CaMKII in Vascular Signalling: "Friend or Foe"?

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.

Impaired intracellular calcium homeostasis enhances protein O-GlcNAcylation and promotes vascular calcification and stiffness in diabetes

Vascular calcification is accelerated in patients with diabetes mellitus and increases risk of cardiovascular events and mortality. Vascular smooth muscle cells (VSMC) play a key role in regulating vascular tone and contribute significantly to the development of diabetic vasculopathy. In this study, the function of stromal interaction molecule 1 (STIM1), an important regulator for intracellular calcium homeostasis, in diabetic vascular calcification was investigated, and the underlying molecular mechanisms were uncovered. A SMC-specific STIM1 deletion mouse model (STIM1Δ/Δ) was generated by breeding the STIM1 floxed mice (STIM1f/f) with SM22α-Cre transgenic mice. Using aortic arteries from the STIM1Δ/Δ mice and their STIM1f/f littermates, we found that SMC-specific STIM1 deletion induced calcification of aortic arteries cultured in osteogenic media ex vivo. Furthermore, STIM1 deficiency promoted osteogenic differentiation and calcification of VSMC from the STIM1Δ/Δ mice. In the low-dose streptozotocin (STZ)-induced mouse model of diabetes, SMC-specific STIM1 deletion markedly enhanced STZ-induced vascular calcification and stiffness in the STIM1Δ/Δ mice. The diabetic mice with SMC-specific STIM1 ablation also exhibited increased aortic expression of the key osteogenic transcription factor, Runx2, and protein O-GlcNAcylation, an important post-translational modulation that we have reported to promote vascular calcification and stiffness in diabetes. Consistently, elevation of O-GlcNAcylation was demonstrated in aortic arteries and VSMC from the STIM1Δ/Δ mice. Inhibition of O-GlcNAcylation with a pharmacological inhibitor abolished STIM1 deficiency-induced VSMC calcification, supporting a critical role of O-GlcNAcylation in mediating STIM1 deficiency-induced VSMC calcification. Mechanistically, we identified that STIM1 deficiency resulted in impaired calcium homeostasis, which activated calcium signaling and increased endoplasmic reticulum (ER) stress in VSMC, while inhibition of ER stress attenuated STIM1-induced elevation of protein O-GlcNAcylation. In conclusion, the study has demonstrated a causative role of SMC-expressed STIM1 in regulating vascular calcification and stiffness in diabetes. We have further identified a novel mechanisms underlying STIM1 deficiency-induced impairment of calcium homeostasis and ER stress in upregulation of protein O-GlcNAcylation in VSMC, which promotes VSMC osteogenic differentiation and calcification in diabetes.

Capsaicin: A Potential Treatment to Improve Cerebrovascular Function and Cognition in Obesity and Ageing

Impaired cognition is the primary symptom of dementia, which can lead to functional disability and reduced quality of life among an increasingly ageing population. Ageing is associated with increased oxidative stress, chronic low-grade systemic inflammation, and endothelial dysfunction, which reduces cerebrovascular function leading to cognitive decline. Chronic low-grade systemic inflammatory conditions, such as obesity, exacerbate this decline beyond normal ageing and predispose individuals to neurodegenerative diseases, such as dementia. Capsaicin, the major pungent molecule of chilli, has recently demonstrated improvements in cognition in animal models via activation of the transient receptor potential vanilloid channel 1 (TRPV1). Capsaicin-induced TRPV1 activation reduces adiposity, chronic low-grade systemic inflammation, and oxidative stress, as well as improves endothelial function, all of which are associated with cerebrovascular function and cognition. This review examines the current literature on capsaicin and Capsimax, a capsaicin supplement associated with reduced gastrointestinal irritation compared to capsaicin. Acute and chronic capsaicin treatment can improve cognition in animals. However, studies adequately assessing the effects of capsaicin on cerebrovascular function, and cognition in humans do not exist. Capsimax may be a potentially safe therapeutic intervention for future clinical trials testing the effects of capsaicin on cerebrovascular function and cognition.

Oxidative stress–induced autonomous activation of the calcium/calmodulin-dependent kinase II involves disulfide formation in the regulatory domain

Calcium/calmodulin-dependent protein kinase II δ (CaMKIIδ) has a pivotal role in cardiac signaling. Constitutive and deleterious CaMKII “autonomous” activation is induced by oxidative stress, and the previously reported mechanism involves oxidation of methionine residues in the regulatory domain. Here, we demonstrate that covalent oxidation leads to a disulfide bond with Cys273 in the regulatory domain causing autonomous activity. Autonomous activation was induced by treating CaMKII with diamide or histamine chloramine, two thiol-oxidizing agents. Autonomy was reversed when the protein was incubated with DTT or thioredoxin to reduce disulfide bonds. Tryptic mapping of the activated CaMKII revealed formation of a disulfide between Cys273 and Cys290 in the regulatory domain. We determined the apparent pKa of those Cys and found that Cys273 had a low pKa while that of Cys290 was elevated. The low pKa of Cys273 facilitates oxidation of its thiol to the sulfenic acid at physiological pH. The reactive sulfenic acid then attacks the thiol of Cys290 to form the disulfide. The previously reported CaMKII mutant in which methionine residues 281 and 282 were mutated to valine (MMVV) protects mice and flies from cardiac decompensation induced by oxidative stress. Our initial hypothesis was that the MMVV mutant underwent a conformational change that prevented disulfide formation and autonomous activation. However, we found that the thiol-oxidizing agents induced autonomy in the MMVV mutant and that the mutant undergoes rapid degradation by the cell, potentially preventing accumulation of the injurious autonomous form. Together, our results highlight additional mechanistic details of CaMKII autonomous activation.

