- Protein phosphorylation maintains the normal function of cloned human Cav2.3 channels. [Journal Article]
- JGJ Gen Physiol 2018 Feb 16
- R-type currents mediated by native and recombinant Cav2.3 voltage-gated Ca2+channels (VGCCs) exhibit facilitation (run-up) and subsequent decline (run-down) in whole-cell patch-clamp recordings. A be...
R-type currents mediated by native and recombinant Cav2.3 voltage-gated Ca2+channels (VGCCs) exhibit facilitation (run-up) and subsequent decline (run-down) in whole-cell patch-clamp recordings. A better understanding of the two processes could provide insight into constitutive modulation of the channels in intact cells, but low expression levels and the need for pharmacological isolation have prevented investigations in native systems. Here, to circumvent these limitations, we use conventional and perforated-patch-clamp recordings in a recombinant expression system, which allows us to study the effects of cell dialysis in a reproducible manner. We show that the decline of currents carried by human Cav2.3+β3channel subunits during run-down is related to adenosine triphosphate (ATP) depletion, which reduces the number of functional channels and leads to a progressive shift of voltage-dependent gating to more negative potentials. Both effects can be counteracted by hydrolysable ATP, whose protective action is almost completely prevented by inhibition of serine/threonine but not tyrosine or lipid kinases. Protein kinase inhibition also mimics the effects of run-down in intact cells, reduces the peak current density, and hyperpolarizes the voltage dependence of gating. Together, our findings indicate that ATP promotes phosphorylation of either the channel or an associated protein, whereas dephosphorylation during cell dialysis results in run-down. These data also distinguish the effects of ATP on Cav2.3 channels from those on other VGCCs because neither direct nucleotide binding nor PIP2synthesis is required for protection from run-down. We conclude that protein phosphorylation is required for Cav2.3 channel function and could directly influence the normal features of current carried by these channels. Curiously, some of our findings also point to a role for leupeptin-sensitive proteases in run-up and possibly ATP protection from run-down. As such, the present study provides a reliable baseline for further studies on Cav2.3 channel regulation by protein kinases, phosphatases, and possibly proteases.
- Emerging concepts in diagnosis and treatment of syncope by pacing. [Review]
- TCTrends Cardiovasc Med 2018 Feb 13
- Neuroendocrine syncope is a newly proposed term to embody both syncope of reflex and adenosine-related etiology. Recent publications on tilt testing have revealed the presence of a hypotensive tenden...
Neuroendocrine syncope is a newly proposed term to embody both syncope of reflex and adenosine-related etiology. Recent publications on tilt testing have revealed the presence of a hypotensive tendency in some patients, even in the face of severe cardioinhibition. This new understanding may allow better selection of older reflex syncope patients, documented by ECG loop recorder, for successful pacing where tilt testing is ideally negative for a good result in terms of few syncope recurrences and prompts a less aggressive management policy when hypotensive medication is required. Furthermore, plasma adenosine levels not only define a new group of patients who have low adenosine and will respond well to cardiac pacing but also, by assessing adenosine receptor affinity, offer a possible explanation for vasodepression accompanying severe cardioinhibition. The question of the timing of loss of consciousness in reflex syncope needs to be addressed because, if consciousness is lost before asystole, pacing is likely to be ineffective.
- Impaired cerebral microcirculation induced by ammonium chloride in rats is due to cortical adenosine release. [Journal Article]
- JHJ Hepatol 2018 Feb 13
- CONCLUSIONS: Vasodilatation of the cerebral microcirculation during exposure to ammonium chloride is associated with an increase in the adenosine tone. Application of a specific adenosine receptor antagonist restores the regulation of the microcirculation. This indicates that adenosine could be a key mediator in the brain dysfunction seen during hyperammonemia and represents a potential therapeutic target.
- Glycyrrhizin attenuates histamine-mediated MUC5AC upregulation, inflammatory cytokine production, and aquaporin 5 downregulation through suppressing the NF-κB pathway in human nasal epithelial cells. [Journal Article]
- CBChem Biol Interact 2018 Feb 13
- Allergic rhinitis (AR) is a chronic respiratory inflammatory disease. Glycyrrhizin is a main bioactive component of the licorice root extract and exhibits anti-inflammatory activity. However, the rol...
