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Shi Y, Peng XH, Li X, Luo GP, Wu MF. Neuroprotective role of dexmedetomidine pretreatment in cerebral ischemia injury via ADRA2A-mediated phosphorylation of ERK1/2 in adult rats. Exp Ther Med 2018; 16:5201-5209. [PMID: 30546415 PMCID: PMC6256861 DOI: 10.3892/etm.2018.6878] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 09/27/2018] [Indexed: 12/29/2022] Open
Abstract
Neuroprotective effects of dexmedetomidine (Dex) have been reported in various models of brain injury. However, to our knowledge, the neuroprotective mechanism of Dex pretreatment in rats remains unknown. The aim of the present study was to detect the expression of the α2A adrenergic receptor (ADRA2A) in focal ischemic brain tissues and to investigate the protective role and corresponding mechanism of Dex pretreatment in cerebral ischemia in rats. A hypoxia/reoxygenation (H/R) cell model in primary cultured astrocytes and a focal cerebral ischemia/reperfusion (I/R) model in adult rats were used. The expression of ADRA2A and extracellular signal-regulated kinases 1 and 2 (ERK1/2) in the primary cultured astrocytes and rat brain ischemic tissues was detected in the different conditions prior to and following Dex pretreatment using western blotting. The H/R model of primary cultured astrocytes and the focal cerebral I/R model in adult rats were successfully constructed. Under the normal oxygen conditions, 500 ng/ml Dex pretreatment increased the expression of ADRA2A and phosphorylated (p)-ERK1/2 in the astrocytes compared with in the control group. Hypoxic culture for 6 h and then reoxygenation for 24 h decreased the levels of p-ERK1/2 in the astrocytes compared with those in control group. This decrease was prevented by Dex pretreatment for 3 h. The hypoxic culture and then reoxygenation increased the expression of ADRA2A. Similarly, compared with those prior to Dex treatment, the levels of ADRA2A and p-ERK1/2 in the brain ischemic tissues following Dex treatment were increased. The levels of ADRA2A and p-ERK1/2 were 0.72±0.23 and 0.66±0.25 following Dex treatment, compared with 0.76±0.22 and 0.31±0.18, respectively, prior to Dex treatment. The effect of Dex pretreatment increasing p-ERK1/2 expression was attenuated by AG1478 pretreatment. In summary, Dex appeared to promote phosphorylation of ERK1/2 in astrocytes under H/R. As a specific agonist of ADRA2A, Dex may activate phosphorylation of ERK1/2 via ADRA2A in astrocytes. Thus, the neuroprotective role of Dex pretreatment against cerebral ischemic injury may function via ADRA2A-mediated phosphorylation of ERK1/2.
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Affiliation(s)
- Yanyan Shi
- Department of Anesthesia, Wuhan Fourth Hospital, Puai Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430033, P.R. China
| | - Xiao-Hong Peng
- Department of Anesthesia, Wuhan Fourth Hospital, Puai Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430033, P.R. China
| | - Xia Li
- Department of Anesthesia, Wuhan Fourth Hospital, Puai Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430033, P.R. China
| | - Gao-Ping Luo
- Department of Anesthesia, Wuhan Fourth Hospital, Puai Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430033, P.R. China
| | - Ming-Fu Wu
- Cancer Biology Research Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China
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Fühlhuber V, Bick S, Tschernatsch M, Dharmalingam B, Kaps M, Preissner KT, Blaes F. Autoantibody-mediated cytotoxicity in paediatric opsoclonus–myoclonus syndrome is dependent on ERK-1/2 phophorylation. J Neuroimmunol 2015; 289:182-6. [DOI: 10.1016/j.jneuroim.2015.10.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 10/28/2015] [Accepted: 10/29/2015] [Indexed: 10/22/2022]
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Zhou J, Du T, Li B, Rong Y, Verkhratsky A, Peng L. Crosstalk Between MAPK/ERK and PI3K/AKT Signal Pathways During Brain Ischemia/Reperfusion. ASN Neuro 2015; 7:7/5/1759091415602463. [PMID: 26442853 PMCID: PMC4601130 DOI: 10.1177/1759091415602463] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The epidermal growth factor receptor (EGFR) is linked to the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and Raf/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK1/2) signaling pathways. During brain ischemia/reperfusion, EGFR could be transactivated, which stimulates these intracellular signaling cascades that either protect cells or potentiate cell injury. In the present study, we investigated the activation of EGFR, PI3K/AKT, and Raf/MAPK/ERK1/2 during ischemia or reperfusion of the brain using the middle cerebral artery occlusion model. We found that EGFR was phosphorylated and transactivated during both ischemia and reperfusion periods. During ischemia, the activity of PI3K/AKT pathway was significantly increased, as judged from the strong phosphorylation of AKT; this activation was suppressed by the inhibitors of EGFR and Zn-dependent metalloproteinase. Ischemia, however, did not induce ERK1/2 phosphorylation, which was dependent on reperfusion. Coimmunoprecipitation of Son of sevenless 1 (SOS1) with EGFR showed increased association between the receptor and SOS1 in ischemia, indicating the inhibitory node downstream of SOS1. The inhibitory phosphorylation site of Raf-1 at Ser259, but not its stimulatory phosphorylation site at Ser338, was phosphorylated during ischemia. Furthermore, ischemia prompted the interaction between Raf-1 and AKT, while both the inhibitors of PI3K and AKT not only abolished AKT phosphorylation but also restored ERK1/2 phosphorylation. All these findings suggest that Raf/MAPK/ERK1/2 signal pathway is inhibited by AKT via direct phosphorylation and inhibition at Raf-1 node during ischemia. During reperfusion, we observed a significant increase of ERK1/2 phosphorylation but no change in AKT phosphorylation. Inhibitors of reactive oxygen species and phosphatase and tensin homolog restored AKT phosphorylation but abolished ERK1/2 phosphorylation, suggesting that the reactive oxygen species-dependent increase in phosphatase and tensin homolog activity in reperfusion period relieves ERK1/2 from inhibition of AKT.
