The CDK9-cyclin T1 complex mediates saturated fatty acid-induced vascular calcification by inducing expression of the transcription factor CHOP.

Vascular calcification (or mineralization) is a common complication of chronic kidney disease (CKD) and is closely associated with increased mortality and morbidity rates. We recently reported that activation of the activating transcription factor 4 (ATF4) pathway through the saturated fatty acid (SFA)-induced endoplasmic reticulum (ER) stress response plays a causative role in CKD-associated vascular calcification. Here, using mouse models of CKD, we 1) studied the contribution of the proapoptotic transcription factor CCAAT enhancer-binding protein homologous protein (CHOP) to CKD-dependent medial calcification, and 2) we identified an additional regulator of ER stress-mediated CHOP expression. Transgenic mice having smooth muscle cell (SMC)-specific CHOP expression developed severe vascular apoptosis and medial calcification under CKD. Screening of a protein kinase inhibitor library identified 16 compounds, including seven cyclin-dependent kinase (CDK) inhibitors, that significantly suppressed CHOP induction during ER stress. Moreover, selective CDK9 inhibitors and CRISPR/Cas9-mediated CDK9 reduction blocked SFA-mediated induction of CHOP expression, whereas inhibitors of other CDK isoforms did not. Cyclin T1 knockout inhibited SFA-mediated induction of CHOP and mineralization, whereas deletion of cyclin T2 and cyclin K promoted CHOP expression levels and mineralization. Of note, the CDK9-cyclin T1 complex directly phosphorylated and activated ATF4. These results demonstrate that the CDK9-cyclin T1 and CDK9-cyclin T2/K complexes have opposing roles in CHOP expression and CKD-induced vascular calcification. They further reveal that the CDK9-cyclin T1 complex mediates vascular calcification through CHOP induction and phosphorylation-mediated ATF4 activation.

Shiozaki Y ，Okamura K ，Kohno S ，Keenan AL ，Williams K ，Zhao X ，Chick WS ，Miyazaki-Anzai S ，Miyazaki M ... -  《-》

PERK-eIF2α-ATF4-CHOP signaling contributes to TNFα-induced vascular calcification.

Masuda M ，Miyazaki-Anzai S ，Levi M ，Ting TC ，Miyazaki M ... -  《Journal of the American Heart Association》

Endoplasmic reticulum stress effector CCAAT/enhancer-binding protein homologous protein (CHOP) regulates chronic kidney disease-induced vascular calcification.

Cardiovascular diseases such as atherosclerosis and vascular calcification are a major cause of death in patients with chronic kidney disease (CKD). Recently, the long-awaited results of the Study of Heart and Renal Protection trial were reported. This large randomized clinical trial found that an extensive cholesterol-lowering therapy through the combination of simvastatin and ezetimibe significantly reduced cardiovascular diseases in a wide range of patients with CKD. However, the mechanism by which this cholesterol-lowering therapy reduces CKD-dependent vascular diseases remains elusive. The objective of the present study was to determine the contribution of the oxysterol-induced pro-apoptotic transcription factor CCAAT/enhancer-binding protein homologous protein (CHOP) on the pathogenesis of CKD-dependent cardiovascular diseases through endoplasmic reticulum stress signaling. CKD increased levels of serum oxysterols such as 7-ketocholesterol in human patients and ApoE(-/-) mice. Treatment with simvastatin plus ezetimibe strongly reduced levels of serum oxysterols and attenuated CKD-dependent atherosclerosis, vascular cell death, vascular calcification, and cardiac dysfunction. This therapy also reduced aortic endoplasmic reticulum stress induced by CKD. The short hairpin RNA-mediated knockdown of CHOP and activating transcription factor-4 in vascular smooth muscle cells attenuated oxysterol-induced mineralization, osteogenic differentiation, and endoplasmic reticulum stress. In addition, CHOP deficiency protected ApoE(-/-) mice from CKD-dependent vascular calcification, cardiac dysfunction, and vascular cell death. These data reveal that the cholesterol-lowering therapy of simvastatin plus ezetimibe attenuates CKD-dependent vascular diseases through a reduction of oxysterol-mediated endoplasmic reticulum stress. CHOP plays a crucial role in the pathogenesis of CKD-dependent vascular calcification.

Miyazaki-Anzai S ，Masuda M ，Demos-Davies KM ，Keenan AL ，Saunders SJ ，Masuda R ，Jablonski K ，Cavasin MA ，Kendrick J ，Chonchol M ，McKinsey TA ，Levi M ，Miyazaki M ... -  《-》

Activating transcription factor 4 regulates stearate-induced vascular calcification.

Masuda M ，Ting TC ，Levi M ，Saunders SJ ，Miyazaki-Anzai S ，Miyazaki M ... -  《-》

Endoplasmic reticulum stress mediates parathyroid hormone-induced apoptosis in vascular smooth muscle cells.

Duan S ，Chen X ，Liu Y ，Guo W ，Liu W ... -  《-》