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Sancho M, Klug NR, Harraz OF, Hill-Eubanks D, Nelson MT. Distinct potassium channel types in brain capillary pericytes. Biophys J 2024; 123:2110-2121. [PMID: 38444160 PMCID: PMC11309962 DOI: 10.1016/j.bpj.2024.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/25/2024] [Accepted: 03/01/2024] [Indexed: 03/07/2024] Open
Abstract
Capillaries, composed of electrically coupled endothelial cells and overlying pericytes, constitute the vast majority of blood vessels in the brain. The most arteriole-proximate three to four branches of the capillary bed are covered by α-actin-expressing, contractile pericytes. These mural cells have a distinctive morphology and express different markers compared with their smooth muscle cell (SMC) cousins but share similar excitation-coupling contraction machinery. Despite this similarity, pericytes are considerably more depolarized than SMCs at low intravascular pressures. We have recently shown that pericytes, such as SMCs, possess functional voltage-dependent Ca2+ channels and ATP-sensitive K+ channels. Here, we further investigate the complement of pericyte ion channels, focusing on members of the K+ channel superfamily. Using NG2-DsRed-transgenic mice and diverse configurations of the patch-clamp technique, we demonstrate that pericytes display robust inward-rectifier K+ currents that are primarily mediated by the Kir2 family, based on their unique biophysical characteristics and sensitivity to micromolar concentrations of Ba2+. Moreover, multiple lines of evidence, including characteristic kinetics, sensitivity to specific blockers, biophysical attributes, and distinctive single-channel properties, established the functional expression of two voltage-dependent K+ channels: KV1 and BKCa. Although these three types of channels are also present in SMCs, they exhibit distinctive current density and kinetics profiles in pericytes. Collectively, these findings underscore differences in the operation of shared molecular features between pericytes and SMCs and highlight the potential contribution of these three K+ ion channels in setting pericyte membrane potential, modulating capillary hemodynamics, and regulating cerebral blood flow.
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Affiliation(s)
- Maria Sancho
- Department of Pharmacology, University of Vermont, Burlington, Vermont; Department of Physiology, Faculty of Medicine, Complutense University of Madrid, Madrid, Spain.
| | - Nicholas R Klug
- Department of Pharmacology, University of Vermont, Burlington, Vermont
| | - Osama F Harraz
- Department of Pharmacology, University of Vermont, Burlington, Vermont; Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine, University of Vermont, Burlington, Vermont
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, Vermont; Vermont Center for Cardiovascular and Brain Health, Larner College of Medicine, University of Vermont, Burlington, Vermont; Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom.
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2
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Mitsui R, Miwa-Nishimura K, Hashitani H. Roles of endothelial prostaglandin I 2 in maintaining synchronous spontaneous Ca 2+ transients in rectal capillary pericytes. J Physiol 2023; 601:5213-5240. [PMID: 37819628 DOI: 10.1113/jp284284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 09/25/2023] [Indexed: 10/13/2023] Open
Abstract
In hollow visceral organs, capillary pericytes appear to drive spontaneous Ca2+ transients in the upstream arterioles. Here, mechanisms underlying the intercellular synchrony of pericyte Ca2+ transients were explored. Ca2+ dynamics in NG2 chondroitin sulphate proteoglycan (NG2)-expressing capillary pericytes were examined using rectal mucosa-submucosa preparations of NG2-GCaMP6 mice. Spontaneous Ca2+ transients arising from endoplasmic reticulum Ca2+ release were synchronously developed amongst capillary pericytes in a gap junction blocker (3 μM carbenoxolone)-sensitive manner and could spread into upstream vascular segments. Spontaneous Ca2+ transients were suppressed by the Ca2+ -activated Cl- channel (CaCC) blocker niflumic acid and their synchrony was diminished by a TMEM16A inhibitor (3 μM Ani9) in accordance with TMEM16A immunoreactivity in pericytes. In capillaries where cyclooxygenase (COX)-2 immunoreactivity was expressed in endothelium but not pericytes, non-selective COX inhibitors (1 μM indomethacin or 10 μM diclofenac) or COX-2 inhibitor (10 μM NS 398) disrupted the synchrony of spontaneous Ca2+ transients and raised the basal Ca2+ level. Subsequent prostaglandin I2 (PGI2 ; 100 nM) or the KATP channel opener levcromakalim restored the synchrony with a reduction in the Ca2+ level. PGI2 receptor antagonist (1 μM RO1138452) also disrupted the synchrony of spontaneous Ca2+ transients and increased the basal Ca2+ level. Subsequent levcromakalim restored the synchrony and reversed the Ca2+ rise. Thus, the synchrony of spontaneous Ca2+ transients in pericytes appears to be developed by the spread of spontaneous transient depolarisations arising from the opening of TMEM16A CaCCs. Endothelial PGI2 may play a role in maintaining the synchrony, presumably by stabilising the resting membrane potential in pericytes. KEY POINTS: Capillary pericytes in the rectal mucosa generate synchronous spontaneous Ca2+ transients that could spread into the upstream vascular segment. Spontaneous Ca2+ release from the endoplasmic reticulum (ER) triggers the opening of Ca2+ -activated Cl- channel TMEM16A and resultant depolarisations that spread amongst pericytes via gap junctions, establishing the synchrony of spontaneous Ca2+ transients in pericytes. Prostaglandin I2 (PGI2 ), which is constitutively produced by the endothelium depending on cyclooxygenase-2, appears to prevent premature ER Ca2+ releases in the pericytes allowing periodic, regenerative Ca2+ releases. Endothelial PGI2 may maintain the synchrony of pericyte activity by stabilising pericyte resting membrane potential by opening of KATP channels.
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Affiliation(s)
- Retsu Mitsui
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan
| | - Kyoko Miwa-Nishimura
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan
| | - Hikaru Hashitani
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan
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3
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Phillips B, Clark J, Martineau É, Rungta RL. Orai, RyR, and IP 3R channels cooperatively regulate calcium signaling in brain mid-capillary pericytes. Commun Biol 2023; 6:493. [PMID: 37149720 PMCID: PMC10164186 DOI: 10.1038/s42003-023-04858-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 04/21/2023] [Indexed: 05/08/2023] Open
Abstract
Pericytes are multifunctional cells of the vasculature that are vital to brain homeostasis, yet many of their fundamental physiological properties, such as Ca2+ signaling pathways, remain unexplored. We performed pharmacological and ion substitution experiments to investigate the mechanisms underlying pericyte Ca2+ signaling in acute cortical brain slices of PDGFRβ-Cre::GCaMP6f mice. We report that mid-capillary pericyte Ca2+ signalling differs from ensheathing type pericytes in that it is largely independent of L- and T-type voltage-gated calcium channels. Instead, Ca2+ signals in mid-capillary pericytes were inhibited by multiple Orai channel blockers, which also inhibited Ca2+ entry triggered by endoplasmic reticulum (ER) store depletion. An investigation into store release pathways indicated that Ca2+ transients in mid-capillary pericytes occur through a combination of IP3R and RyR activation, and that Orai store-operated calcium entry (SOCE) is required to sustain and amplify intracellular Ca2+ increases evoked by the GqGPCR agonist endothelin-1. These results suggest that Ca2+ influx via Orai channels reciprocally regulates IP3R and RyR release pathways in the ER, which together generate spontaneous Ca2+ transients and amplify Gq-coupled Ca2+ elevations in mid-capillary pericytes. Thus, SOCE is a major regulator of pericyte Ca2+ and a target for manipulating their function in health and disease.
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Affiliation(s)
- Braxton Phillips
- Department of Neuroscience, Université de Montréal, Montréal, QC, Canada
- Department of Stomatology, Faculty of Dental Medicine, Université de Montréal, Montréal, QC, H3C3J7, Canada
- Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage, Université de Montréal, Montréal, QC, Canada
| | - Jenna Clark
- Department of Neuroscience, Université de Montréal, Montréal, QC, Canada
- Department of Stomatology, Faculty of Dental Medicine, Université de Montréal, Montréal, QC, H3C3J7, Canada
- Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage, Université de Montréal, Montréal, QC, Canada
| | - Éric Martineau
- Department of Stomatology, Faculty of Dental Medicine, Université de Montréal, Montréal, QC, H3C3J7, Canada
- Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage, Université de Montréal, Montréal, QC, Canada
| | - Ravi L Rungta
- Department of Stomatology, Faculty of Dental Medicine, Université de Montréal, Montréal, QC, H3C3J7, Canada.
- Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage, Université de Montréal, Montréal, QC, Canada.
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Pericyte dysfunction and loss of interpericyte tunneling nanotubes promote neurovascular deficits in glaucoma. Proc Natl Acad Sci U S A 2022; 119:2110329119. [PMID: 35135877 PMCID: PMC8851476 DOI: 10.1073/pnas.2110329119] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2021] [Indexed: 12/14/2022] Open
Abstract
Reduced blood flow and impaired neurovascular coupling are recognized features of glaucoma, the leading cause of irreversible blindness worldwide, but the mechanisms underlying these defects are unknown. Retinal pericytes regulate microcirculatory blood flow and coordinate neurovascular coupling through interpericyte tunneling nanotubes (IP-TNTs). Using two-photon microscope live imaging of the mouse retina, we found reduced capillary diameter and impaired blood flow at pericyte locations in eyes with high intraocular pressure, the most important risk factor to develop glaucoma. We show that IP-TNTs are structurally and functionally damaged by ocular hypertension, a response that disrupted light-evoked neurovascular coupling. Pericyte-specific inhibition of excessive Ca2+ influx rescued hemodynamic responses, protected IP-TNTs and neurovascular coupling, and enhanced retinal neuronal function as well as survival in glaucomatous retinas. Our study identifies pericytes and IP-TNTs as potential therapeutic targets to counter ocular pressure-related microvascular deficits, and provides preclinical proof of concept that strategies aimed to restore intrapericyte calcium homeostasis rescue autoregulatory blood flow and prevent neuronal dysfunction.
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Gezalian MM, Mangiacotti L, Rajput P, Sparrow N, Schlick K, Lahiri S. Cerebrovascular and neurological perspectives on adrenoceptor and calcium channel modulating pharmacotherapies. J Cereb Blood Flow Metab 2021; 41:693-706. [PMID: 33210576 PMCID: PMC7983505 DOI: 10.1177/0271678x20972869] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/12/2020] [Accepted: 10/13/2020] [Indexed: 02/02/2023]
Abstract
Adrenoceptor and calcium channel modulating medications are widely used in clinical practice for acute neurological and systemic conditions. It is generally assumed that the cerebrovascular effects of these drugs mirror that of their systemic effects - and this is reflected in how these medications are currently used in clinical practice. However, recent research suggests that there are distinct cerebrovascular-specific effects of these medications that are related to the unique characteristics of the cerebrovascular anatomy including the regional heterogeneity in density and distribution of adrenoceptor subtypes and calcium channels along the cerebrovasculature. In this review, we critically evaluate existing basic science and clinical research to discuss known and putative interactions between adrenoceptor and calcium channel modulating pharmacotherapies, the neurovascular unit, and cerebrovascular anatomy. In doing so, we provide a rationale for selecting vasoactive medications based on lesion location and lay a foundation for future investigations that will define neuroprotective paradigms of adrenoceptor and calcium channel modulating therapies to improve neurological outcomes in acute neurological and systemic disorders.
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Affiliation(s)
- Michael M Gezalian
- Departments of Neurology and Neurosurgery, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Luigi Mangiacotti
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Padmesh Rajput
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Nicklaus Sparrow
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Konrad Schlick
- Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Shouri Lahiri
- Departments of Neurology, Neurosurgery, and Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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6
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Hariharan A, Weir N, Robertson C, He L, Betsholtz C, Longden TA. The Ion Channel and GPCR Toolkit of Brain Capillary Pericytes. Front Cell Neurosci 2020; 14:601324. [PMID: 33390906 PMCID: PMC7775489 DOI: 10.3389/fncel.2020.601324] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/13/2020] [Indexed: 12/14/2022] Open
Abstract
Brain pericytes reside on the abluminal surface of capillaries, and their processes cover ~90% of the length of the capillary bed. These cells were first described almost 150 years ago (Eberth, 1871; Rouget, 1873) and have been the subject of intense experimental scrutiny in recent years, but their physiological roles remain uncertain and little is known of the complement of signaling elements that they employ to carry out their functions. In this review, we synthesize functional data with single-cell RNAseq screens to explore the ion channel and G protein-coupled receptor (GPCR) toolkit of mesh and thin-strand pericytes of the brain, with the aim of providing a framework for deeper explorations of the molecular mechanisms that govern pericyte physiology. We argue that their complement of channels and receptors ideally positions capillary pericytes to play a central role in adapting blood flow to meet the challenge of satisfying neuronal energy requirements from deep within the capillary bed, by enabling dynamic regulation of their membrane potential to influence the electrical output of the cell. In particular, we outline how genetic and functional evidence suggest an important role for Gs-coupled GPCRs and ATP-sensitive potassium (KATP) channels in this context. We put forth a predictive model for long-range hyperpolarizing electrical signaling from pericytes to upstream arterioles, and detail the TRP and Ca2+ channels and Gq, Gi/o, and G12/13 signaling processes that counterbalance this. We underscore critical questions that need to be addressed to further advance our understanding of the signaling topology of capillary pericytes, and how this contributes to their physiological roles and their dysfunction in disease.
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Affiliation(s)
- Ashwini Hariharan
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Nick Weir
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Colin Robertson
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Liqun He
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Christer Betsholtz
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.,Department of Medicine Huddinge (MedH), Karolinska Institutet & Integrated Cardio Metabolic Centre, Huddinge, Sweden
| | - Thomas A Longden
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
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7
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Acrolein: A Potential Mediator of Oxidative Damage in Diabetic Retinopathy. Biomolecules 2020; 10:biom10111579. [PMID: 33233661 PMCID: PMC7699716 DOI: 10.3390/biom10111579] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 11/05/2020] [Accepted: 11/17/2020] [Indexed: 02/06/2023] Open
Abstract
Diabetic retinopathy (DR) is the leading cause of vision loss among working-age adults. Extensive evidences have documented that oxidative stress mediates a critical role in the pathogenesis of DR. Acrolein, a product of polyamines oxidation and lipid peroxidation, has been demonstrated to be involved in the pathogenesis of various human diseases. Acrolein’s harmful effects are mediated through multiple mechanisms, including DNA damage, inflammation, ROS formation, protein adduction, membrane disruption, endoplasmic reticulum stress, and mitochondrial dysfunction. Recent investigations have reported the involvement of acrolein in the pathogenesis of DR. These studies have shown a detrimental effect of acrolein on the retinal neurovascular unit under diabetic conditions. The current review summarizes the existing literature on the sources of acrolein, the impact of acrolein in the generation of oxidative damage in the diabetic retina, and the mechanisms of acrolein action in the pathogenesis of DR. The possible therapeutic interventions such as the use of polyamine oxidase inhibitors, agents with antioxidant properties, and acrolein scavengers to reduce acrolein toxicity are also discussed.
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Climent B, Santiago E, Sánchez A, Muñoz-Picos M, Pérez-Vizcaíno F, García-Sacristán A, Rivera L, Prieto D. Metabolic syndrome inhibits store-operated Ca 2+ entry and calcium-induced calcium-release mechanism in coronary artery smooth muscle. Biochem Pharmacol 2020; 182:114222. [PMID: 32949582 DOI: 10.1016/j.bcp.2020.114222] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 12/30/2022]
Abstract
BACKGROUND AND PURPOSE Metabolic syndrome causes adverse effects on the coronary circulation including altered vascular responsiveness and the progression of coronary artery disease (CAD). However the underlying mechanisms linking obesity with CAD are intricated. Augmented vasoconstriction, mainly due to impaired Ca2+ homeostasis in coronary vascular smooth muscle (VSM), is a critical factor for CAD. Increased calcium-induced calcium release (CICR) mechanism has been associated to pathophysiological conditions presenting persistent vasoconstriction while increased store operated calcium (SOC) entry appears to activate proliferation and migration in coronary vascular smooth muscle (VSM). We analyze here whether metabolic syndrome might alter SOC entry as well as CICR mechanism in coronary arteries, contributing thus to a defective Ca2+ handling and therefore accelerating the progression of CAD. EXPERIMENTAL APPROACH Measurements of intracellular Ca2+ ([Ca2+]i) and tension and of Ca2+ channels protein expression were performed in coronary arteries (CA) from lean Zucker rats (LZR) and obese Zucker rats (OZR). KEY RESULTS SOC entry stimulated by emptying sarcoplasmic reticulum (SR) Ca2+ store with cyclopiazonic acid (CPA) was decreased and associated to decreased STIM-1 and Orai1 protein expression in OZR CA. Further, CICR mechanism was blunted in these arteries but Ca2+ entry through voltage-dependent L-type channels was preserved contributing to maintain depolarization-induced increases in [Ca2+]i and vasoconstriction in OZR CA. These results were associated to increased expression of voltage-operated L-type Ca2+ channel alpha 1C subunit (CaV1.2) but unaltered ryanodine receptor (RyR) and sarcoendoplasmic reticulum Ca2+-ATPase (SERCA) pump protein content in OZR CA. CONCLUSION AND IMPLICATIONS The present manuscript provides evidence of impaired Ca2+ handling mechanisms in coronary arteries in metabolic syndrome where a decrease in both SOC entry and CICR mechanism but preserved vasoconstriction are reported in coronary arteries from obese Zucker rats. Remarkably, OZR CA VSM at this state of metabolic syndrome seemed to have developed a compensation mechanism for impaired CICR by overexpressing CaV1.2 channels.
