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Sustained increases in cardiomyocyte protein O-GlcNAc levels leads to cardiac hypertrophy and reduced mitochondrial function without systolic contractile impairment

ABSTRACT: Lifestyle and metabolic diseases influence the severity and pathogenesis of cardiovascular disease (CVD) through numerous mechanisms, including regulation via post-translational modifications (PTM). A specific PTM, the addition of O-linked β-N acetylglucosamine (O-GlcNAcylation), has been implicated in both physiological and pathological mechanisms. The current study aimed to test the hypothesis that protein O-GlcNAcylation contributes to cardiac adaptations, and its progression to pathophysiology when sustained in cardiomyocytes. Using an inducible cardiomyocyte-specific dominant-negative O-GlcNAcase (dnOGAh) overexpression transgenic mouse model, we induced dnOGA in 8-10-weeks-old mouse hearts. We examined the effects of 2-weeks (2wk) and 24-weeks (24wk) dnOGA overexpression, which progressed to a 1.8-fold increase in protein O-GlcNAcylation. 2wk increases in protein O-GlcNAc levels did not alter heart weight or function; however, 24wk increases in protein O-GlcNAcylation led to cardiac hypertrophy, reduced mitochondrial function, fibrosis, and diastolic dysfunction. Interestingly, systolic function was maintained in 24wk dnOGA overexpression, despite several changes in gene expression associated with CVD. Specifically, mRNA-seq analysis revealed several gene signatures, including reduction of mitochondrial oxidative phosphorylation, fatty acid and glucose metabolism pathways, and antioxidant response pathways at 24wk. In contrast, cardiac fibrosis pathway genes were induced at 24wk after dnOGA overexpression. Changes in mitochondrial function after 24wk induction were independent of changes in mitochondrial DNA copy number. This study indicates that moderate protein O-GlcNAcylation leads to a differential response with an initial reduction of metabolic pathways (2wk phase), which leads to cardiac remodeling (24wk phase) including cardiac hypertrophy, decreased oxidative phosphorylation pathways, and increased cardiac structural changes. This study shows that sustained exposure of elevated protein O-GlcNAcylation in cardiomyocytes alters gene expression and supports a switch to pathophysiological mechanisms of O-GlcNAcylation in adaptive versus maladaptive changes.

ORGANISM(S): Mus musculus

PROVIDER: GSE211656 | GEO | 2023/08/19

REPOSITORIES: GEO

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Project description:Background The axon guidance cue Slit2 recently has been found to regulate calcium homeostasis and molecular signaling in various stress events in different organs. However, whether Slit2 plays a role in cardiac ischemia-reperfusion (IR) injury has not been reported. Here, we aimed to investigate the role of Slit2 and the underlying mechanisms in cardiac IR injury. Methods Langendorff-perfused isolated hearts from Slit2-overexpressing (Slit2-Tg) mice and their background strain C57BL/6J mice were subjected to 20 min of global ischemia followed by 40 min of reperfusion. Left ventricular function of isolated hearts was monitored. Infarct size of post-IR hearts was determined by staining with 2,3,5-triphenyltetrazolium chloride (TTC) and histological changes of cardiac tissues and cells were determined with hematoxylin-eosin (HE) staining and transmission electron microscopy. Transcriptomic analysis was used to predict the biological processes and signaling pathways affected by Slit2 overexpression in the post-IR myocardium. Pro-Q staining and Western blotting was used to assess the phosphorylation levels of cardiac myofilaments and expression levels of myofilament-associated protein kinase and phosphatases. Results Slit2 overexpression increased post-IR left ventricular developed pressure (LVDP) by 35% and reduced infarct size by 53%, along with decreased myofibrillar disruption, mitochondrial swelling, and mitochondrial cristae dissolution. Slit2 overexpression significantly changed post-IR gene expression profiles. Functional products of these genes include regulation of cation transmembrane transport, cation homeostasis, collagen fibril organization, and regulation of heart rate. And post-IR myocardial KEGG pathways upregulated by Slit2 overexpression include ECM-receptor interaction, PI3K-Akt signaling pathway, and adrenergic signaling. Slit2 overexpression impacted myofilament phosphorylation together with myofilament-associated protein kinase C (PKC) isoforms and protein phosphatases (PPs). IR in C57BL/6J hearts upregulated phosphorylation of cardiac troponin-I (cTnI), which was suppressed by Slit2 overexpression. Myofilament‐associated PKCε, PKCδ, and PP2A were significantly increased post‐IR in C57BL/6J hearts, but in Slit2‐Tg hearts, myofilament‐associated PKCε and PP2A were increased and PKCδ was suppressed. Conclusions Our results demonstrate that Slit2 overexpression protects cardiac function and reduces IR injury, which is associated with Slit2‐induced gene profile shifts. The suppression of MyBP‐C and troponin‐I phosphorylation, and myofilament‐associated PKCδ levels induced by Slit2 overexpression could contribute to the cardioprotection of Slit2 in post-IR myocardium.

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Sustained increases in cardiomyocyte protein O-GlcNAc levels leads to cardiac hypertrophy and reduced mitochondrial function without systolic contractile impairment

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