beaton H, Cordell E, Haynes A, Reed C, Lichter K, McCarthy P, McCarthy S, Monchamp T, Roach J, Manies S, Gunville F, Marosok L, Nelson T, Ackerman K, Rudolph J, Stewart M, McCormick K, May S, Falls T, Barrett T, Dale K, Makusha L, McTernana C, Penny-Thomas K, Sullivan K, Narendran P, Robbie J, Smith D, Christensen R, Koehler B, Royal C, Arthur T, Houser H, Renaldi J, Watsen S, Wu P, Lyons L, House B, Yu J, Holt H, Nation M, Vickers C, Watling R, Heptulla R, Trast J, Agarwal C, Newell D, Katikaneni R, Gardner C, Del Rio A, Logan A, Collier H, Rishton C, Whalley G, Ali A, Ramtoola S, Quattrin T, Mastrandea L, House A, Ecker M, Huang C, Gougeon C, Ho J, Pacuad D, Dunger D, May J, O’Brien C, Acerini C, Salgin B, Thankamony A, Williams R, Buse J, Fuller G, Duclos M, Tricome J, Brown H, Pittard D, Bowlby D, Blue A, Headley T, Bendre S, Lewis K, Sutphin K, Soloranzo C, Puskaric J, Madison H, Rincon M, Carlucci M, Shridharani R, Rusk B, Tessman E, Huffman D, Abrams H, Biederman B, Jones M, Leathers V, Brickman W, Petrie P, Zimmerman D, Howard J, Miller L, Alemzadeh R, Mihailescu D, Melgozza-Walker R, Abdulla N, Boucher-Berry C, Ize-Ludlow D, Levy R, Swenson Brousell C, Scott R, Heenan H, Lunt H, Kendall D, Willis J, Darlow B, Crimmins N, Edler D, Weis T, Schultz C, Rogers D, Latham D, Mawhorter C, Switzer C, Spencer W, Konstantnopoulus P, Broder S, Klein J, Bachrach B, Gardner M, Eichelberger D, Knight L, Szadek L, Welnick G, Thompson B, Hoffman R, Revell A, Cherko J, Carter K, Gilson E, Haines J, Arthur G, Bowen B, Zipf W, Graves P, Lozano R, Seiple D, Spicer K, Chang A, Fregosi J, Harbinson J, Paulson C, Stalters S, Wright P, Zlock D, Freeth A, Victory J, Maheshwari H, Maheshwari A, Holmstrom T, Bueno J, Arguello R, Ahern J, Noreika L, Watson V, Hourse S, Breyer P, Kissel C, Nicholson Y, Pfeifer M, Almazan S, Bajaj J, Quinn M, Funk K, McCance J, Moreno E, Veintimilla R, Wells A, Cook J, Trunnel S, Transue D, Surhigh J, Bezzaire D, Moltz K, Zacharski E, Henske J, Desai S, Frizelis K, Khan F, Sjoberg R, Allen K, Manning P, Hendry G, Taylor B, Jones S, Couch R, Danchak R, Lieberman D, Strader W, Bencomo M, Bailey T, Bedolla L, Roldan C, Moudiotis C, Vaidya B, Anning C, Bunce S, Estcourt S, Folland E, Gordon E, Harrill C, Ireland J, Piper J, Scaife L, Sutton K, Wilkins S, Costelloe M, Palmer J, Casas L, Miller C, Burgard M, Erickson C, Hallanger-Johnson J, Clark P, Taylor W, Galgani J, Banerjee S, Banda C, McEowen D, Kinman R, Lafferty A, Gillett S, Nolan C, Pathak M, Sondrol L, Hjelle T, Hafner S, Kotrba J, Hendrickson R, Cemeroglu A, Symington T, Daniel M, Appiagyei-Dankah Y, Postellon D, Racine M, Kleis L, Barnes K, Godwin S, McCullough H, Shaheen K, Buck G, Noel L, Warren M, Weber S, Parker S, Gillespie I, Nelson B, Frost C, Amrhein J, Moreland E, Hayes A, Peggram J, Aisenberg J, Riordan M, Zasa J, Cummings E, Scott K, Pinto T, Mokashi A, McAssey K, Helden E, Hammond P, Dinning L, Rahman S, Ray S, Dimicri C, Guppy S, Nielsen H, Vogel C, Ariza C, Morales L, Chang Y, Gabbay R, Ambrocio L, Manley L, Nemery R, Charlton W, Smith P, Kerr L, Steindel-Kopp B, Alamaguer M, Tabisola-Nuesca E, Pendersen A, Larson N, Cooper-Olviver H, Chan D, Fitz-Patrick D, Carreira T, Park Y, Ruhaak R, Liljenquist D. A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

