Expression Of Sulfonylurea Receptor Research Articles

Sulfonylurea receptor 1-expressing cancer cells induce cancer-associated fibroblasts to promote non-small cell lung cancer progression

Cancer-associated fibroblasts (CAFs) play a pivotal role in cancer progression; however, how CAFs are induced remains elusive. Sulfonylurea receptor 1 (SUR1) is a tumor-enhancer in non-small cell lung carcinoma (NSCLC). Here, we probed the influence of SUR1-expressing cancer cells on CAFs. Results showed that high SUR1 expression positively correlated with α-SMA positive staining of CAFs in tumor tissues and poor prognosis of NSCLC patients. SUR1 contributed to normal fibroblast (NF) transformation into CAFs and facilitated the growth and metastasis of NSCLC in vivo. Conditioned medium (CM) and exosomes from SUR1-expressing cancer cells induced CAFs and promoted fibroblast migration. In cancer cells, SUR1 promoted p70S6K-induced KH-type splicing regulatory protein (KHSRP) phosphorylation at S395 to inhibit the binding of KHSRP with let-7a precursor (pre-let-7a) and decreasing mature let-7a-5p expression in cancer cells and exosomes. Let-7a-5p delivered by exosomes blocked NF transformation into CAFs by targeting TGFBR1 to inactivate the TGF-β signaling pathway. Glibenclamide, which targets SUR1, restrained CAFs and suppressed tumor growth in patient-derived xenograft models. Furthermore, we found that let-7a-5p was decreased in the tissues and plasma exosomes of NSCLC patients. In summary, SUR1-expressing cancer cells induce NF transformation into CAFs in the tumor microenvironment and promote NSCLC progression by transferring less exosomal let-7a-5p. Glibenclamide is a promising anti-cancer drug, and plasma exosomal let-7a-5p level is a potential diagnostic biomarker for NSCLC patients. These findings provide new therapeutic strategies by targeting SUR1 in NSCLC.

Pituitary Adenylate Cyclase-Activating Polypeptide Attenuates Brain Edema by Protecting Blood-Brain Barrier and Glymphatic System After Subarachnoid Hemorrhage in Rats.

Brain edema is a vital contributor to early brain injury after subarachnoid hemorrhage (SAH), which is responsible for prolonged hospitalization and poor outcomes. Pharmacological therapeutic targets on edema formation have been the focus of research for decades. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to participate in neural development and brain injury. Here, we used PACAP knockout CRISPR to demonstrate that endogenous PACAP plays an endogenous neuroprotective role against brain edema formation after SAH in rats. The exogenous PACAP treatment provided both short- and long-term neurological benefits by preserving the function of the blood-brain barrier and glymphatic system after SAH. Pretreatment of inhibitors of PACAP receptors showed that the PACAP-involved anti-edema effect and neuroprotection after SAH was facilitated by the selective PACAP receptor (PAC1). Further administration of adenylyl cyclase (AC) inhibitor and sulfonylurea receptor 1 (SUR1) CRISPR activator suggested that the AC-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) axis participated in PACAP signaling after SAH, which inhibited the expression of edema-related proteins, SUR1 and aquaporin-4 (AQP4), through SUR1 phosphorylation. Thus, PACAP may serve as a potential clinical treatment to alleviate brain edema in patients with SAH.

Resveratrol reduces cerebral edema through inhibition of de novo SUR1 expression induced after focal ischemia

