Aldehyde dehydrogenase inhibitors: a comprehensive review of the pharmacology, mechanism of action, substrate specificity, and clinical application

Characterization of a Human Respiratory Mucosa Model to Study Odorant Metabolism

Nasal xenobiotic metabolizing enzymes (XMEs) are important for the sense of smell because they influence odorant availability and quality. Since the major part of the human nasal cavity is lined by a respiratory mucosa, we hypothesized that this tissue contributed to nasal odorant metabolism through XME activity. Thus, we built human respiratory tissue models and characterized the XME profiles using single-cell RNA sequencing. We focused on the XMEs dicarbonyl and l-xylulose reductase, aldehyde dehydrogenase (ALDH) 1A1, and ALDH3A1, which play a role in food odorant metabolism. We demonstrated protein abundance and localization in the tissue models and showed the metabolic activity of the corresponding enzyme families by exposing the models to the odorants 3,4-hexandione and benzaldehyde. Using gas chromatography coupled with mass spectrometry, we observed, for example, a significantly higher formation of the corresponding metabolites 4-hydroxy-3-hexanone (39.03 ± 1.5%, p = 0.0022), benzyl alcohol (10.05 ± 0.88%, p = 0.0008), and benzoic acid (8.49 ± 0.57%, p = 0.0004) in odorant-treated tissue models compared to untreated controls (0 ± 0, 0.12 ± 0.12, and 0.18 ± 0.18%, respectively). This is the first study that reveals the XME profile of tissue-engineered human respiratory mucosa models and demonstrates their suitability to study nasal odorant metabolism.

Nanomedicine-based disulfiram and metal ion co-delivery strategies for cancer treatment

Disulfiram (DSF) is a second-line drug for the clinical treatment of alcoholism and has long been proven to be safe for use in clinical practice. In recent years, researchers have discovered the cancer-killing activity of DSF, which is highly dependent on the presence of metal ions, particularly copper ions. Additionally, free DSF is highly unstable and easily degraded within few minutes in blood circulation. Therefore, an ideal DSF formulation should facilitate the co-delivery of metal ions and safeguard the DSF throughout its biological journey before reaching the targeted site. Extensive research have proved that nanotechnology based formulations can effectively realize this goal by strategic encapsulation therapeutic agents within nanoparticle. To be more specific, this is accomplished through precise delivery, coordinated release of metal ions at the tumor site, thereby amplifying its cytotoxic potential. Beyond traditional co-loading techniques, innovative approaches such as DSF-metal complex and metal nanomaterials, have also demonstrated promising results at the animal model stage. This review aims to elucidate the anticancer mechanism associated with DSF and its reliance on metal ions, as well as to provide a comprehensive overview of recent advances in the arena of nanomedicine based co-delivery strategies for DSF and metal ion in the context of cancer therapy.

Acetaldehyde Dehydrogenase 2 Deficiency Aggravates Lung Fibrosis through Mitochondrial Dysfunction and Aging in Fibroblasts

Idiopathic pulmonary fibrosis, a fatal interstitial lung disease, is characterized by fibroblast activation and aberrant extracellular matrix accumulation. Effective therapeutic development is limited because of incomplete understanding of the mechanisms by which fibroblasts become aberrantly activated. Here, we show acetaldehyde dehydrogenase 2 (ALDH2) in fibroblasts as a potential therapeutic target for pulmonary fibrosis. A decrease in ALDH2 expression was observed in patients with idiopathic pulmonary fibrosis and bleomycin-treated mice. ALDH2 deficiency spontaneously induces collagen accumulation in the lungs of aged mice. Furthermore, young ALDH2 knockout mice exhibited exacerbated bleomycin-induced pulmonary fibrosis and increased mortality compared with that in control mice. Mechanistic studies revealed that transforming growth factor (TGF)-β1 induction and ALDH2 depletion constitute a positive feedback loop that exacerbates fibroblast activation. TGF-β1 down-regulated ALDH2 through a TGF-β receptor 1/Smad3-dependent mechanism. The subsequent deficiency in ALDH2 resulted in fibroblast dysfunction that manifested as impaired mitochondrial autophagy and senescence, leading to fibroblast activation and extracellular matrix production. ALDH2 overexpression markedly suppressed fibroblast activation, and this effect was abrogated by PTEN-induced putative kinase 1 (PINK1) knockdown, indicating that the profibrotic effects of ALDH2 are PINK1- dependent. Furthermore, Alda-1-induced ALDH2 activation reversed the established pulmonary fibrosis in both young and aged mice. In conclusion, ALDH2 expression inhibits the pathogenesis of pulmonary fibrosis. Strategies to up-regulate or activate ALDH2 expression could be potential therapies for pulmonary fibrosis.

Metabolic Rewiring in Cancer: Small Molecule Inhibitors in Colorectal Cancer Therapy

Alterations in cellular metabolism, such as dysregulation in glycolysis, lipid metabolism, and glutaminolysis in response to hypoxic and low-nutrient conditions within the tumor microenvironment, are well-recognized hallmarks of cancer. Therefore, understanding the interplay between aerobic glycolysis, lipid metabolism, and glutaminolysis is crucial for developing effective metabolism-based therapies for cancer, particularly in the context of colorectal cancer (CRC). In this regard, the present review explores the complex field of metabolic reprogramming in tumorigenesis and progression, providing insights into the current landscape of small molecule inhibitors targeting tumorigenic metabolic pathways and their implications for CRC treatment.

Pharmacological agents targeting drug-tolerant persister cells in cancer

Current cancer therapy can be effective, but the development of drug resistant disease is the usual outcome. These drugs can eliminate most of the tumor burden but often fail to eliminate the rare, "Drug Tolerant Persister" (DTP) cell subpopulations in residual tumors, which can be referred to as "Persister" cells. Therefore, novel therapeutic agents specifically targeting or preventing the development of drug-resistant tumors mediated by the remaining persister cells subpopulations are needed. Since approximately ninety percent of cancer-related deaths occur because of the eventual development of drug resistance, identifying, and dissecting the biology of the persister cells is essential for the creation of drugs to target them. While there remains uncertainty surrounding all the markers identifying DTP cells in the literature, this review summarizes the drugs and therapeutic approaches that are available to target the persister cell subpopulations expressing the cellular markers ATP-binding cassette sub-family B member 5 (ABCB5), CD133, CD271, Lysine-specific histone demethylase 5 (KDM5), and aldehyde dehydrogenase (ALDH). Persister cells expressing these markers were selected as the focus of this review because they have been found on cells surviving following drug treatments that promote recurrent drug resistant cancer and are associated with stem cell-like properties, including self-renewal, differentiation, and resistance to therapy. The limitations and obstacles facing the development of agents targeting these DTP cell subpopulations are detailed, with discussion of potential solutions and current research areas needing further exploration.

Diethyldithiocarbamate-ferrous oxide nanoparticles inhibit human and mouse glioblastoma stemness: aldehyde dehydrogenase 1A1 suppression and ferroptosis induction

The development of effective therapy for eradicating glioblastoma stem cells remains a major challenge due to their aggressive growth, chemoresistance and radioresistance which are mainly conferred by aldehyde dehydrogenase (ALDH)1A1. The latter is the main stemness mediator via enhancing signaling pathways of Wnt/β-catenin, phosphatidylinositol 3-kinase/AKT, and hypoxia. Furthermore, ALDH1A1 mediates therapeutic resistance by inactivating drugs, stimulating the expression of drug efflux transporters, and detoxifying reactive radical species, thereby apoptosis arresting. Recent reports disclosed the potent and broad-spectrum anticancer activities of the unique nanocomplexes of diethyldithiocarbamate (DE, ALDH1A1 inhibitor) with ferrous oxide nanoparticles (FeO NPs) mainly conferred by inducing lipid peroxidation-dependent non-apoptotic pathways (iron accumulation-triggered ferroptosis), was reported. Accordingly, the anti-stemness activity of nanocomplexes (DE-FeO NPs) was investigated against human and mouse glioma stem cells (GSCs) and radioresistant GSCs (GSCs-RR). DE-FeO NPs exhibited the strongest growth inhibition effect on the treated human GSCs (MGG18 and JX39P), mouse GSCs (GS and PDGF-GSC) and their radioresistant cells (IC50 ≤ 70 and 161 μg/mL, respectively). DE-FeO NPs also revealed a higher inhibitory impact than standard chemotherapy (temozolomide, TMZ) on self-renewal, cancer repopulation, chemoresistance, and radioresistance potentials. Besides, DE-FeO NPs surpassed TMZ regarding the effect on relative expression of all studied stemness genes, as well as relative p-AKT/AKT ratio in the treated MGG18, GS and their radioresistant (MGG18-RR and GS-RR). This potent anti-stemness influence is primarily attributed to ALDH1A1 inhibition and ferroptosis induction, as confirmed by significant elevation of cellular reactive oxygen species and lipid peroxidation with significant depletion of glutathione and glutathione peroxidase 4. DE-FeO NPs recorded the optimal LogP value for crossing the blood brain barrier. This in vitro novel study declared the potency of DE-FeO NPs for collapsing GSCs and GSCs-RR with improving their sensitivity to chemotherapy and radiotherapy, indicating that DE-FeO NPs may be a promising remedy for GBM. Glioma animal models will be needed for in-depth studies on its safe effectiveness.