[Perioperative Outcomes in Correlation to the Learning Curve for Robotic Assisted Partial Nephrectomy: The First 109 Cases of our Clinic]

BACKGROUND

In contrast to conventional laparoscopic partial nephrectomy, the approach of robot-assisted partial nephrectomy (RAPN) shows a steep learning curve with shorter warm ischaemia times (WIT) and comparable postoperative outcomes. Therefore RAPN is considered a good minimally-invasive surgical procedure for patients presenting with a renal cell carcinoma in clinical stage cT1a. The aim of the presented study was to evaluate the perioperative outcomes of our patients after RAPN and to illustrate the learning curve based on characteristic perioperative parameters such as WIT.

MATERIAL AND METHODS

The data of 109 patients treated by RAPN in our clinic between January 2010 and April 2015 were retrospectively analysed regarding perioperative, laboratory and oncological outcomes. Postoperative complications until 30 days after surgery were documented. We analysed the data of the largest patient population treated by a single urologist, comparing WIT, operating time, blood loss and decline of the glomerular filtration rate between the first and the second 30 consecutive cases.

RESULTS

Mean WIT was 18.4 min (SD±10.2), mean operating time was 199 min (SD±20), and mean estimated blood loss was 657 millilitres (SD±715 ml). Mean loss of GFR was reported to be 4.99 mg/dl/1.73 m (2) (SD±15.44). 83 (76%) malignant lesions were removed. 11 patients (10%) had a R1 resection, one patient had a R2 resection and in 2 cases the resection status was Rx. 22% of patients developed postoperative complications. Intraoperative complications were documented in 2 cases. According to the Clavien-Dindo Classification, 6% of patients had grade 1 and 2 complications and 13% developed grade 3 and 4 complications. WIT was significantly lower after 30 consecutive cases treated by one urologist. Regarding operating time, GFR or blood loss no significant correlation was found.

CONCLUSION

Our data is in line with the surgical outcomes described in the literature. RAPN is a safe surgical technique with a steep learning curve. In our experience, 30 surgical cases provide a urologist with sufficient expertise to achieve good perioperative results. Weaknesses of this report include the retrospective design and insufficient documentation in some cases.

Both Astrocytes and Neurons Contribute to the Potentiation Mediated by alpha1-Adrenoceptors of the beta-Adrenergic-Stimulated Cyclic AMP Production in Brain

Using primary neuronal or astrocyte cultures from the striatum of the embryonic mouse, we have observed that the beta-adrenergic agonist isoprenaline (10-5 M) induced a more pronounced accumulation of cAMP in astrocytes than in neurons. In both cell types, the alpha-adrenergic selective agonist methoxamine (10-4 M), which alone did not affect the production of cAMP, potentiated the isoprenaline-evoked response. In support of these observations, when associated alpha2-noradrenergic and D1-dopaminergic responses were prevented, the mixed alpha1- and beta-adrenergic agonist noradrenaline (10-5 M) induced a production of cAMP which was totally blocked by propranolol (10-6 M) and partially abolished by prazosin (10-6 M). Since experiments were made in the presence of 3-isobutyl-1-methylxanthine (1 mM), the observed effects of cAMP accumulation were not related to a modulation of phosphodiesterase activities. In addition, both in astrocytes and in neurons, the potentiation by alpha1-adrenergic agonists of the beta-adrenergic-evoked response required external calcium. Using INDo 1 as a fluorescent probe, methoxamine (25 microM) was shown to induce in astrocytes an increase in cytosolic calcium concentration which was prolonged by isoprenaline (10-5 M) only in the presence of external calcium. These results suggest that the prolonged increase in cytosolic calcium concentration linked to the activation of alpha1- and beta-adrenergic receptors is responsible for the potentiation of the beta-adrenergic-induced production of cAMP, which is partially dependent on external calcium.

