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This review paper explores the critical role of vascular ion channels in the regulation of cerebral artery function and examines the impact of Alzheimer's disease (AD) on these processes. Vascular ion channels are fundamental in controlling vascular tone, blood flow, and endothelial function in cerebral arteries. Dysfunction of these channels can lead to impaired cerebral autoregulation, contributing to cerebrovascular pathologies. AD, characterized by the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles, has been increasingly linked to vascular abnormalities, including altered vascular ion channel activity. Here, we briefly review the role of vascular ion channels in cerebral blood flow control and neurovascular coupling. We then examine the vascular defects in AD, the current understanding of how AD pathology affects vascular ion channel function, and how these changes may lead to compromised cerebral blood flow and neurodegenerative processes. Finally, we provide future perspectives and conclusions. Understanding this topic is important as ion channels may be potential therapeutic targets for improving cerebrovascular health and mitigating AD progression., (© 2024 The Author(s). Microcirculation published by John Wiley & Sons Ltd.)

Background: Calcium (Ca) sparks are elementary units of subcellular Ca release in cardiomyocytes and other cells. Accordingly, Ca spark imaging is an essential tool for understanding the physiology and pathophysiology of Ca handling and is used to identify new drugs targeting Ca-related cellular dysfunction (eg, cardiac arrhythmias). The large volumes of imaging data produced during such experiments require accurate and high-throughput analysis., Methods: We developed a new software tool SparkMaster 2 (SM2) for the analysis of Ca sparks imaged by confocal line-scan microscopy, combining high accuracy, flexibility, and user-friendliness. SM2 is distributed as a stand-alone application requiring no installation. It can be controlled using a simple-to-use graphical user interface, or using Python scripting., Results: SM2 is shown to have the following strengths: (1) high accuracy at identifying Ca release events, clearly outperforming previous highly successful software SparkMaster; (2) multiple types of Ca release events can be identified using SM2: Ca sparks, waves, miniwaves, and long sparks; (3) SM2 can accurately split and analyze individual sparks within spark clusters, a capability not handled adequately by prior tools. We demonstrate the practical utility of SM2 in two case studies, investigating how Ca levels affect spontaneous Ca release, and how large-scale release events may promote release refractoriness. SM2 is also useful in atrial and smooth muscle myocytes, across different imaging conditions., Conclusions: SparkMaster 2 is a new, much-improved user-friendly software for accurate high-throughput analysis of line-scan Ca spark imaging data. It is free, easy to use, and provides valuable built-in features to facilitate visualization, analysis, and interpretation of Ca spark data. It should enhance the quality and throughput of Ca spark and wave analysis across cell types, particularly in the study of arrhythmogenic Ca release events in cardiomyocytes., Competing Interests: Disclosures None.

The cellular mechanisms mediating norepinephrine (NE) functions in brain to result in behaviors are unknown. We identified the L-type Ca 2+ channel (LTCC) Ca V 1.2 as a principal target for G q -coupled α 1 -adrenergic receptors (ARs). α 1 AR signaling increased LTCC activity in hippocampal neurons. This regulation required protein kinase C (PKC)-mediated activation of the tyrosine kinases Pyk2 and, downstream, Src. Pyk2 and Src were associated with Ca V 1.2. In model neuroendocrine PC12 cells, stimulation of PKC induced tyrosine phosphorylation of Ca V 1.2, a modification abrogated by inhibition of Pyk2 and Src. Upregulation of LTCC activity by α 1 AR and formation of a signaling complex with PKC, Pyk2, and Src suggests that Ca V 1.2 is a central conduit for signaling by NE. Indeed, a form of hippocampal long-term potentiation (LTP) in young mice requires both the LTCC and α 1 AR stimulation. Inhibition of Pyk2 and Src blocked this LTP, indicating that enhancement of Ca V 1.2 activity via α 1 AR-Pyk2-Src signaling regulates synaptic strength., Competing Interests: KM, PB, PH, KK, MS, MZ, SH, MN, MN, MH, JH No competing interests declared, (© 2023, Man et al.)