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Affiliation(s)
- Belén Climent
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain.
| | - Elvira Santiago
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Ana Sánchez
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Mercedes Muñoz-Picos
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | | | | | - Luis Rivera
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Dolores Prieto
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
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Li W, Schram MT, Berendschot TTJM, Webers CAB, Kroon AA, van der Kallen CJH, Henry RMA, Schaper NC, Huang F, Dashtbozorg B, Tan T, Zhang J, Abbasi-Sureshjani S, Ter Haar Romeny BM, Stehouwer CDA, Houben AJHM. Type 2 diabetes and HbA 1c are independently associated with wider retinal arterioles: the Maastricht study. Diabetologia 2020; 63:1408-1417. [PMID: 32385602 PMCID: PMC7286946 DOI: 10.1007/s00125-020-05146-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 02/24/2020] [Indexed: 11/29/2022]
Abstract
AIMS/HYPOTHESIS Retinal microvascular diameters are biomarkers of cardio-metabolic risk. However, the association of (pre)diabetes with retinal microvascular diameters remains unclear. We aimed to investigate the association of prediabetes (impaired fasting glucose or impaired glucose tolerance) and type 2 diabetes with retinal microvascular diameters in a predominantly white population. METHODS In a population-based cohort study with oversampling of type 2 diabetes (N = 2876; n = 1630 normal glucose metabolism [NGM], n = 433 prediabetes and n = 813 type 2 diabetes, 51.2% men, aged 59.8 ± 8.2 years; 98.6% white), we determined retinal microvascular diameters (measurement unit as measured by retinal health information and notification system [RHINO] software) and glucose metabolism status (using OGTT). Associations were assessed with multivariable regression analyses adjusted for age, sex, waist circumference, smoking, systolic blood pressure, lipid profile and the use of lipid-modifying and/or antihypertensive medication. RESULTS Multivariable regression analyses showed a significant association for type 2 diabetes but not for prediabetes with arteriolar width (vs NGM; prediabetes: β = 0.62 [95%CI -1.58, 2.83]; type 2 diabetes: 2.89 [0.69, 5.08]; measurement unit); however, there was a linear trend for the arteriolar width across glucose metabolism status (p for trend = 0.013). The association with wider venules was not statistically significant (prediabetes: 2.40 [-1.03, 5.84]; type 2 diabetes: 2.87 [-0.55, 6.29], p for trend = 0.083; measurement unit). Higher HbA1c levels were associated with wider retinal arterioles (standardised β = 0.043 [95% CI 0.00002, 0.085]; p = 0.050) but the association with wider venules did not reach statistical significance (0.037 [-0.006, 0.080]; p = 0.092) after adjustment for potential confounders. CONCLUSIONS/INTERPRETATION Type 2 diabetes, higher levels of HbA1c and, possibly, prediabetes, are independently associated with wider retinal arterioles in a predominantly white population. These findings indicate that microvascular dysfunction is an early phenomenon in impaired glucose metabolism.
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Affiliation(s)
- Wenjie Li
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands
| | - Miranda T Schram
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands
| | - Tos T J M Berendschot
- University Eye Clinic Maastricht, Maastricht University Medical Center+, Maastricht, the Netherlands
| | - Carroll A B Webers
- University Eye Clinic Maastricht, Maastricht University Medical Center+, Maastricht, the Netherlands
| | - Abraham A Kroon
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands
| | - Carla J H van der Kallen
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands
| | - Ronald M A Henry
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands
| | - Nicolaas C Schaper
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands
- CAPHRI Care and Public Health Research Institute, Maastricht University, Maastricht, the Netherlands
| | - Fan Huang
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Behdad Dashtbozorg
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Tao Tan
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Jiong Zhang
- USC Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA
| | - Samaneh Abbasi-Sureshjani
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Bart M Ter Haar Romeny
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Coen D A Stehouwer
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands
| | - Alfons J H M Houben
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands.
- Department of Internal Medicine, Maastricht University Medical Center+, P. Debyelaan 25, 6229HX, Maastricht, the Netherlands.
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10
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Lee YR, Lew BL, Sim WY, Lee J, Hong J, Chung BC. Altered polyamine profiling in the hair of patients with androgenic alopecia and alopecia areata. J Dermatol 2019; 46:985-992. [PMID: 31464015 DOI: 10.1111/1346-8138.15063] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/30/2019] [Indexed: 11/30/2022]
Abstract
Hair follicles are among the most highly proliferative tissues. Polyamines are associated with proliferation, and several polyamines including spermidine and spermine play anti-inflammatory roles. Androgenic alopecia results from increased dihydrotestosterone metabolism, and alopecia areata is an autoimmune disease. This study aimed to investigate differences in polyamine profiles in hair samples between patients with androgenic alopecia and alopecia areata. Polyamine concentrations were determined through high-performance liquid chromatography-mass spectrometry. Hair samples were derivatized with isobutyl chloroformate. Differences in polyamine levels were observed between androgenic alopecia and alopecia areata compared with normal controls. In particular, polyamine levels were higher in alopecia areata patients than in normal controls. Certain polyamines displayed different concentrations between the androgenic alopecia and alopecia areata groups, suggesting that some polyamines, particularly N-acetyl putrescine (P = 0.007) and N-acetyl cadaverine (P = 0.0021), are significantly different in androgenic alopecia. Furthermore, spermidine (P = 0.021) was significantly different in alopecia areata. Our findings suggest that non-invasive quantification of hair polyamines may help distinguish between androgenic alopecia and alopecia areata. Our study provides novel insights into physiological alterations in patients with androgenic alopecia and those with alopecia areata and reveals some differences in polyamine levels in hair loss diseases with two different modes of action.
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Affiliation(s)
- Yu Ra Lee
- Molecular Recognition Research Center, Korea Institute of Science and Technology, Seoul, Korea.,KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul, Korea
| | - Bark Lynn Lew
- Department of Dermatology, Kyung Hee University Hospital at Gangdong, Kyung Hee University, Seoul, Korea
| | - Woo Young Sim
- Department of Dermatology, Kyung Hee University Hospital at Gangdong, Kyung Hee University, Seoul, Korea
| | - Jeongae Lee
- Molecular Recognition Research Center, Korea Institute of Science and Technology, Seoul, Korea
| | - Jongki Hong
- KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul, Korea.,College of Pharmacy, Kyung Hee University, Seoul, Korea
| | - Bong Chul Chung
- Molecular Recognition Research Center, Korea Institute of Science and Technology, Seoul, Korea.,KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul, Korea
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Role of Pericytes in the Initiation and Propagation of Spontaneous Activity in the Microvasculature. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:329-356. [PMID: 31183834 DOI: 10.1007/978-981-13-5895-1_14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The microvasculature is composed of arterioles, capillaries and venules. Spontaneous arteriolar constrictions reduce effective vascular resistance to enhance tissue perfusion, while spontaneous venular constrictions facilitate the drainage of tissue metabolites by pumping blood. In the venules of visceral organs, mural cells, i.e. smooth muscle cells (SMCs) or pericytes, periodically generate spontaneous phasic constrictions, Ca2+ transients and transient depolarisations. These events arise from spontaneous Ca2+ release from the sarco-endoplasmic reticulum (SR/ER) and the subsequent opening of Ca2+-activated chloride channels (CaCCs). CaCC-dependent depolarisation further activates L-type voltage-dependent Ca2+ channels (LVDCCs) that play a critical role in maintaining the synchrony amongst mural cells. Mural cells in arterioles or capillaries are also capable of developing spontaneous activity. Non-contractile capillary pericytes generate spontaneous Ca2+ transients primarily relying on SR/ER Ca2+ release. Synchrony amongst capillary pericytes depends on gap junction-mediated spread of depolarisations resulting from the opening of either CaCCs or T-type VDCCs (TVDCCs) in a microvascular bed-dependent manner. The propagation of capillary Ca2+ transients into arterioles requires the opening of either L- or TVDCCs again depending on the microvascular bed. Since the blockade of gap junctions or CaCCs prevents spontaneous Ca2+ transients in arterioles and venules but not capillaries, capillary pericytes appear to play a primary role in generating spontaneous activity of the microvasculature unit. Pericytes in capillaries where the interchange of substances between tissues and the circulation takes place may provide the fundamental drive for upstream arterioles and downstream venules so that the microvasculature network functions as an integrated unit.
