Coronary heart disease and ischemic stroke are the main causes of morbidity and mortality in diabetic patients. Endothelial injury and dysfunction are common starting points for diabetic angiopathy. It is thus important to investigate the cellula and molecular mechanisms involved in coronary vascular endothelial dysfunction in diabetes. Endothelial function is regulated by changes in cytosolic Ca2+ concentration ([Ca2+]cyt) in endothelial cells (ECs). [Ca2+]cyt is controlled by the Ca2+ mobilization from intracellular stores coupled to Ca2+ influx from the external medium. In ECs, the endoplasmic reticulum (ER) accounts for approximately 75% of the total intracellular Ca2+ stores and the [Ca2+] in the ER ([Ca2+]ER) determines in great part the generation of important Ca2+ signals. The objective of this study is to examine whether [Ca2+]ER is altered in diabetic ECs and how abnormal [Ca2+]ER leads to vascular endothelial dysfunction in diabetic heart.
In Aim 1, we will examine whether and how the rise in [Ca2+]cyt due to Ca2+ release from the ER (indicative of the level of [Ca2+]ER) and [Ca2+]ER are attenuated in coronary ECs isolated from diabetic mice. The ER membrane constitutes Ca2+ pumps (sarco/endoplasmic reticulum Ca2+ ATPase (SERCA)) and several classes of intracellular Ca2+ releasing channels. Recently, stromal interaction molecule (STIM) was identified as an essential protein for the store-operated Ca2+ entry (SOCE) and a contributor to the Ca2+ refilling into the ER by interacting with SERCA on the ER membrane.
In Aim 2, we will investigate the potential role of STIM1 in decreased [Ca2+]ER in diabetic coronary ECs. Our preliminary data show that SERCA3 and STIM1 protein expressions are markedly decreased in diabetic coronary ECs and STIM1 overexpression in diabetic coronary ECs significantly increases Ca2+ leak from the ER. In addition, Ca2+ transported to mitochondria from the ER plays a crucial role in cell apoptosis; increased mitochondrial Ca2+ ([Ca2+]mit) can trigger mitochondrial fragmentation, loss of mitochondrial integrity and cell death in many cell types. Our results show that [Ca2+]mit is significantly increased in coronary ECs in diabetes.
In Aim 3, we will define whether Ca2+ transportation from the ER to mitochondria is increased in coronary ECs in diabetes and examine the role of the Ca2+ communication between the ER and mitochondria in endothelial dysfunction in diabetic heart. To examine Ca2+ handling by the ER in diabetic coronary ECs will further our understanding of pathophysiological aspects of coronary vascular complications in diabetes. Completion of this study will provide important insights into developing new therapeutic interventions for cardiac ischemia in diabetes.

Public Health Relevance

More than 25 million people in the Unites States are suffering from diabetes (a disease which your blood sugar level is too high) and 1.9 million people ages 20 years or older are newly diagnosed with diabetes every year. Diabetes is the 7th leading cause of death nationally and nearly 68% of individuals with diabetes die from the complication of diseases related to the heart or blood vessels. This study is designed to identify the cellular defects that cause the abnormalities of the blood vessels in the diabetic heart and to help develop new therapeutic approaches for diabetic patients.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL115578-04
Application #
8883693
Study Section
Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
Olive, Michelle
Project Start
2012-07-03
Project End
2016-06-30
Budget Start
2015-07-01
Budget End
2016-06-30
Support Year
4
Fiscal Year
2015
Total Cost
$376,762
Indirect Cost
$130,512
Name
University of Arizona
Department
Physiology
Type
Schools of Medicine
DUNS #
806345617
City
Tucson
State
AZ
Country
United States
Zip Code
85721
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Makino, Ayako; Dai, Anzhi; Han, Ying et al. (2015) O-GlcNAcase overexpression reverses coronary endothelial cell dysfunction in type 1 diabetic mice. Am J Physiol Cell Physiol 309:C593-9
Cho, Young-Eun; Basu, Aninda; Dai, Anzhi et al. (2013) Coronary endothelial dysfunction and mitochondrial reactive oxygen species in type 2 diabetic mice. Am J Physiol Cell Physiol 305:C1033-40
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Sasaki, Koh; Donthamsetty, Reshma; Heldak, Michael et al. (2012) VDAC: old protein with new roles in diabetes. Am J Physiol Cell Physiol 303:C1055-60

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