One substrate many enzymes virtual screening uncovers missing genes of carnitine biosynthesis in human and mouse

The increasing availability of experimental and computational protein structures entices their use for function prediction. Here we develop an automated procedure to identify enzymes involved in metabolic reactions by assessing substrate conformations docked to a library of protein structures. By screening AlphaFold-modeled vitamin B6-dependent enzymes, we find that a metric based on catalytically favorable conformations at the enzyme active site performs best (AUROC Score=0.84) in identifying genes associated with known reactions. Applying this procedure, we identify the mammalian gene encoding hydroxytrimethyllysine aldolase (HTMLA), the second enzyme of carnitine biosynthesis. Upon experimental validation, we find that the top-ranked candidates, serine hydroxymethyl transferase (SHMT) 1 and 2, catalyze the HTMLA reaction. However, a mouse protein absent in humans (threonine aldolase; Tha1) catalyzes the reaction more efficiently. Tha1 did not rank highest based on the AlphaFold model, but its rank improved to second place using the experimental crystal structure we determined at 2.26 Å resolution. Our findings suggest that humans have lost a gene involved in carnitine biosynthesis, with HTMLA activity of SHMT partially compensating for its function.

Informed by Cancer Stem Cells of Solid Tumors: Advances in Treatments Targeting Tumor-Promoting Factors and Pathways

Cancer stem cells (CSCs) represent a subpopulation within tumors that promote cancer progression, metastasis, and recurrence due to their self-renewal capacity and resistance to conventional therapies. CSC-specific markers and signaling pathways highly active in CSCs have emerged as a promising strategy for improving patient outcomes. This review provides a comprehensive overview of the therapeutic targets associated with CSCs of solid tumors across various cancer types, including key molecular markers aldehyde dehydrogenases, CD44, epithelial cellular adhesion molecule, and CD133 and signaling pathways such as Wnt/β-catenin, Notch, and Sonic Hedgehog. We discuss a wide array of therapeutic modalities ranging from targeted antibodies, small molecule inhibitors, and near-infrared photoimmunotherapy to advanced genetic approaches like RNA interference, CRISPR/Cas9 technology, aptamers, antisense oligonucleotides, chimeric antigen receptor (CAR) T cells, CAR natural killer cells, bispecific T cell engagers, immunotoxins, drug-antibody conjugates, therapeutic peptides, and dendritic cell vaccines. This review spans developments from preclinical investigations to ongoing clinical trials, highlighting the innovative targeting strategies that have been informed by CSC-associated pathways and molecules to overcome therapeutic resistance. We aim to provide insights into the potential of these therapies to revolutionize cancer treatment, underscoring the critical need for a multi-faceted approach in the battle against cancer. This comprehensive analysis demonstrates how advances made in the CSC field have informed significant developments in novel targeted therapeutic approaches, with the ultimate goal of achieving more effective and durable responses in cancer patients.

Flavonostilbenes natural hybrids from Rhamnoneuron balansae as potential antitumors targeting ALDH1A1: molecular docking, ADMET, MM-GBSA calculations and molecular dynamics studies

Several studies have linked Cancer stem cells (CSCs) to cancer resistance development to chemotherapy and radiotherapy. ALDH1A1 is a key enzyme that regulates the gene expression of CSCs and creates an immunosuppressive tumor microenvironment. It was reported that quercetin and resveratrol were among the inhibitors of ALDH1A1. In early 2022, it was reported that new 11 flavonostilbenes (rhamnoneuronal D-N) were isolated from Rhamnoneuron balansae as potential antiaging natural products. Rhamnoneuronal H (5) could be envisioned as a natural hybrid of quercetin and resveratrol. It was therefore hypothesized that 5 and its analogous isolates rhamnoneuronal D-G (1-4) and rhamnoneuronal I-N (6-11) would have potential ALDH1A1 inhibitory activity. To this end, all isolates were subjected to molecular docking, MM-GBSA, ADMET, and molecular dynamics simulations studies to assess their potential as new leads for cancer treatment targeting ALDH1A1. In silico findings revealed that natural hybrid 5 has a similar binding affinity, judged by MM-GBSA, to the ALDH1A1 active site when compared to the co-crystalized ligand (-64.71 kcal/mole and -64.12 kcal/mole, respectively). Despite having lesser affinity than that of the co-crystalized ligand, the rest of the flavonostilbenes, except 2-4, displayed better binding affinities (-37.55 kcal/mole to -58.6 kcal/mole) in comparison to either resveratrol (-34.44 kcal/mole) or quercetin (-36.48 kcal/mole). Molecular dynamic simulations showed that the natural hybrids 1, 5-11 are of satisfactory stability up to 100 ns. ADMET outcomes indicate that these hybrids displayed acceptable properties and hence could represent an ideal starting point for the development of potent ALDH1A1 inhibitors for cancer treatment.Communicated by Ramaswamy H. Sarma.

The Mechanism of Pyroptosis and Its Application Prospect in Diabetic Wound Healing

Pyroptosis defines a form of pro-inflammatory-dependent programmed cell death triggered by gasdermin proteins, which creates cytoplasmic pores and promotes the activation and accumulation of immune cells by releasing several pro-inflammatory mediators and immunogenic substances upon cell rupture. Pyroptosis comprises canonical (mediated by Caspase-1) and non-canonical (mediated by Caspase-4/5/11) molecular signaling pathways. Numerous studies have explored the contributory roles of inflammasome and pyroptosis in the progression of multiple pathological conditions such as tumors, nerve injury, inflammatory diseases and metabolic disorders. Accumulating evidence indicates that the activation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome results in the activation of pyroptosis and inflammation. Current evidence suggests that pyroptosis-dependent cell death plays a progressive role in the development of diabetic complications including diabetic wound healing (DWH) and diabetic foot ulcers (DFUs). This review presents a brief overview of the molecular mechanisms underlying pyroptosis and addresses the current research on pyroptosis-dependent signaling pathways in the context of DWH. In this review, we also present some prospective therapeutic compounds/agents that can target pyroptotic signaling pathways, which may serve as new strategies for the effective treatment and management of diabetic wounds.

Development of substituted benzimidazoles as inhibitors of human aldehyde dehydrogenase 1A isoenzymes

Aldehyde dehydrogenase 1A (ALDH1A) isoforms may be a useful target for overcoming chemotherapy resistance in high-grade serous ovarian cancer (HGSOC) and other solid tumor cancers. However, as different cancers express different ALDH1A isoforms, isoform selective inhibitors may have a limited therapeutic scope. Furthermore, resistance to an ALDH1A isoform selective inhibitor could arise via induction of expression of other ALDH1A isoforms. As such, we have focused on the development of pan-ALDH1A inhibitors, rather than on ALDH1A isoform selective compounds. Herein, we report the development of a new group of pan-ALDH1A inhibitors to assess whether broad spectrum ALDH1A inhibition is an effective adjunct to chemotherapy in HGSOC. Optimization of the CM10 scaffold, aided by ALDH1A1 crystal structures, led to improved biochemical potencies, improved cellular efficacy as demonstrated by reduction in ALDEFLUOR signal in HGSOC cells, and substantial improvements in liver microsomal stability. Based on this work we identified two compounds 17 and 25 suitable for future in vivo proof of concept experiments.

LncRNA CHKB-DT Downregulation Enhances Dilated Cardiomyopathy Through ALDH2

BACKGROUND

Human cardiac long noncoding RNA (lncRNA) profiles in patients with dilated cardiomyopathy (DCM) were previously analyzed, and the long noncoding RNA CHKB (choline kinase beta) divergent transcript (CHKB-DT) levels were found to be mostly downregulated in the heart. In this study, the function of CHKB-DT in DCM was determined.

METHODS

Long noncoding RNA expression levels in the human heart tissues were measured via quantitative reverse transcription-polymerase chain reaction and in situ hybridization assays. A CHKB-DT heterozygous or homozygous knockout mouse model was generated using the clustered regularly interspaced palindromic repeat (CRISPR)/CRISPR-associated protein 9 system, and the adeno-associated virus with a cardiac-specific promoter was used to deliver the RNA in vivo. Sarcomere shortening was performed to assess the primary cardiomyocyte contractility. The Seahorse XF cell mitochondrial stress test was performed to determine the energy metabolism and ATP production. Furthermore, the underlying mechanisms were explored using quantitative proteomics, ribosome profiling, RNA antisense purification assays, mass spectrometry, RNA pull-down, luciferase assay, RNA-fluorescence in situ hybridization, and Western blotting.

RESULTS

CHKB-DT levels were remarkably decreased in patients with DCM and mice with transverse aortic constriction-induced heart failure. Heterozygous knockout of CHKB-DT in cardiomyocytes caused cardiac dilation and dysfunction and reduced the contractility of primary cardiomyocytes. Moreover, CHKB-DT heterozygous knockout impaired mitochondrial function and decreased ATP production as well as cardiac energy metabolism. Mechanistically, ALDH2 (aldehyde dehydrogenase 2) was a direct target of CHKB-DT. CHKB-DT physically interacted with the mRNA of ALDH2 and fused in sarcoma (FUS) through the GGUG motif. CHKB-DT knockdown aggravated ALDH2 mRNA degradation and 4-HNE (4-hydroxy-2-nonenal) production, whereas overexpression of CHKB-DT reversed these molecular changes. Furthermore, restoring ALDH2 expression in CHKB-DT+/- mice alleviated cardiac dilation and dysfunction.

