Expression Of Pyruvate Dehydrogenase Kinase Research Articles

The OGT-c-Myc-PDK2 axis rewires the TCA cycle and promotes colorectal tumor growth.

Deregulated glucose metabolism termed the "Warburg effect" is a fundamental feature of cancers, including the colorectal cancer. This is typically characterized with an increased rate of glycolysis, and a concomitant reduced rate of the tricarboxylic acid (TCA) cycle metabolism as compared to the normal cells. How the TCA cycle is manipulated in cancer cells remains unknown. Here, we show that O-linked N-acetylglucosamine (O-GlcNAc) regulates the TCA cycle in colorectal cancer cells. Depletion of OGT, the sole transferase of O-GlcNAc, significantly increases the TCA cycle metabolism in colorectal cancer cells. Mechanistically, OGT-catalyzed O-GlcNAc modification of c-Myc at serine 415 (S415) increases c-Myc stability, which transcriptionally upregulates the expression of pyruvate dehydrogenase kinase 2 (PDK2). PDK2 phosphorylates pyruvate dehydrogenase (PDH) to inhibit the activity of mitochondrial pyruvate dehydrogenase complex, which reduces mitochondrial pyruvate metabolism, suppresses reactive oxygen species production, and promotes xenograft tumor growth. Furthermore, c-Myc S415 glycosylation levels positively correlate with PDK2 expression levels in clinical colorectal tumor tissues. This study highlights the OGT-c-Myc-PDK2 axis as a key mechanism linking oncoprotein activation with deregulated glucose metabolism in colorectal cancer.

Ginsenoside Rh2 shifts tumor metabolism from aerobic glycolysis to oxidative phosphorylation through regulating the HIF1-α/PDK4 axis in non-small cell lung cancer

BackgroundGinsenoside Rh2 (G-Rh2), a steroidal compound extracted from roots of ginseng, has been extensively studied in tumor therapy. However, its specific regulatory mechanism in non-small cell lung cancer (NSCLC) is not well understood. Pyruvate dehydrogenase kinase 4 (PDK4), a central regulator of cellular energy metabolism, is highly expressed in various malignant tumors. We investigated the impact of G-Rh2 on the malignant progression of NSCLC and how it regulated PDK4 to influence tumor aerobic glycolysis and mitochondrial function.MethodWe examined the inhibitory effect of G-Rh2 on NSCLC through I proliferation assay, migration assay and flow cytometry in vitro. Subsequently, we verified the ability of G-Rh2 to inhibit tumor growth and metastasis by constructing subcutaneous tumor and metastasis models in nude mice. Proteomics analysis was conducted to analyze the action pathways of G-Rh2. Additionally, we assessed glycolysis and mitochondrial function using seahorse, PET-CT, Western blot, and RT-qPCR.ResultTreatment with G-Rh2 significantly inhibited tumor proliferation and migration ability both in vitro and in vivo. Furthermore, G-Rh2 inhibited the tumor’s aerobic glycolytic capacity, including glucose uptake and lactate production, through the HIF1-α/PDK4 pathway. Overexpression of PDK4 demonstrated that G-Rh2 targeted the inhibition of PDK4 expression, thereby restoring mitochondrial function, promoting reactive oxygen species (ROS) accumulation, and inducing apoptosis. When combined with sodium dichloroacetate, a PDK inhibitor, it complemented the inhibitory capacity of PDKs, acting synergistically as a detoxifier.ConclusionG-Rh2 could target and down-regulate the expression of HIF-1α, resulting in decreased expression of glycolytic enzymes and inhibition of aerobic glycolysis in tumors. Additionally, by directly targeting mitochondrial PDK, it elevated mitochondrial oxidative phosphorylation and enhanced ROS accumulation, thereby promoting tumor cells to undergo normal apoptotic processes.

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.

Reducing Oxidative Stress and Inflammation by Pyruvate Dehydrogenase Kinase 4 Inhibition Is Important in Prevention of Renal Ischemia-Reperfusion Injury in Diabetic Mice.

