Aldehyde dehydrogenase activity in brain and liver of the rainbow trout (Salmo gairdneri Richardson)

ALDH7A1 is a protein that protects Atlantic salmon against Aeromonas salmonicida at the early stages of infection

Aldehyde dehydrogenases (ALDHs) belong to a super-family of detoxifying proteins and perform a significant role in developing epithelial homeostasis, protecting cells from toxic aldehydes and drug resistance. However, the activity and function of these detoxifying proteins remain unknown, especially in fish. In our research, we aimed to study functions of aldehyde dehydrogenase 7A1 (ALDH7A1) in Atlantic salmon infected by Aeromonas salmonicida. Recombinant ALDH7A1 (rALDH7A1) was verified by SDS-PAGE and western blot. The molecular mass of the deduced amino acid sequence of rALDH7A1 is 58.9 kDa with an estimated pI of 7.09. Only a low complexity region (¹⁴¹yvegvgevqeyvdv¹⁵³) without a signal peptide existed in rALDH7A1. Results of ELISA indicated that rALDH7A1 exhibited apparent binding activities with A. salmonicida and its expression was highest in fish kidney. A Real-Time PCR (qRT-PCR) assay in kidneys confirmed that fish in this experiment were authentically infected and bacterial loads in rALDH7A1-adminsitered fish were significantly reduced at an early stage of infection. Meanwhile, we found the mRNA expression of NF-kβ, P-38 MAPK, caspase-3 and TNF-α were mainly up-regulated at 72 h in the kidneys and livers of highly infected fish injected with rALDH7A1, and the same variation trend existed in fish spleens at 12 h. Consistent with these observations, neutralization experiments in vivo indicated that rALDH7A1 could obviously reduce the death rate compared to the BSA and control group. Taken together, we concluded that rALDH7A1 could act in host immune defense against bacterial infection and decrease the mortality rate of Atlantic salmon at early stages of infection with A. salmonicida.

Neurotoxicity and metabolism of the catecholamine-derived 3,4-dihydroxyphenylacetaldehyde and 3,4-dihydroxyphenylglycolaldehyde: the role of aldehyde dehydrogenase

Aldehydes are highly reactive molecules formed during the biotransformation of numerous endogenous and exogenous compounds, including biogenic amines. 3,4-Dihydroxyphenylacetaldehyde is the aldehyde metabolite of dopamine, and 3,4-dihydroxyphenylglycolaldehyde is the aldehyde metabolite of both norepinephrine and epinephrine. There is an increasing body of evidence suggesting that these compounds are neurotoxic, and it has been recently hypothesized that neurodegenerative disorders may be associated with increased levels of these biogenic aldehydes. Aldehyde dehydrogenases are a group of NAD(P)+ -dependent enzymes that catalyze the oxidation of aldehydes, such as those derived from catecholamines, to their corresponding carboxylic acids. To date, 19 aldehyde dehydrogenase genes have been identified in the human genome. Mutations in these genes and subsequent inborn errors in aldehyde metabolism are the molecular basis of several diseases, including Sjögren-Larsson syndrome, type II hyperprolinemia, gamma-hydroxybutyric aciduria, and pyridoxine-dependent seizures, most of which are characterized by neurological abnormalities. Several pharmaceutical agents and environmental toxins are also known to disrupt or inhibit aldehyde dehydrogenase function. It is, therefore, possible to speculate that reduced detoxification of 3,4-dihydroxyphenylacetaldehyde and 3,4-dihydroxyphenylglycolaldehyde from impaired or deficient aldehyde dehydrogenase function may be a contributing factor in the suggested neurotoxicity of these compounds. This article presents a comprehensive review of what is currently known of both the neurotoxicity and respective metabolism pathways of 3,4-dihydroxyphenylacetaldehyde and 3,4-dihydroxyphenylglycolaldehyde with an emphasis on the role that aldehyde dehydrogenase enzymes play in the detoxification of these two aldehydes.

Ethanol attenuates Aldh9 mRNA expression in Japanese medaka (Oryzias latipes) embryogenesis

The mechanisms of teratogenic effects of ethanol in Japanese medaka embryogenesis were investigated by testing the hypothesis that ethanol or its metabolite ameliorates the expression of ethanol metabolizing enzymes. We have previously demonstrated that ethanol is unable to alter the expression pattern of alcohol dehydrogenase (ADH) mRNA, the first enzyme of ethanol metabolism, in medaka embryos during development. We, therefore, extended our investigation to aldehyde dehydrogenase (ALDH) system, the next enzyme of alcohol metabolic pathway. As the first step towards studying the regulation of Aldh mRNA expression by ethanol, we have cloned a cDNA by reverse transcriptase polymerase chain reaction (RT-PCR) from adult Japanese medaka (Oryzias latipes) liver representing the medaka ALDH9 gene product, with a coding region of 1515 nucleotides. The deduced amino acid sequences share 81.2% identity with cod liver betaine aldehyde dehydrogenase (BADH, EC 1.2.1.8), and 71.1% identity with human ALDH9A1 sequences. RT-PCR analysis further showed that in adults Aldh9 mRNA is constitutively expressed in all organs tested (brain, eye, gill, GI, heart, liver, kidney, muscle, skin, testis and ovary). Using semi-quantitative (rRT-PCR) and quantitative real time RT-PCR (qRT-PCR), we detected Aldh9 mRNA at all time points of development and the expression was lowest between approximately 1 and 8 h post-fertilization (hpf). Treatment of the embryos with ethanol for 48 h post-fertilization (hpf) attenuates (delayed) the expression of Aldh9 mRNA. This delayed expression of Aldh9 mRNA by ethanol may enhance acetaldehyde concentration in the embryo and induce teratogenesis during development.

Purification and characterization of grass carp mitochondrial aldehyde dehydrogenase

The molecular biology and enzymology of aldehyde dehydrogenase (ALDH) have been extensively investigated. However, most of the studies have been confined to the mammalian forms, while the sub-mammalian vertebrate ALDHs are relatively unexplored. In the present investigation, an ALDH was purified from the hepatopancreas of grass carp (Ctenopharygodon idellus) by affinity chromatographies on alpha-cyanocinnamate-Sepharose and Affi-gel Blue agarose. The 800-fold purified enzyme had a specific activity of 4.46 U/mg toward the oxidation of acetaldehyde at pH 9.5. It had a subunit molecular weight of 55000. Isoelectric focusing showed a single band with a pI of 5.3. N-terminal amino acid sequencing of 30 residues revealed a positional identity of approximately 70% with mammalian mitochondrial ALDH2. The kinetic properties of grass carp ALDH resembled those of mammalian ALDH2. The optimal pH for the oxidation of acetaldehyde was 9.5. The K(m) values for acetaldehyde were 0.36 and 0.31 microM at pH 7.5 and 9.5, respectively. Grass carp ALDH also possessed esterase activity which could be activated in the presence of NAD(+).