Allergic rhinitis (AR) is a chronic respiratory inflammatory disease. Glycyrrhizin is a main bioactive component of the licorice root extract and exhibits anti-inflammatory activity. However, the role of glycyrrhizin in AR has not been studied. The aim of the present study was to investigate the effect of glycyrrhizin on histamine-induced human nasal epithelial cells (HNEpCs). Here, we found that glycyrrhizin (20 or 40 μM) inhibited histamine-induced the mRNA expression and secretion of mucin 5 subtype AC (MUC5AC), interleukin (IL)-6 and IL-8 in HNEpCs. The expression levels of aquaporin 5 (AQP5) and phosphorylated cyclic adenosine monophosphate-responsive element binding protein (p-CREB) were decreased by histamine in HNEpCs and increased in cells treated with glycyrrhizin. The glycyrrhizin treatment inhibited histamine-induced expressions of p-NF-κB p65 and p-IκBα in HNEpCs, indicating that glycyrrhizin inhibited the activation of NF-κB pathway in histamine-induced HNEpCs. In addition, inhibition of the NF-κB pathway exhibited the similar effect with glycyrrhizin on histamine-induced HNEpCs. In summary, the results showed that glycyrrhizin reversed the effect of histamine on MUC5AC expression, inflammatory cytokine production, and AQP5 expression in HNEpCs, and the NF-κB pathway was involved in the effect. Glycyrrhizin might be used for complementary and alternative therapeutics of AR.
- SIRT2 regulates oxidative stress-induced cell death through deacetylation of c-Jun NH2-terminal kinase. [Journal Article]
- CDCell Death Differ 2018 Feb 15
- c-Jun NH2-terminal kinases (JNKs) are responsive to stress stimuli and their activation regulate key cellular functions, including cell survival, growth, differentiation and aging. Previous studies d...
c-Jun NH2-terminal kinases (JNKs) are responsive to stress stimuli and their activation regulate key cellular functions, including cell survival, growth, differentiation and aging. Previous studies demonstrate that activation of JNK requires dual phosphorylation by the mitogen-activated protein kinase kinases. However, other post-translational mechanisms involved in regulating the activity of JNK have been poorly understood. In this work, we studied the functional significance of reversible lysine acetylation in regulating the kinase activity of JNK. We found that the acetyl transferase p300 binds to, acetylates and inhibits kinase activity of JNK. Using tandem mass spectrometry, molecular modelling and molecular dynamics simulations, we found that acetylation of JNK at Lys153 would hinder the stable interactions of the negatively charged phosphates and prevent the adenosine binding to JNK. Our screening for the deacetylases found SIRT2 as a deacetylase for JNK. Mechanistically, SIRT2-dependent deacetylation enhances ATP binding and enzymatic activity of JNK towards c-Jun. Furthermore, SIRT2-mediated deacetylation favours the phosphorylation of JNK by MKK4, an upstream kinase. Our results indicate that deacetylation of JNK by SIRT2 promotes oxidative stress-induced cell death. Conversely, SIRT2 inhibition attenuates H2O2-mediated cell death in HeLa cells. SIRT2-deficient (SIRT2-KO) mice exhibit increased acetylation of JNK, which is associated with markedly reduced catalytic activity of JNK in the liver. Interestingly, SIRT2-KO mice were resistant to acetaminophen-induced liver toxicity. SIRT2-KO mice show lower cell death, minimal degenerative changes, improved liver function and survival following acetaminophen treatment. Overall, our work identifies SIRT2-mediated deacetylation of JNK as a critical regulator of cell survival during oxidative stress.
- Impaired autophagic flux is associated with the severity of trauma and the role of A2AR in brain cells after traumatic brain injury. [Journal Article]
- CDCell Death Dis 2018 Feb 14; 9(2):252
- Recent studies have shown that after traumatic brain injury (TBI), the number of autophagosomes is markedly increased in brain cells surrounding the wound; however, whether autophagy is enhanced or s...
Recent studies have shown that after traumatic brain injury (TBI), the number of autophagosomes is markedly increased in brain cells surrounding the wound; however, whether autophagy is enhanced or suppressed by TBI remains controversial. In our study, we used a controlled cortical impact system to establish models of mild, moderate and severe TBI. In the mild TBI model, the levels of autophagy-related protein 6 (Beclin1) and autophagy-related protein 12 (ATG12)-autophagy-related protein 5 (ATG5) conjugates were increased, indicating the enhanced initiation of autophagy. Furthermore, the level of the autophagic substrate sequestosome 1 (SQSTM1) was decreased in the ipsilateral cortex. This result, together with the results observed in tandem mRFP-GFP-LC3 adeno-associated virus (AAV)-infected mice, indicates that autophagosome clearance was also increased after mild TBI. Conversely, following moderate and severe TBI, there was no change in the initiation of autophagy, and autophagosome accumulation was observed. Next, we used chloroquine (CQ) to artificially impair autophagic flux in the injured cortex of the mild TBI model and found that the severity of trauma was obviously exacerbated. In addition, autophagic flux and trauma severity were significantly improved in adenosine A2Areceptor (A2AR) knockout (KO) mice subjected to moderate TBI. Thus, A2AR may be involved in regulating the impairment of autophagic flux in response to brain injury. Our findings suggest that whether autophagy is increased after TBI is associated with whether autophagic flux is impaired, and the impairment of autophagic flux exacerbates the severity of trauma. Furthermore, A2AR may be a target for alleviating the impairment in autophagic flux after TBI.
