Inhibition of Pyruvate Dehydrogenase Kinase 4 Attenuates Myocardial and Mitochondrial Injury in Sepsis-Induced Cardiomyopathy.

BACKGROUND: Sepsis-induced cardiomyopathy (SIC) is a cardiac dysfunction caused by sepsis, with mitochondrial dysfunction being a critical contributor. Pyruvate dehydrogenase kinase 4 (PDK4) is a kinase of pyruvate dehydrogenase with multifaceted actions in mitochondrial metabolism. However, its role in SIC remains unknown. METHODS: Serum PDK4 levels were measured and analyzed in 27 children with SIC, 30 children with sepsis, and 29 healthy children. In addition, for mice exhibiting SIC, the effects of PDK4 knockdown or inhibition on the function and structure of the myocardium and mitochondria were assessed. RESULTS: The findings from the analysis of children with SIC revealed that PDK4 was significantly elevated and correlated with disease severity and organ injury. Nonsurvivors displayed higher serum PDK4 levels than survivors. Furthermore, mice with SIC benefited from PDK4 knockdown or inhibition, showing improved myocardial contractile function, reduced myocardial injury, and decreased mitochondrial structural injury and dysfunction. In addition, inhibition of PDK4 decreased the inhibitory phosphorylation of PDHE1α (pyruvate dehydrogenase complex E1 subunit α) and improved abnormal pyruvate metabolism and mitochondrial dysfunction. CONCLUSIONS: PDK4 is a potential biomarker for the diagnosis and prognosis of SIC. In experimental SIC, PDK4 promoted mitochondrial dysfunction with increased phosphorylation of PDHE1α and abnormal pyruvate metabolism.

Ferrostatin-1 improves BMSC survival by inhibiting ferroptosis.

OBJECTIVE: To investigate the effect of ferroptosis in BMSCs and explore the protective metabolism of ferrostatin-1 under GSDH treatment. METHODS: BMSCs were treated with GSDH to simulate the damaged microenvironment in vivo to establish a cell injury model. Propidium iodide and CCK8 were utilized to detect the ratio of dead cells and cell viability. DCFH-DA and Amplex Red, FerroOrange, and BPDIPY were used to visualize the cellular fluorescent images of ROS, Fe2+, and lipid droplets, respectively. The quantified detection of MDA was conducted by a Lipid Peroxidation MDA Assay Kit. JC-1 staining, Mito-Tracker staining, and TEM were implemented to detect the membrane potential, morphology, and ultrastructure of mitochondria, respectively. The expression levels of ferroptosis-related proteins such as GPX4 and FTH1 were measured by Western blotting. RESULTS: GSDH treatment induced ferroptosis in BMSCs based on an increased ratio of cell death, Fe2+, ROS, lipid droplets, and MDA in cells plus decreased protein levels of antioxidant systems, such as GPX4, and increased protein levels related to fatty acid synthesis. Compared to the blank group, mitochondria in the GSDH group underwent lower membrane potential, damaged morphology, and shrunken ultrastructure; Ferr-1 rescued the injured BMSCs to a certain extent as the declined ratio of cell death, Fe2+, ROS, lipid droplets, MDA, and the increased level antioxidant protein. AMPK was phosphorylated and activated after Ferr-1 treatment, and its downstream lipid peroxidation and antioxidation proteins changed accordingly. Inhibition of AMPK hindered the curative effect of Ferr-1. CONCLUSION: Ferr-1 rescued ferroptosis-induced injury to BMSCs under GSDH conditions, and AMPK might have a relationship with the mitigative effect of Ferr-1.

AKAP1 Regulates Mitochondrial Dynamics during the Fatty-Acid-Promoted Maturation of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes as Indicated by Proteomics Sequencing.

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are cells with promising applications. However, their immaturity has restricted their use in cell therapy, disease modeling, and other studies. Therefore, the current study focused on inducing the maturation of CMs. We supplemented hiPSC-CMs with fatty acids (FAs) to promote their phenotypic maturity. Proteomic sequencing was performed to identify regulators critical for promoting the maturation of hiPSC-CMs. AKAP1 was found to be significantly increased in FA-treated hiPSC-CMs, and the results were verified. Therefore, we inhibited AKAP1 expression in the FA-treated cells and analyzed the outcomes. FA supplementation promoted the morphological and functional maturation of the hiPSC-CMs, which was accompanied by the development of a mitochondrial network. Proteomic analysis results revealed that AKAP1 expression was significantly higher in FA-treated hiPSC-CMs than in control cells. In addition, increased phosphorylation of the mitochondrial dynamin Drp1 and an increased mitochondrial fusion rate were found in FA-treated hiPSC-CMs. After AKAP1 was knocked down, the level of DRP1 phosphorylation in the cell was decreased, and the mitochondrial fusion rate was reduced. FA supplementation effectively promoted the maturation of hiPSC-CMs, and in these cells, AKAP1 regulated mitochondrial dynamics, possibly playing a significant role.

