Expression of lectin-like oxidized low-density lipoprotein receptors during ischemia-reperfusion and its role in determination of apoptosis and left ventricular dysfunction
Dayuan Li, MD, PhD*,
Victor Williams, MD*,
Ling Liu, MD*,
Hongjiang Chen, MD*,
Tatsuya Sawamura, MD, PhD ,
Francesco Romeo, MD, FACC and
Jawahar L. Mehta, MD, PhD, FACC*,*
* Departments of Internal Medicine, University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare System, Little Rock, Arkansas, USA
Department of Bioscience, National Cardiovascular Center Research Institute, Osaka, Japan
Department of Cardiology, University of Rome "Tor Vergata," Rome, Italy
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Figure 1 Expression of lectin-like oxidized low-density lipoprotein receptor (LOX-1) messenger ribonucleic acid (mRNA) and protein after ischemia-reperfusion (I-R); LOX-1 protein and mRNA were determined by Western and Northern blots, respectively. The expression of LOX-1 was markedly increased in the saline-treated rats subjected to I-R. Ischemia alone did not increase the expression of LOX-1. Administration of blocking antibody to rat LOX-1 attenuated the expression of LOX-1 despite I-R. In contrast, administration of nonspecific immunoglobulin G (IgG) had no effect. Density of LOX-1 mRNA band was normalized by glyceraldehyde-3-phosphate dehydrogenase (GAPDH) band density. Each band density of LOX-1 protein was normalized with that in the sham control rat heart. Left panel shows representative examples; right panel is the summary of data (mean ± SD) from eight separate experiments.
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Figure 2 Expression of lectin-like oxidized low-density lipoprotein receptors (LOX-1) in the ischemic-reperfused (I-R) areas was confirmed by immunostaining. Positive immunoreactivity for LOX-1 was identified mainly in the endocardium and the subendocardial areas of the myocardium. Again, the use of LOX-1 antibody (Ab-LOX-1) reduced LOX-1 staining after I-R, while nonspecific immunoglobulin G (IgG) had no effect.
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Figure 3 Location of lectin-like oxidized low-density lipoprotein receptor (LOX-1) expression in rat cardiac myocytes was confirmed by double immunostaining (brown color = LOX-1; red color = anti-desmin for rat cardiac myocytes); LOX-1 expression was primarily within the cardiac myocytes. Left panel is a negative control specimen, middle panel is myocyte staining in sham control heart, and right panel is double staining showing LOX-1 expression in myocytes. I-R = ischemia-reperfusion.
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Figure 4 Effect of lectin-like oxidized low-density lipoprotein receptor (LOX-1) antibody (Ab-LOX-1) on apoptosis and caspase-3 expression in response to ischemia-reperfusion (I-R). The number of apoptotic cells was increased in the I-R group (saline-treated rats) compared with the sham control group. Use of the LOX-1 antibody reduced the number of apoptotic cells. Nonspecific anti-goat immunoglobulin G (IgG) had no effect. Left top panel shows representative examples of apoptotic cells (green color). Left bottom panel is summary of data on the number of apoptotic cells from 10 separate experiments. Caspase-3 activity in the myocardium was also increased in the I-R group (saline-treated rats) compared with the sham control group. Use of the LOX-1 antibody reduced caspase-3 activity. Nonspecific IgG had no effect (right panel).
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Figure 5 Lectin-like oxidized low-density lipoprotein receptors (LOX-1) expression and lipid peroxidation. Lipid peroxidation was determined by the measurement of malondialdehyde (MDA). Myocardial MDA levels were markedly higher in the saline-treated rats subjected to ischemia-reperfusion (I-R); LOX-1 antibody (Ab-LOX-1) reduced MDA levels, while the nonspecific immunoglobulin G (IgG) had no effect. The data is mean (± SD) of values from 10 separate experiments.
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Figure 6 Lectin-like oxidized low-density lipoprotein receptor (LOX-1) expression and infarct size. The sham control group did not show any necrotic area. The risk area in all ischemia-reperfusion (I-R) groups (saline-treated, LOX-1 antibody [Ab-LOX-1]-treated, and nonspecific immunoglobulin G [IgG]-treated) was similar. Infarct size was smaller in the LOX-1 antibody-treated rats compared with that in the saline-treated or the nonspecific IgG-treated rats. The data on infarct size (mean ± SD) is from 10 separate experiments. AAR = area at risk; LV = left ventricle.
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Figure 7 Lectin-like oxidized low-density lipoprotein receptor (LOX-1) expression and cardiac dysfunction during ischemia-reperfusion (I-R) and dP/dt and mean arterial blood pressure (MABP) during ischemia. Reperfusion further reduced dP/dt, MABP, and heart rate. Administration of LOX-1 antibody significantly improved dP/dt, MABP, and heart rate, whereas nonspecific immunoglobulin G (IgG) had no effect.
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