alpha-7-type acetylcholine receptor localization and its modulation by nicotine and cholesterol in vascular endothelial cells

AYALA PEÑA V.B.; BONINI I.C.; ANTOLLINI S.S.; TOSHIHIDE K.; BARRANTES F.J.

JOURNAL OF CELLULAR BIOCHEMISTRY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New york; Año: 2011 p. 3276 - 3288

0730-2312

The a7 nicotinic acetylcholine receptor (a7AChR), a neuronal-type receptor, is found in various non-neural tissues, including vascular endothelium, where its peculiar ionotropic properties (high Ca2+ permeability) and its supervening Ca2+-mediated intracellular cascades may play important roles in physiology (angiogenesis) and pathology (inflammation and atherogenesis). Changes in molecular (up-regulation, affinity and conformational states) and cellular (distribution, association with membranes) properties of the a7AChR were measured in living endothelial cells. Changes related to angiogenesis (wound-repair cell migration) and atherogenesis (alterations in cholesterol content) prompted by agonist stimulation were also measured with the aim to determine whether such changes constitute early markers of inflammatory response in vascular endothelium. The combination of pharmacological, biochemical and fluorescence microscopy tools showed that a7AChRs in rat arterial endothelial (RAEC) and human venous endothelial (HUVEC) cells undergo agonist (nicotine)-induced up-regulation (from 53.3±16 to 385.2±46.8 fmol/mg protein with 50 mM nicotine), increase their cell-surface exposure, and occur in the "non-raft" subcellular membrane fractions. Cholesterol depletion mediated by cyclodextrin treatment reduced the number of cell-surface a7AChRs. Nicotine exposure markedly stimulated cell migration and accelerated wound repair. Nicotine exerted a positive effect on wound repair, which drastically diminished in cells deprived of the sterol. Under basal conditions, a7AChRs occur at extremely low expression levels (~50 fmol/mg protein) in both RAEC and HUVEC. Nicotine up-regulated (~300-fold) a7AChR cell-surface expression. Nicotine exposure of receptor-enriched membranes obtained from up-regulated HUVEC increased 600-fold the apparent KD of a7AChRs for the open-channel blocker crystal violet. The angiogenic effect of nicotine appears to be synergistic with cholesterol content