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.

Apoptosis inhibitor of macrophage/CD5L is associated with disease activity in rheumatoid arthritis.

OBJECTIVES: To investigate the association between apoptosis inhibitor of macrophage (AIM) and disease activity in patients with rheumatoid arthritis (RA). METHODS: In this study, concentrations of serum AIM in 110 RA patients, 38 patients with osteoarthritis (OA) and 50 sex- and age-matched control subjects were determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: Serum AIM concentrations in RA patients were dramatically higher than those from patients with OA or healthy controls. The levels of synovial fluid AIM displayed a significant increase as compared with OA patients. More importantly, AIM levels were significantly correlated with RA disease activity features such as ESR, CRP and DAS28. The predictive value of AIM on high disease activity was superior to those of CRP and ESR. A noteworthy correlation in our study was observed between the serum AIM levels and laboratory parameters, particularly serum lipids. Furthermore, serum AIM levels could be significantly down-regulated after effective integrative treatment. CONCLUSIONS: AIM may serve as a novel sensitive biomarker to assist disease activity assessment and monitor therapeutic effects in active RA patients.

Oncostatin M Is a Prognostic Biomarker and Inflammatory Mediator for Sepsis.

BACKGROUND: Oncostatin M (OSM) is a pleiotropic cytokine of the interleukin-6 family. The role of OSM in sepsis remains unknown. METHODS: Serum OSM level was determined and analyzed in septic patients on the day of intensive care unit (ICU) admission. Furthermore, the effects of OSM on polymicrobial sepsis induced by cecal ligation and puncture (CLP) were assessed. RESULTS: On the day of ICU admission, septic patients had significantly higher serum OSM levels when compared with ICU patient controls and healthy volunteers, which were related to the severity of sepsis, including parameters such as the sequential (sepsis-related) organ failure assessment score, procalcitonin level, and white blood cell number. A high serum OSM level on ICU admission was associated with 28-day mortality in septic patients. In CLP-induced polymicrobial sepsis, anti-OSM antibody decreased tissue inflammation and injury, and thus improved survival, while local and systemic bacterial dissemination was almost constant. Complementarily, supplementation with recombinant OSM protein in septic mice increased tissue injury, amplified inflammation, and worsened mortality after CLP, while it did not affect bacterial dissemination in septic mice. CONCLUSIONS: Sepsis results in an increased production of OSM, which might be a potential prognostic biomarker and therapeutic target for sepsis.

Interleukin-17D Aggravates Sepsis by Inhibiting Macrophage Phagocytosis.

OBJECTIVES: Interleukin-17D has been shown to participate in the control of viral infections and cancer. Here we hypothesized that interleukin-17D may play a potential role in sepsis. DESIGN: Prospective randomized animal investigation and in vitro human blood studies. SETTING: Research laboratory from a university hospital. SUBJECTS: Female C57BL/6J mice, sepsis patients by Sepsis-3 definitions, ICU patient controls, and healthy individuals. INTERVENTIONS: Serum concentrations of interleukin-17D were measured and analyzed in human sepsis patients, patient controls, and healthy individuals. The contribution of interleukin-17D to sepsis-related survival, bacterial burden, and organ injury was assessed in a murine model of cecal ligation and puncture-induced polymicrobial sepsis by the use of anti-interleukin-17D antibody and recombinant interleukin-17D protein. The effects of interleukin-17D on bacterial phagocytosis by macrophages were also investigated using in vitro cell models. MEASUREMENTS AND MAIN RESULTS: On the day of ICU admission (day 0), septic patients had significantly higher serum concentrations of interleukin-17D than patient controls and healthy individuals. Serum interleukin-17D levels remained significantly elevated in septic patients from ICU admission to day 3 and correlated with Sequential (Sepsis-related) Organ Failure Assessment scores and documented bacteremia on day 0. Furthermore, nonsurvivors of septic patients displayed significantly higher interleukin-17D levels compared with survivors of septic patients on days 0 and 1 of ICU admission. In animal models of sepsis, treatment with anti-interleukin-17D antibody protected mice from cecal ligation and puncture-induced severe sepsis, which was associated with improved bacterial clearance and organ injury. Conversely, administration of recombinant interleukin-17D protein aggravated cecal ligation and puncture-induced nonsevere sepsis. Furthermore, we found that interleukin-17D impaired bacterial phagocytosis by macrophages. Phagocytosis inhibition by interleukin-17D involved its ability to down-regulate the activation of nuclear factor-κB signaling pathway in macrophages upon bacterial infection. CONCLUSIONS: This study indicates a previously undescribed role of interleukin-17D in sepsis and identifies a new target for antisepsis treatment.

Microbiota-driven interleukin-17 production provides immune protection against invasive candidiasis.

BACKGROUND: The intestinal microbiota plays a crucial role in human health, which could affect host immunity and the susceptibility to infectious diseases. However, the role of intestinal microbiota in the immunopathology of invasive candidiasis remains unknown. METHODS: In this work, an antibiotic cocktail was used to eliminate the intestinal microbiota of conventional-housed (CNV) C57/BL6 mice, and then both antibiotic-treated (ABX) mice and CNV mice were intravenously infected with Candida albicans to investigate their differential responses to infection. Furthermore, fecal microbiota transplantation (FMT) was applied to ABX mice in order to assess its effects on host immunity against invasive candidiasis after restoring the intestinal microbiota, and 16S ribosomal RNA gene sequencing was conducted on fecal samples from both uninfected ABX and CNV group of mice to analyze their microbiomes. RESULTS: We found that ABX mice displayed significantly increased weight loss, mortality, and organ damage during invasive candidiasis when compared with CNV mice, which could be alleviated by FMT. In addition, the level of IL-17A in ABX mice was significantly lower than that in the CNV group during invasive candidiasis. Treatment with recombinant IL-17A could improve the survival of ABX mice during invasive candidiasis. Besides, the microbial diversity of ABX mice was significantly reduced, and the intestinal microbiota structure of ABX mice was significantly deviated from the CNV mice. CONCLUSIONS: Our data revealed that intestinal microbiota plays a protective role in invasive candidiasis by enhancing IL-17A production in our model system.

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.

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.

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.