CONCLUSIONS

CHKB-DT is significantly downregulated in DCM. CHKB-DT acts as an energy metabolism-associated long noncoding RNA and represents a promising therapeutic target against DCM.

Homologous recombination contributes to the repair of acetaldehyde-induced DNA damage

Acetaldehyde, a chemical that can cause DNA damage and contribute to cancer, is prevalently present in our environment, e.g. in alcohol, tobacco, and food. Although aldehyde potentially promotes crosslinking reactions among biological substances including DNA, RNA, and protein, it remains unclear what types of DNA damage are caused by acetaldehyde and how they are repaired. In this study, we explored mechanisms involved in the repair of acetaldehyde-induced DNA damage by examining the cellular sensitivity to acetaldehyde in the collection of human TK6 mutant deficient in each genome maintenance system. Among the mutants, mismatch repair mutants did not show hypersensitivity to acetaldehyde, while mutants deficient in base and nucleotide excision repair pathways or homologous recombination (HR) exhibited higher sensitivity to acetaldehyde than did wild-type cells. We found that acetaldehyde-induced RAD51 foci representing HR intermediates were prolonged in HR-deficient cells. These results indicate a pivotal role of HR in the repair of acetaldehyde-induced DNA damage. These results suggest that acetaldehyde causes complex DNA damages that require various types of repair pathways. Mutants deficient in the removal of protein adducts from DNA ends such as TDP1-/- and TDP2-/- cells exhibited hypersensitivity to acetaldehyde. Strikingly, the double mutant deficient in both TDP1 and RAD54 showed similar sensitivity to each single mutant. This epistatic relationship between TDP1-/- and RAD54-/- suggests that the protein-DNA adducts generated by acetaldehyde need to be removed for efficient repair by HR. Our study would help understand the molecular mechanism of the genotoxic and mutagenic effects of acetaldehyde.

Identification of approved drugs with ALDH1A1 inhibitory potential aimed at enhancing chemotherapy sensitivity in cancer cells: an in-silico drug repurposing approach

The aldehyde dehydrogenase 1A1 (ALDH1A1) also known as retinal dehydrogenase, is an enzyme normally involved in the cellular metabolism, development and detoxification processes in healthy cells. However, it's also considered a cancer stem cell marker and its high levels of expression in several cancers, including breast, lung, ovarian, and colon cancer have been associated with poor prognosis and resistance to chemotherapy. Given its crucial role in chemotherapy resistance by detoxification of chemotherapeutic drugs, ALDH1A1 has attracted significant research interest as a potential therapeutic target for cancer. Though a few synthetic inhibitors of ALDH1A1 have been synthesized and their efficacy has been proved in-vitro and in-vivo studies, none of them have passed clinical trials so far. In this scenario, we have performed an in-silico study to verify whether any of the already approved drugs used for various purposes has the ability to inhibit catalytic activity of ALDH1A1, so that they can be repurposed for cancer therapy. Keeping in mind the feasibility of repurposing in a larger population we have selected the approved drugs from five widely used drug categories such as antibiotic, antiviral, antifungal, anti diabetic and antihypertensive for screening. Computational techniques like molecular docking, molecular dynamics simulations and MM-PBSA binding energy calculation have been used in this study to screen the approved drugs. Based on the logical analysis of results, we propose that three drugs - telmisartan, irbesartan and maraviroc can inhibit the catalytic activity of ALDH1A1 and thus can be repurposed to increase chemotherapy sensitivity in cancer cells.Communicated by Ramaswamy H. Sarma.

Evaluating protein cross-linking as a therapeutic strategy to stabilize SOD1 variants in a mouse model of familial ALS

Mutations in the gene encoding Cu-Zn superoxide dismutase 1 (SOD1) cause a subset of familial amyotrophic lateral sclerosis (fALS) cases. A shared effect of these mutations is that SOD1, which is normally a stable dimer, dissociates into toxic monomers that seed toxic aggregates. Considerable research effort has been devoted to developing compounds that stabilize the dimer of fALS SOD1 variants, but unfortunately, this has not yet resulted in a treatment. We hypothesized that cyclic thiosulfinate cross-linkers, which selectively target a rare, 2 cysteine-containing motif, can stabilize fALS-causing SOD1 variants in vivo. We created a library of chemically diverse cyclic thiosulfinates and determined structure-cross-linking-activity relationships. A pre-lead compound, "S-XL6," was selected based upon its cross-linking rate and drug-like properties. Co-crystallographic structure clearly establishes the binding of S-XL6 at Cys 111 bridging the monomers and stabilizing the SOD1 dimer. Biophysical studies reveal that the degree of stabilization afforded by S-XL6 (up to 24°C) is unprecedented for fALS, and to our knowledge, for any protein target of any kinetic stabilizer. Gene silencing and protein degrading therapeutic approaches require careful dose titration to balance the benefit of diminished fALS SOD1 expression with the toxic loss-of-enzymatic function. We show that S-XL6 does not share this liability because it rescues the activity of fALS SOD1 variants. No pharmacological agent has been proven to bind to SOD1 in vivo. Here, using a fALS mouse model, we demonstrate oral bioavailability; rapid engagement of SOD1G93A by S-XL6 that increases SOD1G93A's in vivo half-life; and that S-XL6 crosses the blood-brain barrier. S-XL6 demonstrated a degree of selectivity by avoiding off-target binding to plasma proteins. Taken together, our results indicate that cyclic thiosulfinate-mediated SOD1 stabilization should receive further attention as a potential therapeutic approach for fALS.

β-escin activates ALDH and prevents cigarette smoke-induced cell death

BACKGROUND

The tobacco use is one of the biggest public health threats worldwide. Cigarette smoke contains over 7000 chemicals among other aldehydes, regarded as priority toxicants. β-escin (a mixture of triterpenoid saponins extracted from the Aesculus hippocastanum. L) is a potent activator of aldehyde dehydrogenase (ALDH) - an enzyme catalyzing oxidation of aldehydes to non-toxic carboxylic acids.

PURPOSE

The aim of this study was to evaluate the effect of β-escin on ALDH activity, ALDH isoforms mRNA expression and cytotoxicity in nasal epithelial cells exposed to cigarette smoke extract (CSE).

METHODS

Nasal epithelial cells from healthy non-smokers were treated with β-escin (1 µM) and exposed to 5% CSE. After 6- or 24-hours of stimulation cell viability, DNA damage, ALDH activity and mRNA expression of ALDH isoforms were examined.

RESULTS

24 h β-escin stimulation revised CSE induced cytotoxicity and DNA damage. Cells cultured with β-escin or exposed to CSE responded with strong increase in ALDH activity. This effect was more pronounced in cultures treated with combination of β-escin and CSE. The strongest stimulatory effect on ALDH isoform mRNA expression was observed in cells cultured simultaneously with β-escin and CSE: at 6 h for ALDH1A1 and ALDH3A1, and at 24 h for ALDH1A3, ALDH3A2, ALDH3B1, and ALDH18A1. Combined β-escin and CSE treatment prevented the CSE-induced inhibition of ALDH2 expression at 24 h.

CONCLUSIONS

β-escin is an effective ALDH stimulatory and cytoprotective agent and might be useful in the prevention or supportive treatment of tobacco smoke-related diseases.

Alcohol induces neural tube defects by reducing retinoic acid signaling and promoting neural plate expansion

Introduction: Neural tube defects (NTDs) are among the most debilitating and common developmental defects in humans. The induction of NTDs has been attributed to abnormal folic acid (vitamin B9) metabolism, Wnt and BMP signaling, excess retinoic acid (RA), dietary components, environmental factors, and many others. In the present study we show that reduced RA signaling, including alcohol exposure, induces NTDs. Methods: Xenopus embryos were exposed to pharmacological RA biosynthesis inhibitors to study the induction of NTDs. Embryos were treated with DEAB, citral, or ethanol, all of which inhibit the biosynthesis of RA, or injected to overexpress Cyp26a1 to reduce RA. NTD induction was studied using neural plate and notochord markers together with morphological analysis. Expression of the neuroectodermal regulatory network and cell proliferation were analyzed to understand the morphological malformations of the neural plate. Results: Reducing RA signaling levels using retinaldehyde dehydrogenase inhibitors (ethanol, DEAB, and citral) or Cyp26a1-driven degradation efficiently induce NTDs. These NTDs can be rescued by providing precursors of RA. We mapped this RA requirement to early gastrula stages during the induction of neural plate precursors. This reduced RA signaling results in abnormal expression of neural network genes, including the neural plate stem cell maintenance genes, geminin, and foxd4l1.1. This abnormal expression of neural network genes results in increased proliferation of neural precursors giving rise to an expanded neural plate. Conclusion: We show that RA signaling is required for neural tube closure during embryogenesis. RA signaling plays a very early role in the regulation of proliferation and differentiation of the neural plate soon after the induction of neural progenitors during gastrulation. RA signaling disruption leads to the induction of NTDs through the mis regulation of the early neuroectodermal network, leading to increased proliferation resulting in the expansion of the neural plate. Ethanol exposure induces NTDs through this mechanism involving reduced RA levels.