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Abstract
Microcirculation is the generic name for the finest level of the circulatory system and consists of arteriolar and venular networks located upstream and downstream of capillaries, respectively. Anatomically arterioles are surrounded by a monolayer of spindle-shaped smooth muscle cells (myocytes), while terminal branches of precapillary arterioles, capillaries and all sections of postcapillary venules are surrounded by a monolayer of morphologically different perivascular cells (pericytes). Pericytes are essential components of the microvascular vessel wall. Wrapped around endothelial cells, they occupy a strategic position at the interface between the circulating blood and the interstitial space. There are physiological differences in the responses of pericytes and myocytes to vasoactive molecules, which suggest that these two types of vascular cells could have different functional roles in the regulation of local blood flow within the same microvascular bed. Also, pericytes may play different roles in different microcirculatory beds to meet the characteristics of individual organs. Contractile activity of pericytes and myocytes is controlled by changes of cytosolic free Ca2+concentration. In this chapter, we attempt to summarize the results in the field of Ca2+ signalling in pericytes especially in light of their contractile roles in different tissues and organs. We investigate the literature and describe our results regarding sources of Ca2+, relative importance and mechanisms of Ca2+ release and Ca2+ entry in control of the spatio-temporal characteristics of the Ca2+ signals in pericytes, where possible Ca2+ signalling and contractile responses in pericytes are compared to those of myocytes.
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Shibata M, Nakaizumi A, Puro DG. Electrotonic transmission in the retinal vasculature: inhibitory role of the diabetes/VEGF/aPKC pathway. Physiol Rep 2019; 7:e14095. [PMID: 31087517 PMCID: PMC6513771 DOI: 10.14814/phy2.14095] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 04/24/2019] [Indexed: 12/12/2022] Open
Abstract
The deleterious impact of diabetes on the retina is a leading cause of vision loss. Ultimately, the hypoxic retinopathy caused by diabetes results in irreversible damage to vascular, neuronal, and glial cells. Less understood is how retinal physiology is altered early in the course of diabetes. We recently found that the electrotonic architecture of the retinovasculature becomes fundamentally altered soon after the onset of this disorder. Namely, the spread of voltage through the vascular endothelium is markedly inhibited. The goal of this study was to elucidate how diabetes inhibits electrotonic transmission. We hypothesized that vascular endothelial growth factor (VEGF) may play a role since its upregulation in hypoxic retinopathy is associated with sight-impairing complications. In this study, we quantified voltage transmission between pairs of perforated-patch pipettes sealed onto abluminal cells located on retinal microvascular complexes freshly isolated from diabetic and nondiabetic rats. We report that exposure of diabetic retinal microvessels to an anti-VEGF antibody or to a small-molecule inhibitor of atypical PKCs (aPKC) near-fully restored the efficacy of electrotonic transmission. Furthermore, exposure of nondiabetic microvessels to VEGF mimicked, via a mechanism sensitive to the aPKC inhibitor, the diabetes-induced inhibition of transmission. Thus, activation of the diabetes/VEGF/aPKC pathway switches the retinovasculature from a highly interactive operational unit to a functionally balkanized complex. By delimiting the dissemination of voltage-changing vasomotor inputs, this organizational fragmentation is likely to compromise effective regulation of retinal perfusion. Future pharmacological targeting of the diabetes/VEGF/aPKC pathway may serve to impede progression of vascular dysfunction to irreversible diabetic retinopathy.
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Affiliation(s)
- Maho Shibata
- Department of Ophthalmology and Visual SciencesUniversity of MichiganAnn ArborMichigan
| | - Atsuko Nakaizumi
- Department of Ophthalmology and Visual SciencesUniversity of MichiganAnn ArborMichigan
| | - Donald G. Puro
- Department of Ophthalmology and Visual SciencesUniversity of MichiganAnn ArborMichigan
- Department of Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMichigan
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Purinergic Vasotoxicity: Role of the Pore/Oxidant/K ATP Channel/Ca 2+ Pathway in P2X 7-Induced Cell Death in Retinal Capillaries. Vision (Basel) 2018; 2. [PMID: 30288454 PMCID: PMC6166475 DOI: 10.3390/vision2030025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
P2X7 receptor/channels in the retinal microvasculature not only regulate vasomotor activity, but can also trigger cells in the capillaries to die. While it is known that this purinergic vasotoxicity is dependent on the transmembrane pores that form during P2X7 activation, events linking pore formation with cell death remain uncertain. To better understand this pathophysiological process, we used YO-PRO-1 uptake, dichlorofluorescein fluorescence, perforated-patch recordings, fura-2 imaging and trypan blue dye exclusion to assess the effects of the P2X7 agonist, benzoylbenzoyl-ATP (BzATP), on pore formation, oxidant production, ion channel activation, [Ca2+]i and cell viability. Experiments demonstrated that exposure of retinal microvessels to BzATP increases capillary cell oxidants via a mechanism dependent on pore formation and the enzyme, NADPH oxidase. Indicative that oxidation plays a key role in purinergic vasotoxicity, an inhibitor of this enzyme completely prevented BzATP-induced death. We further discovered that vasotoxicity was boosted 4-fold by a pathway involving the oxidation-driven activation of hyperpolarizing KATP channels and the resulting increase in calcium influx. Our findings revealed that the previously unappreciated pore/oxidant/KATP channel/Ca2+ pathway accounts for 75% of the capillary cell death triggered by sustained activation of P2X7 receptor/channels. Elucidation of this pathway is of potential therapeutic importance since purinergic vasotoxicity may play a role in sight-threatening disorders such as diabetic retinopathy.
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Hashitani H, Mitsui R, Miwa-Nishimura K, Lam M. Role of capillary pericytes in the integration of spontaneous Ca 2+ transients in the suburothelial microvasculature in situ of the mouse bladder. J Physiol 2018; 596:3531-3552. [PMID: 29873405 DOI: 10.1113/jp275845] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/21/2018] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS In the bladder suburothelial microvasculature, pericytes in different microvascular segments develop spontaneous Ca2+ transients with or without associated constrictions. Spontaneous Ca2+ transients in pericytes of all microvascular segments primarily rely on the cycles of Ca2+ uptake and release by the sarco- and endoplasmic reticulum. The synchrony of spontaneous Ca2+ transients in capillary pericytes exclusively relies on the spread of depolarizations resulting from the opening of Ca2+ -activated chloride channels (CaCCs) via gap junctions. CaCC-dependent depolarizations further activate L-type voltage-dependent Ca2+ channels as required for the synchrony of Ca2+ transients in pericytes of pre-capillary arterioles, post-capillary venules and venules. Capillary pericytes may drive spontaneous Ca2+ transients in pericytes within the suburothelial microvascular network by sending CaCC-dependent depolarizations via gap junctions. ABSTRACT Mural cells in the microvasculature of visceral organs develop spontaneous Ca2+ transients. However, the mechanisms underlying the integration of these Ca2+ transients within a microvascular unit remain to be clarified. In the present study, the origin of spontaneous Ca2+ transients and their propagation in the bladder suburothelial microvasculature were explored. Cal-520 fluorescence Ca2+ imaging and immunohistochemistry were carried out on mural cells using mice expressing red fluorescent protein (DsRed) under control of the NG2 promotor. NG2(+) pericytes in both pre-capillary arterioles (PCAs) and capillaries developed synchronous spontaneous Ca2+ transients. By contrast, although NG2-DsRed also labelled arteriolar smooth muscle cells, these cells remained quiescent. Both NG2(+) pericytes in post-capillary venules (PCVs) and NG2(-) venular pericytes exhibited propagated Ca2+ transients. L-type voltage-dependent Ca2+ channel (LVDCC) blockade with nifedipine prevented Ca2+ transients or disrupted their synchrony in PCA, PCV and venular pericytes without dis-synchronizing Ca2+ transients in capillary pericytes. Blockade of gap junctions with carbenoxolone or Ca2+ -activated chloride channels (CaCCs) with 4,4'-diisothiocyanato-2,2'-stilbenedisulphonic acid disodium salt prevented Ca2+ transients in PCA and venular pericytes and disrupted the synchrony of Ca2+ transients in capillary and PCV pericytes. Spontaneous Ca2+ transients in pericytes of all microvascular segments were abolished or suppressed by cyclopiazonic acid, caffeine or tetracaine. The synchrony of Ca2+ transients in capillary pericytes arising from spontaneous Ca2+ release from the sarco- and endoplasmic reticulum appears to rely exclusively on CaCC activation, whereas subsequent LVDCC activation is required for the synchrony of Ca2+ transients in pericytes of other microvascular segments. Capillary pericytes may drive spontaneous activity in the suburothelial microvascular unit to facilitate capillary perfusion.