Cerebral edema is a clinical problem that frequently follows ischemic infarcts. Sulfonylurea receptor 1 (SUR1) is an inducible protein that can form a heteromultimeric complex with aquaporin 4 (AQP4) that mediate the ion/water transport involved in brain tissue swelling. Transcription of the Abcc8 gene coding for SUR1 depends on the activity of transcriptional factor SP1, which is modulated by the cellular redox environment. Since oxidative stress is implicated in the induced neuronal damage in ischemia and edema formation, the present study aimed to evaluate if the antioxidant resveratrol (RSV) prevents the damage by reducing the de novo expression of SUR1 in the ischemic brain. Male Wistar rats were subjected to 2 h of middle cerebral artery occlusion followed by different times of reperfusion. RSV (1.9 mg/kg; i.v.) was administered at the onset of reperfusion. Brain damage and edema formation were recognized by neurological evaluation, time of survival, TTC (2,3,5-Triphenyltetrazolium chloride) staining, Evans blue extravasation, and water content. RSV mechanism of action was studied by SP1 binding activity measured through the Electrophoretic Mobility Shift Assay, and Abcc8 and Aqp4 gene expression evaluated by qPCR, immunofluorescence, and Western blot. We found that RSV reduced the infarct area and cerebral edema, prevented blood-brain barrier damage, improved neurological performance, and increased survival. Additionally, our findings suggest that the antioxidant activity of RSV targeted SP transcription factors and inhibited SUR1 and AQP4 expression. Thus, RSV by decreasing SUR1 expression could contribute to reducing edema formation, constituting a therapeutic alternative for edema reduction in stroke.

Sulfonylurea receptor 1 expression is variable in adult and pediatric brain tumors.

Edema is a significant cause of neuromorbidity in children and adults with brain tumors. Agents used to control this effect, such as corticosteroids, have their own associated morbidities. Sulfonylurea receptor 1 (SUR1) is a transmembrane protein that regulates the activity of ion channels in neurons, glia, and endothelial cells. SUR1 expression is upregulated in neuroinflammatory conditions. Inhibition of SUR1 with glyburide decreases edema and neuroinflammation by countering cytotoxic edema and apoptosis in rodent models of subarachnoid hemorrhage, stroke, trauma, and cerebral metastases. However, the expression of SUR1 in human brain tumors has not been elucidated. The purpose of this study was to determine SUR1 expression and cellular colocalization in a variety of human brain tumor specimens. Six glioblastoma, 12 cerebral metastases, 11 medulloblastoma, 9 supratentorial ependymoma, and 8 posterior fossa ependymoma specimens were analyzed using immunofluorescence. SUR1 expression and colocalization with blood vessels, neurons, and glial cells was analyzed and compared using ANOVA. SUR1 expression was found in all specimens examined as a percentage of the total tissue area (mean±SD): glioblastoma 3.9±4, cerebral metastases 4.1±3.1, medulloblastoma 8.2±7.2, supratentorial ependymoma 9.1±7, and posterior fossa ependymoma 8.1±5.9. SUR1 expression was greater in supratentorial ependymoma compared to glioblastoma and metastases (p < 0.05) and greater in medulloblastoma compared to glioblastoma (p < 0.05). SUR1 colocalized most reliably with the neuronal marker, NeuN, in glioblastoma, metastases, and posterior fossa ependymoma samples (p < 0.05). SUR1 colocalized most reliably with the endothelial cell marker, CD31, in medulloblastoma samples (p < 0.05). SUR1 is a putative therapeutic target to reduce neuroinflammation in adult and pediatric brain tumors. Inhibition of SUR1 may result in neuronal stabilization in glioblastoma, cerebral metastases, and posterior fossa ependymoma and reduced edema in medulloblastoma. .

(121) - Involvement of KATP channels in the peripheral nervous system in the development of morphine tolerance

Opiates are a common treatment for chronic pain, unfortunately for many millions of patients use opiate medication as prescribed, but these individuals can become tolerant, leaving a small therapeutic window for opiate medication over time. Previous data suggests that (1) morphine efficacy may be KATP channel dependent and (2) KATP channels in the peripheral and central nervous system may be beneficial for relieving chronic pain in rodents. The peripheral nervous system is composed of either Kir6.2/SUR1 and Kir6.2/SUR2 KATP channel subunits, but unfortunately we have not carefully examined exactly which receptor subtypes are responsible for their contribution to chronic pain and opioid tolerance. Mice lacking the sulfonylurea receptor 1 (SUR1) protein have reduced opioid efficacy of mechanical paw withdrawal behavioral responses (21% increase) compared to their wild-type (67% increase) and heterozygous littermates (30% increase, 5 mg/kg, morphine). Chronic opioid exposure (5 mg/kg morphine, twice daily) over five days produces significant opioid tolerance, which can be attenuated with intraplantar injections of NN-414 when compared to vehicle treated animals (repeated measures ANOVA, F (2, 17) = 58.69; P < .001). The mRNA expression of the KATP channel subunit SUR1 (Abcc8) was significantly decreased in dorsal root ganglia from morphine tolerant mice compared to vehicle treated mice (unpaired t-test, P = .015), whereas the KATP channel subunit Kir6.2 (Kcnj11) was significantly decreased in the sciatic nerves (unpaired t-test, P = .012). Behavioral studies in mice indicate that intraplantar injection of SUR1 agonists, such as diazoxide (5.4 ± .54 g) and NN-414 (5.2 ± 1.1 g;100 uM, 10uL) improves opiate efficacy of mechanically evoked behavioral responses compared to vehicle treated animals (2.9 ± .31 g; ANOVA, F (4, 27) = 4.3; P = .008). We conclude that increasing KATP channel activity in the peripheral nervous system is a viable option to alleviate opioid tolerance.