Reactive oxygen species (ROS) and inflammation are reported to have a fundamental role in the pathogenesis of ischemia-reperfusion (IR) injury, a leading cause of acute kidney injury. The present study investigated the role of pyruvate dehydrogenase kinase 4 (PDK4) in ROS production and inflammation following IR injury. We used a streptozotocin-induced diabetic C57BL6/J mouse model, which was subjected to IR by clamping both renal pedicles. Cellular apoptosis and inflammatory markers were evaluated in NRK-52E cells and mouse primary tubular cells after hypoxia and reoxygenation using a hypoxia work station. Following IR injury in diabetic mice, the expression of PDK4, rather than the other PDK isoforms, was induced with a marked increase in pyruvate dehydrogenase E1α (PDHE1α) phosphorylation. This was accompanied by a pronounced ROS activation, as well as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1) production. Notably, sodium dichloroacetate (DCA) attenuated renal IR injury-induced apoptosis which can be attributed to reducing PDK4 expression and PDHE1α phosphorylation levels. DCA or shPdk4 treatment reduced oxidative stress and decreased TNF-α, IL-6, IL-1β, and MCP-1 production after IR or hypoxia-reoxygenation injury. PDK4 inhibition alleviated renal injury with decreased ROS production and inflammation, supporting a critical role for PDK4 in IR mediated damage. This result indicates another potential target for reno-protection during IR injury; accordingly, the role of PDK4 inhibition needs to be comprehensively elucidated in terms of mitochondrial function during renal IR injury.

Expression of Pyruvate Dehydrogenase Kinase (PDK) in Lungs during Progression of Pulmonary Hypertension Syndrome in Broilers

Expression of Pyruvate Dehydrogenase Kinase (PDK) in Lungs during Progression of Pulmonary Hypertension Syndrome in Broilers

MicroRNA-148a-3p in pericyte-derived extracellular vesicles improves erectile function in diabetic mice by promoting cavernous neurovascular regeneration

BackgroundTo investigate the regulatory role of microRNA (miR)-148a-3p in mouse corpus cavernous pericyte (MCPs)-derived extracellular vesicles (EVs) in the treatment of diabetes-induced erectile dysfunction (ED).MethodsMouse corpus cavernous tissue was used for MCP primary culture and EV isolation. Small-RNA sequencing analysis was performed to assess the type and content of miRs in MCPs-EVs. Four groups of mice were used: control nondiabetic mice and streptozotocin-induced diabetic mice receiving two intracavernous injections (days − 3 and 0) of phosphate buffered saline, MCPs-EVs transfected with reagent control, or MCPs-EVs transfected with a miR-148a-3p inhibitor. miR-148a-3p function in MCPs-EVs was evaluated by tube-formation assay, migration assay, TUNEL assay, intracavernous pressure, immunofluorescence staining, and Western blotting.ResultsWe extracted EVs from MCPs, and small-RNA sequencing analysis showed miR-148a-3p enrichment in MCPs-EVs. Exogenous MCPs-EV administration effectively promoted mouse cavernous endothelial cell (MCECs) tube formation, migration, and proliferation, and reduced MCECs apoptosis under high-glucose conditions. These effects were significantly attenuated in miR-148a-3p-depleted MCPs-EVs, which were extracted after inhibiting miR-148a-3p expression in MCPs. Repetitive intracavernous injections of MCPs-EVs improved erectile function by inducing cavernous neurovascular regeneration in diabetic mice. Using online bioinformatics databases and luciferase report assays, we predicted that pyruvate dehydrogenase kinase-4 (PDK4) is a potential target gene of miR-148a-3p.ConclusionsOur findings provide new and reliable evidence that miR-148a-3p in MCPs-EVs significantly enhances cavernous neurovascular regeneration by inhibiting PDK4 expression in diabetic mice.

Study of Transcriptomic Analysis of Yak (Bos grunniens) and Cattle (Bos taurus) Pulmonary Artery Smooth Muscle Cells under Oxygen Concentration Gradients and Differences in Their Lung Histology and Expression of Pyruvate Dehydrogenase Kinase 1-Related Factors.

