| 1. |
- Gisselsson, Lennart, et al.
(författare)
-
Rho kinase inhibition protects CA1 cells in organotypic hippocampal slices during in vitro ischemia.
- 2010
-
Ingår i: Brain Research. - : Elsevier BV. - 1872-6240 .- 0006-8993. ; 1316, s. 92-100
-
Tidskriftsartikel (refereegranskat)abstract
- The actin cytoskeleton is a dynamic superstructure that regulates multiple cellular functions and that has been implicated in cell death regulation. We investigated whether modulating the neuronal actin cytoskeleton polymerization by Rho GTPase kinase (ROCK) inhibition influences cell death in hippocampal neuronal cultures and in murine organotypic hippocampal slice cultures subjected to in vitro ischemia (IVI). During IVI, spines on vehicle treated hippocampal neurons collapsed and large dendritic actin aggregates were formed. Following ROCK inhibition by Y27632, the actin aggregates were markedly smaller while large filopodia extended from the dendritic trunk. Y27632 also provided strong neuroprotection of hippocampal pyramidal CA1 neurons, which was of similar magnitude as protection by NMDA receptor blockade. Likewise, treatment with the F-actin depolymerizing agent latrunculin during IVI diminished actin aggregation and mitigated cell death following IVI. We propose that ROCK inhibition protects neurons against ischemic damage by disrupting actin polymerization thereby mitigating NMDA receptor induced toxicity and releasing ATP bound to actin for cellular energy use. We conclude that ROCK inhibitors abrogate multiple detrimental processes and could therefore be useful in stroke therapy.
|
|
| 2. |
- Kucharz, K., et al.
(författare)
-
Fission and Fusion of the Neuronal Endoplasmic Reticulum
- 2013
-
Ingår i: Translational Stroke Research. - : Springer Science and Business Media LLC. - 1868-4483 .- 1868-601X. ; 4:6, s. 652-662
-
Tidskriftsartikel (refereegranskat)abstract
- The endoplasmic reticulum (ER) is central for protein synthesis and is the largest intracellular Ca2+ store in neurons. The neuronal ER is classically described to have a continuous lumen spanning all cellular compartments. This allows neuronal ER to integrate spatially separate events in the cell. Recent in vitro as well as in vivo findings, however, demonstrate that the neuronal ER is a structurally dynamic entity, capable of rapid fragmentation, i.e., ER fission. The ER fragments can fuse back together and reinstate ER continuity. This reversible phenomenon can be induced repeatedly within the same cell, is temperature-dependent, and compatible with cell survival. The key trigger for dendritic ER fission is N-methyl D-aspartate (NMDA) receptor stimulation in the presence of extracellular Ca2+. However, the exact molecular machinery responsible for the fission and fusion of neuronal ER remains unknown. Reversible ER fission represents a new cell biological event downstream of NMDA receptor-gated Ca2+ influx and may thus influence many aspects of neuronal function in physiology and disease. Hence, it constitutes a new field for exploration in neuroscience that will benefit greatly from recent advances in light microscopy imaging techniques allowing dynamic characterization of cellular events in vitro and in vivo.
|
|
| 3. |
- Kucharz, Krzysztof, et al.
(författare)
-
Potassium-induced structural changes of the endoplasmic reticulum in pyramidal neurons in murine organotypic hippocampal slices.
- 2011
-
Ingår i: Journal of Neuroscience Research. - : Wiley. - 1097-4547 .- 0360-4012. ; 89:8, s. 1150-1159
-
Tidskriftsartikel (refereegranskat)abstract
- The endoplasmic reticulum (ER) structure is of central importance for the regulation of cellular anabolism, stress response, and signal transduction. Generally continuous, the ER can temporarily undergo dramatic structural rearrangements resulting in a fragmented appearance. In this study we assess the dynamic nature of ER fission in pyramidal neurons in organotypic hippocampal slice cultures stimulated by depolarizing concentration of potassium (50 mM). The slices were obtained from transgenic mice expressing fluorescent ER-targeted DsRed2 protein. We employed live tissue confocal microscopy imaging with fluorescence recovery after photobleaching (FRAP) to monitor the extent of structural rearrangements of the ER. In control slices, the ER structure was continuous. Potassium stimulation resulted in extensive fragmentation (fission), whereas return to basal potassium levels (2.5 mM) led to ER fusion and normalization of ER structure. This ER fission/fusion could be repeated several times in the same neuron, demonstrating the reversibility of the process. Blockade of the N-methyl-D-aspartate receptor (NMDAR) with the antagonist D-AP5 or removal of extracellular Ca(2+) prevented depolarization-induced ER fission. ER fission is sensitive to temperature, and decreasing temperature from 35°C to 30°C augments fission, implying that the altering of ER continuity may be a protective response against damage. We conclude that events that generate membrane depolarisation in brain tissue lead to the release of endogenous glutamate that may regulate neuronal ER continuity. The rapid and reversible NMDAR-mediated changes in ER structure reflect an adaptive, innate property of the ER for synaptic activation as well as response to tissue stress, injury, and disease. © 2011 Wiley-Liss, Inc.
|
|
| 4. |
- Kucharz, Krzysztof, et al.
(författare)
-
Rapid fragmentation of the endoplasmic reticulum in cortical neurons of the mouse brain in situ following cardiac arrest.
