5-HT,dopamine, norepinephrine,and related metabolites in brain of low alcohol drinking (LAD) rats shift after chronic intra-hippocampal infusion of harman

Harman (1-methyl--carboline) has been shown to induce preference for alcohol in the genetically bred, low alcohol drinking (LAD) rat. This study was undertaken in the LAD rat to determine whether monoamines and their metabolites in different regions of the brain are altered by harman infused chronically into the dorsal hippocampus. For this purpose, a cannula was implanted stereotaxically into the dorsal hippocampus. The cannula was attached to an osmotic minipump implanted subcutaneously within the intrascapular space. The pump was filled with either an artificial cerebrospinal fluid (CSF) vehicle or harman, which was delivered at a rate of 1.0 or 3.0 g/h (i.e., 5.5 or 16.5 nmol/h, respectively) for a period of 14 days. Four days after surgery, a standard preference test for ethyl alcohol was given to the rats over 10 days in which concentrations were increased daily from 3%–30%. The higher concentration of harman infused into the hippocampus elevated the level of serotonin (5-HT), both ipsilateral and contralateral to the hippocampal site of infusion, as well as in the midbrain, frontal cortex, striatum and nucleus accumbens. Similarly, this treatment resulted in a rise in the levels of norepinephrine in the hippocampus and midbrain but aecreases in dopamine levels in the pons. The levels of 5-hydroxyindoleacetic acid (5-HIAA) and: 3,4-dihydroxyphenylacetic acid (DOPAC) were diminished in the pons of rats given 3.0 g/h harman, whereas both concentrations of the -carboline reduced the level of homovanillic acid (HVA) in the frontal cortex. These harman-induced changes in the metabolism of the amines are possibly the result of an inhibition of monoamine oxidase (MAO). When the harman-induced shifts in the neurochemical values were compared to the alcohol intakes of the rats as reported previously, no significant correlation was found. The absence of this concordance suggests that the alterations in the monoamine neurotransmitters produced by harman and the voluntary intake of alcohol induced by this -carboline may not originate from the same systems in the brain.     

Aldehyde reductase gene expression by lipid peroxidation end products,MDA and HNE

Membrane lipid peroxidation results in the production of a variety of aldehydic compounds that play a significant role in aging, drug toxicity and the pathogenesis of a number of human diseases, such as atherosclerosis and cancer. Increased lipid peroxidation and reduced antioxidant status may also contribute to the development of diabetic complications. This study reports that lipid peroxidation end products such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE) induce aldehyde reductase (ALR) gene expression. MDA and HNE induce an increase in intracellular peroxide levels; N-Acetyl-L-cysteine (NAC) suppressed MDA- and HNE-induced ALR gene expression. These results indicate that increased levels of intracellular peroxides by MDA and HNE might be involved in the upregulation of ALR.     

A commentary on the paper: ‘Evaluation of spice and herb as phytoderived selective modulators of human retinaldehyde dehydrogenases using a simple in vitro method’

It is commonly known that aldehyde dehydrogenases (ALDHs) are a promising therapeutic target in many diseases. Bui et al.—the authors of the paper I am discussing here (Biosci Rep (2021) 41(5): BSR20210491 https://doi.org/10.1042/BSR20210491)—point that there is a lack of research on the use of spices and herbs as the sources of naturally occurring modulators of ALDH activity. In order to carry out this type of research, the authors prepared ethanolic extracts of 22 spices and herbs. The main objective of the study was to investigate retinaldehyde dehydrogenases (RALDHs), of which retinal is the main substrate and ALDH2, the mitochondrial isoform, having acetaldehyde as the main substrate.The obtained results indicated that the tested extracts exhibited differential regulatory effects on RALDHs/ALDH2 and some of them showed a potential selective inhibition of the activity of RALDHs.     

Comparison of floral properties and breeding system in dimorphic Buddleja delavayi (Scrophulariaceae)