The aim of this study was to investigate the molecular mechanisms by which hypoxia affects the biological behavior of yak PASMCs, the changes in the histological structure of yak and cattle lungs, and the relationships and regulatory roles that exist regarding the differences in the distribution and expression of PDK1 and its hypoxia-associated factors screened for their role in the adaptation of yak lungs to the plateau hypoxic environment. The results showed that, at the level of transcriptome sequencing, the molecular regulatory mechanisms of the HIF-1 signaling pathway, glucose metabolism pathway, and related factors (HK2/PGK1/ENO1/ENO3/ALDOC/ALDOA) may be closely related to the adaptation of yaks to the hypoxic environment of the plateau; at the tissue level, the presence of filled alveoli and semi-filled alveoli, thicker alveolar septa and basement membranes, a large number of erythrocytes, capillary distribution, and collagen fibers accounted for all levels of fine bronchioles in the lungs of yaks as compared to cattle. A higher percentage of goblet cells was found in the fine bronchioles of yaks, and PDK1, HIF-1α, and VEGF were predominantly distributed and expressed in the monolayers of ciliated columnar epithelium in the branches of the terminal fine bronchioles of yak and cattle lungs, with a small amount of it distributed in the alveolar septa; at the molecular level, the differences in PDK1 mRNA relative expression in the lungs of adult yaks and cattle were not significant (p > 0.05), the differences in HIF-1α and VEGF mRNA relative expression were significant (p < 0.05), and the expression of PDK1 and HIF-1α proteins in adult yaks was stronger than that in adult cattle. PDK1 and HIF-1α proteins were more strongly expressed in adult yaks than in adult cattle, and the difference was highly significant (p < 0.01); the relative expression of VEGF proteins was not significantly different between adult yaks and cattle (p > 0.05). The possible regulatory relationship between the above results and the adaptation of yak lungs to the plateau hypoxic environment paves the way for the regulatory mechanisms of PDK1, HIF-1α, and VEGF, and provides basic information for studying the mechanism of hypoxic adaptation of yaks in the plateau. At the same time, it provides a reference for human hypoxia adaptation and a target for the prevention and treatment of plateau diseases in humans and plateau animals.

Abstract 16945: Aberrant Citric Acid Cycle Metabolites Temporally Coincide With Myocardial Dysfunction in a Rat Model of Stress Cardiomyopathy

Introduction: Stress cardiomyopathy is characterized by transient contractile dysfunction with a poorly understood mechanism. Targeting metabolic derangements has proven efficacious in chronic heart failure, but the role of metabolism in acute cardiac dysfunction is ill-defined. Hypothesis: Characterizing any metabolic alterations in stress cardiomyopathy may help identify potential therapeutic targets. Methods: Sprague-Dawley rats (350 ± 57 g) were given a single intraperitoneal injection of 75 mg/kg isoprenaline. Animals were allocated into groups (N=30 each) based on designated time-points for assessment after injection: control (no injection), day 1, 3, and 7. Rats underwent left ventricular PV loop catheterization followed by harvesting of apical ventricular tissue. Targeted metabolomic analyses were performed via LC-MS and supplemented with enzyme activity assays, qPCR, and Western blotting. Results: Stroke work, cardiac output, and ejection fraction were all significantly reduced by day 1 with recovery by day 7 (Figure A, all p&lt;0.05). Targeted tissue metabolomics revealed peaks in nearly all citric acid cycle metabolites, pyruvate, and lactate that similarly correlated with illness (Figure B). In tandem, anaplerotic amino acids rose with injury while tissue triglycerides decreased. Pyruvate dehydrogenase phosphorylation decreased with decreased expression of pyruvate dehydrogenase kinase (Figure C). However, no differences were noted in tissue acylcarnitine levels despite increased serum fatty acids (all p&gt;0.05). Conclusions: Profound rises in citric acid metabolites with accompanying increases in anaplerotic amino acids are suggestive of metabolic reprogramming in the setting of energetic deficits. Notably, these trends differ from those found in chronic heart failure, and represent a novel phenotypic characterization of stress cardiomyopathy with potential therapeutic implications.

Abstract 12306: CREG1 Attenuates Doxorubicin-Induced Cardiotoxicity via Inhibiting the Ferroptosis of Cardiomyocytes

