The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat

Function of eEF-1γ in the nucleus in response to insulin in hepatocellular carcinoma cells

Insulin promotes HepG2 cell proliferation by inducing phosphorylation of the pyruvate dehydrogenase E1α (PDHA1) subunit at Ser293, a mechanism distinct from normal liver tissue. This study investigates how phosphorylated PDHA1 drives hepatocellular carcinoma cell proliferation. We identified eukaryotic elongation factor-1γ (eEF-1γ) as a key binding protein interacting with p-PDHA1 in response to insulin, facilitating their nuclear translocation. Silencing eEF-1γ (si-eEF-1γ) significantly reduced p-PDHA1 and PKM2 levels, highlighting eEF-1γ's role in stabilizing these proteins. Additionally, eEF-1γ interacts with ATP-citrate lyase (ACL) and p300 acetyltransferase, and its knockdown decreased histone acetylation at H3K9/14, H3K18, and H3K27, along with RBP4 expression. Chromatin immunoprecipitation PCR (ChIP-PCR) confirmed eEF-1γ association with RBP4 promoter. Functionally, si-eEF-1γ reduced cell proliferation and deceased c-Myc and cyclin D1 protein levels. It also suppressed migration, and altered epithelial-mesenchymal transition (EMT) markers, increasing E-cadherin while reducing ZEB1, snail1, vimentin, and N-cadherin levels. Similarly, RBP4 knockdown with siRNA diminished cell proliferation and migration. In vivo, eEF-1γ knockdown in 4T1 xenografts using siRNA led to reduced tumor mass. These findings highlight eEF-1γ as a crucial driver of insulin-induced tumor progression and suggest its potential as a therapeutic target in hepatocellular carcinoma.

Mechanistic considerations linking SARS-CoV-2 infection, inflammation, and the loss of immune tolerance

The immune response to SARS-CoV-2 has been implicated in the onset of multiple, seemingly unrelated, autoimmune diseases. The immune response to SARS-CoV-2 has also been implicated in the unmasking and/or production of multiple autoantibodies, even in the absence of clinical disease. Despite such data, it remains unclear whether antibodies targeting antiviral signaling proteins and mitochondrial antigens reflect bystander activation or alternatively contribute to de novo viral immune escape mechanisms. With these comments in mind, a variety of professional antibody presenting cells and including lung resident macrophages of COVID-19 infected patients are impacted and dependent on the uptake of antibody-opsonized virus by Fcγ receptors; yet infection is aborted via antibody-dependent effector mechanisms or pyroptosis, possibly leading to autoantibody production, and autoinflammatory manifestations, respectively. TRIM21/Ro52, a cytosolic E3-ubiquitin ligase with an Fc-gamma receptor domain, functions as an intracytoplasmic antibody receptor, directs immune complexes binding virions but also autoantigens to autophagy. During autophagy, Ig-virions-TRIM21/Ro52-autoantigens complexes bind directly to class II human leukocyte antigen in lysosomal compartment, leading to subsequent presentation on the cell surface. This process favors the development of a specific humoral immune response but has the potential to lead to loss of tolerance. Interestingly, TRIM21/Ro52 can also contribute to pyroptosis. We propose that TRIM21/Ro52 is well-placed at the crossroad between the inflammatory response and clinical autoimmunity.

Renometabolic disorder in experimental rat model of polycystic ovarian syndrome is reversed by acetate-mediated inhibition of pyruvate dehydrogenase kinase 4

BACKGROUND

Chronic Kidney disorders is a global public health problem, including in women with polycystic ovarian syndrome (PCOS), and is characterized by renal fibrosis, nephrotoxicity and glomerulonephritis, which increases the possibility of renal failure and organ transplant. Pyruvate dehydrogenase kinase 4 (PDK4) has been implicated in mitochondria dysfunction, contributing to metabolic dysregulation in different organs, including kidney. Studies have shown that short chain fatty acids, particularly acetate, alleviates metabolic alterations in experimental models. Hence, the present study investigated the therapeutic potential of acetate on renometabolic disorders associated with experimental PCOS model. The study in addition elucidates the probable involvement of PDK4 in PCOS-associated renometabolic disorders.

