Sesamol Supplementation Mitigates Isoproterenol-Induced Cardiac Toxicity in Rats by Stabilizing Cardiac Mitochondrial and Lysosomal Enzymes

The current investigation was intended to evaluate the antimyocardial ischemic effects of sesamol on lactate dehydrogenase (LDH) isoenzymes, DNA damage, and mitochondrial and lysosomal enzyme activities in isoproterenol (ISO)-induced myocardial infarction (MI) in male albino Wistar strain rats. Rats that received ISO (85 mg/kg body weight (B.W) subcutaneously) for the first 2 consecutive days showed significant reduction in the activities of tricarboxylic acid (TCA) cycle enzymes (isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, malate dehydrogenase, and succinate dehydrogenase) and respiratory chain enzymes (cytochrome c oxidase and nicotinamide adenine dinucleotide hydrogen (NADH) dehydrogenase) in the heart mitochondria. The activities of the lysosomal enzymes (α-and β-glucosidases, α and β-galactosidases, β-glucuronidase and β-N-acetyl glucosaminidase and cathepsin-B and cathepsin-D) were increased significantly in the heart homogenate of ISO-induced MI rats. ISO injection also increased the % of tail DNA, tail length, and tail moment and decreased the % of head DNA. Pretreatment with sesamol (50 mg/kg B.W) every day for a period of 9 days prevented the above abnormalities induced by ISO. In conclusion, it can be inferred that administration of sesamol has a potent beneficial role against ISO-induced damage to the mitochondria, lysosomes, and DNA, thereby preventing MI.

TGF-β signaling suppresses TCA cycle metabolism in renal cancer

ABSTRACTThe Warburg effect is one of most-well studied metabolic phenomenon in cancer cells. For the most part, these studies have focused on enhanced rates of glycolysis observed in various models. The presumption has been that mitochondrial metabolism is suppressed. However, recent studies indicate that the extent of mitochondrial metabolism is far more heterogeneous in tumors than originally presumed. One tumor type with suppression of mitochondrial metabolism is renal cell carcinoma (RCC). Prior studies indicate that suppressed TCA cycle enzyme mRNA expression is associated with aggressive RCC. Yet, the mechanisms that regulate the TCA cycle in RCC remain uncharacterized. Here, we demonstrate that loss of TCA cycle enzyme expression is retained in RCC metastatic tissues. Moreover, proteomic analysis demonstrates that reduced TCA cycle enzyme expression is far more pronounced in RCC relative to other tumor types. Loss of TCA cycle enzyme expression is correlated with reduced expression of the transcription factor peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) which is also lost in RCC tissues. PGC-1α re-expression in RCC cells restores the expression of TCA cycle enzymes in vitro and in vivo and leads to enhanced glucose carbon incorporation into TCA cycle intermediates. Mechanistically, TGF-β signaling, in concert with histone deacetylase 7 (HDAC7), suppresses TCA cycle enzyme expression. In turn, pharmacologic inhibition of TGF-β restores expression of TCA cycle enzyme expression and suppresses tumor growth in an orthotopic model of RCC. Taken together, our findings reveal a novel role for the TGF-β /HDAC7 axis in global suppression of TCA cycle enzymes in RCC and provide novel insight into the molecular basis of altered mitochondrial metabolism in this malignancy.

Genetic requirements and transcriptomics of Helicobacter pylori biofilm formation on abiotic and biotic surfaces

Biofilm growth is a widespread mechanism that protects bacteria against harsh environments, antimicrobials, and immune responses. These types of conditions challenge chronic colonizers such as Helicobacter pylori but it is not fully understood how H. pylori biofilm growth is defined and its impact on H. pylori survival. To provide insights into H. pylori biofilm growth properties, we characterized biofilm formation on abiotic and biotic surfaces, identified genes required for biofilm formation, and defined the biofilm-associated gene expression of the laboratory model H. pylori strain G27. We report that H. pylori G27 forms biofilms with a high biomass and complex flagella-filled 3D structures on both plastic and gastric epithelial cells. Using a screen for biofilm-defective mutants and transcriptomics, we discovered that biofilm cells demonstrated lower transcripts for TCA cycle enzymes but higher ones for flagellar formation, two type four secretion systems, hydrogenase, and acetone metabolism. We confirmed that biofilm formation requires flagella, hydrogenase, and acetone metabolism on both abiotic and biotic surfaces. Altogether, these data suggest that H. pylori is capable of adjusting its phenotype when grown as biofilm, changing its metabolism, and re-shaping flagella, typically locomotion organelles, into adhesive structures.

Lower oxygen consumption and Complex I activity in mitochondria isolated from skeletal muscle of fetal sheep with intrauterine growth restriction

