u-0126 and Brain-Edema

Brain edema is a common and serious complication of ischemic stroke with limited effective treatment. We previously reported that methylene blue (MB) attenuated ischemic brain edema in rats, but the underlying mechanisms remained unknown. Aquaporin 4 (AQP4) in astrocytes plays a key role in brain edema. We also found that extracellular signal-regulated kinase 1/2 (ERK1/2) activation was involved in the regulation of AQP4 expression in astrocytes. In the present study, we investigated whether AQP4 and ERK1/2 were involved in the protective effect of MB against cerebral edema. Rats were subjected to transient middle cerebral artery occlusion (tMCAO), MB (3 mg/kg, for 30 min) was infused intravenously through the tail vein started immediately after reperfusion and again at 3 h after ischemia (1.5 mg/kg, for 15 min). Brain edema was determined by MRI at 0.5, 2.5, and 48 h after tMCAO. The decreases of apparent diffusion coefficient (ADC) values on diffusion-weighted MRI indicated cytotoxic brain edema, whereas the increase of T2 MRI values reflected vasogenic brain edema. We found that MB infusion significantly ameliorated cytotoxic brain edema at 2.5 and 48 h after tMCAO and decreased vasogenic brain edema at 48 h after tMCAO. In addition, MB infusion blocked the AQP4 increases and ERK1/2 activation in the cerebral cortex in ischemic penumbra at 48 h after tMCAO. In a cell swelling model established in cultured rat astrocyte exposed to glutamate (1 mM), we consistently found that MB (10 μM) attenuated cell swelling, AQP4 increases and ERK1/2 activation. Moreover, the ERK1/2 inhibitor U0126 (10 μM) had the similar effects as MB. These results demonstrate that MB improves brain edema and astrocyte swelling, which may be mediated by the inhibition of AQP4 expression via ERK1/2 pathway, suggesting that MB may be a potential choice for the treatment of brain edema.

Topics: Animals; Animals, Newborn; Aquaporin 4; Astrocytes; Brain; Brain Edema; Butadienes; Infarction, Middle Cerebral Artery; Ischemic Stroke; Male; MAP Kinase Signaling System; Methylene Blue; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nitriles; Protein Kinase Inhibitors; Rats, Sprague-Dawley

Moderate hypothermia (MH) used as treatment for neurological diseases has a protective effect; however, its mechanism remains unclear. Neuronal autophagy is a fundamental pathological process of early brain injury in subarachnoid hemorrhage (SAH). We found that moderate activation of autophagy can reduce nerve cells damage. In this study, We found that MH can moderately increase the level of autophagy in nerve cells and improve the neurological function in rats. This type of autophagy activation is dependent on extracellular signal-regulated kinase (ERK) signaling pathways. The level of neuronal autophagy was down-regulated significantly by using U0126, an ERK signaling pathway inhibitor. In summary, these results suggest that MH can moderately activate neuronal autophagy through ERK signaling pathway, reduce nerve cell death, and produce neuroprotective effects.

Topics: Animals; Autophagy; Brain Edema; Brain Injuries; Butadienes; CA1 Region, Hippocampal; Disease Models, Animal; Hypothermia, Induced; Male; MAP Kinase Signaling System; Neurons; Neuroprotection; Nitriles; Rats; Rats, Sprague-Dawley; Subarachnoid Hemorrhage

Less disruption of the blood-brain barrier (BBB) after severe ischemic stroke is one of the beneficial outcomes of ischemic preconditioning (IP). However, the effect of IP on tight junctions (TJs), which regulate paracellular permeability of the BBB, is not well understood. In the present study, we examined IP-induced changes in TJs before and after middle cerebral artery occlusion (MCAO) in mice, and the association between changes in TJs and tolerance to a subsequent insult. After IP, we found decreased levels of transmembrane TJ proteins occludin and claudin-5, and widened gaps of TJs with perivascular swelling at the ultrastructural level in the brain. An inflammatory response was also observed. These changes were reversed by inhibition of extracellular signal-regulated kinase1/2 (ERK1/2) via the specific ERK1/2 inhibitor U0126. After MCAO, reduced brain edema and inflammatory responses were associated with altered levels of angiogenic factors and cytokines in preconditioned brains. Pretreatment with U0126 reversed the neuroprotective effects of IP against MCAO. These findings suggest that ERK1/2 activation has a pivotal role in IP-induced changes in TJs and inflammatory response, which serve to protect against BBB breakdown and inflammation after ischemic stroke.

