Increasing evidence, including from our laboratory, has revealed that opening of ATP sensitive potassium channels(K-ATP channels) plays the neuronal protective roles both in vivo and in vitro. Thus K-ATP channel opene...Increasing evidence, including from our laboratory, has revealed that opening of ATP sensitive potassium channels(K-ATP channels) plays the neuronal protective roles both in vivo and in vitro. Thus K-ATP channel openers(KCOs) have been proposed as potential neuroprotectants. Our previous studies demonstrated that K-ATP channels could regulate glutamate uptake activity in PC12 cells as well as in synaptosomes of rats. Since glutamate transporters(GluTs) of astrocytes play crucial roles in glutamate uptake and KATP channels are also expressed in astrocytes, the present study showed whether and how KATP channels regulated the function of GluTs in primary cultured astrocytes. The results showed that nonselective KCO pinacidil, selective mitochondrial KCO diazoxide, novel, and blood-brain barrier permeable KCO iptakalim could enhance glutamate uptake, except for the sarcolemmal KCO P1075. Moreover pinacidil, diazoxide, and iptakalim reversed the inhibition of glutamate uptake induced by 1-methyl-4-phenylpyridinium(MPP+). These potentiated effects were completely abolished by mitochondrial K-ATP blocker 5-hydroxydecanoate. Furthermore, either diazoxide or iptakalim could inhibit MPP+-induced elevation of reactive oxygen species (ROS) and phosphorylation of protein kinases C(PKC). These findings are the first to demonstrate that activation of K-ATP channel, especially mitochondrial K-ATP channel, improves the function of GluTs in astrocytes due to reducing ROS production and downregulating PKC phosphorylation. Therefore, the present study not only reveals a novel pharmacological profile of KCOs as regulators of GluTs, but also provides a new strategy for neuroprotection.展开更多
Mitochondrial K＋-ATP （mito-KATP） channels play an important role in cellular function and survival following ischemic stress. The present results revealed that intervention with diazoxide, a mito-KATP channel opene...Mitochondrial K＋-ATP （mito-KATP） channels play an important role in cellular function and survival following ischemic stress. The present results revealed that intervention with diazoxide, a mito-KATP channel opener, led to an increase in Bcl-2 expression in the cerebral cortex of rats subjected to cerebral ischemia reperfusion injury. In addition, the intervention also led to clear improvements in neuronal mitochondrial morphology and consciousness post-injury. Glibenclamide a mito-KATP channel blocker, exhibited the converse effects. Both diazoxide and glibenclamide exerted dose-dependent effects （in particular, at 18 mg/kg diazoxide and 25 mg/kg glibenclamide）. These findings suggest that diazoxide exerts a neuroprotective effect on cerebral ischemia reperfusion injury by opening mito-KATP channels and upregulating Bcl-2 expression.展开更多
Hypoxic pulmonary hypertension(HPH) is a syndrome characterized by the increase of pulmonary vascular tone and the structural remodeling of peripheral pulmonary arteries.The aim of specific therapies for hypoxic pulmo...Hypoxic pulmonary hypertension(HPH) is a syndrome characterized by the increase of pulmonary vascular tone and the structural remodeling of peripheral pulmonary arteries.The aim of specific therapies for hypoxic pulmonary hypertension is to reduce pulmonary vascular resistance,reverse pulmonary vascular remodeling,and thereby improving right ventricular function.Iptakalim,a lipophilic para-amino compound with a low molecular weight,has been demonstrated to be a new selective ATP-sensitive potassium(K ATP) channel opener via pharmacological,electrophysiological,biochemical studies,and receptor binding tests.In hypoxia-induced animal models,iptakalim decreases the elevated mean pressure in pulmonary arteries,and attenuates remodeling in the right ventricle,pulmonary arteries and airways.Furthermore,iptakalim has selective antihypertensive effects,selective vasorelaxation effects on smaller arteries,and protective effects on endothelial cells,but no effects on the central nervous,respiratory,digestive or endocrine systems at therapeutic dose.Our previous studies demonstrated that iptakalim inhibited the effects of endothelin-1,reduced the intracellular calcium concentration and inhibited the proliferation of pulmonary artery smooth muscle cells.Since iptakalim has been shown safe and effective in both experimental animal models and phase I clinical trials,it can be a potential candidate of HPH in the future.展开更多
