During cold exposure, cutaneous blood flow is reduced to prevent heat loss. This is mediated by increased sympathetic tone and a cold-induced sensitization of cutaneous arteries to constriction by norepinephrine. The latter effect is mediated by cold-induced amplification of (alpha2-adrenergic receptor (alpha2-AR) function. Although alpha2-ARs comprise 3 subtypes, only alpha2C-ARs respond to cold. Although alpha2C-ARs are not functional at 37 degrees C, they are entirely responsible for the cold-induced amplification of alpha2-AR constriction. At 37 degrees C, alpha2C-ARs are retained in the transGolgi network. Cooling causes alpha2C-AR translocation to the cell surface where they can respond to stimulation. The functional rescue of alpha2C-ARs is mediated by cold-induced activation of RhoA and rho kinase (ROCK). ROCKI inhibition by pharmacological blockade or RNA interference prevents cold-induced mobilization of alpha2C-ARs and cold-induced constriction in cutaneous arteries. We now demonstrate that cooling of tail arteries causes a rapid increase in ROS activity in VSM mitochondria, which precedes RhoA activation. Indeed, inhibition of ROS activity abolished cold-induced activation of RhoA and the functional rescue of alpha2C-ARs. The rescue of alpha2C-ARs was also reduced by a tyrosine kinase inhibitor. We propose that cold stimulates mitochondrial generation of ROS, causing transactivation of a receptor tyrosine kinase and activation of RhoA/ROCKI, enabling the spatial and functional rescue of alpha2C-ARs. We have also identified a novel cyclic AMP signaling pathway in cutaneous VSMs, which activates Rapl and causes profound increases in alpha2C-AR expression. We propose that these novel pathways for regulating the function and expression alpha2C-ARs may contribute to cold-induced vasospasm. Indeed, we present a new model of cold-induced vasospasm, generated by a chemotherapeutic agent that causes Raynaud's Disease in humans. This model displays a selective and dramatic increase in VSM alpha2C-AR activity, which precipitate vasospasm of cutaneous arteries.
Three specific aims are proposed to pursue these novel and exciting findings and to investigate their physiological and pathophysiological significance.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL080119-04
Application #
7383892
Study Section
Hypertension and Microcirculation Study Section (HM)
Program Officer
Goldman, Stephen
Project Start
2005-02-01
Project End
2010-01-31
Budget Start
2008-02-01
Budget End
2009-01-31
Support Year
4
Fiscal Year
2008
Total Cost
$349,879
Indirect Cost
Name
Johns Hopkins University
Department
Anesthesiology
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Chotani, Maqsood A; Flavahan, Nicholas A (2011) Intracellular ?(2C)-adrenoceptors: storage depot, stunted development or signaling domain? Biochim Biophys Acta 1813:1495-503
Goel, Aditya; Su, Baogen; Flavahan, Sheila et al. (2010) Increased endothelial exocytosis and generation of endothelin-1 contributes to constriction of aged arteries. Circ Res 107:242-51
Crassous, P A; Flavahan, S; Flavahan, N A (2009) Acute dilation to alpha(2)-adrenoceptor antagonists uncovers dual constriction and dilation mediated by arterial alpha(2)-adrenoceptors. Br J Pharmacol 158:1344-55
Flavahan, Nicholas A (2008) Regulation of vascular reactivity in scleroderma: new insights into Raynaud's phenomenon. Rheum Dis Clin North Am 34:81-7;vii
Eid, A H; Chotani, M A; Mitra, S et al. (2008) Cyclic AMP acts through Rap1 and JNK signaling to increase expression of cutaneous smooth muscle alpha2C-adrenoceptors. Am J Physiol Heart Circ Physiol 295:H266-72
Eid, A H; Maiti, K; Mitra, S et al. (2007) Estrogen increases smooth muscle expression of alpha2C-adrenoceptors and cold-induced constriction of cutaneous arteries. Am J Physiol Heart Circ Physiol 293:H1955-61
Bailey, S R; Mitra, S; Flavahan, S et al. (2007) In vivo endothelial denudation disrupts smooth muscle caveolae and differentially impairs agonist-induced constriction in small arteries. J Cardiovasc Pharmacol 49:183-90
Krajnak, K; Dong, R G; Flavahan, S et al. (2006) Acute vibration increases alpha2C-adrenergic smooth muscle constriction and alters thermosensitivity of cutaneous arteries. J Appl Physiol 100:1230-7
Flavahan, Nicholas A (2006) A farewell kiss triggers a broken heart? Circ Res 98:1117-9
Zhou, Yingbi; Mitra, Srabani; Varadharaj, Saradhadevi et al. (2006) Increased expression of cyclooxygenase-2 mediates enhanced contraction to endothelin ETA receptor stimulation in endothelial nitric oxide synthase knockout mice. Circ Res 98:1439-45

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