SIRT1 mediates the excitability of spinal CaMKIIα-positive neurons and participates in neuropathic pain by controlling Nav1.3.

AIMS: Neuropathic pain is a common chronic pain disorder, which is largely attributed to spinal central sensitization. Calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα) activation in the spinal dorsal horn (SDH) is a major contributor to spinal sensitization. However, the exact way that CaMKIIα-positive (CaMKIIα+) neurons in the SDH induce neuropathic pain is still unclear. This study aimed to explore the role of spinal CaMKIIα+ neurons in neuropathic pain caused by chronic constriction injury (CCI) and investigate the potential epigenetic mechanisms involved in CaMKIIα+ neuron activation. METHODS: CCI-induced neuropathic pain mice model, Sirt1loxP/loxP mice, and chemogenetic virus were used to investigate whether the activation of spinal CaMKIIα+ neurons is involved in neuropathic pain and its involved mechanism. Transcriptome sequence, western blotting, qRT-PCR, and immunofluorescence analysis were performed to assay the expression of related molecules and activation of neurons. Co-immunoprecipitation was used to observe the binding relationship of protein. Chromatin immunoprecipitation (ChIP)-PCR was applied to analyze the acetylation of histone H3 in the Scn3a promoter region. RESULTS: The expression of sodium channel Nav1.3 was increased and the expression of SIRT1 was decreased in the spinal CaMKIIα+ neurons of CCI mice. CaMKIIα neurons became overactive after CCI, and inhibiting their activation relieved CCI-induced pain. Overexpression of SIRT1 reversed the increase of Nav1.3 and alleviated pain, while knockdown of SIRT1 or overexpression of Nav1.3 promoted CaMKIIα+ neuron activation and induced pain. By knocking down spinal SIRT1, the acetylation of histone H3 in the Scn3a (encoding Nav1.3) promoter region was increased, leading to an increased expression of Nav1.3. CONCLUSION: The findings suggest that an aberrant reduction of spinal SIRT1 after nerve injury epigenetically increases Nav1.3, subsequently activating CaMKIIα+ neurons and causing neuropathic pain.

Ion channel Piezo1 activation aggravates the endothelial dysfunction under a high glucose environment.

BACKGROUND: Vasculopathy is the most common complication of diabetes. Endothelial cells located in the innermost layer of blood vessels are constantly affected by blood flow or vascular components; thus, their mechanosensitivity plays an important role in mediating vascular regulation. Endothelial damage, one of the main causes of hyperglycemic vascular complications, has been extensively studied. However, the role of mechanosensitive signaling in hyperglycemic endothelial damage remains unclear. METHODS: Vascular endothelial-specific Piezo1 knockout mice were generated to investigate the effects of Piezo1 on Streptozotocin-induced hyperglycemia and vascular endothelial injury. In vitro activation or knockdown of Piezo1 was performed to evaluate the effects on the proliferation, migration, and tubular function of human umbilical vein endothelial cells in high glucose. Reactive oxygen species production, mitochondrial membrane potential alternations, and oxidative stress-related products were used to assess the extent of oxidative stress damage caused by Piezo1 activation. RESULTS: Our study found that in VECreERT2;Piezo1flox/flox mice with Piezo1 conditional knockout in vascular endothelial cells, Piezo1 deficiency alleviated streptozotocin-induced hyperglycemia with reduced apoptosis and abscission of thoracic aortic endothelial cells, and decreased the inflammatory response of aortic tissue caused by high glucose. Moreover, the knockout of Piezo1 showed a thinner thoracic aortic wall, reduced tunica media damage, and increased endothelial nitric oxide synthase expression in transgenic mice, indicating the relief of endothelial damage caused by hyperglycemia. We also showed that Piezo1 activation aggravated oxidative stress injury and resulted in severe dysfunction through the Ca2+-induced CaMKII-Nrf2 axis in human umbilical vein endothelial cells. In Piezo1 conditional knockout mice, Piezo1 deficiency partially restored superoxide dismutase activity and reduced malondialdehyde content in the thoracic aorta. Mechanistically, Piezo1 deficiency decreased CaMKII phosphorylation and restored the expression of Nrf2 and its downstream molecules HO-1 and NQO1. CONCLUSION: In summary, our study revealed that Piezo1 is involved in high glucose-induced oxidative stress injury and aggravated endothelial dysfunction, which have great significance for alleviating endothelial damage caused by hyperglycemia.

