Induction Of Aldehyde Dehydrogenase Research Articles

Aged Garlic Extract Prevents Alcohol-Induced Cytotoxicity through Induction of Aldehyde Dehydrogenase 2 intheLiverofMice.

Acetaldehyde is a highly toxic primary metabolite of ethanol, and converts to nontoxic acetic acid by aldehyde dehydrogenase (ALDH). Accumulation of acetaldehyde causes significant damage to human body. Aged garlic extract (AGE) is a functional food material and possesses various health beneficial effects. This study investigates whether AGE contributes to acetaldehyde detoxification through ALDH induction and its underlying mechanism. C57BL/6J mice are orally administrated 10-1000mgkg-1 body weight (BW) of AGE for 1week before ethanol administration. AGE suppresses ethanol-caused accumulation of acetaldehyde level in the plasma through inducing mitochondrial ALDH2 but not cytosolic ALDH1A1. AGE also induces antioxidant enzymes, heme oxygenase-1, and NAD(P)H:quinone oxidoreductase 1, resulting in prevention of lipid peroxidation in the liver. In HepG2 cells, AGE prevents ethanol- and acetaldehyde-caused cytotoxicity. AGE induces mitochondrial ALDH2 through activating nuclear factor-erythroid 2-related factor 2 (Nrf2). AGE inhibits protein degradation of Nrf2 and enhances protein degradation of kelch-like ECH-associated protein 1. Furthermore, S-allyl cysteine and S-allyl mercaptocysteine as the bioactive compounds in AGE also induce ALDH2 and Nrf2. AGE prevents acetaldehyde-induced hepatotoxicity through enhancing acetaldehyde detoxification through Nrf2-dependent induction of mitochondrial ALDH2.

6-(Methylsulfinyl)hexyl isothiocyanate protects acetaldehyde-caused cytotoxicity through the induction of aldehyde dehydrogenase in hepatocytes

In the body, alcohol dehydrogenase rapidly converts ethanol to its toxic metabolite, acetaldehyde, which is further metabolized to non-toxic acetic acid by aldehyde dehydrogenase (ALDH). 6-(methylsulfinyl)hexyl isothiocyanate (6-MSITC), a major bioactive compound in Wasabi (Wasabia japonica) has various physiological effects such as anti-oxidative, anti-inflammatory and anti-cancer effects. However, the effect of 6-MSITC on alcohol metabolism has not been studied. In this study, we investigated the effects of 6-MSITC on hepatic ALDH activity and protein expression both in vitro and in vivo. 6-MSITC inhibited ethanol- and acetaldehyde-induced cytotoxicity. Treatment with 6-MSITC to HepG2 cells enhanced ALDH activity through the induction of mitochondrial ALDH2 expression, but not cytosolic ALDH1A1. Knockdown of Nrf2 canceled the 6-MSITC-induced ALDH2 expression, indicating that Nrf2 regulated ALDH2 expression. Moreover, 6-MSITC increased the nuclear translocation of Nrf2 and the expression levels of HO-1 and SOD2, Nrf2-regulated phase II drug-metabolizing enzymes. Oral administration of 6-MSITC increased the mitochondrial ALDH2 activity and its expression in the liver of C57BL/6J mice. These results suggested that 6-MSITC is possible to protect acetaldehyde toxicity in hepatocytes by induction of mitochondrial ALDH2 expression through Nrf2/ARE pathway.

THE EFFECT OF TESTOSTERONE ON THE ALDEHYDE DEHYDROGENASE ACTIVITY IN RATS INTERNAL TISSUE UNDER CONDITIONS OF IMMOBILIZATION STRESS

It has been shown that under conditions of androgen deficiency increased activity of aldehyde dehydrogenase in liver and heart homogenates of 3-month-old rats. After the effects of stress on the background androgen deficiency observed various changes of aldehyde dehydrogenase activity. They have tissue-specific and age-related character. Only in the heart of 3-month-old castrated rats observed effect of testosterone on aldehyde dehydrogenase induction under stress. Here there is inhibition of enzyme activity under conditions of administration of testosterone.

