The translationally-controlled tumor protein (TCTP) is a highly conserved, ubiquitously expressed... more The translationally-controlled tumor protein (TCTP) is a highly conserved, ubiquitously expressed, abundant protein that is broadly distributed among eukaryotes. Its biological function spans numerous cellular processes ranging from regulation of the cell cycle and microtubule stabilization to cell growth, transformation, and death processes. In this work, we propose a new function for TCTP as a "buffer protein" controlling cellular homeostasis. We demonstrate that binding of hemin to TCTP is mediated by a conserved His-containing motif (His76His77) followed by dimerization, an event that involves ligand-mediated conformational changes and that is necessary to trigger TCTP's cytokine-like activity. Mutation in both His residues to Ala prevents hemin from binding and abrogates oligomerization, suggesting that the ligand site localizes at the interface of the oligomer. Unlike heme, binding of Ca2+ ligand to TCTP does not alter its monomeric state; although, Ca2+ is able ...
International journal of clinical and experimental pathology, 2014
Growing evidence demonstrates that long non coding RNAs (lncRNAs) play an important role in cance... more Growing evidence demonstrates that long non coding RNAs (lncRNAs) play an important role in cancer origination and progression. A novel lncRNA, TSLC1-AS1, is the antisense transcript of tumor suppressor TSLC1. The expression profile and function of TSLC1-AS1 in glioma were investigated using Real-Time Quantitative PCR and siRNA knockdown. The data showed that TSLC1-AS1 expression was down-regulated in tumor tissues compared with that in adjacent normal tissues, and negatively associated with the WHO criteria of the tumors. Overexpression of TSLC1-AS1 resulted in up-regulation of TSLC1 and significant inhibition of cell proliferation, migration and invasion in U87 cells, while knockdown of TSLC1-AS1 in SNB-19 cells showed the opposite effect. The expression of TSLC1-AS1 was also positively correlated with other tumor suppressors NF1, VHL, PIK3R1 and negatively correlated with the oncogene BRAF. The results suggested that TSLC1-AS1 was a tumor suppressor of glioma and a mediator of TS...
European journal of paediatric neurology : EJPN : official journal of the European Paediatric Neurology Society, 2014
To compare outcomes of anterior corpus callosotomy (CCT) with anti-epileptic drugs (AEDs) treatme... more To compare outcomes of anterior corpus callosotomy (CCT) with anti-epileptic drugs (AEDs) treatment in school-aged children with Lennox-Gastaut syndrome (LGS). Sixty school-aged children with LGS were prospectively enrolled and divided into either the medicine or surgery group according the choice of the patients' caregivers. Cases in the medicine group were treated with multiple rational AEDs and patients in the surgery group underwent anterior CCT. Seizure control at 1-5 years after enrollment and changes of intelligence quotient (IQ) and quality of life (QOL) from pre-treatment to the 2-year follow-up were compared between the two groups. The percentages of patients who were totally seizure-free in the surgery group were 17.4% at the 1-year follow-up, 13.0% at the 2-year follow-up and 8.7% at the 5-year follow up, and the data for patients in the medicine group were 2.9%, 5.9% and 2.9%, respectively. Significant differences were found in total seizure control between the two ...
