Vascular CaMKII: heart and brain in your arteries

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.

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.

Role of CaMKII in diabetes induced vascular injury and its interaction with anti-diabetes therapy

Diabetes mellitus is a metabolic disorder denoted by chronic hyperglycemia that drives maladaptive structural changes and functional damage to the vasculature. Attenuation of this pathological remodeling of blood vessels remains an unmet target owing to paucity of information on the metabolic signatures of this process. Ca2+/calmodulin-dependent kinase II (CaMKII) is expressed in the vasculature and is implicated in the control of blood vessels homeostasis. Recently, CaMKII has attracted a special attention in view of its chronic upregulated activity in diabetic tissues, yet its role in the diabetic vasculature remains under investigation.This review highlights the physiological and pathological actions of CaMKII in the diabetic vasculature, with focus on the control of the dialogue between endothelial (EC) and vascular smooth muscle cells (VSMC). Activation of CaMKII enhances EC and VSMC proliferation and migration, and increases the production of extracellular matrix which leads to maladaptive remodeling of vessels. This is manifested by activation of genes/proteins implicated in the control of the cell cycle, cytoskeleton organization, proliferation, migration, and inflammation. Endothelial dysfunction is paralleled by impaired nitric oxide signaling, which is also influenced by CaMKII signaling (activation/oxidation). The efficiency of CaMKII inhibitors is currently being tested in animal models, with a focus on the genetic pathways involved in the regulation of CaMKII expression (microRNAs and single nucleotide polymorphisms). Interestingly, studies highlight an interaction between the anti-diabetic drugs and CaMKII expression/activity which requires further investigation. Together, the studies reviewed herein may guide pharmacological approaches to improve health-related outcomes in patients with diabetes.

Interplay of G-proteins and Serotonin in the Neuroimmunoinflammatory Model of Chronic Stress and Depression: A Narrative Review

INTRODUCTION

This narrative review addresses the clinical challenges in stress-related disorders such as depression, focusing on the interplay between neuron-specific and pro-inflammatory mechanisms at the cellular, cerebral, and systemic levels.

OBJECTIVE

We aim to elucidate the molecular mechanisms linking chronic psychological stress with low-grade neuroinflammation in key brain regions, particularly focusing on the roles of G proteins and serotonin (5-HT) receptors.

METHODS

This comprehensive review of the literature employs systematic, narrative, and scoping review methodologies, combined with systemic approaches to general pathology. It synthesizes current research on shared signaling pathways involved in stress responses and neuroinflammation, including calcium-dependent mechanisms, mitogen-activated protein kinases, and key transcription factors like NF-κB and p53. The review also focuses on the role of G protein-coupled neurotransmitter receptors (GPCRs) in immune and pro-inflammatory responses, with a detailed analysis of how 13 of 14 types of human 5-HT receptors contribute to depression and neuroinflammation.

RESULTS

The review reveals a complex interaction between neurotransmitter signals and immunoinflammatory responses in stress-related pathologies. It highlights the role of GPCRs and canonical inflammatory mediators in influencing both pathological and physiological processes in nervous tissue.

CONCLUSION

The proposed Neuroimmunoinflammatory Stress Model (NIIS Model) suggests that proinflammatory signaling pathways, mediated by metabotropic and ionotropic neurotransmitter receptors, are crucial for maintaining neuronal homeostasis. Chronic mental stress can disrupt this balance, leading to increased pro-inflammatory states in the brain and contributing to neuropsychiatric and psychosomatic disorders, including depression. This model integrates traditional theories on depression pathogenesis, offering a comprehensive understanding of the multifaceted nature of the condition.

Costunolide covalently targets and inhibits CaMKII phosphorylation to reduce ischemia-associated brain damage

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is a leading cause of disability and mortality worldwide. Restoring cerebral blood flow (CBF) through vasodilatation is particularly important in the treatment of CCH. Costunolide (Cos) is a natural sesquiterpenoid compound with vasodilatory effect, but its mechanism is unclear.

PURPOSE

This study aimed to investigate the vasodilatory mechanism of Cos and provide a new therapeutic regimen for treating CCH.