Introduction: Doxorubicin (DOX) is currently one of the most used anthracycline anticancer drugs. However, the cardiotoxicity of DOX limits its application in cancer patients. Cellular repressor of E1A-stimulated genes (CREG1) is an important cardioprotective factor. Hypothesis: We investigated the underlying effects and mechanism of of CREG1 in DOX-induced cardiotoxicity have not been reported. Methods: In vivo, a mouse DOX-induced cardiotoxicity model was established by DOX intraperitoneal injection, the mRNA and protein expression of CREG1 in the myocardium was examined using real-time PCR and western blot. CREG1 transgenic mice and cardiac-specific CREG1 knockout mice were used to establish DOX-induced cardiotoxicity model. HE staining, Masson staining, WGA staining and western blot were applied to examine fibrosis, myocardial hypertrophy and ferroptosis. In vitro, neonatal mouse cardiomyocytes (NMCMs) were stimulated with DOX, CREG1 overexpression adenovirus and small interfering RNA was used to examine the role of CREG1 on the ferroptosis of NMCMs. Results: In vivo, the mRNA and protein expression of CREG1 were significantly reduced in DOX-treated myocardium. CREG1 overexpression alleviated the myocardial damage induced by DOX, and CREG1 deficiency aggravated the DOX-induced cardiotoxicity. The abnormal increase in ferroptosis was shown in the DOX-treated heart tissues. CREG1 overexpression inhibited the ferroptosis, and CREG1 deficiency aggravated the ferroptosis induced by DOX. In vitro, the mRNA and protein of CREG1 was reduced in DOX-treated NMCMs. CREG1 overexpression reduced the ferroptosis of cardiomyocytes, CREG1 knockdown aggravated the ferroptosis of cardiomyocytes induced by DOX. Mechanically, CREG1 inhibited the mRNA and protein expression of pyruvate dehydrogenase kinase 4 (PDK4). The effect of CREG1 overexpression on ferroptosis of cardiomyocytes was reversed by PDK4 overexpression. Conclusion: CREG1 alleviated DOX-induced cardiotoxicity by inhibiting ferroptosis of cardiomyocytes. Our findings might help clarify new roles of CREG1 in the development of DOX-induced cardiotoxicity.

High glucose promotes benign prostatic hyperplasia by downregulating PDK4 expression

As men age, a growing number develop benign prostatic hyperplasia (BPH). According to previous research, diabetes may be a risk factor. Pyruvate dehydrogenase kinase 4 (PDK4) is closely related to glucose metabolism and plays a role in the onset and progression of numerous illnesses. This study aimed to determine the direct effects of high glucose environment on prostate epithelial cells, in particular by altering PDK4 expression levels. In this investigation, normal prostatic epithelial cells (RWPE-1) and human benign prostatic hyperplasia epithelial cells (BPH-1) were treated with 50 mM glucose to show the alteration of high glucose in prostate cells. PDK4-target siRNA, PDK4-expression plasmid were used to investigate the effects of PDK4. Rosiglitazone (RG), a PPARγ agonist, with the potential to up-regulate PDK4 expression was also used for treating prostate cells. The expression of PDK4 in human prostate samples was also analyzed. The effects of high glucose therapy on BPH-1 and RWPE-1 cells were demonstrated to enhance proliferation, epithelial-mesenchymal transition (EMT), suppress apoptosis, and down-regulate PDK4 expression. Additionally, diabetes-related BPH patients had reduced PDK4 expression. Following the application of PDK4-target siRNA, a comparable outcome was seen. The PDK4-expression plasmid therapy, however, produced the opposite results. RG with the ability to elevate PDK4 expression might be used to treat BPH. Changes in the metabolism of lipids and glucose may be the cause of these consequences. These findings showed that high glucose treatment might facilitate BPH development, and may be related to the down-regulation of PDK4. PDK4 might be a potential therapeutic target of BPH.

PDK4 facilitates fibroblast functions and diabetic wound healing through regulation of HIF-1α protein stability and gene expression.

Fibroblast activation disorder is one of the main pathogenic characteristics of diabetic wounds. Orchestrated fibroblast functions and myofibroblast differentiation are crucial for wound contracture and extracellular matrix (ECM) formation. Pyruvate dehydrogenase kinase 4 (PDK4), a key enzyme regulating energy metabolism, has been implicated in modulating fibroblast function, but its specific role in diabetic wounds remains poorly understood. In this study, we investigated the impact of PDK4 on diabetic wounds and its underlying mechanisms. To assess the effect of PDK4 on human dermal fibroblasts (HDFs), we conducted CCK-8, EdU proliferation assay, wound healing assay, transwell assay, flow cytometry, and western blot analyses. Metabolic shifts were analyzed using the Seahorse XF analyzer, while changes in metabolite expression were measured through LC-MS. Local recombinant PDK4 administration was implemented to evaluate its influence on wound healing in diabetic mice. Finally, we found that sufficient PDK4 expression is essential for a normal wound-healing process, while PDK4 is low expressed in diabetic wound tissues and fibroblasts. PDK4 promotes proliferation, migration, and myofibroblast differentiation of HDFs and accelerates wound healing in diabetic mice. Mechanistically, PDK4-induced metabolic reprogramming increases the level of succinate that inhibits PHD2 enzyme activity, thus leading to the stability of the HIF-1α protein, during which process the elevated HIF-1α mRNA by PDK4 is also indispensable. In conclusion, PDK4 promotes fibroblast functions through regulation of HIF-1α protein stability and gene expression. Local recombinant PDK4 administration accelerates wound healing in diabetic mice.

