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RhoA protects the mouse heart against ischemia/reperfusion injury.

ABSTRACT: The small GTPase RhoA serves as a nodal point for signaling through hormones and mechanical stretch. However, the role of RhoA signaling in cardiac pathophysiology is poorly understood. To address this issue, we generated mice with cardiomyocyte-specific conditional expression of low levels of activated RhoA (CA-RhoA mice) and demonstrated that they exhibited no overt cardiomyopathy. When challenged by in vivo or ex vivo ischemia/reperfusion (I/R), however, the CA-RhoA mice exhibited strikingly increased tolerance to injury, which was manifest as reduced myocardial lactate dehydrogenase (LDH) release and infarct size and improved contractile function. PKD was robustly activated in CA-RhoA hearts. The cardioprotection afforded by RhoA was reversed by PKD inhibition. The hypothesis that activated RhoA and PKD serve protective physiological functions during I/R was supported by several lines of evidence. In WT mice, both RhoA and PKD were rapidly activated during I/R, and blocking PKD augmented I/R injury. In addition, cardiac-specific RhoA-knockout mice showed reduced PKD activation after I/R and strikingly decreased tolerance to I/R injury, as shown by increased infarct size and LDH release. Collectively, our findings provide strong support for the concept that RhoA signaling in adult cardiomyocytes promotes survival. They also reveal unexpected roles for PKD as a downstream mediator of RhoA and in cardioprotection against I/R.

SUBMITTER: Xiang SY

PROVIDER: S-EPMC3148727 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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RhoA protects the mouse heart against ischemia/reperfusion injury.

Xiang Sunny Yang SY Vanhoutte Davy D Del Re Dominic P DP Purcell Nicole H NH Ling Haiyun H Banerjee Indroneal I Bossuyt Julie J Lang Richard A RA Zheng Yi Y Matkovich Scot J SJ Miyamoto Shigeki S Molkentin Jeffery D JD Dorn Gerald W GW Brown Joan Heller JH

The Journal of clinical investigation 20110711 8

The small GTPase RhoA serves as a nodal point for signaling through hormones and mechanical stretch. However, the role of RhoA signaling in cardiac pathophysiology is poorly understood. To address this issue, we generated mice with cardiomyocyte-specific conditional expression of low levels of activated RhoA (CA-RhoA mice) and demonstrated that they exhibited no overt cardiomyopathy. When challenged by in vivo or ex vivo ischemia/reperfusion (I/R), however, the CA-RhoA mice exhibited strikingly ...[more]

PMID: 21747165

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Project description:Phosphodiesterase 3A (PDE3A) is a major regulator of cAMP in cardiomyocytes. PDE3 inhibitors are used for acute treatment of congestive heart failure, but are associated with increased incidence of arrhythmias and sudden death with long-term use. We previously reported that chronic PDE3A downregulation or inhibition induced myocyte apoptosis in vitro. However, the cardiac protective effect of PDE3A has not been demonstrated in vivo in disease models. In this study, we examined the role of PDE3A in regulating myocardial function and survival in vivo using genetically engineered transgenic mice with myocardial overexpression of the PDE3A1 isozyme (TG). TG mice have reduced cardiac function characterized by reduced heart rate and ejection fraction (52.5±7.8% vs. 83.9±4.7%) as well as compensatory expansion of left ventricular diameter (4.19±0.19mm vs. 3.10±0.18mm). However, there was no maladaptive increase of fibrosis and apoptosis in TG hearts compared to wild type (WT) hearts, and the survival rates also remained the same. The diminution of cardiac contractile function is very likely attributed to a decrease in beta-adrenergic receptor (β-AR) response in TG mice. Importantly, the myocardial infarct size (4.0±1.8% vs. 24.6±3.8%) and apoptotic cell number (1.3±1.0% vs. 5.6±1.5%) induced by ischemia/reperfusion (I/R) injury were significantly attenuated in TG mice. This was associated with decreased expression of inducible cAMP early repressor (ICER) and increased expression of anti-apoptotic protein BCL-2. To further verify the anti-apoptotic effects of PDE3A1, we performed in vitro apoptosis study in isolated adult TG and WT cardiomyocytes. We found that the apoptotic rates stimulated by hypoxia/reoxygenation or H2O2 were indeed significantly reduced in TG myocytes, and the differences between TG and WT myocytes were completely reversed in the presence of the PDE3 inhibitor milrinone. These together indicate that PDE3A1 negatively regulates β-AR signaling and protects against I/R injury by inhibiting cardiomyocyte apoptosis.

Project description:CD39 or NTPDase1 and other nucleoside triphosphate diphosphohydrolases (NTPDases), including NTPDase2, NTPDase3, and NTPDase8, regulate purinergic signaling through tuning the extracellular levels of purine nucleotides and nucleosides. Purinergic signaling can regulate liver ischemia-reperfusion (I/R) injury and CD39 is protective. However, the role of other NTPDases is unkown. In this study, we have investigated the roles of NTPDase2, NTPDase3, and NTPDase8 in liver I/R injury. Global Entpd2-/-, Entpd3-/-, and Entpd8-/- and control wild-type (WT) mice were subjected to a 60 minutes of warm hepatic ischemia, which was followed by a 6-hour reperfusion period. In addition, WT and Entpd8-/- mice underwent global ischemia induced by hemorrhagic shock and resuscitation. Liver and plasma samples were collected to assess the extent and mechanisms of liver injury. Bone marrow chimeric mice derived from Entpd8-/- and WT were generated to understand the role of NTPDase expression on hematopoietic cells in regulating liver injury. While wild-type (WT), Entpd2-/- and Entpd3-/- mice exhibited comparable levels of liver injury following local IR, Entpd8-/- mice had increased liver injury compared to WT mice. This was evidenced by increased levels of plasma transaminases (ALT and AST) and histological evidence of heightened hepatocellular damage. Studies with bone marrow chimeric mice indicated that NTPDase8 on parenchymal liver cells protected against hepatic injury. This was confirmed by single-nucleus RNAseq showing hepatocytes are the dominant cell type expressing NTPDase8 in the liver. Entpd8-/- mice after I/R injury were noted to have higher ATP concentrations in the liver and plasma. The P2 antagonist suramin decreased plasma ALT and AST levels in Entpd8-/- mice indicating that extracellular ATP-mediated purinergic signaling contributes to liver injury in these mice. Finally, Entpd8-/- mice had increased liver injury compared to WT mice also after global IR induced by hemorrhagic shock and resuscitation.These findings highlight the differential roles of NTPDase family members in the liver, with parenchymal/hepatocyte expression of NTPDase8 emerging as a critical suppressor of the inflammatory and metabolic responses to hepatic ischemia-reperfusion insult, even in the presence of vascular NTPDase1 expression.

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RhoA protects the mouse heart against ischemia/reperfusion injury.

Publications

RhoA protects the mouse heart against ischemia/reperfusion injury.

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