METHODS

The therapeutic effect of Cos on CCH was assessed in a rat model of permanent common carotid artery occlusion. The direct target protein for improving CBF was identified by drug affinity responsive target stability combined with quantitative differential proteomics analysis. The molecular mechanism of Cos acting on its target protein was analyzed by multidisciplinary approaches. The signalling involved was assessed using site-directed pharmacological intervention.

RESULTS

Cos has a significant therapeutic effect on ischemic brain injury by restoring CBF. Multifunctional calcium/calmodulin-dependent protein kinase II (CaMKII) was identified as a direct target of the natural small molecule Cos with a therapeutic effect on CCH. Mechanistic studies revealed that the α,β-unsaturated-γ-lactone ring of Cos covalently binds to the Cys116 residue of CaMKII. It then inhibits the phosphorylation of CaMKII and reduces the calcium concentration in vascular smooth muscle cells, thus playing a role in vasodilation and increasing CBF. Notably, this covalent binding between Cos and CaMKII can exert a long-term vasodilator activity.

CONCLUSION

We reported for the first time that Cos reduced ischemia-associated brain damage by covalently binding to the Cys116 residue of CaMKII, inhibiting CaMKII phosphorylation, and exerting long-term vasodilatory activity. This study not only found a new covalent inhibitor against the phosphorylation of CaMKII but also suggested that pharmacologically targeting CaMKII is a promising therapeutic strategy for CCH.

Tilianin improves cognition in a vascular dementia rodent model by targeting miR-193b-3p/CaM- and miR-152-3p/CaMKIIα-mediated inflammatory and apoptotic pathways

Introduction

Although vascular dementia (VaD) is the second most prevalent form of dementia, there is currently a lack of effective treatments. Tilianin, isolated from the traditional drug Dracocephalum moldavica L., may protect against ischemic injury by inhibiting oxidative stress and inflammation via the CaMKII-related pathways but with weak affinity with the CaMKII molecule. microRNAs (miRNAs), functioning in post-transcriptional regulation of gene expression, may play a role in the pathological process of VaD via cognitive impairment, neuroinflammatory response, and neuronal dysfunction. This study aimed to investigate the role of tilianin in VaD therapy and the underlying mechanism through which tilianin regulates CaMKII signaling pathways based on miRNA-associated transcriptional action.

Methods

Rats with 2-vessel occlusion (2VO), a standard model of VaD, were treated with tilianin, vehicle control, and target overexpression or downregulation. High-throughput sequencing, qRT-PCR, and western blot analyses were utilized to identify the downstream target genes and signaling pathways of tilianin involved in VaD.

Results

Our results showed that tilianin ameliorated cognitive deficits, neurodegeneration, and microglial and astrocytic activation in rats with 2VO. Subsequent high-throughput sequencing and qRT-PCR analyses revealed that tilianin increased the downregulated miR-193b-3p and miR-152-3p levels in the cortex and hippocampus of 2VO rats. Mechanistically, miR-193b-3p targeting CaM and miR-152-3p targeting CaMKIIα were identified to play a role in VaD-associated pathology, inhibiting the p38 MAPK/NF--κB p65 pathway and decreasing TNF-α and IL-6 levels. Further gain- and loss-of-function experiments for these key genes showed that tilianin-exerted cognitive improvement by activating the p38 MAPK/NF--κB p65 and Bcl-2/Bax/caspase-3/PARP pathways in the brain of 2VO rats was abolished by miR-193b-3p and miR-152-3p inhibition. Moreover, CaM and CaMKIIα overexpression eliminated the elevated effects of miR-193b-3p and miR-152-3p on tilianin's protection against ischemic injury through increased inflammatory reactions and apoptotic signaling.

Discussion

Together, these findings indicate that tilianin improves cognition by regulating the miR-193b-3p/CaM- and miR-152-3p/CaMKIIα-mediated inflammatory and apoptotic pathways, suggesting a potential small-molecule regulator of miRNA associated with inflammatory signaling for VaD treatment.

