Effects of Phenylacetylglutamine on the Susceptibility of Atrial Fibrillation in Overpressure-Induced HF Mice.

Phenylacetylglutamine (PAGln), a gut metabolite is substantially elevated in heart failure (HF). The increase of PAGln in plasma is associated with atrial fibrillation (AF), and contributes to AF pathogenesis. However, the role of PAGln in AF with HF remains uncertain. Therefore, this study aimed to determine the effect of PAGln on AF after HF. Thoracic aortic coarctation (TAC) created overpressure-induced HF mice for 4 weeks. Histopathology, biochemical, echocardiographic for assessment of cardiac function, and electrophysiological examination of several electrophysiological indexes (ERP, SNRT, and the occurrence rate of AF) were performed at the end of the HF mice model. We found that plasma PAGln levels were significantly elevated in PAGln-treated HF mice and that PAGln aggravated maladaptive structural remodeling and electrical remodeling, which aggravated the vulnerability of AF, shortened the ERP duration, prolonged the SNRT, increased the occurrence rate of AF in HF mice. Mechanistically, PAGln exacerbated ROS accumulation and increased the levels of phosphorylated PLB and CAMK II. Overall, PAGln played a vital role in promoting the occurrence of AF in HF mice by activating the CAMK II signaling pathway.

Neuroprotective Effect of Solid Lipid Nanoparticles Loaded with Lepidium sativum (L.) Seed Bioactive Components Enhance Bioavailability and Wnt/ß-Catenin/Camk-II Signaling Cascade in SH-SY5Y Neuroblastoma Cells.

The primary pathological hallmark of Alzheimer's disease (AD) is the formation and accumulation of neurofibrillary tangles and plaques, which result from the aggregation of amyloid-ß (Aß) induced by oxidative stress. The effectiveness of Alzheimer's disease (AD) therapeutics significantly hinges on the drug's bioavailability and its ability to penetrate neuronal cells. The current investigation was designed as a first attempt to examine bio-fabricated Lepidium sativum (LS) seed-extract-loaded solid lipid nanoparticles (SLNps) to increase bioavailability and bioefficacy for the prevention of undifferentiated SH-SY5Y neuronal cells from oxidative stress induced by H2O2 and amyloid-ß peptide (Aß,1-42). The SLNps were fabricated using LS extract as a water phase and hyaluronic acid and chia seed fatty acids as a lipid phase, then confirmed and characterized using UV, Zeta size, and SEM methods. The biological safety of synthesized LS-SLNps has been determined using MTT assay and PI staining (nuclear damage) in hMSCs. LS-SLNp-pretreated neuronal cells were induced with oxidative stress and 2 µM of beta-amyloid (Aß,1-42) fibrils; furthermore, the neuroprotective potential of LS-SLNps was determined through the quenching of oxidative stress, enhancing mitochondrial oxidative capacity, and immunoregulatory potential. Observations found that cells treated with both H2O2 and beta-amyloid (Aß,1-42) fibrils showed decreased neuronal cell growth, nuclear damage, and mitochondrial membrane potential due to oxidative stress. However, SH-SY5Y cells pretreated with LS-SLNps for 24 h showed an increase in cell proliferation with uniform morphology and increased mitochondrial membrane potential compared to cells pretreated with LS alone. Gene expression analysis found that LS-SLNps increased the expression of Wnt 3a and 5a, which stimulated the canonical, ß-catenin, and non-canonical Camk-II expressions of nerve cell growth factors, confirming the molecular-level reversal of neurodegenerative diseases.

Vitamin D, Calbindin, and calcium signaling: Unraveling the Alzheimer's connection.