Aldehyde dehydrogenase induction in arsenic-exposed rat bladder epithelium

Arsenic is widely distributed in the environment. Many human cancers, including urothelial carcinoma (UC), show a dose-dependent relationship with arsenic exposure in the south-west coast of Taiwan (also known as the blackfoot disease (BFD) areas). However, the molecular mechanisms of arsenic-mediated UC carcinogenesis has not yet been defined. In vivo study, the rat bladder epithelium were exposed with arsenic for 48h. The proteins were extracted from untreated and arsenic-treated rat bladder cells and utilized two-dimensional gel electrophoresis and mass spectrometry. Selected peptides were extracted from the gel and identified by quadrupole-time of flight (Q-TOF) Ultima-Micromass spectra. The significantly difference expression of proteins in arsenic-treated groups as compared with untreated groups was confirmed by immunohistochemistry (IHC) and western blotting. We found that thirteen proteins were down-regulated and nine proteins were up-regulated in arsenic-treated rat bladder cells when compared with untreated groups. The IHC and western blotting results confirmed that aldehyde dehydrogenase (ALDH) protein was up-regulated in arsenic-treated rat bladder epithelium. Expression of ALDH protein was significantly higher in UC patients from BFD areas than those from non-BFD areas using IHC (p=0.018). In conclusion, the ALDH protein expression could be used as molecular markers for arsenic-induced transformation.

Sulforaphane Accelerates Acetaldehyde Metabolism by Inducing Aldehyde Dehydrogenases: Relevance to Ethanol Intolerance

Many East Asians are highly intolerant to even modest alcohol consumption. These individuals accumulate acetaldehyde, the primary metabolite of ethanol, because of a genetic polymorphism of aldehyde dehydrogenase (ALDH) that metabolizes acetaldehyde to nontoxic acetate. The aim of these studies is to upregulate ALDH by dietary means, thereby reducing acetaldehyde toxicity. Sulforaphane [SF, 1-isothiocyano-4-(methylsulfinyl)butane] derived from its glucosinolate precursor contained in cruciferous vegetables and related inducers of the Keap1/Nrf2/ARE pathway were assessed for their potencies to induce ALDH in murine hepatoma Hepa1c1c7 cells. Inducer potencies for ALDH were compared with those for NQO1, a prototypical cytoprotective enzyme present downstream of the Keap1/Nrf2/ARE pathway. SF (5 or 20 µmol/day) was fed to CD-1 mice for 7 days prior to a single administration of ethanol, and then ALDH induction in organs and pharmacokinetics of acetaldehyde was examined. In addition to SF, other electrophiles, including many Michael reaction acceptors, induce ALDH. Potencies of these agents as inducers parallel their activities in inducing NQO1, and are also dependent on Nrf2. In mice, in vivo, feeding of SF induced tissue ALDH and dramatically increased (doubled) the rate of elimination of acetaldehyde arising from the administration of ethanol. SF and other edible phytochemicals may ameliorate the alcohol intolerance of individuals who are polymorphic with respect to ALDH.

Aldehyde dehydrogenase activity in serous ovarian carcinoma.

e15577 Background: Only specific subpopulations of tumor cells, so called cancer stem cells (CSC) may initiate and maintain tumors. The phenotype and molecular properties of ovarian CSC remain elusive. Aldehyde dehydrogenase (ALDH) activity characterizes (cancer) stem cells in different tissues and has been associated with ovarian CSC (Silva et al, 2011; Kryczek et al, 2012). Contradictory results have been reported on ALDH1 expression and prognosis in ovarian carcinoma. In this study, we explore the role of ALDH in serous ovarian carcinoma (SOC). Methods: Aldefluor-staining was used to assess ALDH activity in different ovarian carcinoma cell-lines and patient samples. ALDH+ and ALDH- cells isolated by FACS and ALDH1 versus control siRNA treated cells were analyzed in sphere forming, proliferation, BrdU and cell cycle assays. In vivo tumorigenicity assays including serial re-transplantations were performed in NOD/SCID/IL2Rγnull mice. ALDH1 and Ki67 expression were assessed immunohistochemically on a tissue microarray of 152 SOC samples. Results: ALDH+ cells formed more tumor spheres than ALDH- cells from the OVCAR-3 cell line and primary SOC and larger spheres (> 5.000 µm²) developed solely from ALDH+ cells. However, in vivo both cell fractions gave rise to tumors. Tumors contained both ALDH+ and ALDH- cells irrespective of the starting population. Notably, ALDH+ cells generated tumors more rapidly and induced larger tumors, suggesting a higher proliferative capacity. Immunohistochemical analysis of a larger cohort of SOC patients confirmed association of ALDH1 expression with the proliferation marker Ki67 (p=0.007). Surprisingly, co-stainings revealed that ALDH1 positive cells were mostly Ki67 negative and cell cycle synchronisation experiments using different agents showed ALDH induction in G0-enriched OVCAR-3 cells. However, inhibition of ALDH by treatment with three distinct siRNAs against ALDH1 did not alter cell cycle distribution. Conclusions: Our data suggest that ALDH is a correlative marker indicating, but not actively sustaining a quiescent stem-cell like state in SOC. Upon exit from G0, ALDH+ cells lose ALDH expression and induce a proliferative response.