The effects of ATP-sensitive mitochondrial K + channel(mitoK ATP) on mitochondrial membrane potential(Δψm),cell proliferation and protein kinase C alpha(PKCα) expression in airway smooth muscle cells(ASMCs) were in...The effects of ATP-sensitive mitochondrial K + channel(mitoK ATP) on mitochondrial membrane potential(Δψm),cell proliferation and protein kinase C alpha(PKCα) expression in airway smooth muscle cells(ASMCs) were investigated.Thirty-six Sprague-Dawley(SD) rats were immunized with saline(controls) or ovalbumin(OVA) with alum(asthma models).ASMCs were cultured from the lung of control and asthma rats.ASMCs were treated with diazoxide(the potent activator of mitoK ATP) or 5-hydroxydencanote(5-HD,the inhibitor of mitoK ATP).Rhodamine-123(R-123) was used to detect Δψm.The expression of PKCα protein was examined by using Western blotting,while PKCα mRNA expression was detected by using real-time PCR.The proliferation of ASMCs was measured by MTT assay and cell cycle analysis.In diazoxide-treated normal ASMCs,the R-123 fluorescence intensity,protein and mRNA levels of PKCα,MTT A values and percentage of cells in S phase were markedly increased as compared with untreated controls.The ratio of G 0 /G 1 cells was decreased(P<0.05) in diazoxide-treated ASMCs from normal rats.However,there were no significant differences between the ASMCs from healthy rats treated with 5-HD and the normal control group.In untreated and diazoxide-treated ASMCs of asthmatic rats,the R-123 fluorescence intensity,protein and mRNA levels of PKCα,MTT A values and the percentage of cells in S phase were increased in comparison to the normal control group.Furthermore,in comparison to ASMCs from asthmatic rats,these values were considerably increased in asthmatic group treated with diazoxide(P<0.05).After exposure to 5-HD for 24 h,these values were decreased as compared with asthma control group(P<0.05).In ASMCs of asthma,the signal transduction pathway of PKCα may be involved in cell proliferation,which is induced by the opening of mitoK ATP and the depolarization of Δψm.展开更多
Cumulative evidence suggests that renal vascular endothelial injury play an important role in initiating and extending tubular epithelial injury and contribute to the development of ischemic acute renal failure.Our pr...Cumulative evidence suggests that renal vascular endothelial injury play an important role in initiating and extending tubular epithelial injury and contribute to the development of ischemic acute renal failure.Our previous studies have demonstrated that iptakalim's endothelium protection is related to activation of SUR2B/Kir6.1 subtype of ATP sensitive potassium channel(K ATP) in the endothelium.It has been reported that SUR2B/Kir6.1 channels are widely distributed in the tubular epithelium,glomerular mesangium,and the endothelium and the smooth muscle of blood vessels.Herein,we hypothesized that activating renal K ATP channels with iptakalim might have directly neroprotective effects.In this study,glomerular endothelial,mesangial and tubular epithelial cells which are the main cell types to form nephron were exposed to oleic acid(OA) at various concentrations for 24 h.0.25 μl/ml OA could cause cellular damage of glomerular endothelium and mesangium,while 1.25μl/ml OA could lead to the injury of three types of renal cells.It was observed that pretreatment with iptakalim at concentrations of 0.1,1,10 or 100 μmol/L prevented cellular damage of glomerular endothelium and tubular epithelium,whereas iptakalim from 1 to 100 μmol/L prevented the injury of mesangial cells.Our data showed iptakalim significantly increased survived cell rates in a concentration-dependent manner,significantly antagonized by glibenclamide,a K ATP blocker.Iptakalim played a protective role in the main cell types of kidney,which was consistent with natakalim,a highly selective SUR2B/Kir6.1 channel opener.Iptakalim exerted protective effects through activating SUR2B/Kir6.1 channels,suggesting a new strategy for renal injury by its endothelial and renal cell protection.展开更多
