Monocarboxylate Transporter 1 (MCT1) mediates succinate export in the retina

Purpose: Succinate is exported by the retina and imported by eyecup tissue. The transporter(s) mediating this process have not yet been identified. Recent studies showed that Monocarboxylate Transporter 1 (MCT1) can transport succinate across plasma membranes in cardiac and skeletal muscle. Retina and retinal pigment epithelium (RPE) both express multiple MCT isoforms including MCT1. We tested the hypothesis that MCTs facilitate retinal succinate export and RPE succinate import. Methods: We assessed retinal succinate export and eyecup succinate import in short term ex vivo culture using gas chromatography-mass spectrometry. We test the dependence of succinate export and import on pH, proton ionophores, conventional MCT substrates, and the MCT inhibitors AZD3965, AR-C155858, and diclofenac. Results: Succinate exits retinal tissue through MCT1 but does not enter RPE through MCT1 or any other MCT. Intracellular succinate levels are a contributing factor that determines if an MCT1-expressing tissue will export succinate. Conclusions: MCT1 facilitates export of succinate from retinas. An unidentified, non-MCT transporter facilitates import of succinate into RPE.

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Metabolic function in aging retina and retinal pigment epithelium remains robust despite vision loss

10.1101/2021.04.06.438698 ◽

2021 ◽

Author(s):

Kristine A. Tsantilas ◽

Whitney M. Cleghorn ◽

Celia M. Bisbach ◽

Jeremy A. Whitson ◽

Daniel T. Hass ◽

...

Keyword(s):

Retinal Pigment Epithelium ◽

Glucose Metabolism ◽

Vision Loss ◽

Ex Vivo ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Glutamine Metabolism ◽

Gas Chromatography Mass Spectrometry ◽

Metabolic Function ◽

Age Related

AbstractPurposeCharacterize how metabolic function in the murine retina and retinal pigment epithelium-choroid-sclera (eyecup) complex is impacted by natural aging.MethodsWe examined scotopic and photopic visual function of young (3-6 months) and aged (23-26 months) C57Bl/6J mice using electroretinograms (ERGs). Metabolic changes in retina and eyecup explants were characterized by measuring uptake and usage of U-13C-glucose or U-13C-glutamine at different timepoints by gas chromatography-mass spectrometry (GC-MS), measuring oxygen consumption rate (OCR) using a perifusion apparatus, and determining ATP levels with a bioluminescence assay.ResultsScotopic and photopic ERG responses declined in aged mice. Glucose metabolism, glutamine metabolism, OCR, and ATP pools in retinal explants were mostly unaffected by the age of the mouse. In eyecups, glutamine usage in the Krebs Cycle decreased while glucose metabolism, OCR, and ATP pools remained stable.ConclusionsThe ex vivo approach in our study to examine aging glucose and glutamine metabolism in retina and RPE showed negligible impact of age on retina and an impairment of glutamine anaplerosis in eyecups. The surprising metabolic stability of these tissues ex vivo suggests age-related metabolic alterations in these tissues may not be intrinsic. Future experiments should focus on determining whether external factors including nutrient supply, oxygen availability, or other structural changes influence ocular metabolism in vivo.

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Ocular Toxoplasmosis: Mechanisms of Retinal Infection and Experimental Models

Parasitologia ◽

10.3390/parasitologia1020007 ◽

2021 ◽

Vol 1 (2) ◽

pp. 50-60

Author(s):

Veronica Rodriguez Fernandez ◽

Giovanni Casini ◽

Fabrizio Bruschi

Keyword(s):

Ex Vivo ◽

Cell Damage ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Treatment Strategies ◽

Experimental Models ◽

Ocular Toxoplasmosis ◽

Cell Infection

Ocular toxoplasmosis (OT) is caused by the parasite Toxoplasma gondii and affects many individuals throughout the world. Infection may occur through congenital or acquired routes. The parasites enter the blood circulation and reach both the retina and the retinal pigment epithelium, where they may cause cell damage and cell death. Different routes of access are used by T. gondii to reach the retina through the retinal endothelium: by transmission inside leukocytes, as free parasites through a paracellular route, or after endothelial cell infection. A main feature of OT is the induction of an important inflammatory state, and the course of infection has been shown to be influenced by the host immunogenetics. On the other hand, there is evidence that the T. gondii phenotype also has an impact on the distribution of the pathology in different areas. Although considerable knowledge has been acquired on OT, a deeper knowledge of its mechanisms is necessary to provide new, more targeted treatment strategies. In particular, in addition to in vitro and in vivo experimental models, organotypic, ex vivo retinal explants may be useful in this direction.