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Affiliation(s)
- Hikaru Hashitani
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Retsu Mitsui
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Kyoko Miwa-Nishimura
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Michelle Lam
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
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Sánchez A, Contreras C, Climent B, Gutiérrez A, Muñoz M, García-Sacristán A, López M, Rivera L, Prieto D. Impaired Ca 2+ handling in resistance arteries from genetically obese Zucker rats: Role of the PI3K, ERK1/2 and PKC signaling pathways. Biochem Pharmacol 2018; 152:114-128. [PMID: 29574066 DOI: 10.1016/j.bcp.2018.03.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/20/2018] [Indexed: 01/12/2023]
Abstract
The impact of obesity on vascular smooth muscle (VSM) Ca2+ handling and vasoconstriction, and its regulation by the phosphatidylinositol 3-kinase (PI3K), mitogen activated protein kinase (MAPK) and protein kinase C (PKC) were assessed in mesenteric arteries (MA) from obese Zucker rats (OZR). Simultaneous measurements of intracellular Ca2+ ([Ca2+]i) and tension were performed in MA from OZR and compared to lean Zucker rats (LZR), and the effects of selective inhibitors of PI3K, ERK-MAPK kinase and PKC were assessed on the functional responses of VSM voltage-dependent L-type Ca2+ channels (CaV1.2). Increases in [Ca2+]i induced by α1-adrenoceptor activation and high K+ depolarization were not different in arteries from LZR and OZR although vasoconstriction was enhanced in OZR. Blockade of the ryanodine receptor (RyR) and of Ca2+ release from the sarcoplasmic reticulum (SR) markedly reduced depolarization-induced Ca2+ responses in arteries from lean but not obese rats, suggesting impaired Ca2+-induced Ca2+ release (CICR) from SR in arteries from OZR. Enhanced Ca2+ influx after treatment with ryanodine was abolished by nifedipine and coupled to up-regulation of CaV1.2 channels in arteries from OZR. Increased activation of ERK-MAPK and up-regulation of PI3Kδ, PKCβ and δ isoforms were associated to larger inhibitory effects of PI3K, MAPK and PKC blockers on VSM L-type channel Ca2+ entry in OZR. Changes in arterial Ca2+ handling in obesity involve SR Ca2+ store dysfunction and enhanced VSM Ca2+ entry through L-type channels, linked to a compensatory up-regulation of CaV1.2 proteins and increased activity of the ERK-MAPK, PI3Kδ and PKCβ and δ, signaling pathways.
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Affiliation(s)
- Ana Sánchez
- Department of Physiology, School of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain.
| | - Cristina Contreras
- NeurObesity Group, Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela 15782, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Belén Climent
- Department of Physiology, School of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Alejandro Gutiérrez
- Department of Physiology, School of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Mercedes Muñoz
- Department of Physiology, School of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Albino García-Sacristán
- Department of Physiology, School of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Miguel López
- NeurObesity Group, Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela 15782, Spain; CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Luis Rivera
- Department of Physiology, School of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Dolores Prieto
- Department of Physiology, School of Pharmacy, Universidad Complutense de Madrid, 28040 Madrid, Spain.
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Saleem S, Azam A, Maqsood SI, Muslim I, Bashir S, Fazal N, Riaz M, Ali SHB, Niazi MK, Ishaq M, Waheed NK, Qamar R, Azam M. Role of ACE and PAI-1 Polymorphisms in the Development and Progression of Diabetic Retinopathy. PLoS One 2015; 10:e0144557. [PMID: 26658948 PMCID: PMC4679138 DOI: 10.1371/journal.pone.0144557] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 11/19/2015] [Indexed: 12/30/2022] Open
Abstract
In the present study we determined the association of angiotensin converting enzyme (ACE) and plasminogen activator inhibitor-1 (PAI-1) gene polymorphisms with diabetic retinopathy (DR) and its sub-clinical classes in Pakistani type 2 diabetic patients. A total of 353 diabetic subjects including 160 DR and 193 diabetic non retinopathy (DNR) as well as 198 healthy controls were genotyped by allele specific polymerase chain reaction (PCR) for ACE Insertion/Deletion (ID) polymorphism, rs4646994 in intron 16 and PAI-1 4G/5G (deletion/insertion) polymorphism, rs1799768 in promoter region of the gene. To statistically assess the genotype-phenotype association, multivariate logistic regression analysis was applied to the genotype data of DR, DNR and control individuals as well as the subtypes of DR. The ACE genotype ID was found to be significantly associated with DR (p = 0.009, odds ratio (OR) 1.870 [95% confidence interval (CI) = 1.04-3.36]) and its sub-clinical class non-proliferative DR (NPDR) (p = 0.006, OR 2.250 [95% CI = 1.098-4.620]), while PAI polymorphism did not show any association with DR in the current cohort. In conclusion in Pakistani population the ACE ID polymorphism was observed to be significantly associated with DR and NPDR, but not with the severe form of the disease i.e. proliferative DR (PDR).
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Affiliation(s)
- Saba Saleem
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Aisha Azam
- Institute of Ophthalmology, Mayo Hospital, Lahore, Pakistan
| | | | - Irfan Muslim
- Institute of Ophthalmology, Mayo Hospital, Lahore, Pakistan
| | - Shaheena Bashir
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Nosheen Fazal
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Moeen Riaz
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | | | - Muhammad Khizar Niazi
- Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan
- Army Medical College, Rawalpindi, Pakistan
| | - Mazhar Ishaq
- Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan
- Army Medical College, Rawalpindi, Pakistan
| | - Nadia Khalida Waheed
- Tufts University Medical School, Boston, Massachusetts, United States of America
| | - Raheel Qamar
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
- Al-Nafees Medical College and Hospital, Isra University, Islamabad, Pakistan
- Pakistan Academy of Sciences, Islamabad, Pakistan
| | - Maleeha Azam
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
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Muir ER, Chandra SB, De La Garza BH, Velagapudi C, Abboud HE, Duong TQ. Layer-Specific Manganese-Enhanced MRI of the Diabetic Rat Retina in Light and Dark Adaptation at 11.7 Tesla. Invest Ophthalmol Vis Sci 2015; 56:4006-12. [PMID: 26098468 DOI: 10.1167/iovs.14-16128] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To employ high-resolution manganese-enhanced MRI (MEMRI) to study abnormal calcium activity in different cell layers in streptozotocin-induced diabetic rat retinas, and to determine whether MEMRI detects changes at earlier time points than previously reported. METHODS Sprague-Dawley rats were studied 14 days (n = 8) and 30 days (n = 5) after streptozotocin (STZ) or vehicle (n = 7) injection. Manganese-enhanced MRI at 20 × 20 × 700 μm, in which contrast is based on manganese as a calcium analogue and an MRI contrast agent, was obtained in light and dark adaptation of the retina in the same animals in which one eye was covered and the fellow eye was not. The MEMRI activity encoding of the light and dark adaptation was achieved in awake conditions and imaged under anesthesia. RESULTS Manganese-enhanced MRI showed three layers, corresponding to the inner retina, outer retina, and the choroid. In normal animals, the outer retina showed higher MEMRI activity in dark compared to light; the inner retina displayed lower activity in dark compared to light; and the choroid showed no difference in activity. Manganese-enhanced MRI activity changed as early as 14 days after hyperglycemia and decreased with duration of hyperglycemia in the outer retina in dark relative to light adaptation. The choroid also had altered MEMRI activity at 14 days, which returned to normal by 30 days. No differences in MEMRI activity were detected in the inner retina. CONCLUSIONS Manganese-enhanced MRI detects progressive reduction in calcium activity with duration of hyperglycemia in the outer retina as early as 14 days after hyperglycemia, earlier than any other time point reported in the literature.
