Description: Rationale:Mitochondria are important cellular organelles and play essential roles in maintaining cell structure and function. Emerging evidence indicates that in addition to having proinflammatory and proapoptotic effects, TNFα (tumor necrosis factor α) can, under certain circumstances, promote improvements in mitochondrial integrity and function, phenomena that can be ascribed to the existence of TNFR2 (TNFα receptor 2).Objective:The present study aimed to investigate whether and how TNFR2 activation mediates the effects of TNFα on mitochondria.Methods and Results:Freshly isolated neonatal mouse cardiac myocytes treated with shRNA targeting TNFR1 were used to study the effects of TNFR2 activation on mitochondrial function. Neonatal mouse cardiac myocytes exhibited increases in mitochondrial fusion, a change that was associated with increases in mitochondrial membrane potential, intracellular ATP levels, and oxygen consumption capacity. Importantly, TNFR2 activation–induced increases in OPA1 (optic atrophy 1) protein expression were responsible for the above enhancements, and these changes could be attenuated using siRNA targeting OPA1. Moreover, both Stat3 and RelA bound to the promoter region of OPA1 and their interactions synergistically upregulated OPA1 expression at the transcriptional level. Stat3 acetylation at lysine 370 or lysine 383 played a key role in the ability of Stat3 to form a supercomplex with RelA. Meanwhile, p300 modulated Stat3 acetylation in HEK293T (human embryonic kidney 293T) cells, and p300-mediated Stat3/RelA interactions played an indispensable role in OPA1 upregulation. Finally, TNFR2 activation exerted beneficial effects on OPA1 expression in an in vivo transverse aortic constriction model, whereby TNFR1-knockout mice exhibited better outcomes than in mice with both TNFR1 and TNFR2 knocked out.Conclusions:TNFR2 activation protects cardiac myocytes against stress by upregulating OPA1 expression. This process was facilitated by p300-mediated Stat3 acetylation and Stat3/RelA interactions, leading to improvements in mitochondrial morphology and function.

Description: Objective—In a previous study, we established diabetic and nondiabetic minipig models with coronary artery in-stent restenosis (ISR). Mass spectrometry showed that high-mobility group box (HMGB) 2 level was higher in ISR than in non-ISR tissue from diabetic minipigs. We here investigated whether serum HMGB2 levels were related to ISR in coronary artery disease patients. The effect of HMGB2 was evaluated in mice with femoral artery wire injury and in human aortic smooth muscle cells.Approach and Results—From 2513 patients undergoing coronary artery intervention and follow-up angiography at ≈1 year, 262 patients were diagnosed with ISR, and 298 patients with no ISR were randomly included as controls. Serum HMGB2 levels were significantly higher in patients with ISR than in those without ISR and were associated with ISR severity. Multivariable logistic regression analysis showed that HMGB2 level was independently associated with ISR. In experiments, HMGB2 expression was increased in vascular tissue after injury. Perivascular HMGB2 administration promoted injury-induced neointimal hyperplasia in C57Bl/6 mice compared with in the control, whereas such pathophysiological features were attenuated in Hmgb2–/– mice. Mechanistically, HMGB2 enhanced neointimal hyperplasia in mice and proliferation and migration in human aortic smooth muscle cells by inducing reactive oxygen species through increased p47phox phosphorylation. Knocking down p47phox, however, inhibited HMGB2-induced effects in human aortic smooth muscle cells. Finally, HMGB2-induced effects were significantly declined in receptor of advanced glycation end products knockdown or deficient cells, but not in Toll-like receptor 4 knockdown or deficient cells.Conclusions—Serum HMGB2 levels were associated with ISR in patients. HMGB2 promoted neointimal hyperplasia in mice with arterial wire injury through reactive oxygen species activation.

Description: Rationale:Cardiac fibrosis is a common feature in left ventricular remodeling that leads to heart failure, regardless of the cause. EphrinB2 (erythropoietin-producing hepatoma interactor B2), a pivotal bidirectional signaling molecule ubiquitously expressed in mammals, is crucial in angiogenesis during development and disease progression. Recently, EphrinB2 was reported to protect kidneys from injury-induced fibrogenesis. However, its role in cardiac fibrosis remains to be clarified.Objective:We sought to determine the role of EphrinB2 in cardiac fibrosis and the underlying mechanisms during the pathological remodeling process.Methods and Results:EphrinB2 was highly expressed in the myocardium of patients with advanced heart failure, as well as in mouse models of myocardial infarction and cardiac hypertrophy induced by angiotensin II infusion, which was accompanied by myofibroblast activation and collagen fiber deposition. In contrast, intramyocardial injection of lentiviruses carrying EphrinB2-shRNA ameliorated cardiac fibrosis and improved cardiac function in mouse model of myocardial infarction. Furthermore, in vitro studies in cultured cardiac fibroblasts demonstrated that EphrinB2 promoted the differentiation of cardiac fibroblasts into myofibroblasts in normoxic and hypoxic conditions. Mechanistically, the profibrotic effect of EphrinB2 on cardiac fibroblast was determined via activating the Stat3 (signal transducer and activator of transcription 3) and TGF-β (transforming growth factor-β)/Smad3 (mothers against decapentaplegic homolog 3) signaling. We further determined that EphrinB2 modulated the interaction between Stat3 and Smad3 and identified that the MAD homology 2 domain of Smad3 and the coil–coil domain and DNA-binding domain of Stat3 mediated the interaction.Conclusions:This study uncovered a previously unrecognized profibrotic role of EphrinB2 in cardiac fibrosis, which is achieved through the interaction of Stat3 with TGF-β/Smad3 signaling, implying a promising therapeutic target in fibrotic diseases and heart failure.

