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Reactive oxygen species from smooth muscle mitochondria initiate cold-induced constriction of cutaneous arteries

Posted Dec 07 2009 11:03pm
By S. R. Bailey and Colleague

Cold constricts cutaneous blood vessels by selectively increasing the activity of smooth muscle 2-adrenoceptors (2-ARs). In mouse tail arteries, 2-AR constriction is mediated by 2A-ARs at 37°C, whereas the cold-induced augmentation in 2-AR activity is mediated entirely by 2C-ARs.

Cold causes translocation of 2C-ARs from the trans-Golgi to the plasma membrane, mediated by cold-induced activation of RhoA and Rho kinase. The present experiments analyzed the mechanisms underlying these responses. Mouse tail arteries were studied in a pressure myograph.

Cooling the arteries (28°C) caused a rapid increase in reactive oxygen species (ROS) in smooth muscle cells, determined by confocal microscopy of arteries loaded with the ROS-sensitive probes, dichlorodihydrofluorescein or reduced Mitotracker Red.

The inhibitor of mitochondrial complex I rotenone (10 µmol/l), the antioxidant N-acetylcysteine (NAC; 20 mmol/l), or the cell-permeable mimic of superoxide dismutase MnTMPyP (50 µmol/l) did not affect vasoconstriction to 2-AR stimulation (UK-14304) at 37°C but dramatically inhibited the response at 28°C.

Indeed, these ROS inhibitors abolished the cold-induced increase in 2-AR constrictor activity. NAC (20 mmol/l) or MnTMPyP (50 µmol/l) also abolished the cold-induced activation of RhoA in human cultured vascular smooth muscle cells and the cold-induced mobilization of 2C-ARs to the cell surface in human embryonic kidney 293 cells transfected with the receptor.

The combined results suggest that cold-induced constriction is mediated by redox signaling in smooth muscle cells, initiated by mitochondrial generation of ROS, which stimulate RhoA/Rho kinase signaling and the subsequent mobilization of 2C-ARs to the cell surface. Altered activity of ROS may contribute to cold-induced vasospasm occurring in Raynaud's phenomenon.
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