Calcium is a ubiquitous second messenger that is indispensable in regulating neurotransmission and memory formation. A precise intracellular calcium level is achieved through the concerted action of calcium channels, and calcium exerts its effect by binding to an array of calcium-binding proteins, including calmodulin (CAM), calcium-calmodulin complex-dependent protein kinase-II (CAMK-II), calbindin (CAL), and calcineurin (CAN). Calbindin orchestrates a plethora of signaling events that regulate synaptic transmission and depolarizing signals. Vitamin D, an endogenous fat-soluble metabolite, is synthesized in the skin upon exposure to ultraviolet B radiation. It modulates calcium signaling by increasing the expression of the calcium-sensing receptor (CaSR), stimulating phospholipase C activity, and regulating the expression of calcium channels such as TRPV6. Vitamin D also modulates the activity of calcium-binding proteins, including CAM and calbindin, and increases their expression. Calbindin, a high-affinity calcium-binding protein, is involved in calcium buffering and transport in neurons. It has been shown to inhibit apoptosis and caspase-3 activity stimulated by presenilin 1 and 2 in AD. Whereas CAM, another calcium-binding protein, is implicated in regulating neurotransmitter release and memory formation by phosphorylating CAN, CAMK-II, and other calcium-regulated proteins. CAMK-II and CAN regulate actin-induced spine shape changes, which are further modulated by CAM. Low levels of both calbindin and vitamin D are attributed to the pathology of Alzheimer's disease. Further research on vitamin D via calbindin-CAMK-II signaling may provide newer insights, revealing novel therapeutic targets and strategies for treatment.

Electroacupuncture attenuates ketamine-induced neuronal injury in the locus coeruleus of rats through modulation of the CAMK II/CREB pathway.

BACKGROUND: Ketamine, despite its efficacy in treating depression, raises concerns regarding safety due to potential abuse, cognitive impairment, and bladder toxicity. Ketamine can affect the locus coeruleus (LC) norepinephrine and attention networks. This study explored the protective effects of electroacupuncture (EA) on the LC of rats exposed to repeated administration of ketamine while investigating the potential role of the Calcium CaM-dependent protein kinase II (CAMK II)/ cAMP response element binding protein (CREB) pathway in mediating EA's impact on ketamine-induced neuronal injury in LC. METHODS: Rats were repeatedly injected intraperitoneally with ketamine hydrochloride (50 mg/kg) once daily for seven days. Subsequently, EA was performed at the acupoints "Zusanli" (ST36) and "Sanyinjiao" (SP-6) once daily following ketamine administration. The Morris water maze test was employed to assess behavioral changes in the rats. Neuronal injury was examined using Nissl staining, and the expression of CAMK II, CREB, and phospho-CREB (p-CREB) was evaluated through immunohistochemistry and western blotting. RESULTS: EA mitigated the cognitive and exploratory impairments and attenuated neuronal injury in the LC induced by repeated administration of ketamine. The expression of CAMK II and p-CREB proteins in the LC increased following 7 days of ketamine administration. However, EA treatment led to a downregulation of CAMK II and p-CREB expression. CONCLUSION: Repeated administration of ketamine in male rats can lead to neuronal injury and neurobehavioral dysfunction. However, EA was found to ameliorate neurodegeneration in the LC and enhance neurobehavioral symptoms. This therapeutic effect of EA may be attributed to its modulation of the CAMKII/CREB pathway, thereby mitigating the aforementioned adverse effects.

Receptor-interacting protein 3-phosphorylated Ca2+ /calmodulin-dependent protein kinase II and mixed lineage kinase domain-like protein mediate intracerebral hemorrhage-induced neuronal necroptosis.