Errata: Middle aged CAMKII-Cre:Cbsfl/fl mice: a new model for studying perioperative neurocognitive disorders.

Zhen Li, Mengfan He, Danqing Dai, Xiaofei Gao, Huazheng Liang and Lize Xiong Exp. Anim. 73(1), 109-123, 2024 https://doi.org/10.1538/expanim.23-0065 In the original publication of the article, the Funding section was incomplete. The correct Funding information is provided below: Funding This work was supported by a grant from the Shanghai Commission of Science and Technology (201409003500), Major Project of National Natural Science Foundation of China (No. 82293640, No. 82293643), Key Project of National Natural Science Foundation of China (No. 82130121), the second round of the three-year action plan for "strengthening and promoting Traditional Chinese Medicine" of Hongkou District (HKGYQYXM-2022-06), and Scientific and technological innovation 2030 - major project of Brain Science and Brain-Like Intelligence Technology (2021ZD0202804) to Dr. Lize Xiong, a grant from the National Natural Science Foundation of China (No.81974535) to Dr. Huazheng Liang, and the Talent Promotion Program of Shanghai Fourth People's Hospital Affiliated to Tongji University School of Medicine (SY-XKZT-2019-3006) and the Discipline Promotion Program of Shanghai Fourth People's Hospital Affiliated to Tongji University School of Medicine (SY-XKZT-2019-1012) to Dr. Zhen Li.

CaMKII activity and metabolic imbalance-related neurological diseases: Focus on vascular dysfunction, synaptic plasticity, amyloid beta accumulation, and lipid metabolism.

Metabolic syndrome (MetS) is characterized by insulin resistance, hyperglycemia, excessive fat accumulation and dyslipidemia, and is known to be accompanied by neuropathological symptoms such as memory loss, anxiety, and depression. As the number of MetS patients is rapidly increasing globally, studies on the mechanisms of metabolic imbalance-related neuropathology are emerging as an important issue. Ca2+/calmodulin-dependent kinase II (CaMKII) is the main Ca2+ sensor and contributes to diverse intracellular signaling in peripheral organs and the central nervous system (CNS). CaMKII exerts diverse functions in cells, related to mechanisms such as RNA splicing, reactive oxygen species (ROS) generation, cytoskeleton, and protein-protein interactions. In the CNS, CaMKII regulates vascular function, neuronal circuits, neurotransmission, synaptic plasticity, amyloid beta toxicity, lipid metabolism, and mitochondrial function. Here, we review recent evidence for the role of CaMKII in neuropathologic issues associated with metabolic disorders.

CaMKIIß deregulation contributes to neuromuscular junction destabilization in Myotonic Dystrophy type I.

BACKGROUND: Myotonic Dystrophy type I (DM1) is the most common muscular dystrophy in adults. Previous reports have highlighted that neuromuscular junctions (NMJs) deteriorate in skeletal muscle from DM1 patients and mouse models thereof. However, the underlying pathomechanisms and their contribution to muscle dysfunction remain unknown. METHODS: We compared changes in NMJs and activity-dependent signalling pathways in HSALR and Mbnl1ΔE3/ΔE3 mice, two established mouse models of DM1. RESULTS: Muscle from DM1 mouse models showed major deregulation of calcium/calmodulin-dependent protein kinases II (CaMKIIs), which are key activity sensors regulating synaptic gene expression and acetylcholine receptor (AChR) recycling at the NMJ. Both mouse models exhibited increased fragmentation of the endplate, which preceded muscle degeneration. Endplate fragmentation was not accompanied by changes in AChR turnover at the NMJ. However, the expression of synaptic genes was up-regulated in mutant innervated muscle, together with an abnormal accumulation of histone deacetylase 4 (HDAC4), a known target of CaMKII. Interestingly, denervation-induced increase in synaptic gene expression and AChR turnover was hampered in DM1 muscle. Importantly, CaMKIIß/ßM overexpression normalized endplate fragmentation and synaptic gene expression in innervated Mbnl1ΔE3/ΔE3 muscle, but it did not restore denervation-induced synaptic gene up-regulation. CONCLUSIONS: Our results indicate that CaMKIIß-dependent and -independent mechanisms perturb synaptic gene regulation and muscle response to denervation in DM1 mouse models. Changes in these signalling pathways may contribute to NMJ destabilization and muscle dysfunction in DM1 patients.