METHODS

Eight-week-old nulliparous female Wistar rats were randomly allotted into four groups (n = 5). Letrozole (1 mg/kg bw) was used to induce PCOS for 3 weeks. Thereafter, acetate (200 mg/kg bw) was administered for 6 weeks, uninterruptedly. Biochemical parameters from the plasma and renal tissue, as well as histology of ovaries were performed with appropriate methods.

RESULTS

Experimental PCOS rats were characterized with elevated circulating testosterone and the presence of multiple ovarian cysts. In addition, rat with PCOS also manifested insulin resistance, increased plasma urea and creatinine levels, increased renal Gamma glutamyl transferase (GGT), malondialdehyde (MDA), Nuclear factor -kappa B (NF-kB), Tumor necrosis factor -alpha (TNF-a), Transforming growth factor -beta 1 (TGF-B1), caspase-6, Histone deacetylase 2 (HDAC2), while a decrease in glucose-6 phosphate dehydrogenase (G6PD), reduced glutathione (GSH), renal nitric oxide (NO) and endothelial nitric oxide synthesis (eNOS), when compared with animals in the control group. These were associated with elevated level of PDK4 in the renal tissue. However, administration of acetate ameliorates these renal/metabolic abnormalities.

CONCLUSION

Altogether, the results from the present study suggests that acetate ameliorates renal dysfunction in PCOS via downregulation of PDK4.

Sarcosine sensitizes lung adenocarcinoma to chemotherapy by dual activation of ferroptosis via PDK4/PDHA1 signaling and NMDAR-mediated iron export

BACKGROUND

Ferroptosis, a regulated cell death driven by iron-dependent lipid peroxidation, is associated with chemoresistance in lung adenocarcinoma (LUAD). This study aims to investigate the role of sarcosine in ferroptosis and its underlying mechanisms.

METHODS

An RSL3-induced ferroptosis model was used to screen a library of 889 human endogenous metabolites and metabolomic profiling was harnessed to identify metabolites associated with ferroptosis. Cell viability, lipid-reactive oxygen species (ROS), ferrous iron, malondialdehyde (MDA), and mitochondrial integrity were assessed to evaluate sarcosine's effects on ferroptosis. Metabolic fate was studied using 15N-labeled sarcosine. Next, we used untargeted metabolomic profiling and next-generation sequencing to dissect metabolic and transcriptomic changes upon sarcosine supplementation. The effects of sarcosine on ferroptosis and chemotherapy were further validated in patient-derived organoids (PDOs), xenograft models, and LUAD tissues.

RESULTS

Sarcosine emerged as a potent ferroptosis inducer in the metabolic library screening, which was further confirmed via cell viability, lipid-ROS, ferrous iron, and MDA measurements. Metabolic flux analysis showed limited conversion of sarcosine to other metabolites in LUAD cells, while untargeted metabolomic profiling and seahorse assays indicated a metabolic shift from glycolysis to oxidative phosphorylation. Sarcosine enhanced pyruvate dehydrogenase activity to generate more ROS by interacting with PDK4, reducing PDHA1 phosphorylation. As a co-activator of N-methyl-D-aspartate receptor (NMDAR), sarcosine also exerted its pro-ferroptosis effect via regulating ferrous export through the NMDAR/MXD3/SLC40A1 axis. Given the significance of ferroptosis in chemotherapy, we validated that sarcosine enhanced the sensitization of cisplatin by promoting ferroptosis in LUAD cells, PDOs, and xenograft models.

CONCLUSION

Sarcosine promotes ferroptosis and enhances chemosensitivity, suggesting its potential as a therapeutic agent in treating LUAD.

