Rates of induction of mitochondrial aldehyde dehydrogenase in rat liver.
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ABSTRACT:
SUBMITTER: Horton AA
PROVIDER: S-EPMC1163729 | biostudies-other | 1976 Apr
REPOSITORIES: biostudies-other
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Project description:Aldehyde dehydrogenase (ALDH) isozymes are critically important in the metabolism of acetaldehyde, thus preventing its accumulation after ethanol-exposure. We previously reported that mitochondrial ALDH2 could be inactivated via S-nitrosylation in ethanol-exposed rats. This study was aimed at investigating whether cytosolic ALDH1, with a relatively-low-Km value (11-18 microM) for acetaldehyde, could be also inhibited in ethanol-exposed rats. Chronic or binge ethanol-exposure significantly decreased ALDH1 activity, which was restored by addition of dithiothreitol. Immunoblot analysis with the anti-S-nitroso-Cys antibody showed one immunoreactive band in the immunoprecipitated ALDH1 only from ethanol-exposed rats, but not from pair-fed controls, suggesting S-nitrosylation of ALDH1. Therefore inactivation of ALDH1 via S-nitrosylation can result in accumulation of acetaldehyde upon ethanol-exposure.
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Project description:Lipid peroxidation-derived aldehydes, such as acrolein, the most reactive aldehyde, have emerged as key culprits in sustaining post-spinal cord injury (SCI) secondary pathologies leading to functional loss. Strong evidence suggests that mitochondrial aldehyde dehydrogenase-2 (ALDH2), a key oxidoreductase and powerful endogenous anti-aldehyde machinery, is likely important for protecting neurons from aldehydes-mediated degeneration. Using a rat model of spinal cord contusion injury and recently discovered ALDH2 activator (Alda-1), we planned to validate the aldehyde-clearing and neuroprotective role of ALDH2. Over an acute 2 day period post injury, we found that ALDH2 expression was significantly lowered post-SCI, but not so in rats given Alda-1. This lower enzymatic expression may be linked to heightened acrolein-ALDH2 adduction, which was revealed in co-immunoprecipitation experiments. We have also found that administration of Alda-1 to SCI rats significantly lowered acrolein in the spinal cord, and reduced cyst pathology. In addition, Alda-1 treatment also resulted in significant improvement of motor function and attenuated post-SCI mechanical hypersensitivity up to 28 days post-SCI. Finally, ALDH2 was found to play a critical role in in vitro protection of PC12 cells from acrolein exposure. It is expected that the outcome of this study will broaden and enhance anti-aldehyde strategies in combating post-SCI neurodegeneration and potentially bring treatment to millions of SCI victims. All animal work was approved by Purdue Animal Care and Use Committee (approval No. 1111000095) on January 1, 2021.
| S-EPMC8771087 | biostudies-literature
Project description:1. Distribution of aldehyde dehydrogenase activity in rat liver was studied by measuring the rate of disappearance of acetaldehyde in the presence of each of the subcellular fractions. These were obtained by rough separation of particulate fractions from the soluble portion of the cell, by differential centrifugation, and by isopycnic gradient centrifugation. 2. The maximal rate of acetaldehyde oxidation was 3.7 mumol/min per g, with an apparent K(m) value below 10(-5)m. The highest rate of activity was observed in phosphate buffers of high P(i) concentration (above 60mm). 3. The activity measured was completely dependent on NAD(+). 4. The microsomal fraction and the nuclei were inactive in the assay. Of the total activity 80% was found in the mitochondrial fraction and the remaining 20% in the cytoplasm. 5. The distribution pattern is important from the point of view of acetaldehyde oxidation during ethanol metabolism. The apparent discrepancy of the results obtained by different workers and the localization of acetaldehyde oxidation in vivo is discussed.