Endogenous acetaldehyde toxicity during antral follicular development in the mouse ovary

The biosynthesis of androgens requires multiple steps and during the conversion of pregnenolone to 17α-hydroxypregnenolone and dehydroepiandrosterone (DHEA) by CYP17a1. Acetaldehyde is potentially formed as a by-product in theca cells during antral follicular development. In this study, acetaldehyde level was significantly increased after eCG stimulation and reached a maximum level at 36-h post-eCG. By 48h, the level of acetaldehyde decreased in association with the induction of aldehyde dehydrogenase (ALDH) type 1 family members. When immature mice were co-injected with the ALDH inhibitor, cyanamide, and eCG, the expression of genes involved in the differentiations of granulosa cells was suppressed and the number of ovulated oocytes was reduced. The in vitro studies showed that ALDH inhibitors prevented FSH-induced granulosa cell differentiation. These results indicate that acetaldehyde is generated as a by-product during steroidogenesis and can exert toxic effects to impair the differentiation of granulosa cells, reduce ovulation and decrease oocyte quality.

Fluorimetric Detection of Aldehyde Dehydrogenase Activity in Human Blood, Saliva, and Organ Biopsies and Kinetic Differentiation between Class I and Class III Isozymes

Two highly fluorogenic aldehydes, 7-methoxy-1-naphthaldehyde (MONAL-71) and 6-methoxy-2-naphthaldehyde (MONAL-62), were examined as indicators of the aldehyde dehydrogenase (ALDH) activity in human tissue homogenates and accessible body fluids. Both compounds were previously found to be excellent substrates for the ALDH from erythrocytes and for the purified class I (cytosolic) ALDH from human liver. By contrast, only MONAL-62, but not the isomeric MONAL-71, was oxidized by class III ALDH present in human saliva. The apparentKmfor the former compound reacting with saliva ALDH is 0.24 μm, with the reaction rate (Vmax) close to that of benzaldehyde oxidation. There is also a fully competitive inhibition of the fluorogenic oxidation of the MONAL-62 by benzaldehyde. Both NAD+and NADP+can be used as oxidants in this reaction, with comparable rates, a fact previously reported for the human class III aldehyde dehydrogenase. In human liver homogenate (cytosolic + microsomal fraction), the ALDH activity is easily detectable using either MONAL-71 or MONAL-62, with specific activities of approximately 2.5 and 3.2 units per gram of protein, respectively. The low apparentKmvalues, 0.85 and <0.03 μm, respectively, together with the inhibition profile by propionic aldehyde (ID50in the micromolar range) indicate that both compounds are oxidized primarily by the class I ALDH, further confirmed by low activity (0.4 U/g) with NADP+as oxidant. By contrast, in human stomach, containing mostly class III ALDH, the activity measured with MONAL-71, 0.4 U/g, is much lower than that with MONAL-62 (5.1 U/g with NAD+and 3.1 U/g with NADP+), the latter being virtually insensitive to 1 mmpropionic aldehyde. Hence, in a stomach homogenate, class I and class III ALDH activities can be measured selectively with the two fluorogenic substrates described. In all experiments, the activity of aldehyde oxidase was at least 10-fold lower than that of the ALDH. Addition of 5 mm4-methylpyrazole, a known inhibitor of the alcohol dehydrogenase, did not change the resultant ALDH activities by more than 10%, indicating lack of interference by the former enzyme. A preliminary screening of two liver tumour samples showed diminished class I ALDH activities (0.7 and 0.03 U/g), but no evidence for class III ALDH induction. The above observations are discussed in relation to the mechanism of detoxication of cyclophosphamide.