Fetal sheep with placental insufficiency-induced intrauterine growth restriction (IUGR) have lower hindlimb oxygen consumption rates (OCRs), indicating depressed mitochondrial oxidative phosphorylation capacity in their skeletal muscle. We hypothesized that OCRs are lower in skeletal muscle mitochondria from IUGR fetuses, due to reduced electron transport chain (ETC) activity and lower abundances of tricarboxylic acid (TCA) cycle enzymes. IUGR sheep fetuses ( n = 12) were created with mid-gestation maternal hyperthermia and compared with control fetuses ( n = 12). At 132 ± 1 days of gestation, biceps femoris muscles were collected, and the mitochondria were isolated. Mitochondria from IUGR muscle have 47% lower State 3 (Complex I-dependent) OCRs than controls, whereas State 4 (proton leak) OCRs were not different between groups. Furthermore, Complex I, but not Complex II or IV, enzymatic activity was lower in IUGR fetuses compared with controls. Proteomic analysis ( n = 6/group) identified 160 differentially expressed proteins between groups, with 107 upregulated and 53 downregulated mitochondria proteins in IUGR fetuses compared with controls. Although no differences were identified in ETC subunit protein abundances, abundances of key TCA cycle enzymes [isocitrate dehydrogenase (NAD+) 3 noncatalytic subunit β (IDH3B), succinate-CoA ligase ADP-forming subunit-β (SUCLA2), and oxoglutarate dehydrogenase (OGDH)] were lower in IUGR mitochondria. IUGR mitochondria had a greater abundance of a hypoxia-inducible protein, NADH dehydrogenase 1α subcomplex 4-like 2, which is known to incorporate into Complex I and lower Complex I-mediated NADH oxidation. Our findings show that mitochondria from IUGR skeletal muscle adapt to hypoxemia and hypoglycemia by lowering Complex I activity and TCA cycle enzyme concentrations, which together, act to lower OCR and NADH production/oxidation in IUGR skeletal muscle.

Tricarboxylic Acid (TCA) Cycle Enzymes and Intermediates Modulate Intracellular Cyclic di-GMP Levels and the Production of Plant Cell Wall–Degrading Enzymes in Soft Rot Pathogen Dickeya dadantii

Dickeya dadantii is a plant-pathogenic bacterium that causes soft-rot in a wide range of plants. Although we have previously demonstrated that cyclic bis-(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP), a bacterial secondary messenger, plays a central role in virulence regulation in D. dadantii, the upstream signals that modulate c-di-GMP remain enigmatic. Using a genome-wide transposon mutagenesis approach of a Δhfq mutant strain that has high c-di-GMP and reduced motility, we uncovered transposon mutants that recovered the c-di-GMP-mediated repression on swimming motility. A number of these mutants harbored transposon insertions in genes encoding tricarboxylic acid (TCA) cycle enzymes. Two of these TCA transposon mutants were studied further by generating chromosomal deletions of the fumA gene (encoding fumarase) and the sdhCDAB operon (encoding succinate dehydrogenase). Disruption of the TCA cycle in these deletion mutants resulted in reduced intracellular c-di-GMP and enhanced production of pectate lyases (Pels), a major plant cell wall–degrading enzyme (PCWDE) known to be transcriptionally repressed by c-di-GMP. Consistent with this result, addition of TCA cycle intermediates such as citrate also resulted in increased c-di-GMP levels and decreased production of Pels. Additionally, we found that a diguanylate cyclase GcpA was solely responsible for the observed citrate-mediated modulation of c-di-GMP. Finally, we demonstrated that addition of citrate induced not only an overproduction of GcpA protein but also a concomitant repression of the c-di-GMP-degrading phosphodiesterase EGcpB which, together, resulted in an increase in the intracellular concentration of c-di-GMP. In summary, our report demonstrates that bacterial respiration and respiration metabolites serve as signals for the regulation of c-di-GMP signaling.

Rescue of TCA Cycle Dysfunction for Cancer Therapy

Mitochondrion, a maternally hereditary, subcellular organelle, is the site of the tricarboxylic acid (TCA) cycle, electron transport chain (ETC), and oxidative phosphorylation (OXPHOS)—the basic processes of ATP production. Mitochondrial function plays a pivotal role in the development and pathology of different cancers. Disruption in its activity, like mutations in its TCA cycle enzymes, leads to physiological imbalances and metabolic shifts of the cell, which contributes to the progression of cancer. In this review, we explored the different significant mutations in the mitochondrial enzymes participating in the TCA cycle and the diseases, especially cancer types, that these malfunctions are closely associated with. In addition, this paper also discussed the different therapeutic approaches which are currently being developed to address these diseases caused by mitochondrial enzyme malfunction.

Reductive TCA cycle enzymes and reductive amino acid synthesis pathways contribute to electron balance in aRhodospirillum rubrumCalvin cycle mutant

Purple nonsulfur bacteria (PNSB) use light for energy and organic substrates for carbon and electrons when growing photoheterotrophically. This lifestyle generates more reduced electron carriers than are required for biosynthesis, even during consumption of some of the most oxidized organic substrates like malate and fumarate. Excess reduced electron carriers must be oxidized for photoheterotrophic growth to occur. Diverse PNSB commonly rely on the CO2-fixing Calvin cycle to oxidize excess reduced electron carriers. Some PNSB also produce H2or reduce terminal electron acceptors as alternatives to the Calvin cycle.Rhodospirillum rubrumCalvin cycle mutants defy this trend by growing phototrophically on malate or fumarate without H2production or access to terminal electron acceptors. We used13C-tracer experiments to examine how aRs. rubrumCalvin cycle mutant maintains electron balance under such conditions. We detected the reversal of some TCA cycle enzymes, which carried reductive flux from malate or fumarate to α-ketoglutarate. This pathway and the reductive synthesis of amino acids derived from α-ketoglutarate are likely important for electron balance, as supplementing the growth medium with α-ketoglutarate-derived amino acids preventedRs. rubrumCalvin cycle mutant growth unless a terminal electron acceptor was provided. Flux estimates also suggested that the Calvin cycle mutant preferentially synthesized isoleucine using the reductive threonine-dependent pathway instead of the less-reductive citramalate-dependent pathway. Collectively, our results suggest that alternative biosynthetic pathways can contribute to electron balance within the constraints of a relatively constant biomass composition.