- 2011
-
Ingår i: Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 1559-7016. ; 31, s. 1663-1667
-
Tidskriftsartikel (refereegranskat)abstract
- Neuronal endoplasmic reticulum (ER), continuous from soma to dendritic spines, undergoes rapid fragmentation in response to N-methyl-D-aspartate (NMDA) receptor stimulation in hippocampal slices and neuronal primary cultures. Here, we show that ER fragments in the mouse brain following cardiac arrest (CA) induced brain ischemia. The ER structure was assessed in vivo in cortical pyramidal neurons in transgenic mice expressing ER-targeted GFP using two-photon laser scanning microscopy with fluorescence recovery after photobleaching (FRAP). Endoplasmic reticulum fragmentation occurred 1 to 2 minutes after CA and once induced, fragmentation was rapid (<15 seconds). We propose that acute ER fragmentation may be a protective response against severe ischemic stress.Journal of Cerebral Blood Flow & Metabolism advance online publication, 6 April 2011; doi:10.1038/jcbfm.2011.37.
|
|
| 5. |
- Ng, Ai Na, et al.
(författare)
-
Dendritic EGFP-STIM1 activation after type I metabotropic glutamate and muscarinic acetylcholine receptor stimulation in hippocampal neuron.
- 2011
-
Ingår i: Journal of Neuroscience Research. - : Wiley. - 1097-4547 .- 0360-4012. ; 89:8, s. 1235-1244
-
Tidskriftsartikel (refereegranskat)abstract
- Several signaling pathways in neurons engage the endoplasmic reticulum (ER) calcium store by triggering calcium release. After release, ER calcium levels must be restored. In many non-neuronal cell types, this is mediated by store-operated calcium entry (SOCE), a cellular homeostatic mechanism that activates specialized store-operated calcium channels (SOC). Although much evidence supports the existence of SOCE in neurons, its importance has been difficult to determine because of the abundance of calcium channels expressed and the lack of SOC-specific pharmacological agents. We have explored the function of the SOCE-inducing protein STIM1 in neurons. In EGFP-STIM1-expressing hippocampal neurons, the sarco- and endoplasmic reticulum calcium ATPase (SERCA) inhibitor thapsigargin caused rapid aggregation (i.e., activation) of STIM1 in soma and dendrites. Upon STIM1 activation by thapsigargin, a dramatic reduction in STIM1 mobility was detected by fluorescence recovery after photobleaching (FRAP). By triggering release of ER calcium with 3,5-dihydroxyphenylglycine (DHPG) or carbachol (Cch), agonists of type I metabotropic glutamate receptors (mGluR) and muscarinic acetylcholine receptors (mAChR), respectively, STIM1 was activated, and calcium entry (likely to represent SOCE) occurred in dendrites. It is therefore possible that neuronal SOCE is activated by physiological stimuli, some of which may alter the postsynaptic calcium signaling properties. © 2011 Wiley-Liss, Inc.
|
|
| 6. |
- Ng, Ai Na, et al.
(författare)
-
Endoplasmic reticulum dynamics in hippocampal dendritic spines induced by agonists of type I metabotropic glutamate but not by muscarinic acetylcholine receptors.
- 2011
-
Ingår i: Synapse. - : Wiley. - 1098-2396 .- 0887-4476. ; 65:4, s. 351-355
-
Tidskriftsartikel (refereegranskat)abstract
- Neurons in the hippocampus exhibit subpopulations of dendritic spines that contain endoplasmic reticulum (ER). ER in spines is important for synaptic activity and its associated Ca(2+) signaling. The dynamic distribution of ER to spines is regulated by diacylglycerol and partly mediated by protein kinase C, metalloproteinases and γ-secretase. In this study, we explored whether pharmacological activation of type I metabotropic glutamate receptors (mGluRs) and muscarinic acetylcholine receptors (mAChRs) known to activate phospholipase C would have any effect on spine ER content. We found that DHPG (100 μM) but not carbachol (10 μM) caused a reduction in the number of spines with ER. We further found that ER Ca(2+) depletion triggered by thapsigargin (200 nM) had no effect on ER localization in spines.
|
|
| 7. |
- Ruscher, Karsten, et al.
(författare)
-
The sigma-1 receptor enhances brain plasticity and functional recovery after experimental stroke.
- 2011
-
Ingår i: Brain. - : Oxford University Press (OUP). - 1460-2156 .- 0006-8950. ; 134:3, s. 732-746
-
Tidskriftsartikel (refereegranskat)abstract
- Stroke leads to brain damage with subsequent slow and incomplete recovery of lost brain functions. Enriched housing of stroke-injured rats provides multi-modal sensorimotor stimulation, which improves recovery, although the specific mechanisms involved have not been identified. In rats housed in an enriched environment for two weeks after permanent middle cerebral artery occlusion, we found increased sigma-1 receptor expression in peri-infarct areas. Treatment of rats subjected to permanent or transient middle cerebral artery occlusion with 1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine dihydrochloride, an agonist of the sigma-1 receptor, starting two days after injury, enhanced the recovery of lost sensorimotor function without decreasing infarct size. The sigma-1 receptor was found in the galactocerebroside enriched membrane microdomains of reactive astrocytes and in neurons. Sigma-1 receptor activation increased the levels of the synaptic protein neurabin and neurexin in membrane rafts in the peri-infarct area, while sigma-1 receptor silencing prevented sigma-1 receptor-mediated neurite outgrowth in primary cortical neuronal cultures. In astrocytic cultures, oxygen and glucose deprivation induced sigma-1 receptor expression and actin dependent membrane raft formation, the latter blocked by sigma-1 receptor small interfering RNA silencing and pharmacological inhibition. We conclude that sigma-1 receptor activation stimulates recovery after stroke by enhancing cellular transport of biomolecules required for brain repair, thereby stimulating brain plasticity. Pharmacological targeting of the sigma-1 receptor provides new opportunities for stroke treatment beyond the therapeutic window of neuroprotection.
|
|