WTAP Mediated the N6-methyladenosine Modification of PDK4 to Regulate the Malignant Behaviors of Colorectal Cancer Cells In Vitro and In Vivo.

The role of WT1-associated protein (WTAP) in mediating the N6-methyladenosine (m6A) modification of pyruvate dehydrogenase kinase 4 (PDK4) in colorectal cancer (CRC) has been previously reported. This research manages to unveil the function and mechanism of WTAP mediating the m6A modification in CRC. Expressions of PDK4 and WTAP in CRC were assessed by bioinformatics analysis and verified by Western blot. After the transfection with short hairpin RNAs (shRNAs) for WTAP (shWTAP) and PDK4 (shPDK4) to manipulate the expressions of PDK4 and WTAP, the viability, proliferation, migration, invasion, and levels of m6A, PDK4 and WTAP in CRC cells were determined by cell counting kit-8 (CCK-8), colony formation, transwell, Western blot, or M6A-RNA immunoprecipitation (MeRIP)-qPCR assays. M6A binding sites in PDK4 were additionally predicted through bioinformatics analysis, and the interaction of PDK4 and WTAP was confirmed using an RNA pull-down assay. Tumor volume and weight in the constructed xenograft-tumor mouse model were recorded. PDK4 expression was low, yet WTAP and m6A expressions were high in CRC cells. WTAP bound with the m6A binding sites in PDK4. PDK4 silencing facilitated the viability, proliferation, migration and invasion, inhibited the expression of PDK4 in CRC cells, and accelerated the growth of xenografts in vivo. However, the depletion of WTAP4 exerted the opposite effects and further offset the impact of PDK4 silencing. WTAP mediates the m6A modification of PDK4 to regulate the malignant behaviors of CRC cells in vitro and in vivo.

Arginine methylation of PPP1CA by CARM1 regulates glucose metabolism and affects osteogenic differentiation and osteoclastic differentiation.

The imbalance between osteoblasts and osteoclasts may lead to osteoporosis. Osteoblasts and osteoclasts have different energy requirements, with aerobic glycolysis being the prominent metabolic feature of osteoblasts, while osteoclast differentiation and fusion are driven by oxidative phosphorylation. By polymerase chain reaction as well as Western blotting, we assayed coactivator-associated arginine methyltransferase 1 (CARM1) expression in bone tissue, the mouse precranial osteoblast cell line MC3T3-E1 and the mouse monocyte macrophage leukaemia cell line RAW264.7, and expression of related genes during osteogenic differentiation and osteoclast differentiation. Using gene overexpression (lentivirus) and loss-of-function approach (CRISPR/Cas9-mediated knockout) in vitro, we examined whether CARM1 regulates osteogenic differentiation and osteoblast differentiation by metabolic regulation. Transcriptomic assays and metabolomic assays were used to find the mechanism of action of CARM1. Furthermore, in vitro methylation assays were applied to clarify the arginine methylation site of PPP1CA by CARM1. We discovered that CARM1 reprogrammed glucose metabolism in osteoblasts and osteoclasts from oxidative phosphorylation to aerobic glycolysis, thereby promoting osteogenic differentiation and inhibiting osteoclastic differentiation. In vivo experiments revealed that CARM1 significantly decreased bone loss in osteoporosis model mice. Mechanistically, CARM1 methylated R23 of PPP1CA, affected the dephosphorylation of AKT-T450 and AMPK-T172, and increased the activities of phosphofructokinase-1 and pructose-2,6-biphosphatase3, causing an up-regulation of glycolytic flux. At the same time, as a transcriptional coactivator, CARM1 regulated the expression of pyruvate dehydrogenase kinase 3, which resulted in the inhibition of pyruvate dehydrogenase activity and inhibition of the tricarboxylic acid cycle, leading to a subsequent decrease in the flux of oxidative phosphorylation. These findings reveal for the first time the mechanism by which CARM1 affects both osteogenesis and osteoclast differentiation through metabolic regulation, which may represent a new feasible treatment strategy for osteoporosis.