In this study, floral color, scent composition and emission rate, nectar property, pollinators, and breeding system of dimorphic Buddleja delavayi Gagnep. were investigated. Flower color of B. delavayi was determined using a standard color chart and spectrophotometer, and two distinct color polymorphisms were observed having purple or white flowers. Floral scents of B. delavayi were collected using dynamic headspace adsorption and identified with coupled gas chromatography and mass spectrometry. In total, 28 compounds were identified from the flowers of B. delavayi. The identified scents were divided into three chemical classes based on their biosynthetic origin: terpenes, fatty acid derivatives, and benzenoids. The scent profiles in all individuals were dominated by a few components, such as lilac aldehyde and alcohol, 4-oxoisophorone, benaldehyde, and oxoisophorone oxide. Floral scent composition (benzenoids and terpenes) showed a significant difference between white and purple flower morphs. Flower color–flower scent associations in B. delavayi were identified with two distinct scent profiles in the two color phenotypes. The studies of other floral characteristics (nectar, floral visitors, breeding system, and fruit set) indicated that floral scent emission rate, nectar volume, visitor visitation frequency, and natural fruit set were not significantly different between the two flower color morphs. Bagging experiments revealed that seed production of B. delavayi is dependent mainly on honeybee Apis cerana. Lastly, this study implies that dimorphic floral color in B. delavayi may have been maintained by floral visitors and nectar guide color.     

Formation and role of glycine betaine in the moderate halophile Vibrio costicola

The moderate halophile Vibrio costicola, growing on a chemically-defined medium, transformed choline into glycine betaine (betaine) by the membrane-bound enzyme choline dehydrogenase and the cytoplasmic enzyme betainal (betaine aldehyde) dehydrogenase. Choline dehydrogenase was strongly induced and betainal dehydrogenase less strongly induced by choline. The formation of these enzymes was also regulated by the NaCl concentration of the growth medium, increasing with increasing NaCl concentrations. Intracellular betaine concentrations also increased with increasing choline and NaCl concentrations in the medium. This increase was almost completely blocked by chloramphenicol, which does not block the increase in salt-tolerant active transport on transfer from a low to a high salt concentration.Choline dehydrogenase was inhibited by chloride salts of Na⁺, K⁺, and NH _inf4 ^su+ , the inhibition being due to the Cl^- ions. Betainal dehydrogenase was stimulated by 0.5 M salts and could function in up to 2.0 M salts.Cells grew as well in the presence as in the absence of choline in 0.5 M and 1.0 M NaCl, but formed no intracellular betaine. Choline stimulated growth in 2.0 M NaCl and was essential for growth in 3.0 M NaCl. Thus, while betaine is important for some of the adaptations to high salt concentration by V. costicola, it by no means accounts for all of them.Abbreviations CDMM chemically-defined minimal medium - PPT proteose-peptone tryptone medium - SDS sodium dodecyl sulfate Deceased, 1987     

Structural and biochemical characterization of a novel aldehyde dehydrogenase encoded by the benzoate oxidation pathway in Burkholderia xenovorans LB400

The recently identified benzoate oxidation (box) pathway in Burkholderia xenovorans LB400 (LB400 hereinafter) assimilates benzoate through a unique mechanism where each intermediate is processed as a coenzyme A (CoA) thioester. A key step in this process is the conversion of 3,4-dehydroadipyl-CoA semialdehyde into its corresponding CoA acid by a novel aldehyde dehydrogenase (ALDH) (EC 1.2.1.x). The goal of this study is to characterize the biochemical and structural properties of the chromosomally encoded form of this new class of ALDHs from LB400 (ALDH_C) in order to better understand its role in benzoate degradation. To this end, we carried out kinetic studies with six structurally diverse aldehydes and nicotinamide adenine dinucleotide (phosphate) (NAD ⁺ and NADP ⁺). Our data definitively show that ALDH_C is more active in the presence of NADP ⁺ and selective for linear medium-chain to long-chain aldehydes. To elucidate the structural basis for these biochemical observations, we solved the 1.6-Å crystal structure of ALDH_C in complex with NADPH bound in the cofactor-binding pocket and an ordered fragment of a polyethylene glycol molecule bound in the substrate tunnel. These data show that cofactor selectivity is governed by a complex network of hydrogen bonds between the oxygen atoms of the 2′-phosphoryl moiety of NADP ⁺ and a threonine/lysine pair on ALDH_C. The catalytic preference of ALDH_C for linear longer-chain substrates is mediated by a deep narrow configuration of the substrate tunnel. Comparative analysis reveals that reorientation of an extended loop (Asn478-Pro490) in ALDH_C induces the constricted structure of the substrate tunnel, with the side chain of Asn478 imposing steric restrictions on branched-chain and aromatic aldehydes. Furthermore, a key glycine (Gly104) positioned at the mouth of the tunnel allows for maximum tunnel depth required to bind medium-chain to long-chain aldehydes. This study provides the first integrated biochemical and structural characterization of a box-pathway-encoded ALDH from any organism and offers insight into the catalytic role of ALDH_C in benzoate degradation.     

