The results suggest that isoflurane administrated after OGD or brain ischemia provides neuroprotection. Mitochondrial adenosine 5'-triphosphate-sensitive potassium channels may be involved in this protection.

BACKGROUND AND PURPOSE WNK kinases, including WNK3, and the associated downstream SPAK and OSR1 kinases, comprise an important signaling cascade that regulates the cation-chloride cotransporters. Ischemia-induced stimulation of the bumetanide-sensitive Na+-K+-Cl- cotransporter (NKCC1) plays an important role in the pathophysiology of experimental stroke, but the mechanism of its regulation in this context is unknown. Here, we investigated the WNK3-SPAK/OSR1 pathway as a regulator of NKCC1 stimulation and their collective role in ischemic brain damage. METHOD Wild-type WNK3 (WT) and WNK3 knockout (KO) mice were subjected to ischemic stroke via transient middle cerebral artery (MCA) occlusion. Infarct volume, brain edema, blood brain barrier (BBB) damage, white matter demyelination, and neurological deficits were assessed. Total and phosphorylated forms of WNK3 and SPAK/OSR1 were assayed by immunobloting and immunostaining. In vitro ischemia studies in cultured neurons and immature oligodendrocytes were conducted using the oxygen-glucose deprivation/reoxygenation method. RESULTS WNK3 KO mice exhibited significantly decreased infarct volume and axonal demyelination, less cerebral edema, and accelerated neurobehavioral recovery compared to WNK3 WT mice subjected to MCA occlusion. The neuroprotective phenotypes conferred by WNK3 KO were associated with a decrease in stimulatory hyper-phosphorylations of the SPAK/OSR1 catalytic T-loop and of NKCC1 stimulatory sites Thr203/Thr207/Thr212, as well as with decreased cell surface expression of NKCC1. Genetic inhibition of WNK3 or siRNA knockdown of SPAK/OSR1 increased the tolerance of cultured primary neurons and oligodendrocytes to in vitro ischemia. CONCLUSION These data identify a novel role for the WNK3-SPAK/OSR1-NKCC1 signaling pathway in ischemic neuroglial injury, and suggest the WNK3-SPAK/OSR1 kinase pathway as a therapeutic target for neuroprotection following ischemic stroke.

Postoperative cognitive decline is a clinical syndrome. Volatile anesthetics are commonly used during surgery. It is conceivable that volatile anesthetics may contribute to postoperative cognitive decline. Isoflurane can impair cognitive functions of animals under certain conditions. However, the mechanisms for this impairment are not clear. Here, male 18-month old Fisher 344 rats or 10-week old mice were exposed to 1.2 or 1.4% isoflurane for 2 h. Our studies showed that isoflurane impaired the cognitive functions of the rats in Barnes maze. Isoflurane-exposed rats had reduced freezing behavior during the training sessions in the fear conditioning test. This isoflurane effect was attenuated by lidocaine, a local anesthetic with anti-inflammatory property. Rats that had training sessions and were exposed to isoflurane 30 min later had freezing behavior similar to that of control animals. Isoflurane increased the expression of interleukin 1β (IL-1β), interleukin-6 and activated caspase 3 in the hippocampus of the 18-month old rats. IL-1β positive staining was co-localized with that of NeuN, a neuronal marker. The increase of IL-1β and activated caspase 3 but not interleukin-6 was attenuated by lidocaine. Isoflurane also impaired the cognitive functions of 10-week old C57BL/6J mice and increased IL-1β in their hippocampi. However, isoflurane did not affect the cognitive functions of IL-1β deficient mice. Our results suggest that isoflurane impairs the learning but may not affect the recall of the aged rats. IL-1β may play an important role in this isoflurane effect.