The role of pyruvate dehydrogenase in the lifespan determination of daphnids

The general association between longevity and energy metabolism has been well-documented for some time, yet the specific metabolic processes that regulate longevity remain largely unexplored. In contrast to the common active swimming daphnids (e.g., Daphnia sinensis), Simocephalus vetulus is notable for being sedentary and having a lower metabolic rate, yet it has a longer lifespan than D. sinensis. In this study, metabolomic analysis and drug validation experiments are employed to demonstrate that the lower pyruvate dehydrogenase (PDH) activity reduces the locomotor performance of S. vetulus and to identify PDH activity as a regulator of the lifespan of daphnids. Inhibition of PDH activity in daphnids by CPI-613 attenuates its ATP supply and locomotor performance but significantly induces longevity. The study also determines that the invertebrate neurotransmitter octopamine and temperature have a significant impact on PDH activity and modulate daphnids lifespan. And when the effects of temperature and octopamine on PDH activity are counteracted by inhibitors or agonists, the impact on lifespan becomes ineffective. These results support an important role for PDH in lifespan regulation and locomotor performance in daphnids and provide insights into the metabolic regulation of lifespan.

DLAT activates EMT to promote HCC metastasis by regulating GLUT1-mediated aerobic glycolysis

BACKGROUND

Metabolic reprogramming is a hallmark of hepatocellular carcinoma (HCC) progression, driving aberrant cellular processes in response to pathological stimuli. While dihydrolipoyl transacetylase (DLAT) has been implicated in the development of various cancers, its specific role and underlying mechanisms in HCC remain unclear. This study aimed to investigate the expression, function, and mechanistic impact of DLAT in HCC.

METHODS

A comprehensive analysis was conducted using RNA sequencing data, tissue microarrays, in vitro and in vivo functional assays, and mechanistic studies to evaluate DLAT expression, its functional role in tumor progression, and associated molecular pathways in HCC.

RESULTS

Our study revealed a significant upregulation of DLAT expression in HCC, which was linked to a poor prognosis. Furthermore, we discovered that DLAT facilitated tumor metastasis by driving metabolic reprogramming in HCC cells. Mechanistically, DLAT was found to enhance glucose transporter 1 (GLUT1) expression via H3K18 acetylation, thereby promoting aerobic glycolysis and epithelial-to-mesenchymal transition (EMT), which subsequently augmented metastasis of HCC both in vitro and in vivo. Finally, we confirmed a positive correlation between DLAT and GLUT1 expression in HCC tissues.

CONCLUSIONS

These findings establish DLAT as a key regulator in HCC progression and suggest its potential as a promising predictive biomarker and therapeutic target for improving HCC diagnosis and treatment.

Metabolic dysregulation in myelodysplastic neoplasm: impact on pathogenesis and potential therapeutic targets

Despite significant advancements in the research of the pathogenesis mechanisms of Myelodysplastic Neoplasm (MDS) in recent years, there are still many gaps to fill. The advancement of metabolomics studies has led to a research booming in clarifying the impact of metabolic abnormalities during the pathogenesis of MDS. The present review primarily focuses on the dysregulated metabolic pathways, exploring the influences on the pathogenesis of MDS and their roles during the course of the disease. Furthermore, we discuss the potential of relevant metabolic pathways as therapeutic targets, along with the latest metabolic-related treatment drugs and approaches.

Comparative proteomic analysis of male and female androgenetic alopecia: elucidating gender-specific molecular patterns

This study presents a comprehensive comparative proteomic analysis aimed at elucidating the molecular mechanisms underlying male androgenetic alopecia (AGA) and female AGA. Scalp samples from both male AGA and female AGA patients, along with their respective normal controls, were subjected to proteomic analysis, followed by bioinformatics investigations. Our findings revealed distinct proteomic profiles between male AGA and female AGA, with a total of 68 differentially expressed proteins identified in male AGA and 84 in female AGA. Among these, specific proteins were altered in male AGA and female AGA, highlighting the sex-specific molecular pathways involved in the pathogenesis of pattern hair loss. Protein-protein interaction network analyses further delineated the most impacted biological processes, including cytoskeleton organization, stress response, and metabolic pathways, with particular emphasis on the differing altered stress responses and metabolic states associated with hair loss between sexes. Our study not only uncovered the complex molecular landscape of male AGA and female AGA but also identified potential biomarkers and therapeutic targets, offering new insights into the sex-specific pathogenesis of pattern hair loss.