Activating adenosine A1 receptor accelerates PC12 cell injury via ADORA1/PKC/KATP pathway after intermittent hypoxia exposure

Obstructive sleep apnea hypopnea syndrome (OSAHS) is associated with the neurocognitive deficits as a result of the neuronal cell injury. Previous studies have shown that adenosine A1 receptor (ADORA1) played an important role against hypoxia exposure, such as controlling the metabolic recovery in rat hippocampal slices and increasing the resistance in the combined effects of hypoxia and hypercapnia. However, little is known about whether ADORA1 takes part in the course of neuronal cell injury after intermittent hypoxia exposure which was the main pathological characteristic of OSAHS. The present study is performed to explore the underlying mechanism of neuronal cell injury which was induced by intermittent hypoxia exposure in PC12 cells. In our research, we find that the stimulation of the ADORA1 by CCPA accelerated the injury of PC12 cells as well as upregulated the expression of PKC, inwardly rectifying potassium channel 6.2(Kir6.2) and sulfonylurea receptor 1(SUR1) while inhibition of the ADORA1 by DPCPX alleviated the injury of PC12 cells as well as downregulated the expression of PKC, Kir6.2, and SUR1. Moreover, inhibition of the PKC by CHE, also mitigated the injury of PC12 cells, suppressed the Kir6.2 and SUR1 expressions induced by PKC. Taken together, our findings indicate that ADORA1 accelerated PC12 cells injury after intermittent hypoxia exposure via ADORA1/PKC/KATP signaling pathway.

Mithramycin A Improves Functional Recovery by Inhibiting BSCB Disruption and Hemorrhage after Spinal Cord Injury.

After spinal cord injury (SCI), blood-spinal cord barrier (BSCB) disruption and progressive hemorrhage lead to secondary injury, subsequent apoptosis and/or necrosis of neurons and glia, causing permanent neurological deficits. Growing evidence indicates that mithramycin A (MA), an anti-cancer drug, has neuroprotective effects in ischemic brain injury and Huntington's disease (HD). However, the precise mechanism underlying its protective effects is largely unknown. Here, we examined the effect of MA on BSCB breakdown and hemorrhage as well as subsequent inflammation after SCI. After moderate spinal cord contusion injury at T9, MA (150 μg/kg) was immediately injected intraperitoneally (i.p.) and further injected once a day for 5 days. Our data show that MA attenuated BSCB disruption and hemorrhage, and inhibited the infiltration of neutrophils and macrophages after SCI. Consistent with these findings, the expression of inflammatory mediators was significantly alleviated by MA. MA also inhibited the expression and activation of matrix metalloprotease-9 (MMP-9) after injury, which is known to disrupt BSCB and the degradation of tight junction (TJ) proteins. In addition, the expression of sulfonylurea receptor 1 (SUR1) and transient receptor potential melastatin 4 (TRPM4), which are known to mediate hemorrhage at an early stage after SCI, was significantly blocked by MA treatment. Finally, MA inhibited apoptotic cell death and improved functional recovery after injury. Thus, our results demonstrated that MA improves functional recovery by attenuating BSCB disruption and hemorrhage through the downregulation of SUR1/TRPM4 and MMP-9 after SCI.