Journal of Molecular and Cellular Cardiology, 2007
Reduction of nitrite to nitric oxide during ischemia protects the heart against injury from ische... more Reduction of nitrite to nitric oxide during ischemia protects the heart against injury from ischemia/reperfusion. However the optimal dose of nitrite and the mechanisms underlying nitrite-induced cardioprotection are not known. We determined the ability of nitrite and nitrate to confer protection against myocardial infarction in two rat models of ischemia/reperfusion injury and the role of xanthine oxidoreductase, NADPH oxidase, nitric
Journal of Molecular and Cellular Cardiology, 2008
The lanthanide cation, gadolinium (Gd) attenuates post-ischemic myocardial stunning. This study t... more The lanthanide cation, gadolinium (Gd) attenuates post-ischemic myocardial stunning. This study tests the hypothesis that Gd also preconditions the myocardium against infarction following ischemia-reperfusion (IR), and explores potential mechanisms underlying Gd-induced cardioprotection. Regional myocardial infarction was induced in rats by occluding the left anterior descending artery for 30 minutes and reperfusing for 120 minutes. Rats (n = 6/group) were administered intravenous Gd (1 to 100 μmol/kg) 15 minutes prior to ischemia. Hearts were excised after reperfusion to determine infarct size (IS) and area at risk (AAR). The ratio IS/AAR (%) was reduced by Gd in a "U"-shaped, dose-dependent manner. The minimum dose that reduced IS/AAR was 5 μmol/kg (52 ± 5% vs. 64 ± 4%), while the dose that reduced IS/AAR maximally was 20 μmol/ kg (44 ± 4%). Gd also reduced IS/AAR when given 1 minute before reperfusion (47 ± 3%) but not when given 10 seconds after reperfusion (60 ± 3%). Cardioprotection was maintained if I-R was delayed 24-72 hours after Gd administration. Cardioprotection by Gd was abolished by inhibition of JAK-2 with AG-490, of p42/44 MAPK with PD98059 or of K ATP channels with glibenclamide. None of these agents given alone altered IS/AAR compared with controls. Inhibition of JAK-2 also blocked Gd-induced delayed cardioprotection. Gd may have broad potential roles in IR, as it confered immediate cardioprotection when given prior to ischemia or prior to reperfusion, and delayed cardioprotection for up to 72 hours after administration. The mechanism underlying Gd-induced preconditioning appears to be multi-factorial, involving JAK-2, STAT-3 and p44 MAPK pathways, as well as K ATP channels.
In recent years, cationic polymeric magnetic liposomes have shown greater stability and prolonged... more In recent years, cationic polymeric magnetic liposomes have shown greater stability and prolonged circulation half-life over traditional liposomes. Here, we examined the capability of cationic polymeric magnetic liposomes in delivering drugs into the brain under magnetic targeting with paclitaxel as the loaded agent. We found that the fabricated paclitaxel-loaded magnetic liposomes had a uniform diameter of 20 nm and were superparamagnetic. After they were injected into rats by the caudal vein, brain paclitaxel concentration increased 2-5 folds without magnetic targeting and 5-15 folds after magnetic targeting. The high brain concentration was maintained for more than 8 h, which was significantly longer than that for pure paclitaxel injection. When the liposomes were given via the internal carotid artery at 10% of the dose given via the caudal vein, paclitaxel in the brain was increased by 1.5 folds, indicating that intra-arterial administration enhanced delivery efficiency remarkably. Prussian blue staining of the cortex showed that the magnetic liposomes were aggregated in the cortex vasculature and the cortex cells were under magnetic targeting, indicating that the drugs were delivered across the nearly impermeable blood-brain barrier. These results showed that the nano-sized cationic polymeric magnetic liposomes are potential tools for magnetic drug delivery to the brain.
Erythropoietin is known to stimulate red cell production and has recently been shown to protect t... more Erythropoietin is known to stimulate red cell production and has recently been shown to protect the heart against injury from ischemia/reperfusion. However, it is unknown whether darbepoetin alfa (Dpa), a long-acting analog of erythropoietin, can play a protective role against myocardial infarction. We assessed the potential protective role of Dpa in an in vivo rat model of myocardial ischemia/reperfusion and the underlying mechanisms. We found that a single intravenous Dpa treatment immediately before 30 minutes of regional ischemia reduced myocardial necrosis following 120 minutes of reperfusion in a dose-dependent manner. Optimal protection with Dpa against myocardial infarction was manifest at a dose of 2.5 microg/kg. Dpa conferred cardioprotection when administered after the onset of ischemia and at the start of reperfusion. Dpa (2.5 microg/kg) also reduced infarct size and Troponin I leakage 24 hours after reperfusion. Inhibition of p42/44 MAPK (PD98059), p38 MAPK (SB203580), mitochondrial ATP-dependent potassium (KATP) channels (5-HD), sarcolemmal KATP channels (HMR 1098), but not phosphatidylinositol-3 (PI3) kinase/Akt (Wortmannin and LY 294002) abolished Dpa-induced cardioprotection. Dpa confers immediate and sustained cardioprotection in rats, suggesting a potential therapeutic role of this long-acting erythropoietin analog for the treatment of acute myocardial infarction.
