Advanced glycation end-products (AGEs) have been associated with poorer outcomes after myocardial infarction (MI), and linked with heart failure. Methylglyoxal (MG) is considered the most important AGE precursor, but its role in MI is unknown. In this study, we investigated the involvement of MG-derived AGEs (MG-AGEs) in MI using transgenic mice that over-express the MG-metabolizing enzyme glyoxalase-1 (GLO1). MI was induced in GLO1 mice and wild-type (WT) littermates. At 6 h post-MI, mass spectrometry revealed that MG-H1 (a principal MG-AGE) was increased in the hearts of WT mice, and immunohistochemistry demonstrated that this persisted for 4 weeks. GLO1 over-expression reduced MG-AGE levels at 6 h and 4 weeks, and GLO1 mice exhibited superior cardiac function at 4 weeks post-MI compared to WT mice. Immunohistochemistry revealed greater vascular density and reduced cardiomyocyte apoptosis in GLO1 vs. WT mice. The recruitment of c-kit cells and their incorporation into the vasculature (c-kitCD31 cells) was higher in the infarcted myocardium of GLO1 mice. MG-AGEs appeared to accumulate in type I collagen surrounding arterioles, prompting investigation in vitro. In culture, the interaction of angiogenic bone marrow cells with MG-modified collagen resulted in reduced cell adhesion, increased susceptibility to apoptosis, fewer progenitor cells, and reduced angiogenic potential. This study reveals that MG-AGEs are produced post-MI and identifies a causative role for their accumulation in the cellular changes, adverse remodeling and functional loss of the heart after MI. MG may represent a novel target for preventing damage and improving function of the infarcted heart.

The mechanisms for the development of diabetic cardiomyopathy remain largely unknown. Methylglyoxal (MG) can accumulate and promote inflammation and vascular damage in diabetes. We examined if overexpression of the MG-metabolizing enzyme glyoxalase 1 (GLO1) in macrophages and the vasculature could reduce MG-induced inflammation and prevent ventricular dysfunction in diabetes. Hyperglycemia increased circulating inflammatory markers in wild-type (WT) but not in GLO1-overexpressing mice. Endothelial cell number was reduced in WT-diabetic hearts compared with nondiabetic controls, whereas GLO1 overexpression preserved capillary density. Neuregulin production, endothelial nitric oxide synthase dimerization, and Bcl-2 expression in endothelial cells was maintained in the hearts of GLO1-diabetic mice and corresponded to less myocardial cell death compared with the WT-diabetic group. Lower receptor for advanced glycation end products and tumor necrosis factor-α (TNF-α) levels were also observed in GLO1-diabetic versus WT-diabetic mice. Over a period of 8 weeks of hyperglycemia, GLO1 overexpression delayed and limited the loss of cardiac function. In vitro, MG and TNF-α were shown to synergize in promoting endothelial cell death, which was associated with increased angiopoietin 2 expression and reduced Bcl-2 expression. These results suggest that MG in diabetes increases inflammation, leading to endothelial cell loss. This contributes to the development of diabetic cardiomyopathy and identifies MG-induced endothelial inflammation as a target for therapy.

No abstract

Methylglyoxal (MG) is a highly reactive dicarbonyl and the main precursor of advanced glycation end-products (AGEs). After myocardial infarction (MI), MG-derivedAGEs accumulate in the heart and contribute to adverse remodeling and loss of cardiac function. In this study, the flavonoid fisetin, a dicarbonyl scavenger, is used to reduce the negative effects of MG in the post-MI heart. A fisetin-loaded collagen type I hydrogel (fisetin-HG) is injected intramyocardially in mice at 3 h post-MI, and compared to fisetin-alone, hydrogel-alone, or saline treatment. Fisetin-HG treatment increases the level of glyoxalase-1 (the main MG-metabolizing enzyme), reduces MG-AGE accumulation, and decreases oxidative stress in the MI heart, which is associated with smaller scar size and improved cardiac function. Treatment with fisetin-HG also promotes neovascularization and increases the number of pro-healing macrophages in the infarct area, while reducing the number of pro-inflammatory macrophages.Taken together, the results demonstrate that the fisetin-collagen hydrogel therapy can reduce the accumulation and negative effects of MG post-MI. This therapy may be a promising approach to limit adverse cardiac remodeling, prevent damage, and preserve function of the infarcted heart.

Live-cell imaging techniques are essential for acquiring vital physiological and pathophysiological knowledge to understand and treat heart disease. For live-cell imaging of transient alterations of [Ca2+]i in human cardiomyocytes, we engineered human-induced pluripotent stem cells carrying a genetically-encoded Ca2+-indicator (GECI). To monitor sarcomere shortening and relaxation in cardiomyocytes in real-time, we generated a α-cardiac actinin (ACTN2)-copepod (cop) green fluorescent protein (GFP+)-human-induced pluripotent stem cell line by using the CRISPR-Cas9 and a homology directed recombination approach. The engineered human-induced pluripotent stem cells were differentiated in transgenic GECI-enhanced GFP+-cardiomyocytes and ACTN2-copGFP+-cardiomyocytes, allowing real-time imaging of [Ca2+]i transients and live recordings of the sarcomere shortening velocity of ACTN2-copGFP+-cardiomyocytes. We developed a video analysis software tool to quantify various parameters of sarcoplasmic Ca2+ fluctuations recorded during contraction of cardiomyocytes and to calculate the contraction velocity of cardiomyocytes in the presence and absence of different drugs affecting cardiac function. Our cellular and software tool not only proved the positive and negative inotropic and lusitropic effects of the tested cardioactive drugs but also quantified the expected effects precisely. Our platform will offer a human-relevant in vitro alternative for high-throughput drug screenings, as well as a model to explore the underlying mechanisms of cardiac diseases.