Hypoxia and stretch regulate intercellular communication in vascular smooth muscle cells through reactive oxygen species formation.
OBJECTIVE
We hypothesized that the alterations in vasomotor tone and adaptive remodeling responses that occur in the circulation because of hypoxia were dependent on changes in cell to cell communication through regulation of gap junction protein expression and function. Consequently, we studied the amount, distribution, and permeability of the principal vascular smooth muscle cell (VSMC) gap junction protein, connexin43, in rat aortic cultures exposed to oxygen partial pressures of 150 or 15 mm Hg.


RESULTS
Immunohistochemical staining, immunoblot assays, and Northern blot analyses demonstrated that connexin43 expression was reversibly increased in hypoxic cultures. As a result, hypoxic cells exhibited greater intercellular communication as determined by fluorescence recovery after photobleaching experiments. Using a fluorogenic substrate, hypoxic VSMCs showed increased reactive oxygen species generation, which could be prevented by the glutathione peroxidase mimic ebselen and the mitochondrial complex I inhibitor rotenone but not with the redox-sensitive thiol pyrrolidine dithiocarbamate. The rise in connexin43 expression attributable to hypoxia could be attenuated by ebselen and rotenone treatment. Interestingly, the previously reported induction of connexin43 expression by tensile stretch was also contingent on oxidative activity.


CONCLUSIONS
Hypoxia and stretch increased gap junctional intercellular communication in VSMCs attributable to enhanced connexin43 expression initiated by reactive oxygen species formation.
Cowan
Douglas B
DB
Department of Anesthesiology, Children's Hospital Boston and Harvard Medical School, 02115, USA. douglas.cowan@childrens.harvard.edu
Jones
Mara
M
Garcia
Lina M
LM
Noria
Sabrena
S
del Nido
Pedro J
PJ
McGowan
Francis X
FX
D000818:Animals; D002450:Cell Communication; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D015151:Immunoblotting; D008465:Mechanoreceptors / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015854:Up-Regulation
D018031:Connexin 43; D012333:RNA, Messenger; D017382:Reactive Oxygen Species