Nature Medicine
9, 1187 - 1194 (2003)
Published online: 24 August 2003; | doi:10.1038/nm920
L-type Ca2+ channels provide a major pathway for iron entry into cardiomyocytes in iron-overload cardiomyopathyGavin Y Oudit1, 4, Hui Sun1, Maria G Trivieri1, Sheryl E Koch3, Fayez Dawood1, Cameron Ackerley2, Mehrdad Yazdanpanah1, Greg J Wilson2, Arnold Schwartz3, Peter P Liu1, 4
& Peter H Backx1, 41
Heart and Stroke/Richard Lewar Centre of Excellence, Departments of Medicine and Physiology, University of Toronto, Ontario M5S 3E2, Canada. 2
Department of Pathology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada. 3
Institute of Molecular Pharmacology and Biophysics, CVRC University of Cincinnati Medical Center, Cincinnati, Ohio 45267-0828, 4
Division of Cardiology, University Health Network, Toronto, Ontario M5G 2C4, Canada. USA.
Correspondence should be addressed to Peter H Backx p.backx@utoronto.caUnder conditions of iron overload, which are now reaching epidemic proportions worldwide, iron-overload cardiomyopathy is the most important prognostic factor in patient survival. We hypothesize that in iron-overload disorders, iron accumulation in the heart depends on ferrous iron (Fe2+) permeation through the L-type voltage-dependent Ca2+ channel (LVDCC), a promiscuous divalent cation transporter. Iron overload in mice was associated with increased mortality, systolic and diastolic dysfunction, bradycardia, hypotension, increased myocardial fibrosis and elevated oxidative stress. Treatment with LVDCC blockers (CCBs; amlodipine and verapamil) at therapeutic levels inhibited the LVDCC current in cardiomyocytes, attenuated myocardial iron accumulation and oxidative stress, improved survival, prevented hypotension and preserved heart structure and function. Consistent with the role of LVDCCs in myocardial iron uptake, iron-overloaded transgenic mice with cardiac-specific overexpression of the LVDCC  1-subunit had twofold higher myocardial iron and oxidative stress levels, as well as greater impairment in cardiac function, compared with littermate controls; LVDCC blockade was again protective. Our results indicate that cardiac LVDCCs are key transporters of iron into cardiomyocytes under iron-overloaded conditions, and potentially represent a new therapeutic target to reduce the cardiovascular burden from iron overload.
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