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INTACT RETINAL TISSUE AND RETINAL PIGMENT EPITHELIUM IDENTIFIED WITHIN A COLOBOMA BY HIGH-SPEED, ULTRAHIGH-RESOLUTION OPTICAL COHERENCE TOMOGRAPHY

Retinal Cases & Brief Reports ◽

10.1097/icb.0b013e3181cafc49 ◽

2011 ◽

Vol 5 (1) ◽

pp. 46-48 ◽

Cited By ~ 1

Author(s):

Christopher H Judson ◽

Laurel N Vuong ◽

Iwona Gorczynska ◽

Vivek J Srinivasan ◽

James G Fujimoto ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Retinal Pigment Epithelium ◽

High Speed ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Optical Coherence ◽

Ultrahigh Resolution ◽

Retinal Tissue

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A novel nutrient sensing mechanism underlies substrate-induced regulation of monocarboxylate transporter-1

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00308.2012 ◽

2012 ◽

Vol 303 (10) ◽

pp. G1126-G1133 ◽

Cited By ~ 51

Author(s):

Alip Borthakur ◽

Shubha Priyamvada ◽

Anoop Kumar ◽

Arivarasu A. Natarajan ◽

Ravinder K. Gill ◽

...

Keyword(s):

Intestinal Inflammation ◽

Apical Membrane ◽

Nutrient Sensing ◽

Monocarboxylate Transporter ◽

Rat Colon ◽

Intracellular Camp ◽

Short Term ◽

Monocarboxylate Transporter 1 ◽

Sensing Mechanism ◽

And Function

Monocarboxylate transporter isoform-1 (MCT1) plays an important role in the absorption of short-chain fatty acids (SCFAs) in the colon. Butyrate, a major SCFA, serves as the primary energy source for the colonic mucosa, maintains epithelial integrity, and ameliorates intestinal inflammation. Previous studies have shown substrate (butyrate)-induced upregulation of MCT1 expression and function via transcriptional mechanisms. The present studies provide evidence that short-term MCT1 regulation by substrates could be mediated via a novel nutrient sensing mechanism. Short-term regulation of MCT1 by butyrate was examined in vitro in human intestinal C2BBe1 and rat intestinal IEC-6 cells and ex vivo in rat intestinal mucosa. Effects of pectin feeding on MCT1, in vivo, were determined in rat model. Butyrate treatment (30–120 min) of C2BBe1 cells increased MCT1 function {p-(chloromercuri) benzene sulfonate (PCMBS)-sensitive [14C]butyrate uptake} in a pertussis toxin-sensitive manner. The effects were associated with decreased intracellular cAMP levels, increased Vmax of butyrate uptake, and GPR109A-dependent increase in apical membrane MCT1 level. Nicotinic acid, an agonist for the SCFA receptor GPR109A, also increased MCT1 function and decreased intracellular cAMP. Pectin feeding increased apical membrane MCT1 levels and nicotinate-induced transepithelial butyrate flux in rat colon. Our data provide strong evidence for substrate-induced enhancement of MCT1 surface expression and function via a novel nutrient sensing mechanism involving GPR109A as a SCFA sensor.

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Ex vivo expansion with stem cell factor and interleukin-11 augments both short-term recovery posttransplant and the ability to serially transplant marrow

Blood ◽

10.1182/blood.v87.11.4589.bloodjournal87114589 ◽

1996 ◽

Vol 87 (11) ◽

pp. 4589-4595 ◽

Cited By ~ 65

Author(s):

TL Holyoake ◽

MG Freshney ◽

L McNair ◽

AN Parker ◽

PJ McKay ◽

...

Keyword(s):

Stem Cell ◽

Stem Cell Factor ◽

Ex Vivo ◽

Culture Conditions ◽

Ex Vivo Expansion ◽

Short Term ◽

Ex Vivo Culture ◽

Interleukin 11 ◽

Transplantation Model

The characterization of many cytokines involved in the control of hematopoiesis has led to intense investigation into their potential use in ex vivo culture to expand progenitor numbers. We have established the optimum ex vivo culture conditions that allow substantial amplification of transient engrafting murine stem cells and which, simultaneously, augment the ability to sustain serial bone marrow transplantation (BMT). Short-term incubation of unfractionated BM cells in liquid culture with stem cell factor (SCF) and interleukin-11 (IL- 11) produced a 50-fold amplification of clonogenic multipotential progenitors (CFU-A). Following such ex vivo expansion, substantially fewer cells were required to rescue lethally irradiated mice. When transplanted in cell doses above threshold for engraftment, BM cells expanded ex vivo resulted in significantly more rapid hematopoietic recovery. In a serial transplantation model, unmanipulated BM was only able to consistently sustain secondary BMT recipients, but BM expanded ex vivo has sustained quaternary BMT recipients that remain alive and well more than 140 days after 4th degree BMT. These results show augmentation of both short-term recovery posttransplant and the ability to serially transplant marrow by preincubation in culture with SCF and IL-11.

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Dietary Supplementation with Beta-Cryptoxanthin (BCX) Protects Against Light-Induced Retinal Damage

Current Developments in Nutrition ◽

10.1093/cdn/nzaa041_030 ◽

2020 ◽

Vol 4 (Supplement_2) ◽

pp. 126-126

Author(s):

Deshanie Rai ◽

Kazim Sahin ◽

Emre Sahin ◽

Mehmet Tuzcu ◽

...