ALDEFLUOR activity, ALDH isoforms, and their clinical significance in cancers

High aldehyde dehydrogenase (ALDH) activity is a metabolic feature of adult stem cells and various cancer stem cells (CSCs). The ALDEFLUOR system is currently the most commonly used method for evaluating ALDH enzyme activity in viable cells. This system is applied extensively in the isolation of normal stem cells and CSCs from heterogeneous cell populations. For many years, ALDH1A1 has been considered the most important subtype among the 19 ALDH family members in determining ALDEFLUOR activity. However, in recent years, studies of many types of normal and tumour tissues have demonstrated that other ALDH subtypes can also significantly influence ALDEFLUOR activity. In this article, we briefly review the relationships between various members of the ALDH family and ALDEFLUOR activity. The clinical significance of these ALDH isoforms in different cancers and possible directions for future studies are also summarised.

The construction of hierarchical assemblies with in situ generation of chemotherapy drugs to enhance the efficacy of chemodynamic therapy for multi-modal anti-tumor treatments

The effectiveness of chemodynamic therapy (CDT) in cancer treatment is limited by insufficient endogenous H2O2 levels in tumor tissue and an increasing ratio of high valence metal ions. To overcome these challenges, a novel nanotherapeutic approach, named GOx-CuCaP-DSF, has been proposed. This approach involves the design of nanotherapeutics that aim to self-supply H2O2 within cancer cells and provide a supplement of low valence metal ions to enhance the performance of CDT. GOx-CuCaP-DSF nanotherapeutics are engineered by incorporating glucose oxidase (GOx) into Ca2+-doped calcium phosphate (CaP) nanoparticles and loading disulfiram (DSF) through surface adsorption. Under the tumor microenvironment, GOx catalyzes the conversion of tumor-overexpressed glucose (Glu) to liberate H2O2. The degradation of CaP further lowers the pH, facilitating the release of Cu2+ ions and DSF. The rapid reaction between Cu2+ and DSF leads to the generation of Cu+, increasing the Cu+/Cu2+ ratio and promoting the Cu+-based Fenton reaction, which enhances the efficiency of CDT. Simultaneously, DSF undergoes conversion to diethyldithiocarbamate acid (ET), forming a copper(II) complex (Cu(II)ET) by strong chelation with Cu ions. This Cu(II)ET complex, a potent chemotherapeutic drug, exhibits a synergistic therapeutic effect in combination with CDT. Moreover, the elevated Cu+ species resulting from DSF reaction promotes the aggregation of toxic mitochondrial proteins, leading to cell cuproptosis. Overall, the strategy of integrating the chemodynamic therapy efficiency of the Fenton reaction with the activation of efficacious cuproptosis using a chemotherapeutic drug presents a promising avenue for enhancing the effectiveness of multi-modal anti-tumor treatments.

N-Acyloxymethyl-phthalimides deliver genotoxic formaldehyde to human cells

Formaldehyde is a pollutant and human metabolite that is toxic at high concentrations. Biological studies on formaldehyde are hindered by its high reactivity and volatility, which make it challenging to deliver quantitatively to cells. Here, we describe the development and validation of a set of N-acyloxymethyl-phthalimides as cell-relevant formaldehyde delivery agents. These esterase-sensitive compounds were similarly or less inhibitory to human cancer cell growth than free formaldehyde but the lead compound increased intracellular formaldehyde concentrations, increased cellular levels of thymidine derivatives (implying increased formaldehyde-mediated carbon metabolism), induced formation of cellular DNA-protein cross-links and induced cell death in pancreatic cancer cells. Overall, our N-acyloxymethyl-phthalimides and control compounds provide an accessible and broadly applicable chemical toolkit for formaldehyde biological research and have potential as cancer therapeutics.

Thinking outside the CaaX-box: an unusual reversible prenylation on ALDH9A1

Protein lipidation is a post-translational modification that confers hydrophobicity on protein substrates to control their cellular localization, mediate protein trafficking, and regulate protein function. In particular, protein prenylation is a C-terminal modification on proteins bearing canonical motifs catalyzed by prenyltransferases. Prenylated proteins have been of interest due to their numerous associations with various diseases. Chemical proteomic approaches have been pursued over the last decade to define prenylated proteomes (prenylome) and probe their responses to perturbations in various cellular systems. Here, we describe the discovery of prenylation of a non-canonical prenylated protein, ALDH9A1, which lacks any apparent prenylation motif. This enzyme was initially identified through chemical proteomic profiling of prenylomes in various cell lines. Metabolic labeling with an isoprenoid probe using overexpressed ALDH9A1 revealed that this enzyme can be prenylated inside cells but does not respond to inhibition by prenyltransferase inhibitors. Site-directed mutagenesis of the key residues involved in ALDH9A1 activity indicates that the catalytic C288 bears the isoprenoid modification likely through an NAD+-dependent mechanism. Furthermore, the isoprenoid modification is also susceptible to hydrolysis, indicating a reversible modification. We hypothesize that this modification originates from endogenous farnesal or geranygeranial, the established degradation products of prenylated proteins and results in a thioester form that accumulates. This novel reversible prenoyl modification on ALDH9A1 expands the current paradigm of protein prenylation by illustrating a potentially new type of protein-lipid modification that may also serve as a novel mechanism for controlling enzyme function.

Repurposing Drugs for Inhibition against ALDH2 via a 2D/3D Ligand-Based Similarity Search and Molecular Simulation

Aldehyde dehydrogenase-2 (ALDH2) is a crucial enzyme participating in intracellular aldehyde metabolism and is acknowledged as a potential therapeutic target for the treatment of alcohol use disorder and other addictive behaviors. Using previously reported ALDH2 inhibitors of Daidzin, CVT-10216, and CHEMBL114083 as reference molecules, here we perform a ligand-based virtual screening of world-approved drugs via 2D/3D similarity search methods, followed by the assessments of molecular docking, toxicity prediction, molecular simulation, and the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) analysis. The 2D molecular fingerprinting of ECFP4 and FCFP4 and 3D molecule-shape-based USRCAT methods show good performances in selecting compounds with a strong binding behavior with ALDH2. Three compounds of Zeaxanthin (q = 0), Troglitazone (q = 0), and Sequinavir (q = +1 e) are singled out as potential inhibitors; Zeaxanthin can only be hit via USRCAT. These drugs displayed a stronger binding strength compared to the reported potent inhibitor CVT-10216. Sarizotan (q = +1 e) and Netarsudil (q = 0/+1 e) displayed a strong binding strength with ALDH2 as well, whereas they displayed a shallow penetration into the substrate-binding tunnel of ALDH2 and could not fully occupy it. This likely left a space for substrate binding, and thus they were not ideal inhibitors. The MM-PBSA results indicate that the selected negatively charged compounds from the similarity search and Vina scoring are thermodynamically unfavorable, mainly due to electrostatic repulsion with the receptor (q = -6 e for ALDH2). The electrostatic attraction with positively charged compounds, however, yielded very strong binding results with ALDH2. These findings reveal a deficiency in the modeling of electrostatic interactions (in particular, between charged moieties) in the virtual screening via the 2D/3D similarity search and molecular docking with the Vina scoring system.

Valproic acid reprograms the metabolic aberration of cisplatin treatment via ALDH modulation in triple-negative breast cancer cells

We recently demonstrated that the histone deacetylase inhibitor valproic acid (VPA) reprograms the cisplatin-induced metabolome of triple-negative breast cancer (TNBC) cells, including a shift in hexose levels. Accordingly, here, we tested the hypothesis that VPA alters glucose metabolism in correlation with cisplatin sensitivity. Two TNBC cell lines, MDA-MB-231 (a cisplatin-resistant line) and MDA-MB-436 (a cisplatin-sensitive line), were analyzed. The glycolysis and oxidative metabolism were measured using the Glycolysis Stress Test kit. The expression of aldehyde dehydrogenases (ALDHs), enzymes linked to drug resistance, was investigated by Western blot and real-time PCR analyses. We additionally studied the influence of ALDH inhibition by disulfiram on the viability of MDA-MB-231 cells and on a TNBC patient-derived organoid system. Cisplatin treatment reduced the extracellular acidification rate in MDA-MB-436 cells but not MDA-MB-231 cells, whereas VPA addition increased the extracellular acidification rate in both cell lines. VPA further reduced the oxygen consumption rate of cisplatin-treated MDA-MB-436 cells, which correlated with cell cycle alterations. However, in MDA-MB-231 cells, the cell cycle distribution did not change between cisplatin/VPA-cisplatin treatments. In both cell lines, VPA increased the expression of ALDH isoform and ALDH1A1 expression. However, only in MDA-MB-231 cells, VPA synergized with cisplatin to augment this effect. Disulfiram sensitized the cells to the cytotoxic effects of the VPA-cisplatin combination. Furthermore, the disulfiram-VPA-chemotherapy combination was most effective in TNBC organoids. Our results show that ALDH overexpression may act as one mechanism of cellular resistance to VPA in TNBC and that its inhibition may enhance the therapeutic efficacy of VPA-chemotherapeutic drug combinations.