Induction of a pleiotropic response by phenobarbital and related compounds: Response in various inbred strains of rats, response in various species and the induction of aldehyde dehydrogenase in copenhagen rats

The ability of phenobarbital (PB) to induce a “pleiotropic response” which includes both cytochromes P450 (CYP) as well as other drug-metabolizing enzymes was investigated in mice, rabbits, hamsters, and various inbred strains of rats. PB induced similar drug-metabolizing enzymes (CYP2B, CYP3A, and epoxide hydrolase) in rats, mice, rabbits and hamsters. PB and two structural analogues (ethylphenylhydantoin and barbital) induced a variety of drug-metabolizing enzymes (CYP2B, CYP3A, CYP2A, epoxide hydrolase) in a series of inbred strains of rats. In contrast, levels of aldehyde dehydrogenase (ALDH) (propionaldehyde, NAD +) which were expressed constitutively in all strains of rats were induced by PB in only two of the eight strains (ACI, Copenhagen). Further investigations of ALDH induction by structurally diverse compounds in Copenhagen rats demonstrated a strong correlation between the induction of ALDH and other elements of the pleiotropic response (CYP2B, CYP3A, epoxide hydrolase). These results imply that induction of ALDH (propionaldehyde, NAD +) is associated with the PB pleiotropic response in Copenhagen rats.

Aldehyde dehydrogenase induction by glutamate in Escherichia coli

In Escherichia coli, an aldehyde dehydrogenase that catalyzes the oxidation of L-lactaldehyde to L-lactate is induced not only by L-fucose, L-rhamnose or D-arabinose, but also by growth in the presence of glutamate or amino acids yielding glutamate, with the exception of proline. Induction by these amino acids requires glutamate accumulation. 4-Aminobutyric acid also induces this aldehyde dehydrogenase through its transamination to glutamate. Growth on 2-oxoglutarate, the tricarboxylic acid cycle intermediate with which glutamate is in equilibrium, also induces this aldehyde dehydrogenase. Conditions in which the conversion of 2-oxoglutarate into glutamate is highly restricted displayed unchanged rates of induction by 2-oxoglutarate, indicating that glutamate induces the aldehyde dehydrogenase through 2-oxoglutarate formation. Evidence is presented showing that L-fucose- and 2-oxoglutarate-inducing systems share the same regulatory protein. Induction by growth on either of these two compounds is repressed both by glucose and by glycerol. Addition of cAMP to these cultures partially recovers the glucose-repressed aldehyde dehydrogenase activity, while this nucleotide has no effect on the glycerol-mediated repression. These results indicate that ald is under carbon regulation mediated by at least two different mechanisms.

Changes in the inducibility of a hepatic aldehyde dehydrogenase by various effectors.

A hepatic soluble aldehyde dehydrogenase (ALDH), inducible by polycyclic aromatic hydrocarbons, was studied in Wistar rats in connection with substances known to affect drug metabolism or aldehyde dehydrogenase activity, such as phenobarbital (PB), disulfiram (DS), beta-diethylaminoethyl diphenylpropylacetate (SKF 525A) and calcium cyanamide (CC). 3-Methylcholanthrene (MC) was given as a model inducer of ALDH (100 mg/kg, i.p., as a single dose) and the animals were killed after 3 days. Pretreatment with PB (1 g/l drinking water, for 2 weeks) enhanced the inducing effect of MC. On the contrary, pretreatment with DS (100 mg/kg, i.p., daily x 4) reduced by 70% the expected increase in ALDH activity. Neither SKF 525A (25 mg/kg, i.p., daily x 4), nor CC (5 mg/kg, i.p., daily x 4) could affect the action of the inducer. At the above doses, basal ALDH activity was inhibited by DS (30%) and CC (70%), but was not affected at all by PB or SKF 525A. The results were somewhat different when the various effectors tested were administered to animals already treated with MC (20 mg/kg, i.p., daily x 6). In this case, DS did not affect the already induced ALDH activity. On the contrary, CC was still an effective inhibitor. Unexpectedly, post-treatment with SKF 525A further enhanced the initial induction brought about by MC. Our findings show that substances affecting microsomal drug metabolism can interfere with the process of ALDH induction by MC. The additive result of PB pretreatment is probably due to the enhanced accumulation of an active metabolite of MC.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of acrolein in allyl alcohol-induced lipid peroxidation and liver cell damage in mice

