Protective effects of TREK-1 against oxidative injury induced by SNP and H2O2.

AIM: TREK-1 (TWIK-related K+ channel-1) is a 2-pore-domain K+ channel subtype. The present study investigated the role of TREK-1 in cell death induced by oxidative stress. METHODS: The cell viability of wild-type Chinese hamster ovary (CHO) and TREK-1-transfected CHO cells (TREK-1/CHO cells) was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in the presence of sodium nitroprusside (SNP) or hydrogen peroxide (H2O2). Apoptosis of wild-type CHO and TREK-1/CHO cells was detected using Hoechst33342 staining. RESULTS: Both SNP and H2O2 caused dose- and time-dependent growth inhibition of wild-type CHO and TREK-1/ CHO cells. Following a 12 h exposure to SNP, the 50% inhibition (IC(50)) values for wild-type CHO and TREK-1/CHO cells were calculated as 0.69 mmol/L and 1.14 mmol/L, respectively. The IC(50) values were 0.07 mmol/L and 0.09 mmol/L in H2O2-treated wild-type CHO and TREK-1/CHO cells, respectively, following 12 h exposure to H2O2. Moreover, SNP/H2O2 induced less apoptosis in TREK-1/ CHO cells than that in wild-type CHO cells (P<0.05). CONCLUSION: The results demonstrated that TREK-1 played a protective role against oxidative injury.

Selective alteration of expression of Na+/Ca2+ exchanger isoforms after transient focal cerebral ischemia in rats.

The Na+/Ca2+ exchanger (NCX) is an antiporter located in the plasma membrane of many cells, which can maintain the intracellular Ca(2+) homeostasis. Some studies have shown the close relationship of NCX and cerebral ischemia. But controversial results were obtained. Three NCX isoforms, NCX1, NCX2, and NCX3 were distributed selectively in central nervous system, which suggests that each isoform may have different function in cerebral ischemia. In this study we investigated the time-related alteration of gene and protein expressions of NCX1, NCX2, and NCX3 in rat brain cortex after 2 h of transient middle cerebral artery occlusion (tMCAO). Reverse transcription-polymerase chain reaction (RT-PCR) was used to investigate the mRNA levels of each NCX isoform at 2, 6, 12, and 24 h of reperfusion, respectively. Western blot was used to measure the protein expressions of each NCX isoform at 2, 12, and 24 h of reperfusion, respectively. The results showed that NCX1 mRNA level was reduced by 42.1% and 27.8%, respectively, at 2 and 6h of reperfusion and restored to normal level at 12 and 24 h of reperfusion. NCX1 protein was decreased by 36.6% at 2 h of reperfusion and recovered at 12 and 24 h of reperfusion. The mRNA and protein levels of NCX2 and NCX3 did not change significantly over time. These results suggest that NCX1 might play an important role in transient focal cerebral ischemia.

Enhanced expressions of arachidonic acid-sensitive tandem-pore domain potassium channels in rat experimental acute cerebral ischemia.

To further explore the pathophysiological significance of arachidonic acid-sensitive potassium channels, RT-PCR and Western blot analysis were used to investigate the expression changes of TREK channels in cortex and hippocampus in rat experimental acute cerebral ischemia in this study. Results showed that TREK-1 and TRAAK mRNA in cortex, TREK-1 and TREK-2 mRNA in hippocampus showed significant increases 2 h after middle cerebral artery occlusion (MCAO). While the mRNA expression levels of the all three channel subtypes increased significantly 24 h after MCAO in cortex and hippocampus. At the same time, the protein expressions of all the three channel proteins showed significant increase 24 h after MCAO in cortex and hippocampus, but only TREK-1 showed increased expression 2 h after MCAO in cortex and hippocampus. Immunohistochemical experiments verified that all the three channel proteins had higher expression levels in cortical and hippocampal neurons 24 h after MCAO. These results suggested a strong correlation between TREK channels and acute cerebral ischemia. TREK channels might provide a neuroprotective mechanism in the pathological process.

[A simple and repeatable model of subarachnoid hemorrhage in rats].

AIM: To build a simple and repeatable animal model of subarachnoid hemorrhage (SAH). METHODS: SAH was produced by passing a nylon thread up through the right internal carotid artery and piercing a hole in the right anterior cerebral artery. At 12 h and 24 h after SAH operation, the rats were evaluated with rotarod test and the behavior scale (5-point scale). RESULTS: The rats were trained through rotarod test and then randomly divided into three groups, including vehicle group treated with vehicle after SAH, nimodipine treated group (i.p. 0.25 mg x kg(-1), 5 min, 6 h, 12 h after SAH) and sham group. At the point of the perforation there was usually a capping clot. There was always blood in the basal cisterns with some spread over the hemisphere. After 12 h and 24 h of SAH operation, the time of rotarod test of rats decreased significantly and the rats had serious neurological deficit. Nimodipine could alleviate the neurological deficit after 24 h of SAH. CONCLUSION: To present a simple and reliable model of SAH in the rats, which allows evaluating novel compounds and new drugs for treatment of SAH.