A patent review on aldehyde dehydrogenase inhibitors: an overview of small molecule inhibitors from the last decade

INTRODUCTION

Physiological and pathophysiological effects arising from detoxification of aldehydes in humans implicate the enzyme aldehyde dehydrogenase (ALDH) gene family comprising of 19 isoforms. The main function of this enzyme family is to metabolize reactive aldehydes to carboxylic acids. Dysregulation of ALDH activity has been associated with various diseases. Extensive research has since gone into studying ALHD isozymes, their structural biology and developing small-molecule inhibitors. Novel chemical strategies to enhance the selectivity of ALDH inhibitors have now appeared.

AREAS COVERED

A comprehensive review of patent literature related to aldehyde dehydrogenase inhibitors in the last decade and half (2007-2022) is provided.

EXPERT OPINION

Aldehyde dehydrogenase (ALDH) is an important enzyme that metabolizes reactive exogenous and endogenous aldehydes in the body through NAD(P)±dependent oxidation. Hence this family of enzymes possess important physiological as well as toxicological roles in human body. Significant efforts in the field have led to potent inhibitors with approved clinical agents for alcohol use disorder therapy. Further clinical translation of novel compounds targeting ALDH inhibition will validate the promised therapeutic potential in treating many human diseases.The scientific/patent literature has been searched on SciFinder-n, Reaxys, PubMed, Espacenet and Google Patents. The search terms used were 'ALDH inhibitors', 'Aldehyde Dehydrogenase Inhibitors'.

Histone H3 K27M-mediated regulation of cancer cell stemness and differentiation in diffuse midline glioma

Therapeutic resistance remains a major obstacle to preventing progression of H3K27M-altered Diffuse Midline Glioma (DMG). Resistance is driven in part by ALDH-positive cancer stem cells (CSC), with high ALDH1A3 expression observed in H3K27M-mutant DMG biopsies. We hypothesized that ALDH-mediated stemness and resistance may in part be driven by the oncohistone itself. Upon deletion of H3K27M, ALDH1A3 expression decreased dramatically and was accompanied by a gain in astrocytic marker expression and a loss of neurosphere forming potential, indicative of differentiation. Here we show that the oncohistone regulates histone acetylation through ALDH1A3 in a Wnt-dependent manner and that loss of H3K27M expression results in sensitization of DMGs to radiotherapy. The observed elevated Wnt signaling in H3K27M-altered DMG likely stems from a dramatic suppression of mRNA and protein expression of the Wnt inhibitor EYA4 driven by the oncohistone. Thus, our findings identify EYA4 as a bona fide tumor suppressor in DMG that upon suppression, results in aberrant Wnt signaling to orchestrate stemness and differentiation. Future studies will explore whether overexpression of EYA4 in DMG can impede growth and invasion. In summary, we have gained mechanistic insight into H3K27M-mediated regulation of cancer stemness and differentiation, which provides rationale for exploring new therapeutic targets for DMG.

Human Aldehyde Dehydrogenases: A Superfamily of Similar Yet Different Proteins Highly Related to Cancer

The superfamily of human aldehyde dehydrogenases (hALDHs) consists of 19 isoenzymes which are critical for several physiological and biosynthetic processes and play a major role in the organism's detoxification via the NAD(P) dependent oxidation of numerous endogenous and exogenous aldehyde substrates to their corresponding carboxylic acids. Over the last decades, ALDHs have been the subject of several studies as it was revealed that their differential expression patterns in various cancer types are associated either with carcinogenesis or promotion of cell survival. Here, we attempt to provide a thorough review of hALDHs' diverse functions and 3D structures with particular emphasis on their role in cancer pathology and resistance to chemotherapy. We are especially interested in findings regarding the association of structural features and their changes with effects on enzymes' functionalities. Moreover, we provide an updated outline of the hALDHs inhibitors utilized in experimental or clinical settings for cancer therapy. Overall, this review aims to provide a better understanding of the impact of ALDHs in cancer pathology and therapy from a structural perspective.

Mitochondria in the Spotlight: C. elegans as a Model Organism to Evaluate Xenobiotic-Induced Dysfunction

Mitochondria play a crucial role in cellular respiration, ATP production, and the regulation of various cellular processes. Mitochondrial dysfunctions have been directly linked to pathophysiological conditions, making them a significant target of interest in toxicological research. In recent years, there has been a growing need to understand the intricate effects of xenobiotics on human health, necessitating the use of effective scientific research tools. Caenorhabditis elegans (C. elegans), a nonpathogenic nematode, has emerged as a powerful tool for investigating toxic mechanisms and mitochondrial dysfunction. With remarkable genetic homology to mammals, C. elegans has been used in studies to elucidate the impact of contaminants and drugs on mitochondrial function. This review focuses on the effects of several toxic metals and metalloids, drugs of abuse and pesticides on mitochondria, highlighting the utility of C. elegans as a model organism to investigate mitochondrial dysfunction induced by xenobiotics. Mitochondrial structure, function, and dynamics are discussed, emphasizing their essential role in cellular viability and the regulation of processes such as autophagy, apoptosis, and calcium homeostasis. Additionally, specific toxins and toxicants, such as arsenic, cadmium, and manganese are examined in the context of their impact on mitochondrial function and the utility of C. elegans in elucidating the underlying mechanisms. Furthermore, we demonstrate the utilization of C. elegans as an experimental model providing a promising platform for investigating the intricate relationships between xenobiotics and mitochondrial dysfunction. This knowledge could contribute to the development of strategies to mitigate the adverse effects of contaminants and drugs of abuse, ultimately enhancing our understanding of these complex processes and promoting human health.

Enhanced pH-Responsive Chemo/Chemodynamic Synergistic Cancer Therapy Based on In Situ Cu2+ Di-Chelation

Considering the chemodynamic therapy and chemotherapy independent of external stimulus witnessing great advantage in the clinical translation, developing a smart nanoplatform that can realize enhanced chemo/chemodynamic synergistic therapy in the tumor microenvironment (TME) is of great significance. Herein, we highlight the enhanced pH-responsive chemo/chemodynamic synergistic cancer therapy based on in situ Cu2+ di-chelation. The alcohol-withdrawal drug disulfiram (DSF) and chemotherapeutic drug mitoxantrone (MTO) were embedded into PEGylated mesoporous CuO (denoted as PEG-CuO@DSF@MTO NPs). The acidic TME triggered the collapse of CuO and the concurrent release of Cu2+, DSF, and MTO. Then, the in situ complexation between Cu2+ and DSF, as well as the coordination between Cu2+ and MTO not only prominently enhanced the chemotherapeutic performance but also triggered the chemodynamic therapy. In vivo mouse model experiments demonstrated that the synergistic therapy can remarkably eliminate tumors. This study provides an interesting strategy to design intelligent nanosystems, which could proceed to clinical translations.

The perspectives of NETosis on the progression of obesity and obesity-related diseases: mechanisms and applications

Obesity is a disease commonly associated with urbanization and can also be characterized as a systemic, chronic metabolic condition resulting from an imbalance between energy intake and expenditure. The World Health Organization (WHO) has identified obesity as the most serious chronic disease that is increasingly prevalent in the world population. If left untreated, it can lead to dangerous health issues such as hypertension, hyperglycemia, hyperlipidemia, hyperuricemia, nonalcoholic steatohepatitis, atherosclerosis, and vulnerability to cardiovascular and cerebrovascular events. The specific mechanisms by which obesity affects the development of these diseases can be refined to the effect on immune cells. Existing studies have shown that the development of obesity and its associated diseases is closely related to the balance or lack thereof in the number and function of various immune cells, of which neutrophils are the most abundant immune cells in humans, infiltrating and accumulating in the adipose tissues of obese individuals, whereas NETosis, as a newly discovered type of neutrophil-related cell death, its role in the development of obesity and related diseases is increasingly emphasized. The article reviews the significant role that NETosis plays in the development of obesity and related diseases, such as diabetes and its complications. It discusses the epidemiology and negative impacts of obesity, explains the mechanisms of NETosis, and examines its potential as a targeted drug to treat obesity and associated ailments.

The role of aldehyde dehydrogenase 2 in cardiovascular disease

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme involved in the detoxification of alcohol-derived acetaldehyde and endogenous aldehydes. The inactivating ALDH2 rs671 polymorphism, present in up to 8% of the global population and in up to 50% of the East Asian population, is associated with increased risk of cardiovascular conditions such as coronary artery disease, alcohol-induced cardiac dysfunction, pulmonary arterial hypertension, heart failure and drug-induced cardiotoxicity. Although numerous studies have attributed an accumulation of aldehydes (secondary to alcohol consumption, ischaemia or elevated oxidative stress) to an increased risk of cardiovascular disease (CVD), this accumulation alone does not explain the emerging protective role of ALDH2 rs671 against ageing-related cardiac dysfunction and the development of aortic aneurysm or dissection. ALDH2 can also modulate risk factors associated with atherosclerosis, such as cholesterol biosynthesis and HDL biogenesis in hepatocytes and foam cell formation and efferocytosis in macrophages, via non-enzymatic pathways. In this Review, we summarize the basic biology and the clinical relevance of the enzymatic and non-enzymatic, tissue-specific roles of ALDH2 in CVD, and discuss the future directions in the research and development of therapeutic strategies targeting ALDH2. A thorough understanding of the complex roles of ALDH2 in CVD will improve the diagnosis, management and prognosis of patients with CVD who harbour the ALDH2 rs671 polymorphism.