CaMKII regulates neuromuscular activity and survival of the human blood fluke Schistosoma mansoni

Calcium/calmodulin dependant protein kinase II (CaMKII), an important transducer of Ca²⁺ signals, orchestrates multiple cellular functions in animals. Here we investigated the importance of CaMKII to Schistosoma mansoni, a blood parasite that causes human schistosomiasis. We demonstrate that phosphorylated (activated) CaMKII is present in cercariae, schistosomula and adult worms, and show that striking activation occurs in the nervous tissue of these parasite life-stages; CaMKII was also activated in the tegument and muscles of adult worms and the vitellaria of females. Exposure of worms to the anti-schistosomal drug praziquantel (PZQ) induced significant CaMKII activation and depletion of CaMKII protein/activation in adult worms resulted in hypokinesia, reduced vitality and death. At medium confidence (global score ≥ 0.40), S. mansoni CaMKII was predicted to interact with 51 proteins, with many containing CaMKII phosphorylation sites and nine mapped to phosphoproteome data including sites within a ryanodine receptor. The CaMKII network was functionally enriched with mitogen-activated protein kinase, Wnt, and notch pathways, and ion-transport and voltage-dependent channel protein domains. Collectively, these data highlight the intricacies of CaMKII signalling in S. mansoni, show CaMKII to be an active player in the PZQ-mediated response of schistosomes and highlight CaMKII as a possible target for the development of novel anti-schistosome therapeutics.

CaMKII Splice Variants in Vascular Smooth Muscle Cells: The Next Step or Redundancy?

Vascular smooth muscle cells (VSMCs) help to maintain the normal physiological contractility of arterial vessels to control blood pressure; they can also contribute to vascular disease such as atherosclerosis. Ca²⁺/calmodulin-dependent kinase II (CaMKII), a multifunctional enzyme with four isoforms and multiple alternative splice variants, contributes to numerous functions within VSMCs. The role of these isoforms has been widely studied across numerous tissue types; however, their functions are still largely unknown within the vasculature. Even more understudied is the role of the different splice variants of each isoform in such signaling pathways. This review evaluates the role of the different CaMKII splice variants in vascular pathological and physiological mechanisms, aiming to show the need for more research to highlight both the deleterious and protective functions of the various splice variants.

Calcium/Calmodulin-Dependent Protein Kinase II in Cerebrovascular Diseases

Cerebrovascular disease is the most common life-threatening and debilitating condition that often leads to stroke. The multifunctional calcium/calmodulin-dependent protein kinase II (CaMKII) is a key Ca2+ sensor and an important signaling protein in a variety of biological systems within the brain, heart, and vasculature. In the brain, past stroke-related studies have been mainly focused on the role of CaMKII in ischemic stroke in neurons and established CaMKII as a major mediator of neuronal cell death induced by glutamate excitotoxicity and oxidative stress following ischemic stroke. However, with growing understanding of the importance of neurovascular interactions in cerebrovascular diseases, there are clearly gaps in our understanding of how CaMKII functions in the complex neurovascular biological processes and its contributions to cerebrovascular diseases. Additionally, emerging evidence demonstrates novel regulatory mechanisms of CaMKII and potential roles of the less-studied CaMKII isoforms in the ischemic brain, which has sparked renewed interests in this dynamic kinase family. This review discusses past findings and emerging evidence on CaMKII in several major cerebrovascular dysfunctions including ischemic stroke, hemorrhagic stroke, and vascular dementia, focusing on the unique roles played by CaMKII in the underlying biological processes of neuronal cell death, neuroinflammation, and endothelial barrier dysfunction triggered by stroke. We also highlight exciting new findings, promising therapeutic agents, and future perspectives for CaMKII in cerebrovascular systems.

The Calcium/Calmodulin-Dependent Kinases II and IV as Therapeutic Targets in Neurodegenerative and Neuropsychiatric Disorders

CaMKII and CaMKIV are calcium/calmodulin-dependent kinases playing a rudimentary role in many regulatory processes in the organism. These kinases attract increasing interest due to their involvement primarily in memory and plasticity and various cellular functions. Although CaMKII and CaMKIV are mostly recognized as the important cogs in a memory machine, little is known about their effect on mood and role in neuropsychiatric diseases etiology. Here, we aimed to review the structure and functions of CaMKII and CaMKIV, as well as how these kinases modulate the animals’ behavior to promote antidepressant-like, anxiolytic-like, and procognitive effects. The review will help in the understanding of the roles of the above kinases in the selected neurodegenerative and neuropsychiatric disorders, and this knowledge can be used in future drug design.

