BACKGROUND: ALDH-2 has been considered an important molecular target for the treatment of drug addiction due to its involvement in the metabolism of the neurotransmitter dopamine: however, the molecular basis for the selective inhibition of ALDH-2 versus ALDH-1 should be better investigated to enable a more pragmatic approach to the design of novel ALDH-2 selective inhibitors. OBJECTIVE: In the present study, we investigated the molecular basis for the selective inhibition of ALDH-2 by the antioxidant isoflavonoid daidzin (IC50 = 0.15 μM) compared to isoform 1 of ALDH through molecular dynamics studies and semiempirical calculations of the enthalpy of interaction. METHODS: The applied methodology consisted of performing the molecular docking of daidzin in the structures of ALDH-1 and ALDH-2 and submitting the lower energy complexes obtained to semiempirical calculations and dynamic molecular simulations. RESULTS: Daidzin in complex with ALDH-2 presented directed and more specific interactions, resulting in stronger bonds in energetic terms and, therefore, in enthalpic gain. Moreover, the hydrophobic subunits of daidzin, in a conformationally more restricted environment (such as the catalytic site of ALDH-2), promote the better organization of the water molecules when immersed in the solvent, also resulting in an entropic gain. CONCLUSION: The molecular basis of selective inhibition of ALDH-2 by isoflavonoids and related compounds could be related to a more favorable equilibrium relationship between enthalpic and entropic features. The results described herein expand the available knowledge regarding the physiopathological and therapeutic mechanisms associated with drug addiction.

• Keywords
• ALDH-2, daidzin, isoflavonoids, molecular dynamics, nucleus accumbens, selective inhibition,
• MeSH
• Aldehyde Dehydrogenase metabolism   MeSH
• Dopamine metabolism   MeSH
• Enzyme Inhibitors pharmacology   MeSH
• Isoflavones pharmacology   MeSH
• Substance-Related Disorders drug therapy   MeSH
• Molecular Docking Simulation MeSH
• Structure-Activity Relationship MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Aldehyde Dehydrogenase MeSH
• daidzin MeSH Browser
• Dopamine MeSH
• Enzyme Inhibitors MeSH
• Isoflavones MeSH

Aldehyde dehydrogenases (ALDHs) are responsible for oxidation of biogenic aldehyde intermediates as well as for cell detoxification of aldehydes generated during lipid peroxidation. So far, 13 ALDH families have been described in plants. In the present study, we provide a detailed biochemical characterization of plant ALDH2 and ALDH7 families by analysing maize and pea ALDH7 (ZmALDH7 and PsALDH7) and four maize cytosolic ALDH(cALDH)2 isoforms RF2C, RF2D, RF2E and RF2F [the first maize ALDH2 was discovered as a fertility restorer (RF2A)]. We report the crystal structures of ZmALDH7, RF2C and RF2F at high resolution. The ZmALDH7 structure shows that the three conserved residues Glu(120), Arg(300) and Thr(302) in the ALDH7 family are located in the substrate-binding site and are specific to this family. Our kinetic analysis demonstrates that α-aminoadipic semialdehyde, a lysine catabolism intermediate, is the preferred substrate for plant ALDH7. In contrast, aromatic aldehydes including benzaldehyde, anisaldehyde, cinnamaldehyde, coniferaldehyde and sinapaldehyde are the best substrates for cALDH2. In line with these results, the crystal structures of RF2C and RF2F reveal that their substrate-binding sites are similar and are formed by an aromatic cluster mainly composed of phenylalanine residues and several nonpolar residues. Gene expression studies indicate that the RF2C gene, which is strongly expressed in all organs, appears essential, suggesting that the crucial role of the enzyme would certainly be linked to the cell wall formation using aldehydes from phenylpropanoid pathway as substrates. Finally, plant ALDH7 may significantly contribute to osmoprotection because it oxidizes several aminoaldehydes leading to products known as osmolytes.

• MeSH
• Aldehyde Dehydrogenase chemistry   genetics   metabolism   MeSH
• Phylogeny MeSH
• Pisum sativum enzymology   genetics   MeSH
• Isoenzymes chemistry   genetics   metabolism   MeSH
• Catalytic Domain genetics   MeSH
• Kinetics MeSH
• Crystallography, X-Ray MeSH
• Zea mays enzymology   genetics   MeSH
• Models, Genetic MeSH
• Models, Molecular MeSH
• Molecular Sequence Data MeSH
• NAD metabolism   MeSH
• Plant Proteins chemistry   genetics   metabolism   MeSH
• Plants enzymology   genetics   MeSH
• Amino Acid Sequence MeSH
• Gene Expression Profiling MeSH
• Substrate Specificity MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Aldehyde Dehydrogenase MeSH
• Isoenzymes MeSH
• NAD MeSH
• Plant Proteins MeSH