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Affiliation(s)
- Eric R Muir
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States 2Departments of Ophthalmology, Radiology, and Physiology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Saurav B Chandra
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Bryan H De La Garza
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Chakradhar Velagapudi
- Department of Medicine, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Hanna E Abboud
- Department of Medicine, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Timothy Q Duong
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, Texas, United States 2Departments of Ophthalmology, Radiology, and Physiology, University of Texas Health Science Center, San Antonio, Texas, United States 4South Texas Ve
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Chang RCA, Shi L, Huang CCY, Kim AJ, Ko ML, Zhou B, Ko GYP. High-Fat Diet-Induced Retinal Dysfunction. Invest Ophthalmol Vis Sci 2015; 56:2367-80. [PMID: 25788653 DOI: 10.1167/iovs.14-16143] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
PURPOSE The purpose of this study was to investigate the impact of obesity-induced prediabetes/early diabetes on the retina to provide new evidence on the pathogenesis of type 2 diabetes-associated diabetic retinopathy (DR). METHODS A high-fat diet (HFD)-induced obesity mouse model (male C57BL/6J) was used in this study. At the end of the 12-week HFD feeding regimen, mice were evaluated for glucose and insulin tolerance, and retinal light responses were recorded by electroretinogram (ERG). Western immunoblot and immunohistochemical staining were used to determine changes in elements regulating calcium homeostasis between HFD and control retinas, as well as unstained human retinal sections from DR patients and age-appropriate controls. RESULTS Compared to the control, the scotopic and photopic ERGs from HFD mice were decreased. There were significant decreases in molecules related to cell signaling, calcium homeostasis, and glucose metabolism from HFD retinas, including phosphorylated protein kinase B (pAKT), glucose transporter 4, L-type voltage-gated calcium channel (L-VGCC), and plasma membrane calcium ATPase (PMCA). Similar changes for pAKT, PMCA, and L-VGCC were also observed in human retinal sections from DR patients. CONCLUSIONS Obesity-induced hyperglycemic and prediabetic/early diabetic conditions caused detrimental impacts on retinal light sensitivities and health. The decrease of the ERG components in early diabetes reflects the decreased neuronal activity of retinal light responses, which may be caused by a decrease in neuronal calcium signaling. Since PI3K-AKT is important in regulating calcium homeostasis and neural survival, maintaining proper PI3K-AKT signaling in early diabetes or at the prediabetic stage might be a new strategy for DR prevention.
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Affiliation(s)
- Richard Cheng-An Chang
- Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States
| | - Liheng Shi
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States
| | - Cathy Chia-Yu Huang
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States
| | - Andy Jeesu Kim
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States
| | - Michael L Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States
| | - Beiyan Zhou
- Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States
| | - Gladys Y-P Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, United States 3Texas A&M Institute of Neuroscience, Texas A&M University, College Station, Texas, Unite
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20
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Marin Garcia PJ, Marin-Castaño ME. Angiotensin II-related hypertension and eye diseases. World J Cardiol 2014; 6:968-984. [PMID: 25276298 PMCID: PMC4176806 DOI: 10.4330/wjc.v6.i9.968] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 06/17/2014] [Accepted: 07/14/2014] [Indexed: 02/07/2023] Open
Abstract
Systemic vascular disease, especially hypertension, has been suspected as a risk factor for some eye diseases including, diabetic retinopathy and age-related macular degeneration. Hypertension can contribute to chronic diseases by hemodynamic injury and/or cellular actions induced by hypertension-related hormones or growth factors. Among the most important is Angiotensin II (Ang II), which controls blood pressure and induces different cellular functions that may be dependent or independent of its effect on blood pressure. Importantly, as is true for heart, kidney and other organs, the renin-angiotensin system (RAS) is present in the eye. So, even in the absence of hypertension, local production of Ang II could be involved in eye diseases. The goal of this manuscript is to review the most relevant scientific evidence supporting the role of the RAS activation, in the development of age-related macular degeneration and diabetic retinopathy, and highlight the importance of Ang II in the etiology of these diseases.
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Involvement of the carrier-mediated process in the retina-to-blood transport of spermine at the inner blood-retinal barrier. Exp Eye Res 2014; 124:17-23. [DOI: 10.1016/j.exer.2014.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 02/21/2014] [Accepted: 05/04/2014] [Indexed: 01/06/2023]
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Burdyga T, Borysova L. Calcium signalling in pericytes. J Vasc Res 2014; 51:190-9. [PMID: 24903335 DOI: 10.1159/000362687] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 04/06/2014] [Indexed: 11/19/2022] Open
Abstract
Recent advances in pericyte research have contributed to our understanding of the physiology and pathophysiology of microvessels. The microvasculature consists of arteriolar and venular networks located upstream and downstream of the capillaries. Arterioles are surrounded by a monolayer of spindle-shaped myocytes, while terminal branches of precapillary arterioles, capillaries and all sections of postcapillary venules are encircled by a monolayer of morphologically diverse pericytes. There are physiological differences in the response of pericytes and myocytes to vasoactive molecules, suggesting that these two vascular cell types could have different functional roles in the regulation of local blood flow. The contractile activity of pericytes and myocytes is controlled by changes of cytosolic free Ca(2+) concentration. In this short review, we summarize our results and those of other authors on the contractility of pericytes and their Ca(2+) signalling. We describe results regarding sources of Ca(2+) and mechanisms of Ca(2+) release and Ca(2+) entry in control of the spatiotemporal characteristics of the Ca(2+) signals in pericytes.
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Affiliation(s)
- Theodor Burdyga
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
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23
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Abcouwer SF, Gardner TW. Diabetic retinopathy: loss of neuroretinal adaptation to the diabetic metabolic environment. Ann N Y Acad Sci 2014; 1311:174-90. [PMID: 24673341 DOI: 10.1111/nyas.12412] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Diabetic retinopathy (DR) impairs vision of patients with type 1 and type 2 diabetes, associated with vascular dysfunction and occlusion, retinal edema, hemorrhage, and inappropriate growth of new blood vessels. The recent success of biologic treatments targeting vascular endothelial growth factor (VEGF) demonstrates that treating the vascular aspects in the later stages of the disease can preserve vision in many patients. It would also be highly desirable to prevent the onset of the disease or arrest its progression at a stage preceding the appearance of overt microvascular pathologies. The progression of DR is not necessarily linear but may follow a series of steps that evolve over the course of multiple years. Abundant data suggest that diabetes affects the entire neurovascular unit of the retina, with an early loss of neurovascular coupling, gradual neurodegeneration, gliosis, and neuroinflammation occurring before observable vascular pathologies. In this article, we consider the pathology of DR from the point of view that diabetes causes measurable dysfunctions in the complex integral network of cell types that produce and maintain human vision.
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Affiliation(s)
- Steven F Abcouwer
- Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, Michigan
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Narayanan SP, Rojas M, Suwanpradid J, Toque HA, Caldwell RW, Caldwell RB. Arginase in retinopathy. Prog Retin Eye Res 2013; 36:260-80. [PMID: 23830845 PMCID: PMC3759622 DOI: 10.1016/j.preteyeres.2013.06.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 06/14/2013] [Accepted: 06/25/2013] [Indexed: 12/12/2022]
Abstract
Ischemic retinopathies, such as diabetic retinopathy (DR), retinopathy of prematurity and retinal vein occlusion are a major cause of blindness in developed nations worldwide. Each of these conditions is associated with early neurovascular dysfunction. However, conventional therapies target clinically significant macula edema or neovascularization, which occur much later. Intra-ocular injections of anti-VEGF show promise in reducing retinal edema, but the effects are usually transient and the need for repeated injections increases the risk of intraocular infection. Laser photocoagulation can control pathological neovascularization, but may impair vision and in some patients the retinopathy continues to progress. Moreover, neither treatment targets early stage disease or promotes repair. This review examines the potential role of the ureahydrolase enzyme arginase as a therapeutic target for the treatment of ischemic retinopathy. Arginase metabolizes l-arginine to form proline, polyamines and glutamate. Excessive arginase activity reduces the l-arginine supply for nitric oxide synthase (NOS), causing it to become uncoupled and produce superoxide and less NO. Superoxide and NO react and form the toxic oxidant peroxynitrite. The catabolic products of polyamine oxidation and glutamate can induce more oxidative stress and DNA damage, both of which can cause cellular injury. Studies indicate that neurovascular injury during retinopathy is associated with increased arginase expression/activity, decreased NO, polyamine oxidation, formation of superoxide and peroxynitrite and dysfunction and injury of both vascular and neural cells. Furthermore, data indicate that the cytosolic isoform arginase I (AI) is involved in hyperglycemia-induced dysfunction and injury of vascular endothelial cells whereas the mitochondrial isoform arginase II (AII) is involved in neurovascular dysfunction and death following hyperoxia exposure. Thus, we postulate that activation of the arginase pathway causes neurovascular injury by uncoupling NOS and inducing polyamine oxidation and glutamate formation, thereby reducing NO and increasing oxidative stress, all of which contribute to the retinopathic process.