BACKGROUND ATP-sensitive K^+(KATP)channels were originally found in cardiac myocytes by Noma in 1983.KATP channels were formed by potassium ion-passing poreforming subunits(Kir6.1,Kir6.2)and regulatory subunits SUR1,S...BACKGROUND ATP-sensitive K^+(KATP)channels were originally found in cardiac myocytes by Noma in 1983.KATP channels were formed by potassium ion-passing poreforming subunits(Kir6.1,Kir6.2)and regulatory subunits SUR1,SU2A and SUR2B.A number of cells and tissues have been revealed to contain these channels including hepatocytes,but detailed localization of these subunits in different types of liver cells was still uncertain.AIM To investigate the expression of KATP channel subunits in rat liver and their localization in different cells of the liver.METHODS Rabbit anti-rat SUR1 peptide antibody was raised and purified by antigen immunoaffinity column chromatography.Four of Sprague-Dawley rats were used for liver protein extraction for immunoblot analysis,seven of them were used for immunohistochemistry both for the ABC method and immunofluorescence staining.Four of Wistar rats were used for the isolation of hepatic stellate cells(HSCs)and Kupffer cells for both primary culture and immunocytochemistry.RESULTS Immunoblot analysis showed that the five kinds of KATP channel subunits,i.e.Kir6.1,Kir6.2,SUR1,SUR2A,and SUR2B,were detected in liver.Immunohistochemical staining showed that Kir6.1 and Kir6.2 were weakly to moderately expressed in parenchymal cells and sinusoidal lining cells,while SUR1,SUR2A,and SUR2B were mainly localized to sinusoidal lining cells,such as HSCs,Kupffer cells,and sinusoidal endothelial cells.Immunoreactivity for SUR2A and SUR2B was expressed in the hepatocyte membrane.Double immunofluorescence staining further showed that the pore-forming subunits Kir6.1 and/or Kir6.2 colocalized with GFAP in rat liver sections and primary cultured HSCs.These KATP channel subunits also colocalized with CD68 in liver sections and primary cultured Kupffer cells.The SUR subunits colocalized with GFAP in liver sections and colocalized with CD68 both in liver sections and primary cultured Kupffer cells.In addition,five KATP channel subunits colocalized with SE-1 in sinusoidal endothelial cells.CONCLUSION Observations from the present study indicated that KATP channel subunits expressed in rat liver and the diversity of KATP channel subunit composition might form different types of KATP channels.This is applicable to hepatocytes,HSCs,various types of Kupffer cells and sinusoidal endothelial cells.展开更多
文摘Increasing evidence, including from our laboratory, has revealed that opening of ATP sensitive potassium channels(K-ATP channels) plays the neuronal protective roles both in vivo and in vitro. Thus K-ATP channel openers(KCOs) have been proposed as potential neuroprotectants. Our previous studies demonstrated that K-ATP channels could regulate glutamate uptake activity in PC12 cells as well as in synaptosomes of rats. Since glutamate transporters(GluTs) of astrocytes play crucial roles in glutamate uptake and KATP channels are also expressed in astrocytes, the present study showed whether and how KATP channels regulated the function of GluTs in primary cultured astrocytes. The results showed that nonselective KCO pinacidil, selective mitochondrial KCO diazoxide, novel, and blood-brain barrier permeable KCO iptakalim could enhance glutamate uptake, except for the sarcolemmal KCO P1075. Moreover pinacidil, diazoxide, and iptakalim reversed the inhibition of glutamate uptake induced by 1-methyl-4-phenylpyridinium(MPP+). These potentiated effects were completely abolished by mitochondrial K-ATP blocker 5-hydroxydecanoate. Furthermore, either diazoxide or iptakalim could inhibit MPP+-induced elevation of reactive oxygen species (ROS) and phosphorylation of protein kinases C(PKC). These findings are the first to demonstrate that activation of K-ATP channel, especially mitochondrial K-ATP channel, improves the function of GluTs in astrocytes due to reducing ROS production and downregulating PKC phosphorylation. Therefore, the present study not only reveals a novel pharmacological profile of KCOs as regulators of GluTs, but also provides a new strategy for neuroprotection.