A tumor microenvironment-responsive core-shell tecto dendrimer nanoplatform for magnetic resonance imaging-guided and cuproptosis-promoted chemo-chemodynamic therapy

Theranostic nanoplatforms for combination tumor therapy have gained lots of attention recently due to the optimized therapeutic efficiency and simultaneous diagnosis performance. Herein, a novel tumor microenvironment (TME)-responsive core-shell tecto dendrimer (CSTD) was assembled by phenylboronic acid- and mannose-modified poly(amidoamine) dendrimers via the phenylboronic ester bonds that are responsive to low pH and reactive oxygen species (ROS), and efficiently loaded with copper ions and chemotherapeutic drug disulfiram (DSF) for tumor-targeted magnetic resonance (MR) imaging and cuproptosis-promoted chemo-chemodynamic therapy. The formed CSTD-Cu(II)@DSF could be specifically taken up by MCF-7 breast cancer cells, accumulated to the tumor model after circulation, and released drugs in response to the weakly acidic TME with overexpressed ROS. The enriched intracellular Cu(II) ions could induce the oligomerization of lipoylated proteins and proteotoxic stress for cuproptosis, and lipid peroxidation for chemodynamic therapy as well. Moreover, the CSTD-Cu(II)@DSF could cause the dysfunction of mitochondria and arrest the cell cycle at the G2/M phase, leading to enhanced DSF-mediated cell apoptosis. As a result, CSTD-Cu(II)@DSF could effectively inhibit the growth of MCF-7 tumors by a combination therapy strategy integrating chemotherapy with cuproptosis and chemodynamic therapy. Lastly, the CSTD-Cu(II)@DSF also displays Cu(II)-associated r1 relaxivity, allowing for T1-weighted real-time MR imaging of tumors in vivo. The developed tumor-targeted and TME-responsive CSTD-based nanomedicine formulation may be developed for accurate diagnosis and synergistic treatment of other cancer types. STATEMENT OF SIGNIFICANCE: Constructing an effective nanoplatform for the combination of therapeutic effects and real-time tumor imaging remains a challenge. In this study, we reported for the first time an all-in-one tumor-targeted and tumor microenvironment (TME) responsive nanoplatform based on core-shell tecto dendrimer (CSTD) for the cuproptosis-promoted chemo-chemodynamic therapy and enhanced MR imaging. The efficient loading, selective tumor-targeting, and TME-responsive release of Cu(II) and disulfiram could enhance the intracellular accumulation of drugs, induce cuproptosis of cancer cells, and amplify the synergistic chemo-chemodynamic therapeutic effect, resulting in enhanced MR imaging and accelerated tumor eradication. This study sheds new light on the development of theranostic nanoplatforms for early accurate diagnosis and effective treatment of cancers.

Identifying the Molecular Drivers of Pathogenic Aldehyde Dehydrogenase Missense Mutations in Cancer and Non-Cancer Diseases

Human aldehyde dehydrogenases (ALDHs) comprising 19 isoenzymes play a vital role on both endogenous and exogenous aldehyde metabolism. This NAD(P)-dependent catalytic process relies on the intact structural and functional activity of the cofactor binding, substrate interaction, and the oligomerization of ALDHs. Disruptions on the activity of ALDHs, however, could result in the accumulation of cytotoxic aldehydes, which have been linked with a wide range of diseases, including both cancers as well as neurological and developmental disorders. In our previous works, we have successfully characterised the structure-function relationships of the missense variants of other proteins. We, therefore, applied a similar analysis pipeline to identify potential molecular drivers of pathogenic ALDH missense mutations. Variants data were first carefully curated and labelled as cancer-risk, non-cancer diseases, and benign. We then leveraged various computational biophysical methods to describe the changes caused by missense mutations, informing a bias of detrimental mutations with destabilising effects. Cooperating with these insights, several machine learning approaches were further utilised to investigate the combination of features, revealing the necessity of the conservation of ALDHs. Our work aims to provide important biological perspectives on pathogenic consequences of missense mutations of ALDHs, which could be invaluable resources in the development of cancer treatment.

NET Proteome in Established Type 1 Diabetes Is Enriched in Metabolic Proteins

BACKGROUND AND AIMS

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by a T-cell-mediated destruction of the pancreatic insulin-producing beta cells. A growing body of evidence suggests that abnormalities in neutrophils and neutrophil extracellular trap (NET) formation (NETosis) are associated with T1D pathophysiology. However, little information is available on whether these changes are primary neutrophil defects or related to the environmental signals encountered during active disease.

METHODS

In the present work, the NET proteome (NETome) of phorbol 12-myristate 13-acetate (PMA)- and ionomycin-stimulated neutrophils from people with established T1D compared to healthy controls (HC) was studied by proteomic analysis.

RESULTS

Levels of NETosis, in addition to plasma levels of pro-inflammatory cytokines and NET markers, were comparable between T1D and HC subjects. However, the T1D NETome was distinct from that of HC in response to both stimuli. Quantitative analysis revealed that the T1D NETome was enriched in proteins belonging to metabolic pathways (i.e., phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase, and UTP-glucose-1-phosphate uridylyltransferase). Complementary metabolic profiling revealed that the rate of extracellular acidification, an approximate measure for glycolysis, and mitochondrial respiration were similar between T1D and HC neutrophils in response to both stimuli.

CONCLUSION

The NETome of people with established T1D was enriched in metabolic proteins without an apparent alteration in the bio-energetic profile or dysregulated NETosis. This may reflect an adaptation mechanism employed by activated T1D neutrophils to avoid impaired glycolysis and consequently excessive or suboptimal NETosis, pivotal in innate immune defence and the resolution of inflammation.

ALDH2 Inhibition by Lead and Ethanol Elicits Redox Imbalance and Mitochondrial Dysfunction in SH-SY5Y Human Neuroblastoma Cell Line: Reversion by Alda-1

Lead (Pb), a common environmental contaminant, and ethanol (EtOH), a widely available drug of abuse, are well-known neurotoxicants. In vivo, experimental evidence indicates that Pb exposure affects oxidative EtOH metabolism with a high impact on living organisms. On these bases, we evaluated the consequences of combined Pb and EtOH exposure on aldehyde dehydrogenase 2 (ALDH2) functionality. In vitro exposure to 10µM Pb, 200mM EtOH, or their combination for 24h reduced ALDH2 activity and content in SH-SY5Y human neuroblastoma cells. In this scenario, we observed mitochondrial dysfunction characterized by reduced mass and membrane potential, decreased maximal respiration, and spare capacity. We also evaluated the oxidative balance in these cells finding a significant increase in reactive oxygen species (ROS) production and lipid peroxidation products under all treatments accompanied by an increase in catalase (CAT) activity and content. These data suggest that ALDH2 inhibition induces the activation of converging cytotoxic mechanisms resulting in an interplay between mitochondrial dysfunction and oxidative stress. Notably, NAD⁺ (1mM for 24h) restored ALDH2 activity in all groups, while an ALDH2 enhancer (Alda-1, 20µM for 24h) also reversed some of the deleterious effects resulting from impaired ALDH2 function. Overall, these results reveal the crucial role of this enzyme on the Pb and EtOH interaction and the potential of activators such as Alda-1 as therapeutic approaches against several conditions involving aldehydes accumulation.

Enzymatic cofactor regeneration systems: A new perspective on efficiency assessment

Nowadays, the specificity of enzymatic processes makes them more and more important every year, and their usage on an industrial scale seems to be necessary. Enzymatic cofactors, however, play a crucial part in the prospective applications of enzymes, because they are indispensable for conducting highly effective biocatalytic activities. Due to the relatively high cost of these compounds and their consumption during the processes carried out, it has become crucial to develop systems for cofactor regeneration. Therefore, in this review, an attempt was made to summarize current knowledge on enzymatic regeneration methods, which are characterized by high specificity, non-toxicity and reported to be highly efficient. The regeneration of cofactors, such as nicotinamide dinucleotides, coenzyme A, adenosine 5'-triphosphate and flavin nucleotides, which are necessary for the proper functioning of a large number of enzymes, is discussed, as well as potential directions for further development of these systems are highlighted. This review discusses a range of highly effective cofactor regeneration systems along with the productive synthesis of many useful chemicals, including the simultaneous renewal of several cofactors at the same time. Additionally, the impact of the enzyme immobilization process on improving the stability and the potential for multiple uses of the developed cofactor regeneration systems was also presented. Moreover, an attempt was made to emphasize the importance of the presented research, as well as the identification of research gaps, which mainly result from the lack of available literature on this topic.