Sphingosine-1-phosphate induces proliferation of astrocytes: regulation by intracellular signalling cascades

Sphingosine-1-phosphate (S1P) is a potent lysophospholipid mediator mostly released by activated platelets. It is involved in several functions in peripheral tissues, but its effects in the central nervous system are poorly documented. Therefore, we have examined the effects of S1P on the proliferation of striatal astrocytes from the mouse embryo. These cells have been found to express mRNAs for the S1P receptors, Edg-1 and Edg-3. S1P stimulated thymidine incorporation and induced activation of extracellular signal-regulated kinases (Erks). Both effects were prevented by U0126, an Erk kinase inhibitor. The S1P-evoked activation of Erk1 was totally blocked in astrocytes pretreated with a combination of either phorbol ester (24 h) and LY294002, or phorbol ester (24 h) and pertussis toxin (PTX). Each individual treatment only partially inhibited Erk1 activation. This suggests that several separate mechanisms mediate this process, one involving protein kinase C and another involving Gi/Go proteins and phosphatidylinositol 3-kinase. In contrast, the stimulatory effect of S1P on astrocyte proliferation was totally blocked by either PTX or LY294002, but not by a downregulation of protein kinase C. S1P dramatically inhibited the evoked production of cyclic AMP, a response that was impaired by PTX. Finally, S1P stimulated the production of inositol phosphates and increased intracellular calcium by mobilization from thapsigargin-sensitive stores. These latter effects were mainly insensitive to PTX. Probably, Gi/Go protein activation and phosphoinositide hydrolysis are early events that regulate the activation of Erks by S1P. Altogether, these observations show that astrocytes are targets for S1P. Their proliferation in response to S1P could have physiopathological consequences at sites of brain lesions and alterations of the blood-brain barrier.

Antiproliferative properties of sphingosine-1-phosphate in human hepatic myofibroblasts

Sphingosine-1-phosphate (S1P) is a potent lysophospholipid mediator mostly released by activated platelets. It is involved in several functions in peripheral tissues, but its effects in the central nervous system are poorly documented. Therefore, we have examined the effects of S1P on the proliferation of striatal astrocytes from the mouse embryo. These cells have been found to express mRNAs for the S1P receptors, Edg-1 and Edg-3. S1P stimulated thymidine incorporation and induced activation of extracellular signal-regulated kinases (Erks). Both effects were prevented by U0126, an Erk kinase inhibitor. The S1P-evoked activation of Erk1 was totally blocked in astrocytes pretreated with a combination of either phorbol ester (24 h) and LY294002, or phorbol ester (24 h) and pertussis toxin (PTX). Each individual treatment only partially inhibited Erk1 activation. This suggests that several separate mechanisms mediate this process, one involving protein kinase C and another involving Gi/Go proteins and phosphatidylinositol 3-kinase. In contrast, the stimulatory effect of S1P on astrocyte proliferation was totally blocked by either PTX or LY294002, but not by a downregulation of protein kinase C. S1P dramatically inhibited the evoked production of cyclic AMP, a response that was impaired by PTX. Finally, S1P stimulated the production of inositol phosphates and increased intracellular calcium by mobilization from thapsigargin-sensitive stores. These latter effects were mainly insensitive to PTX. Probably, Gi/Go protein activation and phosphoinositide hydrolysis are early events that regulate the activation of Erks by S1P. Altogether, these observations show that astrocytes are targets for S1P. Their proliferation in response to S1P could have physiopathological consequences at sites of brain lesions and alterations of the blood-brain barrier.

Pleiotropic effects of lysophosphatidic acid on striatal astrocytes

Lysophosphatidic acid (LPA) is a potent lipid mediator that is likely involved in diverse functions in the brain. Several recent studies have suggested that astrocytes are important target cells for LPA. In the present study, we have identified the signal transduction pathways activated following LPA stimulation in mouse striatal astrocytes in primary culture. In cells prelabeled with myo-[3H]inositol, LPA stimulated the formation of [3H]inositol phosphates (EC50 = 0.7 microM). This effect was reproduced neither by other lysophospholipids nor by phosphatidic acid. Astrocyte pretreatment with pertussis toxin partially abolished this LPA response indicating the involvement of a Gi/Go protein. In [3H]adenine-prelabeled cells, LPA strongly inhibited the formation of [3H]cyclic AMP induced by forskolin (EC(50) = 0.3 microM) and by isoproterenol and PACAP-38. These inhibitory effects were strongly reduced by pertussis toxin treatment. Although with a lesser potency (EC50 = 5 microM), LPA also stimulated the release of [3H]arachidonic acid from [3H]arachidonic acid-prelabeled astrocytes. This latter effect was totally inhibited by mepacrine, did not involve a pertussis toxin-sensitive G protein, and was highly dependent on external calcium. LPA also stimulated the activity of both extracellular signal-regulated kinases (Erk) Erk1 and Erk2 by a mechanism involving a Gi/Go protein. Surprisingly, in contrast to that observed in fibroblasts, LPA was totally ineffective in stimulating DNA synthesis. These results provide additional evidence in favor of an important physiological role of LPA in the astrocytic functions.