The human touch: Utilizing AlphaFold 3 to analyze structures of endogenous metabolons

Computational structural biology aims to accurately predict biomolecular complexes with AlphaFold 3 spearheading the field. However, challenges loom for structural analysis, especially when complex assemblies such as the pyruvate dehydrogenase complex (PDHc), which catalyzes the link reaction in cellular respiration, are studied. PDHc subcomplexes are challenging to predict, particularly interactions involving weaker, lower-affinity subcomplexes. Supervised modeling, i.e., integrative structural biology, will continue to play a role in fine-tuning this type of prediction (e.g., removing clashes, rebuilding loops/disordered regions, and redocking interfaces). 3D analysis of endogenous metabolic complexes continues to require, in addition to AI, precise and multi-faceted interrogation methods.

Masks As a New Hotspot for Antibiotic Resistance Gene Spread: Reveal the Contribution of Atmospheric Pollutants and Potential Risks

The consumption of disposable surgical masks (DSMs) considerably increased during the coronavirus pandemic in 2019. Herein, we explored the spread of antibiotic resistance genes (ARGs) and the potential risks of antibiotic resistant bacteria (ARB) on DSMs. At environmentally relevant concentrations, the conjugate transfer frequency (CTF) of ARGs increased by 1.34-2.37 folds by 20 μg/m3 of atmospheric water-soluble inorganic ions (WSIIs), and it increased by 2.62-2.86 folds by 80 ng/m3 of polycyclic aromatic hydrocarbons (PAHs). Total suspended particulates (TSP) further promoted the CTF in combination with WSIIs or PAHs. Under WSII and PAH exposure, gene expression levels related to oxidative stress, cell membrane, and the adenosine triphosphate (ATP) were upregulated. WSIIs predominantly induced cellular contact, while PAHs triggered ATP formation and membrane damage. Molecular dynamics simulations showed that WSIIs and PAHs reduced membrane lipid fluidity and increased membrane permeability through interactions with the phosphatidylcholine bilayer. DSM filtering performance decreased, and the CTF of ARGs increased with the wearing time. The gut simulator test showed that ARB disrupted the human gut microbial community and increased total ARG abundance but did not change the ARG abundance carried by ARB themselves. A mathematical model showed that long-term WSII and PAH exposure accelerated ARG dissemination in DSMs.

Natural Products and Derivatives Targeting Metabolic Reprogramming in Colorectal Cancer: A Comprehensive Review

Metabolic reprogramming is a critical pathogenesis of colorectal cancer (CRC), referring to metabolic disorders that cancer cells make in response to the stimulating pressure. Metabolic reprogramming induces changes in genetic material and promotes CRC progression and has been proven to be an efficient target of CRC. As natural products have garnered interest due to notable pharmacological effects and potential in counteracting chemoresistance, an increasing body of research is delving into the impact of these natural products on the metabolic reprogramming associated with CRC. In this review, we collected published data from the Web of Science and PubMed, covering the period from January 1980 to October 2023. This article focuses on five central facets of metabolic alterations in cancer cells, glucose metabolism, mitochondrial oxidative phosphorylation (OXPHOS), amino acid metabolism, fatty acid synthesis, and nucleotide metabolism, to provide an overview of recent advancements in natural product interventions targeting metabolic reprogramming in CRC. Our analysis underscores the potential of natural products in disrupting the metabolic pathways of CRC, suggesting promising therapeutic targets for CRC and expanding treatment options for metabolic-associated ailments.