Hydrogen Peroxide and the Proliferation of Bhk-21 Cells

Intracellular levels of H2O2 in BHK-21 cells are not static but decline progressively with cell growth. Exposure of cells to inhibitors of catalase, or glutathione peroxidase, not only diminishes this decline but also depresses rates of cell proliferation, suggesting important growth regulatory roles for those antioxidant enzymes. Other agents which also diminish the growth-associated decline in intracellular levels of H₂O₂, such as the superoxide dismutase mimic, copper II—(3,5-diisopropylsalicylate)₂, or docosahexaenoic acid, also reduced cell proliferation. In contrast, proliferation can be stimulated by the addition of 1 μM exogenous H₂O₂ to the culture medium. Under these conditions, however, intracellular levels of H₂O₂ are unaffected, whereas there is a reduction in intracellular levels of glutathione. It is argued that critical balances between intracellular levels of both H₂O₂ and glutathione are of significance in relation both to growth stimulation and inhibition. In addition growth stimulatory concentrations of H₂O₂, whilst initially leading to increased intracellular levels of lipid peroxidation breakdown products, appear to “trigger” their metabolism, possibly through aldehyde dehydrogenase, whose activity is also stimulated by H₂O₂     

The Biosynthesis of Branched Dialkylpyrazines in Myxobacteria

The biosynthesis of the volatiles 2,5‐ and 2,6‐diisopropylpyrazine ( 2 and 3 , resp.) released by the myxobacteria Nannocystis exedens subsp. cinnabarina (Na c29) and Chondromyces crocatus (strains Cm c2 and Cm c5) was studied. Isotopically labeled precursors and proposed pathway intermediates were fed to agar plate cultures of the myxobacteria. Subsequently, the volatiles were collected by use of a closed loop stripping apparatus (CLSA), and incorporation into the pyrazines was followed by GC/MS analysis. [²H₈]Valine was smoothly incorporated into both pyrazines clearly establishing their origin from the amino acid pool. The cyclic dipeptide valine anhydride ( 16 ) – a potential intermediate on the biosynthetic pathway to branched dialkylpyrazines – was synthesized containing ²H₁ labels in specific positions. Feeding of [²H₁₆]‐ 16 and [²H₁₂]‐ 16 in both valine subunits mainly resulted in the formation of pyrazines derived from only one labeled amino acid, whereas only traces of the expected pyrazines with two labeled subunits were found. To investigate the origin of nitrogen in the pyrazines, a feeding experiment with [¹⁵N]valine was performed, resulting in the incorporation of the ¹⁵N label. The results contradict a biosynthetic pathway via cyclic dipeptides, but rather point to a pathway on which valine is reduced to valine aldehyde. Its dimerization to 2,5‐diisopropyldihydropyrazine 36 and subsequent oxidation results in 2 . The proposed biosynthetic pathway neatly fits the results of earlier labeling studies and also explains the formation of the regioisomer 2,6‐diisopropylpyrazine 3 by isomerization during the first condensation step of two molecules valine aldehyde. A general biosynthetic pathway to different classes of pyrazines is presented.     

Human liver mitochondrial aldehyde dehydrogenase: three-dimensional structure and the restoration of solubility and activity of chimeric forms

Human liver cytosolic and mitochondrial isozymes of aldehyde dehydrogenase share 70% sequence identity. However, the first 21 residues are not conserved between the human isozymes (15% identity). The three-dimensional structures of the beef mitochondrial and sheep cytosolic forms have virtually identical three-dimensional structures. Here, we solved the structure of the human mitochondrial enzyme and found it to be identical to the beef enzyme. The first 21 residues are found on the surface of the enzyme and make no contact with other subunits in the tetramer. A pair of chimeric enzymes between the human isozymes was made. Each chimera had the first 21 residues from one isozyme and the remaining 479 from the other. When the first 21 residues were from the mitochondrial isozyme, an enzyme with cytosolic-like properties was produced. The other was expressed but was insoluble. It was possible to restore solubility and activity to the chimera that had the first 21 cytosolic residues fused to the mitochondrial ones by making point mutations to residues at the N-terminal end. When residue 19 was changed from tyrosine to a cysteine, the residue found in the mitochondrial form, an active enzyme could be made though the Km for NAD+ was 35 times higher than the native mitochondrial isozyme and the specific activity was reduced by 75%. This residue interacts with residue 203, a nonconserved, nonactive site residue. A mutation of residue 18, which also interacts with 203, restored solubility, but not activity. Mutation to residue 15, which interacts with 104, also restored solubility but not activity. It appears that to have a soluble or active enzyme a favorable interaction must occur between a residue in a surface loop and a residue elsewhere in the molecule even though neither make contact with the active site region of the enzyme.