Necroptosis-mediated cell death is an important mechanism in intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI). Our previous study has demonstrated that receptor-interacting protein 1 (RIP1) mediated necroptosis in SBI after ICH. However, further mechanisms, such as the roles of receptor-interacting protein 3 (RIP3), mixed lineage kinase domain-like protein (MLKL), and Ca2+ /calmodulin-dependent protein kinase II (CaMK II), remain unclear. We hypothesized that RIP3, MLKL, and CaMK II might participate in necroptosis after ICH, including their phosphorylation. The ICH model was induced by autologous blood injection. First, we found the activation of necroptosis after ICH in brain tissues surrounding the hematoma (propidium iodide staining). Meanwhile, the phosphorylation and expression of RIP3, MLKL, and CaMK II were differently up-regulated (western blotting and immunofluorescent staining). The specific inhibitors could suppress RIP3, MLKL, and CaMK II (GSK'872 for RIP3, necrosulfonamide for MLKL, and KN-93 for CaMK II). We found the necroptosis surrounding the hematoma and the concrete interactions in RIP3-MLKL/RIP3-CaMK II also both decreased after the specific intervention (co-immunoprecipitation). Then we conducted the short-/long-term neurobehavioral tests, and the rats with specific inhibition mostly had better performance. We also found less blood-brain barrier (BBB) injury, and less neuron loss (Nissl staining) in intervention groups, which supported the neurobehavioral tests. Besides, oxidative stress and inflammation were also alleviated with intervention, which had significant less reactive oxygen species (ROS), tumor necrosis factor (TNF)-α, lactate dehydrogenase (LDH), Iba1, and GFAP surrounding the hematoma. These results confirmed that RIP3-phosphorylated MLKL and CaMK II participate in ICH-induced necroptosis and could provide potential targets for the treatment of ICH patients.

Verapamil inhibited the development of ureteral stricture by blocking CaMK II-mediated STAT3 and Smad3/JunD pathways.

BACKGROUND: Ureteral stricture (US) is a fibrotic process that leads to urinary tract obstruction and even kidney damage, with the characteristic of reduced extracellular matrix (ECM) degradation and increased collagen synthesis. Verapamil, as a calcium channel blocker, was reported to prevent scar formation. Our work aimed to investigate the biological effects and mechanism of verapamil in US. METHODS: Fibroblasts were subjected to transforming growth factor-beta 1 (TGF-ß1) to stimulate collagen synthesis, and the messenger ribonucleic acid (mRNA) and protein expressions in fibroblasts were assessed using quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. The location of phosphorylation-signal transducer and activator of transcription 3 (p-STAT3) and Jund proto-oncogene subunit (JunD) in fibroblasts were determined by immunofluorescence (IF). The binding relationship between signal transducer and activator of transcription 3 (STAT3) and collagen type I alpha1 (COL1A1)/collagen type III alpha 1 chain (COL3A1) and the binding relationship between JunD and tissue inhibitor of metalloproteinases-1 (TIMP-1) were verified by dual luciferase reporter gene and chromatin Immunoprecipitation (ChIP) assays. RESULTS: Herein, we found that verapamil could inhibit TGF-ß1/Ca2 + /calmodulin-dependent protein kinase II (CaMK II)-mediated STAT3 activation in fibroblasts, and STAT3 inhibition repressed collagen production. In addition, verapamil could inhibit TGF-ß1/CaMK II-mediated Mothers against DPP homolog 3 (Smad3)/JunD pathway activation in fibroblasts, and JunD silencing inhibited TIMP1 (a matrix metalloproteinase inhibitor) expression. Our subsequent experiments revealed that STAT3 bound with COL1A1 promoter and COL3A1 promoter and activated their transcription, and JunD bound with TIMP1 promoter and activated its transcription. Moreover, as expected, STAT3 activation could eliminate the inhibitory effect of verapamil treatment on TGF-ß1-induced collagen production in fibroblasts, and JunD overexpression reversed the inhibitory effect of verapamil treatment on TGF-ß1-induced TIMP1 expression in fibroblasts. CONCLUSION: Verapamil inhibited collagen production and TIMP-1 expression in US by blocking CaMK II-mediated STAT3 and Smad3/JunD pathways.

Autophagy promotes membrane trafficking of NR2B to alleviate depression by inhibiting AQP4 expression in mice.

