Premium
Ca 2+ paradox injury mediated through TRPC channels in mouse ventricular myocytes
Author(s) -
Kojima Akiko,
Kitagawa Hirotoshi,
OmatsuKanbe Mariko,
Matsuura Hiroshi,
Nosaka Shuichi
Publication year - 2010
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2010.00986.x
Subject(s) - trpc , transient receptor potential channel , trpc1 , chemistry , myocyte , trpc3 , endoplasmic reticulum , trpc6 , extracellular , sodium calcium exchanger , biophysics , medicine , endocrinology , intracellular , biochemistry , receptor , biology
BACKGROUND AND PURPOSE The Ca 2+ paradox is an important phenomenon associated with Ca 2+ overload‐mediated cellular injury in myocardium. The present study was undertaken to elucidate molecular and cellular mechanisms for the development of the Ca 2+ paradox. EXPERIMENTAL APPROACH Fluorescence imaging was performed on fluo‐3 loaded quiescent mouse ventricular myocytes using confocal laser scanning microscope. KEY RESULTS The Ca 2+ paradox was readily evoked by restoration of the extracellular Ca 2+ following 10–20 min of nominally Ca 2+ ‐free superfusion. The Ca 2+ paradox was significantly reduced by blockers of transient receptor potential canonical (TRPC) channels (2‐aminoethoxydiphenyl borate, Gd 3+ , La 3+ ) and anti‐TRPC1 antibody. The sarcoplasmic reticulum (SR) Ca 2+ content, assessed by caffeine application, gradually declined during Ca 2+ ‐free superfusion, which was further accelerated by metabolic inhibition. Block of SR Ca 2+ leak by tetracaine prevented Ca 2+ paradox. The Na + /Ca 2+ exchange (NCX) blocker KB‐R7943 significantly inhibited Ca 2+ paradox when applied throughout superfusion period, but had little effect when added for a period of 3 min before and during Ca 2+ restoration. The SR Ca 2+ content was better preserved during Ca 2+ depletion by KB‐R7943. Immunocytochemistry confirmed the expression of TRPC1, in addition to TRPC3 and TRPC4, in mouse ventricular myocytes. CONCLUSIONS AND IMPLICATIONS These results provide evidence that (i) the Ca 2+ paradox is primarily mediated by Ca 2+ entry through TRPC (probably TRPC1) channels that are presumably activated by SR Ca 2+ depletion; and (ii) reverse mode NCX contributes little to the Ca 2+ paradox, whereas inhibition of NCX during Ca 2+ depletion improves SR Ca 2+ loading, and is associated with reduced incidence of Ca 2+ paradox in mouse ventricular myocytes.