Activating transcription factor-4 promotes mineralization in vascular smooth muscle cells
Masashi Masuda, Shinobu Miyazaki-Anzai, Audrey L. Keenan, Yuji Shiozaki, Kayo Okamura, Wallace S. Chick, Kristina Williams, Xiaoyun Zhao, Shaikh Mizanoor Rahman, Yin Tintut, Christopher M. Adams, Makoto Miyazaki
Masashi Masuda, Shinobu Miyazaki-Anzai, Audrey L. Keenan, Yuji Shiozaki, Kayo Okamura, Wallace S. Chick, Kristina Williams, Xiaoyun Zhao, Shaikh Mizanoor Rahman, Yin Tintut, Christopher M. Adams, Makoto Miyazaki
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Research Article Vascular biology

Activating transcription factor-4 promotes mineralization in vascular smooth muscle cells

Abstract

Emerging evidence indicates that upregulation of the ER stress–induced pro-osteogenic transcription factor ATF4 plays an important role in vascular calcification, a common complication in patients with aging, diabetes, and chronic kidney disease (CKD). In this study, we demonstrated the pathophysiological role of ATF4 in vascular calcification using global Atf4 KO, smooth muscle cell–specific (SMC-specific) Atf4 KO, and transgenic (TG) mouse models. Reduced expression of ATF4 in global ATF4-haplodeficient and SMC-specific Atf4 KO mice reduced medial and atherosclerotic calcification under normal kidney and CKD conditions. In contrast, increased expression of ATF4 in SMC-specific Atf4 TG mice caused severe medial and atherosclerotic calcification. We further demonstrated that ATF4 transcriptionally upregulates the expression of type III sodium-dependent phosphate cotransporters (PiT1 and PiT2) by interacting with C/EBPβ. These results demonstrate that the ER stress effector ATF4 plays a critical role in the pathogenesis of vascular calcification through increased phosphate uptake in vascular SMCs.

Authors

Masashi Masuda, Shinobu Miyazaki-Anzai, Audrey L. Keenan, Yuji Shiozaki, Kayo Okamura, Wallace S. Chick, Kristina Williams, Xiaoyun Zhao, Shaikh Mizanoor Rahman, Yin Tintut, Christopher M. Adams, Makoto Miyazaki

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Figure 1

ATF4 haploinsufficiency attenuates medial calcification.

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ATF4 haploinsufficiency attenuates medial calcification. (A) Representat...
(A) Representative photographs (original magnification, ×10) of the lesions in aortic sinuses stained with von Kossa from 8-week-old Atf4+/+ and Atf4+/– mice (n = 8–10) on DBA/2J background. Mice were subjected to either sham operation for normal kidney condition (NKD) or 5/6 nx for chronic kidney disease condition (CKD). The mice were sacrificed 12 weeks after the surgeries. (B) Quantitative analysis of calcified lesions in the aortic sinus. More NKD data are shown in Supplemental Figure 1G. (C) Aortic calcium content in Atf4+/– mice. (D) Representative micrographs show more TUNEL-positive signal (pink) in nuclei (blue) of aortic sinus lesions from Atf4+/+ mice than from Atf4+/– mice. (E) Quantitative analysis of TUNEL-positive nuclei (pink) conducted on lesions from Atf4+/– mice. (F) Immunofluorescence analysis of CHOP (pink) in the aortic sinuses of Atf4+/– mice. One-way ANOVA with a Student-Newman post-hoc test was used for comparison between Atf4+/+ and Atf4+/– mice. Two-way ANOVA was used for comparison between NKD and CKD. **P < 0.01, ***P < 0.001. Scale bar: 100 μm.