Background: Secondhand smoke (SHS) is a significant risk factor for cardiovascular morbidity and mortality with an estimated 80% of SHS-related deaths attributed to cardiovascular causes. Public health measures and smoking bans have been successful both in reducing SHS exposure and improving cardiovascular outcomes in non-smokers. Soluble epoxide hydrolase (sEH) inhibitors have been shown to attenuate tobacco exposure-induced lung inflammatory responses, making them a promising target for mitigating SHS exposure-induced cardiovascular outcomes. Objectives: The objectives of this study were to determine 1) effects of environmentally relevant SHS exposure on cardiac autonomic function and blood pressure (BP) regulation and 2) whether prophylactic administration of an sEH inhibitor (TPPU) can reduce the adverse cardiovascular effects of SHS exposure. Methods: Male C57BL/6J mice (11 weeks old) implanted with BP/electrocardiogram (ECG) telemetry devices were exposed to filtered air or 3 mg/m 3 of SHS (6 hr/d, 5 d/wk) for 12 weeks, followed by 4 weeks of recovery in filtered air. Some mice received TPPU in drinking water (15 mg/L) throughout SHS exposure. BP, heart rate (HR), HR variability (HRV), baroreflex sensitivity (BRS), and BP variability were determined monthly. Results: SHS exposure significantly decreased 1) short-term HRV by ∼20% ( p < 0.05) within 4 weeks; 2) overall HRV with maximum effect at 12 weeks (-15%, p < 0.05); 3) pulse pressure (-8%, p < 0.05) as early as week 4; and 4) BRS with maximum effect at 12 weeks (-11%, p < 0.05). Four weeks of recovery following 12 weeks of SHS ameliorated all SHS-induced cardiovascular detriments. Importantly, mice exposed to TPPU in drinking water during SHS-related exposure were protected from SHS cardiovascular consequences. Discussion: The data suggest that 1) environmental relevant SHS exposure significantly alters cardiac autonomic function and BP regulation; 2) cardiovascular consequences from SHS can be reversed by discontinuing SHS exposure; and 3) inhibiting sEH can prevent SHS-induced cardiovascular consequences., Competing Interests: SH and BH are authors of University of California patents on soluble epoxide hydrolase inhibitors currently in human trials sponsored by EicOsis Human Health. EK is an employee and owns stock in AstraZeneca. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Pan, Karey, Nieves-Cintron, Chen, Hwang, Hammock, Pinkerton and Chen.)

The L-type Ca 2+ channel Ca V 1.2 controls gene expression, cardiac contraction, and neuronal activity. Calmodulin (CaM) governs Ca V 1.2 open probability (Po) and Ca 2+ -dependent inactivation (CDI) but the mechanisms remain unclear. Here, we present electrophysiological data that identify a half Ca 2+ -saturated CaM species (Ca 2 /CaM) with Ca 2+ bound solely at the third and fourth EF-hands (EF3 and EF4) under resting Ca 2+ concentrations (50-100 nM) that constitutively preassociates with Ca V 1.2 to promote Po and CDI. We also present an NMR structure of a complex between the Ca V 1.2 IQ motif (residues 1644-1665) and Ca 2 /CaM 12' , a calmodulin mutant in which Ca 2+ binding to EF1 and EF2 is completely disabled. We found that the CaM 12' N-lobe does not interact with the IQ motif. The CaM 12' C-lobe bound two Ca 2+ ions and formed close contacts with IQ residues I1654 and Y1657. I1654A and Y1657D mutations impaired CaM binding, CDI, and Po, as did disabling Ca 2+ binding to EF3 and EF4 in the CaM 34 mutant when compared to WT CaM. Accordingly, a previously unappreciated Ca 2 /CaM species promotes Ca V 1.2 Po and CDI, identifying Ca 2 /CaM as an important mediator of Ca signaling., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Rationale: Cardiotoxic β 1 adrenergic receptor (β 1 AR)-CaMKII (calmodulin-dependent kinase II) signaling is a major and critical feature associated with development of heart failure. SAP97 (synapse-associated protein 97) is a multifunctional scaffold protein that binds directly to the C-terminus of β 1 AR and organizes a receptor signalosome., Objective: We aim to elucidate the dynamics of β 1 AR-SAP97 signalosome and its potential role in chronic cardiotoxic β 1 AR-CaMKII signaling that contributes to development of heart failure., Methods and Results: The integrity of cardiac β 1 AR-SAP97 complex was examined in heart failure. Cardiac-specific deletion of SAP97 was developed to examine β 1 AR signaling in aging mice, after chronic adrenergic stimulation, and in pressure overload hypertrophic heart failure. We show that the β 1 AR-SAP97 signaling complex is reduced in heart failure. Cardiac-specific deletion of SAP97 yields an aging-dependent cardiomyopathy and exacerbates cardiac dysfunction induced by chronic adrenergic stimulation and pressure overload, which are associated with elevated CaMKII activity. Loss of SAP97 promotes PKA (protein kinase A)-dependent association of β 1 AR with arrestin2 and CaMKII and turns on an Epac (exchange protein directly activated by cAMP)-dependent activation of CaMKII, which drives detrimental functional and structural remodeling in myocardium. Moreover, we have identified that GRK5 (G-protein receptor kinase-5) is necessary to promote agonist-induced dissociation of SAP97 from β 1 AR. Cardiac deletion of GRK5 prevents adrenergic-induced dissociation of β 1 AR-SAP97 complex and increases in CaMKII activity in hearts., Conclusions: These data reveal a critical role of SAP97 in maintaining the integrity of cardiac β 1 AR signaling and a detrimental cardiac GRK5-CaMKII axis that can be potentially targeted in heart failure therapy. Graphical Abstract: A graphical abstract is available for this article.