KATP channels in high glucose-induced rat mesangial cell proliferation and release of MMP-2 and fibronectin

ATP-sensitive potassium (KATP) channels are well characterized in cardiac, pancreatic and many other muscle cells. The purpose of this study was to determine if KATP channels play a role in diabetic nephropathy (DN). In the present study, functional expression of the KATP channel was examined in rat mesangial cells with or without high glucose (HG) stimulation. The mesangial cell proliferation and the release of matrix metalloproteinase (MMP)-2 and fibronectin in response to high glucose with a selective opener of KATP (diazoxide, DZX), or with a selective inhibitor of KATP (5-hydroxydecanoate, 5-HD) were also measured. The cell proliferation was observed using Cell Counting Kit-8 assay, and the mRNA expressions of KATP subunit, including Kir6.1, Kir6.2, sulfonylurea receptor 1 (SUR1), SUR2A and SUR2B, were assessed using quantitative real-time PCR. MMP-2 and fibronectin release was measured by ELISA. The present study clarified expression of SUR subunit of KATP in plasma. HG treatment could cause increased cell proliferation and release of MMP-2 and fibronectin in a dose-dependent manner. HG also significantly decreased the expression of Kir6.1, SUR2A and SUR2B. Pretreatment of DZX markedly decreased the expression of SUR1, SUR2A and SUR2B, but had no effect on Kir6.1 expression compared with HG alone, while these changes were inhibited by 5-HD pretreatment. Moreover, DZX also inhibited cell proliferation and release of MMP-2 and fibronectin in HG-induced rat mesangial cells, and that was corrected by 5-HD. These data suggest that HG stimulates mesangial cell proliferation and cellular matrix release via inhibiting KATP channel activity, leading us to propose that KATP channel dysfunction may be involved in the development of DN.

Malignant infarction of the middle cerebral artery in a porcine model. A pilot study.

Background and purposeInterspecies variability and poor clinical translation from rodent studies indicate that large gyrencephalic animal stroke models are urgently needed. We present a proof-of-principle study describing an alternative animal model of malignant infarction of the middle cerebral artery (MCA) in the common pig and illustrate some of its potential applications. We report on metabolic patterns, ionic profile, brain partial pressure of oxygen (PtiO2), expression of sulfonylurea receptor 1 (SUR1), and the transient receptor potential melastatin 4 (TRPM4).MethodsA 5-hour ischemic infarct of the MCA territory was performed in 5 2.5-to-3-month-old female hybrid pigs (Large White x Landrace) using a frontotemporal approach. The core and penumbra areas were intraoperatively monitored to determine the metabolic and ionic profiles. To determine the infarct volume, 2,3,5-triphenyltetrazolium chloride staining and immunohistochemistry analysis was performed to determine SUR1 and TRPM4 expression.ResultsPtiO2 monitoring showed an abrupt reduction in values close to 0 mmHg after MCA occlusion in the core area. Hourly cerebral microdialysis showed that the infarcted tissue was characterized by reduced concentrations of glucose (0.03 mM) and pyruvate (0.003 mM) and increases in lactate levels (8.87mM), lactate-pyruvate ratio (4202), glycerol levels (588 μM), and potassium concentration (27.9 mmol/L). Immunohistochemical analysis showed increased expression of SUR1-TRPM4 channels.ConclusionsThe aim of the present proof-of-principle study was to document the feasibility of a large animal model of malignant MCA infarction by performing transcranial occlusion of the MCA in the common pig, as an alternative to lisencephalic animals. This model may be useful for detailed studies of cerebral ischemia mechanisms and the development of neuroprotective strategies.

SUR1-Associated Mechanisms Are Not Involved in Ischemic Optic Neuropathy 1 Day Post-Injury.

