Connexin 43 in cardiomyocyte mitochondria and its increase by ischemic preconditioning.
OBJECTIVE
Connexin 43 (Cx43) is involved in infarct size reduction by ischemic preconditioning (IP); the underlying mechanism of protection, however, is unknown. Since mitochondria have been proposed to be involved in IP's protection, the present study analyzed whether Cx43 is localized at mitochondria of cardiomyocytes and whether such localization is affected by IP.


RESULTS
Western blot analysis on mitochondrial preparations isolated from rat, mouse, pig, and human hearts showed the presence of Cx43. The preparations were not contaminated with markers for other cell compartments. The localization of Cx43 to mitochondria was also confirmed by FACS sorting (double staining with MitoTracker Red and Cx43) and immuno-electron and confocal microscopy. To study the role of Cx43 in IP, mitochondria were isolated from the ischemic anterior wall (AW) and the control posterior wall (PW) of pig myocardium at the end of 90 min low-flow ischemia without (n=13) or with (n=13) a preceding preconditioning cycle of 10 min ischemia and 15 min reperfusion. With IP, the mitochondrial Cx43/adenine nucleotide transporter ratio was 3.4+/-0.7 fold greater in AW than in PW, whereas the ratio remained unchanged in non-preconditioned myocardium (1.1+/-0.2, p<0.05). The enhancement of the mitochondrial Cx43 protein level occurred rapidly, since an increase of mitochondrial Cx43 was already detected with two cycles of 5 min ischemia/reperfusion in isolated rat hearts to 262+/-63% of baseline.


CONCLUSIONS
These data demonstrate that Cx43 is localized at cardiomyocyte mitochondria and that IP enhances such mitochondrial localization.
Boengler
Kerstin
K
Institut für Pathophysiologie, Zentrum für Innere Medizin, Universitätsklinikum Essen, Hufelandstr. 55, 45122 Essen, Germany.
Dodoni
Giuliano
G
Rodriguez-Sinovas
Antonio
A
Cabestrero
Alberto
A
Ruiz-Meana
Marisol
M
Gres
Petra
P
Konietzka
Ina
I
Lopez-Iglesias
Carmen
C
Garcia-Dorado
David
D
Di Lisa
Fabio
F
Heusch
Gerd
G
Schulz
Rainer
R
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D018031:Connexin 43 / Q000032:analysis* / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D008929:Mitochondria, Heart / Q000737:chemistry* / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000737:chemistry / Q000378:metabolism; D017202:Myocardial Ischemia / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013552:Swine
D018031:Connexin 43