The vestigial enzyme D-dopachrome tautomerase protects the heart against ischemic injury
Dake Qi, Kwame Atsina, Lintao Qu, Xiaoyue Hu, Xiaohong Wu, Bin Xu, Marta Piecychna, Lin Leng, Günter Fingerle-Rowson, Jiasheng Zhang, Richard Bucala, Lawrence H. Young
Dake Qi, Kwame Atsina, Lintao Qu, Xiaoyue Hu, Xiaohong Wu, Bin Xu, Marta Piecychna, Lin Leng, Günter Fingerle-Rowson, Jiasheng Zhang, Richard Bucala, Lawrence H. Young
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Research Article Cardiology

The vestigial enzyme D-dopachrome tautomerase protects the heart against ischemic injury

Abstract

The cellular response to stress involves the recruitment and coordination of molecular signaling pathways that prevent cell death. D-dopachrome tautomerase (DDT) is an enzyme that lacks physiologic substrates in mammalian cells, but shares partial sequence and structural homology with macrophage migration inhibitory factor (MIF). Here, we observed that DDT is highly expressed in murine cardiomyocytes and secreted by the heart after ischemic stress. Antibody-dependent neutralization of secreted DDT exacerbated both ischemia-induced cardiac contractile dysfunction and necrosis. We generated cardiomyocyte-specific DDT knockout mice (Myh6-Cre Ddtfl/fl), which demonstrated normal baseline cardiac size and function, but had an impaired physiologic response to ischemia-reperfusion. Hearts from Myh6-Cre Ddtfl/fl mice exhibited more necrosis and LV contractile dysfunction than control hearts after coronary artery ligation and reperfusion. Furthermore, treatment with DDT protected isolated hearts against injury and contractile dysfunction after ischemia-reperfusion. The protective effect of DDT required activation of the metabolic stress enzyme AMP-activated protein kinase (AMPK), which was mediated by a CD74/CaMKK2-dependent mechanism. Together, our data indicate that cardiomyocyte secretion of DDT has important autocrine/paracrine effects during ischemia-reperfusion that protect the heart against injury.

Authors

Dake Qi, Kwame Atsina, Lintao Qu, Xiaoyue Hu, Xiaohong Wu, Bin Xu, Marta Piecychna, Lin Leng, Günter Fingerle-Rowson, Jiasheng Zhang, Richard Bucala, Lawrence H. Young

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Figure 4

DDT activates AMPK through a CaMKK-dependent mechanism.

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DDT activates AMPK through a CaMKK-dependent mechanism. (A) Time-depende...
(A) Time-dependent activation of the AMPK pathway in adult rat adult ventricular cardiomyocytes treated with recombinant DDT (400 ng/ml). (B) Effect of the CaMKK inhibitor STO-609 (2 εM) on rDDT-induced AMPK activation in cardiomyocytes. (C) Intracellular calcium imaging was performed with fura-2-acetoxymethyl ester (2 εM) in rat cardiomyocytes incubated without (baseline) or with rDDT (400 ng/ml). Original magnification, ×20. The ratio of 340 nm to 380 nm fluorescence intensity [R(340/380)] was recorded as a relative measure of intracellular calcium concentration. (D) Effect of binding intracellular calcium with BAPTA-AM (10 εM) on rDDT stimulation of AMPK phosphorylation in cardiomyocytes. (E) WT mouse hearts were perfused with and without rDDT (5–50 ng/ml) for 15 minutes, and phospho- and total AMPK and ACC were assessed in immunoblots of heart homogenates. (F) DDT perfusion was also performed in Camkk2–/– hearts, and phospho- and total AMPK and ACC were subsequently assessed. (G) DDT activates AMPK through a Ca2+/CaMKK-dependent pathway. p-Thr172, phosphorylation of AMPK at the Thr172 activating site in the catalytic domain. Data are mean ± SEM, n = 4–6 per group. *P < 0.05 vs. respective control.