Ischemia-reperfusion injury after central nervous system (CNS) injury presents a major health care challenge with few promising treatments. Recently, it has become possible to reduce edema after CNS injury by antagonizing a sulfonylurea receptor 1 (SUR1) regulated ion channel expressed after injury. SUR1 upregulation after injury is a necessary precondition for the formation of this channel, and has been implicated in white matter injury after clinical spinal cord trauma. Glibenclamide, an SUR1 antagonist, appears to have neuroprotective effect against cerebral stroke in an open-label small clinical trial and great effectiveness in reducing damage after varied experimental CNS injury models. Despite its importance in CNS injuries, SUR1 upregulation appears to play no part in rodent anterior ischemic optic neuropathy (rAION) injury as tested by real-time PCR and immunohistochemical staining of rAION-injured rat optic nerve (ON). Furthermore, the SUR1 antagonist glibenclamide administered immediately after rAION injury provided no protection to proximal ON microvasculature 1 day post-injury but may reduce optic nerve head edema in a manner unrelated to ON SUR1 expression. Our results suggest that there may be fundamental differences between rAION optic nerve ischemia and other CNS white matter injuries where SUR1 appears to play a role.

Glibenclamide enhances the effects of delayed hypothermia after experimental stroke in rats

In order to evaluate whether glibenclamide can extend the therapeutic window during which induced hypothermia can protect against stroke, we subjected adult male Sprague-Dawley rats to middle cerebral artery occlusion (MCAO). We first verified the protective effects of hypothermia induced at 0, 2, 4 or 6h after MCAO onset, and then we assessed the effects of the combination of glibenclamide and hypothermia at 6, 8 or 10h after MCAO onset. At 24h after MCAO, we assessed brain edema, infarct volume, modified neurological severity score, Evans Blue leakage and expression of Sulfonylurea receptor 1 (SUR1) protein and pro-inflammatory factors. No protective effects were observed when hypothermia was induced too long after MCAO. At 6h after MCAO onset, hypothermia alone failed to decrease cerebral edema and infarct volume, but the combination of glibenclamide and hypothermia decreased both. The combination also improved neurological outcome, ameliorated blood-brain barrier damage and decreased levels of COX-2, TNF-α and IL-1β. These results suggest that glibenclamide enhances and extends the therapeutic effects of delayed hypothermia against ischemia stroke, potentially by ameliorating blood-brain barrier damage and declining levels of pro-inflammatory factors.

Gene transfer of cystathionine β-synthase into RVLM increases hydrogen sulfide-mediated suppression of sympathetic outflow via KATP channel in normotensive rats

Hydrogen sulfide has been shown to have a sympathoinhibitory effect in the rostral ventrolateral medulla (RVLM). The present study examined the function of cystathionine β-synthase (CBS)/hydrogen sulfide system in the RVLM, which plays a crucial role in the control of blood pressure and sympathetic nerve activity. Adenovirus vectors encoding CBS (AdCBS) or enhanced green fluorescent protein (AdEGFP) were transfected into the RVLM in normotensive rats. Identical microinjection of AdCBS into the RVLM had no effect on systolic blood pressure and heart rate (HR) in conscious rats. Acute experiments were performed at day 7 after gene transfer in anesthetized rats. Microinjection of the CBS inhibitors hydroxylamine (HA) or amino-oxyacetate into the RVLM produced an increase in the renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), and HR. There was a potentiation of the increases in RSNA, MAP, and HR because of the CBS inhibitors in AdCBS-injected rats compared with AdEGFP-injected rats. Pretreatment with pinacidil, a ATP-sensitive potassium (KATP) channel activator, abolished the effects of HA in two groups. Microinjection of glibenclamide, a KATP channel blocker, produced increases in RSNA, MAP, and HR in AdCBS-injected rats. No changes in behavior were observed in AdEGFP-injected rats. Furthermore, Western blot analysis indicated an increase in the expression of sulfonylurea receptor 2 and inward rectifier K(+) 6.1 in AdCBS-injected rats. These results suggest that the increase in KATP channels in the RVLM may be responsible for the greater sympathetic outflow and pressor effect of HA in AdCBS-injected rats compared with AdEGFP-injected rats.