Keyword(s):

Oxidative Stress ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Angiogenic Factor ◽

Retinal Damage ◽

Waste Products ◽

Health Technologies ◽

Retinal Tissue ◽

Age Related ◽

Markers Of Oxidative Stress

Abstract Objectives The retinal pigment epithelium (RPE) regulates the transport of nutrients and waste products to and from the retina and protects against light and oxidative stress. Structural or physiological dysfunction of RPE leads to retinal conditions such as age-related eye disease (ARED). It is well-established that artificial and natural light is an important factor in the progression of ARED as it can induce oxidative damage and photochemical lesions. Recently, the use of LED in general lighting has raised concerns regarding the effects of this light source on the RPE. The goal was to investigate whether beta-cryptoxanthin, an efficient pro-vitamin A carotenoid can exert protective effects against LED-induced RPE cell damage. Methods Rats were fed with BCX for 4 weeks at a dose of 2 and 4 mg/kg body weight followed by retinal damage by exposing the eye to bright LED light for 48 hrs. Commercially available white LED sources, which are widely used in rat housing studies was used to induce retinal damage. Animals were sacrificed at the end of the study and retinal tissue and blood samples were collected and evaluated for retinal damage and markers of oxidative stress. Results BCX supplementation significantly reduced retinal damage as demonstrated by histopathology measurements including total retinal thickness, outer nuclear layer thickness, and swelling. Similarly, markers of oxidative stress including serum and retinal tissue levels of malondialdehyde, superoxide dismutase, glutathione peroxidase, and catalase were beneficially modulated by BCX supplementation. In parallel, BCX supplementation reduced inflammatory markers (IL-1β, IL-6, NF-κB), angiogenic factor VEGF, apoptotic proteins (Caspase-3, GAP43, GFAP, NCAM, HO-1) and mitochondrial stress markers (ATF4, ATF6, Grp78, Grp97) in retinal tissue. Conclusions Our study supports that oral supplementation of BCX dose-dependently exerts a protective effect against retinal damage induced by high-intensity light in a rat model by reducing oxidative stress, inflammation, angigogenesis and protection against mitochondrial DNA damage. BCX dietary intakes and supplementation throughout all stages of life can help protect against ARED that may start early in life. Funding Sources OmniActive Health Technologies.

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Isolation of plasma membranes from the bovine retinal pigment epithelium

Biochimica et Biophysica Acta (BBA) - Biomembranes ◽

10.1016/0005-2736(85)90232-9 ◽

1985 ◽

Vol 813 (2) ◽

pp. 183-194 ◽

Cited By ~ 14

Author(s):

Sharon C. Braunagel ◽

Daniel T. Organisciak ◽

Hih-min Wang

Keyword(s):

Retinal Pigment Epithelium ◽

Plasma Membranes ◽

Pigment Epithelium ◽

Retinal Pigment

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Short-term training increases human muscle MCT1 and femoral venous lactate in relation to muscle lactate

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1998.274.1.e102 ◽

1998 ◽

Vol 274 (1) ◽

pp. E102-E107 ◽

Cited By ~ 46

Author(s):

A. Bonen ◽

K. J. A. McCullagh ◽

C. T. Putman ◽

E. Hultman ◽

N. L. Jones ◽

...

Keyword(s):

Skeletal Muscle ◽

Vastus Lateralis ◽

Venous Blood ◽

Maximal Oxygen Consumption ◽

Bicycle Ergometer ◽

Monocarboxylate Transporter ◽

Short Term ◽

Bicycle Ergometry ◽

Muscle Lactate ◽

Monocarboxylate Transporter 1

We examined the effects of increasing a known lactate transporter protein, monocarboxylate transporter 1 (MCT1), on lactate extrusion from human skeletal muscle during exercise. Before and after short-term bicycle ergometry training [2 h/day, 7 days at 65% maximal oxygen consumption (V˙o 2 max)], subjects ( n = 7) completed a continuous bicycle ergometer ride at 30%V˙o 2 max (15 min), 60%V˙o 2 max (15 min), and 75% V˙o 2 max (15 min). Muscle biopsy samples (vastus lateralis) and arterial and femoral venous blood samples were obtained before exercise and at the end of each workload. After 7 days of training the MCT1 content in muscle was increased (+18%; P < 0.05). The concentrations of both muscle lactate and femoral venous lactate were reduced during exercise ( P < 0.05) that was performed after training. High correlations were observed between muscle lactate and venous lactate before training ( r = 0.92, P < 0.05) and after training ( r = 0.85, P < 0.05), but the slopes of the regression lines between these variables differed markedly. Before training, the slope was 0.12 ± 0.01 mM lactate ⋅ mmol lactate−1 ⋅ kg muscle dry wt−1, and this was increased by 33% after training to 0.18 ± 0.02 mM lactate ⋅ mmol lactate−1 ⋅ kg muscle dry wt−1. This indicated that after training the femoral venous lactate concentrations were increased for a given amount of muscle lactate. These results suggest that lactate extrusion from exercising muscles is increased after training, and this may be associated with the increase in skeletal muscle MCT1.

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