endothelin-1 and Status-Epilepticus

Recently, we have reported that LIM kinase 2 (LIMK2) involves programmed necrotic neuronal deaths induced by aberrant cyclin D1 expression following status epilepticus (SE). Up-regulation of LIMK2 expression induces neuronal necrosis by impairment of dynamin-related protein 1 (DRP1)-mediated mitochondrial fission. However, we could not elucidate the upstream effecter for LIMK2-mediated neuronal death. Thus, we investigated the role of endothelin-1 (ET-1) in LIMK2-mediated neuronal necrosis, since ET-1 involves neuronal death via various pathways.. Following SE, ET-1 concentration and its mRNA were significantly increased in the hippocampus with up-regulation of ETB receptor expression. BQ788 (an ETB receptor antagonist) effectively attenuated SE-induced neuronal damage as well as reduction in LIMK2 mRNA/protein expression. In addition, BQ788 alleviated up-regulation of Rho kinase 1 (ROCK1) expression and impairment of DRP1-mediated mitochondrial fission in CA1 neurons following SE. BQ788 also attenuated neuronal death and up-regulation of LIMK2 expression induced by exogenous ET-1 injection.. These findings suggest that ET-1 may be one of the upstream effectors for programmed neuronal necrosis through abnormal LIMK2 over-expression by ROCK1.

Topics: Amides; Animals; Apoptosis; Blood-Brain Barrier; Caveolin 1; Endothelin-1; Hippocampus; Lim Kinases; Male; Mitochondrial Dynamics; Models, Biological; Necrosis; Neurons; Nitric Oxide Synthase Type I; Oligopeptides; Peptides; Piperidines; Pyridines; Rats, Sprague-Dawley; Receptors, Endothelin; rho-Associated Kinases; RNA, Messenger; Status Epilepticus

In models of status epilepticus ghrelin displays neuroprotective effects mediated by the growth hormone secretagogue-receptor 1a (GHS-R1a). This activity may be explained by anticonvulsant properties that, however, are controversial. We further investigated neuroprotection and the effects on seizures by comparing ghrelin with a more effective GHS-R1a agonist, JMV-1843. Rats were treated either with ghrelin, JMV-1843 or saline 10 min before pilocarpine, which was used to induce status epilepticus. Status epilepticus, developed in all rats, was attenuated by diazepam. No differences were observed among the various groups in the characteristics of pilocarpine-induced seizures. In saline group the area of lesion, characterized by lack of glial fibrillary acidic protein immunoreactivity, was of 0.45 ± 0.07 mm(2) in the hippocampal stratum lacunosum-moleculare, and was accompanied by upregulation of laminin immunostaining, and by increased endothelin-1 expression. Both ghrelin (P<0.05) and JMV-1843 (P<0.01) were able to reduce the area of loss in glial fibrillary acidic protein immunostaining. In addition, JMV-1843 counteracted (P<0.05) the changes in laminin and endothelin-1 expression, both increased in ghrelin-treated rats. JMV-1843 was able to ameliorate neuronal survival in the hilus of dentate gyrus and medial entorhinal cortex layer III (P<0.05 vs saline and ghrelin groups). These results demonstrate diverse protective effects of growth hormone secretagogues in rats exposed to status epilepticus.

Topics: Animals; Corpus Striatum; Endothelin-1; Gene Expression Regulation; Ghrelin; Glial Fibrillary Acidic Protein; Indoles; Male; Muscarinic Agonists; Oligopeptides; Pilocarpine; Rats; Rats, Sprague-Dawley; Status Epilepticus; Tryptophan

Status epilepticus (SE) induces vasogenic edema in the piriform cortex with disruptions of the blood-brain barrier (BBB). However, the mechanisms of vasogenic edema formation following SE are still unknown. Here we investigated the endothelin B (ETB) receptor-mediated pathway of SE-induced vasogenic edema. Following SE, the release of tumor necrosis factor-α (TNF-α) stimulated endothelin-1 (ET-1) release and expression in neurons and endothelial cells. In addition, TNF-α-induced ET-1 increased BBB permeability via ETB receptor-mediated endothelial nitric oxide synthase (eNOS) activation in endothelial cells. ETB receptor activation also increased intracellular reactive oxygen species by NADPH oxidase production in astrocytes. These findings suggest that SE results in BBB dysfunctions via endothelial-astroglial interactions through the TNF-α-ET-1-eNOS/NADPH oxidase pathway, and that these ETB receptor-mediated interactions may be an effective therapeutic strategy for vasogenic edema in various neurological diseases.

Topics: Animals; Astrocytes; Blood-Brain Barrier; Brain Edema; Cerebral Cortex; Disease Models, Animal; Endothelial Cells; Endothelin-1; Gene Expression Regulation; Male; Microdialysis; NADPH Oxidases; Neurons; Nitric Oxide Synthase Type III; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Receptor, Endothelin A; Signal Transduction; Status Epilepticus; Stereotaxic Techniques; Tumor Necrosis Factor-alpha

Endothelin-1 (ET-1) is one of potential factors to induce vasogenic edema formation, since exogenous ET-1 treatment decreases aquaporin 4 (AQP4) expression and increases chemokines induction. To identify the role of endogenous ET-1 in vasogenic edema formation, we examined the correlation between endogenous ET-1 expression and vasogenic edema formation in the pirifom cortex following status epilepticus (SE). In the present study, SMI-71 (a brain-blood barrier marker) immunoreactivity was significantly reduced in blood vessels at 1 day after SE when vasogenic edema and neuronal damage were observed. ET-1 expression was up-regulated in endothelial cells prior to reduction in SMI-71 immunoreactivity. Furthermore, ET-1 expressing endothelial cells showed the absence of SMI-71 immunoreactivity. Increase in ET-1 expression was followed by reduced AQP4 immunoreactivity prior to vasogenic edema formation. Only a few microglia showed monocyte chemotactic protein-1 (a chemokine induced by ET-1) outside vasogenic edema lesion. Taken together, our findings suggest that endothelial ET-1 expression may contribute to SE-induced vasogenic edema formation via brain-blood barrier disruption at AQP4/MCP-1 independent manners.

Topics: Animals; Aquaporin 4; Blood-Brain Barrier; Brain Edema; Cerebral Cortex; Chemokine CCL2; Endothelin-1; Endothelium, Vascular; Male; Neurons; Rats; Rats, Sprague-Dawley; Status Epilepticus; Up-Regulation