Pyruvate Dehydrogenase Kinase 1 inhibition mediated oxidative phosphorylation enhancement in cartilage promotes osteoarthritis progression

Osteoarthritis (OA) is a common disease characterized by cartilage degradation. Growing evidence showed that glucose metabolism impacts joint homeostasis and an imbalance between glycolysis and oxidative phosphorylation (OXPHOS) may exacerbate OA progression, however, a definitive link is yet to be established. Here, we report that pyruvate metabolism and oxidative phosphorylation pathway is enriched in OA cartilage through gene set enrichment analysis (GSEA) and expression of Pyruvate Dehydrogenase Kinase 1 (PDK1), an enzyme that can phosphorylate Pyruvate Dehydrogenase (PDH), and inhibit pyruvate fluxes into the tricarboxylic acid (TCA) cycle and to OXPHOS, in articular cartilage is notably reduced through destabilization of medial meniscus (DMM). Moreover, by inhibiting PDK1, cartilage loss is markedly accelerated in DMM-induced OA through extracellular matrix (ECM) degradation and apoptosis of chondrocytes. These results indicate that PDK1 is involved in the progression of OA through accelerating cartilage matrix degradation and synovium inflammation to ameliorate cartilage degeneration.

Human Umbilical Cord Mesenchymal Stem Cells Protect against Renal Ischemia-Reperfusion Injury by Secreting Extracellular Vesicles Loaded with miR-148b-3p That Target Pyruvate Dehydrogenase Kinase 4 to Inhibit Endoplasmic Reticulum Stress at the Reperfusion Stages.

Renal ischemia-reperfusion (I/R) injury is a leading cause of acute kidney injury (AKI), with high mortality. Recent studies have reported that human umbilical cord mesenchymal stem cells (HucMSCs) play an important role in repairing organ and tissue injuries because of their unique characteristics. However, the potential of HucMSC extracellular vesicles (HucMSC-EVs) to promote the repair of renal tubular cells remains to be explored. This study found that HucMSC-EVs derived from HucMSCs played a protective role and were associated with kidney I/R injury. We found that miR-148b-3p in HucMSC-EVs had a protective effect against kidney I/R injury. HK-2 cells overexpressing miR-148b-3p were protected against I/R injury by inhibiting apoptosis. Next, the target mRNA of miR-148b-3p was predicted online, and the target mRNA, pyruvate dehydrogenase kinase 4 (PDK4), was identified and verified using dual luciferase. We discovered that I/R injury significantly increased endoplasmic reticulum (ER) stress, whereas siR-PDK4 inhibited these effects and protected against I/R injury. Interestingly, after administrating HucMSC-EVs to HK-2 cells, PDK4 expression and ER stress induced by I/R injury were significantly inhibited. HK-2 ingested miR-148b-3p from HucMSC-EVs, and its ER induced by I/R injury was significantly deregulated. This study suggests that HucMSC-EVs protect kidneys from I/R injury during the early I/R stage. These results suggest a new mechanism for HucMSC-EVs in treating AKI and provide a new treatment strategy for I/R injury.

A Conceptual Approach for Examining Effects of the Adolescent Bone Marrow Milieu on MSC Phenotype.

Children with bone fragility often exhibit elevated bone marrow lipid levels, which may affect mesenchymal stem cell (MSC) differentiation potential and ultimately bone strength via cell-autonomous and/or non-cell-autonomous factors. Here, we use standard co-culture techniques to study biological effects of bone marrow cell-derived secretome on MSC. Bone marrow was collected during routine orthopedic surgery, and the entire marrow cell preparation, with or without red blood cell (RBC) reduction, was plated at three different densities. Conditioned medium (secretome) was collected after 1, 3, and 7 days. ST2 cells, a murine MSC line, were then cultured in the secretomes. Exposure to the secretomes was associated with reductions of up to 62% in MSC MTT outcomes that depended on the duration of secretome development, as well as marrow cell plating density. Reduced MTT values were not associated with diminished cell number and viability assessed using Trypan Blue exclusion. Expression of pyruvate dehydrogenase kinase 4 was modestly elevated, and β-actin levels were transiently reduced in ST2 cells exposed to secretome formulations that had elicited maximal reductions in MTT outcomes. The findings from this study can inform the design of future experimental studies to examine contributions of cell-autonomous and non-cell-autonomous factors in the bone marrow to MSC differentiation potential, bone formation, and skeletal growth. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Preventative effect of TSPO ligands on mixed antibody-mediated rejection through a Mitochondria-mediated metabolic disorder