Depression is a high-incidence mental illness that seriously affects human health. AQP4 has been reported to be closely associated with depression, while the underlying mechanism is still unclear. This work aimed to investigate the functional role of AQP4 in depression. Depression mouse model was constructed by administration of chronic social defeat stress (CSDS). We found that AQP4 was highly expressed in the hippocampal tissues of CSDS mice. AQP4 knockdown alleviated depression and enhanced the expression of NR2B and PSD95 in CSDS mice. Moreover, primary hippocampal neurons were treated with N-methyl-d-aspartate (NMDA) to induce neuron injury. AQP4 overexpression repressed cell viability and promoted apoptosis of NMDA-treated primary hippocampal neurons. AQP4 up-regulation repressed the expression of NR2B (surface), and enhanced the expression of NR2B (intracellular), P-NR2B, CaMK II and CK2 in the NMDA-treated primary hippocampal neurons. The influence conferred by AQP4 up-regulation was abolished by KN-93 (CaMK II inhibitor) or TBB (CK2 inhibitor) treatment. Rapamycin treatment enhanced the expression of NR2B (surface), and repressed the expression of AQP4, NR2B (intracellular) and P-NR2B in the primary hippocampal neurons by activating autophagy. The activated autophagy alleviated depression in CSDS mice by repressing AQP4 expression. In conclusion, our data demonstrated that autophagy ameliorated depression by repressing AQP4 expression in mice, and AQP4 knockdown promoted membrane trafficking of NR2B and inhibited phosphorylation of NR2B via CaMK II/CK2 pathway. Thus, our work suggests that AQP4 may be a promising molecular target for the development of antidepressant drugs.

Pharmacodynamic Mechanism of Kuanxiong Aerosol for Vasodilation and Improvement of Myocardial Ischemia.

OBJECTIVE: To explore the effect of Kuanxiong Aerosol (KXA) on isoproterenol (ISO)-induced myocardial injury in rat models. METHODS: Totally 24 rats were radomly divided into control, ISO, KXA low-dose and high-dose groups according to the randomized block design method, and were administered by intragastric administration for 10 consecutive days, and on the 9th and 10th days, rats were injected with ISO for 2 consecutive days to construct an acute myocardial ischemia model to evaluate the improvement of myocardial ischemia by KXA. In addition, the diastolic effect of KXA on rat thoracic aorta and its regulation of ion channels were tested by in vitro vascular tension test. The influence of KXA on the expression of calcium-CaM-dependent protein kinase II (CaMK II)/extracellular regulated protein kinases (ERK) signaling pathway has also been tested. RESULTS: KXA significantly reduced the ISO-induced increase in ST-segment, interventricular septal thickness, cardiac mass index and cardiac tissue pathological changes in rats. Moreover, the relaxation of isolated thoracic arterial rings that had been precontracted using norepinephrine (NE) or potassium chloride (KCl) was increased after KXA treatment in an endothelium-independent manner, and was attenuated by preincubation with verapamil, but not with tetraethylammonium chloride, 4-aminopyridine, glibenclamide, or barium chloride. KXA pretreatment attenuated vasoconstriction induced by CaCl2 in Ca2+-free solutions containing K+ or NE. In addition, KXA pretreatment inhibited accumulation of Ca2+ in A7r5 cells mediated by KCl and NE and significantly decreased p-CaMK II and p-ERK levels. CONCLUSION: KXA may inhibit influx and release of calcium and activate the CaMK II/ERK signaling pathway to produce vasodilatory effects, thereby improving myocardial injury.

Pharmacodynamic Mechanism of Kuanxiong Aerosol for Vasodilation and Improvement of Myocardial Ischemia / 中国结合医学杂志