The adipose-neural axis is involved in epicardial adipose tissue-related cardiac arrhythmias.

Dysfunction of the sympathetic nervous system and increased epicardial adipose tissue (EAT) have been independently associated with the occurrence of cardiac arrhythmia. However, their exact roles in triggering arrhythmia remain elusive. Here, using an in vitro coculture system with sympathetic neurons, cardiomyocytes, and adipocytes, we show that adipocyte-derived leptin activates sympathetic neurons and increases the release of neuropeptide Y (NPY), which in turn triggers arrhythmia in cardiomyocytes by interacting with the Y1 receptor (Y1R) and subsequently enhancing the activity of the Na+/Ca2+ exchanger (NCX) and calcium/calmodulin-dependent protein kinase II (CaMKII). The arrhythmic phenotype can be partially blocked by a leptin neutralizing antibody or an inhibitor of Y1R, NCX, or CaMKII. Moreover, increased EAT thickness and leptin/NPY blood levels are detected in atrial fibrillation patients compared with the control group. Our study provides robust evidence that the adipose-neural axis contributes to arrhythmogenesis and represents a potential target for treating arrhythmia.

Effect of electroacupuncture stimulation of "Sibai"(ST2) and "Quanliao"(SI18) on excitatory neurons of sensorimotor cortex in mice. / 电针"四白"和"颧髎"æ¿€æ´»å°é¼ èº¯ä½“æ„Ÿè§‰è¿åŠ¨çš®å±‚çš„å ´å¥‹æ€§ç¥žç»å ƒ.

OBJECTIVES: To observe the activation state and neuronal types of somatosensory cortex and the primary motor cortex induced by electroacupuncture (EA) stimulation of "Sibai" (ST2) and "Quanliao" (SI18) acupoints in mice. METHODS: Male C57BL/6J mice were randomly divided into blank control and EA groups, with 6 mice in each group. Rats of the EA group received EA stimulation (2 Hz, 0.6 mA) at ST2 and SI18 for 30 minutes. Samples were collected after EA intervention, and immunofluorescence staining was performed to quantify the expression of the c-Fos gene (proportion of c-Fos positive cells) in the somatosensory cortex and primary motor cortex. The co-labelled cells of calcium/calmodulin-dependent protein kinase Ⅱ (CaMKⅡ) and gamma-aminobutyric acid (GABA) in the somatosensory cortex and primary motor cortex were observed and counted by using microscope after immunofluorescence staining. Another 10 mice were used to detect the calcium activity of excitatory neurons in the somatosensory cortex and primary motor cortex by fiber photometry. RESULTS: In comparison with the blank control group, the number of c-Fos positive cells, and the proportion of c-Fos and CaMKⅡ co-labelled cells in both the somatosensory cortex and primary motor cortex were significantly increased after EA stimulation (P<0.05). No significant changes were found in the proportion of c-Fos and GABA co-labeled cells in both the somatosensory cortex and primary motor cortex after EA. Results of fiber optic calcium imaging technology showed that the spontaneous calcium activity of excitatory neurons in both somatosensory cortex and primary motor cortex were obviously increased during EA compared with that before EA (P<0.01), and strikingly reduced after cessation of EA compared with that during EA (P<0.05). CONCLUSIONS: Under physiological conditions, EA of ST2 and SI18 can effectively activate excitatory neurons in the somatosensory cortex and primary motor cortex.

[Inhibition of glutamatergic neurons in the dorsomedial periaqueductal gray alleviates excessive defensive behaviors of mice with post-traumatic stress disorder].

