Adipocyte-derived small extracellular vesicles exacerbate diabetic ischemic heart injury by promoting oxidative stress and mitochondrial-mediated cardiomyocyte apoptosis.

Diabetes increases ischemic heart injury via incompletely understood mechanisms. We recently reported that diabetic adipocytes-derived small extracellular vesicles (sEV) exacerbate myocardial reperfusion (MI/R) injury by promoting cardiomyocyte apoptosis. Combining in vitro mechanistic investigation and in vivo proof-concept demonstration, we determined the underlying molecular mechanism responsible for diabetic sEV-induced cardiomyocyte apoptosis after MI/R. Adult mice were fed a high-fat diet (HFD) for 12 weeks. sEV were isolated from plasma or epididymal adipose tissue. HFD significantly increased the number and size of plasma- and adipocyte-derived sEV. Intramyocardial injection of an equal number of diabetic plasma sEV in nondiabetic hearts significantly increased cardiac apoptosis and exacerbated MI/R-induced cardiac dysfunction. Diabetic plasma sEV significantly activated cardiac caspase 9 but not caspase 8, suggesting that diabetic sEV induces cardiac apoptosis via the mitochondrial pathway. These pathologic alterations were phenotyped by intramyocardial injection of sEV isolated from diabetic adipocytes or HGHL-challenged 3T3L1 adipocytes. To obtain direct evidence that diabetic sEV promotes cardiomyocyte apoptotic cell death, isolated neonatal rat ventricular cardiomyocytes (NRVMs) were treated with sEV and subjected to simulated ischemia/reperfusion (SI/R). Treatment of cardiomyocytes with sEV from diabetic plasma, diabetic adipocytes, or HGHL-challenged 3T3L1 adipocytes significantly enhanced SI/R-induced apoptosis and reduced cell viability. These pathologic effects were replicated by a miR-130b-3p (a molecule increased dramatically in diabetic sEV) mimic and blocked by a miRb-130b-3p inhibitor. Molecular studies identified PGC-1α (i.e. PGC-1α1/-a) as the direct downstream target of miR-130b-3p, whose downregulation causes mitochondrial dysfunction and apoptosis. Finally, treatment with diabetic adipocyte-derived sEV or a miR-130b-3p mimic significantly enhanced mitochondrial reactive oxygen species (ROS) production in SI/R cardiomyocytes. Conversely, treatment with a miR-130b-3p inhibitor or overexpression of PGC-1α extremely attenuated diabetic sEV-induced ROS production. We obtained the first evidence that diabetic sEV promotes oxidative stress and mitochondrial-mediated cardiomyocyte apoptotic cell death, exacerbating MI/R injury. These pathological phenotypes were mediated by miR-130b-3p-induced suppression of PGC-1α expression and subsequent mitochondrial ROS production. Targeting miR-130b-3p mediated cardiomyocyte apoptosis may be a novel strategy for attenuating diabetic exacerbation of MI/R injury.

Gan L ，Zhao J ，Yao P ，Christopher TA ，Lopez B ，Lau WB ，Koch W ，Gao E ，Ma X ，Wang Y ... -  《Redox Biology》

Small Extracellular Microvesicles Mediated Pathological Communications Between Dysfunctional Adipocytes and Cardiomyocytes as a Novel Mechanism Exacerbating Ischemia/Reperfusion Injury in Diabetic Mice.

Gan L ，Xie D ，Liu J ，Bond Lau W ，Christopher TA ，Lopez B ，Zhang L ，Gao E ，Koch W ，Ma XL ，Wang Y ... -  《-》

CircCHSY1 protects hearts against ischemia/reperfusion injury by enhancing heme oxygenase 1 expression via miR-24-3p.

Circular RNAs are important players involving in a variety of physiological and pathological processes. However, their functions and mechanisms during myocardial ischemic injury and protection remain largely unknown. We recently found significant alterations of many circRNAs including circCHSY1 following myocardial ischemia/reperfusion (I/R) injury, whereas their exact functions are unclear. Here, we investigated roles of circCHSY1 in the acute myocardial I/R injury and the potential mechanisms involved. The expression of circCHSY1 was detected in cardiomyocytes from mouse, rat and human embryonic stem cells (hESC-CMs). It was further upregulated in mouse I/R (30 min/24 h) hearts, oxygen glucose deprivation/reperfused (OGD/R, 6 h/2 h) primary neonatal rat ventricular cardiomyocytes (NRCMs) and OGD/R (48 h/2 h) hESC-CMs. Adenovirus-mediated circCHSY1-overexpression significantly decreased infarct size and lactate dehydrogenase (LDH) release in mouse I/R hearts. Consistently, circCHSY1 overexpression reduced the LDH release in the OGD/R NRCMs and hESC-CMs, improved cell viability, and preserved mitochondrial function in the OGD/R NRCMs, whereas there were no significant differences in cell viability and LDH release between the OGD/R NRCMs with and without siRNA-mediated circCHSY1 knockdown. Mechanistically, circCHSY1 was detected to bind with miR-24-3p analyzed by dual luciferase assay and RNA pull-down assays. CircCHSY1 overexpression-mediated protective effects on cells and mitochondria in OGD/R NRCMs were reversed by the miR-24-3p mimic. Further, dual luciferase assay showed that miR-24-3p directly bound to heme oxygenase 1 (HO1) via its 3'UTR. The protein level of HO1 was downregulated by miR-24-3p mimic in OGD/R NRCMs but enhanced by the circCHSY1 overexpression in vitro and in vivo. Functionally, the HO1 knockdown by adenovirus in vivo and by siRNA in vitro eliminated cardioprotective effects of circCHSY1 overexpression. CircCHSY1 is upregulated following myocardial I/R injury. The higher level of circCHSY1 protects I/R hearts and cardiomyocytes. The protection of circCHSY1 is mediated through enhancement of the HO1 level, resulting in preserving mitochondrial homeostasis via targeting miR-24-3p in cardiomyocytes. These findings suggest circCHSY1 as a protective factor.

Tan J ，Min J ，Jiang Y ，Liu S ，Ke M ，Wang Z ，Yang HT ... -  《-》

The Protective Role of miR-130b-3p Against Palmitate-Induced Lipotoxicity in Cardiomyocytes Through PPARγ Pathway.

Alonso-Villa E ，Mangas A ，Bonet F ，Campuzano Ó ，Quezada-Feijoo M ，Ramos M ，García-Padilla C ，Franco D ，Toro R ... -  《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

《Jove-Journal of Visualized Experiments》