Disabled-2 (Dab2) targets membranes and triggers a wide range of biological events, including end... more Disabled-2 (Dab2) targets membranes and triggers a wide range of biological events, including endocytosis and platelet aggregation. Dab2, through its phosphotyrosine-binding (PTB) domain, inhibits platelet aggregation by competing with fibrinogen for α(IIb)β(3) integrin receptor binding. We have recently shown that the N-terminal region, including the PTB domain (N-PTB), drives Dab2 to the platelet membrane surface by binding to sulfatides through two sulfatide-binding motifs, modulating the extent of platelet aggregation. The three-dimensional structure of a Dab2-derived peptide encompassing the sulfatide-binding motifs has been determined in dodecylphosphocholine micelles using NMR spectroscopy. Dab2 sulfatide-binding motif contains two helices when embedded in micelles, reversibly binds to sulfatides with moderate affinity, lies parallel to the micelle surface, and when added to a platelet mixture, reduces the number and size of sulfatide-induced aggregates. Overall, our findings identify and structurally characterize a minimal region in Dab2 that modulates platelet homotypic interactions, all of which provide the foundation for rational design of a new generation of anti-aggregatory low-molecular mass molecules for therapeutic purposes.
Magnetic drug carrier has been employed in drug delivery for over 30 years. Modern nanotechnology... more Magnetic drug carrier has been employed in drug delivery for over 30 years. Modern nanotechnology has improved its efficiency dramatically by decreasing its diameter into nano-scale. It may help chemotherapeutic agents penetrate BBB and raise local drug concentration in brain, which is the ideal model for glioma treatment. In our study, magnetic carrier was fabricated with octadecyl quaternized caroxymethyl chitosan (OQCMC), hydrophobic Fe₃O₄ ferrofluid and cholesterol, which showed a uniform diameter of 20 nm under transmission electronic microscopy and superparamagnetic character in vibration sample magnetical measurement system. To investigate the efficacy of drug delivery, paclitaxel was used as loaded drug and analyzed by the HPLC. Results showed that magnetic carrier released drugs for more than 20 d in vitro and maintain the drug concentration above 0.4 μg/g for 16 h in rat brain after magnetic targeting. Drug concentration increased by 1-3 folds when delivered by carrier without magnetic targeting, and by 3-15 folds after magnetic targeting. Cellular study revealed that the magnetic carrier was clearly localized in the targeted cortex neural cells and U251-MG cell lines. These results showed that this magnetic carrier is capable of maintaining high drug concentration in magnetically targeted area and carrying drugs or genes into cells, which is potentially promising for local chemotherapy to brain tumors.
Aims-Thrombopoietin (Tpo) is known for its ability to stimulate platelet production. However, it ... more Aims-Thrombopoietin (Tpo) is known for its ability to stimulate platelet production. However, it is currently unknown whether Tpo plays a physiological function in the heart.
■ Abstract Myocardial ischemia/reperfusion (I/R) injury is partly mediated by thrombin. In suppor... more ■ Abstract Myocardial ischemia/reperfusion (I/R) injury is partly mediated by thrombin. In support, the functional inhibition of thrombin has been shown to decrease infarct size after I/R. Several cellular responses to thrombin are mediated by a G-protein coupled protease-activated receptor 1 (PAR1). However, the role of PAR1 in myocardial I/R injury has not been well characterized. Therefore, we hypothesized that PAR1 inhibition will reduce the amount of myocardial I/R injury.After we detected the presence of PAR1 mRNA and protein in the rat heart by RT-PCR and immunoblot analysis, we assessed the potential protective role of SCH 79797, a selective PAR1 antagonist, in two rat models of myocardial I/R injury. SCH 79797 treatment immediately before or during ischemia reduced myocardial necrosis following I/R in the intact rat heart. This response was dose-dependent with the optimal dose being 25 μg/kg IV. Likewise, SCH 79797 treatment before ischemia in the isolated heart model reduced infarct size and increased ventricular recovery following I/R in the isolated heart model with an optimal concentration of 1 μM. This reduction was abolished by a PAR1 selective agonist. SCH 79797-induced resistance to myocardial ischemia was abolished by wortmannin, an inhibitor of PI3 kinase; L-NMA, a NOS inhibitor; and glibenclamide, a nonselective K ATP channel blocker. PAR1 activating peptide, wortmannin, L-NMA and glibenclamide alone had no effect on functional recovery or infarct size. A single treatment of SCH 79797 administered prior to or during ischemia confers immediate cardioprotection suggesting a potential therapeutic role of PAR1 antagonist in the treatment of injury resulting from myocardial ischemia and reperfusion.