Knock-out of the neural death effector domain protein PEA-15 demonstrates that its expression protects astrocytes from TNFalpha-induced apoptosis

Apoptosis is a very general phenomenon, but only a few reports concern astrocytes. Indeed, astrocytes express receptors for tumor necrosis factor (TNF) alpha, a cytokine demonstrated on many cells and tissues to mediate apoptosis after recruitment of adaptor proteins containing a death effector domain (DED). PEA-15 is a DED-containing protein prominently expressed in the CNS and particularly abundant in astrocytes. This led us to investigate if PEA-15 expression could be involved in astrocytic protection against deleterious effects of TNF. In vitro assays evidence that PEA-15 may bind to DED-containing protein FADD and caspase-8 known to be apical adaptors of the TNF apoptotic signaling. After generation of PEA-15 null mutant mice, our results demonstrate that PEA-15 expression increases astrocyte survival after exposure to TNF.

Anandamide and WIN 55212-2 inhibit cyclic AMP formation through G-protein-coupled receptors distinct from CB1 cannabinoid receptors in cultured astrocytes

The effects of anandamide and the cannabinoid receptor agonists WIN 55212-2 and CP 55940 on the evoked formation of cyclic AMP were compared in cultured neurons and astrocytes from the cerebral cortex and striatum of mouse embryos. The three compounds inhibited the isoproterenol-induced accumulation of cyclic AMP in neuronal cells, and these responses were blocked by the selective CB1 receptor antagonist SR 141716A. The three agonists were more potent in cortical than striatal neurons. Interestingly, WIN 55212-2, CP 55940 and anandamide also inhibited the isoproterenol-evoked accumulation of cyclic AMP in astrocytes but, in contrast to WIN 55212-2 and CP 55940, anandamide was much more potent in striatal than cortical astrocytes. Inhibition was prevented by pertussis toxin pretreatment, but not blocked by SR 141716A. Therefore, G-protein-coupled receptors, distinct from CB1 receptors, are involved in these astrocytic responses. Moreover, specific binding sites for [3H]-SR 141716A were found in neurons but not astrocytes. Furthermore, using a polyclonal CB1 receptor antibody, staining was observed in striatal and cortical neurons, but not in striatal and cortical astrocytes. Taken together, these results suggest that glial cells possess G-protein-coupled receptors activated by cannabinoids distinct from the neuronal CB1 receptor, and that glial cells responses must be taken into account when assessing central effects of cannabinoids.

Endothelin induces a calcium-dependent phosphorylation of PEA-15 in intact astrocytes: identification of Ser104 and Ser116 phosphorylated, respectively, by protein kinase C and calcium/calmodulin kinase II in vitro

PEA-15 (phosphoprotein enriched in astrocytes, Mr = 15,000) is an acidic serine-phosphorylated protein highly expressed in the CNS, where it can play a protective role against cytokine-induced apoptosis. PEA-15 is a major substrate for protein kinase C. Endothelins, which are known to exert pleiotropic effects on astrocytes, were used to analyze further the processes involved in PEA-15 phosphorylation. Endothelin-1 or endothelin-3 (0.1 microM) induced a robust phosphorylation of PEA-15 that was abolished by the removal of extracellular calcium, but only diminished by inhibitors of protein kinase C. Microsequencing of phosphopeptides generated by digestion of PEA-15 following endothelin-1 treatment identified two phosphorylated residues: Ser104, previously recognized as the protein kinase C site, and a novel phosphoserine, Ser116, located in a consensus motif for either protein kinase casein kinase II or calcium/calmodulin-dependent protein kinase II (CaMKII). Partly purified PEA-15 was a substrate in vitro for CaMKII, but not for casein kinase II. Two-dimensional phosphopeptide mapping demonstrated that the site phosphorylated in vitro by CaMKII was also phosphorylated in intact astrocytes in response to endothelin. CaMKII phosphorylated selectively Ser116 and had no effect on Ser104, but in vitro phosphorylation by CaMKII appeared to facilitate further phosphorylation by protein kinase C. Treatment of intact astrocytes with okadaic acid enhanced the phosphorylation of the CaMKII site. These results demonstrate that PEA-15 is phosphorylated in astrocytes by CaMKII (or a related kinase) and by protein kinase C in response to endothelin.

