Integrins protect cardiomyocytes from ischemia/reperfusion injury
Hideshi Okada, … , Joshua I. Goldhaber, Robert S. Ross
Hideshi Okada, … , Joshua I. Goldhaber, Robert S. Ross
Published September 16, 2013
Citation Information: J Clin Invest. 2013;123(10):4294-4308. https://doi.org/10.1172/JCI64216.
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Research Article Cardiology

Integrins protect cardiomyocytes from ischemia/reperfusion injury

Abstract

Ischemic damage is recognized to cause cardiomyocyte (CM) death and myocardial dysfunction, but the role of cell-matrix interactions and integrins in this process has not been extensively studied. Expression of α7β1D integrin, the dominant integrin in normal adult CMs, increases during ischemia/reperfusion (I/R), while deficiency of β1 integrins increases ischemic damage. We hypothesized that the forced overexpression of integrins on the CM would offer protection from I/R injury. Tg mice with CM-specific overexpression of integrin α7β1D exposed to I/R had a substantial reduction in infarct size compared with that of α5β1D-overexpressing mice and WT littermate controls. Using isolated CMs, we found that α7β1D preserved mitochondrial membrane potential during hypoxia/reoxygenation (H/R) injury via inhibition of mitochondrial Ca2+ overload but did not alter H/R effects on oxidative stress. Therefore, we assessed Ca2+ handling proteins in the CM and found that β1D integrin colocalized with ryanodine receptor 2 (RyR2) in CM T-tubules, complexed with RyR2 in human and rat heart, and specifically bound to RyR2 amino acids 165–175. Integrins stabilized the RyR2 interdomain interaction, and this stabilization required integrin receptor binding to its ECM ligand. These data suggest that α7β1D integrin modifies Ca2+ regulatory pathways and offers a means to protect the myocardium from ischemic injury.

Authors

Hideshi Okada, N. Chin Lai, Yoshitaka Kawaraguchi, Peter Liao, Jeffrey Copps, Yasuo Sugano, Sunaho Okada-Maeda, Indroneal Banerjee, Jan M. Schilling, Alexandre R. Gingras, Elizabeth K. Asfaw, Jorge Suarez, Seok-Min Kang, Guy A. Perkins, Carol G. Au, Sharon Israeli-Rosenberg, Ana Maria Manso, Zheng Liu, Derek J. Milner, Stephen J. Kaufman, Hemal H. Patel, David M. Roth, H. Kirk Hammond, Susan S. Taylor, Wolfgang H. Dillmann, Joshua I. Goldhaber, Robert S. Ross

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Figure 1

Combined expression of integrin α and β subunits is required for highest level of cell surface expression of integrins.

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Combined expression of integrin α and β subunits is required for highest...
(A) Expression of integrins in ARVMs 48 hours after adenovirus infection. Western blot detecting LacZ, β1D integrin (β1D), α5 integrin (α5), and α7 integrin (α7) indicates increased expression of respective integrin subunits following viral infection. (B) Densitometric quantification of integrin expression in virally infected cells. Note that immature (precursor) form of β1D integrin subunit is increased when the cells are infected with the β1D subunit alone but not when they are infected with both α and β subunits. *P < 0.05 vs. LacZ, n = 6 per group (1-way ANOVA). (C) Representative immunofluorescent images of CMs following adenoviral-mediated OE of LacZ (control), β1D integrin alone, or β1D integrin in combination with α5 integrin or α7B integrin. β1D expression is noted on the cell membrane as well as in the cytoplasm when the β1D integrin subunit is overexpressed alone. When combined OE of α and β subunits occurs, the integrin expression is dominantly at the membrane, with little detected in the cytoplasm. Antibodies detect β1D (green), α7 (red), or α5 (green). Nuclei were stained with DAPI (blue). Scale bar: 20 μm. (D) Western blot analysis of β1D integrin expression in cytosolic and cell membrane fractions in ARVMs. As confirmation of the microscopic data, Western blotting shows that β1D integrin singly infected cells expressed integrin dominantly in the cytosolic fraction, while combined αβ integrin subunit infection allowed dominant cell membrane fraction expression.