The Wnt-dependent, b-catenin-independent pathway modulates cell movement and behavior. A downstre... more The Wnt-dependent, b-catenin-independent pathway modulates cell movement and behavior. A downstream regulator of this signaling pathway is Dishevelled (Dvl), which, among other multiple interactions, binds to the Frizzled receptor and the plasma membrane via phosphatidic acid (PA) in a mechanism proposed to be pH-dependent. While the Dvl DEP domain is central to the b-catenin-independent Wnt signaling function, the mechanism underlying its physical interaction with the membrane remains elusive. In this report, we elucidate the structural and functional basis of PA association to the Dvl2 DEP domain. Nuclear magnetic resonance, molecular-dynamics simulations, and mutagenesis data indicated that the domain interacted with the phospholipid through the basic helix 3 and a contiguous loop with moderate affinity. The association suggested that PA binding promoted local conformational changes in helix 2 and b-strand 4, both of which are compromised to maintain a stable hydrophobic core in the DEP domain. We also show that the Dvl2 DEP domain bound PA in a pH-dependent manner in a mechanism that resembles deprotonation of PA. Collectively, our results structurally define the PA-binding properties of the Dvl2 DEP domain, which can be exploited for the investigation of binding mechanisms of other DEP domain-interacting proteins.
The translationally-controlled tumor protein (TCTP) is a highly conserved, ubiquitously expressed... more The translationally-controlled tumor protein (TCTP) is a highly conserved, ubiquitously expressed, abundant protein that is broadly distributed among eukaryotes. Its biological function spans numerous cellular processes ranging from regulation of the cell cycle and microtubule stabilization to cell growth, transformation, and death processes. In this work, we propose a new function for TCTP as a "buffer protein" controlling cellular homeostasis. We demonstrate that binding of hemin to TCTP is mediated by a conserved His-containing motif (His76His77) followed by dimerization, an event that involves ligand-mediated conformational changes and that is necessary to trigger TCTP's cytokine-like activity. Mutation in both His residues to Ala prevents hemin from binding and abrogates oligomerization, suggesting that the ligand site localizes at the interface of the oligomer. Unlike heme, binding of Ca2+ ligand to TCTP does not alter its monomeric state; although, Ca2+ is able ...
International journal of clinical and experimental pathology, 2014
Growing evidence demonstrates that long non coding RNAs (lncRNAs) play an important role in cance... more Growing evidence demonstrates that long non coding RNAs (lncRNAs) play an important role in cancer origination and progression. A novel lncRNA, TSLC1-AS1, is the antisense transcript of tumor suppressor TSLC1. The expression profile and function of TSLC1-AS1 in glioma were investigated using Real-Time Quantitative PCR and siRNA knockdown. The data showed that TSLC1-AS1 expression was down-regulated in tumor tissues compared with that in adjacent normal tissues, and negatively associated with the WHO criteria of the tumors. Overexpression of TSLC1-AS1 resulted in up-regulation of TSLC1 and significant inhibition of cell proliferation, migration and invasion in U87 cells, while knockdown of TSLC1-AS1 in SNB-19 cells showed the opposite effect. The expression of TSLC1-AS1 was also positively correlated with other tumor suppressors NF1, VHL, PIK3R1 and negatively correlated with the oncogene BRAF. The results suggested that TSLC1-AS1 was a tumor suppressor of glioma and a mediator of TS...