文摘Mitochondrial K＋-ATP （mito-KATP） channels play an important role in cellular function and survival following ischemic stress. The present results revealed that intervention with diazoxide, a mito-KATP channel opener, led to an increase in Bcl-2 expression in the cerebral cortex of rats subjected to cerebral ischemia reperfusion injury. In addition, the intervention also led to clear improvements in neuronal mitochondrial morphology and consciousness post-injury. Glibenclamide a mito-KATP channel blocker, exhibited the converse effects. Both diazoxide and glibenclamide exerted dose-dependent effects （in particular, at 18 mg/kg diazoxide and 25 mg/kg glibenclamide）. These findings suggest that diazoxide exerts a neuroprotective effect on cerebral ischemia reperfusion injury by opening mito-KATP channels and upregulating Bcl-2 expression.
基金supported by National Major Scientific and Technological Special Project for"Significant New Drugs Development"(2011ZX09302-003-02)
文摘Hypoxic pulmonary hypertension(HPH) is a syndrome characterized by the increase of pulmonary vascular tone and the structural remodeling of peripheral pulmonary arteries.The aim of specific therapies for hypoxic pulmonary hypertension is to reduce pulmonary vascular resistance,reverse pulmonary vascular remodeling,and thereby improving right ventricular function.Iptakalim,a lipophilic para-amino compound with a low molecular weight,has been demonstrated to be a new selective ATP-sensitive potassium(K ATP) channel opener via pharmacological,electrophysiological,biochemical studies,and receptor binding tests.In hypoxia-induced animal models,iptakalim decreases the elevated mean pressure in pulmonary arteries,and attenuates remodeling in the right ventricle,pulmonary arteries and airways.Furthermore,iptakalim has selective antihypertensive effects,selective vasorelaxation effects on smaller arteries,and protective effects on endothelial cells,but no effects on the central nervous,respiratory,digestive or endocrine systems at therapeutic dose.Our previous studies demonstrated that iptakalim inhibited the effects of endothelin-1,reduced the intracellular calcium concentration and inhibited the proliferation of pulmonary artery smooth muscle cells.Since iptakalim has been shown safe and effective in both experimental animal models and phase I clinical trials,it can be a potential candidate of HPH in the future.
基金supported by grants from Natural Science Foundation of Hubei Province,China (No. 2010CDB096)the National Key Technology R&D Program of the 12th National Five-year Development Plan of China (No. 2012BAI05B01)
文摘The effects of ATP-sensitive mitochondrial K + channel(mitoK ATP) on mitochondrial membrane potential(Δψm),cell proliferation and protein kinase C alpha(PKCα) expression in airway smooth muscle cells(ASMCs) were investigated.Thirty-six Sprague-Dawley(SD) rats were immunized with saline(controls) or ovalbumin(OVA) with alum(asthma models).ASMCs were cultured from the lung of control and asthma rats.ASMCs were treated with diazoxide(the potent activator of mitoK ATP) or 5-hydroxydencanote(5-HD,the inhibitor of mitoK ATP).Rhodamine-123(R-123) was used to detect Δψm.The expression of PKCα protein was examined by using Western blotting,while PKCα mRNA expression was detected by using real-time PCR.The proliferation of ASMCs was measured by MTT assay and cell cycle analysis.In diazoxide-treated normal ASMCs,the R-123 fluorescence intensity,protein and mRNA levels of PKCα,MTT A values and percentage of cells in S phase were markedly increased as compared with untreated controls.The ratio of G 0 /G 1 cells was decreased(P<0.05) in diazoxide-treated ASMCs from normal rats.However,there were no significant differences between the ASMCs from healthy rats treated with 5-HD and the normal control group.In untreated and diazoxide-treated ASMCs of asthmatic rats,the R-123 fluorescence intensity,protein and mRNA levels of PKCα,MTT A values and the percentage of cells in S phase were increased in comparison to the normal control group.Furthermore,in comparison to ASMCs from asthmatic rats,these values were considerably increased in asthmatic group treated with diazoxide(P<0.05).After exposure to 5-HD for 24 h,these values were decreased as compared with asthma control group(P<0.05).In ASMCs of asthma,the signal transduction pathway of PKCα may be involved in cell proliferation,which is induced by the opening of mitoK ATP and the depolarization of Δψm.