OBJECTIVE: To investigate the role of glutamatergic neurons in the dorsomedial periaqueductal grey (dmPAG) in regulating excessive defensive behaviors in mice with post-traumatic stress disorder (PTSD). METHODS: Eight-week-old male C57BL/6 mice were subjected to stereotactic injections of different recombinant adeno- associated viral vectors (rAAV2/9-CaMKII-mCherry, rAAV2/9-CaMKII-hM3Dq-mCherry and rAAV2/9-CaMKII-hM4Di-mCherry) into the bilateral dmPAG for chemogenetic activation or inhibition of the glutamatergic neurons, followed 2 weeks later by PTSD modeling by single prolonged stress. The looming test, response to whisker stimulation test and contextual fear conditioning (CFC) test were used to observe changes in defensive behaviors of the PTSD mice. The activity of glutamatergic neurons in the dmPAG were observed using immunofluorescence staining. RESULTS: Compared with the control mice, the mouse models of PTSD showed a shortened latency of flights with increased time spent in the nest, response scores of defensive behaviors and freezing time (all P<0.01). Immunofluorescence staining revealed significantly increased c-fos-positive glutamatergic neurons in the dmPAG of PTSD mice with defensive behaviors. Activation of the glutamatergic neurons in the dmPAG (in PTSD hM3Dq group) did not cause significant changes in the latency of flights or time in nest but obviously increased response scores of defensive behaviors and freezing time of the mice, whereas inhibiting the glutamatergic neurons in the dmPAG (in PTSD hM4Di group) caused the reverse changes and obviously alleviated defensive behaviors in the PTSD mice (P<0.05 or 0.01). CONCLUSION: Inhibiting the activity of glutamatergic neurons in the dmPAG can alleviate defensive behaviors in mice with PTSD.

An In Silico Cardiomyocyte Reveals the Impact of Changes in CaMKII Signalling on Cardiomyocyte Contraction Kinetics in Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is characterised by asymmetric left ventricular hypertrophy, ventricular arrhythmias, and cardiomyocyte dysfunction that may cause sudden death. HCM is associated with mutations in sarcomeric proteins and is usually transmitted as an autosomal-dominant trait. The aim of this in silico study was to assess the mechanisms that underlie the altered electrophysiological activity, contractility, regulation of energy metabolism, and crossbridge cycling in HCM at the single-cell level. To investigate this, we developed a human ventricular cardiomyocyte model that incorporates electrophysiology, metabolism, and force generation. The model was validated by its ability to reproduce the experimentally observed kinetic properties of human HCM induced by (a) remodelling of several ion channels and Ca2+-handling proteins arising from altered Ca2+/calmodulin kinase II signalling pathways and (b) increased Ca2+ sensitivity of the myofilament proteins. Our simulation showed a decreased phosphocreatine-to-ATP ratio (-9%) suggesting a negative mismatch between energy expenditure and supply. Using a spatial myofilament half-sarcomere model, we also compared the fraction of detached, weakly bound, and strongly bound crossbridges in the control and HCM conditions. Our simulations showed that HCM has more crossbridges in force-producing states than in the control condition. In conclusion, our model reveals that impaired crossbridge kinetics is accompanied by a negative mismatch between the ATP supply and demand ratio. This suggests that improving this ratio may reduce the incidence of sudden death in HCM.

The CaMK Family Differentially Promotes Necroptosis and Mouse Cardiac Graft Injury and Rejection.

Organ transplantation is associated with various forms of programmed cell death which can accelerate transplant injury and rejection. Targeting cell death in donor organs may represent a novel strategy for preventing allograft injury. We have previously demonstrated that necroptosis plays a key role in promoting transplant injury. Recently, we have found that mitochondria function is linked to necroptosis. However, it remains unknown how necroptosis signaling pathways regulate mitochondrial function during necroptosis. In this study, we investigated the receptor-interacting protein kinase 3 (RIPK3) mediated mitochondrial dysfunction and necroptosis. We demonstrate that the calmodulin-dependent protein kinase (CaMK) family members CaMK1, 2, and 4 form a complex with RIPK3 in mouse cardiac endothelial cells, to promote trans-phosphorylation during necroptosis. CaMK1 and 4 directly activated the dynamin-related protein-1 (Drp1), while CaMK2 indirectly activated Drp1 via the phosphoglycerate mutase 5 (PGAM5). The inhibition of CaMKs restored mitochondrial function and effectively prevented endothelial cell death. CaMKs inhibition inhibited activation of CaMKs and Drp1, and cell death and heart tissue injury (n = 6/group, p < 0.01) in a murine model of cardiac transplantation. Importantly, the inhibition of CaMKs greatly prolonged heart graft survival (n = 8/group, p < 0.01). In conclusion, CaMK family members orchestrate cell death in two different pathways and may be potential therapeutic targets in preventing cell death and transplant injury.

γ-Oryzanol from Rice Bran Antagonizes Glutamate-Induced Excitotoxicity in an In Vitro Model of Differentiated HT-22 Cells.