Endothelin stimulates phospholipase D in striatal astrocytes

In primary cultures of mouse striatal astrocytes prelabeled with [3H]myristic acid, endothelin (ET)-1 induced a time-dependent formation of [3H]phosphatidic acid and [3H]diacylglycerol. In the presence of ethanol, a production of [3H]phosphatidylethanol was observed, indicating the activation of a phospholipase D (PLD). ET-1 and ET-3 were equipotent in stimulating PLD activity (EC50 = 2-5 nM). Pretreatment of the cells with pertussis toxin partially abolished the effect of ET-1, indicating the involvement of a Gi/G(o) protein. Inhibition of protein kinase C by Ro 31-8220 or down-regulation of the kinase by a long-time treatment with phorbol 12-myristate 13-acetate (PMA) totally abolished the ET-1-induced stimulation of PLD. In contrast, a cyclic AMP-dependent process is not involved in the activation of PLD, because the ET-1-evoked formation of [3H]phosphatidylethanol was not affected when cells were coincubated with either isoproterenol, 8-bromo-cyclic AMP, or forskolin. Acute treatment with PMA also stimulated PLD through a protein kinase C-dependent process. However, the ET-1 and PMA responses were additive. Furthermore, the ET-1-evoked response, contrary to that of PMA, totally dependent on the presence of extracellular calcium. These results suggest that at least two distinct mechanisms are involved in the control of PLD activity in striatal astrocytes. Finally, ET-1, ET-3, and PMA also stimulated PLD in astrocytes from the mesencephalon, the cerebral cortex, and the hippocampus.

Synergistic effects of acetylcholine and glutamate on the release of arachidonic acid from cultured striatal neurons

The activation of muscarinic and NMDA receptors by carbachol and NMDA, respectively, stimulated the release of [3H]arachidonic acid ([3H]AA) from cultured striatal neurons. Striking synergistic effects were observed when both agonists were coapplied. This synergistic response was suppressed by atropine or (5R, 10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-im ine hydrogen maleate and inhibited by magnesium. It was markedly reduced in the absence of external calcium and suppressed by mepacrine. NMDA strongly elevated the intracellular calcium concentration ([Ca2+]i), but carbachol was ineffective. Ionomycin, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate, or potassium depolarization, which increased [Ca2+]i but was ineffective on [3H]AA release, also potentiated the carbachol response. Sphingosine and Ro 31-8220 suppressed the responses evoked by carbachol, NMDA, or both agonists. However, no synergistic responses could be observed when phorbol 12-myristate 13-acetate was associated with either carbachol or NMDA. Together, these results suggest that both the massive influx of calcium induced by NMDA and the coupling of muscarinic receptors with a putative phospholipase A2 are required for the strong synergistic effects of carbachol and NMDA on [3H]AA release. Synergistic effects were also observed with acetylcholine and glutamate in the presence of magnesium, further revealing the physiological relevance of this process.

Cellular expression, developmental regulation, and phylogenic conservation of PEA-15, the astrocytic major phosphoprotein and protein kinase C substrate

PEA-15 has recently been identified as a major phosphoprotein in astrocytes and an endogenous substrate for protein kinase C. This 15-kDa protein exists under three molecular forms, an unphosphorylated form, N, and two phosphorylated forms, Pa and Pb. Antisera were raised against synthetic peptides corresponding to the internal sequences of the mouse protein containing the two specific phosphorylation sites and affinity-purified antibodies were used for immunoblotting. PEA-15 was found mainly in the cytosol, but its protein kinase C-phosphorylated form, Pb, was also detectable in association with the membrane and remained with the fraction that contains stabilized microtubules. Abundant in astrocytes, particularly in the hippocampus, PEA-15 was also detected in all cultured brain cell types examined, indicating a more ubiquitous distribution of the protein, further demonstrated by its detection in the eye and in the lung. Parallel to the increase in expression levels, phosphorylation of PEA-15 also increased during development. This paralleled results obtained in primary cultures, whereas PEA-15 levels increase with cell maturation. Finally, physiological importance of PEA-15 phosphorylation was illustrated by immunoreactivity observed in brain homogenates of different mammals, birds, amphibians, and fish.

Homotypic and heterotypic coupling mediated by gap junctions during glial cell differentiation in vitro

Intercellular communication mediated by gap junctions was investigated during oligodendrocyte differentiation in primary and secondary cell cultures from newborn and adult rats. Two types of communication were considered: ionic coupling and dye-coupling between similar oligodendrocytes selected at the same stage of differentiation (homotypic) and dye-coupling between oligodendrocytes and astrocytes (heterotypic). Intercellular diffusion of fluorescent probes and double whole-cell recordings were used to test the incidence of dye and ionic communication respectively. Progenitor cells, identified with A2B5 antibodies, were characterized by the absence of ionic and dye-coupling, whereas oligodendrocytes, identified with galactosylceramide antibodies, exhibited both types of communication. This homotypic coupling was inhibited by various uncoupling agents, but unaffected by treatments which increased the intracellular concentration of cAMP. In cocultures of astrocytes and oligodendrocytes, Lucifer yellow and sulphorhodamine B were exchanged in both directions. This heterotypic dye-coupling, which could be blocked by octanol, first appeared after 3 weeks in culture and increased to an incidence of 25% after 6 weeks, a developmental pattern comparable to homotypic dye-coupling between oligodendrocytes. In contrast, during the same period, progenitors and microglia were never observed to be dye-coupled with astrocytes.

