YBX1 inhibits mitochondrial-mediated apoptosis in ischemic heart through the PI3K/AKT signaling pathway

Background:Myocardial infarction(MI)is associated with higher morbidity and mortality in the world,especially in cold weather.YBX1 is an RNA-binding protein that is required for pathological growth of cardiomyocyte by regulating cell growth and protein synthesis.But YBX1,as an individual RNA-binding protein,regulates cardiomyocytes through signaling cascades during myocardial infarction remain largely unexplored.Methods:In vivo,the mouse MI model was induced by ligating the left anterior descending coronary artery(LAD),and randomly divided into sham operation group,MI group,MI+YBX1 knockdown/overexpression group and MI+negative control(NC)group.The protective effect of YBX1 was verified by echocardiography and triphenyltetrazolium chloride staining.In vitro,mitochondrial-dependent apoptosis was investigated by using CCK8,TUNEL staining,reactive oxygen species(ROS)staining and JC-1 staining in hypoxic neonatal mouse cardiomyocytes(NMCMs).Results:YBX1 expression of cardiomyocytes was downregulated in a mouse model and a cellular model on the ischemic condition.Compared to mice induced by MI,YBX1 overexpression mediated by adeno-associated virus serotype 9(AAV9)vector reduced the infarcted size and improved cardiac function.Knockdown of endogenous YBX1 by shRNA partially aggravated ischemia-induced cardiac dysfunction.In hypoxic cardiomyocytes,YBX1 overexpression decreased lactic dehydrogenase(LDH)release,increased cell viability,and inhibited apoptosis by affecting the expression of apoptosis related proteins,while knockdown of endogenous YBX1 by siRNA had the opposite effect.Overexpression of YBX1 restored mitochondrial dysfunction in hypoxic NMCMs by increasing mitochondrial membrane potential and ATP content and decreasing ROS.In hypoxic NMCMs,YBX1 overexpression increased the expression of phosphorylated phosphatidylinositol 3 kinase(PI3K)/AKT,and the anti-apoptosis effect of YBX1 was eliminated t by LY294002,PI3K/AKT inhibitor.Conclusion:YBX1 protected the heart from ischemic damage by inhibiting the mitochondrial-dependent apoptosis through PI3K/AKT pathway.It is anticipated that YBX1 may serve as a novel therapeutic target for MI.

ProBDNF Acts as an Angiogenesis Inhibitor

Brain-derived neurotrophic factor (BDNF) has been considered a new angiogenesis mediator. ProBDNF, the precursor of BDNF, plays opposite neuronal functions to BDNF, but the role of proBDNF on angiogenesis remains unknown. We found human umbilical vein endothelial cells (HUVEC) expressing BDNF, proBDNF, p75NTR, Sortilin and TrkB. ProBDNF significantly decreased HUVEC viability in MTT assay, and this inhibition was neutralized by anti-proBDNF. Endothelial cell tube formation assay showed that proBDNF significantly inhibits HUVEC angiogenesis in vitro. Matrigel plug assay disclosed that proBDNF also impeded angiogenesis in vivo, while anti-proBDNF greatly facilitated angiogenesis. Immunostaining of CD31 and α-SMA in Matrigel plugs confirmed the inhibitive effect of proBDNF on angiogenesis. In conclusion, proBDNF can act as an angiogenesis inhibitor. It added more evidence to the “Yin-Yang” theory by showing mBDNF is a mediator of angiogenesis as “Yang” and proBDNF works as an angiogenesis inhibitor as “Yin”.

lncRNA Gm20257 alleviates pathological cardiac hypertrophy by modulating the PGC-1α–mitochondrial complexⅣaxis

Pathological cardiac hypertrophy,a major contributor to heart failure,is closely linked to mitochondrial function.The roles of long noncoding RNAs(lncRNAs),which regulate mitochondrial function,remain largely unexplored in this context.Herein,a previously unknown lncRNA,Gm20257,was identified.It markedly increased under hypertrophic stress in vivo and in vitro.The suppression of Gm20257 by using small interfering RNAs significantly induced cardiomyocyte hypertrophy.Conversely,the overexpression of Gm20257 through plasmid transfection or adeno-associated viral vector-9 mitigated angiotensinⅡ-induced hypertrophic phenotypes in neonatal mouse ventricular cells or alleviated cardiac hypertrophy in a mouse TAC model respectively,thus restoring cardiac function.Importantly,Gm20257 restored mitochondrial complexⅣlevel and enhanced mitochondrial function.Bioinformatics prediction showed that Gm20257 had a high binding score with peroxisome proliferator–activated receptor coactivator-1(PGC-1α),which could increase mitochondrial complex IV.Subsequently,Western blot analysis results revealed that Gm20257 substantially affected the expression of PGC-1α.Further analyses through RNA immunoprecipitation and immunoblotting following RNA pull-down indicated that PGC-1αwas a direct downstream target of Gm20257.This interaction was demonstrated to rescue the reduction of mitochondrial complex IV induced by hypertrophic stress and promote the generation of mitochondrial ATP.These findings suggest that Gm20257 improves mitochondrial function through the PGC-1α-mitochondrial complexⅣaxis,offering a novel approach for attenuating pathological cardiac hypertrophy.