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Project description:Supramolecular assembly of metabolic enzymes has been studied both in vivo and in vitro for nearly a decade. Experimental evidence has suggested a close relationship between enzymatic activity and enzyme assembly/disassembly. However, most cases were studied with the cytosolic enzymes. Here, I report the evidence for a mitochondrial enzyme with its ability in forming visible intracellular structures. By removing the mitochondrial targeting sequence, yeast mitochondrial enzyme aldehyde dehydrogenase (Ald4p) exhibits reversible supramolecular assembly in the cytoplasm, thus creating a useful system for further characterization of the regulatory factors that modulate the assembly/disassembly of this mitochondrial enzyme.
| S-EPMC5906672 | biostudies-literature
Project description:Mitochondrial aldehyde dehydrogenase (ALDH2) may be involved in the biotransformation of glyceryl trinitrate (GTN), and the inactivation of ALDH2 by GTN may contribute to the phenomenon of nitrate tolerance. We studied the GTN-induced inactivation of ALDH2 by UV/visible absorption spectroscopy. Dehydrogenation of acetaldehyde and hydrolysis of p-nitrophenylacetate (p-NPA) were both inhibited by GTN. The rate of inhibition increased with the GTN concentration and decreased with the substrate concentration, indicative of competition between GTN and the substrates. Inactivation of p-NPA hydrolysis was greatly enhanced in the presence of NAD(+), and, to a lesser extent, in the presence of NADH. In the presence of dithiothreitol (DTT) inactivation of ALDH2 was much slower. Dihydrolipoic acid (LPA-H(2)) was less effective than DTT, whereas glutathione, cysteine, and ascorbate did not protect against inactivation. When DTT was added after complete inactivation, dehydrogenase reactivation was quite modest (< or =16%). The restored dehydrogenase activity correlated inversely with the GTN concentration but was hardly affected by the concentrations of acetaldehyde or DTT. Partial reactivation of dehydrogenation was also accomplished by LPA-H(2) but not by GSH. We conclude that, in addition to the previously documented reversible inhibition by GTN that can be ascribed to the oxidation of the active site thiol, there is an irreversible component to ALDH inactivation. Importantly, ALDH2-catalyzed GTN reduction was partly inactivated by preincubation with GTN, suggesting that the inactivation of GTN reduction is also partly irreversible. These observations are consistent with a significant role for irreversible inactivation of ALDH2 in the development of nitrate tolerance.
| S-EPMC2576553 | biostudies-literature
Project description:Aldehyde dehydrogenases (ALDHs) represent large family members of NAD(P)+-dependent dehydrogenases responsible for the irreversible metabolism of many endogenous and exogenous aldehydes to the corresponding acids. Among 19 ALDH isozymes, mitochondrial ALDH2 is a low Km enzyme responsible for the metabolism of acetaldehyde and lipid peroxides such as malondialdehyde and 4-hydroxynonenal, both of which are highly reactive and toxic. Consequently, inhibition of ALDH2 would lead to elevated levels of acetaldehyde and other reactive lipid peroxides following ethanol intake and/or exposure to toxic chemicals. In addition, many East Asian people with a dominant negative mutation in ALDH2 gene possess a decreased ALDH2 activity with increased risks for various types of cancer, myocardial infarct, alcoholic liver disease, and other pathological conditions. The aim of this review is to briefly describe the multiple post-translational modifications of mitochondrial ALDH2, as an example, after exposure to toxic chemicals or under different disease states and their pathophysiological roles in promoting alcohol/drug-mediated tissue damage. We also briefly mention exciting preclinical translational research opportunities to identify small molecule activators of ALDH2 and its isozymes as potentially therapeutic/preventive agents against various disease states where the expression or activity of ALDH enzymes is altered or inactivated.
| S-EPMC3177986 | biostudies-literature
Project description:Sheep liver mitochondrial aldehyde dehydrogenase reacts with 2,2'-dithiodipyridine and 4,4'-dithiodipyridine in a two-step process: an initial rapid labelling reaction is followed by slow displacement of the thiopyridone moiety. With the 4,4'-isomer the first step results in an activated form of the enzyme, which then loses activity simultaneously with loss of the label (as has been shown to occur with the cytoplasmic enzyme). With 2,2'-dithiodipyridine, however, neither of the two steps of the reaction has any effect on the enzymic activity, showing that the mitochondrial enzyme possesses two cysteine residues that must be more accessible or reactive (to this reagent at least) than the postulated catalytically essential residue. The symmetrical reagent 5,5'-dithiobis-(1-methyltetrazole) activates mitochondrial aldehyde dehydrogenase approximately 4-fold, whereas the smaller related compound methyl l-methyltetrazol-5-yl disulphide is a potent inactivator. These results support the involvement of mixed methyl disulphides in causing unpleasant physiological responses to ethanol after the ingestion of certain antibiotics.