European journal of paediatric neurology : EJPN : official journal of the European Paediatric Neurology Society, 2014
To compare outcomes of anterior corpus callosotomy (CCT) with anti-epileptic drugs (AEDs) treatme... more To compare outcomes of anterior corpus callosotomy (CCT) with anti-epileptic drugs (AEDs) treatment in school-aged children with Lennox-Gastaut syndrome (LGS). Sixty school-aged children with LGS were prospectively enrolled and divided into either the medicine or surgery group according the choice of the patients' caregivers. Cases in the medicine group were treated with multiple rational AEDs and patients in the surgery group underwent anterior CCT. Seizure control at 1-5 years after enrollment and changes of intelligence quotient (IQ) and quality of life (QOL) from pre-treatment to the 2-year follow-up were compared between the two groups. The percentages of patients who were totally seizure-free in the surgery group were 17.4% at the 1-year follow-up, 13.0% at the 2-year follow-up and 8.7% at the 5-year follow up, and the data for patients in the medicine group were 2.9%, 5.9% and 2.9%, respectively. Significant differences were found in total seizure control between the two ...
Journal of Molecular and Cellular Cardiology, 2007
Reduction of nitrite to nitric oxide during ischemia protects the heart against injury from ische... more Reduction of nitrite to nitric oxide during ischemia protects the heart against injury from ischemia/reperfusion. However the optimal dose of nitrite and the mechanisms underlying nitrite-induced cardioprotection are not known. We determined the ability of nitrite and nitrate to confer protection against myocardial infarction in two rat models of ischemia/reperfusion injury and the role of xanthine oxidoreductase, NADPH oxidase, nitric
Journal of Molecular and Cellular Cardiology, 2008
The lanthanide cation, gadolinium (Gd) attenuates post-ischemic myocardial stunning. This study t... more The lanthanide cation, gadolinium (Gd) attenuates post-ischemic myocardial stunning. This study tests the hypothesis that Gd also preconditions the myocardium against infarction following ischemia-reperfusion (IR), and explores potential mechanisms underlying Gd-induced cardioprotection. Regional myocardial infarction was induced in rats by occluding the left anterior descending artery for 30 minutes and reperfusing for 120 minutes. Rats (n = 6/group) were administered intravenous Gd (1 to 100 μmol/kg) 15 minutes prior to ischemia. Hearts were excised after reperfusion to determine infarct size (IS) and area at risk (AAR). The ratio IS/AAR (%) was reduced by Gd in a "U"-shaped, dose-dependent manner. The minimum dose that reduced IS/AAR was 5 μmol/kg (52 ± 5% vs. 64 ± 4%), while the dose that reduced IS/AAR maximally was 20 μmol/ kg (44 ± 4%). Gd also reduced IS/AAR when given 1 minute before reperfusion (47 ± 3%) but not when given 10 seconds after reperfusion (60 ± 3%). Cardioprotection was maintained if I-R was delayed 24-72 hours after Gd administration. Cardioprotection by Gd was abolished by inhibition of JAK-2 with AG-490, of p42/44 MAPK with PD98059 or of K ATP channels with glibenclamide. None of these agents given alone altered IS/AAR compared with controls. Inhibition of JAK-2 also blocked Gd-induced delayed cardioprotection. Gd may have broad potential roles in IR, as it confered immediate cardioprotection when given prior to ischemia or prior to reperfusion, and delayed cardioprotection for up to 72 hours after administration. The mechanism underlying Gd-induced preconditioning appears to be multi-factorial, involving JAK-2, STAT-3 and p44 MAPK pathways, as well as K ATP channels.