Muscarinic cholinergic agonists stimulate arachidonic acid release from mouse striatal neurons in primary culture

In cultured striatal neurons from embryonic mice, carbachol was found to stimulate the release of arachidonic acid (AA) EC50 = 87 microM) and formation of inositol phosphates (IPs) (EC50 = 54 microM). Both responses were reproduced by muscarinic but not nicotinic agonists, and both exhibited the same pharmacological profile toward four muscarinic antagonists. Furthermore, both responses were insensitive to pertussis toxin, providing additional evidence for the involvement of the same muscarinic receptor(s), most probably of the m1 subtype. Both carbachol-evoked responses were also highly sensitive to the presence of external calcium. The calcium ionophore ionomycin, ineffective alone on AA release, strongly potentiated the carbachol response. In contrast, ionomycin alone stimulated the formation of IPs but did not significantly modify the carbachol response. Protein kinase C activation positively regulated the carbachol-evoked release of AA because this response was markedly potentiated by phorbol 12-myristate 13-acetate (PMA) and was abolished by sphingosine and Ro 31-8220. In contrast, PMA markedly inhibited the carbachol-evoked formation of IPs. The carbachol-evoked release of AA was not mimicked by the combined applications of ionomycin and PMA, which suggests that phospholipase C stimulation alone is not sufficient to trigger AA release. Taken together, these results suggest that the coupling of m1 receptors to a putative phospholipase A2 that is positively regulated by protein kinase C and by calcium is necessary for the carbachol-evoked release of AA.(ABSTRACT TRUNCATED AT 250 WORDS)

Is protein kinase C activity required for the N-methyl-D-aspartate-evoked rise in cytosolic Ca2+ in mouse striatal neurons?

The present study investigates the roles of protein kinase C (PKC) and A (PKA) activities in NMDA-mediated Ca2+ entry in primary cultures of mouse striatal neurons. Inhibitors of protein kinases, such as sphingosine, RO 31-8220 and staurosporine inhibited the NMDA- but also the KCl-induced rise in cytosolic Ca2+. However, the PKA antagonist Rp-adenosine-3',5'monophosphothioate (Rp-cAMPS) did not alter the NMDA+D-serine response, whereas it completely suppressed the KCl response. The NMDA+D-serine-evoked rise in cytosolic Ca2+, observed in the absence of external Mg2+, was potentiated by the PKC activator phorbol 12-myristate 13-acetate (PMA) only when submaximal effective concentrations of this agonist and co-agonist were used. In addition, the PKC activator did not alter the NMDA+D-serine-evoked response in the presence of varying concentrations of Mg2+. Confirming the dependence on PKC activity, desensitization of PKC resulting from long-term PMA treatment led to an impairment of the NMDA response, leaving the KCl-induced response intact. We therefore propose that PKC not only potentiates but is also required for the NMDA-evoked elevation in cytosolic Ca2+ in mouse striatal neurons.

Synergistic regulation of cytosolic Ca2+ concentration by somatostatin and alpha 1-adrenergic agonists in mouse astrocytes

The effects of somatostatin and alpha 1-adrenergic receptor agonists on cytosolic Ca2+ in striatal astrocytes from the embryonic mouse in primary culture have been investigated by microfluorimetry. Methoxamine or somatostatin induced a transitory increase in cytosolic Ca2+, but their combined addition led to a sustained increase in cytosolic Ca2+ which seems to be due to a Ca2+ influx since it was not observed in the absence of external Ca2+. Voltage-independent Ca2+ channels contribute to this process. Indeed, voltage-operated calcium channels are not involved since neither dihydropyridines nor La3+ were effective in suppressing the sustained cytosolic Ca2+ elevation. Moreover, depolarization by 50 mM KCl, which was ineffective alone, suppressed the effect of somatostatin observed in the presence of the alpha 1 agonist, methoxamine. The implication of arachidonic acid in the observed potentiation is suggested by the following observations: 1) arachidonic acid induced a sustained elevation of cytosolic Ca2+ similar to that evoked by the co-application of methoxamine and somatostatin; 2) the addition of ETYA, an inactive and non-metabolizable analogue of arachidonic acid suppressed the calcium plateau produced by the agonists. In addition, direct activation of PKC by an exogeneous diacylglycerol analogue allowed somatostatin alone to evoke a sustained elevation of cytosolic Ca2+. Therefore, methoxamine through the successive activation of PLC and PKC could allow a lipase, probably PLA2, to be stimulated by somatostatin. Since arachidonic acid has already been shown to trigger the opening of K+ channels and the formation of inositol phosphates, somatostatin, through the arachidonic acid-mediated hyperpolarization could increase the Ca2+ driving force and thus improve Ca2+ influx through the inositol phosphate gated channels.