The pyruvate dehydrogenase complex at the epigenetic crossroads of acetylation and lactylation

The pyruvate dehydrogenase complex (PDC) is remarkable for its size and structure as well as for its physiological and pathological importance. Its canonical location is in the mitochondrial matrix, where it primes the tricarboxylic acid (TCA) cycle by decarboxylating glycolytically-derived pyruvate to acetyl-CoA. Less well appreciated is its role in helping to shape the epigenetic landscape, from early development throughout mammalian life by its ability to "moonlight" in the nucleus, with major repercussions for human healthspan and lifespan. The PDC's influence on two crucial modifiers of the epigenome, acetylation and lactylation, is the focus of this brief review.

Single-cell transcriptomics across 2,534 microbial species reveals functional heterogeneity in the rumen microbiome

Deciphering the activity of individual microbes within complex communities and environments remains a challenge. Here we describe the development of microbiome single-cell transcriptomics using droplet-based single-cell RNA sequencing and pangenome-based computational analysis to characterize the functional heterogeneity of the rumen microbiome. We generated a microbial genome database (the Bovine Gastro Microbial Genome Map) as a functional reference map for the construction of a single-cell transcriptomic atlas of the rumen microbiome. The atlas includes 174,531 microbial cells and 2,534 species, of which 172 are core active species grouped into 12 functional clusters. We detected single-cell-level functional roles, including a key role for Basfia succiniciproducens in the carbohydrate metabolic niche of the rumen microbiome. Furthermore, we explored functional heterogeneity and reveal metabolic niche trajectories driven by biofilm formation pathway genes within B. succiniciproducens. Our results provide a resource for studying the rumen microbiome and illustrate the diverse functions of individual microbial cells that drive their ecological niche stability or adaptation within the ecosystem.

Pyruvate dehydrogenase complex deficiency masked by septic shock-induced lactic acidosis: a case report

Pyruvate dehydrogenase complex (PDHC) deficiency is a common genetic disorder leading to lactic acidosis, which can also result from several nongenetic conditions, such as septic shock. The present study reports a case of PDHC deficiency masked by septic shock-induced lactic acidosis. This case involved a 16-year-old adolescent with poor exercise tolerance compared with his peers, and no underlying diseases. The disease onset was characterized by cough, fever, and dyspnea, with hypotension and elevated lactate levels, which indicated septic shock. However, severe hypoglycemia and lactic acidosis persisted despite resolution of a pulmonary infection and correction of septic shock, requiring continuous intravenous infusion of 50% glucose. Although the patient did not experience acute kidney injury and had normal urine output, continuous renal replacement therapy was used to regulate the internal environment owing to the severity of the acidosis. The diagnosis of PDHC deficiency was considered on the basis of the persistent hypoglycemia and hyperlactatemia, before genetic mutation testing was completed. The clinical thinking process required a rich accumulation of pathophysiological knowledge. This article reports a case of PDHC deficiency masked by septic shock-induced lactic acidosis to raise awareness of the disease and avoid misdiagnosis and missed diagnosis.

The alpha-ketoacid dehydrogenase complexes of Drosophila melanogaster

The conserved family of alpha-ketoacid dehydrogenase complexes (AKDHCs) catalyze essential reactions in central metabolism and their dysregulation is implicated in several human diseases. Drosophila melanogaster provides an excellent model system to study the genetics and functions of these complexes. However, a systematic account of Drosophila AKDHCs and their composition has been lacking. Here, I identify and classify the genes encoding all Drosophila AKDHC subunits, update their functional annotations and integrate this work into the FlyBase database.

Changes in cuproptosis-related gene expression in periodontitis: An integrated bioinformatic analysis