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Affiliation(s)
- Jing Zhou
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Ting Du
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Baoman Li
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Yan Rong
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
| | - Alexei Verkhratsky
- Faculty of Life Science, The University of Manchester, UK Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain University of Nizhny Novgorod, Russia
| | - Liang Peng
- Laboratory of Metabolic Brain Diseases, Institute of Metabolic Disease Research and Drug Development, China Medical University, Shenyang, P. R. China
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Maurya SK, Rai A, Rai NK, Deshpande S, Jain R, Mudiam MKR, Prabhakar YS, Bandyopadhyay S. Cypermethrin Induces Astrocyte Apoptosis by the Disruption of the Autocrine/Paracrine Mode of Epidermal Growth Factor Receptor Signaling. Toxicol Sci 2011; 125:473-87. [DOI: 10.1093/toxsci/kfr303] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Du T, Li B, Li H, Li M, Hertz L, Peng L. Signaling pathways of isoproterenol-induced ERK1/2 phosphorylation in primary cultures of astrocytes are concentration-dependent. J Neurochem 2010; 115:1007-23. [PMID: 20831657 DOI: 10.1111/j.1471-4159.2010.06995.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Stimulation of β-adrenoceptors activates the canonical adenylate cyclase pathway (via G(s) protein) but can also evoke phosphorylation of extracellular-regulated kinases 1 and 2 (ERK(1/2) ) via G(s)/G(i) switching or β-arrestin-mediated recruitment of Src. In primary cultures of mouse astrocytes, activation of the former of these pathways required micromolar concentrations of the β(1)/β(2) -adrenergic agonist isoproterenol, that acted on β(1)-adrenoceptors, whereas the latter was activated already by nanomolar concentrations, acting on β(2) receptors. Protein kinase A activity was required for G(s)/G(i) switching, which was followed by Ca(2+) release from intracellular stores and G(iα)- and metalloproteinase-dependent transactivation of the epidermal growth factor receptor (EGFR; at its Y1173 phophorylation site), via its receptor-tyrosine kinase, β-arrestin 1/2 recruitment, and MAPK/ERK kinase-dependent ERK(1/2) phosphorylation. ERK(1/2) phosphorylation by Src activation depended on β-arrestin 2, but not β-arrestin 1, was accompanied by Src/EGFR co-precipitation and phosphorylation of the EGFR at the Src-phosphorylated Y845 site and the Y1045 autophosphorylation site; it was independent of transactivation but dependent on MAPK/ERK kinase activity, suggesting EGFR phosphorylation independently of the receptor-tyrosine kinase or activation of Ras or Raf directly from Src. Most astrocytic consequences of activating either pathway (or both) are unknown, but morphological differentiation and increase in glial fibrillary acidic protein in response to dibutyryl cAMP-mediated increase in cAMP depend on G(s)/G(i) switching and transactivation.
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Affiliation(s)
- Ting Du
- Department of Clinical Pharmacology, China Medical University, Shenyang, China
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Role of calcineurin signaling in membrane potential-regulated maturation of cerebellar granule cells. J Neurosci 2009; 29:2938-47. [PMID: 19261889 DOI: 10.1523/jneurosci.5932-08.2009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
At the early postnatal period, cerebellar granule cells proliferate, differentiate, migrate, and finally form refined synaptic connections with mossy fibers. During this period, the resting membrane potential of immature granule cells is relatively depolarized, but it becomes hyperpolarized in mature cells. This investigation was conducted to examine the role of this alteration in membrane potential and its downstream signaling mechanism in development and maturation of granule cells. Experiments were designed to precisely characterize the ontogenic processes of developing granule cells by combining organotypic cerebellar cultures with the specific expression of EGFP (enhanced green fluorescent protein) in granule cells by use of DNA transfection. Multiple approaches using morphology, electrophysiology, and immunohistochemistry demonstrated that granule cells developed and matured at the physiological KCl concentration in organotypic cultures in a temporally regulated manner. We addressed how persistent membrane depolarization influences the developmental and maturation processes of granule cells by depolarizing organotypic cultures with high KCl. Depolarization preserved the developmental processes of granule cells up to the stage of formation of immature dendrites but prevented the maturation processes for synaptic formation by granule cells. Importantly, this blockade of the terminal maturation of granule cells was reversed by inactivation of calcineurin with its specific inhibitor. This investigation has demonstrated that alteration of the membrane potential and its downstream calcineurin signaling play a pivotal role in triggering the maturation program for the synaptic organization of postnatally developing granule cells.