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.

Vascular endothelial growth factor on Runt-related transcript factor-2 in aortic valve cells

BACKGROUND

Calcific aortic valve disease is associated with ageing and high mortality. However, no effective pharmacological treatment has been developed. Vascular endothelial growth factor (VEGF) and its receptor are overexpressed in the calcified aortic valve tissue. However, the role of VEGF in calcific aortic valve disease pathogenesis and its underlying mechanisms remain unclear.

MATERIALS AND METHODS

Runt-related transcription factor 2 expression and calcium-related signalling were investigated in porcine valvular interstitial cells with or without human VEGF-A recombinant protein (VEGF₁₆₅ , 1-100 ng/mL) treatment and/or calmodulin-dependent kinase II (CaMKII) inhibitor (KN93, 10 µmol/L) and inositol triphosphate receptor inhibitor (2-aminoethyldiphenyl borate, 30 µmol/L) for 5 days.

RESULTS

VEGF₁₆₅ -treated cells had higher Runt-related transcription factor 2 expression and CaMKII/ adenosine 3',5'-monophosphate response element-binding protein (CREB) signalling activation than did control cells. KN93 reduced Runt-related transcription factor 2 expression and CREB phosphorylation in VEGF₁₆₅ -treated cells. The 2-aminoethyldiphenyl borate also reduced Runt-related transcription factor 2 expression in VICs treated with VEGF₁₆₅ .

CONCLUSION

VEGF upregulated Runt-related transcription factor 2 expression in VICs by activating the IP3R/CaMKII/CREB signalling pathway.

Role of CaMKII in the regulation of fatty acids and lipid metabolism

BACKGROUND & AIMS

Previous studies have reported the beneficial roles of the activation of calmodulin-dependent protein kinase (CaMK)II to many cellular functions associated with human health. This review aims at discussing its activation by exercise as well as its roles in the regulation of unsaturated, saturated, omega 3 fatty acids, and lipid metabolism.

METHODS

A wide literature search was conducted using online database such as 'PubMed', 'Google Scholar', 'Researcher', 'Scopus' and the website of World Health Organization (WHO) as well as Control Disease and Prevention (CDC). The criteria for the search were mainly lipid and fatty acid metabolism, diabetes, and metabolic syndrome (MetS). A total of ninety-seven articles were included in the review.

RESULTS

Calmodulin-dependent protein kinase activation by exercise is helpful in controlling membrane lipids related with type 2 diabetes and obesity. CaMKII regulates many health beneficial cellular functions in individuals who exercise compared with those who do not exercise. Regulation of lipid metabolism and fatty acids are crucial in the improvement of metabolic syndrome.

CONCLUSIONS

Approaches that involve CaMKII could be a new avenue for designing novel and effective therapeutic modalities in the treatment or better management of metabolic diseases such as type 2 diabetes and obesity.

Broad-Spectrum Flavivirus Inhibitors: a Medicinal Chemistry Point of View

Infections by flaviviruses, such as Dengue, West Nile, Yellow Fever and Zika viruses, represent a growing risk for global health. There are vaccines only for few flaviviruses while no effective treatments are available. Flaviviruses share epidemiological, structural, and ecologic features and often different viruses can co-infect the same host. Therefore, the identification of broad-spectrum inhibitors is highly desirable either for known flaviviruses or for viruses that likely will emerge in the future. Strategies targeting both virus and host factors have been pursued to identify broad-spectrum antiflaviviral agents. In this review, we describe the most promising and best characterized targets and their relative broad-spectrum inhibitors, identified by drug repurposing/libraries screenings and by focused medicinal chemistry campaigns. Finally, we discuss about future strategies to identify new broad-spectrum antiflavivirus agents.

Benzenesulfonamide Derivatives as Calcium/Calmodulin-Dependent Protein Kinase Inhibitors and Antiviral Agents against Dengue and Zika Virus Infections

Emerging and resurging mosquito-borne flaviviruses are an important public health challenge. The increased prevalence of dengue virus (DENV) infection has had a significant socioeconomic impact on epidemic countries. The recent outbreak of Zika virus (ZIKV) has created an international public health emergency because ZIKV infection has been linked to congenital defects and Guillain-Barré syndrome. To develop potentially prophylactic antiviral drugs for combating these acute infectious diseases, we have targeted the host calcium/calmodulin-dependent kinase II (CaMKII) for inhibition. By using CaMKII structure-guided inhibitor design, we generated four families of benzenesulfonamide (BSA) derivatives for SAR analysis. Among these substances, N-(4-cycloheptyl-4-oxobutyl)-4-methoxy-N-phenylbenzenesulfonamide (9) showed superior properties as a lead CaMKII inhibitor and antiviral agent. BSA 9 inhibited CaMKII activity with an IC₅₀ value of 0.79 μM and displayed EC₅₀ values of 1.52 μM and 1.91 μM against DENV and ZIKV infections of human neuronal BE(2)C cells, respectively. Notably, 9 significantly reduced the viremia level and increased animal survival time in mouse-challenge models.