- Quantitative Flow Ratio Identifies Nonculprit Coronary Lesions Requiring Revascularization in Patients With ST-Segment-Elevation Myocardial Infarction and Multivessel Disease. [Journal Article]
- CCCirc Cardiovasc Interv 2018; 11(2):e006023
- CONCLUSIONS: In a limited and selected study population, our study showed that QFR computation may be a safe and reliable tool to guide coronary revascularization of NCLs in ST-segment-elevation myocardial infarction patients.
- Evaluating the Effect of Six Proton Pump Inhibitors on the Antiplatelet Effects of Clopidogrel. [Journal Article]
- JSJ Stroke Cerebrovasc Dis 2018 Feb 12
- CONCLUSIONS: These data do not demonstrate a significant interaction between common individual PPIs and clopidogrel in healthy volunteers who respond to clopidogrel alone. This adds data to a growing body of evidence indicating that the addition of a PPI may have a weak effect on clopidogrel's antiplatelet properties, and may only be relevant in specific clinical circumstances.
- Characterization of a SUPERMAN-like Gene, MdSUP11, in apple (Malus × domestica Borkh.). [Journal Article]
- PPPlant Physiol Biochem 2017 Dec 06; 125:136-142
- Arabidopsis SUPERMAN and its family members of its family play important roles in plant growth and floral organ development; yet much less is known about their functions expanding in apple tree devel...
Arabidopsis SUPERMAN and its family members of its family play important roles in plant growth and floral organ development; yet much less is known about their functions expanding in apple tree development. Previous work has identified 12 SUP-like genes in the apple (Malus × domestica Borkh.) genome, and the MdSUP11 which is expressed in both vegetative and reproductive organs of apple. However, the function of MdSUP11 remains obscure. In this study, the β-glucuronidase expression driven by the MdSUP11 native promoter was detected in roots, young leaves, and floral organs of transgenic Arabidopsis. In transgenic tobacco, overexpression of MdSUP11 lead to dwarfism, aberrant leaf shapes, and morphological changes of floral organs. Endogenous concentrations of auxin (indole-3-acetic acid), abscisic acid, isopentenyl adenosine and zeatin riboside were significantly higher in young MdSUP11-transformed tobacco plants than in non-transformed plants. Gene expression analysis using real-time quantitative PCR showed up-regulation of NtDFR2 and NtANS1 expression in unopened transgenic flowers, whereas NtCHS expression was not changed significantly. Together, these results suggest that MdSUP11 is associated with apple's vegetative and reproductive development. Its overexpression in tobacco affects leaf and flower organ development and plant height; potentially by changing NtDFR2 and NtANS1 expression and endogenous levels of indole-3-acetic acid, cytokinins and abscisic acid.
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- Evidence and prospective of plant derived flavonoids as antiplatelet agents: Strong candidates to be drugs of future. [Journal Article]
- FCFood Chem Toxicol 2018 Feb 12
- Platelets are involved in hemostasis, inflammation, and thrombosis processes. Following a vascular damage, the endothelium releases protein factors, allowing the adhesion of subendothelium to platele...
Platelets are involved in hemostasis, inflammation, and thrombosis processes. Following a vascular damage, the endothelium releases protein factors, allowing the adhesion of subendothelium to platelets. Then platelets are activated, leading to the secretion of biologically-active ligands including thromboxane A2, adenosine diphosphate and serotonin. Aspirin, clopidogrel and warfarin are the most common drugs used to meet the challenges of platelet aggregation. However, these agents face issues with aspirin resistance and bleeding. New therapeutically effective and safe agents are therefore strongly needed, and natural substances could be ideal candidates. Flavonoids, a chemically diverse group of polyphenols, might be important in this regard. Consumption of flavonoids is responsible for several health-promoting properties. A number of flavonoids have shown outstanding preclinical antiplatelet effects through various mechanisms. Flavonoids could provide an ideal approach as templates for new, clinically-effective and safe antiplatelet agents due to their inherent safety and multiple useful pharmacological hits. This review aims to report data from literature regarding flavonoids with antiplatelet activity, with a particular focus on possible mechanisms of action, pharmacokinetic profiles and overall safety, thus providing a strong rationale for the design of selective and well-directed antiplatelet agents of natural origin.