Topics: Animals; Brain Edema; Brain Infarction; Butadienes; Disease Models, Animal; Enzyme Inhibitors; Gene Expression Regulation; Infarction, Middle Cerebral Artery; Ischemic Preconditioning, Myocardial; Male; Mice; Mice, Inbred C57BL; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Muscle Strength; Neurologic Examination; Nitriles; Tight Junctions; Time Factors; Vascular Endothelial Growth Factor A

Microglia accumulation plays detrimental roles in the pathology of germinal matrix hemorrhage (GMH) in the immature preterm brain. However, the underlying mechanisms remain poorly defined. Here, we investigated the effects of a cannabinoid receptor 2 (CB2R) agonist on microglia proliferation and the possible involvement of the mitogen-activated protein kinase (MAPK) family pathway in a collagenase-induced GMH rat model and in thrombin-induced rat microglia cells. We demonstrated that activation of CB2R played a key role in attenuating brain edema, neuronal degeneration, microglial accumulation and the phosphorylated extracellular signal-regulated kinase (p-ERK) protein level 24 h following GMH. In vitro, Western blot analysis and immunostaining indicated that ERK and P38 phosphorylation levels in microglia stimulated by thrombin were decreased after JWH-133 (CB2R selective agonist) treatment in a concentration-dependent manner. Microglia proliferation (EDU + microglia) and inflammatory and oxidative stress responses were attenuated by UO126 (ERK pathway inhibitor) 24 h after thrombin stimulation, an activity that was prevented by AM630 (CB2R selective antagonist). Overall, these findings suggest that activation of the endocannabinoid system might attenuate inflammation-induced secondary brain injury after GMH in rats by reducing microglia accumulation through a mechanism involving ERK dephosphorylation. Enhancing CB2R activation is a potential treatment to slow down the course of GMH in preterm newborns.

Topics: Animals; Brain; Brain Edema; Butadienes; Cannabinoids; Cell Proliferation; Cells, Cultured; Disease Models, Animal; Extracellular Signal-Regulated MAP Kinases; Indoles; Intracranial Hemorrhages; Male; Microglia; Nerve Degeneration; Neuroimmunomodulation; Nitriles; Oxidative Stress; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Protein Kinase Inhibitors; Random Allocation; Receptor, Cannabinoid, CB2; Thrombin

The mechanism by which MCI-186 (3-methyl-1-phenyl-2-prazolin-5-one) exerts protective effects during cerebral infarction, other than its function as a radical scavenger, has not been fully elucidated. Here, we found that MCI-186 stimulates intracellular survival signaling in vivo and in vitro. In a rat infarction model, the infarct area was significantly smaller and the degree of edema was reduced in MCI-186-treated animals. In the MCI-186-treated rats, the number of single stranded (ss) DNA-positive damaged cells in the peri-infarct area was decreased compared with the control, suggesting that MCI-186 protects cerebral tissues from cell damage. To clarify the mechanisms underlying the effect of MCI-186, we also examined the survival-promoting effect of this agent on cultured cortical neurons. In this in vitro system, MCI-186 blocked serum-free induced neuronal cell death. Interestingly, an increase in the activation of both Akt (a component of the PI3 kinase pathway) and ERK (a component of the MAP kinase pathway) was observed in the cortical cultures after MCI-186 exposure. Furthermore, the MCI-186-dependent survival effect in vitro was blocked by U0126, an MEK (an upstream of ERK) inhibitor, and also by LY294002, a PI3 kinase inhibitor. We also observed similar increases in the activation of Akt and ERK in the in vivo model, further suggesting that the antiapoptotic role of MCI-186 is mediated via the PI3 kinase and MAP kinase signaling pathways. We therefore conclude that, in addition to its role as a free radical scavenger, MCI-186 functions as an antiapoptotic factor by enhancing intracellular survival signaling.

Topics: Animals; Animals, Newborn; Antipyrine; Brain Edema; Butadienes; Cell Death; Cells, Cultured; Cerebral Infarction; Chromones; Dose-Response Relationship, Drug; Drug Interactions; Edaravone; Enzyme Inhibitors; Free Radical Scavengers; Male; Morpholines; Nerve Tissue Proteins; Neurons; Nitriles; Oncogene Protein v-akt; Phosphatidylinositol 3-Kinases; Rats; Rats, Wistar; Signal Transduction; Time Factors