Reduced L-carnitine transport in aortic endothelial cells from spontaneously hypertensive rats

PLoS One. 2014 Feb 28;9(2):e90339. doi: 10.1371/journal.pone.0090339. eCollection 2014.

Abstract

Impaired L-carnitine uptake correlates with higher blood pressure in adult men, and L-carnitine restores endothelial function in aortic rings from spontaneously hypertensive rat (SHR). Thus, endothelial dysfunction in hypertension could result from lower L-carnitine transport in this cell type. L-Carnitine transport is mainly mediated by novel organic cation transporters 1 (Octn1, Na(+)-independent) and 2 (Octn2, Na(+)-dependent); however, their kinetic properties and potential consequences in hypertension are unknown. We hypothesize that L-carnitine transport kinetic properties will be altered in aortic endothelium from spontaneously hypertensive rats (SHR). L-Carnitine transport was measured at different extracellular pH (pHo 5.5-8.5) in the absence or presence of sodium in rat aortic endothelial cells (RAECs) from non-hypertensive Wistar-Kyoto (WKY) rats and SHR. Octn1 and Octn2 mRNA relative expression was also determined. Dilation of endothelium-intact or denuded aortic rings in response to calcitonine gene related peptide (CGRP, 0.1-100 nmol/L) was measured (myography) in the absence or presence of L-carnitine. Total L-carnitine transport was lower in cells from SHR compared with WKY rats, an effect due to reduced Na(+)-dependent (Na(+) dep ) compared with Na(+)-independent (Na(+) indep ) transport components. Saturable L-carnitine transport kinetics show maximal velocity (V max), without changes in apparent K m for Na(+) indep transport in SHR compared with WKY rats. Total and Na(+) dep component of transport were increased, but Na(+) indep transport was reduced by extracellular alkalization in WKY rats. However, alkalization reduced total and Na(+) indep transport in cells from SHR. Octn2 mRNA was higher than Octn-1 mRNA expression in cells from both conditions. Dilation of artery rings in response to CGRP was reduced in vessels from SHR compared with WKY rats. CGRP effect was endothelium-dependent and restored by L-carnitine. All together these results suggest that reduced L-carnitine transport (likely via Na(+)-dependent Octn2) could limit this compound's potential beneficial effects in RAECs from SHR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aorta / drug effects
  • Aorta / metabolism*
  • Aorta / pathology
  • Biological Transport
  • Blood Pressure
  • Calcitonin Gene-Related Peptide / pharmacology
  • Carnitine / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cells, Cultured
  • Endothelial Cells / drug effects
  • Endothelial Cells / metabolism*
  • Endothelial Cells / pathology
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / metabolism*
  • Endothelium, Vascular / pathology
  • Gene Expression
  • Humans
  • Hydrogen-Ion Concentration
  • Hypertension / metabolism*
  • Hypertension / pathology
  • Hypertension / physiopathology
  • Kinetics
  • Male
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Organic Cation Transport Proteins / genetics
  • Organic Cation Transport Proteins / metabolism
  • Rats
  • Rats, Inbred SHR
  • Rats, Inbred WKY
  • Sodium / metabolism
  • Solute Carrier Family 22 Member 5
  • Solute Carrier Proteins
  • Symporters
  • Tissue Culture Techniques
  • Vasodilation / drug effects

Substances

  • Carrier Proteins
  • Membrane Proteins
  • Organic Cation Transport Proteins
  • Slc22a4 protein, rat
  • Slc22a5 protein, rat
  • Solute Carrier Family 22 Member 5
  • Solute Carrier Proteins
  • Symporters
  • Sodium
  • Calcitonin Gene-Related Peptide
  • Carnitine

Grants and funding

This work was supported by Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT 1110977, 11100192, 3130583), Chile; Programa de Investigación Interdisciplinario (PIA) from Comisión Nacional de Investigación en Ciencia y Tecnología (CONICYT) (Anillos ACT-73); and Fellowship Apoyo de Tesis CONICYT (AT-24120944, AT-24120940), Chile. E. Guzmán-Gutiérrez and P. Arroyo hold CONICYT-PhD (Chile) fellowships. P. Arroyo was a recipient of Faculty of Medicine, Pontificia Universidad Católica de Chile-Ph.D. fellowship. C. Salomón holds a postdoctoral fellowship at The University of Queensland Centre for Clinical Research (Australia). S. Zambrano, M.V. Ruiz-Armenta and A.J. Blanca were supported by grants from Consejería de Salud, Junta de Andalucía (PI 0034/2008, 0060/2012) and Instituto de Salud Carlos III-Subdirección General de Evaluación y Fomento de la Investigación, PN de I+D+I 2008-2011, Agencia Española de Cooperación Internacional para el Desarrollo (AECID) (C/024225/09, D/031187/10, A1/036123/11), Spain. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.