OBJECTIVE@#To explore the effect of Kuanxiong Aerosol (KXA) on isoproterenol (ISO)-induced myocardial injury in rat models.@*METHODS@#Totally 24 rats were radomly divided into control, ISO, KXA low-dose and high-dose groups according to the randomized block design method, and were administered by intragastric administration for 10 consecutive days, and on the 9th and 10th days, rats were injected with ISO for 2 consecutive days to construct an acute myocardial ischemia model to evaluate the improvement of myocardial ischemia by KXA. In addition, the diastolic effect of KXA on rat thoracic aorta and its regulation of ion channels were tested by in vitro vascular tension test. The influence of KXA on the expression of calcium-CaM-dependent protein kinase II (CaMK II)/extracellular regulated protein kinases (ERK) signaling pathway has also been tested.@*RESULTS@#KXA significantly reduced the ISO-induced increase in ST-segment, interventricular septal thickness, cardiac mass index and cardiac tissue pathological changes in rats. Moreover, the relaxation of isolated thoracic arterial rings that had been precontracted using norepinephrine (NE) or potassium chloride (KCl) was increased after KXA treatment in an endothelium-independent manner, and was attenuated by preincubation with verapamil, but not with tetraethylammonium chloride, 4-aminopyridine, glibenclamide, or barium chloride. KXA pretreatment attenuated vasoconstriction induced by CaCl2 in Ca2+-free solutions containing K+ or NE. In addition, KXA pretreatment inhibited accumulation of Ca2+ in A7r5 cells mediated by KCl and NE and significantly decreased p-CaMK II and p-ERK levels.@*CONCLUSION@#KXA may inhibit influx and release of calcium and activate the CaMK II/ERK signaling pathway to produce vasodilatory effects, thereby improving myocardial injury.

Verapamil inhibits ureteral scar formation by regulating CaMK II-mediated Smad pathway.

Verapamil is reported to prevent scar formation. However, whether verapamil is involved in the ureteral stricture scar and the underlying mechanism need further investigation. Fibroblasts were isolated from ureteral scar tissues. TGF-ß1 stimulation was used to induce fibrosis of fibroblasts. Inhibition of CaMK II was achieved by shRNA transfection. CCK-8 was performed to evaluate cell viability. qRT-PCR was applied to determine the level of mRNA while western blotting was used to determine the level of proteins. Immunofluorescence was used to detect the level of vimentin, collagen I and collagen III. Primary fibroblasts was successfully isolated from ureteral scar tissues. TGF-ß1 stimulation was capable to induce collagen production and fibrosis in primary fibroblasts while inhibition of CaMK II attenuate collagen production. Overexpression of wild type CaMK II lead to further increase of collagen production upon TGF-ß1 stimulation while the mutated CaMK II did not exert this promotion. Treatment of verapamil inhibits TGF-ß1 induced collagen production via inhibiting CaMK II. In present study, we revealed a vital role of Verapamil and CaMK II in the formation of ureteral scar. Verapamil inhibited TGF-ß1 induced collagen fiber formation by regulating CaMK II. Our finding might provide new insight into mechanism of prevention and treatment of ureteral scar.

Oxoglaucine mediates Ca2+ influx and activates autophagy to alleviate osteoarthritis through the TRPV5/calmodulin/CAMK-II pathway.

BACKGROUND AND PURPOSE: Stimulation of calcium influx and suppression of autophagy play important roles in the pathogenesis of osteoarthritis (OA). In this study, we used a novel inhibitor of TRPV5 cation channels - oxoglaucine to attenuate progression of deterioration and pathological changes in OA patient-derived chondrocytes and OA animal model, by activating autophagy. EXPERIMENTAL APPROACH: Inhibition by oxoglaucine of calcium influx was assessed in cells.. Analyses were also carried out to investigate the effect of oxoglaucine on OA by detection of anti-inflammatory response, TRPV5/CAMK-II/calmodulin pathway, autophagy, and cartilage protection both in vitro and in vivo. demonstrated by macroscopic evaluation and histological findings. KEY RESULTS: Oxoglaucine suppressed expression of proinflammatory and apoptosis-related proteins, including TNF-α, IL-6, IL-1ß, MMP-13, CASP-3, and BAX, and prevented matrix degradation in OA chondrocytes. It also successfully blocked Ca2+ influx, activating autophagy dose-dependently asshown by up-regulated expression of LC-3II/I, Beclin-1, ATG5, ATG7, higher autophagic influx and formation of autophagic vesicles. It also decreased expression of mRNA and protein of TRPV5, CAMK-II, and calmodulin. Conversely, 1,25-dihydroxyvitamin D3, anagonist of TRPV5 channels, reversed the oxoglaucine-induced calcium influx inhibition and autophagy activation, demonstrating the association of oxoglaucine with TRPV5. Further, oxoglaucine prevented the apoptosis and matrix degradation of articular cartilage in a rat model of OA. CONCLUSION AND IMPLICATIONS: Oxoglaucine protects against cartilage damage by blocking the TRPV5/CAMK-II/calmodulin pathway to inhibit Ca2+ influx and activate autophagy. Our results indicate that oxoglaucine has the potential to become a candidate drug for treatment of OA.