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Affiliation(s)
- S. Priya Narayanan
- Vision Discovery Institute, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
- Vascular Biology Center, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
| | - Modesto Rojas
- Vision Discovery Institute, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
- Vascular Biology Center, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
| | - Jutamas Suwanpradid
- Vision Discovery Institute, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
- Vascular Biology Center, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
| | - Haroldo A. Toque
- Department of Pharmacology & Toxicology, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
| | - R. William Caldwell
- Vision Discovery Institute, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
- Department of Pharmacology & Toxicology, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
| | - Ruth B. Caldwell
- Vision Discovery Institute, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
- Vascular Biology Center, Georgia Regents University, 1459 Laney Walker Boulevard, Augusta, 30912, USA
- VA Medical Center, One Freedom Way, Augusta, GA, USA
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25
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Abstract
Genetics and environmental factors have important roles in autoimmune diseases but neither has given us sufficient understanding of these mysterious diseases. Therefore, we are now looking closer at epigenetics, an interface between genetics and environmental factors. Epigenetics can be defined as reversible heritable changes to chromatin that can alter gene expression without altering the gene's DNA sequence. Methylation of DNA and histones are primary means of epigenetic control. By adding methyl groups to DNA and histones, it can limit accessibility of the underlying gene thereby altering the amount of gene expression. The methyl group is derived from an essential molecule in the cell, S-adenosylmethionine (SAM). However, a group of small molecules called polyamines also require SAM for their synthesis. Polyamines are essential for many cellular functions and polyamine activity is increased in many autoimmune diseases. Presented here is the "polyamine hypothesis" in which increased polyamine synthesis competes with cellular methylation (epigenetic control) for SAM. It is proposed that increased polyamine activity can cause disruption of cellular methylation, which can lead to abnormal expression of previously sequestered genes and disruption of other methylation-dependent cellular processes.
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Kur J, Newman EA, Chan-Ling T. Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease. Prog Retin Eye Res 2012; 31:377-406. [PMID: 22580107 DOI: 10.1016/j.preteyeres.2012.04.004] [Citation(s) in RCA: 450] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 04/17/2012] [Accepted: 04/22/2012] [Indexed: 02/06/2023]
Abstract
We review the cellular and physiological mechanisms responsible for the regulation of blood flow in the retina and choroid in health and disease. Due to the intrinsic light sensitivity of the retina and the direct visual accessibility of fundus blood vessels, the eye offers unique opportunities for the non-invasive investigation of mechanisms of blood flow regulation. The ability of the retinal vasculature to regulate its blood flow is contrasted with the far more restricted ability of the choroidal circulation to regulate its blood flow by virtue of the absence of glial cells, the markedly reduced pericyte ensheathment of the choroidal vasculature, and the lack of intermediate filaments in choroidal pericytes. We review the cellular and molecular components of the neurovascular unit in the retina and choroid, techniques for monitoring retinal and choroidal blood flow, responses of the retinal and choroidal circulation to light stimulation, the role of capillaries, astrocytes and pericytes in regulating blood flow, putative signaling mechanisms mediating neurovascular coupling in the retina, and changes that occur in the retinal and choroidal circulation during diabetic retinopathy, age-related macular degeneration, glaucoma, and Alzheimer's disease. We close by discussing issues that remain to be explored.
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Affiliation(s)
- Joanna Kur
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
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Fukumoto M, Nakaizumi A, Zhang T, Lentz SI, Shibata M, Puro DG. Vulnerability of the retinal microvasculature to oxidative stress: ion channel-dependent mechanisms. Am J Physiol Cell Physiol 2012; 302:C1413-20. [PMID: 22345512 DOI: 10.1152/ajpcell.00426.2011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although oxidative stress is a hallmark of important vascular disorders such as diabetic retinopathy, it remains unclear why the retinal microvasculature is particularly vulnerable to this pathophysiological condition. We postulated that redox-sensitive ion channels may play a role. Using H(2)O(2) to cause oxidative stress in microvascular complexes freshly isolated from the adult rat retina, we assessed ionic currents, cell viability, intracellular oxidants, and cell calcium by using perforated-patch recordings, trypan blue dye exclusion, and fura-2 fluorescence, respectively. Supporting a role for the oxidant-sensitive ATP-sensitive K (K(ATP)) channels, we found that these channels are activated during exposure of retinal microvessels to H(2)O(2). Furthermore, their inhibition by glibenclamide significantly lessened H(2)O(2)-induced microvascular cell death. Additional experiments established that by increasing the influx of calcium into microvascular cells, the K(ATP) channel-mediated hyperpolarization boosted the vulnerability of these cells to oxidative stress. In addition to the K(ATP) channel-dependent mechanism for increasing the lethality of oxidative stress, we also found that the vulnerability of cells in the capillaries, but not in the arterioles, was further boosted by a K(ATP) channel-independent mechanism, which our experiments indicated involves the oxidant-induced activation of calcium-permeable nonspecific cation channels. Taken together, our findings support a working model in which both K(ATP) channel-independent and K(ATP) channel-dependent mechanisms render the capillaries of the retina particularly vulnerable to oxidative stress. Identification of these previously unappreciated mechanisms for boosting the lethality of oxidants may provide new targets for pharmacologically limiting damage to the retinal microvasculature during periods of oxidative stress.
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Affiliation(s)
- Masanori Fukumoto
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan 48505, USA
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Nakaizumi A, Zhang T, Puro DG. The electrotonic architecture of the retinal microvasculature: diabetes-induced alteration. Neurochem Int 2012; 61:948-53. [PMID: 22349410 DOI: 10.1016/j.neuint.2012.02.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 01/19/2012] [Accepted: 02/04/2012] [Indexed: 10/28/2022]
Abstract
Although microvascular cell death is a well established hallmark of diabetic retinopathy, which is a major cause of vision loss, much remains to be learned about the functional changes that precede the onset of morphological damage to retinal blood vessels. Early alterations of function are of interest since they may contribute to the development of irreversible pathological events. Because one of the earliest retinal effects of diabetes is the dysregulation of blood flow, we asked whether diabetes alters the functional organization of the capillary/arteriolar complex, which is the operational unit that plays an important role in regulating local perfusion. In this study, the effect of diabetes on the electrotonic architecture of the retinal microvasculature was characterized. To do this, we quantified the efficacy by which voltages are transmitted between pairs perforated-patch pipettes sealed onto abluminal cells located at well defined locations in capillary/arteriolar complexes freshly isolated from the retinas of rats made diabetic by streptozotocin. Results of these dual recording experiments were compared with data from similar experiments performed on non-diabetic retinal microvessels. These experiments revealed that diabetes caused a ∼5-fold increase in the rate at which a voltage decays as it axially spreads through the retinal microvasculature. In contrast, the efficacy of radial abluminal cell/endothelial cell transmission was not significantly affected by diabetes. Based on the results of this study, which is the first to characterize how diabetes affects voltage transmission in capillary/arteriolar complexes of any tissue, we concluded that by selectively inhibiting axial transmission, diabetes alters the electrotonic architecture of the retinal microvasculature. This diabetes-induced alteration in the functional organization of the capillary/arteriolar unit is likely to impair its ability to efficiently and effectively regulate blood flow and thereby, may contribute to the progression of sight-threatening complications of diabetic retinopathy.
