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Open Access Publications from the University of California

Scholarly Works (33 results)

  • Thesis
  • Peer Reviewed
UC Davis Electronic Theses and Dissertations (2023)

Cyclic adenosine monophosphate (cAMP) plays a significant role in vascular smooth muscle (VSM) biology, including proliferation, and differentiation. Moreover, cAMP signaling regulates VSM contractility. For instance, agonists acting through -adrenergic receptors (-AR) produce vasodilation by triggering adenylyl cyclases (ACs) activity and increasing cAMP levels VSM. 1-8 It has been shown by our group that VSM from mice exposed to secondhand smoke (SHS) had an attenuated cAMP level in response to the β-AR agonist isoproterenol (ISO), resulting in altered vascular reactivity. Tobacco smoke (TS) contains over 7,000 chemicals, including nicotine. 9 Nicotine is the primary addictive component in tobacco cigarettes (TCs) and has been shown to alter cellular cAMP production. 10,11 Yet, how nicotine impacts cAMP signaling in the vasculature, particularly in VSM, and the implications of these changes in vascular reactivity are unclear. Here we addressed this knowledge gap by systematically evaluating the effects of nicotine on cAMP production in native VSM from mice. Firstly, we determined the effects of nicotine on ISO-induced β-AR-mediated cAMP levels using a mouse expressing a cAMP biosensor specifically in smooth muscle (CAMPERSM). Then we determined the vascular reactivity in vessels of mice infused with nicotine using wire myography. Finally, we determined the expression of key proteins involved in cAMP synthesis and degradation. These experiments were designed to understand how nicotine alters cAMP signaling and the physiological consequences of nicotine exposure at the artery level. Our findings suggest that nicotine alters ISO-induced cAMP levels in VSM from intact arteries. This was correlated with impaired VSM relaxation in response to ISO. Our studies show that the altered ISO-induced cAMP synthesis and VSM relaxation in nicotine-treated mice can be rescued by inhibiting phosphodiesterases (PDEs). We also found that nicotine-infused mice have a decrease in AC6 abundance, which could contribute to impaired ISO-induced cAMP levels in VSM. Overall, this study uncovered mechanisms mediating nicotine impairment of cAMP synthesis and VSM relaxation, which may underlie alterations in vascular function in people exposed to or using nicotine products.

    Cover page: Nicotine Alters cAMP Signaling in Vascular Smooth Muscle
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2020)
    In this issue of Science Signaling, Thakore et al. report that the Ca2+-permeable channel TRPML1 closely associates with ryanodine receptors to induce Ca2+ sparks in native arterial myocytes. Functional studies revealed a key role for TRPML1 channels in regulation of arterial myocyte contractility and blood pressure.
      Cover page: TRPML1ng on sparks
      • Article
      • Peer Reviewed
      UC Davis Previously Published Works (2023)

      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.
        Cover page: SparkMaster 2: A New Software for Automatic Analysis of Calcium Spark Data
        • Article
        • Peer Reviewed
        UC Davis Previously Published Works (2015)

        Rationale

        Mitochondria are key integrators of convergent intracellular signaling pathways. Two important second messengers modulated by mitochondria are calcium and reactive oxygen species. To date, coherent mechanisms describing mitochondrial integration of calcium and oxidative signaling in arterial smooth muscle are incomplete.

        Objective

        To address and add clarity to this issue, we tested the hypothesis that mitochondria regulate subplasmalemmal calcium and hydrogen peroxide microdomain signaling in cerebral arterial smooth muscle.

        Methods and results

        Using an image-based approach, we investigated the impact of mitochondrial regulation of L-type calcium channels on subcellular calcium and reactive oxygen species signaling microdomains in isolated arterial smooth muscle cells. Our single-cell observations were then related experimentally to intact arterial segments and to living animals. We found that subplasmalemmal mitochondrial amplification of hydrogen peroxide microdomain signaling stimulates L-type calcium channels, and that this mechanism strongly impacts the functional capacity of the vasoconstrictor angiotensin II. Importantly, we also found that disrupting this mitochondrial amplification mechanism in vivo normalized arterial function and attenuated the hypertensive response to systemic endothelial dysfunction.