Differential effects of propofol and ketamine on cytosolic calcium concentrations of astrocytes in primary culture

Propofol has been shown recently to alter cellular communication mediated by gap junctions between astrocytes (a glial cell subpopulation involved in major brain functions). As marked increases in concentrations of cytosolic calcium ([Ca2+]i) produce closure of the gap junction, we have investigated the effects of both propofol and ketamine on resting [Ca2+]i concentrations in mouse cultured astrocytes using microfluorimetry with the indo-1 fluorescent probe. Propofol 10(-5) and 10(-4) mol litre-1 induced a monophasic transitory Ca2+ peak in a large subpopulation of the cells tested. This response exhibited characteristics close to those of the peak elicited by [L-Pro9] substance P (10(-7) mol litre-1), an activator of phospholipase C in astrocytes. In both cases, it possibly corresponded to mobilization of Ca2+ from endogenous stores. In a few cases, however, administration of propofol induced a moderate, but sustained increase in [Ca2+]i corresponding to the entry of external Ca2+ into the cells. In contrast, ketamine 10(-5) and 10(-4) mol litre-1 failed to affect [Ca2+]i resting concentrations. These findings indicate that clinically relevant concentrations of propofol, but not ketamine, increased [Ca2+]i concentration in astrocytes.

Role of arachidonic acid and glutamate in the formation of inositol phosphates induced by noradrenalin in striatal astrocytes

The noradrenalin-evoked production of [3H]inositol phosphates in mouse striatal astrocytes in primary culture appeared to be the result of the combined stimulation of alpha 1- and alpha 2-adrenergic receptors. Indeed, the noradrenalin (100 microM) response was only partially reproduced by a maximally effective concentration of methoxamine (100 microM), a selective agonist of alpha 1-adrenergic receptors. In addition, the noradrenalin (100 microM)-induced production of [3H]inositol phosphates, which was completely suppressed by the alpha 1-adrenergic antagonist prazosin (1 microM), was also partially inhibited by yohimbine, a selective antagonist of alpha 2-adrenoceptors (maximum inhibition = -57 +/- 11%, measured in the presence of 10 microM yohimbine; six experiments). Finally, UK14.304, a selective alpha 2-adrenergic agonist that was ineffective alone, enhanced the methoxamine-evoked production of [3H] inositol phosphates (EC50 = 86 +/- 21 nM; three experiments). These results suggest that the stimulation of alpha 1-adrenergic receptors is required for the alpha 2-adrenergic receptor-mediated enhancement of phospholipase C activity. The increased production of [3H]inositol phosphates resulting from the stimulation of alpha 2-adrenergic receptors involved pertussis toxin-sensitive G proteins (Gi/o) and depended on extracellular calcium. As shown using the fluorescent dye indo-1, noradrenalin (100 microM) induced a long-lasting increase in cytosolic calcium in striatal astrocytes. Moreover, noradrenalin (100 microM) stimulated [3H]arachidonic acid release from these cells. These two latter responses may result from synergistic effects due to the combined stimulation of alpha 1- and alpha 2-adrenergic receptors, because they were inhibited by either prazosin (1 microM) or yohimbine (10 microM). Finally, the noradrenalin-evoked production of [3H]inositol phosphates seems to result partly from an inhibition by arachidonic acid of glutamate uptake into astrocytes, leading to the stimulation of glutamate metabotropic receptors coupled to phospholipase C. Indeed, the alpha 2-adrenergic component of the noradrenalin response was suppressed by either enzymatic removal of external glutamate or addition of 2-amino-3-phosphonopropionic acid (1 mM), an antagonist of glutamate metabotropic receptors that blocked the glutamate-evoked production of [3H]inositol phosphates in striatal astrocytes, and was reproduced by the direct application of either glutamate or an inhibitor of glutamate uptake, beta-methyl-DL-aspartic acid.