BackgroundImmune-mediated rejection was the major cause of graft dysfunction. Although the advances in immunosuppressive agents have markedly reduced the incidence of T-cell-mediated rejection after transplantation. However, the incidence of antibody-mediated rejection (AMR) remains high. Donor-specific antibodies (DSAs) were considered the major mediators of allograft loss. Previously, we showed that treatment with 18-kDa translocator protein (TSPO) ligands inhibited the differentiation and effector functions of T cells and reduced the rejection observed after allogeneic skin transplantation in mice. This study we further investigate the effect of TSPO ligands on B cells and DSAs production in the recipients of mixed-AMR model.MethodsIn vitro, we explored the effect of treatment with TSPO ligands on the activation, proliferation, and antibody production of B cells. Further, we established a heart-transplantation mixed-AMR model in rats. This model was treated with the TSPO ligands, FGIN1-27 or Ro5-4864, to investigate the role of ligands in preventing transplant rejection and DSAs production in vivo. As TSPO was the mitochondrial membrane transporters, we then investigated the TSPO ligands effect on mitochondrial-related metabolic ability of B cells as well as expression of downstream proteins.ResultsIn vitro studies, treatment with TSPO ligands inhibited the differentiation of B cells into CD138+CD27+ plasma cells; reduced antibodies, IgG and IgM, secretion of B cells; and suppressed the B cell activation and proliferation. In the mixed-AMR rat model, treatment with FGIN1-27 or Ro5-4864 attenuated DSA-mediated cardiac-allograft injury, prolonged graft survival, and reduced the numbers of B cells, including IgG+ secreting B cells, T cells and macrophages infiltrating in grafts. For the further mechanism exploration, treatment with TSPO ligands inhibited the metabolic ability of B cells by downregulating expression of pyruvate dehydrogenase kinase 1 and proteins in complexes I, II, and IV of the electron transport chain.ConclusionsWe clarified the mechanism of action of TSPO ligands on B-cell functions and provided new ideas and drug targets for the clinical treatment of postoperative AMR.

Promotive role of eukaryotic translation initiation factor 4A isoform 3 in ovarian cancer cell growth and aerobic glycolysis through the pyruvate dehydrogenase kinase 4 signaling.

Ovarian cancer (OC) represents one of the most detrimental gynecological malignancies. RNA-binding protein eukaryotic translation initiation factor 4A isoform 3 (EIF4A3) is well-regarded as a definitive oncogene that contributes to the development of multiple malignant tumors. This study sought to elucidate the molecular mechanism of EIF4A3 in OC growth and aerobic glycolysis by regulation of pyruvate dehydrogenase kinase 4 (PDK4) mRNA stability. We determined the EIF4A3 and PDK4 expression levels in OC cell lines and normal ovarian epithelial cells, and subsequently evaluated the cell viability and colony formation by cell counting kit-8 and colony formation assays. The degree of cell aerobic glycolysis was evaluated by measurements of lactic acid production, glucose intake, adenosine triphosphate level, extracellular oxygen consumption, and protein levels of pyruvate kinase isozymes M2 and hexokinase-2. Afterwards, we verified the binding of EIF4A3 and PDK4 mRNA via RNA immunoprecipitation, and determined the mRNA stability after actinomycin D treatment. Finally, a series of rescue experiments was performed with pcDNA3.1-PDK4. EIF4A3 and PDK4 were upregulated in OC cells. Silencing EIF4A3 obstructed cell proliferation and aerobic glycolysis, while the same was annulled by EIF4A3 overexpression. Mechanically, EIF4A3 could bind to PDK4 mRNA to stabilize its mRNA and upregulate its protein levels. PDK4 overexpression inverted the inhibitory role of silencing EIF4A3 in proliferation and aerobic glycolysis. Overall, our findings highlighted that EIF4A3 induced OC progression by stabilizing PDK4 mRNA.