Periodontitis causes inflammatory destruction of tooth-supporting tissues; however, the complex mechanism underlying its etiology remains unclear. Cuproptosis is a type of cell death caused by an imbalance in intracellular copper homeostasis that leads to excess copper. However, changes in the expression and biological function of cuproptosis-related genes (CRGs) in periodontitis are not yet fully understood. This study investigated the comprehensive effects of differentially expressed CRGs (DE-CRGs) on periodontitis via bioinformatic analysis. Nine DE-CRGs were discovered using normal and periodontitis gingival samples, and single-cell RNA sequencing data were analyzed to identify them changes in diverse cell clusters. We then detected the correlation between DE-CRGs and immune infiltration, immune factors, mitochondrial dysfunction, diagnostic efficacy, and predicted drugs. Moreover, changes of DE-CRG in whole periodontitis tissue and a human gingival fibroblast cell line (HGF-1) were confirmed and copper content changes in HGF-1 cells were investigated. Most DE-CRG expression trends were reversed between the periodontal tissues and cell clusters, which may be related to the proportion of cell clusters changes caused periodontitis. Furthermore, most DE-CRG trends in periodontitis cell clusters were inconsistent with the effects of cuproptosis. In HGF-1 cells treated with Porphyromonas gingivalis lipopolysaccharide (Pg-LPS), the intracellular copper content increased by more than threefold, indicating that although some periodontitis cells had excess copper, the amount may not have been sufficient to trigger cuproptosis. Additionally, DE-CRGs were closely associated with multiple biological functions, antibiotic drugs, and natural herbal medicines. Our findings may provide an overview of DE-CRGs in the pathogenesis and treatment of periodontitis.

Antifungal effects of carvacrol, the main volatile compound in Origanum vulgare L. essential oil, against Aspergillus flavus in postharvest wheat

Plant volatile organic compounds (VOCs) with antimicrobial activity could potentially be extremely useful fumigants to prevent and control the fungal decay of agricultural products postharvest. In this study, antifungal effects of volatile compounds in essential oils extracted from Origanum vulgare L. against Aspergillus flavus growth were investigated using transcriptomic and biochemical analyses. Carvacrol was identified as the major volatile constituent of the Origanum vulgare L. essential oil, accounting for 66.01 % of the total content. The minimum inhibitory concentrations of carvacrol were 0.071 and 0.18 μL/mL in gas-phase fumigation and liquid contact, respectively. Fumigation with 0.60 μL/mL of carvacrol could completely inhibit A. flavus proliferation in wheat grains with 20 % moisture, showing its potential as a biofumigant. Scanning electron microscopy revealed that carvacrol treatment caused morphological deformation of A. flavus mycelia, and the resulting increased electrolyte leakage indicates damage to the plasma membrane. Confocal laser scanning microscopy confirmed that the carvacrol treatment caused a decrease in mitochondrial membrane potential, reactive oxygen species accumulation, and DNA damage. Transcriptome analysis revealed that differentially expressed genes were mainly associated with fatty acid degradation, autophagy, peroxisomes, the tricarboxylic acid cycle, oxidative phosphorylation, and DNA replication in A. flavus mycelia exposed to carvacrol. Biochemical analyses of hydrogen peroxide and superoxide anion content, and catalase, superoxide dismutase, and glutathione S-transferase activities showed that carvacrol induced oxidative stress in A. flavus, which agreed with the transcriptome results. In summary, this study provides an experimental basis for the use of carvacrol as a promising biofumigant for the prevention of A. flavus contamination during postharvest grain storage.

Clinical physiology and pharmacology of GSTZ1/MAAI

Herein I summarize the physiological chemistry and pharmacology of the bifunctional enzyme glutathione transferase zeta 1 (GSTZ1)/ maleylacetoacetate isomerase (MAAI) relevant to human physiology, drug metabolism and disease. MAAI is integral to the catabolism of the amino acids phenylalanine and tyrosine. Genetic or pharmacological inhibition of MAAI can be pathological in animals. However, to date, no clinical disease consequences are unequivocally attributable to inborn errors of this enzyme. MAAI is identical to the zeta 1 family isoform of GST, which biotransforms the investigational drug dichloroacetate (DCA) to the endogenous compound glyoxylate. DCA is a mechanism-based inhibitor of GSTZ1 that significantly reduces its rate of metabolism and increases accumulation of potentially harmful tyrosine intermediates and of the heme precursor δ-aminolevulinic acid (δ-ALA). GSTZ1 is most abundant in rodent and human liver, with its concentration several fold higher in cytoplasm than in mitochondria. Its activity and protein expression are dependent on the age of the host and the intracellular level of chloride ions. Gene association studies have linked GSTZ1 or its protein product to various physiological traits and pathologies. Haplotype variations in GSTZ1 influence the rate of DCA metabolism, enabling a genotyping strategy to allow potentially safe, precision-based drug dosing in clinical trials.