Protective effect of treatment with low-dose gliclazide in a model of middle cerebral artery occlusion and reperfusion in rats

The aim of this study was to explore the expression of sulfonylurea receptor 1 (SUR1), the regulatory subunit of the NCCa-ATP channel, and to investigate the protective effects of gliclazide following middle cerebral artery occlusion (MCAO)/reperfusion in male Wistar rats. Adult rats underwent 2h of the left MCAO using the intraluminal thread technique before reperfusion. The core areas of the infarct at different reperfusion time points were examined for the mRNA level and protein expression of SUR1 using reverse transcription-polymerase chain reaction (RT-PCR) and western blotting respectively. Gliclazide was administered intravenously into the right jugular vein for 12h simultaneously with the reperfusion. The number of apoptotic cells was determined using the TUNEL assay. The neurological functional deficits were evaluated using Bederson׳s test, and the cerebral infarction volume was visualized with TTC staining. We found up-regulation of SUR1 mRNA and protein levels in ischemic infarct tissues after reperfusion following MCAO, and SUR1 mRNA and protein were maximally upregulated 8–12h after a 2-hour ischemia. The treatment with low-dose of gliclazide reduced the total number of TUNEL-positive cells, the neurological functional deficits and the brain infarct volume. These results suggest that the SUR1-regulated NCCa-ATP channel may be associated with MCAO/reperfusion injury and the infarct-reducing effects of intravenous treatment with gliclazide may be due, in part, to the blocked upregulation of SUR1 expression, the decreased infarct size and the reduced apoptosis in the ischemia–reperfusion brain.

Inhibition of SUR1 Decreases the Vascular Permeability of Cerebral Metastases

Inhibition of sulfonylurea receptor 1 (SUR1) by glyburide has been shown to decrease edema after subarachnoid hemorrhage. We investigated if inhibiting SUR1 reduces cerebral edema due to metastases, the most common brain tumor, and explored the putative association of SUR1 and the endothelial tight junction protein, zona occludens-1 (ZO-1). Nude rats were intracerebrally implanted with small cell lung carcinoma (SCLC) LX1 or A2058 melanoma cells (n = 36). Rats were administered vehicle, glyburide (4.8 µg twice, orally), or dexamethasone (0.35 mg, intravenous). Blood-tumor barrier (BTB) permeability (Ktrans) was evaluated before and after treatment using dynamic contrast-enhanced magnetic resonance imaging. SUR1 and ZO-1 expression was evaluated using immunofluorescence and Western blots. In both models, SUR1 expression was significantly increased (P < .05) in tumors. In animals with SCLC, control mean Ktrans (percent change ± standard error) was 101.8 ± 36.6%, and both glyburide (-21.4 ± 14.2%, P < .01) and dexamethasone (-14.2 ± 13.1%, P < .01) decreased BTB permeability. In animals with melanoma, compared to controls (117.1 ± 43.4%), glyburide lowered BTB permeability increase (3.2 ± 15.4%, P < .05), while dexamethasone modestly lowered BTB permeability increase (63.1 ± 22.1%, P > .05). Both glyburide (P < .001) and dexamethasone (P < .01) decreased ZO-1 gap formation. By decreasing ZO-1 gaps, glyburide was at least as effective as dexamethasone at halting increased BTB permeability caused by SCLC and melanoma. Glyburide is a safe, inexpensive, and efficacious alternative to dexamethasone for the treatment of cerebral metastasis-related vasogenic edema.

Sequential Activation of Hypoxia-Inducible Factor 1 and Specificity Protein 1 is Required for Hypoxia-Induced Transcriptional Stimulation ofAbcc8

Cerebral ischemia causes increased transcription of sulfonylurea receptor 1 (SUR1), which forms SUR1-regulated NC(Ca-ATP) channels linked to cerebral edema. We tested the hypothesis that hypoxia is an initial signal that stimulates transcription of Abcc8, the gene encoding SUR1, via activation of hypoxia-inducible factor 1 (HIF1). In the brain microvascular endothelial cells, hypoxia increased SUR1 abundance and expression of functional SUR1-regulated NC(Ca-ATP) channels. Luciferase reporter activity driven by the Abcc8 promoter was increased by hypoxia and by coexpression of HIF1α. Surprisingly, a series of luciferase reporter assays studying the Abcc8 promoter revealed that binding sites for specificity protein 1 (Sp1), but not for HIF, were required for stimulation of Abcc8 transcription by HIF1α. Luciferase reporter assays studying Sp1 promoters of three species, and chromatin immunoprecipitation analysis in rats after cerebral ischemia, indicated that HIF binds to HIF-binding sites on the Sp1 promoter to stimulate transcription of the Sp1 gene. We conclude that sequential activation of two transcription factors, HIF and Sp1, is required to stimulate transcription of Abcc8 following cerebral ischemia. Sequential gene activation in cerebral ischemia provides a plausible molecular explanation for the prolonged treatment window observed for inhibition of the end-target gene product, SUR1, by glibenclamide.