Disulfiram accelerates diabetic foot ulcer healing by blocking NET formation via suppressing the NLRP3/Caspase-1/GSDMD pathway

Diabetic foot ulcer (DFU) is among the most frequent complications of diabetes and is associated with significant morbidity and mortality. Excessive neutrophil extracellular traps (NETs) delay wound healing in diabetic patients. Therefore, interventions targeting NET release need to be developed to effectively prevent NET-based wound healing impairment. Gasdermin D (GSDMD), a pore-forming protein acts as a central executioner of inflammatory cell death and can activate inflammasomes in neutrophils to release NETs. A precise understanding of the mechanism underlying NET-mediated delay in diabetic wound healing may be valuable in identifying potential therapeutic targets to improve clinical outcomes. In this study, we reported that neutrophils were more susceptible to NETosis in diabetic wound environments of patients with DFU. By in vitro experiments and using in vivo mouse models of diabetic wound healing (wide-type, Nlrp3^-/-, Casp-1^-/-, and Gsdmd^-/- mice), we demonstrated that NLRP3/caspase-1/GSDMD pathway on activation controls NET release by neutrophils in diabetic wound tissue. Furthermore, inhibition of GSDMD with disulfiram or genic deletion of Gsdmd abrogated NET formation, thereby accelerating diabetic wound healing. Disulfiram could inhibit NETs-mediated diabetic foot ulcer healing impairment by suppressing the NLRP3/Caspase-1/GSDMD pathway. In summary, our findings uncover a novel therapeutic role of disulfiram in inhibiting NET formation, which is of considerable value in accelerating wound healing in patients with DFU.

DOPAL initiates αSynuclein-dependent impaired proteostasis and degeneration of neuronal projections in Parkinson's disease

Dopamine dyshomeostasis has been acknowledged among the determinants of nigrostriatal neuron degeneration in Parkinson's disease (PD). Several studies in experimental models and postmortem PD patients underlined increasing levels of the dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is highly reactive towards proteins. DOPAL has been shown to covalently modify the presynaptic protein αSynuclein (αSyn), whose misfolding and aggregation represent a major trait of PD pathology, triggering αSyn oligomerization in dopaminergic neurons. Here, we demonstrated that DOPAL elicits αSyn accumulation and hampers αSyn clearance in primary neurons. DOPAL-induced αSyn buildup lessens neuronal resilience, compromises synaptic integrity, and overwhelms protein quality control pathways in neurites. The progressive decline of neuronal homeostasis further leads to dopaminergic neuron loss and motor impairment, as showed in in vivo models. Finally, we developed a specific antibody which detected increased DOPAL-modified αSyn in human striatal tissues from idiopathic PD patients, corroborating the translational relevance of αSyn-DOPAL interplay in PD neurodegeneration.

Clinical, pharmacological, and formulation evaluation of disulfiram in the treatment of glioblastoma - a systematic literature review

INTRODUCTION

Glioblastoma (GB) is one of the most challenging central nervous system (CNS) tumors in treatment options and response, urging the development of novel management strategies. The anti-alcoholism drug, disulfiram (DS), has a potential anticancer activity, and its complex mechanism of action is assumed to be well exploited against the heterogeneous GB.

AREA COVERED

Through a systematic literature review about repositioning DS to GB treatment, an evaluation of the clinical, pharmacological, and formulation strategies is provided to specify the challenges of drug delivery and thus to advance its clinical translation. From six databases, 35 articles were selected, including case report (1); clinical trials (3); original articles mainly representing in vitro and preclinical pharmacological data, and 10 dealing with technological approaches.

EXPERT OPINION

The repositioning of DS in GB treatment is facing drug and tumor-associated limitations due to the oral drug's low bioavailability, unwanted metabolism, and inefficient delivery to brain-tumor tissue. Development strategies using molecular encapsulation of DS and the parenteral dosage forms improve the anticancer pharmacology of the drug. The development of optimized drug delivery systems (DDS) shows promise for the clinical translation of DS into GB adjuvant therapy.

Investigating the Functional Roles of Aldehyde Dehydrogenase 3A1 in Human Corneal Epithelial Cells

Aldehyde dehydrogenase 3A1 (ALDH3A1) oxidizes medium-chain aldehydes to their corresponding carboxylic acids. It is expressed at high rates in the human cornea, where it has been characterized as a multi-functional protein displaying various cytoprotective modes of action. Previous studies identified its association with the DNA damage response (DDR) pathway. Here, we utilized a stable transfected HCE-2 (human corneal epithelium) cell line expressing ALDH3A1, to investigate the molecular mechanisms underlying the cytoprotective role(s) of ALDH3A1. Our data revealed morphological differences among the ALDH3A1-expressing and the mock-transfected HCE-2 cells accompanied by differential expression of E-cadherin. Similarly, the ALDH3A1/HCE-2 cells demonstrated higher mobility, reduced proliferation, upregulation of ZEB1, and downregulation of CDK3, and p57. The expression of ALDH3A1 also affected cell cycle progression by inducing the sequestration of HCE-2 cells at the G2/M phase. Following 16 h cell treatments with either H₂O₂ or etoposide, a significantly lower percentage of ALDH3A1/HCE-2 cells were apoptotic compared to the respective treated mock/HCE-2 cells. Interestingly, the protective effect of ALDH3A1 expression under these oxidative and genotoxic conditions was accompanied by a reduced formation of γ-H2AX foci and higher levels of total and phospho (Ser15) p53. Finally, ALDH3A1 was found to be localized both in the cytoplasm and the nucleus of transfected HCE-2 cells. Its cellular compartmentalization was not affected by oxidant treatment, while the mechanism by which ALDH3A1 translocates to the nucleus remains unknown. In conclusion, ALDH3A1 protects cells from both apoptosis and DNA damage by interacting with key homeostatic mechanisms associated with cellular morphology, cell cycle, and DDR.

Disulfiram: Mechanisms, Applications, and Challenges

Background: Since disulfiram’s discovery in the 1940s and its FDA approval for alcohol use disorder, other indications have been investigated. This review describes potential clinical applications, associated risks, and challenges. Methods: For this narrative review, a PubMed search was conducted for articles addressing in vivo studies of disulfiram with an emphasis on drug repurposing for the treatment of human diseases. The key search terms were “disulfiram” and “Antabuse”. Animal studies and in vitro studies highlighting important mechanisms and safety issues were also included. Results: In total, 196 sources addressing our research focus spanning 1948–2022 were selected for inclusion. In addition to alcohol use disorder, emerging data support a potential role for disulfiram in the treatment of other addictions (e.g., cocaine), infections (e.g., bacteria such as Staphylococcus aureus and Borrelia burgdorferi, viruses, parasites), inflammatory conditions, neurological diseases, and cancers. The side effects range from minor to life-threatening, with lower doses conveying less risk. Caution in human use is needed due to the considerable inter-subject variability in disulfiram pharmacokinetics. Conclusions: While disulfiram has promise as a “repurposed” agent in human disease, its risk profile is of concern. Animal studies and well-controlled clinical trials are needed to assess its safety and efficacy for non-alcohol-related indications.

A comparative study of smart nanoformulations of diethyldithiocarbamate with Cu4O3 nanoparticles or zinc oxide nanoparticles for efficient eradication of metastatic breast cancer

Metastatic tumor is initiated by metastatic seeds (cancer stem cells "CSCs") in a controlled redox microenvironment. Hence, an effective therapy that disrupts redox balance with eliminating CSCs is critical. Diethyldithiocarbamate (DE) is potent inhibitor of radical detoxifying enzyme (aldehyde dehydrogenase "ALDH"1A) causing effective eradication of CSCs. This DE effect was augmented and more selective by its nanoformulating with green synthesized copper oxide (Cu₄O₃) nanoparticles (NPs) and zinc oxide NPs, forming novel nanocomplexes of CD NPs and ZD NPs, respectively. These nanocomplexes exhibited the highest apoptotic, anti-migration, and ALDH1A inhibition potentials in M.D. Anderson-metastatic breast (MDA-MB) 231 cells. Importantly, these nanocomplexes revealed more selective oxidant activity than fluorouracil by elevating reactive oxygen species with depleting glutathione in only tumor tissues (mammary and liver) using mammary tumor liver metastasis animal model. Due to higher tumoral uptake and stronger oxidant activity of CD NPs than ZD NPs, CD NPs had more potential to induce apoptosis, suppress hypoxia-inducing factor gene, and eliminate CD44⁺CSCs with downregulating their stemness, chemoresistance, and metastatic genes and diminishing hepatic tumor marker (α-fetoprotein). These potentials interpreted the highest tumor size reduction with complete eradicating tumor metastasis to liver in CD NPs. Consequently, CD nanocomplex revealed the highest therapeutic potential representing a safe and promising nanomedicine against the metastatic stage of breast cancer.

Targeting aldehyde dehydrogenase enzymes in combination with chemotherapy and immunotherapy: An approach to tackle resistance in cancer cells

Modern cancer chemotherapy originated in the 1940s, and since then, many chemotherapeutic agents have been developed. However, most of these agents show limited response in patients due to innate and acquired resistance to therapy, which leads to the development of multi-drug resistance to different treatment modalities, leading to cancer recurrence and, eventually, patient death. One of the crucial players in inducing chemotherapy resistance is the aldehyde dehydrogenase (ALDH) enzyme. ALDH is overexpressed in chemotherapy-resistant cancer cells, which detoxifies the generated toxic aldehydes from chemotherapy, preventing the formation of reactive oxygen species and, thus, inhibiting the induction of oxidative stress and the stimulation of DNA damage and cell death. This review discusses the mechanisms of chemotherapy resistance in cancer cells promoted by ALDH. In addition, we provide detailed insight into the role of ALDH in cancer stemness, metastasis, metabolism, and cell death. Several studies investigated targeting ALDH in combination with other treatments as a potential therapeutic regimen to overcome resistance. We also highlight novel approaches in ALDH inhibition, including the potential synergistic employment of ALDH inhibitors in combination with chemotherapy or immunotherapy against different cancers, including head and neck, colorectal, breast, lung, and liver.