The excessive activation of glutamate in the brain is a factor in the development of vascular dementia. γ-Oryzanol is a natural compound that has been shown to enhance brain function, but more research is needed to determine its potential as a treatment for vascular dementia. This study investigated if γ-oryzanol can delay or improve glutamate neurotoxicity in an in vitro model of differentiated HT-22 cells and explored its neuroprotective mechanisms. The differentiated HT-22 cells were treated with 0.1 mmol/L glutamate for 24 h then given γ-oryzanol at appropriate concentrations or memantine (10 µmol/L) for another 24 h. Glutamate produced reactive oxygen species and depleted glutathione in the cells, which reduced their viability. Mitochondrial dysfunction was also observed, including the inhibition of mitochondrial respiratory chain complex I activity, the collapse of mitochondrial transmembrane potential, and the reduction of intracellular ATP levels in the HT-22 cells. Calcium influx triggered by glutamate subsequently activated type II calcium/calmodulin-dependent protein kinase (CaMKII) in the HT-22 cells. The activation of CaMKII-ASK1-JNK MAP kinase cascade, decreased Bcl-2/Bax ratio, and increased Apaf-1-dependent caspase-9 activation were also observed due to glutamate induction, which were associated with increased DNA fragmentation. These events were attenuated when the cells were treated with γ-oryzanol (0.4 mmol/L) or the N-methyl-D-aspartate receptor antagonist memantine. The results suggest that γ-oryzanol has potent neuroprotective properties against glutamate excitotoxicity in differentiated HT-22 cells. Therefore, γ-oryzanol could be a promising candidate for the development of therapies for glutamate excitotoxicity-associated neurodegenerative diseases, including vascular dementia.

THSG alleviates cerebral ischemia/reperfusion injury via the GluN2B-CaMKII-ERK1/2 pathway.

BACKGROUND: The potential therapeutic targeting of PINK1-PARK2-mediated mitophagy against cerebral ischemia/reperfusion (CI/R) injury involves the pathophysiological processes of neurovascular unit (NVU) and is closely associated with N-methyl-D-aspartate receptors (NMDARs) commonly expressed in NVU. 2,3,5,4'-Tetrahydroxy-stilbene-2-O-ß-D-glucoside (THSG), a compound derived from the traditional Chinese medicine Polygonum multiflorum Thunb., has demonstrated notable neuroprotective properties against CI/R injury. However, it remains unclear whether THSG exerts its protective effects through GluN2B related PINK1/ PARK2 pathway. PURPOSE: This study aims to explore the pharmacological effects of THSG on alleviating CI/R injury via the GluN2B-CaMKII-ERK1/2 pathway. METHODS: THSG neuroprotection against CI/R injury was studied in transient middle cerebral artery occlusion/reversion (tMCAO/R) model rats and in oxygen and glucose deprivation/ reoxygenation (OGD/R) induced neurons. PINK1-PARK2-mediated mitophagy involvement in the protective effect of THSG was investigated in tMCAO/R rats and OGD/R-induced neurons via THSG and 3-methyladenine (3-MA) treatment. Furthermore, the beneficial role of GluN2B in reperfusion and its contribution to the THSG effect via CaMKII-ERK1/2 and PINK1-PARK2-mediated mitophagy was explored using the GluN2B-selective antagonist Ro 25-6981 both in vivo and in vitro. Finally, the interaction between THSG and GluN2B was evaluated using molecular docking. RESULTS: THSG significantly reduced infarct volume, neurological deficits, penumbral neuron structure, and functional damage, upregulated the inhibitory apoptotic marker Bcl-2, and suppressed the increase of pro-apoptotic proteins including cleaved caspase-3 and Bax in tMCAO/R rats. THSG (1 µM) markedly improved the neuronal survival under OGD/R conditions. Furthermore, THSG promoted PINK1 and PARK2 expression and increased mitophagosome numbers and LC3-II-LC3-I ratio both in vivo and in vitro. The effects of THSG were considerably abrogated by the mitophagy inhibitor 3-MA in OGD/R-induced neurons. Inhibiting GluN2B profoundly decreased mitophagosome numbers and OGD/R-induced neuronal viability. Specifically, inhibiting GluN2B abolished the protection of THSG against CI/R injury and reversed the upregulation of PINK1-PARK2-mediated mitophagy by THSG. Inhibiting GluN2B eliminated THSG upregulation of ERK1/2 and CaMKII phosphorylation. The molecular docking analysis results demonstrated that THSG bound to GluN2B (binding energy: -5.2 ± 0.11 kcal/mol). CONCLUSIONS: This study validates the premise that THSG alleviates CI/R injury by promoting GluN2B expression, activating CaMKII and ERK1/2, and subsequently enhancing PINK1-PARK2-mediated mitophagy. This work enlightens the potential of THSG as a promising candidate for novel therapeutic strategies for treating ischemic stroke.