In recent years, cationic polymeric magnetic liposomes have shown greater stability and prolonged... more In recent years, cationic polymeric magnetic liposomes have shown greater stability and prolonged circulation half-life over traditional liposomes. Here, we examined the capability of cationic polymeric magnetic liposomes in delivering drugs into the brain under magnetic targeting with paclitaxel as the loaded agent. We found that the fabricated paclitaxel-loaded magnetic liposomes had a uniform diameter of 20 nm and were superparamagnetic. After they were injected into rats by the caudal vein, brain paclitaxel concentration increased 2-5 folds without magnetic targeting and 5-15 folds after magnetic targeting. The high brain concentration was maintained for more than 8 h, which was significantly longer than that for pure paclitaxel injection. When the liposomes were given via the internal carotid artery at 10% of the dose given via the caudal vein, paclitaxel in the brain was increased by 1.5 folds, indicating that intra-arterial administration enhanced delivery efficiency remarkably. Prussian blue staining of the cortex showed that the magnetic liposomes were aggregated in the cortex vasculature and the cortex cells were under magnetic targeting, indicating that the drugs were delivered across the nearly impermeable blood-brain barrier. These results showed that the nano-sized cationic polymeric magnetic liposomes are potential tools for magnetic drug delivery to the brain.
Erythropoietin is known to stimulate red cell production and has recently been shown to protect t... more Erythropoietin is known to stimulate red cell production and has recently been shown to protect the heart against injury from ischemia/reperfusion. However, it is unknown whether darbepoetin alfa (Dpa), a long-acting analog of erythropoietin, can play a protective role against myocardial infarction. We assessed the potential protective role of Dpa in an in vivo rat model of myocardial ischemia/reperfusion and the underlying mechanisms. We found that a single intravenous Dpa treatment immediately before 30 minutes of regional ischemia reduced myocardial necrosis following 120 minutes of reperfusion in a dose-dependent manner. Optimal protection with Dpa against myocardial infarction was manifest at a dose of 2.5 microg/kg. Dpa conferred cardioprotection when administered after the onset of ischemia and at the start of reperfusion. Dpa (2.5 microg/kg) also reduced infarct size and Troponin I leakage 24 hours after reperfusion. Inhibition of p42/44 MAPK (PD98059), p38 MAPK (SB203580), mitochondrial ATP-dependent potassium (KATP) channels (5-HD), sarcolemmal KATP channels (HMR 1098), but not phosphatidylinositol-3 (PI3) kinase/Akt (Wortmannin and LY 294002) abolished Dpa-induced cardioprotection. Dpa confers immediate and sustained cardioprotection in rats, suggesting a potential therapeutic role of this long-acting erythropoietin analog for the treatment of acute myocardial infarction.
Disabled-2 (Dab2) targets membranes and triggers a wide range of biological events, including end... more Disabled-2 (Dab2) targets membranes and triggers a wide range of biological events, including endocytosis and platelet aggregation. Dab2, through its phosphotyrosine-binding (PTB) domain, inhibits platelet aggregation by competing with fibrinogen for α(IIb)β(3) integrin receptor binding. We have recently shown that the N-terminal region, including the PTB domain (N-PTB), drives Dab2 to the platelet membrane surface by binding to sulfatides through two sulfatide-binding motifs, modulating the extent of platelet aggregation. The three-dimensional structure of a Dab2-derived peptide encompassing the sulfatide-binding motifs has been determined in dodecylphosphocholine micelles using NMR spectroscopy. Dab2 sulfatide-binding motif contains two helices when embedded in micelles, reversibly binds to sulfatides with moderate affinity, lies parallel to the micelle surface, and when added to a platelet mixture, reduces the number and size of sulfatide-induced aggregates. Overall, our findings identify and structurally characterize a minimal region in Dab2 that modulates platelet homotypic interactions, all of which provide the foundation for rational design of a new generation of anti-aggregatory low-molecular mass molecules for therapeutic purposes.