The Calcium Signaling Mechanisms in Arterial Smooth Muscle and Endothelial Cells

The contractile state of resistance arteries and arterioles is a crucial determinant of blood pressure and blood flow. Physiological regulation of arterial contractility requires constant communication between endothelial and smooth muscle cells. Various Ca²⁺ signals and Ca²⁺ -sensitive targets ensure dynamic control of intercellular communications in the vascular wall. The functional effect of a Ca²⁺ signal on arterial contractility depends on the type of Ca²⁺ -sensitive target engaged by that signal. Recent studies using advanced imaging methods have identified the spatiotemporal signatures of individual Ca²⁺ signals that control arterial and arteriolar contractility. Broadly speaking, intracellular Ca²⁺ is increased by ion channels and transporters on the plasma membrane and endoplasmic reticular membrane. Physiological roles for many vascular Ca²⁺ signals have already been confirmed, while further investigation is needed for other Ca²⁺ signals. This article focuses on endothelial and smooth muscle Ca²⁺ signaling mechanisms in resistance arteries and arterioles. We discuss the Ca²⁺ entry pathways at the plasma membrane, Ca²⁺ release signals from the intracellular stores, the functional and physiological relevance of Ca²⁺ signals, and their regulatory mechanisms. Finally, we describe the contribution of abnormal endothelial and smooth muscle Ca²⁺ signals to the pathogenesis of vascular disorders. © 2021 American Physiological Society. Compr Physiol 11:1831-1869, 2021.

MicroRNA-219a-5p-mediated inhibition of CaMKIIγ facilitates vestibular compensation in acute vertigo by promoting protein kinase C expression

Vestibular compensation (VC) refers to a behavioral recovery process in which firing rates of bilateral vestibular nuclei neurons are rebalanced. Our study aimed to investigate the underlying mechanism by which miR-219a-5p regulates Ca²⁺ /calmodulin-dependent protein kinase II γ isoform (CaMKIIγ) and protein kinase C (PKC) in VC. A unilateral vestibular deafferentation rat model was established by unilateral labyrinthectomy (UL), after which VC was evaluated in rats with UL-induced vertigo-like behavior by measuring vestibular defect behavior and performing rotarod tests, as well as by BrdU immunohistochemistry on medial vestibular nuclei. We found that miR-219a-5p was increased while CaMKIIγ was decreased during VC in the medial vestibular nucleus of rats that had undergone UL. Next, gain- and loss-of-function assays were conducted to evaluate the effects of miR-219a-5p and CaMKIIγ on the vestibular defect behaviors and VC, the results of which suggested that in rats after UL overexpression of CaMKIIγ inhibited VC, while overexpression of miR-219a-5p facilitated VC. A dual-luciferase reporter gene assay identified that miR-219a-5p targeted CaMKIIγ. This led to additional experiments showing that miR-219a-5p aptomir expression downregulated CaMKIIγ in cortical cells with a concomitant increase in PKC expression, which were verified further in vivo. In summary, in rats with acute vertigo, miR-219a-5p overexpression inhibits CaMKIIγ and elevates PKC, thereby facilitating VC. Our study offers possible targets for further evaluation as treatment of acute vertigo in humans.

The Intrinsic Virtues of EGCG, an Extremely Good Cell Guardian, on Prevention and Treatment of Diabesity Complications

The pandemic proportion of diabesity—a combination of obesity and diabetes—sets a worldwide health issue. Experimental and clinical studies have progressively reinforced the pioneering epidemiological observation of an inverse relationship between consumption of polyphenol-rich nutraceutical agents and mortality from cardiovascular and metabolic diseases. With chemical identification of epigallocatechin-3-gallate (EGCG) as the most abundant catechin of green tea, a number of cellular and molecular mechanisms underlying the activities of this unique catechin have been proposed. Favorable effects of EGCG have been initially attributed to its scavenging effects on free radicals, inhibition of ROS-generating mechanisms and upregulation of antioxidant enzymes. Biologic actions of EGCG are concentration-dependent and under certain conditions EGCG may exert pro-oxidant activities, including generation of free radicals. The discovery of 67-kDa laminin as potential EGCG membrane target has broaden the likelihood that EGCG may function not only because of its highly reactive nature, but also via receptor-mediated activation of multiple signaling pathways involved in cell proliferation, angiogenesis and apoptosis. Finally, by acting as epigenetic modulator of DNA methylation and chromatin remodeling, EGCG may alter gene expression and modify miRNA activities. Despite unceasing research providing detailed insights, ECGC composite activities are still not completely understood. This review summarizes the most recent evidence on molecular mechanisms by which EGCG may activate signal transduction pathways, regulate transcription factors or promote epigenetic changes that may contribute to prevent pathologic processes involved in diabesity and its cardiovascular complications.