Abstract 361: PDK4 is dispensable for PDAC chachexia

Abstract Cachexia is an involuntary weight loss and muscle wasting that affects up to 80% of advanced cancer patients. It is an independent prognostic marker for response to treatment and overall survival and accounts for 20% of cancer-associated deaths. Skeletal muscles of cachectic patients manifest metabolic abnormalities, notably increased dependence on lipids as a source of energy at the expense of glucose. Pyruvate Dehydrogenase Kinase 4 (PDK4) is upregulated in the muscles of patients and mice with cancer cachexia. PDK4 inhibits the enzyme responsible for the conversion of pyruvate to acetyl coenzyme A which is further oxidized in the tricarboxylic acid cycle. As a result, lipids become the major substrate for oxidative metabolism at the expense of glucose. Recent reports suggested that PDK4 is responsible for metabolic dysregulation in cachexia, proposing PDK4 as a potential drug target. Here, we hypothesized that the deletion of PDK4 would protect against muscle wasting in an orthotopic model of pancreatic ductal adenocarcinoma (PDAC) by countering metabolic abnormalities driven by PDK4. Methods: 50,000 KPC (LSL-KrasG12D:LSL-Trp53R172H:Pdx1-Cre) cells were injected into the pancreas of male PDK4 knockout mice or wild-type controls. For each genotype, a sham surgery group without implantation was included. Body weight was measured at baseline and later every other day starting from day 7 after implantation. Body composition, i.e., lean and fat mass, was assessed at baseline and then once a week using EchoMRI. In-vivo muscle force production measured by the Aurora Scientific system and locomotor activity measured by Auto-Track were used as readouts of muscle function. Tissue was harvested at early and late stages of disease progression representing early and late cachexia. All measurements were normalized to initial body weight. Two-way ANOVA or Student’s t-test was used for statistical analysis as appropriate. Results: Consistent with previous results, PDAC cachexia induced an increase in the expression of PDK4 in muscle both at mRNA and protein. Expression of other members of the PDK family did not change with cachexia or genotype. Mice with KPC tumors produced less muscle force (-7%, p = 0.03), walked less distance (-30%), and had a longer resting time (17%), p &amp;lt; 0.05 without difference between genotypes. At euthanasia, both genotypes had similar tumor burdens (p &amp;gt;0.9) and exhibited similar degrees of muscle (-13 and -17%, p &amp;lt; 0.0001) and adipose tissue wasting (-50%, p &amp;lt; 0.0001). Deletion of PDK4 did not protect against induction of the muscle-specific E3 ubiquitin ligases in PDAC: FBXO32 and TRIM63 (10.7 fold and 13.6 fold on average, respectively, p &amp;lt; 0.01), molecular hallmarks of muscle atrophy. Overall, our work shows that the knockout of PDK4 does not protect against the development of PDAC cachexia suggesting that PDK4 might be a marker of cachexia but not necessarily a driving mechanism. Citation Format: Omnia U. Gaafer, Joseph Rupert, Joshua Huot, Daenique Jengelley, Andrea Bonetto, Leonidas Koniaris, Teresa Zimmers. PDK4 is dispensable for PDAC chachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 361.

Pyruvate Dehydrogenase Kinase 4 Deficiency Increases Tumorigenesis in a Murine Model of Bladder Cancer.

Pyruvate dehydrogenase kinase 4 (PDK4) is a mitochondrial isozyme in the PDK family (PDK1-4) partially responsible for phosphorylation of pyruvate dehydrogenase (PDH). Phosphorylation of PDH is thought to result in a pro-proliferative shift in metabolism that sustains growth of cancer cells. Previous data from our lab indicate the pan-PDK inhibitor dichloroacetate (DCA) or acute genetic knockdown of PDK4 blocks proliferation of bladder cancer (BCa) cells. The goal of this study was to determine the role of PDK4 in an in vivo BCa model, with the hypothesis that genetic depletion of PDK4 would impair formation of BCa. PDK4-/- or WT animals were exposed to N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN) for 16 weeks, and tumors were allowed to develop for up to 7 additional weeks. PDK4-/- mice had significantly larger tumors at later time points. When animals were treated with cisplatin, PDK4-/- animals still had larger tumors than WT mice. PDK4 expression was assessed in human tissue and in mice. WT mice lost expression of PDK4 as tumors became muscle-invasive. Similar results were observed in human samples, wherein tumors had less expression of PDK4 than benign tissue. In summary, PDK4 has a complex, multifunctional role in BCa and may represent an underrecognized tumor suppressor.