        Conclusions

        From these observations, we conclude that mitochondrial amplification of subplasmalemmal calcium and hydrogen peroxide microdomain signaling is a fundamental mechanism regulating arterial smooth muscle function. As the principle components involved are fairly ubiquitous and positioning of mitochondria near the plasma membrane is not restricted to arterial smooth muscle, this mechanism could occur in many cell types and contribute to pathological elevations of intracellular calcium and increased oxidative stress associated with many diseases.
          Cover page: Arterial Smooth Muscle Mitochondria Amplify Hydrogen Peroxide Microdomains Functionally Coupled to L-Type Calcium Channels
          • Article
          • Peer Reviewed
          UC Davis Previously Published Works (2022)
          Ion channels that influence membrane potential and intracellular calcium concentration control vascular smooth muscle excitability. Voltage-gated calcium channels (VGCC), transient receptor potential (TRP) channels, voltage (KV), and Ca2+-activated K+ (BK) channels are key regulators of vascular smooth muscle excitability and contractility. These channels are regulated by various signaling cues, including protein kinases and phosphatases. The effects of these ubiquitous signaling molecules often depend on the formation of macromolecular complexes that provide a platform for targeting and compartmentalizing signaling events to specific substrates. This manuscript summarizes our current understanding of specific molecular complexes involving VGCC, TRP, and KV and BK channels and their contribution to regulating vascular physiology.
            Cover page: Ion channel molecular complexes in vascular smooth muscle
            • Article
            • Peer Reviewed
            UC Davis Previously Published Works (2021)
            Diabetes affects millions of people worldwide. This devastating disease dramatically increases the risk of developing cardiovascular disorders. A hallmark metabolic abnormality in diabetes is hyperglycemia, which contributes to the pathogenesis of cardiovascular complications. These cardiovascular complications are, at least in part, related to hyperglycemia-induced molecular and cellular changes in the cells making up blood vessels. Whereas the mechanisms mediating endothelial dysfunction during hyperglycemia have been extensively examined, much less is known about how hyperglycemia impacts vascular smooth muscle function. Vascular smooth muscle function is exquisitely regulated by many ion channels, including several members of the potassium (K+) channel superfamily and voltage-gated L-type Ca2+ channels. Modulation of vascular smooth muscle ion channels function by hyperglycemia is emerging as a key contributor to vascular dysfunction in diabetes. In this review, we summarize the current understanding of how diabetic hyperglycemia modulates the activity of these ion channels in vascular smooth muscle. We examine underlying mechanisms, general properties, and physiological relevance in the context of myogenic tone and vascular reactivity.
              Cover page: Cellular and molecular effects of hyperglycemia on ion channels in vascular smooth muscle
              • Article
              • Peer Reviewed
              UC Davis Previously Published Works (2017)
              Enhanced L-type Ca2+ channel (LTCC) activity in arterial myocytes contributes to vascular dysfunction during diabetes. Modulation of LTCC activity under hyperglycemic conditions could result from membrane potential-dependent and independent mechanisms. We have demonstrated that elevations in extracellular glucose (HG), similar to hyperglycemic conditions during diabetes, stimulate LTCC activity through phosphorylation of CaV1.2 at serine 1928. Prior studies have also shown that HG can suppress the activity of K+ channels in arterial myocytes, which may contribute to vasoconstriction via membrane depolarization. Here, we used a mathematical model of membrane and Ca2+ dynamics in arterial myocytes to predict the relative roles of LTCC and K+ channel activity in modulating global Ca2+ in response to HG. Our data revealed that abolishing LTCC potentiation normalizes [Ca2+]i, despite the concomitant reduction in K+ currents in response to HG. These results suggest that LTCC stimulation may be the primary mechanism underlying vasoconstriction during hyperglycemia.
                Cover page: Predominant contribution of L-type Cav1.2 channel stimulation to impaired intracellular calcium and cerebral artery vasoconstriction in diabetic hyperglycemia
                • Article
                • Peer Reviewed
                UC Davis Previously Published Works (2018)
                Voltage-gated potassium (KV ) channels are key regulators of vascular smooth muscle contractility and vascular tone, and thus have major influence on the microcirculation. KV channels are important determinants of vascular smooth muscle membrane potential (Em ). A number of KV subunits are expressed in the plasma membrane of smooth muscle cells. Each subunit confers distinct kinetics and regulatory properties that allow for fine control of Em to orchestrate vascular tone. Modifications in KV subunit expression and/or channel activity can contribute to changes in vascular smooth muscle contractility in response to different stimuli and in diverse pathological conditions. Consistent with this, a number of studies suggest alterations in KV subunit expression and/or function as underlying contributing mechanisms for small resistance artery dysfunction in pathologies such as hypertension and metabolic disorders, including diabetes. Here, we review our current knowledge on the effects of these pathologies on KV channel expression and function in vascular smooth muscle cells, and the repercussions on (micro)vascular function.
                  Cover page: Regulation of voltage‐gated potassium channels in vascular smooth muscle during hypertension and metabolic disorders
                  • Article
                  • Peer Reviewed
                  UC Davis Previously Published Works (2020)
                  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.
                    Cover page: Purinergic Signaling During Hyperglycemia in Vascular Smooth Muscle Cells
                    • Article
                    • Peer Reviewed
                    UC Davis Previously Published Works (2022)
                    Diabetic vasculopathy is a significant cause of morbidity and mortality in the diabetic population. Hyperglycemia, one of the central metabolic abnormalities in diabetes, has been associated with vascular dysfunction due to endothelial cell damage. However, studies also point toward vascular smooth muscle as a locus for hyperglycemia-induced vascular dysfunction. Emerging evidence implicates hyperglycemia-induced regulation of vascular L-type Ca2+ channels CaV1.2 as a potential mechanism for vascular dysfunction during diabetes. This chapter summarizes our current understanding of vascular CaV1.2 channels and their regulation during physiological and hyperglycemia/diabetes conditions. We will emphasize the role of CaV1.2 in vascular smooth muscle, the effects of elevated glucose on CaV1.2 function, and the mechanisms underlying its dysregulation in hyperglycemia and diabetes. We conclude by examining future directions and gaps in knowledge regarding CaV1.2 regulation in health and during diabetes.
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