Total flavones of Dracocephalum moldavica L. protect astrocytes against H2O2-induced apoptosis through a mitochondria-dependent pathway

BACKGROUND

The active components of Dracocephalum moldavica L. (TFDM) can inhibit myocardial ischemia by inhibiting oxidative stress. However, the effects of TFDM on astrocytes have not been investigated in vitro. The current study aimed to explore whether TFDM protects astrocytes against H₂O₂-induced apoptosis through a mitochondria-dependent pathway.

METHODS

The human glioma cell line U87 was used to investigate the ability of TFDM to protect astrocytes against H₂O₂-induced apoptosis. The cell counting kit-8 assay and flow cytometry were used to detect cell viability, apoptosis, MMP, Ca²⁺ influx and reactive oxygen species (ROS). Lactate dehydrogenase (LDH) and malonic dialdehyde (MDA) levels were measured by ELISA. In addition, protein and mRNA expression changes were detected by Western blotting and qRT-PCR.

RESULTS

TFDM (0.78~200 μg/ml) had limited cytotoxic effects on the viability of U87 cells. Compared with the model group (treated with H2O2 only), cells treated with medium- and high-dose TFDM exhibited reduced MDA concentrations (P < 0.05) and ROS production (P < 0.05) and decreased MMP (P < 0.05) and reduced apoptosis (P < 0.05). The percentage of annexin V-FITC-stained cells was markedly suppressed by TFDM, confirming its anti-apoptotic properties. WB results showed that protein expression of Bcl-2-associated X protein (BAX), Caspase-3, Caspase-9, Caspase-12, and B-cell leukemia/lymphoma 2 (Bcl2) was reduced in the TFDM group compared with that in the model group (P < 0.05) and that expression of these proteins was normalized by TFDM treatment in a dose-dependent manner. According to RT-qPCR results, TFDM pretreatment resulted in reduced mRNA expression of BAX, Caspase-9, Caspase-12, p38MAPK, and CaMKII and increased mRNA expression of mTOR compared with the model group.

CONCLUSIONS

The current study revealed the protective effects of TFDM on U87 cells under oxidative stress conditions through the inhibition of a mitochondria-dependent pathway that is associated with the CaMKII/P38MAPK/ERK1/2 and PI3K/AKT/mTOR pathways.

Endothelial Ca2+ Signaling, Angiogenesis and Vasculogenesis: just What It Takes to Make a Blood Vessel

It has long been known that endothelial Ca²⁺ signals drive angiogenesis by recruiting multiple Ca²⁺-sensitive decoders in response to pro-angiogenic cues, such as vascular endothelial growth factor, basic fibroblast growth factor, stromal derived factor-1α and angiopoietins. Recently, it was shown that intracellular Ca²⁺ signaling also drives vasculogenesis by stimulation proliferation, tube formation and neovessel formation in endothelial progenitor cells. Herein, we survey how growth factors, chemokines and angiogenic modulators use endothelial Ca²⁺ signaling to regulate angiogenesis and vasculogenesis. The endothelial Ca²⁺ response to pro-angiogenic cues may adopt different waveforms, ranging from Ca²⁺ transients or biphasic Ca²⁺ signals to repetitive Ca²⁺ oscillations, and is mainly driven by endogenous Ca²⁺ release through inositol-1,4,5-trisphosphate receptors and by store-operated Ca²⁺ entry through Orai1 channels. Lysosomal Ca²⁺ release through nicotinic acid adenine dinucleotide phosphate-gated two-pore channels is, however, emerging as a crucial pro-angiogenic pathway, which sustains intracellular Ca²⁺ mobilization. Understanding how endothelial Ca²⁺ signaling regulates angiogenesis and vasculogenesis could shed light on alternative strategies to induce therapeutic angiogenesis or interfere with the aberrant vascularization featuring cancer and intraocular disorders.