TRPM2 and CaMKII Signaling Drives Excessive GABAergic Synaptic Inhibition Following Ischemia.

Excitotoxicity and the concurrent loss of inhibition are well-defined mechanisms driving acute elevation in excitatory/inhibitory (E/I) balance and neuronal cell death following an ischemic insult to the brain. Despite the high prevalence of long-term disability in survivors of global cerebral ischemia (GCI) as a consequence of cardiac arrest, it remains unclear whether E/I imbalance persists beyond the acute phase and negatively affects functional recovery. We previously demonstrated sustained impairment of long-term potentiation (LTP) in hippocampal CA1 neurons correlating with deficits in learning and memory tasks in a murine model of cardiac arrest/cardiopulmonary resuscitation (CA/CPR). Here, we use CA/CPR and an in vitro ischemia model to elucidate mechanisms by which E/I imbalance contributes to ongoing hippocampal dysfunction in male mice. We reveal increased postsynaptic GABAA receptor (GABAAR) clustering and function in the CA1 region of the hippocampus that reduces the E/I ratio. Importantly, reduced GABAAR clustering observed in the first 24 h rebounds to an elevation of GABAergic clustering by 3 d postischemia. This increase in GABAergic inhibition required activation of the Ca2+-permeable ion channel transient receptor potential melastatin-2 (TRPM2), previously implicated in persistent LTP and memory deficits following CA/CPR. Furthermore, we find Ca2+-signaling, likely downstream of TRPM2 activation, upregulates Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, thereby driving the elevation of postsynaptic inhibitory function. Thus, we propose a novel mechanism by which inhibitory synaptic strength is upregulated in the context of ischemia and identify TRPM2 and CaMKII as potential pharmacological targets to restore perturbed synaptic plasticity and ameliorate cognitive function.

[PI3K/Akt/Erk signaling pathway mediates neuroprotection of CaMK⠡γ and CaMK⠡δ against ischemic reperfusion injury in mice].

OBJECTIVE: To observe neuroprotective effects of Ca2+/calmodulin-dependent kinase Ⅱ (CaMK Ⅱ)γ and CaMkII δ against acute neuronal ischemic reperfusion injury in mice and explore the underlying mechanism. METHODS: Primary cultures of brain neurons isolated from fetal mice (gestational age of 18 days) were transfected with two specific siRNAs (si-CAMK2G and si-CAMK2D) or a control sequence (si-NT). After the transfection, the cells were exposed to oxygen-glucose deprivation/reperfusion (OGD/R) conditions for 1 h followed by routine culture. The expressions of phosphatidylinositol-3-kinase/extracellular signal-regulated kinase (PI3K/Akt/Erk) signaling pathway components in the neurons were detected using immunoblotting. The expressions of the PI3K/Akt/Erk signaling pathway proteins were also detected in the brain tissues of mice receiving middle cerebral artery occlusion (MCAO) or sham operation. RESULTS: The neuronal cells transfected with siCAMK2G showed significantly lower survival rates than those with si-NT transfection at 12, 24, 48, and 72 h after OGD/R (P < 0.01), and si-CAMK2G transfection inhibited OGD/R-induced upregulation of CaMKⅡγ expression. Compared to si-NT, transfection with si-CAMK2G and si-CAMK2D both significantly inhibited the expressions of PI3K/Akt/Erk signaling pathway components (P < 0.01). In the mouse models of MCAO, the expressions of CaMKⅡδ and CaMKⅡγ were significantly increased in the brain, where activation of the PI3K/Akt/Erk signaling pathway was detected. The expression levels of CaMKⅡδ, CaMKⅡγ, Erk, phosphorylated Erk, Akt, and phosphorylated Akt were all significantly higher in MCAO mice than in the sham-operated mice at 24, 48, 72, and 96 h after reperfusion (P < 0.05). CONCLUSION: The neuroprotective effects of CaMKⅡδ and CaMKⅡγ against acute neuronal ischemic reperfusion injury are mediated probably by the PI3K/Akt/Erk pathway.

