Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Numerous studies have reported effects of antiviral nucleoside analogs on mitochondrial function, but they have not correlated well with the observed toxic side effects. By comparing the effects of the five Food and Drug Administration-approved anti-human immunodeficiency virus nucleoside analogs, zidovudine (3'-azido-3'-deoxythymidine) (AZT), 2',3'-dideoxycytidine (ddC), 2', 3'-dideoxyinosine (ddI), 2',3'-didehydro-2',3'-deoxythymidine (d4T), and beta-L-2',3'-dideoxy-3'-thiacytidine (3TC), as well as the metabolite of AZT, 3'-amino-3'-deoxythymidine (AMT), on mitochondrial function in a human hepatoma cell line, this issue has been reexamined. Evidence for a number of mitochondrial defects with AZT, ddC, and ddI was found, but only AZT induced a marked rise in lactic acid levels. Only in mitochondria isolated from AZT (50 microM)-treated cells was significant inhibition of cytochrome c oxidase and citrate synthase found. Our investigations also demonstrated that AZT, d4T, and 3TC did not affect the synthesis of the 11 polypeptides encoded by mitochondrial DNA, while ddC caused 70% reduction of total polypeptide content and ddI reduced by 43% the total content of 8 polypeptides (including NADH dehydrogenase subunits 1, 2, 4, and 5, cytochrome c oxidase subunits I to III, and cytochrome b). We hypothesize that in hepatocytes the reserve capacity for mitochondrial respiration is such that inhibition of respiratory enzymes is unlikely to become critical. In contrast, the combined inhibition of the citric acid cycle and electron transport greatly enhances the dependence of the cell on glycolysis and may explain why apparent mitochondrial dysfunction is more prevalent with AZT treatment.
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PMID:Differential effects of antiretroviral nucleoside analogs on mitochondrial function in HepG2 cells. 1068 9

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related mortality after lung and stomach cancers. This work was undertaken to investigate some of the biochemical mediators/pathways associated with or implicated in the pathogenesis of HCC. Male albino mice were classified into two groups: normal control group and HCC group. Early stage HCC was induced by injection of diethylnitrosamine (DEN) i.p. 200 mg/kg as a single dose, and after 2 weeks, the mice were given i.p. injection of thioacetamide (TAA) 100 mg/kg twice per week for 4 weeks. Mice were left for further 2 weeks without any treatment, after which, mice were sacrificed; blood and liver samples were collected. Serum was used for determination of activities of glucose-6-phosphate dehydrogenase (G6PDH) and aldolase as well as levels of insulin-like growth factor-1 (IGF-1) and epithelial cadherin (E-cadherin). One portion of the liver was used for histopathological examination and immunohistochemical staining of the tumor suppressor p53 protein. Another portion of the liver was used for determination of citrate synthase activity. Induction of HCC in mice resulted in significant increase in G6PDH and aldolase activities, and E-cadherin level, but significant decrease in IGF-1. HCC mice group showed moderate expression of p53 protein. These results suggest that the molecular pathogenesis of HCC in mice involves reduction of serum level of IGF-1 and increased serum level of E-cadherin accompanied by dysregulation of p53 protein expression. HCC was also associated with reprogrammed metabolic profile shifted toward increased glycolysis and lipogenesis.
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PMID:Biochemical/metabolic changes associated with hepatocellular carcinoma development in mice. 2452 22

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most widely studied ligand of the aryl hydrocarbon receptor (AHR). The AHR-dependent TCDD-induced mitochondrial hyperpolarization (Tappenden et al., 2011) [1] and reduced oxygen consumption rate of intact mouse hepatoma cells (Huang et al., in press) [2] in the previous studies suggest that these alterations can be related to enzymatic activities of the electron transport chain (ETC) and ATP synthase in oxidative phosphorylation (OXPHOS) system. Here, we evaluated the activity of each complex in the OXPHOS system using in vitro enzymatic assays. The calculated enzymatic activity of each complex was normalized against the activity of citrate synthase. To combine each value from an independent experiment, normalized enzyme activities from cells exposed to TCDD were converted to fold changes via comparison to the activity relative to time-matched vehicle control. The averaged fold change for each treatment suggests more replicates are needed in order to clearly evaluate a difference between treatments.
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PMID:Data of enzymatic activities of the electron transport chain and ATP synthase complexes in mouse hepatoma cells following exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). 2728 69

Sorafenib is a multi-kinase inhibitor and one of the few systemic treatment options for patients with advanced hepatocellular carcinomas (HCCs). Resistance to sorafenib develops frequently and could be mediated by the nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin (SIRT)1. We aimed to test whether sorafenib efficacy is influenced by cellular NAD levels and NAD-dependent SIRT1 function. We analyzed sorafenib effects on apoptosis induction, NAD salvage, mitochondrial function, and related signaling pathways in HCC cell lines (HepG2, Hep3B, und HUH7) overexpressing SIRT1 or supplemented with the NAD metabolite nicotinamide mononucleotide (NMN) compared to controls. Treatment of HCC cell lines with sorafenib dose-dependently induced apoptosis and a significant decrease in cellular NAD concentrations. The SIRT1 protein was downregulated in HUH7 cells but not in Hep3B cells. After sorafenib treatment, mitochondrial respiration in permeabilized cells was lower, citrate synthase activity was attenuated, and cellular adenosine triphosphate (ATP) levels were decreased. Concomitant to increased phosphorylation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), sorafenib treatment led to decreased activity of the mechanistic target of rapamycin (mTOR), indicative of energy deprivation. Transient overexpression of SIRT1, as well as NAD repletion by NMN, decreased sorafenib-induced apoptosis. We can, therefore, conclude that sorafenib influences the NAD/SIRT1/AMPK axis. Overexpression of SIRT1 could be an underlying mechanism of resistance to sorafenib treatment in HCC.
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PMID:Sorafenib-Induced Apoptosis in Hepatocellular Carcinoma Is Reversed by SIRT1. 3143 Sep 57