CAMKII as a therapeutic target for growth factor-induced retinal and choroidal neovascularization

While anti-VEGF drugs are commonly used to inhibit pathological retinal and choroidal neovascularization, not all patients respond in an optimal manner. Mechanisms underpinning resistance to anti‑VEGF therapy include the upregulation of other proangiogenic factors. Therefore, therapeutic strategies that simultaneously target multiple growth factor signaling pathways would have significant value. Here, we show that Ca2+/calmodulin-dependent kinase II (CAMKII) mediates the angiogenic actions of a range of growth factors in human retinal endothelial cells and that this kinase acts as a key nodal point for the activation of several signal transduction cascades that are known to play a critical role in growth factor-induced angiogenesis. We also demonstrate that endothelial CAMKIIγ and -δ isoforms differentially regulate the angiogenic effects of different growth factors and that genetic deletion of these isoforms suppresses pathological retinal and choroidal neovascularization in vivo. Our studies suggest that CAMKII could provide a novel and efficacious target to inhibit multiple angiogenic signaling pathways for the treatment of vasoproliferative diseases of the eye. CAMKIIγ represents a particularly promising target, as deletion of this isoform inhibited pathological neovascularization, while enhancing reparative angiogenesis in the ischemic retina.

Physiological and unappreciated roles of CaMKII in the heart

In the cardiomyocyte, CaMKII has been identified as a nodal influencer of excitation-contraction and also excitation-transcription coupling. Its activity can be regulated in response to changes in intracellular calcium content as well as after several post-translational modifications. Some of the effects mediated by CaMKII may be considered adaptive, while effects of sustained CaMKII activity may turn into the opposite and are detrimental to cardiac integrity and function. As such, CaMKII has long been noted as a promising target for pharmacological inhibition, but the ubiquitous nature of CaMKII has made it difficult to target CaMKII specifically where it is detrimental. In this review, we provide a brief overview of the physiological and pathophysiological properties of CaMKII signaling, but we focus on the physiological and adaptive functions of CaMKII. Furthermore, special consideration is given to the emerging role of CaMKII as a mediator of inflammatory processes in the heart.

Cerebrovascular dysfunction with stress and depression

Maintenance of adequate tissue perfusion through a dense network of cerebral microvessels is critical for the perseveration of normal brain function. Regulation of the cerebral blood flow has to ensure adequate delivery of nutrients and oxygen with moment-to-moment adjustments to avoid both hypo- and hyper-perfusion of the brain tissue. Even mild impairments of cerebral blood flow regulation can have significant implications on brain function. Evidence suggests that chronic stress and depression elicits multifaceted functional impairments to the cerebral microcirculation, which plays a critical role in brain health and the pathogenesis of stress-related cognitive impairment and cerebrovascular events. Identifying the functional and structural changes to the brain that are induced by stress is crucial for achieving a realistic understanding of how related illnesses, which are highly disabling and with a large economic cost, can be managed or reversed. This overview discusses the stress-induced alterations in neurovascular coupling with specific attention to cerebrovascular regulation (endothelial dependent and independent vasomotor function, microvessel density). The pathophysiological consequences of cerebral microvascular dysfunction with stress and depression are explored.

CaMKII in Vascular Signalling: "Friend or Foe"?

Signalling mechanisms within and between cells of the vasculature enable function and maintain homeostasis. However, a number of these mechanisms also contribute to the pathophysiology of vascular disease states. The multifunctional signalling molecule calcium/calmodulin-dependent kinase II (CaMKII) has been shown to have critical functional effects in many tissue types. For example, CaMKII is known to have a dual role in cardiac physiology and pathology. The function of CaMKII within the vasculature is incompletely understood, but emerging evidence points to potential physiological and pathological roles. This review discusses the evidence for CaMKII signalling within the vasculature, with the aim to better understand both positive and potentially deleterious effects of CaMKII activation in vascular tissue.