CaMK II/Ca2+ dependent endoplasmic reticulum stress mediates apoptosis of hepatic stellate cells stimulated by transforming growth factor beta 1.

Previous studies by our group have demonstrated that the calcium imbalance in rat hepatic stellate cells (HSCs) can induce endoplasmic reticulum stress (ERS) and promote cell apoptosis. KN-62, an inhibitor of Calmodulin kinase II (CaMK II), can decrease the expression of CaMK II that plays a major role in regulating the steady state of intracellular Ca2+. Uridine triphosphate (UTP) plays a biological role in increasing indirectly the level of intracellular Ca2+. In the experiment, we demonstrate that KN-62 and UTP can inhibit the proliferation and promote the apoptosis in HSCs, increase the level of intracellular Ca2+ and the expression of ERS protein GRP78, and increase the apoptosis protein Caspase-12 and Bax expression, while decrease the expression of Bcl-2 protein. Our findings indicate that the CaMK II/Ca2+ signaling pathway regulates the ERS apoptosis pathway and induces HSC apoptosis.

miRNA-338-3p/CAMK IIα signaling pathway prevents acetaminophen-induced acute liver inflammation in vivo.

INTRODUCTION AND OBJECTIVES: N-acetyl-p-aminophenol (APAP)-induced liver injury is a major clinical challenge worldwide. The present study investigated the molecular role of microRNA (miR)-338-3p in the development of APAP-induced acute liver injury. MATERIALS AND METHODS: B6 mice were treated with an miR-338-3p agomir, antagomir, and intraperitoneally injected with APAP 24h later to induce acute liver injury. Histological analysis was performed to evaluate the degree of liver injury. The gene expression of miR-338-3p and its downstream regulators was measured by reverse transcription-quantitative PCR and western blot. The miR target was validated using a luciferase reporter assay. RESULTS: The results revealed that miR-338-3p was significantly upregulated following the intraperitoneal administration of APAP. Augmenting miR-338-3p alleviated acute liver injury caused by APAP overdose, while silencing of miR-338-3p exhibited a detrimental effect. Moreover, miR-338-3p inhibited the expression of pro-inflammatory cytokines by preventing the aberrant activation of inflammatory signaling pathways, including the nuclear factor kappa-B (NF-κB)/mitogen-activated protein kinase (MAPK) signaling pathway. Furthermore, calcium/calmodulin-dependent protein kinase IIα (CAMK IIα) was identified as a direct target of miR-338-3p. CONCLUSION: The present study demonstrated that miR-338-3p inhibited inflammation in APAP-induced acute liver injury.

Cyclovirobuxine D ameliorates aldosterone-induced primary neonatal rat cardiac myocyte injury via Ca / 中国药理学通报

Aim To investigate the protective effect of cyclovirobuxine D(CVB-D) on aldosterone (ALD)-induced primary neonatal rat cardiac myocytes (PNRC-Ms) injury and the possible mechanism. Methods PNRCMs were extracted by trypsin, and the PNRCMs injury model was established by ALD (10 μmol · L

DCMQA, a caffeoylquinic acid derivative alleviates NMDA-induced neurotoxicity via modulating GluN2A and GluN2B-containing NMDA receptors in vitro.