Ca2+/CaM dependent protein kinase II (CaMKII)α and CaMKIIß hub domains adopt distinct oligomeric states and stabilities.

Ca2+ /calmodulin-dependent protein kinase II (CaMKII) is a multidomain serine/threonine kinase that plays important roles in the brain, heart, muscle tissue, and eggs/sperm. The N-terminal kinase and regulatory domain is connected by a flexible linker to the C-terminal hub domain. The hub domain drives the oligomeric organization of CaMKII, assembling the kinase domains into high local concentration. Previous structural studies have shown multiple stoichiometries of the holoenzyme as well as the hub domain alone. Here, we report a comprehensive study of the hub domain stoichiometry and stability in solution. We solved two crystal structures of the CaMKIIß hub domain that show 14-mer (3.1 Å) and 16-mer (3.4 Å) assemblies. Both crystal structures were determined from crystals grown in the same drop, which suggests that CaMKII oligomers with different stoichiometries likely coexist. To further interrogate hub stability, we employed mass photometry and temperature denaturation studies of CaMKIIß and CaMKIIα hubs, which highlight major differences between these highly similar domains. We created a dimeric CaMKIIß hub unit using rational mutagenesis, which is significantly less stable than the oligomer. Both hub domains populate an intermediate during unfolding. We found that multiple CaMKIIß hub stoichiometries are present in solution and that larger oligomers are more stable. CaMKIIα had a narrower distribution of molecular weight and was distinctly more stable than CaMKIIß.

TRPV4 antagonist suppresses retinal ganglion cell apoptosis by regulating the activation of CaMKII and TNF-α expression in a chronic ocular hypertension rat model.

Glaucoma is characterized by a progressive loss of retinal ganglion cells (RGCs), leading to irreversible visual function impairment. Sustained increase in intraocular pressure represents a major risk factor for glaucoma, yet the underlying mechanisms of RGC apoptosis induced by intraocular pressure remains unclear. This study aims to investigate the role of TRPV4 in RGC apoptosis in a rat model of chronic ocular hypertension (COH) and the underlying molecular mechanism. In the COH rat models, we evaluated the visual function, retinal pathological changes and RGC apoptosis. TRPV4 expression and downstream signaling molecules were also detected. We found that RGC density decreased and RGC apoptosis was induced in COH eyes compared with control eyes. TRPV4 expression increased significantly in response to elevated IOP. TRPV4 inhibition by the TRPV4 antagonist HC-067047 (HC-067) suppressed RGC apoptosis and protected visual function. HC-067 treatment upregulated the phosphorylation of CaMKII in both control and COH eyes. Finally, HC-067 treatment suppressed the production of TNF-α induced by ocular hypertension. The TRPV4 antagonist HC-067 might suppress RGC apoptosis by regulating the activation of CaMKII and inhibiting the production of TNF-α in the COH model. This indicated that TRPV4 antagonists may be a potential and novel therapeutic strategy for glaucoma.

The Role and Mechanism of STIM1/Orai1-Regulated Ca2+ Influx in Myocardial Hypertrophy in Type 2 Diabetes Mellitus.