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Li B, Du T, Li H, Gu L, Zhang H, Huang J, Hertz L, Peng L. Signalling pathways for transactivation by dexmedetomidine of epidermal growth factor receptors in astrocytes and its paracrine effect on neurons. Br J Pharmacol 2008; 154:191-203. [PMID: 18311185 DOI: 10.1038/bjp.2008.58] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Stimulation of astrocytes by the alpha(2)-adrenoceptor agonist dexmedetomidine, a neuroprotective drug, transactivates epidermal growth factor (EGF) receptors. The present study investigates signal pathways leading to release of an EGF receptor ligand and those activated during EGF receptor stimulation, and the response of neurons to dexmedetomidine and to astrocyte-conditioned medium. EXPERIMENTAL APPROACH Phosphorylation of ERK(1/2) was determined by western blotting and immunocytochemistry, and phosphorylation of EGF receptors by immunoprecipitation and western blotting. mRNA expression of fos family was measured by RT-PCR. KEY RESULTS Pertussis toxin (0.2 microg ml(-1)) an inhibitor of betagamma subunit dissociation from Galpha(i) protein, and GF 109203X (500 nM), a protein kinase C inhibitor, abolished ERK(1/2) phosphorylation. PP1 (10 microM), inhibiting Src kinase and GM 6001 (10 microM), an inhibitor of Zn-dependent metalloproteinase, abolished ERK(1/2) phosphorylation by dexmedetomidine (50 nM), but not that by EGF (10 ng ml(-1)), showing Src kinase and metalloproteinase activation during the first stage only; AG 1478 (1 microM), an inhibitor of the EGF receptor tyrosine kinase, abolished ERK(1/2) phosphorylation. Dexmedetomidine-induced EGF receptor phosphorylation was prevented by AG 1478, GM 6001, PP1 and GF 109203X and its induction of cfos and fosB by AG 1478 and by U0126 (10 microM), an inhibitor of ERK phosphorylation, indicating downstream effects of ERK(1/2) phosphorylation. EGF and conditioned medium from dexmedetomidine-treated astrocytes, but not dexmedetomidine itself, induced ERK phosphorylation in primary cultures of cerebellar neurons. CONCLUSIONS AND IMPLICATIONS Dexmedetomidine-induced transactivation pathways were delineated. Its paracrine effect on neurons may account for its neuroprotective effects.
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Affiliation(s)
- B Li
- Department of Clinical Pharmacology, China Medical University, Shenyang, PR China
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Peng L, Gu L, Hu X, Zhao L, Hertz L. Complexity of Depolarization-mediated ERK Phosphorylation in Cerebellar Granule Cells in Primary Cultures. Neurochem Res 2007; 33:328-35. [DOI: 10.1007/s11064-007-9510-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Accepted: 09/13/2007] [Indexed: 01/31/2023]
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Joslin EJ, Opresko LK, Wells A, Wiley HS, Lauffenburger DA. EGF-receptor-mediated mammary epithelial cell migration is driven by sustained ERK signaling from autocrine stimulation. J Cell Sci 2007; 120:3688-99. [PMID: 17895366 DOI: 10.1242/jcs.010488] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
EGF family ligands are synthesized as membrane-anchored precursors whose proteolytic release yields mature diffusible factors that can activate cell surface receptors in autocrine or paracrine mode. Expression of these ligands is altered in pathological states and in physiological processes, such as development and tissue regeneration. Despite the widely documented biological importance of autocrine EGF signaling, quantitative relationships between protease-mediated ligand release and consequent cell behavior have not been rigorously investigated. We thus explored the relationship between autocrine EGF release rates and cell behavioral responses along with activation of ERK, a key downstream signal, by expressing chimeric ligand precursors and modulating their proteolytic shedding using a metalloprotease inhibitor in human mammary epithelial cells. We found that ERK activation increased monotonically with increasing ligand release rate despite concomitant downregulation of EGF receptor levels. Cell migration speed was directly related to ligand release rate and proportional to steady-state phospho-ERK levels. Moreover, migration speed was significantly greater for autocrine stimulation compared with exogenous stimulation, even at comparable phospho-ERK levels. By contrast, cell proliferation rates were approximately equivalent at all ligand release rates and were similar regardless of whether the ligand was presented endogenously or exogenously. Thus, in our mammary epithelial cell system, migration and proliferation are differentially sensitive to the mode of EGF ligand presentation.
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