Male NMRI mice were fed a sucrose diet for 48 hr in order to reduce the hepatic glutathione content and to level off its diurnal variation. After administration of allyl alcohol (AA: 1.1 mmol/kg), hepatic glutathione (24.3 ± 7.0 nmol GSH/mg protein) was almost totally lost within the first 15min (<0.5 nmol GSH/mg protein). Subsequently, a massive lipid perioxidation was observed, i.e. the animals exhaled 414 ± 186 nmol ethane/kg/hr compared to 0.9 ± 0.8 of controls, and the hepatic TBA- reactive compounds had increased from 55 ± 16 pmol/mg protein in controls to 317 ± 163 after 1 hr. Concomitantly, a 40–45% loss of the polyunsaturated fatty acids (arachidonic and docosahexaenoic acid) in the liver lipids was observed. About 80% of the cytosolic alcohol dehydrogenase activity and about 50% of the microsomal P450-content were destroyed. In vivo-inhibition of alcohol dehydrogenase by pyrazole or induction of aldehyde dehydrogenase by phenobarbital abolished AA-induced liver damage as well as glutathione depletion and lipid peroxi- dation, while inhibition of aldehyde dehydrogenase by cyanamide made a subtoxic dose of AA (0.60 mmol/kg) highly toxic. These results strongly favour the importance of acrylic acid formation as an additional detoxification pathway. Enhanced hepatic levels of glutathione protected in vivo against the damaging effects of AA. Depletion of the liver glutathione content by phorone or diethylmaleate alone caused marginally enhanced lipid peroxidation (phorone) but no liver cell damage. Mono- oxygenase inhibitors (metyrapone, diethyldithiocarbamate, α-naphthoflavone) or an inducer (benz( a)pyrene) did not affect AA-induced toxicity. The ferric iron chelator desferoxamine- methanesulfonate prevented AA-induced lipid peroxidation and liver cell damage in vivo. In vitro, acrolein alone failed to initiate lipid peroxidation in soy bean phospholipid liposomes or in mouse liver microsomes. Thus, acrolein not only impairs the glutathione defense system but also directly destroys cellular proteins and evokes lipid peroxidation by an indirect iron-depending mechanism.

Sequential 2-acetylaminofluorene--phenobarbital exposure induces a cytosolic aldehyde dehydrogenase during rat hepatocarcinogenesis.

A significant change in hepatic aldehyde dehydrogenase activity has been observed in normal Sprague-Dawley rat liver during the promotion phase of hepatocarcinogenesis induced by brief feeding of 2-acetylaminofluorene (2-AAF) followed by tumor promotion using dietary phenobarbital (PB) exposure. Animals receiving only 2-AAF or PB do not possess this new aldehyde dehydrogenase activity. The phenotype is characterized by the appearance of a new cytosolic isozyme kinetically, electrophoretically and immunochemically distinct from the normal liver aldehyde dehydrogenase isozymes and from aldehyde dehydrogenases inducible in 2-AAF-induced hepatomas. The new isozyme is NAD-dependent, disulfiram-sensitive and cross-reacts with antiserum to a normal liver aldehyde dehydrogenase inducible in several lines of rats by PB. However, the population of animals used in this study has been shown previously to be non-responsive to aldehyde dehydrogenase induction by dietary PB. Since no animals receiving only PB express this new isozyme, the carcinogen must play a significant role in its induction. Moreover, that not all animals receiving carcinogen and promoter possess the phenotype suggests this carcinogen/promoter interaction has a genetic basis.