Palladium-Catalyzed Highly Chemo- and Stereoselective Bisthiolation of Terminal Alkynes with Allyl Phenyl Sulfides via C-S Bond Cleavage.

A facile and general method for palladium-catalyzed stereoselective bisthiolation of terminal alkynes with allyl phenyl sulfides has been developed. The scope and versatility of the reaction have been demonstrated, and a broad range of substrates bearing electron-donating and -withdrawing groups on the aromatic rings were all compatible with this reaction, providing the desired (Z)-1,2-dithio-1-alkenes in moderate to good yields. Preliminary mechanistic studies demonstrated that the sulfur source of the desired products may be successively incorporated into alkynes via C-S bond cleavage of two molecules of allyl phenyl sulfides and ruled out the possibility of vinyl sulfides, alkynyl sulfides, and disulfide intermediates being involved in this reaction.

Inhibition of Pyruvate Dehydrogenase Kinase 4 Protects Cardiomyocytes from lipopolysaccharide-Induced Mitochondrial Damage by Reducing Lactate Accumulation.

Mitochondrial dysfunction is considered one of the major pathogenic mechanisms of sepsis-induced cardiomyopathy (SIC). Pyruvate dehydrogenase kinase 4 (PDK4), a key regulator of mitochondrial metabolism, is essential for maintaining mitochondrial function. However, its specific role in SIC remains unclear. To investigate this, we established an in vitro model of septic cardiomyopathy using lipopolysaccharide (LPS)-induced H9C2 cardiomyocytes. Our study revealed a significant increase in PDK4 expression in LPS-treated H9C2 cardiomyocytes. Inhibiting PDK4 with dichloroacetic acid (DCA) improved cell survival, reduced intracellular lipid accumulation and calcium overload, and restored mitochondrial structure and respiratory capacity while decreasing lactate accumulation. Similarly, Oxamate, a lactate dehydrogenase inhibitor, exhibited similar effects to DCA in LPS-treated H9C2 cardiomyocytes. To further validate whether PDK4 causes cardiomyocyte and mitochondrial damage in SIC by promoting lactate production, we upregulated PDK4 expression using PDK4-overexpressing lentivirus in H9C2 cardiomyocytes. This resulted in elevated lactate levels, impaired mitochondrial structure, and reduced mitochondrial respiratory capacity. However, inhibiting lactate production reversed the mitochondrial dysfunction caused by PDK4 upregulation. In conclusion, our study highlights the pathogenic role of PDK4 in LPS-induced cardiomyocyte and mitochondrial damage by promoting lactate production. Therefore, targeting PDK4 and its downstream product lactate may serve as promising therapeutic approaches for treating SIC.

Dynamic Constitutive Relationship of Mg-Gd-Y-Zr-Ag Alloy during High Temperature Deformation Process.

The thermal deformation behavior of the Mg-Gd-Y-Zr-Ag alloy was studied by isothermal hot compression tests at high temperatures. The flow stress increased with increased strain rates and decreased temperatures, first increasing and finally remaining stable with increased strain. A hot processing map was built. Using the processing map and microstructural analysis, the temperature should remain at 673-773 K for this alloy to ensure the deformation quality. The primary softening mechanism is discontinuous dynamic recrystallization (DDRX). Rising temperatures and declining strain rates facilitated the emergence and growth of Dynamic recrystallization (DRX) grains. An original JC (O-JC) model and a modified JC (M-JC) model were established. The M-JC model indicated a better prediction than the O-JC model. Still, it was deficient in predicting flow stresses with insufficient coupling effects. Hence, based on the M-JC model, a newly modified JC (NM-JC) model, which further enhances the interaction between strain and strain rate as well as strain and temperature, is proposed. Its projected values can better align with the tested values.

Nickel-Catalyzed Metathesis between Carboxylic Acids and Thioesters: A Direct Access to Thioesters.

We describe a unique strategy for generating thioesters from carboxylic acids and thioesters. This transformation features operational simplicity and high step-economy, wherein the -SR moiety of thioesters was smoothly transferred to carboxylic acid from thioacetates as the starting material. Various substrates with different levels of electronic nature were all applicable to this reaction, furnishing thioesters in moderate to outstanding yields. According to the preliminary mechanistic studies, the anhydride intermediates may be involved in the present reaction.

SIRT3 promotes metabolic maturation of human iPSC-derived cardiomyocytes via OPA1-controlled mitochondrial dynamics.