| S-EPMC1138814 | biostudies-other
Project description:OBJECTIVE:To investigate whether CaN-NFAT3 pathway mediates the protective effects of aldehyde dehydrogenase (ALDH) 2 in high glucose-treated neonatal rat ventricular myocytes. METHODS:The ventricular myocytes were isolated from the heart of neonatal (within 3 days) SD rats by enzyme digestion and cultured in the presence of 5-Brdu. After reaching confluence, the cultured ventricular myocytes were identified using immunofluorescence assay for ?-SA protein. The cells were then cultured in either normal (5 mmol/L) or high glucose (30 mmol/L) medium in the presence of ALDH2 agonist Alda-1, ALDH 2 inhibitor Daidzin, or Alda-1 and NFAT3 inhibitor (11R-VIVIT). Fluorescent probe and ELISA were used to detect intracellular Ca2+ concentration and CaN content, respectively; ALDH2, CaN and NFAT3 protein expressions in the cells were detected using Western blotting. RESULTS:Compared with cells cultured in normal glucose, the cells exposed to high glucose showed a significantly decreased expression of ALDH2 protein (P < 0.05) and increased expressions of CaN (P < 0.05) and NFAT3 proteins with also increased intracellular CaN and Ca2+ concentrations (P < 0.01). Alda-1 treatment significantly lowered Ca2+ concentration (P < 0.05), intracellular CaN content (P < 0.01), and CaN and NFAT3 protein expressions (P < 0.05), and increased ALDH2 protein expression (P < 0.05) in high glucose- exposed cells; Daidzin treatment significantly increased Ca2+ concentration (P < 0.01) and intracellular CaN content (P < 0.05) in the exposed cells. Compared with Alda-1 alone, treatment of the high glucose-exposed cells with both Alda-1 and 11R-VIVIT did not produce significant changes in the expression of ALDH2 protein (P>0.05) but significantly reduced the expression of NFAT3 protein (P < 0.05). CONCLUSIONS:Mitochondrial ALDH2 protects neonatal rat cardiomyocytes against high glucose-induced injury possibly by negatively regulating Ca2+-CaN-NFAT3 signaling pathway.
| S-EPMC6744117 | biostudies-literature
Project description:The pI approximately 5.2 isoenzymes of mitochondrial aldehyde dehydrogenase were separated from the other isoenzymes by pH-gradient chromatography on DEAE-Sephacel. The pI approximately 5.2 material is immunologically identical with cytosolic aldehyde dehydrogenase. It also shows sensitivity to 20 microM-disulfiram and insensitivity to 4M-urea in assays. These and other criteria seem to establish that the material is identical with the cytosolic enzyme. Mitochondrial enzyme that had been purified to remove pI approximately 5.2 isoenzymes shows concentration-dependent lag phases in assays. These effects are possibly due to the slow establishment of equilibrium between tetramer and either dimers or monomers, with the dissociated species being intrinsically more active than the tetramer.
| S-EPMC1144409 | biostudies-other
Project description:BACKGROUND:Only a subset of patients with excessive alcohol use develop alcoholic liver disease (ALD), though the exact mechanism is not completely understood. Once ingested, alcohol is metabolized by 2 key oxidative enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). There are 2 major ALDH isoforms, cytosolic and mitochondrial, encoded by the aldehyde ALDH1 and ALDH2 genes, respectively. The ALDH2 gene was hypothesized to alter genetic susceptibility to alcohol dependence and alcohol-induced liver diseases. The aim of this study is to determine the association between aldehyde dehydrogenase 2 (rs671) glu504lys polymorphism and ALD. METHODS:ALDH2 genotyping was performed in 535 healthy controls and 281 patients with ALD. RESULTS:The prevalence of the common form of the single nucleotide polymorphism rs671, 504glu (glu/glu) was significantly higher in patients with ALD (95.4%) compared to that of controls (73.7%, P < 0.0001). Among controls, 23.7% had the heterozygous (glu/lys) genotype compared to 4.6% in those with ALD (odds ratio [OR] = 0.16, 95% CI: 0.09-0.28). The allele frequency for 504lys allele in patients with ALD was 2.3%, compared to 14.5% in healthy controls (OR = 0.13, 95% CI: 0.07-0.24). CONCLUSIONS:Patients with ALDH2 504lys variant were less associated with ALD compared to those with ALDH2 504glu using both genotypic and allelic analyses.
| S-EPMC6063768 | biostudies-literature