In this issue of Science Signaling , Thakore et al. report that the Ca 2+ -permeable channel TRPML1 closely associates with ryanodine receptors to induce Ca 2+ sparks in native arterial myocytes. Functional studies revealed a key role for TRPML1 channels in regulation of arterial myocyte contractility and blood pressure., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

The activation of purinergic receptors by nucleotides and/or nucleosides plays an important role in the control of vascular function, including modulation of vascular smooth muscle excitability, and vascular reactivity. Accordingly, purinergic receptor actions, acting as either ion channels (P2X) or G protein-coupled receptors (GCPRs) (P1, P2Y), target diverse downstream effectors, and substrates to regulate vascular smooth muscle function and vascular reactivity. Both vasorelaxant and vasoconstrictive effects have been shown to be mediated by different purinergic receptors in a vascular bed- and species-specific manner. Purinergic signaling has been shown to play a key role in altering vascular smooth muscle excitability and vascular reactivity following acute and short-term elevations in extracellular glucose (e.g., hyperglycemia). Moreover, there is evidence that vascular smooth muscle excitability and vascular reactivity is severely impaired during diabetes and that this is mediated, at least in part, by activation of purinergic receptors. Thus, purinergic receptors present themselves as important candidates mediating vascular reactivity in hyperglycemia, with potentially important clinical and therapeutic potential. In this review, we provide a narrative summarizing our current understanding of the expression, function, and signaling of purinergic receptors specifically in vascular smooth muscle cells and discuss their role in vascular complications following hyperglycemia and diabetes., (Copyright © 2020 Martin-Aragon Baudel, Espinosa-Tanguma, Nieves-Cintron and Navedo.)

The L-type Ca 2+ channel Ca V 1.2 governs gene expression, cardiac contraction, and neuronal activity. Binding of α-actinin to the IQ motif of Ca V 1.2 supports its surface localization and postsynaptic targeting in neurons. We report a bi-functional mechanism that restricts Ca V 1.2 activity to its target sites. We solved separate NMR structures of the IQ motif (residues 1,646-1,664) bound to α-actinin-1 and to apo-calmodulin (apoCaM). The Ca V 1.2 K1647A and Y1649A mutations, which impair α-actinin-1 but not apoCaM binding, but not the F1658A and K1662E mutations, which impair apoCaM but not α-actinin-1 binding, decreased single-channel open probability, gating charge movement, and its coupling to channel opening. Thus, α-actinin recruits Ca V 1.2 to defined surface regions and simultaneously boosts its open probability so that Ca V 1.2 is mostly active when appropriately localized., (© 2020 The Authors.)

G protein-coupled receptors (GPCRs) transduce pleiotropic intracellular signals in mammalian cells. Here, we report neuronal excitability of β-blockers carvedilol and alprenolol at clinically relevant nanomolar concentrations. Carvedilol and alprenolol activate β 2 AR, which promote G protein signaling and cAMP/PKA activities without action of G protein receptor kinases (GRKs). The cAMP/PKA activities are restricted within the immediate vicinity of activated β 2 AR, leading to selectively enhance PKA-dependent phosphorylation and stimulation of endogenous L-type calcium channel (LTCC) but not AMPA receptor in rat hippocampal neurons. Moreover, we have engineered a mutant β 2 AR that lacks the catecholamine binding pocket. This mutant is preferentially activated by carvedilol but not the orthosteric agonist isoproterenol. Carvedilol activates the mutant β 2 AR in mouse hippocampal neurons augmenting LTCC activity through cAMP/PKA signaling. Together, our study identifies a mechanism by which β-blocker-dependent activation of GPCRs promotes spatially restricted cAMP/PKA signaling to selectively target membrane downstream effectors such as LTCC in neurons., Competing Interests: AS, DC, MK, PB, BX, QS, JM, KM, MN, JH, MN, XY, YX No competing interests declared, (© 2019, Shen et al.)

G protein-coupled receptors (GPCRs) transduce pleiotropic intracellular signals in a broad range of physiological responses and disease states. Activated GPCRs can undergo agonist-induced phosphorylation by G protein receptor kinases (GRKs) and second messenger-dependent protein kinases such as protein kinase A (PKA). Here, we characterize spatially segregated subpopulations of β 2 -adrenergic receptor (β 2 AR) undergoing selective phosphorylation by GRKs or PKA in a single cell. GRKs primarily label monomeric β 2 ARs that undergo endocytosis, whereas PKA modifies dimeric β 2 ARs that remain at the cell surface. In hippocampal neurons, PKA-phosphorylated β 2 ARs are enriched in dendrites, whereas GRK-phosphorylated β 2 ARs accumulate in soma, being excluded from dendrites in a neuron maturation-dependent manner. Moreover, we show that PKA-phosphorylated β 2 ARs are necessary to augment the activity of L-type calcium channel. Collectively, these findings provide evidence that functionally distinct subpopulations of this prototypical GPCR exist in a single cell.