Compound DCMQA (4, 5-O-dicaffeoyl-1-O-[4-malic acid methyl ester]-quinic acid) is a natural caffeoylquinic acid derivative isolated from Arctium lappa L. roots. Caffeoylquinic acid derivatives have been reported to possess neuroprotective effects through inhibiting oxidative stress and apoptosis in vitro. However, whether DCMQA exerts protective effects on N-methyl-D-aspartate (NMDA)-induced neurotoxicity and the underlying mechanism has not been elucidated. In this study, the results indicated that pretreatment of DCMQA prevented the loss of cell viability and attenuated the LDH leakage in SH-SY5Y cells exposed to NMDA. Hoechst 33342 staining and Annexin V-PI double staining illustrated that DCMQA suppressed NMDA-induced morphological damage and neuronal apoptosis. Moreover, DCMQA inhibited NMDA-mediated Ca2+ influx, excessive intracellular ROS generation and loss of mitochondrial membrane potential (MMP). Western blot analysis showed that DCMQA attenuated the Bax/Bcl-2 ratio, release of cytochrome c as well as expression of caspase-9 and caspase-3. Besides, DCMQA down-regulated GluN2B-containing NMDA receptors (NMDARs) and up-regulated GluN2A-containing NMDARs, promoted the disruption of nNOS and PSD95 as well as activation of CaMK II-α. Furthermore, computational docking study indicated that DCMQA possessed a good affinity for NMDARs. These results indicated that DCMQA protects SH-SY5Y cells against NMDA-induced neuronal damage. In addition, the underlying mechanisms of DCMQA-mediated neuroprotection are associated with modulating NMDARs and disruption of nNOS-PSD95 as well as the activation of CaMK II-α.

Exendin-4 Reduces Ventricular Arrhythmia Activity and Calcium Sparks-Mediated Sarcoplasmic Reticulum Ca Leak in Rats with Heart Failure.

The aim of this study was to investigate the effect of exendin-4 (Ex-4) on ventricular arrhythmias and calcium sparks-mediated calcium leak in a myocardial infarction-heart failure model.We studied the influence of exendin-4 on ventricular arrhythmogenesis in a rat myocardial infarction-heart failure model. In vivo arrhythmia studies (electrocardiogram [ECG] telemetry studies), ex vivo arrhythmia studies calcium sparks tests, and analysis of total and phosphorylated ryanodine receptor (RyR) 2 and CaMK-II were carried out in sham group, myocardial infarction (MI) group, MI + Ex-4 and MI + Ex-4 + Exendin9-39 (Ex9-39) groups.ECG telemetry studies showed an antiarrhythmic effect of exendin-4 with reduction of spontaneous ventricular arrhythmias. Exendin-4 abbreviated the APD90, which was longer in the heart failure model, and increase the APD alternans thresholds. Exendin-4 also reduced the susceptibility to burst pacing-induced arrhythmia ex vivo. Subcellular sarcoplasmic reticulum (SR) calcium leak characteristics were tested in four groups of rat cardiomyocytes. Exendin-4 reduced calcium spark mass, spark frequency, and calcium leak, which may be due to reduced S2814-RyR2 and CaMK-II phosphorylation. Co-administration of exendin 9-39 with exendin-4 partly abolished the above-mentioned effect of exendin-4.These findings suggest that exendin-4 exerts an antiarrhythmic effect through decreasing SR calcium leak in spontaneous and burst pacing-induced ventricular arrhythmias, which may be due to reduced RyR2 phosphorylation and suppressed CaMK-II activity. Exendin-4 may act as a novel antiarrhythmic strategy in heart failure.

Ketamine inhibits aerobic glycolysis in colorectal cancer cells by blocking the NMDA receptor-CaMK II-c-Myc pathway.