The metabolic patterns and energetics of human induced pluripotent stem cell-derived cardiomyocytes (HiPSC-CMs) are much less than those of normal adult cardiomyocytes, which has limited their application in disease therapy and regenerative medicine. It has been demonstrated that SIRT3, a mitochondria-target deacetylase, controls mitochondrial metabolism in physiological and pathological conditions. In this research, We investigated the role and regulatory mechanism of SIRT3 in energy metabolism in HiPSC-CMs. We found that the expression of SIRT3 was increased during the differentiation and maturation of HiPSC-CMs. Knocking down SIRT3 impaired mitochondrial structure, mitochondrial respiration capacity, and fatty acid oxidation but enhanced glycolysis. However, honokiol, a pharmacological activator of SIRT3, improved the mitochondrial ultrastructure and energetics, and promoted oxidative phosphorylation in HiPSC-CMs. Furthermore, SIRT3 regulated the acetylation of OPA1, and the knockdown of OPA1 blocked the promotion of energy metabolism by honokiol, meanwhile, knocking down OPA1 impaired mitochondrial fusion, mitochondrial respiration capacity, and fatty acid oxidation which were reversed by M1 (a mitochondrial fusion promoter) in HiPSC-CMs. In summary, SIRT3 regulated energetics and promoted metabolism remodeling by targeting the OPA1-controlled mitochondrial dynamics in HiPSC-CMs, and targeting SIRT3 may have revelatory implications in the treatment of cardiovascular diseases and the application of HiPSC-CMs to regenerative medicine.

Palladium-Catalyzed Thiocarbonylation of Aryl Iodides with S-Aryl Thioformates via Thioester Transfer.

Herein we reported a novel approach to synthesize thioesters with S-aryl thioformates as thioester sources. The reaction proceeded at ambient temperature using widely available starting ingredients, wherein the thioester moiety was smoothly transferred to aryl iodides from S-aryl thioformates. A variety of substrates with various electronic natures were all tolerated under the reaction conditions to furnish desirable thioesters in ranges from moderate to excellent yields. The gram-scale reaction was also conducted, and there was virtually little change in chemical yield, indicating that large-scale synthesis of thioesters may be viable using this method.

Effects of Quenching Cooling Rate on Residual Stress and Mechanical Properties of a Rare-Earth Wrought Magnesium Alloy.

To investigate the effect of quenching rate on microstructure, residual stress (RS) and mechanical properties of a rare-earth wrought magnesium alloy Mg-Gd-Y-Zr-Ag-Er, RS in 20 °C water quenching (WQ (20 °C)), 100 °C water quenching (WQ (100 °C)) or air cooling (AC) conditions were measured and compared with the simulation results, corresponding mechanical properties and microstructure in quenching and aging state were studied. The decrease of quenching rate has little effect on the grain size but makes the twinning disappear, precipitates increase and the texture weakened, leading to easier brittle fracture after aging. WQ (100 °C) is the best quenching condition in this study, with a significant decline in RS and only 4.9% and 3.7% decrease in yield stress (YS) and hardness compared with WQ (20 °C). The results make it feasible to invent an appropriate quenching method of greatly reducing RS while maintaining mechanical properties. The research conclusions would be beneficial to the application of the alloy.

Andrographolide protects bone marrow mesenchymal stem cells against glucose and serum deprivation under hypoxia via the NRF2 signaling pathway.

BACKGROUND: Bone marrow mesenchymal stem cell (BMSCs) therapy is an important cell transplantation strategy in the regenerative medicine field. However, a severely ischemic microenvironment, such as nutrient depletion and hypoxia, causes a lower survival rate of transplanted BMSCs, limiting the application of BMSCs. Therefore, improving BMSCs viability in adverse microenvironments is an important means to improve the effectiveness of BMSCs therapy. OBJECTIVE: To illustrate the protective effect of andrographolide (AG) against glucose and serum deprivation under hypoxia (1% O2) (GSDH)-induced cell injury in BMSCs and investigate the possible underlying mechanisms. METHODS: An in vitro primary rat BMSCs cell injury model was established by GSDH, and cellular viability, proliferation and apoptosis were observed after AG treatment under GSDH. Reactive oxygen species levels and oxidative stress-related genes and proteins were measured by flow cytometry, RT-qPCR and Western blotting. Mitochondrial morphology, function and number were further assessed by laser confocal microscopy and flow cytometry. RESULTS: AG protected BMSCs against GSDH-induced cell injury, as indicated by increases in cell viability and proliferation and mitochondrial number and decreases in apoptosis and oxidative stress. The metabolic status of BMSCs was changed from glycolysis to oxidative phosphorylation to increase the ATP supply. We further observed that the NRF2 pathway was activated by AG, and treatment of BMSCs with a specific NRF2 inhibitor (ML385) blocked the protective effect of AG. CONCLUSION: Our results suggest that AG is a promising agent to improve the therapeutic effect of BMSCs.