The long term objective of this research proposal is to determine the molecular mechanisms of vascular calcification in order to identify novel target(s) for the treatment of chronic kidney disease (CKD)-dependent vascular calcification. Vascular calcification is closely associated with cardiovascular morbidity and mortality in patients with CKD. In fact, more than half of all deaths in CKD subjects can be attributed to cardiovascular diseases. We hypothesized that a central event in the pathogenesis of CKD-dependent vascular calcification is increased expression of phosphorylated activating transcription factor 4 (ATF4). ATF4 is a member of the cAMP-responsive element-binding protein (CREB) family of basic zipper-containing transcription factors that regulates osteogenesis and also mediates unfolded protein response (UPR) in the endoplasmic reticulum (ER). Our hypothesis is based on the following evidence derived from a series of preliminary results from our lab: 1) total and phosphorylated ATF4 protein levels were induced by a number of positive regulatory factors for vascular calcification, such as inorganic phosphate, inflammatory cytokines (TNFa) and saturated fatty acids through the activation of the PERK-elF2a axis of the UPR in vascular smooth muscle cells (VSMCs);2) adenovirus-mediated overexpression of ATF4 induced mineralization of VSMCs;3) ATF4 knockdown, on the other hand, attenuated vascular calcification;4) serine-phosphorylation of ATF4 (p-ATF4) was induced by PKA activation by forskolin, which is known to promote vascular calcification;5) PKA and ERK inhibitors inhibited the phosphorylation of ATF4, resulting in the reduction of vascular calcification;6) Total ATF4 and p-ATF4 proteins were increased in the aortas of murine models of atherosclerotic calcification such as ApoE knockout mice with 5/6 nephrectomy (5/6 nx), and medial calcification such as DBA2/J mice with 5/6 nx and klotho knockout mice;7) ATF4 targets (CHOP and GADD34) increased in these models and 8) ATF4 regulates the expression of Pit-1, a major phosphate transporter in VSMCs. To determine the pivotal role of ATF4 in the pathogenesis of vascular calcification, we propose three specific aims.
Specific Aim 1 : Determine whether global ATF4 deficiency and overexpression modulate CKD-dependent medial and atherosclerotic calcification.
Specific Aim 2 : Determine whether VSMC-specific activation and inhibition of ATF4 influence CKD-dependent medial and atherosclerotic calcification.
Specific Aim 3 : Elucidate molecular mechanisms by which ATF4 regulates osteoblastic differentiation and mineralization of VSMCs.

Public Health Relevance

Vascular calcification is common in chronic kidney disease (CKD) and associated with increased morbidity and mortality. This research project will enhance our understanding of the molecular mechanisms of vascular calcification, and identify novel target(s) for treatment of CKD-dependent vascular calcification.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK096030-01A1
Application #
8502965
Study Section
Atherosclerosis and Inflammation of the Cardiovascular System Study Section (AICS)
Program Officer
Kusek, John W
Project Start
2013-04-01
Project End
2018-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
1
Fiscal Year
2013
Total Cost
$429,112
Indirect Cost
$151,145
Name
University of Colorado Denver
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
041096314
City
Aurora
State
CO
Country
United States
Zip Code
80045
Miyazaki-Anzai, Shinobu; Masuda, Masashi; Levi, Moshe et al. (2014) Dual activation of the bile acid nuclear receptor FXR and G-protein-coupled receptor TGR5 protects mice against atherosclerosis. PLoS One 9:e108270
Miyazaki-Anzai, Shinobu; Masuda, Masashi; Demos-Davies, Kimberly M et al. (2014) Endoplasmic reticulum stress effector CCAAT/enhancer-binding protein homologous protein (CHOP) regulates chronic kidney disease-induced vascular calcification. J Am Heart Assoc 3:e000949
Masuda, Masashi; Miyazaki-Anzai, Shinobu; Levi, Moshe et al. (2013) PERK-eIF2*-ATF4-CHOP signaling contributes to TNF*-induced vascular calcification. J Am Heart Assoc 2:e000238