Decreased propionyl-CoA metabolism facilitates metabolic reprogramming and promotes hepatocellular carcinoma

BACKGROUND & AIMS

Alterations of multiple metabolites characterize distinct features of metabolic reprograming in hepatocellular carcinoma (HCC). However, the role of most metabolites, including propionyl-CoA (Pro-CoA), in metabolic reprogramming and hepatocarcinogenesis remains elusive. In this study, we aimed to dissect how Pro-CoA metabolism affects these processes.

METHODS

TCGA data and HCC samples were used to analyze ALDH6A1-mediated Pro-CoA metabolism and its correlation with HCC. Multiple metabolites were assayed by targeted mass spectrometry. The role of ALDH6A1-generated Pro-CoA in HCC was evaluated in HCC cell lines as well as xenograft nude mouse models and primary liver cancer mouse models. Non-targeted metabolomic and targeted energy metabolomic analyses, as well as multiple biochemical assays, were performed.

RESULTS

Decreases in Pro-CoA and its derivative propionyl-L-carnitine due to ALDH6A1 downregulation were tightly associated with HCC. Functionally, ALDH6A1-mediated Pro-CoA metabolism suppressed HCC proliferation in vitro and impaired hepatocarcinogenesis in mice. The aldehyde dehydrogenase activity was indispensable for this function of ALDH6A1, while Pro-CoA carboxylases antagonized ALDH6A1 function by eliminating Pro-CoA. Mechanistically, ALDH6A1 caused a signature enrichment of central carbon metabolism in cancer and impaired energy metabolism: ALDH6A1-generated Pro-CoA suppressed citrate synthase activity, which subsequently reduced tricarboxylic acid cycle flux, impaired mitochondrial respiration and membrane potential, and decreased ATP production. Moreover, Pro-CoA metabolism generated 2-methylcitric acid, which mimicked the inhibitory effect of Pro-CoA on citrate synthase and dampened mitochondrial respiration and HCC proliferation.

CONCLUSIONS

The decline of ALDH6A1-mediated Pro-CoA metabolism contributes to metabolic remodeling and facilitates hepatocarcinogenesis. Pro-CoA, propionyl-L-carnitine and 2-methylcitric acid may serve as novel metabolic biomarkers for the diagnosis and treatment of HCC. Pro-CoA metabolism may provide potential targets for development of novel strategies against HCC.

IMPACT AND IMPLICATIONS

Our study presents new insights on the role of propionyl-CoA metabolism in metabolic reprogramming and hepatocarcinogenesis. This work has uncovered potential diagnostic and predictive biomarkers, which could be used by physicians to improve clinical practice and may also serve as targets for the development of therapeutic strategies against HCC.

Identification and characterisation of the tegument-expressed aldehyde dehydrogenase SmALDH_312 of Schistosoma mansoni, a target of disulfiram

Schistosomiasis is an infectious disease caused by blood flukes of the genus Schistosoma and affects approximately 200 million people worldwide. Since Praziquantel (PZQ) is the only drug for schistosomiasis, alternatives are needed. By a biochemical approach, we identified a tegumentally expressed aldehyde dehydrogenase (ALDH) of S. mansoni, SmALDH_312. Molecular analyses of adult parasites showed Smaldh_312 transcripts in both genders and different tissues. Physiological and cell-biological experiments exhibited detrimental effects of the drug disulfiram (DSF), a known ALDH inhibitor, on larval and adult schistosomes in vitro. DSF also reduced stem-cell proliferation and caused severe tegument damage in treated worms. In silico-modelling of SmALDH_312 and docking analyses predicted DSF binding, which we finally confirmed by enzyme assays with recombinant SmALDH_312. Furthermore, we identified compounds of the Medicine for Malaria Venture (MMV) pathogen box inhibiting SmALDH_312 activity. Our findings represent a promising starting point for further development towards new drugs for schistosomiasis.

Oxidation of Aldehydes into Carboxylic Acids by a Mononuclear Manganese(III) Iodosylbenzene Complex through Electrophilic C-H Bond Activation

The oxidation of aldehyde is one of the fundamental reactions in the biological system. Various synthetic procedures and catalysts have been developed to convert aldehydes into corresponding carboxylic acids efficiently under ambient conditions. In this work, we report the oxidation of aldehydes by a mononuclear manganese(III) iodosylbenzene complex, [Mn^III(TBDAP)(OIPh)(OH)]²⁺ (1), with kinetic and mechanistic studies in detail. The reaction of 1 with aldehydes resulted in the formation of corresponding carboxylic acids via a pre-equilibrium state. Hammett plot and reaction rates of 1 with 1°-, 2°-, and 3°-aldehydes revealed the electrophilicity of 1 in the aldehyde oxidation. A kinetic isotope effect experiment and reactivity of 1 toward cyclohexanecarboxaldehyde (CCA) analogues indicate that the reaction of 1 with aldehyde occurs through the rate-determining C-H bond activation at the formyl group. The reaction rate of 1 with CCA is correlated to the bond dissociation energy of the formyl group plotting a linear correlation with other aliphatic C-H bonds. Density functional theory calculations found that 1 electrostatically interacts with CCA at the pre-equilibrium state in which the C-H bond activation of the formyl group is performed as the most feasible pathway. Surprisingly, the rate-determining step is characterized as hydride transfer from CCA to 1, affording an (oxo)methylium intermediate. At the fundamental level, it is revealed that the hydride transfer is composed of H atom abstraction followed by a fast electron transfer. Catalytic reactions of aldehydes by 1 are also presented with a broad substrate scope. This novel mechanistic study gives better insights into the metal oxygen chemistry and would be prominently valuable for development of transition metal catalysts.

Control of Explosive Chemical Reactions by Optical Excitations: Defect-Induced Decomposition of Trinitrotoluene at Metal Oxide Surfaces

Interfaces formed by high energy density materials and metal oxides present intriguing new opportunities for a large set of novel applications that depend on the control of the energy release and initiation of explosive chemical reactions. We studied the role of structural defects at a MgO surface in the modification of electronic and optical properties of the energetic material TNT (2-methyl-1,3,5-trinitrobenzene, also known as trinitrotoluene, C₇H₅N₃O₆) deposited at the surface. Using density functional theory (DFT)-based solid-state periodic calculations with hybrid density functionals, we show how the control of chemical explosive reactions can be achieved by tuning the electronic structure of energetic compound at an interface with oxides. The presence of defects at the oxide surface, such as steps, kinks, corners, and oxygen vacancies, significantly affects interfacial properties and modifies electronic spectra and charge transfer dynamics between the oxide surface and adsorbed energetic material. As a result, the electronic and optical properties of trinitrotoluene, mixed with an inorganic material (thus forming a composite), can be manipulated with high precision by interactions between TNT and the inorganic material at composite interfaces, namely, by charge transfer and band alignment. Also, the electron charge transfer between TNT and MgO surface reduces the decomposition barriers of the energetic material. In particular, it is shown that surface structural defects are critically important in the photodecomposition processes. These results open new possibilities for the rather precise control over the decomposition initiation mechanisms in energetic materials by optical excitations.

Aldehyde dehydrogenase in solid tumors and other diseases: Potential biomarkers and therapeutic targets

The family of aldehyde dehydrogenases (ALDHs) contains 19 isozymes and is involved in the oxidation of endogenous and exogenous aldehydes to carboxylic acids, which contributes to cellular and tissue homeostasis. ALDHs play essential parts in detoxification, biosynthesis, and antioxidants, which are of important value for cell proliferation, differentiation, and survival in normal body tissues. However, ALDHs are frequently dysregulated and associated with various diseases like Alzheimer's disease, Parkinson's disease, and especially solid tumors. Notably, the involvement of the ALDHs in tumor progression is responsible for the maintenance of the stem-cell-like phenotype, triggering rapid and aggressive clinical progressions. ALDHs have captured increasing attention as biomarkers for disease diagnosis and prognosis. Nevertheless, these require further longitudinal clinical studies in large populations for broad application. This review summarizes our current knowledge regarding ALDHs as potential biomarkers in tumors and several non-tumor diseases, as well as recent advances in our understanding of the functions and underlying molecular mechanisms of ALDHs in disease development. Finally, we discuss the therapeutic potential of ALDHs in diseases, especially in tumor therapy with an emphasis on their clinical implications.

The Expanding Role of Cancer Stem Cell Marker ALDH1A3 in Cancer and Beyond

Aldehyde dehydrogenase 1A3 (ALDH1A3) is one of 19 ALDH enzymes expressed in humans, and it is critical in the production of hormone receptor ligand retinoic acid (RA). We review the role of ALDH1A3 in normal physiology, its identification as a cancer stem cell marker, and its modes of action in cancer and other diseases. ALDH1A3 is often over-expressed in cancer and promotes tumor growth, metastasis, and chemoresistance by altering gene expression, cell signaling pathways, and glycometabolism. The increased levels of ALDH1A3 in cancer occur due to genetic amplification, epigenetic modifications, post-transcriptional regulation, and post-translational modification. Finally, we review the potential of targeting ALDH1A3, with both general ALDH inhibitors and small molecules specifically designed to inhibit ALDH1A3 activity.