基金supported by grants from National New Drug Research and Development of Key Project(2010ZX09401-307,2008ZX09101-006,2008ZXJ09004-018 and 2009ZX09301-002)
文摘Cumulative evidence suggests that renal vascular endothelial injury play an important role in initiating and extending tubular epithelial injury and contribute to the development of ischemic acute renal failure.Our previous studies have demonstrated that iptakalim's endothelium protection is related to activation of SUR2B/Kir6.1 subtype of ATP sensitive potassium channel(K ATP) in the endothelium.It has been reported that SUR2B/Kir6.1 channels are widely distributed in the tubular epithelium,glomerular mesangium,and the endothelium and the smooth muscle of blood vessels.Herein,we hypothesized that activating renal K ATP channels with iptakalim might have directly neroprotective effects.In this study,glomerular endothelial,mesangial and tubular epithelial cells which are the main cell types to form nephron were exposed to oleic acid(OA) at various concentrations for 24 h.0.25 μl/ml OA could cause cellular damage of glomerular endothelium and mesangium,while 1.25μl/ml OA could lead to the injury of three types of renal cells.It was observed that pretreatment with iptakalim at concentrations of 0.1,1,10 or 100 μmol/L prevented cellular damage of glomerular endothelium and tubular epithelium,whereas iptakalim from 1 to 100 μmol/L prevented the injury of mesangial cells.Our data showed iptakalim significantly increased survived cell rates in a concentration-dependent manner,significantly antagonized by glibenclamide,a K ATP blocker.Iptakalim played a protective role in the main cell types of kidney,which was consistent with natakalim,a highly selective SUR2B/Kir6.1 channel opener.Iptakalim exerted protective effects through activating SUR2B/Kir6.1 channels,suggesting a new strategy for renal injury by its endothelial and renal cell protection.
基金Supported by the Program of the network-type joint Usage/Research Center for Radiation Disaster Medical Science of Hiroshima University,Nagasaki University,and Fukushima Medical University
文摘BACKGROUND ATP-sensitive K^+(KATP)channels were originally found in cardiac myocytes by Noma in 1983.KATP channels were formed by potassium ion-passing poreforming subunits(Kir6.1,Kir6.2)and regulatory subunits SUR1,SU2A and SUR2B.A number of cells and tissues have been revealed to contain these channels including hepatocytes,but detailed localization of these subunits in different types of liver cells was still uncertain.AIM To investigate the expression of KATP channel subunits in rat liver and their localization in different cells of the liver.METHODS Rabbit anti-rat SUR1 peptide antibody was raised and purified by antigen immunoaffinity column chromatography.Four of Sprague-Dawley rats were used for liver protein extraction for immunoblot analysis,seven of them were used for immunohistochemistry both for the ABC method and immunofluorescence staining.Four of Wistar rats were used for the isolation of hepatic stellate cells(HSCs)and Kupffer cells for both primary culture and immunocytochemistry.RESULTS Immunoblot analysis showed that the five kinds of KATP channel subunits,i.e.Kir6.1,Kir6.2,SUR1,SUR2A,and SUR2B,were detected in liver.Immunohistochemical staining showed that Kir6.1 and Kir6.2 were weakly to moderately expressed in parenchymal cells and sinusoidal lining cells,while SUR1,SUR2A,and SUR2B were mainly localized to sinusoidal lining cells,such as HSCs,Kupffer cells,and sinusoidal endothelial cells.Immunoreactivity for SUR2A and SUR2B was expressed in the hepatocyte membrane.Double immunofluorescence staining further showed that the pore-forming subunits Kir6.1 and/or Kir6.2 colocalized with GFAP in rat liver sections and primary cultured HSCs.These KATP channel subunits also colocalized with CD68 in liver sections and primary cultured Kupffer cells.The SUR subunits colocalized with GFAP in liver sections and colocalized with CD68 both in liver sections and primary cultured Kupffer cells.In addition,five KATP channel subunits colocalized with SE-1 in sinusoidal endothelial cells.CONCLUSION Observations from the present study indicated that KATP channel subunits expressed in rat liver and the diversity of KATP channel subunit composition might form different types of KATP channels.This is applicable to hepatocytes,HSCs,various types of Kupffer cells and sinusoidal endothelial cells.