Magnetic drug carrier has been employed in drug delivery for over 30 years. Modern nanotechnology... more Magnetic drug carrier has been employed in drug delivery for over 30 years. Modern nanotechnology has improved its efficiency dramatically by decreasing its diameter into nano-scale. It may help chemotherapeutic agents penetrate BBB and raise local drug concentration in brain, which is the ideal model for glioma treatment. In our study, magnetic carrier was fabricated with octadecyl quaternized caroxymethyl chitosan (OQCMC), hydrophobic Fe₃O₄ ferrofluid and cholesterol, which showed a uniform diameter of 20 nm under transmission electronic microscopy and superparamagnetic character in vibration sample magnetical measurement system. To investigate the efficacy of drug delivery, paclitaxel was used as loaded drug and analyzed by the HPLC. Results showed that magnetic carrier released drugs for more than 20 d in vitro and maintain the drug concentration above 0.4 μg/g for 16 h in rat brain after magnetic targeting. Drug concentration increased by 1-3 folds when delivered by carrier without magnetic targeting, and by 3-15 folds after magnetic targeting. Cellular study revealed that the magnetic carrier was clearly localized in the targeted cortex neural cells and U251-MG cell lines. These results showed that this magnetic carrier is capable of maintaining high drug concentration in magnetically targeted area and carrying drugs or genes into cells, which is potentially promising for local chemotherapy to brain tumors.
Aims-Thrombopoietin (Tpo) is known for its ability to stimulate platelet production. However, it ... more Aims-Thrombopoietin (Tpo) is known for its ability to stimulate platelet production. However, it is currently unknown whether Tpo plays a physiological function in the heart.
■ Abstract Myocardial ischemia/reperfusion (I/R) injury is partly mediated by thrombin. In suppor... more ■ Abstract Myocardial ischemia/reperfusion (I/R) injury is partly mediated by thrombin. In support, the functional inhibition of thrombin has been shown to decrease infarct size after I/R. Several cellular responses to thrombin are mediated by a G-protein coupled protease-activated receptor 1 (PAR1). However, the role of PAR1 in myocardial I/R injury has not been well characterized. Therefore, we hypothesized that PAR1 inhibition will reduce the amount of myocardial I/R injury.After we detected the presence of PAR1 mRNA and protein in the rat heart by RT-PCR and immunoblot analysis, we assessed the potential protective role of SCH 79797, a selective PAR1 antagonist, in two rat models of myocardial I/R injury. SCH 79797 treatment immediately before or during ischemia reduced myocardial necrosis following I/R in the intact rat heart. This response was dose-dependent with the optimal dose being 25 μg/kg IV. Likewise, SCH 79797 treatment before ischemia in the isolated heart model reduced infarct size and increased ventricular recovery following I/R in the isolated heart model with an optimal concentration of 1 μM. This reduction was abolished by a PAR1 selective agonist. SCH 79797-induced resistance to myocardial ischemia was abolished by wortmannin, an inhibitor of PI3 kinase; L-NMA, a NOS inhibitor; and glibenclamide, a nonselective K ATP channel blocker. PAR1 activating peptide, wortmannin, L-NMA and glibenclamide alone had no effect on functional recovery or infarct size. A single treatment of SCH 79797 administered prior to or during ischemia confers immediate cardioprotection suggesting a potential therapeutic role of PAR1 antagonist in the treatment of injury resulting from myocardial ischemia and reperfusion.
The Wnt-dependent, b-catenin-independent pathway modulates cell movement and behavior. A downstre... more The Wnt-dependent, b-catenin-independent pathway modulates cell movement and behavior. A downstream regulator of this signaling pathway is Dishevelled (Dvl), which, among other multiple interactions, binds to the Frizzled receptor and the plasma membrane via phosphatidic acid (PA) in a mechanism proposed to be pH-dependent. While the Dvl DEP domain is central to the b-catenin-independent Wnt signaling function, the mechanism underlying its physical interaction with the membrane remains elusive. In this report, we elucidate the structural and functional basis of PA association to the Dvl2 DEP domain. Nuclear magnetic resonance, molecular-dynamics simulations, and mutagenesis data indicated that the domain interacted with the phospholipid through the basic helix 3 and a contiguous loop with moderate affinity. The association suggested that PA binding promoted local conformational changes in helix 2 and b-strand 4, both of which are compromised to maintain a stable hydrophobic core in the DEP domain. We also show that the Dvl2 DEP domain bound PA in a pH-dependent manner in a mechanism that resembles deprotonation of PA. Collectively, our results structurally define the PA-binding properties of the Dvl2 DEP domain, which can be exploited for the investigation of binding mechanisms of other DEP domain-interacting proteins.
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