CAMKIIγ suppresses an efferocytosis pathway in macrophages and promotes atherosclerotic plaque necrosis

Atherosclerosis is the underlying etiology of cardiovascular disease, the leading cause of death worldwide. Atherosclerosis is a heterogeneous disease in which only a small fraction of lesions lead to heart attack, stroke, or sudden cardiac death. A distinct type of plaque containing large necrotic cores with thin fibrous caps often precipitates these acute events. Here, we show that Ca2+/calmodulin-dependent protein kinase γ (CaMKIIγ) in macrophages plays a major role in the development of necrotic, thin-capped plaques. Macrophages in necrotic and symptomatic atherosclerotic plaques in humans as well as advanced atherosclerotic lesions in mice demonstrated activation of CaMKII. Western diet-fed LDL receptor-deficient (Ldlr-/-) mice with myeloid-specific deletion of CaMKII had smaller necrotic cores with concomitantly thicker collagen caps. These lesions demonstrated evidence of enhanced efferocytosis, which was associated with increased expression of the macrophage efferocytosis receptor MerTK. Mechanistic studies revealed that CaMKIIγ-deficient macrophages and atherosclerotic lesions lacking myeloid CaMKIIγ had increased expression of the transcription factor ATF6. We determined that ATF6 induces liver X receptor-α (LXRα), an Mertk-inducing transcription factor, and that increased MerTK expression and efferocytosis in CaMKIIγ-deficient macrophages is dependent on LXRα. These findings identify a macrophage CaMKIIγ/ATF6/LXRα/MerTK pathway as a key factor in the development of necrotic atherosclerotic plaques.

Calcium/calmodulin-dependent kinase 2 mediates Epac-induced spontaneous transient outward currents in rat vascular smooth muscle

KEY POINTS

The Ca2+ and redox-sensing enzyme Ca2+ /calmodulin-dependent kinase 2 (CaMKII) is a crucial and well-established signalling molecule in the heart and brain. In vascular smooth muscle, which controls blood flow by contracting and relaxing in response to complex Ca2+ signals and oxidative stress, surprisingly little is known about the role of CaMKII. The vasodilator-induced second messenger cAMP can relax vascular smooth muscle via its effector, exchange protein directly activated by cAMP (Epac), by activating spontaneous transient outward currents (STOCs) that hyperpolarize the cell membrane and reduce voltage-dependent Ca2+ influx. How Epac activates STOCs is unknown. In the present study, we map the pathway by which Epac increases STOC activity in contractile vascular smooth muscle and show that a critical step is the activation of CaMKII. To our knowledge, this is the first report of CaMKII activation triggering cellular activity known to induce vasorelaxation.

ABSTRACT

Activation of the major cAMP effector, exchange protein directly activated by cAMP (Epac), induces vascular smooth muscle relaxation by increasing the activity of ryanodine (RyR)-sensitive release channels on the peripheral sarcoplasmic reticulum. Resultant Ca2+ sparks activate plasma membrane Ca2+ -activated K+ (BKCa ) channels, evoking spontaneous transient outward currents (STOCs) that hyperpolarize the cell and reduce voltage-dependent Ca2+ entry. In the present study, we investigate the mechanism by which Epac increases STOC activity. We show that the selective Epac activator 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3', 5-cyclic monophosphate-AM (8-pCPT-AM) induces autophosphorylation (activation) of calcium/calmodulin-dependent kinase 2 (CaMKII) and also that inhibition of CaMKII abolishes 8-pCPT-AM-induced increases in STOC activity. Epac-induced CaMKII activation is probably initiated by inositol 1,4,5-trisphosphate (IP3 )-mobilized Ca2+ : 8-pCPT-AM fails to induce CaMKII activation following intracellular Ca2+ store depletion and inhibition of IP3 receptors blocks both 8-pCPT-AM-mediated CaMKII phosphorylation and STOC activity. 8-pCPT-AM does not directly activate BKCa channels, but STOCs cannot be generated by 8-pCPT-AM in the presence of ryanodine. Furthermore, exposure to 8-pCPT-AM significantly slows the initial rate of [Ca2+ ]i rise induced by the RyR activator caffeine without significantly affecting the caffeine-induced Ca2+ transient amplitude, a measure of Ca2+ store content. We conclude that Epac-mediated STOC activity (i) occurs via activation of CaMKII and (ii) is driven by changes in the underlying behaviour of RyR channels. To our knowledge, this is the first report of CaMKII initiating cellular activity linked to vasorelaxation and suggests novel roles for this Ca2+ and redox-sensing enzyme in the regulation of vascular tone and blood flow.