Crystal structure of histone deacetylase 6 complexed with (R)-lipoic acid, an essential cofactor in central carbon metabolism

The enzyme cofactor (R)-lipoic acid plays a critical role in central carbon metabolism due to its catalytic function in the generation of acetyl-CoA, which links glycolysis with the tricarboxylic acid cycle. This cofactor is also essential for the generation of succinyl CoA within the tricarboxylic acid cycle. However, the biological functions of (R)-lipoic acid extend beyond metabolism owing to its facile redox chemistry. Most recently, the reduced form of (R)-lipoic acid, (R)-dihydrolipoic acid, has been shown to inhibit histone deacetylases (HDACs) with selectivity for the inhibition of HDAC6. Here, we report the 2.4 Å-resolution X-ray crystal structure of the complex between (R)-dihydrolipoic acid and HDAC6 catalytic domain 2 from Danio rerio, and we report a dissociation constant (KD) of 350 nM for this complex as determined by isothermal titration calorimetry. The crystal structure illuminates key affinity determinants in the enzyme active site, including thiolate-Zn2+ coordination and S-π interactions in the F583-F643 aromatic crevice. This study provides the first visualization of the connection between HDAC function and the biological response to oxidative stress: the dithiol moiety of (R)-dihydrolipoic acid can serve as a redox-regulated pharmacophore capable of simultaneously targeting the catalytic Zn2+ ion and the aromatic crevice in the active site of HDAC6.

Glutathionylation of pyruvate dehydrogenase complex E2 and inflammatory cytokine production during acute inflammation are magnified by mitochondrial oxidative stress

Lipopolysaccharide (LPS) is a known inducer of inflammatory signaling which triggers generation of reactive oxygen species (ROS) and cell death in responsive cells like THP-1 promonocytes and freshly isolated human monocytes. A key LPS-responsive metabolic pivot point is the 9 MDa mitochondrial pyruvate dehydrogenase complex (PDC), which provides pyruvate dehydrogenase (E1), lipoamide-linked transacetylase (E2) and lipoamide dehydrogenase (E3) activities to produce acetyl-CoA from pyruvate. While phosphorylation-dependent decreases in PDC activity following LPS treatment or sepsis have been deeply investigated, redox-linked processes have received less attention. Data presented here demonstrate that LPS-induced reversible oxidation within PDC occurs in PDCE2 in both THP-1 cells and primary human monocytes. Knockout of PDCE2 by CRISPR and expression of FLAG-tagged PDCE2 in THP-1 cells demonstrated that LPS-induced glutathionylation is associated with wild type PDCE2 but not mutant protein lacking the lipoamide-linking lysine residues. Moreover, the mitochondrially-targeted electrophile MitoCDNB, which impairs both glutathione- and thioredoxin-based reductase systems, elevates ROS similar to LPS but does not cause PDCE2 glutathionylation. However, LPS and MitoCDNB together are highly synergistic for PDCE2 glutathionylation, ROS production, and cell death. Surprisingly, the two treatments together had differential effects on cytokine production; pro-inflammatory IL-1β production was enhanced by the co-treatment, while IL-10, an important anti-inflammatory cytokine, dropped precipitously compared to LPS treatment alone. This new information may expand opportunities to understand and modulate PDC redox status and activity and improve the outcomes of pathological inflammation.