Description: Background:Folate deficiency is an independent risk factor for congenital heart disease (CHD); however, the maternal plasma folate level is paradoxically not a good diagnostic marker. Genome-wide surveys have identified variants of nonfolate metabolic genes associated with the plasma folate level, suggesting that these genetic polymorphisms are potential risk factors for CHD.Methods:To examine the effects of folate concentration-related variations on CHD risk in the Han Chinese population, we performed 3 independent case-control studies including a total of 1489 patients with CHD and 1745 control subjects. The expression of the Fidgetin (FIGN) was detected in human cardiovascular and decidua tissue specimens with quantitative real-time polymerase chain reaction and Western blotting. The molecular mechanisms were investigated by luciferase reporter assays, surface plasmon resonance, and chromatin immunoprecipitation. FIGN-interacting proteins were confirmed by tandem affinity purification and coimmunoprecipitation. Proteasome activity and metabolite concentrations in the folate pathway were quantified with a commercial proteasome activity assay and immunoassays, respectively.Results:The +94762G〉C (rs2119289) variant in intron 4 of the FIGN gene was associated with significant reduction in CHD susceptibility (P=5.1×10−14 for the allele, P=8.5×10–−13 for the genotype). Analysis of combined samples indicated that CHD risks in individuals carrying heterozygous (GC) or homozygous (CC) genotypes were reduced by 44% (odds ratio [OR]=0.56; 95% confidence interval [CI]=0.47–0.67) and 66% (OR=0.34; 95% CI=0.23–0.50), respectively, compared with those with the major GG genotype. Minor C allele carriers who had decreased plasma folate levels exhibited significantly increased FIGN expression because the transcription suppressor CREB1 did not bind the alternative promoter of FIGN isoform X3. Mechanistically, increased FIGN expression led to the accumulation of both reduced folate carrier 1 and dihydrofolate reductase via inhibition of their proteasomal degradation, which promoted folate absorption and metabolism.Conclusions:We report a previously undocumented finding that decreased circulating folate levels induced by increased folate transmembrane transport and utilization, as determined by the FIGN intronic variant, serves as a protective mechanism against CHD. Our results may explain why circulating folate levels do not have a good diagnostic value.

Description: Background and Purpose—Multipotent mesenchymal stromal cell (MSC) harvested exosomes are hypothesized as the major paracrine effectors of MSCs. In vitro, the miR-17–92 cluster promotes oligodendrogenesis, neurogenesis, and axonal outgrowth. We, therefore, investigated whether the miR-17–92 cluster–enriched exosomes harvested from MSCs transfected with an miR-17–92 cluster plasmid enhance neurological recovery compared with control MSC-derived exosomes.Methods—Rats subjected to 2 hours of transient middle cerebral artery occlusion were intravenously administered miR-17–92 cluster–enriched exosomes, control MSC exosomes, or liposomes and were euthanized 28 days post–middle cerebral artery occlusion. Histochemistry, immunohistochemistry, and Golgi–Cox staining were used to assess dendritic, axonal, synaptic, and myelin remodeling. Expression of phosphatase and tensin homolog and activation of its downstream proteins, protein kinase B, mechanistic target of rapamycin, and glycogen synthase kinase 3β in the peri-infarct region were measured by means of Western blots.Results—Compared with the liposome treatment, both exosome treatment groups exhibited significant improvement of functional recovery, but miR-17–92 cluster–enriched exosome treatment had significantly more robust effects on improvement of neurological function and enhancements of oligodendrogenesis, neurogenesis, and neurite remodeling/neuronal dendrite plasticity in the ischemic boundary zone (IBZ) than the control MSC exosome treatment. Moreover, miR-17–92 cluster–enriched exosome treatment substantially inhibited phosphatase and tensin homolog, a validated miR-17–92 cluster target gene, and subsequently increased the phosphorylation of phosphatase and tensin homolog downstream proteins, protein kinase B, mechanistic target of rapamycin, and glycogen synthase kinase 3β compared with control MSC exosome treatment.Conclusions—Our data suggest that treatment of stroke with tailored exosomes enriched with the miR-17–92 cluster increases neural plasticity and functional recovery after stroke, possibly via targeting phosphatase and tensin homolog to activate the PI3K/protein kinase B/mechanistic target of rapamycin/glycogen synthase kinase 3β signaling pathway.