Glibenclamide Reduces Hippocampal Injury and Preserves Rapid Spatial Learning in a Model of Traumatic Brain Injury

Cognitive disturbances after traumatic brain injury (TBI) are frequent, even when neuroimaging shows no overt hemorrhagic or other abnormality. Sulfonylurea receptor 1 (SUR1) plays a key role in various forms of CNS injury, but its role in hippocampal dysfunction after mild to moderate TBI is unknown. To assess the hypothesis that postinjury SUR1 upregulation in the hippocampus is associated with a later disturbance in learning, we studied a rat model of cortical impact TBI calibrated to avoid primary and secondary hemorrhage in the underlying hippocampus. The transcription factor, specificity protein 1, which regulates expression of SUR1 and caspase-3, was activated in the hippocampus 15 minutes after injury. Upregulation of SUR1 protein and of Abcc8 (which encodes SUR1) messenger RNA was evident by 6 hours. To assess the role of SUR1, injured rats were administered vehicle or a low dose of the specific sulfonylurea inhibitor glibenclamide for 1 week. At 2 weeks, the increase in activated caspase-3 in the hilus of glibenclamide-treated rats was half of that in vehicle-treated rats. Testing for rapid learning in a Morris water maze at 4 weeks showed significantly better performance in glibenclamide-treated rats; performance inversely correlated with Fluoro-Jade staining for degenerated neurons in the hilus. We conclude that glibenclamide may have long-term protective effects on the hippocampus after mild-to-moderate TBI.

Expression of sulfonylurea receptors in rat taste buds

To test the possibility that a fast-onset promoting agent repaglinide may initiate prandial insulin secretion through the mechanism of cephalic-phase insulin release, we explored the expression and distribution character of sulfonylurea receptors in rat taste buds. Twenty male Wistar rats aged 10 weeks old were killed after general anesthesia. The circumvallate papillae, fungiform papillae and pancreas tissues were separately collected. Immunohistochemical staining was used to detect the expression and distribution of sulfonylurea receptor 1 (SUR1) or sulfonylurea receptor 2 (SUR2) in rat taste buds. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to analyze the expression of SUR1 or SUR2 mRNA. The pancreatic tissues from the same rat were used as positive control. This is the first study to report that SUR1 is uniquely expressed in the taste buds of fungiform papillae of each rat tongue, while the expression of SUR1 or SUR2 was not detected in the taste buds of circumvallate papillae. SUR1 is selectively expressed in rat taste buds, and its distribution pattern may be functionally relevant, suggesting that the rapid insulin secretion-promoting effect of repaglinide may be exerted through the cephalic-phase secretion pathway mediated by taste buds.

Key Role of Sulfonylurea Receptor 1 in Progressive Secondary Hemorrhage after Brain Contusion

An important but poorly understood feature of traumatic brain injury (TBI) is the clinically serious problem of spatiotemporal progression ("blossoming") of a hemorrhagic contusion, a phenomenon we term progressive secondary hemorrhage (PSH). Molecular mechanisms of PSH are unknown and efforts to reduce it by promoting coagulation have met with equivocal results. We hypothesized that PSH might be due to upregulation and activation of sulfonylurea receptor 1 (SUR1)-regulated NC(Ca-ATP) channels in capillary endothelial cells, predisposing to oncotic death of endothelial cells and catastrophic failure of capillary integrity. Anesthetized adult male rats underwent left parietal craniectomy for induction of a focal cortical contusion. The regulatory subunit of the channel, SUR1, was prominently upregulated in capillaries of penumbral tissues surrounding the contusion. In untreated rats, PSH was characterized by progressive enlargement of the contusion deep into the site of cortical impact, including corpus callosum, hippocampus, and thalamus, by progressive accumulation of extravasated blood, with a doubling of the volume during the first 12 h after injury, and by capillary fragmentation in penumbral tissues. Block of SUR1 using low-dose (non-hypoglycemogenic) glibenclamide largely eliminated PSH and capillary fragmentation, and was associated with a significant reduction in the size of the necrotic lesion and in preservation of neurobehavioral function. Antisense oligodeoxynucleotide against SUR1, administered after injury, reduced both SUR1 expression and PSH, consistent with a requirement for transcriptional upregulation of SUR1. Our findings provide novel insights into molecular mechanisms responsible for PSH associated with hemorrhagic contusions, and point to SUR1 as a potential therapeutic target in TBI.