Induction of aldehyde dehydrogenase by polycyclic aromatic hydrocarbons in rats

Short-term intragastric administration of selected polycyclic aromatic hydrocarbons (100 mg/kg daily for 4 days) to male Wistar rats resulted in marked changes in liver cytosolic aldehyde dehydrogenase activity. Non-carcinogenic anthracene, phenanthrene and chrysene produced a 2.5–3-fold increase in the activity assayed with propionaldehyde as substrate and NAD as coenzyme. Weakly carcinogenic 1,2-benzanthracene enhanced aldehyde dehydrogenase activity 9-fold and the potent carcinogens 3,4-benzpyrene and 3-methylcholanthrene 30-fold. With benzaldehyde as substrate and NADP as coenzyme the differences between the groups were even more pronounced. Somewhat similar but less manifest effects on aldehyde dehydrogenase activity were detected also in the liver microsomes and in the postmitochondrial fractions of the small intestinal mucosa. On the basis of their ability to induce aldehyde dehydrogenase activity the compounds could be divided into three groups. This classification was found to correlate well with the carcinogenic potency of the compounds. It appeared that the exposure to polycyclic aromatic hydrocarbons, especially the carcinogenic ones, was followed by synthesis of a new aldehyde dehydrogenase form. This new form was differentiated from the normally existing cytosolic aldehyde dehydrogenase by its ability to oxidize benzaldehyde in the presence of NADP.

Inducible aldehyde dehydrogenases in the hepatic cytosol of the rat.

Rats of the Wistar/Af/Han/Mol/(Han 67) strain have previously been shown to respond in a variable way to phenobarbital treatment, as far as the induction of aldehyde dehydrogenase activity is concerned (Marselos 1976). This biochemical property is genetically determined and concerns the high-Km aldehyde dehydrogenase of the hepatic cytosol. In this study, administration of phenobarbital (1 mg/mo of drinking water, for 1 week) produces a uniform induction of aldehyde dehydrogenase in all rats, when measured with micromolar substrate concentration. The inducible low-Km enzyme of the cytosol is not genetically determined like the high-Km enzyme, and shows a wide specificity for aliphatic as well as for aromatic aldehydes. Despite the inducibility of the cytosolic enzymes, no alterations are found in the mitochondrial aldehyde dehydrogenase activities after phenobarbital treatment. The oxidation of D-glucuronolactone takes place only in the cytosol, and seems to be dependent on the low-Km aldehyde dehydrogenase. This is consistent with NMR studies, which showed that a very minimal amount of D-glucuronolactone is in aldehyde form under the measurement conditions usually applied. Further, the oxidation of D-glucuronolactone is also enhanced by phenobarbital in all rats without a genetic predisposition, and its dose-response curve is very similar to that of the low-Km aldehyde dehydrogenase.

Induction of aldehyde dehydrogenase in a mitochondrial fraction

Mitochondrial membranes suffer irreversible structural and functional damage if exposed to aldehydes; membranes of other subcellular particles may be affected similarly. The need for an in vivo protective mechanism may be satisfied by aldehyde dehydrogenase (aldehyde:NAD + oxidoreductase, EC 1.2.1.3) which is specifically induced in a subcellular fraction isolated from livers of rats administered ethanol orally.

Ethanol utilization by Streptococcus faecalis

Studies were carried out on the utilization of ethanol for the growth of Streptococcus faecalis 10C1. Almost all the radioactivity in the cells grown with ethanol-1- 14C was found in the lipid fraction. In extracts of the cells grown with ethanol, activities of an alcohol dehydrogenase and a CoA-dependent aldehyde dehydrogenase were detected. These results indicated that ethanol was utilized for lipid synthesis after being converted to acetyl-CoA via acetaldehyde. Induction of aldehyde dehydrogenase was observed. In the presence of ethanol, the activity of the enzyme increased in growing cells. Chloramphenicol arrested this increase. In contrast, addition of acetate to the ethanol-containing medium causde a repression of the enzyme synthesis, whereas the rate of growth was not affected. A possible mechanism for this phenomenon was also discussed.