Effects of general anesthetics on intercellular communications mediated by gap junctions between astrocytes in primary culture

BACKGROUND

Astrocytes represent a major nonneuronal cell population in the central nervous system (CNS) and are actively involved in several brain functions. These cells are coupled by gap junctions (GJ) into a syncytial-like network resulting in cellular communication through ionic and metabolic exchange between adjacent astrocytes. Whether anesthetics affect astrocyte function is not known. In the present study, the effects of general anesthetics on GJ permeability were investigated in primary cultures of mouse striatal astrocytes.

METHODS

Junctional permeability was determined by using the fluorescent probe Lucifer yellow and the scrape loading/dye transfer technique. Confluent cells were preincubated 5 min with various concentrations of anesthetic agents and GJ permeability was estimated by measuring the area occupied by the dye from digitalized images taken 8 min after cell loading.

RESULTS

Of the intravenous anesthetics tested, only propofol (P: 10(-4) M, P < 0.01 and 10(-5) M, P < 0.05) and etomidate (ET: 10(-4) M, P < 0.05, but not 10(-5) M) induced a significant reduction of GJ permeability. In contrast, diazepam (10(-5) M), morphine (10(-4) M), ketamine (10(-4) M), thiopental (10(-4) M), and clonidine (10(-7) M) did not affect junctional permeability. In addition, the halogenated anesthetics halothane, enflurane, and isoflurane induced a dose-dependent closure of GJ. For halothane, enflurane, and isoflurane, the maximum effect was achieved with a 10(-4) M, 1.6 x 10(-3) M, and 10(-3) M anesthetic concentration, respectively. Removal of volatile anesthetics resulted in the restoration of the control fluorescence area between 15 and 45 min. The time course of recovery of GJ permeability was examined more precisely for shorter periods of halothane administration (5 min, 1 mM). Under these conditions, the rate of dye spread returned to control values following anesthetic washout, while, during the same period of time, complete uncoupling of GJ was still observed in the presence of a 1 mM halothane concentration.

CONCLUSIONS

These results indicate that general anesthetics differentially affect GJ permeability in cultured astrocytes. This uncoupling effect (closure of gap junctions) may contribute to the mechanisms of action of some anesthetic agents (primarily volatile anesthetics) at the level of the CNS by altering astrocyte communication.

Characterization of PEA-15, a major substrate for protein kinase C in astrocytes

Astrocytes in the central nervous system are involved in a variety of functions including storage of glycogen, maintenance of the extracellular ionic equilibrium, and support for the migration and the differentiation of neurons. Astrocytes express membrane receptors allowing them to respond to extracellular signals. Activation of receptors induces a cascade of events, such as stimulation of protein kinases and subsequent phosphorylation of target proteins. To understand the regulatory processes underlying neuroglial interactions, attempts were made to identify major phosphorylated proteins in striatal astrocytes, grown in primary culture and labeled with [32P]phosphate. Two-dimensional gel electrophoresis revealed a major doublet, Pa and Pb, of highly labeled spots, with a low molecular weight (M(r) = 15,000) and acidic pI (pI = 5.2 and 5.3, respectively). Using an enriched, heat-stable, cytosolic fraction, Pa and Pb were eluted from semi-preparative two-dimensional gels and subjected to a limited proteolysis and partial microsequencing. The same sequences were obtained within Pa and Pb and had no homology with other known protein. Antibodies raised against corresponding synthetic peptides confirm that the doublet represents two isoelectric variants of the same protein, which also exists under a nonphosphorylated form, N. We propose to name this protein PEA-15, for Phosphoprotein Enriched in Astrocytes-15 kDa, according to its large enrichment in these cells. Treatment of intact astrocytes with 12-O-tetradecanoylphorbol-13-acetate (TPA), which stimulates protein kinase C (PKC), increased the phosphorylation of the more acidic spot (Pb) while decreasing Pa intensity. Stimulations of astrocytes known to increase PKC activity, i.e. noradrenaline, or its inhibition by decreasing extracellular calcium concentrations, staurosporine, or desensitization following long term treatment with TPA, induced a phosphorylation or a dephosphorylation of PEA-15, respectively. Using purified PKC, PEA-15 appeared to be a good substrate in vitro. Two-dimensional peptide mapping revealed that the phosphorylation site in intact cells was identical with the site phosphorylated by PKC in vitro. Mapping the phosphopeptides by HPLC following endolysine C treatment lead to the identification of a sequence, phosphorylated in intact astrocytes and in vitro by PKC, containing a consensus site for PKC: LTRIPSAKK. Antibodies raised against a synthetic peptide derived from this sequence recognized N and Pa in control conditions and Pb after its dephosphorylation. Thus, PEA-15 is an endogenous substrate for PKC, the kinase mediating the transition from Pa to Pb.