17β-Estradiol Modulates Apoptosis in Pancreatic β-Cells by Specific Involvement of the Sulfonylurea Receptor (SUR) Isoform SUR1

Apoptosis of pancreatic beta-cells is an important factor in the pathophysiology of diabetes. Previously, we have shown that the "phytoestrogen" resveratrol can induce beta-cell apoptosis dependent on the expression of sulfonylurea receptor (SUR) 1, the regulatory subunit of pancreatic ATP-sensitive K(+) channels. Here, we investigate whether 17beta-estradiol also influences beta-cell apoptosis in a SUR1-dependent manner. Therefore, islets from wild type or SUR1 knock-out mice, clonal beta-cells, or HEK293 cells expressing different SUR forms were treated with 17beta-estradiol or estrone. Different apoptotic parameters were determined and estrogen binding to SUR was analyzed. In murine islets, 17beta-estradiol treatment resulted in significant apoptotic changes, which in their nature (either apoptotic or anti-apoptotic) were dependent on the age of the animal. These effects were not observed in SUR1 knock-out mice. Furthermore, 17beta-estradiol, which specifically binds to SUR, induced enhanced apoptosis in SUR1-expressing HEK293 cells and clonal beta-cells, whereas apoptosis in recombinant cells expressing SUR2A or SUR2B (cardiac or vascular SUR-isoforms) or sham-transfected control cells was significantly lower. The apoptotic potency of 17beta-estradiol was much higher than that of resveratrol or estrone. SUR1-specific 17beta-estradiol-induced apoptosis was either abolished by the mutation M1289T in transmembrane helix 17 of SUR1 or clearly enhanced by two mutations in nucleotide binding fold 2 (R1379C, R1379L). In conclusion, 17beta-estradiol treatment modulates beta-cell apoptosis under specific involvement of SUR1 in an age-dependent manner. 17beta-Estradiol-induced apoptosis can be influenced by certain SUR1 mutations. These findings may contribute to the understanding of pathophysiological changes in beta-cell mass and could, for instance, provide interesting aspects concerning the etiology of gestational diabetes.

Glibenclamide Reduces Inflammation, Vasogenic Edema, and Caspase-3 Activation after Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) causes secondary brain injury due to vasospasm and inflammation. Here, we studied a rat model of mild-to-moderate SAH intended to minimize ischemia/hypoxia to examine the role of sulfonylurea receptor 1 (SUR1) in the inflammatory response induced by SAH. mRNA for Abcc8, which encodes SUR1, and SUR1 protein were abundantly upregulated in cortex adjacent to SAH, where tumor-necrosis factor-alpha (TNFalpha) and nuclear factor (NF)kappaB signaling were prominent. In vitro experiments confirmed that Abcc8 transcription is stimulated by TNFalpha. To investigate the functional consequences of SUR1 expression after SAH, we studied the effect of the potent, selective SUR1 inhibitor, glibenclamide. We examined barrier permeability (immunoglobulin G, IgG extravasation), and its correlate, the localization of the tight junction protein, zona occludens 1 (ZO-1). SAH caused a large increase in barrier permeability and disrupted the normal junctional localization of ZO-1, with glibenclamide significantly reducing both effects. In addition, SAH caused large increases in markers of inflammation, including TNFalpha and NFkappaB, and markers of cell injury or cell death, including IgG endocytosis and caspase-3 activation, with glibenclamide significantly reducing these effects. We conclude that block of SUR1 by glibenclamide may ameliorate several pathologic effects associated with inflammation that lead to cortical dysfunction after SAH.