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Affiliation(s)
- Atsuko Nakaizumi
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
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Puro DG. Retinovascular physiology and pathophysiology: new experimental approach/new insights. Prog Retin Eye Res 2012; 31:258-70. [PMID: 22333041 DOI: 10.1016/j.preteyeres.2012.01.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 01/28/2012] [Accepted: 01/31/2012] [Indexed: 01/09/2023]
Abstract
An important challenge in visual neuroscience is to understand the physiology and pathophysiology of the intra-retinal vasculature, whose function is required for ophthalmoception by humans and most other mammals. In the quest to learn more about this highly specialized portion of the circulatory system, a newly developed method for isolating vast microvascular complexes from the rodent retina has opened the way for using techniques such as patch-clamping, fluorescence imaging and time-lapse photography to elucidate the functional organization of a capillary network and its pre-capillary arteriole. For example, the ability to obtain dual perforated-patch recordings from well-defined sites within an isolated microvascular complex permitted the first characterization of the electrotonic architecture of a capillary/arteriole unit. This analysis revealed that this operational unit is not simply a homogenous synctium, but has a complex functional organization that is dynamically modulated by extracellular signals such as angiotensin II. Another recent discovery is that a capillary and its pre-capillary arteriole have distinct physiological differences; capillaries have an abundance of ATP-sensitive potassium (K(ATP)) channels and a dearth of voltage-dependent calcium channels (VDCCs) while the converse is true for arterioles. In addition, voltage transmission between abluminal cells and the endothelium is more efficient in the capillaries. Thus, the capillary network is well-equipped to generate and transmit voltages, and the pre-capillary arteriole is well-adapted to transduce a capillary-generated voltage into a change in abluminal cell calcium and thereby, a vasomotor response. Use of microvessels isolated from the diabetic retina has led to new insights concerning retinal vascular pathophysiology. For example, soon after the onset of diabetes, the efficacy of voltage transmission through the endothelium is diminished; arteriolar VDCCs are inhibited, and there is increased vulnerability to purinergic vasotoxicity, which is a newly identified pathobiological mechanism. Other recent studies reveal that K(ATP) channels not only have an essential physiological role in generating vasomotor responses, but their activation substantially boosts the lethality of hypoxia. Thus, the pathophysiology of the retinal microvasculature is closely linked with its physiology.
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Affiliation(s)
- Donald G Puro
- Department of Ophthalmology & Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA.
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Nakaizumi A, Puro DG. Vulnerability of the retinal microvasculature to hypoxia: role of polyamine-regulated K(ATP) channels. Invest Ophthalmol Vis Sci 2011; 52:9345-52. [PMID: 22039232 DOI: 10.1167/iovs.11-8176] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE It is uncertain why retinal capillaries are particularly vulnerable to hypoxia. In this study, it was hypothesized that their specialized physiology, which includes being the predominant microvascular location of functional adenosine triphosphate-sensitive potassium (K(ATP)) channels, boosts their susceptibility to hypoxia-induced cell death. METHODS Cell viability, ionic currents, intracellular calcium, and pericyte contractility in microvascular complexes freshly isolated from the rat retina were assessed using trypan blue dye exclusion, perforated-patch recordings, fura-2 fluorescence, and time-lapse videos. Chemical hypoxia was induced by antimycin, an oxidative phosphorylation inhibitor. RESULTS In freshly isolated retinal microvascular complexes, chemical hypoxia caused more cell death in capillaries than in arterioles. Indicative of the role of polyamine-dependent K(ATP) channels, antimycin-induced capillary cell death was markedly decreased in microvessels treated with the polyamine synthesis inhibitor, difluoromethylornithine, or the K(ATP) channel inhibitor, glibenclamide. These inhibitors also diminished the antimycin-induced hyperpolarization, as well as the antimycin-induced intracellular calcium increase, which was significantly dependent on extracellular calcium and was diminished by the inhibitor of calcium-induced calcium release (CICR), dantrolene. Consistent with the importance of the CICR-dependent increase in capillary cell calcium, dantrolene significantly decreased hypoxia-induced capillary cell death. We also found that activation of the polyamine/K(ATP) channel/Ca(2+) influx/CICR pathway not only boosted the vulnerability of retinal capillaries to hypoxia, but also caused the contraction of capillary pericytes, whose vasoconstrictive effect may exacerbate hypoxia. CONCLUSIONS The vulnerability of retinal capillaries to hypoxia is boosted by a mechanism involving the polyamine/K(ATP) channel/Ca(2+) influx/CICR pathway. Discovery of this pathway should provide new targets for pharmacological interventions to minimize hypoxia-induced damage in retinal capillaries.
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Affiliation(s)
- Atsuko Nakaizumi
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan 48505, USA
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31
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Berkowitz BA, Bissig D, Bergman D, Bercea E, Kasturi VK, Roberts R. Intraretinal calcium channels and retinal morbidity in experimental retinopathy of prematurity. Mol Vis 2011; 17:2516-26. [PMID: 21976962 PMCID: PMC3185031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 09/22/2011] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To test the hypothesis that intraretinal calcium channels participate in retinal morbidity in a variable oxygen (VO) model of retinopathy of prematurity. METHODS In control and VO Long Evans (LE) rats, either untreated or treated with voltage- or ligand-gated calcium channel antagonists, we measured retinal neovascular (NV) incidence and severity (adenosine diphosphatase staining), and retinal thickness and intraretinal ion channel activity (manganese-enhanced magnetic resonance imaging). Comparisons with the commonly studied Sprague Dawley rats were performed. Visual performance (optokinetic tracking) in untreated VO LE rats was also evaluated. RESULTS In control LE rats, specific L-type voltage calcium channel antagonism, but not ligand-gated channel blockers, suppressed retinal manganese accumulation, while the inhibition of L-type channels normalized intraretinal uptake in VO LE rats. VO LE rats developed more severe NV than VO Sprague Dawley rats. Following VO, both strains demonstrated significant and similar degrees of retinal thinning and supernormal intraretinal manganese uptake. However, over time, intraretinal uptake remained elevated only in VO LE rats. Visual performance was subnormal in VO LE rats. L-type voltage-gated calcium channel antagonism reduced NV severity by 28% (p<0.05) in experimental LE rats compared to that in the control group. CONCLUSIONS Abnormal intraretinal calcium channel activity is linked with retinal morbidity in experimental retinopathy of prematurity.
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Affiliation(s)
- Bruce A. Berkowitz
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI,Department of Ophthalmology, Wayne State University, Detroit, MI
| | - David Bissig
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI
| | - Deborah Bergman
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI
| | - Emanuela Bercea
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI
| | - Vijaya K. Kasturi
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI
| | - Robin Roberts
- Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI
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Zhang T, Wu DM, Xu GZ, Puro DG. The electrotonic architecture of the retinal microvasculature: modulation by angiotensin II. J Physiol 2011; 589:2383-99. [PMID: 21486796 DOI: 10.1113/jphysiol.2010.202937] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The capillary/arteriole complex is the key operational unit regulating local perfusion to meet metabolic demand. However, much remains to be learned about how this multi cellular unit is functionally organized. To help address this challenge, we characterized the electrotonic architecture of the retinal microvasculature, which is particularly well adapted for the decentralized control of blood flow. In this study, we quantified the transmission of voltage between pairs of perforated-patch pipettes sealed onto abluminal cells located on microvascular complexes freshly isolated from the adult rat retina. These complexes consisted of capillaries,as well as tertiary and secondary arterioles. Dual recording experiments revealed that voltage spreading axially through a capillary, tertiary arteriole or secondary arteriole is transmitted very efficiently with a decay rate of only ∼5% per 100 μm. However, the retinal microvasculature is not simply a well-coupled syncytium since we detected significant voltage dissipation with radial abluminal cell-to-endothelium transmission and also at branch points between a capillary and its tertiary arteriole and between tertiary and secondary arterioles. Consistent with capillaries being particularly well-suited for the task of transmitting voltages induced by vasoactive signals, radial transmission is most efficient in this portion of the retinal microvasculature. Dual recordings also revealed that angiotensin II potently inhibits axial transmission. As a functional consequence, the geographical extent of the microvasculature's response to voltage-changing inputs is markedly restricted in the presence of angiotensin. In addition, this effect of angiotensin established that the electrotonic architecture of the retinal microvasculature is not static, but rather, is dynamically modulated by vasoactive signals.
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Affiliation(s)
- Ting Zhang
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
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