OBJECTIVE: Diabetic cardiomyopathy (DCM) is the most common cardiovascular complication of type 2 diabetes mellitus (T2DM). Patients affected with DCM face a notably higher risk of progressing to congestive heart failure compared to other populations. Myocardial hypertrophy, a clearly confirmed pathological change in DCM, plays an important role in the development of DCM, with abnormal Ca2+ homeostasis serving as the key signal to induce myocardial hypertrophy. Therefore, investigating the mechanism of Ca2+ transport is of great significance for the prevention and treatment of myocardial hypertrophy in T2DM. METHODS: The rats included in the experiment were divided into wild type (WT) group and T2DM group. The T2DM rat model was established by feeding the rats with high-fat and high-sugar diets for three months combined with low dose of streptozotocin (100mg/kg). Afterwards, primary rat cardiomyocytes were isolated and cultured, and cardiomyocyte hypertrophy was induced through high-glucose treatment. Subsequently, mechanistic investigations were carried out through transfection with si-STIM1 and oe-STIM1. Western blot (WB) was used to detect the expression of the STIM1, Orai1 and p-CaMKII. qRT-PCR was used to detect mRNA levels of myocardial hypertrophy marker proteins. Cell surface area was detected using TRITC-Phalloidin staining, and intracellular Ca2+ concentration in cardiomyocytes was measured using Fluo-4 fluorescence staining. RESULTS: Through animal experiments, an upregulation of Orai1 and STIM1 was revealed in the rat model of myocardial hypertrophy induced by T2DM. Meanwhile, through cell experiments, it was found that in high glucose (HG)-induced hypertrophic cardiomyocytes, the expression of STIM1, Orai1, and p-CaMKII was upregulated, along with increased levels of store-operated Ca2+ entry (SOCE) and abnormal Ca2+ homeostasis. However, when STIM1 was downregulated in HG-induced cardiomyocytes, SOCE levels decreased and p-CaMKII was downregulated, resulting in an improvement in myocardial hypertrophy. To further elucidate the mechanism of action involving SOCE and CaMKII in T2DM-induced myocardial hypertrophy, high-glucose cardiomyocytes were respectively treated with BTP2 (SOCE blocker) and KN-93 (CaMKII inhibitor), and the results showed that STIM1 can mediate SOCE, thereby affecting the phosphorylation level of CaMKII and improving cardiomyocyte hypertrophy. CONCLUSION: STIM1/Orai1-mediated SOCE regulates p-CaMKII levels, thereby inducing myocardial hypertrophy in T2DM.

Activation of CaMKII/HDAC4 by SDF1 contributes to pulmonary arterial hypertension via stabilization Runx2.

Stromal derived factor 1 (SDF1) has been shown to be involved in the pathogenesis of pulmonary artery hypertension (PAH). However, the detailed molecular mechanisms remain unclear. To address this, we utilized primary cultured rat pulmonary artery smooth muscle cells (PASMCs) and monocrotaline (MCT)-induced PAH rat models to investigate the mechanisms of SDF1 driving PASMCs proliferation and pulmonary arterial remodeling. SDF1 increased runt-related transcription factor 2 (Runx2) acetylation by Calmodulin (CaM)-dependent protein kinase II (CaMKII)-dependent HDAC4 cytoplasmic translocation, elevation of Runx2 acetylation conferred its resistance to proteasome-mediated degradation. The accumulation of Runx2 further upregulated osteopontin (OPN) expression, finally leading to PASMCs proliferation. Blocking SDF1, suppression of CaMKII, inhibition the nuclear export of HDAC4 or silencing Runx2 attenuated pulmonary arterial remodeling and prevented PAH development in MCT-induced PAH rat models. Our study provides novel sights for SDF1 induction of PASMCs proliferation and suggests that targeting SDF1/CaMKII/HDAC4/Runx2 axis has potential value in the management of PAH.

Post-ischemic ubiquitination at the postsynaptic density reversibly influences the activity of ischemia-relevant kinases.

Ubiquitin modifications alter protein function and stability, thereby regulating cell homeostasis and viability, particularly under stress. Ischemic stroke induces protein ubiquitination at the ischemic periphery, wherein cells remain viable, however the identity of ubiquitinated proteins is unknown. Here, we employed a proteomics approach to identify these proteins in mice undergoing ischemic stroke. The data are available in a searchable web interface ( https://hochrainerlab.shinyapps.io/StrokeUbiOmics/ ). We detected increased ubiquitination of 198 proteins, many of which localize to the postsynaptic density (PSD) of glutamatergic neurons. Among these were proteins essential for maintaining PSD architecture, such as PSD95, as well as NMDA and AMPA receptor subunits. The largest enzymatic group at the PSD with elevated post-ischemic ubiquitination were kinases, such as CaMKII, PKC, Cdk5, and Pyk2, whose aberrant activities are well-known to contribute to post-ischemic neuronal death. Concurrent phospho-proteomics revealed altered PSD-associated phosphorylation patterns, indicative of modified kinase activities following stroke. PSD-located CaMKII, PKC, and Cdk5 activities were decreased while Pyk2 activity was increased after stroke. Removal of ubiquitin restored kinase activities to pre-stroke levels, identifying ubiquitination as the responsible molecular mechanism for post-ischemic kinase regulation. These findings unveil a previously unrecognized role of ubiquitination in the regulation of essential kinases involved in ischemic injury.