Lower plant species including some green algae, non-vascular plants (bryophytes) as well as the oldest vascular plants (lycopods) and ferns (monilophytes) possess a unique aldehyde dehydrogenase (ALDH) gene named ALDH21, which is upregulated during dehydration. However, the gene is absent in flowering plants. Here, we show that ALDH21 from the moss Physcomitrella patens codes for a tetrameric NADP+ -dependent succinic semialdehyde dehydrogenase (SSALDH), which converts succinic semialdehyde, an intermediate of the γ-aminobutyric acid (GABA) shunt pathway, into succinate in the cytosol. NAD+ is a very poor coenzyme for ALDH21 unlike for mitochondrial SSALDHs (ALDH5), which are the closest related ALDH members. Structural comparison between the apoform and the coenzyme complex reveal that NADP+ binding induces a conformational change of the loop carrying Arg-228, which seals the NADP+ in the coenzyme cavity via its 2'-phosphate and α-phosphate groups. The crystal structure with the bound product succinate shows that its carboxylate group establishes salt bridges with both Arg-121 and Arg-457, and a hydrogen bond with Tyr-296. While both arginine residues are pre-formed for substrate/product binding, Tyr-296 moves by more than 1 Å. Both R121A and R457A variants are almost inactive, demonstrating a key role of each arginine in catalysis. Our study implies that bryophytes but presumably also some green algae, lycopods and ferns, which carry both ALDH21 and ALDH5 genes, can oxidize SSAL to succinate in both cytosol and mitochondria, indicating a more diverse GABA shunt pathway compared with higher plants carrying only the mitochondrial ALDH5.

• Keywords
• Physcomitrella patens, ALDH21, ALDH5, X-ray crystallography, aldehyde dehydrogenase, site-directed mutagenesis, structure-function, succinic semialdehyde, γ-aminobutyric acid,
• MeSH
• Bryophyta enzymology   genetics   MeSH
• Phylogeny MeSH
• gamma-Aminobutyric Acid analogs & derivatives   metabolism   MeSH
• Ferns enzymology   genetics   MeSH
• Protein Conformation MeSH
• Succinic Acid metabolism   MeSH
• Genes, Plant genetics   physiology   MeSH
• Substrate Specificity MeSH
• Succinate-Semialdehyde Dehydrogenase genetics   metabolism   MeSH
• Structure-Activity Relationship MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• gamma-Aminobutyric Acid MeSH
• Succinic Acid MeSH
• succinic semialdehyde MeSH Browser
• Succinate-Semialdehyde Dehydrogenase MeSH

PURPOSE: CXCR1, one of the receptors for CXCL8, has been identified as a druggable target on breast cancer cancer stem cells (CSC). Reparixin (R), an investigational oral inhibitor of CXCR1, was safely administered to metastatic breast cancer patients in combination with paclitaxel (P) and appeared to reduce CSC in a window-of-opportunity trial in operable breast cancer. The fRida trial (NCT02370238) evaluated the addition of R to weekly as first-line therapy for metastatic (m) TNBC. SUBJECTS AND METHODS: Subjects with untreated mTNBC were randomized 1:1 to R or placebo days 1-21 in combination with weekly P 80 mg/m2 on days 1, 8, 15 of 28-day cycles. The primary endpoint was PFS by central review. RESULTS: 123 subjects were randomized (62 to R + P and 61 to placebo + P). PFS was not different between the 2 groups (median 5.5 and 5.6 months for R + P and placebo + P, respectively; HR 1.13, p = 0.5996). ALDH+ and CD24-/CD44+ CSC centrally evaluated by IHC were found in 16 and 34 of the 54 subjects who provided a metastatic tissue biopsy at study entry. Serious adverse events (21.3 and 20% of subjects) and grade ≥ 3 adverse reactions (ADR) (9.1 and 6.3% of all ADRs) occurred at similar frequency in both groups. CONCLUSION: fRida is the first randomized, double-blind clinical trial of a CSC-targeting agent in combination with chemotherapy in breast cancer. The primary endpoint of prolonged PFS was not met. CLINICAL TRIAL REGISTRATION/DATE OF REGISTRATION: NCT01861054/February 24, 2015.

• Keywords
• CXCR1, Cancer stem cells, Reparixin, TNBC,
• MeSH
• Humans MeSH
• Paclitaxel adverse effects   MeSH
• Antineoplastic Combined Chemotherapy Protocols adverse effects   MeSH
• Sulfonamides MeSH
• Triple Negative Breast Neoplasms * drug therapy   MeSH
• Check Tag
• Humans MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Clinical Trial, Phase II MeSH
• Randomized Controlled Trial MeSH
• Names of Substances
• Paclitaxel MeSH
• reparixin MeSH Browser
• Sulfonamides MeSH