Epilepsy: Mitochondrial connections to the 'Sacred' disease

Over 65 million people suffer from recurrent, unprovoked seizures. The lack of validated biomarkers specific for myriad forms of epilepsy makes diagnosis challenging. Diagnosis and monitoring of childhood epilepsy add to the need for non-invasive biomarkers, especially when evaluating antiseizure medications. Although underlying mechanisms of epileptogenesis are not fully understood, evidence for mitochondrial involvement is substantial. Seizures affect 35%-60% of patients diagnosed with mitochondrial diseases. Mitochondrial dysfunction is pathophysiological in various epilepsies, including those of non-mitochondrial origin. Decreased ATP production caused by malfunctioning brain cell mitochondria leads to altered neuronal bioenergetics, metabolism and neurological complications, including seizures. Iron-dependent lipid peroxidation initiates ferroptosis, a cell death pathway that aligns with altered mitochondrial bioenergetics, metabolism and morphology found in neurodegenerative diseases (NDDs). Studies in mouse genetic models with seizure phenotypes where the function of an essential selenoprotein (GPX4) is targeted suggest roles for ferroptosis in epilepsy. GPX4 is pivotal in NDDs, where selenium protects interneurons from ferroptosis. Selenium is an essential central nervous system micronutrient and trace element. Low serum concentrations of selenium and other trace elements and minerals, including iron, are noted in diagnosing childhood epilepsy. Selenium supplements alleviate intractable seizures in children with reduced GPX activity. Copper and cuproptosis, like iron and ferroptosis, link to mitochondria and NDDs. Connecting these mechanistic pathways to selenoproteins provides new insights into treating seizures, pointing to using medicines including prodrugs of lipoic acid to treat epilepsy and to potential alternative therapeutic approaches including transcranial magnetic stimulation (transcranial), photobiomodulation and vagus nerve stimulation.

Crystal Structure of Histone Deacetylase 6 Complexed with ( R )-Lipoic Acid, an Essential Cofactor in Central Carbon Metabolism

The enzyme cofactor ( R )-lipoic acid plays a critical role in central carbon metabolism due to its catalytic function in the generation of acetyl-CoA, which links glycolysis with the tricarboxylic acid cycle. This cofactor is also essential for the generation of succinyl CoA within the tricarboxylic acid cycle. However, the biological functions of ( R )-lipoic acid extend beyond metabolism owing to its facile redox chemistry. Most recently, the reduced form of ( R )-lipoic acid, ( R )-dihydrolipoic acid, has been shown to inhibit histone deacetylases (HDACs) with selectivity for the inhibition of HDAC6. Here, we report the 2.4 Å-resolution X-ray crystal structure of the HDAC6-( R )-dihydrolipoic acid complex, and we report a dissociation constant (K D ) of 350 nM for this complex as determined by isothermal titration calorimetry. The crystal structure illuminates key affinity determinants in the enzyme active site, including thiolate-Zn 2+ coordination and S-π interactions in the F583-F643 aromatic crevice. This study provides the first visualization of the connection between HDAC function and the biological response to oxidative stress: the dithiol moiety of ( R )-dihydrolipoic acid can serve as a redox-regulated pharmacophore capable of simultaneously targeting the catalytic Zn 2+ ion and the aromatic crevice in the active site of HDAC6.

Contribution of carbohydrate-related metabolism in Herpesvirus infections

Human herpesviruses are enveloped viruses with double-stranded linear DNA genomes highly prevalent in the human population. These viruses are subdivided into three subfamilies, namely alphaherpesvirinae (herpes simplex virus type 1, HSV-1; herpes simplex virus type 2, HSV-2; and varicella-zoster virus, VZV), betaherpesvirinae (human cytomegalovirus, HCMV; human herpesvirus 6, HHV-6; and human herpesvirus 7, HHV-7) and gammaherpesvirinae (Epstein-Barr virus, EBV; and Kaposi's sarcoma-associated herpesvirus, KSHV). Besides encoding numerous molecular determinants to evade the host antiviral responses, these viruses also modulate cellular metabolic processes to promote their replication. Here, we review and discuss existing studies describing an interplay between carbohydrate metabolism and the replication cycle of herpesviruses, altogether highlighting potentially new molecular targets based on these interactions that could be used to block herpesvirus infections.