u-0126 and Ischemic-Stroke

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

In acute ischemic stroke, the only FDA-approved drug; recombinant tissue plasminogen activator (rt-PA) is limited by restricted time-window due to an enhanced risk of hemorrhagic transformation which is thought to be caused by metalloproteinase (MMP). In experimental stroke inhibitors of the mitogen-activated protein kinase kinase extracellular signal-regulated kinase kinase (MEK) 1/2 pathways reduce the MMPs. This study evaluated whether a MEK1/2 inhibitor in combination with rt-PA can prevent the detrimental effects of delayed rt-PA therapy in stroke. Thromboembolic stroke was induced in C57 black/6J mice and the MEK1/2 inhibitor U0126 was administrated 3.5 h and rt-PA 4 h post stroke-onset. Treatment with rt-PA demonstrated enhanced MMP-9 protein levels and hemorrhagic transformation which was prevented when U0126 was given in conjunction with rt-PA. By blocking the MMP-9 with U0126 the safety of rt-PA administration was improved and demonstrates a promising adjuvant strategy to reduce the harmful effects of delayed rt-PA treatment in acute ischemic stroke.

Topics: Animals; Butadienes; Disease Models, Animal; Drug Discovery; Drug Therapy, Combination; Drug-Related Side Effects and Adverse Reactions; Hemorrhage; Humans; Ischemic Stroke; Male; Matrix Metalloproteinase 9; Mice; Mitogen-Activated Protein Kinase Kinases; Nitriles; Signal Transduction; Tissue Plasminogen Activator; Treatment Outcome