Aerobic glycolysis plays a crucial role in cancer progression. Ketamine is often used for cancer pain relief in clinical settings. Moreover, ketamine inhibits proliferation and induces apoptosis in many cancer cell types. However, the anti-tumour mechanism of ketamine is still poorly understood. In the present study, we survey whether and how ketamine inhibits aerobic glycolysis in colon cancer cells. Glycolysis of colon cancer cells was determined by detecting the extracellular acidification rate in HT29 and SW480 cells. Quantitative real-time PCR was employed to determine mRNA expression. Calcium levels were detected with a Fluo-3 AM fluorescence kit. Micro-positron emission tomography/computed tomography (microPET/CT) imaging was employed to assess glycolysis in the tumours of the xenograft model. Ketamine treatment inhibited colon cancer cell viability and migration in HT29 and SW480 cells. Moreover, ketamine decreased aerobic glycolysis and decreased the expression of glycolysis-related proteins in HT29 and SW480 cells. MicroPET/CT demonstrated that ketamine decreased 18F-FDG uptake in the xenograft model. In addition, ketamine inhibited c-Myc expression and CaMK II phosphorylation and decreased calcium levels. Further, dizocilpine (an NMDAR inhibitor), and KN93 (a CaMK II inhibitor), decreased CaMK II phosphorylation, c-Myc expression, and cancer cell glycolysis; these results were similar to those with ketamine treatment. Furthermore, the anti-tumour effect of ketamine was counteracted by rapastinel (an NMDAR activator). Ketamine inhibited aerobic glycolysis in colon cancer cells probably by blocking the NMDA receptor-CaMK II-c-Myc pathway, thus attenuating colon cancer cell viability and migration.

Protein phosphatase 2A is essential to maintain meiotic arrest, and to prevent Ca2+ burst at spawning and eventual parthenogenesis in the larvacean Oikopleura dioica.

Unfertilized eggs of most animals are arrested at a certain point in the meiotic cell cycles. Reinitiation of meiosis and the start of embryogenesis are triggered by fertilization. This arrest is essential for preventing parthenogenetic activation and for promoting proper initiation of development by fertilization. In the larvacean Oikopleura dioica, which is a simple model organism for studies of chordate development, the unfertilized egg is arrested at metaphase of meiosis I. We show here that protein phosphatase 2A (PP2A) is essential for maintenance of meiotic arrest after spawning of oocytes. Knockdown (KD) of the maternal PP2A catalytic subunit, which was found in functional screening of maternal factors, caused unfertilized eggs to spontaneously release polar bodies after spawning, and then start pseudo-cleavages without fertilization, namely, parthenogenesis. Parthenogenetic embryos failed to undergo proper mitosis and cytokinesis because of lack of a centrosome, which is to be brought into the egg by a sperm. Activation of the KD oocytes was triggered by possible rise of ambient and intracellular pH upon their release from the gonad into seawater at spawning. Live recording of intracellular calcium level of the KD oocytes indicated that the pH rise caused an aberrant Ca2+ burst, which mimicked the Ca2+ burst that occurs at fertilization. Then, the aberrant Ca2+ burst triggered meiosis resumption through Calcium/calmodulin-dependent protein kinase (CaMK II). Therefore, PP2A is essential for maintenance of meiotic arrest and prevention of parthenogenesis by suppressing the aberrant Ca2+ burst at spawning.

Widespread Roles of CaMK-II in Developmental Pathways.

The multifunctional Ca2+/calmodulin-dependent protein kinase type 2 (CaMK-II) was first discovered in brain tissue and shown to have a central role in long term potentiation, responding to Ca2+ elevations through voltage dependent channels. CaMK-II has a unique molecular mechanism that enables it to remain active in proportion to the degree (frequency and amplitude) of Ca2+ elevations, long after such elevations have subsided. Ca2+ is also a rapid activator of early development and CaMK-II is expressed and activated in early development. Using biochemical, pharmacological and genetic approaches, the functions of CaMK-II overlap remarkably well with those for Ca2+ elevations, post-fertilization. Conclusion. Activated CaMK-II plays a central role in decoding Ca2+ signals to activate specific events during early development; a majority of the known functions of elevated Ca2+ act though CaMK-II.